JPH01186925A - Image forming device - Google Patents

Abstract

PURPOSE:To simplify the mechanical constitution of an image producing device and to attain the reduction in cost by detecting the size of an original and the setting direction of the original by a sensor means. CONSTITUTION:A 1st comparison means compares a signal from a 1st optical sensor means 51 with a reference value to judge the existence of the original and a 2nd counting means executes counting while the original does not exist according to the judged result of the 1st comparison means and judges the length of the original from the counted value which is stored last in a 1st storage means when the counted value exceeds a specified value. Meanwhile, a 2nd optical sensor means 52 receives the reflected light from a position on the original and the output signal thereof is compared with the reference value. And a width direction judging means judges the existence of the original on the detection position of the 2nd optical sensor means according to the contents stored in a 2nd storage means. An original judging means judges the size of the original placed on an original platen and the setting direction of the original based on the judged results of a length judging means and the width direction judging means. Thus, the original can be surely detected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image forming apparatus having means for detecting the size and setting direction of a document placed on a document table.

[Conventional technology and its problems]

In an image forming device, such as a copying machine, which includes a document table on which a document is placed and an optical system that scans the document on the document table,
The size of the original placed on the document glass is automatically detected.
Some copy paper sizes are selected according to the detected original size, and the lens is moved according to the copy magnification determined by the original size and the copy paper size.

Conventional copying machines use a light sensor that receives reflected light from a document and outputs a signal according to the light intensity, and a sensor that compares the output signal of the light sensor with a fixed reference value that is unrelated to the document size. and a comparator that outputs a signal indicating the presence or absence of a document, and the document size is determined at the time when the comparator outputs a signal indicating that there is no document.
0-4974).

However, originals have various densities and patterns, and the intensity of the reflected light from the original is thick (varies).For this reason, it is extremely difficult to set a standard value for the presence or absence of light for various originals. In addition, it is difficult to reliably detect the presence or absence of a document because the intensity of the reflected light may exceed the standard value even if there is a document, and a signal indicating that there is no document may be output. Met.

Therefore, in the above-mentioned conventional copying machine, there is a possibility that the document size may be detected incorrectly, leading to incorrect selection of copy paper or setting of copy magnification.

In addition, in conventional copying machines, preliminary scanning is performed over the entire length of the document table to detect the document size, so it takes time to detect the document size, and the start-up speed of the copier (first copy There was also the problem that speed) decreased.

SUMMARY OF THE INVENTION In view of the above-mentioned problems, an object of the present invention is to provide an image forming apparatus that can accurately and quickly detect the document size and the document setting direction, and can prevent the start-up speed from decreasing.

[Means to solve the problem]

The present invention provides an image forming apparatus that includes a document table on which a document is placed and an optical system that scans the document on the document table. a first optical sensor means and a second optical sensor means that output corresponding signals; and a scanning drive means that moves the light received by the first and second optical sensor means relative to the document; Reference point detection means for detecting a reference point of the scanning drive means; first counter means for starting counting upon detection by the reference point detection means; and comparing the signal from the first optical sensor means with a reference value. and a first memory for storing the count value of the first counter means when the judgment of the first comparison means changes from the presence of a document to the absence of a document. means, a second counter means for counting while the first comparison means determines that there is no document; a length determining means for determining the document length from the count value stored in the second optical sensor; a second comparing means for comparing the signal from the second optical sensor with a reference value; a second storage means for storing the comparison result of the comparison means;
width direction determining means for determining the presence or absence of a document according to the content stored in the second storage means; and determining the document size and document setting direction from the determination results of the length determining means and the width direction determining means. The present invention is characterized by comprising a document determining means.

[For production]

The first and second photosensor means receive light from the optical system or light reflected from the document by a dedicated light projector, and output a signal according to the intensity of the light. The reference point detection means detects a reference point between the first optical sensor means and the document, and the counting operation of the first counter means starts from the point in time when the reference point is detected.

The first comparison means compares the signal from the first photosensor means with a reference value to determine the presence or absence of a document, and when the determination result changes from the presence of a document to the absence of a document, a first counter means. The count value of is stored in the first storage means. In other words, each time the judgment result of the first comparison means changes from document present to document absent, the count value of the first counter means at that time is sequentially rewritten or updated to the latest value. is stored in the storage means.

The second counting means counts while the first comparing means determines that there is no document, and when the count value exceeds a predetermined value, the length determining means stores the last document in the first storage means. The document length is determined from the count value stored in the .

On the other hand, the second photosensor means receives reflected light from a different position on the document than the first photosensor, and its output signal is compared with a reference value by the second comparison means.

In the second storage means, the comparison results by the second comparison means are stored a predetermined number of times at regular intervals. The second storage means stores, for example, the number of comparisons and the number of times a specific comparison result is obtained.

The width direction determination means determines the presence or absence of a document at the detection position of the second photosensor means according to the content stored in the second storage means.

The document determining means determines whether s! Determine the size of the placed original and its setting direction.

Based on the judgment result of the original judgment means, copy paper selection, magnification setting, etc. are performed.

Note that in the present invention, the document size refers to A4, A5, B
It may be a standard size type such as No. 5, or a type based on other suitable rankings.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a front sectional view showing the general structure of a copying machine.

A photoreceptor drum 1 that can be rotated counterclockwise is disposed approximately in the center of the copying machine body, and around it are a main eraser lamp 2, an LED array 4, a charger 5, a developing device 6a, 6b.

A 6C1 transfer charger 7, a separation charger 8, and a blade type cleaning device 9 are provided. The photoreceptor drum 1 has a photoreceptor layer provided on its surface, and its surface is uniformly charged by passing through an eraser lamp 2 and a charger 5, and receives image exposure from an optical system 10.

The optical system 10 is installed below the original glass 16 so as to be able to scan the image on the original, and is composed of a light source 11a, movable mirrors 11, 12, 13, a lens 14, and a mirror 15. The scanner 31 equipped with the light source 11a and the movable mirror 11 moves at a speed of v/n (n is the copying magnification) with respect to the peripheral speed V of the photosensitive drum 1, and the slider 32 equipped with the movable mirror 12.13 moves at a speed of v/n (n is the copying magnification). It is driven by a scan motor to move at a speed of v/2n.

Note that 17 is a document cover, and the lower surface of the document cover 17, that is, the surface that presses the document tray, is colored yellow to facilitate optical detection of the presence or absence of the document tray.

FIG. 2 shows the optical path of the optical system 10, developed in a straight line, between the light emitted from the light source 11a and reflected by the original document reaching the lens 14, the first sensor 51, and the second sensor 52. It is a schematic diagram.

Referring also to the figure, a reference position sensor 50 is provided below the tip of the original glass 16, which is turned on and off as the scanner 31 moves. Detects the position of the tip and outputs a reference signal. Further, near the lens 14, there is a first sensor 51 for receiving the light emitted from the light source 11a and reflected by the document tray, and detecting the presence or absence of the document at a specific position in the length and width direction of the document tray. and a second sensor 52 are provided.

The first sensor 51 is connected in the length direction of the original document (scanner 3
This is to detect the size of the scan direction (1).
The scanner 31 is arranged to receive reflected light from the document plate during preliminary scanning by the scanner 31 for all standard-sized documents placed on the document glass 16 .

In other words, if the copying machine is of a type in which the document tray is set at the center position in the width direction of the document glass 16, the first sensor 51 is placed toward the center of the document glass 16 in the width direction.
Due to the preliminary scan of the scanner 31, reflected light from near the center position of the document tray is received.

Further, the second sensor 52 receives reflected light from a position different from that of the first sensor 51, and the second sensor 52 receives reflected light from a position different from that of the first sensor 51.
This is to detect the setting direction, whether it is placed vertically or horizontally on the top. It is disposed toward a position where it can receive only the reflected light from the original placed in the horizontal direction without receiving the reflected light from the document.

The first sensor 51 and the second sensor 52 are provided with blue transmission filters, which, together with the fact that the document cover is colored yellow, facilitates optical detection of document defects. In addition, 53 performs automatic exposure adjustment,
This is an AE sensor that detects the density of the document.

On the other hand, there are paper feed rollers 21 on the left side of the copying machine body.
．． A top drawing paper section 20 and a bottom drawing paper section 22 are provided, and the copy paper fed from either of them is transferred to a roller pair 24,
Timing roller pair 26, conveyor belt 27, fixing device 2
8 and a pair of discharge rollers 29, during which the image on the photosensitive drum 1 is transferred, fixed by the fixing device 28, and discharged onto the discharge tray 30.

FIG. 3 is a plan view of the operation panel 70 provided on the top surface of the copying machine.

The operation panel 70 includes a print start key 71 for starting the copying operation, a display section 72 consisting of a 7-segment LED, etc., and displaying the number of copies and other information.
Consisting of 10 numeric keys from 9 to 9, a numeric keypad 80 for inputting the number of copies, etc., an interrupt key 90 for specifying interrupt copying, and a clear/stop key 91 for copy paper (paper) in paper feed cassettes installed in multiple stages. A paper selection key 92 for specifying the copy paper by size and vertical/horizontal direction, a paper display section 92a for displaying the size and vertical/horizontal direction of the selected copy paper, automatic paper selection mode, automatic magnification selection mode, and manual mode sequentially. A mode switching key 93 for switching, mode display sections 93a to 93c for displaying the switched mode, etc. are arranged, and although not shown, there is also an up key for changing and setting the copy image density in steps. A down key, a density display section for displaying the set density, a magnification setting key for manually setting the copying magnification, a magnification display section for displaying the set magnification, etc. are arranged.

FIG. 4 is a circuit diagram showing a control circuit of the copying machine.

201 is a CPU (central processing unit) consisting of a microcomputer, and the analog input terminal of this CPU U2O5 is connected to amplification units 203 and 204 that amplify the outputs of the first sensor 51 and the second sensor 52.
The various keys mentioned above, the display section, and the drive circuits for the motor and clutch are connected.

In this embodiment, before the scanner 31 performs exposure scanning for copying, in order to detect the size of the document paper,
During a preliminary scan in which the scanner 31 performs a preliminary scan in which the document tray is irradiated and moved, reflected light from the document tray is transmitted to the first sensor 51 and the second sensor 52.
incident on . The first sensor 51 and the second sensor 52 output a signal according to the intensity of the received light, and after the signal is amplified by the amplifying sections 203 and 204, the first CP
Input to U2O5. ' The CPU 201 digitally converts the signals input from the amplifiers 203 and 204, and based on the data obtained, determines the size of the document sheet and its setting direction (II or horizontal direction) according to a program stored inside the CPU 201. )
It detects the document size and executes control according to the document size and setting direction.

The reference position sensor 50 is used to detect the leading edge of an image during a copying operation, and obtains a reference signal that serves as a reference point for measuring the document length during a preliminary scan for detecting the document size. used for

FIG. 5 is a timing chart showing signal states when detecting the document size by preliminary scanning. The document size detection operation will be explained with reference to this figure.

When the print start key 71 is turned on, a preliminary scan is started, and the scanner 31 starts moving in the scanning direction.

When the scanner 31 reaches near the leading edge of the document tray, the scanner 31 activates the reference position sensor 50.
A reference signal is output from the reference position sensor 50.

A first counter inside the CPU 201 is started at the timing when the reference signal is output. Thereafter, the first counter counts up at regular intervals.

The CPU 2 O 5 samples the signal from the first sensor 51 and digitally converts it into detection data, and compares this detection data with a certain reference value. When this data is larger than the reference value, it is determined that there is no document, and when the opposite is true, it is determined that there is a document.

When the judgment of CPU U2O5 changes from document present to document absent, the count value of the first counter at that time is
It is stored in the length memory, which is the internal memory of P U2O5. The contents of the length memory are rewritten every time there is a change from the presence of a document to the absence of a document, so that only the latest count value is stored.

Also, at the same time as the document changes from having a manuscript to not having a manuscript, the CP
A second counter inside U201 starts. The second counter that has started stops when there is a change from no document to a document present, and then when the state changes again to no document, the count value is cleared and the count is started again.

If the count value of the second counter exceeds a predetermined value (predetermined time), it is assumed that there is no document residue in the position of the scanner 31 at that time, and the preliminary scan is terminated, and the scanner 31 is returned to its original position (home position).

The document length is determined by the count value finally stored in the length memory.

In other words, even if the signal from the first sensor 51 fluctuates depending on the pattern or density of the original, and it is determined that there is no original even though there is original When the state changes to document present during the time, only the count value when the document changes to no document next time is stored in the length memory, and the document length is ultimately determined by the final count value.

Therefore, the light intensity varies depending on the pattern and density of the original, and even if it is determined that there is no original while the original is being detected, this is ignored, and the original length is short (
The correct document length is detected without being detected.

The second sensor 52 is used to detect the setting direction of the document tray as described above, and to measure the presence or absence of the document in the width direction of the document. After the reference signal described above is output, the CPU 2O5 2 sensor 52 signal (amplifier 2
04 output) at a constant period, converts it into digital data, and compares the obtained data with a constant reference value. When this data is larger than the reference value, it is determined that there is no document, and when the opposite is true, it is determined that there is a document. If the number of times it is determined that there is a document out of the predetermined number of data is greater than or equal to a predetermined number, it is determined that the document tray is set in the horizontal direction.

Based on the results of determining the document length and setting direction, the document size such as A4, A5, BS, etc. and cent direction are correctly detected. Moreover, since the length of the document in the document tray can be detected after scanning the length of the document tray for a certain period of time, if the length of the document tray is short, the scanner 31 can detect the length of the document on the document glass. It is not necessary to perform a full scan over the entire length of 16 pages, the document size can be detected in a short time, and it is possible to suppress a decrease in the start-up speed (first copy speed) of the copying machine as much as possible.

Next, based on the flowcharts in FIGS. 7 to 10,
The copying operation and original size detection operation of the copying machine will be explained.

FIG. 7 is a main flowchart of the copying machine.

In step #1, the CPU 2O5 is initialized after the power is turned on, and initial settings are made to put the copying machine into the initial mode.

In step #2, an internal timer is set to define the length of one routine. This will result in steps #3~
Processing No. 10 is performed at regular intervals.

In step #3, various keys on the operation panel 70, the reference position sensor 50, the first sensor 51, and the second sensor 52 are used.
, and other input routines for inputting signals from switches and sensors (not shown).

In step #4, based on the input result of step #3,
Detects the operating status of the copying machine, such as the occurrence of trouble or jams. Based on the result, it is determined in step #5 whether a copying operation is possible.

If the copying operation is possible, a copying operation routine is executed in step #6, and if not, an abnormality handling routine is executed in step #7.

In step #8, a document size detection routine for detecting the document size is executed.

' In step #9, data to be displayed on each display section of the operation panel 70 is processed, and in step #10,
It displays the data and outputs signals to control each part of the copying machine.

After performing these processes, in step #11, the previously set internal timer is waited for, and the length of one routine is controlled to be constant.

FIG. 8 is a flowchart of the input routine of step #3 described above.

In step #21, it is determined whether the mode switching key 93 has been pressed or not, and if the key has been pressed, the processing from step #22 onwards is performed.

In step #22, the content of the document size detection mode counter is checked, and a detection mode is selected according to the content.

Detection mode is automatic paper selection mode (automatic paper selection mode) that detects the original size and selects paper of the same size based on the result.
APS mode), automatic magnification selection mode (AMS mode) that detects the document size and sets the copy magnification based on the result and the preselected paper size, and paper selection without detecting the document size. There are three types of detection modes: a manual mode in which the detection mode and the copy magnification are set using the manual, and when each detection mode is selected, a message to that effect is displayed on the mode display section 93amc.

In the APS mode, set the flag FAPS indicating the APS mode to "l" and reset the flag FAMSSFMANUAL indicating other detection modes (Step #23). Set the state and width state to "1" (step #24), and set the content of the document size detection mode counter to "1".
1” (step #25).

In AMS mode, set the flag FAMS indicating AMS mode to "1", reset the flags indicating other detection modes (step #26), and set the length state and width state to "1" (step #26). 27) Set the content of the document size detection mode counter to "2" (step #2B).

In manual mode, set the flag FMANUAL indicating manual mode to "1" and reset the flags indicating other detection modes (step #29).
, in order to not perform document size detection, reset the length state and width state to "0" in step #30.
), the content of the document size detection mode counter is set to "O" (step #31).

Through the above processing, each time the mode switching key 93 is pressed, the mode is switched in a rotational manner: APS mode→AMS mode→manual mode→APS mode...

In step #32, it is determined whether or not the print start key 71 has been pressed, and if it has been pressed, the scan request flag is set to "1" and control according to the above-described detection mode is started.

In step #34, signals from other keys on the operation panel 70, sensors arranged in various parts of the copying machine, etc. are input.

FIG. 9 is a flowchart of the copy operation routine of step #6 described above.

The length state and the width state are states that control document size detection, and during detection, they hold values of "1" to "4" depending on the state at that time.

These states become "O" in two cases: in a manual mode in which document size detection is not performed, and in a case in which the optical system 10 returns to the home position after completion of document size detection.

First, in step 441.42, it is determined whether or not the document size detection process is in progress depending on whether the length state and cap state are not "0". If it is determined that the document size detection process is not in progress, the process proceeds to step #46 and copies are made. Execute the process for creating (including the process in standby state). If it is determined that the process is in progress, the process of step #43 is executed.

In step #43, the presence or absence of a scan request is checked. If there is a scan request, the scanner 31 is caused to scan in step #44. If there is no scan request,
In step #45, processing for returning the scanner 31 is performed.

FIGS. 10a to 10c are flowcharts of the document size detection routine of step #8 described above.

In step #50, the contents of the length state are checked, and if the length state is between "rl" and "4", step #51.61. Branch to either '71.81.

When the length state is "1" and "2", the document length is detected, and when the length state is "3", the document size is detected based on the document length and the document setting direction. will be held.

When APS mode or AMS mode is selected, the length state is set to "1" in step #24.27.
, the process starts from step #51.

When the manual mode is selected, the length state is "0", so these steps are not executed and the process proceeds to step #90.

When the length state is "1", first step #5
1, it is determined whether or not a reference signal is output from the reference position sensor 50 located in the middle of the moving route of the scanner 31. When the reference signal is being output, the first counter is cleared in order to measure the document length, and the length memory that stores the content of the first counter at the time when the document changes from document present to document absent, and document length memory. Initialize the original flag indicating the presence or absence of the document.

In step #53, the length state is set to "2".

Thereafter, the process proceeds to step #90 in which a process for detecting the setting direction is performed, but the process for detecting the document length will be described first.

When the state is "2", the first counter is incremented in step #61, and in step #62,
The output of the first sensor 51 is checked to determine the presence or absence of document paper in the length direction. If it is determined that there is a manuscript (
Step #62: No), the original flag is set to "0" (original present).

As the scanning by the scanner 31 progresses and it is determined that there is no document (YES in step #62), the document flag is checked (step #63). The contents of the document flag checked here are the document presence/absence status one routine before, so if the document flag is "0" (document present), the process advances to step #64 and changes from document presence to no document. Perform the processing when it happens.

That is, in step #64, the original flag is set to "1".
(No original) is set, and the contents of the first counter at that time are stored in the length memory. Next, in step #65, the second counter is cleared and counting is started in order to determine whether or not there continues to be no document. .

From now on, each time this routine is executed, the process proceeds in the order of step #61 -> step #62 -> step #63 -> step #66.

In step #66, the second counter is incremented, and in step #67 it is determined whether the second counter has reached a predetermined value, and if it has reached the predetermined value, the length state is set to "3".
(Step #68).

The flow described so far is used to process a document with almost no density contrast. However, documents that are actually used have various density patterns. For example, in a document with solid black, the intensity of reflected light decreases extremely when scanning the solid black portion, and the first sensor 5
The signal of 1 will be at the level of no document. Even in such a case, the document length can be detected correctly by the process described below.

Hereinafter, the document length detection operation will be explained with reference to FIG. 6, which shows an example of data fluctuations.

When the scanner 31 is in the section 81 in FIG. 6, that is, when the first sensor 51 is detecting the section B1 in FIG. 6, it is determined that there is a document, so step #6
The determination in step #2 is no, and the process proceeds to step #69.

When the first sensor 51 reaches point B2 in the figure,
The process changes from having a manuscript to not having a manuscript, and the determination at step #62 becomes YES, and the process proceeds to step #63. Since the manuscript flag is still "0," the determination at step #63 becomes YES, and the process proceeds to step #64. Here, the original flag becomes "l".

When the first sensor 51 detects the section 83 (for example, the solid black part) in the figure, it is determined that there is no document, and the document flag is "1", so step #6
Perform the processing from step 6 onwards.

If the interval of B3 is within the length corresponding to the predetermined value of step #67, by reaching the point of B4, step #6 is executed before the determination of yes is made in step #67.
2 is judged as no. Then, in step #69, the document flag becomes "0", and the next time there is no document, the second counter is reset in step #65. Therefore, the length state update process in step #68 is not executed, and the document length detection continues.

As a result, an erroneous determination that there is no original due to a solid black part in the middle of the original is ignored.

When the first sensor 51 detects the section B5 and the point B6, the same processing as that for the section B1 and point B2 described above is performed, and the contents of the length memory are detected at the point 86. The count value of the first counter is updated at .

If the length of the section B7 is longer than the predetermined value in step #67, it is assumed that there is actually no document left when the point B8 is reached, and the length state is set to "3" in step #68. , and finishes detecting the document length.

When the length state is "3", it is determined in step #71 whether the width state is "4", that is, whether the detection in the width direction of the document has been completed. The processing after gaff 2 is bypassed, and the processing here waits until the width state becomes "4".

When the width state becomes "4", in step #72, the document size and the document setting direction are determined from the detection result of the document length and the document width direction.

In this example, among the sizes A3 to A5 and B4 to B6, the dimensions in the length direction are different except for the cases of A4 width and A5 length, and B5 width and 86 length. Since the setting direction can be determined only from the detection result of the document length, only in the above case, the setting direction is determined based on the detection result of the width direction of the document. Therefore, in the above case, if the detection result in the width direction is that there is a document, the setting direction is horizontal (A4 or B5), and if there is no document, the setting direction is r41 (A5 or B6).

Then, in step #73, the scan request is set to "0" in order to return the scanner 31, and in step #74, the length state is updated to "4".

When the length state is "4", it is determined in step #81 whether the scanner 31 has returned to the home position, and if it has returned, both the length state and the width state are set to "4" in step #82. 0" and return to the main routine.

Next, the processing from step #90 onwards will be described regarding detection in the width direction of the document.

In step #90, the content of the width state is checked, and if the width state is between "1" and "3", the process branches to steps #91, 101, and 111, respectively.

When the APS mode or AMS mode is selected, the width state is "1", so the process is executed from step #91.

When the manual mode is selected, the width state is "0", so these steps are not executed and the process returns to the main routine.

When the width state is "1", first step #91
In this step, it is determined whether or not a reference signal is output by the operation of the reference position sensor 50. When the reference signal is output, step # is activated to detect the document width direction.
92, a third counter for defining the measurement interval, a fourth counter for counting the number of measurements, and a fifth counter for counting the number of times when the measurement result indicates that a document is present.
Clear each counter.

In step #93, the width memory for storing the detection result in the width direction is cleared, and in step #94, the width state is updated to "2".

When the width state is "2", in step #101,
incrementing a third counter defining a measurement interval;
In step #102, it is checked whether the contents of the third counter have reached a predetermined value.

If the number has not been reached, the process returns to the main routine, and if the number has been reached, step #103 and subsequent steps are executed.

In step #103, the fourth counter is incremented and the third counter is cleared. As a result, the processes after step #102 are performed at regular intervals.

In step #104, the count value of the fourth counter, ie, whether or not the measurement has been performed a predetermined number of times, is checked. If the measurement is within a predetermined number of times, the process advances to step #105, and the presence or absence of a document is checked based on the signal from the second sensor 52. If there is a document, the fifth counter is incremented in step #106, and if there is no document, step #106 is bypassed.

As a result, the fifth counter counts the number of times there is a document present.

If measurements have been made a predetermined number of times (step #104)
(No), the width state is updated to "3" in step #107, and the process returns to the main routine.

When the width state is "3", the fifth counter is checked in step #111 to determine whether or not the number of times there is a document is greater than or equal to a predetermined number, and if it is greater than or equal to the predetermined number, step #112 is performed. The width memory is set to "1" (original present) in , and if the predetermined number of times is not reached, step #112 is bypassed. Finally, step #11
3 updates the width state to "4" and returns to the main routine.

When the width state is "4", the process immediately returns to the main routine.

According to the embodiment described above, the length of the document can be detected by the first sensor 51, and the light intensity varies depending on the pattern and density of the document, so that it is determined that there is no document while the document size is being detected. Even if this happens, this is ignored and the correct document length is detected without the document being detected as short.

Further, the second sensor 52 measures the width of the document in the width direction, so that the direction in which the document is set can be easily detected.

Based on these determination results of the document length and setting direction, the document size and setting direction are correctly detected.

Moreover, since the length of the document in the document tray can be detected after scanning the length of the document tray for a certain period of time, if the length of the document tray is short, the scanner 31 can detect the length of the document on the document glass. It is not necessary to perform a full scan over the entire length of 16 pages, the document size can be detected in a short time, and it is possible to suppress a decrease in the start-up speed of the copying machine as much as possible.

In the above-described embodiment, the first sensor 51 and the second sensor 52 are provided near the lens 14 to receive the light reflected by the original document from the light source 11a.
Although the document tray is scanned in the length direction by moving the scanner 31 provided with It may be attached to 31. Further, the first sensor 51 and the second sensor 52 may be scanned by a driving means different from the scanner 31. The scanner 31, the first sensor 51, the second sensor 52, etc. may be fixed, and the original glass 16 may be moved together with the original.

In the above embodiment, the first to fifth counters, each comparing means, and each determining means for detecting the document size are
Although this has been realized by software using the P U2O5 program, it may also be realized by hard logic or the like.

〔Effect of the invention〕

According to the present invention, the document size and the document setting direction are detected accurately and quickly, and the image forming apparatus starts up quickly.

Further, since the document size and document setting direction are detected by a small number of sensor means, the mechanical configuration of the image forming apparatus is simple, and costs can be reduced.

[Brief explanation of the drawing]

The drawings show embodiments of the present invention; FIG. 1 is a front cross-sectional view showing the general configuration of a copying machine, FIG. 2 is a schematic diagram showing the optical path of the optical system developed in a straight line, and FIG. 4 is a circuit diagram showing the control circuit of the copying machine; FIG. 5 is a timing chart showing the signal state when detecting the document size by preliminary scanning; FIG. FIG. 6 is a timing chart showing an example of fluctuations in detection data for explaining the document length detection operation, and FIGS. 7 to 10 are flowcharts showing processing of the copying operation and document size detection operation in the CPU 2O5. be. 10...Optical system, 16... Original glass (original platen),
31... Scanner (scanning drive means), 50... Reference position sensor (reference point detection means), 51... First sensor (first optical sensor means), 52... Second optical sensor means'), 201...CPU. Applicant Minolta Camera Co., Ltd. Agent Patent Attorney Yukio Kubo Figure 4 Figure 7 Figure 9 Figure 10 b

Claims (1)

[Claims] In an image forming apparatus that includes a document table on which a document is placed and an optical system that scans the document on the document table, reflected light from different positions of the document is received and a signal corresponding to the light intensity is generated. a first optical sensor means and a second optical sensor means for outputting, and a scanning drive means for moving the light received by the first and second optical sensor means relative to the document;
Reference point detection means for detecting a reference point of the scanning drive means; first counter means for starting counting upon detection by the reference point detection means; and comparing the signal from the first optical sensor means with a reference value. The first step is to determine whether there is a manuscript or not.
a first storage means for storing the count value of the first counter means when the judgment of the first comparison means changes from document present to document absent; a second counter means for counting while the determination is that there is no document; and when the second counter means exceeds a predetermined value, the document length is determined from the count value last stored in the first storage means. a second comparing means for comparing the signal from the second optical sensor means with a reference value; and a second comparing means for storing the comparison result of the second comparing means at a constant period. a width direction determining means for determining the presence or absence of a document according to the content stored in the second storage means; and determining the document size and the width of the document from the determination results of the length determining means and the width direction determining means. 1. An image forming apparatus comprising: document determining means for determining a setting direction.