A fast-Fourier-transform method of topography and interferometry is proposed. By computer processing of a noncontour type of fringe pattern, automatic discrimination is achieved between elevation and depression of the object or wave-front form, which has not been possible by the fringe-contour-generation techniques. The method has advantages over moire topography and conventional fringe-contour interferometry in both accuracy and sensitivity. Unlike fringe-scanning techniques, the method is easy to apply because it uses no moving components.

Fourier-transform method of fringe-pattern analysis for computer-based topography and interferometry

Methods and apparatus for super-resolution in integral photography are described Several techniques are described that, alone or in combination, may improve the super-resolution process and/or the quality of super-resolved images that may be generated from flats captured with a focused plenoptic camera using a super-resolution algorithm At least some of these techniques involve modifications to the focused plenoptic camera design In addition, at least some of these techniques involve modifications to the super-resolution rendering algorithm The techniques may include techniques for reducing the size of pixels, techniques for shifting pixels relative to each other so that super-resolution is achievable at more or all depths of focus, and techniques for sampling using an appropriate filter or kernel These techniques may, for example, reduce or eliminate the need to perform deconvolution on a super-resolved image, and may improve super-resolution results and/or increase performance

Methods and Apparatus for Super-Resolution in Integral Photography

Methods and apparatus for reducing plenoptic camera artifacts. A first method is based on careful design of the optical system of the focused plenoptic camera to reduce artifacts that result in differences in depth in the microimages. A second method is computational; a focused plenoptic camera rendering algorithm is provided that corrects for artifacts resulting from differences in depth in the microimages. While both the artifact-reducing focused plenoptic camera design and the artifact-reducing rendering algorithm work by themselves to reduce artifacts, the two approaches may be combined.

Methods and apparatus for reducing plenoptic camera artifacts

Methods, apparatus, and computer-readable storage media for simulating artistic effects in images rendered from plenoptic data. An impressionistic-style artistic effect may be generated in output images of a rendering process by an “impressionist” 4D filter applied to the microimages in a flat captured with focused plenoptic camera technology. Individual pixels are randomly selected from blocks of pixels in the microimages, and only the randomly selected pixels are used to render an output image. The randomly selected pixels are rendered to generate the artistic effect, such as an “impressionistic” effect, in the output image. A rendering technique is applied that samples pixel values from microimages using a thin sampling kernel, for example a thin Gaussian kernel, so that pixel values are sampled only from one or a few of the microimages.

Methods and Apparatus for Rendering Output Images with Simulated Artistic Effects from Focused Plenoptic Camera Data

Methods, apparatus, and computer-readable storage media for rendering focused plenoptic camera data. A depth-based rendering technique is described that estimates depth at each microimage and then applies that depth to determine a position in the input flat from which to read a value to be assigned to a given point in the output image. The techniques may be implemented according to parallel processing technology that renders multiple points of the output image in parallel. In at least some embodiments, the parallel processing technology is graphical processing unit (GPU) technology.

Methods, apparatus, and computer-readable storage media for depth-based rendering of focused plenoptic camera data

A new interferometry configuration combines the strengths of two existing interferometry methods, improving the quality and extending the dynamic range of both. On the same patterned mask, placed near the image-plane of an optical system under test, patterns for phase-shifting point diffraction interferometry and lateral shearing interferometry coexist. The former giving verifiable high accuracy for the measurement of nearly diffraction-limited optical systems. The latter enabling the measurement of optical systems with more than one wave of aberration in the system wavefront. The interferometry configuration is a hybrid shearing and point diffraction interferometer system for testing an optical element that is positioned along an optical path including: a source of electromagnetic energy in the optical path; a first beam splitter that is secured to a device that includes means for maneuvering the first beam splitter in a first position wherein the first beam splitter is in the optical path dividing light from the source into a reference beam and a test beam and in a second position wherein the first beam splitter is outside the optical path: a hybrid mask which includes a first section that defines a test window and at least one reference pinhole and a second section that defines a second beam splitter wherein the hybrid mask is secured to a device that includes means for maneuvering either the first section or the second section into the optical path positioned in an image plane that is created by the optical element, with the proviso that the first section of the hybrid mask is positioned in the optical path when first beam splitter is positioned in the optical path; and a detector positioned after the hybrid mask along the optical path.

Hybrid shearing and phase-shifting point diffraction interferometer

A device and method to facilitate the gross alignment of patterned object- and image-plane masks in optical systems such as the phase-shifting point diffraction interferometer are provided. When an array of similar pinholes or discreet mask fields is used, confusion can occur over the alignment of the focused beams within the field. Adding to the mask pattern a circumscribed or inscribed set of symbols that are identifiable in situ facilitates the unambiguous gross alignment of the object- and/or image-plane masks. Alternatively, a system of markings can be encoded directly into the window shape to accomplish this same task.

In Situ alignment system for phase-shifting point-diffraction interferometry

A hybrid spatial/temporal-domain point diffraction interferometer (dual-domain PS/PDI) that is capable of suppressing the scattered-reference-light noise that hinders the conventional PS/PDI is provided. The dual-domain PS/PDI relies on a more restrictive PS/PDI mask guaranteeing the elimination of spatial-frequency crosstalk between the signal and the scattered-light noise arising from scattered-reference-light interfering with the test beam, a new dual-domain analysis method eliminating scattered-light noise arising from both the scattered-reference-light interfering with the test beam and the scattered-reference-light interfering with the 'true' pinhole-diffracted reference light. The dual-domain PS/PDI is a three-tiered filtering system composed of lowpass spatial-filtering the test-beam electric field using the more restrictive PS/PDI mask, bandpass spatial-filtering the individual interferogram irradiance frames making up the phase-shifting series, and bandpass temporal-filtering the phase-shifting series as a whole.

Dual-domain point diffraction interferometer

Diffraction phase gratings are employed in phase-shifting point diffraction interferometers to improve the interferometric fringe contrast. The diffraction phase grating diffracts a zeroth-order diffraction of light at a first power level to the test-beam window of a mask that is positioned at the image plane and a first-order diffraction at a second power to the reference-beam pinhole. The diffraction phase grating is preferably selected to yield a desired ratio of the first power level to second power level.

Phase-shifting point diffraction interferometer phase grating designs

In a phase-shifting point diffraction interferometer, different image-plane mask designs can improve the operation of the interferometer. By keeping the test beam window of the mask small compared to the separation distance between the beams, the problem of energy from the reference beam leaking through the test beam window is reduced. By rotating the grating and mask 45°, only a single one-dimensional translation stage is required for phase-shifting. By keeping two reference pinholes in the same orientation about the test beam window, only a single grating orientation, and thus a single one-dimensional translation stage, is required. The use of a two-dimensional grating allows for a multiplicity of pinholes to be used about the pattern of diffracted orders of the grating at the mask. Orientation marks on the mask can be used to orient the device and indicate the position of the reference pinholes.

Kenneth A. Goldberg

Papers

Hybrid shearing and phase-shifting point diffraction interferometer

In Situ alignment system for phase-shifting point-diffraction interferometry

Dual-domain point diffraction interferometer

Phase-shifting point diffraction interferometer phase grating designs

Phase-shifting point diffraction interferometer mask designs