Abstract: A lens evaluation method includes diffracting light derived from a lens so that two diffracted rays of different orders (e.g., a 0th-order diffracted ray and a +1st-order diffracted ray) interfere with each other, thereby obtaining a shearing interference figure, and changing phases of the diffracted rays. The method also includes in the shearing interference figure, determining phases of light intensity changes at a plurality of measuring points on a measuring line which passes through a midpoint of a line segment interconnecting optical axes of the two diffracted rays, and determining characteristics (defocus amount, coma, astigmatism, spherical aberration and a higher-order aberration) of the lens based on the phases.

Abstract: A method for evaluating aberrations of an optical element such as optical head for use with an optical system such as DVD. In this method, light is transmitted through the optical element and then diffracted into 0, ±1, ±2, . . . order diffraction lights, for example. Among others, first and second lights (e.g., 0 and +1, 0 and −1, +1 and −1, or 0 and ±1 order diffracted lights) are overlapped to form an image shared by the first and second lights. Then, light intensity at first and second points in the shared image are detected. At this moment, light intensity at the first and second points are changed. Then, a phase difference in light intensity of between first and second points is determined. Using the phase difference, aberrations of the optical element are determined.

Abstract: The illuminating system comprises a linear light source, and a light guide member with the light source placed beside a side face thereof, in which the top face and the bottom face of the light guide member are generally parallel to each other and in which slits made of a different material or air are arranged at specified intervals in the top face of the light guide member. Therefore, most of light propagating within the light guide member is totally reflected at the slits formed in the light guide member so as to be outputted from the light guide member, thereby illuminating a reflecting plate. Its reflected light is incident again on the light guide member and the resulting totally reflected light is transmitted to the observer's side at places other than the slits, while the observer's field of view is not obstructed at the slit portions.

Abstract: The illuminating system comprises a linear light source, and a light guide member with the light source placed beside a side face thereof, in which the top face and the bottom face of the light guide member are generally parallel to each other and in which slits made of a different material or air are arranged at specified intervals in the top face of the light guide member. Therefore, most of light propagating within the light guide member is totally reflected at the slits formed in the light guide member so as to be outputted from the light guide member, thereby illuminating a reflecting plate. Its reflected light is incident again on the light guide member and the resulting totally reflected light is transmitted to the observer's side at places other than the slits, while the observer's field of view is not obstructed at the slit portions.

Abstract: In order to improve signal modulation characteristics and detect a position at a higher precision, collimated light of wavelength .lambda. and beam radius D enters a fixed diffraction plate and a movable diffraction plate comprising a grating of pitch "p". The grating has main diffraction components of orders .+-.1. The plates are arranged in parallel with a distance "g" between them and generally perpendicular to an optical axis of the beam. The beam diffracted by the diffraction plates and in parallel to the optical axis of the beam is condensed with a condenser lens for limiting an incident pupil size to be within D-2 g.lambda./p. The amount of the light condensed by the condenser lens is detected by a photosensor. In a different example, a collimated light beam enters a first fixed plate and a rotary diffraction plate successively to transmit diffracted light of orders .+-.1. Then, the transmitting light is guided to a symmetrical point with respect to a rotation center of the rotary plate.

Abstract: A highly efficient, luminous and energy-saving panel-form illuminating system suitable for mass-production, comprising at least a photoconductor, a linear light source at one side of the photoconductor, and a reflector; wherein grooves or protrusions are formed on the bottom surface of the photoconductor.

Abstract: A position detecting element that enables a position to be detected at high speed and high precision, and a range sensor using the same. The position detecting element is provided with a PIN photodiode array 1 having n segments and a parallel arithmetic processing portion 2 that calculates the segment having maximum intensity by comparing n outputs from the segments of the PIN photodiode array 1. The range sensor includes a light source by which the object to be measured is irradiated by optical beam, a lens that gathers rays of the reflected light from the surface of the object to be measured and the position detecting element mentioned above that detects the position of the light gathered by the lens.

Abstract: A back light illuminator for liquid crystal display apparatus comprises a fluorescent lamp, a light guide member, and a reflection plate enclosing the fluorescent lamp and an incident portion of the light guide member so as to reflect light rays toward the incident portion of the light guide member. The reflection plate has at least a curved portion having a parabolic cross-section or a elliptical cross-section so as not to reflect the light rays in a direction to the fluorescent lamp. Thus, absorption of reflected light by the fluorophor of the fluorescent lamp is minimized, and the luminance of the back light illuminator is increased.

Abstract: The present invention provides an optical encoder capable of using the recesses and convexes of a movable plate and a fixed plate to accurately generate a Z phase signal in synchronism with an A/B phase signal. Phase type diffraction gratings on the moving and fixed plates including a plurality of tracks with different grating pitches cause parallel coherent beams to interfere with one another, and a light receiving part detects the intensity of light to obtain a plurality of synchronous signals with different periods. On the other hand, the light receiving part detects light spots formed by condensing elements on the movable plate to generates a single pulse per rotation as a reference position. One of the plurality of synchronous signals that has the shortest period is selected as an A/B phase signal that depends on the movement of the movable plate.

Abstract: An efficient, luminous and energy-saving panel-form illuminating system suitable for mass-production, comprising at least a photoconductor, a linear light source at one side of the photoconductor, and a reflector; wherein grooves or protrusions are formed on the bottom surface of the photoconductor.

Abstract: An array light source 1 with semiconductor laser sources disposed one-dimensionally and a projective lens 2 are used to illuminate an inspected object so that light beams projected from the array light source form a dotted line on the object. A line sensor is used to receive through an objective lens 3 light emitted from an imaging area 11 away from an illuminated area 12. An image signal, fed to an image processing unit 8 through a pre-processing unit 7 producing an image from signals from the line sensor 4 and a stage 5 is processed, while the stage 5 bearing the object 6 is being gradually moved, to inspect the object 6 for crack defects 9 and 10 by detecting an optically nonhomogeneous portion of the object. The method allows a crack defect of an object, such as a ceramic substrate or a sintered metal product, to be detected fast with high accuracy.

Abstract: A light having a single wavelength which is emitted from a light emitting element comprising a light emitting diode, a semiconductor laser or the like is changed to a parallel light by a collimator lens. The parallel light emitted from the collimator lens which has been changed or is being changed to such a beam as to keep a small beam diameter for a long distance by a conical lens is irradiated on a surface of an object to be measured. The light diffused from the surface of the object to be measured is collected into a position detecting element by a condenser lens so that a distance on the surface of the object to be measured can be measured.

Abstract: A phase grating has a concave part of rectangular shape type substantially, of which grating depth is deeper in a specific range than depth d' calculated in a formula.vertline.n-n.sub.0 .vertline..times.(p-d'/e)/p.times.d'=(.lambda./2).times.(1+2m) (where m=0, .+-.1, .+-.2, . . . )in terms of center wavelength .lambda. of light having partial interference to be diffracted by the phase grating, pitch length p of the phase grating, refractive index n of base material of the phase grating, refractive index n.sub.0 of medium surrounding the phase grating, and shape ratio e as the ratio of grating depth to width of slope of the concave part.

Abstract: A method for foreign particles inspection includes illuminating an inspection surface of an inspection object with a beam which is, one of s-polarized and p-polarized relative to the inspection surface of the inspection object. The illumination utilizes an optical axis which is generally parallel to the inspection surface or which intersects the inspection surface at an angle that is greater than or equal to 1.degree. and less than 5.degree.. Reflected and scattered light is detected utilizing an optical axis which makes an acute angle with the inspection surface and which makes a differential angle of 30.degree. or less with the optical axis of the illumination beam. The detection of foreign particles is accomplished by detecting the component of the reflected and scattered light which is the other of s-polarized and p-polarized relative to the inspection surface.

Abstract: A liquid crystal layer is interposed between two polarizers arranged in a parallel Nicol or crossed Nicol manner, and a phase plate is set between two polarizers so that the transmission direction of the first polarizer coincides with the optical axis. Then, a rotation angle at which optical intensity transmitted through the second polarizer has an extreme value to be determined, and the thickness of the birefringence layer is calculated according to the rotation angle of the phase plate. In a different method, a half-wave plate is used. First, the liquid crystal layer is set at a position where an optical intensity of the transmission light has an extreme value, and the half-wave plate provided between the two polarizers is set so that a transmission direction of the first polarizer coincides with the optical axis. Then, a rotation angle of the phase plate is determined at which an optical intensity of light transmitted through the second polarizer has an extreme value.

Abstract: A foreign substance inspection apparatus having a good signal to noise ratio with optical detection accuracy capable of detecting infinitesimal foreign substances, comprising a lighting portion to irradiate with an S polarized laser light beam and having the optical axis parallel to the substrate to be inspected, a detecting portion having an optical axis located in a position set by rotating the optical axis of the lighting portion by 120.degree. to 160.degree. with the point of intersection of the optical axis of the lighting portion and the surface to be inspected as the center of rotation so as to have an angle made with the surface to be inspected of 45.degree.

Abstract: Phase-type spatial modulation of light is achieved by placing a twisted pneumatic liquid crystal cell between two polarizers, such that a direction of alignment of liquid crystal molecules at an input side of the liquid crystal cell is parallel to a transmission access of a first one of the polarizers, and such that a direction of alignment liquid crystal molecules at an output side of the liquid crystal cell is parallel to a transmission access of a second one of the polarizers. Also, phase modulation which is substantially free from amplitude variations can be realized by placing two twisted pneumatic liquid crystal cells between two polarizers.

Abstract: The present invention provides an inspecting method and an apparatus therefor. A light illuminates an object to be inspected having optical diffusive characteristics such as a ceramics plate. A part of the light diffuses in the object from an illumination area is reflected at or passes through a defect such as a crack and reaches an imaging area. An image sensor detects the image of the imaging area. A signal showing a larger change is processed thereby to inspect the defect. The object is displaced stepwise relative to the light source and the image sensor. Thus, a crack or the like in an object can be inspected with high accuracy and at a high speed.

Abstract: An optical encoder including a light source and a first grating plate having a first diffraction grating for diffracting a light beam emitted from the light source. The optical encoder further includes a second grating plate having a second diffraction grating including a blazed diffraction grating for further diffracting the light beam diffracted by the first diffraction grating so as to allow the light beam to be incident on the first grating plate. The optical encoder also includes a light-receiving portion for receiving the light beam reentering the first grating plate and diffracted by the first grating plate.

Abstract: An optical encoder includes: a light source; a first grating plate having a first diffraction grating for diffracting a light beam emitted from the light source; a second grating plate having a second diffraction grating for further diffracting the light beam diffracted by the first diffraction grating; a reflector for reflecting the light beam from the second grating plate so as to allow the light beam to reenter the second grating plate; and a light-receiving portion for receiving the light beam reflected by the reflector and successively diffracted by the second and first grating plates, wherein a diffraction angle of plus and minus first-order diffracted light beams of the first diffraction grating is substantially equal to that of the plus and minus first-order diffracted light beams of the second diffraction grating, and the light-receiving portion generates an electric signal in accordance with the amount of the plus and minus first-order diffracted light beams of the first diffraction grating.