Confocal optical microscopy is a technique for increasing the contrast of microscope images, particularly in thick specimens. By restricting the observed volume, the technique keeps overlying or nearby scatterers from contributing to the detected signal. The price for this is that the instrument must observe only one point at a time (in the scanning laser version) or a group of separated points with very little light (in the disc version). This paper describes how the confocal advantage comes about and how it is implemented in actual instruments.

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Confocal optical microscopy

We describe a novel technique, based on optical coherence tomography, for enhanced optical sectioning in confocal microscopy. Confocal imaging deep into highly scattering media is demonstrated and compared with the predictions of a single-backscatter theory.

Optical coherence microscopy in scattering media.

Optical coherence microscopy in scattering media

A new geometrical arrangement is proposed to improve performances of optical triangulation Two scanners in synchronization allow a linear position sensor to be used for surface topography measurement Besides a large increase in speed of measurement (approximately megahertz), the new geometry allows considerable reduction of the optical head size compared with usual geometries, so the shadow effects are reduced proportionally It also provides a means to obtain a very large field of view without compromising on resolution Geometrical analysis and experimental results are presented

Laser range finder based on synchronized scanners

Systems of two-dimensional (2-D) imaging arrays and apertures are considered from the point of view of their performance in the imaging of spatially incoherent as well as coherent source distributions. Such systems find applications in radar, sonar, and ultrasound imaging, as well as in applications such as seismology and radio astronomy. For linear imaging techniques related to beamforming and based on the Fourier transform relationship between the source distribution and the aperture plane measurements, the point spread function of the system completely characterizes its performance. This function is determined by the geometry of the physical aperture or array as well as the weighting that can be applied to measurements. It is shown that the introduction of the concept of coarray, both for receive apertures in incoherent imaging and for transmit/receive systems in reflection-mode coherent imaging, provides a convenient and elegant framework within which many apparently isolated techniques for point-spread function or aperture synthesis can be understood. In addition to this unifying role, coarray concept gives new insight into the aperture synthesis process, which allows interesting new imaging techniques to be developed, especially in coherent imaging. >

The unifying role of the coarray in aperture synthesis for coherent and incoherent imaging

A new optical heterodyne scanning microscope is described in which both the illumination beam and reference beam scan the object in synchronization. Characteristics of the microscope are similar to those of the laser scanning microscope. The present system, however, has additional advantages in that the object illumination can be at least one order of magnitude less intense and that ambient light has no effect for images. Preliminary experimental results will be shown, including a two-dimensional cross-section pattern from a 3–D object, unfocused image rejection characteristics, and images of some biological samples.

Optical Heterodyne Scanning Microscope

The elevation angle of a low angle target is accurately measured by subtracting from the received radar signal signals derived from an estimated value of target elevation which reduces the resulting signal to a minimum. The estimated value is an accurate measure of target elevation.

Low angle radar processing means

An arrangement for measuring the profile of surfaces having a characteristic one-directional lay with sufficient resolution to determine the surface roughness thereof is disclosed, comprising a device for illuminating a small spot on the surface, with an image of the spot projected through an objective lens onto a large area light detector positioned to generate a signal corresponding to the total illumination produced by the image. The device also includes a second light detector which views a second image of the spot focused by the objective lens through a slit disposed perpendicularly to the direction of the surface lay. The respective detector signals are divided to produce signals corresponding to the ratio thereof, which, according to the present invention, correspond to the variations of the surface height occuring as the illuminated spot is scanned across the surface. A graphical profile of the surface may be obtained by recording these signals as a function of the scanned distance.

Surface profile measuring device and method

The marked chromatic aberration of a Fresnel-zone-plate lens can be used as a variable narrow-band optical filter, and thus a holographic spectrometer. The filtering properties of the zone plate are analyzed, with particular emphasis on the effect of a central stop over the low-order rings. It is shown that the central stop can markedly improve the rejection of frequencies outside the pass band without significant degradation of the spectrometer resolution.

Fresnel-Zone-Plate Spectrometer with Central Stop*

A noncontacting optical transducer, which measures the profile of machined surfaces, was constructed and tested. The profile transducer consists of a microscope objective, a point-source illuminator, and two photodetectors. The dynamic range of the instrument is typically 500 microinches with an accuracy of better than 10 microinches. The output of this transducer is a profile signal along a line on the surface under examination. The profile of a machined surface obtained by the optical-transducer correlates very well with that obtained by a mechanical Proficorder which uses a diamond stylus. Principles of operation, results of various performance tests, and potential applications of the optical-transducer are discussed.

Takeo Sawatari

Papers

Optical Heterodyne Scanning Microscope

Low angle radar processing means

Surface profile measuring device and method

Fresnel-Zone-Plate Spectrometer with Central Stop*

Optical Profile Transducer