JPH01263540A - Pattern detecting apparatus - Google Patents

Abstract

PURPOSE:To enable the detection of a metal pattern in high contrast, by a method wherein the wavelength of an irradiation light is limited to a range of 350 to 750nm, the irradiation light is polarized linearly, and only a polarized component in the direction perpendicular to the direction of polarization of the irradiation light is sensed by a detector. CONSTITUTION:A substance 10 to be detected, which is prepared by forming a metal pattern 2 on a ceramic substrate 1, is irradiated obliquely from above by a light source 3 through an optical filter 4 transmitting light of 350 to 750nm and a polarizing plate 5. A polarizing plate 6, a lens 7 and an image pickup means 8 are provided above said substance 10, and the polarizing plates 5 and 6 are so provided that the directions of polarization thereof are perpendicular to each other. The irradiation light from the light source 3 is made to be of the wavelength 350 to 750nm by the filter 4 and polarized by the polarizing plate 5, and the substance 10 is irradiated by a linearly polarized light. Since the substrate 1 is constituted of minute particles, the irradiation light is reflected diffusedly and the direction of polarization of a reflected light is diffused. Since the direction of polarization of the polarizing plate 6 intersects the polarizing plate 5 perpendicularly, besides, a reflected light from the pattern 2 is intercepted and the pattern 2 is detected as black, while the substrate 1 is detected as white since a reflected light from the substrate 1 is passed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a pattern detection device, which detects metal patterns (fine particles) formed on a substrate made of fine particles, such as a ceramic substrate, etc. The present invention relates to a pattern detection device suitable for high-contrast, high-speed detection of particles (including those made of particulate metal).

[Conventional technology]

As one of the conventional techniques for detecting patterns formed on ceramic substrates with high contrast, Japanese Patent Laid-Open No. 59-2
There is one described in Publication No. 31402.

In this conventional technology, a pattern and a substrate are irradiated with polarized bright-field illumination light, and among the reflected light, the polarized component in the same direction as the polarization direction of the bright-field illumination light is blocked, and the polarization direction is perpendicular to the polarization direction of the bright-field illumination light. Patterns are detected by extracting only directional polarization components.

Furthermore, Japanese Patent Application Laid-Open No. 61-274208 discloses a printing plate surface @ area ratio measurement method for measuring the area ratio of an image on the printing plate surface in order to adjust the amount of ink supplied to the printing plate of an offset printing machine. has been done. In this conventional technology, a light source is provided diagonally above the surface of the printing plate in order to measure contrast between the image on the printing plate and the pristine surface other than the image. After polarizing the light and aligning it with parallel light, it is irradiated onto the printing plate, and the WC2 polarizing plate blocks the transmission of the diffusely reflected light rays that are diffusely reflected on the surface of the printing plate, and a trap is created in which only the light that has passed through the second polarizing plate is received. There is.

[Invention tries to solve it! Problem 11] The above conventional technology does not take into account the polarization property (extinction ratio performance) K of the polarizing plate, and there is a problem in that the polarization property is significantly reduced by infrared rays and ultraviolet rays emitted by the light source used. Polarizing plates are generally manufactured by heating a polyvinyl alcohol transparent film to about 90°C, stretching it in one direction, soaking it in an iodine-calcium iodide aqueous solution, and drying it, so it is sensitive to heat and cannot be heated to temperatures above about 50°C to 60°C. If this happens, the polarization performance will deteriorate.Moreover, metal patterns drawn on ceramic and other substrates are now mounted with high density, so it is difficult to inspect the quality of the patterns or perform alignment. It is necessary to detect patterns at a high distance using high-intensity illumination to improve workability. However, in the above-mentioned conventional technology, when high-intensity illumination is performed, the heat generated by infrared rays is high, and the polarization characteristics of the polarizing plate are further deteriorated, making it impossible to perform pattern detection at high speed.

An object of the present invention is to provide a pattern detection device that can detect a pattern drawn on a substrate made of fine particles with high contrast (contrasting brightness and darkness) at high speed.

[Means to solve the problem]

The above object is to provide a pattern detection device that irradiates a pattern and a base material with light and detects the pattern by receiving the reflected light with a detector, and a light irradiation means that irradiates the pattern and the base material with light from an oblique direction. , the wavelength of the irradiation light is 350 nm ~ 7
a wavelength limiting means for limiting the wavelength to a range of 50 nm; a first polarizing means for linearly polarizing the irradiated light; and a first polarizing means for linearly polarizing the irradiated light, and blocking a polarized component in the same direction as the polarization direction of the irradiated light among the reflected light from the pattern and the base material. This is achieved by providing a second polarizing means that allows the detector to receive only polarized components in a direction perpendicular to the polarization direction of the light.

In a preferred embodiment of the present invention, the light irradiation means are provided opposite to each other, the first polarization means is further provided with a cooling means, and furthermore, the wavelength range of the irradiation light is limited to a wavelength range that is absorbed by the pattern. will be established.

[Effect]

In the present invention, the wavelength range of the irradiation light is 350 nm to 750 nm.
nmK, so the polarizing plate through which the irradiated light passes will not be irradiated with ultraviolet rays or infrared rays, and the polarizing properties of the polarizing plate will not deteriorate.In addition, infrared rays, which cause heat, are also cut, so the polarizing plate Thermal deterioration of the board is also avoided.

Furthermore, in the preferred embodiment of the present invention, since the polarizing plate is cooled by the cooling means, it is possible to prevent the temperature of the polarizing plate from increasing due to infrared rays that have not been completely cut. Furthermore, since oblique illumination is performed from two directions, it is possible to achieve extremely bright linearly polarized illumination in which the polarization direction of the illumination system is in the same direction, and even in patterns with steps on the base material, the shadows of the illumination caused by the steps are opposite to each other. Since the light is canceled out by the polarized illumination system, it is possible to detect the pattern width etc. with high accuracy. Furthermore, since the base material and pattern are illuminated with light in the wavelength range that is absorbed by the metal pattern,
For example, between the illumination light source and the polarizing plate, 35 Orun to 45
If an optical filter that transmits 0 nm is provided, a gold pattern formed on a ceramic substrate or the like will absorb 50 nm or more of light in this wavelength range. Therefore, the extinction ratio of the gold pattern can be further improved, and the gold pattern can be detected with high contrast.

〔Example〕

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a basic configuration diagram of a pattern detection device according to an embodiment of the present invention. An object to be detected 10 having a metal pattern 2 formed on a ceramic substrate 1 is illuminated obliquely from above by a light source 3 via a light transmission optical filter 4 of 350 nm to 750 nm and a polarizing plate 5. A polarizing plate 6, a lens 7, and an imaging means 8 are arranged above the object to be detected 10, and are configured to detect the metal pattern 2 on the substrate 1. The polarizing plate 5 and the polarizing plate 6 are arranged so that their polarization directions are perpendicular to each other. In the above configuration, in which a fluid is injected from a nozzle 9 onto the surface 5a of the polarizing plate 5 (the supply source is not shown), the illumination light from the light source 3 has a wavelength of 350 to 750 nm through the optical filter 4, The illumination light irradiated onto the polarizing plate 5 is polarized, and the object to be detected 10 is illuminated with linearly polarized light. Since the ceramic substrate 1 is composed of fine particles, the illumination light is diffusely reflected, and the polarization direction of the reflected light is disturbed even though it is linearly polarized by the polarizing plate 5. on the other hand,
Since the reflection on the surface of the metal pattern is regular reflection, the polarization direction of one reflected light is the same as the polarization direction by the polarizing plate 5.

Since the polarization direction of the polarizing plate 6 is perpendicular to the polarizing plate 5 of the illumination system, most of the reflected light generated by the metal pattern 2 is blocked and the metal pattern 2 is detected as a black spot, and most of the reflected light from the ceramic substrate 1 passes through. Therefore, the substrate 1 is detected as white. FIG. 2 is a graph showing the spectral transmittance of the optical filter 4 and the polarizing plate 5. When detecting patterns on ceramic substrates or green sheets, these substrates are composed of non-uniform fine particles, so it is necessary to prevent interference between the unevenness of these particles. It is effective to use illumination light having a predetermined wavelength width (to prevent speckles from occurring). Furthermore, when illuminating with a polarizing plate, the transmittance decreases significantly in a wavelength range shorter than 350 nm, as shown in FIG. 750 again
In this example, the wavelength range of 350 nm to 750 nm becomes a heat source and deteriorates the polarization performance of the polarizing plate.
The wavelength range is used. However, the optical filter 4
In this case, the light having a wavelength of 750 nm or more that becomes a heat source cannot be completely cut off as shown in Figure @2. Therefore, fluid is injected from the nozzle 9 onto the surface of the polarizing plate 50 to reduce the temperature rise of the polarizing plate 5. Preventing.

FIG. 3 shows another embodiment of the present invention, in which parts having the same functions as those in FIG. 1 are given the same reference numerals. 1st
The difference from the figure is that in addition to the first polarized illumination system consisting of a light source 3a, an optical filter 41, and a polarizing plate 51, a second polarized illuminating system consisting of a light source 3b, an optical filter 42, and a polarizing plate 52 are arranged opposite to each other. It is arranged so that the object to be detected 10 can be illuminated diagonally from two directions above. In the embodiment of FIG.
A pattern 22 with steps formed on the substrate 11 as shown in FIG. 4 can be detected with high precision. That is, the fourth
As shown in the figure, with oblique illumination from one direction, a shadow 100 is created on the side surface of the pattern 22 due to the step difference in the pattern 22. Therefore, at the time of detection, the pattern width is detected to be thicker ((=L+z)) than the actual pattern width, and the binarized signal width is also thicker9, resulting in a detected image that is thicker than the actual pattern 22. In the example shown, since the illumination is from two opposing directions, the shadow 100 shown in FIG. 4 is canceled out and the pattern @ can be detected faithfully.
Compared to FIG. 1, twice as bright illumination is possible. Compared to the bright-field illumination method disclosed in Japanese Patent Application Laid-Open No. 59-231402, the present method shown in FIG. 3 can provide about eight times the brightness when the same components are used.

FIG. 5 is a diagram showing the configuration of the specific embodiment of FIG.
The basic functions are the same as those in FIG. 3, and parts having the same functions as those in FIG. 3 are given the same reference numerals. Mercury lamp 501
The emitted light beams a and 501b pass through collector lenses 502a and 501b, respectively.
502b and reflection fi 503a, 503b, through optical filter 41.42, reflection mirror 504a, 504
b, polarized by the polarizing plates 51 and 52, compressed into a slit shape by the cylindrical lenses 505a and 505b, and illuminated as polarized slit light onto the object 1o obliquely from above. In the above embodiment, since the linear sensor 506 is used in the imaging device, a cylindrical lens is used as the condensing lens, but depending on the imaging means, -
An in-shell focusing lens may be used. The above illumination system is similar to that shown in FIG. The second two polarized illumination systems are arranged to face each other. 1st. It is preferable that the angular error of each of the incident angles θ and 02 from the second polarized illumination system be within ±5°. Above the object to be detected 10, a polarizing plate 51 and 52 are arranged so that the polarization direction is orthogonal. A polarizing plate 6 and a lens 7 are arranged, and a linear sensor 506 is arranged to detect a pattern on the object 10 to be detected. Further, clean fluid (air, N2 gas) is blown out from nozzles 507a and 507b, respectively, onto the surfaces of the polarizing plates 51 and 52 for cooling.

In the above configuration, the polarizing plates 51 and 52 may be set at positions other than those shown in the figure as long as the illumination light passes through the optical filters 41 and 42.
It is preferable to install it at a position where the light beam is spread out, for example, into a parallel light beam.In the above configuration, extremely bright polarized light compressed into a slit shape is focused on the object to be detected 10, so high-speed detection is possible. . - For example, in an illumination system that uses a ceramic substrate as the object to be detected, a 250 W mercury lamp, an optical filter with a wavelength range of 350 to 750 nm, and a polarizing plate with a transmittance of about 40 cm, the detector The CCD linear sensor used can be driven at a high speed of 30 MHz. In addition, the temperature of the polarizing plate surface is about 40℃ or less when the light is turned on continuously for 8 hours, and it can be kept below room temperature (about 20℃) by cooling with air. Even though a brightness light source is used, the surface temperature of the polarizing plate can be kept at an extremely low temperature, and stable and high-intensity polarized illumination can be achieved.

FIG. 6 shows a simpler embodiment of the present invention. The difference from Fig. 3 is that the light source is an optical fiber illumination 601.
．． 602 was used. The light source supplied to the optical fiber may be any of a mercury lamp, a Xe lamp, a halogen lamp, a tungsten lamp, etc.

The advantage of this embodiment is that the wavelength of the emitted light from the optical fiber can be reduced to 350
Since the wavelength is set within the range of ~750 nm and an optical fiber is used, the heat source hardly acts on the polarizing plate. Compact cold polarized illumination can be achieved by simply attaching the filter and polarizing plate to the tip of the optical fiber.

FIG. 7 shows an example in which the light transmission wavelength range of the optical filter is set to the wavelength range that the metal pattern absorbs in the embodiment shown in FIG. 1. The difference from the embodiment shown in FIG.
Heat ray absorption filter 701 and short wavelength band optical filter 70
The point is that the polarizing plate 5 is irradiated with the illumination light 3 through the polarizing plate 5 and the polarizing plate 5. - Generally, metals have the property of absorbing specific wavelength ranges. FIG. 8 is a graph showing the spectral reflectance of different materials. For example, in the case of gold, the reflectance decreases to about 40% in a wavelength range shorter than 450 nm. Therefore,
The transmission wavelength range of the short wavelength range optical filter 702 is 350
~450 nm, the reflectance of ceramic substrates, etc. is approximately 90 cm or more in the wavelength range of 200 nm to 11,000 nm, so there is a 2:1 contrast difference between the gold pattern on the ceramic substrate and the ceramic substrate. occurs. Moreover, since polarized illumination is used, the contrast ratio is further increased, making it possible to detect patterns with high contrast between the white ceramic substrate and the black gold pattern. It is suitable for detecting thinly plated patterns, etc. Similarly, although a gold pattern has been described in this embodiment, the present invention is not limited thereto, and any material that absorbs light in the range of 350 nm to 750 nm is effective.

〔Effect of the invention〕

According to the present invention, a pattern drawn on a substrate made of fine particles can be printed at high contrast (contrasting light and dark) at high speed without deteriorating the polarization characteristics of the polarizing means and avoiding deterioration caused by heat rays. can be detected. Also, 2
When performing polarized illumination from any direction, in combination with a condensing lens, extremely bright illumination can be achieved, and patterns with good contrast can be detected even faster, and the pattern width can be reduced when detecting patterns with steps. More accurate detection becomes possible. Furthermore, when a cooling means is used, deterioration due to heat rays is further prevented. Furthermore, if the wavelength of the polarized illumination light is set to a wavelength that is absorbed by the pattern to be detected, pattern detection with extremely good contrast can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a basic configuration diagram of a pattern detection device according to an embodiment of the present invention, FIG. 2 is a graph showing the transmittance of a polarizing plate and an optical filter, and FIG. A basic configuration diagram of a pattern detection device according to another embodiment, FIG. 4 is an explanatory diagram of detecting a pattern with steps, FIG. 5 is a specific configuration diagram of the embodiment shown in FIG. 3, and FIG. 6 is a diagram of the original fiber. Fig. 7 is a block diagram of yet another embodiment of the present invention using illumination light of a wavelength that is absorbed by the pattern, and Fig. 8 shows the spectral reflectance of a substance. This is a characteristic graph. 1... Ceramic substrate 2... Metal patterns 5.5a, 3b... Light source 4.41.42... Optical filter 5.6, 51.52... Polarizing plate 7... Lens 8. ...Imaging means 9...Nozzle Fig. 1 Fig. 2 5s-length (7'1m) 3rd mouth 1...Ceramic, Noah base 3 types...Optical recording,
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Claims (4)

[Claims] 1. A pattern detection device that irradiates a pattern and a base material with light and detects the pattern by receiving the reflected light with a detector includes a light irradiation means that irradiates the pattern and the base material with light from an oblique direction; A wavelength limiting means for limiting the wavelength to a range of 350 nm to 750 nm, a first polarizing means for linearly polarizing the irradiated light, and blocking a polarized light component in the same direction as the polarization direction of the irradiated light among the light reflected from the pattern and the base material. and a second polarizing means for causing a detector to receive only polarized light components in a direction perpendicular to the polarization direction of the irradiated light. 2. 2. The pattern detection device according to claim 1, wherein two of said light irradiation means are provided to face each other, and light is irradiated obliquely onto the pattern and the base material from two directions. 3. 3. The pattern detecting device according to claim 1, wherein the first polarizing means includes a cooling means. 4. In the pattern detection device according to any one of claims 1 to 3, the wavelength range of the irradiation light in the wavelength range is
A pattern detection device further comprising means for setting a range in which the pattern absorbs light.