JP3362981B2 - Defect inspection method for transparent body with edge - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of inspecting a transparent body having an edge such as a cathode ray tube panel. 2. Description of the Related Art A cathode ray tube panel is manufactured by pressing a molten glass gob into a predetermined shape using a molding die. The manufactured CRT panel is inspected for glass defects such as bubbles and the inner surface curvature. Conventionally,
The glass defect inspection of a CRT panel is performed by irradiating light from the back surface (lower surface) and observing the transmitted light from the front surface side. If there is a glass defect such as a bubble, light is irregularly reflected at that point, and a difference in transmitted light amount from other normal parts is created.
This is done using the distinction. [0003] In the above inspection method, the CRT panel has a seal edge extending to the back side around the periphery thereof for joining with a funnel. For this reason, the amount of transmitted light is smaller in the periphery of the CRT panel than in other portions by an amount corresponding to the thickness of the seal edge, and is a dark portion. Since the thickness of the seal edge does not become an effective surface of the CRT panel, it is not a target of glass defect inspection.However, when the above inspection is automated by image processing, the thickness of the seal edge is required. Must be excluded. [0006] In general, unnecessary portions are removed by conventional software in a method called window processing or mask processing. However, all of these methods involve, for example, enclosing a necessary portion with a frame in a state where an image signal captured by an imaging camera is converted into a two-dimensional image (window processing) or masking an unnecessary portion (mask processing). It is necessary to automatically determine these ranges and incorporate a program to be executed, and it is difficult to eliminate the restrictions on memory capacity and the complexity of the processing procedure when creating a program. was there. In addition, these conventional methods are limited to a simple boundary such as a straight line between an unnecessary part and a necessary part, and cannot be applied to a case where the boundary is curved, a waveform or other complicated curve. An object of the present invention is to solve the above-mentioned problems of the prior art and to provide a defect inspection method for a transparent body having an edge capable of removing unnecessary portions by relatively simple means. [0006] In order to achieve the above object, the present invention provides a video camera in which light is irradiated from one side of an inspected object having an edge around and two CCD cameras photographed from the other side. The signal is sent to the waveform processing interface, where the line-shaped pixel signals equally divided in the width direction of the inspection object are sequentially scanned by the video clock from one end in the width direction of the inspection object, and the video signal is picked up. Then, when recognizing the first falling portion of each of the video signals from the edge side , the sample and hold voltage is set to the same voltage as the voltage before the falling by the number of video clock pulses set according to the edge thickness. In addition, the edge thickness equivalent portion is removed, the processed video signal is sent to an image processing device, and the image signal is converted into an image by the image processing device.
The object is converted into a two-dimensional image, a defective portion is detected from the two-dimensional image, and the above process is performed by relatively moving the object to be inspected, the light source, and the CCD camera in a direction orthogonal to the width direction of the object to be inspected. The whole inspection object is inspected. According to the present invention, it is only necessary to previously set the number of video clock pulses corresponding to the edge thickness of the object to be inspected. When the falling part is recognized, the part corresponding to the edge thickness can be removed by adding the sample and hold voltage that is the same voltage as the voltage before the falling by the number of video clock pulses set according to the edge thickness. ,
The present invention can be similarly applied to an inspection object having any shape. FIG. 1 is a schematic view of a system according to the present invention. An inspection object 1 is transported from a pre-process apparatus 2 to an inspection step 4 of the present invention by a roller conveyor 3. The inspected object 1 is sent to the inspection step 4 of the present invention after being put on the roller conveyor 3 by the putting unit 5 and centered by the centering unit 6. In the inspection step 4 of the present invention, a light source 7 illuminating from one side of the inspection target 1 and a CCD for photographing the inspection target 1 from the other side with respect to this light source 7
A camera 8 is provided. The CCD camera 8 is connected to a camera controller 9, and the camera controller 9 is connected to an image processing device 10. The image processing device 10 is a personal computer 1
1 and an image monitor 12. FIG. 2 is a diagram showing an inspection process according to the present invention.
The video signal photographed by the D camera 8 is sent to the waveform processing interface, where the edge processing of the waveform is performed. In this edge processing, as shown in FIG. 3A, the video signal of the CCD camera 8 at the position of PP of the inspection object 1 having an edge 1a around it is shown in FIG. 3B. Waveform. In the figure, the voltage is plotted on the vertical axis and the width direction of the test object 1 is plotted on the horizontal axis.
An edge portion of the inspection object 1 is shown, and a portion b is the inspection object 1
Represents a defective portion. As described above, if nothing is done, the voltage of the edge part a and the defective part b is reduced as a dark part on the video signal waveform. Therefore, the present invention removes the edge portion a. Specifically, as shown in FIG. 3C, the CCD camera 8 in the portion outside the edge 1a of the inspection object 1 is provided. The waveform voltage c of the video signal is sampled and held in advance, and when the first falling portion of the voltage of the video signal waveform of the CCD camera 8 is recognized, the sampled voltage is divided by the thickness corresponding to the thickness of the edge 1a. Are added by the number of video clock pulses. The thickness of the edge 1a is measured in advance by measuring the thickness of the edge of the object 1 to be inspected, and the value is input in advance by, for example, a key operation of the personal computer 11 in units of mm. In this way, the hardware in the waveform processing interface connected to the CCD camera 8 can set the CCD
When the first falling portion of the video signal waveform of the camera 8 is recognized, the video clock set according to the edge thickness is recognized.
The same voltage as the voltage before falling by the number of clock pulses
Apply sample hold voltage to remove edge thickness equivalents
To be processed . As a result, as shown in FIG. 3C, a video waveform voltage from which edges have been removed is obtained.
If there is a defect, it can be detected. That is, as shown in FIG. 2, the video signal after the edge processing is performed by the waveform processing interface is sent to the image processing apparatus 10, where it is imaged and converted into a two-dimensional image. Detect defective parts. Also,
If necessary, calculate the area of the defective part and the fillet diameter,
The result is displayed on the image monitor 12. When the inspection object 1 has a defect, as shown in FIG. 1, the defect marking means 13 automatically attaches a defect marking to the inspection object 1. [0010] The two CCD cameras 8 are used, the object 1 is photographed in half in the width direction, and the video signal is scanned from the side having the edge 1a. It is what is done. FIG. 1 shows a case where a light source 7 and a CCD camera 8 are fixed at fixed positions,
Is moved by the roller conveyor 3 to inspect the entire inspection object 1, but may be reversed. In the case of FIG. 1, the inspection object 1 is photographed linearly in the width direction by the CCD camera 8 from between the rollers of the roller conveyor 3. According to the present invention described above, even when the contour of the edge 1a is curved as shown in FIG. Inspection can be done. Although the above embodiment illustrates a case where the invention is applied to a panel of a cathode ray tube, it is needless to say that the invention can be applied to another inspection object having a similar edge. According to the present invention, the inspection range can be set in a form following the shape of the edge portion by relatively simple means without the need for complicated operations and complicated programs. The effective inspection surface can be greatly expanded, and the video signal of the CCD camera can be processed directly by hardware and only the edges are removed from the video signal in real time, so that computer image processing can be performed smoothly. Therefore, the processing speed can be greatly improved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a system schematic diagram of the present invention. FIG. 2 is an inspection process diagram of the present invention. FIG. 3 is a diagram illustrating the principle of edge processing according to the present invention. FIG. 4 is a plan view showing an example of the shape of an inspection object that can be advantageously inspected by the present invention. [Description of Signs] 1 Inspection object 3 Roller conveyor 7 Light source 8 CCD camera 9 Camera controller 10 Image processing device 1a Edge a Edge b in video signal waveform b Defect in video signal waveform

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01N 21/88-21/896 G06T 7/00 H04N 7/18

Claims (1)

(57) [Claims] [Claim 1] Light is radiated from one of the objects having an edge around it, and video signals photographed by two CCD cameras from the other are sent to a waveform processing interface. obtaining a video signal equal split linear pixel signals in the width direction of the object to be inspected at the interface by sequentially scanning the video clock from the width direction of the one end of the object to be inspected is picked up, each edge of the video signal When the first falling part from the side is recognized, the sample and hold voltage, which is the same as the voltage before the falling, is removed by the number of video clock pulses set according to the edge thickness, and the part corresponding to the edge thickness is removed. Processing, sending the processed video signal to an image processing device, and converting the video signal into an image by the image processing device;
The object is converted into a two-dimensional image, a defective portion is detected from the two-dimensional image, and the above process is performed by relatively moving the object to be inspected, the light source, and the CCD camera in a direction orthogonal to the width direction of the object to be inspected. A defect inspection method for a transparent body having an edge, which inspects the entire inspection object.