JPS62202289A - Inspection method for display pattern - Google Patents

Abstract

PURPOSE:To inspect a correct display pattern without an individual difference by calculating a display pattern position concerning the molded goods of two colors, determining a binarization threshold and detecting automatically the presence and absence of the existence of foreign matters, by a TV image. CONSTITUTION:In case of a key top product formed to two colors, the product is photographed by an image pick-up tube and by the threshold set beforehand, a binary image is displayed on a CRT. Next, the display position of a display image is determined from the intersection of four chips 2 set on the CRT beforehand and an image 3. Next, concerning the product which is the trapezoid of the cross section of a key top and has a slope 4, the painting-out of the background part is executed. To plural characters, a frame 5 is fixed and concerning individual cut-out patterns, the comparing inspection with a standard pattern is executed. In such a case, the image thicker than the standard pattern by a prescribed bit and the thinner than it by the prescribed bit are made, overlapped with the individual inspected pattern and the adaptation is automatically detected. Next, the raw area except the frame 5 is divided into plural areas and the presence and absence of the foreign matters are detected.

Description

[Detailed Description of the Invention] [Summary] The process of inspecting the display pattern of a product using a television image includes determining the image position of the product, binarization filtering, determining the position of a pattern formed on the product,
An inspection method comprising inspecting the pattern, inspecting the presence or absence of foreign matter, and inspecting the presence or absence of foreign matter in an area other than the pattern position.

[Industrial application field]

The present invention relates to a method for inspecting display patterns such as letters and numbers, and specifically relates to a method for inspecting two-color molded products.

Currently, parts such as dials and knobs used in electronic devices are made of resin molds, and characters and figures are displayed on the surface to identify their functions.

Here, conventionally, products have been manufactured in which the display portion is pre-concave and patterned at the molding stage, and the product is manufactured by filling the concave portions with resins of different colors.

However, a two-color molding method was developed as a method to further improve productivity, and has come to be commonly used.

In this method, the display pattern part is molded in a first process, and the main body part except this part is molded in a second process, thereby producing a molded product in which the display pattern stands out.

The present invention relates to a highly accurate quality inspection method for such two-color molded products.

[Conventional technology]

The inspection method for two-color molded products has conventionally been carried out by visual inspection.

The visual inspection is performed with high precision to detect contamination of different types of molded objects and foreign objects in positions other than the display pattern area of the product. When it comes to points, it is difficult to determine and there are individual differences, and even individuals' evaluations differ from day to day.

Therefore, the only option was to train individuals to match their judgment criteria to a standard pattern.

However, keyboards with many different letters and numbers, such as keys and keys, are easy to compare from the user's perspective, and are not subject to equipment quality evaluation. Therefore, a highly accurate quality inspection method was required.

[Problems to be solved by invention C] As mentioned above, visual inspection of two-color molded products cannot be performed with high accuracy due to individual differences in delicate points such as the thickness of the pattern, so an alternative inspection method is needed. is necessary.

[Means for solving problems]

The above problem can be solved by using television images to inspect the quality of display patterns such as letters and numbers formed on products. A threshold value suitable for value conversion is determined in advance, and for each product that is sent one after another, it is determined by the intersection of four reticle marks set in advance around the center of the CRT and the displayed product image. For products formed with a trapezoidal cross-sectional shape, the process of determining the product position from the origin of After illuminating multiple Bakun positions, each pattern is overlaid with a large and small master pattern whose size is shifted by 1 bit from the previous pattern and projected, and the deviation from the standard value of the pattern and foreign objects are detected. A display pattern comprising: a process of inspecting the presence of foreign matter; and a process of setting a plurality of regions outside the pattern formation position and detecting the position of foreign matter in each region. This can be solved by testing methods.

[Effect]

The present invention automatically inspects two-color molded products by comparing the display pattern with a standard pattern using a cathode ray tube, instead of using conventional visual inspection.

This method is ■Determining the darkness value necessary for binarizing a gradation image.

■Identification of the image position of the object to be inspected.

■Binarization filtering process that excludes positions that are within the inspection target position but are likely to be determined as noise.

■If there are multiple patterns within the inspection target position, cut out each pattern.

■Comparative inspection of display pattern against standard pattern thickness.

■Detection of foreign objects located within the inspection target position but excluding the displayed pattern.

The problem can be solved by following the following testing procedure.

〔Example〕

Keyboard keys below (use ship name keysop)
An example will be described.

The key top has vertical and horizontal dimensions of 20111 x 20 silk, the vertical cross section is trapezoidal, and the upper surface is narrowed to about 13 wa x 13 dragon. Names, numbers, kanji, etc. are molded in two colors.

Figures 1 and 2 show the inspection process of the example.
The process number and process name are shown on the left, and a simple explanatory diagram is shown on the right.

First, process 1 is a two-color pattern of key tops that is displayed as an image on a cathode ray tube using an image pickup tube. In this example, as shown in Figure (A), a black letter C is molded in two colors on a white background. .

In this embodiment, as a method of manufacturing a large number of such key tops and inspecting them one after another, an image with a standard pattern width is divided into pixels of 512 sections vertically and horizontally, and then each pixel is divided into 64 tones of color. and draw a histogram as shown in Figure (B).

In this example, the color tone is divided into two, dark and dark, and the dashed line at the middle position is the provisional value of the threshold value 1.

That is, a light tone below the darkness value is regarded as white, and a tone above the threshold value is regarded as black.

(This is Process 2. Temporary threshold value) Next, draw a standard pattern (binarized image) of C using this binarized darkness value, and superimpose this with the projection image (standard image) shown in Process 1. Evaluate compliance status.

If the binarized image is thin, the dark value is shifted to the right to correct the dark value.

In this way, a standard binary image (master pattern) is determined as shown in FIG.

(Process 3. Evaluation of binarized dark values) This completes the preparation work and moves on to inspecting each key top.

First, an image of the produced Gee-Tomp is taken with an image pickup tube, and a binary image is displayed on the cathode ray tube using the previously determined threshold value 1 as shown in FIG.

(The above process 4. Binary image human power) Next, the display position of the display image is determined.

As shown in the same figure (E), this method uses four sections (reticles) 2 that are programmed in advance on the CRT.
The absolute stranding of the image is determined from the intersection of and image 3.

In the case of this embodiment, the origin of the coordinates is determined to be the upper left corner of the cathode ray tube.

This determines the address of the binary image.

(That's all for Process 5. Determining the detection target position) Next, for a test object that has a trapezoidal cross section and a slope 4 around it, like the key top whose plan view is shown in Figure (F), even though the slope 4 is white, Regardless, it looks black on a cathode ray tube.

Therefore, the background portion is filled in so that this portion is not seen as a foreign object.

(Link to process 6, binarization filter) Up until now, to simplify the discussion, I have described the case where there is only the alphabetic letter C on the key top, but in reality, multiple letters, symbols, etc. are molded in two colors. In many cases.

Therefore, a case will be described below in which the five characters "Cancel" are molded on the top surface of the key 1 knob.

In the case of -/characters, the inspection method for one of these characters is the same.

First, as shown in the same figure (G), using a projection method that projects in the X-axis direction and the A character frame 5 as shown by the broken line is determined.

(Process 7, pattern cutting) Next, process 2 for each cut out pattern first.
Perform a comparative inspection with the standard pattern determined in .

This method takes an image that is thicker by N pits and an image that is thinner by N hints than the master pattern, and superimposes these on the individual patterns.

Here, in the case of this embodiment, one hit is 4'll per pixel, which is 25 μm square.

In this case, if the individual two-color molding 1: pattern is molded correctly, the edge of the test pattern should fall into the master pattern shifted by N bits, and the degree of non-matching (hit number) is automatically counted.

Furthermore, if foreign matter is present outside the pattern, it is automatically counted in the same way.

The degree of non-matching is inspected for the five frames cut out in this way.

(This is Process 81 Inspection of individual patterns) Next, as a method of inspecting foreign objects at positions other than patterns, the white part of the character other than 5 shown in Process 7 is divided into multiple areas parallel to the X and Y axes. do.

In this example, seven foreign object detection ranges are determined.

(Process 9. Setting foreign object detection range) Next, each detection range is checked and if a foreign object is present, this position is automatically detected.

(Process 1 (11E piece position detection) above) However, during measurement, noise is often measured as a foreign object.

Therefore, in the case of this example, the experimental results are shown in the same figure (Jul.
As shown, if the size of the foreign object was 9 bits or more, it was considered to be a foreign object, and if it was 8 bits or less, it was considered to be noise and ignored.

(Processes above) 1. Confirmation inspection for foreign objects) By performing automatic inspection in this way, it is now possible to accurately inspect items that are difficult to judge, such as the size of wall thickness, such as two-color molded products. Ta.

〔Effect of the invention〕

As described above, by implementing the present invention, it has become possible to perform accurate pattern inspection without individual differences as in the past.

Although key tops have been described as an embodiment of the present invention, the present invention is not limited to two-color molded parts such as dials, but can be applied to inspection of parts mass-produced in different colors.

[Brief explanation of drawings]

FIG. 1 shows the inspection process of the embodiment (part 1), and FIG. 2 shows the inspection process of the embodiment (part 2). In the figure, 1 is the darkness value, 2 is the intercept, 3 is the image, 4 is the slope, and 5 is the text frame. t)

Claims (1)

[Claims] As a method for inspecting the quality of display patterns such as letters and numbers formed on products using television images, the density of the display pattern is decomposed into a plurality of gradations to create a histogram. A threshold value that is more suitable for binarization is determined in advance, and for each product that is sent one after another, the intersection position of the four reticle marks set in advance around the center of the cathode ray tube and the displayed product image is determined. A process of determining the product position from the origin of the cathode ray tube, a binarization filtering process of filling in the sloped part of the product pattern as a non-inspection area for products molded with a trapezoidal cross-sectional shape, and After determining the positions of multiple patterns, each pattern is overlaid with a master pattern of different sizes that are shifted in size by N bits from the previous pattern and projected, and the deviation from the standard value of the pattern and the presence of foreign objects are inspected. and a process of setting a plurality of regions outside the pattern formation position and detecting the position of a foreign object in each region. .