Reconstruction of reference error in high overlapping density subaperture stitching interferometry.

The vibration modulated stitching interferometry acquires many subaperture phases timely forming the high overlapping density subapertures for asphere phase stitching. The large number of overlapping subapertures had been proven effective in suppressing the reference error. In this research, we propose a pixel-by-pixel reference calibration method by using the averaged difference between the stitched phase and compensated phase within the overlapping subapertures. The measurement for both tested optics and calibration of the reference optics are accomplished in a single phase stitching process. The requirement for a high-quality reference optics or dedicated reference calibration procedure for subaperture stitching interferometry is therefore significantly eliminated. Both the simulation and experimental results shows the feasibility of the proposed method for high frequency reference error and most of the form error in the third order Zernike aberrations.

High resolution full field wavefront measurement of a misaligned miniature lens.

Compared with the industry standard MTF consequential testing result, the full field transmitted wavefront testing is more analytical for field aberration analysis. A novel wavefront measuring device specialized for the miniature lens testing application is developed to measure the full field aberration in a high resolution of 35x36 radial-azimuthal fields. The device adapts the high dynamic range Shack-Hartman wavefront sensor to minimize the alignment uncertainty induced from collimator under high field angle. The plane symmetrical aberration due to elements misalignment is identified and quantified throughout the measured field. The field constant coma and field linear astigmatism contributes most aberration errors to the edge of the field as expected. Through the field dependent aberration analysis. This device proves that the miniature lens image quality near the edge of the field is practically limited by the misalignment of the optical elements.

Solar concentrator with a toroidal relay module.

III-V multijunction solar cells require solar concentrators with a high concentration ratio to reduce per watt cost and to increase solar energy transforming efficiency. This paper discusses a novel solar concentrator design that features a high concentration ratio, high transfer efficiency, thin profile design, and a high solar acceptance angle. The optical design of the concentrator utilizes a toroidal relay module, which includes both the off-axis relay lens and field lens design in a single concentric toroidal lens shape. The optical design concept of the concentrator is discussed and the simulation results are shown. The given exemplary design has an aspect ratio of 0.24, a high averaged optical concentration ratio 1230×, a maximum efficiency of 76.8%, and the solar acceptance angle of ±0.9°.

Wavefront measurement made by an off-the-shelf laser-scanning pico projector.

Focal plane testing methods such as the Shack-Hartmann wavefront sensor and phase-shifting deflectometry are valuable tools for optical testing. In this study, we propose a novel wavefront slope testing method that uses a scanning galvo laser, in which a single-mode Gaussian beam scans the pupils of the tested optics in the system. In addition, the ray aberration is reconstructed by the four-step phase-shifting measurement by modulating the angular domain. The measured wavefront is verified by a Fizeau interferometer in terms of Zernike polynomials.

Optical design and testing: introduction.

Optical design and testing have numerous applications in industrial, military, consumer, and bio-medical settings. This issue features original research ranging from the optical design of image and nonimage optical stimuli for human perception, optics applications, bio-optics applications, displays, and solar energy systems to novel imaging modalities from deep UV to infrared spectral imaging, a systems perspective to imaging, as well as optical measurement. In addition, new concepts and trends for optics and further optical systems will be especially highlighted in this special issue.

Measurement improvement by high overlapping density subaperture stitching interferometry.

The vibration-modulated subaperture stitching interferometer acquires the interferogram on the fly dynamically. With its highly improved measurement throughput, we applied the device for high overlapping density subaperture stitching interferometry to acquire hundreds of overlapping subapertures in a single phase stitching measurement. The averaging effect of the high overlapping density stitching interferometer is discussed. In the experiment, the proposed high overlapping density stitching interferometer is also proved to reduce measurement uncertainty and improve measurement quality effectively.

Interferometer reference error suppression by the high-overlapping-density phase-stitching algorithm.

The subaperture stitching interferometer is a flexible testing device that measures either high-numerical-aperture or large aperture optics without the requirement of additional auxiliary optics. In the measurement, the interferometer reference optics error can contaminate the stitched phase of the complete tested optics and reduce measurement accuracy. We propose high-overlapping-density subaperture stitching interferometry (HOD-SSI) to reduce the impact of reference optics errors on the stitched phase. The tested optics surface deformation phase is determined by averaging the multiple subaperture measurements taken at different rotational angles. Simulation and experiment show that HOD-SSI can effectively reduce the stitched phase errors due to the static reference optics errors.

Optical design and testing: introduction.

Optical design and testing has numerous applications in industrial, military, consumer, and medical settings. Assembling a complete imaging or nonimage optical system may require the integration of optics, mechatronics, lighting technology, optimization, ray tracing, aberration analysis, image processing, tolerance compensation, and display rendering. This issue features original research ranging from the optical design of image and nonimage optical stimuli for human perception, optics applications, bio-optics applications, 3D display, solar energy system, opto-mechatronics to novel imaging or nonimage modalities in visible and infrared spectral imaging, modulation transfer function measurement, and innovative interferometry.

Vibration modulated subaperture stitching interferometry.

A novel subaperture stitching interferometry is developed to measure the surface deformation of the lens by utilizing the mechanical vibration induced from a motorized stage. The interferograms of different subapertures are acquired on the fly while the tested optics is rotating against its symmetrical axis. The measurement throughput and the subaperture positioning accuracy are improved simultaneously by adopting both the synchronous rotational scanning mechanism and the non-uniform phase shifting algorithm. The experimental measurement shows the stitched phase RMS error of 0.0037 waves proving the feasibility of the proposed phase acquisition method.

Iterative phase-shifting algorithm immune to random phase shifts and tilts.

An iterative phase-shifting algorithm based on the least-squares principle is developed to overcome the random piston and tilt wavefront errors generated from the phase shifter. The algorithm iteratively calculates the phase distribution and the phase-shifting map to minimize the sum of squared errors in the interferograms. The performance of the algorithm is evaluated via computer simulations and validated by the Fizeau interferometer measurements. The results show that the proposed algorithm has a fast convergence rate and satisfactory phase-estimation accuracy, improving the measurement precision of the phase-shifting interferometers with significant phase-shifter errors.

Phase shifting grating-slit test with a cross slit.

A general graphical convolution method for fringe analysis of testing methods that use a spatially incoherent light source is presented. Results are shown for the grating-slit test using optical narrow and cross slits. The convolution method shows that phase shifting grating-slit test can be done with the cross slit at the expense of a reduced fringe contrast ratio. A phase shifting measurement with a cross-slit modulator yields high measurement precision and validates our fringe contrast theory.

Geometrical optics modeling of the grating-slit test.

A novel optical testing method termed the grating-slit test is discussed. This test uses a grating and a slit, as in the Ronchi test, but the grating-slit test is different in that the grating is used as the incoherent illuminating object instead of the spatial filter. The slit is located at the plane of the image of a sinusoidal intensity grating. An insightful geometrical-optics model for the grating-slit test is presented and the fringe contrast ratio with respect to the slit width and object-grating period is obtained. The concept of spatial bucket integration is used to obtain the fringe contrast ratio.