JP7021939B2 - Information display device - Google Patents

Description

The present invention relates to an information display device that projects video information onto a windshield or combiner of an automobile, train, aircraft, or the like, and observes the video information as a virtual image through the windshield.

A so-called head-up display (HUD) that projects video light onto the windshield or combiner of a car to form a virtual image and displays traffic information such as route information and traffic jam information, as well as car information such as fuel level and cooling water temperature. ) The device is known. For example, Patent Document 1 proposes a compact display device including a device for displaying an image and a projection optical system for projecting (projecting) the displayed image, with little screen distortion over the entire viewpoint region of the driver. Has been done.

Further, for example, in Patent Document 2, a laser beam for pixel display emitted from a light source unit is deflected by a two-dimensional deflecting means (MEMS mirror) and reflected toward a curved screen which is a transmissive member via a concave mirror. , The configuration that forms the intermediate image is disclosed. In this device, the intermediate image is then reflected by a concave mirror, and the image light is projected onto the windshield or combiner of an automobile to form a virtual image.

Japanese Unexamined Patent Publication No. 2015-194707 Japanese Unexamined Patent Publication No. 2016-136222

In this type of information display device, it is desired to expand the area where the driver can observe the virtual image, but it is also an important performance factor that the virtual image has high resolution and high visibility. In addition, the head-up display device requires a windshield or combiner as the final reflective surface that provides a virtual image to the driver, and the inventors have made further improvements in order to obtain high visibility and good resolution performance. I realized it was important.

Generally, in order to widen the visible range of the virtual image generated by the concave mirror, it is better to move the object point closer to the focal point and make the concave mirror larger with respect to the object size, but in order to obtain the desired magnification, the concave mirror Since the radius of curvature of is small, it is difficult to achieve both of these. As a result, the mirror size becomes small, and the magnifying power is effectively large, but only a virtual image having a small observable range can be obtained.

Therefore, in order to simultaneously satisfy (1) the desired virtual image size and (2) the required virtual image magnification, the dimensions of the concave mirror should be adjusted to the observation range, and the magnification of the virtual image should be determined in consideration of the image display unit. I had no choice but to do it. Therefore, in the prior art, in order to obtain a large virtual image in a desired observation range, the distance from the concave mirror to the virtual image is increased, that is, the distance between the windshield or combiner, which is the final reflecting surface, and the concave mirror is increased, and at the same time. , It was necessary to increase the size of the concave mirror. These demands are factors that hinder the miniaturization of equipment.

The above-mentioned Patent Documents 1 and 2 do not disclose a technique for miniaturizing the configuration of an apparatus and obtaining a large virtual image in a desired observation range. Further, as the device is miniaturized, the distortion and aberration of the virtual image visually recognized by the driver increase, but the technique for effectively solving this is not disclosed.

In view of the above-mentioned problems of the prior art, an object of the present invention is to propose a technical means for obtaining a larger virtual image in a desired observation range while reducing the size of the apparatus. At the same time, it is an object of the present invention to provide an information display device for forming a highly visible virtual image by reducing the distortion and aberration of the virtual image visually recognized by the driver to a level where there is no practical problem.

The present invention is an information display device that projects an image on a projection member, and has an image display unit that arranges a light source on the back side to generate image light of the image and the image light generated by the image display unit. An optical system that reflects light with a concave mirror and projects it onto the projection member to display a virtual image in front of the projection member is provided so that the display surface of the image display unit has a curved shape toward the concave mirror. It is characterized by being formed in. Here, the curvature of the display surface of the image display unit is determined so as to reduce the curvature of field generated in the virtual image due to the shape of the concave mirror.

According to the present invention, an information display device that obtains a larger virtual image in a desired observation range while reducing the size of the device, reduces distortion and aberration of the virtual image visually recognized by the driver, and forms a highly visible virtual image. Can be realized.

It is a schematic block diagram which shows the information display device and its peripheral device. It is a figure explaining the generation principle of a virtual image. It is a top view of the automobile equipped with an information display device. It is a figure which shows the curved surface shape of a windshield. It is a figure which shows the angle characteristic in the vertical direction of the backlight brightness of a liquid crystal panel. It is a figure which shows the angle characteristic in the vertical direction of the contrast of a liquid crystal panel. It is an overall block diagram of the virtual image optical system in FIG. It is a figure which shows the basic structure of a virtual image optical system. It is a figure which shows the positional relationship between a concave mirror and an image display part. It is a figure which shows the relationship between the distance Z and the volume of an information display device. It is a figure explaining the state of a typical curvature of field (distortion). It is a figure which shows typically the structure which made the liquid crystal panel surface into a curved shape. It is a figure which shows the structure which curved the exit surface of a light source together with the liquid crystal panel surface. It is a ray diagram of the whole virtual image optical system of this embodiment. FIG. 6 is an enlarged ray diagram of a part of the virtual image optical system of FIG. It is an external view of a liquid crystal panel and a backlight. It is an enlarged view of the light source unit in a backlight. It is a figure which shows the appearance of a light guide body. It is a cross-sectional enlarged view of the main part of a light guide body. It is a figure which shows the simulation result of the emitted light which passed through a liquid crystal panel. It is a figure which shows the luminance distribution of the emission surface of a liquid crystal panel.

Hereinafter, examples of the present invention will be described in detail with reference to the drawings and the like. The present invention is not limited to the following description, and various modifications and modifications can be made by those skilled in the art within the scope of the technical idea disclosed in the present specification. Further, in all the drawings for explaining the present invention, those having the same function may be designated by the same reference numerals, and the repeated description thereof may be omitted.

<Configuration of information display device>
FIG. 1 is a schematic configuration diagram showing an information display device and its peripheral devices according to an embodiment of the present invention. Here, as an example thereof, the information display device 100 that projects video information onto the windshield of an automobile will be described.

This information display device 100 forms a virtual image V1 in front of the own vehicle at the driver's viewpoint (eye point) 8, so that various information reflected by the projection member 6 (in the present embodiment, the inner surface of the windshield) is reflected. Is a device that displays a virtual image as a VI (Virtual Image), a so-called head-up display (HUD) device. The projection member 6 may be any member as long as it is a member on which video information is projected, and may be not only a windshield but also another projection member such as a combiner. The video information displayed as the virtual image VI includes, for example, vehicle information such as vehicle speed and foreground information taken by an in-vehicle camera.

The configuration of the information display device 100 consists of a video display unit 4 such as a liquid crystal display (LCD) that generates video light of video information to be displayed, and a backlight 5 that is arranged on the back side of the video display unit 4 and is a light source of video light. It has a concave mirror 1 that reflects the image light generated by the image display unit 4, and an optical element 2 such as a lens provided between the image display unit 4 and the concave mirror 1, and these are housed in a housing 7. ing. The optical element 2 is for correcting distortions and aberrations that occur when an image light is projected to form a virtual image. The image light reflected by the concave mirror 1 is reflected by the projection member 6 and heads toward the driver's viewpoint 8 to display a virtual image VI.

The video display unit 4 and the backlight 5 are controlled by the control unit 40. From the navigation system 61, the control unit 40 obtains various information such as the speed limit and the number of lanes of the road corresponding to the current position where the own vehicle is traveling, and the planned movement route of the own vehicle set in the navigation system 61. It is acquired as foreground information (that is, information displayed in front of the own vehicle by the above-mentioned virtual image).

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

The peripheral monitoring device 63 is a device that monitors the situation around the own vehicle, and as an example, a camera that detects an object existing around the own vehicle based on an image taken around the own vehicle, or an exploration wave. It is an exploration device that detects objects existing around the own vehicle based on the result of transmitting and receiving.

The control unit 40 acquires information from such a driving support ECU 62 (for example, the distance to the preceding vehicle, the direction of the preceding vehicle, the position where an obstacle or a sign exists, etc.) as foreground information. Further, the ignition (IG) signal and the own vehicle state information detected by various sensors 64 are input to the control unit 40. Among these information, the own vehicle state information is information acquired as vehicle information, and for example, it means that a predetermined abnormal state such as the remaining amount of fuel of the internal combustion engine and the temperature of the cooling water has occurred. Contains warning information to represent. In addition, the operation result of the direction indicator, the traveling speed of the own vehicle, and the shift position information are also included. The control unit 40 described above is activated when an ignition signal is input.

In the configuration of the optical system in the information display device 100, the image display unit 4, the backlight 5, the concave mirror 1, and other optical components form the virtual image optical system described below.

FIG. 2 is a diagram illustrating the principle of generating a virtual image. When the object (image source) AB is placed inside the focal point F of the concave mirror 1'which is the reflecting surface (position a on the reflecting surface side in the figure), a virtual image is formed at position b with the size of A'B'. Will be done. When the reflecting surface is a lens surface, a virtual image is formed at a position (not shown) relative to the reflecting surface.

In FIG. 1, the shape of the concave mirror 1 for reducing the distortion of the displayed virtual image will be described. In the upper region of the concave mirror 1, a light beam is incident below the windshield 6 and the distance (L1 + L2) from the driver's viewpoint 8 is relatively short, so the radius of curvature is reduced so that the magnification is large. On the other hand, in the lower region of the concave mirror 1, a light beam is incident above the windshield 6 and the distance from the driver's viewpoint 8 is relatively long, so the radius of curvature is increased so that the magnification is small. Further, the distortion itself can be reduced by inclining the image display unit 4 with respect to the optical axis of the concave mirror 1 to correct the above-mentioned difference in virtual image magnification.

Further, in the virtual image optical system, the curved surface shape of the windshield 6 of the automobile is corrected.
FIG. 3 is a top view of an automobile equipped with an information display device, and FIG. 4 is a diagram showing a curved surface shape of the windshield 6. Unlike the radius of curvature Rh in the horizontal direction and the radius of curvature Rv in the vertical direction with respect to the automobile main body 101, there is generally a relationship of Rh> Rv. Therefore, if the windshield 6 is regarded as a reflective surface, it becomes a toroidal concave mirror. Therefore, the shape of the concave mirror 1 in the information display device 100 is such that the virtual image magnification due to the shape of the windshield 6 is corrected. That is, the average radius of curvature differs between the horizontal direction and the vertical direction so as to correct the difference in the radius of curvature Rh and Rv between the horizontal direction and the vertical direction of the front glass 6.

At this time, it is preferable that the shape of the concave mirror 1 is corrected as a function of the coordinates (x, y) of the surface of the mirror surface from the optical axis as the shape of the free curved surface shown in the following [Formula 1]. This is because a spherical or aspherical shape (shown by [Formula 2] below) symmetrical to the optical axis is a function of the distance r from the optical axis, and the horizontal and vertical cross-sectional shapes at distant places cannot be controlled individually. Because.

Further, in FIG. 1, for example, a lens element is arranged as an optical element 2 between the image display unit 4 and the concave mirror 1, thereby controlling the emission direction of light rays to the concave mirror 1. As a result, the distortion aberration of the virtual image is corrected in combination with the correction function of the concave mirror 1. At the same time, the optical element 2 realizes the aberration correction of the virtual image including astigmatism caused by the difference in the radius of curvature Rh and Rv in the horizontal direction and the vertical direction of the windshield 6 described above.

Further, in order to improve the aberration correction ability, an optimally designed optical element may be provided between the concave mirror 1 and the image display unit 4. In addition, by changing the thickness of the optical element 2 in the optical axis direction described above, in addition to the original aberration correction, the optical distance between the concave mirror 1 and the image display unit 4 is changed to change the display position of the virtual image. It can also be changed continuously from a distant position to a close position. Further, by arranging the image display unit 4 at an angle with respect to the optical axis normal of the concave mirror 1, it is possible to correct the difference in the vertical magnification of the virtual image.

On the other hand, as a factor of deteriorating the image quality of the information display device 100, the image light emitted from the image display unit 4 toward the concave mirror 1 is reflected by the surface of the optical element 2 arranged in the middle and reflected on the image display unit 4. It may return, reflect again, and be superimposed on the original image light, degrading the image quality. Therefore, not only is an antireflection film formed on the surface of the optical element 2 to suppress reflection, but also the shape of at least one of the image light incident surface and the emitted surface of the optical element 2 can be changed, for example, the image display unit. The shape is such that the concave surface is directed toward 4, so that the above-mentioned reflected light is not focused on a part of the image display unit 4.

Next, in the image display unit 4 (hereinafter, also referred to as a liquid crystal panel), in order to absorb the reflected light from the optical element 2 described above, in addition to the first polarizing plate arranged in the vicinity of the liquid crystal panel 4. Further, if the second polarizing plate is arranged separately from the liquid crystal panel 4, the deterioration of the image quality can be reduced. Further, the backlight 5 of the liquid crystal panel 4 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. At this time, if the divergence angle of the light flux incident on the liquid crystal panel 4 is reduced, not only the image light can be efficiently directed to the driver's viewpoint 8 but also a high-contrast and highly visible image can be obtained. Is possible.

FIG. 5 is a diagram showing the vertical angular characteristics of the backlight brightness of the liquid crystal panel. Further, FIG. 6 is a diagram showing the vertical angular characteristics of the contrast of the liquid crystal panel. As described above, the contrast performance with respect to the divergence angle of the image is within ± 20 degrees in the vertical direction, and excellent characteristics can be obtained. In order to further improve the contrast performance, it is preferable to use a backlight flux within ± 10 degrees.

On the other hand, as the light emitting element of the light source (backlight) 4, a solid-state light source having a long product life, particularly an LED (Light Emitting Diode) having a small change in light output with respect to fluctuations in ambient temperature is preferable. Then, it is preferable to perform polarization conversion using a PBS (Polarizing Beam Splitter) provided with an optical means for reducing the emission angle of light.

In the liquid crystal panel 4, polarizing plates are arranged on the light incident surface side and the light emitting surface side, thereby increasing the contrast ratio of the image light. A high contrast ratio can be obtained by using an iodine-based polarizing plate having a high degree of polarization as the polarizing plate provided on the light incident surface side. On the other hand, by using a dye-based polarizing plate on the light emitting surface side, high reliability can be obtained even when external light is incident or the environmental temperature is high.

Further, when a liquid crystal panel is used as the image display unit 4, particularly when the driver wears polarized sunglasses, a problem occurs in which a specific polarization is shielded and the image cannot be seen. In order to prevent this, it is possible to arrange a λ / 4 plate on the optical element 2 side of the polarizing plate arranged on the exit surface side of the liquid crystal panel 4, thereby converting the image light aligned in a specific polarization direction into circular polarization. preferable.

<Details of virtual image optical system>
Next, the virtual image optical system and the image display unit according to this embodiment will be described in detail.
As described above in FIG. 3, a windshield 6 as a projection member is present in the front portion of the driver's seat of the automobile main body 101. The windshield 6 has a different inclination angle with respect to the vehicle body depending on the type of automobile. The inventors investigated the radius of curvature of the windshield 6 in order to realize the optimum virtual image optical system. As a result, as shown in FIG. 4, the front glass 6 differs between the horizontal radius of curvature Rh parallel to the ground plane of the automobile and the vertical radius of curvature Rv orthogonal to the horizontal axis, and Rh. It was found that there is generally a relationship of Rh> Rv between and Rv. Specifically, it was also found that the ratio Rh / Rv of the radius of curvature is often in the range of 1.5 times to 2.5 times.

Further, a commercially available product was investigated for the inclination angle of the windshield 6. As a result, although it varies depending on the vehicle body type, it was 20 to 30 degrees for the light vehicle and the 1Box type, 30 to 40 degrees for the sedan type, and 40 degrees or more for the sports type. Therefore, in this embodiment, the virtual image optical system is designed in consideration of the difference between the horizontal radius of curvature Rh and the vertical radius of curvature Rv of the windshield and the inclination angle of the windshield.

More specifically, since the horizontal radius of curvature Rh and the vertical radius of curvature Rv of the front glass 6 are significantly different, they are in the plane orthogonal to the optical axis (Z axis), that is, perpendicular to the horizontal direction (X axis) of the front glass 6. Good aberration correction was realized by providing an optical element 2 whose axis is asymmetric with respect to the direction (Y-axis) in the imaginary optical system.

Next, the miniaturization of the information display device 100 will be described. As a condition for studying miniaturization, the viewing angle (FOV) was set to 7 degrees in the horizontal direction and 2.6 degrees in the vertical direction, and the virtual image distance was set to 2 m. First, in the preliminary study, a concave mirror 1 for generating a virtual image, an image display unit 4, and a backlight 5 were used as a basic configuration, and one optical path folding mirror was arranged between the image display unit 4 and the concave mirror 1. Then, a simulation was performed using the arrangement of each member and the distance from the image display unit 4 to the concave mirror 1 as parameters so that the volume of the information display device 100 is minimized.

As a result, when the video light from the video display unit 4 was arranged so as not to interfere with each component, the volume of the information display device 100 was 3.6 liters. After that, with the aim of further miniaturization, a direct method excluding the optical path folding mirror (a plane mirror provided to increase the optical path length or to reduce the volume) was examined.

FIG. 7 is an overall configuration diagram of the virtual image optical system in FIG. 1, and shows the information display device 100 together with the windshield 6 and the driver's viewpoint 8. Further, FIG. 8 is a diagram showing a basic configuration of a virtual image optical system, and the miniaturization will be described based on this. In the drawing, the concave mirror 1 is drawn as a flat mirror for the sake of simplicity. Further, for the sake of simplification of the description, the optical element 2 for correcting aberrations is omitted. A liquid crystal panel is assumed for the image display unit 4, and the backlight 5 is basically arranged behind the image display unit 4.

The image display unit 4 arranges the displayed image so that a virtual image can be obtained by the concave mirror 1. The constraint condition is that with respect to the light beam shown in FIG. 8, the image light R1 from the upper end of the screen, the image light R2 from the center, and the image light R3 from the lower end of the image display unit 4 are reflected by the concave mirror 1, respectively. In addition, it is arranged so as not to interfere with the image display unit 4 and block the light.

The distance between the concave mirror 1 and the image display unit (liquid crystal panel) 4 so as to satisfy the above-mentioned constraint conditions and the above-mentioned examination conditions (FOV horizontal: 7 degrees, vertical: 2.6 degrees, virtual image distance 2 m). The volume of the information display device 100 was obtained with Z as a parameter. The distance Z is a distance along the image light R2, and is a horizontal distance between the central portion of the concave mirror 1 and the central portion of the image display unit 4.

FIG. 9 is a diagram showing the positional relationship between the concave mirror 1 and the image display unit 4, and shows the distance Z as a parameter. When the distance Z is 100 mm, the configuration shown in (c) is obtained, and in this case, the vertical dimension of the concave mirror 1 can be minimized. When the distance Z is 75 mm, as shown in (b), 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. When the distance Z is further shortened to 50 mm or less, as shown in (a), the angle α3 between the horizontal plane and the concave mirror 1 becomes large, and the vertical dimension of the concave mirror 1 also becomes large. As described above, the relationship between the height and the depth of the information display device (set) 100 with the distance Z as a parameter is that the set depth can be reduced by reducing the distance Z, but the set height is increased.

FIG. 10 is a diagram showing the relationship between the distance Z and the volume of the information display device 100. Regarding the relationship between the distance Z and the set volume, the change in the set volume (including the LCD drive circuit, the light source drive circuit, the backlight volume, etc.) is steeper than the change in the space volume from the image display unit 4 to the concave mirror 1. .. Then, based on the case where the distance Z is 100 mm, it was found that the set volume becomes about 80% (= 3 / 3.7 liters) or less by setting the distance Z to 60 mm or less, and the size can be sufficiently reduced.

From the above, in order to reduce the size of the information display device 100, it is necessary to realize a virtual image optical system having a short distance Z for directly magnifying the image displayed on the image display unit 4 by the concave mirror 1. FIG. As shown in (a), it was found that the center of the image display unit 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 unit 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 unit 4 and the lower end of the concave mirror 1 (corresponding to the light ray R3) is short. Therefore, it is preferable to arrange the image display unit 4 so that the distance between the image display unit 4 and the concave mirror 1 is as uniform as possible. Then, the optimum value of the distance Z is determined so as to satisfy the condition that the distance between the image display unit 4 and the concave mirror 1 becomes uniform.

In the virtual image optical system of this embodiment, the optical element 2 is provided between the image display unit 4 and the concave mirror 1 to correct the distortion of the virtual image and the aberration generated by the virtual image due to the miniaturization of the device. Further, in order to supplement the correction ability of the optical element 2, the display surface (hereinafter referred to as the panel surface) of the liquid crystal panel, which is the image display unit 4, is characterized by having a curved shape. Hereinafter, these will be described in detail.

In the virtual image optical system of this embodiment, the optical element 2 is arranged in order to reduce the distortion and aberration generated in the concave mirror 1. The optical element 2 is a transmissive optical lens, and has the following configuration in order to reduce the change in the refractive index and shape of the lens due to a change in the ambient temperature and the change in the refractive power of the lens.

(1) The shape is such that the entrance surface and the exit surface of the lens are almost parallel and do not have a local lens action. At this time, the image light incident on the reflecting surface of the concave mirror 1 as a telecentric light flux contributes to the correction of the incident position on the concave mirror 1 and the aberration generated.

(2) The image light from the image display unit 4 is diverged by the optical element 2 and refracted so that the position where the image light is incident on the concave mirror 1 is separated from the optical axis, thereby correcting the distortion generated locally. can do. At this time, since the lens action of the optical element 2 has a negative refractive power on the optical axis, it is necessary to increase the relative positive refractive power of the concave mirror 1.

(3) Distortion aberration that occurs locally can also be corrected by condensing the video light from the video display unit 4 by the optical element 2 and bringing the position where the video light is incident on the concave mirror 1 closer to the optical axis. can. At this time, since the lens action of the optical element 2 has a positive refractive power on the optical axis, the relative positive refractive power of the concave mirror 1 can be reduced.

(4) The above is the correction of distortion near the optical axis of the concave mirror 1. By making the shape of the optical element 2 an aspherical shape, an eccentric aspherical shape away from the optical axis, or a free curved shape. , The optical element 2 is provided with a local positive or negative refractive power, and distortion can be corrected to a higher degree.
Further, by making at least one of the incident surface and the exit surface of the optical element 2 an aspherical surface, an eccentric aspherical surface, or a free curved surface, the degree of freedom of aberration correction is increased, and the above-mentioned distortion aberration is also corrected. Although one optical element has been described in this embodiment, a plurality of transmissive optical elements may be used.

<Technology for reducing curvature of field>
On the other hand, in order to realize miniaturization of the apparatus, it is indispensable to increase the positive refractive power of the concave mirror 1, but the ability of the optical element 2 to correct the curvature of field is insufficient, and as a result, the ability to correct other aberrations is also insufficient. Therefore, it has been found that the resolution of the image reflected by the concave mirror 1 is lowered, and an image with high visibility cannot be obtained. That is, there is a problem that the curvature of field increases as the positive refractive power of the concave mirror 1 is increased. Specifically, in a portion away from the optical axis, the image plane tilts backward and curvature of field occurs.

FIG. 11 is a diagram illustrating a typical field curvature (distortion) state. (A) is an image pattern without distortion, (b) shows a state in which pincushion type distortion has occurred, and (c) shows a state in which barrel type distortion has occurred.
Therefore, the virtual image optical system of this embodiment is characterized in that the liquid crystal panel surface of the image display unit 4 has a curved shape.

FIG. 12 is a diagram schematically showing a configuration in which the liquid crystal panel surface has a curved shape. The curvature of field generated by bending the panel surface 4a (shown by a solid line), which is the display surface of the image display unit 4, so as to be concave with respect to the concave mirror 1 is reduced. An optical system using such a concave panel will be referred to as a "first virtual image optical system". As a result, by supplementing the aberration correction ability of the optical element 2 described above, a good virtual image with high visibility can be obtained.

On the other hand, as a modification, the panel surface may be oriented in the opposite direction as shown by the reference numeral 4b (indicated by the broken line), and may be curved so as to be a convex surface with respect to the concave mirror 1 (indicated by the broken line). An optical system using such a convex panel is called a "second virtual image optical system". In this optical system, the curvature of field that occurs is increased, and the image plane position is moved further away from the driver. As a result, the position where the virtual image is formed becomes far away, and the size of the virtual image that can be obtained also increases. In this case, in order to correct the generated aberration with higher accuracy, the aberration correction ability can be supplemented by providing a plurality of the above-mentioned optical elements 2, and a good virtual image with high visibility can be obtained.

Further, by bending the windshield 6 so as to be compatible with the curved surface, it is possible to reduce the curvature of the image plane from the image display unit 4. Specifically, since the radius of curvature Rv in the vertical direction of the windshield 6 is smaller than the radius of curvature Rh in the horizontal direction, if the windshield 6 is replaced with a concave mirror, the optical power in the vertical direction is large. Therefore, the radius of curvature in the vertical direction of the panel surface 4a is reduced with respect to the horizontal direction to reduce curvature of field. This can be realized by forming the panel surface 4a into a shape (first virtual image optical system) that is convexly curved with respect to the light source 5. Since the windshield 6 has different radii of curvature in the vertical direction and the horizontal direction as described above, the curved shape of the panel surface 4a is also set corresponding to the different radii of curvature of the windshield 6. Is preferable.

In this way, by curving the panel surface 4a, which is the image display unit 4 constituting the virtual image optical system, the device can be miniaturized and the curvature of field due to the optical element 2 which is indispensable for the miniaturization of the device can be reduced. Then, it is possible to display a highly visible virtual image with high resolution by the reflection by the concave mirror 1.

FIG. 13 is a diagram showing a configuration in which the emission surface of the light source 5 is curved together with the liquid crystal panel surface. In the first virtual image optical system, the radius of curvature of the emission surface of the light source 5a (indicated by a solid line) is substantially the same as the radius of curvature of the panel surface 4a, and is configured to be concave with respect to the concave mirror 1. According to such a configuration, it is possible to conform to the curved surface on the incident side of the optical element 2 which is indispensable for realizing the miniaturization of the device, and at the same time, it is possible to more efficiently capture the light source light into the above-mentioned virtual image optical system. .. Therefore, it is possible to display a highly visible virtual image with higher luminance and resolution by reflection by the concave mirror 1.

Similarly, in the second virtual image optical system, the radius of curvature of the emission surface of the light source 5b (indicated by a broken line) is substantially the same as the radius of curvature of the panel surface 4b, and is configured to be a convex surface with respect to the concave mirror 1. .. The effect in this case is the same as that in the case of the first virtual image optical system.

14A and 14B show an overall ray diagram of the virtual image optical system of this embodiment, where FIG. 14A is a cross-sectional view in the vertical direction (Y-axis direction) and FIG. 14B is a cross-sectional view in the horizontal direction (X-axis direction). .. AB represents a video light source, A'B'represents the position of a virtual image, and indicates the positional relationship between the concave mirror 1 and the windshield 6.

FIG. 15 shows an enlarged ray diagram of a part of the virtual image optical system of FIG. 14, and enlarges the vicinity of the optical element 2, the concave mirror 1, and the windshield 6. In this example, the optical element 2 is composed of two lens elements.

<Manufacturing method of curved image display unit>
A method of bending a liquid crystal panel, which is an image display unit, according to an embodiment of the present invention will be described below. In order to realize a curved liquid crystal panel, it is necessary to make the cover glass as a base material into the required curved shape. For this purpose, a flat glass substrate is heated to a heat distortion temperature and pressed by a mold having a desired curved surface shape to be deformed and pre-cooled to obtain a desired shape. A liquid crystal panel is attached to the obtained curved glass substrate according to the curved surface. At this time, it is advisable to perform bonding in a vacuum so that air bubbles do not enter between the curved glass and the liquid crystal panel. However, in this method, two members are introduced into the vacuum chamber and inside the chamber before bonding. It is evacuated and taken out of the vacuum after pasting to prevent air bubbles from entering the pasting surface.

In the above-mentioned method, the device may become large, the manufacturing tact may be long, and the productivity may be low. However, as a method for attaching a liquid crystal panel or the like to a member curved in the atmosphere, for example, Japanese Patent Application Laid-Open No. 2016-179600 is described. There is technology.

<Mounting structure of light source (backlight)>
Next, a suitable mounting structure of the image display unit (liquid crystal panel) 4 and the light source (backlight) 5 in the miniaturized information display device 100 will be described.

FIG. 16 is an external view of the image display unit (liquid crystal panel) 4 and the light source (backlight) 5. The liquid crystal panel 4 is composed of a panel display surface 11, a frame 12, and a flexible substrate 10, and the backlight 5 is composed of an exterior member 16 for accommodating a light source unit, a diffusion member 14, a frame 15, and heat radiation fins 13. The liquid crystal panel 4 displays an image on the panel display surface 11 by modulating the light from the backlight 5 with the image signal input from the flexible substrate 10. The displayed image is converted into a virtual image by the virtual image optical system and transmitted to the driver as image information. Here, the exit surfaces of the liquid crystal panel 4 and the backlight 5 are shown as flat surfaces for the sake of simplicity, but as shown in FIGS. 12 and 13, they are assumed to have a curved shape as necessary.

In the above configuration, a relatively inexpensive and highly reliable LED light source is used as the solid-state light emitting element for the light emitting element of the backlight 5. Since the LED uses a surface light emitting type in order to increase the output, the light utilization efficiency is improved by using a technical device described later. The luminous efficiency with respect to the input power of the LED varies depending on the emission color, but is about 20 to 30%, and most of the rest is converted into heat. Therefore, the frame 15 to which the LED is mounted is provided with fins 13 for heat dissipation made of a member having a high thermal conductivity (for example, a metal member such as aluminum) to dissipate heat to the outside, whereby the luminous efficiency of the LED itself is achieved. To improve.

In particular, LEDs currently on the market that use red as the emission color have a significantly reduced luminous efficiency when the junction temperature rises, and at the same time, the chromaticity of the image also changes. It is preferable to increase the area of the corresponding heat radiating fin 13 to improve the cooling efficiency. Further, in order to efficiently guide the diffused light from the LED to the liquid crystal panel 4, a light guide body (reference numeral 18 in FIG. 17) is used, but the entire structure is covered with an exterior member 16 so that dust or the like does not adhere. It is preferable to do so.

FIG. 17 is an enlarged view of the light source unit 9 in the backlight 5. The light source unit 9 includes a light funnel unit 20 including a plurality of LED light sources, a light guide body 18, and a diffusion member 14. The light funnel unit 20 captures the divergent rays from the plurality of LEDs 21 at the openings 23 of the corresponding plurality of light funnels 22. At that time, the opening 23 is a flat surface, and a medium is inserted between the opening 23 and the LED 21 to optically connect the light, or the convex shape has a condensing effect so that the emitted light source light is as parallel as possible. As a result, the incident angle of the light incident on the interface of the light funnel 22 is reduced. As a result, since the divergence angle can be further reduced after passing through the light funnel 22, it becomes easy to control the light source light directed to the liquid crystal panel 4 after being reflected by the light guide body 18.

Further, in order to improve the utilization efficiency of the divergent light from the LED 21, polarization conversion is performed at the junction 25 of the light funnel 22 and the light guide body 18 using a polarization conversion element (PBS), and the light funnel 22 and the light guide body 18 are converted into a desired polarization direction. By doing so, the efficiency of the incident light on the liquid crystal panel 4 can be improved.

When the polarization directions of the light source lights are aligned, a material having less birefringence is used as the material of the light guide body 18, and when the direction of polarization rotates and passes through the liquid crystal panel 4, for example, a black display is displayed. It is even better to avoid problems such as coloring from time to time.

The luminous flux from the LED 21 with the reduced divergence angle is controlled by the light guide body 18, is reflected by the total reflection surface provided on the slope of the light guide body 18, and is a diffusion member arranged between the facing surface and the liquid crystal panel 4. After being diffused by 14, it is incident on the liquid crystal panel 4. In this embodiment, the diffusion member 14 is arranged between the light guide body 18 and the liquid crystal panel 4, but a structure in which the end face of the light guide body 18 has a diffusion effect, for example, a structure having a fine uneven shape is also available. A similar effect can be obtained.

FIG. 18 is a diagram showing the appearance of the light guide body 18. The luminous flux whose divergence angle is reduced by the light funnel 22 shown in FIG. 17 is incident on the incident surface 18a of the light guide body 18 and is emitted from the exit surface 18c. At this time, the divergence angle in the vertical direction (vertical direction in FIG. 19) is controlled by the shape effect of the incident surface 18a (the cross-sectional shape is shown in FIG. 19), and the light propagates efficiently in the light guide body 18.

FIG. 19 is an enlarged cross-sectional view of a main part of the light guide body 18. As shown in (a), the light source light whose divergence angle is reduced by the light funnel 22 is incident from the incident surface 18a via the junction 25, and is totally reflected by the prism 18b provided on the facing surface and emitted. Head to surface 18c. The total reflection prism 18b has a shape in the vicinity of the incident surface 18a (Fig. (B), enlarged part B) and an end portion (Fig. (C), enlarged part A), and its shape determines the divergence angle of the light flux incident on each surface. Correspondingly, it is divided into steps and formed, thereby controlling the angle of the total reflection surface. On the other hand, after the reflected light flux is reflected, the divided dimension of the reflecting surface of the total reflection prism 18b is used as a variable so that the light beam incident on the liquid crystal panel 4 has a uniform light amount distribution in the emission surface of the liquid crystal panel 4. Control the arrival position and the amount of energy.

FIG. 20 is a diagram showing a simulation result in a state where the light emitted from the backlight 5 has passed through the liquid crystal panel 4. (A) shows the light emission state seen from the longitudinal direction of the liquid crystal panel 4, and (b) shows the light emission state seen from the short side of the liquid crystal panel 4. In this embodiment, in order to widen the horizontal angle of the FOV beyond the design, the horizontal diffusion angle is increased with respect to the vertical direction, and even when the driver shakes his head or the eye position moves. It is designed so that the brightness of the imaginary image seen by the left and right eyes does not change drastically. Further, by reducing the divergence angle in the vertical direction of the backlight 5, the divergence angle in the vertical direction of the screen of the image displayed on the liquid crystal panel 4 is reduced, and the generation of the double image is suppressed.

FIG. 21 is a diagram showing a luminance distribution on the emission surface of the liquid crystal panel 4. Here, the light guide body 18 is used for the backlight 5 to control the light emission direction and the intensity. As is clear from the figure, it is possible to reduce the inclination of the brightness decrease outside the effective range in the screen horizontal direction (X-axis direction) with respect to the brightness distribution in the screen vertical direction (Y-axis direction).

In this way, the angle of the total reflecting surface of the light guide body 18 and the light source light from the LED 21 by the light funnel 22 so that the light emitted from the liquid crystal panel 4 taken into the virtual image optical system can be obtained as light as perpendicular to the screen as possible. By controlling the divergence angle of the backlight 5 and narrowing down the viewing angle characteristic of the backlight 5 to a small range, high brightness was obtained. Specifically, in order to obtain a high-brightness image, light in the range of ± 30 ° is used for the left and right viewing angles, and considering the contrast performance, it is possible to reduce the image quality to ± 20 ° or less at the same time. I was able to obtain a virtual image using images.

As described above, the contrast performance that affects the image quality of the image display unit is determined by how much the brightness (black brightness) in the case of black display, which is the basis for determining the image quality, can be lowered. 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 5. On the other hand, by using a dye-based polarizing plate as the polarizing plate provided on the light emitting surface side of the liquid crystal panel 4, high reliability can be obtained even when external light is incident or the environmental temperature is high.

When color display is performed on the liquid crystal panel 4, a color filter corresponding to each pixel is provided. Therefore, when the light source color of the backlight 5 is white, the light absorption by the color filter is large and the loss is large. Therefore, as shown in FIG. 17 above, using a plurality of LEDs 21, a plurality of LEDs 21 are used.
(1) Add a green LED that contributes more to brightness than when a plurality of white LEDs are used.
(2) Add a red or blue LED to the white LED to enhance the glossiness of the image.
(3) By arranging the red, blue, and green LEDs individually and adding a green LED that contributes greatly to the brightness and driving the LEDs individually, the color reproduction range can be expanded and the glossiness can be enhanced. At the same time, the brightness is improved.
(4) By carrying out the above (3), the transmittance of each color filter with respect to the peak luminance of the red, blue, and green LEDs is increased, and the overall brightness is improved.
(5) Further, as a second embodiment of the backlight, by arranging PBS between the light funnel and the light guide to align with a specific polarization, damage to the polarizing plate on the incident side of the liquid crystal panel is reduced. do. The polarization direction of the polarizing plate arranged on the incident side of the liquid crystal panel may be the direction in which the polarization aligned in a specific direction passes after passing through PBS.

Although the embodiments of the present invention have been described in detail above, various modifications are possible.
As the image display unit 4, it is also possible to provide a λ / 4 plate on the emission surface of the liquid crystal panel so that the emitted light is circularly polarized. As a result, the driver can observe a good virtual image even when wearing polarized sunglasses.

Further, the liquid crystal panel is assumed to have a structure in which a liquid crystal is sealed between transparent glass substrates, but the present invention is not limited to this, and for example, a flexible liquid crystal panel in which a liquid crystal is sealed between transparent polyimide substrates. There may be. Further, the backlight is not limited to the side light type using a light guide, and may be a direct type. Further, the curved shape of the liquid crystal panel may be one in which one axis is curved or one in which two or more axes are curved. In that case, the curvature at the center of the liquid crystal panel and the curvature at the periphery may be different. Further, when the curvature is formed on two or more axes, the curvature may be different for each axis. If it is difficult to say that the windshield is curved more than two axes, it is possible to make a curved surface having only one axis corresponding to the vertical curvature Rv having a small radius of curvature of the windshield.

Furthermore, by forming the reflective film of the reflective mirror used in the imaginary optical system with a metal multilayer film, the angle dependence of the reflectance is small, and the reflectance may change depending on the polarization direction (P wave or S wave). Therefore, it is possible to keep the chromaticity and brightness of the screen uniform.

Further, by providing an optical member between the virtual image optical system and the front glass, which is a combination of an ultraviolet reflecting film, an infrared reflecting film, or both, even if external light (sunlight) is incident, the liquid crystal is displayed. Since the panel and the polarizing plate can be reduced from the temperature rise and damage, the reliability of the information display device is not impaired.

The imaginary optical system of this embodiment is optimally designed including the difference between the radius of curvature in the vehicle horizontal direction and the radius of curvature in the vertical direction of the windshield, which is a projection member, and the windshield 5 and the image display unit 4 (or an intermediate image). A concave mirror 1 having a concave surface facing the windshield 6 side is arranged between the display units), whereby the image of the image display unit 4 is enlarged and reflected by the windshield 6. At this time, the optical element 2 is arranged between the concave mirror 1 and the image display unit 4, and on the other hand, an enlarged image (virtual image) of the image formed corresponding to the viewpoint position 8 of the driver. The image luminous flux forming the image passes through the optical element 2 arranged between the image display units 4 and corrects distortion and aberration generated in the concave mirror 1. Therefore, it is possible to obtain a virtual image with significantly reduced distortion and aberration as compared with the conventional virtual image optical system having only the concave mirror 1.

Further, in the configuration shown in FIG. 1, the virtual image VI obtained by being reflected by the upper part of the windshield 6 (the upper part in the vertical direction of the vehicle body) needs to be imaged farther. Therefore, in order to satisfactorily image the image luminous flux emitted from the upper part of the image display unit 4 on which the corresponding image is displayed, the optics arranged between the concave mirror 1 and the image display unit 4 described above The focal length f1 of the element 2 is set short. On the contrary, the virtual image obtained by being reflected by the lower part of the windshield 6 (the lower part in the vertical direction of the vehicle body) needs to be imaged closer. Therefore, in order to satisfactorily image the image luminous flux emitted from the lower part of the image display unit 4 on which the corresponding image is displayed, a plurality of optics arranged between the concave mirror 1 and the image display unit 4 described above. The combined focal length f2 of the element 2 may be set relatively long.

Further, in this embodiment, virtual image optics is used to correct the screen distortion of the virtual image observed by the driver because the horizontal radius of curvature (parallel to the ground) of the front glass 6 and the radius of curvature in the direction perpendicular to the radius of curvature are different. By arranging the optical elements 2 having different axial symmetries with respect to the optical axis in the system, the above-mentioned distortion correction is realized.

The case where the information display device of this embodiment is mounted on an automobile and observed as a virtual image through the front glass has been described, but the present invention is not limited to this, and the information display device is mounted on a "vehicle" such as a train or an aircraft to be mounted on a driver (maneuvering). The same can be applied when the person) observes.

The configurations of various optical systems according to the information display device of the present invention have been described above. The present invention is not limited to the above-mentioned examples, but includes various modifications. For example, the above-described embodiment describes the entire apparatus in detail in order to explain the present invention in an easy-to-understand manner, and is not necessarily limited to the one including all the configurations described. Further, it is possible to replace a 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. Further, it is possible to add / delete / replace a part of the configuration of each embodiment with another configuration.

1 ... concave mirror, 2 ... optical element, 4 ... image display unit (liquid crystal panel, LCD), 5 ... light source (backlight), 6 ... projection member (front glass), 7 ... housing, 8 ... driver's point of view , 9 ... Light source unit, 10 ... Flexible substrate, 11 ... Panel display surface, 12 ... Frame, 13 ... Radiation fin, 14 ... Diffuse member, 15 ... Frame, 16 ... Exterior member, 18 ... Light guide body, 20 ... Light funnel Unit, 21 ... LED, 22 ... light funnel, 23 ... opening, 25 ... junction, 40 ... control unit, 100 ... information display device, VI ... virtual image.

Claims (11)

In an information display device that projects an image on a projection member
Light source and
An image display unit that arranges the light source on the back side and generates the image light of the image, and
An optical system that reflects the image light generated by the image display unit by a concave mirror and projects it onto the projection member to display a virtual image in front of the projection member is provided.
The display surface of the image display unit is formed so as to have a concave shape with respect to the concave mirror.
The light source includes an optical means that converts light into substantially parallel light, and a light guide that reflects the light that has become substantially parallel light by the optical means and causes the light to enter the image display unit.
The light guide has a reflecting surface that reflects light from the optical means, and the light emitting direction of light incident on the image display unit is set according to the concave shape of the display surface of the image display unit. Adjust according to the shape of
The vertical center of the display surface of the image display unit is arranged below the center of the concave mirror.
An information display device characterized in that the horizontal distance between the central portion of the concave mirror and the central portion of the image display unit is set to 60 mm or less. In an information display device that projects an image on a projection member
Light source and
An image display unit that arranges the light source on the back side and generates the image light of the image, and
An optical system is provided that reflects the image light generated by the image display unit with a concave mirror and projects it onto the projection member to display a virtual image in front of the projection member.
The optical system further has an optical element between the image display unit and the concave mirror, and the optical element corrects the distortion generated in the virtual image due to the shape of the concave mirror.
The display surface of the image display unit is formed so as to have a concave shape with respect to the optical element.
The light source includes an optical means that converts light into substantially parallel light, and a light guide that reflects the light that has become substantially parallel light by the optical means and causes the light to enter the image display unit.
The light guide has a reflecting surface that reflects light from the optical means, and the light emitting direction of light incident on the image display unit is set according to the concave shape of the display surface of the image display unit. Adjust according to the shape of
The vertical center of the display surface of the image display unit is arranged below the center of the concave mirror.
An information display device characterized in that the horizontal distance between the central portion of the concave mirror and the central portion of the image display unit is set to 60 mm or less. In the information display device according to claim 1 or 2.
An information display device characterized in that the concave shape of the display surface of the image display unit is determined so as to reduce the curvature of field generated in the virtual image due to the shape of the concave mirror. In the information display device according to claim 3,
An information display device characterized in that the concave shape of the display surface of the image display unit is further determined to reduce the curvature of field generated in the virtual image due to the curvature of the projection member. In the information display device according to claim 1 or 2.
An information display device characterized in that the emission surface of the light source is formed so as to have a concave shape similar to the concave shape of the display surface of the image display unit. In the information display device according to claim 1 or 2.
An information display device characterized in that a liquid crystal panel is used as the image display unit. In the information display device according to claim 6,
Information display characterized in that after the light emitted from the light guide has passed through the liquid crystal panel, the light emitted from the longitudinal direction of the liquid crystal panel and the light emitted from the lateral direction are different. Device. In the information display device according to claim 6,
An information display device characterized in that a λ / 4 plate is provided on the exit surface side of the liquid crystal panel. In the information display device according to claim 6,
Light that reflects at least one of ultraviolet rays and infrared rays between the optical system and the projection member.
An information display device characterized by being equipped with academic members. In the information display device according to claim 1 or 2.
An information display device characterized in that the image display unit is arranged so that the distance between the concave mirror and the upper end to the lower end of the image display unit is uniform. In the information display device according to claim 10,
Information display characterized in that the horizontal distance between the central portion of the concave mirror and the central portion of the image display unit is set so as to satisfy the condition that the distance between the image display unit and the concave mirror is uniform. Device.

Images