DATA INPUT DEVICE AND ITS METHOD FOR DETECTING MOVEMENT OF TRACKING SURFACE BY LASER SPECKLE PATTERN

摘要

PROBLEM TO BE SOLVED: To provide a data input device having a coherent light source for projecting a coherent light beam onto a tracking surface for scattering the coherent light beam.

SOLUTION: An optical system 47A guides the projected coherent light beam 29 toward the tracking surface 31 and comprises a first boundary 55 facing the coherent light source 25 and a second boundary 55 opposite the first boundary 55. A detector 49 detects a portion of the scattered light beam 33 comprising a speckle pattern. The optical system is arranged such that the tracking surface 31 is spaced from the second boundary 57 by a distance sufficient to inhibit any retro-reflection 63 of the coherent light beam 29 striking the second boundary 57 from striking the detector 49. A controller 73 operates the device in a tracking mode by utilizing the detected speckle pattern to track relative movement between the device and the tracking surface.

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