Multiplex techniques for real-time shearing interferometry

Abstract

Real-time wavefront sensors can be viewed as processing channels that convert a continuous, two-dimensional wavefront phase variation into a parallel array of sampled wavefront values. In general, two pieces of data are required for each wavefront sample: the x gradient and the y gradient. We achieve efficient use of the electro-optical portion of this channel through optical multiplexing techniques that combine the x and y data into one signal. Time multiplexing, temporal frequency multiplexing, and spatial frequency multiplexing have each been implemented successfully in high performance, grating-based, shearing interferometers. The two frequency multiplexing techniques are examined in this paper. A 1000 point wavefront sensor is described as an example of spatial frequency multiplexing, and a typical design is used as the example of temporal frequency multiplexing. Performance of multiplexed sensors is not sacrificed, as demonstrated by the nearly 1000:1 dynamic range (total tilt:rms error) of the latter type of sensor.