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Publication numberUS3677148 A
Publication typeGrant
Publication dateJul 18, 1972
Filing dateDec 28, 1970
Priority dateDec 28, 1970
Publication numberUS 3677148 A, US 3677148A, US-A-3677148, US3677148 A, US3677148A
InventorsPhilip L Chen
Original AssigneeXerox Corp
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Optical recorder
US 3677148 A
Abstract
Non-impact printing or recording apparatus adapted for use with a digital computer. The apparatus is characterized by the employment of an optical character generator and timing system therefor capable of printing information on a moving photoresponsive medium.
Images(8)
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Claims  available in
Description  (OCR text may contain errors)

United States Patent Chen [451 July 18, 1972 [54] OPTICAL RECORDER [72] Inventor: Philip L. Chen, Penfield, NY.

[73] Assignee: Xerox Corporation, Stamford, Conn.

[22] Filed: Dec. 28, 1970 [21] Appl.No.: 101,671

3,249,028 5/1966 Higonnet et a1 ..95/4.5 R 2,726,940 12/1955 Buhler ....95/4.5 R 3,252,392 5/1966 Ward ....95/4.5 R 3,262,379 7/ 1966 Bauer et a]. ..95/4.5 R

Primary Examiner-Samuel S. Matthews Assistant Examiner-Robert P. Greiner Attorney-James J. Ralabate, John E. Beck and Benjamin B. Sklar 5.7 ABSTRACT Non-impact printing or recording apparatus adapted for use with a digital computer. The apparatus is characterized by the employment of an optical character generator and timing system therefor capable of printing infonnation on a moving photoresponsive medium.

10 Chins, 14 Drawing Figures PATENTED JULI 8 I972 SHEET 1 [1F 8 INVENTOR PHILIP L. CHEN msmm m 1 a ma sum 2 [IF 8 PAYENTED Jun 8 m2 7 SHEET 5 UB8 M NNNNNNN PATENTEU JUU 8 I972 SHEET 8 OF 8 PATENTED JUL 1 8 I972 SHEET 7 OF 8 I PATENTED H l972 $677,148

' SHEET 8 UF 8 ME COLUMN l 2 3 4 T o sTART OFLINE V ONE T CHARAC ER (START OF FIRST QUADRANT). SPACES) OPTICAL I l AXIS l sec. (END OF FIRST QUADRANT) 9 SEC.

(sTART OF SECOND QUADRANT) b d/ sec. (START OF THIRD IQUADRANT) sec.

(END OF THIRD QUADRANT) SEC.

(START OF FOURTH QUADRANT) 9 sec.

(END OF FOURTH QUADRANT) Z END OF um:

FIG /3 OPTICAL RECORDER BACKGROUND OF THE INVENTION This invention relates, in general, to high speed printing and, more particularly, to optical character printers compatible with digital computer output.

Earlier attempts at computer output printing of the type herein contemplated led to the development of shadowgraph printing wherein illumination from a flash lamp passes through transparent characters to thereby form a shadow image or images on a recording medium.

Exposure in such a system is determined by the solid angle subtended by the flash lamp arc at the character mask. Hence, exposure increases as the arc size is increased or as a given lamp is moved closer to the character mask. Since a finite distance is required to separate a photosensitive recording medium such as selenium from the character mask, the light rays from the lamp are constrained in angular deviation to small angles for acceptable character image quality. Consequently, image quality directly opposes exposure in that the lamp arc must be either made smaller or moved away from the character mask to improve image quality. Such movement, in turn, necessitates a higher power input.

A compromise solution to the foregoing problem results in the employment of a very small flash lamp, requiring a very small xenon fill pressure which varies widely in the manufacturing process, resulting in variations in light output from lamp to lamp. Furthermore, the wall area to electrode volume ratio is small, consequently, lamp blacking caused by electrode sputtering limits the life of the lamp to about flashes at 8 millijoules per flash. Still further such lamps are limited to 1: 1 printing.

In solving the foregoing problem one may utilize small unconfined, commercially available, arc lamps which have a life greater than 10 flashes at 8 millijoules per flash. A simple lamp cover enclosing each lamp can be provided as a partial diffuse integrating cavity. To carry the light from the lamp to the recording medium, with shadowgraphing or optical imaging, an incoherent fiber bundle could be provided. Such an arrangement exhibits a very low efficiency (i. e. about 20 percent) which requires a very high energy input which substantially shortens the life of the lamp.

characteristically incoherent fiber bundles when illu minated with a small light source placed in close proximity thereto produces uneven illumination. Moreover, such devices are bulky and complicated. For example, for a computer printout format of 132 columns, the printer needs 132 flash lamps and related circuitry plus 132 fiber bundles all of which have to be packed into a character mask structure.

Accordingly, the general object of the invention is to provide new and improved printing apparatus.

It is a more particular object of this invention to provide new and improved printing apparatus wherein computer outputs of 132 characters per line can be printed on an 11 inch wide copy sheet.

Another object of this invention is to provide a new and improved optical system for an optical printer.

Still another object of this invention is to provide a new and improved character mask for use in an optical printer.

Yet another object of this invention is to provide a new and improved printing apparatus utilizing optical imaging on a rotating photoconductive drum.

BRIEF DESCRIPTION OF THE INVENTION Briefly, the above-cited objects are accomplished by the provision of a transparent character drum having staggered columns or sets of characters extending about the circumference thereof. In the preferred embodiment there are 132 such columns divided into groups of four such that each group of four columns extends around the entire circumference of the character drum. In this manner there are 33 groups of four columns each.

The groups are spaced apart along the longitudinal axis of the drum a distance at least equal to the distance across one group. This permits the projection of properly spaced, enlarged images, onto a rotating photoconductive drum.

A strip prism arrangement of equivalent mirror system cooperates with 33 commercially available flash lamps and suitable condenser lenses to transmit illumination from the lamps through the character drum images in the direction of a strip lens structure serving to form the images on a rotating photoconductive drum. The individual elements of the prism arrangement are disposed relative to one another so as to intercept light travelling in three different directions and transmit the light therefrom in one direction so that in conjunction with suitable timing means associated with the character drum, an entire line can be printed for each revolution of the character drum.

The timing means comprises a plurality of slits on the character drum which are so arranged with respect to the characters on the character drum that all the characters to be contained in a line on the photoconductive drum can be registered in that line even though the various characters forming the line pass the light from the prisms at different points in time and even though the photoconductive drum is continuously rotating.

DETAILED DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates a schematic view of printing apparatus representing the invention;

FIG. 2 is a schematic perspective view of an optical character mask and optical projection system forming a part of the apparatus illustrated in FIG. 1;

FIG. 3 is a block diagram depicting the cycle of operation for generating optical characters by means of the mask and projection system of FIG. 2;

FIG. 4 is an expanded view as viewed from the outside of .the character mask illustrated in FIG. 2;

FIG. 5 is an expanded view as viewed from the outside of a character mask utilized for the purpose of providing a better understanding of the invention;

FIGS. 6 and 7 are schematic perspective views of the character drum of FIG. 5 illustrating the projection of the characters thereof onto a photoconductive surface;

FIGS. 8-10 are similar to FIGS. 5-7, but illustrate a timing slit arrangement and its effect on the projection of characters onto the photoconductive surface;

FIG. 11 is an enlarged schematic perspective view of the optical system forming a part of the invention;

FIG. 12 is a schematic perspective view illustrating a field mark forming a part of the projection system hereof;

FIG. 13 is a time sequential representation of the characters on the character mask at the time of their projection onto the photoconductive surface as viewed through a stationary field mask; and

FIG. 14 is an enlarged plan view of the field mask and character mask illustrating the simultaneous projection of three consecutive characters of the character mask.

DETAILED DESCRIPTION OF THE INVENTION GENERAL As shown schematically in FIG. 1, the automatic xerographic recording apparatus comprises a xerographic plate 20 including a photoconductive layer or light-receiving surface on a conductive backing and formed in the shape of a drum, which is mounted on a shaft journalled in a frame to rotate in the direction indicated by the arrow to cause the drum surface sequentially to pass a plurality of xerographic processing stations.

For the purpose of the present disclosure, the several xerographic processing stations in the path of movement of the drum surface may be described functionally, as follows:

A charging station, at which a uniform electrostatic charge is deposited on the photoconductive layer of the xerographic drum;

An exposure station, at which a light or radiation pattern of information to be recorded is projected onto the drum surface to dissipate the drum charge in the exposed areas thereof and thereby form latent electrostatic images of the information to be recorded;

A developing station, at which xerographic developing material including toner particles having electrostatic charges opposite to that of the electrostatic latent images are cascaded over the drum surface, whereby the toner particles adhere to the electrostatic latent images to form xerographic powdered images in the configuration of the information being recorded.

A transfer station, at which the xerographic powder images are electrostatically transferred from the 'drum surface to a transfer material or support surface; and,

A drum cleaning and discharge station, at which the drum surface is brushed to remove residual toner particles remaining thereon after image transfer, and at which the drum surface is exposed to a relatively bright light source to effect substantially complete discharge of any residual electrostatic charge remaining thereon.

The charging station is preferably located, as indicated by reference character A. As shown, the charging arrangement includes a corona charging device 21 which includes a corona discharge array of one or more corona discharge electrodes that extend transversely across the drum surface and are energized from a high potential source and are substantially closed within a shielding member.

Next subsequent thereto in the path of motion of the xerographic drum is an exposure station E. A flash expose optical projection system is provided to project an image onto the surface of the photoconductive drum.

The optical projection system comprises a stationary lens and prism structure generally indicated 23 comprising a plurality of prisms arranged to reflect light, emanating from a plurality of directions, in one direction through a character mask in the shape of a drum 24. The lamps associated with the prisms and character mask are adapted to be flashed in accordance with output from a digital computer, in such a manner as to enable printing of an entire line for each revolution of the character drum.

Adjacent to the exposure station is a developing station C in which there is positioned a developer apparatus 30 including a casing or housing having a lower or sump portion for accumulating developer material. A bucket type conveyor is used to carry the developing material to the upper part of the developer housing where it is cascaded over a hopper chute onto the xerographic drum to effect development. A toner dispenser 35 is used to accurately meter toner to the developing material as toner particles are consumed during the developing operation.

Positioned next and adjacent to the developing station is the image transfer station D which includes a sheet feeding arrangement adapted to feed sheets of support material, such as paper or the like, successively to the xerographic drum in coordination with the presentation of the developed image on the drum surface at the transfer station.

The sheet feeding mechanism includes a sheet feed device 40 adapted by means of vacuum feeders to feed the top sheet of a stack of sheets on a tray 41, to rollers 42 cooperating with the belts of paper transport 44 for advancing the sheet sulficiently to be held by paper transport 44 which in turn, conveys the sheet to a sheet registration device 45 positioned adjacent to the xerographic drum. The sheet registration device arrests and aligns each individual sheet of material and then in timed relation to the movement of the xerographic drum, advances the sheet material into contact with the xerographic drum in registration with a previously formed xerographic powder image on the drum.

The transfer of the xerographic powder image from the drum surface to the sheets of support material is effected by means of a corona transfer device 51 that is located at or immediately after the line of contact between the support material and the rotating drum. In operation, the electrostatic field rotating brush 71, and a discharge lamp LMP1 adapted to flood the xerographic drum with light to cause dissipation of any residual electrical charge remaining on the xerographic drum.

For collecting powder particles removed from the xerographic drum by the brush 7], there is provided a dust hood 73 that is formed to encompass approximately two-thirds of the brush area. To ensure thorough cleaning of the brush, a flicking bar 74 is secured to the interior of the dust hood adjacent the edge of the outlet duct 75 of the dust hood and in interfering relation with the ends of the brush bristles whereby dust particles may be dislodge therefrom.

For removing dust particles from the brush and dust hood, an exhaust duct 76 is arranged to cover the outlet of the dust hood, the exhaust duct being connected at its other end to the wall of a filter box 77 attached to the dust hood. A filter bag 78 is secured within the filter box, with the mouth of the filter bag in communication with exhaust duct. Motor fan unit MOT-6, connected to the filter box, produces a flow of air through the filter box drawing air through the area surrounding the xerographic drum and the dust hood, the air entraining powder particles removed from the drum by the brush as the air flows through the dust hood. Powder particles are separated from the air as it flows through the filter bag so that only clean air reaches the motor unit.

Suitable drive means are provided to drive the drums and sheet feed mechanism at predetermined speeds relative to each other and to effect operation of the bucket-type conveyor and toner dispenser mechanism and the other operating mechanisms.

The character mask or drum 24 form a part of an optical projection system comprising the lens and prism structure 23, to be discussed in detail hereinafter, and a plurality of flash lamps 100.

The flash lamps are flashable in accordance with information derived from a computer, the illumination therefrom being directed by means of the lens and prism structure 23 through characters of the character mask 24 which characters may be either opaque or transparent. The characters so formed produce latent electrostatic images of alphanumeric characters on the photoconductive plate 20.

Each of the character space occupied by a character on the xerographic plate is associated with a transparent slit or aperture 102, the slits being disposed about the circumference of the drum. A slit sensor 104 disposed adjacent the outer surface of the drum intercepts a light from a light source 106 each time a slit 102 passes between the sensor and the light source. Pulses generated by the sensor 104 are utilized, as will be discussed hereinafter, to effect firing of the lamps 100.

The block diagram of FIG. 3 illustrates, in general, the cycle of operation for firing of the flash lamps in accordance with the output from a computer 108 which is utilized as a buffer storage device containing sufficient data to print a complete page of 66 lines. A model DD? 516 computer manufactured by Honeywell Corporation has been satisfactorily employed to demonstrate the operation of the printer.

Initially only a portion of the data contained in the buffer device 108 is written into a memory device 110 which may comprise a pair of F1 40 fast access memory cards having a capacity of 16 two-character words at 16 bits per word. Such cards are manufactured by Xerox Data Systems. Writing into memory is accomplished by means of a process control shift register 112 driven by a 5 MHz clock. The shift register also controls the reading of the data into a comparator 114 which may comprise suitable logic components, for example, AND gates (not shown) for deriving outputs when positive comparisons are made. The other input to the AND gates may be derived from a counter 116.

The counter 116 is preset to a code representing the first character on the character drum 24. Accordingly, when the first or initial portion of data is read into the comparator 110 it is compared to the code representing the aforementioned first character or in other words the preset value of the counter. Each successive character on the character drum is represented by a code in the counter on incrementing thereof. This incrementing of the counter is accomplished by virtue of the pulses from the slit sensor 104. It can be seen that the code representing the second character on the drum will be represented by the preset value of the counter plus 1.

When the code in the comparator 114 is the same as the code from the memory 110, a latch 118, which may comprise a flip-flop (not shown) is set. Pulses from the sensor 104 are ANDed with the outputs from the latches to thereby actuate lamp firing circuits 120.

In accordance with the objects of the present invention, the' character mask or drum 24, as illustrated in FIG. 4, comprises columns 124 of characters disposed on the periphery thereof in groups of four columns. In the preferred embodiment of the invention 33 such groups of four columns each, are disposed along the longitudinal axis of the drum, each group being spaced from adjacent groups by at least a distance equal to the width of one group of columns. The circumferential extent of one group of columns is such that each column of a group occupies a different quadrant of the drum. This produces a staggered arrangement of the columns or character sets which permits utilization of one flash lamp for each group of four columns. If the columns were not staggered but were disposed in a side by side array, a lamp would be required for each column. 7

Since the columns 124 are staggered, each flash lamp 100 is fired four times for each revolution of the character drum. Accordingly, during one revolution, data corresponding to the first column of each group is put into the comparator 114 and compared against the code in the counter 116. Since one fourth of the data in the buffer is handled at one time, this quantity of data may be thought of as one quadrant of data.

For each column of information from the memory 110 that contains an A, a corresponding latch 118 is set. Subsequent thereto, when the slit 102 associated with the character space for the A is sensed by the sensor 104, the lamp firing circuits 120 corresponding to the latches previously set are triggered. Simultaneously, the pulse from the sensor 104 increments the counter 116 by one. The code for the letter B is now in the comparator and is subsequently compared to the first quadrant of data from the buffer. Each character of the first column is compared in the foregoing manner to the first quadrant of data.

At the end of each column 124 adjacent the last character space of that column there is provided a transparent slit 125 which effects pulsing of a photodetector 132, the pulse from which conditions the register 112 for writing the second quadrant of data from the buffer into memory with subsequent reading from memory into the comparator. The second quadrant of data is read into the comparator, as before, for each character of the second column, each character of the second column being placed one at a time into the comparator as above. The sequence of operation for the third and fourth quadrants of data from the buffer is the same as described above.

As can be seen from FIG. 4, the slits 102 do not occupy the same relative position with respect to their associated character spaces. In other words the slit associated with the first letter of any first column is disposed adjacent the trailing edge of the first character space assuming that the character mask of FIG. 4 is moving upwardly past a flash exposure station. The slit associated with the last character of the group is adjacent the leading edge of that character space.

The purpose of the specific arrangement of the slits 102 will be better understood by first considering the operation of a character mask on which the slits are spaced the same, relative to each character space i. e., adjacent the trailing edge of the wherein there is disclosed an expanded view as viewed from the outside (FIG. 5) of a character mask or drum having a plurality of columns 142 of characters disposed thereon in a side by side relationship. The character drum is adapted for rotation in the counterclockwise direction while a photosensitive insulating plate 144 optically aligned therewith is adapted for rotation in the clockwise direction.

Each column 142 of characters, herein illustrated as the capital letters of the alphabet, represents a character set which extends over the entire circumference of the character drum. In the present embodiment it is desired to print a complete line of characters on the photoconductive plate 144 which line comprises one character from each column of the character drum. Accordingly, flash lamps, not shown, associated, one with each column, will flash once for each revolution of the character drum. Meanwhile, the photoconductive plate rotates the equivalent of one character space. A column of timing slits, one for each character of a column, generally indicated by reference character 146, is sensed to thereby cooperate with an output from a computer to cause flashing of the lamps in accordance with the characters to be recorded. In this particular embodiment each timing slit occupies the same position relative to the character space associated with a particulate character, as all other slits. In other words, each timing slit is in line with the trailing edge of the character space occupied by the character associated therewith.

As shown in FIG. 5, the character A from the first column from the left, is projected onto the photoconductive plate in the position shown, which position lies below a stationary reference line 148 used herein for illustration purposes only. Assuming that the Z of the fourth column is to be projected onto the plate, it will be seen that because the photoconductive plate has moved clockwise a full line or character space the Z is projected onto the drum, not on the same line space as the A but one line space below. This is due to the fact that with such a timing slit arrangement all characters are projected below the reference line and by the time the Z moves through the optical axis the line space on the drum containing the A has moved above the reference line.

In order to obviate this problem a plurality of differently spaced timing slits 150, one for each character set is provided adjacent the right edge of a character drum 152. (See FIGS. 8-10). These slits or indicia may be apertures in the character drum or transparent windows in an opaque mask. Either of the foregoing may be employed, the essential requirement being the capability of passing light from the light source 106 to the light sensor 104 which may be a photodiode. The sensor and light source are in line with the optical axis extending between the two drums.

The slits or windows, as shown in FIG. 8 are arranged relative to columns 154 of character drum 152 such that the one associated with the A is substantially in line with the trailing edge of the character space occupied by the A and the one associated with the character space occupied by the Z is substantially in line with the leading edge of the character space occupied by the Z. The slits or windows intermediate the ones associated with the A and Z are incrementally progressed such that the one associated with the M is substantially in line with the middle of the character space occupied thereby. It can be seen from FIG. 8 that when the slit associated with the A (first column from left) passes the light sensor 104, the A is projected onto a plate 156 in an area that lies below an reference line 158. From FIG. 10, it can be seen that when the slit associated with the Z (fourth column from left) passes the light sensor, the Z on the drum is in a position so as to be projected onto the plate in a position above the reference line, which position due to the clockwise rotation of the plate is in line with the position of the A.

In the preferred embodiment of the character mask, columns 124, as shown in FIG. 4, are placed on a character drum 24 in groups of four, the drum being sufficiently long (i. e. 9.9 inches) to place thirty-three such groups thereon with a space between groups greater than the distance across the columns in any one group. As shown the columns of each group are staggered such that the columns in one group, beginning with the first character of the first column or set from the left, and ending with the last character of the fourth column or set, extend substantially the circumference of the drum. As in the case of the embodiment of FIGS. -7, it is intended that a line comprising a character from each column or set be printed for each revolution of the drum.

Since the columns of one group, in the embodiment shown, occupy only one fourth of the circumferential extent or one quadrant of the drum, four characters from each group must be projected onto the same line of a photoconductor plate for each revolution of the character drum 24. Expressed another way, a character from each column in a group must be projected for every one-quarter revolution of the character drum. During this quarter revolution the line space on the photoconductive plate moves one fourth its total distance. This means that for the characters for any two adjacent columns to be projected onto the same line space of the plate, the timing slits 102 associated with those two characters should be approximately one fourth the total distance between the first and last timing slits of one group. To this end the character drum 24 is, as shown in FIG. 4, the first one of timing slits 102 is in line with the trailing edge of the character space associated with the A and the last timing slit of fourth column of the first group is in line with the leading edge of the character space associated with the last Z in that group. It will be seen upon further examination that the tinting slit associated with the character space associated with the z of second column of the same group occupies a space in line with the middle of the Z.

While the number of columns in each group is illustrated as being four, this need not be the case. Any number of convenient columns may be employed depending on the particular application and the end result desired.

By referring to FIGS. 1 and 4 and bearing in mind the discussion relative to FIGS. 5-7, it can be seen that for each group of columns, an A, by way of example, can be projected onto and along the same line of the plate 20 for each column position of the character drum. Projection of characters commences when the timing slit associated with the first A of the first column is sensed by the light sensor. At this time the first A is projected onto the plate which then rotates clockwise one fourth of a line space while the character drum rotates approximately a quarter of a revolution. Now the timing slit for the second A is sensed by the light sensor. It will be apparent that the differential spacing of these two timing slits relative to their respective A's causes the second A to be projected onto the photoconductive plate a distance one fourth of a line space higher than the preceding A thereby placing the second A on exactly the same line on the plate as the first A. With respect to the third A, it will be seen that its timing slit will have the effect of causing the third A to be projected one half of a line space higher on the plate thereby placing it on the same line with the first two characters. Simultaneously, the projection of other first, second and third As of the other groups has taken place along the same line of the plate.

The slit sensor 104 is disposed, for sake of convenience 90 from the optical axis. However, it may occupy any location relative to the mask.

The lens and prism structure 23, as best shown in FIGS. 1 and 11, comprises a prism structure 160 which may be fabricated as a single piece or may be assembled from individual pn'sm elements 162 and blocks 163. A plurality of strip condensers 164 comprising individual condenser elements 166 cooperate with condenser elements 167 molded on the strip prism to collect the illumination from the lamps 100 for transmission to the prism elements 162.

The lamps 100 of which there are thirty-three in the preferred embodiment are arranged in three rows to form an arc of approximately 270 about the top, bottom and rear sides of the strip prism structure 160. The rows of lamps are offset to each other, the top row being offset to the right side of the back row, as viewed from the left in FIG. 11, while the bottom row is offset to the left side of the top row. The amount of offsetting in each of the foregoing cases is equal to four column widths at the photoreceptor 20. The collected light from each lamp in the top and bottom rows is reflected by the strip prism structure in the forward direction toward the character mask 24. While the orientation of the top and bottom lamps are illustrated as being approximately 90 from the back row any practical angle orientation is considered within the scope of this invention.

The light output from the back row of the lamps travels straight through the blocks 163 which are disposed intermediate a pair of prism elements 162.

The illuminated characters are magnified approximately three times and are projected onto the photoconductive drum 20 by means of a strip lens 170. One element (i. e. one individual lens) of the strip lens covers or images" four characters on the drum. As shown, these reduced size character columns are grouped on the character drum leaving the aforementioned spaces between groups, hence, the character groups are readily baffled by means of a bafile structure 172 to thereby prevent optical cross-talk between strip lens elements.

A stationary field mask 180 (FIG. 12) interposed between the strip lens and the photoconductive drum or plate 20 permits center-to-center (measured circumferentially) compression of characters on a character mask 181 resulting in optimization of the required rotational velocity of the character mask and the required optical magnification from the character mask to the photoconductive drum 20. The field mask comprises an opaque portion 182 and a plurality of clear portions or windows 185, one such clear portion for each character. Each group of four windows forms a stepped pattern which in combination with the slits 102 serves a purpose which will be discussed hereinafter.

FIG. [3 illustrate the time sequence of the characters A and Z on the outside of the character mask 181 at the time of their projection. By way of example, these two characters are intended to represent the first and last characters of each column or character set. One group of four columns is taken as representative of the entire character mask. It follows from a study of FIG. 13 that the stationary field mask illustrated in FIGS. 12 and 14 in no way inhibits the projection of any of the characters shown in FIG. 13. It is noted that the vertical height of the transparent portions 184 is 25 percent larger than one character space.

FIG. 14 illustrates that if the characters within a character set or column are separated by one quarter of a character space, and the mask is employed, one and only one character from a particular column is projected at a given time. The stepped portions are repetitive for each group of drum diameter and angular velocity to remain the same while increasing the size of the characters on the character drum and hence reduce the required optical magnification of the characters. Also, the resulting system has advantageous tolerancing effects as will be appreciated by those skilled in the art.

What is claimed is: 1. Apparatus for recording alphanumeric characters, said apparatus comprising:

an endless member having staggered columns of transparent characters extending about the circumference thereof, said columns being disposed in groups of at least two columns which groups extend transversely of said endless member and are spaced apart at least the distance across a single group of columns,

first optical means for projecting in one direction, collimated light emanating from a plurality of directions, said optical means being disposed within said endless member,

a plurality of flash lamps, one for each group of columns,

said flash lamps being disposed in rows of equally spaced lamps which rows are offset one from the other and disposed in an arc extending about said first optical means;

second optical means for focusing light passing through said endless member at a focal point;

light responsive recording structure positioned at said focal point for receiving focused images of alphanumeric characters;

means for rotating said endless member at a uniform speed,

and

means for selectively flashing lamps in accordance with information to be recorded.

2. Apparatus according to claim 1, including means for moving said light responsive structure in synchronization with said endless member, and wherein said means for selectively flashing said lamps comprises means for effecting flashing of said lamps in a predetermined time relationship to said lamps whereby a line of input characters in focused on said light sensitive member in a substantially straight line.

3. Apparatus according to claim 1, wherein said light responsive recording medium comprises an electrostatic charge-retentive surface and said apparatus further comprises:

means for placing a uniform charge on said surface which is dissipated in accordance with images focused thereon to thereby form an electrostatic image, and

means for developing said latent image in order to render visible.

4. Apparatus according to claim 3, further including means for transferring an image to a copy sheet.

5. Apparatus according to claim 1, wherein:

said means for transmitting collimated light comprises a row of prisms in parallel blocks having light receiving and light emanating surfaces, said light emanating surfaces being disposed in one row while said light receiving surfaces of said prism are arranged in two rows and the light receiving surface of said parallel blocks are disposed and a third row, all rows being spaced a multiple 90 from said light emitting surfaces.

6. Projection imaging apparatus for use in an alphanumeric recording apparatus employing a light responsive recording medium, said structure comprising:

a character mask having light transmitting characters formed thereon;

means for moving said character mask at a substantially uniform speed;

means for intercepting collimated light emanating form a plurality of directions and transmitting said light through said character mask along a fixed line;

a plurality of rows of selectively flashable lamps disposed in an are extending partially around said light intercepting means, and

means for flashing said lamps in accordance with information to be recorded.

7. Structure according to claim 6, wherein said means for tramsmitting light comprises a row of prisms and parallel blocks having light receiving and light emitting surfaces, said light emitting surfaces being disposed in one row while said light receiving surfaces are disposed in a plurality of rows which are spaced at least from said light emitting row.

8. Structure as specified in claim 7, including means for focusing images onto a light responsive recording medium.

9. Structure as specified in claim 8, wherein said character mask comprises groups of circumferentially staggered columns of characters and wherein the number of flashable lamps is equal to the number of groups of columns.

10. Apparatus for recording alphanumeric characters, said apparatus comprising:

an endless member having staggered columns of transparent characters extending about the circumference thereof, said columns being disposed in groups of at least two columns which groups extend transversely of said endless member;

means for selectively producing illumination in accordance with information to be recorded; means for pro ecting illumination through said endless member and focusing character images on a light responsive member;

means for rotating said endless member at a uniform speed;

a light responsive member and means for moving said member at a speed such that it moves a distance equal to He X s during l/c of revolution of said endless member, where c is equal to the number of columns in one group and s is equal to the height of a character on said light responsive member; and

means for energizing said illumination means in accordance with the relative positions of said endless member and said light responsive member whereby the character images formed during one revolution of said endless member are formed along the same line on said light responsive member.

* IIK

Patent Citations
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US2726940 *Nov 3, 1954Dec 13, 1955IbmXerographic printer
US2944147 *Sep 23, 1957Jul 5, 1960IbmXerographic printer
US3249028 *Mar 30, 1964May 3, 1966Photon IncHigh speed photorecorder
US3252392 *Jul 12, 1963May 24, 1966Us Scientific InstrumentsApparatus for character recording
US3262379 *May 11, 1964Jul 26, 1966Hughes Aircraft CoApparatus for high speed photographic printing
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Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US4000944 *Feb 18, 1975Jan 4, 1977Xerox CorporationPhotoreceptor for electrostatic reproduction machines with built-in electrode
US4167324 *Oct 17, 1977Sep 11, 1979Burroughs CorporationApparatus for xerographically printing a composite record based on fixed and variable data
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Classifications
U.S. Classification399/220, 396/559
International ClassificationG06K15/14, G06K15/12
Cooperative ClassificationG06K15/12, G06K15/14
European ClassificationG06K15/12, G06K15/14