Patent ID: 7208714

Claim:
An optical displacement sensor comprising: a light source disposed at one of a reference object and a measurement object; and a light receiving means disposed at the other one thereof at which the light source is not disposed, and functioning to receive light emitted from the light source thereby measuring rotational displacement of the measurement object relative to the reference object with respect to two-axis directions in a plane perpendicular to an optical axis of the light emitted from the light source, wherein the light emitted from the light source, at least when received at the light receiving means, has its intensity distribution shaped in an oval configuration with two symmetry axes oriented so as to match the two-axis directions, respectively, the two symmetry axes including a major axis and a minor axis not equal to the major axis, and wherein light intensity from the light source in a first portion of the light receiving means is compared against light intensity from the light source in a second portion of the light receiving means to enable rotational adjustment of the light receiving means with respect to the light source to achieve alignment about an optical axis.