Showing papers on "Angular aperture published in 1996"

Objective lens system for endoscopes having an image transfer optical fiber bundle

Abstract: An objective lens system for an endoscope having an image transfer optical fiber bundle comprises from the object end a first lens of negative power having a concave image side surface, a second lens of positive power having a radius of curvature greater on an image side than on an object side, a third lens of positive power having a radius of curvature greater on the object side than on the image side, a doublet lens of positive power which comprises a forth lens element and a fifth lens element, and an aperture diaphragm interposed between the second and third lenses and satisfies the following relations: |d·f/f.sub.R.sup.2 |<0.11 v2<45.0 where f is the equivalent focal length of the entire objective lens system, f R is the equivalent focal length of the rear lens group including the third, fourth and fifth lens elements, d is the axial distance between the aperture diaphragm and the front focal point of the rear lens group, and v2 is the Abbe number of glass for the second lens.

Optical scanner having enhanced item side coverage

Abstract: A dual aperture optical scanner which produces horizontal, vertical, and diagonal scan patterns. The optical scanner includes a housing having a substantially vertical surface containing a first aperture and a substantially horizontal surface containing a second aperture. A laser diode produces a laser beam. A spinner produces first, second, and third groups of scanning beams. A plurality of pattern mirrors reflects the first group of scanning beams in a substantially horizontal direction through the first aperture, the second group of scanning beams in a substantially downward diagonal direction through the first aperture, and the third group of scanning beams in a substantially vertical direction through the second aperture.

Confocal theta fluorescence microscopy with annular apertures.

Abstract: In a confocal theta fluorescence microscope, two objective lenses with circular apertures are used, one to illuminate the sample and the other to detect the emitted light at an angle to the illumination axis. We show that annular illumination and detection apertures lead to a reduction in the extent of the point-spread function. A spatial resolution improved by more than 50% can be achieved with a central obstruction blocking the inner 80% of the diameter. For the limit of a very narrow annular aperture and a numerical aperture of 0.75, the volume at half-maximum of the point-spread function is reduced from 15 to 5 aL. A mixed setup with an annular illumination aperture and a circular detection aperture is also considered.

Wide angle lens system for camera

Abstract: A wide angle lens comprises in order from the object end an aperture stop, a first meniscus lens L1 having a convex object end surface and a second positive power lens element L 2 , the lens satisfying the following conditions: -0.10

Emission angle variable flash apparatus

Abstract: An emission angle variable flash apparatus of the invention alters an angular aperture to be formed by side reflection plates disposed oppositely to both side surfaces of a reflector in linkage with a change of a distance between a Xe tube and a reflector on their optical axis, thereby enhancing the efficiency of utilization of flash from a light source and expanding a variable range of an emission angle in the horizontal direction. As a result, the emission angle variable flash apparatus of the invention is made smaller in size than in the prior art.

Optical disk system having an objective lens with a numerical aperture related to the thickness of the protective layer

Abstract: Disclosed is a magneto-optical disc system comprising a magneto-optical disc 40 with a light-transmitting cover 41, an objective lens 2 for bundling or focusing a laser beam on a magnetic recording layer 43 of the magneto-optical disc 40 in order to perform recording and/or reproduction, and a magnetic field generating unit 9 obtained by forming a coil pattern 7 in an optical glass 8. In the above system, the thickness t2 of the light-transmitting cover 41 is set to fall within the range of 0.6 to 0.1 mm, and the numerical aperture (NA) of the objective lens 2 is set to fall within the range of 0.55 to 0.70, so as to obtain high-density recording and/or reproduction.

Shallow velocity-depth model imaging by refraction tomography1

Abstract: A tomographic imaging technique combined with coherence inversion is proposed for constructing a near-surface model from refraction events. A model obtained from coherence inversion serves as a good background model for the tomographic reconstruction. A simultaneous iterative reconstruction technique (SIRT) algorithm was used for this purpose. This is a simple algorithm and can be easily adapted to irregular acquisition geometry and limited angular aperture. Using synthetic data it was shown that the proposed procedure can be used for determination of local velocity anomalies in a shallow subsurface. The technique was also tested on a real data set.

Wide angular aperture holograms in photorefractive crystals by the use of orthogonally polarized write and read beams

Abstract: We demonstrate a method of simultaneous holographic recording and readout in photorefractive crystals that provides high write–read beam isolation and wide angular bandwidth. The method uses orthogonally polarized read and write beams and parallel tangent diffraction geometry near the equal curvature condition to provide spatially separable, orthogonally polarized diffracted output beams with high isolation and wide Bragg-matched angular bandwidth. The available angular bandwidth of this read–write technique is analyzed, simulated, and experimentally investigated. The measured angular bandwidth internal to the crystal is approximately 18° × 6° for our 45°-cut BaTiO3 crystal, yet the entire hologram still demonstrates high Bragg selectivity. In contrast, traditional nonparallel-tangent geometries yield angular apertures of the order of 1° × 4°.

Optical system for producing uniform line illumination

Abstract: A system for creating a bright and uniform line of illumination. The "hot spot" of an arc lamp is imaged onto a narrow, circular pinhole aperture. Light passing through the pinhole aperture is collimated and passed through a second aperture (the apodizing aperture), before being focused to a line of illumination by a cylindrical lens. The spatial profile of the apodizing aperture is tailored to remove non-uniformities in the illumination source thereby allowing a highly uniform line of illumination to be created. Alternatively, the spatial profile of the apodizing aperture can be tailored to produce a line of illumination having a desired non-uniform intensity profile.

Image display device provided with condensing element

Abstract: PROBLEM TO BE SOLVED: To increase an effective numerical aperture and to make an exit angle small by means of a structure for independently determining the effective numerical aperture and the exit angle in an image display device for displaying an image and having a part, preventing a light beam from passing through it, in each pixel representing the image signal. SOLUTION: A micro-mirror 17, whose cross sectional shape is a triangle and front surface is a reflection surface, is formed on a light shielding layer 6. Incident light beams 10, 11 are made incident, directly or after reflected by the micro-mirror 17, on an aperture part 8. At this time, since an effective numerical aperture E and an exit angle ψ are independently designed, an image display device with a converging elements is provided suitable for a system. By facilitating the manufacture by making the cross sectional shape a trapezoid and forming the structure for refracting a light beam after reflection, the smaller exit angle is obtained.

Gauss lens with image stabilizing function

Abstract: A Gauss lens having image stabilizing function with sufficient brightness, back focal length and excellent imaging quality is provided. The present invention includes, in order from object side, at least a first lens group with positive refractive power and a second lens group with positive refractive power. A negative lens component having a divergent surface with a convex surface facing the object side is placed closest to the image side in the first lens group G1 and a negative lens component having a divergent surface with a convex surface facing the image side is placed adjacent to the image side of the aperture stop. A displacement mechanism moves the second lens group in the direction substantially perpendicular to the optical axis to prevent vibration. The focal length f2 of the second lens group and the focal length f of the totality of the lens system satisfy the condition: 0.2

Apparatus for measuring the photometric and colorimetrics characteristics of an object

Abstract: Apparatus comprising a measurement lens (2) forming the image of the Fourier transform (102) of the elementary area (101) in its image focal plane (Fi), a transfer lens (3) forming the image of the elementary area on a sensor (4) formed by detectors (4i,j), a diaphragm (5) for defining the aperture of the elementary area (101), and a processing circuit (6). The lens (2) producing the Fourier transform is associated with a field lens (10), the combination of these two means (2, 10) and of the circular aperture of diameter (d) which is defined by the diaphragm (5) making it possible, for any light beam having an angle of incidence θ and an angle of azimuth ψ, to select a measurement area of elliptical shape on the object (1) analyzed.

Far-field characterization of sub-wavelength sized apertures

Abstract: A method and apparatus for determining the optical aperture diameter `d` of tips suitable for use in near-field scanning optical microscopy (NSOM). Several functional relationships are found between the far-field angular intensity distribution function I(θ) for light of wavelength `λ` emitted out of the aperture, the angle `θ` being that formed between the direction of travel of the photon concerned and the perpendicular to the plane of the aperture. It is found that I(θ) depends sensitively on the aperture `d`. In one embodiment tip diameters can be measured for diameters in the range of λ/6

Standard lens system having a large aperture ratio

Abstract: A standard lens system composed, in order from the object side, of a first lens unit having a positive refractive power, an aperture stop, a second lens unit having a positive refractive power and a third lens unit having a negative refractive power: the first lens unit being composed of at least one positive meniscus lens component which has a convex surface on the object side, and at least one doublet which consists of a positive meniscus lens component and a negative lens component; the second lens unit being composed of at least one cemented doublet which consists of a negative lens element and a positive lens element, and a positive lens component; and the third lens unit being composed of at least one positive lens component and a negative lens component or at least one negative lens component.

Microscope objective with ball lens and protection plate

Abstract: An objective lens system with protection glass for a microscope and having a numerical aperture of 1.25 and using an immersion oil, having a first, second, third and fourth lens groups, the first lens group being a plano-parallel plate cemented to a hemispherical lens, the second lens group being one aplanatic meniscus, the third lens group being three cemented doublets, and the fourth lens group being two lens components including a positive and a negative meniscus component which are arranged with their concave surface opposite each other. The objective lens system has a relatively small number of lens components, and the aberration, especially chromatic, spherical, coma, astigmatic difference and curvature of field, are corrected favorably.

Large aperture wide angle type photographic lens system

Abstract: A large aperture wide angle type photographic lens system comprises a positive meniscus lens having a convex surface directed toward an object, a bi-concave lens provided at the image side with respect to the positive meniscus lens, a bi-convex lens provided at the image side with respect to the bi-concave lens and a negative meniscus lens having a convex surface directed toward an image and provided at the image side with respect to the bi-convex lens. The characteristics of the lenses have predetermined relationship.

Lens system with switchable soft focus

Abstract: A lens system is disclosed that can be used in either a normal sharp-focus configuration or in any of several soft-focus configurations for obtaining, for example, sharply focused or soft-focus photographic images of an object. The lens system has simple construction and axially comprises, in the normal sharp-focus configuration and from the object side, a first lens group having positive refractive power, an aperture stop, and a rear lens group having negative refractive power. To obtain a sharp-focus image, light passes through both lens groups and the aperture stop. For obtaining a soft-focus image, the second lens group is retracted (i.e., displaced from the optical axis such that light from the object does not pass through the second lens group), and light passes only through the first lens group and the aperture stop.

Crossed aperture lenses for the correction of chromatic and aperture aberrations

Abstract: The chromatic and aperture aberrations of crossed five‐aperture lenses are analyzed by direct ray tracing. The apertures are rectangular and the voltages are applied in such a way that the first‐order properties of the crossed lens are similar to those of a quadrupole doublet. It is shown that in astigmatic modes the chromatic and aperture aberrations of one of the linear images can be simultaneously eliminated or made negative. It is also shown that stigmatic modes exist in which the magnification is different in two perpendicular planes and in which the image blurring caused by the chromatic and aperture aberrations in the direction of smaller magnification is ten times smaller than that given by a round lens of the same focal length and the blurring in the other direction is at least two times smaller. The stigmatic crossed lens also gives a larger working distance than the equivalent round lens. The crossed lens will therefore be preferable for many probe forming systems.

Method of making an aperture plate for a multibeam pattern drawing apparatus

Abstract: For an aperture plate to be used to form dot images of a two dimensional aperture pattern by projection through an imaging optical system in a normal direction, a pattern of markings in ideal positions is projected through an imaging optical system in the reverse direction to normal imaging operations. The image of the pattern is recorded at the position of the aperture plate, and the recorded image is used as a guide to form corrected apertures in the aperture plate. Accordingly, locational errors of the dot images in the normal direction are corrected when the corrected aperture plate is used.

Large numerical aperture imaging device

Abstract: A microscope having a high effective numerical aperture (NA) is achieved in an apparatus in which a real, three-dimensional image is formed of an object placed in an aperture at the apex of one of two facing, axially-aligned concave mirrors. The three-dimensional image is acquired by a video camera positioned in a counterpart aperture at the apex of the other mirror and the acquired image is processed by computer. The processing corrects the acquired image using the point spread function of the mirror system which was previously obtained by positioning a point source of light throughout the object space and measuring the pixel values recorded by the camera's array of sensing element while the camera was positioned at different axial distances in the image space. When the diameter of the mirrors is large compared to the specimen object, substantially all of the light leaving the specimen is captured by the mirrors and focused upon the camera, thereby achieving a high effective numerical aperture for the system which affords excellent resolution, especially when examining transparent specimens.

Shape-dimension optimization of contact medical laser delivery systems

Abstract: The paper deals with a problem of light focusing on the tissue for laser surgery, diagnostic and therapeutics with assistance by tapered tips. Optimization of the shape and geometrical dimensions of laser scalpels sought to minimize tissue damage by means of exception of light leaking through the tapered surface and decrease of distal end inner reflection. These results can be achieved by simultaneous attaching,spherical shape to the front surface of tapered tip also optimization of fiber-tip distance and tip dimensions. Analytical and ray-tracing calculations have been performed for sapphire (n equals 1.75) and silica (n equals 1.45) tip materials and air or saline (n equals 1.33) mediums. The diameter of aperture diaphragm and reflection number of incident beam in the tip have been varied from 1 to 5 fiber core diameter and from 1 to 10, respectively. Several numerical methods for evaluation of tip efficiency for optimized and conventional tips were discussed. Some versions of commercially available tip modernization have been presented. Modification of front surface of the tapered tip increased the angular aperture from 4 degrees to 12 degrees (in air) and from 8 degrees to 15 degrees (in saline) with obviating light leaking in commercial tip by Hans Sttetler SA, Switzerland. Replacement of the contact flat laser scalpel (surgical laser technologies, Malvern, PA) to an optimized one allowed us to increase the taper angle from 1.9 degrees to 10 degrees and produced, therefore, shorter and stronger tip without reducing its optical properties.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Wide angle photographic lens

Abstract: A small, light weight wide angle photographic lens has attachment size of less than approximately 3.5 times the focal length and has a field angle of approximately 100°. The wide angle photographic lens includes a first lens L 1 having a negative refractive power and a concave surface facing the image side; a second lens L 2 with a positive refractive power having the convex surface facing the object side; a third lens L 3 having a negative refractive power cemented to the second lens L 2 and having a surface with a larger absolute value of index of refraction on the image side; a fourth lens L 4 having a positive refractive power cemented to the third lens L 3 and having a surface with a larger index of refraction on the object side; and a plurality of lenses on the image side of the fourth lens L 4 , wherein the concave surface of the first lens L 1 is an aspherical surface with a conical constant κ greater than 0.3 and less than 0.3 with a curvature of the concave surface decreasing monotonically with increasing distance from the optical axis. The wide angle photographic lens also satisfies conditions 0

Objective lens system for microscopes

Abstract: An objective lens system for microscopes composed of only two lens components each of which is a radial type graded refractive index lens component, and having a numerical aperture of at least 0.2 and favorably corrected aberrations.

Wide-angular-aperture acousto-optic devices

Abstract: A new class of acousto-optic device that simultaneously achieves a wide angular aperture, broad bandwidth, and high diffraction efficiency is presented. Parallel tangents and beam steering are used simultaneously, which enhances the product of acceptance angle, bandwidth, and diffraction efficiency to be larger than that of isotropic acousto-optic devices by more than one order of magnitude and to be larger than that of tangentially matched acousto-optic devices by more than four times. A wide-angular-aperture acousto-optic device with a center frequency of 150 MHz and operating at 514.5 nm was optimally designed, fabricated, and its performance measured. The consistency between experiment and theory is excellent. This device can also be used as a high speed and high efficiency modulator without any change in design. This was verified experimentally and risetime of 11.7 ns was obtained. Thus, this device can be optimally used as both a wide-angular-aperture Bragg cell/deflector and a high speed modulator.

Tapered fiber optic sensors for laser medicine

Abstract: Biomedical science and practical medicine need special techniques for reliable real-time remote detection and determination information from human tissue. Most applications of these techniques in interior organs are based on optical fibers which should not only be able to deliver excitation light with minimal loss but provide effective light gathering from tissue being under the test. As emitted from tissue optical signal is often weak especially if autofluorescence spectroscopy is chosen for diagnostics, an efficient collection by fiber optics probe became essential. The main part of the proposed fiber optics probes is a specially designed tapered tip with one flat surface and another spherical one. This tip operates as a collector, transmitter and coupler to deliver light to the tissue and backward to the detector simultaneously. To find geometrical dimensions of tips optimized for these purposes calculating formulas have been adduced. These optimized tips could collect fluorescence signal from biological sites in wide angular aperture region and could transport light without leakage on tapered surface. When delivery fibers are placed at the focal plane of tip spherical surface an efficient optical coupling with them is achieved. Ray tracing of the tapered tips has been performed on sapphire and quartz tip materials in air and in saline to determine the best sensor design.

Optical head device with large tolerance to tilting

Abstract: An optical head device includes a collimating lens (9) or an aperture structure (13) which is disposed between a semiconductor laser (1) and a beam splitter (3;28) with the collimating lens or the aperture structure having an effective aperture smaller than an effective aperture of an objective lens (4). The device also includes a polarization aperture structure (11) and a quarter-wave plate (12) which, out of the light in a polarization direction, allow a portion of the light that is incident on an aperture portion whose diameter is smaller than the effective aperture of the objective lens to pass through, while allowing the remaining portion of the light to be diffracted, absorbed or reflected such that the light orthogonally directed thereto passes as it is through entire surfaces of the polarization aperture structure and the quarter-wave plate. The light passed is led to the optical detector without the reflected light being spatially lost. It is possible to increase a range of tolerance for the tilting of the optical disk, and to reduce any deterioration caused by the tilting of the optical disk.

Polarization characteristics of the radiation field from an aperture in an impedance surface

Abstract: The radiation field from an aperture in an impedance surface is studied by using a newly proposed expression of an equivalent magnetic current. Simple relations between the polarization and the surface impedance are derived concerning two subjects: the currents on a reflector illuminated by an aperture in an impedance surface and the cross polarization of the aperture.