JP2023041669A - head-up display device - Google Patents

Abstract

The present invention provides a small-sized information display device that can display video information as a virtual image on a windshield. [Solution] A head-up display device includes a display panel that displays an image and a reflection mirror that reflects light from the display panel, and a virtual image obtained by being reflected at the upper part of the windshield is reflected at the lower part. The optical distance between the reflective mirror and the display panel is changed so that the virtual image is formed further away from the driver's viewpoint than the virtual image obtained by the driver, and the display position of the virtual image is continuously changed from a far position to a close position. let [Selection diagram] Figure 1

Description

The present invention relates to an information display device that projects an image onto the windshield of an automobile, train, aircraft, etc. (hereinafter also generally referred to as "vehicles"), and the image is observed through the windshield as a virtual image. The present invention relates to a projection optical system and an information display device using the same.

A so-called head-up display (HUD) displays traffic information such as route information and traffic information, and vehicle information such as remaining fuel and cooling water temperature by projecting image light onto the windshield of an automobile to form a virtual image. -Display) device is already known from the following patent document 1.

In this type of information display device, miniaturization is desired because the main body of the HUD device is arranged between the steering wheel and the window glass in front of the driver's seat.

On the other hand, there has also been proposed a device for attaching a main body to the vicinity of the ceiling (sun visor) of an automobile, such as disclosed in Non-Patent Document 1 below.

JP 2015-194707 A

PIONEER R&D (Vol.22, 2013)

As shown in FIG. 27, the principle of the virtual image generation by the concave mirror that realizes the head-up display device according to the prior art is based on the point O on the optical axis of the concave mirror 1' inside the focal point F (focal length f). By arranging the object point AB, a virtual image can be obtained by the concave mirror 1'. In FIG. 27, for the convenience of explanation, the concave mirror 1′ is assumed to be a convex lens having the same positive refractive power, and the object point and the convex lens (indicated by the concave mirror in FIG. 27 for convenience of explanation) and the generated virtual image. showed relationship.

In the prior art, in order to enlarge the size of the virtual image generated by the concave mirror 1', it is preferable to bring the object point AB closer to the focal point F, but in order to obtain the desired magnification, the radius of curvature of the concave mirror becomes small. . As a result, the size of the mirror becomes small, and only a virtual image with a small viewable range is obtained although the magnification is effectively large. Therefore, in order to satisfy (1) the desired virtual image size and (2) the required virtual image magnification M=b/a at the same time, the dimensions of the concave mirror should be matched to the viewing range and the image display device. It is necessary to determine the magnification of the virtual image by .

Therefore, in the prior art, as shown in FIG. 27, in order to obtain a virtual image of a desired size, it is necessary to increase the distance from the concave mirror 1' to the virtual image, resulting in a large size of the information display device. I had to.

Furthermore, as described above, the size of the virtual image visually recognized by the driver is determined by the distance a between the image display device and the concave mirror 1′ caused by the tilt of the windshield and the distance b between the concave mirror 1′ and the virtual image. Since the upper end and the lower end of the virtual image are different, it is difficult to make the image magnification of the upper end of the virtual image and the image magnification of the lower end of the virtual image approximately coincide with each other. For this reason, it becomes necessary to reduce the partial change in image magnification (distortion of the image) by relatively reducing the upper and lower optical path differences by increasing the dimension b described above. A study has been made to reduce the volume of the information display device by providing an optical path folding mirror between '.

Further, in the example of the head-up display device disclosed in the above Patent Document 1, a device for displaying an image and a projection optical system for projecting the image displayed on the display device are provided. having a first mirror and a second mirror in the optical path of the user, the incident angle of the image major axis direction on the first mirror and the incident angle of the image minor axis direction on the first mirror, and the image display surface of the display device and the first mirror , and the width of the virtual image viewed by the viewer in the horizontal direction satisfies a predetermined condition, thereby achieving miniaturization.

However, as will be described later, as a result of examination by the inventors, it was found that in order to minimize the volume of the set, the focal length of the concave mirror (122 in FIG. 2 of Patent Document 1) that creates the virtual image should be shortened and the display It was found that by shortening the position of the device and the distance to the focal point of the concave mirror, the size of the virtual image can be maintained without the folding mirror (121 in FIG. 2 of Patent Document 1).

On the other hand, in the device that attaches the main body to the vicinity of the ceiling (sun visor) of the automobile as disclosed in Non-Patent Document 1, if the HUD device comes off when the automobile causes a collision accident, the driver may be injured. The inventors thought that the method described in the above-mentioned Patent Document 1 would become mainstream in the future, because safety issues remain, such as due to the fact that the method is not flexible.

Furthermore, in the above Patent Document 1, when there are a plurality of viewpoint positions of the driver, the reflective surface of the windshield, which is the projection target member (220), has a radius of curvature in the vertical direction of the vehicle body and a radius of curvature in the horizontal direction of the vehicle body of the windshield. , the projection optical system is optimized by considering the windshield as having a toroidal shape, as shown in all the embodiments.

In addition, in the first, second, third, fourth, sixth, and seventh embodiments of Patent Document 1, two mirrors are arranged in substantially the same plane between the driver and the display device, thereby reducing the size of the set. In order to reduce the size of the second mirror, which has a concave reflecting surface that generates a virtual image, and to reduce the size of the second mirror, the reflecting surface of each of the first mirrors, which has a convex reflecting surface, is a free-form surface. Virtual image distortion is reduced to a level that does not pose a problem in actual use over the entire viewing area.

Further, in the fifth embodiment, the first mirror is a reflecting surface of a toroidal surface having a convex shape, thereby facilitating the manufacture of the mirror. On the other hand, the second mirror is a concave mirror having a free-form curved surface, as in the other embodiments.

In the invention disclosed in Patent Document 1 described above, it is necessary to place two mirrors between the observer and the display device, and the light beam reflected by the first mirror is not blocked by the second mirror. In order to arrange them in such a manner, the degree of freedom of arrangement is lost and they cannot be arranged close to each other, which hinders the miniaturization of the set. On the other hand, with regard to the correction of aberrations occurring in the virtual image viewed by the driver, the need for correction and specific reduction means for the correction have not been described or taken into consideration.

In order to reduce the size of the device, the present invention uses a single mirror having a concave reflecting surface that forms a virtual image, and a mirror having a concave cross section on at least one surface between the driver and the display device. By arranging the lens (having negative refractive power), the distortion and aberration of the virtual image seen by the driver are reduced to a practically non-problematic level while suppressing the size and complexity of the set. An object of the present invention is to provide an information display device capable of forming a virtual image.

The present invention, which has been made to achieve the above object, provides, as an example thereof, a head-up display device comprising a display panel for displaying an image, a reflecting mirror for reflecting light from the display panel, and a front The optical distance between the reflecting mirror and the display panel is such that the virtual image obtained by being reflected on the upper part of the glass is formed farther from the viewpoint of the driver than the virtual image obtained by being reflected by the lower part of the glass. is changed to continuously change the display position of the virtual image from a distant position to a close position.

According to the present invention, it is possible to provide an information display device capable of forming a highly visible virtual image in which the distortion and aberration of the virtual image observed by the driver are corrected, while the size of the device is reduced. becomes.

1 is a schematic configuration diagram showing a schematic configuration of an information display device and peripheral devices assigned to the information display device; FIG. 1 is a top view of an automobile equipped with an information display device of the present invention; FIG. FIG. 4 is a configuration diagram explaining a difference in radius of curvature of the windshield; 1 is a schematic configuration diagram showing an information display device, a windshield, and a viewpoint position of a driver; FIG. 1 is a schematic configuration diagram showing an embodiment of a virtual image optical system of an information display device of the present invention; FIG. 1 is a schematic configuration diagram showing the arrangement of a virtual image optical system of an information display device as an example of the present invention; FIG. It is a figure which shows the distance of the concave-surface mirror of the virtual image optical system of the information display apparatus of this invention, and an image display apparatus, and the dimension relationship of an apparatus. It is a figure which shows the relationship between the distance of the concave-surface mirror of the virtual image optical system of the information display apparatus of this invention, and an image display apparatus, and the volume of an apparatus. 1 is a schematic diagram illustrating the principle of the present invention; FIG. 1 is a configuration diagram showing the arrangement of an image display device and a light source device in an information display device of the present invention; FIG. 1 is a schematic configuration diagram showing a configuration of a light source device of an image display section of the present invention; FIG. It is a schematic block diagram which shows the shape of the light guide of the light source device of this invention. It is a schematic block diagram which shows the cross-sectional shape of the light guide of the light source device of this invention. FIG. 3 is a schematic diagram illustrating how light beams are emitted from a video display device and a light source device in the information display device of the present invention; FIG. 4 is a characteristic diagram for explaining the emitted light distribution of the luminous flux from the image display device light source device in the information display device of the present invention. FIG. 2 is a conceptual diagram showing a method of evaluating characteristics of a liquid crystal panel as a video display device; FIG. 4 is a characteristic diagram showing transmittance characteristics in the horizontal direction of the screen of a liquid crystal panel as a video display device; FIG. 4 is a characteristic diagram showing angular characteristics of luminance in the horizontal direction of a screen when white is displayed on a liquid crystal panel as a video display device; FIG. 4 is a characteristic diagram showing lateral angle characteristics of backlight luminance of a liquid crystal panel as a video display device; FIG. 4 is a characteristic diagram showing angular characteristics of transmittance in the vertical direction of a liquid crystal panel as an image display device; FIG. 4 is a characteristic diagram showing angular characteristics of luminance in the vertical direction during white display of a liquid crystal panel as a video display device; FIG. 4 is a characteristic diagram showing vertical angle characteristics of backlight luminance of a liquid crystal panel as a video display device; FIG. 4 is a characteristic diagram showing lateral angle characteristics of contrast of a liquid crystal panel as a video display device; FIG. 10 is a characteristic diagram showing lateral angle characteristics of black display luminance of a liquid crystal panel as a video display device; FIG. 10 is a characteristic diagram showing vertical angle characteristics of contrast of a liquid crystal panel as a video display device; FIG. 4 is a characteristic diagram showing vertical angle characteristics of black display luminance of a liquid crystal panel as a video display device; It is a schematic diagram for explaining the principle of a virtual image optical system according to the prior art.

Various embodiments of the present invention will be described in detail below with reference to the drawings. The following description shows specific examples of the contents of the present invention, and the present invention is not limited to these descriptions. Various changes and modifications are possible. In addition, in all the drawings for explaining the present invention, parts having the same functions are denoted by the same reference numerals, and repeated explanations thereof may be omitted.

<Embodiment of information display device>
FIG. 1 is a block diagram and a schematic configuration diagram showing the configuration of peripheral equipment of an information display device according to an embodiment of the present invention. will be explained.

Since the information display device 100 forms a virtual image V1 in front of the vehicle in the line of sight 8 of the driver, various information reflected by the projection target member 6 (the inner surface of the windshield in this embodiment) is displayed as the virtual image VI. (Virtual Image) is a device (so-called HUD (Headup Display)). The projection target member 6 may be any member on which information is projected, and may be not only the windshield described above, but also a combiner. That is, in the information device 100 of the present embodiment, it is sufficient that a virtual image is formed in front of the vehicle in the line of sight 8 of the driver and visually recognized by the driver. For example, it is natural that vehicle information and foreground information captured by a camera (not shown) such as a surveillance camera or an around viewer are also included.

In the information display device 100, the image display device 4 projects image light for displaying information, and distortion and aberration generated when the image displayed on the image display device 4 is formed into a virtual image by the concave mirror 1 are corrected. A correction lens group 2 is provided between the image display device 4 and the concave mirror 1 for correction.

The information display device 100 includes the image display device 4 and a control device 40 that controls the backlight 5 . The optical parts including the image display device 4 and the backlight 5 are a virtual image optical system to be described below, and include a concave mirror 1 for reflecting light. Further, the light reflected by the optical component 5 is reflected by the projection target member 6 and directed toward the driver's line of sight 8 (EyeBox, which will be described in detail later).

Examples of the image display device 4 include an LCD (Liquid Crystal Display) having a backlight and a self-luminous VFD (Vacuum Flourescent Display).

On the other hand, instead of the image display device 4 described above, an image is displayed on a screen by a projection device, and the image is converted into a virtual image by the aforementioned concave mirror 1 and reflected by the windshield 6, which is the member to be projected, and directed to the driver's viewpoint 8. You can dodge.

As such a screen, for example, a microlens array in which microlenses are arranged two-dimensionally may be used.

More specifically, in order to reduce the distortion of the virtual image, the shape of the concave mirror 1 is adjusted to the upper portion shown in FIG. ), the radius of curvature is relatively small so that the magnification is large, and on the other hand, in the lower portion (the area where the light rays are reflected above the windshield 6, which is relatively long from the driver's viewpoint), the magnification is It is preferable that the radius of curvature is relatively large so that the .DELTA. Also, by tilting the image display device 4 with respect to the optical axis of the concave mirror to correct the difference in the magnification of the virtual image and reduce the distortion itself, a better correction can be realized.

On the other hand, as shown in FIG. 2, the windshield 6 of a passenger car has a different radius of curvature Rv in the vertical direction and a radius of curvature Rh in the horizontal direction, and generally has a relationship of Rh>Rv. Therefore, as shown in FIG. 3, when the windshield 6 is taken as a reflecting surface, it becomes the toroidal surface of the concave mirror. Therefore, in the information display device of the present invention shown in FIG. 3, the shape of the concave mirror 1 is designed to correct the virtual image magnification due to the shape of the windshield 6, that is, to compensate for the difference in the radius of curvature of the windshield in the vertical and horizontal directions. Different average radii of curvature may be used in the horizontal and vertical directions so as to compensate. At this time, the shape of the concave mirror 1 is a function of the distance r from the optical axis in the case of a spherical or aspherical shape symmetrical with respect to the optical axis (the shape represented by Equation 2, which will be described later). Since the shape of the cross section and the shape of the vertical cross section cannot be controlled separately, it is preferable to correct the mirror surface as a function of the coordinates (x, y) of the surface from the optical axis as a free-form surface represented by Equation 1, which will be described later.

Returning to FIG. 1 again, a transmissive optical component such as a lens element 2 is arranged between the image display device 4 and the concave mirror 1, thereby controlling the direction of light emitted to the concave mirror. Distortion is corrected in conjunction with the shape of the concave mirror, and at the same time, virtual image aberration correction including astigmatism caused by the difference between the radius of curvature of the windshield 6 in the horizontal direction and the radius of curvature in the vertical direction is realized. .

Further, in order to further enhance the aberration correction capability, the optical element 2 may be composed of a plurality of lenses. Alternatively, the distortion can be reduced by placing a curved mirror instead of the lens element and controlling the incident position of the light beam on the concave mirror 1 at the same time as the optical path is turned back. As described above, even if an optical element optimally designed to improve the ability to correct aberrations is provided between the concave mirror 1 and the image display device 4, it would be outside the technical idea or scope of the present invention. It goes without saying that it is not. Further, by changing the thickness of the optical element 2 in the optical axis direction, the optical distance between the concave mirror 1 and the image display device 4 is changed in addition to the original aberration correction, thereby moving the display position of the virtual image farther. to the close position.

Also, the image display device 4 may be tilted with respect to the normal to the optical axis of the concave mirror 1 to correct the difference in vertical magnification of the virtual image.

On the other hand, as a factor that degrades the image quality of the information display device, the image light rays emitted from the image display device 4 toward the concave mirror 1 are reflected by the surface of the optical element 2 disposed in the middle, return to the image display device, and return to the image display device. It is known to be reflected and superimposed on the original image light, degrading the image quality. For this reason, in the present invention, in addition to suppressing reflection by forming an antireflection film on the surface of the optical element 2, either one of the image light incident surface and the output surface of the optical element 2, or both lens surfaces It is preferable to design the shape so that the reflected light described above is not extremely focused on a part of the image display device 4 .

Next, if the image display device 4 is a liquid crystal panel having a polarizing plate for absorbing the reflected light from the optical element 2, the deterioration of the image quality can be reduced. Further, the backlight 5 of the liquid crystal panel is controlled so that the incident direction of the light incident on the liquid crystal panel 4 is efficiently incident on the entrance pupil of the concave mirror 1 . Furthermore, as the light source, it is preferable to adopt a solid-state light source with a long product life, and furthermore, a PBS provided with optical means for reducing the divergence angle of light as an LED (Light Emitting Diode) with little change in light output due to fluctuations in ambient temperature. (Polarizing Beam Splitter) is preferably used for polarization conversion.

A polarizing plate is arranged on the backlight 5 side (light incident surface) and the optical element 2 side (light emitting surface) of the liquid crystal panel to increase the contrast ratio of the image light. If an iodine-based polarizing plate having a high degree of polarization is used for the polarizing plate provided on the backlight 5 side (light incident surface), a high contrast ratio can be obtained. On the other hand, by using a dye-based polarizing plate on the optical element 2 side (light exit surface), it is possible to obtain high reliability even when external light is incident or when the environmental temperature is high.

When a liquid crystal panel is used as an image display device, a particular polarized wave is blocked and the image cannot be seen, especially when the driver is wearing polarized sunglasses. In order to prevent this, it is preferable to arrange a λ/4 plate on the optical element side of the polarizing plate arranged on the optical element 2 side of the liquid crystal panel, thereby converting the image light aligned in a specific polarization direction into circularly polarized light. .

From the navigation system 61, the control device 40 receives various information such as the speed limit and the number of lanes of the road corresponding to the current position on which the vehicle is traveling, the planned travel route of the vehicle set in the navigation system 61, and the like. Information is acquired as foreground information (that is, information displayed in front of the vehicle using the virtual image).

The driving support ECU 62 is a control device that realizes driving support control by controlling the driving system and the control system according to the obstacles detected as a result of monitoring by the surroundings monitoring device 63. The driving support control includes, for example, , cruise control, adaptive cruise control, pre-crash safety, lane keeping assist and other well-known technologies.

The surroundings monitoring device 63 is a device for monitoring the surroundings of the own vehicle. It is a survey device that detects objects existing around the own vehicle based on the result of transmitting and receiving the.

The control device 40 acquires such information from the driving assistance ECU 62 (for example, the distance to the preceding vehicle, the direction of the preceding vehicle, the positions of obstacles and signs, etc.) as foreground information. Furthermore, an ignition (IG) signal and host vehicle state information are input to the control device 40 . Among these pieces of information, the own vehicle state information is information acquired as vehicle information. Contains warning information that represents In addition, the operation result of the direction indicator, the traveling speed of the host vehicle, and the shift position information are also included. The control device 40 described above is activated when an ignition signal is input. The above is the description of the entire system of the information display device of the present invention.

<First Embodiment of Virtual Image Optical System>
Next, further details of the virtual image optical system and the image display device according to the present invention will be described below.

As described above, FIG. 2 is a top view of an automobile equipped with the information display device of the present invention. In front of the driver's seat of the automobile body 101, there is a windshield as a projection member 6. FIG. The angle of inclination of the windshield with respect to the vehicle body differs depending on the type of automobile. Furthermore, the inventors investigated this radius of curvature in order to realize an optimum virtual image optical system. As a result, the windshield, as shown in FIG. It has been found that, in general, there is the following relationship between Rv.
Rh>Rv

It was also found that the difference in radius of curvature, that is, Rh with respect to Rv, was often in the range of 1.5 to 2.5 times.

Next, the inventors investigated commercially available products with respect to the inclination angle of the windshield. As a result, although it varies depending on the vehicle type, it was 20 to 30 degrees for mini vehicles and 1 box types, 30 to 40 degrees for sedans, and 40 degrees or more for sports types. Therefore, in the present invention, considering the difference between the horizontal radius of curvature Rh of the windshield parallel to the ground plane of the automobile and the vertical radius of curvature Rv perpendicular to the horizontal axis, and the tilt angle of the windshield, A virtual image optical system was designed.

More specifically, since the horizontal radius of curvature Rh and the vertical radius of curvature Rv of the windshield, which is the member to be projected, differ greatly, By providing the optical element 2 which is axially asymmetric with respect to the axis of the virtual image in the virtual image optical system, good aberration correction is realized.

Next, the inventors studied miniaturization of the information display device 100 . As conditions for the study, the FOV was set to 7 degrees horizontally and 2.6 degrees vertically, and the virtual image distance was set to 2 m. At the beginning of the study, a concave mirror 1 for generating a virtual image (in FIGS. 5 and 6 below, shown simply as a plane mirror), an image display device 4 and a backlight 5 were used as a basic configuration, and the image display device 4 and the concave surface In order to minimize the volume of the information display device 100 by arranging one optical path folding mirror between the mirrors 1, a simulation was performed using the arrangement of each member and the distance from the image display device 4 to the concave mirror 1 as parameters. gone.

As a result, the volume was 3.6 liters when the components were arranged so that the image light from the image display device 4 did not interfere with them. After that, aiming at further miniaturization, we investigated a direct method without the optical path folding mirror. The results of the study are summarized in FIGS. 5 and 6. FIG. Table 1 shows the actual numerical values in FIG.

The configuration of the virtual image optical system of the present invention will be described with reference to FIG. FIG. 5 is an overall configuration diagram showing the basic configuration for studying miniaturization in the virtual image optical system of the first embodiment of the present invention shown in FIG. For simplification of explanation, optical elements for correcting aberrations and distortion are omitted, and the vertical cross-sectional shape thereof is shown in the same manner as the window glass 6 shown in FIG. The image display device 4 is assumed to be a liquid crystal panel, and has a configuration in which a backlight 5 is arranged as a basic configuration.

At this time, as shown in FIG. 5, the image light R2 generated from the image at the center of the screen of the image display device 4, the image light R1 from the upper end, and the image light R3 from the lower end are respectively reflected by the concave mirror 1. Arranging the light so as not to interfere with the image display device 4 and block the light when reflected is a design constraint.

In consideration of the design constraints mentioned above, FIG. 5), the volume of the information display device 100 was determined using the distance Z as a parameter. When the distance Z is 100 mm, the configuration shown in FIG. 6C is obtained, in which case the vertical dimension of the concave mirror 1 can be minimized. When the distance Z is 75 mm, as shown in FIG. 6B, the angle α2 between the horizontal plane and the concave mirror 1 becomes large, and the vertical dimension of the concave mirror 1 also becomes large. If the distance Z is further shortened to 50 mm or less, the angle α3 between the horizontal plane and the concave mirror 1 increases, and the vertical dimension of the concave mirror 1 also increases, as shown in FIG. 6(a).

FIG. 7 shows the result of simulating the relationship between the set height and the set depth of the image display device 4 using the distance Z as a parameter. When the distance Z is reduced, the set depth can be reduced, but the set height is increased. Similarly, FIG. 8 summarizes the relationship between the distance Z and the set volume L. The set volume (LCD (including the drive circuit, light source drive circuit, and backlight unit volume) changes with the distance Z of 60 mm as the boundary.

From the above, in order to miniaturize the information display device 100, it is necessary to realize a virtual image optical system with a short distance Z that directly magnifies the image displayed on the image display device 4 with a concave mirror. It was found that the center of the image display section 4 in the vertical direction of the screen needs to be arranged below the center of the concave mirror 1 .

On the other hand, in this arrangement, the distance between the image display device 4 and the upper end of the concave mirror 1 (corresponding to the light ray R1) is long, and the distance between the image display device 4 and the lower end of the concave mirror 1 (corresponding to the light ray R3) is short. . Therefore, the image display device 4 is moved in the direction of the arrow in FIG. It is better to place it so that

In the virtual image optical system of the present invention, distortion correction of the virtual image and aberration correction by an optical element for correcting aberration generated in the virtual image are performed between the image display device 4 and the concave mirror 1. This will be described with reference to FIG. . That is, by arranging the image display device 4 (object point) inside the focal point F (focal length f) with respect to the point O on the optical axis of the concave mirror 1, a virtual image by the concave mirror 1 can be obtained. In FIG. 9, for convenience of explanation, the concave mirror 1 is assumed to be a convex lens having the same positive refractive power, and the relationship between the object point, the convex lens (indicated by a concave mirror in FIG. 9 for convenience of explanation), and the virtual image generated is Indicated.

In the present invention, the optical element 2 is arranged in order to reduce the distortion and aberration generated in the concave mirror 1. FIG. This optical element, which may be a transmissive optical lens or a concave mirror, allows the image light from the image display device 4 to:
(1) When incident on the reflecting surface as a telecentric luminous flux, the refractive power of the lens or concave mirror 1 is almost zero;
(2) When the image light from the image display device 4 diverges and enters the optical element, the optical element has a positive refractive power;
(3) When the image light from the image display device 4 is condensed and enters the optical element, the optical element has a negative refractive power;
In this manner, the direction (angle and position) of the light beam incident on the concave mirror is controlled to correct the distortion aberration of the generated virtual image. Furthermore, in the case of a transmissive optical lens, the interaction between the incident surface on the image display device 4 side and the exit surface on the concave mirror 1 side corrects the aberration related to the imaging performance that occurs in the virtual image.

At this time, the size of the virtual image visually recognized by the driver is determined by the distance a between the image display device 4 and the concave mirror 1 caused by the inclination of the windshield and the distance b between the concave mirror 1 and the virtual image, as described above. and lower end.

Therefore, the inventors found that by tilting the image display device 4 with respect to the optical axis of the concave mirror 1 as shown in FIG. It has been found that it is even better to reduce the generated distortion aberration by substantially matching the image magnification M=b/a of the part.

Further, by setting the average curvature radius of the vertical cross-sectional shape and the average curvature radius of the horizontal cross-sectional shape of the optical element 2 to different values, the difference between the vertical curvature radius Rv and the horizontal curvature radius Rh of the windshield described above It corrects the distortion caused by the optical path difference and the aberration that deteriorates the imaging performance of the virtual image.

As described above, in the information display device 100 that obtains a virtual image by reflecting image light directly on the windshield 6, the optical path difference caused by the difference between the vertical curvature radius Rv and the horizontal curvature radius Rh of the windshield 6 causes Correction of the generated aberration is the most important factor in ensuring the imaging performance of the virtual image.

For this reason, the inventors have used an aspherical shape (see Equation 2 below) that defines the shape of a lens surface or mirror surface as a function of the distance r from the optical axis, which has been used in conventional optical design. , by using a free-form surface shape (see Equation 1 below) that can define the shape of the surface as a function of the absolute coordinates (x, y) from the optical axis, the above-mentioned windshield This reduces the deterioration of the imaging performance of virtual images due to the difference in the curvature radius.

Note that the aspherical shape that defines the shape of the lens surface and mirror surface as a function of the distance r from the optical axis is represented by Equation 2 below.

FIG. 10 is an enlarged view of the essential parts of the liquid crystal panel and the backlight source 5 as the video display device 4 of the virtual image optical system according to the first embodiment described above. An image is displayed on the liquid crystal panel display surface 11 by modulating the light from the backlight according to the image signal input from the flexible substrate 10 of the liquid crystal panel, and the displayed image is transmitted to the virtual image optical system (in the embodiment, a free curved concave surface). Mirrors and free-form surface optical elements) generate a virtual image and transmit image information to the driver.

In the above configuration, the light source element of the backlight source 5 is a relatively inexpensive and highly reliable LED light source as a solid-state light source. Since a surface-emitting type LED is used in order to increase the output, the efficiency of light utilization is improved by using technical measures to be described later. The luminous efficiency with respect to the input power of the LED is about 20 to 30%, although it varies depending on the emission color, and most of the rest is converted into heat. For this reason, as a frame for mounting the LED, heat dissipation fins 13 made of a member with high thermal conductivity (for example, a metal member such as aluminum) are provided to dissipate the heat to the outside, thereby improving the luminous efficiency of the LED itself. You can get the effect of improving.

In particular, when the junction temperature rises, the luminous efficiency of the LEDs currently on the market that emit red light drops significantly, and the chromaticity of the image changes at the same time. It is preferable to increase the area of the corresponding radiation fins to increase the cooling efficiency. In order to efficiently guide the diffused light from the LEDs to the liquid crystal panel 4, the light guide 18 is used in the example shown in FIG. It is preferably grouped as a light source.

Further, FIG. 11 shows an enlarged view of a main part of a light source unit including an LED as a light source, a light guide and a diffusion plate. Apertures 21a, 22a, 23a, and 24a for taking in the diverging light beams from the LEDs of , 24 are made flat and optically connected to the LEDs by inserting a medium between them, or are made convex to have a light-collecting function. As a result, the diverging light source light is made parallel as much as possible, and the incident angle of the light incident on the interface of the light funnel is reduced. As a result, after passing through the light funnel, the angle of divergence can be further reduced, which facilitates control of the light from the light source that travels toward the liquid crystal panel after being reflected by the light guide 18 .

Furthermore, in order to improve the utilization efficiency of the divergent light from the LED, a PBS ((Polarizing Beam Splitter)) is used at the junction 25 between the light funnels 21 to 24 and the light guide 18 to convert the polarization into a desired polarization direction. can improve the efficiency of light incident on the LCD.

As described above, when the polarization direction of light from the light source is aligned, a material with low birefringence is used as the material of the light guide 18. When the polarization direction is rotated and passes through the liquid crystal panel, for example, when black is displayed, It is even better if problems such as coloring do not occur.

As described above, the luminous flux from the LED whose divergence angle is reduced is controlled by the light guide, reflected by the total reflection surface provided on the slope of the light guide 18, and reflected between the opposing surface and the liquid crystal panel. After being diffused by the arranged diffusing member 14, the light enters the liquid crystal panel 4 as an image display device. In this embodiment, the diffusion member 14 is arranged between the light guide 18 and the liquid crystal panel 4 as described above. The same effect can be obtained even if it is provided.

Next, the configuration of the light guide body 18 described above and the effects obtained therefrom will be described with reference to FIGS. 12 and 13. FIG. FIG. 12 is an external view showing the light guide 18 of the present invention. The luminous flux whose divergence angle has been reduced by the light funnels 21 to 24 shown in FIG. The angle of divergence in the vertical direction (vertical direction in FIG. 13) is controlled, and the light propagates through the light guide 18 efficiently.

FIG. 13 is an enlarged cross-sectional view of the main part of the light guide, and the light from the light source whose divergence angle is reduced in the light funnels 21 to 24 passes through the joint 25 and enters from the incident surface 18a as described above. , is totally reflected by the prism 18 provided on the opposing surface and travels toward the opposing surface 17 . The total reflection prism 18 is divided stepwise in the vicinity of the incident surface 18a (enlarged view of B) and at the end (enlarged view of A) according to the divergence angle of the light beam incident on each surface. It controls the angle of the total reflection surface. On the other hand, the luminous flux is divided by using the above-described division dimension of the total reflection surface as a variable so that the light amount distribution in the emission surface of the liquid crystal panel 4 of the luminous flux incident on the liquid crystal panel 4, which is an image display device, becomes uniform. control the arrival position and energy amount after reflection.

FIG. 14 shows the result of simulating the state in which the light emitted from the backlight passes through the liquid crystal panel in the information display device 100 of the present invention. FIG. 14(a) is a diagram showing the light emission state viewed from the longitudinal direction of the liquid crystal panel, and FIG. 14(b) shows the light emission state viewed from the lateral direction of the liquid crystal panel. In the present invention, in order to widen the horizontal angle of the FOV more than the design, the horizontal diffusion angle is increased with respect to the vertical direction, so that even when the driver shakes his head and the position of his eyes moves, the left and right It is designed so that the brightness of the virtual image visually recognized by the eye does not change significantly.

Also, as in the embodiment of the present invention, the luminance distribution of the emission surface of the liquid crystal panel 4 and the characteristic evaluation of the liquid crystal panel in the case of using a backlight in which the light emission direction and intensity are controlled by using the light guide 18 are shown. The method is illustrated in FIGS. 15 and 16. FIG. As is clear from the figure, the slope of luminance reduction outside the effective range in the screen vertical direction (long side direction) can be reduced with respect to the luminance distribution in the screen vertical direction (short side direction).

The emitted light (image light) from the liquid crystal panel used as the image display device in the information display device 100 of the present invention, as shown in FIGS. It shows a given transmittance in the range of °. If the viewing angle range is within ±40°, better transmittance characteristics can be obtained. As a result, as shown in FIGS. 18 and 21, the brightness of the screen greatly differs depending on the viewing direction (visual angle) in the horizontal direction and the vertical direction of the display screen. This is due to the angular characteristics of the backlight luminance shown in FIGS. 19 and 22. FIG.

For this reason, the inventors determined the angle of the total reflection surface of the light guide 18 and the light funnels 21 to 24 so that the light emitted from the liquid crystal panel 4 taken into the virtual image optical system can be obtained as light perpendicular to the screen as much as possible. By controlling the divergence angle of the light source light from the LEDs by , the viewing angle characteristics of the backlight are narrowed down to a small range, thereby obtaining high brightness. Specifically, as shown in FIGS. 18 and 21, in order to obtain a high-brightness image, light within a range of ±30° is used in the left and right viewing angles, and the contrast shown in FIGS. Considering the performance as well, it was possible to simultaneously obtain a virtual image using a source image with good image quality by reducing the angle to ±20° or less.

As described above, contrast performance, which determines the image quality of a video display device, determines how much the luminance when displaying black (marked as black display luminance in FIGS. 24 and 26), which is the basis for determining image quality, can be reduced. Determined by Therefore, it is preferable to use an iodine-based polarizing plate having a high degree of polarization between the liquid crystal panel 4 and the backlight.

On the other hand, by using a dye-based polarizing plate as the polarizing plate provided on the optical element 2 side (light exit surface), high reliability can be obtained even when external light is incident or when the environmental temperature is high.

When the liquid crystal panel 4 performs color display, a color filter corresponding to each pixel is provided. Therefore, when the light source color of the backlight is white, the color filter absorbs a large amount of light, resulting in a large loss. So, we used multiple LEDs, as shown in FIG. 11 above, to:
(1) Add a green LED that contributes more to brightness than when a plurality of white LEDs are used.
(2) Adding red or blue LEDs to white LEDs to enhance the glossiness of the image.
(3) By arranging red, blue, and green LEDs individually, adding a green LED that contributes greatly to brightness, and driving the LEDs individually, the color reproduction range is expanded and the lustrous color is enhanced. At the same time, the brightness is also improved.
(4) By implementing the above (3), the transmittance of each color filter with respect to the peak luminance of the red, blue, and green LEDs is increased to improve the brightness as a whole.
(5) Furthermore, as a second embodiment of the backlight, by placing a PBS between the light funnel and the light guide and aligning it with a specific polarized wave, the damage to the polarizing plate on the incident side of the liquid crystal panel is reduced. do. Needless to say, the polarization direction of the polarizing plate arranged on the incident side of the liquid crystal panel may be the direction in which polarized waves aligned in a specific direction pass after passing through a PBS (Polarizing Beam Splitter).

As described above, as the image light source device 4 according to the embodiment of the present invention, it is also possible to provide a λ/4 plate on the exit surface of the liquid crystal display panel to circularly polarize the emitted light. As a result, the driver can monitor a good virtual image even when wearing polarized sunglasses.

Furthermore, by forming the reflective film of the reflective mirror used in the virtual image optical system with a metal multilayer film, the angular dependence of the reflectance is small, and the reflectance can change depending on the polarization direction (P wave or S wave). Therefore, the chromaticity and brightness of the screen can be kept uniform.

Furthermore, by providing an optical member combining an ultraviolet reflective film or an ultraviolet reflective film and an infrared reflective film between the virtual image optical system and the windshield, even if external light (sunlight) is incident, the liquid crystal display panel In addition, since the temperature rise and damage to the polarizing plate can be reduced, the reliability of the information display device is not impaired.

In addition, the virtual image optical system is optimally designed taking into consideration the difference between the horizontal and vertical curvature radii of the windshield, which has been used as a projection target in the prior art. A concave mirror 1 having a concave surface facing the windshield 6 side is arranged between the image display units to magnify the image of the image display device and reflect it on the windshield 6 . At this time, an optical element is arranged between the aforementioned concave mirror 1 and the image display device 4, and on the other hand, an enlarged image (virtual image) of the image formed corresponding to the driver's viewpoint position is formed. The resulting image light flux passes through the optical element arranged between the image display devices, and corrects distortion and aberration occurring in the concave mirror 1 . Therefore, it is possible to obtain a virtual image in which distortion and aberration are greatly reduced compared to a conventional virtual image optical system having only a concave mirror.

Furthermore, in the present invention shown in FIG. 1, the virtual image obtained by being reflected on the upper portion of the windshield 6 (the upper portion in the vertical direction of the vehicle body) must be imaged at a greater distance. For this reason, in order to satisfactorily form the image light flux diverging from the upper part of the image display device on which the corresponding image is displayed, the optical element disposed between the concave mirror 1 and the image display device 4 is required. The focal length f1 of is short, and conversely, the virtual image obtained by being reflected on the lower part of the windshield 6 (the lower part in the vertical direction of the vehicle body) needs to be imaged closer. For this reason, a plurality of optical elements are arranged between the aforementioned concave mirror 1 and the image display device 4 in order to satisfactorily form the image light flux diverging from the lower portion of the image display device on which the corresponding image is displayed. is preferably set relatively long.

In addition, in the present invention, the screen distortion of the virtual image viewed by the driver is reduced by the difference in the radius of curvature of the windshield 6 in the horizontal direction (parallel to the ground) and the radius of curvature in the vertical direction (perpendicular to the horizontal direction of the windshield). For correction, optical elements having different axial symmetry with respect to the optical axis are arranged in the virtual image optical system, thereby realizing the correction of the distortion described above.

A planar light source device suitable for use in an electronic device having an image display device according to various embodiments of the present invention has been described above. However, the present invention is not limited to the above-described embodiments, and includes various modifications. For example, the above-described embodiments describe the entire system in detail in order to explain the present invention in an easy-to-understand manner, and are not necessarily limited to those having all the configurations described. In addition, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. Moreover, it is possible to add, delete, or replace a part of the configuration of each embodiment with another configuration.

DESCRIPTION OF SYMBOLS 100... Information display apparatus, 101... Automobile, 1... Concave mirror, 2... Optical element, 4... Liquid crystal display panel, 5... Backlight light source, 6... Projection member (front glass), 7... Housing, V1... Virtual image , 8... eye box (observer's eye), 9... light source unit, R1... upper limit image light, R2... center image light, R3... lower limit image light, 10... flexible substrate, 11... image display surface, 12... frame, DESCRIPTION OF SYMBOLS 13... Fin, 14... Diffusion member, 16... Exterior member, 17... Emission surface, 18... Light guide, 20... Light funnel unit, 21... Light funnel, 22... Light funnel, 23... Light funnel, 24... Light funnel , 21a... Light funnel opening, 22a... Light funnel opening, 23a... Light funnel opening, 24a... Light funnel opening, 25... Joint part (PBS).

Claims (9)

A head-up display device,
a display panel for displaying images;
a reflecting mirror that reflects light from the display panel;
with
The optical arrangement of the reflecting mirror and the display panel is such that the virtual image obtained by being reflected on the upper part of the windshield is formed farther from the driver's viewpoint position than the virtual image obtained by being reflected on the lower part of the windshield. changing the distance to continuously change the display position of the virtual image from a distant position to a close position;
Head-up display device. The head-up display device according to claim 1,
The transmittance of light emitted from the display panel exhibits a predetermined transmittance within a viewing angle range of ±50 degrees in the horizontal direction of the display panel.
Head-up display device. The head-up display device according to claim 1,
An iodine-based polarizing plate is provided on the incident surface of the display panel, and a dye-based polarizing plate is provided on the output surface of the display panel.
Head-up display device. The head-up display device according to claim 1,
The distance between the display panel and the upper end of the reflecting mirror is longer than the distance between the display panel and the lower end of the reflecting mirror,
Head-up display device. The head-up display device according to claim 1,
The distance between the display panel and the reflecting mirror and the distance between the reflecting mirror and the virtual image are different between the upper part and the lower part of the virtual image,
Head-up display device. The head-up display device according to claim 1,
The reflecting mirror is arranged so that reflected light from the reflecting mirror is not blocked by the display element.
Head-up display device. The head-up display device according to claim 1,
The center of the display area of the display element is arranged below the center of the reflecting mirror with respect to the vertical direction.
Head-up display device. The head-up display device according to claim 1,
The reflecting mirror is arranged between the display element and the projection surface of the windshield on the optical path.
Head-up display device. The head-up display device according to claim 1,
The display element is arranged at an angle with respect to the optical axis of the reflecting mirror,
Head-up display device.

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