Image forming apparatus with increased throughput from simultaneous scanning and original feed

An image reading apparatus has an automatic original transporting device, a scanning device for effecting exposure scanning of the original while moving relative to the original over a platen glass, and a control circuit for controlling the scanning device to cause it to effect exposure scanning while moving it in a direction opposite to the direction in which the original is being transported. An image forming apparatus which includes the above image reading apparatus is also provided.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to an image reading apparatus, such as a 
copying machine, a printer or a laser beam printer, provided with original 
feeding means for automatically feeding an original to an original platen, 
and to an image forming apparatus provided with such an image reading 
apparatus. 
2. Related Background Art 
Conventional methods of feeding an original by means of a sheet-material 
transporting device and reading an image therefrom by means of an image 
forming apparatus such as a copying machine are divided into two major 
types. One method comprises the steps of exposing and reading a sheet 
original upon halting it at a predetermined position on a glass platen, 
while moving an optical system, and the other method comprises the steps 
of exposing and reading a sheet original by means of an optical system 
fixed in position, while transporting sheet originals one after another. 
The former method is utilized in a recurrence type of original transporting 
apparatus disclosed in Japanese Patent Laid-Open No. 58-148150. This 
apparatus is disposed on the top of the main body of a copying machine, 
and sheet originals are stacked on a tray with their processing surfaces 
facing up. One sheet original is sequentially separated from the original 
stack at the lowermost position thereof at a time and transported onto a 
platen glass disposed on the main body of the copying machine. After the 
sheet original has been halted in a predetermined position, only an 
optical system is moved to expose the sheet original. After completion of 
the exposure, the sheet original is discharged from the original platen. 
After the leading edge of the original is securely captured by the first 
grip rollers on the downstream side, the next original is transported onto 
the platen glass. Replacement of originals on the platen glass is 
accomplished by the operation of causing the successive originals to pass 
each other. 
However, this conventional arrangement has a number of disadvantages. For 
example, replacement of originals is performed by the operation of causing 
the exposed original and the next original to pass each other. 
Accordingly, transport of the next original cannot be performed before the 
leading edge of the exposed original is securely gripped by the first 
transporting means on the downstream side. As a result, the time required 
for the leading edge of the original to be securely gripped after the 
completion of the exposure is needed for the replacement of the originals 
in spite of a lost time. This makes it difficult to improve throughput to 
a great extent. 
A conventional arrangement utilizing the latter method is disclosed in 
Japanese Patent Laid-Open Nos. 60-140364 and 61-32836. In this 
arrangement, a continuous copying operation is achieved by sequentially 
transporting a sheet original to an exposure position, halting the sheet 
original at a predetermined position, moving an optical system alone, 
replacing the original with the next original immediately after reading 
has reached the trailing edge of the original, and simultaneously 
returning the optical system to its home position. The continuous copying 
operation leads to the improved throughput of the copying machine. 
However, the above method has the following disadvantage. The distance 
traveled by the next original from the leading edge of the halt position 
to the reading start position need be made equal to the length of the 
original plus the distance between successive originals. As a result, 
original replacement requires a long time and the throughput of the 
copying machine deteriorates. 
The aforesaid method has a critical problem. Since the same portion is 
continuously illuminated by the illumination lamp of the optical system, 
the temperature of the platen glass or the original transporting device 
disposed thereon increases. In particular, an arrangement of a 
high-throughput type requires a high intensity lamp, and the amount of 
heat increases. 
In order to solve the above problem, Japanese Patent Laid-Open No. 
60-178441 discloses a method in which each time a predetermined number of 
originals are exposed, the halt position of an optical system is shifted. 
This method, however, still has a number of problems. For example, each 
time the halt position of the optical system is shifted, the read start 
position of the leading edge of the original varies. Accordingly, a 
complicated control method for positioning is required. The time required 
for the optical system to move to a different halt position is consumed as 
a lost time, thus leading to a decrease in throughput. 
This method has further problems. For example, if the throughput of the 
method is to be improved to a further extent, it is also possible to adopt 
a method of reducing the time of image reading merely by increasing the 
moving speed of the original. In such method, since a sheet original is 
held by the friction of belts, rollers or the like, as the moving speed 
increases, the amount of slip or variation in the speed of rotation of a 
motor may increase. As a result, an image may be blurred and a 
satisfactory image cannot be obtained. If these problems are to be 
improved, a motor or a driving system having torque or inertia greater 
than would be otherwise unnecessary must be prepared, so that the cost and 
size of the apparatus will increase. 
SUMMARY OF THE INVENTION 
It is therefore an object of the present invention to provide an improved 
image reading apparatus and an improved image forming apparatus provided 
with such image reading apparatus. 
It is another object of the present invention to provide an image reading 
apparatus capable of improving throughput by means of a simple arrangement 
and an image forming apparatus provided with such image reading apparatus. 
It is another object of the present invention to provide an image reading 
apparatus capable of realizing a low cost and compact arrangement but of 
minimizing the formation of imperfect images, and an image forming 
apparatus provided with such image reading apparatus. 
It is another object of the present invention to provide an image reading 
apparatus which involves no excessive temperature rise and which enables 
easy control of scanning of scanning means, and an image forming apparatus 
provided with such image reading apparatus. 
It is another object of the present invention to provide an image reading 
apparatus in which the relative reading speed is increased without the 
need to increase the moving speed of an original by executing reading 
while causing the original and a scanning means to pass each other, and to 
provide an image forming apparatus provided with such image reading 
apparatus. 
It is another object of the present invention to provide an image reading 
apparatus in which the throughput of a multicopy operation can be improved 
and an image forming apparatus provided with such image reading apparatus. 
It is another object of the present invention to provide an image reading 
apparatus which effects a multicopy operation by performing reading while 
causing an original and a scanning means to pass each other, then 
refeeding the original after the completion of the reading, and then 
repeating a similar reading operation, and to provide an image forming 
apparatus provided with such image reading apparatus. 
It is another object of the present invention to provide an image reading 
apparatus which performs reading while causing an original and a scanning 
means to pass each other and whose throughput is improved by rendering the 
reversing position of a scanning means variable, and to provide an image 
forming apparatus provided with such image reading apparatus. 
In accordance with these objects there is provided an image reading 
apparatus comprising original transporting means for automatically 
transporting a plurality of originals one by one onto an original platen; 
scanning means for effecting exposure scanning of the original while 
moving relative to said original which is being transported over said 
original platen by said original transporting means; and controlling means 
for controlling said scanning means so as to cause said scanning means to 
effect exposure scanning while moving said scanning means in a direction 
opposite to the direction of original feed during the transport of said 
original by said original transporting means. 
The above and other objects, features and advantages of the present 
invention will be apparent from the following description of preferred 
embodiments of the invention with reference to the accompanying drawings.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
Embodiments of the present invention will be explained below with reference 
to the accompanying drawings. 
FIG. 1 is a partially omitted cross-sectional view showing the internal 
arrangement of an image forming apparatus to which one embodiment of the 
present invention is applied. In the drawing, the main body of a copying 
machine having an image reading function and an image recording function 
is indicated generally at 100, and a recurrence type of document original 
feeder (hereinafter referred to as a "RDF") is indicated generally at 300. 
A. MAIN BODY 100 
The main body 100 comprises the following major elements: an original 
support glass on which an original is placed; an illumination lamp 
(exposure lamp) 103 for illuminating an original; first to third scanning 
reflection mirrors (scanning mirrors) 105, 107 and 109 for changing the 
optical path of light reflected from the original; a lens 111 having the 
functions of effecting focusing and changing magnifications; and a fourth 
reflection mirror (scanning mirror) 113 for changing the optical path of 
the reflected light. The main body 100 also comprises an optical system 
motor 115 for actuating an optical system, and sensors 117 and 119 for 
sensing the position of the optical system. 
The main body 100 also comprises a photosensitive drum 131, a main motor 
133 for actuating the photosensitive drum 131, a high voltage unit 135, a 
blank exposure unit 137, a developing unit 139, a developing roller 140, a 
transfer charger 141, a separating charger 143, and a cleaning device 145. 
The main body 100 further comprises an upper stage casette 151, a lower 
stage casette -53, a manual feed port 171, paper feed rollers 115 and 157, 
and a registration roller 159. A carriage belt 161 transports recording 
paper on which an image is recorded, and a fixing unit 163 fixes a toner 
image on the received recording paper by the application of heat and 
pressure. 
The surface of the photosensitive drum 131 is made from a seamless 
photosensitive member employing a photoconductive member and an electrical 
conductor. The drum 131, which is supported for rotation about its axis, 
is actuated to rotate in the direction of the arced arrow shown thereon in 
FIG. 1 by the motion of the main motor 133 which is actuated in response 
to the operation of pressing a copy start key which will be explained 
later. Then, when predetermined rotation control and potential control 
processing (preprocessing) for the drum 131 have been completed, the 
original placed on the original platen glass 101 is illuminated by the 
illumination lamp 103 integral with the first scanning mirror 105, and 
light reflected from the original is focused on the photosensitive drum 
131 over the optical path formed by the first scanning mirror 105, the 
second scanning mirror 107, the third scanning mirror 109, the lens 111, 
and the fourth scanning mirror 113. 
The photosensitive drum 131 is corona-discharged by the high voltage unit 
135. Thereafter, the photosensitive drum 131 is slit-exposed to the image 
(original image) illuminated by the illumination lamp 103, and an 
electrostatic latent image is formed on the drum 131 by a known Carlson 
method. 
Then, the electrostatic latent image on the photosensitive drum 131 is 
developed by the developing roller 140 of the developing unit 139 so that 
it is formed as a visible toner image. The toner image is transferred to 
transfer paper by means of the transfer charger as will be explained 
later. 
More specifically, either the transfer paper set in the upper stage casette 
151 or the lower stage casette 153 or the transfer paper set in the manual 
feed port 171 is fed into the main body 100 by the paper feed roller 155 
or 157, and is then fed toward the photosensitive drum 131 at an accurate 
timing by the registration roller 159, whereby the tip of the latent image 
is made coincident with the leading edge of the transfer paper. 
Thereafter, the toner image is transferred from the photosensitive drum 
131 to the transfer paper by passing the transfer paper through the gap 
between the transfer charger 141 and the photosensitive drum 131. After 
the transfer step has been completed, the transfer paper is separated from 
the photosensitive drum 131 by the separating charger 143 and conducted 
into the fixing unit 163 by the carriage belt 161. In the fixing unit 163. 
the transferred image is fixed by the application of pressure and heat. 
The fixed paper is then discharged out of the main body 100 and stacked on 
a discharge tray 172. 
After the transfer, the photosensitive drum 131 continues rotating, whereby 
its surface is cleaned by the cleaning device 145 made up of a cleaning 
roller and an elastic blade. 
B. RDF (RECURRENCE TYPE OF ORIGINAL DOCUMENT FEEDER) 300 
In the RDF 300, a bundle 302 of originals is set on a stacking tray 301. 
The original bundle 302 set on the stacking tray 301 is sensed by an 
original set sensor 351. If the original bundle 302 is a bundle of 
one-sided originals, the RDF 300 operates as follows. The originals are 
separated from the original bundle 302 at the lowermost power thereof in a 
one-by-one fashion by means of a semicircular roller 304 and a separating 
roller 303, which are actuated by a separating roller motor 321. The 
original thus separated is transported to a predetermined position on the 
platen glass 101 along paths I and II by means of a carriage roller 305 
and a flat-face belt 306 both of which are actuated by a belt motor 323. 
When a predetermined time passes after the original has been sensed by a 
registration sensor 353 positioned midway in the path I, the transport of 
the original is stopped and a copy operating is started. The original is 
fed into paths IV and V over a path III by a carriage large roller 307 
which is actuated by a carriage large roller motor 327 (FIG. 2). After the 
original has been sensed by a discharge sensor 355 positioned in the path 
IV, it is returned to the top of the original bundle 302 by means of a 
discharge roller 308. Carriage rollers 311 and 312 are disposed around the 
outer periphery of the carriage large roller 307 so that they individually 
press the carriage large roller 307 to assure the required transporting 
force. The transporting force created by the carriage large roller 307 and 
the carriage roller 311 is selected to be greater than that of the 
flat-face belt 306. Accordingly, during an original discharge operation, 
when the leading edge of the original is captured by the carriage large 
roller 307 and the carriage roller 311, it is possible to reliably remove 
the original from the platen glass 101 even if the flat-face belt 306 
stops or reverses. A recycle lever 309 senses one cycle of original 
feeding by means of a sensor 359. During an original feed start, the 
recycle lever 309 is rotated and placed on the top of the original bundle 
by means of the motor 329. The originals are fed one-by-one and, when the 
trailing edge of the final original passes by the recycle lever 309, the 
recycle lever 309 falls by its own weight, thereby making it possible to 
sense the completion of one cycle of original feeding operation. 
If the original bundle 302 is a bundle of double-sided originals, the RDF 
300 operates as follows. The original is likewise conducted into the path 
III over the paths I and II. Then, a rotatable switching flapper 310 is 
switched by a solenoid SL 331 (FIG. 2) to conduct the leading edge of the 
original into the path IV. The original is then passed through the path II 
by the carriage roller 305, transported to the platen glass 101 by the 
flat-face belt 306, and stopped in position. In other words, the carriage 
large roller 307 and the route formed by the paths III-IV-II cooperate to 
reverse the original. 
In addition, since the originals are one-by-one fed from the original 
bundle 302 over the paths I-II-III until the recycle lever 309 senses the 
completion of one cycle of original feeding operation, the number of 
originals can be automatically counted. 
FIG. 2 shows in block form the circuit arrangement of a control device 500 
in the embodiment of FIG. 1. 
In FIG. 2, a central processing unit (CPU) 501 performs arithmetic control 
for controlling the operation of the copying machine and, for example, a 
microcomputer V50 manufactured by NEC (Nippon Electric Co., Ltd.) may be 
utilized. A read-only memory (ROM) 503 stored control procedures (control 
program), and the CPU 510 controls individual elements connected thereof 
via buses in accordance with the control procedures stored in the ROM 503. 
A random access memory (RAM) 505 constitutes a main memory for use as an 
input-data storing area or a working memory area. 
An interface (I/O) 507 outputs the control signal supplied from the CPU 501 
to a predetermined load, such as the main motor 133. The interface (I/O) 
507 also serves to output a speed data signal, a rotational direction 
signal or the like to a motor controller 110 which controls the optical 
system motor 115. An interface 509 receives a signal output from an image 
tip sensor 117 or the like and transfers it to the CPU 501. An interface 
511 outputs a control signal, supplied from the CPU 501, to a load such as 
a separating roller motor 321 of RDF or the like. An interface 513 
receives a signal output from the registration sensor 353 of the RDF or 
another sensor. The interfaces 507, 509, 510 and 513 may utilize, for 
example, .mu.PD8255 supplied by NEC. 
FIG. 3 is a circuit diagram showing a controller section 110 for the 
optical system motor 115. In FIG. 3, a PLL control section 1106 provides 
constant speed control over the optical system motor 115. As is known, the 
PLL control section 1106 compares a reference frequency FS 512 
corresponding to the desired speed of revolution of the motor 115 with a 
signal FG 1101 which is output from an encoder 1108. The encoder 1108 
electrically converts the speed of revolution of the motor 115 into the 
signal FG. The PLL control section 1106 detects the phase difference 
between them and outputs it as a motor drive signal. The signal FG 1101 is 
input to the interface 509. 
A comparator 1105 compares the drive output from the PLL control section 
1106 with a triangular wave 1107 obtained from an oscillator 1109, a 
resistor and a capacitor, and outputs a PWM (pulse width 
modulation)-controlled signal, thereby applying a drive voltage to the 
optical system motor 115. The reciprocal motion of the optical system by 
the optical system motor 115 is performed in the following manner. A FW/RV 
signal 1104 is output from the I/O output section 507 of the main body 
control section. If the FW/RV signal 1104 is at its low level, an 
electrical current is supplied to the optical system motor 115 through 
transistors 1110 and 1113. The motor 115 is thus actuated in the forward 
direction, thereby causing the optical system to move forwardly. If the 
FW/RV signal 1104 is at its high level, an electrical current is supplied 
to the optical system motor 115 through transistors 1111 and 1112. The 
motor 115 is thus actuated in the reverse direction, thereby causing the 
optical system to move rearwardly. 
Although the speed of revolution of the motor 115 is determined by the 
reference frequency FS 512, this reference frequency FS 512 is output from 
the CPU 501 which controls the present apparatus, and also the CPU 501 can 
select an arbitrary frequency. More specifically, as the reference 
frequency FS is increased, the motor speed increases so that the speed 
reciprocal movement of the optical system can be increased. In contrast, 
as the reference frequency FS is decreased, the motor speed decreases so 
that the speed of reciprocal movement of the optical system can be 
reduced. Accordingly, during a copying operation, the CPU 501 changes the 
reference frequency FS, as required, to change the speed of movement of 
the optical system, thereby reducing power dissipation. 
A motor controller 325 of the RDF 300 may be constructed by using the 
arrangement of a similar PLL control and the optical system motor 
controller 110 of FIG. 3. Although no detailed explanation is given, the 
motor controller 325 can also select an arbitrary speed of revolution on 
the basis of a reference frequency FS 333. In addition, an encoder (belt 
FG) 357 electrically converts the speed of rotation of the belt in a 
signal. This signal is input to the interface 513 and supplied to the CPU 
501. The driving force of the belt motor 323 is transmitted to the 
flat-face belt 306 and the carriage roller 305 through a first clutch 361 
(refer to FIG. 2). In addition, the first clutch 361 (refer to FIG. 2). In 
addition, the first clutch 361 serves to separate the rotational force of 
the belt motor 323 from the driving force of the flat-face belt 306 and 
the carriage roller 305. A brake 363 (refer to FIG. 2) is connected to the 
flat-face belt 306 so that the flat-face belt 306 can be instantaneously 
stopped. 
The carriage roller 305 includes a one-way clutch. Accordingly, during the 
reverse motion of the belt motor 323, no driving force is transmitted to 
the carriage roller 305, while the separating roller motor 321 (FIG. 2) 
and a clutch 365 (FIG. 2) cooperate to transmit driving force to the 
carriage roller 305. In this manner, the separating roller 303 and the 
carriage roller 305 can be actuated irrespective of the belt motor 323. 
Copying operation employing the RDF of the image forming apparatus 
according to the present invention will be explained below with reference 
to FIGS. 4-1 to 4-4, which shows the operation of the RDF, and the 
flowchart of FIG. 5. 
First of all, the operation of a single-oridinal-copy mode will be 
explained below. In response to a copy start command, the recycle lever 
motor 329 is activated to place the recycle lever 309 on the original 
bundle 302 placed on the stacking tray 301 (Step 1). The semicircular 
roller 304 and the separating roller 303 are rotated for a predetermined 
time to extract one original from the original bundle 302 at the lowermost 
position thereof. The leading end of the original is moved into contact 
with the carriage roller 305 so that the original is looped. This step 
prevents the sheet original from being fed obliquely (Step 2) (FIG. 4-1). 
Thereafter, the carriage roller 305 and the flat-face belt 306 are rotated 
(Step 3) to transport the original through the path 11 to a predetermined 
position .gamma. on the platen glass 101. Although the transporting speed 
up to this point is set to a full speed, the original can be stopped with 
a high positional accuracy by engaging the first clutch 311 and by 
instantaneously energizing the brake 363. Then, the optical system motor 
115 is turned on, and the first scanning mirror 105 starts to move in the 
direction of arrow A for scanning purposes. The first scanning mirror 105 
moves at a speed SM under constant speed of the PLL control section. At 
the same time, the belt motor 323 is rotated in the reverse direction at a 
speed SB under constant speed of the PLL control section (Step 6). When 
the first scanning mirror 105 reaches the position where the home position 
sensor 119 is turned off (point .beta. of FIG. 4-2), the belt brake 363 is 
energized and the first clutch 361 is engaged. Thus, the original whose 
leading edge is located at the position .gamma. on the platen glass 101 is 
transported in the direction of arrow B (Step 7). In this manner, the 
first scanning mirror 105 and the original are moved in directions 
opposite to each other at predetermined speeds, respectively. When the 
first scanning mirror 105 reaches a position coincident with the leading 
edge of the original (point .alpha. of FIG. 4-2), the original is read to 
start the operation of forming an electrostatic latent image corresponding 
to the original image on the photosensitive drum 131 (Step 8). 
In the meantime, it is determined whether or not the recycle lever 309 has 
fallen down, that is, whether or not the final original has reached (Step 
9). If the recycle lever 309 has not yet fallen down, the separating 
roller 303 and the second clutch 365 are worked for a predetermined time 
to separate the next original from the original bundle 302. This original 
is moved into contact with the carriage roller 305 to form a loop (Step 
9). In parallel with the above-described original reading, the next 
original is on stand-by in a looped form in contact with the carriage 
roller 305. When the second clutch 365 is engaged and the separating 
roller motor 321 is activated, the separating roller 303 and the carriage 
roller 305 are rotated to transport the next original through the path II. 
When the leading edge of the original reaches a position (point d) 
immediately before the platen glass 101, the original is stopped for 
stand-by (Step 10). This operation makes it possible to minimize the 
distance between the stand-by position of the next original and the 
predetermined position on the platen glass 101, thereby enabling the 
original to be moved in a reduced time (Refer to FIG. 4-3). The above 
operation is executed by the time when the first scanning mirror 105 
reaches a position corresponding to the trailing edge of the original 
which is being transported in the direction of arrow B. When the first 
scanning mirror 105 reaches the trailing edge of the original, the 
original reading operation is completed and the optical system motor 115 
is reversed to move the first scanning mirror 105 in a direction opposite 
to that of arrow A (Steps 12, 13 and 14). At the same time, the carriage 
large roller motor 327 is turned on to rotate the carriage large roller 
307, thereby discharging the exposed original (Step 15). It is then 
determined whether or not the recycle lever 309 has been fallen down (Step 
16). If it has not yet fallen down, it is determined that the next 
original is on stand-by at point d immediately before the platen glass 
101. The belt motor 323 is turned on to rotate the carriage roller 305 and 
the flat-face belt 306 in the forward direction, and the next original is 
moved at a full speed in a direction opposite to the direction of arrow B 
and is transported onto the platen glass 101 (Step 17). At this point in 
time, the leading edge of the original from which a copy has been 
produced, is clamped between the carriage large roller 307 and the 
carriage roller 311 (refer to FIG. 4-4). Accordingly, the original is 
reliably discharged onto the tray 301. Then, the optical system is reset 
to and halted at the home position (Step 18) and the process returns to 
Step 4, where it waits for the next original to be positioned at the 
position .gamma. on the platen glass 101. If the recycle lever 309 falls 
down, it is determined that the next original is the last one, and after 
the next original has been discharged, the operation is completed (Step 
20). 
By repeating the operation explained in connection with FIGS. 4-1 to 4-4 
and Steps 3-18, a continuous copying operation is enabled. 
The respective moving speeds of the first scanning mirror 105 and the 
flat-face belt 306 and the coincidence of the optical system and the 
original's leading edge will be explained with reference to FIGS. 4-1 to 
6. In the following description, it is assumed that SM represents the 
moving speed the first scanning mirror 105, SB the moving speed of the 
flat-face belt 306, the circumferential speed SD of of the photosensitive 
drum 131 in the main body of the copying machine, l1 the length of the 
original, l2 the distance between the position .alpha. where the read 
position of the first scanning mirror 105 coincides with the original's 
leading edge and the position of the nip between the carriage roller 311 
and the carriage large roller 307, and l3 the distance between the 
position .alpha. where the read position of the first scanning mirror 105 
coincides with the original's leading edge and the original's trailing 
edge. 
It is further assumed that the relative speed difference SM+SB between the 
first scanning mirror 105 and the flat-face belt 306 is set to a speed 
(SM+SB=SD) equal to the circumferential speed SD of the photosensitive 
drum 131. This setting makes it possible to form an electrostatic latent 
image of equal quality on the photosensitive drum 131, whether or not the 
RDF is in use. Accordingly, it is possible to produce a copy image of the 
same quality in either case. 
If the intervals of transporting originals onto the platen glass 101 are to 
be made as small as possible, originals on the platen glass 101 must be 
replaced at a close timing. Accordingly, it is necessary that, when 
reading of a desired original is completed, the leading edge of the 
original be reliably nipped between the carriage roller 311 and the 
carriage large roller 307. Accordingly, it is necessary to satisfy the 
condition l2/SB.ltoreq.l3/SM, where l3=l1-l2. By satisfying the above two 
conditions SM+SB=SD and l2/SB&lt;l3/SM, it is possible to realize an original 
replacement without taking account of loss time which results from the 
intervals of close original replacement. 
Referring further to FIG. 7, which is a timing chart of the operation of 
the apparatus of the above embodiment, the operation of positioning an 
image tip will be explained in detail below. In the above embodiment, at 
the instant when the optical system reaches the point .beta. positioned 
ahead of the home position sensor 119, the movement of the original, whose 
leading edge is positioned at point .gamma., is started so that both 
coincide with each other at point .alpha.. In this arrangement, the point 
.alpha. is set to a position corresponding to the timing of turning on the 
image tip sensor 117, that is, image tip timing which is the same as that 
utilized in normal scanning when the RDF is not used. In practice, in 
order to cause the leading edge of the original to coincide with the home 
position sensor 119 at the point .alpha., the position of the point 
.gamma. may be determined so that the time TM required for the optical 
system to move from the point .beta. to the point .alpha. can be made 
equal to the time TB required for the original to engage the first clutch 
361 and move from the point .gamma. to the point .alpha.. The time TB is 
the time required from the flat-face belt 306 to rise from zero to its 
steady speedy. Accordingly, although the time TB is an uncertain factor, 
it will be readily understood by those skilled in the art that the above 
setting is feasible, for example, by means of position adjustment. 
Even if the timing changes due to a deterioration in clutch, motor, etc. 
with time, the change may be corrected in the following manner: the CPU 
501 counts, for example, signals from the encoder (belt FG) 357 within the 
time TB to consistently check the status, thereby shifting the position of 
the point .gamma. to correct the amount of deviation. 
[Another Embodiment] 
The following is an explanation, referring to FIGS. 8-1 to 8-4, of another 
embodiment in which an image reading operation is performed while 
image-reading means and a sheet original are being moved in mutually 
opposite directions in such a manner that they will pass each other. 
FIG. 8-1 is a cross-sectional front elevational view showing another 
embodiment of the recycle original document feeder (RDF) according to the 
present invention. FIG. 8-4 is a cross-sectional front elevational view 
showing an automatic original document feeder (ADF), and FIGS. 8-2 and 8-3 
are schematic views showing the operation of the RDF shown in FIG. 8-1. 
In these figures, the same reference numerals are used to denote the like 
or corresponding elements shown in FIG. 1. In particular, the ADF of FIG. 
8-4 is constructed so that each sheet is separated from the bundle 302 of 
"face-down" originals 302 by the cooperation between the upper separating 
rollers 304 and 303. 
In this embodiment, the original is transported in the direction of arrow C 
over the platen glass 101, while the first scanning mirror 105 moves from 
the home position of the optical system shown in FIG. 8-1 in the direction 
of arrow D. When the reading part of the first scanning mirror 105 
coincides with the leading edge of the original which is being 
transported, a reading operation is started. In this operation, the 
succeeding original is successively transported and its leading edge is 
positioned at the point P1 (FIG. 8-2). When the first scanning mirror 105 
which is being transported coincides with the trailing position of the 
original, the reading operation is completed and the first scanning mirror 
105 moves to the home position in the direction opposite to the direction 
of arrow D. Since the preceding original and the succeeding original are 
transported at the same speed, the leading edge of the succeeding original 
is positioned at the point P2. Accordingly, the succeeding original is 
transported by a distance corresponding to (L1=L2) during the reading of 
the preceding original. While the optical system is moving in a direction 
opposite the direction of arrow D, the succeeding original is further 
transported and the optical system again starts to move from the home 
position in the direction indicated by arrow D. When the optical system 
coincides with the leading edge of the succeeding original, reading of the 
succeeding original is started. By repeating the above operation in 
sequence, a continuous copying operation is enabled. 
In the above arrangement, even while reading of the preceding original is 
being performed, the leading edge of the succeeding original is 
transported. Accordingly, as compared to the arrangement in which reading 
is performed by moving only the optical system while keeping the original 
at rest as disclosed in Japanese Patent Laid-Open Nos. 60-140364 and 
61-32836 referred to in the description of the related art, the above 
embodiment enables originals at the reading part to be replaced at a 
timing which is reduced by an interval corresponding to the distance 
(L1-L2). If the transporting speed of the succeeding original is increased 
compared to the transporting speed in an ordinary reading operation from 
the time when the optical system coincides with the trailing edge of the 
original until it returns to the home position, it is possible to further 
reduce the time required to replace originals. 
As a matter of course, the embodiment is provided with an arrangement 
having at least two modes: the mode of effecting image reading by causing 
an optical system to scan an original which is halted at a predetermined 
position and the mode of effecting image reading by moving the original 
and the optical system in mutually opposite directions in such a manner 
that they pass each other. These modes can be switched by means of a 
selector switch 120. 
According to the embodiments described above, since image reading is 
effected while the scanning means and the original are being moved in 
mutually opposite directions in such a manner that they pass each other, 
relative reading speed can be increased without the need to increase the 
speed of movement of the original. In addition, since the intervals of 
transportation of originals can be reduced, it is possible to remarkably 
improve a throughput, such as productivity, while minimizing the 
probability that imperfect images such as blurred images will be formed. 
Since the scanning means is continuously moved, an excessive temperature 
rise can be prevented. Also, since scan control is easy, a low-cost, 
compact arrangement can be achieved. 
The following is an explanation yet another embodiment in which the 
reversing position of a scanning means is varied, depending on an original 
size. 
FIGS. 9A and 9B are control flowcharts showing this embodiment, and the 
operation of the embodiment is explained with reference to these figures 
as well as FIGS. 4-1 to 4-4 and 7 and the flowcharts of FIGS. 9A-9B. 
When a plurality of originals 302 are placed on the stacking tray 2 as 
shown in FIG. 4-1 and a copy start key is turned on, the lever motor 329 
(M4) is actuated by a predetermined amount to place the recycle lever 309 
on the aforesaid originals 302 (Step 101). Then, the separating roller 
motor 321 (M1) is actuated by a predetermined period to cause the 
semicircular roller 304 and the separating roller 303 by a predetermined 
amount, thereby separating one sheet from the bundle of original at the 
lowermost position thereof. The leading edge of the separated original is 
brought into contact with the carriage roller 353 to loop the original, 
thereby preventing it from moving obliquely (Step 102). 
Subsequently, the first clutch 361 is engaged and, at the same time, the 
belt motor 323 (M2) is actuated forwardly, thereby causing the carriage 
roller 353 and the flat-face belt 306 to rotate at full speeds in the 
direction indicated by arrow a (Step 103). Thus, while a size detection 
processing for the original 302 is being performed, the original 302 is 
transported onto the platen glass 7 via the path II. The size detection 
processing will be explained in detail later. 
When, as shown in FIG. 4-2, the trailing edge of the original 302 is 
transported to the predetermined position .gamma. on the platen glass 101, 
the belt motor M2 is halted, and the first clutch 361 is disengaged and 
the brake 363 is energized. Thus, the transportation of the original is 
stopped instantaneously (Steps 105 and 106). 
Then, an optical system reversal data processing is executed (Step 107), 
and the optical system motor 115 (M5) is actuated forwardly at a 
predetermined speed under PLL speed control to move the first scanning 
mirror 105 in the direction of arrow c. At the same time, the belt motor 
M2 is actuated reversely at a predetermined speed under PLL speed control 
to rotate the flat-face belt 306 in the direction of arrow b (Steps 108 
and 109). 
When the home position sensor 119 is turned off, that is, when the first 
scanning mirror 105 reaches the point .beta., the brake 363 is 
de-energized and the first clutch 361 is engaged to transport the original 
302 at a predetermined speed in the direction of arrow b (Step 110, 111). 
In this manner, the first scanning mirror 105 and the original 302 are 
moved at the respective predetermined speeds in mutually opposite 
directions in such a manner that they pass each other. 
Then, reading of the original 302 is started at the instant (point .alpha.) 
when the first scanning mirror 105 coincides with the leading edge of the 
original 302. Simultaneously with the read operation, a latent image 
corresponding to the read information is formed on the photosensitive drum 
131, whereby an image is recorded on a recording sheet. In addition, when 
the first original 302 is transported in parallel with the aforesaid 
reading operation, if the lever sensor 359 is not turned on, that is, if 
the recycle lever 309 has not yet fallen down, it indicates that the 
second original exists on the stacking tray 301. Accordingly, the 
separating motor M1 and the second clutch 365 are energized for a 
predetemined time to transport the leading edge of the second original to 
the carriage roller 305 so that the original is looped to prevent it from 
moving obliquely. Thereafter, the leading edge of the original is 
transported to a position (point .alpha.) immediately before the platen 
glass 101, and placed in a stand-by state (Steps 112-116). This is because 
the time required to transport each original for reading the second sheet 
et sqq. is minimized. 
As shown in FIG. 4-4, the aforesaid read operation is executed until the 
first scanning mirror 105 reaches a position corresponding to the data set 
in the optical system reversal data processing (Step 7). At this point in 
time, the reading of the first original is completed (Step 118). 
When the reading of the original is completed, the optical system motor M5 
is reversed to return the first scanning mirror 105 to the home position 
(Step 119) and simultaneously to actuate a carriage large roller motor M3 
to transport the original by means of the carriage large roller 307. 
If the second original or a subsequent original remains, that is, if a 
lever sensor S4 is off (Step 121), the process returns Step 103 of FIG. 9, 
where the second original is transported onto the platen glass 101. At 
this time, the second original is transported onto the platen glass 101 by 
the rotation of the flat-face belt 306 before the original which has been 
read returns to the stacking tray 301. However, there is no problem since 
the read original has already been nipped between the carriage large 
roller 307 and the carriage roller 311. In parallel with the aforesaid 
original transporting operation, it is determined whether or not the first 
scanning mirror 105 has returned to the home position (Step 122). When the 
first scanning mirror 105 returns to the home position, the optical system 
motor 115 (M&gt;) is stopped and placed in a stand-by state at the home 
position (Step 123). Then, the process returns to Step 104 of FIG. 9, 
where it waits for the trailing edge of the second original to stop at the 
predetermined position .gamma. on the platen glass 101. 
If it is determined in Step 121 that there is no original on the stacking 
tray 301, that is, the lever sensor S4 is on, the original is returned to 
the stacking tray 301 by the carriage large roller 307, thereby completing 
the reading operation (Steps 124 and 125). 
The following is an explanation, referring to the flowchart of FIG. 10, of 
the original size detection processing (Step 104 in FIG. 9) for changing 
the revering position of the first scanning mirror 105 in accordance with 
the original size. 
In this processing, first of all, the belt motor M2 is actuated forwardly 
to cause the original an original from the path I to the path II by the 
driving of the carriage roller 305 and the flat-face belt 306 and, at the 
same time, size check counter is started. The size check counter performs 
counting operation in response to clock signals supplied from a belt clock 
interrupter (not shown) (Step 141). 
The size check counter is stopped at the same time that the trailing edge 
of the original passes by the registration sensor 353 (S2) (Steps 142 and 
143). The data obtained by the counting is added to a correction value 
corresponding to the distance from the nip position of the carriage roller 
305 to the registration sensor S2, thereby preparing an actual original 
size l1. The thus-detected original l1 is transmitted as data to the main 
body of the apparatus, and the process initializes the size check counter 
and returns the previous step (Steps 145 and 146). In this manner, the 
size of the original to be transported is detected. 
The following is an explanation, referring to the flowchart of FIG. 11, of 
an optical system reversal data processing (Step 7 of FIG. 9) for setting 
the reversing of the first scanning mirror 105 in accordance with the 
original size l1. As shown in FIG. 11, the main body of the apparatus 
receives data representing the original size l1 obtained in the above 
original size detecting processing. Then, a distance l3 to the reversing 
position of the first scanning mirror 105 shown in FIG. 6 is calculated as 
follows by using the above data, the moving speed SM of the first scanning 
mirror 105 that is set by PLL speed control, and the moving speed SB of 
the original transported by the belt motor M2: 
EQU l3=SM.multidot.l1/(SM+SB) (1) 
The data thus calculated is set as reversal data l.gamma. (Step 172). 
Accordingly, at the instant when the distance traveled by the first 
scanning mirror 105 of FIG. 6 from an image tip coincidence point .alpha. 
becomes equals to the aforesaid reversal data distance l3, it is 
determined in Step 117 of FIG. 9 that the reversal timing has been 
reached. The first scanning mirror 105 is reversed at the corresponding 
position. In this manner, the first scanning mirror 105 is reversed in 
accordance with each original size, whereby the reading of the original is 
performed efficiently and rapidly. 
The following is an explanation of a procedure for effecting variable 
setting of the reversing position of the first scanning mirror 105 in 
accordance with a cassette size (the size of a recording sheet) and a copy 
magnification each of which is selected by an operator. 
In this procedure, an optical system reversal data processing is executed 
as shown in the flowchart of FIG. 12. 
In the apparatus shown in FIG. 1, it is determined whether the upper stage 
cassette 151 has been selected by an operator (Step 171). If the upper 
stage cassette 151 is selected, a cassette size lc is set to the 
upper-stage cassette size (for example, B5 size) (Step 172). If it is 
determined in Step 171 that the upper stage cassette 151 is not selected, 
the process proceeds to Step 173, where it is determined whether or not a 
lower stage cassette 153 is selected. If the lower stage cassette 153 is 
selected, the cassette size is set to the lower stage cassette size (for 
example, B4 size) (Step 174). If it is determined in Step 173 that the 
lower stage cassette 153 is not selected, it is determined that a manual 
feed mode is selected, and the cassette size lc is set to the maximum size 
(for example, A3 size) which can be handled by the apparatus. Then, a copy 
magnification m (e.g., a magnification of .times.2) is set as selected by 
the operator. 
Then, the reversal data l.gamma. of the first scanning mirror 105 is 
calculated as follows by using the cassette size lc, the copy 
magnification m, the moving speed SM of the first scanning mirror 105 and 
the moving speed SB of the original transported by the driving of the belt 
motor M2: 
EQU lr=(SM.multidot.lc/m)/(SM+SB) (2) 
The result is set to the reversal data of Step 105 shown in FIG. 9 (Step 
177). 
In this manner, the first scanning mirror 105 is reversed at a position 
corresponding to the cassette size l1 and the copy magnification m. 
The following is an explanation of a procedure for setting a reversal 
timing. In this procedure, the reversing position of the first scanning 
mirror 105, which is calculated from the moving speed SM of the first 
scanning mirror 105 and the moving speed SB and original size l1 of the 
original, is compared with the reversing position of the first scanning 
mirror 105 which is calculated from the size SM of a recording sheet and 
the copy magnification m. The reversing position of the first scanning 
mirror 105 which travels a shorter distance is set as the reversal timing. 
In this procedure, the optical system reversal data processing is executed 
as shown in the flowchart of FIG. 13. 
First of all, as described previously, a particular original size is 
received (Step 181) and reversal data lr1 on the first scanning mirror 105 
corresponding to the original size is calculated by using Equation 
(1)(Step 182): 
EQU lr1=SM.multidot.l1/(SM+SB) 
Then, from the cassette size lc and the copy magnification m which are 
selected by the operator, reversal data lr2 on the first scanning mirror 
105 is calculated by using Equation (2) (Steps 73-75) 
EQU lr2=(SM.multidot.lc/m)/(SM+SB) 
Then, the data lr1 and lr2 are compared by a comparing means such as an 
operation amplifier (Step 186). If lr1.gtoreq. lr2, the data lr2 is set as 
reversal data, while, if lr1&lt;lr2, the data lr1 is set as reversal data 
(Steps 187 and 188). 
In this manner, the data calculated from the original size is compared with 
the data calculated from the cassette and the copy magnification, and the 
first scanning mirror 105 is reversed on the basis of the data 
corresponding to a shorter moving distance. Accordingly, it is possible to 
effect efficient image reading in a reduced time. 
As described above, the variable setting of the reversing position of the 
reading means remarkably improves the speed of image formation utilizing 
the reciprocal movement of the reading means. Accordingly, it is possible 
to remarkably improve a throughput. 
The following is an explanation of another embodiment which has two kinds 
of multicopy mode. In one mode, originals are successively fed onto a 
platen by repeating a feed operation by a set number of times, and the 
originals are fed while the next originals are fed after the set number of 
copies have been produced. In the other mode, one copy is produced in each 
original feeding operation and the original is replaced with the next 
original, and this operation is repeated by the set number of times until 
the set number of copies is obtained. 
FIG. 14 is a cross-sectional view showing the inner construction of an 
image forming apparatus according to the above embodiment. 
The apparatus shown in FIG. 14 basically comprises: the main body 100 
having an image reading function and an image recording function; a 
pedestal 200 having the double-sided processing function of reversing a 
recording medium (sheet) during a double-sided recording and the 
multiple-recording function of repeating recording with respect to the 
same recording medium by a plurality of times; the automatic original 
document feeder (RDF) 300 for automatically feeding originals; and a 
sorter 400. The pedestal 200, the automatic original feeder 300 and the 
sorter 400 can be freely combined with the main body 100. 
A. MAIN BODY (100) 
In FIG. 14, the same reference numerals are used to denote the like or 
corresponding elements explained in the embodiment described previously. 
Original size detecting sensors 124, 125 and 126 detect the presence or 
absence of an original on the original platen glass 101. A feeder 
switching detecting sensor 127 senses a timing immediately before the RDF 
300 or a pressure plate (not shown) is closed. A pedestal sensor 128 is 
used for double-sided recording. A potential sensor 138 senses the surface 
electrode of the photosensitive drum 137. 
B. PEDESTAL (200) 
As shown in FIG. 14, the pedestal 200 is provided with a deck 201 capable 
of accommodating, for example, two thousand transfer sheets, and an 
intermediate tray 202 for double-sided recording. The deck 201 has a 
lifter 203 which rises in accordance with the number of transfer sheets so 
as to consistently maintain a transfer sheet in contact with a paper feed 
roller 204. 
In FIG. 14, a discharge flapper 205 is disposed outside the main body 100 
for switching a sheet feed path between the discharge side and the 
double-sided recording or multiple-recording side (sorter 400). A transfer 
sheet which is fed by discharge rollers 165 is switched to the 
double-sided recording or multiple-recording side by the discharge flapper 
205. Carriage belts 206 and 207 reverse the transfer paper transported by 
the discharge rollers 165 and conduct it to the intermediate tray 202. A 
weight 208 serves to forces the accommodated transfer sheet against the 
intermediate tray 202. A multi-flapper 209 switches the sheet feed path 
between the double-sided recording side and the multiple-recording side. 
The multi-flapper 209 is disposed between the carriage belts 206 and 207 
and rotates upwardly to conduct the transfer sheet to a multiple-recording 
transport path 210. A multi-sensor 211 senses the trailing edge of each 
transfer sheet passing by the multi-flapper 209. A paper feed roller 212 
feed the transfer sheet to the photosensitive drum 131. 
Discharge rollers 214 are disposed in the vicinity of the discharge flapper 
205 for discharging the transfer sheet, switched to the discharge side by 
the paper feed flapper 205, out of the apparatus. 
For double-sided recording or multiple-recording, the discharge flapper 205 
is forced up, and copied transfer sheets are accommodated in the 
intermediate tray 202 in a state reversed by the carriage belts 206 and 
207. For double-sided recording, the multi-flapper 209 is moved down, 
while the transfer sheets accommodated in the intermediate tray 202 are 
forced down by the weight 208. For the subsequent reverse-side recording 
or multi-recording, the transfer sheets accommodated in the intermediate 
tray 202 are conducted one-by-one from the lowermost position thereof to 
the registration roller 118 of the main body over the path 213 by the 
action of the paper feed roller 212 and the weight 208. 
C. RDF (AUTOMATIC ORIGINAL DOCUMENT FEEDER) (300) 
The RDF 300 has a construction similar to that shown in FIG. 1 and is 
capable of performing the following two operations when a one-sided 
original is handled. In one operation, the originals are separated from 
the original bundle 302 at the lowermost power thereof in a one-by-one 
fashion by means of the semicircular roller 304 and the separating roller 
303, and each separated original is transported to the exposure position 
on the original platen glass 101 over the paths I and II by means of the 
other carriage roller 305 and the flat-face belt 306. At the same time 
that the image formation operation is started, the original placed on the 
carriage large roller 307 is transported over the path III to the path VI 
by means of the carriage large roller 307. Finally, the original is again 
placed on the top of the original bundle 302. In the other operation, at 
the same time that an image formation operation is started, the original 
is transported toward the carriage large roller 307 over the path III. The 
original is switched back via the path IV by the reverse rotation of the 
carriage large roller 307 and the movement of the flat-face belt 306 and 
transported to the exposure position on the platen glass 101. 
During double-sided recording, the original is temporarily conducted to the 
path III through the paths I and II. At the path III, the leading edge of 
the original (original discharged from the platen) is conducted to the 
path IV by switching a switching flapper 311. The original is transported 
over the path II to the platen glass 101 by the carriage rollers 307 and 
305. In other words, the carriage large roller 307 and the route formed by 
the paths III-IV-II are used to reverse the original. The number of 
originals can be counted by transporting the originals of the bundle 302 
one by one over the paths I-II-III-IV-V until the recycle lever 309 
detects the completion of one cycle of sheet feed operation. 
D. SORTER (400) 
The sorter 400 serves as a sheet postprocessing device for recording sheets 
such as transfer paper, and is provided with 25-bin trays for sorting. The 
image-formed transfer paper is sequentially discharged from the main body 
100 through the discharge rollers 214, captured by carriage rollers 401 in 
the sorter 400, and inserted into each bin 404 through a path 402 by 
discharge rollers 403. 
FIG. 15 shows an example of the configuration of an operation panel 
provided on the aforesaid main body 100. The operator panel is provided 
with a key group 600 and a display group 700 which will be explained 
later. 
E. KEY GROUP (600) 
Referring FIG. 15, a copy start key 601 is pressed to start a copy 
operation. A clear/stop key 602 functions as a clear key in a stand-by 
state and a stop key during a copy operation. A ten-key pad 603 is pressed 
to set the number of copies, and copy density keys 604 and 605 are pressed 
to manually adjust copy density. An AE (automatic exposure) key 606 is 
pressed when it is desired to automatically adjust copy density in 
accordance with the density of each original or when it is desired to 
switch the density adjustment from AE control to manual control. A 
cassette selecting key 607 is pressed to select the upper stage cassette 
114, the lower stage cassette 115 or the deck 201. A double-sided copy key 
608 is pressed when a double-sided copy is produced from a one-sided 
original, when a double-sided copy is produced from a double-sided 
original or when a one-sided copy is produced from a double-sided 
original. A two-color multi-key 609 is pressed when images of different 
colors are formed (synthesized) on the same surface of copy paper from one 
original. A selection key 610 is used to select a discharging method 
(sorting or grouping). If a sorting tray (sorter) is connected to the main 
body 100, it is possible to select or cancel the sorting mode or the group 
mode. 
F. DISPLAY GROUP (700) 
Referring to FIG. 15, an LCD(liquid-crystal device) type of message display 
reproduces one character consisting of, for example, 5.times.7 dots. The 
message display 701 is a semi-transparent liquid-crystal display, and two 
backlight colors are employed. Normally, green backlight lights but, in an 
emergency or a copy-disable state, orange backlight lights. 
A copy-number indicator 702 indicates the number of copies or a 
self-diagnosis code. A selected-cassette indicator 703 indicates which of 
the upper stage cassette 114, the lower stage cassette 115 and the deck 
201 is selected. An AE indicator 704 lights when an AE mode (automatic 
copy density adjustment mode) is selected through an AE key 606. A 
ready/wait indicator 705 utilizes a green-emitting LED and an 
orange-emitting LED. In a ready state (copy-enable state), the green LED 
lights and, in a wait state (copy-disable state), the orange LED lights. A 
double-sided copy indicator 706 indicates the contents selected through 
the double-sided copy key 608, that is, whether the production of a 
double-sided copy from a double-sided original or the production of a 
double-sided copy from a one-sided copy is selected. A power source lamp 
707 lights by turning on a power switch 708. 
G. CONTROL DEVICE (800) 
FIG. 16 is a block diagram showing a control device 800 used in the above 
embodiment. In the drawing, a master CPU and slave CPU are denoted by 801 
and 802. A read-only memory (ROM) 803 stores the control procedure 
(control program) shown in FIG. 17, and the CPU 801 controls each element 
connected thereto via a bus in accordance with the control procedure 
stored in the ROM 803. A random access memory (RAM) 804 is a main storage 
device which is used as an input-data storing or working area. 
An interface (I/0) 805 outputs control signals from the CPU 801 to each 
load, for example, the main motor 133. An interface 806 receives an signal 
from the image tip sensor 117 and transmits it to the CPU 801, and an 
interface 807 provides input/output control over the key group 600 and the 
display group 700. Each of the interfaces 805, 806 and 807 may utilize, 
for example, an input/output circuit port .mu.PD8255 manufactured by NEC. 
The display group 700 corresponds to the indicators shown in FIG. 15, and 
utilizes LEDs or LCDs. The key group 600 corresponds to the keys shown in 
the same drawing, and the CPU 801 can detect which key is pressed by 
utilizing a known key matrix. 
The CPU 802 controls the blank exposure unit 137 in accordance with the 
blank data calculated by the CPU 801. The CPU 802 effects 
analog-to-digital conversion of the potential sensor 138 and the original 
size detecting sensors 124, 125 and 126, and transfer the digital data to 
the CPU 801 through a dual-port RAM 808. 
A watchdog circuit 309 monitors the state of the CPU 801. If an anomalous 
state is detected, the watchdog circuit 309 generates reset signals for 
the CPUs 801 and 802. 
An electrical power source is denoted by 810, and a circuit 811 converts 
the switching condition of the power switch 708 (power switch for turning 
on and off the power source 810 with respect to all the loads other than 
the control section) from 24 V(ON)/0 V(OFF) to 5 V/0 V. When the CPU 801 
detects the opening of the power switch 708, it generates a pseudo 
anormality signal in accordance with the program. The CPU 801 then 
transmits this signal to the watchdog circuit 809 and causes it to provide 
a signal to the reset input of each watchdog circuit 809, thereby turning 
off all load driving. 
The operation of the above embodiment will be explained below with 
reference to the flowchart of FIG. 17 and the operational sequence diagram 
of FIG. 20. 
FIG. 20 shows a multi-image formation process in which, for example, two 
copies are produced from each of three originals (the number of images to 
be formed is two for each original). 
Referring to FIG. 20, the optical system 105 advances at a speed of, for 
example, 150 m/sec and, after the image tip sensor 117 has generated a 
signal, a first original a is discharged from the platen glass 101 at a 
speed of 150 m/sec by the motion of the flat-face belt 306. In other 
words, the optical system 105 and the original a are moved in mutually 
opposite directions in such a manner that they pass each other, whereby 
exposure and reading of the original a is effected (the original a is 
exposed and read at a relative speed of 300 m/sec). When the first cycle 
of exposure and reading of the original a is completed, the discharged 
original a is again fed to the platen glass 101 by means of the flat-face 
belt 306. The original is then subjected to the second cycle of exposure 
and reading which is similar to the first cycle. 
After image formation for two sheets has been completed and the original a 
has been discharged, another original b (the second original) is fed to 
the platen glass 101 and the optical system 105 likewise advances while 
the original b is being discharged for exposure and reading. After image 
formation for two sheets has been completed and the original b has been 
discharged from the platen glass 101, the other original c (the third 
original) is fed to the platen glass 101 and similar image reading is 
executed. 
More specifically, when the predetermined number of copies is produced, the 
original is discharged and, at the same time, the next original is fed. In 
other cases, before dynamic reading and discharging is completed (when 
image reading is completed), the same original is again returned to the 
platen glass 101. 
The control procedure of the ROM 803 for effecting the above operation will 
be explained with reference to FIG. 17. 
In Step S1000, originals are set on the stacking tray 301 of the RDF 300 
and image formation is started. Then, in step S1001, the first original is 
fed from the RDF 300 and in Step S1002 it is determined whether or not 
this original has been set on the platen glass 101. Before the setting has 
been completed, the process proceeds to Step S1003, where the optical 
system 105 has been advanced. 
In Step S1004, it is determined whether or not the image tip sensor 117 has 
generated a signal. After this signal has been generated, in Step S1005, 
original dynamic reading and discharging is started and a reversing timer 
for the optical system 105 is set. In Step S1005, the optical system 105 
and the original are moved in mutually opposite directions in such a 
manner that they will pass each other. 
In Step S1008, it is determined whether image formation for the present 
number of copies has been completed. If it has not yet completed, in Step 
S1009, the original is again fed to the platen glass 101 and the process 
then returns to Step S1002. If the image formation has been completed, 
whether or not all the originals have been copied is determined in Step 
S1010. If the copying has not yet been completed, in Step S1011 the next 
original is fed to the platen glass 101 from the RDF 300, and the process 
then returns to Step S1002. 
When image formation for all the originals has been completed, the process 
ends in Step S1012. 
As is apparent from the foregoing, by moving the optical system 105 and the 
original in mutually opposite directions in such a manner that they pass 
each other in each original copying operation, it is possible to 
remarkably improve the efficiency of image formation as compared with 
either a conventional arrangement in which only the optical system runs 
back and forth to read the original or a conventional arrangement in 
which, only at the time of replacement of originals, the optical system 
and the original are moved in mutually opposite directions in such a 
manner that they pass each other. 
Another example of operation will be explained with reference to the 
operational sequence diagram of FIG. 21. 
In the operational sequence shown in FIG. 21, one image forming process 
includes producing one copy from each of the originals a, b and c, and 
this image forming proces is repeated by the number of times corresponding 
to the set number of sheets (Each of the originals is circulated between 
the stacking tray 301 and the platen glass 101 by the number of times 
corresponding to the set number of copies.) 
In operation, the optical system 105 advances at a speed of, for example, 
150 m/sec. After the image tip sensor 117 has generated a signal, the 
first original a is discharged from the platen glass 101 at a speed of 150 
m/sec by the operation of the flat-face belt 306. At this time, the 
optical system 105 and the original a are moved in mutually opposite 
direction in such a manner that they pass each other, thereby effecting 
exposure and reading of the original a (at a relative speed of 300 m/sec). 
The discharged original a is returned to the stacking tray 301 and stacked 
on the original c and, at the time of the reversal of the optical system 
105, the second original b is fed to the platen glass 101. Then, 
similarly, the optical system 105 advances and, at the same time, the 
original b is discharged for the purposes of exposure and reading. 
The discharged original b is returned to the stacking tray 301 and stacked 
on the original a and, at the time of the reversal of the original system 
105, the third original c is fed to the platen glass 101. Then, similarly, 
the optical system 105 advances and, at the same time, the original c is 
discharged for the purposes of exposure and reading. The discharged 
original c is returned to the stacking tray 301 and stacked on the 
original b. 
In this manner, one step is completed and a similar operation is again 
started with the original a. 
With this arrangement, it is also possible to remarkably improve the 
efficiency of image formation with respect to the conventional 
arrangements described previously. 
FIG. 18 is a flowchart showing the operation of effecting switching between 
the operational mode of FIG. 20 and the operational mode of FIG. 21 in 
accordance with the state of image formation. 
More specifically, two kinds of mode are selectively used in accordance 
with the state of image formation. In the first mode, the operation of 
reading an image from an original while moving the optical system 105 and 
the original in mutually opposite directions in such a manner that they 
passe each other and then returning the original to the platen glass 101, 
is repeated by a set number of times. In the second mode, the operation of 
reading an image from an original while moving the optical system 105 and 
the original in mutually opposite directions in such a manner that they 
passe each other and then discharging and returning the original to the 
stacking tray 301, is repeated by a set number of times. Originals are 
successively fed onto a platen by repeating a feed operation by the set 
number of times, and the originals are fed while the next originals are 
fed after the set number of copies have been produced. In the other mode, 
one copy is produced in each original feeding operation and the original 
is replaced with the next original, and this operation is repeated by the 
set number of times until the set number of copies is obtained. 
To perform the above selection in accordance with the state of image 
formation is, for example, to do that in accordance with the kind of sheet 
output device (or the presence or absence of a sheet output device) or the 
state of discharge (sorting, grouping or the like). In this case, the CPU 
80 performs selection between the first mode and the second mode in 
response to a signal input through the selection key 610. 
The contents of control for achieving the above two modes will be explained 
with reference to FIG. 18. 
In Step S1500, originals are set on the stacking tray 301 of the RDF 300 
and image formation is started. Then, in Step S1501, it is determined 
whether or not a sort mode has been specified through the selection key 
610 with no sorter 400 connected to the main body 100. 
If the answer is "NO", the first mode is selected and reading from the 
original is performed in the first mode (reading from the original is 
performed in accordance with the procedures shown in FIG. 17.) If the 
answer is "YES", the second mode is selected and reading from the original 
is performed in the second mode (reading from the original is performed in 
accordance with the procedures shown in FIG. 21.) 
More specifically, the process proceeds to Step S1502, wherein the first 
original is fed to the platen glass 101. Then, in Step S1503, it is 
determined whether or not the original has been set on the platen glass 
101. When this setting is completed, the process proceeds to Step S1504, 
where the optical system 105 is advanced. 
Then, in Step S1505, it is determined whether or not the image tip sensor 
117 has generated a signal. After the signal has been generated, in Step 
S1506, original dynamic reading and discharging is started and the 
reversing timer for the optical system 105 is set. In Step S1506, the 
optical system 105 and the original are moved in mutually opposite 
directions in such a manner that they will pass each other, thereby 
effecting exposure and reading of the original. 
In Step S1507, it is determined whether or the reversing timer has reached 
the state of time-up. After the state of time-up has been reached, the 
process proceeds to Step S1508, where the optical system 105 is reversed. 
In Step S1509, it is determined whether or not reading from all the 
originals has been completed. If the reading has not yet been completed, 
the process proceeds to Step S1510, where the next original is fed to the 
platen glass 101. Then, the process returns to Step S1503. If reading of 
all the originals has been completed, the process proceeds to Step S1511, 
where it is determined whether or not the originals have been circulated 
by the number of times corresponding to the set number of copies. If this 
operation has not yet been completed, the process proceeds to Step S1512, 
where the next original is fed to the platen glass 101. Then, the process 
returns to Step S1503. If the operation is completed, the process ends in 
Step S1513. 
With the above arrangement, it is possible to effect high-speed image 
reading in an appropriate mode corresponding to the state of image 
formation. 
In the apparatus of the embodiment described above, it is possible for a 
user to perform image formation while directly pressing an original 
against the platen glass 101 without the use of the RDF 300. For this 
reason, the ROM 803 stores control having the contents shown in the 
flowchart of FIG. 19. 
The procedure shown in the flowchart of FIG. 19 will be explained below. 
The flow starts in Step S200, where it is determined whether or not a 
feeder copy operation is selected (a book copy operation is selected). If 
the original sensor 351 generates a signal, that is, if an original is fed 
from the RDF 300, it indicates that the feeder copy original is selected. 
In this case, the process proceeds to Step S1001 shown in FIG. 17, and 
reading from the original is executed in accordance with the contents of 
the flowchart shown in FIG. 17 (reading from the original is performed in 
the first mode). 
If the book copy operation is selected, the process proceeds to Step S2002, 
where whether or not the RDF 300 is closed through the feeder switching 
detecting sensor 127. If the RDF 300 is closed, it indicates that a sheet 
original is set and the process proceeds to Step S2003. Although not 
shown, a switch for selecting the execution or the non-execution of a book 
sheet dynamic reading mode is provided on the present apparatus. In Step 
S2003, it is determined whether or not the book sheet dynamic reading mode 
is performed. If the above switch is pressed to select the book sheet 
dynamic reading mode, the process proceeds to Step S2005. If no sheet 
original is set or a sheet dynamic reading mode is inhibited, the process 
proceeds to Step S2004, where only the optical system 105 reciprocally 
runs to effect reading from the original, thereby forming an image. The 
operation is completed in Step 2013. 
If the sheet dynamic reading mode is executed, the process proceeds to Step 
S2005, where reading from the original is effected in the first mode. 
In Step S1507, it is determined whether or not the optical system 105 is 
advanced and the reversing timer is set. Then, it is determined whether or 
not the image tip sensor 117 has generated a signal. If the signal is 
generated, the process proceeds to Step S2007, where as an original 
dynamic discharge is performed, reading from the original is performed. 
(While the optical system 105 is being advances, the original is 
discharged and reading from the original is performed.) Then, in Step 
S2008, it is determined whether or not the reversing timer has reached the 
state of time-up. If the state of time-up is reached, the optical system 
105 is reversed in Step S2009 and in Step S2010 it is determined whether 
or not image formation for a set number of sheets has been completed. If 
the answer is "NO", the process proceeds to Step S2011, where the original 
is again fed to the platen glass 101. The process then proceeds to Step 
S2012, where it is determined whether or not the original has been set. If 
the original is set, the process returns to Step S2005 and a similar 
operation is repeated. If image formation for a set number of sheets is 
completed, the process ends in Step S2013. 
As is apparent from the foregoing, even if a user sets an original directly 
on the platen glass 101, the sheet original can be identified so that it 
is possible to remarkably improve the efficiency of copy processing. 
Although, in the above description, each embodiment is applied to an analog 
copying machine employing an electrophotographic process, the present 
invention may of course be applied to a digital copying machine, an image 
reader or the like. 
The present invention can be applied not to one-sided recording but to 
double-sided recording or multiple-recording. 
The above description has been made with reference to the example in which 
the number of copies per image is two. However, this number is not 
limitative and two or more copies may be produced from each image. 
The image formation method is not limited to the electrophotographic 
process and, for example, an ink-jet method may be employed. 
While the present invention has been described with respect to what is 
presently considered to be the preferred embodiments, it is to be 
understood that the invention is not limited to the disclosed embodiments. 
To the contrary, the present invention is intended to cover various 
modifications and equivalent arrangements included within the spirit and 
scope of the appended claims. The scope of the following claims is to be 
accorded the broadest interpretation so as to encompass all such 
modifications and equivalent structures and functions.