Photonics Technology Letters
An x-y active alignment system based on Risley beam steerers is described. The demonstrator features a quadrant detector which detects the misalignment error between the center of a spot of light and the center of the quadrant detector. This misalignment error is then used by a new algorithm to calculate the rotational displacement required for the two Risley beam steerers to steer the spot of light to the center of the quadrant detector. The experimental results indicate that any spot misaligned by up to 160 μm on the quadrant detector will be systematically centered by the demonstrator system.
G. C. Boisset, B. Robertson, H. S. Hinton, "Design and Construction of an Active Alignment Demonstrator for a Free-space Interconnect," Photonics Technology Letters, Vol. 7, No. 6, June 1995, pp. 676-679.