Image read system and program

Abstract

To suppress a decrease in picture quality as compared with a case in which a read image is output as it is without executing processing to relatively reduce noise.SOLUTION: An image read part 12 has a surface image read part 42 which generates a read image read by irradiating an object with emission light that a first light source 72 emits and receiving reflected light reflected by the object by a first read sensor 82, and a CPU 184. The CPU 184 receives first read data obtained by reading a first white reference board 68 by the surface image read part 42, and performs edge emphasis processing on the read image by a spatial filter and outputs it when the difference between the first read data and first reference data exceeds a previously set value.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an image reading system and a program. [Background technology]

[0002] Patent Document 1 discloses technology relating to an image processing device, an image processing system, and a program. In this prior art, in functions such as copying an image, the original image signal output from the CCD image sensor is amplified in an amplifier with an amplification factor set based on the reference intensity of the image signal. In contrast, the image signal used in the paper fingerprint processing unit is not amplified in the amplifier, but is generated based on the original image signal output from the CCD image sensor. At that time, the control unit controls a motor drive circuit to reduce the speed of the document reading in the sub-scanning direction, thereby increasing the exposure amount at the CCD image sensor by an amount corresponding to the amplification factor, and raising the original image signal to the reference intensity. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2012-39506 A Summary of the Invention [Problem to be solved by the invention]

[0004] Light emitted from a light source is reflected by an object such as a document, and the reflected light is received by a light receiving unit to generate a read image of the object. When the amount of light decreases due to deterioration of the light source over time, and the amount of light received by the light receiving unit decreases, the noise ratio increases, the S / N ratio of the read image decreases, and the image quality of the read image deteriorates. However, in order to reduce the noise ratio and increase the S / N ratio to suppress deterioration in the image quality of the read image, for example, a process of increasing the output of the light source above the rated value or a process of decreasing the reading speed below normal is required.

[0005] An object of the present invention is to suppress deterioration in image quality compared to when a scanned image is output as is without executing processing for relatively reducing noise. [Means for solving the problem]

[0006] The first aspect is a reading system having a reading unit that irradiates an object with light emitted by a light source, receives light reflected from the object with a light receiving unit, and outputs a read image, and a processor, in which the processor receives read data obtained by the reading unit reading a white reference, and when a difference between the read data and the reference data exceeds a preset value, performs edge enhancement processing on the read image using a spatial filter and outputs it as a processed image.

[0007] A second aspect is the reading system according to the first aspect, wherein the processor increases the strength of the edge enhancement process of the spatial filter when a difference between the read data and the reference data is large compared to when the difference is small.

[0008] A third aspect is the reading system according to the first aspect, wherein the processor performs frequency filtering on the read image with a low-pass filter before performing edge enhancement processing with the spatial filter.

[0009] A fourth aspect is a reading system according to the third aspect, wherein the processor increases the strength of the edge enhancement processing of the spatial filter and decreases the frequency of the low-pass filter when the difference between the read data and the reference data is large compared to when the difference is small.

[0010] A fifth aspect is the reading system according to the first aspect, wherein the processor reduces the output of the light source below the rated output until a difference between the read data and the reference data exceeds the set value.

[0011] A sixth aspect is the reading system according to the fifth aspect, wherein the processor reduces the output of the light source below a rated value when the light receiving unit is of a contact optical system.

[0012] A seventh aspect is a reading system described in the fifteenth aspect, in which, when the output of the light source is less than a rated output, the output of the light source is brought to the rated output and then reduced below the rated value until the difference between the read data and the reference data exceeds the set value.

[0013] An eighth aspect is a program for a reading system having a reading unit that irradiates an object with light emitted from a light source, receives the reflected light reflected by the object with a light receiving unit, and outputs a read image, and a processor, in which the reading unit receives read data obtained by reading a white reference, and when a difference between the read data and the reference data exceeds a preset value, outputs a processed image in which edge enhancement processing has been performed on the read image using a spatial filter.This is the program for the reading system for executing processing. Effect of the Invention

[0014] According to the reading system of the first aspect, degradation of image quality can be suppressed compared to the case where the read image is output as is without executing a process for relatively reducing noise.

[0015] According to the reading system of the second aspect, image quality is improved compared to when the strength of edge enhancement processing of the spatial filter is constant.

[0016] According to the reading system of the third aspect, noise enhancement is reduced compared to when the read image is directly subjected to edge enhancement processing using a spatial filter.

[0017] According to the reading system of the fourth aspect, noise enhancement due to edge enhancement processing is reduced, compared to when the frequency of the low-pass filter is constant.

[0018] According to the reading system of the fifth aspect, deterioration of the light source over time is suppressed, compared to a case in which the output of the light source is always equal to or higher than the rated value.

[0019] According to the reading system of the sixth aspect, noise enhancement due to edge enhancement processing is reduced, compared to when the light receiving section is of a reduced optical type.

[0020] According to the reading system of the seventh aspect, degradation of image quality can be suppressed compared to the case where the output of the light source is kept reduced.

[0021] According to the reading system program of the eighth aspect, degradation of image quality can be suppressed compared to the case where the read image is output as is without executing a process for relatively reducing noise. [Brief description of the drawings]

[0022] [Figure 1] 1 is a schematic perspective view showing an example of a configuration of an image forming apparatus according to an embodiment of the present invention. [Diagram 2] 2 is a schematic cross-sectional view showing an example of the configuration of an image reading unit shown in FIG. 1. [Diagram 3] 2 is a schematic cross-sectional view showing an example of the configuration of a back-side image reading unit shown in FIG. 1. [Figure 4] 2 is a block diagram showing an example of a main configuration of an electrical system of the image forming apparatus shown in FIG. 1. [Diagram 5] 2 is a block diagram showing an example of a main configuration of an electrical system of an image reading unit shown in FIG. 1. [Figure 6] 2 is a block diagram showing an example of a functional configuration of an image reading unit shown in FIG. 1. [Figure 7] 2 is a functional block diagram showing an example of a configuration of a back-side image reading unit shown in FIG. 1. [Figure 8] 10 is a flowchart showing an example of a flow of image processing on a read image read by a front image reading unit. [Figure 9] 10 is a flowchart showing an example of a flow of image processing on a read image read by a back-side image reading unit. [Figure 10] 10 is an explanatory diagram for explaining an LUT used in image processing for a read image read by a front image reading unit; FIG. [Figure 11]11 is an explanatory diagram for explaining an LUT used in image processing for a read image read by a back-side image reading unit; FIG. [Figure 12] FIG. 11 is an explanatory diagram for explaining the results of an experiment for creating an LUT. [Figure 13] 11A and 11B are explanatory diagrams illustrating how noise deterioration is compensated for by edge enhancement processing; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] <Image forming device> First, the image forming apparatus according to the present embodiment will be described. The width direction of the image forming apparatus 10 shown in Fig. 1 is the X direction, the height direction is the Z direction, and the depth direction is the Y direction, which are indicated by arrows X, Y, and Z, respectively.

[0024] (Schematic configuration of image forming apparatus) Fig. 1 is a schematic perspective view showing an example of the configuration of an image forming apparatus according to the present embodiment. As shown in Fig. 1, an image forming apparatus 10 includes an image reading unit 12, an image forming unit 14, a paper supply unit 16, an operation panel 18, etc.

[0025] The image reading unit 12, as an example of a reading system, is composed of a manuscript table 22 on which manuscript paper is placed, a manuscript discharge unit 24 where the manuscript paper after the image has been read is discharged, a transport mechanism for transporting the manuscript paper placed on the manuscript table 22, an image reading sensor for optically reading images on the manuscript paper, etc., and a scanning mechanism for scanning the manuscript paper.

[0026] The image reading unit 12 of this embodiment is configured as a "double-sided reading device" that reads the front and back images of the original paper in one conveyance. Note that here, the external configuration is described, and the specific configuration of the image reading unit 12, such as the conveyance mechanism, image reading sensor, and scanning mechanism, will be described later.

[0027] A pair of guides 26A, 26B are provided on the upper surface of the manuscript table 22 to guide the manuscript paper when the manuscript paper placed on the manuscript table 22 is transported. At least one of the pair of guides 26A, 26B is configured to move in the Y direction, which is the width direction of the manuscript paper placed on the manuscript table 22. The pair of guides 26A, 26B moves in accordance with the width of the manuscript paper placed on the manuscript table 22.

[0028] The image forming section 14 is configured to include an image forming mechanism that forms an image on the paper supplied from the paper supply section 16, and a discharge mechanism that discharges the paper on which the image has been formed to the paper discharge section 32. The image forming mechanism includes an image forming unit that forms an image by, for example, an electrophotographic method, and a fixing device. The image forming unit includes a photosensitive drum, a charging device, an exposure device, a developing device, a transfer device, a cleaning device, and the like. With the above configuration, the image forming section 14 forms an image on the paper supplied from the paper supply section 16, and discharges the paper on which the image has been formed to the paper discharge section 32.

[0029] Paper supply unit 16 is configured to include a paper storage unit that stores paper, a supply mechanism that supplies paper from the paper storage unit to image forming unit 14, and the like. The supply mechanism is configured with a pick-up roller that removes paper from the paper storage unit, a transport roller, and the like. Depending on the type and size of paper, multiple paper storage units may be provided. With the above configuration, paper supply unit 16 supplies paper to image forming unit 14.

[0030] The operation panel 18 includes a touch panel 34 for displaying various screens such as a setting screen, and various buttons 36 such as a start button and a numeric keypad. With the above configuration, the operation panel 18 functions as a UI (user interface) that accepts user operations and displays various information to the user.

[0031] (Image reading unit configuration) Next, the configuration of the image reading unit 12 will be described.

[0032] Fig. 2 is a schematic cross-sectional view showing an example of the configuration of the image reading unit 12 shown in Fig. 1. As described above, the image reading unit 12 is configured as a "double-sided reading device."

[0033] The image reading unit 12 includes an original transport unit 40 that transports an original placed on the original table 22, a front image reading unit 42 that reads an image on the front side of the original paper, and a back image reading unit 66 that reads an image on the back side of the original paper. The back image reading unit 66 is provided within the original transport unit 40. The back image reading unit 66 is provided downstream of the front image reading unit 42 in the transport direction of the original paper.

[0034] The document transport section 40 includes a lifting mechanism 44 which raises and lowers the document table 22, a take-in roller 46 which contacts the uppermost surface of a stack of document papers placed on the document table 22 raised by the lifting mechanism 44 and takes in the document papers one by one, a supply roller 50 which supplies the document papers taken in by the take-in roller 46 to a transport path 48, and various transport rollers 52, 54, 56, 58, 60 which transport the document papers further downstream in the transport direction along the transport path 48. The rotation axis of each roller extends in the Y direction which is perpendicular to the transport direction of the document papers.

[0035] Further, the document transport section 40 is provided with a guide mechanism 62 that rotates about a fulcrum depending on the loop state of the transported document paper, and a discharge roller 64 that discharges the document paper to the document discharge section 24. Here, the loop state of the document paper means that the transport path 48 for the document paper is bent so as to form a loop, and the document paper is curved along the transport path 48.

[0036] The surface image reading unit 42, which is an example of a reading unit, includes a transparent first platen glass 70A, a transparent second platen glass 70B, a first light source 72 that irradiates illumination light toward the manuscript paper, reflecting mirrors 74, 76, 78 that bend the optical path of the light reflected by the manuscript paper, a lens 80 that forms an image of the light reflected by the reflecting mirror 78, and a first image reading sensor 82 arranged at the imaging position of the lens 80. Note that "transparent" means that the illumination light and reflected light are transmitted through the material.

[0037] As described above, the image reading unit 12 of the present embodiment is configured as a "double-sided reading device" that reads images on both the front and back sides of a document being transported by the document transport unit 40. However, when reading an image on one side of a document, the document may be placed on the first platen glass 70A without using the document transport unit 40, and the image on the side facing the first platen glass 70A may be read.

[0038] The first platen glass 70A is provided in the center of the upper surface of the front image reading unit 42 in order to read an image on one side of a document placed on the first platen glass 70A. A light-shielding member (not shown) for blocking illumination light and reflected light is disposed on the periphery of the upper surface of the front image reading unit 42, i.e., around the first platen glass 70A.

[0039] On the other hand, the second platen glass 70B is an opening formed in the above-mentioned light-shielding member (not shown) in order to read the front image of the original paper being transported by the original transport unit 40. Therefore, the second platen glass 70B is provided in part of the periphery of the upper surface of the front image reading unit 42. The second platen glass 70B is disposed so as to face the transport roller 58 of the original transport unit 40. In other words, the front image of the original paper is read at the position where the transport roller 58 is disposed. Hereinafter, this position will be referred to as the "front image reading position."

[0040] In this embodiment, the primary light source 72 uses an LED array in which a plurality of LEDs (Light Emitting Diodes) are arranged along the Y direction perpendicular to the transport direction of the original paper. The primary light source 72 and the reflecting mirror 74 are mounted on a carriage 83A, and the reflecting mirrors 76 and 78 are mounted on a carriage 83B. The carriages 83A and 83B are controlled by an image reading control unit 92, which will be described later, and are moved in the Y direction. That is, the primary light source 72 and the reflecting mirrors 74, 76, and 78 are each moved in the Y direction.

[0041] In this embodiment, the first image reading sensor 82 as an example of a light receiving unit uses a CCD line sensor in which multiple CCDs (Charge Coupled Devices) are arranged along the Y direction perpendicular to the conveying direction of the original paper. In other words, the first image reading sensor 82 is a light receiving unit of a reduced optical system.

[0042] A first white reference plate 150 is provided on the left side in the X direction of the "surface image reading position" in Fig. 2. The first white reference plate 150 is a plate with a uniform reflectance in the Y direction, which is the main scanning direction. The first white reference plate 150 is optically read by the first image reading sensor 82 to obtain image information for performing image processing such as shading correction and edge enhancement processing using a spatial filter.

[0043] The back-side image reading unit 66, which is an example of a reading unit, is disposed between the transport roller 58 and the transport roller 60 of the document transport unit 40. In the present embodiment, a second image reading sensor 100 (described later) of the back-side image reading unit 66 uses a contact image sensor (CIS: Contact Image Sensor) that is brought into close contact with the document paper and reads the image. Therefore, the back-side image reading unit 66 is disposed so as to face the back side of the document paper transported along the transport path 48. That is, the back side image of the document paper is read at the position where the back-side image reading unit 66 is disposed. Hereinafter, this position is referred to as the "back-side image reading position."

[0044] Fig. 3 is a schematic cross-sectional view showing an example of the configuration of the back-side image reading unit 66 shown in Fig. 1 and Fig. 2. As shown in Fig. 3, the back-side image reading unit 66 includes a second light source 101 that irradiates illumination light toward the back side of the document paper transported by the document transport unit 40 or the second white reference plate 68, a lens 107 that forms an image of the light reflected by the back side of the document paper or the second white reference plate 68, and a second image reading sensor 100 arranged at an imaging position of the lens 107. Each of the second light source 101, the lens 107, and the second image reading sensor 100 is fixed to a predetermined position in a housing 109 and stored in the housing 109.

[0045] In this embodiment, the second light source 101 is a light source using an LED. In addition, in this embodiment, the second image reading sensor 100 as an example of a light receiving unit is a contact image sensor (CIS: Contact Image Sensor) that is in close contact with the original paper and reads the image, as described above. The lens 107 is configured as a rod lens array in which a plurality of rod lenses are arranged along the Y direction perpendicular to the conveying direction of the original paper.

[0046] A second white reference plate 68 is provided at a position facing the back side image reading unit 66 across the transport path 48. The second white reference plate 68 is a plate with a uniform reflectance in the Y direction, which is the main scanning direction. The second white reference plate 68 is used for obtaining image information that is optically read by the second image reading sensor 100 and used for image processing such as shading correction and edge enhancement processing using a spatial filter.

[0047] (Image reading unit operation) Next, the operation of the image reading unit 12 will be described. The image reading unit 12 is controlled by the image reading control unit 92, which will be described later, to perform the following double-sided reading operation. Note that driving of various operations is performed by a drive unit 196 (see FIG. 5) of the image reading control unit 92. Also, the image reading control unit 92 controls each of the first light source 72 and the reflecting mirrors 74, 76, and 78 so that the carriage 83A of the first light source 72 and the reflecting mirror 74 is positioned directly below the "front image reading position."

[0048] 2, when a piece of original paper is placed on platen 22 with its front side facing up, platen 22 is raised by lifting mechanism 44. When platen 22 rises to a predetermined position and stops, take-in roller 46 comes into contact with the uppermost surface of the stack of original paper placed on platen 22, and the original paper is taken in one by one by take-in roller 46. The original paper that reaches supply roller 50 is supplied to transport path 48 by supply roller 50, and transport of the original paper begins. The original paper that reaches transport roller 52 is transported downstream in the transport direction by transport roller 52.

[0049] The original paper that has reached the transport rollers 54 is transported downstream in the transport direction by the transport rollers 54. The leading edge of the transported original paper hits the stopped transport rollers 56, causing the original paper to curve and loop along the transport path 48. When the original paper is in a loop state, the guide mechanism 62 rotates around the fulcrum so as to open outward, and guides the original paper while maintaining the loop state of the original paper. The stopped transport rollers 56 start rotating in sync with the start of image reading.

[0050] The original paper that has reached the transport rollers 56 is aligned by the transport rollers 56 and transported downstream in the transport direction. The transport rollers 56 also supply the original paper to a "front image reading position" where the transport rollers 58 are disposed. At the front image reading position, the front side of the original paper faces the second platen glass 70B. The original paper that has reached the transport rollers 58 is transported downstream in the transport direction while being pressed against the second platen glass 70B by the transport rollers 58. The front image reading unit 42 reads the front image of the original paper being transported via the second platen glass 70B.

[0051] The original paper from which the front side image has been read is transported downstream in the transport direction and supplied to a "back side image reading position" where the back side image reading unit 66 is located. At the back side image reading position, the back side of the original paper faces the back side image reading unit 66. The back side image of the original paper being transported is read by the back side image reading unit 66. The original paper from which the back side image has been read is transported downstream in the transport direction by the transport rollers 60. The original paper that has reached the discharge rollers 64 is discharged to the original discharge unit 24 by the discharge rollers 64.

[0052] As described above, when a document is placed on the upper surface of the first platen glass 70A, an image on one side of the document is read by the front image reading unit 42 in the following manner.

[0053] While moving the first light source 72 and the reflecting mirrors 74, 76, and 78 to the right in the Y direction, the illumination light emitted from the first light source 72 is irradiated onto the manuscript paper. That is, one side of the manuscript paper is scanned with the illumination light. The illumination light passes through the first platen glass 70A and is irradiated onto the manuscript paper, and is reflected by the manuscript paper. The reflected light passes through the first platen glass 70A, and the optical path is bent by the reflecting mirrors 74, 76, and 78, and the light enters the lens 80. The light that enters the lens 80 is imaged by the lens 80 on the first image reading sensor 82. As a result, the image on one side of the manuscript paper is read.

[0054] When reading the above-mentioned first white reference plate 150 , the image reading control unit 92 controls the first light source 72 and the carriage 83 A of the reflecting mirror 74 to be positioned directly below the first white reference plate 150 .

[0055] (Hardware configuration) Next, the electrical configuration of the image forming apparatus 10 will be described.

[0056] Fig. 4 is a block diagram showing an example of a main configuration of an electrical system of the image forming apparatus 10 shown in Fig. 1. As shown in Fig. 4, the image forming apparatus 10 includes a main controller 81, a secondary storage device (HDD) 90 such as a hard disk device, an image reading control unit 92, an image formation control unit 94, an external interface 96, and an operation panel 18.

[0057] The main controller 81 is configured as a computer that controls the entire device and performs various calculations. The main controller 81 includes a CPU (Central Processing Unit) 84, a ROM (Read Only Memory) 86, and a RAM (Random Access Memory) 88. The CPU 84 reads out a program stored in the ROM 86 or HDD 90, and executes the program using the RAM 88 as a work area.

[0058] The image reading control unit 92 is disposed in the image reading unit 12 and is a control unit that controls the entire image reading process. The image reading control unit 92 controls each part of the image reading unit 12, and performs various calculations and image processing, as described later.

[0059] The image formation control unit 94 is a control unit that is disposed in the image forming unit 14 and controls the entire image formation process. The image formation control unit 94 is configured as a computer including a CPU, ROM, RAM, etc. (not shown), and controls each part of the image forming unit 14 and performs various calculations.

[0060] The external interface 96 is an interface for communicating with an external device via a wired or wireless communication line. For example, it functions as an interface for communicating with a computer connected to a network such as a LAN (Local Area Network). The HDD 90 stores various data such as log data, various programs for controlling the entire device, and the like.

[0061] The CPU 84, ROM 86, RAM 88, HDD 90, image reading control unit 92, image forming control unit 94, external interface 96, and operation panel 18 are each electrically connected via a bus 98. The main controller 81 exchanges information with each of the HDD 90, image reading control unit 92, image forming control unit 94, and operation panel 18 via the bus 98. The main controller 81 also exchanges information with external devices via the bus 98 and the external interface 96.

[0062] Next, the hardware configuration of the image reading control unit 92 will be described. As shown in FIG. 5, the image reading control unit 92 includes a front image reading unit 42, a back image reading unit 66, a drive unit 196, a CPU (Central Processing Unit) 184 as an example of a processor, a ROM (Read Only Memory) 186, a RAM (Random Access Memory) 188, and a HDD 190, and controls each part of the image reading unit 12 and performs various calculations and image processing, etc.

[0063] The CPU 184, which is an example of a processor, reads out a program stored in the ROM 186 or the HDD 190, and executes the program by using the RAM 188 as a work area. The front image reading unit 42, the back image reading unit 66, the drive unit 196, the CPU 184, the ROM 186, the RAM 188, and the HDD 190 are electrically connected via a bus 198.

[0064] Next, an example of the functional configuration of the image reading control unit 92 will be described.

[0065] As shown in FIG. 6, the image reading control unit 92 includes a receiving unit 200, a difference unit 202, a comparison unit 204, and a processing unit 206.

[0066] The reception unit 200 receives first read data and second read data, which are described below, obtained by reading the first white reference plate 150 and the second white reference plate 68. The difference unit 202 obtains the difference between the first read data received by the reception unit 200 and the first reference data, and the difference between the second read data and the second reference data. The comparison unit 204 compares the difference obtained by the difference unit 202 with a set value. When the difference obtained by the comparison unit 204 exceeds the set value, the processing unit 206 performs frequency filtering with a low-pass filter on the read images read by the front image reading unit 42 and the back image reading unit 66, and performs edge enhancement processing with a spatial filter. The difference between the first read data and the first reference data and the difference between the second read data and the second reference data will be described later.

[0067] <Image processing> Next, a description will be given of image processing performed by the image reading control unit 92 on images read from the document by the front image reading unit 42 and the back image reading unit 66. The image processing is performed by the CPU 184 (see FIG. 5) reading a program stored in the ROM 186 or the HDD 190 (see FIG. 5), expanding it in the RAM 188 (see FIG. 5), and executing it.

[0068] The image output by performing the image processing in this process is referred to as a processed image. The image processing described here is a process in which the scanned image is subjected to frequency filtering using a low-pass filter and then edge enhancement processing using a spatial filter, but other image processing may also be performed.

[0069] The image processing settings are performed when the power is turned on and the device is started up, and periodically after the power is turned on. Here, periodically means, for example, every time a predetermined time has elapsed since the power was turned on, or every time a predetermined number of sheets have been read.

[0070] In image processing, a low-pass filter is a low-pass filter that leaves the low-frequency spatial frequency components contained in an image and removes the high-frequency components. By filtering the frequency with a low-pass filter, areas with sudden changes in brightness become smoother.

[0071] The spatial filter process converts a pixel of interest in a scanned image based on the pixel of interest and its surrounding pixels, while the spatial filter edge enhancement process enhances edges in the scanned image.

[0072] Next, edge enhancement processing using a spatial filter will be briefly described with reference to FIG.

[0073] FIG. 7(A) shows a portion of a scanned image. FIG. 7(B) is an example of a spatial filter that performs edge enhancement processing. And FIG. 7(C) shows a processed image after edge enhancement processing has been performed on a portion of the scanned image using the spatial filter of FIG. 7(B). Thus, in the scanned image of FIG. 7(A), the three columns on the right side of the figure are pixels with a value of 100, but in the processed image of FIG. 7(C), the first and second columns from the left side of the figure are pixels with a value of 25, indicating that the edges have been enhanced. Note that the calculation of the edge enhancement filter in FIG. 7 takes the absolute value of the calculation result.

[0074] (Surface image reading unit) First, image processing for the image read by the front image reading unit 42 will be described.

[0075] As shown in the flowchart of Fig. 8, in step S100, the CPU 184 (see Fig. 5) of the image reading control unit 92 moves the first light source 72 and the carriage 83A of the reflecting mirror 74 so as to be positioned directly below the first white reference plate 150 (see Fig. 2). Then, the first white reference plate 150 is irradiated with irradiation light emitted from the first light source 72, and the reflected light reflected by the first white reference plate 150 is received and read by the first image reading sensor 82 (see Fig. 2) to obtain first read data.

[0076] Next, in step S102, the CPU 184 obtains the difference between the acquired first read data and first reference data stored in the HDD 190 (see FIG. 5) or the like. The "first read data" and "second read data" described later are specifically data of a white reference level. The white reference level is data for standardizing the maximum output level of the input range of the image reading unit 12.

[0077] Next, in step S104, CPU 184 determines whether the difference between the first read data and the first reference data exceeds a preset value. If this difference does not exceed the preset value (No), that is, if the difference is equal to or less than the preset value, the process ends. In this case, the read image is output as is without performing the image processing described herein. If this difference exceeds the preset value (Yes), the process proceeds to step S106.

[0078] Next, in step S106, the CPU 184 sets the intensity of edge enhancement in the image processing in accordance with the difference. Note that a method for setting the intensity of edge enhancement in accordance with the difference will be described later.

[0079] Next, in step S108, the CPU 184 sets the frequency of the low-pass filter according to the strength of the edge enhancement process. Specifically, the CPU 184 lowers the frequency of the low-pass filter as the strength of the edge enhancement process increases.

[0080] This sets image processing for passing the read image read by the surface image reading unit 42 through a low-pass filter with a set frequency and a spatial filter with a set edge enhancement processing intensity. In other words, the read image read by the surface image reading unit 42 is subjected to frequency filtering with a low-pass filter, and then image processing for edge enhancement processing with a spatial filter is performed, and the image is output as a processed image.

[0081] (Backside image reading section) Next, image processing for the image read by the back side image reading unit 66 will be described.

[0082] As shown in the flowchart of Fig. 9, in step S200, the CPU 184 (see Fig. 5) of the image reading control unit 92 determines whether the output of the secondary light source 101 (see Fig. 3) is less than the rated value. In this embodiment, the output is the current value supplied to the secondary light source 101. If it is less than the rated value (Yes), the process proceeds to step S202, and if it is the rated value (No), the process proceeds to step S206. If the process proceeds to step S202, the CPU 184 sets the output of the secondary light source 101 to the rated value.

[0083] Next, in step S206, the CPU 184 irradiates the second white reference plate 68 with the light emitted from the second light source 101, and receives and reads the light reflected by the second white reference plate 68 with the second image reading sensor 100 (see Figure 3) to obtain second reading data.

[0084] Next, in step S208, the CPU 184 obtains the difference between the acquired second read data and second reference data stored in the HDD 190 (see FIG. 5) or the like.

[0085] Next, in step S210, CPU 184 determines whether the difference between the second read data and the second reference data exceeds a preset value. If this difference does not exceed the preset value (No), that is, if the difference is equal to or less than the preset value, the process proceeds to step S204. If this difference exceeds the preset value (Yes), the process proceeds to step S212.

[0086] In step S204, the CPU 184 reduces the output of the second light source 101 by a predetermined output value, and returns to step S206, and steps S206 to S210 are repeated.

[0087] If the difference again does not exceed the preset value in step S210 (No), CPU 184 further reduces the output of second light source 101 and returns to step S206. In other words, CPU 184 continues to reduce the output of second light source 101 until the difference between the second read data and the second reference data exceeds the preset value.

[0088] As described above, if the difference exceeds the preset value in step S210 (Yes), the process proceeds to step S212.

[0089] Next, in step S212, the CPU 184 sets the intensity of edge enhancement in the image processing in accordance with the difference. Note that a method for setting the intensity of edge enhancement in accordance with the difference will be described later.

[0090] Next, in step S214, the CPU 184 sets the frequency of the low-pass filter according to the strength of the edge enhancement process. Specifically, the CPU 184 lowers the frequency of the low-pass filter as the strength of the edge enhancement process increases.

[0091] This sets image processing for passing the read image read by the back side image reading unit 66 through a low pass filter with a set frequency and a spatial filter with a set edge enhancement processing strength. In other words, the read image read by the back side image reading unit 66 is subjected to frequency filtering by the low pass filter, and then image processing for edge enhancement processing by the spatial filter is performed, and the image is output as a processed image.

[0092] (Edge emphasis processing strength setting) Next, an example of settings for edge enhancement processing of a spatial filter will be described.

[0093] 10 is a diagram showing a schematic diagram of a LUT (Lookup Table) used in the front image reading unit 42, which is stored in the HDD 190 etc. In the above-mentioned step S106, the CPU 184 converts the difference into the strength of the spatial filter by the LUT.

[0094] 11 is a diagram showing a typical LUT (Lookup Table) used for the back side image reading unit 66, which is stored in the HDD 190 etc. In the above-mentioned step S212, the CPU 184 converts the difference into the strength of the spatial filter by the LUT.

[0095] Here, the solid line R1 in FIG. 11 is the LUT used for the back image reading unit 66, and the dashed dotted line R2 is the LUT used for the front image reading unit 42 in FIG. 10, which is shown for comparison reference and is not actually used.

[0096] As described above, the first image reading sensor 82 of the front image reading unit 42 is of a reduction optical system, and the second image reading sensor 100 of the back image reading unit 66 is of a contact optical system. The second image reading sensor 100 of the contact optical system has a higher CTF (Contrast Transfer Function) than the first image reading sensor 82 of the reduction optical system. Therefore, even if the difference is the same, the intensity can be reduced. Therefore, as shown in FIG. 11, the LUT used in the back image reading unit 66 has a lower intensity even if the difference is the same.

[0097] (How to create a LUT) Next, an example of a method for creating an LUT will be described.

[0098] Fig. 12 is a graph showing the relationship between noise (S / N ratio) and CTF (Contrast Transfer Function). Noise (S / N ratio) is a value that represents the absolute amount of noise because the white reference of the scanner is constant. CTF is a value that serves as an index of resolution.

[0099] Line K is the boundary line between OK and NG when image quality is judged by creating multiple images with different noise (S / N ratio) and CTF. Also, a low CTF reduces the scanner's resolution and results in a coarse read image, so a certain value or higher is necessary. In this example, a CTF of 25% or more is OK. Therefore, the shaded area above line K and above a CTF of 25% is the OK range.

[0100] The intensity of edge emphasis in the LUT is set to fall within the shaded OK range in FIG.

[0101] <effect> Next, the operation of this embodiment will be described.

[0102] When the amount of light of the first light source 72 of the front image reading unit 42 and the second light source 101 of the back image reading unit 66 of the image reading unit 12 of the image forming apparatus 10 decreases due to deterioration over time, the amount of light received by the first image reading sensor 82 and the second image reading sensor 100 decreases. When the amount of light received by the first image reading sensor 82 and the second image reading sensor 100 decreases, the noise ratio of the read image increases, the signal-to-noise ratio decreases, and the image quality of the read image decreases.

[0103] However, when reducing the noise ratio to increase the S / N ratio and suppress deterioration in image quality of the read image, for example, increasing the output of the first light source 72 and the second light source 101 will shorten the lifespan of the first light source 72 and the second light source 101, or slowing down the reading speed to increase the amount of light received will reduce productivity.

[0104] In response to these problems, in the image reading unit 12 of the image forming apparatus 10 of this embodiment, when the amount of light decreases due to deterioration over time of the first light source 72 of the surface image reading unit 42 and the difference between the read data read from the first white reference plate 150 and the first reference data exceeds a preset value, the image reading unit 12 performs edge enhancement processing on the read image using a spatial filter and outputs it as a processed image.

[0105] Similarly, when the amount of light decreases due to deterioration over time of the second light source 101 of the back-side image reading unit 66 and the difference between the read data read from the second white reference plate 68 and the second reference data exceeds a preset value, the image reading unit 12 performs edge enhancement processing on the read image using a spatial filter and outputs it as a processed image.

[0106] Therefore, degradation of image quality can be suppressed compared to when the scanned image is output as is without performing processing to relatively reduce noise.

[0107] From another perspective, the deterioration of the first light source 72 and the second light source 101 over time reduces the amount of light, resulting in a decrease in the signal-to-noise ratio of the scanned image. This is prevented by using a spatial filter to perform edge enhancement processing to increase the resolution, thereby preventing a decrease in image quality.

[0108] Next, the control method of this embodiment will be described with reference to FIG.

[0109] FIG. 13 is a diagram illustrating the graph of FIG. 12 showing the relationship between noise (SN ratio) and CTF (Contrast Transfer Function), to which an explanation of the control method of this embodiment is added.

[0110] The circle mark M1 and square mark N1 in the figure indicate a state in which the signal-to-noise ratio of the scanned image is reduced due to a decrease in the amount of light caused by deterioration of the first light source 72 and the second light source 101 over time, resulting in a decrease in image quality. The arrows L1 and L2 indicate that image quality is improved by increasing the resolution through edge enhancement processing using a spatial filter. In this way, this control improves image quality by increasing the resolution through edge enhancement processing using a spatial filter to improve image quality by improving the image quality by improving the image quality by increasing the resolution, thereby improving the image quality by improving the image quality by improving the image quality by increasing the resolution through edge enhancement processing using a spatial filter. The square mark N2 and arrow L3 will be explained later.

[0111] Here, when edge enhancement processing is performed using a spatial filter, noise in the read image may be emphasized. Therefore, in this embodiment, the enhancement of noise is suppressed by frequency filtering the read image using a low-pass filter before performing edge enhancement processing using a spatial filter. In other words, noise enhancement is reduced and image quality is improved compared to when edge enhancement processing is performed directly on the read image using a spatial filter.

[0112] In this embodiment, the intensity of the edge enhancement process of the spatial filter is set to be higher when the difference between the first and second read data and the first and second reference data is large than when the difference is small, using the LUT, thereby improving image quality compared to when the intensity of the edge enhancement process is constant.

[0113] In addition, in this embodiment, when the strength of the edge enhancement process of the spatial filter is large, the frequency of the low-pass filter is lower than when the strength is small. Therefore, noise enhancement due to the edge enhancement process is reduced compared to when the frequency of the low-pass filter is constant.

[0114] In this embodiment, if the difference between the second read data from the back surface image reading unit 66, which is a contact optical system, and the second reference data does not exceed the set value, the output of the second light source 101 is reduced below the rated output until the difference exceeds the set value. Then, edge enhancement processing of the spatial filter is performed.

[0115] In this way, by lowering the output of the secondary light source 101 below the rated value, deterioration over time of the secondary light source 101 is suppressed. Therefore, deterioration over time of the secondary light source 101 is suppressed compared to a case where the output of the secondary light source 101 is always equal to or higher than the rated value. In addition, by lowering the output of the secondary light source 101 below the rated value, the amount of heat generated by the secondary light source 101 is reduced, and therefore a decrease in sensitivity due to a rise in temperature of the second image reading sensor 100 is suppressed.

[0116] As described above, the first image reading sensor 82 of the front image reading unit 42 is of a reduction optical type, and the second image reading sensor 100 of the back image reading unit 66 is of a contact optical type. The second image reading sensor 100 of the contact optical type has a higher CTF (Contrast Transfer Function) than the first image reading sensor 82 of the reduction optical type. Therefore, even if the difference is the same, the intensity can be reduced. Therefore, noise emphasis due to edge emphasis processing caused by lowering the output of the second light source 101 of the back image reading unit 66 of the contact optical type is reduced.

[0117] Furthermore, in this embodiment, when the output of the secondary light source 101 is reduced, the output of the secondary light source 101 is returned to the rated value and is reduced below the rated output until it exceeds the set value again. Thus, since the output can be reduced in accordance with deterioration of the secondary light source 101 over time, deterioration in image quality can be suppressed compared to when the output of the secondary light source 101 is kept reduced.

[0118] Next, a control method for reducing the output of the secondary light source 101 in this embodiment will be described with reference to FIG.

[0119] The square mark N2 in the figure indicates a state in which the amount of light from the second light source 101 is sufficient, that is, the difference does not exceed the set value and the image quality is still within an OK range.

[0120] Arrow L3 in the figure represents the intentional reduction in the light intensity of the secondary light source 101 until the difference exceeds a set value, resulting in a state in which image quality is degraded (□ (square) mark N1). As described above, arrow L2 represents the improvement in image quality by using a spatial filter to perform edge enhancement processing and increase the resolution. In this way, this control intentionally reduces the output of the secondary light source 101 to degrade image quality, and then uses a spatial filter to perform edge enhancement processing to increase the resolution and improve image quality, even when the secondary light source 101 has not deteriorated over time.

[0121] <Other> The present invention is not limited to the above embodiment.

[0122] For example, in the above embodiment, when the difference between the second read data of the back side image reading unit 66 and the second reference data does not exceed the set value, the output of the second light source 101 is reduced below the rated output until the difference exceeds the set value, but this is not limited to this. The output of the second light source 101 may be used at the rated output. Also, when the difference between the first read data of the back side image reading unit 66 and the first reference data does not exceed the set value, the output of the first light source 72 may be reduced below the rated output until the difference exceeds the set value.

[0123] In the above embodiment, the present invention is applied to the image reading unit 12 of the image forming apparatus 10, which is a multifunction machine, but the present invention is not limited to this. The present invention may be applied to a standalone image reading apparatus.

[0124] Furthermore, the present invention can be embodied in various forms without departing from the spirit and scope of the present invention. A plurality of embodiments and modifications can be implemented in appropriate combination.

[0125] <Additional Notes> (((1))) a reading unit that irradiates an object with light emitted from a light source and receives light reflected from the object with a light receiving unit to generate a read image; A processor; having The processor, receiving read data obtained by reading a white reference by the reading unit; When the difference between the read data and the reference data exceeds a preset value, an edge enhancement process is performed on the read image using a spatial filter, and the image is output as a processed image. Reading system.

[0126] (((2))) The processor, When the difference between the read data and the reference data is large, the strength of the edge enhancement process of the spatial filter is made larger than when the difference is small. A reading system as described in (((1))).

[0127] (((3))) The processor, before performing edge enhancement processing using the spatial filter, frequency filtering is performed on the read image using a low-pass filter; A reading system according to ((1))) or (((2))).

[0128] (((4))) The processor, when the difference between the read data and the reference data is large, the intensity of the edge enhancement process of the spatial filter is increased and the frequency of the low-pass filter is decreased compared to when the difference is small. A reading system according to any one of ((1))) to (((3))).

[0129] (((5))) The processor, reducing the output of the light source below the rated output until the difference between the read data and the reference data exceeds the set value; A reading system according to any one of ((1))) to (((4))).

[0130] (((6))) The processor, When the light receiving unit is of a contact optical system, the output of the light source is reduced below a rated value. A reading system according to (((5))).

[0131] (((7))) The processor, When the output of the light source is less than the rated output, the output of the light source is brought to the rated output and then reduced below the rated value until the difference between the read data and the reference data exceeds the set value. A reading system according to ((5))) or ((6))).

[0132] (((8))) A program for a reading system having a reading unit that irradiates an object with light emitted from a light source, receives light reflected from the object with a light receiving unit, and outputs a read image, the program comprising: receiving read data obtained by reading a white reference by the reading unit; When the difference between the read data and the reference data exceeds a preset value, a processed image is output, which is obtained by performing edge enhancement processing on the read image using a spatial filter. A program for the reading system to execute the process.

[0133] According to the reading system (((1))), degradation of image quality can be suppressed compared to when the read image is output as is without performing processing to relatively reduce noise.

[0134] According to the reading system (((2))), image quality is improved compared to the case where the strength of the edge enhancement process of the spatial filter is constant.

[0135] According to the reading system (((3))), noise enhancement is reduced compared to when the read image is directly edge-emphasized using a spatial filter.

[0136] According to the reading system of (((4))), noise enhancement due to edge emphasis processing is reduced compared to the case where the frequency of the low-pass filter is constant.

[0137] According to the reading system of (((5))), deterioration of the light source over time is suppressed compared to a case in which the output of the light source is always equal to or higher than the rated value.

[0138] According to the reading system (((6))), noise enhancement due to edge emphasis processing is reduced compared to when the light receiving section is of a reduced optical type.

[0139] According to the reading system of (((7))), degradation of image quality can be suppressed compared to the case where the output of the light source is kept reduced.

[0140] According to the program of the reading system of (((8))), degradation in image quality can be suppressed compared to when the read image is output as is without executing a process to relatively reduce noise. [Explanation of symbols]

[0141] 10 Image forming device 12 Image reading unit (an example of a reading system) 42 Surface image reading unit (an example of a reading unit) 66 Back side image reading unit (example of reading unit) 68 Second white reference plate 72 First light source 82 First image reading sensor (an example of a light receiving unit) 100 Second image reading sensor (an example of a light receiving unit) 101 Second light source 150 Daiichi White Reference Plate 184 CPU (an example of a processor)

Claims

1. a reading unit that irradiates an object with light emitted from a light source and receives light reflected from the object with a light receiving unit to generate a read image; A processor; having The processor, receiving read data obtained by reading a white reference by the reading unit; When the difference between the read data and the reference data exceeds a preset value, an edge enhancement process is performed on the read image using a spatial filter, and the image is output as a processed image. Reading system.

2. The processor, When the difference between the read data and the reference data is large, the strength of the edge enhancement process of the spatial filter is made larger than when the difference is small.

2. The reading system according to claim 1.

3. The processor, before performing edge enhancement processing using the spatial filter, frequency filtering is performed on the read image using a low-pass filter; 2. The reading system according to claim 1.

4. The processor, when the difference between the read data and the reference data is large, the intensity of the edge enhancement process of the spatial filter is increased and the frequency of the low-pass filter is decreased compared to when the difference is small. A reading system according to claim 3.

5. The processor, reducing the output of the light source below the rated output until the difference between the read data and the reference data exceeds the set value; 2. The reading system according to claim 1.

6. The processor, When the light receiving unit is of a contact optical system, the output of the light source is reduced below a rated value. A reading system according to claim 5.

7. The processor, When the output of the light source is less than the rated output, the output of the light source is brought to the rated output and then reduced below the rated value until the difference between the read data and the reference data exceeds the set value. A reading system according to claim 5.

8. A program for a reading system having a reading unit that irradiates an object with light emitted from a light source, receives light reflected from the object with a light receiving unit, and outputs a read image, the program comprising: receiving read data obtained by reading a white reference by the reading unit; When the difference between the read data and the reference data exceeds a preset value, a processed image is output, which is obtained by performing edge enhancement processing on the read image using a spatial filter. A program for the reading system to execute the process.

Images