Image projection device and image projection method

Abstract

Provided are an image projection device and an image projection method configured so that, with regard to image display position adjustment processing, it is possible to execute high-precision initialization with a simple configuration. An image projection device (10) that projects a virtual image via a display unit is characterized by comprising: an image radiation unit (11) that radiates image display light (GL) for forming a virtual image; a movable mirror (12) that guides the image display light (GL) to the display unit; a drive unit (13) that rotates a reflection surface of the movable mirror (12) so as to change the direction of the image display light (GL); a control unit (20) that controls the drive unit (13); a control substrate (20a) on which the control unit (20) is mounted; and a switch (15) that is mounted on the control substrate (20a). The image projection device is also characterized in that the control unit (20) identifies an initial position Pi of the movable mirror (12) on the basis of contact between the movable mirror (12) and the switch (15).

Description

Image projection device and image projection method

[0001] The present invention relates to an image projection device and an image projection method.

[0002] Conventionally, an instrument panel that displays icons by lighting them has been used as a device for displaying various types of information inside a vehicle. However, because the instrument panel is located below the windshield (front glass) of the vehicle, the driver must move their eyes downward while driving in order to see the information displayed on the instrument panel, which is undesirable. Therefore, image projection devices such as head-up displays (hereinafter referred to as "HUDs") have been proposed that project images onto the windshield so that the driver can read information when looking ahead of the vehicle.

[0003] In the above-described conventional image projection device, an image projection unit such as a liquid crystal display device emits light containing an image (hereinafter referred to as "image display light"), which is reflected by one or more free-form surface mirrors (hereinafter sometimes referred to as "optical system"), and the light reaches the eyebox of a driver or the like so that an image (virtual image, hereinafter referred to as "display image") is formed in space. As a result, the driver or the like can perceive the display image as being displayed at an imaging position in the depth direction in front of the vehicle due to the image display light incident on the eyebox. Patent Document 1 discloses an example of such a conventional HUD.

[0004] Japanese Patent Application Laid-Open No. 2022-156071

[0005] Here, the height of the eyebox may differ for each driver. This is because the position of the driver's viewpoint varies depending on the driver's height, seat position, etc. Therefore, it may be necessary to adjust the display position of the image (hereinafter referred to as "image display position") for each driver (hereinafter referred to as "image display position adjustment"). As an example, image display position adjustment can be performed by adjusting the tilt of a mirror included in the optical system. Figure 5 shows a conventional image projection device 100 equipped with such a mirror tilt adjustment mechanism.

[0006] As shown in Fig. 5, the image projection device 100 includes an image projection unit 11, a fixed mirror 16, a movable mirror 12, a drive unit 13, and a control unit 50. The image display light GL emitted from the image projection unit 11 is reflected by a windshield (not shown) and sent to the driver's viewpoint, forming a display image. The movable mirror 12 is provided with a drive unit 13 that rotates the movable mirror 12 in the direction of the double-headed arrow D shown in the figure, thereby adjusting the tilt in the direction D of the image display light GL emitted from the image projection unit 11 and reflected by the fixed mirror 16. In the image projection device 100, the image display position is adjusted by the above-mentioned configuration. The control unit 50 performs overall control of the image projection device 100.

[0007] Here, a rotating body such as the movable mirror 12 that is rotatable by the drive unit 13 generally has a target position that can change in various ways. Therefore, for such a rotating body, it is necessary to determine a reference position (hereinafter referred to as the "initial position") for the amount of rotation (e.g., the rotation angle). For example, movement to the initial position (hereinafter referred to as "initialization") can be performed by using a motor with an initial position setting function. However, such motors are generally expensive and are not desirable from the perspective of cost reduction. Therefore, there is a demand for an image projection device with a simple configuration and low cost. Furthermore, the accuracy of the initial position detection must be maintained.

[0008] Therefore, the present invention has been made in consideration of the above-mentioned conventional problems, and aims to provide an image projection device and an image projection method that are capable of performing high-precision initialization with a simple configuration in the image display position adjustment process.

[0009] In order to solve the above problem, the image projection device of the present invention is an image projection device that projects a virtual image via a display unit, and includes an image irradiation unit that irradiates image display light to form the virtual image, a reflection unit that guides the image display light to the display unit, a drive unit that rotates the reflective surface of the reflection unit to change the direction of the image display light, a control unit that controls the drive unit, a substrate that mounts the control unit, and a position detection unit for the reflection unit mounted on the substrate, and is characterized in that the control unit identifies the initial position of the reflection unit based on the detection result of the position detection unit.

[0010] The image projection device of the present invention includes an image projection unit that irradiates image display light to form a virtual image, a reflector that directs the image display light to the display unit, a drive unit that rotates the reflective surface of the reflector to change the direction of the image display light, a control unit that controls the drive unit, a substrate that mounts the control unit, and a position detection unit for the reflector mounted on the substrate, and the control unit identifies the initial position of the reflector based on the detection result of the position detection unit. As a result, high-precision initialization can be performed with a simple configuration in the image display position adjustment process.

[0011] In one aspect of the present invention, the position detection unit is a contact switch having contacts, the substrate is arranged behind the reflecting unit, and the initial position of the reflecting unit is determined based on contact between the back surface of the reflecting unit and the contacts of the contact switch.

[0012] In one aspect of the present invention, the control unit rotates the reflecting unit in a first direction and stops it at the initial position, then rotates it in a second direction opposite to the first direction and stops it at the standby position of the reflecting unit.

[0013] In addition, in one aspect of the present invention, the image display light forms a virtual image through the display unit, and the initial position is used to identify a reference position for the reflecting unit when adjusting the position of the virtual image.

[0014] In order to solve the above problem, the image projection method of the present invention is an image projection device that projects a virtual image via a display unit, and is an image projection method using an image projection device that includes an image irradiation unit that irradiates image display light to form the virtual image, a reflection unit that directs the image display light to the display unit, a drive unit that rotates the reflective surface of the reflection unit to change the direction of the image display light, a control unit that controls the drive unit, a substrate that mounts the control unit, and a position detection unit for the reflection unit mounted on the substrate, and is characterized in that the control unit identifies the initial position of the reflection unit based on the detection result of the position detection unit.

[0015] The present invention can provide an image projection device and an image projection method that are capable of performing highly accurate initialization with a simple configuration in the image display position adjustment process.

[0016] Fig. 1 is a longitudinal sectional view showing an example of the configuration of an image projection device according to an embodiment. Fig. 2 is a block diagram showing an example of the configuration of an image projection device according to an embodiment. Fig. 3 is a flowchart showing the processing flow of an image display position adjustment program executed by an image projection device according to an embodiment. Fig. 4 is a longitudinal sectional view showing an example of the configuration of an image projection device according to an embodiment, and Fig. 5 is a perspective view showing an example of the configuration of an image projection device according to an embodiment, and Fig. 6 is a perspective view showing an example of the configuration around a movable mirror. Fig. 7 is a longitudinal sectional view showing the configuration of an image projection device according to a conventional technique.

[0017] 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 as appropriate. In the following description, an embodiment in which an image projection device of the present invention is applied to a HUD mounted on a vehicle or the like will be described as an example. The HUD of this embodiment displays, for example, driving assistance information that assists the driver in driving.

[0018] An image projection device and an image projection method according to this embodiment will be described with reference to Figures 1 to 4. Figure 1 is a longitudinal cross-sectional view showing an example of the configuration of an image projection device 10 according to this embodiment. The main body of the image projection device 10 is disposed, for example, below the dashboard of a vehicle. As shown in Figure 1, the image projection device 10 includes an image irradiation unit 11, a movable mirror 12, a drive unit 13, a switch 15, a fixed mirror 16, a control unit 20, a control board 20a, a housing 30, and a light-transmitting unit 31. Note that in Figure 1, the vehicle travels to the left of the page.

[0019] The image projection unit 11 projects image display light GL to form a display image ahead of the vehicle. The image projection unit 11 is configured, for example, with a liquid crystal panel, an organic EL panel, or the like. FIG. 1 also shows the path of the image display light GL. That is, the image display light GL projected from the image projection unit 11 passes through a light-transmitting portion 31 provided in a part of a housing 30 (described later) and heads toward a windshield (not shown). The "windshield" is an example of the "display unit" according to the present invention.

[0020] The fixed mirror 16 is a fixed reflecting member that does not have a movable part, and reflects the image display light GL irradiated from the image irradiation unit 11 toward the movable mirror 12. Note that the fixed mirror 16 is an auxiliary component, and may be omitted so that the image display light GL from the image irradiation unit 11 is directly irradiated onto the movable mirror 12.

[0021] The movable mirror 12 is an optical member that guides the image display light GL emitted from the image projection unit 11 to the windshield. The shape of the movable mirror 12 is not particularly limited, but in this embodiment, a concave mirror is used. The image display light GL emitted to the windshield is reflected by the windshield, forming an eye box for the driver and forming a display image as a virtual image in front of the vehicle. This reduces the amount of line-of-sight movement required by the driver to visually recognize the driving assistance information. While this embodiment describes an optical system using two mirrors, a fixed mirror 16 and a movable mirror 12, the present invention is not limited to this, and other reflective members, such as a free-form mirror, may also be included. The "movable mirror 12" is an example of a "reflective unit" according to the present invention.

[0022] The drive unit 13 includes a motor 13a and has the function of changing the rotation angle of the movable mirror 12 in a vertical plane around the rotation mechanism 13b during initialization of the movable mirror 12, as described below. That is, the movable mirror 12 according to this embodiment is rotatable in the directions of arrows D1 and D2 around the rotation axis of the rotation mechanism 13b, which is engaged with the motor 13a. Here, the "vertical plane" according to this embodiment refers to a plane perpendicular to the ground. The motor used is not particularly limited, and examples include a synchronous motor that operates in synchronization with input pulse power, a stepping motor, and the like. While this embodiment has been described with reference to an example using the rotation mechanism 13b engaged with the motor 13a, the orientation of the movable mirror 12 may be changed directly around the rotation axis of the motor 13a.

[0023] The control unit 20 controls the entire image projection device 10 and executes an image display position adjustment program, which will be described later. The control unit 20 includes a CPU, ROM, RAM, etc., which are not shown. The control unit 20 may be an ECU (Engine Control Unit) of a vehicle that mounts the image projection device 10. The control unit 20 according to this embodiment is, for example, configured as an LSI, and is mounted on a control board 20a. The control board 20a is, for example, configured as a printed circuit board. Details of the control board 20a will be described later. The "control board 20a" is an example of a "board" according to the present invention.

[0024] The switch 15 has a function of detecting an initial position Pi during an initialization process, which will be described later. The switch 15 is, for example, a contact switch, and is mounted on the control board 20a. Details of the switch 15 will be described later. The "switch 15" is an example of the "position detection unit" according to the present invention.

[0025] The housing 30 accommodates the above-described components and forms a single unit. A light-transmitting portion 31 is provided in a part of the housing 30, and transmits the image display light GL from the image irradiating unit 11. The light-transmitting portion 31 is formed of, for example, a transparent resin.

[0026] Next, the electrical configuration of the image projection device 10 according to this embodiment will be described with reference to FIG. 2 . As shown in FIG. 2 , the image projection device 10 includes a control unit 20, an image projection unit 11, a drive unit 13, a switch 15, and a storage unit 24. The control unit 20 is connected to an HCU 40. The HCU (Human Machine Interface Control Unit) 40 is one of the vehicle's ECUs and has the function of controlling a Human Machine Interface (HMI) system. The HMI has an input interface function that accepts operations by the vehicle driver and an output interface function that presents information to the driver. The input / output interface 41 provides these interface functions to the driver, primarily inputting operational instructions from the driver and displaying various information to the driver. The input / output interface 41 is not particularly limited and can be configured with a liquid crystal panel, an organic electroluminescence (EL) panel, or the like. The input / output interface 41 may also be configured to accept operations via a touch panel. Furthermore, the HCU 40 sends instructions corresponding to the operations input by the driver to the control unit 20.

[0027] The control unit 20 includes a processing unit 21, a drive control signal generation unit 22, and an image control signal generation unit 23. The processing unit 21 mainly controls the image projection unit 11, the drive unit 13, the switch 15, and the memory unit 24 based on an image display position adjustment instruction from the HCU 40, an image display position for each driver stored in the memory unit 24, etc. The drive control signal generation unit 22 generates an instruction signal for rotating the movable mirror 12. The instruction signal is sent to the motor 13b, which in turn controls the drive unit 13. The image control signal generation unit 23 generates a signal for causing the image projection unit 11 to emit image display light GL.

[0028] The storage unit 24 is a storage means for storing an image display position adjustment program and the like in the image display position adjustment process (described later) executed by the image projection device 10. The storage unit 24 may store information related to the image display position adjustment, such as the image display position for each driver. The form of the storage unit 24 is not particularly limited, and may be, for example, a RAM, a hard disk drive (HDD), or the like.

[0029] Next, a method for adjusting the image display position in the image projection device 10 will be described with reference to Fig. 3. Fig. 3 is a flowchart showing the processing flow of an image display position adjustment program, which describes the image display position adjustment process executed by the control unit 20. This image display position adjustment program is stored in the storage unit 24 or a storage means such as a ROM (not shown), and is read out by the CPU, expanded into a RAM, etc., and executed.

[0030] An overview of the image display position adjustment performed by the image projection device 10 according to this embodiment is as follows. That is, when the driver issues an instruction to adjust the image display position via the input / output interface 41, the instruction is sent to the control unit 20 via the HCU 40. The control unit 20, which has received the instruction to adjust the image display position, rotates the movable mirror 12 based on the image display position adjustment program, thereby adjusting the image display position. Within the image display position adjustment process, an initialization process is executed to detect the initial position Pi of the movable mirror 12, which is one of the features of the image projection device 10 according to this embodiment.

[0031] 3, in step S10, control unit 20 waits until it receives a start instruction from HCU 40. The start instruction is generated when the engine of the vehicle is started, for example.

[0032] In step S11, the control unit 20 determines whether initialization processing has already been performed on the movable mirror 12. Information on whether initialization processing has already been performed is stored in a storage unit such as the storage unit 24. If the determination is negative, the process proceeds to step S12, and if the determination is positive, the process proceeds to step S16.

[0033] In step S12, the control unit 20 controls the drive unit 13 to rotate the movable mirror 12 in the direction D1 shown in FIG.

[0034] In step S13, the control unit 20 waits until it receives a contact signal from the switch 15. The contact signal is a signal indicating that the movable mirror 12 has contacted the switch 15. When the control unit 20 receives a contact signal for the first time, this indicates that the initialization process has already been performed, and this fact is stored in a storage unit such as the storage unit 24.

[0035] In step S14, the control unit 20 controls the driving unit 13 to stop the rotation of the movable mirror 12. This stop position of the movable mirror 12 is the initial position Pi.

[0036] In step S15, the control unit 20 controls the drive unit 13 to rotate the movable mirror 12 in the D2 direction and stop it at a standby position Ps. The standby position Ps is a reference position for the movable mirror 12 when performing the image display position adjustment process. The standby position Ps can be appropriately set in consideration of, for example, the movable range of the movable mirror 12. As an example, the standby position can be approximately the center position of the movable range of the movable mirror 12. Note that the standby position Ps may be the initial position Pi.

[0037] In step S16, the control unit 20 determines whether an image display position adjustment instruction has been received from the HCU 40. If the determination is affirmative, the process proceeds to step S17, and if the determination is negative, the process proceeds to step S18. Steps S12 to S15 constitute the initialization process according to this embodiment.

[0038] In step S17, the control unit 20 executes an image display position adjustment process. More specifically, based on a specific instruction for the image display position input by the driver from the input / output interface 41 and received via the HCU 40, the control unit 20 controls the drive unit 13 to rotate the movable mirror 12 from the standby position Ps to a position corresponding to the instruction.

[0039] In step S18, the control unit 20 determines whether an end instruction has been received for the image projection device 10. If the determination is negative, the process proceeds to step S11, and if the determination is positive, the image display position adjustment program is terminated. That is, in this embodiment, since steps S11 to S18 are looped while the vehicle engine is running, it is also possible to respond to image display position adjustment instructions during this time. Note that the determination of whether an end instruction has been received may also be made based on, for example, an engine stop signal.

[0040] Next, a perspective view of the image projection device 10 will be described with reference to Fig. 4. Fig. 4 shows an example of the overall configuration of the image projection device 10, which is close to the actual configuration, and Fig. 4 shows an example of the configuration around the movable mirror 12.

[0041] In the image projection device 10 according to this embodiment, the image projection unit 11, movable mirror 12, fixed mirror 16, and control board 20a are arranged as shown in FIG. 4A, for example. The control board 20a is equipped with a control unit 20 serving as a control LSI, a switch 15, and other components (not shown). The rear surface of the movable mirror 12 faces the switch 15 on the control board 20a. Because the switch 15 is mounted on the control board 20a in the image projection device 10, a board or wiring for the switch 15 is not required, resulting in a simple configuration. Furthermore, because the movable mirror 12 and the switch 15 are in direct contact with each other, the initial position Pi can be detected with little variation and high precision.

[0042] As shown in FIG. 4B , in this embodiment, the control board 20a is disposed behind the movable mirror 12, and the back surface of the movable mirror 12 faces the switch 15 (the control unit 20 is not shown in FIG. 4B ). This allows the initial position Pi of the movable mirror 12 to be detected with high accuracy. Note that disposing the control board 20a behind the movable mirror 12 is just one example, and the control board 20a can be disposed anywhere as long as contact between the back surface of the movable mirror 12 and the switch 15 is ensured. The switch 15 may be mounted on the control board 20a via a dedicated base. Providing a base makes it easy to adjust the height of the switch 15. Furthermore, a reinforcing member may be provided on the back surface of the movable mirror 12 at a position where it will come into contact with the switch 15. This reinforcing member can reduce wear on the movable mirror 12.

[0043] In this embodiment, a contact switch is used as the switch 15, but a non-contact switch may also be used. For example, a photoelectric switch having a light-emitting unit and a light-receiving unit is used as the switch 15, and a reflector is provided at a position corresponding to the initial position of the movable mirror 12. In this embodiment, the initial position is set to the position where the light-receiving unit receives light that is emitted from the light-emitting unit and reflected by the reflector.

[0044] As described above in detail, the image projection device and image projection method according to this embodiment can provide an image projection device and image projection method that are capable of performing high-precision initialization with a simple configuration in the image display position adjustment process.

[0045] This international application claims priority based on Japanese Patent Application No. 2023-208110, filed on December 9, 2023, the entire contents of which are incorporated herein by reference.

[0046] The above descriptions of specific embodiments of the present invention have been presented for purposes of illustration. They are not intended to be exhaustive or to limit the invention to the precise forms described. Numerous modifications and variations will be apparent to those skilled in the art in light of the above description.

[0047] DESCRIPTION OF SYMBOLS 10, 100... Image projection device 11... Image irradiation unit 12... Movable mirror 13... Drive unit 13a... Motor 13b... Rotation mechanism 15... Switch 16... Fixed mirror 20... Control unit 20a... Control board 21... Processing unit 22... Drive control signal generation unit 23... Image control signal generation unit 24... Storage unit 30... Housing 31... Light-transmitting unit 40... HCU 41... Input / output interface 50... Control unit D, D1, D2... Direction GL... Image display light Pi... Initial position Ps... Standby position

Claims

1. An image projection device which projects a virtual image via a display unit, comprising: an image irradiation unit which irradiates image display light to form the virtual image; a reflection unit which guides the image display light to the display unit; a drive unit which rotates the reflective surface of the reflection unit to change the direction of the image display light; a control unit which controls the drive unit; a substrate on which the control unit is mounted; and a position detection unit for the reflection unit mounted on the substrate, wherein the control unit identifies an initial position of the reflection unit based on the detection result of the position detection unit.

2. An image projection device as described in claim 1, wherein the position detection unit is a contact switch having contacts, the substrate is arranged behind the reflecting unit, and the initial position of the reflecting unit is identified based on contact between the rear surface of the reflecting unit and the contacts of the contact switch.

3. An image projection device as described in claim 1, characterized in that the control unit rotates the reflecting unit in a first direction and stops it temporarily at the initial position, and then rotates it in a second direction opposite to the first direction and stops it at the standby position of the reflecting unit.

4. An image projection device as described in claim 1, wherein the image display light forms a virtual image through the display unit, and the initial position is used to identify a reference position for the reflecting unit when adjusting the position of the virtual image.

5. An image projection method using an image projection device that projects a virtual image via a display unit, the image projection method comprising: an image irradiation unit that irradiates image display light to form the virtual image; a reflecting unit that directs the image display light to the display unit; a driving unit that rotates the reflective surface of the reflecting unit to change the direction of the image display light; a control unit that controls the driving unit; a substrate on which the control unit is mounted; and a position detection unit for the reflecting unit mounted on the substrate, the image projection method being characterized in that the control unit identifies an initial position of the reflecting unit based on the detection result of the position detection unit.

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