JPH05161001A - Original reader - Google Patents

Abstract

PURPOSE:To attain precise picture reproduction by detecting a degree of a warp of an original when reading the original and applying density interpolation processing and expansion processing to a picture in response to the result of detection. CONSTITUTION:A range finder circuit 22 measures the height of an original, a spline interpolation circuit 24 applies 3rd-order spline interpolation processing based on the measured data to obtain shape data of the original. A picture expansion rate calculation circuit 25 calculates a picture expansion rate based on the data and sends the value to a picture expansion circuit 31. On the other hand, a CCD 28 picks up an image of the original and a picture correction circuit 30 restores the picture based on the image pickup data. The picture expansion circuit 31 applies picture expansion processing to the restored picture data based on the picture expansion rate and an output section 32 reproduces a beautiful and easy to see picture.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a document reading device for photographing a document from above and for detecting and correcting the degree of bending of a document that is spatially curved.

[0002]

2. Description of the Related Art In a device of this type, when a bound document is photographed and read from above, the paper surface is curved at the seam portion of the book, so if the photographed data is reproduced as it is, The image is compressed in parts,
The image becomes distorted. In order to cope with this, conventionally, for example, as shown in Japanese Patent Laid-Open No. 62-143557, a line sensor is used for scanning and reading, and a distance sensor for detecting the distance between the document surface is used for reading. The one in which the reading pitch of the line sensor in the sub-scanning direction is changed according to the distance sometimes detected, or, as shown in JP-A-3-117965, depending on the degree of bending of the original at the time of reading the original, There is a system in which a captured image is expanded.

[0003]

However, in the former device described above, since the reading pitch of the line sensor in the sub-scanning direction is changed when reading the original, the mechanical structure is complicated and the distance sensor is used. Is costly to use. Further, in the latter device, since the density reproduction interpolation process is not performed when the captured image is expanded, the image may not be beautifully reproduced in the vicinity of the seam of the document where the ratio of expanding the image is large. The present invention solves the above problem, and detects the degree of bending of a document at the time of reading the document, without using a mechanical correction unit that changes the reading pitch of the line sensor in the sub-scanning direction at the time of reading the document. It is an object of the present invention to provide a document reading apparatus capable of performing density reproduction interpolation processing when expanding an image according to the result and performing image reproduction as if a flat original was photographed.

[0004]

In order to achieve the above object, the present invention is based on an original reading unit for reading an original, an image pickup unit having a plurality of pixels in the original reading unit, and an output read by the reading unit. Shape measuring means for measuring the shape of the original document, calculating means for calculating the image expansion rate of each pixel according to the output of this shape measuring means, and density reproduction interpolation of each pixel output according to the output of this calculating means. And a decompression means for decompressing the pixels.

[0005]

According to the above structure, the document is read by the document reading unit and the image pickup unit to obtain image information, and
The height of the document is measured by the shape measuring means, and the shape data of the document is detected based on the measured value. An accurate image can be reproduced by calculating the pixel expansion rate of each pixel based on the detected document shape data and expanding the image based on the result.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows an external configuration of a document reading apparatus which is an embodiment of the present invention. The original 1 is placed upward on the original table 10 of the desk-shaped apparatus body, and the reading unit 2 is supported by the support member 3 at a position where the original 1 can be read from above. To have a predetermined interval. This distance is such that at least the readable area on the surface of the original 1 is always visible, and this space forms a working space between the surface of the original 1 and the reading unit 2. Further, the apparatus is provided with a bending correction circuit section 5 for correcting the output of the operation switches 4 and the document reading means.

2 and 3 show the detailed structure of the reading unit 2. As shown in FIG. The image information of the document 1 is read by the image sensor 6 through the imaging lens 7 of the reading unit 2. The image sensor 6 is a semiconductor photoelectric conversion element such as a CCD and may be an area sensor or a line sensor. 2 is an area sensor,
FIG. 3 shows the configuration in the case of a line sensor. The bend detection board 9 measures the height of one surface of the original using a so-called triangulation method, in which the reflected light emitted from the IR light emitting element 8a and reflected by the one surface of the original is received by the light receiving element 8b to measure the distance. Then, the bending detection board 9 provided with the IR light emitting element 8a and the light receiving element 8b is scanned above the document 1 to measure the change in height of the document 1 surface. The distance measuring method is not limited to the triangulation distance measuring method, and may be the phase difference distance measuring method.

FIG. 4 is a block diagram showing the flow of electric signals in the document reading apparatus according to this embodiment. FIG. 5 shows a series of processes of a copy operation using the document reading apparatus according to this embodiment. The configuration and operation of this embodiment will be described below with reference to FIGS. When the manuscript 1 is set on the manuscript table 10 (YES in # 1) and the copy button is turned on (YES in # 2), the distance measuring circuit 22 is driven by a command from the CPU 21 in FIG. Then, the bending detection board 9 in FIG. 2 scans and measures the height of 10 points on one page of the document 1, that is, 20 points in total on both left and right pages. The height of each point is measured by the triangulation method using the light emitting element 8a and the light receiving element 8b of FIG. 2 (# 3).

The measured height data is A / D converted by an A / D converter 23 as shown in FIG. 4 and then sent to a spline interpolation circuit 24 to be subjected to cubic spline interpolation processing. The shape data of the original 1 is obtained (# 4). The shape data of the document 1 output from the spline interpolation circuit 24 is sent to the image expansion rate calculation circuit 25, the image expansion rate is calculated (# 5), and the calculated expansion rate value is prepared for execution of the image expansion processing. It is stored in the memory 26.

When the above processing is completed, the CPU 2 of FIG.
The CCD drive circuit 27 is driven by the command 1 and the CCD 2
The document 1 is imaged by 8 (# 6). The imaged data is A / D converted by the A / D converter 29 as shown in FIG. 4, and then sent to the image restoration circuit 30 to restore the image (# 7). Next, the image data output from the image restoration circuit 30 is sent to the image expansion circuit 31. On the other hand, the memory 26
The value of the image expansion rate stored in is also sent to the image expansion circuit 31, and image expansion processing is performed based on this data and the image data (# 8). The data output from the image decompression circuit 31 is sent to the output unit 32, printed out (# 9), and a series of copy operations is completed.

Each of the above processes will be specifically described below. First, the interpolation processing in the spline interpolation circuit 24 will be described. FIG. 6 is a diagram for explaining the processes of # 3 and # 4 of FIG. FIG. 6A shows the height measurement value and its measurement position, and the envelope curve shows the bending of the document. Figure 6
The dashed arrow in (b) is the interpolated value of the height calculated by the cubic spline interpolation process. By this interpolation processing, measurement data having a height of 450 points is obtained in accordance with the number of dots of the reproduction printer.

The reason for calculating the height interpolation value by the spline interpolation process in addition to the height measurement value will be described below. Figure 6
Taking the measurement positions x1 and x2 in (a) as an example, the length of the image compressed by the bending of the document and the actual length of the document are
In the triangle ABC in FIG. 7A, the length of the compressed image is the length of the straight line AC, and the actual length of the original is AB.
If the bending of the original document in between can be approximated to a straight line, it can be approximated to the length of the straight line AB. Actually, when the image is expanded, it is possible to easily obtain the length of the straight line AB from the length of the straight line AC from AB = AC · (1 / cos θ).

However, the actual bending of the original is shown in FIG.
It cannot be approximated to a straight line because it is curved like the curve AB in (b). However, if the height measurement points are closely spaced and a large amount of height measurement data is taken, the bending of the document can be approximated to a straight line. Therefore, when measuring the height of a document, if the number of height measurement points is small and the curve of the document cannot be approximated to a straight line, cubic spline interpolation processing is performed based on the values of each measurement point. By calculating the height interpolation values at a plurality of points (hereinafter referred to as interpolation points) between the measurement points, it is possible to obtain a curve that approximates the bending of the document, and it is possible to perform decompression processing. Become. For the above reason, in addition to the height measurement value, the height interpolation value must be calculated by spline interpolation processing. However, in the distance measuring method of FIG. 2, if it is possible to obtain the measurement data having the same number of heights as the number of pixels of one line imaged from the CCD, it is possible to obtain the accuracy without the cubic spline interpolation process. A high linear approximation can be obtained.

By the cubic spline interpolation, x in FIG.
To obtain the cubic spline function of 1 to x10,
The height values at x0 and x11 in FIG. 8 are needed. As shown in Figure 8, x0 is just the seam of the book,
The height h ₀ is processed as ₀ . Further, in order to obtain the interpolated value in the section of x0 to x1 near the seam of the document,
To indicate x _- height in ₁ requires, in this case, x _-
1 in the height h _{- 1} = -h by approximating the _1, x0
The interpolated value of x1 is calculated. Further, since x11 is the end portion of the document, it is assumed that the document and the document table are substantially horizontal,
The height at x11 is treated as h _{1 1} = h _{1 0} . This makes it possible to obtain a cubic spline function in the entire range on the document surface. Alternatively, interpolation with a quadratic spline function will be easier.

Next, the processing in the image expansion rate calculation circuit 25 will be described. The measured data h ₁ , ..., H _{4 at} the height of x1, ..., x450 obtained by the spline interpolation circuit 24
_{5 0} data to calculate the image elongation in the original. The image expansion rate is the value of AB / AC in FIG. The image expansion rate α is calculated from FIG.

[Equation 1]

[0016] By successively calculating this from k = 1, α (1), ..., α (449) can be obtained. This image expansion rate α (k) (k = 1, ..., 44
The image expansion rate calculation circuit 25 performs the process of obtaining 9).

Next, the processing in the image restoration circuit 30 will be described. The image restoration circuit 30 performs two processes, a blur restoration process and a brightness unevenness correction process. First, the blur restoration process will be described. In the vicinity of the seam of the document, there is a large difference in height between the high part and the low part of the document, so that the image is blurred. A Laplacian process is a method for repairing this blur. By performing the Laplacian processing on the image data, the edges in the gradation of the bright and dark parts of the image are emphasized, and the blur of the image pickup is improved. further,
When the A / D conversion process is performed on the path of the electric signal as in this embodiment, noise of the electric signal is likely to occur. Therefore, noise is removed by the gamma (γ) conversion process to further reduce the image quality. Sharpening can be realized.

Next, the brightness unevenness correction processing will be described. For example, in the read image data, the image data in the i-th row and the j-th column before the luminance unevenness correction processing is set to a (i, j),
The image data after the brightness unevenness correction processing is set to b (i, j). In the brightness unevenness correction processing, first, one line of image data a (k, j) in the white background portion without letters or pictures at the upper end portion or the lower end portion of the document is detected. This a
The concentration distribution at (k, j) is shown in FIG. The density distribution of FIG. 12 is the density distribution in the x-axis direction of FIG. 12
In, the point A where the density has decreased corresponds to the seam portion of the document placed upward, and in order to correct the image data of this portion, the value of max / a (k, j) is calculated,
Multiplying this value by each image data a (k, j) of k rows, b
The density values of (k, j) are all max, and the uneven brightness is eliminated. This is shown in FIG. This max / a (k,
When the value of j) is multiplied by all the image data of the same corresponding column, the uneven brightness is corrected for all the image data.

If the image data in the k-th row before the brightness unevenness correction processing is a white background, the image data a (i, j) in the i-th row and j-column before the brightness unevenness correction processing and the image after the brightness unevenness correction processing are performed. The relationship with the data b (i, j) is

[Equation 2] Becomes Image restoration can be realized by the above-described blur correction processing and luminance unevenness correction processing.

Next, a method of expanding image data in the image expansion circuit 31 will be described. FIG. 9 shows an example of [x _k ,
x _{k + 1} ], 10 pieces of image data are expanded at an image expansion ratio of 1.4. In this example,
_{[X k, x k + 1} ] Ten number of pixels in the interval of 1, 2 from x1 sequentially, ..., and 10. Where i
When the pixel in the row j-th column is expanded at the image expansion rate α, where m is the number of expanded pixels and n is the cumulative number of expanded pixels, the following relational expression holds: m = α · i−i−n. However, m is a value obtained by rounding off the right side.

Therefore, the relational expression of the decompression process is as follows: m = f (αi-i-n) x-y≥0.5 f (x) = y + 1 x-y <0.5 f (x) = y x: (α · i−i−n) value y: (α · i−i−n) integer part value When i = 1, m = f (0.
From 4) = 0, n = 0. Similarly, i =
Calculations are made for 2, 3, ..., 10. In FIG. 9, k = 1,
Pixel data before decompression processing i = 2, ...
1, 2, ..., 10 are shown in FIG. These processes are [x
The image can be expanded by applying it to the pixels in all the [1, x450] intervals.

Further, as a better method, when the data of the i-th row and the j-th column is expanded to m pieces, the value of the m pixels after the expansion processing is made the value of the pixel data of the i-th row and the j-th column. Instead, the processing shown in FIG. 11 is performed based on the pixel data of the i-th row and j-th column and the i-th row (j + 1) th column. That is, the image data is expanded by density-interpolating the pixel data to be expanded by the pixel data of the i-th row and the j-th column and the i-th row (j + 1) th column while providing an average density gradation. Row i (j +
l) Image data a of the 1st column (l = 0, 1, ..., M-1)
(I, j + 1) can be calculated by the following formula.

[Equation 3] When m = 0 a (i, j + 1) = a (i, j)

Next, the reason why the image restoration is performed before the image expansion is explained. Since the density interpolation process is performed when the image is expanded, the gradation of the image data after the expansion process is small and the edge is gentle. Therefore,
Even if the Laplacian process in the image restoration is performed after the image expansion, the edge is hard to be emphasized and the effect of the image restoration is small. On the other hand, when the image is expanded after the Laplacian processing, the edges are emphasized and become thicker, which is extremely effective for restoring thin characters or small characters.

The image sensor for reading the original may be a line sensor or an area sensor,
The range of application becomes wider. Further, when performing distance measurement, as shown in FIG. 14, by increasing the distance measurement data near the seam of the original,
The distance measurement data can be reduced as the distance from the seam is increased, and by doing so, more accurate spline interpolation can be performed. Further, the spline interpolation can be performed with any number of distance measurement data. With this, it is possible to perform an appropriate interpolation process according to the specifications of the device (hardware).

A distance measuring means according to an embodiment different from the above-mentioned embodiment is shown in FIGS. In this example, a board 90 having photosensors 91 arranged perpendicularly to the original table 10 is placed on the original table 10, and the original 1 is brought into close contact with the board 90.
The document 1 is arranged so that 1 is shielded from light. With this configuration, the height of the document 1 can be measured in accordance with the output of the photo sensor 91.

[0026]

As described above, according to the present invention, at the time of reading a document, the shape of the document, that is, the degree of bending of the document that is spatially bent, is detected, and the image expansion processing and density reproduction are performed according to the detection result of the bending. Since the interpolation process is performed, it is possible to reproduce an image as if a flat document was photographed. In particular, the density reproduction interpolation process for performing the expansion process can be performed by obtaining the average value of the density data before and after the pixel. By performing density interpolation and expansion in this way, a beautiful image can be restored.

[Brief description of drawings]

FIG. 1 is an external configuration diagram of a document reading apparatus according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a configuration of a reading unit.

FIG. 3 is a perspective view showing a configuration of a reading unit.

FIG. 4 is a block diagram showing a flow of an electric signal.

FIG. 5 is a flowchart of an image copy operation.

FIG. 6 is an explanatory diagram of spline interpolation.

FIG. 7 is an explanatory diagram of linear approximation.

FIG. 8 is an explanatory diagram of approximate data in spline interpolation.

FIG. 9 is an explanatory diagram of image expansion processing.

FIG. 10 is an explanatory diagram of image expansion processing.

FIG. 11 is an explanatory diagram of density reproduction interpolation.

FIG. 12 is a diagram showing a density distribution before correction of luminance unevenness.

FIG. 13 is a diagram showing a density distribution after luminance unevenness correction.

FIG. 14 is an explanatory diagram of spline interpolation when the number of measurement points is changed depending on the location.

FIG. 15 is an external configuration diagram of a document reading apparatus according to an embodiment using a photo sensor as a distance measuring unit.

FIG. 16 is a side view of distance measuring means using a photo sensor.

[Explanation of symbols]

 2 reading unit 5 bending correction circuit unit 6 image sensor 8a IR light emitting element 8b light receiving element 21 CPU 22 distance measuring circuit 24 spline interpolation circuit 25 image expansion rate calculation circuit 28 CCD 30 image restoration circuit 31 image expansion circuit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshihiko Karazaki 2-3-13 Azuchi-cho, Chuo-ku, Osaka Inside the Osaka International Building Minolta Camera Co., Ltd. (72) Satoshi Nakamura 2-chome, Azuchi-cho, Chuo-ku, Osaka 3-13 Osaka International Building Minolta Camera Co., Ltd. (72) Inventor Shinya Matsuda 2-3-3 Azuchicho, Chuo-ku, Osaka City Osaka International Building Minolta Camera Co., Ltd.

Claims (1)

[Claims] 1. An original reading means for reading an original, an image pickup means having a plurality of pixels in the original reading means, a shape measuring means for measuring the shape of the original on the basis of a read output by the reading means, and this shape measurement. The present invention is characterized in that it has arithmetic means for computing the image expansion rate of each pixel according to the output of the means, and decompressing means for performing pixel expansion by performing density reproduction interpolation of each pixel output according to the output of this arithmetic means. Document reading device.