HEAD-UP DISPLAY AND PROGRAM

Abstract

Head-up display, comprising: a display unit (10) which displays an image in a display area formed in a front windshield of a vehicle; a vehicle information acquirer (30, S200) that acquires vehicle information representing a driving state of the vehicle; a forward environment information acquirer (30, S300) that acquires forward environment information representing a forward environment of the vehicle as viewed in the traveling direction; a detector (30, S400) for a display-tracking object which, based on the vehicle information and the forward surroundings information, detects a display-tracking object on which guidance information is to be displayed in the display area of the front windshield; and a display controller (30, S500) which generates a guide image for superimposing the guide information on the front windshield and performs a superimposed display of the guide image on the front windshield with the display unit (10) so that at the time when the object to be displayed, which is detected by the object to be displayed detector (30, S400), is seen from inside a passenger compartment of the vehicle, the guide information and the object to be displayed are superimposed on each other, wherein an apparent size of the guide image is constant within the display area, the display area has a predetermined display setting area which is located within the display area, is smaller than the display area and is located near a center point of the display area, when a position of the object to be tracked is within the display area, the display control is set to a normal brightness for normal display, and when a position of the object to be tracked by display changes and moves out of the predetermined display setting area, the display controller (30, S500) decreases a display brightness of the guide image so that the guide image becomes darker as a distance of the object to be tracked by display from a center of the predetermined display setting area increases.

Description

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application is based on Japanese Patent Application No. 2013-138971, filed on July 2, 2015, the disclosure of which is incorporated by reference. TECHNICAL FIELD

[0002] The present invention relates to a head-up display and a program for displaying information on a front windshield of a vehicle. STATE OF THE ART

[0003] A driving assistance device for vehicles has been proposed (see, for example, JP 2006 - 23 277 A), in which a display unit with a horizontally elongated display screen is installed below the front windshield, and an object to be tracked in front of the vehicle (in particular in its direction) is displayed on the display screen.

[0004] The proposed device estimates, based on a positional relationship between the vehicle and the object to be tracked by display, a current direction to the object to be tracked by display relative to an eye point position of the driver and sets a display position of the object to be tracked by display to a position in the display screen intersecting with this direction.

[0005] When this technology is applied to a head-up display (hereinafter also referred to as HUD), a specific guide image (a graphic or the like) representing an object to be tracked by the display can be superimposed on a position of the object to be tracked by the display in the driver's field of vision.

[0006] Regarding a head-up display, the inventors of the present application have found the following.

[0007] In the technology proposed above, the display is enlarged as the object to be tracked approaches the vehicle. When the object to be tracked leaves the display area in a left or right direction, an icon is displayed on a left or right edge of the display screen.

[0008] Consequently, if the technology proposed above is applied to a head-up display to enable the superimposed display of the object to be tracked, this may create a confusing impression for the driver.

[0009] More specifically, when the guidance image superimposed on the object to be tracked is enlarged as the vehicle approaches the object to be tracked, the foresight in the vehicle direction decreases and causes problems.

[0010] Furthermore, if the position of the trackable object moves outside the front windshield display area within the driver's field of vision, the guide image will suddenly disappear, and an icon will be displayed on the left or right edge of the display screen. This creates a confusing display for the driver.

[0011] In particular, when an object to be tracked on the display (e.g., a traffic signal) moves from an upper part of the front windshield to a rear part, the display of the icon representing its direction on the left edge or right edge of the display screen causes a confusing impression for the driver.

[0012] US 2009 / 0 135 092 A1 is known from the prior art, in which an information display device in the vehicle contains a virtual image generator which projects a virtual image onto the windshield of a vehicle in a first projection mode and / or a second projection mode, wherein in the first projection mode the virtual image gradually becomes darker from bottom to top and in the second projection mode the virtual image gradually becomes lighter gray from bottom to top.

[0013] From US 2010 / 0 066 925 A1 a head-up display is known, comprising a display information generation module that generates information to be projected, a combination device that directs this information to a predetermined position, a light adjustment control module that changes a transmitted light quantity of the combination device based on the brightness of a background, and a front image recognition module that recognizes the brightness of the background in order to adjust the transmitted light quantity of the combination device using the light adjustment control module.

[0014] US 2013 / 0 249 684 A1 discloses a vehicle information transmission device that provides a virtual image for notification corresponding to the degree of accident risk with the object on a portion of a windshield corresponding to the position or direction of the object. Furthermore, a virtual image for attention allocation, different from the virtual image for notification, is provided on a portion of the windshield corresponding to the position or direction of the object.

[0015] From DE 10 2011 112 717 A1 a head-up display is known which has at least two types of display and selects depending on whether the respective display location is in a central field of vision or in a peripheral field of vision of the driver, whereby intensive colours and strong colour contrasts are preferred in the central field of vision and time-varying displays are preferred in the peripheral field of vision.

[0016] From DE 601 20 329 T2 a display device is known, wherein a display is arranged at a position of the vehicle which is close to a dashboard surface of the vehicle, and the brightness of a screen of the display is gradually reduced in a predetermined direction which is further away from the direction of the line of sight of a vehicle occupant when the vehicle occupant looks forward. SUMMARY OF THE INVENTION

[0017] It is an object of the present invention to enable a head-up display that displays a specific guidance image by superimposing it on an object to be tracked in a field of view from a passenger compartment of a vehicle to change the guidance image display without creating a confusing impression for a driver when the object to be tracked moves out of the display area.

[0018] In one example of the present invention, a head-up display includes: a display unit that displays an image in a display area configured in a front windshield of a vehicle; a vehicle information acquirer; a forward surroundings information acquirer; a detector for an object to be tracked by display; and a display controller.

[0019] The vehicle information acquirer acquires vehicle information representing a driving state of the vehicle. The forward environment information acquirer acquires forward environment information representing the environment in the direction of travel ahead of the vehicle. The trackable object detector detects, based on the vehicle information and the forward environment information, a trackable object for which guidance information is to be displayed in the display area of the front windshield.

[0020] The display controller generates a guide image for superimposing the guide information on the front windshield and performs superimposing of the guide image on the front windshield with the display unit so that when the trackable object detected by the trackable object detector is viewed from inside a passenger compartment of the vehicle, the vehicle information and the trackable object are superimposed on each other.

[0021] When a position of the object to be tracked by the display changes and moves out of a certain display setting range, the display controller darkens the guide image or changes the guide image from a normal image to a simplified image which is smaller than the normal image.

[0022] In the head-up display according to the invention, when the position of the object to be tracked, which is a position as seen from inside the vehicle passenger compartment, moves outside a specific display setting range, the guide image superimposed on the object to be tracked does not disappear abruptly. It is possible to prevent this display change from creating a confusing impression for the driver.

[0023] Furthermore, although the guide image is darkened or changed into a smaller simplified image from the normal image when the position of the object to be displayed changes and moves out of the specific display setting range, the display position still corresponds to the position of the object to be displayed, and thus it is possible to prevent this display change of the object to be displayed from creating a confusing impression for a driver.

[0024] Thus, the head-up display according to the invention is particularly advantageous with regard to its applicability to an occupant, for example a driver or the like.

[0025] The vehicle information acquirer, the forward environment information acquirer, the detector for the object to be tracked on the display, and the display control in the head-up display can be implemented by a program executed by a computer.

[0026] In this configuration, the computer can function as the above inventive units if, for example, the program is stored in a computer-readable storage medium such as a DVD-ROM, CD-ROM, and hard disk and is loaded into the computer when necessary, or if the computer receives the program via a communication line. SHORT DESCRIPTION OF THE DRAWING Fig. 1 is a block diagram showing the configuration of a head-up display of an embodiment; Fig. 2 is a flowchart showing a display control process performed by a control unit; Fig. 3 is a flowchart showing a vehicle information acquisition process in Fig. 2 represents, Fig. 4 is a flowchart showing a forward environment information acquisition process in Fig. 2 represents; Fig. 5 is a display parameter setting process in Fig. 2; Fig. 6 is an illustration of a data field for setting a brightness correction value according to a distance; Fig. 7 is a diagram showing a brightness change of a guide image when an object to be tracked on display is large; Fig. 8 is an illustration of a data field for setting a brightness correction value corresponding to a display position; Fig. 9 is a diagram showing a brightness change of a guide image according to the display position; Fig. 10 is a flowchart of a first modification of a display parameter setting process; Fig. 11 is a diagram of a guide image change according to a display parameter setting process of Fig. 10; Fig. 12 is a flowchart of a second modification of a display parameter setting process; Fig. Fig. 13 is an illustration of the manner of switching a guide image according to the display parameter setting process of Fig. 12; and Fig. 14 is a diagram of a guidance image change according to a display parameter setting process of Fig. 12. EMBODIMENTS FOR CARRYING OUT THE INVENTION

[0027] Embodiments are described using the drawing.

[0028] According to Fig. 1, a head-up display (HUD) 2 of the present embodiment includes a display unit 10 and a control unit 30. The display unit 10 emits a display light for displaying an image on a front windshield of a vehicle, so that a virtual image is visually displayed such that the virtual image is superimposed on the actual field of view in front of the vehicle. The control unit 30 controls the display unit 10.

[0029] The control unit 30 includes a microcomputer having a CPU, a ROM, a RAM, etc., and generates various guide images and displays the guide images (virtual images) through the front windshield via the display unit 10.

[0030] The control unit 30 is in communication with a multi-display 12, a GPS receiver 14, a map database 16, a vehicle speed sensor 18, a radar device 20, a road / vehicle communication 22, a display setting switch (SW) 24, a camera 26, etc., to obtain a number of items of information necessary for generating the guidance images.

[0031] The control unit 30 is further connected to on-vehicle devices, such as an ACC ECU 4 and a navigation device 6, via a communication line 8 constituting an on-vehicle LAN. By communicating with these on-vehicle devices, the control unit 30 can obtain information from other on-vehicle devices.

[0032] The multi-display 12 includes, for example, a color display with a display screen, such as a liquid crystal display, and a pointer-type display. The multi-display 12 is located in the instrument panel in front of the driver's seat and displays various vehicle states. The control unit 30 displays an operating state of the HUD 2 on the multi-display 12 and determines the vehicle state from the multi-display 12 on an as-needed basis.

[0033] The GPS receiver 14 receives electromagnetic waves from GPS satellites and detects vehicle position, vehicle speed, acceleration, etc. The control unit 30 obtains this information from the GPS receiver 14.

[0034] The GPS receiver 14 can receive electromagnetic waves from GPS satellites operated by the United States of America and can detect vehicle position, vehicle speed, acceleration, etc. In addition to receiving electromagnetic waves from GPS satellites, the GPS receiver 14 can receive electromagnetic waves transmitted from other satellites of satellite positioning systems (GLONASS, Galileo, Quasizenith satellites) and can detect vehicle position, vehicle speed, acceleration, etc. Alternatively, a device for receiving electromagnetic waves from satellites for satellite positioning systems other than GPS and detecting vehicle position, vehicle speed, acceleration, etc. may be used instead of the GPS receiver 14.

[0035] The map database 16 stores map data (node data, link data, cost data, road data, topographic data, marker data, intersection data, stop point data, facility data, etc.) and is used to keep the stored map data available for the control unit 30.

[0036] The vehicle speed sensor 18 is provided on an idler wheel or a drive shaft and generates a pulse signal corresponding to the respective rotation and is used to detect the traveling speed of the vehicle (vehicle speed) based on time intervals of the pulse signals.

[0037] The radar device 20 transmits a radar wave toward the front of the vehicle and is used to detect a distance to a vehicle in front (leading vehicle) and a relative speed.

[0038] The road / vehicle communication 22 performs wireless communication with roadside devices located near the vehicle's travel route and is used to obtain road traffic information (congestion information, traffic regulation information, etc.) from the roadside devices.

[0039] The display setting switch 24 is used to set a display mode of the HUD 2, for example, a guidance image type, which is displayed on the vehicle windshield via the display unit 10, and includes a switch operable by a user.

[0040] The camera 26 captures an image in the vehicle's travel direction (ahead surroundings image). The captured image is used by the control unit 30 to detect an object to be tracked on the display, which is an object for which the guidance image is to be displayed.

[0041] The ACC-ECU 4 is an electronic control unit for implementing ACC (auto-cruise control). The navigation device 6 displays a road map on a display in front of the driver's seat and provides route guidance.

[0042] Conventional elements can be used for the above elements. A display control process performed by the control unit 30 will be described below.

[0043] The microcomputer of the control unit 30 executes a program stored in a storage medium such as ROM to implement the display control process.

[0044] If according to Fig. 2, the display control process is started, the control unit 30 first performs S100 (S means step) to acquire information regarding the startup of the vehicle-side devices connected via the communication line 8 and to acquire the operation mode of the HUD 2 set via the display setting switch 24.

[0045] For example, in step S100, the control unit 30 acquires ON / OFF of the route guidance of the navigation device 6, ON / OFF of the ACC-ECU 4, ON / OFF of the warning about speed limits, traffic signs, etc. As a result, the control unit 30 can identify a type of trackable object for which the guidance image is to be displayed in superimposed form through the windshield.

[0046] Subsequently, in step S200, the control unit 30 performs a vehicle information acquisition process to acquire a driving state of the vehicle and environmental conditions. In step S300, the control unit 30 performs a forward environmental information acquisition process to acquire forward environmental information, such as the road condition ahead of the vehicle and concerning a preceding vehicle.

[0047] In step S400, based on the information from S100 to S300, the control unit 30 determines whether or not the trackable display object for which the guidance image would be displayed in superimposed form through the windshield is present. The trackable display object may be a road traffic signal, a traffic sign, an advertisement, a preceding vehicle, a pedestrian, or the like.

[0048] When the control unit 30 determines at S400 that there is an object to be tracked by display, the control unit 30 goes to S500 and sets a display parameter corresponding to the object to be tracked by display, for example, type of guide image, display position, and display method.

[0049] At S600, based on the display parameter set in the display parameter setting process of S500, the control unit 30 performs a display process and then proceeds to S100. In the display process, the guide image 4 for display is generated and output to the display unit 10 so that, as viewed from the driver's eye point, the guide image (specifically, a graphic corresponding to the object to be tracked for display) is displayed at a position that is in accordance with the position of the object to be tracked for display in the windshield.

[0050] If it is determined at S400 that there is no object to be tracked by display, the control unit 30 proceeds to S700 and determines whether or not the guide image is currently displayed. If the guide image is currently displayed, the control unit 30 proceeds to S800 to perform a non-display process so that the guide image is not displayed, and then proceeds to S100. If the guide image is not currently displayed, the control unit 30 proceeds to S100.

[0051] In the non-display process in S800, the brightness of the guide image is gradually decreased with a given attenuation time constant, and the display is gradually extinguished, so that the guide image does not disappear abruptly (in other words, a sudden change in brightness is avoided).

[0052] For example, the vehicle information acquisition process in S200 is based on the Fig. 3 is carried out in the manner shown.

[0053] Specifically, in the vehicle information acquisition process, the control unit 30 acquires a vehicle speed using the vehicle speed sensor 18, the GPS receiver 14, or the like at S210. The vehicle speed can be acquired by integrating the acceleration detected by an acceleration sensor (not shown). The vehicle speed can be acquired from the GPS receiver 14. Alternatively, the vehicle speed can be acquired via the communication line 8 from another on-vehicle device having a vehicle speed detection function.

[0054] Subsequently, at S220, the control unit 30 obtains the acceleration of the vehicle (vehicle acceleration) from an acceleration sensor (not shown), the GPS receiver 14, or other vehicle-side device connected via the communication line 8.

[0055] At S230, the control unit 30 obtains a coordinate point of the vehicle (vehicle position) from the GPS receiver 14, an inertial navigation device (not shown), matching these recognition results with the map database 16, a navigation device 6 in connection with the communication line 8, or the like.

[0056] Subsequently, at S240, the control unit 30 obtains information about a vehicle orientation (angular velocities around X, Y, X axes, angular accelerations, directions of respective axes) from a gyro sensor (not shown), a geomagnetism sensor (not shown), or other vehicle-side device connected via the communication line 8.

[0057] At S250, the control unit 30 obtains a steering angle of the vehicle from a steering angle sensor (not shown) mounted on a steering column or a steering gear, or from another vehicle-side device connected via the communication line 8.

[0058] Subsequently, at S260, the control unit 30 obtains a brake pressure (in other words, a braking force) from a pressure sensor (not shown) on an oil pressure system associated with the brake or from another vehicle-side device (ABS-ECU, etc.) connected via the communication line 8.

[0059] At S270, the control unit 30 acquires an opening degree of a throttle valve (throttle opening degree) from a throttle position sensor (not shown) on the engine of the vehicle or from another vehicle-side device (engine ECU, etc.) connected via the communication line 8.

[0060] At S280, the control unit 30 acquires the brightness outside the vehicle (exterior light) from a brightness sensor (not shown) or from another vehicle-side device (e.g., an air conditioning ECU, etc.) connected via the communication line 8.

[0061] As described above, the vehicle information acquisition process acquires the vehicle information such as vehicle speed, vehicle acceleration, vehicle position, vehicle orientation, steering angle, brake pressure, throttle opening degree, external illumination, etc. In the vehicle information acquisition process, the order of S210 to S280 may be changed or some of S210 to S280 may be omitted.

[0062] For example, the advance environment information acquisition process at S300 is as shown in Fig. 3 shown.

[0063] More specifically, in the forward environment information acquisition process, the control unit 30 first acquires a vehicle-to-vehicle distance between the vehicle and the preceding vehicle from the radar device 20 at S310. Subsequently, at S320, the control unit 30 acquires the speed of the preceding vehicle from the radar device 20. At S330, the control unit 30 acquires attitude information of the preceding vehicle relative to the vehicle (azimuth, altitude, and depression) from the radar device 20.

[0064] These types of information can be obtained via the communication line 8 from other on-vehicle devices that have the same function as the radar device.

[0065] Subsequently, at S340, the control unit 30 obtains position information (azimuth, elevation / depression angle, distance) of a traffic sign ahead of the vehicle based on image processing of the image captured by the camera 26, the vehicle position information at S230, the map data in the map database 16, etc.

[0066] Subsequently, at S350, the control unit 30 acquires position information (azimuth, elevation / depression angle, distance) of a road traffic signal ahead of the vehicle based on image processing of the image captured by the camera 26, the vehicle position information at S230, the map data in the map database 16, etc.

[0067] At S340 and S350, the control unit 30 may use the navigation device 6 connected via the communication line 8 to obtain the position information of a traffic sign and a road traffic signal.

[0068] In the above manner, the ahead environment information acquisition process acquires the vehicle-to-vehicle distance to the preceding vehicle, the speed of the preceding vehicle, the position information of the preceding vehicle, the position information of the traffic sign, and the position information of the road traffic signal.

[0069] In the advance environment information acquisition process, the order of S310 to S350 may be changed. Some of S310 to S350 may be omitted.

[0070] The display parameter setting process at S500 is based on the Fig. 5 shown manner.

[0071] In the display parameter setting process, the control unit 30 first determines whether or not the size of the object to be tracked in the display is larger than a certain threshold TH_VAL[m].

[0072] When the object to be tracked on display is larger than the threshold value TH_VAL[m], the control unit 30 goes to S512 and sets a brightness correction value for correcting the brightness of the guide image superimposed on the object to be tracked on display.

[0073] The brightness correction is performed by multiplying a reference brightness by the brightness correction value. The brightness correction value is calculated using a data array with the properties according to Fig. 6 set.

[0074] When the object to be tracked on display is larger than the threshold TH_VAL[m], the brightness of the guidance image is set according to the distance between the vehicle and the object to be tracked on display, so that the larger the distance, the smaller the brightness, and vice versa.

[0075] If according to Fig. 7 If the object to be tracked by the display is larger than the threshold value TH_VAL[m], the brightness of the guidance image superimposed on the object to be tracked by the display decreases with increasing distance between the host vehicle and the object to be tracked by the display and with increasing apparent size of the object to be tracked by the display as viewed through the windshield. In other words, the guidance image is darker when the distance between the host vehicle and the object to be tracked by the display is smaller and when the apparent size of the object to be tracked by the display as viewed through the windshield is larger.

[0076] In Fig. 7, the HUD display area refers to a display area within which the display unit displays the guide image (the figures in Fig. 7) on the windshield. The sensor detectable area refers to an area within which the forward environment information acquisition process can detect the preceding vehicle, traffic sign, road traffic signal, etc.

[0077] If it is determined at S511 that the object to be displayed is less than or equal to the threshold value TH_VAL[m], the control unit 30 goes to S513 and determines whether or not, as seen from the driver's eye point, the object to be displayed (more precisely, the guide image superimposed on the object to be displayed) is within the range A of Fig. 8 is.

[0078] Area A refers to a display setting area designed to be smaller than the HUD display area.

[0079] When the object to be tracked on display is within the area A, the control unit 30 goes to S514, in which the brightness correction value for a normal display is set as the brightness correction value for the guide image superimposed on the object to be tracked on display.

[0080] If the object to be tracked on display is outside the area A, the control unit 30 goes to S514, in which the brightness correction value is set according to the amount of deviation of the guide image from the area A.

[0081] As in Fig. 8, a data field for setting the brightness correction value is defined such that the brightness correction value decreases as the amount of deviation from the amount A increases, and the brightness correction value has the value “0” at the edge of the HUD display area.

[0082] As a result, according to Fig. 9, when the size of the object to be tracked by display (traffic sign in the drawing) is not larger than the threshold value TH_VAL[m], the brightness of the guidance image superimposed on the object to be tracked by display is set to a normal brightness for a normal display when the position of the object to be tracked by display, as seen from the driver, is within the area A, and the brightness of the guidance image is corrected to a smaller value when the object to be tracked by display moves out of the area A.

[0083] Consequently, the guidance image becomes darker as the position of the object to be tracked moves toward the outside of area A as seen from the driver. At the end of the HUD display area, the brightness reaches "0" and the guidance image disappears.

[0084] After setting the brightness correction value at S512, S514 and S515, the control unit 30 goes to S516 and sets the display position, size and display brightness of the guide image superimposed on the object to be tracked, and ends the display parameter setting process.

[0085] At S516, based on the direction and distance to the object to be tracked on display and the vehicle's orientation direction, speed, acceleration, etc., the control unit 30 sets the display position and size of the object to be tracked on display so that the displayed guidance image is adapted to the movement of the surrounding environment. The display brightness of the guidance image is calculated by setting the reference brightness based on the ambient brightness obtained at S280 and multiplying the reference brightness by the brightness correction value from S512, S514, and S515.

[0086] In the above embodiment, the guidance image is displayed superimposed on the trackable object. In this manner, when the trackable object is larger than the threshold value, the display brightness of the guidance image decreases as the distance between the host vehicle and the trackable object decreases (in other words, as the display range of the guidance image increases), and the guidance image becomes darker.

[0087] When the object to be tracked by display is less than or equal to the threshold value and is outside the area A of the display area, the display brightness of the guide image decreases according to this deviation amount, and the guide image darkens.

[0088] Therefore, when the object to be tracked by display is outside the display range of the front windshield HUD 2, the HUD 2 of the present embodiment can prevent the guide image from disappearing abruptly and prevent this display change from creating a confusing impression for the driver.

[0089] When the object to be tracked is smaller than or equal to the threshold and the position of the object to be tracked moves outside of the area A, the guidance image gradually darkens. This prevents the brightness change of the guidance image from creating a confusing impression for the driver.

[0090] Although one embodiment of the present invention has been illustrated, embodiments of the present invention are not limited to the above embodiment and may have various forms.

[0091] In the above embodiment, the brightness of the guide image superimposed on the trackable object is changed according to the size or position of the trackable object as seen from the driver, so that confusing impressions for the driver due to the display of the guide image are reduced.

[0092] In another configuration, the shape of the guidance image, which is displayed over the object to be tracked, can be changed. This can also reduce driver confusion caused by the guidance image display.

[0093] A display parameter setting process for this configuration is described as the first modification and the second modification. <Erste Abwandlung>

[0094] As in Fig. 10, in the display parameter setting process according to the first modification, the control unit 30 first determines at S521 whether or not, from the driver's perspective, the position of the object to be tracked by the display is within the HUD display range.

[0095] When it is determined at S521 that the position of the object to be tracked by display is within the HUD display area, the control unit 30 goes to S520 and determines whether or not the position of the object to be tracked by display is within an area B from the driver's perspective.

[0096] As in Fig. 11, the area B is a preset display setting area which is within the HUD display area and smaller than the HUD display area.

[0097] If it is determined at S522 that the position of the object to be displayed is within the area B, the control unit 30 sets a normal display for the object to be displayed (traffic sign in the drawing) to be superimposed on a preset normal guide image (rectangular in the drawing) as shown in Fig. 11 shown.

[0098] If it is determined at S522 that the position of the object to be tracked by display is not within the area B, the control unit 30 goes to S524 and performs display setting to display the normal guide image and an icon serving as a simplified image and indicating a direction to the object to be tracked by display, as shown in Fig. 11 shown.

[0099] When it is determined at S521 that the position of the object to be tracked is outside the HUD display area, the control unit 30 performs display setting to display only the icon at the edge position where the object to be tracked moves out of the HUD display area so that the direction of the object to be tracked is perceptible.

[0100] When the normal display is set or the display setting for displaying normal guide image and icon is performed or the display setting for displaying only the icon is performed at S523, S524 or S252, the control unit 30 sets the display position, size and display brightness of the guide image according to the set display content and ends the display parameter setting process.

[0101] In the first modification, when the object to be tracked is within area B from the driver's seat view, the normal guidance image is displayed superimposed on the object to be tracked. When the object to be tracked is outside area B but within the HUD display area, the icon is displayed superimposed on the object to be tracked in addition to the normal guidance image. When the object to be tracked is outside the HUD display area, only the icon is displayed at the edge of the HUD display area.

[0102] Therefore, in the first modification, the guidance image does not suddenly disappear, even if the object to be tracked moves out of the HUD 2 display area on the windshield from the driver's perspective. This prevents confusing impressions for the driver due to these display changes.

[0103] Furthermore, since the icon indicating the direction of the object to be tracked is displayed at the edge of the HUD display area when the object to be tracked moves to the outside of the HUD display area, the driver can recognize the direction of the object to be tracked. <Zweite Abwandlung>

[0104] As in Fig. 11, in the display parameter setting process according to the second modification, the control unit 30 first determines at S531 whether or not a distance from the driver's eye point to the object to be tracked by the display (a preceding vehicle in the drawing) is smaller than a selected distance (see Fig. 13). The selected distance is a distance that allows the guidance image to be displayed superimposed on the object to be tracked by means of the display unit 10 (see Fig. 13).

[0105] Taking into account the display image distance (see Fig. 13) and the accommodative power of the human eye, this setting distance is set in advance to such a distance that the HUD image does not appear to be “stuck” in an object to be tracked, for example a vehicle driving ahead.

[0106] When the distance to the object to be tracked by display is greater than or equal to the selected distance, the control unit 30 goes to S532 and sets the display position, size, and display brightness of the guide image to perform the normal display of the guide image, and then ends the display parameter setting process.

[0107] If the distance to the object to be tracked by display is smaller than the selected distance, the control unit 30 proceeds to S533 and stops the normal display of the guide image and displays the icon, which is the simplified image of the guide image, in a non-overlapping display area, and then terminates the display parameter setting process. The non-overlapping display area is different from the display area for overlaying the guide image.

[0108] More specifically, when the guidance image is displayed superimposed on the display object in a situation where the distance to the object to be tracked by the display is smaller than the selected distance, the guidance image is “stuck” in the object to be tracked by the display, which leaves a strange impression for the driver.

[0109] In view of this, the second modification is designed so that if the distance from the driver’s eye point to the object to be tracked is smaller than the selected distance, as in Fig. 13, then it is determined that the position of the object to be tracked by the display moves out of the display setting area, and the guide image is switched from the normal display according to Fig. 14 changed to the icon image display in the non-overlaid display area.

[0110] Therefore, in the second modification, even if the vehicle approaches the preceding vehicle serving as an ACC target and the distance to the preceding vehicle becomes smaller than the selected distance, the guidance image is displayed so as not to be “stuck” in the preceding vehicle, and the driver is prevented from having an irritating impression.

[0111] In Fig.14, the non-overlaid display area is located below the HUD display area. An icon indicating the ACC control in operation is displayed in the non-overlaid display area.

[0112] Since it is sufficient for this icon to inform the driver that the ACC control is in operation, the non-overlaid display area may also be arranged in the multi-display 12, and the multi-display 12 may display the image signal indicating that the ACC control is in operation.

[0113] In the above embodiments and modifications, the control unit 30 performing S200 functions as an embodiment of a vehicle information acquirer. The control unit 30 performing S300 functions as an embodiment of a forward environment information acquirer. The control unit 30 performing S400 functions as an embodiment of a display-tracking object detector. The control unit 30 performing S500 functions as an embodiment of a display controller.

[0114] According to a first aspect, there is provided a head-up display comprising: a display unit (10) that displays an image in a display area formed in a front windshield of a vehicle; a vehicle information acquirer (30, S200) that acquires vehicle information representing a traveling state of the vehicle; a forward surroundings information acquirer (30, S300) that acquires forward surroundings information representing a traveling environment ahead of the vehicle; a trackable object detector (30, S400) that detects, based on the vehicle information and the forward surroundings information, a trackable object on which guidance information is to be displayed in the display area of the front windshield;and a display controller (30, S500) that generates a guide image for superimposing the guide information on the front windshield and performs superimposing of the guide image on the front windshield with the display unit (10) so that when the trackable object detected by the trackable object detector (30, S400) is viewed from inside a passenger compartment of the vehicle, the guide information and the trackable object are superimposed on each other, wherein when a position of the trackable object changes and moves out of a predetermined display setting range, the display controller (30, S500) darkens the guide image or changes the guide image from a normal image to a simplified image that is smaller than the normal image.

[0115] According to a second aspect developing the first aspect, when the position of the object to be tracked by display, which is a position as seen from inside the passenger compartment of the vehicle, moves out of the display setting area which is smaller than the display area and remains within the display area of the front windshield, the display controller (30, S500) darkens the guide image.

[0116] According to a third aspect developing the second aspect, the head-up display is configured such that when the position of the object to be tracked by the display, which is the position as seen from inside the passenger compartment of the vehicle, starts to move from an inside of the display area, the display controller (30, S500) changes the brightness of the guide image such that the guide image disappears at the time the position of the object to be tracked by the display reaches an edge of the display area.

[0117] According to a fourth aspect which develops the first aspect, the head-up display is configured such that when the position of the object to be tracked by the display, which is a position viewed from inside the passenger compartment of the vehicle, moves out of the display setting area which is smaller than the display area while remaining within the display area, the display controller (30, S500) switches the guidance information from the normal image to the simplified image.

[0118] According to a fifth aspect which develops the first aspect, the head-up display is configured such that when the object to be tracked by display approaches the vehicle and a distance between the object to be tracked by display and the vehicle becomes smaller than a selected distance, the display controller determines that the position of the object to be tracked by display moves beyond the display setting range and changes the guide image to the simplified image if the selected distance is a distance which allows the display unit (10) to superimpose the guide image.

[0119] According to a sixth aspect, there is provided a program for causing a computer to operate as the vehicle information acquirer (30, S200), the forward surroundings information acquirer (30, S300), the trackable object detector (30, S400), and the display controller (30, S500) of the head-up display according to any one of claims 1 to 5.

[0120] According to a seventh aspect, storage media are provided for storing the program according to the sixth aspect.

Claims

[1] Head-up display, comprising: a display unit (10) which displays an image in a display area formed in a front windshield of a vehicle; a vehicle information acquirer (30, S200) that acquires vehicle information representing a driving state of the vehicle; a forward environment information acquirer (30, S300) that acquires forward environment information representing a forward environment of the vehicle as viewed in the traveling direction; a detector (30, S400) for a display-tracking object which, based on the vehicle information and the forward surroundings information, detects a display-tracking object on which guidance information is to be displayed in the display area of the front windshield; and a display controller (30, S500) which generates a guide image for superimposing the guide information on the front windshield and performs a superimposed display of the guide image on the front windshield with the display unit (10) so that at the time when the object to be displayed, which is detected by the object to be displayed detector (30, S400), is seen from inside a passenger compartment of the vehicle, the guide information and the object to be displayed are superimposed on each other, wherein an apparent size of the guide image is constant within the display area, the display area has a predetermined display setting area which is located within the display area, is smaller than the display area and is located near a center point of the display area, when a position of the object to be tracked is within the display area, the display control is set to a normal brightness for normal display, and when a position of the object to be tracked by display changes and moves out of the predetermined display setting area, the display controller (30, S500) decreases a display brightness of the guide image so that the guide image becomes darker as a distance of the object to be tracked by display from a center of the predetermined display setting area increases. [2] A head-up display according to claim 1, wherein, in response to the position of the object to be tracked by display, which is the position as viewed from inside the passenger compartment of the vehicle, moving from an inside of the display area, the display controller (30, S500) changes the brightness of the guide image such that the guide image disappears at the time the position of the object to be tracked by display reaches an edge of the display area. [3] A head-up display according to claim 1, wherein, in response to the position of the object to be tracked by display, which is a position as viewed from inside the passenger compartment of the vehicle, moving out of the display setting area which is smaller than the display area while remaining within the display area, the display controller (30, S500) switches the guidance information from the normal image to a simplified image which is smaller than the normal image. [4] A head-up display according to claim 1, wherein, in response to the object to be tracked by display approaching the vehicle and a distance between the object to be tracked by display and the vehicle becoming smaller than a selected distance, the display controller determines that the position of the object to be tracked by display moves beyond the display setting range and changes the guide image into a simplified image smaller than the normal image when the selected distance is a distance that allows the display unit (10) to superimpose the guide image. [5] Head-up display, comprising: a display unit (10) which displays an image in a display area formed in a front windshield of a vehicle; and a display controller (30, S500) configured to control the display unit (10), wherein the display control (30, S500) has: a vehicle information acquirer (30, S200) that acquires vehicle information representing a driving state of the vehicle; a forward environment information acquirer (30, S300) that acquires forward environment information representing a forward environment of the vehicle as viewed in the traveling direction; a detector (30, S400) for a display-tracking object which, based on the vehicle information and the forward surroundings information, detects a display-tracking object on which guidance information is to be displayed in the display area of the front windshield; and a guide image generating device that generates a guide image for superimposing the guide information on the front windshield and performs a superimposed display of the guide image on the front windshield with the display unit (10) so that the object to be tracked, which is detected by the object to be tracked detector (30, S400), is seen from inside a passenger compartment of the vehicle, and a display brightness setting unit that sets a display brightness of the generated guide image, wherein the display unit (10) performs an overlay display of the guide image, of which the display brightness of the guide image has been set by the display brightness setting unit, on the front windshield by emitting a display light, the display area has a predetermined display setting area which is smaller than the display area and which is located near a center of the display area, when a position of the object to be tracked is within the display range, the display brightness setting unit sets the display brightness of the guide image for normal display, and the position of the object to be tracked by display goes beyond the predetermined display setting range, the display brightness setting unit sets a display brightness of the guide image smaller as a distance of the object to be tracked by display from a center point of the predetermined display setting range increases. [6] A program for causing a computer to operate as the vehicle information acquirer (30, S200), the forward environment information acquirer (30, S300), the trackable object detector (30, S400) and the display controller (30, S500) of the head-up display according to any one of claims 1 to 5. [7] A storage medium for storing a program for causing the computer to function as the vehicle information acquirer (30, S200), the forward environment information acquirer (30, S300), the detector (30, S400) for an object to be tracked by display, and the display controller (30, S500) of the head-up display according to any one of claims 1 to 5. [8] A head-up display according to any one of claims 1 to 5, wherein the predetermined display setting area is included in the display area.

Images