Image projection device and image projection method

Abstract

To provide an image projection device and an image projection method suppressing a sense of incongruity when visually recognizing a front display image even if a preceding vehicle approaches.SOLUTION: An image projection device (10) projecting a projection image to a wind shield (16) for displaying virtual images (17 and 18), is equipped with an image irradiating portion (11) that irradiates the projection image, optical portions (12, 13, 14, and 15) that irradiates the projection image to the wind shield (16) as image light, distance measuring means (20) that detects the overlapping of the virtual images (17 and 18) on a preceding vehicle, and a control portion (30) that controls a projection position of the projection image so as to avoid the overlapping of the virtual images (17 and 18) and the preceding vehicle, on the basis of a degree of the overlapping.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

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

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

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

[0005] In a vehicle equipped with a HUD, the driver visually recognizes an image (hereinafter referred to as a "forward display image") displayed as a virtual image in front of the vehicle. The vertical display position of the forward display image is usually set assuming that there is no preceding vehicle. Therefore, when a preceding vehicle approaches the driver's vehicle on the road, the forward display image may overlap with the preceding vehicle, making it difficult for the driver to view the forward display image, which may cause the driver to feel uncomfortable. From the perspective of safety, it is desirable to eliminate such discomfort as much as possible.

[0006] 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 suppress the sense of discomfort when viewing a forward display image even when a preceding vehicle is approaching. [Means for solving the problem]

[0007] In order to solve the above problem, the image projection device of the present invention is an image projection device that projects a projection image onto a display unit for displaying a virtual image, and includes: an image projection unit that irradiates the projection image; an optical unit that irradiates the projection image onto the display unit as image light; a detection unit that detects overlap between the virtual image and a preceding vehicle; and a control unit that controls a projection position of the projection image based on the degree of overlap so as to avoid overlap between the virtual image and the preceding vehicle. At night, the control unit allows the virtual image to overlap with the preceding vehicle and moves the virtual image above the taillights of the preceding vehicle. It is characterized by: In addition, in order to solve the above problem, the image projection device of the present invention is an image projection device that projects a projection image onto a display unit for displaying a virtual image, and is equipped with an image irradiation unit that irradiates the projection image, an optical unit that irradiates the projection image onto the display unit as image light, a detection unit that detects overlap between the virtual image and a preceding vehicle, and a control unit that controls the projection position of the projection image based on the degree of overlap so as to avoid overlap between the virtual image and the preceding vehicle, and is characterized in that when the preceding vehicle enters or exits another lane, the control unit controls the projection position of the projection image over a predetermined time period so as to avoid overlap between the virtual image and the preceding vehicle. In addition, in order to solve the above problem, the image projection device of the present invention is an image projection device that projects a projection image onto a display unit for displaying a virtual image, and is equipped with an image irradiation unit that irradiates the projection image, an optical unit that irradiates the projection image onto the display unit as image light, a detection unit that detects overlap between the virtual image and a preceding vehicle, and a control unit that controls the projection position of the projection image so as to avoid overlap between the virtual image and the preceding vehicle based on the degree of overlap, and is characterized in that the control unit determines the need to avoid overlap between the virtual image and the preceding vehicle by taking into account the color relationship between the virtual image and the preceding vehicle.

[0008] The image projection device of the present invention includes an image projection unit that projects a projected image, an optical unit that projects the projected image as image light onto a display unit that displays a virtual image, and a detection unit that detects overlap between the virtual image and a preceding vehicle. The control unit controls the projection position of the projected image based on the degree of overlap to avoid overlap between the virtual image and the preceding vehicle. As a result, when the driver views the road ahead, overlap between the virtual image and the preceding vehicle is eliminated. This reduces the sense of discomfort felt when viewing the forward display image, even when a preceding vehicle is approaching.

[0009] In one aspect of the present invention, the control unit prevents the virtual image from overlapping with the preceding vehicle. In this case, the virtual image is moved downward. The projection position of the projected image is controlled.

[0011] In one aspect of the present invention, the detection unit is a distance measurement means that measures the distance to the preceding vehicle, and the control unit acquires the degree of overlap based on the distance to the preceding vehicle.

[0012] In one aspect of the present invention, the detection unit is an image capturing means for capturing an image of the preceding vehicle, and the control unit obtains the degree of overlap using an image of the preceding vehicle.

[0013] In one aspect of the present invention, the control unit controls the projection position of the projected image while maintaining a constant relative positional relationship between the leading vehicle and the virtual image.

[0016] In one aspect of the present invention, the control unit controls the projection position of the projection image using a display position adjustment unit included in the image projection unit that adjusts the display position of the projection image.

[0017] In one aspect of the present invention, the control unit controls the projection position of the projection image using a reflection means included in the optical unit, the reflection means having an adjustable angle relative to the projection image.

[0018] In order to solve the above-mentioned problems, the image projection method of the present invention is an image projection device that projects a projection image onto a display unit for displaying a virtual image, the image projection method using an image projection device that includes an image projection unit that irradiates the projection image, an optical unit that irradiates the projection image onto the display unit as image light, and a detection unit that detects overlap between the virtual image and a preceding vehicle, and controls the projection position of the projection image based on the degree of overlap so as to avoid overlap between the virtual image and the preceding vehicle. At night, the virtual image is allowed to overlap with the preceding vehicle, and the virtual image is moved above the taillights of the preceding vehicle. It is characterized by: In addition, in order to solve the above-mentioned problems, the image projection method of the present invention is an image projection method using an image projection device that projects a projection image onto a display unit for displaying a virtual image, the image projection method including an image projection unit that irradiates the projection image, an optical unit that irradiates the projection image onto the display unit as image light, and a detection unit that detects overlap between the virtual image and a preceding vehicle, and is characterized in that the projection position of the projection image is controlled based on the degree of overlap to avoid overlap between the virtual image and the preceding vehicle, and when the preceding vehicle enters or exits another lane, the projection position of the projection image is controlled over a predetermined time period to avoid overlap between the virtual image and the preceding vehicle. In addition, in order to solve the above-mentioned problems, the image projection method of the present invention is an image projection method using an image projection device that projects a projection image onto a display unit for displaying a virtual image, the image projection method including an image projection unit that irradiates the projection image, an optical unit that irradiates the projection image onto the display unit as image light, and a detection unit that detects overlap between the virtual image and a preceding vehicle, and is characterized in that the projection position of the projection image is controlled based on the degree of overlap so as to avoid overlap between the virtual image and the preceding vehicle, and the necessity of avoiding overlap between the virtual image and the preceding vehicle is determined by taking into account the color relationship between the virtual image and the preceding vehicle. [Effects of the Invention]

[0019] The present invention can provide an image projection device and an image projection method that suppress the sense of discomfort felt when viewing a forward display image even when a preceding vehicle is approaching. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a block diagram showing an example of the configuration of an image projection device according to a first embodiment. [Figure 2] 3 is a schematic diagram showing an example of the configuration of a display area of ​​an image projection unit according to the first embodiment. FIG. [Figure 3] 6 is a flowchart showing a processing flow of a display position adjustment program executed by the image projection device according to the first embodiment. [Figure 4] 5A and 5B are schematic diagrams showing a method for calculating an adjusted depression angle in the image projection device according to the first embodiment. [Figure 5] 5(a) to 5(c) are schematic diagrams showing the operation of the image projection device according to the first embodiment. [Figure 6] FIG. 11 is a block diagram showing an example of the configuration of an image projection device according to a fifth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0021] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. The same or equivalent components, parts, and processes shown in each drawing will be assigned the same reference numerals, and redundant explanations will be omitted as appropriate. In the following explanation, an embodiment in which an image projection device according to the present invention is applied to a HUD mounted on a vehicle or the like will be described as an example.

[0022] (First embodiment) An image projection device and an image projection method according to this embodiment will be described with reference to FIGS. 1 to 5. FIG. 1 is a block diagram 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. The image projection device 10 exemplifies an image projection device employing an image projection method capable of projecting two forward display images on a single screen. That is, the image projection device 10 is capable of displaying a distant image formed as a virtual image relatively far in front of the vehicle, and a near image formed as a virtual image relatively close in front of the vehicle. However, the present invention is not limited to this, and may be applied to an image projection device that projects three or more forward display images on a single screen, an image projection device that projects one forward display image on a single screen, or an image projection device that projects multiple forward display images on multiple screens.

[0023] As shown in Fig. 1, an image projection device 10 according to this embodiment includes an image projection unit 11, a reflecting mirror 12, a free-form surface mirror 13, a light branching unit 14, a free-form surface mirror 15, a distance measuring means 20, an imaging means 21, and a control unit 30. Fig. 1 also shows a windshield 16 onto which a projected image from the image projection device 10 is projected. The "windshield 16" is an example of a "display unit" according to the present invention. The "reflecting mirror 12," "free-form surface mirror 13," "light branching unit 14," and "free-form surface mirror 15" are examples of an "optical unit" according to the present invention.

[0024] The image projection unit 11 projects an image for forming a virtual far image or a near image in front of the vehicle. The image projection unit 11 is configured, for example, with a liquid crystal panel, an organic EL panel, a DMD (Digital Micro Mirror Device), or the like. The image projection unit 11 is divided into a far display area that displays an image for forming a far image, and a near display area that displays an image for forming a near image. In FIG. 1, the optical path of the far image light projected from the far display area is indicated by a dashed line, and the optical path of the near image light projected from the near display area is indicated by a dashed line.

[0025] Image projection device 10 is configured so that the distant image (virtual image 18) displayed in front of the vehicle can be moved up and down (vertically). Therefore, it is configured so that the position of the image displayed in the distant display area of ​​image projection unit 11 can be changed. By moving the image displayed in the distant display area, the projection position of distant image light from image projection unit 11 onto windshield 16 is adjusted, and as a result, the vertical direction of the distant image is adjusted.

[0026] The movement of the display image in the far display area will be described in more detail with reference to FIG. 2. FIG. 2 is a schematic diagram showing a display area 40 in which an image is displayed by the image projection unit 11. The display area 40 is the entire area in which an image can be displayed as a display. The display area 40 includes a far display area 41 that displays a far image formed in the distance, and a near display area 43 that displays a near image formed in the near distance. In the image projection device 10, far image light that irradiates the far image displayed in the far display area 41 is formed as a virtual image 18 in the distance via the optical branching unit 14, etc. Further, near image light that irradiates the near image displayed in the near display area 43 is formed as a virtual image 17 in the near distance via the reflecting mirror 12, etc.

[0027] A margin area 42 is provided around the far display area 41, and the image displayed in the far display area 41 can be moved within the margin area 42 in directions D1 and D2 indicated by the arrows in Fig. 2. This adjusts the position at which the far image light is irradiated onto the windshield 16, and as a result, the vertical position of the far image is adjusted.

[0028] 1, the image projection unit 11 is connected to the control unit 30, which controls the movement of the position of the image displayed in the far display area, i.e., the vertical movement of the far image. In this embodiment, the "far display area 41" in which the position of the displayed image can be changed is an example of the "display position adjustment means" according to the present invention.

[0029] In this embodiment, the far image can be moved up and down by the image displayed in the far display area, but if the near image causes discomfort, the near image may be moved up and down by moving the image displayed in the near display area. Alternatively, both the far image and the near image may be moved up and down.

[0030] The optical branching unit 14 is a component that branches the far image light emitted from the far display area, and is configured, for example, by a prism. As shown in FIG. 1, the far image light passes through the optical branching unit 14, is reflected by the free-form surface mirror 15, the free-form surface mirror 13, and the windshield 16, and reaches the driver's viewpoint 52. As a result, a virtual image 18 (far image) is formed relatively far in front of the vehicle. The display position of the far image is, for example, about 15 m in front of the vehicle. In FIG. 1, a "driving assistance display" is illustrated as an example of the content of the far image.

[0031] On the other hand, as shown in Figure 1, near image light is emitted from the near display area, and then reflected by reflector 12, free-form mirror 13, and windshield 16, before reaching driver's viewpoint 52. As a result, a virtual image 17 (near image) is formed relatively close in front of the vehicle. As an example, the display position of the near image is about 3 m in front of the vehicle. Figure 1 shows "vehicle speed display, etc." as an example of the content of the near image.

[0032] With the above configuration, the image projection device 10 projects the virtual image 18 at a distance several degrees below the horizontal, reducing the driver's line-of-sight movement required to visually recognize the driving assistance information. Furthermore, the virtual image 17 is projected further below at a closer distance, allowing the driver to clearly see the vehicle speed display and other information by shifting their line of sight.

[0033] The distance measuring means 20 is a part that measures the distance to objects around the vehicle, and is composed of, for example, LiDAR (Light Detection and Ranging) or radar. In this embodiment, the distance measuring means 20 is mainly used to measure the distance between the vehicle and a preceding vehicle traveling ahead (hereinafter referred to as "inter-vehicle distance"). The measured distance is sent to the control unit 30. The "distance measuring means 20" is an example of the "detection unit" according to the present invention.

[0034] The imaging means 21 is a part that captures images of the area ahead of the vehicle, and is configured, for example, by an on-board camera. The camera may be a monocular camera or a stereo camera. If it is a stereo camera, it can also function as a distance measuring means. In this embodiment, the imaging means 21 is mainly used to detect overlap between a distant image and a preceding vehicle. The imaging means 21 is connected to the control unit 30, and the images captured by the imaging means 21 are sent to the control unit 30 for image processing. Note that the imaging means 21 is not used in this embodiment, but is used in the second embodiment described below.

[0035] The control unit 30 controls the entire image projection device 10 and executes a display position adjustment program, which will be described later. The control unit 30 includes a CPU, ROM, RAM, etc., which are not shown. The control unit 30 may be an ECU (Engine Control Unit) of a vehicle in which the image projection device 10 is mounted.

[0036] As described above, when a preceding vehicle approaches the vehicle on a roadway, the distant image may overlap with the preceding vehicle, making it difficult for the driver to see the distant image, which may cause discomfort. Therefore, in this embodiment, the overlap between the distant image and the preceding vehicle is estimated, and based on the result, the distant image is moved downward to avoid overlapping with the preceding vehicle. More specifically, the distance to the preceding vehicle, i.e., the inter-vehicle distance, is measured by distance measuring means 20, and when the inter-vehicle distance satisfies a predetermined condition, an adjustment depression angle for adjusting the depression angle of the distant image is calculated, and the position of the image displayed in the distant display area of ​​image projection unit 11 is adjusted. As a result, the projection position of the distant image light from image projection unit 11 onto windshield 16 is adjusted, and the vertical position of the distant image is adjusted. Note that, since the present invention is applied to a distant image in this embodiment, the "distant image" will be referred to as the "forward display image" in the following description.

[0037] The procedure for adjusting the display position of a forward display image executed by the image projection device 10 according to this embodiment will be described with reference to Fig. 3. Fig. 3 is a flowchart showing the processing flow of a display position adjustment program, which shows the procedure for the display position adjustment process executed by the control unit 30 of the image projection device 10. The display position adjustment program is stored in storage means such as a ROM (not shown), and is read out by the CPU, expanded into a RAM, etc., and executed.

[0038] In step S10, the control unit 30 waits for detection of a preceding vehicle. If the determination in step S10 is affirmative, the process proceeds to step S11.

[0039] In step S11, it is determined whether the depression angle of the forward display image needs to be adjusted.

[0040] An example of a method for determining whether adjustment of the depression angle is necessary, which is executed in the image projection device 10 according to this embodiment, will be described with reference to FIG. 4. FIG. 4 illustrates a vehicle 51 as the subject vehicle traveling on a road 50, and a preceding vehicle 54 ahead of the vehicle 51. The symbol hr indicates the horizon stretched from the driver's viewpoint 52. In this embodiment, when the forward display image overlaps with the preceding vehicle 54, the destination of the forward display image is assumed to be below the bottom edge of the rear license plate 55. If the inter-vehicle distance is L, the distance to the horizon hr measured from the road surface of the road 50 is H, and the distance to the bottom edge of the rear license plate 55 measured from the road surface is h, the depression angle θ shown in FIG. 4 can generally be calculated using the following (Equation 1). θ=arctan((Hh) / L) (Formula 1)

[0041] On the other hand, the minimum depression angle θmin is defined as the depression angle measured from the horizontal line hr when the upper edge of the forward display image in the standard display position overlaps the lower edge of rear license plate 55. If the inter-vehicle distance between vehicle 51 and preceding vehicle 54 measured by distance measuring means 20 at this time is the maximum inter-vehicle distance Lmax, the minimum depression angle θmin is calculated from (Equation 1) using the following (Equation 2). θmin=arctan((Hh) / Lmax) (Formula 2)

[0042] As described above, in the image projection device 10, when the front display image overlaps with the preceding vehicle 54, a position below the lower end of the rear license plate 55 is assumed as the position to move the front display image. That is, it is assumed that at this position, the front display image can be visually recognized by the driver without being obstructed by the preceding vehicle 54. Of course, the minimum depression angle θmin is not limited to the above concept, and it may be set assuming other locations of the preceding vehicle 54. The distance H from the road surface to the horizontal line hr can be set in advance if a standard value is adopted as the position of the viewpoint 52. However, it is not limited to this, and it may be set for each driver. On the other hand, the distance h from the road surface to the license plate can also be set in advance if a standard value is adopted. However, it is not limited to this, and it may be set for each vehicle. In the present embodiment, H and h are set in advance, and (H - h) is treated as a constant.

[0043] Based on the above assumptions, the depression angle θ of the lower end of the rear license plate 55 of the preceding vehicle 54 can generally be calculated from the above (Equation 1) using the vehicle-to-vehicle distance L. And in the present embodiment, in step S11, when θ > θmin, it is determined that adjustment of the depression angle is necessary. Since the depression angle θ and the vehicle-to-vehicle distance L correspond 1:1, when L < Lmax, it may also be determined that adjustment of the depression angle is necessary.

[0044] Referring to FIG. 3 again, in step S12, the adjusted depression angle θa is obtained. The adjusted depression angle θa is basically the depression angle θ calculated by substituting the vehicle-to-vehicle distance L measured by the distance measuring means 20 into (Equation 1). However, it is not limited to this, and some correction such as multiplying the calculated θ by a coefficient considering safety may be performed.

[0045] In step S13, it is determined whether the adjusted depression angle θa obtained in step S12 is within the adjustment range of the depression angle. If the determination is affirmative, the process proceeds to step S14, and if the determination is negative, the process proceeds to step S15.

[0046] In this embodiment, adjustment of the depression angle θ begins when the depression angle θ becomes θ>θmin, and the depression angle θ is increased as the inter-vehicle distance L becomes smaller than the maximum inter-vehicle distance Lmax. A maximum depression angle θmax, which is the upper limit of the depression angle θ, may be set in advance. Step S13 is the process performed when this maximum depression angle θmax has been determined. The maximum depression angle θmax may be set, for example, within the range in which the distant display area 41 can move within the margin area 42, or within the tilt angle adjustment range of the free-form surface mirror 13 in the fifth embodiment described below. It may also be set within the range in which the driver can view the forward display image. When the maximum depression angle θmax is set, the minimum inter-vehicle distance Lmin is necessarily set.

[0047] In step S14, the projection position adjustment unit, that is, in this embodiment, the image projection unit 11, is adjusted. More specifically, the image displayed in the far display area 41 of the display area 40 is moved based on the adjusted depression angle θa, and the projection position of the far image light projected from the image projection unit 11 onto the windshield 16 is adjusted, thereby adjusting the projection position of the far image.

[0048] On the other hand, in step S15, the forward display image, i.e., the distant image, is turned off because if the forward display image continues to be displayed while the depression angle is beyond the adjustment range, there is a high probability that the forward display image will overlap with the preceding vehicle 54.

[0049] In step S16, it is determined whether an end instruction has been issued. If the determination is negative, the process proceeds to step S10, where detection of the preceding vehicle continues. In other words, in this embodiment, detection of the preceding vehicle continues at all times, so the relative positional relationship between the preceding vehicle 54 and the display position of the forward display image is continuously and smoothly adjusted. On the other hand, if the determination is positive, the display position adjustment program is terminated. An end instruction may be, for example, by turning off the power to the image projection device 10.

[0050] Referring to FIG. 5, the operation and effects of the image projection device 10 according to the present embodiment will be described in more detail. FIG. 5(a) shows a state where the preceding vehicle 54 is far away and the front display image (virtual image 18, distant image) is located sufficiently below the preceding vehicle 54, that is, a state where the depression angle θ satisfies θ≦θmin (the inter-vehicle distance L satisfies L≧Lmax).

[0051] Next, when the vehicle 51 approaches the preceding vehicle 54 and the depression angle θ satisfies θ>θmin (the inter-vehicle distance L satisfies L<Lmax), as shown in FIG. 5(b), the front display image (virtual image 18) overlaps with the preceding vehicle 54, making it difficult for the driver to visually recognize the front display image (virtual image 18).

[0052] FIG. 5(c) shows a state where, as a result of the above display position adjustment process, the front display image (virtual image 18) has moved to the lower part of the preceding vehicle 54, eliminating the difficulty of visual recognition.

[0053] In the above description, the color of the preceding vehicle 54 is not considered. However, the color relationship between the preceding vehicle 54 and the front display image may be used as one of the criteria for determining overlap. That is, for example, if the color of the front display image is a bright color and the color of the preceding vehicle 54 is a dark color such as black, the degree of difficulty in visual recognition for the driver is also low, so there is no need to move the front display image deliberately. In such cases, it may be determined that the movement of the front display image is unnecessary. More specifically, step S11 of the flowchart shown in FIG. 3 may include a comparison determination of the color of the preceding vehicle 54 acquired by the imaging means 21 or the like and the color of the front display image.

[0054] As described in detail above, according to the image projection device and the image projection method according to the present embodiment, it is possible to provide an image projection device and an image projection method in which the discomfort when visually recognizing the front display image is suppressed even when the preceding vehicle approaches.

[0055] (Second Embodiment) An image projection device 10A and an image projection method according to this embodiment will be described with reference to FIGS. 1 to 3 and 5. This embodiment is a modified version of the first embodiment in that the method for detecting a preceding vehicle and the method for detecting overlap between the forward display image and the preceding vehicle are changed. That is, in this embodiment, the imaging means 21 shown in FIG. 1 is used to detect a preceding vehicle, detect overlap between the forward display image and the preceding vehicle, and prevent overlap between the forward display image and the preceding vehicle. The configuration of the image projection device according to this embodiment is the same as that of the first embodiment except for the imaging means 21, so detailed description will be omitted. However, this embodiment can also be applied to the fifth embodiment described below. In the image projection device 10A, the forward display image to be prevented from overlapping with the preceding vehicle is a distant image (virtual image 18), similar to the image projection device 10. The "imaging means 21" is an example of a "detection unit" according to the present invention.

[0056] The imaging means 21 is connected to the control unit 30, and under the control of the control unit 30, acquires an image of the area ahead of the vehicle, such as an image as shown in FIG. 5 (hereinafter referred to as a "peripheral image"), and sends it to the control unit 30. The control unit 30 processes the peripheral image and recognizes, for example, the outline of the preceding vehicle. Meanwhile, the control unit 30 grasps the display position of the forward display image based on, for example, the depression angle. The image projection unit 11 of the image projection device 10A according to this embodiment also has the configuration shown in FIG. 2, and is capable of moving the distant display area 41, i.e., adjusting the forward display image in the vertical direction.

[0057] The basic procedure of the image projection method according to this embodiment is the same as that shown in Fig. 3. That is, the image projection device 10A also executes the display position adjustment process shown in Fig. 3. Hereinafter, the display position adjustment process executed by the control unit 30 according to this embodiment will be described with reference to Fig. 3.

[0058] In step S10, the system waits until a preceding vehicle is detected, and if the determination is affirmative, the system proceeds to step S11.

[0059] In step S11, it is determined whether the depression angle of the display position of the forward display image needs to be adjusted. This determination is made, for example, by image recognition, when the preceding vehicle 54 and the virtual image 18 overlap, as shown in FIG. 5B. Note that the determination that depression angle adjustment is necessary does not necessarily have to be made when the preceding vehicle 54 and the virtual image 18 completely overlap, but may also be made when a predetermined percentage of the virtual image 18 overlaps, for example, 50% or more.

[0060] In step S12, the adjustment depression angle, that is, the depression angle required to avoid overlapping, is obtained. The adjustment depression angle is calculated by, for example, using image recognition to calculate the depression angle when the virtual image 18 is located below the leading vehicle 54.

[0061] The processing from step S13 onwards is the same as that of the image projection device 10 according to the first embodiment, and therefore a description thereof will be omitted. In this embodiment as well, steps S10 to S16 are looped unless an end instruction is given in step S16, so that the relative positional relationship between the preceding vehicle 54 and the display position of the forward display image is continuously and smoothly adjusted.

[0062] As described above, the image projection device and image projection method according to this embodiment make it possible to provide an image projection device and an image projection method that suppress the sense of discomfort felt when viewing the forward display image, even when a preceding vehicle approaches.

[0063] (Third embodiment) The image projection device and image projection method according to this embodiment are configured to perform a predetermined display position adjustment process when a vehicle is traveling at night. The configuration of the image projection device according to this embodiment is the same as that shown in FIG. 1, so the drawing is omitted. The image projection device and image projection method according to this embodiment can be applied to any of the above-described first and second embodiments, or the fifth embodiment described below.

[0064] As described above, if the color of the forward display image is a light color and the color of the preceding vehicle 54 is a dark color such as black, the driver's visibility will be minimal, and there is no need to move the forward display image. Considering this point further, at night, the rear of the preceding vehicle 54 is dark except for lighting fixtures such as taillights (rear combination lamps). Therefore, in the display position adjustment process for the forward display image, while the forward display image is generally moved downward when it overlaps with the preceding vehicle 54, it may also be moved upward only at night. In this case, overlap with the taillights must be avoided, so it may be moved above the taillights. The determination of nighttime and the detection of taillights are performed, for example, by the control unit 30 processing images captured by the imaging means 21. Of course, the determination of nighttime may also be performed using a clock.

[0065] 3, the specific processing of this embodiment includes, for example, processing for determining whether it is nighttime and processing for detecting taillights in step S11. Then, in step S12, a depression angle for moving upward to avoid taillights, etc. is calculated. In this embodiment as well, steps S10 to S16 are looped unless an end command is given in step S16, so the relative positional relationship between the preceding vehicle 54 and the display position of the forward display image is continuously and smoothly adjusted.

[0066] As described above, the image projection device and image projection method according to the present embodiment also make it possible to provide an image projection device and image projection method that suppresses discomfort when viewing a forward display image even when a preceding vehicle is approaching. Furthermore, the image projection device and image projection method according to the present embodiment move the forward display image not only downward but also upward, so that the display position of the forward display image can be set to be more easily visible to the driver.

[0067] (Fourth embodiment) The image projection device and image projection method according to this embodiment are configured to execute a predetermined display position adjustment process when a preceding vehicle suddenly enters or exits. The configuration of the image projection device according to this embodiment is the same as that shown in FIG. 1, so the drawing is omitted. The image projection device and image projection method according to this embodiment can be applied to any of the first and second embodiments described above, or the fifth embodiment described below.

[0068] The display position adjustment process according to each of the above embodiments does not take into consideration a change in course of the preceding vehicle 54 or the vehicle itself. However, on an actual road, the vehicle itself may change lanes, or the preceding vehicle 54 may suddenly enter or exit. In such cases, it is expected that the display position of the forward display image (in this embodiment, the distant image) will change suddenly as the vehicle itself or the preceding vehicle 54 changes course. Such a sudden movement of the forward display image may cause discomfort to the driver, so it is best to avoid it as much as possible. Therefore, in this embodiment, a configuration is made such that the display position of the forward display image does not change suddenly when the vehicle itself changes lanes or when the preceding vehicle suddenly enters or exits.

[0069] First, a case where a preceding vehicle 54 suddenly enters will be described according to the flow shown in FIG. 3. The determination of the sudden entry of the preceding vehicle 54 is included in step S10, for example. More specifically, it is assumed that the distance measuring means 20 suddenly detects a preceding vehicle 54 located at a small inter-vehicle distance L. When the preceding vehicle 54 suddenly enters, the positional relationship between the preceding vehicle 54 and the forward display image (virtual image 18) shown in FIG. 5(b) may suddenly appear. In this case, if the display position adjustment process is performed according to the flow shown in FIG. 3, the sudden entry of the preceding vehicle 54 and the sudden movement of the forward display image may overlap, causing the driver to feel uncomfortable.

[0070] Therefore, in this embodiment, the movement of the display position of the forward display image (virtual image 18) from FIG. 5(b) to FIG. 5(c) is performed over a predetermined time. More specifically, the depression angle adjustment in step S14 of the flow shown in FIG. 3 is performed over a predetermined time. The predetermined time varies depending on the position of the preceding vehicle 54, the display position (depression angle) of the forward display image, etc., but is typically about several seconds. This makes it possible to suppress the driver's discomfort caused by the movement of the preceding vehicle 54 and the forward display image.

[0071] Next, a case where the preceding vehicle 54 suddenly withdraws will be described with reference to the flow shown in FIG. 3. The determination of the sudden withdrawal of the preceding vehicle 54 is included in, for example, step S10. More specifically, this occurs when, for example, the distance measuring means 20 detects a state in which it is suddenly unable to measure the distance to the preceding vehicle 54 (or a state in which the distance has become longer than a certain distance). When the preceding vehicle 54 suddenly withdraws, the forward display image (virtual image 18) is suddenly left behind in the positional relationship between the preceding vehicle 54 and the forward display image (virtual image 18) shown in FIG. 5(c). In such a case, even if a normal display position adjustment process is performed, it can be said that the driver feels less discomfort than when the preceding vehicle 54 suddenly enters. However, for safety reasons, the forward display image may also be moved over a predetermined period of time. More specifically, the depression angle adjustment in step S14 of the flow shown in FIG. 3 is performed over a predetermined period of time. In this case, the adjusted depression angle is the depression angle at the standard display position of the distant image, i.e., the minimum depression angle θmin, so the depression angle of the virtual image 18 shown in Figure 5(c) gradually moves toward the minimum depression angle θmin. The predetermined time varies depending on the position of the preceding vehicle 54, the display position (depression angle) of the forward display image, etc., but is approximately several seconds. This makes it possible to suppress any discomfort felt by the driver due to the movement of the preceding vehicle 54 and the forward display image.

[0072] As described above, the image projection device and image projection method according to the present embodiment can also provide an image projection device and an image projection method that can suppress the sense of discomfort felt when viewing a forward display image even when a preceding vehicle approaches. The image projection device and image projection method according to the present embodiment can suppress the sense of discomfort felt when a preceding vehicle suddenly enters or exits the road.

[0073] (Fifth embodiment) An image projection device and an image projection method according to this embodiment will be described with reference to Fig. 6. The image projection device 10B according to this embodiment is a configuration in which the projection position adjustment unit is changed from the image projection device 10 according to the above embodiment. Therefore, the same components as those in Fig. 1 are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0074] As shown in FIG. 6, in image projection device 10B, a free-form surface mirror 13 is connected to control unit 30 instead of image projection unit 11. "Free-form surface mirror 13" corresponds to the "projection position adjustment unit" shown in step S14 of FIG. 3. Free-form surface mirror 13 is provided with a mechanism for adjusting the tilt angle (not shown), and by adjusting this tilt angle, the projection position of the distant image light from image projection unit 11 onto windshield 16 is adjusted, and as a result, the vertical direction of the distant image is adjusted. Specific methods and procedures for adjusting the display position of the forward display image are as shown in FIGS. 3 and 5. Note that free-form surface mirror 13 is an example of the "reflection means" according to the present invention.

[0075] In the case of image projection device 10B shown in Fig. 6, adjusting the tilt angle of free-form surface mirror 13 simultaneously moves the near image. However, since the display position of the near image is less sensitive to changes in the tilt angle than the display position of the forward display image, this is not a problem in most cases. However, if you want to move only the forward display image, you can move light branching unit 14 or free-form surface mirror 15. Alternatively, separate free-form surface mirrors 13 may be provided for the far image light and the near image light.

[0076] As described above, the image projection device and the image projection method according to this embodiment also make it possible to provide an image projection device and an image projection method that suppress the sense of discomfort felt when viewing a forward display image even when a preceding vehicle is approaching. In particular, the image projection device and the image projection method according to this embodiment have the advantage that the range of movement of the forward display image in the up and down direction can be increased compared to the first embodiment, and there is no need to increase the display area 40 of the image projection unit 11.

[0077] Although the image projection device and image projection method according to each embodiment have been described individually in the above embodiments, a plurality of embodiments may be combined. For example, the first embodiment and the fifth embodiment may be combined to enable both the movement of the forward display image by the image projection unit 11 and the movement of the forward display image by the free-form surface mirror 13. In this case, a priority may be set between the movement of the forward display image by the image projection unit 11 and the movement of the forward display image by the free-form surface mirror 13. For example, the movement of the forward display image by the image projection unit 11 may be prioritized, and the movement of the forward display image by the free-form surface mirror 13 may be applied to a range beyond the capability of the image projection unit 11.

[0078] In the above embodiments, the display position adjustment program shown in Fig. 3 has been described as constantly detecting a preceding vehicle, but the present invention is not limited to this and may be configured to detect the preceding vehicle periodically or intermittently. When detecting the preceding vehicle periodically, a timer may be provided before step S10. When detecting the preceding vehicle intermittently, the control unit 30 may execute the display position adjustment program shown in Fig. 3 when necessary. [Explanation of symbols]

[0079] 10...Image projection device 11...Image irradiation unit 12...Reflector 13...Free-form mirror 14...Optical branching section 15...Freeform mirror 16...Windshield 17, 18...Virtual image 20…Distance measurement means 21...imaging means 30...Control unit 40…display area 41…Far display area 42...Margin area 43…Near display area 50…Runway 51...Vehicle 52...Viewpoint 54... Leading vehicle 55...Rear license plate D1, D2…direction hr…horizontal line H, h…distance L…Distance between vehicles Lmin…Minimum inter-vehicle distance Lmax…Maximum inter-vehicle distance θ…Angle of depression θmin…Minimum depression angle θmax…Maximum depression angle

Claims

1. An image projection device that projects a projection image onto a display unit for displaying a virtual image, an image projection unit that projects the projected image; an optical unit that irradiates the projected image onto the display unit as image light; a detection unit that detects an overlap between the virtual image and a preceding vehicle; a control unit that controls a projection position of the projection image based on the degree of overlap so as to avoid overlapping of the virtual image with the preceding vehicle, In the case of nighttime, the control unit allows the virtual image to overlap with the preceding vehicle and moves the virtual image above the taillights of the preceding vehicle.

2. An image projection device that projects a projection image onto a display unit for displaying a virtual image, an image projection unit that projects the projected image; an optical unit that irradiates the projected image onto the display unit as image light; a detection unit that detects an overlap between the virtual image and a preceding vehicle; a control unit that controls a projection position of the projection image based on the degree of overlap so as to avoid overlapping of the virtual image with the preceding vehicle, The control unit controls the projection position of the projected image over a predetermined period of time to avoid overlapping of the virtual image with the preceding vehicle when the preceding vehicle enters or exits another lane.

3. An image projection device that projects a projection image onto a display unit for displaying a virtual image, an image projection unit that projects the projected image; an optical unit that irradiates the projected image onto the display unit as image light; a detection unit that detects an overlap between the virtual image and a preceding vehicle; a control unit that controls a projection position of the projection image based on the degree of overlap so as to avoid overlapping of the virtual image with the preceding vehicle, The image projection device is characterized in that the control unit determines the need to avoid overlapping of the virtual image with the preceding vehicle by taking into account a color relationship between the virtual image and the preceding vehicle.

4. 4. The image projection device according to claim 1, The image projection device, wherein the control unit controls the projection position of the projected image by moving the virtual image downward when overlapping of the virtual image with the preceding vehicle is to be avoided.

5. 5. The image projection device according to claim 1, the detection unit is a distance measurement means for measuring the distance to the preceding vehicle, The image projection device is characterized in that the control unit obtains the degree of overlap based on the distance to the preceding vehicle.

6. 5. The image projection device according to claim 1, the detection unit is an imaging means for imaging the preceding vehicle, The image projection device is characterized in that the control unit obtains the degree of overlap using an image of the preceding vehicle.

7. 7. The image projection device according to claim 1, The image projection device, wherein the control unit controls the projection position of the projection image by a display position adjustment unit included in the image projection unit, the display position adjustment unit adjusting the display position of the projection image.

8. 7. The image projection device according to claim 1, The image projection device is characterized in that the control unit controls the projection position of the projected image by a reflecting means included in the optical unit and whose angle with respect to the projected image is adjustable.

9. An image projection method using an image projection device that projects a projection image onto a display unit for displaying a virtual image, the image projection device including an image irradiation unit that irradiates the projection image, an optical unit that irradiates the projection image onto the display unit as image light, and a detection unit that detects overlapping of the virtual image with a preceding vehicle, controlling a projection position of the projected image based on the degree of overlap to avoid overlapping of the virtual image with the preceding vehicle; In the case of nighttime, the image projection method allows the virtual image to overlap with the preceding vehicle, and moves the virtual image above the taillights of the preceding vehicle.

10. An image projection method using an image projection device that projects a projection image onto a display unit for displaying a virtual image, the image projection device including an image irradiation unit that irradiates the projection image, an optical unit that irradiates the projection image onto the display unit as image light, and a detection unit that detects overlap between the virtual image and a preceding vehicle, controlling a projection position of the projected image based on the degree of overlap to avoid overlapping of the virtual image with the preceding vehicle; An image projection method characterized by controlling the projection position of the projected image over a predetermined time period to avoid overlapping of the virtual image with the preceding vehicle when the preceding vehicle enters or exits from another lane.

11. An image projection method using an image projection device that projects a projection image onto a display unit for displaying a virtual image, the image projection device including an image irradiation unit that irradiates the projection image, an optical unit that irradiates the projection image onto the display unit as image light, and a detection unit that detects overlap between the virtual image and a preceding vehicle, controlling a projection position of the projected image based on the degree of overlap to avoid overlapping of the virtual image with the preceding vehicle; An image projection method, characterized in that the necessity of avoiding overlapping of the virtual image with the preceding vehicle is determined by taking into consideration a color relationship between the virtual image and the preceding vehicle.

Images