JP6508573B2 - Image reader - Google Patents

Description

  The present invention relates to an image reading apparatus.

  2. Description of the Related Art Conventionally, there is an image reading apparatus that reads an image of a document using a line sensor in which light receiving elements arranged in one row are divided into a plurality of blocks. The image reading apparatus acquires black data for black correction before reading an image of a document, and executes black correction using the acquired black data. When light from the outside of the image reading device (hereinafter referred to as "external light") enters the light receiving element when the image reading device acquires black data, the black data changes due to the influence of the external light. Black correction could not be performed.

  The image reading apparatus described in Patent Document 1 updates black data by determining the presence or absence of external light. Specifically, the image reading apparatus determines the presence or absence of external light for each block of a plurality of light receiving elements arranged in a line in the black data update process, and black data for a block having no external light. , And black data is not updated for blocks having external light.

JP, 2013-150175, A

  However, if the temporal conditions such as the temperature of the light receiving element change due to the temperature characteristics of the light receiving element, the black data also changes. Therefore, as in Patent Document 1, when black data at different acquisition times exist, there arises a problem that the black data is changed.

  Therefore, the present invention is made in view of the above-described circumstances, and black data is updated for light receiving elements without external light, and black correction is performed using accurate black data even when black data is not updated for light receiving elements with external light. It is an object of the present invention to provide an image reading apparatus capable of

  In order to achieve the above object, in the aspect of the invention according to claim 1, the image reading apparatus has a light source and a large number of light receiving elements arranged in one line, and a reading unit which lights and reads the light source; A cover that can be opened and closed in a closed state covering the reading unit and an open state opening the reading unit; a correction unit that performs black correction on a value read by the reading unit based on correction data; And a control unit that executes an execution process after the preparation process is performed. The preparation process is performed by turning off the light source and reading the light from the reading unit while the cover is closed. The first black data acquisition process for acquiring first black data of each light receiving element, and the execution process is performed by turning off the light source and reading by the reading unit while the cover is open. 2nd Black Day A second black data acquisition process of acquiring the second black data, a determination process of determining whether or not outside light is incident on the light receiving elements based on the second black data, and it is determined that the outside light is not incident Adjustment data calculation processing for calculating black adjustment data based on the second black data and the first black data in each light receiving element, and the first black data for each light receiving element determined to be incident with external light Third black data calculation processing for calculating third black data based on the black adjustment data, and the third black data is determined as the correction data in each of the light receiving elements determined that the outside light is incident; Correction data determination processing for determining the second black data as the correction data in each light receiving element determined that external light is not incident, reading an image of a document, and performing black correction based on the correction data Including a reading process, the.

  In the specific aspect according to claim 2, the multiple light receiving elements of the reading unit are divided into a plurality of groups, and in the determination processing, the group in which the outside light is incident in each of the plurality of groups And a first determination process of determining a group to which the outside light is not incident as the outside light-free group, and a light receiving element to which the outside light is incident in each light receiving element of the outside light existing group. The adjustment data calculation processing includes subtracting the first black data from the second black data in all the light receiving elements of the non-external light group; The black adjustment data is calculated by averaging all values calculated by subtraction at each light receiving element, and the third black data calculation process adds the black adjustment data to the first black data to calculate the black adjustment data. 3 to calculate the black data.

  In the specific aspect according to claim 3, each group of the plurality of groups is configured by the light receiving element having the same output characteristic, and the first determination process is performed by detecting a plurality of light received in each group of the plurality of groups. The smallest value is subtracted from the largest value of the second black data of the element, and if the subtracted value exceeds a predetermined first threshold, the group is determined to be the outside light present group.

  In the specific aspect according to claim 4, the determination processing is a continuous group group determination processing of determining a group group of all the groups to which the outside light present group is adjacent as a continuous group group, and the continuous group group And a detail group determination process of determining the first group and the last group as the detail group, and the second determination process determines the extraneous light presence pixels in the extraneous light group which is the detailed group. The ambient light presence pixel is not determined in the ambient light presence group that is not the detail group.

  The specific process according to claim 5, wherein the preparation process includes an averaging process of calculating first group black average values by averaging first black data of all light receiving elements of each of the plurality of groups. The execution process includes a second threshold value calculation process of calculating a second threshold value by adding the black adjustment data to the group black average value and adding a predetermined predetermined value to the added value. In the second judgment process, when the second black data exceeds the second threshold in each light receiving element of the detail group, it is determined that the external light is incident in the light receiving element.

  In the aspect of the invention according to claim 1, the preparation process includes a first black data acquisition process of acquiring the first black data of each light receiving element by turning off the light source and reading by the reading unit when the cover is closed. The execution process includes a second black data acquisition process for acquiring second black data of each light receiving element by turning off the light source and reading by the reading unit with the cover open, and external light based on the second black data. Determination processing for determining whether or not light is incident on each light receiving element, and black adjustment data is calculated based on the second black data and the first black data in each light receiving element determined that external light is not incident Adjustment data calculation processing, third black data calculation processing for calculating third black data based on the first black data and the black adjustment data in each light receiving element determined to have the outside light incident, and the outside light Is judged to be incident Correction data determination processing in which the third black data is determined as correction data in each light receiving element, and the second black data is determined as correction data in each light receiving element determined as having no external light incident, and an image of the document And a reading process for performing black correction based on the correction data. Therefore, even when the second black data changes with respect to the first black data, black correction can be performed using the correct third black data.

  According to a specific aspect of the present invention, in each of the plurality of groups, the determination processing determines that the group into which the external light is incident is the group with external light, and the group into which the external light is not incident is no external light The adjustment data calculation process includes a first determination process of determining a group and a second determination process of determining a light receiving element on which external light is incident in each light receiving element of an external light group as an external light presence pixel. The black adjustment data is calculated by subtracting the first black data from the second black data in all the light receiving elements of the non-light group and averaging all the values calculated by subtraction at each light receiving element The black data calculation process calculates third black data by adding black adjustment data to the first black data. Therefore, it is possible to judge the incident of the external light faster than the judgment of the incident of the external light to all the light receiving elements, and calculate the black adjustment data with high accuracy even for the black data which is easily fluctuated. And accurate third black data can be calculated.

  In the specific aspect according to claim 3, each group of the plurality of groups is configured by the light receiving element having the same output characteristic, and the first determination processing is performed by using the second of the plurality of light receiving elements in each group of the plurality of groups. Among the black data, the smallest value is subtracted from the largest value, and if the subtracted value exceeds a first predetermined threshold, it is determined that the group is a group with external light. Therefore, in each group, the fluctuation of the black data becomes small, and the small fluctuation can be used to judge the incident of the external light with high accuracy.

  In the specific aspect according to claim 4, the determination process is a continuous group group determination process of determining the group group of all the groups to which the external light exist group is adjacent as the continuous group group, and the head of the continuous group group. The second determination process includes a detailed group determination process of determining the group and the final group as the detailed group, and the second determination process determines the extraneous light presence pixels in the extraneous light group that is the detailed group, and the extraneous light is not the detailed group Do not judge the pixel with ambient light in the group. Therefore, since only the head group and the final group determine the outside light presence pixels, it is possible to determine the outside light presence pixels faster.

  According to a specific aspect of the present invention, the preparation process includes an averaging process of calculating the group black average value by averaging the first black data of all light receiving elements of each group of a plurality of groups, and the execution process The second determination process includes a second threshold value calculation process of calculating a second threshold value by adding the black adjustment data to the group black average value and adding a predetermined predetermined value to the added value. If the second black data exceeds the second threshold in each light receiving element of the group, it is determined that the external light is incident on the light receiving element. Therefore, since the second threshold is calculated using the first black data without incidence of external light and the black adjustment data which is the change of black data from the first black data to the second black data, the accuracy is high. The incidence of ambient light can be determined.

It is drawing which shows the internal structure of image reader SM which concerns on embodiment of this invention. FIG. 5 is a top view of a document placement table DT. FIG. 2 is a block diagram showing a configuration of a light receiving unit 22 of the reading unit 20. FIG. 2 is a block diagram showing an electrical configuration of an image reading device SM. It is a flow chart which shows maintenance main processing. It is a flow chart which shows reading main processing. It is a flowchart which shows 2nd black data BK2 substitution process R7. It is a flow chart which shows substitution black data RPBK calculation processing RA7. It is a figure explaining start detail chip SCB and end detail chip ECB. It is a figure explaining start pixel position SCP and end pixel position ECP.

<Configuration of Image Reading Device SM>
FIG. 1A shows a front view of the image reading apparatus SM. The image reading apparatus SM includes a document placement table DT and a cover CV. The document placement table DT includes a main body MB and a transparent plate TP. The main body MB is a housing for housing various members (for example, the transparent plate TP, the reading unit 20, and the like). The transparent plate TP is accommodated in the main body MB and fixed to the main body MB. A document to be read is placed on the transparent plate TP. The cover CV is disposed on the top of the main body MB and can be opened and closed with respect to the main body MB. The cover CV has a rotation axis on the back side of the main body MB (the back side in the direction perpendicular to the sheet of FIG. 1A, the upper side of FIG. 1B), and the front side of the body MB (in the direction perpendicular to the sheet of FIG. Opening and closing).

  The image reading device SM further includes a reading unit 20 accommodated in the main body MB below the transparent plate TP. The reading unit 20 is movable along the sub scanning direction (that is, the left and right direction in FIG. 1A) with respect to the main body MB. The reading unit 20 reads an original placed on the transparent plate TP. The reading unit 20 is configured by a CIS (abbreviation for Contact Image Sensor), and specifically includes a light source 21, a rod lens 24, and a light receiving unit 22. The light source 21 is composed of red, blue, and green light emitting diodes, and emits light toward the transparent plate TP. The rod lens 24 receives the reflected light of the light emitted from the light source 21.

  In FIG. 2, the light receiving unit 22 has 16 sensor IC chips CH1 to CH16 arranged linearly in the main scanning direction, and each sensor IC chip CH has a large number of photoelectric conversions arranged in the main scanning direction. It includes an element 23 and incorporates a shift register and an amplifier (not shown). The top pixel is the pixel at the end not adjacent to the sensor IC chip CH in the sensor IC chip CH1, and the final pixel is the side not adjacent to the sensor IC chip CH in the sensor IC chip CH16. It is a pixel at the end. That is, the head pixel is the pixel located most upstream in the main scanning direction, and the last pixel is the pixel located most downstream in the main scanning direction. In the present embodiment, the light receiving unit 22 includes 16 sensor IC chips CH1 to CH16, but may have less than 16 sensor IC chips CH or a large number of sensor ICs. It may have a chip CH. The sensor IC chips CH1 to CH16 have different output characteristics, but the same sensor IC chip CH has the same output characteristics. One line is a pixel group including the head pixel to the final pixel. The sensor IC chips CH1 to CH16 are hereinafter referred to as chips CH1 to CH16.

  FIG. 1B shows a top view of the document placement table DT as viewed from above. The upper surface of the document placement table DT has the upper surface of the main body MB and a surface where the transparent plate TP is exposed to the cover CV side. The upper surface of the main body MB has a cover sensor 27 and a pivot. The transparent plate TP has a rectangular shape constituted by a long side extending along the sub scanning direction and a short side extending along the main scanning direction. In the following description, the lower direction of FIG. 1B is described as the downstream in the main scanning direction, and the right direction in FIG. 1B is described as the downstream in the sub scanning direction. Among the exposed surfaces of the transparent plate TP, a reference point BP is provided on the upstream side in the main scanning direction and on the upstream side in the sub scanning direction. A document is placed on the transparent plate TP with the reference point BP as a base point. The transparent plate TP has a document placement area PR on the downstream side in the main scanning direction and the downstream side in the sub scanning direction from the reference point BP. The document placement area PR is an area surrounded by a two-dot chain line. The pivoting axis is an axis that pivots when opening and closing the cover CV, and is disposed at two upstream sides in the main scanning direction of the main body MB. The cover sensor 27 is disposed in the vicinity of the pivot shaft, and is turned on when the cover CV is opened and in the open state, and turned off when the cover CV is closed and in the closed state.

  The image reading device SM further includes a reference member BM fixed to the upper surface of the transparent plate TP. The reference member BM is provided at the end of the transparent plate TP on the upstream side (i.e., the left side in FIG. 1B) in the sub-scanning direction, and is fixed to the area marked with a horizontal line. The reference member BM is a white member extending along the main scanning direction, and is used when acquiring white data WH described later, or when adjusting the light source 21. Hereinafter, the position at which the reference member BM is provided in the sub scanning direction will be referred to as “home position HP”. The reading unit 20 is configured to be movable in the sub-scanning direction based on the home position HP.

<Electric Configuration of Image Reading Device SM>
The electrical configuration of the image reading apparatus SM will be described with reference to FIG. In FIG. 3, the image reading apparatus SM includes, as main components, a CPU 30, a ROM 31, a RAM 32, a flash ROM 33, a device control unit 34, an analog front end (hereinafter referred to as AFE) 35, an image processing unit 36 and a drive circuit 37. Prepare. These components are connected to the operation mechanism OM, the display mechanism DM, and the cover sensor 27 via the bus 38. The operating mechanism OM is composed of a plurality of keys such as a start button and an enter button. The user can input various instructions to the image reading device SM by operating the operation mechanism OM. The display mechanism DM is a display for displaying various information.

  The ROM 31 stores programs for executing various operations of the image reading apparatus SM, such as maintenance main processing to be described later, reading main processing, and processing of a subroutine in each main processing. The CPU 30 controls each part in accordance with the program read from the ROM 31. The flash ROM 33 is a readable and writable non-volatile memory, and stores various data generated by control processing of the CPU 30, for example, various data acquired by maintenance main processing. The RAM 32 temporarily stores calculation results and the like generated by control processing of the CPU 30.

  The device control unit 34 is connected to the reading unit 20, and transmits to the reading unit 20 a signal for controlling turning on / off of the light source 21 and a signal for controlling the current value flowing to the light source 21 based on an instruction from the CPU 30. . In addition, the device control unit 34 is a serial for simultaneously transferring electric signals of many photoelectric conversion elements 23 of the chips CH1 to CH16 of the light receiving unit 22 to the shift register as shown in FIG. 2 based on an instruction from the CPU 30. A clock signal CLK for outputting the in signal SI and the electric signal of the shift register in order is transmitted to the light receiving unit 22. When the reading unit 20 receives these signals from the device control unit 34, the reading unit 20 turns on the light source 21 and transmits an analog signal according to the amount of light received by the light receiving unit 22 to the AFE 35.

  The AFE 35 is connected to the reading unit 20, and converts an analog signal transmitted from the reading unit 20 into digital data based on an instruction from the CPU 30. The AFE 35 has a predetermined input range and resolution. For example, if the resolution is 10 bits, it is a gradation from "0" to "1023". In this case, the AFE 35 converts the analog signal transmitted from the reading unit 20 into 10-bit (0 to 1023) gradation data as digital data. The digital data converted by the AFE 35 is transmitted to the image processing unit 36. The image processing unit 36 is composed of an ASIC, which is a dedicated IC for image processing, and performs various types of image processing on digital data. The image processing is various correction processing such as shading correction and gamma correction. The image processing unit 36 can be set not to perform various types of image processing, or can be set to perform all image processing. The image processing unit 36 applies the set image processing to the digital data to generate digital image data. This digital image data is stored in the RAM 32 via the bus 38. Here, shading correction is, for example, white correction and black correction. Black correction is correction that subtracts black data BK1 and BK2 described later from digital data in each pixel.

  The drive circuit 37 is connected to the transport motor MT, and drives the transport motor MT based on a drive command transmitted from the CPU 30. The drive circuit 37 rotates the transport motor MT according to the rotation amount and the rotation direction instructed by the drive instruction. When the transport motor MT rotates by a predetermined amount, the moving mechanism MM rotates by a predetermined angle, and the reading unit 20 is transported by a predetermined distance in the sub-scanning direction.

<Operation of Embodiment>
Next, the operation of the image reading apparatus SM will be described with reference to the drawings. The image reading apparatus SM mainly executes maintenance main processing executed before reading a document and reading main processing for reading a document. The processing of steps M1 to M5 in the maintenance main processing, the processing of steps R1 to R11 in the reading main processing, and the processing of steps of each subroutine are processing that the CPU 30 executes.

(Maintenance main processing)
In the maintenance main process shown in FIG. 4, a worker such as a service person can operate the operation mechanism OM of the image reading device SM before the image reading device SM is shipped from the factory or when the service person performs maintenance inspection after shipment. It starts by operating according to a special operation method. In the present embodiment, the case where 600 DPI is used as the reading resolution will be described.

  When the maintenance main process is started, the CPU 30 causes the drive circuit 37 to move the reading unit 20 to the home position HP, and thereafter initializes the device control unit 34, the AFE 35, and the image processing unit 36 (M1). Specifically, the CPU 30 transmits a drive command to the drive circuit 37, and moves the reading unit 20 so that the reading position of the reading unit 20 becomes the home position HP. Further, the CPU 30 acquires settings of the clock signal CLK and the serial in signal SI corresponding to the reading resolution of 600 DPI from the flash ROM 33 and sets them in the device control unit 34. The CPU 30 acquires the setting of the signal to the light source 21 corresponding to the color mode from the flash ROM 33 and sets it in the device control unit 34. The CPU 30 acquires the offset adjustment value and the gain adjustment value of the AFE 35 from the flash ROM 33 and sets the AFE 35. Here, the offset adjustment value is a value for shifting the level of the analog signal input to the AFE 35, and the gain adjustment value is a value for adjusting the gain of the analog signal input to the AFE 35. The CPU 30 sets, in the image processing unit 36, setting values that are not subjected to various image processing.

  The CPU 30 determines whether the cover CV is in the closed state (M2). Specifically, when the cover sensor 27 is off, the CPU 30 determines that the cover CV is in the closed state (M2: Yes), and proceeds to processing M4. When the cover sensor 27 is on, the CPU 30 determines that the cover CV is in the open state (M2: No), and proceeds to processing M3. When the process proceeds to the process M3, the CPU 30 causes the display mechanism DM to display that the cover CV is in the open state, close the cover CV, and execute again (M3), and the maintenance main process ends.

  In the process M2, when it is determined that the cover CV is in the closed state, the CPU 30 acquires the first black data BK1 of the reading unit 20 (M4). Specifically, the CPU 30 turns off the light source 21 and reads the reference member BM. Then, the CPU 30 acquires digital image data of each pixel of one color in one line read as the first black data BK1. The CPU 30 stores the first black data BK1 in the flash ROM 33. The first black data BK1 is one color because the light sources 21 of three colors are turned off and acquired.

  The CPU 30 calculates a chip maintenance black BBK1 (M5). Specifically, the CPU 30 divides the first black data BK1 into data groups of each chip CH, and averages the first black data BK1 of each divided data group to maintain the chips of each chip CH in one line. Calculate black BBK1. The CPU 30 stores the chip maintenance black BBK1 in the flash ROM 33. When the process M5 ends, the maintenance main process ends.

(Reading main processing)
The reading main process shown in FIG. 5 is started by the user placing a document on the document placement table DT and pressing the start button of the operation mechanism OM. The reading main process of the present embodiment will be described when the reading resolution is set to 600 DPI, the color mode is set, and an A4 size document is placed.

  When the reading main process is started, the CPU 30 causes the driving circuit 37 to move the reading unit 20 to the home position HP, and thereafter initializes the device control unit 34, the AFE 35, and the image processing unit 36 (R1). Specifically, the CPU 30 transmits a drive command to the drive circuit 37, and moves the reading unit 20 so that the reading position of the reading unit 20 becomes the home position HP. Further, the CPU 30 acquires settings of the clock signal CLK and the serial in signal SI corresponding to the reading resolution of 600 DPI from the flash ROM 33 and sets them in the device control unit 34. The CPU 30 acquires the offset adjustment value and the gain adjustment value of the AFE 35 from the flash ROM 33 and sets the AFE 35. The CPU 30 sets, in the image processing unit 36, setting values that are not subjected to various image processing.

  The CPU 30 acquires black data BK2 of the reading unit 20 (R2). Specifically, the CPU 30 turns off the light source 21 and reads the reference member BM. Then, the CPU 30 acquires digital image data of each pixel of one color read in one line as the second black data BK2.

  The CPU 30 determines whether the cover CV is in the closed state (R3). Specifically, when the cover sensor 27 is off, the CPU 30 determines that the cover CV is closed (R3: Yes), and proceeds to processing R8. When the cover sensor 27 is on, the CPU 30 determines that the cover CV is in the open state (R3: No), and proceeds to processing R4.

  The CPU 30 calculates the chip variation BF (R4). Specifically, the CPU 30 divides the second black data BK2 into data groups of each chip CH, extracts the maximum value and the minimum value from the second black data BK2 of each divided data group, and extracts the extracted maximum values. The chip variation BF of each chip CH in one line is calculated by subtracting the extracted minimum value. The CPU 30 stores the chip variation BF in the RAM 32 in association with the position of the chip CH.

  The CPU 30 detects the outside light chip position BN which is the position of the chip CH on which the outside light is incident (R5). Specifically, the CPU 30 compares the chip variation BF with the threshold value THA in each chip CH. The CPU 30 detects the position of the chip CH associated with the chip variation BF larger than the threshold value THA as the external light chip position BN. The CPU 30 stores the ambient light chip position BN in the RAM 32. Here, the threshold THA is 60 corresponding to 60 mV. The 60 mV is a voltage value obtained by adding a predetermined margin to the black signal fluctuation amount 55 mV which is the fluctuation of the black signal of each pixel in the chip. In the present embodiment shown in FIG. 8, the shaded chips CH2, CH3, CH6, CH7 and CH11 to CH14 are detected as the external light chip position BN.

  The CPU 30 determines whether ambient light is incident on all the chips CH (R6). Specifically, when the position of the chip CH is not stored as the external light chip position BN, the CPU 30 determines that the external light is not incident on all the chips CH (R6: Yes), and proceeds to processing R8. . When the position of the chip CH is stored as the external light chip position BN, the CPU 30 determines that the external light is incident on the chip CH (R6: No), and proceeds to processing R7.

  The CPU 30 replaces the second black data BK2 (R7). Although the details will be described later, the CPU 30 replaces the second black data BK2 of the pixels included in the chip CH stored as the external light chip position BN. By replacing the second black data BK2 of the pixel included in the chip CH on which the external light is incident, accurate black correction can be performed using the second black data BK2 in which the influence of the external light is reduced.

  The CPU 30 adjusts the light amount ST of the light source 21 (R8). Specifically, the CPU 30 irradiates light from the light source 21 of the reading unit 20 toward the reference member BM, and each color so that the analog signal when reading the reflected light becomes the maximum of the input range of the AFE 35. Adjust the light intensity ST of Here, each color indicates three colors of red, blue and green used in the color mode.

  The CPU 30 acquires the white data WH of the reading unit 20 (R9). Specifically, the CPU 30 lights the light amount ST of each color of the light source 21 and reads the reference member BM. Then, the CPU 30 acquires digital image data of each pixel of each color of one line read as white data WH. The CPU 30 stores the acquired white data WH in the RAM 32.

  The CPU 30 calculates the black-and-white difference data WBdif of the reading unit 20 (R10). Specifically, the CPU 30 subtracts the second black data BK2 from the white data WH of each pixel of each line of one line, and stores the result in the flash ROM 33 as black-and-white difference data WBdif of each pixel of each color of one line.

  The CPU 30 reads a document (R11). Specifically, the CPU 30 sets, in the image processing unit 36, set values for performing various image processing, sets the second black data BK2 as black correction data, and sets the black-and-white difference WBdif as white correction data. The CPU 30 outputs a command to the drive circuit 37, moves the reading unit 20 by the drive circuit 37, irradiates the light source 21 of the reading unit 20 with the light amount ST, and reads the document. In this manner, the image reading apparatus SM can perform black correction using the black data BK2 replaced in the process R7, and can perform accurate black correction.

(Second black data BK2 replacement process R7)
When the second black data BK2 substitution process (R7) shown in FIG. 6 is started, the CPU 30 determines whether or not outside light is incident on all the chips CH (RA1). Specifically, when the positions of all the chips CH are not stored as the outside light chip position BN, the CPU 30 determines that the outside light is not incident on all the chips CH (RA1: No), and the process RA3 Go to When the positions of all the chips CH are stored as the outside light chip position BN, the CPU 30 determines that the outside light is incident on all the chips CH (RA1: Yes), and proceeds to processing RA2.

  If it is determined Yes in the process RA1, the CPU 30 stores the substituted black data RPBK2 (RA2). Specifically, the CPU 30 stores the first black data BK1 of each pixel in one line acquired in the process M4 in the RAM 32 as the substituted black data RPBK. When the process RA2 is completed, the process proceeds to the process RA8.

  If it is determined No in the process RA1, the CPU 30 calculates a line black difference LBKdif (RA3). Specifically, the CPU 30 subtracts the first black data BK1 from the second black data BK2 in each pixel included in all the chips CH not stored as the external light chip position BN, The line black difference LBKdif is calculated by averaging all values calculated by subtraction in.

  The CPU 30 calculates a threshold value THB (RA4). Specifically, the CPU 30 adds the line black difference LBKdif to the chip maintenance black BBK1 of each chip CH in one line calculated in the process M5, and adds 100 to the added value to add each chip in one line. The threshold THB of is calculated. Here, 100 finally added is a value corresponding to 100 mV. The 100 mV is a voltage value obtained by adding all the margins assumed to the black signal fluctuation amount 55 mV which is the fluctuation of the black signal of each pixel in the chip. In the present embodiment shown in FIG. 9, the threshold value THB of the chip CH2 is 132, and the threshold value THB of the chip CH3 is 152. The threshold value THB is calculated as follows. The chip maintenance black BBK1 of the chip CH2 is 25, and the line black difference LBKdif is 7. Therefore, the threshold THB of the chip CH2 is 132. Similarly, since the chip maintenance black BBK1 of the chip CH3 is 45 and the line black difference LBKdif is 7, the threshold THB of the chip CH3 is 152.

  The CPU 30 detects the continuous chip LCB (RA5). Specifically, the CPU 30 detects the first chip CH on the head pixel side stored as the external light chip position BN as the first continuous chip LCB1. The CPU 30 continues detecting the chip CH adjacent to the final pixel side in the first continuous chip LCB1 as the first continuous chip LCB1, and continues to the first chip CH immediately before the chip CH not stored as the external light chip position BN. It detects as chip LCB1. In the present embodiment shown in FIG. 8, the chip CH2, which is the first chip CH on the head pixel side stored in the external light chip position BN, is detected as the first continuous chip LCB1. Since the chip CH3 which is the next chip CH adjacent to the final pixel side of the chip CH2 is stored as the external light chip position BN, the chip CH3 is detected as the first continuous chip LCB1. Since the chip CH4, which is the next chip CH adjacent to the final pixel side of the chip CH3, is not stored as the external light chip position BN, the chips CH2 to CH3 are detected as the first continuous chip LCB1.

  The CPU 30 detects, among the chips CH stored as the external light chip position BN, the first chip CH on the head pixel side other than the chip CH detected as the first continuous chip LCB1 as the second continuous chip LCB2. The CPU 30 continues to detect the chip CH adjacent to the final pixel side in the second continuous chip LCB2 as the second continuous chip LCB2, and continues to the second chip up to the chip CH immediately before the chip CH not stored as the external light chip position BN. It detects as chip LCB2. In the present embodiment shown in FIG. 8, the chips CH6 to CH7 are detected as the second continuous chip LCB2 similarly to the first continuous chip LCB1.

  The CPU 30 sets the first chip CH on the head pixel side to the third continuous chip other than the chips CH detected as the first continuous chip LCB1 and the second continuous chip LCB2 among the chips CH stored as the external light chip position BN. Detect as LCB3. The CPU 30 continues to detect the chip CH adjacent to the final pixel side in the third continuous chip LCB3 as the third continuous chip, and continues to the third chip until the chip CH immediately before the chip CH not stored as the external light chip position BN. Detect as LCB3. In the present embodiment shown in FIG. 8, among the chips CH stored in the external light chip position BN, the first chip CH on the leading pixel side other than the chips detected as the first continuous chip LCB1 and the second continuous chip. A certain chip CH11 is detected as a third continuous chip LCB1. Since the chip CH12 which is the next chip CH adjacent to the final pixel side of the chip CH11 is stored as the external light chip position BN, the chip CH12 is detected as the third continuous chip LCB3. Similarly, the chip CH13 and the chip CH14 are detected as the third continuous chip LCB3. Since the chip CH15 which is the next chip CH adjacent to the final pixel side of the chip CH14 is not stored in the external light chip position BN, the chips CH11 to CH14 are detected as the third continuous chip LCB3. In this manner, when there is a chip CH stored as the external light chip position BN on the final pixel side of the third continuous chip LCB3 as described above, the CPU 30 sequentially detects as the fourth continuous chip LCB4 and is the final chip. The chips up to the chip CH16 are sequentially detected as a continuous chip LCB.

  The CPU 30 determines the start detail chip SCB and the end detail chip ECB (RA6). Specifically, the CPU 30 determines the first chip CH on the top pixel side in each successive chip LCB as the start detail chip SCB, and determines the last chip CH on the last pixel side of one line as the end detail chip ECB. Do. In the present embodiment shown in FIG. 8, the chip CH2, which is the first chip CH on the head pixel side in the first consecutive chip LCB1, is determined as the start detail chip SCB, and the last chip CH on the last pixel side of one line is selected. One chip CH3 is determined as the end detail chip ECB. Similarly, the start detail chip SCB of the second consecutive chip LCB2 is determined to be the chip CH6, and the end detail chip ECB is determined to be the chip CH7. The start detail chip SCB of the third consecutive chip LCB3 is determined to be the chip CH11, and the end detail chip ECB is determined to the chip CH14.

  The CPU 30 calculates replacement black data RPBK (RA7). Although details will be described later, the CPU 30 determines the start pixel position SCP which is the position of the pixel at which the incident of external light has started in each successive chip LCB and the end pixel position ECP which is the position of the pixel at which the incident of external light is completed. Do. The CPU 30 averages the second black data BK2 from the tip pixel of the start detail chip SCB to the pixel immediately before the start pixel position SCP in the start detail chip SCB of each successive chip LCB and substitutes the black data RPBK for the start detail chip SCB. calculate. The CPU 30 calculates second black data RPBK of the end detail chip ECB by averaging the second black data BK2 from the pixel immediately after the end pixel position ECP to the end pixel in the end detail chip ECB of each successive chip LCB. The CPU 30 averages the second black data BK2 of all the pixels included in all the chips CH not stored as the external light chip position BN, and substitutes the black data of the chips CH other than the start detail chip SCB and the end detail chip ECB. Calculated as RPBK. Here, the front end pixel is a pixel located on the most upstream side in the main scanning direction on the leading pixel side of each chip, and the end pixel is a pixel located on the most downstream side in the main scanning direction located on the final pixel side of each chip.

  The CPU 30 replaces the second black data BK2 (RA8). Specifically, when the replacement black data RPBK is calculated in process RA7, the CPU 30 replaces the second black data BK2 of the pixels from the start pixel position SCP to the end pixel position ECP in each successive chip LCB. Replace with RPBK. In other words, the CPU 30 replaces the second black data BK2 of the pixels from the start pixel position SCP to the end pixel position ECP included in the start detail chip SCB in each successive chip LCB with the replacement black data RPBK calculated in processing RB3, and ends The second black data BK2 of the pixels from the start pixel position SCP to the end pixel position ECP included in the detail chip ECB is replaced with the replacement black data RPBK calculated in the processing RB5, and the chips CH other than the start detail chip SCB and the end detail chip ECB The second black data BK2 of the pixels from the start pixel position SCP to the end pixel position ECP included in are replaced with the substituted black data RPBK calculated in processing RB7. When the start detail chip SCB and the end detail chip ECB are the same chip CH, the CPU 30 substitutes the second black data BK2 of the pixels from the start pixel position SCP to the end pixel position ECP in processing RB3. Replace with When the replacement black data RPBK is stored in the process RA2, the CPU 30 replaces the second black data BK2 of each pixel in one line with the replacement black data RPBK stored in the process RA1. The CPU 30 stores, in the flash ROM 33, the second black data BK2 of each pixel in one replaced line. When the process RA8 ends, the second black data BK2 substitution process (R7) ends.

(Replacement black data RPBK calculation)
When the replacement black data RPBK calculation process (RA7) shown in FIG. 7 is started, the CPU 30 sets a target continuous chip TLCB (RB1). Specifically, if the target continuous chip TLCB is set, the CPU 30 sets the next continuous chip LCB on the final pixel side as the target continuous chip TLCB, and if the target continuous chip TLCB is not set, 1) The continuous chip LCB1 is set as a target continuous chip TLCB.

  The CPU 30 determines the start pixel position SCP (RB2). Specifically, the CPU 30 determines whether the second black data BK2 is larger than the threshold value THB in order from the tip pixel of the start detail chip SCB of the target continuous chip TLCB to the end pixel of the same chip CH. The CPU 30 determines, as the start pixel position SCP, the pixel position of the pixel that is first determined that the second black data BK2 is larger than the threshold value THB. The start pixel position SCP is the first pixel position on the tip pixel side where external light is estimated to be incident on the target consecutive chip TLCB. The determination of the start pixel position SCP of the first continuous chip LCB1 in the present embodiment will be described with reference to FIG. The threshold THB of the chip CH2, which is the start detail chip SCB of the first continuous chip LCB1, is 132. It is determined whether the second black data BK2 is larger than 132 in order from the tip pixel to the end pixel of the chip CH2. Since it is first determined that 420 which is the second black data BK2 of the pixel of the 647th pixel is larger than 132 which is the threshold value THB, the pixel position of the pixel of the 647th pixel is determined as the start pixel position SCP.

  The CPU 30 calculates replacement black data RPBK of the start details chip SCB of the target continuous chip TLCB (RB3). Specifically, the CPU 30 calculates the average value of the second black data BK2 from the tip pixel of the target continuous chip TLCB to the pixel immediately before the start pixel position SCP, and the average value is used as the start detail chip of the target continuous chip TLCB. Calculated as SCB replacement black data RPBK. When the number of pixels from the tip pixel of the target continuous chip TLCB to the pixel at the start pixel position SCP is one, replacement of the second black data BK2 of the tip pixel of the target continuous chip TLCB with the start detail chip SCB of the target continuous chip TLCB It is assumed that black data RPBK.

  The CPU 30 determines an end pixel position ECP (RB4). Specifically, the CPU 30 determines whether the second black data BK2 is larger than the threshold value THB in order from the end pixel of the end detail chip ECB of the target continuous chip TLCB to the tip pixel of the same chip CH. The CPU 30 determines, as the end pixel position ECP, the pixel position that is first determined that the second black data BK2 is larger than the threshold value THB. The end pixel position ECP is the first pixel position on the terminal pixel side where external light is estimated to be incident on the target consecutive chip TLCB. The determination of the end pixel position ECP of the first continuous chip LCB1 in the present embodiment will be described with reference to FIG. The threshold value THB of the chip CH3, which is the end detail chip ECB of the first continuous chip LCB1, is 152. It is determined whether the second black data BK2 is larger than 152 in order from the end pixel to the end pixel of the chip CH3. Since it is first determined that the second black data BK2 520 of the 969th pixel is larger than the threshold value THB 152, the pixel position of the 969th pixel is determined as the end pixel position ECP.

  The CPU 30 calculates replacement black data RPBK of the end details chip ECB of the target continuous chip TLCB (RB5). Specifically, the CPU 30 calculates the average value of the second black data BK2 from the end pixel of the target continuous chip TLCB to the pixel immediately after the end pixel position ECP, and the average value is used as the end detail chip of the target continuous chip TLCB. Calculated as substituted black data RPBK of ECB. When the number of pixels from the end pixel of the target continuous chip TLCB to the pixel at the end pixel position ECP is one, the second black data BK2 of the end pixel of the target continuous chip TLCB is replaced with the end detail chip ECB of the target continuous chip TLCB. It is assumed that black data RPBK.

  The CPU 30 determines whether or not the next continuous chip LCB next to the target continuous chip TLCB is present (RB6). Specifically, when the continuous chip LCB does not exist at the position on the final pixel side from the target continuous chip TLCB, the CPU 30 determines that the next continuous chip LCB does not exist (RB6: No), and sets the target continuous chip TLCB. Is deleted, and the process proceeds to processing RB7. When the continuous chip LCB is present at a position on the final pixel side from the target continuous chip TLCB, the CPU 30 determines that the next continuous chip LCB is present (RB6: Yes), and proceeds to processing RB1.

  The CPU 30 calculates replacement black data RPBK of the chips CH other than the start detail chip SCB and the end detail chip ECB (RB7). Specifically, the CPU 30 calculates the substitution black data RPBK of the chip CH other than the start detail chip SCB and the end detail chip ECB by adding the line black difference LBKdif to the second black data BK2 in each pixel in one line. Do. When the process RB7 ends, the replacement black data RPBK calculation process (RA7) ends.

<Effect of the embodiment>
In the present embodiment, after the process M4 of the maintenance main process determines that the cover is closed in the process M2, the first black data BK1 of each pixel in one line is acquired. The process R2 of the reading main process acquires the second black data BK2 of each pixel in one line. The process R5 compares the chip variation BF with the threshold THA in each chip CH, and detects the position of the chip CH associated with the chip variation BF larger than the threshold THA as the external light chip position BN. The processing RB2 of the substituted black data RPBK calculation RA7 determines whether the second black data BK2 is sequentially larger than the threshold THB from the tip pixel of the start detail chip SCB of the target consecutive chip TLCB to the end pixel of the same chip CH, The pixel position of the pixel initially determined to be larger than the threshold value THB is determined as the start pixel position SCP. The processing RB5 determines whether the second black data BK2 is larger than the threshold value THB in order from the end pixel of the end detail chip ECB of the target continuous chip TLCB to the tip pixel of the same chip CH, and the second black data BK2 is a threshold value. The pixel position of the pixel initially determined to be larger than THB is determined as the end pixel position ECP. The process RA3 of the second black data BK2 replacement R7 subtracts the first black data BK1 from the second black data BK2 in each pixel included in all the chips CH not stored at the external light chip position BN, The line black difference LBKdif is calculated by averaging all the values calculated by subtraction in. The processing RB3 of the substituted black data RPBK calculation RA7 calculates the average value of the second black data BK2 from the tip pixel of the target continuous chip TLCB to the pixel immediately before the start pixel position SCP, and the average value is calculated for the target continuous chip TLCB. It is calculated as replacement black data RPBK of the start detail chip SCB. The processing RB5 calculates the average value of the second black data BK2 from the end pixel of the target continuous chip TLCB to the pixel immediately after the end pixel position ECP, and the average value is used as the end detail chip ECB for the target continuous chip TLCB. Calculated as data RPBK. The process RB7 adds the line black difference LBKdif to the second black data BK2 in each pixel in one line to calculate replacement black data RPBK of the chip CH other than the start detail chip SCB and the end detail chip ECB. The process RA8 of the second black data BK2 replacement R7 replaces the second black data BK2 of the pixels from the start pixel position SCP to the end pixel position ECP with the substituted black data RPBK in each successive chip LCB. Therefore, since the substituted black data RPBK is calculated using the second black data BK2 on which no external light is incident, the substituted black data RPBK can be calculated with higher accuracy, and black correction with high accuracy is performed. be able to.

[Correspondence between embodiment and invention]
The image reading device SM and the cover CV are an example of the image reading device and the cover of the present invention. The reading unit 20 and the AFE 35 are an example of the reading unit of the present invention. The image processing unit 36 and the CPU 30 are an example of the correction unit and the control unit of the present invention. The process M4 is an example of the first black data acquisition process of the present invention. Process R2 is an example of the second black data acquisition process of the present invention. The process R4, the process R5, the process RA5, the process RA6, the process RB2, and the process RB4 are an example of the determination process of the present invention. Process RA3 is an example of the adjustment data calculation process of the present invention. The processing RB3, the processing RB5, and the processing RB7 are an example of the third black data calculation processing of the present invention. Process RA8 is an example of the correction data determination process of the present invention. Process R11 is an example of the reading process of the present invention.

  Process R5 is an example of the first determination process of the present invention. Process RB2 and process RB4 are examples of the 2nd judgment process of this invention. Process RA5 is an example of the continuous group determination process of the present invention. Process RA6 is an example of the detailed group determination process of the present invention. The process M5 is an example of the averaging process of the present invention. Process RA4 is an example of the second threshold value calculation process of the present invention.

[Modification]
The present invention is not limited to the present embodiment, and various modifications can be made without departing from the scope of the present invention. An example of the modification is described below.

  (1) The image reading apparatus SM of the present embodiment may be applied to a multifunction peripheral provided with a printer unit. In the present embodiment, the case of one reading unit 20 has been described, but a plurality of reading units 20 may be used.

  (2) In the present embodiment, the maintenance main process shown in FIG. 4 and the reading main process shown in FIG. 5 are all executed by the CPU 30, but the present invention is not limited to this configuration. For example, a part of M3 to M5 of the maintenance main process and a part of R4 to R7 and R10 of the reading main process may be executed by the image processing unit 36, the device control unit 34, or the AFE 35. Further, the maintenance main process may be executed by an external device independent of the image reading apparatus SM, such as a computer.

  (3) In the present embodiment, although the case where the light receiving unit 22 is configured by 16 chips CH1 to CH16 has been described, the number of chips CH less than 16 may be used, or more than 16 chips may be used. It may be CH.

  (4) In the present embodiment, although the case where the light receiving unit 22 is configured by the photoelectric conversion element 23 of one line is described, the light receiving unit 22 may be configured by the photoelectric conversion element 23 of multiple lines.

  (5) In the present embodiment, after the chip variation BF of the second black data BK is calculated and the incident of the external light is determined for each chip CH, the second black data BK is compared with the threshold value THB to determine the outside for each pixel. Although the incidence of light was determined, the incidence of ambient light may be determined by comparing the second black data BK with the threshold value THB for all pixels, or the second black data BK and the white data WH The incidence of ambient light may be determined by comparison.

  (6) In the present embodiment, in the calculation of the replacement black data RPBK of the processing RB7, the line black difference LBKdif is added to the second black data to calculate the replacement black data RPBK, but the second black data BK2 is calculated as the first black After calculating a value corresponding to the line black difference LBKdif by dividing by the data BK1, the substituted black data RPBK may be calculated by multiplying the first black data BK1 by the divided value.

SM: image reader, OM: operation mechanism, CV: cover, 20: reading unit, 21: light source, 22: light receiving unit, 23: photoelectric conversion element, 30: CPU, 33: flash ROM, 34: device control unit, 35 ... AFE, 36 ... image processing unit, 27 ... cover sensor, 37 ... drive circuit

Claims (5)

A reading unit having a light source and a large number of light receiving elements arranged in one line, and lighting the light source to read it;
A cover that can be opened and closed in a closed state covering the reading unit and an open state opening the reading unit;
A correction unit that performs black correction on the value read by the reading unit based on the correction data;
A control unit that executes preparation processing and then executes the preparation processing;
The preparation process is
And a first black data acquisition process of acquiring first black data of each light receiving element of the plurality of light receiving elements by turning off the light source and reading by the reading unit with the cover closed.
The execution process is
Second black data acquisition processing for acquiring second black data of each of the light receiving elements by turning off the light source and reading by the reading unit with the cover in an open state;
A determination process of determining whether external light is incident on each of the light receiving elements based on the second black data;
Adjustment data calculation processing in which black adjustment data is calculated based on the second black data and the first black data in each light receiving element determined that external light is not incident;
Third black data calculation processing for calculating third black data based on the first black data and the black adjustment data in each of the light receiving elements determined to be exposed to external light;
The third black data is determined as the correction data in each of the light receiving elements determined that the outside light is incident, and the second black data is corrected in each of the light receiving elements determined that the outside light is not incident Correction data determination processing determined as data;
An image reading apparatus comprising a reading process for reading an image of a document and performing black correction based on the correction data. The multiple light receiving elements of the reading unit are divided into a plurality of groups,
The determination process is
A first determination process of determining a group into which external light is incident as an external light presence group in each of the plurality of groups, and determining a group into which external light is not incident as an external light non-existence group;
A second determination process of determining the light receiving element on which the outside light is incident in each light receiving element of the outside light present group as an outside light present pixel,
In the adjustment data calculation process, the first black data is subtracted from the second black data in all the light receiving elements of the non-external light group, and all the values calculated by subtracting in the respective light receiving elements are calculated. Calculate the black adjustment data on average
The image reading apparatus according to claim 1, wherein the third black data calculation process calculates the third black data by adding the black adjustment data to the first black data. Each group of the plurality of groups is composed of the light receiving element having the same output characteristic,
The first determination process subtracts the smallest value from the largest value of the second black data of the plurality of light receiving elements in each group of the plurality of groups, and the value obtained by subtraction is a first value determined in advance 3. The image reading apparatus according to claim 2, wherein if the threshold is exceeded, the group is determined to be the outside light present group. The determination process is
A continuous group determination process of determining the group group of all the groups to which the extraneous light group is adjacent as the continuous group group;
And a detailed group determination process of determining a leading group and a final group as the detailed group for the continuous group group,
The second determination process is characterized in that the outside light presence pixel is determined in the outside light presence group that is the detail group, and the outside light presence pixel is not determined in the outside light presence group that is not the detail group. An image reading apparatus according to claim 2 or claim 3. The preparation process is
And averaging the first black data of all light receiving elements of each group of the plurality of groups to calculate a group black average value,
The execution process is
Including a second threshold value calculation process of calculating a second threshold value by adding the black adjustment data to the group black average value and adding a predetermined predetermined value to the added value;
The second determination processing is characterized in that, when the second black data exceeds the second threshold in each light receiving element of the detail group, it is determined that outside light is incident in the light receiving element. The image reading apparatus according to any one of claims 1 to 4.