Triple coding empowered FDMA-CDMA mode high-security CAOS camera.

For the first time, to the best of our knowledge, the hybrid triple coding empowered frequency division multiple access (FDMA)-code division multiple access (CDMA) mode of the coded access optical sensor (CAOS) camera is demonstrated. Compared to the independent FDMA and CDMA modes, the FDMA-CDMA mode has a novel high-security space-time-frequency triple signal encoding design for robust, faster, linear irradiance extraction at a moderately high dynamic range (HDR). Specifically, this hybrid mode simultaneously combines the linear HDR strength of the FDMA-mode fast Fourier transform (FFT) digital signal processing (DSP)-based spectrum analysis with the high signal-to-noise ratio (SNR) provided by the many simultaneous CAOS pixels' photodetection of the CDMA mode. In particular, the demonstrated FDMA-CDMA mode with P FDMA channels provides a P times faster camera operation versus the equivalent linear HDR frequency modulation (FM)-CDMA mode. Visible band imaging experiments using a digital-micromirror-device-based CAOS camera operating in its passive light mode demonstrates a P=4 channels FDMA-CDMA mode, illustrating high-quality image recovery of a calibrated 64 dB six-patch HDR target versus the CDMA and FM-CDMA CAOS modes, which limit dynamic range and speed, respectively. For the first time to our knowledge, we demonstrate the simultaneous dual image capture capability of the FDMA-CDMA mode using silicon (Si) and germanium (Ge) large-area point photodetectors, allowing the capture of the ultraviolet-near-infrared 350-1,800 nm full spectrum. The active FDMA-CDMA mode CAOS camera operation is also demonstrated using P=3 LED light sources, each with its unique optical spectral content driven by its independent FDMA frequency. This illuminated target spectral signature matched active CAOS mode allows simultaneous capture of P images without the use of P time-multiplexed slot operation tunable optical filters. Applications for such a FDMA-CDMA camera includes controlled light illumination food inspection to bright light exposure security systems.

CAOS line camera.

Proposed and demonstrated is the coded access optical sensor (CAOS) line camera, a one-dimensional or line version of the two-dimensional (2D) digital-micromirror-device (DMD)-based CAOS camera. The proposed line camera design includes a precise dual-axis mirror scanning galvo system incorporating feedback control that eliminates the need for mechanical motion of either the camera or the target. CAOS line scan imaging experiments using a white light source with two test targets are conducted and compared with non-scan 2D CAOS imaging. Specifically, a 2D DMD operated as both a full-frame and a line modulator is used to demonstrate both full-frame (${127} \times {45}$127×45 pixels) and line (127 pixels) scan CAOS imaging. Also demonstrated is an increase in field of view (FOV) of the camera unit using the galvo system with FOV increased by factors of 2.87 and 1.67 in the horizontal and vertical directions, respectively. In addition, proposed for future implementation is a CAOS line camera design that allows analog and hybrid analog-digital time-frequency CAOS-mode irradiance coding for realizing improved inter-pixel cross talk. The CAOS line camera versus a 2D image sensor camera is suited for broad-spectrum large area/FOV imaging applications where high linear dynamic range and low contrast recovery are critical challenges, such as in active illumination inspection of archeological and art works and industrial machine parts.

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

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 633 nm He-Ne laser near-Gaussian focusing beam, experimentally acquired are 13.68 µm spatial resolution laser beam map CAOS images with dynamic ranges of 44.78 dB, 45.28 dB, 83.90 dB, and 94.9 dB 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.

Demonstration of the CDMA-mode CAOS smart camera.

Demonstrated is the code division multiple access (CDMA)-mode coded access optical sensor (CAOS) smart camera suited for bright target scenarios. Deploying a silicon CMOS sensor and a silicon point detector within a digital micro-mirror device (DMD)-based spatially isolating hybrid camera design, this smart imager first engages the DMD starring mode with a controlled factor of 200 high optical attenuation of the scene irradiance to provide a classic unsaturated CMOS sensor-based image for target intelligence gathering. Next, this CMOS sensor provided image data is used to acquire a focused zone more robust un-attenuated true target image using the time-modulated CDMA-mode of the CAOS camera. Using four different bright light test target scenes, successfully demonstrated is a proof-of-concept visible band CAOS smart camera operating in the CDMA-mode using up-to 4096 bits length Walsh design CAOS pixel codes with a maximum 10 KHz code bit rate giving a 0.4096 seconds CAOS frame acquisition time. A 16-bit analog-to-digital converter (ADC) with time domain correlation digital signal processing (DSP) generates the CDMA-mode images with a 3600 CAOS pixel count and a best spatial resolution of one micro-mirror square pixel size of 13.68 µm side. The CDMA-mode of the CAOS smart camera is suited for applications where robust high dynamic range (DR) imaging is needed for un-attenuated un-spoiled bright light spectrally diverse targets.