JP2017227806A - Display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a display device capable of reducing a change in chromaticity when display brightness is changed based on required brightness.SOLUTION: A HUD device includes: three light sources; a display element for controlling an angle by which light is reflected; a control part for generating illumination light having a desired color by sequentially switching one selected light sources and reflecting the light corresponding to the image among the illumination lights; and a luminous intensity sensor for detecting the intensity of the light. The control part makes a display period rate small according as the required illumination is reduced in a staircase pattern. In a boundary area E that sandwiches change points (intensity La, Lb)at which the display period rate changes, the current is supplied to each light source according to first and second current control values A1, A2 set so that a pre-stored RGB ratio becomes a desired value. In a center area C set between two boundary areas E, the current is supplied to each light source so that the RGB ratio becomes the desired value based on the intensity of the light detected by the luminous intensity sensor.SELECTED DRAWING: Figure 8

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 Document 1 selectively emits any one of three light sources that emit red, green, and blue light, and switches the light sources to be emitted at high speed for each subframe. Thus, it operates by a so-called field sequential method that generates illumination light of a desired color.

  For example, the display device described in Patent Document 1 includes a control unit that supplies current to each light source in a field sequential manner. The controller, when supplying current to the light source, PWM (Pulse Width Modulation) control that changes the on-duty ratio, which is the current supply period occupying the subframe, and PAM (Pulse Amplitude Modulation) control that changes the current value, Are executed at the same time. Specifically, the control unit performs PWM control so that the on-duty ratio decreases stepwise as the required light source luminance (required luminance) decreases, and the on-duty ratio is at a predetermined value. PAM control is performed to reduce the current value supplied to the light source as the luminance required for the light source decreases. Thereby, the display brightness according to the required brightness is realized.

JP 2014-066920 A

  In the display device described in Patent Document 1, the control unit linearly changes the current between two adjacent changing points among the plurality of changing points at which the on-duty ratio changes in accordance with a required change in luminance. The value is changed. Therefore, the current value does not take into account the chromaticity of the actual light source between the two change points, and there is room for improvement in terms of chromaticity adjustment.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a display device that can reduce the change in chromaticity when the display luminance is changed based on the required luminance.

  In order to achieve the above object, a display device according to the present invention includes a plurality of light sources that emit light of different colors, a display element that includes a plurality of reflection units that control the angle at which the light is reflected, and the plurality of light sources. The selected one light source emits light by supplying current, and is emitted from the plurality of light sources by a field sequential method in which the selected one light source is sequentially switched for each subframe constituting a frame that is a control cycle. A control unit that generates illumination light of a desired color from light and reflects light corresponding to a display image out of the illumination light through the reflection unit, and an illuminance for detecting the illuminance of the light emitted from each light source A display device including a sensor, wherein the frame drives the light source, generates a display image, turns off the light source, and displays the display image. A non-display period that is not generated, and the control unit reduces the display period ratio that is the ratio of the display period to the frame as the required luminance of the light source decreases in a stepwise manner, and In the boundary region including the changing point at which the display period ratio changes, the current according to the current control value set so that the light ratio, which is the ratio of the amount of light from each of the light sources stored in advance, becomes a desired value. In the central region set between the two boundary regions, the light ratio is set to the desired value based on the illuminance of the light detected by the illuminance sensor. A current is supplied to each light source.

  According to the present invention, when the display luminance is changed based on the required luminance, the change in chromaticity can be reduced.

It is a mimetic diagram of a vehicle carrying a head up display device concerning a 1st embodiment. It is the schematic which shows the structure of the head-up display apparatus which concerns on 1st Embodiment. It is the schematic which shows the structure of the illuminating device which concerns on 1st Embodiment. 1 is a block diagram showing an electrical configuration of a head-up display device according to a first embodiment. It is a block diagram which shows the structure of the integral signal generation part which concerns on 1st Embodiment. It is a flowchart which shows the process sequence of the integral control of the integral signal generation part which concerns on 1st Embodiment. (A) which concerns on 1st Embodiment is a flowchart which shows the process sequence which concerns on the display period ratio control by a control part, (b) is a flowchart which shows the process procedure which concerns on PAM control by a control part. (A) which concerns on 1st Embodiment is a graph which shows the relationship between a request | requirement brightness | luminance and an electric current value, (b) is a graph which shows the relationship between a request | requirement brightness | luminance and a display period ratio, (c) is a request | requirement brightness | luminance and actual. It is a graph which shows the relationship of the brightness | luminance. (A) which concerns on 1st Embodiment is the figure which showed the correspondence of light source temperature and a data table, (b) is the graph showing the data table set for every light source temperature. It is a timing chart which shows the state of the display element concerning a 1st embodiment, and the current supplied to each light source. (A) which concerns on 2nd Embodiment is the graph showing the data table set for every light source temperature, (b) is the figure which expanded a part of (a). It is a flowchart which shows the process sequence which concerns on PAM control by the control part which concerns on 2nd Embodiment.

(First embodiment)
A first 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, an illuminance sensor 500, an illumination optical system 20, a display element 30, a control unit 110, a projection optical system 40, a screen 50, and a plane mirror 61. A concave mirror 62, a housing 70, and a translucent part 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 fitted into the opening 70 a so as to close the opening 70 a of the housing 70. The translucent part 71 is formed to be curved, for example, in order to prevent the reached external light 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 unit 11, a circuit board 12, a multiplexing unit 13, a luminance unevenness reducing unit 14, a transmission film 15, a temperature sensor 17, Is provided.

  The light source unit 11 includes, 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 light source 11r, 11g, and 11b is controlled by the control unit 110, and emits light at a predetermined light intensity and timing.

  The circuit board 12 is a printed circuit board. On the circuit board 12, the light sources 11r, 11g, and 11b and the temperature sensor 17 are mounted.

The temperature sensor 17 detects the temperatures of the light sources 11r, 11g, and 11b, and outputs the detection results to the control unit 110 (more precisely, the microcomputer 100 described later).

The multiplexing unit 13 generates the illumination light C by matching the optical axes of the red light R, the green light G, or the blue light B sequentially emitted from the light sources 11r, 11g, and 11b, and reduces the luminance unevenness of the illumination light C. The light is emitted toward the portion 14.
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 several percent, and transmits most of the illumination light C that has reached through the luminance unevenness reducing unit 14 as it is, but a part of the light is transmitted to the illuminance sensor 500. Reflect towards.

  The illuminance sensor 500 is formed of 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 illuminance sensor 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. Therefore, the display element 30 projects only the light corresponding to the image M out of the illumination light C toward the projection optical system 40 by individually driving the micromirrors 30a under the control of the control unit 110. .

  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.

  As illustrated in FIG. 10, the control unit 110 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. In the display period Fa, the control unit 110 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, the control unit 110 supplies a current I (IR, IG, IB) to different light sources 11r, 11g, and 11b for each subframe Fs to sequentially turn on the light sources 11r, 11g, and 11b. Perform sequential control. In addition, the control unit 110 turns off all the light sources 11r, 11g, and 11b during the non-display period Fb. The control unit 110 obtains a period during which each micromirror 30a is turned on in the display period Fa (hereinafter also referred to as an on period) or a rate at which the micromirror 30a is turned on (hereinafter also referred to as an on ratio). According to the ON ratio, the ON period or the ON ratio in the non-display period Fb is determined, and each micromirror 30a is driven. For example, the micromirror 30a having a long ON period in the display period Fa is controlled so that the OFF period in the non-display period Fb is long. The controller 110 drives the micromirror 30a of the display element 30 so that the on period and the off period of the micromirror 30a in the frame F are substantially the same. In other words, the controller 110 determines that the sum of the on period in the display period Fa and the on period in the non-display period Fb is approximately half of the frame F, according to the on period in the display period Fa. The on period in the non-display period Fb is adjusted. As described above, the non-display period Fb is set, so that the failure of each micromirror 30a of the display element 30 is suppressed.

  As shown in FIG. 4, the control unit 110 includes a microcomputer 100, a light source driving circuit 430, and a display element controller 200. Each component of the control unit 110 is mounted on a printed circuit board (not shown) other than the circuit board 12 disposed in the housing 70, for example. A part or all of the configuration of the control unit 110 may be mounted on the circuit board 12.

The microcomputer 100 includes a microcontroller having a CPU (Central Processing Unit), a memory, and the like. The microcomputer 100 receives a video signal for displaying the image M from a vehicle ECU (Electronic Control Unit) 6 of the vehicle 2 by LVDS (Low Voltage Differential Signal) communication or the like.
The microcomputer 100 outputs the input video signal to the display element controller 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 display element controller 200 via an image processing IC (not shown) or the like without passing through the microcomputer 100.
Further, the microcomputer 100 causes the light sources 11r, 11g, and 11b to be displayed in accordance with display control data for displaying the display image M requested by the video signal on the display element 30 and driving of the display element 30 based on the display control data. The illumination control data to be driven is output to the display element controller 200.
In the memory 100a of the microcomputer 100, a plurality of data tables Dt (Dtx, Dty, Dtz...) Corresponding to the light source temperature T (Tx, Ty, Tz...) Are stored in advance.

  As shown in FIG. 4, the display element controller 200 is an LSI (Large Scale Integration) that realizes a desired function by hardware. For example, the display element controller 200 is an ASIC (Application Specific Integrated Circuit) or an FPGA (Field Programmable Gate Array). It is configured.

  The display element controller 200 performs on / off control of each micromirror 30a in the display element 30 based on display control data from the microcomputer 100. The display element controller 200 controls the light emission timing of the light source unit 11 according to the illumination control data from the microcomputer 100. Thereby, the display element controller 200 can synchronize the light emission timing of the light source unit 11 with the screen control of the display element 30.

  The light source drive circuit 430 switches the switching circuit 431 at an appropriate timing under the control of the microcomputer 100 and the display element controller 200, and the switching circuit 431 that switches the current supply target among the three light sources 11r, 11g, and 11b. A logic circuit 432.

  As shown in FIG. 4, the HUD device 1 further includes an integration signal generation unit 410 and an amplification circuit 440 between the control unit 110 and the illuminance sensor 500. The amplification circuit 440 amplifies the detection signal of the illuminance sensor 500 and outputs the amplified detection signal to the integrated signal generation unit 410. The integration signal generation unit 410 integrates the amplified detection signal of the illuminance sensor 500 to calculate an integration signal obtained by integrating the light amounts of the light sources 11r, 11g, and 11b in a certain period.

  The integration signal generation unit 410 integrates the detection signal from the illuminance sensor 500 and outputs the integration signal to the control unit 110 (microcomputer 100) and the light source driving circuit 430. As shown in FIG. 5, the integration signal generation unit 410 includes an integration circuit 411 that integrates an input signal, an operational amplifier 412 that amplifies an integration signal obtained by integrating the detection signal by the integration circuit 411, and an amplification circuit 440 (illuminance sensor 500 ) Including a signal transmission unit 413 that transmits the detection signal from the integration circuit 411 to the integration circuit 411, a transmission timing adjustment unit 414, and a discharge unit 415 that resets by discharging the integration signal of the integration circuit 411.

The signal transmission unit 413 transmits the amplified detection signal from the amplification circuit 440 to the integration circuit 411, and switches between transmission and non-transmission based on the signal from the transmission timing adjustment unit 414. The transmission timing adjustment unit 414 adjusts the timing so that the detection signal detected in the subframe Fs of a specific color among the three colors of the light sources 11r, 11g, and 11b is intermittently transmitted to the integration circuit 411. For example, when detecting one color for each frame F, the signal transmission unit 413 integrates the detection signal into the signal transmission unit 413 for each of a plurality or all of the subframes Fs in which one specific color of the frame F is selected. In the sub-frame Fs that is transmitted to the circuit 411 and the other two colors are selected, the signal transmission unit 413 does not transmit the detection signal to the integration circuit 411. The transmission timing adjustment unit 414 of the present embodiment inputs a signal specifying the color detected in the frame F from the microcomputer 100 from the microcomputer 100 and inputs a signal specifying the color selected by the subframe Fs from the display element controller 200. Although the transmission timing is adjusted based on these signals, the transmission timing may be adjusted using other signals. Further, the function of the signal transmission unit 413 and / or the transmission timing adjustment unit 414 may be provided in the microcomputer 100 or the display element controller 200.
The integration signal generation unit 410 outputs the amplified integration signal to the control unit 110 (microcomputer 100) and the light source driving circuit 430 through the operational amplifier 412. The microcomputer 100 switches the gains of the amplifier circuit 440 and the operational amplifier 412 at changing points described later.

The integration control will be described with reference to the flowchart of FIG.
The signal transmission unit 413 detects the red light R detection signal detected in the sub-frame Fs in which red is selected, the green light G detection signal detected in the sub-frame Fs in which green is selected, and the sub signal in which blue is selected. The blue light B detection signal detected in the frame Fs is continuously input in a time division manner (step S11). The transmission timing adjustment unit 414 receives a signal indicating a specific color to be detected within a certain period (1 frame F) from the microcomputer 100, and determines a color to be detected within the certain period (1 frame F) (step) S12). The transmission timing adjustment unit 414 intermittently transmits detection signals in a plurality or all of the subframes Fs of the specific color determined in step S12 to the integration circuit 411, and in the subframe Fs in which the other two colors are selected, The signal transmission unit 413 is driven so as not to transmit the detection signal to the integration circuit 411 (step S13). The microcomputer 100 determines whether a certain period for detecting a specific color has ended (step S14), and repeats the integration of the detection signal for the specific color in step S13 until the predetermined period ends. The microcomputer 100 reads an integration signal obtained by integrating the detection signals detected in a plurality or all of the subframes Fs in which a specific color is selected (step S15). Thereafter, the microcomputer 100 controls the discharging unit 415 to reset the integration signal (step S16). Thereby, since the microcomputer 100 can refer to the detection signals detected in the plurality of subframes Fs in which the specific color is selected, the S / N ratio can be increased, and the light emitted from the light source unit 11 The light intensity of the light source unit 11 can be detected with high accuracy, and the output of the light source unit 11 can be accurately adjusted to a desired output. In particular, by integrating and reading the detection signals detected in all the subframes Fs in which a specific color in one frame F is selected, the microcomputer 100 can actually detect the light in one frame F that generates an image. Since the total amount of light can be referred to, an image having a desired luminance / color can be generated more reliably.

(Control content of control unit 110)
The control unit 110 simultaneously performs display period ratio control and PAM control so as to change the display luminance of the image M according to the required luminance while keeping the chromaticity of the image M constant. The control contents of the control unit 110 described below are executed by the microcomputer 100 via the display element controller 200 and the light source driving circuit 430.

Here, the display period ratio control will be described with reference to the flowchart of FIG.
First, the control unit 110 acquires the required luminance included in the illumination control data (S101). Then, the control unit 110 determines a display period ratio based on the required luminance (S102), and ends the process according to the flowchart. The display period ratio is the ratio of the display period Fa in the frame F as shown in FIG. In the frame F, the control unit 110 supplies current to the light sources 11r, 11g, and 11b at the determined display period ratio.

  For example, as shown in FIGS. 8B and 8C, the control unit 110 reduces the display period ratio stepwise as the required luminance decreases. In this example, the required luminance decreases from the maximum luminance Lmax to the luminance La and luminance Lb, and the display period ratio decreases from 100% to Ra% and Rb%. In this case, the control unit 110 determines the display period ratio to be 100% when the required luminance is equal to or lower than the maximum luminance Lmax and higher than the luminance La. Further, the control unit 110 changes the display period ratio from 100% to Ra% when the requested luminance reaches the luminance La, which is the changing point. The control unit 110 determines the display period ratio to be Ra% when the required luminance is equal to or lower than the luminance La and higher than the luminance Lb. In addition, when the requested luminance reaches the luminance Lb that is the change point, the control unit 110 changes the display period ratio from Ra% to Rb%. Thereafter, similarly, the control unit 110 decreases the display period ratio in accordance with the decrease in the required luminance.

Next, PAM control is demonstrated, referring the flowchart of FIG.7 (b).
First, the control unit 110 acquires the light source temperature detected by the temperature sensor 17 (S201). Then, as shown in FIG. 9A, the control unit 110 selects data tables Dtx, Dty, Dtz... Corresponding to the light source temperatures Tx, Ty, Tz. The control unit 110 selects the data tables Dtx, Dty, Dtz... Of the light source temperatures Tx, Ty, Tz... Closest to the detected light source temperature.
Here, it is generally known that as the light source temperature changes, the peak wavelengths of the light R, G, B shift and the output of the light R, G, B changes. Each of the data tables Dtx, Dty, Dtz... Includes first and second current control values A1, such that the RGB ratio becomes constant at a desired value, taking into account peak wavelength shift and output change due to changes in the light source temperature. Includes A2. The RGB ratio is a ratio of the amount of light R, G, B from each of the light sources 11r, 11g, 11b in a certain time, and is a value relating to the chromaticity of the image M. For example, the light source temperatures Tx, Ty, Tz... Are set at equal temperature intervals (several degrees C. to several tens of degrees C. intervals).

  Next, the control part 110 acquires the required brightness | luminance contained in illumination control data (S203). The control unit 110 determines whether or not the requested luminance is in the boundary area E (S204). As shown in an enlarged view in FIG. 8D, the boundary region E is a region around the changing point with the luminance La, Lb... Being the changing point, and is directly above the point La1, which is larger than the luminance La, Lb. It is set between Lb1 and lower points La2 and Lb2 which are smaller than the luminances La, Lb. When determining that the required luminance is in the boundary region E (YES in S204), the controller 110 determines the light source 11r based on the first and second current control values A1 and A2 of the selected data tables Dtx, Dty, and Dtz. , 11g and 11b are supplied with current (S205). More specifically, as shown in FIGS. 8A and 8D, when the required luminance is at the directly above points La1 and Lb1, the control unit 110 has a current value that matches the first current control value A1. Is supplied to the light sources 11r, 11g, and 11b. When the required luminance is at the direct points La2 and Lb2, a current having a current value that matches the second current control value A2 is supplied to the light sources 11r, 11g, and 11b. In the boundary region E between the directly above points La1, Lb1 and the immediately below points La2, Lb2, the control unit 110 generates a current having a current value corresponding to a straight line connecting the first and second current control values A1, A2. You may supply to the light sources 11r, 11g, and 11b.

  The first and second current control values A1 and A2 are made up of current control values of the currents IR, IG, and IB supplied to the light sources 11r, 11g, and 11b, and are set so that the RGB ratio is constant. . That is, the second current control value A2 after the display period ratio becomes smaller is set to a value larger than the first current control value A1 before the display period ratio becomes smaller. The RGB ratio may be different according to the required luminance after taking into account the peak wavelength shift and output change due to changes in the light source temperature.

On the other hand, when determining that the requested luminance is not in the boundary region E (NO in S204), the control unit 110 determines that the requested luminance is in the central region C (S206). As shown in FIG. 8A, the center area C is a period excluding the boundary area E among the periods in which the display period ratio has a constant value. When determining that the required luminance is in the central region C (S206), the control unit 110 receives an integrated signal obtained by integrating the detection signal of the illuminance sensor 500, and changes the RGB ratio so that the RGB ratio becomes constant based on the integrated signal. 3 (see FIG. 8A) is set (S207), and a current having a current value corresponding to the set third current control value A3 is supplied to the light sources 11r, 11g, and 11b. The third current control value A3 is made up of current control values of the currents IR, IG, and IB supplied to the light sources 11r, 11g, and 11b that have a constant RGB ratio in consideration of the detection result of the illuminance sensor 500. . Specifically, the control unit 110 stores in advance only one color of the light sources 11r, 11g, and 11b in a desired amount of light according to the required luminance in the central region C. First, according to the required luminance. Based on the detection signal of the illuminance sensor 500, the light amount of one color serving as a reference is adjusted (a third current control value A3 is determined) so that the obtained light amount is output. Thereafter, the light amounts of the other two colors are adjusted (a third current control value A3 is determined) so that the ratio to the reference light amount becomes a desired value. As an example, in order to make the RGB ratio constant, the control unit 110 first determines the light amount of the green light G having the highest specific visibility, and then determines the light amounts of the red light R and the blue light B. That is, the controller 110 first determines the current control value of the current IG supplied to the green light source 11g, and then determines the current control values of the currents IR and IB supplied to the other light sources 11r and 11b. Thereby, the control part 110 can perform the control which makes RGB ratio constant quickly in the center area | region C. FIG.
In addition, when the process of step S205 or step S207 is completed, the control unit 110 determines whether or not the change in required luminance has been completed (S208). If control unit 110 determines that the change in required luminance has not ended (NO in S208), it returns to the process in step S203. That is, as long as the required luminance continues to change, the processes of steps S203 to S207 are repeated. When control unit 110 determines that the change in required luminance has ended (YES in S208), it ends the process according to the flowchart.

(effect)
As mentioned above, according to 1st Embodiment demonstrated, there exist the following effects.

(1) The HUD device 1 includes three light sources 11r, 11g, and 11b that emit red light R, green light G, and blue light B, respectively, and a plurality of micromirrors 30a that control the angles at which the light R, G, and B are reflected. The display element 30 having one of the plurality of light sources 11r, 11g, and 11b is selected to emit light by supplying a current to the selected one light source 11r, 11g, and 11b. The illumination light C of a desired color is generated from the light emitted from the plurality of light sources 11r, 11g, and 11b by the field sequential method that sequentially switches the light sources, and the light corresponding to the image M among the illumination light C through the micromirror 30a. Illuminance sensor 500 for detecting the illuminance of light R, G, B emitted from the plurality of light sources 11r, 11g, 11b, Provided. The control unit 110 decreases the display period ratio, which is the ratio of the display period Fa that supplies current to the light sources 11r, 11g, and 11b in the frame F, in a stepwise manner as the required luminance of the light sources 11r, 11g, and 11b decreases. In addition, in the boundary region E sandwiching the change points (luminances La and Lb) where the display period ratio changes, the light ratio that is the ratio of the amount of light from each of the light sources 11r, 11g, and 11b stored in advance is the desired value. In the central region C set between the two boundary regions E by supplying current to the light sources 11r, 11g, and 11b according to the first and second current control values A1 and A2 set to be Based on the illuminance of the light R, G, B detected by the illuminance sensor 500, current is supplied to each of the light sources 11r, 11g, 11b so that the RGB ratio becomes a desired value.
According to this configuration, current is supplied to each of the light sources 11r, 11g, and 11b so that the RGB ratio becomes a desired value according to the illuminance of the actual lights R, G, and B in the central region C. As a result, the RGB ratio is maintained at a desired value even in the central region C. Therefore, when the display brightness is changed based on the required brightness, the change in chromaticity can be reduced.

(2) The control unit 110 supplies currents corresponding to the first current control value A1 to the light sources 11r, 11g, and 11b at the points La1 and Lb1 directly above the changing points located at the upper limit of the boundary region E, Currents corresponding to the second current control value A2 larger than the first current control value A1 are supplied to the light sources 11r, 11g, and 11b at the points La2 and Lb2 immediately below the changing points located at the lower limit of the region E.
According to this configuration, changes in chromaticity at the directly above points La1, Lb1 and the directly below points La2, Lb2 are suppressed.

(Second Embodiment)
A second embodiment in which a display device according to the present invention is embodied as a HUD device will be described with reference to the drawings. In the present embodiment, when the appropriate data tables Dtx, Dty, Dtz... Are not selected in the intermediate region C, the appropriate data tables Dtz, Dty, Dtz. Hereinafter, the difference from the first embodiment will be mainly described.

  Each data table Dtx, Dty, Dtz... Includes an expected current value H and a threshold Th (Th1, Th2) in addition to the first and second current control values A1, A2. As shown in FIG. 11B, the expected current value H is a current value expected to be supplied to the light sources 11r, 11g, and 11b in the central region C. The threshold value Th is set between the expected current values H of the data tables Dtx, Dty, Dtz. For example, the threshold value Th1 of the data table Dty is set between the expected current value Hy and the expected current value Hz, as shown in FIG. 11B, and the threshold value Th2 of the data table Dty is set to the expected current value Hx and the expected current. It is set between the values Hy.

  Specifically, the expected current value Hx corresponding to the light source temperature Tx in the central area C is stored in the data table Dtx, and the expected current value corresponding to the light source temperature Ty in the central area C is stored in the data table Dty. Hy is stored, and the expected current value Hz corresponding to the light source temperature Tz in the central region C is stored in the data table Dtz.

  Next, the control procedure of the control unit 110 will be described with reference to the flowchart of FIG. The process according to the flowchart is executed between steps S206 and S207 in the flowchart of FIG.

  When determining that the requested luminance is in the central region C as in step S206 of FIG. 7 described above, the control unit 110 determines whether or not the actual current value IZ exceeds the threshold Th (S301). When determining that the actual current value IZ exceeds the threshold value Th (YES in S301), the control unit 110 reselects the data table Dt (S302), and uses the reselected data table Dt while performing step S207. Perform the following processing.

  For example, when the actual current value IZ exceeds the threshold value Th1 of the data table Dty, as shown by “●” in FIG. The data table Dtz having the expected current value Hz closest to the actual current value IZ is selected again.

  On the other hand, when determining that the actual current value IZ does not exceed the threshold Th (NO in S301), the control unit 110 performs the processing from step S207 onward without reselecting the data table Dt. Note that the reselection of the table data may be performed only in the boundary region E, not in the central region C.

(effect)
As mentioned above, according to 2nd Embodiment demonstrated, there exist the following effects.

  (1) The HUD device 1 includes a temperature sensor 17 that detects the temperatures of the light sources 11r, 11g, and 11b. The control unit 110 includes first and second current control values A1 and A2, an expected current value H (Hx, Hy, Hz) expected to be supplied in the central region C, and a threshold Th for each light source temperature. A plurality of different data tables Dt (Dtx, Dty, Dtz...) Are stored. Further, the control unit 110 selects the data tables Dtx, Dty, Dtz... Matching the temperatures of the light sources 11r, 11g, 11b detected by the temperature sensor 17, and then supplies them to the light sources 11r, 11g, 11b in the central region C. The difference between the actual current value IZ (the same current value as the third current control value A3) and the predicted current values Hx, Hy, Hz of the selected data tables Dtx, Dty, Dtz... Exceeds the threshold Th In this case, the data tables Dtx, Dty, Dtz... Having the expected current values Hx, Hy, Hz close to the actual current value IZ are selected again. The threshold value Th is set between the expected current values Hx, Hy, Hz of each data table Dtx, Dty, Dtz.

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

In the above embodiment, the control unit 110 may switch the gains of the amplifier circuit 440 and the operational amplifier 412 when reaching at least one of the plurality of boundary regions E.
According to this configuration, for example, as the required luminance decreases, the light emission levels of the light sources 11r, 11g, and 11b decrease. At this time, the control unit 110 increases the gains of the amplifier circuit 440 and the operational amplifier 412 in order to increase the resolution of the detection signal of the illuminance sensor 500 and the integration signal of the integration signal generation unit 410. In the boundary region E, current is supplied to the light sources 11r, 11g, and 11b based on the first and second current control values A1 and A2 stored in advance, not the detection result of the illuminance sensor 500. For this reason, by increasing the gain in the boundary region E, changes in luminance and chromaticity can be suppressed as compared with the case where the gain is increased in the central region C where the detection result of the illuminance sensor 500 affects the supply current.

  In the above embodiment, the display element controller 200 may execute part of the control contents of the microcomputer 100, and conversely, the microcomputer 100 may execute part of the control contents of the display element controller 200. .

  In the above embodiment, the light source temperatures Tx, Ty, Tz... Corresponding to the data tables Dtx, Dty, Dtz... Are set at equal temperature intervals (several degrees C. to several tens of degrees C.), but are not limited thereto. For example, the control unit 110 selects any one of the data tables Dtx, Dty, Dtz... Set at equal temperature intervals from 40 ° C. to 85 ° C., and in a low temperature region other than 40 ° C. to 85 ° C. and a normal temperature region. May use the same data table. Further, the light source temperatures Tx, Ty, Tz... In which the data tables Dtx, Dty, Dtz... Are provided may be set so that the temperature interval becomes narrower as the temperature is shifted to the high temperature side or the low temperature side.

In the above embodiment, the control unit 110 sets the third current control value A3 so that the RGB ratio is constant (desired value) when the display period ratio is 100%. When the required brightness is between the maximum brightness Lmax and the brightness Lc, the third current control value A3 is set so that the RGB ratio becomes the first desired value B1. When the luminance is between the luminance Lc and the luminance Lb, the third current control value A3 may be set so that the RGB ratio becomes the second desired value B2. The control unit 110 may switch the RGB ratio between desired values of 3 or more. Further, the control unit 110 may similarly change the RGB ratio according to the required luminance even when the display period ratio is other than 100%.
According to this configuration, for example, even when there is no linearity in the relationship between the current control value and the luminance, the current value can be accurately controlled, and changes in luminance and chromaticity in the central region C are suppressed. can do.

  In the above embodiment, the light sources 11r, 11g, and 11b are configured as independent light sources, but may emit light of a plurality of colors from a common light source. Further, the light source may be any light source that emits light of a plurality of colors, may be composed of only two colors, and may be composed of four or more colors (including white).

  In the above-described embodiment, the illuminance sensor 500 is installed in a part of the optical path of the illumination light C. However, it is only necessary to detect the light intensity of each of the light R, G, and B. You may provide in the location which can detect the light intensity | strength of each of previous light R, G, B. In addition, the illuminance sensor 500 may be appropriately provided at a location where the light intensity of a part of the illumination light C emitted from the illumination optical system 20 can be detected.

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

DESCRIPTION OF SYMBOLS 1 ... HUD apparatus 2 ... Vehicle 3 ... Windshield 4 ... Viewer 6 ... Vehicle ECU
DESCRIPTION OF SYMBOLS 10 ... Illuminating device 11 ... Light source part 11r ... Red light source 11g ... Green light source 11b ... Blue light source 12 ... Circuit board 13 ... Multiplexing part 14 ... Brightness nonuniformity reduction part 15 ... Transmission film 20 ... Illumination optical system 30 ... Display element 30a ... Micromirror 40 ... Projection optical system 50 ... Screen 61 ... Plane mirror 62 ... Concave mirror 70 ... Housing 71 ... Translucent unit 100 ... Microcomputer 110 ... Control unit 200 ... Display element controller 410 ... Integration signal generation unit 411 ... Integration circuit 412 ... Operational amplifier 440 ... Amplifier circuit 430 ... Light source drive circuit 500 ... Illuminance sensor

Claims (3)

A plurality of light sources emitting light of different colors,
A display element having a plurality of reflecting portions for controlling the angle at which the light is reflected;
The plurality of light sources are caused to emit light by supplying current to the selected one light source, and the selected one light source is sequentially switched for each subframe constituting a frame that is a control cycle. A controller that generates illumination light of a desired color from light emitted from a light source and reflects light corresponding to a display image among the illumination light through the reflector;
An illuminance sensor that detects the illuminance of the light emitted from each of the light sources, and a display device comprising:
The frame has a display period in which the light source is driven and the display image is generated, and a non-display period in which the light source is turned off and the display image is not generated.
The controller is
As the required luminance of the light source decreases, the display period ratio, which is the ratio of the display period occupying the frame, is reduced stepwise, and stored in advance in a boundary region including a change point at which the display period ratio changes. Supplying a current to each of the light sources in accordance with a current control value set so that a light ratio that is a ratio of the amount of light from each of the light sources is a desired value;
In the central region set between the two boundary regions, based on the illuminance of the light detected by the illuminance sensor, current is supplied to each light source so that the light ratio becomes the desired value.
A display device characterized by that. The controller is
The current corresponding to the first current control value, which is the current control value, is supplied to each of the light sources at a point immediately above the change point located at the upper limit of the boundary region, and the change located at the lower limit of the boundary region Supplying a current corresponding to a second current control value larger than the first current control value, which is the current control value, to each of the light sources at a point immediately below the point;
The display device according to claim 1. A temperature sensor for detecting the temperature of the light source;
The control unit stores a plurality of different data tables for each temperature of the light source, which includes the current control value and an expected current value expected to be supplied in the central region.
The control unit selects the data table that matches the temperature of the light source detected by the temperature sensor, and then the actual current value supplied to the light source in the central area and the selected data table. If the difference with the expected current value exceeds a threshold, reselect the data table with the expected current value close to the actual current value,
The threshold is set between the expected current values of each data table.
The display device according to claim 1 or 2.

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