Abstract: In a diffractive optical element, which is formed by laminating at least three layers of diffraction gratings made of at least three kinds of materials which differ in dispersion, at least three design wavelengths are set.

Abstract: In order to obtain a diffractive optical element with which a high diffraction efficiency can be obtained in a wide wavelength range and color flare is not noticeable and a picture taking apparatus using this diffractive optical element, an image is formed on a picture taking unit by using a diffractive optical element in an optical system. The diffractive optical element has a grating structure obtained by stacking a plurality of diffraction gratings made of at least two types of materials with different dispersion properties to enhance diffraction efficiency for a particular design order throughout a predetermined wavelength region and a plurality of design wavelengths which exist in a predetermined design order and at which a maximum optical path length difference in the grating structure becomes an integer multiple of a wavelength, the diffractive optical element having a design wavelength &lgr;0 satisfying predetermined conditions.

Abstract: A diffractive optical element of the blazed-binary grating type is disclosed, with which a high diffraction efficiency can be achieved over substantially the entire used wavelength region. The diffractive optical element has a periodic structure taking a grating unit including a plurality of grating portions with different grating width and grating interval as one period. The diffraction element further includes a plurality of first grating portions made of a first material and a plurality of second grating portions made of a second material having a different refractive index than the first material that are arranged between the first grating portion.

Abstract: A layered diffractive optical element is disclosed, with which a high diffraction efficiency is attained over a broad region of used wavelengths, and with which diffraction light of unnecessary diffraction orders can be suppressed. A diffractive optical element of the present invention includes a plurality of diffraction gratings made of materials with different Abbe numbers, the plurality of diffraction gratings being layered with each other. Moreover, the partial dispersion ratio with respect to a g-line and a F-line of the material constituting at least one of the plurality of diffraction gratings satisfies the condition represented by a specified expression.

Abstract: A diffractive optical element includes a diffraction optical part provided with a phase-type diffraction grating. The diffraction grating of the diffraction optical part has on the surface thereof minute uneven structure of which the period is substantially constant. The period is smaller than a wavelength used.

Abstract: A diffractive optical element includes a plurality of laminated diffraction grating surfaces. Each of the diffraction grating surfaces is formed to have a sufficiently small grating thickness as compared with a grating pitch thereof.

Abstract: In a lens system having one or a plurality of diffracting surfaces and one or a plurality of refracting surfaces, a power of each surface and a distance between the surfaces are set such that an optical characteristic of the lens system, such as a focal length (focal point) and/or a spherical aberration, remains substantially unvarying relative to temperature variations within a predetermined range and that an achromatic effect is substantially attained for the focal length (focal point) and/or the spherical aberration within a predetermined region of wavelength.

Abstract: A diffractive optical element is composed of a plurality of diffraction gratings which differ in dispersion from each other and are laminated while being spaced to enhance diffraction efficiency for a particular order (design order) throughout an entire usable wavelength region, wherein edges of at least part of corresponding grating portions of the plurality of diffraction gratings are shifted from each other in a direction of arrangement of grating portions of each diffraction grating.

Abstract: In a projection display apparatus, light from a light source is separated into a plurality of beams having different wavelength regions, a plurality of image display elements (123r, 123g, 123b) are inserted in the optical paths of the respective separated beams so as to be illuminated by the beams. A color combiner (XDP) is provided for combining the beams emerging from the plurality of image display elements. The beams combined by the color combiner are projected on a projection surface. A diffraction optical element (124) is inserted in at least one of a plurality of optical paths between the plurality of image display elements and the color combiner.

Abstract: In a diffractive optical element, first and second diffraction gratings of 10 &mgr;m or less in thickness made from materials of respective different Abbe numbers are laminated through an air layer. The grating thickness of the first diffraction grating is made to be 7.5 &mgr;m, and the grating thickness of the second diffraction grating is made to be 6.54 &mgr;m. Glass of the Abbe number of 63.8 is used for the material of the first diffraction grating, and an ultraviolet curable polymer of the Abbe number of 23.0 is used for the material of the second diffraction grating. Accordingly, the diffraction efficiency of the diffractive optical element is improved to 97% or higher throughout the entire visible spectrum.

Abstract: To obtain a diffractive optical element of high diffraction efficiency over a wide range of wavelengths with no conspicuous color flare and a photographic optical system having the diffractive optical element, at least two diffraction gratings of different materials in dispersion are stratified, the first order is chosen as the design order and two wavelengths which, when multiplied one times, amounts to the maximum optical path length difference in the grating structure are used as the design wavelengths, wherein each of the values of the plurality of design wavelengths is determined so as to make white or nearly white flare caused by the diffracted light in the zero and second orders.

Abstract: To obtain a diffractive optical element of high diffraction efficiency over a wide range of wavelengths with no conspicuous color flare and a photographic optical system having the diffractive optical element, at least two diffraction gratings of different materials in dispersion are stratified, the first order is chosen as the design order and two wavelengths which, when multiplied one times, amounts to the maximum optical path length difference in the grating structure are used as the design wavelengths, wherein each of the values of the plurality of design wavelengths is determined so as to make white or nearly white flare caused by the diffracted light in the zero and second orders.

Abstract: This invention provides an image reading device capable of precise detection of the optical signal over a wide wavelength range, by forming a photoelectric converting unit for converting the visible light into an electrical signal and a photoelectric converting unit for converting the invisible light into an electrical signal, in monolithic manner on a single semiconductor chip.

Abstract: In a diffractive optical element having a diffraction grating formed at an interface between different substances, a total sum of values obtained by multiplying rates of change in refractive index due to temperature variations of the substances by a grating thickness of the diffraction grating is smaller than a useful wavelength.

Abstract: In a diffractive optical element, which is formed by laminating at least three layers of diffraction gratings made of at least three kinds of materials which differ in dispersion, at least three design wavelengths are set.

Abstract: In a lens system having one or a plurality of diffracting surfaces and one or a plurality of refracting surfaces, a power of each surface and a distance between the surfaces are set such that an optical characteristic of the lens system, such as a focal length (focal point) and/or a spherical aberration, remains substantially unvarying relative to temperature variations within a predetermined range and that an achromatic effect is substantially attained for the focal length (focal point) and/or the spherical aberration within a predetermined region of wavelength.

Abstract: Disclosed is a diffractive optical element which is made of at least two materials of different dispersions and which includes at least two diffraction gratings being accumulated one upon another, wherein each diffraction grating is formed on a curved surface of a substrate, and wherein a diffraction grating, of the at least two diffraction gratings, in which a curvature radius of the curved surface and a curvature radius of a grating surface in a portion where a grating pitch is largest, have different signs, is one of the at least two diffraction gratings which has a smallest grating thickness.

Abstract: In order to obtain a diffractive optical element with which a high diffraction efficiency can be obtained in a wide wavelength range and color flare is not noticeable and a picture taking apparatus using this diffractive optical element, an image is formed on a picture taking unit by using a diffractive optical element in an optical system. The diffractive optical element has a grating structure obtained by stacking a plurality of diffraction gratings made of at least two types of materials with different dispersion properties to enhance diffraction efficiency for a particular design order throughout a predetermined wavelength region and a plurality of design wavelengths which exist in a predetermined design order and at which a maximum optical path length difference in the grating structure becomes an integer multiple of a wavelength, the diffractive optical element having a design wavelength &lgr;0 satisfying predetermined conditions.

Abstract: A diffractive optical element includes a diffraction optical part provided with a phase type diffraction grating. The diffraction grating of the diffraction optical part has on the surface thereof minute uneven structure of which the period is substantially constant. The period is smaller than a wavelength used.

Abstract: A diffractive optical element is composed of a plurality of diffraction gratings which differ in dispersion from each other and are laminated while being spaced to enhance diffraction efficiency for a particular order (design order) throughout an entire usable wavelength region, wherein edges of at least part of corresponding grating portions of the plurality of diffraction gratings are shifted from each other in a direction of arrangement of grating portions of each diffraction grating.