Abstract: A radially non-symmetric beamforming element for transforming the input energy profile of an input laser beam subject to lateral shift that is variable in radial direction and magnitude into a desired output energy profile of an output laser beam. The beam forming element includes an optical element having a profile transformation function that includes a first profile transformation function for transforming the input energy profile into the desired output energy profile and a profile correction transformation function superimposed on the first profile transformation function for modifying the first profile transformation function to correct distortions in the output energy profile introduced be a lateral shift of the input laser beam.

Abstract: A first optical system (11) has a first beam splitter (211). The first beam splitter (211) splits light arriving through a first optical path (P1) into two light beams, and outputs one light beam to a second optical path (P2) and the other light beam to a third optical path (P3). A second optical system (21) outputs the light output from the first beam splitter (221) to the second optical path (P2) and arriving at the second optical system (21) upon giving the light an intensity change with wavelength dependence and a phase change, and has a second beam splitter (221), first reflecting mirror (223), and second reflecting mirror (222). This makes it possible to provide an optical filter (200) which can realize a characteristic excellent in isolation with a very simple arrangement.

Abstract: Devices and methods for information processing in optical communications are provided. In its simplest embodiments, collimated light (1) passes through a non-grating diffractive structure (2) and a lens (3). The light is spatially processed in the focal plane (4) of the lens (3). Thereafter, the light can, for example, be coupled into a fiber or detector array (5).

Abstract: An HMD device is provided, comprising an image element for generating an image and imaging optics projecting the image such that it is perceivable by a user wearing said HMD device, wherein said imaging optics comprise a first optical group including a first lens, which has negative refractive power, and a second lens, which has positive refractive power, a deflecting element arranged following the first optical group as well as a second optical group following the deflecting element, said second optical group comprising a third lens, and wherein, for correction of astigmatism and distortion, at least one surface of the first and second lenses is aspheric and, for correction of the spherical aberration, at least one surface of the third lens is aspheric.

Abstract: Optical properties with high non-linearity such as a modulation transfer function (MTF) are efficiently optimized at high speed compared to conventional methods. An optimal solution of an optical system is obtained in a first optimization unit using a merit function on aberration. Weights or target values of the merit function on aberration is automatically adjusted in a second optimization unit in a manner that an evaluated value of the MTF or the like approaches a desired value. The first optimization unit re-optimizes the optical system using the weights or target values which have been automatically adjusted. Thus, automated is a function equivalent to the operation which has been conducted by a designer such as adjustment to weights or target values.

Abstract: A compact reflector telescope has a spherical primary reflector and a secondary reflector with a negative lens interposed there between in axial alignment therewith. Light reflected from the primary reflector is passed through the negative lens and is diverted by the secondary reflector to a positive lens at the side of the telescope tube. The positive lens focuses the light rays onto an eye piece or ocular or onto a photographic emulsion or electronic detector. The telescope reduces or substantially eliminates spherical aberration and can be configured to have a focal ratio significantly greater than the focal ratio of the primary reflector. The telescope produces a flat field of view and an image which is substantially diffraction limited.

Abstract: A high-performance and low-cost image-forming optical system with a reduced number of constituent optical elements that is made compact and thin by folding an optical path using reflecting surfaces arranged to minimize the number of reflections. The image-forming optical system has a first prism and a second prism between a stop and an image plane. The first prism includes an entrance surface, a first reflecting surface, a second reflecting surface, and an exit surface. The first reflecting surface and the exit surface are the identical surface. The second prism includes an entrance surface, a first reflecting surface, a second reflecting surface, and an exit surface. In the second prism, the second reflecting surface and the entrance surface are the identical surface.

Abstract: The invention is an apparatus for lengthening the path of a light beam. The apparatus includes an at least partially enclosed chamber having a first opening and a second opening. A first reflective surface is disposed within the chamber and is obliquely oriented with respect to an incoming path of the beam. The beam reflects off of the first reflective surface after the beam enters the chamber through the first opening. Second and third reflective surfaces are disposed within the chamber and are generally parallel to the incoming path of the beam. The beam is reflected a plurality of times between the second and third reflective surfaces after the beam is reflected by the first reflective surface. A fourth reflective surface is disposed within the chamber and is obliquely oriented with respect to the incoming path of the beam. The fourth reflective surface directs the beam through the second opening after the beam has been reflected a plurality of times between the second and third reflective surfaces.

Abstract: Optical systems (1-19) for endoscopes and the like are characterized by an integrated design in which the locations of the components and the aberration corrections are no longer tied to the optical functions of the objective (1-6) and the relays (7-19), and in which the relays may depart from symmetry. The power requirements can thus be shifted from one group to another, thereby reducing the overall power requirement. Moreover, the aberration correction can be shared between the optical group of the integrated system.

Abstract: The present invention relates to a high-performance image-forming optical system made compact and thin by folding an optical path using reflecting surfaces arranged to minimize the number of reflections. A prism member 10 has a first entrance surface 11, first to fourth reflecting surfaces 12 to 15, and a first exit surface 16. An optical path incident on the first reflecting surface 12 and an optical path reflected from the second reflecting surface 13 form intersecting optical paths. An optical path incident on the third reflecting surface 14 and an optical path reflected from the fourth reflecting surface 15 form intersecting optical paths. At least either one of the first reflecting surface 12 and the second reflecting surface 13 and at least either one of the third reflecting surface 14 and the fourth reflecting surface 15 have a rotationally asymmetric curved surface configuration that gives a power to a light beam and corrects aberrations due to decentration.

Abstract: An optical element comprising an object-side imaging element for imaging an object on an intermediate image plane in an optical path before a final image plane and an image-side imaging element for reimaging an object image formed on the intermediate image plane, on the final image plane, wherein at least one of the object-side imaging element and the image-side imaging element comprises an off-axial curved surface, and wherein aberration is generated by both of the object-side imaging element and the image-side imaging element, thereby flattening (disturbance of) a light intensity distribution caused on the final image plane by a noise source at or near the intermediate image plane.

Abstract: A catadioptric objective is provided with a beam splitter surrounded at least partially by a mount, with a mirror, with a plurality of lenses and with a &lgr;/4 plate arranged between the mirror and the beam splitter.

Abstract: The present invention relates to a high-performance image-forming optical system made compact and thin by folding an optical path using reflecting surfaces arranged to minimize the number of reflections. A prism member 10 has a first entrance surface 11, first to fourth reflecting surfaces 12 to 15, and a first exit surface 16. An optical path incident on the first reflecting surface 12 and an optical path reflected from the second reflecting surface 13 form intersecting optical paths. An optical path incident on the third reflecting surface 14 and an optical path reflected from the fourth reflecting surface 15 form intersecting optical paths. At least either one of the first reflecting surface 12 and the second reflecting surface 13 and at least either one of the third reflecting surface 14 and the fourth reflecting surface 15 have a rotationally asymmetric curved surface configuration that gives a power to a light beam and corrects aberrations due to decentration.

Abstract: A light guide for display devices of the head-mounted or head-up type comprises: a body of the light guide (22) at least in part transparent to visible light; a coupling device (24) associated to the body of the light guide (22) and designed to couple the body (22) to an optical system (18) designed to generate an image, the coupling device (24) being obtained in such a way that the light beams coming from the optical system (18) enter the body of the light guide (22) and propagate within the body (22) by total internal reflection; and an image-extraction grating, designed to extract the light beam that propagate in the body of the light guide (22) so as to enable an observer to visualize the extracted image against a background visible in transparency through the body of the light guide (22), wherein the extraction grating (32) is set in the proximity of one of the outer surfaces of the guide and has a saw-tooth profile, and wherein the extraction grating (32) is coated with a partially reflecting coating

Abstract: An objective lens for an optical pickup has a single lens element. One surface of the objective lens is divided into a central area and a peripheral area, and a step providing a level difference along a direction of the optical axis is formed at a boundary therebetween. The step provides a phase shift between light passing through the central area and the peripheral area. The level difference is formed such that a thickness on the peripheral area side is greater than a thickness on the central area side at the boundary. In one case, the objective lens satisfies a condition: 0.83<hx/hmax<0.97, where hx is a radius of the boundary, and hmax is an effective radius defining a numerical aperture of the surface formed with the step.

Abstract: A terrestrial telescope with digital camera includes objective lenses, an imaging element located downstream of the objective lenses, a retractable optical-path splitter between the objective lenses and the imaging element, and an optical system for observing an optical image divided from the optical path of the imaging optical system by the optical-path splitter. An optical element is inserted into the optical axis of the imaging optical system to correct for any change in the image-formation position when the optical-path splitter is retracted from the optical path of the imaging optical system during imaging.

Abstract: A single-element objective lens for an optical pick-up directs an incident light beam to a data recording surface of an optical disc through a cover layer to form a beam spot thereon. A numerical aperture of the objective lens is 0.7 or more. The objective lens is configured to compensate for coma such that a characteristic of a change of spherical aberration due to a degree of divergence/convergence of the incident beam is comparable with respect to a characteristic of a change of spherical aberration due to variation of the cover layer so that the change of spherical aberration due to variation of the cover layer can be cancelled by the change of spherical aberration due to a degree of divergence/convergence of the incident beam.

Abstract: A parallel glass plate mounted on a rotating fixture is used to precisely control the optical path length of a light beam. The glass plate refracts the incident optical signal to increase the length of its optical path as a function of the angle of incidence. The device can easily achieve a precision in the order of nanometers and is particularly suitable to fine tune the cavity length of a resonator and the optical path difference of an interferometer. Accordingly, the preferred application of the invention is in an interferometric interleaver. The glass plate can also be coated with a partially reflective coating to attenuate the optical signal passing therethrough. By judiciously selecting the refractive index, the thermal coefficient of refraction, and the coefficient of thermal expansion of the glass, thermal effects may be virtually eliminated.

Abstract: Embodiments of the present invention provide methods and systems of temporally smoothing the distortion of a light beam caused by imperfections of an optical element or optical system through which the light beam passes. The optical element is moved relative to the light beam to change a position of the imperfections in the path of the light beam to distribute the distortion of the light beam caused by the imperfection without substantially changing the path of the light beam. In some embodiments, the optical element is axially symmetric with respect to its optical axis, and the distortion of the light beam is distributed by rotating the optical element around its optical axis. In some embodiments, the optical element has geometric uniformity relative to a plane or along a line in a plane, and the distortion of the light beam is distributed by moving the optical element along the plane, or along the line of symmetry in the plane.

Abstract: Apparatus and methods for reducing optical distortion in an optical system by thermal means are disclosed. The apparatus includes a heating/cooling system spaced apart from and in thermal communication with an internally reflecting surface of a refractive element in the optical system. The heating/cooling system is adapted to create a select temperature distribution in the refractive optical element near the internally reflecting surface to alter the refractive index and/or the surface profile in a manner that reduces residual distortion.

Abstract: Disclosed is an objective lens of an optical pick-up that converges light beams of two different wavelengths onto recording layers of optical discs of two different standards, respectively. The objective lens includes a refractive lens having a positive power and a diffractive lens structure formed on one surface of the refractive lens. The diffractive lens structure has a plurality of concentric ring areas with minute steps at the boundaries therebetween. The diffractive lens structure maximizes the diffraction efficiency of the third order diffracted light at the shorter wavelength and maximizes the diffraction efficiency of the second order diffracted light at the longer wavelength. This enables the diffractive lens structure to correct the chromatic aberration at the respective wavelengths with keeping high diffraction efficiency.

Abstract: The invention relates generally to optical interference filters and interferometers. Methods, devices and device components are presented for separating closely spaced optical channels with minimized cross talk. The invention provides optical interference filters having parallel phase control elements which efficiently transmit light of a selected optical channel or a plurality of selected channels with decreased light loss, particularly decreased insertion loss. An exemplary interference filter of the present invention provides minimized vertical and horizontal recombination error and improved optical path length matching. The invention further provides methods of fabricating optical interference filters with improved piece-to-piece reproducibility.

Abstract: An optical pickup apparatus, in which the quantity of light incident to an aperture diaphragm of an objective lens and the “rim intensity (RI)” are maintained constant even when a spherical aberration is corrected by passing a light beam through an expander lens unit before it reaches the objective lens, and which is able to adequately read/write information signals from/to optical recording media, and a read/write apparatus which includes the optical pickup apparatus are provided. The expander lens unit includes a first lens group and a second lens group, and is disposed such that a focal position of the second lens group, which is closer to the objective lens than the first lens group, is on the aperture diaphragm of the objective lens.

Abstract: The present invention relates to an image display apparatus, e.g. a head-mounted image display apparatus, in which an image from a single image display device is led to two eyes without using a half-mirror, thereby allowing observation of a bright image. The image display apparatus has an optical path distributing mirror 1 for distributing the image of a single display device 10 to an optical path for a right eye and an optical path for a left eye, and an ocular prism 2R for the right eye and an ocular prism 2L for the left eye, which are placed on the right- and left-hand sides, respectively, of the optical path distributing mirror 1.

Abstract: A system and method for providing images for an operator of a vehicle include the capability to receive electrical signals representing electromagnetic radiation at an image source and to generate a visual image based on the electrical signals. The system and method further include the capability to reflect different portions of the visual image with a magnifying optical element for presentation at different viewing locations, the visual image appearing as a virtual image, wherein at least one dimension of the visual image is larger than the magnifying optical element can use to present an image at one of the viewing locations.

Abstract: A wavelength controller includes a wavelength locker module, having a prism for dividing incident light into first and second branched light beams, a first light quantity detector for receiving the first branched light beam through a wavelength selective filter and a second light quantity detector for directly receiving the second branched light beam, and detects and suppresses a wavelength variation in incident light entering the module based on outputs of the light quantity detectors.

Abstract: A high-performance image-forming optical system made compact and thin by folding an optical path using reflecting surfaces arranged to minimize the number of reflections. The image-forming optical system has a single prism. When image-side three surfaces of the prism are defined as a surface A, a surface B and a surface C in order from the image plane side thereof, at least one of the surfaces B and C has a rotationally asymmetric curved surface configuration that gives a power to a light beam and corrects aberrations due to decentration. The optical system leads light rays from an object to the image plane without forming an image in the prism and has a pupil in the prism. The surface A is a transmitting surface through which rays exit from the prism. The surfaces B and C are internally reflecting surfaces, which are positioned to face each other to form a Z-shaped optical path.

Abstract: An extremely compact prism optical element, image observation apparatus and image display apparatus which are capable of providing an observation image that is clear and has minimal aberration and minimal distortion even at a wide field angle. Light rays emitted from an image display device (7) enter an ocular optical system (12) through a fourth surface (6) and are totally reflected toward an observer's pupil (1) by a third surface (5). The reflected light rays are reflected by a first surface (3) disposed immediately in front of the observer's pupil (1) and then reflected toward the observer's pupil (1) by a second surface (4). The reflected light rays pass through the first surface (3) and are projected into an observer's eyeball (15) with the observer's iris position as an exit pupil (1).

Abstract: An aberration-correcting optical relay for an optical system. The relay comprises front and rear converging optical units together with a correcting meniscus or two correcting meniscuses placed symmetrically relative to each other, the meniscus(es) having main faces that are substantially concentric, and preferably exactly concentric, the two converging optical units being placed on a common axis and the correcting meniscus(es) being placed on said axis between the two converging optical units. The front converging optical unit situated upstream from the correcting meniscus(es) is placed in such a manner that the distance from an image point of the portion of the optical system upstream from the optical relay to the front converging optical unit is equal to the focal length of the front converging optical unit, said unit thus transforming a beam coming from said image point into a parallel beam.

Abstract: An optical pickup apparatus comprises two light sources having two wavelengths (&lgr;1<&lgr;2) and a converging optical system having an objective lens. The objective lens comprises a central region; a peripheral region provided at an outside of the central region on at least one optical surface of the objective lens; a diffractive ring-shaped zones which is blazed on a basis of a wavelength &lgr;0 (&lgr;1<&lgr;0<&lgr;2) and is formed on each of the central region and the peripheral region; and a phase difference suppressing structure to suppress a phase difference between a wavefront of a light flux passing the central region and a wavefront of a light flux passing the peripheral region when recording or reproducing information is conducted for the first optical information recording medium.

Abstract: A microlithographic illumination method for imaging a pattern arranged in an object plane of a projection lens onto an image plane of the projection lens, under which a special means for optically correcting the optical path lengths of s-polarized and p-polarized light such that light beams of both polarizations will either traverse essentially the same optical path length between the object plane and the image plane or any existing difference in their optical path lengths will be retained, largely independently of their angles of incidence on the image plane, which will allow avoiding contrast variations due to pattern orientation when imaging finely structured patterns, is disclosed. The contrast variations may be caused by uncorrected projection lenses due to their employment of materials that exhibit stress birefringence and/or coated optical components, such as deflecting mirrors, that are used at large angles of incidence.

Abstract: Systems and methods for adjusting optical path length of an optical path are provided. The systems and methods can be used to controllably adjust optical path length in an external cavity laser. A representative optical path having a first end and a second end comprises a first transparent refractive element located in the optical path between the first end and the second end. The transparent refractive element is adjustable to adjust the optical path length of the optical path without changing the physical distance between the first end and the second end. A representative method includes introducing a transparent refractive element into the optical path and adjusting the transparent refractive element to change the optical path length without changing the physical distance between the first end and the second end of the optical path.

Abstract: The light which is input from an optical fiber to a first port is output to an optical path. The light which is input from the optical path to a half mirror is branched into two, and is output to the optical paths. The light which is output to the optical path reaches to and is reflected from a first reflecting mirror, and returns to the half mirror by an optical path. The light which is input to the half mirror by the optical path is branched into two, and is output to the optical paths. The light which is output to the optical path reaches to and is reflected from a second reflecting mirror, and returns to the half mirror by an optical path. The light which is input to the half mirror by the optical path is branched into two, and is output to the optical paths. The light which is output to the optical path is output from a second port to an optical fiber, and the light which is output to the optical path is output from a third port to an optical fiber.

Abstract: An optical recording/reproducing apparatus has a light source that radiates a laser beam, an optical detector that detects reflected light from the optical disc, a collimator lens that converts the radiated light of the light source into a fine divergent pencil of rays, and an objective lens that focuses these rays on the optical disc. The collimator lens has a surface that is curved to form a wavefront shape that increasingly corrects a coma aberration of the radiated light in correspondence to a radial distance between the center of the collimator lens and a position at which the radiated light intersects the collimator lens.

Abstract: An arrangement is disclosed for illumination with a plurality of wavelengths in a microscope. The arrangement comprises correction optics which are provided in a parallel beam path within illumination/imaging optics for generating an exact overlapping of the wavelengths in the specimen volume in an adjustable manner. The correction optics generate an adjustable directional change for at least one wavelength to compensate transverse chromatic aberrations for the wavelength.

Abstract: A prism body has three or more optical surfaces, inclusive of a decentered optical surface with curvature, and has a positive refractive power. The optical surfaces include a diffracting surface having a rotationally asymmetric phase distribution, or the optical surfaces include a diffracting surface having a rotationally symmetric phase distribution on a surface with refractive powers differing depending upon azimuthal angles. An image display apparatus has the prism body and is constructed in such structure that, using the prism body, light from a display displaying image information is guided to the pupil position of an observer to permit the observer to observe the image information displayed on the display.

Abstract: The present invention relates to a compact and low-cost image pickup apparatus capable of photographing a high-quality image comparable to silver halide photographs, particularly an image in which color shift is inconspicuous. In the image pickup apparatus, an image of an object produced by an optical system 10 is formed on an electronic image pickup device 20, thereby obtaining image information concerning the object. The electronic image pickup device 20 and the optical system 10 satisfy the conditions: (1) 1.5<P<7.0; (2) 3.0<N<20; (3) 1.0×P<67 <5.0×P; and (4) nL/nT<0.25; where P is the pixel pitch (given in micrometers) of the image pickup device; N is the number of pixels (given in million) of the image pickup device; and &thgr; is the angle (°) at which the central ray of a light beam exiting from the optical system or a ray passing through the center of a stop is incident on the image pickup device at the maximum image height.

Abstract: A high-performance and low-cost image-forming optical system has a reduced number of constituent optical elements and is made extremely thin, particularly in a direction perpendicular to an image pickup device, by folding an optical path using only three reflecting surfaces. The image-forming optical system has a front unit including a first prism 10, an aperture stop 2, and a rear unit including a second prism 20. The first prism 10 has a first transmitting surface 11, a first reflecting surface 12, and a second transmitting surface 13. The second prism 20 has a first transmitting surface 21, a first reflecting surface 22, a second reflecting surface 23, and a second transmitting surface 24. An optical path incident on the first reflecting surface 22 and an optical path exiting from the second reflecting surface 23 intersect each other.

Abstract: A microlens has a material composition gradient that varies along the z-axis of the microlens to provide desired refractive properties in conjunction with the surface shape of the microlens. A method for designing the microlens may include defining a microlens surface shape, defining desired refraction properties of the microlens, and determining a refractive index gradient of the microlens in the direction of the z-axis using the desired refraction properties and the defined surface shape of the microlens. A method for fabricating the microlens may include depositing a material having a material composition gradient that is determined based on a lens shape and desired refractive parameters, and forming the microlens having the desired surface shape in the material.

Abstract: A de-centered optical system includes a first optical element having at least three surfaces surrounding a portion having a refractive index of more than 1, and a second optical element whose surface further from the first optical element is a convex surface and has a positive power and produces chromatic aberration of magnification. When the de-centered optical system is used as an ocular optical system of an image observation apparatus, the image size observed through the de-centered optical system in the blue wavelength is larger than that formed in the green wavelength, and that formed in the green wavelength is larger than that formed in the red wavelength. The difference can be compensated by an electronic compensation means. This optical system can be used as an image taking optical system by setting the light traveling direction inversely to that in case when it is used as an ocular optical system.

Abstract: The present invention has as its object to provide a thin type optical system which enables both of image information displayed on display means such as a liquid crystal display to be observed and image information of which image is substantially equal to the image observed via therethrough and which is taken by image pickup means and a compound display apparatus using such optical system.

Abstract: The invention relates to a compact electronic camera which enables an electronic image to be displayed on a two-dimensional display element while it is phototaken or after it has been phototaken, so that the image can be magnified and displayed by a compact magnifying optical system constructed of a curved reflecting mirror to view a phototaken image of high precision. An electronic camera for photoelectrically converting a subject image formed by a phototaking optical system 2 into an electronic image to be recorded comprises a two-dimensional display element 4 for displaying an electronic image during or after phototaking and a magnifying optical system 5 for magnifying an image displayed on the two-dimensional display element 4 in the form of a virtual image. The magnifying optical system 5 is constructed of at least one curved reflecting mirror 26 and a surface 28 having a combined reflecting and transmitting action.

Abstract: An objective lens of an optical pick-up is formed to provide axial astigmatism corresponding to wavefront aberration of 0.01&lgr; [rms] or more when a shorter wavelength laser beam emitted by a first laser diode is converged on a first optical disc, and to provide coma so that its sign when the shorter wavelength laser beam is converged on the first optical disc will be opposite to its sign when a longer wavelength laser beam emitted by a second laser diode is converged on a second optical disc.

Abstract: The present invention is a beam splitter for splitting an incident beam into first and second beams so that the first and second beams have a fixed separation and are parallel upon exiting. The beam splitter includes a first prism, a second prism, and a film located between the prisms. The first prism is defined by a first thickness and a first perimeter which has a first major base. The second prism is defined by a second thickness and a second perimeter which has a second major base. The film is located between the first major base and the second major base for splitting the incident beam into the first and second beams. The first and second perimeters are right angle trapezoidal shaped. The beam splitter is configured for generating equal optical path length beams.

Abstract: A wearable display system including a display panel to display a signal processed in a predetermined way. The wearable display system includes a grating to diffract a signal output from the display panel, a waveguide to guide the propagation of a signal diffracted by the grating; and a magnifying lens to magnify the signal propagating through the waveguide and to direct the signal toward an eye of a user. The waveguide is formed by a combination of two or more substrates. According to the wearable display system, optical devices are easily and simply arranged on the waveguide to conform to specifications, and furthermore, are individually manufactured and attached to the waveguide. Therefore, the wearable display system is manufactured with minimum time and effort.

Abstract: A color image display system and a color image pickup system adapted to electronically correct the color shift of color separation images caused by a decentered optical system used to display or capture a color image. The color image display system has an image display apparatus including a color image display device for displaying a color image composed of color separation images superimposed on one another. The displayed color image is projected into an eyeball of an observer through a viewing optical system that is formed from a decentered optical system including a decentered prism having at least a decentered internally reflecting surface with a power, together with an entrance surface and an exit surface, which are transmitting surfaces. The pixel position of each color separation image to be displayed on the color image display device is shifted so as to cancel a color shift of the corresponding color separation image caused by the decentered optical system.

Abstract: The present invention has as its object to provide a projection type display apparatus which suffers little from the occurrence of the distortion of the surface of a dichroic mirror in a color combining optical system, and the occurrence of the deformation of a projected image by the angular deviation of the surface of the dichroic mirror and in which the correction of the chromatic aberration of magnification of a projection lens is stably possible during mass production. So, the color combining system of the present invention is provided with at least three prisms, two dichroic mirror layers for reflecting lights differing in wavelength area from each other, the two dichroic mirror layers being formed so as not to intersect with each other with one of the three prisms which is located most adjacent to the light exit side interposed therebetween, and at least one optical element having positive or negative refractive power.

Abstract: An optical head scans the information layer (3) of an optical record carrier (1) by means of a radiation beam (13). Optical aberrations in the beam such as coma and spherical aberration, caused by tilt and thickness variations in the optical disc respectively, are compensated by an aberration compensator (27) arranged in the radiation beam. The tilt or thickness variation is measured by a detector (30) and used to control the aberration compensator. The radiation beam is focused onto the information layer by an objective system (11). A displacement of the objective system in the transverse direction (26) as used for radial tracking of the optical beam, causes a mismatch between the wavefront to be compensated and the wavefront introduced by the aberration compensator (27). The mismatch is reduced by using a position detector (33) for measuring the transverse position of the objective system and using the position signal (34) as input for the control of the aberration compensator.

Abstract: A Shack-Hartmann aberrometer for measuring ophthalmic wavefront aberrations having improved dynamic range is described. In one embodiment, a single lenslet only of the wavefront sensor microlens array is optically or physically altered. In another embodiment, a sub-array of immediately adjacent lenslets are altered. In an alternative embodiment, preferably only two non-adjacent lenslets are altered. The alteration provides for identification of the correspondence between spot images of the unknown wavefront formed by the microlens array and the respective lenslets forming the spot images. Once all the spot images are correctly identified, analysis of the incoming wavefront is simplified even when the magnitude of aberration is increased. Thus, the dynamic range and accuracy of the Shack-Hartmann aberrometer are no longer limited by the dimensions and optical properties of the lenslets.

Abstract: The invention provides a dichroic prism capable of reducing displacements of projection pixels of colors caused by chromatic aberration of magnification. A dichroic prism is formed in the shape of a quadrangular prism as a whole by joining four rectangular prisms together. A red reflecting dichroic plane and a blue reflecting dichroic plane intersect to form substantially an X shape along junction surfaces of the prisms. The red reflecting dichroic plane is convex-shaped by partly changing the thickness of an adhesive layer for connecting the rectangular prisms together. Accordingly, since a red beam can be guided to a projection optical system while being enlarged, it is possible to reduce a projection image of the red beam to be projected onto a projection plane via the projection optical system. This makes it possible to reduce relative displacements of projection pixels of color beams caused by chromatic aberration of magnification.