JPH02141720A - Head-up display device - Google Patents

Abstract

PURPOSE:To prevent a double or triple image from being formed owing to reflection on many surfaces and to secure the brightness of a display image by providing a windshield with a polarizing direction adjusting means, making S-polarized light or P-polarized light on its internal surface at a Brewster angle, and eliminating reflection on the internal or external surface of the windshield. CONSTITUTION:Light which is transmitted in the windshield 4 as to display light which is made incident on the internal surface of the windshield 4 has its polarizing direction rotated by 90 deg. through the polarizing direction adjusting means 5, and neither the P-polarized light which is made incident at the Brewster angle nor P-polarized light which is projected from the external surface are reflected by the surface. Therefore, the S-polarized light with is made incident on the internal surface of the windshield 4 at the Brewster angle is reflected with a constant reflection factor to form a display image in the front visual field of a driver. At this time, the S-polarized light which is not reflected, but transmitted through a reflecting layer is made into P-polarized light by the polarizing direction adjusting means 5 and the P-polarized light travels to the external surface of the windshield 4 at the Brewster angle, so only the reflection on the external surface is eliminated. Consequently, the brightness of the reflected display image is secured, a double image is eliminated, and the visibility is improved.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention provides a head-up display device that improves visibility by eliminating reflections on either the inner surface or the outer surface of a windshield. Regarding.

[Conventional technology]

2. Description of the Related Art Head-up display devices that display information such as vehicle speed in front of a windshield have been proposed. Furthermore, in order to prevent the displayed image from appearing double and reducing visibility, the direction of the electric field of the polarized light of the display light incident on the windshield 10 is adjusted to the birch shown in FIG.
A configuration has been proposed in which the light is linearly polarized so as to be parallel to the incident plane (the plane including the optical path of the incident light and the reflected light) (hereinafter referred to as polarized light), and the incident angle to the windshield 10 is the Brewster angle θ8. (For example, Japanese Patent Application Laid-Open No. 61-45218
Publication No.). In this configuration, since the incident angle is the Brewster's angle, the windshield 10 is transmitted through the reflective layer on the inner surface of the windshield, and there is no reflection at the inner and outer surfaces, and the polarization direction of the wavelength-selected transmitted light is changed. Only the reflection from the polarization direction film 11 rotated by 90' is visible to the driver.

It is characterized by having an adjustment means.

[Problem to be solved by the invention]

However, in the above configuration, the wavelength selective film 11
Since the incident angle is close to Brewster's angle, its reflectance also decreases, and the reflected display image may become dark.

Therefore, the present invention provides a head-up display device that improves visibility by eliminating double images while ensuring the brightness of a reflected display image.

[Means to solve the problem]

Accordingly, the present invention provides polarizing means for making the electric field direction of the polarized light of the display light incident on the windshield into linearly polarized light perpendicular to (S-polarized light) or parallel (P-polarized light) to the plane of incidence of the windshield; [Function] According to the above structure, the transmitted light that is transmitted into the inside of the glass out of the display light that has entered the inner surface of the windshield is controlled by the polarization direction adjusting means. The polarization direction can be rotated by 90''.

Here, the P-polarized light incident on the inner surface of the windshield at Brewster's angle and the P-polarized light emitted from the outer surface of the windshield at Brewster's angle have zero reflection on that surface.

Therefore, the S-polarized light incident on the inner surface of the windshield at Brewster's angle is reflected at a predetermined reflectance by the reflective layer on the inner surface of the windshield, and a display image is formed in the driver's front field of vision. At this time, the S-polarized light that is transmitted without being reflected by the reflective layer on the inner surface of the windshield becomes P-polarized light by the polarization direction adjusting means. Since this P-polarized light travels to the outer surface of the windshield at Brewster's angle, only the reflection at the outer surface of the windshield becomes zero.

Similarly, when the light incident on the inside surface of the windshield at Brewster's angle is P-polarized light, only the reflection on the inside surface of the glass becomes zero, but it passes through the polarization direction adjustment means and becomes S-polarized light. The display light is reflected at a predetermined reflectance from the outer surface of the windshield, and is imaged in the driver's front field of vision.

〔Effect of the invention〕

As described above, the present invention provides a polarization direction adjusting means on the windshield and has a configuration in which S-polarized light or P-polarized light is incident on the inside surface of the windshield at the Brewster angle. Reflection from only one side can be made zero. Therefore, it is possible to prevent double or triple images reflected from multiple surfaces and to ensure the brightness of the displayed image.

〔Example〕

Hereinafter, a first embodiment of the present invention will be described based on the drawings.

As shown in Fig. 1, on a part of the dash board D of the vehicle,
As a display means for displaying information such as vehicle speed necessary for the vehicle,
A fluorescent indicator 1 is provided. The display light from display 1 is
The light passes through the polarizing film 2, is reflected by a reflecting mirror or a hologram concave mirror for distant magnification 3, and is incident on a windshield 4 at a Hebliest angle θB.

This polarizing film 2 polarizes the display light into linearly polarized light (having an electric field vector perpendicular to the plane of S-polarization) perpendicular to the plane of incidence on the windshield.

In the windshield 4, a phase film 5 serving as a polarization adjustment means for rotating the polarization direction by 90 degrees is sandwiched between two laminated glasses.

In FIG. 4, the reflectance of the polarized light component (referred to as P component or P polarized light) parallel to the incident plane (the plane containing the optical paths of incident light and reflected light) becomes zero at Brewster's angle θ8. Therefore,
If the incident light is made into linearly polarized light (polarized light) having only a P component, reflected light can be eliminated. Further, a polarized light component perpendicular to the plane of incidence (referred to as an S component or S-polarized light) exhibits a reflectance of nearly 20% at the Brewster angle θ1. Incidentally, FIG. 4 shows the case of glass (refractive index -1.5).

Next, the action of the phase film 5 will be explained.

The phase film 5 includes a λ/2 film, etc.
The film has the function of rotating the polarization direction of incident light having a wavelength λ by 90° with respect to the direction in which the light travels. In other words,
When the incident light is P-polarized, it is polarized to S-polarized light, and the incident light is S-polarized.
When the light is polarized, it has the effect of polarizing the light into P-polarized light.

Here, as shown in FIG. 1, if the light incident on the windshield 4 is linearly polarized light with only S polarization and is made incident on the windshield 4 at a Brewster angle θ, then the windshield 4
Since the light is S-polarized on the inner surface of
% is slightly reflected and forms a display image within the driver's forward field of vision.

On the other hand, light other than that reflected from the surface is transmitted into the windshield 4, and the S-polarized light becomes P-polarized light at the phase film 5. When the light is emitted to the outside from the windshield 4, the angle is Brewster's angle θ6, so the P polarized light that has passed through the windshield 4 is completely transmitted without being reflected by the outer surface of the windshield 4, The reflection on the outer surface is zero.

Therefore, the light is reflected only on the inner surface of the windshield 4, and there is only one displayed image, eliminating double images and greatly improving visibility.

Next, a second embodiment will be described based on FIG. 2.

In the second embodiment, a phase film 5 in which a wavelength selection film 6 is provided as a reflection film is attached to the inner surface of a windshield 4 by vapor deposition or the like.

As a result, the S-polarized light incident on the inner surface of the windshield 4 at Brewster's plane θ is reflected at a predetermined reflectance determined by the wavelength selection film 6, and a display image is formed within the driver's front field of vision. do. On the other hand, the remaining S-polarized light that has passed through the wavelength selection film 6 becomes P-polarized light by the phase film 5, travels through the windshield 4, and is emitted at Brewster's angle θ. Therefore, the reflection of this P-polarized light on the outer surface of the windshield 4 is zero.

Next, a third embodiment will be described based on FIG. 3.

In the third embodiment, the light incident on the windshield 4 is made into P polarized light, and the reflection on the inner surface of the windshield 4 is made zero,
A display image is displayed using reflection on the outer surface of the windshield 4.

That is, the windshield 4 has a plutor angle θ toward the inner surface.
The P-polarized light incident at , is not reflected, but is entirely transmitted into the glass, and becomes S-polarized light at the phase film 4.

This S-polarized light is reflected at a predetermined reflectance on the outer surface of the windshield 4, becomes P-polarized light again by the phase film 4, and forms a display image within the driver's front field of vision.

As mentioned above, since the windshield is provided with a phase film and S-polarized light or P-polarized light is incident on the inside of the windshield at Brewster's angle, either the inside surface or the outside surface of the windshield is Since it is possible to reduce the reflection to zero, double and triple images can be prevented and the brightness of the displayed image can be ensured.

Also, when the incident angle deviates from Brewster's angle θ, it is reflected by S-polarized light. FIG. 5 shows the results of measuring the reflectance of the normal image formed and the noise image (an image that should originally disappear) due to reflection of P-polarized light. In FIG. 5, S indicates the reflectance of the normal image, and P indicates the reflectance of the noise image. N indicates the light amount ratio (S/P) between the normal image and the noise image. The sample used was measured using an argon laser (514.5 mm) with a phase film placed in the middle. As can be seen from Figure 5, the incident angle is Brewster's angle θ8 (57°
), a good display image with no double images will be obtained. Furthermore, there is a region in which a double image is not perceived even if the incident angle deviates somewhat from the Brewster angle θ. This is the sensitivity region where the light amount ratio N is 30 or more, and in this example it is (θ, -5).
to (θ, +3)''. However, the refractive index of the glass was set to 1.52. Therefore, if the light is incident within this region, a displayed image with almost no double images can be confirmed.

Incidentally, the polarizing film 2 of the above-described embodiment may be omitted if a liquid crystal display is used as the display 1 itself and polarized light similar to that described above can be incident on the windshield 4.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram showing the first embodiment of the present invention, Figure 2 is a partial diagram of the second embodiment, Figure 3 is a partial diagram of the third embodiment, and Figure 4 is S-polarized light. , an explanatory diagram showing the reflectance of P polarized light and Brewster angle θ3, FIG.
, a characteristic diagram showing the measured reflectance in the vicinity, and FIG. 6 is a diagram for explaining a conventional example. 1...Display device, 2...Polarizing film, 3...Reflector. 4... Windshield, 5... Phase film (polarization direction adjustment means). Representative Patent Attorney Takashi Okabe

Claims (1)

[Claims] Information displayed on a display means provided on the inside of the windshield is reflected by a reflective layer on the inside or outside surface of the windshield, and is displayed as an image within the driver's forward field of vision. In a head-up display device, the electric field direction of the polarized light of the display light incident on the windshield is set perpendicular (S polarization) or parallel (P polarization) to the windshield entrance plane.
polarizing means for linearly polarizing the light (polarized light); display means arranged so that the angle of incidence of the display light on the windshield is Brewster's angle; and the polarization direction of the transmitted light that has passed through the reflective layer on the inner surface of the windshield. A head-up display device equipped with a polarization direction adjustment means that rotates the polarization direction by 90 degrees.