A simple and effective algorithm for detection of arbitrary Hartmann-Shack patterns

The Hartmann-Shack sensor is well known for its capability of detecting optical aberrations from telescopic images, normally caused by the atmospheric turbulence. Since the mid-1990s, this sensor has been adapted to work with ophthalmic instrumentation to measure aberrations of the human eye. In astronomical applications, the image processing is implemented using robust closed-loop hardware systems, allowing for very high frequencies (usually in the range of 30-500 Hz). In ophthalmic instruments, this hardware solution is not proper, for two reasons: first, prices of ophthalmic instrumentation have to be at more accessible prices and, second, there is no need for ultra-high frequency closed-loop systems; in fact, as we will see along the text, recent studies of the dynamics of the eye's aberrations show that closed-loop systems of very much lower frequencies (from 10 to 40 Hz) may well eliminate the undesired micro-fluctuations in the eye's aberrations and allow for diffraction limited measurements. We have developed an effective algorithm for detection of HS patterns using an affordable commercial hardware configuration and easy to implement software. To our knowledge, this type of information has not been thoroughly disclosed elsewhere, probably due to proprietary reasons.