JPH10138794A - Head-up display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To adjust the brightness in accordance with external light and to diminish a displayed image by external light. SOLUTION: A light signal 31 emitted from a display unit 21 is projected onto a combiner 11 which therefore reflects a light signal 32 for visualizing a displayed image 82. The light signal 31 emitted from the display unit 21 is linearly polarized, and a movable polarizer 15 having a polarizing plane which can be rotated about the optical axis of the light signal 31 is located between the display unit 21 and the combiner 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a head-up display device, and more particularly to a head-up display device suitable for use in an environment where strong light such as external light is incident.

[0002]

2. Description of the Related Art In normal driving of an automobile, in order to confirm a speed display or the like, it is necessary to temporarily move a line of sight from an outside scene to instruments on an instrument panel. This operation is indispensable for driving, but is a very troublesome act. It is also said that frequent eye movements cause considerable fatigue for the driver. Therefore,
In recent years, there has been proposed a head-up display in which information necessary for driving such as speed can be superimposed on an external scene at the same time by using a combiner such as a hologram optical element (Japanese Patent Laid-Open No. 57-182540; 62-27
835, etc.).

That is, as shown in FIG. 6, a head-up display 90 transmits optical information (signal light 31) radiated from a display 92 such as a CRT through an optical element 93 such as a lens or a hologram or directly. Is projected onto a combiner 91 such as a half mirror or a hologram, and is superimposed on an outside scene 83 so that a display image 82 is visually recognized by a viewer 85. As a result, the movement of the line of sight and the operation of adjusting the focus for the viewer 85 can be reduced.

However, in the vehicle head-up display 90, the brightness of the outside scene 83 varies greatly depending on the outside situation. , The brightness of the display image 82 must be changed in the range of several cd / m ² to several thousand cd / m ² . Therefore, the head-up display 90 is provided with an illuminance sensor for detecting the intensity of external light and a dimming circuit for adjusting the intensity of the signal light 31.

[0005]

As described above, the head-up display is a device having many advantages as compared with the conventional instrument panel instrument, but the conventional head-up display device has an external view as described above. An illuminance sensor and a dimming circuit are required in order to cope with the brightness, and this has a first problem that the device becomes large and expensive. The second problem is that when strong light such as sunlight enters from a specific direction, a display image washout (not visible) phenomenon occurs, and the display image 82 cannot be visually recognized.

That is, as shown in FIG. 7, the sunlight 39 enters from the back surface of the combiner 91 and the surface 921 of the display 92
Illuminates the surface 921, and the display image 82 (FIG. 6) becomes invisible (so-called display image washout phenomenon). Furthermore, when such a washout phenomenon occurs, the display 92 may be heated by the sunlight 39 at the same time, causing a problem such as a decrease in the performance of the display 92. The present invention has been made in view of such a conventional problem, and provides a head-up display device capable of inexpensively realizing dimming corresponding to external light and preventing washout due to external light with a simple configuration. What you want to do.

[0007]

The head-up display device according to the first aspect of the present invention is characterized in that the signal light emitted from the display is linearly polarized light, and a polarization plane is provided between the display and the combiner. A movable polarizing plate that can be rotated is provided. That is, the signal light emitted from the display is linearly polarized light, and a movable polarizing plate is arranged in front of the combiner. Therefore, the intensity of the signal light incident on the combiner can be freely adjusted by operating the polarizing plate to change the direction of the polarization plane.

That is, when the direction of the linearly polarized light is the same as the direction of the easy transmission axis of the polarizing plate, nearly 100% of the signal light is transmitted. When the angle with respect to the easy transmission axis is ψ, the intensity of the signal light becomes maladic. Attenuates cos ² ψ times by the law of
= 90 °, no transmitted light). Therefore, it is possible to adjust the transmission intensity of the signal light by rotating the polarizing plate according to the intensity of the external light. The operation of the polarizing plate can be performed manually or automatically by a driving device such as an optical sensor and a motor.

It is extremely easy to obtain a linearly polarized light by using, for example, a liquid crystal display or the like. Rotating the polarizing plate has a configuration that is more complicated than controlling the light amount of a light source by a conventional dimming circuit. It becomes much simpler. At the same time, the head-up display can be reduced in size and cost. In addition, when the external light such as sunlight enters the display, the optical path includes the above-mentioned polarizing plate. Since the sunlight and the like need to pass through the polarizing plate, the amount of the external light is substantially reduced by the polarizing plate. Halved. Therefore, the washout phenomenon of the display image is less likely to occur, and the heating of the display due to external light is suppressed, and the deterioration of the performance of the display due to an increase in temperature can be suppressed.

A display device that directly emits linearly polarized light includes, for example, a backlight type liquid crystal display device. As another type of display for obtaining linearly polarized light, there is a type that extracts only linearly polarized light in a certain direction from signal light containing display information. For example, as described in claim 3, a display device that emits signal light that is not linearly polarized light is combined with a polarizing plate, and a polarizing plate is disposed at a subsequent stage. Display devices that do not emit linearly polarized light include, for example, fluorescent display tubes and light emitting diodes.

In the case of a head-up display for a vehicle, the display, the polarizing plate and the combiner are preferably housed in a single case and arranged near the dashboard of the vehicle. It is. By integrating the head-up display device into a single case, it is possible to manufacture the head-up display device on an independent manufacturing line, and adjustment and assembly are facilitated. Also, removal from the vehicle becomes easy, and maintenance and repair become easy.

In the case of a head-up display for a vehicle, the combiner can be arranged on the windshield. By doing so, the viewer (driver) can have a sense of unity between the vehicle and the head-up display, and can feel the presence of the head-up display as natural. As the combiner, there are those using a reflection hologram and those using a half mirror such as a metal film or a dielectric multilayer film. The hologram combiner can be miniaturized to easily realize various characteristics, and the half mirror is easy to manufacture and inexpensive.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 In this embodiment, as shown in FIG. 1, a signal light 31 radiated from a display 21 is projected onto a hologram combiner 11 and displayed by a signal light 32 (diffracted light) reflected by the hologram combiner 11. This is a head-up display device 1 configured to visually recognize an image 82. The signal light 31 radiated from the display 21 is linearly polarized light, and a movable polarization between the display 21 and the combiner 11 is capable of rotating a polarization plane around the optical axis of the signal light 31. A plate 15 is arranged.

The display 21 is a backlight type liquid crystal display device having a cold cathode tube 211 as a backlight source, a polarizing plate 212 and a liquid crystal element 213. The liquid crystal display element 213 is a DSTN (Double STN) type liquid crystal, and the signal light 31 radiated from the display 21 is
It is linearly polarized light. The display 21, the polarizing plate 15, and the combiner 11 are housed in a single case 41, and are arranged near a dashboard 51 of the vehicle.

The following is a supplementary explanation for each. As shown in FIG. 1, the head-up display device 1 of the present embodiment is integrated so that each member can be accommodated in a case 41, and a display 21 that emits a signal light 31 and a hologram that converts the signal light 31 into a hologram. A mirror 22 for reflecting light in the direction of the combiner 11, a rotatable movable polarizing plate 15, a hologram combiner 11, a cold cathode tube 21, and a liquid crystal display device 2.
And a circuit 45 for controlling the circuit 13.

The hologram combiner 11 is attached to the case 41 so as to be rotatable about a holder shaft 42, and the angle of the hologram combiner 11 with respect to the upper surface of the case 41 can be changed. That is, the angle of the combiner 11 can be adjusted to an angle that is most easily seen according to the position of the eyes of the viewer 85. The polarizing plate 15 can be rotated about 90 degrees around the optical axis of the signal light 31 by manually operating the holder 43. Then, the direction of the crystal axis of the polarization plane (direction of the axis of easy transmission) changes depending on the rotation angle, and the transmittance of the signal light 31 which is linearly polarized light changes.

That is, the light amount of the incident signal light 31 is defined as Io,
Assuming that the angle between the direction of the easy transmission axis on the polarization plane of the polarizing plate 15 and the direction of the linear polarization of the incident signal light is ψ, the light amount I of the output signal light 311 (FIG. 3) corresponding to the angle ψ is As shown in FIG. 2, it changes in proportion to cos ² ψ. As a result, as shown in FIG. 3 (a), a large amount of the signal light 31 is transmitted when ψ is near 0 °, and when ψ is near 90 °, the signal light 31 shown in FIG.
As shown in (b), the signal light 31 is hardly transmitted (I
$ 0). The arrows in FIG. 3 schematically show the polarization directions of the signal light 31.

Therefore, the viewer (driver) 85 can adjust the brightness of the display image 82 to a level that makes it easy to see by operating the holder 43 by hand. Actually, when the brightness of the display image 82 was measured while rotating the polarizing plate 15 using the polarizing plate 15 including a liquid crystal display element and a cold cathode tube of a backlight, it was found that the brightness was about 3000 cd / m ² to about 0 cd.
/ M ² could be changed in luminance.

As shown in FIG. 7, when externally polarized light, such as sunlight, enters the display 21 from the back side of the hologram combiner 11, the polarizing plate 15
, The amount of external light is reduced by about half.
The amount of external light reflected on the front surface of the display device becomes about half, and the washout phenomenon of the display image 82 due to the external light can be suppressed. Further, the display 2 whose characteristics are easily changed by heat.
The disadvantage that the one liquid crystal element 212 is heated by external light and the characteristics are changed can also be suppressed. Also,
Since the polarizing plate 15 closes the case 41 and suppresses the entrance of external dust into the inside, the reliability of the device 1 is also prevented from deteriorating.

As shown in FIG. 4, the hologram combiner 11 is provided on one surface of the transparent resin substrate 111 (signal light 3).
A hologram element 112 on which a concave mirror is recorded is formed on the entrance / exit surfaces of the light emitting elements 1 and 32, and an anti-reflection coating 113 is provided on the surface of the hologram element 112 to prevent external damage and to prevent a noise image due to reflected light. . The other surface of the transparent resin substrate 111 is subjected to a so-called crimping process 115 which has been subjected to fine unevenness processing, so that the signal light 31 transmitted through the combiner 11 is scattered and becomes an interface toward the viewer 85. Reflected noise light (noise image) can be suppressed. In addition, the graining 115 also has an effect of suppressing the intensity by scattering when external light such as sunlight enters.

The function of suppressing the entrance of external light, as in the case of the graining 115, can also be achieved by an angle-selective film that selectively inhibits external light entering the display 21 at an angle. be able to. The display 21 that can obtain linearly polarized light can also be realized by disposing a polarizing plate at a subsequent stage such as a fluorescent display tube or a light emitting diode (LED). That is, the light of a fluorescent display tube or a light emitting diode (LED) having a random polarization direction is
The polarizing plate allows only linearly polarized light in a certain direction to pass through,
It can be linearly polarized light. Furthermore, combiner 11
Alternatively, a half mirror in which a metal film or a dielectric multilayer film is deposited on the substrate 111 may be used.

Embodiment 2 As shown in FIG. 5, this embodiment differs from Embodiment 1 in that the hologram combiner 13 is replaced with the windshield 55 of the vehicle.
This is another embodiment in which other components such as the display 21 and the combiner 13 are separately provided. In this example, the signal light 31 emitted from the display 21 is used.
Is directly radiated to the polarizing plate 15 without passing through a mirror. The indicator 21 is housed inside the dashboard 51 of the vehicle, and the signal light 3 of the dashboard 51 is provided.
A polarizing plate 15 is disposed at one of the emission sections.

The polarizing plate 15 can rotate the plane of polarization by operating a holder 431 provided in the opening of the dashboard 51. Note that the display 2 is the same as in the first embodiment.
The optical path of the signal light 31 may be changed by disposing a mirror 22 (FIG. 1) between the first and the polarizing plates 15. Others are the same as in the first embodiment.

[Brief description of the drawings]

FIG. 1 is a system configuration diagram of a head-up display device according to a first embodiment.

FIG. 2 is a diagram illustrating a relationship between a rotation angle of a polarizing plate based on a polarization direction of signal light and transmittance in the head-up display according to the first embodiment.

FIGS. 3A and 3B schematically show the relationship between the angle between the axis of easy transmission and the direction of polarization (electric field) of incident light and the intensity of transmitted light in the polarizing plate of Embodiment 1; FIG. To
(B) shows an angle around 90 °).

FIG. 4 is an enlarged cross-sectional view of the hologram combiner according to the first embodiment.

FIG. 5 is a system configuration diagram of a head-up display device according to a second embodiment.

FIG. 6 is a system configuration diagram of a conventional head-up display device.

FIG. 7 is a diagram schematically showing an optical path when a washout phenomenon of a display image occurs in a conventional head-up display device.

[Explanation of symbols]

 11. . . Combiner, 15. . . Polarizing plate, 21. . . Display, 31, 32. . . Signal light, 82. . . Display image,

Claims (7)

[Claims] 1. A head-up display device configured to project a signal light emitted from a display onto a combiner and to visually recognize a display image by the signal light reflected by the combiner. Signal light is linearly polarized light, and between the display and the combiner,
A head-up display device comprising a movable polarizing plate capable of rotating a polarization plane. 2. The head-up display device according to claim 1, wherein the display device is a backlight type liquid crystal display device including a polarizing plate and a liquid crystal element. 3. The display according to claim 1, wherein the display comprises a display device that emits signal light that is not linearly polarized, and a polarizing plate, and the polarizing plate is disposed on a subsequent stage. A head-up display device characterized by the above-mentioned. 4. The display device according to claim 1, wherein the display, the polarizing plate, and the combiner are housed in a single case and are arranged near a dashboard of the vehicle. A head-up display device for a vehicle, comprising: 5. The head-up display device for a vehicle according to claim 1, wherein the combiner is disposed on a windshield. 6. The head-up display device according to claim 1, wherein the combiner is a hologram combiner. 7. The head-up display device according to claim 1, wherein the combiner is a half mirror.