JP2013127489A - See-through display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a see-through display which has high adaptability to mass production and is inexpensive.SOLUTION: In see-through display which has a light source, a projection optical system for spatially modulates intensity of light to form an image, and a hologram for deflecting the light having been emitted from the projection optical system; and visually recognizes an image having been projected by the projection optical system through the hologram, the hologram includes a relief type hologram having a relief structure formed on the surface of a predetermined material, coats a notch filter for reflecting light of a predetermined wavelength on a lattice surface of the relief structure, and the lattice surface of the relief type hologram is fitted by a material having the same refractive index as that of the predetermined material without a space.

Description

  The present invention relates to a see-through display mainly used for a head-up display (HUD), a head-mounted display (HMD) and the like.

  A head-up display (HUD) is an image that displays information necessary for driving an automobile or aircraft, such as speed or altitude, as if it were in the space in front of the windshield, mainly in the cockpit of an automobile or aircraft. It is a display device. The head-mounted display (HMD) is a video display device that is mounted like glasses and displays the image as if it were in the space in front of the lenses constituting the glasses. Both are called see-through displays because they are seen through transparent members such as windshields and lenses, and have been actively developed in recent years. For example, in a car equipped with a HUD, it is possible to see the information necessary for driving with a small amount of line of sight while visually checking the front while driving, so that convenience can be improved while ensuring safety. it can. In addition, by viewing the video using the HMD, it is possible to view a large-sized image with extremely low power consumption. Furthermore, since viewing is possible regardless of location, necessary information can be obtained anytime and anywhere.

  In a see-through display, it is necessary to mix natural light incident from the outside such as scenery and an image to be displayed. For example, when an HUD is configured in an automobile, an image to be displayed and natural light incident from the outside are mixed by a combiner near the windshield. When mixing, it is desirable to mix while suppressing loss of natural light incident from the outside and light of each image to be displayed.

  On the other hand, a conventional see-through display uses a volume hologram as a combiner as disclosed in Patent Document 1, for example. When a hologram is used as the combiner, an image formed by the HUD can be enlarged by the lens action of the hologram, and a larger size image can be displayed. Furthermore, since the volume hologram does not diffract at a predetermined incident angle except for a predetermined wavelength, the rate at which natural light incident from the outside is diffracted by the volume hologram and lost can be kept low. Furthermore, if a volume hologram is used, it has a high diffraction efficiency at a predetermined wavelength. For example, if a laser light source is used as the light source, the wavelength width of the laser light is narrow, so that a HUD with high light utilization efficiency can be configured. Can do.

Japanese Patent No. 2585717

  However, the volume hologram used in the conventional configuration or the like needs to be subjected to interference exposure on the hologram photosensitive material in the production process. Interference exposure requires a high-accuracy exposure apparatus, resulting in high costs and problems in maintenance. Further, in order to alleviate the aberration caused by the difference in incident angle and wavelength when the light-sensitive material is exposed and when the image is illuminated, it is necessary to make the hologram light-sensitive material thin. When the hologram photosensitive material is thinned, the diffraction efficiency is lowered, so that the light utilization efficiency is low, and there is a problem that the power consumption is high to construct a see-through display having the same luminance.

  The present invention mainly solves the above-described conventional problems, and an object thereof is to provide a see-through display that can be manufactured at low cost, has high light utilization efficiency, and low power consumption.

  In order to achieve the above object, the see-through display of the present invention includes a light source that emits light, a projection optical system that forms an image by spatially modulating the intensity of the light, and the light emitted from the projection optical system. The hologram includes a relief-type hologram having a relief structure on the surface of a predetermined material, wherein the image projected by the projection optical system is viewed through the hologram. The grating surface of the structure was coated with a notch filter that reflects light of a predetermined wavelength, and the grating surface of the relief hologram was closely adhered with a material having the same refractive index as the predetermined material.

  Furthermore, the relief structure may be a blaze structure.

  Furthermore, the light incident on the relief hologram may be P-polarized light, and at least a part of the light may be incident on the relief hologram at a Brewster angle.

  Further, the notch filter may be composed of a dielectric multilayer film.

  Furthermore, the dielectric multilayer film may be applied only to the flat portion of the lattice plane.

  Furthermore, the notch filter may be a rugate filter.

  Further, a laser light source may be used as the light source.

  Furthermore, in the head-up display using the see-through display, the relief hologram may be attached to the indoor side of the windshield.

  Further, the present invention relates to a head-up display in which the relief hologram is sandwiched between laminated glasses constituting a windshield, wherein the windshield sandwiches an ultraviolet absorbing layer inside, and the relief hologram is more than the ultraviolet absorbing layer. It may be arranged indoors.

  Furthermore, in the head mounted display using the relief hologram, the relief hologram may be disposed closer to the eye than the spectacle lens.

  Further, the light source may be a two-color light source that emits light having different wavelengths, and the hologram may be composed of two types of relief holograms that diffract the light of each color.

  Further, the light source includes a blue light source that emits blue light (center wavelength: 400 nm to 490 nm), a green light source that emits green light (center wavelength: 490 nm to 570 nm), and a red light that emits red light (center wavelength: 570 nm to 680 nm). The hologram may be composed of three types of relief holograms that diffract the light of each color.

  Further, the three types of relief holograms may be laminated in the order of a relief hologram that diffracts blue light, a relief hologram that diffracts green light, and a relief hologram that diffracts red light.

  Further, in the head-up display using the relief type hologram, the relief type hologram that diffracts the light having the shortest wavelength may be arranged on the most outdoor side.

  In the see-through display of the present invention, a relief hologram is used as a combiner. By using a structure that does not generate higher-order diffracted light while using a relief hologram, a see-through display that does not generate stray light and has excellent visibility can be configured. In particular, by using a relief hologram having a blazed structure, a see-through display with high light utilization efficiency and low power consumption can be configured. Furthermore, since the light utilization efficiency is high, it can be diffracted by P-polarized light. By defining the incident angle as the Brewster angle, there is no surface reflection and excellent visibility without occurrence of a double image or the like. A see-through display can be constructed. In addition, since high-precision exposure is not required for manufacturing a hologram and it can be manufactured by molding, a see-through display that is highly suitable for mass production and inexpensive can be configured.

  Further, by laminating three types of relief holograms for red light, green light, and blue light, a see-through display capable of full color display can be configured.

  In addition, the diffraction efficiency can be easily set by configuring the notch filter provided on the grating surface of the relief hologram with a dielectric multilayer film and applying the dielectric multilayer film only to the flat portion of the grating surface. Therefore, the ratio of the natural light incident from the outside and the display image to be mixed can be set inexpensively and easily.

  In addition, by using a laser light source as a light source, light use efficiency is high, and further, blurring of an image due to the spread of wavelength can be reduced, so that a see-through display with low power consumption and high image quality can be configured.

  Moreover, when using a relief type hologram for HUD, it becomes possible to comprise HUD excellent in reliability by attaching to a room inner side rather than a windshield. Furthermore, by sandwiching the laminated glass constituting the windshield inside the room from the ultraviolet absorbing layer, the relief hologram is prevented from swelling due to moisture in the air being absorbed, and the HUD with excellent reliability can be obtained. Can be configured.

  In addition, when the see-through display is used for an HMD, a relief hologram having the same shape can be provided to a person wearing glasses by arranging the spectacle lens on the outside of the relief hologram. Therefore, it is possible to configure an HMD that is suitable for mass production and inexpensive.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic configuration diagram when a see-through display according to a first embodiment is applied to a HUD 10; (a) a schematic configuration diagram when a projection optical system is configured using a liquid crystal panel; (b) a MEMS mirror in a projection optical system; Schematic configuration diagram when configured using (A) Schematic configuration diagram of a relief hologram used in the see-through display according to the first embodiment, (b) Schematic diagram showing a manufacturing process FIG. 4 is a characteristic example of a notch filter applied to the grating surface of the relief hologram according to the first embodiment; The diffraction efficiency of the relief hologram according to the first embodiment, (a) a diagram showing the diffraction efficiency when S-polarized light is incident, (b) a diagram showing the diffraction efficiency when P-polarized light is incident The figure which shows the structural example at the time of comprising the notch filter given to the relief type hologram concerning Embodiment 1 with a dielectric multilayer film. BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic block diagram of the relief type hologram at the time of applying the see-through display to HUD concerning Embodiment 1, (a) Schematic block diagram when arrange | positioning indoors rather than a windshield, (b) Inside of a windshield Schematic configuration diagram when placed in The schematic block diagram at the time of applying the see-through display using the light source of three colors concerning HUD2 to HUD Schematic configuration diagram of a relief hologram according to the second embodiment. (A) The figure which shows the example of a characteristic of the notch filter given to the grating | lattice surface of the relief type hologram concerning Embodiment 2, (b) When the relief type hologram which diffracts the light of the shortest wavelength is arrange | positioned on the outermost outdoor side, Diagram showing characteristic example of notch filter (A)-(d) Schematic which shows the preparation process of the relief type hologram 54 (A) Schematic configuration diagram when the see-through display according to the third embodiment is applied to the HUD 70, (b) Schematic configuration diagram when the relief hologram 74 is applied to the HUD 70 The figure which shows the example of a characteristic of the notch filter given to the grating | lattice surface of the relief type hologram concerning Embodiment 3. (A)-(b) Schematic which shows the preparation process of the relief type hologram concerning Embodiment 3. FIG. (A) Schematic configuration diagram when see-through display according to the third embodiment is applied to an HMD, (b) Schematic configuration diagram of a relief hologram used for the HMD according to the third embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The drawings are schematically shown for easy understanding.

(Embodiment 1)
As an example of the see-through display according to the first embodiment, a head-up display (HUD) shown in FIG. FIG. 1A shows a schematic configuration diagram of the HUD 10. The HUD 10 includes a laser light source 11 that emits a laser beam 12, a projection optical system 18, and a relief hologram 20 attached to the indoor side of the windshield 21. . Furthermore, in the first embodiment, the projection optical system 18 includes the lens 13, the folding mirror 14, the liquid crystal panel 15, the projection lens 16, and the screen 17. The laser light source 11 and the liquid crystal panel 15 are connected to the control unit 19.

  A mechanism of operation of the HUD 10 according to the first embodiment will be described. The laser light 12 emitted from the laser light source 11 by a signal from the control unit 19 illuminates the liquid crystal panel 15 two-dimensionally. At this time, as shown in FIG. 1A, the laser beam 12 may be enlarged using the lens 13 so as to illuminate the liquid crystal panel 15 without waste. In addition, the laser beam 12 may be folded back by the folding mirror 14 so that the apparatus can be made compact. Of course, depending on the specifications of the HUD 10 and the characteristics of the light source 11, the lens 13 and the folding mirror 14 may not be used. By illuminating the liquid crystal panel 15 with the laser beam 12 in a state where an image pattern to be displayed is displayed on the liquid crystal panel 15 by a signal from the control unit 19, the intensity of the laser beam 12 is two-dimensionally modulated, and the liquid crystal panel 15. Emanates from. The emitted laser light 12 is imaged on the screen 17 by the projection lens 16 and displays an image on the screen 17. The laser beam 12 emitted from the screen 17 is diffracted by the relief hologram 20 and deflected toward the driver 22 side. As described above, the driver 22 sees the virtual image 23 enlarged by the relief hologram 20 through the windshield 21.

  Further, as shown in FIG. 1B, the projection optical system 18 is configured to form an image directly on the screen 17 by two-dimensionally scanning the laser light 12 with a MEMS mirror 30 or the like. It doesn't matter. In this case, the intensity of the laser beam 12 is directly modulated by the control unit 19 according to the image data to be displayed and the direction of the MEMS mirror, and an image is formed on the screen 17.

  As long as the projection optical system 18 has the same function, the projection optical system 18 may be other than those shown in FIGS. 1A and 1B, and does not limit the application range.

  Next, the operation mechanism of the relief hologram 20 will be described with reference to FIG. The relief hologram 20 is composed of resin materials 20a and 20c that are substantially transparent in the visible range and have the same refractive index, and a diffraction grating having a relief structure on the resin material 20c side as a grating surface 20b. It is carved. Further, the surface of the resin material 20c on the resin material 20a side has a complementary shape with respect to the lattice surface 20b of the resin material 20a, and the resin materials 20a and 20c are in close contact with each other without a gap. Furthermore, a notch filter 24 that reflects only the wavelength near the laser beam 12 with a predetermined reflectance is coated on the lattice surface 20b of the resin material 20a in advance. The notch filter is an optical filter that reflects only light having a single wavelength (usually several nm to several tens nm) with a predetermined reflectance and transmits the remaining light. For example, when the wavelength of the laser beam 12 is in the vicinity of 532 nm, the notch filter 24 of the first embodiment ideally has a predetermined reflectance of around 532 nm, which is the wavelength of the laser beam 12, as shown in FIG. (50% as an example in FIG. 3), and the reflectance is 0 in other wavelength regions. The notch filter 24 having such a wavelength characteristic can be constituted by, for example, a filter (Lugart filter) in which the refractive index in the film constituting the notch filter 24 changes continuously. In addition, it is also possible to configure with a dielectric multilayer film or an interference filter.

  Such a relief hologram can be produced, for example, by the following process. First, the resin material 20a is produced by molding such as injection molding. At this stage, the relief structure is provided on the lattice plane 20b. Next, a notch filter 24 is applied to the lattice plane 20b. The application of the notch filter may be vapor deposition, coating, or another method. Next, the resin material 20c is disposed on the resin material 20a. When, for example, an ultraviolet curable resin is used as the resin material 20c, the resin material 20c is applied to the lattice surface 20b side of the resin material 20a as shown in FIG. By doing so, the resin material 20c can be cured without a gap between the resin material 20c and the resin material 20a. Here, as described above, the resin materials 20a and 20c need to have the same refractive index. Through the above steps, the relief hologram 20 can be manufactured.

  With the above configuration, the HUD 10 of the present embodiment has the following effects. One is that although it is a relief hologram, the generation of stray light due to natural light is suppressed. Generally, when light incident on a relief hologram is diffracted, higher-order diffracted light exists. Therefore, when a relief hologram is used for the HUD, stray light due to higher-order diffracted light is generated. On the other hand, in the HUD 10 according to the first embodiment, since there is no gap between the resin material 20a and the resin material 20b, the light reflected by the notch filter 24 with respect to the natural light 25 incident on the relief hologram 20 from the outside. Other than (here, light in the vicinity of 532 nm), the relief hologram 20 functions as a single resin plate having no diffraction function. Therefore, although it is a relief hologram, most of the visible light constituting the natural light 25 enters the room without being diffracted. Further, even if the light incident on the relief hologram 20 from the outside is included in the reflection band of the notch filter 24, the grating surface 20b is made blazed as shown in FIG. The next diffracted light is hardly generated. Therefore, even when the driver 22 looks through the relief hologram 20 outside the room, stray light due to higher-order diffracted light is not generated in the room and stray light is incident on the driver 22's eyes. Does not occur. That is, it is possible to configure a HUD that does not generate stray light and has excellent visibility.

  Further, as shown in FIG. 2A, an extremely high-efficiency HUD 10 can be configured by making the grating surface 20b of the relief hologram 20 a blazed structure. FIG. 4A shows the calculation result of the wavelength dependence of diffraction efficiency in S-polarized light when the shape of the grating surface 20b is optimized with a blazed structure for laser light having a wavelength of 532 nm. However, the reflectance of the notch filter 24 is 50% in the entire band. As can be seen from this graph, a diffraction efficiency of 40% or more is obtained in the vicinity of a wavelength of 532 nm, and it is understood that high-order diffracted light is suppressed and extremely high diffraction efficiency is obtained. Therefore, by using a relief hologram as a combiner, a HUD with high light utilization efficiency and low power consumption can be configured. Note that the pitch P and blaze angle φ of each relief may be optimized for each relief.

  In addition, the diffraction efficiency of the relief hologram can be high even for P-polarized light. FIG. 4B shows the wavelength dependence calculation result of the diffraction efficiency when the light is incident on the relief hologram with P-polarized light. The calculation conditions are the same as in FIG. 4A except that the polarization direction of the incident laser light is different, and the reflectance of the notch filter 24 is calculated as 50% in the entire band. As can be seen from this graph, even in the P-polarized light, a high diffraction efficiency of 25% or more is obtained in the vicinity of the wavelength of 532 nm. In volume holograms, it is necessary to make the hologram photosensitive material as thin as possible in order to alleviate aberrations caused by the difference in the incident angle between the exposure of the photosensitive material and the illumination of the image and the wavelength fluctuation of the light that illuminates the image. For this reason, the diffraction efficiency is only about 10% even for S-polarized light, and only about several% is obtained for P-polarized light. Therefore, P-polarized light is not usually used from the viewpoint of light utilization efficiency and power consumption. However, if the relief hologram 20 is used as a combiner as in this embodiment, sufficient diffraction efficiency can be obtained even if P-polarized light is used. Can be reduced. Furthermore, this has the following effects. When the laser beam is incident on the relief hologram at an incident angle θ as shown in FIG. 2A, if the P-polarized light and θ are incident at the Brewster angle, The surface reflection on the outside surface of the windshield is eliminated, and the occurrence of surface reflection can be eliminated without applying a non-reflective coating or the like to each surface. For example, when the refractive index of the resin material 20c and the windshield 21 is 1.5, by making the incident angle θ near 56 °, the interior surface of the resin material 20c or the outdoor side of the windshield 21 It is possible to prevent surface reflection on the surface. Therefore, by using the relief hologram of the present embodiment, it becomes possible to use P-polarized light, whereby surface reflection can be prevented without applying a non-reflective coating or the like to the windshield surface. It has the effect that a high-quality HUD without multiple images can be constructed at low cost.

  Furthermore, since the relief hologram 20 of the HUD 10 can be composed of the resin materials 20a and 20c, it can be formed by molding as described above. Therefore, a large amount of relief hologram 20 can be produced in a short time, and a general-purpose material can be used as the resin material, so that the HUD 10 can be configured at low cost.

  Next, another configuration example of the notch filter 24 will be described with reference to FIG. FIG. 5 shows the relief hologram 20 attached to the indoor side of the windshield 21, but the fact that the dielectric multilayer film 26 is applied as a notch filter at a predetermined duty for each relief on the lattice plane is shown in FIG. ) Is different. In order to reduce the loss of natural light incident from the outside, it is conceivable to set the reflectance of the notch filter 24 to be lower than 100% (for example, about 50%). In that case, for example, it is conceivable to apply a notch filter having a reflectance of about 50% to the entire grating surface 20b. However, the creation of a notch filter having a reflectance of about 50% with a dielectric multilayer film limits the thin film materials that can be used. Therefore, the cost may increase. Therefore, for example, in order to create a notch filter having a reflectivity of 50%, a dielectric multilayer film 26 having a reflectivity of 100% with respect to the laser beam 12 is coated on the grating surface 20b with a duty of 50% as shown in FIG. A notch filter having a reflectance of about 100% can be formed of a general-purpose thin film material such as SiO 2 or TiO 2, and can be formed at low cost. By doing so, half of the laser beam 12 incident on the grating surface 20b is reflected approximately 100% by the dielectric multilayer film 26 and the rest is transmitted through the grating surface 20b, so that the reflectance is 50% macroscopically. The laser beam 12 can be reflected by the grating surface 20b. At this time, since the pitch P of the grating surface 20b in the visible region is about several microns, the deposition position of the dielectric multilayer film 26 cannot be recognized by visual observation. Is not visible. In this way, even if an inexpensive dielectric multilayer film material is used, by setting the duty of the vapor deposition region, a coat having a reflectance of 100% or less can be easily applied to the lattice plane, and an inexpensive HUD can be obtained. Can be configured.

  Here, it is desirable that the dielectric multilayer film 26 be provided on a relief-shaped plane portion provided on the lattice plane. The dielectric multilayer film generally has an incident angle dependency in wavelength characteristics. For example, since the apex portion of the blazed shape has a predetermined curvature, the dielectric multi-layer film has a predetermined curvature, so that the dielectric multilayer film is incident on the dielectric multilayer film incident on the apex portion. In some cases, desired reflection characteristics may not be obtained. On the other hand, for example, by providing the dielectric multilayer film 26 in a blazed flat surface portion as shown in FIG. 5, the dielectric multilayer film exists only at a predetermined angle with respect to the laser beam 12. Therefore, desired reflection characteristics can be easily obtained. With the above configuration, it is possible to easily configure a HUD with high light utilization efficiency, low power consumption, and high image quality.

  In the present embodiment, the relief hologram 20 is composed of the resin materials 20a and 20b. However, this may be glass, for example, and the material is limited if it has the same refractive index and is substantially transparent in the visible range. It is not a thing.

  Moreover, as shown in FIG. 1, in this Embodiment, the relief type hologram 20 was attached to the indoor side of the windshield. This has the following effects especially when the relief hologram 20 is made of a resin material. In general, it is known that when light is incident on a resin material, molecules inside the resin are excited by the light and the deterioration of the resin material proceeds. In particular, when ultraviolet light or light having a shorter wavelength than ultraviolet light is incident on a resin material such as an ultraviolet curable resin, the ultraviolet light is absorbed and the resin material is likely to deteriorate. On the other hand, in recent years, a windshield in which an intermediate layer including an ultraviolet absorbing layer 27 and the like is sandwiched between two laminated glasses 28 as shown in FIG. In this case, as shown in FIG. 6, by attaching the relief hologram 20 to the indoor side of the windshield 21, ultraviolet rays are absorbed by the ultraviolet absorbing layer 27 in the natural light 25 incident on the windshield 21, so that the relief is provided. Ultraviolet rays do not enter the mold hologram 20. Therefore, by attaching the relief hologram 20 to the indoor side of the windshield 21, the resin materials 20a and 20c are prevented from being deteriorated by ultraviolet rays, and in particular, a resin that is easily deteriorated by light such as an ultraviolet curable resin is used for the resin material 20c. Even in such a case, it is possible to configure a HUD having excellent reliability.

  Similar effects can also be achieved by arranging the relief hologram 20 between the laminated glasses 28 on the indoor side of the ultraviolet absorbing layer 26 as shown in FIG. 6B. Even with such an arrangement, it is possible to prevent the ultraviolet rays that cause the deterioration of the resin material from entering the relief hologram 20, and therefore, a resin that is easily deteriorated by light such as an ultraviolet curable resin is used for the resin material 20c. Even if it is a case, HUD excellent in reliability can be comprised.

  Further, as shown in FIG. 6B, the relief hologram 20 is sandwiched between the laminated glasses 28, so that the outside air does not directly contact the relief hologram 20. By doing so, it is possible to prevent swelling of the relief hologram 20 that occurs by absorbing moisture in the air. This is because the laminated glass 28 is usually in close contact with an intermediate layer such as an ultraviolet absorbing layer, so that the outside air does not penetrate into the laminated glass 28. When swelling due to moisture absorption, it is considered that the relief hologram 20 mainly expands in the thickness direction and the blaze angle φ increases. That is, when swollen due to moisture absorption or the like, it is conceivable that the image quality deteriorates such that the diffraction angle fluctuates and the diffraction efficiency of a predetermined wavelength decreases. On the other hand, since the moisture absorption can be prevented by sandwiching the laminated glass as shown in FIG. 6B, it is possible to prevent the image quality from being deteriorated due to the swelling, and to form a highly reliable HUD.

  Further, the linear expansion coefficient of the laminated glass is about 9 × 10 ^ (− 6) / ° C., whereas the linear expansion coefficient of the resin material is about 7 × 10 ^ (− 5) / ° C., which is a relief type. The hologram 20 has a linear expansion coefficient that is an order of magnitude larger and is likely to expand and contract due to temperature fluctuations. Further, when the liquid crystal expands and contracts due to temperature fluctuations, it can be considered that the image quality deteriorates such as fluctuations in diffraction angle and reduction in diffraction efficiency. On the other hand, as shown in FIG. 6B, the expansion and contraction of the relief hologram 20 due to temperature fluctuation can be mitigated by sandwiching the laminated glass 28 inside. This is because the expansion and contraction of the resin material is reduced by being sandwiched inside the laminated glass having a small linear expansion coefficient. Therefore, by sandwiching the relief hologram 20 inside the laminated glass as shown in FIG. 6B, a reduction in image quality due to temperature fluctuation can be reduced, and an HUD having excellent reliability can be configured.

  In the present embodiment, the laser light source 11 is used as a light source, but another light source such as an LED may be used. However, since the laser light source has a narrow wavelength range of emitted laser light compared to LEDs and the like, the use of a laser light source as the light source increases the diffraction efficiency of the hologram, suppresses blurring of the image due to the spread of the wavelength, and reduces power consumption. A power and high quality HUD can be configured.

  Furthermore, although the liquid crystal panel is used as the spatial modulation element, it is possible to use another spatial modulation element without departing from the spirit and scope of the present invention. For example, as an alternative to the light source 11 and the projection optical system 18, an LED array light source in which LEDs are two-dimensionally arranged may be used.

  In the first embodiment, the see-through display has been described using the HUD as an example. However, this is merely an example, and the present configuration can naturally be applied to other see-through displays such as an HMD.

(Embodiment 2)
An example of the see-through display according to the second embodiment will be described using a HUD 50 shown in FIG. The HUD 50 is similar to the HUD 10 of the first embodiment, but the configurations of the light source and the relief hologram are different. Three types of light sources are used as a light source: a red laser light source 51r having a central wavelength of 570 nm to 680 nm that emits red laser light 52r, a green laser light source 51g that emits green laser light 52g, and a blue laser light source 51b that emits blue laser light 52b. . Each of the three light sources is connected to the control unit 19, and the output of each laser light source is controlled. The blue laser light 52b emitted from the blue laser light source 51b is combined with the red laser light 52r emitted from the red laser light source 51r by the dichroic mirror 53b, and further the green laser light 52g emitted from the green laser light source 51g by the dichroic mirror 53a. It is combined and enters the lens 13. The process from entering the lens 13 to exiting the screen 17 is the same as the HUD 10 of the first embodiment. The laser beams 52r, 52g, and 52b emitted from the screen 17 are diffracted and deflected by a relief hologram 54 attached to the windshield 21, and the driver 22 fronts the virtual image 23 enlarged by the relief hologram 54. It can be seen through the glass 21.

  The structure of the relief hologram 54 will be described with reference to FIG. Although the relief hologram 54 is similar to the relief hologram 20 of the first embodiment, the relief hologram 20 has a two-layer structure in which two resin materials 20a and 20c having the same refractive index are brought into close contact with each other. The relief hologram 54 has a four-layer structure in which four resin materials 54a, 54c, 54d, and 54e having the same refractive index are brought into close contact with each other through the grating surfaces 54r, 54g, and 54b. The grating surface 54r is provided with a notch filter 55r so that only the red laser light is reflected at a desired incident angle, and the relief structure is such that the red laser light 52r is diffracted in a desired direction. Is provided. Similarly, the grating surface 54g is provided with a notch filter 55g so that only the green laser light is reflected at a desired incident angle, and further, the green laser light 52g is diffracted in a desired direction. A relief structure is provided. Similarly, the grating surface 54b is provided with a notch filter 55b so that only blue laser light is reflected at a desired incident angle, and further, the blue laser light 52b is diffracted in a desired direction. A relief structure is provided. For example, the center wavelength of red laser light is 635 nm, the center wavelength of green laser light is 532 nm, the center wavelength of blue laser light is 445 nm, and the reflectance at each wavelength is 50% at the maximum. Each notch filter 55r, 55g, 55b may be set so as to reflect only in the vicinity of the center wavelength as shown in FIG. In FIG. 9 (a), the reflectance at each wavelength is set to 50% at the maximum, but of course, it may be higher or lower. Increasing the reflectivity increases the light use efficiency as the HUD, while decreasing the reflectivity can relatively brighten the room because the amount of light entering the room can be relatively increased among the natural light incident from the outside. These can be set freely according to the specifications you want to achieve.

  An example of a method for manufacturing such a relief hologram 54 will be described with reference to FIG. First, similarly to the resin material 20a of the first embodiment, the resin material 54a is manufactured by injection molding or the like, and a notch filter 55b is provided on the lattice surface 54b of the resin material 54a as shown in FIG. Next, a resin material 54c is applied on the resin material 54a. Here, as an example of the resin material 54c, it is assumed that an ultraviolet curable resin is used as in the resin material 20c of the first embodiment. At this time, as shown in FIG. 10B, the transparent stamper 56a is disposed on the applied resin material 54c, and the ultraviolet light is irradiated from above the transparent stamper 56a, so that the resin material 54a is interposed between the resin material 54c and the resin material 54c. The resin material 54c can be laminated without a gap. Next, the transparent stamper 56a is removed, and a notch filter 55g is applied to the lattice surface 54g. Further, a resin material 54d is applied on the resin material 54c. Here, it is assumed that an ultraviolet curable resin is used for the resin material 54d as well as the resin material 54c. In this case, as shown in FIG. 10C, a transparent stamper 56b is disposed on the applied resin material 54d, and ultraviolet rays are irradiated from above the transparent stamper 56b, so that the resin material 54d is interposed between the resin material 54c and the resin material 54c. The resin material 54d can be laminated without a gap. Finally, a notch filter 55r is provided on the lattice surface 54r, and a resin material 54e is applied thereon. If the resin material 54e is also an ultraviolet curable resin like the resin materials 54d and 54c, the relief hologram 54 is formed by irradiating the ultraviolet light as shown in FIG. 10 (d) with the surface of the resin material 54e uniform. Complete. The resin materials 54a, 54c, 54d, and 54e have the same refractive index as described above.

  In the relief hologram 54 described above, the red laser light 52r incident on the grating surface 54r is reflected at a predetermined ratio by the notch filter 55r as described above, and is diffracted in a predetermined direction from the relief hologram 54 to the driver 22. It is emitted toward and is visually recognized as an image. The red laser beam 52r that has been reflected and left behind passes through the grating surface 54r, and is emitted without being reflected by the grating surfaces 54g and 54b and the windshield 21, so it does not contribute to image formation. Next, the green laser light 52g incident on the relief hologram 54 is transmitted without being reflected by the grating surface 54r provided with the notch filter 55r, and is incident on the grating surface 54g. A predetermined ratio of the green laser beam 52g is reflected on the grating surface 54g provided with the notch filter 55g, and is diffracted in a predetermined direction and emitted from the relief hologram 54 toward the driver 22. Then, an image is formed together with the red laser beam 52r reflected by the grating surface 54r. The green laser beam 52g remaining without being reflected by the grating surface 54g passes through the grating surface 54g, passes through the grating surface 54b and the windshield 21, and is emitted to the outside. Finally, the blue laser beam 52b incident on the relief hologram 54 is not reflected at all on the grating surfaces 54r and 54g on which the notch filters 55r and 55g are applied, passes through the grating surfaces 54r and 54g, and enters the grating surface 54b. Incident. A blue laser beam 52b is reflected at a predetermined ratio on the grating surface 54b provided with the notch filter 55b, diffracted in a predetermined direction, emitted from the relief hologram 54, and reflected by the grating surface 54r. Together with the green laser light 52g reflected by the grating 52r and the grating surface 54g, it contributes to image formation. The blue laser light 52b that has not been reflected by the grating surface 54b passes through the grating surface 54b, then passes through the windshield 21, and is emitted outside the room.

  By adopting the configuration as described above, the virtual image 23 is configured by the red laser beam 52r, the green laser beam 52g, and the blue laser beam 52g, so that full color display is possible. Therefore, it is possible to color the contents that can be displayed even though it is a HUD using a relief hologram. For example, by displaying it in yellow or red, the driver 22 is alerted and the driving safety is further improved. It is possible to configure the HUD that has been set.

  Similarly to the first embodiment, the resin materials 54a, 54c, 54d, and 54e are in close contact with each other on the lattice surfaces 54b, 54g, and 54r, so that each of the natural light 25 from the outside world is shown in FIG. Light that is not included in the reflection bands of the notch filters 55r, 55g, and 55b passes through the relief hologram 54 without being diffracted. Therefore, since most of the natural light 25 incident on the windshield enters the room without being diffracted, stray light due to higher-order diffracted light that occurs in a normal relief hologram does not occur, and the driver There is no occurrence of a phenomenon that disturbs driving such as stray light entering the 22 eyes. That is, it is possible to configure a HUD that does not generate stray light and has excellent visibility.

  Further, when the relief hologram 54 is produced, in FIG. 10D, a grating surface 54b for diffracting the blue laser light having the shortest wavelength among the used laser lights is arranged in the lowermost layer. A grating surface 54g for diffracting the green laser light having the next longest wavelength is disposed thereon, and a grating surface 54r for diffracting the red laser light having the longest wavelength is sequentially disposed thereon. In general, when the diffraction angle is the same, the longer the wavelength, the longer the pitch (p) of the hologram, and the relief unevenness (D) becomes larger. However, as shown in FIG. 10, when a resin material is applied, molded with a stamper, and cured, it is preferable to first produce a relief hologram with small irregularities (D). When the relief hologram has a smaller unevenness (D), an in-plane pressure difference is less likely to occur when the stamper is pressed, and the shape can be transferred more accurately. Therefore, if the short wavelength side with small unevenness (D), which is easy to transfer the shape accurately, is manufactured first, the shape error given to the upper layer to be transferred later can be made smaller, so the shape can be transferred more accurately as a whole. As a result, a relief hologram with higher accuracy and higher image quality can be produced.

  Further, when the blue laser beam 51b is diffracted by the outermost grating surface (lattice surface 54b in FIG. 8) of the relief hologram 54 of the HUD 50, the following configuration is possible. As the notch filter 55b to be applied to the grating surface 54b, as shown in FIG. 9B, ultraviolet light having a shorter wavelength than the blue laser light 52b (wavelength 400 nm or less) including the blue laser light 52b to be reflected is given a predetermined reflectance ( When a coating that reflects the light at 50% in FIG. 9B is applied, it is possible to reflect and remove the ultraviolet rays contained in the natural light 25 on the lattice surface 54b. In particular, as described in FIG. 10, when the resin materials 54c, 54d, and 54e are made of an ultraviolet curable resin or the like, it is possible to prevent the ultraviolet curable resin that absorbs a lot of ultraviolet rays from absorbing and deteriorating the ultraviolet rays. Therefore, it is possible to configure a HUD having excellent reliability. Here, the reason why the grating surface 54b that diffracts the blue laser light 51b is arranged on the most outdoor side is that the film formation of the notch filter becomes the simplest. As shown in FIG. 9B, the coating that reflects ultraviolet rays and the coating that reflects blue laser light 51b do not need to reduce the reflectance in the wavelength range between them, and can be configured as a simple low-pass filter. It becomes possible to do. On the other hand, in order to add a characteristic of reflecting ultraviolet rays to the notch filter 55g that reflects the green laser light 52g and the notch filter 55r that reflects the red laser light 52r, the reflectance is always in the band near 445 nm of the blue laser light 52b. Must be reduced to 0%. It is very difficult to form such a film, and the cost increases. Therefore, in the light to be used, the grating surface that diffracts the blue laser light that has the shortest wavelength is arranged on the outermost outdoor side, and the notch filter applied to the grating surface includes a coat that also reflects ultraviolet rays. A highly reliable HUD can be configured at low cost.

  In FIG. 9, the reflectance of the ultraviolet rays of the notch filter 55b is set to 50%, but of course, a higher reflectance may be set.

  Further, in the present embodiment, the red laser light source 51r, the green laser light source 51g, and the blue laser light source 51b are used as the light sources, but another LED such as an LED that emits red, green, or blue light or a white LED is used. A light source may be used. However, since the laser light source has a narrow wavelength range of emitted laser light compared to LEDs and the like, the use of a laser light source as the light source increases diffraction efficiency in the hologram, suppresses blurring of the image, and reduces power consumption and high image quality. A simple HUD can be configured.

  Further, although the liquid crystal panel is used as the spatial modulation element, it is possible to use other spatial modulation elements within the scope of the present invention and within the scope, and further, the red laser light source 51r, the green laser light source 51g, the blue color As an alternative to the laser light source 51b and the projection optical system 18, an LED array light source or the like in which LEDs that emit light of red, green, and blue are two-dimensionally arranged may be used.

(Embodiment 3)
As an example of the see-through display according to the third exemplary embodiment, a HUD 70 illustrated in FIG. 11A will be described. The HUD 70 is similar to the HUD 50 and the like of the second embodiment, except that the light source is a red laser light source 71r that emits red laser light 72r and a blue-green laser light source 71bg that emits blue-green laser light 72bg. As shown in FIG. 11B, the relief type hologram 74 is different in that it is composed of three layers of resin materials 74a, 74c, and 74d.

  The red laser light 72r emitted from the red laser light source 71r and the blue-green laser light 72bg emitted from the blue-green laser light source 71bg are combined by the dichroic mirror 73a, and the projection optical system 18 as in the first and second embodiments. And is projected onto a relief hologram 74 attached to the windshield 21. The red laser beam 72r and the blue-green laser beam 72bg projected onto the relief hologram 74 are diffracted and deflected by the relief hologram 74, and the driver 22 views the virtual image 23 enlarged by the relief hologram 74 on the windshield 21. You can see it over.

  As shown in FIG. 11B, the relief hologram 74 has two grating surfaces, a grating surface 74r and a grating surface 74bg. The grating surface 74r is provided with a notch filter 75r for diffracting the red laser beam 72r, and the grating surface 74bg is provided with a notch filter 75bg for diffracting the blue-green laser beam 72bg. For example, when the center wavelength of the red laser beam 72r is 635 nm and the center wavelength of the blue-green laser beam 72bg is 488 nm, the notch filters 75r and 75bg ideally have characteristics as shown in FIG. By providing a notch filter with such characteristics, as in the first and second embodiments, the light that forms an image as a HUD is diffracted with high efficiency, and the natural light 25 incident from the outside is mostly diffracted. Therefore, it is possible to configure the HUD with low power consumption and excellent visibility without stray light.

  The relief hologram 75 according to the third embodiment has an effect that it is particularly easy to produce. The outline of the process of producing the relief hologram 75 will be described with reference to FIG. First, the resin materials 74a and 74d are individually manufactured by injection molding or the like. At this stage, the grating surfaces 74r and 74bg are formed with relief shapes. Further, a notch filter 75r is provided on the lattice surface 74r, and a notch filter 75bg is provided on the lattice surface 74bg. Next, the resin material 74c is applied to the resin material 74a as shown in FIG. Here, if the resin material 74c is an ultraviolet curable resin like the resin material 54c of the second embodiment, the resin material 74d is disposed on the resin material 74c as shown in FIG. Thus, the resin material 74c is cured, and the relief hologram 74 is completed. As described above, the relief hologram 74 can be manufactured very easily.

  With the above configuration, it is possible to configure a HUD capable of displaying three colors of white, red, and blue-green by using two types of red laser light source and a blue-green laser light source that is a complementary color thereof. Particularly in HUD and the like, the content to be displayed is limited, and there are few cases where full-color display is required, so there are many cases where there is no problem even with three colors in actual use. Further, as described above, the relief hologram 74 can be easily manufactured by using two types of light sources. Therefore, by using two types of light sources, there is an effect that an inexpensive HUD can be configured without reducing convenience in actual use.

  In this embodiment, the light source used is a red laser light source and a blue-green laser light source that is a complementary color thereof. However, other combinations may be used, for example, a blue laser light source and a complementary yellow laser light source may be used. A purple laser light source and a complementary yellow-green laser light source may be used. If two light sources having complementary colors are used, white can be displayed by mixing colors. Of course, if there is no need to display white depending on the content to be displayed, a combination not having complementary colors may be used.

(Embodiment 4)
As an example of the see-through display according to the fourth embodiment, a head mounted display (HMD) 100 shown in FIG. The HMD 100 is similar to the HUD 50 as components, and includes a red laser light source 101r having a center wavelength of 570 nm to 680 nm that emits red laser light 102r as a light source, a green laser light source 101g that emits green laser light 102g, and a blue laser light 102b. It consists of a three-color light source of a blue laser light source 101 b that emits, a MEMS mirror 105 as a projection optical system, and a relief hologram 107. The red laser light 102r emitted from the red laser light source 101r is combined with the green laser light 102g emitted from the green laser light source 101g by the dichroic mirror 103a, and further emitted from the blue laser light source 101b by the dichroic mirror 103b. It is combined with the blue laser light 102 b and enters the folding mirror 104. The red laser beam 102 r, the green laser beam 102 g, and the blue laser beam 102 b reflected by the folding mirror 104 are deflected and scanned two-dimensionally by the MEMS mirror 105 and enter the relief hologram 107. Here, the red laser light source 101r, the green laser light source 101g, the blue laser light source 101b, and the MEMS mirror 105 are respectively connected to the control unit 111, control the swing angle of the MEMS mirror 105, and further each laser beam 102r, The intensity of each laser beam is also modulated according to the scanning positions of 102g and 102b and the image to be displayed.

  Next, the state of diffraction of each laser beam by the relief hologram 107 is shown in FIG. Similar to the relief hologram 54 of the second embodiment, the relief hologram 107 is made of resin materials 107a, 107c, 107d, and 107e having the same refractive index, and is adjacent to the adjacent resin material on the grating surfaces 107b, 107g, and 107r. It is in close contact with no gap. Furthermore, on the grating surfaces 107b, 107g, and 107r, notch filters 108b that reflect only the blue laser light 102b and the notch filters 108g that reflect only the green laser light 102g, respectively, similar to FIG. A notch filter 108r that reflects only the red laser beam 102b is provided. Further, as shown in FIG. 14B, the grating surfaces 107r, 107g, and 107b have the optimum relief shape depending on the position on the relief hologram 107 so that each incident laser beam is diffracted toward the eyeball 109. It has become. With the above configuration, the red laser light 102 r incident on the relief hologram 107 is diffracted only on the grating surface 107 r provided with the notch filter 108 r that reflects only the red laser light, and is deflected toward the eyeball 109. Similarly, the green laser beam 102g incident on the relief hologram 107 is diffracted only at the grating surface 107g provided with the notch filter 108g that reflects only the green laser beam, and the blue laser beam 102b reflects only the blue laser beam. The light is diffracted only at the grating surface 107 b provided with the notch filter 108 b to be deflected toward the eyeball 109. The light that has not been diffracted passes through the relief hologram 107 as it is. The red laser beam 102r, the green laser beam 102g, and the blue laser beam 102b deflected toward the eyeball 109 are recognized as an image by passing through the pupil 109a and forming an image on the retina 109b. Similarly to the HUD 50 of the second embodiment, if the light incident surface 107 f and the light exit surface 107 h of the relief hologram 107 are parallel, the natural light 110 incident on the relief hologram 107 is diffracted by the relief hologram 107. Without being distorted and the image is not distorted by refraction, it is recognized as an external scene. In FIG. 14B, the relief hologram 107 is curved while maintaining the parallel relationship between the incident surfaces 107f and 107h.

  With the above configuration, while using the relief hologram, most of the natural light 110 passes through the relief hologram 107 without being diffracted, so that no problem such as stray light entering the eye occurs. An HMD having excellent visibility that does not generate stray light can be configured. In addition, since a high diffraction efficiency can be obtained by making the grating surface blazed as shown in FIG. 14, an HMD with high light utilization efficiency and low power consumption can be configured. Further, since the relief hologram 107 can be manufactured by molding, it is possible to configure an inexpensive HMD with high mass productivity.

  In addition, when a person wearing glasses wears an HMD, it is necessary to adjust the focus position of the scenery of the outside world with the eyeglass lens with respect to the outside world. Regardless, the image is formed on the retina. When an HMD is constructed using a volume hologram, a hologram can be produced by directly exposing a volume hologram attached to an eyeglass lens, so that an optimum hologram for each person can be obtained regardless of the position of the eyeglass lens. Can be configured. However, when the relief hologram 107 of the fourth embodiment is mass-produced by molding, for example, unlike the volume hologram, it cannot be optimized in accordance with the shape of each person's eyeglass lens. In this case, as shown in FIG. 14A, by arranging the relief hologram 107 closer to the eyeball 109 than the eyeglass lens 106, a relief hologram having the same structure manufactured in mass production can be used. That is, by arranging the relief hologram 107 and the MEMS 105 at a predetermined position with respect to the position of the eyeball 109, an image formed by the HMD can be appropriately formed on the retina. On the other hand, by attaching the eyeglass lens 106 to the outside world side, a scene from the outside world can be appropriately imaged on the retina. In this way, by arranging the spectacle lens closer to the outside of the relief hologram, it is possible to provide a relief hologram with the same shape to a person wearing glasses, so that mass production is appropriate and inexpensive. An HMD can be configured.

  It should be noted that each of the above-described embodiments is a possible example, and does not limit the scope of application, and it is easily understood that various modifications and combinations can be made without departing from the spirit and scope of the present invention. Will.

  The see-through display of the present invention has low power consumption due to its high light utilization efficiency, and is excellent in visibility and can be constructed at low cost, and can be applied to all see-through displays such as HUD and HMD. It is.

10, 50, 70 Head-up display (HUD)
DESCRIPTION OF SYMBOLS 11 Laser light source 12 Laser light 13 Lens 14,104 Folding mirror 15 Liquid crystal panel 16 Projection lens 17 Screen 18 Projection optical system 19,110 Control part 20,54,74,107 Relief type hologram 20a, 20c, 54a, 54c, 54d, 54e, 74a, 74c, 74d, 107a, 107c, 107d, 107e Resin material 20b, 54r, 54g, 54b, 74r, 74bg, 107r, 107g, 107b Lattice surface 21 Windshield 22 Driver 23 Virtual image 24, 55r, 55g, 55b, 75r, 75bg, 108r, 108g, 108b Notch filter 25, 109 Natural light 26 Dielectric multilayer film 27 Ultraviolet absorbing layer 28 Laminated glass 30, 105 MEMS mirror 51r, 71r, 101r Red laser light source 51g, 101g Green laser light source 51b, 101b Blue laser light source 71bg Blue green laser light source 52r, 72r, 102r Red laser light 52g, 102g Green laser light 52b, 102b Blue laser light 72bg Blue green laser light 53a, 53b, 73a, 103a, 103b Dichroic mirror 56a, 56b Transparent stamper 100 Head mounted display (HMD)
106 Eyeglass lens 109 Eyeball 109a Pupil 109b Retina

Claims (14)

A light source that emits light;
A projection optical system that forms an image by spatially modulating the intensity of the light;
Having a hologram for deflecting the light emitted from the projection optical system;
In the see-through display for visually recognizing the image projected by the projection optical system through the hologram,
The hologram includes a relief type hologram having a relief structure formed on the surface of a predetermined material, the grating surface of the relief structure is coated with a notch filter that reflects light of a predetermined wavelength, and the grating of the relief type hologram The see-through display is characterized in that the surface is in close contact with a material having the same refractive index as the predetermined material without any gap. The see-through display according to claim 1, wherein the relief structure is a blaze structure. The see-through display according to claim 2, wherein the light incident on the relief hologram is P-polarized light, and at least a part of the light is incident on the relief hologram at a Brewster angle. . The see-through display according to claim 1, wherein the notch filter is made of a dielectric multilayer film. The see-through display according to claim 4, wherein the dielectric multilayer film is provided only on a planar portion of the lattice plane. The see-through display according to claim 1, wherein the notch filter comprises a rugate filter. The see-through display according to claim 1, wherein a laser light source is used as the light source. The head-up display using the see-through display according to claim 1, wherein the relief hologram is attached to the indoor side of the windshield. 2. The head-up display in which the relief hologram in the see-through display according to claim 1 is sandwiched between laminated glasses constituting a windshield, wherein the windshield has an ultraviolet absorbing layer sandwiched therein, and the relief hologram Is a head-up display, which is disposed on the indoor side of the ultraviolet absorbing layer. The head-mounted display, wherein the relief hologram in the see-through display according to claim 1 is arranged closer to the eye than the spectacle lens. 2. The light source according to claim 1, wherein the light source includes two color light sources that emit light having different wavelengths, and the hologram includes two types of relief holograms that diffract the light of each color. See-through display as described. The light source includes a blue light source that emits blue light (center wavelength: 400 nm to 490 nm), a green light source that emits green light (center wavelength: 490 nm to 570 nm), and a red light source that emits red light (center wavelength: 570 nm to 680 nm). The see-through display according to claim 1, wherein the hologram further comprises three types of relief holograms for diffracting the light of each color. The three types of relief holograms are laminated in the order of a relief hologram that diffracts blue light from the bottom, a relief hologram that diffracts green light, and a relief hologram that diffracts red light. The see-through display according to 12. 13. A head-up display, wherein a relief hologram that diffracts light having the shortest wavelength among the relief holograms in the see-through display according to claim 11 or 12 is arranged on the outermost outdoor side.

Images