Abstract: A light-sensing device comprises a light source consisting of a semiconductor laser, a light-transmitting optical system having a lens surface and a diffraction grating surface arranged on the optical axis of light emitted from this light source, and a light-receiving detection system that detects any of the emitted light that is reflected from an object to be inspected. This emitted light is diffracted in at least two intersecting directions by the diffraction grating surface.

Abstract: The focus detection mechanism of the invention diffracts the return light reflected off target surface by means of holographic element. The diffracted beams are both received by two long photodetection means as two astigmatic convergent beams that forms circles of least confusion on the same plane near focal plane of a lens. The focus detection signal is obtained from differential output of them. Since the mechanism can form two diffracted beams having circles of least confusion on the same plane, the photodetection means for detection can be disposed side by side, thus simplifying production with increased dimensional accuracy. Also, although a holographic element is used, wavelength fluctuation can be absorbed to provide extremely high reliability.

Abstract: A semiconductor laser comprises AlGaAs-type semiconductor layers deposited on a substrate and a current constriction layer having at least one stripe-shaped current injection region. This semiconductor layers comprise: a first cladding layer of the first conductivity type, a first optical waveguide layer of the first conductivity type formed on the first cladding layer, an active layer formed on the first optical waveguide layer and having a quantum-well structure, a second optical waveguide layer of a second conductivity type formed on the active layer, a second cladding layer of the second conductivity type formed on the second optical waveguide layer, and a contact layer formed on the second cladding layer. The active layer has flatness of such a degree that roughness with respect to a reference surface within a unit area of 1 mm.times.1 mm is no more than .+-.0.1 .mu.m, the width of the current injection region of the current constriction layer is between 100 .mu.m to 250 .mu.

Abstract: An eyeglass lens of the present invention has a surface which is a refracting surface arranged such that two coordinate axes X and Y are set to contact with the refracting surface at a determined point thereon while directions of the coordinate axes and an XY plane including the two axes are determined, that a perpendicular line is dropped toward the XY plane from an arbitrary point on the refracting surface, and then X, Y coordinates of an intersecting point between the perpendicular line and the XY plane are denoted by x and y, respectively, and the length of the perpendicular line by z, and that a value of z is expressed as follows: ##EQU1## where r.sup.2 =x.sup.2 +y.sup.2 ; C.sub.x, C.sub.y, K.sub.x, K.sub.y, A.sub.n,m,j are constants to define the shape of lens;n, m, j are integers satisfying conditions of 2.ltoreq.n, 0.ltoreq.m, 0.ltoreq.j, and 1.ltoreq.m+j;coefficients satisfy the following conditions: ##EQU2## which cannot be simultaneously zero.

Abstract: A small and inexpensive optical head for detecting a recorded signal, a focusing error signal and a tracking error signal, and an optical memory device utilizing the optical head. A diffraction device (103) is provided having two chirped grating regions (103A, 103B) for dividing a light beam from an optical recording medium (105) and directing the divided beams toward four band-shaped photoelectric transducers (106) and an astigmatism generator formed by the diffraction device (103) and a positive lens (102). The four photoelectric transducers are positioned in a plane inclined with respect to the optical axis of zero-order diffraction light, and the longitudinal axes of each of the band-shaped photoelectric transducers are radially arranged relative to the optical axis.

Abstract: A lens for eyeglasses which corrects an astigmatism includes a first refracting surface and a second refracting surface. Each refracting surface has an optical center and a periphery. At least one of the refracting surfaces is divided into a first portion and a second portion in which the first portion has a variation in curvature of the lens which is greater than the variation of curvature of the second portion.

Abstract: A lens for eyeglasses which corrects an astigmatism includes a first refracting surface and a second refracting surface. Each refracting surface has an optical center and a periphery. At least one of the refracting surfaces is divided into a first portion and a second portion in which the first portion has a variation in curvature of the lens which is greater than the variation of curvature of the second portion.

Abstract: A traveling pipe cutter which includes an upper blade and a lower blade mounted on a blade holder such that the blade holder moves in response to a crank mechanism to cut the pipe with every one-cycle motion of the crank. The clamp which holds the pipe during the cutting process also serves as the blade guide for both the upper and lower blades.

Abstract: An optical system, that includes a light source having sufficient coherency to provide a predominate operating wavelength and a diffraction grating lens system to focus the light from the light source to an image point on the optical axis of the optical system, provides for change of position of the image point along the optical axis over a wide focusing range with suppression of generated aberration. In particular, the optical system comprises a light source both movable in the direction of the optical axis and capable of variation in wavelength and a diffraction grating lens system that condenses the beam from the light source onto an image point on and along the optical axis, which system is effective in cancelling out aberration generated due to movement of the light source.