Optical Testing Papers
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Brad Kimbrough, James Millerd, James Wyant,
and John Hayes
Proceedings of SPIE Vol. 6292, page
62920F-1-12, 2006
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. |
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Robert M. Neal and James
C.
Wyant
APPLIED OPTICS, Vol. 45, page
3463, 20 May
2006
A new instrument, the polarization phase-shifting
point-diffraction interferometer, has been developed by use of a
birefringent pinhole plate. The interferometer uses polarization to
separate the test and reference beams, interfering what begin as orthogonal
polarization states. The instrument is compact, simple to align, and
vibration insensitive and can phase shift without moving parts or separate
reference optics. The theory of the interferometer is presented, along with
properties and fabrication techniques for the birefringent pinhole plate and
a new model used to determine the quality of the reference wavefront from
the pinhole as a function of pinhole size and test optic aberrations. The
performance of the interferometer is also presented, along with a detailed
error analysis and experimental results.
URL:
http://www.opticsinfobase.org/abstract.cfm?URI=ao-45-15-3463 |
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Matt Novak, James
Millerd, Neal
Brock, Michael
North-Morris, John
Hayes, and James
Wyant
APPLIED OPTICS, Vol. 44, page
6861, 10 November
2005
Recent technological
innovations have enabled
the development
of a new
class of dynamic
(vibration-insensitive) interferometer
based on a
CCD pixel-level
phase-shifting approach.
We present
theoretical and
experimental results for
an interferometer
based on this
pixelated phase-shifting
technique. Analyses
of component
errors and instrument
functionality are
presented. We show
that the majority
of error sources
cause relatively
small magnitude
peak-to-valley errors in
measurement of
the order of
0.002–0.005 . These
errors are
largely mitigated by
high-rate data
acquisition and
consequent data
averaging. URL:
http://www.opticsinfobase.org/abstract.cfm?URI=ao-44-32-6861 |
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James C. Wyant
Proceedings of SPIE Vol. 6024, page
602401-1-11, 2005
The addition of electronics, computers, and software
to interferometry has provided tremendous improvements in the measurement of
surface shape and roughness. This talk will describe three such
improvements; use of computer generated holograms for testing aspheric
surfaces, techniques for performing interferometric measurements more
accurate than the reference surface, and two single-shot interferometric
techniques for reducing the sensitivity of an optical test to vibration and
measuring dynamically changing surface shapes. |
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Neal Brock, John Hayes, Brad Kimbrough, James Millerd, Michael
North-Morris, Matt Novak and James C. Wyant
Proceedings of SPIE Vol. 5875 (SPIE, Bellingham, WA, 2005), page
58750F-1, 2005
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. |
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James Millerd, Neal Brock, John Hayes, Brad Kimbrough, Matt Novak,
Michael North-Morris and James C. Wyant
Proceedings of SPIE Vol. 5856 (SPIE, Bellingham, WA, 2004), page
14, 2004
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 and the normal double frequency errors generally associated with
phase-shifting interferometry. |
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James E. Millerd, Stephen J. Martinek, Neal J. Brock, John B. Hayes and
James C. Wyant
Proceedings of SPIE Vol. 5380 (SPIE, Bellingham, WA, 2004), page
422, 2004
We demonstrate an instantaneous phase-shift, point diffraction
interferometer that achieves high accuracy and is capable of measuring a
single pulse of light at NA greater than 0.8. |
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James E. Millerd, Neal J. Brock, John B. Hayes and James C. Wyant
Proceedings of SPIE Vol. 5531 (SPIE, Bellingham, WA, 2004), page
264, 2004
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. |
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James Millerd, Neal Brock, John Hayes, Michael North-Morris, Matt Novak
and James Wyant
Proceedings of SPIE Vol. 5531 (SPIE, Bellingham, WA, 2004), page
304, 2004
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. |
Advances
in Interferometric MetrologyJames C. Wyant
Proceedings
of SPIE,
Vol. 4927,
pp. 154-162,
September 2002
Modern electronics, computers, and software have made
interferometry an extremely powerful tool in many fields
including the testing of optical components and optical systems. This
paper will discuss some of the recent advances in
reducing the sensitivity of phase-shifting interferometers to vibration. |
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White Light
Interferometry James C. Wyant
Proceedings
of SPIE,
Vol. 4737,
pp. 98-107, July
2002
White light interferometry is an extremely powerful tool
for optical measurements. This paper discusses the
advantages and disadvantages of white light interferometry compared to laser
light interferometry. Three different white
light interferometers are discussed; 1. diffraction grating interferometers,
2. vertical scanning or coherence probe
interferometers, and 3. white light scatterplate interferometers. |
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Michael B. North-Morris, Jay VanDelden, and James C. Wyant
APPLIED OPTICS, Vol. 41, page
668, February
2002
We realized what we believe is a new phase-shifting scatterplate
interferometer by exploiting the polarization
characteristics of a birefringent scatterplate. The common-path design of
the interferometer reduces its sensitivity to
environmental effects, and phase shifting allows quick and accurate
quantitative measurements of the test surface. A major feature of the
birefringent scatterplate approach for phase
shifting is that no high-quality optical components are required in the test
setup. The theory of the interferometer is
presented, the procedure for the fabrication of the birefringent
scatterplate is described, and experimental
results are shown. URL:
http://www.opticsinfobase.org/abstract.cfm?URI=ao-41-4-668 |
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Michael B. North-Morris and James C. Wyant
Proceedings
of SPIE,
Vol. 4231,
pp. 59-66,
2000
The advantages of common path interferometers for
reducing effects of vibrations are well known. A scatterplate
interferometer is one common-path interferometer that is well suited for the
testing of large concave mirrors, however due to the common path
characteristics it is difficult to perform phase-shifting. This paper
describes a phase-shifting scatterplate interferometer where the
phase-shifting is achieved by making use of the polarization characteristics
of a birefringent scatterplate. The major advantage of this design is
that it does not require any optical components to be placed near the
surface under test. The theory of the interferometer is presented and
experimental results are shown. |
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R. Keski-Kuha, P. Bely, R. Burg, J.
Burge, P. Davila, J. Geary, J. Hagopian, D. Jacobson, A. Lowman, S. Macenka,
J. Mangus, C. Perrygo, D. Redding, B. saif, S. Smith, and J.
Wyant
Proceedings
of SPIE,
Vol. 4013,
pp. 826-835,
2000
An Integrated Product Team (IPT) was formed to develop
a detailed concept for optical test methodology for testing of the NGST
individual primary, secondary and tertiary mirrors and the full telescope
system on the ground. The large, lightweight, deployable primary
mirror, and the cryogenic operating environment make optical testing of NGST
OTA (Optical Telescope Assembly) extremely challenging. A telescope of
the complexity of NGST has never been built and tested on the ground in 1-g
environment. A brief summary of the preliminary metrology test plan at
the mirror component and telescope system level is presented. |
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Michael B. North-Morris, Jay VanDelden
and James C. Wyant
Proceedings
of SPIE,
Vol. 3749,
pp. 432-433, 1999
A new phase shifting scatterplate
interferometer is realized by exploiting the polarization
characteristics of a birefringent scatterplate. The
advantages of this design are that it does not require any optical
components to be placed near the surface under test and the hot spot and
background intensity, which are inherent to scatterplate interferometers,
are eliminated. The theory of the interferometer is presented. |
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Erik Novak, Chiayu Ai, and, James C. Wyant
Proceedings
of SPIE,
Vol. 3134,
pp. 114-121, 1997
Large, high power laser systems such as that being constructed by
Lawrence Livermore National Laboratories for the
National Ignition Facility (NIF) require accurate measurement of spatial
frequencies of up to 2.5lines/mm over a 100mm
field of view. In order to ensure accurate
measurements of the parts, the test apparatus must be well characterized.
The system transfer function (SiT) of
the interferometer under development to perform these measurements was
calculated by comparing the power spectra of
measurements of known phase objects to their theoretical power spectra.
Several potential problem areas were identified and studied. Of
primary concern was the effect on the STF of the
rotating diffuser and incoherent relay system employed in most commercial
laser Fizeau interferometers. It was determined
that such an arrangement degraded the transfer function beyond
acceptability. The other major concern was possible inability
to measure certain frequencies due to propagation between the test
piece and alignment of the system optics. Use of strictly
coherent imaging and small propagation distances between the test
piece and return flat, the system transfer function could be
kept at acceptable levels within the range of interest. |
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Erik Novak, Chiayu Ai, and, James C. Wyant
Proceedings
of SPIE,
Vol. 3134,
pp. 456-460, 1997
Most commercial
laser Fizeau interferometers employ a rotating diffuser on an intermediate
image plane. The image formed on this plane is relayed to the detector using
incoherent imaging, eliminating potential interference effects from elements
after the diffuser. Systems requiring high spatial frequency resolution
cannot employ the diffuser or incoherent relay system to the degradation
they cause to the system transfer function. With strictly coherent imaging,
however, nearly parallel optical elements such as the CCD cover glass will
produce interference fringes. Though these elements are common path, fringes
will be visible in the phase measurement unless one of several specific
conditions are met. This paper explores the theory behind the
formation of these fringes and examines cases where this error may be
eliminated. Theoretical calculations are compared with actual measurements
taken on a laser Fizeau interferometer. The errors evident in the final
phase measurement may be minimized with proper coating of the system optics,
sufficient wedge in the elements, or removal of the nearly parallel elements
from the system.
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Joe Lamb, James Semrad, James Wyant, Chiayu Ai, Robert
Knowlden, Erik Novak, John Downie, and Robert Wolfe
Proceedings
of SPIE,
Vol. 3047,
pp. 415-426, 1997
WYKO Corporation is currently designing and manufacturing specialized
phase shifting interferometers to aid in the
qualification of large optics for the U.S. N.I.F. program. The
interferometers will be used to qualify homogeneity of
raw material and provide in-process inspection information and final
inspection qualification data. The 24" systemsw
ill be the largest commercially available Fizeau phase shifting
interferometers ever manufactured. Systems will be
produced using traditional CCD cameras as well as a megapixel CCD camera for
applications requiring higher lateral resolution.
Mechanical and optical design considerations include vibration and
distortion control of critical optical elements,
polarization control of the laser source, imaging system design, and optical
transfer function optimization. We also
address effects in the test cavity arising from measuring transmitted and
reflected wavefronts of optics mounted at
Brewster's angle |
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Erik Novak, Chiayu Ai, and James C. Wyant
Proceedings
of SPIE,
Vol. 2870,
pp. 545-552, 1996
Accurate interferometric measurement of large laser slabs requires
spatial frequencies of 1mm/cycle to 33mm/cycle
over a 100mm field of view to be passed by the system with no more than 25%
loss in modulation. To eliminate noise and
artifacts due to strictly coherent imaging, many commercial
interferometers employ a rotating diffuser on an intermediate
image plane and relay this image incoherently onto a detector.
Unfortunately, this process may adversely affect the resolution
of the instrument. Through measurement of a sinusoidal phase grating
an fused silica step, the transfer function a laser
Fizeau interferometer was measured for both a system with and without
the incoherent relay system. Results are compared to
those predicted by diffraction theory. Studies of the effects of
defocus and propagation on the measurement were also made.
Using strictly coherent imaging dramatically increases the system's
ability to measure features of high spatial frequency and
allows the measurement requirements for laser slabs to be met. |
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Chiayu Ai and James C. Wyant
Proceedings
of SPIE,
Vol. 1994,
pp. 102-110, 1994
Multiple reflections between two surfaces of a window introduce a fixed
pattern error in the transmitted wavefront. In a
Fizeau or Twyman-Green interferometer, this wavefront is reflected
by a return flat and transmits through the window. The fixed pattern
error is carried in the measurement result. This
error is negligible, only if the wedge angle is so
large that the interference fringes formed by the
two surfaces are too dense for the detector to resolve. However, if the
wedge angle is small (e.g. several arc-seconds), the phase error (pv)
could be up to 0.025 fringes for most glass (n
=1.5). By tilting both the window and the return flat properly, it is
possible to cancel the effect of multiple
reflections of a window. |
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Chiayu Ai and James C. Wyant
APPLIED OPTICS, Vol. 32
No. 25,
page 4904, 1 September 1993
Multiple reflections between two surfaces of a window
introduce a fixed pattern error in optical measurements. One way to
remove these spurious reflections is to use a reasonably large wedge so that
the interference fringes formed by the two surfaces are too dense for the
detector to resolve. However, this method does not work if the wedge
angle is small, e.g., several arcseconds. By tilting both the window
and the return mirror properly, it is possible to remove the effect of
multiple reflections of a window. Theory and experimental results are
presented. URL:
http://www.opticsinfobase.org/abstract.cfm?URI=ao-32-25-4904 |
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Chiayu Ai and James C. Wyant
APPLIED OPTICS, Vol. 32
No. 25,
page 4698, 1 September 1993
We describe a modified three-flat
method. In a Cartesian coordinate system, a flat can be expressed as
the sum of even-odd, odd-even, even-even, and odd-odd functions. The
even-odd and the odd-even functions of each flat are obtained first, and
then the even-even function is calculated. All three functions are
exact. The odd-odd function is difficult to obtain. In theory,
this function can be solved by rotating the flat 90o, 45o,
22.5o, etc. The components of the Fourier series of this
odd-odd function are derived and extracted from each rotation of the flat.
A flat is approximated by the sum of the first
three functions and the known components of the odd-odd function. In
the experiments, the flats are oriented in six configurations by rotating
the flats 180o, 90o, and 45o with respect
to one another, and six measurements are performed. The exact profiles
along every 45o diameter are obtained, and the profile in the
area between two adjacent diameters of these diameters is also obtained with
some approximation. The theoretical derivation, experimental results,
and error analysis are presented. URL:
http://www.opticsinfobase.org/abstract.cfm?URI=ao-32-25-4698 |
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Chiayu Ai and James C. Wyant
APPLIED OPTICS, Vol. 32
No. 19,
page 3470, 1 July 1993
Phase errors in a Fizeau phase-shifting interferometer
caused by multiple-reflected beams from a retroreflective optics, such as a
corner cube and a right-angle prism, are studied. Single- and
double-pass configurations are presented, and their measurement results are
compared. An attenuator is not needed in a double-pass configuration
because light is reflected by the retroreflective optics twice and the
reference surface once and hence the intensities match. It is more
accurate to test a corner cube or a right-angle prism in a double-pass
configuration than in a single-pass configuration. Simulations and
experimental results are presented. URL:
http://www.opticsinfobase.org/abstract.cfm?URI=ao-32-19-3470 |
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Katherine Creath and James C. Wyant
APPLIED OPTICS, Vol. 31, page
4350, 1 August 1992
A technique for measuring the quality of spherical
surfaces that provides a quasi-absolute result is presented. It
requires only two measurement positions rather than the traditional method
of absolute sphere measurement that requires three measurement positions.
A measurement is taken with a mirror at the focus of the interferometer
diverger lens and is subtracted from a measurement of the sphere tested at
its center of curvature. This test assumes that the test sphere does
not contain any aberrations with odd symmetry so that these aberrations can
be subtracted to provide a fast, quasi-absolute measurement. We
describe the new technique and compare measurement results from testing a
l/12 peak-to-valley sphere (numerical aperture =
0.4) by using a phase-measuring Fizeau interferometer with results from the
three-position absolute sphere measurement technique. The
repeatability of this measurement technique is ±0.01 waves peak to valley.
URL:
http://www.opticsinfobase.org/abstract.cfm?URI=ao-31-22-4350 |
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Chiayu Ai and James C. Wyant
Proceedings
of SPIE,
Vol. 1776,
pp. 73-83, 1992
This paper describes a method for measuring the absolute flatness of
flats. A function in a Cartesian coordinate system
can be expressed as the sum of even-odd, odd-even, even-even, and odd-odd
functions. Three flats are measured at eight orientations; one flat is
rotated 180°, 90°, and 45°with respect to
another flat. From the measured results the
even-odd and the odd-even functions of each flat are obtained first,
then the even-even function is calculated. All
three functions are exact. The odd-odd function is difficult to
obtain. For the points on a circle centered at the origin, the
odd-odd function has a period of 180° and can be
expressed as a Fourier sine series. The sum of one half of the Fourier
sine series is obtained from the 90o
rotation group. The other half is further
divided into two halves, and one of them is
obtained from the 45° rotation
group. Thus, after each rotation, one half
of the unknown components of the Fourier sine series of the odd-odd
function is obtained. The flat is approximated by the sum of the
first three functions and the known components of
the odd-odd function. In the simulation, three flats (each is an
OPD map obtained from a Fizeau interferometer) are reconstructed. The
theoretical derivation and the simulating results
are presented. |
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Chiayu Ai and James C. Wyant
OPTICAL ENGINEERING, Vol. 30 No. 9,
page 1399, September 1991
We describe three methods to measure the inhomogeneity of a window material.
The first method immerses the window in a liquid between two planes. However, this method
is inconvenient for some applications. The second method measures the optical figure of
the front surface and then measures the return wavefront that transmits through the window
and reflects from the rear surface of the window. The advantage of this method is that it
can remove the contributions of both the surface figures and the return fiat plus the
system error of the interferometer. The disadvantage is that a small wedge must be
fabricated between the two surfaces to eliminate spurious interference. The third method
derives the inhomogeneity of the window material by measuring the optical figure of the
front surface of the window and then flipping the mirror to measure the back surface. The
advantage of this method is that it is not necessary to have a wedge between the two
surfaces. The disadvantage of the window-flipping method is that the contribution of
system error can increase. |
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Chiayu Ai and James C. Wyant
Proceedings
of SPIE,
Vol. 1531,
pp. 165-172, 1991
This paper describes a method to measure the birefringence of an optical
window. The transmitting wavefront includes the
contributions from the two surfaces, the material inhomogeneity, and
the birefringence. Because of the birefringence, the transmitting
wavefront has different profiles for different
orientations of polarization of linearly polarized beams. From this
difference, the amount of phase difference for the
fast and slow axes is obtained. Thus, the birefringence is calculated. With
this method, the contributions from the two
surfaces and the material inhomogeneity are removed. A laser rod
was measured with different methods. The theoretical derivation,
comparison of different methods, and experimental
results are presented. |
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Katherine Creath and James C. Wyant
APPLIED OPTICS, Vol. 29, page
3823, 10 September
1990
In an interferometer which uses a reference surface,
the measured surface heights correspond to the difference between the test
and reference surfaces. To accurately determine the rms roughness of
supersmooth surfaces, the effects of the reference surface roughness needs
to be removed. One technique for doing this involves averaging a
number of uncorrelated measurements of a mirror to generate a reference
surface profile which can then be subtracted from subsequent measurements so
that they do not contain errors due to the reference surface. The
other technique provides an accurate rms roughness of the surface by taking
two uncorrelated measurements of the surface. These two techniques for
measurement of supersmooth surfaces are described in detail, and results of
the measurement of a 0.7-Å rms surface roughness
mirror are presented. The expected error in the rms roughness
measurement of a supersmooth mirror due to instrument noise is 0.02 Å.
URL:
http://www.opticsinfobase.org/abstract.cfm?URI=ao-31-22-4350 |
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Katherine Creath and James C. Wyant
Proceedings
of SPIE,
Vol. 1332, pages 2-7, 1990
The testing of
spherical surfaces using the three-measurement technique outlined by Jensen
requires very precise alignment of the sphere relative to the
interferometer. An easier technique for the absolute measurement of
spherical surfaces has been developed which does not require the precise
alignment of the Jensen technique and uses only two measurements. As long as
the test surface does not contain any aberrations with odd symmetry, these
aberrations can be subtracted from the measurement and an absolute
measurement of the test surface can be obtained. This paper describes and
compares these two techniques and shows results of testing a
l/12
P-V (peak-to-valley) sphere (N.A.=0.4) using both techniques with a
phase-measuring Fizeau interferometer. These measurement techniques are
repeatable to ±0.01waves P-V.
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Katherine Creath and James C. Wyant
Proceedings
of SPIE,
Vol. 645, page 101, 1986
Two-wavelength holography and phase-shifting
interferometry are combined to measure aspheric surface contours with
variable sensitivity. In this technique, the surface is effectively
tested at a synthesized longer equivalent wavelength leq=la
lb/Abs[la
- lb] using measurements made at
wavelengths la and
lb where the difference of the phases measured for
la and lb
yields modulo 2p phase at leq.
A mask of point apertures is placed over the detector array in order to
resolve closely spaced fringes. This technique has an rms
repeatability of leq/100. Limits
to this technique are discussed and results are shown. |
Katherine Creath, Yeou-Yen Cheng, and James C.
Wyant
Optica Acta, Vol. 32, page 1455, 1985
Two-wavelength holography and phase-shifting interferometry are combined to
measure the phase contours of deep wavefronts and surfaces, such as those produced by
aspherics, with a variable sensitivity. When interference fringes are very closely spaced,
the phase data contain high frequencies where 2p ambiguities
cannot be resolved. In this technique, the surface is tested at a synthesized longer
equivalent wavelength. The phase of the wavefront is calculated modulo 2p
using phase-shifting techniques at each of two visible wavelengths. The difference
between these two phase sets is the phase of the wavefront as it would be measured at leq =l1l2/|l1-l2|, assuming that 2p ambiguities can be removed at leq. This
technique enables surfaces to be contoured to an accuracy of leq/l00. |
K. N. Prettyjohns, S. DeVore, Eustace Dereniak, and
J. C. Wyant
APPLIED OPTICS, Vol. 24, page 2211, July 15 1985
A direct phase measurement interferometer
designed and constructed to operate at a 3.8-µm wavelength is described. The
interferometer uses a deuterium fluoride laser as the light source, zinc selenide
transmitting optics, and a 32- X 64-element PtSi infrared CCD detector array with digital
processing electronics and a graphics display on a desktop microcomputer. The instrument,
which is useful for measuring a figure error caused by thickness variations in dielectric
coatings applied to infrared optics, gives a wave front measurement repeatability of <l/50 rms.
URL:
http://www.opticsinfobase.org/abstract.cfm?URI=ao-24-14-2211 |
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Self-referencing wavefront sensor (1220 KB)
K. Underwood, J.C. Wyant, and C.L. Koliopoulos
Proceedings
of SPIE,
Vol. 351, page 108, 1983
A modified Smartt
point-diffraction interferometer employing phase-shifting electronic phase
measurement techniques is described. Special techniques making it
possible for the interferometer to give good visibility interference fringes
for a large range of input tilts are discussed. A trade-off between
acceptable values of wavefront tilt and light efficiency is presented. |
John Hayes, K. L. Underwood, John S. Loomis, Robert E. Parks,
and James C. Wyant
APPLIED OPTICS, Vol. 20, page 235, January 15 1981
The extreme alignment sensitivity
of nonlinear diamond-turned reflaxicons makes them difficult to test and analyze. To
evaluate the wave front it is necessary to know what portion results from alignment
errors. This paper describes the setup, alignment, and testing of a nonlinear
diamond-turned independent-element reflaxicon manufactured at the Union Carbide, Oak Ridge
Y-12 plant. Interferograms taken with the center cone misaligned a known amount are
analyzed using the axicon preprocessing option in FRINGE [J. S. Loomis (ASTM Report STP
666 and Proc. Soc. Photo-Opt. Instrum. Eng. 171, 64 (1979)]. The results show that FRINGE
correctly removes the cone and decenter errors introduced by the misalignments. It is also
shown how the resulting interferograms are unfolded to give the OPD errors as seen on the
outer cone.URL:
http://www.opticsinfobase.org/abstract.cfm?URI=ao-20-2-235 |
Osuk Kwon, J. C. Wyant, and C. R. Hayslett
APPLIED OPTICS, Vol. 19, page 1662, June 1 1980
An IR Twyman-Green interferometer
is described. It uses a cw CO2 laser as a light source operating at a 10.6-µm wavelength.
Theoretical analysis and experimental measurements of the relationship between the
contrast of the interference fringes and the rms roughness of test surfaces are discussed.
Interferometric testing results and special alignment methods are shown for rough surface
optics.URL:
http://www.opticsinfobase.org/abstract.cfm?id=24025 |
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James C. Wyant
SCIENCE, Vol. 206, page 168,
12 October 1979
Increased performance requirements for modern optical
systems have necessitated the development of more precise optical testing
techniques. The need for accurate and rapid measurements is being met
by the use of laser interferometers, microprocessors to gather test data,
and computers to analyze the data and remove errors in the test equipment. |
Lawrence F. Rubin and James C.
Wyant
J. Opt. Soc. Am., Vol. 69, No. 9, page 1305, September 1979
In this paper, a Fourier-optics
approach to scatterplate interferometry is introduced. In particular, it is used to
explain how energy is conserved for both "phase"- and "density"-type
scatterplates.URL:
http://www.opticsinfobase.org/abstract.cfm?URI=josa-69-9-1305 |
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C. Koliopoulos, O. Kwon, R. Shagam, J. C. Wyant, and C. R. Hayslett
OPTICS LETTERS, Vol. 3, page 118, September 1978
A point-diffraction interferometer (PDI) for use in the infrared is discussed. It is
shown that the PDI is simple and easy to use and also yields fringes of constant optical
path difference similar to those obtained with a Twyman-Green interferometer. The
fabrication of the PDI is described, and typical results obtained using the interferometer
at a wavelength of 10.6 µm are shown. URL:
http://www.opticsinfobase.org/abstract.cfm?id=24025 |
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R. N. Shagam, R. E. Sladky, and J. C. Wyant
OPTICAL ENGINEERING, Vol.
16 No. 4,
page 375, July-August 1977
This paper demonstrates that the optical testing of
diamond-turned surfaces is best accomplished by interferometry and not by
tests which measure wavefront slope. Certain conditions regarding the
interferometer configuration must be met in order to generate meaningful and
accurate interferograms. A 40 cm diameter aperture modified Mach-Zehnder
interferometer mounted directly on the diamond-turning lathe to facilitate
rapid testing of figure between fabrication cuts is described. Results
for a spherical surface tested in a Twyman-Green interferometer and an
off-axis parabola tested in the Mach-Zehnder interferometer are illustrated. |
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David A. Thomas and J. C. Wyant
J. Opt. Soc. Am., Vol. 67, No. 4, page 467, April 1977
A technique is devised for calculating the magnitudes of the dihedral angle errors of a
comer cube from a single Twyman-Green interferogram. Experimental examples are given in
which the dihedral angles of two corner cubes are determined to within 2 arcsec by this
procedure. These values are also shown to be in good agreement with independent goniometer
measurements. URL:
http://www.opticsinfobase.org/abstract.cfm?URI=josa-67-4-467 |
J. C. Wyant and F. D. Smith
APPLIED OPTICS, Vol. 14, page 1607, July 1975
The use of a lateral shear
interferometer in measuring the power variation of ophthalmic lenses is described and
demonstrated. It is shown that an appropriate lateral shear interferometer directly
measures the power variation of an ophthalmic lens. If the ophthalmic lens has a toric
surface, the power for each axis can be measured separately. Individual surfaces can be
tested, as well as the whole lens or the different segments of a multifocal lens. The
sensitivity of the test can be selected by varying the amount of lateral shear. Because of
the demonstrated simple relationship between fringe spacing and dioptric power,
qualitative examination of the fringes has proved a useful adjunct to conventional quality
control methods.URL:
http://www.opticsinfobase.org/abstract.cfm?URI=ao-14-7-1607 |
