JP3334960B2 - Defect inspection method for periodic pattern - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shadow mask used for a cathode ray tube for a color television, a color separation filter for a color image pickup tube, a color filter for a liquid display, a mesh electrode used for an electron tube, a VDT filter, a photomask, and a Fresnel lens. , A unit having a certain optical property and shape (hereinafter a unit pattern) such as a lenticular lens
An industrial product or a unit pattern that is regularly and repeatedly arranged in a two-dimensional direction or a two-dimensional direction is repeatedly arranged while its optical properties, shapes, and arrangement pitches in one-dimensional and two-dimensional directions are gradually changed. The present invention relates to a method for detecting defects in certain industrial products.

[0002]

2. Description of the Related Art Conventionally, for the defect inspection of industrial products as described above, a method of recognizing a pattern by examining a video signal with a microscope photographing apparatus capable of resolving an array unit and a defect shape, and a method of recognizing a pattern having no defect in the same manner. A method of detecting defects by means such as comparing with a signal obtained by photographing, or for a product having a periodic aperture, an optical Fourier using a light diffraction phenomenon by a periodic pattern when irradiating coherent light. Although a method of detecting a defect by a conversion and a spatial filtering method and the like have been proposed, any of the methods requires an inspection time, and it is difficult to detect a finer defect. To solve this problem, TV cameras with area or line sensors
There has been proposed a method of detecting a defect from a video signal obtained by capturing light transmitted through a sample.

[0003]

However, in the method of photographing the sample transmitted light with a television camera, the resolution of the camera must be increased in order to detect finer defects, and when an area sensor camera is used, Since the obtained area data must be stored, there arises a problem that the data amount increases and the inspection takes time. In addition, when a line sensor camera is used, the amount of data to be stored is smaller than that of an area sensor camera, so that inspection can be performed in a short time even with a high-resolution camera. Since the generated signal and the edge signal of the outer peripheral portion of the pattern area are detected together with the defect, it is necessary to remove this signal. As a removal method, there is a method of reconstructing the obtained signal into a two-dimensional image and removing it by a masking process. However, this method results in an increase in the amount of data to be stored as in the case of the area sensor camera. Requires a large amount of memory and takes a long time for inspection.

An object of the present invention is to solve the above-mentioned problem. A camera scans a signal generated outside a pattern area and a pattern area outer edge signal based on the address of the outer peripheral position of a periodic pattern portion. Since it is not necessary to save as area data by performing inspection after removing each time, inspection can be performed in a short time without using a large capacity memory using a line sensor camera with higher resolution than before. It is an object of the present invention to provide a periodic pattern defect inspection method capable of performing the defect inspection.

[0005]

SUMMARY OF THE INVENTION According to the present invention, there is provided a primary light source which illuminates a sample having a periodic pattern moving at a constant speed by a sample moving device with a light source, and photographs the transmitted light with one or a plurality of line sensors. Smoothing processing based on the original data,
Performing the binarization processing, expansion processing, reduction processing, and expansion processing in this order, and recognizes both ends of the connected component of the obtained binary signal as the position of the outer periphery of the area having the periodic pattern, and occurs outside the recognized area. A periodic pattern defect inspection method for detecting a defect occurring only in a region where a periodic pattern of a sample is formed, by removing a signal to be generated, the pixel being expanded and contracted in the expansion and contraction processing. The number is set such that an area several pixels inside the outermost circumference of the periodic pattern portion can be recognized as the outer circumference.

[0006]

According to the present invention, there is provided a method for inspecting a defect generated in a periodic pattern composed of a repetitive arrangement of unit patterns. The specimen moving device illuminates a sample moving at a constant speed with a light source, and transmits the transmitted light to a line sensor. Image data (one-dimensional data) of a periodic pattern obtained by shooting with a camera
By recognizing the outer periphery of the periodic pattern portion on the basis of the signal, removing signals generated outside the recognized region (signals generated outside the pattern region and edge signals of the outer periphery of the pattern region) one by one, and performing defect inspection. Thus, the inspection can be performed at a higher speed than before.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail based on embodiments. FIG. 1 is a view showing one embodiment of the present invention, and a case where a shadow mask is used as a sample will be described. In the figure, 1 is a line sensor camera, 2 is a shadow mask, 3
Denotes a transport device, 4 denotes a light source, 5 denotes a camera controller, 6 denotes a signal processing device, 7 denotes a host computer, and 8 denotes a transport control device. The shadow mask 2 (hereinafter, referred to as SM) sent at a constant speed by a uniaxial transfer device 3 capable of transferring in both directions.
Is transmitted by the light source 4 and the SM transmitted light obtained by CC
A defect generated in the SM is extracted from an image signal obtained by photographing with the D line sensor camera 1 (hereinafter, line sensor).

A method of recognizing the outer peripheral position of the periodic pattern will be described with reference to FIG. In FIG. 2, the vertical axis represents the magnitude of the image signal (the transmitted light intensity of the sample), and the horizontal axis represents the number of pixels. FIG. 2A shows a waveform when the signal processing device 6 performs a smoothing process on the image signal obtained by the line sensor of FIG. 2A, 10 is a periodic pattern, 11 is a defect generated in a frequency pattern, 12 is a trimming positioning hole provided at an end of the SM, and 13 is a light source light at an end of the work. The state in which the gas has directly entered is exemplarily shown. When the signal of FIG. 2A is sliced at a predetermined level, a binary signal as shown in FIG. 2B is obtained. In FIG. 2B, the signal at the end of the work is removed. In order to recognize the outer periphery of the periodic pattern 10 from this signal, signals generated in portions other than the periodic pattern portion are removed, and the positions of both ends of a portion (signal connection component) where the signal corresponding to the periodic pattern portion is continuous are determined. Since the signal needs to be obtained, the signal in FIG. In this process, a predetermined number of pixels are added to the outer peripheral portion of each signal. In this manner, the periodic pattern portions divided by the defect 11 are connected to obtain a signal shown in FIG.
At this time, the signal of the trimming positioning hole is also widened by the expansion processing. Next, the signal shown in FIG. 2C is subjected to degeneration processing, and as shown in FIG. 2D, a signal generated in a portion other than the periodic pattern portion such as a trimming alignment hole is removed. Since the signal shown in FIG. 2D is narrower than the actual periodic pattern due to the degeneration processing, the signal shown in FIG. 2E is obtained by expanding the signal by a predetermined number of pixels. The number of pixels to be expanded and contracted is set to be several pixels inward from the outermost periphery of the periodic pattern portion so as not to detect a signal of a luminance difference between the periodic pattern portion emphasized by the differential processing and the other outer periphery. Set so that it can be recognized as. Both ends a and b of the signal of FIG. 2E obtained by the above processing are recognized as the outer peripheral address of the periodic pattern portion. Note that the perimeter address is determined in advance for a standard product during inspection or is determined each time for an actual inspection product.

FIG. 3 shows an example in which the above-described removal by outer periphery recognition is performed by inspection. Signal obtained by shooting (Fig. 3
(A)), a and b are recognized as the outer peripheral addresses by the method described with reference to FIG. Next, FIG. 3B shows a signal obtained by subjecting the signal of FIG. 3A to second-order differentiation. 0 of this signal
A signal other than the periodic pattern portion generated in the area of the pixels a to b and the pixels b to N is removed to obtain the signal of FIG. Slice processing is performed on this signal to extract defects. Inspection by the above method enables defect detection for each scan of the camera, and eliminates the need to store a large amount of data. Therefore, high-speed inspection can be performed even when a high-resolution camera is used.

[0010]

As described above, according to the present invention, high-speed inspection with a line sensor camera having a higher resolution than before can be realized without using a large amount of memory.

[Brief description of the drawings]

FIG. 1 is a diagram for implementing an inspection method of the present invention.

FIG. 2 is a diagram illustrating an outer periphery recognition method.

FIG. 3 is a diagram illustrating an outer periphery removing method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Line sensor camera, 2 ... Shadow mask, 3 ... Transport device, 4 ... Light source, 5 ... Camera controller, 6 ... Signal processing device, 7 ... Host computer, 8 ... Transport control device, 10 ... Periodic pattern, 11 ... Defects, 12: signal corresponding to trimming alignment hole, 13: signal corresponding to workpiece end.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-120448 (JP, A) JP-A-61-256237 (JP, A) JP-A-5-225336 (JP, A) 20157 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01N 21/84-21/958 G06T 1/00-9/40

Claims (1)

(57) [Claims] 1. A sample having a periodic pattern moving at a constant speed by a sample moving device is illuminated by a light source, and the transmitted light is photographed by one or a plurality of line sensors.
Based on the one-dimensional data, a smoothing process, a binarization process, an expansion process, a degeneration process, and an expansion process are performed in this order, and both ends of a connected component of the obtained binary signal are located at the outer periphery of a region having a periodic pattern. A periodic pattern defect inspection method for removing a signal generated outside the recognized area, and detecting a defect occurring only in a region where the periodic pattern is formed on the sample, A defect inspection method for a periodic pattern, wherein the number of pixels to be expanded and contracted in the expansion processing and the reduction processing is set so that a few pixels inside the outermost circumference of the periodic pattern portion can be recognized as the outer circumference.