JP2769874B2 - Inspection method and apparatus for resin molding distortion - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for inspecting resin molding distortion in a light-transmitting resin molded product such as an optical disk and a compact disk.

(Summary of the Invention) The present invention applies the principle of photoelasticity to a change in luminance by applying the principle of photoelasticity to distortion (flow mark, stress concentration) generated during resin molding of a light-transmitting resin molded product such as an optical disk and a compact disk. Extract by camera. This allows
High resolution and stable distortion detection and processing can be simplified.

(Prior Art) A conventional method for inspecting distortion of optical disks, compact disks, and the like after resin molding uses a CCD matrix camera having a rectangular two-dimensional field of view 2 with respect to the optical disk 1 as shown in FIG. In addition, the inspection area of the optical disc 1 is moved by intermittently rotating the optical disc 1 illuminated by the light source located on the opposite side of the camera. (Problems to be Solved by the Invention) By the way, when a CCD matrix camera is used as the inspection means, the field of view is a rectangular two-dimensional field, so that the illumination within the field of the optical disc 1 becomes non-uniform, and the light source is used together with a light source. Due to the effect of the polarization direction of the polarizing plate, the brightness varies depending on the position of the distortion on the screen of the CCD matrix camera, and stable distortion (Flolark: streak-like distortion that occurs mainly in the radial direction, stress concentration: There was dislike that detection of point-like distortion) could not be obtained.

In addition, since distortion occurs in the radial direction of the optical disc 1, the directionality of the molding distortion 3 is not determined on the CCD matrix camera screen as shown in FIG. That is, the molding distortion has an arbitrary inclination depending on the position on the screen, and there is a dislike that image processing becomes complicated.

In view of the above, the present invention captures a distortion image with a line camera, and further enables high-resolution and stable distortion detection by combining with a signal processing unit that extracts a luminance change in a radial direction. An object of the present invention is to provide a method and an apparatus for inspecting resin molding distortion which can be simplified.

(Means for Solving the Problems) In order to achieve the above object, a method for inspecting resin molding distortion according to the present invention is directed to a method for inspecting a rotating light transmissive resin molded article having a single wavelength of circularly polarized light on one surface. Light is made incident, and an image of the light-transmitting resin molded product in which a light having a specific polarization direction is selected from transmitted light of the light-transmitting resin molded product, a one-dimensional visual field in a radial direction of the light-transmitting molded product is displayed. A portion of the line camera whose luminance changes due to photoelasticity from a video signal of the line camera is detected.

Further, the resin molding distortion inspection apparatus of the present invention includes a rotation driving mechanism for rotating the light transmitting resin molded product, a light source disposed on one side of the light transmitting resin molded product, the light source and the light source. A polarizing plate and a quarter-wave plate, each of which is disposed between a transparent resin molded product and a circularly polarized light having a single wavelength and is incident on the transparent resin molded product, and the transparent resin A line camera that is arranged on the other side of the molded article and has a one-dimensional visual field in the radial direction of the light transmissive resin molded article; and a line camera that is arranged between the light transmissive resin molded article and the line camera. The 変 動 wavelength plate and the polarizing plate that select a specific polarization direction from the transmitted light of the light-transmitting resin molded article and enter the line camera, and the luminance fluctuates due to photoelasticity from the video signal of the line camera. And a signal processing unit for detecting the And it has a formation.

(Operation) In the present invention, attention is paid to the fact that the resin molding distortion is mainly generated in the radial direction of the light transmitting resin molded product, and the radial direction of the light transmitting resin molded product rotating in the one-dimensional visual field of the line camera. To match. For this reason, light of a single wavelength that has become circularly polarized is incident on a light-transmitting resin molded product, and a light having a specific polarization direction is selected from the transmitted light, and the image captured by a line camera is converted into a floating binary image. It is possible to extract a distortion defect whose luminance is changed on the principle of photoelasticity by processing using a relatively simple fixed algorithm such as differentiation, filtering processing, or the like. This extraction processing can be performed at high speed. In addition, since it is a one-dimensional visual field, it is possible to perform stable extraction without being affected by uneven irradiation and polarization direction. further,
If a high-resolution line camera is employed, it is possible to measure the strain defect size with high accuracy.

(Example) Hereinafter, an example of a method and an apparatus for inspecting resin molding distortion according to the present invention will be described with reference to the drawings.

FIG. 1 shows the configuration of an optical system according to an embodiment of the present invention.
The figure shows a signal processing unit that processes a video signal of a line camera. In these figures, reference numeral 1 denotes an optical disc, which is a light-transmitting resin molded product, which is rotatably supported by a rotation drive mechanism 11. A light source 12 such as a mercury lamp is disposed below the optical disc 1, and a single-wavelength filter 13, a diffusion plate 14, a polarizing plate 15 and a 1/1 are provided between the light source 12 and the optical disc 1 from below.
The four-wavelength plates 16 are arranged in this order. Also, the optical disk 1
A CCD line camera 20 is disposed above the optical disk 1, and a 波長 wavelength plate 21 and a polarizing plate 22 are disposed between the optical disc 1 and the line camera 20 in this order from below.

The line camera 20 has a high-resolution one-dimensional visual field, and the one-dimensional visual field S is set so as to capture the radial direction of the optical disc 1 in a linear slit shape as shown in FIG. However, by rotating the optical disc 1, the entire disc area can be covered. The polarizing plates 15 and 1 /
The four-wavelength plate 16 works to make the light incident on the disk circularly polarized, and the quarter-wave plate 21 and the polarizing plate 22 extract the phase difference of the light transmitted through the disk and convert it to a luminance difference. Work.

The video signal from the line camera 20 is stored in a memory 27 via a video processing unit (A / D conversion unit) 25 and an extraction processing unit (line buffer) 26. Here, the video processing unit 25 performs processing such as digitizing a video signal that is an analog signal, and the extraction processing unit 26 performs floating binarization, differentiation, or filtering processing on the signal after the video processing. To do.

In the configuration of the above embodiment, the light emitted from the light source 12 has a specific wavelength selected by the single wavelength filter 13,
At 14, the light is uniformly diffused over the field of view of the line camera 20 and reaches the polarizer 15. Then, light of a single wavelength that has become circularly polarized light is incident on the lower surface of the optical disc 1 by the action of the polarizing plate 15 and the quarter-wave plate 16. The light transmitted through the optical disc 1 is
A lens having a specific polarization direction is selected by the quarter-wave plate 21 and the polarizing plate 22 and is taken into the lie camera 20. Although the field of view S of the line camera 20 has a linear slit shape in the radial direction as shown in FIG. 3, the entire surface of the optical disk 1 can be covered by rotating the optical disk 1 by the rotation drive mechanism 11.

A video signal indicating the luminance of the field of view S of the line camera 20 is output from the line camera 20 to the video processing unit 25, and the video processing unit 25 outputs a signal that has undergone necessary A / D conversion or the like to the extraction processing unit 26. Output. The extraction processing unit 26 performs floating binarization, differentiation, or filtering on the signal after the video processing to extract a portion where the luminance has suddenly changed.

For example, in the case of the floating binarization processing, the threshold level is changed according to the situation, and the input signal is binarized depending on the situation. The point at which the luminance has changed compared to the surroundings according to the stored signal is determined to be a distortion defect.

In the case of the differential processing, the signal after the differential processing including the point where the luminance is rapidly changed by differentiating the input signal is stored in the memory 27.
The point at which the luminance changes abruptly compared to the surroundings is determined as a distortion defect based on the stored signal after the differential processing stored in the memory 27.

FIG. 4 shows an example of an algorithm in the case of the filtering process. In this case, the extraction processing unit 26 has at least three line buffers LB,
The LB temporarily stores information of pixels 1 to 2048 of the line camera 20. In FIG. 4, the processed line (l) corresponding to the line camera view S, the processed line (l-1) and the processed line (l + 1) after the video processing are held in the line buffer LB. Indicates a state in which The extraction processing unit 26 further has an operation function, executes the operation of the following expression using the values of the three line buffers LB, and outputs the result to the memory 27.

N-th operation processing value of processing line (l) = {n-th value of processing line (l-1)} × (−1) + {n-th value of processing line (l + 1)} × (+1) (1) (However, n performs processing from 1 to 2048 pixels) A signal subjected to filtering processing using the above equation (1) has a large arithmetic processing value corresponding to a pixel whose luminance has changed compared to the surroundings. It becomes a value, and the distortion defect position can be detected from the stored signal stored in the memory 27.

Note that the dotted line in FIG. 2 indicates that the video signal of the line camera 20 can be directly added to the extraction processing unit 26 when the extraction processing unit 26 has a function of performing floating binarization or differentiation processing as an analog signal. (The video processing unit 25 can be omitted).

(Effects of the Invention) As described above, according to the present invention, circularly polarized light having a single wavelength is incident on a light-transmitting resin molded product, and a light having a specific polarization direction is selected from the transmitted light. And captures it with a line camera to display the strain (flow mark, stress concentration) generated during resin molding of optically transparent resin molded products such as optical disks and compact disks in a one-dimensional view in the radial direction of the optically transparent resin molded product. And can be extracted stably with high resolution by using a line camera with. In addition, the light-transmitting resin molded product can be inspected in a continuous rotation state, and image processing of the line camera can be simplified, so that high-speed inspection is possible.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an optical system of an embodiment of a method and an apparatus for inspecting resin molding distortion according to the present invention, FIG. 2 is a configuration diagram showing a signal processing unit for processing a video signal of a line camera, and FIG. Is an explanatory diagram showing the field of view of the line camera, FIG. 4 is an explanatory diagram showing a case where filtering processing is performed by the extraction processing unit, FIG. 5 is an explanatory diagram showing a conventional method for inspecting resin molding distortion, and FIG. 6 is a matrix camera. FIG. 4 is an explanatory diagram showing a screen of FIG. 1 ... optical disk, 11 ... rotary drive mechanism, 12 ... light source,
13 ... Single wavelength filter, 14 ... Diffusion plate, 15, 22 ... Polarizer, 16, 21 ... 1/4 wavelength plate, 20 ... Line camera, 25 ...
Video processing unit, 26 ... Extraction processing unit, 27 ... Memory.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G01N 21/88-21/89 G01B 11/16

Claims (2)

(57) [Claims] 1. A light of a single wavelength, which has become a circularly polarized light, is incident on one surface of a rotating light-transmitting resin molded product, and a light having a specific polarization direction is transmitted from the light-transmitting resin molded product. The image of the selected light-transmitting resin molded product is captured by a line camera having a one-dimensional visual field in the radial direction of the light-transmitting resin molded product, and the portion where the luminance fluctuates due to photoelasticity from the video signal of the line camera. A method for inspecting resin molding distortion, characterized by detecting the following. 2. A rotary drive mechanism for rotating a light-transmitting resin molded product, a light source disposed on one side of the light-transmitting resin molded product, and a light source and the light-transmitting resin molded product. A polarizing plate and a quarter-wave plate, each of which is arranged so that light of a single wavelength that has become a circularly polarized light is incident on the light-transmitting resin molded product, and is disposed on the other side of the light-transmitting resin molded product. A line camera having a one-dimensional visual field in the radial direction of the light-transmitting resin molded product, and the light-transmitting resin molded product disposed between the light-transmitting resin molded product and the line camera. A quarter-wave plate and a polarizing plate that select a specific polarization direction from the transmitted light and enter the line camera, and a signal processing unit that detects a portion whose luminance has changed due to photoelasticity from a video signal of the line camera. Resin molding distortion characterized by having Inspection equipment.