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.