Neal Brock - Academia.edu (original) (raw)

Papers by Neal Brock

Summaries of papers presented at the Conference on Lasers and Electro-Optics, 1996

Summary form only given. We have shown that photorefractive semiconductors, in particular ZnTe:V,... more Summary form only given. We have shown that photorefractive semiconductors, in particular ZnTe:V,Mn, may be used to record and reconstruct high-quality, real-time resonant holographic interferometry (RHI) interferograms with 6 nanosecond laser pulses. The diffraction efficiency and time response of our ZnTe:V,Mn crystal was shown to be adequate for RHI applications using a laser diode of modest power.

The largest limitation of phase-shifting interferometry for optical testing is the sensitivity to... more The largest limitation of phase-shifting interferometry for optical testing is the sensitivity to the environment, both vibration and air turbulence. An interferometer using temporal phase-shifting is very sensitive to vibration because the various phase shifted frames of interferometric data are taken at different times and vibration causes the phase shifts between the data frames to be different from what is desired. Vibration effects can be reduced by taking all the phase shifted frames simultaneously and turbulence effects can be reduced by averaging many measurements. There are several techniques for simultaneously obtaining several phase-shifted interferograms and this paper will discuss two such techniques: 1) Simultaneous phase-shifting interferometry on a single detector array (PhaseCam) and 2) Micropolarizer phase-shifting array. The application of these techniques for the testing of large optical components, measurement of vibrational modes, the phasing of segmented optical components, and the measurement of deformations of large diffuse structures is described.

We demonstrate a new type of spatial phase-shifting, dynamic interferometer that can acquire phas... more We demonstrate a new type of spatial phase-shifting, dynamic interferometer that can acquire phase-shifted interferograms in a single camera frame. The interferometer is constructed with a pixelated phase-mask aligned to a detector array. The phase-mask encodes a high-frequency spatial interference pattern on two collinear and orthogonally polarized reference and test beams. The phase-difference between the two beams can be calculated using conventional N-bucket algorithms or by spatial convolution. The wide spectral response of the mask and true common-path design permits operation with a wide variety of interferometer front ends, and with virtually any light source including white-light.

Tribute to James C. Wyant: The Extraordinaire in Optical Metrology and Optics Education

Optics and Lasers in Engineering

Publications of the Astronomical Society of the Pacific

In the last decade, imaging polarimeters based on micropolarizer arrays have been developed for u... more In the last decade, imaging polarimeters based on micropolarizer arrays have been developed for use in terrestrial remote sensing and metrology applications. Micropolarizer-based sensors are dramatically smaller and more mechanically robust than other polarimeters with similar spectral response and snapshot capability. To determine the suitability of these new polarimeters for astronomical applications, we developed the RIT Polarization Imaging Camera to investigate the performance of these devices, with a special attention to the low signal-to-noise regime. We characterized the device performance in the lab, by determining the relative throughput, efficiency, and orientation of every pixel, as a function of wavelength. Using the resulting pixel response model, we developed demodulation procedures for aperture photometry and imaging polarimetry observing modes. We found that, using the current calibration, RITPIC is capable of detecting polarization signals as small as ∼ 0.3%. To demonstrate the stability of RITPIC's calibration and its extreme portability, we performed imaging polarimetry of the Solar corona in Madras, Oregon during the total Solar eclipse of 2017. The maximum polarization we measured was ∼ 46%, which agrees well with the maximum value predicted for a Thomson scattering corona. Similarly, we found no strong deviations in the angle of linear polarization from the tangential direction. The relative ease of data collection, calibration, and analysis provided by these sensors suggest than they may become an important tool for a number of astronomical targets.

Proceedings of the Adaptive Optics for Extremely Large Telescopes 5

We show that the segments of the Keck telescopes suffer from small but significant surface artifa... more We show that the segments of the Keck telescopes suffer from small but significant surface artifacts that limit segment phasing accuracy. Both the segment surface artifacts themselves and the limits they place on segment phasing have important implications for adaptive optics, high contrast imaging, and seeing limited observations. These surface artifacts are likely by-products of the segment polishing, most likely the Ion Beam Figuring (IBF) process that constitutes the final step of the segment surface figuring. The surface artifacts diffract a significant amount of light out past ±3.5 arcseconds and generate chromatic effects that limit segment phasing accuracy. We present on-sky measurements of the diffracted intensity. Segment surface roughness measurements are also presented, which show that surface roughness is not the source of the problem. These results have direct relevance to segment manufacturing for the Thirty Meter Telescope (TMT) and other segmented mirror telescopes.

The Journal of Imaging Science and Technology, 1997

... D. Michael S. Brown, Ph. D. Neal J. Brock METROLASER, INC. 18010 SKYPARK CIRCLE# 100 IRVINE, ... more ... D. Michael S. Brown, Ph. D. Neal J. Brock METROLASER, INC. 18010 SKYPARK CIRCLE# 100 IRVINE, CA 92614-6428 This report summarizes our progress in the area of resonant holographic interferometry (RHI) during the last year. ...

Frontiers in Optics 2015, 2015

Physics of Fluids A Fluid Dynamics

34th Aerospace Sciences Meeting and Exhibit, 1996

Polarization Science and Remote Sensing V, 2011

A pixel-level micropolarizer array bonded to a scientific camera has been developed for use in co... more A pixel-level micropolarizer array bonded to a scientific camera has been developed for use in commercial dynamic interferometers. The pixelated array includes the 0, 45, 90, and, 135 degree polarization orientations. Micropolarizer arrays with elements as small as 7.4 microns and array sizes as large 4 Mega-pixels have been fabricated for use across the visible spectrum. The pixelated polarization camera acquires the four polarization orientations in a single video frame, which enables instantaneous interferometric or polarimetric measurements. Examples of each type of measurement are presented. Details of how the pixelated camera is used in interferometry are reviewed and the spatial resolution performance of the camera when used in interferometry is discussed.