Wavefront sensor using hybrid optical/electronic heterodyne techniques

US7218402B1 · kind B1 · utility

Assignee

• NORTHROP GRUMMAN CORPORATION · US

Inventors

• Stephen J. Brosnan · Rancho Palos Verdes, US
• Mark E. Weber · Hawthorne, US

Key dates

• Filing date: Dec 4, 2003
• Grant date: May 15, 2007
• Expiry date: Sep 15, 2024

Classification

• Technology area (CPC G): Physics
• CPC primary: G01J9/04
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

A hybrid optical/electronic wavefront sensor includes an electro-acoustical device used to upshift an optical reference signal. An optical test signal and the frequency upshifted optical reference signal are optically heterodyned to create a signal having a frequency equivalent to the beat frequency of the two signals, for example, the RF driving frequency of the Bragg cell. The optically heterodyned signal is then converted by way of a detector to an electronic signal having the same phase as the optical test signal. The output of the detector is a sinusoidal signal having the same phase as the phase of the optical test signal. This signal is filtered by way of an AC filter and mixed with a second clock signal, for example, a clock signal that is offset in frequency from the electro-acoustical drive signal by a frequency, for example, between 100 kHz and 1 MHz. These two signals are mixed by way of a mixer. The low frequency product of the mixer is passed by way of a filter and converted to a square wave by way of a comparator. The output of the comparator is applied to a simple pulse counter and used to disable the pulse counter. The pulse counter counts the clock pulses while it…