JPH0634346A - Surface evaluation device - Google Patents

Abstract

(57) [Summary] (Modified) [Configuration] A point light source 1, a convex lens 2, a beam splitter 3, a two-color filter 4, a two-color filter moving means 8, a color video camera 7, and a computer are components, The source light is incident on the beam splitter, the transmitted component is reflected on the surface to be measured, and the reflected light returned to the beam splitter is condensed by the convex lens between the beam splitter and the two-color filter onto the two-color filter, The transmitted light is connected to the surface image of the color video camera, and the moving means changes the position of the two-color filter so that the point light source image on the two-color filter moves in the direction perpendicular to the color boundary line. The change in the color of each pixel of the measured image captured by the camera is tracked, and the inclination of the position of the measured surface corresponding to each pixel is calculated from the moving distance of the two-color filter when the color changes. A surface evaluation device that calculates two-dimensionally the inclination of the surface to be measured by calculating [Effect] The inclination information representing the distortion of the scene reflected on the surface can be obtained with a simple optical device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for evaluating the mirror surface characteristics of a coated surface or the surface of a plastic molded product.

[0002]

[Prior Art] The beauty of painted surfaces and plastic molded products,
Glossiness and luster are greatly influenced by slight undulations, minute dents, convex portions, and wrinkles existing on these surfaces.

[0003] It is important to evaluate the characteristics of the surface, which is caused by the non-smoothness of the surface, in order to develop more beautiful coatings and molded products, and various evaluation methods have been actually used. For example, a gloss meter and an image clarity measuring device are used to evaluate the appearance of the surface. In addition, there are contact and non-contact surface roughness meters and flatness inspectors using laser interferometers that directly measure the surface shape.

[0004]

The above-mentioned appearance evaluation device measures the angular distribution of reflected light and the sharpness when an image of a slit or a grating is imaged. Since no direct information about the surface shape can be obtained, it has a drawback that it can be judged whether it is good or bad, but it is not very useful for analyzing the reason.

Further, although the surface profile can be known with a considerable degree of accuracy by the surface profile measuring device, it is surprisingly not easy to actually connect such information to the appearance characteristics quantitatively. It is considered that this is because these measuring instruments measure the height of the surface, while the appearance is due to the angle of the reflected light changing due to the inclination of the surface (differential height). .

[0006] Taking a painted surface as an example, in general, there are different irregularities on the surface due to several different causes, from a slight undulation of a wavelength of several millimeters to a small depression of 0.1 mm or less in diameter, and Small size irregularities coexist. Since the degree of influence of these irregularities on the appearance depends on the size of the inclination, not the size of the irregularities, a component with a short wavelength affects the appearance even with a slight amplitude, and an irregularity with a wavelength of 0.1 mm has a wavelength of 1 mm. An amplitude of 1/10 of the unevenness of has the same effect. Under these circumstances, a fairly large dynamic range (10 ³ to 10 ⁴ ) is required for measurement in order to link the result of shape measurement to the appearance, and measurement in a somewhat wide range (several millimeters or more) is required. Although required, such measurements are somewhat difficult.

[0007]

The surface evaluation apparatus of the present invention comprises a point light source, at least one convex lens, a beam splitter, a two-color filter having different colors with a straight line as a boundary, and the point light source or the two colors. The point light source is composed of a means for moving either one of the filters, a color video camera, and a computer having an image input function.
The light from the point light source is incident on the beam splitter, and either the transmitted component or the reflected component is reflected on the surface to be measured so that the incident optical axis is perpendicular to the surface to be reflected, and then returned to the beam splitter. The reflected light extracted in a direction different from that of the point light source is placed anywhere between the point light source and the beam splitter or between the beam splitter and the surface to be measured or between the beam splitter and the two-color filter. If necessary, the at least one convex lens converges on the two-color filter, and the light passing through the two-color filter is combined with the color video camera to form an image of the surface to be measured. ~ A lens provided between the color video cameras guides the light, and the moving means provided on either one of the point light source or the two-color filter causes a point light on the two-color filter. By changing the position of the point light source or the two-color filter so that the image moves in a direction perpendicular to the color boundary line, the color change of each pixel of the measured image captured by the color video camera is tracked by the computer. The inclination of the measured surface is calculated two-dimensionally by calculating the inclination of the position of the measured surface corresponding to each pixel from the moving distance of the point light source or the two-color filter when the color changes. It is what

[0008]

The surface characteristic evaluation device of the present invention evaluates the surface shape by an optical method applying the color schlieren method, and therefore, as described above, information directly related to the appearance can be obtained.

FIG. 1 is a plan view of a portion excluding a computer section according to one embodiment of the present invention, and FIG. 4 is a perspective view of the apparatus. The operation of this device will be described with reference to FIGS.
In this embodiment, a halogen lamp is used as the point light source 1. FIG. 7 is a partially enlarged view of FIG. 1 and shows a case where the surface to be measured is a flat surface. The light from the point light source is converted into parallel light by the convex lens 2a and irradiated on the surface 6 to be measured, and a part of the reflected light is reflected by the beam splitter 3 and focused on the two-color filter 4 by the convex lens 2b. At this time, all the lights reflected at different positions A, B, and C on the surface to be measured are focused on the same position on 4 to form a clear image of the point light source (here, an image of the filament) as shown in FIG.

When the two-color filter 4 is moved in the positive or negative direction of the u-axis, the image of the surface to be measured captured by the color video camera 7 is located at the position where the light source image comes to the color boundary as shown in FIG. At the boundary, the whole changes from green to red or red to green at the same time. Since the actual surface to be measured has undulations as shown in FIG. 9, the light reflected at different positions A, B, and C on the surface to be measured are reflected at different angles, and reach different positions on 4 and as shown in FIG. The light source images a,
Connect b and c. The actual light source image is the sum of all the reflected lights that reach 4, so that it becomes totally blurred. If you move 4 in the same way as before, the positions of a, b, and c will be different this time, so A, B, and C captured by the color video camera.
The color of does not change at the same time, but changes at each of the four different positions.

Now, the image of the color video camera is loaded into a computer, the change in color is tracked for each pixel, and the moving distance of the two-color filter 4 when the color changes is adjusted to an appropriate position (specifically, the surface to be measured). It is better to choose a position of 4 where half of the color is red and the other half is green), and let D be the inclination of the measured surface at the position corresponding to the pixel along the x-axis. ∂z / ∂x can be obtained by ∂z / ∂x = D / f2b (f2b: focal length of lens 2b) (b).

[0012]

The present invention will be described in more detail with reference to the following examples. FIG. 2 is the simplest embodiment of the invention using only one convex lens. In this embodiment, the two-color filter 4
Instead of moving, the point light source 1 is placed on the moving stage 8 and moved, and the same measurement is performed. Of course, similarly to the embodiment of FIG. 1, the point light source 1 may be fixed and the two-color filter 4 may be set on the moving stage. Alternatively, in the embodiment of FIG. 1, the two-color filter 4 may be fixed and the point light source 1 may be moved. The above is also one of the embodiments of the present invention.

FIG. 5 shows an embodiment in which the position of the lens 2b of the embodiment of FIG. 1 is changed and a lens 2c is further added. Figure 1
Lens 2b has a function of converging the reflected light on the dichroic filter 4 and a function of projecting the image of the surface to be measured onto the image sensor 5, whereas in FIG. 5, the latter function is changed to 2c. Since 2b and 2c are shared and used in tandem, the projection magnification can be easily changed by replacing 2c with a lens having a different focal length. It is also possible to use a zoom lens for 2c. In order to change the projection magnification in FIG. 1, it is necessary to change the position of the two-color filter 4 or the color video camera 7 with the replacement of 2b.

FIG. 3 shows lenses 2a and 2b of the embodiment of FIG.
This is an embodiment in which the number of parts is reduced by having one lens 2ab also perform the function of. In this case, it is preferable to use an antireflection film coated on 2ab so that the light reflected on the surface of 2ab does not interfere with the measurement when entering the color video camera. Alternatively, as in the embodiment of FIG. 6, polarization filters 10 and 11 having polarization axes orthogonal to each other are placed between the point light source 1 and the beam splitter 3 and between 3 and the color video camera, and the lens 2
It is also possible to place a quarter-wave plate 9 between ab and the surface 6 to be measured, and rotate the polarization plane by 90 ° only for the reflected light from 6 to remove the reflected light from the lens surface.

In the embodiment shown in FIG. 11, the beam splitter 3 shown in FIG. 3 is replaced with a polarizing beam splitter 12, and the influence of reflected light on the surface of 2ab is eliminated by combining with the 1/4 wavelength plate 9. The same applies to the case of FIG. 6, but since the reflected light on the surface of the 1/4 wavelength plate 9 on the measured surface side is not removed by the polarization beam splitter 9, 9 is slightly inclined so as not to be parallel to the measured surface. It is preferable to install it so that the reflected light does not enter the color video camera 7.

FIG. 12 shows an example in which a coated plate having waviness called fine skin is measured by using the apparatus shown in FIG. 6, and FIG. 13 shows an example in which a coated sheet having good smoothness is measured by the apparatus. The point light source 1 is a 20 W halogen bulb and lenses 2ab and 2c.
The focal lengths are 100 mm and 75 mm, respectively.

The color change is detected by comparing the sizes of the R and G components of the input image, but the transmission characteristics of the color filter, the color temperature of the light source, the wavelength sensitivity characteristics of the color video camera, etc. are corrected. Was determined by the sign of G-aR (a is a positive real number).

(1) First, the two-color filter 4 is moved in the negative direction of the u-axis to a position where all the pixels to be measured in the image on the surface to be measured are green (G-aR> 0), and (2) then An image is input at a constant time interval while moving 4 in the positive direction of the u axis at a constant speed, and the moving distance of 4 is obtained from the elapsed time when the color of each pixel changes to red (G-aR <0). (3) When all the measurement pixels turn red, stop the measurement and set the average movement distance to D = 0.
As a (reference), D of each pixel is obtained, and the inclination ∂z / ∂x is obtained by the equation (a).

The above series of operations was automatically performed by a computer. The computer used is a commercially available inexpensive 16-bit personal computer. Graph of the inclination of the painting surface Figures 12 and 13 show how the image is distorted when the landscape is projected on the painting board.
This is in good agreement with the visual impression, and it was found that this evaluation method is suitable for evaluation of the coating appearance. For the point light source used in the present invention, a high brightness white light source such as a tungsten lamp having a small filament size, a halogen lamp or a xenon lamp having a small light emitting area is suitable, and particularly when it is desired to observe the sample surface at high magnification, A high light source is needed.

The color video camera used in the present invention must have a high color signal resolution. From this point, a high-resolution camera equipped with RGB independent output is suitable. Although expensive, the three-plate or three-tube type is most preferable. In the embodiment of the present invention, the two-color filters of green and red shown in FIGS. 8 and 10 were used. However, the sensitivity of the color video camera used was high from green to red and low with respect to blue light. But it was because I tried to use the highly sensitive part.

[0021]

According to the surface characteristic evaluation apparatus of the present invention, it becomes possible to obtain the tilt information representing the distortion of the scene reflected on the surface by a combination of a simple optical device, a color video camera and a computer.

[Brief description of drawings]

FIG. 1 is a plan view of an optical device portion of an embodiment of the present invention.

FIG. 2 is a plan view of an optical device portion of an embodiment of the present invention.

FIG. 3 is a plan view of an optical device portion according to an embodiment of the present invention.

FIG. 4 is a perspective view of an optical device portion according to an embodiment of the present invention.

FIG. 5 is a plan view of an optical device portion according to an embodiment of the present invention.

FIG. 6 is a plan view of an optical device portion according to an embodiment of the present invention.

7 is an explanatory diagram explaining the principle of the present invention, and FIG.
Alternatively, it is a partially enlarged view of the plan view of FIG. 5.

FIG. 8 is an explanatory diagram illustrating the principle of the present invention, and is a diagram showing images of a two-color filter and a point light source.

9 is an explanatory diagram for explaining the principle of the present invention, and FIG.
Alternatively, it is a partially enlarged view of the plan view of FIG. 5.

FIG. 10 is an explanatory diagram illustrating the principle of the present invention,
It is the figure which showed the image of a color filter and a point light source.

FIG. 11 is a plan view of the optical device portion of the embodiment of the present invention.

FIG. 12 is a graph showing a measurement example using the surface evaluation device of the present invention.

FIG. 13 is a graph showing a measurement example using the surface evaluation device of the present invention.

[Explanation of symbols]

 1 Point light source (light bulb) 2a Convex lens 2b Convex lens 2c Convex lens 2ab Convex lens 3 Beam splitter 4 Two-color filter 5 Image sensor 6 Measurement surface (Sample) 7 Color video camera 8 Moving stage 9 1/4 Wave plate 10 Polarization filter 11 Polarization filter 12 Polarizing beam splitter

Claims (1)

[Claims] 1. A point light source, at least one convex lens, a beam splitter, and two different colors with a straight line as a boundary.
A color filter, a means for moving one of the point light source and the two-color filter, a color video camera, and a computer having an image input function are components, and the point light source emits light from the point light source into the beam. The point light source of the reflected light that is incident on the splitter and is reflected by the surface to be measured so that either the transmitted component or the reflected component is perpendicular to the surface to be reflected and returned to the beam splitter. Light extracted in a different direction from the point light source to the beam splitter or the beam splitter to the surface to be measured or the beam splitter to at least one convex lens placed between the two-color filter, If necessary, the light condensed on the two-color filter and the light passing through the two-color filter may be formed on the color video camera to form an image of the surface to be measured. A lens provided between the two-color filter and the color video camera guides, and the moving means provided on either one of the point light source and the two-color filter causes a point light source image on the two-color filter to be formed. While changing the position of the point light source or the two-color filter so as to move in a direction perpendicular to the color boundary line, the computer monitors the color change of each pixel of the measured image captured by the color video camera, It is characterized in that the inclination of the position of the measured surface corresponding to each pixel is calculated from the moving distance of the point light source or the two-color filter when the Surface evaluation device.