| 摘要 |
PURPOSE:To enable to perform a positioning control in a stable manner by a method wherein the coefficient of illuminance of light source of the changing rate of reflection factor is led out from the quantity of light of the entire flux of light to be projected on a dichotomized light-receiving element, and said changing rate is fed back to the upper limit and the lower limit of the blind sector which is already set and an appropriate blind sector is formed at all times. CONSTITUTION:An optical or dichotomized light-receiving element 1 is provided at the intended position of an object 21 in such a manner that a luminous flux 3 is equally divided by light- receiving elements 1a and 1b. When there is a change in the illuminance of the luminous flux 3, the area of luminous flux which is made incident on the dichotomized light-receiving element 1 is unchanged and the electric output is in proportion to the illuminance. Therefore, the changing rate R=(Va+Vb)/Vr of the illuminance (Va+Vb) of the present point of time for the reference illuminance can be obtained from the output of a divider 24 which performs an arithmetic operation at all times. The changing rate R calculated by the divider 24 is inputted to multipliers 25 and 26, an arithmetic operation of RVu and RVd is performed for the reference blind sector values Vu and Vd, which were calculated already, by the multipliers 25 and 26. The result of said arithmetic operation is inputted to a blind sector circuit 15 as an actual blind sector value, and a blind sector coincided with the target accuracy can be obtained. |
