Experimental systems implementation of a hybrid optical–digital correlator

Sharp, J. H.; Mackay, Nick E; Tang, Pei Chin; Watson, Ian; Scott, Barbara; Budgett, David; Chatwin, Chris; Young, Rupert; Tonda, S.; Huignard, Jean‐Pierre; Slack, T. G.; Collings, N.; Pourzand, A.R.; Duelli, Markus; Grattarola, A.; Braccini, C.

doi:10.1364/ao.38.006116

Cited by 3 publications

(2 citation statements)

References 23 publications

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“…With the help of the laser coherent light, these plates have to be "written" with the joint image in the input plane and the reference fringe-adjusted filter in the Fourier plane. Alternatively a hybrid (optical-digital) (FA-AJTC) can be built up that is implemented with amplitude spatial modulator (ASLM) and a square law image capture device (CCD camera) (Demoli et al, 1997;Sharp et al, 1999). A coherent laser beam light is projected on the (ASLM1) which is addressed by a computer with the joint image in the input plane.…”

Section: Scn U V H U V Scn U V Ref Uv T Uv Ix X U Iyyvmentioning

confidence: 99%

Additive noise robustness of phase-input joint transform correlators for face recognition

Teușdea¹,

Gabor²

2011

Reviews, Refinements and New Ideas in Face Recognition

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Section: Scn U V H U V Scn U V Ref Uv T Uv Ix X U Iyyvmentioning

confidence: 99%

Additive noise robustness of phase-input joint transform correlators for face recognition

Teușdea¹,

Gabor²

2011

Reviews, Refinements and New Ideas in Face Recognition

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“…Later, using LC-TV (television) 31 devices, phase and amplitude modulation were exploited for applications in optical correlation. 32 Phase-modulating LCOS devices are now important optical engines for a wide range of applications.…”

Section: Brief Introduction To Lcos Devicesmentioning

confidence: 99%

Fundamentals of phase-only liquid crystal on silicon (LCOS) devices

2014

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This paper describes the fundamentals of phase-only liquid crystal on silicon (LCOS) technology, which have not been previously discussed in detail. This technology is widely utilized in high efficiency applications for real-time holography and diffractive optics. The paper begins with a brief introduction on the developmental trajectory of phase-only LCOS technology, followed by the correct selection of liquid crystal (LC) materials and corresponding electro-optic effects in such devices. Attention is focused on the essential requirements of the physical aspects of the LC layer as well as the indispensable parameters for the response time of the device. Furthermore, the basic functionalities embedded in the complementary metal oxide semiconductor (CMOS) silicon backplane for phase-only LCOS devices are illustrated, including two typical addressing schemes. Finally, the application of phase-only LCOS devices in real-time holography will be introduced in association with the use of cutting-edge computer-generated holograms. The architecture of LCOS devices is similar to conventional LC devices except that a silicon backplane constitutes one of the substrates (Figure 1). The silicon CMOS backplane consists of the electronic circuitry that is buried underneath pixel arrays to provide a high 'fill factor'. The pixels are aluminum mirrors deposited on the surface of the silicon backplane. The incident light is transmitted through the LC layer with almost zero absorption. The integration of high-performance driving circuitry allows the applied voltage to be changed on each pixel, thereby controlling the phase retardation of the incident wavefront across the device. Currently, there are two types of light modulation using LCOS devices, amplitude modulation and phase modulation. In the former case, the amplitude of the light signal is modulated 6,7 by varying the linear polarzation direction of the incident light passing through a linear polarizer, the same principle used in a standard LC television. In the latter case, the phase delay is accomplished by electrically adjusting the optical refractive index along the light path, which is possible because of the non-zero birefringence of the LC materials in use but should be carefully characterized. [8][9][10][11][12][13] In a phase-only LCOS SLM modulator, no light absorption by polarizers or other light-absorbing components will occur, such that the maximum light efficiency can be expected.Currently, most of the conventional LC devices are not able to efficiently modulate the phase of an incident wavefront. For instance, the LC device structure using thin film transistors is not suitable for phase modulation because an appropriate electro-optic effect has not been used (see the section on 'Twisted nematic (TN) configuration' and the section on 'VAN configuration' for details). Moreover, the pixels of this type of device are too large to provide acceptably large diffraction angles. In addition, the pixel circuitry and connection tracks are in the light path such that the ...

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