Image forming apparatus utilizing a light image memory

An image forming apparatus with an image memory plate having a light image memory is disclosed. The light image memory stores image information of a document when reflected light having the image information from the document is projected onto a first surface thereof, and also reads out the image information stored therein in the form of reflected light when light is projected onto a second surface thereof by a light source. The image forming apparatus comprises a movable holder for detachably holding the image memory plate.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to an image forming apparatus for forming an 
image of image information, in accordance with light having the image 
information such as light reflected from a document, and more particularly 
to an image forming apparatus utilizing a light image memory for storing 
the image information temporarily. 
2. Description of the Related Art 
Recently, an image forming apparatus such as an electrophotographic copying 
machine has been implemented with various kinds of functions such as 
multiple copying, both side copying, composite copying etc. 
Generally, the conventional copying machine has a document scan type 
optical system comprising a scanner movable along a document set on a 
document table, wherein light reflected from the document is projected 
onto a photoconductive drum through mirrors and lenses. Therefore, in the 
optical system, it is necessary to scan the whole area of the document 
once in order to produce a copy of the document. In order to produce 
plural copies of the document, it is necessary to scan the document a 
number of times repeatedly corresponding to the number of copies, 
resulting in that it takes a long time to produce those plural copies. In 
this case, each time the document is scanned, a return time required for 
the scanner to return from the end position of the scanner in the scan 
operation to an original position thereof tends to take a longer time. 
Furthermore, after plural copies of a set of documents are produced, the 
produced plural copies are discharged every set of documents in the order 
of the documents by using either of the following apparatuses: 
(1) a sorter for discharging each set of copied papers corresponding to 
each set of documents, to each of plural trays, respectively. 
(2) a document circulation type automatic feeding apparatus for producing 
plural copies of documents by circulating the documents a number of times 
corresponding to the number of copies. 
However, such a problem is caused that the copying machine comprising the 
sorter becomes large, and also, in the copying machine comprising the 
above automatic feeding apparatus such a problem is caused that the 
document is damaged easily. 
In order to solve the above problems, there has been proposed an automatic 
document processing apparatus in the Japanese Laid-open Patent Publication 
(JP-A) No. 140542/1979. There has also been proposed a method for 
projecting reflected light of an image written in a light image memory 
which is arranged on each surface of a regular polyhedron member so as to 
form an electrostatic latent image on a photoconductive body in the 
Japanese Laid-open Utility Model Publication (JP-A) No. 139852/1979. In 
former apparatus, an image of a document is temporarily written in a light 
image memory including liquid crystal, an electrochromic material, PLZT 
(compound of Pb, La, Zr and Ti), and thereafter, the image of the document 
is read out from the light image memory, and it is recorded onto a 
recording body, or an electrostatic latent image corresponding to the 
image of the document is formed onto a photoconductive body. 
However, when image information is written in the aforementioned light 
image memory and is read out therefrom many times repeatedly, the 
performance of writing image information and the performance of storing 
image information deteriorate, resulting in that the image information may 
not be stored therein properly. 
Furthermore, since the aforementioned light image memory can store image 
information for a certain time, the same image can be repeatedly formed 
thereon to make plural copies. However, on the contrary, there is a 
possibility of leaking image information of a secret document. 
Furthermore, foreign matter such as dust may adhere to the aforementioned 
light image memory, and then, the image of the dust is formed as an image 
defect with the image of the document to be formed. Particularly, in the 
case that the aforementioned light image memory is mounted detachably to 
the main body of the copying machine so as to exchange it for another 
light image memory having photosensitivity characteristics, dust may 
adhere to the detached light image memory and also the surface thereof may 
be marred, resulting in that they are formed as an image defect thereon. 
In the aforementioned copying machine, the reflected light from the 
document is projected onto the photoconductive body so as to form an 
electrostatic latent image thereon. For example, in the case of a 
photoconductive body having a photoconductive layer, after the surface of 
the photoconductive body has been uniformly electrified, the reflected 
light from the document is projected on to the photoconductive layer. 
Then, the resistance of the photoconductive layer onto which the reflected 
light is projected decreases, and part of the charge on the surface 
thereof is canceled so as to form an electrostatic latent image on the 
photoconductive body. Thereafter, generally, toner is applied to a portion 
where the charge has not been canceled, i.e., the reflected light has not 
been projected, to render the latent image to be developed into a visible 
toner image. 
However, in the case that the image is formed by using the aforementioned 
light image memory, toner may adhere to the circumference of the image 
forming portion. This is caused because of the following reason. Since 
light is not projected onto the circumference of the image forming 
portion, the charge on the surface thereof is not canceled, resulting in 
that excessive toner may adhere to the circumference of the portion (the 
image forming portion) corresponding to the light image memory. If a sheet 
of paper onto which the toner image is transferred has approximately the 
same size as that of the light image memory, the excessive toner remains 
on the photoconductive body, and then, the excessive toner is abandoned. 
On the other hand, if the size of the paper is larger than that of the 
light image memory, the excessive toner is transferred onto the paper, and 
then, the excessive toner image having a frame shape is formed in the 
circumference of the image forming portion. Furthermore, when the 
excessive toner is used for each image formation, such a problem is caused 
that the cost required for forming the image increases. 
SUMMARY OF THE INVENTION 
An essential object of the present invention is to provide an image forming 
apparatus comprising an image memory plate having a light image memory to 
which the image memory plate is detachably mounted so as to exchange it 
easily, and also to prevent image information of a secret document from 
leaking. 
Another object of the present invention is to provide an image forming 
apparatus comprising a light image memory which is able to protect the 
light image memory. 
A further object of the present invention is to provide an image forming 
apparatus comprising a light image memory which is able to prevent 
excessive toner from adhering to a circumference of an image forming 
portion. 
According to one aspect of the present invention, there is provided an 
image forming apparatus comprising: 
an image memory plate having a light image memory for storing image 
information of a document when reflected light having the image 
information from the document is projected onto a first surface thereof, 
and for reading out the image information stored therein in the form of 
reflected light when light is projected onto a second surface thereof by a 
light source; 
a holder means for detachably holding the image memory plate; 
a moving means for moving said holder means so as to project the reflected 
light from the document onto the first surface of said light image memory 
and to project the light from said light source onto the second surface of 
said light image memory; and 
image formation means for forming the image of the image information onto a 
paper in accordance with the reflected light from said light image memory. 
According to another aspect of the present invention, there is provided an 
image forming apparatus comprising: 
an image memory plate having a light image memory for storing image 
information of a document when reflected light having the image 
information from the document is projected onto a first surface thereof 
through a first lens, and for reading out the image information stored 
therein in the form of reflected light when light is projected onto a 
second surface thereof by a light source; 
a holder means for detachably holding the image memory plate; 
a moving means for moving said holder means so as to project the reflected 
light from the document onto the first surface of said light image memory 
and to project the light from said light source onto the second surface of 
said light image memory; 
image formation means for forming the image of the image information onto a 
paper in accordance with the reflected light from said light image memory 
through a second lens; 
a first transparent protection cover for protecting the first surface of 
said light image memory, said first transparent protection cover being 
arranged at a distance from the first surface of said light image memory 
larger than the depth of focus of said first lens; and 
a second transparent protection cover for protecting the second surface of 
said light image memory, said second transparent protection cover being 
arranged at a distance from the second surface of said light image memory 
larger than the depth of focus of said second lens. 
According to a further aspect of the present invention, there is provided 
an image forming apparatus comprising: 
an image memory plate having a frame member and a light image memory for 
storing image information of a document when reflected light having the 
image information from the document is projected onto a first surface 
thereof, and for reading out the image information stored therein in the 
form of reflected light when light is projected onto a second surface 
thereof by a light source, said light image memory being mounted in said 
frame member, a surface of said frame member on the side of the second 
surface of said light image memory being made of a light reflection 
material; 
a holder means for detachably holding the image memory plate; 
a moving means for moving said holder means so as to project the reflected 
light from the document onto the first surface of said light image memory 
and to project the light from said light source onto the second surface of 
said light image memory; and 
image formation means for forming the image of the image information onto a 
paper in accordance with the reflected light from said light image memory. 
Further scope of applicability of the present invention will become 
apparent from the detailed description given hereinafter. However, it 
should be understood that the detailed description and specific examples, 
while indicating preferred embodiments of the invention, are given by way 
of illustration only, since various changes and modifications within the 
spirit and scope of the invention will become apparent to those skilled in 
the art from this detailed description.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
The preferred embodiment according to the present invention will be 
described below in the order of the following items with reference to the 
attached drawings: 
(1) Composition of Light Image Memory 
(2) Action of Light Image Memory 
(3) Composition of Copying Machine with Light Image Memory 
(4) Action of Copying Machine with Light Image Memory 
(5) Other Modifications 
(1) Composition of Light Image Memory 
Referring to FIG. 1, a light image memory 1 is comprised of an upper base 
1a, a lower base 1b, and a liquid crystal layer 15 made of ferroelectric 
liquid crystal which is arranged between the bases 1a and 1b. The upper 
base 1a is comprised of a glass substrate 11a, a transparent electrode 12a 
made of an electrically conductive material such as ITO, or indium tin 
oxide, which is formed on the bottom surface of the glass substrate 11a, a 
photoconductive layer 13 formed on the bottom surface of the transparent 
electrode 12a, and a reflection layer 14 formed on the bottom surface of 
the photoconductive layer 13. The lower base 1b is comprised of a glass 
substrate 11b, and a transparent electrode 12b made of an electrically 
conductive material such as ITO which is formed on the top surface of the 
glass substrate 11b. 
The transparent electrode 12a is connected to one terminal of a writing-in 
power source 16 for applying a predetermined direct-current voltage to the 
photoconductive layer 13 so as to write image information therein as 
described in detail later, and one terminal of an erasing power source 17 
for applying a predetermined alternating-current voltage to the 
photoconductive layer 13 so as to erase the image information written 
therein as described in detail later. On the other hand, the transparent 
electrode 12b is connected to a common terminal 18c of a switch 18. A 
first terminal 18a of the switch 18 is connected to another terminal of 
the writing-in power source 16, and a second terminal 18b of the switch 18 
is connected to another terminal of the erasing power source 17. The 
switch 18 is switched over so that the common terminal 18c thereof is 
selectively connected to either of the first terminal 18a or the second 
terminal 18b, and therefore, either of the writing-in power source 16 or 
the erasing power source 17 is selectively connected to the transparent 
electrodes 12a and 12b. It is to be noted that, in the present preferred 
embodiment, the writing-in power source 16 is a direct-current power 
source, and the erasing power source 17 is an alternating-current power 
source. However, suitable power sources may be used as power sources 16 
and 17, respectively, depending on the type of the liquid crystal layer 
15, the type of the photoconductive layer 13, and the thickness of the 
liquid crystal layer 15. 
The aforementioned photoconductive layer 13 is made of an inorganic 
photoconductive material such as CdS, CdSe, As.sub.2 Se.sub.3, SeTe, 
amorphous silicon, amorphous germanium etc., or an organic photoconductive 
material such as polyvinyl carbazole, trinitrofluorenon, etc. When light 
is projected onto those photoconductive materials, the resistance thereof 
decreases. 
Since the liquid crystal layer 15 is made of ferroelectric liquid crystal 
as described above, dielectric polarization is caused in the crystal layer 
15 when a predetermined electric field is applied to the layer 15, and 
thereafter, the dielectric polarization still remains even though the 
electric field is removed. Furthermore, the polarity of the dielectric 
polarization is reversed by reversing the direction of the electric field 
to be applied to the layer 15. Concretely, smectic C phase liquid crystal, 
nematic-cholesteric fixed liquid crystal, etc., are provided as the 
aforementioned ferroelectric liquid crystal. In the present preferred 
embodiment, a fixed liquid crystal comprised of 5% cholesteric liquid 
crystal and 95% nematic liquid crystal is used. 
Furthermore, the reflection layer 14 shields light projected from the upper 
side above the glass substrate 11a so as to prevent the light from passing 
through the liquid crystal layer 15 and the base 1b, and also reflects 
light projected from the lower side below the glass substrate 11b. 
Furthermore, the reflection layer 14 prevents the photoconductive layer 13 
and the liquid crystal layer 15 from being in contact with each other so 
as to prevent any chemical reaction from occurring between both of the 
layers 13 and 15. 
(2) Action of Light Image Memory 
In FIG. 2, 13R and 13C denote the resistance and the capacitance of the 
photoconductive layer 13, respectively, which are connected in parallel to 
each other so as to form a parallel circuit 13P, and 15R and 15C denote 
the resistance and the capacitance of the liquid crystal layer 15, 
respectively, which are connected in parallel to each other so as to form 
a parallel circuit 15P. The parallel circuits 13P and 15P are connected in 
series with each other, and the parallel circuits 13P and 15P connected in 
series with each other are selectively connected to either of the 
writing-in power source 16 or the erasing power source 17 through the 
switch 18. 
When writing-in light WL having image information such as reflected light 
from a document, etc., is projected onto the top surface of the light 
image memory 1 from the upper side above the glass substrate 11a (referred 
to as a writing-in side hereinafter), the resistance 13R of the 
photoconductive layer 13 at the portion onto which the writing-in light WL 
is projected (referred to as a light projected portion hereinafter) 
decreases so that the electric field applied to a first portion of the 
liquid crystal layer 15 facing the light projected portion of the 
photoconductive layer 13 increases, resulting in that dielectric 
polarization is caused at the first portion of the liquid crystal layer 
15. Then, the light transmittance of the first portion of the liquid 
crystal layer 15 decreases since the light projected thereonto is 
scattered. On the other hand, the resistance 13R of the photoconductive 
layer 13 at the portion onto which the writing-in light WL is not 
projected (referred to as a not projected portion hereinafter) does not 
vary so that the electric field applied to a second portion of the liquid 
crystal layer 15 facing the non-projected portion of the photoconductive 
layer 13 does not vary, resulting in that the above dielectric 
polarization is not caused at the second portion of the liquid crystal 
layer 15, and the light transmittance of the second portion of the liquid 
crystal layer 15 does not vary. Thus, the light transmittance of the first 
portion of the liquid crystal layer 15 facing the light projected portion 
of the photoconductive layer 13 becomes lower than that of the second 
portion of the liquid crystal layer 15 facing the non-projected portion of 
the photoconductive layer 13. That is, when the writing-in light WL having 
image information is projected onto the top surface of the light image 
memory 1 from the writing-in side, the light transmittance of the first 
portion of the liquid crystal layer 15 facing the light projected portion 
of the photoconductive layer 13 varies, resulting in that the image 
information is written in the light image memory 1. 
Thereafter, when reading-out light RL is projected onto the light image 
memory 1 from the lower side below the glass substrate 11b (referred to as 
a reading-out side hereinafter) by a light source, the projected 
reading-out light RL passes through the second portion of the liquid 
crystal layer 15 where the light transmittance thereof has not varied in 
the above process since the light transmittance thereof is higher than 
that of the first portion of the liquid crystal layer 15 where the light 
transmittance thereof has varied, and is reflected by the reflection layer 
14. On the other hand, the projected reading-out light RL is scattered at 
the first portion of liquid crystal layer 15 where the light transmittance 
thereof has varied. Then, the light which has been reflected by the 
reflection layer 14 and has not been reflected becomes an image 
information light, and is projected onto a photoconductive body such as a 
photoconductive drum of an electrophotographic copying machine so as to 
form an electrostatic latent image thereon. 
In the case that the image information written in the light image memory 1 
is erased, when light is projected onto the whole bottom surface of the 
light image memory 1 from the writing-in side on condition that the 
erasing power source 17 is connected to the transparent electrodes 12a and 
12b, a predetermined alternating-current electric field is applied to the 
whole surface of the liquid crystal layer 15, and then, the light 
transmittance of the first portion of the liquid crystal layer 15 
increases and becomes substantially the same as that of the second portion 
of the liquid crystal layer 15 where the light transmittance thereof has 
not varied, resulting in that the image information which has been written 
therein is erased. 
It is to be noted that the liquid crystal layer 15 is a storage type liquid 
crystal layer, that is, image information which has been written therein 
is not erased even though connection between the writing-in power source 
16 and the transparent electrodes 12a and 12b is canceled, and therefore, 
the image information can be stored in the light image memory 1 for a long 
time. Due to this, it is not necessary to provide a power source for 
storing image information in the light image memory 1. In the light image 
memory 1, an electrochromic material, PLZT, a compound of lead, lanthanum, 
zirconium, and titanium, etc. having an action for storing image 
information may be used instead of the aforementioned liquid crystal. 
(3) Composition of Copying Machine with Light Image Memory 
FIG. 3 shows an electrophotographic copying machine comprising an image 
storage unit 3 having an image memory plate 31 with a plurality of light 
image memories 31-1 to 31-n respectively having the same composition as 
that of the aforementioned light image memory 1. 
Referring to FIG. 3, an automatic document feeding apparatus (referred to 
as an ADF hereinafter) 2 is arranged on the top surface of the main body 
of the copying machine. The ADF 2 comprises a document feeding tray 21, a 
feeding roller 22, a transportation belt 23, a paper discharging tray 24, 
etc. Documents to be copied are set on the document feeding tray 21 so 
that each surface thereof on which an image is formed (referred to as an 
image surface hereinafter) faces the top surface of the document feeding 
tray 21, and the documents are fed from the top document one by one by the 
feeding roller 22. The document fed by the feeding roller 22 is 
transported by the transportation belt 23 so that it is set on a document 
table 25. Thereafter, light is projected onto the image surface of the 
document set thereon by an image writing-in optical system as described 
later, and the reflected light from the document (referred to as a 
document reflected light hereinafter) is projected onto the top surface of 
the light image memory 1 of the image storage apparatus 3. Thereafter, the 
document onto which the light has been projected is discharged to the 
paper discharging tray 24 by the transportation belt 23. 
The image storage unit 3 comprising the image memory plate 31 is arranged 
in the center portion of the copying machine. Referring to FIGS. 4 and 5, 
the image storage unit 3 comprises the image memory plate 31 having a 
plurality of the light image memories 31-1 to 31-n, and a holding unit 70 
for detachably holding the image memory plate 31 and moving the plate 31 
in directions respectively indicated by arrows A and B as shown in FIG. 5. 
Referring back to FIG. 3, below the document table 25, there is arranged 
the image writing-in optical system comprising light sources 26a and 26b, 
and a lens 27. Light is projected onto a document set on the document 
table 25 by the light sources 26a and 26b, and the light reflected from 
the document is projected onto the top surface of the image memory plate 
31 of the image storage unit 3 through the lens 27. Furthermore, above the 
image storage unit 3, there is arranged an erasing lamp 28 for erasing 
image information written in the light image memory 1. 
Referring back to FIG. 4, the image memory plate 31 comprises a frame 
member 31a, a plurality of the light image memories 31-1 to 31-n embedded 
in the frame member 31a, and electrodes 32 arranged at one end portion of 
the frame member 31a. The top surface of the frame member 31a corresponds 
to the aforementioned writing-in side, and the bottom surface thereof 
corresponds to the aforementioned reading-out side. The top surface of the 
frame member 31a is formed so as to absorb light, and the bottom surface 
thereof is formed so as to reflect light. For example, the frame member 
31a is constituted by a metal plate made of Al, etc., which is capable of 
reflecting light like a mirror, and only the top surface thereof is coated 
with black color paint. Therefore, light is absorbed by the top surface of 
the frame member 31a so as to prevent the reflected light from the top 
surface thereof from being incident onto the light image memories 31-1 to 
31-n as a stray light. On the other hand, light is totally reflected by 
the bottom surface of the frame member 31a so as to completely cancel the 
charge on the circumferences of the light image memories 31-1 to 31-n upon 
forming an electrostatic latent image on a photoconductive drum 4 by the 
reflected light from one of the light image memories 31-1 to 31-n. It is 
to be noted that the width W of the frame member 31a is approximately the 
same as that of the photoconductive drum 4, and then, the reflected light 
from one of the light image memories 31-1 to 31-n is projected onto the 
surface of the photoconductive drum 4 almost completely in the direction 
of the width thereof (the longitudinal direction thereof), and the 
reflected light from the frame member 31a can be prevented from being 
incident to the other portion of the copying machine as a stray light. 
Furthermore, another frame member may be used as the frame member 31a on 
condition that the top surface thereof absorbs light and the bottom 
surface thereof reflects light as follows. A frame member made of a 
synthetic resin may be shaped, and the top surface thereof may be coated 
with black color paint or a black synthetic plate may be stuck to the top 
surface of the frame member. The bottom surface of the frame member may be 
metal-plated, or an Al sheet for reflecting light like a mirror is stuck 
to the bottom surface thereof. It is to be noted that the light 
reflectance of the bottom surface of the frame member 31a is preferably 
almost the same as that of the reflection layer 14 of the light image 
memories 31-1 to 31-n. 
As described above, the light image memories 31-1 to 31-n comprise the 
photoconductive layer 13 and the liquid crystal layer 15. When the 
document reflected light is projected thereonto from the writing-in side, 
the light transmittance of the portion of the liquid crystal layer 15 
facing the light projected portion of the photoconductive layer 13 
decreases so as to form an image on the liquid crystal layer 15. 
Respective light image memories 31-1 to 31-n are made so that the size 
thereof is substantially coincident with the maximum one of respective 
sizes of the documents to be set on the document table 25, and the image 
writing-in optical system is provided so that the size thereof is 
substantially coincident therewith. For example, in the copying machine of 
the present preferred embodiment, the maximum one of the documents to be 
set on the document table 25 has a size of A3, maximum A3 size of 
respective images are written in the light image memories 31-1 to 31-n, 
respectively, by projecting the document reflected light thereonto by the 
image writing-in optical system. The image memory plate 31 is moved in the 
direction indicated by the arrows A and B shown in FIGS. 3 and 5 by the 
holding unit 70 described in detail later, so that one of the light image 
memories 31-1 to 31-n is positioned at an image forming position at which 
an image is formed by the aforementioned image writing-in optical system, 
and at an exposure position at which light is projected by a reading-out 
optical system described in detail later, and then, image information is 
written in one of the light image memories 31-1 to 31-n or is read out 
therefrom. 
As described above, the electrodes 32 are arranged at one end portion of 
the image memory plate 31. In the image memory plate 31, the electrodes 32 
are connected to the transparent electrodes 12a and 12b of respective 
light image memories 31-1 to 31-n, respectively, and also the electrodes 
32 are connected to the writing-in power source 16 or the erasing power 
source 17 through the switch 18 as described above. 
The image memory plate 31 is mounted in the holding unit 70 shown in FIG. 
5. The holding unit 70 comprises a holding member 33 having a window frame 
shape with rectangular opening 33h, and the aforementioned image memory 
plate 31 is embedded the opening 33h of the holding member 33 in such a 
manner that the image memory plate 33 bites the opening 33h so that it is 
installed at a predetermined position thereof. A connector 34 for 
connecting the aforementioned electrodes 32 with the writing-in power 
source 16 or the erasing power source 17 through a flat cable 35 is 
arranged at one end portion of the holding member 33. 
Below the holding member 33, there are arranged cylindrical driving rollers 
33a1 and 33a2 so that engaging gears formed on the outer cylindrical 
surface of the driving rollers 33a1 and 33a2 are engaged in engaging 
portions (not shown) formed on the bottom surface of the holding member 33 
respectively. Not only the rollers 33a1 and 33a2, but also a belt pully 
33e are connected to a shaft 33b, and a belt 33d is tensed by the belt 
pully 33e and another belt pully 33c which is connected to a motor 33f. 
When the motor 33f is rotated, the driving force thereof is transmitted to 
the belt pully 33e through the belt pully 33c and the belt 33d, and then, 
the belt pully 33e, and the rollers 33a1 and 33a2 are rotated so that the 
holding member 33 comprising the image memory plate 31 is moved in the 
directions respectively indicated by the arrows A and B in FIG. 5. A 
detecting piece 36 for detecting the position of the holding member 33 is 
arranged integrally with the holding member 33 at the edge portion 
thereof, and a photosensor 37 for detecting the detecting piece 36 is 
arranged so as to face the detecting piece 36 at a predetermined reference 
position of the image memory plate 31. When the photosensor 37 detects the 
detecting piece 36, the image memory plate 31 is positioned at the 
reference position, and then, the writing-in light WL (the document 
reflected light) is projected onto the top surface of the light image 
memory 31-1 by the image writing-in optical system, and the reading-out 
light RL is projected onto the bottom surface of the light image memory 
31-1 by the image reading-out light RL. 
The image memory plate 31 is mounted detachably in the holding member 33 so 
that the electrodes 32 thereof are connected to the connector 34 of the 
holding member 34 which is connected to the writing-in power source 16 or 
the erasing power source 17 through the switch 18, and then, the power 
source 16 or 17 supplies a predetermined voltage to the transparent 
electrodes 12a and 12b of the image memory plate 31. Since the image 
memory plate 31 is mounted detachably in the holding member 33 which is 
arranged in the main body of the copying machine, the image memory plate 
31 can be easily exchanged for another image memory plate, for example, if 
the storage characteristics of the light image memories 31-1 to 31-n 
deteriorate. Furthermore, the image memory plate 31 can be easily 
exchanged for another sort of image memory plate, such as an image memory 
plate comprising a different number of light image memories, an image 
memory plate comprising light image memories having different sensitivity 
characteristics, etc. It is to be noted that the top and bottom surfaces 
of the holding member 33 are coated with black color paint so as to absorb 
light. 
FIG. 6 shows an electric circuit of the image memory plate 31. 
Referring to FIG. 6, a transparent electrode 12a-1 of the light image 
memory 31-1 is connected to a connecting point CP through a switch 38-1, a 
transparent electrode 12a-2 of the light image memory 31-2 is connected to 
the connecting point CP through a switch 38-2, and similarly, a 
transparent electrode 12a-n of the light image memory 31-n is connected to 
the connecting point CP through a switch 38-n. The connecting point CP is 
connected to terminals of the writing-in power source 16 and the erasing 
power source 17. On the other hand, respective transparent electrodes 
12b-1 to 12b-n of the light image memories 31-1 to 31-n are connected 
together to the common terminal 18c of the switch 18. 
When image information is written in one of the light image memories 31-1 
to 31-n, only one of the switches 38-1 to 38-n corresponding to a selected 
one of the light image memories 31-1 to 31-n is turned ON, and the switch 
18 is switched over so that the common terminal 18c thereof is connected 
to the terminal 18a thereof, and then, the writing-in power source 16 
applies a predetermined direct-current voltage to the transparent 
electrodes of the selected one of the light image memories 31-1 to 31-n. 
On the other hand, when the image information written in the light image 
memories 31-1 to 31-n is erased, all of the switches 38-1 to 38-n are 
turned ON, and the switch 18 is switched over so that the common terminal 
18c thereof is connected to the terminal 18b thereof, and then, the 
erasing power source 17 applies a predetermined alternating-current 
voltage to the transparent electrodes of all of the light image memories 
31-1 to 31-n. 
Referring to FIGS. 7 and 8, in order to prevent a foreign matter such as 
dust, etc., from adhering to the top and bottom surfaces of the light 
image memories 31-1 to 31-n, an upper protection cover 39a is arranged on 
the top surface of the image memory plate 31 so as to cover almost the 
whole top surface thereof except for the electrodes 32, and a lower 
protection cover 39b is arranged on the bottom surface of the image memory 
plate 31 so as to cover almost the whole bottom surface thereof except for 
the electrodes 32. The upper and lower protection covers 39a and 39b have 
an approximately rectangular parallelopiped box shape, and are made of 
light transparent material such as glass, synthetic resin film, plastic 
resin wherein light passing through the covers 39a and 39b has a 
wavelength band which is sensitive to the light image memories 31-1 to 
31-n. The upper and lower protection covers 39a and 39b are arranged so as 
to protect the top and bottom surfaces of the light image memories 31-1 to 
31-n. The height d.sub.1 of the upper protection cover 39a is equal to or 
larger than the depth of field of the lens 27 of the image writing-in 
optical system, and the height d.sub.2 of the lower protection cover 39b 
is equal to or larger than the depth of field of the lens of the image 
reading-out optical system. Therefore, even though dust etc. adheres to 
the protection covers 39a and 39b, the dust can be prevented from 
influencing images formed on the top surface of the light image memories 
31-1 to 31-n, and the surface of the photoconductive drum 4. The heights 
d.sub.1 and d.sub.2 are preferably about 2 to 30 mm. 
It is to be noted that a photographic filter suitable for the sensitivity 
characteristics of the photoconductive layer 13 of the light image 
memories 31-1 to 31-n may be mounted on the top surface of the upper 
protection cover 39a, and a photographic filter suitable for the 
sensitivity characteristics of the photoconductive drum 4 may be mounted 
on the bottom surface of the lower protection cover 39b. A heat absorbing 
filter for absorbing heat radiated from the above optical systems may be 
mounted thereon. Furthermore, respective side portions 39as and 39bs of 
the upper and lower protection covers 39a and 39b may be constituted by a 
light opaque material, and then, stray light can be prevented from 
entering the light image memories 31-1 to 31-n. 
Referrring back to FIG. 3, the photoconductive drum 4 is arranged at the 
lower portion of the main body of the copying machine, and a 
photoconductive layer is formed on the surface of the photoconductive drum 
4. Around the photoconductive drum 4, there are arranged a corona charger 
41, a development unit 42, a transfer charger 43, etc. After the surface 
of the photoconductive drum 4 is uniformly electrified by the corona 
charger 41, it is exposed to light projected by the image reading-out 
optical system. The image reading-out optical system comprises a light 
source 51, mirrors 52 and 53, and a lens 54 which are arranged below the 
image storage unit 3. In the image reading-out optical system, light 
projected by the light source 51 is reflected by the bottom surface of one 
of the light image memories 31-1 to 31-n of the image memory plate 31, and 
the reflected light from the image memory plate 31 is projected onto the 
surface of the photoconductive drum 4 through the mirror 52, the lens 54, 
and the mirror 53 so as to form an electrostatic latent image thereon. 
Thereafter, the electrostatic latent image is developed by the development 
unit 42 into a visible toner image with toner. A paper feeding cassette 61 
for feeding copying papers is arranged at the left side portion of the 
main body of the copying machine, and a copying paper is fed from the 
paper feeding cassette 61 to the transfer charger 43 by a pick-up roller 
64 and feeding rollers 65. After the transfer charger 43 transfers the 
visible toner image onto the copying paper, the copying paper is fed to 
the fixing unit 62 in order to fix the visible toner image thereon, and 
then, is discharged to a paper discharging tray 63 arranged at the left 
side portion of the main body of the copying machine and above the paper 
feeding cassette 61. 
(4) Action of Copying Machine with Light Image Memory 
An action of the copying machine in the case of copying plural documents 
continuously, i.e., producing plural copies of many documents will be 
described below with reference to the drawings. In this case, first of 
all, the document reflected light having image information of each 
document is projected onto the top surface of respective light image 
memories 31-1 to 31-n so as to write the image information of each 
document therein, respectively, and thereafter, the image information of 
each document written in respective light image memories 31-1 to 31-n is 
read out as reflected light by projecting light onto the bottom surface 
thereof, and the images of respective documents are formed on copying 
papers by the reflected light from respective light image memories 31-1 to 
31-n, respectively, wherein n is the number of the documents. 
When the image information is written in respective light image memories 
31-1 to 31-n, the switch 18 is switched over so that the common terminal 
18c thereof is connected to the terminal 18a thereof, and one of the 
switches 38-1 to 38-n is turned ON in order. For example, first of all, 
after only the switch 38-1 is turned ON and the other switches 38-2 to 
38-n are turned OFF, the reflected light from the first document is 
projected onto the top surface of the light image memory 31-1 of the image 
memory plate 31 so as to write the image information of the first document 
therein. Thereafter, the holding member 33 is moved in the direction 
indicated by the arrow A as shown in FIGS. 3 and 5 by a distance between 
the adjacent light image memories (referred to as a step distance 
hereinafter). 
Next, after only the switch 38-2 is turned ON and the other switches 38-1 
and 38-3 to 38-n are turned OFF, the reflected light from the second 
document is projected onto the top surface of the light image memory 31-2 
of the image memory plate 31 so as to write the image information of the 
second document therein. 
Similarly, after the copied document is exchanged for the next document by 
the ADF 2 and the image memory plate 31 is moved in the direction 
indicated by the arrow A by the step distance, the reflected light from 
each document is projected onto the top surface of each light image memory 
31-3 to 31-n so as to write the image information of each document 
therein, respectively, and then, the image writing-in process is 
completed. It is to be noted that, in the aforementioned image writing-in 
process, since the top surface of the frame member 31a of the image memory 
plate 31 absorbs light, light reflected by the frame member 31a can be 
prevented from projecting onto the light image memories 31-1 to 31-n as 
stray light, resulting in that the image information of each document can 
be written in the light image memories 31-1 to 31-n properly. 
Next, in the case that the image information of respective documents 
written in the light image memories 31-1 to 31-n of the image memory plate 
31 is read out and the image of the written image information is formed on 
a copying paper, after the holding member 33 is moved in the direction 
indicated by the arrow B so as to return to the reference position 
thereof, the image information of respective documents is read out in 
order from the light image memories 31-1 to 31-n, and then, respective 
images corresponding to the read-out image information are formed on 
copying papers, respectively. In the image reading-out process, the 
holding member 33 is moved in the direction indicated by the arrow A so 
that the image information written in the light image memories 31-1 to 
31-n is scanned, and then, the reflected light from each light image 
memory 31-1 to 31-n is projected onto the surface of the photoconductive 
drum 4 by the image reading-out optical system, so as to form an 
electrostatic latent image of the image information thereon. Thereafter, 
an image corresponding to the latent image is formed on a copying paper in 
a known photographic copying process. In the above process, the moving 
velocity of the holding member 33 in the direction indicated by the arrow 
A is set according to the rotation speed of the photoconductive drum 4 and 
the magnification for copying. 
In the case that a copy of plural documents is produced, the holding member 
33 is moved continuously in the direction indicated by the arrow A, and 
then, each image information written in the light image memories 31-1 to 
31-n is read out in order by the image reading-out optical system so that 
the image of each image information is formed on a copying paper as 
described above. Furthermore, in the case that plural copies of a document 
are produced, after the holding member 33 is moved to the position of the 
light image memory 31-n, the holding member 33 is moved in the direction 
indicated by the arrow B so as to return to the reference position 
thereof, and then, the holding member 33 is moved in the direction 
indicated by the arrow A again so as to form the image of each image 
information on a copying paper as described above. 
Since the frame member 31a of the image memory plate 31 reflects light, 
when the reflected light from each light image memory 31-1 to 31-n is 
projected onto the surface of the photoconductive drum 4 so as to form an 
electrostatic latent image thereon, the charge in the circumference of the 
portion on the surface of the photoconductive drum 4 where the 
electrostatic latent image is formed (corresponding to the frame member 
31a) is canceled, resulting in that toner can be prevented from adhering 
to the above portion. 
Since the holding member 33 is moved continuously in the direction 
indicated by the arrow A so as to continuously form respective images of 
plural documents on copying papers, respectively, the processing time for 
producing a copy of plural documents becomes shorter than that of the 
conventional copying machine. Furthermore, in the case that plural copies 
of a set of documents are produced, since the images of each set of 
documents are respectively formed on the copying papers every set of 
documents and each set of copying papers is discharged to one paper 
discharging tray 63, it is not necessary to provide a sorter etc., 
resulting in that the copying machine can be prevented from becoming 
larger. Furthermore, since it is not necessary to circulate the documents 
many times, the documents can be prevented from being damaged. 
Thereafter, in the case that the image information written in the light 
image memories 31-1 to 31-n is erased, all the switches 38-1 to 38-n are 
turned ON, the switch 18 is switched over so that the common terminal 18c 
thereof is connected to the terminal 18b thereof so that a predetermined 
alternating-current voltage is applied to the transparent electrodes of 
the light image memories 31-1 to 31-n, and the erasing lamp 28 is turned 
ON, and then, the image information written in the light image memories 
31-1 to 31-n is erased. 
As described above, an image of a document is formed on a copying paper by 
using the light image memories 31-1 to 31-n. It is to be noted that, in 
the present preferred embodiment, the electrophotographic photoconductive 
drum 4 comprising the photoconductive layer is used as the photoconductive 
body, however, another sort of photoconductive body such as a media sheet 
coated with microcapsules including a photohardening material and 
colorless dyes may be used. Since the microcapsules onto which light is 
projected harden in the media sheet, an image receiving sheet coated with 
developer is superimposed on the media sheet and a pressure is applied 
thereto by using a pressing roller, and then, the microcapsules which are 
not hardened are broken, and colorless dyes flow out therefrom onto the 
developer of the image receiving sheet so as to form a colored image 
thereon. Therefore, in this case, since the microcapsules in the 
circumference of the image forming portion of the media sheet (the portion 
corresponding to the light image memories 31-1 to 31-n) harden in 
accordance with the light reflected by the frame member 31a, the 
microcapsules can be prevented from being broken unnecessarily. 
Furthermore, stain can be prevented from adhering to the formed image on 
the copying paper, and also the inside of the main body of the copying 
machine can be prevented from becoming dirty. 
In the case that a negative image is formed, for example, an image is 
formed by using a photoconductive body having a photoconductive layer, 
when toner is made to adhere to a portion where the charge is canceled, a 
negative image comprised of reversed white image and reversed black image 
can be obtained. In this case, the surface of the frame member 31a of the 
image memory plate 31 may be made of a light absorbing material, and then, 
toner can be prevented from adhering to the circumference of the image 
forming portion. 
It is to be understood that various other modifications will be apparent to 
and can be readily made by those skilled in the art without departing from 
the scope and spirit of the present invention. Accordingly, it is not 
intended that the scope of the claims appended hereto be limited to the 
description as set forth herein, but rather that the claims be construed 
as encompassing all the features of patentable novelty that reside in the 
present invention, including all features that would be treated as 
equivalents thereof by those skilled in the art to which the present 
invention pertains.