JP2000046515A - Document detecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a document detecting device using a scanning document detecting sensor from erroneously detecting the size of a document by giving a maximum document size discriminating ability to the detecting device. SOLUTION: A document detector detects the position and size of a document in such a way that the detector projects two concentrated light beams upon a document platen from the bottom side, scans the document with the light beams in curved states, and detects the reflected light rays of the light beams from the document. Then the detector measures the relative light receiving timing lag from the detection of reflected light from a reference plate for starting measuring to the detection of the reflected light from the document on each light beam, processes the timing lags into data, and analyzes the measured data to each light beam. When the timing lags from the detection of the reflected light from the reference plate to the detection of the reflected light from the document are equal to or longer the data of a certain document size (for example, B-4 side), the device compulsorily processes the data as the data of the maximum document size (for example, A-3 size).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a document detection device which is provided in a document reading section or an image reading device of an image forming apparatus such as a copying machine or a facsimile and detects and determines the size of a document placed on a document table. Related to the device.

[0002]

2. Description of the Related Art In an image forming apparatus such as a copying machine provided with a document detecting device, the size of a document placed on a contact glass (or platen glass) of a document table is detected by the document detecting device, and the detection is performed. In this case, a paper corresponding to the size of the selected document is selected, fed from the paper feeding unit to the image forming unit, and a copying process is performed. As a means for detecting the size of a document placed on the platen of the device, a plurality of sensors consisting of a light emitting unit and a light receiving unit are arranged at positions where a document size difference can be obtained on the platen surface. The document size is determined based on the combination of detection results obtained by a plurality of sensors. However, since there are many types of manuscripts, such as A, B, inch, and other sizes determined in each country, the arrangement of sensors is set according to the destination (by specification). However, it is not always possible to arrange sensors at the optimal position.Moreover, in order to support various document sizes, it is necessary to arrange multiple sensors at positions corresponding to various document sizes, and the number of sensors increases. There was a disadvantage that the cost was high. What has been conceived is a means for irradiating a beam from below the platen toward the platen and detecting the size and position of the document by scanning the beam. The following technologies are available.

For example, Japanese Patent Application Laid-Open No. 2-308236 discloses a document pressing means for fixing a placed document on a platen glass, and a detecting means for detecting the open / close state of the document pressing means. A light scanning means for continuously irradiating a predetermined area of the document with light based on a detection signal from the detection means, a displacement means for changing a position of the light scanning means, and a drive time of the light scanning means. Information based on the first scanning light from the light scanning means, and the second scanning light from the light scanning means at the position after the change by the displacement means, which is detected by the detection means. A document size / position detecting device having a control unit for detecting the size of the document on the platen glass and the mounting state of the document by comparing the driving time with the driving time is disclosed. . In this document size / position detecting device, a document table (platen glass) is scanned with first and second scanning lights to detect a light receiving signal from the document, and the locus of the first scanning light and the second scanning light The size and position of the document are determined by comparing position information obtained from the measurement data of the trajectory with predetermined setting information.

Japanese Patent Application Laid-Open No. 7-295116 discloses a document pressing plate for pressing a document on a document table, opening / closing state detecting means for detecting the open / close state of the document pressing plate, and a document placed on the document table. To detect a position at which the size can be determined, a driving unit that is arranged at the lower portion of the platen and rotates in parallel or substantially parallel to the platen, and a rotating unit of a unit that detects a rotation angle of the driving unit A document detecting means for detecting a document comprising a light emitting portion and a light receiving portion provided; and a light guide portion for guiding the light from the document detecting portion to the document surface so that the document detecting portion detects the document. Reflecting means for guiding light to the document detecting means, a density reference plate provided on a member supporting the document table, control means for comparing and judging an output signal from the document detecting means, and control processed by the control means Output contents Copying apparatus is disclosed having a Shimesuru display means. In this copying apparatus, the open / closed state of the document pressing plate is detected by the open / closed state detecting means, and the open / closed state of the document pressing plate is detected by the open / closed state detecting means. Since scanning can be performed, detection information without malfunction can be obtained, and erroneous detection of a document can be suppressed. In addition, while guiding the light from the document detection means to the document surface,
A document size and a document placed on a document table are configured so that the document is detected by a reflection device having an angle for guiding the reflected light from the document to the document detection device and the document detection device including a light emitting unit and a light receiving unit. The position can be accurately detected without erroneous detection, and stable copying operation can be automated. Further, in this copying apparatus, a density reference plate is provided on a member supporting the document table, and a reflection output of the density reference plate and an output signal from the document detection unit are compared by a control unit, and the density detection plate of the document detection unit is compared. Sensitivity correction and the like are performed, and this density reference plate is installed at a place other than the exposure movement.

Japanese Patent Application Laid-Open No. 9-163083 discloses that a scanning cycle is recognized on the basis of a scanning cycle signal output for each scanning, and that a signal input to a light receiving means at the beginning or the last in one scanning period is recognized. Sudden rise or fall,
There is disclosed a document edge detecting device in which the document edge defining means defines a light reception signal from the edge of the document. Further, in this document edge detecting device, in order to eliminate the influence of the stain on the original press, the original surface is scanned with a light emitting diode beam having a beam diameter larger than the pitch of the stain on the original press. The threshold value of the amount of received light for recognizing the edge is updated according to a change in the reflectance of the document. Further, the original is scanned by an inexpensive combination of a light emitting diode and a single lens, and light diffused from the light emitting diode is efficiently taken in by a focusing element for scanning. In addition, a wide-angle light receiving means for receiving the reflected light of the entire scanning area is used as the light receiving means, and this light receiving means has at least four light receiving areas arranged at positions symmetrical with respect to the center thereof. A lens for condensing light at one point and a cylindrical lens or edge are provided.

The present applicant also generates a reference signal indicating the start of scanning of scanning light, measures the position of the scanning light after the start of scanning, and measures measurement data at the time when light reflected from the original is first received. A document detection device has been proposed in which the measurement data at the time of the last light reception is used as both-end data of the document. In this document detection device, the document detection operation is repeatedly performed when the document pressing means is open, and the result is as follows. It is updated each time. Furthermore, the present applicant generates a reference signal indicating the start of scanning of the scanning light and a position at predetermined intervals of the scanning light, and determines the position of the scanning light by a pulse count value of the reference signal and a clock for interpolating between the pulses. A document detection device that measures with a signal count value has been proposed.

[0007]

A method of irradiating a beam from below the platen to the platen, and scanning the beam to detect the size and position of the platen, and in particular, to detect two beams with a platen detection sensor (Scanning light), the reflected light from the original is detected, and the original is detected from the measurement data of the scanning trajectories (scanning trajectory 1 and scanning trajectory 2) of the two beams. From the measurement data of
Since the position and size of a document crossing the beam of a book can be determined, an arbitrary document size can be detected.

FIG. 6 is a diagram showing an example of a document detection sensor of a type for detecting a document by scanning two beams. As shown in FIG. 6A, a light emitting diode (LE) is used.
Light from a light source 6 such as D) is condensed by a condensing lens 7, and the condensed beam is reflected by a reflection mirror (partial reflection mirror or half mirror) 8 and travels toward the rotating mirror 10. The rotating mirror 10 is rotated by a motor 9 to scan the beam. As shown in FIG. 6B, the rotating mirror 10 has two mirrors 10 having different angles.
a and 10b, the rotating mirror is irradiated with a beam at a different angle every half rotation.
The beams are scanned alternately. FIG. 7 is a diagram showing an example of a scanning locus by two beams. The light that is scanned by the rotating mirror 10 and reflected by the original surface, the pressure plate, and the like returns astigmatism by the cylindrical lens 12, and the spot shape on the light receiving element 11 changes depending on the distance to which the beam is applied. By distinguishing the change, it is distinguished whether the light is reflected light from the document surface or reflected light from the pressure plate.

A signal that detects only the reflected light from the document surface (referred to as an RCV signal) is a signal obtained by reflecting the reflected light from the reference plate 15 and the reflected light from the document as a series of signals for starting measurement. The position and size of the document can be detected by measuring the relative light receiving timing difference between these reflected lights. As means for measuring, the motor 9
Scans two beams by the encoder 1
4, a signal indicating the start of scanning and the position of the scanning beam after the start of scanning (this signal is referred to as an ST signal) is generated at predetermined intervals. The measurement is performed with the clock signal to be counted. The measurement result is taken into a microcontroller or the like, and the position and size are determined.

As described above, when a scanning type document detection sensor as shown in FIG.
The result of signal processing by means for generating measurement data up to the document based on the two types of RCV signals and ST signals obtained from the two scanning beams (scanning trajectories 1 and 2) is determined by a microcontroller or the like. Have gone. That is, the size is determined by comparing these measurement data with data corresponding to a predetermined document size. However, in the case of a large original such as B4 size or larger, the measured data shows a small value because the distance from the reference plate 15 to the original is short as shown in FIG. Is also reduced, which may cause an error in the size determination.

In the original detecting apparatus using the original detecting sensor shown in FIG. 6, the relative light receiving timing difference between the reflected light from the reference plate 15 for starting the measurement and the reflected light from the original is determined by two beams. Is measured and converted into data, and the data and the data for the two beams are analyzed to detect the position and size of the original. Therefore, the original must be separated from the reference plate 15 (for this reason, The reference plate 15 is provided on the side of the document table 3 opposite to the document reference). However, as shown in FIG. 7, the mounting position of the reference plate 15 is located at the boundary between the platen (contact glass) 3 and the platen frame. The boundary between the plate and the document disappears, and measurement may not be performed.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and a first object of the present invention is to prevent an erroneous detection of a document size in a document detection device using a scanning type document detection sensor as described above. Is to determine the maximum original size from the stable measurement results. A second object of the present invention is to avoid an unmeasurable state that occurs when a document is placed on the entire surface of a document table in a document detection device using a scanning type document detection sensor. A third object is to perform appropriate size determination even when a document is placed on the entire surface of a document table.

[0013]

In order to achieve the first object, the invention according to claim 1 irradiates two beams condensed from below the platen toward the platen, and further comprises: A document detection device that scans the two beams in a curved shape and detects the position and size of the document by detecting the reflected light of the irradiated beam from the document. The relative light receiving timing difference from the detection of light to the detection of reflected light from the document is measured for each of the two beams, converted into data, and the measured data for the two beams is analyzed to determine the position of the document. In the document detection device for detecting the size and size of the document, if the light receiving timing difference from the reference plate to the document is data larger than a certain document size, the data is forcibly processed as the maximum document size. Those were.

[0014] In order to achieve the second object, a second aspect is provided.
The invention according to the invention irradiates two beams converged toward the original table from below the original table, further scans the two beams in a curved shape, and reflects the reflected light of the irradiated beam from the original. A document detecting device for detecting the position and size of a document by detecting the relative light receiving timing difference between the detection of the reflected light by the reference plate for detecting the start and the detection of the reflected light by the document. In a document detection device that measures each beam, converts it into data, and analyzes each measurement data for the two beams to detect the position and size of the document, the light receiving timing difference cannot be clearly determined, When the light receiving signal from the reference plate is continued for a predetermined time or more, the measurement data is forcibly replaced with certain fixed data.

According to a third aspect of the present invention, there is provided a document detecting apparatus according to the second aspect, wherein the reference plate and the document are placed on the entire surface of the document table. Becomes a continuous light receiving signal, the light receiving timing difference disappears, and some fixed data is forcibly formed.In this case, it is determined that the original is placed on the entire surface of the platen, and the processing is performed with the maximum original size. The configuration is such that:

[0016]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a diagram showing an example of a document detection unit and a control system of an image forming apparatus (for example, a copying machine) equipped with a document detection device according to the present invention. In FIG. 1, the configuration of the sensor unit of the document detection device is the same as that of the document detection sensor 4 shown in FIG. The scanning locus of the two beams scanned by the document detection sensor 4 and the mounting position of the reference plate are the same as those in FIG.

In FIG. 1, a document detecting sensor 4 is a document table (contact glass) of a document reading section 1 of an image forming apparatus.
3 below. This document detection sensor 4
Is a light source (for example, a light emitting diode (LED)) 6 for emitting a scanning beam, a condenser lens 7 for condensing light emitted from the light source 6, and directing the collected beam to a rotating mirror 10. (Partial reflection mirror or half mirror) 8, a rotating mirror 10 as a beam scanning means, a rotating mirror driving motor 7 for rotating the rotating mirror, a rotation speed and a rotation position (angle) of the rotation mirror 10. ) To detect the beam scanning position, an encoder disk 14a and an encoder detection sensor 14b), a cylindrical lens 12 for condensing light reflected from the document 2, and a condensed reflected light. A light receiving element 13 for receiving light is provided, and these constituent members are housed in a case 5. Note that the case 5 is provided with a beam exit window covered with a protective glass 11.
6B, the rotating mirror 10 has two mirrors 10a and 10b having different angles with respect to the rotation axis.
Is attached, and the rotating mirror 10 emits a beam at a different angle every half-turn, whereby the two beams (beam 1 and beam 2) are alternately emitted toward the platen. Are scanned in a curved shape. FIG. 7 shows a platen (contact glass) 3 using the two beams.
An example of the upper scanning trajectory is shown, and the scanning of these two scanning trajectories 1 and 2 is started from a reference plate 15 provided on one end side of the document table 3.

As shown in FIG. 1, a control section 22 of the image forming apparatus controls the light emission of the light source 6 of the document detection sensor 4 and the driving of the motor 9 of the scanning means via drive circuits 20 and 21 to detect the document. An output signal of the light receiving element 13 of the sensor 4;
The output signal of the encoder detection sensor 14b of the encoder 14 is detected by the detection circuits 17 and 18 of the signal processing unit 16, and the detection signal is sent to the signal processing circuit 19 to generate measurement data. 22. Although not shown, the upper part of the platen 3
A document pressing means for pressing a document on the document table, for example, a pressure plate is provided so as to be openable and closable, and an opening / closing detection sensor 32 for detecting the open / closed state and the opening / closing angle of the pressure plate is provided at the open / close fulcrum of the pressure plate. The output signal of the open / close detection sensor 32 is input to the control unit 22, and when the opening of the pressure plate is detected by the output signal of the open / close detection sensor 32, the control unit 22 of the image forming apparatus activates the document detection sensor 4. The document size detection and determination process is executed.

The control unit 22 includes a microcontroller 23 including an arithmetic processing unit (CPU), a clock, a counter, a control circuit, and the like; a read-only memory ROM 24 storing a control program and a control data table;
A rewritable memory RAM 25 for storing the measurement data and other various input data;
6, the output interface 27, etc., and based on the measurement data input from the document detection sensor 4, the microcontroller 23 determines the size and position of the document, and the various parts of the image forming apparatus (the document reading unit 1, the image reading unit 1, A series of image forming operations (document size detection, paper selection, reading of a document image, image formation (charging, optical writing, developing), feeding) by controlling the forming unit 29, the sheet feeding unit 30, the operation / display unit 31, and the like. Paper, transfer, fixing, paper discharge, etc.). Also,
The control unit 22 includes, in addition to the measurement data from the document detection sensor 4 and the pressure plate opening / closing information from the opening / closing detection sensor 32, signals from various sensors provided in each unit of the image forming apparatus, and input from the operation unit. Information is entered.

In the configuration shown in FIG. 1, the control unit 22 activates the document detection sensor 4 to irradiate two beams focused from below the document table (contact glass) 3 toward the document table. , And further scans the beam in a curved shape, and
In this method, the size of the document 2 is detected by receiving the reflected light from the light receiving element 13 and the position and any size of the document that crosses the two beams can be detected.

More specifically, light from the LED light source 6 of the document detection sensor 4 is condensed by the condenser lens 7, travels toward the rotating mirror 10 via the reflecting mirror 8, and is deflected by the rotating mirror 10. Scanned, but the rotating mirror 1
At 0, two mirrors 10a and 10b having different angles are attached, so that the rotating mirror 10 emits a beam toward the document table 3 at a different angle every half rotation. The beams are scanned alternately. The light reflected back to the document surface, the pressure plate, or the like is reflected by the rotating mirror 10, passes through the reflecting mirror 8, and passes through the cylindrical lens 1.
2 is incident. Then, astigmatism is generated by the cylindrical lens 12, and the shape of the spot on the light receiving element 13 changes depending on the distance of the beam, and the output of the light receiving element 13 changes. Therefore, the change in the output of the light receiving element 13 is detected by the detection circuit 17 of the signal processing unit 16 and distinguished by the signal processing circuit 19 to determine whether the light is reflected light from the document surface.
It is distinguished whether the light is reflected light from the pressure plate (normally, since the document is detected when the pressure plate is opened, a signal based on the reflected light from the document surface can be easily detected). The signal (RCV signal) that detects only the reflected light from the document surface is reflected light from the reference plate 15 for measurement start and reflected light from the document as a series of signals. By measuring the light receiving timing difference, the position and size of the document can be detected. As means for measuring, when the rotating mirror 10 is rotated by the motor 9 to scan the beam, the scanning angle of the rotating mirror 10 is detected by the encoder 14 including the encoder disk 14a and the encoder detection sensor 14b, and scanning is started and Measurement can be performed by generating a signal (ST signal) indicating the position of the scanning beam after the start of scanning, and counting the ST signal using a clock signal having a constant cycle.

Here, the scanning positions of the two beams by the original detection sensor are represented as scanning trajectory 1 (beam 1) and scanning trajectory 2 (beam 2) in FIG. A reference plate 15 serving as a scanning reference for each beam is disposed at a boundary between the document table (contact glass) 3 and the document frame as shown in FIG. When specific light from the outside enters this border,
Since the received light signal may be disturbed, the point in time when the light passes through the reference plate 15 cannot be used as the start point of measurement. Therefore, before the beam continuously scanned reaches the boundary of the reference plate having a certain width, the measurement is started at ST (start of scanning).
A signal is generated, the light receiving signal (RCV signal) of the reference plate at this time is confirmed, and this time is defined as the start of measurement. That is, at the same time when the ST signal is generated from the position of the reference plate 15 for each beam, beam measurement starts. Each beam is scanned from the reference plate 15 toward the document position. As the light receiving signal of the light receiving element 13, the beam 1 and the beam 2 are output as a series of one signal. FIG. 2 is a diagram showing an example of the output timing. As shown in FIG.
The CV signal is output at the start of the ST signal generated from the position of the reference plate 15, and is output at the position of the reference plate and the position of the document surface. Therefore, depending on the position and size of the original, the RCV
The signal generation time is different, the light receiving timing difference T1, T2 between the RCV signal by the reference plate of the beam 1 and the beam 2 and the RCV signal by the original is measured by the signal processing unit 16, and the measurement data is used by the microcontroller of the control unit 22. The position and the size of the document are determined by taking the determination into the document 23.

Incidentally, the detection size of the original is determined for each copying machine, and the maximum detection size is determined. As is clear from FIGS. 7 and 2, the two beams are scanned from the reference plate 15 located on the opposite side of the document table 3 from the document reference. It can be seen that the measured data of the scanning trajectories 1 and 2 (measured values T1 and T2 from the reference plate to the document edge) become smaller. The distance from the reference plate 15 to the document edge is larger in the scanning locus 1 than in the scanning locus 2 (because the angle from the reference plate is larger in the scanning locus 1). The difference between the data of the scanning trajectory 2 becomes smaller. For this reason, an error may occur in the size determination as the document size increases. Therefore, according to the first aspect of the invention, when the light receiving timing difference from the reference plate 15 to the original is data larger than a certain original size, the processing is forcibly performed as the maximum original size.

In an embodiment of the present invention, a process is performed in which attention is paid to the size of the document immediately before the maximum size of the original, and when the data of this size becomes certain data, all the sizes are determined as the maximum size of the original. As an example, a case in which size detection is performed using only the data of scan trajectory 1 will be described.
3, the data of the scanning trajectory 1 is set to 500, the size of the immediately preceding document is set to B4, and the data of the scanning trajectory 1 is set to 1300.
Then, the processing is as shown in the flowchart of FIG. That is, the microcontroller 23 of the control unit 22
When the document detection operation is started by the
6, the measurement data of the scanning trajectory 1 and the scanning trajectory 2 are read (S1), and it is determined whether the measurement data of the scanning trajectory 1 is 1300 or less (S2). If the measurement data is larger than 1300, the scanning trajectory 1 and the scanning trajectory are determined. A normal document size determination process is performed using the measurement data of No. 2 (S3). Also,
If the measurement data of the scanning trajectory 1 is equal to or less than 1300, then the measurement data of the scanning trajectory 1 is (1)
It is determined whether the measured data is equal to or less than (300-α) (S4). If the measured data is larger than (1300-α), the size is determined to be B4 (S5). If the measured data is equal to or smaller than (1300-α), the size is determined to be A3. As a result, the maximum document size can be determined from the stable measurement result, and erroneous size detection can be prevented.

Next, when the document 2 is placed on the entire surface of the document table 3, the mounting position of the reference plate 15 is as shown in FIG.
Since the platen is arranged at the boundary between the platen (contact glass) 3 and the platen frame, there is no boundary between the reference plate 15 and the document, so that the measurement of the document end may not be possible. FIG.
Is the RCV signal and S when the document is placed on the entire surface of the platen.
4 shows an example of the output timing of the T signal. As shown in FIG. 4, when the RCV signal by the reference plate and the RCV signal by the document are continuous, the measurement data is inaccurate because the reference plate is extended for a long time and the end of the document cannot be detected. The original size cannot be measured. Therefore, according to the invention of claim 2, when the light receiving timing difference cannot be clearly determined and the light receiving signal from the reference plate continues for a predetermined time or more, the measured data is forcibly replaced with certain fixed data. Make up.

According to the second embodiment, since the size of the reference plate 15 is predetermined, the time (distance) of passing through the reference plate can be predicted, so that the ST signal is detected as shown in FIG. If the RCV signal is not interrupted for a certain time (distance) after that, the signal processing unit 16 performs a process of forcibly changing both measurement data of the two beams to certain fixed data. Note that when a fixed-size document is accurately placed on the platen, the two beams do not have the same value, so the same data is used. However, this is for the sake of simplicity of processing. is there.

As described above, when an original is placed on the entire surface of the original platen, the measurement data is replaced with certain fixed data. It is determined that the document is placed on the entire surface, and processing is performed with the maximum document size.

According to a third embodiment, the microcontroller 23 of the control unit 22 determines whether or not the respective measurement data of the scanning trajectories 1 and 2 by the two beams are the same. Is performed. FIG. 5 shows an example of the processing operation. That is, as shown in FIG. 5, when the document detection operation is started by the microcontroller 23 of the control unit 22, first, the signal processing unit 16
Then, the measurement data of the scanning trajectory 1 and the scanning trajectory 2 are read (T1), and it is determined whether the measurement data of the scanning trajectory 1 and the scanning trajectory 2 are the same (T2). If they are not the same, normal document size determination processing is performed based on the measurement data of the scanning trajectory 1 and the scanning trajectory 2 (T3). If the measurement data of the scanning trajectory 1 and the scanning trajectory 2 are not the same, the maximum document size (for example, A3 size) is determined (T4). With the above processing, it is possible to perform appropriate size determination even when a document is placed on the entire surface of the document table.

As another method for setting the above-mentioned fixed data, the microcontroller can easily determine even if it is set outside the range of the measurement data obtained during normal operation. When the original is placed on the entire surface of the table, the same effect can be obtained by setting the measurement data of the scanning trajectory 1 and the scanning trajectory 2 to certain individual data.

[0030]

As described above, in the document detecting apparatus according to the first aspect, when the light receiving timing difference from the reference plate to the document is data larger than a certain document size,
Since the maximum document size is forcibly processed, the maximum document size can be determined from stable measurement results, erroneous detection of the document size can be prevented, and miscopying can be reduced. In addition, the operability of a copying machine or the like can be improved.

In the document detecting apparatus according to the second aspect, when the light receiving timing difference cannot be clearly determined, and the light receiving signal from the reference plate continues for a predetermined time or more, the measurement data is forcibly added to the original detecting device. Since it is configured to replace with fixed data, it is possible to avoid the unmeasurable state that occurs when a document is placed on the entire surface of the document table, and it becomes a judgment material that it is not the normal size detection state, Useful for judgment processing.

According to a third aspect of the present invention, in addition to the configuration of the second aspect, when an original is placed on the entire surface of the original platen, the reference plate and the original become continuous light receiving signals,
Since there is no difference in light reception timing and some fixed data is forcibly applied, in this case, it is determined that the original is placed on the entire surface of the original platen, and the processing is performed with the maximum original size. Appropriate size determination can be performed even when a document is placed on the entire surface of the table, the maximum document size can be determined, and erroneous detection of the document size can be prevented.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an example of a document detection unit and a control system of an image forming apparatus equipped with a document detection device according to the present invention.

FIG. 2 is a diagram illustrating an example of output timing of an ST signal and an RCV signal by a document detection sensor.

FIG. 3 is a flow chart showing an example of a document size determination processing operation executed by the microcontroller of the control unit shown in FIG. 1;

FIG. 4 is a diagram illustrating an example of output timings of an ST signal and an RCV signal by a document detection sensor when a document is placed on the entire surface of a document table.

FIG. 5 is a flow chart showing an example of a document size determination processing operation executed by the microcontroller of the control unit shown in FIG. 1 according to the embodiment of claim 3;

FIG. 6 is a diagram illustrating an example of a scanning type document detection sensor.

FIG. 7 is an explanatory diagram of a beam scanning position on a document table by the scanning document detection sensor shown in FIG. 6;

[Explanation of symbols]

 1: Document reading unit 2: Document 3: Document table (contact glass) 4: Document detection sensor 5: Case 6: Light source 7: Condensing lens 8: Reflection mirror 9: Rotating mirror driving motor 10: Rotating mirror 11: Protection Glass (emission window) 12: cylindrical lens 13: light receiving element 14: encoder 14a: encoder disk 14b: encoder detection sensor 15: reference plate 16: signal processing unit 17: light receiving element output detection circuit 18: encoder output detection circuit 19: signal Processing circuit 20: Light source drive circuit 21: Motor drive circuit 22: Control unit 23: Microcontroller 24: ROM (read only memory) 25: RAM (rewritable memory)

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Claims (3)

[Claims] 1. A method according to claim 1, further comprising: irradiating two beams converged toward the original table from below the original table, scanning the two beams in a curved shape, and reflecting reflected light from the original on the irradiated beam. A document detecting device for detecting the position and size of a document by detecting the relative light receiving timing difference between the detection of the reflected light by the reference plate for detecting the start and the detection of the reflected light by the document. In a document detection device that measures each beam, converts it into data, and analyzes the measurement data for each of the two beams to detect the position and size of the document, the light receiving timing difference from the reference plate to the document is A document detection device characterized in that when data of a certain document size or larger is processed, the data is forcibly processed as the maximum document size. 2. A method of irradiating two beams condensed from below the document table toward the document table, further scanning the two beams in a curved shape, and reflecting reflected light from the document on the irradiated beam. A document detecting device for detecting the position and size of a document by detecting the relative light receiving timing difference between the detection of the reflected light by the reference plate for detecting the start and the detection of the reflected light by the document. In a document detection device that measures each beam, converts it into data, and analyzes each measurement data for the two beams to detect the position and size of the document, the light receiving timing difference cannot be clearly determined, A document detection device characterized in that, when a light receiving signal from a reference plate continues for a predetermined time or more, measurement data is forcibly replaced with certain fixed data. 3. An original detecting apparatus according to claim 2, wherein when the original is placed on the entire surface of the original plate, the reference plate and the original become a continuous light receiving signal, and the light receiving timing difference is eliminated.
In this case, since fixed data is forcibly obtained, in this case, it is determined that the document is placed on the entire surface of the document table, and the processing is performed with the maximum document size.