Showing papers on "Zone plate published in 1979"

Phase shift multifocal zone plate

Abstract: A multifocal zone plate construction suitable for use in optical systems with multifocal requirements. It is designed as a phase shift multifocal zone plate to provide multiple focii with bright images. This is accomplished by adjusting the zone plate spacings such that some of the zone plate focii actually coincide with some of the multifocal Fresnel lens focii.

X-ray zone plates fabricated using electron-beam and x-ray lithography

Abstract: Fresnel zone plate patterns, free of spherical aberration, with diameters of up to 0.63 mm and linewidths as small as 1000 A were fabricated on polyimide membrane x‐ray masks using scanning electron beam lithography. Distortion of the electron beam scan raster was reduced to ?2500 A over a 2×2 mm field by applying deflection corrections, while viewing the distortion using a Moire method. CK x‐ray lithography was used to replicate the zone plate pattern in thick PMMA over a 100 A thick plating base on a glass substrate. Zones plates in 1.3 μm thick gold were fabricated by plating, and made free‐standing by removal of the plating base and the supporting glass substrate. Zone plates were tested as imaging elements with visible light and soft x‐rays.

Aberration corrections for a POS hologram scanner.

Abstract: Use of an optically generated IZP (interferometric zone plate) hologram scanner enables highly accurate reading in a supermarket point-of-sale (POS) label reader with a simple optical arrangement. The laser beam spots on the scanning plane which construct the lattice scan pattern designed for the POS label reader cause severe aberrations when a conventional IZP hologram is used. A simple and effective method for removing the aberration is discussed from both the theoretical and experimental aspects, and the feasibility of the method is demonstrated. This method employs oblique-angle coherent plane-wave illumination in the IZP hologram recording process.

White light diffraction patterns of amplitude and phase zone plates

Abstract: The polychromatic properties of the Fresnel zone plate, Gabor zone plate, phase reversal zone plates and kinoform lens are studied. The polychromatic intensity in the diffraction patterns on these plates has been computed and the influence of Gaussian spectral filters is shown. Also, the distributions of illuminance and chromaticity in the diffraction patterns and along the optical axis, have been calculated for several zone numbers. The results obtained are discussed and compared for the different plates.

Frequency-modulated zone plate for coherent noise reduction.

Abstract: Laser images and holographic reconstructions are highly affected by dust and imperfections present in various optical components of the imaging system, which create noiselike structures in the final images. To reduce this speckle noise, a phase plate based on a frequency-modulated zone plate is proposed. It can be fabricated by holographic techniques, and it does not require a separate Fourier transforming lens. Experimental results are presented showing the capabilities of the phase plate.

Recording and reconstructing method of hologram

Abstract: PURPOSE:To obtain scanning lines of high quality , in a hologram constructed by recording interference patterns of plane waves and spherical waves, by making the wavelength in reconstruction different from that in construction, changing its ratio, and reducing the aberration on the plane spaced a certain distance from said hologram CONSTITUTION:When making an interference zone plate (IZP), an interference pattern of plane wave 11 with wavelength lambda1 inciding vertically and spherical wave 12 with wavelength lambda1 spaced from point S1 to IZP by distance flambda1 is composed on IZP When reconstructing, by inciding spherical wave 13 with wavelength lambda2 from point S2 spaced from IZP plaue distance (a), the aberration of polarized light 14 at point P spaced from IZP plaue by distance b(x) will be reduced in relation with ratio 2/lambda1 of the wavelength lambda1 in making hologram to the wavelength lambda2 in reconstruction