Katsuyuki Okada

Measurement of large plane surface shapes by connecting small-aperture interferograms

We propose a method to obtain the shape of a large plane surface by connecting phase distributions measured by a small-aperture interferometer. These separately measured phase distributions cannot be connected directly because the object will tilt or have vertical displacement during the measurements. To correct these errors, the measurements are made so that the adjacent interferograms have common areas, and these interferograms are connected to minimize the difference of the phase distributions in the common areas. A matrix equation is derived to obtain coefficients to correct tilt and vertical displacement, and the accuracy of connection increases in proportion to an exponent of 1.5 of the width of the common area.

Simultaneous calculation of phase distribution and scanning phase shift in phase shifting interferometry

Abstract This paper shows the possibility of finding the phase distribution of the wavefront and the mean phase difference between two interfering beams from the series of interferograms used in conventional phase shifting technique, without any additional measurement. A method for finding these phases is presented which can be applied under weak a nonlinearity of the phase shift.

Separate measurements of surface shapes and refractive index inhomogeneity of an optical element using tunable-source phase shifting interferometry.

A phase shifting interferometer using a tunable laser as a light source is proposed for measuring shapes of both surfaces of a glass plate and the distribution of refractive index. To separate the superimposed interferograms generated with many wavefronts reflected from the plate, the phase shift associated with the wavelength shift is applied in the phase shifting interferometer with unequal optical paths in testing and reference beams. A laser diode is used for the tunable light source, and the data processing for obtaining phase distribution is based on the least-squares fitting in interferograms. The rms errors of the measurements are <1/50 wavelength for the surface shape, and 10(-5) of the refractive index for a 5-mm thick optical glass plate.

Measurement of large plane surface shape with interferometric aperture synthesis

It is difficult to measure the optical surface shape of large area plane using interferometers. A part of the area of the sample is measured repeatedly by using a small aperture interferometer. The connection of the adjacent areas data is made with the aid of the least square method. This paper shows a method of connection of the measurement and shows some results of experiment.

Wavelength Scanning Interferometry For The Measurement Of Both Surface Shapes And Refractive Index Inhomogeneity

A wavelength scanning interferometer is proposed for measuring both the shapes of the front and the rear surfaces and the inhomogeneity of the refractive index of an optical parallel plate. To separate the superimposed interferograms generated with many wavefronts reflected from the plate, it is utilized the property of a wavelength scanning interferometry that the phase shift associated with wavelength shift is in proportion to the optical path difference of the interfering beams. By an experiment, the rms error of the measurement is shown to be less than 1/50 wavelength.

Color conical holographic stereogram

A new method to record a color holographic stereogram and its application in the synthesis of a conical holographic stereogram are presented. The method consists in recording three rainbow holograms on each slit hologram component of the holographic stereogram. To obtain the three images reconstructed on the same place, the position of the projection screen is changed when recording the three rainbow holograms. The difference of the projected images size coming from the movement of the screen is corrected by introducing a cylindrical lens in the projection system. Results of the method, feasibility, and distortion of the image are discussed.

Holographic Three-Dimensional Display Of X-Ray Tomogram

In the field of medical diagnosis, many X-ray tomograms are taken at the different slice planes of affected parts and organs so as to grasp their three dimensional structures. Multiple recording hologram in which all slices are recorded on single holographic material is used for this purpose. To avoid the faults of usual incoherent superposition and to make possible white light reconstruction, we present a new recording method for making a multiple recording hologram. The hologram is made by two step process and can be reconstructed by white light illumination. Some example of hologram is also shown.

Error analysis on the phase calculation from superimposed interferograms generated by a wavelength scanning interferometer

Abstract An error analysis of wavelength scanning interferometry is shown, in which the interferogram obtained is constructed from more than one interferogram. Computer simulations are carried out to confirm the theoretical considerations in calculating the phase distribution of the individual interferograms.

Radius measurement by a zone plate interferometer

In this paper, we propose a differential interferometry to measure the radius of a concave mirror. This technique needs two sequential measurements before and after shifting the sample perpendicular to the optical axis. The radius of the spherical mirror is calculated from the difference of the phase distributions of the interferograms, and so the reference wavefront does not influence the measurement.

Common path interferometer for flat surface measurement

In this paper, we propose a new common path interferometer, that needs only typical beam splitters to split and couple the reference and object beams. Some experiments show the common path configuration reduces the influence of vibration of the mirror effectively.