JPH0717301A - Head-up display device - Google Patents

Abstract

PURPOSE:To prevent a doubled display and a difficulty with visibility by determining the specific relationship between a thickness of windshield, a refractive index of the windshield, an angle of reflection at a combiner, an angle of a discrimination limit, and a value of a virtual image distance. CONSTITUTION:A relationship between a thickness of windshield T, a refractive index of the windshield (n), an angle of reflection theta1 at a combiner, an angle theta0 of a discrimination limit, and a virtual image distance L0 satisfies an expression shown separately. One of the ways of satisfying this relationship is increasing the virtual image distance L0, and the virtual image distance L0 is prolonged by putting a reflecting mirror 7 on the way of the light from a display device 3 to the combiner 3. Light emitted from a point P of the display device 3 enters eyes of a driver via a course passing the point P, the reflecting mirror 7, the combiner 2, and eye point E in this order. In this way, the driver sees a virtual image A and knows the indicated contents of the point P.

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 device for displaying display contents on a driver by reflecting the display contents on the inner surface of a windshield.

[0002]

2. Description of the Related Art In a head-up display device, a combiner for improving the reflection is applied to a part of the inner surface of the windshield, and the light emitted from the display is reflected on the combiner so that the driver can reflect the light. It is a display device. It is mainly used in large vehicles such as buses and trucks.

FIG. 2 shows a conventional head-up display device. In FIG. 2, 1 is a windshield, 2 is a combiner, 3 is a display, 4 is a hood, 5 is a steering wheel, P is a light emitting point on the display 3, A and B are virtual images, and E is a driver's eye point (eye). Position). The light emitted from point P is reflected by combiner 2 and eyepoint E
As the driver enters, the driver visually recognizes the point P as a virtual image A. As a result, the driver can know the display content of the display device 3.

As a conventional document relating to the head-up display device, there is, for example, Japanese Utility Model Laid-Open No. 2-75327.

[0005]

[Problems to be Solved by the Invention]

(Problem) However, the above-described conventional head-up display device has a problem in that two virtual images are formed and it is difficult to visually recognize the display content.

(Explanation of Problems) In order to avoid obstructing the field of view in front of the windshield 1, the combiner 2 is not made so as to reflect light completely. Passes through the combiner 2 and is reflected by the inner surface on the outside of the windshield 1 to enter the eyepoint E. As a result, the second virtual image B is created, and the driver sees two virtual images A and B. Therefore, the images are duplicated and the displayed contents are hard to see. This phenomenon will be described in more detail as follows.

FIG. 3 is a principle diagram of virtual image formation. Due to the space of the drawing, the glass thickness T is exaggerated and the positions of the point P and the eye point E are drawn closer than they actually are. Reference numeral corresponds to FIG. 2, T is glass thickness, 1-1 is the inner surface of the windshield 1, 1-2 is the outer inner surface of the windshield 1, C, D, F, G, M are points, and L ₀ is a virtual image. distance,
L ₁ , L ₂ , H, and K are lengths, and θ, θ ₁ , θ ₂ , and θ ₃ are angles. The virtual image distance L ₀ is from the eye point E to the inner surface 1
It is the distance to the virtual image A due to the reflection of -1. L ₁ is the length from the eye point E to the reflection point C, and L ₂ is the length from the point P to the reflection point C.

Of the light emitted from the point P, the light reflected by the inner surface 1-1 of the windshield 1 and entering the eye point E is the point P.
→ Follow the route of point C → eye point E. Of the light emitted from the point P, the light reflected by the outer inner surface 1-2 and entering the eye point E follows the route of point P → point D → point M → point F → eye point E. At points D and F, the light is refracted at the refractive index of glass. Therefore, the driver has eye point E → point C
Look at the virtual image A on the extension of the straight line toward
→ Since the virtual image B is seen on the extension of the straight line toward the point F, the image becomes double. An object of the present invention is to solve such a problem.

[0009]

In order to solve the above problems, the present invention provides a head-up display device for displaying light emitted from a display device by reflecting the light on a combiner coated on the inner surface of the windshield. Is T, the refractive index of the windshield is n, the reflection angle at the combiner is θ ₁ , the discrimination limit angle is θ ₀ , and the virtual image distance is L ₀ , Configured to satisfy the relationship. One of the measures for satisfying this relationship is to increase the virtual image distance L _0. For that purpose, a reflecting mirror for reflecting the light from the display and making it enter the combiner is provided. A concave mirror may be used as the reflecting mirror.

[0010]

[Operation] If the head-up display device is configured to satisfy the above formula, even if the virtual image is doubled,
Since the angle between the virtual images is smaller than the recognition limit angle for the human eye, it cannot be seen as double by the human eye. A powerful way to configure to satisfy the above equation is to provide a reflector that reflects the light from the display and makes it enter the combiner. The length of the optical path from the display to the eyes of the driver is equal to the virtual image distance L ₀ , but the above formula is satisfied by providing a reflecting mirror and increasing the length.

[0011]

Embodiments of the present invention will now be described in detail with reference to the drawings. As shown in the principle diagram of FIG. 3, the angle at which the virtual images A and B are viewed from the eyepoint E is θ (hereinafter sometimes referred to as “angle between virtual images”), but the human eye
It is not possible to identify this to an infinitely small angle.
Medical studies have reported that below a certain angle θ ₀ , the human eye can no longer be distinguished as two things. That angle is the "discrimination limit angle"
However, θ ₀ is said to be about 0.08 °.
Therefore, in the case of the head-up display device, if the angle θ between the virtual images for viewing the virtual images A and B is smaller than θ ₀ (= 0.08 °), the driver does not see a double image. The present invention has taken this point into consideration and devised a configuration in which a double image cannot be seen.

First, the relationship between the virtual image angle θ and other numerical values is clarified from the principle diagram of FIG. 3, and then the virtual image angle θ is satisfied in order to be smaller than the discrimination limit angle θ _0. Guide the right relationship. In FIG. 3, the length L ₁ is the eye point E.
And the point C (reflection point), and the length L ₂ is the point P.
And the point C (reflection point). Since the virtual image A is at a position symmetrical to the point P with respect to the inner surface 1-1 which is the reflecting surface, the length between the point C and the virtual image A is also L ₂ . Therefore, L ₀
= L ₁ + L ₂ . The length H is the length from the point of the virtual image A to the intersection G of the line drawn at a right angle to the straight line AE and the straight line EB. The length K is the length of a perpendicular line drawn from the point F to the straight line AE.

From ΔGAE, the following equation is obtained. H = EA tan θ = L ₀ tan θ (1) When the refractive index of the glass is n, the following equation is obtained by paying attention to the refraction state at the point F (definition equation of refractive index). However, θ ₃ + θ = θ ₁ , and in the head-up display device, the virtual image angle θ is equal to the refraction angle θ ₃
Since it is much smaller than, θ ₃ ≈ θ ₁ .

Next, pay attention to the line segment FD. FD is △ E
The sum of the side FC of CF and the side DC of ΔPCD (FD = FC
+ DC) can be seen. On the other hand, it can also be seen as the side FD of ΔMFD. Hereinafter, an equation for calculating the line segment FD will be obtained based on each viewpoint.

First, it is proved that ΔECF and ΔPCD are similar to each other. Both ∠ECF and ∠PCD are angles of θ ₁ . Therefore, ∠ECF = ∠PCD. Also, ∠EF
Both C and ∠PDC are angles obtained by adding θ ₃ to the right angle, so ∠EFC = ∠PDC. Since the two corners are the same, △ EC
F and ΔPCD are similar. If the shapes are similar, the ratio of sides is equal, On the other hand, since EC = L ₁ and PC = L ₂ , Therefore,

FIG. 4A shows ΔEFC from the principle diagram of FIG.
It is the figure which extracted. Point R is a foot of a perpendicular line drawn from the point F to the side CE, and K is the length of the perpendicular line. From CFR, Substituting (5) and (6) into FD = FC + DC, the following equation is obtained.

Next, an equation for calculating K is obtained. Figure 4
In ΔEFR of (a), K = ERtan θ (8) ER = L ₁ -CR (9) CR = Ktan θ ₁ (10) (10) is substituted into (9), and it is (8) ), K = (L ₁ −Ktan θ ₁ ) tan θ (11)

FIG. 4B shows the ΔMFD from the principle diagram of FIG.
It is the figure which extracted. The point N is a foot of a perpendicular line drawn from the point M to the side FD. The length of the vertical line is nothing but the glass thickness T. ∠FMN and ∠DMN are point F (or point D)
Is the refraction angle θ ₂ on the glass side. FD = 2NF = 2Ttan θ ₂ (13)

From (7) and (13), Substituting (12) into (14),

[0020] When transformed, L ₀ tan θ = 2T tan θ ₂ cos θ ₁ (1 + tan θ ₁ tan θ) = 2T tan θ ₂ cos θ ₁ + 2T tan θ ₂ cos θ ₁ tan θ ₁ tan θ = 2T tan θ ₂ cos θ ₁ + 2T tan θ ₂ sinθ ₁ tan θ … (15)

From FIG. 3, tan θ = H / L ₀ , and θ
₂ is from (3) Therefore, by substituting these into (15), In the case of a head-up display device, L ₀ >> T, sin
θ ₁ <1, and Therefore, the denominator of the above formula H is approximately equal to L _0, and the following formula is approximately obtained.

On the other hand, from FIG. 3, H = L ₀ tan θ, and as described at the beginning, even if the images are doubled, if the virtual image angle θ <the discrimination limit angle θ ₀ , the human being Cannot be identified as double, so H <L ₀ tan θ ₀ (17) should be satisfied. By (16) and (17),
We obtain

Therefore, when designing a head-up display device, the relationship between T, θ ₁ , n, and L ₀ can be calculated by (18)
If it is designed to satisfy the formula, the double image will not be visible. The configuration of the head-up display device,
It is a basic idea of the present invention that the constitution satisfies the formula (18). In constructing the head-up display device, an effective configuration method for satisfying the expression (18) is to reduce the glass thickness T or increase the virtual image distance L ₀ . Next, a specific design example will be shown.

(Specific Example 1) θ ₁ = 40 °, n = 1.5
(Lens of glass), If L ₀ = 3 m, what is the thickness T of the windshield 1 for preventing the double image from being seen? To obtain it, the above value and θ ₀ = 0.08 ° may be substituted into the equation (18). Then, the relationship of T <5.76 mm is obtained.
Therefore, it can be seen that glass thinner than 5.76 mm should be used.

(Specific Example 2) θ ₁ = 40 °, n = 1.5
(Glass refractive index), where T = 6.5 mm, what is the length of the virtual image distance L ₀ for making the double image invisible? To obtain it, the above value and θ ₀ = 0.08 ° may be substituted into the equation (18). Then, the relationship of L ₀ > 3383.2 mm is obtained.

It is apparent from the above-mentioned first embodiment that the double image cannot be seen if the glass thickness T of the windshield 1 is made thin, but the glass thickness T is too thin in consideration of safety and strength. It is not possible (currently, the glass thickness T is 4 to 5 mm for passenger cars and 6 to 7 mm for large commercial vehicles). Therefore, the structural ingenuity performed to satisfy the expression (18) is mainly directed to increasing the virtual image distance L ₀ .

(Embodiment of the Present Invention) FIG. 1 is a diagram showing an embodiment of a head-up display device of the present invention. Reference numerals correspond to those of FIG. 2, 6 is a roof, and 7 is a reflecting mirror. In this embodiment, the virtual image distance L ₀ is lengthened by interposing the reflecting mirror 7 in the path through which the light from the display device 3 reaches the combiner 2.

The light emitted from the point P of the display 3 enters the eyes of the driver through the route of point P → reflecting mirror 7 → combiner 2 → eye point E. As a result, the driver can see the virtual image A
To know the display content of the point P. The reflecting mirror 7 is used as a means for increasing the length L ₂ in FIG. Since L ₀ = L ₁ + L ₂ as shown in FIG. 3, it is possible to increase the virtual image distance L ₀ by increasing L ₂ .

Therefore, the reflecting mirror 7 may be a plane mirror, but the concave mirror has a function of further increasing L ₂ (the smaller the curvature of the concave mirror, the larger L ₂ is. Since it can be said that the plane mirror is a concave mirror having an infinite curvature, it is possible to create a large virtual image distance L ₀ in a narrow cab. For example, point P in FIG. 1 → reflecting mirror 7 → combiner 2 →
When the total path to the eye point E is 1,750 mm and a concave mirror having a curvature of 1,900 R is adopted as the reflecting mirror 7, L ₀ = about 7 m can be obtained. It should be noted that any means other than a reflecting mirror may be used as long as it has a function of increasing the virtual image distance L ₀ .

[0030]

As described above, according to the head-up display device of the present invention, since it is configured to satisfy the expression (18), even if two virtual images are formed, the angle between virtual images θ The angle is smaller than the discrimination limit angle θ ₀ , and the driver does not see a double image. Therefore, the display is not duplicated and difficult to see.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of a head-up display device of the present invention.

FIG. 2 is a diagram showing a conventional head-up display device.

FIG. 3 Principle diagram of virtual image formation

FIG. 4 is a diagram showing a part of the principle diagram taken out.

[Explanation of symbols]

1 ... Windshield, 2 ... Combiner, 3 ... Indicator,
4 ... bonnet, 5 ... handle, 6 ... roof, 7 ... reflector, T ... glass thickness, L ₀ ... virtual image distance, A, B ... virtual image, E
… Eye point

Claims (3)

[Claims] 1. A head-up display device for displaying light emitted from a display device by reflecting the light onto a combiner coated on the inner surface of the windshield, wherein T is the thickness of the windshield, n is the refractive index of the windshield, and is the combiner. Where the reflection angle at ₁ is θ ₁ , the discrimination limit angle is θ ₀ , and the virtual image distance is L ₀ , A head-up display device characterized by satisfying the relationship of 2. A virtual image distance L in a head-up display device for displaying light emitted from a display device by reflecting the light on a combiner coated on the inner surface of a windshield.
The head-up display device according to claim 1, further comprising a reflecting mirror that reflects the light from the display unit and makes the light incident on the combiner in order to increase ₀ . 3. The head-up display device according to claim 2, wherein a concave mirror is used as the reflecting mirror.