Patent Application
20160004077
The present invention relates to a technical field of visualizing images as virtual images.
Conventionally, it is known a display device such as a head-up display (hereinafter referred to as “HUD”) which visualizes images as virtual images (for example, Patent References 1 and 2). Normally, by the HUD, real images formed by a real image display device (i.e., images on an LCD display or images projected on a screen by a projector) is recognized by a driver as virtual images by the use of a half mirror, called as a combiner, disposed ahead of a visual field of the driver. Thus, the driver can visually recognize meters, navigation information and the like, in a manner superimposed on a front view, while keeping his or her visual line ahead without dropping the visual line.
Patent Reference 1: Japanese Patent Application Laid-open under No. 06-270716
Patent Reference 2: Japanese Patent Application Laid-open under No. 2002-052953
When the size of the combiner is fixed, the maximum viewing angle of the virtual image visually recognized by the driver is determined dependently upon the distance between the combiner and the driver. Namely, the viewing angle becomes large when the combiner is near to the driver, and the viewing angle becomes small when the combiner is far from the driver. Therefore, in order to visualize as large virtual image as possible, it is desired to position the combiner as close to the driver as possible. However, the combiner is frequently arranged on the dashboard in terms of the place where the combiner can be set (For example, see Patent Reference 1).
On the other hand, recently there has been proposed a HUD in which the combiner is mounted near the ceiling (i.e., near the sun visor) so as to enlarge the viewing angle (For example, see Patent Reference 2). In this HUD, since the real image display device must be arranged on the driver side with respect to the combiner (to make the reflected light of the real image incident upon eyes), basically it is also necessary to mount the real image display device on the ceiling. Therefore, there are such disadvantages that the driver feels a sense of oppression and that the power lines must be drawn to the ceiling, making the mounting work troublesome.
The above is an example of the problem to be solved by the present invention. It is an object of the present invention to provide a virtual image generation device capable of appropriately visualize desired virtual images, without making the user feel the sense of oppression and/or discomfort.
According to the invention described in claims, a virtual image generation device which visualizes images formed by an image forming unit as virtual images comprises: a first optical element and a second optical element arranged opposite to each other along a travelling direction of an image light corresponding to the images, wherein the first optical element and the second optical element have a characteristic of reflecting the light having a wavelength corresponding to the image light in accordance with an incident angle of the light and transmitting the light having the wavelength other than the wavelength corresponding to the image light, and give a predetermined optical effect only to the image light.
Also, according to the invention described in claims, a head-up display comprises: an image forming unit; and the virtual image generation device which visualizes the image formed by the image forming unit as the virtual images.
According to one aspect of the present invention, there is provided a virtual image generation device which visualizes images formed by an image forming unit as virtual images, comprising: a first optical element and a second optical element arranged opposite to each other along a travelling direction of an image light corresponding to the images, wherein the first optical element and the second optical element have a characteristic of reflecting the light having a wavelength corresponding to the image light in accordance with an incident angle of the light and transmitting the light having the wavelength other than the wavelength corresponding to the image light, and give a predetermined optical effect only to the image light.
The above virtual image generation device includes a first and a second optical elements serving as wavelength filters having dependence to the incident angle (a wavelength-selective transmission layer or a wavelength-selective reflection layer), and gives the predetermined optical effect only to the image light. Thus, desired virtual images can be appropriately generated for the images formed by the image forming unit.
In one mode of the above virtual image generation device, the first optical element and the second optical element are arranged in parallel with each other, and give the image light an effect of reflecting the light by an angle different from the incident angle, as the predetermined optical effect.
In this mode, the first and second optical elements give the image light the diffractive-reflection effect which reflects the light with the reflection angle different from the incident angle. According to this mode, by utilizing the diffractive-reflection, the incident angle and the reflection angle freely set can be used.
In other mode of the above virtual image generation device, the first optical element at least has the characteristic of reflecting the image light having a first angle as the incident angle, the first angle being an angle of the image light entering the virtual image generation device, and the second optical element at least has the characteristic of reflecting the image light having a second angle as the incident angle, the second angle being an angle with which the image light reflected by the first optical element enters. Thus, only the image light is passed through the virtual image generation device to change its light direction and is guided to the desired direction.
In still another mode of the above virtual image generation device, the second optical element has the characteristic of transmitting the image light having the first angle as the incident angle, and the first optical element has the characteristic of transmitting the image light having a third angle as the incident angle, the third angle being an angle with which the image light reflected by the second optical element enters.
Preferably, in the above virtual image generation device, the first optical element has the characteristic of reflecting the image light entered with the first angle by the second angle larger than the first angle, and the second optical element has the characteristic of reflecting the image light entered with the second angle by the third angle smaller than the second angle.
In still another mode of the above virtual image generation device, the first optical element and the second optical element further give the image light a lens effect as the predetermined optical effect. Thus, the virtual image generation device having a magnification can be realized, and the distance of the virtual image may be changed far or near.
In a preferred embodiment, the first and second optical elements are volume type HOEs. In another preferred embodiment, the first and second optical elements are dielectric multilayers. In still another preferred embodiment, at least one of the first and second optical elements is a volume type HOE. In still another preferred embodiment, at least one of the first and second optical elements is a dielectric multilayer.
According to another aspect of the present invention, a head-up display comprises: an image forming unit; and the virtual image generation device which visualizes the image formed by the image forming unit as the virtual images. For example, the image forming unit may be provided near the dashboard of the vehicle, and the virtual image generation device may be provided near the ceiling of the vehicle or formed in the glasses-shape (sunglasses shape).
Preferred embodiments of the present invention will be described below with reference to drawings.
Here, the basic concept of the embodiments will be described.
First, a problem of a general HUD will be described with reference to
When the size of the combiner is fixed, the maximum viewing angle of the virtual image visually recognized by the driver is determined dependently upon the distance between the combiner and the driver. Namely, the viewing angle becomes large when the combiner is near to the driver, and the viewing angle becomes small when the combiner is far from the driver. Therefore, in order to visualize as large virtual image as possible, it is preferred to position the combiner as close to the driver as possible. However, in terms of the place where the combiner can be set, the combiner 100x is frequently arranged on the dashboard as shown in
On the other hand, as shown in
The embodiments employ a configuration that can solve the above-described problems of the HUD300x, 300y.
By the HUD 300 according to the embodiments, the viewing angle of the virtual image visually recognized by the driver can be ensured. Also, in comparison with the HUD 300y shown in
The present invention is not limited to the example shown in
The combiner 100 (including the combiners 100a to 100c described later) corresponds to an example of “a virtual image generation device” of the present invention, and the real image display device 200 corresponds to an example of “an image forming unit” of the present invention.
Next, specific examples of the above combiner 100 according to the embodiments will be described below. Specifically, the combiners 100a to 100c according to first to third embodiments will be described. It is noted that the combiners 100a to 100c according to the first to third embodiments are applied to the HUD 300 shown in
The first embodiment will be described.
2-1. Configuration of Combiner According to First Embodiment
As shown in
The volume type HOE 11 corresponds to “a first optical element” according to the present invention, and the volume type HOE 12 corresponds to “a second optical element” according to the present invention.
In the first embodiment, as shown by the arrows A1 to A4 in
Specifically, the light entered the combiner 100a from the real image display device 200 with the incident angle θin first passes through the volume type HOE 12 as shown by the arrow A1, and is reflected by the volume type HOE 11 as shown by the arrow A2. In this case, due to the characteristic of the volume type HOE 11, the reflection by the volume type HOE 11 becomes the diffraction reflection in which the incident angle θin to the volume type HOE 11 is different from the reflection angle θmid from the volume type HOE 11. Generally, the volume type HOE has such a characteristic that the incident angle and the reflection angle can be freely set by the diffraction reflection, and hence the volume type HOE 11 is configured such that “the incident angle θin<reflection angle θmid” by taking advantage of this characteristic.
Thereafter, the light diffraction-reflected by the volume type HOE 11 is reflected by the volume type HOE 12 as shown by the arrow A3. In this case, due to the characteristic of the volume type HOE 12, the reflection by the volume type HOE 12 becomes the diffraction reflection in which the incident angle θmid to the volume type HOE 12 is different from the exit angle θout from the volume type HOE 12. The volume type HOE 12 is configured such that “the incident angle θmid>exit angle θout” by taking advantage of the above-mentioned characteristic that the incident angle and the reflection angle can be freely set. Thereafter, the light diffraction-reflected by the volume type HOE 12 passes through the volume type HOE 11 as shown by the arrow A4 and exits the combiner 100a with the exit angle θout.
The incident angle 74in is determined based on the installation positions of the real image display device 200 and the combiner 100a, and the exit angle θout is determined based on the position of the head and the display position of the virtual image. The angle θmid (internal waveguide angle) may be freely determined to some extent. In an example, 30 [°] is used as the incident angle θin, 60 [°] is used as the angle θmid (internal waveguide angle), and 5 [°] is used as the exit angle θout.
Next, with reference to
As shown in
Specifically, as shown by the graph G11, the volume type HOE 11 is configured to transmit the light incident with the angle and reflect the light incident with the angle θin. As shown by the graph G12, the volume type HOE 12 is configured to transmit the light incident with the angle θin and reflect the light incident with the angle θmid. By this, the real image displaying light can be guided as shown by the arrows A1 to A4 in
Next, with reference to
Here, description will be given of why the combiner 100a is formed, not by a single volume type HOE, but by two volume type HOEs. Namely, description will be given of the reason why the optical function of the combiner 100a described above cannot be achieved by only one HOE. In order to achieve the transmission-type combiner by only one HOE, it is necessary to use, as the HOE, not a volume type HOE, but a transmission-type HOE giving the optical effect to the transmission light. However, the transmission-type HOE cannot have the wavelength-selectivity as shown in
2-2. Modified Examples of First Embodiment
Next, modified examples of the first embodiment will be described. The following modified examples may be implemented in an arbitrary combination.
2-2-1. First Modified Example
2-2-2. Second Modified Example
In the second modified example of the first embodiment, the combiner 100a further has a lens effect as the optical effect given to the real image displaying light. For example, the combiner 100a has a light collecting function and/or a light diffusion function. Such a combiner 100a can be produced by applying, not the parallel lights, but convergent lights or diffused lights as the reference light (corresponding to the incident light to the combiner 100a) for the exposure of the volume type HOE 11 and the object light (corresponding to the exit light from the combiner 100a) for the exposure of the volume type HOE 12. According to the second modified example of the first embodiment, it is possible to produce the combiner 100a having a magnification, and the distance of the virtual image may be changed to be farther or nearer.
Next, a second embodiment will be described.
3-1. Configuration of Combiner According to Second Embodiment
Also in the second embodiment, as indicated by the arrows B1 to B4 in
Specifically, the light entered the combiner 100b from the real image display device 200 with the incident angle θin is refracted by the base plate 23 to have the angle θin′, and passes through the dielectric multilayer 21 to exit with the exit angle α′ as shown by the arrow B1. Then, the light passed through the dielectric multilayer 21 is regularly reflected by the dielectric multilayer 22 as shown by the arrow B2. Specifically, the light passed through the dielectric multilayer 21 enters the dielectric multilayer 22 with the incident angle θin and is reflected by the dielectric multilayer 22 with the reflection angle θin′. Then, the light regularly reflected by the dielectric multilayer 22 is further regularly reflected by the dielectric multilayer 21 as shown by the arrow B3. Specifically, the light reflected by the dielectric multilayer 22 enters the dielectric multilayer 21 with the incident angle β′ and is reflected by the dielectric multilayer 21 with the reflection angle β′. Thereafter, the light reflected by the dielectric multilayer 21 enters the dielectric multilayer 22 with the incident angle θout′ and passes through the dielectric multilayer 22 to exit the combiner 100b with the exit angle θout.
Here, the incident angle θin is determined based on the arrangement positions of the real image display device 200 and the combiner 100b, and the exit angle θout is determined based on the positions of the head and the display position of the virtual image. The angles θin′, θout′ correspond to the angles θin, θout inside the base plate, respectively, and are obtained from the equations (1) and (2) by the Snell's law.
θin′=sin−1(sin θin/n) (1)
θout′=sin−1(sin θout/n) (2)
Also, the above angles α′, β′, φ are expressed by the equations (3), (4), (5), respectively, by using the angles θin′, θout′.
α′=(3θin′−θout′)/2 (3)
β′=(θin′+θout′)/2 (4)
φ=(θin′−θout′)/2 (5)
Further, the angles α′, β′ are converted to the angles α, β in the air by the Snell's law, as expressed by the equations (6), (7).
α=sin−1(n·sin α′) (6)
β=sin−1(n·sin β′) (7)
In an example wherein the angle θin is 30 [°] and the angle θout is 10 [°], the angles θin′, θout′ are obtained from the equations (1) and (2), “α′≈25.9 [°]” is obtained by substituting the angles θin′, θout′ for the equation (3), and “β′≈13.1 [°]” is obtained by substituting the angles θin′, θout′ for the equation (4). Then, “α≈40.9 [°]” is obtained by substituting the angle α′ for the equation (6), and “19.8 [°]” is obtained by substituting the angle β′ for the equation (7). Further, “φ≈6.4 [°]” is obtained by substituting the angles θin′, θout′ for the equation (5). Therefore, in the above example, it is necessary to arrange the dielectric multilayer 21 to be inclined by 6.4 [°] with respect to the dielectric multilayer 22.
Next, with reference to
As shown by the graph G21, the dielectric multilayer 21 is formed to transmit the light entering with the angle α and reflect the light entering with the angle β. Also, as shown by the graph G22, the dielectric multilayer 22 is formed to transmit the light entering with the angle θout and reflect the light entering with the angle θin. Thus, the real image displaying light can be guided as shown by the arrows B1 to B4 in
If the dielectric multilayer 21 has the characteristic of transmitting the light entering with the angle α and reflecting the light entering with the angle β, it may have any characteristic at other angles. For example, the dielectric multilayer 21 may have the characteristic shown by the broken-line graph G21′. Similarly, if the dielectric multilayer 22 has the characteristic of transmitting the light entering with the angle θout and reflecting the light entering with the angle θin, it may have any characteristic at other angles. For example, the dielectric multilayer 22 may have the characteristic shown by the broken-line graph G22′.
Since the volume type HOEs 11, 12 described in the first embodiment can diffraction-reflect the light (namely, the incident angle and the reflection angle may be freely set), it is not necessary to intentionally tilt one of the volume type HOEs 11, 12 in order to achieve the optical function of outputting the light incident with the incident angle θin with the exit angle θout different from the incident angle θin. Therefore, the volume type HOE 11 and the volume type HOE 12 are arranged in parallel with each other. In contrast, since the dielectric multilayer 21, 22 according to the second embodiment regularly reflect the light (namely, the incident angle and the reflection angle become equal, i.e., the incident angle and the reflection angle cannot be freely set), the dielectric multilayer 21 is tilted with respect to the dielectric multilayer 22 in order to achieve the optical function of outputting the light incident with the incident angle θin with the exit angle θout different from the incident angle θin.
3-2. Modified Examples of Second Embodiment
Next, modified examples of the second embodiment will be described. The following modified examples may be implemented in an arbitrary combination.
3-2-1. First Modified Example
According to the first modified example of the second embodiment as described above, by using the dielectric multilayer 21a which itself is not inclined, instead of the dielectric multilayer 21 inclined in its entirety, the thickness of the combiner 100b1 can be made thinner than the thickness of the combiner 100b described above.
3-2-2. Second Modified Example
In the second modified example of the second embodiment, the above-described combiner 100b further has a lens effect as the optical effect given to the real image displaying light. For example, the combiner 100bhas a focusing function and/or a diffusion function of the light. Such a combiner 100b may be realized by forming the dielectric multilayer 21 (the reflection plane existing inside the base plate) into a moderately curved surface. According to the second modified example of the second embodiment as described above, the combiner 100b having a magnification can be realized, and the distance of the virtual image may be changed far or near.
It is noted that the first modified example may be applied to the dielectric multilayer 21 formed with the moderately curved surface as described above. Namely, the dielectric multilayer 21 maybe formed into the curved surface and into the serrate shape at the same time. In that case, the dielectric multilayer 21 may be of a Fresnel lens shape.
3-2-3. Third Modified Example
The third modified example may be implemented in combination with the first modified example and/or the second modified example. Namely, the dielectric multilayer 22b may be formed into the curved surface or the serrate shape. When the dielectric multilayer 22b is formed into the curved surface and the serrate shape at the same time, the dielectric multilayer 22bbecomes the Fresnel lens shape.
In another example, both the dielectric multilayer 21 and the dielectric multilayer 22 may be formed inside the combiner 100b. In that case, it is not limited that only one of the dielectric multilayer 21 and the dielectric multilayer 22 is formed to be inclined with respect to the horizontal plane of the combiner 100b, and both the dielectric multilayer 21 and the dielectric multilayer 22 may be formed to be inclined with respect to the horizontal plane of the combiner 100b. In addition, the first modified example and/or the second modified example may be applied to one of or both of the dielectric multilayer 21 and the dielectric multilayer 22.
3-2-4. Fourth Modified Example
In the fourth modified example of the second embodiment, two volume type HOEs are used instead of the dielectric multilayers 21, 22. In that case, the volume type HOEs need to have the characteristic as shown in
The fourth modified example may be implemented in combination with at least one of the first to third modified examples. In that case, if the volume type HOEs need to have the lens effect, it is preferred that the volume type HOEs are not formed by the curved surface, but the volume type HOEs formed by the method described in the second modified example of the first embodiment are used.
3-2-5. Fifth Modified Example
In the second embodiment described above, while the dielectric multilayer is used as the wavelength selective transmission layer or the wavelength selective reflection layer, the wavelength selective transmission layers or the wavelength selective reflection layer of various kind, other than the dielectric multilayer, may be used.
Next, the third embodiment will be described.
4-1. Configuration of Combiner according to Third Embodiment
The dielectric multilayer 31 and the base plate 33 are held by the holding part 35, and the dielectric multilayer 32 and the base plate 34 are held by the holding part 36. The holding part 35 and the holding part 36 are attached in a manner rotatable around a common axis. Thus, the dielectric multilayer 31 and the base plate 33 held by the holding part 35 swings in the direction shown by the arrow Ar1, and the dielectric multilayer 32 and the base plate 34 held by the holding part 36 swings in the direction shown by the arrow Ar2. Therefore, the angle φ formed by the dielectric multilayer 31 and the dielectric multilayer 32 may be suitably changed.
It is not limited that the combiner 100c is configured such that both the dielectric multilayer 31 and the dielectric multilayer 32 swing. The combiner 100c may be configured such that one of the dielectric multilayer 31 and the dielectric multilayer 32 is fixed and only the other of the dielectric multilayer 31 and the dielectric multilayer 32 swings.
Specifically, the light entering the combiner 100c from the real image display device 200 with the incident angle “θin+φ” passes through the dielectric multilayer 31 as shown by the arrow C1, and is regularly reflected by the dielectric multilayer 32 as shown by the arrow C2. In this case, the light passed through the dielectric multilayer 31 enters the dielectric multilayer 32 with the incident angle “θin”, and is reflected by the dielectric multilayer 32 with the reflection angle “θin”. Then, the light reflected by the dielectric multilayer 32 is further regularly reflected by the dielectric multilayer 31 as shown by the arrow C3. In this case, the light reflected by the dielectric multilayer 32 enters the dielectric multilayer 31 with the incident angle “θin−φ”, and is reflected by the dielectric multilayer 31 with the reflection angle “θin−φ”. Then, the light reflected by the dielectric multilayer 31 passes through the dielectric multilayer 32 as shown by the arrow C4 and exit the combiner 100c with the exit angle θout (θout=θin−2φ).
In one example, “10±5 [°]” is used as the angle φ, “40±5 [°]” is used as the incident angle “θin+φ” (θin=30 [°] in this case), and “10±10 [°]” is used as the exit angle θout.
Next, with reference to
As shown by the graph G31, the dielectric multilayer 31 is formed to transmit the light entering with the angle “θin+φ” and reflects the light entering with the angle “θin−φ”. As shown by the graph G32, the dielectric multilayer 32 is formed to transmit the light entering with the angle θout and reflect the light entering with the angle θin. Thus, the real image displaying light can be guided as shown by the arrows C1 to C4 in
Preferably, the characteristics of the dielectric multilayers 31, 32 shown in
If the dielectric multilayer 31 has the characteristic of transmitting the light entering with the angle “θin+φ” and reflecting the light entering with the angle “θin−φ”, it may have any characteristic at other angles. For example, the dielectric multilayer 31 may have the characteristic shown by the broken-line graph G31′. Similarly, if the dielectric multilayer 32 has the characteristic of transmitting the light entering with the angle θout and reflecting the light entering with the angle θin, it may have any characteristic at other angles. For example, the dielectric multilayer 32 may have the characteristic shown by the broken-line graph G32′.
In the configuration of the first embodiment and the second embodiment described above, the angle formed by the angle θin and the angle θout cannot be changed even if the mounting angle (tilt angle) of the combiner 100a, 100b itself. Therefore, if the seating height of the driver changes, the light from the real image display device 200 does not appropriately reach the head of the driver. In contrast, since the combiner 100c according to the third embodiment is formed to be able to change the angle φ between the dielectric multilayer 31 and the dielectric multilayer 32, the exit angle θout becomes “θout=θin−2φ”. Therefore, the difference of the seating height of the drivers can be absorbed by changing the angle φ. Namely, according to the third embodiment, the light from the real image display device 200 can appropriately reach the head of the driver even if the seating height of the driver changes. Also, since the member (the flat parallel plate) formed by the dielectric multilayer 31 and the base plate 33 and the member (the flat parallel plate) formed by the dielectric multilayer 32 and the base plate 34 can be made thin in the third embodiment, the weight of the combiner 100c itself can be reduced in comparison with the second embodiment.
4-2. Modified Examples of Third Embodiment
Next, modified examples of the third embodiment will be described. The following modified examples may be implemented in an arbitrary combination.
4-2-1. First Modified Example
In the combiner 100c1 shown in
4-2-2. Second Modified Example
According to the combiner 100c4, in addition to the optical effect of the above-described combiner 100c, it is possible to further give the lens effect to the real image displaying light. Therefore, according to the second modified example of the third embodiment, the combiner 100c4 having a magnification can be realized, and the distance of the virtual image may be changed far or near.
Instead of the dielectric multilayer 31, the dielectric multilayer 32 may be formed to have a gentle curvature, and both the dielectric multilayer 31 and the dielectric multilayer 32 may be formed to have a gentle curvature.
Further, the second modified example and the first modified example may be implemented in combination.
4-2-3. Third Modified Example
In the third modified example of the third embodiment, two volume type HOEs are used instead of the dielectric multilayers 31, 32. In that case, the volume type HOEs need to have the characteristic as shown in
The third modified example may be implemented in combination with the first modified example and/or the second modified example. In that case, if the volume type HOEs need to have the lens effect, it is preferred that the volume type HOEs are not formed by the curved surface, but the volume type HOEs formed by the method described in the second modified example of the first embodiment are used.
4-2-4. Fourth Modified Example
In the third embodiment described above, while the dielectric multilayer is used as the wavelength selective transmission layer or the wavelength selective reflection layer, the wavelength selective transmission layers or the wavelength selective reflection layer of various kind, other than the dielectric multilayer, may be used.
The above-described embodiments recite an example of using the volume type HOEs as the first optical element and the second optical element and an example of using the dielectric multilayers as the first optical element and the second optical element. Instead, the volume type HOE may be used as one of the first optical element and the second optical element, and the dielectric multilayer may be used as the other of the first optical element and the second optical element. Further, the volume type HOE or the dielectric multilayer may be used as one of the first optical element and the second optical element, and an optical element other than the volume type HOE and the dielectric multilayer may be used as the other one of the first optical element and the second optical element.
While the combiner 100 is provided near the ceiling of the vehicle in the embodiments described above, the combiner 100 may be of glasses-type (sunglasses type).
While the above embodiments described the examples of applying the present invention to the HUD, the application of the present invention is not limited to this. The present invention may be applied to various display devices which visualizes the image as the virtual image. For example, the present invention is applicable to a head mount display.
11, 12 Volume type HOE
12, 23, 24, 33, 34 Base plate
21, 22, 31, 32 Dielectric multilayer
35, 36 Holding part
100, 100a, 100b, 100c Combiner
200 Real image display device
300 HUD
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2013/059125 | 3/27/2013 | WO | 00 |
