WO2018097121A1

WO2018097121A1 - Image display apparatus and head-up display

Info

Publication number: WO2018097121A1
Application number: PCT/JP2017/041779
Authority: WO
Inventors: 誠秦
Original assignee: 日本精機株式会社
Priority date: 2016-11-24
Filing date: 2017-11-21
Publication date: 2018-05-31

Abstract

The present invention reduces work during manufacturing and ensures display quality. A display control unit 310 changes, in a stepwise manner, a display ratio R which is the ratio of the time Fa in which a display element 201 generates an image M with respect to a prescribed time F. A light source control unit 320 adjusts the luminance of the image M by controlling a control value P for adjusting an output of a light source 101 while the display ratio R of the display element 201 is constant. The display control unit 310 controls the display element 201 by switching between first display ratio control S30 in which the change amounts R11, R12 of the display ratio R changed in a stepwise manner is large and second display ratio control S40 in which the change amount R21, R22 of the display ratio R changed in a stepwise manner is smaller than that of the first display ratio control S30.

Description

Image display device, head-up display

The present invention relates to an image display device and a head-up display for displaying a virtual image.

For example, a conventional image display device is known in which a DMD (Digital Micro-mirror Device) as a display element is provided. This type of image display apparatus generates image light by reflecting illumination light with a plurality of micromirrors of the DMD. For example, the image 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, the illumination light whose color is switched in a time-division manner is generated.

For example, the image display device described in Patent Document 1 includes a control unit that sequentially supplies current to each light source. When supplying current to the light source, the control unit performs PWM (Pulse Width Modulation) control that changes the on-duty ratio, which is the current supply period in the subframe, and PAM (Pulse Amplitude Modulation) control that changes the current control value Are executed simultaneously. Specifically, the control unit performs PWM control so that the on-duty ratio decreases stepwise as the required luminance of the light source (required luminance level) decreases, and the on-duty ratio is at a predetermined value. PAM control is performed to reduce the current control value supplied to the light source as the required luminance decreases. Thereby, display luminance according to the required luminance level is realized.

In the image display device described in Patent Document 1, the control unit refers to the table data stored in advance in the storage unit, and sets the current control value (control value) at a constant rate with respect to the change in the required luminance level. It is changing. In such table data, typically, individual differences in light sources are taken into account by calibration at the manufacturing stage of the image display device, and an adjusted current control value is associated with a specific required luminance level. . A predetermined current control value is associated with other required luminance levels by performing linear interpolation with reference to the current control value associated with the specific required luminance level by calibration.

JP 2014-066920 A

However, if the number of current control values determined by calibration is small, linear interpolation will control with a control value that deviates from the output characteristics of the light source (the relationship between current and output light flux). The light cannot be emitted to the light source, and an image with desired luminance and desired color cannot be obtained. Further, if the number of current control values determined by calibration is increased, there is a possibility that the calibration work at the time of manufacture increases.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an image display device and a head-up display that can reduce work during manufacturing and can ensure display quality.

In order to achieve the above object, an image display device according to the present invention includes a plurality of light sources (101g, 101r, 101b) that emit time-divisionally different color lights (Lg, Lr, Lb), respectively.
A display element (201) that generates an image (M) by optically modulating the colored light from the plurality of light sources;
Display control capable of adjusting the brightness of the image by stepwise changing a display ratio (R), which is a ratio of the time (Fa) for generating the image by the display element at a predetermined time (F). Part (310);
While the display ratio of the display element is constant, the brightness of the image can be adjusted by controlling a control value (P) for adjusting the output of the light source of one or more colors among the plurality of light sources. A light source controller (320) for adjusting the control value in a direction to suppress a change in luminance of the image when the display controller changes the display ratio of the display element;
The display control unit changes the display ratio changed in stages in comparison with the first display ratio control (S30) in which the change amount (R11, R12) of the display ratio changed in stages is large. The display element is controlled by switching between the second display ratio control (S40) with a small ratio change amount (R21, R22).

The head-up display of the present invention includes the image display device and a projection unit that visually recognizes the virtual image of the image by projecting the image displayed by the image display device on a transmission / reflection unit positioned in front of the viewer. (20).

According to the present invention, it is possible to reduce work during manufacturing and to ensure display quality.

It is the schematic which shows the structure of the head-up display which concerns on embodiment of this invention. It is a figure explaining the display ratio in the image display apparatus of FIG. 1 shows various control data when the image display apparatus of FIG. 1 executes the first display ratio control, (a) shows the first display ratio control data in which the required luminance level is associated with the display ratio, (B) shows the 1st light source control data which matched the request | required brightness | luminance level and the display ratio, (c) shows the relationship between a request | requirement brightness | luminance level and the brightness | luminance of a virtual image. (A) is an enlarged view of a key point H in FIG. 3 (b), and (b) is a diagram showing a relationship between a required luminance level and a gain. 1 shows various control data when the image display apparatus of FIG. 1 executes the second display ratio control, (a) shows the second display ratio control data in which the required luminance level is associated with the display ratio, (B) shows the 2nd light source control data which matched the request | requirement brightness | luminance level and the display ratio, (c) shows the relationship between a request | requirement brightness | luminance level and the brightness | luminance of a virtual image. It is a flowchart which shows the process sequence of the image display part of FIG. It is a flowchart which shows the process sequence of 1st display ratio control and 2nd display ratio control in the image display part of FIG.

Embodiments in which the image display device 10 according to the present invention is embodied in a head-up display 1 (hereinafter referred to as HUD 1) will be described with reference to the drawings.

(Configuration of HUD1)
FIG. 1 is a diagram illustrating the configuration of the HUD 1 according to the present embodiment.
The HUD 1 includes an image display device 10, a projection unit 20 that directs the image M displayed by the image display device 10 toward the windshield, and an external light detection unit 30 that can detect light intensity such as an illuminance sensor. The HUD 1 is installed on a dashboard of a vehicle (not shown), the image display device 10 displays an image M, and the windshield (illustrated) is an example of a transmission reflection unit in which the projection unit 20 is positioned in front of the viewer. The virtual image of the image M is displayed to the viewer. In the image M, information about the vehicle (for example, engine speed, navigation information, etc.) is displayed. The transmission / reflection part is not limited to the windshield of the vehicle, but reflects part of light and transmits part of light (light from a real scene in front of the viewer through the transmission / reflection part). It may be a light combiner.

Further, the HUD 1 in the present embodiment can detect the illuminance outside the HUD 1 (external light illuminance) by the external light detection unit 30 and automatically adjust the luminance B of the virtual image to be generated based on the external light illuminance. . The external light detection unit 30 does not need to be provided in the HUD 1 and may be replaced by the vehicle-side external light detection unit 3 provided in the vehicle on which the HUD 1 is mounted. In this case, the HUD 1 (image display device 10) receives external light illuminance information related to the external light illuminance from the input unit 330 described later via the network of the vehicle.

(Image display device 10)
The image display device 10 generates an image M by spatially modulating the backlight unit 100 capable of emitting a plurality of color lights Lg, Lr, and Lb of different colors and the color lights Lg, Lr, and Lb from the backlight unit 100. Display unit 200, backlight unit 100, and control unit 300 that controls display unit 200, and displays image M on a display surface (screen 202 described later). Note that the image display apparatus 10 in the present embodiment generates the image M by the field sequential color method.

The backlight unit 100 is based on, for example, a light source 101 including three LEDs (Light Emitting Diode) that emit different color lights Lg, Lr, and Lb, and a control value P input from the control unit 300 (light source control unit 320). The light source driving unit 102 including a circuit for adjusting the output of the light source 101 and a light receiving element having a photodiode, for example, and the color light Lg, Lg, Lr, and Lb emitted from the light source 101 are branched. Light intensity information output from the light intensity detector 103, connected between the light intensity detector 103 and the light source controller 320, and a light intensity detector 103, which is a light intensity sensor that detects the light intensities of Lr and Lb. A gain adjusting unit 104 that adjusts the gain G of the FS and outputs the amplified light intensity information FS to the light source control unit 320. Specifically, the light source 101 includes a first light source 101g that emits green color light Lg, a second light source 101r that emits red color light Lr, and a third light source 101b that emits blue color light Lb.

The backlight unit 100 of the present embodiment automatically adjusts the output of the light source 101 based on the external light illuminance. Here, the output of the light source 101 is the total light energy of the color light L emitted from the light source 101 within a predetermined time. That is, the output adjustment of the light source 101 is an instantaneous output adjustment by adjusting the power (current, voltage) supplied to the light source 101 and the time during which the power is supplied to the light source 101 within a predetermined time. And cumulative output adjustment. The predetermined time is preferably a time corresponding to a critical fusion frequency or higher at which a person can visually recognize flicker, for example, one frame period or less for generating one image, and generally 1/60 seconds or less. .

In addition, the backlight unit 100 of the present embodiment includes a light intensity detection unit 103 and performs feedback control for correcting the output of the light source 101 based on the light intensity information FS of the color light L detected by the light intensity detection unit 103. As a result, it is possible to obtain an output according to the design value corresponding to a characteristic change due to a temperature change of the light source 101, a characteristic change due to aging, and the like. Thereby, the brightness | luminance and color of the image M (the said virtual image) which the image display apparatus 10 (HUD1) produces | generates can be brought close to a desired value. In the backlight unit 100 of the present embodiment, the light intensity information FS detected by the light intensity detection unit 103 is appropriately amplified by the gain adjustment unit 104. Thereby, even when the output of the light source 101 is set to a low output in order to reduce the luminance of the generated image M, the light intensity information FS can be measured with high accuracy.

The light source driving unit 102 inputs a control value P for controlling the output of the light source 101, and adjusts the output of the light source 101 based on the control value P. The control value P is, for example, a value for controlling a current control value flowing in the light source 101 and / or a value for controlling a voltage value applied to the light source 101 and / or a value for controlling a lighting period or / and a light intensity detecting unit 103. Is a reference value to be compared with the light intensity FS input from. The control value P is data associated with the required luminance level Lv, which is a plurality of stages of data indicating the luminance B of the virtual image generated by the HUD 1, and will be described in detail later.

The light source driver 102 may receive the light intensity information FS from the light intensity detector 103 and adjust the output of the light source 101 based on the light intensity information FS. Specifically, for example, the light source driving unit 102 includes a comparator (comparator), and compares the light intensity information FS input from the light intensity detection unit 103 with the reference value (target light intensity) input from the light source control unit 320. The current flowing through the light source 101 may be automatically adjusted.

The display unit 200 includes a display element 201 made of DMD and a screen 202 which is a display surface for displaying an image M generated by the display element 201. Note that the DMD 201 includes a plurality of movable micromirrors constituting pixels, and the plurality of micromirrors individually turn on the color light L from the light source 101 toward the screen 202 or the color light L from the light source 101. Are sequentially switched to an off state directed in a different direction from the screen 202, whereby an image M having a desired luminance and color is displayed on the screen 202 by additive color mixing by time division in the frame F. Note that a transmissive liquid crystal display, a reflective LCoS (registered trademark), or the like may be applied to the display element 201. In general, between the backlight unit 100 and the display element 201 and between the display element 201 and the screen 202, a relay optical system such as a lens or a mirror for the HUD 1 to generate an appropriate virtual image (illustration is illustrated). Not provided), but the description is omitted.

The screen 202 is a transmissive screen composed of a holographic diffuser, a microlens array, a diffusion plate, etc., but may be composed of a reflective screen.

The control unit 300 is composed of one or a plurality of microcomputers, FPGAs, ASICs, and the like that are operated by a program. The control unit 300 includes an input unit 330 that inputs various signals from the outside, a display control unit 310 that controls the display element 201 based on the various signals input from the input unit 330, and a light source control unit 320 that controls the light source 101. It is comprised by. The control unit 300 according to the present embodiment inputs an image signal (not shown) from the outside of the HUD 1 (for example, the vehicle ECU 2), and controls the display element 201 based on the image signal to display an image M indicating predetermined information. The control unit 300 has a GPU (Graphics Processing Unit), receives a predetermined signal from the outside of the HUD 1 (for example, the vehicle ECU 2 or various sensors of the vehicle), and generates the image signal based on this signal. May be.

Further, the control unit 300 adjusts the luminance B and color of the virtual image displayed by the HUD 1 to desired values by adjusting the output of the light source 101 that emits the respective color lights Lg, Lr, and Lb. The control unit 300 acquires external light information EL related to illuminance (brightness) outside the HUD 1 from the input unit (external light information acquisition unit) 330. Based on the input external light information EL, the controller 300 determines a required luminance level Lv that indicates the luminance B of the virtual image that the HUD 1 should display. The control unit 300 includes the light source control data 600 in which the control value P for controlling the output of the light source 101 is associated with the required luminance level Lv, and the display element 201 in the predetermined period F is also imaged at the required luminance level Lv. The display ratio control data 500 associated with the display ratio R, which is the ratio occupied by the display period Fa for generating M, is stored in a storage unit (not shown) in advance, and the required luminance level Lv determined based on the external light information EL is stored. Accordingly, the output of the light source 101 and the display ratio R of the display element 201 are controlled to adjust the brightness B of the virtual image generated by the HUD 1. A display control method of the HUD 1 will be described in detail later. The above is the configuration of the image display apparatus 10.

The projection unit 20 is an optical member that reflects the image M displayed by the image display device 10 on the transmission and reflection unit. For example, the first reflection unit 21 that reflects the light of the image M displayed by the image display device 10; The second reflection unit 22 is configured to reflect the light of the image M reflected by the first reflection unit 21 toward the transmission reflection unit. The projection unit 20 mainly has a function of enlarging the image M displayed by the image display device 10 and a function of determining the imaging position of the virtual image generated by the HUD 1, but the virtual image that is generated due to distortion of the transmission / reflection unit or the like. Other functions such as a distortion suppression function for reducing the distortion may be included. The projection unit 20 may be a combination of a light refraction member such as a lens, a diffractive optical member, or the like instead of a light reflection member such as a mirror. The above is the configuration of the HUD 1 of the present embodiment. The virtual image display control method performed by the control unit 300 according to the present embodiment will be described with reference to FIGS.

First, the display ratio R will be described with reference to FIG. FIG. 2 is a diagram illustrating an operation example of the light source 101 and the display element 201 in the frame F when the display ratio R is 50%. A frame F, which is a control cycle for displaying the image M, includes a display period Fa and a non-display period Fb. In the display period Fa, the display control unit 310 turns on or off each pixel of the display element 201 in a time-sharing manner based on the image signal, and the light source control unit 320 uses different colors from the plurality of

light sources

101g, 101r, and 101b. Color lights Lg, Lr, and Lb are sequentially emitted. In the display period Fa, since the light sources 101 are sequentially turned on, the image M is displayed on the screen 202 when the pixels of the display element 201 are turned on. On the other hand, in the non-display period Fb, the display control unit 310 calculates the on / off time or ratio of each pixel in the display period Fa, and on / off of each pixel in the non-display period Fb based on the calculation result. Determine time or percentage. Then, the display control unit 310 turns each pixel on and / or off within the non-display period Fb based on the on / off time or ratio of each pixel during the non-display period Fb. For example, a pixel that is long on in the display period Fa is turned off in the non-display period Fb, and a pixel that is short on in the display period Fa is turned on in the non-display period Fb. For each of the plurality of frames F, adjustment is made so that the ON period and the OFF period are substantially equal. Accordingly, it is possible to prevent an extremely long period of being turned on or an extremely long period of being turned off in each pixel of the display element 201 and to prevent a failure of each pixel of the display element 201. Can do. In the non-display period Fb, the light source control unit 320 drives all the light sources 101 off or with a considerably low output, so that the image M is displayed on the screen 202 even when the display element 201 is turned on to prevent failure. Therefore, the unnecessary image M generated during the non-display period Fb is prevented from being viewed by the viewer as the virtual image. The display ratio R is the ratio of the display period Fa in the frame F. In FIG. 2, since the ratio of the display period Fa in the frame F is half, the display ratio R can be said to be 50%. Note that the display control unit 310 of the present embodiment can change the display ratio R stepwise as described later.

In the present embodiment, the display control unit 310 associates the display ratio R with the required luminance level Lv that is data for instructing the luminance B of the virtual image, and displays the display element 201 according to the switching of the required luminance level Lv. First display ratio control data 510 and second display ratio control data 520, which are display ratio control data 500 for adjusting the ratio R in stages, are stored in at least a storage unit (not shown).

Further, the light source control unit 320 associates the control value P with the required luminance level Lv, and the light source control data 600 that continuously adjusts the control value P (current control value) of the light source 101 in accordance with the switching of the required luminance level Lv. The first light source control data 610 and the second light source control data 620 are stored in a storage unit (not shown).

The control unit 300 converts the display ratio control data 500 for controlling the display element 201 by the display control unit 310 according to the temperature information T indicating the temperature inside the HUD 1, the first display ratio control data 510 or the second display ratio control. The light source control unit 320 switches the light source control data 600 for controlling the light source 101 to the first light source control data 610 or the second light source control data 620. When the received temperature information T is equal to or less than the first threshold value TH1, the display control unit 310 switches the display ratio control data 500 to the first display ratio control data 510, and the light source control unit 320 converts the light source control data 600 into the first display ratio control data 510. The first light source control data 610 is switched. When the received temperature information T is equal to or higher than the second threshold value TH2 higher than the first threshold value TH1, the display control unit 310 switches the display ratio control data 500 to the second display ratio control data 520, and the light source control unit. 320 switches the light source control data 600 to the second light source control data 620. Hereinafter, the display control unit 310 controls the display element 201 with the first display ratio control data 510 that adjusts the display ratio R relatively coarsely with respect to the change in the required luminance level Lv, together with the first display ratio control S30. In addition, controlling the display element 201 with the second display ratio control data 520 that adjusts the display ratio R relatively finely with respect to the change in the required luminance level Lv is also referred to as second display ratio control S40. The temperature information T is data indicating the temperature inside the HUD 1. For example, the temperature information T is provided in the vicinity of the light source 101, and is provided in the vicinity of the temperature sensor 401 for detecting the temperature of the light source 101 or the display element 201. Is output to the controller 300 from the temperature sensor 403 that detects the temperature. Although described later as a modification, the trigger for switching between the display ratio control data 500 and the light source control data 600 is not limited to the temperature information T.

FIG. 3 is a diagram illustrating changes in the display ratio R, the control value P, and the brightness B of the virtual image according to the required brightness level Lv when the display control unit 310 performs the first display ratio control S30 on the display element 201. It is. FIG. 3A shows the first display ratio control data 510 that associates the display ratio R with the required luminance level Lv and adjusts the display ratio R of the display element 201 stepwise in accordance with the switching of the required luminance level Lv. FIG. 3B associates the control value P with the required luminance level Lv, and continuously applies the control value P (current control value) of the light source 101 in response to switching of the required luminance level Lv while the display ratio R is constant. The 1st light source control data 610 adjusted automatically is shown. In the first display ratio control S30 of the present embodiment, the display control unit 310 gradually increases the display ratio R of the display element 201 based on the first display ratio control data 510 according to the decrease in the required luminance level Lv. The light source control unit 320 continuously decreases the control value P of the light source 101 based on the first light source control data 610 according to the decrease in the required luminance level Lv while the display ratio R is constant. In addition, the light source control unit 320 suppresses a rapid decrease in the brightness B of the virtual image caused by the decrease in the display ratio R when the display ratio R of the display element 201 decreases by one step according to the decrease in the required brightness level Lv. The current control value (control value P) flowing through the light source 101 is increased. As shown in FIG. 3C, the horizontal axis indicates the required luminance level Lv and the vertical axis indicates the luminance B of the virtual image by the stepwise change in the display ratio R and the continuous change in the control value P. In accordance with the change in the luminance level Lv, the luminance B of the virtual image is continuously changed. As shown in FIG. 3C, the relationship between the required luminance level Lv in a plurality of stages and the luminance B of the virtual image in the image display device 10 of the present embodiment is such that the inclination of the luminance B of the virtual image on the low luminance side is The inclination of the brightness B of the virtual image is smaller than the inclination on the high brightness side. That is, the amount of change on the low luminance side of the luminance B of the virtual image by switching the required luminance level Lv is set to be smaller than the amount of change on the high luminance side of the luminance B of the virtual image. The brightness B can be set finely, but is not limited to this.

The first display ratio control data 510 and the first light source control data 610 will be specifically described.
While the required luminance level Lv is between the required luminance level Lv1y corresponding to the highest luminance B1 of the virtual image luminance B and the required luminance level Lv1x, the first display ratio control data 510 does not depend on the change in the required luminance level Lv. The display ratio R of the display element 201 is maintained at 70%, and the first light source control data 610 continuously decreases the control value P of the light source 101 as the required luminance level Lv decreases from Lv1y to Lv1x. When the required luminance level Lv changes from Lv1x to Lv2y, which is one level lower than Lv1x, the first display ratio control data 510 changes the display ratio R of the display element 201 from 70% to 60%. The first light source control data 610 reduces the current control value (control value P) flowing through the light source 101 so as to suppress the rapid decrease in the brightness B of the virtual image caused by the decrease in the display ratio R. increase.
Further, when the required luminance level Lv is from the required luminance level Lv2y to the required luminance level Lv2x, the first display ratio control data 510 sets the display ratio R of the display element 201 to 60% regardless of the change in the required luminance level Lv. The first light source control data 610 continuously decreases the control value P of the light source 101 as the required luminance level Lv decreases from Lv2y to Lv2x. When the required luminance level Lv changes from Lv2x to Lv3y, which is one level lower than Lv2x, the first display ratio control data 510 changes the display ratio R of the display element 201 from 60% to 50%. The first light source control data 610 reduces the current control value (control value P) flowing through the light source 101 so as to suppress the rapid decrease in the brightness B of the virtual image caused by the decrease in the display ratio R. increase. FIG. 4 shows an enlarged view of the key point H in the first display ratio control data 510 of FIG.

As shown in FIG. 4A, the first light source control data 610 (light source control data 600) associates the control value P of the light source 101 with each of a plurality of required luminance levels Lv by calibration at the time of manufacture. Two points of reference control data Ap, Aq, and interpolation control data C in which the control value P of the light source 101 is associated with the required luminance level Lv by linear interpolation from the two points of reference control data Ap, Aq; The light source control unit 320 controls the control value P of the light source 101 according to the required luminance level Lv based on the reference control data Ap and Aq and the interpolation control data C stored in advance in the storage unit. Specifically, two points of reference control data A12p and A12q in which control values P are associated with predetermined two required luminance levels Lv12p and Lv12q are determined by calibration at the time of manufacture, and these two points of reference control are determined. By linearly interpolating between the data A12p and A12q, the control value P is associated with the required luminance level Lv between two predetermined required luminance levels Lv12p and Lv12q, and stored in the storage unit in advance. I can keep it. The display control unit 310 stores in advance two points of reference control data Ap and Aq in which the control value P of the light source 101 is associated with each of the plurality of required luminance levels Lv by calibration, and the two points of reference control. Interpolation control data C in which the control value P of the light source 101 is associated with the required luminance level Lv by linear interpolation from the data Ap and Aq, and the reference control data Ap, Aq and Based on the interpolation control data C calculated each time, the control value P of the light source 101 may be controlled according to the required luminance level Lv. Note that the interpolation control data C may be obtained by an approximate expression based on three or more reference control data determined by calibration. Further, the interpolation control data C may be obtained by polynomial interpolation instead of linear interpolation.

As shown in FIG. 3, the light source control data 600 in the present embodiment includes two criteria associated with consecutive required luminance levels Lv1x and Lv2y (or Lv2x and Lv3y) that do not have the interpolation control data C in the interval E1. The display control unit 310 includes the control data Ax and Ay, and the display control unit 310 includes two reference control data Ax and Ay associated with the required luminance levels Lv1x and Lv2y (or Lv2x and Lv3y) that the light source control unit 320 continues. When the control value P of the light source 101 is largely adjusted, the display ratio R of the display element 201 is switched. In other words, the light source control data 600 does not have the interpolation control data C in E1 between the required luminance levels Lv1x to Lv2y in which the display control unit 310 changes the display ratio R of the display element 201. In E1 between the required luminance levels Lv1x and Lv2y for changing the display ratio R (or E1 between Lv2x and Lv3y), the light source control unit 320 performs a linear interpolation between the light source 101 in order to significantly change the control value P of the light source 101. However, there is a possibility that a large error occurs in the output of the actual light source 101. However, in the light source control data 600 of the present embodiment, E1 (or Lv2x, Lv3y) between the required luminance levels Lv1x and Lv2y for changing the display ratio R During E1), since there is no interpolation control data C in which the required luminance level Lv and the control value P are associated by linear interpolation, this can be prevented.

FIG. 4B is a diagram showing the transition of the gain G based on the change in the required luminance level Lv. The gain adjustment unit 104 switches the gain G when the light source control unit 320 switches the control value P of the light source 101 at E1 or E2 between two reference control data Ap and Aq associated with the continuous required luminance level Lv. . Specifically, the light source control unit 320 increases the gain G from G3 to G2 during E2 while switching from A12q to A13p so as to decrease the output of the light source 101. Thereby, even when the output of the light source 101 is low, the light intensity information FS can be measured with high accuracy.

Next, the second display ratio control S40 will be described with reference to FIG.
FIG. 5A shows second display ratio control data 520 that adjusts the display ratio R of the display element 201 stepwise in response to switching of the required brightness level Lv, and FIG. 5B shows the required brightness level Lv. The second light source control data 620 for adjusting the control value P (current control value) of the light source 101 in accordance with the switching is shown. In the second display ratio control S40 of the present embodiment, the display control unit 310 changes the display ratio R of the display element 201 based on the second display ratio control data 520 in accordance with the decrease in the required luminance level Lv. The light source control unit 320 reduces the control value P of the light source 101 based on the second light source control data 620 according to the decrease in the required luminance level Lv while the display ratio R is constant. Is continuously reduced. In addition, the light source control unit 320 suppresses a rapid decrease in the brightness B of the virtual image caused by the decrease in the display ratio R when the display ratio R of the display element 201 decreases by one step according to the decrease in the required brightness level Lv. The current control value (control value P) flowing through the light source 101 is increased. As shown in FIG. 5C, the horizontal axis represents the required luminance level Lv and the vertical axis represents the luminance B of the virtual image by the stepwise change of the display ratio R and the continuous change of the control value P. In accordance with the change in the luminance level Lv, the luminance B of the virtual image is continuously changed.

The second display ratio control data 520 and the second light source control data 620 will be specifically described.
While the required luminance level Lv is from the required luminance level Lv1y corresponding to the highest luminance B2 of the virtual image luminance B to the required luminance level Lv1z, the second display ratio control data 520 does not depend on the change in the required luminance level Lv. The display ratio R of the display element 201 is maintained at 70%, and the first light source control data 610 continuously decreases the control value P of the light source 101 as the required luminance level Lv decreases from Lv1y to Lv1z. When the required luminance level Lv changes from Lv1z to a level one lower than Lv1z, the second display ratio control data 520 indicates that the display ratio R of the display element 201 is changed from 70% to 69% by a predetermined change amount R21. The first light source control data 610 is decreased by (1%), and the current control value (control value P) flowing through the light source 101 is increased so as to suppress the rapid decrease in the brightness B of the virtual image caused by the decrease in the display ratio R. . That is, the second display ratio control data 520 in the second display ratio control S40 is smaller in the amount of change in the display ratio R that changes in one step than the first display ratio control data 510 in the first display ratio control S30. . Specifically, the amount of change R11, R12,... In one stage of the display ratio R that changes in accordance with the change in the required luminance level Lv in the first display ratio control data 510 is 10%, whereas The amount of change R21, R22,... In one stage of the display ratio R that changes in accordance with the change in the required luminance level Lv in the 2 display ratio control data 520 is 1%. As described above, in the second display ratio control S40, the display ratio R is finely switched in accordance with the change in the required luminance level Lv. Therefore, it is possible to suppress the change amount of the control value P when the display ratio R changes by one step. Therefore, the temperature change due to self-heating of the light source 101 before and after changing the control value P is suppressed, and the output characteristics due to the temperature change of the light source 101 (relationship between control value P and output light beam) Can be suppressed, and the color light L having a desired light intensity can be emitted from the light source 101.

Note that the interval D between the two reference control data Ap and Aq for generating the interpolation control data C in the second display ratio control data 520 when the second display ratio control S40 is executed is the same as when the first display ratio control S30 is executed. It is preferable to make the interval smaller than the interval D between the two reference control data Ap and Aq for generating the interpolation control data C in the first display ratio control data 510. In other words, the number of interpolation control data C to be interpolated with the plurality of reference control data Ap and Aq when executing the first display ratio control S30 is interpolated with the plurality of reference control data Ap and Aq when executing the second display ratio control S40. It is preferable that the number be larger than the number of interpolation control data C to be performed. Thereby, the ratio (interpolation ratio) of the interpolation control data C generated by the interpolation at the time of executing the second display ratio control S40 can be made lower than the ratio at the time of executing the first display ratio control S30. When the second display ratio control S40 is executed, the light source 101 is expected to be hot, and in this case, the output characteristics of the light source 101 tend to depart from linear. Therefore, when executing the second display ratio control S40 in which the output characteristics of the light source 101 are non-linear, the interval D between the two reference control data Ap and Aq is narrowed, and the ratio of the interpolation control data C is reduced, thereby interpolating. The error between the control data C and the actual output of the light source 101 can be reduced. On the other hand, when the first display ratio control S30 is executed, the light source 101 is expected not to be at a high temperature. When the light source 101 is not at a high temperature, the output characteristics of the light source 101 are almost linear. Therefore, even when the interval D between the two reference control data Ap and Aq for generating the interpolation control data C is widened, the interpolation control data C And the actual output of the light source 101 can be kept small. That is, in the first display ratio control data 510 at low temperature, it is possible to adjust the output of the light source 101 with high accuracy while reducing the number of reference control data Ap and Aq determined by calibration at the time of manufacture.

Next, a display control method of the HUD 1 will be described with reference to the flowchart of FIG.
First, in step S10, the control unit 300 acquires temperature information T indicating the temperature inside the HUD1. Specifically, the temperature of the light source 101 is detected from the temperature sensor 401, or the temperature of the display element 201 is detected from the temperature sensor 403. In step S20, the controller 300 determines whether the temperature information T acquired in step S10 is equal to or less than the first threshold value TH1. When the temperature information T is equal to or lower than the first threshold value TH1 (YES in step S20), the control unit 300 (display control unit 310) selects the first display ratio control S30 and uses it in the first display ratio control S30. First display ratio control data 510 and first light source control data 610 are read from the storage unit. When the temperature information T is larger than the first threshold (NO in step S20), the control unit 300 (display control unit 310) selects the second display ratio control and uses the second display ratio control for the second display ratio control. Data 520 and second light source control data 620 are read from the storage unit.

Next, a specific control method in the first display ratio control S30 will be described with reference to the flowchart of FIG. Since the first display ratio control S30 and the second display ratio control S40 are different only in the display ratio control data 500 and the light source control data 600 used in the control, only the first display ratio control S30 will be described below. A detailed description of the second display ratio control S40 will be omitted.

In step S31, the control unit 300 acquires the external light information EL related to the illuminance outside the HUD 1 from the input unit 330. Specifically, the external light information EL is acquired from the external light detection unit 30 provided in the HUD 1 or the vehicle-side external light detection unit 3 provided in the vehicle on which the HUD 1 is mounted. In step S32, the display control unit 310 determines the display ratio R corresponding to the external light information EL detected in step S31 based on the display ratio control data 500 selected in step S30 or S40. In step S33, the light source control unit 320 determines the control value P corresponding to the external light information EL detected in step S31 based on the light source control data 600 selected in step S30 or S40. In step S34, the display control unit 310 and the light source control unit 320 update the driving conditions of the light source 101 and the display element 201. Specifically, the display control unit 310 controls the display element 201 at the display ratio R determined at step S32, and at the same time, the light source control unit 320 uses the control value P determined at step S33 to control the light source 101. To control. By this step S34, the control unit 300 acquires the light intensity information FS of the color light L emitted from the light source 101 from the input unit 330 (step S35), and the color balances of the color lights Lg, Lr, and Lb of different colors are matched. If it does not match, the control value P of the light source 101 that emits the color light L that needs to be corrected is corrected (step S37). Then, the process returns to step S10.

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

The image display apparatus 10 according to the present embodiment includes a plurality of

light sources

101g, 101r, and 101b that emit color lights Lg, Lr, and Lb of different colors in a time-sharing manner, and color lights Lg, The display element 201 that generates the image M by optically modulating Lr and Lb, and the display ratio R that is the ratio of the time Fa for generating the image M to the display element 201 in a predetermined time F are changed in stages. Thus, the display control unit 310 that can adjust the luminance of the image M and the control that adjusts the output of one or more light sources among the plurality of

light sources

101g, 101r, and 101b while the display ratio R of the display element 201 is constant. By controlling the value P, the brightness of the image M can be adjusted, and when the display control unit 310 changes the display ratio R of the display element 201, the change in the brightness of the image M is suppressed. The light source control unit 320 that adjusts the control value P in the direction and the display control unit 310 include a first display ratio control S30 and a first display ratio control S30 in which the change amounts R11 and R12 of the display ratio R that are changed in stages are large. The display element 201 is controlled by switching between the second display ratio control S40 in which the amount of change R21, R22 of the display ratio R that is changed stepwise is small. In this way, since the second display ratio control S40 that switches the display ratio R finely can be executed, the amount of change in the control value P when the display ratio R changes by one step can be kept small. Therefore, it is possible to suppress temperature change due to self-heating of the light source 101 before changing the control value P and after changing the control value P, and to suppress unintended change in output characteristics due to temperature change of the light source 101. The color light L having a desired light intensity can be emitted from the light source 101.

Further, the image display apparatus 10 according to the present embodiment receives temperature information T from a temperature sensor 401 that detects the temperature of the light source 101, a temperature sensor 403 that detects the temperature of the display element 201, and the like, and based on the temperature information T, You may perform 1st display ratio control S30 or 2nd display ratio control S40. Thereby, based on the temperature change which is a factor which changes the output characteristic of the light source 101, it can switch to 1st display ratio control S30 or 2nd display ratio control S40.

Specifically, when the internal temperature is low, the display control unit 310 executes the first display ratio control S30 that switches the display ratio R roughly. If the light source 101 is at a low temperature, the output characteristic of the light source 101 (control value P—the relationship between the output light flux) is approximately linear. Therefore, when the display ratio R is changed by one step by the first display ratio control S30. Even when the amount of change in the control value P increases, the output adjustment of the light source 101 can be accurately performed. Further, in the first display ratio control data 510 used in the first display ratio control S30, reference control data (Ap, Aq) which is a part of the first display ratio control data 510 is determined in order to switch the display ratio Ra roughly. Therefore, when the image display device 10 is manufactured, the number of display ratios Ra to be switched can be reduced, and the manufacturing cost can be suppressed.

Further, when the internal temperature is high, the display control unit 310 executes the second display ratio control for finely switching the display ratio R. When the light source 101 is at a high temperature, the output characteristic (control value P-output light flux relationship) of the light source 101 tends to deviate from linear. Therefore, the display ratio R is set to one level by the second display ratio control S40. By reducing the amount of change in the control value P when changing, the temperature change due to self-heating of the light source 101 before changing the control value P and after changing the control value P is suppressed, and the temperature change of the light source 101 The unintended change in the output characteristics due to the light can be suppressed, and the color light L having a desired light intensity can be emitted from the light source 101.

The display control unit 310 receives the temperature estimation information Ta that can estimate the temperature inside the HUD 1 or the image display device 10, and based on the temperature estimation information Ta, the first display ratio control S30 or the second display ratio control. S40 may be executed. The temperature estimation information Ta is, for example, temperature information T from the vehicle-side temperature detection unit 4 provided outside the HUD 1. In this case, the display control unit 310 may estimate that the HUD 1 and the inside of the image display device 10 are at a high temperature when the temperature indicated by the temperature information T from the vehicle-side temperature detection unit 4 is high. The temperature estimation information Ta is, for example, external light information EL from the external light detection unit 30 provided inside the HUD 1, external light information EL from the vehicle-side external light detection unit 3 outside the HUD 1, and the like. . The display control unit 310 may estimate that the inside of the HUD 1 and the image display device 10 is at a high temperature when the external illuminance indicated by the external light information EL is high. The temperature estimation information Ta is a combination of, for example, current information I from the current detection unit 402 that detects a current value flowing through the light source 101 provided in the light source 101 and light intensity information FS from the light intensity detection unit 103. Information. In this case, when the output efficiency combining the value of the current flowing through the light source 101 indicated by the current information I and the light intensity information FS corresponding to the actual output of the light source 101 is low, the display control unit 310 has the HUD 1 and the image display device 10. It may be presumed that the inside of is hot.

In the image display device 10 according to the present embodiment, the light source control unit 320 uses a plurality of reference control data Ap and Aq in which the control value P of the light source 101 is determined by calibration, and the plurality of reference control data Ap and Aq. Based on the interpolation control data C that determines the control value P of the light source 101 by linear interpolation or polynomial interpolation, the control value P of the light source 101 of one or more colors among the plurality of

light sources

101g, 101r, 101b is controlled. Also good.

The light source control unit 320 stores in advance a plurality of reference control data Ap and Aq in which the control value P of the light source 101 is determined by calibration, and performs linear interpolation or polynomial interpolation using the plurality of reference control data Ap and Aq. The interpolation control data C for determining the control value P of the light source 101 is calculated, and based on the reference control data Ap, Aq and the interpolation control data C, the control value of the light source 101 of one or more colors among the plurality of

light sources

101g, 101r, 101b. P may be controlled. In this way, by providing the interpolation control data C that is linearly or polynomially interpolated with the reference control data Ap and Aq, the number of reference control data Ap and Aq that determine the control value P by calibration at the time of manufacture can be reduced. Manufacturing cost can be reduced.

Further, in the image display device 10 of the present embodiment, the display control unit 310 determines the light intensity of the first color light Lg emitted from the first light source 101g that is driven based on the reference control data Ap, Aq and the interpolation control data C. The control value P of the

light sources

101r and 101b that emit the color lights Lr and Lb of one or more colors different from the first color light Lg may be corrected so that the light intensity ratio becomes a desired value.

Further, when the temperature information T becomes equal to or lower than the predetermined first threshold value, the display control unit 310 switches from the second display ratio control S40 to the first display ratio control S30, and the temperature information T is controlled by the first threshold value. When the second threshold value is larger than the second threshold value, control may be performed by switching from the first display ratio control S30 to the second display ratio control S40. That is, the switching point from the second display ratio control S40 to the first display ratio control S30 is different from the switching point from the first display ratio control S30 to the second display ratio control S40. Also good.

Also, the highest brightness B2 of the virtual image brightness B in the second display ratio control S40 may be lower than the highest brightness B1 of the virtual image brightness B in the first display ratio control S30. In other words, the luminance B of the virtual image at the time of the second display ratio control S40 may have a dynamic range smaller than the luminance B of the virtual image at the first display ratio control S30. Thereby, the highest brightness B2 of the virtual image brightness B in the second display ratio control S40 can suppress the amount of change in the control value P of the light source 101 with respect to the change in the required brightness level Lv. Temperature change due to self-heating of the light source 101 when changing B can be suppressed to a low level.

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

In the above-described embodiment, the interpolation control data C is provided. However, the calibration is performed for all the required luminance levels Lv, and the light source control data 600 is all the reference control data Ap, Aq for determining the control value P by calibration. You may comprise.

In the above embodiment, as shown in FIG. 4, the interpolation control data C12 is interpolated from the reference control data A12p and A12q determined by calibration, and the reference control data A13p and A13q that do not overlap with the reference control data A12p and A12q. Thus, the interpolation control data C13 is interpolated. That is, one interpolation control data C is interpolated from two dedicated reference control data Ap and Aq that are not used for interpolation of other interpolation control data C, but it is also used for interpolation of other interpolation control data C 2 One interpolation control data C may be generated from two reference control data Ap and Aq. Specifically, the reference control data A12q shown in FIG. 4 may be omitted, the interpolation control data C12 may be interpolated from the reference control data A12p, A13p, and the interpolation control data C13 may be interpolated from the reference control data A13p, A13q. .

In the above embodiment, the

light sources

101r, 101g, and 101b 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).

1: head-up display, 2: vehicle ECU, 3: vehicle side outside light detection unit, 4: vehicle side temperature detection unit, 10: image display device, 20: projection unit, 30: outside light detection unit, 101: light source, 102: Light source drive unit, 103: Light intensity detection unit, 104: Gain adjustment unit, 200: Display unit, 201: Display element, 202: Screen, 300: Control unit, 310: Display control unit, 320: Light source control unit, 330: input unit, 401: temperature sensor, 402: current detection unit, 403: temperature sensor, 500: display ratio control data, 510: first display ratio control data, 520: second display ratio control data, 600: light source control Data, 610: first light source control data, 620: second light source control data, Ap: reference control data, Aq: reference Control data, Ax: reference control data, Ay: reference control data, B: luminance, B1: luminance, B2: luminance, C: interpolation control data, EL: external light information, F: frame, FS: light intensity information, Fa : Display period, Fb: Non-display period, G: Gain, L: Color light, Lv: Required luminance level, M: Image, P: Control value, R: Display ratio, R11: Change amount, R12: Change amount, R21: Change amount, R22: Change amount, Ra: Display ratio, S30: First display ratio control, S40: Second display ratio control, T: Temperature information, TH1: First threshold, TH2: Second threshold, Ta: Temperature estimation information

Claims

A plurality of light sources (101g, 101r, 101b) that emit color lights (Lg, Lr, Lb) of different colors in a time-sharing manner;
A display element (201) that generates an image M by optically modulating the colored light from the plurality of light sources;
Display control capable of adjusting the brightness of the image by stepwise changing a display ratio (R), which is a ratio of the time (Fa) for generating the image by the display element at a predetermined time (F). Part (310);
While the display ratio of the display element is constant, the brightness of the image can be adjusted by controlling a control value (P) for adjusting the output of the light source of one or more colors among the plurality of light sources. A light source controller (320) for adjusting the control value in a direction to suppress a change in luminance of the image when the display controller changes the display ratio of the display element;
The display control unit changes the display ratio changed in stages in comparison with the first display ratio control (S30) in which the change amount (R11, R12) of the display ratio changed in stages is large. An image display apparatus that controls the display element by switching between the second display ratio control (S40) with a small ratio change amount (R21, R22).
The display control unit performs the first display ratio control or the second display ratio control based on the received temperature information (T) indicating the internal temperature or temperature estimation information (Ta) capable of estimating the internal temperature. The image display device according to claim 1, which is executed.
The light source control unit performs a plurality of reference control data (Ap, Aq) defining the control value of the light source by calibration and linear control or polynomial interpolation using the plurality of reference control data, thereby controlling the light source. The image display device according to claim 1, wherein the control value of the light source of one or more colors among the plurality of light sources is controlled based on the interpolation control data (C) that defines the value.
The light source control unit stores in advance a plurality of reference control data (Ap, Aq) in which the control value of the light source is determined by calibration, and linear interpolation or polynomial interpolation is performed by the plurality of reference control data. Interpolation control data (C) for determining the control value is calculated, and the control values of the light sources of one or more colors among the plurality of light sources are controlled based on the reference control data and the interpolation control data. The image display device according to claim 1 or 2.
The light source control unit interpolates the number of interpolation control data to be interpolated with the plurality of reference control data at the time of execution of the first display ratio control by the plurality of reference control data at the time of execution of the second display ratio control. The image display device according to claim 3, wherein the number is larger than the number of the interpolation control data.
The light source control data includes two reference control data (Ax, Ay) that do not have the interpolation control data between (E1),
6. The display control unit according to claim 3, wherein the display control unit switches the display ratio of the display element when the light source control unit switches the control value of the light source between the two reference control data. Image display device.
A light intensity detector (103) for detecting light intensity information (FS) of the color light emitted from the light source;
The light source control unit compares a predetermined target light intensity with the light intensity detected by the light intensity detection unit, and corrects the control value so that the light intensity approaches the target light intensity. The image display device according to claim 1.
A gain adjustment unit (130) that adjusts the gain (G) of the signal indicating the light intensity in a stepwise manner between the light intensity detection unit and the light source control unit;
The light source control data includes two reference control data (Ap, Aq) that do not have the interpolation control data between (E1),
The image display device according to claim 7, wherein the gain adjustment unit switches the gain when the light source control unit switches the control value of the light source between the two reference control data.
The light source control unit calculates the light intensity of the first color light (Lg, Lr, Lb) emitted from the first light source (101g, 101r, 101b) driven based on the reference control data and the interpolation control data. Correcting the control value of the light source (101g, 101r, 101b) emitting at least one color light (Lg, Lr, Lb) different from the first color light so that the light intensity ratio becomes a desired value; The image display device according to claim 7 or 8.
The plurality of light sources include a green light source (100g) that emits green color light (Lg), a red light source (100r) that emits red color light (Lr), and a blue light source that emits blue color light (Lb). 100b), and
The light source control unit controls the red light source and the blue light source so that the light intensity ratio of the green color light emitted from the green light source having the light source control data to the light intensity becomes a desired value. The image display device according to claim 9, wherein the value is adjusted.
The display control unit switches the display element from the second display ratio control to the first display ratio control when the temperature information is equal to or lower than a predetermined first threshold (TH1), and controls the temperature information. 11. The control device according to claim 2, wherein the display element is controlled by switching from the first display ratio control to the second display ratio control when the value becomes equal to or greater than a second threshold (TH 2) greater than the first threshold. The image display device described in 1.
An image display device according to any one of claims 1 to 10,
A head-up display comprising: a projection unit (20) that visually recognizes a virtual image of the image by projecting the image displayed by the image display device on a transmission / reflection unit positioned in front of the viewer.
An external light information acquisition unit (330) for acquiring external light information (EL) related to external light illuminance;
The head-up display according to claim 12, further comprising: a control unit (300) that switches the luminance of the image based on the external light information acquired by the external light information acquisition unit.