Showing papers on "Zone plate published in 1983"

Method of forming laser diffraction grating for beam sampling device

Abstract: A combined holographic grating that samples a high energy laser beam and focuses the sample into a spot is formed by the cross-modulation term of a linear holographic grating and a holographic zone plate

The Effects of Manufacturing Inaccuracies on the Imaging Properties of Fresnel Zone Plates

Abstract: The imaging properties of Fresnel zone plates are discussed in terms of possible manufacturing inaccuracies such as non-circularity and displacement of zones. The degradation of the on-axis intensity is used to establish manufacturing tolerances.

Method for manufacturing Fresnel phase reversal plate lenses

Abstract: A Fresnel phase plate lens of either the phase reversal plate or sinusoidal phase reversal plate type is formed in materials hitherto not available to be used to Fresnel phase plate lenses. The material for the desired Fresnel phase plate lens may be chosen for its optimum spectral transmission range. For example, for infrared spectral transmission, silicon and germanium are chosen for the materials to have the Fresnel phase plate lens formed therein. For the visible spectral transmission range various glasses such as crowns, flints, and borosilicates glasses of suitable optical quality are useful. High silica glasses and fused quartz (silicon dioxide) are useful as the lens material for ultraviolet spectral range.

Electrooptic Fresnel lens-scanner with an array of channel waveguides

Abstract: A new type of beam scanner is discussed based on a 1-D Fresnel zone plate consisting of titanium-diffused channel waveguides on LiNbO3. By electrooptically controlling the guided-wave phase, both beam scanning and 1-D focusing are achieved without a condensing lens. It was experimentally confirmed using the scanner with twenty-one Fresnel zones that the beam spot with a diameter of ∼50 μm at half-power level of diffraction pattern is scanned over a distance of ±70 μm in the focal plane with an applied voltage of ±40 V at 633 nm.

Fresnel zone plate

Abstract: PURPOSE:To eliminate a difference in sphericity and to reduce coma-aberration by regarding the concave surface side of a plano-concave lens as an incident surface where parallel light strikes, forming a Fresnel zone on the plane side, and specifying the radii of rings and the thickness, refractive index, radius of curvature, etc., of said plano-concave lens. CONSTITUTION:A Fresnel zone plate 3 uses the concave surface of the plano- concave lens 19 as the incident surface where the parallel light strikes and has the Fresnel zone 2 on the plane side; and simultaneous equations I -VI hold for radii of rings, and the refractive index, thickness, and radius of curvature of the plano-concave lens 19 are so determined that the evaluated amount of residual coma-aberration is reduced, thereby reducing the spot diameter of a diffraction limit and coma-aberration in a transparent material 8 which has a >=1 refractive index. Thus, the radii rk of rings of the Fresnel zone, thickness d1 and refractive index n1 of the concave transparent plate, and thickness d2 and refractive index n2 of the parallel transparent plate are determined, and consequently the coma- aberration of projected light is eliminated even if the incident parallel light slants to an optical axis, so that a sharp spot is obtained at a convergence point 7.

Rear projection television screen having a multi-surface Fresnel lens

Abstract: A rear projection television receiver comprising a rear projection screen that incorporates a compound Fresnel field lens. The field lens comprises two circular Fresnel lenses that together provide the total refraction for the light impinging on the screen. The angle of incidence of the light striking the individual Fresnel elements is reduced, thereby reducing the amount of light reflected from the Fresnel surfaces. The screen efficiency, especially near the edges of the screen, is thereby increased.

Self-imaging Phenomenon Lateral Shift of Fresnel Images

Abstract: The conditions determining the lateral localization of Fresnel images of a linear binary amplitude grating with respect to the optical axis are derived. The conditions represent the third basic parameter, besides the axial localization and the lateral magnification, characterizing the diffraction images formed by the self-imaging phenomenon.

Application Of Zone Plates To Alignment In X-Ray Lithography

Abstract: Fresnel zone plate patterns, when printed on masks and wafers and suitably illuminated, form images that are useful for alignment in microlithography. These images are observed to be largely unaffected by poor edge definition or by pattern defects arising from variations in processing and linewidth control. This paper describes how these zone plates are used for automatic alignment in x-ray lithography. To obtain high contrast bright images with good signal-to-noise ratio (important in automatic alignment), the zone plates are illuminated with a collimated HeNe laser beam. The images formed at the focus are found to be nearly diffraction limited with diameters determined by the zone plate aperture ratio. With zone plates approximately 100 um in diameter and 300 um focal length, we have observed signal-to-noise ratios better than 20 dB and have been able to obtain position accuracies better than ±0.1 um. Our geometry is chosen so that magnification errors in the mask or wafer up to ~1 um are automatically compensated. A microprocessor-based system that performs all the alignment functions automatically is described.

Zone Plate Encoded Neutron Holography

Abstract: Recent progress in the understanding of the neutron holographic process is summarized, together with some new experimental results. System limitations are identified and the results of a Monte Carlo simulation of the technique are presented.

A zone plate shadow camera for 100 keV x rays and 6 MeV protons

Abstract: We have fabricated and tested a zone plate coded imaging camera for use with high energy x rays and charged particles. The camera system has demonstrated a higher order resolution capability of 4 μm with 100 keV x rays and 9 μm with 6 MeV protons. The unique components of this zone plate shadow camera are its thick zone plate coded aperture and recording medium for protons. The coded aperture is a free‐standing, 75 μm thick, gold micro‐Fresnel zone plate with 30 μm minimum zone width. It was fabricated by extending reactive ion etching and gold microplating techniques to ‘‘thick’’ structures. The proton recording medium is CR‐39, a polycarbonate plastic, which serves as a high resolution nuclear track detector highly sensitive to protons.

Variational design of zone plates for the VUV and soft X-ray ranges

Abstract: Many materials become appreciably translucent in the soft X-ray range, making them suitable for use as optical elements. However, since none is Perfectly transparent, it is crucial that optimum design procedures be followed in order to minimize unnecessary optical losses. In this paper we demonstrate such a solution for the ordinary metallic zone plate and compare its performance to some recently proposed configurations which were advanced on the basis of more restricted considerations.

An Approach To Real Time Holography

Abstract: Various diagnostic procedures in medicine, industry and defense produce 3-Dimensional data bases adequate to calculate a hologram. In most cases the nearer to real time the hologram can be produced the more beneficial. Since a hologram is a superposition of Fresnel zone plate patterns from each point source in the object volume on to the image plane a cellular array processor is suggested which will produce a factor of a million reduction in the time to calculate a hologram.© (1983) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

A Lithography System For X-Ray Process Development

Abstract: An x-ray system usable for process development and pilot line production is described, which utilizes technology based on a fixed palladium anode source. The alignment system employs three microscope objectives and optical channels to view the appropriate alignment target. The optical system has been optimized for use with circular fresnel zone plate targets. Alignment is electronically assisted using a detection system and associated electronics. The wafer stage is piezo motor driven with 6 degrees of freedom capable of placing the wafer under the mask within the allowable tolerance. The stage design incorporates a combination of flexures and air bearings to achieve the required precision. Essential features of the source, stage and alignment subsystems are described.

Detector for inclination of plane plate

Abstract: PURPOSE:To measure the inclination of a mask stably with a simple constitution, by irradiating an array of Fresnel zones, which is formed on the rear face of the mask, with rays and observing an optical image converged by the reflected light of a wafer. CONSTITUTION:Eight Fresnel zone plates similar to a zone plate 13-8 are arranged on the rear face of a mask 11 to form one set of a zone array 13. When the mask 11 is irradiated with a parallel light from above, the third-order focus of the zone array 13 is observed as a light spot by the reflected light from a wafer 12. If the mask 11 and the wafer 12 are parallel with each other, only a light spot 16 looks bright. If the wafer 11 is inclined, plural zone plates have bright centers. Thus, the inclination of the wafer 11 is measured stably with a simple constitution.

Device for detecting relative position of mask substrate and wafer

Abstract: PURPOSE:To detect a relative position of a mask and a wafer insufficiently spaced from each other by using a Fresnel zone plate, instead of a lens, as an image forming element to be inserted between the mask and the wafer. CONSTITUTION:A Fresnel zone plate 3 which is an aggregate of diffraction lattices becoming finer from the center to wafer with a certain regularity, is located between the mask 1 and the wafer having a registration standard 2a on it. Said Fresnel zone is then irradiated with a monochromatic light with an appropriate wavelength, whereby the image of the registration standard 2a is formed on the registration standard 1a of the mask by way of the Fresnel plate. This image is detected through a mirror 4 and a lens 4 to give information concerning relative position of the mask 1 and wafer 2, based on which precise positioning is made possible. when the standard 1a is focused using a Fresnel plate with a focal length f1, with respect to the wavelength lambda1, the standard 2a is in focus by using the wavelength lambda2 satisfying f1lambda1=(f1+d)lambda2 where d is a distance between the mask and the wafer 2, whereby the detection of relative position is possible at the distance L1not equal to L2, facilitating position detection at the distances of several millimeters - several ten millimeters.

Improvements in or relating to the manufacture of zone plates

Abstract: The use of zone plates has been restricted by low efficiency and marked chromatic aberration. The increasing use of lasers reduces the disadvantage of chromatic aberration; and blazed zone plates have improved efficiency, but have been difficult to make. In the method of the invention, a Fabry Perot interferometer (28), capable of producing a concentric fringe image of high finesse, is made adjustable so that the image can be expanded (or contracted) over, typically, a range one fringe spacing. The image is projected onto a layer (12) of photo resist on a suitable substrate (10). While the image is expanded (say) through one fringe spacing, the light intensity in the image is varied, so that when the photo resist (12) is developed, the radial cross section between any two fringe positions takes on a wedge shape (18); which is that required in a blazed zone plate. Suitable chemical treatment can extend the wedge shape into the substrate partly or wholly. Efficiency of the order of 60% can be achieved.

Holographic Figure Sensing Of Large Primary Mirrors

Abstract: A holographic technique for sensing the optical figure of a deformable mirror is described. This technique uses the coherent summation of subaperture zone plate to achieve full aperture interferograms. As such, it is inherently scalable to arbitrarily large mirrors. Experimental confirmation of feasibility is presented.