43 may be defined as an effective area through which light passes when light from the imaging device 2 is incident on the polarization mirror 4, and it is desirable to specially process the parts excluding this effective area to prevent light reflection.

The polarization reflection area 44 may comprise a processed portion 45 formed on the surface 41 (see FIG. 1) of the polarization mirror 4 facing the imaging device 2. The processed portion 45 may comprise an etched surface on the surface 41 facing the imaging device 2, or may comprise a black painted surface on the surface of the polarization mirror 4 facing the imaging device 2. The processed portion 45 may be formed in a closed loop cross-sectional shape on the surface of the polarization mirror 4 facing the imaging device 2.

This processed portion 45 may improve problems such as double images, which deteriorate image performance due to reflection occurring in surfaces other than the transmission area 43.

FIG. 4 (a) is an example in which the effective area is located approximately in the center of the polarization mirror 4, FIG. 4 (b) is an example in which the effective area is located lower than in FIG. 4 (a), and FIG. 4 (b) is an example in which the effective area is located higher than in the case in FIG. 4 (a).

The effective area may be determined according to the height or position of the imaging device 2, and the polarization mirror 4 may be different according to the height or position of the imaging device 2.

The area of the polarization mirror 4 in which the processed portion 45 is not formed may be defined as the transmission area 43, and the area of the polarization mirror 4 other than the transmission area 43 may be defined as the polarization reflection area 44.

FIG. 5 is a longitudinal cross-sectional view of the polarization mirror illustrated in FIG. 1, and FIG. 6 is a cross-sectional view of the polarization mirror illustrated in FIG. 1.

The polarization mirror 4 may comprise a polarization film 46 and a lens 47 on which the polarization mirror 45 is disposed, and the processed portion 45 may be formed in a partial area of the front surface of the lens 47.

An area of the lens 47 where the processed portion 45 is not formed may be a transmission area 43, and an area of the lens 47 where the processed portion 45 is formed may be a reflection area.

The front surface of the polarization mirror 4 may be the surface of the lens 47 where the processed portion 45 is formed, and the rear surface of the polarization mirror 4 may be the rear surface of the polarization film 46.

The front surface of the polarization mirror 4 may be convex, and the rear surface of the polarization mirror 4 may be concave.

The second linearly polarized light S generated from the phase retardation mirror 5 may be reflected from the front and rear surfaces of the lens 47, respectively.

In the polarization mirror 4, an image by light reflected by the windshield WS after the lens 47 is reflected from the rear surface, and an image by the light reflected by the windshield WS after the lens 47 is reflected from the front surface may be formed to overlap each other.

The thickness of the polarization mirror 4 in the vertical direction Z and the thickness of thereof in the left and right directions Y may not be constant.

The front and rear surfaces of the polarization mirror 4 are not parallel, and the thickness t1 of the upper end 48 of the polarization mirror 4 may be different from the thickness t2 of the lower end 49 of the polarization mirror 4.

The polarization mirror 4 may have a wedge shape. The polarization mirror 4 may have a wedge shape in the vertical direction. The polarization mirror 4 may have a wedge shape, and a thickness of the wedge shape gradually becomes thinner.

The thickness t1 of the upper end 48 of the polarization mirror 4 illustrated in FIGS. 1 and 5 may be thinner than the thickness t2 of the lower end 49. The polarization mirror 4 illustrated in FIGS. 1 and 5 may be formed in a shape whose thickness becomes thinner as it goes from the lower end 49 to the upper end 48, and in this case, the image by the light reflected by the windshield WS after the lens 47 is reflected from the rear surface and the image by the light reflected by the windshield WS after the lens 47 is reflected from the front surface may at least partially overlap.

As illustrated in FIG. 6, the thickness of the polarization mirror 4 may not be constant in the left and right direction Y. The thickness of the left end 50a of the polarization mirror 4 and the thickness of the right end 40b of the polarization mirror 4 may be different from the thickness t4 of the central portion 50c of the polarization mirror 4.

The thickness t3 of the left end 50a of the polarization mirror 4 and the thickness t3 of the right end 40b of the polarization mirror 4 may be thicker than the thickness t4 of the central portion 50c of the polarization mirror 4.

The polarization mirror 4 may be symmetrical in the left and right direction Y, or the polarization mirror 4 may also be asymmetrical.

When the polarization mirror 4 is asymmetric, the thickness of the left end 50a of the polarization mirror 4 and the thickness of the right end 40b of the polarization mirror 4 may be different, and the thickness of the left end 50a of the polarization mirror 4 and the thickness of the right end 40b of the polarization mirror 4 may each be thicker than the thickness t4 of the central portion 50c of the polarization mirror 4.

An example of the polarization mirror 4 may be a concave mirror with a concave rear surface, and the radius of curvature of the front surface may be different from the radius of curvature of the rear surface.

The surface 42 of the polarization mirror 4 facing the phase retardation mirror 5 may be concave.

The radius of curvature of the front surface of the polarization mirror 4 may be larger than the radius of curvature of the rear surface of the polarization mirror 4.

FIG. 7 is a view illustrating a first modified example of an example of a head-up display according to this embodiment.

In the first modified example of an example of the head-up display, the configuration other than the polarization mirror 4 may be the same as the configuration of an example of the head-up display illustrated in FIGS. 1 to 3, and the description of the housing 1, the imaging device 2, and the phase retardation mirror 5 is omitted to avoid redundant description.

In the head-up display illustrated in FIG. 7, the thickness t1 of the upper end 48 of the polarization mirror 4 may be thicker than the thickness t2 of the lower end 49 of the polarization mirror 4. In this case, the polarization mirror 4 may be formed in a shape whose thickness increases from the lower end 49 to the upper end 48.

In the polarization mirror 4 illustrated in FIG. 7, at least part of an image by light reflected by the windshield WS after the lens 47 is reflected from the rear surface and an image by light reflected by the windshield WS after the lens 47 is reflected from the front surface may overlap.

In the polarization mirror 4 illustrated in FIG. 7, other configurations except that the thickness t1 of the upper end 48 is thicker than the thickness t2 of the lower end 49 may be the same as the polarization mirror 4 illustrated in FIGS. 1 and 3 to 6, and detailed description thereof will be omitted to avoid redundant description.

FIG. 8 is a view illustrating a second modified example of an example of a head-up display according to this embodiment.

In the second modified example of an example of the head-up display, the configuration other than the polarization mirror 4 may be the same as the example of the head-up display illustrated in FIGS. 1 to 3, and descriptions of the housing 1, the imaging device 2, and the phase retardation mirror 5 are omitted to avoid redundant explanation.

In the head-up display illustrated in FIG. 8, the surface 42 of the polarization mirror 4 facing the phase retardation mirror 5 may be a flat surface.

The front and rear surfaces of the polarization mirror 4 may be flat surfaces that are neither concave nor convex.

The thickness t1 of the upper end 48 of the polarization mirror 4 may be thinner than the thickness t2 of the lower end 49 of the polarization mirror 4. The polarization mirror 4 illustrated in FIG. 5 may be formed in a shape whose thickness becomes thinner from the lower end 49 to the upper end 48.

The polarization mirror 4 may be formed in a shape whose thickness becomes thinner linearly from the lower end 49 to the upper end 48.

FIG. 9 is a view illustrating a third modified example of an example of a head-up display according to this embodiment.

In the third modified example of an example of a head-up display, the configuration other than the polarization mirror 4 may be the same as the example of the head-up display illustrated in FIGS. 1 to 3, and descriptions of the housing 1, the imaging device 2, and the phase retardation mirror 5 are omitted to avoid redundant explanation.

In the head-up display illustrated in FIG. 9, the front and rear surfaces of the polarization mirror 4 may be flat without being concave or convex, and the thickness t1 of the upper end 48 may be thicker than the thickness t2 of the lower end 49. The polarization mirror 4 illustrated in FIG. 9 may be formed in a shape whose thickness increases from the lower end 49 to the upper end 48.

FIG. 10 is a view illustrating an example of a head-up display according to this embodiment saving space in a vehicle.

As illustrated in FIG. 10, an example of a head-up display may be assembled to a frame 31 installed in a vehicle and may be spaced apart from the steering 32 and the brake 33. An example of a head-up display may be disposed in a space formed below the dashboard skin 34.

One example of a head-up display may reduce the overall height (length in the vertical direction) and occupy a relatively small volume when mounted in a vehicle.

As an example, the head-up display may increase the degree of freedom of the space formed below the dashboard skin 34.

A space OS may be secured between an example of the head-up display and the steering 32 and between an example of the head-up display and the brake 33 by using the example of the head-up display.

The polarization mirror 4 functions to transmit and reflect light, and when double or triple images are generated by the polarization mirror (4), image performance may deteriorate.

As in this embodiment, when the wedge-shaped polarization mirror 4 is applied, double and triple images may be minimized, and degradation of image performance provided by the head-up display may be minimized.

Hereinafter, the optical path of an example of a head-up display will be described as follows.

The imaging device 2 may emit first linearly polarized light P, and the first linearly polarized light P emitted from the imaging device 2 passes through the transmission area 43 of the polarization mirror 4 and then may be incident on a phase retardation mirror 5.

The phase retardation mirror 5 may phase retard and reflect the first linearly polarized light P and convert it into the second linearly polarized light S, and the second linearly polarized light S may be incident on the polarization mirror 4.

The second linearly polarized light S incident on the polarization mirror 4 may be reflected by the polarization reflection area 44, and the second linearly polarized light S reflected by the polarization mirror 4 is transmitted to the windshield WS, and the driver may recognize the virtual image I of the position in front of the windshield WS.

FIG. 11 is a view illustrating another example of a head-up display according to this embodiment.

In another example of a head-up display, as illustrated in FIG. 11, the imaging device 2′ may be located behind the polarization mirror 4′, and the phase retardation mirror 5′ may be located in the front of the polarization mirror 4′.

The imaging device 2′ may emit the first linearly polarized light P from behind the polarization mirror 4′ toward the polarization mirror 4′. The front surface of the imaging device