Sophie Vo

Computational optical distortion correction using a radial basis function-based mapping method

A distortion mapping and computational image unwarping method based on a network interpolation that uses radial basis functions is presented. The method is applied to correct distortion in an off-axis head-worn display (HWD) presenting up to 23% highly asymmetric distortion over a 27°x21° field of view. A 10(-5) mm absolute error of the mapping function over the field of view was achieved. The unwarping efficacy was assessed using the image-rendering feature of optical design software. Correlation coefficients between unwarped images seen through the HWD and the original images, as well as edge superimposition results, are presented. In an experiment, images are prewarped using radial basis functions for a recently built, off-axis HWD with a 20° diagonal field of view in a 4:3 ratio. Real-time video is generated by a custom application with 2 ms added latency and is demonstrated.

Application of radial basis functions to shape description in a dual-element off-axis magnifier

We previously demonstrated that radial basis functions may be preferred as a descriptor of free-form shape for a single mirror magnifier when compared to other conventional descriptions such as polynomials [Opt. Express 16, 1583 (2008)]. A key contribution is the application of radial basis functions to describe and optimize the shape of a free-form mirror in a dual-element magnifier with the specific goal of optimizing the pupil size given a 20 degrees field of view. We demonstrate a 12 mm exit pupil, 20 degrees diagonal full field of view, 15.5 mm eye clearance, 1.5 arc min resolution catadioptric dual-element magnifier design operating across the photopic visual regime. A second contribution is the explanation of why it is possible to approximate any optical mirror shape using radial basis functions.

Application of radial basis functions to shape description in a dual-element off-axis eyewear display: Field-of-view limit

— Previously, it was demonstrated that radial basis functions may be preferred as a free-form shape descriptor for a single-mirror magnifier, justified by a performance increase measured by the MTF, when compared to other conventional descriptions such as multivariate polynomials (e.g., Zernike polynomials or x-y polynomials). The benefit in performance increase can be used to expand the pupil diameter from 8 to 12 mm given a 20° field of view and a 15-mm eye clearance or to increase the field of view. The main contribution in this paper is the investigation of the field-of-view limit in a dual-element magnifier where the free-form mirror is described with radial basis functions. Our main result in this paper is an estimate of the field-of-view limit of the dual-element magnifier to be approximately 25° full-field diagonal, given the specific geometry described in the paper. The impact of the astigmatic node placement in a rectangular image field on the modulation transfer function is also analyzed for the particular dual-element magnifier geometry.

Optical free-form surfaces in off-axis head-worn display design

Head-worn displays are becoming a viable visual display option for mobile augmented reality. In this paper, we highlight the challenges and some recent progress towards compact and lightweight head-worn displays tending towards the eyeglass form factor. Single and dual-element eyeglass display designs that leverage the advances in free-form optics fabrication technology will be presented. There are three new contributions in this paper: first, we present a single-element eyeglass display design and the fabricated mirror prototype; second, we present our second generation dual-element eyeglass display design with the revised opto-mechanical packaging; third, we present our initial studies on the field of view limit with an 8 mm pupil for the dual-element design.

P‐105: Benefits of a Radial Basis Function Network Representation in Describing Free‐Form Optical Surfaces for Head‐Worn Displays

This paper studies the application of radial basis function networks to the description, design and optimization of free-form optical surfaces, which find key applications in head-worn displays.

Optical Coherence Tomography Using Bessel Beams

We demonstrate that the sidelobes of a Bessel function generated by an axicon were suppressed by more than 20 dB over 5 mm depth of focus in a Fourier domain optical coherence tomography using a single mode fiber. We also show a rotational image in biological tubular in vivo samples with 2.5 μm axial resolution, 8 μm lateral resolution, and 5 mm depth of focus using a custom-designed axicon.

Airy Beams: Beyond Geometric Optics

Airy beams are a new class of nondiffracting beam predicted in 1979 and observed in 2007. Beam propagation methods are shown to be an effective way to study the behavior of the beams in propagation.

Optical Coherence Microscopy Using Bessel Beam

We demonstrate that the side lobes of a Bessel function generated by an axicon are suppressed by more than 20 dB over 5 mm depth of focus in a confocal imaging system using a fiber.