JP2000022904A - Image reader and image reading method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a high definition image by producing an image signal by performing an arithmetic mean operation of the pixel data of each pixel between adjacent pixels respectively in an oblique direction. SOLUTION: A glass plate is supported perpendicularly to the direction of an optical axis at the time of performing 1st scan and the glass plate is slightly inclined and shifted as much as 1/2 pixel pitch P of an optical axis CCD at the time of performing 2nd scan. And, balancing processing circuits 48 and 49 respectively calculates average values S31 and S32 from two pixel data strings S11 and S12. Next, balancing processing circuits 50 and 51 respectively calculate average values S33 and S34 from two pieces of pixel data strings S11 and S23 and pixel data strings S11 and S24. And, dot sequential processing circuits 52 and 53 alternately arrange pixel data strings S31 and S32 and pixel data strings S33 and S34 in 1/2 data cycle and produce pixel data strings S41 and S42. And, a line sequential processing circuit 54 alternately outputs the strings S41 and S42 every line to obtain a data pixel string S5 having double data amount in both horizontal/vertical scan directions.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an image reading apparatus and an image reading method.

[0002]

2. Description of the Related Art Conventionally, an image scanner using a CCD linear image sensor (hereinafter referred to as CCD) has been known as an image reading apparatus.

FIGS. 15 (a) and 15 (b) simply show a configuration example of what is generally called a flatbed type scanner. FIG. 15 (a) is a top view and FIG. 15 (b) is a side view. . D is a read original placed on a platen glass 150, and the reflected light illuminated by the light source 151 is turned back by mirrors 152, 153, and 154, and
5 forms an image on the CCD 156.

A light source 151 and mirrors 152, 153,
154, lens 155 and CCD 156 are the reading unit 1
57, the reading unit 157 is moved parallel to the platen glass 150 from left to right as viewed in FIG.
An image signal for one page is obtained from the CD 156. In this case, the direction from top to bottom in FIG. 15A is the main scanning direction, and the direction from left to right is the sub-scanning direction.

FIGS. 16 (a) and 16 (b) schematically show the structure of a CCD. In FIG.
Are photoelectric conversion pixel columns arranged one-dimensionally at equal pitches, and 202-a, b, c, d... Are photoelectric conversion pixel columns 201-a, b, c,. Reference numeral d denotes a transfer gate for transferring the photoelectrically converted charges, reference numeral 203 denotes a transfer unit for sequentially transferring the transferred charges, and reference numeral 204 denotes an output circuit for reading the transferred charges as an output signal in a line. FIG.
FIG. 16B shows the photoelectric conversion pixels 201-a and 201-b of FIG.
The part is shown enlarged.

As described above, the original D is illuminated linearly in the main scanning direction, and the optical image formed on the photoelectric conversion pixel rows 201-a, b, c, d...
It moves at a predetermined speed in the sub-scanning direction shown in FIG. Charges photoelectrically converted and accumulated in the photoelectric conversion pixel columns 201-a, b, c, d,... During a predetermined period in which the formed image moves from the position A to the position B shown in FIG. The image is transferred and then read from the output circuit 204 during a predetermined period during which the image formed moves from the position B to the position C. Thereafter, this is repeated to obtain a periodic line-sequential signal, that is, a main scanning line signal.

Generally, as shown in FIG. 16B, the distance AB (and the distance BC) is set to be equal to the photoelectric conversion pixel pitch P in the main scanning direction so that the resolution is equal in both the main scanning and sub-scanning directions. ing.

[0008]

In the prior art described above, if the resolution is to be increased, for example, by a factor of two, the photoelectric conversion pixel pitch P must be reduced to 1/2. The pixel size of a, b, c, d... has to be と も in both the main scanning and sub-scanning directions, and the period for the above readout has to be １ ／. Therefore, since the area of the photoelectric conversion pixel is reduced to 、 and the time required for the photoelectric conversion is reduced to 感 度, the sensitivity is reduced to ８ and there is a problem that the image quality is extremely deteriorated. Further, when the transfer speed is doubled, the transfer performance of the charge is deteriorated, and the heat generation and the power in the transfer unit are increased. Needless to say, these deteriorate the image quality of the image reading apparatus. Furthermore, as the pixel size decreases, it is necessary to improve the resolution of the lens itself, which increases the cost of the lens.

[0009] Among the above-mentioned problems, a method of increasing the size of the photoelectric conversion pixel and decreasing the imaging magnification of the lens can be considered for the lack of sensitivity. For example, if the size of the photoelectric conversion pixel is about 2.8 times in both the main scanning and sub-scanning directions, the sensitivity will be the same as the conventional one, but the size of the transfer unit will also be large, so that the transfer performance will deteriorate and heat will be generated. Is further increased, and the deterioration of the image quality is further increased. Also,
The chip size in the main scanning direction also becomes about 2.8 times, which causes a problem that the cost of the CCD and the lens is greatly increased.

In order to solve these problems, it is possible to shift the position of the optical image formed on the image sensor and the relative position between the photoelectric conversion pixels of the image sensor by a predetermined amount in the main scanning direction. The applicant of the present invention has filed an application for an image reading apparatus capable of obtaining a high-definition image by the pixel shifting means as Japanese Patent Application No. 10-11217.

For example, if two sub-scans are performed so that the pixel data of each image signal is shifted by approximately 1/2 of the pixel pitch, an arbitrary pixel at the time of each sub-scan is set to a predetermined image reading range. X from the end in the main scanning direction of the predetermined image reading range and the y-th line from the end in the sub-scanning direction.
And the reading position of the x-th pixel on the y-th line in the second sub-scan is different from the reading position of the x-th pixel on the y-line in the first sub-scan in the main scanning direction and When the pixel data is located at a position shifted from the pixel pitch by approximately １ ／ in both the sub-scanning directions, the pixel data at the x-th and x + 1-th intermediate positions of the y-th line in the first sub-scan is converted to the x-th pixel of the y-th line. Data and x + 1-th pixel data on the y-th line, 2
The x-th pixel data of the y-th line at the time of the second sub-scan and y
The pixel data at the intermediate position between the x-th y-th line and the y + 1-th line at the time of the first sub-scan is generated by adding four pixel data with the x-th pixel data of the -1st line.
X-th pixel data in the line and x in the y + 1 line
Since the pixel data is generated by adding the pixel data of the x-th pixel data of the y-th line and the (x−1) -th pixel data of the y-line at the time of the second sub-scan, The MTF characteristics are slightly reduced. Therefore, when a black line or the like in each of the main scanning direction and the sub-scanning direction is read, the black and white edges of the image data generated by adding the data of four pixels are slightly blurred, and this is repeated every other pixel. As a result, the image was rather unsightly.

An object of the present invention is to solve the above-mentioned problems and to provide a clear image reading apparatus and a clear image reading method which are low in cost, have high image quality, and have little reduction in MTF.

[0013]

Means for Solving the Problems In order to solve the above problems, the present invention is characterized in that an image sensor in which a plurality of photoelectric conversion pixels are arranged in a line and a document Scanning means for scanning in a sub-scanning direction orthogonal to a main scanning direction which is a direction of a linear reflected optical image incident on the image sensor; and a position of the optical image formed on the image sensor. A pixel shifting unit for shifting a relative position between the photoelectric conversion pixel and the pixel pitch of the image sensor in the main scanning direction by approximately １ ／, and controlling the scanning unit to control the image sensor. Twice at a pitch substantially equal to the pixel pitch of the image sensor and shifted in the sub-scanning direction by a position corresponding to approximately の of the pixel pitch of the image sensor in the sub-scanning direction. Rutotomoni, and controls the pixel shifting means, between the first sub-scan and the second sub-scan,
A control unit for performing a pixel shift of の of the pixel pitch, and performing an averaging operation between adjacent pixels in a diagonal direction on pixel data of each pixel obtained by the two sub-scans. And an image signal generating means for generating an image signal.

The feature of the invention described in claim 2 of the present application is that, in the invention described in claim 1,
In the image reading apparatus, the pixel shifting unit may include an optical system that optically changes an incident position of an incident image on a pixel of the image sensor.

The feature of the invention described in claim 3 of the present application is that, in the invention described in claim 1,
The image reading apparatus is configured such that the pixel shift unit optically changes an incident position of each pixel by moving the image sensor in the main scanning direction.

According to the invention described in claim 4 of the present application, an image sensor in which a plurality of photoelectric conversion pixels are arranged in a line, and a linear reflection optical image incident on the image sensor with respect to an original document. Scanning means for scanning in the sub-scanning direction orthogonal to the main scanning direction, the position of the optical image formed on the image sensor, and the relative position of the photoelectric conversion pixels in the main scanning direction. A pixel shifting means for shifting the pixel sensor by approximately の of a pixel pitch; controlling the scanning means and the pixel shifting means to perform sub-scanning twice by the scanning means; Control means for causing the pixel shift means to perform image shift by performing pixel shift substantially every half of the pixel pitch of the image sensor, the pixel shift means and the scanning means; Image signal generating means for generating an image signal from a plurality of pixel data obtained by the operation of the above, wherein the image signal generating means is moved in the sub-scanning direction by the scanning means every repetition cycle of the line-sequential image signal Is substantially equal to the pixel pitch of the image sensor, and the positions of the optical images of the respective line-sequential image signals formed on the image sensor by the two sub-scans are mutually set to the pixels of the image sensor. Approximate pitch 1
/ 2 is shifted in the sub-scanning direction by an amount corresponding to / 2, and an arbitrary pixel at the time of each sub-scan is set to the y-th line from the end of the predetermined image reading range in the sub-scanning direction, and to the main scanning of the predetermined image reading range. The x-th pixel on the y-th line at the time of the first sub-scan,
The reading position of the x-th pixel on the y-th line at the time of the second sub-scanning is approximately 1 / の of the pixel pitch in the main scanning direction and the sub-scanning direction.
When the positions are shifted by two, the x-th pixel data of the y-th line at the time of the first sub-scan and the x-th pixel data of the y-th line at the time of the second sub-scan are averaged. Is generated as new 2x-th pixel data of the 2y-th line, and the x-th pixel data of the y-th line in the first sub-scan and the (x−1) -th pixel data of the y-th line in the second sub-scan The sum of the pixel data and the average is generated as the 2x-1st pixel data on the new 2yth line, and the xth pixel data on the yth line and the second subscanning at the first subscanning Is added and averaged with the x-th pixel data of the y-1 line to generate new 2x-th pixel data of the 2y-1 line, and the x-th pixel data of the y-th line in the first sub-scan is obtained. Pixel data and y- at the second sub-scan
The image reading apparatus is characterized in that a value obtained by adding and averaging the (x-1) -th pixel data of the first line is generated as new 2x-1-th pixel data of the (2y-1) -th line.

According to the invention described in claim 5 of the present application, in the invention described in claim 1 or 4, the first sub-scanning direction and the second sub-scanning direction are opposite to each other. An image reading device is characterized.

According to the invention described in claim 6 of the present application, a plurality of photoelectric conversion pixels are arranged in a line, and an incident linear optical image is accumulated as signal charges in each of the photoelectric conversion pixels. An image sensor that outputs a line-sequential image signal every fixed period, and a document is scanned in a sub-scanning direction orthogonal to a main scanning direction that is a direction of a linear reflection optical image incident on the image sensor. Scanning means, a position of an optical image formed on the image sensor,
Controlling a relative position between the photoelectric conversion pixel and a pixel shift unit capable of shifting the relative position with respect to the pixel pitch of the image sensor in the main scanning direction by approximately １ ／, and controlling the scanning unit and the pixel shift unit; The distance in the sub-scanning direction that is moved by the scanning unit in each repetition cycle of the line-sequential image signal is set to approximately 略 of the pixel pitch of the image sensor, and the pixel is moved in each repetition cycle of the line-sequential image signal. A control unit for performing a pixel shift of approximately の of a pixel pitch of the image sensor by a shift unit; and a plurality of pixel data obtained by the operations of the control pixel shift unit and the scanning unit, and forming an image signal. Image signal generating means for generating an image signal, wherein the image signal generating means sets an arbitrary pixel to a y-th line from an end in a sub-scanning direction of a predetermined image reading range. And expressed as x th from the main scanning direction of the end portion of the predetermined image reading range, y-th line of x
When the reading position of the x-th pixel on the y + 1-th line is shifted from the reading position of the y-th pixel by approximately の of the pixel pitch in both the main scanning direction and the sub-scanning direction, x The pixel data of the y-th line and the x-th pixel data of the y + 1-th line are added and averaged to generate new x-th pixel data of the y-th line, and the x-th pixel data of the y-th line and the y + 1-th line The value obtained by averaging the pixel data of the (x−1) -th pixel of the x-th pixel is calculated as x−
Generated as the first pixel data, and averaging the x-th pixel data on the y-th line and the x-th pixel data on the y-1-th line, the x-th pixel on the new y-1-th line The x-th pixel data on the y-th line and the x-th pixel data on the y-th line are added and averaged, and the x-th pixel data on the new y-th line is calculated. An image reading apparatus configured to generate data is featured.

According to the invention described in claim 7 of the present application, in the invention described in claim 4 or 6, the pixel shifting means is disposed between a document table on which the document is placed and the image sensor. An image reading apparatus comprising a light refraction plate and means for changing the angle of the light refraction plate with respect to the optical axis is characterized. Further, according to the invention described in claim 8 of the present application, in the invention described in claim 4 or 6, the image reading device is characterized in that the pixel shifting means is means for moving the image sensor in the main scanning direction. I do.

According to a ninth aspect of the present invention, in the fourth or sixth aspect of the present invention, the image shifting means is means for moving the original platen or the original in the main scanning direction. A reading device is characterized.

According to a tenth aspect of the present invention, in the fourth aspect, the image sensor does not output signal charges accumulated in the photoelectric conversion pixels as line-sequential image signals. And a sweeping means for sweeping away, and when performing a pixel shift of approximately の of a pixel pitch of the image sensor, during a period in which the position of the optical image relative to the photoelectric conversion pixel is relatively moving. And an image reading apparatus configured to sweep away signal charges accumulated in the photoelectric conversion pixels by the sweeping means.

According to the invention described in claim 11 of the present application, an image sensor in which a plurality of photoelectric conversion pixels are arranged in a line, and a linear reflection optical image incident on the image sensor with respect to an original document. Scanning means for scanning in the sub-scanning direction orthogonal to the main scanning direction, the position of the optical image formed on the image sensor, and the relative position of the photoelectric conversion pixels in the main scanning direction. A method for controlling an image reading apparatus including a pixel shift unit capable of shifting the pixel pitch of the image sensor by approximately 1/2, wherein the scanning unit is controlled to be substantially equal to a pixel pitch of the image sensor. The position in the sub-scanning direction at the same pitch is set to approximately の of the pixel pitch of the image sensor.
Is performed twice in a relationship shifted in the sub-scanning direction by an amount equivalent to the pixel pitch, and the pixel shifting means is controlled to perform 1/1 of the pixel pitch between the first sub-scan and the second sub-scan. 2. An image in which an image signal is generated by performing two pixel shifts and performing an averaging operation between adjacent pixels in an oblique direction on pixel data of each pixel obtained by the two sub-scans. It is characterized by a reading method.

According to a twelfth aspect of the present invention, in the image reading method according to the eleventh aspect, the two sub-scanning directions are opposite in the first and second scanning directions. It is characterized by.

According to the thirteenth aspect of the present invention, there is provided an image sensor in which a plurality of photoelectric conversion pixels are arranged in a line, and an image of a linear reflected optical image incident on the image sensor with respect to a document. Scanning means for scanning in the sub-scanning direction orthogonal to the main scanning direction, the position of the optical image formed on the image sensor, and the relative position of the photoelectric conversion pixels in the main scanning direction. A pixel shifting means for shifting the pixel pitch of the image sensor by approximately １ ／, wherein a sub-scan is performed twice by the scanning means,
For each sub-scan, when the image is read by performing the pixel shift of approximately の of the pixel pitch of the image sensor by the pixel shift unit, the sub-unit moved by the scanning unit for each repetition cycle of the line-sequential image signal. The distance in the scanning direction is made substantially equal to the pixel pitch of the image sensor, and the positions of the optical images of the line-sequential image signals formed on the image sensor by the two sub-scans are mutually set to the image sensor. １ ／ of the pixel pitch of
Is shifted in the sub-scanning direction by an amount corresponding to the above, and an arbitrary pixel at the time of each sub-scanning is set to a y-th line from an end of the predetermined image reading range in the sub-scanning direction, and in the main scanning direction of the predetermined image reading range. Expressed as the x-th pixel from the end, the reading position of the x-th pixel on the y-th line in the second sub-scanning is compared with the reading position of the x-th pixel on the y-th line in the first sub-scanning.
If the pixel is located at a position shifted by approximately ず れ of the pixel pitch in both the main scanning direction and the sub-scanning direction, the x-th pixel data of the y-th line in the first sub-scanning and the y-th pixel data in the second sub-scanning
A value obtained by adding and averaging the x-th pixel data of the line is generated as the 2x-th pixel data of the new 2y-th line, and the x-th pixel data of the y-th line and the second time of the second sub-scan are obtained. Are added and averaged with the (x-1) -th pixel data of the y-th line at the time of the sub-scanning to generate new 2x-1-th pixel data of the 2y-th line, and the y-line at the time of the first sub-scanning An average of the x-th pixel data of the x-th pixel data and the x-th pixel data of the y-1 line at the time of the second sub-scan is generated as 2x-th pixel data of a new 2y-1 line. X-th pixel data on the y-th line in the first sub-scan and y-1 in the second sub-scan
An image reading method for generating an image signal by generating an average of the x-1 pixel data of the line and the 2x-1 pixel data of a new 2y-1 line is performed. Features.

According to a fourteenth aspect of the present invention, there is provided the image reading method according to the thirteenth aspect, wherein the second sub-scanning direction is opposite to the first sub-scanning direction. It is characterized by.

According to the invention of claim 15 of the present application, a plurality of photoelectric conversion pixels are arranged in a line, and an incident linear optical image is accumulated in each of the photoelectric conversion pixels as a signal charge. An image sensor that outputs a line-sequential image signal every fixed period, and a document is scanned in a sub-scanning direction orthogonal to a main scanning direction that is a direction of a linear reflection optical image incident on the image sensor. Scanning means, a position of an optical image formed on the image sensor,
A method of controlling an image reading apparatus comprising: a pixel shift unit configured to shift a relative position with respect to the photoelectric conversion pixel in the main scanning direction by approximately 画素 of a pixel pitch of the image sensor, Controlling the scanning means and the pixel shifting means, the distance in the sub-scanning direction moved by the scanning means for each repetition cycle of the line-sequential image signal, to about 1/2 of the pixel pitch of the image sensor, In addition, a plurality of pixels obtained by the operation of the scanning unit and the pixel shifting unit are caused to perform a pixel shift of approximately の of a pixel pitch of the image sensor by the pixel shifting unit in each repetition cycle of the line-sequential image signal. With respect to the pixel data, an arbitrary pixel is positioned at the y-th line from the end in the sub-scanning direction of the predetermined image reading range, and the end in the main scanning direction of the predetermined image reading range. Expressed as Luo x th, the reading position of the x-th pixel in the y-th line, y + 1 th line x
When the reading position of the 画素 th pixel is located at a position shifted by about の of the pixel pitch in both the main scanning direction and the sub-scanning direction, the x-th pixel data of the y-th line and the x-th pixel data of the y + 1-th line Are added and averaged to generate new x-th pixel data on the y-th line, and x
The value obtained by averaging the pixel data of the y-th line and the (x−1) -th pixel data of the (y + 1) -th line is calculated as x
-1st pixel data, the x-th pixel data of the y-th line and the x-th pixel data of the y-1 line are added and averaged, and the x-th pixel data of the new y-1 line is calculated. It is generated as pixel data, and the result of adding and averaging the x-th pixel data of the y-th line and the x-1-th pixel data of the y-th line is calculated as x-1 of the new y-1 line
The image reading method is characterized in that an image signal is generated by generating the image signal as the pixel data of the second order.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an image reading apparatus according to the present invention will be described below in detail with reference to the drawings.

(First Embodiment) FIG. 1 (a) is a structural view of a part of an image reading apparatus embodying the present invention as viewed from an original table side, and FIGS. It is an enlarged view of one part.

Reference numeral 11 denotes a glass plate, which is inserted between the imaging lens 155 and the CCD 156 in this embodiment. The configuration other than the glass plate 11 of the image reading apparatus is the same as that of the conventional example. The angle of inclination of the glass plate 11 can be changed within a predetermined range with respect to the optical axis.

In the above configuration, the two scans are both performed from left to right in FIGS. 15 (a) and 15 (b). First, at the time of the first scanning, the glass plate 11 is supported perpendicular to the optical axis direction as shown in FIG. Next, at the time of the second scanning, the glass plate 11 is slightly tilted as shown in FIG. 1C and shifted by １ ／ of the pixel pitch P of the optical axis CCD 156. Therefore, the glass plate 11
May be determined from the thickness and the refractive index of the glass plate 11 so that the shift amount of the optical axis becomes P / 2.

In the present embodiment, the scanning speed is controlled so that the distance in the sub-scanning direction in each scanning cycle of the line-sequential signal during each scan is substantially equal to the pixel pitch of the CCD 156. . Then, as shown in FIG. 16B, the positions of the optical images of the respective line-sequential signals formed on the CCD by the two scans are compared with each other as shown in FIG.
The readout timing of each line-sequential signal is shifted by about の of the repetition period of the line-sequential signal by an amount corresponding to approximately の of the pixel pitch P of D.

FIG. 2 is a diagram showing the relative movement of the optical image to be formed with the pixel position, focusing on one pixel of the photoelectric conversion pixel.
It is considered that the position of the optical image at each scanning does not move in the main scanning direction, but the pixel position moves. In FIG. 2, reference numeral 21 shown by a solid line denotes a main scanning line (this is referred to as a y-th line) which is a predetermined line from an end in the sub-scanning direction of a predetermined image reading range at the time of the first scanning. The x-th pixel position in the scanning direction, indicated by a dotted line 22, is the x-th pixel in the main scanning direction of the y-th line from the end in the sub-scanning direction of the predetermined image reading range at the time of the second scan. The center position of each pixel is shifted by P / 2 in both main scanning and sub-scanning.

The center position of the pixel moves from position A to position B on the y-th line during the first scan and from position B to position C on the y + 1-th line during the repetition cycle of the line-sequential signal. . Similarly, at the y-th line at the time of the second scanning, it moves from position D to position E, and at the y + 1-th line, it moves from position E to position F. Each travel distance is equal to P.

Therefore, in the above configuration, the pixel data at the time of the first scan and the pixel data at the time of the second scan are
In both the main scanning and sub-scanning directions, spatial sampling is performed at positions different from each other by P / 2.

FIG. 3 shows a method of using the pixel data obtained by the two scans thus obtained to generate new pixel data in which the adjacent pixel data pitch becomes 1/2 times in both the main scanning and sub-scanning directions. In the figure, the solid line indicates the position of the pixel data in the first scan, the dotted line indicates the position of the pixel data in the second scan, and the x-th pixel data on the y-th line in the first scan. And D2 (x, y) as the x-th pixel data of the y-th line in the second scanning.
y).

Then, D1 (x, y) and D2 (x, y)
Are added and averaged as the 2x-th pixel data of the new 2y line, and D1 (x, y) and D2 (x−1,
The data obtained by averaging with y) is added to the second
Let x-1 th pixel data be D1 (x, y) and D2
The data obtained by averaging with (x, y-1) is added to a new 2y-
As the 2x-th pixel data of the first line, D1 (x,
The data obtained by averaging y) and D2 (x-1, y-1) is used as the 2x-1st pixel data of the new 2y-1 line.

As described above, the generation of pixel data by averaging four times related to D1 (x, y) is performed for all the first pixels.
By performing the process on the pixel data at the time of scanning, a data amount four times as large as the pixel data amount obtained by one sub-scan is obtained.

FIG. 4 is a circuit block diagram for performing the averaging process as described above. 4, reference numeral 40 denotes an image pickup device such as a CCD as an image pickup means; 41, a signal amplifier;
And A and D converters, and 43 and 44 are page memories capable of storing data of respective image data obtained by two scans.

45 and 47 are memories capable of storing one pixel, 46 are memories capable of storing one line, and 48 and 4
9, 50 and 51 are averaging circuits for two pixel data,
Reference numerals 52 and 53 denote a dot sequential processing circuit for two pixel data,
Reference numeral 4 denotes a line sequential processing circuit for a two-line pixel data sequence.

Reference numeral 55 denotes an interface (IF) circuit for performing data communication with the PC 56. The processing sequence of these circuit blocks is controlled by the CPU 57.

FIG. 5 is a signal waveform diagram showing only one gradation data of a pixel data column of each circuit block portion, and the operation of the circuit block having the above configuration will be described in detail with reference to FIG. S
11 and S21 are pixel data strings output from the page memories 43 and 44, respectively. S22 is an output obtained by delaying S21 by one pixel via the one-pixel memory 45, and S23 is S23.
21 is an output obtained by delaying one line via the one-line memory 46.

S24 is an output obtained by delaying S23 by one pixel via the one-pixel memory 47.

In order to obtain an average value corresponding to FIG. 4, first, an averaging circuit 48 calculates an average value S31 from the two pixel data strings S11 and S21. , S22, an average value S32 is calculated from the two pixel data strings.

Next, S11 and S2 are performed by the averaging circuit 50.
The average value S33 is calculated from the two pixel data columns of No. 3 and the average value processing circuit 51 calculates the average value S34 from the two pixel data columns of S11 and S24.

Then, in the dot sequential processing circuit 52, S31
And the pixel data strings of S32 are alternately arranged at a data cycle of 、 to generate S41. Similarly, the dot sequential processing circuit 42
Then, the pixel data strings of S33 and S34 are alternately arranged at a data period of 、 to generate a pixel data string S42.

Then, the line-sequencing processing circuit 54 executes S41.
And the pixel data string of S42 are alternately output line by line,
As a result, a pixel data string S5 having twice the data amount in both the main scanning and sub-scanning directions is obtained.

In this embodiment, the image data memory is mounted on the image reading device side. However, the image data memory may be mounted on the PC 56 side. It can be said that it is more realistic to use a memory or the like built in the device. In this case, control is performed such that the above-described writing and reading of the memory and the dot sequential processing are performed on the PC 56 side by application software.

Here, the sensitivity distribution in the case of averaging the two pixel data in this embodiment will be described.

First, each photoelectric conversion pixel of the CCD 156 is a square pixel having an aperture ratio of 100%. Instead of moving the optical image by the pixel pitch P in the sub-scanning direction in each repetition cycle of the main scanning line, it is assumed that the photoelectric conversion pixel itself moves by almost P in the direction opposite to the sub-scanning direction. Therefore, when the sensitivity distribution of the one pixel data D1 (x, y) is three-dimensionally shown, as shown in FIG.
It becomes a trihedron with F as the top. These volumes become P ² , and the sensitivity of the top EF becomes the maximum value “1”.

Next, as shown in FIG.
For pixel data D1 (x, y) and D2 (x, y),
FIG. 7 shows a three-dimensional representation of the respective sensitivity distributions superimposed. As in FIG.
The trihedron with F as the top is the sensitivity distribution of the pixel data D1 (x, y), the trihedron with the square GHIJ as the bottom and KL as the top is the sensitivity distribution of the pixel data D2 (x, y),
These are superimposed. That is, the square M
FNK is defined as the maximum sensitivity “0.75” in the sensitivity distribution, and its center is set as the sensitivity center of gravity. The sensitivity gradually decreases in the sub-scanning direction from the sensitivity center of gravity, and 0.375 in the main scanning direction. The sensitivity distribution is such that the sensitivity is obtained.

As is clear from the comparison between FIG. 6 and FIG.
In the sensitivity distribution obtained when the pixel data is averaged, the sensitivity distribution slightly widens in both the main scanning direction and the sub-scanning direction. It does not decline.

Similarly to the above, the two pixel data D1 (x, y), D2 (x-1, y) and D1 (x, y) in FIG.
And D2 (x, y-1), D1 (x, y) and D2 (x-
Inspection of the sensitivity distribution of the new pixel data obtained by adding and averaging each of (1, y-1) shows that the sensitivity distribution has the center of gravity at the center of the square KNCQ, the square RHSF, and the square GRFM in FIG. Therefore, it is possible to read a density change pattern on a document in which the distance P / 2 in the main scanning / sub-scanning direction of these four squares is set to 繰 り 返 し of the repetition period.

As described above, in the case of this embodiment, MT
Although F is not greatly reduced as compared with FIG. 6, this slight deterioration can be corrected by a simple digital filter in both main scanning and sub-scanning. For example, as shown in FIG. 8, a target pixel 1 obtained by averaging two pixel data
By forming a matrix filter such that the coefficient to be multiplied by 71 is 9/5 and the coefficient to be multiplied by two in each of the main scanning and sub-scanning directions with respect to the target pixel 171 is −１, FIG. Square MFN including sensitivity center of gravity position shown
The sensitivity of K can be set to “1”, and the MTF can be sufficiently increased.

As described above, in this embodiment, a high-definition image is obtained in which the number of spatial samplings is doubled in both the main scanning and sub-scanning directions as compared with image data obtained by one sub-scanning. be able to.

In this embodiment, the sub-scanning directions of the two scans are the same, but the sub-scanning direction may be reversed between the first scan and the second scan. I do not care. That is, the original is scanned from the opposite end without returning to the original position after the first scan. In this case, reading from the page memory 44 storing the image data at the time of the second scanning in FIG. 4 may be performed in the reverse order in the sub-scanning direction.

Image data D (x, y) at the time of the first scan
The second image data at the same position as that of D (x, z−y + 1) where z is the total number of scanning lines in a predetermined image reading range.
Given as Thus, a high-definition image can be obtained by the averaging process and the dot-sequentialization / line-sequentialization process similar to the above-described method.

As described above, by setting the sub-scanning directions to be opposite in the first and second scans, it is possible to shorten the entire reading time as compared with the case of the same direction.

(Second Embodiment) In this embodiment, the number of sub-scannings is only one, and the distance in the sub-scanning direction moved by the scanning means in each repetition cycle of the line-sequential signal is determined by the distance between the photoelectric conversion pixels. The pixel is shifted by approximately P / 2 units in the main scanning direction by a pixel shifting unit which is set to be approximately の of the pitch P and in each repetition cycle of the line-sequential signal. The pixel shifting means is the same as that of the first embodiment, and uses a glass plate 11 as shown in FIG.

The operation of the above configuration will be described with reference to FIG. FIG. 8 shows the relative movement of the optical image to be formed with the pixel position, focusing on one pixel of the photoelectric conversion pixel. The position of the optical image of each main scanning line is not shifted in the main scanning direction. Think of the position as moving. In FIG. 8, reference numeral 81 indicated by a solid line denotes an x-th pixel in the main scanning direction on a main scanning line (this is referred to as a y-th line) which is a predetermined line from an end in the sub-scanning direction of a predetermined image reading range. The position, indicated by the dotted line 82, is the x-th pixel position of the y + 1 line, and the solid line 83 is the x-th pixel position of the y + 2 line. The center position A of the pixel on the y-th line is first moved to the position B by the pixel shifting means during the repetition cycle of the line-sequential signal, and then moved from the position B to y + by the scanning in the sub-scanning direction.
It moves to the center position C of the pixel on the first line.

Then, during the repetition period of the next line-sequential signal, the pixel shift means moves from position C to position D,
Next, with the scanning in the sub-scanning direction, the pixel moves from the position D to the center position E of the pixel on the y + 2 line. That is, the moving distance of the center position of the pixel in both the main scanning direction and the sub-scanning direction is P / 2.
Becomes

Accordingly, in the above configuration, the pixel data on the y-th line and the pixel data on the y + 1-th line are
In both the sub-scanning directions, spatially different positions are different from each other by P / 2.

At this time, the distance L in the sub-scanning direction from the position A to the position B and from the position C to the position D is proportional to the moving time of the optical image by the pixel shifting means. If this movement time is sufficiently shorter than the repetition cycle of the line-sequential signal, the sensitivity of this pixel in one cycle of the line-sequential signal due to the signal charges photoelectrically converted and accumulated during the movement from position A to position C FIG. 9 shows a three-dimensional representation of the distribution. That is, in FIG. 9, a tetrahedron-shaped sensitivity distribution having the square ABCD as the bottom surface and the square EFGH as the top surface is obtained, and the sensitivity of the square EFGH is “1”. Further, a three-dimensional representation of the sensitivity distribution during the period of movement from the position C to the position E is a distribution shifted by P / 2 in both the main scanning and the sub-scanning from FIG.

FIG. 10 shows a method for generating new pixel data in which the pitch of adjacent pixel data is halved in both the main scanning and sub-scanning directions using the pixel data obtained by such a scanning method. In the same figure, 101 shown by a solid line is D
(X, y), 102 and 103 indicated by dotted lines are defined as x-th and x−1-th pixel data on the (y + 1) th line, respectively.
(X, y + 1) and D (x-1, y + 1).
The data obtained by averaging D (x, y) and D (x, y + 1) is used as the 2x-th pixel data of the new y-th line, and D (x, y) and D (x-1, y + 1) are obtained. The data obtained by adding and averaging the 2x-1st pixel data on the new y-th line is used.

As described above, 2 related to D (x, y)
Generating the pixel data by the averaging of the times is performed for all the pixel data of the y line, so that the pixel data amount of the y line in the main scanning direction can be doubled.

FIG. 11 is a circuit block diagram for performing the averaging process as described above. 11, components having the same functions as those in FIG. 4 are denoted by the same reference numerals, and description thereof will be omitted. 11
1 is a memory for one line, 112 is a memory for one pixel,
113 and 114 are averaging circuits for two pixel data,
Reference numeral 115 denotes a dot-sequential processing circuit for two pixel data.
Is an IF circuit for performing data communication with the PC 118, and the processing sequence of these circuit blocks is the CPU 1
17.

FIG. 12 is a signal waveform diagram showing only one gradation data of a pixel data column of each circuit block portion, and the operation of the circuit block having the above configuration will be described in detail with reference to FIG.
S1 is a pixel data string output from the AD converter 41, S2 is an output of S1 through the one-line memory 111, and S3 is an output of S2 through the one-pixel memory 112.

In order to obtain an average value corresponding to FIG.
The averaging circuit 113 calculates an average value S4 from the two pixel data strings S1 and S2, and the averaging circuit 114 calculates an average value S5 from the two pixel data strings S1 and S3. Next, in the dot sequential processing circuit 115, S4 and S5
Are alternately arranged at a data period of 1/2, and S6
Generate By repeating this for each line, a pixel data string having twice the data amount in both main scanning directions can be obtained.

As described in the first embodiment, the image data memory is mounted on the image reading device side.
It can be mounted on the C118 side without any problem. In this case, the writing and reading of the memory and the dot-sequential processing may be controlled by the application software on the PC 118 side.

FIG. 13 shows the sensitivity distribution of the two-pixel data thus obtained after the averaging process. That is, the sensitivity distribution of the pixel data D (x, y) in FIG. 10 is distributed as shown by the square ABCD as described in FIG. 9, and the sensitivity distribution of the pixel data D (x, y + 1) is the square IJKL. Are distributed as shown in FIG. As is apparent from FIG. 13, by using the average value of the two-pixel data, the position of the center of gravity of the sensitivity becomes the center of the line segment MG having the length P / 2. Also, the line segment MG
The maximum sensitivity is "1.0" on the line of, and the sensitivity is "0.5" from P / 4 to 3P / 4 in both the left and right directions in the main scanning direction from the center of the line segment MG. The sensitivity distribution in the sub-scanning direction gradually attenuates as the distance from the line segment MG increases in both the upper and lower directions, and becomes zero at the distance P. Accordingly, the sensitivity distribution becomes narrower than the sensitivity distribution of FIG. 7 shown in the first embodiment, and as a result, the MTF is slightly increased, so that a higher-definition image can be read.

On the other hand, if the moving time of the optical image by the pixel shifting means cannot be ignored compared to the repetition period of the line-sequential signal, the signal charge photoelectrically converted and accumulated during the period from position A to position B in FIG. Can be swept away.

FIG. 14 shows an example of the configuration of a CCD linear image sensor suitable for such a purpose. In FIG. 14, 131-a, b, c, d,... 132-a,
, and 135-a, b, c, d... are transfer gates for transferring charges photoelectrically converted by the photoelectric conversion pixel columns 131-a, b, c, d.
a transfer unit for sequentially transferring the charges transferred by a, b, c, d,..., an output circuit 134 for reading the transferred charges as an output signal in a line, and 136 a transfer gate 135
-A drain that sweeps away the charges transferred by a, b, c, d ...

In the above configuration, during the period from position A to position B in FIG.
The electric charges photoelectrically converted at d ... are transferred to transfer gates 135-a,
By turning on b, c, d...
Swept away. Thereafter, the transfer gates 135-a, b,
With c, d... turned OFF, the charges photoelectrically converted by the photoelectric conversion pixel columns 131-a, b, c, d... during the period from the position B to the position C are transferred to the transfer gates 132-a, b, c, d. Are turned on to transfer to the transfer section 133 and output through the output circuit 134.

By repeating the above, a line-sequential signal that does not include electric charges accumulated during the period when the optical image is moving can be obtained by the pixel shifting means. 13, which is almost the same.

As described above, in this embodiment, a higher-definition image quality can be obtained by scanning only once in the sub-scanning direction than in the first embodiment, and compared with the first embodiment. Thus, the entire scanning time can be reduced.

In the first and second embodiments described above,
Although the glass plate 11 is inserted between the imaging lens 155 and the CCD 156 in FIG. 1 as a means for shifting pixels in the main scanning direction, it may be located anywhere between the original and the CCD. What is necessary is just to determine the inclination from the thickness and the refractive index of the glass plate so that the required shift amount can be realized on the photoelectric conversion pixels of the CCD.

As a means for shifting pixels in the main scanning direction, a method of moving the CCD 156 by a necessary amount in the main scanning direction, or a method of moving the original table 150 or the original D itself in FIG. The method can also be easily configured.

Further, in the embodiments described so far, an image reading apparatus using a CCD linear image sensor has been described. However, the present invention can be applied to an image reading apparatus using a contact linear image sensor. In this case, as the pixel shifting means in the main scanning direction, a method of moving the contact linear image sensor, the document table, or the document itself by a necessary amount in the main scanning direction can be applied.

Further, in the embodiments described so far, the so-called flatbed type image reading apparatus having a document table has been described. However, the present invention is a so-called sheet feed type in which the document itself is moved in the sub-scanning direction and scanned. It is also possible to apply the present invention to an image reading apparatus. In that case, as the pixel shifting means in the main scanning direction, a method of moving the contact linear image sensor or the original document by a necessary amount in the main scanning direction can be applied.

[0079]

As described above, according to the present invention, an image read by shifting the spatial sampling position by a predetermined amount in both the main scanning and sub-scanning directions without increasing the number of pixels of the image sensor in order to increase the resolution. , The number of spatial samplings can be doubled, so that a high-definition image can be obtained.

[Brief description of the drawings]

FIG. 1 illustrates an image reading apparatus according to a first embodiment of the present invention.
FIG. 2 is a configuration diagram of a part viewed from a document table side.

FIG. 2 is a diagram illustrating the arrangement of pixels and a relative position of an optical image of the image reading apparatus according to the first embodiment of the present invention.

FIG. 3 is a layout diagram of pixel data of the image reading apparatus according to the first embodiment of the present invention.

FIG. 4 is a circuit block diagram of the image reading apparatus according to the first embodiment of the present invention.

FIG. 5 is a signal waveform diagram for explaining the circuit block diagram of FIG. 4;

FIG. 6 is a sensitivity distribution diagram of one pixel data of FIG. 3;

FIG. 7 is a sensitivity distribution after averaging processing of the two-pixel data in FIG. 3;

FIG. 8 is a diagram illustrating an example of matrix coefficients of a digital filter for correcting MTF according to the first embodiment.

FIG. 9 is a diagram illustrating an arrangement of pixels and a relative position of an optical image of an image reading apparatus according to a second embodiment of the present invention.

FIG. 10 is a sensitivity distribution diagram of one pixel data of the image reading apparatus according to the second embodiment of the present invention.

FIG. 11 is a layout diagram of pixel data of an image reading apparatus according to a second embodiment of the present invention.

FIG. 12 is a circuit block diagram of an image reading apparatus according to a second embodiment of the present invention.

FIG. 13 is a signal waveform diagram for explaining the circuit block diagram of FIG.

FIG. 14 is a sensitivity distribution diagram after the averaging process of the two-pixel data of FIG. 11;

FIG. 15 is a configuration diagram of a CCD linear image sensor used in a second embodiment of the present invention.

FIG. 16 is a configuration diagram of a conventional image reading apparatus.

FIG. 17 is a configuration diagram of a CCD linear image sensor used in a conventional example.

 ────────────────────────────────────────────────── ─── Continued on the front page F term (reference) 5C072 AA01 BA04 DA02 DA21 DA23 EA05 FB23 MB01 MB04 MB08 TA04 UA09 UA11 UA20

Claims (15)

[Claims] An image sensor in which a plurality of photoelectric conversion pixels are arranged in a line, and a sub-scanning direction orthogonal to a main scanning direction which is a direction of a linear reflection optical image incident on the image sensor with respect to a document. A scanning unit that scans in a scanning direction, a position of an optical image formed on the image sensor, and a relative position between the photoelectric conversion pixel and the pixel are shifted by a half of a pixel pitch of the image sensor in the main scanning direction. Controlling the scanning means so that the position in the sub-scanning direction is substantially equal to the pixel pitch of the image sensor, and the position in the sub-scanning direction is equivalent to approximately １ ／ of the pixel pitch of the image sensor. The pixel shift is performed twice in the sub-scanning direction by the same amount, and the pixel shift unit is controlled to control the pixel pitch between the first sub-scan and the second sub-scan. 1/2 of j
A control unit for performing pixel shift of (a), and an image for generating an image signal by performing an averaging operation between adjacent pixels in a diagonal direction on pixel data of each of the pixels obtained by the two sub-scans. An image reading apparatus, comprising: signal generation means. 2. The image reading apparatus according to claim 1, wherein the pixel shift unit has an optical system that optically changes an incident position of an incident image on a pixel of the image sensor. 3. The pixel shifter according to claim 1, wherein the pixel shift unit optically changes an incident position on each pixel by moving the image sensor in the main scanning direction. An image reading apparatus, comprising: 4. An image sensor in which a plurality of photoelectric conversion pixels are arranged in a line, and a sub-scanner orthogonal to a main scanning direction which is a direction of a linear reflection optical image incident on the image sensor with respect to a document. A scanning unit that scans in a scanning direction, a position of an optical image formed on the image sensor, and a relative position between the photoelectric conversion pixel and the pixel are shifted by a half of a pixel pitch of the image sensor in the main scanning direction. Controlling the scanning means and the pixel shifting means, performing the sub-scanning twice by the scanning means, and setting the pixel pitch of the image sensor of the image sensor by the pixel shifting means for each sub-scanning. Control means for performing image shift by performing pixel shift every half, and a plurality of pixel data obtained by the operation of the pixel shift means and the scanning means. Image signal generating means for generating an image signal, the image signal generating means, the distance in the sub-scanning direction to be moved by the scanning means for each repetition cycle of the line-sequential image signal, the pixel pitch of the image sensor The positions of the optical images of the line-sequential image signals formed on the image sensor by the two sub-scans are substantially equal to each other, and the positions of the optical images are approximately 互 い に of the pixel pitch of the image sensor.
In the sub-scanning direction, an arbitrary pixel at the time of each sub-scanning is shifted from the end of the predetermined image reading range in the sub-scanning direction to the y-th line, and in the main scanning direction of the predetermined image reading range. Expressed as the x-th pixel from the end, the reading position of the x-th pixel on the y-th line in the second sub-scanning is compared with the reading position of the x-th pixel on the y-th line in the first sub-scanning. If the pixel is located at a position shifted by approximately ず れ of the pixel pitch in both the main scanning direction and the sub-scanning direction, the x-th pixel data of the y-th line in the first sub-scanning and the y-th pixel data in the second sub-scanning A value obtained by averaging the x-th pixel data of the line is generated as 2x-th pixel data of a new 2y-th line, and the x-th pixel data of the y-th line in the first sub-scan and the second x-th pixel data are generated. And the x-1st pixel data of the y-th line in the sub-scanning The ones that were average, a new 2y line of 2x
-1st pixel data is generated, and the x-th pixel data of the y-th line in the first sub-scan and the x-th pixel data of the y-th line in the second sub-scan are averaged. Is generated as 2x-th pixel data of a new 2y-1 line, the x-th pixel data of the y-th line in the first sub-scan, and the y-th pixel data of the y-1 line in the second sub-scan An image reading apparatus configured to generate an average of x-1 pixel data and 2x-1 pixel data of a new 2y-1 line as 2x-1 pixel data. 5. The method according to claim 4, wherein the first sub-scanning direction and the second sub-scanning direction are
An image reading apparatus, wherein the directions are opposite to each other. 6. An image in which a plurality of photoelectric conversion pixels are arranged in a line, an incident linear optical image is stored as signal charges in each of the photoelectric conversion pixels, and is output as a line-sequential image signal at regular intervals. A sensor, scanning means for scanning a document in a sub-scanning direction orthogonal to a main scanning direction which is a direction of a linear reflection optical image incident on the image sensor, and an image formed on the image sensor Pixel shifting means for shifting a position of an optical image and a relative position between the photoelectric conversion pixels in the main scanning direction by approximately 画素 of a pixel pitch of the image sensor; and the scanning means and the pixel shifting. And controlling the distance in the sub-scanning direction moved by the scanning means for each repetition cycle of the line-sequential image signal to about 1/2 of the pixel pitch of the image sensor. And, by the pixel shifting means for each repetition cycle of the line-sequential image signal,
A control unit for performing a pixel shift of approximately の of a pixel pitch of the image sensor; an image for generating an image signal by combining a plurality of pixel data obtained by the operation of the control pixel shift unit and the scanning unit A signal generating unit, wherein the image signal generating unit is configured to set an arbitrary pixel from a y-th line from an end in a sub-scanning direction of a predetermined image reading range and from an end in a main scanning direction of the predetermined image reading range. It is represented as the x-th pixel, and the reading position of the x-th pixel on the y-th line is represented by y
When the reading position of the x-th pixel on the + 1-th line is located at a position shifted by approximately の of the pixel pitch in both the main scanning direction and the sub-scanning direction, the x-th pixel data on the y-th line and y + 1
A value obtained by averaging the x-th pixel data on the line is generated as new x-th pixel data on the y-th line, and the x-th pixel data on the y-th line and x on the y + 1-th line
A value obtained by adding and averaging the (-1) -th pixel data is generated as new (x-1) -th pixel data on the y-th line, and the x-th pixel data on the y-th line and x on the (y-1) -th line
The value obtained by averaging the pixel data of the
Generated as x-th pixel data on the first line, x-th pixel data on the y-th line and x on the y-1 line
An image reading apparatus characterized in that the image reading apparatus is configured to add and average the (-1) -th pixel data and the (x-1) -th pixel data on a new (y-1) -th line. 7. The pixel shifter according to claim 4, wherein the pixel shifting unit includes a light refraction plate disposed between a document table on which the document is placed and the image sensor, and an angle of the light refraction plate with respect to an optical axis. An image reading apparatus, comprising: means for changing. 8. An image reading apparatus according to claim 4, wherein said pixel shift means is means for moving said image sensor in a main scanning direction. 9. The image reading apparatus according to claim 4, wherein the pixel shifting unit is a unit that moves the document table or the document itself in a main scanning direction. 10. The image sensor according to claim 4, wherein the image sensor has sweeping means for sweeping out signal charges accumulated in the photoelectric conversion pixels without outputting the signal charges as line-sequential image signals. When shifting the pixel by approximately １ ／ of the pitch, the signal charge accumulated in the photoelectric conversion pixel is removed during the period in which the position of the optical image with respect to the photoelectric conversion pixel is relatively moving. An image reading apparatus characterized in that the image reading apparatus is configured to be swept away. 11. An image sensor in which a plurality of photoelectric conversion pixels are arranged in a line, and a sub-scanning direction orthogonal to a main scanning direction which is a direction of a linear reflection optical image incident on the image sensor with respect to a document. Scanning means for scanning in a scanning direction, a position of an optical image formed on the image sensor,
A method of controlling an image reading apparatus comprising: a pixel shift unit configured to shift a relative position with respect to the photoelectric conversion pixel in the main scanning direction by approximately 画素 of a pixel pitch of the image sensor, A relationship in which the scanning unit is controlled to shift the position in the sub-scanning direction in the sub-scanning direction by a pitch substantially equal to the pixel pitch of the image sensor and by an amount corresponding to approximately の of the pixel pitch of the image sensor. Is performed twice, and the pixel shift unit is controlled to perform a half of the pixel pitch between the first sub-scan and the second sub-scan.
The pixel data of each pixel obtained by the two sub-scans is averaged between adjacent pixels in an oblique direction to generate an image signal. Characteristic image reading method. 12. The image reading method according to claim 11, wherein the two sub-scanning directions are opposite in the first and second scanning directions. 13. An image sensor in which a plurality of photoelectric conversion pixels are arranged in a line, and a sub-scanning direction orthogonal to a main scanning direction, which is a direction of a linear reflection optical image incident on the image sensor, with respect to a document. Scanning means for scanning in a scanning direction, a position of an optical image formed on the image sensor,
A method of controlling an image reading apparatus, comprising: a pixel shift unit configured to shift a relative position with respect to the photoelectric conversion pixel in the main scanning direction by approximately の of a pixel pitch of the image sensor; When the sub-scan is performed twice by the scanning unit, and the image is read by performing the pixel shift by approximately 画素 of the pixel pitch of the image sensor by the pixel shifting unit for each sub-scan, and performing the image reading, The distance in the sub-scanning direction moved by the scanning means in each repetition period is made substantially equal to the pixel pitch of the image sensor, and the line-sequential image signals formed on the image sensor by the two sub-scans Are shifted in the sub-scanning direction by an amount corresponding to approximately one-half of the pixel pitch of the image sensor. Are represented as the y-th line from the end in the sub-scanning direction of the predetermined image reading range and the x-th from the end in the main scanning direction of the predetermined image reading range. Position where the reading position of the x-th pixel on the y-th line at the time of the second sub-scanning is shifted from the reading position of the x-th pixel by approximately 画素 of the pixel pitch in both the main scanning direction and the sub-scanning direction. , The x-th pixel data of the y-th line at the time of the first sub-scan and the x-th pixel data of the y-th line at the time of the second sub-scan are added and averaged to obtain a new average. It is generated as 2x-th pixel data on the 2y-th line, and the x-th pixel data on the y-th line in the first sub-scan and the (x−1) -th pixel data on the y-line in the second sub-scan The result of the averaging is 2x on a new 2y line.
-1st pixel data is generated, and the x-th pixel data of the y-th line in the first sub-scan and the x-th pixel data of the y-th line in the second sub-scan are averaged. Is generated as 2x-th pixel data of a new 2y-1 line, the x-th pixel data of the y-th line in the first sub-scan, and the y-th pixel data of the y-1 line in the second sub-scan Image reading is characterized in that an image signal is generated by generating an average of the x-1 pixel data and the 2x-1 pixel data of a new 2y-1 line. Method. 14. The image reading method according to claim 13, wherein a second sub-scanning direction is reversed with respect to the first sub-scanning direction. 15. An image in which a plurality of photoelectric conversion pixels are arranged in a line, an incident linear optical image is stored as signal charges in each of the photoelectric conversion pixels, and is output as a line-sequential image signal at regular intervals. A sensor, scanning means for scanning a document in a sub-scanning direction orthogonal to a main scanning direction which is a direction of a linear reflected optical image incident on the image sensor, and an image formed on the image sensor The relative position between the position of the optical image and the photoelectric conversion pixel is set to approximately １ ／ of the pixel pitch of the image sensor in the main scanning direction.
A method for controlling an image reading apparatus including a pixel shifting unit capable of shifting, wherein the scanning unit and the pixel shifting unit are controlled, and the scanning unit controls the repetition period of the line-sequential image signal by the scanning unit. The distance moved in the sub-scanning direction is set to approximately の of the pixel pitch of the image sensor, and the pixel shifting unit is provided for each repetition cycle of the line-sequential image signal.
A pixel shift of approximately の of a pixel pitch of the image sensor is performed, and a plurality of pixel data obtained by the operations of the scanning unit and the pixel shift unit are used to perform arbitrary sub-scanning of a predetermined image reading range on a predetermined pixel. The y-th line from the end in the direction, and the x-th from the end in the main scanning direction of the predetermined image reading range, with respect to the reading position of the x-th pixel in the y-line,
When the reading position of the x-th pixel on the y + 1-th line is located at a position shifted by approximately 略 of the pixel pitch in both the main scanning direction and the sub-scanning direction, the x-th pixel data on the y-th line and y +
An average of the x-th pixel data of the first line and the x-th pixel data of the y-th line is generated as new x-th pixel data of the y-th line.
A value obtained by adding and averaging the (-1) -th pixel data is generated as new (x-1) -th pixel data on the y-th line, and the x-th pixel data on the y-th line and x on the (y-1) -th line
The value obtained by averaging the pixel data of the
Generated as x-th pixel data on the first line, x-th pixel data on the y-th line and x on the y-1 line
An image reading method, characterized in that an image signal is generated by generating a value obtained by averaging the (-1) -th pixel data and the (x-1) -th pixel data on a new (y-1) -th line. .