JPH0391092A - Pattern comparator - Google Patents

Abstract

PURPOSE:To eliminate the need of adjustment of an optical system and to obtain simple and high by accurate pattern comparison by projecting a standard pattern and writing it optically in an optically in an optical element, and also, projecting a pattern to be inspected to the optical element by the same optical system. CONSTITUTION:One pattern SP in two patterns SP, TP is displayed on a pattern display means 3, and projected to an optical element 6 by an optical means 4. The pattern projected to the optical element 6 is sroted therein due to a difference of light intensity. Subsequently, the other pattern TP is displayed as a comparison object on the pattern display means 3, brought to image formation in the optical element 6 by the optical means 4, and a pattern difference is detected by a detecting means 7 due to a difference of electo-optical effects of a storage area and an unstorage area of the optical element 6. Accordingly, one pattern SP and the other pattern TP of the comparison object are projected by the same optical system 6, can be compared, and also, the storage pattern can be set arbitrarily. In such a way, it becomes unnecessary to adjust the optical axis and the magnification, and the pattern comparison can be executed simply and with high accuracy.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to pattern comparison used for detecting surface defects in materials such as steel plates, silicon wafers, and CeraQ7 substrates, and for identifying characters, figures, parts, etc. Regarding equipment.

[Conventional technology]

Conventionally, a known method for optically comparing patterns is to project a pattern to be inspected onto a glass dry plate or optical mask on which a standard pattern has been printed, and to compare two patterns by detecting the difference. . For example, Japanese Patent Publication No. 59-33855 discloses that the reflected and scattered light from a material to be inspected is used as a pattern to be inspected, and is detected by a plurality of photodetectors each having a standard pattern inside. A method is disclosed for detecting a state and detecting defects on the surface of a material to be inspected based on the results. Also, a method is known in which the surface of a steel plate is irradiated with a laser beam, the diffraction pattern thereof is used as a pattern to be inspected, and the pattern is compared with a standard pattern to detect irregularities defects on the surface of the steel plate. However, when performing pattern comparison using a single standard pattern,
When the pattern to be inspected changes due to factors that are not defects, such as the roughness of the surface of the steel plate or the adhesion of oil, there is a risk that it will not be able to respond to this change and that it will be determined to be a defect even if it is not a defect. It was possible to perform only a rough inspection using .

Therefore, when it is necessary to perform high-precision inspection and various standard patterns are required, it is necessary to replace the standard patterns each time, which poses a problem in that complicated work is required.

To solve this problem, there is a method of writing a standard pattern on a variable optical filter using liquid crystal or the like. FIG. 3 is a schematic diagram illustrating a conventional pattern comparison device using a liquid crystal as a variable optical filter. In the figure, 32 is ITV
, is a display controller that controls a display 33 (to be described later) to display a pattern to be inspected TP as a comparison target inputted by an input device (not shown) consisting of an imaging means such as a COD camera; The pattern to be inspected TP that is controlled to be displayed is displayed on the display 33. The display 33 uses a CRT display and projects the displayed pattern to be inspected TP. The projected pattern to be inspected TP enters the lens 34 and is imaged onto the variable optical filter 36. A standard pattern SP is written in advance on the variable optical filter 36 by a pattern writer 40 so as not to transmit light, and the difference between the projected pattern to be inspected TP and the standard pattern SP is detected by the lens 38.
is projected onto a detector 39 through which a pattern difference is detected.

[Problem to be solved by the invention]

However, in a conventional pattern comparison device using a variable optical filter, in order to compare the standard pattern written on the variable optical filter and the pattern to be inspected with high precision, the optical axis of the pattern to be inspected must be aligned with the optical axis of the standard pattern. In addition to matching the axis, it was necessary to match the magnification with that of the standard pattern.

That is, when optical axes mismatch occurs, a shift occurs between the pattern to be inspected and the standard pattern, and a pattern difference is detected by the detector even though both patterns match.

Furthermore, if a mismatch in magnification occurs, there is a possibility that a pattern difference will not be detected even though the two patterns do not match.

Therefore, it is necessary to adjust the optical system in order to match the optical axis and magnification, which makes the structure complicated, requires a highly accurate optical system, and makes the apparatus expensive.

The present invention was made in view of the above circumstances, and it is possible to adjust the optical system by projecting a standard pattern and optically writing it onto the optical element, and by projecting the pattern to be inspected onto the optical element using the same optical system. The objective is to provide a simple and highly accurate pattern comparison device that eliminates the need for

[Means to solve the problem]

A pattern comparison device according to the present invention is a pattern comparison device that optically compares two patterns, and includes a pattern display device that selectively displays one of the patterns, an optical device that projects the displayed pattern, and a pattern comparison device that optically compares two patterns. an optical element that electro-optically stores the pattern that has been created according to the difference in light intensity, and changes the optical properties of the pattern transmitted through the storage area by an electro-optical effect; a pattern stored in the optical element;
It is characterized by comprising a detection means for detecting a pattern difference with a pattern transmitted through the optical element.

[Effect]

In the present invention, one of the two patterns is displayed on a pattern display means and projected onto an optical element by an optical means. The pattern projected onto the optical element is stored there due to the difference in light intensity.

Next, the other pattern is displayed on the pattern display means as a comparison target, the image is formed on the optical element by the optical means, and the pattern difference is detected by the detection means based on the difference in the electro-optic effect between the storage area and the unstored area of the optical element. Detect. Therefore, one pattern and the other pattern to be compared can be projected by the same optical system and compared, and the pattern to be stored can be arbitrarily set.

〔Example〕

Hereinafter, the present invention will be explained based on drawings showing embodiments thereof. FIG. 1 is a schematic block diagram showing the configuration of a pattern comparison device according to the present invention (hereinafter referred to as the device of the present invention).
In the figure, ll is the pattern to be inspected T as a comparison target.
It is an input device consisting of an imaging means such as an ITV or a CCD camera for selectively inputting a two-dimensional image of a standard pattern SP or a standard pattern SP. is a long wavelength,
The display is controlled so that the standard pattern is displayed in red, which has a low light intensity, and the standard pattern is displayed in green, which has a short wavelength and high light intensity, and is displayed on the multicolor display 3. Multicolor display 3 is color CRT
B50 (Bi, SiO□) is transmitted through a polarizer 5 that transmits light having a predetermined polarization angle among the light input to the lens 4 to transmit each displayed pattern using a display.

Dansmuth S 1licon Danwide)
The image is formed on the element 6.

The BSO element 6 is an element exhibiting a photodielectric effect and an electro-optical effect (Pockels effect), and has a predetermined number of pixels. Further, the BSO element 6 is controlled by the BSO controller 10 into two modes: a write mode and a read mode. In the write mode, the electric field of the image of the standard pattern SP is modulated according to the light intensity by localized light irradiation of the standard pattern SP using the photo-dielectric effect of the BSO element 6, thereby writing the standard pattern SP.
Write.

In addition, in the read mode, the internal electric field is modulated according to the electro-optic effect of the BSO element 6, causing birefringence, that is, changing the plane of polarization of the light irradiated from the outside, so that the standard pattern sp
Detect storage area. The light transmitted through the BSO element 6 passes through an analyzer 7 that transmits light with the same polarization angle as that of the polarizer 5, and a lens 8 to form an image on a detector 9, where a comparison result between both patterns is detected.

Next, the operation of the device of the present invention will be explained.

First, the standard pattern sp is input from the human-powered device 11,
The display controller 2 displays the image in green on the multicolor display 3.

This is because green light has a high intensity and is suitable for writing. The displayed standard pattern SP is imaged onto the BSO element 6 by the lens 4. At this time, the light of the standard pattern sp having a predetermined polarization angle is transmitted through the polarizer 5. B.S.
The O element 6 is controlled to write mode by the BSO controller 10, and writes the standard pattern SP by modulating its electric field according to the light intensity. Next, the BSO element 6 is controlled to read mode by the BSO controller 10. Then, the pattern to be inspected TP is inputted from the input device 11, controlled to be red by the display controller 2, and displayed on the multicolor display 3. This is because reading is performed using light with as low a light intensity as possible to reduce the influence on the photodielectric effect of the BSO element 6. At this time, the multicolor display 3 is controlled by the display controller 2 so as to display the pattern to be inspected TP and the standard pattern SP at the same position.

The displayed pattern to be inspected TP is then imaged onto the BSO element 6 in the same manner as in the write mode. At this time, in the BSO element 6, the electric field in the area where the standard pattern SP is written is modulated with respect to the electric field in other areas. The transmitted light of the portion focused on the area and the transmitted light of other portions have different polarization angles due to the Pockels effect. Therefore, the transmitted light of the part focused on the area where the standard pattern sp is written has a different polarization angle from the transmitted light of other parts, and does not pass through the analyzer 7.
Only the transmitted light of the other portions passes through the analyzer 7. That is, when the pattern to be inspected TP is larger than the standard pattern SP, light from other parts passes through the analyzer 7. By detecting the transmitted light from the analyzer 7 with the detector 9, it is possible to detect a pattern difference between the pattern to be inspected TP and the standard pattern SP, and to easily compare the pattern with the standard pattern SP. Become.

Note that writing of the standard pattern SP can be executed at any time in a short time of several milliseconds to several seconds, and can be rewritten to the optimal standard pattern SP at any time.

Next, an example in which the apparatus of the present invention is applied to a steel sheet surface defect inspection apparatus using laser light will be described.

FIG. 2 is a block diagram showing the configuration of a steel plate surface defect inspection device. In the figure, reference numeral 1 denotes a pattern comparator of the present invention, which is substantially the same as that in FIG. 1, so a description thereof will be omitted. 20 is a steel plate wound onto a reel, and above the steel plate 20 are a laser source 22 that irradiates a laser beam, and an ITV and a CC that two-dimensionally receives the diffraction pattern of the reflected light from the steel plate 20.
An input device 11 consisting of an imaging means such as a D-camera is provided. Further, a position detector 21 is provided below the steel plate 20 to detect the position of the steel plate in the feeding direction. The display controller 2 receives the standard pattern SP of the normal part from the input device 11.
and the pattern to be inspected TP at the time of inspection is input, and
Input control is performed by the calculator 25. The calculator 25 controls the display controller 2 and instructs the BSO controller 10 to write and read. Further, the position information PD from the position detector 21 is given, and the inspection result data TR is output based on the position information PD and the comparison result from the data processor 24 that data-processes the comparison result detected by the detector 9. .

In the steel sheet surface defect inspection apparatus configured in this manner, the diffraction pattern of the normal portion of the steel sheet 20 can be written into the BSO element 6 at all times as the optimal standard pattern SP, thereby enabling highly accurate inspection.

Note that in the above embodiments, patterns were displayed in green and red on the multicolor display in order to improve efficiency during writing and reading, but the present invention is not limited to this, and the display may be in a single color. Needless to say.

〔effect〕

As explained above, according to the present invention, the comparison target pattern and the standard pattern are displayed at the same position on the display means and projected by the same optical system, making it unnecessary to adjust the optical axis and magnification. By writing the standard pattern on the optical element, the standard pattern can be changed at will, and excellent effects such as easy and highly accurate pattern comparison can be achieved.

[Brief explanation of drawings]

FIG. 1 is a schematic block diagram showing the configuration of a pattern comparison device according to the present invention, FIG. 2 is a block diagram showing the configuration of a steel sheet surface defect inspection device using the pattern comparison device of the present invention,
FIG. 3 is a diagram illustrating a conventional pattern comparison device using a liquid crystal. 1...Pattern comparison device 3...Multicolor display 4.8
... Lens 5 ... Polarizer 6 ... BSO element 7
...Analyzer 9...Detector sp...Standard pattern TP...Test pattern

Claims (1)

[Claims] 1. A pattern comparison device that optically compares two patterns, comprising: pattern display means for selectively displaying one of the patterns; optical means for projecting the displayed pattern; and a pattern comparison device for optically comparing two patterns. an optical element that electro-optically stores a pattern in accordance with the difference in light intensity thereof and changes the optical properties of the pattern transmitted through a storage area by an electro-optic effect; 1. A pattern comparison device comprising a detection means for detecting a pattern difference between a pattern stored in an optical element and a pattern transmitted through the optical element.