Head-up display device and control method for head-up display device

Abstract

To provide a head-up display device with which, while preventing breakage due to sunlight, it is possible to reduce time slots in which a user is unable to view a virtual image, and a method for controlling the same, contributing to Sustainable Development Goal 3: Ensure healthy lives and promote well-being for all at all ages.SOLUTION: A video display device 35 displays a video and emits the video light of the displayed video. A mirror (video light projection unit) M1 projects, and causes to be reflected, the video light emitted from the video display device 35 to a display region 5, so that the projected video light is visually recognized as a virtual image by a user. A shutter 68 is disposed on an optical path 30 of the video light, and switches between an optical path forming state in which the optical path of the video light is formed and an optical path non-forming state in which the optical path of the video light is not formed.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a head-up display device and a control method thereof, and more particularly to a technology of a head-up display device using, for example, AR (Augmented Reality).

Background Art

[0002] Patent Document 1 discloses a head-up display device capable of effectively preventing the intrusion of external light such as sunlight. The head-up display device includes a shutter unit having a plurality of shutters, and by changing the size of a transmission window formed in the shutter unit according to the size of a display image displayed by a display unit, the intrusion of external light and thus the damage of the display unit are prevented.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] For example, vehicles such as automobiles may be equipped with a head-up display (abbreviated as "HUD" in the specification). The HUD projects and displays driving information such as vehicle speed and engine speed, as well as navigation information, etc. on a windshield (front glass). When using the HUD, the driver can obtain the information necessary for driving without moving the line of sight to the instrument panel incorporated in the dashboard, that is, the so-called instrument panel. Therefore, it becomes possible to contribute to safe driving.

[0005] On the one hand, in recent years, there has been a demand for the use of AR in HUD to add various information to real-world scenic objects and display them. In particular, in an HUD using AR (referred to as AR-HUD), a large display area is required. To expand the display area, it is necessary to widen the aperture provided on the optical path of the video light, that is, on the optical path from the display panel to the windshield. However, the wider the aperture, the easier it is for sunlight to enter along the optical path opposite to that of the video light. As a result, the display panel is more likely to be damaged.

[0006] Therefore, a method of changing the size of the transmissive window portion, as in Patent Document 1, can be considered. However, even when the size of the transmissive window portion is changed according to the size of the display image, a condensing point of sunlight may still occur on the display panel, so sufficient protection cannot always be achieved. To achieve sufficient protection, for example, it is desirable to block the optical path through which sunlight enters. However, usually, when blocking the optical path of sunlight, the optical path of the video light from the display panel is also blocked at the same time, resulting in a time period when the user cannot visually recognize the virtual image.

[0007] The present invention has been made in view of such circumstances, and one of its objectives is to provide a head-up display device and its control method capable of reducing the time period when the user cannot visually recognize the virtual image while preventing damage caused by sunlight.

[0008] The above and other objectives and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

Means for Solving the Problems

[0009] Briefly explaining the outline of typical ones among the inventions disclosed in the present application, it is as follows.

[0010] A typical head-up display device is a head-up display device for a vehicle, comprising a video display device, a video light projection unit, and a shutter. The video display device emits video light of a video. The video light projection unit projects and reflects the video light emitted from the video display device onto a display area, thereby displaying a virtual image in front of the vehicle. The shutter is provided on the optical path of the video light and switches between an optical path forming state for forming the optical path of the video light and an optical path non-forming state for not forming the optical path of the video light.

Advantages of the Invention

[0011] Among the inventions disclosed in the present application, briefly explaining the effects obtained by typical ones, in a head-up display device, it becomes possible to reduce the time period during which a user cannot visually recognize a virtual image while preventing damage caused by sunlight.

Brief Description of the Drawings

[0012]

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Mode for Carrying Out the Invention

[0013] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In all the drawings for explaining the embodiments, the same members are generally denoted by the same reference numerals, and repeated explanations thereof are omitted.

[0014] (Embodiment 1) <Overview of HUD Device> FIG. 1 is a schematic diagram showing a configuration example of a vehicle equipped with a head-up display device according to Embodiment 1. The head-up display (HUD) device 1 shown in FIG. 1 is mounted on a vehicle 2 which is one type of vehicle. The vehicle 2 is typically an automobile, but is not necessarily limited thereto, and may be a railway vehicle or the like. Further, the vehicle is not limited to a vehicle, and may be an aircraft or the like. In addition, the vehicle 2 is usually equipped with a control unit (not shown) called an ECU (Electronic Control Unit).

[0015] The control unit acquires vehicle information 4 from, for example, various sensors installed in each part of the vehicle 2 and, in addition, a navigation device or the like. The various sensors detect, for example, various events occurring in the vehicle 2 and also detect various parameter values related to the driving situation. The HUD device 1 acquires the vehicle information 4 acquired by the control unit using, for example, CAN (Controller Area Network) communication or the like.

[0016] The vehicle information 4 includes, for example, speed information, gear information, steering wheel steering angle information, lamp lighting information, outside light information, distance information, infrared information, engine ON / OFF information, camera image information inside and outside the vehicle, acceleration gyro information, GPS (Global Positioning System) information, navigation information, vehicle-to-vehicle communication information, and road-to-vehicle communication information. The GPS information also includes information such as the current time. Based on such vehicle information 4, the HUD device 1 projects an image onto a display area 5 such as a windshield 3. Thereby, the HUD device 1 allows a user such as a driver to visually recognize the image projected onto the display area 5 as a virtual image, specifically as a virtual image superimposed on the scenery in front of the vehicle 2.

[0017] Figure 2 is a schematic diagram showing a configuration example of the main part of the HUD device in Figure 1. The HUD device 1 shown in Figure 2 includes a shutter 68 in addition to a video display device 35 and mirrors M1 and M2 which are light reflection members. The video display device 35 is, for example, a projector, an LCD (Liquid Crystal Display), etc., and displays a video based on the input video data, generates and emits video light of the displayed video. Specifically, the video display device 35 includes a light source 65, an optical component 63a, and a display panel 64.

[0018] The light source 65 is, for example, an LED (Light Emitting Diode) light source, a laser light source, etc., and irradiates the display panel 64 with backlight. Specifically, when the light source 65 is controlled to be on, the backlight is turned on, and when it is controlled to be off, the backlight is turned off. The optical component 63a is, for example, a lens for the light source, and adjusts the optical path of the backlight so that the backlight from the light source 65 irradiates the display panel 64 uniformly. The display panel 64 is typically a liquid crystal panel (LCD: Liquid Crystal Display). The display panel 64 displays a video by modulating the backlight from the light source 65 according to the input video data, specifically, by modulating the transmittance for each pixel.

[0019] The mirror M2 is, for example, a plane mirror, and is provided on the optical path 30 of the video light between the video display device 35 and the mirror M1. The mirror M2 functions as a video light reflection part that reflects the video light from the video display device 35 to the mirror M1. The mirror M1 is, for example, a concave mirror (magnifying glass), and is provided on the optical path 30 of the video light between the mirror M2 and the display area 5. The mirror M1 functions as a video light projection part that projects the video light emitted from the video display device 35 onto the display area 5, and makes the projected video light visible as a virtual image to a user such as the driver 6. That is, the video light projection part projects and reflects the video light emitted from the video display device 35 onto the display area 5 of the vehicle, and displays a virtual image in front of the vehicle.

[0020] Specifically, the mirror (image light projection unit) M1 reflects and enlarges the image light reflected by the mirror (image light reflection unit) M2, and projects it onto the display area 5 through the opening 7. The image light projected onto the display area 5 is reflected by the display area 5 and enters the eyes of the driver 6. As a result, the driver 6 visually recognizes the image light projected onto the display area 5 as a virtual image in front of the transparent windshield 3, superimposed on the scenery outside the vehicle (such as roads, buildings, people, etc.). The information represented by the virtual image includes various things, such as road signs, the current speed of the vehicle itself, and various information added to the objects in the scenery, that is, AR information, etc.

[0021] Note that the mirrors M1 and M2 may be, for example, free-form mirrors or mirrors having an asymmetric optical axis shape. Here, the installation angle of the mirror (image light reflection unit) M2 is fixed. On the other hand, the mirror (image light projection unit) M1 includes a drive mechanism 62. Thereby, the installation angle of the mirror M1 is variably adjusted via the drive mechanism 62. The drive mechanism 62 includes, for example, a motor, and rotates the mirror M1 by the rotational operation of the motor. By adjusting the angle of the mirror M1 while rotating around the rotation axis, it is possible to switch between a projection mode in which the image light is projected onto the display area 5 and a non-projection mode in which the image light is not projected onto the display area 5.

[0022] Also, by adjusting the installation angle of the mirror M1 in the projection mode, the position of the display area 5 on the windshield 3, that is, the vertical position of the virtual image visually recognized by the driver 6, can be adjusted. Further, for example, by increasing the area of the mirror M1 and the opening 7, the area of the display area 5 can be enlarged, and more information can be projected onto the display area 5. Thereby, an AR function of adding and displaying various information to the objects in the scenery can be realized.

[0023] The shutter 68 is provided on the optical path 30 of the video light. In the example shown in FIG. 2, it is provided on the optical path 30 of the video light between the video display device 35 and the mirror (video light reflection part) M2. The shutter 68 is controlled to an optical path forming state that forms the optical path of the video light or an optical path non-forming state that does not form the optical path of the video light. In the example shown in FIG. 2, the shutter 68 transmits light in the optical path forming state and blocks light in the optical path non-forming state. The shutter 68 is typically a liquid crystal shutter or the like that can switch between transmission and light blocking at high speed. Although details will be described later, the switching between the optical path forming state and the optical path non-forming state is performed at a speed fast enough for the driver 6 to visually recognize the video light projected onto the display area 5 as a virtual image.

[0024] <Details of the HUD device> FIG. 3 is a diagram showing a more detailed configuration example and operation example of the HUD device in FIG. 2. FIG. 4 is a perspective view showing an external shape example of the HUD device shown in FIG. 3. The HUD device 1 shown in FIG. 3 includes a video display device 35, a shutter 68, mirrors M1 and M2, and a drive mechanism 62, which are the same as those in the case of FIG. 2, inside a housing 61. Further, in FIG. 3, a solar sensor 66 and an optical component 63b are provided inside the housing 61.

[0025] The solar sensor 66 detects the position of the sun 60 and the intensity of the sunlight 31. The optical component 63b is a projection lens and is provided on the optical path of the video light between the video display device 35 and the shutter 68. The optical component 63b adjusts, for example, the spread of the video light from the display panel 64. In FIG. 3, for the sake of simplicity of description, the illustration of the optical component 63a inside the video display device 35 shown in FIG. 2 is omitted.

[0026] Here, the mirror (image light projection unit) M1 is controlled to a projection mode in which image light is projected onto the display area or a non-projection mode in which image light is not projected onto the display area by adjusting the installation angle via the drive mechanism 62. The arrow direction shown in FIG. 3 is the direction in which the mirror M1 rotates and is the direction for switching from the projection mode to the non-projection mode. In the projection mode, while the image light is projected onto the display area, sunlight 31 can enter the display panel 64 through the optical path 33a in the direction opposite to the optical path of the image light. As a result, the display panel 64 may be damaged. Therefore, by controlling the mirror M1 to the non-projection mode, an optical path 33b can be formed so that the sunlight 31 does not enter the display panel 64.

[0027] Note that in FIG. 3, since the shutter 68 is provided, even if the mirror M1 is controlled to the projection mode, the incidence of the sunlight 31 on the display panel 64 can be prevented by fixing the shutter in a non-optical path forming state, for example, in a light-shielding state. However, depending on the material and the like, the shutter 68 may deteriorate when irradiated with strong sunlight 31. For this reason, it is desirable to provide a non-projection mode and adjust the installation angle of the mirror M1 so as to form the optical path 33b that is out of the shutter 68.

[0028] Whether to control the mirror (image light projection unit) M1 to the non-projection mode can be determined based on, for example, the detection result of the solar radiation sensor 66. Also, although not shown, a temperature sensor for detecting the ambient temperature may be further installed in the housing 61. Then, based on the ambient temperature, it may be determined whether to control the mirror M1 to the non-projection mode. However, for example, when obtaining the ambient temperature from a temperature sensor installed in the vehicle 2, it is not necessary to install a temperature sensor in the housing 61.

[0029] In FIG. 4, an opening 7 shown in FIG. 3 is formed in the housing 61, and a transparent cover member 71 called a glare trap or the like is installed in the opening 7. As shown in FIG. 3, a mirror (image light projection unit) M1 is installed in the housing 61 so as to reflect the light from the mirror (image light reflection unit) M2 to the cover member 71, that is, the opening 7. Further, a solar sensor 66 is installed in the housing 61, for example, around the cover member 71 or the like.

[0030] The solar sensor 66 may be configured and arranged to detect the solar light intensity when the position (azimuth and elevation angle) of the sun 60 is within a predetermined range. For example, depending on the incident angle of the solar light 31 with respect to the mirror M1, and thus the position of the sun 60, the optical path of the solar light 31 may deviate from the display panel 64, so that the possibility of damage to the display panel 64 can be ignored. That is, depending on the season, time zone, the orientation of the vehicle 2, etc., the possibility of damage can be ignored.

[0031] The range of the incident angle in which this possibility of damage can be ignored, in other words, the range of the incident angle in which the possibility of damage cannot be ignored, can be determined in advance based on the optical conditions (for example, installation position, installation angle, size, etc.) of the optical system including the mirrors M1, M2 and the optical component 63b. Therefore, the solar sensor 66 uses the range of the incident angle (position of the sun 60) in which the possibility of damage to the display panel 64 cannot be ignored as a predetermined range, and detects the solar light intensity within this predetermined range.

[0032] As a specific configuration of the solar sensor 66, for example, a method of physically restricting the incident angle of the solar light incident on the light receiving element by appropriately installing an opening, a shielding plate, etc. around the light receiving element such as a photodiode can be mentioned. Alternatively, a known solar sensor capable of detecting both the position of the sun 60 and the solar light intensity (for example, a sensor that detects the position by the light intensity balance of four light receiving elements) may be used, and signal processing may be performed by combining the detected position information and the solar light intensity information. Note that the solar sensor 66 does not necessarily have to detect the position of the sun 60, and may be configured and arranged to detect at least the solar light intensity.

[0033] <Configuration of the Control System of the HUD Device> FIG. 5 is a block diagram showing a configuration example of the main part of the control system included in the HUD device shown in FIG. 3. The HUD device 1 shown in FIG. 5 includes a control unit 10, a video processing unit 11, an audio processing unit 12, a communication unit 13, an information acquisition unit 14, a temperature detection unit 15, a non-volatile memory 17, a volatile memory 18, a shutter drive unit 21, a light source drive unit 22, and a drive mechanism 62, which are connected to each other by a bus. Further, the HUD device 1 includes an audio driver 19, a display driver 20, a speaker 25, a display panel 64, a light source 65, a solar sensor 66, a shutter 68, and a mirror (image projection unit) M1.

[0034] Various programs and various data are stored in the non-volatile memory 17. The various programs and various data stored in the non-volatile memory 17 are appropriately copied to the volatile memory 18 and referred to by the processor. The information acquisition unit 14 is composed of, for example, a CAN interface circuit or a LIN (Local Interconnect Network) interface circuit, and acquires vehicle information 4 from the control unit using CAN communication or LIN communication as described in FIG. 1. The communication unit 13 is composed of, for example, a wired communication interface circuit or a wireless communication interface circuit based on a predetermined communication standard, and communicates various control information other than the vehicle information 4 with the outside of the HUD device 1.

[0035] The light source drive unit 22 is composed of, for example, an LED driver circuit or the like, and drives the light source 65. As one of them, the light source drive unit 22 controls the brightness of the backlight from the light source 65 by periodically switching the application / non-application of voltage to the light source 65. Specifically, the light source drive unit 22 controls the brightness of the backlight using, for example, PWM (Pulse Width Modulation) control or the like.

[0036] The image processing unit 11 generates image data that determines the image to be displayed on the display panel 64 and, consequently, the image to be projected onto the display area 5 shown in FIG. 2, based on vehicle information 4 and the like. At this time, the image processing unit 11 generates, for example, image data after correcting various distortions that may occur due to the curvature of the windshield 3 or the like. The image processing unit 11 is realized, for example, by a processor executing an image processing program stored in the volatile memory 18.

[0037] The display driver 20 is constituted by, for example, an LCD driver circuit or the like. The display driver 20 drives each display element (pixel) included in the display panel 64 based on the image data from the image processing unit 11. Thereby, the display driver 20 modulates the backlight from the light source 65 on the display panel 64 and causes the display panel 64 to display an image based on the image data.

[0038] The audio processing unit 12 generates audio data based on vehicle information 4 and the like as necessary. The audio data is generated, for example, when performing voice guidance of a navigation device or when issuing a warning to the driver 6 by means of an AR function. The audio driver 19 drives the speaker 25 based on the audio data from the audio processing unit 12 and outputs audio to the speaker 25. The audio processing unit 12 is realized, for example, by a processor executing an audio processing program stored in the volatile memory 18.

[0039] The shutter drive unit 21 is constituted by, for example, a driver circuit corresponding to the type of the shutter 68. As described in FIG. 2, the shutter drive unit 21 controls the shutter 68 to be in an optical path forming state or an optical path non-forming state. The drive mechanism 62 is constituted by, for example, a motor and a motor driver circuit that drives the motor. The drive mechanism 62 adjusts the installation angle of the mirror M1.

[0040] The temperature detection unit 15 detects the temperature of the video display device 35, specifically, the display panel 64. At this time, although details will be described later, the temperature detection unit 15 estimates the temperature of the display panel 64 by calculation based on the detection result from the solar radiation sensor 66, that is, the solar light intensity or the like. That is, due to implementation constraints or the like, it may be difficult to directly detect the temperature of the display panel 64. The temperature detection unit 15 is provided in such a case and indirectly detects the temperature of the display panel 64 by a predetermined calculation. The temperature detection unit 15 is realized, for example, when a processor executes a temperature detection program stored in the volatile memory 18.

[0041] The control unit 10 controls the entire HUD device 1. As one of them, the control unit 10 controls the luminance of the backlight from the light source 65 via the light source drive unit 22. That is, the control unit 10 controls the on / off of the light source 65, that is, the presence / absence of voltage application to the light source 65, using PWM control or the like. Further, the control unit 10 controls the shutter 68 via the shutter drive unit 21 so that the optical path forming state and the non-optical path forming state are periodically switched. The control unit 10 is realized, for example, when a processor executes a control program stored in the volatile memory 18.

[0042] Note that the control unit 10, the video processing unit 11, the audio processing unit 12, the communication unit 13, the information acquisition unit 14, the temperature detection unit 15, the non-volatile memory 17, and the volatile memory 18 can be realized by a microcontroller or the like including a processor and various peripheral circuits. However, some or all of these may be realized by an FPGA (Field Programmable Gate Array), an ASIC (Application Specific Integrated Circuit), or the like as appropriate.

[0043] FIG. 6 is a block diagram showing a configuration example of a portion related to the information acquisition unit in FIG. 5. The information acquisition unit 14 acquires the vehicle information 4 generated by an information acquisition device such as various sensors via a control unit (not shown). FIG. 6 shows an example of the information acquisition device.

[0044] In FIG. 6, the vehicle speed sensor 41 detects the speed of the vehicle 2 in FIG. 1 and generates speed information as the detection result. The shift position sensor 42 detects the current gear and generates gear information as the detection result. The steering wheel steering angle sensor 43 detects the current steering wheel steering angle and generates steering wheel steering angle information as the detection result. The headlight sensor 44 detects the ON / OFF of the headlights and generates lamp lighting information as the detection result. The illuminance sensor 45 and the chromaticity sensor 46 detect the external light and generate external light information as the detection result.

[0045] The distance measurement sensor 47 detects the distance between the vehicle 2 and an external object and generates distance information as the detection result. The infrared sensor 48 detects the presence or absence and distance of an object in the vicinity of the vehicle 2 and generates infrared information as the detection result. The engine start sensor 49 detects the ON / OFF of the engine and generates ON / OFF information as the detection result. The acceleration sensor 50 and the gyro sensor 51 respectively detect the acceleration and angular velocity of the vehicle 2 and generate acceleration gyro information representing the attitude and behavior of the vehicle 2 as the detection result. The temperature sensor 52 detects the temperature inside and outside the vehicle and generates temperature information as the detection result.

[0046] The road-vehicle communication wireless transceiver 53 generates road-vehicle communication information through road-vehicle communication between the vehicle 2 and roads, signs, traffic lights, etc. The vehicle-vehicle communication wireless transceiver 54 generates vehicle-vehicle communication information through vehicle-vehicle communication between the vehicle 2 and other surrounding vehicles. The in-vehicle camera 55 and the out-vehicle camera 56 respectively generate in-vehicle camera video information and out-vehicle camera video information by photographing the inside and outside of the vehicle. The in-vehicle camera 55 is, for example, a camera for DMS (Driver Monitoring System) that photographs the posture of the driver 6, the position and movement of the eyes, etc. shown in FIG. 2. In this case, by analyzing the captured video, the fatigue status and the position of the line of sight of the driver 6 can be grasped.

[0047] On the other hand, the external camera 56 of the vehicle, for example, captures the surrounding situation such as the front and rear of the vehicle 2. In this case, by analyzing the captured video, it becomes possible to grasp the presence or absence of obstacles such as other vehicles and people existing in the vicinity, the road surface conditions such as buildings, terrain, rain, snow accumulation, freezing, unevenness, etc., and road signs. Further, the external camera 56 includes, for example, a drive recorder that records the situation during driving in video.

[0048] The GPS receiver 57 generates GPS information obtained by receiving GPS signals. For example, it is also possible to acquire the current time by the GPS receiver 57. The VICS (Vehicle Information and Communication System, registered trademark) receiver 58 generates VICS information obtained by receiving VICS signals. The GPS receiver 57 and the VICS receiver 58 may be provided as part of the navigation device. Regarding the various information acquisition devices shown in FIG. 6, it is possible to appropriately delete them, add other types of devices, or replace them with other types of devices.

[0049] <Regarding the temperature detection unit and sunlight countermeasures> FIGS. 7A and 7B are diagrams for explaining an example of the processing content of the temperature detection unit in FIG. 5. FIG. 7A shows the same HUD device 1 as in the case of FIG. 3. FIG. 7B shows an extraction of the portion of the video display device 35 in FIG. 7A. As shown in FIG. 7B, the temperature of the display panel 64 can be estimated by the ambient temperature Ta of the video display device 35, the temperature increase amount ΔT(I) associated with the sunlight 31, and the temperature increase amount ΔT(L) associated with the heat radiation from the light source 65.

[0050] As described with reference to FIG. 3, the ambient temperature Ta is detected by a temperature sensor installed in the HUD device 1 or a temperature sensor 52 installed in the vehicle 2. The temperature rise amount ΔT(I) associated with the sunlight 31 is calculated based on the sunlight intensity detected by the sunlight sensor 66. The temperature rise amount ΔT(L) associated with the thermal radiation from the light source 65 is calculated based on the brightness of the backlight set for the light source 65, that is, the duty ratio of the PWM control or the like. The temperature detection unit 15 indirectly detects the temperature of the display panel 64 by performing an operation using such ambient temperature Ta, temperature rise amount ΔT(I), and temperature rise amount ΔT(L).

[0051] Here, the temperature rise amount ΔT(L) associated with the thermal radiation from the light source 65 is a parameter controllable by the brightness of the backlight. Therefore, for example, when the temperature of the display panel 64 detected by the temperature detection unit 15 exceeds a predetermined threshold value, the control unit 10 can suppress the temperature rise of the display panel 64 by lowering the brightness of the backlight, that is, by lowering the duty ratio of the PWM control.

[0052] On the other hand, for example, when the temperature rise amount ΔT(I) associated with the sunlight 31 is very large, it may be difficult to suppress the temperature rise of the display panel 64 even if such backlight brightness control is used. In such a case, the control unit 10 may control the mirror (image light projection unit) M1 to the non-projection mode via the drive mechanism 62. However, when the mirror M1 is controlled to the non-projection mode, the driver 6 cannot visually recognize the virtual image. Therefore, it is beneficial to perform control as described below using the shutter 68.

[0053] <Details of the shutter> FIG. 8 is a time chart showing an example of a method for controlling the light source in FIG. 3. As described with reference to FIG. 7B, the control unit 10 can control the brightness of the backlight in order to suppress the temperature rise amount ΔT(L) associated with the thermal radiation from the light source 65. In addition, the control unit 10 may control the brightness of the backlight in response to a request from the driver 6, for example, an operation by the driver 6.

[0054] In such a case, the control unit 10 controls the on / off of the light source 65 using, for example, PWM control as shown in FIG. 8 via the light source driving unit 22. Each PWM cycle Tpwm is provided with an on period Ton during which a voltage Vf is applied to the light source 65 and an off period Toff during which no voltage is applied to the light source 65. The light source 65 lights up during the on period Ton and goes out during the off period Toff. The ratio of the on period Ton to the PWM cycle Tpwm (= Ton / Tpwm) is called the duty ratio [%]. The video light becomes brighter as the duty ratio approaches 100% and darker as it approaches 0%.

[0055] FIG. 9 is a time chart showing an example of the control method of the shutter in FIG. 3. FIGS. 10A and 10B are diagrams for explaining a specific application example of the shutter in FIG. 3 and an operation example at that time. As shown in FIG. 9, during the on period Ton in which the control unit 10 applies the voltage Vf to the light source 65, the control unit 10 controls the shutter 68 to be in an optical path forming state, for example, transmission, and during the off period Toff in which no voltage is applied to the light source 65, the control unit 10 controls the shutter 68 to be in an optical path non-forming state, for example, light shielding. Specifically, the control unit 10 controls the transmission / light shielding of such a shutter 68 via the shutter driving unit 21.

[0056] FIGS. 10A and 10B show the operation in the projection mode in which the video light 32 is projected onto the display area. As a specific example, the shutter 68 shown in FIGS. 10A and 10B is, for example, a transmissive / absorptive liquid crystal shutter. As shown in FIG. 10A, the shutter 68 is controlled to be in an optical path forming state during the on period Ton of the light source 65 to transmit light. That is, the video light 32 from the video display device 35 passes through the shutter 68 and enters the mirror M2. Also, the sunlight 31 from the mirror M2 passes through the shutter 68 and enters the video display device 35. On the other hand, as shown in FIG. 10B, the shutter 68 is controlled to be in an optical path non-forming state during the off period Toff of the light source 65 to absorb light. That is, the shutter 68 absorbs the sunlight 31 to shield the sunlight 31 from reaching the display panel 64.

[0057] When using a liquid crystal shutter, the shutter 68 itself can generate heat due to the absorption of sunlight 31. To prevent damage to the shutter 68 caused by this, it is desirable for the control unit 10 to perform temperature management of the shutter 68 in addition to, for example, the display panel 64. As a specific example, the control unit 10 can estimate the temperature of the shutter 68 based on, for example, the sunlight intensity detected by the solar sensor 66, the duty ratio when performing PWM control on the shutter 68, and the ambient temperature Ta, etc. Then, when the estimated temperature of the shutter 68 exceeds the threshold value, the control unit 10 may prevent damage to the shutter 68 by controlling the mirror M1 to the non-projection mode.

[0058] Also, the installation location of the shutter 68 is not limited to the optical path of the video light 32 between the optical component 63b and the mirror (video light reflection part) M2 as shown in FIGS. 10A and 10B. For example, the installation location of the shutter 68 may be on the optical path of the video light 32 between the video display device 35 and the optical component 63b, or between the mirror (video light reflection part) M2 and the mirror (video light projection part) M1. At this time, the shutter 68 may be installed in contact with the reflection surface of the mirror M2. Alternatively, the installation location of the shutter 68 may be on the optical path of the video light 32 between the mirror (video light projection part) M1 and the display area 5, for example, at the location of the opening 7.

[0059] However, since the video light 32 can spread as it approaches the opening 7, the area of the shutter 68 required accordingly can also increase. Also, if the installation location of the shutter 68 is too close to the display panel 64, heat radiation from the shutter 68 that has absorbed sunlight 31 may cause the temperature of the display panel 64 to rise. From the perspective of balancing these two matters, the installation location of the shutter 68 is preferably the location shown in FIGS. 10A and 10B.

[0060] Here, the length of the PWM period Tpwm shown in FIG. 8 is not particularly limited, but is, for example, on the order of ms. When such a PWM period Tpwm is used, the driver 6 can continuously visually recognize the virtual image despite the existence of the off period Toff due to the afterimage of the virtual image projected during the on period Ton. In the embodiment, PWM control is used as the control method for the shutter 68, but PWM control is not necessarily required. That is, as a necessary condition, the length of the off period Toff, during which the shutter 68 is controlled to the non-light-path-forming state here, may be any length as long as the driver 6 can continuously visually recognize the image light 32 as a virtual image.

[0061] In the specification, as shown in FIG. 9, a control mode for controlling the shutter 68 so that the light-path-forming state and the non-light-path-forming state are periodically switched is called a switching control mode or a first control mode. As a representative example of the switching control mode, as shown in FIG. 9, the control unit 10 controls the shutter 68 to the light-path-forming state / non-light-path-forming state in conjunction with the on / off of the light source 65.

[0062] On the other hand, in the specification, different from the case of FIG. 9, a control mode for fixing the shutter 68 to the light-path-forming state, for example, fixing it to transmission, regardless of the on / off of the light source 65 is called a light-path-forming control mode or a second control mode. Similarly, a control mode for fixing the shutter 68 to the non-light-path-forming state, for example, fixing it to light-shielding, regardless of the on / off of the light source 65 is called a non-light-path-forming control mode or a third control mode.

[0063] For example, when the light-path-forming control mode is used, the driver 6 can visually recognize the image light 32 as a virtual image, but on the other hand, the sunlight 31 may enter the image display device 35. Also, when the non-light-path-forming control mode is used, the entry of the sunlight 31 into the image display device 35 can be prevented, but on the other hand, the driver 6 cannot visually recognize the image light 32 as a virtual image. On the other hand, when the switching control mode is used, it is possible to suppress the entry of the sunlight 31 into the image display device 35 while allowing the driver 6 to visually recognize the image light 32 as a virtual image.

[0064] Specifically, in the switching control mode, the shutter 68 can transmit all the video light 32 from the display panel 64 emitted during the on-period Ton. Also, the shutter 68 can block the incidence of sunlight 31 on the display panel 64 during the off-period Toff when the video light 32 from the display panel 64 is not emitted. As a result, since the period during which sunlight 31 is incident is limited to the on-period Ton within the PWM period Tpwm, the amount of temperature rise ΔT(I) associated with the sunlight 31 shown in Fig. 7B can be suppressed. By these means, while preventing damage to the video display device 35, specifically the display panel 64, due to the sunlight 31, it becomes possible to reduce the time period during which the driver 6 cannot visually recognize the virtual image.

[0065] Note that the shutter 68 may exist in two types: one with a default state of transmission and the other with a default state of light blocking. When the default state of the shutter 68 is transmission, it is controlled to block light by applying the voltage Vf. When the default state of the shutter 68 is light blocking, it is controlled to transmit light by applying the voltage Vf. Using the shutter 68 with a default state of transmission can suppress the power consumption associated with the control of the shutter 68. That is, in the general usage form of the HUD device 1, the period during which the shutter 68 is controlled to transmit is longer than the period during which the shutter 68 is controlled to block light. On the other hand, using the shutter 68 with a default state of light blocking can prevent damage to the display panel 64 even if the shutter 68 cannot be controlled for some reason.

[0066] Fig. 11 is a time chart showing an example of the relationship between the control method of the light source and the shutter in Fig. 3 and the sunlight intensity. As shown in Fig. 11, when the sunlight intensity increases, the control unit 10 performs control to decrease the duty ratio of the PWM control for the light source 65. Thereby, the amount of temperature rise ΔT(L) associated with the light source 65, and thus the temperature rise of the display panel 64, can be suppressed.

[0067] Furthermore, the control unit 10 controls the shutter 68 in a switching control mode in conjunction with the PWM control of the light source 65. As a result, during the off period Toff, which becomes longer as the duty ratio decreases, the sunlight 31 can be blocked by the shutter 68, so that the amount of temperature rise ΔT(I) due to the sunlight 31, and thus the temperature rise of the display panel 64, can be more effectively suppressed. In this way, by controlling the on / off of the light source 65 using PWM control and controlling the shutter 68 to be in the optical path forming state / optical path non-forming state in conjunction with the on / off of the light source 65, it becomes possible to synergistically obtain the effect of suppressing the temperature rise of the display panel 64.

[0068] <Modification Example of Switching Control Mode> In FIG. 9, the switching control mode is used so as to be interlocked with the on / off of the light source 65. However, in some cases, it is also possible to use a method in which the display panel 64 is constantly emitting video light, that is, the light source 65 is constantly on, and the shutter 68 is PWM-controlled. Even in such a case, the effect of suppressing the amount of temperature rise ΔT(I) due to the sunlight 31 can be obtained. However, in this case, compared with the case of being interlocked with the on / off of the light source 65, the amount of temperature rise ΔT(L) due to the light source 65 increases, and further, the power consumption generated by the light source 65 also increases. From this point of view, it is beneficial to use the switching control mode so as to be interlocked with the on / off of the light source 65.

[0069] <Details of Shutter Control Method> Figure 12 is a flowchart showing an example of the processing content of the control unit associated with the control of the shutter in FIG. 5. The control unit 10 repeatedly executes the flow shown in FIG. 12 at a predetermined control cycle. In FIG. 12, the control unit 10 performs a conditional determination on determination item A (step S100). When the determination result in step S100 is determination result [1], the control unit 10 controls the shutter 68 in a switching control mode (step S101). That is, the control unit 10 controls the shutter 68 so that the optical path forming state / non-optical path forming state periodically switches. Specifically, for example, the shutter 68 is controlled to be in the optical path forming state / non-optical path forming state in conjunction with the on / off of the light source 65.

[0070] On the other hand, when the determination result in step S100 is determination result [2], the control unit 10 controls the shutter 68 in an optical path forming control mode (step S102). That is, the control unit 10 fixes the shutter 68 in the optical path forming state. Also, when the determination result in step S100 is determination result [3], the control unit 10 controls the shutter 68 in a non-optical path forming control mode (step S103). That is, the control unit 10 fixes the shutter 68 in the non-optical path forming state.

[0071] Figure 13 is a diagram showing a specific example of the conditional determination (step S100) shown in FIG. 12. Figure 14 is a diagram supplementing FIG. 13 and showing an example of the positional relationship between the sun and the vehicle. In FIG. 13, as specific examples of the conditional determination (step S100) in FIG. 12, Examples 1 to 13 are shown. In Examples 1 to 13, the correspondence between determination item A and determination results [1], [2], and [3] is shown.

[0072] In Example 1, the control unit 10 determines whether the sunlight 31 is detected by the solar radiation sensor 66. Specifically, the control unit 10 determines the substantial presence or absence of the sunlight 31 based on the detection result of the solar radiation sensor 66, for example, in categories such as daytime / nighttime, sunny / cloudy. When the control unit 10 determines that the sunlight 31 is detected, as the determination result [1], it controls the shutter 68 in the switching control mode. When it determines that the sunlight 31 is not detected, as the determination result [2], it controls the shutter 68 in the optical path formation control mode. Note that in Example 1, the determination result [3] is not used.

[0073] In Example 2, the control unit 10 determines whether the sunlight intensity detected by the solar radiation sensor 66 exceeds a threshold value. Specifically, the control unit 10 determines, based on the threshold value, whether the sunlight intensity detected by the solar radiation sensor 66, for example, is such that it can cause damage to the display panel 64. Therefore, in Example 2, a relatively large threshold value is used. Note that the control unit 10 may determine the presence or absence of the sunlight 31 using a threshold value that is sufficiently smaller than that in the case of Example 2 in Example 1. Also, in Examples 1 and 2, the control unit 10 may make a determination including the position of the sun 60 according to the configuration and arrangement of the solar radiation sensor 66 as described in FIG. 4.

[0074] When the sunlight intensity exceeds the threshold value, as the determination result [1], the control unit 10 controls the shutter 68 in the switching control mode. When the sunlight intensity does not exceed the threshold value, as the determination result [2], it controls the shutter 68 in the optical path formation control mode. By using the switching control mode when the sunlight intensity exceeds the threshold value, it becomes possible to suppress the amount of temperature increase ΔT(I) associated with the sunlight 31. On the other hand, when the sunlight intensity does not exceed the threshold value, by using the optical path formation control mode, it becomes possible to reduce the frequency of the on / off operation of the shutter 68, reduce power consumption, and suppress the wear of the shutter 68. Note that in Example 2, the determination result [3] is not used.

[0075] In Example 3, the control unit 10 determines whether or not the estimated temperature of the display panel 64 at the current time, which is estimated from the ambient temperature Ta, the temperature rise amount ΔT(L) corresponding to the video luminance, and the temperature rise amount ΔT(I) corresponding to the sunlight intensity, exceeds a threshold value. That is, the control unit 10 makes a determination based on the detection result of the temperature detection unit 15. When the estimated temperature of the display panel 64 at the current time exceeds the threshold value, the control unit 10 controls the shutter 68 in the switching control mode as the determination result [1], and when the sunlight intensity does not exceed the threshold value, the control unit 10 controls the shutter 68 in the optical path formation control mode as the determination result [2]. Note that in Example 3, the determination result [3] is not used.

[0076] In Example 4, unlike in the case of Example 3, the control unit 10 determines whether or not the temperature of the display panel 64 after a certain period of time, which is estimated from the ambient temperature Ta, the temperature rise amount ΔT(L) corresponding to the video luminance, and the temperature rise amount ΔT(I) corresponding to the sunlight intensity, exceeds a threshold value. Specifically, the control unit 10 estimates the temperature of the display panel 64 after a certain period of time by reflecting, for example, the change rates of the temperature rise amounts ΔT(L) and ΔT(I) and transient characteristics, and when the estimated temperature exceeds the threshold value, the switching control mode is applied at the current time. In Example 3, when a rapid temperature rise occurs, the temperature of the display panel 64 may rise beyond the assumption due to control delay. By using Example 4, it becomes possible to handle such cases as well.

[0077] In Example 5, the control unit 10 determines whether or not an abnormality is detected in the drive mechanism 62 attached to the mirror M1. When the control unit 10 determines that an abnormality is detected, the control unit 10 controls the shutter 68 in the non-optical path formation control mode as the determination result [3]. Note that in Example 5, the determination results [1] and [2] are not used. The case where an abnormality is detected is, for example, when an overcurrent, an overload, an over-temperature, etc. are detected in the drive mechanism 62 such as a motor. In this case, since the protection operation using the mirror M1, that is, the transition to the non-projection mode, cannot be executed, by using the non-optical path formation control mode, damage to the display panel 64 can be surely prevented.

[0078] In Example 6, the control unit 10 determines whether the control state of the mirror M1 is in the non-projection mode. When the control state of the mirror M1 is in the non-projection mode, the control unit 10 controls the shutter 68 in the optical path formation control mode as the determination result [2], or controls the shutter 68 in the optical path non-formation control mode as the determination result [3]. In the non-projection mode, since the shutter 68 is in a standby state without the sunlight 31 being incident, it may be controlled in either the optical path formation control mode or the optical path non-formation control mode. Note that in Example 6, the determination result [1] is not used.

[0079] In Example 7, the control unit 10 determines whether the ambient temperature Ta of the video display device 35 exceeds a threshold value. When the ambient temperature Ta exceeds the threshold value, the control unit 10 controls the shutter 68 in the switching control mode as the determination result [1], and when it does not exceed the threshold value, the control unit 10 controls the shutter 68 in the optical path formation control mode as the determination result [2]. When the ambient temperature Ta exceeds the threshold value, the allowable value of the temperature rise amount ΔT(I) associated with the sunlight 31 decreases accordingly. Therefore, by using the switching control mode, the temperature rise amount ΔT(I) is suppressed to prevent damage to the display panel 64. Note that in Example 7, the determination result [3] is not used.

[0080] In Example 8, the control unit 10 determines whether the altitude (in other words, the elevation angle) of the sun 60 calculated based on the position information of the vehicle 2, for example, latitude and longitude information, and the information of the current date and time is within a predetermined range. The position information of the vehicle 2 and the information of the current date and time can be obtained from, for example, GPS information included in the vehicle information 4. When the altitude of the sun 60 is within the predetermined range, the control unit 10 controls the shutter 68 in the switching control mode as the determination result [1], and when it is not within the predetermined range, the control unit 10 controls the shutter 68 in the optical path formation control mode as the determination result [2]. The predetermined range is, for example, a range of relatively high altitude and a range in which the sunlight intensity can become relatively strong. Note that in Example 8, the determination result [3] is not used.

[0081] In Example 9, the control unit 10 determines whether the altitude (or elevation angle) “α” of the sun 60 and the relative azimuth angle “β - γ” of the sun 60, which are calculated based on the position information of the vehicle 2, for example, latitude and longitude information, and the information of the current date and time, are within a predetermined range, respectively. “β” is the azimuth angle of the sun 60, and “γ” is the azimuth angle (or direction) of the vehicle 2. As shown in FIG. 14, the relative azimuth angle “β - γ” of the sun 60 represents the azimuth angle of the sun 60 based on the direction of the vehicle 2. The azimuth angle “β” of the sun 60 is calculated based on, for example, the position information of the vehicle 2 and the information of the current date and time, such as the GPS information included in the vehicle information 4. The direction “γ” of the vehicle 2 is calculated based on the acceleration gyro information, GPS information, etc. included in the vehicle information 4.

[0082] When the altitude “α” of the sun 60 is within a predetermined range, that is, satisfies Amin ≤ α ≤ Amax, and the relative azimuth angle “β - γ” of the sun 60 is within a predetermined range, that is, satisfies Bmin ≤ β - γ ≤ Bmax, the control unit 10 controls the shutter 68 in the switching control mode as the determination result [1]. On the other hand, when the altitude “α” of the sun 60 is not within the predetermined range or the relative azimuth angle “β - γ” is not within the predetermined range, the control unit 10 controls the shutter 68 in the optical path formation control mode as the determination result [2]. Note that in Example 9, the determination result [3] is not used.

[0083] Here, in Example 8, if the altitude of the sun 60 is within a predetermined range, it is determined that strong sunlight 31 can be incident, and the switching control mode is used. Thereby, the amount of temperature increase ΔT(I) associated with the sunlight 31 is suppressed. On the other hand, in Example 9, even if the altitude of the sun 60 is within a predetermined range, if the vehicle 2 is in a direction such that the sunlight 31 does not enter the display panel 64, it is determined that strong sunlight 31 does not enter, and the optical path formation control mode instead of the switching control mode is used. Thereby, compared with the case of Example 8, the frequency of the on / off operation of the shutter 68 is reduced, it becomes possible to reduce the power consumption, suppress the wear of the shutter 68, etc. Note that in Example 9, the determination result [3] is not used.

[0084] In Example 10, the control unit 10 determines whether the illuminance acquired from the illuminance sensor 45 of the vehicle 2 via the information acquisition unit 14 exceeds a threshold value. When the acquired illuminance exceeds the threshold value, the control unit 10 controls the shutter 68 in the switching control mode as the determination result [1], and when the illuminance does not exceed the threshold value, the control unit 10 controls the shutter 68 in the optical path formation control mode as the determination result [2]. In Example 10, based on the detection result of the illuminance sensor 45, the sunlight intensity and the like are indirectly determined. Then, when it is determined that the sunlight intensity and the like are strong, the control unit 10 suppresses the temperature rise amount ΔT(I) associated with the sunlight 31 using the switching control mode. Note that in Example 10, the determination result [3] is not used.

[0085] In Example 11, the control unit 10 determines whether the temperature acquired from the temperature sensor 52 of the vehicle 2 via the information acquisition unit 14 exceeds a threshold value. When the acquired temperature exceeds the threshold value, the control unit 10 controls the shutter 68 in the switching control mode as the determination result [1], and when the temperature does not exceed the threshold value, the control unit 10 controls the shutter 68 in the optical path formation control mode as the determination result [2]. In Example 11, the control unit 10 detects or estimates the ambient temperature Ta or the like based on, for example, the temperature acquired from the temperature sensor 52, and controls the shutter 68 based on the result. Note that in Example 11, the determination result [3] is not used.

[0086] In Example 12, the control unit 10 determines whether there is an abnormality detection in the operation of the HUD device 1. When it is determined that there is an abnormality detection, the control unit 10 controls the shutter 68 in the non-optical path formation control mode as the determination result [3]. For example, when an abnormality occurs in the video display device 35 and strong video light 32 is emitted from the video display device 35, there is a possibility that the driving may be hindered by the driver 6 visually recognizing the video light 32. Represented by such a situation, in order to ensure safety even when an abnormality occurs in the HUD device 1, when it is determined that there is an abnormality detection, the non-optical path formation control mode is used. Note that in Example 12, the determination result [1] and the determination result [2] are not used.

[0087] In Example 13, if the HUD device 1 is operating, the control unit 10 controls the shutter 68 in the switching control mode as the determination result [1]. That is, in Example 13, the optical path formation control mode and the optical path non-formation control mode are not used, and the switching control mode is always used. Even in this case, for example, by combining with control of the duty ratio according to the sunlight intensity with respect to the light source 65 or the protection operation by the mirror M1, it is possible to sufficiently prevent damage to the display panel 64.

[0088] Note that each determination item A shown in Examples 1 to 12 can be used alone or in appropriate combination.

[0089] <Various application examples of the shutter> FIGS. 15A and 15B are diagrams for explaining another specific application example of the shutter in FIG. 3 and the operation example at that time. The shutter 68 shown in FIGS. 15A and 15B is, for example, a transmissive / diffusive liquid crystal shutter. As shown in FIG. 15A, during the on period Ton of the light source 65, the shutter 68 is controlled to be in the optical path formation state and transmits light in the same manner as in the case of FIG. 10A.

[0090] On the other hand, as shown in FIG. 15B, during the off period Toff of the light source 65, the shutter 68 is controlled to be in the optical path non-formation state and diffuses light, unlike the case of FIG. 10B. That is, the shutter 68 diffuses the sunlight 31 to block the sunlight 31 from reaching the display panel 64. In this case, although a part of the diffused sunlight 31 may be incident on the display panel 64, since the incident energy is small, substantially, the sunlight 31 is blocked.

[0091] Regarding the installation location of the shutter 68, it is not limited to the location between the optical component 63b and the mirror M2 as shown in FIGS. 15A and 15B, and can be appropriately changed as in the case of FIGS. 10A and 10B. That is, the installation location of the shutter 68 may be a location between the image display device 35 and the optical component 63b, or a location between the mirror (image light reflection part) M2 and the mirror (image light projection part) M1, or a location such as the opening 7. Further, the shutter 68 may be installed in contact with the reflection surface of the mirror M2.

[0092] However, when the installation location of the shutter 68 is too close to the display panel 64, for example, when it is a location between the image display device 35 and the optical component 63b, the diffused sunlight 31 is likely to be incident on the display panel 64. From this perspective, the installation location shown in FIGS. 15A and 15B is desirable for the shutter 68. Further, the sunlight diffused by the shutter 68 may become stray light and reach the eyes of the driver 6 after being emitted from the opening 7. For this reason, it is desirable to install, for example, wall-shaped light-shielding components around the shutter 68.

[0093] FIGS. 16A and 16B are diagrams for explaining still another specific application example of the shutter in FIG. 3 and the operation example at that time. The shutter 68 shown in FIGS. 16A and 16B is, for example, a MEMS (Micro Electro Mechanical Systems) shutter. As shown in FIG. 16A, during the on period Ton of the light source 65, the shutter 68 is controlled to be in an optical path forming state and transmits light in the same manner as in the case of FIG. 10A. On the other hand, as shown in FIG. 16B, during the off period Toff of the light source 65, the shutter 68 is controlled to be in an optical path non-forming state and reflects light, unlike the case of FIG. 10B. That is, the shutter 68 blocks the sunlight 31 from reaching the display panel 64 by reflecting the sunlight 31.

[0094] Here, in FIG. 16B, unlike the case of FIG. 10B, the sunlight 31 reflected by the shutter 68 may exit from the opening 7 through an optical path opposite to the incident optical path and then reach the eyes of the driver 6. Therefore, as shown in FIGS. 16A and 16B, it is desirable that the shutter 68 be installed so that the reflected light does not face the mirror M2. Specifically, it is desirable that the shutter 68 be installed such that the surface normal SN of the shutter 68 intersects the optical axis of the video light 32. Also, the portion of the housing 61 where the reflected light hits is preferably made of a high heat-resistant material or a material with high heat dissipation. Alternatively, heat dissipation fins or the like may be installed at the portion where the reflected light hits.

[0095] Regarding the installation location of the shutter 68, it is not limited to the location between the optical component 63b and the mirror M2 as shown in FIGS. 16A and 16B, and can be appropriately changed as in the cases of FIGS. 10A and 10B. In this case, even when the shutter 68 is installed near the display panel 64, problems such as heat dissipation to the display panel 64 as in the case of FIG. 10B or the problem of incident diffused light to the display panel 64 as in the case of FIG. 15B are unlikely to occur. On the other hand, as the installation location of the shutter 68, a location between the mirror (video light projection unit) M1 and the display area 5, for example, the location of the opening 7, where the reflected light does not reach the eyes of the driver 6 is preferably excluded.

[0096] <Main effects of Embodiment 1> In the HUD device 1 of the first embodiment described above, the shutter 68 is provided on the optical path of the image light 32, and the shutter 68 is controlled so that the optical path forming state and the non-optical path forming state are periodically switched. As a result, it is possible to reduce the time period during which the user cannot visually recognize the virtual image while preventing damage to the display panel 64 due to the sunlight 31. Further, in addition to such a switching control mode, an optical path forming control mode and a non-optical path forming control mode are provided so that the optical path forming control mode and the non-optical path forming control mode can also be selected according to various conditions, thereby eliminating unnecessary on / off operations of the shutter. Furthermore, by combining with the protection operation by the mirror (image light projection unit) M1, it becomes possible to more reliably prevent damage to the display panel 64.

[0097] (Second Embodiment) <Application Example of Shutter> FIGS. 17A and 17B are diagrams for explaining a specific application example of the shutter and an operation example at that time in the HUD device according to the second embodiment. The shutter 68 shown in FIGS. 17A and 17B is, for example, a transmissive / reflective type MEMS shutter, similar to the cases of FIGS. 16A and 16B. However, in FIGS. 17A and 17B, the image display device 35 and the shutter 68 are arranged so that the shutter 68 reflects the image light from the image display device 35 to the mirror M2.

[0098] Accordingly, as shown in FIG. 17A, unlike the case of FIG. 16A, the shutter 68 reflects light during the on period Ton of the light source 65, that is, in the optical path forming state, instead of transmitting it. Specifically, the shutter 68 reflects the image light 32 from the image display device 35 to the mirror M2, and also reflects the sunlight 31 from the mirror M2 to the image display device 35.

[0099] On the one hand, as shown in FIG. 17B, unlike the case of FIG. 16B, the shutter 68 transmits light instead of reflecting it during the off period Toff of the light source 65, that is, in the non-light path forming state. By transmitting the sunlight 31, the shutter 68 blocks the sunlight 31 from reaching the display panel 64. The portion of the housing 61 that is hit by the transmitted light is preferably made of a high heat-resistant material or a material with high heat dissipation. Alternatively, heat dissipation fins or the like may be installed at the portion where the transmitted light hits.

[0100] In FIGS. 17A and 17B, an example of separately installing the shutter 68 is shown. As another modification using the reflection characteristics of the shutter 68, for example, in FIGS. 10A and 10B, it is also possible to replace the mirror M2 with a MEMS shutter. In this case, the MEMS shutter reflects light during the on period Ton of the light source 65, that is, in the light path forming state, and accordingly, an optical path similar to that in the case of FIG. 10A is formed. On the other hand, the MEMS shutter transmits light during the off period Toff of the light source 65, that is, in the non-light path forming state, and an optical path is formed such that the mirror M2 transmits the sunlight 31 in FIG. 10B.

[0101] As described above, by using the HUD device 1 of the second embodiment, effects similar to the various effects described in the first embodiment can also be obtained.

[0102] As described above, the invention made by the present inventor has been specifically described based on the embodiments. However, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist thereof. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. Also, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Further, for a part of the configuration of each embodiment, addition, deletion, or replacement with other configurations is possible.

[0103] For example, when using the technology according to the embodiment, as described above, it becomes possible to prevent damage to the display panel caused by sunlight and reduce the time periods during which the user cannot visually recognize the virtual image. In addition to displaying navigation information such as the destination and speed projected on the front glass or the like, it is possible to visually recognize images of information necessary for driving, such as alert information display when detecting an oncoming vehicle or a pedestrian, and provide an information display device (head-up display device) that reduces the driver's viewpoint movement and contributes to safe driving support. This makes it possible to prevent traffic accidents. Furthermore, it becomes possible to contribute to "3. Ensure healthy lives and promote well-being for all" among the Sustainable Development Goals (SDGs) advocated by the United Nations.

Explanation of Signs

[0104] 1…Head-up display (HUD) device, 2…Vehicle, 4…Vehicle information, 5…Display area, 6…Driver (user), 10…Control unit, 14…Information acquisition unit, 15…Temperature detection unit, 30…Optical path of image light, 32…Image light, 35…Image display device, 60…Sun, 62…Drive mechanism, 64…Display panel, 65…Light source, 68…Shutter, M1…Mirror (image light projection unit), M2…Mirror (image light reflection unit), SN…Normal to the surface

Claims

1. A head-up display device for a vehicle, comprising: a video display device that generates and emits video light of a video; a video light projection unit that projects and reflects the video light emitted from the video display device onto a display area of the vehicle to display a virtual image in front of the vehicle; a shutter provided on an optical path of the video light, the shutter switching between an optical path forming state in which the optical path of the video light is formed and an optical path non-forming state in which the optical path of the video light is not formed; wherein the length of a period during which the shutter is switched to the optical path non-forming state is a length during which the video light can be visually recognized as a virtual image; the shutter transmits light in the optical path forming state and absorbs or diffuses light in the optical path non-forming state; a head-up display device.

2. The head-up display device according to claim 1, further comprising: a video light reflector provided on the optical path of the video light between the video display device and the video light projection unit, the video light reflector reflecting the video light from the video display device to the video light projection unit. a head-up display device.

3. The head-up display device according to claim 2, wherein the shutter is provided on the optical path of the video light between the video display device and the video light reflector. a head-up display device.

4. The head-up display device according to claim 2, wherein the shutter is provided on the optical path of the video light between the video light reflector and the video light projection unit. a head-up display device.

5. The head-up display device according to claim 1, further comprising: a control unit that controls the video display device and the shutter. a head-up display device.

6. The head-up display device according to claim 5, wherein the control unit controls the shutter so that the optical path forming state and the optical path non-forming state are switched. a head-up display device.

7. The head-up display device according to claim 5, wherein the control unit controls the shutter so that the optical path forming state and the optical path non-forming state are periodically switched. a head-up display device.

8. The head-up display device according to claim 7, wherein the video display device is A light source that turns on the backlight when controlled to on and turns off the backlight when controlled to off, A display panel that displays the video by modulating the backlight from the light source, Comprising, The control unit controls the on / off of the light source using PWM control, and in conjunction with the on / off of the light source, controls the shutter to be in the optical path forming state / the optical path non-forming state, A head-up display device.

9. In the head-up display device according to claim 7 or 8, The control unit performs condition determination, and based on the determination result of the condition determination, uses a first control mode that periodically switches between the optical path forming state and the optical path non-forming state, or a second control mode that fixes the optical path forming state, to control the shutter, A head-up display device.

10. In the head-up display device according to claim 9, The control unit further controls the video light projection unit, The video light projection unit, A mirror that reflects the video light toward the display area, A drive mechanism that adjusts the installation angle of the mirror, Having, The control unit controls the video light projection unit to be in a non-projection mode in which the video light is not projected onto the display area, or a projection mode in which the video light is projected onto the display area, by adjusting the installation angle of the mirror via the drive mechanism, A head-up display device.

11. In the head-up display device according to claim 10, When the control unit detects an abnormality in the operation of the drive mechanism, it controls the shutter using a third control mode that fixes the optical path non-forming state, A head-up display device.

12. A head-up display device for a vehicle, A video display device that generates and emits video light of a video, A video light projection unit that projects and reflects the video light emitted from the video display device onto the display area of the vehicle, thereby displaying a virtual image in front of the vehicle, A shutter provided on the optical path of the video light, which switches between an optical path forming state that forms the optical path of the video light and an optical path non-forming state that does not form the optical path of the video light, Comprising, The length of the period during which the shutter is switched to the optical path non-forming state is the length at which the video light can be visually recognized as a virtual image, The shutter transmits light in the optical path forming state and reflects light in the optical path non-forming state, The shutter is installed so that the normal to the surface of the shutter intersects the optical axis of the image light. A head-up display device. **Claim 13**: A head-up display device for a vehicle, comprising: An image display device that generates and emits image light of an image; An image light projection unit that projects the image light emitted from the image display device onto a display area of the vehicle and reflects it, thereby displaying a virtual image in front of the vehicle; A shutter provided on the optical path of the image light, which switches between an optical path forming state for forming the optical path of the image light and an optical path non-forming state for not forming the optical path of the image light; A control unit that controls the image display device and the shutter; wherein: The length of the period during which the shutter is switched to the optical path non-forming state is a length during which the image light can be visually recognized as a virtual image. The control unit performs condition determination, and based on the determination result of the condition determination, controls the shutter using a first control mode in which the optical path forming state and the optical path non-forming state are periodically switched, or a second control mode in which the optical path forming state is fixed. It has a temperature detection unit that detects the temperature of the image display device. When the temperature detected by the temperature detection unit exceeds a threshold value, the control unit controls the shutter using the first control mode, and when the temperature does not exceed the threshold value, the control unit controls the shutter using the second control mode. A head-up display device. **Claim 14**: A head-up display device for a vehicle, comprising: An image display device that generates and emits image light of an image; An image light projection unit that projects the image light emitted from the image display device onto a display area of the vehicle and reflects it, thereby displaying a virtual image in front of the vehicle; A shutter provided on the optical path of the image light, which switches between an optical path forming state for forming the optical path of the image light and an optical path non-forming state for not forming the optical path of the image light; A control unit that controls the image display device and the shutter; wherein: The length of the period during which the shutter is switched to the optical path non-forming state is a length during which the image light can be visually recognized as a virtual image. The control unit performs condition determination, and based on the determination result of the condition determination, controls the shutter using a first control mode in which the optical path forming state and the optical path non-forming state are periodically switched, or a second control mode in which the optical path forming state is fixed. The control unit calculates the altitude of the sun based on the position information of the vehicle and the information of the current date and time. When the calculated altitude of the sun is within a predetermined range, the shutter is controlled using the first control mode. When it is not within the predetermined range, the shutter is controlled using the second control mode. Head-up display device.

15. A control method for a head-up display device mounted on a vehicle, comprising: acquiring information about the vehicle; displaying an image representing the acquired information about the vehicle, emitting image light of the displayed image; projecting the emitted image light onto a display area, and allowing the user to visually recognize the projected image light as a virtual image; controlling the optical path of the image light using a shutter provided on the optical path of the image light and controlled to an optical path forming state that forms the optical path of the image light or an optical path non-forming state that does not form the optical path of the image light; when controlling the optical path of the image light, switching the shutter to a first control mode in which the optical path forming state and the optical path non-forming state periodically switch, a second control mode in which the optical path forming state is fixed, or a third control mode in which the optical path non-forming state is fixed; the shutter transmits light in the optical path forming state and absorbs or diffuses light in the optical path non-forming state; Control method for a head-up display device.

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