Field of the Invention
The present invention relates to acquisition of the multi-angular reflectance property of an object surface.
Description of the Related Art
A goniophotometer is known as a measurement apparatus that acquires a multi-angular reflectance property as the multi-angular property of the reflectance on an object surface. Japanese Patent Laid-Open No. 2006-275955 (literature 1) discloses a measurement apparatus that switches the irradiation direction of light with respect to an object to irradiate the object with light, and also switches the capturing direction, with respect to the object, of a camera configured to capture the object placed on a table. The measurement apparatus disclosed in literature 1 can acquire the two-dimensional distribution of the multi-angular reflectance property of an object. Such a measurement apparatus acquires a multi-angular reflectance property by changing geometric conditions such as the irradiation direction of light and the capturing direction.
However, the reflectance of a metal or the like in the neighborhood of the specular reflection direction greatly varies by even a small difference of the angle. For example, the above-mentioned measurement apparatus takes a long time for measurement because measurement is repeated while changing geometric conditions at a small step such as a 0.2 degree step in the neighborhood of the specular reflection direction. Since geometric conditions need to be changed at high accuracy, a device such as a multi-angle stage configured to change the angle of a placed object becomes expensive.