Elimination of optical phase sensitivity in a shift, scale, and rotation invariant hybrid opto-electronic correlator via off-axis operation.

The hybrid opto-electronic correlator (HOC) uses a combination of optics and electronics to perform target recognition. Achieving a stable output from this architecture has previously presented a significant challenge due to a high sensitivity to optical phase variations, limiting the real-world feasibility of the device. Here we present a modification to the architecture that essentially eliminates the dependence on optical phases, and demonstrate verification of the proposed approach.

Integration of a PQ:PMMA holographic memory device into the hybrid opto-electronic correlator for shift, scale, and rotation invariant target recognition.

The hybrid optoelectronic correlator (HOC) combines optical and electronic signal processing to achieve the same functionality as traditional optical correlators but without the need for dynamic materials. Here we propose and demonstrate the integration of a PQ:PMMA holographic memory device (HMD) into the HOC as a high-speed all-optical database for reference images. Using a PQ:PMMA HMD for one of the inputs eliminates one of the key speed limitations in the HOC.

Thick PQ:PMMA transmission holograms for free-space optical communication via wavelength-division multiplexing.

Phenantrenequinone doped poly(methyl-methacrylate) (PQ:PMMA) is a holographic substrate that can be used for angle or wavelength multiplexed Bragg gratings. However, efficient writings can be done only using a high-power, long-coherence volume laser over a limited wavelength range. This constraint makes it difficult to write gratings that would diffract several different read wavelengths into a single direction.

Demonstration of shift, scale, and rotation invariant target recognition using the hybrid opto-electronic correlator.

Previously, we had proposed a hybrid opto-electronic correlator (HOC), which can achieve the same functionality as that of a holographic optical correlator but without using any holographic medium. Here, we demonstrate experimentally that the HOC is capable of detecting objects in a scale, rotation, and shift invariant manner. First, the polar Mellin transformed (PMT) versions of two images are produced, using a combination of optical and electronic signal processing.