JPH0476426B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for measuring diffuse reflection brightness as an optical reflection characteristic of an object.

(Prior technology) Conventionally, for measuring the amount of reflected light, JIS
There are methods disclosed in Z8722 and JIS Z8741,
These are related to object color measurement methods and specular gloss measurement methods, and there is no particular method related to measurement of diffuse reflection brightness.

When measuring diffuse reflection luminance, the problem is how to remove the specular reflection component and extract only the diffuse reflection component. Conventionally, in order to do this, detailed geometric conditions regarding illumination and light reception ( for example,
By satisfying JIS Z8722 clauses 4, 3, 1, etc.), specular reflection components were prevented from entering the light receiving system of the luminance measuring device.

Note that in this specification, diffuse reflection refers to reflection that diffuses light in many directions on a diffusive reflective surface, macroscopically, regardless of the law of reflection.
Specular reflection refers to the reflection of light that follows the law of reflection when viewed macroscopically on a diffusive reflective surface.

(Problems to be Solved by the Invention) However, in the above-mentioned conventional method, detailed geometrical conditions are a constraint, and the object to be measured and the measuring instrument,
There were difficulties in setting up lighting equipment, etc.

The present invention has been made to solve the problems of the prior art, and provides a method for easily and accurately measuring the diffuse reflection luminance of an object by eliminating or minimizing the specular reflection component. The purpose is to provide.

(Means for Solving the Problems) The present invention provides a method for measuring diffuse reflection brightness in which the surface to be measured of an object is uniformly irradiated from substantially all directions and the brightness due to diffuse reflection on the surface to be measured is measured by a brightness measuring means. In order to solve the problems of the prior art described above, when the surface to be measured is a reflective surface, means is provided for removing the specular reflection component in a direction that gives the specular reflection component to the light receiving system of the brightness measuring means. It is designed to perform measurements. Ideally, a material or object that absorbs all of the incident light is ideal as a means to remove the specular reflection component, but in reality, a material or object that has a reflectance that does not affect measurement accuracy is used. Ru.

(Function) Since the means for removing the specular reflection component removes or minimizes the specular reflection component that enters the light receiving system of the luminance measurement means, only the diffuse reflection component to be measured is effectively extracted, and this is detected by the luminance measurement means. It becomes possible to measure from any angle except the normal direction of the surface to be measured. Therefore, the diffuse reflection luminance can be easily and accurately measured without being constrained by detailed geometrical conditions.

(Example) Hereinafter, the measuring method of the present invention will be explained in detail based on FIG. In the figure, 1 is a surface to be measured, 2 is a luminance measuring device, and 3 is a black object (hereinafter referred to as a black board) provided to remove or minimize specular reflection components. The one-dot chain line indicates the normal to the surface to be measured 1, α indicates the angle between the optical axis of the luminance measuring device 2 and the normal, and θ indicates the approximate angle between the blackboard 3 and the normal. Furthermore, the surface to be measured 1 is illuminated uniformly from all directions so that no shadow is cast on the surface to be measured 1 by the brightness measuring device 2 or the black board 3.

The installation condition for each element is that the optical axis of the luminance measuring device 2, the normal to the surface to be measured 1, and the blackboard 3 are in the same plane. Furthermore, the installation position of the blackboard 3 is such that θ=α (≠0°) because the purpose of its installation is to remove or minimize specular reflection components that macroscopically follow the law of reflection. It is an absolute requirement to do so.

Further, the size of the blackboard 3 is required to be such that the projected image of the blackboard 3 itself onto the surface to be measured 1 sufficiently encompasses the measurement field of the luminance measuring device 2. Therefore, the size of the blackboard 3 is determined depending on the installation distance between the blackboard 3 and the surface 1 to be measured.

The ideal blackboard 3 is a substance or object that absorbs all the incident light. An example of such an object would be a Kirchhoff dark box, but it is generally a black board that does not affect measurement accuracy. (reflectance). The reflectance of the object used as the blackboard 3 directly affects the measurement accuracy in the sense of removing specular reflection, so the required accuracy of the measurement and the reflection characteristics of the surface to be measured 1 should be fully considered to reduce the effect on the measurement accuracy. Care must be taken to minimize this. In particular, the larger the proportion of specular reflection components in the reflection of the surface to be measured 1, the greater the influence on measurement accuracy.When measuring such objects, it is recommended to use an object with low reflectance as the blackboard 3 to improve measurement accuracy. It is important to raise

(Effects of the Invention) As described above in detail, according to the present invention,
Since the specular reflection component is removed using a specular reflection component removal means (black board), it is possible to easily measure the diffuse reflection luminance from any angle except on the normal line of the surface to be measured, and it is possible to easily measure the diffuse reflection brightness from any angle except on the normal line of the surface to be measured. Even when it is difficult to move or install the object to be measured due to the above, it can be dealt with relatively flexibly, and the measurement becomes easy. The present invention uses, for example, the diffuse reflection brightness as a measure of visibility of a CRT surface or a screen filter attached to a CRT display monitor, or the brightness ratio (the brightness of an object illuminated and observed under the same conditions and the brightness of a completely diffuse reflection surface). It is effective in measuring the ratio of

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining a method for measuring diffuse reflection luminance according to the present invention. 1... Surface to be measured, 2... Luminance detector, 3... Specular reflection component removal means (black board).

Claims (1)

[Claims] 1. A method for measuring diffuse reflection brightness in which a surface to be measured of an object is uniformly irradiated from substantially all directions and the brightness due to diffuse reflection on the surface to be measured is measured by a brightness measurement means, comprising: 1. A method for measuring diffuse reflection brightness, characterized in that when a reflective surface is used, a measurement is performed by providing means for removing a specular reflection component in a direction in which the specular reflection component is applied to a light receiving system of a brightness measurement means.