JP7002061B2 - Display device - Google Patents

Description

The present disclosure relates to a display device for displaying an image.

A so-called electronic mirror is known in which a camera mounted on a vehicle captures the rear of the vehicle and a rear-view image captured by the camera is displayed on a rear-view mirror type display device in the vehicle (see, for example, Patent Document 1). ).

The display device of Patent Document 1 includes a housing, a display, a half mirror, and a concave mirror. The display, half mirror and concave mirror are arranged inside the housing. The display shows a rear image taken by the camera.

The light emitted from the display is reflected by the half mirror and then incident on the concave mirror. The emitted light reflected by the concave mirror passes through the half mirror and then enters the driver's eyes. By seeing the rear image reflected by the concave mirror, the driver appears to the driver that the virtual image of the rear image is displayed at the display position in front of the vehicle rather than the concave mirror.

Japanese Unexamined Patent Publication No. 2017-210229

In the display device of Patent Document 1, the distance from the driver's eyes to the display position of the virtual image (hereinafter referred to as "viewing distance") is until the light emitted from the display reaches the concave mirror via the half mirror. Determined by the optical path length. Therefore, in order to secure the viewing distance, it is necessary to set the optical path length to a predetermined length, but the distance between each component (display, half mirror and concave mirror) becomes longer by that amount, and the housing However, there is a problem that the size of the mirror increases.

Therefore, the present disclosure provides a display device capable of miniaturization while ensuring a viewing distance.

The display device according to one aspect of the present disclosure includes a display element having a display surface for displaying an image, at least two mirrors that reflect light emitted from the display surface of the display element, and a polarizing element. The polarizing element has a configuration capable of reflecting and transmitting the emitted light, and the emitting light is reflected by at least two mirrors and emitted to the outside of the display device. It is reflected twice and transmitted once through the polarizing element.

According to the display device according to one aspect of the present disclosure, it is possible to reduce the size while ensuring the viewing distance.

It is a figure which shows an example of the vehicle which mounted the display device which concerns on Embodiment 1. FIG. It is sectional drawing of the display device which concerns on Embodiment 1. FIG. It is sectional drawing of another embodiment of the display device which concerns on Embodiment 1. FIG. It is sectional drawing of still another form of the display device which concerns on Embodiment 1. FIG. It is a schematic diagram for demonstrating the operation of the display device which concerns on Embodiment 1. FIG. It is a figure for demonstrating the state which made the display surface of a display element face the eyes of a driver in the display device which concerns on Embodiment 1. FIG. It is a figure for comparing the display device which concerns on Embodiment 1 and the display device which concerns on a comparative example. It is sectional drawing of the display device which concerns on Embodiment 2. FIG. It is a schematic diagram for demonstrating the operation of the display device which concerns on Embodiment 2. FIG. It is a schematic diagram for demonstrating the operation of the display device which concerns on the modification of Embodiment 2. It is sectional drawing of the display device which concerns on Embodiment 3. FIG. It is a schematic diagram for demonstrating the effect obtained by the display device which concerns on Embodiment 3. FIG. It is a schematic diagram for demonstrating the effect obtained by the display device which concerns on Embodiment 3. FIG. It is sectional drawing of the display device which concerns on Embodiment 4. FIG. It is sectional drawing which enlarges and shows a part of the 1st mirror of the display device which concerns on Embodiment 4. FIG. It is sectional drawing of the display device which concerns on the modification of Embodiment 4. It is sectional drawing which enlarges and shows a part of the 1st mirror of the display device which concerns on the modification of Embodiment 4. It is a perspective view which shows a part of the structure of the display device which concerns on Embodiment 5. It is a front view which shows the polarization element and the 2nd mirror of the display device which concerns on Embodiment 5. FIG. It is a top view which shows the 2nd mirror of the display device which concerns on Embodiment 5. It is sectional drawing of the display device which concerns on Embodiment 6. It is sectional drawing of the display device which concerns on Embodiment 7.

The display device according to one aspect of the present disclosure includes a display element having a display surface for displaying an image, at least two mirrors that reflect light emitted from the display surface of the display element, and a polarizing element. The polarizing element has a configuration capable of reflecting and transmitting the emitted light, and the emitting light is reflected by at least two mirrors and emitted to the outside of the display device. It is reflected twice and transmitted once through the polarizing element.

According to this aspect, since the light emitted from the display surface is reflected twice by the polarizing element and transmitted once through the polarizing element, the optical path to the polarizing element can be increased to a total of three times. As a result, the optical path length can be lengthened, so that the entire device can be miniaturized while ensuring the viewing distance.

For example, the emitted light is reflected by the polarizing element, then reflected by one of the at least two mirrors, then transmitted through the polarizing element, and then reflected by the other of the at least two mirrors. , The polarizing element may be configured to reflect again.

According to this aspect, the reflected light path can be formed on both sides of the polarizing element as a boundary, and the emitted light can be transferred from one reflected light path to the other reflected light path by passing through the polarizing element. .. As a result, the emitted light follows one reflected optical path, then transitions and follows the other reflected optical path, so that the optical path length can be lengthened by that amount. As a result, it is possible to reduce the size of the entire device while ensuring the viewing distance.

For example, the at least two mirrors have a first mirror and a second mirror, the first mirror is arranged on one of the upper end side and the lower end side of the display surface, and the second mirror is , The polarizing element is arranged on the other side of the upper end side and the lower end side of the display surface, and the polarizing element is arranged between the first mirror and the second mirror so as to face the display surface. The apparatus further comprises a first λ / 4 plate disposed between the polarizing element and the first mirror, the polarizing element facing each of the display surface and the first mirror. It has a reflective polarizing plate arranged on the side and a second λ / 4 plate arranged on the side facing the second mirror, and the emitted light is (a) the reflective polarizing plate. (B) transmitted through the first λ / 4 plate, (c) transmitted through the first λ / 4 plate again by being reflected by the first mirror, and (d) the reflection. Each of the type polarizing plate and the second λ / 4 plate is transmitted, (e) is reflected by the second mirror, (f) is transmitted through the second λ / 4 plate, and (g) the reflection. The second λ / 4 plate may be configured to be transmitted again by being reflected by the type polarizing plate.

According to this aspect, the light emitted from the display surface is (i) reflected by the reflective polarizing plate, (ii) reflected by the first mirror, (iii) reflected by the second mirror, and (iv). It is reflected by the reflective polarizing plate. That is, the light emitted from the display surface is reflected at least four times in total. As a result, when the optical path length until the light emitted from the display surface passes through the polarizing element and the first mirror and reaches the second mirror via the polarizing element again is set to a predetermined length. The distance between each component (display element, polarizing element, first mirror and second mirror) can be kept short. As a result, it is possible to reduce the size of the entire device while ensuring the viewing distance.

For example, at least one of the first mirror and the second mirror may be configured to be a concave mirror.

According to this aspect, for example, when the display device is applied as an electronic mirror for a vehicle, the driver can drive by seeing the light emitted from the display surface (light forming a rear image) reflected by the concave mirror. To the person, it seems that the virtual image of the rear image is displayed at the display position in front of the vehicle rather than the concave mirror. As a result, it is possible to obtain the effect that the amount of focus adjustment of the eyes is relatively small when the driver shifts his / her line of sight to the virtual image of the rear image while the driver is looking at the front of the vehicle through the windshield.

For example, the second mirror is a concave mirror, and at least one of the upper end portion and the lower end portion when facing the second mirror is formed in a convex curved shape. It may be configured.

According to this aspect, the second mirror can be arranged close to the polarizing element, and the miniaturization of the entire device can be more effectively achieved.

For example, the second mirror is a concave mirror, and the end portion of the polarizing element on the second mirror side has a shape curved in a convex shape corresponding to the shape of the second mirror on the concave side. It may be configured to be formed in.

According to this aspect, the end portion of the polarizing element on the second mirror side can be arranged close to the concave surface side of the second mirror, and the miniaturization of the entire device can be more effectively achieved.

For example, the display device further includes a transmissive polarizing plate arranged so as to face the second λ / 4 plate of the polarizing element, the transmissive polarizing plate, and the second λ / 4 plate. The emitted light is provided with a third λ / 4 plate arranged between the two, and the emitted light transmitted through the second λ / 4 plate again by being reflected by the reflective polarizing plate is the third λ. It may be configured to transmit through each of the / 4 plate and the transmissive polarizing plate.

According to this aspect, when the stray light generated inside the display device passes through the transmissive polarizing plate, the stray light can be attenuated. As a result, it is possible to suppress reflection on the image displayed on the display surface of the display element.

For example, the polarizing element is formed in a wedge shape in cross section, and the thickness of the end portion of the polarizing element on the second mirror side is different from the thickness of the end portion of the polarizing element on the first mirror side. It may be configured.

According to this aspect, the double image can be suppressed.

For example, the first mirror may be configured to be a Fresnel mirror.

According to this aspect, since the first mirror is a Fresnel mirror, for example, the first mirror can be arranged parallel to the horizontal direction, and the miniaturization of the entire device can be more effectively achieved by that amount. be able to.

For example, the first λ / 4 plate may be configured to be tilted with respect to the first mirror.

According to this aspect, the double image can be suppressed.

For example, the perpendicular line of the display surface may be configured to be non-parallel to the optical path of the emitted light that has passed through the second λ / 4 plate again by being reflected by the reflective polarizing plate. ..

According to this aspect, it is possible to suppress reflection on the image displayed on the display surface of the display element.

For example, the emitted light from the display surface is linearly polarized light having a polarization direction orthogonal to the transmission axis of the reflective polarizing plate, and the polarizing element is the polarization direction of the linearly polarized light. It may be configured so as to be arranged at an angle with respect to the display surface around a parallel axis.

According to this aspect, when the display device is viewed from an oblique direction with respect to the perpendicular line of the display surface, a part of the light emitted from the display surface passes through the reflective polarizing plate without reflecting the reflective polarizing plate. It is possible to prevent leakage to the outside.

For example, the display device further includes the display element, the at least two mirrors, and a housing having an opening for emitting the emitted light, and the at least two mirrors are the first. When viewed from the opening, the display element is on the upper part of the housing, the first mirror is on the back of the housing, and the second mirror is on the back of the housing. The polarizing element is arranged in the lower part of the housing so as to be between the display element and the second mirror and the upper end portion of the polarizing element is inclined so as to be on the opening side. It may be configured to be.

According to this aspect, since the display element is arranged on the upper part of the housing, the air warmed by the heat of the display element is dissipated from the upper part of the housing, so that the influence of heat on other members is suppressed. be able to.

Hereinafter, embodiments will be specifically described with reference to the drawings.

It should be noted that all of the embodiments described below show comprehensive or specific examples. The numerical values, shapes, materials, components, arrangement positions and connection forms of the components, steps, the order of steps, etc. shown in the following embodiments are examples, and are not intended to limit the present disclosure. Further, among the components in the following embodiments, the components not described in the independent claim indicating the highest level concept are described as arbitrary components.

(Embodiment 1)
[1-1. Display device overview]
First, the outline of the display device 2 according to the first embodiment will be described with reference to FIG. FIG. 1 is a diagram showing an example of a vehicle 4 equipped with a display device 2 according to the first embodiment.

As shown in FIG. 1, the display device 2 is attached to, for example, a portion of the windshield 6 (windshield) of the vehicle 4 on the side close to the ceiling 8 via a bracket 10. As a result, the display device 2 is arranged at a position within the field of view of the driver 14 with the driver 14 seated in the driver's seat 12 facing forward. In this embodiment, the case where the display device 2 is attached to the windshield 6 will be described, but the present invention is not limited to this, and the display device 2 may be attached to, for example, an overhead console.

In the following description, the forward direction of the vehicle 4 is referred to as "forward", and the backward direction of the vehicle 4 is referred to as "rear". In FIG. 1, the front-rear direction (horizontal direction) of the vehicle 4 is the X-axis direction, the left-right direction of the vehicle 4 is the Y-axis direction, and the vertical direction (vertical direction) of the vehicle 4 is the Z-axis direction. Further, in FIG. 1, "front" is the minus side of the X axis, "rear" is the plus side of the X axis, "upper" is the plus side of the Z axis, and "lower" is the minus side of the Z axis.

The vehicle 4 is, for example, an ordinary passenger car, a vehicle such as a bus or a truck. A camera (not shown) for photographing the rear of the vehicle 4 is mounted on the rear bumper, the trunk hood, or the like of the vehicle 4. In the present embodiment, the case where the display device 2 is mounted on the vehicle 4 as a mobile body will be described, but the present invention is not limited to this, and the display device 2 is mounted on various mobile bodies such as construction machinery, agricultural machinery, ships, and aircraft. May be done.

The display device 2 is a so-called electronic mirror for displaying a rear image taken by a camera. The driver 14 can confirm the rear of the vehicle 4 reflected in the rear image by looking at the rear image displayed on the display device 2. That is, the display device 2 is used as a substitute for a conventional physical rear-view mirror that reflects the rear of the vehicle 4 by utilizing the reflection of light.

[1-2. Display device configuration]
Next, the configuration of the display device 2 according to the first embodiment will be described with reference to FIGS. 1 to 3B. FIG. 2 is a cross-sectional view of the display device 2 according to the first embodiment. FIG. 3A is a cross-sectional view of another form of the display device 2 according to the first embodiment. FIG. 3B is a cross-sectional view of still another form of the display device 2 according to the first embodiment.

As shown in FIG. 2, the display device 2 includes a housing 16, a display element 18, a polarizing element 20, a first mirror 22, a first λ / 4 plate 24, and a second mirror 26. It is equipped with. In addition, in this specification, a "board" is a concept including not only a board but also a member such as a film or a sheet.

The housing 16 is made of, for example, synthetic resin or the like, and has a storage space 28 inside. The display element 18, the polarizing element 20, the first mirror 22, the first λ / 4 plate 24, and the second mirror 26 are housed in the storage space 28 of the housing 16. As shown in FIG. 1, the housing 16 is suspended from the windshield 6 of the vehicle 4 via the bracket 10.

An opening 30 communicating with the storage space 28 is formed on the side surface of the housing 16 (the surface facing the driver 14). The opening 30 is formed in a horizontally long rectangular shape. That is, the dimension of the opening 30 in the left-right direction (Y-axis direction) is larger than the dimension in the vertical direction (Z-axis direction). The upper side of the opening 30 (plus side of the Z axis) is configured to have a larger length (height) in the Z axis direction than the lower side of the opening 30. As a result, unnecessary reflection can be suppressed. The opening 30 of the housing 16 is closed by a plate-shaped dustproof cover 32 made of, for example, transparent resin or glass. As a result, it is possible to prevent external dust and the like from entering the storage space 28 of the housing 16 through the opening 30. The dustproof cover 32 is arranged so as to be inclined with respect to the vertical direction so that the surface facing the driver 14 faces diagonally upward. As a result, it is possible to suppress the reflection of external light on the dustproof cover 32.

The display element 18 is, for example, a liquid crystal display (LCD: Liquid Crystal Display). The display element 18 has a display surface 34 for displaying a rear image taken by the camera of the vehicle 4. The display surface 34 is arranged so as to be inclined with respect to the vertical direction so as to face diagonally upward, for example. The display surface 34 is formed in a horizontally long rectangular shape, and is arranged so as to face the opening 30 of the housing 16. That is, the horizontal dimension of the display surface 34 is larger than the vertical dimension. The display surface 34 emits light for forming a rear image (hereinafter, referred to as “emitted light”). The light emitted from the display surface 34 is linearly polarized light having a polarization direction in the first direction d1 (the direction perpendicular to the paper surface in FIG. 2 and the Y-axis direction). The emission direction of the emitted light from the display surface 34 is inclined upward with respect to the perpendicular line 36 of the display surface 34. In addition, in this specification, "vertical" not only means that it is completely vertical, but also means that when it is substantially vertical, it includes an error of, for example, several degrees.

The polarizing element 20 is arranged so as to face the display surface 34 of the display element 18. The polarizing element 20 has a glass substrate 38, a reflective polarizing plate 40, and a second λ / 4 plate 42. The polarizing element 20 is formed in a flat plate shape as a whole, and is inclined with respect to the display surface 34 around an axis parallel to the polarization direction of the light emitted from the display surface 34 of the display element 18 (around the Y axis). And are arranged. In addition, in this specification, "parallel" not only means that it is completely parallel, but also means that when it is substantially parallel, it includes an error of, for example, several degrees. Here, the upper end portion 20a (the end portion on the positive side of the Z axis) of the polarizing element 20 is arranged on the side close to the display surface 34 of the display element 18, and the lower end portion 20b (the negative side of the Z axis) of the polarizing element 20 is arranged. The end portion) is arranged on the side far from the display surface 34 of the display element 18. The polarizing element 20 is configured by superimposing the reflective polarizing plate 40, the glass substrate 38, and the second λ / 4 plate 42 on each other in this order from the side closer to the display surface 34 of the display element 18. Instead of such a configuration, in the polarizing element 20, for example, the glass substrate 38, the reflective polarizing plate 40, and the second λ / 4 plate 42 are placed in this order from the side closer to the display surface 34 of the display element 18. It may be configured by superimposing.

The glass substrate 38 is a substrate for supporting the reflective polarizing plate 40 and the second λ / 4 plate 42, and is formed of, for example, transparent glass. A reflective polarizing plate 40 is superposed on the first surface of the glass substrate 38 (the surface of the display element 18 on the side facing each of the display surface 34 and the first mirror 22). Further, a second λ / 4 plate 42 is superposed on the second surface (the surface on the side facing the second mirror 26) opposite to the first surface of the glass substrate 38.

The reflective polarizing plate 40 reflects the linearly polarized light component in the first direction d1 of the light incident on the reflective polarizing plate 40, and is a second direction orthogonal to the first direction d1. The linearly polarized light component of d2 (the direction in the paper surface of FIG. 2 and the direction in the XZ plane) is transmitted. That is, the reflection axis of the reflective polarizing plate 40 is in the first direction d1, the transmission axis of the reflective polarizing plate 40 is in the second direction d2, and both are orthogonal to each other. In addition, in this specification, "orthogonal" not only means that they intersect at a perfect right angle, but also means that they intersect at a substantially right angle, for example, including an error of about several degrees.

The second λ / 4 plate 42 is a retardation plate for converting the light incident on the second λ / 4 plate 42 from linearly polarized light to circularly polarized light (or from circularly polarized light to linearly polarized light). The second λ / 4 plate 42 has a phase difference of 1/4 of the wavelength λ (that is, 90 ° position) between the linearly polarized light components orthogonal to each other in the light incident on the second λ / 4 plate 42. It has a function of causing a phase difference).

The first mirror 22 and the second mirror 26 are arranged on the lower end side and the upper end side of the display surface 34 of the display element 18 in the vertical direction, respectively. That is, the polarizing element 20 is arranged between the first mirror 22 and the second mirror 26.

The display device 2 shown in FIG. 2 may have a configuration in which the arrangement of each component inside the housing 16 is reversed in the vertical direction (Z-axis direction), except for the housing 16 and the dustproof cover 32. .. This configuration is shown in FIG. 3A. In this case, the first mirror 22 and the second mirror 26 are arranged on the upper end side and the lower end side in the vertical direction of the display surface 34 of the display element 18, respectively. Therefore, the first mirror 22 is arranged on one of the upper end side and the lower end side of the display surface 34, and the second mirror 26 is arranged on the other of the upper end side and the lower end side of the display surface 34.

In each embodiment and each modification described later, the arrangement of each component inside the housing 16 (16D) may be inverted in the vertical direction in the same manner as described above.

Further, in FIG. 3A, the display element 18 and the polarizing element 20 are arranged so as to partially overlap when viewed from the Z-axis direction. With this configuration, the depth (length in the X-axis direction) of the housing 16 can be reduced. In each embodiment and each modification described later, the display element 18 and the polarizing element 20 may be arranged so as to partially overlap when viewed from the Z-axis direction as described above.

Here, also in FIG. 3A, as described with reference to FIG. 2, the upper side (plus side of the Z axis) of the opening 30 has a larger length (height) in the Z axis direction than the lower side of the opening 30. It is configured to be. In this case, since the upper side of the opening 30 becomes thicker, a support member for the dustproof cover 32 may be arranged on the upper side of the opening 30 as shown in FIG. 3B in order to improve the appearance. Even with this configuration, unnecessary reflection can be suppressed. In the case of this configuration, the upper end of the polarizing element 20 is shortened by the amount in which the support member is arranged. The configuration of FIG. 3B may be applied in other configuration diagrams.

The first mirror 22 is a planar mirror and has a planar reflecting surface 44. The first mirror 22 is formed by depositing a reflective metal film such as aluminum on the surface of a glass base material, for example. The first mirror 22 is arranged below the polarizing element 20, and the reflecting surface 44 is arranged so as to face the reflective polarizing plate 40 of the polarizing element 20. The first mirror 22 is arranged so as to be inclined with respect to the horizontal direction in a direction in which the reflecting surface 44 faces the opening 30 side of the housing 16.

The first λ / 4 plate 24 is a retardation plate for converting the light incident on the first λ / 4 plate 24 from linearly polarized light to circularly polarized light (or from circularly polarized light to linearly polarized light). The first λ / 4 plate 24 has a phase difference of 1/4 of the wavelength λ (that is, 90 ° position) between the linearly polarized light components orthogonal to each other in the light incident on the first λ / 4 plate 24. It has a function of causing a phase difference). The first λ / 4 plate 24 is arranged so as to cover the reflecting surface 44 of the first mirror 22. That is, the first λ / 4 plate 24 is arranged between the polarizing element 20 and the first mirror 22. The slow phase axes of the first λ / 4 plate 24 and the second λ / 4 plate 42 are parallel or perpendicular to each other, and may be appropriately selected depending on the slow phase distribution characteristics at the transmission wavelength. can.

The second mirror 26 is a concave mirror and has a reflecting surface 46 having a free curved surface. The second mirror 26 is formed by depositing a reflective metal film such as aluminum on the surface of a resin-molded member, for example. The second mirror 26 is arranged above the polarizing element 20, and the reflecting surface 46 is arranged so as to face the second λ / 4 plate 42 of the polarizing element 20.

[1-3. Display device operation]
Next, the operation of the display device 2 according to the first embodiment will be described with reference to FIGS. 1, 4 and 5. FIG. 4 is a schematic diagram for explaining the operation of the display device 2 according to the first embodiment. FIG. 5 is a diagram for explaining a state in which the display surface 34 of the display element 18 faces the eyes of the driver 14 in the display device 2 according to the first embodiment. Note that FIG. 4 schematically shows the arrangement and shape of each component of the display device 2, and may differ from the actual arrangement and shape. This also applies to each schematic diagram in each embodiment described later.

As shown in FIG. 4, the light emitted from the display surface 34 of the display element 18 is incident on the reflective polarizing plate 40 of the polarizing element 20. At this time, the polarization direction of the emitted light incident on the reflective polarizing plate 40 is the same first direction d1 as the reflection axis of the reflective polarizing plate 40. Therefore, the emitted light incident on the reflective polarizing plate 40 is reflected by the reflective polarizing plate 40.

The emitted light reflected by the reflective polarizing plate 40 passes through the first λ / 4 plate 24, then enters the reflecting surface 44 of the first mirror 22, and is reflected by the reflecting surface 44 of the first mirror 22. do. At this time, the emitted light transmitted through the first λ / 4 plate 24 is converted from linearly polarized light in the first direction d1 to circularly polarized light.

The emitted light reflected by the reflecting surface 44 of the first mirror 22 passes through the first λ / 4 plate 24 again and then enters the reflective polarizing plate 40. At this time, the emitted light transmitted through the first λ / 4 plate 24 again is converted from circularly polarized light to linearly polarized light in the second direction d2.

The polarization direction of the emitted light incident on the reflective polarizing plate 40 is the same second direction d2 as the transmission axis of the reflective polarizing plate 40. Therefore, the emitted light incident on the reflective polarizing plate 40 passes through the reflective polarizing plate 40.

The emitted light transmitted through the reflective polarizing plate 40 passes through each of the glass substrate 38 and the second λ / 4 plate 42, and then enters the reflecting surface 46 of the second mirror 26 to enter the second mirror 26. It is reflected by the reflecting surface 46 of. At this time, the emitted light transmitted through the second λ / 4 plate 42 is converted from linearly polarized light in the second direction d2 to circularly polarized light.

Here, in the present embodiment, as an example, the reflection angle of the emitted light on the reflection surface 46 of the second mirror 26 is set to an angle range of 8 ° to 15 °. However, the reflection angle of the emitted light on the reflection surface 46 of the second mirror 26 is not limited to this angle range, and may be smaller or larger than this angle range.

The emitted light reflected by the reflecting surface 46 of the second mirror 26 passes through each of the second λ / 4 plate 42 and the glass substrate 38, and then is incident on the reflective polarizing plate 40. At this time, the emitted light transmitted through the second λ / 4 plate 42 is converted from circularly polarized light to linearly polarized light in the first direction d1. The polarization direction of the emitted light incident on the reflective polarizing plate 40 is the same first direction d1 as the reflection axis of the reflective polarizing plate 40. Therefore, the emitted light incident on the reflective polarizing plate 40 is reflected by the reflective polarizing plate 40.

The emitted light reflected by the reflective polarizing plate 40 passes through the glass substrate 38 and then again through the second λ / 4 plate 42, and is incident on the dustproof cover 32 (see FIG. 2). At this time, the emitted light transmitted through the second λ / 4 plate 42 again is converted from linearly polarized light in the first direction d1 to circularly polarized light. The emitted light incident on the dustproof cover 32 is incident on the eyes of the driver 14 (see FIG. 2) after passing through the dustproof cover 32.

As described above, the light emitted from the display surface 34 of the display element 18 is (i) reflected by the reflective polarizing plate 40, (ii) reflected by the reflection surface 44 of the first mirror 22, and (iii). After being reflected by the reflecting surface 46 of the second mirror 26 and reflected by the (iv) reflective polarizing plate 40, it is incident on the eyes of the driver 14. That is, the light emitted from the display surface 34 of the display element 18 is reflected inside the housing 16 a total of four times and then enters the eyes of the driver 14.

That is, the light emitted from the display surface 34 of the display element 18 is reflected by the first mirror 22 and the second mirror 26 (hereinafter, these are collectively referred to simply as “mirror”) from the inside of the housing 16. Before it is emitted to the outside of the housing 16 through the dustproof cover 32, it is reflected twice by the polarizing element 20 and transmitted once through the polarizing element 20. Specifically, the emitted light is first reflected by the polarizing element 20, then reflected by the first mirror 22, then transmitted through the polarizing element 20, then reflected by the second mirror 26, and then the polarizing element. Reflects again at 20.

By seeing the rear image reflected by the reflecting surface 46 of the second mirror 26 by the driver 14, as shown in FIG. 1, the driver 14 is in a display position in front of the vehicle 4 with respect to the display device 2. It seems that the virtual image 48 of the rear image is displayed. As a result, the amount of eye focus adjustment when the driver 14 shifts his / her line of sight to the virtual image 48 of the rear image while looking at the front of the vehicle 4 through the windshield 6 is relatively small.

Here, the polarization direction of the light emitted from the display surface 34 of the display element 18 is preferably the first direction d1. Temporarily, the polarization direction of the light emitted from the display surface 34 of the display element 18 is the second direction d2, the transmission axis of the reflective polarizing plate 40 is the first direction d1, and the reflection axis is the second direction d2. In this case, due to the characteristics of the reflective polarizing plate 40, when the driver 14 views the display device 2 from diagonally below, a part of the light emitted from the display surface 34 of the display element 18 is a reflective polarizing plate. It penetrates 40 and leaks to the outside.

On the other hand, when the polarization direction of the light emitted from the display surface 34 of the display element 18 is the first direction d1 as in the present embodiment, the driver 14 displays the display device 2 from diagonally below. When viewed, it is possible to prevent a part of the light emitted from the display surface 34 of the display element 18 from passing through the reflective polarizing plate 40 and leaking to the outside.

Further, as shown by the solid line in FIG. 5, it is preferable that the display surface 34 of the display element 18 does not face the eyes of the driver 14. Specifically, it is preferable that the perpendicular line 36 of the display surface 34 of the display element 18 is non-parallel to the optical path L of the emitted light transmitted through the dustproof cover 32 and incident on the eyes of the driver 14. For convenience of explanation, in FIG. 5, the eyes of the driver 14 are shown so as to be located at the same height as the display surface 34 of the display element 18, but the eyes of the driver 14 are actually displayed. It is assumed that the element 18 is located below the display surface 34.

As shown by the alternate long and short dash line in FIG. 5, the display surface 34 of the display element 18 faces the eyes of the driver 14 (that is, the display surface 34 is inclined so as to face diagonally downward with respect to the vertical direction). Think about the case. In this case, as shown by the arrow P in FIG. 5, for example, the external light such as the headlight of the following vehicle passes through the dustproof cover 32 and the like and is reflected by the display surface 34 of the display element 18, and then the reflected external light P1. Will pass through the dustproof cover 32 and the like again and enter the eyes of the driver 14. As a result, external light is likely to be reflected in the rear image displayed on the display surface 34 of the display element 18.

On the other hand, when the display surface 34 of the display element 18 does not face the eyes of the driver 14, as in the present embodiment, the reflected external light P2 reflected by the display surface 34 of the display element 18 is generated. , It is reflected toward the ceiling 8 side and is less likely to be incident on the driver 14's eyes. As a result, it is possible to suppress the reflection of external light on the rear image displayed on the display surface 34 of the display element 18.

Further, in the present embodiment, as described above, the emission direction of the emitted light from the display surface 34 is inclined upward with respect to the perpendicular line 36 of the display surface 34. When it is not tilted, the external light incident from a position comparable to the height of the viewpoint of the driver 14 follows the backlight path and enters the display surface 34, and then the reflected external light is emitted from the display surface 34. Since it follows the same optical path as the normal optical path in a state of being superimposed on the light of the image (rear image) and reaches the viewpoint of the driver 14, reflection from the outside of the vehicle interior is likely to occur. By inclining the emission direction of the light of the rear image upward with respect to the perpendicular line 36 of the display surface 34 as in the present embodiment, the possibility that the reflected external light is superimposed on the rear image is reduced. It is possible to suppress reflection on the rear image displayed on the display surface 34 of the display element 18.

Further, in the present embodiment, as described above, the first mirror 22 is arranged so as to be inclined with respect to the horizontal direction. This also makes it possible to suppress reflection on the rear image displayed on the display surface 34 of the display element 18.

[1-4. effect]
Hereinafter, by comparing the display device 2 according to the first embodiment with the display device 100 according to the comparative example with reference to FIG. 6, the effect obtained by the display device 2 according to the first embodiment will be described. FIG. 6 is a diagram for comparing the display device 2 according to the first embodiment and the display device 100 according to the comparative example.

As shown in FIG. 6A, the display device 100 according to the comparative example includes a housing 102, a display element 104 composed of a liquid crystal display or the like, a polarizing element 106, and a concave mirror 108. ..

A display element 104, a polarizing element 106, and a concave mirror 108 are housed inside the housing 102. A dustproof cover 112 is arranged in the opening 110 of the housing 102. The display element 104 has a display surface 114 for displaying a rear image, and a λ / 4 plate is arranged on the outermost surface.

The polarizing element 106 is arranged so as to face the display surface 114 of the display element 104, and is arranged so as to be inclined with respect to the display surface 114. The polarizing element 106 is configured by superimposing a reflective polarizing plate and a λ / 4 plate on each other.

The concave mirror 108 is a concave mirror having a free curved surface, and is arranged so as to face the polarizing element 106.

The light emitted from the display surface 114 of the display element 104 is reflected by the polarizing element 106 and then incident on the concave mirror 108. The emitted light reflected by the concave mirror 108 passes through the polarizing element 106 and then passes through the dustproof cover 112 and is incident on the driver's eyes.

As described above, the light emitted from the display surface 114 of the display element 104 is (i) reflected by the polarizing element 106, reflected by (ii) the concave mirror 108, and then incident on the driver's eyes. That is, the light emitted from the display surface 114 of the display element 104 is reflected twice in total inside the housing 102 and then enters the driver's eyes.

Here, the viewing distance from the driver's eyes to the display position of the virtual image of the rear image is the optical path length until the light emitted from the display surface 114 of the display element 104 reaches the concave mirror 108 via the polarizing element 106. It is determined by (the distance shown by the two-dot chain line in (a) of FIG. 6). Therefore, in order to secure the viewing distance, it is necessary to set the optical path length to a predetermined length, but the distance between each component (display element 104, polarizing element 106, and concave mirror 108) is correspondingly longer. Therefore, there arises a problem that the housing 102 becomes large.

On the other hand, as shown in FIG. 6B, in the display device 2 according to the first embodiment, the light emitted from the display surface 34 of the display element 18 is reflected by (i) the reflective polarizing plate 40. Then, (ii) it is reflected by the reflecting surface 44 of the first mirror 22, (iii) it is reflected by the reflecting surface 46 of the second mirror 26, (iv) it is reflected by the reflective polarizing plate 40, and then the driver 14 It is incident on the eyes of. That is, the light emitted from the display surface 34 of the display element 18 is reflected inside the housing 102 a total of four times, and then enters the eyes of the driver 14.

From this, the light emitted from the display surface 34 of the display element 18 is reflected by the mirrors (first mirror 22 and the second mirror 26) from the inside of the housing 16 via the dustproof cover 32. Before it is emitted to the outside of 16, it is reflected twice by the polarizing element 20 and transmitted once through the polarizing element 20. Specifically, the emitted light is first reflected by the polarizing element 20, then reflected by the first mirror 22, then transmitted through the polarizing element 20, then reflected by the second mirror 26, and then the polarizing element. Reflects again at 20.

As a result, the light emitted from the display surface 34 is reflected twice by the polarizing element 20 and transmitted once through the polarizing element, so that the optical path leading to the polarizing element 20 can be increased to a total of three times. Therefore, since the optical path length can be lengthened, the size of the housing 16 can be reduced while ensuring the viewing distance. Further, a reflected light path can be formed on both sides of the polarizing element 20 as a boundary, and by transmitting through the polarizing element 20, the emitted light can be transferred from one reflected light path to the other reflected light path. Therefore, since the emitted light follows one reflected optical path, then transitions and follows the other reflected optical path, the optical path length can be lengthened by that amount. As a result, it is possible to reduce the size of the entire device while ensuring the viewing distance.

Further, the optical path length until the light emitted from the display surface 34 of the display element 18 reaches the second mirror 26 via the polarizing element 20 and the first mirror 22 (two-dot chain line in FIG. 6B). When the distance shown by (1) is set to the predetermined length, the distance between each component (display element 18, polarizing element 20, first mirror 22 and second mirror 26) can be kept short. The size of the housing 16 can be reduced.

That is, the optical path length in (a) of FIG. 6 is the same as the optical path length in (b) of FIG. 6, but the size D1 in the front-rear direction of the housing 16 of the display device 2 according to the first embodiment. Is smaller than the size D2 in the front-rear direction of the housing 102 of the display device 100 according to the comparative example. Therefore, in the display device 2 according to the first embodiment, it is possible to obtain the effect that the entire device can be miniaturized while ensuring the viewing distance.

(Embodiment 2)
[2-1. Display device configuration]
The configuration of the display device 2A according to the second embodiment will be described with reference to FIG. 7. FIG. 7 is a cross-sectional view of the display device 2A according to the second embodiment. In each of the following embodiments, the same components as those in the first embodiment are designated by the same reference numerals, and the description thereof will be omitted.

As shown in FIG. 7, the display device 2A according to the second embodiment has a glass substrate 50, a transmissive polarizing plate 52, and a third λ instead of the dustproof cover 32 described in the first embodiment. It is equipped with a / 4 plate 54. The third λ / 4 plate 54, the glass substrate 50, and the transmissive polarizing plate 52 are arranged in the opening 30 of the housing 16 in a state of being overlapped with each other in this order from the side closer to the display surface 34 of the display element 18. ing. The third λ / 4 plate 54, the glass substrate 50, and the transmissive polarizing plate 52 function as the dustproof cover 32 described in the first embodiment by closing the opening 30 of the housing 16. .. In each embodiment and each modification described later, the glass substrate 50, the transmissive polarizing plate 52, and the third λ / 4 plate 54 are used instead of the dustproof cover 32 as in the present embodiment. It may be provided.

The glass substrate 50 is a substrate for supporting the transmissive polarizing plate 52 and the third λ / 4 plate 54, and is formed of, for example, transparent glass. A third λ / 4 plate 54 is superposed on the first surface of the glass substrate 50 (the surface of the polarizing element 20 on the side facing the second λ / 4 plate 42). Further, a transmissive polarizing plate 52 is superposed on the second surface opposite to the first surface of the glass substrate 50. Further, the glass substrate 50 is inclined so that the lower side thereof is closer to the driver 14 (see FIG. 1) side with respect to the plane perpendicular to the emitted light.

The transmissive polarizing plate 52 absorbs the linearly polarized light component in the first direction d1 and transmits the linearly polarized light component in the second direction d2 out of the light incident on the transmissive polarizing plate 52. That is, the absorption axis of the transmissive polarizing plate 52 is in the first direction d1, the transmission axis of the transmissive polarizing plate 52 is in the second direction d2, and both are orthogonal to each other.

The third λ / 4 plate 54 is a retardation plate for converting the light incident on the third λ / 4 plate 54 from linearly polarized light to circularly polarized light (or from circularly polarized light to linearly polarized light). The third λ / 4 plate 54 has a phase difference of 1/4 of the wavelength λ (that is, 90 ° position) between the linearly polarized light components orthogonal to each other in the light incident on the third λ / 4 plate 54. It has a function of causing a phase difference). The third λ / 4 plate 54 is arranged so as to cover the first surface of the glass substrate 50. That is, the third λ / 4 plate 54 is arranged between the second λ / 4 plate 42 of the polarizing element 20 and the transmissive polarizing plate 52.

[2-2. Display operation]
Next, the operation of the display device 2A according to the second embodiment will be described with reference to FIG. FIG. 8 is a schematic diagram for explaining the operation of the display device 2A according to the second embodiment.

As shown in FIG. 8, the light emitted from the display surface 34 of the display element 18 is reflected by (i) the reflective polarizing plate 40 and (ii) the first mirror 22 as in the first embodiment. It is reflected by the reflecting surface 44, (iii) is reflected by the reflecting surface 46 of the second mirror 26, and (iv) is reflected by the reflective polarizing plate 40. The emitted light reflected by the reflective polarizing plate 40 passes through each of the glass substrate 38 and the second λ / 4 plate 42, and then enters the third λ / 4 plate 54.

The emitted light incident on the third λ / 4 plate 54 is transmitted to each of the third λ / 4 plate 54 and the glass substrate 50, and then incident on the transmissive polarizing plate 52. At this time, the emitted light transmitted through the third λ / 4 plate 54 is converted from circularly polarized light to linearly polarized light in the second direction d2.

The polarization direction of the emitted light incident on the transmissive polarizing plate 52 is the same second direction d2 as the transmission axis of the transmissive polarizing plate 52. Therefore, the emitted light incident on the transmissive polarizing plate 52 is transmitted through the transmissive polarizing plate 52. The emitted light transmitted through the transmissive polarizing plate 52 is incident on the eyes of the driver 14.

[2-3. effect]
In the present embodiment, since the transmissive polarizing plate 52 and the third λ / 4 plate 54 are arranged in the opening 30 of the housing 16, the stray light generated inside the housing 16 (the imaginary image 48 shown in FIG. 1) This stray light can be attenuated when the light that does not contribute to the display passes through the transmissive polarizing plate 52. As a result, it is possible to suppress reflection on the rear image displayed on the display surface 34 of the display element 18.

Further, since the glass substrate 50 is inclined so that the lower side thereof is closer to the driver 14 side with respect to the surface perpendicular to the emitted light, when the external light is incident on the surface of the transmissive polarizing plate 52, it is reflected. The outside light can be directed to the ceiling 8 (see FIG. 1) side, and the reflection can be suppressed.

In the present embodiment, the transmissive polarizing plate 52 is used, but the present invention is not limited to this, and a reflective polarizing plate is arranged in place of the transmissive polarizing plate 52, and the entire housing 16 is vertically and vertically and. An adjustment mechanism that can rotate in the left-right direction may be provided, and the display / non-display of the rear image may be switched. As a result, with the rear image hidden, the entire housing 16 is rotated in the vertical and horizontal directions by the adjustment mechanism so that the reflected image behind the vehicle 4 (see FIG. 1) faces the driver 14. By doing so, it becomes possible to switch to a normal optical mirror.

[2-4. Modification example]
The configuration and operation of the display device 2B according to the modified example of the second embodiment will be described with reference to FIG. 9. FIG. 9 is a schematic diagram for explaining the operation of the display device 2B according to the modified example of the second embodiment.

As shown in FIG. 9, the display device 2B according to the modified example of the second embodiment includes a fourth λ / 4 plate 56 in addition to the above-mentioned configuration requirements. The third λ / 4 plate 54, the glass substrate 50, the transmissive polarizing plate 52, and the fourth λ / 4 plate 56 are superposed on each other in this order from the side closer to the display surface 34 of the display element 18.

The fourth λ / 4 plate 56 is a retardation plate for converting the light incident on the fourth λ / 4 plate 56 from linearly polarized light to circularly polarized light (or from circularly polarized light to linearly polarized light). The fourth λ / 4 plate 56 has a phase difference of 1/4 of the wavelength λ (that is, 90 ° position) between the linearly polarized light components orthogonal to each other in the light incident on the fourth λ / 4 plate 56. It has a function of causing a phase difference).

As shown in FIG. 9, the emitted light transmitted through the transmissive polarizing plate 52 is transmitted through the fourth λ / 4 plate 56. The emitted light transmitted through the fourth λ / 4 plate 56 enters the eyes of the driver 14 (see FIG. 1) after being converted from linearly polarized light in the second direction d2 to circularly polarized light.

Thereby, for example, even when the driver 14 wears polarized sunglasses or the like, the emitted light transmitted through the fourth λ / 4 plate 56 can be incident on the eyes of the driver 14.

(Embodiment 3)
[3-1. Display device configuration]
The configuration of the display device 2C according to the third embodiment will be described with reference to FIG. 10. FIG. 10 is a cross-sectional view of the display device 2C according to the third embodiment.

As shown in FIG. 10, in the display device 2C according to the third embodiment, the configuration of the polarizing element 20C is different from that of the first embodiment. Specifically, the polarizing element 20C is formed in a wedge shape in cross section. The thickness of the upper end portion 20a (end portion on the second mirror 26 side) of the polarizing element 20C is smaller than the thickness of the lower end portion 20b (end portion on the first mirror 22 side).

[3-2. effect]
The effect obtained by the display device 2C according to the third embodiment will be described with reference to FIGS. 11 and 12. 11 and 12 are schematic views for explaining the effect obtained by the display device 2C according to the third embodiment.

As shown by the solid line arrow in FIG. 11, most of the emitted light reflected by the reflecting surface 46 of the second mirror 26 (hereinafter referred to as “display light”) is the second λ / 4 plate of the polarizing element 20C. After passing through 42 and reflecting on the surface on the side of the reflective polarizing plate 40, the polarizing element 20C is transmitted again and is incident on the eyes of the driver 14. Further, as shown by the arrow of the alternate long and short dash line in FIG. 11, a part of the emitted light reflected by the reflecting surface 44 of the second mirror 26 (hereinafter referred to as “surface reflected light”) is the second λ / 4. After being reflected by the surface on the plate 42 side, it is incident on the eyes of the driver 14.

At this time, since the polarizing element 20C is formed in a wedge shape in cross section, the surface reflected light reflected on the surface of the polarizing element 20C on the second λ / 4 plate 42 side and the reflective polarizing plate transmitted through the polarizing element 20C. It almost overlaps with the display light reflected by 40. As a result, similarly to the above, it is possible to suppress the occurrence of the phenomenon that the rear image looks like a double image due to the display light and the surface reflected light being shifted and superimposed.

In addition, in FIG. 11, the case where the polarizing element 20C has a configuration in which the reflective polarizing plate 40 and the second λ / 4 plate 42 are arranged on both sides of the glass substrate 38, respectively, has been described. As described above, the case where the polarizing element 20C is laminated on one side of the glass substrate 38 with the reflective polarizing plate 40 and the second λ / 4 plate 42 in this order will be described with reference to FIG. ..

As shown by the solid line arrow in FIG. 12, most of the light emitted from the display surface 34 of the display element 18 (hereinafter referred to as “display light”) passes through the glass substrate 38 of the polarizing element 20C and is transmitted through the glass substrate 38 of the polarizing element 20C. After reflecting on the surface of the reflective polarizing plate 40 on the side of the above, the glass substrate 38 of the polarizing element 20C is transmitted again and incident on the reflecting surface 44 of the first mirror 22. Further, as shown by the arrow of the alternate long and short dash line in FIG. 12, a part of the light emitted from the display surface 34 of the display element 18 (hereinafter referred to as “surface reflected light”) is the surface of the glass substrate 38 of the polarizing element 20C. After being reflected by, it is incident on the reflecting surface 44 of the first mirror 22.

At this time, since the polarizing element 20C is formed in a wedge shape in cross section, the display light reflected on the surface of the polarizing element 20C on the reflective polarizing plate 40 side and the surface reflection reflected on the surface of the glass substrate 38 of the polarizing element 20C. It almost overlaps with the light. As a result, it is possible to suppress the occurrence of the phenomenon that the rear image looks like a double image due to the display light and the surface reflected light being shifted and superimposed.

In the third embodiment, the thickness of the upper end portion 20a of the polarizing element 20C is smaller than the thickness of the lower end portion 20b, but the configuration is not limited to this, and the arrangement of the polarizing element 20C and the arrangement position of the display device 2C are not limited to this. The thickness of the upper end portion 20a of the polarizing element 20C may be larger than the thickness of the lower end portion 20b. Even with such a configuration, the above-mentioned effect can be obtained. Therefore, the thickness of the upper end portion 20a and the thickness of the lower end portion 20b of the polarizing element 20C may be different.

(Embodiment 4)
[4-1. Display device configuration]
The configuration of the display device 2D according to the fourth embodiment will be described with reference to FIGS. 13 and 14. FIG. 13 is a cross-sectional view of the display device 2D according to the fourth embodiment. FIG. 14 is an enlarged cross-sectional view showing a part of the first mirror 22D of the display device 2D according to the fourth embodiment.

As shown in FIGS. 13 and 14, in the display device 2D according to the fourth embodiment, the configuration of the first mirror 22D is different from that of the first embodiment. Specifically, the first mirror 22D is a Fresnel mirror and has a Fresnel-like reflecting surface 44D. As shown in FIG. 14, on the reflecting surface 44D, a plurality of prism portions 58 extending in a long shape along the left-right direction (Y-axis direction) are arranged side by side in the front-rear direction (X-axis direction). Further, the first mirror 22D is arranged parallel to the horizontal direction so that the reflecting surface 44D faces vertically upward.

A glass substrate 60 for supporting the first λ / 4 plate 24 is arranged between the first mirror 22D and the first λ / 4 plate 24.

[4-2. effect]
In the first embodiment, since the first mirror 22 is a planar mirror, in order to control the reflection direction of the emitted light by the first mirror 22 in a specific direction, the first mirror 22 is set in the horizontal direction. On the other hand, it is necessary to incline and arrange it.

On the other hand, in the present embodiment, since the first mirror 22D is a Fresnel mirror, the light emitted by the first mirror 22D is emitted in a state where the first mirror 22D is arranged parallel to the horizontal direction. The reflection direction can be controlled in the above-mentioned specific direction.

As a result, as shown in FIG. 13, the size of the housing 16D in the vertical direction is larger than that in the case where the first mirror 22 is tilted with respect to the horizontal direction as in the first embodiment. The size can be reduced by D3, and the size of the entire device can be reduced more effectively. In addition, the field of view in front can be expanded by the amount that the area below the housing 16D is reduced.

[4-3. Modification example]
Next, the display device 2E according to the modified example of the fourth embodiment will be described with reference to FIGS. 15 and 16. FIG. 15 is a cross-sectional view of the display device 2E according to the modified example of the fourth embodiment. FIG. 16 is an enlarged cross-sectional view showing a part of the first mirror 22D of the display device 2E according to the modified example of the fourth embodiment.

As shown in FIGS. 15 and 16, in this modification, each of the first λ / 4 plate 24E and the glass substrate 60E is arranged so as to be inclined forward with respect to the first mirror 22D. It should be noted that each of the first λ / 4 plate 24E and the glass substrate 60E may be arranged so as to be inclined rearward with respect to the first mirror 22D.

As shown by the solid line arrow in FIG. 16, a part of the emitted light reflected by the reflective polarizing plate 40 (see FIG. 15) passes through each of the first λ / 4 plate 24E and the glass substrate 60E, and then is passed through each of the first λ / 4 plate 24E and the glass substrate 60E. It reflects on the surface of the glass substrate 60E opposite to the first λ / 4 plate 24E and passes through each of the glass substrate 60E and the first λ / 4 plate 24E again. Further, as shown by the arrow of the alternate long and short dash line in FIG. 16, the other part of the emitted light reflected by the reflective polarizing plate 40 is reflected by the first λ / 4 plate 24E.

At this time, since each of the first λ / 4 plate 24E and the glass substrate 60E is arranged so as to be inclined forward with respect to the first mirror 22D, the incident surface of the first λ / 4 plate 24E The reflected reflected light and the reflected light reflected by the glass substrate 60E can be made to greatly deviate from the normal optical path as shown by the broken line arrow in FIG. As a result, it is possible to suppress the occurrence of the phenomenon that the rear image looks like a double image.

(Embodiment 5)
[5-1. Display device configuration]
The configuration of the display device 2F according to the fifth embodiment will be described with reference to FIGS. 17 to 19. FIG. 17 is a perspective view showing a part of the configuration of the display device 2F according to the fifth embodiment. FIG. 18 is a front view showing the polarizing element 20F and the second mirror 26F of the display device 2F according to the fifth embodiment. FIG. 19 is a top view showing a second mirror 26F of the display device 2F according to the fifth embodiment. For convenience of explanation, the first mirror 22 is not shown in FIG.

As shown in FIGS. 17 and 18, in the display device 2F according to the fifth embodiment, the configurations of the polarizing element 20F and the second mirror 26F are different from those of the first embodiment. Specifically, first, in FIG. 18, the front view of the second mirror 26F reflected on the polarizing element 20F is shown by a broken line. As shown by the broken line, the upper end portion when the second mirror 26F is viewed directly is formed in a convex curved shape. As a result, as shown in FIG. 17, the second mirror 26F can be arranged close to the polarizing element 20F, and the miniaturization of the entire display device 2F can be more effectively achieved.

Further, the upper end portion 20a of the polarizing element 20F on the second mirror 26F side is formed in a convexly curved shape corresponding to the shape of the concave surface side (reflection surface 46 side) of the second mirror 26F. .. The lower end portion 20b of the polarizing element 20F is formed in a linear shape. As a result, the upper end portion 20a of the polarizing element 20F can be arranged close to the concave surface side of the second mirror 26F, and the miniaturization of the entire device can be achieved more effectively, and the driver 14 (FIG. 1). The height of the upper part (apparent width of the frame on the upper side) in the opening 30 (see FIG. 2) when the display device 2F is viewed from (see FIG. 2) can be reduced. In particular, in FIGS. 17 and 18, when the configuration of FIG. 3A in which the vertical direction (Z-axis direction) is inverted is suspended from the ceiling of the vehicle 4 (see FIG. 1) or the upper part of the windshield, the opening of the display device 2F. Since the height of the lower portion (width of the lower side frame) in the portion 30 can be reduced, the area where the front is blocked by the lower side frame can be reduced.

Further, in the top view shown in FIG. 19, the front end portion 26a on the display element 18 side of the second mirror 26F is formed into a convexly curved shape corresponding to the shape of the upper end portion 20a of the polarizing element 20F. There is. In the top view shown in FIG. 19, the rear end portion 26b of the second mirror 26F is formed in a straight line. As a result, as shown by the broken line in FIG. 18, the reflected image of the second mirror 26F can be projected onto the polarizing element 20F without chipping.

(Embodiment 6)
[6-1. Display device configuration]
The configuration of the display device 2G according to the sixth embodiment will be described with reference to FIG. 20. FIG. 20 is a cross-sectional view of the display device 2G according to the sixth embodiment. In FIG. 20, the same components as those in FIG. 3A are designated by the same reference numerals, and detailed description thereof will be omitted.

As shown in FIG. 20, the characteristic configuration in the present embodiment is that the arrangement of the display element 18 and the arrangement of the first mirror 22 are interchanged as compared with the configuration of FIG. 3A. Specifically, when viewed from the opening 30, the display element 18 is arranged on the upper portion (plus side of the Z axis) of the housing 16. Similarly, the first mirror 22 is arranged in the inner part of the housing 16 (minus side of the X axis), and the second mirror 26 is arranged in the lower part of the housing 16 (minus side of the Z axis). The polarizing element 20 is inclined between the display element 18 and the second mirror 26 so that the upper end portion 20a (the end portion on the plus side of the Z axis) of the polarizing element 20 is on the opening 30 side. Be placed.

Also in this embodiment, the light emitted from the display surface 34 of the display element 18 is reflected by the mirrors (first mirror 22 and second mirror 26) from the inside of the housing 16 through the dustproof cover 32. Before it is emitted to the outside of the housing 16, it is reflected twice by the polarizing element 20 and transmitted once through the polarizing element 20, that is, in detail, the emitted light is first reflected by the polarizing element 20. Then, the display element 18 and the first mirror 22 are reflected so as to be reflected by the first mirror 22 and then transmitted through the polarizing element 20, then reflected by the second mirror 26 and then reflected again by the polarizing element 20. The angle of is adjusted.

With such a configuration, the entire device can be miniaturized, and the heat-generating display element 18 can be arranged on the upper part of the housing 16 (plus side in the Z-axis direction), so that the display can be displayed. The heat generated by the element 18 and the heat of the air warmed by the display element 18 are dissipated from the upper part of the housing 16. As a result, the influence of heat on the mirror and the polarizing element 20 can be suppressed.

In the configuration of FIG. 20, the light emitted from the display surface 34 of the display element 18 is emitted to the dustproof cover 32 side from the normal line 36 of the display surface 34. On the other hand, even if the display element 18a is arranged as shown by the broken line in FIG. 20, the light emitted from the display surface 34a is emitted to the first mirror 22 side from the normal line 36a of the display surface 34a. good.

(Embodiment 7)
[7-1. Display device configuration]
The configuration of the display device 2H according to the seventh embodiment will be described with reference to FIG. 21. FIG. 21 is a cross-sectional view of the display device 2H according to the seventh embodiment. In FIG. 21, the same components as those in FIG. 3A are designated by the same reference numerals, and detailed description thereof will be omitted.

As shown in FIG. 21, the characteristic configuration in the present embodiment is that a third mirror 62 is added as compared with the configuration of FIG. 3A. The third mirror 62 is the same planar mirror as the first mirror 22, and has a planar reflecting surface 64.

The light emitted from the display surface 34 of the display element 18 is reflected by the polarizing element 20 and then reflected in the order of the reflecting surface 64 of the third mirror 62 and the reflecting surface 44 of the first mirror 22 to cause the polarizing element 20. To Penetrate. The optical path after that is the same as in FIG. 3A.

With such a configuration, the optical path length can be further extended by the amount reflected by the third mirror 62. Even in the configuration of the present embodiment, the light emitted from the display surface 34 of the display element 18 is reflected by the mirrors (first mirror 22, second mirror 26, and third mirror 62) to form a housing. It is reflected twice by the polarizing element 20 and transmitted once through the polarizing element 20 until it is emitted from the inside of the 16 to the outside of the housing 16 via the dustproof cover 32. Specifically, the emitted light is first reflected by the polarizing element 20, then reflected by the third mirror 62 and the first mirror 22, then transmitted through the polarizing element 20, and then reflected by the second mirror 26. After that, it is reflected again by the polarizing element 20.

(Other variants)
Although the display device according to one or more embodiments has been described above based on each of the above embodiments, the present disclosure is not limited to each of the above embodiments. As long as it does not deviate from the gist of the present disclosure, a form in which various modifications conceived by those skilled in the art are applied to each of the above embodiments, or a form constructed by combining components in different embodiments is also a form of one or a plurality of embodiments. It may be included in the range.

In each of the above embodiments, the light emitted from the display surface 34 of the display element 18 is linearly polarized light having a polarization direction in the first direction d1, but the light is not limited to this and is not limited to the second direction d2. It may be linearly polarized light having a polarization direction.

In each of the above embodiments, the first mirror 22 (22D) is a planar mirror, but the present invention is not limited to this, and the first mirror 22 (22D) may be a concave mirror. In this case, the second mirror 26 (26F) may be either a concave mirror or a flat mirror. Further, the first mirror 22 may be a convex mirror and the second mirror 26 may be a concave mirror. Further, in the seventh embodiment, the third mirror 62 is a planar mirror, but the present invention is not limited to this, and the third mirror 62 may be a concave mirror.

In each of the above embodiments, the second mirror 26 (26F) is a concave mirror having a free curved surface, but the present invention is not limited to this, and for example, a spherical concave mirror, an aspherical concave mirror, a cylindrical mirror, or the like may be used.

In each of the above embodiments, the dustproof cover 30 or the transmissive polarizing plate 52 is arranged in the opening 30, but instead of these configurations, a liquid crystal display capable of electrically switching between light reflection and transmission. The optical element may be provided in the opening 30.

The display device of the present disclosure can be applied to, for example, an electronic mirror mounted on a vehicle.

2,2A, 2B, 2C, 2D, 2E, 2F, 2G, 2H, 100 Display device 4 Vehicle 6 Windshield 8 Ceiling 10 Bracket 12 Driver's seat 14 Driver 16, 16D, 102 Housing 18, 18a, 104 Display element 20, 20C, 20F, 106 Polarizing element 20a Upper end 20b Lower end 22, 22D First mirror 24, 24E First λ / 4 plate 26, 26F Second mirror 26a Front end 26b Rear end 28 Storage space 30 , 110 Opening 32, 112 Dustproof cover 34, 34a, 114 Display surface 36, 36a Horizontal wire 38, 50, 60, 60E Glass substrate 40 Reflective polarizing plate 42 Second λ / 4 plate 44, 44D, 46, 64 Reflective surface 48 Virtual image 52 Transmissive polarizing plate 54 Third λ / 4 plate 56 Fourth λ / 4 plate 58 Prism unit 62 Third mirror 108 Concave mirror

Claims (11)

It ’s a display device,
A display element having a display surface for displaying an image, and
At least two mirrors that reflect the light emitted from the display surface of the display element, and
With a polarizing element,
The polarizing element has a configuration capable of reflecting and transmitting the emitted light.
The emitted light is reflected by the polarizing element, then reflected by one of the at least two mirrors, then transmitted through the polarizing element, then reflected by the other of the at least two mirrors, and then the above. It is reflected again by the polarizing element, and it is reflected again.
The at least two mirrors have a first mirror and a second mirror.
The first mirror is arranged on one of the upper end side and the lower end side of the display surface.
The second mirror is arranged on the other side of the upper end side and the lower end side of the display surface.
The polarizing element is arranged between the first mirror and the second mirror so as to face the display surface.
The display device further comprises a first λ / 4 plate disposed between the polarizing element and the first mirror.
The polarizing element is
A reflective polarizing plate arranged on the side facing each of the display surface and the first mirror, and
It has a second λ / 4 plate arranged on the side facing the second mirror, and has.
The emitted light is (a) reflected by the reflective polarizing plate, (b) transmitted through the first λ / 4 plate, and (c) reflected by the first mirror, thereby causing the first λ. The / 4 plate is transmitted again, (d) each of the reflective polarizing plate and the second λ / 4 plate is transmitted, (e) is reflected by the second mirror, and (f) the second plate is transmitted. It is transmitted through the λ / 4 plate, and (g) is reflected by the reflective polarizing plate to be transmitted again through the second λ / 4 plate.
Display device. It ’s a display device,
A display element having a display surface for displaying an image, and
At least two mirrors that reflect the light emitted from the display surface of the display element, and
With a polarizing element,
The polarizing element has a configuration capable of reflecting and transmitting the emitted light.
The emitted light is reflected by the polarizing element, then reflected by one of the at least two mirrors, then transmitted through the polarizing element, then reflected by the other of the at least two mirrors, and then the above. It is reflected again by the polarizing element, and it is reflected again .
The display device further includes a housing including the display element, the at least two mirrors, and the polarizing element, and having an opening from which the emitted light is emitted.
The at least two mirrors have a first mirror and a second mirror.
When viewed from the opening, the display element is in the upper part of the housing, the first mirror is in the inner part of the housing, the second mirror is in the lower part of the housing, and the polarizing element is in the lower part of the housing. Between the display element and the second mirror, the upper end portion of the polarizing element is inclined so as to be on the opening side, and each of them is arranged.
The polarizing element is arranged between the first mirror and the second mirror so as to face the display surface.
The display device further comprises a first λ / 4 plate disposed between the polarizing element and the first mirror.
The polarizing element is
A reflective polarizing plate arranged on the side facing each of the display surface and the first mirror, and
It has a second λ / 4 plate arranged on the side facing the second mirror, and has.
The emitted light is (a) reflected by the reflective polarizing plate, (b) transmitted through the first λ / 4 plate, and (c) reflected by the first mirror, thereby causing the first λ. The / 4 plate is transmitted again, (d) each of the reflective polarizing plate and the second λ / 4 plate is transmitted, (e) is reflected by the second mirror, and (f) the second plate is transmitted. It transmits through the λ / 4 plate and (g) transmits through the second λ / 4 plate again by being reflected by the reflective polarizing plate.
Display device. The display device according to claim 1 or 2 , wherein at least one of the first mirror and the second mirror is a concave mirror. The second mirror is a concave mirror, and the second mirror is a concave mirror.
The display device according to claim 3 , wherein at least one of the upper end portion and the lower end portion when facing the second mirror is formed in a convex curved shape. The second mirror is a concave mirror, and the second mirror is a concave mirror.
The display according to claim 3 or 4 , wherein the end portion of the polarizing element on the second mirror side is formed in a convexly curved shape corresponding to the shape on the concave side of the second mirror. Device. The display device further
A transmissive polarizing plate arranged so as to face the second λ / 4 plate of the polarizing element,
A third λ / 4 plate arranged between the transmissive polarizing plate and the second λ / 4 plate is provided.
The emitted light transmitted through the second λ / 4 plate again by being reflected by the reflective polarizing plate passes through each of the third λ / 4 plate and the transmissive polarizing plate. Claims 1 to 1. The display device according to any one of 5 . The polarizing element is formed in a wedge shape in cross section.
The display device according to any one of claims 1 to 6 , wherein the thickness of the end portion of the polarizing element on the second mirror side is different from the thickness of the end portion of the polarizing element on the first mirror side. The display device according to any one of claims 1 to 7 , wherein the first mirror is a Fresnel mirror. The display device according to claim 8 , wherein the first λ / 4 plate is arranged at an angle with respect to the first mirror. Any one of claims 1 to 9 , wherein the perpendicular line on the display surface is non-parallel to the optical path of the emitted light that has passed through the second λ / 4 plate again by being reflected by the reflective polarizing plate. The display device described in the section. The emitted light from the display surface is linearly polarized light having a polarization direction orthogonal to the transmission axis of the reflective polarizing plate.
The display device according to any one of claims 1 to 10 , wherein the polarizing element is arranged at an angle with respect to the display surface around an axis parallel to the polarization direction of the linearly polarized light.

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