JP2008252217A - Image reader - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image reader which prevents deterioration in image quality by actualizing suitable linear correction even when an image output varies owing to variation in quantity of light of a light source etc. <P>SOLUTION: The image reader includes a lens which converges light reflected by a document, a sensor chip which receives the light converged by the lens, an analog/digital converter which converts a signal photoelectrically converted by the sensor chip into a digital signal, a black correcting unit which generates dark-time output data of the sensor chip to correct the digitally converted photoelectric conversion output by equalization, a first linearity correcting unit which differences and then linearity-corrects the data corrected by the black correcting unit and pixel data sampled while an exposure quantity is previously varied in steps relative to a reference exposure quantity and stored in a storage elements for respective pixels, and a white correcting unit which generates and equalization-corrects light-time output data output from the first linearity correcting unit. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image reading apparatus that digitally reads information on an original, such as a scanner, a FAX, and a copier.

As a reading unit of a scanner, a FAX, a copier, or the like, a technique is widely used in which an image reading device such as a contact image sensor that reads an image by arranging a plurality of sensor chips in series is widely used.
The factors that cause the linearity characteristics of the contact image sensor to collapse from the ideal are the deterioration of the linearity characteristics of the sensor chip and the reflection phenomenon (diffuse reflection There is a thing caused by the reflection phenomenon). In particular, when a variation in linearity characteristics occurs between the sensor chips, a large output step is generated at the joint of the sensor chips, which causes a significant deterioration in image quality.

As a correction means for solving the electrical variation of the components of the image reading device (contact type image sensor) having a low input light quantity (black level) and a high input light quantity (white level), a light source is turned on and uniform. It is common to read the reflected light from a white reference plate having reflection characteristics and the dark output when the light source is turned off, and perform shading correction (monochrome correction) so that the respective output values match in pixel units. is there. The correction amount is updated every time the apparatus is turned on or each time the document is read.

In addition, as a correction means to solve the variation in linearity, a reference gray scale original (halftone original) having a plurality of density portions is read, and linearity correction is performed so that the output value of each density is uniform at a certain level. The method of performing is known. In general, the correction amount is corrected at the time of inspection before shipment or maintenance, and thereafter, the correction value is used in a fixed manner.

For example, as a method for performing shading correction and linearity correction using a white reference plate or a gray scale document, Japanese Patent Application Laid-Open No. 2003-219172 (see Patent Document 1) includes a CIS (contact image sensor) module 202. Are sorted by a rearrangement unit 102, a gain offset adjustment circuit that performs gain offset adjustment on signals from the respective output units (OS 1 to OS 16), an analog signal processing unit 101 having an AD converter that converts the signals to digital signals, and a rearrangement unit 102. An image processing apparatus is disclosed that incorporates a shading correction unit 103 that performs shading correction on each signal for each color, and a linearity correction unit 104 that performs linearity correction on a plurality of image signals having different linearity characteristics. White reference plate 206 It performs a shading correction of the output data is used, is doing the linearity correction after the shading correction by using a half-tone chart (halftone original).

Japanese Patent Laid-Open No. 2003-219172 (FIG. 1)

  However, in the apparatus described in Patent Document 1, when a black and white level is first uniformed using a white reference plate, a plurality of reference originals having a known density ratio are read, and the original density ratio and the original are read. The correction values are derived so that the output ratios of the two coincide. For this reason, the linearity correction circuit is provided after the shading correction circuit as an image processing circuit that realizes these corrections, and the linearity correction is performed on the output after the shading correction is performed. Issues remain.

  First, the linearity characteristic of the sensor (sensor chip) mainly depends on the conversion efficiency characteristic of the light receiving element part that performs photoelectric conversion and the input / output characteristic of the analog circuit part, and is defined by the output voltage with respect to the incident light amount. For this reason, when the amount of light from the light source fluctuates due to changes over time, the output voltage when the reference document is read differs from the output voltage at the past time when the correction value was derived, but the correction value is fixed. Therefore, there is a problem that sufficient correction is not performed, and as a result, unevenness occurs in the read image.

  Further, in order to solve this problem, there is a problem that it is necessary to read the reference document again and update the correction value by maintenance or the like.

In order to minimize the number of missing pixels in the chip connection portion, the sensor chip used in the contact image sensor is arranged with the light receiving element portions located at both ends of the chip as close to the chip end as possible. Therefore, the light receiving element portion near the chip end portion has a larger variation in characteristics than those in the inner region. For this reason, when uniform linearity correction is performed in units of sensor chips, there is a problem in that correction near the end of the chip cannot be performed sufficiently and image unevenness occurs.

  The present invention has been made to solve the above-described problems. Even when the image output fluctuates due to a change over time such as the light amount of the light source, the image quality is deteriorated by realizing appropriate linearity correction. An object of the present invention is to provide an image reading apparatus capable of preventing the above-described problem.

  According to a first aspect of the present invention, there is provided an image reading apparatus including at least two light sources that irradiate a document, a lens that converges light reflected by the document, and a plurality of pixels that receive light converged by the lens. Two or more sensor chips, an analog / digital conversion unit that performs analog / digital conversion on an analog signal photoelectrically converted by the sensor chip, and a photoelectric conversion output digitally converted by the analog / digital conversion unit. A black correction unit that generates output data at the same time and corrects the uniformity, data corrected by the black correction unit, and an exposure amount that is stepwise changed in advance with respect to a reference exposure amount. A first linearity correction unit that corrects linearity after subtracting the pixel data stored in the storage element, and the light source output from the first linearity correction unit Generating an irradiation output data at the time of light of the sensor chip each pixel were those with a white correction unit that corrects uniform.

  According to a second aspect of the present invention, there is provided an image reading apparatus including at least two light sources that irradiate a document, a lens that converges light reflected by the document, and a plurality of pixels that receive light converged by the lens. More than one sensor chip, an analog / digital converter that performs analog / digital conversion on the analog signal photoelectrically converted by the sensor chip, and a photoelectric conversion output that has been digitally converted by the analog / digital converter is used as a reference exposure amount in advance. A first linearity correction unit that performs linearity correction on pixel data stored in a storage element over each pixel, and is output from the first linearity correction unit, and is extracted from the first linearity correction unit. A black correction unit that generates and uniformizes output data of the sensor chip in the dark, and a light output data of each pixel of the sensor chip irradiated by the light source. It generates a data is obtained and a white correction unit that corrects uniform.

  According to a third aspect of the present invention, there is provided an image reading apparatus including at least two light sources for irradiating a document, a lens for converging light reflected by the document, and a plurality of pixels for receiving light converged by the lens. More than one sensor chip, an analog / digital converter that performs analog / digital conversion on the analog signal photoelectrically converted by the sensor chip, and a photoelectric conversion output that has been digitally converted by the analog / digital converter is used as a reference exposure amount in advance. A first linearity correction unit that corrects linearity of pixel data stored in a storage element over each pixel, and outputs output data in the dark state of the sensor chip. A black correction unit that performs uniform correction; a white correction unit that generates and uniformizes and corrects output data at the time of each pixel of the sensor chip irradiated by the light source; and The linearity correction unit, the black correction unit, and the white correction unit are installed in conjunction with respective input units, and the photoelectric conversion output digitally converted by one opening / closing operation is transferred from the black correction unit to the first linearity correction unit. Input to the white correction unit via the correction unit, and input the photoelectric conversion output digitally converted by the other opening / closing operation from the first linearity correction unit to the white correction unit via the black correction unit And a switching means.

  According to a fourth aspect of the present invention, there is provided an image reading apparatus including at least two light sources that irradiate a document, a lens that converges light reflected by the document, and a plurality of pixels that receive light converged by the lens. Two or more sensor chips, an analog / digital conversion unit that performs analog / digital conversion on an analog signal photoelectrically converted by the sensor chip, and a photoelectric conversion output digitally converted by the analog / digital conversion unit. A black correction unit that generates output data at the same time and corrects the uniformity, data corrected by the black correction unit, and an exposure amount that is stepwise changed in advance with respect to a reference exposure amount. A first linearity correction unit that corrects linearity after subtracting the pixel data stored in the storage element, and the light source output from the first linearity correction unit A white correction unit that generates and uniformizes and corrects the output data at the time of each pixel of the irradiated sensor chip, and the storage element includes a pixel around the end of the sensor chip and a periphery of the end of the sensor chip A correction coefficient different from that of the other pixels is given in advance, and the correction coefficient is added to the pixel data of each pixel to perform arithmetic processing.

According to a fifth aspect of the present invention, there is provided an image reading apparatus including at least two light sources that irradiate a document, a lens that converges light reflected by the document, and a plurality of pixels that receive light converged by the lens. More than one sensor chip, an analog / digital converter that performs analog / digital conversion on the analog signal photoelectrically converted by the sensor chip, and a photoelectric conversion output that has been digitally converted by the analog / digital converter is used as a reference exposure amount in advance. A first linearity correction unit that performs linearity correction on pixel data stored in a storage element over each pixel, and is output from the first linearity correction unit, and is extracted from the first linearity correction unit. A black correction unit that generates and uniformizes output data of the sensor chip in the dark, and a light output data of each pixel of the sensor chip irradiated by the light source. A white correction unit that generates and uniformizes the correction of pixels, and the pixels around the edge of the sensor chip and the pixels other than the periphery of the edge of the sensor chip have different correction coefficients in advance, and the correction coefficient is It is characterized by being added to pixel data of each pixel and performing arithmetic processing.

  According to a sixth aspect of the present invention, there is provided an image reading apparatus including at least two light sources that irradiate a document, a lens that converges light reflected by the document, and a plurality of pixels that receive light converged by the lens. More than one sensor chip, an analog / digital converter that performs analog / digital conversion on the analog signal photoelectrically converted by the sensor chip, and a photoelectric conversion output that has been digitally converted by the analog / digital converter is used as a reference exposure amount in advance. A first linearity correction unit that corrects linearity of pixel data stored in a storage element over each pixel, and outputs output data in the dark state of the sensor chip. A black correction unit that performs uniform correction; a white correction unit that generates and uniformizes and corrects output data at the time of each pixel of the sensor chip irradiated by the light source; and The linearity correction unit, the black correction unit, and the white correction unit are installed in conjunction with respective input units, and the photoelectric conversion output digitally converted by one opening / closing operation is transferred from the black correction unit to the first linearity correction unit. Input to the white correction unit via the correction unit, and input the photoelectric conversion output digitally converted by the other opening / closing operation from the first linearity correction unit to the white correction unit via the black correction unit Switching means for providing a pixel with a different correction coefficient in advance for pixels around the edge of the sensor chip and pixels other than the edge around the sensor chip, and adding the correction coefficient to the pixel data of each pixel. It is characterized by performing arithmetic processing.

  As described above, according to the first aspect of the present invention, the black correction unit that corrects the output data in the dark when the photoelectric conversion output is obtained, and the pixel data that is acquired by changing the exposure amount stepwise with respect to the reference exposure amount in advance. Since the linearity correction is performed after the difference is corrected, the linearity characteristic in consideration of the dark output is obtained. Therefore, it is possible to obtain an image reading apparatus with excellent linearity characteristic in which variations in dark output are improved.

  According to the second aspect of the present invention, the linearity correction is performed after obtaining the linearity characteristics based on the pixel data obtained by changing the exposure amount stepwise with respect to the reference exposure amount in advance. It is possible to adjust the dark output characteristic variation, which is particularly useful for adjusting the dark output of a light receiving unit having a specific dark output characteristic.

According to the invention of claim 3, since the circuit configuration can be made by switching between the first linearity correction unit and the black correction unit as necessary, the effect of claim 1 and the effect of claim 2 are selected. can do.

  According to the inventions according to claims 4 to 6, the correction amount (κ) based on the installation position of each pixel is stored in the ROM in advance, and the input / output characteristics vary depending on the position of the light receiving portion of the sensor chip by correcting this. This also has the advantage of further improving the image quality of the image reading apparatus.

Embodiment 1 FIG.
Embodiment 1 of the present invention will be described below with reference to FIG. FIG. 1 is a block diagram of the image reading apparatus according to the first embodiment. In FIG. 1, reference numeral 1 denotes a sensor chip (sensor), which is a multi-chip image sensor, and 2 is a multi-chip image sensor. An analog gain offset adjustment unit that amplifies the analog signal photoelectrically converted by the sensor chip 1 and adjusts the gain and offset amount of the analog voltage, and 3 is an analog / digital conversion unit that digitally converts the analog signal that has been gain and offset adjusted. Reference numeral 4 denotes a digital gain offset adjustment unit for amplifying the digitally converted photoelectric conversion signal and determining the reference position, that is, adjusting the gain and offset amount of the digital voltage.

  5 is a black correction unit that corrects black level variations, 6 is a first linearity correction unit that corrects linearity variations in photoelectrically converted output, 7 is a white correction unit that corrects white level variations, and 8 is an output A second linearity correction unit 9 for correcting the linearity variation, 9 is a changeover switch (switching means) constituted by an analog switch or the like for changing the input order of the black correction unit 5 and the first linearity correction unit 6.

  Reference numeral 10 denotes a lens array (lens body) such as a rod lens array for forming an image of diffused light from the original, 11 denotes a light source using an LED or the like that illuminates the original, and 12 controls a lighting pulse width of the light source 11. A light source control unit (lighting control circuit). A CPU 13 controls the first linearity correction unit 5 and the second linearity correction unit 8 and includes a ROM (storage element). In the drawings, the same reference numerals indicate the same or corresponding parts.

  Next, the operation will be described. In FIG. 1, the light emitted from the light source 11 is scattered and reflected on the document surface and then imaged on the sensor chip 1 through the lens array 10.

  The sensor chip 1 has a light receiving region (light receiving unit), and incident light is photoelectrically converted and then output as an analog voltage of the sensor chip 1, and an output level is adjusted by the gain offset adjusting unit 2. The digital conversion unit 3 converts the digital signal. The output level of the digitally converted output is adjusted by the gain offset adjustment unit 4 and input to the black correction unit 5 or the first linearity correction unit 6 via the changeover switch 9.

  Next, a case where the changeover switch 9 is connected to the black correction unit will be described. The black correction unit 5 performs black correction when the light source 11 is turned off, so that there are a case where the fixed pattern noise of the photoelectric conversion element is corrected over all pixels (all pixel correction) and a case where correction is performed in a certain pixel unit. . In any case, correction is performed by a known means so as to align with a constant value (for example, “0h” with 10-bit accuracy).

  Next, the signal input to the first linearity correction unit 6 is corrected so that the output with respect to the amount of light incident on the sensor chip 1 becomes linear based on a preset correction table.

  Next, the correction table will be described. FIG. 2 is a diagram for explaining the relationship between the amount of incident light and the sensor output when light is incident on the light receiving portion of the sensor chip 1. In FIG. 2, it can be seen that a constant dark output is generated even when there is no incident light amount, and the relationship between the incident light amount and the sensor output is not in a linear state. FIG. 3 is a diagram for explaining the relationship between the sensor density and the document density at which the reflectance changes when the light quantity of the light source 11 is set to a constant value and light is incident on the light receiving portion of the sensor chip 1. In FIG. 3, the sensor output has an output value that is slightly higher than the dark output level even if a certain dark output occurs and a black document having an original density OD (Optical Density) of 1.6. I understand that.

4 is a cross-sectional view of the image reading apparatus, in which 20 is a light guide that propagates light from the light source 11, 21 is a sensor substrate on which the sensor chip 1 is mounted, 22 is a printed wiring board on which the light source 11 is mounted, and the like. The substrate 23 includes a gain offset adjustment unit 2, an A / D converter, a gain offset adjustment unit 4, a black correction unit 5, a first linearity correction unit 6, a white correction unit 7, a second linearity correction unit 8, and This is an ASIC (signal processing IC) containing a functional circuit such as the CPU 13.
A housing 24 accommodates or holds the lens array 10, the light guide 20, the sensor substrate 21, the substrate 22, and the like. In the figure, the same reference numerals as those in FIG. 1 denote the same or corresponding parts.

  In the image reading apparatus, since the light guide 20 and the casing 24 are grounded close to the document surface, light reflected and reflected by the light guide 20 and the casing 24 exists. FIG. 5 is a diagram for explaining the relationship between the document density and the exposure amount when light is incident on the light receiving portion of the sensor chip 1. In FIG. 5, the non-linear curve deviates from the original linear curve as the density region of the white original is increased due to the light reflection phenomenon.

  FIG. 6 is a diagram for explaining a light receiving region of the sensor chip 1 in which a plurality of sensor chips 1 are linearly arranged on the sensor substrate 21. In FIG. 6, since there is a gap between the adjacent sensor chips 1, it can be seen that the light receiving part (pixel) in the outermost region is in a geometrically singular position than the light receiving parts in the other inside. Therefore, the light receiving part located in the periphery of the outermost region causes a change in output even if the performance of the element itself is the same as that of the light receiving part region inside.

  FIG. 7 is a diagram for explaining a correction table data processing method for providing a correction amount (κ) corresponding to each pixel. In FIG. 7, the pixel data for general processing is a correction table defined at a fixed pixel interval from the top pixel position of the sensor chip 1, while the pixels around the chip end are defined in pixel units as data for chip end processing. A correction table is used. With respect to the correction table defined at a constant pixel interval, the pixel position while the correction table is not defined is derived by linear interpolation based on the correction tables defined before and after the correction table. For pixels around the chip edge, a ROM for each pixel is used for each pixel based on an instruction from the CPU 13 when a correction table defined at regular intervals is used and when a correction table defined in pixel units is used. Select by register setting.

  That is, for pixels around the chip end, the definition position interval of the correction table is made denser than the pixels around the center of the chip, so that the linearity correction is performed even if the linearity characteristics around the chip end of the sensor chip 1 are greatly degraded. Make sure to correct it.

  Next, a method for deriving the correction amount will be described. Since the first linearity correction unit 6 needs to correct the output characteristic with respect to the amount of light incident on the sensor chip 1 so as to be linear, the output characteristic with respect to the amount of incident light is measured in advance. Using the light source 11, the light source controller (lighting control circuit) 12 reads the reference white original while changing the lighting pulse width of the light source, thereby obtaining output characteristics with respect to the incident light amount. In FIG. 8, the lighting time of the light source 11 is such that a plurality of pulse-controlled light sources are turned on corresponding to one cycle of the reading line, and the duty is controlled by the D / t ratio for each pulse. The relationship between the exposure amount and the sensor output is obtained so that the exposure amount and the sensor output have a linear relationship as shown in FIG.

  Since the reference white original is uniform, the influence of the reflection phenomenon of the light source 11 is also constant, so that the time for driving the light source 11 (lighting pulse width) and the amount of light input to the sensor chip 1 have a proportional relationship. The correction amount is determined so that this relationship is linear based on the output characteristics with respect to the obtained incident light quantity. In the first embodiment, the amount of incident light is adjusted by adjusting the lighting pulse width of the light source 11, but the same effect can be obtained by changing the accumulation time of the sensor chip 1 driven at a constant period. These correction amounts are stored in the ROM in advance.

  Next, the white correction unit 7 performs black correction by the first linearity correction unit 6 and receives the output corrected for each pixel from the correction table stored in the ROM, and performs white correction. This white correction is performed on the basis of the reflected light from a reference white original or a white correction plate provided corresponding to some pixels, and a predetermined gain is applied so that the output of each pixel becomes a constant value. For example, correction is performed so as to align to “3E8h”) with 10-bit accuracy.

  Next, the second linearity correction unit 8 performs correction by multiplying the coefficient based on the gain of each pixel obtained by the white correction unit 7.

  As described above, as an effect of the first linearity correction unit 6, the dark output variation data is collected by the black correction unit 5 and stored in a RAM or the like, and the first linearity correction unit 6 corrects the variation of the dark output level. At the same time, a correction amount (κ) based on the installation position of each pixel is stored in the ROM in advance, and by correcting this, variations in input / output characteristics depending on the position of the light receiving portion of the sensor chip 1 are corrected. There is an advantage that the quality is greatly improved.

  Note that the effect of the light source reflection phenomenon is mainly due to the arrangement of the housing of the reading device and the mechanism of the light source 11, so that the hardware can be improved by changing the arrangement of components. In that case, when the amount of variation due to the input / output characteristics of the sensor chip 1 is compared with the amount of variation due to the reflection phenomenon, the amount of variation due to the reflection phenomenon is small, so the influence on the image quality is small. Therefore, it is possible to maintain the image quality in actual use without mounting the second linearity correction unit 8 and without performing correction in consideration of the reflection phenomenon from the light source 11.

Embodiment 2. FIG.
In the first embodiment, the case where the changeover switch 9 is connected to the black correction unit 5 has been described. That is, the output of the analog / digital conversion signal input to the black correction unit 5 is input to the first linearity correction unit 6, but in the second embodiment, the changeover switch 9 is connected to the first linearity correction unit 6. Will be described. In this case, since the first linearity correction unit 6 does not perform black correction, the correction table stored in the ROM becomes the target of linearity correction, and the RAM data of the black correction unit 5 and the white correction unit 7 is the second. The linearity correction unit 8 is used for the linearity correction using a known means.

  Next, the operation will be described. The light source control unit (lighting control circuit) 12 reads the reference white original while changing the lighting pulse width of the light source, thereby obtaining output characteristics with respect to the incident light amount. This operation is the same as that described in the first embodiment. These correction amounts are stored in advance in the ROM together with interpolation correction and terminal processing correction data.

  FIG. 10 is a diagram for explaining the relationship between the document density and the incident light amount when the light amount of the light source 11 is changed. In FIG. 10, when the brightness of the light source 11 is reduced due to the initial state of the light amount of the light source 11 and the change with time, the state after the change with time of the light amount is reduced with respect to the initial state (output source). In (output and display), the amount of decrease in light quantity is a waveform having a similar shape multiplied by a constant light quantity ratio, but the relationship with the ideal output set initially is different.

Since the input signal of the first linearity correction unit 6 is not significantly different from the initial state in the input / output characteristics of the photoelectric conversion region such as the light receiving unit of the sensor chip 1, the input characteristics with respect to the incident light amount are not significantly different from the initial state. Since the amount of incident light at the time of reading the same document density changes, the output characteristics of the sensor with respect to the document density are linear (ideal output) when influenced by the reflection phenomenon as shown in FIG. On the other hand, the initial state (output and display) is greatly different.

Accordingly, in the first embodiment, the first linearity correction is performed on the initial illuminance. However, in the second embodiment, the illuminance assumed after the change with time is corrected by linearity correction in advance. That is, as shown in FIG. 12, when the maximum change over time of the light source 11 is reduced by 30% with respect to the initial illuminance, the linearity correction is also set to be smaller than the illuminance set in the initial state, and a constant value of the reference exposure amount is set. This is output to the second linearity correction unit 8.

As in the first embodiment, the reference white original is read to obtain the output characteristic with respect to the incident light quantity. However, the same effect can be obtained even if a halftone original having a lower reflectance than that of the white original is used.

  As described above, according to the second embodiment, as an effect of the first linearity correction unit 6, the correction amount (κ) based on the installation position of each pixel is stored in the ROM in advance, and this is corrected to correct the sensor chip 1. The first linearity correction unit 6 corrects variations in input / output characteristics depending on the position of the light receiving unit, and sets the linearity at the time when the illuminance of the light source 11 is reduced. Therefore, there is an advantage that deterioration in image quality due to aging can be reduced. Further, since the correction using the black correction data is performed by the second linearity correction unit 8, the correction effect due to the position environment of the light receiving unit of the sensor chip 1 can be maximized.

  In the first and second embodiments, since the first linearity correction unit 6 and the black correction unit 5 are configured using the changeover switch 9, the correction is performed in consideration of the halftone level in addition to the correction based on the reference level. As a result, not only deterioration of the image quality due to changes with time but also the improvement of the halftone image quality can be achieved.

1 is a block configuration diagram of an image reading apparatus according to Embodiment 1 of the present invention. It is explanatory drawing which shows the relationship between the light-receiving part incident light quantity of the image reading apparatus by Embodiment 1 of this invention, and a sensor output. It is a figure explaining the relationship between the document density | concentration of the image reading apparatus by Embodiment 1 of this invention, and a sensor output. 1 is a cross-sectional configuration diagram of an image reading apparatus according to Embodiment 1 of the present invention. It is a figure explaining the relationship between the document density of the image reading apparatus by Embodiment 1 of this invention, and exposure amount. 1 is a plan view of a sensor chip of an image reading apparatus according to Embodiment 1 of the present invention. It is a figure explaining the corrected amount with respect to each pixel of the image reading apparatus by Embodiment 1 of this invention. It is a figure explaining the duty control of the light source by the light source control part of the image reading apparatus by Embodiment 1 of this invention. It is a figure explaining the exposure amount and sensor output of the image reading apparatus by Embodiment 1 of this invention. It is a figure explaining the relationship between the document density at the time of the light quantity change of the image reading apparatus by Embodiment 2 of this invention, and incident light quantity. It is a figure explaining the relationship between the document density and output of the image reading apparatus by Embodiment 2 of this invention. It is a figure explaining the relationship between the exposure amount and linearity output of the image reading apparatus by Embodiment 2 of this invention.

Explanation of symbols

1. ・ Sensor chip (sensor) 2. ・ Gain offset adjuster (analog)
3 ・ ・ Analog ・ Digital conversion part 4 ・ ・ Gain offset adjustment circuit (digital)
5 .. Black correction unit 6. First linearity correction unit 7. White correction unit 8. Second linearity correction unit 9. Changeover switch (switching means)
10..Lens array (lens body) 11..Light source
12 .... Light source controller (lighting control circuit) 13 .... CPU
20 .. Light guide 21 .. Sensor board 22 .. Board
23..Signal processing IC (ASIC)
24..Case

Claims (6)

A light source for illuminating the original, a lens for converging light reflected from the original, a plurality of pixels on which a plurality of pixels for receiving the light converged by the lens are formed, and the sensor chip An analog-to-digital converter that performs analog-to-digital conversion on the converted analog signal, and a black that generates and outputs an output data in the dark of the sensor chip for the photoelectric conversion output digitally converted by the analog-to-digital converter The difference between the correction unit, the data corrected by the black correction unit, and the pixel data collected in advance by changing the exposure amount stepwise with respect to the reference exposure amount and stored in the storage element over each pixel A first linearity correction unit that corrects the linearity of the sensor chip, and each sensor chip pixel output from the first linearity correction unit and irradiated by the light source. An image reading apparatus and a white correction unit that corrects the generated equalized output data when. A light source for illuminating the original, a lens for converging light reflected from the original, a plurality of pixels on which a plurality of pixels for receiving the light converged by the lens are formed, and the sensor chip Analog-to-digital converter that converts the converted analog signal into analog-to-digital, and photoelectric conversion output digitally converted by this analog-to-digital converter, sampled by changing the exposure amount stepwise with respect to the reference exposure amount in advance A first linearity correction unit that corrects the linearity of the pixel data stored in the storage element over each pixel, and output from the first linearity correction unit to generate output data in the dark of the sensor chip to be uniform A black correction unit that corrects the correction, and a white correction unit that generates and equalizes and corrects output data at the time of each pixel of the sensor chip irradiated by the light source. Image reading apparatus provided with. A light source for illuminating the original, a lens for converging light reflected from the original, a plurality of pixels on which a plurality of pixels for receiving the light converged by the lens are formed, and the sensor chip Analog-to-digital converter that converts the converted analog signal into analog-to-digital, and photoelectric conversion output digitally converted by this analog-to-digital converter, sampled by changing the exposure amount stepwise with respect to the reference exposure amount in advance A first linearity correction unit that corrects linearity of pixel data stored in a storage element over each pixel, a black correction unit that generates and uniformizes correction of dark output data of the sensor chip, and the light source. A white correction unit for generating and uniforming correction of light output data for each pixel of the irradiated sensor chip, the first linearity correction unit, and the black correction And the white correction unit, which is installed in conjunction with each input unit of the white correction unit and digitally converted by one opening / closing operation from the black correction unit via the first linearity correction unit And a switching unit that inputs the photoelectric conversion output digitally converted by the other opening / closing operation from the first linearity correction unit to the white correction unit via the black correction unit. . A light source for illuminating the original, a lens for converging light reflected from the original, a plurality of pixels on which a plurality of pixels for receiving the light converged by the lens are formed, and the sensor chip An analog-to-digital converter that performs analog-to-digital conversion on the converted analog signal, and a black that generates and outputs an output data in the dark of the sensor chip for the photoelectric conversion output digitally converted by the analog-to-digital converter The difference between the correction unit, the data corrected by the black correction unit, and the pixel data collected in advance by changing the exposure amount stepwise with respect to the reference exposure amount and stored in the storage element over each pixel A first linearity correction unit that corrects the linearity of the sensor chip, and each sensor chip pixel output from the first linearity correction unit and irradiated by the light source. A white correction unit that generates output data at the same time and performs uniform correction, and the storage element has different correction coefficients for pixels around the edge of the sensor chip and pixels other than the edge around the sensor chip in advance. An image reading apparatus characterized in that the correction coefficient is added to the pixel data of each pixel to perform arithmetic processing. A light source for illuminating the original, a lens for converging light reflected from the original, a plurality of pixels on which a plurality of pixels for receiving the light converged by the lens are formed, and the sensor chip Analog-to-digital converter that converts the converted analog signal into analog-to-digital, and photoelectric conversion output digitally converted by this analog-to-digital converter, sampled by changing the exposure amount stepwise with respect to the reference exposure amount in advance A first linearity correction unit that corrects the linearity of the pixel data stored in the storage element over each pixel, and output from the first linearity correction unit to generate output data in the dark of the sensor chip to be uniform A black correction unit that corrects the correction, and a white correction unit that generates and equalizes and corrects output data at the time of each pixel of the sensor chip irradiated by the light source The pixel around the end of the sensor chip and the pixel other than the periphery of the end of the sensor chip have different correction coefficients in advance, and this correction coefficient is added to the pixel data of each pixel and processed. A characteristic image reading apparatus. A light source for illuminating the original, a lens for converging light reflected from the original, a plurality of pixels on which a plurality of pixels for receiving the light converged by the lens are formed, and the sensor chip Analog-to-digital converter that converts the converted analog signal into analog-to-digital, and photoelectric conversion output digitally converted by this analog-to-digital converter, sampled by changing the exposure amount stepwise with respect to the reference exposure amount in advance A first linearity correction unit that corrects linearity of pixel data stored in a storage element over each pixel, a black correction unit that generates and uniformizes correction of dark output data of the sensor chip, and the light source. A white correction unit for generating and uniforming correction of light output data for each pixel of the irradiated sensor chip, the first linearity correction unit, and the black correction And the white correction unit, which is installed in conjunction with each input unit of the white correction unit and digitally converted by one opening / closing operation from the black correction unit via the first linearity correction unit Switching means for inputting the photoelectric conversion output digitally converted by the other opening / closing operation from the first linearity correction unit to the white correction unit via the black correction unit, and the sensor chip An image reading characterized in that a pixel around the edge of the pixel and a pixel outside the edge of the sensor chip have different correction coefficients in advance, and the correction coefficient is added to the pixel data of each pixel for calculation processing. apparatus.

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