Multiple mode image processing apparatus and method

A multiple mode image processing apparatus and method. The apparatus, in a copy mode, processes copies xerographically. In a write mode, images derived from image signals are written on the apparatus photoreceptor by a raster scanner, and in a read mode, the raster scanner scans images developed on the photoreceptor to produce image signals representative thereof. A multiple speed drive is provided for the photoreceptor to move the photoreceptor at a high speed when processing copies xerographically and at a lower speed compatible with the data transmission rate for image signals when writing or reading images.

The invention relates to a multi-mode reproduction apparatus and method, 
and more particularly to apparatus and method for accommodating 
discrepancies between xerographic processing rates and data transmission 
rates of communication networks without resorting to large scale 
buffering. 
In a reproduction apparatus capable of processing copies both 
xerographically and electronically, a differential often exists between 
the rate at which copies may be processed xerographically and the rate at 
which image signals or data can be transmitted. Typically, in an apparatus 
of this type, a copying mode is provided to permit copying xerographically 
of document originals. In this operational mode, the xerographic 
processing is done at relatively high photoreceptor speeds. 
In another mode, such as an electronic image writing mode, a flying spot 
type scanner may be employed to write the electrostatic latent images on 
the apparatus photoreceptor from image signals input thereto through a 
data transmission link. The source of the image signals may be a memory, 
or a data communication link such as used with facsimile equipment, etc. 
The electrostatic images produced by the scanner are thereafter processed 
xerographically to provide copies of the image represented by the image 
signals. 
Alternately, the scanner may be used to read images developed on the 
photoreceptor and the image signals produced therefrom transmitted to a 
remote site through the data transmission link. 
However, for operations of these latter types, the rate at which image 
signals can be transmitted over a data transmission link is usually much 
less than the rate at which copies can be processed xerographically, 
primarily due to the bandwidth limitations of present day communication 
and storage facilities. Additionally, transmission of image signals may be 
asynchronous rather than synchronous as where the communication system or 
network protocol is packet switched. 
In an effort to accommodate this discrepancy between xerographic processing 
rates and data transmission rates, buffers may be used to buffer the image 
signals on a per page basis when writing or reading images electronically. 
When buffering of a page of image signals is completed, the raster 
scanner, when writing images for example, is actuated to image the 
photoreceptor in accordance with the buffered image signals. The resulting 
electrostatic image is processed xerographically, the scanning and 
xerographic processing taking place at the relatively high photoreceptor 
speed associated with xerographic processing. 
While the above procedure may be feasible, the high cost of buffers having 
the capacity required is a major drawback. 
This invention relates to a method of accommodating differences between the 
rate at which images are processed xerographically and the image signal 
transmission rate of a data transmission system, the image signals being 
transmitted in either synchronous or asynchronous fashion by the data 
transmission system, the steps which comprise: in a xerographic processing 
mode, moving a photoconductive member at a first speed while processing 
images xerographically; in a scan mode, reading the images on the 
photoconductor member as the images are being xerographically processed by 
scanning the photoconductive member to produce image signals 
representative of the images read; while reading the images, moving the 
photoconductive member uninterruptedly or in steps at a second speed 
compatible with the image signal transmission rate whereby the 
photoconductive member acts as a buffer to accommodate the difference 
between the image signal transmission rate and the xerographic processing 
rate; and following reading of the images, returning the photoconductive 
member to the first speed for further xerographic processing of the images 
read. 
The invention further relates to a xerographic type reproduction apparatus 
comprising, in combination: a movable photoconductive member, means for 
producing images on the photoconductive member; image reading means for 
reading the images on the photoconductive member to provide image signals 
representative of the images read; data transmission means for the image 
signals, the data transmission means being adapted to transmit the image 
signals at a predetermined image signal transmission rate; and drive means 
for moving the photoconductive member either continuously or in steps at a 
speed compatible with the predetermined image signal transmission rate.

Referring particularly to FIG. 1 of the drawings, there is shown the 
multi-mode reproduction apparatus 10 of the present invention. As will 
appear, reproduction apparatus 10 is operable selectively in a COPY mode 
(MODE I) to xerographically make copies of original documents in the 
manner typical of xerographic copiers or machines, in a WRITE mode (MODE 
II) to xerographically produce copies from image signals input thereto 
using a flying spot type scanner, and in a READ mode (MODE III) to read 
images developed on the machine photosensitive member with the same flying 
spot scanner to produce image signals representative thereof and thereby 
convert the image to electronic signals. 
Reproduction apparatus 10 includes a viewing station or platen 12 where 
document originals 13 to be copied or converted to image signals are 
placed. For operation particularly in the COPY mode, as will appear more 
fully herein, a light/lens imaging system 11 is provided, the light/lens 
system including one or more exposure lamps 15 for illuminating the 
original 13 on platen 12 and a lens 16 for transmitting image rays 
reflected from the original 13 to an exposure station 21. There, the image 
rays impinge upon a photoconductive surface 19 illustrated herein in the 
form of a photoreceptor drum 18. 
Charging, developing, transfer and cleaning stations 20, 22, 26, 32 
respectively are disposed about the periphery of drum 18 in operative 
relationship thereto. Charging station 20 includes a corona charging means 
23 with power supply 37 therefor (see FIG. 3 also), charging means 23 
depositing a uniform electrostatic charge on the photoconductive surface 
19 when actuated. A suitable developing mechanism, which may for example, 
comprise a magnetic brush type developer roll 25, is provided at 
developing station 22 for developing the latent electrostatic images 
produced on drum 18. Developer roll 25 is driven by motor 38. 
At transfer station 26, corona transfer means 27 effects transfer of the 
developed image to a suitable copy substrate material such as copy sheets 
28. For this purpose, a supply of copy sheets 28 is provided in tray 29. A 
suitable sheet feeder, exemplified herein by sheet feed roll 30 and driven 
by motor 39 feeds one sheet at a time forward from tray 29 to transfer 
station 26. A suitable corona power supply 40 is provided for transfer 
corona means 27. 
A suitable photoreceptor cleaning device such as cleaning brush 33 is 
provided at cleaning station 32 for cleaning drum 18 of leftover developer 
materials following transfer of the developed image to a copy sheet at 
transfer station 26. Brush 33 is disposed in an evacuated housing 34 
through which the leftover developer materials removed by brush 33 are 
exhausted. A brush drive motor 41 is provided for rotating cleaning brush 
33. 
In the example shown, photoconductive surface 19 comprises a uniform layer 
of photoconductive material such as amorphous selenium on the surface of 
drum 18. Drum 18, which is supported for rotation in suitable journals 
(not shown), is driven by motor 31. Drum motor 31 is drivingly coupled to 
drum 18 by suitable drive means (not shown). Motor 31 rotates drum 18 in 
the direction shown by the solid line arrow when processing copies. 
When operating in the copy mode (MODE I), the photoconductive surface 19 is 
charged to a uniform level by corona charging means 23. Platen 12 and the 
original document 13 thereon is irradiated by light source 15, the light 
reflected from document 13 being focused onto the photoconductive surface 
19 of drum 18 by lens 16 at exposure station 21. Platen 12 and the 
document 13 thereon are at the same time moved in synchronism with 
rotation of drum 18. The light reflected from the original 13 selectively 
discharges the previously charged photoconductive surface in a pattern 
corresponding to the image that comprises the original document. 
The latent electrostatic image created on the photoconductive surface 19 of 
drum 18 is developed by developer roll 25 at developing station 22 and 
transferred to a copy sheet 28 at transfer station 26 through the action 
of transfer corona means 27. Following transfer, the photoconductive 
surface is cleaned by cleaning brush 33 to remove leftover developer 
material. A suitable fuser or fixing device (not shown) fixes the image 
transferred to the copy sheet 28 to render the copy permanent. 
While the photoreceptor is illustrated in the form of a drum 18 other 
photoreceptor types such as belt, web, etc. may be envisioned. 
Additionally, the photoreceptor may be opaque, that is impervious to 
light, or wholly or partially transparent. While the exemplary drum 18 
typically has an aluminum substrate which renders the drum opaque, other 
substrate materials such as glass may be contemplated, which would render 
drum 18 wholly or partially transparent. Organic photoconductive materials 
may also be contemplated, as for example an aluminized Mylar substrate 
having a layer of selenium dispersed in poly N-vinyl carbazole with a 
transparent polymer overcoating containing a charge transport compound 
such as pyrene. And while a scan type image system is illustrated, other 
types of imaging systems such as full frame flash, may be contemplated. 
Reproduction apparatus includes a suitable raster scanner 59 illustrated 
herein as a flying spot scanner. Scanner 59 has a suitable flux source 
such as laser 60. The collimated beam 61 of monochromatic radiation 
generated by laser 60 is passed to a modulator 65 which for operation in a 
second image write mode, modifies the beam 61 in accordance with 
information contained in image signals input thereto along data 
transmission line 66 as will appear. Modulator 65 may comprise any 
suitable electro-optical or acousto-optical modulator or waveguide for 
imparting the informational content of the image signals input thereto to 
beam 61. For example, modulator 65 may be a Pockel's cell having a 
potassium dihydrogen phosphate crystal whose index of refraction is 
periodically varied by the application of the image input signal thereto. 
The beam 61 output by modulator 65 passes to an imaging lens 75. Lens 75 
focuses a light from laser 60 to a selected spot in the focal plane 
proximate the surface 19 of photoconductor drum 18, as will appear. 
The beam 61 from lens 75 is reflected from the mirrored surfaces 70 of a 
rotating scanning polygon 69 onto the photoconductive surface 19 at a 
point upstream of developing station 22. Polygon 69 is driven by motor 72. 
As will be understood by those skilled in the art, rotation of polygon 69 
repeatedly scans the light spot across the surface of drum 18 to form what 
is known as a flying spot scanner. Light reflected from the 
photoconductive surface 19 of drum 18 is collected in an integrating 
cavity 100 and there converted to image signals when operating in a third 
READ mode (MODE III), as will appear. 
Referring particularly to FIG. 2, integrating cavity 100 consists of an 
elongated hollow cylindrical housing 105 disposed adjacent to and in 
predetermined spaced relationship to the surface 19 of drum 18, housing 
105 being supported such that the longitudinal axis of housing 105 
substantially parallels the axis of drum 18. Housing 105 is provided with 
an elongated slit-like aperture 107 in the wall thereof opposite 
photoconductive surface 19, housing 105 being located such that light 
reflected from the photoconductive surface of drum 18 passes through 
aperture 107 into the interior 106 of housing 105. A pair of 
photodetectors 108,108' are provided in housing 105 at the ends thereof, 
photodetectors 108,108' generating analog signals in response to the 
presence or absence of light. To enhance the light responsiveness of 
housing 105, the interior wall 106 thereof is preferably finished with a 
highly reflective material such as highly reflective lambertian coating. 
It will be understood that where the photoreceptor is transparent, 
integrating cavity 100 is suitably supported within the interior of drum 
18 to receive light transmitted through the photoconductive material. 
When operating in the copy mode (MODE I), latent electrostatic images are 
formed on the photoconductive surface 19 through exposure of the document 
13 on platen 12 as described heretofore. In the WRITE mode, (MODE II) 
scanner 59 is actuated to write latent electrostatic images on the 
photoconductive surface 19 by scanning the surface with beam 61 modulated 
in accordance with the image signals input thereto through data 
transmission line 66. In this mode, modulator 65 modulates the light 
intensity of the scanning beam 61 in accordance with the content of the 
image signals input thereto so that scanning beam 61 dissipates the 
electrostatic charge on the drum surface to create a latent electrostatic 
image representative of the image signals input thereto. The electrostatic 
image created is thereafter developed by developer roll 25 and transferred 
to a copy sheet 28 at transfer station 26. Following transfer, the 
photoconductive surface is cleaned by cleaning brush 33 as described 
heretofore. 
In this mode of operation and in the READ mode (MODE III) described below, 
polygon 69 may be continually driven at a substantially constant speed by 
motor 72. 
In the READ mode, (MODE III) where it is desired to read original 13 and 
convert the content thereof to image signals, the photoconductor drum 18 
is cycled twice for each read operation. During the first cycle, a latent 
electrostatic image is created on the drum photoconductive surface 19, 
normally through exposure of the original 13 on platen 12 as described 
heretofore. The latent electrostatic image is thereafter developed by 
developer roll 25. The developed image is carried by drum 18 past transfer 
station 26, cleaning station 32, charging station 20 and exposure station 
21. On the second cycle of drum 18, as the developed image comes opposite 
the point where beam 61 scans the photoreceptive surface 19, the developed 
image is scanned line by line. The light from beam 62 is reflected from 
the surface of the photoconductive surface 19 in accordance with the 
presence or absence of toner to integrating housing 105, it being 
understood that where the light beam strikes toner, the light is absorbed 
and hence not reflected whereas the light beam strikes the uncovered 
portions of the photoconductive surface, the light is reflected back by 
the photoconductive surface. The presence or absence of light in housing 
105 is sensed by photodetectors 108,108' to provide analog signals 
representative of the developed image scanned to data transmission line 
76. 
To permit the developed image to pass transfer station 22 and cleaning 
station 32 unimpeded, tranfer corona means 27 is inactivated and suitable 
means such as camming element 80 is provided to separate cleaning brush 33 
and housing 34 thereof from the photoconductive surface 19. Camming 
element 80, which is driven by one-half revolution step motor 84 is 
activated in timed synchronism with rotation of the drum 18 as will 
appear. It will be understood that corona generating means 23 and 
light/lens imaging system 11 are inactivated while the developed image 
moves therepast. 
A camming element 81, which may be driven by one-half revolution step motor 
85, is similarly provided to move developing roll 25 out of contact with 
the surface of drum 18 during the second drum cycle to permit the 
previously developed image to pass thereby following reading thereof by 
scanning beam 61. The developed image may thereafter be transferred to 
copy sheet 28 following which the drum surface is cleaned by cleaning 
brush 33 as described heretofore. For this purpose, camming element 80 is 
reset to return cleaning brush 33 to operative contact with the 
photoconductive surface 19, and corona transfer means 27 activated to 
transfer the developed image to a copy sheet 28. 
As will be understood by those skilled in the art, the rate at which image 
signals may be input to modulator 65 through data transmission line 66 
when operating in the WRITE mode is limited by the slowest component in 
the system. In a communication or facsimile type system, for example, the 
maximum rate of data transmission is normally limited by the bandwidth of 
the data communication channel or network being used which is often less 
than the rate at which images are processed xerographically by the 
reproduction apparatus 10. Similarly, the rate at which image signals may 
be output to data transmission line 76 when operating in the READ mode is 
limited by the transmission rate of the data communication channel or 
network. Further, the communication network protocol may be packet 
switched with the result that image signals may be received or transmitted 
asynchronously. 
To accommodate the difference between the rate at which images are 
processed xerographically and the rate at which image signals are 
transmitted or received while avoiding the need for large relatively 
expensive electronic buffers, the photoconductor drum 18 itself is 
utilized as a buffer to store the image data when operating the multi-mode 
reproduction apparatus 10 in either the image WRITE (MODE II) or image 
READ (MODE III) modes. To effectuate this, the operating speed of 
photoreceptor drum 18 is changed when operating scanner 59 to synchronize 
drum speed with the data transmission rate of data transmission lins 
66,76. Since drum 18 is operated during transmission of image signals, it 
will be understood that in the case of packet switching, drum 18 is 
operated in stepped fashion wherever image signals are transmitted or 
received by the communication network. 
In the embodiment shown in FIG. 1, photoconductor drum drive motor 31 
comprises a two-speed motor having a first or high speed for processing 
copies xerographically and a second or low speed when drum 18 is being 
scanned by scanner 59. It is understood that the high speed is chosen to 
provide an optimum xerographic processing speed while the motor low speed 
is chosen to accommodate the data transmission rate of the associated 
communication network. 
Referring now to FIGS. 3 and 4 particularly, a mode controller 115 is there 
provided for regulating enablement of the various machine operating 
components as will appear in accordance with the operational mode 
selected. A mode selector 116, which may be conveniently located on the 
machine operator console (not shown), permits the user or operator to 
select the operational mode desired, that is, COPY (MODE I), WRITE (MODE 
II) or READ (MODE III). The output of mode selector 116 is input via lead 
117 to mode controller 115. 
Output leads 120 (MODE I), 121 (MODE II) and 122 (MODE III) from controller 
115 are input via OR gate 124 to high speed control gate 125. Lead 127 
couples gate 125 to the control section of drum drive motor 31, triggering 
of gate 125 causing motor 31 to operate at high speed. MODE II, III leads 
121, 122 are coupled to OR gate 128. The output of gate 128 is coupled by 
lead 129 to low speed control gate 130, the output of gate 130 being 
coupled to the control section of motor 31 by lead 131 such that 
triggering of gate 130 causes motor 31 to operate at low speed. 
MODE I lead 120 is input via inverters 135, 135' to step motor control 
gates 136,137 controlling step motors 84,85. MODE II and III leads 121,122 
respectively are input via OR gates 138,139 and leads 140,141 to AND gates 
143,144. Leads 145,146 couple the output of gates 143,144 to step motor 
control gates 136,137. 
MODE I lead 120 is input to exposure lamp control gate 150, gate 150 
controlling energization of exposure lamp 15. MODES II and III leads 
121,122 respectively are input via inverters 151,151' to gate 150. MODE I 
lead 120 is input via inverters 154,154' to laser control gate 155 and 
polygon drive motor control gate 156. Gates 155 and 156 control 
energization of laser 60 and drive motor 72 for polygon 69. MODE II and 
III leads are input to gates 155,156 via OR gates 157,158. 
MODE I and II leads 120,121 are input via inverters 160,160' to detector 
control gate 162. MODE III lead 122 is input to gate 162. Gate 162 
controls energization of light detectors 108,108' of integrating cavity 
100. 
Timed activation of the various components of multi-mode reproduction 
machine 10 is provided by a machine programmer 170 in response to timing 
signals generated by a suitable encoder 172. Encoder 172 is conveniently 
disposed on the output shaft of drum drive motor 31, encoder 172 
responding to rotation of motor 31 and movement of photoreceptor drum 18 
to generate a succession of timing signals for timing operation of the 
various machine components in accordance with preset operational programs 
for each operating mode stored in programmer 170. As will be understood by 
those skilled in the art, the aforementioned operational programs may be 
in the form of software, or alternately, programmer 170 may be hardwired 
for this purpose. 
Motor control output leads 175,176 from programmer 170 are coupled to high 
and low speed motor control gates 125,130 respectively. Developer and 
cleaning separation control leads 178,179 from programmer 170 are coupled 
to step motor control gates 143,144 respectively. And exposure lamp 
control lead 180, laser control lead 181, and polygon drive motor control 
lead 182 from programmer 170 are coupled to lamp control gate 150, laser 
control gate 155, and polygon motor control gate 156 respectively. 
Detector control lead 184 from programmer 170 is coupled to detector 
control gate 162. 
Control leads 190, 191, 192, 193, and 194 from programmer 170 control 
actuation of developer roll drive motor 38, corona transfer means power 
supply 40, sheet feed roll drive motor 39, cleaning brush drive motor 41 
and corona charge means power supply 37. 
For operation in the COPY mode, the MODE I signal from controller 115 
enables exposure lamp 15 and sets photoreceptor drum drive motor 31 for 
high speed operation. Polygon drive motor 72 and laser 60 of scanner 59 
are disabled as are step motor 84, 85 for developing and cleaning station 
separation cams 80,81. Developing station 22 and cleaning station 32 
accordingly remain in operative contact with the photoconductive surface 
19 of drum 18. 
As described, latent electrostatic images are created through exposure of 
the charged photoconductive surface 19 to a light image of the original 13 
on platen 12, the image being developed by developer roll 25 at developing 
station 22 and transferred to a copy sheet 28 fed forward in timed 
sequence by sheet feed roll 30 at transfer station 26. Following transfer, 
leftover developer materials are removed from the photoconductor drum 
surface by brush 33 at cleaning station 32. Control signals from 
programmer 170 actuate photoconductor drum drive motor 31, exposure lamp 
15, developer roll drive motor 38, sheet feed motor 39, cleaning brush 
drive motor 41, power supply 37 for corona charge means 23, and power 
supply 40 for corona transfer means 27 in predetermined timed order as 
required to produce the copy or copies desired. 
For operation in the WRITE mode, the MODE II signal from controller 115 
enables polygon drive motor 72 and laser 60 of scanner 59 to permit 
scanning of the photoconductive surface 19 by scanning beam 61 and writing 
of images thereon in accordance with image signals input to modulator 65 
through data transmission line 66. 
Additionally, the MODE II signals from controller 115 set photoreceptor 
drum drive motor 31 for low speed operation and ready step motors 84,85 of 
developing and cleaning station separation cams 80,81 respectively for 
operation under the control of control signals output by programmer 170. 
Latent electrostatic images are written on the photoconductive surface of 
drum 18 by scanner 59 in accordance with the image signal input to 
modulator 65 from data transmission line 66, control signals from 
programmer 170 operating photoconductor drum drive motor 31 at low speed 
in response to the transmission of image signals. As described herein, the 
rotational speed imparted to drum 18 at the motor low speed setting is 
preferably chosen to be compatible with the rate .phi. (Pixel Clock), at 
which image signals are transmitted in data transmission line 66. 
During this period, step motors 84,85 are operated to separate cleaning 
brush 33 and developer roll 25 from drum 18 to permit the latent image to 
pass developing and cleaning stations 22, 32 unimpeded. 
Following completion of the image page, scanner 59 is inactivated while 
photorecetor drum drive motor 31 is switched to high speed. Motor 85 
resets cam 81 to return developer roll 25 into operative contact with the 
drum surface before the leading edge of the latent image reaches 
developing station 22 to enable the latent image to be developed. The 
developed image is thereafter transferred to a copy sheet 28 at transfer 
station 26. With passage of the latent image past cleaning station 32, 
motor 84 resets cam 80 to return cleaning brush 33 into operative contact 
with the surface of drum 18 to enable cleaning of leftover developing 
materials from drum 18 following transfer of the developed image to copy 
sheet 28. 
For operation in the READ mode, and presuming that original 13 on platen 12 
comprises the image to be read by scanner 59, the MODE III signal from 
controller 115 sets photoreceptor drum driving motor 31 for high speed 
operation and enables exposure lamp 15 and step motor 84, the latter to 
separate cleaning brush 33 from drum 18 through cam 80. During copying, 
control signals from programmer 170 actuate drum driving motor 31 (at high 
speed), power supply 37 of corona charging means 23, exposure lamp 15, and 
drive motor 38 of developer roll 25 to create a developed image of the 
original on the photo-conductive surface of drum 18. 
To permit the developed image to pass unimpeded past cleaning station 32, a 
control signal from programmer 170 actuates step motor 84 to separate 
cleaning brush 33 from drum 18. Corona transfer means 27, sheet feed motor 
31, and exposure lamp 15 are held inactive as the developed image passes 
the operating station associated therewith. 
As the leading edge of the developed image approaches the point where the 
scanning light beam 61 impinges on photoconductive drum 18, drum drive 
motor 31 is set for low speed operation and laser 60 is enabled. At the 
same time, polygon drive motor 72, photodetectors 108,108' and step motor 
85 may be actuated, the latter to separate developer roll 25 from drum 18. 
On a receive Signal, scanner 59 scans the developed image line by line. 
Control signals from programmer 170 operate laser 60 and drive motor 31, 
the latter to move drum 18 at low speed while the developed image thereon 
is scanned. Light reflected from the photoconductive surface of drum 18 is 
sensed by photodetectors 108,108' to produce image signals representative 
of the developed image on drum 18. The image signals produced are 
accordingly output via line 76 to a suitable user or storage device (not 
shown) at a rate commensurate with the data transmission rate limitations 
of data transmission line 76. 
Following reading of the developed image, scanner 59 is inactivated and 
drum drive motor 31 is set for high speed operation. Step motor 84 is 
inactivated to permit cam 80 to return cleaning brush 33 into engagement 
with the surface 19 of drum 18. As the developed image moves through 
transfer station 26, corona transfer means 27 is actuated to transfer the 
developed image to a copy sheet 28 fed forward by feed roll 30. Following 
transfer, the surface of drum 18 is cleaned by brush 33 at cleaning 
station 32. 
While scanning beam 61 of scanner 59 is illustrated as impinging on drum 18 
at a point upstream of developing station 22, it will be understood that 
beam 61 may be arranged, as by means of suitable reflecting surfaces, to 
impinge upon the photoconductive surface of drum 18 at a point downstream 
of developing station 22 and before transfer station 26 when operating 
reproduction machine 10 in the READ mode (MODE III) as for example in the 
manner described in co-pending application Ser. No. 111,520 filed on Apr. 
17, 1981 in the names of Charles J. Kramer, David B. Kay and Christopher 
Snelling. In that type of arrangement, drum 18 need cycle only once when 
operating in the READ mode. 
While photoreceptor drum drive motor 31 is illustrated herein as comprising 
a two-speed motor which may be operated in stepped fashion during scanning 
to permit asynchronous transmission or reception of image signals, other 
motor types such as a variable speed motor, or stepping motor, etc., may 
be contemplated. In the case of a variable speed motor, suitable control 
means for setting the motor to a speed compatible with the existing data 
transmission rate is employed. 
Where drive motor 31 comprises a stepping motor, the motor is stepped for 
each line of image data written during WRITE mode (MODE II) or read during 
READ mode (MODE III). In this circumstance, image signals are preferably 
processed at the same rate as copies are processed xerographically with 
drum 18 moved at the relatively high xerographic processing speed. Since 
this results in a scanning rate at which the image signals are written 
(MODE II) or read (MODE III) at a rate higher than the rate at which the 
image signals are transmitted, a small one or two line buffer may be 
utilized to buffer the image signals until a line thereof has been 
accumulated when operating in the WRITE mode or to buffer the line of 
image signals read pending transmission thereof when operating in the READ 
mode. 
While the image signal transmission/reception rate has been described 
herein as being less than the xerographic processing rate, the invention 
is not intended to be so limited, but to instead, include systems where 
the xerographic processing rate is equal to or less than the image signal 
transmission/reception rate as well. And it will be understood that where 
image signal reception and transmission rates are not the same, different 
effective photoreceptor speeds are provided to match photoreceptor 
operating speed in Modes II and III with the rate at which image signals 
are being received or transmitted as described herein. 
While the invention has been described with reference to the structure 
disclosed, it is not confined to the details set forth, but is intended to 
cover such modifications or changes as may come within the scope of the 
following claims: