Optical system for imaging an electrophotographic member

A digital plate maker system to receive graphics and text data and selectively discharge incremental areas of a charged electrophotographic member to form thereon the latent images represented by the graphics and text data, the imaged member thereafter being toned and output from the system. Thereafter, the toned image may be fused on the member and the member being used in an offset lithographic printing press. The digital platemaker system includes an optical system which may form a maximum of 22 individual rays which are direct deflected twice through a field flattening lens and then onto the charged member. The optical system further includes an optical scale or grating which provides electrical signals indicating the precise location of the individual rays along scan lines on the member. The digital plate maker system further includes an electronic system which generates electrical signals to form the 22 individual rays. The text data is used to modulate signals produced by the graphics data, the result of the modulation being the beam control signals used to form the 22 individual rays. The digital plate maker system further includes a toning system which provides a vertical meniscus which is essentially stationary with the electrophotographic member as the electrophotographic member is rotated past the toning station.

References made hereinafter to a co-pending application Ser. No. 11,320 
filed Feb. 13, 1979 and entitled "DIGITAL LASER PLATE MAKER AND METHOD", 
the applicant being Lysle D. Cahill. 
References also made herein to a U.S. Pat. No. 4,025,339 issued on May 24, 
1979 to Manfred R. Kuehnle. 
Both the application and the patent above identified are owned by the 
Assignee of the application herein. 
FIELD AND BACKGROUND OF THE INVENTION 
The field of the invention comprises apparatus and a method for imaging 
electrophotographic members by means of radiant energy devices such as 
lasers, the imaged electrophotographic members being thereafter used for 
printing. In the case of lithographic offset printing, the actual imaged 
member itself is treated to render toned and untoned parts hydrophobic and 
hydrophilic respectively and the member comprises the plate without 
further processing. In other cases, the toned electrophotographic member 
may be used as an information source by reading the images or projecting 
them if transparent or photographically reproducing them if desired. The 
preferred use of the invention is to make the printing plates upon metal 
such as stainless steel. Each of these substrates is coated with a type of 
photoconductive coating which will be described hereinbelow. 
In the printing industry, printing plates for printing both graphics and 
text have in the past been produced manually with the graphics images 
being reproduced using the so-called half tone process. In this process 
several photographic steps are used to reproduce the graphics image in an 
array of dots of varying size to reproduce the image on the printing 
plate. Text information has in the past been hand set, but now may be set 
by machine under control of electronic devices. 
Forming printing plates carrying both graphics and text images may involve 
several steps, especially when color graphics are to be reproduced. In 
such a case, several color separation plates must be made for each color 
to be printed with the text information located on the plate in which 
color is to be printed. When text information is to be located within the 
field of the graphics image, additional steps are required to form the 
solid printing areas for the plates in that particular color and to remove 
the graphics image from those same text areas on the remainder of the 
color separation plates. This of course adds to the number of processed 
steps required to produce the desired graphics and text images. The steps 
of forming the graphics image to be printed in the graphics field is 
commonly known as overburning while the process of removing the graphics 
image from those same text areas in the other color separation plates to 
be printed is referred to or is commonly known as stripping. 
In overburning, the negatives which form the graphics image and the text 
image to be formed in that field are overlayed one on another to form the 
desired color separation printing plate. In stripping, other techniques 
must be used to remove the graphics information from those same text image 
areas. 
The process of forming printing plates containing both graphics and text 
data recently has been effected using essentially the same methods as were 
performed manually. Advanced systems however are able to compile from 
various input devices data which may be used to form both graphics and 
text information on a printing plate. But these systems have their 
drawbacks in that separate scanning cycles must be performed to form the 
graphics and text images on a single printing plate and in addition, 
complex switching circuits must be constructed to switch between text and 
graphics image formation when text images are to be formed within the 
field of a graphics image. 
The apparatus and method of the present invention overcome these drawbacks 
presented by the manual and electronics systems by providing a system 
which in one pass of a beam of radiant energy may form both graphics and 
text images in response to graphics and text data input thereto. Formation 
of the graphics and text images may occur independently of one another so 
that different imaging schemes may be used to form scaled densities of the 
graphics images and the binary densities of the text images. 
Formatting of the data is such that the graphics data contains information 
related to the relative scale densities of incremental areas of the 
graphics image with the remainder of the graphics data being a nullity to 
clear the surface of a charged electrophotographic member. The text data 
is formated such that it does not affect the formation of the images 
carried by the graphics data except in locations where text images are to 
be formed. 
Formation of text images within the field of graphics images for several 
different color separation plates is performed simply by reversing the 
logical sense of a control bit of every text data digital word. Thus to 
produce text images of one color such as blue a multicolor printed 
graphics image, the same data may be used for all of the color separation 
plates with the control bit for the color separation plate used to print 
the color blue set to one logical state and being set to the other logical 
state for the remainder of the separation plates. 
Thus the apparatus and method of the invention provide for imaging of an 
entire printing plate with graphics and text information in a single pass 
of a beam of radiant energy. 
The apparatus and method of the invention include an optical system in 
which a beam of radiant energy from a monochromatic source such as a laser 
is used to selectively discharge and leave charged incremental areas of a 
charged electrophotographic member. Part of the beam is split and used as 
a reference beam. The remainder of the beam is modulated to provide a 
scanning beam or a fine beam comprised of individual rays of radiant 
energy with each ray able to discharge an incremental of the member. The 
reference beam and scanning beam or fine beam are aligned vertically with 
one another with the vertical alignment being used in an optical grating 
system to precisely determine the location of the scanning beam along the 
surface of the member. A field flattening lens is used in which both the 
reference and fine beams passed therethrough and back again to the member, 
the field flattening lens providing the maintenance of a focused image on 
the surface of the member across every scan line. 
A common technique to determine the instantaneous position of the scanning 
beam along a scan line of the member is to employ an optical scale or 
grating composed of alternate bars or spaces of opaque and transparent or 
reflecting surfaces or areas. These alternating spaces occur at intervals 
equal to the spacing between elements on the member to provide electrical 
signals indicating the alignment of the scanning beam with the elements. 
Light passing through or being reflected from such a grating is detected 
with a photosensitive device which converts the energy into electrical 
pulses. 
Over relatively short scan widths, say 10" or so, the problem of accurately 
gathering or collecting light pulses from an optical scale and directing 
them to the photosensor is readily accomplished with relatively simple 
optics. In much greater scan widths however the cost of collecting optics 
rises exponentially and quickly reaches prohibitive levels. The acting 
apparatus of the invention herein has an active scan length of 24". The 
cost of conventional optics for collecting a reference beam across such a 
length and establishing a beam feed-back within 1/300" accuracy is 
prohibited. 
The concept of using a glass rod or fiber in such a grating collection 
system is known. The principle used to eliminate the fiber along its 
cylindrical surface to collect the intercepted energy and detect the 
intercepted energy as it exits the rod at either end thereof. Original 
results with a short piece 3/8 inches diameter glass provided poor 
results, it being believed that most of the energy was transmitted through 
the diameter of the rod so that the light output at either end of the rod 
was too low to be of use. 
The concept of using a hollow metal tube with a high reflective interior 
surface to include transmissive losses also was investigated. The tube 
used had a very narrow length-wise slit to prevent entrance of the radiant 
energy reference beam, and a photosensor was mounted at one end with a 
mirror located at the other to reinforce the refected energy levels. It 
was believed that the reference beam would strike the rear internal 
surface of the tube and give rise to multiple reflections which would 
propagate along the tube and result in a useful output level at the end 
mounted sensor. The optical surface smoothness on the interior was 
difficult to control and in turn satisfactory reflections and 
distributions were not obtained. At a consequencey thereof, signal levels 
obtained from the hollow metal tube vary greatly as a function of the beam 
position from the sensor along the scan length. Automatic gain and 
compensation techniques were implemented to modulate the electronic signal 
from the sensor, but none of these proved successful. In reevaluating the 
glass fiber technique, it was believed that if the transmissive losses of 
energy could be prevented by containing the light within the fiber as 
within the hollow tube, the rod collecting/scheme might succeed. 
A 1 3/4 inch rod was used because the internal diameter of the existing 
hollow tube was about 2 inches and this would faciliate concentric 
mounting of the rod within the tube, and would further minimize further 
energy losses by decreasing the concentric area. Essentially the glass 
fiber rod was mounted within the length of the tube. Initial tests met 
with little success until a strip of masking tape was attached to the far 
side of the rod opposite the beam entry point. Increased energy level from 
the non-reflecting surface of the tape was immediately recognized to be 
the result of eliminately the air-gap index of refraction (a high loss 
component) while containing and reflecting the entrapped energy. It was 
quickly determined that highly reflective material such as a typewriter 
corrector fluid applied to rod's cylindrical surface would be highly 
efficient in preventing the transmissive loss and aid in providing good 
Lambertian distributions. It was later determined that it was not 
necessary to coat the entire surface of the cylinder or rod. A narrow 
stripe of about 1/4 of an inch wide along the rod proved to be more than 
adequate. Test results for rods of 0.78", 1.0", 1.5" and 1.75" indicated 
that test results for the bar collector used in the present invention 
would be obtained with a bar diameter somewhere between 1.5" and 1.75". 
Two prior art patents which disclose using a bar collector in an optical 
scanning or sensing apparatus are U.S. Pat. Nos. 4,040,748 and 4,040,745. 
These patents however do not appear to disclose the use of a bar collector 
over the length required by the invention herein. 
The apparatus and method of the invention further include an electronic 
system which performs the graphics and text imaging process of the 
invention. As has been explained, this method of the invention provides 
for the intermixed formation of graphics and text images on the 
electrophotographic member in one sweep o pass of the imaging beam of 
radiant energy. To allow formation of the graphics images with a processed 
desired, the electronics provided are such that formation of the graphics 
and text images occur independently of one another. That is to say, that 
unless there is text image to be formed in a particular location on the 
charged member, formation of the graphics image occurs independently of 
the text. 
Electrophotographic member used with the apparatus and method of the 
invention allows the incremental areas to be imaged which are finer than 
that presently available and allows those elements to be formed at a more 
rapid rate and with less energy than as previously been provided for. This 
electrophotographic coating will be further referred to hereinafter. 
The apparatus and method of the invention further include a toning system 
which applies minute toning particles to the areas of the latent image, 
which remain charged. This toning system provides an essentially vertical 
meniscus closely adjacent the plane at which imaging of the member occurs 
so that there is a minimal loss of voltage representing the latent image 
on the electrophotographic member from imaging to toning. Toning systems 
are known in which toning fluid is applied to the bottom of a rotating 
drum carrying the electrophotographic member wherein the distance from the 
imaging to the toning is minimal. In the apparatus of the present 
invention however, a large drum is used which rotates relatively slowly so 
that if a toning system were used which is located at the bottom of the 
drum, essentially all of the latent image would become discharged by the 
time the member was rotated to the toning station. Therefore, the toning 
station must be located closely adjacent the plane in which imaging 
occurs, which requires that toning fluid be applied in a layer which is 
essentially vertical. 
This vertical layer or meniscus is provided by used a supply system or 
pressure system sealed to the atmosphere, allowing toning fluid to escape 
from the pressure as the layer or meniscus of toning fluid and controlling 
the rate of escape of the toning fluid by a valve admitting atmosphere to 
the otherwise sealed pressure system so that the rate of flow of the 
toning fluid is essentially equal to the movement of the member past the 
toning station, and there is provided a vertical meniscus of toning fluid 
which is essentially stationary relative to the member. 
SUMMARY OF THE INVENTION 
A digital plate maker system and apparatus which receives binary digital 
graphics and text data to form a toned latent image on electrophotographic 
member, the toned image thereafter being fused to the member and the 
member being used as a printing plate in an offset lithographic printing 
press. The plate maker system including an optical system, an electronics 
system and a toning system. 
The optical system providing 22 individual rays of radiant energy with 
which to discharge incremental areas of the electrophotographic member. 
The optical system further providing field flattening to maintain a 
focused image of the individual rays across every scan line across the 
original image. An optical scale or grating system is provided which 
receives a reference beam of radiant energy vertically aligned with a fine 
beam which may be comprised of the 22 individual rays, the bar collector 
receiving the reference beam across the length of every scan line. The bar 
collector directs the radiant energy from the reference beam to a sensor 
which provides electrical signals indicating the position of the fine beam 
along the scan line. 
A method of forming the text and graphics images on the member is 
implemented in electronic system. The graphic data is used to generate 
beam modulation signals to form the desired number of individual rays. The 
text data is used to modulate the beam modulation signals so that text 
images may be overlayed on graphic images or formed outside of fields of 
graphics images. 
A toning system is used in the digital platemaker system to tone the latent 
images. The vertical meniscus, which as it flows is essentially stationary 
relative to the movement of the imaged electrophotographic member as it 
passes a toning station.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
In the preferred embodiment, the imaging device receives digital data 
representing the graphics and text images to be printed or otherwise 
reproduced. This digital data is received from a compiling system which 
obtains raw data from such as optical scanning system, text input 
stations, etc., and compiles or formats the data representing the graphics 
and text materials into a form which may be used by the imaging device of 
the invention herein. The data received by the imaging device also may be 
generated or synthesized by a computer or by other means and may be 
presented to the imaging device from a memory in which it has been stored 
or it may be presented on line as it is generated or synthesized if the 
generation or sythesization rate if equal to or less than the imaging rate 
of an imaging device herein. 
The output of the imaging device herein is an electrophotographic member 
carrying a toned latent image of charged and discharged incremental areas 
formed in response to the digital data. The toned member thereafter may be 
fused and processed for use as a printing plate in an offset lithographic 
printing press with the toned areas carrying ink to a receptor to form the 
tonal graphics and text images. If color printing is desired, as many 
electrophotographic members carrying toned latent images are formed, as 
there are colors which are desired to be printed, one member carrying a 
toned latent image for each of what is commonly known as a color 
separation. 
The imaging device or imager used in the preferred embodiment of this 
invention uses a lazer beam to image an electrophotographic member that 
includes a photoconductive coating that previously has been charged. The 
member is carried on a rotary drum, is toned on the drum and thereafter 
may be used to transfer the toned image or to servce as a medium for 
projection or printing of the image. In the case of printing, the toned 
image is used to carry ink in a printing press, the member having been 
treated to achieve hydrophilic and hydrophobic areas to enable offset 
lithographic use of member as a printing plate. 
The preferred use of the imaged member herein is as a printing plate and 
has the same type of photoconductive imagable coating is preferably the 
receptor of the lazar beams which comprise the output from the apparatus 
of the invention. Such coating is that which is described and claimed in 
U.S. Pat. No. 4,025,339. 
The apparatus and method of the invention may best be understood by 
considering that the binary digital data input to the apparatus is used to 
binarily modulate a beam of radiant energy from a lazar to selectively 
discharge and leave changed incremental areas of a charged 
electrophotographic member. Thereafter, the selectively charged and 
discharged pattern or image carried on the member is toned and output from 
the apparatus. 
The electrophotographic member is carried on the outer circumference of a 
drum which is rotated along its longitudinal axis. Charging, imaging and 
toning of the member on the drum occurs sequentially at adjacent stations 
as the member is moved past the stations by the rotating drum. Charging of 
the electrophotographic member may be of any means desired and in the 
preferred embodiment occurs by placing adjacent the outer circumference of 
the drum a wire having a high voltage applied thereto. Toning of the 
imaged member occurs by applying to the member a quantity of carrier fluid 
obtaining toner particles. The charging and toning occurring at stations 
respectively above and below an imaging plane. Imaging of the charged 
electrophotographic member occurs by passing a fine beam of radiant energy 
from a lazer across the surface of the member in image lines which are 
parallel to the longitudinal axis of the drum and lie in the imaging 
plane. Imaging of the entire surface of the charged member occurs in 
sequential image lines as the member is moved by the drum past the imaging 
plane. 
The digital input to the imaging apparatus is in the form of two channels 
of graphics data and one channel of text data. Each digital word of the 
graphics data is used to form a picture element or a graphics pixel on the 
electrophotographic member. Every imaging line is comprised of two scan 
lines of graphics pixels with each channel of graphic's data respectively 
controlling the forming of graphics pixels in one scan line. 
The text data controls the formation of text pixels across the entire scan 
line and therefore only one channel of text data is required. Every word 
of the text data is comprised of 8-bits of information with the least 
significant six bits each controlling the binary density of a text pixel, 
the next least significant bit serving as a control bit, and the most 
significant bit not being used. 
The graphics data and text data are formated such that they may 
individually form respective graphics or text images across the entire 
area of the electrophotographic member. The electronics of the invention 
herein uses both text and graphics data to form one channel of laser 
modulation signals. Further, in the imaging apparatus herein, the 
information carried by the text data is used to gate the formation of the 
individual rays of the fine beam of radiant energy, each of which rays are 
used to discharge an incremental area on the charged electrophotographic 
member. Simply stated, it may be thought of that the text data is used to 
gate or modulate the formation of graphics pixels in response to the 
graphic data. Thus if the text data is a nullity, no text images are to be 
formed on the member, the information carried by the graphics data will 
form the graphic image represented thereby and discharge the remaineder of 
the member. 
Where the text data contains information representing a text image to be 
formed on the member, the text data may either inhibit the formation of 
individual rays of the fine beam or depending on the logical state of the 
control bit included in each word of text data. When the text data 
inhibits the formation of individual rays of the fine beam, the text image 
is formed on the member which will be toned and in the printing plate will 
carry ink to the receptor to print a solid image. This is a case where 
black text is desired on any background. When the text data forms 
individual rays of the fine beam, text pixels are discharged on the member 
with the discharged areas of the member forming areas of the printing 
plate which do not print on the receptor or which remain clear. This is 
the case where clear text is desired within a graphics image. Within the 
preferred embodiment of the invention, the text pixels are nine times more 
numerous than the graphics pixels, i.e., for every graphics pixel, there 
are nine text pixels which may be discharged or left charged. The 
resolution provided by the text pixels is not however nine times the 
resolution provided by the graphics pixels because of overlap of the text 
pixels. Of course it will be understood that the electrophotgraphic member 
is not physically divided into pixels of any type, scan lines or image 
lines, and that these terms are used only to describe the operation of the 
imaging apparatus and method. 
Referring now to FIG. 1 of the drawings, the apparatus of the invention 
there is illustrated diagrammatically is indicated generally by the 
reference character 30. Two channels of graphics data are received by the 
apparatus respectively on channel A and channel B graphics data buffers 32 
and 34. Text data is received into text data buffer 36. The graphics data 
contained in data buffers 32 and 34 individually are applied to pattern 
generators 38 and 40 over leads 42 and 44. In pattern generators 38 and 
40, the density information carried by the digital words of the graphics 
data are converted into patterns of elements which are to be formed in 
graphics pixels on the member, the pixel patterns representing the 
densities indicated by the graphics data. The pattern information produced 
by pattern generators 38 and 40 then is applied to modulator 46 on leads 
48 and 50 together with the text data from text data buffer 36 on lead 52. 
In modulator 46, the text data is used to modulate the pattern information 
from pattern generators 38 and 40. The output of modulator 46 which is 
applied to acousto-optic modulator 54 is the ray data which controls the 
formation of individual rays in the fine beam. The output of modulator 46 
is carried to the acousto-optic modulator 54 on lead 56. A radiant energy 
source 58 is provided which produces a beam of radiant energy 60 which 
essentially at one wave length and which is directed to acousto-optic 
modulator 54. Radiant energy source 58 is in the preferred embodiment a 
lazar with the wave length of the beam of radiant energy 60 being chosen 
to most advantageously discharge area of the electrophotographic member. 
Acousto-optic modulator 54 modulates the beam of radiant energy 60 to 
provide a fine beam 62 of radiant energy comprised of a plurality of 
individual rays and in some cases as little as a single ray. 
The fine beam 62 is directed onto an electrophotographic member 64 carried 
on a drum 66 rotating in the direction indicated by arrow 68. The 
thickness of member 64 is exagerated in FIG. 1 only so that member 64 may 
easily be seen on the circumference of drum 66. Charging of member 64 
occurs at charging station 70 prior to the time at which fine beam 62 is 
applied to member 64 and toning of member 64 occurs after imaging by fine 
beam 62 at station 72. 
It should be pointed out that while the preferred purpose of the invention 
is to make offset lithographic plates by electrostatic techniques 
described herein, any use of an electrophotographic member will find 
advantages where a member has been imaged according to the invention. 
It will be appreciated that in forming several different color separation 
plates, it may be desired to form text images of a single color (for 
example blue text) in a field of a graphic image or otherwise. Thus in the 
blue printing separation plate, the text image must be found solid. On the 
other color separation plates that same area must be cleared so that only 
the color blue will be printed therein or the recepta. Thus by selectively 
using the solid forming and clearing capabilities of the text data, one 
may form the solid printing blue text image in the field of graphics or 
otherwise as may be desired. 
Turning now to FIGS. 2 and 3, the preferred embodiment of the digital plate 
maker is illustrated including some of the cabinetry provided therewith. 
The apparatus 30 includes an optical cabinet 80 which encloses a left-hand 
optical system 82 and a right hand optical system 84. Drum 66 extends the 
width of the left-hand and right-hand optical systems 82 and 84 so that an 
electrophotographic member carried thereon may be simultaneously and 
separately imaged by respective optical systems. Drum 66 is supported at 
each end by supports 86 and 88 and is rotationally driven by motor 90. As 
shown in FIG. 2, the drum is enclosed by a housing 92, which protects a 
member carried on drum 66 from ambient light. Optical cabinet 80 and 
housing 92 adjoin each other there being only a small slit opening between 
them through which the fine beam passes on its way to the charged 
electrophotographic member. 
The electrophotographic member is held on drum 66 by a magnetic chuck which 
is formed of magnetic strips extending the length of drum 66 at the 
circumference thereof. The magnetic field produced by these magnetic 
strips is strong enough so that an electrophotographic member having a 
substrate of such as stainless steel will be securely held on the drum. In 
the preferred embodiment, the drum circumference is 1250 mm. while the 
drum length is 1, 100 mm. The drum is continuously rotated at a speed of 
0.125 RPM which corresponds to 180 revolutions per day or 8 minutes per 
revolution. This provides a drum speed of 2.6 mm per second. 
The center line of the charging station 70 is arranged to be 25 degrees 
above the image plane, while the center line of the toning station 72 is 
arranged to be 30 degrees below the imaging plane. 
The maximum size electrophotographic member which may be carried by the 
drum 66 is a member which is 1.040 by 1.040 mm and the area of the member 
which may be imaged by each of the left and right hand optical systems is 
50 cm. axial of the drum by 70 cm. circumferential of the drum or an area 
which is 20.times.28 inches. 
A cabinet 94 is provided in which the toning tanks and pumps are contained 
with the hydraulic and nomadic connections between cabinet 94 and toning 
station 72 (not shown in the drawings for clarity purposes.) Mounted on 
the exterior of cabinet 80 are two lazers 96 and 98, which provide the 
radiant energy respectively to the left-hand and right-hand optical 
systems 82 and 84. The entire apparatus 30 is supported by a frame 100 
having the general configuration of a table. Auxillary equipment for 
operating the apparatus 30 such as power supplies for the lazers 96 and 98 
serve or control electronics for the motor 90 and auxillary tanks for the 
toning system may be be mounted under frame 100, and are not shown in FIG. 
2 for clarity of the drawing. 
As may be seen in FIG. 3, the left-hand and right-hand optical systems 82 
and 84, are mirror images of one another so that a description of one is a 
description of the other. Referring also to FIGS. 4, 5 , 6 and 7, lazer 96 
provided the beam of radiant energy 60 to special filter 110 which 
provides what may be termed a pinhole aperture to obtain a desired 
cross-sectional size of the beam. The beam 60 is transmitted through 
spatial filter 110 to folding mirror 112 which deflects beam 60 to beam 
splitter 114. A portion of beam 60 is transmitted through beam splitter 
114 and forms a reference beam 118 which is deflected by folding mirror 
120 and 122 to a spot forming lens 124. The portion of beam 60 which is 
deflected by beam splitter 114 is directed to acousto-optic deflector 54 
which forms of beam 60 the individual rays which have been refered to as 
the fine beam 62. Fine beam 62 exits acousto-optic deflector 54 and passes 
through spot forming lens 126 and passes under folding mirror 128. 
Reference beam 118 passes through spot forming lens 124 as deflected by 
folding mirror 128. After fine beam 62 passes under folding mirror 128, 
fine beam 62 and reference beam 118 are vertically aligned with one 
another through the remainder of the optical path. Referring to FIG. 5, 
reference beam 118 which is transmitted through beam splitter 114 is 
represented by a crossed line indicating the light in reference beam 118 
is exiting the drawing figure. Folding mirror 128 also is shown in FIG. 5 
located above fine beam 62 after it passes through spot forming lens 126 
and the circle at the center of folding mirror 128 representing that 
reference beam 118 is directed into drawing FIG. 5. Fine beam 62 and 
reference beam 118 then are deflected by folding mirror 130 with the 
crossed lines in FIG. 5 on folding mirror 130 indicating the light is 
exiting from the drawing figure while the circles on folding mirror 130 on 
FIG. 6 indicate that the light is entering the drawing figure. 
Fine beam 62 and reference beam 118 then are passed through a relay lens 
132 to a folding mirror 134. Again the crossed lines on folding mirror 134 
on FIG. 6 representing that the beams are exiting the drawing figure. As 
also is shown in FIG. 7, beams 62 and 118 are deflected by folding mirror 
134 through an f.theta. lens system 136 to a galvanometer mirror 138. 
Galvanometer mirror 138 is rotatably oscillated in the directions 
indicated by arrow 142 and directs fine beam 62 back through the f.theta. 
lens system 136 through an aperture 144 extending through the front plate 
146 of cabinet 80 and then onto the charged electrophotographic member 64. 
Reference beam 118 is deflected by galvanometer mirror 138 back through 
f.theta. lens system 136 and onto a folding mirror 148 to an optical scale 
or grating system 150. 
It will be noted that the deflection of fine beam 62 and reference beam 118 
in horizontal directions by galvanometer mirror 138 does not disturb the 
vertical alignment of these two beams so that the position of reference 
beam 118 may be sensed by the optical scale or grating system and 
precisely locate the position of fine beam 62 which is used to image or 
write the images on the electrophotographic member 64. Galvanometer mirror 
138 deflects fine beam 62 through a scan line 152 illustrated in FIG. 6 
and deflects reference beam 118 along a scan line 154 lying on deflecting 
mirror 148. The extent to which the galvanometer mirror deflects fine beam 
62 and reference beam 118 are represented in FIG. 4 by dashed lines 156. 
It will be noted that as illustrated in FIGS. 6 and 7, fine beam 62 and 
reference beam 118 are located below the imaging plane defined by fine 
beam 62 as it passes through aperture 144 and is directed onto 
electrophotographic member 64. The F.theta. lens lens system 136 provides 
field flattening for both fine beam 62 and reference beam 118 so that they 
may be maintained in focus respectively across the surface of the 
electrophotographic member 64 and across the surface of the optical scale 
or grating system 150. It will be noted that the distance travelled by 
fine beam 62 along an optical path from spot focusing lens 126 to member 
64 is equal to the distance travelled along the optical path by reference 
beam 118 from spot forming lens 124 to optical scale or grating system 
150. 
The spacial filter or folding mirrors, beam splitters, spot forming lenses, 
relay lens and galvanometer mirror are all common optical elements which 
readily may be contructed and arranged in a system as has been described 
as may be desired. 
In the preferred embodiment this spot forming lenses have a focal length of 
26 mm, the relay lens has a focal length of 200 mm and the F.theta. system 
has a focal length of 870 mm. The distance between the spot forming lens 
and the relay lens is 559.2 mm while the distance between the relay lens 
and the F.theta. lens is 1,190 mm. The distance from the F.theta. system 
to the focal plane at the electrophotographic member 64 and the optical 
scale system 150 is of course 870 mm. 
The f.theta. lens system 136 is illustrated in FIG. 8 and comprises 
elements L1 through L4 having surfaces defined by radii R1 through R8 as 
shown. 
The lens of FIG. 8 comprises from the object end a first positive group L1, 
L2 having a concave object side surface; a second positive group L3 having 
a flat object side surface; and a third positive group L4 having a flat 
object side surface and a convex image side surface. 
The lens of FIG. 8 is defined substantially by the data of Table I, as 
scaled to a focal length of 870 mm; 
______________________________________ 
Axial Distance 
LENS Radius Between Surfaces (mm) 
N.sub.d 
V.sub.d 
______________________________________ 
R1 -161.744 
L1 15.00 1.617 
36.6 
R2 .infin. 
6.97 
R3 -216.311 
L2 28.871 1.523 
58.6 
R4 -213.119 
0.20 
R5 -2575.204 
L3 18.06 1.523 
58.6 
R6 -264.288 
0.20 
R7 .infin. 
L4 13.00 1.523 
58.6 
R8 -265.847 
______________________________________ 
The lens disclosed may of course be scaled otherwise as is desired. 
The acousto-optic deflector 54 is capable of separating beam 60 into as 
many as 22 individual rays or beamlets which form fine beam 62. In the 
preferred embodiment as many as 22 individual radio frequency signals may 
be applied to acousto-optic deflector 54 to deflect the 22 individual rays 
each radio frequency signal being capable of deflecting one individual 
ray. Acousto-optical deflector 54 is constructed and arranged so that the 
individual rays which are deflected from beam 60 are aligned vertically in 
fine beam 62 and so that in the focused images formed on the 
electro-photographic member 64 are arranged adjacent and spaced 
equidistant from one another. Thus a radio frequency signal of the first 
frequency will form one individual ray while the next radial frequency 
signal will form an adjacent ray and so on. In the preferred embodiment 
acousto-optic deflector 54 is capable of deflecting 22 individual rays and 
although deflector 54 operates on the principle of acoustically deflecting 
the individual rays other deflection apparatus may be used in place of. 
The optical scale or grating system 150 comprises a grating 160, a bar 
collector 162 carrying a narrow stripe of reflective material 164 on the 
outer surface thereof and a sensor 166 such as a photomultiplier tube. As 
is illustrated in the drawing FIGS. 9 and 10 the optical scale or grating 
system extends the entire length of the scan lines across which fine beam 
62 and reference beam 118 are deflected. In turn grating 160 and bar 
collector 162 extend over this length of the scan lines across which the 
beams may be deflected. 
Grating 160 is an elongate transparent member carrying alternating opaque 
and transparent lines or spaces having a frequency related to the 
frequency of the rows in an imaging line. Grating 160 is arranged so that 
reference beam 118 is deflected across the opaque or transparent areas or 
lines on every imaging line. 
Bar collector 162 is an elongate cylindrical member which extends the 
length of grating 160 and is arranged relative to grating 160 so that when 
reference beam 118 passes through grating 160, reference beam 118 passes 
through the diameter of bar collector 162 to strike transparent material 
164. When reference beam 118 strikes reflective material 164, a lambertion 
distribution of the scattering of reflective light occurs in the bar 
collector 162 and the light so enterning bar collector 162 remains therein 
and is transmitted to the end of bar collector 162 where it is sensed by 
sensor 166. As shown in FIG. 10, the end of bar collector 162 opposite 
sensor 166 carries a mirror thereon or is a mirrored surface to reflect 
light along the length of the collector to the sensor 166. Sensor 166 
provides an analog electrical signal on leads 170 which indicate reference 
beam 118 entering the bar collector 162. 
In the preferred embodiment bar collector 162 has a diameter of 1.75 inches 
and is made of such as acrylic materials although material known under the 
trademark of lucite has provided good results. The narrow stripe of 
reflective material 164 may be any highly reflective material and in the 
preferred embodiment a typewritter correction fluid is used. The length of 
the bar collector 162 is about 24 inches to provide the desired 20 inch 
imaging line plus sufficient length for housekeeping and related needs. 
In evaluating the glass fiber technique used herein for the bar collector 
162 it was discovered by placing a strip of masking tape along the length 
of bar collector 162 opposite the point of entry of reference beam 118 
that a significant increase in the energy transmitted by bar collector 162 
was obtained. The increased energy level from the nonreflecting surface of 
the tape was immediately recognized to be the result of eliminating twice 
the area-gap index of refraction (a high loss component) while containing 
and rereflecting the trapped energy beam. It was quickly determined that a 
highly reflective material such as typewritter correction fluid applied to 
the rod's cylindrical surface would be highly efficient in preventing the 
transmissive loss and aid in providing good lambertion distribution of 
reference beam 118 striking the same. Further investigations showed that 
is was necessary to coat only a stripe of about 1/4 of an inch wide along 
the length of the rod to provide more than adequate energy for the sensor 
166. Best results for 24 inches long rods indicated that the best energy 
response was obtained by using a rod diameter of from 1.5 inches to 1.75 
inches. 
In the preferred embodiment the grating 160 has a three hundred line per 
inch optical scale to provide the signals from sensor 166 to locate the 
position of fine beam 60 along electrophotographic member 64. 
It should be noted that it is important that the sensor 166 not look at the 
entire cross-section of the end of the collector tube 162, but only at a 
smaller area centered around the longitudinal axis of a bar collector 162. 
It also is important that only the single narrow stripe of reflective 
material 164 is on the circumference of the bar and the remainder of the 
circumference of the bar is otherwise clean to maximize the internal 
reflection of light on the bar. The leads 170 from the sensor 166 in the 
preferred embodiment are connected to an automatic gain control amplifier 
to smooth out the signal from the bar collector 162 in response to beam 
118 entering the collector at different distances from the sensor. In the 
preferred embodiment the signal from the automatic amplifier is used in a 
phase locked loop to provide the desired signals indicating the location 
of a fine beam 62 along the imaging lines on the member 64. 
It is important that the reference beam 118 present a focused image across 
the entire length of grating 160 so that the signals provided from sensor 
166 will be well defined. If reference beam presents focused images which 
are off the plane of grating 160, the edges of the pulses generated from 
sensor 166 will not be well defined and the location of fine beam 62 along 
the imaging lines will not be precise. 
As has been stated digital data which is input to the digital platemaker is 
in the form of graphics data and text data. The graphics data is used to 
reproduce graphic images on the electrophotographic member 64 with one 
black and white image or one color separation image being formed on each 
member. 
The graphics data is in the form of binary digital words with the value of 
each word representing a scaled areal density to be formed on an imaging 
area on the member. Each word is used to select a pattern of elements from 
a memory or other storage device which represents the scaled density equal 
to the value of the graphics digital word. 
The patterns selected from the memory are formed on the member by 
discharging and leaving charged elements in an imaging area. The elements 
are arranged equispaced across the surface of the member and are arranged 
in rows and columns. Selective elements in the imaging areas are used to 
form the patterns and in the preferred embodiment are grouped together in 
irregular hexagonal picture elements or pixels. It should be remembered 
that the configuration of the pixels is a choice of the designer the 
imaging areas in which the configurations may be formed being of a 
predetermined number of rows and of a predetermined number of columns. One 
pattern then may be formed in one pixel. 
The columns at which the elements are located are defined by the lines 
which would be formed by the individual rays or beamlets of the fine beam 
62 as they are passed across an imaging line. The rows of the imaging 
lines are defined by sample clock signals produced from the grating system 
150. 
The imaging lines are comprised of two scan lines of graphics pixels with 
each scan line of graphics pixels being controlled by one graphics data 
channel. Thus graphics channel a controls the graphics pixels to be formed 
in scan line A, and the graphics data in channel B controls the graphics 
pixels to be formed in scan line B. 
It bears repeating that if the text data contains no information to be 
formed on the electrophotographic member 64, the graphics data is formated 
so that the graphics image or images contained therein will be formed on 
the member 64 while the remainder of the surface of light 64 will be 
discharged. Thus the printing plate formed by such graphics and text data 
will print on the receptor only the graphics image or images and leave a 
clear background. 
The text data is used to reproduce text images and line graphics such as 
charts and graphs on member 64. While the graphics data provides for the 
scale density of the imaging areas to be formed on member 64, the text 
data is used to provide binary imaging of image areas of the member 64 
which in the preferred embodiment are the same as text pixels. 
In the preferred embodiment the text pixels have a definite relationship to 
the graphics pixels. 
In every imaging line the text pixels are aligned six abreast with the text 
pixels being two rows wide. Specifically, what may be called the first 
text pixel or scan line covers the area defined by the first four columns 
of individual rays by two rows deep. The next test pixel is three columns 
wide by the same two rows deep. The next two test pixels are each four 
columns wide and the same two rows deep. The next test pixel is three 
columns wide and the same two rows deep, and the last test pixel is four 
columns wide by the same two rows deep. Thus it may be said that the text 
pixels are arranged across the imaging line at every two rows. Every word 
of the text data represents the binary imaging to be formed in test pixels 
formed along the same two rows of the image line. For each of the six test 
pixels in those two rows, there are four possible states of conditions. 
The first two states are defined as being the normal states, the first of 
which will inhibit the formation of rays of fine beam 62 to be charged 
areas of the member 62. These charged areas will form solid printing which 
will print such as black ink on a white background. The second condition 
is to enable the formation of individual rays of fine beam 62 as 
determined by the graphics data for that row. The last two states are 
defined as being the reverse mode, the first condition of the reverse 
causes a formation of rays of fine beam 62 to discharge areas of the 
member 64. These discharged areas will then form text images in areas 
otherwise formed of graphics images to provide printing plates which print 
clear text in graphics images. The last state of the reverse mode enables 
the formation of rays under control of the graphics data. 
These four states are formed of the binary combination of a control bit and 
one data bit of every word of the text data. Thus as will be explained 
hereinafter, one data bit and one control bit of every word controls 
inhibiting of the formation of rays, enabling of formation of rays by the 
graphics data or causes the formation of rays in every text pixel. 
If the graphics data is a nullity and is used only to clear the entire 
plate, then the information contained in the text data will be able to 
form text images only by inhibiting the formation of rays to leave charged 
areas which will print solid on the receptor. This is the first condition 
under the normal state. It will be noted that text images will not be able 
to be formed by the first condition of the reverse which causes the 
formation of rays because the graphics data is clearing the plate and 
there will be no background against which to form the clear text images. 
If the graphics data is full density for the entire plate no rays will be 
formed anywhere across the plate by the graphics data. In such a case, the 
only text images which may be formed are under the reverse mode first 
condition which causes the formation of the rays to discharge areas in an 
undischarged field to print clear in a field of solid printing area. It 
will be noted that in such a case the first state or condition of the 
normal mode has no effect to create or form a text image by inhibiting the 
formation of rays because there are no rays being formed by the graphics 
data. 
Thus the relationship between the graphics and text data may be described 
as one where the graphics data is able to form graphics images across the 
entire imaging area of the member 64 and depending upon the images so 
formed the text data may form text images. Moreover, the graphics data 
contains enough information to image across the entire imaging area of 
member 64 as does the text data with formation of patterns in the graphics 
pixels and the formation of the text pixels being entirely independent of 
one another. Imaging the graphics then text in this matter has advantages 
in that different imaging schemes for the graphics may be implemented 
without interfering between the relationship between the graphics and text 
imaging. 
Referring now to drawing FIGS. 11, 12 and 13, there is illustrated in FIG. 
11 a chart of three imaging lines which are formed on the 
electrophotoconductive member 64. Imaging lines 1 and 2 illustrate the 
formation of graphics pixels while image line 3 illustrates the formation 
of text pixels. Image lines 1 and 2 each comprise an A-channel scan line 
and a B-channel scan line, there being six thousand (6,000) image 
positions in each of the A-channel and B-channel scan lines with the 
imaging positions in the B-channel scan lines being offset relative to the 
imaging positions in the A-channel scan lines. Thus in each of image lines 
1 and 2, there are 6,000 graphic pixels which may be formed. 
Referring now to FIG. 12, there is depicted a field of graphics pixels 
which may be presumed to be laid out on the surface of the 
electrophotographic member. The pixels are irregular hexagonal areas 
designated GP1, GP2, GP3, GP4 and GP5 inclusive and are parts of an 
overall pattern of hexagons which cover the surface of member 64. 
Obviously the defining lines illustrated in FIGS. 11, 12 and 13 are 
imaginary and merely represent a theoretical geometric pattern which for 
convenience describes the manner in which the imaging is effected. 
The individual rays of fine beam 62 are going to remove charge from the 
graphics pixel respectively. The possibility for removal is represented in 
this case by elements of discharge which are generally circular and which 
count for the entire interior of each graphics pixel. The graphics pixels 
according to the invention are arranged in interleaved columns so that the 
field of pixels may be considered to occupy all of the area. 
Graphics pixels GP1, GP2 and GP3 are shown with their flat sides 
respectively in common at 200 and 202 while the flat sides of graphics 
pixels GP4 and GP5 are in common at 204. The adjoining pixels to the left 
and to the right of these pixels are also arranged in this way but are not 
illustrated. The graphics pixels in adjacent scan lines are interleaved or 
staggered relative to one another; hence, pixels GP4 and GP5 have their 
top apexes at the location of the common flat sides 200 and 202 as 
indicated for example at 206 and 208. This interleaving is illustrated for 
adjoining scan lines in FIG. 11. 
Graphics pixels GP1, GP2, GP4 and GP5 have centering points laid out in 
them which are numbered and which can be seen to be formed at the 
junctures of rows and columns that are marked above and to the left of the 
field of pixels. The columns are defined as imaginary lines described by 
each of the individual rays of fine beam 62 as fine beam 62 is swept 
across each image line. The rows are defined along the image line by the 
optical grating system 150 and occur at equidistant intervals along every 
image line. 
In the preferred embodiment, the image positions illustrated in FIG. 11 are 
defined as having six rows numbered 0-5 and 11 columns. Scan line A is 
formed of columns 1-11 while scan line B is formed of columns 12 through 
22, the column numbers corresponding to the number of individual rays. 
While the graphic pixels GP1 through GP5 in the preferred embodiment have 
been defined as irregular hexagons having the number of elements 
illustrated, the graphics pixels may be defined as having any geometric 
configuration desired which fits the limitations of the six rows and 
eleven columns. As will be described more fully hereinafter concerning the 
electronics, the limitations of six rows and eleven columns is purely one 
of electronics such that by modifying the electronics any number of the 
number of columns and rows may be defined to be an imaged area and in turn 
any geometric configuration desired may be formed therein. 
In the preferred embodiment there are 19 centering points for the elements 
in each graphics pixel and these are arranged in fifteen horizontal 
columns and six vertical rows. The columns are all confined within each 
graphics pixel between its top and bottom apexes. All graphics pixels are 
considered to be oriented exactly the same with their long flat surfaces 
left and right and apexes top and bottom. While the rows are formed 
somewhat differently. Five of the rows will have centering points that are 
within the confines of the graphics pixel between left and right flat 
sides, while the sixth row image will never have centering points located 
thereon is coincident with the left and right flat sides of the graphics 
pixels. This is a spacing expedient to be explained later. 
The centering points which have been described are the centers of the 
circular dischargable or formable elements such as 210 which are going to 
be discharged by the individual rays. As seen the circular element 210 
which is the same as all others is large enough so that in addition to 
covering a certain area within its graphics pixel overlaps into adjoining 
pixel. Thus the circular element 88 not only discharges the area within 
the graphics pixel GP3 which it encompasses but also has a cordal slice or 
segment which it discharges at each of graphics pixels GP6 and GP7 as 
indicated at 212 and 214. 
If we drew a line between each of the centering points vertically and 
diagonally, we would see the overall patterns of general hexagonal area 
which can be seen in the pixels GP1 GP2, GP4, GP5 and of course these 
hexagons have the appearance that they are made up of equilateral 
triangles. Thus the circular discharge elements such as 210 will discharge 
the area around its centering point comprised of the six equilateral 
triangle surrounding that centering point plus six more cordal segments 
beyond that hexagon defined by those triangles. And since every other 
circular element will also discharge the photoconductive surface of the 
electrophotographic member in the same way, the discharged circular 
elements which are side by side always overlap. 
Graphics pixels GP3 has six of the top circular elements shown in outline 
at 216 and there overlapped areas are obvious. In addition, there can be 
seen the 8 overlapped cordal segments of discharge area that protrude into 
adjoining pixels including the pixels GP2 and GP7. For explanatory 
purposes, the total discharged area of any graphics pixel can be 
approximated by the triangles which are included in the circular elements 
discharged. The more circular elements of discharge in a given graphics 
pixel equals the approximation because of the overlap within the graphics 
pixel. In the circular element 210 the equilateral triangles are 
identified as TR1 to TR6 inclusive. It is illustrated in graphics pixels 
GP1 and GP4 that in the horizontal columns there is only one centering 
point in each of columns 1, 11, 12, and 22; two centering points in each 
of columns 2,4,6, 8, 10, 13, 15, 17, 19 and 21; and three points in each 
of columns, 3, 5, 7, 9, 14, 16, 18 and 20. These conditions are 
requirements of the electronics and may be altered by altering the 
electronics as is desired. In the preferred embodiment these conditions 
are requirements of the electronics and must be met during the laying down 
of the discharge elements. 
The fine beam 62 which makes one pass to provide the horizontal column 
information for generation of the centering points for the graphics pixels 
which are being described in an image line will be composed of a maximum 
of 22 individual rays all passing over the total image line at any one 
time. It is assumed that all rays will be used for the graphics pixels in 
an image line but the maximum number of rays or beamlets that will be 
operating at any given time for the configuration illustrated in FIG. 12 
will be 9, because as is illustrated in FIG. 12, there are no more than 9 
centering points along any one row. This is shown in FIG. 12 and graphics 
pixels GP2 and GP4 have scan line A rows 0 and 1 and scan line B rows 4 
and 5. Along scan line A row 0 and scan line B row 4 centering points 1, 
2, 3 and 4 of graphics pixel 2 are defined while centering points 16, 17, 
18, 19 and 20 of graphics pixel 4 are defined. Of course the minimum 
number of rays or beamlets operating will be zero. 
Summarizing then, the horizontal columns of centering points are controlled 
by the number of individual rays in a fine beam 62. The rows are 
controlled by the information that is obtained from the optical grating 
system 150. The row information is used in the beam modulation electronics 
to discharge the desired elements as will be described hereinafter. The 
patterns which are imaged in the graphics pixels in response to the 
density values indicated by the digital words of the graphics data may be 
of any configuration desired to represent the equivalent density and the 
preferred embodiment, there is one predetermined pattern which is to be 
formed in the graphics pixel for every density value indicated by the 
graphics data. 
In the preferred embodiment the distance between the center lines of scan 
line A and scan line B is 169.3 microns while the distance between the 
flat sides of each graphics pixel is 171.7 microns. The diameter at each 
of the discharged elements is 35 microns with all of these values being 
based upon a 150 line per inch resolution. 
It will be noted that as there are 24 individual elements in each graphics 
pixel which may be either charged or discharged there are a total of 
.sup.24 2 or approximately 16 million combinations of discharge elements 
which are available to image the desired density patterns. Thus, even if 
the graphics data may only represent 256 steps of density with 8 bits of 
information per graphics digital word, each step of the 256 step grade 
scale may be represented by a plurality of the 16 million available 
patterns which have density values equal to or approximately equal 
thereto. 
The text pixels which are formed in response to the text data are 
illustrated in FIGS. 11 and 13. As shown in FIG. 11, the image line 3, 
there are six scan lines of text pixels per image line. The text pixels 
are arranged 3 wide for every graphics data scan line and are two rows 
deep. The arrangement of the text pixels relative to the graphics pixels 
and the rows and columns described hereinbefore is illustrated in FIG. 13. 
The text pixels are arranged slightly shifted in relative to the graphics 
pixels, and there are about 9 test pixels per graphics pixels or graphics 
image area. Referring to FIG. 11, along one image line there are 18,002 
test pixel rows with six text pixels per row. The 18.002 rows of text 
pixels results by multiplying the 3,000 graphics pixel per scan line by 3 
rows of test pixels per graphics pixel plus two additional rows of test 
pixels required to cover the area corresponding to the channel B pixels 
which are shifted relative to the channel A pixels. 
The relationship of the test pixels to the graphics pixels in the A channel 
scan line and B channel scan line is illustrated in both FIGS. 11 and 13. 
The relationship of the test pixels to the columns defined by the 
individual rays is illustrated in FIG. 13. 
FIG. 13 illustrates text pixels 1-48 arranged along one image line and 
illustrates in dashed lines the relationship thereto of graphics pixels 
GP1, GP2,GP4 and GP5. The electronics of the digital platemaker system are 
arranged so that each word of the text data received thereby operates on 1 
text pixel row of six abreast text pixels. Thus successive words of the 
text data operate on the rows of text pixels TP1-TP6, TP7-TP12 TP13 
through TP 14, and so on. 
The text pixels are defined as being that area which incloses a certain 
number of discharge elements which are formable by certain rays of the 
fine beam 62 across two successive graphic channel rows. By reference to 
FIG. 12 it will be seen that the rows indicated at the top of FIG. 13 
correspond to the rows indicated at the top of FIG. 12. The areas enclosed 
by the text pixels with reference to the formable discharge elements are 
shown in FIG. 13 where text pixel 31 is formed of the area including the 
elements formed by rays 1, 2, 3 and 4 in the graphics A channel rows 3 and 
4. Text pixel 32 is formed of the area including the elements formed by 
rays 5, 6 and 7 in the same rows 3 and 4. Text pixel 33 is formed of the 
area including the elements formed by rays 8, 9, 10 and 11 in the same 
rows 3 and 4. Text pixel 34 is formed of the area including the elements 
formed by rays 12, 13, 14 and 14 in the same rows three and 4 Text pixel 
35 is formed of the area including the elements which are formed by rays 
16, 17 and 18 in the same rows 3 and 4. And text pixel 36 is formed of the 
area including the elements formed by rays 19, 20, 21 and 22 in the same 
rows 3 and 4. 
Every text pixel of the field of text pixels across the entire imaging area 
of the member 64 of which the text pixel TP1-TP48 illustrated in FIG. 13 
are representative, may be operated on one of four ways as has been 
described hereinbefore. These four ways result from the binary combination 
of one information bit and one control bit of the digital words of the 
text data. These four states or conditions are divided into two modes, the 
normal mode and the reverse mode. In the normal mode the text data may 
inhibit the formation of rays in any text pixel, this inhibiting the 
formation of rays causing to leave the area of that particular text pixel 
charged which will be toned and will print solid upon a receptor. The 
second state of the normal mode is where the text data enables the 
formation of rays under control of the graphics data. The first state of 
the reverse mode causes the formation of rays in the area of a text pixel 
to form a clear text image in a field of a graphics image. On the receptor 
then the text will be clear within the confines of the printed image. The 
second state of the reverse mode is where the text data enables the 
formation of rays under control of the graphics data to produce a graphics 
image represented therein. 
It therefore may readily be seen that the second states of the normal and 
reverse mode simply allow the formation of the graphics image carried by 
the graphics data. That the first state of the normal mode inhibits the 
formation of any rays or discharge elements in the entire area of the text 
pixels, and the first state of the reverse mode causes the formation of 
rays or discharge elements in a text pixel. Thus the member 64 may be 
imaged with text data to obtain a resolution which is three times finer 
than that obtainable using the graphics pixels. Further the text and 
graphics data does not have to be especially formated; nor does the 
electronics have to be constructed or arranged to switch back and forth 
between the text and graphics data. 
In an manner similar to the predefined positions of the discharge elements 
of the graphics pixels, there are predetermined centering points or 
positions for the discharge of elements in the text pixels. It may readily 
be ascertained by viewing FIG. 13 that not all of the formable elements in 
a text pixel may be discharged to clear the total area of a text pixel 
during the first state of the reverse mode, only half of the formable 
elements. 
In fact, it may observed in FIG. 13 that only half of the dischargable 
elements in any one text pixel need by discharged to discharge the entire 
area of that text pixel. This is illustrated in text pixel 43 wherein 
there are four discharged elements represented by the four circles 218. 
Thus it may be ascertained that by discharging the elements whose 
centering points have x or crossed line as is illustrated text pixels 
TP32-TP36 the entire areas of those text pixels may be discharged. Thus it 
may be seen in the reverse mode, in the condition which causes the 
formation of rays to discharge the areas of the text pixels, only every 
other ray need be formed in any one row of dischargable elements, while in 
the next successive row only those elements which were not formed in the 
preceeding row need be formed. Thus in text pixel 31, rays 2 and 4 are 
formed in row 3 while rays 1 and 3 are formed in row 4. Thus to perform 
the reverse mode function which causes the formation of rays to discharge 
elements of the text pixel, the electronics need only form alternating 
rays in alternating rows. The formation of these rays in the reverse mode 
then may be described as text mode odd and text mode even, the odd and 
even referring to the desired rays which are to be formed in the even 
numbered rows and the rays which are to be formed in the odd numbered 
rows. The implementation of this odd and even arrangement will be 
discussed more fully hereinafter in conjunction with the electronics. 
The text data may be used to form solid printing areas such as 
alfanumerics, high receptor and further may be used to print on a receptor 
line graphics such as engineering drawings, charts, graphs, etc. 
There are two sets of electronics or electrical systems for the digital 
platemaker, each electronic system being dedicated and acting in 
conjunction with only the left or right hand optical system. The 
electronics or electronics system is referred to the electronics required 
to receive graphics and text data and apply radio frequency signals to the 
acousto-optic deflector, which discharges incremental areas on the 
electrophotographic member 64. Both electronics systems perform the same 
functions and are identical to each other in all respects so that a 
description of one electronic system is a description of the other 
electronic system, and reference to an electronic system in conjunction 
with the modulation of the lazar beam in a singular refers to electronic 
systems of the left and right hand optical systems. 
The electronics system illustrated in FIG. 1 generally illustrates the 
operation of both the electronic systems while the electronics system 
illustrated in FIG. 14 is a more detailed illustration of the same. 
Data is input to the electronics system on input leads 250, which are 
illustrated with arrows having a width to illustrate that the input data 
is comprised of digital words having several parallel bits conveying the 
desired information. In the preferred embodiment the data is input to 
graphics data buffers 32 and 34 and text data buffers sequentially, that 
is to say that buffer 32 is loaded first, buffer 34 is loaded next and 
then buffer 36 is loaded last. The data contained in each buffer is the 
information or density values required to form graphics pixels along one 
scan line and text pixels across an entire image line. Inputting of the 
data to the buffers 32, 34 and 36 may be under control of such as a 
central controller 252 by way of leads 254. Central controller 252 may be 
interfaced with whatever system that the text and graphics data are 
supplied from and may take form of a hard wired controller of a 
programmable controller as is desired. In the preferred embodiment, 
central controller 252 is a programmable micr processor. 
During an intialization period before the actual text and graphics data are 
input to the digital plate maker the patterns which are selected by the 
graphics data are loaded into the pattern generators 38 and 40 by way of 
input lead 250 under control of central controller 252. In this 
initialization period, data in form of the patterns which are to be loaded 
in the generators 38 and 40 are input into buffers 32 and 34 and carried 
by leads 42 and 44, leads 256 and 258 to the inputs of pattern generators 
38 and 40 indicated by arrow heads 260 and 262. Thus, it may be determined 
that pattern generators 38 and 40 comprise memory devices which may be 
loaded, such devices being called random access memories or RAM. Loading 
of the pattern genrators 38 and 40 is under control of central controller 
252 by way of lead or leads 264. Suitable gating is provided which will be 
described hereinafter so that the graphics data carried by leads 42 and 44 
to pattern generators 38 and 40 will not interfere with the patterns 
output by generators 38 and 40. After the initialization period has been 
completed and all the patterns are loaded into the pattern generators, the 
operational period of the imaging cycle is commenced in which the pattern 
generators become output devices. 
Generation of the patterns is in response to graphics data applied to 
pattern generators 38 and 40 by way of leads 42 and 44. Control of the 
generation of patterns and indication of the location of fine beam 62 
along the scanning line occurs by way of leads 264 from central controller 
252. Central controller 252 is connected to optical grating system 150 by 
way of leads 256. 
The output of pattern generators 38 and 40 are applied on leads 48 and 50 
to beam logic 46 which also has applied thereto the text data over leads 
52. Control of the beam logic including indication of the position of fine 
beam 62 along the scan line is from central controller 252 to beam logic 
46 over leads 268. 
In the beam logic the modulation of the graphics patterns to be formed by 
the individual rows are modulated by the text data as has been described 
hereinbefore with the output of the beam logic on leads 56 comprising the 
radio frequency signals required to produce the image indicated by the 
text and graphics data. Generation of the fine beam 62 and reference beam 
118 is as has been previously described and therefore need not be 
redescribed. It suffices to say that optical path 270 illustrated in FIG. 
14 generally comprises the optical elements between the acousto-optic 
deflector 54 and the electrophotographic member 64. Reference beam 118 is 
diagrammatically illustrated as being part of fine beam 118, after fine 
beam 62 exists the optical path 270. This is shown for illustration 
purposes only. 
Turning now to FIG. 15, the pattern generators 38 and 40 are more 
specifically shown as is the gating required to load pattern generators 38 
and 40 during the initial period. Latching line driver 280 is applied with 
data on leads 256, which in FIG. 15 are represented by single lines for 
clarity of the drawing. During the initial period in which patterns are 
loaded into pattern generator 38, the latching line driver 280 under 
control of leads 282 allows the data on leads 256 to pass therethrough and 
be input by channel A pattern RAM 284 which is placed in the read mode by 
lead 286. In a like manner, data which is supplied on leads 258 are 
applied to latching line driver 286, which during the initial period pass 
the data therethrough and it is input by channel B pattern RAM 288. 
Channel B pattern RAM is placed in the read mode also by lead 286. At the 
end of the initial period and at the commencement of the operation of the 
imaging cycle, latching line drivers 280 and 286 have their outputs placed 
to a tri-state level which places no load on leads 260, 48, 262 and 50. 
Thus in the operational period, the data appearing on leads 48 and 50 will 
be only the outputs of pattern RAMS 284 and 288. 
During the operational period, graphics data is supplied to pattern 
generators 38 and 40 by way of leads 42 and 44. The graphics data is input 
therefrom to channel A latching counter 290 and channel B latching counter 
292, respectively. The input of latching counters 290 and 292 is in the 
form of parallel words having 8 bits of information each. The output of 
latching counters 290 and 292 are 11 bits of information, the 8 most 
significant bits of the output being the same as the graphics data input 
thereto and the three least significant bits being generated in response 
to signals from the optical grating system. Loading of latching counters 
290 and 292 is by way of a load lead 294. 
To understand the selection of the patterns from the pattern RAMs 284 and 
288, it must be understood that the value carried by each graphics data 
word represents a scaled density of an incremental area which is to be 
produced or reproduced on member 64. It further will be remembered as is 
illustrated in FIGS. 12 and 13, the graphics pixels have a pattern 
produced in five sequential rows, the sixth row being used to space 
between graphics pixels. Thus to form one pattern in a graphics pixel, 
information must be applied to the acousto-optic deflector one row at a 
time to form the individual rays or beamlets required to discharge the 
elemental areas and produce the pattern indicated by the pattern RAMS 284 
and 288. In the preferred embodiment, this generation of the patterns 
across the five rows of the graphics pixels occurs by using the value of 
the graphics words to select a group of addresses in the pattern RAMS and 
288. Then a row clock signal produced from the signals produced by the 
optical grating system 150 is used to clock or step through the selected 
group of addresses. The outputs of the pattern RAMS 284 and 288 at each 
step of the group of addresses then are the binary indications of whether 
an individual ray is to be formed or not. Simply stated, the graphics 
words are used to select a group of memory locations while a row clock is 
used to step through the locations. The output of the memory step by step 
is the information needed to turn on or off the individual rays in fine 
beam 62. 
Thus the clocks for latching counters 290 and 292 are applied on leads 296 
and 298. The outputs of the pattern RAMS 284 and 288 are eleven bits of 
information each which are used to form the 22 individual rays. 
The inputs to latching counters 290 and 292 are indicated as graphics data 
bits GD1-GD8. The outputs of latching counters 290 and 292 and the inputs 
to pattern RAMS 284 and 288 respectively are indicated as A-channel 
address leads AA0 through AA10 and B channel address leads BA0 through 
BA10. The output of pattern RAMs 284 and 288 are indicated as being 
pattern bits PB1 through PB11 and PB12 through PB22. 
Concerning the stepping through the groups of memory location, it will be 
observed that three input bits 300 and 302 respectively of latching 
counters 290 and 292 are tied to ground. Thus when counters 290 and 292 
are loaded by way of the signal on lead 294, the outputs AA0 to AA2 and 
BA0 to BA2 are at zero logic levels. Thus when clock signals are applied 
on leads 296 and 298, latching counters 290 and 292 respectively count up 
in binary manner from 0. Referring back to FIGS. 11, 12 and 13, it will be 
noted that the rows are numbered accordingly as binary numbers from 0 to 
5, which correspond respectively to the counts produced at the outputs of 
latching counters 290 and 292. It should further be noted that the rows 
for the A and B channels of graphics data are shifted relative to one 
another to form the desired irregular hexagons having apexes interleaved 
between one another. It therefore should be understood that the clocking 
of the channel A latching counter 290 commences earlier than the clocking 
of the channel B latching counter 292 to provide the patterns from the 
respective RAMS at the proper times. 
The leads 282, 286, 294, 296 and 298 used to control the functions of the 
latching line drivers and pattern generators generally are the leads 264 
indicated earlier in FIG. 14 coming from central controller 252. 
In FIG. 16, there is illustrated in more detail the beam logic 46. In FIG. 
16, pattern bits 1-22 are illustrated as being applied to a 22 bit one of 
four multiplexer 304 on one lead which is indicated as being 48 and 50. 
This is for clarity of the drawing. While multiplexer 304 is indicated as 
being one unit, which is able to select between one of four inputs, in the 
preferred embodiment multiplexer 304 is a plurality of multiplexers which 
may be individually or jointly operated upon. Beam logic 46 further 
comprises three switch arrays 306, 308 and 310, each of which supplies 22 
individual leads of logic signals with each of the logic signals being 
controlled by a resistor switch network such as is illustrated in each 
block representing the switch arrays. Basically the network consists of 
the output lead being tied to a plus-5 volt source through a 1-K resistor, 
there being a programmable switch which may be closed to short the output 
lead to ground. When the switch is open, the logic level of the outputs of 
the switch arrays are at a logic of 1; while when the switches are closed 
the outputs are at logic state zero. 
Array 306 is labelled as being the text reverse even switch array 
indicating that the outputs of this array indicate which of the individual 
rays are to be formed during a reverse mode even row indicated by the text 
data. The array 308 is labelled as being a text reverse odd switch array, 
the label indicating that the outputs of this array indicate the 
individual rays which are to be formed during a reverse mode odd row 
condition indicated by the text data. Array 310 is labelled as being a 
text normal switch array with its outputs indicating the rays which are to 
be inhibited. The outputs of each array, TRE1-TRE22, TRO1-TR022 and 
TN1-TN22 are applied to the inputs multiplexer 304 over leads 306, 308 and 
310 respectively. 
Text data represented by text data bits TD1-TD8 at 312 of FIG. 16 are 
applied through a gating 314 to the A and B select inputs of multiplexer 
304 on leads 316 and 318. Also applied to gating 314 is address lead AA0 
from the A channel latching counter 290. 
The outputs of multiplexer 304 are indicated as being ray data RD1-RD22, 
each output corresponding to the formation of an individual ray of fine 
beam 62 and acousto-optic deflector 54 from beam 60. The outputs of 
multiplexer 304 pass on lead 320 to a 22 bit latch 322, which holds the 
output data in response to a latch signal on lead 324. The output of the 
22 bit latch is applied through leads 326 to 22 individual bit drivers 
328, there being one individual bit driver for each of the output bits RD1 
through RD22. The 22 bit drivers are enabled by a signal on lead 330 and 
provide their outputs by way of leads 332 to 22 RF oscillators 334, there 
being one RF or radio frequency oscillator for each of the signals from 
bit drivers 328 and the outputs of the 22 RF oscillators 334 appearing on 
leads 56 and being applied to acousto-optic deflector 54. 
In operation of the beam logic circuit, instead of there being a straight 
forward gating of the pattern bits PB1-PB22 by the bits of the text data 
TD1-TD8, the bits of the text data are used to select for each of the 
groups of individual rays indicated in FIG. 13 between the four inputs to 
multiplexer 304, pattern bits, reverse mode even bits, reverse mode odd 
bits, and normal mode bits. But to this extent the illustration of 
multiplexer 304 in FIG. 16. as selecting between one of the four inputs 
for all of the ray data bits is somewhat misleading. 
A better illustration of the multiplexing which occurs is illustrated in 
FIG. 18 with FIG. 17 illustrating in chart form which bits of the text 
data are used to modulate the individual rays. In FIG. 18, there is 
illustrated one of four multiplexer 336 having four groups of input bits, 
one group for each of the ray data bits output therefrom. As may be seen 
in FIG. 17, text data 1 is used to operate on or select the proper output 
for rays 1-4. Thus the outputs of one of four multiplexer 336 are 
indicated as being the ray data bits RD1 through RD4, these of course 
being the logic signals which determine whether or not rays 1-4 are formed 
or not. Thus to produce ray data bit R1, multiplexer 336 may select one of 
pattern bit 1, text reverse even bit 1, text reverse odd bit 1 and text 
normal bit 1. Multiplexer 336 may make a light selection for each of ray 
data bits RD2-RD4. It should be remembered that when the ray data bits are 
such as a logic of 1, they indicate that an individual ray should be 
formed in fine beam 62 while when the ray data bits are at a logic of zero 
(0), they indicate that no individual ray should be formed in fine beam 
62. 
Concerning gating 314 which is illustrated more fully in FIG. 18, it should 
be remembered that binary combination of a control bit which is shown in 
FIG. 17 to be the text data bit TD7 and an information bit such as text 
data bit TD1 which are used to select between the four states. Gating 
circuit 314 provides for this in addition for providing for the turning on 
of the desired individual rays during a reverse mode and the even and odd 
rows. 
To this end, it will be noted that a signal which is a logic level 1 
indicating that the beam logic is out of the text mode is applied to 
norgate 340 to lead 342, that the output thereof is a logic of zero (0) 
which is applied to AND gates 344 and 346 on lead 340 respectively. The 
outputs of AND gates 344 and 346 thus may only be a logic of zero (0) 
which would apply to the A and B outputs of multiplexer 336 selects the 
pattern bits to be output as the ray data bits RD1-RD4. The same thing 
occurs when the T1 input to norgate 340 is a logic of 1, indicating that 
the pattern bits generated by the graphics data are to be formed in the 
text pixel or pixels corresponding to rays R1-R4. When the text mode 
signal is a logic of zero (0) and the TD1 is a logic of 0 (zero), then the 
output of Norgate 3-4 is a logic of 1, which enables AND gate 344 and 346 
to provide signal which will select other than the graphics data to be 
formed in text pixels corresponding to rays R1-R4. 
In such a case, if signal TD7 is a logic of 1, indicating a normal mode, 
then the outputs of norgates 350 and 352 also will be a logic of 1, which 
is applied respectively by way of leads 354 and 356 to AND gates 344 and 
346. The outputs of AND gates 344 and 346 then will both be logic of 1, 
which will select as the ray data bits RD1-RD4 the logical levels 
appearing on the signals labelled TN1-TN4 or text normal. The outputs from 
the text normal switch array 310 illustrated in FIG. 16 thus must be 
programmed in logical zeros (0's) so that the formation of individual rays 
R1-R4 is inhibited. It may be stated at this time that switch arrays 
306,308, 310 are provided in the preferred embodiment to provide 
versatility of the apparatus. 
Further in the case where the signals on lead 342 and the logic level of 
bit TD1, the logical zeroes, if the TD7 signal is a logical zero 
indicating the reverse mode, then the outputs of Norgates 350 and 352 will 
be controlled by the logical level input thereto by the A channel address 
bit zero, A--A zero. It will be understood that this signal A--A zero is 
continuously being oscillated between a logic of zero and a logic of 1 
state, as the fine beam 62 is paased across the surface of the 
electrophotographic member 64. Thus when bit TD7 is a logical zero, the 
output of Or gate 350 is directly controlled by the logical level of 
signal A--A zero, while the output of Or gate 52 is the inverse thereof 
due to inverter 358. Thus for an even row, the outputs provided by AND 
gates 344 and 346 will be such that multiplexer 336 outputs as ray data 
bits RD1-RD4 the logical levels appearing at the signals TRE1 through 
TRE4. At an odd number row, logic levels output by multiplexer 336 as ray 
data bits RD1-RD4 will be the logical levels input thereto by signals 
TR01-TR04. 
It will be appreciated that the one of four multiplexer used to form the 
ray data bit RD1-RD4 is an example of the multiplexer circuit used to 
provide the ray data bits for each of the groups of rays illustrated in 
connection with the text pixels of FIG. 13. The gating circuit 314 also is 
the same for each of those multiplexer circuits with only the information 
bit TD1 being changed for the groups of rays to the corresponding text 
data bit. 
After the electro-photographic member 64 has been charged at charging 
station 70 and has been imaged with fine beam 62, the latent image carried 
thereon is toned at toning station 72, which is a portion of the vertical 
toning system of the digital platemaker. 
The vertical toning system may best be understood by considering that its 
purpose is to apply toner (carrier fluid having suspending therein toner 
particles) to the electrophotographic member 64. The areas of member 64 
which remain charged after imaging are the areas which accept the toning 
particles. The toned member thereafter has the toned particles fused to 
the member for use as a printing plate in such as a lithographic printing 
press, but this fusing step occurring otherwise than in the digital 
platemaker. 
The toner which is supplied to the electrophotographic member is in the 
form of a carrier fluid known as "ISO", which is a registered trademark 
of the Exxon Corporation. The carrier fluid carrying finely ground 
particles of resinous material which may be positively or negatively 
charged and in the preferred embodiment herein the particles are 
positively charged. Hereinafter, the term "toner fluid" will refer to this 
carrier fluid containing the resinous toner particles, while the term 
"carrier fluid" will refer only to the "ISO" without the resinous 
particles. 
As has been stated, the member 64 is mounted on drum 66 and is rotated 
thereby past charging station 70, imaging plane represented by the fine 
beam 62 and the toning station 62, at whic the toner fluid is applied to 
the member. 
It will be noted that electrophotographic member 64 comprises a substrate 
carrying a photoconductive coating, the substrate in the preferred 
embodiment being a magnetic material such as stainless steel and the 
electrophotoconductive coating being the coating disclosed and claimed in 
U.S. Pat. No. 4,025,399, which has been incorporated herein by reference. 
The member is held in the drum by magnetic strips embedded at the outer 
circumference of the drum, of course, other hold-down systems such as 
vacuum systems could be used to maintain the member in fixed relationship 
to the outer circumference of the drum. These other systems could further 
include clamps, springs, etc. 
As the member rotates past the toning station 72, there is first applied 
thereto a quantity of carrier fluid which wets the surface of the member 
for purposes which will be described hereinafter. This wetting of the 
surface occurs at what may be called an upper chamber of the toning 
station 72. Thereafter, the toner fluid is applied to the member into 
phases which may be referred to as the initialization phase and the 
operational phase. During the initialization phase, a meniscus of toner 
fluid is established between toning station 72 and member 64, while during 
the operational phase, the meniscus is maintained between the toning 
station 72 and the member. It should be noted, as illustrated in FIG. 1, 
toning station 72 is essentially verticle along the circumference of drum 
66, and thereby the meniscus established between toning station 72 and 
member 64 is essentially vertical. 
Turning now to FIG. 19, there is shown in block diagram form the toning 
system which is indicated generally by the reference character 400. The 
toning station 72 illustrated in the earlier drawings comprises left and 
right hand shoes 402 and 404, respectively. It is the shoes which are used 
to apply the toner fluid to the member 64, and it is between the shoes and 
the member 64 then the vertical meniscus is established and maintained. As 
may be readily understood, the left-hand shoe 402 is used in conjunction 
with the left hand optical system 82, while the right hand shoe 404 is 
used in conjunction with the right hand optical system 84. It will be 
understood that an explanation of the toning system for the right-hand 
optical system is an explanation of the toning system for the left-hand 
optical system, the toning systems for both sides being mere images or 
exactly the same for both sides. Thus FIG. 19 is a block diagram of both 
the left and right hand toning systems, although only one set of elements 
is illustrated. 
During the initialization phase, carrier fluid is supplied from reservoir 
system 406 to the right hand shoe 404 by way of tubing 408 under action of 
pump 410. Pump 410 operates in response to or under control of controller 
412 by way of lead 414. Toner fluid is carried to right hand shoe 404 from 
the pressure system 416 by way of tubing 418 under control of pump 420, 
pump 420 being controlled in turn by controller 412 by leads 422. Excess 
toner fluid is returned to pressure system 416 from right hand shoe 404 by 
way of tubing 424. 
Used toner fluid is carried to sump system 426 by way of tubing 428, sump 
system 426 being at a vacuum or having a vacuum with which to remove the 
used toner fluid from the member. Used toner fluid contained in sump 
system 426 may be returned to the reservoir system 406 by way of tubing 
430 by action of pump 432, pump 432 in turn being controlled by controller 
412 by way of leads 444. 
After the meniscus has been established during the initialization phase, 
valve 436 is used to admit air into pressure system 416 over tubing 438 to 
aid in the maintanance of the meniscus between the shoe 404 and the member 
64. 
It is important that the application of the carrier and toner fluids and 
the operation of the vacuum sump system occur at the proper time intervals 
as the member 64 is rotated past the shoe 404 and to obtain the timing 
information and sensor 440 is coupled to drum 66 and supplies the timing 
information to controller 412 by way of leads 444. 
The toning station 72 is generally illustrated in FIG. 20 wherein left and 
right hand shoes 402 and 404 are carried by backplate 440. The back plate 
440 carries four rollers, 442, two at each end which are in rolling 
contact with drum 66 along surfaces 444. Rollers 442 are adjustable by way 
of a cam mounting to adjust the spacing between shoes 402, 404, and drum 
66. The spacing required between the shoes 402, 404 and drum 66 must be 
sufficient for the electrophotographic members 64 to pass there between 
and there must be additional spacing to provide for the meniscus of toner 
fluid established therebetween. 
Toning station 72 has two positions, one being with the rollers engaged 
against the surfaces 444 of drum 66 during an imaging and toning cycle, 
and the other position being spaced from the drum and at a level below the 
drum in a non-toning position. A neumatic of hydraulic cylinder 446 is 
provided to move the toning station 72 between these two positions and 
further is used to provide the toning station 72 between these two 
positions, and further is used to provide a slight bias to maintain 
rollers 442 in contact with surfaces 444. Rollers 442 are engaged against 
surfaces 444 at the two longitudinal ends of drum 66 so as not to 
interfere with member 64 which is carried on drum 66 therebetween. Of 
course any surfaces as may be desired may be provided upon which the 
rollers of plate 440 may ride. 
Right handshoe 404 has as is illustrated in FIG. 21, is essentially a 
rectangular solid with a surface 446 which is to be placed adjacent the 
drum 66, having a portion 448 which is concave. The radius of this concave 
portion 448 is essentially equal to the radius of the drum 66 so that the 
concave portion 448 may be spaced equidistant from drum 66 across the 
entire area of the concave portion 448. 
A seal member 450 is mounted on shoe 404 at the concave portion 448. This 
seal member 450 generally has the shape of a H with the cross-bar of H 
being biased towards the top of the seal. The seal is made from a 
resilient material such as polyurethane and is mounted into slots 
extending into the shoe. The seal is constructed so that when the shoe 404 
is in the toning position, the edges of the seal 450 extending furthest 
from the shoe are engaged against the outer surface of the 
electrophotographic member 64. 
The cross-bar 452 of the seal 450 separates the concave portion 448 into 
upper and lower portions 454 and 456. In the upper portion 454, clear 
carrier fluid is applied to the member 64 for several reasons. These 
include precoating or wetting the member 64 with this wetting acting as a 
barrier against toner particles which are not charged to reduce fogging of 
the latent image and further provides a lubricant for the seal 450 to 
reduce wear of the seal, improve the sealing characteristics thereof and 
reduce the power which would otherwise be required to be supplied by motor 
90 to drive the drum 66. 
Cross-bar 52 is constructed to provide a wiper blade portion 458 which 
allows only a microscopic coating of the carrier fluid to be applied to 
the member 64 as it passes thereby. Of course, the wiper blade portion 458 
as it is wiped across the member 64 does not disturb the quality or 
characteristics of the latent image carried thereon. It will further be 
appreciated that the carrier fluid also does not affect the quality or 
characteristics of the latent image on member 64. 
The upper portion 454 comprises an upper chamber 460 extending into shoe 
404 and opening to concave surface 448. Supply ports 462 are arranged 
spaced from one another along the inner wall of a upper chamber 460 supply 
carrier fluid transported by tubing 408 from reservoir system 406, which 
is supplied thereto for application to the member 64. A baffle 464 shown 
in FIG. 22 is contained in upper chamber 460 so that carrier fluid from 
ports 462 may be evenly supplied to member 64 across the length of chamber 
460. 
The lower portion 456 of the concave portion 448 is the portion where toner 
fluid is applied to member 64. A lower chamber 466 extends into shoe 404 
and opens to concave portion 448. Chamber 466 extends essentially the 
length of the shoe. It will be noted that the cross-bar 452 essentially is 
the dividing between divides the upper and lower portions 454 and 456. 
Toner fluid is applied to lower chamber 466 by the way of inlet ports 468, 
spaced along the length of chamber 466 with the toner fluid being supplied 
from pressure system 416 by way of tubing 418. A baffle 470 may be 
provided in lower chamber 466 to evenly supply toner fluid to member 64 
from the individual inlet ports 468. 
From lower chamber 466, toner fluid may flow down in the direction 
indicated by arrow 472 along concave portion 448 to vaccuum slot 474. 
At vacuum slot 474, a reduction in atmospheric pressure of vacuum is 
created by sump system 426 by way of tubing 428. This vacuum operates to 
remove toner fluid from both member 64 and shoe 404 as the toner fluid 
flows down along the concave portion 448. From vacuum slot 474, toner 
fluid is carried to sump system 426 by tubing 428. 
It should be noted then there are outlet ports 474 spaced along the length 
of lower chamber 466 and against the inner wall thereof, as is illustrated 
in FIG. 22. These outlet ports 474 provide for return of excess toner 
fluid by way of tubing 424 to pressure system 416. It also should be noted 
that the vacuum provided by sump system 426 may be formed by any means 
desired. 
FIG. 22 generally illustrates the angular relationship between charging 
station 70, the incidence of fine beam 62 on member 64, and the position 
of shoe 404. In the preferred embodiment, the angle between the center 
line of charging station 70 and fine beam 62 is 25.degree.. The angle 
between fine beam 62 and the center line of shoe 404 is 30.degree.. While 
these angles are indicative of the preferred embodiment, it is desired to 
reduce these angles to be as small as possible so that there is a minimum 
time between the charging of the member 64 and the toning of the latent 
image on member 64. 
It may be seen in FIG. 22 that charging station 70 comprises a charging 
wire 480 with a guard 482 forming a three-sided channel which is open 
towards drum towards drum 66. Wire 480 of course extends along the length 
of drum 66 as does guard 482. In the preferred embodiment, wire 480 
carries a negative voltage and cover 482 may be made of conductive 
material and forms an electrostatic mirror. 
Circle 484 along the interface between drum 66 and 244 is shown enlarged in 
FIG. 23 to illustrate the relative positions between drum 66, 
electrophotographic member 64, toner fluid 486 and shoe 404. The relative 
thicknesses of the elements are expanded in FIG. 23 for illustration 
purposes. 
The operation of the toning system may best be understood by considering 
that as has been stated there are phases to its operation. The first phase 
is known as the initial phase, and during this phase, the toner system 
establishes a meniscus of toner fluid between shoe 404 and member 64. 
During the operation phase this meniscus is maintained between member 64 
and shoe 404, and is allowed to flow in the direction indicated by arrow 
472 at a controlled rate essentially equal to the angular rotation of the 
drum. Thus as member 64 is moved past chamber 466, it supplies toner fluid 
to the meniscus. A quantity of toner fluid is applied against member 64 
and remains stationary relative to member 64, until it is removed as 
vacuum slot 474. Thus, there is a minimum amount of sheer between the 
meniscus and member 64 which provides for suitable toning of the latent 
image with the toning particles. 
At this point, it will be discussed how the pre-wetting reduces the fogging 
of the latent image. The toner fluid, as has been said, contains particles 
of resinous material. These particles are very sticky in that they will 
readily adhere to most any surface they are brought into contact. Now when 
the toner fluid is manufactured, these particles are given in this case, a 
positive charge so that they will be attracted only to the areas which 
retain their negative charge from charging station 70. Not all of these 
particles however remain charged by the time they are used in the toning 
system herein. 
When the toning fluid is used in the toning system, the charged particles 
readily are attracted to the oppositely charged areas of the latent image 
carried by member 64. The non-charged particles however are not so 
attracted and will stick to any surface to which they may come into 
contact with. By pre-wetting the surface of member 64, a barrier is formed 
through which these non-charged particles generally will not pass. 
Although this pre-wetting is referred to as a barrier the action which is 
involved is more along the lines of the non-charged particles not passing 
through the pre-wet because there is no force which will drive them 
through the pre-wet. 
During the initial phase of the toning cycle toner fluid is applied to the 
lower chamber 466 and falls essentially by means of gravity into the space 
established between concave portion 448 and member 64. The rate at which 
toner fluid is supplied to chamber 466 is much greater than the rate at 
which toner fluid may flow between concave surface 448 and member 64 with 
excess toner fluid being returned to the pressure system 416 through the 
outlet ports 476 by way of tubing 424. Pressure system 416 is sealed from 
the atmosphere and as toner fluid is removed from the pressure system by 
way of the meniscus which is formed between concave surface 448 and member 
64, a negative pressure is formed in the pressure tank. When this negative 
pressure reaches a magnitude of from two to three inches of water, the 
toner fluid ceases to flow between the concave surface and the member 64. 
Air control valve 436 which is preset to allow a controlled and 
predetermined amount of air into the closed pressure system 416, then 
controls the flow rate of the toner fluid in the meniscus between the 
concave surface 448 and member 64. 
If the air flow control valve 446 were to be closed, the meniscus would 
essentially remain stationary in the vertical position discounting of 
course losses from the lower edge thereof occurring from gravity and from 
the vacuum slot 474. As the air flow control valve 436 is opened, the rate 
of flow of toner fluid through the vertical meniscus increases. The 
establishment of this negative pressure in the pressure system 416 and the 
simultaneous establishment of the meniscus between concave portion 448 and 
member 64 is what has been defined to be the initial phase. Once the 
initial phase is completed, operation of the toning occurs through what 
has been described the operation phase. It should be understood that there 
are not two separate phases which are in operation of the toning system, 
but rather two phases which are used to describe the operation of the 
toning system. 
The rate at which air is allowed into the pressure system 416 through 
control valve 436 is predetermined so that the flow-rate of toner fluid 
therebetween occurs at the same speed as the angular rate of rotation of 
drum 66. Thus the toner fluid flows essentially stationary to the member 
64. As the lower edge of the meniscus approaches the vacuum slot 474, 
toner fluid less the toner particles attracted to the member 64 by the 
latent image is removed from the member 64 with the described atmospheric 
vacuum. 
In summary, the vertical toning system provides a meniscus of toning fluid 
which is essentially vertical and which is essentially stationary relative 
to the movement fo the electrophotographic member 64 to provide toning of 
the latent image on the member 64. Control of the flow of the meniscus 
relative to the member may be easily controlled through a suitable air 
control valve 436 and the toner fluid is applied to member 64 after a 
period of time which is relatively short after imaging of the member has 
occurred. 
It will be noted that clear carrier fluid is indicated in upper chamber 460 
by reference character 490, while toner fluid is indicated in the lower 
chamber 466 by reference character 46. 
In the preferred embodiment, the meniscus has a thickness or the concave 
portion 48 as spaced from member 64 a distance of about 13/1000 of an 
inch. Shoe 404 may be made of any material which is nonreactive to the 
"ISO" carrier fluid, such as aluminum or stainless steel. It further 
should be noted that when the toning station 72 is removed from being 
adjacent drum 66 to the non-toning position, the vacuum which is created 
at vacuum slot 474 is increased to clear off both the shoe and the member. 
It is important that the commencement of the flowing of the carrier fluid 
and toner fluid to the shoe occurs at the proper time in relationship to 
the movement of the member 64 across the shoe 404. If these fluids are 
applied to the shoe too early, they are not contained within the seals 
provided by seal member 450 and may cause a mess while if the fluids are 
applied too late, the seals may stick to the member 64. 
Referring back to the description of the electronics, one method of forming 
the graphic pattern in pattern generators 38 and 40 is described and 
claimed in a copending application Ser. No. 11,320 filed Feb. 13, 1979 and 
entitled DIGITAL LASER PLATEMAKER AND METHOD, the applicant being Lysle D. 
Cahill which application is incorporated herein by reference. 
Referring back to the two toner shoes 402 and 404, it is entirely possible 
that one toning shoe could be used in place of the two shoes. 
Modifications and variations of the present invention are possible in light 
of the above teachings. It is therefore to be understood that within the 
scope of the apended claims the invention may be practiced otherwise than 
is specifically described.