Head-up display device

Abstract

To provide a head-up display device which offers improved display quality when re-displaying images.SOLUTION: A head-up display device 100 configured to output display light L to a windshield 201 is provided, comprising a light source 18a for outputting illumination light, a display 14 configured to output display light L when irradiated with the illumination light, and a drive control unit configured to perform driving operation for turning on and off the light source 18a according to an entered requested brightness signal Sa.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] For example, the head-up display device described in Patent Document 1 includes an LED (Light Emitting Diode), a microcomputer that outputs a first PWM signal and acquires the cathode voltage of the LED, and a driver that receives the first PWM signal from the microcomputer and outputs a second PWM signal that is a boosted version of the first PWM signal to the LED, thereby lighting up the LED. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2020 / 235683 Summary of the Invention [Problem to be solved by the invention]

[0004] The inventors have discovered for the first time that there is room for improvement in the display quality of such a head-up display device when it is turned on again (re-displayed) from a temporary off (non-displayed) state.

[0005] SUMMARY OF THE INVENTION In view of the above-mentioned problems, an object of the present invention is to provide a head-up display device with improved display quality when re-displaying. [Means for solving the problem]

[0006] In order to achieve the above object, a head-up display device according to the present invention comprises: A head-up display device that emits display light to a projection member, a light source that emits illumination light; a display that emits the display light when illuminated by the illumination light; Entered a drive control unit that performs a drive operation to turn on and off the light source in response to a control signal; Equipped with The drive control unit turns off the light source. When switching to lighting at a first luminance, an operation of lighting at a second luminance brighter than the first luminance and then lighting at the first luminance is performed; The drive control unit performs the operation only when the first luminance is lower than a predetermined luminance. .

[0007] In another aspect, the head-up display device according to the present invention comprises: A head-up display device that emits display light to a projection member, a light source that emits illumination light; a display that emits the display light when illuminated by the illumination light; a drive control unit that performs a drive operation to turn on and off the light source in response to an input control signal; Equipped with When switching the light source from off to on at a first luminance, the drive control unit turns on the light source at a second luminance that is brighter than the first luminance and then turns on the light source at the first luminance. Action Work stomach, The drive control unit performs the operation only when the light source is turned on again within a predetermined period of time from the time the light source was turned off. .

[0009] In another aspect, the head-up display device according to the present invention comprises: A head-up display device that emits display light to a projection member, a light source that emits illumination light; a display that emits the display light when illuminated by the illumination light; a drive control unit that performs a drive operation to turn on and off the light source in response to an input control signal; Equipped with The drive control unit driving the light source by changing a pulse width modulation signal and a current value; The on-duty ratio of the pulse width modulation signal is Value of When the brightness that is smaller than the above is defined as a third brightness, The aforementioned When switching to lighting at the third brightness, the on-duty ratio of the pulse width modulation signal is so that it is equal to or greater than the predetermined valueWhile increasing the current value Low reduce Action Perform the work. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic diagram of a vehicle equipped with a head-up display device 100 according to a first embodiment. [Figure 2] 1 is a schematic diagram of a head-up display device 100 according to a first embodiment. [Figure 3] FIG. 1 is a block diagram of head-up display devices 100, 101, and 103. [Figure 4] FIG. 1 is a block diagram of a head-up display device 102. DETAILED DESCRIPTION OF THE INVENTION

[0011] An embodiment of a head-up display device according to the present invention will be described with reference to the drawings. [First embodiment] 1-1.Configuration explanation 1-2. Explanation of behavior 1-3. Variations [Second embodiment] 2-1. Explanation of behavior 2-2. Variations [Third embodiment] 3-1. Description of the configuration 3-2. Explanation of behavior [Fourth embodiment] [Variations]

[0012] [First embodiment] <1-1. Description of the configuration> 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 that displays 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.

[0013] 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 .

[0014] 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 device 14 and an illumination device 18.

[0015] 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 it. The plane mirror 20 may be a concave mirror.

[0016] The housing 60 is made of non-transparent resin or metal and has a hollow, substantially rectangular parallelepiped shape. The housing 60 houses each component of the head-up display device 100. 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.

[0017] 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.

[0018] 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 a control unit 70 (an example of a drive control unit). Each light source 18a is made up of an LED.

[0019] Next, the electrical configuration of the display unit 10 and the control unit 70 will be described. 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 80 (an example of a transformer circuit).

[0020] The input voltage switching circuit 80 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 80 is in the ON state, a transformed voltage obtained by transforming the input power supply voltage Vc to a level that can be input to the light source 18a is applied to the light source driver IC 72. The transformed voltage is a voltage used for the operation of the light source driver IC 72. When the input voltage switching circuit 80 is in the OFF state, application of the transformed voltage to the light source driver IC 72 is stopped.

[0021] The light source driver IC 72 is a switch circuit that receives the transformed voltage and generates a second PWM (Pulse Width Modulation) signal Spwm2 (drive signal) by boosting a first PWM signal Spwm1 (lighting signal) (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.

[0022] The microcomputer 71 includes a processing unit such as a CPU (Central Processing Unit) that executes an operating program, a ROM (Read Only Memory) in which the operating program of this processing unit is stored, and a RAM (Random Access Memory) that is used as a work area for this processing unit. The microcomputer 71 includes, as functional blocks, a dimming unit 71a, a brightness abnormality determining unit 71b, and a display control unit 71c that controls the display device 14.

[0023] 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 (an example of a control signal) indicating a requested luminance from the outside, and lights up the light source 18a via the light source driver IC 72 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), for example. The requested luminance signal Sa may also be a signal that sets the luminance to zero (turns off) by operation of the viewer 1 or the like. When the power supply of the display unit 10 is turned on, the dimmer 71a outputs an enable signal Sen to the light source driver IC 72 to permit operation of the light source driver IC 72. After determining that there is a luminance abnormality, which will be described later, the dimmer 71a stops outputting the enable signal Sen to disable operation of the light source driver IC 72.

[0024] The dimming unit 71a adjusts the duty ratio of the first PWM signal Spwm1 and the duty ratio of the ADIM (analog dimming input) signal Sadim to adjust the brightness of the light source 18a. The higher the on-duty ratio of the first PWM signal Spwm1, the longer the time (on-time) during one period during which 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 to, for example, 1 kHz to several hundred kHz, and the frequency of the ADIM signal Sadim is set to, for example, several tens of kHz, preferably 50 kHz.

[0025] When the required brightness is within the normal brightness range, the dimming unit 71a switches to the normal brightness mode, and generates the first PWM signal Spwm1 with a duty ratio according to the required brightness while fixing the duty ratio of the ADIM signal Sadim to a specified value. In the normal brightness mode, the higher the required brightness, the higher the on-duty ratio of the first PWM signal Spwm1 is set.

[0026] When the required brightness is within a low brightness range that is set lower than the normal brightness range, the dimming unit 71a enters a low brightness mode, and 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 its lower limit. In the low brightness mode, the higher the required brightness, the higher the on-duty ratio of the ADIM signal Sadim is set. The lower limit of the on-duty ratio of the first PWM signal Spwm1 is set to, for example, 0.2%.

[0027] The display control unit 71c controls the display unit 14 to change the content displayed on the display unit 14 in accordance with the input signal.

[0028] <1-2. Explanation of behavior> In order to provide a head-up display device with improved display quality at the time of redisplay, the head-up display device 100 operates in the following manner.

[0029] When switching the light source 18a from an off state to an on state in response to a requested luminance signal, the control unit 70, which is an example of a drive control unit, performs a delay operation to delay switching to on state by a first period.

[0030] Specifically, when a request luminance signal Sa indicating that the light source 18a should be switched from an off state to an on state is input to the control unit 70, the control unit 70 switches the light source 18a to the on state with a delay of a first period from the time of input.

[0031] In conventional head-up display devices, when a requested brightness signal Sa is input, the light source 18a is switched on without a significant delay. For example, in this conventional example, the only delay is due to the response characteristics of a typical electrical circuit, resulting in a delay of at most 1 microsecond. In such conventional head-up display devices, if the light source is turned on while the state of the electrical circuit (mainly the state of residual charge) is unstable, such as immediately after the light source is turned off, the light source may flicker (blink, brightness may fluctuate), resulting in a decrease in display quality. The inventors were the first to discover this problem.

[0032] In this embodiment, the delay operation delays the switching to the lighting state by a first period (for example, about 1 to 5 seconds) from the input of the request luminance signal Sa. The control unit 70 may perform the delay operation based on a program that delays the signal by a predetermined period based on a clock signal, or may perform the delay operation by dulling the signal using a capacitor or the like. The delay operation may be performed by the microcomputer 71 provided in the control unit 70 or by the light source driver IC 72. The delay operation is preferably about 3 seconds.

[0033] The head-up display device 100 that performs this delay operation can prevent the light source 18a from being turned on when the internal charge state is unstable, such as immediately after the light source 18a is turned off, thereby resulting in a head-up display device with improved display quality when re-displaying.

[0034] <1-3. Variations> Although the first embodiment has been described above, the head-up display device of the present invention is not limited to this configuration.

[0035] For example, in the first embodiment, the control unit 70 performs a delay operation to delay switching to on for a first period of time, but it is more preferable that the control unit 70 performs the delay operation only when switching the light source from off to on at a low brightness.

[0036] The light source used in a head-up display device may be illuminated at an extremely low brightness because it is also used for displaying in environments such as at night or inside a tunnel. At such extremely low brightness (for example, 5% or less, more preferably 1% or less, of the maximum brightness of the light source), the current and voltage of the drive signal that drives the light source also become small, and fluctuations in the operation of the control unit 70 and the input voltage switching circuit 80 tend to become noticeable. For example, if the operation fluctuation occurs when lighting is started at low brightness, the second PWM signal Spwm2 becomes a relatively weak signal (low voltage and small on-duty ratio), and it may be relatively difficult for the light source driver IC 72 and the input voltage switching circuit 80 to stably output such a signal immediately after lighting is started.

[0037] Therefore, with this configuration, while achieving the objectives of the present application, by limiting the conditions for delay operation, a head-up display device can be obtained that can display information as quickly as before when performing a driving operation that is relatively unlikely to cause display disturbances.

[0038] Furthermore, for example, it is more preferable that the control unit 70 performs the delay operation only when the light source 18a is turned on again within a predetermined period of time after it was turned off.

[0039] Immediately after light source 18a is turned off, the state within the circuit is not in a steady state, and charges may remain in each circuit and element. Therefore, if light source 18a is turned on again immediately after being turned off, fluctuations in the operation of control unit 70 and input voltage switching circuit 80 are likely to occur.

[0040] Therefore, with this configuration, while achieving the objectives of the present application, by limiting the conditions for delay operation, a head-up display device can be obtained that can display information as quickly as before when performing a driving operation that is relatively unlikely to cause display disturbances.

[0041] The two modifications shown here may be combined.

[0042] [Second embodiment] In the second embodiment, a description will be given of a head-up display device 101. Regarding the head-up display device 101, differences in configuration from the head-up display device 100 shown in the first embodiment will be described in detail.

[0043] <2-1. Explanation of behavior> In order to provide a head-up display device with improved display quality at the time of redisplay, the head-up display device 101 operates in the following manner based on the configuration shown in FIG.

[0044] When switching the light source 18a from an off state to a lit state at a first brightness in response to a requested brightness signal, the control unit 70, which is an example of a drive control unit, performs a buffer operation of lighting the light source 18a at a second brightness that is brighter than the first brightness, and then lighting the light source 18a at the first brightness.

[0045] Specifically, when a requested brightness signal Sa indicating that the light source 18a should be switched from an off state to a lighting state at a first brightness is input to the control unit 70, the control unit 70 turns on the light source 18a at a second brightness that is brighter than the requested first brightness, and then turns on the light source 18a at the first brightness.

[0046] In a conventional head-up display device, when a requested luminance signal Sa is input, the light source 18a is turned on at the luminance (first luminance) indicated by the requested luminance signal Sa. In this conventional example, although there may be slight fluctuations in luminance due to the characteristics of general electrical circuits, the light source 18a is turned on at a luminance that roughly corresponds to the first luminance. However, in a conventional head-up display device, when the light source is switched from an off state to an on state at low luminance, the state of the electrical circuit (mainly the state of residual charge) may cause the light source to flicker (blink, the luminance fluctuates), resulting in a decrease in display quality. The inventors were the first to discover this problem.

[0047] In this embodiment, the buffering operation is performed by the control unit 70, after receiving a request luminance signal Sa requesting lighting at a first luminance, lighting the light source 18a at a second luminance and then lighting it at the first luminance. For example, if the luminance of the light source 18a is low when lighting begins, the light source driver IC 72 and the input voltage switching circuit 80 may experience a delay in the rise of their output. However, if the control unit 70 lights the light source 18a at a second luminance brighter than the first luminance and then lights it at the first luminance, the rise delay can be eliminated.

[0048] The head-up display device 101 that performs this buffering operation can suppress flickering of the light source 18a even if there is a delay in the rise of the output of the control unit 70 or the input voltage switching circuit 80 immediately after the light source 18a starts to light up, thereby resulting in a head-up display device with improved display quality when re-displaying.

[0049] <2-2. Modifications> Although the second embodiment has been described above, the head-up display device of the present invention is not limited to this configuration.

[0050] For example, in the second embodiment, it is more preferable that the control unit 70 performs the buffering operation only when the first luminance is lower than a predetermined luminance. Delays in the rise of the output of the control unit 70 or the input voltage switching circuit 80 tend to occur when lighting starts at a low luminance. The predetermined luminance is, for example, about 5% of the maximum luminance of the light source 18a, more preferably about 1%.

[0051] As an example, when the control unit 70 receives a requested brightness signal Sa instructing lighting at a brightness of about 0.5% (first brightness), the control unit 70 lights the light source 18a at a brightness of about 1% (second brightness) and then lights the light source 18a at a brightness of about 0.5%.

[0052] Therefore, with this configuration, while achieving the object of the present application, by limiting the conditions for performing the buffering operation, when performing a driving operation that is relatively unlikely to cause display disturbance, the head-up display device can quickly display at the required brightness as before.

[0053] Furthermore, for example, it is more preferable that the control unit 70 performs the delay operation only when the light source 18a is turned on again within a predetermined period of time after it was turned off.

[0054] According to this configuration, while achieving the objectives of the present application, by limiting the conditions for delay operation, a head-up display device can be obtained that can display information as quickly as before when performing a driving operation that is relatively unlikely to cause display disturbances.

[0055] The two modifications shown here may be combined.

[0056] Furthermore, when switching from the second brightness to the first brightness, it is more desirable that the control unit 70 switch to the first brightness by gradually changing the brightness over a predetermined number of seconds (approximately 1 to 5 seconds, for example, approximately 3 seconds).

[0057] [Third embodiment] In the third embodiment, a description will be given of a head-up display device 102. Regarding the head-up display device 102, differences in configuration from the head-up display device 100 shown in the first embodiment will be described in detail.

[0058] <3-1. Description of the configuration> 4 shows a block diagram of the head-up display device 102. The head-up display device 102 includes a discharge circuit 74 that electrically connects the microcomputer 71 and the anode side wiring (power supply line) of the light source 18a.

[0059] The discharge circuit 74 discharges the charge remaining in the anode wiring of the light source 18a when the light source 18a is switched from a lit state to an extinguished state. Specifically, the discharge circuit 74 is a circuit that switches the anode wiring between a high impedance state and a state connected to ground potential. The discharge circuit 74 switches this switching state depending on the potential of the output IO port of the microcomputer 71.

[0060] <3-2. Explanation of behavior> While the light source 18a is on, the discharge circuit 74 puts the anode side wiring into a high impedance state, enabling the light source driver IC 72 to drive the light source 18a. Also, while the light source 18a is off, the discharge circuit 74 connects the anode side wiring to ground potential.

[0061] In conventional head-up display devices, when the light source is turned off, a charge may remain in the power supply line (for example, the anode wiring of an LED), causing the light source 18a to temporarily light up when the display is restored, but the light soon returns to being off, and then lights up again when normal power is supplied. This problem was discovered for the first time by the inventors.

[0062] Therefore, by providing a discharge circuit 74, the residual charge when the light source 18a is turned off can be discharged, preventing the light from lighting up (flashing) when the light is re-displayed, thereby resulting in a head-up display device with improved display quality when the light is re-displayed.

[0063] The discharge circuit 74 does not necessarily have to discharge charges based on control by the microcomputer 71. For example, the discharge circuit 74 may discharge charges based on an enable signal from the light source driver IC 72, or may discharge charges based on a signal that controls the lighting of the light source and the start of display.

[0064] Furthermore, the discharge circuit 74 may continue to discharge charges while the light source 18a is turned off, or may discharge charges for only a predetermined period (for example, a period of less than one second) after the light source 18a has turned off.

[0065] [Fourth embodiment] In the fourth embodiment, a description will be given of a head-up display device 103. Regarding the head-up display device 103, differences in configuration from the head-up display device 100 shown in the first embodiment will be described in detail.

[0066] <3-1. Explanation of behavior> If the luminance at which the on-duty ratio of the second PWM signal Spwm2 becomes smaller than a predetermined value is defined as the third luminance, when the microcomputer 71 (drive control unit) switches the light source 18a from an off state to an on state at the third luminance, the microcomputer 71 (drive control unit) performs a buffering operation to turn on the light source 18a with a larger on-duty ratio than normal but with a light source current Iled smaller than normal.

[0067] In conventional head-up display devices, the light source is turned on using a PWM signal. However, if the on-duty ratio of the PWM signal becomes smaller than a predetermined value, the rise time of the output of the drive control unit such as the light source driver IC and the power unit such as the input voltage switching circuit and the transformer circuit may become slow. The inventors were the first to discover this problem.

[0068] Therefore, in the head-up display device 103, as described above, the control unit 70 increases the on-duty ratio of the PWM signal when the on-duty ratio is small. However, if this continues, the luminance of the light source 18a will increase more than necessary, so the light source current Iled is reduced.

[0069] This configuration also provides a head-up display device with improved display quality when re-displaying. In the fourth embodiment, a configuration that combines the modifications shown in Section 1-3 and Section 2-2 may also be adopted. In such modifications, the conditions for performing the buffering operation can be limited, and the control of the light source can be simplified.

[0070] [Variations] 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. An example of a modification is described below. The following modifications may be combined as appropriate.

[0071] 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 Micromirror Device) element.

[0072] 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.

[0073] Also, the embodiment has been shown in which power is supplied to the light source 18a from the input voltage switching circuit 80 via the light source driver IC 72. However, the light source 18a may be directly connected to the input voltage switching circuit 80 and supplied with power. In this case, the power supplied by the input voltage switching circuit 80 may be supplied from the anode side wiring of the light source 18a, and the light source driver IC 72 may drive the light source 18a by controlling whether or not a current flows in the cathode side wiring of the light source 18a. [Explanation of symbols]

[0074] 1. Viewer 10 Display 14 Display 18 Lighting equipment 18a light source 20 plane mirror 30 concave mirror 50 Window 60 cabinets 61 Opening 70 Control Unit 71 Microcomputer 71a Dimming section 71c Display control unit 72 Light source driver IC 73 Signal conditioning circuit 80 Input voltage switching circuit 100 Head-up display device 200 vehicles 201 Windshield L display light V Virtual Image Sa required luminance signal Sc control signal Vc power supply voltage Sen enable signal Sfp PWM feedback signal Vct Cathode voltage Iled light source current Spwm1 1st PWM signal Spwm2 2nd PWM signal Sadim ADIM signal

Claims

1. A head-up display device that emits display light to a projection member, a light source that emits illumination light; a display that emits the display light when illuminated by the illumination light; a drive control unit that performs a drive operation to turn on and off the light source in response to an input control signal; Equipped with the drive control unit, when switching the light source from off to on at a first luminance, performs an operation of lighting the light source at a second luminance that is brighter than the first luminance and then lighting the light source at the first luminance, The drive control unit performs the operation only when the first luminance is lower than a predetermined luminance. Head-up display device.

2. A head-up display device that emits display light to a projection member, a light source that emits illumination light; a display that emits the display light when illuminated by the illumination light; a drive control unit that performs a drive operation to turn on and off the light source in response to an input control signal; Equipped with the drive control unit, when switching the light source from off to on at a first luminance, performs an operation of lighting the light source at a second luminance that is brighter than the first luminance and then lighting the light source at the first luminance, The drive control unit performs the operation only when the light source is turned on again within a predetermined period of time from the time the light source was turned off. Head-up display device.

3. A head-up display device that emits display light to a projection member, a light source that emits illumination light; a display that emits the display light when illuminated by the illumination light; a drive control unit that performs a drive operation to turn on and off the light source in response to an input control signal; Equipped with The drive control unit driving the light source by changing a pulse width modulation signal and a current value; If the luminance at which the on-duty ratio of the pulse width modulation signal becomes smaller than a predetermined value is defined as a third luminance, when the light source is switched from off to on at the third luminance, the on-duty ratio of the pulse width modulation signal is increased so as to become equal to or greater than the predetermined value, while the current value is reduced. Head-up display device.

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