JPH07186777A - Head up display and its design method, and combiner - Google Patents

Abstract

PURPOSE:To respectively secure a transparent view having no complementary color and a color tone resembling white being little in color change by applying a hologram exposed so as to turn into a specified state to a combiner which is arranged on the windshield glass of a vehicle to diffract light for making a driver visibly recognize it. CONSTITUTION:A head up display has an information display source provided below a windshield glass 7 in a vehicle. The information display source turns light issued from a light source 6 into information through a lens system 4 and a display body 5, and irradiates it onto the combiner 2 of the windshield glass 7 to make a driver visibly recognize it. On the other hand, the display images of speed 8 and an alarm 8 are formed far away as occasion demands. In this case, the combiner 2 is formed from a hologram. The hologram is exposed so that the central wave length, half-value width and diffraction efficiency of diffraction spectrum may be combined so as to lessen a color difference from the average color tone between light source light and reflection light or to lessen the square sum of color difference.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a head-up display (hereinafter referred to as HUD) for displaying driving information and the like to a driver of a vehicle, a combiner used for the head-up display, and a method for designing the HUD.

[0002]

2. Description of the Related Art HUD has recently been used as a method of displaying information to a driver in an automobile or the like.
This is because the optical information projected from the information projection means such as a liquid crystal display device is projected on a combiner composed of a hologram or a half mirror incorporated in the windshield of an automobile, etc., and the driver almost moves the viewpoint from the driving state. The information can be read without any need.

In particular, a hologram using a hologram as a combiner can have a lens function and the like as well as a function of diffracting optical information toward the driver.
Optical information can be diffracted in the direction of the driver's visual field, or an image can be formed at an arbitrary position without using an optical system such as a lens, and the high brightness can be obtained without impairing the foreground brightness. HU has the feature that a display image of brightness can be obtained.
It is effective as a D combiner.

FIG. 9 is a conceptual diagram showing an example of a conventional HUD. The light 43 including the information to be displayed, which is emitted from the light source 46 and passed through the transmissive liquid crystal display element 45 via the lens system 44, is applied to the hologram 42 provided on the windshield 47 of the vehicle body and is diffracted to be transmitted to the driver. It is visually recognized at the observation position 41.

The lens system 44 has a function as a collimator, and the function is the hologram 4.
It can be attached to 2 and speed display 48, warning display 49
It is also possible to form the display image of (1) in the distance.

Further, since the hologram 42 has a wavelength selection function, an image of a desired color can be displayed. Usually, the color is often single, but multi-color display by multiple exposure is also possible, and the quantity and quality of display information can be improved. For example, by setting the speed display 48 to green and the warning display 49 to red, the information can be more accurately transmitted to the driver.

As described above, since the conventional HUD diffracts light of a specific wavelength, when the driver looks outside through the hologram, the color of the transmitted light is a color corresponding to the diffraction wavelength of the hologram (display color). ) Is a complementary color. That is, when the display color is only green as shown in FIG. 6, when the white light 72 from the outside is transmitted through the hologram 71, it is partially reflected and diffracted by the diffraction grating inside the hologram, and the reflected light 73 becomes green. Become. Therefore, the transmitted light 74 becomes magenta (pink to red) which is the complementary color of the transmitted light 74, and is perceived as an irritating and unpleasant color for the driver 75. Further, as a result, the color tone of the background is affected, and the visibility of the condition outside the vehicle such as the road during driving is impaired, which is a safety issue.

On the other hand, as shown in FIG. 7, the outside light 82 is applied to an observer 85 (a pedestrian, a driver of an oncoming vehicle, etc.) outside the vehicle.
Due to the angle dependence of the diffraction wavelength of the diffraction grating inside the hologram 81, the reflected color of the changes greatly from red (observation near the front) 83 to green (oblique observation) 84 depending on the angle of observation, which also gives an unpleasant impression, As a result, there was a problem that the designability and commercialability of the vehicle equipped with it were impaired.

FIG. 8 is a chromaticity diagram showing a simulation result of the color change of the reflected color. The chromaticity diagram is JIS-Z8
The color is quantitatively expressed by the chromaticity coordinates x and y defined by 701. In FIG. 7, a dot X shown as a light source represents white. The closer the color of the hologram is to this point, the closer it is to white and the more preferable the color is for the observer.

However, the color of the reflected light of the monochromatic hologram used in the conventional HUD is, for example, a wavelength of 545 nm,
When the diffraction efficiency is 60%, it changes as shown by the black diamonds in FIG. That is, it turns out that the color near the front becomes red, and as it becomes oblique, it changes greatly to orange, yellow, and green. When viewed from the front, the color is red, which is a stimulus color, and when viewed from an angle, it becomes a glare green with high visibility and gives an unpleasant impression to the observer.

Therefore, Japanese Laid-Open Patent Publication No. 4-110984,
In USP 5,153,751, in order to improve the color tone of the reflected light by the first hologram used for display in order to improve the color tone of the reflected light for the observer outside the vehicle, the reflection color of the first hologram is complemented. A HUD is disclosed that stacks or multiple-exposes a second hologram that reflects a near color. However, since it is composed of two holograms corresponding to two colors, the color tone may not be improved completely in some cases. Especially for green light (light having a wavelength of about 500 to 560 nm) frequently used as a display color, light having a wavelength corresponding to a complementary color does not exist. Therefore, there is a drawback that it is actually difficult to improve the color tone of the reflected color,
Moreover, the color tone of the transmitted light was not improved.

Further, in Japanese Patent Laid-Open No. 3-179418, in order to improve the color tone of light transmitted through a combiner,
A wavelength λ that is a complementary color to the reflection wavelength λ ₁ of the hologram for display.
HU that combines optical elements that reflect or attenuate ₂ light
D is disclosed. Also in this example, since the color correction is performed by the two-color configuration as in the above-mentioned known example, there is a similar drawback that the green light cannot be completely improved, and the color tone of the reflected light is improved. There wasn't.

Japanese Patent Laid-Open No. 4-291221 discloses that light in a wavelength range complementary to the reflection wavelength λ ₁ of a hologram for display is synthesized so that the color tone of transmitted light of a combiner can be improved even with respect to green light. A HUD is disclosed that combines optical elements that reflect or attenuate multiple possible wavelength ranges.
Since this example is an improvement only on the color tone of the transmitted light, it is effective only at a specific angle connecting the hologram and the observer. Therefore, the color tone of the reflected light of the hologram was not necessarily improved for the observer outside the vehicle. For example, in the disclosed embodiment, in order to improve the color tone of the transmitted light of the hologram that diffracts the light of 530 nm, 530
A hologram that diffracts light of 460 nm and 630 nm capable of synthesizing complementary colors of nm light is used.
%, And the half-value width is about 10 nm.
A color tone simulation of the reflected color of the combiner observed outside the vehicle based on this characteristic is as shown in FIG. 10, and it can be seen that the oblique observation makes it relatively white, but the front observation makes it yellow green.

As described above, it has been proposed to use a plurality of holograms in order to improve the color tone of the reflected light and the transmitted light of the holographic combiner, but since the characteristics are not optimized, a sufficient improvement effect is obtained. There was a problem that was not obtained.

[0015]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and is an information display that includes at least a light source and a display body that displays information to be displayed, and that generates information to be displayed as light. In a HUD including at least a light source and a combiner provided on a windshield of a vehicle and diffracting the light toward an observer in the vehicle, the combiner is an external light transmitted from the outside of the vehicle to the inside of the vehicle through the combiner. The color tone and the color tone of the reflected light of the outside light by the combiner observed outside the vehicle, which is a hologram exposed by light of a plurality of colors selected so as to be close to white when observed from any angle, the information comprising When the light emitted from the display source toward the combiner is diffracted toward the observer in the vehicle, the central wavelength λ, the half width Δλ and the diffraction efficiency And is a combination that reduces the color difference between the color tone of the light source and the average color tone of the reflected light when observing at different angles, or the color tone of the light source when observing at different angles and the combiner A HUD characterized by being a hologram that is exposed so as to form a combination that reduces the sum of squares of the color difference with the color tone of the reflected light.

Further, the present invention is a HUD combiner which is provided on a windshield of a vehicle and diffracts light containing information from an information display source toward an observer in the vehicle, from outside the vehicle through the combiner. The color tone of the external light transmitted through the vehicle, and the color tone of the reflected light of the external light by the combiner observed outside the vehicle, by the light of a plurality of colors selected so as to be close to white even when observed from any angle, When the light emitted from the information display source toward the hologram is diffracted toward the observer in the vehicle, the center wavelength λ of the diffraction spectrum, the half width Δλ and the diffraction efficiency η are the same as the color tone and the angle of the light source. Is it a combination that reduces the color difference from the average color tone of the reflected light by the combiner when changing and observing,
There is provided a combiner comprising a hologram exposed so as to make a combination that reduces a sum of squares of color differences between a color tone of a light source light and a color tone of reflected light by the combiner when observed at different angles.

Further, according to the present invention, an information display source that includes at least a light source and a display body that displays information to be displayed and that generates information to be displayed as light, and a windshield of a vehicle are provided with the light. Is a method for designing a HUD including at least a combiner that diffracts light toward an observer in the vehicle, wherein the combiner serves as a color tone of external light transmitted from the outside of the vehicle through the combiner into the vehicle and the outside of the vehicle. When using the hologram exposed by the light of multiple colors selected so that the color tone of the reflected light of the external light by the combiner is close to white when viewed from any angle, from the information display source to the combiner. When the emitted light is diffracted toward the observer in the vehicle, the center wavelength λ of the diffraction spectrum, the half width Δλ and the diffraction efficiency η are Provide a method for designing a HUD, characterized in that a hologram exposure condition is set by selecting a combination that reduces the color difference between the color tone of light and the average color tone of light reflected by a combiner when observed at different angles. To do.

The color difference is expressed by the following definition, for example.

(1) L ^* specified by JIS-Z8730
a ^* b ^{* is the} color difference ΔE ^* _ab due to the color system, the difference in lightness index is ΔL ^* , the difference in chromaticness index is Δa ^* , Δb.
^{As *} , ΔE ^* _ab = [(ΔL ^* ) ² + (Δa ^* ) ² +
(Δb ^* ) ² ] ^1/2 .

(2) L ^* specified by JIS-Z8730
a ^* b ^{* is the} color difference ΔE ^* _ab due to the color system, the difference in lightness index is ΔL ^* = 0, and the difference in chromaticness index is Δa.
^{As *} and Δb ^* , ΔE ^* _ab = [(Δa ^* ) ² + (Δb
^* ) ² ] ^{Expressed as 1/2} .

(3) L ^* specified by JIS-Z8730
u ^* v ^{* is the} color difference ΔE ^* _uv due to the colorimetric system, the difference in lightness index is ΔL ^* , the difference in chromaticness index is Δu ^* , Δv.
^{As *} , ΔE ^* _uv = [(ΔL ^* ) ² + (Δu ^* ) ² +
(Δv ^* ) ² ] ^1/2 .

(4) L ^* specified by JIS-Z8730
u ^* v ^{* is the} color difference ΔE ^* _uv due to the color system, the difference in the lightness index is ΔL ^* = 0, the difference in the chromaticness index is Δu ^* ,
As Δv ^* , ΔE ^* _uv = [(Δu ^* ) ² + (Δv ^* )
² ] ^1/2 .

(5) The color difference ΔE _AN according to the Adams-Nickerson color difference formula defined by JIS-Z8730,
The difference in lightness index is ΔV _Y , and the difference in chromaticness index is Δ
(V _X −V _Y ), Δ (V _Z −V _Y ), ΔE _AN = 4
0 [{0.23ΔV _Y } ² + {Δ (V _X −V _Y )} ² +
It is represented by {0.4Δ (V _Z −V _Y )} ² ] ^1/2 .

(6) The color difference ΔE _AN according to the Adams-Nickerson color difference formula defined by JIS-Z8730,
Let ΔV _Y = 0 be the difference in lightness index and Δ (V _X −V _Y ), Δ (V _Z −V _Y ) be the difference in chromaticness index, and ΔE _AN
= 40 [{Δ (V _X −V _Y )} ² + {0.4Δ (V _Z −
V _Y )} ² ] ^1/2 .

(7) Color difference ΔE _H according to the Hunter color difference formula defined by JIS-Z8730, where the difference in lightness index is ΔL and the difference in chromaticness index is Δa and Δb.
ΔE _H = [(ΔL) ² + (Δa) ² + (Δb) ² ] ^1/2
It is represented by.

(8) Color difference ΔE _H according to Hunter's color difference formula defined by JIS-Z8730, where ΔE _H = [(ΔL), where ΔL = 0 is the difference in lightness index and Δa and Δb are the differences in chromaticness index. ² + (Δa) ² + (Δb) ² ]
^{Expressed as 1/2} .

(9) XY specified by JIS-Z8701
In the chromaticity coordinates in the Z color system, the distance between the chromaticity coordinate point of the light source and the chromaticity coordinate point of the reflected light of the combiner [(Δ
x) ² + (Δy) ² ] ^1/2 .

(10) X specified by JIS-Z8701
₁₀ Y ₁₀ Z _{10 In} the chromaticity coordinates in the color system, the distance between the chromaticity coordinate point of the light source and the chromaticity coordinate point of the reflected light of the combiner [(Δx ₁₀ ) ² + (Δy ₁₀ ) ² ] ^1/2 Represent

(11) L specified by JIS-Z8729
^* u ^* v ^{* In} the chromaticity coordinates in the color system, the distance between the chromaticity coordinate point of the light source and the chromaticity coordinate point of the reflected light of the combiner [(Δu ') ² + (Δv') ² ] ^1/2 Represent

(12) L specified by JIS-Z8729
^* u ^* v ^{* In} the chromaticity coordinates in the color system, the distance between the chromaticity coordinate point of the light source and the chromaticity coordinate point of the reflected light of the combiner [(Δu ₁₀ ') ² + (Δv ₁₀ ') ² ] ^{1 /} Expressed as ² .

(13) It is represented by the difference between the saturation of the light source and the saturation of the reflected light of the combiner in the three attributes defined by JIS-Z8721, that is, in the color display method based on hue, brightness and saturation.

(14) The difference between the saturation of the light source and the Munsell chroma of the reflected light from the combiner in the Munsell color system devised by Munsell and specified by the Colorimetric Committee of the Optical Society of America in 1943.

These color differences are all functions of the central wavelength λ of light diffracted by the hologram, the half width Δλ, and the diffraction efficiency η. That is, these color differences are the tristimulus values X of the object color due to reflection or transmission in the XYZ color system,
It is obtained from Y and Z (other color systems are represented by the XYZ color system).

The tristimulus values X, Y and Z of the object color due to reflection in the XYZ color system are determined by the following equations.

[0035]

[Equation 1]

The tristimulus values X, Y and Z of the object color due to transmission in the XYZ color system are determined by the following equations.

[0037]

[Equation 2]

[0038]

[Equation 3]

On the other hand, when the hologram exposed at a predetermined angle is observed from a certain angle, the center wavelength λ, the half width Δλ and the diffraction efficiency η of the diffraction spectrum of the hologram are R
It is determined by (λ) and τ (λ), and is based on the Bragg condition and the coupled wave theory of Hewing Kogelnik (The Bell System Technical Journal, Vol. 48, pages 2909 to 2947 (1969)). Can be calculated. Therefore, it can be seen that the color difference is a function of the central wavelength λ, the half width Δλ, and the diffraction efficiency η.

Thus, the central wavelength λ, the half width Δλ, and the diffraction efficiency η can be selected as various combinations based on the above equation so as to reduce the color difference.

[0041]

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

FIG. 1 is a conceptual diagram showing an example of the HUD of the present invention. An information display source is provided below the windshield 7. In this information display source, the light emitted from a light source 6 using a hot cathode tube or the like passes through a lens system 4 which is a collimator, passes through a display body 5 which is a transmissive color liquid crystal display element, and outputs information to be displayed. It is issued as 3. The light 3 is applied to the combiner 2 made of a hologram provided on the windshield 7 of the vehicle body, diffracted, and visually recognized by the driver at the observation position 1.

The lens system 4 has a function as a collimator. Also, the hologram can be provided with this function, and the lens system 4 can be omitted. If the hologram has a lens function, it is possible to form the display images such as the speed display 8 and the warning display 9 at a distance.

If necessary, another hologram or lens for aberration correction may be arranged between the display 5 and the combiner 2.

Since the hologram has a wavelength selecting function, an image of a desired color can be displayed. Further, multi-exposure or stacking of a plurality of holograms enables multicolor display, and the quantity and quality of display information can be improved. For example, by setting the speed display 8 to green, the warning display 9 to red, or a mixture of green and red to amber (orange),
It becomes possible to transmit information to the driver more accurately.

FIG. 2 is a schematic sectional view showing an example of the structure of the hologram of the present invention. In this example, a structure example is shown in which three holograms, which are independently exposed by light of each wavelength corresponding to the three primary colors, are stacked. The diffraction wavelength of each hologram is matched with the emission wavelength peak of the hot cathode tube which is the light source. Specifically, the incident angle and the diffraction angle in consideration of the arrangement of the information display source and the arrangement of the combiner, which are determined by the specifications of the vehicle (in this embodiment, the incident angle is 45 °, the diffraction angle is 60 °).
, The first hologram 11 has a peak wavelength of 612n
m (red) light is reflected and diffracted, and the second hologram 12 reflects and diffracts light having a peak wavelength of 545 nm (green).
The hologram 13 is exposed so that light having a peak wavelength of 433 nm (blue) is reflected and diffracted.

The hologram according to the present invention may be of the laminated type shown in FIG. 2, but one hologram obtained by so-called multiple exposure, in which one photosensitive material is irradiated with laser light of a plurality of wavelengths, can also be used. . In this case, it is preferable in the case of preventing the image shift of each wavelength and the decrease of the transmittance of the combiner which may occur in the case of the laminated type.

Each hologram is exposed so that the diffraction gratings formed therein all have the same inclination. Thus, by making the incident angle of light incident on the hologram the same for all colors of light,
The diffraction angle diffracted by the hologram is also the same for all colors of light. If these angles are different,
Since the diffracted directions differ depending on the light of each color, what should originally be white is divided into three colors, which may be perceived as an unpleasant color by the observer.

As described above, in order to manufacture a reflection type hologram in which the inclinations of the diffraction gratings inside each hologram are all the same, the incident angle of the laser beam applied to both sides of the hologram photosensitive material with respect to the hologram photosensitive material. Should be the same for all lights on the respective surface sides of the photosensitive material. Further, even when the incident angles of the laser light at the time of exposure are not the same, by adjusting the incident angles of the laser light having one or two peak wavelengths on both sides of the hologram photosensitive material, the diffraction grating formed inside can be adjusted. The slopes can be the same.

The hologram of this embodiment is of a three-layer type, and three holograms exposed by light of three different wavelengths corresponding to red, green and blue are layered, and external light transmitted through the layered hologram is laminated. The color tone of the above, and the color tone of the external light reflected by the laminated hologram are close to white when observed from any angle.

The center wavelength of the diffraction spectrum of the diffracted light of the light from the information display source that is incident on the thus-exposed laminated hologram is (red, green, blue) =
(612 nm, 545 nm, 433 nm), and the half width is (red, green, blue) = (15 nm, 15 nm1
5 nm). Regarding the diffraction efficiency, the color tone of the light source,
It was determined by optimization so that the color difference from the average color tone of the reflected light by the combiner when observed at different angles was minimized.

As the color difference, the color difference ΔE ^* _ab in which the term of the difference ΔL ^* in the lightness index is zero in the color difference formula based on the L ^* a ^* b ^* color system specified by JIS-Z8730, that is, the difference in the chromaticness index is Δa. ΔE when ^* , Δb ^*
* _ab = [(Δa ^* ) ² + (Δb ^* ) ² ] ^1/2 was used.

Observations with different angles were carried out within a vertical section (for example, within the plane of FIG. 9). The observation angle range is −70 ° to + 50 ° with respect to the hologram, and the observation is performed every 10 ° N.
= 13 points. Assuming that the chromaticity index of the color tone of the reflected light at each point is a ^* _i and b ^* _i , the average chromaticity index of the color tone is (Σa ^* _i ) / N, (Σb ^* _i ) /
N, (i = 1 to 13). The standard light D ₆₅ defined by CIE was used as the light source. From the definition, the chromaticity index of the light source is a ^* = 0 and b ^* = 0. Therefore, the color difference between the average color tone of the reflected light and the color tone of the light source is ΔE
^* _ab = [(Δa ^* ) ² + (Δb ^* ) ² ] ^1/2 = [{(Σ
a ^* _i ) / N} ² + {(Σb ^* _i ) / N} ² ] ^1/2 .
Therefore, in the present embodiment, the diffraction efficiency of the above three-color hologram is set (red, green, blue) so as to minimize this ΔE ^* _ab.
= (20%, 60%, 60%).

In this embodiment, the center wavelength λ, the half width Δλ and the diffraction efficiency η that minimize the color difference are determined. Minimizing the color difference is an example of the most preferable case. As the degree of small color difference, the difference 1 from the minimum color difference
Even if it is about 0%, a color tone that is acceptable in terms of design and products when observing the hologram is sufficient.
The value is not limited to the above value as long as it is within the allowable range.

FIG. 3 is a chromaticity diagram showing the color change of the external light reflection color when the three-color exposure hologram thus produced is observed at different angles. This hologram has less color change than the case of the monochromatic hologram in FIG. 7 or the three-color hologram in which the diffraction characteristics of the hologram in FIG. 9 are not optimized, and the hologram is separated from the peripheral portion of the chromaticity diagram at any observation angle. Approaching the light source, its color tone is approaching white.

Since the transmitted color in this case is considered to have a complementary color relationship with the reflected color, it is close to the position of point symmetry with respect to the light source x mark in FIG. 3 when the hologram and the windshield are not colored. It becomes a color tone. That is, when the color tone of the reflected color approaches white, the color tone of the transmitted color also approaches white.

As described above, the hologram according to the present invention was able to improve the color tone of both the reflection color and the transmission color as compared with the conventional hologram.

Thus, by enclosing the hologram of this embodiment inside the windshield laminated glass of the vehicle to form a combiner, it was possible to realize the HUD in which the color tones of the external light reflection color and the transmission color were improved.

The hologram normally has an area of about several 10 mm to several 100 mm square and a thickness of several μm to several 10 μm, and has a light diffraction function. Although such a hologram is desirable in that a volume / phase type hologram such as a Lippmann type can obtain high diffraction efficiency, a hologram called an embossed type or a rainbow type can be widely used. As the hologram material, various photosensitive materials such as polyvinyl carbazole, acrylic-based photopolymers, dichromated gelatin, photoresists, and silver salts can be used.

Such a hologram is provided in the windshield, for example, the surface of the windshield (the outer surface of the vehicle).
It may be provided on the inner surface of the vehicle. In view of protection of the hologram, it is preferable to use it by enclosing it in the windshield which is a laminated glass.

The information display source in the present invention has a function of emitting light to display. It irradiates light emitted from a light source composed of a hot cathode tube (HCT), a cold cathode tube, a fluorescent display tube (VF), a halogen lamp, an LED, etc. to a display body composed of a so-called light receiving display element such as a liquid crystal display element. Yes, it may have both of these functions.

When the combiner of the present invention is used for color display, the liquid crystal display element includes a color filter and a transmission type twist nematic type liquid crystal element, a color liquid crystal display element including a super twist nematic type liquid crystal display element and the like. It can be preferably used. Thereby, the light emitted from one light source can be irradiated as light of a desired color.

In this way, light of a plurality of colors can be emitted from the same information display source. When the lights of these plural colors are displayed simultaneously, the display images are displayed in an overlapping manner. On the contrary, in order to prevent the overlapping of the display images, a color filter and a light source are combined as necessary, or a color liquid crystal display device is provided. It is also possible to prevent light of a plurality of colors from being irradiated at the same time by controlling.

Alternatively, instead of using the light receiving display element, the light source itself may be patterned and arranged to generate specific information as light. In the case where the light source is used together with the light receiving display element, an appropriate light collimating means such as a lens system or a curved reflecting mirror, and a suitable light guiding means such as a light guide plate are provided between the light receiving display element and the light source. You may arrange. Further, if necessary, an optical polarization means or KNO is provided in the optical path until the light is projected on the hologram.
Non-linear optical elements such as ₃ may be arranged.

When the HUD of the present invention is displayed in color, color display can be performed in the same plane if the distance from the combiner to the display image is the same for each color. Further, when the color is changed, a three-dimensional image in which the display image is viewed at different distances can be obtained depending on the display color.

In the present embodiment, the three-color display hologram has been described, but the same effect can be obtained with a hologram capable of displaying four or more colors.

The hologram in the present invention is not limited to the reflection type hologram as described above, but may be a HUD using a transmission type hologram.

As a second embodiment, a case will be described in which holograms of three-color exposure are subjected to multiple exposure on one photosensitive material having a thickness of 20 μm. When the combiner is installed on the windshield, the incident angle of light from the information display source to the combiner is 45 °,
Exposure is performed so that the peaks of the respective diffraction wavelengths when the diffraction angle toward the observer in the vehicle is 60 ° are 612 nm for red, 545 nm for green, and 433 nm for blue, as in the first embodiment. did.

The diffraction efficiency and the full width at half maximum were optimized and determined so that the sum of squares of the color difference between the color tone of the light source light and the color tone of the light reflected by the combiner when observed at different angles was minimized.

As for the color difference, the same as in the first embodiment, JIS
-A color difference ΔE where the term of the difference ΔL ^* in the lightness index is zero in the color difference formula based on the L ^* a ^* b ^* color system specified by Z8730.
^* _ab , that is, the difference in the chromaticness index is Δa ^* , Δ
b ^* and the ΔE of the time _{^{* ab = [(Δa *)}} 2 + (Δb
^* ) ² ] ^1/2 was used.

Observations with different angles were carried out within a vertical section (for example, within the plane of FIG. 6). The observation angle range is −70 ° to + 50 ° with respect to the hologram, and the observation is performed every N °.
= 121 points. The chromaticness index of the color tone of the reflected light at each point is defined as a ^* _i and b ^* _i . When D ₆₅ is used as the light source, the chromaticness index of the light source is a ^* =
0 and b ^* = 0. Therefore, the sum of squares of the color difference between the color tone of the light source light to be minimized and the color tone of the reflected light by the combiner is Σ (ΔE ^* _abi ) ² = Σ [(Δa ^* _i ) ² + (Δb ^*
_i ) ² ] = Σ [(a ^* _i ) ² + (b ^* _i ) ² ], (i = 1 to 1
121). Therefore, in the present embodiment, this Σ (ΔE ^*
_abi ) ² is optimized so that the diffraction efficiencies and half widths of the above three primary color holograms are optimized, and the diffraction efficiencies (red, green,
Blue) = (35%, 60%, 65%), and half widths (red, green, blue) = (8 nm, 8 nm, 5 nm).

FIG. 4 is a chromaticity diagram showing changes in the external light reflection color of the hologram of this embodiment. As can be seen from FIG. 4, the change in the external light reflection color of the hologram of this embodiment does not surround the light source as in the first embodiment. However, as a whole, the distance from the light source on the chromaticity diagram is closer than in the first embodiment, and it can be seen that the color tone of the hologram is closer to white.

As a third embodiment, a case where the hologram of three color exposure is subjected to multiple exposure on one photosensitive material having a thickness of 20 μm as in the second embodiment will be described. In the present embodiment, when the combiner is provided on the windshield, the angle of incidence of light from the information display source to the combiner is 50 °, and the diffraction angle toward the observer in the vehicle is 65 °. ,
Similar to the first embodiment, exposure was performed so that the wavelength was 637 nm for red, the wavelength was 540 nm for green, and the wavelength was 448 nm for blue.

The diffraction efficiency and the full width at half maximum were optimized and determined so that the sum of squares of the color difference between the color tone of the light source light and the color tone of the light reflected by the combiner when observed at different angles was minimized.

As for the color difference, the same as in the first embodiment, JIS
-The distance between the chromaticity point of the light source and the chromaticity point of the reflected light in the chromaticity coordinates of the XYZ color system defined by Z8701 ((Δx) ²
+ (Δy) ² ) ^1/2 was used.

Observations with different angles were carried out within a vertical cross section (for example, within the plane of FIG. 9). The observation angle range was −70 ° to + 50 ° with respect to the hologram, and the observation was performed at N = 13 points every 10 °. The chromaticity of the reflected light at each point is x _i , y _i
And When D ₆₅ is used as the light source, the chromaticity of the light source is x ₀ = 0.3127 and y ₀ = 0.3291 by definition.
Therefore, the sum of squares of the color difference between the color tone of the light source light to be minimized and the color tone of the reflected light from the combiner is Σ (ΔE _xy ).
² = Σ [(Δx _i ) ² + (Δy _i ) ² ] = Σ [(x _i −
x ₀ ) ² + (y _i −y ₀ ) ² ], (i = 1 to 13).

Therefore, in the present embodiment, this Σ (ΔE _xy ) ²
The diffraction efficiency and the half width of the above three primary color holograms are optimized to minimize the diffraction efficiency (red, green, blue) =
(60%, 60%, 20%), full width at half maximum (red, green,
Blue) = (11 nm, 9 nm, 6 nm).

FIG. 5 is a chromaticity diagram showing changes in the external light reflection color of the hologram of this embodiment. As can be seen from FIG. 5, the change in the external light reflection color of the hologram of the present embodiment does not surround the light source as in the first embodiment. On the other hand, the distance on the chromaticity diagram to the light source is sufficiently short as a whole.

In this example, the degree of white in the color tone of the hologram is smaller than that in the first and second examples. However, when the observation is performed with the angle changed, the change in color tone is smaller than in the first and second embodiments. In this sense, since the color tone of the hologram is gently observed, the hologram is observed with a color tone close to white.

In this way, the holographic combiner exposed by light of a plurality of wavelengths corresponding to at least three primary colors has its diffraction characteristics (center wavelength of diffraction spectrum, half width, diffraction efficiency) optimized by the method according to the present invention. By doing so, it is possible to improve the color tones of the reflected light and the transmitted light, which have been a problem in the past, and bring them closer to white.

By enclosing the hologram of this embodiment in the windshield laminated glass of the vehicle to form a combiner, it is possible to realize the HUD in which the color tones of the external light reflection color and the transmission color are improved as in the previous embodiments. The structure of the hologram of this embodiment, the manufacturing method, the light source in the case of the HUD, and the like can be the same as those in the previous embodiments.

As described above, the hologram used as the combiner in the present invention has a color tone of the external light transmitted from the outside of the vehicle to the inside of the vehicle through the combiner and a tone of the reflected light of the outside light observed by the combiner outside the vehicle. , Which is exposed by light having a plurality of center wavelengths corresponding to a plurality of colors selected so as to be close to white when viewed from any angle. The diffraction characteristics of the hologram (center wavelength λ of diffraction spectrum, full width at half maximum Δλ, diffraction efficiency η) are the color difference between the color tone of the light source and the average color tone of the reflected light by the combiner when observed at different angles. Is a combination optimized to reduce the color difference, or a combination optimized to reduce the sum of squares of the color difference between the color tone of the light source light and the color tone of the light reflected by the combiner when observed at different angles. is there.

Therefore, the color tone of transmitted light which is transmitted from the outside of the vehicle through the combiner and visually recognized by an observer such as a driver, and the color tone of reflected light of the outside light by the combiner outside the vehicle are
Compared to the conventional combiner, the color is closer to white, giving the driver a transparent view with no complementary color to enhance safety, and there is little color change depending on the angle of observation to the outside observer and a color tone close to white. HUD is obtained. Especially, 500 to 560 nm which is often used as a display color
It is possible to effectively improve the color tone even for a certain degree of green light.

[0084]

As described above, in the hologram used as the combiner in the present invention, the color tone of the external light transmitted from the outside of the vehicle to the inside of the vehicle through the combiner and the color tone of the outside light by the combiner observed outside the vehicle are It was exposed by light having a plurality of center wavelengths corresponding to a plurality of colors selected so as to be close to white when viewed from any angle. The diffraction characteristics of the hologram (center wavelength λ of diffraction spectrum, full width at half maximum Δλ, diffraction efficiency η) are the color differences between the color tone of the light source and the average color tone of the reflected light by the combiner when observed at different angles. The combination is optimized so as to be small, or the combination is optimized so that the sum of squares of the color difference between the color tone of the light source light and the color tone of the light reflected by the combiner when observed at different angles is reduced.

Therefore, the color tone of the transmitted light which is transmitted from the outside of the vehicle through the combiner to be visually recognized by an observer such as a driver or the color tone of the reflected light of the outside light by the combiner outside the vehicle is
Compared to the conventional combiner, the color is closer to white, giving the driver a transparent view without complementary colors to enhance safety, and to external observers there is less color change depending on the viewing angle and it is close to white. A color HUD is obtained.

In particular, it is often used as a display color.
The color tone can be effectively improved even for green light of about 0 to 560 nm.

Furthermore, the combiner in the present invention is
Since at least three colors of light can be displayed, a HUD capable of displaying information in a plurality of colors can be obtained while the transmitted color from outside the vehicle and the reflected color outside the vehicle are white.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing an example of a HUD of the present invention.

FIG. 2 is a schematic sectional view showing an example of the structure of a hologram in the present invention.

FIG. 3 is a chromaticity diagram showing a color change of an external light reflection color of the hologram in the present invention.

FIG. 4 is a chromaticity diagram showing the color change of the external light reflection color of the hologram in the present invention.

FIG. 5 is a chromaticity diagram showing the color change of the external light reflection color of the hologram in the present invention.

FIG. 6 is a conceptual diagram illustrating a transmission color of a conventional hologram.

FIG. 7 is a conceptual diagram illustrating a reflection color of a conventional hologram.

FIG. 8 is a chromaticity diagram showing a change in external light reflection color of a conventional hologram.

FIG. 9 is a sectional view showing a conventional vehicle-mounted HUD.

FIG. 10 is a chromaticity diagram showing a change in external light reflection color of a hologram in which a conventional diffraction characteristic is not optimized.

[Explanation of symbols]

 1: Driver's observation position 2: Combiner 3: Light including information 4: Lens system 5: Display element 6: Light source 7: Windshield 8: Speed display 9: Warning display

Claims (14)

[Claims] 1. An information display source that includes at least a light source and a display that displays information to be displayed, and an information display source that generates information to be displayed as light, and a windshield of a vehicle, the light being provided inside the vehicle. In a head-up display including at least a combiner that diffracts toward an observer,
The combiner is selected so that the color tone of the external light transmitted from the outside of the vehicle to the inside of the vehicle through the combiner and the color tone of the reflected light of the outside light by the combiner observed outside the vehicle are close to white even if observed from any angle. A hologram exposed by a plurality of colors of light, wherein the light emitted from the information display source toward the combiner is diffracted toward the observer in the vehicle, the central wavelength λ and the half width Whether Δλ and diffraction efficiency η are a combination that reduces the color difference between the color tone of the light source and the average color tone of the reflected light by the combiner when observed at different angles,
Alternatively, a head-up display characterized by comprising holograms that are exposed so as to reduce the sum of squares of the color difference between the color tone of the light source light and the color tone of the reflected light from the combiner when observed at different angles. 2. The head-up display according to claim 1, wherein the combiner is a single-layer hologram that is multiple-exposed with light having a plurality of center wavelengths. 3. The head-up display according to claim 1, wherein the combiner is a stack of a plurality of holograms exposed by light having a single central wavelength or a plurality of central wavelengths. 4. The incident angles of lights of a plurality of colors that are incident on the combiner from the information display source are all substantially the same, and the diffraction angles of the lights of a plurality of colors diffracted by the combiner are all substantially the same. The head-up display according to any one of claims 1 to 3. 5. The central wavelengths corresponding to the lights of the plurality of colors are 580 to 650 nm, 500 to 570 nm, and 4 respectively.
The head-up display according to any one of claims 1 to 4, which has a wavelength corresponding to three colors selected from the range of 20 to 490 nm. 6. A combiner for a head-up display, which is provided on a windshield of a vehicle and diffracts light containing information from an information display source toward an observer in the vehicle.
Multiple colors selected so that the color tone of the external light transmitted from the outside of the vehicle through the combiner to the inside of the vehicle and the color tone of the reflected light of the outside light by the combiner observed outside the vehicle are close to white even if observed from any angle. When the light emitted from the information display source toward the hologram by the light is diffracted toward the observer in the vehicle, the center wavelength λ, the half width Δλ and the diffraction efficiency η are the source light. Either the color tone and the average color tone of the reflected light from the combiner when observed at different angles, or the combination of the light source light color when observed at different angles and the reflected light tone from the combiner. A combiner characterized by comprising holograms exposed so as to form a combination that reduces the sum of squares of the color difference of. 7. The combiner according to claim 6, wherein the combiner comprises a single-layer hologram that is multiple-exposed with light having a plurality of central wavelengths. 8. The combiner of claim 6, comprising a stack of a plurality of holograms exposed by light having a single center wavelength or light having a plurality of center wavelengths. 9. Central wavelengths corresponding to the lights of the plurality of colors are 580 to 650 nm, 500 to 570 nm, and 4 respectively.
The combiner according to any one of claims 6 to 8, which has a wavelength corresponding to three colors selected from the range of 20 to 490 nm. 10. An information display source that includes at least a light source and a display body that displays information to be displayed, and an information display source that generates information to be displayed as light, and a windshield of the vehicle, the light being provided inside the vehicle. A method of designing a head-up display having at least a combiner diffracting toward an observer, wherein, as the combiner, a color tone of external light transmitted from outside the vehicle into the vehicle through the combiner,
With the color tone of the reflected light of the outside light by the combiner observed outside the vehicle, when using the hologram exposed by the light of multiple colors selected so as to be close to white when viewed from any angle, from the information display source The center wavelength λ, the half-value width Δλ and the diffraction efficiency η of the diffraction spectrum when the light emitted toward the hologram is diffracted toward the observer in the vehicle were observed by changing the color tone and angle of the light source light. A method for designing a head-up display, characterized in that a hologram exposure condition is set by selecting a combination that reduces a color difference from the average color tone of the reflected light by the combiner. 11. The method of designing a head-up display according to claim 10, wherein the combiner is a single-layer hologram that is multiple-exposed with light having a plurality of center wavelengths. 12. The method of designing a head-up display according to claim 10, wherein the combiner is a stack of a plurality of holograms exposed by light having a single wavelength or a plurality of wavelengths. 13. The incident angles of a plurality of colors of light which are incident on the combiner from the information display source are all substantially the same, and the diffraction angles of the plurality of colors of light diffracted from the combiner are all substantially the same. The method for designing a head-up display according to any one of claims 10-12. 14. Central wavelengths corresponding to the lights of a plurality of colors are 580 to 650 nm, 500 to 570 nm,
14. The wavelengths corresponding to three colors selected from the range of 420 to 490 nm, respectively.
Head up display design method.