Abstract: A laser beam synthesizing member of a semiconductor laser module used as an optical amplifier that has a prism configured to correct respective optical paths of a plurality of laser beams, a beam synthesizing member configured to synthesize the plurality of laser beams once passed from the prism, and a holder member configured to integrally hold the prism and the beam synthesizing member, and where the beam synthesizing member has a first input part on which a first laser beam is incident, at least one other input part on which an other laser beam is incident, and an output part from which the first laser beam emerging from the first input part and the other laser beam emerging from the at least one other input part are multiplexed and emitted as a multiplexed laser beam.

Abstract: A beamsplitter prism for transmitting and reflecting cylindrical waves without magnification, which includes at least first and second surfaces arranged opposite each other; a semi-reflecting layer diagonally arranged from a lower portion of the first surface to an upper portion of the second surface. The first and second surfaces are adapted to have a cylindrical shape, with the first surface having a smaller radius than the second surface to form two concentric cylinders. A cylindrical wave which strikes the first surface will pass through the semi-reflecting layer and exit through the second surface without having the beamsplitter prism introduce distortion to the wave. The second surface may be substantially orthogonal to the first surface, so that a cylindrical wave may reflect off the semi-reflecting layer and exit through a cylindrical surface. A third planar surface may be arranged on the prism to permit the passage of plane waves without distortion.

Abstract: A beam splitter cube and two roof mirrors are used as a beam spacer to interlace and closely space four parallel laser beams.

Abstract: The invention relates to a multimirror device for rotating the polarization of an electromagnetic signal, especially a light signal, through 90°, the output ray having approximately the same direction as the input ray. This device comprises at least one combination (40) of three mirrors (42, 44, 46) which are arranged in such a way that a ray entering one of the mirrors at an angle of incidence of 45° is reflected at the same angle off the other mirrors, the polarization vector (V) of the incident ray being presented in such a way with respect to the mirrors that a reflection off one of the three mirrors changes the direction of polarization while the reflections off the other two mirrors does not change this direction of polarization. Preferably, a plurality of multiple-mirror combinations (40, 40′, 40″) is provided on a sheet, each combination forming a pattern which is repeated regularly, the patterns all having identical shapes and sizes.

Abstract: A projection type display device constructed so that light source beams via a polarization beam splitter are separated of colors by a color separating/synthesizing optical system and enter light valves disposed for every color light, the light beams exiting from the respective light valves are synthesized by the color separating/synthesizing optical system, the synthesized light beams exit, the polarization beam splitter analyzes the synthesized light beams and takes out the analyzed light beams, and the analyzed light beams are projected on a screen through a projection lens. A normal line of an outgoing surface of the polarization beam splitter with respect to the light source beams exiting toward the color separating/synthesizing optical system from the polarization beam splitter, has a predetermined angle larger than zero degree with respect to an optical axis of the light source beams.

Abstract: The invention is aimed at providing an optical switch using tilt mirrors, in which easy mounting of the optical components is possible by simplifying the construction, and in which a short spatial propagation distance for the light beam is realized. To this end, the optical switch using tilt mirrors of the present invention comprises; a collimator array and a tilt mirror array each formed with an input section and an output section aligned and integrated, and a shift type turn-back mirror that shifts the optical path of the incident light in a predetermined direction and turns back and outputs this.

Abstract: An optical path splitting element for splitting a light beam from a single object into two optical paths (left and right) is made compact in size and given a power to reduce the number of components thereof. An image display apparatus uses the optical path splitting element. The left and right optical paths are not in plane symmetry with each other but in 180-degree rotational symmetry with respect to only a straight line passing through the center of the object. When a pair of reflecting surfaces (left and right) closest to the object side are defined as first reflecting surfaces and a pair of reflecting surfaces (left and right) closest to the exit side are defined as final reflecting surfaces, axial principal rays incident on the first reflecting surfaces and those exiting from the final reflecting surfaces are not coplanar with each other in either of the left and right optical paths.

Abstract: A color combining optical system according to this invention aims at reducing the size of an optical system and suppressing the occurrence of color unevenness. According to this invention, there is provided a color combining optical system for combining color light reflected by a dichroic film and color light transmitted through the dichroic film. The optical thickness of the dichroic film increases or decreases from one end side to the other end side in the inclining direction of the dichroic film with respect to the incident optical axis of the color light reflected by the dichroic film.

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 image separating device connected to a rigid endoscope has a Pechan prism to shift the optical axis of an objective optical system contained in the rigid endoscope, X- and Y-stages and a moving mechanism for moving the Pechan prism in a direction perpendicular to the optical axis of the objective optical system, and an enlarging optical system having an optical axis parallel with the optical axis of the objective optical system. As the Pechan prism is shifted, the image formed through the objective optical system is relatively shifted within its image plane, so that the image re-formed through a first image re-forming optical system is picked up by a first CCD camera without any decentering aberration, inclination relative to a direction perpendicular to the optical axis of the first image re-forming optical system, nor image rotation about the optical axis.

Abstract: Disclosed is a prism having a light incident surface, a light emerging surface, and at least one light reflection surface. The light incident on the light incident surface is reflected, inside the prism, by the light reflection surface, and emerged from the light emerging surface. At least one light reflection surface has a reflecting surface which does not satisfy a total reflection condition. A reflection area is formed on the at-least-one light reflection surface by applying light reflecting material. The reflection-area corresponds to a portion on which a normal light is incident. Further, a portion of the-at least-one reflection surface other than the reflection area is formed to be a low-reflection area-which has a lower reflectance index than the reflection area.

Abstract: A lightweight and homogeneous optical element exhibiting favorably weak birefringence and hygroscopicity as well as superior productivity and producing minimal chromatic aberrations is formed by using an organic-inorganic composite material having both the properties of a glass material and those of a plastic material. The optical element has at least one entrance refracting surface and at least one exit refracting surface. The optical element is formed from an organic-inorganic composite material having an inorganic phase dispersed in the three-dimensional network (matrix) of an organic phase.

Abstract: An optical turning film has a first surface including an array of prisms. The array has a plurality of first prisms, with each of the first prisms having a first prism configuration, and a plurality of second prisms, with each of the second prisms having a second prism configuration different from the first prism configuration. The optical film also has a second surface opposing the first surface, and light rays incident to the first surface are directed by the plurality of first prism and the plurality of second prisms along a direction substantially parallel to a viewing axis.

Abstract: The object is to display an image projected by a display device, installed in a vehicle dashboard, for displaying an information data in the optimum field of vision for a driver and to make a driver recognize visually.

Abstract: An image display apparatus includes a light source for supplying illumination light, a reflection type display element for modulating the illumination light into image light by reflecting the light, an illumination optical system for guiding the illumination light to the reflection type display element, and a projection optical system for guiding the image light to an observer. The image light is incident on the projection optical system via at least a portion of the illumination optical system. The illumination optical system has a part, in an area where both the illumination light and the image light pass, which changes an optical action depending on a state of incident light. The part acts to deflect the illumination light to decrease an incident angle with respect to the reflection type display element as compared with a case where the part does not exist.

Abstract: A beam splitting prism system includes, at least, a first prism for extracting a first light beam along an advancing direction of a light beam coming from an objective lens, an air separation, and a second prism having a predetermined apical angle and having a reflecting surface for extracting a second light beam, wherein the second prism is arranged to cause the second light beam reflected by the reflecting surface to be totally reflected by a surface of the second prism adjacent to the air separation and then exit from the second prism, and the apical angle of the second prism is set such that interference fringes which occur due to reflection of the second light beam by a solid-state image sensor disposed within the optical path of the second light beam do not overlap in a central portion of an image plane of the solid-state image sensor disposed within the optical path of the second light beam.

Abstract: A red-reflecting film and a blue-reflecting film are formed in a substantially X shape on joint surfaces defined by the respective side faces of four columnar prisms or right-angle prisms. The red-reflecting film is continuously formed without separating at an intersection of the two reflecting films. The blue-reflecting film is, on the other hand, divided into two pieces by the red-reflecting film and an adhesive. It is preferable that that four columnar prisms are obtained from one block of sheet glass. This arrangement ensures an improvement in properties of a resulting light-selective prism.

Abstract: A beam splitting optical system for an automatic focusing apparatus includes a telescopic system having an objective optical system and a viewing optical system, a beam splitter which splits object-carrying light transmitted through the objective optical system from the telescopic optical system via a splitter surface, and a focus detection optical system having a pair of light receivers which receive object-carrying light beams split by the splitter surface. The focus detection optical system is arranged so that the object-carrying light beams to be received by the light receivers are incident upon the splitter surface of the beam splitter at different incident angles. The splitter surface is coated with a thin metal coating.

Abstract: A virtual image display system is provided which comprises a non-emissive, reflective microdisplay which forms a source object; an optical system which forms a magnified, virtual image of the source object from light reflected off the microdisplay; a light source system which produces light to illuminate the display system; and an illumination system which forms at least two virtual light sources to illuminate the display system.

Abstract: An integrating rod (100) for combining light beams from two or more sources. A first light beam (104) enters the integrating rod 100 through a first entrance face (102) to a first reflecting face (110). The light is reflected by the first reflecting face (110) and travels along the major axis (114) of the integrating rod (100) to an exit face (116). A second light beam (108) from a second light source enters the integrating rod (100) through a second entrance face (106). The second light beam may be reflected by a second reflecting face (112) and travels along the major axis (114) to the exit face (116). The two light beams experience multiple reflections as they travel along the integrating rod and leave the integrating rod (100) through the exit face (116) as a single homogenous light beam.

Abstract: A prism system for image inversion in a visual observation beam path, which uses a roof prism and a reflecting prism. The roof prism has a roof edge inclined with respect to a bottom face, and a gable face which is placed at an angle with respect to the bottom face and which acts as a beam splitter. The reflecting prism has a beam-pass face parallel to the bottom face of the roof prism. The bottom face of the roof prism and the beam-pass face of the reflecting prism have areas separated geometrically from one another for the passage of observation beams and for the passage of a further beam path which reflects a measured-value display into an exit-side observation beam path and/or reflects a rangefinder measuring beam path into an entry-side observation beam path.

Abstract: Methods and apparatus for reconfiguring a generally elliptically shaped beam produced by a laser diode bar into a single modified beam of substantially symmetrical shape. The methods and apparatus include the provision and utilization of a prism assembly which includes an entrance aperture, an exit aperture, and four total internal reflection surfaces. An incident beam is totally reflected at the total internal reflection surfaces step by step and is chopped into a specific number of parts which have the same width as that of the exit aperture from which they emerge stacked one on top of another. Three embodiments, according to the types of prism assemblies and entrance and exit apertures, are presented.

Abstract: An optical system for illumination spatial light modulators. The optical system includes a tall color splitting prism (16) with substantially symmetrical face bonding areas, thereby eliminating the need for external holding plates. The face bonding areas (62) are outside the optically active area. The tall prism (16) allows for better control of stray light, including a heat sink (41) for absorbing stray or OFF state light, preventing overheating of the optical assembly. The tall prism (16) also allows adjustments to be made to any other optical components such as projection lenses and TIR prisms (14).

Abstract: A virtual image display system is provided which comprises a non-emissive, reflective microdisplay which forms a source object; an optical system which forms a magnified, virtual image of the source object from light reflected off the microdisplay; a light source system which produces light to illuminate the display system; and an illumination system which forms at least two virtual light sources to illuminate the display system.

Abstract: A secondary image formation type view finder comprising an objective optical system, a first mirror for folding an optical axis, a relay lens system and a second mirror for folding the optical axis, wherein an optical axis of the relay lens system is disposed so as to be included in a plane nearly perpendicular to an optical axis of the objective optical system, and the first mirror and the second mirror and disposed nearly in parallel with each other, thereby reducing a space to be occupied by the view finder.

Abstract: A polarizing beamsplitter cube, such as for midwave infrared spectral applications, comprises two ZnSe 45° prisms, an adhesion layer and a thin-film polarization coating layer that are deposited onto the hypotenuse of the first prism, a refractive index liquid layer that provides an interface between the prisms that defeats total internal reflection when the prisms are joined together, and a urethane adhesive that permanently seals and encapsulates the liquid. The adhesion layer consists of 100 Å thorium fluoride and 50 Å chromium layers. The polarization coating (PC) comprises alternating layers of zinc sulfide (ZnS) and germanium (Ge) which are deposited by vapor deposition.

Abstract: A color separation device useful in information display systems is assembled from three prisms in an arrangement that provides for air equivalent thickness adjustment for each color. The air equivalent thickness adjustment provides for the correction of deviations in any of the three prisms, as well as providing a method to correct for the chromatic aberration arising from other optical elements in the information display system. The color separation device improves image quality and provides opportunities to lower the display system cost by using low tolerance components and/or plastic optical components normally having a high chromatic aberration.

Abstract: Apparatus are disclosed that provide a high-luminance projected image with no color shading or uneven contrast. Light from a light source undergoes color separation by passing through a color-separation optical system (e.g., a cross-dichroic mirror or cross-dichroic prism). The light from the light source can also be split into first and second polarized lights by passage through, e.g., a first polarized-light beamsplitter (PBS). Each color-separated light is modulated by a respective color-signal light valve and undergoes color combining by, e.g., a cross-dichroic prism. The second polarized light, if formed, is modulated by a luminance-signal light valve, undergoes color combining and polarized-light combining by, e.g., a second PBS, and is projected by a projection lens (that comprises an aperture stop). The PBSs, cross-dichroic mirrors, and cross-dichroic prisms are situated where principal rays (defined by the aperture stop) are parallel to the optical axis.

Abstract: The invention provides an optical device suitable for use with an optical amplifier, for example, in an optical communication system and advantageous in that different functions of a plurality of optical elements are achieved using an optical element of a simple construction and the optical device can be produced in a reduced size at a reduced cost. The optical device includes a tapered prism constructed such that a first face and a second face thereof opposing to each other do not extend in parallel to each other. A dielectric multi-layer film is formed on the first face of the tapered prism positioned on an optical signal inputting side. A reflection film is formed on the second face for reflecting the optical signal inputted to the tapered prism through the first face at least once toward the first face.

Abstract: An optical element is made of a material that is transparent to a selected spectral band and has an embedded optical layer system. The optical layer system has a first optical system in a first plane which at least predominately reflects light from a first band in the spectral band, and at least predominately transmits light from a second band in the spectral band. A second optical system is also provided in a second plane that intersects the first plane in a central area of the body of the optical element. The second system predominately transmits light from the first band and predominately reflects light from the second band. Optical paths are defined in the optical element between first and second entrances and exits for the light of the first and second bands.

Abstract: There is disclosed an optical system adapted for use in an image taking device. The optical system comprises an optical element having an entrance surface, a curved internal reflective surface and an exit surface on the surface of a transparent member composed for example glass, in which the light beam from an object is refracted at the entrance surface, thus being incident on the interior of the optical element, then is internally reflected by the reflective surface and refracted at the exit surface, thus emerging from the optical element and focusing on an imaging plane. The internal reflective surface is an off-axis reflective surface, and the entrance surface, the internal reflective surface or surfaces and the exit surface are so designed as to cancel the chromatic aberration generated at the refractive surfaces, while satisfactorily correcting other optical aberrations.

Abstract: A device for switching the operating modes of a microscope tube between the observation position, recording position and simultaneous observation and recording position, with a fully reflecting first element for full deflection of the radiation coming from the microscope objective, and with a partially reflecting second element for splitting the radiation coming from the microscope objective, wherein the first element and second element are arranged on a first guide carriage and second guide carriage which are displaceable jointly as well as opposite to one another in a plane.

Abstract: A prism for color dispersion and recombination and a projector incorporating the prism. The prism comprises an aperture for a light beam and the normal to the aperture defines an optic axis. A first surface, intersecting the optic axis, is oriented at a first angle to the optic axis. The first angle is greater than 45.degree.. The first surface disperses the light beam into a first component and an intermediate component. A second surface, intersecting the optic axis, is oriented at a second angle to the optic axis. The second surface disperses the intermediate component of the light beam into a second component and a third component.

Abstract: Illuminated instruments in aircraft cockpits often create reflections from the canopy which interfere with the pilots vision. A wedge of optical material positioned adjacent the instrument retracts the light rays such that the canopy reflections are deflected away from the eyes of the pilot.

Abstract: An improved polarization beam splitter formed by a collimator and two similarly shaped, birefringent crystal prisms is provided. The light from the collimator is incident upon the first face of the first birefringent crystal prism which also has second and third faces. The collimated light is incident upon the second face at an angle .phi. with respect to a line normal to the second face so that light polarized perpendicular to a plane of incidence upon the second face is reflected toward the third face and light polarized in the plane of incidence is refracted at the second face. The second birefringent crystal prism has a second face parallel to, and in close proximity with, the second face of the first birefringent prism so that light refracted at the second face of said first prism is refracted at the second face of the second prism and into the second prism.

Abstract: An apparatus and method for characterizing light beam collimation and alignment. A liquid crystal device receiving a light beam from a collimation lens has a lenslet array generated thereon. A corresponding array of point spread functions are detected by a charge coupled device camera, from which light beam collimation and alignment are characterized. The data may be further used to adjust the collimation lens to correct misalignment.

Abstract: Apparatus is disclosed that provides a high-luminance projected image with no color shading or uneven contrast. Light from a light source undergoes color separation by passing through a color-separation optical system (e.g., a cross-dichroic mirror or cross-dichroic prism). The light from the light source can also be split into first and second polarized lights by passage through, e.g., a first polarized-light beamsplitter (PBS). Each color-separated light is modulated by a respective color-signal light valve and undergoes color combining by, e.g., a cross-dichroic prism. The second polarized light, if formed, is modulated by a luminance-signal light valve, undergoes color combining and polarized-light combining by, e.g., a second PBS, and is projected by a projection lens (that comprises an aperture stop). The PBSs, cross-dichroic mirrors, and cross-dichroic prisms are situated where principal rays (defined by the aperture stop) are parallel to the optical axis.

Abstract: An improved polarization beam splitter formed by a collimator and two similarly shaped, birefringent crystal prisms is provided. The light from the collimator is incident upon the first face of the first birefringent crystal prism which also has second and third faces. The collimated light is incident upon the second face at an angle .phi. with respect to a line normal to the second face so that light polarized perpendicular to a plane of incidence upon the second face is reflected toward the third face and light polarized in the plane of incidence is refracted at the second face. The second birefringent crystal prism has a second face parallel to, and in close proximity with, the second face of the first birefringent prism so that light refracted at the second face of said first prism is refracted at the second face of the second prism and into the second prism.

Abstract: An optical filter is provided for use in color projection display imaging systems which utilize liquid crystal light valves for image modulation. The optical filter is a dichroic coating which separates light into different colors. The optical filter is located on a light transmissive surface of a color splitting device such as a Philips prism. The optical filter is formed from layers of at least two different dielectric materials including a high refractive index material, such as zirconium oxide and a low refractive index material such as aluminum oxide. The low refractive index material has an average refractive index of no less than about 1.6. The high refractive index material has an average refractive index which is sufficiently greater than the average refractive index of the low refractive index such that the average refractive index of the high refractive index material divided by the average refractive index of the low refractive index material yields a ratio that is greater than about 1.

Abstract: An assembly method of an air gap prism which has an air gap between a first glass member and a second glass member, the assembly method having steps of setting a first glass member on a positioning member, setting a sheet member on the positioning member so as to cover the first glass member, setting a second glass member on the first glass member covered with the sheet member so as to sandwich the sheet member between the first glass member and the second glass member, and cutting a portion of the sheet member protruding from the first glass member and the second glass member.

Abstract: An optical prism having a first glass member which has a first surface on which an specific light is irradiated, a second surface which reflects a part of the specific light and passes through the rest of the specific light, and a third surface on which the part of the specific light reflected by the second surface is irradiated in a substantially vertical direction; and a second glass member which has a fourth surface which passes through the rest of the specific light passing through the second surface, and a fifth surface on which the rest of the specific light passing through the forth surface is irradiated in a substantially vertical direction; wherein the third surface and the fifth surface have a resin which hardens by being irradiated the specific light.

Abstract: A light source for projecting rectangular color light bands includes a white-light source, a color separation device for separating the white light into red, green and blue components, and separate optics for forming images of rectangular red, green and blue light bands at predetermined positions. The light source is particularly useful in projection television apparatus having single panel light valves.

Abstract: A dichroic mirror for reflecting red light for optical separating and a dichroic mirror for reflecting red light for optical synthesizing are installed on the same plane in an image generating apparatus of the present invention. In addition, a dichroic mirror for reflecting blue light for optical separating and a dichroic mirror for reflecting blue light for optical synthesizing are installed on the same plane. Accordingly, a compact configuration can be realized. Since a main reflecting mirror is a rotating elliptic mirror and a lamp is located on a focus or around the focus, a lighting equipment which irradiates conic luminous flux can be realized.

Abstract: The invention is directed to a confocal scanning microscope for viewing an object. The confocal scanning microscope includes an illuminating device for transmitting an illuminating beam along an illuminating beam path and an optic for defining an imaging beam path. A beamsplitter is mounted in the imaging beam path and has a partially reflecting layer for deflecting a component of the illuminating beam toward the object whereby the component is reflected back toward the beamsplitter and passes through the beamsplitter into the imaging beam path with unwanted reflections occurring within the beamsplitter. The beamsplitter has two prisms conjointly defining the partially reflecting layer and has an external form defined by the optical faces of the prisms with each two mutually adjacent ones of the optical faces conjointly defining an angle unequal to 90.degree. whereby the unwanted reflections are substantially prevented from entering the imaging beam path.

Abstract: A prism optical system provided with: a first prism on which a light ray coming from an objective lens is incident; a second prism on which the light ray coming from this first prism is incident, and from which this incident light ray is emitted; and a plate-like member which is interposed between the aforesaid prisms so as to provide a predetermined air space therebetween and which has a diaphragm opening and a light blocking portion. Further, an uneven portion, which consists of depressions and projections and has a serrate section, for preventing light rays, which have been reflected from the surface of the light blocking portion of this plate-like member, from entering a field stop is provided in the light blocking portion thereof. Thereby, occurrences of ghosts and flares due to stray light are prevented. Moreover, ghosts and flares are reduced.

Abstract: A miniature virtual image color display having a viewing aperture, the display including a plurality of semiconductor chips each defining a plurality of pixels. The plurality of pixels of each semiconductor chip form a complete real image and each semiconductor chip is formed to provide the complete real image in a different color. An optical system combines the different colored real images and produces, from the plurality of complete real images, a single virtual image in color. The single virtual image is magnified so as to be viewable through the viewing aperture. The miniature virtual image display is designed to be incorporated into a communications receiver, such as a pager or two-way radio.

Abstract: The invention provides an optical system which is well corrected in terms of both curvature of field and coma at a field angle of about 120.degree. and a pupil diameter of about 15 mm and may be applied to both image pickup and ocular systems. Dioptric elements 11 are located the pupil plane side E and/or image plane side I of a concentric element 12 including two semitransparent surfaces 121 and 122, said two semitransparent surfaces 121 and 122 being concave on the pupil plane side E and located such that they transmit light at least once and reflect light at least once.

Abstract: A method and device for wavelength locking is provided, wherein an element having a wavelength dependent characteristic such as a Fabry Perot etalon is used to provide an output signal having an intensity that varies with wavelength. The intensity of a reference signal derived from an input signal is compared with an output from the Fabry Perot etalon to provide a feedback signal that corresponds to the frequency of the input signal. The system is calibrated before wavelength locking is performed to determine a ratio of intensities that determines a locked state or condition.

Abstract: A zonal beamsplitter for use with surgical microscopes including a pair of right triangular prisms positioned adjacent to each other in opposing relation along substantially planar surfaces defining their respective hypotenuses. The planar surface of one prism is bi-zonal and includes a first zone for diverting substantially all of a portion of an image-quality optical signal at an angle from the direction of travel of the optical signal, and a second zone for conducting substantially all of the remaining image-quality optical signal therethrough. The plane of the first zone may be offset from that of the second zone and/or coated with an opaque reflective surface such as a metal foil.

Abstract: A thin-film color-selective beam splitter and the method of fabricating the same are disclosed. The method includes the steps of: (i) forming a main prism by a pre-selected material, and deciding a first base angle and a second base angle according to the substance and coating characteristics of the pre-selected material; (ii) coating a first multilayer film and a second multilayer film on two slopes of the main prism, in which tilt angles for coating the first multilayer film and the second multilayer film and tilt angles of light entering and emerging the main prism are different, so that spectra of the first multilayer film and the second multilayer film are different, and the first multilayer film can be a red reflective film and the second multilayer film can be a blue reflective film; and (iii) using the pre-selected material to form interface prisms, and adhering the interface prisms to the main prism, so that light can perpendicularly enter and emerge from surfaces of the prism.