| 摘要 |
PROBLEM TO BE SOLVED: To reduce the detection error to the minimum even in the case the interval between a scale and a light receiving element changes different from the essentially moving direction. SOLUTION: A surface emission laser 1 radiates divergent light with an intensity distribution I represented by an equation (1), the surface emission laser 1 and a light receiving element 2 are arranged so as to satisfy an equation (2), and the distance between a light emission surface 11 and the scale surface including the light receiving surface of a light receiving element 2 is set in the range of 0.75 to 1.4 times of a reference value y. The equation (1) is represented: I(r)=I0 expä-2(r/w)<SP>2</SP>}. Herein, I(r) represents intensity on the surface perpendicular to the light axis of the surface light emission laser 1 at a distance d from the light source and on the surface at a distance r from the light axis, the I0 represents the light intensity of the light axis on the surface at the distance d from the surface light emission laser 1, and w represents a constant specified by the surface at the distance d from the surface light emission laser 1. The equation (2) is represented: (δ/δx) expä-(dx/wy)<SP>2</SP>}/ä2y(4y<SP>2</SP>+x<SP>2</SP>)<SP>1/2</SP>}=0. Herein, a notationδin the equation is substitution of the partial differential notation. COPYRIGHT: (C)2007,JPO&INPIT
|
