JP2019002959A - Head-up display device - Google Patents

Abstract

To provide a head-up display device capable of more properly setting display luminance of an image.SOLUTION: A HUD (Head-Up Display) device 1 is connected to each of an upper illuminance sensor 4 which detects illuminance on an upper side of a vehicle (hereinafter referred to as upper illuminance) and a front illuminance sensor 5 which detects illuminance on a front side of the vehicle (hereinafter referred to as front illuminance). When an absolute value of a difference between the upper illuminance and the front illuminance is a prescribed threshold or more, the HUD device 1 displays a HUD image 10 in a luminance according to blending illuminance made by blending the upper illuminance and the front illuminance using a prescribed blend coefficient. The blend coefficient β is sequentially adjusted so that components derived from the front illuminance in the blending illuminance may be larger toward a dark area to be an area in which illuminance around the vehicle is relatively low such as a tunnel.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a head-up display device.

  Conventionally, by projecting light representing an image (hereinafter referred to as image light) onto a projection member such as a windshield of the vehicle, a position in front of the vehicle as viewed from an occupant seated in the driver's seat (hereinafter referred to as a driver) There is a head-up display (hereinafter, HUD: Head-Up Display) device that displays an image as a virtual image.

  Further, Patent Document 1 uses an illuminance sensor to detect the front brightness (hereinafter referred to as front illuminance) and the upper brightness (hereinafter referred to as upper illuminance) of the vehicle, respectively. A configuration for determining the display brightness of an image based on the higher illuminance is disclosed.

JP 2007-94130 A

  Depending on the environment surrounding the vehicle, there may be a difference between the upper illuminance and the front illuminance. For example, in a scene immediately before entering a tunnel during a fine daytime, the upper illuminance takes a relatively high value, while the front illuminance indicating the illuminance inside the tunnel takes a relatively low value.

  In such a situation where the front illuminance is relatively low with respect to the upper illuminance, the display luminance is controlled in accordance with the relatively higher illuminance (that is, the upper illuminance) as in Patent Document 1. The display by the HUD device may be too bright, causing the driver to feel dazzled.

  The present invention has been made based on this situation, and an object of the present invention is to provide a head-up display device capable of more appropriately setting the display luminance of an image.

  The present invention for achieving the object is a head-up display device that is used in a vehicle and displays a virtual image at a predetermined position in front of a driver seat by projecting light representing the image onto a projection member, An upper illuminance acquisition unit (F2) that acquires the detection result of the upper illuminance sensor, which is an illuminance sensor arranged to detect the illuminance above the vehicle, as the upper illuminance, and so as to detect the illuminance in a predetermined area in front of the vehicle A front illuminance acquisition unit (F3) that acquires a detection result of a front illuminance sensor, which is an illuminance sensor, as a front illuminance, and a target luminance setting unit (F4) that determines a target luminance that is a target value of image display luminance And a luminance adjustment unit (F5) that displays an image with the target luminance determined by the target luminance setting unit, and the target luminance setting unit acquires the upper illuminance and the front illuminance acquired by the upper illuminance acquisition unit. If the absolute value of the difference from the front illuminance acquired by the is greater than or equal to a predetermined deviation threshold, a mixed illuminance that is a value obtained by mixing the front illuminance and the upper illuminance is calculated using a predetermined blend coefficient, and the calculation is performed. The display luminance of the image is determined based on the mixed illuminance.

  In a situation where the front illuminance is relatively low with respect to the upper illuminance, a difference equal to or greater than a predetermined deviation threshold value is generated between the upper illuminance and the front illuminance. When there is a difference between the upper illuminance and the front illuminance that is equal to or greater than the predetermined deviation threshold, the above configuration is obtained by mixing the front illuminance and the upper illuminance using a predetermined blend coefficient. A target luminance is determined based on the mixed illuminance.

  Since the mixed illuminance is obtained by mixing the upper illuminance and the front illuminance at a predetermined ratio, the mixed illuminance is an intermediate value between the upper illuminance and the front illuminance. Therefore, the mixed illuminance is a value lower than the upward illuminance. As a result, the target luminance is set to a lower value than when the display luminance is determined based only on the upper illuminance. Specifically, the display luminance is set to an intermediate luminance between the display luminance based only on the upper illuminance and the display luminance determined based only on the front illuminance.

  According to such a configuration, when the front illuminance has a relatively low value with respect to the upper illuminance, the risk of causing the driver to feel dazzling can be reduced. That is, the display brightness of the image can be set more appropriately.

  In addition, the code | symbol in the parenthesis described in the claim shows the correspondence with the specific means as described in embodiment mentioned later as one aspect, Comprising: The technical scope of this invention is limited is not.

1 is a block diagram showing a schematic configuration of a HUD device 1. FIG. It is a figure which shows an example of the image which the HUD apparatus 1 displays a virtual image. It is a figure which shows the attachment attitude | position of the upper illumination intensity sensor 4 and the front illumination intensity sensor 5. FIG. It is a figure which shows an example of the detection angle range of the upper illumination intensity sensor 4 and the front illumination intensity sensor 5. FIG. It is a figure for demonstrating the relationship between the attachment attitude | position of the front illumination intensity sensor 5, and the road surface area | region which exists in a detection-axis direction. 3 is a block diagram schematically illustrating a configuration of a HUD control unit 11. FIG. It is a figure which shows an example of the correspondence of upper illumination intensity Su and the target brightness | luminance L. FIG. It is a figure which shows the relationship between residual distance Drst and blend coefficient (beta). It is a flowchart for demonstrating a brightness | luminance adjustment process. It is a figure for demonstrating the action | operation and effect of embodiment. It is a figure which shows the modification of a structure of the HUD apparatus. It is a figure which shows the modification of a structure of the HUD apparatus. 6 shows a modification of the configuration of the HUD control unit 11. It is the figure which showed an example of the display mode in the case of displaying the same kind of information with a some display mode. 14 is a flowchart for explaining a luminance adjustment process in Modification 4; It is a flowchart for demonstrating a correction process. It is the figure which showed an example of the relationship between correction amount (DELTA) L and the number N of color addition pixels.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing an example of a schematic configuration of a head-up display (hereinafter, HUD: Head-Up Display) device 1 according to the present invention. The HUD device 1 is mounted on a vehicle such as a four-wheeled vehicle. Each of the image signal source 2, the vehicle speed sensor 3, the upper illuminance sensor 4, and the front illuminance sensor 5 mounted on the vehicle, It is connected via a built-in in-vehicle network.

  The connection mode between the HUD device 1 and the image signal source 2 may be designed as appropriate. For example, the HUD device 1 and the image signal source 2 may be connected by a dedicated line for video signal lines. The connection mode with various in-vehicle sensors (for example, the upper illuminance sensor 4) is the same. For example, the upper illuminance sensor 4 may be electrically connected directly. The vehicle speed sensor 3 may be indirectly connected via an electronic control device (hereinafter, ECU: Electronic Control Unit) mounted on the vehicle. The communication mode between the HUD device 1 and the sensor may be wireless communication.

  The HUD device 1 roughly displays an image 10 in a predetermined area in front of the driver's seat as shown in FIG. 2 by projecting image light onto a predetermined projection area on the windshield of the vehicle. is there. The display position of the image 10 is on the vehicle front extension line of the line connecting the eyes of the occupant seated in the driver's seat and the projection area. The windshield is a windshield on the front side of the vehicle. A windshield should just be implement | achieved, for example using the laminated glass formed from two sheets of glass and the intermediate film provided in the middle. The windshield corresponds to the projection member recited in the claims. The projection member may be a member that functions as a half mirror such as a combiner.

  The image light here refers to light that forms a virtual image as the image 10. With this HUD device 1, an occupant (hereinafter referred to as a driver) seated in the driver's seat can visually recognize the HUD image 10 and the foreground of the vehicle in a superimposed manner. For convenience, hereinafter, the image 10 perceived by the driver is referred to as a HUD image 10.

  The type of information indicated by the HUD image 10 may be designed as appropriate. In FIG. 2, as an example, a mode in which an image indicating a traveling direction at an intersection or the like (an image as a so-called turn-by-turn) is illustrated. Of course, as another aspect, the HUD image 10 may be an image indicating any one or more of the traveling speed, the engine speed, the engine coolant temperature, the battery voltage, and the like as the vehicle information when the vehicle is traveling. Moreover, it is good also as a map image in the navigation system for vehicles. Furthermore, the image may represent an operating state of a system that provides an advanced driving support function or a system that provides an automatic driving function.

  The HUD device 1 is accommodated in an instrument panel 20 that extends from the lower end of the windshield to the rear of the vehicle interior and further downward. Note that an opening through which the image light emitted from the HUD device 1 passes is provided on the upper surface of the instrument panel 20. A dust-proof cover having translucency is provided in the opening.

  The image signal source 2 is a device that outputs an image signal that is a source of the HUD image 10 (for example, a route guidance image). The image signal here is still image data or a video signal. The image signal source 2 is, for example, a navigation device or an electronic control unit (ECU) that provides an automatic driving function. The vehicle speed sensor 3 is a sensor that detects the traveling speed (that is, the vehicle speed) of the host vehicle. The vehicle speed sensor 3 sequentially outputs data indicating the current vehicle speed to the HUD device 1.

  The upper illuminance sensor 4 is an illuminance sensor that detects brightness (that is, upper illuminance) Su above the vehicle. The upper illuminance sensor 4 is realized using, for example, a phototransistor or a photodiode. As shown in FIG. 3, the upper illuminance sensor 4 is installed on the upper surface portion of the instrument panel 20 so that the center (hereinafter, detection axis) Axu of the detection angle range φu faces the upper side of the vehicle.

  The detection angle range φ for the illuminance sensor is light whose output level is a predetermined threshold (for example, 50%) or more when the output level when light is incident from the detection axis direction is set as a reference (that is, 100%). Refers to the range of incident angles. The wider the detection angle range φ, the smaller the attenuation of the output level derived from the light incident direction.

  In this embodiment, as an example, an illuminance sensor configured so that the detection angle range φu is relatively wide is used as the upper illuminance sensor 4. Specifically, as shown in FIG. 4, it is assumed that the range in which the angle formed with respect to the detection axis is 45 degrees or less is the detection angle range φu.

  In the present embodiment, the upper illuminance sensor 4 is arranged in a posture in which the detection axis direction is parallel to the height direction of the vehicle (that is, vertically upward), but is not limited thereto. The detection axis direction may be attached in a posture inclined to the vehicle front side by a predetermined angle (for example, about 30 degrees) with respect to the vehicle height direction. It suffices if the detection axis direction is attached in a posture that is directed upward to some extent (for example, 45 degrees or more) from the vehicle horizontal plane. The upper illuminance sensor 4 may be mounted in the vicinity of the rear mirror or the upper end of the windshield. The upper illuminance sensor 4 sequentially outputs a signal indicating the upper illuminance Su as a detection result to the HUD device 1.

  The front illuminance sensor 5 is an illuminance sensor that detects the brightness (ie, front illuminance) Sf of a predetermined area in front of the vehicle. The front illuminance sensor 5 is realized using, for example, a phototransistor or a photodiode. As shown in FIG. 3, the front illuminance sensor 5 is attached to the rearview mirror 40 so that the center (hereinafter, detection axis) Axf of the detection angle range φf faces the front of the vehicle. Of course, the attachment posture and the attachment position of the front illuminance sensor 5 may be designed as appropriate, and are not limited to the above-described aspects. The front illuminance sensor 5 may be attached to the vicinity of the upper end of the windshield, the upper surface of the instrument panel 30, the front bumper, or the like.

  As an example, the front illuminance sensor 5 of the present embodiment is an illuminance sensor having a relatively narrow detection angle range φf. Specifically, as shown in FIG. 4, the front illuminance sensor 5 is an illuminance sensor configured such that a range in which an angle formed with respect to the detection axis is 5 degrees or less is a detection angle range φf. The front illuminance sensor 5 sequentially outputs a signal indicating the front illuminance Sf as a detection result to the HUD device 1.

  In addition, the front illuminance sensor 5 is arranged in a posture in which the detection axis is inclined downward by a predetermined angle (for example, 3 degrees) with respect to the vehicle horizontal plane. Thereby, as shown in FIG. 5, the front illuminance sensor 5 can detect the brightness of the road surface region positioned forward by a predetermined detection distance Dx from the attachment position of the front illuminance sensor 5. The detection distance Dx is determined based on the mounting height of the front illuminance sensor 5 and the inclination angle (so-called pitch angle) of the detection axis with respect to the vehicle horizontal plane. Specifically, if the mounting height H of the front illuminance sensor 5 is 1.6 m and the pitch angle θ of the detection shaft is 3 degrees, the detection distance Dx is H / tan θ = 1.6 / 0.035. = 45.7 m.

  The HUD device 1 includes a HUD control unit 11 and a display 12 as shown in FIG. The HUD control unit 11 is configured to control the operation of the display device 12 based on inputs from the image signal source 2, the upper illuminance sensor 4, and the like. The HUD control unit 11 is connected to the display device 12 so as to be able to perform data communication or electrically. The HUD control unit 11 is configured as a computer. In other words, the HUD control unit 11 connects the CPU 111 that executes various arithmetic processes, the RAM 112 that is a volatile memory, the flash memory 113 that is a nonvolatile memory, the I / O 114 as an input / output port, and the configuration thereof. A bus line is provided. The CPU 111 may be realized using, for example, a microprocessor. The I / O 114 is an interface for the HUD control unit 11 to input and output data with a configuration provided outside the housing of the HUD device 1 such as the image signal source 2. The I / O 114 may be realized using an IC, a digital circuit element, an analog circuit element, or the like.

  The flash memory 113 stores a program for causing a normal computer to function as the HUD control unit 11 (hereinafter referred to as a HUD control program). Note that the above-described HUD control program only needs to be stored in a non-transitory tangible storage medium, and the specific storage medium is not limited to the flash memory 113. Executing the HUD control program by the CPU 111 corresponds to executing a method corresponding to the HUD control program. The HUD control unit 11 provides various functions when the CPU 111 executes a HUD control program.

  For example, the HUD control unit 11 controls the operation of the display device 12 to output image light corresponding to the image signal input from the image signal source 2 with a predetermined luminance. Other various functions of the HUD control unit 11 will be described later separately.

  The display 12 is configured to emit image light indicating predetermined information corresponding to a signal input from the HUD control unit 11. As the display device 12, for example, a device (so-called liquid crystal projector) that outputs image light by transmitting light from a backlight to the liquid crystal panel can be used. The display 12 may be a projector (so-called laser projector) that displays an image by scanning laser light in a two-dimensional direction using a MEMS (Micro Electro Mechanical Systems) scanner. Furthermore, a known projector such as a DLP (Digital Light Processing: registered trademark) projector using a digital mirror device may be employed.

  Note that the image light emitted from the display device 12 may be configured to be projected onto the windshield via an optical member such as a concave mirror or a plane mirror. That is, the HUD device 1 may include a mirror member such as a concave mirror or a plane mirror (not shown), a lens, and the like.

<About the function of the HUD control unit 11>
The HUD control unit 11 provides various functions shown in FIG. 6 when the CPU 111 executes a display control program stored in the flash memory 113. That is, the HUD control unit 11 includes a vehicle speed acquisition unit F1, an upper illuminance acquisition unit F2, a front illuminance acquisition unit F3, a target luminance setting unit F4, and a luminance adjustment unit F5 as functional blocks.

  A part or all of the functional blocks provided in the HUD control unit 11 may be realized as one or hardware. The aspect realized as hardware includes an aspect realized using one or a plurality of ICs. In addition, some or all of the functional blocks included in the HUD control unit 11 may be realized by a combination of software execution by the CPU 111 and hardware members.

  The vehicle speed acquisition unit F1 sequentially acquires data indicating the traveling speed of the host vehicle output from the vehicle speed sensor 3. The upper illuminance acquisition unit F2 sequentially acquires data indicating the upper illuminance Su that is sequentially output from the upper illuminance sensor 4. The front illuminance acquisition unit F3 sequentially acquires data indicating the front illuminance Sf sequentially output from the front illuminance sensor 5.

  The target luminance setting unit F4 calculates the target luminance L that is the target display luminance of the HUD image 10 based on the upper illuminance Su acquired by the upper illuminance acquisition unit F2 and the front illuminance Sf acquired by the front illuminance acquisition unit F3. It is a configuration to set. The detailed operation of the target luminance setting unit F4 will be described with reference to a separate flowchart, but is roughly as follows. First, when the absolute value of the difference between the upper illuminance Su and the front illuminance Sf is less than a predetermined threshold (hereinafter referred to as a deviation threshold) Th, the target luminance L of the HUD image 10 is determined according to the upper illuminance Su. A control signal is output to the display device 12 so that the determined target luminance L is obtained.

  Note that the target luminance L corresponding to the upper illuminance Su may be determined using an upper illuminance-luminance table prepared in advance. The upper illuminance-luminance table is data indicating the target luminance L corresponding to the upper illuminance Su, as shown in FIG. Basically, the target luminance L is set to be higher as the upward illuminance Su is higher. It is assumed that a lower limit value (hereinafter, lower limit luminance) and an upper limit value (hereinafter, upper limit luminance) are set for the target luminance L.

When the absolute value of the difference between the upper illuminance Su and the front illuminance Sf is equal to or greater than the deviation threshold Th, the mixed illuminance is a value obtained by mixing the upper illuminance Su and the front illuminance Sf using a predetermined blend coefficient β. A target luminance L is determined based on Sb. Specifically, the mixed illuminance Sb is calculated based on the following formula 1.
Sb = β · Su + (1−β) · Sf Equation 1

Then, the target luminance L is determined by multiplying the mixed illuminance Sb obtained by the above equation 1 by a predetermined conversion coefficient α for making the illuminance correspond to the target luminance L. That is, when the absolute value of the difference between the upper illuminance Su and the front illuminance Sf is equal to or greater than the deviation threshold Th, the target luminance L is determined by the following equation 2.
L = α · Sb = α {β · Su + (1−β) · Sf} Equation 2

  The blend coefficient β used above functions as a parameter for determining a ratio when the upper illuminance Su and the front illuminance Sf are mixed. The specific value of the blend coefficient β is dynamically changed (in other words, adjusted) by a β adjustment unit F42 described later. However, it is assumed that a range of values that can be set (in other words, a minimum value and a maximum value) is set in advance for the blend coefficient β. The range of values that can be taken by the blend coefficient β may be appropriately designed within a range satisfying 0 <β <1. Here, as an example, the range of values in which the blend coefficient β can be set is set to 0.2 ≦ β ≦ 1. The minimum value of the blend coefficient β is 0.2 here, but is not limited thereto, and a specific value may be designed as appropriate. Here, the maximum value of the blending coefficient β is set to 0.95, but the specific value may be appropriately designed within a range smaller than 1, for example, 0.9 or 0.8. .

  The target luminance setting unit F4 sets the target luminance L to the lower limit luminance when the target luminance L calculated by the above equation 2 is lower than the lower limit luminance, and the target luminance L calculated by the equation 2 sets the upper limit luminance. If it exceeds the target luminance L, the upper limit luminance is set. As another aspect, a predetermined constant term for the target brightness L to take a value equal to or higher than the lower limit brightness may be added to Expression 2.

  The target luminance setting unit F4 has a remaining distance calculation unit F41 and a β adjustment unit F42 as a finer configuration (in other words, a sub function) for adjusting the display luminance of the HUD image 10 according to the upper illuminance Su and the front illuminance Sf. Is provided.

  The remaining distance calculation unit F41 is configured to sequentially calculate the remaining distance Drst that is the remaining distance to the underdrain area, which is an area where the illuminance around the vehicle (for example, the side) is assumed to be less than the predetermined undercover threshold value Sd. is there. The underdrain area is, for example, a road inside a tunnel. In addition, roads that are shaded or shaded by trees can also fall under the culvert area. The culvert area corresponds to an area where the illuminance on the side of the vehicle as well as in front of the host vehicle is equal to or less than the culvert threshold Sd.

  Among the sections that are the culvert area in the traveling path of the host vehicle, the point closest to the host vehicle is referred to as a darkening point. The darkening point is, for example, an entrance of a tunnel or an end of a road section in the shade of a tree or a tree on the own vehicle side. The specific value of the underdrain threshold Sd may be designed as appropriate assuming the illuminance inside the tunnel or the like. In the following, for the sake of convenience, the inside of the tunnel is assumed as the underdrain area.

  The residual distance calculation unit F41 of the present embodiment detects a dark spot based on the level of the upper illuminance Su and the level of the front illuminance Sf, and calculates the dark residual distance. Specifically, it is as follows. First, as a premise, the front illuminance sensor 5 of the present embodiment is arranged so as to detect the amount of light from the road surface area ahead of the predetermined detection distance Dx from the host vehicle, as described with reference to FIG. Therefore, during the daytime in fine weather, the output of the front illuminance sensor 5 (that is, the front illuminance Sf) becomes less than the dark culm threshold Sd at the timing when the remaining distance to the darkening point (for example, the tunnel entrance) cuts the detection distance Dx. . On the other hand, during sunny daytime, as long as the vehicle is located outside the tunnel, it is expected that the upward illuminance Su will be equal to or greater than the underglow threshold Sd.

  Therefore, the remaining distance calculation unit F41 of the present embodiment is configured such that the remaining distance Drst is the detection distance Dx when the upper illuminance Su is equal to or greater than the underglow threshold Sd and the forward illuminance Sf is less than the underglow threshold Sd. Judge that there is. In addition, the current remaining distance Drst is sequentially calculated based on the elapsed time from the time when the forward illuminance Sf becomes less than the dark-light threshold Sd (hereinafter, the dark-light area detection time) and the vehicle speed of the host vehicle. For example, for each predetermined unit time, a value obtained by multiplying the current vehicle speed acquired by the vehicle speed acquisition unit F1 by the unit time as a unit travel distance, and a value obtained by subtracting the unit travel distance from the previously calculated remaining distance Drst Is adopted as the current residual distance Drst. If the remaining distance Drst cannot be calculated, for example, when the upper illuminance Su is not equal to or greater than the dark threshold value Sd, the detection distance Dx that is the maximum value is substituted for the remaining distance Drst for convenience. Shall.

  The remaining distance Drst calculated by the remaining distance calculation unit F41 is stored in a RAM or the like. The output level of the front illuminance sensor 5 suddenly drops at the timing when the remaining distance to the tunnel entrance cuts the predetermined detection distance Dx, while the output level of the upper illuminance sensor 4 is after the output level of the front illuminance sensor 5 has decreased. However, it is maintained at a relatively high value for a while. This is because the upper illuminance sensor 4 is mounted so as to detect the illuminance above the vehicle. The case where the upper illuminance Su is less than the culvert threshold Sd is a case where the host vehicle enters a culvert area such as a tunnel. That is, until the own vehicle enters the tunnel, the state in which the difference between the upper illuminance Su and the front illuminance Sf continues.

  The β adjustment unit F42 is configured to adjust the value of the blend coefficient β within a predetermined range that can be set as the blend coefficient β based on the remaining distance Drst calculated by the remaining distance calculation unit F41. The β adjustment unit F42 sets the blend coefficient β to a smaller value as the remaining distance Drst is smaller. For example, as indicated by the solid line in FIG. 8, the value of the blend coefficient β is linearly decreased from the maximum value to the minimum value as the remaining distance Drst approaches 0. Such a configuration corresponds to a configuration in which the blend coefficient β is set so that the proportion of the component derived from the front illuminance Sf in the mixed illuminance Sb increases as the remaining distance Drst decreases. That is, the β adjustment unit F42 corresponds to the mixing ratio adjustment unit described in the claims.

  Note that, as another aspect, the β adjustment unit F42 may be changed in a curved manner as indicated by a one-dot chain line in FIG. The blend coefficient β corresponding to the remaining distance Drst may be set in advance. A configuration in which the value of the blend coefficient β is linearly decreased from the maximum value to the minimum value as the residual distance Drst approaches 0 is a configuration in which the relationship between the residual distance Drst and the blend coefficient β is associated with a linear function. It corresponds to.

  The luminance adjustment unit F5 displays the HUD image 10 so that the display luminance of the HUD image 10 matches the target luminance L set by the target luminance setting unit F4, in other words, the HUD image 10 is displayed at the target luminance L. The operation of the device 12 is controlled. The display luminance adjustment itself may be realized by a known method according to the type of the display device 12. For example, when the display 12 is a liquid crystal projector, the brightness of the backlight provided in the display 12 may be adjusted. The display brightness of the HUD image 10 may be adjusted by adjusting the color tone of the image data itself output to the display device 12. When the display 12 is a laser projector, the output level of the laser light source (in other words, the light emission amount) may be adjusted.

<Brightness adjustment processing>
Next, the brightness adjustment processing performed by the HUD control unit 11 will be described using the flowchart shown in FIG. The flowchart shown in FIG. 9 may be executed sequentially (for example, every 100 milliseconds) while power is supplied to the HUD device 1 from an in-vehicle power source (not shown). Note that the execution conditions of the brightness adjustment processing are items that should be designed as appropriate, and are not limited thereto. For example, the luminance adjustment process may be executed sequentially only when the HUD image 10 is displayed. The execution interval of the brightness adjustment process is also an item to be designed as appropriate.

  First, in step S101, the upper illuminance acquisition unit F2 acquires the upper illuminance Su from the upper illuminance sensor 4, and the front illuminance acquisition unit F3 acquires the front illuminance Sf from the front illuminance sensor 5 and proceeds to step S102. In step S102, the target luminance setting unit F4 calculates the absolute value of the difference between the upper illuminance Su and the front illuminance Sf, and whether the absolute value of the difference between the upper illuminance Su and the front illuminance Sf is greater than or equal to a predetermined deviation threshold Th. Determine whether or not.

  The deviation threshold Th used in step S102 is determined based on the difference between the upper illuminance Su and the front illuminance Sf observed just before the vehicle enters the tunnel during the daytime in fine weather. As described above, the output level of the front illuminance sensor 5 is less than the under-threshold threshold Sd at the timing when the remaining distance to the tunnel entrance is less than the predetermined detection distance Dx during the daytime in fine weather, while the output level of the upper illuminance sensor 4 is It is maintained at a relatively high level until the vehicle enters the tunnel. The deviation threshold Th is a parameter for detecting or determining that the surrounding of the vehicle is an environment where the front of the vehicle is darker than the vehicle upper side by a predetermined threshold or more.

  If the absolute value of the difference between the upper illuminance Su and the front illuminance Sf is less than the deviation threshold Th, a negative determination is made in step S102 and the process proceeds to step S103. On the other hand, if the absolute value of the difference between the upper illuminance Su and the front illuminance Sf is greater than or equal to the deviation threshold Th, an affirmative determination is made in step S102 and the process proceeds to step S104.

  In addition, the case where the absolute value of the difference between the upper illuminance Su and the front illuminance Sf is greater than or equal to the deviation threshold Th is, paradoxically, that the remaining distance to the tunnel entrance is less than the detection distance Dx in the daytime in fine weather. Means. That is, when the determination in step S102 is affirmative, it is expected that the remaining distance Drst is calculated by the remaining distance calculation unit F41.

  In step S103, the target luminance setting unit F4 determines the target luminance L based on the upper illuminance Su without using the front illuminance Sf, and proceeds to step S106. An example of a method for determining the target luminance L based on the upward illuminance Su is as described above with reference to FIG.

  In step S104, the latest remaining distance Drst calculated by the remaining distance calculation unit F41 is read, and the process proceeds to step S105. If the remaining distance Drst has not been calculated at the time of executing step S104, it is considered that the remaining distance Drst = Dx and the process proceeds to the next step S105.

  In step S105, the target luminance setting unit F4 calculates the target luminance L using Equation 2 described above. That is, based on the mixed illuminance Sb determined by substituting the blend coefficient β determined according to the current upper illuminance Su, the front illuminance Sf, and the current remaining distance Drst acquired in step S101 into the formula 1, To decide. When step S105 is completed, the process proceeds to step S106.

  In step S <b> 106, the HUD control unit 11 outputs a control signal for displaying the HUD image 10 with the target luminance L to the display unit 12 and ends the present flow. When the display brightness of the HUD image 10 at the start of this flow matches the target brightness L determined in step S103 or step S105, the current display brightness may be maintained. That is, if the display brightness of the HUD image 10 at the start of this flow matches the target brightness L determined in step S103 or step S105, step S106 can be omitted.

<Operation and Effect of Embodiment>
For example, when the vehicle is traveling toward the tunnel entrance in the daytime in fine weather (hereinafter referred to as a culvert area approaching state), there is a large difference between the output level of the upper illuminance sensor 4 and the output level of the front illuminance sensor 5. May occur. Specifically, the upper illuminance Su is a relatively high value when the host vehicle is located in front of the tunnel entrance and the front illuminance sensor 5 detects the illuminance inside the tunnel. On the other hand, the front illuminance Sf indicating the illuminance inside the tunnel takes a relatively low value.

  FIG. 10 is a diagram conceptually showing transitions of output levels of the upper illuminance sensor 4 and the front illuminance sensor 5 in the process of entering the tunnel, and the horizontal axis represents the passage of time. The vertical axis represents the output level. FIG. 10A shows the transition of the output level of the front illuminance sensor 5, and FIG. 10B shows the transition of the output level of the upper illuminance sensor 4.

  Since the upper illuminance sensor 4 is mounted so as to detect the illuminance above the vehicle, even after the output level of the front illuminance sensor 5 decreases at the culvert area detection time Tf, the output level is relatively set for a while. Maintained at a high value. The case where the upper illuminance Su is less than the culvert threshold Sd is a case where the host vehicle enters a culvert area such as a tunnel. That is, until the host vehicle enters the tunnel, a state in which a predetermined difference is generated between the upper illuminance Su and the front illuminance Sf continues as shown in FIG. Note that Tf shown in FIG. 10 is a timing when the remaining distance to the tunnel entrance (that is, the darkening point) cuts the detection distance Dx, and the absolute value of the difference between the upper illuminance Su and the front illuminance Sf becomes equal to or greater than the deviation threshold Th. Tu represents the timing at which the host vehicle entered the tunnel.

  In such a culvert area approaching situation, as in Patent Document 1, if the display brightness of the image is determined based on the higher illuminance of the front illuminance or the upper illuminance, the display by the HUD device is too bright and the driver There is a risk that it will make you feel dazzling. This is because, in the configuration of Patent Document 1, an image is displayed with a luminance matching the upper illuminance to a driver who is viewing a dark area inside the tunnel.

  On the other hand, according to the configuration of the present embodiment, the remaining distance to the tunnel entrance (that is, the remaining distance) Drst is less than the predetermined detection distance Dx, and the absolute value of the difference between the upper illuminance Su and the front illuminance Sf is the deviation threshold Th. After the above point, the target luminance L is determined according to the mixed illuminance Sb obtained by mixing the upper illuminance Su and the front illuminance Sf at a ratio according to a predetermined blend coefficient β.

  The mixed illuminance Sb is a value that is smaller than the upper illuminance Su and larger than the front illuminance Sf because the upper illuminance Su and the front illuminance Sf are mixed at a predetermined ratio. That is, the mixed illuminance Sb is an intermediate value between the upper illuminance Su and the front illuminance Sf. As a result, the target luminance L itself is also set to a lower value than the configuration in which the display luminance is determined based only on the upper illuminance Su that has a relatively high output level. Therefore, according to the configuration of the present embodiment, the risk of causing the driver to feel dazzling is reduced as compared with the configuration in which the display luminance of the image is determined based on the higher illuminance as in Patent Document 1. can do. That is, the display brightness of the image can be set more appropriately.

  Further, according to the configuration of the present embodiment, the value of the blend coefficient β is decreased as the remaining distance Drst is decreased. That is, as shown in FIG. 10C, the blend coefficient β gradually decreases as the host vehicle approaches the tunnel entrance, and the ratio of the component derived from the front illuminance Sf in the mixed illuminance Sb gradually increases. As a result, the mixed illuminance Sb itself gradually decreases, and the target luminance L also decreases. As a result, the HUD image 10 gradually darkens as the host vehicle approaches the tunnel entrance, and finally the target luminance L at the timing when the host vehicle enters the tunnel is adapted to the brightness inside the tunnel. It can be set to brightness.

  As described above, according to the configuration in which the blend coefficient β is dynamically changed according to the remaining distance Drst, it is possible to reduce the possibility that the display luminance of the HUD image 10 is suddenly changed. In addition, it is possible to reduce a possibility that the driver feels uncomfortable or bothered by abruptly changing the display brightness of the HUD image 10. That is, the display brightness of the image can be set more appropriately.

  In the above, for the sake of convenience, the same symbol Sd is given to each of the culvert threshold for the upper illuminance sensor 4 and the culvert threshold for the front illuminance sensor 5. However, the culvert threshold for the upper illuminance sensor 4 and the culvert threshold for the front illuminance sensor 5 do not have to be the same value. In other words, the culling threshold for the upper illuminance sensor 4 and the culling threshold for the front illuminance sensor 5 may be different values. The culvert threshold of the upper illuminance sensor 4 may be appropriately determined according to the detection capability and output range of the upper illuminance sensor 4. The culvert threshold value of the front illuminance sensor 5 may be appropriately determined according to the detection capability and output range of the front illuminance sensor 5. The culling thresholds of the various illuminance sensors may be set based on the result of an actual test / simulation of the output level when the host vehicle is in the culvert area.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the above-mentioned embodiment, The various modifications described below are also contained in the technical scope of this invention, and also in addition to the following However, various modifications can be made without departing from the scope of the invention. In addition, the embodiment and various modifications can be combined as appropriate.

  In addition, about the member which has the same function as the member described in the above-mentioned embodiment, the same code | symbol is attached | subjected and the description is abbreviate | omitted. In addition, when only a part of the configuration is mentioned, the configuration of the above-described embodiment can be applied to the other portions.

[Modification 1]
In the above-described embodiment, the configuration in which the remaining distance Drst is estimated based on the elapsed time from the culvert area detection time point and the vehicle speed of the host vehicle is disclosed, but is not limited thereto. As shown in FIG. 11, when the HUD device 1 is connected to a locator 6 described later, the remaining distance Drst may be calculated sequentially based on data output from the locator 6.

  The locator 6 is a device that sequentially detects the current position of the host vehicle and sequentially outputs map data around the current position of the host vehicle in association with position information indicating the current position. The locator 6 is realized using, for example, a GNSS receiver 61, an inertial sensor 62, and a map database (hereinafter referred to as DB) 63. The GNSS receiver 61 sequentially detects the current position of the GNSS receiver 61 (for example, every 100 milliseconds) by receiving navigation signals transmitted from positioning satellites that constitute a GNSS (Global Navigation Satellite System). It is a device. The inertial sensor 62 is, for example, a triaxial gyro sensor or a triaxial acceleration sensor. The map DB 63 is a non-volatile memory that stores map data indicating road connection relationships and the like. The map data includes, for example, node data regarding points (hereinafter referred to as nodes) where a plurality of roads intersect, merge and branch, and link data regarding roads (hereinafter referred to as links) connecting the points. The link data also includes information indicating the position of the entrance and exit of the tunnel as information indicating the tunnel section.

  The locator 6 combines the positioning result of the GNSS receiver, the measurement result of the inertial sensor, and the map data, so that the current position of the host vehicle Hv and the road on which the host vehicle is traveling (hereinafter referred to as a travel path) are obtained. Identify sequentially. Then, the vehicle position data indicating the specified current position is sequentially provided to the HUD device 1. The current position of the host vehicle may be expressed by, for example, latitude, longitude, and altitude.

  Further, the locator 6 reads out a predetermined range of map data (hereinafter referred to as surrounding map data) determined from the map DB 63 with the current position as a reference, and provides it to the HUD device 1. When the travel path passes through the tunnel, it is assumed that the surrounding map data also includes information indicating the position of the entrance of the tunnel (hereinafter, tunnel position information). The map data may be obtained from an external server or the like via a wide area communication network. Further, locator 6 only needs to have the above-described function, and when a navigation device is mounted on the host vehicle, the navigation device may be used as locator 6.

  Then, when the data indicating the location of the tunnel entrance is provided from the locator 6, the remaining distance calculation unit F <b> 41 in the first modification example sequentially calculates the remaining distance to the tunnel entrance. That is, the remaining distance calculation unit F41 according to the first modification sequentially calculates the remaining distance Drst using the position information indicating the current position and the map data.

  According to such a configuration, the remaining distance Drst can be calculated more accurately than in the above-described embodiment in a situation where the GNSS receiver 61 can measure the current position. The configuration of the above-described embodiment has an advantage that the remaining distance Drst can be calculated even in a situation where the GNSS receiver 61 cannot measure the current position.

  Of course, the HUD device 1 may have a configuration (hereinafter referred to as a composite configuration) in which the configuration of the modification 1 and the configuration of the embodiment are combined. That is, when the GNSS receiver 61 can perform the positioning calculation, the remaining distance is calculated using the output data of the locator 6, while when the GNSS receiver 61 cannot perform the positioning calculation, the elapsed time from the culvert area detection time Tf. The remaining distance Drst may be calculated based on the time. Note that the situation where the GNSS receiver 61 cannot measure the current position is when the radio waves from the positioning satellites are shielded by mountains, buildings, etc., and the number of positioning satellites supplemented by the GNSS receiver 61 is less than four. It is. Mountains exist around the road where the tunnel is provided, and reception of radio waves from positioning satellites is not always good. In view of such circumstances, the configuration of the embodiment and the composite configuration are preferable.

[Modification 2]
In the embodiment described above, the control mode in which the blend coefficient β is dynamically adjusted according to the remaining distance Drst is disclosed, but the present invention is not limited to this. The value of the blend coefficient β may be fixed to an arbitrary value larger than 0 and smaller than 1 (for example, 0.5 or 0.6). According to such a configuration, a series of calculation processing for calculating the remaining distance Drst can be omitted, and the calculation load on the HUD device 1 can be reduced.

[Modification 3]
The method of determining the target luminance L based on the upper illuminance Su and the front illuminance Sf is not limited to the method of calculating using Expression 2. Similarly to the upper illuminance-luminance table, a table indicating the target luminance L corresponding to the mixed illuminance Sb may be prepared in advance, and the target luminance L may be determined using the table.

<Supplement>
In the case where the remaining distance Drst is calculated based on the output of the locator 6 as described in the first modification, or in the case where the blend coefficient β is set to a constant value as described in the second modification, The blend coefficient β is not dynamically changed according to the output level of the front illumination sensor 5. When adopting a configuration in which the blend coefficient β is not dynamically changed according to the output level of the front illuminance sensor 5 as described above, the front illuminance sensor 5 has a relative detection angle range φ as in the upper illuminance sensor 4. An illuminance sensor set to a wide angle can be employed. That is, the front illuminance sensor 5 may be an illuminance sensor with a wide detection angle range φ.

  The wide-angle illuminance sensor here is an illuminance sensor in which the limit value of the detection angle range φ is 30 degrees or more. The limit value of the detection angle range φ is that the output level is equal to or higher than a predetermined threshold (for example, 50%) when the output level when light is incident from the detection axis direction is set as a reference (that is, 100%). This corresponds to the upper limit of the incident angle of light. Further, the illuminance sensor having a narrow detection angle range φ refers to an illuminance sensor in which the limit value of the detection angle range φ is set to 10 degrees or less.

[Modification 4]
As shown in FIG. 12, the HUD device 1 is connected to each of a narrow angle front illuminance sensor 5A and a wide angle front illuminance sensor 5B as illuminance sensors for detecting the illuminance in front of the vehicle. The target luminance L of the HUD image 10 may be adjusted based on the detection results of the front illuminance sensor 5A and the wide-angle front illuminance sensor 5B. Hereinafter, such a configuration is disclosed as a fourth modification.

  In the following, the narrow-angle front illuminance sensor 5A is an illuminance sensor in which the detection angle range φ is set to a relatively narrow angle (for example, 10 degrees or less), and the detection axis faces the front of the vehicle. It is an illuminance sensor set to. The wide-angle front illuminance sensor 5B is an illuminance sensor in which the detection angle range φ is set to a relatively wide angle (for example, 30 degrees or more), and the illuminance sensor is set so that the detection axis faces the front of the vehicle. It is. The narrow-angle front illuminance sensor 5A is preferably installed in a state in which the detection axis is directed downward from the vehicle horizontal plane so as to detect the illuminance of a road surface area separated from the vehicle to some extent (for example, 30 m or more).

  The narrow-angle forward illuminance sensor 5A sequentially outputs data indicating the detection result (hereinafter, narrow-angle forward illuminance Sfn) to the HUD device 1. The wide-angle front illuminance sensor 5B also sequentially outputs data indicating the detection result (hereinafter, wide-angle front illuminance Sfw) to the HUD device 1.

  As shown in FIG. 13, the HUD control unit 11 in Modification 4 provides various functions shown in FIG. 13 when the CPU 111 executes a display control program stored in the flash memory 113. That is, the HUD control unit 11 in the modified example 4 includes, as functional blocks, a vehicle speed acquisition unit F1, an upper illuminance acquisition unit F2, a narrow-angle forward illuminance acquisition unit F3A, a wide-angle forward illuminance acquisition unit F3B, a target luminance setting unit F4, and a luminance adjustment unit. F5, a display area specifying unit F6, and a correction unit F7 are provided.

  The vehicle speed acquisition unit F1 and the upper illuminance acquisition unit F2 have the same configuration as that of the above-described embodiment. The narrow-angle forward illuminance acquisition unit F3A sequentially acquires data indicating the narrow-angle forward illuminance Sfn sequentially output from the narrow-angle forward illuminance sensor 5A. The wide-angle front illuminance acquisition unit F3B sequentially acquires data indicating the wide-angle front illuminance Sfw sequentially output from the wide-angle front illuminance sensor 5B.

  The target luminance setting unit F4 in the fourth modification is configured to adjust the display luminance of the HUD image 10 based on at least one of the upper illuminance Su, the narrow-angle forward illuminance Sfn, and the wide-angle forward illuminance Sfw.

  The detailed operation of the target luminance setting unit F4 will be described with reference to a separate flowchart, but is roughly as follows. First, when the absolute value of the difference between the upper illuminance Su and the narrow-angle forward illuminance Sfn is less than a predetermined first deviation threshold Th1, the target luminance L of the HUD image 10 is determined according to the upper illuminance Su. The first deviation threshold Th1 here is a parameter corresponding to the deviation threshold Th in the above-described embodiment.

  When the absolute value of the difference between the upper illuminance Su and the narrow-angle forward illuminance Sfn is less than the first divergence threshold Th1, the absolute value of the difference between the narrow-angle forward illuminance Sfn and the wide-angle forward illuminance Sfw is a predetermined second divergence. It is determined whether it is less than the threshold Th2. The second deviation threshold Th2 is a threshold for determining whether or not the narrow-angle forward illuminance Sfn and the wide-angle forward illuminance Sfw are at the same level, and may be designed as appropriate.

  When the absolute value of the difference between the narrow-angle front illuminance Sfwn and the wide-angle front illuminance Sfw is equal to or greater than the second deviation threshold Th2, the target luminance L is determined based on the wide-angle front illuminance Sfw. On the other hand, when the absolute value of the difference between the narrow-angle forward illuminance Sfn and the wide-angle forward illuminance Sfw is less than the second deviation threshold Th2, the target luminance L is determined based on the narrow-angle forward illuminance Sfn. Specifically, the narrow-angle front illuminance sfn is handled in the same manner as the front illuminance Sf in the above-described embodiment, and the target luminance L is determined using Equation 2.

  The target luminance setting unit F4 includes a residual distance calculation unit F41 and a β adjustment unit F42 as sub-functions as in the above-described embodiment. The remaining distance calculation unit F41 in the modified example 4 calculates a time point when the narrow-angle forward illuminance Sfn is less than the under-threshold threshold value Sd instead of the forward illuminance Sf in the above-described embodiment (in other words, under-dark region detection time point). The remaining distance Drst is calculated based on the vehicle speed and the like. Of course, the remaining distance calculation unit F41 may calculate the remaining distance Drst by the method described in the first modification.

  The display area specifying unit F6 is configured to calculate the size (in other words, the area) of the image displayed as the HUD image 10. The size of the HUD image 10 is, for example, an image in which color information other than colorless and transparent is actually added to represent predetermined information in an area that can be displayed as the HUD image 10 (in other words, the HUD image 10 May be expressed by the number of pixels (hereinafter, the number of color-added pixels).

  For example, the display area specifying unit F6 analyzes the image data to be displayed on the display 12, and counts the number of pixels to which color information other than colorless and transparent is added, thereby specifying the number of color-added pixels as the display area. Just do it. Note that the display area may be expressed by the ratio of the number of color-added pixels to the total number of pixels Nal composing a region that can be displayed as the HUD image 10 (hereinafter, image filling rate).

  Note that the display area when the display 12 is a laser projector corresponds to the ratio of the portion that is actually irradiated with the laser light in the scanning range of the laser light (that is, the filling rate of the laser light). It means that the higher the filling rate of laser light, that is, the larger the display area, the more times the laser light is irradiated in one scan.

  The display area of the HUD image 10 varies depending on information (in other words, content) displayed as the HUD image 10. For example, the display area of the HUD image 10 representing text information such as the vehicle speed is smaller than that of the HUD image 10 representing a figure whose outline is filled with a predetermined color. Moreover, as shown in FIG. 14, even if it is the content of the same kind, you may be comprised so that the design from which a display area differs according to a condition may be employ | adopted. 14A and 14B each show an example of a turn-by-turn display mode. In FIG. 14, a dot pattern hatched area represents an area to which color information that is not colorless and transparent is added. A broken line shown in FIG. 14 represents an outline of an area that can be displayed as the HUD image 10. In the present embodiment, it is assumed that the display mode (design or the like) of the HUD image 10 is determined by the image signal source 2 that is the source of the original data of the HUD image 10. Of course, as another aspect, the design of the HUD image 10 may be configured to be determined by the HUD control unit 11.

  The correcting unit F7 is configured to correct the target luminance L determined by the target luminance setting unit F4 with the display area specified by the display area specifying unit F6. Details of the operation of the correction unit F7 will be described later.

<Brightness adjustment processing>
Next, the brightness adjustment processing performed by the HUD control unit 11 of the modification 4 will be described using the flowchart shown in FIG. The flowchart shown in FIG. 15 may be started sequentially at a predetermined execution interval when conditions designed as appropriate are satisfied as in the flowchart shown in FIG.

  First, in step S201, the upper illuminance Su, the narrow-angle forward illuminance Sfn, and the wide-angle forward illuminance Sfw are acquired, and the process proceeds to step S202. This step S201 is executed by the upper illuminance acquisition unit F2, the narrow-angle front illuminance acquisition unit F3A, and the wide-angle front illuminance acquisition unit F3B.

  In step S202, the target luminance setting unit F4 calculates the absolute value of the difference between the upper illuminance Su and the narrow-angle forward illuminance Sfn, and the absolute value of the difference between the upper illuminance Su and the narrow-angle forward illuminance Sfn is a predetermined first deviation. It is determined whether or not the threshold value is Th1 or more. If the absolute value of the difference between the upper illuminance Su and the narrow-angle forward illuminance Sfn is greater than or equal to the first deviation threshold Th1, an affirmative determination is made in step S202 and the process proceeds to step S204. On the other hand, if the absolute value of the difference between the upper illuminance Su and the narrow-angle forward illuminance Sfn is less than the first deviation threshold Th1, a negative determination is made in step S202 and the process proceeds to step S203.

  In step S203, the target luminance setting unit F4 determines the target luminance L corresponding to the upper illuminance Su without using the narrow-angle forward illuminance Sfn and the wide-angle forward illuminance Sfw, and proceeds to step S208. The target luminance L based on the upper illuminance Su may be determined using, for example, an upper illuminance-luminance table as illustrated in FIG.

  In step S204, the target luminance setting unit F4 calculates the absolute value of the difference between the narrow-angle forward illuminance Sfn and the wide-angle forward illuminance Sfw, and the absolute value of the difference between the narrow-angle forward illuminance Sfwn and the wide-angle forward illuminance Sfw is a predetermined first value. It is determined whether or not it is equal to or greater than 2 deviation threshold Th2. If the absolute value of the difference between the narrow-angle forward illuminance Sfn and the wide-angle forward illuminance Sfw is greater than or equal to the second deviation threshold Th2, an affirmative determination is made in step S204 and the process proceeds to step S205. On the other hand, if the absolute value of the difference between the narrow-angle forward illuminance Sfn and the wide-angle forward illuminance Sfw is less than the second deviation threshold Th2, a negative determination is made in step S204 and the process proceeds to step S206.

In step S205, the target luminance setting unit F4 determines the target luminance L based on the upper illuminance Su and the wide-angle front illuminance Sfw. For example, the target luminance setting unit F4 calculates a mixed illuminance Sb ′ that is a value obtained by mixing the upper illuminance Su and the wide-angle front illuminance Sfw using a predetermined static blend coefficient β ′, and sets the mixed illuminance Sb ′ to a predetermined value. A value obtained by multiplying the conversion coefficient α is set as the target luminance L. That is, the target luminance L is set based on the following formula 3.
L = α · Sb ′ = α {β ′ · Su + (1−β ′) · Sfw} Equation 3

  The specific value of the static blend coefficient β ′ may be appropriately designed in a range larger than 0 and smaller than 1. For example, it is assumed that β ′ is set to 0.5. Of course, β ′ may be set to 0.4, 0.6, 0.7, or the like.

  Note that the method of determining the target luminance L based on the upward illuminance Su and the wide-angle forward illuminance Sfw is not limited to the method of calculating using Equation 3 above. Similarly to the upper illuminance-luminance table, a table indicating the target luminance L corresponding to the mixed illuminance Sb ′ may be prepared in advance, and the target luminance L may be determined using the table.

  In step S206, the latest remaining distance Drst calculated by the remaining distance calculation unit F41 is read, and the process proceeds to step S207. If the remaining distance Drst is not calculated at the time when step S206 is executed, the remaining distance Drst is regarded as the detection distance Dx, and the process proceeds to the next step S207. In step S207, the target luminance setting unit F4 calculates the target luminance L using Equation 2 described above, and proceeds to step S208.

  In step S208, the correcting unit F7 corrects the target luminance L determined by the target luminance setting unit F4 in any of steps S203, S205, and S207 according to the display area specified by the display area specifying unit F6. is there. Schematically, the correction unit F7 corrects the target luminance L to a smaller value so that the display luminance is suppressed as the display area is larger.

Here, as an example, the correction process is executed according to the flowchart shown in FIG. In step S301 as the first step of the correction process, an image to be displayed on the display device 12 (hereinafter referred to as a base image) is analyzed, and the number N of color-added pixels is specified. Next, in step S302, an average luminance value Ave for each pixel when only the pixels to which color information is added in the base image is used as a population is calculated. In step S303, the final target luminance La is determined by correcting the target luminance L using Equation 4 below. In Expression 4, δ is a constant parameter designed as appropriate.
La = L · Ave · Nal / N · δ Equation 4

Here, as an example, the target luminance L is corrected using the above-described equation 4, but the present invention is not limited to this. For example, the target luminance L may be corrected using the following formula 4a.
La = L · Ave · {1−δ · N / Nal} Expression 4a

  Further, as shown in FIG. 17, data (hereinafter, correction data) in which the number N of color-added pixels and the luminance correction amount ΔL are associated with each other is prepared in advance, and the final correction is performed using the correction data. The target luminance La may be determined. In that case, a value obtained by adding a correction amount ΔL determined using the correction data to the target luminance L calculated by the target luminance setting unit F4 may be set as the final target luminance La (that is, La = L + ΔL). Note that Nb in FIG. 17 represents the number N of color-added pixels in which the correction amount ΔL is zero. Nb may be a value obtained by multiplying the total number of pixels Nal by a predetermined coefficient smaller than 1 (for example, 0.4, 0.5, 0.6, etc.). Nb is preferably set to about half of the total number of pixels Nal.

  When the correction process is completed, the process returns to the caller luminance adjustment process, and step S209 is executed. In step S209, the luminance adjustment unit F5 outputs a control signal for displaying the HUD image 10 with the target luminance L to the display unit 12, and the present flow is ended. Note that if the display brightness of the HUD image 10 at the start of this flow matches the target brightness L determined in step S208, the current display brightness may be maintained. That is, if the display brightness of the HUD image 10 at the start of this flow matches the target brightness L determined in step S208, step S209 can be omitted.

  According to the above configuration, in a scene in which the light and darkness of the narrow-angle forward illuminance Sfn is repeated in a short period due to the shadow of the tree-lined tree, the absolute value of the difference between the narrow-angle forward illuminance Sfn and the wide-angle forward illuminance Sfw is the second divergence. It can be expected that the target luminance L is determined by using the wide-angle front illuminance Sfw instead of the narrow-angle front illuminance Sfn in step S205. For this reason, in a scene where the brightness of the narrow-angle forward illuminance Sfn is repeated in a short cycle due to the shadow of the tree lined tree, there is a risk that the brightness of the HUD image 10 will be darkened more than necessary, and the HUD image may be changed due to frequent switching of the display brightness. The risk of flickering 10 can be reduced.

  In the configuration of the fourth modification, the target luminance L is corrected according to the display area, and the display luminance is changed. As a result of various tests conducted by the inventors, even when the HUD image 10 is displayed with the same luminance, the amount of light entering the driver's field of view increases as the display area increases, causing the driver to feel dazzling. I got the knowledge that there was something. The correction process based on the display area is a configuration introduced based on the above knowledge, and the target luminance L is set to a smaller value as the display area is larger. That is, control is performed such that the display luminance is suppressed as the display area is increased. According to such a configuration, the risk of causing the driver to feel dazzling can be further reduced.

[Modification 5]
In the above-described embodiment, the configuration in which the target luminance L is determined based on the upper illuminance Su when the absolute value of the difference between the upper illuminance Su and the front illuminance Sf is less than a predetermined deviation threshold is disclosed. Not exclusively. When the absolute value of the difference between the upper illuminance Su and the front illuminance Sf is less than the deviation threshold, the target luminance L may be determined based on the front illuminance Sf. When the absolute value of the difference between the upper illuminance Su and the front illuminance Sf is less than the deviation threshold, the target luminance L is determined based on the higher of the front illuminance Sf and the upper illuminance Su. It may be configured.

1 HUD device (head-up display device), 2 image signal source, 3 vehicle speed sensor, 4 upward illumination sensor, 5 forward illumination sensor, 5A narrow angle forward illumination sensor, 5B wide angle forward illumination sensor, 6 locator, F1 vehicle speed acquisition unit, F2 upper illuminance acquisition unit, F3 forward illuminance acquisition unit, F4 target luminance setting unit, F41 residual distance calculation unit, F42 β adjustment unit (mixing ratio adjustment unit), F5 luminance adjustment unit, F6 display area specification unit, F7 luminance correction unit

Claims (8)

A head-up display device that is used in a vehicle and displays a virtual image on a predetermined area in front of a driver seat by projecting light representing an image onto a projection member,
An upper illuminance acquisition unit (F2) that acquires the detection result of the upper illuminance sensor, which is an illuminance sensor arranged to detect the illuminance above the vehicle, as upper illuminance;
A front illuminance acquisition unit (F3) that acquires a detection result of a front illuminance sensor, which is an illuminance sensor arranged to detect the illuminance of a predetermined area in front of the vehicle, as front illuminance;
A target luminance setting unit (F4) for determining a target luminance which is a target value of the display luminance of the image;
A luminance adjustment unit (F5) that displays the image at the target luminance determined by the target luminance setting unit,
When the absolute value of the difference between the upper illuminance acquired by the upper illuminance acquisition unit and the front illuminance acquired by the front illuminance acquisition unit is equal to or greater than a predetermined deviation threshold, the target luminance setting unit A head-up display that calculates a mixed illuminance, which is a value obtained by mixing the front illuminance and the upper illuminance using a blend coefficient, and determines the display luminance of the image based on the calculated mixed illuminance. apparatus. The head-up display device according to claim 1,
A residual distance calculation unit that estimates a residual distance to a culvert area where the illuminance on the side of the vehicle is assumed to be less than the culvert threshold when the upper illuminance is equal to or greater than a predetermined culvert threshold. (F41)
A mixing ratio adjustment unit (F42) that adjusts the value of the blend coefficient based on the residual distance estimated by the residual distance calculation unit;
The mixing ratio adjusting unit sets the blending coefficient so that a ratio of components derived from the front illuminance in the mixed illuminance increases as the remaining distance decreases, and the target luminance setting unit adjusts the mixing ratio. The target brightness is determined based on the mixed illuminance determined using the blend coefficient adjusted by a unit. The head-up display device according to claim 2,
A vehicle speed acquisition unit (F1) that sequentially acquires the traveling speed of the vehicle;
The front illuminance sensor is installed in the vehicle with a predetermined detection distance and a posture capable of detecting the brightness of a road surface located in front of the vehicle,
The residual distance calculation unit determines that the residual distance is the detection distance when the front illuminance is less than the undercast threshold, and a lapse from the time when the forward illuminance falls below the undercast threshold. The head-up display device characterized by sequentially calculating the remaining distance based on time and the traveling speed sequentially acquired by the vehicle speed acquisition unit. The head-up display device according to any one of claims 1 to 3,
When the absolute value of the difference between the upper illuminance and the front illuminance is less than the deviation threshold, the target luminance setting unit does not use the front illuminance and changes the display luminance of the image based on the upper illuminance. A head-up display device characterized by determining. The head-up display device according to claim 1,
The front illuminance sensor is a narrow-angle front illuminance sensor in which a detection angle range is set to a predetermined angle or less,
The head-up display device is an illuminance sensor in which a detection angle range is set wider than that of the narrow-angle forward illuminance sensor, and the wide-angle forward illuminance sensor arranged to detect the illuminance in front of the vehicle. Connected,
The front illuminance acquisition unit acquires the detection result of the narrow-angle front illuminance sensor as a narrow-angle front illuminance, and acquires the detection result of the wide-angle front illuminance sensor as a wide-angle front illuminance.
When the upper illuminance is equal to or greater than a predetermined undercast threshold, a remaining distance that estimates the remaining distance that is the remaining distance to the undercast point that is assumed to be less than the undercast threshold. A calculation unit (F41);
A mixing ratio adjustment unit (F42) that adjusts the value of the blend coefficient based on the residual distance estimated by the residual distance calculation unit;
The target luminance setting unit has an absolute value of a difference between the upper illuminance and the narrow-angle forward illuminance that is equal to or greater than a first divergence threshold as the divergence threshold, and the narrow-angle forward illuminance and the wide-angle forward illuminance When the absolute value of the difference is less than a predetermined second deviation threshold, a value obtained by mixing the narrow-angle forward illuminance and the upper illuminance using the blend coefficient adjusted by the mixing ratio adjustment unit , Determine the target brightness using the mixed illuminance,
The mixing ratio adjustment unit sequentially updates the blending coefficient so that the proportion of components derived from the narrow-angle forward illuminance increases in the mixed illuminance as the residual distance calculated by the residual distance calculation unit decreases. A head-up display device. The head-up display device according to claim 5,
The target luminance setting unit has an absolute value of a difference between the upper illuminance and the narrow-angle front illuminance that is equal to or greater than the first divergence threshold, and an absolute value of a difference between the narrow-angle front illuminance and the wide-angle front illuminance. Is equal to or greater than the second deviation threshold, the target luminance is determined using the value obtained by mixing the wide-angle forward illuminance and the upper illuminance using a predetermined static blend coefficient as the mixed illuminance. A head-up display device. The head-up display device according to claim 5 or 6,
The target luminance setting unit determines the display luminance of the image based on the upper illuminance when the absolute value of the difference between the upper illuminance and the narrow-angle forward illuminance is less than the first deviation threshold. A head-up display device. The head-up display device according to any one of claims 1 to 7,
The target brightness setting unit
A display area specifying unit (F6) for specifying a display area indicating the size of the image;
A head-up display device comprising: a correction unit (F7) that corrects the target luminance according to the display area acquired by the display area specifying unit.

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