JP6680110B2 - Image reading apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to an image reading device and an image forming device.

  In the image reading apparatus, shading data obtained by reading the density reference member is used in order to correct the variation in the light amount of the light source in the main scanning direction of the reading optical system and the variation in the sensitivity of each pixel of the sensor chip. In the case of generating this shading data, in order to reduce the influence of dirt on the density reference member, conventionally, a movable mechanism for changing the relative positions of the image sensor and the density reference member has been provided.

  However, a reading module such as a contact image sensor (CIS) for reading a document is often provided in a small space in an ADF (Auto Document Feeder) device, and when it is movably changed to the ADF, This leads to increased complexity, larger size, and higher cost.

  Therefore, as a technique for reducing the influence of stains on the concentration reference member even if no movable mechanism is provided, for example, in Japanese Patent Application Laid-Open No. 2004-242, there is an initial method of acquiring a non-volatile memory with a clean concentration reference member at the time of product manufacturing. When shading data is stored and the original reading shading data that was acquired immediately before reading the original is attached to the original shading data without dirt, the lens pitch unevenness of the initial data can be adjusted to the lens of the current data. A shading correction device that corrects so as to match the phase of pitch unevenness is disclosed.

  Further, if the initial shading data acquired at the time of manufacturing the product is affected by the foreign matter, it may not be possible to correct the shading data normally. Therefore, in Patent Document 2, the reflected light from the white reference member is read. Data is received by the device, and the data of the pixel row output from the reading device is acquired as white reference data, and based on the white reference data, each pixel of the pixel row is the target pixel, and the target pixel, If the absolute value of the difference in pixel value from the contrast pixel corresponding to the light receiving element that is away from the target pixel by an integer multiple of the lens array interval exceeds a threshold value, an abnormality determination process for determining an abnormal pixel is executed. An image reading device is disclosed.

  However, in the conventional method of determining an abnormal pixel by using a pixel corresponding to a light receiving element close to a position distant from the pixel of interest by an integral multiple of the array interval of the rod lens as a comparison pixel, the rod lens array interval is a complete integer pixel interval. Since they do not match, there is a problem that highly accurate foreign matter detection cannot be performed.

  The present invention has been made in view of the above, and even if the arrangement interval of the plurality of lenses that image light on the photoelectric conversion element is not an integral multiple of the arrangement interval of the plurality of pixels in the photoelectric conversion element. An object of the present invention is to provide an image reading apparatus and an image forming apparatus that can detect foreign matters on the density reference member and glass with high accuracy.

In order to solve the above-mentioned problems and to achieve the object, the present invention has a plurality of irradiation units that are arranged to irradiate light that extends in one direction, and reflected or transmitted light of the light that the irradiation unit irradiates. photoelectrically converted for each pixel, a plurality of pixels and photoelectric conversion element which outputs the respective pixel values, wherein the irradiation unit is arranged in the same diameter you imaging the reflected or transmitted light into the photoelectric conversion element of light to be irradiated And a plurality of pixel values output by the photoelectric conversion element when each of the lenses forms an image of the reflected light of the light irradiated on the density reference member by the irradiation unit on the photoelectric conversion element. A comparison pixel generation unit that generates a pixel value at a position separated from the target pixel by the arrangement interval of the lenses as a pixel value of a comparison pixel; Imaged on the photoelectric conversion element When the pixel value of the pixel of interest output by the photoelectric conversion element and the pixel value of the comparison pixel generated by the comparison pixel generation unit, and a comparison result and a predetermined threshold value by the comparison unit based on, it has a, a foreign matter determination unit that determines whether the pixel value of the pixel of interest the comparison unit is compared is the pixel value affected by foreign matter, the comparative pixel generation unit, the irradiation unit By performing the interpolation using the plurality of pixel values around the pixel of interest output by the photoelectric conversion element when the reflected light of the light applied to the density reference member is imaged on the photoelectric conversion element by each of the lenses. , Generate the pixel value of the comparison pixel .

  ADVANTAGE OF THE INVENTION According to this invention, even if the arrangement | sequence spacing of the several lens which images light on a photoelectric conversion element is not the integral multiple of the arrangement | sequence spacing of the several pixel in a photoelectric conversion element, a density | concentration reference member and glass are highly accurate. It is possible to detect the foreign matter.

FIG. 1 is a cross-sectional view illustrating the configuration of the image reading apparatus according to the embodiment. FIG. 2 is a block diagram showing an outline of a controller that controls the image reading apparatus and its peripherals. FIG. 3 is a block diagram illustrating a main part of an electric circuit of the second reading unit. FIG. 4 is a flowchart showing an outline of the operation of the ADF for generating shading data. FIG. 5 is a diagram showing the relationship between the configuration of the second reading unit and its surroundings and the output level of the second reading unit. FIG. 6 is a block diagram showing an outline of the function of the ADF for detecting a foreign substance. FIG. 7 is a flowchart showing a processing example in which the ADF determines the presence / absence of a foreign matter in shading data. FIG. 8 is a diagram showing the positions of the four closest pixels at a position away from the target pixel position by D + d which is the arrangement interval of the rod lenses. FIG. 9 is a diagram showing the correction coefficient. FIG. 10 is a diagram schematically showing output levels of a plurality of sensors arranged in the main scanning direction. FIG. 11 is a block diagram showing a first modification of the function of the ADF for detecting foreign matter. FIG. 12 is a block diagram showing a second modified example of the function of the ADF for detecting foreign matter. FIG. 13 is a diagram showing positions where pixel values are generated in the second modification of the foreign matter determination function. FIG. 14 is a flowchart showing a process for determining the presence / absence of a foreign substance in the second modified example of the foreign substance determination function. FIG. 15 is a flowchart showing the processing performed by the comparison pixel generation unit. FIG. 16 is a block diagram showing a third modified example of the function of the ADF for detecting foreign matter. FIG. 17 is a diagram showing positions where pixel values are generated in the third modification of the foreign matter determination function. FIG. 18 is a diagram showing the axis of the sensor and the central axis of the rod lens array. FIG. 19 is a diagram showing a state in which the shading data is divided in the main scanning direction. FIG. 20 is a flowchart showing a processing example in which the ADF determines the presence / absence of a foreign matter in shading data. FIG. 21 is a diagram illustrating output levels of a plurality of sensors. FIG. 22 is a diagram showing a range in which the pixel of interest is located. FIG. 23 is a diagram showing the positions of the target pixel and the comparison pixel. FIG. 24 is a diagram showing the positions of the target pixel and the comparison pixel. FIG. 25 is a diagram illustrating a case where the pixel value at the sensor end is lower than the other pixel values. FIG. 26 is a diagram showing a threshold change range. FIG. 27 is a diagram illustrating the threshold value. FIG. 28 is a flowchart showing another operation example of the ADF. FIG. 29 is a diagram showing the configuration of an image forming apparatus having an ADF.

  Embodiments of an image reading apparatus will be described in detail below with reference to the accompanying drawings. FIG. 1 is a cross-sectional view illustrating the configuration of the image reading device 10 according to the embodiment. The image reading apparatus 10 according to the embodiment is, for example, an automatic document feeder (ADF: Auto Document Feeder) provided on the upper part of the image forming apparatus 300 (see FIG. 29) and having a function of reading an image. Further, FIG. 2 is a block diagram showing an outline of the controller 11 that controls the image reading apparatus 10 and its periphery. Hereinafter, the image reading device 10 will be described as ADF 10.

  The ADF 10 conveys a document to be read to a fixed reading device unit, and performs image reading while conveying the document at a predetermined speed. The controller 11 includes, for example, a CPU and a memory, and controls each unit included in the ADF 10.

  The ADF 10 includes a document setting section A, a separation / feeding section B, a registration section C, a turn section D, a first reading / conveying section E, a second reading / conveying section F, a sheet discharging section G, and a stack section H. The document setting unit A sets a read document bundle. The separating / feeding unit B separates and feeds the originals one by one from the set bundle of originals. The registration section C has a function of performing primary abutting alignment of the fed original document and a function of pulling out and transporting the aligned original document. The turn section D turns the conveyed document and conveys the document surface toward the reading side (downward). The first reading / conveying unit E causes the front surface image of the document to be read from below the contact glass. The second reading / conveying unit F reads the back side image of the document after reading. The paper discharge unit G discharges the document whose front and back sides have been read out of the machine. The stack unit H stacks and holds the documents after the reading is completed.

  The document stack 130 to be read is set on the document table 132 including the movable document table 131 with the document surface facing upward. Further, the width direction of the document stack 130 is positioned by a side guide in a direction orthogonal to the conveying direction. The setting of the document is detected by the set filler 133 and the document setting sensor 100, and is transmitted to the main body control unit 122 by the I / F 114.

  Further, a document length detection sensor 134 or 135 (a reflection type sensor or an actuator type sensor capable of detecting even one document) provided on the surface of the document table 132 is used to roughly determine the length of the document in the conveyance direction. To be done.

  The movable original table 131 is configured to be movable up and down in the directions a and b shown in the figure by the bottom plate lifting motor 112, and when it is detected by the set filler 133 and the document setting sensor 100 that the bottom plate lifting motor 112 is set. 112 is rotated in the normal direction and the movable document table 131 is raised so that the uppermost surface of the document stack 130 comes into contact with the pickup roller 148. The pickup roller 148 is operated by a cam mechanism in the c and d directions shown in the figure by the pickup motor 108, and the movable original table 131 is raised and pushed by the upper surface of the original on the movable original table 131 to be raised in the c direction and proper feeding is performed. The position sensor 102 can detect the upper limit.

  When the print key is pressed by the operation unit 121 and a document feed signal is transmitted from the main body control unit 122 to the controller 11 via the I / F 114, the pickup roller 148 drives the roller to rotate by the forward rotation of the feed motor 109. Then, several original documents (ideally one original document) on the original document table 132 are picked up. The rotation direction is the direction in which the uppermost document is conveyed to the paper feed port. The operation unit 121 has a function as a setting unit that performs each setting for the ADF 10 according to an input by the user, and a function as a display unit (output unit) that performs a display for the user.

  The paper feed belt 136 is driven in the paper feed direction by the normal rotation of the paper feed motor 109, and the reverse roller 137 is rotationally driven in the direction opposite to the paper feed by the normal rotation of the paper feed motor 109, and the uppermost document and the lower part thereof are driven. The originals are separated and only the uppermost original can be fed. More specifically, the reverse roller 137 contacts the paper feed belt 136 at a predetermined pressure, and when the reverse roller 137 is in direct contact with the paper feed belt 136 or is in contact with one original, the paper feed belt 136 is rotated. Is rotated counterclockwise, and when two or more originals enter between the paper feed belt 136 and the reverse roller 137, the follow-up force is set to be lower than the torque of the torque limiter. 137 rotates in the clockwise direction, which is the original driving direction, works to push back an extra document, and prevents double feeding.

  The original separated into one sheet by the action of the paper feed belt 136 and the reverse roller 137 is further fed by the paper feed belt 136, the leading edge of which is detected by the abutment sensor 105 and further abuts the pull-out roller 138 which is stopped. . After that, the paper is fed by a predetermined distance from the detection of the abutment sensor 105, and as a result, the paper feed motor 109 is stopped in a state where the pull-out roller 138 is pressed with a predetermined amount of flexure to feed the paper. The driving of the belt 136 is stopped. At this time, by rotating the pickup motor 108, the pickup roller 148 is retracted from the upper surface of the original document and the original document is sent only by the conveying force of the paper feed belt 136, so that the front end of the original document enters the nip of the pair of upper and lower rollers of the pullout roller 138. Then, the tip alignment (skew correction) is performed.

  The pull-out roller 138 has a skew correction function and is a roller for conveying the skew-corrected original document to the intermediate roller 139 after separation, and is driven by the reverse rotation of the paper feed motor 109. Further, at this time (when the paper feeding motor 109 rotates in the reverse direction), the pull-out roller 138 and the intermediate roller 139 are driven, but the pickup roller 148 and the paper feeding belt 136 are not driven.

  A plurality of document width sensors 104 are arranged in the depth direction and detect the size of the document conveyed by the pull-out roller 138 in the width direction orthogonal to the conveyance direction. Further, the length of the document in the conveying direction is detected by a motor pulse by reading the front end and the rear end of the document with the abutment sensor 105.

  When a document is conveyed from the registration section C to the turn section D by driving the pull-out roller 138 and the intermediate roller 139, the conveyance speed in the registration section C is set to be higher than the conveyance speed in the first reading conveyance section E. The processing time for sending the original to the reading unit is shortened. When the leading edge of the original is detected by the reading entrance sensor 103, deceleration is started at the same time as the leading edge of the original enters the nip of the pair of upper and lower rollers of the reading entrance roller 140 so that the original feeding speed becomes the same as the reading feeding speed. The reading motor 110 is driven in the normal direction to drive the reading entrance roller 140, the reading exit roller 141, and the CIS exit roller 142. When the leading edge of the document is detected by the registration sensor 107, the registration sensor 107 decelerates over a predetermined transport distance, pauses before the reading position 143, and transmits a registration stop signal to the main body control unit 122 via the I / F 114. .

  Subsequently, when the reading start signal is received from the main body control unit 122, the original whose registration is stopped is accelerated and conveyed so as to rise to a predetermined conveying speed before the leading edge of the original reaches the reading position. At the timing when the leading edge of the document detected by the pulse count of the reading motor 110 reaches the reading unit, a gate signal indicating an effective image area of the first surface in the sub-scanning direction is sent to the main body control unit 122 by the first reading unit. It is sent until the trailing edge of the original is removed.

  In the case of single-sided original reading, the original that has passed through the first reading / conveying section E is conveyed to the sheet discharging section G via the second reading section 113. At this time, when the leading edge of the document is detected by the paper ejection sensor 106, the paper ejection motor 111 is driven in the normal direction to rotate the paper ejection roller 144 counterclockwise. Further, the discharge motor pulse count is detected from the detection of the leading edge of the document by the discharge sensor 106, and the discharge motor drive speed is reduced immediately before the trailing edge of the document comes out of the nip of the pair of upper and lower rollers of the discharge roller 144 to discharge the sheet. The documents discharged onto the tray 145 are controlled so as not to jump out.

  In the case of double-sided document reading, the controller controls the second reading unit 113 at the timing when the leading end of the document reaches the second reading unit 113 by the pulse count of the reading motor 110 after the document discharge sensor 106 detects the leading end of the document. A gate signal indicating the effective image area in the sub-scanning direction is transmitted from 11 through the second reading unit 113 until the trailing edge of the document passes. The density reference member 146 facing the second reading unit 113 suppresses the floating of the document in the second reading unit 113, and at the same time, is a fixed plate-shaped reference white portion for acquiring the shading data in the second reading unit 113. Is.

  FIG. 3 is a block diagram illustrating a main part of an electric circuit of the second reading unit 113. As shown in FIG. 3, the second reading unit 113 has a light source unit 500 including an LED, a fluorescent lamp, a cold cathode tube, or the like. The light source unit 500 corresponds to the light source unit 40 and the light guide body 41 shown in FIG. 5, and constitutes an irradiation unit that emits light in the main scanning direction together with the light guide body and the like. In addition, each unit forming the second reading unit 113 illustrated in FIG. 3 operates under the control of the controller 11.

  The second reading unit 113 includes a plurality of sensors (sensor chips: photoelectric conversion elements) 43 arranged in the main scanning direction (direction corresponding to the document width direction), and a plurality of amplifier circuits individually connected to each sensor 43. 502, and also has a plurality of A / D conversion units 503 individually connected to the respective amplifier circuits 502. The output signal of the A / D converter 503 has a black level offset in addition to the signal component. The second reading unit 113 has a black correction unit 504 that removes the black level offset. The white correction unit 505 performs white correction on the output signal of the black correction unit 504 to remove the influence on the image data due to the unevenness of the light source unit 500 and the uneven sensitivity of the sensor 43. Further, the white correction unit 505 reads the density reference member 146, and obtains the degree of light amount reduction (correction coefficient) based on the comparison between the read result of the density reference member 146 and the read result of the past density reference member 146, A function of further correcting the correction result based on the shading correction data may be installed. The second reading unit 113 also includes an image processing unit 506, a frame memory 507, an output control circuit 508, an I / F circuit 509, and the like.

  The sensor 43 includes, for example, a photoelectric conversion element called a 1: 1 contact image sensor (CIS) and a condenser lens (rod lens). A lighting ON signal is sent from the controller 11 to the light source unit 500 before the document enters the reading position by the second reading unit 113. As a result, the light source unit 500 is turned on and the light is emitted toward the document.

  The reflected light reflected by the document is condensed on the photoelectric conversion element by the condenser lenses in the plurality of sensors 43 and read as image information. The image information read by each sensor 43 is amplified by the amplifier circuit 502 and then converted into digital image information (pixel value of each of a plurality of pixels) by the A / D conversion unit 503. When the digital image information is represented by 8 bits, for example, the black pixel value becomes 0 and the white pixel value becomes 255.

  The offset components of these digital image information are removed by the black correction unit 504 (black correction), corrected by the white correction unit 505, input to the image processing unit 506 and subjected to line-to-line correction, and then the frame memory 507. Is temporarily stored in.

  Thereafter, the digital image information is converted by the output control circuit 508 into a data format that can be received by the main body control unit 122, and then output to the main body control unit 122 via the I / F circuit 509. It should be noted that from the controller 11, a timing signal for notifying the timing at which the leading edge of the document reaches the reading position by the second reading unit 113 (image data after that timing is treated as valid data), a light source lighting signal, a power source, etc. Is output.

  FIG. 4 is a flowchart showing an outline of the operation of the ADF 10 for generating shading data. In order to remove the offset component of the sensor 43, the ADF 10 turns off the light source unit 500 and acquires the data read by the sensor 43 as black level data for each pixel (S100). Next, the ADF 10 turns on the light source unit 500 (S102), the sensor 43 reads the density reference member 146 (S104), subtracts black level data from the read data (performs black correction), and shading data. Is generated (S106).

  Next, the shading data generated by the ADF 10 will be described in detail. FIG. 5 is a diagram showing the relationship between the configuration of the second reading unit 113 and its surroundings and the output level of the second reading unit 113. The second reading unit 113 is a reading module which is, for example, a contact image sensor (CIS) using a rod lens array extending in one direction.

  In the second reading section 113, a light source section 40 such as an LED is provided at an end (both ends) of a light guide body 41 extending in the main scanning direction. The light guide body 41, the rod lens array 42, and the sensor 43 are arranged substantially parallel to each other. The light source section 40 and the light guide body 41 are irradiation sections (light source section 500: FIG. 3) that extend in one direction and emit light. The rod lens array 42 has a plurality of rod lenses 420 arranged in the main scanning direction and having substantially the same diameter. Note that “substantially the same” means that the difference is less than or equal to a predetermined threshold. A plurality of pixels 430 are arranged on the sensor 43 in the main scanning direction. The rod lens array 42 forms an image of the light emitted by the irradiating section on the original or the reflected light (or transmitted light) from the density reference member 146 on the sensor 43. Each sensor 430 converts the amount of light imaged by the rod lens array 42 into an electric signal of a plurality of pixels 430 arranged in the main scanning direction.

  The rod lens 420 easily collects light near the center and has a high output level, but the output level decreases at the ends. Therefore, in the rod lens array 42, a high output level and a low output level are periodically generated according to the arrangement interval of the rod lenses 420. Further, when the arrangement interval of the rod lenses 420 is, for example, 0.3 mm, when converted into a pixel resolution of 600 dpi, the number of pixels per arrangement interval of the rod lenses 420 is 7.09 pixels, which is not necessarily an integer pixel. That is, the difference between the pixel value of a certain pixel of interest and the pixel value of the comparison pixel close to the position spaced by the array distance of the rod lens 420 from the pixel of interest is calculated, and it is determined whether the difference exceeds a predetermined threshold value. Even if the determination is made, it is not possible to accurately detect whether or not a foreign substance is attached to the density reference member 146.

  Therefore, the ADF 10 performs the following processing to determine whether or not a foreign substance or the like is attached to the density reference member 146, and generates shading data in which the influence of the foreign substance or the like is reduced to improve the image reading accuracy. Is improving. First, a processing example in which the ADF 10 detects a foreign substance (determines the presence or absence) will be described with reference to FIGS. 6 to 9.

  FIG. 6 is a block diagram showing an outline of a function (foreign matter determination function) that the ADF 10 has for detecting a foreign matter (determining presence / absence). FIG. 7 is a flowchart showing a processing example in which the ADF 10 determines the presence / absence of a foreign matter in shading data. As shown in FIG. 6, the ADF 10 includes a first storage unit 60, a second storage unit 61, a comparison pixel generation unit 62, a comparison unit 63, and a foreign matter determination unit 64. The comparison pixel generation unit 62, the comparison unit 63, and the foreign matter determination unit 64 are partially or wholly configured by a program executed by a CPU included in the controller 11 or hardware. The 1st memory | storage part 60 and the 2nd memory | storage part 61 are comprised by the memory with which the controller 11 is equipped, for example.

  First, the controller 11 stores the shading data in the first storage unit 60, which is a volatile memory, and initializes the pointer P of the pixel position of the pixel of interest (S200). As described above, when the arrangement interval of the rod lenses 420 is converted into the number of pixels in the predetermined resolution, it does not become an integer. Therefore, here, the integer part of the number of pixels (pixel width) is defined as D, and the decimal part is defined as d. (S202).

  For example, when the array interval of the rod lenses 420 is 0.3 mm, the array interval of the rod lenses 420 is 7.09 pixels when converted into the number of pixels of 600 dpi. In this case, D = 7 and d = 0.09. Becomes The interpolation calculation described later is performed based on the values of D and d. The parameters D and d are not constant due to individual variations in the diameter of the rod lens 420 during manufacturing and variations in the assembly of a contact image sensor (CIS), so that the operation unit 121 accepts an operation input. It may be changeable accordingly. In this case, the operation unit 121 serves as the arrangement interval setting unit, and the operation input is input to the comparison pixel generation unit 62.

  The controller 11 reads out the pixel values of the pointers P, P + D-1, P + D, P + D + 1, and P + D + 2 (S204). Here, the pixel value at the pixel position of the pointer P is S (P). Further, the pointer P indicates the target pixel position, and the four points P + D-1, P + D, P + D + 1, and P + D + 2 are D + d, which is the array interval of the rod lenses 420 from the target pixel position P, as shown in FIG. The position of the closest four pixels in the distant position is shown.

  The comparison pixel generation unit 62 generates (calculates) a pixel value at a virtual pixel position (this is referred to as a comparison pixel value) by using the pixel value total of 4 points at the positions of the pointers P + D-1, P + D, P + D + 1, and P + D + 2. Yes (S206). This pixel value is called S (P + D + d). The comparison pixel value is a pixel value at a position distant from the pixel of interest by the arrangement interval (D + d) of the rod lenses 420.

  The comparison unit 63 compares the two pixel values obtained in the processing of S204 and S206, for example, takes a difference and sets this as ΔS (= S (P) −S (P + D + d)) (S208). At this time, since S (P) and S (P + D + d) are pixel values at positions apart from the arrangement interval (D + d) of the rod lenses 420, the output values of the sensor 43 are equal, but the density reference member 146 is not contaminated by foreign matter. Makes a difference.

  When ΔS calculated in the process of S208 exceeds a predetermined threshold value, the controller 11 determines that there is a foreign substance and terminates the process (S210: Yes), and when it does not exceed the threshold value, determines normal and determines S212. The process proceeds to (S210: No).

  When the pointer P is not at the final pixel position (S212: No), the controller 11 increments the value of the pointer P by 1 (S216), returns to the processing of S204, and determines whether there is a foreign substance in the next pixel in the main scanning direction. Make a decision. Further, when the pointer P is at the final pixel position (S212: Yes), it means that the shading data is not affected by the foreign matter at this time, so the shading stored in the first storage unit 60 is performed. The data is stored in the second storage unit 61, which is a non-volatile memory, and the process ends (S214).

  The comparison pixel generation unit 62 uses, for example, a bicubic method (third-order function convolution method) to separate the array distance (D + d) of the rod lenses 420 from the pixel of interest (the comparison pixel position shown by a white circle in FIG. 8). ) Pixel value is obtained. For example, if the pixel values at the pixel positions indicated by the pointers P + D-1, P + D, P + D + 1, and P + D + 2 are S (P + D-1), S (P + D), S (P + D + 1), and S (P + D + 2), the comparison pixel position to be obtained. The pixel value S (P + D + d) in is expressed by the following Expression 1.

S (P + D + d) = W1 · S (P + D-1) + W2 · S (P + D)
+ W3 · S (P + D + 1) + W4 · S (P + D + 2) ・ ・ ・ (1)

  Here, W1 to W4 are correction coefficients. When it is possible to correspond to the resolution up to 1/32 pixel (≈0.031 pixel) with respect to the decimal part d of the number of pixels, the correction coefficients W1 to W4 are as shown in FIG.

  The fractional part d of the number of pixels corresponding to the arrangement interval of the rod lenses 420 may be a negative value as well as a positive value. For example, if the array interval of the rod lenses 420 is 6.9 pixels, D = 7 and d = -0.1 may be set. When d is a negative value, the comparison pixel position shown in FIG. 8 is on the left side of the pixel position of P + D in the drawing. Therefore, the pixel positions used in the bicubic method are four points P + D-2, P + D-1, P + D, and P + D + 1, which are shifted by one pixel from the pixel positions in the example of FIG.

  Further, although the comparison unit 63 takes the difference between the target pixel and the comparison pixel here, foreign matter can be detected by the same method by taking the ratio between the target pixel and the comparison pixel.

  As described above, the ADF 10 generates a pixel value at a position distant from the pixel of interest by the array distance of the rod lens 420, and sets the pixel value as a comparison target with the pixel of interest, and thereby the positional relationship apart from the rod lens 420 by the array interval. The pixel values can be compared, and the foreign substance on the density reference member 146 and the glass surface at the reading position can be detected with high accuracy.

  Next, a first modification of the function (foreign matter determination function) that the ADF 10 has for detecting foreign matter will be described. FIG. 10 is a diagram schematically showing output levels (shading data) of the plurality of sensors 43 arranged in the main scanning direction.

  The shading data is comparatively high in the main scanning direction due to the influence of the unevenness of illumination caused by the structure of the light source unit 500 including the light guide 41 in addition to the relatively high-frequency fluctuation component caused by the structure of the rod lens array 42. It is known to have a gentle fluctuation (low frequency component). In particular, at both ends in the main scanning direction, the output level decreases as shown in FIG.

  If the fluctuation of the shading data is not taken into consideration, the difference between the pixel value of interest and the comparison pixel value becomes large even in the range where there is no foreign substance, and erroneous detection may occur if there is a foreign substance. Therefore, the ADF 10 smoothes the shading data shown in FIG. 10A from the shading data shown in FIG. 10A, that is, the fluctuation component (low frequency component) shown in FIG. 10B. Subtract and remove. As a result, as shown in FIG. 10C, data including the fluctuation component due to the rod lens array 42 and the fluctuation component due to the foreign matter is extracted.

  FIG. 11 is a block diagram showing a first modified example of the function of the ADF 10 for detecting a foreign substance (determining presence / absence). Note that the functions that the ADF 10 has and that are substantially the same have the same reference numerals. As shown in FIG. 11, in the first modification of the foreign matter determination function, the ADF 10 includes a first storage unit 60, a second storage unit 61, a comparison pixel generation unit 62, a comparison unit 63, a foreign matter determination unit 64, and a high frequency component extraction. It has a part 65.

  The high frequency component extraction unit 65 has a smoothing unit 650 and a subtraction unit 652. The smoothing unit 650 smoothes the shading data. The subtraction unit 652 subtracts the data smoothed by the smoothing unit 650 from the shading data. That is, the controller 11 reads the shading data from the first storage unit 60, removes the low frequency components of the shading data in the high frequency component extraction unit 65, and then performs the above-described foreign matter determination.

  Next, a second modified example of the function (foreign matter determination function) that the ADF 10 has for detecting (determining presence / absence) of foreign matter will be described. FIG. 12 is a block diagram showing a second modified example of the function of the ADF 10 for detecting a foreign substance (determining presence / absence). As shown in FIG. 12, in the second modified example of the foreign matter determination function, the ADF 10 includes the first storage unit 60, the second storage unit 61, the comparison pixel generation units 62-1 to 62-2n, the comparison unit 63, and the foreign matter determination. It includes a unit 64, a comparison pixel number setting unit 66, and an averaging unit (first averaging unit) 67.

  Further, FIG. 13 is a diagram showing positions where pixel values are generated in the second modification of the foreign matter determination function. FIG. 14 is a flowchart showing a process for determining the presence / absence of a foreign substance in the second modified example of the foreign substance determination function. In the shading data, when the pixel values at the same position in the main scanning direction of the rod lenses 420 are compared, the pixel values do not match completely due to the influence of random noise of the sensor 43 and the like. Therefore, in the second modified example of the foreign matter determination function, several comparison pixels for the target pixel are acquired, and the comparison pixels of the several points are averaged and compared with the target pixel.

  As shown in FIG. 14, the controller 11 stores the shading data in the first storage unit 60, which is a volatile memory, and initializes the pointer P of the pixel position of the pixel of interest (S300). Next, the controller 11 defines the integer part of the number of pixels (pixel width) of the array interval (D + d) of the rod lenses 420 as D and the decimal part as d, and determines the averaging range n from the pixel of interest (S302). ). n is a parameter indicating how many cycles around the pixel of interest are the target of comparison pixels. For example, if n = 2, the target pixel position P and the surrounding two cycles are targets of comparison pixels. The total number of comparison pixels generated by the comparison pixel generation units 62-1 to 62-2n is four. The parameter n is set by the comparison pixel number setting unit 66.

  The comparison pixel generation units 62-1 to 62-2n perform a process of generating each comparison pixel (S40). Here, the process of S40 performed by the comparison pixel generation units 62-1 to 62-2n will be described in detail with reference to FIG. FIG. 15 is a flowchart showing processing performed by the comparison pixel generation units 62-1 to 62-2n.

  First, the controller 11 determines the value of the parameter k to be -n (S400). The parameter k indicates which cycle the comparison pixel value is generated for the target pixel. For example, when n = 2, k = -2, and as shown in FIG. 13, the pixel value at a position two cycles away from the target pixel position P on the front end side (left side in FIG. 13) of the sensor (sensor chip) 43. Indicates to generate.

  Next, the controller 11 determines the positive / negative of k at that time (S402). Here, the bicubic method shown in FIG. 8 is used, and the pixel value at the comparison pixel position to be obtained is generated by using the pixel values of the surrounding four points. Whether the pixel value of the left side of 13 or the pixel value of the rear end side (right side of FIG. 13) of the sensor 43 is generated, since the pointers indicating the four pixel positions used for generation are different, The sign of k is judged.

  In the processing of S404 and S422, it is determined whether the integer multiple of the decimal part d of the number of pixels exceeds 1 pixel. If the number of pixels exceeds one pixel, the pointers indicating the pixel positions of the four points used to generate the pixel value are shifted by the integer pixel (C: S416, S428) that exceeds the number of pixels, so the determination in S404 and S422 is made. Is required.

  The controller 11 reads out pixel values of four pixels around the comparison pixel indicated by the pointer (S406, S418, S424, S430).

  The controller 11 generates a virtual pixel value (comparison pixel value) from the four pixel values in the comparison pixel generation unit of FIG. 12 (S408, S420, S426, S432).

  Then, the controller 11 determines whether or not k = n (S410). If k = n is not satisfied (S410: No), the controller 11 increments k (S412), and again generates the comparison pixel value of the next cycle (in the case of FIG. 13, next k = −1). Pixel value of).

  The controller 11 determines that k is not 0 (S414). When k = 0, the controller 11 indicates the target pixel position and does not need to generate a pixel value. Therefore, the controller 11 again proceeds to the processing of S412 and increments k (S414: No). If k ≠ 0, the controller 11 proceeds to the process of S402.

  When the controller 11 determines that k = n (when all comparison pixel values have been generated), the controller 11 proceeds to the process of S304.

  Then, the controller 11 causes the averaging unit 67 to calculate the average value S (Ave) of the pixel values generated in the process of S40 (FIG. 14: S304).

  The controller 11 calculates the pixel value S (P) at the pixel position of the pointer P (S306). The comparison unit 63 takes the difference between the two pixel values and calculates ΔS = S (P) −S (Ave) (S308).

  When ΔS calculated in the process of S308 exceeds a predetermined threshold value, the controller 11 determines that there is a foreign substance and terminates the process (S310: Yes), and when it does not exceed the threshold value, determines that it is normal and determines S312. The process proceeds to (S310: No).

  When the pointer P is not at the final pixel position (S312: No), the controller 11 increments the value of the pointer P by 1 (S316), returns to the processing of S40, and determines whether there is a foreign substance in the next pixel in the main scanning direction. Make a decision. Further, when the pointer P is at the final pixel position (S312: Yes), it means that the shading data is not affected by the foreign matter at this time, so the shading stored in the first storage unit 60 is determined. The data is stored in the second storage unit 61, which is a non-volatile memory, and the process ends (S314).

  Note that the ADF 10 may acquire the shading data a plurality of times (several lines) and average each pixel, and then perform the process according to the second modification of the foreign matter determination function. In this case, for example, a line averaging unit that averages the input data input to the first storage unit 60 may be provided. The ADF 10 performs foreign object determination after averaging the shading data, thereby reducing the influence of random noise of the sensor 43 and the temporal change of the light amount of the light source unit 500, and performs more accurate foreign object determination (foreign object detection). It becomes possible.

  Next, a third modified example of the function (foreign matter determination function) that the ADF 10 has for detecting (determining the presence or absence) of a foreign matter will be described. FIG. 16 is a block diagram showing a third modification of the function of the ADF 10 for detecting a foreign substance (determining the presence / absence). FIG. 17 is a diagram showing positions where pixel values are generated in the third modification of the foreign matter determination function. As shown in FIG. 16, in the third modification of the foreign matter determination function, the ADF 10 includes a first storage unit 60, a second storage unit 61, comparison pixel generation units 62-1 to 62-n ′, a comparison unit 63, and a foreign matter. It includes a determination unit 64, a comparison pixel number setting unit 66, an averaging unit 67, and an averaging unit (second averaging unit) 67a.

  In the second modification of the foreign matter determination function, the influence of noise is suppressed by taking the average value of the comparison pixels with respect to the target pixel, and the foreign matter detection accuracy is improved. By calculating the value, the influence of noise of the pixel of interest itself is reduced.

  Specifically, in the third modification example of the foreign matter determination function, the controller 11 obtains the target pixel average value for the target pixel A by using the surrounding pixels B and C, and determines the target pixels A, B, and C as pixels. On the other hand, the pixel values of the pixels A ′, B ′, and C ′ at the positions separated by the array distance of the rod lens 420 are generated by the bicubic method. Then, the controller 11 calculates the average value (comparison pixel average value) thereof, and then compares the difference between the target pixel average value calculated by the averaging unit 67a and the comparison pixel average value calculated by the averaging unit 67. 63, and the foreign matter determination unit 64 performs foreign matter determination.

  The number of target pixels and the number of comparison pixels to be acquired and averaged is determined by the comparison pixel number setting unit 66 by setting the parameter n ′. For example, when comparing the average value of the pixel values of the pixels A, B, and C shown in FIG. 17 with the average value of the pixel values of the pixels A ′, B ′, and C ′, n ′ = 3.

  Note that the target pixel and the comparison pixel are averaged by the pixel values of three points respectively (n '= 3), but if n'is too large, the influence of foreign matter is averaged and the foreign matter detection accuracy decreases, so the maximum rod lens One cycle interval is appropriate.

  Further, in the ADF 10, the rod lens array 42 may be flexibly arranged when the contact image sensor of the second reading unit 113 is assembled. For example, as shown in FIG. 18, the center axis of the rod lens array 42 may deviate from the axis of the sensor 43 due to the deflection of the rod lens array 42.

  As shown in FIG. 18, the number of pixels corresponding to the width of the rod lens 420 varies depending on the location. A difference (a <b) occurs between the number a of pixels on the end side of the rod lens array 42 and the number b of pixels on the center side of the rod lens array 42. That is, the parameter d representing the fractional part of the number of pixels varies depending on the location, which may affect foreign matter detection.

  Therefore, as shown in FIG. 19, the ADF 10 divides the shading data into Z blocks in the main scanning direction, and arbitrarily sets the integer part D and the decimal part d of the array interval (D + d) of the rod lenses 420 in each block. It may be configurable. For example, the integer part D and the decimal part d may be individually set for each block, such as 1 block has D1, d1, 2 blocks has D2, d2, ..., and Z block has DZ, dZ.

  In this case, the controller 11 performs the processing shown in FIG. That is, the controller 11 stores the shading data in the first storage unit 60 that is a volatile memory, initializes the pointer P of the pixel position that is the target pixel (S500), and determines the block division number Z and the pixel number (pixel width). ), The integer part D and the decimal part d are defined for each block and determined (S502).

  The controller 11 reads the pixel values of the pointers P, P + D-1, P + D, P + D + 1, and P + D + 2, and sets the pixel value at the pixel position of the pointer P to S (P) (S504).

  The comparison pixel generation unit 62 generates (calculates) the pixel value S (P + D + d) at the virtual pixel position by using the four pixel value totals at the positions of the pointers P + D-1, P + D, P + D + 1, and P + D + 2 (S506).

  The comparison unit 63 compares the two pixel values obtained in the processing of S504 and S506, for example, takes a difference and sets this as ΔS (= S (P) −S (P + D + d)) (S508). At this time, since S (P) and S (P + D + d) are pixel values at positions apart from the arrangement interval (D + d) of the rod lenses 420, the output values of the sensor 43 are equal, but the density reference member 146 is not contaminated by foreign matter. Makes a difference.

  If ΔS calculated in the process of S508 exceeds the predetermined threshold value, the controller 11 determines that there is a foreign substance and terminates the process (S510: Yes), and if it does not exceed the threshold value, determines that it is normal and determines S512. (S510: No).

  When the pointer P is not at the final pixel position (S512: No), the controller 11 proceeds to the process of S516. The controller 11 determines whether or not it is the final pixel of each divided block (S516), and if it is the final pixel (S516: Yes), increments Z in the process of S518 to determine the foreign substance in the adjacent block. Start. If it is not the final pixel (S516: No), the controller 11 increments the value of the pointer P by 1 (S520), returns to the process of S504, and determines the presence / absence of foreign matter in the next pixel in the main scanning direction. To do.

  If the pointer P is at the final pixel position (S512: Yes), it means that the shading data is not affected by the foreign matter at this point, and thus the shading stored in the first storage unit 60 is not detected. The data is stored in the second storage unit 61, which is a non-volatile memory, and the process ends (S514).

  Further, since the contact-type image sensor of the second reading unit 113 has a configuration in which a plurality of sensors (chips) 43 having a plurality of pixels 430 are arranged in the main scanning direction, the sensitivity difference (variation) between the sensors 43. Therefore, even if the incident light amount is uniform, the pixel values may be different between the adjacent sensors 43 as shown in FIG.

  Further, as shown in FIG. 21, a gap for one pixel physically exists at the joint of the sensor 43. Therefore, when the target pixel or the comparison pixel straddles the sensors 43, the influence of the sensitivity difference between the sensors 43 and the influence of the shift of the pixel interval due to the gap of one pixel are included, and therefore the foreign matter detection is performed. Must be avoided. Therefore, the ADF 10 does not straddle the sensor 43 and makes a foreign matter determination.

  Here, a case (n = 1) in which up to one cycle around the pixel of interest is the target of comparison pixels will be described as an example. As described above, assuming that the array interval of the rod lenses 420 is D + d (D: integer part, d: pixel decimal part) and there are X pixels per sensor 43, a pointer indicating the position of the pixel of interest in the range shown in gray in FIG. When there is P, the influence of the sensitivity difference for each sensor 43 can be avoided by generating the comparison pixel value from the center side of each sensor 43.

  Specifically, as shown in FIG. 22, the adaptive range for the N-th chip of the sensor 43 is such that when the pointer P indicating the target pixel position is the following Expression 2, the tip end side of the sensor 43 (the left side of the chip in FIG. 22). ) Does not generate comparison pixels.

  (N-1) · X + 1 ≦ P ≦ (N−1) · X + D (2)

  In addition, when the pointer P indicating the position of the pixel of interest is the following Expression 3, the comparison pixel is not generated from the rear end side of the sensor 43 (right side of the chip in FIG. 22) (see FIG. 23).

  N · X−D + 1 ≦ P ≦ N · X (3)

  Here, the case where one cycle around the target pixel is set as the target of the comparison pixel (n = 1) is shown, but when the range of several cycles around the target pixel (n ≧ 2) is set as the target of the comparison pixel, For all of the cases where the pointer P is the expression 4 or 5, the comparison pixel value on the center side of the sensor 43 is not generated, but the pixel value on the end side of the sensor 43 is generated as much as possible as shown in FIG. By doing so, the comparison data increases and the detection accuracy increases.

(N−1) · X + 1 ≦ P ≦ (N−1) · X + nD (4)
N · X−nD + 1 ≦ P ≦ N · X (5)
(However, when n · d does not exceed 1 pixel)

  Furthermore, the ADF 10 may change the threshold value when performing the foreign matter determination as follows. For example, due to the internal circuit configuration of the sensor 43, a predetermined pixel region in the sensor 43 may exhibit linearity characteristics different from those of other pixel groups. FIG. 25 is a diagram illustrating a case where the pixel value at the end of the sensor 43 is lower than the other pixel values.

  As shown in FIG. 25, if the pixel of interest or the comparison pixel is in a range where the pixel value decreases (hereinafter referred to as a decrease range), the comparison result will be large and the foreign substance may be erroneously detected. is there. Therefore, the ADF 10 is configured to change the threshold value for foreign matter determination in the decreasing range. As shown in FIG. 26, the foreign matter detection threshold value changing range is a range in which the pixel position P ′ is represented by the following equation 6 or 7 when the decreasing range is a pixels.

(N−1) · X + 1 ≦ P ′ ≦ (N−1) · X + a (6)
N · X−a + 1 ≦ P ′ ≦ N · X (7)

  More specifically, as shown in FIG. 27, even if the foreign substance detection threshold is normally set to 0 ± 1 digit, the foreign substance detection threshold is set to −5 ± 1 digit when the target pixel is included in the decrease range. And

  Further, the ADF 10 may also change the threshold value for foreign matter detection when the comparison pixel is included in the decrease range. Further, the comparison result (ΔS in FIG. 27) varies depending on how much the pixel value used when generating the comparison pixel is included in the decrease range. Therefore, the decrease range is masked (from the target as the pixel value for generating the comparison pixel). May be excluded).

  Next, another operation example of the ADF 10 will be described. FIG. 28 is a flowchart showing another operation example of the ADF 10. The controller 11 stores the shading data in the first storage unit 60, which is a volatile memory, initializes the pointer P of the pixel position that is the target pixel (S600), and sets the integer part of the number of pixels (pixel width) to D and the decimal. The part is defined as d and is determined (S602).

  The controller 11 reads out the pixel values of the pointers P, P + D-1, P + D, P + D + 1, and P + D + 2, and sets the pixel value at the pixel position of the pointer P to S (P) (S604).

  The comparison pixel generation unit 62 generates (calculates) the comparison pixel value S (P + D + d) at the virtual pixel position using the four pixel value totals at the positions of the pointers P + D-1, P + D, P + D + 1, and P + D + 2 (S606). .

  The comparing unit 63 compares the two pixel values obtained in the processing of S604 and S606, for example, takes a difference and sets this as ΔS (= S (P) −S (P + D + d)) (S608).

  When ΔS calculated in the process of S608 exceeds the predetermined threshold value (S610: Yes), the controller 11 determines that there is a foreign substance and proceeds to the process of S618. In the processing of S618, the controller 11 causes the operation unit 121 to display that the foreign matter is detected and its position. If the ΔS calculated in the process of S608 does not exceed the predetermined threshold value, the controller 11 determines that it is normal and proceeds to the process of S612 (S610: No).

  When the pointer P is not at the final pixel position (S612: No), the controller 11 increments the value of the pointer P by 1 (S616), returns to the processing of S604, and determines whether there is a foreign substance in the next pixel in the main scanning direction. Make a decision. Further, when the pointer P is at the final pixel position (S612: Yes), it means that the shading data is not affected by the foreign matter at this time, so the shading stored in the first storage unit 60 is performed. The data is stored in the second storage unit 61, which is a non-volatile memory, and the process ends (S614).

  As described above, when the comparison result between the target pixel and the comparison pixel exceeds the threshold value and the foreign matter is detected, the ADF 10 detects the foreign matter on the operation unit 121 and displays the position thereof to detect the foreign matter. The user can be informed of this.

  Next, the image forming apparatus 300 having the ADF 10 will be described. FIG. 29 is a diagram showing the configuration of the image forming apparatus 300 having the ADF 10. The image forming apparatus 300 includes a sheet feeding unit 303, an image forming apparatus main body 304, a scanner (image reading apparatus) 200, and an ADF 10.

  In the image forming apparatus main body 304, a tandem type image forming unit 305, a resist roller 308 that supplies recording paper from the paper feeding unit 303 to the image forming unit 305 via a conveyance path 307, an optical writing device 309, The fixing / conveying unit 310 and the double-sided tray 311 are provided.

  In the image forming unit 305, four photoconductor drums 312 corresponding to four colors of YMCK are arranged side by side, and each photoconductor drum 312 is surrounded by a charging device, a developing device 306, a transfer device, a cleaner, and a neutralizer. Image forming elements are arranged.

  Further, an intermediate transfer belt 313, which is stretched between a driving roller and a driven roller while being sandwiched between the nip of the transfer device and the photosensitive drum 312, is arranged.

  In the tandem-type image forming apparatus 300 configured as described above, optical writing is performed on the photoconductor drums 312 corresponding to each color of YMCK, the developing device 306 develops for each color toner, and the intermediate transfer belt 313. For example, primary transfer is performed in the order of Y, M, C, K on top.

  Then, the full-color image in which the four colors are superposed by the primary transfer is secondarily transferred to the recording paper, and then fixed and discharged to form the full-color image on the recording paper.

  As described above, the ADF 10 determines the pixel value at the position apart from the pixel of interest of the shading data by the arrangement interval of the rod lenses 420, for example, when manufacturing the product or when the second reading unit 113 and the density reference member 146 are replaced. By generating and comparing with the pixel of interest, it is possible to highly accurately detect whether or not the foreign matter is attached to the density reference member 146 and the glass surface.

10 ADF (image reading device)
11 controller 42 rod lens array 43 sensor 60 first storage unit 61 second storage unit 62 comparison pixel generation units 62-1 to 62-2n comparison pixel generation units 62-1 to 62-n 'comparison pixel generation unit 63 comparison unit 64 Foreign matter determination unit 65 High frequency component extraction unit 66 Comparison pixel number setting unit 67 Averaging unit 67a Averaging unit 113 Second reading unit 121 Operation unit 146 Density reference member 300 Image forming device 420 Rod lens 430 Pixel 500 Light source unit 650 Smoothing unit 652 Subtraction unit

JP, 2016-039416, A JP, 2013-157922, A

Claims (14)

An irradiation unit that extends in one direction and emits light,
A photoelectric conversion element that photoelectrically converts reflected light or transmitted light of light emitted by the irradiation unit for each of a plurality of arranged pixels, and outputs a pixel value of each of the plurality of pixels,
A plurality of lenses the irradiation unit are arranged in the same diameter you imaging the reflected or transmitted light into the photoelectric conversion element of light irradiation,
Using a plurality of pixel values output by the photoelectric conversion element when each of the lenses forms an image of the reflected light of the light that the irradiation unit irradiates on the density reference member, from the pixel of interest to the lens A comparison pixel generation unit that generates pixel values at positions separated by the array interval as pixel values of comparison pixels;
The pixel value of the pixel of interest output by the photoelectric conversion element when each of the lenses forms an image of the reflected light of the light that the irradiation section irradiates on the density reference member, and the comparison pixel generation section generates A comparison unit for comparing the pixel value of the compared pixel,
Based on the result of comparison by the comparison unit and a predetermined threshold value, a foreign matter determination unit that determines whether or not the pixel value of the target pixel compared by the comparison unit is a pixel value affected by a foreign matter,
Have a,
The comparison pixel generation unit,
Interpolation is performed using a plurality of pixel values around the pixel of interest output by the photoelectric conversion element when each of the lenses forms an image of the reflected light of the irradiation of the density reference member by the irradiation unit on the photoelectric conversion element. Generate a pixel value for the comparison pixel by doing
An image reading device characterized by the above. A smoothing unit that smoothes a plurality of pixel values output by the photoelectric conversion element when each of the lenses forms an image on the photoelectric conversion element by reflected light of the light that the irradiation unit irradiates on the density reference member,
A plurality of pixel values output by the photoelectric conversion element when the plurality of pixel values smoothed by the smoothing unit are reflected by the irradiation unit and the reflected light of the light applied to the density reference member is imaged on the photoelectric conversion element by each of the lenses. A subtraction unit that subtracts from the pixel value of
Further has
The comparison pixel generation unit,
Using the plurality of pixel values subtracted by the subtraction unit to generate a pixel value of a comparison pixel,
The comparison unit is
The image reading apparatus according to claim 1, wherein the pixel value of the target pixel subtracted by the subtraction unit is compared with the pixel value of the comparison pixel generated by the comparison pixel generation unit. A position separated from the target pixel by an integer multiple of the arrangement interval of the lenses, using a plurality of pixel values output by the photoelectric conversion element that are imaged by the other lens around the lens to be focused on the target pixel Other comparison pixel generation unit that generates the pixel value of as the pixel value of the comparison pixel,
A first averaging unit that averages pixel values of a plurality of comparison pixels generated by the comparison pixel generation unit and the other comparison pixel generation unit;
Further has
The comparison unit is
The pixel value of the pixel of interest output by the photoelectric conversion element when each of the lenses forms an image of the reflected light of the light that the irradiation section irradiates on the density reference member, and the first averaging section the image reading apparatus according to claim 1 or 2, characterized in that comparing the pixel values averaged. A second averaging unit that averages the pixel values around the pixel of interest as a plurality of pixels of interest;
The comparison pixel generation unit and the other comparison pixel generation unit,
The pixel values around the pixel of interest are also regarded as multiple pixels of interest, and the pixel value of the comparison pixel is generated.
The comparison unit is
The image reading device according to claim 3 , wherein the pixel value averaged by the first averaging unit is compared with the pixel value averaged by the second averaging unit. Further comprising a setting unit for setting an integer part and a decimal part representing the number of pixels per lens,
The comparison pixel generation unit,
Based on the integer part and the fractional part the setting unit has set, from the pixel of interest according to claim 1, wherein the generating a pixel value of the comparison pixel the pixel values of the array interval fraction away of the lens The image reading device according to any one of items. The setting unit,
The image reading apparatus according to claim 5 , wherein an integer part and a decimal part that represent the number of pixels per lens are set for each of a plurality of pixels divided into a plurality of blocks. The photoelectric conversion element,
A plurality of the irradiation units are arranged in a group in the extending direction,
The setting unit,
The image reading apparatus according to claim 5 , wherein the acquisition range of the plurality of pixel values used by the comparison pixel generation unit is set so as not to cross the groups of the plurality of photoelectric conversion elements. The setting unit,
The image reading apparatus according to any one of claims 5 to 7, characterized in that to set so as to vary the threshold value of the foreign substance determination unit for each predetermined region. The setting unit,
The image reading apparatus according to any one of claims 5 to 8, characterized in that the setting to exclude the foreign matter determination unit determines a pixel value a predetermined pixel of the photoelectric conversion element. The comparison pixel generation unit,
Shading data for a plurality of lines output by the photoelectric conversion element a plurality of times when each of the lenses images the reflected light of the light applied to the density reference member on the photoelectric conversion element for each pixel, the image reading apparatus according to any one of claims 1 to 9, characterized in that it comprises a line averaging unit for averaging the. The comparison unit is
The pixel value of the pixel of interest output by the photoelectric conversion element when each of the lenses forms an image of the reflected light of the light that the irradiation section irradiates on the density reference member, and the comparison pixel generation section generates the image reading apparatus according to any one of claims 1 to 10 and a pixel value of the comparison pixels, and comparing by calculating the difference. The comparison unit is
The pixel value of the pixel of interest output by the photoelectric conversion element when each of the lenses forms an image of the reflected light of the light that the irradiation section irradiates on the density reference member, and the comparison pixel generation section generates the image reading apparatus according to any one of claims 1 to 10 and the pixel values of the comparison pixels, and comparing by calculating the ratio. The image reading apparatus according to any one of claims 1 to 12, further comprising a display unit for displaying the result the foreign substance determination unit determines. An image forming apparatus having an image reading apparatus according to any one of claims 1 to 13.