| 摘要 |
<p>PROBLEM TO BE SOLVED: To enable to control the illuminance of a floor surface in nearly constant by computing the dimming level on the basis of the brightness of a reference part, which is set by a control unit in a discriminated surface to be lighted, on the basis of the brightness of each small area of the surface to be lighted, which is detected by a light detecting unit, so as to control the optical output of a light source. SOLUTION: A light detecting unit 3 is fitted to a lower surface of an apparatus main body so as to measure the brightness of each small area, which is formed of 310,000 picture elements of CCD element 3b and which is obtained by dividing the whole into 64×480. An initial set brightness value as a brightness of a reference material 10a placed on the floor surface 5a and an initial set dimming level are stored in a memory unit. A control unit lights a lamp at the initial set dimming level, and stores the brightness of the all small areas. Reflectance is obtained on the basis of the brightness value of a desirable small area as a starting point, and a temporarily dimming level is computed on the basis of the predetermined formula, and in the case where this level stratifies the predetermined condition, the temporary dimming level is controlled as a dimming level of the light source. Consequently, even there is a material, of which brightness is different from that of the floor surface 5a, nearly constant illuminance is obtained.</p> |
