WO2011121949A1

WO2011121949A1 - See-through display

Info

Publication number: WO2011121949A1
Application number: PCT/JP2011/001733
Authority: WO
Inventors: 愼一式井; 研一笠澄; 愼一門脇; 博之古屋
Original assignee: パナソニック株式会社
Priority date: 2010-03-29
Filing date: 2011-03-24
Publication date: 2011-10-06
Also published as: JP2013127489A

Abstract

Disclosed is a see-through display provided with: a light source which emits light: a projection optical system which spatially modulates the intensity of the light and generates imaging light for displaying an image; and a hologram which deflects the imaging light that is emitted from the projection optical system. The hologram includes: a transparent layer which permits passage of the imaging light, and which includes a first face onto which the imaging light is directed, and a second face on the side opposite to the first face; a grating face which has a relief structure that diffracts the imaging light between the first face and the second face; and a notch filter which covers at least part of the grating face and reflects incident light of a specific wavelength component that is directed onto the grating face. The transparent layer has a uniform refractive index from the first face to the second face.

Description

See-through display

The present invention mainly relates to a see-through display used in a video display device such as a head-up display (HUD) or a head-mounted display (HMD).

A video display device called a head-up display (HUD) mainly displays information required for a steering operation in a cockpit of an automobile or an aircraft. An automobile driver or an aircraft pilot can perceive the information displayed by the HUD as if the display information exists in front of the windshield.

A video display device called a head mounted display (HMD) is mounted in the same manner as general eyeglasses for correcting vision. A user wearing the HMD can perceive an image displayed by the HMD as if the display information exists in the space in front of the lens portion.

Both the HUD and the HMD allow the user to visually recognize an image through a substantially transparent member such as a windshield and a lens member. Therefore, these video display devices are referred to as “see-through displays”. In recent years, the development of these video display devices has become active.

For example, a driver of an automobile equipped with a HUD can view information necessary for driving with a small amount of line of sight while facing forward while driving. Therefore, HUD can provide high safety and convenience.

The HMD can provide a user with a large-sized image with a very small power consumption. Further, the user can view the image regardless of the place, and can obtain the necessary upper part anytime and anywhere.

The see-through display needs to mix external light (natural light) incident from the outside such as scenery with the image to be displayed. For example, an HUD used in an automobile mixes an image to be displayed and external light incident from the outside using a combiner in the vicinity of the windshield. During the mixing of the image to be displayed and the external light incident from the outside, it is preferable that the light loss of the external light incident from the external world and the light to be displayed is reduced.

A conventional see-through display uses a volume hologram as a combiner (see, for example, Patent Document 1). If a hologram is used as a combiner, the image displayed by the HUD is enlarged as a result of the lens action of the hologram. As a result, the user can visually recognize a large size image.

Furthermore, the volume hologram has a characteristic that diffraction does not occur except at a predetermined wavelength at a predetermined incident angle. Therefore, the volume hologram can reduce the ratio of the loss of external light from the outside due to diffraction by the volume hologram.

In addition, the volume hologram has a high diffraction efficiency for a predetermined wavelength. For example, if a laser light source is used as the light source, the HUD has high light utilization efficiency as a result of the narrow wavelength width of the laser light.

In the production process of a volume hologram used in a conventional see-through display, interference exposure is performed on the hologram sensitive material. The interference exposure process requires a highly accurate exposure apparatus. As a result, the volume hologram becomes expensive. In addition, there is a problem that maintenance of the exposure apparatus is required.

A thin hologram sensitive material may be used in order to mitigate the aberration caused by the difference in incident angle and wavelength between when the hologram sensitive material is exposed and when an image is displayed. However, since the diffraction efficiency of the thin hologram sensitive material is low, the light use efficiency of the see-through display is low. Therefore, a see-through display using a thin hologram sensitive material consumes more power in order to display an image having a luminance equivalent to that of a see-through display using a thick hologram sensitive material.

Japanese Patent No. 2585717

An object of the present invention is to provide a see-through display that can be manufactured at low cost, has high light utilization efficiency, and low power consumption.

A see-through display according to one aspect of the present invention includes a light source that emits light, a projection optical system that spatially modulates the intensity of the light and generates image light for displaying an image, and the projection optical system. A hologram for deflecting the image light, wherein the hologram includes a first surface on which the image light is incident, and a second surface opposite to the first surface, and transmitting the image light A transmissive layer that allows light to pass, a grating surface having a relief structure that diffracts the image light between the first surface and the second surface, and at least partially covering the grating surface and entering the grating surface And a notch filter that reflects incident light having a specific wavelength component, wherein the transmission layer has a uniform refractive index from the first surface to the second surface.

According to another aspect of the present invention, a head-up display mounted on a vehicle having a windshield including an inner surface defining an indoor boundary includes the see-through display described above, and the hologram is attached to the inner surface. And

According to still another aspect of the present invention, a head-up display mounted on a vehicle having a windshield including an inner surface defining an indoor boundary includes the see-through display described above, and the light source includes first light having a first wavelength. A first light source that emits light, and a second light source that emits second light having a second wavelength different from the first wavelength, wherein the hologram diffracts the first light; A second hologram that diffracts two light, wherein the first light has a shorter wavelength than the second light, and the second hologram is disposed between the first hologram and the inner surface. It is characterized by being.

According to still another aspect of the present invention, a head mounted display including a lens unit disposed in front of a user's eye includes the above-described see-through display, and the hologram is disposed between the lens unit and the eye. It is characterized by being.

It is the schematic of the head-up display illustrated as a see-through display according to the first embodiment. It is the schematic of the other head-up display illustrated as a see-through display according to the first embodiment. It is a schematic sectional drawing of the relief type hologram used for the head up display shown in Drawing 1A and Drawing 1B. 3 is a schematic graph showing characteristics of a notch filter of the relief hologram shown in FIG. 2. It is the schematic which shows the manufacturing method of the relief type hologram shown by FIG. It is a graph which shows roughly the calculation result with respect to the wavelength dependence of the diffraction efficiency with respect to S polarization | polarized-light. It is a graph which shows roughly the calculation result to the wavelength dependence of diffraction efficiency to P polarization. It is the schematic showing the other method for removing a stray light. It is the schematic showing the other method for removing a stray light. It is the schematic of the head-up display illustrated as a see-through display according to 2nd Embodiment. It is the schematic of the other head-up display illustrated as a see-through display according to 2nd Embodiment. FIG. 8 is a schematic cross-sectional view of a relief-type hologram used in the head-up display shown in FIGS. 7A and 7B. It is a schematic sectional drawing of the hologram attached to the windshield containing an ultraviolet absorption layer. It is a schematic sectional drawing of the windshield which pinches | interposes a hologram. It is the schematic of the head-up display illustrated as a see-through display according to 3rd Embodiment. It is a schematic sectional drawing of the relief type hologram used for the head up display shown in FIG. 12 is a schematic graph showing characteristics of the notch filter of the relief hologram shown in FIG. 12 is a schematic graph showing another characteristic of the notch filter of the relief hologram shown in FIG. It is the schematic which shows the manufacturing method of the relief type hologram shown by FIG. It is the schematic of the head-up display illustrated as a see-through display according to the fourth embodiment. FIG. 15 is a schematic cross-sectional view of a relief hologram used in the head-up display shown in FIG. 14. FIG. 16 is a schematic graph showing characteristics of the notch filter of the relief hologram shown in FIG. 15. FIG. FIG. 16 is a schematic view showing a method for manufacturing the relief hologram shown in FIG. 15. It is the schematic of the head mounted display illustrated as a see-through display according to 5th Embodiment. FIG. 19 is a schematic cross-sectional view of a relief hologram used in the head mounted display shown in FIG. 18.

Hereinafter, a see-through display according to an embodiment will be described with reference to the drawings. In the drawings, the same reference numerals are given to components that perform the same or similar operations or operations. In order to avoid redundant descriptions, redundant descriptions are omitted as necessary. To assist in understanding the principles of a series of embodiments, the components shown in the drawings are schematically shown. Therefore, the shapes of the components shown in the drawings are also schematic, and do not limit the principles of the embodiments described below.

(First embodiment)
FIG. 1A is a schematic view of a head-up display (hereinafter referred to as HUD) exemplified as a see-through display. A head-up display is described with reference to FIG. 1A.

(Configuration of head-up display)
The HUD 100 schematically shown in FIG. 1A is mounted on, for example, an automobile. FIG. 1A shows a windshield 210 of an automobile. The windshield 210 includes an inner surface 211 that defines an inner boundary of the passenger compartment and an outer surface 212 opposite to the inner surface.

The HUD 100 includes a laser light source 110 that emits a laser beam LB, a projection optical system 180, and a relief hologram 200 that is attached to the inner surface 211 of the windshield 210. The projection optical system 180 includes a lens 130, a folding mirror 140, a liquid crystal panel 150, a projection lens 160, and a screen 170. In the present embodiment, the laser light source 110 is exemplified as a light source that emits light.

The HUD 100 further includes a control unit 190. The laser light source 110 and the liquid crystal panel 150 are electrically connected to the control unit 190. Thus, the laser light source 110 and the liquid crystal panel 150 operate under the control of the control unit 190.

The operation of the HUD 100 of this embodiment will be described. The laser light source 110 emits a laser beam LB based on a control signal from the control unit 190. The laser beam LB illuminates the liquid crystal panel 150 two-dimensionally.

The lens 130 shown in FIG. 1A expands the laser beam LB. As a result, the laser beam LB can illuminate the liquid crystal panel 150 without waste. The folding mirror 140 folds the enlarged laser beam LB. Thus, a small HUD 100 is formed. Note that the magnifying lens and the folding mirror may be omitted depending on the specifications of the HUD and the characteristics of the light source.

The liquid crystal panel 150 displays an image pattern to be displayed based on a control signal from the control unit 190. The laser beam LB folded back by the folding mirror 140 illuminates the liquid crystal panel 150. The liquid crystal panel 150 two-dimensionally modulates the intensity of the laser beam LB (spatial modulation) and generates video light IL for displaying an image. The projection lens 160 images the video light IL emitted from the liquid crystal panel 150 on the screen 170. As a result, a desired image is displayed on the screen 170.

The relief hologram 200 diffracts the image light IL emitted through the screen 170. As a result, the image light IL is deflected toward the driver DR. As a result, the driver DR can visually recognize the virtual image VI magnified by the relief hologram 200 through the windshield 210.

FIG. 1B is a schematic diagram of another head-up display exemplified as a see-through display. Another configuration of the head-up display will be described with reference to FIG. 1B.

The HUD 100A schematically shown in FIG. 1B includes a projection optical system 180A in addition to the laser light source 110, the control unit 190, and the hologram 200 similar to the HUD 100 described with reference to FIG. 1A. The projection optical system 180A includes a MEMS mirror 300 in addition to the screen 170 of the projection optical system 180 described with reference to FIG. 1A.

The MEMS mirror 300 is electrically connected to the control unit 190. The MEMS mirror 300 two-dimensionally scans the laser light LB emitted from the laser light source 110 under the control of the control unit 190, and directly forms an image on the screen 170. Video light IL is emitted through the screen 170. The laser beam LB of the HUD 100A shown in FIG. 1B is directly intensity-modulated according to the image data to be displayed and the direction of the MEMS mirror 300. As a result, an image is formed on the screen 170.

The projection optical system is not limited to the configuration of the projection

optical systems

180 and 180A described with reference to FIGS. 1A and 1B. Other projection optical systems that can spatially modulate the intensity of light and generate video light for displaying an image may be used.

(Configuration of hologram)
FIG. 2 is a schematic cross-sectional view of a relief hologram 200. The structure and optical principle of the hologram 200 will be described with reference to FIGS. 1A to 2.

The relief-type hologram 200 includes a first surface 221 on which the image light IL is incident and a second surface 231 opposite to the first surface 221. The first surface 221 defines the inner boundary of the automobile cabin. The second surface 231 is fixed to the inner surface 211 of the windshield 210.

The relief-type hologram 200 includes a first resin material 220 that forms the first surface 221 and a second resin material 230 that forms the second surface 231. The first resin material 220 and the second resin material 230 are substantially transparent in the visible range. Accordingly, the video light IL incident on the first surface 221 passes through the first resin material 220. Further, outside light EL from outside the vehicle enters the second surface 231 through the windshield 210 and passes through the second resin material 230. In this embodiment, the 1st resin material 220 and / or the 2nd resin material 230 are illustrated as a permeable layer. The first resin material 220 is exemplified as the first transmission layer. The second resin material 230 is exemplified as the second transmission layer.

The first resin material 220 has a refractive index substantially equal to that of the second resin material 230. Preferably, the first resin material 220 is formed from the same material as the second resin material 230. Therefore, the hologram 200 has a substantially uniform refractive index between the first surface 221 and the second surface 231.

The hologram 200 includes a grating surface 240 having a relief structure 241 formed between the first surface 221 and the second surface 231. The grating surface 240 diffracts the image light IL toward the driver DR.

A relief structure 241 is formed on the surface of the first resin material 220 opposite to the first surface 221. A complementary relief structure 241 is also formed on the surface of the second resin material 230 opposite to the second surface 231. The relief structure 241 of the first resin material 220 and the relief structure 241 of the second resin material 230 are engaged with each other. As a result, the first resin material 220 and the second resin material 230 form a lattice surface 240 that is in close contact with the gap. In the present embodiment, the term “relief structure” means a discontinuous uneven surface structure.

The hologram 200 further includes a notch filter 245 coated on the grating surface 240 of the second resin material 230. The notch filter 245 is coated so as to at least partially cover the lattice surface 240 before the first resin material 220 is bonded to the second resin material 230. The notch filter 245 preferably reflects only the wavelength near the image light IL incident on the grating surface 240 with a predetermined reflectance. In the following description, the term “notch filter” refers to reflecting only light of a single wavelength (usually several nm to several tens of nm) with a predetermined reflectance and transmitting light of other wavelengths. Means an optical filter capable of

FIG. 3 is a graph schematically showing ideal reflection characteristics of the notch filter 245. The reflection characteristics of the notch filter 245 will be described with reference to FIGS. 1A to 3.

The laser light source 110 described with reference to FIGS. 1A and 1B emits laser light LB having a wavelength in the vicinity of 532 nm, for example. In the present embodiment, as shown in FIG. 3, the notch filter 245 reflects light in the vicinity of the wavelength 532 nm of the laser light LB with a predetermined reflectance (FIG. 3 illustrates a reflectance of 50%). The notch filter 245 has a reflectance of “0” with respect to light of other wavelengths.

The notch filter 245 having the reflection characteristics shown in FIG. 3 may be, for example, a rugate filter. By continuously changing the refractive index in the rugate filter film, the reflection characteristics shown in FIG. 3 can be obtained. Alternatively, the notch filter 245 may be a dielectric multilayer film or an interference filter. Even if these filter elements are used, the reflection characteristics shown in FIG. 3 can be obtained.

(Hologram production method)
FIG. 4 schematically shows a manufacturing process of the relief hologram 200. A method of manufacturing the hologram 200 will be described with reference to FIG.

First, the second resin material 230 is created by a technique such as injection molding. One surface (second surface 231) of the injection-molded second resin material 230 is formed to be substantially flat, while a relief structure 241 is formed on the surface opposite to the second surface 231. .

Thereafter, a layer of the notch filter 245 is formed on the relief structure 241 of the second resin material 230. Formation of the layer of notch filter 245 may be by vapor deposition techniques, coating techniques, or other techniques that can at least partially cover the relief structure 241.

Next, the first resin material 220 is disposed on the second resin material 230. For example, if an ultraviolet curable resin is used as the first resin material 220, a liquid ultraviolet curable resin formed on the first resin material 220 is applied on the relief structure 241 of the second resin material 230. As a result, the upper surface (first surface 221) of the first resin material 220 is substantially flat, while the lower surface of the first resin material 220 is complementary to the relief structure 241 of the second resin material 230. . Thereafter, the first resin material 220 is irradiated with ultraviolet rays. As a result, the liquid ultraviolet curable resin (first resin material 220) is cured on the second resin material 230. In this way, a lattice surface 240 is formed in which the first resin material 220 and the second resin material 230 are in close contact with each other without any gap. The first resin material 220 and the second resin material 230 preferably have the same refractive index. The relief hologram 200 is formed through a series of steps described with reference to FIG.

(Optical action of head-up display)
The optical action of the

HUDs

100 and 100A will be described with reference to FIGS. 1A to 4.

Generally, a relief-type hologram generates higher-order diffracted light as incident light is diffracted. Therefore, if a relief hologram is used for the HUD, stray light due to higher-order diffracted light is generated.

However, the

HUDs

100 and 100A according to the present embodiment sufficiently reduce stray light caused by the external light EL (natural light) and display a high-quality image to the driver DR. Hereinafter, the principle of reducing stray light according to this embodiment will be described.

As described with reference to FIG. 4, the first resin material 220 and the second resin material 230 are in close contact with each other with almost no gap. Therefore, the relief type hologram 200 has a diffraction function except for light reflected by the notch filter 245 (in this embodiment, light having a wavelength near 532 nm) with respect to the external light EL incident on the hologram 200 from outside the passenger compartment. It functions as a single resin plate that does not have. Therefore, the relief hologram 200 allows most of the visible light component included in the external light EL to enter the room without being diffracted.

In this embodiment, as shown in FIG. 2, the relief structure 241 is a blaze structure that forms a serrated contour surface. The blazed grating surface 240 hardly generates high-order diffracted light even for the light component in the reflection band of the notch filter 245. Since stray light caused by higher-order diffracted light hardly occurs in the passenger compartment, even when the driver DR looks outside the passenger compartment through the relief hologram 200, stray light hardly enters the eyes of the driver DR. Therefore, the driver DR can continue safe driving without being affected by stray light. Thus,

HUDs

100 and 100A excellent in visibility that hardly generate stray light are provided.

FIG. 5A is a graph schematically showing a calculation result with respect to wavelength dependency of diffraction efficiency with respect to S-polarized light. The wavelength dependence of the diffraction efficiency is described with reference to FIGS. 2 and 5A.

As described above, the relief structure 241 shown in FIG. 2 is a blaze structure. The blazed lattice surface 240 can achieve high light utilization efficiency.

The graph shown in FIG. 5A is obtained based on a lattice plane 240 having a blazed structure optimized for a laser beam LB having a wavelength of 532 nm. The reflectance of the notch filter 245 is set to “50%” in the total reflection region.

From the graph shown in FIG. 5A, it can be seen that a diffraction efficiency of 40% or more is obtained for light in the vicinity of a wavelength of 532 nm. Further, it can be seen that high-order diffracted light is suppressed and very high diffraction efficiency is achieved. Therefore, if the relief hologram 200 is used as a combiner, the

HUDs

100 and 100A with high light utilization efficiency and low power consumption are formed. Note that the pitch P and the blaze angle φ of the relief (uneven region) may be optimized for each relief.

FIG. 5B is a graph schematically showing a calculation result with respect to wavelength dependency of diffraction efficiency with respect to P-polarized light. The wavelength dependence of the diffraction efficiency is described with reference to FIGS. 2, 5A and 5B.

The relief hologram 200 achieves high diffraction efficiency even for P-polarized light. The calculation result shown in FIG. 5B is obtained based on the same conditions as those described with reference to FIG. 5A except that the image light IL incident on the hologram 200 is P-polarized light. Therefore, the reflectance of the notch filter 245 is also set to 50% in the entire band.

From the graph of FIG. 5B, it can be seen that the relief hologram 200 achieves a high diffraction efficiency of 25% or more for the light component in the vicinity of the wavelength of 532 nm even under the condition of P-polarized light.

In general, if a volume hologram is used for the HUD, the difference in the incident angle of light between the exposure of the hologram photosensitive material and the illumination for displaying the image, and the wavelength variation of the light for displaying the image In order to alleviate the aberration caused by the hologram sensitive material, the hologram sensitive material is formed as thin as possible. As a result, the diffraction efficiency of the volume hologram is generally only about 10% even in the case of S-polarized light. In the case of P-polarized light, the diffraction efficiency of the volume hologram is about several percent. In a HUD using a volume hologram, P-polarized light is generally not used from the viewpoint of light utilization efficiency and power consumption.

However, in this embodiment, since the relief hologram 200 is used as a combiner, the hologram 200 achieves sufficiently high diffraction efficiency even if it is P-polarized light. Therefore, even with the

HUDs

100 and 100A using P-polarized light, it is possible to achieve sufficiently reduced power consumption as compared with the conventional case.

The relief-type hologram 200 further has the following effects.

The image light IL shown in FIG. 2 is incident on the first surface 221 of the relief hologram 200 at an incident angle θ. The image light IL from the projection

optical systems

180 and 180A is P-polarized light. Further, the incident angle θ is a Brewster angle. At this time, surface reflection on the first surface 221 of the first resin material 220 and the outer surface 212 of the windshield 210 hardly occurs. Therefore, the occurrence of surface reflection is reduced without the non-reflective coating on the first surface 221 of the first resin material 220 and the outer surface 212 of the windshield 210. For example, if the refractive index of the second resin material 230 and the front glass 210 is “1.5” and the incident angle θ of the image light IL is about 56 °, the first surface 221 of the hologram 200 and the front surface Surface reflection at the outer surface 212 of the glass 210 hardly occurs. Therefore, the relief-type hologram 200 according to the present embodiment enables the use of P-polarized light. In addition, the relief hologram 200 can suppress surface reflection without surface treatment on the windshield 210 such as a non-reflective coating. Thus, the

HUDs

100 and 100A can display a high-quality image without generating a double image due to surface reflection. Further, the

HUDs

100 and 100A are manufactured at a relatively low cost.

6A and 6B are schematic diagrams showing another method for removing stray light. 1A, 1B, 4, 6A and 6B are used to describe other methods for removing stray light.

The image light IL shown in FIG. 6A is incident on the first surface 221 of the relief hologram 200 at an incident angle θ1. Thereafter, the image light IL is refracted in the direction of the angle θ 2 on the first surface 221 and propagates through the relief hologram 200. As a result, the image light IL enters the grating surface 240 on which the layer of the notch filter 245 is formed at an incident angle θa. Thereafter, the image light IL diffracted by the grating surface 240 is incident on the first surface 221 of the relief hologram 200 at an angle θ3. Finally, the image light IL is emitted from the relief hologram 200 in the direction of the angle θ4. As a result, as described with reference to FIGS. 1A and 1B, the driver DR can visually recognize the virtual image VI.

FIG. 6A shows the external light EL that is incident on the windshield 210 from outside the vehicle compartment at the same incident angle θ1 as that of the image light IL. In FIG. 6A, the external light EL is incident on the grating surface 240 at an incident angle θa ′. At this time, if the incident angle θa of the image light IL with respect to the grating surface 240 is substantially equal to the incident angle θa ′ of the outside light EL with respect to the grating surface 240, light having the same wavelength component as that of the image light IL included in the outside light EL. The rate of propagation from the grid surface 240 to the vehicle interior side is minimized. As a result, the generation of stray light is suppressed.

The following formula shows the condition that the incident angle θa and the incident angle θa ′ are equal.

(Formula 1)
φ + θ2 = φ-θ2

(Formula 2)
φ + θ2 = θ2-φ

If the condition of Equation 1 or Equation 2 is satisfied, the incident angle θa and the incident angle θa ′ are equal. If “φ = 0” or “θ2 = 0”, the condition of Equation 1 or Equation 2 is satisfied.

FIG. 6B is a schematic diagram showing the optical action of the relief hologram 200 when “θ2 = 0”.

6B, when “θ2 = 0”, the image light IL from the projection

optical systems

180 and 180A is incident on the first surface 221 of the relief hologram 200 substantially perpendicularly. If the diffraction efficiency of the image light IL incident on the grating surface 240 is expressed by “η%”, the external light EL incident substantially perpendicularly to the relief hologram 200 has a wavelength equal to that of the image light IL. The light component is incident on the grating surface 240 at an angle equal to the incident angle of the image light IL incident on the grating surface 240. As a result, “η%” of the light component of the external light EL having the same wavelength as the image light IL is diffracted by the grating surface 240. The remaining “(100−η)%” light component reaches the first surface 221 of the relief hologram 200.

Of the external light EL that has reached the first surface 221 of the relief hologram 200, a certain proportion (usually about 5%) of the light is reflected from the surface and reenters the grating surface 240. Light outside the wavelength of the image light IL out of the external light EL that has reached the grating surface 240 again is not diffracted according to the characteristics of the notch filter 245, and therefore passes through the grating surface 240. As a result, the light components of the outside light EL other than the wavelength of the image light IL are emitted outside the passenger compartment through the windshield 210. Since the driver DR hardly sees the light components of the external light EL other than the wavelength of the video light IL, the light components of the external light EL other than the wavelength of the video light IL have little influence on the driving of the driver DR.

Of the external light EL that has reached the grating surface 240 again, the light component having the same wavelength as the image light IL is diffracted with a predetermined diffraction efficiency (“η%” in the present embodiment). If the surface reflectance is “5%”, the total light amount visually recognized by the driver DR is “(100−η)% × 5% × η%”.

If the incident angle θ1 of the image light IL with respect to the first surface 221 is not perpendicular, the diffraction efficiency of the external light EL incident from the outside is necessarily η or less. Therefore, the transmittance is “(100−η)%” or more, and the total amount of light visually recognized by the driver DR is necessarily “(100−η) × 5% × η%” or more.

As shown in FIG. 6B, if the incident angle θ1 of the image light IL with respect to the first surface 221 of the relief hologram 200 is set to be substantially vertical, the amount of light seen by the driver DR in the external light EL is “ (100−η)% × 5% × η% ”. Thus, the

HUDs

100 and 100A can display high quality images with reduced stray light.

In the above description, the diffraction efficiency of the grating surface 240 with respect to the image light IL is “η%”. The value of “η” is preferably set to a value approximate to “100%” or “0%”. As a result, the amount of stray light visually recognized by the driver DR is reduced.

The diffraction efficiency η is determined by setting the reflectance of the notch filter 245, for example. For example, if “η = 99%”, the ratio of the amount of light visually recognized by the driver DR is “(100−99)% × 5% × of the same wavelength component as the image light IL in the incident external light EL. 99% = 0.05% ”, and sufficiently reduced stray light is achieved.

If the value of the diffraction efficiency η is set high, the light amount of the laser light LB required when the driver DR visually recognizes an image having a predetermined light amount is set low. Therefore, the power consumption of the

HUDs

100 and 100A is advantageously reduced.

As shown in FIG. 6B, if the projection

optical systems

180 and 180A project the image light IL substantially perpendicularly to the first surface 221 of the relief hologram 200 (at least at one point), stray light is preferably generated. The

HUDs

100 and 100A can display high-quality images.

The relief hologram 200 used for the

HUDs

100 and 100A is created using the first resin material 220 and the second resin material 230. As will be described in connection with FIG. 4, the hologram 200 is preferably created using a molding technique. Therefore, a large number of relief holograms 200 are created in a short period of time. The first resin material 220 and the second resin material 230 may be general-purpose resin materials. Therefore, the

HUDs

100 and 100A are made relatively inexpensively.

(Second Embodiment)
7A and 7B are schematic views of the HUD of the second embodiment. The HUD of the second embodiment will be described with reference to FIGS. 1A, 1B, 7A, and 7B.

7A includes a relief hologram 200B in addition to the laser light source 110, the projection optical system 180, and the control unit 190 similar to the HUD 100 described with reference to FIG. 1A. The HUD 100C shown in FIG. 7B includes a relief hologram 200B in addition to the laser light source 110, the projection optical system 180A, and the control unit 190 similar to the HUD 100A described with reference to FIG. 1B. The relief hologram 200B shown in FIGS. 7A and 7B is attached to the inner surface 211 of the windshield 210, respectively.

FIG. 8 is a schematic cross-sectional view of a relief hologram 200B attached to the inner surface 211 of the windshield 210. The hologram 200B is described with reference to FIGS. 2 and 7A to 8.

The hologram 200B includes a first resin material 220 and a second resin material 230 joined to the first resin material 220, similarly to the hologram 200 described with reference to FIG. The hologram 200 </ b> B includes a grating surface 240 of a relief structure 241 (blazed structure) at the boundary between the first resin material 220 and the second resin material 230. The grating surface 240 includes a diffractive surface 242 that diffracts the image light IL from the projection

optical systems

180 and 180A, and a sub surface 243 that is bent with respect to the diffractive surface 242.

The hologram 200B further includes a dielectric multilayer film 260 used as the notch filter 245B. The dielectric multilayer film 260 is formed on each of the diffraction surfaces 242. Unlike the notch filter 245 of the hologram 200 described with reference to FIG. 2, in this embodiment, the dielectric multilayer film 260 covers only a part of the diffractive surface 242 (that is, with a predetermined duty). It is formed.

The reflectance of the notch filter 245B may be set to less than 100% (for example, about 50%). As a result, the loss of the external light EL that enters from outside the passenger compartment is reduced. If necessary, a notch filter having a reflectance of about 50% may be formed so as to cover the entire grating surface 240. However, using a dielectric multilayer film to create a notch filter having a reflectivity of about 50% potentially results in high manufacturing costs because the thin film materials that can be used are limited.

As shown in FIG. 8, in this embodiment, the dielectric multilayer film 260 having a reflectance of 100% with respect to the image light IL covers the diffractive surface 242 with a duty of about 50%, for example, about 100%. A notch filter 245B having a reflectance is formed. Examples of suitable materials for forming a notch filter having a reflectance of about 100% include general-purpose thin film materials such as SiO ₂ and TiO ₂ . Therefore, inexpensive film formation is achieved.

8 Half of the image light IL incident on the grating surface 240 of the relief hologram 200B shown in FIG. 8 is reflected by the dielectric multilayer film 260 with a reflectance of approximately 100%. The remaining half of the image light IL passes through the grating surface 240. Thus, the image light IL is reflected by the grating surface 240 with a macroscopic reflectance of approximately 50%.

In the present embodiment, the pitch of the diffractive surfaces 242 in the visible range is about several microns. Therefore, the driver DR hardly perceives the deposition position of the dielectric multilayer film 260 visually. Therefore, the driver DR hardly perceives artifacts (for example, a periodic striped pattern due to the blazed structure of the grating surface 240) even when looking outside the passenger compartment through the relief hologram 200B.

As described above, a reflective layer having a reflectance of less than 100% can be relatively easily formed on the lattice plane 240 by setting the duty of a deposition region where an inexpensive dielectric multilayer material is deposited. Thus,

inexpensive HUDs

100B and 100C are provided.

The dielectric multilayer film 260 is preferably provided in a plane portion between the

bent portions

246 and 247 formed between the sub surface 243 and the diffraction surface 242. The wavelength characteristic of a dielectric multilayer film generally has a dependency on the incident angle. For example, since the apex portion of the blazed structure is curved or bent with a predetermined curvature, the reflection characteristics for the image light incident on the dielectric multilayer film disposed at the apex portion of the blazed structure may not be desired. There is sex. On the other hand, as shown in FIG. 8, the dielectric multilayer film 260 provided in the plane portion between the

bent portions

246 and 247 formed between the sub surface 243 and the diffractive surface 242 is provided for the image light IL. And inclined at a certain angle. Therefore, desired reflection characteristics can be easily obtained. Thus, the

HUDs

100B and 100C can achieve high light utilization efficiency and display high-quality images. Moreover, HUD100B and 100C will be manufactured comparatively simply.

In the first embodiment and the second embodiment, the first resin material 220 and the second resin material 230 are exemplified as the transmission layer. Alternatively, glass may be used as the transmissive layer. Further alternatively, any material having the same refractive index and substantially transparent in the visible range may be used as the transmission layer.

FIG. 1A, FIG. 1B, FIG. 7A and FIG. 7B are used to explain the effects associated with the mounting positions of the

relief holograms

200 and 200B.

The

relief holograms

200 and 200B described in relation to the first embodiment and the second embodiment are attached to the inner surface 211 of the windshield 210. As described in relation to the first embodiment and the second embodiment, if the transmission layer is formed of a resin material (the first resin material 220 and the second resin material 230), the inner surface 211 of the windshield 210 is reached. The installation of the

holograms

200 and 200B is advantageous.

It is generally known that excitation of molecules inside a resin material by light incident on the resin material causes deterioration of the resin material. In particular, when high energy light (ultraviolet light or light having a shorter wavelength than ultraviolet light) is incident on a resin material such as an ultraviolet curable resin, the resin material absorbs ultraviolet light, and the deterioration of the resin material is likely to proceed.

FIG. 9A is a schematic cross-sectional view showing a hologram 200 attached to a windshield 210 including an ultraviolet absorbing layer. The effect of mounting the hologram 200 on the inner surface 211 of the windshield 210 will be described with reference to FIGS. 1A, 1B, and 9A. The effects described below are common to the hologram 200B described in relation to the second embodiment.

The front glass 210 includes an inner glass 213 that forms the inner surface 211, an outer glass 214 that forms the outer surface 212, and an intermediate layer such as an ultraviolet absorption layer 270 sandwiched between the inner glass 213 and the outer glass 214. The windshield 210 schematically shown in FIG. 9A is relatively widespread.

As shown in FIG. 9A, if the relief hologram 200 is attached to the inner surface 211 of the windshield 210, the ultraviolet absorbing layer 270 absorbs the ultraviolet light from the external light EL incident on the windshield 210. It becomes difficult to enter the relief hologram 200. Therefore, if the relief hologram 200 is attached to the inner surface 211 of the windshield 210, the first resin material 220 and the second resin material 230 are hardly deteriorated due to ultraviolet rays. In particular, even if the second resin material 230 is formed using a resin material such as an ultraviolet curable resin that is easily deteriorated by ultraviolet rays, the second resin material 230 is hardly deteriorated, so that the reliability of the

HUDs

100 and 100A is increased. .

FIG. 9B is a schematic cross-sectional view of the windshield sandwiching the hologram 200. 1A, 1B, and 9B, the effect of suppressing deterioration due to the interpolation of the hologram 200 into the windshield will be described. The effects described below are common to the hologram 200B described in relation to the second embodiment.

The windshield 210A schematically shown in FIG. 9B includes an inner glass 213A that forms the inner surface 211, an outer glass 214 that forms the outer surface 212, and an ultraviolet absorbing layer 270A between the inner glass 213A and the outer glass 214. A layer. The ultraviolet absorbing layer 270A absorbs ultraviolet rays between the inner glass 213A and the outer glass 214. In the present embodiment, the inner glass 213A is exemplified as the first glass. The outer glass 214 is exemplified as the second glass. The ultraviolet absorbing layer 270A is exemplified as the absorbing layer.

The hologram 200 is disposed between the ultraviolet absorbing layer 270A and the inner glass 213A. The effect of suppressing deterioration due to ultraviolet rays described in relation to FIG. 9A is also achieved by the arrangement of the hologram 200 shown in FIG. 9B. Ultraviolet light that degrades the second resin material 230 and / or the first resin material 220 is absorbed by the ultraviolet absorption layer 270 </ b> A, and therefore hardly enters the relief hologram 200. In particular, even if the second resin material 230 is formed using a resin material such as an ultraviolet curable resin that is easily deteriorated by ultraviolet rays, the second resin material 230 is hardly deteriorated, so that the reliability of the

HUDs

100 and 100A is increased. .

The inner glass 213A and the outer glass 214 are in close contact with each other through an intermediate layer such as an ultraviolet absorbing layer 270A. Therefore, outside air hardly enters the inside of the windshield 210A. As shown in FIG. 9B, if the inner glass 213A and the outer glass 214 sandwich the relief hologram 200, direct contact between the relief hologram 200 and the outside air is suppressed. Since the relief hologram 200 hardly absorbs moisture in the air, the swelling of the relief hologram 200 is suitably suppressed.

The moisture absorption of the relief hologram mainly causes expansion of the relief hologram in the thickness direction. Therefore, the expansion of the relief-type hologram due to moisture absorption potentially causes a fluctuation in diffraction angle and a decrease in diffraction efficiency with respect to light of a predetermined wavelength. A change in diffraction angle or a decrease in diffraction efficiency with respect to light of a predetermined wavelength ultimately leads to a decrease in image quality of an image displayed by the HUD.

As shown in FIG. 9B, the windshield 210A sandwiching the relief-type hologram 200 suitably suppresses the moisture absorption of the hologram 200, so that image quality deterioration due to the swelling of the hologram 200 hardly occurs. Therefore, the reliability of the

HUDs

100 and 100A is increased.

The linear expansion coefficients of the inner glass 213A and the outer glass 214 used for the windshield 210A are typically about 9 × 10 ^ (− 6) / ° C. On the other hand, the linear expansion coefficients of the resin materials (first resin material 220 and second resin material 230) used in the relief hologram 200 are typically about 7 × 10 ^ (− 5) / ° C. Therefore, the linear expansion coefficient of the relief hologram 200 is an order of magnitude larger than that of the windshield 210A. That is, the relief hologram 200 is more susceptible to temperature fluctuations than the windshield 210A (that is, the hologram 200 is likely to expand or contract with temperature fluctuations).

The expansion or contraction of the hologram due to the temperature variation causes a variation in diffraction angle and a decrease in diffraction efficiency. Therefore, the temperature variation of the hologram potentially causes a decrease in image quality of the image displayed by the HUD.

As shown in FIG. 9B, the windshield 210A sandwiching the relief hologram 200 alleviates expansion and / or contraction of the relief hologram 200 due to temperature fluctuation. That is, since the hologram 200 is sandwiched between the inner glass 213A and the outer glass 214 having a small linear expansion coefficient, the expansion and / or contraction of the resin material (the first resin material 220 and the second resin material 230) is preferably suppressed. . Therefore, the arrangement of the hologram 200 sandwiched between the inner glass 213A and the outer glass 214 suitably suppresses deterioration in image quality due to temperature fluctuations. Thus,

HUDs

100 and 100A having high reliability are provided.

In the first embodiment and the second embodiment, the laser light source 110 is exemplified as the light source. Alternatively, other light source elements such as LEDs may be used as the light source. Since the wavelength range of the laser beam LB emitted from the laser light source 110 is narrower than other light sources such as LEDs, the use of the laser light source 110 as the light source can achieve high diffraction efficiency in the

holograms

200 and 200B. it can. Therefore, if the laser light source 110 is used as the light source, blurring of the image due to the spread of the wavelength is suitably suppressed. Thus, the

HUDs

100, 100A, 100B, and 100C can display high-quality images with low power consumption.

In the first embodiment and the second embodiment, the liquid crystal panel 150 is used as a spatial modulation element. Alternatively, a light source element such as an LED array light source including two-dimensionally arranged LEDs may be used as the light source and the projection optical system. Further alternatively, other spatial modulation elements that can apply the principles described in connection with the first and second embodiments may be incorporated into the HUD.

In connection with the first embodiment and the second embodiment, the

HUDs

100, 100A, 100B, and 100C are exemplified as the see-through display. Alternatively, the principles described in connection with the first and second embodiments are equally applicable to other see-through displays such as HMDs.

(Third embodiment)
FIG. 10 is a schematic diagram of a HUD exemplified as a see-through display according to the third embodiment. The HUD of the third embodiment will be described using FIG.

The HUD 500 includes a red laser light source 510r, a green laser light source 510g, and a blue laser light source 510b in addition to the projection optical system 180 and the control unit 190 similar to the HUD 100 described in relation to the first embodiment. The red laser light source 510r, the green laser light source 510g, and the blue laser light source 510b are electrically connected to the control unit 190, respectively. In the present embodiment, the red laser light source 510r is exemplified as a red light source. The green laser light source 510g is exemplified as a green light source. The blue laser light source 510b is exemplified as a blue light source.

The red laser light source 510r emits red laser light L (r) having a center wavelength of 570 nm to 680 nm under the control of the control unit 190. The green laser light source 510g emits green laser light L (g) having a center wavelength of 490 nm to 570 nm under the control of the control unit 190. The blue laser light source 510b emits blue laser light L (b) having a center wavelength of 400 nm to 490 nm under the control of the control unit 190.

In the present embodiment, the blue laser light source 510b may be exemplified as the first light source. At this time, the blue laser light L (b) is exemplified as the first light. Further, the green laser light source 510g or the red laser light source 510r is exemplified as the second light source. Furthermore, the green laser light L (g) emitted from the green laser light source 510g or the red laser light L (r) emitted from the red laser light source 510r is exemplified as the second light.

Alternatively, the green laser light source 510g may be exemplified as the first light source. At this time, the green laser light L (g) is exemplified as the first light. The red laser light source 510r is exemplified as the second light source. Furthermore, the red laser light L (r) emitted from the red laser light source 510r is exemplified as the second light.

The HUD 500 further includes a first dichroic mirror 531. The blue laser light L (b) emitted from the blue laser light source 510b and the red laser light L (r) emitted from the red laser light source 510r are combined by the first dichroic mirror 531. Thereafter, the combined laser light travels to the projection optical system 180.

The HUD 500 further includes a second dichroic mirror 532 disposed between the first dichroic mirror 531 and the projection optical system 180. The laser light combined by the first dichroic mirror 531 and the green laser light L (g) emitted from the green laser light source 510 g are combined by the second dichroic mirror 532. The laser beam combined by the second dichroic mirror enters the lens 130 of the projection optical system 180.

Processing for laser light from the lens 130 to the screen 170 (for example, generation processing of the video light IL) is the same as that of the HUD 100 described in relation to the first embodiment. In the present embodiment, since the three colors of laser light are used to generate the image light IL, the driver DR can visually recognize the full-color virtual image VI drawn based on the image light IL.

The HUD 500 further includes a relief hologram 540 attached to the windshield 210. The relief hologram 540 diffracts and deflects the image light IL toward the driver DR. Thus, the driver DR can see the virtual image VI magnified by the relief hologram 540 through the windshield 210.

FIG. 11 is a schematic cross-sectional view of a relief hologram 540. A relief hologram 540 is described with reference to FIGS. 10 and 11.

The relief-type hologram 540 includes a second resin material 230 attached to the inner surface 211 of the windshield 210, similarly to the

holograms

200 and 200B described in relation to the first and second embodiments. The relief hologram 540 further includes a first resin material 220 </ b> A laminated on the second resin material 230. Unlike the first resin material 220 described in relation to the first embodiment, the first resin material 220A includes a first layer 542b that forms a lattice surface 541b of the relief structure with the second resin material 230, and a first layer 542b. A second layer 542g that forms a layer 542b and a lattice surface 541g with a relief structure; and a third layer 542r that forms a lattice surface 541r with a relief structure and a second layer 542g. The first layer 542b, the second layer 542g, and the third layer 542r each have substantially the same refractive index as that of the second resin material 230. Therefore, the refractive index is uniform between the first surface 221 formed by the third layer 542r and the second surface 231 formed by the second resin material 230. The relief structure of the lattice surfaces 541b, 541g, and 541r shown in FIG. 11 is a blaze structure having a serrated contour surface.

The relief hologram 540 includes a first notch filter 550b that at least partially covers the grating surface 541b, a second notch filter 550g that at least partially covers the grating surface 541g, and a third notch that at least partially covers the grating surface 541r. And a notch filter 550r. The image light IL incident on the first surface 221 includes the red laser light L (r), the green laser light L (g), and the blue laser light L (b) as described with reference to FIG.

The third notch filter 550r provided in the relief structure of the grating surface 541r reflects only the red laser light L (r) in the desired direction out of the image light IL incident on the first surface 221 at a desired incident angle. The image light IL that has reached the grating surface 541r further propagates in the second layer 542g, and then reaches the grating surface 541g.

The second notch filter 550g provided in the relief structure of the grating surface 541g reflects only the green laser light L (g) in the desired direction out of the image light IL reaching the grating surface 541g. The image light IL that has reached the lattice plane 541g further propagates in the first layer 542b, and then reaches the lattice plane 541b.

The first notch filter 550b provided in the relief structure of the grating surface 541b reflects only the blue laser light L (b) in the desired direction out of the image light IL reaching the grating surface 541b. In the present embodiment, the first layer 542b is exemplified as the first hologram element. The second layer 542g is exemplified as the second hologram element. The third layer 542r is exemplified as the third hologram element. The blue laser light L (b) is exemplified as blue light. The green laser light L (g) is exemplified as green light. The red laser light L (r) is exemplified as red light.

FIG. 12A is a schematic graph showing characteristics of the first notch filter 550b, the second notch filter 550g, and the third notch filter 550r. The characteristics of the first notch filter 550b, the second notch filter 550g, and the third notch filter 550r are described with reference to FIGS. 10 to 12A.

As shown in FIG. 12A, for example, the center wavelength of the red laser light L (r) is set to 635 nm, the center wavelength of the green laser light L (g) is set to 532 nm, and the blue laser light L (b) May be set to 445 nm. If the maximum reflectance for each wavelength of the relief hologram 540 is set to “50%”, the first notch filter 550b, the second notch filter 550g, and the third notch filter 550r are as shown in FIG. 12A. , It is designed to reflect light having a wavelength component only in the vicinity of each central wavelength. Note that the reflectances of the first notch filter 550b, the second notch filter 550g, and the third notch filter 550r shown in FIG. 12A are each set to 50% at the maximum. Alternatively, the reflectivity of the first notch filter 550b, the second notch filter 550g, and the third notch filter 550r may have a maximum value greater than 50%, or have a maximum value less than 50%. May be. When the reflectivity of the first notch filter 550b, the second notch filter 550g, and the third notch filter 550r is set to a high value, the light use efficiency of the HUD 500 increases. When the reflectance of the first notch filter 550b, the second notch filter 550g, and the third notch filter 550r is set to a low value, the amount of external light EL that enters the vehicle interior from the outside of the vehicle interior relatively increases. The passenger compartment becomes brighter. The reflectivity of the first notch filter 550b, the second notch filter 550g, and the third notch filter 550r may be appropriately set according to the specifications of the vehicle to be mounted according to the above-described characteristics.

FIG. 12B is a schematic graph showing other characteristics of the first notch filter 550b, the second notch filter 550g, and the third notch filter 550r. 11 and 12B, other characteristics of the first notch filter 550b, the second notch filter 550g, and the third notch filter 550r will be described.

The characteristics of the second notch filter 550g and the third notch filter 550r shown in FIG. 12B are the same as the characteristics shown in FIG. 12A. As described with reference to FIG. 11, before reaching the grating surface 541b, the red laser light L (r) and the green laser light L (g) are reflected by the third notch filter 550r and the second notch filter 550g, respectively. Therefore, the first notch filter 550b may reflect not only light in the vicinity of the center wavelength of the blue laser light L (b) but also light having a wavelength equal to or less than the center wavelength of the blue laser light L (b). (For example, with a reflectance of about 50%).

FIG. 13 is a schematic view showing a method for manufacturing the relief hologram 540. A method of manufacturing the relief hologram 540 will be described with reference to FIG.

(Step S100)
Similar to the first embodiment, the second resin material 230 is manufactured by a molding technique such as injection molding. Through the molding process, a relief-structured lattice plane 541b is formed on the upper surface of the second resin material 230. A first notch filter 550b is applied or deposited on the lattice plane 541b. Thereafter, step S110 is executed.

(Step S110)
In step S110, a liquid resin material (in this embodiment, an ultraviolet curable resin is exemplified as the resin material in the present embodiment, as in the first embodiment) formed on the second resin material 230 in the first layer 542b. Applied. Thereafter, a transparent stamper 560 is disposed on the liquid resin material layer formed on the first layer 542b. Further, ultraviolet rays are irradiated from above the transparent stamper 560. As a result, the first layer 542b is laminated on the second resin material 230. In addition, there is almost no gap between the first layer 542b and the second resin material 230. When the transparent stamper 560 is removed, a lattice surface 541g having a relief structure is formed on the upper surface of the first layer 542b. Thereafter, step S120 is executed.

(Step S120)
In step S120, the second notch filter 550g is applied or deposited on the lattice plane 541g. Thereafter, a liquid resin material (in this embodiment, an ultraviolet curable resin is exemplified as the resin material in the present embodiment as in the first layer 542b) is applied to the first layer 542b. The Thereafter, a transparent stamper 561 is disposed on the liquid resin material layer formed on the second layer 542g. Further, ultraviolet rays are irradiated from above the transparent stamper 561. As a result, the second layer 542g is stacked on the first layer 542b. In addition, there is almost no gap between the first layer 542b and the second layer 542g. When the transparent stamper 561 is removed, a lattice surface 541r having a relief structure is formed on the upper surface of the second layer 542g. Thereafter, step S130 is executed.

(Step S130)
In step S130, the third notch filter 550r is applied or deposited on the lattice plane 541r. Thereafter, a liquid resin material (in this embodiment, an ultraviolet curable resin is exemplified as the resin material in the present embodiment as in the first layer 542b) is applied to the second layer 542g. The Note that the upper surface of the liquid resin material layer formed in the third layer 542r is planarized. Thereafter, the layer of the liquid resin material on the second layer 542g is irradiated with ultraviolet rays to form the third layer 542r. Thus, the relief hologram 540 is completed. As described above, the first layer 542b, the second layer 542g, and the third layer 542r have the same refractive index as that of the second resin material 230.

11 to 12B, the optical action of the relief hologram 540 will be described.

As described above, the third notch filter 550r reflects a predetermined ratio of the red laser light L (r) incident on the grating surface 541r in a predetermined direction. As a result, the red laser light L (r) is emitted from the relief hologram 540 toward the driver DR and is visually recognized as an image. The red laser light L (r) remaining without being reflected by the third notch filter 550r passes through the grating surface 541r. Thereafter, the red laser light L (r) is emitted outside the passenger compartment without being reflected by the lattice surfaces 541g and 541b and the windshield 210. Therefore, the remaining red laser light L (r) does not contribute to the formation of an image that is visually recognized by the driver DR.

The green laser light L (g) incident on the first surface 221 of the relief hologram 540 is not reflected by the grating surface 541r provided with the third notch filter 550r. Therefore, the green laser light L (g) is incident on the grating surface 541g after passing through the grating surface 541r.

The second notch filter 550g provided on the grating surface 541g reflects a predetermined ratio of the green laser light L (g) incident on the grating surface 541g in a predetermined direction. As a result, the green laser light L (g) is emitted from the relief hologram 540 toward the driver DR. Therefore, the green laser light L (g) reflected by the grating surface 541g forms an image together with the red laser light L (r) reflected by the grating surface 541r.

The green laser light L (g) remaining without being reflected by the second notch filter 550g passes through the lattice plane 541g. Thereafter, the green laser light L (g) is emitted outside the passenger compartment without being reflected by the lattice plane 541b and the windshield 210. Therefore, the remaining green laser light L (g) does not contribute to the formation of an image visually recognized by the driver DR.

The blue laser light L (b) incident on the first surface 221 of the relief-type hologram 540 is not reflected by the grating surface 541r provided with the third notch filter 550r and the grating surface 541g provided with the second notch filter 550g. . Accordingly, the blue laser light L (b) is transmitted through the grating surface 541r and the grating surface 541g and then enters the grating surface 541b.

The first notch filter 550b provided on the grating surface 541b reflects a predetermined ratio of the blue laser light L (b) incident on the grating surface 541b in a predetermined direction. As a result, the blue laser light L (b) is emitted from the relief hologram 540 toward the driver DR. Therefore, the blue laser beam L (b) reflected by the grating surface 541b forms an image together with the red laser beam L (r) reflected by the grating surface 541r and the green laser beam L (g) reflected by the grating surface 541g. Form.

The blue laser light L (b) remaining without being reflected by the first notch filter 550b passes through the grating surface 541b. Thereafter, the blue laser light L (b) is emitted outside the passenger compartment without being reflected by the windshield 210. Therefore, the remaining blue laser light L (b) does not contribute to the formation of an image visually recognized by the driver DR.

As described above, since the virtual image VI is drawn by the red laser light L (r), the green laser light L (g), and the blue laser light L (b), the driver DR visually recognizes a full color image. Therefore, the HUD 500 including the relief hologram 540 can color the content (image) to be displayed. If the displayed content is expressed in, for example, a yellow or red hue, an alert to the driver DR is prompted. Therefore, the HUD 500 can contribute to the improvement of driving safety.

As in the first embodiment, the resin materials (second resin material 230, first layer 542b, second layer 542g, and third layer 542r) are in close contact with each other on the lattice surfaces 541b, 541g, and 541r. . Of the outside light EL from outside the passenger compartment, notch filters (first notch filter 550b, second notch filter 550g, and third notch filter 550r) described in relation to FIGS. 12A and 12B are not included in the reflection bands. The light component passes through the relief hologram 540 without being diffracted. Therefore, most of the external light EL incident on the windshield 210 is not diffracted, but is incident on the vehicle interior. As a result, stray light caused by higher-order diffracted light generated in a general relief hologram is not generated. Almost does not occur. Since stray light hardly enters the eyes of the driver DR, the driver can drive safely without being disturbed by the stray light. Therefore, since the HUD 500 hardly generates stray light, an image with excellent visibility can be displayed. Similar to the first embodiment, the projection optical system 180 is preferably designed so that the incident angle of the image light IL is substantially vertical at at least one location on the first surface 221 of the relief hologram 540. As a result, the HUD 500 can display a high-quality image with almost no stray light.

The effects related to the stacking order of the first layer 542b, the second layer 542g, and the third layer 542r will be described with reference to FIGS.

In the manufacturing process of the relief hologram 540 shown in FIG. 13, a grating surface 541b for diffracting the blue laser light L (b) having the shortest wavelength among the optical components of the image light IL is formed at the lowermost position. . A grating surface 541g for diffracting the green laser light L (g) having the second longest wavelength is formed above the grating surface 541b. On the grating surface 541g, a grating surface 541r for diffracting the red laser beam L (r) having the longest wavelength among the light components of the image light IL is formed. Therefore, as shown in FIG. 11, the third layer 542r, the second layer 542g, and the first layer 542b are sequentially stacked from the first surface 221 to the second surface 231.

Generally, if the diffraction angles are the same, longer wavelength light requires a longer pitch (p) lattice plane shape. As a result, if the diffraction angles are the same, the relief unevenness dimension (D) becomes larger for light having a longer wavelength.

If a relief-type hologram is created according to the manufacturing method shown in FIG. 13, the liquid resin material is cured by irradiating ultraviolet rays from the stampers 560 and 561 placed on the applied liquid resin material. As a result, lattice planes 541b, 541g, and 541r are formed, respectively.

Such lattice planes

541b, 541g, and 541r are preferably formed from a layer having a small unevenness dimension (D).

When the concave and convex dimension (D) is small, the pressure difference in the pressurization surface during pressurization by the stampers 560 and 561 is unlikely to occur, so that the lattice plane shape of the stampers 560 and 561 is transferred with high accuracy. If a lattice surface with a small uneven dimension (D) is formed before the formation of a lattice surface with a relatively large uneven dimension (D), a shape error that affects the shape of the lattice surface with a relatively large uneven dimension (D). Becomes smaller. Therefore, accurate transfer of the lattice plane is achieved for the relief hologram 540 as a whole. Since the relief hologram 540 is manufactured with high accuracy, the HUD 500 can display an image with high image quality.

As shown in FIG. 11, the grating surface 541b that diffracts the blue laser light L (b) is disposed on the outermost side (closest to the windshield 210). As described with reference to FIG. 12B, the first notch filter 550b formed on the grating surface 541b has not only the blue laser light L (b) but also an ultraviolet ray having a shorter wavelength than the blue laser light L (b). If (with a wavelength of 400 nm or less) is reflected with a predetermined reflectance (FIG. 12B shows a reflectance of about 50%), the first notch filter 550b reflects (that is, removes) the ultraviolet light included in the external light EL. can do. In particular, as described with reference to FIG. 13, if the first layer 542b, the second layer 542g, and the third layer 542r are formed of an ultraviolet curable resin that absorbs a large amount of ultraviolet rays, the first notch filter 550b. Suitably suppresses deterioration of the first layer 542b, the second layer 542g, and the third layer 542r due to ultraviolet absorption. Therefore, the reliability of the HUD 500 is improved.

As a result of the outermost grating surface 541b that diffracts the blue laser light L (b) being formed, the first notch filter 550b can be easily formed. As shown in FIG. 12B, the reflection characteristic of the first notch filter 550b is not required to reduce the reflectance between the ultraviolet wavelength region and the blue laser light L (b). Therefore, the coat layer for reflecting the ultraviolet rays and the coat layer for reflecting the blue laser light L (b) may be formed as a simple low-pass filter. Thus, the coating of the first notch filter 550b is facilitated.

On the other hand, it is not easy to add the characteristic of reflecting ultraviolet rays to the second notch filter 550g that reflects the green laser light L (g) and the third notch filter 550r that reflects the red laser light L (r). If the second layer 542g and the second notch filter 550g or the third notch filter 550r of the third layer 542r disposed between the first layer 542b and the first surface 221 are added with a characteristic of reflecting ultraviolet rays. In the band around the center wavelength of 445 nm of the blue laser light L (b), the reflectance must be set to “0%”. However, it is very difficult or expensive to form a notch filter having such characteristics. Therefore, it is preferable that the grating surface 541b that diffracts the blue laser light L (b) having the shortest wavelength in the image light IL is formed on the outermost side. The first notch filter 550b formed on the lattice plane 541b preferably includes a coat layer having a property of reflecting ultraviolet rays. Thus, the highly reliable HUD 500 is manufactured at low cost.

Note that the reflectance of the ultraviolet rays of the first notch filter 550b shown in FIG. 12B is about 50%. Alternatively or preferably, the ultraviolet reflectance of the first notch filter 550b may be set to a value exceeding 50%.

In this embodiment, examples of the light source include a red laser light source 510r, a green laser light source 510g, and a blue laser light source 510b. Alternatively, other light source elements such as LEDs that emit red, green, and blue light or white LEDs may be used as the light source. The wavelength ranges of the red laser light L (r), green laser light L (g), and blue laser light L (b) emitted from the red laser light source 510r, the green laser light source 510g, and the blue laser light source 510b are LEDs. Since it is narrower than the other light sources, the use of the red laser light source 510r, the green laser light source 510g, and the blue laser light source 510b as light sources can achieve high diffraction efficiency in the hologram 540. Therefore, if the red laser beam L (r), the green laser beam L (g), and the blue laser beam L (b) are used as the light source, the blurring of the image due to the spread of the wavelength is suitably suppressed. Thus, the HUD 500 can display high-quality images with low power consumption.

In the present embodiment, the liquid crystal panel 150 is used as a spatial modulation element. Alternatively, a light source element such as an LED array light source including two-dimensionally arranged LEDs may be used as the light source and the projection optical system. Further alternatively, other spatial modulation elements to which the principles described in connection with this embodiment can be applied may be incorporated in the HUD.

(Fourth embodiment)
FIG. 14 is a schematic diagram of a HUD exemplified as a see-through display according to the fourth embodiment. The HUD of the fourth embodiment will be described using FIG.

The HUD 500A includes a blue-green laser light source 510bg in addition to the red laser light source 510r, the projection optical system 180, and the control unit 190 similar to the HUD 500 described in relation to the third embodiment. The red laser light source 510r is electrically connected to the control unit 190 as in the third embodiment. Similarly, the blue-green laser light source 510bg is also electrically connected to the control unit 190. The red laser light source 510r emits red laser light L (r) under the control of the control unit 190. The blue-green laser light source 510bg emits blue-green laser light L (bg) under the control of the control unit 190. In the present embodiment, the blue-green laser light source 510bg is exemplified as the first light source. The red laser light source 510r is exemplified as the second light source. Further, the blue-green laser light L (bg) emitted from the blue-green laser light source 510bg is exemplified as the first light. The red laser light L (r) emitted from the red laser light source 510r is exemplified as the second light.

The HUD 500A further includes a dichroic mirror 533. The blue-green laser light L (bg) emitted from the blue-green laser light source 510bg and the red laser light L (r) emitted from the red laser light source 510r are combined by the dichroic mirror 533. Thereafter, the combined laser light travels toward the lens 130 of the projection optical system 180.

The HUD 500A further includes a relief hologram 540A attached to the windshield 210. As in the first to third embodiments, the projection optical system 180 generates image light IL using laser light. The hologram 540A diffracts the image light IL toward the driver DR. As a result, the driver DR visually recognizes the virtual image VI through the windshield 210.

FIG. 15 is a schematic cross-sectional view of a relief hologram 540A. The relief hologram 540A is described with reference to FIGS.

The relief hologram 540A includes a second resin material 230 attached to the inner surface 211 of the windshield 210, and a first resin material 220B laminated on the second resin material 230. The first resin material 220B includes a first layer 740bg laminated on the second resin material 230 and a second layer 740r laminated on the first layer 740bg. Therefore, unlike the relief type hologram 540 described in relation to the third embodiment, the relief type hologram 540A has a three-layer structure.

As shown in FIG. 14, the projection optical system 180 projects the image light IL onto a relief hologram 540A attached to the windshield 210. The image light IL is incident on the first surface 221 formed by the second layer 740r. Relief-type hologram 540A diffracts and deflects blue-green laser beam L (bg) and red laser beam L (r) included in image light IL toward driver DR, respectively. Thus, the driver DR can visually recognize the virtual image VI enlarged by the relief hologram 540A through the windshield 210.

As shown in FIG. 15, the relief hologram 540A is formed between the grating surface 741r formed between the first layer 740bg and the second layer 740r, and between the first layer 740bg and the second resin material 230. Grid surface 741bg. Relief-type hologram 540A further includes a first notch filter 750bg formed on grating surface 741bg and a second notch filter 750r formed on grating surface 741r.

FIG. 16 is a schematic graph showing ideal characteristics of the first notch filter 750bg and the second notch filter 750r. The characteristics of the first notch filter 750bg and the second notch filter 750r will be described with reference to FIGS.

As shown in FIG. 16, for example, the center wavelength of the red laser beam L (r) may be set to 635 nm, and the center wavelength of the blue-green laser beam L (bg) may be set to 488 nm. If the maximum reflectance for each wavelength of the relief-type hologram 540A is set to “50%”, the first notch filter 750bg and the second notch filter 750r have the respective center wavelengths as shown in FIG. It is designed to reflect light of wavelength components only in the vicinity. Note that the reflectance of the first notch filter 750bg and the second notch filter 750r shown in FIG. 16 is set to 50% at the maximum. Alternatively, the reflectivity of the first notch filter 550bg and the second notch filter 550r may have a maximum value greater than 50%, or may have a maximum value less than 50%. When the reflectivity of the first notch filter 750bg and the second notch filter 750r is set to a high value, the light use efficiency of the HUD 500A increases. When the reflectance of the first notch filter 750bg and the second notch filter 750r is set to a low value, the amount of external light EL that enters the vehicle interior from the outside of the vehicle interior relatively increases, so the interior of the vehicle becomes bright. The reflectivities of the first notch filter 750bg and the second notch filter 750r may be appropriately set according to the specifications of the vehicle to be mounted according to the above-described characteristics.

If the first notch filter 750bg and the second notch filter 750r have the reflection characteristics shown in FIG. 16, respectively, the HUD 500A uses the video light for forming an image, as in the first to third embodiments. IL can be diffracted with high efficiency. In addition, the HUD 500 </ b> A allows most outside light EL incident from outside the vehicle compartment to enter the vehicle interior. Therefore, the HUD 500A can provide the driver DR with a low power consumption and an image with low stray light and excellent visibility.

FIG. 17 is a schematic view of a manufacturing method of the relief type hologram 540A. The manufacturing method of the relief hologram 540A shown in FIG. 17 is relatively simple.

(Step S200)
The second resin material 230 and the second layer 740r are individually created using a molding technique such as injection molding. As a result of the injection molding of the second resin material 230, a lattice surface 741bg having a relief structure is formed on the upper surface of the second resin material 230. Further, as a result of injection molding of the second layer 740r, a lattice surface 741r having a relief structure is formed on the lower surface of the second layer 740r.

Thereafter, a first notch filter 750bg is applied or deposited on the lattice plane 741bg. A second notch filter 750r is applied or deposited on the lattice surface 741r.

Thereafter, a liquid resin material (in this embodiment, the resin material is an ultraviolet curable resin as in the above-described series of embodiments) formed on the first layer 740bg is applied onto the lattice plane 741bg. . Thereafter, step S210 is executed.

(Step S210)
In step S210, the second layer 740r is placed on the liquid resin material layer formed on the first layer 740bg. Thereafter, when the ultraviolet ray is irradiated, the liquid resin material between the second layer 740r and the second resin material 230 is cured to become the first layer 740bg. Thus, the relief hologram 540A is created using a very simple manufacturing method.

In this embodiment, the HUD 500A includes a red laser light source 510r that emits red laser light L (r), and a blue-green laser light L (having a complementary color to the hue (red) of the red laser light L (r). bg), and a blue-green laser light source 510bg. Therefore, the HUD 500A can display an image expressed using three colors of white, red, and blue-green.

Generally, in the see-through display such as HUD, there are not many kinds of displayed contents. Therefore, a full color image representation is not required much. In many cases, the content to be displayed is expressed using three hues. Therefore, although the HUD 500A has only two types of light sources, it can perform practically sufficient color expression. As a result of the number of light sources of the HUD 500A being two, an inexpensive HUD 500A is provided while maintaining practical convenience.

In this embodiment, the HUD 500A includes a red laser light source 510r that emits red laser light L (r), and a blue-green laser light L (having a complementary color to the hue (red) of the red laser light L (r). bg), and a blue-green laser light source 510bg. Alternatively, the HUD may comprise a set of laser light sources that achieve other hue combinations. For example, the HUD may include a blue laser light source that emits blue laser light and a yellow laser light source that emits yellow laser light having a hue complementary to the hue (blue) of the blue laser light. Further alternatively, the HUD includes a violet laser light source that emits violet laser light, and a yellow-green laser light source that emits yellow-green laser light having a hue complementary to the hue (purple) of the violet laser light. May be. By using a set of light sources that emit two-color laser beams having complementary colors, an image is expressed using white. However, if white is not required to represent an image, a set of light sources that emit laser beams of two colors that are not in a complementary color relationship may be used for the HUD.

(Fifth embodiment)
FIG. 18 is a schematic view of a head mounted display (HMD) exemplified as a see-through display according to the fifth embodiment. The HMD of the fifth embodiment is described with reference to FIG.

The HMD 700 includes a control unit 190, a red laser light source 510r, a green laser light source 510g, a blue laser light source 510b, a first dichroic mirror 531 and a second dichroic mirror 532, similarly to the HUD 500 of the third embodiment. The red laser light source 510r, the green laser light source 510g, and the blue laser light source 510b are electrically connected to the control unit 190, respectively.

The HMD 700 further includes a projection optical system 180B. The projection optical system 180B includes a folding mirror 140B and a MEMS mirror 300B. The MEMS mirror 300B is electrically connected to the control unit 190.

The blue laser light L (b) emitted from the blue laser light source 510b and the red laser light L (r) emitted from the red laser light source 510r are combined by the first dichroic mirror 531. Thereafter, the combined laser light travels to the second dichroic mirror 532. The laser light combined by the first dichroic mirror 531 and the green laser light L (g) emitted from the green laser light source 510 g are combined by the second dichroic mirror 532. The laser beam combined by the second dichroic mirror is incident on the folding mirror 140B of the projection optical system 180B. The red laser light L (r), green laser light L (g), and blue laser light L (b) reflected by the folding mirror 140B are two-dimensionally deflected and scanned by the MEMS mirror 300B. As a result, the image light IL is emitted from the projection optical system 180B.

The red laser light source 510r, the green laser light source 510g, the blue laser light source 510b, and the MEMS mirror 300B operate under the control of the control unit 190. For example, the control unit 190 controls the swing angle of the MEMS mirror 300B. In addition, the control unit 190 controls the red laser light source 510r, the green laser light depending on the scanning position of the red laser light L (r), the green laser light L (g), and the blue laser light L (b) and the image to be displayed. The light source 510g and the blue laser light source 510b are controlled, and the intensity of the red laser light L (r), the green laser light L (g), and the blue laser light L (b) is also modulated.

The HMD 700 further includes a lens unit 710 disposed in front of the user's eyes, and a relief hologram 940 attached to the lens unit 710. The relief hologram 940 is disposed between the lens unit 710 and the user's eye. The video light IL emitted from the projection optical system 180B is incident on a relief hologram 940 attached to the inner surface 711 of the lens unit 710 facing the user's eye.

FIG. 19 is a schematic cross-sectional view of a relief hologram 940. A relief hologram 940 is described with reference to FIGS. 11, 18 and 19.

The relief hologram 940 has a structure substantially similar to the relief hologram 540 described in relation to the third embodiment. The relief hologram 940 includes a second resin material 930 attached to the inner surface 711 of the lens unit 710. The relief hologram 940 further includes a first resin material 920 laminated on the second resin material 930. The first resin material 920 includes a second resin material 930 and a first layer 942b that forms a relief-structured lattice surface 941b, a first layer 942b and a second layer 942g that forms a relief-structured lattice surface 941g, And a third layer 942r forming a relief-structured lattice plane 941r. The first layer 942b, the second layer 942g, and the third layer 942r have substantially the same refractive index as that of the second resin material 930. Therefore, the refractive index is uniform between the first surface 921 formed by the third layer 942r and the second surface 931 formed by the second resin material 930. The second resin material 930, the first layer 942b, the second layer 942g, and the third layer 942r are preferably in close contact with each other without a gap.

The relief hologram 940 includes a first notch filter 950b that at least partially covers the grating surface 941b, a second notch filter 950g that at least partially covers the grating surface 941g, and a third that at least partially covers the grating surface 941r. A notch filter 950r. The image light IL incident on the first surface 921 includes the red laser light L (r), the green laser light L (g), and the blue laser light L (b) as described with reference to FIG.

The third notch filter 950r provided in the relief structure of the grating surface 941r reflects only the red laser light L (r) in the desired direction out of the image light IL incident on the first surface 921 at a desired incident angle. The image light IL that has reached the grating surface 941r further propagates in the second layer 942g, and then reaches the grating surface 941g.

The second notch filter 950g provided in the relief structure of the grating surface 941g reflects only the green laser light L (g) in the desired direction out of the image light IL reaching the grating surface 941g. The image light IL that has reached the grating surface 941g further propagates through the first layer 942b, and then reaches the grating surface 941b.

The first notch filter 950b provided in the relief structure of the grating surface 941b reflects only the blue laser light L (b) out of the image light IL reaching the grating surface 941b in a desired direction.

The relief structure of the lattice planes 941b, 941g, and 941r shown in FIG. 19 is a blaze structure having a serrated contour surface. The relief structures of the grating surfaces 941b, 941g, and 941r have red laser light L (r), green laser light L (g), and blue laser light L (b) incident on the hologram 940, as shown in FIG. Optimized to be diffracted toward the user's eye.

The red laser light L (r) included in the image light IL incident on the relief hologram 940 is diffracted by the grating surface 941r provided with the third notch filter 950r that reflects only the red laser light L (r). As a result, it is deflected toward the user's eyeball. The green laser light L (g) included in the image light IL incident on the relief hologram 940 is diffracted by the grating surface 941g provided with the second notch filter 950g that reflects only the green laser light L (g). As a result, it is deflected toward the user's eyeball. The blue laser light L (b) included in the image light IL incident on the relief hologram 940 is diffracted by the grating surface 941b provided with the first notch filter 950b that reflects only the blue laser light L (b). As a result, it is deflected toward the user's eyeball. The red laser light L (r), green laser light L (g), and blue laser light L (b) that are not diffracted by the grating surfaces 941r, 941g, and 941b pass through the relief hologram 940 as they are.

The red laser light L (r), green laser light L (g), and blue laser light L (b) deflected toward the user's eyeball pass through the eyeball and are imaged on the retina. As a result, the user can recognize the video light IL as an image.

Similar to the relief hologram 540 of the HUD 500 described in relation to the third embodiment, the first surface 921 on which the image light IL is incident (the incident surface of the image light IL) is preferably attached to the lens unit 710. Is substantially parallel to the second surface 931 (the exit surface of the image light IL). As a result, the external light EL transmitted through the lens unit 710 and incident on the relief hologram 940 is hardly diffracted by the relief hologram 940 and is hardly affected by refraction. Reach the eyeball. Therefore, the user can visually recognize an external scene with less distortion.

The first surface 921 of the relief hologram 940 shown in FIG. 19 is curved while maintaining a substantially parallel relationship with the second surface 931. Alternatively, both the first surface 921 and the second surface 931 may form a flat surface.

As described above, even in the HMD 700 in which the relief hologram 940 is incorporated, most of the external light EL can pass through the relief hologram 940 without being diffracted. Therefore, the generation of stray light and the incidence of stray light on the eyes hardly occur. Therefore, the HMD 700 can display an image with excellent visibility.

In this embodiment, the grating surfaces 941r, 941g, and 941b of the relief hologram 940 have a blaze structure. As a result, the relief hologram 940 achieves high diffraction efficiency. Since the light utilization efficiency of the HMD 700 is improved, the power consumption of the HMD 700 is reduced. In addition, the relief hologram 940 is created using a molding technique. Therefore, an inexpensive HMD 700 with high productivity is provided.

The user may wear an HMD together with eyesight correction glasses. The lens of the eyeglasses is adjusted in order to appropriately view the outside scene. On the other hand, the image formed by the HMD is stored in the retina regardless of visual acuity.

In manufacturing an HMD using a general volume hologram, the volume hologram is directly exposed after being attached to a lens of eyesight correction glasses. As a result, a hologram optimal for the user is created regardless of the position of the eyeglass lens.

As one of advantageous features of this embodiment, as described above, the relief hologram 940 can be mass-produced (for example, using a molding technique). However, the above-described HMD manufacturing method (that is, a method of directly exposing a volume hologram attached to a spectacle lens) is not suitable for mass production.

In this embodiment, the relief hologram 940 is disposed between the lens unit 710 and the user's eyeball. Accordingly, the relief hologram 940 having the same structure manufactured in mass production is attached to the desired lens unit 710, and the HMD 700 optimized for the user is formed. As a result of the relief-type hologram 940 and the MEMS 300B being arranged at predetermined positions with respect to the position of the user's eyeball, the image formed by the HMD 700 is appropriately formed on the retina. The lens unit 710 outside (that is, the outside world side) from the relief hologram 940 performs focus adjustment according to the visual acuity of the user and appropriately stores the scenery from the outside world on the retina. As a result of the lens unit 710 being disposed on the outside of the relief hologram 940, the HMD 700 is formed using the relief hologram 940 having the same shape even for a user wearing eyeglasses for correcting vision. The image to be viewed can be viewed. Thus, the HMD 700 of the present embodiment has high mass productivity and is manufactured at a low cost.

The series of embodiments described above is merely an example of a see-through display. Therefore, the above description does not limit the scope of application of the principle of the present embodiment. It should be readily understood by those skilled in the art that various modifications and combinations can be made without departing from the spirit and scope of the principles described above.

The embodiment described above mainly includes the following configuration.

The see-through display according to one aspect of the above-described embodiment includes a light source that emits light, a projection optical system that spatially modulates the intensity of the light and generates image light for displaying an image, and an emission from the projection optical system. A hologram for deflecting the image light, wherein the hologram includes a first surface on which the image light is incident, and a second surface opposite to the first surface, A transmission layer that allows transmission; a grating surface that has a relief structure that diffracts the image light between the first surface and the second surface; and at least partially covers the grating surface and is incident on the grating surface And a notch filter that reflects incident light having a specific wavelength component, wherein the transmission layer has a uniform refractive index from the first surface to the second surface.

According to the above configuration, the projection optical system spatially modulates the intensity of light emitted from the light source, and generates video light for displaying an image. The hologram deflects image light emitted from the projection optical system. The transmission layer of the hologram includes a first surface on which image light is incident and a second surface opposite to the first surface, and allows transmission of the image light. The hologram grating surface has a relief structure that diffracts image light between the first surface and the second surface. The notch filter that at least partially covers the grating surface reflects incident light having a specific wavelength component incident on the grating surface. Since the transmissive layer has a uniform refractive index from the first surface to the second surface, it is difficult for high-order diffracted light to be generated. Therefore, the viewer can suitably view the image with little influence of stray light.

In the above configuration, the hologram includes a first transmission layer that forms the first surface and a second transmission layer that forms the second surface, and has a refractive index equal to that of the second transmission layer. It is preferable that the first transmission layer is in close contact with the second transmission layer without a gap.

According to the above configuration, the hologram includes the first transmission layer that forms the first surface and the second transmission layer that forms the second surface. The first transmissive layer having the same refractive index as the second transmissive layer is in close contact with the second transmissive layer without any gap, so that high-order diffracted light is less likely to be generated. Therefore, the viewer can suitably view the image with little influence of stray light.

In the above-described configuration, it is preferable that the projection optical system causes the image light to enter the first surface substantially perpendicularly.

According to the above configuration, the projection optical system causes the image light to enter the first surface substantially perpendicularly, so that stray light is appropriately reduced. Therefore, since high-precision exposure is not required for manufacturing a hologram, the hologram is manufactured at a low cost. In addition, since the hologram can be manufactured by a molding technique, it is excellent in mass productivity.

In the above configuration, the relief structure preferably includes a blaze structure.

According to the above configuration, since the relief structure includes a blaze structure, the light utilization efficiency is increased. Thus, the power consumption of the see-through display is reduced.

In the above configuration, it is preferable that the image light is P-polarized light, and the projection optical system causes the image light to be incident at least partially on the first surface at a Brewster angle.

According to the above configuration, the image light is P-polarized light. Since the projection optical system causes the image light to be incident at least partially on the first surface at a Brewster angle, it is difficult for the viewer to visually recognize the double image due to the surface reflection.

In the above configuration, the notch filter preferably includes a dielectric multilayer film.

According to the above configuration, since the notch filter includes the dielectric multilayer film, the diffraction efficiency is easily set.

In the above configuration, it is preferable that the grating surface includes a diffractive surface that diffracts the image light, and the dielectric multilayer film is disposed only on the diffractive surface.

According to the above configuration, since the dielectric multilayer film is disposed only on the diffractive surface that diffracts the image light, the diffraction efficiency for obtaining desired reflection characteristics can be easily set. Thus, the mixing ratio between the external light incident from the outside and the image is set inexpensively and simply.

In the above configuration, the notch filter preferably includes a rugate filter.

According to the above configuration, since the notch filter includes the rugate filter, incident light having a specific wavelength component incident on the grating surface is appropriately reflected.

In the above configuration, the light source preferably includes a laser light source that emits laser light.

According to the above configuration, since the light source includes a laser light source that emits laser light, high light use efficiency is achieved. In addition, image blur due to the spread of the wavelength is appropriately reduced. Thus, a see-through display with low power consumption and high image quality is provided.

In the above configuration, the light source includes: a first light source that emits first light having a first wavelength; and a second light source that emits second light having a second wavelength different from the first wavelength. The transmission layer preferably includes a first hologram element that diffracts the first light and a second hologram element that diffracts the second light.

According to the above configuration, the light source includes the first light source that emits the first light having the first wavelength and the second light source that emits the second light having the second wavelength different from the first wavelength. The first transmission layer includes a first hologram element that diffracts the first light and a second hologram element that diffracts the second light, so that the viewer can appropriately visually recognize images drawn in various hues. can do.

In the above configuration, the light source includes a blue light source that emits blue light, a green light source that emits green light, and a red light source that emits red light, and the first transmission layer diffracts the blue light. It is preferable to include a first hologram element to be diffracted, a second hologram element that diffracts the green light, and a third hologram element that diffracts the red light.

According to the above configuration, the light source includes a blue light source that emits blue light, a green light source that emits green light, and a red light source that emits red light. The first transmission layer includes a first hologram element that diffracts blue light, a second hologram element that diffracts green light, and a third hologram element that diffracts red light. Can be visually recognized.

In the above configuration, it is preferable that the third hologram element, the second hologram element, and the first hologram element are sequentially laminated from the first surface toward the second surface.

According to the above configuration, since the third hologram element, the second hologram element, and the first hologram element are sequentially laminated from the first surface to the second surface, the hologram is accurately formed. Thus, the viewer can view high-quality images.

A head-up display mounted on a vehicle having a windshield including an inner surface defining an indoor boundary according to another aspect of the above-described embodiment includes the above-described see-through display, and the hologram is attached to the inner surface. It is characterized by.

According to the above configuration, the head-up display mounted on the vehicle having the windshield including the inner surface defining the indoor boundary includes the above-described see-through display. Since the hologram is attached to the inner surface, a highly reliable head-up display is provided.

In the above configuration, the windshield absorbs ultraviolet rays between the first glass forming the inner surface, the second glass forming the outer surface opposite to the inner surface, and the first glass and the second glass. It is preferable that the hologram is disposed between the first glass and the absorption layer.

According to the above configuration, the windshield includes a first glass that forms an inner surface, a second glass that forms an outer surface opposite to the inner surface, and an absorption layer that absorbs ultraviolet rays between the first glass and the second glass. And including. Since the hologram is disposed between the first glass and the absorbing layer, it is less susceptible to ultraviolet rays. In addition, the hologram is less likely to expand due to moisture absorption in the air. Therefore, a highly reliable head-up display is provided.

A head-up display mounted on a vehicle having a windshield including an inner surface defining an indoor boundary according to another aspect of the above-described embodiment includes the above-described see-through display, and the first light is the second light. The first light has a shorter wavelength than the second light, and the second hologram element is disposed between the first hologram element and the first surface. It is characterized by that.

According to the above configuration, the head-up display mounted on the vehicle having the windshield including the inner surface that defines the indoor boundary includes the above-described see-through display. The first light has a shorter wavelength than the second light. Since the second hologram is disposed between the first hologram and the inner surface, it is easy to add a characteristic for reflecting ultraviolet rays.

A head-mounted display including a lens unit disposed in front of a user's eye according to another aspect of the above-described embodiment includes the above-described see-through display, and the hologram is disposed between the lens unit and the eye. It is provided.

According to the above configuration, the head mounted display including the lens unit disposed in front of the user's eyes includes the above-described see-through display. Since the hologram is disposed between the lens unit and the eye, an image is also provided to a viewer who wears glasses using the same shape hologram. Therefore, an inexpensive head-mounted display that is excellent in mass productivity is provided.

The principle of this embodiment provides a see-through display with high light utilization efficiency. The see-through display according to the principle of this embodiment has low power consumption and excellent visibility. In addition, the see-through display according to the principle of the present embodiment has high mass productivity and is manufactured at low cost. The see-through display according to the principle of the present embodiment can be applied to various see-through display devices such as HUD and HMD.

Claims

A light source that emits light;
A projection optical system that spatially modulates the intensity of the light and generates image light for displaying an image;
A hologram for deflecting the image light emitted from the projection optical system,
The hologram is
A transmission layer that includes a first surface on which the image light is incident and a second surface opposite to the first surface, and allows transmission of the image light;
A grating surface having a relief structure that diffracts the image light between the first surface and the second surface;
A notch filter that at least partially covers the grating surface and reflects incident light of a specific wavelength component incident on the grating surface;
The see-through display, wherein the transmissive layer has a uniform refractive index from the first surface to the second surface.
The hologram includes a first transmission layer that forms the first surface, and a second transmission layer that forms the second surface,
The see-through display according to claim 1, wherein the first transmissive layer having a refractive index equal to that of the second transmissive layer is in close contact with the second transmissive layer without a gap.
The see-through display according to claim 1 or 2, wherein the projection optical system causes the image light to be incident substantially perpendicular to the first surface.
The see-through display according to any one of claims 1 to 3, wherein the relief structure includes a blaze structure.
The image light is P-polarized light,
The see-through display according to claim 4, wherein the projection optical system causes the image light to be incident at least partially on the first surface at a Brewster angle.
The see-through display according to any one of claims 1 to 5, wherein the notch filter includes a dielectric multilayer film.
The grating surface includes a diffraction surface that diffracts the image light,
The see-through display according to claim 6, wherein the dielectric multilayer film is disposed only on the diffractive surface.
The see-through display according to any one of claims 1 to 7, wherein the notch filter includes a rugate filter.
The see-through display according to any one of claims 1 to 8, wherein the light source includes a laser light source that emits laser light.
The light source includes: a first light source that emits first light having a first wavelength; and a second light source that emits second light having a second wavelength different from the first wavelength;
10. The first transmission layer according to claim 1, wherein the first transmission layer includes a first hologram element that diffracts the first light and a second hologram element that diffracts the second light. See-through display described in 1.
The light source includes a blue light source that emits blue light, a green light source that emits green light, and a red light source that emits red light,
The first transmission layer includes a first hologram element that diffracts the blue light, a second hologram element that diffracts the green light, and a third hologram element that diffracts the red light. The see-through display according to claim 2.
The see-through display according to claim 11, wherein the third hologram element, the second hologram element, and the first hologram element are sequentially laminated from the first surface toward the second surface.
A head-up display mounted on a vehicle having a windshield including an inner surface that defines an indoor boundary,
The see-through display according to claim 1,
The head-up display, wherein the hologram is attached to the inner surface.
The front glass includes a first glass that forms the inner surface, a second glass that forms an outer surface opposite to the inner surface, and an absorption layer that absorbs ultraviolet light between the first glass and the second glass. Including,
The head-up display according to claim 13, wherein the hologram is disposed between the first glass and the absorption layer.
A head-up display mounted on a vehicle having a windshield including an inner surface that defines an indoor boundary,
The see-through display according to claim 10,
The first light has a shorter wavelength than the second light;
The head-up display, wherein the second hologram element is disposed between the first hologram element and the first surface.
A head mounted display including a lens unit disposed in front of a user's eyes,
The see-through display according to claim 1,
The head mounted display, wherein the hologram is disposed between the lens unit and the eye.