JP3583295B2 - Document detection device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
1. Field of the Invention The present invention relates to a document detecting device that is provided in a document reading unit 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.
[0002]
[Prior art]
In an image forming apparatus such as a copying machine provided with a document detecting device, the size of the document placed on the contact glass (or platen glass) of the document table is detected by the document detecting device, and the detected document size is reduced. The paper is selected from the paper supply unit and fed to the image forming unit to perform the copying process.In this case, as a technology related to the document detection device, conventionally, a document table of an image forming device such as a copying machine is used. As a means for detecting the size of the placed document, 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 surface of the document table. The document size is determined based on a combination of detection results obtained by a plurality of sensors. However, since there are various sizes of manuscripts, such as A, B, and 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 devised 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.
[0003]
For example, Japanese Unexamined Patent Application Publication No. 2-308236 discloses a document pressing means for fixing a placed document on a platen glass, a detecting means for detecting the open / close state of the document pressing means, Light scanning means for continuously irradiating a predetermined area of the document with light based on a detection signal from the means, displacement means for changing the position of the light scanning means, and detection means for detecting a drive time of the light scanning means The first scanning light from the light scanning means, and information based on the second scanning light from the light scanning means at the position after the change by the displacement means, and the driving time detected by the detection means By comparison, a document size / position detection device having a control unit for detecting the size of the document on the platen glass and the placement state of the document 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 the position information obtained from the measurement data of the trajectory with predetermined setting information.
[0004]
Japanese Patent Application Laid-Open No. 7-295116 discloses a document pressing plate for pressing a document on a document plate, an open / closed state detecting means for detecting an open / closed state of the document pressing plate, and a discrimination of a size of a document placed on the document plate. A driving unit that is disposed below the platen and rotates parallel or substantially parallel to the platen, and a rotation unit of the unit that detects a rotation angle of the driving unit so as to detect a possible position. Document detection means for detecting a document comprising a light-emitting portion and a light-receiving portion; light from the document detection means is guided to a document surface so that the document detection means performs document detection; A reflection unit that guides the document detection unit; a density reference plate provided on a member supporting the document table; a control unit that compares and determines an output signal from the document detection unit; and outputs a control content processed by the control unit. Display to display Copying apparatus is disclosed having a stage. In this copying apparatus, the open / closed state of the original pressing plate is detected by the open / closed state detecting means, and the open / closed state of the original 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. Further, the light from the document detecting means is guided to the document surface, and the document detection is performed by the reflecting means having an angle for guiding the reflected light from the document to the document detecting means, and the document detecting means including the light emitting portion and the light receiving portion. With this configuration, it is possible to accurately detect the size and position of the original placed on the original table without causing erroneous detection, and to stably automate the copying operation. Further, in this copying apparatus, a density reference plate is provided on a member supporting the document table, and the reflection output of the density reference plate and the output signal from the document detection means are compared by the control means, and the density of the document detection means is reduced. Sensitivity correction and the like are performed, and this density reference plate is installed at a place other than the exposure movement.
[0005]
Japanese Patent Application Laid-Open No. Hei 9-163803 discloses that a scan cycle is recognized based on a scan cycle signal output for each scan, and a sudden rise of a signal input to the light receiving means at the beginning or end of the one scan period. Alternatively, there is disclosed a document edge detecting device in which the falling edge is defined by a document edge defining means as a light receiving 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 diffusing from the light emitting diode is efficiently taken in by a focusing element for scanning. Further, 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.
[0006]
In addition, the applicant generates a reference signal indicating the start of scanning of the scanning light, measures the position of the scanning light after the scanning is started, and measures the measurement data at the time when the reflected light from the original is first received and the light receiving at the end. A document detection device that uses the measured data at the time of both ends of the document as data is proposed.In this document detection device, the document detection operation is performed repeatedly when the document pressing means is open, and the result is updated each time. I am trying to be.
Furthermore, the present applicant generates a reference signal indicating the scanning start 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]
[Problems to be solved by the invention]
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 document. In particular, the document detection sensor scans the document by scanning two beams (scanning light). In the method of detecting the reflected light from the scanning trajectory and detecting the original from the measurement data of the scanning trajectories (scanning trajectory 1 and scanning trajectory 2) of the two beams, the two beams are measured based on the measurement data of the scanning trajectories 1 and 2. Since the position and size of a document that crosses the document can be determined, an arbitrary document size can be detected.
[0008]
Here, FIG. 6 is a diagram showing an example of a document detection sensor of a type that performs document detection by scanning two beams, and as shown in FIG. 6A, a light source 6 composed of a light emitting diode (LED) or the like. Is condensed by a condenser lens 7, and the condensed beam is reflected by a reflection mirror (partially 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. However, as shown in FIG. 6B, the rotating mirror 10 has two mirrors 10a and 10b having different angles. The mirror is irradiated with a beam at a different angle every half rotation, and the two beams are alternately scanned. 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 due to the cylindrical lens 12, and the spot shape on the light receiving element 11 changes depending on the distance from which the beam hits. By distinguishing the change, it is determined whether the light is reflected light from the document surface or reflected light from the pressure plate.
[0009]
A signal that detects only the reflected light from the document surface (referred to as an RCV signal) is a combination of the reflected light from the reference plate 15 for starting the measurement and the reflected light from the document as a series of signals. By measuring the relative light reception timing difference, the position and size of the document can be detected. As means for measurement, when two beams are scanned by the motor 9, the encoder 14 generates a signal indicating the scanning start and the position of the scanning beam after the scanning is started at predetermined intervals (this signal is referred to as an ST signal). The measurement is performed by using a clock signal that counts a predetermined period of the ST signal with a clock having a shorter fixed period. The measurement result is taken into a microcontroller or the like, and the position and size are determined.
[0010]
As described above, when the scanning type document detection sensor as shown in FIG. 6 is used, the size of the document is determined by the two types of RCV signals obtained from the two scanning beams (scanning trajectories 1 and 2). The result of signal processing by means for generating measurement data up to the original based on the ST signal and the ST signal is determined by a microcontroller or the like. That is, these measurement data are compared with data corresponding to a predetermined document size to determine the size.
However, in the case of a large original such as a 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.
[0011]
In the document detecting apparatus using the document 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 document is determined for each of the two beams. Since the position and size of the document are detected by measuring and converting the data into data and analyzing the respective data for the two beams, the reference plate 15 and the document need to be always separated (for this reason, the reference plate 15 Is located on the opposite side of the original table 3 from the original 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.
[0012]
The present invention has been made in view of the above circumstances, and a first object of the present invention is to prevent a document size from being erroneously detected in a document detection device using a scanning type document detection sensor as described above, and to achieve stable operation. This is to determine the maximum document size from the measurement result.
A second object of the present invention is to avoid an unmeasurable state that occurs when an original is placed on the entire surface of an original platen in an original detection device using a scanning type original 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]
[Means for Solving the Problems]
In order to achieve the first object, the invention according to claim 1 irradiates two beams condensed from below the document table toward the document table, and further divides the two beams into a curved shape. A document detection device that scans and detects the position and size of a document by detecting reflected light of the irradiated beam from the document, and detects reflected light from the document based on detection of reflected light by a reference plate for starting measurement. A document detection device that measures the relative light receiving timing difference until detection for each of the two beams, converts it into data, and analyzes each measurement data for the two beams to detect the position and size of the document. When the light receiving timing difference from the reference plate to the document is data larger than a certain document size, the processing is forcibly performed as the maximum document size.
[0014]
In order to achieve the second object, the invention according to claim 2 irradiates two beams condensed from below the document table toward the document table, and further divides the two beams into a curved shape. A document detection device that scans and detects the position and size of a document by detecting reflected light of the irradiated beam from the document, and detects reflected light from the document based on detection of reflected light by a reference plate for starting measurement. A document detection device that measures the relative light receiving timing difference until detection for each of the two beams, converts it into data, and analyzes each measurement data for the two beams to detect the position and size of the document. 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 longer, the measurement data is forcibly replaced with certain fixed data. Than it is.
[0015]
In order to achieve the third object, the invention according to claim 3 is the original detection device according to claim 2, wherein when the original is placed on the entire surface of the original platen, the reference plate and the original are continuous. In this case, the light receiving signal is generated, the light receiving timing difference is eliminated, and certain fixed data is forcibly formed. 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. It was done.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described 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.
[0017]
In FIG. 1, a document detection sensor 4 is disposed below a document table (contact glass) 3 of a document reading unit 1 of the image forming apparatus. The document detection sensor 4 includes 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 a condensing beam. A mirror (partially reflecting mirror or half mirror) 8 that reflects toward the rotating mirror 10, a rotating mirror 10 as beam scanning means, a rotating mirror driving motor 7 that rotates the rotating mirror, and a rotation speed of the rotating mirror 10 Encoder 14 (encoder disk 14a and encoder detection sensor 14b) for detecting the beam scanning position by detecting the rotation position (angle), the cylindrical lens 12 for condensing the reflected light from the document 2, and the condensing light And a light receiving element 13 for receiving the reflected light. These components are housed in the case 5. The case 5 is provided with a beam exit window covered with a protective glass 11. Similarly to FIG. 6B, the rotating mirror 10 is provided with two mirrors 10a and 10b having different angles with respect to the rotation axis, and the rotating mirror 10 emits a beam at a different angle every half rotation. Thus, two beams (beam 1 and beam 2) are alternately irradiated toward the document table, and each is scanned in a curved shape. FIG. 7 shows an example of the scanning trajectory on the document table (contact glass) 3 by the two beams. The two scanning trajectories 1 and 2 are provided at one end of the document table 3. Scanning is started from the reference plate 15.
[0018]
As shown in FIG. 1, the control unit 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 unit via the driving circuits 20 and 21, and controls the document detection sensor 4. The output signal of the light receiving element 13 and the output signal of the encoder detection sensor 14b of the encoder 14 are 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. Then, the measurement data is input to the control unit 22. Although not shown, a document pressing means for pressing a document on the document table, for example, a pressure plate is provided at the upper portion of the document table 3 so as to be openable and closable. An open / close detection sensor 32 for detecting an open / close state and an open / close angle is provided. An 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 operates the document detection sensor 4 to execute document size detection and determination processing.
[0019]
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; It is composed of a rewritable memory RAM 25 for storing various input data, an input interface 26, an output interface 27, and the like. Based on the measurement data input from the document detection sensor 4, the microcontroller 23 determines the size and position of the document. At the same time, each part of the image forming apparatus (document reading unit 1, image forming unit 29, paper feeding unit 30, operation / display unit 31, etc.) is controlled to perform a series of image forming operations (document size detection, paper selection, document image Reading, image formation (charging, optical writing, development), paper feeding, transfer, fixing, paper ejection, etc.) Control to. 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, the control unit 22 also receives signals from various sensors provided in each unit of the image forming apparatus, Is input.
[0020]
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. Since the beam is scanned in a curved shape and the reflected light from the document 2 is received by the light receiving element 13 to detect the size of the document 2, the position or arbitrary size of the document that crosses the two beams is determined. Can be detected.
[0021]
More specifically, light from the LED light source 6 of the document detection sensor 4 is condensed by the condenser lens 7, advances toward the rotating mirror 10 via the reflecting mirror 8, and is deflected and scanned by the rotating mirror 10. However, since the rotating mirror 10 is provided with two mirrors 10a and 10b having different angles, the rotating mirror 10 emits a beam toward the document table 3 at a different angle every half rotation. The two beams are alternately scanned. The light reflected back on the document surface, the pressure plate, or the like is reflected by the rotating mirror 10, passes through the reflecting mirror 8, and enters the cylindrical lens 12. Then, astigmatism is generated by the cylindrical lens 12, and the spot shape on the light receiving element 13 changes depending on the distance of the beam, and the output of the light receiving element 13 changes. Accordingly, 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, so that the reflected light from the original surface or the reflected light from the pressure plate can be distinguished. (Normally, document detection is performed when the pressure plate is opened, so that a signal based on light reflected from the document surface can be easily detected.) The signal (RCV signal) that detects only the reflected light from the document surface is a relative signal between the reflected light from the reference plate 15 and the 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. 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 period.
[0022]
Here, the scanning positions of the two beams by the document detection sensor are represented as scanning trajectory 1 (beam 1) and scanning trajectory 2 (beam 2) in FIG. The reference plate 15 serving as a scanning reference for each beam is disposed at the boundary between the document table (contact glass) 3 and the document frame as shown in FIG. If specific light from the outside enters this boundary, there is a possibility that the received light signal will be disturbed, so that the time when the light passes through the reference plate 15 cannot be used as the measurement start point. Therefore, before the constantly scanned beam reaches the boundary of the reference plate having a certain width, an ST signal for starting measurement (start of scanning) is generated, and a light receiving signal (RCV signal) of the reference plate at this time is generated. Is confirmed, and this point is regarded as the start of measurement. That is, the beam measurement is started at the same time when the ST signal is generated from the position of the reference plate 15 for each beam. 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. 2, the RCV 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, the generation time of the RCV signal varies depending on the position and size of the document, and the signal processing unit 16 measures the light receiving timing differences T1 and T2 between the RCV signal of the beam 1 and the beam 2 by the reference plate and the RCV signal of the document. By taking the measurement data into the microcontroller 23 of the control unit 22 and making a determination, the position and size of the document are determined.
[0023]
Incidentally, the detection size of the document 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 measurement data of the scanning trajectories 1 and 2 (measured values T1 and T2 from the reference plate to the edge of the document) 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 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.
[0024]
In the 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 the scanning trajectory 1 will be described. The maximum document size is A3, the data of the scanning trajectory 1 is 500, the size of the immediately preceding document is B4, and the data of the scanning trajectory 1 is 1300. Then, processing as shown in the flowchart of FIG. 3 is performed. That is, when the document detection operation is started by the microcontroller 23 of the control unit 22, first, the measurement data of the scanning trajectory 1 and the scanning trajectory 2 is read from the signal processing unit 16 (S1), and the measurement data of the scanning trajectory 1 is 1300. If the measured data is larger than 1300, a normal document size determination process is performed based on the measured data of the scanning trajectory 1 and the scanning trajectory 2 (S3). If the measurement data of the scanning trajectory 1 is equal to or less than 1300, it is determined whether the measurement data of the scanning trajectory 1 is equal to or less than (1300-α) by setting α as a fixed value (S4). If it is larger than (1300-α), it is determined to be B4 size (S5), and if it is smaller than (1300-α), it is determined to be A3 size. As a result, the maximum original size can be determined from the stable measurement result, and erroneous size detection can be prevented.
[0025]
Next, when the original 2 is placed on the entire surface of the original platen 3, the reference plate 15 is attached at the boundary between the original platen (contact glass) 3 and the original platen frame as shown in FIG. In some cases, the boundary between the reference plate 15 and the document disappears, and the measurement of the document edge cannot be performed. FIG. 4 shows an example of the output timing of the RCV signal and the ST signal when a document is placed on the entire surface of the document table. As shown in FIG. 4, when the RCV signal from the reference plate and the RCV signal from 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, in 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 measurement data is forcibly replaced with certain fixed data. Make up.
[0026]
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. If the RCV signal is not interrupted for a certain period of time (distance), the signal processing unit 16 performs a process of forcibly changing both measurement data of the two beams to a certain fixed data. Note that when a standard size document is accurately placed on the platen, the two beams of measurement data do not have the same value. Therefore, the same data is used. is there.
[0027]
As described above, when a document is placed on the entire surface of the platen, the measurement data is replaced with certain fixed data. Is determined, and processing is performed with the maximum original size.
[0028]
As an embodiment of the third aspect, the microcontroller 23 of the control unit 22 determines whether each measurement data of the scanning trajectories 1 and 2 by two beams is the same, and if the same fixed data, determines that the document is the maximum original. Perform processing. 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 measurement data of the scanning trajectory 1 and the scanning trajectory 2 is read from the signal processing unit 16 (T1). It is determined whether the measurement data of the scanning trajectory 2 is the same as the measurement data of the scanning trajectory 2 (T2). If they are not the same, a normal document size determination process 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.
[0029]
As another method for setting the above fixed data, the microcontroller can easily determine by setting the fixed data outside the range of the measurement data obtained during normal operation. In the case where the original is placed, the same effect can be obtained by setting the measurement data of the scanning trajectory 1 and the scanning trajectory 2 to individual certain data.
[0030]
【The invention's effect】
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, the process is forcibly performed as the maximum document size. With this configuration, the maximum original size can be determined from the stable measurement results, erroneous detection of the original size can be prevented, erroneous copying can be reduced, and the operability of copying machines and the like can be improved. I can do it.
[0031]
In the document detecting apparatus according to 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 measurement data is forcibly changed to a certain fixed data. Since it is configured to replace with the original, it is possible to avoid the unmeasurable state that occurs when an original is placed on the entire surface of the original platen, and it becomes a source of judgment that it is not the normal size detection state, and it can be used for judgment processing by a microcontroller etc. Useful.
[0032]
In the document detection device according to the third aspect, in addition to the configuration of the second aspect, when the document is placed on the entire surface of the document table, the reference plate and the document become a continuous light receiving signal, there is no difference in light receiving timing, Since fixed data is forcibly obtained, 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. In this case, an appropriate size determination can be performed, 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 timing 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.
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: Reflecting mirror 9: Rotating mirror driving motor 10: Rotating mirror 11: Protective 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)

Claims (3)

By irradiating two beams condensed toward the platen from below the platen, further scanning the two beams in a curve, and detecting reflected light of the irradiated beam from the document, A document detection device that detects the position and size of a document, and measures the relative light reception timing difference from the detection of reflected light by the reference plate to the start of measurement to the detection of reflected light by the document for each of the two beams. In a document detection device that detects the position and size of a document by analyzing the measured data for the two beams,
A document detection device, wherein when 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. By irradiating two beams condensed toward the platen from below the platen, further scanning the two beams in a curve, and detecting reflected light of the irradiated beam from the document, A document detection device that detects the position and size of a document, and measures the relative light reception timing difference from the detection of reflected light by the reference plate to the start of measurement to the detection of reflected light by the document for each of the two beams. In a document detection device that detects the position and size of a document by analyzing the measured data for the two beams,
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 replaced with certain fixed data. Document detection device. In the document detecting device according to claim 2, when the document is placed on the entire surface of the document table, the reference plate and the document become a continuous light receiving signal, the light receiving timing difference is eliminated, and the fixed data is forcibly obtained. In this case, the original detecting apparatus is characterized in that 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.

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