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Publication numberUS3836917 A
Publication typeGrant
Publication dateSep 17, 1974
Filing dateApr 16, 1973
Priority dateApr 16, 1973
Publication numberUS 3836917 A, US 3836917A, US-A-3836917, US3836917 A, US3836917A
InventorsMee J
Original AssigneeMee J
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
High-speed non-impact laser printing apparatus
US 3836917 A
Abstract
A printing apparatus for laser recording of data in which a complete row of characters is simultaneously formed by a two dimensional matrix of parallel diode lasers selectively activated to emit light in character shapes upon a photosensitive medium. The invention is adapted to provide rapid non-impact printout, in alphanumeric characters, of computer data. The system simultaneously imprints a complete row of characters on a medium transported through the system at high speed, and for each character in the row the system includes a decoder for converting data in computer binary code into individual signals each representing a single alphanumeric character. The individual signals are applied through a hardwiring distribution circuit or core distribution circuit to selected diode lasers in the two dimensional matrix to cause those lasers to emit parallel beams of light in a pattern approximating the shape of the character. The emitted light beams directly strike a photosensitive medium, causing it to record the character shape. Spacing between rows of characters is controlled by a timing signal supplied by the means transporting the photosensitive medium through the system.
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United States Patent [191 Mee [451 Sept. 17, 1974 HIGH-SPEED NON-IMPACT LASER PRINTING APPARATUS [76] Inventor: John L. Mee, 42 Highwood Rd.,

Farmington, Conn. 06032 [22] Filed: Apr..l6, 1973 [21] Appl. No.: 351,620

[52] US. Cl. 354/5, 354/7 [51] Int. Cl B4lb 21/14 [58] Field of Search 95/45; 340/378, 324; 354/5, 7

[56] References Cited UNITED STATES PATENTS 3,267,455 8/1966 McGuire 340/324 3,611,891 10/1971 McNaney 95/45 Primary Examiner-John M. Horan Attorney, Agent, or Firm-Joseph L. Lazaroff [57] ABSTRACT A printing apparatus for laser recording of data in IIOOOOII 2 which a complete row of characters is simultaneously formed by a two dimensional matrix of parallel diode lasers selectively activated to emit light in character shapes upon a photosensitive medium. The invention is adapted to provide rapid non-impact printout, in alphanumeric characters, of computer data. The system simultaneously imprints a complete row of characters on a medium transported through the system at high speed, and for each character in the row the system includes a decoder for converting data in computer binary code into individual signals each representing a single alphanumeric character. The individual signals are applied through a hardwiring distribution circuit or core distribution circuit to selected diode lasers in the two dimensional matrix to cause those lasers to emit parallel beams of light in a pattern approximating the shape of the character. The emitted light beams directly strike a photosensitive medium, causing it to record the character shape. Spacing between rows of characters is controlled by a timing signal supplied by the means transporting the photosensitive medium v through the system.

14 Claims, 12 Drawing Figures Pmmms'tnmu 3.838-,91T

T ms or 7 J COMPUTER FIGURE 2 j- TRANS.

3 INTERFACE I Anmw I 3.836.917 SHEET-50F 7 F-IIGUREI 4 4 3 TERMINAL 4 I TERMINAL LJZIY Pmmmsm m V sIHEU 70$ 7- FIGURE e COMPUTER HIGH-SPEED NON-IMPACT LASER PRINTING APPARATUS BACKGROUND OF THE INVENTION 1. Field of the Invention The field of the present invention relates to printing and the graphic arts, and more particularly to high speed, non-impact printers suitable for performing computer data printout tasks.

2. Description of the Prior Art The rate at which a computer can supply output data far outstrips the ability of conventional mechanical printers to record that data. Accordingly, many attempts have been made to find substitutes for mechanical printers to attain high printing speeds and thus more efficient computer use.

Various arrangements have been proposed for high speed non-impact printing using a photosensitive medium and optical character generation techniques with laser light sources. In one such arrangement, disclosed in US. Pat. Nos. 3,396,401; 3,506,779; 3,654,864; and 3,656,] 75, a laser light source, providing either a point or line of light, scans the recording medium in a series of parallel lines, with switching means controlling emission to generate character shapes.

In another prior art arrangement, disclosed in U'.S. Pat. No. 3,220,013, a laser light source is deflected through a character mask, and isthen deflected to-a common point, from which it is deflected to the recording medium.

In still another prior art arrangement, disclosed in US. Pat. Nos. 3,4l0,203; 3,617,702; 3,653,067; 3,688,281; and 3,704,929, a deflected laser'li'ght beam is used in conjunction with a holographic character storage medium to generate character shapes which are to be directed upon a recording medium.

Such prior art printing apparatus of the general type referred to above has not been'fully satisfactory in providing rapidnon-impact printout in alphanumeric'characters of computer data. While gains'have been made inspeed by eliminating impact, a large disparity from the speed of thecomputer output-persists. Moreover, many of the prior art devices employ elements such as scanners or deflectors which limit speed and require a large amount of space, and record data either a characterat a time or a scan line at a time in sequential fashion, often requiring very rapid switching, a laser light source with a high duty cycle, or a considerable amount of activation time per unit of data recorded.

SUMMARY OF THE INVENTION It is a principal object of this invention to provide an improved high speed, non-impact printer of computer data. It is a specific object of the invention to provide a printer in which a complete row of characters may be simultaneously formed, and in which all character formation may be controlled by electrical or electronic means without mechanical devices. Still another object of the invention is to provide ahigh speed, non-impact printer which is compact, simple in design, and more suitable for commercial use.

In a preferred embodiment of the invention to be described hereinbelow in detail, the printer comprises a row of character printing elements, each with a twodimensional matrix of parallel diode lasers arranged to emit light upon a photosensitive medium continuously transported through the system at high speed. Electron ically coded signals for a complete row of characters 'are supplied simultaneously to the printing elements by, e.g., a computer. Within each printing element the coded signals for a single character are decoded into alphanumeric character signals which are supplied to a character image generator. The character image generator produces a pattern of on and off signals which drive selected diode lasers in the two-dimensional matrix to cause those lasers to emit parallel beams of light in a pattern approximating the shape of the character. The light beams emitted by the row of printing elements simultaneously strike the photosensitive medium, causing it to record the shapes of the characters 'in'the row. This arrangement affords rapid printing of successive rows of characters. The arrangement further is advantageous in that is is compact and without the problems introduced by mechanical constituents.

Other objects, aspects and advantages of the invention will be pointed out in, or apparent from, the detailed description hereinbelow, considered together with the following drawings.

DESCRIPTION OF THE DRAWINGS FIG. I is a schematic view of a portion of a printing apparatus used for recording data on a photosensitive mediiiin'inaccordance with the present'invention;

FIGS. 1A 10 are illustrations of recorded character shapes produced by the printing apparatus of FIG. 1 on a photosensitive medium, using various laser output unit configurations;

printer which utilizes the laser printing section shown in FIG. 5.

DESCRIPTION or THE PREFERRED EMBODIMENTS The present invention provides a printing apparatus arranged to receive character data in electronic form from a computer and, in response to such data, to print successive rows of visible characters a row at a time on a moving sheet of photosensitive recording medium.

'For simplicity a single printing element P, printing a single character in the row, is illustrated schematically in FIG. 1. As shown, printing element P receives character data 2 in electronic form from computer 1 and prints a single character in the row on photosensitive recordingmedium 15. The photosensitive recording medium 15 is mounted on rollers 14 for rapid continuous transport through a printing station S where printing element P imprints a character by means of short duration light signals or beams 12 emitter from its laser output unit 10 spaced from photosensitive medium 15. Laser output unit 10 contains component lasens 11 in a two dimensional laser matrix or array, which is typically a X 7 rectangular array comprising 35 lasers.

Selected lasers in the array emit parallel beams of light 12 in a pattern approximating the shape of the character. The emitted light beams 12 directly strike the photosensitive medium 15, causing it to record the character shape, shown typically by the character shape 17 in FIG. 1A, illustrated by the character C'.

Laser output consists of a multi-planar grid or network of parallel semiconductor lasers in which planar rows of parallel lasers are stacked upon one another. The semiconductor lasers 11 are of a type suitable for recording images on a photosensitive medium at high speeds. At present, suitable lasers for the application include the single heterojunction (SH), double heterojunction (DH) and large optical cavity (LOC) semiconductor lasers. All three types of lasers have the advantage of being able to operate at very rapid pulsing rates (e.g., less than 10 nanoseconds) at comparatively heavy duty cycles for reasonably long lifespans. They can withstand vibration and operate continuously at room temperature with only moderate heat-sinking requirements.

Of the three types of presently-suitable lasers, the gallium aluminum arsenide LOC injection laser is preferred. As a refinement of the DH laser, the LOC laser possesses the high quantum efficiency and low threshold current density and heat-sinking requirements of the DH laser, and it is substantially less susceptible to damage by pulsing variations than the DH laser. LOC lasers of the type described may be e.g. the RCA C30025 LOC laser, which can be driven by currents as low as 5 amperes at or above room temperature.

Selective activation of the individual lasers 11 in output unit 10 (shown greatly enlarged) is accomplished as follows: A source of electronic output signals, such as computer 1, transmit an electronically coded signal representing a numeric, alphanumeric or special character of information, such as binary-coded signal 2, to interface 3. Interface 3 decodes the signal, and applies the decoded signal to a character image generator 48 comprising a character translator 4, character sense wires 6, pulser 7, and pulser wires 9. The decoded signal from interface 3 instructs character translator 4 to activate the particular one of storage elements 5 which corresponds to the number, letter or symbol represented by the decoded signal. The storage element so activated transmit a unique pattern of electrical impulses through character sense wires 6 in parallel circuit.

Character sense wires 6 connect with pulser 7 which contains separate driving circuits or modules 8 for each of the semiconductor lasers 11 and serves to convert the presence of current in any character sense wire which contains current to an amplified pulse sufficient to drive the associated one of the semiconductor lasers 11 in output unit 10. Each one of character sense wires 6 is connected to one of the identical pulser modules 8 which are equal in number to the number of semiconductor lasers 1] in output unit 10. A pulser module 8 switches the low-current signals from the character sense wires 6 in a circuit comprising, for example, a class C operation mode RF transistor amplifier in a pulsed mode of operation. The resulting pulses, typi cally 40 nanoseconds wide, are transmitted to output unit 10 by means of pulser wires 9, which would normally be low-inductance ribbon leads.

A one-to-one correspondence exists between each one of pulser modules 8, one of pulser wires 9, and one of semiconductor lasers 1]. The unique pattern of electrical impulses produced in character sense wires 6 by the activated one of storage elements 5 is such that the presence of low-level current is introduced in those of character sense wires 6 which are connected to those of pulser modules 8 which serve to drive lasers whose position in the network of semiconductor lasers 1] physically resemble a graphic outline of the number, letter or symbol corresponding to the storage element activated.

Thus a two dimensional pattern of electric pulses is transmitted in parallel circuit via pulser wires 9 directly to corresponding lasers 11 in output unit 10, causing a selective and simultaneous activation of those lasers in the array needed to form a composite character beam 13 in the shape of the number, letter or symbol corresponding to the storage element activated. Due to the fact that character-shaped laser beam 13 is a composite of many smaller, parallel beams, it is initially emitted by the apparatus in its final form, and may directly strike photosensitive recording medium 15 to record an image thereon.

Photosensitive recording medium 15 may typically be embodied as a 14 by 11 inch continuous fanfold sheet, chemically treated with a photopolymer, photoconductor, or photochromic compound sensitive to infrared light at a wavelength ofapproximately 9000 angstrom units with a minimum radiant flux density of 20.83 watts/mil? For tractor-fed transport, this continuous sheet would normally have a 16 to 20 pound bond weight, and would be supplied at its peripheries with typical tractor feeding holes.

Transport rollers 14, typically tractor feeds, impart to photosensitive medium 15 a continuous, rapid vertical motion. The rate of this vertical motion may be associated with the pulse width of character-shaped laser beam 13 to product various types of recorded images, as discussed hereinbelow. Upon striking photosensitive recording medium 15, the parallel beams of light 12 forming character-shaped laser beam 13 cause individual recordings 16, shown greatly enlarged in FIG. 1A, to be made in an overall graphic shape 17 approximating that of the desired character. Due to the fact that only one set of electrical impulses is transmitted by the storage element activated, the selected lasers deactivate immediately following the laser emission of character-shaped beam 13, leaving output unit 10 ready to accept a new set of electrical impulses for the next character to be printed at the character portion of unit 10 in the-succeeding row of characters. Between successive activations of lasers 11, the transport rollers 14 continue to advance photosensitive recording medium 15 so that it will be positioned to receive the next row of character beams 13 emitted.

As illustrated in FIGS. 1B, 1C, 1D and 1E, one of four types of output unit configurations 10W, 10X, l0Y or 102 may be employed by the printing apparatus P to obtain different types of character shapes 17W or 17Y on photosensitive recording medium 15. Each output configuration employs lenses to rectify the divergenceangle which occurs in present state-of-the-art semiconductor lasers. FIGS. 1B and 1C show short emission time versions of the output unit 10W and 10X which employ narrow laser pulse widths (typically less than 40 nanoseconds). In FIG. 18, individual lenses 19W are fitted over the emitting junctions 18W of the lasers in a manner well known in the art. The lenses 19W, having a large numerical aperture, serve to focus the light emitted from lasing junctions 18W, producing the narrow lines comprising character shape 17W. In FIG. 1C, one large collecting lens 20X is used to focus the light emitted from all of the lasing junctions 18X, producing a similar character shape 17X. However, not all of the divergence angle must be rectified by the lenses; in fact, beam divergence serves to spread or enlarge the individual image recordings formed by the parallel laser beam as they strike the photosensitive medium, yielding a more continuous and intelligible character shape of the type illustrated in FIG. 1F.

Shown in FIGS. 1D and 1E are the character shapes l7Y and l7Z produced by a modification of the invention which utilizes extended laser pulse widths. In this version of the invention, the semiconductor lasers in output unit 10Y or 10Z are arranged with their laseremitting junctions l8Y and 182 perpendicular to the vertical direction of motion of photosensitive medium 15. For any given speed of vertical motion of photosensitive medium 15, the laser pulse duration used to produce this type of character shape is normally 5 to 8 times greater than the short emission pulse used to produce the type of character shape 17W or 17X shown in FIGS. 18 and 1C. During this extended pulse, photosensitive medium will have a maximum vertical motion equal to the distance Q shown in FIGS. 1D and 1E, causing the perpendicular active regions 18Y or 18Z to record broad, flat vertical strokes on the moving medium with their laser beams. In FIG. 1D and 1E the output units NY and 10Z employ individual lenses 19Y and a large collecting lens 202 in the manner previously described. If a small precentage of divergence were allowed to occur in these cases, an extended character shape of the type illustrated in FIG. 10 would be produced.

The extended pulse width to produce character shapes l7Y and l7Z is determined by the following formula: Where:

T Total time allotted to print a horizontal row of characters V Vertical spacing per line of characters (normally I/6 inch) PW Pulse width Q Height of the array/Vertical number of lasers X a tolerance factor, typically 90-95 percent For an output unit l0Y or 102 0.1 inch high comprised of 7 horizontal rows of lasers (i.e. seven vertical lasers), using a tolerance factor or 95 percent, 0 has a value of 0.0135 inch. For printing 6 characters to the vertical inch, V would have a value of 0.1666 inch. Calculation with these factors shows that the duty cycle required for the lasers at any printing speed is solely a function of the percent of vertical extension of recordings along the distance 0 which may be selected. Major values are summarized in the following table:

Percent of Vertical Extension Laser Duty Cycle Percent 12.3 1.0 2s 2.02s 50 4.050 75 6.075 100 (full 0) 8.1

Thus for the LOC lasers mentioned, which currently have a 1 percent duty cycle, a vertical recording extension of slightly over 12 percent of the distance Q shown in FIG. ID and FIG. 1E may be obtained. Numerous modifications of the apparatus may bedevised to increase this percentage. For example, the LOC lasers may be cryogenically cooled to 77 K to obtain a 4 percent duty cycle. The height of the array may be reduced or the vertical number of lasers may be increased.

For any given duty cycle, the pulse width employed I to obtain the corresponding percentage of recording distance 0 shown in the above table varies inversely with the speed of vertical motion of photosensitive medium 15. The speed of vertical motion is directly proportional to the number of character-shaped laser beams emitted per minute by the output unit IOY or 102. This relationship can also be said to occur in the short emission time version of the output unit (FIGS. 18 and 1C), in that the limit of the maximum pulse width employed by this version varies inversely with printing speed. The environment in which output units 10W, 10X, l0Y or 10Z will operate may require fixed or variable printing speeds. In applications where sustained periods of operation are required at constant speeds, the pulse width may be fixed as a constant. In applications requiring operation at varying printing speeds, or applications requiring frequent start-up and shut-down, the pulse width may be synchronized with printing speed. However it should be mentioned that sustained periods of operation at top-rated speeds are the expected and most productive environment for the apparatus.

Where clarity of character shapes is the primary concern, the extended character shapes l7Y and 172 shown in FIGS. 1D and 1E are preferred. However, the largest recorded area per character is provided by the character shape shown in FIG. 16, in which the output unit IOY or 10Z makes use of a small portion of the divergence angle. The intelligibility of this character shape is also high. The shorter pulse widths used in short emission time printing can provide a substantially lighter duty cycle for the lasers, which may be retained or traded off for higher printing speeds. For recognition purposes, the short emission time character shape shown in FIG. 1F (with a portion of the divergence angle) is preferred. A similar trade off may be made in the extended pulsing versions of the output unit 10Y or 102, in which a portion of the extended recording area along the distance 0 is traded off for a reduced pulse width, allowing for a lighter duty cycle or a higher printing speed. The arrangement of the laser-emitting junctions l8Y or 182 in a perpendicular orientation to the vertical direction of motion of photosensitive medium 15 gives these versions of the output unit 10Y and 102 the greatest degree of flexibility. At present, it is preferable to use the extended pulsing versions of the output unit using either lens arrangement (FIG. 1D or IE) to fully rectify the divergence angle, because these versions afford the greatest flexibility, and because the vertically-extended character shapes l7Y and 172, which may be produced only by these versions, have the highest optical character recognition quality.

FIG. 2 shows in greater detail one particular embodiment of the elements 4 through 6 shown schematically in FIG. 1. In this embodiment, the character translator 4 has its storage elements 5 each formed by an independent group of character wires 27A, 27B, 27C 27N, whereN is the number of unique characters to be formed by the apparatus, and N l is the number of unique electronically-coded signals which may be received by the apparatus (one signal representing a blank or space character). The value of N 1 would normally be 48 or 64, depending upon the number of special symbols provided for in the character font of the apparatus. Assigning the preferred value of 64 to N 1 would yield 63 separate groups of character wires 27A27N i.e., one group of character wires for each character in the printable font except for the space character.

When computer 1 transmits to interface unit 3 an electronically-coded signal representing a printable character, such as binary coded signal 2, interface unit 3 decodes the electronic signal and supplies a signal to one particular address sense wire 21A, 21B, 21C 2lN l assigned to the decoded character and arranged to cause current to be introduced into the group of character wires 27A27N corresponding to the decoded printable character. The signal in the one address sense wire 21A-21N so isolated by the interface 3 closes a corresponding address sense switch 22A, 22B, 22C 22N, which may typically be a transistor relay. A voltage source such as transformer 23 is connected by transformer wire 24 to each of the address sense switches 22A-22N to complete a circuit through whichever address sense switch is closed. Voltage from the transformer having a value equal to k,. is applied to the selected group ofcharacter wires 27A 27N. The

- value of k,. is selected to meet the voltage requirement of pulser 7 for converting a signal in one character wire to an amplifier pulse sufficient to drive a semiconductor laser of the type used in the output unit. For typical pulsers, the input signal voltage requirement is valued at approximately 2 volts and is applied through the groups of character wires 27A27N in parallel. As transformer 23 is connected through whichever address sense switch 22A-22N is closed, it activates a corresponding timing circuit 25A, 25B, 25C 25N, such as an RC circuit, which is connected to reopen the closed address sense switch after a predetermined interval of time. In amplifier type pulsers where the pulse width is determined by the input signal, this interval of time would normally be equal to the rise time of the pulser, eg 6 nanoseconds, plus the width of the pulse desired, e.g. 40 nanoseconds, and thus is typically 46 nanoseconds. ln latching type pulsers where a fixed pulse width is triggered by the input signal, this interval of time is equal to the rise time of the pulser plus a buffer, normally 6 plus 12 nanoseconds. Thus the address sense switches 22A, 22B, 22N are regulated to direct a short activating input signal pulse through address resistors 26A, 26B, 26N connected in series between transformer 23 and the groups of character wires 27A 27N. The address resistors 26A 26N, which have a value related to the source resistance of transformer 23 and to the resistances of the pulser modules 8, are used to establish the appropriate level of input signal current for the pulser modules 8 in each of the individual character wires 28 in a group.

Current through an address resistor 26A-26N is applied to the corresponding group of character wires 27A, 27B, 27C, 27D 27N. These groups of character wires could typically be etched on a printed circuit board or boards in a manner well known in the art, or could be contained in one or more LSI chips. Each group of character wires is comprised of a number of individual character wires 28. Forming parallel circuits, these individual character wires 28 carry an actuating current, typically about 4 milliamperes, to individual pulser modules 8. Because a one-to-one correspondence exists between each of the individual character wires 28 in a group of character wires 27A27N and a semiconductor laser 11 in output unit 10 needed to form a character, it can be seen that large variations will occur in the numbers of individual character wires 28 in the various groups of character wires 27A27N. For example, the group of character wires corresponding to the letter W would contain almost four times the number of individual character wires 28 in the group forming the number 1. In order for each of the individual character wires 28 used in the formation of W to contain the same amount of current as each of the individual character wires 28 used in he formation of l, the total amperage in the group of character wires 27A27N corresponding to W must be almost four times as great as the total amperage in the group of character wires corresponding to 1. Therefore the resistance of the address resistor 26A, 26B, etc. used for the W group of character wires is selected to carry almost four times the current as that of the address resistor used for the 1 group of character wires.

Accordingly, character translator 4 supplies a signal of predetermined length through each of the individual character wires 28 in the group 27A27N to pulser 7 for the duration of its activation and rise or pulsing time at the voltage and amperage it requires to produce one pulse.

The method of character-image generation provided by the embodiment of FIG. 2 is as follows: All groups of character wires 27A27N converge upon pulser 7 in such a way that the pulser modules 8 to which the individual character wires 28 in each group are connected serve to activate via pulser wires 9 those of semiconductor lasers 11 in output unit 10 whose positions in the two dimensional laser array physically resemble a graphic outline of the number, letter or symbol corresponding to the group of character wires, This concept is illustrated in FIG. 2 by circles 29, which highlight those of pulser modules 8 to which individual character wires 28 from the group of character wires 27C are connected, and by asterisks 29A, which indicate those of semiconductor lasers 11 in the laser array activated by those of pulser modules 8 highlighted by circles 29.

Circles 29 and asterisks 29A form the shape of a C" in the drawing. The group of character wires 27C corresponds to the character C in this illustration; which is to say that given a binary coded electronic signal 2 of 1100 0011 (which represents C" in EBCDIC), in-, terface 3 will isolate the current of the signal into address sense wire 21C which will direct a signal from transformer 23 through address sense switch 22C for a period of time determined by timing circuit 25C.

Each wire in the group of character wires 27C carries the resulting activation current in parallel circuit to pulser 7 where, by means of the selected ones of pulser modules 8 to which the individual character wires 28 in group 27C are affixed, the one dimensional impulse group of activation currents is transformed into a two dimensional character outline of amplified laser-drive pulses. The semiconductor lasers 11 upon which this two dimensional character outline of amplified pulses is superimposed by means of pulser wires 9 are highlighted by asterisks 29A in H6. 2.

Through a wiring consolidation which may be achieved by a printed circuit board, all groups of character wires 27A-27N converge upon pulser 7, and almost every one of pulser modules 8 serve to consolidate the circuit paths of individual character wires 28 from several groups of character wires 27A-27N into a common laser pulse source corresponding to one point in the graphic array of the network of lasers 11.

Though each of the pulser modules 8 in pulser 7 serves one or most often a plurality of individual character wires 28 from various groups 27A-27N, only some of the pulser modules 8 may be activated at any given time. This is due to the fact that interface 3 causes electric current to be introduced into only one group of character wires 27A-27N at any one time, and no group of character wires 27A-27N uses all of the semiconductor lasers 11 in output unit 10. Thus in each case of character emission, the component lasers 1] in output unit 10 are selectively energized. 1n the case of emission of the character C, the pattern of presence and absence of drive pulses in pulser wires 9 is such that the positions of the component lasers in output unit 11 which are activated by this pattern of drive pulses will physically resemble a C. For any character in the font of the apparatus, a corresponding charactershaped laser beam 13 will be formed by output unit 10 in the manner described. Reception of this charactershaped beam 13 by photosensitive recording medium 15 will cause character-image 17 to be formed on recording medium 13. Absence of further electric current in the individual character wires 28'causes the selectively-activated lasers 11 in output unit 10 to deactivate, leaving output unit 10 ready to accept a new pattern of signals for the next character to be printed.

For engineering purposes it is likely that pulser 7, utilizing present state-of-the-art hardware, would have the shape of an elongated, thin printed circuit board; the end of which terminating in pulser wires 9 would be adjacent to laser output unit 10. The shape of pulser 7 is shown in the illustrations as spatially coherent with that of output unit 10 for the purpose of clarity. Referring to FIG. 3, another embodiment of the invention is illustrated in which the character translator 4 has storage elements 5 in the form of a read-only core memory. Core stack 30 is comprised of core planes 31A, 31B, 31X, where X is the number of semiconductor lasers 1] in output unit 10. Core planes 31A 31X are constructed so that the number of cores 32 in each plane 31A 31X is equal to the number of unique characters to be formed by the apparatus. Assigning the preferred value of 64 characters to the printable font of the apparatus would yield 64 characters in combination with the 5 X 7 matrix of lasers 11 as illustrated would yield a core memory comprised of 35 planes of 64 cores each. As will be apparent to those skilled in the art, this method of memory construction is in effect simply defining one register for each character in the font such that each register has one bit for each laser in the output unit. The condition of each bit (l or 0) will determine the condition of a corresponding laser (on or off) in the manner described hereinbelow.

A source of electronic output signals, such as computer l, transmits an electronically-coded signal representing a printable character, such as binary-coded signal 2, to interface 3. lnterface unit 3 decodes the electronic signal by isolating its current into the corresponding one of address sense wires 2lA-21N, where N represents the number of characters in the font of the apparatus; e.g. 64. Given a binary-coded signal 2 of 1100 0011 (representing C in EBCDlC), interface 3 will isolate the signal current into the address sense wires 21C shown in this illustration. Current in the address sense wire 21C will cause a non-destructive read out of the contents of the cores 32 which are shown to be contained in C register 33. In this way, the contents of the selected register, in this case the C register, are transferred to the sense wires 34A, 34B, 34C 34X in the form of the presence or absence of electrical impulses. As FIG. 3 shows in detail, the sense wires 34A-34X are connected to pulser 7 in a predetermined, sequential pattern. All cores 32 in core plane 31A affect only pulser module 8A in pulser 7 via sense wires 34A. All cores 32 in core plane 31B affect only pulser module 8B in pulser 7 via sense wire 34B, and so forth for all the planes 31A-31X in the stack 30.

The reading of a core 32 in a binary condition of 1 will cause a magnetic induction of electric current into the sense wire 34A34X serving the plane 31A-31X which contains the core. Because the sense wires 34A-34X are connected to the pulser modules 8 in pulser 7 in the logical manner described, the method of character-image generation provided by the embodiment of FIG. 3 emerges as follows: For each of the 64 registers in the memory, a binary number can be divised and stored which, when read into the sense wires 34A-34X, will cause the presence and absence of current to be introduced to pulser 7 in such a way that the presence of electric current is introduced into those of pulser modules 8 which serve to activate those of semiconductor lasers 11 in output unit 10 whose locations in the two dimensional laser array physically resemble a graphic outline of the number, letter or symbol corresponding to the register. This concept is illustrated in detail for the letter C. Cores 32 from C register 33 are shown along with their corresponding binary values. Those cones 32 having a value of 1 located in planes 31A-31X served by sense wires 34A-34X terminating in pulser modules 8, as indicated by circles 29, will activate those of semiconductor lasers 11 whose positions in output unit 10 physically belong to the graphic shape of the letter C. All other cores in the register have a binary value of 0. Thus when the C register is read, the sense wires will carry the presence of electric current induced by the reading of the 1 cores to those pulser modules highlighted by circles 29. Being solely a function of the binary number stored in a register, this process of forming a two dimensional character-image comprised of electrical pulses in the same for all registers in the memory.

The initial pulsing of low-level current which was accomplished in FIG. 2 for signals in the address sense wires 21A-21N by the address sense switches 22A-22N and timing circuits 25A25N is accomplished in this embodiment for the core impulses from the sense wires 34A-34X by a similarly-constructed pre-pulsing section in each of pulser modules 8. The resulting low-current pulse is then converted in the normal way into a pulse of sufficient magnitude and desired width to drive a semiconductor laser. When this process occurs following the reading of a storage register, the resulting amplified pattern of pulses is superimposed upon the network of lasers 11 in output unit causing selective activation of those lasers in the array needed to form the charactershaped laser beam. Reception of this character-shaped beam 13 by suitable recording medium 15 will cause character-image 17 to be formed on recording medium 15. Absence of further electric current in the sense wires 34A-34X causes the selectively-activated lasers 11 in output unit 10 to deactivate, leaving output unit 10 ready to accept a new pattern of impulses for the next character to be printed.

In the construction of a high speed laser printing apparatus arranged to print a row of characters simultaneously and employing a plurality of the individual character printing elements P illustrated in FIG. 1, it becomes advantageous for two or more units of the apparatus which receive electronically coded signals at one point in time to emit the corresponding charactershaped laser beams at the same time, regardless of which character signals were received. This requires that interface unit 3, whose circuitry comprises typically 64 unique signal paths, use the same amount of time in completing each different path. Owing to the fact that the interface paths used in the decoding of some character signals will require more branch decisions than the paths used in decoding other character signals, interface 3 preferably is arranged as shown schematically in FIG. 4 to standardize the interval of time required by interface 3 to decode any electronically-coded signal 2 it receives. Specifically, a circuit is shown in FIG. 4 whereby the current in two dissimilar signal paths in the interface circuitry undergoes the same number of switchings to selected paths of logical decision units in the interface before being isolated as a signal in an address sense wire such as 21Y or 212. Source lead 35, which will be assumed to contain current, and test lead 36, which may or may not contain current, depending on whether a corresponding bit of signal 2 is a l or a 0, converge upon circuit switch 37. Circuit switch 37, typically a high-speed transistor relay, operates such that the absence of current in test lead 36 will allow the current in source lead 35 to flow through normal path 38, and that the presence of current in test lead 36 will cause the current in source lead 35 to be switched or diverted away from normal path 38 and channelled into selected path 39. A dummy switch 40, which is identical in construction to circuit switch 37, is inserted into normal path 38 in the manner shown. Normal path 38 is split into two wires above dummy switch 40, so that the presence of current in normal path 38 will act as its own test current, causing dummy switch 40 to faithfully divert the normal path current into dummy selected path 41. A resistor 42 is provided to prevent by-pass of dummy switch 40. Thus, current in source lead 35 undergoes the same number of switchings through a selected path of a logical decision unit before it is isolated in terminal 43, for address sense wire 212, or terminal 44, for address sense wire 21Y. This technique of equalizing the number of switchings through the selected paths of logical decision units is used at every decision point throughout the interface circuitry. Since some character signal paths will contain more of these branch decision points than other character signal paths, additional dummy switches are added to the shorter character signal paths. The result is that all signal paths in the interface require the same number of switchings as the number required by the longest signal path in the interface. Equalizing the number of these selected switchings required for all signal paths is equivalent to equalizing the amount of time required to interface any signal. Thus a uniform interface time for all signals is obtained.

Referring to FIG. 5, multiple printing elements P, whose interfaces 3, character image generators 48, and laser output units 10 are individually depicted in FIG. 1, are shown arranged in a laser printing section suitable for use in a high-speed, non-impact, on-liner printer. Multiple laser output units 10A, 10B, ION are arranged in a stationary, horizontal row which is parallel to and adjacent to the surface of photosensitive recording medium 15 and which extends transversely to the direction of travel of the recording medium. In this configuration, N represents the number of printing positions in a row of characters to be simultaneously printing in the apparatus. Normally N would have a value of 132 or 144 printing positions as these are standard in the industry. Assigning the preferred value of 144 to N would yield a stationary, horizontal row of 144 laser output units 10A 10N. As discussed hereinbelow, all of these output units 10A 10N are simultaneously activated so that an entire 144 character line is'printed on photosensitive recording medium 15. The photosensitive recording medium 15 is in continuous vertical motion, which enables it to receive consecutive lines of information from the stationary horizontal row of laser output units 10A 10N at considerable speed.

As shown in FIG. 5, a computer output cable 45 is comprised of I44 signal cables 46A, 46B, 46C, 46D 46N which in turn (for an EBCDIC 64 character font) are comprised of 8 wires each carrying one bit of information (not shown). Each of the signal cables 46A 46N is connected to a corresponding one of the interface units 3A, 3B, 3C, 3D 3N by means of a cable plug 47A, 47B, 47C, 47D 47N. Upon program command to print a line of information, a computer will simultaneously transmit, via signal cables 46A 46N, I44 binary-coded signals which correspond to the characters to be printed. (The pattern of presence and absence of electric current in the 8 wires comprising each signal cable 46A 46N represents each binary signal, as is well-known in the art.) The computer transmission is simultaneously received by the 144 interface units 34A 3N, which decode the signals with a uniform time delay in the manner previously described with reference to FIG. 4. Character image generators 48A, 48B, 48C, 48D 48N are instructed by their corresponding interface units 3A 3N to form those patterns of electrical impulses which correspond to the characters whose signals were decoded. Transfer of these impulse patterns to laser output units 10A 10N causes selective activation of those semiconductor lasers needed to form corresponding character-shaped laser beams 13A, 13B, 13C, 13D 13N. Reception of these character-shaped laser beams l3A- 13N by photosensitive recording medium 15 results in the formation of character images 17A, 17B, 17C, 17D 17N on photosensitive recording medium 15. Deactivation of the selected lasers in output units 10A ION occurs in the manner previously described, leaving the printing section ready to accept a new discrete set of 144 electronically'coded signals corresponding to .the next row of characters to be printed.

Turning now to the overall aspects of the printing apparatus it can be seen that the elements 3, 48 and 10, forming printing elements P for individual characters, are arranged in rows, indexed by the letters A, B, C, D N. The printing elements P are ideally suited to function in the printing apparatus because of their ability to be synchronized. As depicted in FIG. 4, interface units 3A-3N may be constructed in such a way that the time necessary to decode an electronic output signal received is a constant for any signal. Character-image generators 48A-48N may utilize a hard'wiring scheme as shown in FIG. 2. Given that the address sense switches 22A-22N shown in FIG. 2 are of identical construction, and given that the time required by the pulser to generate in parallel any pattern of electric pulses may be considered as constant, it will be apparent that the apparatus illustrated in FIG. 2 requires the same amount of time to generate any character-image. Character-image generators 48A-48N may alternatively utilize a core memory scheme as shown in FIG. 3. It will be apparent that the same amount of time is required to read any register in a core memory of the size illustrated. Thus, whether a hard-wiring or core storage scheme is used for character-image generators 48A-48N, the generation of each of the 64 characterimages provided for will require the same amount of time. Referring to the laser output units lA-l0N it can be appreciated that the amount of time necessary to activate any number of semiconductor lasers in parallel circuit is a constant. Due to the fact the the semiconductor lasers in each output unit l0A-l0N are in a parallel circuit, the length of time required for the selective laser formation of any character in the 64 character font is a constant. Thus the reception-emission time T defined as the interval of time starting with the reception of one electronically-coded signal via one of the signal cables 46A-46N and ending with the emission of one of the corresponding character-shaped laser beams l3A-l3N, emerges as a constant for any decodable signal received by a printing element, and if all electronically coded signals for a row are received simultaneously, all characters in a row will be printed simultaneously.

The interval of time T typically involves a l nanosecond activation time (rise time of radiant flux) for the LOC injection lasers mentioned, a6 nanosecond pulser rise time and a uniform interface time of 90 nanoseconds, and thus a 100 nanosecond receptionemission time is typical for a printing element employing a hard-wired character-image generator. For a printing element employing a core memory characterimage generator, the reception-emission time would be somewhat longer.

In FIG. it can be seen that each group of the components 3, 48 and 10 forming a printing element P is identical in each of the rows A, B, C, D, N; in other words, all of the 144 printing elements are identical. This uniformity of elements greatly enhances the ease of manufacturing the laser printing apparatus, as well as the ease of servicing its components. The interchangeability of the printing elements in the printing section is important also because it allows for a higherorder level of synchronization in the device. Since all elements are identical, it follows that all printing elements have the same reception-emission time T for any character in the printable font, and simultaneous reception of electronically coded signals means that all characters in a row are formed simultaneously.

Thus 144 printing elements which each receive one of a discrete set of 144 electronically-coded output signals at the same instant in time will, following the reception-emission time interval T simultaneously emit the 144 character-shaped laser beams which correspond to the electronic signals received. Due to the fact that the printing section can simultaneously receive yet independently process all of the signals in a discrete set of electronically coded output signals, the entire printing section illustrated operates within one reception-emission time interval T for each discrete set of electronically coded output signals it receives. The operating time for the entire printing section thus is equivalent to the T for any one of the composite printing elements. Given the simultaneous reception of 144 electronically-coded output signals by a laser printing section having an overall operating time equal to the T of each ofits composite printing elements, it follows that the interval of time starting with the earliest laser-emission of a character-shaped beam and ending with the latest laser-emission of a character-shaped beam would be zero; i.e., the entire 144 character lightimage line of print would be emitted at one exact instant in time.

Theoretically, printing can occur at a number of lines per second limited only by the duration of T Naturally, this is a theoretical ideal which is limited not only by the allowance of laser de-activation time, but by the variances, however small, in the printing section circuitry timing as well as the circuitry timing of the output source computer. However the design of the printing section itself compensates to some degree for both possible imperfections in its own electronic components and for non-simultaneous computer transmis- T,.,= l/M V/lOO where M represents the maximum number of inputs of discrete sets of electronically-coded signals per second,

and V represents the greatest allowable percent of vertical position variance in the line of characters 17A-17N appearing upon the rapidly-moving recording medium 15.

Though it is not uncommon to find electromechanical printouts with a horizontal variance of as much as 20 percent, the far stricter value of 3 percent is normally assigned to V. The formula shows that large time variances in the printing section components and the reception of individual electronically-coded signals in a discrete set of output signals can be tolerated by the laser printing section at slow speeds.

For example, at l00,000 lines per minute, the transport mechanism of the printing device shown in FIG. 6 will produce continuous vertical motion in continuous photosensitive recording medium 15 at the rate of 15.7821 miles per hour, in order ot obtain 6 lines of print to the vertical inch. A 3 percent horizontal variance within the vertical 1/6 inch allotted to each line of print would amount to 0.005 inch. At 15.7821 miles per hour, this 0.005 inch of continuous photosensitive paper 15 would be transported past the stationary, horizontal row of laser output units lA-10N in 18 microseconds. lt follows then that in order for the one character image (17A-17N) whose character-shaped laser beam was emitted last to appear no lower on rapidlymoving photosensitive paper than 0.005 inch from the one character image (17A17N) whose charactershaped laser beam was emitted first, the interval of time between the first and last laser-emissions of characters in the 144 character line must be no longer than 18 microseconds. Thus for V equal to 3 percent, the accumulation of all variances in printing section components and signal reception may be tolerated up to and including a total of 18 microseconds of variance, which therefore is the time T,., for the printing speed and other conditions mentioned. With a selected V held constant, the relationship of T and lines per minute forms a normal hyperbola; for example, T at 350,000 LPM would be 5.14285 microseconds, and at 500,000 LPM T would be 3.60 microseconds for V at 3 percent. Given that all electronically-coded signals in a discrete set of output signals corresponding to a line of characters to be printed are transmitted by the output source computer via parallel circuit in one operational cycle, the advantages of higher speeds may be obtained simply by insuring that the time variances in the printing section components, primarily any operational time variances in the interface solid-state relays and any activation time variances in the injection diode lasers, are properly controlled and sufficiently refined.

Thus multiple character printing elements P as depicted in FIG. 1 are arranged in a row as a laser printing section, forming a stationary, horizontal row of laser output units 10A-l0N. Each printing element simultaneously receives and independently processes one of a discrete set of computer signals which correspond to a line of characters to be printed. At the end of its operating phase, each printing element emits a charactershaped laser beam 13A13N which corresponds to the signal it received, causing the line of printed characters 17Al7N to be formed on a rapidly-moving recording medium 15. Due to the interchangeability of the printing elements, the operating phase of the printing section is theoretically identical to the operating phase of each of the printing elements. The design of the printing section allows it to compensate for relatively large divergences from this theoretical ideal at slow speeds. Owing to the fact that a full line of characters is printed without moving parts, the primary limit to the highest printing speed attainable by the device is only the maximum duty cycle of the lasers employed, in conjunction with the degree of refinement and control which can be accomplished in the time variances of its electronic components, and in the synchronization of the output source computer itself.

Turning now to FIG. 6, a high-speed, non-impact printing apparatus according to the invention is depicted. An electronic signal source, such as computer 1, transmits output signals to the printing device through cable 45. These signals are received, translated and processed by printer circuitry 49, which would include the interfaces and character-image generators for each signal. Attached to printer circuitry 49 is a stationary horizontal row of laser output units 50, arranged such that each available printing position along the length of pinfeed drum 51, carrying a sheet photosensitive recording medium 15, corresponds to a unique output unit in the row. Drive motor 52 rotates the pinfeed drum 5] in a clockwise direction, thus accomplishing pinfed transport of the continuous sheet of photosensitive recording medium 15 in a manner well known in the art. Drive motor control 53 includes a rheostat to allow manual regulation of the speed of rotation of the pinfed drum 51. Because this speed of rotation may be considerable, retension rollers 54 are employed to insure smooth feeding of the continuous sheet of recording medium 15 through the device. The rate at which the electronic signal source, such as computer 1, transmits its output signals to the printing device is synchronized with the rotation of pinfeed drum 51 means of a synchronization device 55. The operation of this device is as follows: The circuit connection between lead wire 56 and 57 is controlled by a photoelectric switch 58, above which the perimiter of pinfeed drum 51 rotates. Narrow light-admitting slits 59 are located in the circumference of penfeed drum 51 such that a 1/6 inch spacing exists between each of the slits. Thus for every 1/6 inch of'rotation of pinfeed drum 5], one of the narrow light-admitting slits 59 passes between constant light source 60 and photoelectric switch 58. Light striking photoelectric switch 58 causes it to complete the circuit between lead wires 56 and 57. Completion of this circuit indicates to the electronic signal source, such as computer 1, that the printing device is in a receiving status for the next line of output information to be printed. In this way the printing device is synchronized to print 6 lines to the vertical inch at any printing speed which may be selected.

Although specific embodiments of the invention have been disclosed herein in detail, it is to be understood that this is for the purpose of illustrating the invention, and should not be construed as necessarily limiting the scope of the invention, since it is apparent that many changes can be made to the disclosed structures by those skilled in the art to suit particular applications.

The invention claimed is: l. A high-speed non-impact printing apparatus arranged to receive character data in the form of coded electronic signals and, in response to such data, to print successive rows of alphanumeric characters on a sheet of photosensitive recording medium continuously transported through the apparatus in a direction transverse to the rows, comprising:

optical output means formed of a two-dimensional matrix of parallel semiconductor lasers arranged to occupy an area corresponding to a row of characters to be printed and having a group of lasers for each character position in the row, said optical output means having for each laser an input for receiving a laser activation signal to independently activate the laser, the optical output means being mounted adjacent to but out of direct contact with the photosensitive recording medium so that light emitted from activated lasers in the matrix will transmit to and strike the medium and record an image thereon;

.interface means for simultaneously decoding a set of coded electronic signals corresponding to a row of characters to be printed and for simultaneously producing, for each character position in the row, an individual signal'representing the single alphanumeric character to be printed in that character position; and character-image generating means having inputs for receiving the simultaneous decoded individual signals corresponding to the row of characters to be printed and having outputs connected to the inputs of the optical output means, the character-image generating means simultaneously supplying to each group of lasers in the optical output means a corresponding pattern of laser activation signals to cause the activated lasers in the group to emit parallel beams of light in a pattern approximating the shape of the character to be printed at that position;

said character image generating means having, for each character position in the row, storage means for associating each separate decoded individual signal with a corresponding pattern of laser activation signals at the outputs to approximate the shape of the corresponding character, and means for generating said patterns of laser activation signals in response to said decoded individual signals;

means for transporting the photosensitive recording medium through the printing apparatus;

means for applying the set of coded electronic signals tothe interface means; and

means for coordinating the recording medium transporting means with the electronic signal applying means to provide uniform spacing between successive rows of characters printed on the recording medium despite variations in relative speed of presentation for printing of the recording medium and coded electronic signals, said coordinating means including means for providing a timing signal corresponding to the availability for printing of a row of coded character signals and a row of recording medium, and means responsive to the timing signal for synchronizing the application of the character signals with the transport of the recording medium to provide even spacing between rows of printed characters;

whereby said printing apparatus simultaneously imprints a complete row of character shapes upon said photosensitive recording medium, and whereby spacing between successive rows of characters on the recording medium will be uniform.

2. A high speed non-impact printing apparatus as claimed in claim 1 wherein the interface means for simultaneously decoding a set of coded electronic signals comprises logical decision units receiving said coded signals and performing switching operations to complete a path to an output terminal to provide one of said individual signals in accordance with the coded information, said decision units being arranged so that each path therethrou'gh to a separate output terminal representing an individual signal contains the same number of switching operations, whereby the switching delay is equalized for each separate individual signal, and the separate individual signals for all the characters in the row are simultaneously produced.

3. A high speed non-impact printing apparatus as claimed in claim 1 wherein, in said character-image generating means, the storage means associating each separate decoded individual signal with a corresponding pattern of laser activation signals at said output comprises independent groups of character wires connected to complete a circuit in common to the corresponding patterns of outputs, and wherein the means for generating said pattern of laser activation signals comprises means for applying a signal to a selected group of character wires. v

4. A high speed non-impact printing apparatus as claimed in claim 3 wherein said character image generating means comprises pulsing means for each of said lasers, and wherein the means applying a signal in each of said character wires applys a predetermined signal necessary to activate said pulsing means.

5. A high-speed non-impact printing apparatus as claimed in claim 1 wherein, in said character image generating means, the storage means for associating each separate decoded individual signal with a corresponding pattern of laser activation signals at said outputs comprises a core memory with a plurality of registers corresponding in number to the number of sepa rate decoded individual signals, each register having a number of storage elements corresponding to the number of lasers in each group of lasers for a character position, said storage elements being connected to said outputs and being set to provide the corresponding pattern of laser activation signals at the output upon reading of each storage register.

6. A high speed non-impact printing apparatus as claimed in claim 1 wherein the means for transporting said photosensitive recording medium to the printing apparatus comprises a drum rotating at a speed proportional to the speed of the recording medium, and the means providing a timing signal includes means associated with said drum for providing a timing signal corresponding to the advance of said recording medium by a predetermined distance selected to be the spacing between successive rows of characters on the recording medium, and the means responsive to the timing signal includes means for applying the set of coded electronic signals to the interface means in synchronization with the timing signal, whereby spacing between successive rows of characters on the recording medium will be uniform despite variations in speed of the recording medium through the printing apparatus.

7. A high speed non-impact printing apparatus as claimed in claim 6 wherein the means for generating a timing signal comprises a mask rotating with said drum and photosensitive means detecting apertures in said mask.

8. A high speed non-impact printing apparatus as claimed in claim 1 wherein said character image generating means is arranged to supply laser activation signals having a duration correlated with the speed of the photosensitve recording medium through the apparatus to cause the images recorded on the photosensitive medium to be extended into the spaces between adjacent lasers in the matrix. 7

9. A high speed non-impact printing element arranged to receive character data in the form of coded electronic signals and, in response to such data, to print successive alphanumeric characters on a sheet of photosensitive recording medium continuously transported by the printing element, comprising:

optical output means formed of a two dimensional matrix of parallel semiconductor lasers arranged to occupy an area corresponding to a character position to be printed, said optical output means having for each laser an input for receiving a laser activation signal to independently activate the laser, the optical output means being mounted adjacent to the photosensitive recording medium so that light emitted from activated lasers in the matrix will strike the medium and record and image thereon;

interface means for simultaneously decoding a set of coded electronic signals corresponding to the character to be printed and for producing, with a uniform time for each different character, an individual signal representing the single alphanumeric character to be printed in that character position; and

character-image generating means having inputs for receiving the decoded individual signals corresponding to the character to be printed and having outputs connected to the inputs of the optical output means, the character-image generating means simultaneously supplying to the lasers in the optical output means a corresponding pattern of laser acti vation signals to cause the activated lasers in the group to emit parallel beams of light in a pattern approximating the shape of the character to be printed at that position;

said character-image generating means having storage means for associating each separate decoded individual signal with a corresponding pattern of laser activation signals at the outputs to approximate the shape of the corresponding character, and means for generating said patterns of laser activation signals in response to said decoded individual signals;

means for transporting the photosensitive recording medium past the printing element;

means for applying the set of coded electronic signals to the interface means; and

means for coordinating the recording medium trans porting means with the electronic signal applying means to provide uniform spacing between successive characters printed on the recording medium despite variations in relative speed of presentation for printing of the recording medium in coded electronic signals, said coordinating means including means for providing a timing signal corresponding to the availability for printing the coded character signals and an element of recording medium, and means responsive to the timing signal for synchronizing the application of the coded electronic signals with the transport of the recording medium to provide even spacing between printed character elements.

10. A high speed non-impact printing apparatus as claimed in claim 9 wherein the interface means for simultaneously decoding a set of coded electronic signals comprises logical decision units receiving said coded signals and performing switching operations to complete a path to an output terminal to provide one of said individual signals in accordance with the coded information, said decision units being arranged so that each path therethrough to a separate outut terminal representing an individual signal contains the same number of switching operations, whereby the switching delay is equalized for each separate individual signal.

11. A high speed non-impact printing apparatus as claimed in claim 9 wherein, in said character-image generating means, the storage means associating each separate decoded individual signal with a correspond ing pattern of laser activation signals at said output comprises independent groups of character wires connected to complete a circuit in common to the corresponding patterns of outputs, and wherein the means for generating said pattern of laser activation signals comprises means for applying a signal to a selected group of character wires.

12. A high speed non-impact printing apparatus as claimed in claim 11 wherein said character-image generating means comprises pulsing means for each of said lasers, and wherein the means applying a signal in each of said character wires applies a predetermined signal necessary to activate said pulsing means.

13. A high speed non-impact printing apparatus as claimed in claim 9 wherein, in character image generating means, the storage means for associating each separate decoded individual signal with a corresponding pattern of laser activation signals at said outputs comprises a core memory with a plurality of registers corresponding in number to the number of separate decoded individual signals, each register having a number of storage elements corresponding to the number of lasers in the optical output means, said storage elements being connected to said outputs and being set to provide the corresponding pattern of laser activation signals at the output upon reading of each storage register.

14. A high speed non-impact printing apparatus as cent lasers in the matrix.

. i Page 1 of 3 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION John L. Mee

Inventor(s) It is certified that error appears in the above-identified patent and that said Letters Patentare hereby corrected as shown below:

In the specification 1 Column 2, line 66, change "emitter" to -emitted-.

.1 Column 2, ,line 68, change lasens" to -lasers-.

Column 3, line 9,- after "output" insert unit. Column 3 line 37, change "transmit" to -transmits-:. Column 3, line 48, change "transmit" to transmits-i. Column 4, line 39, change "product" toproduce.

Column 5, line 12, change "beam" to -beams-. I Column 5, line 20, change "and" to or.

lg Column 5, line 35, change "precentage" to percentage-. I

Column 5, line 40, change "and" to or-.

? Column 5, line 53, change "or" to -of.

Column 7, line 35, change "amplifier" to amplified.

FORM PO-1 (10- uscoMM-oc 60376-P69 Q U.5 GOVERNMENT PRINTING OFFICE l99 0-856-33L Page 2 of 5 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 5 ,9 7 Dated Sept. 17, 197A Inventor(s) John L. Mee

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 9, line 7, change "serve" to servesm Column 9 line 58, after "yield" insert 64 cores per plane. Thus, for example, a font of-.

Column 10, line 11, change "wires" to wire-.

Column 10, line 22, v change "wires" to -wire.

Column 10, line 45, change "cones" to cores-; change 1" to l'. i

Column vl0, line 51, change "0" to 'O Q 7 Column 12, line 13, change "on-liner" to -online.

Column 12, line 21, change "printing" to printed.

Column 12, line 50, change "34A" to 3A.

Column 13, line 18, change "as" to -a-.

Column 15, line 1, change "ot" to to.

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Classifications
U.S. Classification396/549, 396/551
International ClassificationG06K15/12, B41J2/455
Cooperative ClassificationG06K15/1238, B41J2/45
European ClassificationB41J2/45, G06K15/12D