Head-up displays and display devices

Abstract

To provide a head-up display suppressing deterioration in visibility of a virtual image generated when reflected light from the outside overlaps with the virtual image.SOLUTION: A head-up display 1 comprises a light source 20, a liquid crystal panel 40 for transmitting light from the light source 20 to project an image, and a prism sheet 50 for refracting the light transmitted through the liquid crystal panel 40. The prism sheet 50 includes a sheet surface 51 parallel to a plate surface of the liquid crystal display panel 40, and a plurality of prisms 52 facing the plate surface of the liquid crystal display panel 40 on the opposite side of the sheet surface 51 and disposed in parallel. Each of the plurality of prisms 52 is formed into a square cross section by a first prism surface 52a inclined to the sheet surface 51 and a second prism surface 52b inclined to the sheet surface 51 and whose angle formed with the sheet surface 51 is larger than that of the first prism surface 52a, where an angle formed by the first prism surface 52a and the sheet surface 51 is 35° or more.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a head-up display and a display device.

Background Art

[0002] A display device applied to a vehicle head-up display device that projects an image onto a translucent body such as a windshield and allows a user to visually recognize a virtual image is known (for example, Patent Document 1). The display device includes a backlight, a liquid crystal display panel that projects an image by transmitting the light of the backlight, a prism sheet that refracts the light transmitted through the liquid crystal display panel, and a housing.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the display device of Patent Document 1, when light from the outside such as sunlight is reflected by a prism sheet or the like and the reflected light overlaps with the virtual image, the visibility of the virtual image may be reduced.

[0005] The present disclosure has been made in view of the above problems, and an object thereof is to suppress a decrease in the visibility of a virtual image caused by the reflected light from the outside overlapping with the virtual image in a head-up display and a display device.

Means for Solving the Problems

[0006] The head-up display of this disclosure comprises a light source, a liquid crystal panel that transmits light from the light source and projects an image, and a prism sheet that refracts the light transmitted through the liquid crystal panel, wherein the prism sheet has a sheet surface parallel to the surface of the liquid crystal panel, and a plurality of prisms arranged in parallel opposite to the sheet surface and facing the surface of the liquid crystal panel, each of the plurality of prisms having a first prism surface inclined with respect to the sheet surface, and a second prism surface inclined with respect to the sheet surface and having an angle greater than that of the first prism surface, and the angle between the first prism surface and the sheet surface is 35° or more.

[0007] Furthermore, the display device of this disclosure comprises a light source, a liquid crystal panel that transmits light from the light source and projects an image, and a prism sheet that refracts the light transmitted through the liquid crystal panel. The prism sheet has a sheet surface parallel to the surface of the liquid crystal panel, and a plurality of prisms arranged in parallel, facing the surface of the liquid crystal panel on the opposite side of the sheet surface. Each of the plurality of prisms is formed in a cross-sectional angle by a first prism surface inclined with respect to the sheet surface, and a second prism surface inclined with respect to the sheet surface and having an angle greater than that of the first prism surface. The angle between the first prism surface and the sheet surface is 35° or more. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a schematic diagram of a head-up display according to an embodiment. [Figure 2] Figure 2 is a schematic diagram of the light source and image output unit. [Figure 3] Figure 3 is an enlarged side view of the prism sheet. [Figure 4] Figure 4 shows the propagation and reflection of external light in the image output section. [Figure 5] Figure 5 shows an example of the simulation results for reflected light. [Figure 6]Figure 6 is a schematic diagram of an image output unit according to a modified embodiment. [Modes for carrying out the invention]

[0009] The embodiments of this disclosure will be described below with reference to the drawings. This disclosure is not limited to the embodiments described below. Furthermore, the components described below include those that are readily conceivable to those skilled in the art, and those that are substantially the same. In addition, the components described below can be combined as appropriate.

[0010] Furthermore, the disclosure is merely an example, and modifications that a person skilled in the art could easily conceive of while maintaining the spirit of the invention are naturally included within the scope of this disclosure. In addition, the drawings may schematically represent the width, thickness, shape, etc. of each part in order to clarify the explanation, but these are merely examples and do not limit the interpretation of this disclosure. In addition, in this specification and each drawing, elements similar to those described above in previously shown drawings are denoted by the same reference numerals, and detailed explanations may be omitted as appropriate.

[0011] In the drawings, the Dx direction is the height direction of the head-up display 1, the Dy direction is the width direction of the head-up display 1, and the Dz direction is the depth direction of the head-up display 1. Note that the directions Dx, Dy, and Dz are examples, and this disclosure is not limited to these directions.

[0012] Figure 1 is a schematic diagram of a head-up display according to an embodiment. The head-up display (hereinafter referred to as HUD) 1 is an example of a display device that projects an image onto a translucent body 2 to allow the user U to view a virtual image VG. The translucent body 2 is, for example, a windshield, but is not limited to this; any configuration on which the image of the HUD 1 is projected is acceptable.

[0013] The HUD1 comprises a housing 10, a light source 20, an image output unit 30, and an optical element 70. The housing 10 is box-shaped and includes the light source 20, the image output unit 30, and the optical element 70.

[0014] Figure 2 is a schematic diagram of the light source and image output unit. The light source 20 has a light-emitting element (not shown), such as an LED (Light Emitting Diode), inside a rectangular parallelepiped case. The light source 20 irradiates the image output unit 30 with light. The optical axis of the light emitted from the light source 20 is perpendicular to the light source emission surface 21 of the light source 20. The light source emission surface 21 is parallel to the Dy direction and is inclined around an axis (not shown; hereinafter referred to as the Dy axis) parallel to the Dy direction with respect to the output axis Vz. The output axis Vz is the axis along which the optical axis of the emitted light Lc, which will be described later, emitted from the image output unit 30 is aligned. Specifically, the output axis Vz is parallel to the Dz direction and extends from the image output unit 30 toward the optical element 70.

[0015] The angle between the perpendicular V1 of the light source emission surface 21 and the output axis Vz is called the first inclination angle θ1. The first inclination angle θ1 is acute. The light source emission surface 21 may be perpendicular to the output axis Vz, rather than being inclined. In this case, the first inclination angle θ1 is zero.

[0016] Light emitted from the light source 20 is incident on the image output unit 30 as incident light La. The optical axis of the incident light La is parallel to the perpendicular V1. The image output unit 30 transmits and refracts the incident light La and emits output light Lc along the output axis Vz. The image output unit 30 comprises a liquid crystal panel 40, a prism sheet 50, and a support 60.

[0017] The liquid crystal panel 40 projects an image by transmitting light from the light source 20. The liquid crystal panel 40 is a transmissive liquid crystal display panel. The liquid crystal panel 40 has a panel incident surface 41 facing the light source 20, to which light from the light source 20 enters as incident light La, and a panel exit surface 42 to which the incident light La is emitted as transmitted light after passing through the liquid crystal panel 40.

[0018] The panel incident surface 41 and the panel exit surface 42 are parallel to each other. Also, the panel incident surface 41 and the panel exit surface 42 are inclined about the Dy axis with respect to the light source exit surface 21.

[0019] The liquid crystal panel 40 has a plurality of pixels driven by an active matrix system. The plurality of pixels are two-dimensionally arranged along the plate surface of the liquid crystal panel 40. In an image output region (not shown) where the plurality of pixels are arranged, a light transmission pattern corresponding to an image projected as a virtual image VG is formed by individually controlling the plurality of pixels. Thereby, when the incident light La passes through the image output region, the amount of light is adjusted and emitted as transmitted light. The optical axis of the incident light La and the optical axis of the transmitted light are parallel to each other.

[0020] The prism sheet 50 refracts the light transmitted through the liquid crystal panel 40. Specifically, the prism sheet 50 refracts the transmitted light emitted from the panel exit surface 42 and emits it along the output axis Vz as the emitted light Lc. That is, the optical axis of the emitted light Lc is inclined with respect to the optical axis of the incident light La parallel to the optical axis of the transmitted light. The prism sheet 50 emits the emitted light Lc toward the optical member 70. The prism sheet 50 has a sheet surface 51 and a plurality of prisms 52.

[0021] The sheet surface 51 is parallel to the plate surface of the liquid crystal panel 40. Specifically, the sheet surface 51 is parallel to the panel exit surface 42 of the liquid crystal panel 40. Also, the sheet surface 51 and the panel exit surface 42 are inclined about the Dy axis with respect to the output axis Vz. The angle formed by the perpendicular V2 to the sheet surface 51 and the output axis Vz is referred to as the second inclination angle θ2.

[0022] The second inclination angle θ2 corresponds to the emission angle of the emitted light Lc emitted from the sheet surface 51. The second inclination angle θ2 is an acute angle and is larger than the first inclination angle θ1. Note that the second inclination angle θ2 may be the same angle as the first inclination angle θ1.

[0023] The multiple prisms 52 are facing the surface of the liquid crystal panel 40 on the side opposite to the sheet surface 51. Specifically, the multiple prisms 52 are facing the panel emission surface 42 of the liquid crystal panel 40.

[0024] Figure 3 is an enlarged side view of the prism sheet 50. The multiple prisms 52 are arranged on a plane S parallel to the sheet surface 51. Each of the multiple prisms 52 is formed in a rectangular cross-section by a first prism surface 52a and a second prism surface 52b.

[0025] The first prism surface 52a and the second prism surface 52b are each inclined with respect to the sheet surface 51 around the Dy axis. The angle between the second prism surface 52b and the sheet surface 51 is greater than that between the second prism surface 52a and the sheet surface 51. In other words, the first prism angle α of the first prism surface 52a with respect to the sheet surface 51 is smaller than the second prism angle β of the second prism surface 52b with respect to the sheet surface 51. Details of the first prism angle α and the second prism angle β will be described later.

[0026] Furthermore, the multiple prisms 52 are arranged in parallel. Specifically, the edges R formed by the first prism surface 52a and the second prism surface 52b of each of the multiple prisms 52 are arranged along the Dy axis. In other words, the multiple prisms 52 are arranged so that their respective edges R are parallel to each other.

[0027] Furthermore, in two adjacent prisms 52 among the multiple prisms 52, the first prism surface 52a of one prism 52 and the second prism surface 52b of the other prism 52 are formed continuously. In other words, the plane S is not exposed.

[0028] As shown in Figure 2, the support 60 supports the liquid crystal panel 40 and the prism sheet 50. The support 60 includes a first support portion 61 that supports the liquid crystal panel 40 and a second support portion 62 that supports the prism sheet 50. The first support portion 61 supports the peripheral edge of the panel incident surface 41 and is bonded to the peripheral edge of the panel incident surface 41 by adhesive or the like. The first support portion 61 also supports the second support portion 62. The second support portion 62 supports the peripheral edge of the sheet surface 51 and is bonded to the peripheral edge of the sheet surface 51 by adhesive or the like.

[0029] As shown by the dashed arrow in Figure 1, the optical member 70 guides the emitted light Lc to the light-transmitting body 2 through the opening 11 of the housing 10. Specifically, the optical member 70 is a concave mirror. The optical member 70 may also be composed of multiple concave mirrors and reflecting mirrors.

[0030] The emitted light Lc guided by the optical element 70 is projected onto the translucent body 2. User U, who directs their gaze towards the emitted light Lc projected onto the translucent body 2, sees the virtual image VG.

[0031] As described above, the emitted light Lc from the image output unit 30 is emitted along the output axis Vz, and the panel output surface 42 of the liquid crystal panel 40 is inclined around the Dy axis with respect to the output axis Vz. As a result, the user U can perceive the virtual image VG as having a three-dimensional effect in the Dz direction.

[0032] Furthermore, as described above, the light source emission surface 21 of the light source 20 is inclined around the Dy axis with respect to the output axis Vz. In this case, compared to the case where the light source emission surface 21 is perpendicular to the output axis Vz, the incident angle of the incident light La emitted from the light source emission surface 21 and incident on the panel incident surface 41 becomes smaller. This makes it possible to suppress the decrease in brightness of the light that forms the virtual image VG and the contrast of the virtual image VG.

[0033] Next, the first prism angle α and the second prism angle β will be explained in detail. The first prism angle α and the second prism angle β are defined as the angles at which the transmitted light emitted from the panel emission surface 42 of the liquid crystal panel 40 is refracted along the output axis Vz.

[0034] Furthermore, in the HUD1, external light such as sunlight (hereinafter referred to as external light) Lg may enter the housing 10 through the opening 11, travel along the output axis Vz in the opposite direction to the direction of travel of the emitted light Lc, and be reflected by the prism sheet 50, etc. If this reflected light overlaps with the virtual image VG, the visibility of the virtual image VG will decrease. The first prism angle α and the second prism angle β are set to angles that suppress the overlap of reflected light with the virtual image VG. Specifically, the first prism angle α and the second prism angle β are set based on the reflection angle of the reflected light shown below.

[0035] Figure 4 shows the propagation and reflected light of external light in the image output unit. In Figure 4, the propagation of external light Lg is shown by a dashed line. The reflected light is the light emitted from the image output unit 30 after the external light Lg is reflected by the prism sheet 50 and the panel emission surface 42. The reflection angle of the reflected light is defined as the angle between the optical axis of the reflected light and the output axis Vz.

[0036] Figure 4 shows the case where the second inclination angle θ2 of the sheet surface 51 and the panel emission surface 42 with respect to the output axis Vz is 45°, the first prism angle α is 40°, and the second prism angle β is 90°.

[0037] The external light Lg travels along the output axis Vz and reaches point A on the sheet surface 51. A portion of the external light Lg that reaches point A is reflected at point A on the sheet surface 51. The external light Lg reflected at point A is called the first reflected light Lr1, and the reflection angle of the first reflected light Lr1 is called the first reflection angle θr1. The first reflected light Lr1 is reflected once at point A on the sheet surface 51.

[0038] Furthermore, external light Lg that is not reflected at point A on the sheet surface 51 is refracted at point A and enters the prism sheet 50, and is refracted at point B on the first prism surface 52a and exits from the prism sheet 50. The angle at which the external light Lg is refracted depends on the relative refractive index of the material of the prism sheet 50 and the air outside the prism sheet 50.

[0039] A portion of the external light Lg emitted from point B on the first prism surface 52a is reflected at point C on the second prism surface 52b, and further reflected at point D on the panel emission surface 42. The external light Lg reflected at point D is refracted at point E on the first prism surface 52a and enters the prism sheet 50, and is refracted at point F on the sheet surface 51 and exits from the prism sheet 50. The external light Lg emitted from point F is called the second reflected light Lr2, and the reflection angle of the second reflected light Lr2 is called the second reflection angle θr2.

[0040] The second reflected light Lr2 is reflected a total of two times at point C on the second prism surface 52b and at point D on the panel emission surface 42. The prism sheet 50 and the liquid crystal panel 40 have a specific reflectivity (e.g., 8%) based on their materials. Therefore, the more times there are reflections, the lower the light intensity. The second reflected light Lr2 is reflected more times than the first reflected light Lr1, and the light intensity of the second reflected light Lr2 is lower than that of the first reflected light Lr1.

[0041] On the other hand, the external light Lg that was not reflected at point C on the second prism surface 52b is refracted at point C and incident on the prism sheet 50, and is refracted at point G on the first prism surface 52a and exits from the prism sheet 50. The external light Lg that exits from point G is reflected at point H on the panel exit surface 42, and is further refracted at point I on the first prism surface 52a and incident on the prism sheet 50, and is refracted at point J on the sheet surface 51 and exits from the prism sheet 50. The external light Lg that exits from point J is called the third reflected light Lr3, and the reflection angle of the third reflected light Lr3 is called the third reflection angle θr3.

[0042] The third reflected light Lr3 is reflected once at point H on the panel emission surface 42. The second reflected light Lr2 is reflected more times than the third reflected light Lr3, and the light intensity of the second reflected light Lr2 is less than that of the third reflected light Lr3. When the light intensity of the reflected light is relatively small, as with the second reflected light Lr2, the visibility of the virtual image VG does not decrease even if the reflected light overlaps with the virtual image VG.

[0043] Furthermore, if the reflected light is significantly tilted with respect to the output axis Vz, the reflected light does not overlap with the virtual image VG, and the reduction in the visibility of the virtual image VG is suppressed. Therefore, the first prism angle α and the second prism angle β are determined so that the reflected light with one reflection is tilted relatively significantly with respect to the output axis Vz. In other words, the first prism angle α and the second prism angle β are determined so that the first reflection angle θr1 and the third reflection angle θr3, which are the reflection angles of the optical axes of the first reflected light Lr1 and the third reflected light Lr3 with respect to the output axis Vz, respectively, are relatively large. It is also desirable that the second reflection angle θr2 of the second reflected light Lr2 with respect to two reflections be relatively large.

[0044] Figure 4 illustrates the propagation of external light Lg when it reaches point A on the prism sheet 50. However, external light Lg may also reach points other than point A on the prism sheet 50, resulting in reflected light with a different reflection angle from the first reflected light Lr1, second reflected light Lr2, and third reflected light Lr3 shown in Figure 4. Therefore, when determining the first prism angle α and the second prism angle β, a simulation is performed to derive the reflection angle of the reflected light based on multiple external light Lg points that enter the prism sheet 50 at different positions.

[0045] Figure 5 shows an example of the simulation results for reflected light. In Figure 5, the second inclination angle θ2 of the sheet surface 51 and the panel exit surface 42 with respect to the output axis Vz is 45°, the first prism angle α is 40°, and the second prism angle β is 90°. 100 light rays, representing external light Lg along the output axis Vz, are incident on the sheet surface 51 from different positions.

[0046] External light Lg incident on the sheet surface 51 is reflected and refracted by the sheet surface 51 and the prism 52 as described above, and is emitted from the sheet surface 51 as multiple reflected rays Lr. The number of reflections is limited to one. However, total internal reflection is not counted as a reflection.

[0047] Table 1 shows an example of the simulation results for reflected light Lr. Table 1 shows the smallest reflection angle among multiple reflected light Lr for each case where the second inclination angle θ2 of the sheet surface 51 and the panel exit surface 42 with respect to the output axis Vz is 45°, and the second prism angle β is 90°, and the first prism angle α is changed in 5° increments from 20° to 50°.

[0048] The larger the reflection angle of the reflected light Lr, the more the reflected light Lr is tilted with respect to the output axis Vz, and the less it overlaps with the virtual image VG. In other words, a larger reflection angle indicates better results.

[0049] In Table 1, when the first prism angle α is 35° or greater, the reflection angle is relatively large. In other words, it is preferable that the first prism angle α is 35° or greater. Furthermore, it is more preferable that the first prism angle α is between 35° and 45°.

[0050] [Table 1]

[0051] Furthermore, if the first prism angle α is less than 20°, the incident angle of the incident light La that exits from the light source emission surface 21 and enters the panel incidence surface 41 becomes larger, resulting in a reduced improvement in the brightness of the light forming the virtual image VG and the contrast of the virtual image VG. Also, if the first prism angle α is greater than 50°, the prism sheet 50 cannot refract the transmitted light from the liquid crystal panel 40 along the output axis Vz. Therefore, in the simulation, the first prism angle α is set to between 20° and 50°.

[0052] Table 2 shows an example of the simulation results for reflected light Lr. Table 2 shows the smallest reflection angle among multiple reflected light Lr for each case where the second inclination angle θ2 of the sheet surface 51 and the panel exit surface 42 with respect to the output axis Vz is 45°, and the first prism angle α is 40°, and the second prism angle β is changed in 5° increments from 60° to 90°.

[0053] In Table 2, when the second prism angle β is 75° or less, the reflection angle is relatively large. In other words, it is preferable that the second prism angle β is 75° or less.

[0054] [Table 2]

[0055] Furthermore, when the second prism angle β is less than 60°, the amount of light that passes through the liquid crystal panel 40 and incident on the second prism surface 52b is relatively large, and the amount of light that passes through the prism sheet 50 in the Vz direction is relatively small, resulting in a relatively low brightness of the emitted light Lc. Also, when the second prism angle β is greater than 90°, the second prism surface 52b becomes an inverse tapered surface, increasing the difficulty of manufacturing the prism sheet 50. For this reason, the second prism angle β is set to a range of 60° to 90° in the simulation.

[0056] As described above, it is preferable that the first prism angle α is 35° or more, and the second prism angle β is 75° or less. In other words, when the prism sheet 50 is composed of multiple prisms 52, each having a first prism angle α of 35° or more and a second prism angle β of 75° or less, the reflected light Lr of the external light Lg does not overlap with the virtual image VG, and the decrease in the visibility of the virtual image VG is suppressed.

[0057] Furthermore, by combining the first prism angle α and the second prism angle β, which showed favorable results in Tables 1 and 2, the reflection angle of reflected light Lr with two reflections was derived through simulation.

[0058] Table 3 shows an example of simulation results for reflected light Lr with two reflections. Table 3 shows the smallest reflection angle among multiple reflected light Lr for each case where the second inclination angle θ2 of the sheet surface 51 and the panel exit surface 42 with respect to the output axis Vz is 45°, the first prism angle α is 35° and 40°, and the second prism angle β is 70° and 75°.

[0059] Table 3 shows that some reflected light Lr have relatively small reflection angles. However, this simulation involves only two reflections, the intensity of the reflected light Lr is relatively weak, and only 1-2 of the 100 reflected light Lr have relatively small reflection angles. Therefore, the impact of reflected light Lr with relatively small reflection angles on virtual image visibility is extremely small. Furthermore, even in the simulation results for reflected light Lr with two reflections, when the first prism angle α is 40° and the second prism angle β is 70°, the reflection angle is relatively large even for reflected light Lr with two reflections, showing particularly good results.

[0060] [Table 3]

[0061] Furthermore, when the first prism angle α is set to 35° or more and 40° or less, and the second prism angle β is set to 70° or more and 75° or less, the transmitted light from the liquid crystal panel 40 can be refracted by the prism sheet 50 along the output axis Vz, and the prism sheet 50 is easy to manufacture.

[0062] Furthermore, in the above simulation, the second tilt angle θ2 of the sheet surface 51 and the panel emission surface 42 with respect to the output axis Vz is 45°. However, even in simulations where the second tilt angle θ2 is different from 45°, similar to the results of the above simulation, when the first prism angle α is 35° or less and the second prism angle β is 75° or less, the reflection angle is relatively large and good results are obtained. Note that when the second tilt angle θ2 is in the range of 45±3°, good results similar to those when the second tilt angle θ2 is 45° are obtained. Moreover, in simulations where the second tilt angle θ2 is different from 45°, when the first prism angle α is 35° and 40° and the second prism angle β is 70°, the reflection angle is relatively large and good results are obtained even for reflected light Lr with 2 reflections. Note that when the second tilt angle θ2 is in the range of 45±3°, good results similar to those when the second tilt angle θ2 is 45° are obtained.

[0063] Furthermore, any other effects and advantages brought about by the embodiments described above that are obvious from this specification or that can be appropriately conceived by a person skilled in the art are naturally provided by this disclosure.

[0064] Figure 6 is a schematic diagram of an image output unit according to a modified embodiment. The modified image output unit 30 further includes a diffuser plate 180 between the liquid crystal panel 40 and the prism sheet 50. The diffuser plate 180 is attached to the panel emission surface 42. The diffuser plate 180 diffuses and transmits the incident light. The diffuser plate 180 can reduce moiré caused by light interference. In addition, the diffuser plate 180 suppresses the amount of reflected light Lr that is reflected at the panel emission surface 42 and emitted from the sheet surface 51. Therefore, the diffuser plate 180 can suppress a decrease in the visibility of the virtual image VG.

[0065] Furthermore, this disclosure is also applicable to display devices other than HUD1, such as navigation systems, smartphones, tablets, and VR (Virtual Reality) goggles. [Explanation of Symbols]

[0066] 1. Head-up display 20 light source 30 Image output section 40 LCD panels 42 Panel ejection surface (the surface of the LCD panel) 50 prism sheets 51 Seat surface 52 Prisms 52a First prism surface 52b Second prism surface

Claims

1. Light source and A liquid crystal panel that transmits light from the aforementioned light source and projects an image, The system comprises a prism sheet that refracts light transmitted through the liquid crystal panel, The prism sheet is A sheet surface parallel to the surface of the aforementioned liquid crystal panel, It has a plurality of prisms arranged in parallel, facing the surface of the liquid crystal panel on the opposite side of the sheet surface, Each of the multiple prisms is formed in a cross-sectional angular shape by a first prism surface inclined with respect to the sheet surface and a second prism surface inclined with respect to the sheet surface and having an angle with respect to the sheet surface that is greater than that of the first prism surface. The angle between the first prism surface and the sheet surface is 35° or greater. Head-up display.

2. The angle between the second prism surface and the sheet surface is 75° or less. The head-up display according to claim 1.

3. The angle between the first prism surface and the sheet surface is 35° or more and 40° or less. The angle between the second prism surface and the sheet surface is 70° or more and 75° or less. The head-up display according to claim 1.

4. In two adjacent prisms, the first prism surface of one prism and the second prism surface of the other prism are formed continuously. The head-up display according to claim 1.

5. Light source and A liquid crystal panel that transmits light from the aforementioned light source and projects an image, The system comprises a prism sheet that refracts light transmitted through the liquid crystal panel, The prism sheet is A sheet surface parallel to the surface of the aforementioned liquid crystal panel, It has a plurality of prisms arranged in parallel, facing the surface of the liquid crystal panel on the opposite side of the sheet surface, Each of the multiple prisms is formed in a cross-sectional angular shape by a first prism surface inclined with respect to the sheet surface and a second prism surface inclined with respect to the sheet surface and having an angle with respect to the sheet surface that is greater than that of the first prism surface. The angle between the first prism surface and the sheet surface is 35° or greater. Display device.

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