JP2007208929A - Image reader, image reading method, and image reading program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image reader, an image reading method and an image reading program which can correct the level of an image signal on the basis of a crosstalk quantity. <P>SOLUTION: A white reference plate 105 is read, a correction coefficient (hereinafter referred to a crosstalk coefficient) between adjacent channels is independently calculated, and the reading level of a digital signal output from each of the channels is corrected on the basis of the crosstalk coefficient. Specifically, an arithmetically operating unit 211 calculates a crosstalk coefficient from the reading level of image data obtained by reading the white reference plate 105. The calculated crosstalk coefficient is stored in a memory 211b, and the arithmetically operating unit 211a reads the crosstalk coefficient from the memory 211b at the time of correction operation of usual scanning, and performs correction operation of the image data. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image reading apparatus, an image reading method, and an image reading program, and more particularly to an image reading apparatus, an image reading method, and an image reading program that correct an image signal level based on a crosstalk amount.

  In a color CCD used in a digital copying machine, even pixels (even) and odd pixels (odd) are output in parallel for each of R / G / B in order to increase the transfer speed. In this case, the flow of the image data is simultaneously performed on 6 channels.

In Patent Document 1, only a synchronization signal necessary for generating an image sensor drive signal is generated from a substrate on which a circuit for processing an image signal read by an image sensor is mounted on a substrate on which the image sensor is mounted. There has been proposed an image reading apparatus capable of preventing the image signal from being deteriorated by transmitting the image sensor drive signal without being affected by electromagnetic noise.
JP 2000-244716 A

  However, the above invention has the following problems.

  When this analog image signal flows through the circuit in the order shown above in parallel with 6 channels due to the arrangement of the output pins of the CCD and the layout of the circuit, as shown in FIG. 3, between adjacent channels (Rodd, Geven, God, (Beven) causes crosstalk of the analog electrical signal, and the finally obtained image data fluctuates. As a result, as shown in FIG. 4, a level difference also occurs between even and odd of the same color channel, resulting in poor color reproducibility. In recent years, an analog processing IC with 6-channel input has been developed, and crosstalk may further occur depending on the input pin and internal structure of the IC.

  Therefore, the present invention reads the white reference plate, independently calculates the correction coefficient between each adjacent channel, and corrects the reading level of the digital signal output from each channel based on the crosstalk coefficient, thereby An object of the present invention is to propose an image reading apparatus, an image reading method, and an image reading program capable of reducing the influence on image data due to occurrence of image quality and improving color reproducibility.

  The invention according to claim 1 is an image reading apparatus having a plurality of photoelectric conversion elements for each separation color in parallel and an analog processing IC for processing an image signal read by each photoelectric conversion element. Computation means for calculating a correction coefficient from the image signal level of the adjacent channel when the conversion element is turned off and reading the white reference plate, and storage means for storing the correction coefficient calculated by the calculation means When the original is read, the image signal level of the adjacent channel is corrected based on the correction coefficient stored in the storage means.

  According to a second aspect of the present invention, in the image reading apparatus according to the first aspect, a difference between the correction coefficient Gn + 1 calculated by the calculation unit and the correction coefficient Gn already stored in the storage unit is obtained. Determining means for determining whether or not it is within the threshold Gth, and updating means for updating the correction coefficient Gn stored in the storage means with the correction coefficient Gn + 1 when the difference is within the threshold Gth. And notification means for notifying the abnormality of the image reading apparatus when the difference in the previous period is not within the threshold value Gth.

  According to a third aspect of the present invention, in the image reading apparatus according to the first or second aspect, the image reading apparatus further comprises control means for independently controlling ON / OFF of each of the photoelectric conversion elements.

  According to a fourth aspect of the present invention, in the image reading apparatus according to any one of the first to third aspects, the calculation unit independently calculates a correction coefficient between the adjacent channels.

  According to a fifth aspect of the present invention, in the image reading apparatus according to any one of the second to fourth aspects, the correction coefficient is updated by the updating unit every time the power of the image reading apparatus is turned on. It is characterized by.

  The invention according to claim 6 is an image reading method of an image reading apparatus having a plurality of photoelectric conversion elements for each separation color in parallel and an analog processing IC for processing an image signal read by each photoelectric conversion element. A calculation step of calculating a correction coefficient from the image signal level of the adjacent channel when the adjacent photoelectric conversion element is turned off and the white reference plate is read, and a storage step of storing the correction coefficient calculated by the calculation step And a step of correcting the image signal level of the adjacent channel based on the correction coefficient stored in the storage means when the original is read.

  The invention according to claim 7 is an image reading program for an image reading apparatus having a plurality of photoelectric conversion elements for each separation color in parallel and an analog processing IC for processing an image signal read by each photoelectric conversion element. A calculation process for calculating a correction coefficient from the image signal level of the adjacent channel when the adjacent photoelectric conversion element is turned off and the white reference plate is read, and a storage process for storing the correction coefficient calculated by the calculation step And a process of correcting the image signal level of the adjacent channel based on the correction coefficient stored in the storage means when the original is read.

  The present invention reads a white reference plate, independently calculates a correction coefficient between adjacent channels, and corrects the reading level of a digital signal output from each channel based on the crosstalk coefficient, thereby generating crosstalk. Can reduce the influence on image data and improve color reproducibility. Also, the accuracy of the correction calculation can be improved by calculating the crosstalk coefficient independently between each adjacent channel.

  The configuration and operation of the image reading apparatus according to an embodiment of the present invention will be described below.

  First, the configuration of the image reading apparatus according to the present embodiment will be described with reference to FIG.

  The image reading apparatus according to this embodiment includes a traveling body 101, a lens 103, a photoelectric conversion element 104, a white reference plate 105, and a contact glass 106.

  The scanning operation of the original 102 is performed by reading the original 102 from the original 102 as original information while moving the original 102 on the contact glass 106 in the sub-scanning direction at the time of reading the pressure plate and moving the original 102 at the time of sheet-through reading. Read the reflected light. Reflected light from the original 102 is imaged on the photoelectric conversion element CCD 104 via the lens 103, and is converted into an analog electric signal by photoelectric conversion in the photoelectric conversion element CCD 104. The image reading apparatus performs analog processing and digital processing on the obtained analog electric signal and reads image information as digital data. Further, shading correction is performed in order to make the main scanning distribution of the document uniform. Note that the read data of the white reference plate 105 for shading correction is acquired before the original is scanned.

  Next, the system configuration of the image reading apparatus according to the present embodiment will be described with reference to FIG.

  The system configuration of the image reading apparatus includes a photoelectric conversion element 201, an analog buffer 202, an AC coupling 203, a line clamp 204, an S & H 205, a VGA 206, an A / D converter 207, an averaging circuit 208, a peak detection circuit 209, a CPU 210, and a correction operation. The unit 211 is configured.

  The photoelectric conversion element 201 converts the reflected light of the document image into an analog electric signal by photoelectric conversion. The analog buffer 202 buffers an analog electric signal output from the photoelectric conversion element 201.

  An analog electrical signal obtained in the photoelectric conversion element CCD 201 is input to an analog processing IC that performs analog processing via an analog buffer 202 and an AC coupling 203.

  In the analog processing IC, first, the line clamp circuit 204 performs clamping in the black pixel output period in one CCD output line so as to keep the potential between one line constant. During this black pixel output period, the photoelectric conversion element 20 is shielded from light, and the level does not fluctuate even when light (document reflected light) enters. Therefore, the output of the photoelectric conversion element 201 during this black pixel output period is referred to as “black level” with the absolute black reference of the image data. That is, there is no signal at a level lower than this.

  The S & H unit 205 converts the image signal into a continuous analog signal by sampling and holding the image signal with a sample pulse. A VGA (variable gain amplifier) 206 amplifies the image signal sampled and held in the S & H unit 205 with a gain value.

  The A / D conversion circuit 207 converts to a digital signal based on a reference level generated from a reference voltage, and outputs digital data of image data.

  Digital data output from the analog processing IC is input to the averaging circuit 208. The averaging circuit 208 calculates the average of the image signal levels of the pixels constituting each block included in the digital data of the white reference plate 105, and outputs the average value of the image signal levels of each block to the Peak detection circuit 209.

  The Peak detection circuit 209 detects a block having the highest average image signal level and outputs the average image signal level of the block to the CPU 210. The CPU 210 calculates a difference between the average value input from the peak detection circuit 209 and a preset value, and calculates a gain value. The gain value calculated by the CPU 210 is input to the VGA 206, and the image signal is amplified using the gain value.

  As shown in FIG. 3, in the color CCD used in the image reading apparatus according to the present embodiment, even pixels (even) and odd pixels (odd) are respectively used for R / G / B in order to increase the transfer speed. ) Are output in parallel. In this case, the flow of the image data is simultaneously performed on 6 channels. In the present embodiment, the white reference plate 105 is read, a correction coefficient between adjacent channels (hereinafter referred to as a crosstalk coefficient) is independently calculated, and a digital signal output from each channel is read based on the crosstalk coefficient. Correct the level. By this processing, the influence on the image data due to the occurrence of crosstalk can be reduced, and the color reproducibility can be improved. Also, the accuracy of the correction calculation can be improved by calculating the crosstalk coefficient independently between the adjacent channels.

  The image reading apparatus according to this embodiment includes a correction calculation unit 211 that calculates, holds, and corrects a crosstalk coefficient based on a digital signal output from an analog processing IC. The correction calculation unit 211 corrects the digital signal output from the analog processing IC, thereby reducing the influence of crosstalk received by all of the photoelectric conversion element 201, the analog buffer 202, and the analog processing IC.

  Here, a specific configuration of the correction calculation unit 211 will be described with reference to FIG. The correction calculation unit 211 includes a calculation unit 211a and a memory 211b. The calculation unit 211 calculates a crosstalk coefficient from the reading level of the image data obtained by reading the white reference plate 105. The calculated crosstalk coefficient is stored in the memory 211b, and the calculation unit 211a reads out the crosstalk coefficient from the memory 211b and corrects the image data during the normal scan correction calculation.

  Next, a specific method for reducing the influence of crosstalk on image data will be described.

  Processing for correcting crosstalk occurring between Rodd and Geven shown in FIG. 3 will be described with reference to FIGS.

  First, the white reference plate 105 is read in order to calculate a crosstalk coefficient. When the white reference plate 105 is read, the R and B channel TG signals of the photoelectric conversion element 201 are turned off. A method for controlling ON / OFF of each channel of the photoelectric conversion element 201 will be described later. As a result, the output from the R and B photoelectric conversion elements 201 is cut off, and only the electrical signal of the G component is output on the circuit.

  Therefore, the read level of the digital signal corresponding to the final Rodd should be 0. However, in actuality, as shown in FIG. 6, the electrical signal component of Geven is propagated to the Rodd channel due to the influence of the crosstalk, which is digitized by the A / D conversion circuit 207 and is generated as image data of several digits. Therefore, in this embodiment, the ratio of the read level between Rodd and Geven at this time (shown in Equation 1) is calculated as a crosstalk coefficient (Clogge) between Rodd and Geven.

  Then, the read level of the image data affected by the crosstalk between Rodd and Geven obtained during normal scanning is corrected using the crosstalk coefficient. Specifically, the read levels of Rodd and Geven are corrected according to Equation 2. In Equation 2, ro and ge are read levels of image data affected by crosstalk before correction, and Ro and Ge are read levels of image data with reduced influence of crosstalk after correction. The correction calculation unit 211 calculates Ro and Ge after correction from the simultaneous equations shown in Equation 2.

  Although explanation is omitted here, the correction of crosstalk between Godd and Even calculates the crosstalk coefficient by the same processing as described above, and the reading level of the image data output from each channel using the crosstalk coefficient. Correct.

  Next, a method for controlling ON / OFF of each channel of the photoelectric conversion element 201 will be described with reference to FIGS.

  As shown in FIG. 9, the photoelectric conversion element 201 is connected to an AND circuit of a TG signal branched by R / G / B and each control signal of R / G / B. When the white reference plate 105 is read to calculate the crosstalk coefficient, the TG signal input of each channel is switched on / off by a control signal.

  That is, the TG signal is input to the photoelectric conversion element 201 when the control signal is asserted, and the input of the TG signal to the photoelectric conversion element 201 is blocked when the control signal is negated. During normal scanning, all R / G / B control signals are asserted. For example, when calculating the crosstalk coefficient between Rodd and Geven, as shown in FIG. 10, only G control signal is asserted, only G component TG signal input is allowed, and R and B components are TG signal inputs. Block input. With the above-described configuration, output / blocking of each color of the photoelectric conversion element 201 is controlled.

  Next, an operation procedure of processing for calculating a crosstalk coefficient will be described with reference to FIG.

  When the power of the image reading apparatus is turned on (step S1101), the traveling body 101 reads the white reference plate 105 and acquires image data for gain adjustment (step S1102). An analog electrical signal of image data output from the photoelectric conversion element 201 is input to an analog processing IC, subjected to predetermined processing, and then output to the averaging circuit 208 as a digital signal. Then, the CPU 210 calculates a gain value based on the digital signal that has passed through the averaging circuit 208 and the peak detection circuit 209, and sets the gain value in the VGA 206 (step S1103).

  When the adjustment of the gain value is completed, the traveling body 101 moves again below the white reference plate 105 and reads the white reference plate 105 again for calculating the crosstalk coefficient (step S1104). The analog electrical signal of the image data output from the photoelectric conversion element 201 is input to the analog processing IC, subjected to predetermined processing, and then input to the correction calculation unit 211 via the LVDS. The correction calculation unit 211 calculates the crosstalk coefficient in the calculation unit 211a by the above-described processing (step S1105), and stores the crosstalk coefficient in the memory 211b (step S1106).

  When the storage of the crosstalk coefficient in the memory 211b is completed, the image reading apparatus transitions to a standby state waiting for a request for an image reading operation from the user (step S1107). The storage of the crosstalk coefficient is performed every time the image reading apparatus is turned on, and follows the minute fluctuation of the crosstalk amount.

  Next, the configuration and operation of an image reading apparatus according to another embodiment will be described.

  First, the system configuration of the image reading apparatus according to the present embodiment will be described with reference to FIG. Since the configuration other than the correction calculation unit 211 is the same as that of the above-described embodiment, the description of the configuration other than the correction calculation unit 211 is omitted.

  The correction calculation unit 211 according to the present embodiment includes a calculation unit 211a, a memory 211b, and a determination unit 211c. The correction calculation unit first calculates a crosstalk coefficient Gn + 1 from the read level of the image data read from the white reference plate 105 by the calculation unit 211a. Next, the determination unit 211c reads Gn calculated at the time of the previous power-on from the memory 211b, calculates the change amount of the crosstalk coefficient Gn and the crosstalk coefficient Gn + 1, and the change amount is within the threshold Gth. It is determined whether or not. When the amount of change is within the threshold Gth, the crosstalk coefficient Gn + 1 is stored in the memory 211b. In the normal scan, the calculation unit 211a reads out the crosstalk coefficient from the memory 211b and performs a correction calculation of the image data.

  Next, an operation procedure of processing for calculating a crosstalk coefficient will be described with reference to FIG.

  When the power source of the image reading apparatus is turned on (step S1301), the traveling body 101 reads the white reference plate 105 and acquires image data for gain adjustment (step S1302). An analog electrical signal of image data output from the photoelectric conversion element 201 is input to an analog processing IC, subjected to predetermined processing, and then output to the averaging circuit 208 as a digital signal. Then, the CPU 210 calculates a gain value based on the digital signal that has passed through the averaging circuit 208 and the peak detection circuit 209, and sets the gain value in the VGA 206 (step S1303).

  When the adjustment of the gain value is completed, the traveling body 101 moves again under the white reference plate 105 and reads the white reference plate 105 again for calculating the crosstalk coefficient (step S1304). The analog electrical signal of the image data output from the photoelectric conversion element 201 is input to the analog processing IC, subjected to predetermined processing, and then input to the correction calculation unit 211 via the LVDS. The correction calculation unit 211 calculates the crosstalk coefficient Gn + 1 in the calculation unit 211a by the above-described processing (step S1305).

  Next, the determination unit 211c reads Gn calculated at the time of the previous power-on from the memory 211b, calculates the change amount of the crosstalk coefficient Gn and the crosstalk coefficient Gn + 1, and the change amount is within the threshold Gth. It is determined whether or not (step S1306). When the amount of change is within the threshold Gth (step S1306 / YES), the crosstalk coefficient Gn + 1 is stored in the memory 211b (step S1307). On the other hand, when the change amount is not within the threshold value Gth (step S1306 / NO), the information is transmitted to the operation unit or the like to notify the user of the occurrence of an abnormality in the circuit or the reference white board (step S1308).

  When the storage of the crosstalk coefficient Gn + 1 in the memory 211b is completed, the image reading apparatus transitions to a standby state waiting for a request for an image reading operation from the user (step S1309). The storage of the crosstalk coefficient is performed every time the image reading apparatus is turned on, and follows the minute fluctuation of the crosstalk amount.

1 is a schematic diagram of an image reading apparatus according to an embodiment. It is a block diagram which shows the system configuration | structure of the conventional image reading apparatus. 1 is a block diagram illustrating a system configuration of an image reading apparatus having a 6-channel analog processing IC. FIG. It is a figure which shows the reading level of each channel output from the analog processing IC in the conventional image reading apparatus. It is a block diagram showing an analog processing IC of 6 channels of the image reading apparatus according to the present embodiment. It is a figure which shows the reading level of each channel of the image data of a white reference board. It is a block diagram showing an analog processing IC of 6 channels of the image reading apparatus according to the present embodiment. It is a block diagram showing an analog processing IC of 6 channels of the image reading apparatus according to the present embodiment. It is a figure which shows the mechanism which controls ON / OFF of a photoelectric conversion element in the image reading apparatus concerning this embodiment. It is a figure which shows the control signal which controls ON / OFF of a photoelectric conversion element. It is a flowchart of the process which calculates a crosstalk coefficient. It is a block diagram showing an analog processing IC of 6 channels of the image reading apparatus according to the present embodiment. It is a flowchart of the process which calculates a crosstalk coefficient.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Traveling body 102 Document 103 Lens 104, 201 Photoelectric conversion element 105 White reference plate 202 Analog buffer 203 AC coupling 204 Line clamp 205 S & H
206 VGA
207 A / DC
208 Averaging circuit 209 Peak detection circuit 210 CPU

Claims (7)

In an image reading apparatus having a plurality of photoelectric conversion elements for each separation color in parallel and an analog processing IC for processing an image signal read by each photoelectric conversion element,
An arithmetic means for calculating a correction coefficient from the image signal level of the adjacent channel when the adjacent photoelectric conversion element is turned off and the white reference plate is read.
Storage means for storing the correction coefficient calculated by the calculation means,
An image reading apparatus for correcting an image signal level of the adjacent channel based on the correction coefficient stored in the storage unit when a document is read. Determining means for determining whether or not a difference between the correction coefficient Gn + 1 calculated by the calculating means and the correction coefficient Gn already stored in the storage means is within a threshold Gth;
Updating means for updating the correction coefficient Gn stored in the storage means with the correction coefficient Gn + 1 when the difference is within the threshold Gth;
The image reading apparatus according to claim 1, further comprising a notification unit configured to notify an abnormality of the image reading apparatus when a difference in the previous period is not within the threshold Gth.   The image reading apparatus according to claim 1, further comprising a control unit that independently controls ON / OFF of each of the photoelectric conversion elements.   4. The image reading apparatus according to claim 1, wherein the calculating unit independently calculates a correction coefficient between the adjacent channels. 5.   5. The image reading apparatus according to claim 2, wherein the correction coefficient is updated by the updating unit every time the power of the image reading apparatus is turned on. In an image reading method of an image reading apparatus having a plurality of photoelectric conversion elements for each separation color in parallel and an analog processing IC for processing an image signal read by each photoelectric conversion element,
When the adjacent photoelectric conversion element is turned off and the white reference plate is read, a calculation step of calculating a correction coefficient from the image signal level of the adjacent channel;
A storage step of storing the correction coefficient calculated by the calculation step;
And a step of correcting an image signal level of the adjacent channel based on the correction coefficient stored in the storage means when the original is read. In an image reading program of an image reading apparatus having a plurality of photoelectric conversion elements for each separation color in parallel and an analog processing IC for processing an image signal read by each photoelectric conversion element,
When the adjacent photoelectric conversion element is turned off and the white reference plate is read, a calculation process for calculating a correction coefficient from the image signal level of the adjacent channel;
A storage process for storing the correction coefficient calculated by the calculation step;
An image reading program comprising: a process of correcting an image signal level of the adjacent channel based on the correction coefficient stored in the storage unit when a document is read.

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