JP2017200020A - Image reading device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve accurate black correction.SOLUTION: A light source irradiates a subject with light. An image sensor has, as line sensors having photoelectric conversion elements formed in a main scanning direction and having different transmitting wavelength regions, a first line sensor including filters that can receive reflected light from the subject according to the irradiation of light by the light source and a second line sensor including filters that block the reflected light from the subject, arranged side by side in a sub scanning direction orthogonal to the main scanning direction. An acquisition part acquires a read value read by the second line sensor as a black level in synchronization with reading performed by the first line sensor while the light source is turned on. A black correction part executes black correction processing on the read value read by the first line sensor by using the acquired black level.SELECTED DRAWING: Figure 2

Description

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

  2. Description of the Related Art Conventionally, CIS (Contact Image Sensor) has been adopted in image reading apparatuses such as scanner apparatuses for reasons such as downsizing of the apparatus and suppression of the amount of light from a light source. In an image reading apparatus employing CIS, the black level (the output level of the chip in a state where no light enters) changes due to the temperature rise of the CIS sensor chip. In the CIS in which a plurality of sensor chips are arranged, the change in the black level is not uniform among the sensor chips due to individual differences between the sensor chips, so that the luminance level is different for each image area corresponding to each sensor chip. May cause a significant deterioration in image quality.

  Therefore, in an image reading apparatus employing CIS, a black level (black offset level) that is an output level of a sensor chip in a state where light does not enter is detected and held in a memory, and when reading a document or the like, The black level is corrected by subtracting the black level from the level of the signal component obtained by the incident reflected light. For example, in Patent Document 1 (Japanese Patent No. 5652058), a photoelectric conversion element including a plurality of chips in which a light receiving portion that receives reflected light from a subject caused by light irradiation of a light source and a light shielding portion that is shielded is formed. The output level of the light receiving unit and the light shielding unit is stored as a black level with the light source turned off, and a change in the black level of the light shielding unit is detected by comparison with the stored black level. An image reading apparatus that feeds back a change to a stored black level and subtracts the stored black level from the output levels of the light receiving unit and the light shielding unit when reading a subject is disclosed.

  However, the conventional technique has a problem that it is difficult to realize high-accuracy black correction. Specifically, in the prior art, the detection of the black level of the light-shielding part is not performed in synchronization with the reading of the light-receiving part at the time of lighting. It cannot be said that the black level detection having the noise component is accurately performed, and it is difficult to accurately cancel the noise fluctuation.

  The present invention has been made in view of the above, and an object thereof is to realize highly accurate black correction.

  In order to solve the above-described problems and achieve the object, an image reading apparatus according to the present invention includes a light source that irradiates light to a subject, and a line sensor in which a photoelectric conversion element is formed in the main scanning direction and the transmitted wavelength range is different. A first line sensor having a filter capable of receiving reflected light from the subject in response to light irradiation by the light source, and a second line sensor having a filter shielding light reflected from the subject. The second line sensor in synchronization with the reading by the first line sensor in a state where the image sensor arranged in the sub-scanning direction orthogonal to the main scanning direction and the light source are turned on. An acquisition unit that acquires the read value as a black level, and a read value that is read by the first line sensor using the acquired black level And a black correction unit that performs a black correction process.

  According to one aspect of the present invention, there is an effect that highly accurate black correction can be realized.

FIG. 1 is a diagram illustrating a configuration example of an image forming apparatus according to the first embodiment. FIG. 2 is a diagram illustrating a configuration example of a mechanism unit of the image reading apparatus according to the first embodiment. FIG. 3 is a block diagram illustrating a configuration example of a control system of the image reading apparatus according to the first embodiment. FIG. 4A is a diagram illustrating an example of a cross section of the second reading unit according to the first embodiment. FIG. 4B is a diagram illustrating an example of components of the second reading unit according to Embodiment 1. FIG. 5 is a diagram illustrating a configuration example of the line sensor according to the first embodiment. FIG. 6 is a timing chart showing an example of pixel data reading timing according to the first embodiment. FIG. 7 is a block diagram illustrating a functional configuration example for black correction processing according to the first embodiment. FIG. 8A is a diagram illustrating an example of an arrangement position of a line sensor serving as a light shielding unit according to Embodiment 1. FIG. 8B is a diagram illustrating an example of an arrangement position of a line sensor serving as a light shielding unit according to Embodiment 1. FIG. 9 is a diagram for explaining an example of the black correction process according to the second embodiment.

  Embodiments of an image reading apparatus and an image forming apparatus according to the present invention will be described below with reference to the accompanying drawings. In addition, this invention is not limited by the following embodiment. It should be noted that the embodiments can be appropriately combined as long as the contents are not contradictory.

(Embodiment 1)
[Configuration of Image Forming Apparatus]
The configuration of the image forming apparatus 1 according to the first embodiment will be described with reference to FIG. FIG. 1 is a diagram illustrating a configuration example of an image forming apparatus 1 according to the first embodiment.

  As shown in FIG. 1, the image forming apparatus 1 includes an image reading device 10 having a function as an automatic document feeder (ADF), a paper feeding unit 2, and an image forming unit 3. The sheet feeding unit 2 is configured to store the sheet feeding cassette 21 and the sheet feeding cassette 22 that store recording sheets having different sheet sizes, and the sheet forming cassette 21 and the recording sheet stored in the sheet feeding cassette 22 to the image forming position of the image forming unit 3. And a sheet feeding means 23 composed of various rollers.

  The image forming unit 3 forms an image. For example, the image forming unit 3 forms an image based on an output (read image) from an image reading device 10 described later. The image forming unit 3 includes an exposure device 31, a photosensitive drum 32, a developing device 33, a transfer belt 34, and a fixing device 35. The image forming unit 3 forms a latent image on the photosensitive drum 32 by exposing the photosensitive drum 32 by the exposure device 31 based on the image data of the document read by the image reading unit inside the image reading device 10. The developing device 33 supplies toner of different colors to the photosensitive drum 32 and develops it. The image forming unit 3 transfers the image developed on the photosensitive drum 32 by the transfer belt 34 onto the recording paper supplied from the paper feeding unit 2, and then transfers the toner image transferred to the recording paper by the fixing device 35. The toner is melted to fix the color image on the recording paper.

[Configuration of Image Reading Apparatus]
Next, the configuration of the image reading apparatus 10 according to the first embodiment will be described with reference to FIGS. 2 and 3. FIG. 2 is a diagram illustrating a configuration example of a mechanism unit of the image reading apparatus 10 according to the first embodiment. FIG. 3 is a block diagram illustrating a configuration example of a control system of the image reading apparatus 10 according to the first embodiment. In FIG. 3, the first reading unit 120 shown in FIG. 2 is not shown.

  The image reading apparatus 10 includes a document setting unit A, a separation feeding unit B, a registration unit C, a turn unit D, a first reading conveyance unit E, a second reading conveyance unit F, and a paper discharge unit G. And a stack portion H. A document bundle 101 is set in the document setting section A. The separation feeding unit B separates and feeds the originals one by one from the set original bundle 101. The registration unit C performs primary abutting alignment of the fed document, and pulls out and transports the aligned document. The turn part D conveys a reading surface (for example, an image surface for a single-sided original, or a surface that is one side for a double-sided original) toward the reading side (downward). The first reading / conveying unit E reads the surface image of the document from below the contact glass. The second reading conveyance unit F reads the back image of the original after reading (double-sided original). The paper discharge unit G discharges a document whose surface image or double-sided image has been read out of the apparatus. The stack unit H stacks and holds the originals after reading.

  Further, the image reading apparatus 10 includes a pickup motor 151, a paper feed motor 152, a reading motor 153, a paper discharge motor 154, and a bottom plate raising motor 155, which are driving units for driving the above-described transport operation. In addition, the image reading apparatus 10 includes a controller unit 150 for controlling a series of operations.

  The document bundle 101 for reading images is set on the document table 102 including the movable document table 103 of the document setting unit A. The user sets the document bundle 101 so that the image surface (the front surface in the case of a double-sided document) is facing upward. Further, positioning of the document bundle 101 in the width direction (direction orthogonal to the conveyance direction) is performed by a side guide (not shown). The set document is detected by the set filler 104 and the document set sensor 105. Detection information indicating that the document is set is transmitted from the controller unit 150 to the main body control unit 159 via the interface 157.

  A document length detection sensor 130 or a document length detection sensor 131 provided on the table surface of the document table 102 determines an outline of the length in the document transport direction. For example, as the document length detection sensor 130 or the document length detection sensor 131, a reflection type sensor or an actuator type sensor that can detect even one document is used. In order to make the determination possible, the sensor arrangement is at least capable of determining whether the document size is vertical or horizontal.

  The movable document table 103 can be moved up and down in the a and b directions shown in FIG. 1 by a bottom plate raising motor 155 and is normally located at a home position (HP) detected by the bottom plate HP sensor 106. ing. Thereafter, when it is detected by the set filler 104 and the document setting sensor 105 that the document has been set, the controller unit 150 that has received the detection information rotates the bottom plate raising motor 155 in the normal direction so that the uppermost surface of the document bundle 101 is positioned. The movable document table 103 is raised to a position where it comes into contact with the pickup roller 107. The pickup roller 107 is operated by the pickup motor 151 in the c and d directions shown in FIG. 1 by the cam mechanism, and the movable document table 103 is raised and is pushed by the upper surface of the document on the movable document table 103 to be raised in the c direction. The upper limit can be detected by the proper paper feed position sensor 108.

  A print key on the main body operation unit 158 is pressed, and a notification to that effect is sent to the main body control unit 159 via the interface 156, and a document feed signal is transmitted from the main body control unit 159 to the controller unit 150 via the interface 157. Then, the pickup roller 107 rotates the roller by the normal rotation of the paper feed motor 152 and picks up the number of documents (ideally one) on the document table 102. The rotation direction is a direction in which the uppermost document is conveyed (paper fed) to the paper feeding port.

  The sheet feeding belt 109 is driven in the sheet feeding direction by the normal rotation of the sheet feeding motor 152, and the reverse roller 110 of the separation feeding unit B is rotated in the reverse direction to the sheet feeding by the sheet feeding motor 152 in the forward direction. The upper document and the document below the upper document are separated, and only the uppermost document can be fed. More specifically, the reverse roller 110 is in contact with the paper feeding belt 109 at a predetermined pressure, and when the paper is in direct contact with the paper feeding belt 109 or in contact with a single document, the reverse roller 110 rotates. When the document is rotated counterclockwise and an original enters between the sheet feeding belt 109 and the reverse roller 110, the rotation force is set to be lower than the torque of the torque limiter. The reverse roller 110 is rotated in the clockwise direction, which is the original driving direction, to push back the excess original, thereby preventing double feeding.

  The original separated by the action of the paper feed belt 109 and the reverse roller 110 is further fed by the paper feed belt 109, the leading edge is detected by the abutting sensor 111 of the registration portion C, and further advances and stops. It hits the pull-out roller 112 that is present. The document that has struck the pull-out roller 112 is fed by a predetermined amount from the detection point of the butt sensor 111. As a result, the document is fed in a state where it is pressed against the pull-out roller 112 with a predetermined amount of bending. By stopping the motor 152, the driving of the paper feeding belt 109 is stopped, and a standby state is entered.

  At this time, by rotating the pickup motor 151, the pickup roller 107 is retracted from the upper surface of the document, and the document is fed only by the conveying force of the paper feed belt 109. Entry and tip alignment (skew correction) are performed. The pull-out roller 112 has a skew correction function and is a roller for conveying the skew-corrected document after separation to the intermediate roller 114, and is driven by the reverse rotation of the paper feed motor 152. Further, when the paper feed motor 152 is rotated in the reverse direction, the pull-out roller 112 and the intermediate roller 114 are driven, but the pickup roller 107 and the paper feed belt 109 are not driven.

  A plurality of document width sensors 113 are arranged in the depth direction and detect the size in the width direction (main scanning direction) orthogonal to the transport direction (sub-scanning direction) of the document transported by the pull-out roller 112. The length of the document in the conveyance direction is detected by the abutting sensor 111 at the leading edge and the trailing edge of the document, and the output pulse of the paper feed motor 152 is counted from the leading edge detection time to the trailing edge detection time. Is detected. When the document is conveyed from the registration unit C to the turn unit D by driving the pull-out roller 112 and the intermediate roller 114, the conveyance speed at the registration unit C is higher than the conveyance speed at the first reading conveyance unit E. The processing time for setting and feeding the document to the first reading conveyance unit E is shortened.

  When the leading edge of the document is detected by the reading entrance sensor 115, the document is decelerated so that the document conveying speed is the same as the reading conveying speed before the leading edge of the document enters the nip between the upper and lower rollers of the reading inlet roller 116. At the same time, the reading motor 153 is rotated forward to drive the reading inlet roller 116, the reading outlet roller 123, and the CIS outlet roller 127. When the leading edge of the document is detected by the registration sensor 117, the controller unit 150 decelerates over a predetermined conveyance distance, temporarily stops before the reading position by the first reading unit 120, and interfaces to the main body control unit 159. A registration stop signal is transmitted via 157.

  After that, when the controller unit 150 receives a reading start signal from the main body control unit 159, the document whose registration has been stopped increases so that it rises to a predetermined conveyance speed before the leading edge reaches the reading position by the first reading unit 120. It is transported at high speed. Then, at the timing when the leading edge of the document detected by counting the output pulses of the reading motor 153 reaches the reading position by the first reading unit 120, the controller unit 150 causes the main body control unit 159 to perform the first document reading. Transmission of the gate signal indicating the effective image area in the sub-scanning direction of the surface (front surface) is started, and is transmitted until the trailing edge of the document passes through the reading position by the first reading unit 120.

  When reading an image of a single-sided document, the document that has passed through the first reading and conveying unit E is conveyed to the paper discharge unit G via the second reading unit 125 of the second reading and conveying unit F. At this time, when the leading edge of the document is detected by the paper discharge sensor 124, the controller unit 150 drives the paper discharge motor 154 to rotate forward to rotate the paper discharge roller 128. In addition, by counting the output pulses of the paper discharge motor 154 according to the detection of the leading edge of the document by the paper discharge sensor 124, the paper discharge motor immediately before the trailing edge of the document leaves the nip between the upper and lower roller pairs of the paper discharge roller 128. Control is performed so that the document discharged onto the sheet discharge tray 129 constituting the stack portion H does not jump out by reducing the drive speed of 154. The first reading roller 119 also serves as a reference white part for acquiring shading data in the first reading unit 120 while suppressing the floating of the document in the first reading unit 120.

  When reading a double-sided document image, the controller unit 150 counts the output pulse of the reading motor 153 according to the detection of the leading edge of the document by the paper discharge sensor 124, so that the second reading unit 125 reads the position. At the timing when the leading edge of the document arrives, transmission of a gate signal indicating an effective image area in the sub-scanning direction of the second surface (back surface) of the document is started to the main body control unit 159, and the reading position of the second reading unit 125 is set. Sent until the trailing edge of the document comes off. The second reading roller 126 serves as a reference white part for obtaining shading data in the second reading unit 125 as well as suppressing floating of the original in the second reading unit 125.

[Configuration of Second Reading Unit]
Next, the second reading unit 125 according to Embodiment 1 will be described with reference to FIGS. 4A and 4B. FIG. 4A is a diagram illustrating an example of a cross section of the second reading unit 125 according to Embodiment 1. FIG. 4B is a diagram illustrating an example of components of the second reading unit 125 according to Embodiment 1.

  4A and 4B, the second reading unit 125 includes a light source 50 and a light source 51, a light guide 52 and a light guide 53, a lens array 54, a glass plate 55, a reflection plate 56, A resin body 57, a substrate 58, and a sensor chip 59 are included.

  For example, the light source 50 and the light source 51 are LED (Light Emitting Diode) white light sources or the like, and irradiate a subject such as a document with light. The light guide 52 and the light guide 53 guide the light emitted from the light source 50 or the light source 51 in the main scanning direction. The lens array 54 includes lenses formed in an array. For example, the lens array 54 may be a rod lens array in which a large number of rod-shaped lenses are arranged in parallel to form one continuous image as a whole. The glass plate 55 covers the sensor (sensor chip 59), the light guide body 52, the light guide body 53, and the like to prevent it from becoming dirty. The reflection plate 56 is for reflecting light. The resin body 57 is for supporting each component. The sensor chip 59 is a sensor chip having a sensor (image sensor) that is a light receiving element. The sensor chip 59 is bonded on the substrate 58 so as to form a line sensor in the main scanning direction, and is connected to the wiring on the substrate 58 by directly bonding with a wire or the like. On the substrate 58, there are an A / D conversion unit, an output control unit, an I / F circuit, and the like (not shown).

  The sensor chip 59 has a photoelectric conversion element formed as a line sensor in the main scanning direction. The sensor chip 59 includes a first line sensor having a filter capable of receiving reflected light from a subject in response to light irradiation by the light source 50 or the light source 51 as a line sensor having a different wavelength range to transmit, and a subject. And a second line sensor having a filter for blocking the reflected light from the light source are arranged in the sub-scanning direction orthogonal to the main scanning direction. That is, in this embodiment, regarding reading of the subject, the reading value by the line sensor (first line sensor) in which the light receiving portion is formed and the reading by the line sensor (second line sensor) in which the light shielding portion is formed. Values exist. Since the CIS module is often used when reading an image on the back side of a document, the CIS module is used in the second reading unit 125 in the present embodiment, but can also be used in the first reading unit 120. . The sensor chip 59 of the CIS module is roughly classified into two types, one using a CCD (Charge Coupled Device) sensor and one using a CMOS (Complementary Metal Oxide Semiconductor) sensor.

  The analog image signal read by the sensor chip 59 is amplified by a corresponding amplifier circuit, and then converted into a digital image signal by a corresponding A / D converter. The digital image signal is converted into a data format acceptable by the main body control unit 159 by the output control unit, and then output to the main body control unit 159 via the I / F circuit. In the present embodiment, the output level for each pixel by the sensor chip 59 indicates the gradation level of the signal component of the digital image signal output from the corresponding A / D converter.

[Configuration of line sensor]
Next, the configuration of the line sensor according to the first embodiment will be described with reference to FIG. FIG. 5 is a diagram illustrating a configuration example of the line sensor according to the first embodiment.

  As shown in FIG. 5, the line sensor 61 corresponds to the first line sensor described above. The line sensor 62 corresponds to the above-described second line sensor. Each sensor chip has a photoelectric conversion element 60 formed as a line sensor in the main scanning direction. As described above, the sensor chip 59 includes a line sensor 61 having a filter capable of receiving reflected light from a subject in response to light irradiation by the light source 50 or the light source 51 as a line sensor having a different wavelength range to transmit. A line sensor 62 having a filter for blocking reflected light from the subject is arranged in the sub-scanning direction orthogonal to the main scanning direction. In the present embodiment, the line sensor 62 is an area for detecting a black level of a light-shielded pixel (optical black: OPB). Reference numeral 63 includes various amplifiers, memories, timing control units, clock generation units, output control units, I / F circuits, and the like. The A / D conversion unit may be configured in the sensor chip 59, or may be configured as a separate chip outside the sensor chip 59. When configured as a separate chip, the analog data from each chip is received. To summarize.

[Reading timing]
Next, the pixel data reading timing according to the first embodiment will be described with reference to FIG. FIG. 6 is a timing chart showing an example of pixel data reading timing according to the first embodiment.

  Normally, it is composed of a line sensor (corresponding to the line sensor 61) having filters of three colors of RGB (different wavelength ranges). In this embodiment, as shown in FIG. 6, the black level of OPB is detected. A line sensor (corresponding to the line sensor 62) is added. Each line sensor reads pixel data in synchronization with LSYNC indicating a line cycle. That is, the line sensor 62 reads OPB in synchronization with reading of pixel data by the line sensor 61 having RGB color filters.

  In this way, by reading pixel data in synchronization with the line sensor 61 serving as the light receiving unit and the line sensor 62 serving as the light shielding unit, the line sensor 62 also receives noise fluctuations generated by the line sensor 61. . As a result, the black level, which is a reading value by the line sensor 62, can be acquired as a more accurate value, and a black correction process to be described later can be realized with high accuracy. Also, after the reading section, various amplification and correction processes are performed.

[Black correction processing]
Next, the black correction process according to the first embodiment will be described with reference to FIG. FIG. 7 is a block diagram illustrating a functional configuration example for black correction processing according to the first embodiment. In addition, each part shown in FIG. 7 is a function performed by the 2nd reading part 125 grade | etc., As one aspect.

  The acquisition unit 161 acquires a reading value read by the line sensor 61 and the line sensor 62. More specifically, the acquisition unit 161 reads the reading values (mainly read by the line sensor 61 and the line sensor 62 in synchronization with LSYNC indicating the line period in a state where the light source 50 and the light source 51 are turned on. A reading value corresponding to each pixel in the scanning direction) is acquired. That is, the line sensor 62 reads in synchronization with the reading by the line sensor 61. Here, in synchronization with reading by the line sensor 61, the read value read by the line sensor 62 is set to a black level (black level corresponding to each pixel in the main scanning direction) for use in the black correction process.

  The black correction unit 162 performs black correction processing on the reading value read by the line sensor 61. More specifically, the black correction unit 162 performs black correction processing on the read value read by the line sensor 61 using the black level acquired by the acquisition unit 161. For example, the black correction unit 162 uses the black level corresponding to the pixel in the main scanning direction of the line sensor 62 and has the same positional relationship as that of the pixel in the main scanning direction of the line sensor 61 to perform reading. Executes black correction processing for values. By using pixel data corresponding to the same positional relationship in the line sensor 61 and the line sensor 62 for black correction processing, it is possible to acquire a black level reflecting voltage fluctuation and noise propagation at a position on the sensor chip 59. Therefore, it is possible to realize highly accurate black correction processing.

[Arrangement of line sensor]
Next, with reference to FIG. 8A and FIG. 8B, the arrangement position of the line sensor 62 serving as the light shielding unit according to the first embodiment will be described. FIG. 8A and FIG. 8B are diagrams illustrating an example of an arrangement position of the line sensor 62 serving as a light shielding unit according to the first embodiment.

  As shown in FIG. 8A, the line sensor 62 (“OPB” shown in FIG. 8A) is arranged outside the line sensor 61 arranged side by side in the sub-scanning direction. For example, the line sensor 62 (OPB), the line sensor 61 (Green), the line sensor 61 (Red), and the line sensor 61 (Blue) are arranged side by side in the sub-scanning direction. By arranging the line sensor 62 on the outside of the line sensor 61, it is possible to accurately read while not disturbing light reception.

  Further, as shown in FIG. 8B, the line sensors 62 and the line sensors 61 are arranged alternately in the sub-scanning direction. For example, the line sensor 62 (first OPB from the top in FIG. 8B), the line sensor 61 (Green), the line sensor 62 (third OPB from the top in FIG. 8B), the line sensor 61 (Red), and the line sensor 62 (FIG. 8B). The fifth OPB from the top and the line sensor 61 (Blue) are arranged side by side in the sub-scanning direction. By arranging the line sensor 62 so as to be paired with each of the line sensors 61, it is possible to read more accurately. That is, in the arrangement of the line sensor shown in FIG. 8B, the black correction processing is executed using the black level corresponding to the pixel in the main scanning direction of the line sensor 62 that is paired with the line sensor 61, so that more accurate black correction is performed. Can be realized.

[Effects of Embodiment 1]
As described above, the image reading apparatus 10 performs reading in synchronization with the line sensor 61 serving as the light receiving unit and the line sensor 62 serving as the light shielding unit arranged side by side in the sub-scanning direction. The read reading value is acquired as a black level, and black correction processing of the reading value read by the line sensor 61 is executed using the acquired black level. At this time, the image reading apparatus 10 uses the black level corresponding to the pixel in the main scanning direction of the line sensor 62 that has the same positional relationship as the pixel of the line sensor 61, and reads the black value of the read value read by the line sensor 61. Execute correction processing. That is, when the light source is turned on, the image reading apparatus 10 performs reading in synchronism using a line sensor having the same configuration except for the light receiving unit or the light blocking unit, and the black level at this time is corrected to black. Since it is used for processing, highly accurate black correction can be realized.

  In the image reading apparatus 10, the line sensor 61 and the line sensor 62 are alternately arranged in the sub-scanning direction, and the black level of the paired line sensor 62 is used for black correction of the read value of the line sensor 61. As a result, a more accurate black level can be obtained, and more accurate black correction can be realized.

  In addition, since the image reading apparatus 10 arranges the line sensor 62 outside the line sensor 61 arranged side by side in the sub-scanning direction, high-accuracy black correction can be realized without interfering with light reception. Can do.

(Embodiment 2)
The embodiments of the image reading apparatus 10 and the image forming apparatus 1 according to the present invention have been described so far. However, the present invention may be implemented in various different forms other than the above-described embodiments. Therefore, different embodiments of (1) black correction processing and (2) configuration will be described.

(1) Black Correction Processing In the above embodiment, the line sensor 62 acquires the black level corresponding to each pixel in the main scanning direction of the line sensor 62 and has the same positional relationship as the pixel in the main scanning direction of the line sensor 61. The case where the black correction processing of the read value read by the line sensor 61 is executed using the black level corresponding to the pixel in the main scanning direction has been described. Such black correction processing may be performed by averaging black levels corresponding to an arbitrary number of adjacent pixels in the main scanning direction of the line sensor 62 and using the black levels after the averaging processing.

  Specifically, as in the first embodiment, the acquisition unit 161 reads data by the line sensor 61 and the line sensor 62 in synchronization with the LSYNC indicating the line cycle in a state where the light source 50 and the light source 51 are turned on. The obtained read value (read value corresponding to each pixel in the main scanning direction) is acquired. Further, the black correction unit 162 takes an arbitrary number of adjacent pixels in the main scanning direction of the line sensor 61 as one area, and an arbitrary number of adjacent pixels in the main scanning direction of the line sensor 62 that have the same positional relationship as the area. The black level corresponding to the pixel is averaged. Then, the black correction unit 162 performs black correction processing of the read value read by the line sensor 61 using the black level after the averaging processing. That is, the black correction unit 162 uses the black level corresponding to the pixel of the line sensor 62 serving as the light shielding unit, which has the same positional relationship, for the black correction processing of the read value by the line sensor 61 serving as the light receiving unit. Similar to Embodiment 1, the black correction process is executed using the average value of the black levels corresponding to a plurality of pixels.

  FIG. 9 is a diagram for explaining an example of the black correction process according to the second embodiment. For example, as illustrated in FIG. 9, the black correction unit 162 assumes that the sensor chip 59 is divided into several regions (five in FIG. 9), and corresponds to an arbitrary number of pixels included in each region. Average the black level. Then, the black correction unit 162 uses the black level after the averaging process to execute a black correction process for the read value of the area of the line sensor 61 having the same positional relationship. Although FIG. 9 shows an example in which the sensor chip 59 is assumed to be divided into a plurality of regions, it is assumed that the plurality of sensor chips 59 (the entire line sensor) is divided into a plurality of regions. good. Further, since it is only necessary to average the black level corresponding to an arbitrary number of pixels, the number of pixel data included in each region may not be the same. Even in this case, the black level used in the black correction process and the read value by the line sensor 61 have the same positional relationship. A black level corresponding to an arbitrary number of adjacent pixels is averaged, and the black level is corrected using the black level after the leveling process, enabling more accurate black correction with less specific variation in pixels. Can be realized.

  In the above embodiment, the black level corresponding to an arbitrary number of adjacent pixels in the main scanning direction of the line sensor 62 is averaged, and the black correction process is executed using the black level after the averaging process. Explained. Such black correction processing may be performed using the black level after the averaging processing and the black level corresponding to each pixel.

  Specifically, in the same manner as in the first embodiment, the acquisition unit 161 uses the line sensor 61 and the line sensor 62 in synchronization with LSYNC that represents the line period in a state where the light source 50 and the light source 51 are turned on. The read reading value (read value corresponding to each pixel in the main scanning direction) is acquired. Further, the black correction unit 162 takes an arbitrary number of adjacent pixels in the main scanning direction of the line sensor 61 as one area, and an arbitrary number of adjacent pixels in the main scanning direction of the line sensor 62 that have the same positional relationship as the area. The black level corresponding to the pixel is averaged. Then, the black correction unit 162 uses the black level corresponding to the pixel in the main scanning direction of the line sensor 62 and the black level after the averaging process, which are in the same positional relationship as the pixel in the main scanning direction of the line sensor 61. Thus, black correction processing of the reading value read by the line sensor 61 is executed. That is, the black correction unit 162 performs the black correction processing of the reading value read by the line sensor 61 serving as the light receiving unit, and the black level described in the first embodiment and the averaging processing described in the second embodiment. The black correction process is executed using the subsequent black level.

  Here, the black level described in the first embodiment is referred to as a “first black level”, and the black level after the averaging process described in the second embodiment is described as a “second black level”. For example, with respect to the second black level, the distance from the first black level to the second black level is multiplied by a coefficient to correct the second black level, and then used for the black correction process. It can be derived by the following calculation formula. As a result, it is possible to realize more accurate black correction while suppressing unique variations in pixels.

Black level (n) of pixel at main scanning position n
= Second black level + k * (second black level-first black level (n))
Note that k can be set from the outside and may be variable.

(2) Configuration Information including processing procedures, control procedures, specific names, various data, parameters, and the like shown in the above documents and drawings can be arbitrarily changed unless otherwise specified. Each component of the illustrated apparatus is functionally conceptual and does not necessarily need to be physically configured as illustrated. That is, the specific form of the distribution or integration of the devices is not limited to the illustrated one, and all or a part of the distribution or integration is functionally or physically distributed or arbitrarily in any unit according to various burdens or usage conditions. Can be integrated. For example, the filters of the line sensor 61 are not limited to the three colors RGB, and any color filter may be used as long as it is not an OPB filter.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 10 Image reader 50,51 Light source 59 Sensor chip 60 Photoelectric conversion element 61 Line sensor 62 Line sensor 125 2nd reading part 161 Acquisition part 162 Black correction part

Japanese Patent No. 5652058

Claims (7)

A light source that illuminates the subject,
A first line sensor having a filter capable of receiving reflected light from the subject in response to light irradiation by the light source, as a line sensor having a photoelectric conversion element formed in the main scanning direction and having a different wavelength range for transmission; A second line sensor having a filter for blocking reflected light from the subject, and an image sensor arranged side by side in a sub-scanning direction orthogonal to the main scanning direction;
An acquisition unit that acquires a reading value read by the second line sensor as a black level in synchronization with reading by the first line sensor in a state where the light source is turned on;
An image reading apparatus comprising: a black correction unit that performs black correction processing of a read value read by the first line sensor using the acquired black level.   The image reading apparatus according to claim 1, wherein the first line sensor and the second line sensor are alternately arranged in the sub-scanning direction in the image sensor.   The image reading apparatus according to claim 1, wherein the second line sensor is arranged outside the first line sensor arranged side by side in the sub-scanning direction in the image sensor. . The acquisition unit acquires the black level corresponding to each pixel in the main scanning direction of the second line sensor,
The black correction unit is configured such that an arbitrary number of adjacent pixels in the main scanning direction of the first line sensor are defined as one area, and the adjacent position in the main scanning direction of the second line sensor has the same positional relationship as the area. 4. The black level corresponding to an arbitrary number of pixels to be averaged is processed, and the black correction processing is executed using the black level after the averaging processing. The image reading apparatus described in one. The acquisition unit acquires the black level corresponding to each pixel in the main scanning direction of the second line sensor,
The black correction unit uses the black level corresponding to the pixel in the main scanning direction of the second line sensor, which is in the same positional relationship as the pixel in the main scanning direction of the first line sensor, to perform the black correction. The image reading apparatus according to claim 1, wherein the process is executed. The acquisition unit acquires the black level corresponding to each pixel in the main scanning direction of the second line sensor,
The black correction unit is configured such that an arbitrary number of adjacent pixels in the main scanning direction of the first line sensor are defined as one area, and the adjacent position in the main scanning direction of the second line sensor has the same positional relationship as the area. The black level corresponding to an arbitrary number of pixels is averaged and corresponds to the pixels in the main scanning direction of the second line sensor that have the same positional relationship as the pixels in the main scanning direction of the first line sensor. The image reading apparatus according to claim 1, wherein the black correction process is executed using the black level to be performed and the black level after the averaging process. An image reading apparatus according to any one of claims 1 to 6,
An image forming apparatus comprising: an image forming unit that forms an image based on an output of the image reading apparatus.