Abstract: The object of the invention is to make a viewing unit of the image display compact so that it can be mounted on portable telephones or information terminals. The portable image display of the invention comprises a speaker portion, a microphone portion, an image display device 9 and a viewing optical system for forming an exit pupil to view an image displayed on the image display device and having a generally positive refracting power. The viewing optical system is constructed of at least one prism member 10 comprising an entrance surface through which a light beam emanating from the image display device 9 is entered into the prism, at least one reflecting surface at which the light beam is reflected within the prism and an exit surface through which the light beam leaves the prism. The at least one reflecting surface has a curved surface shape for imparting power to a light beam.

Abstract: A variable magnification optical system comprises at least three optical units which are a first moving optical unit, a fixed optical unit and a second moving optical unit. The three optical units are arranged in that order in a propagation direction of light, and a variation of magnification is effected by a relative movement between the first moving optical unit and the second moving optical unit.

Abstract: A device for eliminating decentration error due to parallax during ophthalmic laser surgery comprises a stereo microscope having a first ocular and a second ocular and an objective lens for viewing a patient's eye, a laser for projecting a laser beam at a patient's eye during ophthalmic laser surgery; and structure for aligning the objective lens relative to the first ocular to center the laser beam with a patient's eye. The device for eliminating decentration error due to parallax also comprises prism positioned between either the first ocular and the objective lens or the objective lens and the laser beam.

Abstract: An optical device includes a substrate 60 and three prisms 10, 20 and 30. The first prism 10 is disposed adjacent to an upper surface of the substrate 60. An incoming beam aperture 65 is positioned adjacent a first surface 12 of the first prism 10, the first surface 12 extending away from the upper surface of the substrate 60. The second prism 30 is disposed adjacent to the upper surface of the substrate 60 and is spaced from the first prism 10 by a first distance. The third prism 20 is also disposed adjacent to the upper surface of the substrate 60. The third prism 20 may be spaced from the second prism 30 by the same first distance. An outgoing beam aperture 66 is positioned adjacent a first surface 22 of the third prism 20. The substrate 60 has phase changing reflective surfaces 40 and 50 along the upper surface between the first prism 10 and the second prism 30 and between the second prism 30 and the third prism 20.

Abstract: In order to provide a grism wherein even if the vertex angle of a prism increases, it does not exceed its critical angle, besides, which can elevate its efficiency, and mass-production of which is possible, whereby reduction in cost of which can be realized. The grism comprises a first prism having a high refractive index, a second prism having a high refractive index, and a volume phase grating used for a diffraction grating; and the vertex angle of the first prism being opposed to the vertex angle of the second prism so as to sandwich the volume phase grating between the first prism and the second prism.

Abstract: A real time fingerprint verification system includes a recording device and a verification device each having a fingerprint scanner for generating a flat, dimensionally undistorted, high contrast, fingerprint image, and an intensity sensitive, spatial light modulator (SLM) for receiving and transforming the flat fingerprint image into a planar, coherent light image. In the recording device, the planar coherent light image beam of the fingerprint from the SLM is Fourier transformed, and input into a microscope objective lens system which expands the Fourier transformed beam image sufficiently to allow mechanical blocking of its central portion or order, whereupon it is directed to interact as an object beam with a reference beam from the particular coherent light source to record a holographic matched filter.

Abstract: An image display apparatus having a three-dimensionally decentered optical path to attain a reduction in overall size of the apparatus and to place constituent members effectively in a dead space, thereby permitting the apparatus to be designed in a variety of ways. The apparatus includes an image display device and a viewing optical system for leading an image formed by the image display device to a pupil. The viewing optical system has at least a first reflecting surface and a second reflecting surface positioned closer to the pupil than the first reflecting surface along the optical path. A first plane defined by the optical axis incident on the first reflecting surface and the optical axis reflected therefrom and a second plane defined by the optical axis incident on the second reflecting surface and the optical axis reflected therefrom intersect each other at an arbitrary angle, thereby forming a three-dimensionally decentered optical path.

Abstract: A real image mode finder optical system is constructed to be independent of a photographing optical system and includes, in order from the object side, an objective optical system with a positive refracting power, a field frame located in the proximity of the imaging position of the objective optical system, and an eyepiece optical system with a positive refracting power. The real image mode finder optical system has an image erecting means, and the focal length of the objective optical system can be made shorter than that of the eyepiece optical system.

Abstract: The invention relates to optical elements comprised of an optical isotropic completely aromatic polyester with a glass transition temperature Tg≧180° C.

Abstract: A counter-rotating anamorphic prism pair assembly with variable spacing allows the simultaneous adjustment of a prism pair using an adjustment member to circularize in cross section a range of elliptical laser beam cross sections. A first prism rotates and translates towards or away from an incident laser beam while a second prism simultaneously rotates towards or away from the laser beam in a fixed counter-rotating relationship with the first prism. The degree of rotation and translation is determined by a mechanical linkage connecting the two prisms.

Abstract: A lighting element in which a plurality of point sources are in the form of LEDs situated between a microprism sheet and a reflective backing arrangement, the microprism sheet being of the type having a plurality of v-shaped grooves. The microprism sheet exhibits a diffusion effect, and the LEDs are situated in the grooves so that light from the LEDs that is directly incident on walls of the grooves, and light that is reflected by the backing, is combined by refraction and diffused to provide an even lighting effect. The lighting element may be made of flexible materials so that they can be formed into tubular lighting elements, or made into flat or curved panels.

Abstract: An applanation tonometer with a replaceable prism for contacting a cornea has emitter and detector ports arranged opposite each other on opposite sides of a longitudinal axis, with the ports aimed at about 45° to the longitudinal axis. Light from an emitter confronting one of the ports is incident on the applanation surface at about 45° so that light reflecting internally of the prism from the applanation surface is directed toward the opposite port for detection. The portion of the light internally reflected from the applanation surface provides a signal indicating the size of the applanated area, from which intraocular pressure is determined.

Abstract: What is described here is a system for as well as a method of geometric beam shaping of the beam profile of a light beam, comprising a first prism and a second prism optically transparent to the light beam, which prisms are so disposed in the optical path of he light beam in such a way that after the passage of the light beam through both prisms the beam profile of the light beam may be expanded or reduced in a direction orthogonal on its direction of propagation by a first factor, and by a second factor different from the first factor in a direction orthogonal on the first direction.

Abstract: An optical prism 100 for reflecting light incident on its light incidence surface 12 suited for incidence of light from an LCD 20 at least twice within itself and emitting the reflected light as emitted light from a light emission surface 14 to the outside. The optical prism is coupled in use with a display element support 30 adapted to suit it. The side surfaces of the optical prism crossing the light incidence surface 12 and light emission surface 14 have projections 90L and 90R for mounting the optical prism on the display element support.

Abstract: An apparatus and method for acquiring an image of a patterned object such as a fingerprint including a light refracting device, a focusing lens, and a light source. The light refracting device can, for example, be a prism and includes an imaging surface, a light receiving surface and a viewing surface. Incident light from the light source is projected through the light receiving surface and reflected off a surface other than the imaging surface. This reflected light is then projected onto the imaging surface to create an image of the patterned object from substantially all scattered light through the viewing surface. The lens is placed adjacent to the viewing surface to focus the light on an image sensor. The apparatus is configured to reduce or substantially eliminate trapezoidal distortion and improve overall image sharpness in an image of an object created by the apparatus.

Abstract: An optical element switching device is provided wherein a plurality of optical elements are held by a guide mechanism for guiding them to move straight or rotate and arranged on a turret, and positioned by a positioning part comprising a spring for pushing a ball into V grooves formed at a rotarys shaft of the turret rotated by a first motor wherein, a selected one of the optical elements is stopped in an optical path (i.e. an optical axis of objectives), and wherein the optical element is moved by a second motor along a direction in which it is guided by the guide mechanism, so that corrections such as adjustment of the contrast and the like are automatically executed at switching operations.

Abstract: A method for installing an electro-optical device to a prism and a manufacturing method for a projector that permit improved positional accuracy, improved fixing operation efficiency, and a simplified fixing operation process of an electro-optical device are provided. The methods are provided with spacer mounting process steps for mounting a spacer via an adhesive agent between a panel frame assembly, which holds an electro-optical device, and a prism, position adjusting process steps for adjusting a position where the panel frame assembly is installed to the prism after the spacer mounting process steps, and panel frame assembly fixing process steps for fixing the panel frame assembly by hardening the adhesive agent after the position adjusting process steps.

Abstract: An aberration correcting apparatus and an optical pickup apparatus using this apparatus, in which a spherical aberration based on a thickness error of an optical disc substrate can be preferably eliminated and a thickness error permission range of the optical disc substrate can be widened even if an objective lens of a high numerical aperture is used.

Abstract: A multilayer ceramic substrate 11 is used, and a prism 14 serving as a component of a hybrid optical module and a chip 12 on which an optoelectric converting element is mounted are mounted on different layers of the multilayer ceramic substrate. The thickness of the chip on which the optoelectric converting element is mounted is substantially equal to the depth of the layer of the multilayer ceramic substrate on which the chip is mounted.

Abstract: An optical element (10, 10′, 10″) for deflecting light beams (18, 19), which enter and re-emerge from the latter, in such a way that their angle of emergence (&ggr;) is limited, in particular for use as a luminaire-cover, having a plate-like core (11, 11′, 11″) of transparent material which on one side is occupied by microprisms (12, 13) that taper—starting from their root (15)—forming furrows (22), wherein all of the top surfaces (14) of the microprisms form the light-entry face and the other side (21) of the core forms the light-emergence face, and wherein the top surfaces (14) of the microprisms are formed convexly or concavely in a continuous or non-continuous manner, and also a method for producing the optical element (10, 10′, 10″).

Abstract: An erecting prism of a binocular includes a first and a second prism, which are held by a holder, and the holder being supported vertically movable and laterally immobile with respect to a thin plate. The thin plate is supported laterally movable and vertically immobile with respect to a right moving body. A shaft reception means is provided, for rotatably supporting a jig, at the right eyepiece cylinder that is attached to the rear wall 303B of the right moving body. The position of erecting prism is adjusted by using a jig to move the holder vertically with respect to the thin plate, and to move the thin plate laterally with respect to the right moving body. The jig may be supported by the shaft reception means and rotated.

Abstract: A thermal birefringence compensator for a double pass laser system, which includes a polarization or conventionally outcoupled laser resonator, a gain medium and a compensator optically coupled to the gain medium. In one implementation, the compensator, which acts as an end reflector, includes a Benson prism, a first quarter waveplate with its principle axes aligned to the fold axis of the Benson prism, and a second quarter waveplate with its principle axes at 45° to the fold axis of the Benson prism. Alternatively, the compensation's prism can be a Porro prism.

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: An image shake correction device for correcting image shake on the focal plane of an optical apparatus due to vibration of the optical apparatus such as a camera. A correction optical element is provided in the optical path of the principal optical system, the correction optical element is driven correspondingly to the detected image shake magnitude, and the image shake on the focal plane of an optical apparatus is corrected. A driving mechanism which utilizes shape memory alloy is used for driving a correction lens for correcting image shake.

Abstract: A surface light source device, comprising a light source (2); a light conductor (1) which has a light incident face (11) on at least one side end surface thereof which confronts the light source (2), and a light emitting face (12) on one surface thereof which is substantially perpendicular to the light incident face (11); and a light angle varying sheet (3) which is disposed at a side of the light emitting face (12) of the light conductor (1). wherein at least one of the light emitting face (12) and a back surface (13) of the light conductor (1) comprises a minute structure having an average slant angle of 0.5 to 7.5 degrees. The light angle varying sheet (3) may comprise a prism sheet having a plurality of prisms (31) which are formed parallel to one another on at least one surface thereof.

Abstract: The present invention is a display apparatus that provides protection against damage for a metallic layer. The display apparatus includes a light modulating layer, a polarizer, and a light directing film. The light directing film includes a prismatic structure having two sides, where one side includes saw tooth formations having tilted surfaces and a metal layer on the side of the prismatic substrate having the saw-tooth formations. A tilt angle of the tilted surfaces offsets an optimal viewing angle for the display from a glare angle for the display. In a first embodiment of the invention, the light directing film of the display apparatus further includes an inorganic protective layer formed on the metal layer, wherein the inorganic protective layer inhibits molecular transfer to the metal layer and balances the color of reflected and transmitted light. The light directing film further includes a pressure sensitive adhesive layer between a polarizer and the inorganic protective layer.

Abstract: In a real-image finder optical system, at least two reflection surfaces are utilized for diopter adjustment, and wherein first and second diopter-adjusting reflection surfaces form a right angle therebetween; an optical axis from the objective optical system to the first diopter-adjusting reflection surface and an optical axis from the second diopter-adjusting reflection surface are parallel with each other; the two optical axes are perpendicular to the optical axis being incident from the object to the objective optical system; diopter adjustment is performed by integrally moving the first and second diopter-adjusting reflection surfaces so that the optical path length from the image forming plane of the objective optical system to the eyepiece optical system is varied; and the following condition is satisfied: 0.1<L1/L2<0.

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

Abstract: A light regulation element regulates both the travelling direction and diffusion state of a light emitted from a surface light source device. Lights from a cylindrical light source 2 such as a cold cathode tube is introduced in a light guide 1. The light guide 1 has an emission surface 1a on the side opposite to a reflection element 4, and a light regulation element 3 is arranged in opposition to the emission surface 1a. Protrusions 3a are formed on one surface or both surfaces of the light regulation element 3. Coated on the surface on the light emission side of the light regulation element 3 is a light diffusion layer 5. The turbidity of the light diffusion layer 5 falls within a range from 1900 cm−1 to 2400 cm−1 . The light emitted from the emission surface 1a of the light guide penetrates the light regulation element 3, thereby causing the light travelling direction to be regulated.

Abstract: A composite optical device comprises an optical element bonded onto a support body with an adhesive, at least a part of surfaces of the optical element being covered by a film made of a hydrophilic material. A method for manufacturing a composite optical device having an optical element bonded onto a support body with an adhesive, comprises the steps of: preparing a bar-shaped optical element having a length not less than twice the width thereof and having surfaces at least a part of which is covered by a film made of a hydrophilic material, and bonding the bar-shaped optical element on the support body with the adhesive; and cutting the bar-shaped optical element, the adhesive and the support body while applying a liquid containing water at least to portions where they are cut.

Abstract: An optical unit for projecting an image including first and second locating lines for substantially eliminating the introduction of visual parallax error. In one preferred form, the optical unit is incorporated into a machine for performing a forming operation on a workpiece and is operative to project an image of a portion of a scale to a position easily read by the user during machine operation. The optical unit includes a prism portion having a first side disposed adjacent the scale, a second side at an angle to the first side for reflecting the image and a third side through which the projected image may be viewed. The first locating line is disposed on the first side and the second locating line is disposed on the third side such that visual alignment eliminates the introduction of visual parallax error associated with reading a scale.

Abstract: A real image type finder optical system comprising, in order from the object side, an objective optical system of non-telecentric system, a first prism having a wedge angle of 3°, a second prism, a third prism, and an eyepiece lens. The second prism has a first face as the entrance surface in contact with the back surface of the first prism, a second face forming an angle of 22.5° with respect to the first face and a third face for transmitting the optical axis bend by these second face and first face. The third prism has a first face as the entrance surface spaced in parallel from and confronting the third face of the second prism, a second face forming 45° with respect to the first face in order to bend the optical axis toward the object side at an angle of 90° within a horizontal plane, and a third face formed as roof faces for bending the optical axis bent by the second face toward the first face at an angle of 45° within a horizontal plane.

Abstract: The present invention relates to an optical element fixing device, and particularly to a prism mounting device for an optical device using light beam which passes through a prism or lens, a lens fixing device for aligning and fixing the center of a lens with a prescribed optical axis, and a device for fixing a reflecting mirror of an optical device. The invention can easily and securely position the prism to be press-contacted to the lens within a case, in which changes in the magnitude of press-contacting with the passage of time is very small. And, the lens can be securely fixed with its center accurately aligned with a prescribed optical axis. Besides, the reflecting mirror is fixed by a simple structure and a contact between the reflecting mirror and a plate spring is not limited to one point.

Abstract: The bottom surfaces of an entering surface-forming portion 1a for forming a light-entering surface 11a of a reflector type prism 11 and of an emitting surface-forming portion 1b for forming a light-emitting surface 11b of the reflector type prism 11 are formed as concave surfaces in a die 1. Even if shrinkage of the reflector type prism 11 occurs during its formation, the light-entering surface 11a and the light-emitting surface 11b are, at least, not formed as concave surfaces, so that a light beam entering the reflector type prism 11 and a light beam emitted from the reflector type prism 11 are prevented from becoming scattered.

Abstract: The present invention is related to a Wollaston prism (WP) comprising two birefringent wedges (W1, W2) joined by their hypotenuse to form a composite block, said wedges having optic axes (OA1, OA2) to each other at right angle. According to the invention, the optic axes (OA1, OA2) of said wedges (W1, W2) are rotated by an angle of 45° or 135°, respectively, with regard to a position wherein one of the optic axes (OA1, OA2) lies parallel to the plane formed by the hypotenuse. In an embodiment of the present invention, liquid crystal is used as material for the wedges (W1, W2) resulting in inexpensive and easy to handle Wollaston prisms.

Abstract: An optical reflection panel made of thermosetting plastic material as a substrate is disclosed. One surface of the substrate is coated with an adherent layer and then an optical reflecting layer is formed on the adherent layer as a reflecting surface for reflecting a light beam. The other surface of the substrate is formed with a reinforcing structure. The reinforcing structure serves to increase the mechanical strength of the optical reflection panel and control the deformation amount. The reinforcing structure includes a number of reinforcing ribs extending along the longitudinal axis of the optical reflection panel and a number of reinforcing ribs perpendicular to the longitudinal axis of the optical reflection panel.

Abstract: Disclosed is a multi-beam optical system, which has a light source having a plurality of light emitting portions from which a plurality of light beams are emitted, respectively; a collimating lens which collimates the plurality of light beams into a plurality of parallel light beams; a beam shaping optical system including at least one wedge prism, the beam shaping optical system shaping cross section of the plurality of parallel beams; an image forming optical system which converges the plurality of parallel beams transmitted through the beam shaping optical system. In such a multi-beam optical system, a plurality of light emitting portions are aligned in a direction perpendicular to a principal section of the wedge prism.

Abstract: It is an object of the present invention to provide a finder prism capable of forming some in-finder information such as an automatic focus target mark and a short distance correction mark by virtue of extremely narrow lines. In detail, the finder prism is provided between an objective lens and an ocular lens, and is adapted to transmit an object image to a camera user under a condition where an automatic focus target mark and an short distance correction mark are overlapped on a photographing object image. In particular, the prism is made of a resin, a shouldered portion is formed on one surface of the prism from which the object light is allowed to exit during a photographing process, thereby forming some in-finder information such as an automatic focus target mark and an short distance correction mark.

Abstract: A projection display apparatus comprises a modulator, an analyzer, and projecting optical system. The modulator includes two-dimensionally arrayed pixel units and it modulates an incident light and emits the modulated light. The analyzer analyzes the emitted light from the modulator. The projection optical system projects the analyzed light from the analyzer. The analyzer includes a polarized beam splitter having a pair of prisms and an adhesive layer held between the pair of prisms. The difference in thickness between thin and thick portions of the adhesive layer is set equal to a predetermined value or less, based on a pixel pitch of the modulator.

Abstract: A prism includes: a first portion made of a first material having a wavelength dependency in a refractive index; and a second portion adhered to the first portion, the second portion being made of a second material having a wavelength dependency in a refractive index which is different from the wavelength dependency in the refractive index of the first material. The first portion and the second portion have shapes such that the wavelength dependency in the refractive index of the first portion and the wavelength dependency in the refractive index of the second portion are substantially cancelled by each other.

Abstract: An all-around reflector for retroreflection of beams which comprises, as reflectors, triple prisms with round light entrance surfaces, wherein the triple prisms are arranged in a housing in such a way that their light entrance surfaces are part of the circumferential surfaces of the housing. The triple prisms are arranged in the housing in such a way that adjacent triple prisms contact, or almost contact, at a point inside the housing. The tips (corners) of the triple prisms lie in a plane extending vertical to the light entrance surfaces of the triple prisms wherein the axes of the triple prisms which intersect at a point are also located in this plane. Triple prisms which are located next to one another are oriented relative to one another so as to be rotated about their axes by 60°.

Abstract: The prism assembly of the present invention includes: a prism made of plastics having light transmittivity; and a glass plate which is joined to a plane of the prism obliquely intersecting a light incidence plane of the prism and whose one surface carries a dichroic layer formed thereon.

Abstract: Flexible, fire resistant, layered reflecting and photoluminous material is provided which combines the advantages of a light reflective component and a luminescent component in a fire resistant structure which meets National Fire Protection Association standards for inclusion in firefighter's protective clothing. The material includes a first layer of microspherical glass bead or prismatic light reflective plastic material having an underlying surface formed with a plurality of minute prism-like formations projecting therefrom at regular spaced intervals and an overlying substantially smooth light transmissive surface; a second layer containing a homogeneous blend of a resin containing effective amounts of fire retardant, photoluminescent and, optionally luminescent additives; and a third layer which is a fire retardant fabric. The layers are joined at a first region such that the prism-like formations are substantially disabled or destroyed.

Abstract: The present invention relates to an optical element fixing device, and particularly to a prism mounting device for an optical device using light beam which passes through a prism or lens, a lens fixing device for aligning and fixing the center of a lens with a prescribed optical axis, and a device for fixing a reflecting mirror of an optical device. The invention can easily and securely position the prism to be press-contacted to the lens within a case, in which changes in the magnitude of press-contacting with the passage of time is very small. And, the lens can be securely fixed with its center accurately aligned with a prescribed optical axis. Besides, the reflecting mirror is fixed by a simple structure and a contact between the reflecting mirror and a plate spring is not limited to one point.

Abstract: At least one of four rectangular prisms in a dichroic prism is made longer than the other rectangular prisms. Parts of the rectangular surfaces of the long rectangular prisms partially protrude from the rectangular surfaces of the other rectangular prisms in the longitudinal direction. The protruding parts of the rectangular surfaces of the long rectangular prisms are not provided with a dichroic film. Such a construction makes it possible to prevent return light, which returns from the light emitting surface side of the dichroic prism and the dichroic prism, from emitting again from the light emitting surface.

Abstract: An optical unit for projecting an image including first and second locating lines for substantially eliminating the introduction of visual parallax error. In one preferred form, the optical unit is incorporated into a machine for performing a forming operation on a workpiece and is operative to project an image of a portion of a scale to a position easily read by the user during machine operation. The optical unit includes a prism portion having a first side disposed adjacent the scale, a second side at an angle to the first side for reflecting the image and a third side through which the projected image may be viewed. The first locating line is disposed on the first side and the second locating line is disposed on the third side such that visual alignment eliminates the introduction of visual parallax error associated with reading a scale.

Abstract: A stereo panoramic view is provided through the use of multiple virtual optical centers. A reflective polyhedral cement, such as a pyramid, redirects the field of view of each camera in a first set of cameras to form a group of substantially co-located virtual optical centers at a first location within the pyramid. The pyramid also redirects the field of view of each camera in a second set of cameras to form a group of substantially co-located virtual optical centers at a second location within the pyramid. Panoramic images from the first and second virtual optical centers provide a stereo panoramic view when one panoramic image is provided to a user's left eye and the other panoramic image is provided to the user's right eye.

Abstract: An exterior rearview mirror for vehicles incorporates a forward vision improving system allowing improved visibility of the opposite roadway forward of the vehicle for safer passing. Preferably, the forward vision system includes a pair of prisms mounted in a mirror housing, one of which is directed at an angle of incidence past and to the left of a front, slower vehicle, the other of which receives the image from the first, and is positioned in the driver's line of sight. In one embodiment of the vision system, the front prism of the pair of prisms is replaced by a divergent lens.

Abstract: A cross dichroic prism comprises four triangular prisms having isosceles right triangular cross sections identical in shape, opposing side faces thereof being bonded and secured together with rectangular portions thereof facing each other; and a dichroic film having an X-shaped cross section formed between the bonding faces of the triangular prisms; wherein, of the four triangular prisms, a given prism and at least one of the prisms adjacent thereto have a refractive index difference therebetween of 0.00005 or less, and the remaining two prisms opposed thereto have a refractive index difference therebetween of 0.00005 or less.

Abstract: The invention relates-to optical coatings of medium refractive index, having refractive index values of about 1.6 to 1.9, which can be obtained by vapor deposition of vapor-deposition materials having a chemical composition corresponding to the formula IYAl.sub.x O.sub.z Iwhereinx=0.5 to 5, andz=3/2.multidot.(1+x) on optical substrates.