JPH1048564A - Head-up display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small type and noise-reduced head-up display using a liquid crystal display panel permitting to obtain a clear image even if a brightness of a background changes in a combiner. SOLUTION: A virtual image of an observation object is formed in front of a combiner 2 by changing an optical path of an image display light beam by the combiner 2 placed forward of an observer. Air flow which is forcibly generated in a housing 5 is exhausted out of an exhaust port 30 on the side of the housing building in a liquid crystal display means 11 emitting the image display light and a light source for back light arranged to face this liquid crystal display means. The direction of the exhaust aid flow is changed to flow farther forward of the exhaust port 30.

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 suitable for being mounted on a vehicle such as an automobile running on the ground.

[0002]

2. Description of the Related Art For example, it has been proposed to use a head-up display as a display device for providing navigation information to a driver of a vehicle. The head-up display includes a combiner arranged in front of an observer, an image display that emits image display light, and a housing that covers the image display, and changes the optical path of the image display light by the combiner. This forms a virtual image of the observation target in front of the combiner. In addition, the light passing through the combiner allows the scene in front of the combiner to be visually recognized. As the image display, an image display having a liquid crystal display panel and a light source for a backlight disposed opposite to the liquid crystal display panel is used.

[0003] Since there is a tunnel or the like on the road of a vehicle for taxiing, the background luminance of the combiner may change instantaneously. Therefore, when the display brightness of the head-up display is fixed, the display image may appear dazzling or may be too thin to be visually recognized.

Therefore, the amount of light is adjusted by controlling the power of a bulb constituting the light source for the backlight of the liquid crystal display panel based on a signal which changes according to the luminance of the background, thereby changing the display luminance. That is being done. For example, PWM control for turning on and off the power supply of the tube at a high speed and changing the ratio of the on time is employed as the power control method.

[0005]

Even if the display brightness is changed in such a manner, if the change width is small, the displayed image is dazzling or too thin to be visually recognized. However, if the change width of the display luminance is increased, the power supplied to the backlight light source during the high luminance display increases, and the amount of heat generated by the light source increases. Therefore, the temperature of the liquid crystal display panel becomes 100 ° C. or higher. When the temperature of the liquid crystal display panel becomes high due to the heat generated by the light source, there is a problem that the display function is deteriorated.

As a countermeasure against such heat generation, it is conceivable to provide the backlight light source with a multilayer reflection filter or a heat ray absorption filter capable of blocking an infrared component of light emitted from the light source.

[0007] However, when the head-up display is installed above the dashboard of an automobile,
Installation space is limited. When the installation space is limited as described above, the interval between the backlight light source and the liquid crystal display panel must be reduced, and the interval may be required to be several mm or less. Then, the amount of heat transferred from the light source to the liquid crystal display panel increases, and the adverse effect on the liquid crystal display panel cannot be sufficiently avoided by merely providing the light source with an infrared cutoff filter.

Therefore, it is conceivable to cool the liquid crystal display panel and the light source for the backlight by an air flow generated by a fan or the like. In this case, it is required to efficiently generate an air flow in a housing in which the image display is built, and to reduce the size of an air flow generation unit such as a fan. Therefore, to reduce the flow resistance of the air flow,
It is necessary to minimize the bending of the air flow passage in the housing and to increase the flow passage area as much as possible. Then, depending on the arrangement of the liquid crystal display panel and the light source for the backlight in the housing,
It may be necessary to provide outlets on the left or right side of the housing for discharging the airflow from the housing.

However, when the outlet is provided on the side of the housing and the airflow is discharged from the side in the left and right direction, a loud exhaust sound is heard by an observer behind the outlet. In particular, when installed on a dashboard of a narrow vehicle or the like, there is a problem that a loud noise is heard by a driver of the vehicle or a passenger in a passenger seat.

An object of the present invention is to provide a head-up display capable of solving the above-mentioned problem.

[0011]

According to the present invention, there is provided a combiner arranged in front of an observer, an image display light emitting means,
A housing housing the emission means of the image display light, wherein the optical path of the image display light is changed by the combiner to form a virtual image of the observation target in front of the combiner. The light emitting means has a liquid crystal display means, and a backlight light source disposed to face the liquid crystal display means, and an air flow generating means for forcibly generating an air flow in the housing is provided. An outlet for discharging the air flow from the housing is provided on a side of the housing,
A means is provided for changing the direction of the airflow discharged from the outlet so as to be directed forward of the outlet. Even if the outlet of the air flow is provided on the side of the housing, the direction of the air flow discharged therefrom is changed so as to be more forward than the discharge port, compared to the case of discharging in the left and right lateral direction. The discharge sound heard by the observer behind the discharge port can be reduced.

The liquid crystal display means and the light source are arranged in front and rear, and the screen of the liquid crystal display means extends along the left-right direction, and a space is formed between the liquid crystal display means and the light source.
The air flow generating means sends out an air flow through the space so that the air flow passes along the left-right direction, and faces at least one of an inlet and an outlet of the air flow in the space. The outlet is preferably provided at a position facing the air flow outlet in the space. An air flow passes through the space between the liquid crystal display means and the light source, thereby preventing the air in the space from becoming high in temperature due to the heat generated by the light source. The amount of heat transfer can be reduced.
By sending out air along the horizontal direction along the screen of the liquid crystal display from a position facing at least one of the inlet and outlet of the air flow in the space, the air flow path is not unnecessarily bent. It is possible to reduce the flow path resistance and efficiently generate an air flow in the space. As a result, the amount of heat transfer to the liquid crystal display means can be efficiently reduced, and the airflow generating means can be downsized. With the outlet facing the outlet of the air flow in the space,
The flow resistance of the air flow from the outlet to the outlet can be made as small as possible, and the air flow generating means can be downsized.

[0013]

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

The head-up display 1 for a vehicle shown in FIGS. 1 and 2 includes a housing 5 and a combiner 2 attached to the housing. The housing 5 has a built-in image display 3, control circuit board 7, mirror 8, and fan 9.

The housing 5 comprises upper and lower members 5A, 5A,
The combiner 2 and the image display 3 are formed in front of an observer (driver) by being formed by connecting B and being attached to, for example, the upper surface of a dashboard. An emission window 5a for image display light is provided on the upper part of the housing 5.
Is formed, and a transparent cover 5b covering the emission window 5a is formed.
Is provided.

The image display 3 emits image display light L corresponding to, for example, navigation information and the like, and is arranged to face the liquid crystal display panel (liquid crystal display means) 11 and the liquid crystal display panel 12. Light source 12 for backlight
And The liquid crystal display panel 11 and the backlight light source 12 are separate units, and are individually fixed to the housing 5.

As shown in FIG. 3, the liquid crystal display panel 1
Reference numeral 1 denotes a panel main body 11a including a polarizing film formed by injecting a liquid crystal between a pair of glass substrates, and a light diffusing plate 11 disposed on the light source 12 side of the panel main body 11a.
b, and a holder 11d for holding the panel body 11a and the light diffusing plate 11b. The holder 11d is mounted on the bottom wall 5 'of the housing 5. The electrodes forming the pixels formed on the panel body 11a are the wirings 1
The liquid crystal display panel 11 is connected to the control circuit board 7 via 1e, and displays an image in response to an image signal sent from the control circuit board 7.

As shown in FIG. 4, the backlight light source 12 includes a case 12a mounted on a bottom wall 5 'of the housing 5, and a tube 1 built in the case 12a.
2b, a holder 12c for supporting the bulb 12b, an infrared cutoff filter 12d for covering an opening 12a 'formed on the liquid crystal display panel 11 side of the case 12a, and a light beam for backlight emitted from the bulb 12b. Reflecting plate 12e. The light emitted by the tube 12b passes through the liquid crystal display panel 11 to become image display light L. The filter 12d may be an infrared cut filter that reflects an infrared component of light emitted from the tube 12b or an infrared absorption filter that absorbs the infrared component, and may be any filter that can block infrared light. The bulb 12b is connected to a power supply via a power control circuit (not shown), and based on a signal from a background luminance sensor of the combiner 2, the light amount is adjusted in the same manner as in the related art according to a change in the background luminance. .

In this embodiment, as shown in FIG. 1, the image display 3 emits the image display light L backward.
The image display light L is reflected by the mirror 8. The image display light L whose optical path has been changed by the reflection by the mirror 8 is emitted from the emission port 5a so as to travel diagonally forward and upward.

The combiner 2, as shown in FIG.
A use position that is swingably attached to the housing 5 via a hinge 6 and that changes the optical path of the image display light L emitted from the emission port 5a and guides the image display light L to the pupil E of the observer by the swing; It can be displaced between a storage position that closes the emission port 5a. As the combiner 2, for example, a plate-like half mirror, a hologram element, or the like can be used. When a half mirror is used, the optical path of the image display light L is changed by reflection, and when a hologram element is used, the optical path of the image display light L is changed by diffraction.

As shown in FIG. 1, by changing the optical path of the image display light L by the combiner 2, a virtual image of the object to be observed is formed at a position P in front of the combiner 2, and the combiner 2 emits light from the front. The transmission allows the observer to visually recognize both the virtual image and the external scenery actually existing in front of the virtual image. Optical path changing surface 2a of the combiner 2
Has a function of condensing the image display light L, and has a curved surface that can be formed farther forward than when the virtual image is simply reflected.

As shown in FIG. 5, the liquid crystal display panel 1
1 and the light source 12 correspond to the screen 1 of the liquid crystal display panel 11.
They are arranged at intervals in the direction orthogonal to 1 '. By arranging the liquid crystal display panel 11 and the light source 12 in front and back, the screen 11 ′ extends in the left-right direction. Thereby, between the filter 12d of the light source 12 and the light diffusing plate 11b of the liquid crystal display panel 11, the upper and left and right sides are opened and the lower space 20 closed by the bottom wall 5 'of the housing 5 is formed. Is formed. In the present embodiment, the surface of the filter 12d and the surface of the light diffusion plate 11b are parallel to each other, so that the liquid crystal display panel 11 in the space 20 is formed.
Are substantially constant in the direction orthogonal to the screen 11 '.

The fan 9 is of an axial flow type having rotating blades 9a which are driven to rotate by a drive circuit (not shown), and forcibly restricts an air flow passing through the space 20 as shown by a two-dot chain line arrow in FIG. To be generated. The fan 9 is in the space 2
The air flow is generated by sending air out of the space 20 along the left-right direction along the screen 11 ′ of the liquid crystal display panel 11. . The fan 9
Is arranged to face the air flow inlet 20b in the space 20, and the air is generated by sending out the air toward the space 20 along the direction along the screen 11 'of the liquid crystal display panel 11. You may.

An air inlet 25 is formed in the housing 5 to introduce air from outside into the housing 5. The air inlet 25 is provided near the air flow inlet 20 b in the space 20.

An outlet 30 is formed on the left side of the housing 5 for discharging air from the inside of the housing 5 to the outside. The outlet 30 is provided at a position facing the airflow outlet 20 a in the space 20, and in the present embodiment, the fan 9 is disposed between the outlet 30 and the space 20.

A fin 31 is provided at the outlet 30. The fins 31 change the flow of the discharged air so as to be forward of the discharge port 30.

The air flow in the space 20 is generated so as to be laminar. That is, generally, the fluid becomes laminar when Re (Reynolds number) is less than about 2000 to 2300.
For the air flowing through the space 20 between the parallel planes as described above, Re is the average flow velocity (m / s) of the air, and d is the direction perpendicular to the screen 11 ′ of the liquid crystal display panel 11 in the space 20. The spacing, ν, is the kinematic viscosity coefficient of air, and
= V · d / ν. In addition, the surface of the filter 12d and the surface of the light diffusion plate 11b constituting the space 20 are sufficiently smooth and have a small roughness without any irregularities so as not to disturb the air flow. The kinematic viscosity coefficient ν (m ² / s) of the air is 15.01 × 10 at 20 ° C.
^-6 , it becomes larger as the temperature rises.
If the rotation speed of the fan 9 is set so that s) × d (mm) = 30 or less, Re can be 2000 or less at room temperature or higher, and the air flow can be laminar.

According to the above configuration, even if the air flow outlet 30 is provided on the side of the housing 5, the direction of the air flow discharged therefrom is changed so as to be forward of the outlet 30. Compared with the case where the paper is discharged in the horizontal direction, the discharge sound heard by the observer behind the discharge port 30 can be reduced.
In particular, when the head-up display 1 is installed on the dashboard of an automobile, the presence of the airflow by the defroster in front of the installation position causes the outlet 30
The airflow from the vehicle can be carried in the airflow in the entire vehicle compartment without being restricted to the exhausted space, so that a form having good consistency with the defroster can be obtained.

The flow of air through the space 20 between the liquid crystal display panel 11 and the light source 12 prevents the air in the space 20 from becoming hot due to the heat generated by the light source 12, and The amount of heat transfer from the substrate to the liquid crystal display panel 11 due to heat conduction can be reduced. In addition, there is no directly connected member between the light source 12 and the liquid crystal display panel 11 except for the bottom wall 5 'of the housing 5 that supports both, and heat transfer by direct heat conduction by such a member. And the amount of heat transfer to the liquid crystal display panel 11 can be reduced.

By making the air flow a laminar flow, heat transfer from the light source 12 to the liquid crystal display panel 11 due to the minute flow is eliminated as compared with a turbulent flow including a minute flow in a direction perpendicular to the flow direction. Thus, the amount of heat transferred to the liquid crystal display panel 11 can be reduced.

The amount of heat transferred to the liquid crystal display panel 11 can be reduced by blocking the infrared component of the light emitted from the light source 12 by the filter 12d.

The air flow outlet 20a in the space 20
Screen 1 of the liquid crystal display panel 11 from the position facing
By sending out the air along the direction along 1 ', the flow resistance of the air flow can be reduced without unnecessary bending, and the air flow can be efficiently generated in the space 20. As a result, the amount of heat transfer to the liquid crystal display panel 11 is efficiently reduced, and the fan 9 that generates the air flow is provided.
Can be reduced in size. Furthermore, since the outlet 30 faces the airflow outlet 20a in the space 20, the flow resistance of the airflow from the outlet 20a to the outlet 30 can be reduced as much as possible, and the fan 9 Can be downsized.

As a result, a clear image can be obtained even if the luminance of the background of the combiner 2 changes, and the liquid crystal display panel 1 suitable for fixing on a dashboard of an automobile or the like.
1 can provide a small head-up display 1 that generates less noise.

The present invention is not limited to the above embodiment. For example, the position of the fin 31 is not particularly limited as long as the direction of the airflow discharged from the outlet 30 can be set forward of the outlet 30. The direction of the air flow is not limited to the fins. For example, the air flow may be formed in a curved tube in which the inner circumference of the discharge port is gradually bent forward from the inside to the outside. The fan 9 may be provided at a position facing the entrance 20a of the space 20. The type of the fan 9 is not particularly limited, and for example, a centrifugal fan may be used. Inside the housing 5 other than the space 20,
Separately, an air flow may be forcibly generated. A reflector that reflects only light in the visible light range may be used as the reflector 12e of the light source 12. The facing surface forming the space 20 is not limited to be parallel, and is, for example, a screen 11 ′ of the liquid crystal display panel 11.
The shape of the space 20 may be formed in a wedge shape by gradually changing the interval in the direction perpendicular to the direction along the flow direction.

[0035]

According to the present invention, a clear image can be obtained even if the brightness of the background of the combiner changes, and a small-sized liquid crystal display panel suitable for fixing on a dashboard of an automobile or the like can be obtained. Thus, it is possible to provide a head-up display that generates a small amount of noise.

[Brief description of the drawings]

FIG. 1 is a configuration explanatory view of a head-up display according to an embodiment of the present invention.

FIG. 2 is a perspective view showing the inside of the head-up display according to the embodiment of the present invention.

FIG. 3 is a partially cutaway perspective view of a liquid crystal display panel of the head-up display according to the embodiment of the present invention.

FIG. 4 is a partially cutaway perspective view of a backlight light source according to an embodiment of the present invention.

FIG. 5 is a plan view of a main part of the head-up display according to the embodiment of the present invention.

[Explanation of symbols]

 2 Combiner 3 Image display 9 Fan 11 Liquid crystal display panel 12 Light source for backlight 12d Infrared cutoff filter 20 Space 30 Outlet 31 Fin

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yukiko Kuwayama 1 Nishinokyo Kuwabara-cho, Nakagyo-ku, Kyoto-shi, Kyoto Prefecture Inside Shimazu Plant Sanjo Plant (72) Inventor Shuichi Yamatani 1-1190 Fujibashi 1-chome 1, Nagaoka-shi, Niigata Japan Inside R & D Center of Seiki Co., Ltd. (72) Inventor Mitsuru Kobayashi 1-190-1, Fujibashi, Nagaoka-shi, Niigata Japan R & D Center of Seiki Co., Ltd.

Claims (2)

[Claims] 1. An image display device comprising: a combiner disposed in front of an observer; an image display light emitting unit; and a housing having the image display light emitting unit. The combiner changes an optical path of the image display light. Thus, in the head-up display that forms a virtual image of the observation target in front of the combiner, the emission unit of the image display light includes a liquid crystal display unit, and a backlight light source arranged to face the liquid crystal display unit. An air flow generating means for forcibly generating an air flow in the housing is provided, and an outlet for discharging the air flow from the housing is provided on a side portion of the housing; A head-up display provided with means for changing the direction of the discharged air flow so as to be directed forward of the outlet. B. 2. The liquid crystal display means and the light source are arranged back and forth in parallel, the screen of the liquid crystal display means extends along the left-right direction, and a space is formed between the liquid crystal display means and the light source. The flow generating means sends out the air flow so that the air flow passes along the space in the left-right direction, and is opposed to at least one of an inlet and an outlet of the air flow in the space. The head-up display according to claim 1, wherein the head-up display is provided at a position facing an air flow outlet in the space.