This paper describes a surface encoder with a multi-spot light source. The surface encoder consists of an angle grid having a two-dimensional (2D) sinusoidal angular pattern on its surface, and a 2D angle sensor used to detect the 2D angle profile of the grid surface. The 2D XY displacements and tilt motions (pitch, roll and yaw) can be detected by the surface encoder. In this paper, a multi-spot light source is employed in the angle sensor. The multi-beams from the light source are projected onto the angle grid surface at the same phase positions in different periods. An averaging effect greatly reduces the effect of the dispersion of the pitch spaces of the angle grid, which acts as the measurement reference of the surface encoder. A laser diode and a grid film are combined to generate the multi-spot beams with pitch spaces of 300 μm, which are the same as those of the angle grid used in the experiments. The surface encoder with the multi-spot light source shows a good performance. A self-calibration technique is also applied to calibrate the surface encoder.
|Translated title of the contribution||A surface encoder with a multi-spot light source|
|Number of pages||5|
|Journal||Journal of the Japan Society for Precision Engineering|
|Publication status||Published - 2002 Jan|