Coordinate Position of Moving Light Source by Using Separated Groups of Detectors Each Group Having an Iris

1. A position detecting apparatus, comprising: a moving light source, and n sets, n an integer not less than 2, of paired detecting sections which are spaced from each other in the direction of the x-axis of a plane perpendicular to an x-z coordinate plane at a constant distance p from the next set in the n sets, the first set in the n sets spaced at the constant distance p from the line x=0, each detecting section comprising: an iris portion making a part of light from the moving light source pass, the iris portion having an opening, the opening having a center, and a divided light receiving portion divided into two light receiving elements toward an alignment-direction of the detecting section, the divided portion having a center, wherein: the divided light receiving portions of all the detecting sections are disposed on a same x-z coordinate plane; the center of the opening of the iris portion and the center of the divided light receiving portion are aligned in the direction of the z axis in each of the detecting sections; received light outputs R.sub.i and L.sub.i are output from the two light receiving elements, respectively, of one of the divided light receiving portions of each of the detecting sections in response to an amount of light from the light source, i=2 to n; received light outputs R.sub.-i and L.sub.-i are output from the two light receiving elements, respectively, of another of the divided light receiving portions of each of the detecting sections in response to an amount of light from the light source, i=2 to n, and from the received light outputs from each of the divided light receiving portions, a position of said moving light source is determined.

2. A method of detecting the position of a moving light source, the method comprising the steps of: receiving R.sub.i, L.sub.i, R.sub.-i, and L.sub.-i, i=2 to n, as defined in claim 1, using the apparatus recited in claim 1; calculating S.sub.i =(R.sub.i -L.sub.i)/(R.sub.i +L.sub.i)+(R.sub.-i -L.sub.-i)/(R.sub.-i +L.sub.-i) for all i, i=2 to n; calculating T.sub.i =(R.sub.i -L.sub.i)/(R.sub.i +L.sub.i)-(R.sub.-i -L.sub.-i)/(R.sub.-i +L.sub.-i) for all i, i=2 to n; ##EQU3## calculating a coordinate position (x.sub.0, z.sub.0) of the moving light source from S and T.

3. The method of claim 2 wherein the coordinate position (x.sub.0, z.sub.0) is calculated according to the formulae: x.sub.0 =(z.sub.0)(a)(S)/(4d)(n) and z.sub.0 =-(2d)(n)(n+1)(p)/(a)(T), wherein a=the size of the opening of the iris member in the x-axis direction and d=the distance between the iris member and the divided light receiving portion in the z-axis direction.

4. The position detecting apparatus of claim 1 wherein the n sets of paired detec ng sections are coaxial.

5. A method of detecting the position of a moving light source, the method comprising the steps of: (a) providing the moving light source; (b) providing n sets, n an integer not less than 2, of paired detecting sections which are spaced from each other in the direction of the x-axis of a plane perpendicular to an x-z coordinate plane at a constant distance p from the next set in the n sets, the first set in the n sets spaced at the constant distance p from the line x=0, each detecting section comprising: an iris portion making a part of light from the moving light source pass, the iris portion having an opening, the opening having a center, and a divided light receiving portion divided into two light receiving elements toward an alignment direction of the detecting section, wherein: the divided light receiving portions of all the detecting sections are disposed on a same plane; the center of the opening of the iris portion and the center of the divided light receiving portion are aligned in the direction of the z axis in each of the detecting sections; received light outputs R.sub.i and L.sub.i are output from the two light receiving elements, respectively, of one of the divided light receiving portions of each of the detecting sections in response to an amount of light from the light source, i=2 to n, and received light outputs R.sub.-i and L.sub.-i are output from the two light receiving elements, respectively, of another of the divided light receiving portions of each of the detecting sections in response to an amount of light from the light source, i=2 to n; (c) calculating S.sub.i =(R.sub.i -L.sub.i)/(R.sub.i +L.sub.i)+(R.sub.-i -L.sub.-i)/(R.sub.-i +L.sub.-i) for all i, i=2 to n; (d) calculating T.sub.i =(R.sub.i -L.sub.i)/(R.sub.i +L.sub.i)-(R.sub.-i -L.sub.-i)/(R.sub.-i +L.sub.-i) for all i, i=2 to n; ##EQU4## (g) calculating a coordinate position (x.sub.0, z.sub.0) of the moving light source from S and T.

6. The method of claim 5 wherein the n sets of paired detecting sections are coaxial.

7. The method of claim 5 wherein the coordinate position (x.sub.0, z.sub.0) is calculated according to the formulae: x.sub.0 =(z.sub.0)(a)(S)/(4d)(n) and z.sub.0 =-(2d)(n)(n+1)(p)/(a)(T), wherein a=the size of the opening of the iris member in the x-axis direction and d=the distance between the iris member and the divided light receiving portion in the z-axis direction.