Image forming apparatus

An image forming apparatus for a photocopy machine. A document table holds the document to be copied. An image area designating panel on the document table designates the area of the document to be copied and generates electrical signals corresponding to the copy area when the panel is pressed. A memory stores the electrical signals generated by the panel and a plurality of light-emitting elements prevents the formation of the electrostatic latent image on the photosensitive body except for the indicated copy area, according to the electrical signals which are read from the memory.

BACKGROUND OF THE INVENTION 
This invention relates to an electrophotographic apparatus. In particular, 
it relates to an image forming apparatus which can form an image by 
designating that part of the document of which a copy is to be produced, 
or by omitting, on the copy, that part not required. 
A demand has arisen recently for the development of an image forming 
apparatus with a facility for editing the document image original which it 
copies. In particullar, there is a strong demand or the development of a 
facility for omitting on the copy the unwanted part of a document image 
original. 
One image forming apparatus has already developed which fulfils this 
requirement (U.S. Pat. No. 4,215,929, Sato et al.). This existing image 
forming apparatus consists of a light source which applies an image area 
control light which controls the formation of the electrostatic latent 
image on a photosensitive body by cutting off or applying light in 
association with the exposure of the document image original, a mask 
member which controls the said control light to a desired width by 
superposition, and a control means for controlling the working of this 
mask member. The aim here is to control the formation of the electrostatic 
latent image by the difference between the two operations, whereby the 
control light mentioned above is either transmitted or masked, and thus to 
obtain an image of the required area of the document image original. 
Depending on the way in which the mask member is superposed, either an 
image of a part of the document image original can be obtained, or the 
part can be erased and an image obtained of the remainder. 
Further, this existing image forming apparatus is provided with a 
monitoring means which displays the document image original, and a 
position determining means, which in association with this monitoring 
means selects as desired that area of the document image original which is 
required. By controlling the mask member in association with the position 
determining means, the required area of the document image original can be 
selected at will as the document image original is displayed, and an image 
of that area obtained. 
However, the existing image forming apparatus as disclosed in U.S. Pat. No. 
4,215,929 has the following drawbacks. 
(1) Mechanical parts, such as a motor and gears, are required to shift the 
mask member between the single and the superposed state, and this makes 
the apparatus complicated. Also, there is a strong possibility that in use 
over a long period the mask member will become deformed, making accurate 
masking impossible. 
(2) The monitoring means consists of a lamp for irradiating the document, a 
mirror and lens for directing the light reflected from the document, and a 
screen on which the image of the document is projected. This monitoring 
means is provided separate from the document table which is provided, 
above the photosensitive body, for the exposure of the document. Space is 
therefore required for the provision of this monitoring means, and this 
increases the overall size of the image forming apparatus. 
SUMMARY OF THE INVENTION 
It is an object of the invention to provide an image forming apparatus in 
which, by using static parts, accurate masking can be achieved over a long 
period. 
It is a further object of the invention to provide, by the provision, on 
the document table on which the document is placed, of a position 
determining means whereby the required area of the document image original 
is selected as desired, an image forming apparatus of which the overall 
size does not thereby have to be made larger. 
The image forming apparatus of this invention comprises a document table 
which holds a document, an image area designating panel provided to the 
document table to designates a required copy area of the document, the 
designating panel generates electrical signals corresponding to the 
required copy area designated by pressing the panel, a memory memorizes 
the electrical signal generated by the panel and a plurality of 
light-emitting elements prevents the formation of the electrostatic latent 
image on the photosensitive body other than of the area to be copied, 
according to the electrical signals read from the memory.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
An explanation follows of an embodiment of the invention referring to the 
accompanying drawings. 
FIGS. 15 and 16 show an image forming apparatus, for example, an 
electrostatic copier. A document table 20 consisting of transparent glass 
which supports the document to be copied, is provided at the top of a main 
body 10 of the copier. This document table 20 is provided with a cover 11 
which can be opened and closed, and which covers document placed on 
document table 20. A work table 22 is provided to the right of document 
table 20, projecting from main body 10. An optical system 24 such that it 
can move in the directions indicated by the arrows A and B, is provided 
below document table 20. Optical system 24 consists of an exposure lamp 26 
which irradiates the document placed on document table 20, and mirrors 28, 
30 and 32 which direct the light reflected from the document. When optical 
system 24 moves from left to right in FIG. 16, it scans the document by 
exposing it to light. Mirrors 30 and 32 move at half the speed of mirror 
28 so as to maintain an optical path of constant length. The light 
reflected from the document as it is scanned by optical system 24, i.e., 
the light from the exposure lamp 26 reflected back from the document, 
after being reflected by mirrors 28, 30 and 32, passes through a lens 
block 34 for varying the enlargement rate of the copy. After being 
reflected by a mirror 36, the reflected light is directed to a 
photosensitive drum 38. An image of the document is then formed on the 
surface of photosensitive drum 38. 
Photosensitive drum 38 rotates in the direction of an arrow C. First, the 
surface of drum 38 is electrically charged by a main charger 40. Next, an 
electrostatic latent image of the document is formed on drum 38 by slit 
exposure. This electrostatic latent image is rendered visible when the 
toner image is formed by the deposition of toner effected by a developing 
unit 42. Paper P is extracted one sheet at a time by a feed roller 48 or 
50 from an upper cassette 44 or lower cassette 46, whichever has been 
selected. The extracted paper P is guided via a paper guide path 52 or 54 
to a pair of aligning rollers 56 and is fed by this pair of rollers 56 to 
the image transfer station. Cassettes 44 and 46 are so arranged that they 
can be readly inserted or withdrawn from main body 10. One of cassettes 44 
and 46 is selected by means of an operation panel (to be described later). 
The cassette size is detected by cassette size sensors 78 and 80 provided 
low down on the right of main body 10. These sensors 78 and 80 are made up 
of a plurality of microswitches which switch on/off according to the 
different size of the cassettes inserted. 
Paper P which has been fed to the image transfer station, adheres closely 
to the surface of photosensitive drum 38 and by this means the toner image 
on photosensitive drum 38 is transferred by the action of a transfer 
charger 58 to paper P. Paper P on to which the toner image has been 
transferred is separated from drum 38 by the action of a separation 
charger 60 and carried on a conveyer belt 62. It is then fed to a pair of 
fixing rollers 64 provided at the end of conveyer belt 62 by means of the 
passage through these rollers of paper P, the toner image on paper P is 
fixed. After fixing, paper P is discharged by a pair of exit rollers 66 on 
to a receiving tray 68 provided outside main body 10. After the transfer 
of the toner image, the residual electric charge is removed from 
photosensitive drum 38 by a charge remover 70 and any residual toner is 
removed by a cleaner 72. Any image remaining on the drum is erased by a 
discharge lamp 74 and the drum is then returned to its initial state. 76 
is a cooling fan to prevent the temperature inside of main body 10 from 
rising. 
FIG. 17 shows a operation panel 82 provided at the top of main body 10. On 
this panel are disposed a COPY button 84 for initiating the copy 
operation, a ten key unit 86 for setting the number of copies, a display 
88 indicating the operating state, paper jam, etc., a cassette selecting 
key 90 for selecting either upper cassette 44 or lower cassette 46, an 
indicator 92 indicating which cassette has been selected, an `erase inside 
selected area` button 94 which order erasure of the part within the area 
designatd by the use of an image area designating panel (to be described 
later), an `erase outside selected area` button 96 which orders erasure of 
the part outside that area, an enlaragement rate setting key 98 which sets 
the rate of enlargement or reduction in prescribed steps, a ZOOM key 100 
which sets the rate or enlargement or reduction without the constraint of 
the prescribed steps, a rate display unit 102 which displays the rate that 
has been set and a density setter 104 which sets the density of the copy. 
FIG. 18 is a perspective view showing the arrangement of the drive sources 
(pulse motors) for each part of this embodiment. Unlike FIG. 15, this view 
is from the back of the apparatus. An enlargement/reduction rate-changing 
motor 106 varies the position of lens block 34. A motor 108 is for varying 
the distance between mirror 28 and mirror 30 (optical path length) when 
the enlargement/reduction rate is altered. A scanning motor 110 is for 
moving exposure lamp 26 and mirrors 28, 30 and 32, so that the document 
can be scanned. A shutter motor 112 is for moving the shutter (not shown 
in the drawings) for adjusting the width of the charge applied by main 
charger 40 to photosenstive drum 38 when the enlargement/reduction rate is 
alterd. A developer motor 114 is for driving the developing rollers etc. 
of developing unit 42. A drum motor 116 is for driving photosensitive drum 
38. A fixing motor 118 is for driving pair of fixing rollers 64 and pair 
of exit rollers 66. A paper feed motor 120 is for driving feed rollers 48 
and 50. A paper transport motor 122 is for driving pair of aligning 
rollers 56. A fan motor 124 is for driving cooling fan 76. 
FIG. 19 is a perspective view showing the scanning mechanism for moving 
optical system 24 consisting of exposure lamp 26 and mirrors 28, 30 and 32 
along document table 20. Exposure lamp 26 and mirror 28 are fixed to a 
first carriage 126 and mirrors 30 and 32 to a second carriage 128. These 
carriages 126 and 128 can move, guided by guide-rails 130 and 132 in the 
direction of the arrows A and B. Scanning motor 110 which is a 4-phase 
pulse motor, drives a pulley 134. An endless belt 138 is wound around this 
pulley 134 and an idle pulley 136. One end 126a of first carriage 126, on 
to which exposure lamp 26 and mirror 28 are fixed, is secured to this belt 
138. A guide 140 forms an intergral part of second carriage 128, on to 
which mirrors 30 and 32 are fixed. This guide 140 straddles guide rail 132 
and can move back and forth along it. Two pulleys 142 and 144 are mounted 
on this guide part 140 with a space between them in such a way that they 
can rotate in the axial direction of rail 132. A wire 146 is wound around 
these pulleys 142 and 144, one end of this wire 146 being secured to a 
fixing piece 148, and the other to fixing piece 148 via a coil spring 150. 
As scanning motor 110 rotates, belt 138 revolves and first carriage 126 is 
moved, and with it second carriage 128 also. When this happens, since 
pulleys 142 and 144 perform the function of a fall block, second carriage 
128 moves at half the speed of first carriage 126, in the same direction. 
The direction in which first and second carriages 126 and 128 move in 
controlled by switching the direction of rotation of scanning motor 110. 
The area which can be copied, corresponding to the paper size that has been 
designated, is displayed on document table 20. If the size of the paper 
selected by the cassette selection key 90 is taken as (Px, Py), and the 
rate of enlargement/reduction designated by rate setting key 98 of ZOOM 
key 100 as K, then the area can be copied (X, Y) is as follows. 
EQU X=Px/K 
EQU Y=Py/K 
In this area that can be copied (X, Y), the X direction is indicated by 
pointers 152 and 154, while the Y direction is indicated by a scale 156 on 
the top of first carriage 126. 
As shown in FIG. 20, pointers 152 and 154 are fixed to a wire 164 wound 
around pulleys 158 and 160 via a coiled spring 162. A pulley 160 receives 
rotary drive from motor 166. The distance between the pointer 152 and 
pointer 154 is altered by the rotation of motor 166 in response to the 
selection of paper size and the enlargement/reduction rate. 
Scanning motor 110 is driven, as a result of the selection of paper size 
and the enlargement/reduction rate, and first carriage 126 moves to a 
prescribed position, i.e., `home` position, appropriate to the 
enlargement/reduction rate, and stops there. When COPY button 84 is 
pressed, first carriage 126 is first moved in the direction of the arrow 
A, and then, as it is in the extreme left position in FIG. 16, exposure 
lamp 26 comes on, whereupon first carriage 126 is moved in the direction 
of the arrow B. During this movement of first carriage 126 in the 
direction B, the document placed on document table 20 is irradiated by 
exposure lamp 26. When the scanning of the document is complete, exposure 
lamp 26 goes off, and first carriage 126 returns to its home position. 
FIG. 21 shows the entire control circuit. The principal components of this 
circuit are a main processor 168 and first and second sub-processors 170 
and 172. Main processor 168 executes the copying operation described above 
by detecting the inputs from operation panel 82 and cassette size sensors 
78 and 80, and by controlling a high voltage transformer 174 (which 
energizes the various charger), discharge lamp 74, a blade solenoid 72a of 
cleaner 72, a heater 64a of pair of fixing rollers 64, exposure lamp 26 
and motors 106-122, 166 and 176. Main processor 168 also executes the 
operation for erasure of the unwanted parts of the document image 
original, by controlling image area designating panel 200, an erasing 
array 210, an array driver 220 and a memory 196 (to be described later). 
Of motors mentioned above 114, 118, 124 and toner motor 176 (for feeding 
toner to developing unit 42) are controlled by main processor 268 via a 
motor driver 178. Motors 106, 108, 110 and 112 are controlled by first 
sub-processor 170 via a pulse motor driver 180. Motors 116, 120, 122 and 
166 are controlled by second sub-processor 172 via a pulse motor driver 
182. Exposure lamp 26 is controlled by main processor 168 via a lamp 
regulator 184. Heater 64a is controlled by main processor 168 via a heater 
controller 186. `Run` or `stop` instructions for the various motors are 
sent from main processor 168 to first and second subprocessors 170 and 
172. A status signal indicating a `run` state or a `stop` state is sent 
from sub-processors 170 and 172 to main processors 168. Position 
information from motor phase sensor 188, which detects each initial 
position of motors 106-112, is input into first sub-processor 170. 
An explanation will now be given of a first embodiment of the essential 
feature of the present invention. In FIG. 1, a support body 12, which can 
hinge independently of document cover 11, is provided above document cover 
11. This support body 12, which is flat and has the same area as document 
cover 11, consists, as shown in FIG. 2, of a rectangular frame 13 and a 
plate of transparent glass 14 fitted within this frame 13. It is 
positioned so that when it is hinged down over document cover 11, one 
corner 15 of transparent glass 14 coincides with the locating part 16, 
provided on the upper surface of document cover 11, for determining the 
position in which the document is to be placed. 
As shown in FIG. 3, an image area designating panel 200 for designating the 
area of which an image is to be formed is provided on the upper surface of 
transparent glass 14. As shown in FIG. 4, this designating panel 200 
comprises a pair of flat transparent films 201 and 202 having the same 
area with transparent glass 14, a flexible electrode sheet 204 provided 
between these films, which carries a group of strips of transparent 
conductive film 203 arrayed in the line direction, and a fixed electrode 
sheet 206 provided between this flexible electrode sheet 204 and 
transparent film 202 which carries a group of strips of transparent 
conductive film 205 arrayed in the row direction. Flexible electrode sheet 
204 and fixed electrode sheet 206 are separated by a small clearance gap 
so that the groups of transparent conductive film strips 203 and 205 do 
not, in the `normal` state, make electrical contact with each other. 
Electrode sheets 204 and 206 are positioned between transparent films 201 
and 202 to which they are bonded so as to form an integral whole in each 
case. Thus the groups of transparent conductive film strips 203 and 205, 
which face each other with a gap between them, form a plurality of 
pressure switches arranged in the form of a matrix as shown schematically 
in FIG. 5. What happens is when pressure is applied to transparent film 
201, then, of the group of transparent conductive film strips 203 on 
flexible electrode sheet 204, that which corresponds to the position at 
which pressure was applied makes contact with that one of the group of 
transparent conductive film strisp 205 on fixed electrode sheet 206 which 
also corresponds to this position, and a signal is achieved denoting the 
position at which pressure was applied. 
As shown in FIG. 5, the group of transparent conductive film strips 203 of 
image area designating panel 200 is connected electrically via an output 
interface 207 to main processor 168, while the group of transparent 
conductive film strips 205 is connected electrically via an input 
interface 208 to main processor 168. The signals outputted cyclically from 
main processor 168 via output interface 207 are fed sequentially to the 
group of film strips 203 of panel 200; when a point of intersection 
corresponding to the position at which pressure was applied causes one of 
the group of film strips 203 to make contact whith one of the group of 
film strips 205, a `pressed` signal is output from that point, and this 
output signal is input via input interface 208 into main processor 168. 
The output signal from panel 200 which has been input into main processor 
168 is supplied via main processor 168 to memory 196, shown in FIG. 21. 
This memory 196 consists of a RAM having a storage capacity matching the 
number of intersection points of the groups of film strips 203 and 205. 
Next, an explanation will be given of how the area of the document to be 
copied is designated. Support body 12 is opened, as shown in FIG. 1, one 
corner of the document D is aligned with a guide part 16 of document cover 
11, so that the side of the document with the image to be copied faces 
support body 12, i.e., upwards. When in this state support body 12 is 
closed, the document D can be seen through transparent glass 14 and image 
area designating panel 200 (FIG. 6A). In FIG. 6A, the groups of 
transparent conductive film strips 203 and 205 of image area designating 
panel 200 are shown by dotted lines, but in fact they are virtually 
transparent and are therefore not visible. 
When, in this state, the four points on image area designating panel 200 
defining the area to be erased of the document which is indicated by the 
oblique lines in FIG. 7A are pressed, and `erase inside selected area` 
button 94 on operation panel 82 is also pressed, a high level signal `1` 
is written via main processor 168 into the addresses corresponding to the 
area to be erased of memory 196, while a low level signal `0` is written 
into the other addresses as shown in FIG. 8A. In this embodiment, these 
signals are written into memory 196 mapped on to the mirror image of 
support body 12. What happens is that since, when the document D is 
actually to be copied, the corner D.sub.1 of the document D is aligned 
with a corner 20a of document table 20, and the side to be copied of the 
document D faces document table 20 (FIG. 6B), the signals for memory 196 
are written in a corresponding manner. Again, when the six points on image 
area designating panel 200 defining the area to be erased of the document 
D which is shown by the oblique lines in FIG. 7B are pressed, and the 
`erase inside selected area` button 94 on operation panel 82 is also 
pressed, a high level signal `1` is written via main processor 168 into 
the addresses corresponding to the area to be erased of memory 196, while 
a low level signal `0` is written into the other addresses as shown in 
FIG. 8B. 
An erasing array 210 is provided as the image formation prevent means, 
between and in close proximity to main charger 40 of photosensitive drum 
38 and an exposure zone Ph (FIG. 9). This erasing array 210 has a 
plurality of cylindrical cells 212 arranged in a row at right angles to 
the direction of rotation of photosensitive drum 38 (FIGS. 10 and 11). A 
light-emitting element 214 consisting of a light-emitting diode provided 
within each of these cells 212 (FIGS. 12A and 12B). A lens 216 which 
condenses the light of light-emitting element 214 on to the surface of 
photosensitive drum 38 is provided at the opening of each cell 212 facing 
photosensitive drum 38. The number of light-emitting elements provided in 
this erasing array 210 is identical with the number of film strips in the 
group of transparent conductive film strips 203 in the transverse 
direction of image area designating panel 200. If the width of a cell 212 
is taken as P and the number of cells 212 as N, the overall length of 
erasing array 210 is given by Q=N.times.P. 
Erasing array 210 is driven by the previously-mentioned array driver 220. 
As shown in FIG. 13, this array driver 220 is made up of a shift register 
222 having the same number of bits as the bits in the line direction of 
memory 196, a store register 224 in which the contents of this shift 
register 222 are held and a switch circuit 228 consisting of a plurality 
of switch element 226 which are switched on or off by the output signals 
from this store register 224. A moving contact 226a of each switch element 
226 is earthed and a fixed contact point 226b is connected to the cathode 
of one of light-emitting elements (light-emitting diodes) 214 constituting 
erasing array 210. The anodes of light-emitting elements 214 are 
connected, in each case via a current-limiting resistance R to a power 
source Vcc. 
When after the area to be erased of the document has been designated in the 
manner described, the document D is withdrawn from support body 12 and 
placed on document table 20 as shown in FIG. 6B and COPY button 84 is 
pressed, first carriage 126 and photosensitive drum 38 move, while at the 
same time the data relevant to the first row is read sequentially from 
memory 196 in the row direction (FIGS. 8A and 8B). This data D1 is 
transferred, as it is read, by a clock signal CLK to shift register 222 of 
array driver 220. After the data for the first row has been transferred to 
shift register 222, when the charged part of photosensitive drum 38 
reaches erasing array 210, a latch signal LTH is output from main 
processor 168 and in response to this signal the contents of shift 
register 222 are loaded into store register 224. Since erasing array 210 
is disposed between main charger 40 and exposure zone Ph, the timing of 
the output of the latch signal LTH is controlled so that, if the angle 
between erasing array 210 and exposure zone Ph is taken as .theta..sub.1, 
and photosensitive drum 38 rotates at an angular velocity of .omega., the 
data for the first row output from memory 196 is supplied to store 
register 224 before .theta..sub.1 /.omega.. 
Switch elements 226 of switch circuit 228 are controlled by output signals 
of store register 224. When the output signals of store register 224 are 
high level, switch elements come ON, while when the signals are low level, 
they go OFF. As a result, the light-emitting elemtents 214 connected to 
switch elements 226 are ON when switch elements 226 are ON, and OFF when 
the latter are OFF. Consequently, of the charged parts of photosensitive 
drum 38, those parts opposite where light-emitting 214 have been switched 
on are discharged, and thereafter no electrostatic latent image is formed 
on these parts even when they are exposed, so that erasure of the document 
image original in respect of those parts has been effected. Thereafter, 
data from memory 196 is read one row at a time and image erasure continued 
in the same manner. 
It is also possible as shown in FIG. 14, to have erasing array 210 disposed 
between exposure zone Ph and developing unit 42, so that an area of the 
electrostatic latent image corresponding to that designated by panel 200 
is erased it has been formed. 
It is also possible to have an arrangement (not shown in Figure) such that 
the formation of an electrostatic latent image of the part not required is 
prevented simultaneously with exposure, by irradiating exposure zone Ph 
with light from erasing array 210. 
FIG. 22 shows a second embodiment in which the position of image area 
designating panel of the invention has been changed. In FIG. 1, which 
depicted the first embodiment, support body 12 on which image designating 
panel 200 was provided was placed, in such a way that is could hinge 
freely above document cover 11. In this second embodiment, in contrast, a 
support body 12' is placed, in such a way that it can hinge freely between 
a document table 20' and a document cover 11' and independently of 
document cover 11'. Again, in the first embodiment as shown in FIG. 2, 
image area designating panel 200 was provided on the upper surface of the 
plate of transparent glass 14, whereas in the second embodiment as shown 
in FIG. 23, an image area designating panel 200' is provided on the under 
surface of a plate of transparent glass 14'. This transparent glass 14' is 
positioned so that when support body 12' is hinged down over document 
table 20', the four corners of document table 20' coincide with the four 
corners of transparent glass 14'. 
Consequently, when the area to be copied of the document D' is to be 
designated, the document D' is placed between support body 12' and 
document cover 11' so that it faces transparent glass 14', i.e., downwards 
(FIG. 22). When in this state document cover 11' is closed, and support 
body 12' is then opened with document cover 11', then, as shown in FIG. 
24, the document D' can be seen through transparent glass 14' and image 
area designating panel 200'. In FIG. 24, the groups of the transparent 
conductive film strips of designating panel 200' are shown by dotted 
lines, but in fact they are virtually transparent and are therefore not 
visible. When, with support body 12' and document cover 11' thus in the 
open state, in the same way as in the first embodiment (FIGS. 7A and 7B) a 
high level signal `1` is written into the addresses in memory 196 
corresponding to the area to be erased, and a low level signal `0` into 
the other addresses. 
As already explained, after the area to be copied or erased of the document 
has been designated and this area for erasure written into memory 196, 
document cover 11' and support body 12' are closed, COPY button 84 is 
pressed and the document D' is exposed by irradiation from exposure lamp 
26 (FIG. 16) through document table 20', image area designating panel 200' 
and support body 12' (FIG. 22), and an image is produced on photosensitive 
drum 38. 
The working of the erasure of the latent image is the same as that 
described in connection with the first embodiment, and the explanation is 
therefore not repeated here. 
FIG. 25 shows a third embodiment in which the position of the image area 
designating panel of the invention has been changed again. In this third 
embodiment, only that area of a document which is in direct contact with 
the surface of the table on which the document is placed constitutes the 
area of which an image is formed, the image of any other part being 
erased. An image area designating panel 200" is provided directly on the 
upper surface of a document table 20" of transparent glass on which the 
document is placed. The construction of this panel 200" is the same as 
that described in the case of the first embodiment (FIG. 4). When, as 
shown in FIG. 25, a comparatively thick opened book Bk is placed on 
document table 20", the weight of the book Bk ensures that as shown in 
FIG. 26, that part of panel 200" corresponding to the two adjoing pages 
(indicated by the oblique lines in the drawing) is pressed down so that as 
shown in FIG. 27, a low level `0` signal indicating the area of which an 
image is to be formed, is sent to the addresses in a memory 196" 
corresponding to the parts to which pressure has been applied. The gutter 
part G between the pages and the area around the book Bk, do not press 
down on panel 200", and a high level `1` signal indicating areas for image 
erasure, is therefore remembered at addresses in memory 196" corresponding 
to those parts. 
The operation by which the image is formed is the same as that described in 
connection with the first embodiment, and the explanation is therefore not 
repeated here.