Image reading device

Abstract

To make the size of the installation location for a reference member provided for shading correction and MTF correction to be small.SOLUTION: An image reading unit 21 reads an image of a document while moving the document in a predetermined direction and outputs the read image as image data. A correction processing unit performs shading correction and MTF correction on the image data output from the image reading unit. A correction setting unit derives a white reference value for shading correction on the basis of image data of a white reference area 31 out of the image data of the reference member 6 read by the image reading unit, and derives an MTF value for adjusting the characteristics of the MTF correction on the basis of image data of an MTF chart area 32.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an image reading device. [Background technology]

[0002] One image reading device has a white reference plate for shading correction and an MTF (Modulation Transfer Function) correction chart separately provided, and scans the white reference plate and the MTF correction chart to perform shading correction and MTF correction (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-307870 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the above-described image reading device, the white reference plate and the MTF correction chart are provided separately, which increases the size of the installation space for the white reference plate and the MTF correction chart.

[0005] The present invention has been made in view of the above problems, and has as its object to provide an image reading device in which the size of the installation location for the reference members provided for shading correction and MTF correction can be reduced. [Means for solving the problem]

[0006] The image reading device of the present invention comprises an image reading unit that reads an image of a document while moving the document in a predetermined direction and outputs the read image as image data; a correction processing unit that performs shading correction and MTF correction on the image data output from the image reading unit; and a correction setting unit that derives a white reference value for the shading correction based on image data of the white reference area from the image data of the reference member read by the image reading unit, and derives an MTF value for adjusting the characteristics of the MTF correction based on image data of the MTF chart area. [Effects of the Invention]

[0007] According to the present invention, an image reading device can be obtained in which the size of the installation location for the reference member provided for shading correction and MTF correction can be reduced.

[0008] The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a side view showing the internal configuration of an image reading device according to an embodiment of the present invention. [Figure 2] FIG. 2 is a diagram showing an example of the reference member 6 in FIG. [Figure 3] FIG. 3 is a block diagram showing the electrical configuration of the image reading device according to the embodiment of the present invention. [Figure 4] FIG. 4 is a diagram illustrating the luminance distribution in the main scanning direction of the image data of the reference member 6 in FIG. [Figure 5] FIG. 5 is a flowchart illustrating the operation of the image reading device shown in FIGS. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0011] Fig. 1 is a side view showing the internal configuration of an image reading device according to an embodiment of the present invention. The image reading device shown in Fig. 1 is a device such as a scanner, a copier, a facsimile machine, or a multifunction peripheral. The image reading device shown in Fig. 1 includes contact glasses 1a and 1b, carriages 2 and 3, an imaging lens 4, an image sensor 5, a reference member 6, and a document cover 7.

[0012] The contact glass 1a is installed on the top surface of the image reading device body, and a document is placed on it when image reading is performed without using an ADF (Auto Document Feeder) of the document cover 7.

[0013] The contact glass 1b is installed on the top surface of the image reading device body, and when an image reading is performed while the document is automatically transported by the ADF of the document cover 7, the document passes over the contact glass 1b.

[0014] The carriage 2 is also installed so as to be movable in the sub-scanning direction by a drive source (not shown). The carriage 2 has a light source 11 and a mirror 12. The light source 11 is arranged along the main scanning direction and emits light, for example, from an array of multiple light-emitting diodes. Depending on the position of the carriage 2, the light emitted from the light source 11 is reflected by an original placed on the contact glass 1a, an original passing over the contact glass 1b, a reference member 6 (described later), and the like. The mirror 12 reflects the light reflected from the original, the reference member 6 (described later), and the like. When an image of an original is read using the ADF of the original cover 7, the carriage 2 is fixedly positioned below the contact glass 1b.

[0015] Furthermore, carriage 3 is installed so as to be movable in the sub-scanning direction together with carriage 2 by a drive source (not shown). Carriage 3 has mirrors 13 and 14. Mirrors 13 and 14 reflect light from mirror 12 of carriage 2 and emit the light along the sub-scanning direction.

[0016] The imaging lens 4 focuses the light from the mirror 14 onto the image sensor 5. The image sensor 5 is a one-dimensional image sensor having a predetermined number of light receiving elements arranged in the main scanning direction, and outputs an electrical signal for each line corresponding to the amount of light received by that number of pixels. The image sensor 5 may be, for example, a CCD (Charge Coupled Device).

[0017] The reference member 6 is a plate-like member placed on the top surface inside the device in order to obtain a white reference value for shading correction and an MTF correction value for adjusting the characteristics of MTF correction.

[0018] FIG. 2 is a diagram showing an example of the reference member 6 in FIG. 1. For example, as shown in FIG. 2, the reference member 6 includes a white reference area 31 and an MTF chart area 32. The white reference area 31 is a white area indicating a white reference value. The MTF chart area 32 includes a chart 32a in the main scanning direction and a chart 32b in the sub-scanning direction. The chart 32a has a ladder pattern of a predetermined common line pair. The chart 32b has a ladder pattern of a common or different line pair. Here, the resolution of the charts 32a and 32b is set to anywhere in the range of 200 to 270 line pairs. Furthermore, the white portion of the MTF chart area 32 is the same color as the white reference area 31.

[0019] In this embodiment, the white reference areas 31 and the MTF chart areas 32 are arranged alternately along the main scanning direction on the reference member 6. Furthermore, in the arrangement of the white reference areas 31 and the MTF chart areas 32, the MTF chart areas 32 are arranged at both ends.

[0020] The document cover 7 is a rotatable member that can come into surface contact with the contact glass 1a, and it keeps the document tightly attached to the contact glass 1a and prevents ambient light from entering the device through the contact glass 1a during image reading. The document cover 7 also has a built-in ADF, and documents placed on the document tray 7a are transported one by one by transport rollers 7b, passing over the contact glass 1b.

[0021] Fig. 3 is a block diagram showing the electrical configuration of an image reading device according to an embodiment of the present invention. In Fig. 3, image reading unit 21 includes the mechanical configuration shown in Fig. 1, a drive source for driving each component in the configuration, and an image data generation circuit for generating image data from an electrical signal output from image sensor 5. That is, when image reading is performed using the ADF of document cover 7, image reading unit 21 reads the image of the document while moving the document in a predetermined direction and outputs the read image as image data.

[0022] The correction processing unit 22 performs shading correction and MTF correction on the image data output from the image reading unit 21. The shading correction is performed by an existing method based on the white reference value set by the correction setting unit 25, and the MTF correction is performed using, for example, a digital filter such as edge enhancement with a strength corresponding to the MTF value set by the correction setting unit 25.

[0023] The main memory 23 has a storage area for storing the corrected image data described above. For example, a volatile memory is used for the main memory 23. The data output unit 24 reads the corrected image data stored in the main memory 23, performs other correction processing, image processing, etc. as necessary, and then outputs the image data. For example, the image data may be used for printing, sent to a terminal device via a network or a peripheral device interface, or sent by facsimile communication.

[0024] The correction setting unit 25 derives a white reference value for shading correction based on the image data of the white reference area 31 from the image data of the reference member 6 read by the image reading unit 21, and also derives an MTF value for adjusting the characteristics of MTF correction based on the image data of the MTF chart area.

[0025] For example, the MTF value is calculated using the following formula:

[0026] MTF value = (average value of density peak values (maximum values) in the MTF chart area - average value of density dip values (minimum values)) / black and white reference value x 100%

[0027] The black and white reference value is a constant, and is the difference between the white reference value (background color) and the black reference value (ladder pattern color).

[0028] The characteristics of the MTF correction are adjusted so that the MTF value becomes the reference value.

[0029] The MTF values are derived separately for the chart 32a in the main scanning direction and the chart 32b in the sub-scanning direction, and the MTF value of the chart 32a in the main scanning direction is used to adjust the sub-scanning direction characteristics of the digital filter (two-dimensional spatial filter) in the MTF correction, while the MTF value of the chart 32b in the sub-scanning direction is used to adjust the main scanning direction characteristics of the digital filter (two-dimensional spatial filter) in the MTF correction.

[0030] Fig. 4 is a diagram illustrating the luminance distribution in the main scanning direction of the image data of the reference member 6 in Fig. 1. In this embodiment, as described above, the white reference areas 31 and the MTF chart areas 32 are alternately arranged, and a luminance distribution such as that shown in Fig. 4 is obtained, for example, so that the MTF value for the white reference area in the main scanning direction is derived by linear interpolation or the like from the MTF values of the MTF chart areas adjacent to the white reference area, and the white reference value for the MTF chart area in the main scanning direction is derived by linear interpolation or the like from the white reference value of the white reference area adjacent to the MTF chart area.

[0031] In this embodiment, when deriving a white reference value for shading correction, if the time elapsed since the previous adjustment of the MTF correction characteristics does not exceed a predetermined threshold, the correction setting unit 25 does not adjust the MTF correction characteristics, but if the time elapsed exceeds the threshold, it adjusts the MTF correction characteristics.

[0032] In this embodiment, the correction setting unit 25 adjusts the threshold value in accordance with the internal temperature detected by the temperature sensor 27. For example, if the internal temperature does not exceed a predetermined threshold value, the threshold value is set to a predetermined value, and if the internal temperature exceeds the predetermined threshold value, the threshold value is set to a predetermined value lower than the predetermined value.

[0033] The control unit 26 is a circuit that controls a drive source (not shown) and performs calculation processing in the image reading unit 21. For example, the control unit 26 controls a drive source (not shown) to move the carriages 2 and 3, and operates the transport roller 7b of the document cover 7 to transport the documents placed on the document tray 7a one by one and read the images of the documents.

[0034] The temperature sensor 27 is disposed inside the image reading device and detects the temperature inside the device.

[0035] Next, the operation of the image reading device will be described below. Fig. 5 is a flowchart illustrating the operation of the image reading device shown in Figs.

[0036] Before reading the image of the document, the correction setting unit 25 causes the image reading unit 21 to read the reference member 6, and first derives a white reference value for shading correction and sets it in the correction processing unit 22 (step S1). The white reference value is derived for each main scanning direction position, and for areas that are not in the white reference area 31, it is derived by linear interpolation or the like as described above.

[0037] Next, the correction setting unit 25 determines whether the internal temperature exceeds a predetermined threshold TH (step S2), and if the internal temperature exceeds the predetermined threshold TH, determines whether the time elapsed since the last MTF correction adjustment exceeds a predetermined threshold T1 (step S3). On the other hand, if the internal temperature does not exceed the predetermined threshold TH, determines whether the time elapsed since the last MTF correction adjustment exceeds a predetermined threshold T2 (T2>T1) (step S4). Note that this elapsed time is measured using a timer or the like.

[0038] If it is determined in steps S3 and S4 that the elapsed time exceeds the predetermined thresholds T1 and T2, the correction setting unit 25 derives an MTF value and sets it in the correction processing unit 22 (step S5). If the elapsed time does not exceed the predetermined thresholds T1 and T2, the correction setting unit 25 does not update the MTF value.

[0039] Thereafter, the control unit 26 causes the image reading unit 21 to read the image of the document, and the correction processing unit 22 performs shading correction and MTF correction corresponding to the white reference value and MTF value set by the correction setting unit 25 (step S6). The image data subjected to the shading correction and MTF correction is output.

[0040] As described above, according to the above embodiment, the image reading unit 21 reads an image of the document while moving the document in a predetermined direction and outputs the read image as image data. The correction processing unit 22 performs shading correction and MTF correction on the image data output from the image reading unit 21. The correction setting unit 25 derives a white reference value for shading correction based on image data of the white reference region 31 out of the image data of the reference member 6 read by the image reading unit 21, and derives an MTF value for adjusting the characteristics of the MTF correction based on image data of the MTF chart region 32.

[0041] As a result, the white reference value for shading correction and the MTF value for MTF correction can be obtained from one reference member 6, so the size of the installation location for the reference member 6 can be small, and the white reference value for shading correction and the MTF value for MTF correction can be obtained together in one reading operation.

[0042] It should be noted that various changes and modifications to the above-described embodiments will be apparent to those skilled in the art. Such changes and modifications may be made without departing from the spirit and scope of the subject matter and without diminishing its intended advantages. In other words, it is intended that such changes and modifications be included within the scope of the claims. [Industrial Applicability]

[0043] The present invention is applicable to, for example, scanners, multifunction peripherals, and the like. [Explanation of symbols]

[0044] 6 Reference members 22 Correction processing section 25 Correction setting section 27 Temperature Sensor 31 White reference area 32 MTF chart areas

Claims

1. an image reading unit that reads an image of a document while moving the document in a predetermined direction and outputs the read image as image data; a correction processing unit that performs shading correction and MTF correction on the image data output from the image reading unit; a reference member including a white reference area and an MTF chart area; a correction setting unit that derives a white reference value for the shading correction based on image data of the white reference region out of image data of the reference member read by the image reading unit, and that derives an MTF value for adjusting characteristics of the MTF correction based on image data of the MTF chart region; An image reading device comprising:

2. the white reference areas and the MTF adjustment charts are alternately arranged on the reference member along a main scanning direction, the MTF value for the white reference area in the main scanning direction is derived from the MTF value of the MTF chart area adjacent to the white reference area; the white reference value for the MTF chart area in the main scanning direction is derived from the white reference value of the white reference area adjacent to the MTF chart area; 2. The image reading device according to claim 1, wherein:

3. 2. The image reading device according to claim 1, wherein the correction setting unit does not adjust the characteristics of the MTF correction when deriving the white reference value for the shading correction if the elapsed time since the previous adjustment of the characteristics of the MTF correction does not exceed a predetermined threshold.

4. a temperature sensor for measuring an internal temperature of the image reading device; the correction setting unit adjusts the threshold value in accordance with the internal temperature of the device; 4. The image reading device according to claim 3, wherein:

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