JP2959318B2 - Head-up type vehicle display - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a head-up type vehicle display device which allows a driver to recognize only a diffracted light as a virtual image as a virtual image and superimpose it on a foreground.

[0002]

2. Description of the Related Art As one of conventional head-up type display devices for vehicles, there is a holographic combiner formed by disposing a hologram element between laminated glasses so that an incident angle and a diffraction angle of incident light are different. In addition, there is a head-up type vehicle display device that irradiates the holographic combiner with display light and superimposes only the diffracted light as a virtual image on the foreground and makes the driver recognize the display.

FIG. 3 shows a configuration of a conventional head-up type vehicle display device, in which a holographic element 302 is arranged between laminated glasses 301 and bonded with a PVB interlayer 303 to form a holographic combiner 304. And a light source 305 for irradiating the holographic combiner 304 with display light.

The display light emitted from the light source 305 enters the holographic combiner 304 as incident light 306, is diffracted by the hologram element 302, enters the driver's eyes 308 as diffracted light 307, and forms a virtual image together with the driver in the foreground. Will be recognized. Here, for example, assuming that the content (display information) of the display light is “40 km / h”,
As shown in the figure, the driver recognizes the character “40 km / h” as the virtual image 309 together with the foreground 310.

At this time, the light reflected by the difference in the refractive index at the interface between the air and the laminated glass 301 enters the driver's eyes 308 at the same time as the diffracted light 307, and the same display light (incident light 3
06), the incident angle θ _a and the diffraction angle θ _b formed by the optical axis of the incident light 306 and the diffracted light 307 with respect to the combiner normal L are different angles in order to prevent the information from being recognized as a double image. The diffraction grating of the hologram element 302 has been exposed in advance so that

On the other hand, in the head-up type vehicle display device having such a configuration, since the boundary surface between the above-described air and the laminated glass 301 always exists in front of the hologram element 302, the incident light 306 is incident when the incident light 306 is incident. Loss 306a
Is generated, and the diffracted light loss 3
07a occurs. In order to reduce these losses, it is sufficient to irradiate P-polarized light with low reflectance as incident light from the light source 305. However, since the P-polarized light also lowers the diffraction efficiency in the hologram element 302, finally the diffracted light The amount of light at 307 decreases. Accordingly, it is necessary to use S-polarized light or non-polarized light as incident light, and to increase the luminance of the light source 305 in consideration of the incident light loss 306a and the diffracted light loss 307a in advance.

[0007]

However, according to the conventional head-up type vehicle display device, since a high brightness light source is used, there is a problem that the cost of the light source is increased and the life of the light source is shortened. there were.

The present invention has been made in view of the above, and provides a head-up type vehicle display device that can reduce the cost of a light source and improve the life of the light source by using a low-luminance light source. With the goal.

[0009]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a holographic element formed by disposing a hologram element between laminated glasses so that an incident angle of incident light and a diffraction angle are different. In a head-up type vehicle display device having a combiner and irradiating display light to the holographic combiner and superimposing only a diffracted light as a virtual image on a foreground and recognizing the driver, the polarization direction of the incident light is rotated by 90 degrees. A head-up type vehicle display device comprising: a holographic combiner in which a polarizing element is superimposed on a driver-side surface of a hologram element; and light source means for irradiating P-polarized light as display light. To provide.

Further, in order to achieve the above object, the present invention has a holographic combiner formed by disposing a hologram element between laminated glasses so that the incident angle of incident light and the diffraction angle are different, In a head-up type vehicle display device in which a holographic combiner is irradiated with display light and only a diffracted light is superimposed on a foreground as a virtual image to be recognized by a driver, the polarization direction of the light can be accurately adjusted by 90 degrees in a wide wavelength range. A holographic combiner in which a rotating optical element to be rotated is superimposed on the driver's side of the hologram element;
It is an object of the present invention to provide a head-up type vehicle display device provided with light source means for irradiating polarized light.

[0011]

The head-up type vehicle display device of the present invention comprises:
P-polarized light is emitted from the light source means as display light, and the polarization direction of the incident light is rotated by 90 degrees by a polarization element arranged on the driver side with respect to the hologram element in the holographic combiner. The incident light turned into S-polarized light by rotating by 90 degrees is diffracted by the hologram element, returned to P-polarized light having a low reflectance again by the polarizing element, and emitted as diffracted light.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a head-up type vehicle display device according to the present invention will be described in detail in the order of Embodiment 1 and Embodiment 2 with reference to the drawings.

FIG. 1 shows the structure of a head-up type vehicle display device according to a first embodiment of the present invention.
The hologram element 102 is disposed between the hologram element 102 and the polarization element 103. The polarization element 103 for rotating the polarization direction of the incident light by 90 degrees is disposed so as to overlap the driver-side surface of the hologram element 102. And a light source 106 for irradiating the holographic combiner 105 with display light having a polarization direction of P-polarized light.

The display light emitted from the light source 106 enters the holographic combiner 105 as incident light 107, is diffracted by the hologram element 102, enters the driver's eyes 109 as diffracted light 108, and enters a virtual image 110 (for example, 40 km). / H) together with the foreground 310. Here, when the incident light 107 from the light source 106 enters as P-polarized light, it is converted into S-polarized light by transmitting through the polarizing element 103. The light reaches the hologram element 102 and is diffracted by the S-polarized light, passes through the polarizing element 103 again, and returns to the P-polarized light.

The operation of the above configuration will be described. Since the incident light from the light source 106 is P-polarized light, the reflectance is low at the interface between the air and the laminated glass 101, and the incident light loss 107a is reduced. After that, the polarizing element 103
, The light is diffracted by the hologram element 102 with high diffraction efficiency, and returns to the P-polarized light by the polarization element 103 again.
The diffraction light loss 108a is also reduced. As a result, light attenuation can be significantly reduced, and the light source utilization efficiency improves. In other words, since the light source 106 does not need to be a high brightness light source,
The cost of the light source can be reduced, and the life of the light source can be improved.

For example, the refractive index of glass is about 1.5, the incident / diffraction angle of a hologram element which is considered to be typical is 40 ° / 65 °, and the ratio at which the polarization direction of the polarizing element can be rotated is 95%.
% And ignoring the attenuation of light due to transmission, it is possible to calculate an approximate value of the intensity of the diffracted light depending on the presence or absence of the polarizing element.

The incident angle θ _IN is refracted in the glass to become θ _OUT . Assuming that n is air and m is glass, the refractive index satisfies Equation 1 according to Snell's law. Thus, when the incident angle θ _IN is 40 degrees, θ _OUT is about 25 degrees, and the diffraction angle θ _IN is 6
At 5 degrees, θ _OUT can be calculated as about 37 degrees.

[0018]

(Equation 1)

Next, assuming that the reflectivity of the P-polarized light is R _P and the reflectivity of the S-polarized light is R _S , they can be obtained by Equation 2.

[0020]

(Equation 2)

At the time of incidence, the reflection angles are R _P = 0.014 and R _S = 0.
077, and the reflectance at the time of emission is R _P = 0.013 and R _S = 0.2
28.

[0022] Thus, the reflection loss of the time of incidence, when the degree of polarization of the light source is P-polarized light _{90%, R P = 0.9 ×} 0.01 on reflection amount = P polarization × incidence of P-polarized light
4 = 0.0126 S reflection loss of polarization of the reflected fraction = (1-P polarization) × time of incidence of the _{R S = (1-0.9) × 0.077} = 0.0077 , and the The total of both P Henhikariji is 0.0203
Becomes

[0023] Similarly, when the degree of polarization of the light source is S-polarized light of 90%, reflecting partial = (1-P polarization) of the P-polarized light × time of incidence of the _{R P = (1-0.9) × 0.014} = 0.0014 S polarization R _S = 0.9 × 0.07 on reflection amount = S polarization × incident
7 = 0.0693, and when both are summed, the reflection loss for S-polarized light is 0.0707.
Becomes

As a result, from (reflection loss when S-polarized light) − (reflection loss when P-polarized light) = 0.0707−0.0203 = 0.0504, by setting the light source to P-polarized light, the reflection loss is about 5% of the original light amount. It can be seen that is reduced.

When the light source is P-polarized light, the incident light is converted twice in polarization direction by the optical rotation element. Assuming that the conversion ratio and the optical rotation are 95%, in the first conversion, P-polarized light component = P-polarized light transmission × (1−rotation) + S-polarized light transmission × rotation = (0.9−0.0126) × (1- 0.95) + (0.1-0.
0077) × 0.95 = 0.1321 S-polarized light component = P-polarized light transmission × optical rotation + P-polarized light transmission ×
(1-rotation) = (0.9-0.0126) × 0.95 + (0.1-0.00
77) x (1-0.95) = 0.8476.

After being diffracted by the hologram, the light is similarly converted, and the P-polarized light component = 0.1321 × 0.05 + 0.8476 × 0.95 = 0.8
119 S-polarized light component = 0.1321 x 0.95 + 0.8476 x 0.05 = 0.1
678.

The reflection loss at the time of emission based on the polarization component ratio is: P-polarized light reflection = P-polarized light component × R _P at the time of emission = 0.8119
× 0.013 = 0.0106 S on reflection amount = S-polarized light component × emission of polarized light R _S = .1678
× 0.228 = 0.0383, and when these are summed, the reflection loss for P-polarized light is 0.0
488.

On the other hand, in the case of S-polarized light without conversion by optical rotation element, as it is polarized component ratio, on reflection amount = P-polarized light component × emission of P-polarized _{R P = (0.1- 0.0014) ×} 0.013 = 0.0013 S _{R S = (0.9- 0.0693) ×} 0.228 = 0.1894 next on reflection amount = S-polarized light component × emission of polarized light, the reflection loss of the S Henhikariji the sum of these 0.1
907.

As a result, (reflection loss at the time of S polarization) − (P
(Reflection loss during polarization) = 0.1907-0.0488 = 0.1419 By using P-polarized light source, about 14% of the original light amount
Thus, the reflection loss can be reduced. In addition, in the total reflection loss, these are added to reduce the reflection loss by about 19%.

This indicates that the load on the light source 106 has reached a level that can be greatly reduced. Furthermore, R _P
By setting the angle near the Brewster angle where = 0, the reflection loss can of course be minimized.

Further, even when the luminance level of the light source 106 is the same as that of the related art, the specification of the hologram can be reduced because the display luminance increases.

In general, the performance of a hologram is represented by the “diffraction center wavelength” at a set angle, the “diffraction efficiency” having a maximum value at that wavelength, and the width of a wavelength region having a value half the maximum value. Half width ". According to this embodiment, the "diffraction center wavelength" is kept as it is, and the "diffraction efficiency"
Alternatively, even if the “half width” is reduced, the display luminance can be maintained at the conventional value. This means that the transmittance of extraneous light is improved and the coloration of the combiner due to diffraction is reduced. Light incident from the outside on the holographic combiner 105 is randomly polarized light, but is reflected by a large amount of S-polarized light on the surface and becomes light polarized to P-polarized light. Polarizing element 103
The light is either diffracted by the hologram element 102 as it is without passing through the hologram element 102, or the diffracted light is reduced because it is P-polarized light as described above.

Embodiment 2 FIG. 2 shows the configuration of a head-up type vehicle display device according to Embodiment 2. The second embodiment is different from the first embodiment in that the polarization element 1 for rotating the polarization direction of the incident light by 90 degrees is used.
In this example, an optical rotatory optical element 201 that rotates the polarization direction of light by 90 degrees with high accuracy in a wide wavelength range is used instead of the optical rotation element 03. Reference numeral 202 denotes a hologram element having a plurality of diffraction wavelengths at arbitrary incident angles by multiple exposure.
Other configurations are common to the first embodiment, and description thereof is omitted.

In order to provide a large amount of information with high display quality, it is indispensable to increase the display color. However, 1
A polarizing element typified by a half-wave plate can rotate the polarization direction with high accuracy only near an arbitrary set wavelength, or cannot expect the effect over a wide wavelength range.

Therefore, in order to realize a head-up type vehicle display device for multicolor display, it is necessary to use the hologram element 202 having a plurality of diffraction wavelengths. Even in this case, if a wavelength having high visibility is selected for the main display, the wavelength for the second and subsequent colors is necessarily reduced to a wavelength having low visibility.
In order to effectively and effectively use the display light of even low visibility, attenuation due to reflection at the interface between the laminated glass and air must be prevented at the same level as the main wavelength. In the second embodiment, by using the optical rotatory optical element 201, the reflection loss can be reduced in a wide wavelength range, and a high-quality multicolor display can be obtained.

[0036]

As described above, in the head-up type vehicle display device of the present invention, the hologram element in which the polarization element for rotating the polarization direction of the incident light by 90 degrees is superimposed on the driver side surface of the hologram element. Since it has a graphic combiner and light source means for irradiating light having a polarization direction of P-polarized light as display light, by using a low-luminance light source,
The cost of the light source can be reduced and the life of the light source can be improved. If the same light source is used, the hologram element can be down-specified, the transmittance of extraneous light serving as a foreground can be improved, and the color of the holographic combiner when viewed from the outside can be reduced.

In the head-up type vehicle display device according to the present invention, an optical rotation optical element for rotating the polarization direction of light by 90 degrees with high precision in a wide wavelength range is superimposed on the surface of the hologram element on the driver side. Since the holographic combiner and the light source for irradiating P-polarized light as the display light are provided, it is possible to reduce the cost of the light source and improve the life of the light source by using a low-luminance light source. it can. If the same light source is used, the hologram element can be down-specified, the transmittance of extraneous light serving as a foreground can be improved, and the color of the holographic combiner when viewed from the outside can be reduced. In particular, regarding the coloring of the holographic combiner, the holographic combiner is alleviated from being viewed in all wavelength bands and in all directions of the external light. Further, even in a multi-color display, the reflection loss at each wavelength can be reduced.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating a configuration of a head-up type vehicle display device according to a first embodiment.

FIG. 2 is an explanatory diagram illustrating a configuration of a head-up type vehicle display device according to a second embodiment.

FIG. 3 is an explanatory diagram illustrating a configuration of a conventional head-up type vehicle display device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 101 Laminated glass 102 Hologram element 103 Polarization element 105 Holographic combiner 106 Light source 201 Optical rotatory optical element 202 Hologram element

Claims (2)

(57) [Claims] A holographic combiner formed by arranging a hologram element between laminated glasses so that an incident angle and a diffraction angle of incident light are different from each other; and irradiating display light to the holographic combiner. In a head-up type vehicle display device in which only a diffracted light is superimposed on a foreground as a virtual image and recognized by a driver, a polarizing element for rotating the polarization direction of the incident light by 90 degrees is superimposed on a driver-side surface of the hologram element. A holographic combiner arranged in a vertical direction, and light source means for irradiating light having a polarization direction of P-polarized light as the display light. 2. A holographic combiner formed by arranging a hologram element between laminated glasses so that an incident angle of incident light and a diffraction angle are different from each other, irradiating display light to the holographic combiner, and diffracting the holographic combiner. In a head-up type vehicle display device in which a driver recognizes only light as a virtual image by superimposing it on a foreground, a holographic element driver rotates an optical rotation optical element that rotates the polarization direction of light by 90 degrees with high accuracy in a wide wavelength range. A display device for a head-up type vehicle, comprising: a holographic combiner disposed so as to be superposed on a side surface; and light source means for irradiating light having a polarization direction of P-polarized light as the display light.