Showing papers on "Zone plate published in 1989"

Diffractive multifocal optical device

Abstract: A bifocal lens of the Cohen lens design utilizing phase zone plate optics and a facet depth of one-half wavelength of the design wavelength, where the primary focal points are at two orders, specifically the 0 th and 1 st orders, and the brightness at each primary focal point is equal at about 0.40.

Progressive intensity phase bifocal

Abstract: An ophthalmic lens including a carrier lens having an anterior and a posterior surface. A zone plate is having a plurality of zones is disposed annularly about the optical axis of the carrier lens on at least one of the anterior or posterior sides. Each of the zones of the zone plate is spaced from the optical axis in proportion to the square root of n, where n is the zone number. At least one echelette is disposed in each of the zones, each of the echelettes having a surface through which light propagating along the optical axis traverses. The surface of the echelettes varies in a predetermined manner from the zone nearest the optical axis to the zone furthest from the optical axis so that as the size of the aperture disposed along the optical axis changes, the relative intensity of light diffracted to desired orders changes. A step is provided between each of the echelettes, the height of each step having substantially the same optical path length.

Multifocal optical device with novel phase zone plate and method for making

Abstract: A diffractive multifocal optical element comprising a phase zone plate of a Cohen lens design containing rotationally symmetrical, curved repetitive patterns designed to operate at a specific wavelength and which are also curved in r 2 space.

Position detector employing a sector fresnel zone plate

Abstract: A position detector for use with an X-ray exposure apparatus and the like includes sector Fresnel zone plates (SFZP) which are provided on a mask (14) and a wafer (15) minutely spaced in position in the direction of the optical axis of an exposure X-ray, as alignment marks (16, 17). A laser ray of at least one wavelength is applied to the surfaces of the SFZPs at an angle with respect to the surfaces. The SFZPs are designed such that the principal focal planes of Fresnel diffraction images of the SFZPs to a single wavelength laser ray agree with each other. In the case of illumination rays of a plurality of wavelengths, an objective lens (9) is provided in a detection optical system (10) which objective has such an axial chromatic aberration that focal planes of the objective lens to the plural wavelength rays agree with respective Fresnel diffraction focal planes of the SFZPs to the rays. The image formed on the superposed focal plane of the objective lens is converted into an electric signal, which is handled to detect a relative position between the mask and wafer in the direction perpendicular to the surface thereof.

Electrically Controllable Liquid Crystal Fresnel Lens

Abstract: Two orthogonally aligned liquid crystal lenses with spherical Fresnel zone plate electrode configurations have been demonstrated to focus an unpolarised broadband object with resulting good quality images. Switch on times of 15ms are reported along with modulation depths of 91.5%.

Reflection micro-Fresnel lenses and their use in an integrated focus sensor.

Abstract: Blazed reflection micro-Fresnel lenses and their use in an integrated focus sensor are proposed. Theoretical analysis indicates that the optical characteristics of reflection Fresnel lenses can be improved compared with a conventional transmission micro-Fresnel lens. These reflection Fresnel lenses were fabricated using electron-beam lithography and exhibited the diffraction-limited focusing characteristics with 71% high efficiency. The focus sensor has a folded optical path and includes a beam splitter integrated with thin film components, such as a reflection elliptical Fresnel lens and a quadrant photodetector. The reflection elliptical Fresnel lens in the focus sensor exhibiting excellent astigmatic characteristics agreed with the theoretical results, and the focus error signal was detected. This sensor can be developed as the optical head of an optical disk system.

Characterization of sliced multilayer zone plates for hard x rays (invited)

Abstract: Circular zone plates for hard x rays, fabricated by dc planar magnetron sputtering, have been characterized using monochromatized synchroton x rays. The zone plates consisted of either 5 or 20 pairs of altenating WSi2 and C layers. The minimum focal spot size attained was less than 3 μm× 10 μm in the vertical and horizontal directions, respectively. The efficiency of the zone plate with 20 layer pairs was determined to be about 4.5%. An x‐ray transmission image of a No. 2000 mesh Cu grid and an x‐ray fluorescence image of a patterned Co thin film were measured, and it was demonstrated that a high‐resolution image could be obtained with the present zone plate. The possibility of implementing the phase zone plate in hard x‐ray range is considered.

Diffraction calculations in the near field and the validity of the Fresnel approximation

Abstract: The general theory of the diffraction and propagation of light is considered. Particular attention is paid to the case of uniformly illuminated rectangular or circular apertures, for which the derivative of the field given by the Fresnel approximation is evaluated exactly. The limitations of the Fresnel approximation are considered, and thus a useful, simple way of understanding its validity is produced. This treatment yields an estimate of the accuracy of the Fresnel approximation in the general case and a method by which a modified Fresnel treatment can be used over a substantially extended region.

Holograms For Optical Interconnects For Very Large Scale Integrated Circuits Fabricated By Electron-Beam Lithography

Abstract: High performance holograms are a crucial part of realizing the predicted benefits of optical interconnection of electronic circuits. Fabrication of computer-generated holograms using electron-beam lithography provides access to the needed performance but presents new challenges in design, encoding, and data handling. Two holograms are described that represent different approaches in each of these areas. The first hologram connects a single laser source to several widely separated detectors. A paraxial imaging arrangement allows the holographic interferogram to be encoded as concentric circles of a Fresnel zone plate. The second hologram was designed to replace the row address lines on a 1 kbit RAM chip. In this case, broad separation of the sources prohibits use of the paraxial approximation. Instead, a piecewise approximation to the optimal phase function is encoded with a closed-contour fringe-tracing algorithm. Both holograms were evaluated in experimental systems involving photodetectors integrated onto a VLSI circuit chip and a discrete semiconductor laser.

Vehicle lamp lens having Fresnel lens

Abstract: A lens adapted for use in vehicular lighting employs a Fresnel configuration despite the fact that the lens has no axis of revolution and is formed as a quadric surface to meet vehicle design needs. The basic lens design is obtained by orthographically projecting a planar Fresnel pattern onto the quadric surface. The surfaces of the Fresnel steps are formed so that light emanating from a rear focus is converted into substantially parallel beams by reflection/reflection through the lens. The surfaces may have continuously or incrementally varying angulation, and may be formed by cutting using a 3 or 5 axis milling cutter.

Alignment of mask and semiconductor wafer using linear fresnel zone plate

Abstract: A system for aligning a mask and a semiconductor wafer comprises radiation source for producing a radiation beam, a dual focus linear Fresnel zone plate provided on the mask for focusing the radiation beam incident thereto on a surface of the semiconductor wafer which comprises a first part having a first focal length and a second part having a second focal length substantially smaller than the first focal length, a diffraction grating provided on the surface of the semiconductor wafer in correspondence to the dual focus linear Fresnel zone plate for diffracting the radiation beam focused thereon, a detector held with a predetermined relationship with respect to the radiation source and the mask for detecting the diffracted beam, a movable stage for supporting the semiconductor wafer, and a controller for moving the stage means responsive to an output signal of the detection means.

Arrangement for aligning a lens and opto-electronic component in free beam technology

Abstract: An arrangement for the optical coupling of optical and/or opto-electronic components in free-beam technique includes a lens that is integrally formed with a semiconductor wafer. The semiconductor wafer simultaneously serves as an adjustable carrier. A planar Fresnel lens structure, Fresnel zone plate structure or holographic lens structure may be incorporated into the semiconductor wafer. The coupling arrangement of the invention is employed in light wave guide components and particularly laser modules.

Fabrication Technology And Applications Of Zone Plates

Abstract: The focusing properties of zone plates have a long history spanning over a century. The fabrication technology has continually improved and has made significant advances in the last decade so that zone plates now can be fabricated with the smallest zone widths of several tens of manometers and near diffraction limited performance. For applications such as x-ray microscopy, these high resolution zone plates allow the possibility of observing biological samples in a natural, i.e. wet, environment with resolution an order of magnitude better than optical microscopy. In addition to microscopy, zone plates are critical to many x-ray applications where the focusing, imaging, and dispersive properties can be put to use. The key challenges for making better zone plates are to improve the efficiency and resolution while maintaining comfortable working distances and extend the wavelength range available. In order to meet these challenges, refinements in zone plate fabrication technology, better line placement distortion measurement/control techniques, and new processing ideas are under development.

Image-convolution and enhancement apparatus

Abstract: This is an apparatus for sharpening and otherwise enhancing images such as those produced on a screen or on the face plate of a cathode-ray tube. Regarding an image as being composed of a very large number of elements called "pixels," the apparatus of this invention enhances those of the pixels which appear at points of rapid transition between light and shade in the image. The apparatus comprises a plurality of substrates superimposed upon one another, optically in series. A first such substrate includes an array of filters and lenses which together form a "mask" that operates upon selected portions of the light input thereto to multiply certain portions of the light input with respect to certain other portions of the light input. The light upon which this operation has taken place proceeds to a second substrate where it is detected to generate electrical signals expressive of the intensities of the respective portions of the light input. The detectors cooperate with the filters and lenses of the first substrate to accomplish the aforementioned multiplication and may process the light in accordance with a so-called Laplacian distribution. The lenses of the first substrate may be three-dimensional lenses called "negative lenses." Alternatively, they may be two-dimensional devices called Fresnel zone-plate elements, one such zone plate for each of the aforementioned pixels. In a variation of the invention, the first substrate and the second or detecting substrate may be disposed close to the face plate of a cathode-ray tube. Light is conducted from the face plate to the first substrate by means of fiber optics. The image of the cathode-ray tube is thus enhanced and may be re-displayed directly or may be conveyed to a remote location by summing the detected outputs from the second or detecting substrate and transmitting the summed outputs to a remote display unit.

X‐ray imaging of nanostructure patterns

Abstract: A Fresnel zone plate lens, with a nominal outer zone width of 400 A, has been used to image nanostructures with soft x‐ray synchrotron radiation at 45 A wavelength with the Gottingen x‐ray microscope at BESSY in Berlin. The structures, consisting of gold lines in thin silicon nitride membranes, were selected for tests of spatial resolution and image forming capabilities. Several patterns associated with deep submicron electronic circuits were also imaged, showing clearly resolved features smaller than 0.1 μm. Images of periodic structures, including 600 A lines on 2000 A centers, suggest a spatial resolution approaching the theoretical limit of approximately 500 A.

Phase type zone plate

Abstract: PURPOSE:To obtain the efficiency of utilizing light as sufficiently high as the efficiency of a blazed Fresnel zone plate in practicability by constituting a phase type zone plate in such a manner that the optical path difference between the 1st rays passing respective zones and the 2nd rays passing the optical axis is 2nd integer times a fraction of the 1st integer of the wavelength to be used and that the 1st integer is >=3. CONSTITUTION:The diffracted light rays from the plural zones 13A1-13A4, 13B1-13B4, 13C1 of the prescribed optical path differences are condensed onto the optical axis LO so as to be intensified by each other. The zone plate is so constituted that the optical path difference between the 1st rays passing the respective zones and the 2nd rays passing the optical axis consists of the 2nd integer m times a fraction of the 1st integer M of the wavelength to be used and that the 1st integer M is >=3. The 1st rays passing the respective zones 13A1-13A4, 13B1-13B4, 13C1 are, therefore, condensed at such a phase at which said rays are intensified by the 2nd rays passing the optical axis at the image point on the optical axis LO with each other. The much higher efficiency of utilizing light than the efficiency of the conventional phase type zone plate is thereby obtd.

Resolving Power of Zone Plates

Abstract: The performances of different types of zone plate are analysed and compared. It is shown that, with a modified geometry, the resolution closely matches that of a diffraction-limited lens.

Phase zone plate for x-ray microscope for bioobservation

Abstract: PURPOSE:To relieve the restriction on the intensity of a light source and the sensitivity of an image pickup medium and to enable bioobservation with high accuracy and high sensitivity by forming a phase ring band of titanium, vanadium chromium. CONSTITUTION:An X-ray microscope for which a phase zone plate is used is constituted of an X-ray source 4, a condensing phase zone plate 5, a sample holder 6, an objective position zone plate 7, an image pickup device 8 and a vacuum chamber 9. Since the X-rays of a wavelength region used for observation are absorbed by air, the entire part needs be put into the chamber 9 and, therefore, the holder 6 is hermetically closed and a window to allow transmission of X-rays is provided at the time of observing the vital samples which live in liquid. The condensing phase zone plate 5 and the objective phase zone plate 7 are formed of the ring band consisting of the titanium, vanadium or chromium. The bioobservation with the high accuracy and high sensitivity is thereby enabled.

Focussing device for a microwave antenna

Abstract: A focussing device for a microwave antenna comprises a zone plate(1) which is all transparent to visible light whereby the device can be used as a window without unduly adversely affecting the passage of visible light through the window.

Fabrication of diffraction X-ray elements

Abstract: The use of focusing elements in the X-ray range shows promise for nondestructive chemical analysis of samples with spatial resolution up to fractions of a μm. This paper considers the problems of fabricating Fresnel zone plates of different types: amplitude- and phase-transparent zone plates and reflective zone plates formed on a multilayer mirror, as well as microstructures with a specified zone profile.

Soft x ray microscope using Fourier transform holography

Abstract: A Fourier transform holographic microscope with an anticipated resolution of better than 100 nm has been built. Extensive testing of the apparatus has begun. Preliminary results include the recording of interference fringes using 3.6-nm X-rays. The microscope employs a charge-coupled-device (CCD) detector array of 576 × 384 elements. The system is illuminated by soft X-rays from a high-brightness undulator. The reference point source is formed by a Fresnel zone plate with a finest outer zone width of 50 nm. Sufficient temporal coherence for hologram formation is obtained by a spherical grating monochromator. The X-ray hologram intensities at the recording plane are to be collected, digitized and reconstructed by computer. Data acquisition is under CAMAC control, while image display and off-line processing takes place on a VAX graphics workstation. Computational models of Fourier transform hologram synthesis, and reconstruction in the presence of noise, have demonstrated that numerical methods in two dimensions are feasible and that three-dimensional information is potentially recoverable.

Back projection type stereoscopic video projection televiation

Abstract: PURPOSE: To improve the stereoscopic feeling of a video by using such a Fresnel lens sheet that the mean birefringence in the plate thickness section of the Fresnel lens sheet satisfies a specific condition. CONSTITUTION: The subject projection television is constituted by using the Fresnel lens sheet 2 whose mean birefringence ▵n in the plate thickness section satisfies expression 1, where (t) is the thickness of the Fresnel lens sheet 2, λis the wavelength of light transmitted through the Fresnel lens sheet 2, and θ 1 is the angle of refraction after the incidence of light on the Fresnel lens sheet 2. Consequently, the polarization deviation of image light 3 which is already polarized due to the birefringence presenting in the plate thickness section of the Fresnel lens sheet 2 constituting a screen can be suppressed below a specific value as a phase difference, so the video light 3 which is polarized circularly to the right or left or polarized horizontally or vertically so as to obtain a stereoscopic video can be projected on the screen. Consequently, the video which provides stereoscopic feeling can be observed. COPYRIGHT: (C)1991,JPO&Japio

X‐ray lithography two‐state alignment system

Abstract: We present a novel alignment system for x‐ray lithography. A linear Fresnel zone plate, defined on the mask, is used to focus a laser beam on a wafer mark (a series of dots). A fast electro‐optic modulator is used to make the laser beam hop between two positions at the mark edges. The light diffracted by the periodic mark is measured at each position and a misalignment signal is originated when the mark is not illuminated equally in the two states. A signal that is proportional to the misalignment is generated when the error is within the alignment range (±0.2 μm); outside that range a capture signal is present as long as the beam is on the mark, which would be typically 2–4 μm wide. The method is highly sensitive with resolution in excess of 0.003 μm, has a wide capture range, no moving parts, and is suitable for real‐time alignment during exposure. Sensitivity to gap changes is highly reduced, making the system ideal for synchrotron‐based x‐ray lithography aligners.

Optical element and microscope using said element

Abstract: PURPOSE:To improve operability by installing a Fresnel zone plate for a short wavelength for the purpose of the electromagnetic wave of the wavelength belonging to a wavelength region consisting of a soft X-ray region and UV region and a Fresnel zone plate for visible light on the same plane. CONSTITUTION:A sample 6 is supported by a moving mechanism 7 and is positioned behind a mirror 4 and an optical element 8 is supported and positioned by a moving mechanism 14. He-Ne laser light 2 is first projected on the sample 6 in a state of the air in a vacuum chamber is not evacuated, i.e., in atm and the magnified image of 5mum is imaged on the Fresnel zone plate 8 by the diffracted light of the He-Ne laser light transmitted through the sample. This image is photographed by a television camera 12 and is observed by a monitor television 13. The magnified images of Al of 5mum and 0.05mum are obtd. on the same imaging plane as the image plane for the He-Ne laser light when the soft X-rays are projected on the sample after the mirror 4 is retreated and the air in a vacuum chamber 15 is evacuated. The need for focusing and aligning of the soft X-rays is thus eliminated by using the optical element which can be aligned in the atm.

Reflection-Zone-Plate Antenna

Abstract: Microwave antenna, based on reflection holography, designed and tested. Modified to produce arbitrary beam patterns by controlling relief pattern. Antenna planar or contoured to supporting structure. Low off-axis radar cross section at frequencies removed from operational frequency. Interference pattern produced by spherical wave intersecting plane wave consists of concentric circles similar to Newton's rings. Pattern identical to Fresnel zone plate, which has lens properties. Plane wave incident on hologram, or zone plate, focused to point.

New Evaluation Approach of Alignment Signal from Resist-Coated Patterns

Abstract: A new evaluation approach of alignment signals from resist-coated patterns using a linear Fresnel zone plate alignment method is described. In most alignment methods, signals are greatly influenced by resist topography on the target pattern. For calculations of alignment signals, Fraunhofer diffraction from the target pattern and optical path change through the resist materials are considered. In order to determine resist topography on the pattern, a mass transport method is introduced. Based on these results, a target pattern of shallow step depth (0.09 µm) is selected as the best target for alignment, and an alignment accuracy of 0.09 µm (3σ) is obtained.

Position alignment apparatus

Abstract: PURPOSE:To detect a position satisfactorily by eliminating an influence due to an increased chromatic aberration and with little error by a method wherein an optical element which acts as a lens with reference to an alignment beam and does not have an influence on an exposure beam is provided. CONSTITUTION:After a + or - first-order diffraction beam out of diffraction beams diffracted by a diffraction grating 3 has passed through a reduction-projection lens 4, it is incident on Fresnel's zone plate 5 and forms an image of the diffraction grating 3 on a reticle 7. Because a zero-order beam is shut off by a beam bender 9, it does not reach the reticle 7. An interval of the image formed by the + or - first-order diffracted beam becomes half an interval of the diffraction grating 3 on a wafer 2. This formed image pattern, a diffraction grating pattern 8 on the reticle 7 and a moire fringe are detected by using an image detection means 12 via a mirror 10; their signal is sent to a position control means 14; an alignment operation is executed on the basis of this signal. By this setup, because a chromatic aberration and a mechanical error can be eliminated, the precise alignment operation can be executed stably.

Design and fabrication of condenser zone plates for a soft x‐ray microscopy beamline in Hefei

Abstract: A synchrotron radiation soft x‐ray beamline for scanning microscopy mainly, is being constructed in Hefei. It contains a linear monochromator consisting of a diaphragm of 7 μm diameter and one of three condenser zone plates (CZP). The three CZPs are for three overlapping wavelength ranges 1.97–2.78 nm (CZP23), 2.74–3.87 nm (CZP32), and 3.84–5.44 nm (CZP45), respectively. The processing steps for the condenser zone plate fabrication are summarized, especially the holographic exposure with a special optical system as a key step. Parameters of a prototype of CZP45 fabricated in Hefei are the following: D=2.9 mm, n=826, R1=0.05 mm, and ΔRn≊0.9 μm.

Device for detecting position

Abstract: PURPOSE:To homogenize a distribution of outgoing beams and improve positioning accuracy by a method wherein a plural number of light fluxes are provided and a light flux having a cross section according to the shape of a physical optical element is formed by overlapping a portion of the light fluxes. CONSTITUTION:Light beams emitted from light sources 1, 1a are made parallel by projector lenses 2, 2', respectively, and enters an exposure region including an alignment mark 41M via a beam splitter 92. the alignment mark 41M has a function of a convex lens which focuses the beam to a point Q on a transmission-type zone plate. A wafer alignment mark 41W has a function as a convex mirror which focuses the beams focused to the point Q and forms an image on a detecting plane 90 of a photodetector 38. Difference in position is calculated by the photodetector 38 and a wafer stage 102 is transferred according to this calculated value so as to align a mask 101 and a wafer 102.