FUNDAMENTAL PERFORMANCE COMPARISON OF A HARTMANN AND A SHEARING INTERFEROMETER WAVE-FRONT SENSOR

The performance of ground-based optical imaging systems is severely de graded from the diffraction limit by the random effects of the atmosph ere. Adaptive-optics techniques have been used to compensate for atmos pheric-turbulence effects. A critical component in the adaptive-optics system is the wave-front sensor. At present, two types of sensors are common: the Hartmann-Shack wave-front sensor and the shearing interfe rometer wave-front sensor. In this paper we make a direct performance comparison of these two sensors. The performance calculations are rest ricted to common configurations of these two sensors and the fundament al limits imposed by shot noise and atmospheric effects. These two eff ects encompass the effects of extended reference beacons and sensor su baperture spacings larger than the Fried parameter ro. Our results ind icate comparable performance for good seeing conditions and small beac ons. However, for poor seeing conditions and extended beacons, the Har tmann sensor has lower error levels than the shearing interferometer.