Laser beam imaging via multiple mode operations of the extreme dynamic range CAOS camera.

Abstract

Demonstrated for the first time, to the best of our knowledge, is laser beam imaging via multiple mode operations of the digital micro-mirror device-based coded access optical sensor (CAOS) camera. Specifically, outlined are novel modes of software programmable CAOS imaging, which include the time division multiple access (TDMA) mode, the code division multiple access (CDMA) mode, the CDMA-TDMA mode, the frequency division multiple access (FDMA)-TDMA mode, the frequency modulation (FM)-CDMA-TDMA mode, FM-TDMA mode, and the FDMA-CDMA-TDMA mode. Engagement of FDMA and CDMA modes enables simultaneous multi-pixel improved signal-to-noise ratio photo detection, while use of TDMA prevents optical point detector saturation. The use of the FDMA and FM modes creates high digital signal processing gain via temporal spectrum analysis to produce extreme dynamic range pixel-specific imaging. Using an un-attenuated 633nm He-Ne laser near-Gaussian focusing beam, experimentally acquired are 13.68μm spatial resolution laser beam map CAOS images with dynamic ranges of 44.78dB, 45.28dB, 83.90dB, and 94.9dB for the TDMA, CDMA, FM-CDMA-TDMA, and FM-TDMA modes, respectively. The FM-TDMA mode with its extreme dynamic ranging CAOS pixel-mapping capability experimentally measures the non-Gaussian spatially oscillatory irradiance behavior predicted by Huygens-Fresnel diffraction theory. The demonstrated CAOS camera through software control allows high-flexibility, robust imaging of laser beams across different wavelength bands with widely varying beam irradiance levels and spatial signatures, thus empowering optical system designers to match overall system requirements that are highly dependent on accurate and reliable laser beam metrology.