JPH04128816A - Head-up display device - Google Patents

Abstract

PURPOSE:To offer a display which causes no intense abnormal light emission on the display surface of a fluorescent display tube even when the sunshine is incident on a display optical system by installing an element which reflects light in a irregular reflecting direction in the optical path. CONSTITUTION:When the sunshine (i) is incident on an off-axis reflection type hologram 2 in the opposite direction from display light (h) from a projection optical system unit 19, light except in the reflecting wavelength of the hologram is transmitted or reflected regularly by the surface and never enters a display unit 1. The abnormal light emission of the display unit 1 is greatly reducible. Light in the reflecting wavelength band of the hologram 2 is made incident on the display unit 1, but weaker than the display light (f), so there is no practical problem. Consequently, the head-up display is constituted so that the display light is reflected by a windshield and guided to the eye position of a driver; and a display is easily recognized by irradiating intensely the display unit even when the sunshine is incident in the opposite direction from the display light. Further, a projection optical system is unitized in one body and its installation into a dashboard is facilitated.

Description

[Detailed Description of the Invention] [Summary] It relates to a head-up display device, in particular, a miniaturized head-up display device that projects display light toward a windshield and shows a display image to the driver by reflecting according to the shape of the windshield. For head-up display devices with display optical systems, prevent the phenomenon in which external light such as sunlight travels in the opposite direction of the display light propagation path, illuminating the display tube surface and causing false light emission, resulting in incorrect display. With the aim of The optical system is integrated into a unit, and the projection optical system unit is embedded and installed in a dash board of a car, etc., and the display light is projected onto the windshield through an opening window for display light output provided on the dash board. , so that the component of the projected light reflected by the windshield reaches the position of the driver's eyes. Alternatively, instead of embedding the projection optical system unit in the dash board, it is installed on the dash board and the same display is performed.

[Industrial application field]

The present invention relates to a head-up display device, and more particularly to a head-up display device having a compact display optical system that projects display light onto a windshield and shows a display image to the driver by reflection according to the shape of the windshield. The present invention relates to an up display device.

[Conventional technology]

Head-up display devices display secondary video information superimposed on the scenery within the field of view, and are valuable in that they allow more information to be recognized almost simultaneously without making bold movements or shifting the line of sight. is high. It has already been put into practical use in the cockpits of fighter jets and aircraft. Furthermore, recently, application to automobiles is being considered.

When applying a head-up display device to an automobile, the following three types of combiners that transmit background light and reflect display light can be considered. The first method is to use a reflection hologram and form it integrally with the windshield.As shown in FIG. 12(a), a projection optical system unit 19 including a display is mounted, for example, inside the dash board 1, and the display light is emitted. The image is guided to the driver's eye position 6 by being reflected by a reflection hologram 5 formed on the windshield 15. The second method is to install a separate hologram combiner on the dash board.
As shown in Figure (b), a projection optical system unit 19 including a display is mounted, for example, inside the dash board 17, and the display light is reflected from the hologram combiner 5'7 to the driver's eye position 6. It guides display light towards the target. The third method is to use the windshield itself without forming a hologram or the windshield processed to increase the reflectance as a combiner.As shown in FIG. 12(C), for example, a projection optical system including a display device is used. The system unit 19 is mounted, for example, inside the dash board 17, and the display light is reflected by the windshield 15,
This guides the driver's eyes to position 6.

The first method requires the formation of a reflective hologram in the windshield manufacturing process, which is expensive, and the hologram reflects light from the surroundings, causing the hologram to have a tint when viewed from the outside of the car. , there were problems such as spoiling the sense of luxury. The second method had problems such as the outline of the combiner breaking the continuity of the field of view and the safety of installing a structure on the dash board. On the other hand, the third method has a problem in that the light utilization rate of display light is low, but it can be made at a low cost and there are no safety problems. Therefore, as a head-up display for automobiles,
The third method is most likely.

[Problem to be solved by the invention]

In the third method described above, as shown in FIG.
When sunlight 1 enters the display optical system 19 from the opening 16 on the dash board 17 in the direction opposite to the propagation path of the display light, it illuminates the display 1, and especially when a fluorescent display tube is used as the display, the phosphor Since it is white, the light is strongly scattered, and the display segment will be in a state of emitting light regardless of whether there is a display or not, making it impossible to display correctly.

FIG. 14 is a diagram for explaining a pseudo light emission state.

FIG. 14(a) shows a normal display, where "r80" is displayed. Display segments marked with diagonal lines are not emitting light. FIG. 14(b) shows a pseudo-emission state, in which the entire display segment is illuminated with strong light (sunlight) and the white phosphor scatters the light, making it appear as if it were emitting light. When the intensity of this scattered light is stronger than the display light (sunlight on a clear day is sufficiently strong), it becomes difficult to distinguish whether there is a display or not. Fluorescent display tubes have higher brightness than other displays, and are also inexpensive, making them the most promising device for head-up displays.

Therefore, there has been a need for a solution to the problem of false light emission in fluorescent display tubes.

The present invention was created in view of the above-mentioned conventional drawbacks, and provides a head-up display having a display optical system that does not cause strong abnormal light emission on the display surface of a fluorescent display tube even if sunlight enters the display optical system. The purpose is to provide.

[Means to solve the problem]

In the present invention, the projection optical system unit 19 has a simple configuration consisting of the display 1 and the image magnification optical system 3, and as a means to prevent abnormal light emission of the display 1 when sunlight 1 is incident, the light is An element that reflects in the reflection direction is installed in the optical path. Specifically, an off-axis reflection hologram 2 is installed near the display, the display light f is reflected by the hologram, and the reflected light g is guided to the magnification optical system 3 to magnify the displayed image. do. Generally, when light is reflected by an off-axis reflection hologram, the direction of reflection differs depending on the wavelength and chromatic aberration occurs, but by placing the hologram near the display 1, the chromatic aberration can be virtually ignored.

[For production]

When sunlight entering the projection optical system unit 19 in the opposite direction to the display light enters the off-axis reflection hologram 2, light outside the reflection wavelength band of the hologram 2 is transmitted or specularly reflected by the surface, and the display Since the light does not reach the display device 1, abnormal light emission of the display device 1 can be significantly reduced. Light in the reflection wavelength band of the hologram enters the display 1, but the amount of abnormal light emitted by the display 1 due to this light is weaker than the display light f, so it does not pose a practical problem.

〔Example〕

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

In order to make the description of the configuration and operation easier to understand, the same parts will be designated by the same reference numerals throughout the design and their repeated description will be omitted.

FIG. 1 is a diagram showing essential parts of a first embodiment of the present invention.

In the figure, reference numeral 1 denotes a display (fluorescent display tube) that displays the speed and instruments when the vehicle is running. Reference numeral 2 denotes an off-axis reflection hologram, which is created so that when the light f emitted from the display device 1 is reflected, its reflection angle is different from the incident angle. Here, the incident angle and the reflection angle are defined as the angles formed by the normal line of the hologram 2 and the incident beam and the reflected beam, respectively, in the space on the display 1 side with respect to the hologram 2. The light g reflected by the off-axis reflection hologram 2 generates a virtual image 11, which is further reflected by a concave mirror 30 provided as an enlarging optical system 3. As a result, a virtual image 12 enlarged in the distance is formed. The light reflected by the concave mirror 30 passes through an opening window 18 provided to seal the projection optical system unit 19, and is emitted to the outside of the unit. FIG. 2 shows how the projection optical system unit 19 of the present invention is installed in an automobile. A projection optical system unit 19 is embedded inside the dash board 17, and an opening 16 is provided for emitting display light. The output angle of the display light from the projection optical system unit 19 is designed so that the display light emitted from the projection optical system unit 19 is partially reflected by the windshield 15 and directed toward the driver's eye position 6. Further, the windshield (a plate-shaped member whose reflectance and transmittance are set to predetermined values) 15 may be configured such that the surface that reflects display light is not subjected to any treatment and the interface between the glass and the air is used as a reflective surface, or the surface that reflects display light may be used as a reflective surface. In order to increase the ratio, a thin metal film, a dielectric multilayer film, a specular reflection hologram film, etc. may be provided. As a result of the above, the driver can see the displayed image at the position of the virtual image 13 within his/her visual field.

FIG. 3 is a perspective view of the display l and off-axis reflection hologram 2 in the projection optical system unit 19. The off-axis reflection type hologram 2 is created so as to reflect the display light f, which is incident at an almost vertical angle, in the direction indicated by the arrow g at a large reflection angle θ (for example, 45 degrees). For example, a reflection hologram may be used that can be created by irradiating two plane waves from different surfaces of a hologram dry plate at different incident angles and causing interference. The reflection wavelength band of the off-axis reflection hologram is set to be near the peak value of the emission spectrum of the display 1, as shown in FIG. The effective area of the off-axis reflection hologram 2 is set to be approximately equal to or larger than the display area of the display 1. The details of the required area vary depending on the size of the elements constituting the magnifying optical system 3 (in this case, the concave mirror 30) and the size of the eye position range (visual range) where the driver can see the display. Determined by design.

In this embodiment configured in this way, when sunlight i that is incident in the opposite direction to the display light from the projection optical system unit 19 in FIG. Light outside the band is transmitted or specularly reflected on the surface and does not enter the display 1. Therefore, abnormal light emission of the display device 1 can be significantly reduced. Note that although the light in the reflection wavelength band of the hologram 2 is incident on the display 1, the amount of abnormality generated in the display 1 due to this light is weaker than that of the display light f, and therefore does not pose a practical problem.

FIG. 5 is a diagram for explaining that the chromatic aberration caused by the off-axis reflection hologram 2 can be substantially ignored by placing the hologram near the display 1. Light diverges from each point on the display surface in the form of a spherical wave,
Here, it will be represented by a central ray. The light traveling from the point P on the display surface to the off-axis reflection hologram 2 has various wavelength components. The longest and shortest two wavelengths are selected from among the wavelength components, and each wavelength is λ1. Let it be λ2. Since the direction reflected by the off-axis reflection hologram 2 differs depending on the wavelength, the virtual image of the point P is located at a position P1 . Formed at P2.

A virtual image created by light with a wavelength between λ1 and 22 is point P1 and point P2.
formed between. In other words, the point P, which was originally a negative point, becomes blurred in the form of a line whose ends are approximately the points P1 and P2. This is chromatic aberration, and the degree of blurring largely depends on the distance d between the display 1 and the off-axis reflection hologram 2.

Although the difference in the reflected direction (Δθ) remains constant once the wavelength is determined, the distance between points P1 and P2 can be reduced by reducing d. Considering that the wavelength selection width of Ofaxis reflection hologram is 20 to 30 nm,
If d<20 mm, image blurring can be substantially ignored.

FIG. 6 is a diagram showing essential parts of a second embodiment of the present invention.

In this embodiment, two concave mirrors 3L32 are used as the magnifying optical system 3.
This is an attempt to improve the display magnification rate by using . In order to increase the magnification, a concave mirror 30 with a short focal length may be used in the embodiment shown in FIG. 1, but this increases image distortion and makes it difficult to secure a wide viewing range. Specifically, when the position of the driver's eyes changes, the shape of the displayed image is greatly distorted. Therefore, by using two concave mirrors with relatively long focal lengths, it is possible to easily increase the magnification of the image. Although the optical axis is in a plane in FIG. 6, the direction of emission of the display light can be changed arbitrarily.

Usually, a driver's seat is provided so that a driver of a car can sit on the right or left side of the car. Therefore, the manner in which the display light is reflected by the windshield 15 is not as simple as can be drawn in a plan view, as shown in FIG. That is, as shown in FIG. 7, the display light emitted from the opening 16 on the dash board 17 needs to be reflected by the windshield 15 in a diagonal sliding manner and guided to the driver's eye position 6.

This embodiment configured in this way can significantly reduce abnormal light emission due to sunlight incident in the opposite direction to the display light, similar to the first embodiment, and furthermore, image distortion can be reduced compared to the first embodiment. can be reduced compared to

FIG. 8 is a modification of the second embodiment, and shows an example of the projection optical system unit 19 applicable to the above-mentioned situation. FIG. 8(a) is a top view, and FIG. 8(b) is a side view. The components are the same as in the case of FIG. 6, including a display 1, an off-axis reflection hologram 2, and concave mirrors 31 and 32, but the arrangement and direction of reflection by the off-axis reflection hologram are different. In FIG. 8(b), the relative positional relationship between the display device 1 and the off-axis reflection hologram 2 may be substantially the same as that in FIG. 6, but the direction in which light is reflected is set to be an oblique direction. FIG. 9 is a diagram showing the positional relationship between the display 1 and the off-axis reflection hologram 2. The display light f that is incident approximately perpendicularly to the hologram surface is reflected in an oblique direction as shown by the light ray g. . The method for creating the hologram is the same as that shown in FIG. However, during use, the hologram dry plate must be rotated within its plane so that the light is reflected diagonally. The positional relationship between the display 1, the off-axis reflection hologram 2, and the concave mirror system is also twisted. Two more concave mirrors 3
132 is also made asymmetrical so that after the display light is reflected by the windshield 15, a horizontal character display and an appropriate visible range can be obtained.

Display unit 1, off-axis reflective hologram 2, concave mirror 3
1. The position of the concave mirror 32 is determined by ray tracing.

Since the ray tracing method itself is a well-known technique, its explanation will be omitted.

FIG. 10 is a diagram showing main parts of a third embodiment of the present invention. In this embodiment, an optical lens system 34 is used as the enlarging optical system 3. Although the figure shows a single convex lens, it goes without saying that a group lens may also be used. However, in order to reduce costs, it is desirable to have a lens configuration as simple as possible. This embodiment configured as described above can obtain the same effects as the second embodiment.

FIG. 11 is a diagram showing essential parts of a fourth embodiment of the present invention. In this embodiment, an optical lens 35 and a concave mirror 36 are used as the enlarging optical system 3. This embodiment configured in this manner also provides the same effects as the second embodiment.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, an off-axis reflection hologram is arranged near the display, and after the display light is reflected by the hologram, the image is enlarged by the enlarging optical system. By configuring the head-up display so that the display light from the same optical system is reflected by the windshield and guided to the driver's eye position, even if sunlight enters in the opposite direction to the display light, This has the effect of preventing an abnormal light emission phenomenon that would cause the display device to be strongly illuminated and make it impossible to recognize the display. Furthermore, by integrating the projection optical system into a unit, installation within the dash board can be facilitated.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the main parts of the first embodiment of the present invention, FIG. 2 is a diagram showing an example of a case where the projection optical system unit of the present invention is mounted on a car, and FIG. 3 is a diagram showing the projection optical system unit of the present invention. FIG. 4 is a diagram showing the characteristics of the display device and off-axis reflection hologram, and FIG. 5 is a diagram showing the characteristics of the display device and the off-axis reflection hologram, and FIG. FIG. 6 is a diagram showing the main part of the second embodiment of the present invention, and FIG. FIG. 8 is a diagram showing a modification of the second embodiment of the present invention; FIG. 9 is a diagram showing a modification of the second embodiment of the present invention. FIG. 10 is a diagram showing the relationship between the display device, the off-axis reflection hologram, and the propagation direction of display light in a modified example; FIG.
FIG. 1 is a diagram showing the main parts of the fourth embodiment of the present invention, FIG. 12 is a diagram showing the configuration of three examples of conventional head-up displays, and FIGS. 13 and 14 are the problems to be solved by the invention. FIG. 2 is a diagram for explaining a problem. In the figure, 1 is the display (fluorescent display tube), 2 is the off-axis reflection hologram, 3 is the magnifying optical system, 5.5' is the reflection hologram, 6 is the position of the driver's eyes, 11.12.13 15 is a virtual image, 15 is a windshield (a plate-like member with reflectance and transmittance set appropriately), 16 is an opening of the dash board, 17 is a dash board, 18 is an aperture window of the projection optical system unit, 19 is the projection optical system unit , 20 is a housing, 21 is a transparent plate-like member, 30, 31, 32, and 36 are concave mirrors, 34.35 is a lens system, f is light directed from the display to the off-axis reflective hologram, and g is an off-axis reflective hologram. Light heading from the hologram to the magnifying optical system, h indicates light heading from the enlarging optical system to the windshield, and 1 indicates sunlight. Figure 1 showing the main parts of the first embodiment of the present invention Figure 3... Magnifying optical system 30... Concave mirror Figure 2 showing an example of the case where the projection optical system unit of the present invention is mounted on a car 6... Driver's eye position 18... Opening window 9... Diagram showing the relationship between the propagation directions of the projection optical system and the lid. Figure 3: Emission spectrum of display (G) Off-axis reflection hologram Figure 4 shows the characteristics of the reflection wavelength band display and off-axis reflection hologram. 2 shows another example when the projection optical system unit is mounted on a car Seventh factor 6...Position of the driver's eyes 15...Windshield 16...Opening 17...Dashboard book Modification Example 1 of the Second Embodiment of the Invention Off-axis reflection hologram of the open-open display...Display 2...Off-axis reflection hologram 2 showing essential parts of the third embodiment of the invention Figure 10 shows the main parts of the fourth embodiment of the present invention. Figure 11 shows the main parts of the fourth embodiment of the present invention. Fig. 12 shows the configuration of an example. Fig. 2 shows the problem to be solved by the invention. Normal display (Q). The invention is in an abnormal light emitting state (b). Figure 14

Claims (1)

[Claims] 1. A projection optical system unit (19) having at least a display device (1), and reflecting light (f) emitted from the projection optical system unit (19) to determine the position of the user's eyes ( a plate-like member (15) for directing the plate-like member (15) toward
) is a regular reflection according to its shape, and the head-up allows the user to see the external scenery and the displayed image reflected by the plate-like member (15) superimposed within the field of view. In the display device, the projection optical system unit (19) includes at least a display device (
1), an off-axis reflection hologram (2) disposed near the display (1) and reflecting light from the display (1), and a display image reflected by the hologram (2). The light from the magnifying optical system (3) is reflected by a plate-like member (15) with appropriately set reflectance and transmittance to be visible to the driver's eyes. A head-up display device characterized in that by directing the display image toward the position (6), the displayed image can be visually recognized superimposed on the external scenery. 2. The head-up display device according to claim 1, wherein the magnifying optical system (3) is a single concave mirror (30). 3. The magnifying optical system (3) includes two concave mirrors (31, 32
) The head-up display device according to claim 1. 4. The head-up display device according to claim 1, wherein the magnifying optical system (3) is a lens system (34). 5. The magnifying optical system (3) includes at least one lens (
35) and at least one concave mirror (36). 6. The display device (1), the off-axis reflection hologram (2), and the magnifying optical system (3) are housed in one housing (20), and a transparent aperture window (18) is provided for display light emission. 6. The head-up display device according to claim 1, wherein the housing (20) has a sealed structure by providing a plate-like member (21). 7. Claims 1 to 5, wherein the reflectance of the plate member (15) whose reflectance and transmittance are set to predetermined values is set based on reflection at an interface between the member and air. or 6
The head-up display device described. 8. The reflectance of the plate member (15) whose reflectance and transmittance are set to predetermined values is set by providing a structure for increasing the reflectance. head-up display device. 9. The head-up display device according to claim 8, wherein the structure for increasing the reflectance is a metal thin film, a dielectric multilayer film, or a specular reflection hologram film. 10. Attach the projection optical system unit (19) to a car, and reflect the display light emitted from the projection optical system unit (19) with a windshield (15) whose reflectance and transmittance are set to predetermined values. 10. The head-up display device according to claim 1, wherein the display is superimposed within the driver's front field of vision.