JP2001211297A - Image trader, its method and storage medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image reader, its device and storage medium, capable of dissolving unnaturalness of an image by eliminating difference in signal level due to reading by each area. SOLUTION: Pixel data of a consecutive position (P-VCK) are fetched, an average value AV-ODD-1 of ODD-1 values and an average value AV-ODD-2 of ODD-2 values of data in an area AS are calculated in each block B divided into plural blocks by the signal level of an output pixel signal ODD-2 and a point to be regulated by both average values AV-ODD-1, 2 is defined as a representative point (ratio between both averages). A curve for indicating relation between the output pixel signals ODD-1, 2 is calculated in all signal level areas from the obtained representative point through interpolation calculation, the contents of a lookup table LUT-3 are decided on its basis and set in a consecutive correction circuit 513. Level adjustment on the basis of the table LUT-3 is performed on the actual output pixel signal ODD-2 (input), and the signal approximately coincides with the signal level of the output pixel signal ODD-1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image reading apparatus, method, and storage medium for reading an image using a linear image sensor.

[0002]

2. Description of the Related Art Conventionally, an image reading apparatus for reading an image using a linear image sensor has been known.

FIG. 12 is a diagram showing a configuration of a linear image sensor in a conventional image reading apparatus.

In FIG. 1, reference numeral 101 denotes a light receiving pixel column,
2 and 103 are analog shift registers.
Output amplifiers 104 and 105 convert the charges read from the analog shift registers 102 and 103 into voltage signals and output the converted signals. The electric charge accumulated in each pixel of the light receiving pixel column 101 of the linear image sensor is separated into ODD (odd number) pixels and EVEN (even number) pixels, and are sequentially read out by analog shift registers 102 and 103, respectively. The pixel signals (ODD, EVEN) are output from 104 and 105, respectively.

When reading a document, as shown in FIG. 1, a document 202 placed on a platen glass (platen glass) 201 is illuminated by an illumination lamp 203,
The reflected light is transmitted to first, second, and third mirrors 204, 205,
The image is guided to a lens 207 by 206, and an original image is formed on a light receiving surface of a linear image sensor (208). In addition,
The surface of the white plate 209 and the original 2
The white plate 209 is read at an optical distance equivalent to the plane No. 02 when viewed from the linear image sensor (208), and shading correction processing is performed on the original image based on the read signal.

As described above, when reading the original, the mirrors 204, 205, and 206 move in the sub-scanning direction S, so that the image sensor 208 can read the image of the original 202 two-dimensionally. Also, the light receiving pixel column 101
ODD (odd number) / EVEN
By performing (even number) separation reading, the reading speed is improved in the analog shift registers 102 and 103, which have a limited transfer speed.

However, further improvement in reading speed has been demanded in recent years, and a structure is provided in which four analog shift registers are provided, and in addition to ODD (odd number) / EVEN (even number) separation reading, a light receiving pixel column is divided into right and left to read. Has been already proposed (FIG. 2).

That is, as shown in FIG. 2, the light receiving pixel row 301 of the image sensor 208 is divided into two parts on the left and right sides of the center, and the electric charge accumulated in each pixel of the left light receiving pixel row 301L (reference area) is , ODD pixel and EVEN pixel, and the charges of the ODD pixel and EVEN pixel are read out from the analog shift registers 302 and 304, respectively, and output from the output amplifiers 306 and 308 to output pixel signals (ODD-1,
EVEN-1). On the other hand, similarly, the electric charges accumulated in each pixel of the right-side light receiving pixel column 301R (another region) are read out from the analog shift registers 303 and 305 respectively, and the electric charges of the ODD pixel and the EVEN pixel are read out from the output amplifiers 307 and 309, respectively. Pixel signals (ODD-2, E
VEN-2).

With such a configuration, a reading speed twice as high as that of a simple ODD (odd number) / EVEN (even number) separation reading type image reading apparatus can be realized.

[0010]

However, in the conventional image reading apparatus having a linear image sensor having a structure in which a light receiving pixel column is divided into left and right sides and read in addition to the above-described separation reading, output signals of four channels are generated. However, since there is a slight difference in linearity between the output signals of the respective channels, there is a problem in that if a step in the read signal level occurs between the left and right division positions, the display image is greatly affected and an unnatural display image is produced. Was.

That is, only ODD (odd number) / EVE
In the type that only performs N (even number) separation reading, OD
Even if a difference in the read signal level occurs between D and EVEN, a very fine repetitive pattern is slightly added to the image on the display image and is inconspicuous. However,
In the type in which the light receiving pixel column is divided into left and right sides and read, even if the level difference of the read signal level at the boundary between the left and right division positions is slight, the display image is divided, for example, up and down at the step portion as a boundary, and the boundary is Very noticeable and unnatural display image.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and an object of the present invention is to eliminate an unnatural image by eliminating a signal level difference caused by reading out each area. A reading device, a method, and a storage medium are provided.

[0013]

According to a first aspect of the present invention, there is provided an image reading apparatus for reading an image using a linear image sensor, comprising: a light receiving pixel array of the linear image sensor; Area is divided into a reference area and at least one other area, and readout means for reading out the output pixel signals of both areas for each area, based on the output pixel signals of both areas read out by the readout means Adjusting means for adjusting the signal level of the output pixel signal of the other area to substantially match the signal level of the output pixel signal of the reference area.

In order to achieve the same object, according to a second aspect of the present invention, in the image reading apparatus according to the first aspect, the adjusting means is arranged so that the adjusting means is provided near a boundary position between the reference area and the other area. Compare each output pixel signal,
The signal level of the output pixel signal of the other area is adjusted based on the comparison result.

In order to achieve the same object, according to a third aspect of the present invention, in the image reading apparatus according to the second aspect, the adjusting means is arranged so that the adjusting means is provided near a boundary position between the reference area and the other area. Estimating means for estimating the relationship between the signal level of the reference area and the signal level of the other area based on the ratio of the signal level of each output pixel signal; and estimating the relationship between the other area based on the estimation result by the estimating means. Correction means for correcting the output pixel signal.

In order to achieve the same object, according to a fourth aspect of the present invention, in the image reading apparatus according to the third aspect, the estimating means is configured to determine whether or not the other area in the vicinity of a boundary position with the reference area is located. For each of a plurality of level regions of the output pixel signal divided by the signal level, a ratio of the signal level of each output pixel signal between the reference region and the other region is calculated.

In order to achieve the same object, according to a fifth aspect of the present invention, in the image reading apparatus according to the fourth aspect, the estimating means is configured to determine whether or not the other area in the vicinity of a boundary position with the reference area. When a plurality of output pixel signals exist in the same level area, an average value of the output pixel signals of the other area in the same level area is calculated, and the signal level ratio is calculated based on the calculated average value. It is characterized by doing.

According to a sixth aspect of the present invention, there is provided an image reading apparatus according to the fourth or fifth aspect of the present invention, wherein the estimating means is configured to detect the position of the another area near a boundary position with the reference area. When a predetermined number or more of the output pixel signals of the area do not exist in the same level area, the calculation of the ratio between the average value of the output pixel signals of the other area and the signal level in the same level area is prohibited. And

According to a seventh aspect of the present invention, there is provided an image reading apparatus according to the third aspect of the present invention, wherein the estimating means includes the reference area and the other area. When the difference between the two output pixel signals in the vicinity of the boundary position with the region is equal to or more than a predetermined value, the two output pixel signals are excluded from the data used for calculating the signal level ratio.

To achieve the same object, an image reading apparatus according to claim 8 of the present invention is the image reading apparatus according to any one of claims 4 to 7, wherein the estimating means includes: For a level area near the position where the output pixel signal of the other area does not exist, a ratio of the signal level in the level area is obtained by interpolation.

According to a ninth aspect of the present invention, there is provided an image reading apparatus according to the third aspect of the present invention, wherein the estimating means includes a new object to be read. When an image is read and an output pixel signal of the other area near the boundary position with the reference area is newly obtained, the output pixel signal corresponds to the output pixel signal based on the newly obtained output pixel signal. And updating the ratio of the signal levels in the level region to be updated.

According to a tenth aspect of the present invention, there is provided an image reading apparatus according to any one of the first to ninth aspects, wherein the output after adjusting the signal level by the adjusting means is provided. The gradation number of the image in the pixel signal is set to a value smaller than the gradation number of the image in the output pixel signal before the signal level is adjusted by the adjusting unit.

In order to achieve the same object, an image reading apparatus according to claim 11 of the present invention, in the configuration according to any one of claims 1 to 10, wherein the output pixel signal read by said reading means is provided. A shading correction means for performing shading correction on the output pixel signal after the shading correction is performed by the shading correction means.

In order to achieve the same object, according to a twelfth aspect of the present invention, there is provided an image reading method for reading an image using a linear image sensor. A reading step of dividing output pixel signals of both areas into at least one other area and reading output pixel signals of both areas for each area; and, based on the output pixel signals of the two areas read in the reading step, And adjusting the signal level of the output pixel signal to substantially match the signal level of the output pixel signal in the reference area.

In order to achieve the same object, according to a thirteenth aspect of the present invention, in the image reading method according to the twelfth aspect, the adjusting is performed in the vicinity of a boundary position between the reference area and the other area. Each output pixel signal is compared with each other, and the signal level of the output pixel signal in the other area is adjusted based on the comparison result.

In order to achieve the same object, according to a fourteenth aspect of the present invention, in the image reading method according to the thirteenth aspect, the adjusting step is performed in the vicinity of a boundary position between the reference area and the other area. An estimation step of estimating the relationship between the signal level of the reference area and the signal level of the other area based on the ratio of the signal level of each output pixel signal; and And correcting the output pixel signal.

[0027] In order to achieve the same object, according to a fifteenth aspect of the present invention, in the image reading method according to the fifteenth aspect, the estimating step includes the step of: estimating the other area near the boundary position with the reference area. For each of a plurality of level regions of the output pixel signal divided by the signal level, a ratio of the signal level of each output pixel signal between the reference region and the other region is calculated.

In order to achieve the same object, according to the image reading method of claim 16 of the present invention, in the configuration of claim 15, the estimating step includes the steps of: When a plurality of output pixel signals exist in the same level area, an average value of the output pixel signals of the other area in the same level area is calculated, and the signal level ratio is calculated based on the calculated average value. It is characterized by doing.

In order to achieve the same object, an image reading method according to claim 17 of the present invention is directed to claim 15 or 16 of the present invention.
In the configuration described above, when the output pixel signals of the other area near the boundary position with the reference area do not exist in the same level area by a predetermined number or more, the other step in the same level area may be performed. The calculation of the ratio between the average value of the output pixel signals of the area and the signal level is prohibited.

In order to achieve the same object, according to the image reading method of claim 18 of the present invention, in the configuration according to any one of claims 14 to 17, the estimating step comprises: When the difference between the two output pixel signals in the vicinity of the boundary position with the region is equal to or more than a predetermined value, the two output pixel signals are excluded from the data used for calculating the signal level ratio.

In order to achieve the same object, according to the image reading method of the nineteenth aspect of the present invention, in the configuration according to any one of the fifteenth to eighteenth aspects, the estimating step includes the step of: For a level area near the position where the output pixel signal of the other area does not exist, a ratio of the signal level in the level area is obtained by interpolation.

According to a twentieth aspect of the present invention, there is provided an image reading method according to any one of the fourteenth to nineteenth aspects, wherein the estimating step comprises the steps of: By reading the image,
When an output pixel signal of the other area in the vicinity of the boundary position with the reference area is newly obtained, the signal level in a level area corresponding to the output pixel signal based on the newly obtained output pixel signal The feature is that the ratio of is updated.

In order to achieve the same object, an image reading method according to a twenty-first aspect of the present invention is the image reading method according to any one of the twelfth to twelfth aspects, wherein the output after the signal level is adjusted by the adjusting step is provided. The gradation number of the image in the pixel signal is set to a value smaller than the gradation number of the image in the output pixel signal before the signal level is adjusted in the adjusting step.

According to a second aspect of the present invention, there is provided an image reading method as set forth in any one of the twelfth to twelfth aspects of the present invention, wherein the output pixel signal read in the reading step is provided. And a shading correction step of performing shading correction on the output pixel signal after the shading correction is performed by the shading correction step.

To achieve the same object, a storage medium according to claim 23 of the present invention is a storage medium storing a program used in an image reading method for reading an image using a linear image sensor, The area of the light receiving pixel column is divided into a reference area and at least one other area, and a code of a reading step for reading output pixel signals of both areas for each area, and the two areas read by the code of the reading step And a code for an adjusting step of adjusting the signal level of the output pixel signal of the other area to substantially match the signal level of the output pixel signal of the reference area based on the output pixel signal of the reference area. .

[0036]

Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) FIG. 1 is a diagram showing a configuration of a reading section of an image reading apparatus according to a first embodiment of the present invention.

In FIG. 1, reference numeral 201 denotes a platen glass (platen glass), which is a document 2 to be read.
02 is placed. The original 202 is illuminated by an illumination lamp 203 and the reflected light is reflected by the first, second and third mirrors 2.
The light is guided to the lens 207 by 04, 205, and 206.
The lens 207 forms a document image on a light receiving surface of a linear CCD image sensor 208 (hereinafter simply referred to as “image sensor 208”). Reference numeral 209 denotes a white plate that is read as a reference for the shading correction process. The dummy glass 210 is used to make the surface of the white plate 209 and the surface of the document 202 have the same optical distance when viewed from the image sensor 208.

When reading the original, the mirrors 204, 2
The image sensor 208 can two-dimensionally read the image of the original 202 by moving the sub-scanners 05 and 206 in the sub-scanning direction.

FIG. 2 is a diagram showing a configuration of the image sensor 208.

In the figure, reference numeral 301 denotes a light receiving pixel column;
2, 303, 304, and 305 are analog shift registers (reading means). 306, 307, 3
Reference numerals 08 and 309 denote output amplifiers, which convert electric charges read from the analog shift registers 302, 303, 304 and 305 into voltage signals and output the voltage signals.

The image sensor 208 has a structure in which the light receiving pixel column 301 is divided into left and right sides and read in addition to ODD (odd number) / EVEN (even number) separation reading.
That is, the light receiving pixel column 301 of the image sensor 208 is divided into two parts on the left and right sides of the center, and the left light receiving pixel column 301
The charge accumulated in each pixel of L is separated into an ODD pixel and an EVEN pixel as in the related art, and the charge of the ODD pixel is output from the output amplifier 306, and the charge of the EVEN pixel is output from the output amplifier 308, respectively, from the pixel signal (ODD). -1, EVEN
-1). On the other hand, the right light receiving pixel column 30
Similarly, the electric charge accumulated in each pixel of 1R is the same as that of the ODD pixel and E.
The charge of the ODD pixel is output from the output amplifier 307, and the charge of the EVEN pixel is output from the output amplifier 309.
From the pixel signals (ODD-2, EVEN-2), respectively.
Is output as

FIG. 3 is a diagram showing a configuration of a processing unit in the image reading apparatus according to the present embodiment.

The amplifiers 501, 502, 503, and 504 are respectively AD conversion circuits 505, 506, 507, and 50.
8, a black offset + shading correction circuit 50
9, 510, 511, 512. Black offset + shading correction circuit 509, 510, 51
Reference numerals 1 and 512 are connected to a CPU 519 (adjustment means and estimation means) via a DFF (D-type flip-flop) 517 and a memory 518. The black offset + shading correction circuit 509 is also connected to the memory 516, and the black offset + shading correction circuit 51
0, 511 and 512 are connection correction circuits 513,
It is also connected to the memory 516 via 514 and 515 (adjustment means, correction means).

The amplifiers 501, 502, 503, and 504 have output amplifiers 306, 308, and 3 shown in FIG.
07, 309 (output pixel signal ODD-
1, EVEN-1, ODD-2, EVEN-2). Each input output pixel signal is supplied to an amplifier 501,
Amplified by 502, 503, and 504, the AD conversion circuit 50
The black offset + shading correction circuits 509, 510, 511, and 512 convert the analog signal into a digital signal at 5, 506, 507, and 508, and perform a black offset correction process and a shading correction process of subtracting the black offset. .

Connection correction circuits 513, 514, 515
Are lookup tables LUT-2 and LU described later.
T-3 and LUT-4, the output pixel signal ODD-1
Other output pixel signals EVEN-1, ODD-
2. It is for performing signal level conversion of each signal of EVEN-2 to realize joint correction (reading level correction) of right and left division reading. Connection correction circuits 513 and 5
Reference numerals 14 and 515 have a function of correcting read linearity as well as realizing connection correction. Here, the connection correction circuits 513, 514, and 515 are provided with a black offset + shading correction circuit 510,
Since they are arranged at the subsequent stages of 11, 512, respectively, a constant reading linearity can be obtained regardless of the position of the main scanning.

The memory 516 temporarily stores each output pixel signal output at the timing shown in FIG.
This is for realizing the pixel rearrangement of rearranging and outputting the correct pixel order.

The DFF 517 and the memory 518 store a connection position (rising edge position PV) shown in FIG.
(Indicated by CK) is temporarily held so that the CPU 519 can take in the pixel data. CPU 519
Is stored in the memory 51 several times during reading of the original 202.
8 is fetched, and a look-up table LUT for connection correction is performed by an arithmetic process (look-up table (LUT) setting process in FIG. 6) described later.
-2, LUT-3 and LUT-4 are determined.
Note that a program executed by the CPU 519 is an R (not shown).
It is stored in the OM.

FIG. 4 is a view visually showing an output state of an output pixel signal from the image sensor 208. The figure shows a black offset + shading correction circuit 509,5
10 shows pixel signals after the processing by 10, 511 and 512.

In the figure, HSYNC is a line synchronization signal. The rising edge position P-VCK defines the generation timing of the pixel signal at the left-right divided boundary of the light receiving pixel column 301 of the image sensor 208. The pixel signal numbers 1 to 2n indicate the order of the pixel signals to be read.

As shown in FIG.
Pixel signal ODD from the light receiving pixel column 301L on the left side of FIG.
-1 and EVEN-1 are sequentially read out in turn, such as No. 1 and No. 2, and when the pixel signal of the light receiving pixel column 301L is read up to the nth, then the right light receiving pixel column 301R
, The output pixel signals ODD-2 and EVEN-2 are sequentially read out sequentially in the order of n + 1, n + 2, and
The data is read out to the n-th and effective pixel data for one line is obtained.

As a result of reading in this order, at the rising edge position P-VCK, the output pixel signals ODD-1, EVEN-1, ODD-2, EV
The order of EN-2 is continuous from n-1 to n + 2. The bridging correction described later is performed using these n-1 to n + 2 pixel signals. The reason for this is that these signals are obtained from images at positions close to each other on the document 202, and it is considered that the original signal levels of the respective signals are substantially the same.

It should be noted that even if pixel signals other than the (n-1) to (n + 2) th pixel signals are used, an effect similar to that of the present embodiment can be expected by using a pixel signal near the division position of the light receiving pixel column 301.

FIG. 5 is a diagram showing the relationship between the brightness of the document 202 (horizontal axis) and the signal levels of the output pixel signals ODD-1 and ODD-2 (vertical axis). 10A shows the signal level before the connection correction, and FIG. 10B shows the signal level after the connection correction to the output pixel signal ODD-2 based on the output pixel signal ODD-1.

As shown in FIG. 3A, the output pixel signal O
Since the DD-1 and ODD-2 are converted into digital signals via different circuits such as output amplifiers 306 and 307, even when the original 202 having the same brightness is read,
A slight difference may occur in the read signal level (“Δ” in the figure). Therefore, in the present embodiment, the connection correction circuit 514 converts the output pixel signal ODD-3 using the output pixel signal ODD-1 as a reference channel, and outputs the signal of the output pixel signal ODD-1 as shown in FIG. Match level. The output pixel signals EVEN-1 and EVEN-2 are similarly level-converted by the connection correction circuits 513 and 515, so that the read signal level matches the signal level of the output pixel signal ODD-1.

The connection correction by the connection correction circuits 513, 514, and 515 is performed by lookup tables LUT-2 and LUT-2.
This is performed based on UT-3 and LUT-4. The contents of each of the lookup tables LUT-2, LUT-2, LUT-3, and LUT-2 are set by a lookup table (LUT) setting process described later.

FIG. 6 shows a look-up table (LUT).
FIG. 7 is a diagram illustrating a flowchart of a setting process. In this processing, the setting processing of the contents of the look-up table LUT-3 for adjusting the level of the output pixel signal ODD-2 using the output pixel signal ODD-1 as a reference channel is taken as an example.
Similarly, the output pixel signals EVEN-1 and EVEN-2 have a look-up table LU for level adjustment using the output pixel signal ODD-1 as a reference channel.
The contents of T-2 and LUT-4 are set.

First, the pixel data at the connection position is fetched (step S601). That is, while reading the original,
The pixel data at the rising edge position P-VCK shown in FIG. This reading is performed a plurality of times during the reading of the document 202.

FIG. 7 shows the relationship between the signal levels of the output pixel signal ODD-1 and the output pixel signal ODD-2 at the connection position, which are thus obtained.

Next, in step S602 in FIG. 6, pixel data having a predetermined level difference is excluded from the subsequent arithmetic processing.
That is, data within the area AS shown in FIG. 7 is set as valid data, and data outside the area AS is not used for the arithmetic processing. This eliminates the effect of accidentally obtained data on level correction. Region A
The range of S may be set in consideration of a normally assumed level difference.

Next, in step S603 of FIG.
As shown in the figure, the signal level region is divided into a plurality of blocks B (B1, B2) according to the signal level of the output pixel signal ODD-2.
Etc.).

Next, a representative point is calculated for each block B (step S604). That is, in each block B, the average value A of the ODD-1 values of the data in the area AS
Average value of V-ODD-1 and ODD-2 values AV-ODD-
2 is calculated, and a point defined by both average values AV-ODD-1, 2 is set as a representative point. This representative point is the average value AV-OD
It represents the ratio between D-1 and the average value AV-ODD-2.
Here, when the data in the area AS in each block B is equal to or less than a predetermined number (for example, two), the representative point in the block B is invalidated. This avoids erroneous corrections.

Next, in step S605, an interpolation operation is performed. That is, a curve indicating the relationship between the output pixel signal ODD-1 and the output pixel signal ODD-2 in all signal level regions is obtained from the obtained representative points by a known interpolation operation, and the relationship between the two is estimated. In this interpolation calculation, there is also a block B for which a representative point has not been obtained. In this case, the calculation is performed using the representative point of the adjacent block B.

FIG. 8 shows the output pixel signal ODD-1 and the output pixel signal ODD-2 calculated by the representative point and the interpolation operation.
4 shows an example of a curve indicating the relationship with. As shown in the figure,
In all the level regions, the correspondence between the output pixel signals ODD-1 and ODD-2 is obtained.

Next, in step S606, the contents of the lookup table LUT-3 are set. That is, the output pixel signal ODD-1 and the output pixel signal OD shown in FIG.
The contents of the look-up table LUT-3 are determined based on the curve indicating the relationship with D-2, and are set in the connection correction circuit 514.

FIG. 9 shows a lookup table LUT-3.
FIG. 4 is a diagram showing an example of the contents of the above. This table LUT-3
Indicates how the actual output pixel signal ODD-2 (input) is adjusted and output according to the level area so as to match the signal level of the output pixel signal ODD-1. It is. Accordingly, the signal level when the output pixel signal ODD-2 input from the black offset + shading correction circuit 511 is corrected and output by the connection correction circuit 514 is uniquely determined by the table LUT-3.

Next, the present processing ends.

According to the present embodiment, in the image reading apparatus configured to divide the area of the light receiving pixel column of the linear image sensor 208 into a plurality of parts and read out the output pixel signal for each area, the output pixel signal ODD-1 With reference to output pixel signals (ODD-2, EVEN-1, EVEN-1) of other areas.
Since the signal level of VEN-2) is adjusted so as to be substantially equal to the signal level of the reference output pixel signal, it is possible to eliminate a step in the signal level due to reading for each area and to eliminate unnaturalness of the image. . Also, at this time, the level is corrected based on the pixel signal of each area at the joint position, so that the level difference can be effectively avoided by adjusting based on the signal level near the boundary position where a step occurs. Furthermore, since the representative point is calculated for each of the plurality of blocks B divided according to the signal level, the signal level adjustment processing can be simplified.

The data outside the area AS is excluded from the data used in the lookup table setting process. In addition, if the number of data within the area AS in each block B is less than a predetermined number, the data in the block B Since the representative point is not determined, erroneous adjustment of the signal level can be avoided and the adjustment accuracy can be improved. further,
The output pixel signal ODD-1 and the other output pixel signals ODD- are interpolated, including the block B for which the representative point cannot be obtained.
2. Since the correspondence (ratio) with EVEN-1 and EVEN-2 is obtained, the level can be adjusted in all the level regions.

It should be noted that the reference output pixel signal is not limited to the output pixel signal ODD-1 but may be other output pixel signals ODD.
-2, EVEN-1, or EVEN-2. For example, the output pixel signal ODD-1, EVEN
-1 and EVEN-2 are adjusted to the output pixel signal OD.
You may make it perform based on D-2.

It should be noted that even if there is a level difference from the output pixel signal ODD-1, the output pixel signal EVEN-1 has a very fine repetitive pattern slightly added to the image as described above. And is not noticeable. Therefore, the level adjustment based on the output pixel signal ODD-1 is performed by adjusting the output pixel signal ODD-2 and the output pixel signal EDD.
You may make it perform only about VEN-2. Also,
For the same reason, the level adjustment of the output pixel signal ODD-2 is performed based on the output pixel signal ODD-1, and the level adjustment of the output pixel signal EVEN-2 is performed based on the output pixel signal ODD-.
It may be performed based on the output pixel signal EVEN-2 instead of 1.

In this embodiment, an example of right and left division has been described. However, the present invention is not limited to this, and the present invention can be widely applied to a case of division into a plurality of parts.

(Second Embodiment) In the first embodiment, since the look-up table is newly recreated every time a document is read, correction strongly depends on the document read immediately before. Will be. In the second embodiment, the lookup table is partially updated to avoid this inconvenience. Therefore, the first
This embodiment is different from the first embodiment in the table setting process in step S606 in FIG. 6, and the other configuration is the same as that of the first embodiment.

FIG. 10 is a diagram showing an example of the contents of the lookup table LUT-3 in the present embodiment.
FIG. 7A shows the contents before updating, and FIG. 7B shows the contents after updating.

As described above, representative points are not always obtained for all blocks B. Therefore, the table setting process is performed only for the block B for which the representative point has been obtained, using the new representative point. The update is performed by simply replacing the old representative point with a new representative point and determining the contents of the lookup table LUT-3 by the above-described interpolation operation. A group of points p shown in FIG. 7B is the updated representative point.
The lookup tables LUT-2 and LUT-4 are processed in the same manner.

The updated representative point may be obtained by performing an arithmetic operation (for example, a weighted linear operation) between the old representative point and the new representative point.

According to the present embodiment, when setting the lookup table, it is possible to prevent the influence of the document read immediately before from becoming excessive, and thus the same effects as in the first embodiment can be obtained. In addition, more appropriate joint correction can be performed.

(Third Embodiment) FIG. 11 is a diagram showing a configuration of a reading section of an image reading apparatus according to a third embodiment of the present invention. The configuration of the image reading apparatus according to this embodiment is basically the same as that of the first embodiment, except that a joint correction circuit 900 is provided between a black offset + shading correction circuit 509 and a memory 516, and The difference is that connection correction circuits 913, 914, 915 are provided instead of connection correction circuits 513, 514, 515. The connection correction circuits 913, 914, and 915 perform connection correction in the same manner as the connection correction circuits 513, 514, and 515, but also perform conversion (bit conversion) of the number of tones of an image.

That is, the connection correction circuits 913 and 91
4 and 915 are input with 10-bit signals from the black offset + shading correction circuits 510, 511 and 512, respectively, converted into 8-bit signals and output to the memory 516. Further, a 10-bit signal is input to the connection correction circuit 900 from the black offset + shading correction circuit 509, where the lower 2 bits are truncated and the upper 8 bits are stored in the memory 51.
6 is output.

Therefore, processing is performed with a large number of gradations (10 bits) before the connection correction to ensure the accuracy of the connection correction, while a smaller number of gradations (8 bits) is performed after the connection correction.
To reduce the burden. Note that the number of gradations after the correction may be smaller than that before the connection correction.
And 8 bits are not limited to the combination.

According to the present embodiment, not only the same effects as in the first embodiment can be obtained, but also the burden of image reading processing can be reduced while maintaining the accuracy of signal level adjustment.

A storage medium storing a program code of software for realizing the functions of the above-described embodiments is supplied to the image reading apparatus, and the computer (or CPU or MPU) of the image reading apparatus stores the program in the storage medium. It goes without saying that the object of the present invention is also achieved by reading and executing the program code thus set.

In this case, the program code itself read from the storage medium realizes the novel function of the present invention, and the storage medium storing the program code constitutes the present invention.

As a storage medium for supplying the program code, for example, a floppy disk, hard disk, optical disk, magneto-optical disk, CD-ROM, CD
-R, a magnetic tape, a nonvolatile memory card, a ROM, or the like can be used.

The functions of the above-described embodiments are not only realized by the computer executing the readout program code, but also the OS or the like running on the computer is executed based on the instruction of the program code. It goes without saying that a part or all of the actual processing is performed and the functions of the above-described embodiments are realized by the processing.

Further, after the program code read from the storage medium is written into a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer, the program code is read based on the instruction of the program code. Needless to say, a CPU or the like provided in the function expansion board or the function expansion unit performs part or all of the actual processing, and the processing realizes the functions of the above-described embodiments.

[0087]

As described above, according to the first aspect of the present invention,
According to the image reading apparatus according to the above, the image reading method according to the twelfth aspect, or the storage medium according to the twenty-third aspect, the linear image sensor eliminates a signal level difference due to reading for each area, thereby eliminating unnaturalness of an image. be able to.

According to the image reading apparatus of the second aspect of the present invention or the image reading method of the thirteenth aspect of the present invention, the level difference is adjusted based on the portion where the step occurs, thereby effectively avoiding the noticeable level difference. Naturalness can be eliminated.

According to the image reading apparatus of the third aspect of the present invention or the image reading method of the fourteenth aspect, it is possible to appropriately adjust the signal level near the boundary position to eliminate the unnaturalness of the image. it can.

According to the image reading apparatus or the image reading method of the present invention, it is possible to simplify the signal level adjusting process.

According to the image reading apparatus of the present invention and the image reading method of the present invention, the accuracy of adjusting the signal level can be improved and the unnaturalness of the image can be more appropriately eliminated. .

According to the image reading apparatus of the sixth aspect of the present invention or the image reading method of the seventeenth aspect, incorrect adjustment of the signal level can be avoided.

According to the image reading apparatus and the image reading method of the present invention, it is possible to more appropriately eliminate the unnaturalness of the image by avoiding adjustment based on inappropriate data. Can be.

According to the image reading apparatus according to the eighth aspect of the present invention or the image reading method according to the nineteenth aspect, it is possible to adjust all output pixel signals of the other area.

According to the image reading apparatus of the ninth aspect of the present invention or the image reading method of the twentieth aspect, it is possible to prevent the influence of the object to be read immediately before read from becoming excessive.

According to the image reading apparatus or the image reading method according to the tenth aspect of the present invention,
The load of image reading processing can be reduced while maintaining the accuracy of signal level adjustment.

According to the image reading apparatus of the present invention or the image reading method of the present invention,
The linearity of the output pixel signal after the shading correction can be adjusted.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of a reading unit of an image reading device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of a linear image sensor in the same embodiment.

FIG. 3 is a diagram showing a configuration of a processing unit in the image reading device according to the same embodiment.

FIG. 4 is a diagram visually showing an output state of an output pixel signal from an image sensor in the same embodiment.

FIG. 5 is a diagram showing a relationship between the brightness of a document (horizontal axis) and the signal levels of output pixel signals ODD-1 and ODD-2 (vertical axis) in the same embodiment.

FIG. 6 shows a lookup table (LU)
FIG. T is a diagram showing a flowchart of a setting process.

FIG. 7 is a diagram showing a signal level relationship between an output pixel signal ODD-1 and an output pixel signal ODD-2 at a fetched connection position in the same embodiment.

FIG. 8 shows an output pixel signal ODD-1 and an output pixel signal ODD- calculated by a representative point and an interpolation operation in the same embodiment.
FIG. 4 is a diagram illustrating an example of a curve indicating a relationship with the second curve;

FIG. 9 shows a lookup table LUT- in the same embodiment.
FIG. 6 is a diagram showing an example of the content of No. 3;

FIG. 10 is a diagram illustrating an example of the content of a lookup table LUT-3 according to the second embodiment of the present invention.

FIG. 11 is a diagram illustrating a configuration of a reading unit of an image reading device according to a third embodiment of the present invention.

FIG. 12 is a diagram illustrating a configuration of a linear image sensor in a conventional image reading device.

[Explanation of symbols]

202 Original 208 Linear CCD image sensor 301 Light receiving pixel array 301L Light receiving pixel array (reference area) 301R Light receiving pixel array (other area) 302, 303, 304, 305 Analog shift register (reading means) 519 CPU (adjusting means, estimating means) ) 513, 514, 515 connection correction circuit (adjustment means,
Correction means)

Claims (23)

[Claims] 1. An image reading apparatus for reading an image using a linear image sensor, wherein an area of a light receiving pixel row of the linear image sensor is divided into a reference area and at least one other area, and output pixel signals of both areas are divided. Reading means for reading each area; and a signal level of an output pixel signal of the reference area based on the output pixel signals of the two areas read by the reading means. And an adjusting means for adjusting the image reading device so as to substantially match the image reading device. 2. The method according to claim 1, wherein the adjusting unit compares the output pixel signals in the vicinity of a boundary position between the reference area and the other area, and based on a result of the comparison, determines a signal level of the output pixel signal in the other area. 2. The image reading device according to claim 1, wherein the image reading device adjusts the distance. 3. The signal level of the reference area and the signal level of the other area based on a ratio of the signal level of each output pixel signal near a boundary position between the reference area and the other area. Estimating means for estimating the relationship with
3. The image reading apparatus according to claim 2, further comprising a correction unit configured to correct the output pixel signal of the other area based on a result of the estimation by the estimation unit. 4. The method according to claim 1, wherein the estimating unit is configured to determine the reference region and the other region for each of a plurality of level regions of the output pixel signal in the other region in the vicinity of a boundary position with the reference region. 4. The image reading apparatus according to claim 3, wherein a ratio of the signal level of each output pixel signal to the output pixel signal is calculated. 5. When there are a plurality of output pixel signals of the other area near the boundary position with the reference area in the same level area, the estimating means determines the output pixel signal of the other area in the same level area. 5. The image reading apparatus according to claim 4, wherein an average value of the output pixel signals is calculated, and the signal level ratio is calculated based on the calculated average value. 6. When the output pixel signals of the other area in the vicinity of the boundary position with the reference area do not exist in the same level area by a predetermined number or more, the estimating means outputs the other pixel signal in the same level area. 6. The image reading apparatus according to claim 4, wherein calculation of a ratio between an average value of output pixel signals of the area and the signal level is prohibited. 7. When the difference between both output pixel signals near a boundary position between the reference area and the other area is equal to or greater than a predetermined value, the estimating means compares the two output pixel signals with the signal level ratio. The image reading apparatus according to any one of claims 3 to 6, wherein the image reading apparatus is excluded from data used for calculating the image. 8. A level region in which the output pixel signal of the other region does not exist near the boundary position with the reference region, wherein the ratio of the signal level in the level region is obtained by an interpolation operation. The image reading device according to claim 4, wherein: 9. The method according to claim 1, wherein the estimating unit is configured to, when a new image of the object to be read is read and an output pixel signal of the other area near the boundary position with the reference area is newly obtained, 4. The method according to claim 3, wherein a ratio of the signal level in a level region corresponding to the output pixel signal is updated based on a newly obtained output pixel signal.
9. The image reading device according to any one of 8. 10. The gradation number of an image in an output pixel signal after signal level adjustment by said adjusting means is smaller than the image gradation number in an output pixel signal before signal level adjustment by said adjusting means. The image reading device according to claim 1, wherein the image reading device is set. 11. A shading correction unit for performing shading correction on the output pixel signal read by the reading unit, wherein the adjustment by the adjustment unit is performed after the shading correction is performed by the shading correction unit. The image reading apparatus according to any one of claims 1 to 10, wherein the image reading is performed for: 12. An image reading method for reading an image using a linear image sensor, comprising: dividing an area of a light receiving pixel row of the linear image sensor into a reference area and at least one other area; A reading step for reading out each area, and a signal level of an output pixel signal of the reference area based on the output pixel signals of the two areas read out in the reading step. And an adjusting step of adjusting the image reading so as to substantially match with the image reading method. 13. The adjusting step includes comparing each output pixel signal near a boundary position between the reference area and the other area, and based on a result of the comparison, a signal level of the output pixel signal of the other area. 14. The image reading method according to claim 12, wherein is adjusted. 14. The signal processing method according to claim 1, wherein the adjusting step includes: determining a signal level of the reference area and a signal level of the other area based on a ratio of a signal level of each output pixel signal near a boundary position between the reference area and the other area. 14. An image reading apparatus according to claim 13, further comprising: an estimation step of estimating a relationship between the image data and a correction step of correcting an output pixel signal of the other area based on an estimation result of the estimation step. Method. 15. The method according to claim 15, wherein the estimating step includes, for each of a plurality of level areas divided by a signal level, of the output pixel signal of the other area near a boundary position with the reference area, the reference area and the other area. 15. The image reading method according to claim 14, wherein a ratio between the signal levels of the respective output pixel signals is calculated. 16. The estimating step includes the step of, when a plurality of output pixel signals of the other area near the boundary position with the reference area are present in the same level area, the output pixel signal of the other area in the same level area is determined. 16. The image reading method according to claim 15, wherein an average value of the output pixel signals is calculated, and the signal level ratio is calculated based on the calculated average value. 17. The method according to claim 17, wherein when the output pixel signals of the other area in the vicinity of the boundary position with the reference area do not exist in the same level area by a predetermined number or more, the other level in the same level area is not included. 17. The image reading method according to claim 15, wherein the calculation of the ratio between the average value of the output pixel signals of the area and the signal level is prohibited. 18. The method according to claim 18, wherein when the difference between the two output pixel signals near the boundary position between the reference area and the other area is equal to or greater than a predetermined value, the two output pixel signals are compared with the signal level ratio. The image reading method according to any one of claims 14 to 17, wherein the image reading method is excluded from data used for calculating the image. 19. In the estimation step, for a level region in which there is no output pixel signal of the other region near a boundary position with the reference region, a ratio of the signal level in the level region is obtained by an interpolation operation. The image reading method according to any one of claims 15 to 18, wherein: 20. The estimating step includes the steps of: when an image of a new object to be read is read, and an output pixel signal of the other area near a boundary position with the reference area is newly obtained; 2. A ratio of the signal level in a level region corresponding to the output pixel signal is updated based on a newly obtained output pixel signal.
The image reading method according to any one of claims 4 to 19. 21. The tone number of the image in the output pixel signal after the signal level adjustment in the adjusting step is smaller than the tone number of the image in the output pixel signal before the signal level adjustment in the adjusting step. The image reading method according to any one of claims 12 to 20, wherein the method is set. 22. A shading correction step of performing shading correction on the output pixel signal read by the reading step, wherein the adjustment by the adjustment step is performed by the output pixel signal after the shading correction is performed by the shading correction step. The image reading method according to any one of claims 12 to 21, wherein the method is performed for: 23. A storage medium storing a program used in an image reading method for reading an image using a linear image sensor, wherein a region of a light receiving pixel row of the linear image sensor is a reference region and at least one other region. And a code for a reading step of reading output pixel signals of both areas for each area, and an output pixel signal of the other area based on the output pixel signals of both areas read by the code of the reading step. And a code for an adjusting step of adjusting the signal level of the reference pixel to substantially match the signal level of the output pixel signal of the reference area.