Abstract: In the past there has been a problem that on a detection surface the influence of interference causes a defocusing signal to degrade, narrowing the range in which spherical aberration can be stably detected. Accordingly, a diffraction grating is used to focus the inner and outer sides of luminous flux on separate optical detectors before the optical flux is focused on an optical detector and defocusing signals are independently calculated to find the difference therebetween, thereby providing a spherical aberration signal. This makes it possible to detect spherical aberration signals more stably.

Abstract: An optical pickup device is equipped with a diffraction element that includes a transparent substrate. At least one surface of the transparent substrate is provided with a first region and a second region that encloses the first region. The surface is provided with a plurality of types of diffraction areas each of which generates predetermined diffracted light from only a light beam having a specific wavelength and permits other light beams having other wavelengths to pass through without diffraction. The first region is provided with each of the plurality of types of diffraction areas, while the second region is provided with only a diffraction area that generates the predetermined diffracted light from only a light beam having the maximum incident diameter among the plurality of types of diffraction areas.

Abstract: An optical head is provided with: an objective-lens-use opening that determines an aperture of the objective lens; a light-source light-quantity controlling opening that aperture-controls light that has been separated by the light separation device; a light detector that receives light that has been aperture-controlled by the light-source light-quantity controlling opening; and a light detector that receives light that has been reflected by the optical recording medium, and has an arrangement in which: the length of the optical light path from the spherical aberration correcting device to the objective-lens-use opening is made virtually the same as a length of the optical light path from the spherical aberration correcting device to the light-source light-quantity controlling opening, and the aperture of the light-source light-quantity controlling opening has virtually the same size as the aperture of the objective-lens-use opening.

Abstract: An optical head includes a blue color laser beam sources, a red color laser beam sources, a dichroic prism, a collimator lens, a beam splitter, an objective lens, a photo detector element, a detection lens, and a hologram element having a first hologram and a second hologram and the first hologram changes a phase of a +1st order diffraction light of a blue color laser beam so that its condensing point falls on a second photo detecting portion and the second hologram changes a phase of a ?1st order diffraction light of a red color laser beam so that its condensing point falls on a third photo detecting portion.

Abstract: In a photo pickup device, a hologram element 13 is divided into eight areas. In operation, the hologram elements adds different lens powers to four diffraction lights forming two pairs of diffraction-light groups. In the photo pickup device, a light receiving element 19 is divided into four areas to receive these diffraction lights. The photo pickup device outputs signals corresponding to four quadrants A, B, C and D forming a reflection light from an optical disc 5, allowing a focus-error signal to be calculated in the same logic as an “astigmatism method”.

Abstract: There is disclosed an optical pickup device including: a blue semiconductor laser which emits a first laser light having a wavelength of 450 nm or less to record on or reproduce from an extra-high density optical disc; a red semiconductor laser which emits a second laser light having a wavelength longer than that of the first laser light to record on or reproduce from a DVD having a low recording density; an objective lens; and an aberration correction element. The objective lens is designed for the extra-high density optical disc, and has a numerical aperture (NA) of 0.75 or more. The aberration correction element passes the first laser light as such and thereafter allows the light to be incident upon the objective lens, whereas the element limits an aperture with respect to the second laser light and diffracts the second laser light so as to correct an aberration with respect to the DVD and thereafter allows the light to be incident upon the objective lens.

Abstract: An objective lens module includes a light-converging lens that is coaxially disposed with respect to an optical axis of first laser light having a first wavelength, and a transmission-type diffractive optical element that is coaxially disposed to cause diffracted light of first laser light to be incident on the light-converging lens. The diffractive optical element has an incident surface and an emergent surface, and first, second, and third regions that are provided on at least of the incident surface and the emergent surface in the vicinity of the optical axis, and are sequentially defined according to different radius distances from the optical axis to have different diffraction gratings of different diffraction angles, respectively.

Abstract: Regional borderlines that are the borderlines between the first region and the second region on a diffraction grating of an optical pickup partially overlap a group of y-axis parallel borderlines that are borderlines between pattern A and pattern B that are parallel to a direction parallel to the y-axis.

Abstract: An optical reproducing apparatus that uses a hologram laser module and is applicable to a DVD Multi drive, wherein five sub spots of light in total that are most suitable to perform the differential push-pull tracking both for DVD-RAM and for DVD-R/RW are irradiated on the disk, respectively, and influence of several sub spots that are unnecessary in recording and reproducing a disk is canceled out by calculation, to realize an optical head that is compatible with the DVD Multi drive using a hologram laser module, and thereby providing a small-size, high-performance optical reproducing apparatus.

Abstract: The invention is directed to the provision of a liquid crystal optical element, for correcting wavefront aberrations (principally, coma aberration and spherical aberration), that can be mounted separately from an objective lens, and an optical apparatus using such a liquid crystal optical element. The liquid crystal optical element according to the invention includes a first transparent substrate, a second transparent substrate, a liquid crystal sealed between the first and second transparent substrates, and an electrode pattern as a region for advancing or delaying the phase of a light beam and thereby correcting wavefront aberration, wherein the region is formed smaller than the field of view of the objective lens so that the region substantially stays within the field of view of the objective lens regardless of the tracking motion of tracking means.

Abstract: An aberration correction element is disposed between first to third laser light sources and an objective lens, first and second laser lights emitted from the first and second laser light sources are incident upon the aberration correction element in the form of parallel lights, and a third laser light emitted from the third laser light source is incident upon the aberration correction element in the form of a divergent light.

Abstract: An optical pickup device including a dual wavelength light source module for emitting a selected one of two light beams having different wavelengths, a dual grating for splitting, into three beams, the selected light beam emitted from the dual wavelength light source, and a hologram for focusing the three beams of the selected light beam onto a photodetector having typical 8-section patterns such that the three beams of the selected light beam are focused onto the same spots as those of the other light beam, respectively.

Abstract: An optical scanning device for scanning an optical record carrier comprising an information layer. Crosstalk cancellation is provided using a phase modulating element (40, 140) for generating a non-rotationally-symmetric phase profile in a subsidiary radiation beam. The phase profile varies with an azimuthal angle measured about the optical axis of the beam portion, the phase profile varying such that successively different phases are introduced in at least five locations which are each at successive azimuthal angles (?1, ?2, ?N) and each at a given radial distance from the optical axis, wherein the phase profile is such that the phases introduced, when taken in modulo 2? form, successively cycle through 0 to 2? at least twice, whereby the subsidiary beam spot is provided with an intensity distribution on the information layer which overlaps that of the side-lobe of the main beam spot.

Abstract: An objective is used in an optical pickup apparatus which conducts reproducing and/or recording information for three different types of optical information recording media each having different thickness protective substrate by using three different wavelength light fluxes respectively. The objective comprises a first diffractive structure and in which the diffraction order for the maximum diffraction efficiency is the same for all of light fluxes, and a second diffractive structure that diffracts the second light flux without diffracting the first and third light fluxes.

Abstract: An optical pickup apparatus used in an optical data recording/reproducing apparatus for reading/reproducing data on an optical recording medium, including a light source, a diffracting device configured to transmit a light beam and to diffract a light beam reflected from the optical recording medium, an optical device having a reflecting portion and a transmitting portion configured to reflect one part of the light beam emitted from the light source and to transmit another part of the light beam to the optical recording medium and from the optical recording medium, and a photodetecting device to detect the light beam from the optical recording medium for signal light detection, and the light beam reflected by the reflecting portion of the optical device for monitor light detection of the light source.

Abstract: In an optical pick-up apparatus for recording to or reproducing from an optical information recording medium, the optical pick-up apparatus includes: a light source for emitting light flux; a light converging optical system having an aperture and an objective lens and converging the light flux emitted from the light source on the optical information recording medium; a photodetector for detecting light reflected from the optical information recording medium; and a driving section for driving the objective lens and the aperture in association with the objective lens.

Abstract: Providing an objective lens with a large numerical aperture (NA), the present invention records or plays conventional optical disks such as CDs and DVDs at high light usage efficiency, using an optical head capable of recording or reproducing high-density optical disks. A diffraction optical element (8) is disposed in a light path of a first light beam of a first wavelength ?1 (400 nm to 415 nm) and a second light beam of a second wavelength ?2 (650 nm to 680 nm). And, the present invention principally emits 5th order diffracted light with respect to the first light beam, and principally emits 3rd order diffracted light with respect to the second light beam, from the diffraction optical element (8). Thus, a high diffraction efficiency of substantially 100% can be obtained with respect to both wavelengths.

Abstract: Light emitted from a semiconductor laser (1) is split by a diffractive optical element (3a) into a main beam and sub-beams. The diffractive optical element (3a) is divided into four regions by a straight line parallel to a tangential direction of a disc (7) and a straight line parallel to a radial direction of the disc (7). A phase of grating in two regions arranged diagonally and a phase of grating in the other two regions arranged diagonally are different from each other by ?. A focused spot of the main beam and focused spots of the sub-beams are located on the same track. A focusing error signal is detected by a differential astigmatism method, using the main beam and the sub-beams.

Abstract: An optical pick-up apparatus includes: a semiconductor laser light source that generates an optical beam; a diffraction grating that divides the optical beam into a main beam and side beams; an optical element that guides the main beam and the side beams that are generated by the diffraction grating onto an optical information medium; and a photodetector that detects a signal from reflected light reflected from the optical information medium. The semiconductor laser light source is configured with a 2-wavelength semiconductor laser device in which a semiconductor laser chip that generates an optical beam having a wavelength of ?1 and a semiconductor laser chip that generates an optical beam having a wavelength of ?2 are integrated into one chip or are arranged in proximity to each other.

Abstract: A diffraction grating element including a diffraction grating area which includes: a first area that is one of two areas into which the diffraction grating area is divided by a first straight line, and is divided, by a second straight line perpendicular to the first straight line, into a first sub-area having a first diffraction grating pattern and a second sub-area having a second diffraction grating pattern, the first and second diffraction grating patterns having different diffraction angles; and a second area that is the other of the two areas into which the diffraction grating area is divided by the first straight line, and is divided into three or more divisional areas that align in a direction perpendicular to the second straight line, the first and second diffraction grating patterns being alternately assigned to each of the divisional areas.

Abstract: In a holographic pattern provided in a holographic optical element, a pattern 1a twists a diffracted light beam in a clockwise direction, to form a semi-circular light spot Sa on photodetection parts A and B so as to extend over a dividing line LX in a four-segment photodetection part. A pattern 1b similarly twists the diffracted light beam in a clockwise direction, to form a semi-circular light spot Sb on photodetection parts C and D so as to extend over a dividing line LX in the four-segment photodetection part.

Abstract: A diffraction grating with periodically arranged protrusions and grooves at a relatively narrow pitch and improved diffraction efficiency is disclosed. The protrusions of the grating are made of a material whose index of refraction is greater than that of the grooves, and the ratio of the width D of the protrusion to the pitch ? of the protrusion is set equal to or less than 0.4 (D/??0.4).

Abstract: An objective lens of an optical pickup apparatus converges a divergent light flux onto an information recording surface. The following conditional formula is satisfied: |?SA1/?U|·|?U|+|?SA2/?T|·|?T|?0.07 ?rms where ? represents a wavelength of a light source, ?SA1/?U represents a change of a spherical aberration for an object-to-image distance change ?U (|?U|?0.5 mm) and ?SA2/?T represents a change of spherical aberration for a temperature change ?T (|?T|?30° C.), the object-to-image distance is a distance between the light source (a light emitting point) and the information recording surface.

Abstract: Disclosed is an objective lens for a DVD/CD compatible optical pickup, which improves optical efficiency while minimizing aberration occurring due to different disc thicknesses of different optical storage media. The objective lens has first and second aspherical lens surfaces.

Abstract: This invention is directed to an optical pickup apparatus, condensing optical system, and optical element which can at least reproduce and/or record information from/on a first optical information recording medium having a protective substrate thickness t1 by using a light beam of a first wavelength ?1 emitted from a first light source, and reproduce and/or record information from/on a second optical information recording medium having a protective substrate thickness t2 (t2?t1) by using a light beam of a second wavelength ?2 (?2>?1) emitted from a second light source.

Abstract: Disclosed herein is an optical pickup device. The optical pickup device has a lead frame package and a detecting unit. The lead frame package has a lead frame, a two-wavelength light source module and a hologram optical element. The lead frame has an opening formed to communicate with the outside. The two-wavelength light source module is arranged in a portion of the opening for emitting two beams having different wavelengths toward an optical disc. The hologram optical element is arranged over the two-wavelength light source module. Further, the hologram optical element includes a hologram pattern formed in its top and a wavefront-compensation hologram pattern formed on its bottom. The detecting unit has a board arranged beneath the lead frame package to be separated from and moved independently of the lead frame package, and a photo detector mounted on said board.

Abstract: A device for scanning a first and second type of optical record carriers (2, 40) generators a first and a second radiation beam for scanning the first and second type of record carriers, respectively. The information layers (4, 42) of the first and second type of record carriers is scanned through transparent layers (3, 41) of different thickness. The first radiation beam (17) has a first wavelength and a first numerical aperture NA?1. The second radiation beam (46) has a different, second wavelength and an effective second numerical aperture NA2 smaller NA1. The rays of the second radiation beam having an NA smaller than NA2 form a central sub-beam (48), the rays having a larger NA form an outer sub-beam (49). The device includes a non-periodic phase structure that does not affect the first radiation beam. The phase structure introduces an amount of spherical aberration in the central sub-beam (48). The phase structure is transparent for the central and outer sub-beam (48, 49).

Abstract: In a holographic pattern provided in a holographic optical element, a pattern 1a twists a diffracted light beam in a clockwise direction, to form a semi-circular light spot Sa on photodetection parts A and B so as to extend over a dividing line LX in a four-segment photodetection part. A pattern 1b similarly twists the diffracted light beam in a clockwise direction, to form a semi-circular light spot Sb on photodetection parts C and D so as to extend over a dividing line LX in the four-segment photodetection part.

Abstract: A six-segment holographic surface is divided into regions by dividing lines. A four-segment photodetection part is divided into four photodetection parts equal in area by a section line substantially parallel to the radial direction of an optical disk and a section line orthogonal thereto. A main light beam diffracted in the regions of the six-segment holographic surface are condensed as spots at positions apart from each other on opposite sides on a section line of the four photodetection parts, and the main beam diffracted in the regions is condensed as spots in the center of the photodetection parts of the four-segment photodetection part.

Abstract: An optical pickup apparatus used in an optical data recording/reproducing apparatus for reading/reproducing data on an optical recording medium, including a light source, a diffracting device configured to transmit a light beam and to diffract a light beam reflected from the optical recording medium, an optical device having a reflecting portion and a transmitting portion configured to reflect one part of the light beam emitted from the light source and to transmit another part of the light beam to the optical recording medium and from the optical recording medium, and a photodetecting device to detect the light beam from the optical recording medium for signal light detection, and the light beam reflected by the reflecting portion of the optical device for monitor light detection of the light source.

Abstract: The semiconductor laser device includes a signal light diffraction grating, and a light receiving portion having a pair of photodiodes extending as two strips with a parting portion or a zonal gap interposed therebetween and receiving a focus error detecting beam from the signal light diffraction grating. The light receiving portion is arranged such that its longitudinal direction is orthogonal to the direction of diffraction grooves of the signal light diffraction grating. The pair of photodiodes is arranged such that a spot of the focus error detecting beam moves, due to temperature changes, in a range essentially limited to the parting portion therebetween. Thus, a semiconductor laser device and an optical pickup apparatus suppressing focus errors due to temperature changes and preventing reduction in signal strength can be obtained.

Abstract: An optical pickup apparatus for reproducing information from an optical information recording medium or for recording information onto an optical information recording medium, is provided with a first light source for emitting first light flux having a first wavelength; a second light source for emitting second light flux having a second wavelength, the first wavelength being different from the second wavelength; a converging optical system having an optical axis and a diffractive portion, and a photo detector; wherein in case that the first light flux passes through the diffractive portion to generate at least one diffracted ray, an amount of n-th ordered diffracted ray of the first light flux is greater than that of any other ordered diffracted ray of the first light flux, and in case that the second light flux passes through the diffractive portion to generate at least one diffracted ray, an amount of n-th ordered diffracted ray of the second light flux is greater than that of any other ordered diffracted

Abstract: An optical system utilized in an optical pickup apparatus comprising: an aberration-correcting element made of a plastic material; and a converging lens to converge a light flux emitted from the aberration-correcting element, the converging lens being made of a plastic material, wherein the aberration-correcting element has a first optical surface provided thereon an optical path difference generating structure and has a second optical surface provided thereon a diffractive structure, and the converging lens is a single refractive lens having at least an aspherical surface.

Abstract: An optical pickup unit includes a light source of semiconductor laser chips of different light-emission wavelengths; a plurality of holograms placed between the light source and an optical recording medium, the holograms including at least one non-polarization hologram having a substantially uniform diffraction efficiency irrespective of the direction of polarization of incident light and at least one polarization hologram having a diffraction efficiency varying depending on the direction of polarization of incident light; and a wave plate provided between the optical recording medium and the polarization hologram. The returning beam of a light beam emitted from a selected one of the semiconductor laser chips is diffracted by the corresponding one of said holograms to be received by a light-receiving element. The wave plate turns the direction of polarization of the returning beam to a different direction from that of the emitted light beam.

Abstract: An objective optical element and an optical pickup device at least capable of reproducing and/or recording information from and/or on a high-density optical disk and securing an even light volume. The objective optical element is made of a single lens for use in an optical pickup device at least reproducing and/or recording information from and/or on a first optical information recording medium by focusing a light beam having a wavelength &lgr;1 (380 nm≦&lgr;1≦450 nm) on an information recording surface of the first optical information recording medium having a protected substrate thickness t1 (0 mm<t1≦0.7 mm). The objective optical element has a convex object-side optical surface and a diffracting structure having positive diffraction power at least on one of the object-side and image-side optical surfaces, and is formed from a lens material satisfying 97≦T1≦99 where T1 (%/mm) is an optical transmittance not including a reflection loss for the light beam having the wavelength &lgr;1.

Abstract: In a diffraction grating used in an optical head device leading light, diffracted light exiting from each of the plurality of areas is lead to a corresponding particular photo-detecting area of the photodetector. Each of the plurality of areas of the diffraction grating is produced either by first two-beam interference exposure to interference fringes from first divergent light from a position equivalent to a light emitting point on the light source of the optical head device and second divergent light form a position equivalent to a light receiving point corresponding to each photo-detecting area, or by second two-beam interference exposure to interference fringes from first convergent light converging at the position equivalent to the light emitting point on the light source and second convergent light converging at the point equivalent to the light receiving point corresponding to each photo-detecting area.

Abstract: An optical pickup apparatus includes

Abstract: An optical pickup apparatus for reading/reproducing data on an optical recording medium, includes a plurality of laser diodes configured to emit laser light of different wavelengths respectively, a photodetection device configured to detect each laser light, a diffraction type-optical device configured to transmit each laser light from the plurality of laser diodes to the optical recording medium, and to diffract the light reflected from the optical recording medium to the photodetection device, and wherein the diffraction type-optical device includes a plurality of reflecting type-diffraction elements configured to reflect and diffract each laser light of a corresponding wavelength in the laser light from the plurality of light diodes, to the photodetection device so that the photodetection device can detect each laser light of the corresponding wavelength for monitoring each of the laser light, and a suppression setting device configured to set each of the plurality of reflecting type-diffraction elements t

Abstract: An objective optical system for aberration correction and an optical head adopting the objective optical system are provided. The objective optical system includes a diffraction lens and a refractive lens. The diffraction lens converges incident light and corrects aberration. The refractive lens focuses light transmitted by the diffraction lens on an optical disk. Contamination and damage of the diffraction lens are prevented, and light receiving efficiency is improved.

Abstract: An objective lens comprises at least inner and outer optically functional regions arranged in a direction perpendicular to an optical axis and each of the inner and outer optically functional regions has a diffractive structure. The objective lens comprises a light amount reducing structure to reduce an amount of the light flux passing through a region of the objective lens other than the inner optically functional region when recording or reproducing is conducted for CD.

Abstract: An optical device molding die designing method measures a wavefront aberration amount (&Dgr;) of an optical device molded by a temporary die, calculates a correction wavefront aberration amount (−&Dgr;) compensating for the wavefront aberration amount (&Dgr;), optically designs the optical device again by optimizing its form so as to generate the correction wavefront aberration amount (−&Dgr;), and designs a normal die accordingly.

Abstract: In an optical head for writing and reading data on optical discs (mainly CDs and DVDs) with various specifications using different light source wavelengths, the effective light beam size for the light from each light source differs. This leads to a drop in optical efficiency for the light of a narrower effective beam size. This problem is overcome by providing a dichroic beam expander between the light sources and an objective lens, the dichroic beam expander comprising a substrate with an N-stage step- or sawtooth-shaped blazed diffraction grating formed on both sides thereof. The size of the light beams from the two light sources with different wavelengths is increased or decreased in a wavelength-selective manner, so that the light from each light source can be utilized at high efficiencies.

Abstract: In an optical pickup device for conducting reproducing and/or recording of information in at least two kinds of optical information recording media, an optical element divides a light flux into k(k≧4) pieces of ring-shaped light flux. When reproducing or recording is conduced for a first optical information recording medium, the first light flux and the k-th light flux are converged on the first information recording surface and at least two pieces of light flux of the second light flux to the (k-1)th light flux form an apparent best image plane at a position different from the position of the best image plane formed by the first light flux and the k-th light flux. A wave front aberration of each light flux passing in a required numerical aperture for the first optical information recording medium is made approximately mi&lgr;1.

Abstract: An objective lens and optical pickup device that uses it is disclosed having an optical diffraction surface on its surface nearest a light source which may be switched in wavelength for either CD or DVD recording/replaying. The optical diffraction surface causes a selected wavelength beam to converge or diverge more than the other wavelength beam. Superimposed in a peripheral region of the diffraction grating is a step change in height (higher or lower) which causes destructive interference for light in the peripheral region for only one of the beams. In this way, an objective lens is provided that, with a simple and compact structure, enables a light beam to be converged accurately into a spot on a selected recording medium, despite the need to have the converged beam have different wavelengths and numerical apertures, depending on the recording medium used.

Abstract: A laser diode unit for an optical pick-up apparatus includes a laser diode for emitting a laser beam; a monitor photodiode for controlling recording optical power; an optical disc on which data is written by the laser beam or from which data is read by the laser beam; and a lens module for reflecting a part of the light beam emitted, in the form of a divergent light beam, from the laser diode, thereby focusing the light beam onto the optical disc, the lens module also serving to transmit the remaining part of the light beam therethrough, thereby allowing the transmitted light beam to be converged by the monitor photodiode. The laser diode unit achieves a slimness of the optical pick-up apparatus while reducing the number of elements required for the laser diode unit and the number of process steps required in the manufacture of the laser diode unit.

Abstract: The objective lens is a biconvex plastic lens having first and second surfaces which are both aspheric. The objective lens is divided into an inside area which is inside of a circle of an effective diameter of the objective lens and an outside area which is outside of the circle of the effective diameter. A diffractive lens structure having a plurality of concentric ring-shaped steps is formed in the inside area. A surface of the outside area is continuous with no steps and corresponds to a macroscopic base curve of the inside area. The objective lens has a gap of a spherical aberration between the inside area and the outside area.

Abstract: An optical head device includes a first laser light source that emits a first laser beam with a first wavelength, a second laser light source that emits a second laser beam with a second wavelength which is different from that of the first laser beam, a common objective lens that converges the first laser beam on a recording surface of a first optical recording medium and the second laser beam on a recording surface of a second optical recording medium, a refraction surface that is formed on the common objective lens so as to be divided into a center side refraction surface region around an optical axis of the common objective lens and an outer peripheral side refraction surface region surrounding the center side refraction surface region and a center side diffraction grating that is formed all over the center side refraction surface region and is provided with a number of minute steps in a concentrically circular shape.

Abstract: An optical pick-up includes light sources for emitting light beams having different wavelength, the light sources being switched according to the kind of optical discs, a refractive lens element for converging the light beams from the light sources onto recording layer of the optical disc; and a spherical aberration correcting element on which a concentric phase grating structure is formed, the phase grating structure altering spherical aberration in response to change of wavelength to correct change of the spherical aberration due to change of the thickness of the cover layer. The spherical aberration correcting element has a wavelength dependence such that spherical aberration varies in the undercorrected direction as wavelength of incident light increases.

Abstract: Disclosed herein is an optical pick-up apparatus using a holographic optical element and method of forming holographic gratings of the element. The apparatus includes a light emitting element for generating three beams with different wavelengths, a multiplexed holographic optical element provided with three holographic gratings for receiving beams reflected from an optical disc and diffracting the received beams according to wavelengths of the received beams, and a light receiving element for receiving beams diffracted while passing through the multiplexed holographic optical element. The method includes the steps of forming a first holographic grating on a transparent substrate, forming a first transparent layer on the substrate on which the first holographic grating is formed, forming a second holographic grating on the first transparent layer, forming a second transparent layer on the first layer on which the second holographic grating is formed, and forming a third holographic grating on the second layer.

Abstract: An integrated micro-optical system includes at least two wafers with at least two optical elements provided on respective surfaces of the at least two wafers. An active element having a characteristic which changes in response to an applied field may be integrated on a bottom surface of the wafers. The resulting optical system may present a high numerical aperture. Preferably, one of the optical elements is a refractive element formed in a material having a high index of refraction.