US 3864697 A
A non-impact printing or recording apparatus which is suitable for use with a digital computer is disclosed. The apparatus includes a simultaneous multi-beam acoustooptic light modulating cell adapted to produce a selected number of beams which may be selectively scanned across a photoconductive member to produce latent images of characters, graphical information or other forms of information for subsequent recording on a medium such as paper.
Claims available in
Description (OCR text may contain errors)
United States Patent [191 Dillon et al.
Feb. 4, 1975 CHARACTER PRODUCING APPARATUS (FIG. 3) l4 Primary Examiner-John M. Horan Attorney, Agent, or Firm-R. L. Owens  ABSTRACT A non-impact printing or recording apparatus which is suitable for use with a digital computer is disclosed. The apparatus includes a simultaneous multi-beam acoustooptic light modulating cell adapted to produce a selected number of beams which may be selectively scanned across a photoconductive member to produce latent images of characters, graphical information or other forms of information for subsequent recording on a medium such as paper.
9 Claims, 3 Drawing Figures PATENTEU 4181s SHEET 1 OF 3 1 NON-IMPACT PRINTER CROSS REFERENCE TO RELATED APPLICATIONS Reference is hereby made to commonly assigned US. Pat. application Ser. No. 280,397 filed Aug. 14, 1972, entitled, TONER CONCENTRATION AND AUTO BIAS CONTROL APPARATUS. in the name of Conrad Altmann; commonly-assigned US. Pat. application Ser. No. 217,093, filed Jan. 12, I972, entitled, INTEGRATED CIRCUIT SEQUENCER. in the name of Gareth Lloyd; and commonly assigned US. Pat. application Ser. No. 132,955, filed Apr. 12, 1971, entitled, ACOUSTOOPTIC SCANNER APPARATUS AND METHOD, in the name of R. A. Spaulding.
BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to high speed recording apparatus and more particularly, to non-impact printers compatable with digital computer outputs.
2. Description of the Prior Art There is becoming increasing interest in electrographic type non-impact printers which are especially suitable for use as a computer peripheral. However, presently the most common form of alphanumeric computer printout is an impact line printer which typically is a mechanical apparatus having high cost, slow speed, and requires considerable maintenance. Many attempts have been made, some successful, to improve the speed of mechanical printers. However, the very nature of these devices, for example their mechanical inertia, sets the upper limit of their speed capability. It has been recognized in the'art that non-impact printers have considerable advantage over such systems. Many non-impact printers are of the type wherein light from a selected one of a plurality of flash lamps passes through a transparent character on a character mask to form an image of such character on a photosensitive medium such as an electrophotographic drum (see US. Pat. No. 3,677,148 to Chen). Since a finite distance is required to separate the photoconductive member on the drum from the character mask including a plurality of such transparent characters, light rays from the lamps are constrained in angular deviation to small angulation for acceptable character image quality. Consequently, lamps are generally made small and spaced some distance from the mask to improve image quality. There are problems with these lamp type systems caused by lamp blackening, sputtering and life limitations. Further, by using such mask type systems, there are speed constraints and only a limited number of fonts can be used at any one time.
SUMMARY OF THE INVENTION It is therefore an object of this invention to provide a new and improved non-impact printer capable of producing a high volume of lines per minute and which obviates the need for multiple lamp sources.
In accordance with the preferred embodiment of the invention, there is provided a high speed non-impact printer which includes a simultaneous multi-beam acoustooptic cell and an electrographic apparatus. Characters are formed by scanning selected beams from the cell onto a charged photoconductive surface of the electrographic apparatus. The electrographic apparatus is adapted to develop latent images formed thereby and to transfer them onto a receiving medium such as a copy sheet.
It is a feature of the invention that apparatus in accordance therewith avoids mechanical complexity.
wear, noise and other problems associated with prior impact printers.
Another advantage of the invention is that the optical power associated with beams produced by acoustooptic cells is such that the exposure on a photoconductor is sufficient for direct transfer to a plain paper medium.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an illustration, partially in schematic form, of a non-impact printer in accordance with the inven- 'tion;
FIG. 2 is a schematic illustration of a modified electrographic apparatus which may be used in the nonimpact printer of FIG. 1; and
FIG. 3 is a circuit diagram partially in schematic and partially in block form of the Character Producing Logic shown as block 14 in FIG. 1.
DESCRIPTION OF THE PREFERRED EMBODIMENTS GENERAL For a general understanding of a non-impact reproducing apparatus 8 wherein various stations of an electrographic apparatus 9 and a character forming apparatus 10 are schematically illustrated, reference is made to FIG. 1. The character forming apparatus 10 will be described first. As in most nonimpact printers, there is provided a source of radiation which, in the instant apparatus 8, is a laser source 11 which, for example, may be a five milliwatt HeNe laser. Light from the source 11 is directed to a beam expander 12 (for example having a 3x magnification) and such light then passes into the entrance aperture of a simultaneous multi-beam acoustooptic modulator cell 13. Acoustooptic modulators are commercially available and Model M-4OR manufactured by the Zenith Corporation has been found to perform satisfactorily. The multi-beam acoustooptic cell 13 is under the control of character producing logic block 14 shown in detail in FIG. 3 and is adapted to produce a selected number of beams to form a character or other information. More particularly, a zero order beam 68a and a multiplicity of first order beams 68 are formed. These first order beams represent information such as a character column, graphical data, or other forms thereof. These beams are transmitted through a lens 14a and projected onto a rotating mirrored surface polygon 1S and are then brought to focus as a linear array of beams along an imaginary line shown as 16. For a specific example ofa suitable rotatable mirror 15, see commonly assigned copending US. Pat. application Ser. No. 192,452, entitled, X-Y OPTI- CAL SCANNING SYSTEM, filed Oct. 26, 1971, in the name of Royce D. Pickering. The zero order beam 68a is blocked by a stop member 17 whereas the first order beams 68 are collected and columnated by a spherical mirror 18 having, for example, a 5.25 inch focal length and directs these beams into the entrance pupil of a lens 19. The lens 19 which may be a 50 cm focal length lens, focuses these beams onto a location 20 on a photoconduetive web member or belt 21. The belt 21 is, of course, a part of the electrographic apparatus 9 which will now be described with some specificity.
ELECTROGRAPHIC APPARATUS 9 The photoconductive belt member 21 includes a photoconductive layer with a conductive backing. The photoconductive layer may comprise, for instance. a heterogeneous mixture of a bisphenol A-polycarbonate binder, a triarylmethane organic photoconductor and a pyrylium sensitizing dye. For more specific disclosures, see commonly-assigned US. Pat. Nos. 3,615,406 and 3,615,414, both issued Oct.21, 1971.
The photoconductive belt 21 is trained about drive rollers 22, 23 and 24 and is rotated by a conventional main drive train mechanism 241: at a constant velocity. The moving photoconductive member 21 sequentially passes through a primary charging station 25 which may, for example, include a conventional corona charger adapted to charge the belt surface to about 500 volts; the position 20 wherein spot array is focused onto the moving photoconductive member so that in an electrostatic latent image is formed by the selective dissipation of charge; and into the development station 26 at which the latent image is contacted with finely divided charged toner particles that adhere to the photoconductivelayer in a configuration defined by the latent image. The development station 26 may take various=forms known in the art such as a magnetic brush development apparatus. An example of an exemplary development station is more fully disclosed in commonly-assigned US. Pat. No. 3,543,720 to Drexler et al. Next, the belt 21 enters a transfer station 27 in which the toner particles are transferred in the image configuration to the receiving surface of a copy sheet 28 on which it can be subsequently fused; before entering the primary charger 25, the belt member 21 passes through a conventional cleaning station 29. Copy sheets 28 which may be plain paper or cut sheets of receiving stock are stored in a hopper 29 from where they are fed along a path defined by a continuously moving web 30 to the transfer station 27. At the transfer station 27, the copy sheets are respectively brought into contact with the photoconductive belt 21 by way of fussing rollers 23 and pressure roller 31, to cause the toner image to be transferred to the copy sheet 28. Finally, the transferred image is fused to the copy sheet at a station 32 from which the sheet 28 is delivered into a receiver hopper 33.
In certain known modifications of the electrophotographic apparatus 9, one or more of the foregoing stations may be eliminated. For a more complete description of the general organization of an elect'rophotographic apparatus which may be used in accordance with the invention, reference is made to the commonlyassigned copending electrophotographic applications referred to in the section of the Specification entitled, CROSS REFERENCE TO RELATED APPLICA- TIONS.
In addition to recording data from the character producing circuitry 14, provision is also made to record a previously prepared form located on a form slide. Such form can be superimposed onto the photoconductive belt 21 in alignment with recorded character information. Toward this end, there is provided a source of light 34 which may be a zenon flashlamp and a condensing lens system 35 which cooperates with the light source 34 to provide a short pulse of light which uniformly illuminates a form slide 36 carrying the appropriate form. A lens 37 forms an image of the form onto the photoconductive belt 21 at an area indicated as 38. Alternatively, the forms image can be superimposed at the actual writing area 20.
Turning now to FIG. 2, there is shown another embodiment of an electrographic apparatus 9 which can be used in accordance with the invention. In this em bodiment, a selectable number of light beams formed by an acoustooptical modulator (not shown) is collected by a mirror 40. Elements 11, 12, 13, 14, 15, 16 and 17 are identical to those in FIG. I and will be understood although not shown to be included in this embodiment and function as previously described. The beams reflected from mirror 40 are directed onto a mechanically driven mirror 41 (more fully discussed in connection with FIG. 3) which produces a deflection of the beams in the plane ofthe drawings resulting in complete X-Y scanning required to record a full frame of characters on a stationary photoconductive member. The beams are reflected from mirror 41 and collected by a concave mirror 42 and projected by a lens 43 into the area 20. At position 20, the photo conductive belt member 21 remains stationary for the time required to record a full frame of information while a section of the belt between rollers 22, 23 and 24 travels at a constant velocity. This intermittent motion is provided to the belt by means of rollers 46 by mechanism 49. This intermittent motion causes the belt at point 20 to be advanced a distance of one frame of recorded information at the conclusion of the writing cycle for each frame. Take-up rollers 47 and 48 provide variable length loops which enable the belt between rollers 45 and 46 to advance intermittently while the section of belt between rollers 22, 23 and 24 moves at a constant velocity. The remaining portions of the apparatus portion 9 is identical to those shown in FIG. 1, and therefore, need not be described any further here. It should be noted that the embodiment shown in FIG. 2 has the advantage of providing a longer exposure time for form slides (which have not been shown, but are the same as in FIG. 1) since the photoconductive belt 21 remains fixed for a full frame time. Hence, this configuration requires a lower power for the form flash optical source 34.
As an alternative to using individual copy sheets 28,
a computer fan fold receiver in the form of a continuous web could be disposed along the path defined by the web member 30.
. CHARACTER PRODUCING LOGIC 14 As shown in FIG. 1, there is provided block 14 entitled, CHARACTER PRODUCING LOGIC. Such circuitry is shown in detail in FIG. 3. Turning to FIG. 3, there is shown an information source shown as block 51. It will be understood that the non-impact printer 8 can be either on-line with a computer, or off-line. If the printer 50 is on-line," at computer such as an IBM 360/370 System and necessary control unit interface circuitry would comprise source 11. If the printer 8 is off-line," block 51 may be magnetic tape drive or other suitable data storage device. The particular storage 51 is not part of this invention per se, and therefore no more detailed reference is made thereto. Since information stored in digital computers is generally in binary form, the initial output from information on source 51 is preferably in a binary coded format. As is well known to those skilled in the art. pictures, graphs and charts which can be printed out in accordance with the invention can also be stored in binary form. A sequence of bytes or data (viz., each byte has eight data bits) is applied to temporary storage register 52 which may be formed from integrated circuits which are readily available commercially. A character generator memory 54 receives the output from the temporary storage register 52 and converts this to an output format comprising nine output signals representing nine elements of a vertical character column of a character to be printed. The nine information channel outputs from character storage memory 54 are converted by fixed frequency modulated oscillators 56a-56i into fixed electrical carrier frequencies which are individuallygated either on or off under the control of the character generators 54. In fact, the oscillators may be free running. The frequencies may for a specific example be selected to be in a range of from 31 to 49 mhz.
The plurality of frequencies is combined by the summing network 57 to form a complex electrical signal having a plurality of signal components. This complex signal is impressed upon an ultrasonic transducer 58 connected to the cell 13 through an attenuator circuit (not shown), an automatic gain control circuit 60, and a power amplifier and matching network 61 which matches the impedance of transducer 58 to the power amplifier 61. An example of a suitable commercially available power amplifier is Model 3 IOL Power Amplitier manufactured by Electronics Navigation Industries of Rochester, New York. Althougha resistive summing network is shown comprised of resistors 5711-571, any other suitable method of combining several electrical signals such as transformers can be used. The ultrasonic transducer 58 translates the electrical signal into acoustic waves 64 which are propogated through the acoustooptic modulator cell 13. The acoustic waves 64 within the cell correspond to the fixed frequency electrical signals produced by oscillator 56. Because of the properties of Bragg reflection in the acoustooptic cell, as is explained in some particularity by Robert Adler in an article in the IEEE Spectrum of May 1967, pp. 42-54 entitled, INTERACTION OF LIGHT AND SOUND, every one of the individual acoustic frequencies interacts independently with the light from a laser light source 66 within the acoustooptic cell 13 to modulate and form a phase grating for diffracting a first order beam of light 68 for every frequency present therein. The position of any one of the beams is a function of the frequency producing it and can be adjusted by changing the frequency of the corresponding oscillator. The number of light beams which can be produced simultaneously and therefore, the number of elements in the character vertical column is equal to the resolution of the acoustooptie cell, which is approximately equal to Afr; where Afis the useful frequency range of the attached transducer and 1' is the time required for an acoustic wavefront to pass across the optical beam.
Light from the beams 68 which forms spots can be positioned so that the spots, when they impinge on the photoconductive member 21, are separated or overlap one another. Frequency selections are readily made as a matter of choice since the frequencies of the oscillators determine the frequencies in the acoustooptic cell 13. The frequencies when properly adjusted position the light elements relative to one another on the receiving means. Every light beam at a particular height position in a vertical character column on the photostorage medium corresponds to one frequency. Too. every light beam is independently controlled to be on or off. i.e., to form light or leave dark corresponding individual light element receiving areas on the member 2| in accordance with whether or not the corresponding modulating oscillator for that element is on or off. The row of light beams is preferably scanned in the direction generally horizontally relative to vertical character columns or increments by the scanner 15 which can be a rotating mirrored polygon (FIG. 1 embodiment) or alternatively, and as shown, a scanner mirror controlled by a galvanometer such as disclosed in US Pat. No. 3,624,574 to Montague issued Nov. 30, 1971. If the scanning mirror is used, that it would cooperate with a rotating polygon as previously described. In this manner, the line of character information can be readily recorded on the photoconductive belt 21 in a single scan. In either case, the photoconductive belt 21 can be moved to provide a fresh charged surface. It will be apparent that one scan is all that is required to record an entire line of information since the nine or other number of vertical character column elements of a vertical character column or increment are produced simultaneously by the corresponding plurality of nine light beams. The number of vertical elements in any one column is determined by the number of oscillators used. The character storage memory output 54 determines whether or not a particular output of the corresponding oscillator 56 is introduced to the transducer 58 for any one vertical character column. Since it is preferable that the scanner 15 be continuously rotated, the gating on of the oscillators 56 should be synchronized to the position of the scanner 15. In addition, the speed of the web 21 should be regulated by the speed of the scanner 15. Towards this end, the scanner 15 provides an output to a position sensor 74 which can be any one of such devices well known to those of ordinary skill in the art. The position sensor may be an optical apparatus which includes a photocell responsive to a light beam reflected off a mirrored surface of the scanner 15 to produce a signal representative of the position of the mirror. Other types of commercially available servosystems could also be used. The output of position sensor 74 is directed to sequencer control logic 76 which clocks the transfer of information from the information source 51 to the character generator memory 54 and also provides a signal to the main drive train mechanism 24a. Sequencer control logic 76 also controls a counter 78 for selecting the next character column to be recorded. Counter 78 can control the sequence of the vertical character columns being recorded.
High quality character generation suitable for photo type setting applications may be obtained by increasing the number oflight beams formed by the modulator 13 in the linear array which forms a character column. The storage capacity in the character generator must be correspondingly increased. The justification of the right hand margin of a line of text may be achieved by disk. The required font may then be read into the char-' acter generator as required and used for character writing.
The invention has been described in detail with particular reference to a preferred embodiment thereof,
, but it will be understood that variations and modificamultaneous multi-beam acoustooptic cell coupled tosaid source and responsive to the information therein for simultaneously producing a plurality of light beams which have such information; i
b. movable mirror scanning means for scanning and reflecting the light beams; and
c. electrographic apparatus for receiving the reflected beams to reproduce the information in said light beams on such medium.
2. A non-impact printing apparatus for recording information from a storage source, comprising:
a. an electrographic apparatus having a movable photoconductive member defining a surface responsive to light beams to form latent images;
b. format generating means coupled to ,said storage source and responsive to the information therein for simultaneously producing an electrical signal having a plurality of different fixed frequencies with such different fixed frequencies corresponding to such storage source information;
c. a simultaneous multi-beam accoustooptical cell re- I sponsive to said electrical signal from said format generating means for simultaneously forming a corresponding number of diffracted light beams, each having a diffraction angle uniquely associated with one of the different fixed frequencies, respectively;
I and 4 d. means for imaging the diffracted light beams onto the surface of said photoconductive member for forming latent images thereon corresponding to the storage source information.
3. The invention as set forth in claim 2 wherein said electrographic apparatus is adapted to process such latent images to form toner images and -transfer such toner imagesonto a receiving medium and wherein said imaging means includes a movable optical member for scanning the diffracted light beams across the surface of said photoconductive member.
4. The invention as set forth in claim 3 including position control means responsive to the movement of said optical member for controlling the operation of said format generating means in producingelectrical signals and the movement of said photoconductive member.
5. The invention as'set forth in claim 2 including form slide means adapted to form a latent image of a form on the surface of said photoconductive member in alignment with the recorded storage source information. i
6. A non-impact printing apparatus for recording information from a storage source. comprising:
a. an electrographic apparatus having a movable photoconductive web movable alongan endless path and defining a surface responsive to light beams at a predetermined position along the path to form latent images, said electrographic apparatus including means for stopping said web at said predetermined location prior to receiving such light beams, said electrographic apparatus being adapted to process such latent images to form toner images and transfer such toner images onto a receiving medium,
b. format generating means coupled to said storage source and responsive to the information therein for simultaneously producing an electrical signal having a plurality of different fixed frequencies 1 with such different fixed frequencies corresponding to such storage source information;
. a simultaneous multi-beam acoustooptical cell responsive to said electrical signal from said format generating means for simultaneously forming a corresponding number of diffracted light beams, each having a diffraction angle uniquely associated with one of the different fixed frequencies, respectively; and
d. means for imaging the diffracted light beams onto the surfaceof said photoconductive member for forming latent images thereon corresponding to the storage source information.
I 7. The invention as set forth in claim 6 wherein said imaging means includes a movable optical member for scanning thev diffracted light beams across the surface ofsaid photoconductive member.
8. The invention as set forth in claim 7 including position control means responsive to the movement of said optical member for controlling the operation of said format generating means in producing electrical signals and the movement of said photoconductive member.
9. The invention as set forth in claim 8 including form slide means adapted to form a latent image of a form on'the surface of said photoconductive member in alignment withthe recorded storage source information.
10. The'invention as set forth in claim 1 wherein said optical character generating means includes a source of coherent light, and wherein said acoustooptic cell produces said light beams from light from said light source. l=