JP7517334B2 - Head-up display device - Google Patents

Description

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

For example, there is known a head-up display device that displays a virtual image to a vehicle driver by projecting display light onto a projection member such as a windshield. For example, the head-up display device described in Patent Document 1 includes a liquid crystal display unit, LEDs (Light Emitting Diodes) that irradiate light onto the liquid crystal display unit, and a control unit that controls the liquid crystal display unit and the LEDs. The control unit includes a PWM microcomputer that generates and outputs a PWM signal, and an LED driver IC (Integrated Circuit) that generates a drive current based on the PWM signal from the PWM microcomputer and outputs the generated drive current to the LED.

JP 2018-017878 A

Generally, LED driver ICs have a fault detection function that detects faults such as shorts or opens in the LED circuit. However, for example, if a malfunction of an electronic component or circuit causes a current larger than the desired drive current value to flow, to the extent that the fault detection function does not detect a short, the LED driver IC cannot detect the fault through the fault detection function.

The present invention has been made in consideration of the above-mentioned situation, and aims to provide a head-up display device that can accurately detect malfunctions.

In order to achieve the above object, a head-up display device according to an aspect of the present invention is a head-up display device that displays a virtual image by projecting display light onto a projection member,
the display device includes a light source, a display panel that receives light from the light source and emits the display light, a microcomputer that controls the display panel, outputs a first PWM signal, and acquires a cathode voltage of the light source, and a light source driver that receives the first PWM signal from the microcomputer and outputs a second PWM signal that is an amplified version of the first PWM signal to the light source, thereby turning on the light source, wherein the microcomputer includes a memory unit that stores data indicating a normal range of the cathode voltage and a duty ratio of the first PWM signal, which includes a normal time when there is no luminance abnormality fault related to the luminance of the light source, and a high luminance abnormality range in which the cathode voltage falls outside the normal range with respect to the duty ratio of the first PWM signal, and a processing unit that determines that the luminance abnormality fault has occurred when a specific point identified by the acquired cathode voltage and the duty ratio of the outputted first PWM signal is present within the high luminance abnormality range of the data.

According to the present invention, malfunctions can be accurately detected in a head-up display device.

1 is a schematic diagram of a vehicle equipped with a head-up display device according to an embodiment of the present invention. 1 is a schematic diagram of a head-up display device according to an embodiment of the present invention. 1 is a block diagram of a head-up display device according to an embodiment of the present invention. 4 is a circuit diagram of a smoothing unit according to an embodiment of the present invention. FIG. 11 is a diagram illustrating data showing a normal range, a high luminance abnormal range, and a low luminance abnormal range of the relationship between the duty ratio of the second PWM signal and the cathode voltage according to one embodiment of the present invention. FIG. 5 is a flowchart showing a luminance abnormality determination process according to an embodiment of the present invention. 5 is a timing chart showing a second PWM signal, a light source current, a cathode voltage, and a failure detection signal during normal operation according to an embodiment of the present invention. 6 is a timing chart showing a second PWM signal, a light source current, a cathode voltage, and a fault detection signal when a short circuit fault occurs in one embodiment of the present invention. 6 is a timing chart showing a second PWM signal, a light source current, a cathode voltage, and a fault detection signal when an open fault occurs in one embodiment of the present invention. 11 is a timing chart showing a second PWM signal, a light source current, a cathode voltage, and a failure detection signal when a luminance abnormality occurs in one embodiment of the present invention.

An embodiment of a head-up display device according to the present invention will be described with reference to the drawings.
1, the head-up display device 100 is installed in the dashboard of a vehicle 200. The head-up display device 100 emits display light L representing an image toward a windshield 201, which is an example of a projection target member of the vehicle 200. The display light L is reflected by the windshield 201 and reaches a viewer 1 (mainly the driver of the vehicle 200). As a result, a virtual image V is displayed so as to be visible to the viewer 1.

First, the mechanical configuration of the head-up display device 100 will be described.
As shown in FIG. 2 , the head-up display device 100 includes a display unit 10 , a plane mirror 20 , a concave mirror 30 , a housing 60 , and a control unit 70 .

The display unit 10 emits display light L that displays an image under the control of the control unit 70. The display unit 10 includes a display panel 14 and an illumination device 18.
The plane mirror 20 reflects the display light L emitted by the display unit 10 toward the concave mirror 30. The concave mirror 30 reflects the display light L reflected by the plane mirror 20 toward the windshield 201 while magnifying it.

The housing 60 is made of a non-transparent resin or metal and has a hollow, substantially rectangular parallelepiped shape. Each component of the head-up display device 100 is housed inside the housing 60.
An opening 61 is formed in the housing 60 at a position facing the windshield 201. The housing 60 includes a curved plate-like window portion 50 that closes the opening 61. The window portion 50 is made of a translucent resin such as acrylic that transmits the display light L.

The display panel 14 is a TFT (Thin Film Transistor) type liquid crystal display panel controlled by the control unit 70. The display panel 14 receives light from the lighting device 18 and emits display light L.

The lighting device 18 is located behind the display panel 14 and has a plurality of light sources 18a consisting of a plurality of LEDs that illuminate the display panel 14 under the control of the control unit 70.

Next, the electrical configuration of the head-up display device 100 will be described.
As shown in FIG. 3, the head-up display device 100 includes a control unit 70 including a microcomputer 71 and an LED driver IC 72, a plurality of light sources 18a, the display panel 14, a capacitor C1, and a smoothing unit 73.
The microcomputer 71 controls the display panel 14, and also controls the lighting of the light source 18a via an LED driver IC 72. The microcomputer 71 includes a processing unit 71a consisting of a CPU (Central Processing Unit) that executes an operation program, a ROM (Read Only Memory) 71b in which the operation program of the processing unit 71a, a table Tb, and the like are stored, and a RAM (Random Access Memory) 71c used as a work area for the processing unit 71a.
The microcomputer 71 receives an external light intensity detection signal Sa indicating the surrounding brightness included in vehicle information from an on-board ECU (Electronic Control Unit), generates a first PWM signal Spwm1 having a duty ratio according to the external light intensity detection signal Sa, and outputs the generated first PWM signal Spwm1 to the LED driver IC 72. The higher the light intensity of the external light indicated by the external light intensity detection signal Sa, the higher the duty ratio of the first PWM signal Spwm1 is set.
The microcomputer 71 receives a fault detection signal Sf, which will be described later and indicates the presence or absence of a fault, from the LED driver IC 72. When the microcomputer 71 receives the fault detection signal Sf indicating the presence of a fault, the microcomputer 71 stops outputting the first PWM signal Spwm1, thereby turning off the light source 18a.
The microcomputer 71 also receives a cathode voltage Vk2 (described later) and performs a luminance abnormality determination process in which the microcomputer 71 determines whether or not there is a luminance abnormality in the virtual image V based on the input cathode voltage Vk2 and the duty ratio of the output first PWM signal Spwm1 while referring to a table Tb, and turns off the light source 18a when it determines that there is a luminance abnormality. This luminance abnormality determination process will be described later.

The LED driver IC 72 is a switch circuit that receives a voltage from a voltage source Vc and generates a second PWM signal Spwm2 by boosting (amplifying) the first PWM signal Spwm1. The second PWM signal Spwm2 is a signal synchronized with the first PWM signal Spwm1. The LED driver IC 72 supplies a light source current Iled to a plurality of light sources 18a connected in series via the second PWM signal Spwm2. As shown in FIG. 7, the light source current Iled is a signal synchronized with the second PWM signal Spwm2. As a result, the light source 18a is turned on with a brightness according to the duty ratio of the second PWM signal Spwm2, and a virtual image V is displayed.

A cathode voltage Vk1, which is the voltage on the cathode terminal side of the light source 18a, is input to the LED driver IC 72. The LED driver IC 72 includes a short circuit failure detection unit 72a that detects a short circuit failure in the circuit related to the light source 18a based on the cathode voltage Vk1, an open circuit failure detection unit 72b that detects an open circuit failure in the circuit related to the light source 18a based on the cathode voltage Vk1, and a low voltage failure detection unit 72c that detects a low voltage failure in which the voltage from the voltage source Vc drops.
When a fault is detected by at least one of the short circuit fault detection unit 72a, the open circuit fault detection unit 72b, and the low voltage fault detection unit 72c, the LED driver IC 72 outputs a fault detection signal Sf indicating the presence of a fault to the microcomputer 71.

The anode terminal of the light source 18a is connected to an LED driver IC 72, and the cathode terminal of the light source 18a is connected to both the microcomputer 71 and the LED driver IC 72.
One end of the capacitor C1 is connected between the cathode terminal of the light source 18a and the LED driver IC 72, and the other end of the capacitor C1 is connected to ground. The capacitor C1 has a function of suppressing noise superimposed on the cathode voltage Vk1. A plurality of capacitors C1 may be provided in parallel with each other.

The smoothing unit 73 is connected between the cathode terminal of the light source 18a and the microcomputer 71, generates a constant cathode voltage Vk2 having a voltage value according to the duty ratio of the cathode voltage Vk1, and outputs the generated cathode voltage Vk2 to the microcomputer 71.
More specifically, as shown in FIG. 4, the smoothing unit 73 includes capacitors C2 and C3, a Zener diode ZD, and resistors R1 and R2.
The resistors R1 and R2 are connected in series between the cathode terminal of the light source 18a and the microcomputer 71. One end of the capacitor C3 is connected between the two resistors R1 and R2, and the other end of the capacitor C3 is connected to ground.
The capacitor C3 and the resistors R1 and R2 function to generate a constant cathode voltage Vk2 having a voltage value according to the duty ratio of the cathode voltage Vk1.
The cathode terminal of the Zener diode ZD is connected between the resistor R2 and the cathode terminal of the light source 18a, and the anode terminal of the Zener diode ZD is connected to ground. The Zener diode ZD has a function of suppressing input of a surge current to the microcomputer 71 by breaking down when a surge current is input and causing the surge current to flow to ground.
One end of the capacitor C2 is connected between the resistor R1 and the microcomputer 71, and the other end of the capacitor C2 is connected to the ground. The capacitor C2 has a function of suppressing noise superimposed on the cathode voltage Vk2.

As shown in FIG. 5, the table Tb includes a normal range A1, a high luminance abnormal range A2, and a low luminance abnormal range A3.
Next, a method for generating the table Tb stored in the ROM 71b will be described. The table Tb is generated by a designer.
First, the relationship between the duty ratio of the first PWM signal Spwm1 and the cathode voltage Vk2 in the normal state is plotted at points shown by a triangular shape in FIG. 5, and the plotted points are connected by a line Ln. In the normal state, none of the short circuit failure, open circuit failure, low voltage failure, and luminance abnormality failure described later occurs. The normal range A1 is set to a range centered on the line Ln, with the first difference value Th1 as the lower limit and the second difference value Th2 as the upper limit. The first difference value Th1 and the second difference value Th2 are the difference values of the cathode voltage Vk2. The low luminance abnormal range A3 is set to a range exceeding the second difference value Th2. The high luminance abnormal range A2 is set to a range less than the first difference value Th1.
The first difference value Th1 is set to a value smaller than the second difference value Th2, so that the high luminance abnormality range A2 is set to an area closer to the line Ln than the low luminance abnormality range A3.
The method of using this table Tb will be described later.

Next, the luminance abnormality determination process executed by the microcomputer 71 (processing unit 71a) will be described with reference to the flowchart of Fig. 6. This luminance abnormality determination process is repeatedly executed during the period in which the first PWM signal Spwm1 is output from the microcomputer 71.
First, the microcomputer 71 acquires the duty ratio of the first PWM signal Spwm1 being output and the cathode voltage Vk2 (step S101). Then, the microcomputer 71 refers to the table Tb stored in the ROM 71b and determines whether or not a specific point P identified by the acquired duty ratio and cathode voltage Vk2 is within the normal range A1 (step S102). As illustrated by the specific point P1 in FIG. 5, if it is determined that the specific point P is within the normal range A1 (step S102: YES), it is determined that there is no luminance abnormality (step S103), and the luminance abnormality determination process is terminated.

On the other hand, when the microcontroller 71 determines that the specific point P is not within the normal range A1 (step S102: NO), it determines that a brightness abnormality fault has occurred, that is, the specific point P is within the high brightness abnormal range A2 as illustrated by the specific point P2 in FIG. 5, or the specific point P is within the low brightness abnormal range A3 as illustrated by the specific point P3 in FIG. 5 (step S104).
When the specific point P2 is in the high luminance abnormal range A2, the luminance of the virtual image V becomes higher than the desired value, and the viewer 1 feels that the virtual image V is too bright compared to the background (real scenery) and is dazzling, which reduces visibility. Also, when the specific point P3 is in the low luminance abnormal range A3, the luminance of the virtual image V becomes lower than the desired value, and the viewer 1 feels that the contrast between the virtual image V and the background (real image) decreases, which reduces visibility.

When the microcomputer 71 determines that a luminance abnormality has occurred (step S104), it turns off the light sources 18a (step S105) and ends the luminance abnormality determination process. This causes a luminance abnormality to occur, and the display of the virtual image V with a luminance different from the desired value is stopped.

The above-mentioned brightness abnormality failure is a failure that cannot be detected by the LED driver IC 72. This point will be described with reference to FIGS.
As shown in Fig. 7, during normal operation, the light source current Iled is supplied to the light source 18a in synchronization with the second PWM signal Spwm2. In addition, the cathode voltage Vk1 is a signal obtained by inverting the Hi and Lo of the second PWM signal Spwm2 and the light source current Iled, since the current is consumed by the light source 18a. During normal operation, the cathode voltage Vk1 varies within a preset normal range C. When the cathode voltage Vk1 is within the normal range C, the LED driver IC 72 sets the fault detection signal Sf to Hi (3.3V), which indicates that there is no fault, and when the cathode voltage Vk1 is outside the normal range C, the LED driver IC 72 sets the fault detection signal Sf to Lo (0V), which indicates that there is a fault.

Next, as shown in FIG. 8, in the event of a short circuit failure, the light source current Iled becomes a large current and is not synchronized with the second PWM signal Spwm2. In the event of a short circuit failure, the cathode voltage Vk1 exceeds the short circuit threshold value Ts, which is the upper limit of the normal range C. When the cathode voltage Vk1 exceeds the short circuit threshold value Ts, the LED driver IC 72 sets the failure detection signal Sf to Lo.

Next, as shown in FIG. 9, in the event of an open fault, the light source current Iled becomes zero and does not synchronize with the second PWM signal Spwm2. In the event of an open fault, the cathode voltage Vk1 becomes less than the open threshold value To, which is the lower limit of the normal range C. When the cathode voltage Vk1 becomes less than the open threshold value To, the LED driver IC72 sets the fault detection signal Sf to Lo.

Next, a luminance abnormality failure will be described. In this luminance abnormality failure, for example, the capacitor C1 shown in Fig. 3 has a resistance due to a failure, so that the light source current Iled becomes larger than in a normal state and smaller than when a short circuit occurs.
In the case of this luminance abnormality failure, as shown in FIG. 10, the light source current Iled is supplied to the light source 18a in synchronization with the second PWM signal Spwm2, but the central value of the waveform of the oscillating light source current Iled is greater than the central value of the waveform of the light source current Iled in the normal state shown in FIG. 7. Therefore, the luminance of the light source 18a becomes high. However, in the case of this luminance abnormality failure, the cathode voltage Vk1 changes within the normal range C. When the cathode voltage Vk1 is within the normal range C, the LED driver IC 72 sets the failure detection signal Sf to Hi, which indicates that there is no failure. Therefore, this luminance abnormality failure is not detected by the LED driver IC 72. This luminance abnormality failure that is not detected by the LED driver IC 72 is detected by the above-mentioned luminance abnormality determination process. That is, the above-mentioned luminance abnormality determination process determines the presence or absence of a luminance abnormality failure that is not detected by the LED driver IC 72, and can turn off the light source 18a when it is determined that there is a luminance abnormality failure.

(effect)
According to the embodiment described above, the following effects are achieved.
(1) The head-up display device 100 displays a virtual image V by projecting display light L onto a windshield 201, which is an example of a projection target member. The head-up display device 100 includes a light source 18a formed of an LED, a display panel 14 that receives light from the light source 18a and emits the display light L, a microcomputer 71 that controls the display panel 14, outputs a first PWM signal Spwm1, and acquires a cathode voltage Vk2 of the light source 18a, and an LED driver IC 72, which is an example of a light source driver that receives the first PWM signal Spwm1 from the microcomputer 71, amplifies the first PWM signal Spwm1, and outputs a second PWM signal Spwm2 to the light source 18a to turn on the light source 18a. The microcomputer 71 includes a ROM 71b, which is an example of a storage unit, storing a table Tb showing the relationship between the cathode voltage Vk2 and the duty ratio of the first PWM signal Spwm1, the table having a normal range A1 in a normal state where there is no luminance abnormality fault related to the luminance of the virtual image V, and a high luminance abnormal range A2 where the cathode voltage Vk2 falls outside the normal range A1 and becomes lower with respect to the duty ratio of the first PWM signal Spwm1, and a processing unit 71a that determines that a luminance abnormality fault has occurred when a specific point P2 determined by the acquired cathode voltage Vk2 and the duty ratio of the output first PWM signal Spwm1 is within the high luminance abnormal range A2 of the table Tb, which is data. When the processing unit 71a determines that there is a luminance abnormality fault, it stops outputting the first PWM signal Spwm1 and turns off the light source 18a.
According to this configuration, when the current value supplied to the light source 18a becomes larger than the desired value, although not as large as the overcurrent at the time of a short circuit, due to a malfunction of an electronic component other than a short circuit, the specific point P2 specified by the acquired cathode voltage Vk2 and the duty ratio of the output first PWM signal Spwm1 is within the high brightness abnormal range A2 of the table Tb. At this time, the processing unit 71a judges the luminance abnormality malfunction. Therefore, it becomes possible to detect a luminance abnormality malfunction that is not detected as a short circuit malfunction, and thus it becomes possible to detect the malfunction with high accuracy. In addition, when the processing unit 71a judges the luminance abnormality malfunction, it stops the output of the first PWM signal Spwm1 and turns off the light source 18a. Therefore, a virtual image V that makes the viewer 1 feel dazzled due to a malfunction of an electronic component or circuit that is not detected as a short circuit malfunction is not displayed.

(2) The table Tb has a low luminance abnormal range A3 in which the cathode voltage Vk2 becomes higher than the normal range A1 with respect to the duty ratio of the first PWM signal Spwm1. When the specific point P3 is within the low luminance abnormal range A3 of the table Tb, the processing unit 71a determines that a luminance abnormality failure has occurred, stops outputting the first PWM signal Spwm1, and turns off the light source 18a.
According to this configuration, when the light source current Iled supplied to the light source 18a becomes smaller than the desired value due to a malfunction of an electronic component other than an open circuit malfunction, although not as small as the open circuit malfunction, the specific point P3 specified by the acquired cathode voltage Vk2 and the duty ratio of the output first PWM signal Spwm1 falls within the low brightness abnormal range A3 of the table Tb. At this time, the processing unit 71a judges that a luminance abnormality malfunction has occurred, stops the output of the first PWM signal Spwm1, and turns off the light source 18a. Thus, the luminance of the virtual image V is prevented from decreasing due to a malfunction of an electronic component that is not detected as an open circuit malfunction, and the display of the virtual image V is prevented from continuing in a state of reduced visibility.

(3) A first difference value Th1 of the cathode voltage Vk2 from the specific point P1 (triangular plot in FIG. 5) in the normal state to the high luminance abnormal range A2 in the table Tb is smaller than a second difference value Th2 of the cathode voltage Vk2 from the specific point P1 in the normal state to the low luminance abnormal range A3. The specific point P1 in the normal state is determined based on, for example, the duty ratio and the cathode voltage Vk2 at the initial time when the head-up display device 100 is manufactured.
According to this configuration, when the luminance of the virtual image V increases due to a malfunction of an electronic component, the light source 18a is turned off more quickly than when the luminance of the virtual image V decreases due to a malfunction of an electronic component. Therefore, the virtual image V that causes the viewer 1 to feel dazzled is not displayed.

(4) The LED driver IC 72 includes a short circuit failure detection unit 72a that detects a short circuit failure in the circuit related to the light source 18a when the cathode voltage Vk1 exceeds the short threshold value Ts, and an open circuit failure detection unit 72b that detects an open circuit failure in the circuit related to the light source 18a when the cathode voltage Vk1 is less than the open circuit threshold value To. When the short circuit failure detection unit 72a does not detect a short circuit failure and the open circuit failure detection unit 72b does not detect an open circuit failure, the processing unit 71a determines that a luminance abnormality failure has occurred when the specific point P is within the low luminance abnormality range A3 or the high luminance abnormality range A2 of the table Tb, and stops outputting the first PWM signal Spwm1 to turn off the light source 18a.
According to this configuration, even if a brightness abnormality failure occurs that cannot be detected by the short circuit failure detection unit 72a and the open circuit failure detection unit 72b, the specific point P will be within the high brightness abnormality range A2 or the low brightness abnormality range A3, and the light source 18a will be turned off.

Note that the present invention is not limited to the above-described embodiments and drawings. Modifications (including the deletion of components) can be made as appropriate within the scope of the present invention without changing the gist of the invention. An example of a modification is described below.

(Modification)
In the above embodiment, the table Tb includes the normal range A1, the high luminance abnormal range A2, and the low luminance abnormal range A3, but the low luminance abnormal range A3 may be omitted.
In addition, in the above embodiment, the first difference value Th1 was set to a value smaller than the second difference value Th2, but the first difference value Th1 may be set to the same value as the second difference value Th2, or the first difference value Th1 may be set to a value larger than the second difference value Th2.

In the above embodiment, the display unit 10 was provided with a display panel 14 which was a TFT type liquid crystal display panel, but this is not limited thereto and may also be provided with an organic EL (Electro-Luminescence) type display panel.

In the above embodiment, the LED driver IC 72 was equipped with a short circuit failure detection unit 72a, an open circuit failure detection unit 72b, and a low voltage failure detection unit 72c, but at least one of the short circuit failure detection unit 72a, the open circuit failure detection unit 72b, and the low voltage failure detection unit 72c may be omitted.

In the above embodiment, when the microcomputer 71 determines that there is a luminance abnormality malfunction (step S104), it turns off the multiple light sources 18a (step S105) and ends the luminance abnormality determination process.
When the brightness of the virtual image V becomes higher than the desired value in a dark situation around the vehicle (a situation in which the intensity of external light indicated by the external light intensity detection signal Sa is low), the viewer 1 is particularly likely to find the virtual image V dazzling, and visibility is likely to be reduced.
Therefore, when the microcontroller 71 determines that the light intensity of the external light indicated by the external light intensity detection signal Sa is lower than a predetermined threshold value and that the surroundings of the vehicle are dark, and determines that there is a brightness abnormality fault (step S104), it is preferable to turn off the multiple light sources 18a (step S105).

In the above embodiment, when the microcontroller 71 determines that there is a luminance abnormality malfunction (step S104), it may notify the viewer 1 of the luminance abnormality malfunction through a notification means such as an indicator, while turning off the multiple light sources 18a, or without turning off the multiple light sources 18a.

In the above embodiment, the head-up display device 100 is mounted on the vehicle 200, but it may also be mounted on a vehicle other than the vehicle 200, such as an airplane or a ship. In addition, the projection member is not limited to the windshield, and may be a dedicated combiner.

REFERENCE SIGNS LIST 1: viewer 10: display unit 14: display panel 18: lighting device 18a: light source 20: plane mirror 30: concave mirror 50: window unit 60: housing 61: opening 70: control unit 71: microcomputer 71a: processing unit 71b: ROM
71c RAM
72 LED driver IC
72a Short circuit failure detection unit 72b Open circuit failure detection unit 72c Low voltage failure detection unit 73 Smoothing unit 100 Head-up display device 200 Vehicle 201 Windshield A1 Normal range A2 High brightness abnormal range A3 Low brightness abnormal range C Normal ranges C1, C2, C3 Capacitor L Display light P, P1, P2, P3 Specific points R1, R2 Resistor V Virtual image ZD Zener diode Sa External light intensity detection signal Tb Table Sf Fault detection signal Vc Voltage source Th1 First difference value Th2 Second difference value Vk1, Vk2 Cathode voltage Ts Short circuit threshold To Open circuit threshold Iled Light source current Spwm1 First PWM signal Spwm2 Second PWM signal

Claims (5)

A head-up display device that displays a virtual image by projecting display light onto a projection member,
A light source;
a display panel that receives light from the light source and emits the display light;
a microcomputer that controls the display panel, outputs a first PWM signal, and acquires a cathode voltage of the light source;
a light source driver that receives the first PWM signal from the microcomputer and outputs a second PWM signal obtained by amplifying the first PWM signal to the light source, thereby turning on the light source;
The microcomputer is
a storage unit that stores data indicating a normal range including a normal time when there is no luminance abnormality failure related to the luminance of the light source, for the cathode voltage and the duty ratio of the first PWM signal, and a high luminance abnormal range in which the cathode voltage falls outside the normal range and becomes low with respect to the duty ratio of the first PWM signal;
and a processing unit that determines that the luminance abnormality has occurred when a specific point determined by the acquired cathode voltage and the duty ratio of the output first PWM signal is within the high luminance abnormality range of the data.
Head-up display device. When the processing unit determines that a luminance abnormality has occurred, the processing unit stops outputting the first PWM signal to turn off the light source.
The head-up display device according to claim 1 . the data includes information on a low luminance abnormal range in which the cathode voltage becomes higher than the normal range with respect to the duty ratio of the first PWM signal,
The processing unit determines that the luminance abnormality has occurred when the specific point is within the low luminance abnormality range of the data, and stops outputting the first PWM signal to turn off the light source.
The head-up display device according to claim 2 . In the data, a first difference value of the cathode voltage from the specific point to the high luminance abnormal range in the normal state is smaller than a second difference value of the cathode voltage from the specific point to the low luminance abnormal range in the normal state.
The head-up display device according to claim 3 . The light source driver includes:
a short circuit failure detection unit that detects a short circuit failure in a circuit related to the light source when the cathode voltage exceeds a short circuit threshold;
an open circuit failure detection unit that detects an open circuit failure in the circuit related to the light source when the cathode voltage becomes less than an open circuit threshold;
When the short circuit failure detection unit does not detect a short circuit failure and the open circuit failure detection unit does not detect an open circuit failure, and when the specific point is within the low luminance abnormality range or the high luminance abnormality range of the data, the processing unit determines that the luminance abnormality failure has occurred, stops outputting the first PWM signal, and turns off the light source.
The head-up display device according to claim 3 or 4.

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