JP2014157320A - Display device and lighting system - Google Patents

Abstract

【Task】
Provided are a display device capable of realizing stable low-luminance display without complicating the configuration and information processing, and an illumination device used for the display device.
[Solution]
The control group 90 is illumination control data J that is bit data for selecting the subframe SF that the light source 11 shines from the input signal, and display that is bit data for selecting the subframe SF that is ON-driven for each pixel from the signal. When the control data K is generated, and the luminance of the image required by the signal is equal to or lower than a predetermined value, at least one of the lower bits of the illumination control data J or the display control data K is invalidated and the number of gradations of the light intensity Alternatively, low gradation control means for reducing the number of gradations of the luminance of the image is provided.
[Selection] Figure 8

Description

  The present invention relates to a display device and an illumination device used for the display device.

  As a display device for displaying an image, a device using a DMD (Digital Micro-mirror Device) which is a reflection type display is disclosed in Patent Document 1. This type of display device realizes high-resolution display by reflecting the light emitted from the light source on the individual mirrors of the DMD based on the video signal from the outside.

JP 2002-251163 A

  In such a display device, since a large amount of light must be irradiated to the display in a short time, a high-intensity image is required unless a high-output type light source (for example, an LED with a maximum rated current of several amperes) is used. Could not be secured. When a high-power type light source is used, the minimum current at which light emission is guaranteed increases. For this reason, it has been difficult to realize a stable low-brightness image display.

  The present invention has been made in view of the above circumstances, and provides a display device capable of realizing stable low-luminance display without complicating the configuration and information processing, and an illumination device used for the display device. For the purpose.

  In order to achieve the above object, a lighting device according to the present invention includes a light source that selectively shines for each subframe obtained by time-dividing one frame, and bit data that selects the subframe that the light source shines from an input signal. An illumination control data generation unit that generates illumination control data, and a light source drive unit that performs gradation control of light intensity in one frame emitted from the light source based on the illumination control data. When the light intensity required by the signal is equal to or lower than a predetermined value, low gradation control means for reducing the number of gradations of the light intensity by invalidating lower bits of the illumination control data is provided.

  In the illumination device according to a second aspect, the low gradation control means shifts the illumination control data to the lower side by at least one bit and invalidates the lower bits by the shifted amount. Features.

  In the illumination device according to a third aspect of the invention, the low gradation control means invalidates a plurality of the lower bits in the illumination control data.

  In the illumination device according to a fourth aspect, the light source selectively shines light of different colors for each subframe, and the illumination control data is provided for each color of the light source, The low gradation control means is characterized in that the lower bits of the illumination control data for each color are similarly invalidated to reduce the number of gradations of the light intensity.

  According to another aspect of the present invention, there is provided a display device for displaying an image by a field sequential color method, wherein the illumination device and spatial light modulation for generating an image by spatial light modulation of light emitted from the illumination device. And a vessel.

  According to a second aspect of the present invention, there is provided a display device that displays an image in a field sequential color system, wherein a light source that selectively shines in each sub-frame obtained by time-dividing one frame, and the light source shines from an input signal. An illumination control data generation unit that generates illumination control data that is bit data for selecting the subframe to be performed, and a light source drive unit that performs gradation control of light intensity in one frame emitted from the light source based on the illumination control data And a display device that has a plurality of pixels and selectively turns on the pixels for each subframe, thereby spatially modulating light from the light source to generate the image. A display control data generation unit that generates display control data that is bit data for selecting the subframe to be turned on for each pixel from the signal; A display drive unit that controls gradation of the luminance of the image generated by the pixel based on the display control data, and at least the illumination control when the luminance of the image requested by the signal is a predetermined value or less Low-gradation control means for reducing the number of gradations of the light intensity or the number of gradations of the luminance of the image by invalidating lower bits of either the data or the display control data is provided.

  According to the present invention, stable low-luminance display is possible.

It is a figure for demonstrating the mounting aspect of the HUD apparatus which concerns on one Embodiment of this invention. It is a schematic block diagram of the HUD apparatus which concerns on embodiment same as the above. It is a figure for demonstrating the structure of an illuminating device. It is a block diagram for demonstrating the electric constitution of the HUD apparatus which concerns on embodiment same as the above. It is a figure for demonstrating the display period and non-display period in a display. (A)-(f) is a timing chart for demonstrating the operation timing of each mirror and each light source which a display has. (A) is a figure explaining illumination control data, (b) is a figure for demonstrating display control data. It is a figure for demonstrating the low gradation control processing of the HUD apparatus which concerns on embodiment same as the above. (A)-(f) is a timing chart for demonstrating the operation timing of each mirror and each light source which a display apparatus has at the time of implementing a gradation control process. It is a flowchart for demonstrating the low gradation control process of the HUD apparatus which concerns on embodiment same as the above. It is a figure for demonstrating the gradation control process of the HUD apparatus which concerns on 2nd Embodiment. (A)-(f) is a timing chart for demonstrating the operation timing of each mirror and each light source which a display apparatus has at the time of implementing the gradation control process which concerns on embodiment same as the above. It is a flowchart for demonstrating the gradation control process of the HUD apparatus which concerns on embodiment same as the above.

  A display device according to an embodiment of the present invention will be described with reference to the drawings.

  A display device according to an embodiment of the present invention is a head-up display (HUD) device 1 shown in FIG. As shown in the figure, the HUD device 1 is arranged on the dashboard of the vehicle 2 and emits the display light L representing the generated image M (see FIG. 2) toward the windshield 3. The display light L reflected by the windshield 3 is viewed as a virtual image V of an image formed in front of the windshield 3 by the observer 4 (mainly the driver of the vehicle 2). In this way, the HUD device 1 causes the observer 4 to visually recognize the image M as the virtual image V. The HUD device 1 inputs information related to the vehicle 2 (for example, engine speed, navigation information, etc.) from the vehicle ECU 4 and notifies the observer 4 of the information as an image M.

As shown in FIG. 2, the HUD device 1 includes an illumination device 10, a light intensity detection unit 20, an illumination optical system 30, a display device 40, a projection optical system 50, a screen 60, and a relay optical system 70 ( A plane mirror 71, a concave mirror 72), and a housing 80 having a translucent part 81 are provided.
Further, as shown in FIG. 4, the HUD device 1 includes a first control unit 91, a second control unit 92, and a light source driving unit 93 as a control group 90 that performs electrical control of the HUD device 1. Prepare.

  The illumination device 10 emits light RGB (illumination light C), which will be described later, toward the illumination optical system 30, and as shown in FIG. 3, the illumination unit 11, the circuit board 12, the multiplexing unit 13, and the like. Brightness unevenness reducing means 14 and transmissive film 15.

The illumination means 11 is comprised from the light sources 11b, 11g, and 11r which consist of a light emitting diode (LED (Light Emitting Diode)), for example. The light emitting source 11b emits blue light B, the light source 11g emits green light G, and the light source 11r emits red light R. Each of the light sources 11b, 11g, and 11r is driven by the light source driving unit 93 and emits light at a predetermined light intensity and timing.
The circuit board 12 is a printed circuit board. Light sources 11b, 11g, and 11r are mounted on the circuit board 12.

The multiplexing means 13 is emitted from the light sources 11b, 11g, and 11r, combines the arrived lights R, G, and B, and emits them as light RGB. Specifically, the multiplexing means 13 includes a reflecting portion 13a made of a reflecting mirror, and combining portions 13b and 13c made of dichroic mirrors that reflect light of a specific wavelength but transmit light of other wavelengths. It is configured.
The reflection part 13a is located on the emission side of the light source 11b. The reflection unit 13a reflects the incident blue light B toward the multiplexing unit 13b.
The multiplexing unit 13b is located on the emission side of the light source 11g. The multiplexing unit 13b reflects the incident green light G toward the multiplexing unit 13c and transmits the blue light B from the reflecting unit 13a as it is. Thereby, the light BG obtained by combining the blue light B and the green light G is emitted from the combining unit 13b toward the combining unit 13c.
The multiplexing unit 13c is located on the emission side of the light source 11r. The multiplexing unit 13c reflects the incident red light R toward the illumination optical system 30, and transmits the light BG from the multiplexing unit 13b as it is. In this way, the light RGB (hereinafter also referred to as illumination light C) obtained by combining the light BG and the red light R is emitted from the multiplexing unit 13 c toward the illumination optical system 30.

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 illuminating device 10 converts the light emitted from the illuminating means 11 into light RGB (illumination) via the multiplexing means 13 described above and the luminance unevenness reducing means 14 (and the transmission film 15 described below). The light C) is emitted toward the illumination optical system 30.

  The transmissive film 15 is made of a transmissive member having a reflectivity of, for example, about 5%, and transmits most of the illumination light C that has arrived through the luminance unevenness reducing unit 14 as it is, but detects a part of the light intensity. Reflected in the direction of the part 20.

  The light intensity detector 20 includes a photodiode or the like, receives the illumination light C reflected by the transmission film 15, and detects the light intensities of the lights R, G, and B in a time-sharing manner. Specifically, the light intensity detection unit 20 outputs a detection signal (voltage) corresponding to the light intensity, and this detection signal is converted into a digital value by an A / D converter (not shown) to obtain light intensity data. It is output to the first control unit 91. The light intensity detection unit 20 only needs to be able to detect the light intensities of R, G, and B. For example, each of the light R, G, and B before being combined is not the optical path of the illumination light C. It may be provided at a location where the light intensity can be detected. Further, the light intensity detector 20 may be provided at a location where a part of the light intensity of the illumination light C emitted from the illumination optical system 30 can be detected.

  The illumination optical system 30 is composed of 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 40.

The display 40 is made up of a DMD (Digital Micro-mirror Device) having a plurality of movable micromirrors, and is emitted from the illumination optical system 30 by controlling each mirror in either an on or off state. The illuminated illumination light C is appropriately reflected. The display device 40 projects the image M (light for generating the image M) toward the projection optical system 50 by reflecting the illumination light C in this way.
Specifically, an electrode is provided below the micromirror, and each mirror is turned on or off by driving each mirror with a very short period (for example, on the order of μsec). . Each mirror is movable with a hinge as a fulcrum, and when the mirror is in an on state, the mirror surface is tilted by +12 degrees with the hinge as a fulcrum, and when the mirror is in an off state, the mirror surface is tilted by -12 degrees with the hinge as a fulcrum. The on-state mirror reflects the illumination light C from the illumination optical system 30 in the direction of the projection optical system 50, and the off-state mirror does not reflect the illumination light C in the direction of the projection optical system 50. The display device 40 projects the image M toward the projection optical system 50 by driving each mirror individually.

  The projection optical system 50 is configured by a concave lens or a convex lens, and is an optical system for efficiently projecting the display light L from the display 40 onto the screen 60.

  The screen 60 includes a holographic diffuser, a microlens array, a diffusion plate, and the like, receives the display light L from the projection optical system 50 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 relay optical system 70 projects the image M formed on the screen 60 toward the windshield 3 of the vehicle, and includes a plane mirror 71 and a concave mirror 72.
The plane mirror 71 reflects the display light L representing the image M displayed on the screen 60 toward the concave mirror 72.
The concave mirror 72 emits the reflected light in the direction of the windshield 3 by reflecting the display light L that has arrived from the plane mirror 71 on the concave surface. As a result, the virtual image V to be formed becomes larger than the image M displayed on the screen 60. The display light L reflected by the concave mirror 72 reaches the windshield 3 via the translucent part 81.

The housing 80 houses the illumination device 10, the light intensity detector 20, the illumination optical system 30, the display 40, the projection optical system 50, the screen 60, the relay optical system 70, and the like at predetermined positions. The housing 80 is formed of, for example, a light shielding member.
The translucent part 81 is made of a translucent resin such as acrylic and transmits the display light L from the concave mirror 72. The translucent part 81 is fitted to the housing 80, for example. The translucent part 81 is formed in, for example, a curved shape so that the external light that has reached does not reflect in the direction of the observer 4.

  Next, the electrical configuration of the HUD device 1 will be described.

  The 1st control part 91 consists of microcontrollers, and is provided with CPU, memory (RAM, ROM), etc. The CPU controls each unit by reading and executing a program necessary for the operation of the HUD device 1 stored in advance in the ROM. The first control unit 91 receives a video signal (video data) and a luminance signal for displaying the image M from the vehicle ECU 4 (Electronic Control Unit) of the vehicle 2 by LVDS (Low Voltage Differential Signal) communication or the like. The When the video signal and the luminance signal are input, the first control unit 91 (control group 90) (i) lighting control for controlling the lighting device 10 with the light intensity and the light emission timing required by the video signal and the luminance signal. Data J and (ii) display control data K for displaying the image M required by the video signal and the luminance signal on the display 40 are supplied to the second control unit 92. The first control unit 91 is electrically connected to the light source driving unit 93 and controls the voltage applied to the light sources 11b, 11g, and 11r. In addition, the first control unit 91 acquires light intensity data from the light intensity detection unit 20, and corrects a deviation between the light luminance required by the luminance signal and the actual light emission luminance of the lighting device 10 by an appropriate method. The first control unit 91 adjusts the luminance when the luminance signal from the vehicle 2 side, the operation signal based on the operation of the observer 4, and an illuminance sensor (not shown) that detects the illuminance of external light (for example, a translucent unit). Or a detection signal from the back surface of 81).

The second control unit 92 is an LSI (Large Scale Integration) that implements a desired function by hardware, and is configured by, for example, an ASIC (Application Specific Integrated Circuit). The second control unit 92 may be configured by an FPGA (Field Programmable Gate Array). The second control unit 92 controls the display device 40 and the illumination device 10 (via the light source driving unit 93).
The second control unit 92 drives (lights) the light sources 11b, 11g, and 11r through the light source driving unit 93 by a predetermined pulse width at a predetermined timing (for each subframe SF (see FIG. 6)). In addition, the second control unit 92 performs on / off control of each mirror of the display device 40 using a pulse signal. The mirror E of the driven display 40 reflects the light R, G, B emitted from the illumination device 10 in the direction of the screen 60. As a result, the image M can be expressed in full color by an additive mixing method using the light emission colors of the light sources 11b, 11g, and 11r as basic colors.

  The light source driving unit 93 includes a switching circuit using an n-type channel FET (Field Effect Transistor). The light source driving unit 93 drives (lights) the light sources 11b, 11g, and 11r by a predetermined pulse width at a predetermined timing (for each subframe SF (see FIG. 6)) under the control of the second control unit 92. The color of the illumination light C emitted from the illumination device 10 is sequentially switched at high speed (field sequential color system).

  The first and second control units 91 and 92 are mounted on, for example, a printed circuit board (not shown) disposed in the housing 80. These control units may be disposed outside the HUD device 1 and electrically connected to each unit by wiring.

Here, the display operation of the HUD device 1 will be briefly described as (1) to (5) below.
(1) The first control unit 91 generates illumination control data J and display control data K based on a video signal, a luminance signal, and the like from the outside, and supplies them to the second control unit 92.
(2) Based on the illumination control data J, the second control unit 92 drives the illumination device 10 by a field sequential color method. The driven illumination device 10 emits illumination light C to the display 40.
(3) The second control unit 92 performs on / off control of each mirror of the display 40 based on the display control data K. The controlled indicator 40 projects the illumination light C from the illumination device 10 onto the screen 60 as an image M.
(4) The display light L representing the image M displayed on the screen 60 is reflected by the plane mirror 71 toward the concave mirror 72.
(5) The image M is enlarged to a predetermined size by the concave mirror 72, and the display light L representing the enlarged image M is reflected by the windshield 3, so that the virtual image V of the image M is displayed in front of the windshield 3. Is tied. In this way, the HUD device 1 causes the observer 4 to visually recognize the image M as the virtual image V.
Note that a frame F (for example, 1/60 sec), which is a cycle for displaying the image M, is composed of subframes SF (see FIG. 6) divided into a plurality of times.

  From here, the control method of the HUD device 1 will be described with reference to FIGS.

  The frame F (cycle in which the image M is displayed) includes a display period Fa in which each mirror E of the display 40 is normally driven and a non-display period Fb in which the non-display period is driven.

  The display period Fa is a period during which each mirror E of the display 40 is normally driven. Specifically, during the display period Fa, the illumination device 10 emits the illumination light C in the direction of the display 40 by the field sequential color method based on the illumination control data J, and the display 40 displays the display control data K. This is a period during which the illumination light C from the illumination device 10 is projected as an image M toward the screen 60 by performing on / off control of individual mirrors of the display device 40 based on the on / off control.

  The non-display period Fb is a period during which the illumination device 10 is turned off (all the light sources 11b, 11g, and 11r are turned off) (see FIGS. 6D to 6F), and each mirror E of the display 40 is displayed. Is a period for which on / off control is performed at a predetermined cycle. Hereinafter, driving in which each mirror E is on / off controlled in a predetermined cycle is referred to as “non-display period driving”.

Here, for the following explanation, terms are defined as follows.
The ratio of the display period Fa in the frame F is “display period ratio A”.
In the display period Fa, a period during which the mirror E is turned on (turned on) is referred to as “on drive period Fap within display period”, and a period during which the mirror E is driven off (turned off) is referred to as “off drive period Faq within display period”. "
In the non-display period Fb, a period during which the mirror E is on-driven is referred to as an “non-display period on-drive period Fbp”, and an off-drive period is referred to as an “non-display period off-drive period Fbq”.
In the frame F, the total period during which the mirror E is on-driven (that is, the sum of the on-drive period Fap within the display period and the on-drive period Fbp within the non-display period) is referred to as “total on-drive period Fp”.
In the frame F, the total period during which the mirror E is driven off (that is, the sum of the off-drive period Faq within the display period and the on-drive period Fbq within the non-display period) is referred to as “total off-drive period Fq”.

  Here, the non-display period driving of the display 40 will be specifically described. In the non-display period driving, each of the mirrors E is controlled to be on / off so that the on period and the off period of each mirror E in the frame F are substantially equal (including just and equal). Specifically, referring to FIG. 6, the sum of the on-drive period Fap in the display period and the on-drive period Fbp in the non-display period (total on-drive period Fp), the off-drive period Faq in the display period, and the non-display period The second control unit 92 sets the on-drive period Fbp in the non-display period and the off-drive period Fbq in the non-display period so that the sum (total off drive period Fq) with the inner off-drive period Fbq becomes substantially equal. adjust. For example, the second control unit 92 adjusts so that the display period ratio A is constant at 50% and the total on-drive period Fp and the total off-drive period Fq are substantially equal. By doing in this way, since each mirror E of the indicator 40 is controlled to be turned on / off at a predetermined cycle, it can be prevented that the mirror E is stuck in either the on / off state.

Further, as shown in FIGS. 6A to 6C, in a predetermined frame F, among the mirrors E of the display 40, those that display green in a single color are “monochromatic mirrors Ea”, red and green. The non-display period driving will be described assuming that the mixed color display is “mixed color mirror Eb”, and nothing is displayed (that is, the illumination light C is not reflected in the direction of the projection optical system 50).
As shown in FIG. 6A, the monochromatic mirror Ea is on-controlled at the lighting timing of the light source 11g (see FIG. 6E) in the display period Fa based on the display control data K, and in the non-display period Fb. Is the sum of the ON driving periods in the frame F, and the second control unit 92 sets the ON driving period Fbp in the non-display period Fb so that the total ON driving period Fp is substantially half of the frame F. The non-display period off-drive period Fbq is adjusted, and the monochrome mirror Ea is driven in the non-display period based on the non-display period on-drive period Fbp and the non-display period off-drive period Fbq.

  In the example of the monochromatic mirror Ea, in the non-display period driving, the second control unit 92 drives each mirror so that the ON driving is continued during the non-display period Fb and the ON driving period Fbp within a predetermined non-display period. The second control unit 92 performs ON driving and OFF driving in the non-display period Fb, and ON driving period Fbp in the non-display period and OFF in the non-display period, as in the color mixing mirror Eb illustrated in FIG. It may be adjusted so that the total on-drive period Fp and the total off-drive period Fq are substantially equal by repeating the cycle according to the drive period Fbq. Further, as shown in FIG. 6C, since the extinguishing mirror Ec is driven off over the display period Fa, the non-display period driving is controlled to be turned on over the non-display period Fb.

  As described above, by adjusting the total on-drive period Fp and the total off-drive period Fq to be substantially equal, the mirror E of the display device 40 is fixed in one of the on and off states. Can be prevented, and the life of the display 40 can be extended.

(About drive control)
From here, the gradation control of the display device 1 will be specifically described. The gradation control described below is gradation control for realizing an image M having a desired display chromaticity and required luminance indicated by the video signal from the vehicle 2 side, the luminance signal, and is stored in advance in the ROM, for example. It is executed based on the program data. First, illumination control data J for controlling the gradation of the illumination device 10 and display control data K for controlling the gradation of the display 40 will be described.

The illumination control data J is data for sequentially turning on (turning on) / off (extinguishing) the light sources 11b, 11g, and 11r of the lighting device 10 in a time division manner, and is composed of three signals of red, green, and blue. Further, the signals of each color are divided into 6-bit signals (R5 to R0 in the case of red) instructing the operation of the light source in six subframes (SF5 to SF0). Each subframe SF is, for example, an unequal period in which a value of 2 ^ N (N = 5, 4, 3,..., 0) is assigned, and this unequal six subframes (SF5 ... SF0) can be expressed by 6-bit signals for each color (R5 to R0 in the case of red) to express 64 gradations for each color.
The illumination control data J includes, for example, bits R0, SF1, and SF5 for instructing the operations of the red subframe SF0 and SF1 in order to emit the red illumination light C from the illumination device 10. It consists of a bit R5 for instructing an operation, and by turning each bit R5 to R0 on or off (1 or 0), red can be designated as one of 64 gradations from 0 to 63. Similarly, green and blue are composed of bits G5 to G0 for instructing the operation of the mirror E in the green subframes SF5 to SF0 and bits B5 to B0 for instructing the operation of the mirror E in the blue subframes SF5 to SF0. The illumination control data J for controlling the illumination device 10 during the display period Fa is composed of bits (R5 to R0, G5 to G0, B5 to B0) as shown in FIG. Incidentally, since the illumination device 10 during the non-display period Fb is a period during which all the light sources 11b, 11g, and 11r are turned off, the gradation control as described above is not performed.

The display control data K is data for controlling on / off of the individual mirrors of the display 40. Like the illumination control data J, the display control data K is composed of three signals of red, green, and blue. It is divided into 6-bit signals (R5 to R0 in the case of red) that instruct the operation of the mirror E in six subframes (SF5 to SF0), and each color 6-bit signal (R5 to R0 in the case of red) Mirror E is turned on / off.
The display control data K includes, for example, a bit r0 for instructing the operation of the red subframe SF0, a bit r1 for instructing the operation of SF1, and a bit r5 for instructing the operation of SF5 in order to display red. By turning each bit r5 to r0 on or off (1 or 0), red can be designated as one of 64 gradations from 0 to 63. Similarly, green and blue are composed of bits g5 to g0 for instructing the operation of the mirror E in the green subframes SF5 to SF0 and bits b5 to b0 for instructing the operation of the mirror E in the blue subframes SF5 to SF0. The display control data K for one pixel (mirror) E during the display period Fa is composed of bits (r5 to r0, g5 to g0, b5 to b0) as shown in FIG. 64 gradations can be displayed, whereby 64 × 64 × 64 = 262144 colors can be displayed. That is, the display image M can be expressed in color by controlling the gradation of each mirror E with each bit (r5 to r0, g5 to g0, b5 to b0) of the display control data K. Next, of the gradation control, the low gradation control that is the gradation control when the required luminance falls below a predetermined value will be described.

(Low gradation control processing)
When the control group 90 determines that the required luminance is lower than a predetermined value based on a luminance signal from the vehicle 2 side or an operation signal based on the operation of the observer 4, the control group 90 executes a low gradation control process. In this low gradation control process, the control group 90 reduces the number of gradations of the illumination control data J or the display control data K described above. Specifically, the first control unit 91 receives a video signal and a luminance signal from the vehicle ECU 4 and generates lighting control data J for controlling the lighting device 10 and display control data K for controlling the display 40. If the requested luminance indicated by the input luminance signal is lower than a predetermined value, the bits (6 bits) of each color of the illumination control data J shown in FIG. 5 bits (R5 to R1, G5 to G1, B5 to B1) by truncating (invalidating) LSB (Least Significant Bit)) and turning off the most significant bit (MSB (Most Significant Bit)) Reduce to. That is, when the bits R5 to R0 corresponding to the red SF5 to SF0 of the illumination control data J are all on (1) (“111111”), the red bit data is “011111” by performing the above bit shift. The light sources 11r, 11g, and 11b are turned off in the longest subframe SF5 as indicated by the hatched area Ja in FIGS. With such a configuration, a low light intensity reflecting the upper bit data having a large influence on the gradation of the illumination light C can be obtained only by performing simple information processing for shifting the bit data for controlling the illumination device 10 to the lower side. The illumination light C can be emitted, and as a result, a low-luminance image M corresponding to the low required luminance can be generated. Similarly, the bit data of each color is similarly bit-shifted, so that the illumination light C of each color can be evenly reduced at substantially the same rate, so that a low-brightness image M that does not deteriorate the display quality with good white balance can be obtained. Can be generated.

  In addition, the first control unit 91 does not bit-shift the illumination control data J as described above, but bit-shifts the display control data K, so that the display 40 is moved to, for example, FIGS. 9D and 9E. As shown in the hatched area Ka, the OFF control may be performed in the longest subframe SF5. Even with such a configuration, it is possible to generate a low-luminance image M that reflects higher-order bit data that has a large influence on the gradation control of the display device 40. In this way, when the display control data K is bit-shifted to reduce the number of gradations to reduce the brightness of the image M, the on-drive period Fap within the display period is decreased and the total on-drive period Fp is shortened. Therefore, by increasing the on-drive period Fbp in the non-display period and adjusting the total on-drive period Fp and the total off-drive period Fq to be substantially equal, the life of the display 40 can be extended. it can.

  The operation flow of the low gradation control process as described above will be described with reference to FIG. 10. The first control unit 91 is requested by a luminance signal from the vehicle 2 side or an operation signal based on an operation of the observer 4. It is determined whether the luminance is lower than the predetermined value (S10a). If the required luminance is higher than the predetermined value (S10a: NO), the lighting device 10 and the display 40 are normally controlled, and the required luminance is lower than the predetermined value (S10a: YES). ), The lighting device 10 or the display device 40 is caused to perform low gradation control processing. In S20a, when the low gradation control is performed by selecting the lighting device 10 or the display 40 and the low gradation control processing is performed in the lighting device 10 (S20a: lighting device), each color of the illumination control data J is selected. The bit data representing the gradation is shifted one by one to the lower side (S30a), and the lighting device 10 is controlled to be low gradation based on the bit-shifted illumination control data (S31a). When low gradation control processing is performed in the display device 40 (S20a: display device), bit data representing the gradation of each color of the display control data K is shifted one by one to the lower side (S40a), and this bit shift is performed. Based on the illumination control data that has been set, the illumination device 10 is subjected to low gradation control (S41a). Hereinafter, a second embodiment of the low gradation control process will be described with reference to FIGS.

(Second embodiment)
When the requested luminance indicated by the input luminance signal is lower than a predetermined value, the first control unit 91 has the lower 3 bits (R2 to R0) of the bits (6 bits) of each color of the illumination control data J shown in FIG. , G2 to G0, B2 to B0) are invalidated (off (0)) as shown in FIG. 11B, and bit data of each color is changed to 3 bits (R5 to R3, G5 to G3, B5 to B3). Decrease. That is, when the bits R5 to R0 corresponding to the red SF5 to SF0 of the lighting control data J are all on (1) (“111111”), the lower bit is invalidated as described above, thereby the red bit The data is “111000”, and the light sources 11r, 11g, and 11b are turned off in the lower three subframes SF2 to SF0, as indicated by the hatched area Jb in FIGS. With such a configuration, it is possible to reflect high-order bit data that has a large influence on the gradation of the illumination light C only by performing simple information processing that disables (turns off) the low-order side of the bit data that controls the lighting device 10. Thus, the illumination light C having a low light intensity can be emitted, and as a result, a low-luminance image M corresponding to the low required luminance can be generated. Further, by invalidating the lower 3 bits of the bit data of each color in the same manner as each color, the illumination light C of each color can be reduced uniformly at substantially the same rate, so that the display quality with good white balance does not deteriorate. A low-luminance image M can be generated.

  Further, the first control unit 91 does not invalidate the lower 3 bits of the illumination control data J as described above, but lower 3 bits (r2 to r0, g2 to g0, b2 to b0) of the display control data K. Is invalidated (off), and the display 40 is turned off in the three subframes (SF2, SF1, SF0) on the lower side as shown in, for example, the hatched area Kb in FIGS. You may control. Even with such a configuration, it is possible to generate a low-luminance image M that reflects higher-order bit data that has a large influence on the gradation control of the display device 40. As described above, when the lower side of the display control data K is invalidated to reduce the number of gradations to reduce the luminance of the image M, the on-drive period Fap within the display period is decreased, and the total on-drive period Fp is reduced. Since the on-drive period Fbp in the non-display period is increased and the total on-drive period Fp and the total off-drive period Fq are adjusted to be substantially equal, the lifetime of the display device 40 is extended. be able to.

  The operation flow of the low gradation control processing as described above will be described with reference to FIG. 13. The first control unit 91 is requested by a luminance signal from the vehicle 2 side or an operation signal based on the operation of the observer 4. It is determined whether the luminance is lower than a predetermined value (S10b). If the required luminance is higher than the predetermined value (S10b: NO), the lighting device 10 and the display 40 are normally controlled, and the required luminance is lower than the predetermined value (S10b: YES). ), The lighting device 10 or the display device 40 is caused to perform low gradation control processing. In S20b, the low gradation control is performed by selecting the lighting device 10 or the display 40, and when the low gradation control processing is performed in the lighting device 10 (S20b: lighting device), each color of the illumination control data J is selected. The lower 3 bits of the bit data representing the gray level are invalidated (OFF) (S30b), and the lighting device 10 is controlled to be low gray level based on the illumination control data in which the lower 3 bits are invalidated (S31b). . When the low gradation control process is performed in the display device 40 (S20b: display device), the lower 3 bits of the bit data representing the gradation of each color of the display control data K are invalidated (off) (S40b), Based on the illumination control data in which the lower 3 bits are invalidated, the lighting device 10 is controlled to be low gradation (S41b).

  In addition, this invention is not limited by said embodiment, the following modified example, and drawing. Of course, it is possible to make appropriate changes (including deletion of components).

  In the above-described embodiment, the low gradation control process is performed for all the colors RGB. However, only the illumination control data J or the display control data K related to the green subframe SF with high visibility is described above. Low tone processing is performed, and the white balance is adjusted while lowering the brightness of the image M by performing PWM control and PAM control on the light sources 11r and 11b of colors (red, blue) having a lower visibility than green. Also good. With such a configuration, it is possible to efficiently reduce the luminance while reducing the CPU power (processing capability) required for the low gradation control processing of the first control unit 91 to 1/3 (only G of RGB).

  In the above embodiment, the illumination control data J or the display control data K corresponding to the subframes SF5 to SF0 indicating red, the subframes SF5 to SF0 indicating green, and the subframes SF5 to SF0 indicating blue are each set to 6 bits. However, the number of bits of each data may be increased or decreased as appropriate so that a desired number of gradations can be expressed. Also, in the drawing, the lengths of the subframes SF5 to SF0 indicating red, the subframes SF5 to SF0 indicating green, and the subframes SF5 to SF0 indicating blue are shown in the same manner, but the length of the subframe SF is It may be set as appropriate for each color. In FIG. 7, subframes SF5 to SF0 indicating red, subframes SF5 to SF0 indicating green, and subframes SF5 to SF0 indicating blue are regularly arranged for ease of explanation, but a color break is prevented. From the viewpoint of the above, the order of the subframes SF is appropriately set.

  Further, in the above embodiment, the subframe SF5 (period width 32) having a long period width is continuously provided. However, the subframe SF5 (period width 32) is divided (for example, divided into four (four period widths 8)), and the frame F is divided. For example, when the bit R5, which is the illumination control data J of the red light source 11r corresponding to SF5, is turned on (1), in the divided SF5 (four with a period width of 8), the light source 11r You may make it light. By dividing the sub-frame SF having a long period in this way and arranging the divided sub-frames so as not to be continuous in the frame F, the luminance in the frame F is flattened, and the viewer does not feel uncomfortable. You can display.

  In the above embodiment, the first control unit 91 includes an illumination control data generation unit that generates the illumination control data J and a display control data generation unit that generates the display control data K. Although it had as a function, the 2nd control part 92 may have these generating parts as a function.

DESCRIPTION OF SYMBOLS 1 HUD apparatus 10 Illumination apparatus 20 Light intensity detection part 30 Illumination optical system 40 Indicator 60 Projection optical system 70 Screen 91 1st control part 92 2nd control part 93 Light source drive part 2 Vehicle 3 Windshield 4 Observer M Image L Display Light V virtual image

Claims (6)

A light source that selectively shines in each subframe obtained by time-dividing one frame;
An illumination control data generating unit that generates illumination control data that is bit data for selecting the subframe that the light source shines from the input signal;
A light source driving unit that controls gradation of light intensity in one frame emitted from the light source based on the illumination control data;
When the light intensity required by the signal is less than or equal to a predetermined value, the lighting apparatus comprises low gradation control means for invalidating lower bits of the illumination control data to reduce the number of gradations of the light intensity .   2. The lighting device according to claim 1, wherein the low gradation control unit shifts the illumination control data to at least one bit toward the lower side and invalidates the lower bit by the shifted amount.   The lighting apparatus according to claim 1, wherein the low gradation control unit invalidates a plurality of the lower bits in the lighting control data. The light source selectively shines light of different colors for each subframe,
The illumination control data is provided for each color of the light source,
4. The illumination device according to claim 1, wherein the low gradation control means invalidates the lower bits of the illumination control data for each color in the same manner to reduce the number of gradations of the light intensity. . In a display device that displays an image in a field sequential color system,
The lighting device according to claim 1,
A display device comprising: a spatial light modulator that generates an image by spatially modulating light emitted from the illumination device. In a display device that displays an image in a field sequential color system,
A light source that selectively shines for each subframe obtained by time-dividing one frame, an illumination control data generation unit that generates illumination control data that is bit data for selecting the subframe that the light source shines from an input signal, and the illumination A lighting device having a light source driving unit that controls gradation of light intensity in one frame emitted from the light source based on control data;
A display that has a plurality of pixels and selectively turns on the pixels for each sub-frame to spatially modulate light from the light source to generate the image; A display control data generation unit that generates display control data that is bit data for selecting the subframe to be turned on, and display drive that performs gradation control on luminance of the image generated by the pixel based on the display control data And comprising
When the luminance of the image requested by the signal is less than or equal to a predetermined value, at least the lower bits of either the illumination control data or the display control data are invalidated, and the number of gradations of the light intensity or the luminance of the image A display device comprising low gradation control means for reducing the number of gradations.

Images