To provide a diffractive optical element having a high light utilization efficiency, whereby light spots having a predetermined pattern can be stably formed, a projection device and a measuring device. The diffractive optical element of the present invention comprises a transparent substrate, a convexo-concave portion formed so as to be in contact with one surface of the transparent substrate and a filling portion with which concave portions of the convexo-concave portions are filled and which covers top surfaces of convex portions of the convexo-concave portion for planarizing the convexo-concave portion, wherein the convexo-concave portion has at least two stages on the surface of the transparent substrate; the top surfaces of the respective stages are parallel to one another; among the transparent substrate, the convexo-concave portion and the filling portion, the refractive indexes of at least the convexo-concave portion and the filling portion are different with respect to the incident light which enters from the normal direction of the surface of the transparent substrate; and the refractive indexes of the transparent substrate, the convexo-concave portion and the filling portion with respect to incident light are at most 2.2.

To provide a diffractive optical element having a high light utilization efficiency, whereby light spots having a predetermined pattern can be stably formed, a projection device and a measuring device. The diffractive optical element of the present invention comprises a transparent substrate, a convexo-concave portion formed so as to be in contact with one surface of the transparent substrate and a filling portion with which concave portions of the convexo-concave portions are filled and which covers top surfaces of convex portions of the convexo-concave portion for planarizing the convexo-concave portion, wherein the convexo-concave portion has at least two stages on the surface of the transparent substrate; the top surfaces of the respective stages are parallel to one another; among the transparent substrate, the convexo-concave portion and the filling portion, the refractive indexes of at least the convexo-concave portion and the filling portion are different with respect to the incident light which enters from the normal direction of the surface of the transparent substrate; and the refractive indexes of the transparent substrate, the convexo-concave portion and the filling portion with respect to incident light are at most 2.2.

A method includes selecting a period for a volume Bragg grating (VBG) such that a spectral selectivity of the VBG is at least as wide as a spectral width of a broadband light beam that is to be spatially transformed, selecting a desired beam transformation for the broadband light beam, passing a first light beam from a recording light source through an optical device to a volume holographic recording medium where the optical device is configured to induce the desired beam transformation, directing a second light beam from the recording light source to the recording medium, and converging the first light beam and the second beam at a recording angle such that a spatial refractive index modulation profile is recorded in the recording medium that provides the VBG with the selected period, and a phase profile is embedded in the VBG that induces the desired beam transformation for each spectral component within a spectral width of the VBG.

A method includes selecting a period for a volume Bragg grating (VBG) such that a spectral selectivity of the VBG is at least as wide as a spectral width of a broadband light beam that is to be spatially transformed, selecting a desired beam transformation for the broadband light beam, passing a first light beam from a recording light source through an optical device to a volume holographic recording medium where the optical device is configured to induce the desired beam transformation, directing a second light beam from the recording light source to the recording medium, and converging the first light beam and the second beam at a recording angle such that a spatial refractive index modulation profile is recorded in the recording medium that provides the VBG with the selected period, and a phase profile is embedded in the VBG that induces the desired beam transformation for each spectral component within a spectral width of the VBG.

To reduce an influence of stray light and stably record/reproduce high-quality data in holographic recording/reproduction. A holographic memory device includes an optical system that guides a reference beam to an optical information recording medium at a desired angle of incidence, a control part that controls the angle of incidence of the reference beam generated in the optical system, and a lens part that images the reference beam in a desired position of the optical information recording medium. Further, at least a first light beam at a first angle and a second light beam at a second angle different from the first angle are output from the optical element, and the optical element is provided so that the first light beam may propagate within an effective diameter of the lens part and the second light beam may propagate to an outside of the effective diameter of the lens part.

To reduce an influence of stray light and stably record/reproduce high-quality data in holographic recording/reproduction. A holographic memory device includes an optical system that guides a reference beam to an optical information recording medium at a desired angle of incidence, a control part that controls the angle of incidence of the reference beam generated in the optical system, and a lens part that images the reference beam in a desired position of the optical information recording medium. Further, at least a first light beam at a first angle and a second light beam at a second angle different from the first angle are output from the optical element, and the optical element is provided so that the first light beam may propagate within an effective diameter of the lens part and the second light beam may propagate to an outside of the effective diameter of the lens part.

An optical pickup device includes a semiconductor laser that emits a laser beam, and an object lens that concentrates the laser beam emitted from the semiconductor laser on an optical disc. In this optical pickup device, an optical axis of the object lens is inclined with respect to an optical axis of the laser beam that is incident on the object lens so as to generate flares caused by coma aberration on an entrance side in a forward direction of pits of the optical disc.

Optoelectronic apparatus includes a substrate, such as a semiconductor die and a monolithic array of light-emitting elements formed on the semiconductor die in a grid pattern comprising multiple columns. In one embodiment, the apparatus includes a cylindrical lens, having a cylinder axis that is angled relative to the columns of the grid pattern of the light-emitting elements. A diffractive optical element (DOE) is mounted on the substrate and configured to project the light emitted by the elements so as to generate a pattern of stripes corresponding to the columns of the grid pattern.

In an optical disc apparatus for reproducing information recorded on a track of an optical disc, an optical head irradiates a light beam onto the track, detects a reflected light reflected by the track, and generates a reproduction signal based on the reflected light. A decoder circuit decodes the reproduction signal, and generates a decoded signal including information recorded on the track. A correlation detector circuit calculates a cross-correlation value between the reproduction signal and the decoded signal. A servo circuit detects a deviation amount of an irradiation position of the light beam onto the track, from the reproduction signal, and controls the irradiation position of the optical head based on the cross-correlation value and the deviation amount.

In an optical disc apparatus for reproducing information recorded on a track of an optical disc, an optical head irradiates a light beam onto the track, detects a reflected light reflected by the track, and generates a reproduction signal based on the reflected light. A decoder circuit decodes the reproduction signal, and generates a decoded signal including information recorded on the track. A correlation detector circuit calculates a cross-correlation value between the reproduction signal and the decoded signal. A servo circuit detects a deviation amount of an irradiation position of the light beam onto the track, from the reproduction signal, and controls the irradiation position of the optical head based on the cross-correlation value and the deviation amount.