y? Diagram, a powerful optical design method for laser systems.

We present a new method for synthesizing and analyzing laser systems based on the use of the y? diagram. The diagram is commonly used to represent two rays, the marginal and the chief rays, as they propagate through an optical system. Since a Gaussian beam can be represented by two rays, it is possible to use the y? diagram to represent these rays. This results in a representation of the beam as a single ray line on the y? diagram with simple graphic interpretations for the beam parameters. An equivalent representation of the Gaussian beam on the uu diagram is also presented and discussed. Complex design problems may be reduced to simple graphic problems, which often lead directly to algebraic solutions. Examples of y? diagrams are given for beam transfer through simple optical systems, including gradient optics. Diagram transformations are discussed and design examples are given of a three-element afocal system and a three-element collimator.

A novel method of focus sensing for the laser scanner microscope.

An unconventional approach to the focus-sensing problem in a high-speed cell scanner has resulted in a method of directly detecting the position of the cell layer. This is done by using two coaxial but axially shifted beams, one focused on either side of the cell layer. The modulation induced in each beam by the cell's fine structure is compared electronically to yield the focus-error signal. The beams are orthogonally polarized, therefore separable, and are independently detected. The two detector-output signals are used to form both the focus-error signal and the scanner's primary data signal. This focus-sensing technique has been analytically modeled and experimentally demonstrated for a high-numerical-aperture system. In that system, the depth of focus is less than the thickness of the cell layer. It is shown that a lens fabricated from a birefringent crystal is an attractive means of forming the required orthogonally polarized axially shifted beams.

Dynamic optical tests of a high-speed polygon.

A dynamic optical deformation test for a high-speed polygon is described in which a laser beam is reflected off a rotating polygon and is focused on a pair of Ronchi rulings at 45 degrees to each other. The astigmatism and defocus terms of the deformation are measured and mapped over any one of the polygon facets. The relatively simple and sensitive setup is also used for testing pyramidal error, facet-to-facet angle error, and axis-to-facet interval deviations.

Aberrations of diffracted wave fields.

This paper is an attempt to provide new insight into the behavior of near-field scalar diffraction phenomena by showing that the Rayleigh-Sommerfeld diffraction integral is equivalent to the Fourier transform integral of a generalized pupil function which includes a term that represents phase errors in the aperture. This term can be interpreted as describing a conventional wavefront aberration function. The resulting aberration coefficients are calculated and expressed in terms of the aperture diameter, observation distance, and appropriate field parameter for several different geometrical configurations of incident beam and observation space. These aberrations, which are inherently associated with the diffraction process, are precisely the effects ignored when making the usual Fresnel and Fraunhofer approximations.

Effects of dilution on a six-element synthetic aperture.

An investigation was made of the effects of dilution on a six-element synthetic aperture. The characteristics of both the spread function and the transfer function were obtained for several degrees of dilution. It is shown that small degrees of dilution result in a significant gain over the performance of a single element, whereas more dilute apertures are inferior for direct imagery.

Measurement of the three-dimensional microscope point spread function using a Shack-Hartmann wavefront sensor.

We present a technique to measure the wavefront in the exit pupil of a microscope to determine the microscope's three-dimensional point spread function (PSF) experimentally. The wavefront yields the microscope PSF through a Fourier transform that models propagation of light from the exit pupil to the image plane. A Shack-Hartmann wavefront sensor is used to measure the wavefront shape by recording lateral displacements of a grid of focused spots created by a lenslet array. The displacement of each spot is related to the local wavefront slope. Thus, with appropriate sampling across the exit pupil, the entire wavefront can be reconstructed. This technique does not require the use of a sub-resolution object to obtain the three-dimensional microscope PSF. Consequently, larger, brighter fluorescent objects may be imaged, thereby reducing the requirements for detector sensitivity and leading to a three-fold increase in the axial range over which the PSF is measured. The Shack-Hartmann technique results in a description of the PSF as a continuous function whose sampling is not dependent on the size of the CCD pixels. The Shack-Hartmann sensor is not limited by the numerical aperture of the objective and can easily be calibrated to measure the PSF at any wavelength.

In situ microviscoelastic measurements by polarization-interferometric monitoring of indentation depth.

new type of computer-controlled instrument has been developed to measure microviscoelastic properties of thin materials. It can independently control and measure indentation loads and depths in situ revealing information about material creep and relaxation. Sample and indenter positions are measured with a specially designed polarization interferometer. Indenter loadings can be varied between 0.5 and 10 g and held constant to +/-41 mg. The resulting indentation depths can be measured in situ to +/-1.2 nm. The load required to maintain constant indentation depths from 0.1 to 5.0 microim can be measured in situ to +/-3.3 mg and the depth held constant to +/-15 nm.

Design for a fast fluorescence laser scanning microscope.

The design of a fast fluorescence laser scanning microscope is described and illustrated, with discussion of the design consideration of the principal components, including the optical elements. The system, now under construction at the Optical Sciences Center of the University of Arizona, is expected to provide very-high-speed scanning, at a high spatial sampling density, of large object areas while retaining a flexibility of applications. The projected scanning rate approximates the rate achieved by flow cytometry; the projected rates of information generation should be orders of magnitude higher.

Ultrafast laser scanner microscope: design and construction.

The design of an ultrafast laser scanner microscope has been completed, and an experimental model has been constructed. Details of the novel objective lens design, the automatic focus system, the high-speed polygon scanner and the fast clock system are given. Results from initial tolerance testing as well as the first recorded images are presented.