Scanning differential optical profilometer for simultaneous measurement of amplitude and phase variation

See, C. W.; Appel, Roland K.; Somekh, Michael Geoffrey

doi:10.1063/1.100118

Cited by 28 publications

(4 citation statements)

References 5 publications

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“…In the experimental results described in section 4 the response was indeed obtained in this way as described in the next section. The effective transfer function becomes a summation rather than a integral, thus: i=N Ceff(mO) C(m;O4u i+ 6u) (4) i=-M where i is an integer, iu is the step size in normalised units and du is the distance between the focal plane and the sampling plane closest to the focal plane. Figure 5 shows the effects of varying the step size, u, the continuous plot in figure 5a shows the result of sampling with a normalised step size equal to 5 normalised axial units, where it can be seen that Cef(m;O) is similar to the infocus transfer function.…”

Section: The Effect Of Finite Sampling Interval On the Extended Focusmentioning

confidence: 99%

Confocal operation in differential phase interference microscopy

et al. 1994

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This paper discusses the operation and imaging properties of various types of optical heterodyne interferometer. Conditions needed to achieve confocality in differential interference microscopes are considered. This leads to a novel extended focus phase imaging mode. Results are presented which demonsirate this mode of operation and show the ability of the technique to produce accurate phase measurement on samples with warp and tilt, over a range much greater than the depth of focus of the objective lens. I . INTRODUCTIQNThe scanning confocal optical microscope owes much of its success to the fact that the system eliminates signals from features which are out of focus. The microscope will thus render sharp images in the presence of considerable background scatter. This differs from the response obtained in a conventional full field optical microscope or a type I scanning microscope where the out of focus features contribute significantly to the image distribution, thus resulting in images of poor definition and contrast. This depth discriminating property means that the confocal microscope is an important tool for imaging three dimensional structures. A corollary of the depth resolution of the confocal microscope is the ability to form images with enormous depth of focus. If, in addition to raster scanning the sample, it is also scanned axially and the output from each axial position is added, the image appears to be in focus throughout the scan. This imaging mode is called the extended focus imaging mode and enables the confocal optical microscope to be used to form sharp images on tilted and warped samples.1 It has long been recognised that scanning optical interferometers give a confocal response.2'3 They have the advantage that, with any one particular system configuration, a number of imaging modes are afforded. This leads to systems with a high degree of flexibility and thus provide a diverse applications. In this paper, we describe the operation and the various imaging modes of one such interferometer, namely, the differential heterodyne interference microscope. The first section introduces the different interferometric techniques and explain how confocality is achieved. These have various modes of operation which are reviewed. This is followed by a detailed discussion of a novel extended focus phase imaging (EFPI) modality. The theoretical background for this mode of operation will be given. Experimental results, demonstrating the ability of this technique in providing accurate phase measurement on warped samples, are presented. Finally, we will discuss applications of the other imaging modes and further work that is being undertaken. OPERATION OF HETERODYNE INTERFERENCE MICROSCOPESHeterodyne interferometers have frequency shifting elements incorporated into them such that the optical frequency of one arm of the interferometer is shifted relative to the other. This has the advantage that the signal is well away from 1/f noise, giving an improved signal to noise ratio. Furthermore, the object induced ampli...

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Section: The Effect Of Finite Sampling Interval On the Extended Focusmentioning

confidence: 99%

Confocal operation in differential phase interference microscopy

et al. 1994

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“…Its high-sensitivity results from the phase measurement of the beat signal produced by two parallel incident beams whose frequencies are slightly different from each other (Komatsu et al 1990). In addition, DHI based on common path schemes having the same optical path of two beams (See, Appel, and Somekh 1988), has a strong point compared to non-differential interferometers, as it is less sensitive to environmental disturbances, especially high vibration (Somekh et al 1995).…”

Section: Description Of the Proposed System Differential Heterodyne Imentioning

confidence: 99%

Beam Scanning Confocal Differential Heterodyne Interferometry

Song

Kim

Gweon

2007

International Journal of Optomechatronics

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This article presents a new approach to the design of confocal differential heterodyne interferometer (CDHI), which is a combination of differential heterodyne interferometer (DHI) with confocal laser scanning microscopy (CLSM). The CDHI can measure a step height over a quarter of wavelength of the light source, which can not be accurately measured by DHI and CLSM, respectively. The approach is that it utilizes a beam-scanning method instead of transporting a sample to be measured. The measurement results carried out for samples having step height are found to be comparable in precision with those measured by commercial scanning electron microscopes.

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“…Phase contrast microscopy and DIC microscopy have both traditionally been used to image biological cells or to measure surface profilometry. 130 Laser scanning has been used extensively for surface profiling using dual path interferometry, 131,132 and differential dual-beam systems with either spatial offset, [133][134][135][136] or angular offset for heterodyne detection. 137 Single-beam configurations have detected both amplitude and phase shifts in surface reflectance using a common-path approach.…”

Section: Phase-contrast Biocdmentioning

confidence: 99%

Invited Review Article: Review of centrifugal microfluidic and bio-optical disks

Nolte

2009

Review of Scientific Instruments

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Spinning biodisks have advantages that make them attractive for specialized biochip applications. The two main classes of spinning biodisks are microfluidic disks and bio-optical compact disks ͑BioCD͒. Microfluidic biodisks take advantage of noninertial pumping for lab-on-a-chip devices using noninertial valves and switches under centrifugal and Coriolis forces to distribute fluids about the disks. BioCDs use spinning-disk interferometry, under the condition of common-path phase quadrature, to perform interferometric label-free detection of molecular recognition and binding. The optical detection of bound molecules on a disk is facilitated by rapid spinning that enables high-speed repetitive sampling to eliminate 1 / f noise through common-mode rejection of intensity fluctuations and extensive signal averaging. Multiple quadrature classes have been developed, such as microdiffraction, in-line, phase contrast, and holographic adaptive optics. Thin molecular films are detected through the surface dipole density with a surface height sensitivity for the detection of protein spots that is approximately 1 pm. This sensitivity easily resolves a submonolayer of solid-support immobilized antibodies and their antigen targets. Fluorescence and light scattering provide additional optical detection techniques on spinning disks. Immunoassays have been applied to haptoglobin using protein A/G immobilization of antibodies and to prostate specific antigen. Small protein spots enable scalability to many spots per disk for high-throughput and highly multiplexed immonoassays.

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Scanning differential optical profilometer for simultaneous measurement of amplitude and phase variation

Cited by 28 publications

References 5 publications

Confocal operation in differential phase interference microscopy

Confocal operation in differential phase interference microscopy

Beam Scanning Confocal Differential Heterodyne Interferometry

Invited Review Article: Review of centrifugal microfluidic and bio-optical disks

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