JP2016130066A - Head-up display, control method, program, and storage medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a head-up display which can suitably improve visibility of an image.SOLUTION: A head-up display system displays a virtual image Iv so as to be visible from a cabin of a vehicle Ve by reflecting display light emitted from a light source unit 4 on a reflection surface of a front window 25. The head-up display system is provided with a phase difference plate 5, and the light source unit 4. The phase difference plate 5 is arranged on an optical path between the light source unit 4 and the reflection surface of the front window 25, and rotates a polarization plane of the light emitted from the light source unit 4. A phase difference plate rotation control part 46 of the light source unit 4 rotates the phase difference plate 5 in a direction for improving reflectivity of the display light on the front window 25 based on vehicle information Iw acquired by a vehicle information acquisition part 44.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a technique for improving the visibility of display on a head-up display.

  Conventionally, in a head-up display, there is a technique for improving the visibility of a virtual image by adjusting the polarization direction of light emitted from a projection unit. For example, in Patent Document 1, when a virtual image cannot be clearly seen by wearing polarized sunglasses, the transmittance of polarized sunglasses is improved by placing a phase difference plate on the optical path based on the manual operation of the virtual image observer. A head-up display capable of changing the direction of polarization in the direction to be disclosed is disclosed.

JP 2010-113197 A

  In general, in the case of a head-up display in which a virtual image is viewed through a front window, the reflectance at the front window varies depending on the polarization direction of light incident on the front window, and the apparent luminance of the virtual image changes accordingly. In addition, since the shape and inclination of the front window vary depending on the vehicle type and the like, the optimal polarization direction of light differs for each vehicle. In this regard, Patent Document 1 does not disclose anything.

  The present invention has been made in order to solve the above-described problems, and has as its main object to provide a head-up display capable of suitably improving the visibility of a virtual image.

  The invention described in claim is a head-up that is installed in a vehicle and displays the image so as to be visible from inside the vehicle by reflecting light constituting the image emitted from the light source by a reflecting surface of a front window. A phase difference plate that rotates a polarization plane of light emitted from the light source; an acquisition unit that acquires vehicle information of the vehicle; and a control unit that controls a rotation angle of the phase difference plate. The retardation plate is disposed on an optical path between the light source and the reflective surface of the front window of the vehicle, and the control means is based on the vehicle information acquired by the acquisition means. The retardation plate is rotated in a direction in which the reflectance of the light constituting the image is improved on the reflection surface.

  Further, the invention described in the claims displays the image so that the image can be viewed from the interior of the vehicle by reflecting the light constituting the image emitted from the light source, which is installed in the vehicle, by the reflecting surface of the front window. A control method executed by a head-up display including a phase difference plate that rotates a polarization plane of light emitted from the light source, the acquisition step of acquiring vehicle information of the vehicle, and a rotation angle of the phase difference plate The retardation plate is disposed on an optical path between the light source and the reflective surface of the front window of the vehicle, and the control step is acquired by the acquisition step. Further, based on the vehicle information, the retardation plate is rotated in a direction in which the reflectance of the light constituting the image on the reflection surface is improved.

  Further, the invention described in the claims displays the image so that the image can be viewed from the interior of the vehicle by reflecting the light constituting the image emitted from the light source, which is installed in the vehicle, by the reflecting surface of the front window. A program executed by a computer that controls a head-up display including a phase difference plate that rotates a polarization plane of light emitted from the light source, the acquisition unit acquiring vehicle information of the vehicle, and the phase difference plate The computer functions as control means for controlling the rotation angle of the vehicle, wherein the phase difference plate is disposed on an optical path between the light source and the reflection surface of the front window of the vehicle, and the control means Based on the vehicle information acquired by the means, the retardation plate is rotated in a direction in which the reflectance of the light constituting the image is improved on the reflecting surface. It is characterized in.

1 shows a schematic configuration of a head-up display system according to a first embodiment. It is a functional block diagram of the head up display system concerning the 1st example. The side view in a vehicle interior at the time of mounting a head-up display system in the vehicle of a different vehicle type is shown. The figure which observed the front window from the upper part is shown. The structure of the head up display system which concerns on 2nd Example is shown. It is a functional block diagram of the head up display system concerning a 3rd example. It is a functional block diagram of the head up display system concerning a modification.

  In one preferred embodiment of the present invention, the image that is installed in the vehicle and that constitutes the image emitted from the light source is reflected by the reflecting surface of the front window so that the image can be viewed from the interior of the vehicle. A head-up display that rotates a polarization plane of light emitted from the light source, an acquisition unit that acquires vehicle information of the vehicle, and a control unit that controls a rotation angle of the retardation plate The retardation plate is disposed on an optical path between the light source and the reflecting surface of the front window of the vehicle, and the control means is based on the vehicle information acquired by the acquisition means. Then, the retardation plate is rotated in a direction in which the reflectance of the light constituting the image on the reflection surface is improved.

  The head-up display is installed in the vehicle and reflects the light constituting the image emitted from the light source by the reflecting surface of the front window, thereby displaying the image so as to be visible from the interior of the vehicle. Here, the “image” is displayed as a virtual image. The head-up display includes a phase difference plate, an acquisition unit, and a control unit. The phase difference plate is disposed on the optical path between the light source and the reflection surface of the front window of the vehicle, and rotates the polarization plane of the light emitted from the light source. The acquisition means acquires vehicle information of the vehicle. The control unit controls the rotation angle of the phase difference plate. Here, based on the vehicle information acquired by the acquisition unit, the control unit rotates the phase difference plate in a direction in which the reflectance of the light reflecting surface constituting the image is improved. In this aspect, the head-up display rotates the phase difference plate based on the vehicle information in consideration of the difference in the shape and inclination of the front window depending on the vehicle type and the like. Thereby, the head-up display can improve the reflectance of the light which comprises the image in the reflective surface of a front window, and can improve the visibility of an image suitably.

  In one aspect of the head-up display, the control means reflects the light constituting the image based on a front window attachment angle and / or a curved state indicated by the vehicle information acquired by the acquisition means. The retardation plate is rotated in a direction in which the reflectance at the surface is improved. According to this aspect, the head-up display preferably uses the phase difference plate in a direction in which the reflectance of light constituting the image on the reflection surface of the front window is improved in consideration of the mounting angle and / or the curved state of the front window. Can be rotated.

  In another aspect of the head-up display, the control means recognizes a curved state of the front window at a position where light constituting the image is reflected by the reflecting surface based on information on a display position of the image. And based on the said curved state, the said phase difference plate is rotated in the direction which the reflectance in the said reflective surface of the light which comprises the said image improves. According to this aspect, even when the display position of the image differs depending on the content to be displayed, etc., the polarization of the light constituting the image according to the curved state of the front window at the irradiation position of the light constituting the image The direction can be adjusted, and the reflectance at the reflecting surface can be suitably improved.

  In another aspect of the head-up display, the head-up display further includes determination means for determining whether the image observer of the vehicle wears sunglasses, and the control means uses the determination means to determine whether the image observer is wearing the sunglasses. If it is determined that sunglasses are worn, the phase difference plate is rotated in a direction in which the transmittance of light constituting the image is improved in the sunglasses, and the control means allows the image observer to When it is determined that sunglasses are not worn, the retardation plate is rotated in a direction in which the reflectance of the light constituting the image on the reflection surface is improved based on the vehicle information. According to this aspect, the head-up display adjusts the polarization direction of the light constituting the image according to whether or not the image observer wears sunglasses, and clears the image both when wearing sunglasses and when not wearing sunglasses. Can be visually recognized.

  In another aspect of the head-up display, the head-up display further includes detection means for detecting the brightness around the vehicle, and the control means detects the brightness around the vehicle detected by the detection means. When the brightness is less than or equal to a predetermined brightness, the retardation plate is rotated in such a direction that the reflectance of the light constituting the image on the reflecting surface decreases as the brightness around the vehicle becomes darker. According to this aspect, the head-up display can suitably adjust the apparent luminance of the image so that the image is easy to see according to the brightness around the vehicle.

  In another preferred embodiment of the present invention, the image that is installed in the vehicle and that constitutes the image emitted from the light source is reflected by the reflecting surface of the front window, so that the image can be viewed from inside the vehicle. A control method executed by a head-up display including a phase difference plate that rotates a polarization plane of light emitted from the light source, an acquisition step of acquiring vehicle information of the vehicle, and rotation of the phase difference plate A control step for controlling an angle, wherein the retardation plate is disposed on an optical path between the light source and the reflecting surface of the front window of the vehicle, and the control step is acquired by the acquisition step. The retardation plate is rotated in a direction in which the reflectance of the light constituting the image on the reflecting surface is improved based on the vehicle information. By executing this control method, the head-up display can increase the reflectance of the light constituting the image on the reflective surface of the front window, and can suitably improve the visibility of the image.

  In another preferred embodiment of the present invention, the image that is installed in the vehicle and that constitutes the image emitted from the light source is reflected by the reflecting surface of the front window, so that the image can be viewed from inside the vehicle. And a program executed by a computer that controls a head-up display including a phase difference plate that rotates a polarization plane of light emitted from the light source, the acquisition unit acquiring vehicle information of the vehicle, and the phase difference The computer is made to function as control means for controlling a rotation angle of the plate, the retardation plate is disposed on an optical path between the light source and the reflection surface of the front window of the vehicle, and the control means includes the Based on the vehicle information acquired by the acquisition unit, the retardation plate is rotated in a direction in which the reflectance of the light constituting the image is improved on the reflection surface. To. By executing this program, the computer can increase the reflectance of the light constituting the image on the reflection surface of the front window, and can suitably improve the visibility of the image. Preferably, the program is stored in a storage medium.

  Hereinafter, preferred first to third embodiments of the present invention will be described with reference to the drawings.

<First embodiment>
[Schematic configuration]
FIG. 1 shows a schematic configuration of a head-up display system according to the first embodiment. As shown in FIG. 1, the head-up display system according to the present embodiment mainly includes a light source unit 4, a phase difference plate 5, and a concave mirror 8, and includes a front window 25, a ceiling portion 27, and a bonnet. 28 and a dashboard 29 equipped with a dashboard 29.

  The light source unit 4 is provided in the dashboard 29, and constitutes a display image indicating map information including the current location, route guidance information, traveling speed, and other information for assisting driving (also simply referred to as “display light”). Are emitted toward the concave mirror 8 provided in the dashboard 29. In this case, the light emitted from the light source unit 4 is a polarized laser having a uniform polarization direction, has a predetermined polarization plane, the polarization direction is changed by the phase difference plate 5, and is reflected by the concave mirror 8. The display light reflected by the concave mirror 8 reaches the front window 25 through an opening 89 provided in the dashboard 29 and is further reflected by the front window 25 so that the position of the driver's eyes (“eye point”). Also called). In this way, the light source unit 4 causes the display light to reach the position of the driver's eyes and causes the driver to visually recognize the virtual image “Iv”.

  The phase difference plate 5 is an optical component for giving a phase difference to incident light, and may be one λ / 2 plate or two λ / 4 plates stacked. . The phase difference plate 5 is configured to be rotatable (that is, the rotation angle can be adjusted) based on a control signal transmitted from the light source unit 4 with the incident direction of display light as a rotation axis. Then, the phase difference plate 5 displays the display light according to the angle difference between the optical axis of the phase difference plate 5 and the polarization plane of the display light after the rotation angle is adjusted with respect to the display light incident on the phase difference plate 5. Rotate the plane of polarization.

  The concave mirror 8 reflects the display light emitted from the light source unit 4 toward an opening 89 provided in the dashboard 29 and reaches the front window 25. In this case, the concave mirror 8 magnifies and reflects the image indicated by the display light.

[Function configuration]
FIG. 2 is a block diagram illustrating a functional configuration of the head-up display system. As shown in FIG. 2, the light source unit 4 can communicate with the navigation device 1 existing in the vehicle Ve, and includes a projection unit 40, a communication unit 41, and a control unit 43.

  The navigation device 1 includes an output unit such as a display and an audio output device, a self-supporting positioning device such as a GPS receiver and a gyro sensor, map data, and the like, and performs route guidance of the vehicle Ve. The navigation device 1 transmits information necessary for displaying the virtual image Iv to the light source unit 4. The navigation device 1 is a mobile terminal such as a stationary in-vehicle navigation device or a smartphone, for example.

  The projection unit 40 is a projection device including a screen on which an image is formed, for example, and emits display light toward the front window 25 based on the control of the control unit 43. The communication unit 41 communicates with the navigation device 1, the vehicle control unit (ECU), and the like, and receives information necessary for displaying the virtual image Iv. For example, the communication unit 41 receives current position information, vehicle travel speed information, route guidance route information, and the like from the navigation device 1 based on the control of the control unit 43.

  The control unit 43 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like, and controls the entire light source unit 4. The control unit 43 according to the present embodiment includes a vehicle information acquisition unit 44, a display control unit 45, and a retardation plate rotation control unit 46. The control unit 43 is an example of a computer that executes “acquisition unit”, “control unit”, and a program in the present invention.

  The vehicle information acquisition unit 44 acquires information about the vehicle Ve (also referred to as “vehicle information Iw”). The vehicle information Iw includes information on the mounting angle of the front window 25 with respect to the ground (also simply referred to as “mounting angle”), and the curved state (simply simply) at each position of the front window 25 when the front window 25 is observed from the upper end. (Also referred to as “curved state”). For example, the vehicle information acquisition unit 44 acquires the vehicle information Iw from the vehicle control unit via the communication unit 41. In another example, the vehicle information acquisition unit 44 refers to a database of vehicle information Iw for each vehicle type (model), and when the vehicle type of the vehicle Ve is designated by a user input, the vehicle information is changed from the above database to the vehicle Ve. Corresponding vehicle information Iw is extracted. In addition, the light source unit 4 may memorize | store the above-mentioned database, and the navigation apparatus 1 or server apparatus etc. which can communicate with the communication part 41 may memorize | store it.

  The display control unit 45 generates an image to be displayed as the virtual image Iv, determines the display position of the virtual image Iv on the front window 25, and displays the virtual image Iv indicating the generated image at the determined display position. As described above, display light is emitted to the projection unit 40. At this time, the display control unit 45 may detect the driver's eye point based on a captured image of a camera (not shown) that captures the driver's face and change the display position of the virtual image Iv according to the eye point. . Then, the display control unit 45 transmits information related to the display position of the virtual image Iv on the front window 25 (also referred to as “display position information Idp”) to the phase difference plate rotation control unit 46.

  The retardation plate rotation control unit 46 controls the rotation angle of the retardation plate 5 by transmitting a control signal “Sc” to the retardation plate 5. In this case, the retardation plate rotation control unit 46 displays the display emitted from the light source unit 4 based on the vehicle information Iw acquired by the vehicle information acquisition unit 44 and the display position information Idp supplied from the display control unit 45. The phase difference plate 5 is rotated in a direction that improves the reflectance of the light at the reflection surface of the front window 25. Specifically, the retardation plate rotation control unit 46 has a reflectance based on the mounting angle of the front window 25 and the curved state of the front window 25 at the display position of the virtual image Iv (that is, the reflection position of the display light). The rotation angle of the phase difference plate 5 is adjusted so as to be maximized. In this case, for example, the phase difference plate rotation control unit 46 stores in advance a map indicating the rotation angle of the phase difference plate 5 to be set for each possible combination of the mounting angle and the curved state of the front window 25. By referring to the map, the rotation angle of the phase difference plate 5 is determined. The above-described map is generated in advance based on, for example, experiments or theoretical calculations, and stored in the memory of the light source unit 4.

[effect]
Here, the effect of the process of adjusting the rotation angle of the phase difference plate 5 based on the mounting angle and the curved state of the front window 25 will be supplementarily described with reference to FIGS. 3 and 4.

  FIG. 3 shows a side view of the passenger compartment when the head-up display system is mounted on vehicles of different vehicle types. In the example of FIG. 3, the front window 25 and the light path of the display light for the relatively small vehicle “Ve1” are indicated by solid lines, and the front window 25 and the light path of the display light for the relatively large vehicle “Ve2” are indicated by broken lines. Show.

  As shown in FIG. 3, the attachment angle of the front window 25 differs depending on the vehicle type. Specifically, the attachment angle of the front window 25 of the vehicle Ve1 is larger than the attachment angle of the front window 25 of the vehicle Ve2. Even when display light having the same plane of polarization is incident on the front window 25, the incident angle on the front window 25 varies depending on the mounting angle of the front window 25. The reflectance at is different. Therefore, depending on the vehicle model, the reflectance of the display light on the front window 25 may not be the reflectance that optimizes the visibility of the driver's virtual image Iv.

  Considering the above, the phase difference plate rotation control unit 46 adjusts the rotation angle of the phase difference plate 5 based on the mounting angle of the front window 25 indicated by the vehicle information Iw to change the angle of the polarization plane of the display light. Thereby, the phase difference plate rotation control part 46 can make a driver | operator visually recognize the clear virtual image Iv irrespective of a vehicle model.

  FIG. 4 shows a view of the front window 25 as viewed from above. The ranges “DR1” and “DR2” illustrated in FIG. 4 indicate the range of the front window 25 in which the display light corresponding to each virtual image Iv is incident when the display position of the virtual image Iv is different. As shown in FIG. 4, the curved state of the front window 25 at the position where the display light is incident differs depending on the display position of the virtual image Iv. Further, since the shape of the front window 25 differs depending on the vehicle type, the curved state of the front window 25 at the position where the display light is incident also differs depending on the vehicle type. Therefore, depending on the vehicle type and the display position of the virtual image Iv, the reflectance of the display light on the front window 25 may not be the reflectance at which the visibility of the virtual image Iv of the driver is optimal.

  Considering the above, the retardation plate rotation control unit 46 recognizes the curved state of the front window 25 at the display position of the virtual image Iv based on the vehicle information Iw and the display position information Idp. Then, based on the curved state, the retardation plate rotation control unit 46 adjusts the rotation angle of the retardation plate 5 to change the angle of the polarization plane of the display light. Thereby, the phase difference plate rotation control unit 46 can display a clear virtual image Iv to the driver regardless of the vehicle type and the display position of the virtual image Iv.

  As described above, the head-up display system according to the first embodiment is installed in the vehicle Ve, and reflects the display light emitted from the light source unit 4 on the reflecting surface of the front window 25, whereby the virtual image Iv is displayed on the vehicle. It is displayed so as to be visible from the inside of Ve. The head-up display system includes a phase difference plate 5 and a light source unit 4. The phase difference plate 5 is disposed on the optical path between the light source unit 4 and the reflection surface of the front window 25 and rotates the polarization plane of the light emitted from the light source unit 4. The light source unit 4 includes a vehicle information acquisition unit 44 that acquires the vehicle information Iw, and a phase difference plate rotation control unit 46 that controls the rotation angle of the phase difference plate 5. Here, the phase difference plate rotation control unit 46 rotates the phase difference plate 5 in a direction in which the reflectance of the display light on the front window 25 is improved based on the vehicle information Iw acquired by the vehicle information acquisition unit 44. . Thereby, the head-up display system can raise the reflectance of the display light in the front window 25, and can improve the visibility of the virtual image Iv suitably.

<Second embodiment>
In 2nd Example, when the control part 43 of the light source unit 4 determines the presence or absence of wearing of sunglasses of the driver | operator who is an observer in addition to the process of 1st Example, and judges that he is wearing sunglasses. The rotation angle of the phase difference plate 5 is determined so that the transmittance of display light through sunglasses is maximized.

  FIG. 5A shows a schematic configuration of a head-up display system according to the second embodiment, and FIG. 5B shows a functional block diagram of the head-up display system according to the second embodiment. As shown in FIGS. 5A and 5B, the head-up display system is provided with a vehicle interior photographing camera 6 for photographing a driver's face. Further, as shown in FIG. 5B, the control unit 43 includes a sunglasses wear determination unit 47. In addition, about the structure similar to 1st Example, the same code | symbol is attached | subjected suitably and the description is abbreviate | omitted.

  The sunglasses wearing determination unit 47 acquires an image generated by the vehicle interior photographing camera 6 and performs a known image recognition process on the image to determine whether the driver wears sunglasses. Then, the sunglasses wearing determination unit 47 supplies information regarding whether or not the driver wears sunglasses (also referred to as “sunglasses wearing information Isg”) to the phase difference plate rotation control unit 46. The sunglasses wearing determination unit 47 is an example of the “determination means” in the present invention.

  When the retardation plate rotation control unit 46 determines that the driver is wearing sunglasses based on the sunglasses wearing information Isg, the retardation plate rotation control unit 46 regards the sunglasses as polarized sunglasses, and the transmittance of display light in the polarized sunglasses is high. The phase difference plate 5 is rotated in an improving direction. Specifically, in this case, the retardation plate rotation control unit 46 recognizes the rotation angle of the retardation plate 5 that maximizes the transmittance when the display light reflected from the front window 25 is incident on the polarized sunglasses. The phase difference plate 5 is rotated so that the rotation angle is reached. The rotation angle at which the transmittance is maximized is derived, for example, experimentally or theoretically and stored in advance in the memory of the light source unit 4. Thereby, the phase difference plate rotation control part 46 can make the virtual image Iv be visually recognized suitably, even if it is a case where the driver | operator is wearing polarized sunglasses.

  On the other hand, the phase difference plate rotation control unit 46 determines the rotation angle of the phase difference plate 5 in the same manner as in the first embodiment when it is determined that the driver is not wearing sunglasses. That is, in this case, the retardation plate rotation control unit 46 recognizes the mounting angle of the front window 25 and the curved state at the display position of the virtual image Iv based on the vehicle information Iw and the display position information Idp. The rotation angle of the phase difference plate 5 is determined so that the reflectance of the display light is maximized.

  Next, the effects of the second embodiment will be supplementarily described. In general, polarized sunglasses that are widely used in the market use lenses that can effectively cut glare and reflected light. This lens can cut ultraviolet rays and reflected light while allowing natural light to pass therethrough, and has a function of maintaining good visibility. On the other hand, in the head-up display system, the virtual image Iv is visually recognized by causing the reflected light of the front window 25 to enter the eyes of the driver. Therefore, when the driver wears polarized sunglasses, the visibility of the virtual image Iv is extremely high. There is a problem of being lowered.

  In consideration of the above, in the second embodiment, the retardation plate rotation control unit 46 determines the polarization of the display light reflected from the front window 25 when the sunglasses wearing determination unit 47 determines that the driver is wearing sunglasses. The phase difference plate 5 is rotated in a direction in which the transmittance with sunglasses is improved. Thereby, the driver who is the observer of the virtual image Iv can visually recognize the clearer virtual image Iv.

<Third embodiment>
In the third embodiment, the control unit 43 of the light source unit 4 detects the brightness outside the vehicle in addition to the processing of the first embodiment. The darker the brightness, the reflectivity of the display light on the front window 25 The rotation angle of the phase difference plate 5 is determined so that is lowered. Thereby, the driver is made to visually recognize the virtual image Iv having a luminance suitable for the brightness outside the vehicle.

  FIG. 6 is a functional block diagram of the head-up display system according to the third embodiment. As shown in FIG. 6, the control unit 43 includes a brightness detection unit 48. In addition, about the structure similar to 1st Example, the same code | symbol is attached | subjected suitably and the description is abbreviate | omitted.

  The brightness detection unit 48 determines the brightness outside the vehicle based on a detection signal acquired from a sensor (not shown) attached outside the vehicle, or based on a signal indicating the state of a headlight lighting switch acquired from the control unit of the vehicle. Detect or estimate. Then, the brightness detection unit 48 adjusts the rotation angle of the phase difference plate 5 so that the reflectance of the display light at the front window 25 suitable for the detected or estimated brightness outside the vehicle is obtained. The brightness detector 48 is an example of the “detector” in the present invention.

For example, when the detected or estimated brightness level outside the vehicle is higher than a predetermined value, the retardation plate rotation control unit 46 maximizes the reflectance of the display light on the front window 25 as in the first embodiment. The rotation angle of the phase difference plate 5 is determined so that Thereby, the phase difference plate rotation control unit 46 increases the apparent brightness of the virtual image Iv, and allows the virtual image Iv to be appropriately visually recognized even in a bright time zone such as during the daytime.
On the other hand, the phase difference plate rotation control unit 46 reduces the reflectance of the display light on the front window 25 and reduces the virtual image Iv as the outside of the vehicle is darker when the detected or estimated degree of brightness outside the vehicle is a predetermined value or less. The rotation angle of the phase difference plate 5 is adjusted so as to reduce the luminance. In this case, for example, the retardation plate rotation control unit 46 stores in advance a map of the reflectance at the front window 25 suitable for each brightness level outside the vehicle, and refers to the map or the like to detect or The reflectance of the display light on the front window 25 suitable for the estimated brightness outside the vehicle is recognized. Then, the retardation plate rotation control unit 46 recognizes the rotation angle of the retardation plate 5 necessary to achieve the reflectance of the display light at the target front window 25, and adjusts the rotation angle to be the rotation angle. The phase difference plate 5 is rotated. In this case, preferably, the phase difference plate rotation control unit 46 takes into account the mounting angle and the curved state of the front window 25 recognized from the vehicle information Iw and the display position information Idp, and displays light on the target front window 25. The rotation angle of the phase difference plate 5 necessary to achieve the reflectance is recognized.

  As described above, the head-up display system according to the third embodiment detects the brightness outside the vehicle and determines the rotation angle of the phase difference plate 5 so that the virtual image Iv has a luminance suitable for the brightness. Thereby, the driver can visually recognize the virtual image Iv having a luminance suitable for the brightness outside the vehicle.

<Modification>
Hereinafter, modified examples suitable for the first to third embodiments will be described. The following modifications may be applied to the first to third embodiments in any combination.

(Modification 1)
The phase difference plate rotation control unit 46 may adjust the direction of the polarization plane of the display light by rotating the projection unit 40 instead of rotating the phase difference plate 5.

  In this case, the projection unit 40 is configured to be rotatable about the light emission direction based on the control signal transmitted from the phase difference plate rotation control unit 46. And the phase difference plate rotation control part 46 determines the rotation angle of the projection part 40 so that the direction of the polarization plane of display light may become the optimal direction based on the 1st-3rd Example. In this case, the display control unit 45 changes the orientation of the image to be emitted to the projection unit 40 according to the rotation angle of the projection unit 40 so that the orientation of the image visually recognized as the virtual image Iv does not change. Also according to this aspect, the head-up display system can preferably improve the visibility of the virtual image Iv as in the embodiment.

(Modification 2)
The light source unit 4 may have a retardation plate 5 inside. Even in this case, the phase difference plate 5 is disposed at a position where the light emitted from the projection unit 40 is irradiated.

(Modification 3)
The navigation device 1 may execute processing such as control of the rotation angle of the phase difference plate 5 instead of the light source unit 4.

  FIG. 7 shows a configuration example of a head-up display system according to this modification. In the example of FIG. 7, the navigation device 1 adjusts the rotation angle of the phase difference plate 5 by transmitting a control signal Sc to the phase difference plate 5. In this case, the navigation device 1 includes a CPU that executes processing of the control unit 43 such as the vehicle information acquisition unit 44, the display control unit 45, and the retardation plate rotation control unit 46 described in each embodiment, and the like. Based on the first to third embodiments, the rotation angle of the phase difference plate 5 is adjusted so that the reflectance of the display light at the front window 25 is optimized. In the example of FIG. 7, the navigation device 1 supplies display light to the projection unit 40 by supplying, to the projection unit 40, a control signal that specifies an image to be displayed as a virtual image Iv, a display position, and the like via the communication unit 41. Is injected.

  In the present modification, the CPU of the navigation device 1 is an example of a computer that executes the “acquisition unit”, “control unit”, and program in the present invention.

(Modification 4)
In each embodiment, the light source unit 4 receives information necessary for causing the projection unit 40 to emit display light, such as current position information and map data, from the navigation device 1. Instead, the light source unit 4 includes a self-supporting positioning device such as a GPS receiver and a gyro sensor, map data, and the like, and generates an image to be displayed as a virtual image Iv without communicating with the navigation device 1. Display light may be emitted.

(Modification 5)
The projection unit 40 may be a liquid crystal display. In this case, the liquid crystal display may have all the functions of the light source unit 4, and the navigation device 1 may have the function of the control unit 43 as in the third modification.

DESCRIPTION OF SYMBOLS 1 Navigation apparatus 4 Light source unit 5 Phase difference plate 6 Car interior camera 8 Concave mirror 25 Front window 28 Bonnet 29 Dashboard

Claims (8)

A head-up display that is installed in a vehicle and displays the image so as to be visible from the interior of the vehicle by reflecting light constituting an image emitted from a light source by a reflecting surface of a front window,
A phase difference plate that rotates a polarization plane of light emitted from the light source;
Obtaining means for obtaining vehicle information of the vehicle;
Control means for controlling the rotation angle of the retardation plate;
With
The retardation plate is disposed on an optical path between the light source and the reflecting surface of the front window of the vehicle,
The control means rotates the retardation plate in a direction in which the reflectance of the light constituting the image is improved on the basis of the vehicle information acquired by the acquisition means. Head-up display.   The control means is a direction in which the reflectance of the light constituting the image on the reflection surface is improved based on a front window attachment angle and / or a curved state indicated by the vehicle information acquired by the acquisition means. The head-up display according to claim 1, wherein the phase difference plate is rotated.   The control means recognizes a curved state of the front window at a position where light constituting the image is reflected by the reflecting surface based on information on a display position of the image, and based on the curved state, the image The head-up display according to claim 1, wherein the retardation plate is rotated in a direction in which the reflectance of the light constituting the light beam at the reflection surface is improved. A judgment means for judging whether or not the image observer of the vehicle wears sunglasses;
The control unit rotates the retardation plate in a direction in which the transmittance of the light constituting the image is improved when the image observer determines that the image observer is wearing sunglasses,
If the image observer determines that the image observer does not wear sunglasses, the control means is configured to improve the reflectance of the light constituting the image on the reflection surface based on the vehicle information. The head-up display according to claim 1, wherein the phase difference plate is rotated. Further comprising detection means for detecting brightness around the vehicle,
When the brightness of the surroundings of the vehicle detected by the detection means is equal to or lower than a predetermined brightness, the control surface is configured to reflect the light constituting the image as the brightness of the surroundings of the vehicle becomes darker. The head-up display according to any one of claims 1 to 3, wherein the phase difference plate is rotated in a direction in which the reflectance at the surface decreases. Reflecting the light constituting the image emitted from the light source installed in the vehicle by the reflecting surface of the front window, the image is displayed so as to be visible from the interior of the vehicle, and the polarization of the light emitted from the light source A control method executed by a head-up display including a phase difference plate that rotates a surface,
An acquisition step of acquiring vehicle information of the vehicle;
A control step of controlling the rotation angle of the retardation plate,
The retardation plate is disposed on an optical path between the light source and the reflecting surface of the front window of the vehicle,
The control step rotates the retardation plate in a direction in which the reflectance of the light constituting the image is improved on the basis of the vehicle information acquired by the acquisition step. Control method. Reflecting the light constituting the image emitted from the light source installed in the vehicle by the reflecting surface of the front window, the image is displayed so as to be visible from the interior of the vehicle, and the polarization of the light emitted from the light source A program executed by a computer that controls a head-up display including a phase difference plate that rotates a surface,
Obtaining means for obtaining vehicle information of the vehicle;
Causing the computer to function as control means for controlling the rotation angle of the retardation plate;
The retardation plate is disposed on an optical path between the light source and the reflecting surface of the front window of the vehicle,
The control means rotates the retardation plate in a direction in which the reflectance of the light constituting the image is improved on the basis of the vehicle information acquired by the acquisition means. program.   A storage medium storing the program according to claim 7.

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