JP3340312B2 - Surface defect inspection equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for inspecting a surface of an object, such as a decorative sheet of various colors, which has been visually inspected for defects such as streaks and bumps, by using a CCD camera. The present invention relates to a surface defect inspection apparatus that detects surface shape defects of an object to be inspected in various colors.

[0002]

2. Description of the Related Art Conventionally, there has been performed an appearance inspection method of irradiating an object to be inspected with light to capture unevenness on a surface. A surface defect inspection apparatus having a mechanism for detecting a defect of an inspection object based on a change in light amount is disclosed.

[0003]

However, the conventional method as described above is effective for products of the same color,
When applied to a multi-product group that has many products of different colors and judgments are made based on the same threshold value, the test results differ depending on the product color, and the test results may be weak or severe depending on the color. I could not escape false detection. That is, if the same threshold value is set uniformly, there arises a problem that a non-defective part is recognized as a defective part in a certain color, and a defective part is recognized as a non-defective part in a certain color.

The present inventors have pursued the reason why output data captured by a CCD camera differs depending on the color of an object to be inspected. As a result, there is a certain relationship between the color of the object to be inspected and the output voltage. I found out. That is, optically, C
It became clear that a clear correlation was established between the output voltage from the CD camera and the color of the product.

SUMMARY OF THE INVENTION An object of the present invention is to provide a surface defect inspection apparatus which solves the conventional problems based on the above knowledge and can inspect the surface defects of an object to be inspected in multi-color production. It was done as.

[0006]

According to the first aspect of the present invention, the surface defect of the object to be inspected is, for example, a so-called streak-like defect in which a mountain-shaped or valley-shaped continuous surface is formed on a sheet-shaped object having the same thickness. Or a state where there is a so-called bumpy defect that is partially raised.

The threshold value according to the first aspect of the present invention is obtained by adding an offset value to the average output voltage value of a good sample, and the average output voltage value of a good sample and the abnormal output voltage value of a defective sample. Is determined as appropriate. As the threshold, an upper limit or a lower limit, or both an upper limit and a lower limit can be set.

The invention described in claim 1 of the present application (hereinafter referred to as the present invention)
Says Akira) will be described. This onset Ming, against the beam to the inspection object, the transmitted light or reflected light captured by the CCD camera, the obtained image signals converted output voltage or further differentiated, integrated treated CPU output voltage In the central processing unit, the threshold value corresponding to each color of the inspection object transmitted from the external input device is compared with the output voltage to thereby output an abnormal output of a surface defect portion of the inspection object. In the surface defect inspection apparatus for detecting the threshold value and outputting the threshold value to an output device, the threshold value is obtained for each color from a specific relational expression.

In the present invention, it has been confirmed that the output voltage of the inspection object obtained from the image signal from the CCD camera has the following relationship. V = kΣ + a (1)

The meaning of each symbol in the formula (1) is as follows. V: output voltage of inspection object (unit: volt) k: proportional constant Σ: sum of all light rays (spectral energy distribution of light source × spectral reflectance of product color × relative sensitivity of CCD) a: V intercept

FIG. 1 shows the spectral energy distribution at each wavelength of the irradiation light from the fluorescent lamp light source and the reflected light from the white film of the fluorescent lamp as an example of 中 in the formula (1). 3 illustrates the relative sensitivity of a CCD camera. FIG. 2 shows the relationship between the output voltage V of the test object of various colors actually measured by the CCD camera and the sum Σ of all the light beams of each color.

As described above, Σ includes the spectral reflectance of the product color, that is, the color component as a parameter, and the output voltage of the inspection object optically obtained from the image signal from the CCD camera. A clear correlation was established between the color and the color, and it was clear that the effect of the color difference on the test result was derived from this.

[0013] Therefore, Oite this onset Ming, to clarify the relationship between the color and threshold of the object, so as to be easily calculated threshold for each color from the calculation and simple measurement ,
Inspections with almost the same accuracy can be performed for surface defects of the inspection object of all colors, and differences in inspection results due to colors of the inspection object can be eliminated.

That is, first, the above equation (1) is obtained in advance from a certain number of products. Next, under a certain condition, by measuring Σ of a reference color (for example, white) and Σ of a color of a test object (for example, red), both output voltages and an output voltage ratio under a certain test condition are obtained. Can be Further, a threshold value of a reference color is obtained in advance, and the output voltage ratio is multiplied by the threshold value of the inspection object having almost the same accuracy as the threshold value of the reference color. It can be easily obtained, and as a result, the threshold values of all other required colors can be easily obtained. The object is achieved by storing this in an external input device and transmitting a threshold signal corresponding to the color of the inspection object to the central processing unit at the time of inspection.

Further, by performing differentiation or integration on the output voltage waveform, an abnormal waveform of the output voltage waveform is emphasized, and by comparing the output voltage waveform with a threshold value at this time, an abnormal output can be detected more effectively. Becomes

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. A color film made of a soft vinyl chloride resin was used as an inspection object. (Preparation of soft vinyl chloride resin color film) 100 parts by weight of vinyl chloride resin, 20 parts by weight of dioctyl phthalate as a plasticizer, 5 parts by weight of a Ba-Zn-based stabilizer as a stabilizer, 15 parts by weight of various pigments, and 60 parts by weight of an organic solvent The soft vinyl chloride resin sol composed of the above parts was coated on process paper, dried, and heated and melted to obtain soft vinyl chloride resin color films (thickness: 100 μm) of various colors.

(Preparation of Surface Defect Film) Then, the surface of a white and dark blue soft vinyl chloride resin film having no defect on the surface is visually damaged as a surface defect by a cutter and pressed by a hot roller. A surface defect film was formed by forming streaks.

Embodiment 1 FIG. 3 shows an apparatus used as a surface defect inspection apparatus. In this surface defect inspection apparatus 1, a fluorescent lamp light source 12 is arranged in parallel with the width direction of the roll 11 through which the inspection object 2 is passed. Irradiation light from the fluorescent light source 12 is applied to the inspection object 2,
The CCD camera 13 is arranged so as to capture the reflected light reflected in a direction perpendicular to the incident angle.

The CCD camera 13 is connected to a central processing unit 14 so that an output voltage from the CCD camera 13 can be introduced to the central processing unit 14. Reference numeral 15 denotes an external input device to which a threshold is input,
It is connected to the central processing unit 14 so that the input threshold value can be transmitted to the central processing unit 14.

By comparing the threshold value with the output voltage from the CCD camera, an abnormal output at the surface defect portion is confirmed. An output device 16 is connected to the central processing unit 14 so that an abnormal output of a surface defect portion of the inspection object 2 can be output.

Using the apparatus 1 shown in FIG. 3, light beams from a fluorescent lamp light source 12 are applied to films of various colors as an object to be inspected, and the reflected light is captured by a CCD camera 13, and the obtained output voltage is obtained. Calculation of the relationship between (V) and the sum (Σ) of all the rays resulted in the result shown in FIG. When this relationship is applied to the above-mentioned expression (1), the relationship becomes V = 0.0044 × Σ + 0.62 (2). The maximum value of Σ in the test range at this time was 208.3 for the white film, and the minimum value was 12.2 for the dark blue film.

When the upper limit threshold value determined from the output voltages of the non-defective sample and the defective sample in the actual white film is 5 volts, the corresponding upper limit threshold value of the dark blue film is calculated as follows. 5: X = (0.0044 × 208.3 + 0.62): (0.0044 × 12.2 + 0.62) X = 2.19 (volts). Similarly, calculate the thresholds for the other colors,
It was input to the external input device 15.

As an object to be inspected, a light beam from the fluorescent lamp light source 12 is applied to the surface defect film of each color, the reflected light is captured by the CCD camera 13, and the obtained output voltage (volt) is sent to the central processing unit 14. Then, the determination was made based on the threshold values corresponding to each color of the film transmitted from the external input device 15, and an abnormal output of the surface defect portion of the film was output to the output device. As a result, it was confirmed that all the surface defects of the films of the respective colors were recognized as surface defects.

[0024]

Since the surface defect inspection apparatus of the present invention has the above-described configuration, it can be used, for example, to detect surface defects of a product requiring various kinds of colors, such as a decorative sheet. The threshold value of each color can be easily obtained, and the same level of surface defect inspection can be performed regardless of the color.

[Brief description of the drawings]

FIG. 1 is a graph illustrating the spectral energy distribution at each wavelength of irradiation light from a fluorescent lamp light source and light reflected by a white film, and the relative sensitivity of a CCD at each wavelength, as an example of Σ in equation (1). It is.

FIG. 2 is a graph showing the relationship between the output voltage (V) of the test object of various colors actually measured by a CCD camera and the sum (Σ) of all light rays due to reflection of each color.

FIG. 3 is a schematic diagram illustrating a surface defect inspection device and a surface defect inspection device used in Example 1.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Device 2 Inspection object 11 Roller 12 Fluorescent light source 13 CCD camera 14 Central processing unit 15 External input device 16 Output device

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01N 21/88-21/892 G01J 3/46

Claims (1)

(57) [Claims] 1. A light beam is applied to an object to be inspected, the transmitted light or reflected light is captured by a CCD camera, and an output voltage obtained by converting an obtained image signal or an output voltage obtained by further differentiating and integrating is output to a central processing unit. In the central processing unit, the threshold value corresponding to each color of the inspection object transmitted from the external input device is compared with the output voltage to thereby output an abnormal output of a surface defect portion of the inspection object. When the above threshold value is set in the surface defect inspection device that finds the output and outputs it to the output device, the relationship between each color and the output voltage is determined in advance by the following expression (1): V = kΣ + a (1) , V: output voltage of the test object, k: proportional constant, Σ:
The sum of all the light rays (spectral energy distribution of light source × spectral reflectance of color of inspected object × relative sensitivity of CCD), a: V intercept is shown). A surface defect inspection apparatus for individually setting threshold values for all colors by multiplying the relative ratio between the output voltage of the object and the output voltage of the color of the object.