Abstract: An optical system of an optical pick-up that is capable of using optical discs DVD and CD. The system includes a light source portion for selectively emitting a first laser beam (650 nm) and a second laser beam (780 nm), and an objective lens for converging the laser beam from the light source portion onto an recording layer of the optical disc. The objective lens is provided with a transmittance controlling phase grating in a peripheral region to have a wavelength dependence such that the transmittance for the first laser beam is higher than the transmittance for the second laser beam. The transmittance controlling phase grating is formed as a plurality of concentric grooves. Each of the grooves has a rectangular cross-section in a plane containing an optical axis of the objective lens.

Abstract: An optical system for a binocular is provided with an objective optical system, an erecting system and an eyepiece. The objective optical system includes a front lens group having positive refractive power, and a rear lens group having negative refractive power. The rear lens group is capable of moving in a direction orthogonal to an optical axis to stabilize an image when the binocular is moved due to hand-held shaking of a user.

Abstract: Disclosed is a refractive-diffractive hybrid lens that includes a refractive lens having at least one aspherical surface, and a diffractive lens structure having a plurality of concentric ring-shaped steps that are formed on at least one lens surface of the refractive lens. The refractive lens and the diffractive lens structure are designed such that a change of the spherical aberration due to a change of the refractive index becomes small. That is, the refractive lens is designed to correct a coma and to reduce the change of the spherical aberration due to the variation of the refractive index, and the diffractive lens structure is designed to correct the residual spherical aberration. The refractive lens is a single biconvex lens, and at least one surface is aspherical. The diffractive lens structure generates a negative spherical aberration to reduce the ratio of a change of the spherical aberration to a variation of the refractive index.

Abstract: An optical head for an optical disc drive is provided with a first laser diode that emits a shorter wavelength laser beam, a second laser diode that emits a longer wavelength laser beam, and an objective lens for converging the beams emitted by the laser diodes on the data recording surface of the optical disc. Each of first and second surfaces of the objective lens is rotationally symmetrical, and a rotational axis of the first surface and a rotational axis of the second surface are arranged to be deviated from each other.

Abstract: A beam shaping optical system which is provided with a first wedge prism having two refractive surfaces defining a first principal section, and a second wedge prism having two refractive surfaces defining a second principal section that is parallel to the first principal section, wherein a reference ray of light forms incident angles at each of the refractive surfaces of the prisms satisfying the following condition (1): 1 &LeftBracketingBar; ∑ j = 1 L ⁢ α j &RightBracketingBar; < 0.020 .

Abstract: An optical disc drive using either one of a first disc (e.g., DVD) and a second disc (e.g., CD), is provided with a first laser diode that emits a shorter wavelength beam, a second laser diode that emits a longer wavelength beam, an objective lens, and a driving unit that holds and rotates the optical disc. The optical axis of the objective lens is inclined relative to a normal to the optical disc. The first laser diode is located at a first position so that the coma, which is caused when the first laser beam is converged on a data recording surface of the first disc, is minimized, and the second laser diode is located at a second position so that the coma, which is caused when the second laser beam is converged on a data recording surface of the second disc, is minimized.

Abstract: An objective lens converges a shorter wavelength laser beam on a DVD having a protective layer, which is 0.6 mm thick, and a longer wavelength laser beam on a CD having a protective layer, which is 1.2 mm thick. A common region is defined on the objective lens. The common region provides a numerical aperture appropriate for converging the longer wavelength laser beam on the CD. Coma of the objective lens in the first region is compensated better in a case where the longer wavelength laser beam is converged on the CD than a case where the shorter wavelength laser beam is converged on the DVD.

Abstract: A beam shaping optical system which is provided with a first wedge prism having two refractive surfaces defining a first principal section, and a second wedge prism having two refractive surfaces defining a second principal section that is parallel to the first principal section, wherein a reference ray of light forms incident angles at each of the refractive surfaces of the prisms satisfying the following condition (1): &LeftBracketingBar; ∑ j = 1 L ⁢   ⁢ α j &RightBracketingBar; < 0.020 .

Abstract: Disclosed is an objective lens of an optical pick-up that includes a refractive lens and a diffractive lens structure that is formed as a large number of concentric ring areas having minute steps in an optical axis direction at the boundaries therebetween. The lens surface of the objective lens is divided into a high NA exclusive area for a DVD only, and a common area that is surrouned by the high NA exclusive area. The diffractive lens structure in the common area changes the spherical aberration in the undercorrected direction as the wavelength of the incident laser beam increases. The diffractive lens structure formed in the high NA exclusive area has a smaller wavelength dependence of a spherical aberration than that formed in the common area, and is designed such that a spherical aberration at the short wavelength is adequately corrected for the thin cover type optical disc.

Abstract: An optical system for an optical head employed in an optical disc drive, which uses a plurality of kinds of optical discs having different thickness cover layers, is provided with a light source, an objective lens and a light receiving unit. A plurality of diverging light beams having different wavelengths are emitted from a plurality of light emitting points, respectively. One of the light emitting points is used depending on a thickness of a cover layer of a currently loaded optical disc. The objective lens is capable of converging each diverging beam on a data recording surface of the optical disc. The light receiving unit receives a beam reflected by the optical disc and generates electronic signals representing the recorded data. In this optical system, an image magnification M of the objective lens satisfies a condition: −0.144<M<−0.099.

Abstract: An optical system for a binocular is provided with an objective optical system, an erecting system and an eyepiece. The objective optical system includes a first lens group having positive refractive power, a second lens group having negative refractive power and a third lens group having positive refractive power. The second lens group and/or the third lens group is capable of moving in a direction perpendicular to an optical axis to stabilize an image. The objective optical system satisfies the following conditions: (1) 0.1<d12/f0 (2) 0.7<f0/f1<3.0 where, d12 is a distance between the first lens group and the second lens group, f0 is the focal length of the objective optical system, and f1 is the focal length of the first lens group.

Abstract: A diffusion plate includes a plurality of superimposed basic patterns, each having a large number of microstructures. The microstructures are located in two dimensional periodic arrangements, and lattice vectors, corresponding to the periodic arrangement of the microstructures, vary in accordance with the pattern. The invention also discloses a method for manufacturing a master die for such a diffusion plate, and a focusing screen using the diffusion plate.

Abstract: An objective lens includes a refractive lens having a positive refractive power, and a diffractive grating having a plurality of concentric ring-shaped steps that are formed on at least one lens surface of the refractive lens. The objective lens is a biconvex plastic lens of which first and second surfaces are aspherical. A diffractive grating is formed on the first surface of the objective lens. The diffractive grating is similar to a Fresnel lens, it is formed as many concentric rings each of which has a wedge sectional shape. The boundary between the adjacent rings is a step to give a predetermined optical path difference. The diffractive grating has wavelength dependence such that spherical aberration varies in the undercorrected direction as wavelength of incident light increases.

Abstract: There is provided an eyepiece lens system for viewing an image formed by an objective lens system. The eyepiece lens system includes a first refraction lens having a positive power, a second refraction lens having a positive power and at least one diffraction lens having a phase grating structure. The first and second lenses are arranged on an eye side with respect to a plane on which the image is formed.

Abstract: An objective lens includes a refractive lens having a positive refractive power, and a diffractive lens structure having a plurality of concentric ring-shaped steps that are formed on at least one lens surface of the refractive lens. The objective lens is a biconvex plastic lens having first and second aspherical surfaces. A diffractive lens structure is formed on the first surface of the objective lens. The diffractive lens structure is similar to a Fresnel lens, it is formed as many concentric rings each of which has a wedge sectional shape. The boundary between the adjacent rings is formed as a step giving a predetermined optical path difference. The diffractive lens structure has wavelength dependence such that at least two light beams having different wavelength with an identical diffractive order form appropriate wavefronts for at least two kinds of optical discs respectively provided with cover layers having different thickness.

Abstract: A chromatic aberration correcting element that is a simple lens having at least one aspheric surface, the radius of curvature of which increases from the optical axis toward the periphery. At least one of the surfaces is formed as a diffraction lens surface that consists of annular segments that shift discretely in a direction in which the lens thickness increases as a function of the distance from the optical axis. Also disclosed is a chromatic aberration correcting device having annular segments formed in steps on either a light entrance face or a light exit face or both. The annular segments are composed of planes perpendicular to and concentric with the optical axis.

Abstract: A UV image forming optical system includes a collimating lens for collimating light emitted from a UV light source, an imaging lens for forming an image of the collimated light transmitted through the collimating lens, and a beam splitting optical system positioned in an optical path of the collimated light between the collimating lens and the imaging lens. At least one of the collimated light emitted from the collimating lens and the light transmitted through the imaging lens, reflected by a reflector and transmitted again through the imaging lens is made incident upon an external viewing optical system.

Abstract: A triplet lens system composed of a first positive lens element, a second negative lens element and a third positive lens element. At least one lens surface is provided with a blazed zonal structure having a function of a positive diffractive lens.

Abstract: A beam shaping optical system which is provided with a first wedge prism having two refractive surfaces defining a first principal section, and a second wedge prism having two refractive surfaces defining a second principal section that is parallel to the first principal section, wherein a reference ray of light forms incident angles at each of the refractive surfaces of the prisms satisfying the following condition (1): ##EQU1##

Abstract: A beam projecting apparatus which includes a light source emitting a laser beam; and a beam projecting device which includes a beam projecting portion from which the laser beam is projected outwardly so that the laser beam has a beam waist position at a predetermined position apart from the beam projecting apparatus. The beam projecting apparatus further includes a beam waist position adjusting optical system which is disposed along a light path from the light source to the beam projecting portion, at least one lens element of the beam waist position adjusting optical system being movable along an optical axis thereof; a temperature detecting device for detecting a temperature in the beam projecting apparatus; and a controller for controlling a movement of the at least one lens element in association with the temperature detected by the temperature detecting device so that a deviation of the beam waist position from the predetermined position due to a temperature change is minimized.