APPLICATION OF SHACK-HARTMANN WAVEFRONT SENSORS TO OPTICAL SYSTEM CALIBRATION AND ALIGNMENT

摘要

Optical systems are normally aligned by centering the energy distribution in various apertures. However, the use of both irradiance and phase information can in many cases greatly simplify this process, and can provide information for closed-loop alignment and control of an optical system. This can be accomplished by using a Shack-Hartmann wavefront sensor for alignment and performance testing. While Shack-Hartmann wavefront sensors are commonly used for adaptive optics, they have many other applications. The modern Shack-Hartmann wavefront sensor is compact, rugged, and insensitive to vibration, and has fully integrated data acquisition and analysis. Furthermore, even wavefronts of broad band sources that cannot normally be tested with interferometers can be measured with Shack-Hartmann wavefront sensors. The instrument also provides information about the optical system performance, including peak-to-valley (P-V) wavefront deviation, RMS wavefront error, the modulation transfer function (MTF), and the point spread function (PSF). Since the difference of two wavefronts is easily computed, the effect of individual optical elements on a complex optical system can be examined. In this paper we will present an alignment methodology using the Shack-Hartmann wavefront sensor to setup even complex optical systems. An example of using the methodology to align a lens is presented. Alignment of the Shack-Hartmann wavefront sensor to a 24-inch telescope at Stanford University is presented. The higher-order static aberrations in the telescope are then measured with the Shack-Hartmann wavefront sensor.