JP2011227281A - Transmission type display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transmission type display device which changes a method concerning the countermeasure to surface reflection according to a wavelength width of light source.SOLUTION: When the wavelength width of light source is small, a difference between an incidence angle and an emission angle of a combiner is made larger, and when the wavelength width of light source is large, the countermeasure to the surface reflection is performed by using a circular polarization.

Description

  The present invention superimposes and displays an image on an external scene that can be seen from a transmissive display unit, and operates by superimposing an aiming image on a predetermined external object included in the external scene. The present invention relates to a transmissive display device that can be instructed to operate.

  Drivers who drive vehicles such as moving vehicles are required to perform safe and quick operations such as understanding the conditions outside the vehicle, reading information on the display device of the vehicle, and driving operations. It is desirable that the information on the display device of the vehicle can be read within the range necessary for grasping the situation outside the vehicle while driving. Therefore, for example, realization of an image display device that displays characters or images by irradiating light to a part of a transparent plate such as a windshield of a vehicle is expected.

  As such a transmissive display device, a head-up display (HUD) that displays driving information on the windshield of an automobile, a head-mounted display (Head-Mounted) that displays information on the lens part of the glasses Display, hereinafter referred to as HMD). If such a transmission type device is used, the driver can see driving information (for example, a map and a speedometer) at the same time while visually recognizing the outside world, so the driver is expected to be able to drive more safely. Has been.

  As a conventional HUD, there is one that projects a virtual image on a windshield (for example, Patent Document 1). FIG. 1 shows a conventional HUD described in Patent Document 1. In this example, the use of a highly transmissive hologram combiner for the windshield portion increases the external transmittance and increases the brightness of the display image.

  In FIG. 1, reference numeral 101 denotes a vehicle body on which a HUD is mounted. Reference numeral 102 denotes a HUD optical unit stored inside the dashboard, which includes a display element 103 and deflection means 104 therein. The display element 103 includes a liquid crystal element and a light source, for example, and displays information to be displayed on the driver 108. Display light displayed on the display element 103 is projected toward the deflecting means 104. The deflecting means 104 is constituted by a mirror or the like, and deflects the display light from the display element 103 toward the combiner 106 provided on the windshield 107. The display light deflected by the deflecting unit 104 passes through the opening 105 of the HUD optical unit 102 and is projected onto the combiner 106 formed on the surface of the windshield 107. The combiner 106 deflects the display light from the HUD optical unit 102 toward the driver 108. The driver 108 can visually recognize information related to driving by viewing the display light reflected by the combiner 106. The eye box 109 indicates a range in which an image can be seen when the driver 108 moves his / her head. When the driver's 108 eye is inside the eye box 109, the display light reaches the retina of the driver 108, and the driver 108 visually recognizes the image. can do. The combiner 106 reflects the display light from the HUD optical unit 102 and at the same time transmits light from the outside (outside) of the windshield. Due to the performance of this combiner, the driver 108 can see an external scene outside the windshield together with information displayed by the display element 103. As described above, in the HUD, the driver 108 can see information from the display element without diverting the line of sight from the outside world, so that it is less necessary for the driver to move the line of sight and the safety during driving is improved. In Conventional Example 1, a hologram combiner is used as the combiner 106. The hologram combiner has high wavelength selectivity, for example, reflects only the wavelength used in the display element, and transmits light of other wavelengths, so that the light from the display element is reflected with high brightness and from the outside world. It is said that it becomes possible to transmit the light with high transmittance. Japanese Patent Application Laid-Open No. H10-228561 proposes correcting the image distortion caused by the curvature of the combiner 106 by using the deflecting means 104 as a concave mirror.

  However, in a HUD that displays to the driver by attaching a hologram combiner to such a windshield, the display light from the display means is reflected by the windshield itself in addition to the hologram combiner, and as a result, The driver sees two images: display light diffracted by the hologram combiner and display light reflected by the windshield itself. An example of this is shown in FIG. In FIG. 2, a hologram combiner 201 is installed between the two glasses 202 and 203 constituting the windshield. As shown in FIG. 2, the display light 204 incident on the hologram combiner 201 is also reflected by the front glass 202 and the rear glass 203 to generate two reflected lights 206 and 207. As a result, the light of the display light 204 is visually recognized by the driver in three types of diffracted light 205 by hologram and reflected light 206 and 207 by glass. As a result, display light displayed by the display element is displayed. Will be blurred by the driver in double or triple blur. Hereinafter, in this specification, the problem that the diffracted light from the hologram combiner and the reflected light from the glass are simultaneously recognized by the driver is referred to as a surface reflection problem.

  In order to deal with this surface reflection problem, it has been proposed to use the characteristics of polarized light (for example, Patent Document 2). An example of countermeasures against the surface reflection problem using polarized light is shown in FIG. In the example of FIG. 3, half-wave plates 301 and 302 are disposed between the hologram combiner 201 and the two glasses 202 and 203 constituting the windshield. The display light 303 is composed of a P-polarized component and is incident on the hologram combiner 201. At this time, the angle 306 at which the display light 303 enters the front glass 302 is set to be equal to the Brewster angle of the glass so that the reflectance of the P-polarized light is lowered. Therefore, the P-polarized display light 303 does not generate reflected light on the front glass 302. Further, the display light 303 is converted into S-polarized light by passing through the half-wave plate 302 before entering the hologram combiner 201, and is incident on the hologram combiner 201 with S-polarized light. In general, a hologram combiner composed of a volume hologram or the like has a higher diffraction efficiency for S-polarized light than P-polarized light. Therefore, the hologram combiner 201 diffracts the display light 303 with high diffraction efficiency, generate. The diffracted light 305 passes through the half-wave plate 302 again, is polarized to P-polarized light, passes through the front glass 202, and is visually recognized by the driver. Of the incident light 303, light that has not been diffracted by the hologram combiner 201 and has passed through the hologram combiner 201 passes through the half-wave plate 301, is again P-polarized, and then enters the back glass 203. At this time, the angle at which the P-polarized display light is incident on the back glass is set to an angle close to the Brewster angle, similar to the incident angle 306 when the display light 303 is incident on the front glass 202. The display light 303 does not reflect on the back glass 203 but passes through the back glass 203 as transmitted light 304 and is not visually recognized by the driver. By using polarized light for the display light in this way, it is possible to prevent the reflected light from being generated on the glass and allow the driver to visually recognize only the diffracted light from the hologram combiner.

  Further, as another method for the surface reflection problem, there is a method in which the direction of the diffracted light by the hologram combiner and the direction of the surface reflected light by the glass are set to different values. An example of this is shown in FIG.

  In the example of FIG. 8, the optical performance of the hologram combiner 201 is designed so that the diffracted light 802 is emitted at the diffraction angle 804 with respect to the light incident at the incident angle 306. At this time, the reflected light 803 generated by the back glass 203 is emitted from the windshield at an emission angle 805 having the same size as the incident angle 306. At this time, if the diffraction angle 804 is designed to have a sufficiently large value with respect to the emission angle 805, a hologram combiner is used in the eye box where the driver visually recognizes the display image as shown in FIG. Only the diffracted light 802 is incident, and the reflected light 803 from the glass can be prevented from being visually recognized by the driver. A method of changing the direction of reflected light by glass and the direction of diffracted light by a hologram combiner has already been proposed (for example, Patent Document 3).

Japanese Patent No. 3418985 Japanese Patent No. 2507700 Japanese Patent No. 2751436

  However, when determining the incident angle and the outgoing angle to the hologram combiner, it is necessary to consider the wavelength width of the light source used for display.

  When a large difference is made between the diffraction angle and the emission angle in order to counter the surface reflection problem, image blurring (chromatic aberration) is greatly generated by the hologram combiner. Here, image blur refers to a phenomenon in which incident light is diffracted in a direction different from the design wavelength when light having a wavelength different from the design wavelength of the hologram combiner is incident on the hologram combiner. When the hologram combiner was designed with the center wavelength of the light source, the larger the wavelength width of the light source, the light with a wavelength deviating from the designed wavelength is incident on the hologram combiner. Will diffract the light from the light source in different directions. The greater the difference between the incident angle and diffraction angle of the hologram combiner, the greater the effect of image blur due to this hologram combiner. Therefore, when the wavelength range of the light source is large, if the difference between the incident angle and the diffraction angle of the hologram combiner is increased to prevent the surface reflection problem, the resolution of the image displayed to the driver is increased. descend. In Patent Document 2, no consideration is given to the wavelength width of the light source.

  In the method for dealing with the surface reflection problem using polarized light, the difference between the incident angle and the diffraction angle of the hologram combiner can be reduced, so that the above-mentioned image blur problem does not occur. However, in the method using polarized light as shown in FIG. 3, linearly polarized light is displayed to the driver. When the diffracted light is P-polarized light, there arises a problem that when the driver wears glasses that block the P-polarized light, no display is visible. In addition, even when wearing sunglasses that blocks S-polarized light, the display light is blocked by the polarized glasses when the driver tilts his / her neck, and the driver may not be able to see the display light. In Patent Document 1, no consideration is given to this problem.

  The present invention solves the above-described conventional problems, and an object thereof is to provide a transmissive display device in which appropriate incident angles and outgoing angles of a hologram combiner are appropriately set according to the wavelength width of a light source.

  In order to solve the above-described conventional problems, a transmissive display device of the present invention includes a light source that outputs light, a display unit that forms an image by receiving light emitted from the light source, and a display emitted from the display unit. The light having a wavelength included in the light is reflected toward the user, and has a transmission / reflection unit that transmits the light of other wavelengths, and according to the light source wavelength width that is the wavelength width of the light output from the light source, An angle difference between an incident angle at which the display light is incident on the transmission / reflection unit and a diffraction angle at which the display light is emitted from the transmission / reflection unit is different.

  With this configuration, it is possible to cope with the surface reflection problem according to the wavelength width of the light source used.

  In the transmissive display device of the present invention, when the light source wavelength width of the light source is a certain value or more, an incident angle at which the display light is incident on the transmissive reflecting means, and display light from the transmissive reflecting means is displayed. The difference in angle from the emitted diffraction angle is 5 degrees or less.

  With this configuration, when the light source wavelength width is large, it is possible to prevent the image quality of the image displayed on the driver from being deteriorated.

  In the transmissive display device of the present invention, the constant value of the light source wavelength width is 0.5 nm or more.

  With this configuration, even when a light source having a wide light source wavelength width is used to prevent speckle due to laser, it is possible to prevent the image quality of the image displayed on the driver from being deteriorated.

  In the display means of the present invention, the display means includes polarizing means for converting display light into circularly polarized light, and the transmission and reflection means includes a diffraction element that deflects the direction of display light, and a transparent member that holds the diffraction element. A transparent member for holding the diffractive element and a transparent member for holding the diffractive element in a direction opposite to the transparent element. A rear transparent member, a front transparent member to be held, a rear transparent member, and S-polarized light conversion means for converting circularly polarized light into S-polarized light for the diffraction element between the diffraction means and the front transparent member And a P-polarized light converting means for converting S-polarized light for the diffractive element into P-polarized light for the diffractive element between the diffractive means and the rear transparent member.

  With this configuration, it is possible to visually recognize the display image even when the driver wears polarized glasses that block linearly polarized light.

  In the transmissive display device of the present invention, the difference between the incident angle to the transmissive reflecting means and the Brewster angle of the rear transparent member is within 5 degrees.

  With this configuration, it is possible to prevent the glass reflected light from being generated by the windshield.

  In the transmissive display device of the present invention, the interface of the front transparent member with air is provided with a non-reflective coating that prevents surface reflection.

  With this configuration, it is possible to prevent light reflected by the glass from being generated on the inner surface of the windshield.

  The rear transparent member of the present invention has a wedge shape, and the incident angle of the transmitted light transmitted from the rear transparent member to the rear transparent member is the Brewster angle of the rear transparent member. The inclination angle of the wedge is set.

  With this configuration, it is possible to prevent the generation of glass reflected light even when the angle at which the display light is incident on the windshield depending on the tilt angle of the windshield is different from the Brewster angle of the glass.

  In the transmissive display device of the present invention, the height of the display image displayed by the display unit is limited so that the incident angle to the transmission / reflection unit does not deviate from the Brewster angle of the rear transparent member. It is a characteristic.

  With this configuration, it is possible to prevent the reflected light from being generated by the glass at the upper and lower end portions of the display image.

  In the transmissive display device of the present invention, the refractive index of the rear transparent member according to the inclination of the transmissive reflective means so that the incident angle to the transmissive reflective means becomes the Brewster angle of the rear transparent member. Is determined.

  With this configuration, it is possible to reduce the difference between the angle of incidence on the windshield and the Brewster angle of the glass and prevent the generation of reflected light from the glass.

  In the transmissive display device of the present invention, when the light source wavelength width of the light source is equal to or smaller than a certain value, an incident angle at which the display light is incident on the transmissive reflecting means, and display light from the transmissive reflecting means is displayed. The angle difference from the emitted diffraction angle is 10 degrees or more.

  With this configuration, it is possible to solve the surface reflection problem without adding a wave plate or the like to the windshield.

  In the transmissive display device of the present invention, the constant value of the light source wavelength width is 0.5 nm or less.

  The present invention makes it possible to prevent the occurrence of surface reflection problems when using a laser light source having a small line width.

  In addition, the light source of the present invention is configured by a wavelength conversion element (SHG) having a small wavelength width.

  With this configuration, the wavelength width of the light source can be kept small, and the image quality displayed on the driver can be prevented from being degraded.

  The display element of the present invention includes a spatial modulation element and an intermediate screen, and includes a vibrating means for vibrating the intermediate screen.

  With this configuration, it is possible to prevent speckle noise from occurring even when a light source having a small wavelength width is used.

  According to the transmissive display device of the present invention, it is possible to appropriately set the appropriate incident angle and outgoing angle of the hologram combiner according to the wavelength width of the light source, and display a high-quality image.

Configuration diagram of HUD in Embodiments 1 and 2 of the present invention Diagram showing an example of a conventional surface reflection problem Configuration of conventional hologram combiner Configuration diagram of hologram combiner in Embodiment 1 of the present invention Configuration diagram of display means in Embodiment 1 of the present invention The figure which shows the example of operation | movement of the scanning means in Embodiment 1 of this invention. The figure which shows another structure of the display element in Embodiment 1 of this invention. Configuration diagram of hologram combiner in embodiment 2 of the present invention The figure which shows another structure of the display element in Embodiment 1 of this invention. The figure which shows the example of the polarization reflectance of glass The figure which shows the structure of the display element in Embodiment 2 of this invention The figure which shows the example of the structure of the rear side glass in Embodiment 1 of this invention The figure which shows the example of the structure of the rear side glass in Embodiment 1 of this invention

    Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1)
In this embodiment, a configuration of an optical system for taking measures against a surface reflection problem when the wavelength width of a light source is large will be described.

  FIG. 1 shows a configuration diagram of a HUD (head-up display) in Embodiment 1 of the present invention.

  In FIG. 1, reference numeral 101 denotes a vehicle body on which a HUD is mounted, and includes a HUD optical unit 102 inside the dashboard. The HUD optical unit 102 includes a display unit 103, a deflection unit 104, and an opening 105.

  The display means 103 displays driving information (speedometer and map information) and the like for the driver 108. In the present embodiment, the display means 103 forms an image to be displayed on the driver 108 by performing two-dimensional scanning on the display screen with the output beam from the laser light source. FIG. 5 shows a configuration diagram of the display means 103 in the present embodiment.

  As shown in FIG. 5, in this embodiment, the light source of the display means is a laser light source, and the output laser light from the red laser light source 501, the blue laser light source 502, and the green laser light source 503 is allowed to pass through the collimator 504, and dichroic. The laser beam L is multiplexed by the mirror 505. By appropriately modulating the output from each color laser light source, laser light of any color can be output. In FIG. 5, 501 is a red (R) semiconductor laser light source, 502 is a blue (B) semiconductor laser light source, and 503 is a green (G) semiconductor laser light source, but 503 is an infrared semiconductor laser light source, A combination of SHG (Second Harmonic Generation) elements that convert infrared rays into green may be used, and each light source may be a solid laser, a liquid laser, a gas laser, or a light emitting diode.

  In FIG. 5, the laser light is modulated by each laser light source. However, the laser light may be modulated by using a means for modulating the light output from the laser light source in combination with the laser light source.

  In the present embodiment, at least one of the laser light sources 501 to 503 is a light source having a wavelength width of 0.5 nm or more.

  The polarization unit 509 has a function of polarizing the beam L from the light sources 501 to 503. In the present embodiment, the beam L is converted into circularly polarized light by the polarizing means 509. The polarizing means 509 in the present embodiment is composed of a linear polarizer and a quarter wavelength plate. The beam L incident on the polarizing means 509 is first converted into linearly polarized light by a linear polarizer. At this time, when the beam L enters the combiner 106, the beam L is polarized so as to be P-polarized with respect to the combiner 106. Thereafter, the beam L passes through the quarter-wave plate and is converted into circularly polarized light, and then is emitted from the polarizing means 509.

  The deflecting unit 509 may be realized by a combination of other polarizers. Further, the polarization unit 509 is not necessarily disposed between the light sources 501 to 503 and the scanning unit 506, and may be disposed between the scanning unit 506 and the screen 507.

  The scanning unit 506 performs two-dimensional scanning on the display screen 507 with the beam L from the light sources 501 to 503. The scanning unit 506 is a single-plate small mirror that can deflect an angle two-dimensionally, and is a MEMS (Micro-Electro-Mechanical-System) micromirror. An example of this is shown in FIG. The scanning unit 506 scans the laser beam L incident on the mirror in a two-dimensional direction by vibrating the single-plate small mirror in two directions of the rotation shaft 601 and the rotation shaft 602.

  In this embodiment, the scanning unit 506 employs a method in which one mirror is vibrated in a two-dimensional direction. However, two laser beams that vibrate in different one-dimensional directions are combined to generate two laser beams L. A method of scanning in the dimension direction may be used. In this case, since each mirror vibrates only in a one-dimensional direction, there is an effect that the control of the angle of each mirror is simplified.

  The light from the scanning unit 506 is two-dimensionally scanned on the back surface of the display screen 507 to form a display image. An image formed on the display screen 507 is output from the surface of the display screen 507 to the deflection unit 104 as an image from the display unit 103.

  In the present embodiment, the display unit 103 performs a rear projection on the display screen 507. However, a method of performing a front projection on the display screen 507 may be used. FIG. 7 shows another configuration example of the display unit 103 at this time. In this case, the use of a fly-eye mirror or a bead screen with high diffusion efficiency for the display screen 507 has an effect of improving the brightness of the image displayed to the user.

  Note that the display means 103 may be a system in which laser light is projected directly onto the combiner 106 described later without having the display screen 507. In this case, light can be directly projected onto the retina of the driver, and a clearer image can be displayed on the driver.

  The display means 103 may be a display element composed of a liquid crystal element and a backlight light source instead of a method of scanning with laser light. For example, a configuration may be adopted in which a liquid crystal element is disposed instead of the scanning unit 506 and an optical system for illuminating the liquid crystal element is disposed between the liquid crystal element and the dichroic mirror 505. At this time, a laser light source may be used as the backlight light source, or another light source such as an LED may be used. A configuration diagram of the display means 103 at this time is illustrated in FIG. In FIG. 9, unlike FIG. 5, a liquid crystal element 902 and a folding mirror are arranged instead of the scanning unit 506. Light from the light sources 501 to 503 is diffused by the illumination optical element 901 and then irradiates the liquid crystal element 902 to form display light L.

  The display light L formed by the liquid crystal element 902 is converted into circularly polarized light by the polarizing element 509, and then forms an image on the screen 507 via the folding mirror 903. The light output from the liquid crystal element is usually linearly polarized light. Therefore, when the output light from the liquid crystal element is S-polarized with respect to the combiner 106, the configuration of the polarizing element 509 is formed of a half-wave plate and a quarter-wave plate, and the light from the liquid crystal element is 1 After being polarized to P-polarized light with respect to the combiner 106 by the / 2 wavelength plate, it is converted to circularly polarized light by the ¼ wavelength plate. In addition, when the output light from the liquid crystal element is P-polarized light with respect to the combiner 106, the polarizing element 509 is configured only by a quarter wavelength plate, and converts linearly polarized light into circularly polarized light.

  Note that when a display image is formed by a liquid crystal element instead of a scanning unit, the light emitted from the polarizing element 509 is directly output from the display unit 103 without using the folding mirror 903 and the screen 507 shown in FIG. You may take the structure to be taken. In this case, the display element 103 can be further downsized.

  The deflecting unit 104 changes the direction of the display light L from the display unit 103 and makes it incident on the hologram combiner 106. In the present embodiment, the deflecting means 104 is constituted by a plane mirror, but may be constituted by a concave mirror or a hologram mirror having an enlargement performance. In this case, the optical path length of the optical system can be shortened and the size of the HUD housing 102 can be reduced.

  The combiner 106 is a transmission / reflection unit that reflects the direction of the display light incident from the deflection unit 104 in a direction toward the user's eyes. In the combiner 106 according to the present embodiment, for example, a photopolymer layer is formed inside the windshield (inside the vehicle body 101), and a Lippmann volume hologram is formed on the photopolymer layer. The display light that is incident on is reflected at the diffraction angle 111 toward the user 108.

  In this embodiment, the photopolymer layer is formed with three holograms that reflect red, green, and blue light from each light source.

  In this embodiment, a method of performing multiple exposure of three colors of RGB on one hologram is used, but three layers of holograms corresponding to light of each color may be laminated. In this case, the numerical value of refractive index modulation in the hologram material can be assigned to each color instead of being assigned to the three colors of RGB, so that the diffraction efficiency of each color can be increased.

  When a hologram is used for the combiner, the influence of chromatic aberration (image blur) is caused by the light source wavelength width of the light sources 501 to 503. The larger the angle difference between the incident angle to the hologram combiner and the emission angle from the hologram combiner, and the larger the light source wavelength width, the larger the image blur caused by the hologram. As a result, the image quality of the image displayed on the driver deteriorates. In the present embodiment, in order to reduce the influence of image blur due to the light source wavelength width, the difference between the incident angle 110 of the display light to the hologram combiner 106 and the angle of the diffracted light 111 by the hologram combiner is at least 5 degrees or less. The optical performance of the hologram combiner is designed.

  In order to deal with the surface reflection problem, in the present embodiment, the hologram combiner 106 is attached to the windshield 107 with the structure shown in FIG. In FIG. 4, the hologram combiner 106 is shown as a hologram 201. The windshield 107 is composed of two glasses 202 and 203, and includes a hologram 201, a half-wave plate 301, and a quarter-wave plate 401 inside.

  In FIG. 4, the light from the display element 103 is shown as circularly polarized display light 402 and is incident on the hologram combiner 201 at an incident angle 110. At this time, in the present embodiment, a non-reflective coating 405 (AR coating) is applied on the surface of the front glass 202 (interface between glass and air) so that surface reflection light is not generated on the surface of the front glass 202. Between the front glass 202 and the hologram 201, a ¼ wavelength plate 401 designed to convert the circularly polarized display light 402 into S-polarized light is disposed. The display light 402 polarized to S-polarized light by the quarter-wave plate 401 is emitted as diffracted light 403 by the hologram 201. The diffracted light from the hologram 201 is again converted to circularly polarized light by passing through the quarter-wave plate 401, and after passing through the front glass 202, is displayed on the driver. Since the diffracted light 403 visually recognized by the driver is circularly polarized light as described above, even when the driver wears polarized glasses that blocks linearly polarized light, the driver can display the light without being blocked. It becomes possible to do.

  Of the display light 402 incident on the hologram 201, the amount of light that has passed through the hologram without being diffracted passes through a half-wave plate 301 disposed between the hologram 201 and the rear glass 203, and becomes P-polarized light. Is converted. In the present embodiment, the angle 404 at which the display light polarized into P-polarized light enters the rear glass 203 is set to be the Brewster angle of the glass. Therefore, the P-polarized light is not reflected by the back glass 203 but transmitted to the outside of the vehicle as transmitted light 304. FIG. 10 shows an example of the relationship between the incident angle to glass and the reflectance of P-polarized light and S-polarized light. The range indicated by 1001 in the figure is an incident angle range in which the reflectance with respect to P-polarized light is 0.1% or less, and the incident angle 404 to the rear glass is also within the incident angle range 1001 in this embodiment. The optical system is designed to fit.

  As described above, in the present embodiment, in order to suppress the influence of image blur in the hologram combiner due to the light source wavelength width, the incident angle 110 and the diffraction angle 111 on the hologram combiner are set to be substantially equal values. Designed. Since the value of the diffraction angle 111 from the hologram combiner is determined by the inclination angle of the windshield and the angle at which the driver looks down the screen of the HUD, the incident angle 110 to the hologram combiner is not necessarily shown depending on the vehicle type on which the HUD is mounted. 10 may not exist in the incident angle range 1001 shown in FIG. When both the front glass 202 and the rear glass 203 have a planar shape, since the incident angle 404 to the rear glass 203 has a value equal to the incident angle 110, the incident angle 110 has a value greatly deviating from the Brewster angle. In this case, since the incident angle with respect to the back glass 203 also deviates from the Brewster angle, reflected light is generated on the back glass 203. In order to prevent this, it is possible to adopt a method in which the shape of the back glass 203 is wedged and the surface through which the transmitted light 304 is transmitted through the back glass is tilted with respect to the front glass 202. Examples of this are shown in FIGS. FIG. 12 shows an example in which the incident angle 110 is larger than the Brewster angle, and the back surface 1202 of the back glass 203 is inclined by an angle 1201 with respect to the front glass 202. At this time, since the incident angle on the back glass 203 is a value obtained by subtracting the angle 1201 from the incident angle 110, the incident angle on the back glass 203 can be made closer to the Brewster angle. FIG. 13 shows an example in which the incident angle 110 is smaller than the Brewster angle. The back surface 1202 of the back glass 203 is inclined with respect to the front glass 202 by an angle 1301. At this time, since the incident angle to the back glass 203 is a value obtained by adding the angle 1201 to the incident angle 110, the incident angle to the back glass 203 can be made closer to the Brewster angle, and reflection by the back glass 203 is performed. Generation of light can be prevented.

  By adopting this configuration, it is possible to prevent the generation of reflected light from the glass and to realize information display that is not hindered even when the driver wears polarized glasses or the like.

(Embodiment 2)
In this embodiment, a configuration of an optical system for taking measures against the surface reflection problem when the wavelength width of the light source is small will be described.

  The display device in the present embodiment has the configuration shown in FIG. 1 as in the first embodiment. Note that the description of the same parts as those in Embodiment 1 is omitted. FIG. 11 shows a configuration of the display element 103 in this embodiment. In this embodiment mode, light from the light sources 501 to 503 is scanned by the scanning unit 506 without being polarized and projected onto the screen 1101. In the present embodiment, the light sources 501 to 503 have a small wavelength width of 0.5 nm or less. Therefore, it is possible to suppress the influence of chromatic aberration (image blur) generated by the hologram combiner 106.

  However, in general, when the light source wavelength width is small, speckle noise becomes a problem in a display device using a laser. In this embodiment mode, a vibration device 1101 for vibrating the screen 507 is provided, and speckle noise is prevented by vibrating the screen 507 during display. Note that the vibration device 1101 may be attached to the peripheral portion of the screen 507, and may be configured to vibrate the screen 507 by itself vibrating very slightly due to an electric current or the like, or may be configured by a spring or the like, and vibration from a car may be applied to the screen 507. A configuration may be adopted in which the screen 507 is vibrated by transmission. In the case of using the latter configuration, it is not necessary to provide a movable part to vibrate the screen 507, so that the structure of the HUD housing is simplified and the cost can be reduced.

  Note that although the display element 103 has a structure in which an image is formed by scanning a laser in this embodiment mode, a liquid crystal element may be used as in Embodiment Mode 1.

  FIG. 8 shows the configuration of the hologram combiner 106 in the present embodiment. The hologram combiner 106 includes a hologram 201 and glasses 202 and 203 that hold the hologram. The hologram 201 is designed to emit display light incident at an incident angle 306 as diffracted light 802 at a diffraction angle 804. At this time, the reflected light 803 generated by the glass is emitted at an emission angle 805. At this time, when the diffraction angle 804 at which the diffracted light is emitted from the hologram combiner is sufficiently larger or smaller than the emission angle 805, the diffracted light 802 and the reflected light 803 are separated as shown in FIG. The reflected light 803 can be prevented from entering the eye box. When the distance from the windshield to the driver is 1 m and the size of the eye box is 10 cm in the vertical direction, the optical performance of the hologram 201 is set so that the diffraction angle 804 of the diffracted light differs from the output angle 805 of the reflected light by at least 10 degrees or more. By designing, it becomes possible to prevent the reflected light 803 from entering the eye box 109.

  The transmission type display device according to the present invention has transmission / reflection means made of a hologram, and can be applied to uses such as a display device, a display system, a display method, and a display program.

DESCRIPTION OF SYMBOLS 101 Equipment in which a transmissive display apparatus is installed 105 Optical system opening 107 Windshield 108 User 102 Optical unit 103 Display means 104 Deflection means 106 Transmission reflection means (combiner)
110 Incident angle to combiner 111 Diffraction angle from combiner 501 Red laser light source 502 Blue laser light source 503 Green laser light source 504 Collimator 506 Scanning means 507 Display screen 509 Polarizing means

Claims (13)

A light source that outputs light;
Display means for receiving light emitted from the light source to form an image;
Transmission light reflecting means for reflecting light of a wavelength included in the display light emitted from the display means toward the user, and transmitting light of other wavelengths,
According to the light source wavelength width which is the wavelength width of the light output from the light source,
A transmission type display device, wherein an angle difference between an incident angle at which the display light is incident on the transmission reflection means and a diffraction angle at which the display light is emitted from the transmission reflection means is different. When the light source wavelength width of the light source is a certain value or more,
2. The transmission according to claim 1, wherein an angle difference between an incident angle at which the display light is incident on the transmission reflection means and a diffraction angle at which the display light is emitted from the transmission reflection means is 5 degrees or less. Type display device. The transmissive display device according to claim 2, wherein the constant value of the light source wavelength width is 0.5 nm or more. The display means includes polarization means for converting display light into circularly polarized light,
The transmission and reflection means includes a diffraction element that deflects the direction of display light;
A transparent member for holding the diffraction element, the front transparent member disposed on the side where the display light is incident on the transmission / reflection means,
A transparent member for holding the diffraction element, the transparent member being arranged in the opposite direction across the diffraction element, a front transparent member for holding, a rear transparent member,
S-polarized light converting means for converting circularly polarized light into S-polarized light for the diffractive element between the diffracting means and the front transparent member;
The image display apparatus according to claim 3, further comprising a P-polarization conversion unit that converts S-polarized light with respect to the diffraction element into P-polarized light with respect to the diffraction element between the diffraction unit and the rear transparent member. . 5. The transmissive display device according to claim 4, wherein a difference between an incident angle to the transmissive reflecting means and a Brewster angle of the rear transparent member is within 5 degrees. The transmissive display device according to claim 5, wherein the front transparent member has a non-reflective coating that prevents surface reflection at an interface with the air. The rear transparent member has a wedge shape;
The wedge inclination angle is set so that an incident angle of the transmitted light transmitted from the rear transparent member to the rear transparent member becomes a Brewster angle of the rear transparent member. Item 7. The transmissive display device according to Item 6. The height of a display image displayed by the display unit is limited so that an incident angle to the transmission / reflection unit does not deviate from a Brewster angle of the rear transparent member. Image display device. The refractive index of the rear transparent member is determined according to the inclination of the transmission / reflection means so that the incident angle to the transmission / reflection means becomes the Brewster angle of the rear transparent member. The image display device according to claim 7. When the light source wavelength width of the light source is a certain value or less,
2. The transmission according to claim 1, wherein an angle difference between an incident angle at which the display light is incident on the transmission / reflection unit and a diffraction angle at which the display light is emitted from the transmission / reflection unit is 10 degrees or more. Type display device. The transmissive display device according to claim 10, wherein the constant value of the light source wavelength width is 0.5 nm or less. The transmissive display device according to claim 11, wherein the light source includes a wavelength conversion element (SHG) having a small wavelength width. The transmissive display device according to claim 11, wherein the display element includes a spatial modulation element and an intermediate screen, and includes a vibrating unit that vibrates the intermediate screen.

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