The technique for measuring changes in diffuse surfaces using Electronic Speckle Pattern Interfer... more The technique for measuring changes in diffuse surfaces using Electronic Speckle Pattern Interferometry (ESPI) is well known. We present a new electronic speckle pattern interferometer that takes advantage of a single-frame spatial phase-shifting technique to significantly reduce sensitivity to vibration and enable complete data acquisition in a single laser pulse. The interferometer was specifically designed to measure the stability of the James Webb Space Telescope (JWST) backplane. During each measurement the laser is pulsed once and four phase-shifted interferograms are captured in a single image. The signal is integrated over the 9ns pulse which is over six orders of magnitude shorter than the acquisition time for conventional interferometers. Consequently, the measurements do not suffer from the fringe contrast reduction and measurement errors that plague temporal phase-shifting interferometers in the presence of vibration. This paper will discuss the basic operating principle of the interferometer, analyze its performance and show some interesting measurements.
We demonstrate a phase-shifting, point diffraction interferometer that achieves high accuracy and... more We demonstrate a phase-shifting, point diffraction interferometer that achieves high accuracy and is capable of measuring a single pulse of light. The measurement system utilizes a polarizing point diffraction plate to generate a synthetic reference beam that is orthogonally polarized to the transmitted test beam. The plate has very high polarization contrast, works over an extremely broad angular and spectral range, and is only 100 nanometers thick. The unique features of the polarizing element make the system amenable to measuring strongly convergent light from high numerical aperture optics without the need to use a point reference source to calibrate the system. Results of measuring optics with numerical apertures as high as NA 0.8 are presented.
We demonstrate a scheme for volume holographic storage based on the features of shift selectivity... more We demonstrate a scheme for volume holographic storage based on the features of shift selectivity of a speckle reference-wave hologram. The proposed recording method permits more-efficient use of the recording medium and yields greater storage density than spherical or plane-wave reference beams. Experimental results of multiple hologram storage and replay in a photorefractive crystal of iron-doped lithium niobate are presented. The mechanisms of lateral and longitudinal shift selectivity are described theoretically and shown to agree with experimental measurements.
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 commonpath design permits operation with a wide variety of interferometer front ends, and with virtually any light source including white-light.
Interferometry XIII: Techniques and Analysis, 2006
An on-axis, vibration insensitive, polarization Fizeau interferometer is realized through the use... more An on-axis, vibration insensitive, polarization Fizeau interferometer is realized through the use of a novel pixelated mask spatial carrier phase shifting technique in conjunction with a low coherence source and a polarization delay-line. In this arrangement, coherence is used to effectively separate out the orthogonally polarized test and reference beam components for interference. With both the test and the reference beams on-axis, the common path cancellation advantages of the Fizeau interferometer are maintained. The interferometer has the unique ability to isolate and measure any surface that is substantially normal to the optical axis of the cavity. Additionally, stray light interference is substantially reduced due to the source's short coherence. An expression for the fringe visibility on-axis is derived and compared with that of a standard Fizeau. Using a 15 mW source, the maximum camera shutter speed, used when measuring a 4% reflector, was 150 usec, resulting in very robust vibration insensitivity. We experimentally demonstrate the measurement of both sides of a thin glass plate without the need to modify the plate between measurements. Experimental results show the performance of this new interferometer to be within the specifications of commercial phase shifting interferometers.
Storage and Retrieval for Image and Video Databases, 2000
The measurement accuracy of an interferometric optical test is generally limited by the environme... more The measurement accuracy of an interferometric optical test is generally limited by the environment. This paper discusses two single-shot interferometric techniques for reducing the sensitivity of an optical test to vibration; simultaneous phase-shifting interferometry and a special form of spatial carrier interferometry utilizing a micropolarizer phase-shifting array. In both techniques averaging can be used to reduce the effects of turbulence
Optical Measurement Systems for Industrial Inspection IV, 2005
ABSTRACT The measurement accuracy of an interferometric optical test is generally limited by the ... more ABSTRACT The measurement accuracy of an interferometric optical test is generally limited by the environment. This paper discusses two single-shot interferometric techniques for reducing the sensitivity of an optical test to vibration; simultaneous phase-shifting ...
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
Novel Optical Systems Design and Optimization VIII, 2005
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. In many situations the measurement accuracy is limited by the environment and sometimes the environment is sufficiently bad that the measurement cannot be performed. Recently there have been several advances in dynamic interferometry techniques for reducing effects of vibration. This talk will describe and compare two dynamic interferometry techniques; simultaneous phase-shifting interferometry and a special form of spatial carrier interferometry utilizing a micropolarizer phase-shifting array.
ABSTRACT Digital Speckle Pattern Interferometry (DSPI) is a well-established method for the measu... more ABSTRACT Digital Speckle Pattern Interferometry (DSPI) is a well-established method for the measurement of diffuse objects in experimental mechanics. DSPIs are phase shifting interferometers. Three or four bucket temporal phase shifting algorithms are commonly used to provide phase shifting. These algorithms are sensitive to vibrations and can not be used to measure large optical structures far away from the interferometer. In this research a simultaneous phase shifted interferometer, PhaseCam product of 4D Technology Corporation in Tucson Arizona, is modified to be a Simultaneous phase shifted Digital Speckle Pattern Interferometer (SDSPI). Repeatability, dynamic range, and accuracy of the SDSPI are characterized by measuring a 5 cm x 5 cm carbon fiber coupon.
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. In many situations the measurement accuracy is limited by the environment and sometimes the environment is sufficiently bad that the measurement cannot be performed. Recently there have been several advances in dynamic interferometry techniques for reducing effects of vibration. This
We show that D85N/V49A, a mutant bacteriorhodopsin in which two residues, aspartate (D) at positi... more We show that D85N/V49A, a mutant bacteriorhodopsin in which two residues, aspartate (D) at position 85 and valine (V) at position 49, have been replaced with asparagine (N) and alanine (A), respectively, has signif icantly improved optical properties compared with other forms of blue-membrane Bacteriorhodopsin. Absorption studies of the mutant in gels show that it forms the P(490) state at light levels that are comparable with M-state formation in wild-type f ilms. Theoretical calculations based on Kramers -Kronig transformation of light-induced absorption data predict that the refractive index is three times larger than that of mutant D85N. Holographic measurements performed on gelatin-based f ilms conf irm that the sensitivity is improved by a factor of 50 over that of D85N.
The technique for measuring changes in diffuse surfaces using Electronic Speckle Pattern Interfer... more The technique for measuring changes in diffuse surfaces using Electronic Speckle Pattern Interferometry (ESPI) is well known. We present a new electronic speckle pattern interferometer that takes advantage of a single-frame spatial phase-shifting technique to significantly reduce sensitivity to vibration and enable complete data acquisition in a single laser pulse. The interferometer was specifically designed to measure the stability of the James Webb Space Telescope (JWST) backplane. During each measurement the laser is pulsed once and four phase-shifted interferograms are captured in a single image. The signal is integrated over the 9ns pulse which is over six orders of magnitude shorter than the acquisition time for conventional interferometers. Consequently, the measurements do not suffer from the fringe contrast reduction and measurement errors that plague temporal phase-shifting interferometers in the presence of vibration. This paper will discuss the basic operating principle of the interferometer, analyze its performance and show some interesting measurements.
We demonstrate a phase-shifting, point diffraction interferometer that achieves high accuracy and... more We demonstrate a phase-shifting, point diffraction interferometer that achieves high accuracy and is capable of measuring a single pulse of light. The measurement system utilizes a polarizing point diffraction plate to generate a synthetic reference beam that is orthogonally polarized to the transmitted test beam. The plate has very high polarization contrast, works over an extremely broad angular and spectral range, and is only 100 nanometers thick. The unique features of the polarizing element make the system amenable to measuring strongly convergent light from high numerical aperture optics without the need to use a point reference source to calibrate the system. Results of measuring optics with numerical apertures as high as NA 0.8 are presented.
We demonstrate a scheme for volume holographic storage based on the features of shift selectivity... more We demonstrate a scheme for volume holographic storage based on the features of shift selectivity of a speckle reference-wave hologram. The proposed recording method permits more-efficient use of the recording medium and yields greater storage density than spherical or plane-wave reference beams. Experimental results of multiple hologram storage and replay in a photorefractive crystal of iron-doped lithium niobate are presented. The mechanisms of lateral and longitudinal shift selectivity are described theoretically and shown to agree with experimental measurements.
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 commonpath design permits operation with a wide variety of interferometer front ends, and with virtually any light source including white-light.
Interferometry XIII: Techniques and Analysis, 2006
An on-axis, vibration insensitive, polarization Fizeau interferometer is realized through the use... more An on-axis, vibration insensitive, polarization Fizeau interferometer is realized through the use of a novel pixelated mask spatial carrier phase shifting technique in conjunction with a low coherence source and a polarization delay-line. In this arrangement, coherence is used to effectively separate out the orthogonally polarized test and reference beam components for interference. With both the test and the reference beams on-axis, the common path cancellation advantages of the Fizeau interferometer are maintained. The interferometer has the unique ability to isolate and measure any surface that is substantially normal to the optical axis of the cavity. Additionally, stray light interference is substantially reduced due to the source's short coherence. An expression for the fringe visibility on-axis is derived and compared with that of a standard Fizeau. Using a 15 mW source, the maximum camera shutter speed, used when measuring a 4% reflector, was 150 usec, resulting in very robust vibration insensitivity. We experimentally demonstrate the measurement of both sides of a thin glass plate without the need to modify the plate between measurements. Experimental results show the performance of this new interferometer to be within the specifications of commercial phase shifting interferometers.
Storage and Retrieval for Image and Video Databases, 2000
The measurement accuracy of an interferometric optical test is generally limited by the environme... more The measurement accuracy of an interferometric optical test is generally limited by the environment. This paper discusses two single-shot interferometric techniques for reducing the sensitivity of an optical test to vibration; simultaneous phase-shifting interferometry and a special form of spatial carrier interferometry utilizing a micropolarizer phase-shifting array. In both techniques averaging can be used to reduce the effects of turbulence
Optical Measurement Systems for Industrial Inspection IV, 2005
ABSTRACT The measurement accuracy of an interferometric optical test is generally limited by the ... more ABSTRACT The measurement accuracy of an interferometric optical test is generally limited by the environment. This paper discusses two single-shot interferometric techniques for reducing the sensitivity of an optical test to vibration; simultaneous phase-shifting ...
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
Novel Optical Systems Design and Optimization VIII, 2005
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. In many situations the measurement accuracy is limited by the environment and sometimes the environment is sufficiently bad that the measurement cannot be performed. Recently there have been several advances in dynamic interferometry techniques for reducing effects of vibration. This talk will describe and compare two dynamic interferometry techniques; simultaneous phase-shifting interferometry and a special form of spatial carrier interferometry utilizing a micropolarizer phase-shifting array.
ABSTRACT Digital Speckle Pattern Interferometry (DSPI) is a well-established method for the measu... more ABSTRACT Digital Speckle Pattern Interferometry (DSPI) is a well-established method for the measurement of diffuse objects in experimental mechanics. DSPIs are phase shifting interferometers. Three or four bucket temporal phase shifting algorithms are commonly used to provide phase shifting. These algorithms are sensitive to vibrations and can not be used to measure large optical structures far away from the interferometer. In this research a simultaneous phase shifted interferometer, PhaseCam product of 4D Technology Corporation in Tucson Arizona, is modified to be a Simultaneous phase shifted Digital Speckle Pattern Interferometer (SDSPI). Repeatability, dynamic range, and accuracy of the SDSPI are characterized by measuring a 5 cm x 5 cm carbon fiber coupon.
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. In many situations the measurement accuracy is limited by the environment and sometimes the environment is sufficiently bad that the measurement cannot be performed. Recently there have been several advances in dynamic interferometry techniques for reducing effects of vibration. This
We show that D85N/V49A, a mutant bacteriorhodopsin in which two residues, aspartate (D) at positi... more We show that D85N/V49A, a mutant bacteriorhodopsin in which two residues, aspartate (D) at position 85 and valine (V) at position 49, have been replaced with asparagine (N) and alanine (A), respectively, has signif icantly improved optical properties compared with other forms of blue-membrane Bacteriorhodopsin. Absorption studies of the mutant in gels show that it forms the P(490) state at light levels that are comparable with M-state formation in wild-type f ilms. Theoretical calculations based on Kramers -Kronig transformation of light-induced absorption data predict that the refractive index is three times larger than that of mutant D85N. Holographic measurements performed on gelatin-based f ilms conf irm that the sensitivity is improved by a factor of 50 over that of D85N.
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