JP2015195523A - Image reading device and image reading program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image reading device and an image reading program, capable of suppressing deterioration of image quality while suppressing generation of an abnormal image caused by rubbish and such.SOLUTION: Before performing thinning processing for thinning pixels from second input data, compensation in accordance with the number of thinning pixels is applied to the number of input pixels in accordance with input resolution so as to be capable of obtaining predetermined output resolution. Thereby, since the number of input pixels sufficient for obtaining image quality of predetermined output resolution is secured, deterioration of image quality caused by thinning may be suppressed while suppressing generation of an abnormal image caused by rubbish and such.

Description

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

  There is a scanner equipped with an auto document feeder (hereinafter referred to as “ADF”) that reads an original using a reading unit fixed at a predetermined reading position while conveying the original using the ADF. In such a scanner, a transparent document table is provided between a reading unit for reading a document and a document conveyed by the ADF. Therefore, the reading unit reads the document via the document table. When dust adheres to the document table, the reading unit continuously reads the dust on the document table while reading the document conveyed by the ADF. Therefore, black streaks extending in a streak shape in the document transport direction are generated in the output image.

  Patent Document 1 describes a technique for deleting pixel data of pixels from which dust is detected by setting a thinning clock according to a position where dust is present, as a technique for reducing the influence of dust attached to a reading unit. ing.

JP 2003-163804 A

  However, since the technique described in Patent Literature 1 periodically thins out the dust position, the thinning cycle is shortened depending on the dust position, so that the required number of output pixels cannot be ensured and the image quality is low. There is a risk of significant deterioration.

  The present invention has been made in view of the above-described circumstances, and an object thereof is to provide an image reading apparatus and an image reading program that can suppress deterioration of image quality while suppressing generation of abnormal images due to dust or the like.

  In order to achieve this object, an image reading apparatus according to the present invention uses a document transport unit that transports a document, a document table, and a reading element arranged in the main scanning direction to scan a document transported by the document transport unit. A reading unit that reads through the document table; and a control unit. The control unit receives an instruction to start reading the document, and the reading unit receives the instruction when the instruction receiving unit receives the instruction. The reference plate is read by the unit, and detection means for detecting whether there is an abnormality in the first input data obtained by the reading, and a predetermined output resolution or higher among a plurality of input resolutions prepared in advance If the input setting means for setting the input resolution of 1 and the detection means detects that the first input data obtained by the reading is abnormal, the first input data is configured. Among the input pixels, the argument setting means for setting the number of thinned pixels, which is the number of pixels corresponding to the position of the first input data detected as having an abnormality, and the input resolution set by the input setting means A correction unit that corrects the number of input pixels corresponding to the number of thinned pixels set by the interval parameter setting unit, and a document that is conveyed by the document conveyance unit after being detected by the detection unit, A document reading unit that reads by the reading unit using a reading element corresponding to the number of input pixels corrected by the correcting unit and obtains second input data composed of input pixels corresponding to the reading element, and the document reading Thinning out a pixel corresponding to the position of the first input data detected by the detection means from the input pixels constituting the second input data obtained by the means, It comprises an image processing means for obtaining output data of the preset output resolution, a.

  The present invention can be configured in various modes such as a control device that controls the image reading device, an image reading system, an image reading method, an image reading program, and a recording medium that records the image reading program.

  According to the image reading apparatus of the first aspect, when it is detected that the first input data obtained by reading is abnormal, it is detected that there is an abnormality among the input pixels constituting the first input data. Further, the number of thinned pixels, which is the number of pixels corresponding to the position of the first input data, is set. The number of input pixels corresponding to the set input resolution is corrected according to the set number of thinned pixels. And it reads using the reading element according to the number of input pixels after correction | amendment, The 2nd input data comprised from the input pixel for the said reading element is obtained. Thereafter, a thinning process is performed to thin out pixels corresponding to the position of the first input data detected as abnormal from the input pixels constituting the second input data, thereby outputting an output with a preset output resolution. Get the data.

  Thus, before performing the thinning process for thinning out pixels from the second input data, the number of input pixels corresponding to the input resolution corresponds to the number of thinned pixels so that a preset output resolution can be obtained. Correction is applied. Therefore, a sufficient number of input pixels can be ensured to obtain an image quality with a preset output resolution, so that deterioration of image quality due to thinning can be suppressed while suppressing occurrence of abnormal images due to dust or the like.

  According to the image reading apparatus of claim 2, in addition to the effect of claim 1, the following effect is obtained. The correction applied to the number of input pixels corresponding to the input resolution is performed by adding the number of pixels corresponding to the set number of thinned pixels to the number of input pixels corresponding to the set input resolution. Therefore, by adding the number of pixels to be thinned out to the number of input pixels, the number of input pixels according to the input resolution can be secured, so that deterioration in image quality due to thinning can be suppressed.

  According to the image reading apparatus of claim 3, in addition to the effect of claim 2, the following effect is obtained. The number of pixels obtained by adding the number of pixels corresponding to the set number of thinned pixels to the number of input pixels corresponding to the set input resolution is equal to or less than the maximum number of input pixels that can be read by the reading unit. As a condition, correction for the number of input pixels according to the set input resolution is performed. Therefore, it is possible to perform correction by adding the thinned-out pixels to the number of input pixels within a range that can correspond to the number of input pixels according to the set input resolution.

  According to the image reading apparatus of the fourth aspect, in addition to the effect produced by any one of the first to third aspects, the following effect is produced. When it is detected that there is an abnormality in the first input data, the number of thinned pixels set with respect to the enlargement ratio in the enlargement process for enlarging the pixels after the thinning process to have a preset output resolution Make corrections according to. When it is detected that the first input data is abnormal, the second input data is subjected to enlargement processing at the corrected enlargement ratio. Therefore, it is possible to output an image having a preset output resolution while suppressing the occurrence of an abnormal image due to dust or the like by thinning out pixels.

  According to the image reading apparatus of claim 5, in addition to the effect of claim 4, the following effect is obtained. The correction for the enlargement ratio is performed by changing the reference enlargement ratio calculated from (preset output resolution / set input resolution) to a value larger than the reference enlargement ratio in accordance with the set number of thinned pixels. This is the correction to enlarge. Therefore, it is possible to output an image having a preset output resolution while suppressing the occurrence of an abnormal image due to dust or the like by thinning out pixels.

  According to the image reading apparatus of the sixth aspect, in addition to the effect produced by the fifth aspect, the following effect is produced. The number of pixels obtained by adding the number of pixels corresponding to the set number of thinned pixels to the number of input pixels corresponding to the set input resolution exceeds the maximum number of input pixels that can be read by the reading unit. As shown in FIG. Therefore, when correction by adding the pixels to be thinned out to the number of input pixels is not possible, the enlargement rate is corrected, and the occurrence of abnormal images due to dust or the like is suppressed by thinning out pixels. Output resolution image can be output.

  According to the image reading apparatus of the seventh aspect, in addition to the effect produced by any one of the first to sixth aspects, the following effect is obtained. When there is an abnormality in the first input data, it corresponds to the range of the first input data that is detected to be more than a preset output resolution among a plurality of input resolutions prepared in advance. An input resolution of 1 is set. Therefore, the input resolution capable of obtaining a preset output resolution can be set to a value corresponding to the range of the abnormal first input data.

  According to the image reading apparatus of claim 8, in addition to the effect of claim 7, the following effect is obtained. When there is an abnormality in the first input data, the range of the first input data that is equal to or higher than a preset output resolution among a plurality of input resolutions prepared in advance and is detected as having an abnormality is the smallest. An input resolution of 1 read by the pixel is set. Therefore, the number of pixels to be thinned out can be minimized, and deterioration in image quality can be suppressed.

  According to the image reading apparatus of the ninth aspect, in addition to the effect produced by any one of the first to eighth aspects, it is possible to cope with a thinning process for periodically thinning out pixels.

  The image reading apparatus according to the tenth aspect has the following effect in addition to the effect of the ninth aspect. Since the thinning process is executed on the condition that the position of the first input data detected as abnormal is away from the first pixel of the first input data by a predetermined distance or more, the thinning cycle is shortened. Degradation of image quality caused by

  According to the image reading device of the eleventh aspect, in addition to the effect of the tenth aspect, the distance serving as the threshold value of the condition is set to a larger value as the set input resolution is larger. Appropriate correction can be performed according to the resolution.

  According to the image reading device of the twelfth aspect, in addition to the effect produced by any one of the ninth to eleventh aspects, the following effect is obtained. The thinning-out process is executed on condition that the input resolution of 1 for reading the range of the first input data detected as having an abnormality with the smallest number of pixels is equal to or higher than a preset output resolution. Therefore, output data having a preset output resolution can be obtained.

  According to the image reading program of the thirteenth aspect, the same effect as the image reading apparatus of the first aspect can be obtained.

It is a block diagram which shows the electric constitution of a scanner. It is a schematic diagram which simplifies and shows a part of scanner. (A) And (b) is a flowchart which shows an ADF reading process and a dust detection process, respectively. (A) And (b) is a flowchart which respectively shows an input resolution setting process and a correction process. (A) And (b) is a flowchart which respectively shows the input resolution setting process and correction | amendment process of 2nd Embodiment.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. First, a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a block diagram showing an electrical configuration of a scanner 10 which is an embodiment of an image reading apparatus of the present invention. Although details will be described later, the scanner 10 of the present embodiment is configured to suppress deterioration of image quality while suppressing generation of abnormal images due to dust or the like, for example, generation of black streaks extending in the sub-scanning direction in the output image. The

  The scanner 10 is mainly provided with a CPU 11, ROM 12, RAM 13, EEPROM 14, operation unit 15, LCD 16, CIS 17, reading drive unit 18, ADF 19, USB interface (USB_I / F) 22, and network interface (network I / F) 23. It is done. These units 11 to 19, 22 and 23 are connected to each other via a bus line 24.

  The CPU 11 controls each unit of the scanner 10 according to fixed values and programs stored in the ROM 12 and data stored in the RAM 13. The ROM 12 is a read-only memory.

  The ROM 12 stores a control program 12a that controls the operation of the scanner 10, constants and tables that are referred to when the control program 12a is executed. Each process shown in the flowcharts of FIGS. 3 to 5 described later is a process executed by the CPU 11 in accordance with the control program 12a.

  The RAM 13 is a rewritable volatile memory that temporarily stores information necessary for the processing of the CPU 11. The EEPROM 14 is a non-volatile memory that can be rewritten and can retain its contents even after the power is turned off.

  The operation unit 15 is used to input setting values and instructions to the scanner. Examples of the operation unit 15 include a touch panel provided on the LCD 16 and a mechanical key. The LCD 16 is a liquid crystal display device that displays various screens.

  The CIS 17 is a reading unit that reads a document using a contact image sensor (Contact Image Sensor) method. The CIS 17 forms a linear image sensor having a plurality of light receiving elements arranged linearly in the main scanning direction, a light source having light emitting diodes of RGB three colors, and reflected light reflected by the original on each light receiving element of the image sensor. It has a rod lens array.

  The main scanning direction is a direction parallel to the surfaces of the platen glasses 44 and 45 (see FIG. 2) and is a direction orthogonal to the moving direction of the CIS 17 by the reading drive unit 18. The main scanning direction is also a direction orthogonal to the conveyance direction of the document conveyed on the platen glasses 44 and 45 by the ADF 19.

  The reading drive unit 18 is for moving the CIS 17 in the sub-scanning direction. The reading drive unit 18 includes a motor that is a stepping motor, a motor drive unit that generates a drive signal for step driving the motor, and the like. The sub-scanning direction is a direction along the conveyance direction of the document conveyed on the platen glass 44, 45 by the ADF 19, and is an arrow A direction or an arrow B direction (see FIG. 2).

  The ADF 19 conveys the original set on the original tray 58 (see FIG. 2) to the reading position by the CIS 17 along the conveyance path 57 (see FIG. 2), and the original after reading by the CIS 17 to the discharge tray 59. Transport.

  The USB_I / F 23 is a device for communicatively connecting a storage medium such as a USB memory or other devices such as a personal computer or a hard disk via a USB plug, and is configured by a known device. The network_I / F 24 is an interface for connecting the scanner 10 to a network (not shown) such as a LAN or the Internet.

  FIG. 2 is a schematic diagram showing a part of the scanner 10 in a simplified manner. The housing 43 of the scanner 10 is generally box-shaped, and a first platen glass 44 and a second platen glass 45 are juxtaposed at the top.

  The document cover 46 is connected to the housing 43 so as to be rotatable between a closed posture that covers the platen glasses 44 and 45 and an open posture that opens the platen glasses 44 and 45. The document cover 46 is provided with an ADF 19, a document tray 58, a paper discharge tray 59, and the like.

  Inside the ADF 19, there are a separation roller 50, a suction roller 52 that is rotatably provided at a distal end portion of an arm 51 that is pivotally supported by a shaft that pivotally supports the separation roller 50, a plurality of transport rollers 53, 54, a paper discharge roller 55, and a plurality of driven rollers 56 in pressure contact therewith. The document is transported to these rollers, transported along a transport path 57, passes through a position where it is read by the CIS 17, and is discharged onto a discharge tray 59.

  The CIS 17 is accommodated in the housing 43 of the scanner 10. When reading the document conveyed by the ADF 19, the CIS 17 stops immediately below the second platen glass 45, sets the position as the reading position, and sequentially switches the color of the light source while scanning the document through the second platen glass 45. read. On the other hand, when the CIS 17 reads a document placed on the first platen glass 44, the CIS 17 is moved at a constant speed in the sub-scanning direction (arrow A direction or arrow B direction) using the reading drive unit 18. The original is read while sequentially switching the color of the light source.

  A white reference plate 60 that can be read by the CIS 17 via the second platen glass 45 is provided on the side facing the CIS 17 via the second platen glass 45. In the present embodiment, prior to reading the original, the CIS 17 reads the reference plate 60 to detect the possibility of generating an abnormal image such as dust on the second platen glass 45.

  FIG. 3A is a flowchart showing ADF reading processing executed by the CPU 11 according to the control program 12a. This process is a process of reading the original while conveying the original using the ADF 19. The CPU 11 waits for reception of a document reading instruction using the ADF 19 (S301: No).

  When the CPU 11 receives an instruction to read a document using the ADF 19 (S301: Yes), the CPU 11 executes preparation processing such as light amount adjustment and shading correction (S302). The CPU 11 uses the reading drive unit 18 to move the CIS 17 in the sub-scanning direction and arrange it at a predetermined reading position directly below the second platen glass 45 (S303).

  The CPU 11 executes dust detection processing (S304). Although details will be described later with reference to FIG. 3B, the dust detection process (S304) detects whether or not there is a possibility of generating an abnormal image such as foreign matter such as dust on the second platen glass 45. It is processing. Hereinafter, “possibility of generating an abnormal image” is referred to as “dust”.

  The CPU 11 executes input resolution setting processing (S305). Although details will be described later with reference to FIG. 4A, the input resolution setting process (S305) sets the input resolution according to the output resolution preset by the user and the detection result by the dust detection means (S304). It is processing to do.

  The CPU 11 determines whether 1 is set in the dust detection flag (S306). The “dust detection flag” is a flag for specifying whether dust is detected on the second platen glass 45 or the like, and is provided in the RAM 13. When the dust detection flag is set to 1, it indicates that dust is detected. On the other hand, when the dust detection flag is set to 0, it indicates that no dust is detected.

  When the CPU 11 determines that the value of the dust detection flag is not 1 (S306: No), the CPU 11 proceeds to S308. On the other hand, when the CPU 11 determines that the value of the dust detection flag is 1 (S306: Yes), the CPU 11 executes a correction process (S307), and the process proceeds to S308. Although details will be described later with reference to FIG. 4B, the correction process (S307) corresponds to the number of input pixels corresponding to the input resolution in accordance with the number of pixels to be thinned out in the thinning-out process for thinning out dusty positions. Correction processing.

  In S308, the cpu 11 performs a reading process of reading the original document with the CIS 17 while conveying the original document with the ADF 19 (S308). The CPU 11 performs image processing on the image data obtained by reading (hereinafter referred to as “read image data”) (S309), and ends this processing. In the image processing (S309), thinning processing for thinning out pixels from the read image data and enlargement processing for enlarging the read image data at an enlargement ratio corresponding to the number of input pixels and the number of output pixels are performed.

  In the present embodiment, a thinning process that thins an arbitrary pixel from an input pixel is adopted as the thinning process. In the thinning process according to the present embodiment, pixels that detect dust are thinned out. More specifically, the pixel corresponding to the main scanning position where dust is detected, which is stored in S327 described later, is thinned out by thinning processing.

  FIG. 3B is a flowchart showing the above-described dust detection process (S304). The CPU 11 sets the dust detection flag to 0 and sets the number of thinned pixels to 0 (S321). The CPU 11 sets the maximum input resolution among the input resolutions that can be set by the scanner 10 (S322). The scanner 10 according to the present embodiment is prepared with three types of input resolutions of 300 dpi, 600 dpi, and 1200 dpi. Therefore, in this embodiment, in S322, the CPU 11 sets 1200 dpi as the input resolution.

  The CPU 11 causes the CIS 17 to read one line of the white reference plate 60 provided at a position facing the CIS 17 through the second platen glass 45 at the current reading position (S323). The reference plate 60 is not limited to a white reference plate but may be a gray reference plate. The CPU 11 sets the first pixel in the read image data obtained by reading in S323 as a target pixel (S324).

  The CPU 11 determines whether the pixel value of the target pixel exceeds a threshold value (S325). When the CPU 11 determines that the pixel value of the target pixel does not exceed the threshold value (S325: No), the CPU 11 detects that there is an abnormality in the image data read from the reference plate 60, that is, dust is detected. The flag is set to 1 (S326), and the position in the main scanning direction of the pixel G that is the target pixel (hereinafter referred to as “main scanning position”) is stored in the RAM 13 (S327). The CPU 11 adds 1 to the number of thinned pixels (S328), and the process proceeds to S329. On the other hand, when the CPU 11 determines that the pixel value of the target pixel exceeds the threshold value (S325: Yes), the CPU 11 skips the processes of S326 to S328 and shifts the process to S329.

  In S329, the CPU 11 determines whether or not the determination in S325 has been made for all the pixels constituting the image data obtained by the reading in S323 (S329). When the CPU 11 denies the determination in S329 (S329: No), the CPU 11 moves the target pixel to the next pixel (S332), and shifts the processing to S325.

  If the CPU 11 affirms the determination in S329 (S329: Yes), the CPU 11 determines whether 1 is set in the dust detection flag (S330). If the CPU 11 determines that 1 is not set in the dust detection flag (S330: No), the CPU 11 ends this process.

  On the other hand, when the CPU 11 determines that 1 is set in the dust detection flag (S330: Yes), the CPU 11 obtains the size of the detected dust (S331), and ends this process. In the present embodiment, the size of dust is represented by one of (1/1200) dpi, (1/600) dpi, or (1/300) dpi.

  (1/1200) dpi indicates the size of dust detected by one pixel at a resolution of 1200 dpi. (1/600) dpi indicates the size of dust detected by one pixel at a resolution of 600 dpi. (1/300) dpi indicates the size of dust detected by one pixel at a resolution of 300 dpi. Therefore, the size of the dust is (1/1200) dpi <(1/600) dpi <(1/300) dpi.

  That is, in S331, based on the main scanning position where dust is detected, the CPU 11 determines whether the detected dust is the size of one pixel at a resolution of 1200 dpi or the size of one pixel at a resolution of 600 dpi. Then, it is determined whether the size is one pixel at a resolution of 300 dpi. Note that each dust detected by pixels continuous in the main scanning direction when read at the maximum input resolution is regarded as one dust. That is, the number of pixels in which continuous dust is detected is determined as the size of dust. When there are a plurality of detected dusts, the size of the largest dust is taken.

  FIG. 4A is a flowchart showing the above-described input resolution setting process (S305). The CPU 11 determines the input resolution from the output resolution preset by the user (S401). Specifically, the CPU 11 selects an input resolution that is larger than the output resolution and is closest to the output resolution from among the input resolutions prepared in advance.

  The scanner 10 of this embodiment is prepared with three types of input resolutions of 300 dpi, 600 dpi, and 1200 dpi. Therefore, for example, when 400 dpi is set as the output resolution, the CPU 11 selects 600 dpi as the input resolution.

  The CPU 11 determines whether the dust detection flag is 1 (S402). When the CPU 11 determines that the dust detection flag is not 1 (S402: No), the CPU 11 ends this process. Therefore, when no dust is detected, the input resolution is the value determined in S401.

  When the CPU 11 determines that the dust detection flag is 1 (S402: Yes), the CPU 11 determines the size of the dust (S403). When the CPU 11 determines that the size of the dust is (1/1200) dpi (S403: (1/1200) dpi), the CPU 11 sets the input resolution to 1200 dpi (S404), and ends this processing. .

  On the other hand, when the CPU 11 determines that the size of the dust is (1/600) dpi (S403: (1/600) dpi), the CPU 11 determines whether the set output resolution is 600 dpi or less. (S405). When the CPU 11 determines that the set output resolution is 600 dpi or less (S405: Yes), the CPU 11 sets the input resolution to 600 dpi (S406), and ends this process. In S405, when the set output resolution is larger than 600 dpi (S405: No), the CPU 11 ends this process.

  When the CPU 11 determines that the size of the dust is (1/300) dpi or more (S403: (1/300) dpi or more), the CPU 11 determines whether the set output resolution is 300 dpi or less. (S407). When the CPU 11 determines that the set output resolution is 300 dpi or less (S407: Yes), the CPU 11 sets the input resolution to 300 dpi (S408), and ends this process. In S406, when the set output resolution is larger than 300 dpi (S407: No), the CPU 11 ends this process.

  Therefore, according to the input resolution setting process (S305), not only the set output resolution but also the input resolution corresponding to the size of dust is set. Specifically, an input resolution capable of reading dust with a minimum number of pixels (that is, one pixel) is set. Therefore, the number of pixels to be thinned out can be suppressed to a minimum, so that deterioration in image quality can be suppressed.

  However, although the number of pixels to be thinned out can be minimized, if the input resolution at which dust can be read with one pixel is lower than the output resolution set by the user, the output resolution requested by the user The image cannot be output. Therefore, in such a case, by adopting the input resolution determined in S401, an image with an image quality according to the user's intention can be output.

  FIG. 4B is a flowchart showing the above-described correction process (S307). The CPU 11 acquires the number of thinned pixels according to the input resolution set in the input resolution setting process (S305) (S420). The number of thinned pixels counted in the dust detection process (S304) is a value based on image data read at the maximum input resolution that can be set by the scanner 10. Therefore, it is necessary to correct the number of thinned pixels counted in the dust detection process (S304) according to the input resolution set in the input resolution setting process (S305). In S420, the CPU 11 corrects the number of thinned pixels.

  The CPU 11 sets (input pixel number + decimated pixel number) to a value of X (S421). The number of input pixels in S421 is the number of pixels corresponding to the input resolution set in the input resolution setting process (S305). On the other hand, the number of thinned pixels is the value acquired in S420.

  The CPU 11 determines whether the value of X calculated in S421 exceeds the maximum number of input pixels (S422). The maximum number of input pixels is the maximum number of pixels that can be read by the CIS 17. The maximum number of input pixels depends on the type of CIS 17.

  If the CPU 11 determines that the value of X is equal to or less than the maximum number of input pixels (S422: No), the CPU 11 sets the number of thinned pixels acquired in S420 as the number of thinned pixels in the thinning process. (S425). The CPU 11 sets the number of input pixels to the value of X calculated in S421, that is, a value obtained by adding the number of thinned pixels to the number of input pixels corresponding to the set input resolution (S426).

  The CPU 11 sets the enlargement ratio used in the enlargement process (S427), and ends this process. The enlargement ratio set by the CPU 11 in S427 is (the preset output resolution / input resolution set in the input resolution setting process (S305)).

  On the other hand, when the CPU 11 determines that the value of X exceeds the maximum number of input pixels (S422: Yes), the CPU 11 uses the number of thinned pixels acquired in S420 as the number of thinned pixels to be thinned in the thinning process. Setting is made (S423). The CPU 11 sets the enlargement ratio used in the enlargement process (S424), and ends this process.

  The enlargement ratio set by the CPU 11 in S424 is (maximum input pixel number / (input pixel number−thinned pixel) in (preset output resolution / input resolution set in input resolution setting process (S305)). Number)}. That is, in accordance with the number of pixels to be thinned out from the number of input pixels (that is, the number of pixels to be thinned acquired in S420), the size of the output resolution with respect to the set input resolution, which is a reference enlargement ratio Make corrections. Specifically, correction is performed so that the number of pixels to be thinned out is larger than the reference enlargement ratio.

  According to the first embodiment, the output image can be prevented from including abnormal images such as black streaks by thinning out pixels at positions where dust is detected from the read image data of the document. At this time, before performing the thinning process for thinning out pixels from the read image data, the number of input pixels according to the input resolution is set according to the number of thinned pixels so that an output resolution preset by the user can be obtained. Correction is applied. Specifically, the number of pixels at the time of reading (that is, the number of input pixels) is a number obtained by adding the number of thinned pixels to the number of input pixels corresponding to the input resolution. As a result, the number of input pixels corresponding to the input resolution can be secured even after thinning is performed, so that deterioration of image quality due to thinning of the position where dust is detected can be suppressed.

  In addition, when the number of thinned pixels added to the number of input pixels corresponding to the input resolution exceeds the maximum number of pixels that can be read by the CIS 17 (that is, the maximum number of input pixels), the number of input pixels after addition is obtained. Since this is physically impossible, there is no point in performing correction to add the number of thinned pixels. On the other hand, in the present embodiment, the correction for adding the number of thinned pixels is performed on condition that the number of pixels after the addition of the number of thinned pixels is equal to or less than the maximum number of input pixels. That is, the correction for adding the number of thinned pixels is performed in a range that can be handled by the CIS 17.

  On the other hand, when the number of pixels after the addition of the number of thinned pixels exceeds the maximum number of input pixels, in the enlargement process for enlarging the image data after the thinning to the set output resolution, the enlargement in the enlargement process Correct the rate. Specifically, a correction corresponding to the number of pixels to be thinned out from the number of input pixels is performed on the size of the output resolution with respect to the set input resolution, which is a reference enlargement ratio. Specifically, correction is performed so that the number of pixels to be thinned out is larger than the reference enlargement ratio. Accordingly, it is possible to output an image with an output resolution set by the user while suppressing the occurrence of an abnormal image due to dust or the like by thinning out pixels.

  Next, a second embodiment will be described with reference to FIG. In the first embodiment, a thinning process that thins an arbitrary pixel from an input pixel is adopted as the thinning process. On the other hand, in the second embodiment, as the thinning process, a thinning process in which the input pixels are periodically thinned at a predetermined thinning rate is employed.

  In the second embodiment, the same parts as those in the first embodiment described above are denoted by the same reference numerals, and the description thereof is omitted. Each process shown in the flowcharts of FIGS. 5 and 6 below is executed by the CPU 11 according to the control program 12a of the second embodiment.

  FIG. 5A is a flowchart showing the input resolution setting process (S305) of the second embodiment. A description will be given centering on differences from the input resolution setting processing (FIG. 4A) of the first embodiment. When the CPU 11 determines that the dust size is (1/600) dpi and the set output resolution is larger than 600 dpi (S403: (1/600) dpi, S405: No), the CPU 11 Sets the dust detection flag to 0 (S501), and ends this processing.

  When the CPU 11 determines that the size of the dust is (1/300) dpi or more and the set output resolution is larger than 300 dpi (S403: (1/300) dpi, S407: No. ), The CPU 11 shifts the process to S501.

  If the input resolution at which dust can be read by one pixel is lower than the output resolution set by the user, reading at that input resolution and periodic decimation will result in Significant degradation occurs. On the other hand, according to the input resolution setting process of the present embodiment, in such a case, the presence of the detected dust itself is ignored, so that significant deterioration in image quality can be suppressed.

  FIG. 5B is a flowchart showing the correction process (S307) of the second embodiment. Differences from the correction processing of the first embodiment (FIG. 4B) will be mainly described. The CPU 11 determines whether or not the main scanning position of the pixel G that is a pixel in which dust is detected is less than the threshold value N (S521). The threshold value N is a value indicating that the Nth pixel in the main scanning direction from the first pixel (that is, the 0th pixel) is the thinning-out limited pixel position.

  As the dust position is closer to the first pixel, the thinning cycle becomes shorter (that is, the thinning rate becomes larger), so that the number of pixels drawn for that minute increases, causing deterioration in image quality. Therefore, in this embodiment, a thinning-out limited pixel position is provided, and the thinning-out process is not executed when the pixel G is closer to the head than the thinning-out limited pixel position. The threshold value N varies depending on the set input resolution, and the value of the threshold value N increases as the input resolution increases. For example, the values of the threshold N for input resolutions of 300 dpi, 600 dpi, and 1200 dpi are 100, 200, and 400, respectively.

  If the CPU 11 determines in S521 that the main scanning position of the pixel G is smaller than the threshold value N, that is, if the pixel G is positioned on the head side from the thinning-out limited pixel position (S521: Yes), the CPU 11 ends this processing. To do. That is, in such a case, the thinning process and the enlargement process corresponding to the detection of dust are not performed.

  On the other hand, when the CPU 11 determines in S521 that the main scanning position of the pixel G is greater than or equal to the threshold value N (S521: No), the CPU 11 performs thinning processing and enlargement processing in response to the detection of dust. , S421 and subsequent processes are executed.

  In the present embodiment, unlike the first embodiment, thinning-out processing is employed that periodically thins out input pixels at a predetermined thinning rate. Therefore, the CPU 11 executes a process (S522, S523) for setting a cycle (that is, a thinning rate) in which the pixels G are thinned, which is used in the thinning process, instead of the processes of S423 and S425 of the first embodiment. To do.

  Specifically, the CPU 11 sets a cycle that includes, for example, the pixel G that has detected the largest dust. Alternatively, the CPU 11 sets a cycle in which as many pixels G as possible are thinned out of the pixels G from which the plurality of dusts are detected when a plurality of dusts are detected. In the image processing (S309), the CPU 11 performs a thinning process with the period set in S522 or S523. Therefore, pixels where dust is detected can be thinned out.

  According to the second embodiment, even when the thinning-out method that periodically thins the input pixels at a predetermined thinning rate is adopted, the output image includes abnormal images such as black streaks as in the first embodiment. Can be suppressed. When thinning out pixels periodically, if the main scanning position of the pixel G where dust is detected is closer to the head than the thinning-out restricted pixel position, the thinning-out process is not executed, and therefore the thinning-out cycle is short and the number of thinning-outs is excessive. It is possible to suppress image quality deterioration due to. Since the value of the threshold value N as the thinning-out restricted pixel position is set to a larger value as the input resolution is larger, it is determined whether or not the thinning process is appropriately executed according to the input resolution for the main scanning position of the image G. Can be determined.

  In the above embodiment, the scanner 10 is an example of an image reading apparatus. The control program 12a is an example of an image reading program. The CPU 11 is an example of a control unit. The ADF 19 is an example of a document conveying unit. The second platen glass 45 is an example of a document table. The CIS 17 is an example of a reading unit. The reference plate 60 is an example of a reference plate. The image data obtained by the process of S323 is an example of the first input data. The image data obtained by the process of S308 is an example of second input data.

  The CPU 11 that executes the process of S301 is an example of an instruction receiving unit. CPU11 which performs the process of S305 is an example of an input setting means. The CPU 11 that executes the process of S328 is an example of an interval argument setting unit. The CPU 11 that executes the process of S307 is an example of a correction unit. The CPU 11 that executes the process of S308 is an example of a document reading unit. The CPU 11 that executes the process of S309 is an example of an image processing unit. CPU11 which performs the process of S331 is an example of a 2nd detection means. CPU11 which performs the process of S522 and S523 is an example of a period setting means.

  Although the present invention has been described based on the embodiments, the present invention is not limited to the above-described embodiments, and various improvements and modifications can be easily made without departing from the spirit of the present invention. Can be inferred.

  For example, the numerical values exemplified in the above embodiment are merely examples, and other numerical values can be adopted. For example, other input resolutions such as 2400 dpi can be adopted as the input resolution prepared for the scanner 10.

  In the embodiment described above, (1/1200) dpi, (1/600) dpi, or (1/300) dpi is exemplified as the size of dust, but the size is not limited to this. For example, if the scanner can set (1/2400) dpi as the output resolution, the determination of the size of dust in S403 is (1/2400) dpi, (1/1200) dpi, (1/600). It may be determined whether it is dpi or (1/300) dpi. That is, it is preferable to determine whether the size of the dust is (1 / resolution at which the scanner can output) dpi.

  In the above embodiment, the dpi is used as the unit of the size of the dust. However, the present invention is not limited to this, and various units such as inches and millimeters may be employed. Specifically, in the above embodiment, it is determined in S403 whether the size of the dust is (1/1200) dpi, (1/600) dpi, or (1/300) dpi. ) Inch, (1/600) inch, or (1/300) inch may be determined.

  In the above embodiment, when the CPU 11 determines that the value of X calculated in S421 is equal to or less than the maximum number of input pixels of the scanner 10, the enlargement ratio is set in S427, but the preset output resolution and input If the input resolution set in the resolution setting process (S305) is the same, the process of S427 may be skipped.

  In the above-described embodiment, the scanner 10 is exemplified as the image reading apparatus of the present invention. However, various apparatuses such as a multi-functional peripheral apparatus can be adopted as long as the apparatus can execute reading of a document using the ADF.

  In the above-described embodiment, the CPU 11 has been described as a configuration for executing each process described in FIGS. 3 to 5. However, each of the processes described in each of these drawings is configured to be executed cooperatively by a plurality of CPUs. Also good. Further, an IC such as an ASIC may be configured to execute each process described in each of the above drawings independently or in cooperation with a plurality of ICs. Further, the CPU 11 and an IC such as an ASIC may cooperate to execute each process described in the above drawings.

  Among the processes shown in FIGS. 3 to 5, some of the processes may be omitted or changed without departing from the independent claims. Moreover, it is good also as a structure implemented combining each characteristic demonstrated by the said embodiment and each modification mentioned above suitably.

10: Scanner, 12a: Control program

Claims (13)

A document transport section for transporting a document;
The document table,
A reading unit that reads a document conveyed by the document conveying unit through a document table using reading elements arranged in a main scanning direction;
A control unit,
The controller is
An instruction receiving means for receiving an instruction to start reading a document;
When the instruction is received by the instruction receiving unit, the reference unit is read by the reading unit, and detecting unit that detects whether the first input data obtained by the reading is abnormal,
An input setting means for setting one input resolution that is equal to or higher than a preset output resolution among a plurality of input resolutions prepared in advance;
When it is detected by the detection means that the first input data obtained by the reading is abnormal, among the input pixels constituting the first input data, the first input data detected as having the abnormality Argument setting means for setting the number of thinned pixels that is the number of pixels corresponding to the position;
Correction means for correcting the number of input pixels according to the input resolution set by the input setting means according to the number of thinned pixels set by the interval argument setting means;
After the detection by the detection unit, the document conveyed by the document conveyance unit is read by the reading unit using a reading element corresponding to the number of input pixels corrected by the correction unit, and input pixels corresponding to the reading element are read. Document reading means for obtaining second input data comprising:
Thinning out pixels corresponding to the position of the first input data detected as abnormal by the detection means from the input pixels constituting the second input data obtained by the document reading means; Image processing means for obtaining output data of a preset output resolution;
An image reading apparatus comprising: The correction means adds the number of pixels according to the number of thinned pixels set by the interval argument setting means to the number of input pixels according to the input resolution set by the input setting means,
The document reading means includes:
When it is detected by the detection means that the first input data obtained by the reading is normal, the original is read by the reading unit according to the number of input pixels set by the input setting means. While reading with the element,
When it is detected by the detection means that the first input data obtained by the reading is abnormal, reading is performed using a reading element corresponding to the number of input pixels corrected by the correction means. The image reading apparatus according to claim 1.   The correction means has a number of pixels obtained by adding a number of pixels corresponding to the number of thinned pixels set by the interval argument setting means to the number of input pixels corresponding to the input resolution set by the input setting means. The image reading apparatus according to claim 2, wherein the correction is performed on condition that the number is less than a maximum number of input pixels that can be read by the reading unit. The correction means enlarges the pixel after the thinning process to the preset output resolution when the detection means detects that the first input data obtained by the reading is abnormal. For the enlargement ratio in the enlargement process for performing the correction according to the number of thinned pixels set by the interval argument setting means,
When the detection means detects that the first input data obtained by the reading is abnormal, the image processing means corrects the second input data obtained by the document reading means by the correction means. The image reading apparatus according to claim 1, wherein the enlargement process is executed at a later enlargement ratio.   The correction unit determines a reference enlargement ratio calculated from (the preset output resolution / the input resolution set by the input setting unit) according to the number of thinned pixels set by the interval argument setting unit. The image reading apparatus according to claim 4, wherein the image enlargement ratio is corrected to a value larger than the reference enlargement ratio.   The correction means has a number of pixels obtained by adding a number of pixels corresponding to the number of thinned pixels set by the interval argument setting means to the number of input pixels corresponding to the input resolution set by the input setting means. The image reading apparatus according to claim 5, wherein the correction is performed on condition that the number of input pixels that can be read by the reading unit exceeds a maximum number. The controller is
When it is detected that there is an abnormality in the first input data obtained by the reading, a second detection unit that detects a range of the first input data detected as having the abnormality,
The input setting means, when it is detected that the first input data obtained by the reading is abnormal, is more than the preset output resolution among the plurality of input resolutions prepared in advance, and 7. The image reading apparatus according to claim 1, wherein one input resolution corresponding to a range of the first input data detected by the second detection unit is set.   The input setting means, when it is detected that the first input data obtained by the reading is abnormal, is more than the preset output resolution among the plurality of input resolutions prepared in advance, and 8. The image reading apparatus according to claim 7, wherein one input resolution for reading the range of the first input data detected by the second detection means with the smallest number of pixels is set. The thinning process is a process of periodically thinning out pixels.
The controller is
A period setting unit configured to set a period for thinning out the pixels in the thinning process so as to include the position of the first input data detected as having the abnormality as the pixels to be thinned out by the thinning process; An image reading apparatus according to claim 1, wherein:   The thinning-out process is executed on condition that the position of the first input data detected as having the abnormality is a predetermined distance or more away from the first pixel of the first input data. The image reading apparatus according to 9.   The image reading apparatus according to claim 10, wherein the predetermined distance is set to a larger value as the input resolution set by the input setting unit is larger.   The thinning-out process is executed on condition that one input resolution for reading the range of the first input data detected by the second detection means with the smallest number of pixels is equal to or higher than the preset output resolution. The image reading apparatus according to claim 9, wherein the image reading apparatus is an image reading apparatus. A document transport section for transporting a document;
The document table,
A reading unit that reads a document conveyed by the document conveying unit through a document table using reading elements arranged in a main scanning direction;
An image reading program executable by the control unit of an image reading apparatus comprising:
An instruction receiving means for receiving an instruction to start reading a document;
When the instruction is received by the instruction receiving unit, the reference unit is read by the reading unit, and detecting unit that detects whether the first input data obtained by the reading is abnormal,
An input setting means for setting one input resolution that is equal to or higher than a preset output resolution among a plurality of input resolutions prepared in advance;
When it is detected by the detection means that the first input data obtained by the reading is abnormal, among the input pixels constituting the first input data, the first input data detected as having the abnormality Argument setting means for setting the number of thinned pixels that is the number of pixels corresponding to the position;
Correction means for correcting the number of input pixels according to the input resolution set by the input setting means according to the number of thinned pixels set by the interval argument setting means;
After the detection by the detection unit, the document conveyed by the document conveyance unit is read by the reading unit using a reading element corresponding to the number of input pixels corrected by the correction unit, and input pixels corresponding to the reading element are read. Document reading means for obtaining second input data comprising:
Thinning out pixels corresponding to the position of the first input data detected as abnormal by the detection means from the input pixels constituting the second input data obtained by the document reading means; As an image processing means for obtaining output data of a preset output resolution,
An image reading program for causing the control unit to function.

Images