Head-up display device

Abstract

A head-up display device is provided which, despite a simpler design, can assess a luminance anomaly of a light source more quickly. The head-up display device (100) comprises a display unit (14), a light source (18a) which is switched on so that light is emitted to the display unit (14), a light source driver IC (72) which switches on the light source (18a), and a microcomputer (71) which outputs the ADIM signal (Sadim) instructing the light source current (lled) to the light source driver IC (72), thereby supplying the light source current (lled) instructed by the ADIM signal (Sadim) to the light source (18a) and performing feedback input of the output ADIM signal (Sadim) as an ADIM feedback signal (Sfb).The microcomputer (71) includes a luminosity anomaly assessment part (71b) which assesses whether a luminosity anomaly of the light source (18a) is present by comparing the ADIM signal (Sadim) and the ADIM feedback signal (Sfb).

Description

Head-up display device

[0001] The present invention relates to a head-up display device.

[0002] For example, a head-up display device described in Patent Document 1 includes an LED (Light Emitting Diode) and a microcomputer that outputs a first PWM signal and acquires a cathode voltage of the LED. The microcomputer detects a brightness abnormality fault when it determines that a specific point identified by the cathode voltage and the duty ratio of the first PWM signal is within a high brightness abnormality range.

[0003] International Publication No. 2020 / 235683

[0004] In the configuration described in Patent Document 1, the cathode voltage of the LED is monitored, so an abnormality cannot be detected until a voltage is actually applied to the LED. Also, a configuration that directly monitors the drive line of the LED may require a complicated design to ensure that the configuration does not interfere with the normal lighting of the LED.

[0005] The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide a head-up display device that has a simpler configuration and can more quickly determine abnormalities in the brightness of a light source.

[0006] In order to achieve the above object, a head-up display device according to an aspect of the present invention comprises a display, a light source that lights up to emit light to the display, a driver that lights up the light source, and a microcomputer that outputs a lighting signal that commands a light source current or a light source voltage to the driver, thereby supplying the light source current or the light source voltage commanded by the lighting signal to the light source, and feeds back and inputs the output lighting signal as a feedback lighting signal, and the microcomputer comprises a brightness abnormality determination unit that determines whether or not there is a brightness abnormality in the light source by comparing the output lighting signal with the input feedback lighting signal.

[0007] According to the present invention, in a head-up display device, it is possible to more quickly determine whether a luminance abnormality of a light source has occurred, while still having a simpler configuration.

[0008] 1 is a schematic diagram of a vehicle equipped with a head-up display device according to one embodiment of the present invention. 2 is a schematic diagram of a head-up display device according to one embodiment of the present invention. 3 is a block diagram of a head-up display device according to one embodiment of the present invention. 4 (a) to (c) are diagrams showing waveforms of an ADIM signal and an ADIM feedback signal when there is no luminance abnormality according to one embodiment of the present invention. 5 (a) and (b) are diagrams showing waveforms of an ADIM signal and an ADIM feedback signal when there is a luminance abnormality according to one embodiment of the present invention. 6 (a) and (b) are diagrams showing waveforms of an ADIM signal and an ADIM feedback signal when there is a luminance abnormality according to one embodiment of the present invention. 7 is a flowchart showing the procedure of a luminance abnormality determination process according to one embodiment of the present invention.

[0009] An embodiment of a head-up display device according to the present invention will be described with reference to the drawings. As shown in Fig. 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.

[0010] 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 .

[0011] 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 14 and an illumination device 18.

[0012] 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 (see FIG. 1 ) while magnifying the light. The plane mirror 20 may be a concave mirror.

[0013] The housing 60 is made of non-transparent resin or metal and has a hollow, approximately 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-shaped window 50 that closes the opening 61. The window 50 is made of a translucent resin such as acrylic, through which the display light L passes.

[0014] The display 14 is a TFT (Thin Film Transistor) liquid crystal display panel controlled by the control unit 70. The display 14 receives light from the illumination device 18 and emits display light L.

[0015] The lighting device 18 is located behind the display 14 and illuminates the display 14 with illumination light. The lighting device 18 includes a plurality of light sources 18a that emit light to the display 14 under the control of the control unit 70. Each light source 18a is made of an LED.

[0016] Next, a description will be given of the electrical configurations of the display unit 10 and the control unit 70. As shown in Fig. 3, the display unit 10 includes a plurality of light sources 18a, a display 14, and a signal adjustment circuit 73. The control unit 70 includes a microcomputer 71, a light source driver IC 72, and an input voltage switching circuit 78.

[0017] The input voltage switching circuit 78 is provided between the power supply voltage Vc and the light source driver IC 72, and switches between an ON state and an OFF state in response to a control signal Sc from the microcomputer 71. When the input voltage switching circuit 78 is in the ON state, a voltage from the power supply voltage Vc is applied to the light source driver IC 72. When the input voltage switching circuit 78 is in the OFF state, the application of voltage from the power supply voltage Vc to the light source driver IC 72 is stopped.

[0018] The light source driver IC 72 is a switch circuit that receives a power supply voltage Vc and generates a second PWM (Pulse Width Modulation) signal Spwm2 by boosting a first PWM signal Spwm1 (described later) from the microcomputer 71. The second PWM signal Spwm2 is a signal synchronized with the first PWM signal Spwm1. The light source driver IC 72 supplies a light source current Iled to the multiple light sources 18a via the second PWM signal Spwm2. The anode terminals of the light sources 18a are connected to the light source driver IC 72. The cathode terminals of the light sources 18a are connected to the microcomputer 71 via a signal adjustment circuit 73.

[0019] The signal adjustment circuit 73 receives the voltages (anode voltage and cathode voltage Vct) across the light source 18a, generates a PWM feedback signal Sfp that is a feedback signal for the second PWM signal Spwm2, and outputs the generated PWM feedback signal Sfp to the microcomputer 71. The signal adjustment circuit 73 generates the binarized PWM feedback signal Sfp by comparing the cathode voltage of the light source 18a with a threshold value. The signal adjustment circuit 73 includes a capacitor, a resistor, and a switching element.

[0020] The microcomputer 71 includes a processing section such as a CPU (Central Processing Unit) that executes an operation program, a ROM (Read Only Memory) that stores the operation program of the processing section, and a RAM (Random Access Memory) that is used as a work area for the processing section. The microcomputer 71 includes, as functional blocks, a dimming section 71a, a brightness abnormality determination section 71b, and a display control section 71c that controls the display 14.

[0021] The dimming unit 71a controls the lighting of the light source 18a via the light source driver IC 72. The dimming unit 71a receives a requested luminance signal Sa from an external device and lights the light source 18a at the requested luminance included in the requested luminance signal Sa. The requested luminance signal Sa increases in proportion to an external light intensity detection value indicating the ambient brightness included in vehicle information from an on-board ECU (Electronic Control Unit). When the display unit 10 is powered on, the dimming unit 71a outputs an enable signal Sen to the light source driver IC 72 to enable operation of the light source driver IC 72. After determining a luminance abnormality, which will be described later, the dimming unit 71a disables operation of the light source driver IC 72 by stopping output of the enable signal Sen.

[0022] The dimming unit 71a adjusts the brightness of the light source 18a by adjusting the duty ratio of the first PWM signal Spwm1 and the duty ratio of the ADIM (analog dimming input) signal Sadim. The higher the on-duty ratio of the first PWM signal Spwm1, the longer the time that the light source current Iled is supplied to the light source 18a, and the higher the brightness of the light source 18a. The higher the on-duty ratio of the ADIM signal Sadim, the higher the peak current value of the light source current Iled. The frequency of the first PWM signal Spwm1 is set, for example, to 1 kHz to several hundred kHz. The frequency of the ADIM signal Sadim is set, for example, to several tens of kHz, preferably 50 kHz.

[0023] When the required brightness is within the normal brightness range, the dimming unit 71a generates the first PWM signal Spwm1 having a duty ratio according to the required brightness while fixing the duty ratio of the ADIM signal Sadim to a specified value.Within the normal brightness range, the higher the required brightness is, the higher the on-duty ratio of the first PWM signal Spwm1 is set to.

[0024] When the required brightness is within a low brightness range that is set lower than the normal brightness range, the dimming unit 71a generates an ADIM signal Sadim with a duty ratio corresponding to the required brightness while fixing the duty ratio of the first PWM signal Spwm1 at a lower limit. Within the low brightness range, the higher the required brightness, the higher the on-duty ratio of the ADIM signal Sadim is set. The lower limit of the duty ratio of the first PWM signal Spwm1 is set to, for example, 0.2%.

[0025] The luminance abnormality determination unit 71b determines whether or not there is an abnormality in the luminance of the light source 18a based on the ADIM signal Sadim output from the microcomputer 71 and an ADIM feedback signal Sfb, which is a feedback signal of the ADIM signal Sadim. The ADIM signal Sadim has a pulse waveform that is periodically turned on for an on-time Ton1, as shown in FIG. 4A. Ideally, the ADIM feedback signal Sfb has the same waveform as the ADIM signal Sadim. However, in actual raw data, the waveform is dulled relative to the ADIM signal Sadim due to electronic components such as capacitors, resistors, and switches in the light source driver IC 72, as shown in FIG. 4B.

[0026] As shown in FIGS. 4B and 4C, when the raw data ADIM feedback signal Sfb is equal to or greater than the ON threshold value THon, the brightness abnormality determination unit 71b determines that the ADIM feedback signal Sfb is ON. When the raw data ADIM feedback signal Sfb is equal to or less than the OFF threshold value THoff, the brightness abnormality determination unit 71b determines that the ADIM feedback signal Sfb is OFF. As a result, the ADIM feedback signal Sfb is binarized as shown in FIG. 4C. In this example, the ON threshold value THon is set to a value different from the OFF threshold value THoff, i.e., a value greater than the OFF threshold value THoff. However, this is not limiting, and the ON threshold value THon may be set to a value smaller than the OFF threshold value THoff, or the ON threshold value THon and the OFF threshold value THoff may be set to the same value.

[0027] 4(a) and 4(c), the luminance abnormality determination unit 71b determines that there is no luminance abnormality in the light source 18a when the difference between the on-time Ton1 of the ADIM signal Sadim and the on-time Ton2 of the ADIM feedback signal Sfb is equal to or less than a predetermined value Tk. When the luminance abnormality determination unit 71b determines that there is no luminance abnormality in the light source 18a, the dimming unit 71a continues to control the lighting of the light source 18a.

[0028] On the other hand, as shown in FIGS. 5(a), (b) and 6(a), (b), the luminance abnormality determination unit 71b determines that the light source 18a has a luminance abnormality when the difference ΔT between the on-time Ton1 of the ADIM signal Sadim and the on-time Ton2 of the ADIM feedback signal Sfb is equal to or greater than the specified value Tk. Possible causes of this luminance abnormality include, for example, a malfunction of the microcomputer 71 or a malfunction of the light source 18a. In the example of FIGS. 5(a) and (b), the on-time Ton2 of the ADIM feedback signal Sfb is longer than the on-time Ton1 of the ADIM signal Sadim, and the difference ΔT between the on-times Ton1 and Ton2 is equal to or greater than the specified value Tk. In the example of FIGS. 6(a) and (b), the on-time Ton2 of the ADIM feedback signal Sfb is shorter than the on-time Ton1 of the ADIM signal Sadim, and the difference ΔT between the on-times Ton1 and Ton2 is equal to or greater than the specified value Tk. When the luminance abnormality determination unit 71b determines that the light source 18a has a luminance abnormality, the light control unit 71a executes a shutdown process, which will be described later.

[0029] Next, the luminance abnormality determination process executed by the microcomputer 71 will be described with reference to the flowchart in Fig. 7. This luminance abnormality determination process is repeatedly executed while the microcomputer 71 is controlling the lighting of the light source 18a. When the light source 18a is turned on, the light control unit 71a determines whether or not there is a luminance abnormality in the light source 18a (step S101). If the light control unit 71a determines that there is no luminance abnormality in the light source 18a (step S101; NO), the luminance abnormality determination process ends without performing the processes of steps S102 to S104.

[0030] On the other hand, if the dimming unit 71a determines that the light source 18a has a luminance abnormality (step S101; YES), it executes the shutdown process of steps S102 to S104. Specifically, the dimming unit 71a stops outputting the enable signal Sen to the light source driver IC 72 (step S102). Next, the dimming unit 71a stops outputting the ADIM signal Sadim to the light source driver IC 72 (step S103). Next, the dimming unit 71a turns off the input voltage switching circuit 78 via the control signal Sc (step S104). Through steps S102 to S104, the light source 18a is turned off in each of the three separate systems, shutting down the illumination device 18. This allows for more reliable shutdown of the illumination device 18. This prevents, for example, the light source 18a from becoming abnormally bright and dazzling the driver. For example, if a failure occurs such that the enable signal Sen is fixed at a high level, the light source 18a cannot be turned off by the processing of step S102, but even in such a case, the light source 18a can be turned off by the processing of steps S103 and S104. Furthermore, the display control unit 71c terminates the display on the display 14 when the illumination device 18 is shut down.

[0031] (Effects) According to the embodiment described above, the following effects are achieved. (1) The head-up display device 100 includes a display 14, a light source 18a that lights up to emit light to the display 14, a light source driver IC 72 that is an example of a driver that lights up the light source 18a, and a microcomputer 71 that outputs an ADIM signal Sadim that is an example of a lighting signal that commands a light source current Iled to the light source driver IC 72, thereby supplying the light source current Iled commanded by the ADIM signal Sadim to the light source 18a and feeding the output ADIM signal Sadim back as an ADIM feedback signal Sfb that is an example of a feedback lighting signal. The microcomputer 71 includes a luminance abnormality determination unit 71b that determines whether or not there is a luminance abnormality in the light source 18a by comparing the output ADIM signal Sadim with the input ADIM feedback signal Sfb. According to this configuration, by using the ADIM feedback signal Sfb to determine whether a luminance abnormality has occurred, it is possible to determine whether a luminance abnormality has occurred in the light source 18a more quickly than when the light source current Iled or the light source voltage is used to determine whether a luminance abnormality has occurred. Furthermore, because monitoring the ADIM feedback signal Sfb does not affect the light source current Iled or the light source voltage, a configuration to minimize the effect on the light source current Iled is not required. This allows for a simpler configuration. Furthermore, there is no need to use a current detection amplifier to determine whether a luminance abnormality has occurred, allowing for a simpler configuration.

[0032] (2) The luminance abnormality determination unit 71b compares the on-time Ton1, which is an example of the first on-time of the ADIM signal Sadim, with the on-time Ton2, which is an example of the second on-time of the ADIM feedback signal Sfb, and determines that a luminance abnormality exists when the difference ΔT between the on-time Ton1 and the on-time Ton2 is equal to or greater than a predetermined value Tk. When the luminance abnormality determination unit 71b determines that a luminance abnormality exists, the microcomputer 71 turns off the light source 18a. With this configuration, the luminance abnormality of the light source 18a can be easily determined by comparing the on-time Ton1 of the ADIM signal Sadim with the on-time Ton2 of the ADIM feedback signal Sfb. Furthermore, when the luminance abnormality determination unit 71b determines that a luminance abnormality exists, the light source 18a is turned off. This prevents the luminance of the light source 18a from becoming excessively high, thereby preventing the viewer 1 from being dazzled.

[0033] (3) The light source 18a is an LED. The microcomputer 71 receives an ADIM signal (analog dimming signal) Sadim, which commands the light source current Iled, as an ADIM feedback signal Sfb. Changes in the light source current Iled tend to affect the brightness of the light source 18a. Therefore, by using the ADIM signal Sadim, which commands the light source current Iled, to determine whether a brightness abnormality has occurred, it is possible to suppress the discomfort felt by the viewer 1 due to the brightness abnormality.

[0034] (4) The microcomputer 71 includes a first shutdown unit that stops outputting to the light source driver IC 72 an enable signal Sen that enables operation of the light source driver IC 72, a second shutdown unit that stops outputting the ADIM signal Sadim to the light source driver IC 72, and a third shutdown unit that stops application of the power supply voltage Vc to the light source driver IC 72. When the luminance abnormality determination unit 71b determines that there is a luminance abnormality, the microcomputer 71 sequentially operates the first shutdown unit, the second shutdown unit, and the third shutdown unit to turn off the light source 18a. With this configuration, when the luminance abnormality determination unit 71b determines that there is a luminance abnormality, the light source 18a can be turned off more reliably.

[0035] The present invention is not limited to the above-described embodiments and drawings. Modifications (including the omission of components) can be made as appropriate within the scope of the present invention. An example of a modification will be described below.

[0036] (Modifications) In the shutdown process of the above embodiment, the processes are executed in the order of step S102, step S103, and step S104, but this order can be changed as appropriate. Steps S102 to S104 may also be executed simultaneously. Furthermore, any two of the three steps S102 to S104 may be omitted. The shutdown process may also include stopping the output of the first PWM signal Spwm1. The ADIM feedback signal Sfb may also be a signal that has passed through the light source driver IC 72.

[0037] In the above embodiment, when the luminance abnormality determination unit 71b determines that the light source 18a has a luminance abnormality, the display control unit 71c may switch the display 14 to a non-transmitting state (black display state), thereby preventing the viewer 1 viewing the virtual image V from being dazzled.

[0038] In the above embodiment, the lighting signal is the ADIM signal Sadim and the feedback lighting signal is the ADIM feedback signal Sfb, but this is not limiting, and the lighting signal may be the first PWM signal Spwm1 and the feedback lighting signal may be the detection signal Son.

[0039] In the above embodiment, the display 14 is a liquid crystal display panel, but is not limited to this and may be a reflective display such as a DMD (Digital Micro Mirror Device) element.

[0040] In the above embodiment, when the microcomputer 71 determines that there is a brightness abnormality in the light source 18a (step S101; YES), it turns off the multiple light sources 18a. However, it is also possible to notify the viewer 1 that there is a brightness abnormality through a notification means such as an indicator without turning off the multiple light sources 18a.

[0041] In the above embodiment, the head-up display device 100 is mounted on the vehicle 200, but it may be mounted on a vehicle other than the vehicle 200, such as an airplane or a ship. In addition, the projection target member is not limited to the windshield 201, and may be a dedicated combiner.

[0042] 1 Viewer 10 Display unit 14 Display 18 Illumination device 18a Light source 20 Plane mirror 30 Concave mirror 50 Window unit 60 Housing 61 Opening 70 Control unit 71 Microcomputer 71a Dimming unit 71b Determination unit 71c Display control unit 72 Light source driver IC 73 Signal adjustment circuit 78 Input voltage switching circuit 100 Head-up display device 200 Vehicle 201 Windshield L Display light ΔT Difference V Virtual image Sa Request luminance signal Sc Control signal Vc Power supply voltage Tk Specified value Sfb ADIM feedback signal Sen Enable signal Son Detection signals Ton1, Ton2 On time Iled Light source current THon On threshold THoff Off threshold Spwm1 First PWM signal Spwm2 Second PWM signal Sadim ADIM signal

Claims

1. A head-up display device comprising: a display; a light source that lights up to emit light to the display; a driver that lights up the light source; and a microcomputer that outputs a lighting signal that commands a light source current or a light source voltage to the driver, thereby supplying the light source current or the light source voltage commanded by the lighting signal to the light source, and feeds back and inputs the output lighting signal as a feedback lighting signal, wherein the microcomputer comprises a brightness abnormality determination unit that determines whether or not there is a brightness abnormality in the light source by comparing the output lighting signal with the input feedback lighting signal.

2. The head-up display device according to claim 1, wherein the luminance abnormality determination unit compares the first on-time of the lighting signal with the second on-time of the feedback lighting signal, and determines that a luminance abnormality exists when the difference between the first on-time and the second on-time is equal to or greater than a predetermined value, and the microcomputer turns off the light source when the luminance abnormality determination unit determines that a luminance abnormality exists.

3. A head-up display device according to claim 1 or 2, wherein the light source is an LED, and the microcomputer feedback-inputs an analog dimming signal, which is the lighting signal that commands the light source current, as the feedback lighting signal.

4. A head-up display device as described in claim 1, wherein the microcomputer comprises: a first shutdown unit that stops outputting an enable signal to the driver that enables operation of the driver; a second shutdown unit that stops outputting the lighting signal to the driver; and a third shutdown unit that stops application of power supply voltage to the driver, and when the brightness abnormality determination unit determines that there is a brightness abnormality, the microcomputer operates any two or more of the first shutdown unit, the second shutdown unit, and the third shutdown unit in sequence or simultaneously.

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