JP2005020551A - Image scanner, image forming apparatus, and signal correction method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image scanner for correcting the nonuniformity of reception sensitivity in each channel region, and to provide an image forming apparatus, and a signal correction method. <P>SOLUTION: The image scanner 2 includes variable amplification rate amplifier parts 61 for independently amplifying each one of image signals S<SB>1</SB>-S<SB>4</SB>to be outputted from the respective channel regions Ch1-Ch4 of a photoelectric conversion part 25, so as to allow the signals to reach predetermined target values; and a control part 65 for outputting to each variable amplification rate amplifier part 61 a control instruction to correct the amplification rate of each variable amplification rate amplifier part, so as to relatively equalize the output image signals in largeness at the end parts of the adjacent channel regions. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image reading apparatus such as a copying machine or a scanner, an image forming apparatus including the image reading apparatus, and a signal correction method.
[0002]
[Prior art]
An image reading apparatus such as a scanner or a copying machine reads an image by converting a document image into an electric signal using a photoelectric conversion element such as a CCD. In an image reading apparatus using a one-dimensional image sensor in which CCDs are linearly arranged on a light receiving surface, image signals are acquired line by line along the main scanning direction of the original, and these are stacked to form an entire image of the original. The image signal is synthesized.
[0003]
Some one-dimensional image sensors have a light receiving surface divided into a plurality of channel regions, and an output terminal is provided for each channel region. Such a multi-channel type one-dimensional image sensor contributes to an increase in the image reading speed, but when synthesizing an image signal for one line from an output image signal output from each channel, each channel region Due to the variation in the light receiving sensitivity, the level of the image signal between the ends of the adjacent channel regions is different (see FIG. 2C), and the image at the position corresponding to the joint of the channel regions is generated. Striped density unevenness may occur.
[0004]
Therefore, a method is known in which the variation in the light receiving sensitivity occurring between the channel regions is corrected by adjusting the light amount of the LED array as the light source for each channel region to prevent the occurrence of image density unevenness (for example, , See Patent Document 1).
[0005]
[Patent Document 1]
Japanese Patent Laid-Open No. 2002-300352
[0006]
[Problems to be solved by the invention]
However, in the case of using a light source with non-uniform illuminance distribution such as a xenon lamp that causes peripheral dimming, background correction according to the illuminance distribution is required, and a conventional method (Patent Document 1) is used. It was impossible to correct the variation in the light receiving sensitivity of each channel region by adjusting the amount of light in each channel region of the one-dimensional image sensor.
[0007]
An object of the present invention is to provide an image reading apparatus, an image forming apparatus, and a signal correction capable of correcting variations in light receiving sensitivity of each channel area when an image is read using a photoelectric conversion unit divided into a plurality of channel areas. Is to provide a method.
[0008]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the invention described in claim 1 includes a light source for exposing a document and constituent pixels divided into a plurality of channel regions, and converts reflected light from the document into an electrical signal. In an image reading apparatus comprising: an output photoelectric conversion unit; and an image signal combining unit that combines and outputs an image signal output from each channel region of the photoelectric conversion unit, from each channel region of the photoelectric conversion unit A plurality of variable amplification factor amplifying units that individually amplify each of the output image signals and output to the image signal synthesis unit, and a target set individually for each of the output image signals of each channel region Amplification is performed until the value reaches the value, and then the amplification factor of each variable amplification factor amplification unit is corrected so that the output image signals at the ends of adjacent channel regions are relatively equal in magnitude. A control unit for outputting a command to the respective variable gain amplifier unit, characterized by comprising a.
[0009]
According to the first aspect of the present invention, each of the output image signals of each channel region is individually amplified until reaching a preset target value using a plurality of variable amplification factor amplifiers, and then adjacent to each other. Since the amplification factor of the variable amplification factor amplifier is corrected so that the sizes of the output image signals at the ends of each channel region are relatively equal, it is possible to correct variations in the light receiving sensitivity of each channel region. Thus, it is possible to prevent a difference in density of the image signal at the seam between the channel areas and density unevenness in the image at the position corresponding to the seam between the channel areas.
[0010]
According to a second aspect of the present invention, in the image reading apparatus according to the first aspect, the control unit calculates an amplification factor between the channel regions when the output image signal of the channel region is amplified to the target value. As a result of comparison, as a result of comparison, the channel region showing the lowest amplification factor is set as the reference channel region, and the output image signals between the ends of the adjacent channel regions are based on the size of the output image signal from the reference channel region. A control command for correcting the amplification factor of the amplification means so as to be relatively equal to each other is output to each variable amplification factor amplification unit.
[0011]
According to the second aspect of the present invention, when the image signal output from each channel region is amplified until it reaches a preset target value, the channel region that exhibits the lowest amplification factor is used as a reference. Since the amplification factor of the channel region is corrected, the amplification factor of each output image signal can be suppressed to the minimum necessary, and variations in the light receiving sensitivity can be accurately corrected.
[0012]
According to a third aspect of the present invention, in the image reading apparatus according to the second aspect, the control unit is configured to control the amplification factor of each variable amplification factor amplification unit with respect to an output image signal in a channel region that is not adjacent to the reference channel region. The correction is performed on the basis of the output image signal of the adjacent channel region corrected in advance.
[0013]
According to the third aspect of the invention, the correction of the amplification factor of each variable amplification factor amplification unit for the output image signal of the channel region not adjacent to the reference channel region is performed, and the output signal of the adjacent channel region corrected previously is Can be done as a reference.
[0014]
According to a fourth aspect of the present invention, in the image reading device according to any one of the first to third aspects, the comparison of the magnitude of the output image signal between the reference channel region and each channel region is performed in the channel. This is performed using an average value of image signals output from a plurality of pixels in the region.
[0015]
According to the fourth aspect of the present invention, the comparison of the size of the output image signal between the reference channel region and each channel region is performed using the average value of the image signals output from a plurality of pixels in the channel region. Therefore, the influence of noise and the like appearing in each output image signal can be reduced.
[0016]
According to a fifth aspect of the present invention, an image forming apparatus includes the image reading device according to any one of the first to fourth aspects.
[0017]
According to the invention described in claim 5, by providing the image reading device according to any one of claims 1 to 4, it is possible to read an image with high reproducibility, and it is excellent without image unevenness. A simple image can be output to various output media such as paper.
[0018]
According to a sixth aspect of the present invention, a document is exposed by a light source, and reflected light from the document is converted into an electrical signal by a photoelectric conversion unit in which constituent pixels are divided into a plurality of channel regions, and output. In the signal correction method for correcting each of the output image signals of each channel region when the signal synthesis unit synthesizes the image signal output from each channel region of the photoelectric conversion unit, the output image signal of each channel region is corrected. Until each of the output image signals of each channel region individually reaches a preset target value by using a plurality of variable amplification factor amplification units that individually amplify each and output to the image signal synthesis unit Next, the image signal output from each channel region of the photoelectric conversion unit is amplified, and the output image signal between the ends of each adjacent channel region is amplified. Wherein the is come is equipped with a signal correcting step of correcting the amplification factor of the variable gain amplifier unit so as to be relatively equal.
[0019]
According to the sixth aspect of the present invention, each of the output image signals of each channel region is individually amplified until reaching a preset target value using a plurality of variable amplification factor amplifiers, and then adjacent to each other. Since the amplification factor of the variable amplification factor amplifier is corrected so that the sizes of the output image signals at the ends of each channel region are relatively equal, it is possible to correct variations in the light receiving sensitivity of each channel region. Thus, it is possible to prevent a difference in density of the image signal at the seam between the channel areas and density unevenness in the image at the position corresponding to the seam between the channel areas.
[0020]
The invention according to claim 7 is the signal correction method according to claim 6, wherein, in the signal correction step, an amplification factor between the channel regions at the time of amplification of the output image signal of each channel region to the target value. As a result of the comparison, the channel region showing the lowest amplification factor is set as the reference channel region, and the output image between the ends of the adjacent channel regions is determined based on the magnitude of the output image signal from the reference channel region. The amplification factor of the amplification means is corrected so that the signal magnitudes are relatively equal.
[0021]
According to the seventh aspect of the present invention, when the image signal output from each channel region is amplified until it reaches a preset target value, the channel region that exhibits the lowest amplification factor is used as a reference, and Since the amplification factor of the channel region is corrected, the amplification factor of each output image signal can be suppressed to the minimum necessary, and variations in the light receiving sensitivity can be accurately corrected.
[0022]
The invention according to claim 8 is the signal correction method according to claim 7, wherein, in the signal correction step, the amplification factor of each of the variable amplification factor amplifiers for the output image signal in the channel region not adjacent to the reference channel region. This correction is performed with reference to the output image signal of the adjacent channel region corrected previously.
[0023]
According to the eighth aspect of the present invention, the correction of the amplification factor of each variable amplification factor amplification unit for the output image signal of the channel region not adjacent to the reference channel region is performed, and the output signal of the adjacent channel region corrected in advance is used. Can be done as a reference.
[0024]
According to a ninth aspect of the present invention, in the signal correction method according to any one of the first to third aspects, a comparison of magnitudes of output image signals between the reference channel region and the channel regions is performed on the channel. This is performed using an average value of image signals output from a plurality of pixels in the region.
[0025]
According to the ninth aspect of the present invention, the comparison of the size of the output image signal between the reference channel region and each channel region is performed using the average value of the image signals output from a plurality of pixels in the channel region. Therefore, the influence of noise and the like appearing in each output image signal can be reduced.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
The image forming apparatus 1 is, for example, a copying machine, a printer, a facsimile machine, a scanner, or a complex machine of these, and includes an image reading unit 2, a signal processing unit (not shown), an image forming unit 3, a paper feeding unit 4, and a conveying unit 5. Etc. The configuration of the image reading unit 2 will be described later.
[0027]
The signal processing unit performs signal processing such as encoding / compression / decompression / decoding, image enlargement / reduction processing, and image rotation processing on the image signal acquired by the image reading unit 2 as necessary.
[0028]
The image forming unit 3 executes an image forming operation for forming an image on an output medium such as paper by an electrophotographic method, an inkjet method, or the like based on the image signal subjected to signal processing by the signal processing unit.
[0029]
The paper feed unit 4 includes a plurality of paper feed trays 40 that store recording paper or the like as an output medium, and supplies the recording paper or the like stored in each paper feed tray 40 to the image forming unit 3 via the transport unit 5. .
[0030]
The conveyance unit 5 has a conveyance path 5a provided so as to be connected from the paper supply unit 4 to the image forming unit 3 and the discharge tray 1a, and the recording paper or the like supplied from the paper supply unit 4 is conveyed along the conveyance path 5a. Then, the image forming unit 3 and the discharge tray 1a are conveyed in this order.
[0031]
The image reading unit 2 holds the light source 22, the reflection mechanism 23, the lens 24, the one-dimensional image sensor 25 as a photoelectric conversion unit, the light source 22, and the reflection mechanism 23 below the contact glass 21 and moves them in the sub-scanning direction. The image reading device includes a carriage (not shown) and the like and reads an image from a document placed on the contact glass 21.
[0032]
The light source 22 can be composed of, for example, a xenon lamp tube that is long in the main scanning direction of the document. The light source 22 is provided in parallel with the main scanning direction of the document, and exposes the document image surface line by line. By the carriage, the light source 22 is mechanically moved line by line in the sub-scanning direction. As a result, the entire original image surface is exposed and scanned.
[0033]
The light source 22 has different illuminance characteristics depending on the type. For example, as shown in FIG. 2A, when a xenon lamp tube is used as the light source 22, each position when the one end 22a of the light source 22 is the start point and the other end 22b is the end point (in FIG. The illuminance at (shown as “)” is represented by an illuminance distribution that draws a bow-shaped locus having a maximum illuminance near the center (arrow A). That is, the xenon lamp tube has the highest illuminance at the center, and the periphery is dimmed. Therefore, the central portion of the document in the main scanning direction is exposed with higher illuminance than the end portion of the document.
[0034]
The reflection mechanism 23 (see FIG. 1) includes a plurality of mirrors that guide light including image information reflected from the document image surface (hereinafter referred to as “reflected light”) to the light receiving surface of the one-dimensional image sensor 25. The lens 24 focuses the reflected light L on the light receiving surface of the one-dimensional image sensor 25 to form an image. As a result, one line of reflected light L is imaged on the light receiving surface of the one-dimensional image sensor 25 from the original that has been exposed and scanned line by line.
[0035]
As shown in FIGS. 2B and 3, the one-dimensional image sensor 25 is configured such that photoelectric conversion elements serving as constituent pixels such as a CCD are arranged in a straight line on the light receiving surface. The one-dimensional image sensor 25 of this embodiment is of a so-called four-channel type, and the constituent pixels are divided into four channel regions Ch1 to Ch4 along the array (see FIG. 2B). Output terminals are provided on Ch1 to Ch4. Assuming that one photoelectric conversion element is one pixel, each of the channel regions Ch1 to Ch4 includes the same number of pixels.
[0036]
Image signal S output from each channel region Ch1 to Ch4 ₁ ~ S ₄ Is a serial analog signal in which output signals from each pixel included in each of the channel regions Ch1 to Ch4 are sequentially connected according to the pixel arrangement. Image signals S output from the four channel regions Ch1 to Ch4 ₁ ~ S ₄ Is shown with respect to the displacement of each pixel, a locus substantially similar to the illuminance distribution of the light source 22 is drawn as shown in FIG.
[0037]
Here, “displacement” indicates the position of each pixel when the channel region Ch1 side of the one-dimensional image sensor 25 is the one end portion 25a and the channel region Ch4 side is the other end portion 25b.
[0038]
When the light receiving sensitivities of the channel regions Ch1 to Ch4 are equal, each image signal S ₁ ~ S ₄ When the image signal for one line is synthesized, the image signal draws a smooth arc similar to the illuminance distribution of the light source 22. However, when there is variation in the light receiving sensitivity of the photoelectric conversion elements constituting the channel regions Ch1 to Ch4, as shown in FIG. 2C, when the image signals for one line are combined, the image signals S ₁ ~ S ₄ The signal levels at the joints may become discontinuous between the joints, and a step may occur at the joints. In the present embodiment, each image signal S is individually received by the signal correction circuit 6 described below so that the ends of the adjacent channel regions Ch1 to Ch4 are relatively equal in size. ₁ ~ S ₄ The image signal S output from each channel region Ch1 to Ch4 is adjusted by adjusting the amplification factor of ₁ ~ S ₄ And the variation in the light receiving sensitivity of each of the channel regions Ch1 to Ch4 is corrected.
[0039]
The configuration of the signal correction circuit 6 will be described with reference to FIG. As shown in FIG. 3, the signal correction circuit 6 includes a gain correction circuit (variable amplification factor amplification unit) 61, an A / D conversion circuit 62, an image signal synthesis unit 63, a memory 64, and a gain control unit (control). Part) 65 and a D / A conversion circuit 66.
[0040]
In FIG. 3, the display of the gain correction circuit 61 provided in the channel regions Ch2 and Ch3 is omitted. The same applies to the A / D conversion circuit 62 and the D / A conversion circuit 66.
[0041]
The gain correction circuit 61 is provided in each of the channel regions Ch1 to Ch4, and the image signal S ₁ ~ S ₄ Are individually amplified and output to the image signal synthesis unit. The gain correction circuit 61 can be composed of an analog amplifier, for example, and the gain is variably adjusted by the gain control unit 65.
[0042]
Hereinafter, in the gain correction circuit 61, the image signal S ₁ ~ S ₄ "Gain correction" to amplify the image signal S again based on the corrected amplification factor ₁ ~ S ₄ Is sometimes referred to as “gain recorrection”.
[0043]
The A / D conversion circuit 62 is provided in each gain correction circuit 61. The luminance-corrected analog image signal S output from the gain correction circuit 61 _A1 ~ S _A4 The digital image signal S _D1 ~ S _D4 And output to the image signal synthesis unit 63.
[0044]
The image signal synthesis unit 63 includes a CPU (Central Processing Unit) (not shown) and an internal memory such as a RAM (Random Access Memory) and a ROM (Read Only Memory), and executes image signal synthesis processing by computer control. In the image signal synthesis process, the CPU performs the digital image signal S output from the A / D conversion circuit 62 in accordance with an image signal synthesis program or the like stored in an internal memory or a memory 64 described later. _D1 ~ S _D4 Are once stored in the memory 64, and then the digital image signal S according to the arrangement of the channel regions Ch1 to Ch4. ₁ ~ S ₄ And an image signal corresponding to one line of the original is synthesized. This image signal synthesis process is performed for each line. The combined image signal for one line is output to a subsequent signal processing unit, and the signal processing unit appropriately performs signal processing. By laminating the image signals obtained for each line in the sub-scanning direction, an image signal representing the entire document can be obtained.
[0045]
The gain control unit 65 includes a CPU and an internal memory including a RAM, a ROM, and the like. Each image in the gain correction circuit 61 is controlled by a computer in accordance with a signal correction program stored in the internal memory of the CPU or a memory 64 described below. Signal S ₁ ~ S ₄ The control command for correcting the gain is transmitted to the gain correction circuit 61 via the D / A conversion circuit 66. This signal correction process will be described later.
[0046]
The memory 64 includes a RAM having a work area, a ROM for storing various programs such as a system program, an image signal synthesis program, and a signal correction program, data processed by each program, and the like.
[0047]
Although the image signal synthesis unit 63, the memory 64, and the gain control unit 65 have been described as different components, the present invention is not limited to this. Of course, functions similar to those of the image signal synthesis unit 63, the memory 64, and the gain control unit 65 may be realized by a microcomputer including a CPU, a RAM, a ROM, and the like.
[0048]
Next, the operation of the present embodiment will be described.
FIG. 4 is a flowchart for explaining signal correction processing executed by the gain controller 65 in accordance with the signal correction program.
[0049]
First, for example, as shown in FIG. 5, the image signal S output from each channel region Ch1 to Ch4. ₁ ~ S ₄ Are individually amplified by the gain correction circuit 61 so as to reach a preset target value (step S1).
[0050]
At this time, the amplification factor may be adjusted so that any one pixel in each of the channel regions Ch1 to Ch4 reaches the target value, or the average value of the image signals output from the plurality of pixels is the target value. The amplification factor may be adjusted to reach Furthermore, the amplification factor may be adjusted so that the average value of the image signals of all the pixels included in each channel region Ch1 to Ch4 reaches the target value. By adjusting the respective amplification factors so that the average value of the plurality of pixels reaches the target value, the image signal S ₁ ~ S ₄ It is possible to mitigate the influence of noise and the like appearing on the screen.
[0051]
Next, the image signal S output from each channel region Ch1 to Ch4. ₁ ~ S ₄ In order to prevent the signal levels from becoming discontinuous and causing a step at the joint, a channel region serving as a reference for correcting each amplification factor is determined (step S2).
[0052]
Here, the channel region serving as a reference is the image signal S in step S1. ₁ ~ S ₄ Are compared so as to reach a preset target value, and as a result of comparison, a channel region showing the lowest amplification factor is set as a reference channel region.
[0053]
The channel region showing the lowest amplification factor is a channel region corresponding to the point exposed from the light source 22 with the highest illuminance. For example, in the case shown in FIG. 5, the channel region Ch2 becomes the reference channel region.
[0054]
By setting the channel area that shows the lowest amplification factor when amplified to reach the target value as the reference channel area, the image signal output from other channel areas is necessary without exceeding the preset target value. The image signal S can be reduced to a minimum amplification factor. ₁ ~ S ₄ Can be accurately corrected.
[0055]
Next, using the image signal output from the reference channel region as a reference, the gain of the gain correction circuit 61 is corrected so that the sizes of the output image signals at the ends of the adjacent channel regions are relatively equal. Then, the gain is corrected again (step S3).
[0056]
For example, as shown in FIG. 5, when the channel region Ch2 is set as the reference channel region, the output image signal S at the end portion adjacent to each reference channel region Ch2 of the channel regions Ch1 and Ch3 adjacent to the reference channel region Ch2 is used. ₁ , S ₃ Is the output image signal S at the end of the reference channel region Ch2. ₂ The gain of each gain correction circuit 61 is corrected so as to be relatively equal to the magnitude of the image signal S. ₁ , Image signal S ₃ Gain recorrection is performed (see FIG. 6).
[0057]
Next, the gain of the gain correction circuit 61 for the image signal output from the channel region not adjacent to the reference channel region is corrected with reference to the image signal output from the adjacent channel region corrected earlier, and the gain is restored. Correction is performed (step S4).
[0058]
In the case shown in FIG. 5, the image signal S output from the channel region Ch4 that is not adjacent to the reference channel region Ch2. ₄ Is output from the adjacent channel region Ch3, which has been corrected previously. ₃ , The gain of the corresponding gain correction circuit 61 is corrected so that the magnitudes of the output image signals at the ends are relatively equal, and the image signal S ₄ Gain recorrection is performed (see FIG. 6).
[0059]
The operation in step S4 is repeated until there is no channel area for which gain recorrection is not performed (step S5: N), and the process is terminated.
[0060]
As described above, the gain of the gain correction circuit 61 is corrected so that the sizes of the output image signals at the ends of the adjacent channel regions are relatively equal with respect to the image signal output from the reference channel region. , Each image signal S ₁ ~ S ₄ Is corrected.
[0061]
According to the present embodiment, the signal correction circuit 6 uses the plurality of gain correction circuits 61 to output the image signal S output from each channel region Ch1 to Ch4. ₁ ~ S ₄ Are individually amplified until reaching a preset target value, and then the gain correction circuit is configured so that the magnitudes of the output image signals at the ends of the adjacent channel regions Ch1 to Ch4 are relatively equal to each other. Since the amplification factor 61 is corrected, variations in the light receiving sensitivity of the channel regions Ch1 to Ch4 can be corrected, and the image signal S is connected at the joint of the channel regions Ch1 to Ch4. ₁ ~ S ₄ As a result, a difference in density can be prevented from occurring in an image at a position corresponding to the joint between the channel regions Ch1 to Ch4.
[0062]
Further, the correction of the amplification factor of the gain correction circuit 61 for the output image signal of the channel area not adjacent to the reference channel area can be performed with reference to the output signal of the adjacent channel area corrected previously.
[0063]
Furthermore, since variations in the light receiving sensitivity of the channel regions Ch1 to Ch4 are corrected, the image reading unit 2 can read the image of the document with high reproducibility, and the image forming unit 3 can display excellent images without image unevenness. Can be output to an output medium such as paper.
[0064]
In addition, this invention is not limited to the said embodiment, Of course, it can change suitably in the range which does not deviate from the meaning of this invention.
In the above embodiment, the four-channel type one-dimensional image sensor in which the constituent pixels are divided into the four channel regions Ch1 to Ch4 along the arrangement has been described as an example. However, the number of channels and the channel regions Ch1 to Ch4 are described. However, the method of dividing is not limited to this. For example, the channel region may be divided into pixels arranged at odd positions and pixels arranged at even positions, and the channel region may be further divided into a plurality of channels within the divided channel regions. In this case, the gain of the gain correction circuit is corrected in the same manner as described above for a plurality of channel regions composed of pixels arranged at odd positions and a plurality of channel regions composed of pixels arranged at even positions. do it.
[0065]
【The invention's effect】
According to the first aspect of the present invention, each of the output image signals of each channel region is individually amplified until reaching a preset target value using a plurality of variable amplification factor amplifiers, and then adjacent to each other. Since the amplification factor of the variable amplification factor amplifier is corrected so that the sizes of the output image signals at the ends of each channel region are relatively equal, it is possible to correct variations in the light receiving sensitivity of each channel region. Thus, it is possible to prevent a difference in density of the image signal at the seam between the channel areas and density unevenness in the image at the position corresponding to the seam between the channel areas.
[0066]
According to the second aspect of the present invention, when the image signal output from each channel region is amplified until it reaches a preset target value, the channel region that exhibits the lowest amplification factor is used as a reference. Since the amplification factor of the channel region is corrected, the amplification factor of each output image signal can be suppressed to the minimum necessary, and variations in the light receiving sensitivity can be accurately corrected.
[0067]
According to the third aspect of the invention, the correction of the amplification factor of each variable amplification factor amplification unit for the output image signal of the channel region not adjacent to the reference channel region is performed, and the output signal of the adjacent channel region corrected previously is Can be done as a reference.
[0068]
According to the fourth aspect of the present invention, the comparison of the size of the output image signal between the reference channel region and each channel region is performed using the average value of the image signals output from a plurality of pixels in the channel region. Therefore, the influence of noise and the like appearing in each output image signal can be reduced.
[0069]
According to the invention described in claim 5, by providing the image reading device according to any one of claims 1 to 4, it is possible to read an image with high reproducibility, and it is excellent without image unevenness. A simple image can be output to various output media such as paper.
[0070]
According to the sixth aspect of the present invention, each of the output image signals of each channel region is individually amplified until reaching a preset target value using a plurality of variable amplification factor amplifiers, and then adjacent to each other. Since the amplification factor of the variable amplification factor amplifier is corrected so that the sizes of the output image signals at the ends of each channel region are relatively equal, it is possible to correct variations in the light receiving sensitivity of each channel region. Thus, it is possible to prevent a difference in density of the image signal at the seam between the channel areas and density unevenness in the image at the position corresponding to the seam between the channel areas.
[0071]
According to the seventh aspect of the present invention, when the image signal output from each channel region is amplified until it reaches a preset target value, the channel region that exhibits the lowest amplification factor is used as a reference, and Since the amplification factor of the channel region is corrected, the amplification factor of each output image signal can be suppressed to the minimum necessary, and variations in the light receiving sensitivity can be accurately corrected.
[0072]
According to the eighth aspect of the present invention, the correction of the amplification factor of each variable amplification factor amplification unit for the output image signal of the channel region not adjacent to the reference channel region is performed, and the output signal of the adjacent channel region corrected in advance is used. Can be done as a reference.
[0073]
According to the ninth aspect of the present invention, the comparison of the size of the output image signal between the reference channel region and each channel region is performed using the average value of the image signals output from a plurality of pixels in the channel region. Therefore, the influence of noise and the like appearing in each output image signal can be reduced.
[Brief description of the drawings]
FIG. 1 is a side sectional view showing an example of an image reading apparatus to which the present invention is applied.
2A is a diagram illustrating illuminance characteristics of a light source, FIG. 2B is a schematic diagram illustrating a channel region configuration of a one-dimensional image sensor, and FIG. 2C is a diagram illustrating luminance of an output image signal output from each channel. .
FIG. 3 is a block diagram showing a configuration of a signal correction circuit provided in an image reading apparatus to which the present invention is applied.
4 is a flowchart for explaining the operation of the signal correction circuit of FIG. 3;
FIG. 5 is a diagram for explaining an operation performed in step S1 of FIG.
6 is a diagram for explaining an operation performed in step S4 of FIG. 4;
[Explanation of symbols]
1 Image forming device
2 Image reading unit (image reading device)
21 Contact glass
22 Light source
25 One-dimensional image sensor
3 Image forming section
4 Paper feeder
5 Transport section
6 Signal correction circuit
61 Gain correction circuit (variable gain amplification unit)
63 Image signal synthesizer
65 Gain controller
Ch1-Ch4 channel area
S ₁ ~ S ₄ Image signal

Claims (9)

A light source for exposing a document, and constituent pixels are divided into a plurality of channel regions, a photoelectric conversion unit that converts reflected light from the document into an electrical signal, and outputs from each channel region of the photoelectric conversion unit An image signal synthesizing unit that synthesizes and outputs the image signal to be output,
A plurality of variable amplification factor amplifying units that individually amplify each of the image signals output from each channel region of the photoelectric conversion unit and output to the image signal combining unit;
Each of the output image signals of each channel area is individually amplified until reaching a preset target value, and then the magnitudes of the output image signals at the ends of adjacent channel areas are relatively equal. A control unit that outputs a control command for correcting the amplification factor of each variable amplification factor amplifier to each of the variable amplification factor amplification units,
An image reading apparatus comprising: The image reading apparatus according to claim 1,
The control unit compares the amplification factors between the channel regions at the time of amplification of the output image signal of each channel region to the target value, and as a result of the comparison, the channel region showing the lowest amplification factor is set as a reference channel region. Based on the magnitude of the output image signal from the reference channel area, the amplification factor of the amplification means is corrected so that the magnitudes of the output image signals at the ends of the adjacent channel areas are relatively equal. An image reading apparatus that outputs a control command to each of the variable amplification factor amplifiers. The image reading apparatus according to claim 2,
The control unit corrects the amplification factor of each variable amplification factor amplification unit for the output image signal of the channel region not adjacent to the reference channel region with reference to the output image signal of the adjacent channel region corrected previously. An image reading apparatus. In the image reading device according to any one of claims 1 to 3,
An image reading apparatus, wherein the comparison of the magnitudes of output image signals between the reference channel region and each channel region is performed using an average value of image signals output from a plurality of pixels in the channel region. An image forming apparatus comprising the image reading apparatus according to claim 1. The original is exposed by a light source, and the reflected light from the original is converted into an electrical signal by a photoelectric conversion unit in which constituent pixels are divided into a plurality of channel regions, and the photoelectric signal is output from the photoelectric conversion unit by an image signal synthesis unit. In the signal correction method for correcting each of the output image signals of each channel region when combining the image signals output from each channel region,
Each of the output image signals of each channel region is individually amplified using a plurality of variable amplification factor amplifying units that individually amplify each of the output image signals of each channel region and output to the image signal synthesis unit. Amplification is performed until a preset target value is reached, and then each of the image signals output from each channel region of the photoelectric conversion unit is relatively equal in magnitude to the output image signal between the ends of each adjacent channel region. A signal correction method comprising a signal correction step of correcting the amplification factor of each variable amplification factor amplifier so as to be equal to The signal correction method according to claim 6,
In the signal correction step, the amplification factor between the channel regions is compared at the time of amplification of the output image signal of each channel region to the target value. Based on the magnitude of the output image signal from the reference channel area, the amplification factor of the amplification means is corrected so that the magnitudes of the output image signals at the ends of the adjacent channel areas are relatively equal. And a signal correction method. The signal correction method according to claim 7,
In the signal correction step, the correction of the amplification factor of each variable amplification factor amplification unit with respect to the output image signal of the channel region not adjacent to the reference channel region is performed with reference to the output image signal of the adjacent channel region corrected previously. A signal correction method characterized by comprising: In the signal correction method according to any one of claims 1 to 3,
A signal correction method characterized in that the comparison of the magnitudes of output image signals between the reference channel region and each channel region is performed using an average value of image signals output from a plurality of pixels in the channel region.

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