Showing papers on "Zone plate published in 1997"

Two-dimensional micromechanical bimorph arrays for detection of thermal radiation

Abstract: We demonstrate that two-dimensional arrays of micromechanical bimorphs can be used as thermal sensors to image infrared (IR) radiation. A density of 100 pixels per mm2 is achieved by coiling a bimorph beam into the shape of a flat spiral. Temperature variations of a given spiral are converted to modulations of visible light by illuminating the spiral array with a visible source. The optical properties of the spiral resemble a Fresnel zone plate when light reflected off neighboring rings of the spiral is focused. When a spiral is heated through the absorption of IR radiation, thermally induced bending of the bimorph degrades the focusing efficiency by distorting the spiral. This reduces the optical intensity at the focal point. Arrays of spirals can be monitored with a commercial CCD camera. At 40 Hz, the temperature resolution and noise equivalent power of a 75 μm diam spiral are 50 μK/√Hz and 20 nW/√Hz, respectively, and the thermal response time is 270 μs.

High efficiency diffractive lenses: Deduction of kinoform profile

Abstract: The zone plates (diffractive lenses) are not commonly used as image formation systems owing to their low efficiency and multifocal characteristics. In this paper we make a revision of the Fresnel zone plate principles, and present various kinds of zone plates designed to solve the problem of obtaining a limited number of foci with higher efficiency. The purpose of this work was to design, by using Fermat’s principle, a zone-plate profile with high focusing efficiency in only one or two foci, while maintaining a low efficiency in the others. Applying Fermat’s principle to this task results in the kinoform profile of the plate. Calculation of the kinoform profile efficiency reveals that it is the best possible solution to this problem.

Maskless lithography using a multiplexed array of fresnel zone plates

Abstract: An array of Fresnel zone plates is illuminated by parallel beamlets of narrow-band electromagnetic radiation. The individual zone plates focus a significant fraction of the incident radiation to foci on a substrate located at least several micrometers distant. The beamlets are capable of being individually turned on or off by shutters, or by deflecting small mirrors that would otherwise direct a beamlet to its Fresnel zone plate. Pattern generation is accomplished by moving the substrate while multiplexing the individual beamlets on or off.

Off-axis reflection zone plate for quantitative soft x-ray source characterization

Abstract: A compact system for high-resolution spectroscopy and quantitative photon flux and brilliance measurements of pulsed soft x-ray sources is described. The calibrated system combines a novel elliptical off-axis reflection zone plate with charge-coupled device detection for simultaneous spectral and spatial measurements. Experiments on a water-window droplet-target laser-plasma source demonstrate λ/Δλ⩾1000 spectral resolution and absolute flux and brilliance measurements. © 1997 American Institute of Physics.

Focal shift and focal switch in dual-focus systems

Abstract: The system under consideration consists of a piece of thin diffractive element (the Fresnel zone plate) and a uniform, converging spherical wave that is incident on the diffractive element. The center of curvature of the incident spherical wave and the primary focus of the zone plate are the two foci of the system. The point of absolute maximum intensity switches from the former to the latter when the Fresnel number of the system decreases to a sufficiently low level. Both a mathematical formulation and a physical interpretation of this effect are presented.

Fresnel lens sheet for rear projection screen

Abstract: A Fresnel lens sheet of a multifocal type is intended to be used in combination with a lenticular lens sheet to construct a rear projection screen for a rear projection television receiver. An annular portion (2) of the Fresnel lens sheet at a distance (R) in a range of 0.05 h to 0.5 h, where h is the height of the Fresnel lens sheet, from the optical center (C) of the Fresnel lens sheet, have the shortest focal length fmin among those of other portions of the Fresnel lens sheet, whereby uniformity in brightness of a screen employing the Fresnel lens sheet can be achieved. Alternatively, a portion where an exit angle (θ) of outgoing light ray relative to a normal to the surface of the Fresnel lens sheet is the greatest, lies at a distance (R) in a range of 0.3 h to 0.8 h from the optical center (C) of the Fresnel lens sheet, to obtain the same result.

Fabrication of a hard x-ray sputtered-sliced Fresnel phase zone plate

Abstract: A Fresnel phase zone plate for hard x ray was fabricated by physical vapor deposition alternating transparent and opaque layers onto a fine gold wire core 47 μm in diameter. The zone plate, which is comprised of 25 pairs of alternating Ag and C layers, is designed to operate with a focal length of 124 mm for a parallel beam at 8.1 keV. The thickness of the zone plate is less than 10 μm and is capable of operating as a phase zone plate. Using the brilliant monochromatized x-ray beam from the TRISTAN Main Ring, with an undulator, the minimum focal spot size attained for the first order focal beam was 0.5 μmφ. The light collecting efficiency was determined to be near 11%.

Optical head with a diffractive lens for focusing a laser beam

Abstract: A head slider for flying above a rotating magneto-optic or optical disk and an optical mechanical assembly with a fixed height above a rotating magneto-optic or optical disk contains magnetic coils and a lens plate with a diffractive optic structure for focusing laser light into a small spot on the disk. The diffractive optic structure may be a zone plate, a phase zone plate or a blazed phase zone plate or other diffractive focusing optical element. The diffractive optic structure does not require curved transparent material such as glass or a high index of refraction. The diffractive optic structure is easily manufactured using lithographic or other techniques.

Hard X-ray microbeam experiment at the Tristan main ring test beamline of the KEK.

Abstract: A hard X-ray microbeam with zone-plate optics has been tested at the MR-BW-TL beamline on the Tristan main ring of the KEK, and preliminary experiments on scanning microscopy have also been performed A sputtered-sliced Fresnel zone plate with an Au core and Ag/C multilayer is used as an X-ray focusing device The outermost zone width of the zone plate is 025 microm A focused spot size of approximately 05 mum has been achieved at an X-ray energy of 854 keV In a scanning X-ray microscopy experiment, test patterns with submicrometer fine structure have been clearly resolved

Condenser-monochromator arrangement for x-radiation

Abstract: The description relates to high-transmission condenser-monochromator arrangements providing quasi-monochromatic object illumination and incoherent imaging in X-ray microscopes (5) and are particularly suitable for well-collimated beams from undulators on electron storage rings. As the deflecting optical component, the condenser-monochromator arrangements comprise an off-axis zone plate in transmission (7) or reflection. There is a monochromator diaphragm (11) in the object plane. The exposure aperture of the condenser-monochromator arrangement may be variably set by means of simple plane mirrors (2). The off-axis zone plate (7) and at least one plane mirror (2) are rotated about the optical axis 6 of the X-ray microscope (5) during exposure. In addition, there are fixed elements containing a focusing device with a focusing ring and a downstream system on one or two hollow conical mirrors.

Holographic circle-to-point converter with particular applications for lidar work

Abstract: A holographic optical element is developed that functions as a circle-to-point converter. The holographic plate looks like a zone plate but functions like a collection of field lenses. Each annulus of the holo- graphic plate acts as a separate lens, imaging incident light to a point focus. The plate was developed for use with Fabry-Perot interferom- eters, but other applications are also possible. The plate has high throughput, and when coupled with high quantum efficiency solid state detectors provides an efficient photon-collecting detection system. De- velopment of the plate was driven by need for an efficient Doppler lidar detection system, and specific lidar applications are discussed. © 1997 Society of Photo-Optical Instrumentation Engineers. (S0091-3286(97)02508-7)

Design and fabrication of Fresnel zone plates with large numbers of zones

Abstract: The advent of high-brightness x-ray sources in the 10–40 keV region opens new possibilities of experiments with microbeams. Techniques to form these focused beams may be based on glancing mirrors, phase elements, or diffractive optics, in particular Fresnel zone plates (FZPs). Because of the long focal length and large acceptance, FZPs designed to work in the hard x-ray region tend to have quite large diameters and large numbers of zones. For instance, the zone plate described in this article has a 1860 μm diam, a focal length of f=3 m (for 8 keV), and 1860 zones. On a standard pattern generator, circular shapes are always approximated as simpler structures. The tolerance requirement for shape and positions of zones depends on the number of zones, and it is necessary to guarantee that the circular structures are approximated to the required degree of accuracy while keeping the size of the data structure to a reasonable size for processing by the exposure system. For instance, if polygons are used to appro...

Fresnel zones for modes

Abstract: The notion of Fresnel zones for modes is introduced which is analogous to the usual Fresnel zones introduced for rays. It is shown that by using Fresnel zones for modes one can simplify the analysis of mode scattering at large-scale inhomogeneities in multimode waveguides. The mode amplitude variations due to scattering by an opaque screen and by refractive index inhomogeneities are considered. In the latter case the formulas obtained in the scope of this approach are statistical averaging suited and similar to those of geometrical optics and the Rytov method widely used to calculate fluctuations of ray complex amplitudes. The results of a tank experiment carried out to test the predictions concerning the mode scattering by an opaque screen are presented.

Soft-x-ray Gabor holography by use of a backilluminated CCD camera.

Abstract: A soft-x-ray Gabor hologram was recorded directly by means of a cooled backilluminated CCD camera, and numerical reconstruction was performed. Synchrotron radiation from a bending magnet with beam line 11A at the Photon Factory, National Laboratory for High Energy Physics, Japan, was used. X rays were monochromatized to a wavelength of 2.34 nm with a grasshopper monochromator and focused on a pinhole of diameter 1.0 µm with a zone plate. A specimen was illuminated with soft x rays transmitted through the pinhole, and a shadowgraph with a magnification ratio of 33 at the CCD plane was digitized directly. The transverse resolution of the reconstructed image was estimated to be 1.5 µm, which was in good agreement with a theoretical value.

Dual-band Fresnel zone plate antennas

Abstract: A description is given of a method of designing phase- correcting Fresnel zone plate lens antennas for operation at two or more frequency bands. A new analysis is derived for apportioning the amount of phase correction to give the desired performance at the chosen frequencies. The result permits the development of narrow-beam, high-gain behavior at two or more bands, with reduced gain at other frequencies.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Diffraction type filter

Abstract: PROBLEM TO BE SOLVED: To vary the luminous flux diameter of irradiation light while making excellent corrections of aberrations by a converging lens by forming a zone plate which has a wavelength-selective aberration correcting function in a center part area and a diffraction grating which substantially has a light shielding function in a peripheral part area, converging or diverging only light of specific wavelength on the zone plate, and diffracting the light sideward by the diffraction grating. SOLUTION: A diffraction type filter 8A consists of a 1st area 11 consisting of the center circular part and a 2nd area consisting of its peripheral part. In the 1st area 11, the zone plate 11A (concentric diffraction grating) with wavelength selectivity which transmits light of 635 nm in wavelength and diverges light of 780 nm is provided and in the 2nd area 12, the diffraction grating 12A is provided which has such wavelength selectivity that the light of 635 nm is transmitted as it is, but the majority of the light of 780 nm is diffracted sideward and substantially cut off.

X=ray spectrograph optics

Abstract: Gap free UV or weak X-ray spectrograph which disperses and focusses incident radiation using an off-axis reflecting zone plate. The latter is formed on a flat substrate.

The effect of layer spacing on the properties of double-layer Fresnel zone plate lens

Abstract: The Fresnel zone plate (FZP) antenna has lens-like properties. The FZP lens avoiding the feed blockage in the FZP reflector is studied. There are two types of FZP lens, one where the phase correction is introduced in successive zones, and one where the concentric zones are alternately transparent and opaque; the latter is more interesting because of its printed structure. However, a single-layer lens is not efficient, as about half of the incident energy is reflected backward, so a double-layer lens was proposed to enhance the aperture efficiency. An improved full-wave analysis based on the vector Hankel transform and spectral domain immittance matrix approach were used to analyse the electrically large double-layer FZP lens, and measurements were carried out for a single-layer FZP antenna with a 6-ring and 15-cm focal length at a wavelength of 3.2 cm. In the case of a double-layer lens filled with dielectric substrate, the reflection from the interface of the substrate and possible emergence of the spurious surface waves degrades the focusing properties, therefore, only the case without a dielectric substrate is under consideration in this paper. Some practical design criteria for a double-layer FZP lens can be obtained from various results of field distributions in the focal region of the FZP lens under plane wave incidence. Furthermore, the requirements for feed design can be determined by means of the field distributions along or across the focal axis.

Improved optical modulator/switch

Abstract: An optical modulator/optical switch is disclosed. The modulator/switch includes a reflective zone plate defined in a movable zone plate support. The reflective zone plate focuses an optical signal reflected therefrom. In response to a control signal, a controlled voltage source applies a voltage across the movable zone plate support and a layer spaced from the zone plate support. The applied voltage generates an electrostatic force that causes the zone plate support to move towards the other layer. When the zone plate support moves, the reflective zone plate's orientation to an optical signal incident thereon changes. Such a change in orientation alters the path of the optical signal reflected from the reflective zone plate. The reflected optical signal can be directed to different receiving waveguides by changing the amplitude of the applied voltage.

Beam size measurement of the stored electron beam at the APS storage ring using zone plate optics and undulator radiation

Abstract: Beam sizes of the stored electron beam at the Advanced Photon Source storage ring were measured using zone-plate optics and undulator radiation. A gold Fresnel zone plate (3.5 {micro}m thick) located 33.9 meters from the x-ray source focused radiation of 18 keV, selected by a cryogenically cooled Si(111) crystal in horizontal deflection, and formed a source image in a transverse plane 2.41 m downstream. The sizes of the source image were determined from measured intensity profiles of x-ray fluorescence from a smooth nickel edge (1.5 {micro}m thick), fabricated using a lithographic technique, while the nickel edge was scanned across over the beam in the transverse plane. The measured vertical and horizontal sizes of the electron beam were 60 {+-} 4.3 {micro}m and 300 {+-} 13 {micro}m, respectively, in reasonable agreement with the expected values.

Spectrally resolved image of 120 fs laser-produced plasma

Abstract: A linear zone plate surface structure was created on the surface of mica crystal and used for obtaining spectrally resolved images of 120 fs laser-produced plasma. A linear Fresnel zone structure was optimized on a wavelength λ = 9.16 A and has a focal length of f = 5 cm, minimum zone width Δzn = 300 nm, total length l = 10 cm, total width of zone plate 2rn = 122.6 μm. Images of laser-produced plasma in the spectral range 9.12−9.31 A were obtained. For high Z (Lanthanum) element target the size of the x-ray radiation spot was not more than 20 μm.

A micromechanical optical switch with a zone-plate reflector

Abstract: It is proposed that standard micromechanical structures, such as torsional plates, cantilevers, doubly supported beams and drumheads, can be fitted with zone-plate reflectors to form low-loss, high-contact and high-speed optical switches. Such devices have many potential uses, including fibre-to-the-home applications. This paper focuses on the calculated properties of zone plates for plane-wave, point and Gaussian beam sources.

A Combined Phase Type Optical Element for Realizing Multiple Images

Abstract: In this paper we introduce a new phase type combined optical element. The element is combined with Dammann grating and Fresnel zone plate in the same substrate by microelectronics technique, hence it has splitting functions of the Dammann grating and self-focusing function of the Fresnel plate. It can produce uniform multiple images by itself. We experimentally designed and fabricated an 9x9 multiple image element, and results show that the element can realize the multiple images we require and the intensity of each image is the same. Relative error is less than 5%.

Design of MM-wave Fresnel zone plate reflector antenna with continuous phase structure

Abstract: The phase Fresnel zone plate, whose diffraction efficiency is up 97%, has been made. Because of the advantages of thinner thickness, lighter weight and design flexibility, the phase Fresnel zone plate has been considered for use as a MM-wave antenna so as to increase the diffraction efficiency. However, zone plates with only four phase steps are generally made up to now, so the diffraction efficiency is only about 80%, and the highest gain is no more than 35 dB. To overcome this weakness, a new kind of Fresnel zone plate antenna with a continuous phase structure is designed, and the authors call it a diffraction antenna.

Laser light converging and irradiating device

Abstract: PROBLEM TO BE SOLVED: To obtain a spatial intensity distribution of laser light which has been converged weakly at its center part and intensely at its peripheral part by arranging a specific composite Fresnel zone plate right before or behind a condenser lens. SOLUTION: The composite Fresnel zone plate 1 has a unit cell obtained by providing a Fresnel zone plate, which is optically different in pitch, concentrically in a Fresnel zone plate together. Then this unit cell and a complementary unit cell which is opposite in phase difference of 0 and π radian from the unit cell are arranged in quantities at random on the same plate so that they are in half-and-half proportion. The obtained composite Fresnel zone plate 1 is arranged right before or behind the condenser lens. For example, the laser light L outputted from a large-output laser after passing through the composite Fresnel zone plate 1 is converged by the condenser lens 2. An object 3 is placed almost at a distance of the focal length (f) of the condenser lens 2.

Experimental demonstration of a binary single-lens joint transform correlator using chirp-modulated inputs

Abstract: This paper introduces the single-lens joint transform correlator (SLJTC). The SLJTC is a two-stage processor. The first stage computes the chirp-modulated joint power spectrum. The chirp-encoded joint power spectrum may be viewed as containing an amplitude-encoded lens function or Fresnel zone plate. The correlation output is in the focal plane of this zone plate. As in the chirp-modulated joint transform correlator (JTC), the output contains a single correlation peak. The SLJTC has been experimentally demonstrated with a peak-to-noise ratio (PNR) of 17.1 dB. The same chirp-encoded joint power spectrum used in the second stage of a binary chirp-modulated JTC resulted in 6.5-dB-poorer PNR performance.

The Bandwidth of Fresnel-Zone Plate Antennas

Abstract: Theoretical expressions are presented for the illumination and phase efficiency of three types of Fresnel-zone plate antennas. Using these formulas, the bandwidths of the antennas will be analyzed and compared. Measured data are given to validate the theoretical results.