JP2004037736A - Image reader and its program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image reader capable of preventing focusing at a position not suitable for detecting a focus point regarding the image reader for reading images plotted on a film or paper or the like. <P>SOLUTION: The image reader 1 comprises an original platen 9 for fixing a slide mount 11, a light source 17 for irradiating the slide mount 11 with read light, a read optical system 19 provided with a CCD 25 for detecting the image in the irradiation area of the read light on the slide mount 11 and a focus adjusting function for matching the focus position of the read light. The image reader 1 is provided with a CPU 47 for making two scanning lines close to each other of the CCD 25 perform read, comparing the contrasts of the two scanning lines with each other and deciding whether or not to change the read position of the slide mount 11 on the basis of the result. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image reading device that reads an image drawn on a film, paper, or the like.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, an image reading apparatus that reads an image drawn on a film, paper, or the like has been provided with a focus adjustment function for focusing on a document surface. Such an image reading apparatus is of a type in which an optical system including an illumination system and a projection system is fixed, and a platen holding a document is moved along a document surface and scanned, and a document is fixed to the platen. And a type in which the optical system is moved along the surface of the document and scanned. As the latter image reading apparatus, there is known an image reading apparatus that swings an optical system when performing focus adjustment (for example, see Japanese Patent Application Laid-Open No. 2001-144896).
[0003]
[Problems to be solved by the invention]
However, in an image reading device of the type that swings the optical system, the optical path length from the light source to the document is changed by swinging the optical system, so that the angle of incidence of light on the document surface changes slightly. Then, the reading position of the document changes. Therefore, if focus adjustment is performed on a boundary portion of a picture drawn on a document, that is, a portion having a large contrast difference, a change in contrast during swinging becomes irregular, and an accurate focus point cannot be obtained. was there.
[0004]
Further, when accurate contrast data cannot be obtained, it is necessary to change the reading position on the document surface and perform focusing again, and there is a problem that the work of reading an image may take time and effort.
[0005]
The present invention has been made to solve such a conventional problem, and has as its object to provide an image reading apparatus capable of preventing focusing at a position that is not suitable for detecting a focus point. And
[0006]
[Means for Solving the Problems]
The image reading apparatus according to claim 1, wherein a document table for fixing a document to be read, an illumination optical system for irradiating the document with reading light, and an image of an irradiation area of the document with the reading light are detected. In an image reading apparatus having a reading optical system equipped with an image pickup device and a focus adjustment function for adjusting a focal position of the reading light, the reading is performed by two scanning lines that are close to each other of the image pickup device. The image processing apparatus further includes a processing unit that compares the contrasts of the two scanning lines with each other and determines whether to change the reading position of the document based on the comparison result.
[0007]
The image reading apparatus according to claim 2, further comprising a support member that supports the illumination optical system and the reading optical system, wherein the illumination optical system is connected by the support member. The focus adjustment is performed by making the system and the reading optical system rotatable around a rotation axis arranged in parallel with the document surface of the document.
[0008]
According to a third aspect of the present invention, in the image reading apparatus according to the first or second aspect, the two scanning lines of the image sensor that are adjacent to each other are adjacent scanning lines. Features.
According to a fourth aspect of the present invention, in the image reading apparatus according to any one of the first to third aspects, a step of selecting two mutually adjacent scanning lines among the scanning lines. Performing the photometry of all or some pixels included in the two scanning lines for each of the two scanning lines before the focus adjustment.
[0009]
The image reading device according to claim 5, wherein in the program according to claim 4, for each of the two scanning lines, the output value of each of the measured pixels and the pixel that is measured immediately before the output value of each of the pixels. Calculating the difference between the two output lines, calculating the sum of the absolute values of the differences for each of the two scanning lines, and calculating the difference between the two sums before the focus adjustment. To run.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the drawings.
FIG. 1 shows one use mode of the image reading apparatus of the present invention.
The image reading apparatus 1 is connected to a computer 3 via a cable 2 with a D-SUB connector. Further, a monitor 5 for displaying a read image and a keyboard 7 for inputting information to the computer 3 are connected to the computer 3.
[0011]
An opening 1a is formed in the image reading device 1, and a document table 9 is mounted in the opening 1a. The document table 9 is detachably attached to the image reading device 1. For example, a slide mount 11 is attached to and detached from the platen 9 as fixed image data to be displayed on the monitor 5. Instead of the slide mount 11, a strip film, an APS film having a film in a cartridge, and other originals may be attached and detached.
[0012]
FIG. 2 schematically shows the image reading device 1 by a vertical cross section.
The image reading device 1 has a mechanical body 13, a document table 9 for inserting the slide mount 11, and a drive unit 15 for changing the position of the mechanical body 13.
The mechanical body 13 has a light source 17 that illuminates the horizontally mounted slide mount 11, and a reading optical system 19 that receives reading light transmitted through the slide mount 11 and reads an image drawn on the slide mount 11. are doing. The mechanical body 13 is connected to a support member 14 via a rotation axis O.
[0013]
The reading optical system 19 includes a mirror 21 that reflects the reading light transmitted through the slide mount 11, a projection lens 23 that collects the light reflected by the mirror 21, a CCD 25 that receives the light collected by the projection lens 23, and have.
The drive unit 15 has a scan motor 27 that moves the reading optical system 19 in the sub-scanning direction (the horizontal direction in FIG. 2). Further, the drive unit 15 has an AF drive unit 29 having a focus adjustment function of moving the mechanical body 13 in a direction approaching or separating from the slide mount 11 about the rotation axis O.
[0014]
The AF driving unit 29 includes an AF motor 31, a gear 33 for transmitting the rotation of the AF motor 31, a cam 35 for transmitting the rotation from the gear 33, and a connecting rod 37 for reciprocating the cam 35 to tilt the mechanical body 13. And
The image reading apparatus 1 includes a scan motor drive circuit 39 connected to the scan motor 27, an AF motor drive circuit 41 connected to the AF motor 31, an image processing circuit 43 connected to the CCD 25, and a light source 17 And an illumination drive circuit 45 connected to the Further, the image reading apparatus 1 includes a CPU 47 for controlling the scan motor drive circuit 39, the AF motor drive circuit 41, the image processing circuit 43, and the illumination drive circuit 45, a memory 49 connected to the CPU 47, and an I / F circuit. 51. The I / F circuit 51 is connected to the computer 3 via the cable 2 with a D-SUB connector.
[0015]
FIG. 3A is a diagram when the AF driving unit 29 is operated and the mechanical body 13 is rotated clockwise about the rotation axis O in FIG. The light source 17 is separated from the slide mount 11 as compared with the case where the mechanical body 13 is located horizontally.
FIG. 3B is a diagram when the mechanical body 13 is rotated in a direction opposite to that of FIG. The light source 17 is closer to the slide mount 11 than when the mechanical body 13 is located horizontally.
[0016]
By tilting the mechanical body 13 as shown in FIGS. 3A and 3B, the relative positional relationship between the mechanical body 13 and the slide mount 11 is changed, and the input image to the CCD 25 is focused. .
[0017]
4 and 5 show the details of the internal structure of the image reading device 1. FIG. Here, FIG. 4 shows a vertical cross section in the main scanning direction (the direction perpendicular to the paper surface in FIG. 4), and FIG. 5 shows a cross section along the line VV in FIG.
The outer periphery of the slide mount 11 is fitted into a frame 11a, and the frame 11a is fixed on both sides by two leaf springs 53 on the mounting surface 9a.
[0018]
Then, the reading light of the image of the slide mount 11 emitted from the light source 17 has its optical path changed by about 90 degrees by the toric mirror 55 having different curvatures in the main scanning direction and the sub-scanning direction, and is irradiated on the slide mount 11. The reading light transmitted through the slide mount 11 has its optical path changed by 90 degrees by the mirror 21 and enters the CCD 25 attached to the substantially cylindrical CCD holding unit 57 via the projection lens 23. Here, the light source 17 and the toric mirror 55 constitute an illumination optical system 56.
[0019]
The reading light reflected by the toric mirror 55 is focused at a certain position of the slide mount 11 and the CCD 25 on a vertical section in the main scanning direction, and is focused on a position of the projection lens 23 on a vertical section in the sub-scanning direction. It is used so that it is set to be hot (see JP-A-8-248529). Further, when a scan motor 27 to be described later is operated, the mechanical body 13 moves in the sub-scanning direction along a guide bar 59 shown in FIG.
[0020]
Hereinafter, a method of calculating the focus point in the above-described image reading apparatus 1 will be described.
When the user executes the AF operation, the scan motor 27 starts, and the mechanical body 13 moves to a predetermined position in the sub-scanning direction. Then, the AF motor 31 is driven to cause the mechanical body 13 to swing around the rotation axis O in the direction in which the slide mount 11 and the light source 17 are separated from each other by the operation of the cam 35. Thereby, contrast data in a predetermined angle range is obtained. Here, the contrast data refers to the sum of the absolute values of the output differences between adjacent pixels in the CCD 25. The angle position at which the contrast becomes maximum is called a focus point.
[0021]
Next, a specific example of a method of determining a focus point will be described with reference to FIGS.
When focusing the slide mount 11 as shown in FIG. 6 (c), the mechanical body 13 is swung around the rotation axis O within a predetermined angle range, and at a predetermined angle interval as shown in FIG. 6 (a). Then, the contrast is measured at 5 points. In this case, a predetermined scanning line of the CCD 25 is measured within a dotted line in the slide mount 11. Then, as shown in FIG. 6C, the contrast sum for each point is calculated, and the point having the highest contrast, that is, the third point is set as the focus point.
[0022]
At this time, in determining the relative positional relationship between the slide mount 11 and the light source 17, first, for example, an area A and an area B of the slide mount 11 as shown in FIG. Two contrast data as shown in FIG. 7A are obtained. Then, by calculating these differences, it is estimated whether or not it is near the boundary of the picture. If it is estimated that it is near the boundary of the picture, the mechanical body 13 is moved in the sub-scanning direction, and the measurement position of the slide mount 11 to be measured is changed. The reason for this is that when the mechanical body 13 is oscillated about the rotation axis O at the time of autofocus, the crossing position between the slide mount 11 and the optical axis of the reading light changes, so that an accurate position near the boundary of the pattern is obtained. This is because contrast data may not be able to be obtained.
[0023]
Next, the reason for this will be specifically described with reference to FIG. 8 showing a change in the intersection position between the slide mount 11 and the optical axis of the reading light due to the swing.
As shown in the drawing, when the distance from the center of the rotation axis O to the reading position is X, the swing range of the mechanical body 13 is Y, and the amount of change in the reading position on the slide mount 11 is ΔX, the following is obtained. The following relational expression holds.
[0024]
θ = Y · tan (Y / 2 / X)
Δx = X (1 / cos θ−1)
Here, for example, since the distance X from the center of the rotation axis O to the reading position is 110 mm and the swing range a is 3 mm, the variation ΔX of the reading position is 0.010 mm from the above equation. Therefore, when the minimum pitch at the time of scanning is 0.006 mm, the change in the reading position corresponds to less than two pixels. Therefore, when the reading position is near the boundary of the picture, accurate contrast data cannot be obtained.
[0025]
In order to cause the image reading apparatus 1 to perform the above-described measurement, the memory 49 includes a procedure for selecting two scanning lines that are close to each other among the scanning lines, and a procedure for selecting two scanning lines. For each time, a procedure for photometry of all or a part of the pixels included in the scanning line, and a procedure for measuring contrast for every two scanning lines, that is, the output value of each pixel subjected to photometry and the previous one To calculate the difference between the output value of the pixel and the sum of the absolute values of the differences for each of the two scanning lines, and to calculate the difference between the two sums. The program has been recorded. This program is executed by using the CPU 47 as a processing means.
[0026]
In the image reading apparatus 1 of this embodiment, when adjusting the focal position of the reading light, two adjacent scanning lines of the CCD 25 are read, and the contrasts of the two scanning lines are compared with each other. Whether or not the focus point is near the boundary of the picture can be reliably grasped by calculating the difference between the contrasts of the two scanning lines. Then, when it is determined that it is near the boundary of the pattern, the mechanical body 13 is moved in the sub-scanning direction to acquire contrast of two new scanning lines, and they are compared with each other to determine that they are not near the boundary. If the mechanical body 13 is moved in the sub-scanning direction until the image is moved, the focus point can be separated from the vicinity of the boundary of the picture. Therefore, before performing focusing by the swinging motion of the mechanical body 13, the focus point can be reliably separated from the vicinity of the border of the picture, thereby preventing focusing at a position that is not suitable for detecting the focus point. be able to.
[0027]
Further, in the image reading apparatus 1 of this embodiment, the support member 14 that supports the illumination optical system 56 and the reading optical system 19 is provided, and the illumination optical system 56 and the reading optical system 19 connected by the support member 14 are mounted on a slide mount. Since the focus adjustment is performed by enabling rotation about a rotation axis O arranged in parallel with the original surface of the document 11, the apparatus can be downsized compared to a case where the mechanical body 13 is moved in parallel to perform focusing. be able to. The reason for this is that, in order to perform the parallel movement with sufficient accuracy, there is a tendency that a guide mechanism such as an AF guide bar for regulating the movement direction and a drive mechanism such as a motor for performing the movement are increased in size. It is.
[0028]
In the above-described embodiment, the contrast is compared using two adjacent scanning lines. However, the measurement is performed in consideration of a change in the reading range with respect to the rotation of the mechanical body 13 about the rotation axis O. If the selection of the scanning line is performed, any scanning line may be selected. For example, one or more scanning lines not used for measuring the contrast may intervene between the two scanning lines used for measuring the contrast. Further, the number of scanning lines used for measuring the contrast is not limited to two, but may be three or more.
[0029]
Further, in the above-described embodiment, the example in which the technique of detecting the difference in contrast between two scanning lines is applied to the swing type image reading apparatus 1 has been described. You may apply to an apparatus.
[0030]
【The invention's effect】
As described above, in the image reading apparatus of the present invention, when the focus position of the reading light is adjusted, reading is performed on two adjacent scanning lines of the image sensor, and the contrast of the two scanning lines is adjusted. , It can be grasped whether or not the focus point is near the boundary of the picture. If it is determined that the original is near the boundary of the pattern, the irradiation position of the reading light on the document is moved in the sub-scanning direction, and the contrasts of the two new scanning lines are compared with each other. If the reading position is moved in the sub-scanning direction until it is determined, the focus point can be separated from the vicinity of the border of the picture. Therefore, before performing the focusing, the focus point can be reliably separated from the vicinity of the boundary of the pattern, and in an image reading apparatus of a type that performs a rocking motion, the focusing is performed at a position that is not suitable for detecting the focus point. Can be prevented from happening.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing one use form of an image reading apparatus of the present invention.
FIG. 2 is an explanatory view schematically showing the image reading apparatus of FIG. 1 in a vertical section.
FIG. 3 is an explanatory diagram when a mechanical body is swung.
FIG. 4 is an explanatory diagram showing details of an internal structure of the image reading apparatus of FIG. 1;
FIG. 5 is a sectional view taken along the line VV of FIG. 4;
FIG. 6 is an explanatory diagram of focusing in the image reading device of FIG. 1;
FIG. 7 is an explanatory diagram of focusing in the image reading device of FIG. 1;
FIG. 8 is a diagram illustrating a swing range of a mechanical block of the image reading apparatus of FIG. 1;
[Explanation of symbols]
Reference Signs List 1 image reading device 9 platen 11 slide mount 14 support member 19 reading optical system 25 CCD
56 Illumination optical system

Claims (5)

A platen for fixing a document to be read;
An illumination optical system for irradiating the original with reading light,
A reading optical system including an image sensor that detects an image of the irradiation area of the reading light on the document,
A focus adjustment function for adjusting a focal position of the reading light;
In the image reading device having
The two scanning lines of the image sensor close to each other are read, the contrasts of the two scanning lines are compared with each other, and it is determined whether or not to change the reading position of the document based on the result. An image reading apparatus comprising a processing unit for determining. The image reading device according to claim 1,
Having a support member for supporting the illumination optical system and the reading optical system,
Focus adjustment is performed by enabling the illumination optical system and the reading optical system connected by the support member to rotate around a rotation axis arranged in parallel with the document surface of the document. Image reading device. The image reading device according to claim 1 or 2,
2. An image reading apparatus according to claim 1, wherein the two scanning lines of the image sensor that are adjacent to each other are adjacent scanning lines. The image reading device according to any one of claims 1 to 3,
Selecting two mutually adjacent scanning lines among the scanning lines;
Performing, for each scanning line of the two scanning lines, photometry of all or some pixels included in the scanning line;
Program to execute before focus adjustment. In the program according to claim 4,
Calculating, for each of the two scanning lines, a difference between an output value of each of the measured pixels and an output value of the pixel measured immediately before;
Calculating a sum of absolute values of the differences for each of the two scanning lines;
Calculating the difference between these two sums;
Program to execute before focus adjustment.

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