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

Area of Science:

• Optics and Photonics
• Digital Signal Processing
• Image Sensors

Background:

• Traditional coded access optical sensor (CAOS) cameras operate in independent Frequency Division Multiple Access (FDMA) or Code Division Multiple Access (CDMA) modes.
• These independent modes present limitations in terms of speed, dynamic range, and signal-to-noise ratio (SNR).
• A need exists for a hybrid approach to overcome these limitations and enhance camera performance.

Purpose of the Study:

• To demonstrate, for the first time, a hybrid FDMA-CDMA mode for CAOS cameras.
• To evaluate the performance benefits of this novel triple coding mode compared to existing FDMA and CDMA modes.
• To showcase the capability for simultaneous dual image capture across a wide spectral range.

Main Methods:

• Development and demonstration of a hybrid FDMA-CDMA mode for CAOS cameras.
• Utilizing Fast Fourier Transform (FFT) digital signal processing (DSP) for spectrum analysis in FDMA.
• Employing simultaneous photodetection from multiple CAOS pixels for CDMA signal enhancement.
• Experiments conducted using a digital-micromirror-device-based CAOS camera in both passive and active light modes.

Main Results:

• The FDMA-CDMA mode achieved P times faster camera operation than equivalent Frequency Modulation (FM)-CDMA modes, with P representing the number of FDMA channels.
• High-quality image recovery of a 64 dB high dynamic range (HDR) target was demonstrated with a 4-channel FDMA-CDMA mode.
• Simultaneous capture of ultraviolet-near-infrared (350-1,800 nm) full spectrum images using silicon (Si) and germanium (Ge) detectors was achieved.
• Active mode demonstration showed simultaneous capture of 3 images using 3 LED light sources without tunable filters.

Conclusions:

• The hybrid FDMA-CDMA mode offers a robust, faster, and more secure approach to linear irradiance extraction at a moderately high dynamic range.
• This novel mode significantly enhances CAOS camera performance by combining the strengths of FDMA and CDMA.
• The demonstrated capabilities open new application avenues in areas such as food inspection and security systems.