JP7795383B2 - Image projection device and image projection method - Google Patents

Description

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

Traditionally, dashboards that illuminate icons have been used to display various types of information inside vehicles. Furthermore, as the amount of information to be displayed increases, it has been proposed to embed image display devices in dashboards or to configure the entire dashboard from image display devices.

However, because the instrument panel is located below the vehicle's windshield, the driver has to move their eyes downward while driving in order to see the information displayed on the instrument panel, which is undesirable. Therefore, head-up displays (hereinafter referred to as HUDs) have been proposed, which project images onto the windshield so that the driver can read information when looking ahead of the vehicle (see, for example, Patent Documents 1 and 2).

Japanese Patent Application Laid-Open No. 2019-119248 Japanese Patent Application Laid-Open No. 2019-119262

In a vehicle equipped with a HUD, the driver views a virtual image displayed in front of the vehicle (hereinafter referred to as the "forward display image"). The vertical display position of the forward display image is usually set assuming 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 can cause the driver to feel uncomfortable. From a safety perspective, it is desirable to eliminate this discomfort as much as possible.

The present invention has been developed in consideration of the above-mentioned conventional problems, and aims to provide an image projection device and image projection method that suppresses the sense of discomfort felt when viewing a forward display image, even when a preceding vehicle is approaching.

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, at night, the control unit allows overlap between the virtual image and the preceding vehicle and moves the virtual image above the taillights of 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 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.

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 looks 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.

In one aspect of the present invention, the control unit is characterized in that, when overlapping of the virtual image with the preceding vehicle is to be avoided, the control unit moves the virtual image downward to control the projection position of the projected image.

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 obtains the degree of overlap based on the distance to the preceding vehicle.

In one aspect of the present invention, the detection unit is an imaging means that captures an image of the preceding vehicle, and the control unit obtains the degree of overlap using an image of the preceding vehicle.

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 preceding vehicle and the virtual image.

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

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

In order to solve the above problem, 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 in the case of nighttime, overlap between the virtual image and the preceding vehicle is allowed and the virtual image is moved above the taillights of 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 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.

The present invention provides an image projection device and an image projection method that reduce the sense of discomfort felt when viewing a forward display image, even when a preceding vehicle is approaching.

1 is a block diagram showing an example of a configuration of an image projection device according to a first embodiment. FIG. 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. 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. 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. 5A to 5C are schematic diagrams illustrating the operation of the image projection device according to the first embodiment. FIG. 13 is a block diagram showing an example of the configuration of an image projection device according to a fifth embodiment.

Embodiments of the present invention will be described in detail below with reference to the drawings. Identical or equivalent components, parts, and processes shown in each drawing will be given the same reference numerals, and duplicate explanations will be omitted where appropriate. In the following explanation, an example will be given in which the image projection device according to the present invention is applied to a HUD mounted on a vehicle, etc.

(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 illustrating 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.

As shown in FIG. 1, the 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 the 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.

The image projection unit 11 projects an image to form a virtual distant image or a near image in front of the vehicle. The image projection unit 11 is composed of, for example, a liquid crystal panel, an organic EL panel, or a DMD (Digital Micro Mirror Device). The image projection unit 11 is divided into a distant display area that displays an image to form a distant image, and a near display area that displays an image to form a near image. In Figure 1, the optical path of the distant image light projected from the distant 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 dotted line.

The 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, the position of the image displayed in the distant display area of the image projection unit 11 can be changed. By moving the image displayed in the distant display area, the projection position of the distant image light from the image projection unit 11 onto the windshield 16 is adjusted, and as a result, the vertical direction of the distant image is adjusted.

Referring to Figure 2, the movement of the display image in the far display area will be explained in more detail. Figure 2 is a schematic diagram showing the display area 40 in which an image is displayed by the image projection unit 11. The display area 40 is the entire area capable of displaying an image 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 in the distance as a virtual image 18 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 in the near distance as a virtual image 17 via the reflecting mirror 12, etc.

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 the directions D1 and D2 indicated by the arrows in Figure 2. This adjusts the position at which the far image light is projected onto the windshield 16, thereby adjusting the vertical position of the far image.

As shown in FIG. 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 distance display area, i.e., the vertical movement of the distance image. In this embodiment, the "distance display area 41," which allows the position of the displayed image to be changed, is an example of the "display position adjustment means" of the present invention.

In this embodiment, the image displayed in the far display area is configured to allow vertical movement of the far image, but if the discomfort of the near image is a problem, the near image may be configured to be moved vertically by moving the image displayed in the near display area. Alternatively, both the far image and the near image may be configured to be moved vertically.

The optical branching unit 14 is a component that branches the distant image light emitted from the distant display area, and is configured, for example, by a prism. As shown in FIG. 1, the distant 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 (distant image) is formed relatively far in front of the vehicle. The display position of the distant image is, for example, approximately 15 m in front of the vehicle. In FIG. 1, a "driving assistance display" is shown as an example of the content of the distant image.

On the other hand, as shown in Figure 1, near image light is emitted from the near display area, reflected by reflector 12, free-form mirror 13, and windshield 16, and reaches the 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 approximately 3 m in front of the vehicle. Figure 1 shows "vehicle speed display, etc." as an example of the content of the near image.

With the above configuration, the image projection device 10 projects a virtual image 18 at a distance several degrees below the horizontal, reducing the amount of eye movement the driver needs to make to view driving assistance information. Furthermore, a virtual image 17 is projected even further below, closer to the driver, allowing the driver to clearly view vehicle speed displays and the like by shifting their line of sight.

The distance measuring means 20 is a component 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 primarily 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 a "detection unit" according to the present invention.

The imaging means 21 is a component that captures images of the area ahead of the vehicle, and is composed of, for example, an on-board camera. The camera may be a monocular camera or a stereo camera. If it is a stereo camera, it may also function as a distance measurement means. In this embodiment, the imaging means 21 is primarily used to detect overlap between a distant image and a preceding vehicle. The imaging means 21 is connected to the control unit 30, and 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.

The control unit 30 controls the entire image projection device 10 and executes the display position adjustment program described below. The control unit 30 is configured to include a CPU, ROM, RAM, etc. (not shown). Note that the control unit 30 may also be the ECU (Engine Control Unit) of the vehicle in which the image projection device 10 is installed.

As mentioned above, when a preceding vehicle approaches the vehicle on the road, the distant image may overlap with the preceding vehicle, making it difficult for the driver to see the distant image, which can be uncomfortable. 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 using the distance measurement means 20, and when the inter-vehicle distance satisfies a predetermined condition, an adjustment depression angle is calculated to adjust the depression angle of the distant image, and the position of the image displayed in the distant display area of the image projection unit 11 is adjusted. As a result, the projection position of the distant image light from the image projection unit 11 onto the windshield 16 is adjusted, and the vertical position of the distant image is adjusted. Note that in this embodiment, the present invention is applied to a distant image, so in the following description, the "distant image" will be referred to as the "forward display image."

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 Figure 3. Figure 3 is a flowchart showing the processing flow of a display position adjustment program, illustrating the procedure for the display position adjustment process executed by the control unit 30 of the image projection device 10. This display position adjustment program is stored in storage means such as a ROM (not shown), and is read by the CPU, expanded into RAM, etc., and executed.

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

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

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 a host vehicle traveling on a road 50, and a preceding vehicle 54 ahead of the vehicle 51. The symbol hr indicates a horizon line extending from the driver's viewpoint 52. In this embodiment, when the forward display image overlaps with the preceding vehicle 54, the forward display image is assumed to move to a position below the bottom edge of the rear license plate 55. Let L be the inter-vehicle distance, H be the distance to the horizon hr measured from the road surface of the road 50, and h be the distance to the bottom edge of the rear license plate 55 measured from the road surface. The depression angle θ shown in FIG. 4 can generally be calculated using the following equation (1):
θ=arctan((HH)/L)... (Formula 1)

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 (Equation 2) shown below.
θmin=arctan((HH)/Lmax)... (Formula 2)

As described above, the image projection device 10 assumes that the position to which the forward display image should be moved when it overlaps with the preceding vehicle 54 is a position below the bottom edge of the rear license plate 55. In other words, it is assumed that at this position, the forward display image can be viewed 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 may be set based on another location of the preceding vehicle 54. The distance H from the road surface to the horizon hr can be set in advance if a standard value is used as the position of the viewpoint 52. However, this is not a limitation and may be set for each driver. Meanwhile, the distance h from the road surface to the license plate can also be set in advance if a standard value is used. However, this is not a limitation and may be set for each vehicle. In this embodiment, H and h are set in advance, and (H - h) is treated as a constant.

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 using the inter-vehicle distance L from the above (Equation 1). In this embodiment, in step S11, it is determined that depression angle adjustment is necessary if θ > θmin. Because depression angle θ and inter-vehicle distance L have a 1:1 correspondence, it may also be determined that depression angle adjustment is necessary if L < Lmax.

Referring again to Figure 3, 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 inter-vehicle distance L measured by the distance measurement means 20 into (Equation 1). However, this is not limited to this, and the calculated θ may be corrected in some way, for example by multiplying it by a coefficient that allows for safety.

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

In this embodiment, adjustment of the depression angle θ begins when θ > θmin, and the depression angle θ increases 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 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.

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

On the other hand, in step S15, the forward display image, i.e., the distant image, is turned off. This is 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.

In step S16, it is determined whether an end command 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 adjusted continuously and smoothly. On the other hand, if the determination is positive, the display position adjustment program is terminated. An end command can be issued, for example, by turning off the power to the image projection device 10.

The operation and effects of the image projection device 10 according to this embodiment will be described in more detail with reference to Figure 5. Figure 5(a) shows a state in which a preceding vehicle 54 is far away and the forward display image (virtual image 18, distant image) is positioned sufficiently below the preceding vehicle 54, i.e., the depression angle θ is θ≦θmin (the inter-vehicle distance L is L≧Lmax).

Next, as vehicle 51 approaches preceding vehicle 54 and the depression angle θ becomes θ > θ min (the inter-vehicle distance L becomes L < L max), the forward display image (virtual image 18) overlaps with preceding vehicle 54, as shown in Figure 5(b), making it difficult for the driver to see the forward display image (virtual image 18).

Figure 5(c) shows the state in which, as a result of the above-mentioned display position adjustment process, the forward display image (virtual image 18) has moved to below the leading vehicle 54, eliminating the difficulty in visibility.

While the above explanation did not take into account the color of the preceding vehicle 54, the color relationship between the preceding vehicle 54 and the forward display image may also be used as one of the criteria for determining overlap. That is, for example, if the forward display image is a light color and the preceding vehicle 54 is a dark color such as black, the driver will not have much difficulty in seeing it, and there is no need to move the forward display image. In such cases, it may be determined that moving the forward display image is not necessary. More specifically, step S11 of the flowchart shown in Figure 3 may include a comparison of the color of the preceding vehicle 54 acquired by the imaging means 21 or the like with the color of the forward display image.

As described above in detail, the image projection device and image projection method according to this embodiment make it possible to provide an image projection device and image projection method that suppresses the sense of discomfort felt when viewing the forward display image, even when a preceding vehicle is approaching.

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 which 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, a preceding vehicle is detected using the imaging means 21 shown in FIG. 1 , and overlap between the forward display image and the preceding vehicle is detected to 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, and therefore detailed description thereof 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.

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 the image shown in Figure 5 (hereinafter referred to as the "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 determines 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 Figure 2, and is capable of moving the distant display area 41, i.e., adjusting the forward display image in the vertical direction.

The basic steps of the image projection method according to this embodiment are the same as those shown in FIG. 3. That is, the display position adjustment process shown in FIG. 3 is also executed in the image projection device 10A. The display position adjustment process executed by the control unit 30 according to this embodiment will be described below with reference to FIG. 3.

Step S10 waits until a preceding vehicle is detected, and if the determination is affirmative, proceeds to step S11.

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, and it is determined that depression angle adjustment is necessary when the preceding vehicle 54 and virtual image 18 overlap, as shown in Figure 5(b) as an example. Note that the determination that depression angle adjustment is necessary does not necessarily have to be made when the preceding vehicle 54 and virtual image 18 overlap completely, but may also be made when a predetermined percentage of the virtual image 18 overlaps, for example 50% or more.

In step S12, the adjusted depression angle, i.e., the depression angle required to avoid overlap, is obtained. The adjusted depression angle is calculated, for example, by image recognition, to determine the depression angle when the virtual image 18 is positioned below the leading vehicle 54.

The processing from step S13 onwards is the same as that of the image projection device 10 according to the first embodiment described above, and therefore will not be described here. In this embodiment, steps S10 to S16 are repeated in a loop 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.

As described above, the image projection device and image projection method according to this embodiment can provide an image projection device and image projection method that suppresses the sense of discomfort felt when viewing the forward display image, even when a preceding vehicle is approaching.

(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 first and second embodiments described above, or the fifth embodiment described below.

As mentioned above, if the forward display image is a light color and the preceding vehicle 54 is a dark color such as black, the driver will not have much difficulty seeing it, so there is no need to move the forward display image. Thinking about this 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 that it is nighttime and the detection of taillights are made, for example, by the control unit 30 processing images captured by the imaging means 21. Of course, the determination that it is nighttime can also be made using a clock.

Specific processing in this embodiment includes, for example, a process for determining whether it is nighttime and a process for detecting taillights in step S11 of the display position adjustment process flow shown in Figure 3. Then, in step S12, the depression angle for moving upward to avoid taillights, etc. is calculated. In this embodiment, steps S10 to S16 are repeated in a loop unless an end command is issued 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.

As described above, the image projection device and image projection method according to this embodiment can provide an image projection device and image projection method that suppresses the sense of discomfort felt when viewing a forward display image, even when a preceding vehicle is approaching. Furthermore, the image projection device and image projection method according to this embodiment can move the forward display image upward as well as downward, allowing the display position of the forward display image to be set to be more easily visible to the driver.

(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 , and therefore is not shown in the figure. 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.

The display position adjustment process in each of the above embodiments did not take into account lane changes by 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 (distant image in this embodiment) will change suddenly as the vehicle itself or the preceding vehicle 54 changes lane. Such sudden movements of the forward display image may cause discomfort to the driver, so it is best to avoid them as much as possible. Therefore, in this embodiment, the display position of the forward display image is configured to not change suddenly when the vehicle itself changes lanes or the preceding vehicle suddenly enters or exits.

First, the case where a preceding vehicle 54 suddenly enters will be described according to the flow shown in Figure 3. The determination of the sudden entry of the preceding vehicle 54 is included in step S10, for example. More specifically, assume that the distance measurement 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 Figure 5(b) may suddenly appear. In this case, if the display position adjustment process is performed according to the flow shown in Figure 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.

In this embodiment, therefore, the movement of the display position of the forward display image (virtual image 18) from Figure 5(b) to Figure 5(c) is carried out over a predetermined time. More specifically, the depression angle adjustment in step S14 of the flow shown in Figure 3 is carried out 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 approximately a few seconds. This makes it possible to reduce the discomfort felt by the driver due to the movement of the preceding vehicle 54 and the forward display image.

Next, the case where the preceding vehicle 54 suddenly withdraws will be described according to the flow shown in Figure 3. The determination of the sudden withdrawal of the preceding vehicle 54 is included, for example, in step S10. More specifically, assume that the distance measurement means 20 suddenly detects a state in which it is no longer possible 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 Figure 5(c). In such a case, even if a normal display position adjustment process is performed, it can be said that the discomfort felt by the driver is less 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 Figure 3 is performed over a predetermined period of time. In this case, the adjusted depression angle is the depression angle for 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 typically on the order of a few seconds. This reduces the sense of discomfort felt by the driver due to the movement of the preceding vehicle 54 and the forward display image.

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

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.

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

Here, in the case of the image projection device 10B shown in Figure 6, adjusting the tilt angle of the 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 the light branching unit 14 or the free-form surface mirror 15. Alternatively, separate free-form surface mirrors 13 can be provided for the far image light and the near image light.

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

In the above embodiments, the image projection device and image projection method according to each form were described individually, but multiple embodiments may be combined. For example, the first and fifth embodiments may be combined to enable both movement of the forward display image by the image projection unit 11 and movement of the forward display image by the free-form surface mirror 13. In this case, a priority may be set between movement of the forward display image by the image projection unit 11 and movement of the forward display image by the free-form surface mirror 13. For example, priority may be given to movement of the forward display image by the image projection unit 11, and 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.

In addition, in the above embodiments, the display position adjustment program shown in FIG. 3 has been described as constantly detecting preceding vehicles, but this is not limiting and detection may be performed periodically or intermittently. When detecting preceding vehicles periodically, for example, a timer may be provided before step S10. When detecting preceding vehicles intermittently, the control unit 30 may execute the display position adjustment program shown in FIG. 3 when necessary.

10...Image projection device 11...Image irradiation unit 12...Reflector 13...Free-form surface mirror 14...Light branching unit 15...Free-form surface 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...Lane 51...Vehicle 52...Point of view 54...Preceding vehicle 55...Rear license plate D1, D2...Direction hr...Horizon H, h...Distance L...Inter-vehicle distance Lmin...Minimum inter-vehicle distance Lmax...Maximum inter-vehicle distance θ...Depression angle θmin...Minimum depression angle θmax...Maximum depression angle

Claims (11)

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 . 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. 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. 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. 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. 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. 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. 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. 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 . 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;
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. 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;
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.