JPH1028206A - Picture reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ease a restriction of the direction of setting at the time of reading a spread original, and to improve practical use by reducing the load of an operation. SOLUTION: This is an image picture reader, equipped with an image pickup device which converts an original image into an electric signal for reading an original picture by sub-dividing it into pixels by main scanning and sub- scanning. This device is provided with means 18a and 18b for photographing end faces in two directions, that is, a main scanning direction and a sub-scanning direction in an original BD in a spread state, direction-discriminating means for discriminating the spread direction of the oriental, based on the photographic information of the end face in each direction indicating the curved state of the original surface, and control means for operating the control, corresponding to the curved state of the spread direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus suitable for reading bound originals such as books and magazines.

[0002]

2. Description of the Related Art An image reading apparatus called a book scanner has been commercialized. In this apparatus, an image pickup system is arranged above a document table, and an open space having a height of several tens cm exists between the document table and the image pickup system. When reading a book-shaped original such as a book or magazine (this is referred to as a “book original”), the user sets the book original upward on a platen with the book original opened. The illumination lamp is turned on in response to the start key being turned on, and first, preliminary scanning for measuring the reading environment is performed. The operation is set based on the information obtained by the preliminary scanning, and then the main scanning is started. In the main scanning, the read images are sequentially output to the external device. If the external device is a printer, a copied image is formed in real time. When a book scanner is used, pages can be turned on a document table, so that the efficiency of reading many pages can be improved. Also, compared to opening the book and setting it face down (downward),
The damage to the book can be significantly reduced.
The book manuscript includes a filed document.

Unlike a single-sheet sheet document, the document surface (reading target surface) of a book document is curved. That is, when the document is spread on the left and right and placed on the document table, the height of the document surface varies depending on the position in the left and right direction (spread direction). For this reason,
A so-called out-of-focus state or a distortion corresponding to a curved state occurs in the read image (photographed image). The book scanner measures the bending state, and performs focusing (focus control) and distortion correction according to the measurement result. A read image having the same image quality as when a sheet document is read is output to the external device.
As a method of measuring the curved state of the document surface, there is a method of taking an image of a portion called "head" in a book and performing image analysis (Japanese Patent Laid-Open No. 5-161002). By arranging the mirror obliquely upward on the platen, the top (end face) can be photographed together with the document image.

[0004]

The conventional book scanner is configured to measure the curved state of the document surface only in one direction along the upper surface (document supporting surface) of the document table. In other words, in order to obtain a read image without any out-of-focus or distortion, the setting direction of the book document is limited to one. Specifically, the user has to set the book document so that the facing direction coincides with the left and right direction of the platen.

For example, in the case of printing an original image (A4 size) for one page on one side of an original having a spread size of A3 at an equal size, there is no problem even if the book original is set in a prescribed direction. On the other hand, in the case of printing an image in the A3 size for two pages, in order to print the entire original image, it is required
It is necessary to set in the direction rotated by 0 °. However, there is a problem that the quality of the read image deteriorates when the setting direction is changed.

On the other hand, in a copying machine in which a document is set downward, a function of erasing a shadow at a binding margin (a central portion in a spread direction) of a book document is realized. The direction of the setting may be vertical or horizontal. However, the user needs to specify the setting direction, and if the setting is incorrect, an appropriate copied image cannot be obtained. Further, in order to select a paper size and a copy magnification, a function of measuring the length and width dimensions of a document and judging the setting direction from the relationship of length is also realized. However, specifying the spread direction of the book document by the vertical and horizontal dimensional ratio in the spread state is not practical in terms of reliability.

SUMMARY OF THE INVENTION It is an object of the present invention to alleviate restrictions on the setting direction of an original in reading a book original (spread original) in a spread state, to reduce the operation load, and to enhance the practicality of the image reading apparatus. And

[0008]

According to the present invention, there is provided a function of automatically discriminating the spread direction by utilizing the difference in shape between the end face in the spread direction and the end face in the direction perpendicular to the spread direction. Then, according to the curved state of the document surface in the facing direction, control for improving image quality such as focus control and distortion correction of image pickup is performed.

According to the first aspect of the present invention, there is provided an image reading apparatus which has an image pickup device for converting an original image into an electric signal and reads the original image into pixels by main scanning and sub-scanning. It is configured to be able to photograph the end face in the main scanning direction and the sub-scanning direction of the document in the state, and the spread direction of the document based on the photographing information of the end face in each direction indicating the curved state of the document surface. And reading control means for performing control corresponding to the bending state of the facing direction.

[0010]

FIG. 1 is a perspective view showing an appearance of a book scanner 1, FIG. 2 is a diagram showing a use state of the book scanner 1, and FIG.

The book scanner 1 is an image reading apparatus suitable for reading a book original (spread original), and includes a main body housing 10 for accommodating a power supply circuit and the like, a dark original table 20 for supporting the original, and an electric image for the original. An image pickup unit 30 converts the image into a signal, and a lamp unit 40 illuminates the document. The document table 20 is arranged on the front side of the main body housing 10. The imaging unit 30 is arranged above the document table 20 and is supported in a cantilever manner by a support column 12 extending upward from the upper surface of the main body housing 10. The lamp unit 40 is fixed to a position on the lower surface side of the imaging unit 30 on the support 12. Platen 2
A space 80 between the camera unit 0 and the imaging unit 30 is open to a free space outside the apparatus, and has a sufficient size for setting a book document. The distance between the platen 20 and the lower surface of the imaging unit 30 is 30 cm or more, and the platen 2
It is possible to turn the page above zero.

An operation panel OP including a liquid crystal display is provided at the upper end of the front surface of the main body housing 10.
A main switch 51 is provided on a right side surface of the main body housing 10 toward the operation panel OP. An armrest 25 is provided on the front side of the document table 20.

An L-shaped projection plate unit 18 for detecting the height of the document surface is arranged on the upper surface of the document table 20. The projection plate unit 18 has a projection plate 18 a extending along the rear edge of the document table 20 and a projection plate 18 b extending in the front-rear direction at the left half of the document table 20. The surfaces of the projection plates 18a and 18b are glossy surfaces, and are inclined at 45 degrees with respect to the upper surface of the document table 20. On one of the projection plates 18a and 18b, an image of the end face in the facing direction (referred to as a side face) of the book document appears, and on the other side, a heavenly image which is an end face in the direction perpendicular to the facing direction appears. Then, the projection plates 18a and 18b in that state are photographed together with the document image.

In FIG. 1, an image pickup unit 30 has a CC
A line sensor 31 composed of a D array, an imaging lens 32,
And a mirror 33. The original image is projected on the light receiving surface of the line sensor 31 by the mirror 33 and the imaging lens 32. The imaging lens 32 is provided movably in the front-rear direction, and is positioned by an AF mechanism (lens driving unit) 132. The line sensor 31 is attached to a movable body of a scanning mechanism (not shown), and moves in parallel in the left-right direction (sub-scanning direction) M2 while keeping the arrangement direction of the CCD elements in the up-down direction. By this parallel movement, a two-dimensional document image is captured. That is, in the book scanner 1, a two-dimensional imaging surface is formed by the movement of the line sensor 31. When an area sensor is used in place of the line sensor 31, its light receiving surface becomes an imaging surface. The main scanning direction of the original image is the original platen 2
It is the front-back direction on 0, and the up-down direction on the imaging surface.

When using the book scanner 1, the user places the book document BD upward on the document table 20, as shown in FIG. At this time, the boundary between the left and right pages is aligned with the center of the document table 20 in the left-right direction or the front-back direction, and the front edge of the projection plate 18a or the projection plate 18
The book document BD is pressed against the front edge of b to perform positioning. The boundaries between the projection plates 18a and 18b and the document table 20 are reference lines for setting the document. In the example of FIG. 2A, the book document BD is placed on the document table 20 so that the facing direction is the left-right direction (sub-scanning direction). The setting configuration in this direction is referred to as “vertical setting”. In the vertical setting, an image of the heavens appears on the projection plate 18a, and an image of the side appears on the projection plate 18b. In the example of FIG. 2B, the book document BD is placed so that the facing direction is the front-back direction (main scanning direction). The setting form in this direction is referred to as “horizontal setting”. In the horizontal setting, the image of the side surface appears on the projection plate 18a, and the heavenly image appears on the projection plate 18b. In the book scanner 1, the user can specify the vertical or horizontal orientation by operating the panel. When the user specifies the automatic discrimination mode, the book scanner 1 discriminates between the vertical placement and the horizontal placement.

The book scanner 1 performs preliminary scanning and main scanning on the same document. In the book document BD, since the document surface S1 is curved unlike the sheet document, it is necessary to adjust the focus of imaging according to the curved state. It is also necessary to correct distortions contracted in the sub-scanning direction and to compensate for differences in luminance. For this reason, the bending state is measured by the preliminary scanning, and the operating conditions of the main scanning are set based on the measurement result. The image output to the external device is performed during the main scanning. The reading mode includes a mode in which both the left and right pages are read at a time (sheet document mode), and a mode in which the left and right pages are read separately (book division mode). In either mode, preliminary scanning and main scanning are performed.

FIG. 4 is a diagram for explaining a method of measuring the curved state of the document surface. FIG. 4A shows the read image and the luminance distribution of the line of interest in the case of vertical placement, and FIG.
Indicates a read image in the case of horizontal setting and the luminance distribution of the column of interest. The broken line in the figure indicates the position of the line of interest or the column of interest.

The read image G0 is composed of a photographed image G1 of the book document BD, a photographed image G20 of the document table 20, a photographed image G18a of the projection plate 18a, and a photographed image G18b of the projection plate 18b. An image G182 in the photographed image G18a and an image G183 in the photographed image G18b indicate the shape of the end face (top or side) of the set book document BD. Image G180 other than image 182 in photographed image G18a
Is a background image reflected on the projection plate 18a, and a photographed image G18
An image G181 other than the image 183 in b is a background image reflected on the projection plate 18b.

Since the document table 20 is colored dark as described above, the photographed image G20 of the document table 20 is darker than other images. Therefore, the captured image G1 and the images G182 and G183 can be extracted by determining the luminance of the read image G0. Specifically, when the vertical placement is specified, the luminance (pixel value) is checked in order from the top pixel in the main scanning direction for each line, and the top pixel position (in the range where the luminance exceeds the first threshold th1) is checked. The pixel positions n3 and n4 on the leading and trailing ends of the range where the pixel number) n1 and the luminance exceed the second threshold value th2 (th2> th1) are detected. The number of pixels between the pixel position n1 and the known pixel position n5 corresponding to the front edge of the projection plate 18a corresponds to the height of the document surface in the line of interest, and the number of pixels between the pixel position n3 and the pixel position n4. The number corresponds to the document size in the main scanning direction. When the horizontal setting is specified, the luminance is examined in order from the top pixel in the sub-scanning direction for each column, and the line position (line number) N1 on the head side in the range where the luminance exceeds the threshold th1, and the luminance exceeds the threshold th2. Line positions N3 and N4 at the beginning and end of the range
Is detected. The number of pixels between the line position N1 and the known line position N5 corresponding to the front edge of the projection plate 18b corresponds to the height of the document surface in the column of interest, and the number of pixels between the line position N3 and the line position N4. The number corresponds to the document size in the sub-scanning direction. The curving state of the document surface in the sub-scanning direction is specified by a set of data indicating the height of the document surface in each line, and the curving state in the main scanning direction is specified by a set of data indicating the height of the document surface in each column. You.

In the automatic discrimination mode, the pixel position n1
And the line position N1 are detected. That is, the bending state in both the sub-scanning direction and the main scanning direction is measured. Then, the facing direction of the book document BD is specified by comparing the bending states in each direction.

In the read image G0, the photographed image G
1 is curved because the height of the document surface is not constant. That is, a subject near the imaging surface is imaged larger than a distant subject. At the time of the main scanning, the distortion in the direction orthogonal to the spread direction is also corrected together with the distortion correction in the spread direction. The spread direction distortion correction (expansion processing) is a magnification processing for overlapping lines in accordance with the amount of change (inclination) in the height of the document surface for each minute section. Distortion correction in the direction orthogonal to the facing direction is
This is a scaling process in which a plane at a position at a fixed distance (for example, 5 cm) above the document table 20 is used as a reference surface, and pixels are overlapped in accordance with the height difference between the reference surface and the document surface at each position in the spread direction.

The book scanner 1 adjusts the focus of photographing at the time of the main scanning according to the curved state of the spread direction measured by the above-described method. If the facing direction is the sub-scanning direction, that is, if the vertical position is set, the imaging lens 3 is adjusted so that the in-focus state is obtained in accordance with the progress of the sub-scanning.
Move 2 When the position of each line on the document surface in each line is high, the imaging lens 32 is moved closer to the document surface, and when it is low, it is moved away. The position of the imaging lens 32 can be calculated by the known geometric conditional expression (1).

1 / f = (1 / a) + (1 / b) (1) f: focal length of the imaging lens a: image plane distance (see FIG. 3) b: field distance (see FIG. 3) On the other hand, when the spread direction is the main scanning direction, that is, in the case of horizontal setting, the image forming state of the document image is optimized by inclining the line sensor 31 with respect to the document table 20.

FIG. 5 is a diagram for explaining a method of calculating the degree of curvature in the horizontal setting, FIG. 6 is a schematic diagram of focus adjustment in the horizontal setting, and FIG. 7 is a diagram showing a mounting structure of the line sensor 31.

As shown in FIG. 5, in the case of horizontal setting, the original surface S1 is approximated by a straight line h passing through two points P and Q. Point P
Is a point at a height H1 that is away from the reference pixel position n5 described in FIG. 4 by a length corresponding to １ ／ of the document length W on the rear side in the main scanning direction. The point Q is a point having a height H2 separated from the pixel position n5 by a length corresponding to ３ of the document length W. Here, the document length W is the distance between the pixel positions n5 and n4. The height H1 is a representative value of the height of the rear half (the left half in FIG. 5) of the document surface S1, and is a pixel separated from the pixel position n5 by a length corresponding to a half of the document length W therefrom. This is the height of the maximum frequency when the frequency distribution of the height with respect to the position n6 is obtained. The height H2 is the original surface S
1 is a representative value of the height of the front half (the right half in FIG. 5), and is the maximum frequency when the frequency distribution of the height between the pixel position n6 and the pixel position n4 is obtained. .

The line sensor 31 is inclined as shown in FIG. 6 according to the inclination of the straight line h approximating the document surface S1. that time,
The angle of the inclination is calculated based on the above equation (1). That is, the light receiving portion corresponding to the lower position in the document surface is brought closer to the imaging lens 32, and the light receiving portion corresponding to the higher position is moved away from the imaging lens 32.

As shown in FIG. 7, a line sensor 31 is connected to a scanner (movable body) 30 via piezo elements 311 and 312.
It is attached to a plate 310 supported at zero.
The plate 310 is constantly pressed against the piezo elements 311 and 312 by springs 321 and 322. The line sensor 31 can be inclined by applying an electric field to extend each of the piezo elements 311 and 312.

FIG. 8 is a diagram for explaining the first and second methods for automatically determining the setting direction, and FIG. 9 is a diagram for explaining the third automatic method for determining the setting direction.
As shown in FIG. 8A, the height of the document surface S1 varies depending on the position in the facing direction, whereas the height of the document surface is substantially constant in the direction perpendicular to the facing direction. When the book document BD is placed upward as in the present embodiment, focusing on the height distribution SH1 in the facing direction, the height distribution at the boundary between the left and right pages (book binding margin) is V It is shaped like a letter (this is called a condition). In addition, the height distribution of the middle portion of each page has a gentle mountain shape (this is called a condition). In the direction orthogonal to the facing direction, such a characteristic distribution is not seen.

Therefore, when examining the height distribution in the sub-scanning direction based on the photographed image of the projection plate 18a, two conditions,
If at least one of the conditions is satisfied, the vertical scanning direction is the spread direction, so that the vertical placement can be determined. Conversely, when the height distribution in the main scanning direction is examined by the photographed image of the projection plate 18b, if at least one of the two conditions is satisfied, the main scanning direction is the spread direction, so that the horizontal setting can be determined. . As a case where only the condition is satisfied, a case where a document size of one page is a large size corresponding to the maximum reading size can be considered.
The first automatic determination method determines the setting direction based on the success or failure of the condition.

The second automatic discrimination method is a method of discriminating the setting direction by paying attention to the degree of height change of the document surface. A frequency distribution of heights in each of the main scanning direction and the sub-scanning direction is obtained, and the frequency is higher than a predetermined value and the frequency is equal to a threshold T.
The height range exceeding H2 (height variation width) is calculated. The height fluctuation width ΔH1 in the spread direction is wider than the height fluctuation width ΔH2 in the direction orthogonal to the spread direction. Therefore, if the height fluctuation width in the sub-scanning direction is wider than that in the main scanning direction, the setting is vertical because the sub-scanning direction is the spread direction. Conversely, if the height fluctuation width in the main scanning direction is wider than the sub-scanning direction, the main scanning direction is the spread direction and the setting is horizontal.

The above two automatic discrimination methods are based on the document surface S1.
Although the measurement result of the height is used, the direction of the setting can be determined without depending on the measurement of the height.
The third automatic discrimination method utilizes image distortion in a direction orthogonal to the spread direction described with reference to FIG.

As shown in FIG. 9A, the distance from the reference position O for analyzing the read image G0 to the edge of the photographed image (original image) G1 in the main scanning direction M1 is X, and the reference position O Let Y be the distance from to the edge of the captured image G1 in the sub-scanning direction M2. First, the distance (number of pixels) X at each position in the sub-scanning direction M2 is checked to determine the frequency distribution of the distance X, and the distance Y at each position in the main scanning direction M1 is checked to determine the frequency distribution of the distance Y. Next, the range (variation width) ΔX of the distance X whose frequency exceeds the threshold value TH3,
And the range (fluctuation width) ΔY of the distance Y exceeding. Then, the fluctuation width ΔX and the fluctuation width ΔY are compared. here,
In a normal book document BD, the edge in the facing direction is substantially linear, and the edge in the direction perpendicular to the facing direction is curved. Therefore, when the variation width ΔX is wider than the variation width ΔY (in the case of the example in FIG. 9), the setting is vertical, since the sub-scanning direction is the facing direction. Conversely, when the fluctuation width ΔY is wider than the fluctuation width ΔX, the main scanning direction is the spread direction, and the setting is horizontal.

FIG. 10 shows the signal processing system 1 of the book scanner 1.
It is a block diagram of 00. The signal processing system 100 includes a CPU
101, an AD converter 102, an image memory 104, an image processing circuit 103, a RAM 105, a comparator 111, and a counter 112.

The photoelectric conversion signal output from the line sensor 31 is converted by the AD converter 102 into, for example, 8-bit image data in pixel units. The image data is written to the image memory 104 in the order of scanning. That is, the read image G0 is temporarily stored. The image memory 104 is provided to rotate the read image G0 by 90 ° as needed. The address of the image memory 104 (row address,
The image rotation can be realized by exchanging the correspondence between the column address) and the scanning direction (main scanning direction, sub-scanning direction) between writing and reading. If the read image G0 is rotated by 90 °, for example, even in the case of horizontal setting, data processing such as image analysis and distortion correction may be performed in the same manner as in the case of vertical setting, and control is simplified.

At the time of preliminary scanning, image data read out from the image memory 104 in a predetermined order
The signal is input to the comparator 111. The comparator 111 compares the input image data with the threshold values th1 and th2, and notifies the CPU 101 and the counter 112 of the comparison result. The counter 112 counts the number of pixels exceeding the threshold th1. That is, the height of the document surface S1 is measured. CPU10
1 fetches the count value of the counter 112 and generates document height data DH indicating the curved state of the document surface S1.
Further, the pixel positions n3 and n3 detected by the comparator 111
n4 is fetched to generate size data DS indicating the size of the document in plan view. The document height data DH and the size data DS are temporarily stored in the RAM 105. After the completion of the preliminary scanning, the CPU 101 sets the document height data DH
Based on the size data DS, control data for focus adjustment and image distortion correction is generated as preparation for main scanning. Then, the length (page length) of one page of the document surface S1 in the facing direction is obtained, and the output image range (effective reading range) is set. In addition, automatic paper selection (AP
When performing S) or automatic magnification selection (AMS), a paper size or reading magnification suitable for the page length is set.

At the time of the main scanning, the image data read from the image memory 104 in a predetermined order is input to the image processing circuit 103. Image processing circuit 103
Are processing for correcting uneven illuminance on the original surface S1, MTF correction for improving image quality, correction processing for image distortion due to the curvature of the original surface S1, density correction, and masking for blanking the outside of the output image range. Responsible for the processing of. The image data that has undergone the predetermined image processing is output to an external device (for example, a digital copying machine).

The CPU 101 includes a scanner driving unit 130,
It also controls a drive system including the imaging control circuit 131, the lens drive unit 132, and the lamp control unit 140. The scanner driving unit 130 performs parallel movement of the scanner 300 and application of an electric field to the piezo elements 311 and 312. The imaging control circuit 131 supplies various drive signals to the line sensor 31. The lens driving unit 132 arranges the imaging lens 32 at an appropriate position. Various switches including an operation panel OP and start keys 52 and 53 are connected to the CPU 101. The RAM 105 is used for temporarily storing various data related to control.

The operation of the book scanner 1 will be described below with reference to a flowchart. FIG. 11 is a main flowchart of the reading control operation of the CPU 101 in the manual determination mode.

When the user turns on the start key after completing the necessary specification, the CPU 101
To the lighting of the illumination lamp, and the scanner driving unit 1
32 and the imaging control circuit 131 are instructed to start preliminary scanning (# 11). During the preliminary scanning, the read image G0 is written to the image memory 104 as described above. In writing, the row address is associated with the sub-scanning direction, and the column address is associated with the main scanning direction.

When the preliminary scanning is completed, the contents specified by the user in the setting direction are checked (# 12). When vertical storage is specified,
The vertical storage mode is set (# 13), and the image memory 104 is set.
, Vertical reading setting for reading the read image G0 without rotating it is performed (# 14). When landscape is specified, the landscape mode is set (# 15),
A horizontal reading setting for rotating and reading the read image G0 from the image memory 104 is performed (# 16). # 1
The data of each pixel of the read image G0 is read out in the order set in # 4 or # 16 (# 17), and the height of the document surface is obtained to generate control data for focus adjustment and distortion correction (# 1).
8).

The main scanning is started (# 19), and the setting mode is checked (# 20). In the vertical mode, the vertical focus adjustment is performed (# 2
1) If horizontal mode, horizontal focus adjustment is performed (# 22). Until this scanning is completed
The image data is written in the image memory 104 in the same order as in the prescanning (# 23, # 24). When the main scanning is completed, the image data is read from the image memory 104 in the order set in # 14 or # 16 (# 25).
A correction instruction corresponding to the document height data DH is given to the image processing circuit 103 (# 26). When the image output to the external device is completed, an instruction to turn off the illumination lamp is issued.

FIG. 12 is a flowchart for setting the vertical reading. Similarly to the writing, the column address at the time of reading from the image memory 104 is associated with the main scanning direction, and the row address is associated with the sub-scanning direction (# 141,
142).

FIG. 13 is a flow chart of the horizontal setting reading setting. Contrary to the writing, the row address at the time of reading from the image memory 104 is associated with the main scanning direction, and the column address is associated with the sub-scanning direction (# 161,
162). As a result, an image obtained by rotating the read image G0 by 90 ° is sent to the image processing circuit 103.

FIG. 14 is a flowchart of the vertical focus adjustment. The inclination of the line sensor 31 is fixed to zero (0) (# 211), and the piezo elements 311 and 312 are kept in the initial state (# 212). The movement amount of the imaging lens 32 is calculated (# 213), and a movement instruction is given to the lens driving unit 132 (# 214). That is, in this routine, the focusing control according to the document height change in the sub-scanning direction is executed.

FIG. 15 is a flow chart of horizontal focus adjustment. The moving amount of the imaging lens 32 is fixed to zero (0) (# 221), and the imaging lens 32 is fixed to the focus position (# 222). The inclination angle of the line sensor 31 is calculated (#
223), the piezo elements 311 and
An instruction to expand / contract 312 is given (# 224). That is, in this routine, the focusing control according to the change in the document height in the main scanning direction is performed.

FIG. 16 shows the CPU 1 in the automatic determination mode.
11 is a main flowchart of a read control operation of No. 01.
In response to the start key being turned on, the CPU 101 instructs lighting of the illumination lamp, and instructs the scanner driving unit 132 and the imaging control circuit 131 to start preliminary scanning (# 31). During pre-scanning,
The image data of each pixel of the read image G0 is stored in the image memory 10
Write to 4. In writing, the row address is associated with the sub-scanning direction, and the column address is associated with the main scanning direction.

When the preliminary scanning is completed, the image data is read from the image memory 104 (# 32), and a height calculation process for calculating the height of the document surface by analyzing the read image G0 is performed (# 33). An automatic discrimination process for discriminating the setting direction based on the information obtained by the image analysis and setting the operation mode is executed (# 34), and the main scanning is started (# 35). Check the mode (#
36) In the vertical setting mode, vertical focus adjustment, which is a movement control routine of the imaging lens 32, is executed (# 3).
7), if in horizontal setting mode, piezo elements 311 and 31
The horizontal focus adjustment, which is the second extension control routine, is executed (# 38). Until the main scanning is completed, the image data is written into the image memory 104 in the same order as in the preliminary scanning (# 39, # 40).

When the main scanning is completed, the mode is checked again (# 41). In the portrait mode, the portrait reading setting for reading the read image G0 from the image memory 104 without rotating it is performed (# 4).
2). In the horizontal setting mode, horizontal reading setting for rotating and reading the read image G0 from the image memory 104 is performed (# 16). The data of each pixel of the read image G0 is read from the image memory 104 in the order set in # 42 or # 43 and transferred to the image processing circuit 103 (#
44). Then, a correction instruction corresponding to the document height data DH is given to the image processing circuit 103 (# 45). When the image output to the external device is completed, an instruction to turn off the illumination lamp is issued.

FIG. 17 is a flowchart showing a first example of the automatic discrimination processing. In this routine, the first
The setting direction is determined by the automatic determination method.
First, the height distribution of the document surface in the sub-scanning direction and the main scanning direction is obtained (# 341). Specifically, the counter 112
And the document height data DH is generated for each direction.

Next, it is determined whether or not the height distribution in the sub-scanning direction satisfies the above condition (# 342). If the condition is satisfied, the vertical storage mode is set (# 343). If the condition is not satisfied, it is determined whether the condition is satisfied (# 344). If the condition is satisfied, the vertical storage mode is set (# 343). If the height distribution in the sub-scanning direction does not satisfy either the condition or the condition, it is determined whether the height distribution in the main scanning direction satisfies the condition (# 34).
5). If the condition is satisfied, the horizontal setting mode is set (# 346). If the condition is not satisfied, it is determined whether the condition is satisfied (# 347). If the condition is satisfied, the horizontal setting mode is set (# 346).

If the condition is not satisfied in both the sub-scanning direction and the main scanning direction and the condition is not satisfied, a message indicating that the determination cannot be made is displayed on the display of the operation panel OP. In this case, the user may correct the setting state of the book document BD, or switch the automatic determination mode to the manual determination mode and specify a setting direction.

FIG. 18 is a flowchart showing a second example of the automatic discrimination processing. In this routine, the second
The setting direction is determined by the automatic determination method.
First, the height distribution of the document surface in the sub-scanning direction and the main scanning direction is obtained (# 401). Subsequently, a frequency distribution of the height of the document surface in the sub-scanning direction and the main scanning direction is obtained (#
402). At this time, the frequency is set to the threshold value TH for each direction.
The height range (ΔH1, ΔH2) exceeding 2 (see FIG. 8) is calculated.

Next, the height range in the sub-scanning direction is compared with the height range in the main scanning direction. If the height range in the sub-scanning direction is clearly wider than the height range in the main scanning direction, that is, if the difference between the height ranges is equal to or larger than a predetermined value, the vertical setting mode is set (# 403, 404). Conversely, if the height range in the main scanning direction is clearly wider than the height range in the sub-scanning direction,
The horizontal setting mode is set (# 405, 406). When there is no significant difference between the height ranges in each direction, or when the frequency distribution is flat and the height range cannot be specified, a message indicating that automatic determination cannot be performed is displayed (# 407).

FIG. 19 is a flowchart showing a third example of the automatic discrimination processing. In this routine, the third
The setting direction is determined by the automatic determination method.
First, the pixel position n3 (see FIG. 4) is detected based on the output of the comparator 111, and distances X and Y (see FIG. 9) indicating the position of the document edge in the main scanning direction and the sub-scanning direction are calculated (# 501). Subsequently, the frequency distribution of the document edge position in the main scanning direction and the sub-scanning direction is obtained (# 502). At this time, distance ranges ΔX and ΔY whose frequencies exceed the threshold value TH3 are calculated for each direction.

Next, the distance range ΔX in the main scanning direction is compared with the distance range ΔY in the sub-scanning direction. When the distance range ΔX in the main scanning direction is clearly wider than the distance range ΔY in the sub-scanning direction, that is, when the difference between the distance ranges is equal to or more than a predetermined value,
The vertical setting mode is set (# 503, 504). Conversely, the distance range ΔY in the sub-scanning direction is the distance range ΔX in the main scanning direction.
If it is clearly wider, the horizontal setting mode is set (# 505, 506). There is no remarkable difference in the distance ranges ΔX and ΔY in each direction, and the frequency distribution is flat and the distance range Δ
When X and ΔY cannot be specified, a message indicating that automatic determination cannot be performed is displayed (# 507).

In the above embodiment, the projection plate 18
In the above example, heights in two directions are analyzed by analyzing the images shown in a and 18b. Curve information in the main scanning direction and sub-scanning direction on the document surface by a light projection method of projecting slit light in two directions has been described. Can be obtained. Although the description has been made assuming that the order of writing to the image memory 104 is fixed and the order of reading is switched, rotation of the image may be realized by switching the order of writing while fixing the order of reading.

[0057]

According to the first aspect of the present invention, the restriction on the setting direction of the original when reading the original in the open state is eased, the operation load is reduced, and the practicality of the image reading apparatus is improved. it can.

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating an appearance of a book scanner.

FIG. 2 is a diagram illustrating a use state of the book scanner.

FIG. 3 is a schematic diagram of reading by a book scanner.

FIG. 4 is a diagram for explaining a method of measuring a curved state of a document surface.

FIG. 5 is a diagram for explaining a method of calculating a degree of curvature in horizontal setting.

FIG. 6 is a schematic diagram of focus adjustment in horizontal setting.

FIG. 7 is a diagram showing a mounting structure of a line sensor.

FIG. 8 is a diagram for explaining first and second automatic determination methods of a setting direction.

FIG. 9 is a diagram for explaining a third automatic determination method of a setting direction.

FIG. 10 is a block diagram of a signal processing system of the book scanner.

FIG. 11 is a main flowchart of a reading control operation of a CPU in a manual determination mode.

FIG. 12 is a flowchart of setting of vertical reading.

FIG. 13 is a flowchart of horizontal setting reading setting.

FIG. 14 is a flowchart of vertical focus adjustment.

FIG. 15 is a flowchart of horizontal setting focus adjustment.

FIG. 16 is a main flowchart of a reading control operation of a CPU in an automatic determination mode.

FIG. 17 is a flowchart illustrating a first example of an automatic determination process.

FIG. 18 is a flowchart illustrating a second example of the automatic determination process.

FIG. 19 is a flowchart illustrating a third example of the automatic determination process.

[Explanation of symbols] [Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Book scanner (image reading device) 18a, 18b Projection board 31 Line sensor (imaging device) 101 CPU (direction discriminating means, reading control means) BD Book original (original) G182, G183 Image (photographing information of end face) M1 Main scanning Direction M2 Sub-scanning direction

Claims (1)

[Claims] An image reading apparatus having an image pickup device for converting a document image into an electric signal and reading the document image by subdividing it into pixels by main scanning and sub-scanning, wherein the main scanning direction in a spread original document A direction discriminating unit configured to be capable of photographing an end face in two directions in the sub-scanning direction, based on photographing information of the end face in each direction indicating a curved state of the document surface, An image reading apparatus, comprising: reading control means for performing control corresponding to the bending state of the spread direction.