Compact optically based systems for linear and angular displacement sensing

Two new, compact sensor systems for measuring linear and angular displacements are presented. Both systems have been designed with the aim of being compact, reliable, low-priced, yet performs with reasonable accuracy., Common for both systems is the use of Vertical Surface Emitting Lasers (VCSELs) as the coherent light source. The first system is a device for measuring one component of a linear translation, being it of a solid surface or scattering particles in a flow. A VCSEL array constitutes the illuminating source creating a fringe-like pattern in the measuring volume by imaging. Scattered light from the object is detected with a single detector and a spectral analysis of the signal reveals the traverse velocity, the fringe distance being known. For measuring rotation of a semi-reflective steel ball, a compact system has-been developed, again based on a single, lensless VCSEL as the source. This system is further reduced in size, as compared to the previous system and provides adequate accuracy for its intended purpose.