Hartmann-Shack sensor ASIC’s for real-time adaptive optics in biomedical physics

Hartmann-Shack wavefront sensors are widely used to measure wavefront aberrations. Their applications in biomedical physics are mainly in the fields, where lasers are used for diagnostics or treatment, especially in opthalmology. In a number of applications, e.g. retina scanning, the imaging performance is limited by temporal aberration fluctuations. A fast Hartmann-Shack sensor in combination with an adaptive micro-mirror allows real-time correction of these aberrations. Hartmann-Shack sensors consist of a lenslet array, which splits the aperture of interest into a matrix of subapertures and an image detector in the focal plane. The wavefront is calculated from the lateral shifts of the focal spots. We present application specific integrated circuits (ASIC), which perform the required image acquisition and processing in the 1 kHz range. The presented ASIC’s detect the spots and their position and can substitute slow standard CCD camera-chips to allow real-time processing. A number of chips have been produced in standard industrial CMOS (0.6 μm and 0.35 μm) processes, with the number of detectors ranging from 3 x 3 to 16 x 16 spots.