JP2000032232A - Image scanner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image scanner capable of preventing the generation of distortion in composite images and reading images at a high speed without resulting in enlargement and complication. SOLUTION: In this image scanner constituted of a linear image sensor 1 for main-scanning a read original 6 and obtaining partial images and a sub scanning mechanism 4 for rotating a reflection mirror 3 and changing the read image of the read original 6 to be made incident on the linear image sensor 1 for synthesizing the partial images and obtaining two-dimensional images, an image conversion processor 5 for converting the images obtained by main scanning corresponding to the change of an optical path length from the read original 6 to the linear image sensor 1 is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image scanner that scans an original with a reflecting mirror and reads the original with a one-dimensional image sensor, and more particularly to an image scanner that corrects a distortion of a read image due to a difference in optical path length.

[0002]

2. Description of the Related Art A reading method of an image scanner which uses a one-dimensional image sensor and rotates a reflecting mirror to perform sub-scanning will be described with reference to a conventional example shown in FIG.

FIG. 10A is a perspective view showing the positional relationship between a reading unit 1000 and a document 1004.
FIG. 3B is a diagram illustrating an optical relationship between the reading unit and the document.

The reading unit 1000 uses a plane mirror 1 as a reflecting mirror to reflect light reflected from a reading line of the original 1004.
In 001, the optical path is changed in the direction of the condenser lens 1002, and
An image is formed on the surface of a line CCD 1003, which is a two-dimensional image sensor, and is read (main scanning) as a part (one-dimensional) image indicated by an arrow A in FIG. By rotating the plane mirror 1001 in the direction of the mark C shown in FIG. 10B, the reading line is moved in the direction of arrow B in FIG. Are sequentially read and driven. Line CCD10
By synthesizing the partial images read in 03, a two-dimensional image corresponding to the read document is generated.

The method in which the sub-scanning is performed by rotating the reflecting mirror is advantageous in that the miniaturization is easy because only the reflecting mirror is required to move along with the sub-scanning. However, since the optical path length L3 from the reflecting mirror to the reading line changes with sub-scanning, there is a problem that a two-dimensional image obtained by combining partial images is distorted.

As an example of a method for solving the above problem, there is a method disclosed in Japanese Patent Application Laid-Open No. 62-291259. This method uses a reflecting mirror 110 as shown in FIG.
And rotating the condensing lens 1102 and the one-dimensional image sensor 1101 in the optical axis direction in parallel with the reading surface of the original 1104 to change the optical path length L2 shown in FIG. By correcting the change in the optical path length L3 due to the rotation of the reflecting mirror 1103 with the optical path length L2, distortion occurs in the synthesized image with the optical path length from the one-dimensional image sensor 1101 to the reading line on the original 1104 being constant. It is to prevent that.

[0007] In addition, a zoom lens having a zoom function is used as a condenser lens, and the magnification is changed with the rotation of the reflecting mirror, thereby preventing the occurrence of inaccuracy in the synthesized image.

[0008]

Among the above-described conventional image scanners using a reflecting mirror, which do not have a moving mechanism or a zoom function, there is a problem that distortion occurs in a composite image.

In the system in which the optical path length is kept constant by the parallel movement of the condenser lens and the one-dimensional image sensor, a space and a mechanism for the parallel movement of the condenser lens and the one-dimensional image sensor are required. However, there is a problem that it becomes complicated.

In addition, a change in the center of gravity of the mechanical unit caused by the parallel movement of the condensing lens and the one-dimensional image sensor easily causes vibration, and it is difficult to increase the reading speed without affecting the image quality. There is.

When a zoom lens having a zoom function is used as a condenser lens, the lens portion becomes large, and
There is a problem that the device is large and complicated.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and can prevent the occurrence of distortion in a composite image without increasing the size and complexity. Another object of the present invention is to realize an image scanner capable of reading an image at high speed.

[0013]

An image scanner according to the present invention comprises: a one-dimensional image sensor for obtaining a partial image by main-scanning a read original; and the read original which is incident on the one-dimensional image sensor by rotating a reflecting mirror. And a sub-scanning mechanism for changing the read image of the image.
An image scanner for obtaining a three-dimensional image, comprising: an image conversion processing device for converting an image obtained by main scanning according to a change in an optical path length from the read document to the one-dimensional image sensor; The processing device may include a counter that counts the number scanned by the sub-scanning mechanism, and image conversion means that converts an image obtained by main scanning according to an output from the counter.

In this case, the image conversion processing device has a storage device for storing conversion tables obtained by using different conversion coefficients for each number of scans, and the image conversion means stores the conversion table of each conversion table stored in the storage device. The image conversion may be performed based on the conversion table of the number of scans indicated by the counter output.

Further, the image conversion processing device stores an image of the entire read original, and outputs an image for each partial image obtained by main scanning, a counter for counting the number of outputs of the image memory, Image conversion means for converting an image obtained by the main scanning in accordance with the output from the printer.

In this case, the image conversion processing device has a storage device for storing conversion tables obtained by using different conversion coefficients for each number of scans, and the image conversion means stores the conversion table of each conversion table stored in the storage device. The image conversion may be performed based on the conversion table of the number of scans indicated by the counter output.

Therefore, in the present invention, an image obtained by main scanning is corrected by performing image conversion based on a change in the optical path length, so that the arrangement of the optical system is always constant.

[0018]

Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a perspective view showing the configuration of an example of an image scanner related to the present invention.

In this embodiment, a one-dimensional image sensor 1, a condenser lens 2, a reflecting mirror 3, a sub-scanning mechanism 4 for rotating the reflecting mirror 3,
An image conversion processing device 5 for processing an image detected by the one-dimensional image sensor 1 and a read original 6 are provided.

The reflecting mirror 3 is provided on a reading line 7 on the reading original 6.
The optical path of the reflected light from the lens is changed in the direction of the condenser lens 2. The condenser lens 2 forms an image on the one-dimensional image sensor 1 of the reflected light whose optical path has been converted by the reflecting mirror 3. In this embodiment, as the one-dimensional image sensor 1, a μPD3733 manufactured by NEC having a 2088-bit CCD array element is used. The one-dimensional image sensor 1 converts the input reflected light into an electric signal and transfers it to the image conversion processing device 5 as a partial image.

The sub-scanning mechanism 4 moves the reading line 7 in the direction of arrow B by rotating the reflecting mirror 3 in the direction of arrow A. In this embodiment, a mechanism combining a stepping motor and a speed reduction mechanism is applied as the sub-scanning mechanism 4. 1
The one-dimensional image sensor 1 reads and drives each time the stepping motor is driven one step, and sequentially generates partial images.
Forward.

When the rotation speed of the reflecting mirror 3 by the sub-scanning mechanism 4 is sufficiently constant, the one-dimensional image sensor 1 may be read and driven at regular intervals simultaneously with the start of the rotation driving by the sub-scanning mechanism 4. .

FIG. 2 is a block diagram showing the configuration of the image conversion processing device 5 in FIG.

The image conversion processing device 5 includes an image conversion unit 2
0, a counter 21 that counts as the number N of main scans each time a partial image signal is input from the one-dimensional image sensor 1, an A / D converter 51, a partial image memory 52, and a conversion different for each number N of main scans It is composed of a ROM 53 for storing the conversion table obtained by the coefficients and an image memory 54.

The A / D converter 51 A / D converts the partial image signal from the one-dimensional image sensor 1 and transfers the signal to the partial image memory 52. The image conversion means 20 includes a counter 21
The conversion table corresponding to the number N of main scans by the one-dimensional image sensor 1 notified from the ROM 53 is read out from the ROM 53, and the partial image data stored in the partial image memory 52 is subjected to image conversion processing and sequentially transferred to the image memory 54. I do. The image data stored in the image memory 54 is output to a display device (not shown) as appropriate.

The number of arrays of the one-dimensional image sensor 1 is 20
When the reading drive of the one-dimensional image sensor 1 and the image conversion processing are repeated 3000 times with 88 bits, a two-dimensional image of 2088 × 3000 pixels is stored in the image memory 54.

As described above, the conversion table obtained in accordance with the number of main scans by the one-dimensional image sensor 1 for enlarging a partial image is calculated and stored in the ROM 53 in advance. Regarding the calculation method of the conversion table, the size of the read original 6 is A4 size, the center of the reflecting mirror 3 is located right above the center of the original, and the rotation axis of the reflecting mirror 3 is the height h [ mm] and scanning in the long side direction of an A4 document will be described with reference to FIG.

FIG. 3A is a diagram showing an optical configuration when the reflecting mirror 4 and the read original 6 are viewed from the side. When sub-scanning the read original 6 output from the A4 size original in the long side direction, the rotation angle θ of the reflecting mirror 3 is determined based on an optical axis connecting the center of the reflecting mirror 3 and the center of the zoom lens 2.

[0030]

[Number 1] _{π / 4-θ 0/2} ≦ θ ≦ π / 4 + θ 0/2 becomes [rad]. However,

[0031]

Θ ₀ = tan ⁻¹ (297 / 2h) [rad] In one main scan by the one-dimensional image sensor 1, the small angle at which the sub-scanning mechanism 4 rotates the reflecting mirror 3 is △ θ. Then, the angle θ 'at the time when Anzu Kagami has finished N times,

[0032]

[Number 3] θ '= θ- become _{(π / 4-θ 0/} 2) = N · Δθ ······ (1). Thus, when the rotation angle is θ, the optical path length L3 [mm] from the reflecting mirror 3 to the document is

[0033]

L ₃ = L ₃ <N> = h / cos φ = h / cos (θ ₀ −2θ ′) = h / cos (θ ₀ −2ΔθN) [mm] (2) Here, f <X> indicates that f is a function of X.

On the other hand, the state of the image before conversion and the image after conversion distorted into a barrel shape due to the fluctuation of the optical path length L are shown by the number of main scanning pixels 2
088 and 3000 times of sub-scans as an example, FIG.
(B).

In the image before conversion, x and y coordinate axes with the center of the image as the origin are taken as shown in the figure. Also, in the converted image, u and v coordinate axes with the center of the image as the origin are taken as shown in the figure. In the image before conversion, the width of the image when y = 0, that is, when the optical path length L ₃ = h, is 2088.
Image conversion process, the variation of the optical path length L _3, the length d
What is necessary is just to enlarge and convert the partial image reduced to (y) into 2088, and the processing method is shown below.

X before conversion of a pixel (u, v) after conversion
Assuming that the position in the y coordinate system is (x ′, y ′),

[0037]

(Equation 5) There is a relationship. Here, x 'is a real number. here,
Assuming that the partial image of y = 1500 is obtained when the number of main scans N = 1,

[0038]

(Equation 6) In this embodiment, the nearest neighbor method is used as the density conversion method.
That is, when the pixel value at the point (x, y) of the image before the conversion is p ₀ (x, y), the pixel value p (u, v) at the point (u, v) after the conversion is

[0039]

(Equation 7) And Therefore, the nearest grid point ([x ′], v) or ([x ′] + 1, v) of the pixel (u, v) after the conversion in the image before the conversion is calculated by the above (2) to (4). What is necessary is just to calculate in advance using an equation, store it in the ROM 53, and determine p (u, v) while referring to it.

FIG. 4 is a block diagram showing a main configuration of an embodiment of the present invention. In this embodiment, only the configuration of the image conversion processing device 5 shown in FIG. 2 is different, and FIG.
It is a block diagram showing the internal configuration.

The image conversion processing device 5 in this embodiment is
Since only the configurations of the image conversion means and the counter in the configuration shown in FIG. 2 are different, in FIG. 4, only these symbols are different from those in FIG. 2, and the other parts are the same as those in FIG. The description will be given with the same reference numerals.

The A / D converter 51 converts the partial image signal from the one-dimensional image sensor 1 from analog to digital and converts it into an image memory 52.
Sequentially. This data transfer is repeated during the sub-scanning by the sub-scanning mechanism 4, and the image memory 52 stores the two-dimensional image data of the entire read document 6. Next, partial image data corresponding to one main scan is loaded from the image memory 52 into the partial image memory 54. At this time, counter 3
1 counts the number N of times of loading, and notifies the image conversion means 30. The image conversion means 30 stores a conversion table calculated by a conversion coefficient different for each number N of times.
The conversion table is read from M53 based on the number N of times of partial image data loading notified from the counter 31, and the partial image data stored in the partial image memory 52 is subjected to image conversion processing according to it, and is sequentially transferred to the image memory 54. .

A conversion table for enlarging a partial image corresponding to the number of main scans by the one-dimensional image sensor 1 is calculated and stored in the ROM 53 in advance.
The method of calculating the conversion table may be the same as that in the first embodiment.

FIG. 5 is a perspective view showing the configuration of another example of an image scanner related to the present invention.

In this embodiment, an optical path length sensor 8 for measuring the optical path length from the reflecting mirror 3 to the reading line 7 is provided between the condenser lens 2 and the reflecting mirror 3 in the example shown in FIG. The image conversion processing device 5 is an image conversion processing device 50 that performs a conversion process according to the detection result of the optical path length sensor 8. Since other configurations are the same as those of the example shown in FIG. 1, the same reference numerals as those in FIG.

As the optical path length sensor 8 in this embodiment, a small optical distance measuring sensor may be used. Since the optical path length L ′ from the optical path length sensor 8 to the reflecting mirror 3 is known, the optical path length from the reflecting mirror 3 to the reading line 7 can be measured by subtracting this from the measured value of the optical path length sensor 8. Optical path length sensor 8
Transfers the measured optical path length value to the image conversion processing device 50.

FIG. 6 shows an image conversion processing device 5 according to this embodiment.
FIG. 3 is a block diagram showing a configuration of a 0.

The image conversion processing device 50 in this embodiment differs from the image conversion processing device 50 shown in FIG. 2 only in the configuration of the image conversion means. The other parts will be described with the same reference numerals as in FIG.

The A / D converter 51 performs A / D conversion on the partial image signal from the one-dimensional image sensor 1 and transfers the signal to the partial image memory 52. The image conversion means 60 performs image conversion processing on the partial image data stored in the partial image memory 52 based on the one-dimensional image sensor 1 notified from the optical path length sensor 8 and the optical path length to the reading line 7 to perform image conversion.
Sequentially.

The image conversion means 60 can perform the conversion processing in substantially the same manner as the image conversion processing device 5. For the image conversion unit 60 however, since the optical path length sensor 8 can measure the optical path length L _m of FIG. 7 showing an optical arrangement, L ₃ = L _m -L 'is obtained, the main scanning There is no need to determine the optical path length L3 from the number N, and a ROM for storing the conversion tables required in the first and second embodiments is not required.

FIG. 8 is a perspective view showing the configuration of an example of an image scanner related to the present invention.

In this embodiment, the sub-scanning mechanism 40 is disclosed in
A reflecting mirror rotation angle detecting means 41 for receiving the signal and detecting the rotation angle of the reflecting mirror 3 in response to the signal; Further, the image conversion processing device 90 performs image conversion based on the detection result by the reflection mirror rotation angle detection means 41. Since other configurations are the same as those of the example shown in FIG. 1, the same reference numerals as those in FIG.

In the present embodiment, the reflection mirror rotation angle detecting means 41 detects the rotation angle of the reflection mirror 3 based on the output of the sub-scanning mechanism 40 and notifies the image conversion processing device 90 of the rotation angle.

FIG. 9 shows an image conversion processing device 5 according to this embodiment.
FIG. 3 is a block diagram showing a configuration of a 0.

The image conversion processing device 50 in this embodiment is different from the one shown in FIG. 2 only in the configuration of the image conversion means. In FIG. 6, only these symbols are different from those in FIG. The other parts will be described with the same reference numerals as in FIG.

The A / D converter 51 A / D converts the partial image signal from the one-dimensional image sensor 1 and transfers the signal to the partial image memory 52. The image conversion means 91 obtains the number of scans N based on the rotation angle of the reflecting mirror 3 notified from the reflecting mirror rotation angle detecting means 41, and stores a conversion table calculated by a different conversion coefficient for each number of times N. ROM5
From 3, the conversion table is read based on the partial image data loading count N notified from the counter 31, and the partial image data stored in the partial image memory 52 is subjected to image conversion processing in accordance with the conversion table and sequentially transferred to the image memory 54. .

The image conversion means 91 can perform the conversion processing in substantially the same manner as the image conversion processing device 5.

In the above description, the ROM 53
Has been described assuming that the image conversion means 91 obtains the number of scans N based on the rotation angle of the reflecting mirror 3. And a conversion table created by using the rotation angle θ and the equations (1) to (4).
May perform image conversion using a conversion table according to the rotation angle θ of the reflecting mirror 3 notified from the reflecting mirror rotation angle detecting means 41.

[0059]

According to the image scanner of the present invention, the barrel-shaped distortion generated in the image when the sub-scanning mechanism rotates the reflecting mirror can be removed by the image conversion processing. Need only rotate the reflector. Therefore, compared to the conventional image scanner, the movement of the mechanism unit is small, the vibration can be reduced, and the sub-scanning can be performed at high speed, so that the image quality of the image scanner can be improved and reading can be performed at high speed. There is an effect that can be.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating an example of an image scanner related to the present invention.

FIG. 2 is a configuration diagram illustrating an example of an image conversion processing device 5;

3A is a diagram showing a positional relationship between a reflecting mirror 3 and a read original 6 as viewed from the side, and FIG. 3B is a diagram showing images before and after image conversion processing.

FIG. 4 is a diagram showing a configuration of an image conversion processing device 5 according to the embodiment of the present invention.

FIG. 5 is a configuration diagram illustrating an example of an image scanner related to the present invention.

6 is a diagram showing a configuration diagram of an image conversion processing device 50. FIG.

7 is a diagram showing an optical path length L _m of the optical path length sensor 8 measures.

FIG. 8 is a configuration diagram illustrating an example of an image scanner related to the present invention.

FIG. 9 is a diagram showing a configuration of an image conversion processing device 90.

10A is a projection view of a reading unit and a read original in an image scanner that performs sub-scanning by rotating a reflecting mirror, and FIG. 10B is a reading unit and reading in an image scanner that performs sub-scanning by rotating a reflecting mirror; FIG. 3 is a diagram illustrating a positional relationship of a document.

FIG. 11 shows an image scanner in which a reflecting mirror is rotated and a sub-scan is performed.
FIG. 3 is a diagram showing a configuration of a mechanism for making an optical path length L from a two-dimensional image sensor to a reading line constant.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1-dimensional image sensor 2 Condensing lens 3 Reflecting mirror 4 Sub-scanning mechanism 5 Image conversion processing device 6 Reading original 7 Reading line 8 Optical path length sensor 20 Image converting means 30 Image converting means 31 Counter 40 Sub-scanning mechanism 41 Reflecting mirror rotation angle Detection means 50 Image conversion processing device 51 A / D converter 52 Partial image memory 53 ROM 54 Image memory 60 Image conversion means 90 Image conversion processing apparatus 91 Image conversion means

Claims (4)

[Claims] A one-dimensional image sensor for obtaining a partial image by main-scanning a read document; and a sub-scanning mechanism for changing a read image of the read document incident on the one-dimensional image sensor by rotating a reflecting mirror. An image scanner configured to synthesize a partial image to obtain a two-dimensional image, wherein an image conversion process for converting an image obtained by main scanning according to a change in an optical path length from the read original to the one-dimensional image sensor. The image conversion processing device has a counter that counts the number scanned by the sub-scanning mechanism, and an image conversion unit that converts an image obtained by main scanning according to an output from the counter. An image scanner, characterized in that: 2. The image scanner according to claim 1, wherein the image conversion processing device has a storage device for storing conversion tables obtained by using different conversion coefficients for each number of scans. An image scanner that performs image conversion based on a conversion table of the number of scans indicated by the counter output among the conversion tables stored in the scanner. 3. An image scanner according to claim 1, wherein the image conversion processing device stores an image of the entire read document, and outputs an image for each partial image obtained by main scanning, and an output of the image memory. An image scanner comprising: a counter for counting the number; and image conversion means for converting an image obtained by main scanning according to an output from the counter. 4. An image scanner according to claim 3, wherein the image conversion processing device has a storage device for storing conversion tables obtained by using different conversion coefficients for each number of scans. An image scanner that performs image conversion based on a conversion table of the number of scans indicated by the counter output among the conversion tables stored in the scanner.