Image projection device

Abstract

To provide an image projection device capable of ensuring visibility even when polarized sunglasses are used.SOLUTION: An image projection device (100) for projecting image light onto a display unit (WS) for displaying a virtual image (P) includes: an image irradiation unit (10) for emitting image light; a projection optical unit (20, 30) for projecting the image light onto the display unit (WS); and a polarization switching unit (70) in the optical path of the image light, for switching the polarization direction of the image light. The image light transmitted through the polarization switching unit (70) has one of a first polarization direction and a second polarization direction intersecting the first polarization direction.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an image projection device, and more particularly to an image projection device that reflects light emitted from an image projection unit to reach a viewpoint. [Background technology]

[0002] Conventionally, dashboards that illuminate icons have been used to display various types of information inside vehicles. As the amount of information to be displayed increases, it has been proposed to embed an image display device in the dashboard or to configure the entire dashboard with an image display device.

[0003] However, since the instrument panel is located below the vehicle's windshield, the driver must move their eyes downward while driving in order to see the information displayed on the instrument panel, which is undesirable. Therefore, a head-up display (hereinafter referred to as HUD) has been proposed, which projects an image onto the windshield so that the driver can read information when looking ahead of the vehicle (see, for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-119248 [Patent Document 2] Japanese Patent Application Publication No. 2019-119262 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in conventional image projection devices, the reflectance of light reflected by the windshield tends to be low for the P-polarized component and high for the S-polarized component. For this reason, the polarization direction of the light emitted from the image projection unit is set so that it is S-polarized relative to the windshield. As a result, the light that reaches the viewpoint is only S-polarized light, with no P-polarized light.

[0006] However, when driving in environments with strong external light or on snowy roads, passengers may wear polarized sunglasses to view the outside through the windshield. In this case, light reflected by objects outside the vehicle is also S-polarized, so polarized sunglasses are designed to block S-polarized light and transmit P-polarized light. Therefore, passengers wearing polarized sunglasses have the problem that the S-polarized light reflected by the windshield is blocked by the polarized sunglasses, making it difficult to see the image formed by the irradiated light.

[0007] SUMMARY OF THE INVENTION The present invention has been made in consideration of the above-mentioned conventional problems, and has as its object to provide an image projection device that can ensure visibility even when using polarized sunglasses or the like. [Means for solving the problem]

[0008] In order to solve the above problem, the image projection device of the present invention is an image projection device that projects image light onto a display unit for displaying a virtual image, and has an image irradiation unit that irradiates the image light and a projection optical unit that projects the image light onto the display unit, and is characterized in that a polarization switching unit that switches the polarization direction of the image light is provided in the path of the image light, and the image light that passes through the polarization switching unit is in a first polarization direction or a second polarization direction that intersects the first polarization direction.

[0009] In the image projection device of the present invention, a polarization switching unit is provided in the path of the image light, and the polarization direction of the image light is switched between a first polarization direction and a second polarization direction. This makes it possible to project a virtual image in an appropriate polarization direction depending on whether polarized sunglasses are being worn or not, thereby ensuring visibility even when polarized sunglasses, etc. are used.

[0010] In one aspect of the present invention, the polarization switching section includes a half-wave plate that generates a phase difference of half a wavelength between the slow axis and the fast axis.

[0011] In one aspect of the present invention, the polarization switching unit has a rotation drive unit that rotates the half-wave plate in an in-plane direction, and rotates the directions of the slow axis and the fast axis relative to the polarization direction of the image light incident on the half-wave plate.

[0012] In one aspect of the present invention, a holder for holding the half-wave plate is provided, and the rotation driver rotates the holder.

[0013] In one aspect of the invention, the polarization switching unit has an insertion / removal drive unit that inserts and removes the half-wave plate into and from the path of the image light.

[0014] In one aspect of the present invention, the first polarization direction and the second polarization direction are p-polarized light and s-polarized light, respectively, with respect to the display unit. [Effects of the Invention]

[0015] The present invention can provide an image projection device and an image projection method that can ensure visibility even when using polarized sunglasses or the like. [Brief explanation of the drawings]

[0016] [Figure 1] 1A and 1B are schematic diagrams showing the projection of a virtual image P using the image projection device 100 of the first embodiment, where FIG. 1A shows the case where polarized sunglasses G are not worn, and FIG. 1B shows the case where polarized sunglasses G are worn. [Figure 2] 2 is a schematic cross-sectional view showing an example of the structure of the image projection unit 10 and the polarization switching unit 70 according to the first embodiment. FIG. [Figure 3] 3A and 3B are schematic diagrams illustrating the switching of polarization directions by the polarization switching unit 70, where FIG. 3A shows the case where image light is projected in a first polarization direction, and FIG. 3B shows the case where image light is projected in a second polarization direction. [Figure 4] 4A and 4B are schematic diagrams illustrating the switching of polarization directions by the polarization switching unit 70 according to the second embodiment, where FIG. 4A shows the case where image light is projected in a first polarization direction, and FIG. 4B shows the case where image light is projected in a second polarization direction. [Figure 5] FIG. 10 is a schematic diagram showing the configuration of an image projection device 100 according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0017] (First embodiment) Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. The same or equivalent components, members, and processes shown in each drawing will be assigned the same reference numerals, and redundant explanations will be omitted where appropriate. Figure 1 is a schematic diagram showing the projection of a virtual image P using an image projection device 100 according to this embodiment. Figure 1(a) shows the case where polarized sunglasses G are not worn, and Figure 1(b) shows the case where polarized sunglasses G are worn.

[0018] 1(a) and 1(b), the image projection device 100 includes an image projection unit 10, a first mirror 20, a second mirror 30, a housing unit 50, a dustproof cover 60, and a polarization switching unit 70. Also, as shown in FIGS. 1(a) and 1(b), the image light projected from the image projection device 100 is reflected by a windshield (display unit) WS and irradiated onto a driver's viewpoint position 40. The driver visually recognizes a virtual image P formed on an extension of the optical path along which the image light has entered.

[0019] 1(a), when the driver is not wearing polarized sunglasses G, the image light projected from image projection device 100 is converted to s-polarized light with respect to windshield WS by polarization switching unit 70. Therefore, the image light reaching viewpoint 40 is s-polarized light that has a high reflectivity on windshield WS, and the reduction in the amount of light required to project virtual image P can be suppressed, thereby improving visibility.

[0020] 1(b), when the driver is wearing polarized sunglasses G, the image light projected from image projection device 100 is p-polarized with respect to windshield WS by polarization switching unit 70. Therefore, the image light reaching viewpoint 40 is p-polarized light that passes through polarized sunglasses G, and even when wearing polarized sunglasses G, the amount of light required to project virtual image P is ensured, improving visibility.

[0021] 1(a) and 1(b), each part is controlled by a control unit connected to the other parts so as to be able to communicate information with them. The configuration of the control unit is not limited, but an example includes a CPU (Central Processing Unit) for information processing, a memory device, a recording medium, an information communication device, etc. The control unit controls the operation of each part according to a predetermined program, and sends information including an image (image information) to the image projection unit 10.

[0022] The image projection unit 10 is a part that projects image light containing an image based on image information from the control unit. The specific configuration of the image projection unit 10 is not limited, and a conventionally known device such as a liquid crystal display device can be used. As an example, a device that projects light from a light emitting diode (LED) from the rear side of the liquid crystal display device is used.

[0023] The first mirror 20 is an optical element that receives the image light emitted from the image projection unit 10 and reflects the image light toward the second mirror 30. In the example shown in FIG. 1, the first mirror 20 is a free-form surface mirror with an optical design necessary for projecting the image light as a virtual image P. The second mirror 30 is an optical element that receives the image light reflected by the first mirror 20 and reflects the image light toward the windshield WS. In the example shown in FIG. 1, the second mirror 30 is a free-form surface mirror with an optical design necessary for projecting the image light as a virtual image P. The second mirror 30 may also be configured to be able to change its tilt angle with respect to the horizontal direction, thereby changing the projection direction of the image light and moving the projection position of the virtual image P in the vertical direction.

[0024] The reflective surfaces of the first mirror 20 and the second mirror 30 are designed to expand the light diameter in the driver's line of sight in order to project the image light as a virtual image P through the windshield WS. Here, "expanding the light diameter in the line of sight" refers not only to the case where the light diameter expands consistently after reflection, but also to the case where the light diameter shrinks and then expands after forming an image at an intermediate point. The combination of the first mirror 20 and the second mirror 30 has the function of projecting the image light through the windshield WS and corresponds to the projection optical unit of the present invention. While FIG. 1 shows an example in which the projection optical unit is made up of two mirrors, the first mirror 20 and the second mirror 30, it is also possible to use three or more reflecting mirrors to repeatedly reflect the image light and irradiate it onto the windshield WS.

[0025] The housing 50 is a housing that forms the outer shape of the image projection device 100 and houses the other components inside. An opening is provided at the top of the housing 50, and a dustproof cover 60 is provided over the opening to seal the interior. There are no limitations on the material that can be used to form the housing 50, and light-blocking resin or metal materials can be used.

[0026] The dustproof cover 60 is made of a light-transmitting material and is a member disposed to cover the opening of the housing part 50. Although not shown in Fig. 1, the dustproof cover 60 is fixed to the housing part 50 in a structure that leaves no gap between them, thereby preventing dust and dirt from entering the housing part 50. There are no limitations on the material that makes up the dustproof cover 60, and known resin materials or glass that transmit image light can be used.

[0027] The polarization switching unit 70 is provided in the path of the image light and switches the polarization direction of the image light. The image light transmitted through the polarization switching unit 70 is polarized in either a first polarization direction or a second polarization direction relative to the windshield WS. The first and second polarization directions are polarized light whose polarization directions intersect with each other. For example, if the first polarization direction is s-polarized light, the second polarization direction can be p-polarized light, which is perpendicular to the s-polarized light. For example, if the image light emitted from the image projection unit 10 is s-polarized light, the polarization switching unit 70 either transmits the image light as s-polarized light or rotates the polarization direction 90 degrees to convert it to p-polarized light. While the description here is of s-polarized light and p-polarized light relative to the windshield WS, as long as the image light is primarily s-polarized or p-polarized light, it may also contain small amounts of other polarized light components.

[0028] 1(a) and 1(b), the optical path of the image light is depicted as a single straight line. However, the actual image light is displayed in a predetermined area in the image projection unit 10, and has a predetermined area in a direction perpendicular to the traveling direction. The image light may be reflected by the first mirror 20, its light diameter reduced as it travels, and may be intermediately imaged at an intermediate imaging position F (not shown) between the first mirror 20 and the second mirror 30. When the image light reflected by the first mirror 20 is imaged at the intermediate imaging position F, the cross-sectional area through which the image light passes is minimized at the intermediate imaging position F between the first mirror 20 and the second mirror 30.

[0029] The windshield WS is a part of the vehicle that is provided in front of the driver's seat and transmits visible light. The windshield WS corresponds to the display unit of the present invention because the windshield WS, on the inside surface of the vehicle, reflects image light incident from the second mirror 30 toward the viewpoint and transmits light from outside the vehicle toward the viewpoint. While an example in which the windshield WS is used as the display unit is shown here, a combiner may be provided as a display unit separate from the windshield WS and reflect light from the second mirror 30 toward the viewpoint. Furthermore, the display unit is not limited to being located at the front of the vehicle, and may be located to the side or rear as long as it projects an image toward the viewpoint of the passenger.

[0030] The virtual image P is an image that appears as if it were formed in space when image light reflected by the windshield WS reaches the viewpoint (eyebox) of the driver or the like. The position at which the virtual image P is formed is determined by the angle at which the light irradiated from the image projection unit 10 spreads as it travels toward the viewpoint after being reflected by the first mirror 20, the second mirror 30, and the windshield WS. The display content of the image projected as the virtual image P may include auxiliary information related to driving such as a warning image or emergency information, a volume indicator, a driving direction guide, etc.

[0031] FIG. 2 is a schematic cross-sectional view showing an example of the structure of the image projection unit 10 and polarization switching unit 70 according to this embodiment. As shown in FIG. 2, the image projection unit 10 according to this embodiment includes a substrate 11, a light source unit 12, a lens unit 13, a liquid crystal display unit 14, a housing unit 15, and a guide pin 16. The polarization switching unit 70 includes a half-wave plate 71, a holding unit 72, a gear unit 73, a rotation drive unit 74, and a gear unit 75. The holding unit 72 has a guide groove 72a. The arrows in FIG. 2 schematically show the light irradiated from the light source unit 12 to the liquid crystal display unit 14.

[0032] The substrate 11 is a member on one surface of which a wiring pattern is formed and on which the light source unit 12 is mounted. The substrate 11 may be mounted with electronic components for driving the light source unit 12 to form a drive circuit. The substrate 11 may also be provided with a terminal unit (not shown), and power and control signals may be supplied from a cable or the like connected to the terminal unit.

[0033] The light source unit 12 is mounted on the substrate 11 and is a component that irradiates the liquid crystal display unit 14 with light via the lens unit 13. The light source unit 12 is, for example, a semiconductor light-emitting element such as an LED (Light Emitting Diode). The color of light emitted from the light source unit 12 is not particularly limited, but in this embodiment, white light is used as an example. In this embodiment, the light source unit 12 is arranged in one row, but may be arranged in two or more rows. The light irradiated from the light source unit 12 is unpolarized.

[0034] Lens unit 13 is an optical element disposed in the light emission direction of light source unit 12, and has the function of concentrating the light emitted from light source unit 12 and emitting it as, for example, parallel light or light close to parallel light (hereinafter, both of these will be collectively referred to as "substantially parallel light"). While Fig. 2 shows an example in which one lens array is used as lens unit 13, a plurality of lenses may be combined to adjust the light distribution of the light irradiated onto liquid crystal display unit 14.

[0035] The liquid crystal display unit 14 is a component that receives incident light from the rear surface and emits image light modulated by image information from the display surface. The specific configuration of the liquid crystal display unit 14 is not limited, but one example is a transmissive liquid crystal display device that transmits light incident from the rear surface and emits it from the front surface. In a transmissive liquid crystal display device, only light polarized in a predetermined direction that is incident on the rear surface is transmitted. The polarization direction of the image light emitted from the liquid crystal display unit 14 is defined as a first polarization direction, and a direction intersecting the first polarization direction is defined as a second polarization direction. For example, the first polarization direction is defined as the s-polarized light direction relative to the windshield WS, and the second polarization direction is defined as the p-polarized light direction relative to the windshield WS.

[0036] The housing 15 is a container that houses the substrate 11, the light source 12, the lens 13, and the liquid crystal display 14, and has a polarization switching unit 70 mounted on the top surface. An opening is provided on the top surface of the housing 15, and the image light is irradiated onto the half-wave plate 71 through the opening. A guide pin 16 is provided on the top surface of the housing 15.

[0037] The guide pin 16 is inserted into the guide groove 72a of the holding part 72 to regulate the rotation direction of the holding part 72. Although Fig. 2 shows an example in which the guide pin 16 has a flat, truncated head at the upper end of a rod-like part, the shape and structure are not limited thereto.

[0038] The half-wave plate 71 is an optical element arranged on the path of the image light irradiated from the image irradiation unit 10 and made of a birefringent material having different refractive indices in the slow axis and the fast axis. The half-wave plate 71 is designed so that a phase difference of half the wavelength of the incident light occurs between the slow axis and the fast axis before the incident light is emitted. As will be described later, the slow axis and fast axis of the half-wave plate 71 are capable of changing the angle with respect to the polarization direction (first polarization direction) of the image light irradiated from the image irradiation unit 10.

[0039] The holding portion 72 is a disk-shaped member that holds the half-wave plate 71 inside the opening. The holding portion 72 is arranged on the top surface of the housing portion 15, and has a gear portion 73 on its outer periphery. The holding portion 72 is formed with a guide groove 72a into which the guide pin 16 is inserted. The guide groove 72a is a groove that is formed in an arc shape on the surface of the holding portion 72, with the rotation center of the holding portion 72 as its center. It is preferable that the guide groove 72a is formed in two or more places with the rotation center as the center of point symmetry.

[0040] Gear portion 73 has a concave-convex shape provided along the outer periphery of holding portion 72, and has a shape and pitch that correspond to the concave-convex shape provided on gear portion 75. Gear portion 73 is disposed so as to mesh with gear portion 75, and when gear portion 75 is rotated by rotation drive portion 74, gear portion 73 and holding portion 72 are rotated.

[0041] The rotation drive unit 74 is a part that rotates the holding unit 72 and the half-wave plate 71. Power and a control signal are supplied to the rotation drive unit 74 from the outside via a cable (not shown) or the like, and the power is converted into rotational motion to rotate the gear unit 75, which then rotates the holding unit 72 and the half-wave plate 71 via the gear unit 73. The specific configuration of the rotation drive unit 74 is not limited, and a conventionally known motor device or the like can be used, and as one example, a swivel actuator can be used.

[0042] Gear portion 75 is a gear that is rotated by rotation drive portion 74, and has a shape and pitch that correspond to the concave and convex shapes provided on gear portion 73. Gear portion 75 is arranged to mesh with gear portion 73.

[0043] 3A and 3B are schematic diagrams illustrating switching of the polarization direction by the polarization switching unit 70, with FIG. 3A illustrating a case where image light is projected in a first polarization direction and FIG. 3B illustrating a case where image light is projected in a second polarization direction. In FIGS. 3A and 3B, the double-headed arrows shown in the half-wave plate 71 schematically indicate the direction along the slow axis or fast axis of the half-wave plate 71. Hereinafter, a case where the double-headed arrows indicate the direction along the fast axis will be described as an example, but the slow axis and the fast axis may be interchanged.

[0044] In the state shown in FIG. 3(a), the fast axis of the half-wave plate 71 is aligned in the same direction as the polarization direction (first polarization direction: s-polarized light) of the image light emitted from the liquid crystal display unit 14. Therefore, the polarization direction of the image light emitted from the liquid crystal display unit 14 is maintained and the image light passes through the half-wave plate 71 as s-polarized light. Therefore, as shown in FIG. 1(a), the image light projected from the image projection device 100 to the viewpoint 40 via the windshield WS is also s-polarized light. Therefore, the high reflectance of the s-polarized light on the windshield WS ensures a sufficient amount of image light, improving the visibility of the virtual image P.

[0045] In the state shown in FIG. 3(b), the fast axis of the half-wave plate 71 is oriented in a direction that intersects at 45 degrees with the polarization direction (first polarization direction: s-polarized light) of the image light emitted from the liquid crystal display unit 14. Therefore, the polarization direction of the image light emitted from the liquid crystal display unit 14 is rotated by 90 degrees, becoming p-polarized light, and passing through the half-wave plate 71. Therefore, as shown in FIG. 1(b), the image light projected from the image projection device 100 onto the viewpoint 40 via the windshield WS is also p-polarized light. Therefore, even if the driver is wearing polarized sunglasses G, the p-polarized image light passes through the polarized sunglasses G, allowing the driver to clearly view the virtual image P.

[0046] Here, switching between the state shown in FIG. 3(a) where s-polarized light is transmitted and the state shown in FIG. 3(b) where image light is converted to p-polarized light is performed by controlling the rotational drive of the rotational drive unit 74 to rotate the gear unit 75, the gear unit 73, the holder 72, and the half-wave plate 71. Because the guide pin 16 is inserted into the guide groove 72a, the holder 72 rotates around the center of the arc-shaped guide groove 72a. The rotation of the holder 72 is restricted by the guide pin 16 being positioned at the end of the guide groove 72a. The rotational drive unit 74 can be controlled, for example, by manually operating a switch (not shown), by voice input, or by capturing an image of the interior of the vehicle with an imaging device and detecting the presence or absence of polarized sunglasses G through image recognition.

[0047] As described above, in the image projection device 100 of this embodiment, a polarization switching unit 70 is provided in the path of the image light, and the polarization direction of the image light is switched between a first polarization direction and a second polarization direction. This allows the virtual image P to be projected in an appropriate polarization direction depending on whether polarized sunglasses G are being worn or not, making it possible to ensure visibility even when polarized sunglasses G, etc. are used.

[0048] (Second embodiment) Next, a second embodiment of the present invention will be described with reference to Fig. 4. Description of content that overlaps with the first embodiment will be omitted. Fig. 4 is a schematic diagram illustrating switching of the polarization direction by a polarization switching unit 70 according to this embodiment, with Fig. 4(a) showing a case where image light is projected in a first polarization direction and Fig. 4(b) showing a case where image light is projected in a second polarization direction.

[0049] 4(a) and 4(b), the image projection unit 10 of this embodiment includes a substrate 11, a light source unit 12, a lens unit 13, a liquid crystal display unit 14, and a housing unit 15. The polarization switching unit 70 includes a half-wave plate 71, an insertion / removal drive unit 76, an arm unit 77, and a frame unit 78. The frame unit 78 has an opening 78a formed therein.

[0050] The insertion / removal drive unit 76 is a part that inserts and removes the half-wave plate 71 into and from the path of the image light. The insertion / removal drive unit 76 is supplied with power and a control signal from the outside via a cable (not shown) or the like, and converts the power into linear extension and contraction motion to move the half-wave plate 71. The specific configuration of the insertion / removal drive unit 76 is not limited, and a conventionally known motor device or the like can be used, and as one example, a leveling actuator can be used.

[0051] The arm portion 77 has one end connected to the insertion / removal drive portion 76 and the other end holding the half-wave plate 71. The shape and structure of the arm portion 77 are not limited, and a rod-shaped or plate-shaped arm can be used. Furthermore, since the arm portion 77 holds the half-wave plate 71 at a position extended from the insertion / removal drive portion 76, it needs to be made of a material having a predetermined rigidity, and as an example, a resin material or a metal material can be used.

[0052] The frame portion 78 is a portion that holds the insertion / removal drive portion 76 at a predetermined position relative to the image projection portion 10. The frame portion 78 may also be provided with a guide rail or the like that supports the movement of the arm portion 77. An opening 78a is provided in the frame portion 78 at a position corresponding to the liquid crystal display portion 14, and image light from the liquid crystal display portion 14 passes through the opening 78a and is irradiated onto the first mirror 20.

[0053] In the state shown in FIG. 4(a), the insertion / removal drive unit 76 and the arm unit 77 are in a retracted state, and the half-wave plate 71 is extracted from the opening 78a and removed from the path of the image light. Therefore, the polarization direction of the image light emitted from the liquid crystal display unit 14 is maintained and the image light passes through the opening 78a as s-polarized light. Therefore, as shown in FIG. 1(a), the image light projected from the image projection device 100 to the viewpoint 40 via the windshield WS is also s-polarized light. Therefore, the high reflectivity of the s-polarized light on the windshield WS ensures a sufficient amount of image light, improving the visibility of the virtual image P.

[0054] In the state shown in FIG. 4(b), the insertion / removal drive unit 76 and the arm unit 77 are extended, and the half-wave plate 71 is positioned to block the opening 78a and is disposed in the path of the image light. The fast axis of the half-wave plate 71 is oriented in a direction that intersects at 45 degrees with the polarization direction of the image light (first polarization direction: s-polarized light) emitted from the liquid crystal display unit 14. Therefore, the polarization direction of the image light emitted from the liquid crystal display unit 14 is rotated by 90 degrees, becoming p-polarized light and passing through the half-wave plate 71. Therefore, as shown in FIG. 1(b), the image light projected from the image projection device 100 to the viewpoint 40 via the windshield WS is also p-polarized light. Therefore, even if the driver is wearing polarized sunglasses G, the p-polarized image light passes through the polarized sunglasses G, allowing the driver to clearly view the virtual image P.

[0055] In the image projection device 100 of this embodiment, a polarization switching unit 70 is provided in the path of the image light, and the polarization direction of the image light is switched between a first polarization direction and a second polarization direction, so that the virtual image P can be projected in an appropriate polarization direction depending on whether polarized sunglasses G are being worn or not, and visibility can be ensured even when polarized sunglasses G, etc. are used.

[0056] (Third embodiment) Next, a third embodiment of the present invention will be described with reference to Fig. 5. Description of content that overlaps with the first embodiment will be omitted. Fig. 5 is a schematic diagram showing the configuration of an image projection device 100 according to this embodiment. In the first and second embodiments, an example was shown in which the polarization switching unit 70 was disposed adjacent to the image projection unit 10, but the position of the polarization switching unit 70 is not limited as long as it is on the path of the image light.

[0057] In the example shown in Fig. 5(a), the polarization switching unit 70 is disposed on the path of the image light between the second mirror 30 and the dustproof cover 60. In the example shown in Fig. 5(b), the polarization switching unit 70 is disposed on the path of the image light between the first mirror 20 and the second mirror 30. In the examples shown in Figs. 5(a) and 5(b), as in the first and second embodiments, the image light can be switched between s-polarized light and p-polarized light by rotating the half-wave plate 71 by 45 degrees or by inserting or removing the half-wave plate 71 on the path of the image light.

[0058] In the image projection device 100 of this embodiment, a polarization switching unit 70 is provided in the path of the image light, and the polarization direction of the image light is switched between a first polarization direction and a second polarization direction, so that the virtual image P can be projected in an appropriate polarization direction depending on whether polarized sunglasses G are being worn or not, and visibility can be ensured even when polarized sunglasses G, etc. are used.

[0059] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention. [Explanation of symbols]

[0060] 100...Image projection device 10...Image irradiation unit 20...1st mirror 30...Second mirror 40...Viewpoint position 50...Housing part 60...Dustproof cover 70...Polarization switching section 11... Circuit board 12...Light source section 13...Lens section 14...Liquid crystal display section 15...Housing 16...Guide pin 71...Half-wave plate 72...Holding part 72a...Guide groove 73,75...Gear section 74...Rotation drive unit 76...Insertion / extraction drive unit 77...Arm 78...Frame section 78a…Opening

Claims

1. An image projection device that projects image light onto a display unit for displaying a virtual image, an image irradiating unit that irradiates the image light; a projection optical unit that projects the image light onto the display unit, a polarization switching unit that switches the polarization direction of the image light is provided in a path of the image light, An image projection device, characterized in that the image light transmitted through the polarization switching unit has a first polarization direction or a second polarization direction that intersects with the first polarization direction.

2. 2. The image projection device according to claim 1, The image projection device is characterized in that the polarization switching unit includes a half-wave plate that generates a phase difference of half a wavelength between the slow axis and the fast axis.

3. 3. The image projection device according to claim 2, the polarization switching unit has a rotation drive unit that rotates the half-wave plate in an in-plane direction, An image projection device, characterized in that the directions of the slow axis and the fast axis are rotated with respect to the polarization direction of the image light incident on the half-wave plate.

4. 4. The image projection device according to claim 3, a holding portion for holding the half-wave plate, The image projection device is characterized in that the rotation drive unit rotates the holding unit.

5. 3. The image projection device according to claim 2, The image projection device is characterized in that the polarization switching unit has an insertion / removal drive unit that inserts and removes the half-wave plate into and from the path of the image light.

6. 6. The image projection device according to claim 1, The image projection device, wherein the first polarization direction and the second polarization direction are p-polarized light and s-polarized light, respectively, relative to the display unit.

Images