JPS63274847A - Method for measuring glossiness of coated surface - Google Patents

Abstract

PURPOSE:To evaluate the glossiness of a coated surface over a wide range automatically and quantitatively with high accuracy by mapping a parallel stripe grating arranged on the front of the coated surface on the coating surface, and bringing a two-dimensional image sensor into focus on the coated surface and picking up an image. CONSTITUTION:The focal length of a TV camera 3 at a specific distance is set to the coated surface 1 and the camera is put in an open aperture state. In this state, an image incident on the camera 3 varies in luminosity corresponding to the grating of a longitudinal stripe grating panel 2, the camera 3 outputs an image signal, and a RAM 12 is supplied with a quantized image signal through an A/D converter 11. Further, a computer 13 for analysis processes image data on one image inputted to the RAM 12 to calculate the frequency distribution of the image signal level and find the standard deviation, and quantizes and judges the glossiness, which is indicated to an output device. Further, detected crossing curve points are counted to judge smoothness, which is indicated to the output device similarly. Thus, the coated surface 1 is evaluated over a wide range automatically and quantitatively with high accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for measuring the glossiness of a painted surface of an automobile body or the like using an optoelectronic method.

(Prior art and the problem to be solved by the invention) In this type of measurement method, the painted surface is irradiated with light at a predetermined angle of incidence, and the measurement is based on the ratio of the specular reflection intensity to the predetermined diffuse reflection intensity. There are ways to do this. However, all of these optoelectronic methods perform area-wide evaluations based on point-like measurements, and are only capable of performing measurements all at once.

Therefore, an object of the present invention is to provide a method for measuring the glossiness of a two-dimensional painted surface in which the glossiness of a two-dimensional painted surface can be collectively evaluated by an optoelectronic method over a wide range to M (F).

[Means and effects for solving the problem] In order to achieve this object, the present invention maps a parallel striped grating placed in front of the painted surface onto the painted surface, as shown in FIG. A two-dimensional image sensor focuses on this painted surface and images it.
An image signal whose level changes in accordance with the parallel striped grating image and the grating image in a direction almost perpendicular to the parallel striped grating image was detected. The image signal level of the parallel stripe grating image changes slowly due to the fact that the image sensor is not focused on the parallel stripe grating.

At this time, the gloss of light reflection increases as the ratio of the specular reflection component increases, and therefore, in the case of a painted surface with low gloss, the diffuse reflection component increases, and the level change curve of the image signal corresponding to each grating image peaks. The parts are diffused and the degree to which the bottom part is filled increases. That is, in the case of a painted surface with low gloss, the level difference between the peak and bottom of the image signal of each lattice image becomes small.

Then, the gloss level of the painted surface is determined by statistically processing the level difference between the image signals of each lattice image on the two-dimensional surface of the painted surface.

[Embodiments of the invention]

FIG. 2 shows an example of an apparatus for implementing the present invention, which also measures the smoothness of the painted surface at the same time. That is.

A lattice panel 2 is placed in front of a painted surface 1 with a thickness of several 100 mm, and a vertical striped lattice image reflected on the painted surface 1 is captured by a CCD type TV left camera placed on the side thereof. As shown in FIG. 3, this lattice panel is composed of a plurality of straight tube fluorescent lamps 2a arranged with a black panel 2b as the back surface and arranged at intervals of the tube diameter.

An image signal processing unit IO follows the TV left camera.

That is, this processing section processes the TV generated by the readout scan.
An A/D converter 11 that digitizes the image signal of the left camera and converts this digital signal to a 256×256 TV.
RAM stored in the address corresponding to the pixel of the left camera
12, an analysis computer 13 that takes in image data from this memory and processes it, and a switching circuit 14 that converts the image signal or processed signal into an analog signal using a D/A converter 14b.
It consists of a fluoroun tube monitor 14 that selectively displays images through a.

The analysis computer 13 reads out the image data taken into the RAM 12 in a direction orthogonal to the vertical stripe direction, as shown in the flowchart of FIG. Then, by determining the frequency distribution of the image signal level of each address for the entire painted surface and further determining the standard deviation σ, statistical processing of the level difference between the peak and the bottom is performed for each vertical striped grid image signal.

And RAM in advance! The glossiness signal is compared with a verification curve table indicating the glossiness with respect to the standard deviation σ stored in 3a, and the glossiness signal is outputted to an attached recording device or display device (not shown).

Furthermore, in accordance with the smoothness measurement method disclosed in Japanese Patent Application No. 61-241796, inflection points that overlap at shorter time intervals between the peak and bottom of the level change curve of the image signal of each vertical striped lattice due to the unevenness of the painted surface. is detected by sequentially comparing the signal levels of the previous and next addresses. Then, the inflection points are counted and the orange skin condition of the painted surface is determined from this count (In).

The operation of the glossiness/smoothness measurement station configured as described above will be explained.

The focal length of the TV left camera, which is located a predetermined distance away, is set to the painted surface l, and the aperture is set to an open state. In this state, the brightness of the image incident on the TV left camera changes in accordance with the lattice of the vertical striped lattice panel 2, and the image signal shown in FIG.
2 is supplied with an image signal quantized by the A/D converter 11 as shown in FIG. 5 (the number of inflection points is omitted).

The analysis computer I3 calculates the frequency distribution of the image signal level by processing one screen worth of image data taken into the RAhl12 according to the flowchart shown in FIG. The glossiness is determined, quantified, r4FJ is performed, and the output device is instructed. The larger the standard deviation σ, the higher the gloss level.

Further, the detected inflection points N are counted to determine the degree of smoothness, and the output device is similarly instructed. That is, as the condition of the citron skin deteriorates, the degree of disturbance in brightness increases, and the count value of the inflection point N correspondingly increases.

In addition, if the focus or aperture of the TV left camera is adjusted to sharply image the vertical striped grid panel 2 instead of the painted surface, the difference in brightness of the incident image will be clear, and the image signal will correspond to the vertical striped grid. It appears in a rectangular shape, making it difficult to make the desired measurement.

The evaluation of the level difference between the bottom and peak of the image signal of each lattice image for one screen can also be performed by other methods such as actually calculating the level difference.

Figure 6 shows another embodiment of the lattice panel;
As shown in , the single image signal level corrects the drop in level on both sides of the painted surface due to the fact that as the camera field of view goes outward, the ratio of light diffusely reflected on the painted surface going out of the field of view increases. It is supposed to be done. That is, as shown in the figure, by placing the fluorescent lamp 22 behind the black vertical striped grid 23 and narrowing the width of the iJ portion, which is the gap between the black vertical striped grids 23, at the center, the image signal level can be reduced. It suppresses changes in the periphery.

Figures 7 and 8 have a width of 1 and a distance of 30 and a size of 7.
0ro x 700g+m vertical striped lattice panel, size 250
×200■■ coated plate, focal pressure $50mm (standard 16■■
), using a TV camera with a lens with an aperture of Fl, 8 (open state), and a distance of 1.500 1. An experimental example is shown in which the standard deviation σ and the number of inflection points for various reference coated surfaces were measured under the measurement conditions of 1.20011-1 incident angle and reflection angle of 20° between coated plate and camera. As is clear from this experimental example, the standard deviation of the level distribution of the image signal (when the resolution of ^/D conversion is set to 64 levels) changes in response to various degrees of gloss (FIG. 7). Similarly, it has been confirmed that the number of inflection points changes depending on the skin rank (8th
figure).

(Effects of the Invention) As described above, according to the present invention, it is possible to evaluate the glossiness over a wide range of painted surfaces.
It will be possible to perform with high precision, automatically, and quantitatively.

[Brief explanation of the drawing]

Fig. 1 is a flowchart explaining the method of measuring the glossiness of a painted surface according to the present invention, Fig. 2 is a diagram showing the configuration of a device for carrying out this method, and Fig. 3 is a perspective view of a grid panel of the same embodiment. , FIG. 4 is a flowchart explaining the operation of the same embodiment,
FIG. 5 is a diagram for explaining the operation of the same embodiment, FIG. 6 is a diagram for explaining the grid panel of another embodiment, and FIGS. 7 and 8 are experimental examples for confirming the feasibility of the present invention. FIG. ■...Painted surface, 2...Vertical striped lattice panel, 3-T
V camera.

Claims (1)

[Scope of Claims] A parallel striped grating placed in front of the painted surface is mapped onto the painted surface, the painted surface is imaged by a two-dimensional image sensor with a focus on the painted surface, and the parallel striped grating is imaged in a direction substantially perpendicular to the parallel striped grating image. detecting an image signal whose level changes according to each of the lattice images, and statistically processing the level difference between the peak and bottom of the image signal of each lattice image to determine the glossiness of the painted surface; Glossiness measurement method.