JPH061177B2 - Method of measuring smoothness of coated surface - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is to measure the smoothness of a coating surface by irradiating the coating surface of an automobile body or the like with light and measuring the roughness of the coating surface based on the reflected image. It is about the method.

[Problems to be solved by conventional technology and invention]

When performing such a measurement, light is conventionally irradiated through a vertical stripe grating, and the reflected light is detected using a linear image sensor in which photodiodes are arranged linearly in the orthogonal direction,
The level (amplitude) of the analog output signal along the sensor
The smoothness of the coated surface was evaluated from the distribution. In other words, it is not possible to measure with high accuracy because it depends on human vision and it is difficult to make a face-to-face evaluation.

Therefore, an object of the present invention is to provide a method for measuring the smoothness of a coated surface of the kind described at the beginning that enables highly accurate evaluation of a two-dimensional coated surface.

[Means and Actions for Solving Problems]

In order to achieve this object, the present invention uniformly irradiates a coating surface in a range to be measured, images reflected light whose reflection angle varies due to unevenness of the coating surface with a two-dimensional image sensor, and forms a matrix pixel thereof. As shown in FIG. 1, the image signal of is discriminated in a plurality of stages, and the statistical processing based on the standard deviation of the discriminated level data is used to determine the distribution state of the fluctuation of the image signal level on the painted surface in a predetermined range. The smoothness was measured.

Example of Invention

FIG. 2 shows a coating surface smoothness measuring apparatus for carrying out the method according to the present invention. Reference numeral 10 denotes a coating surface image pickup device, which has an incident angle of 30 ° to the coating surface 1 in a light-shielding case. A light source 11, a condensing lens 12, a diffusion plate 13 for eliminating light unevenness, and a projection lens 14 are housed in order so as to be about 60 °.
Further, a condenser lens 15 and a CCD camera 16 as an image sensor are housed corresponding to the reflection angle. As a result, the area of several squares of the coated surface 1 is irradiated with light,
The reflection image is, for example, 512 × 5 so as to give a sufficient resolution to the reflection image in a matrix form of several millimeters in length and width.
It is incident on a CCD camera 16 having 12 pixels. This CCD camera has a microcomputer as an image processing device.
20 and cathode ray tube display device 21 are attached.

The microcomputer 20 has a ROM 20a that stores a table that ranks the operating procedure and the skin level in, for example, 10 steps based on the standard deviation, and an address that corresponds to the matrix pixels of the CCD camera 16. It includes a RAM 20b for discriminating the image signal level of a pixel into, for example, 32 levels and storing the level data obtained by A / D conversion, and a CPU 20c for performing the following calculation in cooperation with these memories. That is, the 32-step level data of each pixel is stored in the RAM 20b, the level data D ₁ , D ² , D ³ ... D _n are averaged and the average value M _p is calculated. Then this average value
Standard deviation σ of level data for M _p Is calculated (n: number of level data). Further, the calculation result is referred to the table stored in the ROM 20a, the skin level is determined, and the corresponding rank 1 to 1 is displayed on the display 22.
Display at 10. The cathode ray tube display device 21 D / A converts the image signal of the CCD camera 16 stored in the RAM 20b and displays it. The keyboard 23 starts the operation or sets a working area 21a on the image of the cathode ray tube display device 21 when necessary and instructs the microcomputer 20 about the area.

The operation of the smoothness measuring apparatus configured as above will be described with reference to FIGS. 3 and 4.

The reflected image on the coating surface 1 including the orange-colored skin having an uneven wavelength of about 1 to 5 mm changes its reflection angle variously according to the degree, and enters the CCD camera 16 with the brightness of the reflected light varying. To do. The microcomputer 23 is started by operating the keyboard 23, the image signals of 512 × 512 pixels of the CCD camera 16 which fluctuate are sequentially digitized, and stored as level data in the corresponding address of the RAM 20b. This level data has a normal distribution as shown in FIG. 4 according to the degree of yuzu skin. By the way, when the coated surface 1 is perfectly mirror-like, the level is the same. The cathode ray tube display device 21 displays an image of which the brightness changes according to the degree of yuzu skin, and sets the working area 21a according to the measurement range if necessary.
Then, average each level data in this area
Calculate M _D. Then, according to the above equation (1), the standard deviation σ
To calculate. Then, the rank of the yuzu skin to be compared with the table of the ROM 20a is numerically displayed on the display unit 22. The yuzu skin image displayed on the cathode ray tube display device 21 can be recorded as a photograph.

〔The invention's effect〕

As described above, according to the present invention, it is possible to perform a highly accurate quantitative evaluation by a simple process of the smoothness of the coated surface in a wide range, that is, the image signal obtained by capturing the range of the yuzu skin state. Since the statistical processing based on the standard deviation that evaluates the degree of variation with respect to the average value of the level data is performed, the influence of the image signal level caused by the change in the ambient brightness can be avoided, and the measurement can be performed constantly with high accuracy.

[Brief description of drawings]

FIG. 1 is a flow chart for explaining the method of the present invention, FIG. 2 is a diagram showing a configuration of an apparatus for carrying out the method according to the present invention, and FIG. 3 is a flow chart for explaining the operation of the same embodiment and FIG. FIG. 4 is a diagram for explaining the operation of the embodiment. 1 ... Painted surface, 11 ... Light source, 16 ... CCD camera.

Claims (1)

[Claims] 1. A coated surface is illuminated with light, and reflected light of the illuminated illuminated area of the coated surface is imaged by a two-dimensional image sensor, and a plurality of image signal levels of matrix pixels of the image sensor are set. Distinguishing into stages, calculating an average value of these discriminated level data, and calculating a standard deviation of the level data with respect to the average value to determine the smoothness of the painted surface in the predetermined range. Method of measuring smoothness of coated surface.