JP2008024476A - Sheet detecting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately detect the thickness of a single sheet in a sheet detecting device usable for an image forming device for outputting printing information such as a copier, a printer, a facsimile device and a printing machine. <P>SOLUTION: This sheet detecting device 100 has a laser irradiating means 502 irradiating the loading surface of a sheet bundle with a laser beam, and an image sensor 503 detecting an image of an interference mode obtained from the loading surface of the sheet bundle to which the laser beam is irradiated by the laser irradiating means 502, and also has an image processing means 504 applying image processing for discriminating the thickness of a sheet to the image of the interference mode detected by the image sensor 503, and a CPU 501 discriminating the thickness of the sheet on the basis of an image processing result of the image processing part 504. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a sheet detection apparatus that can be used in an image forming apparatus that outputs printing information such as a copying machine, a printer, a facsimile machine, and a printing machine.

  In this type of image forming apparatus, image quality is improved by optimizing the image forming conditions according to the type of sheet, the type of paper, and the like, thereby improving the image quality. For example, depending on the type of sheet, the transfer current of the transfer device that transfers the image (toner) to the sheet, the fixing temperature of the fixing device that fixes the image to the sheet, and the image forming speed (approximately the same as the sheet conveyance speed) Was optimized.

  The optimization of the image forming conditions was initially performed by manual setting by an operator (user). However, in recent years, the type of sheet is automatically determined and is performed based on the determination result. It is coming.

  As an image forming apparatus for automatically discriminating the type of sheet, for example, after receiving an image forming instruction, the amount of transmitted light is measured for one sheet pulled out from a sheet feeding tray along a normal conveyance path by a predetermined distance. Is known (see, for example, Patent Document 1). In this image forming apparatus, a voltage corresponding to the measured transmitted light amount is compared with a predetermined threshold voltage, and the type of sheet is determined based on the comparison result.

  Further, as a means for calculating the thickness and type of the sheet on the sheet stacking apparatus, a top sheet is separated so as to create a gap in the stacked sheets, and the separated sheet is separated. There is known one that irradiates light and discriminates the thickness and type of paper based on the amount of transmitted light (see Patent Document 2).

Further, as a technique for accurately detecting the remaining amount of sheets in the sheet stacking apparatus, there is a technique for detecting the number of sheets according to the transmission state by applying high frequency or ultrasonic waves to the stacked sheets (for example, (See Patent Documents 3 and 4).
JP 7-196207 A JP 2004-315210 A JP 2003-296893 A JP 2003-246494 A

  However, in the image forming apparatus that automatically discriminates the sheet type as described in Patent Document 1, in order to discriminate the sheet type after receiving the print command, the image forming conditions corresponding to the sheet are optimized. In some cases, the image forming operation has to be interrupted and waited.

  For example, if the fixing temperature is too high for the fed sheet and you want to form an image on the fed sheet, you must pause the fed sheet and wait until it falls to the appropriate fixing temperature . It is a wasteful act to reduce the fixing temperature, which is increased by consuming time and power, over time.

  In the color image forming apparatus using the intermediate transfer belt, the distance from the first color photosensitive member to the paper transfer device for transferring the image on the intermediate transfer belt to the sheet is long, and the image formed on the photosensitive member. Takes time to arrive at the paper transfer device. For this reason, image formation is started simultaneously with the paper feed command to shorten the image formation time. When the sheet type is known after the sheet feeding command, image formation has already started, and if the image forming conditions are not optimal for the sheet fed, the image formed must be recreated and wasted.

  Further, as in the above-mentioned Patent Document 1, in a configuration in which a sheet is fed a predetermined distance along a normal conveyance path, the sheet may be caught inside when the cassette is pulled out for addition or replacement of the sheet. There is a risk of malfunction.

  Further, as in Patent Document 2, when the paper thickness is determined by the amount of transmitted light in the sheet stacking apparatus, the paper feeding operation as described in Patent Document 1 is not required. A mechanism for separating the two sheets is required. In particular, in the case of a sheet that is difficult to separate when moisture is absorbed, such as coated paper, there may be a problem that the sheet cannot be separated into one sheet. Further, even when the thickness of the sheet is detected by the amount of transmitted light, the amount of transmitted light varies depending on the material of the sheet, and there is a problem that the thickness cannot be accurately detected with a sheet such as colored or ultra-thick paper.

  In Patent Documents 3 and 4, as a means for accurately detecting the remaining amount of sheets in the sheet stacking apparatus, a technique for detecting the remaining amount of sheets according to the transmission state by applying a high-frequency voltage or ultrasonic waves is proposed. ing. This technology can be used when the number of sheets is small, but it cannot be detected or the error is large when the number of sheets exceeds 100 or the sheet material is special (such as a sheet containing metal or ultra-thick paper). There was a bug that occurred.

  An object of the present invention is to provide a sheet detection apparatus that can accurately detect the thickness of one sheet or can accurately detect the number of sheets stacked.

  In order to achieve the above object, the sheet detection apparatus according to claim 1, a laser irradiation unit that irradiates a stack surface of the sheet bundle with laser light, and a stack of the sheet bundle irradiated with laser light by the laser irradiation unit. Image sensor means for detecting an image of an interference mode obtained from a surface, image processing means for performing image processing for discriminating a thickness of a sheet on the image of the interference mode detected by the image sensor means, Central processing means for determining the thickness of the sheet based on the image processing result of the image processing means.

  The sheet detection apparatus according to claim 9, wherein a laser irradiation unit that irradiates a stack surface of a sheet bundle with laser light, and an image of an interference mode that is obtained from the stack surface of the sheet bundle irradiated with laser light by the laser irradiation unit. Image sensor means for detecting the image, image processing means for performing image processing for discriminating the thickness of the sheet on the interference mode image detected by the image sensor means, the laser irradiation means, and the image sensor means Scanning means for scanning the sheet in the sheet stacking direction, based on the image processing result of the image processing means and the scanning result of the scanning means, the thickness of the sheet and the thickness of the sheet bundle are detected, and the number of sheets stacked from both And a central processing means for detecting.

  The sheet detection apparatus of the present invention is an image for detecting a laser irradiation unit that irradiates a stack surface of a sheet bundle with laser light, and an image of an interference mode obtained from the stack surface of the sheet bundle irradiated with laser light by the laser irradiation unit. Sensor means. Also, an image processing unit that performs image processing for determining the sheet thickness on the interference mode image detected by the image sensor unit, and a center that determines the sheet thickness based on the image processing result of the image processing unit And an arithmetic means. Then, the sheet stacking surface is irradiated with laser light to detect an interference mode obtained from the sheet stacking surface. Accordingly, the interference mode of the sheet cross section corresponding to the thickness of the sheet and the portion corresponding to the gap between the sheets can be detected. Accordingly, the thickness of one sheet can be accurately detected.

  In addition, the sheet detection apparatus of the present invention detects a laser irradiation unit that irradiates a stack surface of a sheet bundle with laser light, and an image of an interference mode obtained from the stack surface of the sheet bundle irradiated with laser light by the laser irradiation unit. Image sensor means. Also, image processing means for performing image processing for discriminating the thickness of the sheet on the interference mode image detected by the image sensor means, and scanning means for scanning the laser irradiation means and the image sensor means in the sheet stacking direction. With. Further, a central processing unit is provided that detects the thickness of the sheet and the thickness of the sheet bundle based on the image processing result of the image processing unit and the scanning result of the scanning unit, and detects the number of stacked sheets from both. Accordingly, the number of sheets stacked can be accurately detected.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a diagram schematically showing a configuration of a sheet detection apparatus according to the first embodiment of the present invention. FIG. 2 is a diagram schematically showing a configuration of an image forming apparatus equipped with the sheet detection apparatus of FIG.

  First, the configuration and operation of the image forming apparatus in FIG. 2 will be described.

  In FIG. 2, an electrophotographic full-color printer as an image forming apparatus includes a printer main body 1 and an image reading device 2 mounted on the printer main body 1.

  Inside the printer main body 1, charging devices 203Y, 203M, 203C, 203BK and cleaners 204Y, 204M, 204C, 204BK are disposed around the photosensitive drums 202Y, 202M, 202C, 202BK of four colors.

  Further, around the photosensitive drum 202, laser scanning units 205Y, 205M, 205C, and 205BK, transfer blades 206Y, 206M, 206C, and 206BK, and developing units 207Y, 207M, 207C, and 207BK are disposed.

  Further, the horizontal surface above the intermediate transfer belt 208 is in contact with the four photosensitive drums 202. The intermediate transfer belt 208 is supported by rollers 210 and 211 and includes a cleaner 212.

  The printer main body 1 also includes a manual sheet lay 213 storing sheets S, pickup rollers 214 and 215, registration rollers 216, a paper feed cassette 217 storing sheets S, and pickup rollers 218 and 219. The printer main body 1 includes a vertical pass roller 220, a rotation roller 221, a secondary transfer roller 222, a fixing unit 223, a paper discharge roller 224, and a paper discharge tray 225.

  Next, the operation will be described. An electrostatic latent image is formed on each color photosensitive drum 202Y, 202M, 202C, 202BK by each laser scanning unit 205Y, 205M, 205C, 205BK using a semiconductor laser as a light source. This electrostatic latent image is developed by each developing device 207Y, 207M, 207C, 207BK.

  The toner images of the respective colors developed on the photosensitive drums 202Y, 202M, 202C, and 202BK are superimposed and transferred onto the intermediate transfer belt 208, and then the four colors are collectively applied to the sheet S by the secondary transfer roller 222. Transcribed. The sheet S is discharged onto the discharge tray 225 by the discharge roller 224 after toner is fused by the fixing unit 223.

  The sheet S is fed from the paper feed cassette 217 or the manual sheet lay 213 and conveyed to the secondary transfer roller 222 while taking registration timing by the registration roller 216. At this time, the pickup rollers 218 and 219, the vertical pass roller 220, the registration roller 216, and the pickup rollers 214 and 215 are driven by independent stepping motors in order to realize a high-speed and stable conveying operation.

  Further, the sheet detection apparatus 100 according to the present invention is disposed at a position where a laser is applied to the stacking direction surface (side surface) of the sheets S stacked on the sheet feeding cassette 217. In FIG. 2, it is arranged below the pickup roller 219 to be fed, but this is an example. Needless to say, the sheet detection apparatus 100 may be arranged at any position on the four sides of the stacked sheets.

  Next, the sheet detection apparatus 100 will be described with reference to FIG. The sheet detection apparatus 100 includes a laser light source 101, a collimator lens 102, an imaging lens 105, and an image sensor 106.

  A laser beam 103 is applied to a side surface (hereinafter referred to as a stacking surface) of a sheet bundle stacked on the sheet feeding cassette 217. The laser light 103 is generated by a laser light source 101 and a collimator lens 102 for making the laser light from the laser light source parallel light. The laser beam 103 irradiated on the stacking surface is reflected by the gap between each sheet end surface of the sheet bundle and the sheet, and interference mode reflected light 104 is generated.

  The generated interference mode reflected light 104 is incident on the image sensor 106 via the imaging lens 105. The image sensor 106 is composed of a two-dimensional image area sensor such as a CCD or a CMOS area sensor, and has a wavelength sensitivity corresponding to the wavelength of the laser beam.

  The interference mode obtained by coherent light consists of a pattern of bright and dark modes called speckles (small spots) at the time of observation or detection. The size of the individual speckles is mainly a function of several device parameters such as the wavelength of the incident light, the diameter of the laser beam (laser light), and the distance of the observer or photosensor from the reflecting surface.

When the parameters of wavelength, laser diameter, and detector distance from the surface are kept constant, the width of each speckle (or speckle length, distance between speckles, distance between tips of two speckles, or two Other suitable pattern feature dimensions, such as the distance between the trailing edges of the speckles, are as follows: That is, it can be assumed that the width of each speckle is, in effect, a statistical average for that dimension as determined by the system configuration. For the average speckle size,
Average spot size = λ · R / d (1)
It is known that

  Where λ is the wavelength, R is the distance from the reflection point, and d is the beam diameter.

  As shown in equation (1), if the laser beam to be used is more strictly limited, it is possible to generate small spots having a Gaussian average of 5 to 10 microns. That is, the distribution of small spots can be remarkably confirmed even with respect to the thickness of the sheet and the delicate gap formed between the stacked sheets.

  The image sensor 106 requires a reading pixel so that the distribution of these individual speckles can be observed. When the read pixel size of the image sensor 106 cannot be reduced, it is also possible to employ a method in which the image is read after being enlarged before and after the imaging lens 105 to obtain a resolution necessary for determining the thickness of the sheet. .

  FIG. 3 is a diagram illustrating an example of an interference mode image read by the sheet detection apparatus of FIG. 1.

  In FIG. 3, the vertical direction corresponds to the sheet stacking direction. A small spot is an image of an interference mode generated by irradiating the end of the sheet stacking surface with laser light and reflecting the coherent light. When the obtained interference mode is observed from the sheet stacking direction, it can be seen that there are a portion where the speckles are dense and a portion where the spot is rough.

  The dense portion is a small spot obtained by the reflected light from the end face of the sheet, and the reflected light is not reflected to the image sensor 106 side in the ancestor portion. It is predicted that it will be a gap. Therefore, it is possible to detect the thickness of the sheet by discriminating the portion where the small spots are dense with respect to the sheet stacking direction as T1 to T4.

  FIG. 4 is an explanatory diagram showing a portion of the interference mode image of FIG. 3 that is image-processed to determine the thickness of the sheet (part 1).

  The line graph in FIG. 4A is a graph of the cumulative number of interference modes obtained by counting the number of interference modes (= small spots) for each pixel line of the image sensor 106 based on the image data in FIG. A broken line in the line graph indicates a threshold value for binarization.

  The rectangular graph in FIG. 4B is a binarized graph of the interference mode cumulative value for each pixel line of the image sensor 106 binarized by the binarization threshold in the line graph in FIG. . The sheet thickness is obtained by binarizing T1 to T4 described in this graph. Further, since these T1 to T4 vary in the sheet thickness depending on the detection result, the finally detected sheet thickness is an average of T1 to T4, and the average value is the sheet thickness.

  FIG. 5 is a diagram schematically showing a control block configuration of the sheet detection apparatus of FIG.

  5, the control block of the sheet detection apparatus 100 includes a CPU 501, a laser irradiation unit 502, an image sensor unit (image sensor 106 in FIG. 1) 503, and an image processing unit 504.

  The CPU 501 is a central processing unit in the full-color printer of FIG. 2, and sheet detection control is based on a command from here. The CPU 501 controls the laser irradiation unit 502 to turn on / off the laser irradiation.

  The laser irradiation means 502 adjusts the current of the laser while monitoring the output obtained from a photodiode (not shown) in the laser light source 101 so that the laser is turned on and the laser beam is always irradiated with constant light. The light quantity is controlled to be constant.

  In addition, the CPU 501 gives an image reading command from the image sensor unit 503 to the image processing unit 504, and obtains information on the sheet thickness after reading.

  The image processing unit 504 controls the timing of reading an image to the image sensor unit 503. Further, as shown in FIG. 4, the image processing unit 504 performs the cumulative addition processing, the binarization processing, and the sheet thickness averaging processing of the interference mode for each pixel line of the image sensor 106 on the read image data. Do. Then, the CPU 501 is notified of sheet thickness data obtained by these processes.

  FIG. 6 is a flowchart illustrating a procedure of sheet detection processing executed by the control block of the sheet detection apparatus in FIG. 5 (part 1).

  In FIG. 6, first, laser irradiation start is executed (step S601). Next, image data of an interference mode is acquired by the image sensor unit 503 (step S602). Next, cumulative addition processing of interference modes for each image sensor pixel line is performed (step S603).

  The image processing unit 504 binarizes the data subjected to the cumulative addition processing, and detects the thickness of each sheet in the detected image area (step S604). Next, the thickness data of each sheet obtained in step S604 is averaged (step S605). Next, the CPU 501 is notified of the sheet thickness data obtained by averaging in step S606 (step S606). When the CPU 501 receives sheet thickness data from the image processing unit 504, the CPU 501 ends the sheet detection process.

  FIG. 7 is an explanatory diagram showing a part of the interference mode image of FIG. 3 that is image-processed to determine the thickness of the sheet (part 2).

  The line graph in FIG. 7A is a graph of the cumulative number of interference modes obtained by counting the number of interference modes (= small spots) for each pixel line of the image sensor 106 based on the image data in FIG.

  The rectangular graph of FIG. 7B is a binarized graph of the interference mode cumulative value for each pixel line of the image sensor binarized by the binarization threshold in the line graph of FIG. However, the subsequent sheet thickness detection processing is different from that in FIG. 4, and P1 to P4 described in this graph indicate the center of gravity position (middle point) of the section considered to be a sheet by binarizing. .

  Further, Q1 to Q3 are obtained by setting Q1 as the center-of-gravity position distance from the center-of-gravity position P1 to P2 located next to it. Since Q1 to Q3 vary in sheet thickness depending on the detection result, the finally detected sheet thickness is the average of Q1 to Q3, and the average value is the sheet thickness.

  FIG. 8 is a flowchart showing the procedure of sheet detection processing executed by the control block of the sheet detection apparatus of FIG. 5 (part 2).

  In FIG. 8, first, laser irradiation start is executed (step S801). Next, the image sensor unit 503 acquires image data of an interference mode (step S802). Next, cumulative addition processing of interference modes for each image sensor pixel line is performed (step S803).

  The image processing unit 504 binarizes the data subjected to the cumulative addition processing, and detects the thickness of each sheet in the detected image area (step S804). Next, center-of-gravity position detection for obtaining the center-of-gravity position (middle point) from the binarized pulse width is performed (step S805).

  The obtained barycentric position and the distance to the adjacent barycentric position are calculated, and the distance is averaged to detect the sheet thickness (step S806). The image processing unit 504 notifies the CPU 501 of the sheet thickness data obtained by the averaging (step S807). When the CPU 501 receives sheet thickness data from the image processing unit 504, the CPU 501 ends the sheet detection process.

  FIG. 9 is a diagram schematically illustrating a front configuration of a sheet detection apparatus according to the second embodiment of the present invention, and FIG. 10 is a perspective configuration of the sheet detection apparatus according to the second embodiment of the present invention. It is a figure which shows a part schematically.

  The sheet detection apparatus according to the second embodiment shown in FIGS. 9 and 10 has a function of detecting the total number of sheets stacked on the sheet feeding cassette 217 in addition to the sheet thickness detection function.

  In the sheet detection apparatus 100 according to the second embodiment, a roller member 300 that abuts against the sheet stacking surface is provided. This is because, in most cases, the sheet stacking surface is not neatly arranged, so that the distance between the sheet stacking section and the sheet detecting device 100 is always kept constant. The roller member 300 is supported by the support member 301.

  The roller member 300 is fixed to the sheet detection apparatus 100. That is, the sheet detection device 100 and the roller member 300 are configured to slide in the abutting direction, although not shown in the drawing, according to the unevenness of the sheet stacking surface. Further, the sheet detection device 100 and the roller member 300 are connected to a wire 303.

  As indicated by a double arrow A in FIG. 9, when the wire 303 is moved up and down by the rotation of the motor 302, the sheet detection device 100 and the roller member 300 are stacked on the sheet stacking surface via the pulleys 304 and 305. It is structured to move up and down in the direction.

  In FIG. 10, there are 300A in the front in the drawing and a roller member 300B in the back in the drawing, and the roller members 300A and 300B are supported by support members 301A and 301B, respectively.

  The supporting members 301A and 301B are fixed to the sheet detecting device 100, and the sheet detecting device 100, the roller members 300A and 300B, and the supporting members 301A and 301B are integrally slid in the direction of a double arrow A in the drawing. It has become. Further, reference numeral 400 in FIG. 10 indicates the irradiation position of the laser irradiated from the sheet detection apparatus 100.

  Next, the sheet thickness detection and the total number of stacked sheets detected by the sheet detection apparatus according to the second embodiment shown in FIGS. 9 and 10 will be described.

  First, the sheet detection apparatus 100 and the roller member 300 are positioned on the uppermost part of the sheet stacking surface. Therefore, the laser irradiation is started, and the sheet detection apparatus 100 and the roller member 300 start moving toward the lowermost part of the sheet stacking by a predetermined movement amount determined in advance by the motor 302.

  The movement amount and the readout timing of the image sensor 106 located in the sheet detection apparatus 100 are always in a synchronized relationship. When the movement amount is moved by a predetermined movement amount, the image data of the interference mode is acquired from the image sensor 106. It has a configuration.

  In this way, the sheet detection device 100 and the roller member 300 are moved to the bottom of the sheet. For example, it is determined based on a signal from a position sensor for detecting that the sheet detection apparatus 100 and the roller member 300 have reached the lowermost part. Further, the arrival may be determined from the image of the interference mode of the image sensor 106.

  Sheet thickness detection is continuously performed while the sheet detection apparatus 100 and the roller member 300 are moving. Regarding the total number of sheets stacked, the number of sheets detected by the sheet detection apparatus 100 is counted in the image processing unit 504, and the total number of sheets can be known from the count value.

  FIG. 11 is a diagram schematically showing a control block configuration of the sheet detection apparatus of FIGS. 9 and 10.

  In FIG. 11, the control block of the sheet detection apparatus 100 includes a CPU 501, a laser irradiation unit 502, an image sensor unit (image sensor 106 in FIG. 1) 503, an image processing unit 504, and a motor control unit 505.

  The motor control unit 505 controls the movement of the sheet detection apparatus 100 and the roller member 300 up and down. The image processing unit 504 has a counter processing function that counts the number of sheets.

  FIG. 12 is a flowchart illustrating a procedure of sheet detection processing executed by the control block of the sheet detection apparatus of FIG.

  In FIG. 12, first, the CPU 501 makes a start determination for detecting the sheet thickness and detecting the total accumulated number of sheets. Next, it is determined whether or not the sensor (sheet detection device 100) is positioned at the top of the stacked sheets (step S901). If the sensor is not at the top of the stacked sheet, the sensor is moved to the top of the stacked sheet (step S902). If it is determined that the sensor is positioned at the top of the stacked sheets, it is then determined whether the sensor has reached the bottom of the paper feed cassette 217 (step S903).

  Here, if it is determined in step S901 that the sensor is positioned at the bottom of the sheet cassette 217 in spite of the sensor being at the top of the stacked sheets, there is no sheet. It means that.

  If it is determined in step S903 that the sensor is not positioned at the lowermost part of the paper feed cassette 217, then the laser beam 103 is irradiated (step S904), and the sheet detection apparatus 100 and the roller member 300 are connected in advance. It is moved by a predetermined movement amount (step S905). Then, an interference mode image is obtained by the image sensor unit 503 (step S603).

  Next, cumulative addition processing of interference modes for each image sensor pixel line is executed (step S907). The following binarization process is performed using the accumulated value of the interference mode for each image sensor pixel line obtained in step S907 (step S908). Here, the sheet number counting (step S909) for counting the number of pulses generated by binarization and the sheet thickness averaging process (step S910) are performed in parallel.

  The CPU 501 is notified of the sheet thickness obtained in step S910 and the number of sheets obtained in step S909 (step S911). Then, the process returns to the determination process of step S903, and it is confirmed whether or not the sensor has reached the lowermost part of the paper feed cassette 217. If it is determined that the lowest position has been reached, the sensor is moved to the uppermost position (step S912), and the processing for detecting the sheet thickness and detecting the total number of stacked sheets is completed.

  As described above, according to the present invention, the mode of interference obtained from the sheet stacking surface is detected by irradiating the laser beam onto the sheet stacking surface (the end surface of the sheet bundle extending in the stacking direction). Accordingly, the interference mode of the sheet cross section corresponding to the thickness of the sheet and the portion corresponding to the gap between the sheets can be detected. As a result, the thickness of one sheet can be accurately detected.

  In addition, by scanning the laser light source and the image sensor in the sheet stacking direction and detecting the total thickness of the sheet stack, it is possible to accurately detect the number of sheets stacked from the determined sheet thickness and the total sheet stack thickness. it can. In addition, the sheet thickness can be detected without changing the thickness reading accuracy depending on the material and thickness of the sheet.

  With these effects, it is possible to notify the user of the image forming apparatus of the accurate sheet remaining amount, so that the downtime of the image forming apparatus can be reduced. In addition, since the sheet thickness can be accurately detected, in an electrophotographic image forming apparatus, the transfer bias is optimally corrected when the toner is transferred to the sheet according to the sheet thickness, and the sheet thickness at the fixing unit is optimal. Temperature setting is possible. Therefore, it is possible to optimize the image forming conditions and achieve high image quality.

  In this embodiment, an example adapted to an electrophotographic printer has been described. However, the sheet detection apparatus according to the present invention is not limited to an electrophotographic apparatus, and includes a paper feed cassette of an ink jet printer and other printing apparatuses. It can also be used for other paper cassettes. Furthermore, it goes without saying that it can be used not only for the paper feeding unit of the printing apparatus but also for sheet detection after printing.

1 is a diagram schematically showing a configuration of a sheet detection apparatus according to a first embodiment of the present invention. FIG. 2 is a diagram schematically showing a configuration of an image forming apparatus equipped with the sheet detection apparatus of FIG. 1. It is a figure which shows an example of the image of the interference aspect read by the sheet | seat detection apparatus of FIG. FIG. 4 is an explanatory diagram illustrating a graph of a portion subjected to image processing to determine the thickness of a sheet in the interference mode image of FIG. 3 (No. 1). It is a figure which shows schematically the control block structure of the sheet | seat detection apparatus of FIG. 6 is a flowchart illustrating a procedure of sheet detection processing executed by a control block of the sheet detection apparatus in FIG. 5 (No. 1). FIG. 4 is an explanatory diagram showing a graph of a portion subjected to image processing to determine the thickness of the sheet in the interference mode image of FIG. 3 (part 2). FIG. 6 is a flowchart illustrating a procedure of sheet detection processing executed by a control block of the sheet detection apparatus in FIG. 5 (part 2). It is a figure which shows roughly the front structure of the sheet | seat detection apparatus which concerns on the 2nd Embodiment of this invention. It is a figure which shows schematically a part of slope structure of the sheet | seat detection apparatus concerning the 2nd Embodiment of this invention. It is a figure which shows roughly the control block structure of the sheet | seat detection apparatus of FIG. 9, FIG. 12 is a flowchart illustrating a procedure of sheet detection processing executed by a control block of the sheet detection apparatus in FIG. 11.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Sheet detection apparatus 101 Laser light source 102 Collimator lens 103 Laser light 104 Interference mode reflected light 105 Imaging lens 106 Image sensor 217: Paper feed cassette 300, 300A, 300B Roller member 301, 301A, 301B Support member 302 Motor 303 Wire 304, 305 Pulley 400 Laser irradiation position 501 CPU (central processing means)
502 Laser irradiation unit 503 Image sensor unit (image sensor unit)
504 Image processing unit (image processing means)
505 Motor controller (scanning means)

Claims (9)

Laser irradiation means for irradiating the stack surface of the sheet bundle with laser light;
Image sensor means for detecting an image of an interference mode obtained from the stacking surface of the sheet bundle irradiated with laser light by the laser irradiation means;
Image processing means for performing image processing for determining the thickness of the sheet on the image of the interference mode detected by the image sensor means;
Central processing means for determining the thickness of the sheet based on the image processing result of the image processing means;
A sheet detection apparatus comprising:   The sheet detection apparatus according to claim 1, wherein the central calculation unit uses a distribution of an average amount of small spots with respect to a sheet stacking direction when determining a sheet thickness based on the image of the interference mode.   The central processing means uses the distribution of the average amount of small spots in the sheet stacking direction when determining the thickness of the sheet based on the image of the interference mode, and the center of gravity of the dense spot distribution in the sheet stacking direction. 2. The sheet detecting apparatus according to claim 1, wherein a position and a center of gravity of the rough portion are obtained, and an average value of a distance between the center of gravity of the small spot distribution and the center of gravity of the rough portion is used.   The sheet detection apparatus according to claim 1, wherein the laser irradiation unit includes a collimator lens.   2. The sheet detection apparatus according to claim 1, wherein the image sensor means includes an imaging lens.   2. The sheet detection apparatus according to claim 1, wherein the image sensor means has a wavelength sensitivity corresponding to the wavelength of the laser of the laser irradiation means.   2. A sheet detecting apparatus according to claim 1, further comprising a mechanical mechanism for always maintaining a constant position between the stacking surface of the sheet bundle and the image sensor means.   The sheet detecting apparatus according to claim 7, wherein the mechanical mechanism includes a roller member in contact with a stacking surface of the sheet bundle. Laser irradiation means for irradiating the stack surface of the sheet bundle with laser light;
Image sensor means for detecting an image of an interference mode obtained from the stacking surface of the sheet bundle irradiated with laser light by the laser irradiation means;
Image processing means for performing image processing for determining the thickness of the sheet on the image of the interference mode detected by the image sensor means;
Scanning means for scanning the laser irradiation means and the image sensor means in a sheet stacking direction;
Based on the image processing result of the image processing means and the scanning result of the scanning means, the central processing means detects the thickness of the sheet and the thickness of the sheet bundle, and detects the number of stacked sheets from both,
A sheet detection apparatus comprising:

Images