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.

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.

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.

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.

Mirau-type full-field optical coherence tomography with switchable partially spatially coherent illumination modes.

A crystalline-fiber-based Mirau-type full-field optical coherence tomography (FF-OCT) system utilizing two partially coherent illumination modes is presented. Using a diode-pumped Ti:sapphire crystalline fiber with a high numerical aperture, spatially-incoherent broadband emission can be generated with high radiance. With two modes of different spatial coherence settings, either deeper penetration depth or higher B-scan rate can be achieved. In a wide-field illumination mode, the system functions like FF-OCT with partially coherent illumination to improve the penetration depth. In a strip-field illumination mode, a compressed field is generated on the sample, and a low-speckle B-scan can be acquired by compounding pixel lines within.