Compact retinal imaging system with liquid-crystal spatial-light-modulation adaptive optics device

The vision science experiment and optical setup mentioned in this paper are employed in order to develop a compact retinal imager with an adaptive optics system (AOS). The AOS dynamically detects the wavefront and then compensates for the distortion caused by internal and external disturbances. The wavefront sensing of this AOS based on a Michelson interferometer with liquid crystal device (LCD) phase-shift interferometry (PSI). Using accurate phase calibration and transient nematic driving of the LCD, the developed three-step PSI procedure can be achieved in a time of 5 ms. The three fringe patterns associated to the wavefront information are detected by a 16×16 photodiode array and converted to a digital two-dimensional phase image. The PC based controller, xPC Target from the Matlab, then computes appropriate multichannel control signals based on the reconstructed phase image to drive a 127-element transmittance spatial light modulator in such a way as to eliminate the aberration of the eye. The current AOS is expected to be capable of suppressing low-frequency disturbances with a signal-to-noise ratio improvement of more than 20dB and a steady-state phase error of less than 0.02 π root mean square when the control loop is operated at a frequency of 30 Hz.