JPH06337316A - Display device - Google Patents

Abstract

PURPOSE:To provide the display device capable of exposing a hologram without using a glass block. CONSTITUTION:The light incident part 36 and the light outgoing part 37 of a light guide 1 are respectively obliquely cut in a wedge shape, and the holograms 4 and 5 are set on the wedge parts 2 and 3. Prisms 6 and 7 are stuck on the holograms 4 and 5, and the display device is one plate whose surface and a back surface are nearly parallel as a whole. A light source device is arranged on the light incident part of the light guide 1. Since the holograms 4 and 5 are obliquely set, an angle obtained when a laser beam is made incident on a hologram photosensitive material can be made equal to or below the critical angle of the hologram in air without using the glass block in the case of exposing the holograms 4 and 5. Thus, the exposing system of the holograms 4 and 5 is simplified.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device using a light guide having a hologram at an entrance portion or an exit portion.

[0002]

2. Description of the Related Art Conventionally, a transparent light guide having holograms installed at an entrance portion and an exit portion is used, and a light beam is made incident from one end of the light guide and guided through the light guide to be provided at another portion of the light guide. There is known a display device in which a light beam is emitted from the hologram. As such a conventional display device, there is a display device disclosed in, for example, Japanese Patent Laid-Open Nos. 1-502465 and 2-241849 and used for a center high mount stop lamp as shown in FIG.

That is, a light source device 102 is installed near the lower end of the light guide 101, a hologram 106 is provided above the light guide 101, and a hologram 107 is provided below the light guide 101.
Are provided respectively. The light source device 102 includes a bulb 103 such as an incandescent bulb, a parabolic mirror 104, and a filter 1.
05, the bulb 103 is arranged at the focal position of the parabolic mirror 104, and the light reflected by the parabolic mirror 104 becomes a parallel light flux. The parallel light flux is filtered by the filter 105 into a predetermined wavelength component such as red light.

In this way, the parallel light flux of a predetermined wavelength output from the light source device 102 enters the light guide from below the light guide 101 and is diffracted by the hologram 107. Then, the total reflection is repeatedly performed at the boundary surface 108 of the light guide 101 with the air, and enters the hologram 106 provided on the upper portion of the light guide 101. The hologram 106 diffracts the incident light flux to the rear of the vehicle and displays a center high mount stop lamp.

FIG. 12 shows an exposure system for the hologram 106 installed at the emitting portion. The exposure is performed according to a known technique. That is, the laser light corresponding to the object light of the center high mount stop lamp, which can be seen from the rear of the automobile, selects the output mode 110 of the diverging light by the spatial filter 111 that selects the mode of the light and widens the light flux. Then, the light enters the unexposed photosensitive material 116 through the glass block 112 made of optical glass. At the same time, after the laser light is made into a point light source by the spatial filter 114, it is made into parallel light reference light 113 by the convex lens 115, and is passed through the glass block 117 to the photosensitive material 116 at an angle equal to or less than the critical angle of the hologram 106. It is incident. Then, the output light 110 and the reference light 113
Are coherent with each other, a kind of interference fringe is recorded on the photosensitive material 116.

FIG. 13 shows an exposure system for the hologram 107 installed at the entrance. Similar to the exposure of the hologram 106 at the emitting portion, the laser light 1 corresponding to the hologram diffracted light
After 18 is made into a point light source by the spatial filter 119, it is made into parallel light by the convex lens 120. Then, the light enters the photosensitive material 122 through the glass block 121 at a critical angle of the hologram 107 or less. At the same time, the laser light 123, which is made into a point light source by the spatial filter 124 as reference light and becomes parallel light by the convex lens 125, is incident on the photosensitive material 122 at an angle equal to or less than the critical angle of the hologram 107 via the glass block 126. . Since the laser beams 118 and 123 are coherent with each other, the photosensitive material 1
Interference fringes are recorded at 22.

[0007]

However, in such a conventional display device, the exposure of the hologram requires the use of a glass block in order to avoid total reflection on the hologram surface. However, when the glass block is used, a jig for fixing the glass block is required, and there is a problem that the periphery of the hologram dry plate carrying the photosensitive material becomes complicated. In addition, since the glass block itself is thick, the spatial filter cannot be brought close to the hologram dry plate.
Therefore, the spread angle of the laser beam for exposing the hologram cannot be increased.

Therefore, the light distribution is limited, and if the light distribution is expanded beyond this limit, further measures are required. For example, when the display device is used as a center high mount stop lamp, the display must be visible within a range of ± 45 degrees from the rear front of the vehicle. Therefore, it is necessary to use a laser beam that spreads ± 45 degrees for hologram exposure. Therefore, as shown in FIG. 14, for example, the hologram size (for one lens) is set to 10
Even if it is a square mm, the thickness of the glass block 127 is 10 m.
In the case of m or more, the point light source must be located inside the glass block 127. As described above, it is often impossible to directly enter the light diverging from the point light source into a predetermined range such as the light emitted from the spatial filter simply by using the glass block.

Further, as shown in FIG. 15, it is conceivable that light is once converged by a convex lens or the like to expose a hologram. In that case, the distance L1 between the glass block 128 and the convex lens 129 is Distance L2 between hologram 130 and convex lens 131 when no glass block is used
However, there is a restriction that the size becomes smaller than that of the above, and the design and assembly of the exposure system becomes difficult. As a countermeasure against this, if a large convex lens is used, it is possible to increase the distance L1 between the glass block 128 and the convex lens 129. However, since the size of the optical component increases, the size of the fixing jig increases. Little practical effect. Moreover, when the size of the optical component is increased,
Vibration may occur due to the influence of air convection and the like, and in that case, the hologram cannot be actually exposed.

As described above, in the conventional display device, it is necessary to use the glass block for the exposure of the hologram, which requires a lot of man-hours for the exposure and it is difficult to increase the spread of the exposure light. There is a problem in that the number of man-hours is further increased and the cost is increased when the size is increased. Therefore, an object of the present invention is to provide a display device which pays attention to such a conventional problem and allows a hologram used to be exposed without using a glass block.

[0011]

For this reason, the present invention has a light source, an incident part and an emission part, and guides a light beam incident on the incidence part to the emission part by reflecting it between reflection surfaces which are substantially parallel to each other. In a display device including a light guide and a hologram provided in at least one of the incident part and the exit part, the hologram is installed in a wedge part obliquely cut with respect to a reflection surface of the light guide, It is assumed that the hologram can be exposed in air at a critical angle or less.

[0012]

The function of the light guide is such that the entrance portion or the exit portion has a wedge shape, and the hologram is installed on this wedge portion. Therefore, when the hologram is exposed, the incident angle of the laser beam to the hologram photosensitive material is adjusted by air without using a glass block or the like. It can be set to be equal to or less than the critical angle of the hologram therein. This simplifies the hologram exposure system.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment in which the present invention is applied to a center high mount stop lamp of an automobile. The light guide 1 is arranged so as to be inclined along with a rear window glass (not shown) of an automobile. The light guide 1 is formed of a parallel plate having a thickness of several mm to several tens of mm and made of a transparent material such as acrylic. The light guide 1 has a lower end portion as an incident portion 36 and an upper end portion as an emitting portion 37, and wedge portions 2 and 3 are formed by obliquely cutting in a wedge shape.

A hologram 4 is installed on the upper wedge portion 2, and a hologram 5 is installed on the lower wedge portion 3. Further, prisms 6 and 7 are attached to these holograms 4 and 5, respectively. Prisms 6 and 7
Is made of the same transparent material as the light guide 1, and has a wedge shape with the same angle as the light guide 1. As a result, the holograms 4 and 5 and the prisms 6 and 7 are sequentially joined at the upper and lower ends of the light guide 1 to form a single plate whose front and back surfaces are substantially parallel to each other as a whole.
Further, the surface of the light guide 1 is protected by the surface protection film 8, and all the edge portions except the wedge portions of the light guide 1 and the prisms 6 and 7 are prevented so that unnecessary light does not enter the light guide 1 from the edges. A light-shielding layer 9 such as a black coating is applied to.

A light source device 10 including a light source 11 such as an incandescent bulb, a parabolic mirror 12 and a color filter 13 is arranged near the lower end of the light guide 1. The light source 11 is arranged at the focal position of the parabolic mirror 12, and the light reflected by the parabolic mirror 12 becomes a parallel light flux. The parallel light flux is filtered by the color filter 13 into a predetermined wavelength component. As a result, in this embodiment, the red light 14 is obtained because of the red display of the center high mount stop lamp.

The red light 14 is incident on the incident portion 3 of the light guide 1.
It is diffracted by the hologram 5 installed at 6. Here, the traveling angle θL is set to be larger than the critical angle of the light guide 1 so that the diffracted light 15 travels in the light guide 1 by repeating total reflection. The light 15 that has traveled through the light guide 1 reaches the hologram 4 installed in the emitting portion 37 and is diffracted by the hologram 4.
Here, the diffracted light has a traveling angle smaller than the critical angle and is emitted to the outside of the light guide 1 as the display light 16 of the center high mount stop lamp.

FIG. 2 shows various angles around the hologram 4 installed in the emitting portion 37. The emission angle of the display light 16 determined from the external conditions of the center high mount stop lamp display direction and the inclination angle of the light guide 1 is θ D,
Let θ L be the traveling angle of the light 15 traveling in the light guide 1. With reference to the normal line 18 to the surface of the light guide 1, the incident angle θin1 of the light 15 traveling in the light guide to the hologram 4 and the outgoing angle θout1 of the reproduction light 17 diffracted by the hologram 4 are as follows. Let nLG be the refractive index and nH be the average refractive index of hologram 4,
Is approximately equal to nLG, θin1 = 90−θL (1) θout1 = sin ⁻¹ (sin (θD) / nLG) (2). The angle unit is (°) (hereinafter the same).

Assuming that the inclination angle of the hologram 4 is θH1, the incident angle θin1 'and the exit angle θout1' with respect to the normal line 19 to the surface of the hologram 4 are θin1 '= θin1−θH1 (3) θout1 ′ = θout1− It becomes θH1 (4). Now, assuming that the wavelength of the reproduction light is equal to the wavelength of the laser light for exposing the hologram, the incident angle of the exposure laser light is the incident angle θin1 'of the reproduction light and the emission angle θou.
Same as t1 '.

The conditions under which exposure is possible without using a glass block are that | θin1 '| and | θout1' | are both smaller than the critical angle θc on the hologram surface, and | θL | <90-θc That is. However, θc = sin ⁻¹ (1 / nH) (5). Here, the refractive index of the glass block is approximately equal to the refractive index nLG of the light guide 1.

According to the above conditions, | θin1 −θH1 | <θc (6) | θout1 −θH1 | <θc (7) Therefore, θin1 −θc <θH1 <θin1 + θc (8) θout1−θc <θH1 <θout1 + θc (9) is obtained.

When the layout is tilted contrary to the layout of FIG. 2, the angle is calculated as negative. Also, θin1 '> 9
Since it is 0, in that case, | 180−θin1 '| <
θc is a condition that does not require a glass block.

Next, based on the above, a specific numerical example will be described. Here, when nH = 1.5, θc = sin ⁻¹ (1 / 1.5) = 41.8. In the example shown in FIG. 2, θD = 60, θL
= 25 and nLG = 1.5, θin1 = 65 θout1 = 35.3 θin1 ′ = 35 θout1 ′ = 5.3.

From equations (8) and (9), 23.2 <θH1 <106.8-6.5 <θH1 <77.1 Therefore, 23.2 <θH1 <77.1 is obtained. Therefore, if the inclination angle θH1 of the hologram 4 is selected to be 30 °, 50 °, or 75 °, the hologram can be exposed without using a glass block. However, if the tilt angle θH1 is set to a large value, the hologram area becomes very small. Therefore, it is generally better to make the value of θH1 as small as possible.

Next, FIG. 3 shows various angles around the hologram 5 installed in the light incident portion 36. Light guide 1
The incident angle of the light 14 from the light source device 10 is θ A, and the traveling angle of the light traveling in the light guide 1, that is, the reproduced light 15 of the hologram 5 is θ L ′. This θL 'has the same absolute value as the traveling angle θL of the light 15 traveling through the light guide described in FIG. Light 22 incident on the hologram 5
Angle θin with respect to the surface normal 20 of the light guide 1 of
2 and the emission angle θout2 of the reproduction light 15 of the hologram 5 is θin2 = sin ⁻¹ (sin (θA) / nLG) (10) θout2 = 90−θL ′ (11).

Assuming that the inclination angle of the hologram 5 is θH2, the incident angle θin2 ′ and the exit angle θout2 ′ with respect to the normal line 21 on the surface of the hologram 5 are θin2 ′ = θin2 + θH2 (12) θout2 ′ = θout2-θH2 (13) Becomes As for the hologram 5, as in the case of the hologram 4 described above, both of | θin2 ′ | and | θout2 ′ | are smaller than the critical angle θc of the hologram 5 in the air. Will be the condition that can be exposed. That is, the following formula may be satisfied. -Θin2 -θc <θH2 <-θin2 + θc (14) θout2-θc <θH2 <θout2 + θc (15)

When tilted in the opposite manner to the layout of FIG. 3, the angle is calculated as negative. Also, θout2 '> 9
Therefore, in this case, | 180−θout2 ′ | <
θc is a condition under which the hologram 5 can be exposed without using a glass block.

Next, specific numerical examples will be described. In the example shown in FIG. 3, θA = 0 and θL ′ = 25. nLG
= 1.5. In this case, θin2 = 0 θout2 = 65 θin2 '= 30 θout2' = 35.

From equations (14) and (15), −41.8 <θH2 <41.8 23.2 <θH2 <106.8 Therefore, 23.2 <θH2 <41.8 is obtained. Therefore, if the inclination angle θH2 of the hologram 5 is selected to be 30 ° or 40 °, the hologram can be exposed without using a glass block. However, in order to secure a large hologram area, it is better to make θH2 smaller.

Next, the exposure of the hologram described above will be described. FIG. 4 shows an exposure system for the hologram 4 as an emitting element. Here, the wavelength of light for exposure and the wavelength of light for reproduction are the same. The exposure is performed according to a known technique. That is, the laser light 23 corresponding to the reproduction light 17 is incident on the unexposed hologram photosensitive material 25 as an angle of incidence s as point light source light by the spatial filter 24.
It is incident at in ⁻¹ ((sin θout1 ′) / n). on the other hand,
The laser light 26 of the reference light is incident on the photosensitive material 25 at an incident angle sin ⁻¹ ((sin θin1 ′) / n) as parallel light from the spatial filter 27 and the convex lens 28. Here, if θH1 is within the range that satisfies the expressions (8) and (9), the laser light 26 of the reference light is not totally reflected.

Since the laser beams 23 and 26 are coherent with each other, a kind of interference fringe is recorded on the photosensitive material 25. At this time, a change in the phase of the laser light 23 relative to the laser light 26 of the reference light causes lateral shift of the interference fringes, and a change in amplitude is recorded as a change in contrast.
All of the information on the phase and amplitude of the laser light 23 is recorded in 5. The hologram 4 is obtained by developing the exposed photosensitive material 25.

Then, as shown in FIGS. 1 and 2,
When the hologram 4 is irradiated with the light 15 which is the reproduction illumination light, the interference fringes recorded in the hologram 4 in the form of brightness and darkness act as a diffraction grating that changes the traveling direction of the light, and the reproduction light 17, and thus the center high light. The display light 16 of the mount stop lamp is obtained.

FIG. 5 shows a hologram 5 as an incident element.
The exposure system of is shown. The laser light 29 corresponding to the light 15 becomes parallel light by the spatial filter 30 and the convex lens 31, and enters the photosensitive material 32 at an incident angle sin ⁻¹ ((sin θout
It is incident at 2 ') / n). On the other hand, the reference laser light 33
Is collimated by the spatial filter 34 and the convex lens 35 and is incident on the photosensitive material 32 at an angle of sin ⁻¹ ((sin θin 2 ') / n). And laser light 29 and 3
Since 3 and 3 are coherent with each other, interference fringes are recorded on the photosensitive material 32. Light-sensitive material 3 thus exposed
The hologram 5 is obtained by developing the hologram 2.

In the display device of this embodiment using the holograms 4 and 5 thus exposed and developed, the light source device 10 is used.
Emits substantially parallel red light 14 when the light source 11 is turned on. The red light 14 enters the light guide 1 and is diffracted by the hologram 5 at an angle larger than the critical angle of the light guide 1. The diffracted light 15 travels in the light guide 1 by repeatedly undergoing total reflection and enters the hologram 4. The light 15 incident on the hologram 4 is diffracted by the hologram 4 at an angle smaller than the critical angle, and the diffracted reproduction light 17 becomes the display light 16 of the center high mount stop lamp and is emitted to the outside of the light guide 1 to exit from the stop lamp. Display.

Even if the prisms 6 and 7 are not attached, the path of the display light is not obstructed, but in this embodiment, the prism 6 is attached to the upper wedge portion 2 of the light guide 1 and the prism 7 is attached to the lower wedge portion 3. As a whole, the front surface and the back surface are substantially parallel to each other, so that the appearance is good, and at the same time, the edge of the edge portion is prevented from being damaged.

6 and 7 show a second embodiment of the present invention. In this embodiment, a transmissive hologram is used as the emitting element of the emitting section. That is, the upper portion of the light guide 41 is obliquely cut in the direction opposite to that of the previous embodiment to form the wedge portion 42. This wedge part 4
The transmission type hologram 43 is attached to the slope of No. 2, and the prism 44 is attached to the outside of the hologram 43.
3 is formed.

The light incident portion 45 has a shape in which the lower end of the light guide 41 is partially increased in thickness in accordance with the incident angle of light to facilitate the incidence of light. Further, below the light guide 41, a light source device 46 including a light source 47 such as an incandescent bulb, a parabolic mirror 48, and a color filter 49 is arranged so as to face the lower end surface of the light guide 41.
The outer surface of the light guide 41 is protected by a surface protection film 52.

As shown in FIG. 7, the prism 44 has a wedge surface having the same angle θH3 as the inclination angle θH3 of the wedge of the light guide 41, and is attached to the hologram 43 on the wedge surface. Face angle θ
It has a wedge shape of W. This controls the extraneous light. That is, when the light 51 having a trajectory opposite to the trajectory of the traveling light 50 in the light guide input to the hologram 43 described later enters from the outside of the light guide, it is diffracted by the hologram 43 in the direction opposite to the traveling light 50. This diffracted light may act as unnecessary light in some cases. Therefore, the wedge shape of the prism 44 is set to the locus 5 so that the extraneous light on the locus 51 does not exist.
As the condition that the light of No. 1 does not exist, it is assumed that the angle θW satisfies θR2 = | 90−θW−θL |> θc (16).

The symbols of the angles in FIG. 7 which are the same as those in the previous embodiment are the same as those in the previous embodiment, so the explanations are omitted. Also in this embodiment, the same effect can be obtained by applying the angle θH1 in the previous embodiment to the wedge angle θH3, and the hologram 4 can be obtained without using the glass block.
3 exposures are possible. In this embodiment, the light source device 4
When the light source 47 of No. 6 is turned on, substantially parallel red light 61 is emitted and enters the light guide 41 from the incident portion 45. The light 50 that has traveled through the light guide 41 by repeating total reflection enters the hologram 43 installed in the emitting portion 63. The light 50 that has entered the hologram 43 is diffracted by the hologram 43 and is emitted to the outside of the light guide 41 to become display light 62 which is displayed by the center high mount stop lamp.

Incidentally, the hologram can be exposed by changing the wavelength for reproducing and displaying and the wavelength for exposing. The hologram exposure is the laser 2 as described above.
Recording a kind of interference fringes formed by the interference of light beams in a holographic photosensitive material. And this interference fringe acts as a diffraction grating. The laser beam used for the exposure satisfies the Bragg condition for this diffraction grating. If this Bragg condition is met during reproduction, diffraction will occur even if the incident angle or wavelength changes. Therefore, by utilizing this characteristic, the display layout and the exposure layout can be changed.

An example using this Bragg condition based on the configuration of FIG. 6 will be described below as a third embodiment. First, the Bragg condition will be described with reference to FIG. If the incident angle to the diffraction grating is θ1 and the diffraction wavelength (exposure wavelength) is λ1,
The Bragg condition is defined as the condition that λ1 / n = 2d · cos θ1 (17) holds, where d is the grating interval of the diffraction grating and n is the refractive index. Where d and n
Is a constant determined by the hologram.

As shown in FIG. 9, the light guide 4 during reproduction.
The incident angle at the time of exposure is calculated from the angles θin3 and θout3 from the normal line 53 of one surface. The angle φ formed by the normal line of the light guide surface and the normal line of the diffraction grating is φ = 90− (θin3−θout3) / 2 (18) The incident angle θ0 of the laser beam on the diffraction grating is θ0 = 90− (θin3 + Θout3) / 2 (19).

When the reproduction wavelength is λ 0 and the exposure wavelength is λ R, the incident angle θ 0 ′ of the light upon exposure to the diffraction grating is θ 0 ′ = cos ⁻¹ ((λ R / λ 0) × cos θ 0) (20) . Hereinafter, the incident angle θR1 and the exit angle θS1 during the exposure with respect to the normal line 53 of the light guide surface are θR1 = 180−φ−θ0 ′ (21) θS1 = φ−θ0 ′ (22) The exposure with respect to the normal line 54 of the hologram surface Incident angle θR
1 ′ and the emission angle θS1 ′ are θR1 ′ = θR1−θH3 (23) θS1 ′ = θS1 + θH3 (24).

By setting both | θR1 ′ | and | θS1 ′ | to be smaller than θc, the hologram 43 is exposed without using the glass block.
That is, the following formula is the condition. θR1−θc <θH3 <θR1 + θc (25) −θS1−θc <θH3 <−θS1 + θc (26)

Next, a specific numerical example will be described. In the configuration shown in FIG. 6, θD = 0, θL = 15, nLG = 1.5, λ0
= 620 and .lambda.R = 488. In this case, θin3 = 75, θout3 = 0 φ = 52.5, θ0 = 52.5 θ0 ′ = 61.4, and θR1 = 66.1 θS1 = −8.9.

From equations (25) and (26), 24.3 <θH3 <107.9-32.9 <θH3 <50.7 From this, 24.3 <θH3 <50.7 is obtained. Therefore, the inclination angle θH3 of the hologram 43
By setting, for example, 30 ° or 40 °, the hologram 43 can be exposed without using a glass block.

FIG. 10 shows an exposure system for the hologram 43.
The laser light 55 corresponding to the hologram emission light is made into a point light source light by the spatial filter 56 and is incident on the unexposed photosensitive material 57 at an angle θS1 ′. On the other hand, the laser light 58 of the reference light is collimated by the spatial filter 59 and the convex lens 60 and is incident on the photosensitive material 57 at an angle θR1 ′. Since the laser beams 55 and 58 are coherent with each other, interference fringes are recorded on the photosensitive material 57. Then, the hologram 43 is obtained by developing this. Although the third embodiment, in which the reproduction wavelength and the exposure wavelength are different, is shown for the transmission type hologram, the same applies to the reflection type hologram.

[0047]

As described above, according to the present invention, the end portion of the light guide is obliquely cut in a wedge shape, and the hologram is set on the wedge portion. Therefore, the incident angle of light to the hologram is set in the air. The hologram can be exposed at a critical angle less than that of the hologram, and the hologram photosensitive material can be exposed without using a glass block. As a result, the hologram exposure system is simplified, the yield is improved, and the divergence angle of the hologram diffracted light can be increased.

[Brief description of drawings]

FIG. 1 is a sectional view showing a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing various angles regarding a hologram installed in an emission unit.

FIG. 3 is an explanatory diagram showing various angles regarding a hologram installed in an incident part.

FIG. 4 is an explanatory diagram showing an exposure system for holograms installed in an emission unit.

FIG. 5 is an explanatory diagram showing an exposure system for holograms installed in an entrance portion.

FIG. 6 is a cross-sectional view showing a second embodiment of the present invention.

FIG. 7 is an explanatory diagram showing various angles regarding a hologram installed in an emission unit.

FIG. 8 is an explanatory diagram showing a black condition of a hologram.

FIG. 9 is an explanatory diagram of angles between exposure and reproduction of a hologram according to the third embodiment.

FIG. 10 is an explanatory diagram showing a hologram exposure system.

FIG. 11 is a cross-sectional view showing a conventional example.

FIG. 12 is an explanatory view showing an exposure system for holograms installed in the emission unit.

FIG. 13 is an explanatory diagram showing an exposure system for holograms installed in the incident part.

FIG. 14 is an explanatory view showing a comparison of the method of incidence of a point light source when a glass block is used and when it is not used in an exposure system.

FIG. 15 is an explanatory diagram showing the positions of convex lenses in the exposure system when the glass block is used and when it is not used.

[Explanation of symbols]

1, 41 Light guide 2, 3, 42 Wedge portion 4, 5, 43 Hologram 6, 7, 44 Prism 10, 46 Light source device 14 Red light 15 Light traveling in light guide 16 Center high mount stop lamp 23, 26, 29, 33, 55, 58 Laser light 25, 32, 57 Photosensitive material 36, 45 Incident part 37, 63 Emitting part θH1, θH2, θH3 Hologram tilt angle θL Travel angles θin1, θin2, θin3 Incident angles to hologram θout1, θout2 , Θout3 Emitted angle of hologram diffracted light (reconstructed light) θR1, θS1 Incident angle during exposure

Claims (3)

[Claims] 1. A light source, a light guide having an entrance portion and an exit portion for guiding a light beam incident on the entrance portion to the exit portion by reflecting the light flux between reflection surfaces substantially parallel to each other, and the entrance portion. In a display device provided with a hologram provided in at least one of the emission parts, the hologram is installed in a wedge part cut obliquely with respect to the reflection surface of the light guide, and the hologram has a critical angle in air. A display device which is configured to be exposed below. 2. The hologram is provided in an emission part, and the hologram is emitted from the light guide with a refractive index of the light guide being nLG and an average refractive index of the hologram being nH, with reference to a normal line of a reflecting surface of the light guide. The output angle of the display light is θ
D, the incident angle of the light incident on the hologram is θin, the outgoing angle of the diffracted light by the hologram is θout, the traveling angle of the light beam traveling in the light guide with respect to the reflecting surface of the light guide is θL, and the inclination of the wedge portion is When the angle is θH, the inclination angle θH is θin−θc <θH <θin + θc θout−θc <θH <θout + θc | θL | <90−θc where θin = 90−θL θout = sin ⁻¹ (sin ( 2. The display device according to claim 1, wherein .theta.D) / nLG) .theta.c = sin ^-1 (1 / nH) is set. 3. The hologram is provided in an incident part, the light guide has a refractive index of nLG, the hologram has an average refractive index of nH, and the light guide is provided with a light source from a light source on the basis of a normal line of a reflecting surface of the light guide. The incident angle of incident light is θA, and the incident angle of light incident on the hologram is θi.
n, the outgoing angle of the diffracted light by the hologram is θout,
The traveling angle of the light beam traveling in the light guide with respect to the reflecting surface of the light guide is θL, and the inclination angle of the wedge portion is θH.
Where, the inclination angle θH is −θin−θc <θH <−θin + θc θout −θc <θH <θout + θc | θL | <90−θc where θin = sin ⁻¹ (sin (θA) / nLG) θout 2. The display device according to claim 1, wherein the display device is set so as to satisfy the following formula: 90-.theta.L.theta.c = sin.sup.- ¹ (1 / nH).