JP2017146401A - Display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a display device that can cause a light source to emit light at desired luminance.SOLUTION: An HUD device comprises: a power supply part 300 supplying current I; a plurality of light sources 11 receiving the current I from the power supply part 300 to emit different colors of light; an inductor stores electric charge with the current I when the current I is supplied to the light source 11; a display element 30 having a plurality of micromirrors controlling a reflection angle of light; and first and second control parts 100, 200 that supply the current I to any one of the plurality of light sources 11 to thereby cause the one to emit light, generate desired illumination light by a field sequential method for sequentially switching the light sources 11, and that reflect, through the micromirror, light of the illumination light corresponding to a display image. Furthermore, the HUD device comprises an electric charge emission part 700 that under the control of the first and second control parts 100, 200, discharges electric charge stored in the inductor to the ground before the light source 11 is turned on.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a display device.

Conventionally, as a display device, for example, a configuration in which a DMD (Digital Micro-mirror Device) as a display element is provided is known. This type of display device generates image light by reflecting illumination light with a plurality of micromirrors of the DMD. For example, the display device described in Patent Literature 1 selectively emits any one of three light sources that emit red, green, and blue light, and switches the light source to emit light at a desired color. It operates by the so-called field sequential system that generates the illumination light.
More specifically, as shown in FIG. 13, in this type of display device, the display period Fa and the non-display period Fb are alternately repeated. In the display period Fa, an image is generated through driving of the display element and the light source. In the non-display period Fb, all the light sources are turned off and the micromirror is driven so as to suppress the failure of the DMD micromirror. Further, as shown in FIG. 13, the display device supplies a high luminance current Ih to each light source when the luminance of the high light source is required. On the other hand, as shown in FIG. 14, this display device supplies a low-intensity current Il smaller than the current Ih to each light source when the luminance of a low light source is required.

  In addition, this type of display device, for example, as described in Patent Document 2, controls the back electromotive force generation coil and the current direction, and supplies the back electromotive force generated in the coil to the light source. And a provided diode.

JP, 2014-010417, A JP 2014-107440 A

  In the configuration described in Patent Document 2, when a current is supplied to the first light source selected by the field sequential method, charges are stored in the first coil corresponding to the first light source by the current. . Next, when a current is supplied to the second light source, the charge stored in the first coil is superimposed on the current. Accordingly, as shown in FIG. 13, at the time t1, t2, t3,..., When current supply to each light source is started, a ripple Rp is superimposed as noise on the current Ih supplied to each light source. When the ripple Rp is superimposed, there is a possibility that the light source is turned on at a luminance higher than the desired luminance, and as a result, there is a possibility that the gradation display in the display device is affected. In particular, as shown in FIG. 14, when the luminance of a low light source is required, the current Il supplied to each light source is small, so that the ratio of the ripple Rp to the current Il is large. For this reason, especially when the luminance of the light source is low, the influence of the ripple Rp on the luminance of the light source becomes large.

  This invention is made | formed in view of the said actual condition, and it aims at providing the display apparatus which can light a light source with desired brightness | luminance.

  In order to achieve the above object, a display device of the present invention includes a power supply unit that supplies current, a plurality of light sources that receive current from the power supply unit, and emits light of different colors, and a current is supplied to each light source. When supplied, a charge part that stores electric charge by the current, a display element having a plurality of reflection parts for controlling the angle at which light is reflected, and the power supply part to any one of the plurality of light sources And generating light of a desired color from the light emitted from the plurality of light sources by a field sequential method in which one of the light sources emits light by supplying a current from the light source, and the light sources to be emitted are sequentially switched. A control unit that reflects light corresponding to a display image of the illumination light through the reflection unit, and under the control of the control unit, before the light source is turned on, It comprises a charge-emitting unit for emitting a charge stored in the serial charge unit.

  According to the present invention, the light source can be turned on with a desired luminance.

It is a mimetic diagram of a vehicle carrying a head up display device concerning one embodiment of the present invention. It is the schematic which shows the structure of the head-up display apparatus which concerns on one Embodiment of this invention. It is the schematic which shows the structure of the illuminating device which concerns on one Embodiment of this invention. It is a block diagram which shows the electric constitution of the light source drive device which concerns on one Embodiment of this invention. It is a block diagram which shows the electric constitution of the logic circuit which concerns on one Embodiment of this invention. It is a circuit diagram which shows the electric constitution which shows the structure of the light source drive circuit which concerns on one Embodiment of this invention. (A)-(f) which concerns on one Embodiment of this invention is a timing chart which shows the various signals and drive current in a sub-frame in the case of a high-intensity mode. (A)-(f) which concerns on one Embodiment of this invention is a timing chart which shows the various signals and drive current in a sub-frame in the case of a low-intensity mode. (A) which concerns on one Embodiment of this invention is a flowchart which shows the process sequence of the 2nd control part in a display period, (b) is a flowchart which shows the process sequence of the 2nd control part in low-luminance mode. . It is a timing chart which shows the state of the display element concerning one embodiment of the present invention, and the current supplied to each light source. It is a timing chart which shows the state of a display element and various signals in a display period concerning one embodiment of the present invention. It is a timing chart which shows the state of a display element in a display period in a modification of the present invention, and various signals. It is a timing chart which shows the state of the display element at the time of the high luminance which concerns on background art, and the electric current supplied to each light source. It is a timing chart which shows the state of the display element at the time of the low brightness | luminance based on background art, and the electric current supplied to each light source.

  An embodiment in which a display device according to the present invention is embodied as a head-up display device (hereinafter referred to as a HUD device) will be described with reference to the drawings.

  As shown in FIG. 1, the HUD device 1 is installed on the dashboard of the vehicle 2, generates display light L representing an image M (see FIG. 2), and emits the generated display light L toward the windshield 3. To do. The display light L is reflected by the windshield 3 and then reaches the viewer 4 (mainly the driver of the vehicle 2). Thereby, the viewer 4 can visually recognize the virtual image V representing the image M formed in front of the windshield 3. In the image M, information related to the vehicle 2 (for example, engine speed, navigation information, etc.) is displayed.

(Configuration of HUD device 1)
As shown in FIG. 2, the HUD device 1 includes an illumination device 10, a light intensity detection unit 500, an illumination optical system 20, a display element 30, a light source driving device 5, a projection optical system 40, and a screen 50. A plane mirror 61, a concave mirror 62, a housing 70, and a translucent portion 71.

The housing 70 is formed in a box shape from a light-shielding material, for example. The housing 70 accommodates the components of the HUD device 1 such as the illumination device 10 and the illumination optical system 20. The housing 70 is formed with an opening 70a through which the display light L passes.
The translucent portion 71 is made of a translucent resin such as acrylic and is provided so as to close the opening 70 a of the housing 70. The translucent part 71 is formed in, for example, a curved shape in order to prevent the external light that has reached from being reflected toward the viewer 4.

  The illumination device 10 generates illumination light C and emits the generated illumination light C toward the illumination optical system 20. Specifically, as illustrated in FIG. 3, the illumination device 10 includes a light source 11, a circuit board 12, a multiplexing unit 13, a luminance unevenness reducing unit 14, and a transmission film 15.

  The light source 11 is composed of, for example, three light sources 11r, 11g, and 11b each composed of an LED (Light Emitting Diode). The light source 11r emits red light R, the light source 11g emits green light G, and the light source 11b emits blue light B. Each of the light sources 11r, 11g, and 11b is driven by the light source driving device 5 as described later, and emits light at a predetermined light intensity and timing.

  The circuit board 12 is a printed circuit board. Light sources 11r, 11g, and 11b are mounted on the circuit board 12.

The dichroic mirror 13c generates the illumination light C by aligning the optical axes of the red light R, the green light G, and the blue light B sequentially emitted from the light sources 11r, 11g, and 11b, and the illumination light C is used as a luminance unevenness reduction unit. 14 is emitted.
Specifically, the multiplexing unit 13 includes a reflection mirror 13a and dichroic mirrors 13b and 13c that reflect light of a specific wavelength and transmit light of other wavelengths other than the specific wavelength. Has been. The reflection mirror 13a is located on the emission side of the light source 11b. The reflection mirror 13a reflects the incident blue light B toward the dichroic mirror 13b. The dichroic mirror 13b is located on the emission side of the light source 11g. The dichroic mirror 13b reflects the incident green light G toward the dichroic mirror 13c and transmits the blue light B from the reflection mirror 13a as it is. The dichroic mirror 13c is located on the emission side of the light source 11r. The dichroic mirror 13c reflects the incident red light R toward the luminance unevenness reducing unit 14 and transmits the light B and G from the dichroic mirror 13b as they are.

  The luminance unevenness reducing unit 14 includes a mirror box, an array lens, and the like, and reduces unevenness of light by irregularly reflecting, scattering, and refracting the illumination light C from the multiplexing unit 13.

  The transmissive film 15 is made of a transmissive member having a reflectance of, for example, about 5%, and transmits most of the illumination light C that has arrived through the luminance unevenness reducing unit 14 as it is, but detects a part of the light intensity. Reflected toward the part 500.

  The light intensity detection unit 500 includes a light receiving element having a photodiode, for example, and is provided at a position for receiving the illumination light C reflected by the transmission film 15. The light intensity detection unit 500 receives a part of the illumination light C and detects the light intensities of the lights R, G, and B constituting the illumination light C in a time division manner.

  As shown in FIG. 2, the illumination optical system 20 includes a concave lens or the like, and adjusts the illumination light C emitted from the illumination device 10 to a size corresponding to the display element 30.

  As shown in FIG. 2, the display element 30 is composed of a DMD provided with a plurality of movable micromirrors 30 a which are an example of a reflecting portion. The micromirror 30a includes an electrode (not shown), and is turned on / off by switching a voltage value applied to the electrode. When the micromirror 30a is on, the micromirror 30a takes a posture inclined, for example, +12 degrees with the hinge as a fulcrum. At this time, the illumination light C emitted from the illumination optical system 20 passes through the projection optical system 40 and the screen 50. Reflect towards When the micromirror 30a is off, the micromirror 30a takes a posture inclined, for example, -12 degrees with the hinge as a fulcrum, and at this time reflects the illumination light C in a direction different from the projection optical system 40. Accordingly, the display element 30 individually drives each micromirror 30a under the control of the light source driving device 5 (specifically, a second control unit 200 described later), so that the image M of the illumination light C is displayed. Only light corresponding to is projected toward the projection optical system 40.

  The projection optical system 40 includes a concave lens or a convex lens, and efficiently projects the display light L from the display element 30 onto the screen 50.

  The screen 50 includes a holographic diffuser, a microlens array, a diffusion plate, and the like. The screen 50 receives the display light L from the projection optical system 40 on the back surface (lower surface in FIG. 2) and receives the front surface (upper side in FIG. 2). Image M is displayed on the screen.

The plane mirror 61 reflects the display light L representing the image M displayed on the screen 50 toward the concave mirror 62.
The concave mirror 62 reflects the display light L from the plane mirror 61 toward the windshield 3. The display light L reaches the windshield 3 after passing through the light transmitting portion 71 of the housing 70. Thereby, the virtual image V to be formed is enlarged as compared with the image M displayed on the screen 50.

(Configuration of the light source driving device 5)
As illustrated in FIG. 4, the light source driving device 5 includes a power feeding unit 300 that supplies a current I to the light source 11, a light source driving unit 400 that drives the light source 11, and a second control unit 200 that controls the display element 30. And the first control unit 100 that controls the light source driving unit 400 and the second control unit 200. Each configuration of the light source driving device 5 is mounted on, for example, a printed circuit board (not shown) other than the circuit board 12 disposed in the housing 70. A part or all of the configuration of the light source driving device 5 may be mounted on the circuit board 12. The first and second control units 100 and 200 are examples of control units.

  As illustrated in FIG. 10, the light source driving device 5 performs control for each frame F that is a control cycle for displaying the image M. The frame F includes a display period Fa and a non-display period Fb. The light source driving device 5 drives each micromirror 30a and the light source 11 of the display element 30 so as to generate the image M in the display period Fa. In the display period Fa, the light source driving device 5 sequentially turns on the light sources 11r, 11g, and 11b by supplying the current I (IR, IG, IB) to the different light sources 11r, 11g, and 11b for each subframe Fs. The light source 11 is driven by a field sequential method. In the non-display period Fb, the light source driving device 5 turns off all the light sources 11r, 11g, and 11b, and the display element 30 is set so that the on period and the off period of the micromirror 30a in the frame F are substantially the same. The micromirror 30a is driven. By setting the non-display period Fb, failure of each micromirror 30a of the display element 30 is suppressed.

As shown in FIG. 4, the first control unit 100 includes a microcontroller including a CPU (Central Processing Unit), a memory, and the like. A video signal for displaying an image M is input to the first control unit 100 from a vehicle ECU (Electronic Control Unit) 6 of the vehicle 2 by LVDS (Low Voltage Differential Signal) communication or the like.
The first control unit 100 outputs the input video signal to the second control unit 200 via an image processing IC (Integrated Circuit) (not shown). Note that the video signal from the vehicle ECU 6 may be directly input to the second control unit 200 via an image processing IC (not shown) or the like without passing through the first control unit 100.
In addition, the first control unit 100 adjusts the display control data for displaying the display image M requested by the video signal on the display element 30 and the driving of the display element 30 based on the display control data. , 11g, and 11b are output to the second control unit 200.
In addition, an external illuminance signal (dimming signal) SL around the vehicle 2 detected through the illuminance sensor 7 is input from the vehicle ECU 6 to the first control unit 100.

  The first control unit 100 adjusts the light emission intensity (luminance) of the light source 11 via the light source driving unit 400 according to the external illuminance signal SL. The first control unit 100 generates a reference signal SA serving as a threshold based on the external illuminance signal SL from the vehicle ECU 6 in order to adjust the light emission intensity of the light source 11, and the reference signal SA is used as the light source driving unit 400 (exactly). Is output to a comparison circuit 410) to be described later. More specifically, for example, the first control unit 100 refers to the table data in which the intensity value indicated by the external illuminance signal SL stored in its non-volatile memory and the set value are associated with each other. By referring to the data, a set value corresponding to the intensity value indicated by the external illuminance signal SL from the vehicle ECU 6 is acquired. Then, the first control unit 100 outputs a pulse signal having a duty ratio corresponding to the acquired set value, and converts the pulse signal into an analog signal by an analog converter (not shown) including an integration circuit. The signal is output as a reference signal SA to the light source driver 400 (more precisely, a comparison circuit 410 described later). The first control unit 100 outputs a reference signal SA having a different magnitude for each subframe Fs (see FIGS. 7 and 8), which is a period during which a selected one of the light sources 11r, 11g, and 11b emits light. . Specifically, the first controller 100 determines the emission colors of the subframe Fs emitted from the red light source 11r, the subframe Fs emitted from the green light source 11g, and the subframe Fs emitted from the blue light source 11b. The reference signal SA is made different for each different subframe Fs.

  As shown in FIG. 4, the second control unit 200 is an LSI (Large Scale Integration) that realizes a desired function by hardware, for example, an ASIC (Application Specific Integrated Circuit) or an FPGA (Field Programmable Gate Array). Etc.

The second control unit 200 outputs a limit signal SC to the light source driving unit 400 (more precisely, a logic circuit 420 described later) under the control of the first control unit 100. As shown in FIG. 7 (d) or FIG. 8 (d), the limit signal SC is either on indicating that the lighting of the light source 11 is permitted or off indicating that the lighting of the light source 11 is prohibited. It is in.
The first control unit 100 sets the on-duty ratio of the limit signal SC in the subframe Fs based on the value of the external illuminance signal SL via the second control unit 200, and the set on-duty ratio limit signal SC is output. Specifically, the first control unit 100 acquires the external illuminance signal SL from the vehicle ECU 6, and when the acquired external illuminance signal SL is less than the threshold, in other words, the surroundings of the HUD device 1 are assumed to be dark. In this case, as shown in FIG. 8D, the second control unit 200 outputs a limit signal SC1 having a low on-duty ratio. On the other hand, when the acquired external illuminance signal SL is greater than or equal to the threshold, in other words, when the surrounding of the HUD device 1 is assumed to be bright, the first controller 100, as shown in FIG. The second control unit 200 outputs a limit signal SC2 having a high on-duty ratio.

Based on the display control data from the first control unit 100, the second control unit 200 performs on / off control of each micromirror 30a in the display element 30 by a PWM (Pulse Width Modulation) method.
The second control unit 200 generates an enable signal EN (R-EN, G-EN, B-EN) for controlling the light emission timing of the light source 11 according to the illumination control data from the first control unit 100, The generated enable signal EN is output to the light source driver 400 (more precisely, a logic circuit 420 described later). The second control unit 200 uses the red enable signal R-EN corresponding to the light source 11r, the green enable signal G-EN corresponding to the light source 11g, and the blue enable signal B-EN corresponding to the light source 11b as the enable signal EN. Are output at different timings. The enable signal EN is in one of an on state indicating that the corresponding light source 11 is allowed to be turned on and an off state indicating that the corresponding light source 11 is prohibited from being turned on. The second control unit 200 synchronizes the light emission timing of the light source 11 with the screen control of the display element 30 through the output of the enable signal EN.
Further, as will be described in detail later, the second control unit 200, when the enable signal EN is switched from OFF to ON (see time ta in FIG. 11), instructs the charge release signal SG to release the stored charge. Is output to the light source driving unit 400 (more precisely, the charge discharging unit 700 described later). Note that the first control unit 100 generates an enable signal EN (R-EN, G-EN, B-EN), and the generated enable signal EN does not pass through the second control unit 200, and the light source driving unit 400. You may output to (the logic circuit 420 mentioned later).

As shown in FIG. 4, the light source driving unit 400 is an LSI that realizes a desired function by hardware. For example, the light source driving unit 400 includes an ASIC, FPGA, or analog circuit independent of the second control unit 200. .
The light source drive unit 400 includes a comparison circuit 410 that compares the reference signal SA and the light intensity detection signal SFB, and a light source drive circuit 430 that includes switch units 431, 432, and 433 that turn on or off the light sources 11r, 11g, and 11b. , A logic circuit 420 that outputs a drive signal SD for controlling the switch units 431, 432, and 433, and a charge discharge unit 700 that discharges the charge stored when the current is supplied to the light source 11 to the outside.
In brief, the light source driving unit 400 receives a light intensity detection signal SFB based on the light intensity of the illumination light C emitted from the illumination device 10 and drives the light source 11 from the light intensity detection signal SFB. SD is generated, and the light source 11 is turned on or off by turning on or off the switch units 431, 432, and 433 based on the drive signal SD.

Specifically, the comparison circuit 410 includes a comparator, compares the light intensity detection signal SFB from the light intensity detection unit 500 with the reference signal SA from the first control unit 100, and compares the comparison result as a comparison result. The signal SB is output to the logic circuit 420 and the second control unit 200.
Specifically, as shown in FIGS. 7B and 7C, the comparison circuit 410 turns off the comparison signal SB when the light intensity detection signal SFB exceeds the reference signal SA. When the comparison signal SB is turned off as described above, the current I flowing through the light source 11 (current IR in the figure) decreases as shown in FIG. 7F. Thus, the emission intensity of the light source 11 is fed back. The light intensity detection signal SFB, which is data, decreases until it becomes less than the reference signal SA.
Further, as shown in FIGS. 7B and 7C, the comparison circuit 410 turns on the comparison signal SB when the light intensity detection signal SFB is equal to or lower than the reference signal SA. When the comparison signal SB is turned on in this way, the current I flowing through the light source 11 (current IR in the figure) increases as shown in FIG. 7F, so that the emission intensity of the light source 11 is fed back. The light intensity detection signal SFB that is data increases until it exceeds the reference signal SA.
In this manner, the comparison circuit 410 is a comparison that is a pulse signal that repeatedly turns on and off by repeatedly repeating the light intensity detection signal SFB below the reference signal SA or the light intensity detection signal SFB exceeding the reference signal SA. A signal SB is generated.
An amplification circuit (not shown) is provided between the light intensity detection unit 500 and the comparison circuit 410, and the light intensity detection signal SFB is amplified by the amplification circuit and input to the comparison circuit 410. Also good. In the amplifier circuit, as described above, the first control unit 100 determines the gain according to the external illuminance signal SL input from the vehicle ECU 6.

The logic circuit 420 receives the limit signal SC, the enable signal EN, and the comparison signal SB, and turns on or off the switch units 431, 432, and 433 corresponding to the light sources 11r, 11g, and 11b based on the signals SC, EN, and SB. To do.
Specifically, as illustrated in FIG. 5, the logic circuit 420 includes a first AND circuit 421, a red AND circuit 422, a green AND circuit 423, and a blue AND circuit 424.

The first AND circuit 421 receives the limit signal SC from the second control unit 200 and the comparison signal SB from the comparison circuit 410, and outputs a drive signal SD that is an AND signal of the limit signal SC and the comparison signal SB to each AND. Output to circuits 422, 423, and 424.
That is, as shown in FIGS. 8C to 8E, the first AND circuit 421 outputs the drive signal SD having substantially the same waveform as the comparison signal SB during the on time Ton when the limit signal SC is on. To do. Therefore, in the on time Ton of the limit signal SC, the drive signal SD is turned on when the comparison signal SB is on, and the drive signal SD is turned off when the comparison signal SB is off. The first AND circuit 421 turns off the drive signal SD regardless of the comparison signal SB during the off time Tof when the limit signal SC is off.

  As shown in FIG. 5, the red AND circuit 422 receives the red enable signal R-EN from the second control unit 200 and the drive signal SD from the first AND circuit 421, and receives the red enable signal R-EN and A red drive signal SDR that is an AND signal of the drive signal SD is output to the red switch unit 431. The green AND circuit 423 receives the green enable signal G-EN from the second controller 200 and the drive signal SD from the first AND circuit 421, and ANDs the green enable signal G-EN and the drive signal SD. A green drive signal SDG that is a signal is output to the green switch unit 432. The blue AND circuit 424 receives the blue enable signal B-EN from the second controller 200 and the drive signal SD from the first AND circuit 421, and is an AND signal of the blue enable signal B-EN and the drive signal SD. A certain blue drive signal SDB is output to the blue switch unit 433.

  In the predetermined subframe Fs shown in FIGS. 7A and 8A, only the red enable signal R-EN among the enable signals EN is turned on. In this case, as shown in FIGS. 7E and 8E, the red AND circuit 422 outputs a red drive signal SDR having the same waveform as the drive signal SD from the first AND circuit 421. In this subframe Fs, the green AND circuit 423 and the blue AND circuit 424 receive the green enable signal G-EN and the blue enable signal B-EN in the off state, respectively, so that the green drive signal SDG and the blue drive in the off state are input. The signal SDB is output.

  As shown in FIG. 4, the power supply unit 300 includes a power supply IC (Integrated Circuit), a switching circuit using a transistor, and the like. The power feeding unit 300 is connected to the anode side of each light source 11r, 11g, 11b. The power feeding unit 300 receives power from a battery (not shown) of the vehicle 2, generates an appropriate voltage for the light source 11 under the control of the first control unit 100, and applies the voltage to the light source 11. . As a result, currents IR, IG, and IB are supplied to the light sources 11r, 11g, and 11b.

The switch units 431, 432, and 433 are, for example, switching elements using n-type channel FETs (Field Effect Transistors). The switch units 431, 432, and 433 are switched to the on state or the off state in accordance with the drive signals SDR, SDG, and SDB from the logic circuit 420.
As shown in FIG. 6, the red switch unit 431 is connected to the cathode side of the red light source 11r, the green switch unit 432 is connected to the cathode side of the green light source 11g, and the blue switch unit 433 is connected to the cathode side of the blue light source 11b. Is done. The red switch unit 431 is turned on when the red drive signal SDR from the red AND circuit 422 is turned on. When the red switch unit 431 is in the on state, a current IR is supplied from the power supply unit 300 to the red light source 11r, and thereby the red light source 11r emits red light R. The red switch unit 431 is turned off when the red drive signal SDR from the red AND circuit 422 is turned off. When the red switch unit 431 is in the off state, the red light source 11r is turned off. Similarly, for the green switch unit 432 and the blue switch unit 433, the green light source 11g and the blue light source 11b are turned on or off according to whether the green drive signal SDG and the blue drive signal SDB are turned on or off.

  For example, as shown in FIG. 7E, in a predetermined subframe Fs, the red switch unit 431 receives a drive signal SD that is a pulse signal that repeatedly turns on and off. Therefore, since the red switch unit 431 is repeatedly turned on and off, the current IR flowing through the red light source 11r is composed of a plurality of pulses P as shown in FIG. In the example of FIG. 11, as shown in the lower part of the drawing, in one subframe Fs, the current IR flowing through the red light source 11r is composed of three pulses P1 to P3. In other sub-frames Fs, the currents IG and IB flowing through the other light sources 11g and 11b are similarly composed of a plurality of pulses P. The luminance of the light source 11 is determined based on the magnitude of the current value supplied to the light source 11 and the time during which the current I is passed (in other words, the number of pulses P). In the example of FIG. 10, the light source 11r, 11g, 11b is supplied with the low-illuminance current Il as the supply current IR, IG, IB.

As shown in FIG. 6, the light source driving circuit 430 includes back electromotive force circuits 53r, 53g, and 53b provided corresponding to the light sources 11r, 11g, and 11b, in addition to the switch units 431, 432, and 433 described above. . Each of the back electromotive force circuits 53r, 53g, and 53b includes inductors (coils) 51r, 51g, and 51b, which are examples of charge units, and diodes 52r, 52g, and 52b. Each inductor 51r, 51g, 51b is connected in series to the anode side of the corresponding light source 11r, 11g, 11b. Each diode 52r, 52g, 52b is connected in parallel to the corresponding inductor 51r, 51g, 51b and the light source 11r, 11g, 11b.
The diodes 52r, 52g, and 52b are connected on the cathode side between the inductors 51r, 51g, and 51b and the power feeding unit 300, and are connected on the anode side to the cathode side of the light sources 11r, 11g, and 11b. The diodes 52r, 52g, and 52b supply the back electromotive force generated by the inductors 51r, 51g, and 51b to the corresponding light sources 11r, 11g, and 11b when the switch units 431, 432, and 433 are turned on or off.

  As shown in FIG. 4, the charge discharging unit 700 is connected between the power feeding unit 300 and the cathode side of each of the light sources 11r, 11g, and 11b. Specifically, as shown in FIG. 6, the charge discharge unit 700 is a switch unit that discharges charges stored in the inductors 51 r, 51 g, 51 b when turned on under the control of the second control unit 200. 700S and a resistor 700R that suppresses an overcurrent from flowing from the power feeding unit 300 to the charge discharging unit 700. The switch unit 700S and the resistor 700R are connected in series. The switch unit 700S is composed of, for example, an FET, and has a source terminal connected to one end of the resistor 700R and a drain terminal connected to the ground. The other end of the resistor 700R is connected to the power feeding unit 300. Further, the charge emission signal SG from the second control unit 200 is input to the gate terminal of the switch unit 700S.

(Operation of Charge Discharge Unit 700)
For example, as shown in FIG. 10, at the time ta when the subframe Fs1 for supplying the current IR to the red light source 11r starts, the current IB is supplied to the blue light source 11b in the subframe Fs2 immediately before the subframe Fs1. Therefore, electric charges are stored in the inductor 51b corresponding to the blue light source 11b. As shown in FIG. 6, the second control unit 200 outputs an on-state charge release signal SG to the switch unit 700S at a time ta at which the subframe Fs1 starts when in the low luminance mode described later. The switch unit 700S receives the on-state charge release signal SG from the second control unit 200 from the time ta to the on-time Tct, and enters the on-state (energized state). Thereby, the electric charge stored in the inductor 51b flows to the ground through the resistor 700R and the switch portion 700S as shown by the flow path La indicated by the one-dot chain line in FIG. The on-time Tct is set to be longer than the time required for all charges stored in the inductor 51b to flow to the ground.
As shown in FIG. 11, the current IR supplied to the red light source 11r is zero during the period in which the switch unit 700S is in the on state (the on time Tct of the charge emission signal SG). Therefore, the charge stored in the inductor 51b flows to the red light source 11r, and as a result, the ripple Rp is suppressed from being superimposed on the pulse P0 immediately after the start of the subframe Fs1 as indicated by the broken line in FIG.

Further, as shown in FIG. 11, the second control unit 200 sets an additional time Tad based on the on-time Tct of the charge emission signal SG, and the on-time Ton of the limit signal SC, that is, the red color by the additional time Tad. The time for turning on the switch unit 431 is extended. In this additional time Tad, the same number of pulses P3 (one in this example) as the pulses P0 of the current IR that are not supplied to the red light source 11r due to the ON time Tct of the charge emission signal SG are added.
The second control unit 200 may set the additional time Tad to the same time as the ON time Tct of the charge emission signal SG. The second control unit 200 counts the number of pulses P of the current I through the first control unit 100, and the counted number of pulses P reaches a predetermined value (three in the example of FIG. 11). The additional time Tad may be set in By setting the additional time Tad, it is possible to supplement the current energy that could not be supplied to the light source 11 in the time for operating the charge emission unit 700 (the on time Tct of the charge emission signal SG). Even when the unit 700 is operated, the desired luminance of the light source 11 can be realized.
Here, the operation of the charge emission unit 700 in the subframe Fs1 for supplying the current IR to the red light source 11r has been described. However, in the subframe for supplying the currents IG and IB to the other light sources 11g and 11b. In this case, the charge discharging unit 700 operates in the same manner as described above.
Further, the ripple Rp described above is dominated by the charge stored in the inductors 51r, 51g, 51b, but is also considered to be affected by the charge stored in the parasitic capacitance of the light source 11. That is, the ripple Rp described above may include a charge due to the charge stored in the parasitic capacitance of the light source 11. In this case, the parasitic capacitance of the light source 11 corresponds to a charge part.

(Processing procedure of second control unit 200)
Next, referring to the flowcharts of FIGS. 9A and 9B, the processing procedure of the second control unit 200 when discharging the charges stored in the inductors 51r, 51g, and 51b through the charge discharging unit 700 is described. explain. Note that the second control unit 200 performs control related to the display element 30 simultaneously with the processing according to the flowcharts of FIGS.

As shown in FIG. 9A, the second controller 200 recognizes the external illuminance signal (dimming signal) SL through the first controller 100 in the display period Fa, and the value of the external illuminance signal SL. Is greater than or equal to a threshold value Th stored in advance in a memory (not shown) (S101). The luminance of the light source 11 is a luminance corresponding to the external illuminance signal SL.
When the surroundings of the vehicle 2 are bright, the second control unit 200 determines that the value of the external illuminance signal SL is equal to or greater than the threshold value Th (YES in S101), and shifts to the high luminance mode (S102). The flowchart according to (a) ends. On the other hand, when the surroundings of the vehicle 2 are dark, the second control unit 200 determines that the value of the external illuminance signal SL is less than the threshold Th (NO in S101), and shifts to the low luminance mode (S103). The flowchart according to FIG. The flowchart according to FIG. 9A is repeatedly executed in the display period Fa.
That is, in this example, the luminance of the light source 11 is recognized through the value of the external illuminance signal SL.
Here, since the current I supplied to the light source 11 decreases as the luminance of the light source 11 decreases, the ratio of the ripple Rp to the current I increases. Thereby, the influence on the brightness | luminance of the light source 11 by the ripple Rp becomes large. The threshold Th is set based on the value of the external illuminance signal SL that is expected to have a large influence on the luminance of the light source 11 due to the ripple Rp.

As shown in FIG. 9B, in the low luminance mode, the second control unit 200 switches the enable signal EN from OFF to ON at the start of the subframe Fs (for example, time ta in FIG. 11). (S201). At the same time, the second controller 200 switches the charge emission signal SG from off to on, and then maintains the charge emission signal SG on for the on time Tct (S202). After the on-time Tct of the charge emission signal SG has passed and the charge control signal SG is switched off again, the second controller 200 turns the limit signal SC on from on to the on-time Ton including the additional time Tad described above. (S203). When in the low brightness mode, the second control unit 200 repeatedly executes the processes of steps S201 to S203 for each subframe Fs (S204).
Note that, in the high luminance mode, the second control unit 200 does not operate the charge emission unit 700 by keeping the charge emission signal SG off and is limited to the start time (time ta) of the subframe Fs. The signal SC is switched from off to on, and the limit signal SC is kept on for a predetermined time Ton from the beginning.

(effect)
As mentioned above, according to one Embodiment described, there exist the following effects.

(1) The HUD device 1 includes a power supply unit 300 that supplies a current I, a plurality of light sources 11r, 11g, and 11b that emit light of different colors in response to the current I from the power supply unit 300, and light sources 11r and 11g. , 11b, when the current I is supplied, the inductors 51r, 51g, 51b in which charges are stored by the current I, the display element 30 having a plurality of micromirrors 30a for controlling the light reflection angle, By supplying the current I from the power supply unit 300 to any one of the light sources 11r, 11g, and 11b, the light source 11r, 11g, and 11b emits light by emitting the light source 11r, 11g, and 11b. A desired color is selected from light R, G, B emitted from a plurality of light sources 11r, 11g, 11b by a field sequential method of sequentially switching 11g, 11b. Comprising generates the illumination light C, the first and second control units 100 and 200 for reflecting light corresponding to the display image M of the illumination light C through a micro-mirror 30a, a. Furthermore, the HUD device 1 controls the charges stored in the inductors 51r, 51g, and 51b to the ground before the light sources 11r, 11g, and 11b are turned on under the control of the first and second control units 100 and 200. A charge discharging unit 700 for discharging is provided.
According to this configuration, the charge stored in the inductors 51r, 51g, and 51b is discharged to the ground by the charge discharge unit 700, so that the current I supplied to the light sources 11r, 11g, and 11b is rippled due to the charge. Rp is suppressed from overlapping. Therefore, the influence of the ripple Rp on the luminance of the light sources 11r, 11g, and 11b can be reduced, and the light sources 11r, 11g, and 11b can be turned on with desired luminance. Thereby, the gradation display of the image M in the HUD apparatus 1 can be made favorable.

(2) The first and second control units 100 and 200 can drive the light source 11 in at least a high luminance mode with high luminance and a low luminance mode with lower luminance than the high luminance mode. Releases the charge stored in the inductors 51r, 51g, and 51b through the charge discharging unit 700 before the light source 11 is turned on.
Generally, the smaller the current I supplied to each light source 11r, 11g, 11b, the greater the proportion of the ripple Rp with respect to the current I. For this reason, especially when the luminance of the light source 11 is low, the influence of the ripple Rp on the luminance becomes large.
According to the above configuration, only when the luminance of the light sources 11r, 11g, and 11b is low (in the low luminance mode), the electric charge stored in the inductors 51r, 51g, and 51b is discharged to the ground by the charge discharging unit 700. The ripple Rp is suppressed from affecting the luminance of the light source 11.
Further, when the luminance of the light sources 11r, 11g, and 11b is high (in the high luminance mode), it is not necessary to control the charge emission unit 700 to be operated by the first and second control units 100 and 200. The control burden on the first and second control units 100 and 200 can be reduced. Further, when the luminance of the light sources 11r, 11g, and 11b is high, the time for the charge emission unit 700 to operate is eliminated, so that the luminance of the light sources 11r, 11g, and 11b can be maximized as necessary. .

(3) The HUD device 1 is provided corresponding to the plurality of light sources 11r, 11g, and 11b, and from the power supply unit 300 when turned on under the control of the first and second control units 100 and 200. There are provided switch units 431 to 433 for supplying a current I to the corresponding light sources 11r, 11g, and 11b. The first and second control units 100 and 200 pass the inductors 51r, 51g, and 51b through the charge discharging unit 700 for a certain period of time (on time Tct of the charge discharging signal SG) before turning on the light sources 11r, 11g, and 11b. The switches 431 to 433 are turned on for an additional time Tad after a lapse of a certain time so as to replenish the current energy that could not be supplied to the light sources 11r, 11g, and 11b during the certain time. Extend the period of state.
According to this configuration, when charges stored in the inductors 51r, 51g, and 51b are discharged through the charge discharging unit 700, the switch units 431 to 433 are turned on for the additional time Tad, that is, the light sources 11r, 11g, and 11b. The current supply time is extended. For this reason, even if the electric charge discharge | release part 700 operate | moves, it is suppressed that the brightness | luminance of the light source 11 falls.

(Modification)
In addition, the said embodiment can be implemented with the following forms which changed this suitably.

  In the above embodiment, as shown in FIG. 11, the second control unit 200 switches the charge emission signal SG on at time ta when the subframe Fs1 starts, but turns on the charge emission signal SG. The switching timing is not limited to this, and the charge emission signal SG may be switched on in the subframe Fs2 immediately before the subframe Fs1. For example, as illustrated in FIG. 12, the second control unit 200 switches on the charge release signal SG at a time tb before the time ta at which the subframe Fs1 starts and turns on the inductors 51r, 51g, and 51b. The stored charge may be released to ground. According to this configuration, the current I can be supplied to the light source 11 from the time ta when the subframe Fs starts.

  In the above-described embodiment, the second control unit 200 may execute a part of the control content of the first control unit 100, or conversely, a part of the control content of the second control unit 200. The 1st control part 100 may perform. The first and second control units 100 and 200 may be configured as one control unit.

In the above embodiment, the second controller 200 is only in the low luminance mode.
Although the charge emission unit 700 is operated by turning on the charge emission signal SG, the charge emission unit 700 may be operated regardless of the luminance of the light source 11. In this case, the process according to the flowchart of FIG. 9A can be omitted, and the process according to the flowchart of FIG. 9B is repeatedly executed during the display period Fa.

  In the above embodiment, as shown in FIG. 11, the second control unit 200 turns off the restriction signal SC during the on-time Tct of the charge release signal SG, but it may turn on the restriction signal SC.

  In the above embodiment, the charge emission unit 700 includes the resistor 700R, but the resistor 700R may be omitted.

In the above embodiment, the light sources 11r, 11g, and 11b are configured as independent light sources 11, but may emit a plurality of colors of light from the common light source 11. The light source 11 only needs to emit light of a plurality of colors, may be composed of only two colors, or may be composed of four or more colors (including white).
Further, when a plurality of colors of light are emitted from one light source 11, the multiplexing unit 13 that matches the optical axes of the light sources 11r, 11g, and 11b may be omitted.

  In the above embodiment, the light intensity detection unit 500 is installed in a part of the optical path of the illumination light C. However, it is sufficient if the light intensity of each of the lights R, G, and B can be detected. It may be provided at a location where the light intensity of each of the lights R, G, B before being detected can be detected. In addition, the light intensity detection unit 500 may be appropriately provided at a location where a part of the light intensity of the illumination light C emitted from the illumination optical system 20 can be detected.

  In the above embodiment, the display device according to the present invention is applied to a vehicle-mounted head-up display device. However, the display device is not limited to a vehicle-mounted device, and may be applied to a head-up display device mounted on a vehicle such as an airplane or a ship. . Further, the display light L from the HUD device 1 is projected onto the windshield 3, but may be projected onto a dedicated combiner. Further, the display device according to the present invention may be applied not to a head-up display device but to a display device such as a projector used indoors or outdoors.

  In the above embodiment, the second control unit 200 has shifted to either the high luminance mode or the low luminance mode based on the value of the external illuminance signal SL. However, the present invention is not limited to this, and the external light intensity is applied to the HUD device 1. It is possible to provide an illuminance sensor (not shown) that obtains the signal and shift to either the high luminance mode or the low luminance mode based on a signal from the illuminance sensor provided in the HUD device 1. Moreover, you may transfer the said mode, when the viewer 4 operates the operation part which is not shown provided in the HUD apparatus 1 or the vehicle 2. FIG. Further, the mode may be shifted according to an operation of a switch for turning on / off the light of the vehicle 2.

DESCRIPTION OF SYMBOLS 1 ... HUD apparatus 2 ... Vehicle 3 ... Windshield 4 ... Viewer 5 ... Light source drive device 6 ... Vehicle ECU
7 ... Illuminance sensor 10 ... Illuminating device 11 ... Light source 11r ... Red light source 11g ... Green light source 11b ... Blue light source 12 ... Circuit board 13 ... Multiplexing unit 14 ... Luminance unevenness reducing unit 15 ... Transmission film 20 ... Illumination optical system 30 ... Display Element 30a ... Micro mirror 40 ... Projection optical system 50 ... Screens 51r, 51g, 51b ... Inductors 52r, 52g, 52b ... Diodes 53r, 53g, 53b ... Back electromotive force circuit 61 ... Plane mirror 62 ... Concave mirror 70 ... Housing 71 ... Transparent Optical unit 100 ... first control unit 200 ... second control unit 300 ... power supply unit 400 ... light source drive unit 410 ... comparison circuit 420 ... logic circuit 421 ... first AND circuit 422 ... red AND circuit 423 ... green AND circuit 424 ... blue AND circuit 430 ... light source drive circuit 431 ... red switch part 432 ... green switch part 433 ... blue switch part 500 ... light Degree detection unit 700 ... charge-emitting portion 700S ... the switch section 700R ... resistance

Claims (3)

A power supply for supplying current;
A plurality of light sources that emit currents of different colors in response to current from the power supply unit;
When a current is supplied to each of the light sources, a charge part that stores a charge by the current; and
A display element having a plurality of reflecting portions for controlling the angle at which light is reflected;
By supplying a current from the power supply unit to any one of the plurality of light sources, the one light source is caused to emit light, and the light sources to be emitted are sequentially switched from the plurality of light sources. A control unit that generates illumination light of a desired color from emitted light and reflects light corresponding to a display image among the illumination light through the reflection unit,
Under the control of the control unit, a charge discharge unit that discharges the charge stored in the charge unit before the light source is turned on,
A display device characterized by that. The control unit can drive the light source at least in a high luminance mode having a high luminance and a low luminance mode having a luminance lower than that in the high luminance mode. In the low luminance mode, the light source is turned on. In addition, the charge stored in the charge part is released through the charge release part.
The display device according to claim 1. Provided corresponding to the plurality of light sources, comprising a switch unit that supplies current from the power supply unit to the corresponding light source when turned on under the control of the control unit,
The controller is
The elapse of the predetermined time so as to discharge the stored charge through the charge emission unit for a predetermined time before turning on the light source, and to replenish the current energy that could not be supplied to the light source in the predetermined time. Then, extend the period for turning on the switch unit,
The display device according to claim 1 or 2.

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