JP2009053019A - Chart, system and method for testing resolution - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a chart for testing the resolution, with reduced effects due to illumination and improves the testing accuracy. <P>SOLUTION: The chart for testing resolution has a pattern for checking, where a stripe pattern, having a plurality of black lines and white lines disposed alternately, a reference pattern consisting of a black thick line, adjoining one side of the stripe pattern and a reference pattern consisting of a white thick line adjoining the other side of the stripe pattern are disposed in a plurality of sets that adjoins the direction of the widths of the lines. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a resolution inspection chart for inspecting the resolution of an image captured by an imaging apparatus including at least an imaging lens and an imaging element, a resolution inspection apparatus for inspecting using the resolution chart, and a resolution inspection method. .

  Conventionally, a small and thin imaging device has been mounted on a portable terminal which is a small and thin electronic device such as a mobile phone or a PDA (Personal Digital Assistant), thereby enabling not only audio information but also images to a remote place. Information can also be transmitted between each other.

  An example of such an imaging apparatus will be described with reference to FIG.

  The image sensor 12 is a CCD (Charge Coupled Device) type image sensor, a CMOS (Complementary Metal-Oxide Semiconductor) type image sensor, or the like. The image sensor 12 is mounted on the substrate 13. The imaging lens 11 that forms an image of the subject on the imaging device 12 is held by a lens frame 15. Further, the lens frame 15 is bonded to the substrate 13 with an adhesive S. An infrared cut filter 16 and a diaphragm plate 14 are disposed on the subject side of the imaging lens 11. In addition to the image sensor 12, a plurality of electronic components 19 such as capacitors are also mounted on the substrate 13.

  Such an imaging apparatus is configured as a single unit, and inspects the imaging apparatus before being mounted on a portable terminal. An important inspection among them is a resolution inspection.

  Various inventions related to resolution inspection are disclosed in the patent publication. As an example, the resolution inspection chart and the color inspection chart are arranged on the same base member, which reduces labor and time and improves inspection workability. An inspection sheet for an imaging apparatus is known (see Patent Document 1).

  The resolution inspection chart in Patent Document 1 includes a plurality of black and white lines having different line widths and pitches, and determines how far adjacent lines are separated from each other for inspection.

On the other hand, there is also a method in which a number of black and white lines having the same line width and pitch are provided, and these are imaged to determine and inspect the contrast ratio of the image. Specifically, a stripe pattern in which a plurality of black lines and white lines are alternately arranged is provided. This stripe pattern is placed at the image height to be inspected at the center and the four surroundings of the resolution inspection chart, and furthermore, by arranging stripe patterns whose line directions are different from each other by 90 degrees, resolution characteristics in different directions can be obtained. Can be inspected. However, in this case, a reference gradation level is required when determining the contrast of the stripe pattern, and for this purpose, a black reference pattern having a predetermined area and a white reference pattern are arranged in the vicinity of the stripe pattern. The luminance data of the black reference pattern and the white reference pattern of the captured image is used as the reference value.
Japanese Patent Laid-Open No. 2006-74556

  Here, in the imaging apparatus, the imaging lens is individually shifted with respect to the imaging element due to a manufacturing error or an assembly error, and variations occur. Since the resolution inspection is performed at a predetermined position (image height) of the captured image, when the resolution inspection chart for determining the contrast as described above is captured, the position of the resolution inspection chart on the captured image. The images are taken out of position. Therefore, even if the contrast of the fringe pattern imaged at a predetermined peripheral position on the image is determined, the corresponding position on the fringe pattern of the resolution inspection chart is different.

  On the other hand, although the resolution inspection chart is illuminated and imaged, it is actually difficult to illuminate uniformly, and even in the stripe pattern, illumination is partially different. For this reason, the gradation level of white is lowered in a dark portion of the stripe pattern. On the other hand, the two black and white reference patterns cannot be formed as large as the fringe pattern, and depending on the variation of the imaging device, the part to be inspected may not be detected by being shifted from the reference pattern. Perform the correction.

  Therefore, even if the gradation level of the reference pattern is constant, the detection position of the fringe pattern differs depending on the variation of the individual imaging devices, and the contrast ratio differs between the bright part and the dark part of the illumination. For this reason, even if it is a good imaging device, there exists a possibility that it may be discriminate | determined as inferior goods depending on which part of the stripe pattern was detected.

  Furthermore, in an apparatus that inspects a plurality of image pickup apparatuses at a time, the positional relationship between the image pickup apparatus and the chart differs among the image pickup apparatuses, so that the reference pattern data differs due to the influence of shading.

  The present invention has been made in view of such problems, and an object of the present invention is to propose a resolution inspection chart, a resolution inspection apparatus, and a resolution inspection method in which the influence of illumination is reduced and the inspection accuracy is improved.

The object is achieved by the invention described below.
1. A stripe pattern in which a plurality of black lines and white lines are alternately arranged, a reference pattern consisting of a black thick line adjacent to one side of the stripe pattern, and a white adjacent to the other side of the stripe pattern A resolution inspection chart, comprising a plurality of sets of reference patterns that are arranged adjacent to each other in the width direction of each line.
2. 2. The resolution inspection chart according to 1, wherein the inspection patterns are arranged at a center and four corners.
3. 3. The resolution inspection chart according to 1 or 2, wherein two inspection patterns whose directions of each line are different from each other by 90 degrees are arranged at a center and four corners.
4). 4. The resolution inspection chart according to claim 1, wherein each of the stripe patterns has four to ten black lines and white lines alternately arranged.
5). 5. The line width of the black reference pattern and the white reference pattern is 2 to 6 times the black line width or the white line width of the stripe pattern. The chart for resolution inspection described in 1.
6). The resolution inspection chart according to any one of 1 to 5, wherein two or more sets of the stripe patterns are arranged in one inspection pattern.
7.1 to 6 chart for resolution inspection according to any one of
An illumination device for illuminating the resolution inspection chart;
An image forming apparatus that forms an image obtained by imaging the resolution inspection chart using an imaging apparatus including at least an imaging lens and an imaging element;
An image discriminating apparatus that discriminates a contrast ratio of the fringe pattern on the basis of a gradation level of the black reference pattern and a gradation level of the white reference pattern in an image formed by the image forming apparatus;
A resolution inspection apparatus comprising:
Illuminating the resolution inspection chart according to any one of 8.1 to 6,
Imaging the resolution inspection chart using an imaging device including at least an imaging lens and an imaging element;
Forming a captured image; and
Determining the contrast ratio of the fringe pattern on the basis of the gradation level of the black reference pattern and the gradation level of the white reference pattern in the formed image;
A resolution inspection method characterized by comprising:

  According to the resolution inspection chart, the resolution inspection device, and the resolution inspection method of the present invention, the imaging device is inspected using the inspection pattern in which the reference pattern is adjacent to the fringe pattern. Even if there is a difference in illumination or uneven illumination on the resolution inspection chart, the effect is small, and the quality of the imaging apparatus can be accurately determined.

  Embodiments relating to a resolution inspection chart, a resolution inspection apparatus, and a resolution inspection method according to the present invention will be described.

  FIG. 2 is a schematic diagram of the resolution inspection apparatus.

  This apparatus is similar to the imaging apparatus described in “Background Art”, and inspects the resolution of an imaging apparatus including at least an imaging lens and an imaging element. In addition to the optical characteristics of the imaging lens itself, the resolution is affected by the appropriateness of focus adjustment of the imaging lens with respect to the imaging element.

  First, an outline of the inspection of the imaging apparatus will be described.

  The imaging device 1 to be inspected is set on an inspection table (not shown) so that the imaging lens 11 faces the resolution inspection chart 2. The resolution inspection chart 2 is illuminated as uniformly as possible by the plurality of illumination devices 3, and the resolution inspection chart 2 is imaged by the imaging device 1.

  The optical image of the resolution inspection chart 2 is photoelectrically converted by the imaging device of the imaging device 1 and output to the image forming device 4 as an image signal.

  In the image forming apparatus 4, predetermined image processing is performed on the image signal to generate an image signal.

  The image determination device 5 determines whether the image signal of the resolution inspection chart 2 is acceptable.

  FIG. 3 is a diagram of the resolution inspection chart 2.

  In the resolution inspection chart 2, inspection patterns 20 for inspecting the resolution are arranged at the center and at the four corners. The inspection pattern 20 is composed of a black line and a white line as will be described later. Then, an inspection pattern 20 in which black and white lines are arranged in the vertical direction to inspect the horizontal resolution of the imaging screen, and a black and white line in the horizontal direction to inspect the vertical resolution of the imaging screen. The inspection patterns 20 thus arranged are respectively arranged.

  FIG. 4 is an enlarged view of the inspection pattern.

  The inspection pattern 20 is provided with a stripe pattern 21 in which a plurality of black lines and white lines are alternately arranged, and a reference pattern 22 made of a black thick line is provided next to the stripe pattern 21, and a stripe is provided next to the reference pattern 22. A pattern 21 is provided, a reference pattern 23 made of a white thick line is provided next to the pattern 21, and a stripe pattern 21 is provided next to the reference pattern 23. In other words, the reference pattern 22 is adjacent to one side of the stripe pattern 21 and the reference pattern 23 is adjacent to the other side of the stripe pattern 21.

  In addition, as for the striped pattern 21, it is desirable that 4 to 10 black lines and white lines are alternately arranged. That is, if the number of black and white lines is 3 or less, the accuracy of inspection to be described later of the image pickup apparatus 1 is lowered, and particularly when the focus adjustment of the image pickup lens with respect to the image pickup element is not appropriate, it is easily affected. . On the other hand, when the number of black and white lines is 11 or more, the stripe pattern 21 is too large, and the influence of illumination unevenness is increased.

  Further, it is desirable that the black thick line width of the reference pattern 22 and the white thick line width of the reference pattern 23 be 2 to 6 times the black or white line width of the stripe pattern 21. That is, if the line widths of the reference patterns 22 and 23 are too narrow, the white line and the black line are close to gray when the focus adjustment of the image pickup lens with respect to the image pickup element is not appropriate, and it is difficult to be a reference for discrimination. On the other hand, when the line widths of the reference patterns 22 and 23 are too large, the inspection pattern 20 becomes large, and as a result, the resolution inspection chart 2 also becomes large, which is not preferable.

  In addition, it is desirable that two or more stripe patterns 21 are provided so that the inspection can be performed at a predetermined position on the imaging screen even if the imaging lens is displaced with respect to the imaging element.

  When a resolution inspection chart 2 having such an inspection pattern 20 is imaged by the imaging apparatus 1 and an image signal is generated by the image forming apparatus 4, a waveform shown in FIG. 5 is obtained.

  FIG. 5A shows a waveform obtained by imaging an imaging apparatus in which the resolution of the imaging lens is good and the focus adjustment of the imaging lens with respect to the imaging element is appropriately performed, and FIG. It is the waveform which imaged the imaging device in which the resolution is not favorable or the focus adjustment of the imaging lens with respect to the imaging device is not properly performed.

  In FIG. 5A, the signal of the reference pattern 22 that is a black thick line has the lowest gradation level, and the signal of the reference pattern 23 that is a white thick line has the highest gradation level. The contrast ratio is set to C11 with the tone level as a reference. In this case, the black line of the stripe pattern 21 also has a sufficiently low gradation level, the white line also has a sufficiently high gradation level, and this contrast ratio is L12. Then, the ratio of L12 to L11 becomes a sufficiently large value.

  On the other hand, in FIG. 5B, if the contrast ratio between the reference pattern 22 and the reference pattern 23 is C21, C21 is not much different from C11. However, the black line of the stripe pattern 21 has a higher gradation level and the white line has a lower gradation level, and this contrast ratio is L22. Then, the ratio of L22 to L21 becomes a small value.

  In this way, the image determination device 5 calculates the contrast ratio of the stripe pattern 21 based on the gradation level of the black reference pattern 22 and the gradation level of the white reference pattern 23, and determines pass / fail.

  In the inspection pattern 20, since the reference patterns 22 and 23 are adjacent to the fringe pattern 21, the imaging lens is individually displaced with respect to the imaging element, or there is uneven illumination on the resolution inspection chart 2. In addition, it is possible to accurately determine whether the imaging apparatus 1 is good or bad.

  Further, even when a plurality of imaging devices are inspected at a time, the quality determination is not affected by the position of the imaging device.

It is sectional drawing of an imaging device. It is a schematic diagram of a resolution inspection apparatus. It is a figure of the chart for resolution inspection. It is a figure of the pattern for a test | inspection. It is a figure of the waveform produced | generated by imaging an inspection pattern.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Imaging device 11 Imaging lens 12 Imaging element 2 Resolution inspection chart 21 Stripe pattern 22, 23 Reference pattern 3 Illumination device 4 Image forming device 5 Image discrimination device

Claims (8)

A stripe pattern in which a plurality of black lines and white lines are alternately arranged, a reference pattern consisting of a black thick line adjacent to one side of the stripe pattern, and a white adjacent to the other side of the stripe pattern A resolution inspection chart, comprising a plurality of sets of reference patterns that are arranged adjacent to each other in the width direction of each line. The resolution inspection chart according to claim 1, wherein the inspection patterns are arranged at a center and four corners. The resolution inspection chart according to claim 1 or 2, wherein two inspection patterns whose directions of each line are different from each other by 90 degrees are arranged at a center and four corners. 4. The resolution inspection chart according to claim 1, wherein four to ten black lines and white lines are alternately arranged in each of the fringe patterns. 5. The line width of the black reference pattern and the white reference pattern is 2 to 6 times the black line width or the white line width of the stripe pattern. The chart for resolution inspection according to item 1. The resolution inspection chart according to any one of claims 1 to 5, wherein two or more sets of the stripe patterns are arranged in one inspection pattern. The resolution inspection chart according to any one of claims 1 to 6,
An illumination device for illuminating the resolution inspection chart;
An image forming apparatus that forms an image obtained by imaging the resolution inspection chart using an imaging apparatus including at least an imaging lens and an imaging element;
An image discriminating apparatus that discriminates a contrast ratio of the fringe pattern on the basis of a gradation level of the black reference pattern and a gradation level of the white reference pattern in an image formed by the image forming apparatus;
A resolution inspection apparatus comprising: Illuminating the resolution inspection chart according to any one of claims 1 to 6;
Imaging the resolution inspection chart using an imaging device including at least an imaging lens and an imaging element;
Forming a captured image; and
Determining the contrast ratio of the fringe pattern on the basis of the gradation level of the black reference pattern and the gradation level of the white reference pattern in the formed image;
A resolution inspection method characterized by comprising:

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