JP2008083689A - Discriminating device for discriminating recording material type and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a discriminating device designed so that time required for a discriminating process may be shortened while conditions for discriminating the type of a recording material are maintained. <P>SOLUTION: The discriminating device includes: a light emitting section that irradiates recording paper with light; a sensor section that has a plurality of imaging elements, receives light reflected by the recording material by means of the imaging elements, thereby picking up images on the surface of the recording material; a converting means for converting the picked up image into image data having a plurality of pixels arranged in prescribed directions; and a calculating means for integrating differences between the density values of the first and the second pixels of the plurality of pixels. The type of a recording material is discriminated on the basis of the integrated values of the density values calculated by the calculating means. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a determination apparatus and an image forming apparatus that determine the type of a recording material.

  Conventionally, electrophotographic systems such as copying machines and laser printers that can automatically determine the type of recording material and change development conditions, transfer conditions, or fixing conditions based on the determined type of recording material An image forming apparatus is known.

  As a method for automatically discriminating the type of recording material, a surface image of the recording material is picked up by a CCD sensor, the obtained surface image is converted into fractal dimension information, the surface smoothness of the recording material is obtained, and the surface smoothness is obtained. There is a method of discriminating the type of recording material based on the degree. For example, Patent Document 1 discloses the following method. First, a surface image of the recording material is picked up by a CCD sensor or a CMOS sensor. Since the surface of the recording material has irregularities due to fibers or the like, a light and shade distribution image with different amounts of light can be obtained depending on the type of the recording material. Next, the roughness of the recording material surface (surface smoothness) is obtained based on the density distribution image, and the type of the recording material is determined based on the surface smoothness.

  However, in the method of discriminating the type of recording material based on the surface smoothness of the recording material, for example, when the surface smoothness of thick paper and the surface smoothness of plain paper thinner than the thick paper are the same, The cardboard is not discriminated as cardboard and is mistakenly discriminated as plain paper. Therefore, as a method for solving this problem, a method of detecting the thickness of the recording material used for image formation and determining the type of the recording material based on the surface smoothness of the recording material and the thickness of the recording material is also proposed. Has been.

  In a recording material discrimination method based on surface smoothness in a conventional image forming apparatus, an imaging sensor measures unevenness in the amount of light by a light source. In the conventional discrimination method, as a parameter for determining the surface smoothness of the recording material, a difference value (Peak to Peak value) between the maximum value and the minimum value of the density of captured image data is used. For this reason, during measurement of the recording material, a deviation due to unevenness in the amount of light occurs in the measurement result of the surface smoothness. The deviation of the measurement result due to the unevenness of the light amount deteriorates the discrimination performance of the recording material. In the prior art, the following processing is performed in order to avoid this problem. First, at the time of recording material measurement, the recording material is photographed a plurality of times while moving the recording material. Next, the unevenness in the amount of light is obtained by averaging the photographing results. That is, shading processing is performed based on a plurality of image data captured a plurality of times to obtain unevenness in the amount of light. Then, the image data corresponding to the unevenness in the amount of light is calculated and removed from the captured image data for use in the final determination.

  Here, details of the conventional method will be described with reference to FIGS. 6, 8, and 9.

  As shown in FIG. 6, images 40, 41, and 42 are images on the surface of the recording material, and when this is digitally processed, images indicated by 43, 44, 45, for example, are obtained. When the paper fibers on the surface are rough like the recording material A, the shadows of the fibers are large, and the difference between the bright and dark portions is large, so the Peak to Peak value is large. Further, like the recording material C, the image of the surface of the recording material with sufficiently compressed fibers and high smoothness has less fiber shadow and a reduced Peak to Peak value.

  The Peak to Peak value obtained from Dmax and Dmin can be calculated for each line (see 43 in FIG. 6) of the digitally processed image data. In the case of the present embodiment, one captured image data is data of 8 pixels × 8 pixels, and data for 8 lines is obtained. Therefore, the CMOS area sensor 801 calculates Peak to Peak values for a plurality of lines, and averages or integrates these values to obtain a recording material detection result for the entire area.

  As described above, in the case of a method for calculating the Peak to Peak value in one line, if there is unevenness in the amount of light of the light source in one line, the Peak to Peak value is shifted due to the unevenness in the amount of light. There is. FIG. 8 shows an explanatory diagram thereof. FIG. 8 shows data obtained by extracting only one line from the output of the measured two-dimensional CMOS area sensor 801. When the Peak to Peak value is calculated for plain paper and glossy paper, there is a difference between the two, but due to the unevenness of the light amount of the light source, a larger slope (swell) of the data than the grayscale data of each pixel due to the actual fiber occurs. This is a measurement error.

  Therefore, in such a conventional method, a calibration process is performed in which a plurality of images are taken and each piece of image data is averaged for each pixel to measure unevenness in the amount of light in the image. Then, correction for removing the measured light amount unevenness, that is, shading correction is performed. In addition, there is a method in which a plurality of images are photographed while the recording material is conveyed instead of photographing and measurement so that the fiber roughness for each pixel is not measured. The shading correction will be described with reference to FIG. The uppermost diagram is a conceptual diagram in which only one line is extracted from the output of the measured two-dimensional CMOS area sensor 801. The light amount data includes light amount unevenness data indicated by a curve. When a plurality of such images are taken and average processing is performed for each pixel, light amount unevenness data (shading processing data) can be acquired as data having a large inclination (swell) close to the light amount unevenness. By subtracting this data from the actual photographed image, it is possible to obtain density data (sharding-corrected data) based on the fibers of the recording material from which the unevenness in the amount of light has been removed.

JP 2002-182518 A

  However, when shading processing is performed in order to remove unevenness in the light source of the sensor, the surface of the recording material is imaged multiple times by the sensor while the recording material is moved, and unevenness in the light amount is measured. Therefore, it takes a long time to shoot the recording material in order to perform the shading process. If the time for photographing the recording material is long, the time for the recording material type determination processing increases, and the start of image formation is delayed. As a result, the completion of printing of the first printed matter is delayed. The printing delay due to the recording material type determination process not only delays the completion of printing of the first printed matter, but also may reduce the speed of continuous printing. For example, when the discrimination process for detecting the type of the recording material is performed for each sheet, the speed reduction becomes significant.

  Further, in the conventional discrimination method using the difference value between the maximum value and the minimum value (Peak to Prak value) of image data captured, the recording material may not be sufficiently discriminated. For example, there are recording materials having various surface states as recording materials used by the user, and it may be difficult to determine whether the recording materials are plain paper or rough paper when the recording materials are determined by a conventional method. It was.

  Accordingly, an object of the present invention is to shorten the time required for the discrimination process while maintaining a discrimination system for the type of recording material.

  The discriminating apparatus of the present invention is a discriminating apparatus for discriminating the type of a recording material, and includes a light emitting unit that irradiates light to the recording material and a plurality of image sensors, and the light reflected by the recording material A sensor unit that receives the light and captures an image of the surface of the recording material, a conversion unit that converts the captured image into image data having a plurality of pixels arranged in a predetermined direction, and a first pixel of the plurality of pixels; And calculating means for integrating the difference between the density values of the second pixels, and determining the type of the recording material based on the integrated value of the density values calculated by the calculating means.

  An image forming apparatus of the present invention includes an image forming unit for forming an image on a recording material, a light emitting unit for irradiating the recording material with light, and a plurality of image sensors, and reflects the light reflected by the recording material. A sensor unit that receives light by the imaging device and captures an image of the surface of the recording material, a conversion unit that converts the captured image into image data having a plurality of pixels arranged in a predetermined direction, and a first of the plurality of pixels Calculating means for integrating the difference between the density values of the pixel and the second pixel, and setting an image forming condition of the image forming unit based on the integrated value of the density values calculated by the calculating means. Features.

  According to the present invention, it is possible to discriminate a recording material that is less affected by unevenness in the amount of light without performing the shading process that has been performed by the conventional method. Therefore, the time required for discriminating the recording material is shortened, and the printing performance can be improved. Further, according to the present invention, the recording material discrimination accuracy can be improved.

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

  The discrimination of the type of the recording material in the present invention is a discrimination of the type based on the surface smoothness of the recording material.

<First Embodiment>
The present invention is applicable to the general image forming apparatus shown in FIG. The image forming apparatus 101 includes a paper cassette 102, a paper feed roller 103, a transport roller 124, a top sensor 125, and a transfer belt drive roller 104. Further, the image forming apparatus 101 includes transfer rollers 110 to 113 for yellow, magenta, cyan, and black colors and cartridges 114 to 117 for yellow, magenta, cyan, and black colors. The image forming apparatus 101 also includes an optical unit 118 to 121 for each color as an image forming unit, a photosensitive drum 106 to 109 for each color, a transfer belt 105, and a fixing unit 122 including a fixing roller.

  The image forming apparatus 101 generally transfers an image of yellow, magenta, cyan, and black superimposed on a recording material using an electrophotographic process, and thermally fixes the toner image transferred by the fixing unit 122 by controlling the temperature. . The optical units 118 to 121 for each color are configured to form a latent image by exposing and scanning the surfaces of the photosensitive drums 106 to 109 with a laser beam. A series of image forming operations are synchronized so that the image is transferred from a predetermined position on the recording material to be conveyed.

  Each of the cartridges 114 to 117 includes photosensitive drums 106 to 109, charging rollers 126 to 129, developing rollers 130 to 133, and toner containers 134 to 137. Before the latent image is formed on the surface of the photosensitive drum, the electric potential on the surface of the photosensitive drum is uniformly charged by the charging roller. When charging is performed, a predetermined voltage is applied from the high voltage power supply unit 219. Thereafter, a latent image is formed by the laser beam, and the formed latent image is developed by supplying toner with a developing roller. When development is performed, a predetermined voltage is applied from the high-voltage power supply unit 219. Then, the developed toner image is transferred to the conveyed recording material. When transfer is performed, a predetermined voltage is applied to the transfer rollers 110 to 113.

  Further, the image forming apparatus 101 includes a paper feed motor (not shown) that feeds and conveys the recording material. The fed recording material is conveyed to the transfer belt 105 and the fixing roller, and a desired image is formed on the surface thereof.

  The fed recording material is conveyed by the conveyance roller 124 at a preset speed. After the top sensor 125 detects the leading edge of the recording material, the recording material conveyance operation is temporarily stopped after a predetermined time has elapsed. The image reading sensor 123 reads the surface image of the recording material while the recording material is temporarily stopped.

  The image reading sensor 123 is disposed upstream of the image forming unit formed by the transfer belt 105 and the photosensitive drum 106 of the yellow cartridge 114 in the recording material conveyance direction. The reflected light of the light irradiated on the surface of the recording material conveyed to the transfer belt 105 is condensed and imaged, and an image of a specific area on the surface of the recording material is read out.

  FIG. 4 shows the configuration of the image reading sensor 123 of FIG. The image reading sensor 123 includes a light emitting unit that irradiates light to the recording material and a sensor unit that receives light reflected from the recording material or transmitted through the recording material. The light emitting unit includes an LED 301 for reflected light as a light source and an LED 302 for transmitted light as a light source. The sensor unit that receives light includes a diffusion plate 305, a lens 303, and a CMOS sensor 211. The CMOS sensor 211 is a sensor having a plurality of image sensors. A photoelectric conversion element is used as the imaging element. The photoelectric conversion elements are arranged in a plurality of rows. The LED 301 is an LED for detecting the smoothness of the surface of the recording material, and the LED 302 is an LED for detecting the thickness of the recording material.

  When the recording material 304 is fed and reaches the position of the sensor 123, the LED 301 irradiates light on the first surface (surface on which the toner image is transferred) at a predetermined angle. The LED 302 irradiates the second surface (the back surface of the first surface) of the recording material 304 with light. The diffusion plate 305 is disposed between the LED 302 and the lens 303 and diffuses the irradiation light of the LED 302 to reduce unevenness of light emission so that the second surface of the recording material 304 is uniformly irradiated with light. The lens 303 condenses the reflected light from the first surface of the recording material 304 and the transmitted light transmitted through the diffusion plate 305 and the recording material 304 on the CMOS sensor 211.

  The image reading sensor 123 may employ a CCD sensor instead of the CMOS sensor 211. In addition, for example, a xenon tube or a halogen lamp can be employed instead of the LED 301 and the LED 302 as the light source.

  The operation of the CPU in the embodiment of the image forming apparatus of the present invention will be described with reference to FIGS. FIG. 2 is a diagram illustrating the configuration of the CPU 210 and each unit controlled by the CPU 210. In FIG. 2, a CPU 210 is connected to optical units 212 to 215 for each color including a CMOS sensor 211, a polygon mirror, a motor, and a laser via an ASIC (application specific IC) 223. The CPU 210 scans the surface of the photosensitive drum with a laser and controls the optical units 212 to 215 for each color in order to draw a desired latent image. The CPU 210 controls the paper feed motor 216, the paper feed solenoid 217, the paper presence / absence sensor 218, the high voltage power supply unit 219, the drum drive motor 220, the belt drive motor 221, the fixing unit 122, and the low voltage power supply unit 222. A paper feed motor 216 conveys a recording material. The paper feed solenoid 217 is used when driving of the paper feed roller 103 for feeding the recording material is started. The paper presence sensor 218 detects whether the recording material is set at a predetermined position. The CPU 210 controls a voltage (hereinafter referred to as a bias) output from the high voltage power supply unit 219, and controls each bias of primary charging, development, primary transfer, and secondary transfer in the electrophotographic process. The drum drive motor 220 drives the photosensitive drums 106 to 109 and the transfer rollers 110 to 113. The belt drive motor 221 drives the rollers of the transfer belt 105 and the fixing unit 122. Further, the CPU 210 monitors the temperature detected by a thermistor (not shown) and performs control to keep the fixing temperature constant.

  The CPU 210 is connected to the memory 224 via a bus or the like. The memory 224 stores a program and data for executing the above control and all or part of the processing performed by the CPU 210 in each embodiment described in the present specification. That is, the CPU 210 controls the operation of each embodiment of the present invention using the program and data stored in the memory 224.

  The ASIC 223 is a hardware circuit that performs operation control of the CMOS sensor 211, motor speed control inside the optical units 212 to 215, and speed control of the paper feed motor 216 based on an instruction from the CPU 210. The motor speed control is performed by detecting a tack signal from a motor (not shown) and outputting an acceleration signal or a deceleration signal to the motor so that the interval between the tack signals is a predetermined time. . The speed control of a plurality of motors has an advantage that the control load of the CPU 210 can be reduced by controlling with hardware such as the ASIC 223 rather than controlling with software.

  When the CPU 210 receives a print command from a host computer (not shown), the CPU 210 determines the presence / absence of a recording material using a paper presence / absence sensor 218. When there is a recording material, the CPU 210 drives the paper feeding motor 216, the drum driving motor 220, the belt driving motor 221, and the paper feeding solenoid 217 to convey the recording material to a predetermined position.

  When the recording material is conveyed to the installation position of the sensor 123 after a predetermined time has elapsed since the leading edge of the recording material was detected by the top sensor 125, the CPU 210 issues an imaging instruction to the ASIC 223. Upon receiving the instruction, the ASIC 223 uses the CMOS sensor 211 to capture the surface image of the recording material. The ASIC 223 activates Sl_select, outputs SYSCLK of a predetermined pulse at a predetermined timing, and captures imaging data output from the CMOS sensor 211 via Sl_out.

  On the other hand, when the CPU 210 sets a predetermined value in a register in the ASIC 223, the ASIC 223 activates Sl_select, outputs SYSCLK of a predetermined pulse at a predetermined timing, and sets the gain of the CMOS sensor 211 via Sl_in.

  The ASIC 223 includes a control circuit to be described later, and the calculation result of the calculation for determining the type of the recording material is stored in a register in the control circuit. Then, the CPU 210 reads the calculation result for determining the type of the recording material stored in the register inside the control circuit, determines the type of the fed recording material, and changes the image forming condition according to the result. Control to do.

  Examples of the control of various image forming conditions executed by the CPU 210 include the following. For example, in the case of so-called rough paper where the surface fibers of the recording material are rough, the voltage at the time of development by the developing roller is lowered than in the case of plain paper, and the amount of toner adhering to the surface of the recording material is suppressed to prevent toner scattering. Control. This is because the amount of toner adhering to the surface of the recording material is large especially in the case of rough paper, so that the problem that the image quality deteriorates due to the scattering of toner due to the paper fiber is solved.

  In addition, the CPU 210 determines the type of the fed recording material, and variably controls the temperature condition of the fixing unit 22 according to the result. In the case of glossy paper, the developing voltage is the same as that in the case of plain paper, but the fixing temperature in the fixing device is set higher than that in the case of plain paper. This is because the surface fibers of the glossy paper have a higher density than usual, and it is necessary to improve the fixability of the toner image.

  Further, the CPU 210 determines the type of the fed recording material, and variably controls the recording material conveyance speed, particularly the conveyance speed in the fixing device, according to the result. For example, in the case of glossy paper, the fixing speed is improved by making the speed slower than the conveying speed of plain paper. The control of the conveyance speed is performed by setting the speed control register value of the ASIC 223 for which the CPU 210 performs speed control.

  Although an example has been described with reference to the voltage during development, the fixing temperature, and the conveyance speed, these parameters such as the voltage during development, the temperature of the fixing device, the parameters of the conveyance speed, and the voltage during transfer depend on the type of recording material Can be changed as appropriate.

  As described above, in the present embodiment, the ASIC 223 performs a calculation for determining the type of the recording material from the surface image of the recording material imaged by the CMOS sensor 211 and stores the result in a register inside the ASIC 223. Next, the CPU 210 reads the calculation result stored in the register inside the ASIC 223, determines the type of the recording material, and according to the type, the voltage condition during development of the high-voltage power source, the fixing temperature of the fixing device, Control is performed to change the conveyance speed of the recording material.

  Note that the voltage condition during development, the fixing temperature of the fixing unit, the conveyance speed of the recording material, and the like may be changed according to the calculation result. In this case, the step of performing the type determination process can be omitted.

  FIG. 3 shows a configuration of the control circuit 702 in the ASIC 223 of FIG.

  The control circuit 702 includes an interface control circuit 704, an arithmetic circuit 705, a register A 706, a register B 707, and a control register 708. When the CPU 210 gives an operation instruction for the CMOS sensor 211 to the control register 708, charges are accumulated in the CMOS sensor 211. Thereafter, the interface control circuit 704 selects the CMOS sensor 211 by outputting the Sl_select signal. Further, the interface control circuit 704 outputs the system clock SYSCLK generated at a predetermined timing to the CMOS sensor 211. The CMOS sensor 211 outputs the captured digital image data to the interface control circuit 704 as an Sl_out signal in synchronization with the system clock SYSCLK.

  The control circuit 702 calculates the irregularity amount on the recording material surface and the irregularity edge amount on the recording material surface based on the digital image data, stores the irregularity amount on the recording material surface in the register A706, and registers the irregularity edge amount on the recording material surface. Store in B707.

  FIG. 5 shows a configuration of the CMOS sensor 211 of FIG.

  When the S1_select signal 813, which is a select signal, becomes active, the light received by the CMOS area sensor 801 capable of imaging a plurality of pixels is photoelectrically converted and electric charges are accumulated. In this embodiment, a CMOS area sensor having photoelectric conversion elements for 8 × 8 = 64 pixels is used. As shown in FIG. 5, the CMOS area sensor has 8 × 8 = 64 photoelectric conversion elements A (1 to 64). Next, the pixel columns read from the vertical direction shift registers 802 and 803 are sequentially selected by the timing generator 807 in synchronization with the system clock SYSCLK 806, and the read data is sequentially stored in the output buffer 804. The Data in the output buffer 804 is transferred to the A / D converter 808 by the horizontal shift register 805 and converted to digital pixel data. That is, the captured images are converted into two-dimensional digital pixel data having a plurality of pixels arranged in a predetermined direction by the vertical shift registers 802 and 803 and the horizontal shift register 805. The digital pixel data is output from the output interface circuit 809 as an Sl_out signal 810 as an output signal at a predetermined timing while the Sl_select signal 813 is active.

  In order to obtain the best image contrast, when the CPU 210 requests to change the A / D conversion gain, the control circuit 702 in the ASIC 223 activates the Sl_select signal 813. Next, the control circuit 702 outputs the system clock SYSCLK 806 to the CMOS sensor 211 at a predetermined timing. In addition, the control circuit 702 outputs an S1_in signal 812 to the CMOS sensor 211. The control circuit 811 in the CMOS sensor 211 to which the Sl_in signal 812 is input changes the A / D conversion gain of the A / D converter 808.

(Determination unit that determines the type of recording material)
When different types of recording materials A, B, and C are irradiated by the LED 301 on the first surface of the recording material and the surface image of the first surface of the recording material is captured by the CMOS sensor 211, for example, 40 in FIG. Images shown in 41 and 42 are obtained. FIG. 6 shows an enlarged image. The recording material A is so-called rough paper in which the fibers of the paper on the surface are relatively clinged. The recording material B is commonly used so-called plain paper (paper having less roughness than rough paper, that is, paper having higher smoothness than rough paper). The recording material C is glossy paper (paper having a higher normality than plain paper) in which the fiber of the paper is sufficiently compressed. The image 40 is an image of the recording material A, the image 41 is an image of the recording material B, and the image 42 is an image of the recording material C. As can be seen from these images, since the recording material mainly has different fiber states on the surface of the recording material, the captured surface image also differs depending on the type of recording material.

  Discrimination of the recording material based on the state of the fibers on the surface of the recording material by the conventional method is performed by the following process as described above. First, a surface image of a recording material is captured, and in each of the obtained images, the pixel density Dmax that is the maximum density and the pixel density Dmin that is the minimum density are detected. Next, a value of Dmax−Dmin is calculated as a Peak to Peak value for each recording material. Next, a recording material having a large Peak to Peak value is determined to be rough paper, a recording material having a small Peak to Peak value is determined to be glossy paper, and a recording material having an intermediate Peak to Peak value is determined to be plain paper. Thus, based on the pixel density of the captured image, the material (smoothness) of the recording material, that is, the type of the recording material is determined.

  In the conventional method, since shading correction has to be performed before an image for discrimination is actually taken, there is a problem that it takes time to detect and process and the printing speed is slow.

  Therefore, the present embodiment proposes a recording material discrimination method that is not affected by unevenness in the amount of light without performing shading correction and that can suppress a decrease in detection accuracy. If the method of this embodiment is used, it is possible to prevent a decrease in printing speed as a result, and a high-speed image forming apparatus can be realized.

  A specific detection method when no shading correction is performed will be described below.

  FIG. 7 is an enlarged schematic view of an example of the surface image of the recording material 304 read by the 8 × 8 pixel CMOS sensor unit 801. Based on such image data of 8 × 8 = 64 pixels, the surface smoothness of the recording material is determined by executing the processing described below.

  FIG. 10 shows data obtained by extracting the output for one line from the measured image data output from the CMOS area sensor 801. In the surface property detection data of plain paper and glossy paper, there are an overall inclination variation due to large unevenness in light amount and a fine variation in which the density (= light amount) of each pixel changes up and down. The conventional method for discriminating based on the aforementioned Peak to Peak value is greatly affected by the overall inclination due to the unevenness in the amount of light. In the present embodiment, the amount of change in the vertical fluctuation of each pixel is integrated in order to reduce the influence of unevenness in the amount of light. That is, the density value difference between the pixels (for example, the density value difference between the first pixel and the second pixel) is integrated. If this method is used, even if there is an overall inclination variation due to unevenness in the amount of light, the integrated value of the difference in density value between the pixels shows a value significantly larger than the unevenness in the amount of light. Accordingly, it is possible to relatively reduce the influence due to the unevenness of the light amount. In addition, each vertex of the broken line in FIG. 10 indicates the density value (= light quantity data value) of each pixel.

  With reference to FIG. 14, the density value difference accumulation process in this embodiment will be described. The basic control using the CMOS sensor 211 is the same as that described with reference to FIG. The captured image data read from the CMOS sensor 211 is written into the FIFO memory 704 in the arithmetic circuit 705 of the ASIC 223. Next, the difference calculation unit 707 calculates a difference between density values of adjacent pixel data in the captured image. The difference value is converted into an absolute value by the absolute value conversion unit 708 and integrated by the integration calculation unit 709. The integration result is stored in the register 706, and the CPU 210 refers to the register 706 when a predetermined image acquisition is completed. On the other hand, a predetermined discrimination threshold value for each recording material is stored in the memory 224, and the CPU 210 discriminates the recording material by comparing the discrimination threshold value with the detection result. This threshold value can be shown as a value α for determining whether the recording material is plain paper or rough paper, and a value β for determining whether the recording material is plain paper or glossy paper. , Α> β.

  FIG. 11 shows image data for one line obtained by photographing plain paper, glossy paper, and rough paper with a CMOS sensor having 64 × 64 pixels. The data is a value obtained by A / D converting an analog voltage pressure corresponding to the amount of light. Compared with the data for one line, the rough paper has the largest amount of vertical change in data, and then the plain paper has the largest amount of vertical change. Glossy paper has the smallest amount of vertical change among these three types of recording materials. The type of the recording material is determined based on the result of performing the above-described integration process in the calculation unit as a parameter indicating the amount of change in these data.

  In addition, although data of 8 × 8 pixels and 64 × 64 pixels are shown, as a CMOS sensor, if the number of pixels is increased and the area to be imaged is increased, the amount of data obtained can be increased and the accuracy can be improved. is there. The number of pixels of the CMOS sensor can be appropriately selected from the viewpoint of the amount of data to be obtained, data processing capability, and cost.

  FIG. 12 is a graph comparing the conventional discrimination method based on the Peak to Peak value from the data shown in FIG. 11 and the method based on the value obtained by integrating the difference data of this embodiment. Three types of recording materials having a peak to peak value (glossy paper, plain paper, rough paper) have small absolute values and are close to each other, making it difficult to determine the type. On the other hand, when the difference data is obtained by integration processing, the amount of change due to unevenness between pixels is integrated, so that the absolute value is large for each of the three types of recording materials, and the difference in the types of recording materials is easy to discriminate. Since this absolute value is large, the dynamic range of measurement is widened, which is very advantageous for improving accuracy.

  FIG. 13 is a graph obtained by normalizing the discrimination method based on the Peak to Peak value and the discrimination method based on the value obtained by integrating the difference data, with 1 for plain paper. From this, it can be seen that it is more advantageous for the discrimination performance to obtain the difference data by integration processing because the data ratio increases. The numerical values are shown in Table 1.

  As described above, it is understood that the discrimination method based on the value obtained by integrating the difference data is more preferable than the discrimination method based on the Peak to Peak value that is easily affected by the unevenness of the light amount of the LED. In other words, since the difference data between a plurality of pixels is integrated, the value is larger than the Peak to Peak value (difference between the maximum density value and the minimum density value), so the same amount of light intensity unevenness is included in the data. When there is a problem, there is little influence and accuracy comes out.

  In the present embodiment, the processing of the image data for one line has been described in detail. However, a value obtained by integrating the image data for a plurality of lines in the same procedure may be used, or a value coughed for each line may be used. A result obtained by averaging for a plurality of lines can also be used.

  Further, although the data for one line in the horizontal direction of the image data in the drawing is processed, the present invention is not limited to this, and one column of data in the vertical direction of the image data may be processed.

  It is possible to determine the types of plain paper, rough paper, and glossy paper, and control the image forming conditions in the electrophotographic process according to the result. As the image forming conditions, as described above, the voltage during development, the fixing temperature, and the conveyance speed can be controlled. In addition, the primary charging voltage, the primary transfer voltage, and the secondary transfer voltage are controlled. It is also possible.

(Detection by transmitted light)
For each recording material, when the light from the transmission LED 302 is diffused by the diffusion plate 305, the second surface of the recording material is irradiated, and the second surface of the recording material is imaged by the CMOS sensor 211, for example, 46 in FIG. , 47 and 48, different images are obtained. FIG. 6 shows an enlarged image.

  The image 46 is an image of the recording material D that is thin paper. An image 47 is an image of the recording material E, which is plain paper. An image 48 is an image of the recording material F which is a thick paper. As described above, depending on the type of the recording material, the fiber state on the surface of the recording material and the density or compression state of the fiber are different, so that the obtained images are different.

  The images obtained by transmitting through the recording material 304 read by the 8 × 8 pixel CMOS sensor area 801 are images obtained by digitally processing the images 46, 47, and 48, respectively. , 51 is displayed.

  Usually, the total amount or the average value of the amount of light incident on each pixel in the entire area of the CMOS sensor area 801 or in a predetermined range is set as the transmitted light amount. The basis weight of the recording material and the transmitted light have a relationship that the recording material with a larger basis weight such as thick paper has a smaller amount of transmitted light and the recording material with a smaller basis weight such as thin paper has a larger amount of transmitted light. Therefore, the thickness of the recording material can be determined based on the transmitted light amount.

Next, a method for discriminating the following seven recording materials will be described.
(1) Thin paper (basis weight: ~ 64g / m2)
(2) Plain paper (basis weight: 65 to 105 g / m2)
(3) Cardboard 1 (basis weight: 106-135 g / m2)
(4) Cardboard 2 (basis weight: 136 / m2)
(5) Glossy paper (6) Glossy film (7) OHT
First, of the seven recording materials, OHT is transparent and has a high light transmittance. Therefore, when the surface property of the recording material is detected, a result that the glossiness of OHT is very high is obtained. Therefore, OHT and the first group excluding OHT can be easily distinguished from the seven recording materials. The first group is a group composed of thin paper, plain paper, thick paper 1, thick paper 2, glossy paper, and glossy film.

  Next, the first group, the second group, the glossy paper, and the glossy film can be distinguished from each other based on the density ratio of the image by the reflected light from the recording material. The second group is a group composed of thin paper, plain paper, thick paper 1, and thick paper 2.

  Further, in the second group, the amount of transmitted light has a relationship of thin paper> plain paper> thick paper 1> thick paper 2. Therefore, based on the transmitted light amount of the recording material, from the second group, thin paper, plain paper, thick paper 1 and thick paper. 2 can be distinguished.

  Note that the recording material has a larger heat capacity than the recording material of different thickness, so the conveying speed in the fixing device of the recording material is decreased to increase the amount of heat per unit time given to the recording material, or fixing. Control to increase the temperature. Further, when this control is applied to the case of OHT, it is effective for the problem that the transparency of OHT is lowered unless the fixing property of the toner adhering to the surface of the recording material is good. For example, for a transmissive recording material such as OHT, the fixing temperature condition is changed and control is performed to raise the fixing temperature in order to increase the permeability. Alternatively, the recording material conveyance speed may be controlled to change depending on whether the type of the recording material is a transmissive type. Since this fixing condition may be a print control different from the condition of the thick recording material described above, it is preferable to have a different setting as the print mode.

  As described above, the recording material discrimination based on the detection of the recording material surface smoothness and the recording material discrimination based on the detection of transmitted light are performed, and the type of the recording material is determined using both results. As a result, it is possible to distinguish many types of recording materials such as thin paper, plain paper, thick paper 1, thick paper 2, glossy paper, glossy film, and OHT.

<Second Embodiment>
The present embodiment is different from the first embodiment in the arithmetic processing in the arithmetic circuit 705 of the ASIC 223. The object of the present embodiment is an embodiment that realizes further improvement in discrimination accuracy by adding a device for removing as much unevenness of light quantity contained in captured image data as possible. The present embodiment is different from the first embodiment only in the arithmetic processing in the portion for imaging the recording material surface. Accordingly, the description of the detection of the transmitted light amount and the outline of the operation of the other image forming apparatus will be omitted.

  FIG. 15 is a diagram for explaining the removal of the uneven light amount component included in the captured image data. FIG. 15 shows data obtained by extracting only one line from the two-dimensional output data measured by the CMOS sensor 211. In the left diagram of FIG. 15, the left side data indicates a larger light amount value than the right side data due to the uneven amount of light component in the image data. As shown in the right figure, in this embodiment, paying attention to the left-right difference of this data, the left-right inclination of the data in one line is obtained. The whole data inclination is obtained by processing such as moving average for the data in one line, and an uneven light amount component included in the data is extracted as shown in the left figure of FIG. In this embodiment, moving average calculation is performed every four pixels, and the value of [maximum value−minimum value] of the inclination component data after moving average processing in one line is used as the inclination component in one line due to unevenness in the amount of light. The extracted light intensity unevenness component value is subtracted from the integrated value of the change amount of the image data described in the first embodiment.

  With reference to FIG. 16, a change amount accumulation process according to the present embodiment will be described. The basic control using the CMOS sensor 211 is the same as that described with reference to FIG. The captured image data read from the CMOS sensor 211 is written into the FIFO memory 704 in the arithmetic circuit 705 of the ASIC. Next, the difference calculation unit 707 calculates a difference in density value between each pixel of the captured image data. The difference value is converted into an absolute value by the absolute value conversion unit 708 and integrated by the integration calculation unit 709. On the other hand, the captured image data is sent to the moving average calculation unit 710, and moving average data of each pixel in one line is generated. The calculation unit 711 calculates the amount of inclination in the one line of the output result of the moving average calculation unit 710. The difference between the calculation result of the amount of inclination in one line and the integrated value of the data fluctuation amount obtained by the integration calculation unit 709 is calculated by the light amount unevenness correction unit 712, and the final recording is performed. The result of detection for the material is stored in the register 706. In this embodiment, since the amount of inclination of this data is simple, it is realized by using [maximum value-minimum value] data. However, the change of the data may be obtained by approximation using a least square method or the like.

  The detection result in the register 706 is referred to by the CPU 210 when a predetermined image acquisition is completed. On the other hand, a predetermined discrimination threshold value for each recording material is stored in the memory 224, and the CPU 210 discriminates the recording material by comparing the discrimination threshold value with the detection result.

  Table 2 shows the detection result based only on the integration of the change amount of the difference data before and after in the first embodiment and the detection result based on the calculation method in the second embodiment. The calculation is normalized with the plain paper data described in FIG. 11 as 1.0. Compared to plain paper, the calculation result of Embodiment 2 shows a smaller value for glossy paper and a larger value for rough paper.

  By realizing the above arithmetic processing method, the influence of unevenness in the amount of light can be further reduced in the method for detecting the surface property of the recording material described in the first embodiment. Therefore, it is possible to provide a system that can detect the type of the recording material with higher accuracy. Further, since the configuration shown in the second embodiment can be easily realized by ASIC or the like, a system can be constructed at a low cost.

  Further, according to the above-described embodiment, desired print control can be performed according to the determined type of the recording material. The desired print control is, for example, when the recording material is detected as glossy paper, conditions such as the conveyance speed of the recording material and the temperature and pressure at the time of fixing so that the developer is appropriately fixed on the recording material, The development density of the developer is changed and control is performed so that optimum printing is performed on glossy paper. Also for a recording material called rough paper having a rough surface, the fixing performance of the developer can be improved by changing the temperature of the fixing device.

  Note that, without determining the type of recording material, the developing bias condition, the fixing temperature of the fixing unit, the conveyance speed of the recording material, etc. may be changed according to the calculation result. The process of performing can be omitted.

1 is a cross-sectional view showing a structure of an image forming apparatus of the present invention. It is a figure explaining the basic composition of this embodiment. 3 is a block diagram showing a configuration of a control circuit 702. FIG. FIG. 2 is a diagram illustrating an example of a configuration of an image reading sensor 123 in FIG. 1. It is a block diagram which shows the structure of the CMOS sensor 211 of FIG. FIG. 3 is a diagram illustrating a surface image of a recording material and an image read and digitized by a CMOS sensor 211 in association with each other. FIG. 6 is a schematic diagram illustrating an example of an image of a surface of a recording material 304 read by an 8 × 8 pixel CMOS sensor unit 801. It is a figure which shows the graph of the Peak to Peak value in the case of plain paper and glossy paper. It is explanatory drawing of a shading correction. It is explanatory drawing of the data change amount difference in a plain paper and glossy paper. It is a figure which shows the graph of the measurement data for 1 line in plain paper, glossy paper, and rough paper. It is a figure which shows the graph for comparing the calculation result by a conventional system, and the calculation result by this embodiment. It is a figure which shows the graph for comparing the calculation result by a conventional system, and the calculation result by this embodiment. 1 is a block diagram illustrating a configuration of a first embodiment. FIG. 6 is a diagram for explaining a second embodiment. 6 is a block diagram showing a configuration of Embodiment 2. FIG.

Explanation of symbols

210 CPU
211 CMOS sensor 224 Memory 704 FIFO memory 705 Operation circuit 706 Register 707 Difference operation unit 708 Absolute value conversion unit 709 Integration operation unit

Claims (10)

A light emitting unit for irradiating the recording material with light;
A sensor unit that has a plurality of imaging elements, receives light reflected by the recording material by the imaging element, and captures an image of the surface of the recording material;
Conversion means for converting the captured image into image data having a plurality of pixels arranged in a predetermined direction;
Computation means for integrating the difference between the density values of the first pixel and the second pixel of the plurality of pixels,
A discriminating apparatus for discriminating a type of recording material based on an integrated value of density values calculated by the calculating means. The image data is two-dimensional image data composed of a plurality of pixels arranged in a first direction and a plurality of pixels arranged in a second direction,
The determination apparatus according to claim 1, wherein the calculation unit determines the type of the recording material based on the integrated value obtained from a plurality of pixels in the first direction.   The discrimination apparatus according to claim 1, wherein the type of the recording material is discriminated by comparing the integrated value with a threshold value.   Further, a moving average process is performed using density values of a plurality of pixels of the image data to calculate a light amount unevenness component, and the type of the recording material is determined based on a result of subtracting the calculated light amount unevenness component from the integrated value. The discriminating apparatus according to claim 1.   The determination apparatus according to claim 1, wherein the first pixel and the second pixel are adjacent pixels. An image forming unit for forming an image on a recording material;
A light emitting unit for irradiating the recording material with light;
A sensor unit that has a plurality of imaging elements, receives light reflected by the recording material by the imaging element, and captures an image of the surface of the recording material;
Conversion means for converting the captured image into image data having a plurality of pixels arranged in a predetermined direction;
Computation means for integrating the difference between the density values of the first pixel and the second pixel of the plurality of pixels,
An image forming apparatus, wherein an image forming condition of the image forming unit is set based on an integrated value of density values calculated by the calculating means. The image data is two-dimensional image data composed of a plurality of pixels arranged in a first direction and a plurality of pixels arranged in a second direction,
The image forming apparatus according to claim 6, wherein the calculation unit determines the type of the recording material based on an integrated value obtained from a plurality of pixels in the first direction. A determination unit that compares the integrated value with a threshold value to determine the type of the recording material;
The image forming apparatus according to claim 6, wherein the image forming condition is set according to the type of the recording material determined by the determining unit.   Further, a moving average process is performed using density values of a plurality of pixels of the image data to calculate a light amount unevenness component, and the image forming condition is set based on a result obtained by subtracting the calculated light amount unevenness component from the integrated value. The image forming apparatus according to claim 6.   The image forming apparatus according to claim 6, wherein the first pixel and the second pixel are adjacent pixels.

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