Ms. Jiang Jian Zhong Profile

Jiang Jian Zhong

at City St George’s, Univ. of London

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Proceedings Article | 8 June 2006 Paper

Characterising a holographic modal phase mask for the detection of ocular aberrations

A. Corbett, D. Gil Leyva, L. Diaz-Santana, T. Wilkinson, J. Zhong

Proceedings Volume 6018, 601808 (2006) https://doi.org/10.1117/12.669247

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The accurate measurement of the double-pass ocular wave front has been shown to have a broad range of applications from LASIK surgery to adaptively corrected retinal imaging. The ocular wave front can be accurately described by a small number of Zernike circle polynomials. The modal wave front sensor was first proposed by Neil et al. and allows the coefficients of the individual Zernike modes to be measured directly. Typically the aberrations measured with the modal sensor are smaller than those seen in the ocular wave front. In this work, we investigated a technique for adapting a modal phase mask for the sensing of the ocular wave front. This involved extending the dynamic range of the sensor by increasing the pinhole size to 2.4mm and optimising the mask bias to 0.75λ. This was found to decrease the RMS error by up to a factor of three for eye-like aberrations with amplitudes up to 0.2μm. For aberrations taken from a sample of real-eye measurements a 20% decrease in the RMS error was observed.

Proceedings Article | 8 June 2006 Paper

Mirror-mode sensing with a holographic modal wavefront sensor

J. Zhong, D. Gil Leyva, A. Corbett, L. Diaz-Santana, T. Wilkinson

Proceedings Volume 6018, 60181I (2006) https://doi.org/10.1117/12.669389

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Currently, in most adaptive optical systems, the control loop between the wavefront sensor and the deformable mirror involves intense mathematical calculations, both during calibration and operation of the system. Although thorough research has been done to optimise the control loop, some issues like error propagation and system bandwidth will always be ultimately limited by the coupling between the mirror and the wavefront sensor. Closed-loop by direct feedback from the wavefront sensor to the deformable mirror was proposed by F. Roddier in his well-quoted curvature wavefront sensing paper. However, due to the natural properties of the defocused-image, this direct feed-back method is limited to bimorph mirror applications only. Recently, M.A.A Neil et al proposed a new modal wavefront sensor (MWFS), which can detect several Zernike modes by a simple intensity subtraction operation. One drawback of this method is that it can only handle a limited number of modes. However, in this paper, we refine this method to detect the orthogonal modes of a deformable mirror instead of Zernike modes in a to-be corrected wavefront. Since the number of actuators of a deformable mirror limits the number of mirror modes, the drawback is minimised in this application. Considering the mirror modes can be directly transformed to the deformable mirror control command set by a proper gain coefficient, it is reasonable to construct a direct-feed back adaptive optical system with the modal wavefront sensing. We will report our first stage investigation on direct feedback adaptive optical system which is to understand the response of MWFS to mirror modes.

Proceedings Article | 26 April 2002 Paper

Flat projection display panel and its near critical angle AR coating

Jiang Jian Zhong, Adrian Travis, Frank Payne, John Moore

Proceedings Volume 4657, (2002) https://doi.org/10.1117/12.463784

KEYWORDS: Coating, Transmittance, Antireflective coatings, Reflection, Refractive index, Interfaces, Projection systems, Flat panel displays, Glasses, Video

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It has recently been shown that a tapered slab glass waveguide (wedge) can be used to make a flat panel display by projecting a video image into the thick edge of the wedge1. In this paper, we present the equations that relate the incident angle to the position where the ray emerges from the wedge. In the analysis, skew rays are also considered. We also present the design and experimental results of an anti-reflection coating that increases the brightness and reduces the blur of the wedge. With the coating, the transmittance of the interface rises from 0 (TIR) to 99% for a 0.35 degree change in incident angle for S-polarised monochromatic light. Without the coating, the transmittance falls below 50%. We also present a chromatic design intended to work with S-polarised rays from an arc lamp.

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