Patent Application
20250085539
Embodiments described herein relate generally to a light source unit, an image display device, and an automobile.
International Publication No. 2016/208195 discusses technology in which light emitted from a display device configured to display an image is sequentially reflected by multiple mirrors, and the light reflected by the final mirror is further reflected toward a user by a reflecting member such as a windshield or the like, thereby causing the user to view a virtual image corresponding to the image displayed by the display device. If, however, the image using the technology discussed in International Publication No. 2016/208195 is to be colorized, pixels must correspond respectively to the colors, which undesirably makes the display device larger.
Embodiments of the invention are directed to a compact light source unit, an image display device, and an automobile that can display a color image.
A light source unit according to one aspect of the present invention includes a display device configured to display an image including a plurality of pixels, a color change sheet on which light emitted from the display device is incident, an imaging optical system, and a drive unit changing a positional relationship of the display device and the color change sheet. The imaging optical system includes an input element and an output element. Light emitted from the color change sheet is incident on the input element. Light traveling via the input element is incident on the output element. Light emitted from the output element forms a first image corresponding to the image. The color change sheet includes a first region on which light from the pixels is incident and a second region on which the light from the pixels is incident. The first region emits light of a first color. The second region emits light of a second color. The second color is different from the first color. The drive unit changes the positional relationship of the display device and the color change sheet between a first positional relationship in which light emitted from one of the pixels is incident on the first region, and a second positional relationship in which the light emitted from the one of the pixels is incident on the second region. The imaging optical system is substantially telecentric at the first image side. The light emitted from the display device has a substantially Lambertian light distribution.
An image display device according to one aspect of the present invention includes the light source unit and a reflection unit separated from the light source unit. The reflection unit reflects light emitted from the imaging optical system. The first image is formed between the light source unit and the reflection unit.
According to embodiments, a compact light source unit, an image display device, and an automobile that can display a color image can be realized.
Exemplary embodiments and their modifications will now be described with reference to the drawings. The drawings are schematic or conceptual, and are enhanced or simplified as appropriate. For example, the relationships between the thickness and width of portions, the proportional coefficients of sizes among portions, etc., are not necessarily the same as the actual values thereof. Furthermore, the dimensions and proportional coefficients may be illustrated differently among drawings, even for identical portions. In the specification of the application and the drawings, components similar to those in a previously described drawing are marked with like reference numerals, and a detailed description is omitted as appropriate.
First, a first embodiment will be described.
As shown in
For example, the image display device 10 is mounted in an automobile 1000, and is included in a HUD (Head Up Display). The automobile 1000 includes a vehicle 13, and the image display device 10 fixed to the vehicle 13. A viewer 14 is a passenger of the automobile 1000, and is, for example, the driver.
The display device 110 of the light source unit 11 displays an image to be viewed by the viewer 14 with the HUD. The color change sheet 130 changes the color of the image displayed by the display device 110 by pixel. This mechanism is described below. The imaging optical system 120 outputs the light emitted from the color change sheet 130 to the reflection unit 12 and forms the first image IM1 between the light source unit 11 and the reflection unit 12. The reflection unit 12 reflects the light emitted from the light source unit 11 toward a front windshield 13a of the vehicle 13. The front windshield 13a includes, for example, glass.
The inner surface of the front windshield 13a reflects the light from the reflection unit 12 and causes the light to enter an eyebox 14a of the viewer 14. As a result, the viewer 14 can view, beyond the front windshield 13a, a second image IM2 corresponding to the image displayed by the display device 110. The second image IM2 is a virtual image that is larger than the first image IM1. “Eyebox” refers to the area of space in front of the eyes of the viewer where the virtual image is visible.
Hereinbelow, the arrangements and configurations of the portions are described using an XYZ orthogonal coordinate system for easier understanding of the description. According to the embodiment, the longitudinal direction of the vehicle 13 is taken as an “X-direction,” the lateral direction of the vehicle 13 is taken as a “Y-direction,” and the vertical direction of the vehicle 13 is taken as a “Z-direction.” The XY-plane is the horizontal plane of the vehicle 13. The direction of the arrow in the X-direction (front) also is called the “+X direction,” and the opposite direction (back) also is called the “−X direction.” The direction of the arrow in the Y-direction (left) also is called the “+Y direction,” and the opposite direction (right) also is called the “−Y direction.” The direction of the arrow in the Z-direction (up) also is called the “+Z direction,” and the opposite direction (down) also is called the “−Z direction.”
In
As shown in
As shown in
The regions 130p include the three types of a first region 130a, a second region 130b, and a third region 130c. The first region 130a emits light of a first color when the light from the pixel 110p of the display device 110 is incident. The second region 130b emits light of a second color, which is different from the first color, when the light from the pixel 110p is incident. The third region 130c emits light of a third color, which is different from the first and second colors, when the light from the pixel 110p is incident.
According to the embodiment, the first region 130a, the second region 130b, and the third region 130c are arranged repeatedly along the first direction (the X-direction) and the second direction (the Y-direction). Therefore, when focusing on a specific region of the color change sheet 130, the first region 130a and the second region 130b are arranged along the first direction (the X-direction), and the first region 130a and the third region 130c are arranged along the second direction (the Y-direction). Although one hundred regions 130p in ten rows and ten columns are shown in
According to the embodiment, the first region 130a includes a blue film, and the first color is blue. The second region 130b includes a green film, and the second color is green. The third region 130c includes a red film, and the third color is red. In other words, the first region 130a emits blue light when white light from the pixel 110p of the display device 110 is incident. The second region 130b emits green light when the white light from the pixel 110p is incident. The third region 130c emits red light when the white light from the pixel 110p is incident. In
As shown in
The configuration of the image display device 10 other than the configuration described above will now be described.
First, the display device 110 will be described.
The display device 110 of the light source unit 11 is an LED display. The multiple LED elements 112 are arranged in a matrix configuration in the display device 110. One or multiple LED elements 112 are located in each pixel 110p of the display device 110.
In the display device 110 as shown in
The semiconductor stacked body 112a includes a p-type semiconductor layer 112p1, an active layer 112p2 located on the p-type semiconductor layer 112p1, and an n-type semiconductor layer 112p3 located on the active layer 112p2. The semiconductor stacked body 112a includes, for example, a gallium nitride compound semiconductor of InXAlYGa1-X-YN (0≤X, 0≤Y, and X+Y<1). According to the embodiment, the light that is emitted by the LED element 112 is visible light.
The anode electrode 112b is electrically connected to the p-type semiconductor layer 112p1. Also, the anode electrode 112b is electrically connected to a wiring part 118b. The cathode electrode 112c is electrically connected to the n-type semiconductor layer 112p3. Also, the cathode electrode 112c is electrically connected to another wiring part 118a. The electrodes 112b and 112c can include, for example, a metal material.
According to the embodiment, a wavelength conversion member 115 is located on each LED element 112. The light that is emitted from the LED element 112 is incident on the wavelength conversion member 115. For example, the wavelength conversion member 115 faces a light-emitting surface 112s of the LED element 112. In the specification, “the light-emitting surface of the LED element” means the surface of the LED element that mainly emits the light that is incident on the imaging optical system 120. According to the embodiment, the surface of the n-type semiconductor layer 112p3 that is positioned at the side opposite to the surface facing the active layer 112p2 corresponds to the light-emitting surface 112s.
The wavelength conversion member 115 includes a fluorescer. According to the embodiment, the LED element 112 emits blue light. The wavelength conversion member 115 includes a fluorescer absorbing blue light and radiating green light, and a fluorescer absorbing blue light and radiating red light. As a result, white mixed light that is made of blue light, green light, and red light is emitted from the wavelength conversion member 115.
Hereinbelow, the optical axis of the light emitted from each pixel 110p is called simply an “optical axis C.” The optical axis C is, for example, a straight line that connects a point a1 in a first plane P1 and a point a2 in a second plane P2, wherein the first plane P1 is positioned at the light-emitting side of the display device 110 and parallel to the XY-plane in which the multiple pixels 110p are arranged, the luminance is a maximum at the point a1 in the range in which the light is irradiated from one pixel 110p, the second plane P2 is parallel to the XY-plane and separated from the first plane P1, and the luminance is a maximum at the point a2 in the range in which the light is irradiated from the pixel 110p. For example, if the luminance has maxima at multiple points, the center of the points may be used as the maximum luminance point. From the perspective of productivity, it is desirable for the optical axis C to be parallel to the Z-axis.
Thus, by providing the wavelength conversion member 115 at the light-emitting surface 112s of each LED element 112, the light that is emitted from the wavelength conversion member 115, i.e., the light that is emitted from each pixel 110p, has a substantially Lambertian light distribution as illustrated by the broken line in
The imaging optical system 120 will now be described in detail.
As shown in
The imaging optical system 120 is substantially telecentric at the first image IM1 side. Here, “the imaging optical system 120 is substantially telecentric at the first image IM1 side” means that the multiple chief rays L that are emitted from mutually-different positions of the display device 110, travel via the imaging optical system 120, and reach the first image IM1 are substantially parallel to each other before and after the first image IM1 as shown in
When the imaging optical system 120 is substantially telecentric at the first image IM1 side, the multiple chief rays L cross each other before being incident on the input element 121. Hereinbelow, the point at which the multiple chief rays L cross each other is called a “focal point F.” Therefore, for example, whether or not the imaging optical system 120 is substantially telecentric at the first image IM1 side can be confirmed by utilizing the backward propagation of light by the following method. First, a light source such as a laser light source or the like that can emit parallel light is disposed at the vicinity of the position at which the first image IM1 is formed. The light that is emitted from the light source is irradiated on the output element 123 of the imaging optical system 120. The light that is emitted from the light source and travels via the output element 123 is incident on the input element 121. Then, if the light that is emitted from the input element 121 condenses at a point, i.e., the focal point F, before reaching the display device 110, then the imaging optical system 120 can be determined to be substantially telecentric at the first image IM1 side.
Because the imaging optical system 120 is substantially telecentric at the first image IM1 side, the light emitted from each pixel of the display device 110 that is mainly incident on the imaging optical system 120 is the light that passes through the focal point F and the vicinity of the focal point F. Optical elements included in the imaging optical system 120 will now be described.
The input element 121 is positioned at the −Z side of the display device 110 and arranged to face the display device 110. The input element 121 is a mirror that includes a concave mirror surface 121a. The input element 121 reflects the light emitted from the display device 110.
The intermediate element 122 is positioned at the −X side of the display device 110 and the input element 121 and arranged to face the input element 121. The intermediate element 122 is a mirror that includes a concave mirror surface 122a. The intermediate element 122 further reflects the light reflected by the input element 121.
The input element 121 and the intermediate element 122 are included in a bending part 120a that bends the multiple chief rays L so that the multiple chief rays L emitted from mutually-different positions of the display device 110 are substantially parallel to each other. According to the embodiment, the mirror surfaces 121a and 122a are biconic surfaces. However, the mirror surfaces may be portions of spherical surfaces or may be freeform surfaces.
The output element 123 is positioned at the +X side of the display device 110 and the input element 121 and arranged to face the intermediate element 122. The output element 123 is a mirror that includes a flat mirror surface 123a. The output element 123 reflects the light traveling via the input element 121 and the intermediate element 122 toward the formation position of the first image IM1. Specifically, the multiple chief rays L that are substantially parallel due to the bending part 120a are incident on the output element 123. The mirror surface 123a is tilted in the +X/−Z direction with respect to the XY-plane, i.e., the horizontal plane of the vehicle 13. As a result, the light that is reflected by the intermediate element 122 is reflected by the output element 123 in a direction tilted in the +X/−Z direction with respect to the Z-direction. As shown in
According to the embodiment, the optical path between the input element 121 and the intermediate element 122 extends in a direction crossing the XY-plane. The optical path between the intermediate element 122 and the output element 123 extends in a direction along the XY-plane. Because a portion of the optical path inside the imaging optical system 120 extends in a direction crossing the XY-plane, the light source unit 11 can be somewhat smaller in directions along the XY-plane. Because another portion of the optical path inside the imaging optical system 120 extends in a direction along the XY-plane, the light source unit 11 can be somewhat smaller in the Z-direction.
The optical path between the display device 110 and the input element 121 crosses the optical path between the intermediate element 122 and the output element 123. Thus, by causing the optical paths to cross each other inside the light source unit 11, the light source unit 11 can be smaller.
However, the optical paths inside the light source unit are not limited to those described above. For example, all of the optical paths inside the imaging optical system may extend in directions along the XY-plane or may extend in directions crossing the XY-plane. The optical paths inside the light source unit may not cross each other.
The input element 121, the intermediate element 122, and the output element 123 each may include a main member made of glass, a resin material, or the like and a reflective film such as a metal film, a dielectric multilayer film, or the like forming the mirror surfaces 121a, 122a, and 123a located at the surface of the main member. The input element 121, the intermediate element 122, and the output element 123 each may be entirely formed of a metal material.
According to the embodiment as shown in
Although the imaging optical system 120 is described above, the configuration and position of the coupling optical system are not limited to those described above as long as the coupling optical system is substantially telecentric at the first image side. For example, the number of optical elements included in the direction modifying part may be two or more.
The reflection unit 12 will now be described.
According to the embodiment as shown in
The light that is irradiated on the front windshield 13a is reflected by the inner surface of the front windshield 13a and enters the eyebox 14a of the viewer 14. As a result, the viewer 14 views, beyond the front windshield 13a, the second image IM2 corresponding to the image displayed in the display device 110.
According to the embodiment, the reflection unit 12 is located at a dashboard part 13c of the vehicle 13. For example, the reflection unit 12 is located at the inner side of a wall 13s2 of the dashboard part 13c of the vehicle 13 exposed inside the vehicle. A through-hole 13h2 through which the light emitted from the output element 123 of the light source unit 11 can pass is provided in the wall 13s2. The light that is emitted from the output element 123 passes through the through-hole 13h1, forms the first image IM1, subsequently passes through the through-hole 13h2, and is irradiated on the reflection unit 12. However, the reflection unit may be mounted to the upper surface of the dashboard part. The reflection unit may be located at the ceiling part, and the light source unit may be located at the dashboard part.
The path of the light that travels from the inner surface of the front windshield 13a toward the eyebox 14a is substantially horizontal, and is exactly horizontal or slightly tilted to be higher at the eyebox 14a side. In other words, the path is substantially parallel to the XY-plane. According to the embodiment, when referenced to the XY-plane including the path of the light, the light source unit 11 is located above (the +Z direction), and the reflection unit 12 is located below (the −Z direction). In other words, the light source unit 11 and the reflection unit 12 are separate with the XY-plane interposed.
Although the reflection unit 12 is described above, the configuration and position of the reflection unit are not limited to those described above. For example, the number of optical elements such as mirrors and the like included in the reflection unit may be two or more. The reflection unit 12 must be arranged so that, for example, sunlight that is irradiated from outside the vehicle via the front windshield 13a is not reflected toward the eyebox 14a.
An operation of the image display device 10 according to the embodiment will now be described.
As shown in
As a result, as shown in
As shown in
As shown in
The pixel 110p is lit by the display device 110 when a region of a specific color is located directly above the pixel 110p. For example, blue light can be emitted from one pixel 110p via the color change sheet 130 by the pixel 110p being lit in a period in which the first region 130a (blue) is located directly above the pixel 110p and by being unlit in other periods. Blue light and green light can be emitted from the pixel 110p via the color change sheet 130 by the pixel 110p being lit in the period in which the first region 130a (blue) is located directly above the pixel 110p and in the period in which a second region 130b (green) is located directly above the pixel 110p, and by the pixel 110p being unlit in a period in which the third region 130c (red) is located directly above the pixel 110p. The viewer 14 views a mixed color of blue and green if the period in which the drive unit 140 moves the color change sheet 130 is sufficiently short. Thus, a color image can be emitted from the light source unit 11 by time-division control of the pixels 110p of the display device 110 while the drive unit 140 changes the positional relationship of the display device 110 and the color change sheet 130.
Thus, light rays L that form a color image are emitted from the color change sheet 130. Based on the image, the imaging optical system 120 of the light source unit 11 forms the first image IM1, which is a real image, at the position P. Then, the light that forms the first image IM1 is reflected by the reflection unit 12 and the front windshield 13a and enters the eyebox 14a of the viewer 14.
As a result, as shown in
Effects of the embodiment will now be described.
According to the embodiment, a color image can be displayed by the display device 110 that emits monochromatic light and the color change sheet 130 that includes the regions 130p of multiple colors by the drive unit 140 changing the positional relationship between the display device 110 and the color change sheet 130. By using a monochromatic display device as the display device 110, the light source unit 11 can be smaller, and so the image display device 10 can be smaller.
It also may be considered for the display device 110 to display a color image by including three subpixels in each pixel 110p of the display device 110, and by including an LED element emitting blue light, an LED element emitting green light, and an LED element emitting red light respectively in the subpixels. However, in such a case, compared with the embodiment, the number of LED elements is three-fold, and so the display device 110 is larger and costs more. It also may be considered to set the number of LED elements to be equal to that of the embodiment, and to reduce the number of pixels. However, in such a case, the image definition degrades. In contrast, according to the embodiment, a compact light source unit and image display device that can display a high-definition color image can be realized.
Because the imaging optical system 120 is substantially telecentric at the first image IM1 side according to the embodiment, a high-quality image can be displayed while making the light source unit 11 and the image display device 10 smaller. This effect is described below in detail.
In
In a light source unit 2011 according to the reference example as shown in
In such a display device 2110, the luminous intensity and/or chromaticity changes according to the viewing angle of the viewer, even when the light is emitted from the same position of the display device 2110. Accordingly, even when the luminance of the light emitted from all of the pixels 2110p is uniform, the luminance and/or chromaticity of the first image IM1 fluctuate if the imaging optical system 2120 receives the light emitted from the pixels 2110p from directions other than the normal direction. In other words, the quality of the first image IM1 degrades. Accordingly, to prevent degradation of the quality of the first image IM1, it is necessary to receive the light emitted from each pixel 2110p of the display device 2110 from the normal direction. As a result, the imaging optical system 2120 is larger.
In contrast, in the light source unit 11 according to the embodiment, the imaging optical system 120 is substantially telecentric at the first image IM1 side, and the light that is emitted from the display device 110 has a substantially Lambertian light distribution. Therefore, the quality of the first image IM1 can be improved while making the light source unit 11 smaller. Specifically, the display device 110 is an LED display including the multiple LED elements 112, and the light that is emitted from each LED element 112 via a wavelength conversion member 15 has a substantially Lambertian light distribution. Therefore, the dependence on the angle of the luminous intensity and/or chromaticity of the light emitted from the pixels 110p of the display device 110 is less than the dependence on the angle of the luminous intensity and/or chromaticity of the light emitted from the pixels 2110p of the display device 2110 in the reference example. In particular, as an exact Lambertian light distribution is approached, that is, as the approximation formula of the light distribution pattern approaches cosnθ wherein n is 1, the luminous intensity and/or chromaticity of the light emitted from each pixel 110p of the display device 110 is substantially uniform regardless of the angle. Therefore, as shown in
Because the imaging optical system 120 forms the first image IM1 mainly of light passing through the focal point F, an increase of the light diameter of the light incident on the imaging optical system 120 can be suppressed. The input element 121 can be smaller thereby. The multiple chief rays L that are emitted from the output element 123 are substantially parallel to each other. The multiple chief rays L emitted from the output element 123 being substantially parallel to each other means that the irradiation range of the light of the output element 123 contributing to the image formation is substantially the same as the size of the first image IM1. Therefore, the output element 123 of the imaging optical system 120 also can be smaller. Thus, the light source unit 11 that is compact and can form a high-quality first image IM1 can be provided.
The image display device 10 according to the embodiment includes the light source unit 11, and the reflection unit 12 that is separated from the light source unit 11 and reflects the light emitted from the imaging optical system 120. The first image IM1 is formed between the light source unit 11 and the reflection unit 12. In such a case, the light that is emitted from one point of the display device 110 is condensed at the formation position of the first image IM1 after traveling via the output element 123. On the other hand, when the first image IM1 is not formed between the light source unit 11 and the reflection unit 12, the light diameter of the light emitted from one point of the display device 110 gradually spreads from the input element 121 toward the reflection unit 12. Accordingly, in the output element 123 according to the embodiment, the range in which the light emitted from one point of the display device 110 is irradiated can be less than when the first image IM1 is not formed. Therefore, the output element 123 can be smaller.
Because the light source unit 11 according to the embodiment is compact, the light source unit 11 can be easily located in the limited space inside the vehicle 13 when the light source unit 11 is mounted in the vehicle 13 and used as a head-up display.
According to the embodiment, the imaging optical system 120 includes the bending part 120a and the direction modifying part 120b. Thus, the design of the imaging optical system 120 is easier because the part of the imaging optical system 120 having the function of making the chief rays L parallel to each other and the part of the imaging optical system 120 forming the first image IM1 at the desired position are separate.
A portion of the optical path inside the imaging optical system 120 extends in a direction crossing the XY-plane. Therefore, the imaging optical system 120 can be somewhat smaller in directions along the XY-plane. Another portion of the optical path inside the imaging optical system 120 extends in a direction along the XY-plane. Therefore, the imaging optical system 120 can be somewhat smaller in the Z-direction.
Light source units according to examples and a reference example will now be described.
The image display devices according to the examples 1 to 12 and the reference example were set in simulation software to include a light source unit and a reflection unit, wherein the light source unit included multiple light-emitting areas arranged in a matrix configuration and an imaging optical system. The light-emitting areas correspond to the pixels 110p of the display device 110 according to the embodiment above.
In
In the examples 2 to 12, the light that was emitted from each light-emitting area was set in the simulation software to have a light distribution pattern in which the luminous intensity in the direction of the angle θ with respect to the optical axis was represented by cosnθ times the luminous intensity at the optical axis. In the example 2, n=2, and n was set to increase by one in order from the example 2 to the example 12.
By investigating the light distribution pattern in one plane of the light emitted from the pixels of an LCD, the light distribution pattern was found to be a light distribution pattern such as that illustrated by the fine broken line of
The imaging optical systems of the examples 1 to 12 and the reference example each were set to be telecentric at the first image side.
Then, the luminance distribution of the second image formed when the luminance was constant for all light-emitting areas was simulated for the examples 1 to 12 and the reference example. In this case, the second image was a rectangle having a long side of 111.2 mm and a short side of 27.8 mm. Also, in this case, the plane in which the second image was formed was divided into square areas having sides of 1 mm, and the luminance value of each area was simulated.
The uniformity of the luminance of the second image was evaluated for this case. Herein, “the uniformity of the luminance” was the value of the ratio of the minimum value to the maximum value of the luminance inside the second image expressed in percent. The results are shown in
As shown in
Accordingly, it was found that when the imaging optical system is configured to be substantially telecentric, it is favorable for the light emitted from the display device to have a substantially Lambertian light distribution to suppress the uneven luminance of the first and second images. Specifically, it was found that it is favorable for n of cosnθ which is the approximation formula of the light distribution pattern to be not more than 11, and more favorably 1. Although the uniformity of the luminance of the second image IM2 degrades as n deviates from 1 as described above, a prescribed luminance distribution can be pre-provided in the display luminance of the display device 110 to remedy such nonuniformity of the luminance. For example, when the luminance at the outer edge portion of the second image IM2 tends to be less than the luminance at the center portion due to the light emitted from the pixels 110p of the display device 110 traveling via the imaging optical system 120, the display device 110 may be controlled so that the outputs of the LED elements 112 of the pixels 110p at the outer edge vicinity of the display device 110 are greater than the outputs of the LED elements 112 of the pixels 110p at the center.
A first modification of the first embodiment will now be described.
Although an example is described in the first embodiment above in which white light is emitted from the pixels 110p of the display device 110, light of the colors of blue, green, and red is emitted from the color change sheet 130, according to an example of the modification, light of the two colors of green and red is emitted from a color change sheet 130e.
As shown in
According to the modification, the first region 130a includes a green film, and the first color is green. The second region 130b includes a red film, and the second color is red. In other words, white light from the pixels 110p of the display device 110 is incident on the first region 130a. The first region 130a transmits the green component of the white light, and shields the other components. Accordingly, the first region 130a emits green light. White light from the pixels 110p is incident on the second region 130b. The second region 130b transmits the red component of the white light, and shields the other components. Accordingly, the second region 130b emits red light.
As shown in
According to the modification, when only the two colors of green and red are necessary to display the image, the light source unit can be smaller than that of the first embodiment. Also, compared to the first embodiment, the luminance of the image is improved because the time that the region 130p of the desired color is located directly above the one pixel 110p lengthens. Otherwise, the configuration, operations, and effects according to the modification are similar to those of the first embodiment.
A second modification of the first embodiment will now be described.
An example is described in the modification in which a transparent region is included in a color change sheet 130f.
As shown in
According to the modification, the first region 130a includes a transparent film. Therefore, the first region 130a transmits the white light emitted from the pixels 110p of the display device 110 substantially as-is. Accordingly, the first color is white. The first region 130a may be an opening without including a transparent film. The second region 130b includes a blue film, and the second color is blue. In
According to the modification, a two-color image of white and blue can be displayed. The second region 130b may include a green film or a red film. In these cases, the second color is green or red. Otherwise, the configuration, operations, and effects according to the modification are similar to those of the first modification.
A second embodiment will now be described.
Although an example is described in the first embodiment above in which white light is emitted from the pixels 110p of the display device 110 and the color change sheet 130 is a color film, according to the example of the embodiment, blue light is emitted from the pixels 110p of the display device 110, and a color change sheet 230 is a fluorescer sheet.
According to the embodiment as shown in
According to the embodiment as shown in
The first region 230a includes a transparent film. Blue light from the pixels 110p of the display device 110 is incident on the first region 230a. The first region 230a transmits the blue light and emits the blue light substantially as-is. Accordingly, the light that is emitted from the first region 230a is blue light, and the first color is blue.
The second region 230b includes a fluorescer layer. The second region 230b includes a fluorescer that absorbs the light emitted from the pixels 110p and radiates green light. As a result, the blue light from the pixels 110p of the display device 110 is incident on the second region 230b, and the fluorescer absorbs the blue light and radiates green light. Accordingly, the second color is green. The light that is emitted from the second region 230b has a substantially Lambertian light distribution.
The third region 230c also includes a fluorescer layer. The third region 230c includes a fluorescer that absorbs the light emitted from the pixels 110p and radiates red light. As a result, the blue light from the pixels 110p of the display device 110 is incident on the third region 230c, and the fluorescer absorbs the blue light and radiates red light. Accordingly, the third color is red. The light that is emitted from the third region 230c also has a substantially Lambertian light distribution.
According to the embodiment, the blue light that is emitted from the LED elements 112 is incident on the first region 230a of the color change sheet 230. The utilization efficiency of the light is high because the first region 230a transmits and emits the incident blue light as-is. Otherwise, the configuration, operations, and effects according to the embodiment are similar to those of the first embodiment.
A first modification of the second embodiment will now be described.
Although an example is described in the second embodiment in which blue light is emitted from the pixels 110p of the display device 110 and light of the colors of blue, green, and red is emitted from the color change sheet 230, in the example according to the modification, blue light is emitted from the pixels 110p, and light of the two colors of green and red is emitted from a color change sheet 230e.
As shown in
According to the modification, when only the two colors of green and red are necessary to display the image, the light source unit can be smaller than that of the second embodiment. Compared to the second embodiment, the luminance of the image is improved because the time that the region 230p of the desired color is located directly above one pixel 110p lengthens. Otherwise, the configuration, operations, and effects according to the modification are similar to those of the second embodiment.
A second modification of the second embodiment will now be described.
An example is described in the modification in which a transparent region is included in a color change sheet 230f.
In the color change sheet 230f according to the modification as shown in
According to the modification, a two-color image of blue and green can be displayed. The second region 230b may include a fluorescer that absorbs blue light and radiates green light, may include a fluorescer that absorbs blue light and radiates red light, or may include a fluorescer that absorbs blue light and radiates yellow light. In such cases, the second color is respectively green, red, or yellow. Otherwise, the configuration, operations, and effects according to the modification are similar to the first modification of the second embodiment.
A third embodiment will now be described.
Although an example is described in the second embodiment above in which blue light is emitted from the pixels 110p of the display device 110, according to the example of the embodiment, ultraviolet is emitted from the pixels 110p of the display device 110.
According to the embodiment as shown in
According to the embodiment, the color selectivity is high because all colors can be modulated by the fluorescers. Otherwise, the configuration, operations, and effects according to the embodiment are similar to those of the second embodiment.
A modification of the third embodiment will now be described.
Although an example is described in the third embodiment in which ultraviolet is emitted from the pixels 110p of the display device 110 and light of the colors of blue, green, and red is emitted from the color change sheet 230g, an example is described in the modification in which light of two colors is emitted from a color change sheet 230h.
In a color change sheet 230h according to the modification as shown in
The combination of the first and second colors is not limited to blue and green, and may be, for example, blue and red, blue and yellow, or green and red. According to the modification, the operation of the drive unit 140, i.e., the change of the positional relationship between the display device 110 and the color change sheet 230h, is as shown in
According to the modification, when only two colors are necessary in the display of the image, the light source unit can be smaller than that of the third embodiment. Compared to the third embodiment, the luminance of the image is improved. Otherwise, the configuration, operations, and effects according to the modification are similar to those of the third embodiment.
As shown in
However, the invention is not limited to the examples shown in
A fourth embodiment will now be described.
In a color change sheet 330 according to the embodiment as shown in
According to the embodiment, the operation of the drive unit 140, i.e., the change of the positional relationship between the display device 110 and the color change sheet 330, is as shown in
A fifth embodiment will now be described.
In a color change sheet 430 according to the embodiment as shown in
A sixth embodiment will now be described.
In a color change sheet 530 according to the embodiment as shown in
A seventh embodiment will now be described.
As shown in
The configuration of the light source unit 11 of the image display device 20 is similar to that of the first embodiment. The light source unit 11 is located at the ceiling part 13b of the vehicle 13. The reflection unit 22 is located at the dashboard part 13c of the vehicle 13. The reflection unit 22 includes the mirror 322. The mirror surface 322a of the mirror 322 is, for example, a concave surface. The mirror surface 322a is arranged at a position and angle facing the eyebox 14a of the viewer 14 when the viewer 14 is in the driver's seat of the vehicle 13. For example, the mirror surface 322a faces a direction between the −X direction (the back) and the +Z direction (up). The angle of the mirror surface 322a can be finely adjusted according to the position of the eyebox 14a of the viewer 14.
The operation of the embodiment will now be described.
The chief rays L that are emitted from the light source unit 11 travel in a direction between the +X direction (the front) and the −Z direction (the lower side), are reflected by the mirror surface 322a of the mirror 322 of the reflection unit 22, travel in a direction between the −X direction (the back) and the +Z direction (up), and enter the eyebox 14a of the viewer 14. The path of the chief rays L from the light source unit 11 toward the reflection unit 12 is positioned inward of the front windshield 13a of the vehicle 13 and is substantially along the front windshield 13a. The chief rays L form the first image IM1 at the position P between the light source unit 11 and the reflection unit 22. At this time, the first image IM1 is a color image including multiple colors due to the time-division control of the display device 110 by the drive unit 140 changing the positional relationship between the display device 110 and the color change sheet 130.
As a result, as shown in
Effects of the embodiment will now be described.
Similarly to the first embodiment, the image display device 20 according to the embodiment is divided into the light source unit 11 and the reflection unit 22 and fixed at separate positions in the vehicle 13. Although the image display device 20 requires a long optical path length to form the second image IM2 at a position several meters frontward, by separating the light source unit 11 and the reflection unit 22, a portion of the optical path length can be formed by utilizing the internal space of the vehicle 13. As a result, it is unnecessary to form the necessary optical path length entirely inside the image display device 20, and the image display device 20 can be smaller.
In the image display device 20, the reflection unit 22 includes only the mirror 322. As a result, the configuration of the reflection unit 22 can be simplified, and the reflection unit 22 can be smaller.
By using the mirror surface 322a located in the dashboard part 13c as the reflecting surface, the viewer 14 can reliably view the second image IM2 without being affected by the background of the reflecting surface. Otherwise, the configuration, operations, and effects according to the embodiment are similar to those of the first embodiment.
The mirror 322 of the reflection unit 22 may include a half mirror or a transparent plate. In such a case as well, the viewer 14 can be prevented from undesirably viewing the interior of the dashboard part 13c by making the interior of the dashboard part 13c dark. Or, the mirror surface 322a of the mirror 322 may be black enough to sufficiently reflect the chief rays L emitted from the light source unit 11. As a result, degradation of the visibility due to external light or the like reflected by the mirror surface 322a of the mirror 322 can be suppressed. The mirror 322 may be arranged to be continuous with the surface of the dashboard part 13c. As a result, it is unnecessary to make a hole in the dashboard part 13c, and the designability of the interior of the automobile 1000 is improved.
An eighth embodiment will now be described.
As shown in
The protective layer 714 covers multiple LED elements 712 arranged in a matrix configuration. The protective layer 714 can include, for example, a light-transmitting material such as a polymer material that includes a sulfur(S)-including substituent group or a phosphorus (P) atom-including group, a high refractive index nanocomposite material in which inorganic nanoparticles having a high refractive index are added to a polymer matrix of polyimide, etc.
The wavelength conversion member 715 is located on the protective layer 714. The wavelength conversion member 715 includes one or more types of wavelength conversion materials such as a general fluorescer material, a perovskite fluorescer material, a quantum dot (QD), etc. The light that is emitted from each LED element 712 is incident on the wavelength conversion member 715. The wavelength conversion material that is included in the wavelength conversion member 715 emits light of a different light emission peak wavelength from the light emission peak wavelength of the LED element 712 by the light emitted from the LED element 712 being incident on the wavelength conversion material. The light that is emitted by the wavelength conversion member 715 has a substantially Lambertian light distribution.
The light-scattering member 716A includes, for example, a light-transmitting resin member, and light-scattering particles or voids located inside the resin member. Examples of the resin member include, for example, polycarbonate, etc. Examples of the light-scattering particles include, for example, materials having a refractive index difference with the resin member such as titanium oxide, etc. A light scattering effect may be obtained by providing an unevenness in the surface of the light-scattering member 716A by surface roughening.
For example, a multilayer stacked thin film polarizing plate in which thin film layers having different polarization characteristics are stacked, etc., can be used as the reflective polarizing element 740. The reflective polarizing element 740 is located on the display device 710A. According to the embodiment, the reflective polarizing element 740 is located on the light-scattering member 716A. Therefore, the light that is emitted from the LED element 712 and the wavelength conversion member 715 is incident on the reflective polarizing element 740. The reflective polarizing element 740 transmits a first polarized light 710p of the light emitted from the display device 710A and reflects, toward the display device 710A, a second polarized light 710s. The oscillation direction of the electric field of the second polarized light 710s is substantially orthogonal to the oscillation direction of the electric field of the first polarized light 710p.
According to the embodiment, the first polarized light 710p is P-polarized light, and the second polarized light 710s is S-polarized light. Herein, “P-polarized light” means light of which the oscillation direction of the electric field is substantially parallel to the XY-plane. “S-polarized light” means light of which the oscillation direction of the electric field is substantially perpendicular to the XY-plane including the incident light and the reflected light.
There are cases where the viewer 14 driving the vehicle 13 wears polarized sunglasses 14b to reduce glare such as sunlight reflected by a puddle or the like in front of the vehicle 13 and transmitted by the front windshield 13a, etc. In such a case, the component corresponding to the P-polarized light of the sunlight reflected by the puddle or the like when viewed from the front windshield 13a is particularly reduced; therefore, the polarized sunglasses 14b are designed to shield the greater part of the S-polarized light. Accordingly, when the viewer 14 wears the polarized sunglasses 14b, there is a possibility that the second image IM2 may be difficult for the viewer 14 to view because the polarized sunglasses 14b undesirably shield the greater part of the S-polarized light included in the light emitted by the display device 710A. In the specification, P-polarized light and S-polarized light are physically defined by reflection objects such as the puddles and the like described above.
According to the embodiment, the reflective polarizing element 740 transmits the first polarized light 710p and reflects the second polarized light 710s of the light emitted from the display device 710A. After traveling via the imaging optical system 120, the reflection unit 12, and the inner surface of the front windshield 13a, the greater part of the first polarized light 710p transmitted by the reflective polarizing element 740 enters the eyebox 14a without being shielded by the polarized sunglasses 14b. The incidence angle of the first polarized light 710p when incident on the inner surface of the front windshield 13a is set to a different angle from Brewster's angle.
Specifically, as shown in
The greater part of the first polarized light 710p included in the short-wavelength and long-wavelength light is transmitted by the reflective polarizing element 740 and emitted from the imaging optical system 120. The greater part of the second polarized light 710s included in the short-wavelength and long-wavelength light is reflected by the reflective polarizing element 740. Scattering reflection of a portion of the second polarized light 710s reflected by the reflective polarizing element 740 is performed by components of the display device 710A such as the light-scattering member 716A, the wavelength conversion member 715, etc. A portion of the second polarized light 710s is converted into the first polarized light 710p by the scattering reflection. A portion of the first polarized light 710p converted from the second polarized light 710s is transmitted by the reflective polarizing element 740 and emitted from the light source unit 71A. Therefore, the luminance of the first image IM1 can be increased while increasing the ratio of the first polarized light 710p included in the light emitted from the light source unit 71A. By improving the luminance of the first image IM1, the luminance of the second image IM2 also is improved. As a result, the viewer 14 easily views the second image IM2.
A portion of the short-wavelength light included in the second polarized light 710s may be reflected by the reflective polarizing element 740 and then incident on the wavelength conversion member 715. In such a case, an effect can be expected in which the wavelength conversion member 715 absorbs the short-wavelength light of the second polarized light 710s and radiates new long-wavelength light. Both the scattered reflection light and the radiated light have substantially Lambertian light distributions. The reflective polarizing element 740 itself may perform scattering reflection of the second polarized light 710s. In such a case as well, a portion of the second polarized light 710s is converted into the first polarized light 710p by the scattering reflection.
According to the embodiment, one reflective polarizing element 740 covers all of the pixels of the display device 710A. However, the light source unit may include multiple reflective polarizing elements, and the reflective polarizing elements may be located respectively on the pixels. The configuration of the display device used in combination with the reflective polarizing element is not limited to the configuration described above. For example, the display device may be configured without a light-scattering member by using the light scattering reflection effect of the wavelength conversion member. The display device may be configured without a wavelength conversion member by using the scattering reflection effect of the light-scattering member. The display device may be configured without a wavelength conversion member or a light-scattering member by using the light scattering reflection effect of multiple recesses or multiple protrusions provided in the light-emitting surface of the LED element as in the first embodiment.
Effects of the embodiment will now be described.
The light source unit 71A according to the embodiment further includes the reflective polarizing element 740 that is located on the display device 710A, transmits the first polarized light 710p of the light emitted from the display device 710A, and reflects the second polarized light 710s of the light emitted from the display device 710A. Therefore, the luminance of the first image IM1 can be increased while increasing the ratio of the first polarized light 710p included in the light emitted from the light source unit 71A.
The light that is emitted from the reflective polarizing element 740 also has a substantially Lambertian light distribution. Therefore, according to the embodiment as well, the light source unit 71A that is compact and can form the high-quality first image IM1 can be provided. Because the multiple LED elements 712 are discretely mounted on the substrate 111, the first image IM1 may have a grainy appearance. The wavelength conversion member 715 has the effect of relaxing the grainy appearance. The light-scattering member 716A can further reinforce the effect of relaxing the grainy appearance. Otherwise, the configuration, operations, and effects according to the embodiment are similar to those of the first embodiment.
A ninth embodiment will now be described.
As shown in
The reflective polarizing element 750 can include, for example, a wire-grid reflective polarizing element using multiple metal nanowires. The reflective polarizing element 750 is located in a part of the optical path from the display device 710A to the reflection unit 12 at which the multiple chief rays L are substantially parallel to each other. According to the embodiment, the multiple chief rays L are substantially parallel to each other in the optical path between the intermediate element 122 and the reflection unit 12, and the reflective polarizing element 750 is located between the intermediate element 122 and the output element 123.
The reflective polarizing element 750 transmits the first polarized light 710p, which is P-polarized light, and reflects the second polarized light 710s, which is S-polarized light, to return the second polarized light 710s to the display device 710A. Specifically, the display device 710A emits light 710a that includes the first and second polarized lights 710p and 710s. The light 710a travels via the input element 121 and the intermediate element 122 and then is incident on the reflective polarizing element 750.
The reflective polarizing element 750 transmits the greater part of the first polarized light 710p included in the light 710a. The greater part of the first polarized light 710p transmitted by the reflective polarizing element 750 travels via the output element 123 and then is emitted from the reflection unit 12.
The reflective polarizing element 750 reflects the greater part of the second polarized light 710s included in the light 710a and returns the greater part of the second polarized light 710s along the optical path from the display device 710A to the reflective polarizing element 750. Specifically, the reflective polarizing element 750 has a flat plate shape. The reflective polarizing element 750 is arranged to be substantially orthogonal to the chief rays L. The reflective polarizing element 750 specularly reflects the greater part of the second polarized light 710s. Therefore, the greater part of the second polarized light 710s reflected by the reflective polarizing element 750 travels via the intermediate element 122 and the input element 121 in this order and then returns to the display device 710A.
Scattering reflection of a portion of the second polarized light 710s returning to the display device 710A is performed by components of the display device 710A such as the light-scattering member 716A, the wavelength conversion member 715, etc. A portion of the second polarized light 710s is converted into the first polarized light 710p by the scattering reflection. A portion of the first polarized light 710p converted from the second polarized light 710s travels via the input element 121 and the intermediate element 122 and then is transmitted by the reflective polarizing element 750. The greater part of the first polarized light 710p transmitted by the reflective polarizing element 750 travels via the output element 123 and then is emitted from the reflection unit 12. Therefore, the luminance of the second image IM2 can be increased while increasing the ratio of the first polarized light 710p included in the light emitted from the image display device 70B. As a result, the viewer 14 easily views the second image IM2.
Similarly to the eighth embodiment, a portion of the short-wavelength light included in the second polarized light 710s returning to the display device 710A may be irradiated on the wavelength conversion member 715. In such a case as well, similarly to the eighth embodiment, the wavelength conversion member 715 absorbs the short-wavelength light of the second polarized light 710s, and an effect of radiating new long-wavelength light can be expected.
The light-shielding member 760 is located between the display device 710A and the input element 121 of the imaging optical system 120. For example, the light-shielding member 760 has a flat plate shape substantially parallel to the XY-plane. An aperture 761 that extends through the light-shielding member 760 in the Z-direction is provided in the light-shielding member 760. The focal point F of the imaging optical system 120 is positioned inside the aperture 761.
The light emitted from the display device 710A and passing through the focal point F and the vicinity of the focal point F passes through the aperture 761 of the light-shielding member 760 and is incident on the input element 121, and the greater part of the light other than the light passing through the aperture 761 is shielded by the light-shielding member 760. The second polarized light 710s that is reflected by the reflective polarizing element 750 and travels along the optical path, i.e., the light that passes through the focal point F and the vicinity of the focal point F, passes through the aperture 761 of the light-shielding member 760 and returns to the display device 710A. On the other hand, the greater part of the second polarized light 710s that is reflected by the reflective polarizing element 750 and travels toward the display device 710A and not along the optical path is shielded by the light-shielding member 760.
Effects of the embodiment will now be described.
The image display device 70B according to the embodiment further includes the reflective polarizing element 750. The reflective polarizing element 750 is located at a part of the optical path from the display device 710A to the reflection unit 12 at which the multiple chief rays L that are emitted from mutually-different positions of the display device 710A and pass through the first image IM1 are substantially parallel to each other, transmits the first polarized light 710p of the light emitted from the display device 710A, and reflects the second polarized light 710s of the light emitted from the display device 710A to return the second polarized light 710s to the display device 710A. Therefore, the luminance of the second image IM2 can be increased while increasing the ratio of the first polarized light 710p included in the light emitted from the image display device 70B.
The light-shielding member 760 is located between the display device 710A and the input element 121. The aperture 761 that transmits the second polarized light 710s returning to the display device 710A along the optical path is provided in the light-shielding member 760. Therefore, the second polarized light 710s that is reflected by the reflective polarizing element 750, does not travel along the optical path, and becomes stray light can be prevented from traveling toward the display device 710A while permitting the second polarized light 710s that is reflected by the reflective polarizing element 750 and travels along the optical path to return to the display device 710A. The quality of the first and second images IM1 and IM2 can be increased thereby. The light that is emitted from the display device 710A, does not travel along the optical path, and becomes stray light can be prevented by the light-shielding member 760 from being reflected by the reflective polarizing element 750 and/or optical elements of the imaging optical system 120, traveling toward the display device 710A, and being re-excited and/or scattered and reflected at unexpected locations.
The light-shielding member 760 may not be included in the image display device 70B. The reflective polarizing element 740 described in the third embodiment may be further provided on the display device 710A of the image display device 70B. In such a case, the second polarized light 710s that could not be reflected by the reflective polarizing element 740 on the display device 710A can be reflected by the reflective polarizing element 750. Therefore, the luminance of the second image IM2 can be increased while increasing the ratio of the first polarized light 710p included in the light emitted from the image display device 70B. Otherwise, the configuration, operations, and effects according to the embodiment are similar to those of the third embodiment.
A modification of the ninth embodiment will now be described.
In
According to the modification as shown in
Embodiments and their modifications described above are examples embodying the invention, and the invention is not limited to these embodiments and their modifications. For example, additions, deletions, or modifications of some of the components or processes of the embodiments and modifications described above also are included in the invention. The embodiments and modifications described above can be implemented in combination with each other.
For example, the invention can be utilized in a head-up display.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2022-087981 | May 2022 | JP | national |
This application is a bypass continuation of PCT Patent Application No. PCT/JP2023/019643, filed on May 26, 2023, which claims priority to Japanese Patent Application No. 2022-087981, filed on May 30, 2022. The entire contents of these applications are incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2023/019643 | May 2023 | WO |
| Child | 18956890 | US |
