A fast modal wave-front sensor

We describe an instantaneous modal wave-front sensor. The sensor uses a Sha ck-Hartmann lenslet array to encode the wave-front distortion. A novel para llel electro-optic processor continuously converts the spot pattern to wave -front modes, e.g. Zernike polynomials, without a separate reconstructor. U sing readily available components, the sensor can achieve MHz bandwidths fo r twenty modes. The bandwidth, sensitivity, and number of bits can vary for each mode to match the sensor to the disturbance in an optimal fashion. Th e proposed sensor has immediate application to beam control and turbulence sensing applications that require wide bandwidths. The measured wave-front modes can also be those of an adaptive optics system, directly providing co ntrol signals for the actuators of a deformable mirror. A similar electroni c reconstructor mode is also described. (C) 2001 Optical Society of America .