JP2000101838A - Image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To apply an optimum gamma correction to gamma characteristics of a photoelectric conversion section by selecting a gamma correction table corresponding to a model of its own reader among model dependent gamma correction table group as a gamma correction table corresponding to each device. SOLUTION: A gamma correction table group is used by a plurality of devices in common and it is not required to change the table group for each device. In the meantime, table selection information is a head address of an optimum gamma correction table to the correction of the gamma characteristic as a result of confirming the gamma characteristic of a photoelectric conversion section 2 mounted on the image reader 1. Since the table selection information differs for each device, the information is stored not in a ROM 8 but in a backed-up RAM 9. While the device configuration relating to gamma correction is made in common independently of the gamma characteristic of the mounted photoelectric conversion section 2, the optimum gamma correction to the gamma characteristic of the photoelectric conversion section 2 of the model of its own reader is realized to obtain an image with high image quality.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus, and more particularly to an image reading apparatus for performing gamma correction.

[0002]

2. Description of the Related Art In a device including an image reading device as a configuration such as a scanner device and a facsimile device, a contact image sensor is often used as a photoelectric conversion element in a photoelectric conversion unit. The individual variation of the light receiving sensitivity characteristic is large, and the output characteristic of the read image varies. Even in a CCD image sensor, a similar variation occurs in output characteristics even though it is not as great as in a contact image sensor.

FIG. 4 shows an example of variations in light receiving sensitivity characteristics of different sensors A and B. The original characteristic A shows the relationship between the amount of light received by the sensor A and the output voltage level. The original characteristic B indicates a similar relationship in the sensor B. When shading correction is performed on image data obtained by A / D converting voltage signals obtained from the sensors A and B having the respective characteristics of the original characteristics A and B shown in FIG. 4, the amount of light received is proportional to the reflectance of the document. The relationship with the image data after shading correction, that is, the gamma characteristics are as shown in gamma characteristics A and B in FIG.
Although the signal level is normalized, the gamma characteristic A becomes an upwardly convex characteristic and the gamma characteristic B is compared with the ideal characteristic in which the amount of received light and the data after shading correction are in a proportional relationship.
Has downwardly convex characteristics.

[0004]

As a result, the difference in gamma characteristics becomes large especially near the intermediate density. Such a difference in gamma characteristics is large between sensors of the same type, and is even greater between sensors of different types. Therefore, with a single gamma correction characteristic, there is a problem that it is not possible to satisfactorily correct a gamma characteristic that differs for each sensor mounted on the photoelectric conversion unit of each device.

The present invention has been made in view of such circumstances, and has as its object to provide an image reading apparatus capable of performing gamma correction optimal for the gamma characteristics of a photoelectric conversion unit.

[0006]

According to a first aspect of the present invention, there is provided an image reading apparatus comprising the steps of: A / D converting an image signal obtained by reading an image by a photoelectric conversion unit; Image reading device that gamma-corrects and outputs the image data that has been subjected to shading correction with reference to a gamma correction table that stores gamma correction values corresponding to each possible value of the image data and outputs the image data Gamma correction means, a gamma correction table group for each model composed of gamma correction tables for each of a plurality of models, and a gamma correction table corresponding to the model to which the own device belongs from the gamma correction table group for each model. Information storing means for preliminarily storing information for performing the selection, and storing the selection information in the model-specific gamma correction table group. Characterized by comprising a setting means for setting a gamma correction table which is specified by the information stored in the unit as a gamma correction table to be referred to said gamma correction means.

According to a second aspect of the present invention, there is provided an image reading apparatus for subjecting an image signal obtained by reading an image by a photoelectric conversion unit to A / D conversion and shading correction, and performing gamma correction on the obtained image data for output. A gamma correction unit that performs gamma correction on the image data after shading correction with reference to a gamma correction table that stores gamma correction values corresponding to respective values that the image data can take, and a plurality of manufacturing lots. Lot-specific gamma correction table group composed of the gamma correction tables of the above, and information for selecting a gamma correction table corresponding to the manufacturing lot to which the photoelectric conversion unit of the own device belongs out of the lot-specific gamma correction table group. Selection information storage means stored in advance, and the selection information storage means of the lot-specific gamma correction table group Characterized by comprising a setting means for setting a gamma correction table that is identified as a gamma correction table to be referred to said gamma correction means by the information stored in the.

According to a third aspect of the present invention, there is provided an image reading apparatus for subjecting an image signal obtained by reading an image by a photoelectric conversion unit to A / D conversion, performing shading correction, and performing gamma correction on the obtained image data for output. A gamma correction unit for performing gamma correction on image data after shading correction with reference to a gamma correction table storing gamma correction values corresponding to respective values of image data, and a plurality of gammas having different characteristics from each other. A gamma correction table group constituted by a correction table, and selection information storage means for storing in advance information for selecting a gamma correction table optimal for the gamma characteristic of the photoelectric conversion unit of the own device from the gamma correction table group Gamma correction specified by information stored in the selection information storage means of the gamma correction table group Characterized by comprising a setting means for setting as the gamma correction table gamma correction unit refers to Buru.

According to a fourth aspect of the present invention, there is provided an image reading apparatus for subjecting an image signal obtained by reading an image by a photoelectric conversion unit to A / D conversion, performing shading correction, and performing gamma correction on the obtained image data for output. A gamma correction unit for performing gamma correction on image data after shading correction with reference to a gamma correction table storing gamma correction values corresponding to respective values of image data, and a plurality of gammas having different characteristics from each other. A gamma correction table group composed of a correction table and an image signal obtained by reading a gray chart having a predetermined density by the photoelectric conversion unit are A / D-converted and subjected to shading correction according to the level of image data obtained. A gamma correction table is selected from the gamma correction table group and the gamma correction table referred to by the gamma correction means is selected. Characterized by comprising a setting means for setting as Le.

According to a fifth aspect of the present invention, there is provided an image reading apparatus for subjecting an image signal obtained by reading an image by a photoelectric conversion unit to A / D conversion, performing shading correction, and performing gamma correction on the obtained image data for output. A gamma correction unit for performing gamma correction on image data after shading correction with reference to a gamma correction table storing gamma correction values corresponding to respective values of image data, and a plurality of gammas having different characteristics from each other. A gamma correction table group including a correction table, mode setting means for setting a reading mode to a normal document reading mode or a gamma correction setting mode, and a case where the gamma correction setting mode is set by the mode setting means. A gray chart having a predetermined density is read by the photoelectric conversion unit in response to the read start instruction input. A gamma correction table that is selected from the gamma correction table group according to the level of image data obtained by A / D converting and shading correction of the image signal obtained by the gamma correction unit and referred to by the gamma correction unit Setting means for setting as

According to a sixth aspect of the present invention, there is provided an image reading apparatus for subjecting an image signal obtained by reading an image by a photoelectric conversion unit to A / D conversion, performing shading correction, and performing gamma correction on the obtained image data for output. A plurality of gamma correction units each capable of performing gamma correction calculation with characteristics corresponding to each of the plurality of models, and a gamma correction unit corresponding to the model to which the device belongs among the plurality of gamma correction units. Information stored in advance in the selection information storage means, and gamma correction means specified by the information stored in the selection information storage means among the plurality of gamma correction means, for each value of the image data after shading correction. Setting means for calculating the corresponding gamma correction value and setting as gamma correction means for outputting gamma-corrected image data To.

According to another aspect of the present invention, there is provided an image reading apparatus for subjecting an image signal obtained by reading an image by a photoelectric conversion unit to A / D conversion and shading correction, and performing gamma correction on the obtained image data for output. A plurality of gamma correction units each capable of performing gamma correction calculation of characteristics corresponding to each of the plurality of production lots, and a plurality of gamma correction units corresponding to a production lot to which the photoelectric conversion unit of the own device belongs. A selection information storage unit storing information for selecting a gamma correction unit to be performed in advance, and a gamma correction unit specified by the information stored in the selection information storage unit among the plurality of gamma correction units. Calculate the gamma correction value corresponding to each value of the subsequent image data and set it as gamma correction means that outputs gamma-corrected image data. Characterized in that a setting means.

According to another aspect of the present invention, there is provided an image reading apparatus for subjecting an image signal obtained by reading an image by a photoelectric conversion unit to A / D conversion and shading correction, and performing gamma correction on the obtained image data for output. A plurality of gamma correction units each capable of performing a gamma correction operation having different characteristics from each other, and a gamma correction unit optimal for a gamma characteristic of the photoelectric conversion unit of the own device among the plurality of gamma correction units. Selection information storage means in which information is stored in advance,
The gamma correction unit specified by the information stored in the selection information storage unit of the plurality of gamma correction units is gamma corrected by calculating a gamma correction value corresponding to each value of the image data after shading correction. Setting means for setting as gamma correction means for outputting image data.

According to another aspect of the present invention, there is provided an image reading apparatus for A / D converting an image signal obtained by reading an image by a photoelectric conversion unit and performing gamma correction on image data obtained by shading correction and outputting the image data. A plurality of gamma correction means each capable of performing gamma correction calculations having different characteristics from each other, and an image signal obtained by reading a gray chart having a predetermined density by the photoelectric conversion unit, performing A / D conversion and performing shading correction. Gamma correction means corresponding to the level of the obtained image data is selected from the plurality of gamma correction means, a gamma correction value corresponding to each value of the image data after shading correction is calculated, and gamma corrected image data is output. Setting means for setting the gamma correction means.

According to another aspect of the present invention, there is provided an image reading apparatus for subjecting an image signal obtained by reading an image by a photoelectric conversion unit to A / D conversion, performing shading correction, and performing gamma correction on the obtained image data for output. A plurality of gamma correction units each capable of performing gamma correction calculations having different characteristics from each other; a mode setting unit for setting a reading mode to a normal document reading mode or a gamma correction setting mode;
An image signal obtained by reading a gray chart of a predetermined density by the photoelectric conversion unit in response to a reading start instruction input when the gamma correction setting mode is set by the mode setting means is subjected to A / D conversion. Gamma correction means corresponding to the level of image data obtained by shading correction is selected from the plurality of gamma correction means, and a gamma correction value corresponding to each value of the image data after shading correction is calculated. Setting means for setting as gamma correction means for outputting the corrected image data.

[0016]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
An embodiment of the present invention will be described in detail.

FIG. 1 shows a block configuration of an image reading apparatus 1 according to the first to fifth embodiments of the present invention.

In FIG. 1, an image reading apparatus 1 includes a photoelectric conversion unit 2, an A / D conversion unit 3, a shading correction unit 4, a gamma correction unit 5, an output unit 6, a control unit 7, a ROM 8, and a RAM.
9, an operation unit 10, and a system bus 11.

The photoelectric conversion unit 2 includes a CCD image sensor,
It is composed of a CIS (contact) image sensor or the like, and generates an analog image signal according to the amount of light received from the reading surface. The A / D converter 3 converts an analog image signal input from the photoelectric converter 2 into multi-valued image data which is a digital signal. Shading correction unit 4
Is for normalizing multi-valued image data by correcting distortion due to irradiation light between pixels of a read line and a difference in light receiving element sensitivity. The gamma correction unit 5 performs gamma correction on the multi-valued image data after the shading correction, and converts a characteristic of the output image data with respect to the document reflectance into a desired output characteristic.

The output unit 6 varies depending on the device to which the image reading device 1 is applied. If the device to which the image reading device 1 is applied is an image scanner device, the output unit 6 is an external interface to a PC or the like, and may be a digital copying machine or a facsimile machine. For example, it is an internal interface to the image processing unit, and outputs multi-valued image data after gamma correction. The control unit 7 is a microcomputer that controls the entire device. ROM8
Is a read-only memory that is read by the control unit 7 and stores various control programs executed by the control unit 7, various data tables, and the like. The RAM 9 is a random access memory serving as a work area of the control unit 7.
The contents of the RAM 9 are retained by a backup circuit (not shown) even when the apparatus is powered off. Operation unit 10
Is provided with various keys for accepting an operation input by the user. The system bus 11 is a signal line through which the above components exchange data. Note that the analog image signal from the photoelectric conversion unit 2 is directly input to the A /
It is input to the D conversion unit 3.

In the first to fourth embodiments, as shown in FIG. 2, a storage area for storing the gamma correction table 9a is secured in the RAM 9.

FIG. 3 shows an image data processing flow in the first to fourth embodiments.

In FIG. 1, the photoelectric conversion unit 2 outputs a voltage corresponding to the amount of received light as an analog image signal. In that case, the relationship between the amount of received light and the output voltage should ideally be proportional, but in practice, the amount of received light and the output voltage are not proportional,
It becomes distorted characteristics. The light receiving sensitivity characteristics of the photoelectric conversion unit 2 include an original characteristic A corresponding to the individual A and an individual characteristic B shown in FIG.
Differs for each individual, as shown in the original characteristic B corresponding to. The original characteristic A includes an upwardly convex gamma characteristic, and the overall light receiving sensitivity is relatively high. The original characteristic B includes a downwardly convex gamma characteristic and has relatively low overall light receiving sensitivity.

The analog image signal from the photoelectric conversion unit 2 is
The A / D converter 3 performs A / D conversion at a predetermined bit resolution.
Although converted and output as digital image data, in the present embodiment, it is assumed that the A / D conversion unit 3 performs A / D conversion with a resolution of 256 gradations from 0 to 255 in 8 bits.

Even after the A / D conversion, the original characteristic A shown in FIG.
Although the variation in the characteristics of B and B is not improved, the shading correction is performed by the shading correction unit 4, and as shown in the gamma characteristics A and B in FIG. Amended,
Only the variation of the gamma characteristic remains.

The image data subjected to shading correction by the shading correction unit 4 is gamma-corrected by the gamma correction unit 5. The gamma correction unit 5 performs gamma correction on input image data by table conversion with reference to the gamma correction table 9a and outputs the gamma correction to the output unit 6. Therefore, the gamma correction table 9a has a range of possible values of the input image data. That is, it is necessary to store gamma correction values corresponding to values from 0 to 255.

For example, in order to correct the upwardly projecting gamma characteristic A in FIG. 5 to make it an ideal characteristic, a table corresponding to the downwardly convex gamma correction characteristic A in FIG. Must be stored as the gamma correction table 9a. However, in that case, the gamma characteristic B cannot be corrected, and the characteristics are rather deteriorated. Therefore, in order to correct the gamma characteristic B, a table corresponding to the gamma correction characteristic B is stored as the gamma correction table 9a. It is necessary to keep.

However, for each device, the gamma characteristic of the mounted photoelectric conversion unit 2 is checked, and a table corresponding to the optimum gamma correction characteristic is created and stored as the gamma correction table 9a. It takes time and effort.

Accordingly, in the first embodiment, as shown in FIG. 7, a gamma correction table group 8b for each model and information for selecting one table from the gamma correction table group 8b for each model. , The head address of the gamma correction table to be selected is set as table selection information 8a.
It is stored in the ROM 8.

The model-specific gamma correction table group 8b is composed of gamma correction tables corresponding to a plurality of models manufactured as the image reading apparatus 1 and having different light-receiving sensitivity characteristics of the photoelectric conversion units 2 provided respectively. In the gamma correction table corresponding to each model, an optimum value is set for correcting the gamma characteristic of the photoelectric conversion unit 2 provided in each model.

That is, the gamma correction table group 8b for each model
Is shared by a plurality of models, and does not need to be changed for each model. On the other hand, the table selection information 8a stores the head address of the gamma correction table corresponding to the model to which the photoelectric conversion unit 2 of a specific type belongs by being attached to the image reading apparatus 1. The contents of the table selection information 8a are the same if they are the same model.

When the power of the apparatus is turned on, the control section 7 reads the table selection information 8a from the head address obtained by reading the table selection information 8a.
The gamma correction table for 6 bytes is read from the gamma correction table 8b for each model and loaded into the gamma correction table 9a. This makes it possible to obtain a good image by performing gamma correction optimal for the gamma characteristic of the photoelectric conversion unit 2 of the model to which the own device belongs while at least sharing the device configuration related to gamma correction regardless of the model.

The table selection information 8a is stored in the RAM 8
Alternatively, the table specified by the table selection information 8a in the gamma correction table group 8b for each model is loaded into the gamma correction table 9a, and the gamma correction unit 5 indirectly refers to the table. rather than,
The gamma correction unit 5 may be provided with the table selection information 8a to directly refer to the corresponding table.

Next, in the second embodiment, as shown in FIG. 8, a lot-specific gamma correction table group 8c and information for selecting one table from the model-specific gamma correction table group 8c. Specifically, the head address of the gamma correction table to be selected is set as table selection information 8a,
It is stored in the ROM 8.

The lot-specific gamma correction table group 8c is composed of gamma correction tables corresponding to the respective production lots of the photoelectric conversion unit 2 provided in the image reading apparatus 1. The gamma correction tables corresponding to the respective production lots are as follows. The optimum value is set for the correction of the gamma characteristic of the photoelectric conversion unit 2 of each production lot. This is because, generally, the photoelectric conversion units 2 are managed so that the light receiving sensitivity characteristics are different between those of different manufacturing lots, but the light receiving sensitivity characteristics are substantially the same in the manufacturing process between the same manufacturing lots. Because it is.

That is, gamma correction table group 8 for each lot
c is shared by a plurality of devices and does not need to be changed for each device. On the other hand, the table selection information 8a stores the head address of the gamma correction table corresponding to the production lot of the photoelectric conversion unit 2 mounted on the image reading device 1. The contents of the table selection information 8a are the same as long as the devices to which the photoelectric conversion units 2 of the same lot are mounted.

When the power of the apparatus is turned on, the control section 7 reads the table selection information 8a from the head address obtained by reading the table selection information 8a.
The 6-byte gamma correction table is read from the lot-specific gamma correction table 8c and loaded into the gamma correction table 9a. Thereby, while at least the device configuration relating to the gamma correction is made common regardless of the manufacturing lot of the photoelectric conversion unit 2 to be mounted, the photoelectric conversion unit 2 of the model to which the own device belongs is provided.
Gamma correction optimal for the gamma characteristic of the image and a good image can be obtained.

The table selection information 8a is stored in the RAM 8
The table specified by the table selection information 8a in the lot-specific gamma correction table group 8c is loaded into the gamma correction table 9a, and the gamma correction unit 5 indirectly refers to the table. Instead of giving the table selection information 8a to the gamma correction unit 5,
The corresponding table may be directly referred to.

Next, in the third embodiment, the gamma correction table group 8d is stored in the ROM 8 as shown in FIG. In addition, as shown in FIG.
The information for selecting one table from the gamma correction table group 8d, specifically, the start address of the gamma correction table to be selected is set as the table selection information 9
b is stored in the RAM 9.

The gamma correction table group 8d is constituted by gamma correction tables having slightly different characteristics, such as a relatively large convex upward, a slight upward convex, a slight downward convex, and a large downward convex.

That is, the gamma correction table group 8d is shared by a plurality of devices, and does not need to be changed for each device. On the other hand, as a result of checking the gamma characteristic of the photoelectric conversion unit 2 mounted on the image reading apparatus 1, the table selection information 9b stores the head address of the gamma correction table that is optimal for correcting the gamma characteristic. The table selection information 9
b is stored in the backed-up RAM 9 instead of the ROM 8 because it differs from device to device.

The control unit 7 reads the table selection information 9b from the head address obtained by reading the
The gamma correction table for 6 bytes is read from the gamma correction table 8d and loaded into the gamma correction table 9a. Thereby, while at least the device configuration relating to the gamma correction is made common regardless of the gamma characteristics of the photoelectric conversion unit 2 to be mounted, the gamma correction optimal for the gamma characteristics of the photoelectric conversion unit 2 of the model to which the own device belongs is performed. It is possible to obtain a perfect image.

The table specified by the table selection information 9b in the gamma correction table group 8d is loaded into the gamma correction table 9a, and is not referred to the gamma correction unit 5 indirectly. The selection information 8a may be provided to directly refer to the corresponding table.

Next, in the fourth embodiment, the gamma correction tables A and B are stored in the ROM 8 as shown in FIG. These correction tables correspond to the gamma correction table group 8d in the third embodiment.

FIG. 12A shows a specific content of the gamma correction table A, and FIG. 12B shows a specific content example of the gamma correction table B. These tables correspond to the gamma correction characteristics A and B shown in FIG.

In the fourth embodiment, as shown in FIG. 13, the operation unit 10 is provided with a gamma correction setting mode selection / cancellation key 10a. When the key 10a is pressed, the mode is switched to the normal document reading mode or the gamma correction setting mode, and the setting state of the mode is stored in the RAM 9 as the value of a predetermined flag.

Then, the reading process shown in FIG. 14 is performed. In the figure, when the reading start is instructed by pressing a predetermined key (not shown) for instructing the reading start of the operation display unit 10, the control unit 7 determines whether or not the current mode is the gamma correction setting mode (determination). 101) In the normal document reading mode (No in decision 101), the set document is read by the photoelectric conversion unit 2, A / D converted, subjected to shading correction, and output after gamma correction. A reading process is performed (process 102).

On the other hand, if the mode is the gamma correction setting mode (Yes in decision 101), the set gray chart is read by the photoelectric conversion unit 2 (process 103). The gray chart set in that case has a reflectance of about 50%
When the photoelectric conversion unit 2 has no distortion of the gamma characteristic, the level after the shading correction is a substantially intermediate value in the density range of 0 to 255. However, in fact, FIG.
As shown in (1), depending on the variation of the light receiving sensitivity characteristics among the individual photoelectric conversion units 2, the characteristics may be upwardly convex such as the gamma characteristic A, or may be downwardly convex such as the gamma characteristic B. Then, the maximum received light amount (2
The data after shading correction corresponding to half (128) of the received light amount of 55) is larger than 128 in the gamma characteristic A, and smaller than 128 in the gamma characteristic B.

Therefore, it is determined whether or not the data after shading correction outputted from the shading correction unit 4 obtained by reading the gray chart in the processing 103 is 128 or more (decision 104). (Yes in decision 104), that is, if the gamma characteristic of the photoelectric conversion unit 2 is an upwardly convex characteristic, the gamma correction table A, which is a downwardly convex characteristic that cancels it, is replaced with a gamma correction table. 9a is loaded into the storage area (process 10).
5). If it is less than 128 (N in decision 104
o) That is, when the gamma characteristic of the photoelectric conversion unit 2 is a downwardly convex characteristic, the gamma correction table B, which is an upwardly convex characteristic that cancels the gamma characteristic, is loaded into the storage area of the gamma correction table 9a. (Step 106).

Thus, the gamma correction in the gamma correction unit 5 at the time of the original reading processing in the subsequent processing 102 is as follows.
The operation is performed with characteristics optimal for the gamma characteristic of the photoelectric conversion unit 2, and a good image can be obtained.

In the fourth embodiment, only two gamma correction tables A and B are stored in the ROM 8 as tables that can be loaded into the storage area of the gamma correction table 9a, but three or more tables having different characteristics are stored. The accuracy of the gamma correction may be increased by storing the data after shading correction in the determination in step 104 into three or more stages so that an optimal table can be loaded.

Next, a fifth embodiment will be described. The fifth embodiment is a modification of the fourth embodiment. As shown in FIG. 15, the gamma correction unit 5 differs from the first to fourth embodiments shown in FIG. RA as shown
Referring to the gamma correction coefficient table 9c stored in M16, gamma correction is performed not by table conversion but by a polygonal line approximation operation.

Therefore, gamma correction coefficient tables A and B are stored in the ROM 8 as shown in FIG. FIG. 18 shows the contents of the coefficient table stored as the gamma correction coefficient table A or B. In FIG.
0, T1 and T2 are values serving as delimiters for dividing the range of 0 to 255 that can be taken by the data after shading correction into four. The coefficients T0, T1 and T2 are between 0 and 25
The range of 5 may be set to a value that divides it at equal intervals, or a range in which the change in the gamma correction characteristic is large may be set to be narrow, and a small range may be set to be divided widely. In addition, in order to increase the accuracy of the polygonal line approximation, it may be divided into five or more divisions.

The coefficients a0 and b0 are values for determining a straight line (a0x + b0) that approximates the gamma correction characteristic within the range of 0 ≦ x <T0, where x is the data after shading correction. Similarly, the coefficients a1 and b1 are given by T0 ≦ x <T
This is a value for determining the straight line (a1.x + b1) in the range of 1. Similarly, the coefficients a2 and b2 are T1 ≦ x <T2
Is a value for determining the straight line (a2.x + b2) in the range of. Similarly, the coefficients a3 and b3 are T2 ≦ x <256
Is a value for determining the straight line (a3.x + b3) in the range of.

The gamma correction coefficient table A is obtained by approximating the gamma correction characteristic A of FIG. 6 with a polygonal line, and the gamma correction coefficient table B is obtained by approximating the gamma correction characteristic B of FIG. 6 with a polygonal line.

In the fifth embodiment, as shown in FIG. 13, the operation unit 10 is provided with a gamma correction setting mode selection / cancellation key 10a, as in the fourth embodiment. When the key 10a is pressed, the mode is switched to the normal document reading mode or the gamma correction setting mode, and the setting state of the mode is stored in the RAM 9 as the value of a predetermined flag.

Then, the reading process shown in FIG. 19 is performed. In the figure, when the reading start is instructed by pressing a predetermined key (not shown) for instructing the reading start of the operation display unit 10, the control unit 7 determines whether or not the current mode is the gamma correction setting mode (determination). 201), in a normal document reading mode (No in decision 201), a normal document which is read by the photoelectric conversion unit 2, A / D converted by the photoelectric conversion unit 2, subjected to shading correction, and output after gamma correction. A reading process is performed (process 202).

On the other hand, if the mode is the gamma correction setting mode (Yes in decision 201), the set gray chart is read by the photoelectric conversion unit 2 (process 203). The gray chart set in that case has a reflectance of about 50%, and the level after shading correction is
If there is no distortion of the gamma characteristic in the photoelectric conversion unit 2, the density becomes a substantially middle value in the density range of 0 to 255. However, in practice, as shown in FIG. 5, due to the variation of the light receiving sensitivity characteristics among the individual photoelectric conversion units 2, the characteristics become convex upward like the gamma characteristic A or downward like the gamma characteristic B. The shading-corrected data corresponding to a half (128) of the maximum amount of received light (255) corresponding to a reflectance of 50% due to a convex characteristic or the like is 12% in the gamma characteristic A.
It is larger than 8 and smaller than 128 in the gamma characteristic B.

Therefore, it is determined whether or not the data after shading correction output from the shading correction unit 4 obtained by reading the gray chart in the process 203 is 128 or more (decision 204). (Yes in determination 204), that is, if the gamma characteristic of the photoelectric conversion unit 2 is an upwardly convex characteristic, the gamma correction coefficient table A corresponding to the downwardly convex characteristic that cancels out the gamma characteristic.
Is loaded into the storage area of the gamma correction coefficient table 9c (process 205). If it is less than 128 (decision 2
04, that is, when the gamma characteristic of the photoelectric conversion unit 2 is a downwardly convex characteristic, the gamma correction coefficient table B corresponding to the upwardly convex characteristic that cancels out the gamma characteristic is stored in the gamma correction table 9a. Load to storage area (Process 20
6).

As a result, the gamma correction operation in the gamma correction unit 5 at the time of the original reading process in the subsequent process 202 is performed with characteristics optimal for the gamma characteristics of the photoelectric conversion unit 2, and a good image can be obtained.

FIG. 20 shows a gamma correction calculation processing procedure of the gamma correction unit 5 in the fifth embodiment.

In the figure, a gamma correction coefficient table 9
gamma correction unit 5 that performs gamma correction calculation while referring to c
When the data x after shading correction is input from the shading correction unit 4, if the data x is equal to or more than 0 and less than T0 (Yes in the determination 301), a0 · x +
b0 is output to the output unit 6 (process 302), and the data x becomes 0
If not less than T0 (N in decision 301
o), if the data x is equal to or more than T0 and less than T1 (Yes in decision 303), a1 · x + b1 is output to the output unit 6 (process 304), and if the data x is not T0 and less than T1 ( No in determination 303), data x
Is greater than or equal to T1 and less than T2 (Ye in decision 305).
s), and outputs a2 · x + b2 to the output unit 6 (process 30).
6) Further, when the data x is not equal to or more than T1 and less than T2 (No in the judgment 305), that is, when the data x is equal to or more than T2 and less than 256, a3 · x + b3 is output to the output unit 6.
(Step 307).

As a result, gamma correction calculation by broken line approximation can be performed. It is needless to say that the gamma correction calculation is not limited to the polygonal line approximation, and that other calculation methods such as curve approximation can be applied.

As described above, in the fifth embodiment, the gamma correction coefficient table to be referred to by the gamma correction section 5 is switched from a plurality of coefficient tables by software, so that the gamma correction section for performing the gamma correction calculation with different characteristics is performed. , And one of the plurality of gamma correction units.
One is a gamma correction unit 5 that gamma-corrects data from a shading correction unit and outputs the data to an output unit 6. However, a plurality of gamma correction units that perform gamma correction calculations with different hardware characteristics are provided. Alternatively, one of the plurality of gamma correction units may be configured as the gamma correction unit 5 that performs gamma correction on data from the shading correction unit and outputs the data to the output unit 6.

This eliminates the need for a large-capacity memory for storing a plurality of gamma correction tables as in the fourth embodiment, and provides the same effects as in the fourth embodiment.

The same modification as the modification from the fourth embodiment to the fifth embodiment can be applied to each of the first to third embodiments.

That is, in the first embodiment, instead of the model-specific gamma correction table group 8b shown in FIG. 7, a model-specific gamma correction coefficient table group is stored in the ROM 8, and the group corresponding to the model to which the own apparatus belongs is stored. If the thigh start address is stored as the table selection information 8a and loaded into the gamma correction coefficient table 9c, a large-capacity memory for storing a plurality of gamma correction tables is not required, and the first embodiment is performed. The same effect as in the embodiment can be obtained. In the second embodiment, a lot-specific gamma correction coefficient table group is stored in the ROM 8 instead of the lot-specific gamma correction table group 8c shown in FIG. By storing the head address of the thing corresponding to the manufacturing lot to which it belongs as table selection information 8a and loading it into the gamma correction coefficient table 9c, a large-capacity memory for storing a plurality of gamma correction tables becomes unnecessary. However, the same effect as in the second embodiment can be obtained. In the third embodiment, instead of the gamma correction table group 8d shown in FIG.
The gamma correction coefficient table group is stored in the ROM 8, and the top address of the one that is optimal for the gamma characteristic of the photoelectric conversion unit 2 provided in the own device is stored in the RAM as table selection information 9b as shown in FIG. By loading the data into the gamma correction coefficient table 9c, the same effect as in the third embodiment can be obtained while eliminating the need for a large-capacity memory for storing a plurality of gamma correction tables.

[0068]

According to the first aspect of the present invention, even if the photoelectric conversion units differ according to the product specifications of each model, the photoelectric conversion unit is optimal for correcting the gamma characteristics of the photoelectric conversion units provided in each model. A gamma correction table is provided for each model, and information for selecting a gamma correction table corresponding to the model to which the device belongs as a result of being equipped with a photoelectric conversion unit having a specific specification is provided. By storing the gamma correction table, a gamma correction table to be referred to by the gamma correction unit can be set to an optimum one for correcting the gamma characteristic of the photoelectric conversion unit provided in the apparatus. As a result, the gamma characteristic of the photoelectric conversion unit of the model to which the own device belongs can be realized while reducing the design man-hours by at least sharing the device configuration related to the gamma correction regardless of the model, and reducing the manufacturing cost due to the mass production effect. In this case, it is possible to obtain the effect that it is possible to perform the optimal gamma correction and obtain a good image.

According to the second aspect of the present invention, the photoelectric conversion portions have different light receiving sensitivity characteristics between different manufacturing lots, but the light receiving sensitivity characteristics of the photoelectric conversion portions of the same manufacturing lot are substantially different in the manufacturing process. In consideration of the fact that they are managed to be the same, a gamma correction table optimal for correcting the gamma characteristic of the photoelectric conversion unit belonging to each production lot is provided for each production lot. By storing information for selecting a gamma correction table corresponding to a manufacturing lot to which the equipped photoelectric conversion unit belongs, the gamma correction table to be referred to by the gamma correction unit can be used as a gamma correction table to be referred to by the photoelectric conversion unit. It is possible to set an optimum value for correcting the gamma characteristic of the conversion unit. This makes it possible to confirm the light-receiving sensitivity characteristics of each photoelectric conversion unit and individually create and store the optimum gamma correction tables for correcting the gamma characteristics of the photoelectric conversion units, without the troublesome work of storing each gamma correction table. By simply storing the created gamma correction table, it is possible to obtain the effect that it is possible to perform the gamma correction optimal for the gamma characteristic of the photoelectric conversion unit provided in the own device and obtain a good image.

According to the third aspect of the present invention, a plurality of gamma correction tables having different characteristics are provided, and the gamma characteristic of the photoelectric conversion unit provided in the own apparatus is checked in advance to optimize the gamma characteristic. By storing the information for selecting the gamma correction table, the gamma correction table to be referred to by the gamma correction means is set to the one most suitable for correcting the gamma characteristic of the photoelectric conversion unit provided in the own device. can do. This makes it possible for each device to operate without confirming the light receiving sensitivity characteristic of each photoelectric conversion unit and individually creating and storing a gamma correction table optimal for correcting the gamma characteristic of the photoelectric conversion unit. Similarly, only information for selecting the most suitable gamma correction of the photoelectric conversion unit actually installed in the own device from among a plurality of gamma correction tables having different characteristics similarly stored is stored in advance. An effect is obtained in which gamma correction optimal for the gamma characteristic of the photoelectric conversion unit provided in the device can be performed and a good image can be obtained.

According to the fourth aspect of the present invention, a plurality of gamma correction tables having different characteristics are provided, and a gray chart having a predetermined density, for example, a gray chart having an intermediate level of a density range which can be read by the photoelectric conversion unit. According to the level of image data obtained by A / D-converting and shading-correcting an image signal obtained by reading the image signal by the photoelectric conversion unit, whether the gamma characteristic of the photoelectric conversion unit is an upwardly convex characteristic. Or, whether the characteristic is convex downward or the degree of convex upward or downward can be estimated, and by selecting a gamma correction table according to that, as a gamma correction table to be referred to by the gamma correction means. In addition, it is possible to set an optimum value for correcting the gamma characteristic of the photoelectric conversion unit provided in the own device. This makes it possible to check the light receiving sensitivity characteristics of each photoelectric conversion unit and individually create and store a gamma correction table optimal for correcting the gamma characteristics of the photoelectric conversion units without troublesome work of storing the gray chart. By simply reading and measuring the level of the image data, it is possible to obtain an effect that it is possible to perform gamma correction optimal for the gamma characteristic of the photoelectric conversion unit provided in the own device and obtain a good image.

According to the fifth aspect of the present invention, when a gamma correction setting mode is set from a normal original reading mode in which an original image is read by the photoelectric conversion unit and image data is output, a reading start instruction input is performed. When there is, a gray chart of a predetermined density set to be readable in the photoelectric conversion unit, for example, a gray chart of a middle density range readable by the photoelectric conversion unit is obtained by reading by the photoelectric conversion unit. Depending on the level of image data obtained by A / D-converting the image signal and performing shading correction, whether the gamma characteristic of the photoelectric conversion unit is an upwardly convex characteristic or a downwardly convex characteristic, The degree of convexity upward or downward can be estimated, and a gamma correction table corresponding to the degree can be estimated. It can be set optimal for correction of the instrumented gamma characteristic of the photoelectric conversion unit. This makes it possible to check the light receiving sensitivity characteristics of each photoelectric conversion unit and individually create and store a gamma correction table optimal for correcting the gamma characteristics of the photoelectric conversion units without troublesome work of storing the gray chart. Just by measuring the level of image data obtained by reading in the same operation procedure as normal document reading, perform gamma correction optimal for the gamma characteristic of the photoelectric conversion unit installed in the device and obtain a good image The effect that becomes possible is obtained.

According to the sixth aspect of the present invention, even when the photoelectric conversion units differ depending on the product specifications of each model, the gamma correction optimal for the correction of the gamma characteristics of the photoelectric conversion units provided in each model. Means is provided for each model, and information for selecting a gamma correction means corresponding to the model to which the apparatus belongs as a result of being equipped with a photoelectric conversion unit of a specific specification is stored. The gamma correction means calculates the gamma correction value corresponding to each value of the image data after the shading correction, and outputs the gamma-corrected image data. The most suitable one can be set. As a result, the gamma characteristic of the photoelectric conversion unit of the model to which the own device belongs can be realized while reducing the design man-hours by at least sharing the device configuration related to the gamma correction regardless of the model, and reducing the manufacturing cost due to the mass production effect. In this case, it is possible to obtain the effect that it is possible to perform the optimal gamma correction and obtain a good image. Also, it is necessary to store a plurality of gamma correction tables by providing a plurality of gamma correction means for performing gamma correction by calculation, rather than storing a plurality of gamma correction tables for the gamma correction means for performing gamma correction by referring to the gamma correction table. This has the advantage that the memory capacity can be reduced and the cost of the device can be reduced.

According to the seventh aspect of the present invention, the photoelectric conversion units have different light receiving sensitivity characteristics between different manufacturing lots. In consideration of the fact that they are managed to be the same, gamma correction means optimal for correcting the gamma characteristic of the photoelectric conversion unit belonging to each production lot is provided for each production lot, and in the own device. By storing information for selecting a gamma correction unit corresponding to a manufacturing lot to which the equipped photoelectric conversion unit belongs, a gamma correction value corresponding to each value of image data after shading correction is calculated and the gamma correction value is calculated. As the gamma correction means for outputting the corrected image data, it is possible to set an optimal gamma correction means for correcting the gamma characteristic of the photoelectric conversion unit provided in the own device. This makes it possible to confirm the light-receiving sensitivity characteristics of each photoelectric conversion unit and to perform a gamma correction operation that is optimal for correcting the gamma characteristics of the photoelectric conversion units. By simply providing the gamma correction means for each lot, it is possible to obtain an effect that it is possible to perform gamma correction optimal for the gamma characteristic of the photoelectric conversion unit provided in the own device and obtain a good image.
Also, it is necessary to store a plurality of gamma correction tables by providing a plurality of gamma correction means for performing gamma correction by calculation, rather than storing a plurality of gamma correction tables for the gamma correction means for performing gamma correction by referring to the gamma correction table. This has the advantage that the memory capacity can be reduced and the cost of the device can be reduced.

According to the invention of claim 8, a plurality of gamma correction means capable of performing gamma correction operations having different characteristics are provided, and the gamma characteristic of the photoelectric conversion unit provided in the own device is checked in advance. The gamma correction value corresponding to each value of the image data after shading correction is calculated by storing information for selecting the most suitable gamma correction means for the correction, and the gamma corrected image data is output. As the gamma correction means, it is possible to set an optimal gamma correction means for correcting the gamma characteristic of the photoelectric conversion unit provided in the own device. This makes it possible to confirm the light receiving sensitivity characteristics of each photoelectric conversion unit and to set a gamma correction unit so as to perform a gamma correction operation optimal for correcting the gamma characteristics of the photoelectric conversion units without troublesome work. Information for selecting the most suitable one for the gamma correction of the photoelectric conversion unit actually installed in the own device among a plurality of gamma correction means similarly capable of performing gamma correction calculations with different characteristics of the device is stored in advance. By doing so, it is possible to obtain an effect that it is possible to perform gamma correction optimal for the gamma characteristic of the photoelectric conversion unit provided in the own device and obtain a good image. Also, it is necessary to store a plurality of gamma correction tables by providing a plurality of gamma correction means for performing gamma correction by calculation, rather than storing a plurality of gamma correction tables for the gamma correction means for performing gamma correction by referring to the gamma correction table. This has the advantage that the memory capacity can be reduced and the cost of the device can be reduced.

According to the ninth aspect of the present invention, a plurality of gamma correction means capable of performing gamma correction operations having different characteristics are provided, and a gray chart having a predetermined density, for example, the photoelectric conversion unit is readable. The gamma characteristic of the photoelectric conversion unit is increased according to the level of image data obtained by A / D converting an image signal obtained by reading an image having an intermediate density range by the photoelectric conversion unit and performing shading correction. The image data after shading correction can be estimated by determining whether the characteristics are convex or convex, or the degree of convexity upward or downward, and selecting a gamma correction unit according to the characteristics. The gamma correction means calculates the gamma correction value corresponding to each of the values and outputs gamma-corrected image data. It is possible to set the proper ones.
This makes it possible to check the light receiving sensitivity characteristics of each photoelectric conversion unit and to perform the gamma correction operation so as to perform the optimal gamma correction calculation for the correction of the gamma characteristics of the photoelectric conversion units. By simply reading the chart and measuring the level of the image data, it is possible to obtain an effect that it is possible to perform gamma correction optimal for the gamma characteristic of the photoelectric conversion unit provided in the own device and obtain a good image. Also, it is necessary to store a plurality of gamma correction tables by providing a plurality of gamma correction means for performing gamma correction by calculation, rather than storing a plurality of gamma correction tables for the gamma correction means for performing gamma correction by referring to the gamma correction table. This has the advantage that the memory capacity can be reduced and the cost of the device can be reduced.

According to the tenth aspect of the present invention, when a gamma correction setting mode is set from a normal original reading mode in which an original image is read by the photoelectric conversion unit and image data is output, an instruction to start reading is input. When there is, a gray chart of a predetermined density set to be readable in the photoelectric conversion unit, for example, a gray chart of a middle density range readable by the photoelectric conversion unit is obtained by reading by the photoelectric conversion unit. Depending on the level of image data obtained by A / D-converting the image signal and performing shading correction, whether the gamma characteristic of the photoelectric conversion unit is an upwardly convex characteristic or a downwardly convex characteristic, The degree of convexity upward or downward can be estimated, and gamma correction means corresponding to each value of the image data after shading correction can be calculated by selecting a gamma correction means according to the degree. As the gamma correction means for outputting the image data gamma corrected, it is possible to set the optimum for correcting the gamma characteristic of the photoelectric conversion unit that is provided to the own device. This makes it possible to check the light receiving sensitivity characteristics of each photoelectric conversion unit and to perform the gamma correction operation so as to perform the optimal gamma correction calculation for the correction of the gamma characteristics of the photoelectric conversion units. Just by measuring the level of the image data obtained by reading the chart in the same operation procedure as normal document reading, it performs gamma correction that is optimal for the gamma characteristics of the photoelectric conversion unit installed in its own device and obtains a good image. The effect that can be obtained is obtained. Also, it is necessary to store a plurality of gamma correction tables by providing a plurality of gamma correction means for performing gamma correction by calculation, rather than storing a plurality of gamma correction tables for the gamma correction means for performing gamma correction by referring to the gamma correction table. This has the advantage that the memory capacity can be reduced and the cost of the device can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a block configuration of an image reading apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing a gamma correction table stored in a RAM in the first to fourth embodiments.

FIG. 3 is a diagram showing a flow of processing of image data in the first to fourth embodiments.

FIG. 4 is a diagram illustrating a relationship between a light receiving amount and an output voltage level in a photoelectric conversion unit.

FIG. 5 is a diagram illustrating a relationship among a light receiving amount, a light receiving amount, and data after shading correction in a photoelectric conversion unit.

FIG. 6 is a diagram illustrating a relationship between an input and an output in gamma correction.

FIG. 7 is a diagram illustrating table selection information and a model-specific gamma correction table group stored in a ROM in the first embodiment.

FIG. 8 is a diagram showing table selection information and a lot-specific gamma correction table group stored in a ROM in a second embodiment.

FIG. 9 is a diagram illustrating a gamma correction table group stored in a ROM in a third embodiment.

FIG. 10 is stored in a RAM in the third embodiment.
It is a figure showing about a gamma correction table and table selection information.

FIG. 11 is stored in a ROM in a fourth embodiment.
FIG. 4 is a diagram illustrating gamma correction tables A and B.

FIG. 12 is a diagram showing specific contents of gamma correction tables A and B.

FIG. 13 is a diagram illustrating a gamma correction setting mode selection / cancellation key provided in an operation unit in the fourth and fifth embodiments.

FIG. 14 is a flowchart illustrating an image reading processing procedure according to a fourth embodiment.

FIG. 15 is a diagram showing a flow of processing of image data in a fifth embodiment.

FIG. 16 is stored in a RAM in the fifth embodiment.
FIG. 9 is a diagram illustrating a gamma correction coefficient table.

FIG. 17 is stored in the ROM in the fifth embodiment.
FIG. 4 is a diagram illustrating gamma correction coefficient tables A and B.

FIG. 18 is a diagram showing the contents of a gamma correction coefficient table.

FIG. 19 is a flowchart illustrating an image reading processing procedure according to the fifth embodiment.

FIG. 20 is a flowchart illustrating a shading correction processing procedure according to a fifth embodiment.

[Explanation of symbols]

 Reference Signs List 1 image reading device 2 photoelectric conversion unit 3 A / D conversion unit 4 shading correction unit 5 gamma correction unit 6 output unit 7 control unit 8 ROM 8a table selection information 8b model-specific gamma correction table group 8c lot-specific gamma correction table group 8d gamma Correction table group 9 RAM 9a Gamma correction table 9b Table selection information 9c Gamma correction coefficient table 10 Operation unit 10a Gamma correction setting mode selection / cancellation key 11 System bus

Claims (10)

[Claims] 1. An image reading apparatus that A / D converts an image signal obtained by reading an image by a photoelectric conversion unit, performs gamma correction on image data obtained by performing shading correction, and outputs the resulting image data. Gamma correction means for performing gamma correction on image data after shading correction with reference to a gamma correction table storing gamma correction values corresponding to the values, and gamma correction tables for each of a plurality of models Gamma correction tables,
Selection information storage means for storing in advance information for selecting a gamma correction table corresponding to the model to which the own device belongs in the model-specific gamma correction table group, and the selection information in the model-specific gamma correction table group An image reading apparatus comprising: a setting unit that sets a gamma correction table specified by information stored in a storage unit as a gamma correction table referred to by the gamma correction unit. 2. An image reading apparatus which A / D converts an image signal obtained by reading an image by a photoelectric conversion unit, performs gamma correction on image data obtained by performing shading correction, and outputs the resulting image data. Gamma correction means for gamma-correcting and outputting image data after shading correction with reference to a gamma correction table storing gamma correction values corresponding to the values, and a gamma correction table for each of a plurality of manufacturing lots A lot-specific gamma correction table group, and selection information storage means in which information for selecting a gamma correction table corresponding to a production lot to which the photoelectric conversion unit of the own device belongs out of the lot-specific gamma correction table group is stored in advance. Specified by the information stored in the selection information storage means of the group of gamma correction tables for each lot. Image reading apparatus characterized by comprising a setting means for setting a gamma correction table for gamma correction table said gamma correction means references. 3. An image reading apparatus which A / D converts an image signal obtained by reading an image by a photoelectric conversion unit, performs gamma correction on image data obtained by performing shading correction, and outputs the image data by gamma correction. Gamma correction means for performing gamma correction on image data after shading correction with reference to a gamma correction table storing gamma correction values corresponding to the values, and gamma correction comprising a plurality of gamma correction tables having different characteristics from each other A table group, selection information storage means storing in advance information for selecting a gamma correction table most suitable for the gamma characteristic of the photoelectric conversion unit of the own device among the gamma correction table group, and a gamma correction table group. The gamma correction table specified by the information stored in the selection information storage means. Reference image reading apparatus characterized by comprising a setting means for setting a gamma correction table. 4. An image reading apparatus which A / D converts an image signal obtained by reading an image by a photoelectric conversion unit, performs gamma correction on image data obtained by performing shading correction, and outputs the resulting image data. Gamma correction means for performing gamma correction on image data after shading correction with reference to a gamma correction table storing gamma correction values corresponding to the values, and gamma correction comprising a plurality of gamma correction tables having different characteristics from each other The gamma correction table is a table group and a gamma correction table corresponding to the level of image data obtained by performing A / D conversion and shading correction on an image signal obtained by reading a gray chart having a predetermined density by the photoelectric conversion unit. Setting means for selecting from a group and setting as a gamma correction table referred to by the gamma correction means; Image reading apparatus characterized by comprising. 5. An image reading apparatus which A / D converts an image signal obtained by reading an image by a photoelectric conversion unit, performs gamma correction on image data obtained by performing shading correction, and outputs the image data by gamma correction. Gamma correction means for performing gamma correction on image data after shading correction with reference to a gamma correction table storing gamma correction values corresponding to the values, and gamma correction comprising a plurality of gamma correction tables having different characteristics from each other In response to a table group, mode setting means for setting a reading mode to a normal document reading mode or a gamma correction setting mode, and a reading start instruction input when the mode setting means sets the gamma correction setting mode. Then, an image signal obtained by reading a gray chart having a predetermined density by the photoelectric conversion unit is A / A Setting means for selecting a gamma correction table corresponding to the level of image data obtained by performing conversion and shading correction from the gamma correction table group and setting the selected gamma correction table as a gamma correction table referred to by the gamma correction means. Characteristic image reading device. 6. An image reading apparatus which performs A / D conversion of an image signal obtained by reading an image by a photoelectric conversion unit, performs gamma correction on image data obtained by performing shading correction, and outputs the resulting image data. A plurality of gamma correction means capable of performing a gamma correction operation having characteristics corresponding to the above, and selection information pre-stored with information for selecting a gamma correction means corresponding to a model to which the own device belongs among the plurality of gamma correction means. The storage unit and the gamma correction unit specified by the information stored in the selection information storage unit of the plurality of gamma correction units calculate a gamma correction value corresponding to each value of the image data after shading correction. Setting means for setting as gamma correction means for outputting gamma-corrected image data. 7. An image reading apparatus for performing A / D conversion of an image signal obtained by reading an image by a photoelectric conversion unit, performing gamma correction on image data obtained by performing shading correction, and outputting the image data, wherein each of the plurality of manufacturing lots is provided. A plurality of gamma correction units capable of performing gamma correction calculation of characteristics corresponding to each of the above, and a gamma correction unit corresponding to a production lot to which the photoelectric conversion unit of the own device belongs among the plurality of gamma correction units. Selection information storage means pre-stored information of, the gamma correction means specified by the information stored in the selection information storage means of the plurality of gamma correction means,
An image reading device comprising: a setting unit configured to calculate a gamma correction value corresponding to each value of the image data after shading correction and to set the output as gamma corrected image data. 8. An image reading apparatus which performs A / D conversion of an image signal obtained by reading an image by a photoelectric conversion unit, performs gamma correction on image data obtained by performing shading correction, and outputs the resulting image data. A plurality of gamma correction units capable of performing gamma correction calculation, and a selection information storage in which information for preliminarily storing information for selecting a gamma correction unit optimal for a gamma characteristic of the photoelectric conversion unit of the own device among the plurality of gamma correction units is stored. Means, the gamma correction means specified by the information stored in the selection information storage means of the plurality of gamma correction means, calculating a gamma correction value corresponding to each value of the image data after shading correction. An image reading device comprising: setting means for setting as gamma correction means for outputting gamma-corrected image data. 9. An image reading apparatus which A / D converts an image signal obtained by reading an image by a photoelectric conversion unit, performs gamma correction on image data obtained by performing shading correction, and outputs the image data, wherein characteristics of the respective image reading devices are different from each other. A plurality of gamma correction means capable of performing gamma correction calculation, and an image signal obtained by reading a gray chart of a predetermined density by the photoelectric conversion unit is represented by A
A gamma correction unit corresponding to the level of image data obtained by performing / D conversion and shading correction is selected from the plurality of gamma correction units, and a gamma correction value corresponding to each value of the image data after shading correction is calculated. Setting means for setting as gamma correction means for outputting image data which has been gamma-corrected. 10. An image reading apparatus for subjecting an image signal obtained by reading an image by a photoelectric conversion unit to A / D conversion, performing shading correction, and performing gamma correction on the obtained image data, and outputting the image data. A plurality of gamma correction means capable of performing gamma correction calculation, a mode setting means for setting a reading mode to a normal document reading mode or a gamma correction setting mode, and a gamma correction setting mode set by the mode setting means. A gamma corresponding to the level of image data obtained by A / D-converting and shading-correcting an image signal obtained by reading a gray chart of a predetermined density by the photoelectric conversion unit in response to the input of the read start instruction. The correction means is selected from the plurality of gamma correction means, and the correction means is provided for each value of the image data after shading correction. Image reading apparatus characterized by comprising a setting means calculates the gamma correction value is set as a gamma correction means for outputting the image data gamma correction.