Koji Tenjimbayashi

Point spread function of optical microscopes imaging through stratified media

We propose a model for imaging point objects through a dielectric interface or stratified media. The model is applicable to conventional and confocal fluorescence microscopy, with single- or multiphoton excitation. An analytical solution is obtained in the form of readily computable functions. When large mismatches occur in the refractive indices of the media of the objective lens and specimen the illumination and detection point spread functions differ significantly, showing that currently used imaging models may fail to correctly predict imaging properties of optical microscopes.

Diffractive element in optical inspection of paper

A computer-generated diffractive optical element to produce 4 x4 spot matrix images was fabricated by electron-beam lithography. The element was applied to the inspection of paper sheets. Images of spot matrices were analyzed, and agreement between the reflectance measured by the present sensor and a spectrophotometer was observed. The sensor image was able to yield information about local curvature as well as defects. Moreover, sensor images from surfaces of different paper samples revealed material surface anisotropy in the cross-correlation analysis of image data.

Light propagation in periodic microcavities

We demonstrated light propagation in a type of optical waveguide, which consisted of periodically arrayed dielectric particles. Although the form is similar to a photonic crystal waveguide, our method used resonance frequencies instead of band-gap frequencies. Advantages provided by this waveguide are that dynamic optical interconnection can be realized and that a multichannel waveguide is easily formed. To fabricate the system of periodic microcavities, we used polystyrene-latex particles that have a uniform size of 15.6 μm. Some discrete frequencies of fluorescence were selected to agree with the phase matching condition and they were propagated through the microspheres. The assembled microspheres can be taken as a multichannel waveguide.

Image processing and analysis of digital speckle pattern interferometric images for monitoring/surface vibration/tilt

A digital speckle pattern interferometric system to monitor surface vibrations and out of plane tilt is presented. The resolution of the system used to measure the out of plane displacement is 1/2 per fringe.

Computer simulation of the scatter plate interferometer by scalar diffraction theory.

Detailed computer simulations of the scatter plate interferometer with random scatterers in the scatter plate are performed, for the first time to our knowledge, by use of the scalar diffraction theory in the paraxial domain. It is shown that the computer simulations produce output image patterns of the expected qualitative characteristics. A qualitative comparison of the computed pattern with the experimentally observed pattern is presented. The effects of translation of the scatter plate and distortion and tilting of the test object are also successfully simulated by the computer.

Testing of off-axis parabola by holo-shear lens

To test quality of the wavefronts number of arrangements are discussed in literature. Out of these the lateral shearing interferometers using diffracting elements are stable and simple devices. Lateral shear obtained by J.C. Waynt, rotation of two gratings by Hariharan et al and Rimmer and Waynt over come some of the drawbacks suffered by Ronchi interferometers. It has already been demonstrated that the two slightly displaced off axis zone plates acts exactly like a double frequency grating. This paper describes the holo-shear lens made on dichromatic gelatin for testing of off axis parabola. Joenathal et al investigate lateral shear interferometry with holo shear lens.

Electron beam fabrication of scatter plate for scatter plate interferometer

Abstract We have fabricated a computer-generated point symmetrical scatter plate with a negligible symmetry error for a scatter plate interferometer using electron beam writing equipment. The feature size of the scatterers in the scatter plate was 5 μm. The small scatterer size permits to test small f -number mirrors since the scattering angle of the light is large. This is the first example of such a fabrication of a scatter plate for the scatter plate interferometer. In this paper the advantages of the electron beam writing of a scatter plate are discussed and interferometric experiments are presented.

Polarized confocal theta microscopy

We propose a comprehensive treatment of theta microscopy based on dipole emission, which better describes fluorescence emission than the isotropic emission model, as fluorescence emission is often polarized. Formulas describing the point spread function for polarized confocal fluorescence theta microscopy are given. Examples are given and some advantages of polarized theta fluorescence microscopy are presented.

Straightness measurement of a moving table by using laser beams

A new method to measure the straightness of a moving table by using a laser beams is proposed. The straightness of a moving table consists of three rotation angle errors and two parallel displacement errors. The former error components are measured by two sets of parallel mirrors and the latter by a corner-cube mirror.

Integrated scatter plate and projection lens for scatter plate interferometer

Scatter plate interferometers provide a precise method to test the quality of concave mirrors. In this article we describe a method to integrate a scatter plate and a projection lens into a single binary micro-optical element, which is a crucial part of the scatter plate interferometer. We have designed an integrated element with the aid of a computer and fabricated it using the e-beam lithography method. We present experimental verification and some computer simulation results.