JPH02151883A - Copying machine - Google Patents

Abstract

PURPOSE:To surely detect that originals of any size are set in a home position on a central reference basis by detecting that an original is set in the home position of an original placing glass on the central reference basis by an original detecting means selected according to a size signal from a size input means. CONSTITUTION:The machine is provided with the means 90d to 90i detecting that originals of any size are set in the home position of the original placing glass on the central reference basis, and a control means CPU selecting any of the original detecting means 90d to 90i according to the size signal from the size input means 83. It is preferable that the original detecting means 90d to 90i are installed by pair in a position corresponding to each size to detect both corners of an original and signals from the detecting means are selectively used to decide whether originals are properly set. Consequently, whether an original of desired size is set in the home position of the original placing glass on the central reference basis can be detected.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a copying machine, and particularly to a copying machine that reproduces an image of a document placed on a document placement glass on a sheet of paper by electrophotography.

Conventional technology and its issues In general, when copying in a copier, a series of operations is performed: first, the document holding cover is opened, the document is placed in a predetermined position on the document placement glass, then the cover is closed, and the print key is pressed. required for each manuscript, which was extremely complicated. Therefore, conventionally, as described in Japanese Unexamined Patent Publication No. 59-22061, the copying operation is started upon detecting that the original cover is closed. A method has been proposed. In addition, in recent years, it has become possible to
Various types of automatic document feeders have been developed that automatically feed sheets one by one onto a document placement glass, and some of them are controlled so as to detect that a document is set on a tray and start a copying operation.

By the way, in order to perform the copying process with a simple operation, it is preferable to detect that the original is set at a fixed position on the original placing glass, and to start the copying operation in response to this detection signal. Therefore, the problems of the present invention are 1. To provide a copying machine that can reliably detect whether or not originals of various sizes are set at fixed positions on an original placing glass with a center reference.

Means and Effects for Solving the Problems In order to solve the above problems, the copying machine according to the present invention includes means for detecting that originals of various sizes are set at fixed positions on the original placing glass with a center reference. and means for inputting the size of the document to be detected, and control means for selecting the document detection means according to the size signal from the size input means. According to this configuration, first, the size of the original to be detected is input using the size input means, the original detection means corresponding to the size signal is selected, the selected original detection means is activated, and the original is placed on the original. It is detected for each document size whether or not it is set on the glass-top fixing device with the central reference. Preferably, a pair of document detection means are installed at positions for detecting both end corners of the document corresponding to each size, and when the document size to be detected is A4, the document detection means are installed at a position corresponding to the A4 size. The signal of the detecting means that is detected is selected as the material for determination.

Furthermore, the copying machine according to the present invention includes means for detecting that the original is set at a fixed position on the original placing glass with reference to the center, and means for moving the original detecting means along the original positioning scale. means for inputting the size of a document to be detected; and control means for driving the moving means in response to a size signal from the size input means to move the document detecting means to a position corresponding to the input document size. Equipped with According to this configuration, the document detection means moves to a detection position corresponding to the document size, and detects whether or not a document of a target size is set at a fixed position on the document placement glass with a center reference.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a copying machine according to the present invention will be described in detail with reference to the accompanying drawings.

[First Example, Figures 1 to 7c] This first example adopts a method in which the original is set on the original placing glass with the center reference, and the original is set in a fixed position. This is detected by a pair of sensors corresponding to each size.

First, the overall configuration of a copying machine is as shown in Figure 1.
A photoreceptor drum (1) is installed so as to be rotatable in the direction of the arrow (,), and an inter-image/machine end eraser device (4) in which a charger (2), an optical system (3), and an LED are arranged in parallel is installed around it.
), magnetic brush developing bag holder (5), transfer charger (6), paper separation charger that discharges AC electric field (
7) A blade-type residual toner cleaning device (8) and a residual charge eraser lamp (9) have been installed. - The optical system (3) includes an exposure lamp (31), mirrors (32), and (33).

(34), a projection lens (35), and a mirror (36). Exposure lamp (31) and first mirror (32
) is attached to the slider (37) as shown in FIG. So, the second
The mirror (33) and the third mirror (34) are attached to a slider (not shown) and can be scanned synchronously in the direction of arrow (b) at a speed of (v/2 m). The image of the original (M) set on the original placing glass (10) is exposed to light between the charger (2) and the eraser device (4) by scanning in the direction of arrow (b) by the optical system (3). is exposed onto the body drum (1).

On the other hand, the paper (P) is stored in a cassette (not shown),
The toner is conveyed to the transfer section ′ [lower part of the photoreceptor drum (10)] via a pair of timing rollers (20), and after the toner image is transferred, the toner is fixed by a fixing device (not shown) and transferred to the outside of the machine. will be released.

Note that the configuration and operation of each of the image forming elements described above are well known, and detailed explanation thereof will be omitted.

As shown in Figures 3a and 3b, on the top of this copying machine,
A document scale (11
) is installed. And A5°B5. The scale and display corresponding to the A4 size are placed on the back side and the front side based on the center of the reference position (A). The reference position (A>) has a slight difference in level from the document placement glass (10) to prevent the document (M) from sliding.The document (M) is first placed on the document placement glass (10) at the reference position. Place it slightly away from (A) (see Figure 3a), move it in the direction of arrow (c) 15, and bring it into contact with the scale (11) according to the size scale to set it in place (see Figure 3a). (See figure 3b, the manuscript is exemplified as B5 size).

Next, the document detection means will be explained.

In FIG. 2, reflective photosensors (90d) to (90i) functioning as document detection means are connected to an optical system (3).
The slider (37) is mounted on the top surface of the slider (37) so that its detection surface faces the document placement glass (10).Figure 2 shows that the optical system (3) is at the home position, that is, the standby position at the start of the copying operation. At this time, the sensors (90d) to (90i) are placed at the reference position so that each detection point is located slightly inside the reference position (A) as shown in Figures 3a and 3b. Sensors (90d) are attached to the slider (37) in one row along (A).
, (90e) is inside the A5 size scale, sensor (90e)
0f), (90g> are installed inside the B5 size scale, and sensors (90h) and (90i) are installed inside the A4 size scale, and by detecting the corners of both ends of each size document (M>), Original detection signal (B4) to (B9)
Output. These sensors (90d) to (90i) are composed of a pair of light-emitting elements and light-receiving elements, and when the document <M) is not completely set, the light from the light-emitting elements is diffused outward, and the light-receiving elements Does not detect light.

On the other hand, when a document (M) is set, reflected light is incident on the light receiving element, and document detection signals (B4) to (B9) are output.

That is, by installing a pair of sensors near the reference position (A) and slightly inside each document size, the document (M)
It is detected whether or not the scale (11) is in contact with and positioned, and whether it is set at a fixed position in the longitudinal direction of the scale (11).

Size detection is performed using a size signal input by the operator from the document size input switch (83) (see Figure 4) provided on the operation panel and each sensor (90d) to (90).
i) in combination with the detection signals (B4) to (B9). That is, the operator operates the switch (83) to input the document size A4, B5, or A5. When the input document size is A5, detection signals (54) from sensors (90d) and (90e),
If (55) is output, it is determined that the A5 size original is set in the normal position. Similarly, when the input document size is B5, the detection signal (56), (S7) is sent from the sensor (90f), (90g), and when the input document size is A4, the detection signal (B8) is sent from the sensor (90h), (90i). ), (
59), it is determined that a B5 size or A4 size original is set in the normal position.

Further, a document holding cover (not shown) that can be opened and closed is installed on the document placement glass (10).

The back surface of this document holding cover is white, and the sensors (90d) to (90i) react to its opening and closing.

Therefore, in the first embodiment, a switch (81) (see FIG. 4) for detecting opening/closing of the document holding cover is separately provided, and the detection signal (0) thereof is used to determine that the cover is open.

FIG. 4 shows the control circuit. Control can be performed mainly by a microcomputer (hereinafter referred to as CPU). From the operation panel, the mode signal (N) or (A) is sent from the copy mode selection switch (80), the original size signal (A4), (B5), (A5) is sent from the switch (83), and the print key is pressed. Instantly activated switch <82
) is input to the input port of the CPU. In addition, document detection sensors (90d) to (90i
) from the original detection signals (B4) to (B9), the switch (
The document holding cover release signal (0) from 81) is sent to the CPU.
is input to the input port of The mode signal (N) is a signal for executing a normal copy operation start mode in which a copy operation is started by operating a print key. The mode signal (A) is a signal for executing an automatic copy operation start mode in which a copy operation is started by document detection signals (S4) to (S9) from document detection sensors (90d) to (90i). These copy start mode signals (N), <A>
are sequentially switched each time the switch (80) is turned on, and the initial setting of the CPU is set to the normal copy operation start mode.

On the other hand, the selected copy mode (N) or (A) is displayed on the display (70) on the operation panel, and the display (71)
) displays the input document size A4, BS, or A5.

Next, the control procedure will be explained with reference to FIGS. 5 to 7C.

FIG. 5 shows the main routine of the CPU.

When the CPU is reset and the program is started, in step (Sl), clearing of the random access memory, initialization of registers, etc., and initial settings for setting each device to the initial mode are processed. Step (S2)
Now start the internal timer. This internal timer can be set to the processing time of the main routine in step (Sl), and also serves as a reference for one count of the timer appearing in each subroutine.

In step (S3), key switch input is processed.

Here, inputs such as the number of copies and paper size settings input by the operator from the operation panel are processed. In step (S4), copy mode auto-reset is processed, and this subroutine will be described in detail below. Step (S
In 5), the copy operation start command is processed, which will be described in detail below. Step (S6) actually activates the winter imaging element and processes execution of the copy operation. Step (S7
) then other CPUs.

For example, if a sorter is attached, it communicates with a CPU for controlling the sorter.

After calling each of the above subroutines, step (
After waiting for the internal timer to end in step S8), the process proceeds to step S2.
) Return to

FIG. 6 shows the copy mode auto-reset subroutine executed in the main routine subroutine (S4).

Here, in step J (510), it is determined whether there is an input edge such as an input signal from various key switches on the operation panel, an input signal from each sensor of the copying machine, or a copy end signal. If there is no input, proceed to step (512), and if there is input, proceed to step (511) to auto-reset.
A set timer (T) is set and the process moves to step (512). In step (512), it is determined whether or not the timer (T) has expired, and if it has, the copy mode is set to the normal copy operation start mode (N) in step (513), and this subroutine is ended.

That is, if there is no input edge of the signal for a predetermined period of time set in the timer (T), the copy mode is set to the normal copy operation start mode. This prevents the problem that the automatic copy operation start mode is activated inadvertently, that is, the copy operation is automatically started when the original (M) is inadvertently set on the original placing glass (10). Prevented.

FIGS. 7a, 7b, and 7c show a subroutine for issuing a copy operation start instruction, which is executed in step (S5) of the main routine. Here, the count state of the state counter is checked in step (520), and the start of the copy operation is instructed according to the count value.

Specifically, when the count value of the state counter is "0", it is determined whether the copy mode is set to normal copy operation start mode (N) or automatic copy operation start mode (A) in step (521). Determine. If the normal copy operation start mode (N) is set, the mode (N) is displayed on the display (70) in step (522), and the state counter is set to "1" in step (523).
Set to . If the automatic copy operation start mode (A) is set, the mode (A) is displayed on the display (70) in step (524), and the state counter is set to "2" in step (525).

When the count value of the state counter is “1”,
The copy operation is started by turning on the print switch (82). That is, in step (S26') it is determined whether the print signal (P) is output from the print switch (82). If the print signal (P) is output, the copy operation is started in step (527), and the process is continued in step (527).
528), the state counter is reset to "0".

On the other hand, if the print signal (P) is not output, the state counter is reset to "0" in step (529).

When the current value of the state counter is "2" (automatic copy operation start mode), in step (550), the switch (83) is used to check the original size input by the operator, and the original size is changed to the input size. Accordingly, in steps (551), (553), and (555), the corresponding size is displayed on the display device (70), and at the same time, in step (555)
52), (554), and (556) set the state counters to "3", "5", and "7pa", respectively.

When the current value of the state counter is “3”,
This is when the document size is A5, and the document detection sensor (90
d) Detection signals from (90e) (54), (5
The copy operation is started by the output of 5). That is, after confirming that the document holding cover release signal <0> is output in step (557), step (558) is performed.

At (559), it is determined whether or not the original detection signals (54) and (55) are output. Original detection signal (54),
(55) is output, that is, the original (M) is placed on the original placing glass (1) with the original holding cover open.
0), the copying operation is started in step (560), and the copying operation is started in step (561).
) to set the state counter to "4". On the other hand, if the document holding cover release signal (0) is not fully output, [NO3 in step (S57) or the document detection signal (
54) or (55) is not output [step < 558), NO3 is determined in (559), and the state counter is reset to "0" in step (562).

When the current value of the state counter is “4”,
After the copying operation in the automatic copying operation start mode (A) is completed, it is checked whether the original (M) has been replaced on the original placing glass (10). That is, in step (S63) it is determined whether the copy mode is set to (N) or (A>. If the mode is (N), step (5) is set.
64), the mode (N) is displayed on the display (70), and the state counter is set to "1'' in step (S65). If mode (A), step (566), (
567), it is determined whether the document detection signals (54) and (55) are output. Signal (54), (55)
If none of these are output, it is determined that the original (M) has been removed from the top of the -tanbara loading glass (10),
In step (568), the state counter is set to "2". If either signal (separate) or (55) is output, it is determined that the original (M) is still placed, and the state counter is set to "4" in step (S69). maintain.

Also, if the state counter's current value is "5" or "
7゛ means that the document size is B5 or A4, and after confirming that the document holding cover release signal (0) is output in steps <570) and (583), step (571) , (572), (58
4).

At (S85), the original detection signal (56), (S7), (
ss>, (59> is output),
Step (573).

The copy operation is started in (586), and the copy operation is started in step (S74).
).

At (587), the state counter is set to "6" and "8".

When the current value of the state counter is "6" or "8", confirm that the document (M>) has been removed from the document placement glass (10) in the same manner as in steps (563) to (569) above. Noue [step (579), (58
0).

(592), (593) NO3, step (581)
), the state counter is set to "2'" in (594). Step (582) if the original (M) has not been removed.

At (595), the state counter is maintained at "6" and "8''.

[Second Embodiment, Figures 8 to 10b] This second embodiment, like the first embodiment, adopts a method in which the original is set on the original placing glass with the center reference, and A pair of sensors that are movable according to the size of the document detects whether the document is set in a fixed position.

In FIG. 8, the document scale (11) has A5. B5. A scale and display corresponding to A4 size are attached.

A reflective photosensor (9) functions as a document detection means.
0j), (90k) are the sensors (90d) to (90k)
Similarly to 0i), when the optical system (3) is on standby at the home position, it is installed on the slider (37) so as to be located slightly inside the reference position (A). Furthermore, this sensor (90j>, (90k) is moved by a sensor movement motor (75) (see Fig. 9) to the detection points inside each document size scale (JAS), (KA5), (JB5),
(KB5), (JA4>, (KA4). In other words, if the document size is n5, the sensor (
90j), (90k) is the detection point (JB5), (KB
5), and detects whether or not the document is in contact with and positioned on the scale (11), and whether or not it is set at a fixed position in the longitudinal direction of the scale (11).

The sensors (90j) and (90k) are moved using the document size input switch (83) (on the operation panel).
(see FIG. 9), and is determined by the size signal inputted by the operator's operation.

FIG. 9 shows the control circuit, and the document detection sensor (90j
), the original detection signal (510) from (90k), (
Sll) is input to the input port of the CPU, and a drive signal is output from the output port of the CPU to the sensor movement motor (75). Note that the other configurations are the same as those shown in FIG. 4 above.

Regarding the control procedure, only the copy operation start command subroutine is changed to the one shown in FIGS. (See Figure 6).

In FIGS. 10a and 10b, step (520)
Check the count status of the state counter with
'' and ``1'', steps (521) to (525) and steps (526) to (
529) and executes mode display and normal copy operation start mode.

When the count value of the state counter is "2" (automatic copy operation start mode), the document size input by the operator is checked using the switch (83) at step (stoo), and the document size is changed according to the input size. The corresponding size is displayed on the display (70) in steps (5101), (5104), and (5107), and the corresponding size is displayed in step (5101), (5104), and (5107).
5102), (5103), (5105), (5
106), (5108), and (5109), the sensor (!1
lOj), (90k) as the detection point of the corresponding size (JAS
).

(KA5), (JB5), (KB5), (JA4
), move to (KA4).

Next, in step (5110), the state counter is set to “
Set to 3゛2.

When the count state of the state counter is 3", the sensor (9i)j is activated at step (Sill), (5112)
), (90k) □ determines whether the movement to the detection point corresponding to the document size has been completed, and if the movement is almost completed, the state counter is set to "4" in step (5113). If not completed, the state counter is maintained at 3'' in step (5114').

When the current value of the state counter is 4'', the document holding cover release signal is output in step (5115), (0>
After confirming that is output, proceed to step (511)
6), (5117), the original detection signal (510), (
511) is output. Detection signal (510).

If (511) is output, step (511g)
The copy operation is started at step (5119), and the state counter is set to "5'".Meanwhile, similarly to steps (557) to (559), etc.
115) to =20- (5117), the state counter is reset to "0" in step (5120).

When the current value of the state counter is "5', similarly to steps (563) to (569), etc., after the copy operation in the automatic copy operation start mode (A) is completed,
Confirm that the original has been removed from the original placing glass (10) [Steps (5124), (512
If the answer is No in 5), the state counter is set to "scarce" in step (5126).If the document has not been removed, the state counter is maintained at "5" in step (5127).

[Third Embodiment, Figures 11 to 13b] In this third embodiment, as in the first and second embodiments, the original is set on the original placing glass with the center reference. In addition, a pair of movable sensors corresponding to the document size and another sensor fixed at a fixed position are used to detect whether the original is set in a fixed position.

In FIG. 11, reflective photosensors (901), (90m), (90n) that function as document detection means are shown.
) are the sensors (90d) to (90i), (90j
), slider (37) in the same positional relationship as (90k)
It is installed in The sensors <901) and (90m) are integrally attached to the sensor unit (91) adjacent to each other along the longitudinal direction of the scale (11), and are moved by the sensor unit movement motor (76) (see Fig. 12). , sensors (901), (90n) have detection points (LA5), (LB5) whose gaps correspond to each document size scale.

(LA4). Another sensor (90n) is installed inside the A5 scale, which is the smallest size, on the front side.

For example, if the document size is B5, the sensor unit (9
1) moves to the detection point (LB5). At this time, when the original is set in the normal position, the front corner of the original will be placed on the sensor (
9On), the sensor is at the far side corner (90m)
The sensor (901) maintains a non-detection state. If the sensor (901) can detect the original,
Was an original larger than B5 size set?
Even if it is B5 size, the position is shifted to the back side and set. The sensor unit (91) is moved based on the size signal from the original size input switch (83) as in the first and second embodiments.

FIG. 12 shows the control circuit, and shows the document detection sensor (90
1), (90m), and (90n) original detection signals (512).

(513) and (514) are input to the input port of the CPU, and a drive signal is output from the output port of the CPU to the sensor unit moving motor (76). Further, in the third embodiment, the sensor (901) can also detect the open/closed state of the document holding cover, and therefore the detection switch (801) can also detect the opening/closing state of the document holding cover.
1) has been omitted. That is, if the document holding cover is closed, the sensor (901) is also turned on.

Note that the other configurations are the same as those shown in FIGS. 4 and 9 above.

Regarding the control procedure, only the subroutine for the copy operation start command is changed to that shown in FIGS. 13a and 13b.
Other processes are executed in the same manner as described in the first embodiment (see FIGS. 5 and 6).

In FIGS. 13a and 13b, step (521)
- (529) performs the same processing as in each of the above-mentioned embodiments,
When the current value of the state counter is "2" (automatic copy operation start mode), the document size input by the operator is checked using the switch (83) in step (5130), and the original size is changed to the input size. Accordingly, the corresponding size is displayed on the display (70) in steps (5131), (5133), and (5135), and the sensor unit (91) of the corresponding size is displayed in steps (5132), (5134), and (5136). Detection point (LA5)
, (LB5), (LA4). continue,
In step (5137), the state counter is set to 3''.

When the current value of the state counter is “3゛2”,
In step (5138) sensor unit (91) #[M
It is determined whether the movement to the detection point corresponding to the size has been completed, and if the movement has been completed, the state counter is set to "4" in step (5139). If not completed (if so, the state counter is maintained at "3" in step (5140)).

When the current value of the state counter is “4”, step (5141), (5142>, (5143>)
Original sensor (901), (90m>, (90n>)
From each detection signal (512), (513).

=24 (514) is output. If the detection signal (512) is output from the sensor (901), it indicates whether the document holding cover is closed, the document is thicker than the input size, or the document is set far from the normal position. Either step (514
6) reset the state counter to “0゛′.Even if the detection signal (512) is not output, the sensor (
90m), (90n) detection signals (513), (5
14) is not fully output, the document is not set in the correct position, and in this case, step (5146) is not completed.
) resets the state counter to "0"'. The detection signal (512) is not output, and the detection signal (513)
), (514) are output, the original is set in the normal position, and step (5144)
The copy operation is started in step (5145), and the state counter is set to "5".

When the current value of the state counter is "5", similarly to steps (563) to (569), etc., after the copy operation in the automatic copy operation start mode (A) is completed,
After confirming that the original has been removed from the original placing glass (10) [steps (5150), (5151)]
If the answer is NO, the state counter is set to "2" in step (5152). If the document has not been removed, the state counter is maintained at "5" in step (5127).

Note that the copy mode is the normal copy operation start mode (N
) [NO in step (5147)]
This is the same as in each of the above embodiments in that the mode (N) is displayed on the display (70) in step (5148) and the state counter is set to "1" in step (5149).

[Other Embodiments] Note that the copying machine according to the present invention is not limited to the above-mentioned embodiments, and can be variously modified within the scope of the gist thereof.

In particular, as the document detection sensors (90d) to (90n), in addition to reflective photosensors, detection means such as transmission photosensors, contact sensors equipped with actuators, etc. can be used.

Further, in each of the embodiments, the document size to be detected is configured to be detected using a switch (83) on the operation panel, but it may be performed by conventionally well-known automatic document size detection means. That is, the operator sets the original in a fixed position on the cumulative placement glass, and presses the copy mode selection switch (8).
When the automatic copy operation start mode (A) is selected in step 0), the document size is automatically detected. At this time, sensors (90d) to (90i) to be used for size detection are selected based on the detected size signal, or sensor (90i) is selected based on the detected size signal.
0j), (90k).

(901), determine the position to move to (90m).

As is clear from the above explanation, according to the present invention, it is selected based on the size signal from the size input means that the original is set at a fixed position on the cumulative placement glass with a center reference. Since the original document detecting means is configured to detect the original document, it is possible to reliably detect that original documents of various sizes are set in a fixed position with respect to the center.

Furthermore, since the document detection means is moved to the detection position corresponding to each size in accordance with the size signal from the size input means, it is possible to reliably detect document sizes of various sizes simply by using a pair of detection means. can.

[Brief explanation of the drawing]

1 to 7c show the first embodiment of the present invention, FIG. 1 is an overall configuration diagram of the copying machine, FIG. 2 is a sectional view showing the main parts of FIG. 1, and FIGS. Figure 3b is a plan view showing the document placement section, Figure 4 is a block diagram showing the control circuit, Figures 5 and 6.
7a, 7b, and 7c are flowcharts showing the control procedure. FIG. 8 is a plan view showing the document resting section of the second embodiment, FIG. 9 is an ivy diagram showing the control circuit of the second embodiment, and FIGS. 10a and 10'b are the control procedures. It is a flowchart figure which shows. Fig. 11 is a plan view showing the document placement section of the third embodiment, Fig. 12 is a block diagram showing the control circuit of the third embodiment, Figs. 13a and 13b.
The figure is a flowchart showing the control procedure. (1)...Photosensitive drum, (3)...Optical system, (1
0)...Original placement glass, (11)...Original scale, (37)...Slider, (75), (76).
...Movement motor, (83)...Document size input switch, (90d) to (90n>...for document detection) odometer, (91)...Sensor unit, (A)...Document reference position .

Claims (1)

[Scope of Claims] 1. In a copying machine that reproduces the image of a document placed on a document placement glass with a center reference on paper using an electrophotographic method, each size of document is placed on the document placement glass at a fixed position. means for detecting that the original is set in a position with a center reference; means for inputting the size of the original to be detected; and control means for selecting the original detecting means according to the size signal from the size input means. A copying machine characterized by: 2. The copying machine according to claim 1, wherein the document detecting means is installed at a position corresponding to each document size. 3. In a copying machine that uses electrophotography to reproduce the image of a document placed on a document placement glass with a center reference, the document is placed in a fixed position on the document placement glass with a center reference. means for detecting, means for moving the document detecting means along a document positioning scale, means for inputting the size of the document to be detected, and driving the moving means in response to a size signal from the size input means. A copying machine comprising: a control means for moving the document detection means to a position corresponding to an input document size.