JP2013005176A - Image reading device, image formation device and line image sensor control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate a difference in concentration in a wide reading device due to variation in paper by using a simple configuration.SOLUTION: In an image reading device, a plurality of CISs 3 are arranged in zigzag form to configure a reading unit in such a way that their end parts in the main scanning direction overlap in the sub-scanning direction. The image reading device includes: a level calculator 404 which extracts the signal level of a read signal in a section where the respective CISs 3 overlap every main scanning line; a gain calculator 405 which calculates a correction value with which to correct a read signal on one side of the respective read signals of two adjacent CISs 3 out of the plurality of CISs 3 arranged in zigzag form so that the extracted signal levels in the overlapping section of the respective read signals will become the same; and an effective region level corrector 403 which corrects a read signal on one side of the respective read signals of two adjacent CISs 3 on the basis of the calculated correction value.

Description

  The present invention relates to an image reading apparatus, an image forming apparatus, and a control method for a line image sensor, and more particularly to processing of a boundary portion of a read signal of line image sensors arranged in a staggered pattern.

  In recent years, there has been a tendency to digitize information, and image processing apparatuses such as printers and facsimiles used for outputting digitized information and scanners used for digitizing documents have become indispensable devices. Such an image processing apparatus is often configured as a multifunction machine that can be used as a printer, a facsimile, a scanner, or a copier by providing an imaging function, an image forming function, a communication function, and the like.

  Among such image processing apparatuses, as one aspect of a scanner used for digitizing information, there is a wide image reading apparatus such as A0 size. Some wide-width image reading apparatuses enable wide-width reading by arranging a plurality of A4 size line image sensors in a staggered manner in the main scanning direction for cost reduction.

  In a wide size paper such as A0 size, there is a problem of paper fluttering that the paper surface undulates depending on the position on the paper surface. For example, as described above, in the case of a configuration in which a plurality of line image sensors of A4 size or the like are arranged in a staggered manner in the main scanning direction, the positions of the line image sensors in the sub scanning direction are different. There may be a difference in the document height at the reading position of the line image sensor. As a result, in reading on the same main scanning line, a reading density difference occurs depending on the position in the main scanning direction, and the density difference becomes conspicuous at the boundary of the line image sensor.

  In order to solve such a problem, a document height detection sensor for detecting the distance between the document and the line image sensor is provided in the vicinity of each line image sensor arranged in a staggered pattern, and each line is detected according to the detected distance. There has been proposed a technique for making the difference in density at the boundary inconspicuous by controlling the light source lighting time of the image sensor (see, for example, Patent Document 1).

  However, in the case of the technique disclosed in Patent Document 1, there are problems such as an increase in the size and cost of the apparatus due to the provision of the document height detection sensor, and complicated control associated with the control of the light source lighting time.

  The present invention has been made in consideration of the above situation, and an object of the present invention is to eliminate a density difference due to paper fluttering with a simple configuration in a wide reading apparatus.

  In order to solve the above-described problem, according to one aspect of the present invention, there is provided a reading unit in which a plurality of line image sensors are arranged in a staggered manner so that end portions in the main scanning direction overlap in the sub-scanning direction; A level extraction unit for extracting a signal level of a read signal in an overlapping portion of each of the line image sensors for each main scanning line; and two adjacently arranged among the plurality of line image sensors arranged in a staggered manner A correction value calculation unit that calculates a correction value for correcting one of the read signals of each of the two line image sensors so that the signal level in the extracted overlapping portion is the same for the read signal of each of the line image sensors; Based on the calculated correction value, one of the read signals of each of the two line image sensors is obtained. Characterized in that it comprises a positive signal correcting unit.

  According to another aspect of the present invention, there is provided an image forming apparatus including the above-described image reading apparatus.

  Another aspect of the present invention is a method for controlling a plurality of line image sensors arranged in a staggered manner so that ends in the main scanning direction overlap in the sub-scanning direction in the image reading apparatus. The signal level of the read signal in the overlapping portion of each line image sensor is extracted every time, and the read signal of each of the two line image sensors arranged adjacent to each other among the plurality of line image sensors arranged in a staggered pattern A correction value for correcting one of the read signals of each of the two line image sensors is calculated so that the signal level in the extracted overlapping portion is the same, and based on the calculated correction value, the 2 One of the read signals of each of the two line image sensors is corrected.

  According to the present invention, in a wide reading apparatus, it is possible to eliminate a density difference due to paper flutter with a simple configuration.

1 is a diagram illustrating an overall configuration of an image reading apparatus according to an embodiment of the present invention. It is a figure which shows the structure of CIS which concerns on embodiment of this invention. It is a figure which shows the example of the read signal which concerns on embodiment of this invention. It is a figure which shows the structure of the CIS controller which concerns on embodiment of this invention. It is a figure which shows operation | movement of the CIS controller which concerns on embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In this embodiment, a wide image reading apparatus corresponding to the A0 size will be described as an example. Note that the present invention can be realized not only as an image reading apparatus but also as a copying machine including a wide image reading apparatus, that is, an image forming apparatus.

  FIG. 1 is a diagram illustrating an overall configuration of an image reading apparatus 100 according to the present embodiment. As shown in FIG. 1, the image reading apparatus 1 according to the present embodiment includes an upper cover 1, a contact glass 2, a CIS (Contact Image Sensor) 3, a CIS controller 4, and a main controller 5.

  The cover 1 is arranged on the upper part of the contact glass 2 that supports the document S, and prevents external light from affecting the reading of the document S. The document S is conveyed between the contact glass 2 and the cover 1 in principle in contact with the contact glass 2. However, a gap is provided between the contact glass 2 and the cover 1, and the original S may flutter up and down as shown in FIG. The gist of the present embodiment is to avoid the deterioration of the read image due to the flutter.

  The CIS 3 is a line image sensor that captures an image of the document S conveyed in close contact with the contact glass 2. The CIS 3 is arranged in a staggered pattern alternately on the upstream side and the downstream side in the document conveyance direction, thereby forming a reading unit that reads an image over the entire main scanning direction. In the image reading apparatus 1 according to the present embodiment, a plurality of A4 size CISs 3 are arranged to support A0 size reading.

  The CIS 3 arranged on the upstream side and the CIS 3 arranged on the downstream side image the same main scanning line by controlling the imaging timing according to the conveyance of the document S, but the upstream CIS 3 and the downstream side When the paper flutters with the CIS3, there is a difference between the document height when reading with the upstream CIS3 and the document height when reading with the downstream CIS3. Due to the difference in brightness due to the depth characteristics, a density difference occurs between read signals by different CISs. The gist of the present embodiment is to eliminate such problems.

  The CIS controller 4 controls reading of a document by the CIS 3 and processes a read signal by the CIS 3 to output image information. At this time, the CIS controller 4 adjusts the gain of the read signal based on the read signal output from each CIS 3, and adjusts the above-described density difference between the CISs. Details of the CIS controller 4 will be described later.

  The main controller 5 acquires the image information output from the CIS controller 4 and executes processing according to the application of the apparatus. In the case of the image reading apparatus 1, the main controller 5 stores the image information output from the CIS controller 4 in a storage medium. In the case of a copying machine, the main controller 5 controls the execution of image formation output based on the image information acquired from the CIS controller 4.

  Next, the CIS 3 according to this embodiment will be described with reference to FIGS. FIGS. 2A and 2B are views showing a state where the CIS 3 according to the present embodiment is viewed from the information in FIG. As shown in FIG. 2A, the CIS 3 according to the present embodiment is staggered so that the first CIS 3a, the second CIS 3b, the third CIS 3c, the fourth CIS 3d, and the fifth CIS 3e overlap each other in the sub-scanning direction, that is, the document conveyance direction. Are arranged in a shape. By providing the overlapping portion in this way, it is possible to avoid the occurrence of image omission when there is a gap due to assembly variation of the CIS or a temperature change.

  FIG. 2B is a diagram showing the invalid area in each CIS 3 by hatching. In the case of the first CIS 3a, invalid areas 3a-1 and 3a-2 are set at both ends in the main scanning direction, and the other parts are used as effective areas. By connecting the effective areas in each CIS 3, the CIS 3 is arranged in the entire main scanning direction, and an image without omission can be obtained. In other words, the read signal based on the effective area in the CIS 3 is used for generating a read image.

  Here, FIG. 3A shows an example of reading signals by the first CIS 3a to the fifth CIS 3e when the paper flutters as shown in FIG. In FIG. 3A, the read signals in one main scanning line from the first CIS 3a to the fifth CIS 3e are shown as the read signal Sa to the read signal Se, respectively.

  As shown in FIG. 3A, when the document height differs at each CIS3 reading position, the signal levels from the reading signal Sa to the reading signal Se of each CIS are not continuous. For example, the portion where the read signal Sa and the read signal Sb overlap, that is, the overlapping region Pab specified by the invalid regions 3a-2 and 3b-1, is the same portion to be read. Should be the same. However, there is a difference in the read signal level due to document flutter.

  Similarly, both ends in the main scanning direction of each reading signal should match the reading signals by the adjacent CIS3, but when the document flutters, the signal level differs as shown in FIG. As a result, the signal levels at both ends in the main scanning direction of the respective read signals do not match.

  In order to deal with such a problem, in the image reading apparatus 100 according to the present embodiment, the reading signal Sc based on the third CIS 3c is used as a reference, and the signal level of the reading signal Sc as shown in FIG. The signal levels of the read signals Sb and Sd of the second CIS 3b and the fourth CIS 3d are matched. Further, the signal level of the read signal Sa of the first CIS 3a is matched with the signal level of the read signal Sb after the signal level correction. Similarly, the signal level of the read signal Se of the fifth CIS 3e is matched with the signal level of the read signal Sd after the signal level correction.

  For example, in the case of the reading signal Sc and the reading signal Sb, a portion where the reading range overlaps in the sub-scanning direction like the overlapping region Pbc indicated by the invalid regions 3b-2 and 3c-1 shown in FIG. And the signal level of the read signal Sb is increased or decreased based on the ratio of the extracted signal levels. Further, in the case of the reading signal Sb and the reading signal Sa, a portion where the reading range overlaps in the sub-scanning direction as in the overlapping area Pab indicated by the invalid areas 3a-2 and 3b-1 shown in FIG. Extract the signal level. At this time, for the read signal Sb, the signal level of the read signal Sb resulting from the increase / decrease is extracted. Then, similarly to the above, the signal level of the read signal Sa is increased or decreased based on the ratio of the extracted signal levels.

  The same processing is performed for the read signals Sd and Se. By such processing, as shown by a solid line in FIG. 3B, the read signal of the image on one main scanning line is corrected to a continuous state without causing a difference in signal level at the boundary portion of CIS3. Is done. The gist of the present embodiment is that the CIS controller 4 that controls the CIS 3 and processes the read signal by the CIS 3 executes such processing.

  Next, the configuration of the CIS controller 4 according to the present embodiment will be described with reference to FIG. FIG. 4 is a block diagram showing the configuration of the CIS controller 4 and the connection relationship with the CIS 3 according to the present embodiment. As shown in FIG. 4, the CIS controller 4 includes processing blocks 400a to 400e (hereinafter collectively referred to as processing blocks 400) corresponding to each of the first CIS 3a to the fifth CIS 3e, and readings processed in the respective processing unit blocks 400. A memory 410 that stores signals, and an image processing unit 420 that performs image processing on read signals stored in the memory 410 and outputs image information.

  4, each processing block 400 includes preprocessing circuits 401a to 401e (hereinafter collectively referred to as preprocessing circuit 401), line alignment memories 402a to 402e (hereinafter generally referred to as line alignment memory 402). And level calculators 404a to 404e (hereinafter collectively referred to as level calculator 404).

  The processing blocks 400 other than the processing block 400c include effective area level correctors 403a, 403b, 403d, and 403e (hereinafter collectively referred to as effective area level correctors 403) and gain calculators 405a, 405b, 405d, and 405e (hereinafter referred to as “effective area level correctors”). In general, the gain calculator 405 is included. The processing block 400c is a processing block corresponding to the third CIS 3c. As described above, since the read signal Sc of the third CIS 3c is a reference signal and is not corrected for increase / decrease, the effective area level corrector and the gain calculator are Not provided.

  The pre-processing circuit 401 is a circuit that executes processing performed by a general image reading apparatus or the like using one CIS, and makes the image signal level uniform when the light source for correcting the black side is turned off. Dark output correction, shading correction for correcting unevenness in the light amount of the light source, condensing unevenness of the lens, sensitivity variation for each pixel of the line image sensor, and the like are performed.

  The line alignment memory 402 temporarily holds the read signal processed by the preprocessing circuit 401 so that the read signal of the same main scanning line is simultaneously output in the read signals by the CISs arranged in a staggered manner. .

  As described with reference to FIGS. 3A and 3B, the level calculator 404 matches the signal level of the read signal by each CIS 3, so that the average value of the signal level of the read signal in the overlapping region with the adjacent CIS 3 Is a level extraction unit that extracts the signal level of the overlapping portion by calculating. For example, in the case of the level calculator 404a corresponding to the first CIS 3a, the average value of the signal levels of the overlapping area Pab of the read signal Sa shown in FIG. In the case of the level calculator 404b corresponding to the second CIS 3b, the average value of the signal levels of the overlapping regions Pab and Pbc of the read signal Sb shown in FIG.

  Note that, as in the level calculator 404 according to the present embodiment, by calculating the average value of the signal levels in the overlapping region and extracting the signal level, it is possible to reduce false detection due to signal noise. It is also possible to use the peak level of the read signal in the overlapping region. In this case, the signal level is adjusted in the brightest part, so that the background level of the most original can be adjusted.

The gain calculator 405 is a correction value calculator that calculates a correction value for increasing or decreasing each read signal based on the ratio of the signal level of the read signal by each CIS 3 extracted by the level calculator 404. For example, in the case of the gain calculator 405b corresponding to the second CIS 3b, Sc-bc is the signal level average value of the read signal Sc in the overlap area Pbc calculated by the level calculator 404c, and the overlap area Pbc is calculated by the level calculator 404b. Assuming that the average value of the signal level of the read signal Sb at Sb−bc, a gain value GSb for increasing or decreasing the read signal Sb is calculated by the following equation (1).

Further, in the case of the gain calculator 405a corresponding to the first CIS 3a, Sc-bc is the signal level average value of the read signal Sc in the overlap area Pbc calculated by the level calculator 404c, and the overlap area Pbc is calculated by the level calculator 404b. , Sb−bc and Sb−ab are average signal level values of the read signal Sb in Pab, and Sa−ab is a signal level average value of the read signal Sa in the overlapping area Pab calculated by the level calculator 404a. The gain value GSa for increasing / decreasing is calculated by the following equation (2).

  The above formula (2) includes the right side of the above formula (1). That is, the expression (2) extracts the signal level of the read signal Sb as a result of the increase / decrease of the read signal Sb, and calculates the ratio between the signal level of the overlapping area Pab of the Sb and the signal level of the overlapping area Pab of Sa. Equivalent to seeking.

In the case of the gain calculator 405d corresponding to the fourth CIS 3d, the average signal level of the read signal Sc in the overlapping region Pcd calculated by the level calculator 404c is Sc-cd, and the reading in the overlapping region Pcd calculated by the level calculator 404d is performed. When the average value of the signal level of the signal Sd is Sd-cd, a gain value GSd for increasing / decreasing the read signal Sd is calculated by the following equation (2).

In the case of the gain calculator 405e corresponding to the fifth CIS 3e, the average signal level of the read signal Sc in the overlap area Pcd calculated by the level calculator 404c is Sc-cd, and the overlap area Pcd calculated by the level calculator 404d. , Sd−cd and Sd−de are average signal level values of the read signal Sd at Pde, and Se−de is an average signal level value of the read signal Se in the overlapping region Pde calculated by the level calculator 404e. The gain value GSe for increasing / decreasing is calculated by the following equation (4).

  In addition, the said Formula (4) contains the right side of the said Formula (3) similarly to the said Formula (2). That is, the expression (4) extracts the signal level of the read signal Sd as a result of the increase / decrease of the read signal Sd, and calculates the ratio between the signal level of the overlap region Pde of the Sd and the signal level of the overlap region Pde of Se. Equivalent to seeking.

  The effective area level corrector 403 uses the gain value calculated in each processing block 400 to correct by increasing / decreasing the read signal stored in the line alignment memory 402 of each processing block 400, and stores it in the memory 410. A signal correction unit for storing. In the present embodiment, the effective area level corrector 403 is calculated based on the signal level of the read signal stored in the memory 402 in order to obtain the gain value in the manner shown in the above formulas (1) to (4). The signal level is increased or decreased by multiplying the gain value.

  In the memory 410 according to the present embodiment, a storage area is set for each main scanning line, and the memory 410 stores the read signal after the effective area level corrector 403 of each processing block 400 increases or decreases the signal level. The storage area of the memory 410 in which the read signal is stored in the storage area and the line alignment memory 402c are determined in advance so that the respective read signals are arranged in order on the main scanning line. Thus, the read signals processed by the processing blocks 400a to 400e are stored in the memory 410 for each main scanning line.

  The image processing unit 420 performs from image processing such as MTF correction, γ correction, image area separation, etc. to binarization processing on image information generated by storing a read signal for each main scanning line in the memory 410. And output to the main controller 5.

  Next, the operation of the CIS controller 4 according to the present embodiment will be described with reference to FIG. In FIG. 5, the operation of the processing blocks 400c, 400d, and 400e corresponding to the third CIS 3c, the fourth CIS 3d, and the fifth CIS 3e will be described. The operation of the processing block 400d corresponds to the processing block 400b, and the operation of the processing block 400e is the processing block. Corresponds to block 400a.

  As shown in FIG. 5, in the processing block 400c corresponding to the third CIS 3c, the preprocessing circuit 401c performs preprocessing (S501), and stores the processed read signal Sc in the line alignment memory 402c (S502). When the read signal Sc is stored in the line alignment memory 402c, the level calculator 404c calculates the signal level average values Sc-bc and Sc-cd of the overlapping areas Pbc and Pcd shown in FIG. 3 (S503). The level calculator 404c outputs Sc-cd among the calculated signal level average values to the gain calculator 405d and the gain calculator 405e. Further, the line alignment memory 402c stores the signal of the effective area of the stored read signal Sc at a predetermined main scanning direction address of the memory 410 (S510).

  In the processing block 400d corresponding to the fourth CIS 3d, the preprocessing circuit 401d executes preprocessing (S504), and stores the processed read signal Sd in the line alignment memory 402d (S505). When the read signal Sd is stored in the line alignment memory 402d, the level calculator 404d calculates the signal level average values Sd-cd and Sd-de of the overlapping regions Pcd and Pde shown in FIG. 3 (S506). The level calculator 404d outputs the calculated signal level average value to the gain calculator 405d and the gain calculator 405e.

  The gain calculator 405d that has acquired the average signal level from the signal level calculators 404c and 404d calculates the gain value GSd for increasing or decreasing the read signal Sd based on the above equation (3) (S511), and the effective region level. Input to the corrector 403d. The effective area level corrector 403d that has acquired the gain value corrects the read signal level of the effective area by multiplying the calculated gain value GSd by the signal level of the read signal Sd, and the corrected read signal is stored in the memory 410 in advance. Store in the determined main scanning direction address (512).

  In the processing block 400e corresponding to the fifth CIS 3e, the preprocessing circuit 401e performs preprocessing (S507), and stores the processed read signal Se in the line alignment memory 402e (S508). When the read signal Se is stored in the line alignment memory 402e, the level calculator 404e calculates the signal level average value Se-de of the overlapping region Pde shown in FIG. 3 (S509). The level calculator 404e outputs the calculated signal level average value to the gain calculator 405e.

  The gain calculator 405e that has acquired the average signal level value from the signal level calculators 404c, 404d, and 404e calculates a gain value GSe for increasing or decreasing the read signal Se based on the above equation (4) (S513), and is effective. This is input to the area level corrector 403e. The effective region level corrector 403e that has acquired the gain value corrects the read signal level of the effective region by multiplying the calculated gain value GSe by the signal level of the read signal Se, and the corrected read signal is stored in advance in the memory 410. The data is stored in the determined main scanning direction address (514).

  When the processing up to S514 is completed, the same processing is executed in the processing blocks 400a and 400b, and the read signal corresponding to one main scanning line is stored in the memory 410, the image processing unit 420 is in the memory 410 described above. Are subjected to various image processing and output as image information (S515).

  As described above, in the CIS controller 4 according to the present embodiment, the signal levels of the overlapping regions where the signal levels of the read signals should originally match are compared between the two read signals of the CIS 3 that are arranged in the sub-scanning direction. By doing so, a gain value for increasing or decreasing one of the signal levels is obtained. By correcting one of the signal levels using the gain value thus determined, it is possible to correct the signal level mismatch caused by the paper fluttering and eliminate the density fluctuation of the image.

  As described above, in this embodiment, it is not necessary to provide a sensor for detecting the document height, and the wide reading apparatus can eliminate the density difference due to paper flutter with a simple configuration. It becomes possible.

  In the above embodiment, as shown in the equations (1) to (4), the ratio of the signal level average value in the overlapping region is obtained as a gain value, and the gain value thus obtained is multiplied by the signal level. Was described as an example. In addition, for example, a signal level can be corrected by obtaining a difference between signal level average values of overlapping regions as a correction value and adding the correction value thus obtained to the signal level.

  In the above embodiment, the case where the five CISs 3 are arranged in a zigzag manner and the signal level of the center third CIS 3c is used as a reference, that is, the case where the center CIS 3 is used as a reference line image sensor has been described as an example. Therefore, the gain values that are correction values of the read signal Sb of the second CIS 3b and the read signal Sd of the fourth CIS 3d are the signal levels and the read signals of the read signals Sb and Sd, respectively, as in the above formulas (1) and (3). Calculation is based on the ratio of Sc to the signal level. The gain values, which are correction values of the read signal Sa of the first CIS 3a and the read signal Se of the fifth CIS 3e, are the signal levels of the read signals Sb and Sd and the read signal Sc as in the above formulas (2) and (4). In addition to the ratio to the signal level, the calculation is performed based on the ratio between the signal level of each of the read signals Sb and Sd and the signal level of each of the read signals Sa and Se.

  On the other hand, when the CIS 3 other than the center, for example, the read signal 3a of the first CIS 3a is used as a reference, the gain value, which is the correction value of the read signal Sb of the second CIS 3b, is the ratio of the read signal Sa and the read signal Sb. Calculate based on. The gain value that is the correction value of the read signal Sc of the third CIS 3c is calculated based on the signal level ratio between the read signal Sb and the read signal Sc in addition to the signal level ratio between the read signal Sa and the read signal Sb. .

  The gain value, which is the correction value of the read signal Sd of the fourth CIS 3d, is the ratio of the signal level between the read signal Sa and the read signal Sb, the ratio of the signal level between the read signal Sb and the read signal Sc, and the read signal Sc. Calculation is based on the ratio of the signal level to the read signal Sd. Thus, when the CIS 3 other than the center is used as a reference, the amount of calculation increases as compared with the case where the center CIS 3 is used as a reference. Accordingly, it is preferable to use the reading signal of the central CIS 3 among the plurality of CISs 3 arranged in a staggered manner as a reference because the calculation amount can be minimized.

  In the above embodiment, the effective area level corrector 403 corrects the signal level of the effective area reading signal among the CIS3 reading signals stored in the visit registration memory 402 as the name suggests. The case of storing in the above has been described as an example. As a result, an extra signal level correction process can be omitted and the processing load can be reduced.

  However, depending on how the image signals are connected in the reading unit in which a plurality of CISs 3 are arranged in a staggered manner, the image signals in the invalid area in FIG. 2B may also be used. In such a case, the signal levels of all read signals are corrected regardless of the valid area and invalid area.

  In the above embodiment, the description has been made without considering the color difference in image reading. For example, in the case of a full-color image reading apparatus, CIS 3 arranged in a staggered manner is provided for each of RGB colors. In such a case, it is preferable to execute a process as shown in FIG. 5 for any one color of RGB to obtain a gain value and apply the gain value to other colors. As a result, the same gain value is applied to all colors, and density correction can be performed without changing the color.

  Further, the CIS controller 4 as shown in FIG. 4 is realized by, for example, a chip integrated circuit. In addition, it can be realized by software. In this case, a program for realizing each functional block shown in FIG. 4 is loaded into a storage medium such as a RAM (Random Access Memory), and an arithmetic unit such as a CPU (Central Processing Unit) is loaded as described above. By performing the calculation according to the program, it can be realized in the same manner as described above, and the same effect can be obtained.

1 Upper cover 2 Contact glass 3 CIS
4 CIS controller 5 Main controller 400 Processing block 401 Preprocessing circuit 402 Line alignment memory 403 Effective area level corrector 404 Level calculator 405 Gain calculator 410 Memory 420 Image processing unit

JP 2008-205726 A

Claims (9)

A plurality of line image sensors, a reading unit configured to be arranged in a staggered manner so that ends in the main scanning direction overlap in the sub scanning direction;
A level extractor for extracting a signal level of a read signal in an overlapping portion of each line image sensor for each main scanning line;
Two line images so that the signal levels in the extracted overlapping portions are the same for the read signals of two line image sensors arranged adjacent to each other among the plurality of line image sensors arranged in a staggered pattern. A correction value calculation unit for calculating a correction value for correcting one of the reading signals of each sensor;
An image reading apparatus comprising: a signal correction unit that corrects one of the read signals of each of the two line image sensors based on the calculated correction value.   The image reading apparatus according to claim 1, wherein the signal correcting unit corrects a reading signal of an effective area used for a reading image among reading signals of the line image sensor. The correction value calculation unit uses a read signal level of a predetermined reference line image sensor among the plurality of line image sensors as a reference value,
The signal level in the extracted overlap portion for the read signal of the adjacent line image sensor arranged adjacent to the reference line image sensor is the signal level in the extracted overlap portion for the read signal of the reference line image sensor. Calculate a correction value for correcting the read signal of the adjacent line image sensor so as to be the same,
The signal level of the extracted overlapping portion of the read signal of the secondary adjacent line image sensor arranged further adjacent to the adjacent line image sensor is corrected by the calculated correction value. The correction value for correcting the read signal of the secondary adjacent line image sensor is calculated so that the read signal becomes the same as the signal level in the extracted overlapping portion. The image reading apparatus described.   The image reading apparatus according to claim 3, wherein a line image sensor arranged at a center in a main scanning direction among the plurality of line image sensors is used as the reference line image sensor.   5. The image reading apparatus according to claim 1, wherein the level extraction unit extracts an average value of signal levels of read signals in the overlapping portion.   5. The image reading apparatus according to claim 1, wherein the level extraction unit extracts a peak value of a signal level of a reading signal in the overlapping portion. The reading unit is configured by staggering the plurality of line image sensors for a plurality of different colors,
The signal correction unit corrects read signals of line image sensors of a plurality of other colors using the correction value calculated based on a read signal of a line image sensor of one color. 7. The image reading apparatus according to any one of items 6 to 6.   An image forming apparatus comprising the image reading apparatus according to claim 1. In the image reading apparatus, a method for controlling a plurality of line image sensors arranged in a staggered manner so that ends in the main scanning direction overlap in the sub-scanning direction,
Extracting the signal level of the read signal in the overlapping part of each line image sensor for each main scanning line,
Two line images so that the signal levels in the extracted overlapping portions are the same for the read signals of two line image sensors arranged adjacent to each other among the plurality of line image sensors arranged in a staggered pattern. Calculate a correction value to correct one of the reading signals of each sensor,
A line image sensor control method, wherein one of the read signals of each of the two line image sensors is corrected based on the calculated correction value.

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