JP2017116667A - Head-up display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress reduction in luminance of a head-up display device.SOLUTION: A head-up display device 1 comprises: a display unit 3; a plane mirror 4; a concave surface mirror 5; and low phase difference plates 6 and 7. The display unit 3, the plane mirror 4 and concave surface mirror 5 are configured to irradiate display light expressing an image to be displayed towards a windshield of a vehicle. The low phase difference plates 6 and 7 are arranged on a route through which the display light passes until the display light arrives at the windshield, and generate a phase difference between mutually vertical two polarization components in the display light. Then, a total sum of the phase difference generating between the two polarization components in the display light by the low phase difference plates 6 and 7 is less than π[rad]. Further, Before and after the display light passes through all of the low phase difference plates 6 and 7, a polarization direction of a linear polarization in the display light varies.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a head-up display device mounted on a moving body.

  The brightness of the head-up display device greatly depends on the reflectance when the display light emitted from the head-up display device is reflected by the windshield of the moving body. Since the reflection at the windshield is Fresnel reflection, the reflectance when the display light is reflected by the windshield is determined by the polarization state of the display light before the display light is reflected by the windshield.

  For this reason, conventionally, as in Patent Document 1, for example, when the display light is linearly polarized light, a method of adjusting the reflectance by rotating the polarization direction of linearly polarized light by using a half-wave plate is known. It has been.

JP 2007-52383 A

  The angle at which the polarization direction of the linearly polarized light is rotated by the half-wave plate is determined by the angle (hereinafter referred to as the azimuth angle) formed by the fast axis of the half-wave plate and the polarization direction of the linearly polarized light. However, there is a possibility that the azimuth angle is shifted due to a change in manufacturing conditions of the half-wave plate and an assembly error when the half-wave plate is assembled to the head-up display device. When the azimuth angle is shifted, the angle at which the polarization direction of the linearly polarized light is rotated by the half-wave plate is shifted by twice the azimuth angle shift, and the brightness of the head-up display device is reduced. End up.

  The present invention has been made in view of these problems, and an object thereof is to suppress a decrease in luminance of a head-up display device.

The head-up display device (1) of the present invention includes an irradiation unit (3, 4, 5) and a plurality of optical elements (6, 7, 16, 17, 24, 26, 27, 29).
An irradiation part irradiates the display light showing the image to display toward the windshield of a moving body. The plurality of optical elements are arranged on a path through which the display light passes through to the windshield, and generates a phase difference between two polarization components perpendicular to each other in the display light.

  The total sum of the phase differences generated between the two polarization components in the display light by the plurality of optical elements is less than π [rad]. In addition, the polarization direction of the linearly polarized light in the display light changes before and after the display light passes through all of the plurality of optical elements.

  The head-up display device of the present invention configured as described above can change the polarization direction of the linearly polarized light in the display light, similarly to the case where one half-wave plate is used. In the head-up display device of the present invention, since the total sum of the phase differences is less than π [rad], the polarization direction shift of the linearly polarized light caused by the shift of the plurality of optical elements is reduced by a half-wave plate. It can be made smaller than the deviation of the polarization direction of the linearly polarized light due to the deviation.

Thereby, the head-up display device of the present invention can suppress a decrease in luminance of the head-up display device due to a shift in the polarization direction of linearly polarized light.
Note that the reference numerals in parentheses described in this column and in the claims indicate the correspondence with the specific means described in the embodiment described later as one aspect, and the technical scope of the present invention. It is not limited.

It is a figure which shows the structure of the HUD apparatus 1 of 1st Embodiment. It is a figure which shows the direction of the fast axis of the low phase difference plates 6 and 7. FIG. It is a figure which shows the Poincare sphere which displays polarization state PC1-3 of 1st Embodiment. It is a figure which shows the Poincare sphere which displays polarization state PC1-3 when the fast axis of the low phase difference plates 6 and 7 has shifted | deviated 5 degree | times. It is a figure which shows the Poincare sphere which displays polarization | polarized-light state PC1-3 when two quarter wave plates are used. It is a figure which shows the Poincare sphere which displays polarization | polarized-light state PC1-3 when the fast axis of two quarter wave plates has shifted | deviated 5 degree | times. FIG. 6 is a diagram showing the direction of the fast axis of the half-wave plate 9. It is a figure which shows the structure of the HUD apparatus 1 of 2nd Embodiment. It is a figure which shows the direction of the fast axis of the low phase difference plates 16 and 17. FIG. It is a figure which shows the Poincare sphere which displays polarization state PC4-6 of 2nd Embodiment. It is a figure which shows the Poincare sphere which displays polarization state PC4-6 when the fast axis of the low phase difference plates 16 and 17 has shifted | deviated 5 degree | times. FIG. 4 is a diagram showing the direction of the fast axis of the half-wave plate 19. It is a figure which shows the structure of the HUD apparatus 1 of the modification 1. It is a graph which shows the relationship between the wavelength equivalent to a phase difference, and the maximum rotation angle of the polarization direction of linearly polarized light. It is a figure which shows the structure of the HUD apparatus 1 of the modification 3. It is a figure which shows the structure of the HUD apparatus 1 of the modification 4. It is a figure which shows the structure of the HUD apparatus 1 of the modification 5. FIG.

[First Embodiment]
A first embodiment of the present invention will be described below with reference to the drawings.
A head-up display device 1 (hereinafter referred to as a HUD device 1) according to this embodiment is mounted on a vehicle and is installed below a windshield (not shown). HUD is an abbreviation for Head-Up Display.

  The HUD device 1 emits display light for displaying an image from below the windshield toward the windshield. As a result, a virtual image is projected onto the windshield, and the driver sitting in the driver's seat in the passenger compartment can visually recognize the projected virtual image while being superimposed on the actual scenery in front of the vehicle.

As shown in FIG. 1, the HUD device 1 includes a housing 2, a display 3, a plane mirror 4, a concave mirror 5, low phase difference plates 6 and 7, and a dustproof window 8.
The housing 2 accommodates the display 3, the plane mirror 4, the concave mirror 5, and the low phase difference plates 6 and 7. The housing | casing 2 is arrange | positioned in the dashboard of a motor vehicle.

  The display 3 is a known liquid crystal display that emits linearly polarized display light by allowing light from the backlight to pass through a liquid crystal panel, a color filter, and a polarizing filter. In the present embodiment, the wavelength of the display light emitted from the display device 3 is 560 nm.

The plane mirror 4 reflects the display light emitted from the display 3 toward the concave mirror 5.
The concave mirror 5 is a mirror for enlarging the display image formed by the display light reflected by the plane mirror 4. The concave mirror 5 reflects the display light reflected by the plane mirror 4 toward the opening 2 a of the housing 2. The opening 2 a of the housing 2 is formed so as to be disposed between the windshield and the concave mirror 5. For this reason, the light reflected by the concave mirror 5 is applied to the windshield.

  The low phase difference plates 6 and 7 are members that cause a phase difference between a polarization component parallel to the fast axis and a polarization component perpendicular to the fast axis. The low retardation plates 6 and 7 of the present embodiment generate a phase difference corresponding to 110 nm (that is, 110 × 2π / 560 = 0.39π [rad]) with respect to 560 nm which is the wavelength of display light. For this reason, the display light incident on the low retardation plates 6 and 7 has the above phase difference between the polarization component parallel to the fast axis and the polarization component perpendicular to the fast axis, and the low retardation plates 6 and 7. Is output from.

  The low phase difference plate 6 is disposed on a path through which the display light irradiated from the display device 3 reaches the plane mirror 4. The low phase difference plate 7 is disposed on a path through which the display light output from the low phase difference plate 6 reaches the plane mirror 4.

The dustproof window 8 is formed of a member that can transmit display light, and is installed so as to close the opening 2 a of the housing 2.
As shown in FIG. 2, the angle θp (hereinafter referred to as azimuth angle θp) formed by the x-axis of the xy plane perpendicular to the traveling direction of the display light and the vibration direction DE in which the electric field of the linearly polarized display light vibrates is 135 degrees. Suppose that In this case, the low phase difference plate 6 is installed such that its fast axis FA1 is inclined by 163.32 degrees with respect to the x-axis. The low phase difference plate 7 is installed such that its fast axis FA2 is inclined 136.68 degrees with respect to the x-axis. Thereby, the display light output from the low phase difference plate 7 is linearly polarized light having an azimuth angle θp of 165 degrees. Hereinafter, the vibration direction DE is also referred to as a polarization direction of linearly polarized light.

  FIG. 3 is a diagram illustrating a Poincare sphere that displays the polarization states PC1, PC2, and PC3 in the HUD device 1 of the first embodiment. The polarization state PC1 is a polarization state before display light enters the low phase difference plate 6. The polarization state PC2 is a polarization state before the display light is incident on the low retardation plate 7. The polarization state PC2 is a polarization state after the display light is output from the low phase difference plate 7.

  As shown in FIG. 3, the polarization state PC1 is linearly polarized light having an azimuth angle θp of 135 degrees. The polarization state PC2 is elliptically polarized light. The polarization state PC3 is linearly polarized light having an azimuth angle θp of 165 degrees.

  FIG. 4 is a Poincare sphere that displays the polarization states PC1, PC2, and PC3 when the fast axis FA1 of the low retardation plate 6 and the fast axis FA2 of the low retardation plate 7 are shifted by 5 degrees in the HUD device 1 of the first embodiment. FIG.

  As shown in FIG. 4, the polarization state PC1 is linearly polarized light having an azimuth angle θp of 135 degrees. The polarization state PC2 is elliptically polarized light. The polarization state PC3 is linearly polarized light having an azimuth angle θp of 158 degrees. That is, the deviation of the azimuth angle θp due to the deviation of the fast axis FA1 and the fast axis FA2 by 5 degrees is 165−158 = 7 [degrees].

FIG. 5 is a diagram showing a Poincare sphere that displays the polarization states PC1, PC2, and PC3 when two quarter-wave plates are used instead of the low retardation plates 6 and 7. FIG.
As shown in FIG. 5, the polarization state PC1 is linearly polarized light having an azimuth angle θp of 135 degrees. The polarization state PC2 is circularly polarized light. The polarization state PC3 is linearly polarized light having an azimuth angle θp of 165 degrees.

FIG. 6 is a diagram showing Poincare spheres that display the polarization states PC1, PC2, and PC3 when the fast axes of the two quarter-wave plates in FIG. 5 are shifted by 5 degrees, respectively.
As shown in FIG. 6, the polarization state PC1 is linearly polarized light having an azimuth angle θp of 135 degrees. The polarization state PC2 is elliptically polarized light. The polarization state PC3 is linearly polarized light having an azimuth angle θp of 155 degrees. That is, the deviation of the azimuth angle θp due to the deviation of the fast axes of the two quarter-wave plates by 5 degrees is 165−155 = 10 [degrees].

  Further, as shown in FIG. 7, instead of the low phase difference plates 6 and 7, one half-wave plate 9 is used, and the fast axis FA3 of the half-wave plate 9 is in relation to the x-axis. When installed so as to be inclined by 150 degrees, the display light output from the half-wave plate 9 is linearly polarized light having an azimuth angle θp of 165 degrees. And the deviation of the azimuth angle θp due to the deviation of the fast axis FA3 of the half-wave plate 9 by 5 degrees is 10 as in the case where the fast axes of the two quarter-wave plates are respectively shifted by 5 degrees. Degree.

The HUD device 1 configured in this way includes a display 3, a plane mirror 4 and a concave mirror 5, and low phase difference plates 6 and 7.
The display 3, the plane mirror 4, and the concave mirror 5 irradiate display light representing an image to be displayed toward the windshield of the vehicle. The low phase difference plates 6 and 7 are arranged on a path through which the display light passes to reach the windshield, and generate a phase difference between two polarization components perpendicular to each other in the display light.

  The sum of the phase differences generated between the two polarization components in the display light by the low retardation plates 6 and 7 is 0.39π × 2 = 0.78π [rad], which is less than π [rad]. Further, the polarization direction of the linearly polarized light in the display light changes from 135 degrees to 165 degrees before and after the display light passes through all of the low retardation plates 6 and 7.

  As described above, the HUD device 1 can change the polarization direction of the linearly polarized light in the display light as in the case of using one half-wave plate. Moreover, since the total sum of the phase differences is less than π [rad] in the HUD device 1, the deviation of the polarization direction of the linearly polarized light caused by the deviation of the low phase difference plates 6 and 7 is caused by the deviation of the half-wave plate. It can be made smaller than the deviation of the polarization direction of linearly polarized light caused by the above. Thereby, the HUD device 1 can suppress a decrease in luminance of the HUD device 1 due to a shift in the polarization direction of linearly polarized light.

  The low retardation plates 6 and 7 are installed in a state where they are not in contact with each other. For this reason, it is possible to reduce the possibility that a fast axis shift due to an assembly error when the low retardation plates 6 and 7 are assembled to the HUD device 1 occurs simultaneously in both of the low retardation plates 6 and 7. The deviation of the polarization direction of the linearly polarized light is smaller when either of the low retardation plates 6 and 7 occurs than when the fast axis deviation occurs in both of the low retardation plates 6 and 7. Thereby, the HUD device 1 can further suppress a decrease in luminance of the HUD device 1 due to a shift in the polarization direction of linearly polarized light.

In the embodiment described above, the display unit 3, the plane mirror 4, and the concave mirror 5 correspond to an irradiation unit, the low phase difference plates 6 and 7 correspond to a plurality of optical elements, and the vehicle corresponds to a moving body.
[Second Embodiment]
A second embodiment of the present invention will be described below with reference to the drawings. In the second embodiment, parts different from the first embodiment will be described. The same reference numerals as those in the first embodiment indicate the same configuration, and the preceding description is referred to.

As shown in FIG. 8, the HUD device 1 according to the second embodiment is different from the first embodiment in that low phase difference plates 16 and 17 are provided instead of the low phase difference plates 6 and 7.
The low phase difference plate 16 generates a phase difference corresponding to 120 nm with respect to 560 nm which is the wavelength of the display light.

The low phase difference plate 17 generates a phase difference corresponding to 80 nm with respect to 560 nm which is the wavelength of the display light.
As shown in FIG. 9, the low phase difference plate 16 is installed such that its fast axis FA4 is inclined by 71.46 degrees with respect to the x-axis. The low retardation plate 17 is installed such that its fast axis FA5 is inclined by 22.93 degrees with respect to the x-axis. Thereby, the display light output from the low phase difference plate 17 becomes linearly polarized light having an azimuth angle θp of 155 degrees.

  FIG. 10 is a diagram illustrating Poincare spheres that display the polarization states PC4, PC5, and PC6 in the HUD device 1 of the second embodiment. The polarization state PC4 is a polarization state before the display light is incident on the low phase difference plate 16. The polarization state PC5 is a polarization state before the display light is incident on the low retardation plate 17. The polarization state PC6 is a polarization state after the display light is output from the low phase difference plate 17.

  As shown in FIG. 10, the polarization state PC4 is linearly polarized light having an azimuth angle θp of 135 degrees. The polarization state PC5 is elliptically polarized light. The polarization state PC6 is linearly polarized light having an azimuth angle θp of 155 degrees.

  FIG. 11 is a Poincare sphere that displays the polarization states PC4, PC5, and PC6 when the fast axis FA4 of the low retardation plate 16 and the fast axis FA5 of the low retardation plate 17 are shifted by 5 degrees in the HUD device 1 of the second embodiment. FIG.

  As shown in FIG. 11, the polarization state PC4 is linearly polarized light having an azimuth angle θp of 135 degrees. The polarization state PC5 is elliptically polarized light. The polarization state PC6 is linearly polarized light having an azimuth angle θp of 151 degrees. That is, the deviation of the azimuth angle θp due to the deviation of the fast axis FA4 and the fast axis FA5 by 5 degrees is 155−151 = 4 [degrees].

  In addition, as shown in FIG. 12, instead of the low retardation plates 16 and 17, one half-wave plate 19 is used, and the fast axis FA6 of the half-wave plate 19 is in relation to the x-axis. When installed so as to be inclined by 145 degrees, the display light output from the half-wave plate 19 is linearly polarized light having an azimuth angle θp of 155 degrees. The deviation of the azimuth angle θp due to the deviation of the fast axis FA6 of the half-wave plate 19 by 5 degrees is 10 degrees.

The HUD device 1 configured as described above includes a display 3, a plane mirror 4 and a concave mirror 5, and low phase difference plates 16 and 17.
The low phase difference plates 16 and 17 are arranged on a path through which the display light passes to reach the windshield, and generate a phase difference between two polarization components perpendicular to each other in the display light. The sum of the phase differences generated between the two polarization components in the display light by the low retardation plates 16 and 17 is less than π [rad]. In addition, before and after the display light passes through all of the low retardation plates 16 and 17, the polarization direction of the linearly polarized light in the display light changes from 135 degrees to 155 degrees.

Thereby, the HUD apparatus 1 of 2nd Embodiment can suppress the fall of the brightness | luminance of the HUD apparatus 1 resulting from the shift | offset | difference of the polarization direction of linearly polarized light similarly to 1st Embodiment.
In the HUD device 1, the low phase difference plates 16 and 17 are different from each other in the phase difference generated for the display light. The HUD device 1 configured as described above can reduce the deviation of the polarization direction of linearly polarized light as compared with the case where the phase difference generated for the display light is the same between the low phase difference plate 16 and the low phase difference plate 17. Can do.

In the embodiment described above, the low retardation plates 16 and 17 correspond to a plurality of optical elements.
As mentioned above, although one Embodiment of this invention was described, this invention is not limited to the said embodiment, As long as it belongs to the technical scope of this invention, a various form can be taken.

[Modification 1]
For example, in the first embodiment, the low phase difference plates 6 and 7 are used to generate the phase difference. However, the dielectric multilayer film may be used instead of the low phase difference plate to generate the phase difference. Good. Moreover, you may make it produce a phase difference using three or more low phase difference plates. For example, as shown in FIG. 13, a dielectric multilayer film 24 may be provided instead of the plane mirror 4, and low phase difference plates 26, 27, and 29 may be provided instead of the low phase difference plates 6 and 7.

The dielectric multilayer film 24 reflects the display light emitted from the display 3 toward the concave mirror 5. The dielectric multilayer film 24 causes a phase difference between P-polarized light and S-polarized light.
The low phase difference plate 26 is arranged on a path through which the display light irradiated from the display device 3 reaches the dielectric multilayer film 24. The low phase difference plate 27 is disposed on a path through which the display light reflected by the dielectric multilayer film 24 reaches the concave mirror 5. The low phase difference plate 29 is disposed on a path through which the display light reflected by the concave mirror 5 passes before reaching the windshield. The total sum of the phase differences generated between the two polarization components in the display light by the dielectric multilayer film 24 and the low retardation plates 26, 27, and 29 is less than π [rad]. The dielectric multilayer film 24 and the low retardation plates 26, 27, and 29 correspond to a plurality of optical elements.

[Modification 2]
In the first embodiment, the total phase difference generated between the two polarization components in the display light by the low retardation plates 6 and 7 is 0.78π [rad]. FIG. 14 is a graph showing the maximum value (hereinafter, the maximum rotation angle) by which the polarization direction of linearly polarized light can be rotated in the case of using a low phase difference plate that produces the same phase difference. As shown in FIG. 14, in the case where two low retardation plates that generate a phase difference corresponding to 110 nm are used, the maximum rotation angle of the polarization direction of linearly polarized light is about 30 degrees. Note that the maximum rotation angle of the polarization direction of linearly polarized light is smaller as the phase difference is smaller.

  Further, when two low retardation plates that generate a phase difference corresponding to 70 nm are used, the maximum rotation angle of the polarization direction of linearly polarized light is about 10 degrees. Actually, it is necessary to rotate the polarization direction of linearly polarized light by 10 degrees or more using a plurality of low phase difference plates. The total sum of the phase differences generated between the two polarization components in the display light by the low retardation plate that generates a phase difference corresponding to 70 nm is 2 × 70 × 2π / 560 = 0.5π [rad].

For this reason, in the HUD device 1, it is preferable that the total sum of the phase differences generated between the two polarization components in the display light by the low phase difference plates 6 and 7 is π / 2 [rad] or more.
[Modification 3]
In the first embodiment, the low phase difference plates 6 and 7 are installed without being in contact with each other. However, as shown in FIG. 15, the surface where the display light is output in the low retardation plate 6 and the surface where the display light is incident on the low retardation plate 7 are in contact with each other. 7 may be installed in a state of being superposed on each other. As a result, the HUD device 1 can prevent air from being sandwiched between the low phase difference plate 6 and the low phase difference plate 7, so that the display light is reflected when the display light enters the low phase difference plate 7. Can be suppressed. For this reason, the HUD device 1 can suppress a decrease in luminance of the HUD device 1.

[Modification 4]
In the first embodiment, the surface on which the display light is incident on the low retardation plates 6 and 7 is perpendicular to the traveling direction of the display light. However, as shown in FIG. 16, at least one of the low retardation plates 6 and 7 may be arranged such that the surface on which the display light is incident is inclined with respect to the traveling direction of the display light. Good. FIG. 16 shows the low phase difference plates 6 and 7 in which the low phase difference plate 7 is inclined obliquely. As a result, when external light incident on the inside of the housing 2 from the outside of the housing 2 is reflected by the low phase difference plate 7, the reflected light passage path coincides with the display light passage path, and the reflected light Occurrence of a situation where the display light is simultaneously irradiated onto the windshield can be suppressed. For this reason, the HUD device 1 can suppress the occurrence of a situation in which it is difficult for the driver to visually recognize the image formed by the display light.

[Modification 5]
Moreover, in the said 1st Embodiment, what provided the low phase difference plates 6 and 7 was shown. However, the low phase difference plates 6 and 7 may be installed at locations where the fast axis is likely to shift when assembled to the HUD device 1. That is, a half-wave plate may be installed instead of the low retardation plate if the fast axis is difficult to shift when assembled to the HUD device 1. For example, as shown in FIG. 17, the HUD device 1 shown in FIG. 13 may be provided with half-wave plates 36 and 39 instead of the low retardation plates 26 and 29. The dielectric multilayer film 24 and the low retardation film 27 correspond to a plurality of optical elements.

  In addition, the functions of one component in the above embodiment may be distributed as a plurality of components, or the functions of a plurality of components may be integrated into one component. Moreover, you may abbreviate | omit a part of structure of the said embodiment. Further, at least a part of the configuration of the above embodiment may be added to or replaced with the configuration of the other embodiment. In addition, all the aspects included in the technical idea specified only by the wording described in the claim are embodiment of this invention.

  In addition to the HUD device 1 described above, the present invention can be realized in various forms such as a system including the HUD device 1 as a component.

  DESCRIPTION OF SYMBOLS 1 ... Head up display apparatus, 3 ... Display, 4 ... Plane mirror, 5 ... Concave mirror, 6, 7, 16, 17, 26, 27, 29 ... Low phase difference plate, 24 ... Dielectric multilayer film

Claims (6)

An irradiation unit (3, 4, 5) for irradiating display light representing an image to be displayed toward the windshield of the moving body;
A plurality of optical elements (6, 7, 16,...) Disposed on a path through which the display light passes to reach the windshield and causing a phase difference between two mutually perpendicular polarization components in the display light. 17, 24, 26, 27, 29),
The sum of the phase differences generated between the two polarization components in the display light by the plurality of optical elements is less than π [rad];
The head-up display device (1), wherein a polarization direction of linearly polarized light in the display light changes before and after the display light passes through all of the plurality of optical elements. 2. The head-up display according to claim 1, wherein a total sum of the phase differences generated between the two polarization components in the display light by the plurality of optical elements is π / 2 [rad] or more. apparatus. The head-up display device according to claim 1 or 2, wherein each of the plurality of optical elements (6, 7) is installed without being in contact with other optical elements. The at least two optical elements (6, 7) of the plurality of optical elements are installed in a state of being overlapped with each other. Head-up display device. At least one optical element (7) of the plurality of optical elements is a phase difference plate that causes the phase difference between a polarization component parallel to a fast axis and a polarization component perpendicular to the fast axis,
The retardation film is disposed in a state where a plane on which the display light is incident is inclined with respect to a traveling direction of the display light. The head-up display device described. The head-up display device according to any one of claims 1 to 5, wherein the plurality of optical elements (16, 17) are different from each other in the phase difference generated for the display light. .