JP2012043611A - Illumination device and display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an illumination device and a display device that can achieve a desired power consumption and brightness when a plurality of light sources including light-emitting diodes are subjected to time division driving.SOLUTION: In an illumination device 1A, the length of light emission period is determined according to a driving current of a light-emitting diode when light sources 10R,10G,10B including light-emitting diodes are subjected to time division driving. Because the light-emitting diode has a characteristic that luminous efficiency is lowered as the driving current increases, a control for decreasing the driving current, for example, may be performed to improve the luminous efficiency. Although brightness may decrease by a reduced amount of the driving current, the total amount of light emission from a plurality of light sources emitting light continuously in time can be increased by setting a longer light emission period. The illumination device 1A can suppress power consumption while keeping the brightness, or improve the brightness without substantially increasing the power consumption.

Description

  The present invention relates to an illumination device and a display device that are suitably used for, for example, a portable projector.

  In recent years, as a video display system of a projector, a color sequential display system (field sequential color system, hereinafter referred to as FS system) that displays red (R), green (G), and blue (B) video in a time-sequential manner (time sequential). Is used). This method uses a white light source such as UHP (Ultra High Performance) and a color filter, and RGB light emitting diodes (LEDs), laser diodes (LDs), and the like. (For example, Patent Document 1). The latter method is attracting attention because it is advantageous in the color reproduction range.

JP 2004-317558 A

  In the FS method using R, G, B LEDs and the like as described above, one frame period is divided into three subframe periods for displaying each of R, G, B images, and these subframe periods are divided. Corresponding to each of these, the R, G, B LED light sources are driven to emit light sequentially in a time-sharing manner. In this method, each LED light source is driven so that the output (emission amount) of each color light is maximized, so that the power consumption is large, and in order to realize brighter display luminance, it is necessary to increase the power consumption. There is. For example, in Patent Document 1, brightness is improved by simultaneously emitting light other than the original color light in each of the R, G, and B subframe periods, but for emitting other color light. Since power is required separately, power consumption increases.

  Such an FS system is also used in the field of small projectors, for example. However, in a small projector, if the power consumption is large, the projection time is shortened and the influence on the heat radiation design is increased. For this reason, there is a case where priority is given to suppressing power consumption rather than improving the brightness (illumination luminance, display luminance) without darkness, particularly as in a small projector. Therefore, it is desired to realize an illuminating device that can control power consumption and brightness to desired values according to applications.

  The present invention has been made in view of such problems, and an object thereof is to provide a lighting device capable of realizing desired power consumption and brightness when driving a plurality of light sources including light emitting diodes in a time-sharing manner. It is to provide a display device.

  The illumination device of the present invention includes at least one light emitting diode, includes a plurality of light sources that emit two or more types of color light, and a light source control unit that drives the plurality of light sources to emit light in a time-sharing manner. While controlling the drive current of a light emitting diode, the length of the light emission period is set according to a drive current.

  A display device according to the present invention includes the above-described illumination device according to the present invention and a light modulation element that modulates light emitted from the illumination device based on a video signal.

  In the illumination device and the display device of the present invention, when a plurality of light sources including a light emitting diode are driven in a time-sharing manner, the length of the light emission period is set according to the driving current of the light emitting diode. Here, since the light emitting diode has a characteristic that the light emission efficiency decreases as the drive current increases, for example, the light emission efficiency can be improved by controlling the drive current to be lowered. On the other hand, when the control is performed to reduce the drive current, the brightness may decrease by that amount. In this case, by setting the light emission period to be longer, a plurality of light sources that emit light continuously in time can be obtained. The total amount of light emitted from the light source can be increased. That is, by controlling the length of the light emission period while maintaining good light emission efficiency, for example, it is possible to supplement the brightness reduced by the control of the drive current, so that power consumption can be reduced while maintaining the brightness. It becomes possible to suppress. Alternatively, the brightness can be improved by increasing the total amount of light emission without significantly increasing the power consumption.

  In the illumination device according to the present invention, the light source control unit causes the light emission period of the light emitting diode to be temporally continuous with at least the first unit period assigned to the light emitting diode in time-division driving. It is desirable to set over the second unit period. When light sources of three colors R, G, and B are used as the plurality of light sources, the light source of at least one of these three colors is a light emitting diode, and the light sources of the other colors are laser diodes. It is desirable to consist of.

  According to the illumination device and the display device of the present invention, since the light source driving unit controls the drive current of the light emitting diode among the plurality of light sources, the light emission efficiency of the light emitting diode can be improved. In addition, since the length of the light emission period is set according to the drive current, it is possible to reduce the power consumption while maintaining the brightness, or improve the brightness without increasing the power consumption. It becomes. Therefore, desired power consumption and brightness can be realized when a plurality of light sources including light emitting diodes are driven in a time-sharing manner.

It is a figure showing the whole structure of the display apparatus which concerns on the 1st Embodiment of this invention. It is a timing diagram showing time division drive operation in each light source and light modulation element concerning a comparative example. It is a timing diagram for demonstrating the light source control operation | movement of the light source control part shown in FIG. It is a characteristic view showing the relationship between the drive current in a light emitting diode (R, G, B) and luminous efficiency. It is a characteristic view showing the relationship between the light emission time of a light emitting diode (G), and brightness. It is an example of the color reproduction range obtained by the light source control operation | movement of the light source control part shown in FIG. FIG. 10 is a timing chart for explaining a light source control operation according to Modification Example 1. FIG. 10 is a timing diagram for explaining a light source control operation according to Modification 2. FIG. 10 is a timing diagram for explaining a light source control operation according to Modification 3. FIG. 10 is a timing diagram for explaining a light source control operation according to Modification Example 4. It is an example of the color reproduction range obtained by the light source control operation | movement which concerns on another modification.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The description will be given in the following order.

1. Embodiment (G light source as an LED, the drive current is lowered, and the light emission period is set longer)
2. Modification 1 (example in which the timing of starting and ending the light emission of the G light source is shifted)
3. Modification 2 (example in which the light emission period of the G light source is set over the R, G, and B subframes and the drive current is set higher in the G subframe than in the R and B subframes)
4). Modified Example 3 (Example in which the drive current is set higher in the G light source emission period than the overlap period in the period that does not overlap in time with the R and B emission periods)
5. Modification 4 (example in which R light source and G light source are LEDs, their drive currents are lowered, and the light emission period is set longer)

<First Embodiment>
[Overall Configuration of Display Device 1]
FIG. 1 shows an overall configuration of a display device (display device 1) according to a first embodiment of the present invention. The display device 1 is a projector that projects an image (image light) onto a projection surface 15 (screen or the like). For example, each color using illumination light of R, G, and B colors by a field sequential color method. Are projected and displayed in a time-division manner. Such a display device 1 includes a lighting device 1A (light sources 10R, 10G, and 10B, an optical path synthesis element 11 and a light source control unit 14), a light modulation element 12, and a projection lens 13.

  The light sources 10R, 10G, and 10B emit red light, green light, and blue light, respectively, and are driven to emit light in a time-sharing manner according to the control of the light source control unit 14. For example, the outputs of the light sources 10R, 10G, and 10B are sequentially switched every period (subframe period described later) corresponding to 1/3 of one frame period. These light sources 10R, 10G, and 10B are made of, for example, a light emitting diode (LED), a laser diode (LD), or the like, but include at least a light emitting diode. In the present embodiment, a case will be described as an example where the light source 10G is a light emitting diode (green LED) and the light sources 10R, 10B are laser diodes (red LD, blue LD) among the light sources 10R, 10G, 10B.

  The light source control unit 14 is connected to the three light sources 10R, 10G, and 10B, and can control the output of each light source. Specifically, the drive current (Peak Power) of each light source is controlled to control the instantaneous light emission amount (per unit time), the length of the light emission period (light emission time, duty), and the light emission start In addition, it is possible to control the timing of the end of light emission. The light source control unit 14 includes a light source drive unit 140, and also includes light emission period setting units 141R, 141G, and 141B and drive current setting units 142R, 142G, and 142B for each light source. The drive current setting units 142R, 142G, and 142B set the drive currents of the respective light sources, and the light emission period setting units 141R, 141G, and 141B are the lengths of the light emission periods of the respective light sources and the timings of the start and end of light emission. Is set. The light source drive unit 140 drives the light sources 10R, 10G, and 10B based on the settings by the drive current setting units 142R, 142G, and 142B and the light emission period setting units 141R, 141G, and 141B, respectively.

  Although details will be described later, the light source control unit 14 compares the drive current and light emission period of the light source 10G as a green LED among the light sources 10R, 10G, and 10B with other light sources (light sources 10R and 10B), The amount of emitted light is controlled.

  The optical path synthesizing element 11 is an element for synthesizing the respective color lights emitted from the light sources 10R, 10G, and 10B on the same optical axis Z. An example of such an optical path combining element 11 is a tichroic prism. Here, the respective color lights from the three light sources 10R, 10G, and 10B are incident on the optical path combining element 11 (dichroic prism) from different optical paths and guided onto one optical path Z. The optical path combining element for each color light is not limited to such a dichroic prism, and for example, a reflection mirror or a dichroic mirror may be used.

  The light modulation element 12 is made of, for example, a transmissive liquid crystal panel, and modulates illumination light from the illumination device 1A based on a video signal supplied from a display control unit (not shown) to emit video light. .

  The projection lens 13 is a lens for projecting (enlarging and projecting) the image light emitted from the light modulation element 12 onto the screen 30, and includes a single lens or a plurality of lenses.

[Operation and Effect of Display Device 1]
(Display operation by FS method)
In the display device 1, in the lighting device 1A, the light source control unit 14 drives the light sources 10R, 10G, and 10B to emit light in a time-sharing manner. Specifically, the light sources 10R, 10G correspond to each of R, G, B three subframe periods (unit periods, subframe periods fr, fg, fb described later) corresponding to a period obtained by dividing one frame period into three. , 10B sequentially emit light. Each color light emitted from the light sources 10R, 10G, and 10B in this way sequentially enters the light modulation element 12, and is modulated according to the video signal of each color for each color light. That is, among the R, G, B subframe periods that are temporally continuous, in the R subframe period, the light source 10R is caused to emit light, and the light modulation element 12 performs light modulation based on the R video signal. Similarly, in the G subframe period and the B subframe period, the light sources 10G and 10B are caused to emit light, respectively, and the light modulation element 12 performs light modulation based on the G and B video signals. At this time, the light modulation element 12 adjusts the gradation at the time of projection of each color image light by controlling the drive time or drive amplitude within each subframe period.

  Thereafter, the light emitted from the light modulation element 12 is projected (enlarged projection) toward the irradiated surface 15 by the projection lens 13. As described above, full-color video display is performed based on each color light emitted from the light sources 10R, 10G, and 10B in a time-sharing manner.

(Time-division drive operation of R, G, B light sources including light-emitting diodes)
Here, in the present embodiment, the three light sources 10R, 10G, and 10B include at least one light emitting diode. For example, in the present embodiment, a green LED is used as the light source 10G, a red LD is used as the light source 10R, and a blue LD is used as the light source 10B. Hereinafter, a time-division drive operation in the case where the R, G, and B light sources include light emitting diodes when performing the above-described FS video display will be described in comparison with a comparative example.

(Comparative example)
2A to 2D are timing diagrams for explaining the time-division driving operation of the R, G, and B light sources according to the comparative example. 2A to 2C schematically show the driving sequence in each light source, with the vertical axis representing the light emission amount P and the horizontal axis representing time t. As described above, each driving sequence in the light sources 10R, 10G, and 10B is a rectangle having a light emission amount (Pr, Pg, Pb) per unit time of each color light as a height and a light emission period (tr, tg, tb) as a width. Expressed as a wave. FIG. 2D schematically illustrates the modulation operation for each color light in the light modulation element 12.

  In this manner, the corresponding light sources 10R, 10G, and 10B are driven to emit light in each of the subframe periods fr, fg, and fb corresponding to the periods obtained by dividing one frame period into three. At this time, in the comparative example, the light sources 10R, 10G, and 10B are set so that the light emission amounts Pr, Pg, and Pb output from the light sources 10R, 10G, and 10B are maximized in any of the subframe periods fr, fg, and fb. For example, these light emission amounts Pr, Pg, and Pb have the same value. The light emission periods tr, tg, and tb of the light sources 10R, 10G, and 10B correspond to predetermined periods in the latter half of each subframe period.

That is, when the light sources 10R, 10G, and 10B are time-divisionally driven when displaying an FS video image, each of the light sources 10R, 10G, and 10B has a maximum light emission amount within a limited subframe period as in the comparative example. Driving. From this state, for example, when the brightness is further improved, for example, the drive current is further increased to control the light emission amount P per unit time to the light emission amount Pg ₁₀₀ . With such control, the brightness can be increased, but the power consumption increases as the drive current increases. Such an increase in power consumption is undesirable especially in a small projector or the like.

  Therefore, in the present embodiment, a light emitting diode (here, the light source 10G as a green LED) is used for at least one of the light sources 10R, 10G, and 10B when performing the above-described FS video display. Then, the light source control unit 14 drives the light sources 10R, 10G, and 10B including such light emitting diodes by, for example, the following drive sequence.

  3A to 3D are timing charts for explaining the time-division driving operation of the R, G, and B light sources in the present embodiment. 3A to 3C schematically show the driving sequence in each light source, with the vertical axis representing the light emission amount P and the horizontal axis representing time t. FIG. 3D schematically shows a modulation operation for each color light in the light modulation element 12. Thus, also in the present embodiment, with respect to each drive sequence of the light sources 10R and 10B as laser diodes, the light emission amounts (Pr, Pb) per unit time of the respective color lights are set high, as in the comparative example. It is represented by a rectangular wave having a width of the light emission period (tr, tb).

  On the other hand, the drive sequence of the light source 10G as a light emitting diode is different from that for the light sources 10R and 10B, for example, the drive current is controlled to a predetermined value, and the length of the light emission period is set according to this drive current. Here, as shown in FIG. 4, the light emitting diode has a characteristic that the light emission efficiency is lowered as the drive current If increases. For this reason, in the light emitting diode, the light emission efficiency can be improved by making the drive current as small as possible. In addition, the light emission efficiency in this specification shall mean the ratio of the emitted light quantity with respect to the electric power input into each light source.

  Therefore, in the present embodiment, the light source control unit 14 performs control to reduce the drive current, for example, when the light source 10G is driven to emit light. Specifically, the drive current setting unit 142G sets the drive current of the light source 10G so that the light emission amount Pg1 of the light source 10G becomes smaller (the height in the rectangular wave becomes smaller). Thereby, the luminous efficiency in the light source 10G can be improved.

  On the other hand, when the control for lowering the drive current of the light source 10G is performed as described above, although the light emission efficiency is improved, the brightness itself is likely to decrease. Therefore, in the present embodiment, the light source control unit 14 sets the light emission period longer according to the drive current of the light source 10G. Specifically, the light emission period setting unit 141G sets the light emission period tg1 of the light source 10G to be longer than the light emission periods tr and tb of the other light sources 10R and 10B (the width in the rectangular wave becomes wider). Here, the light emission period tg1 is set over not only the corresponding subframe period fg but also the temporally continuous subframe periods fr and fb.

  On the other hand, in these light sources 10R, 10G, and 10B, it is desirable that the respective light emission amounts are set so as to obtain a desired white balance, for example. Specifically, the integrated light quantity of each light source (= the light emission quantity × the light emission time) is set so as to achieve a desired white balance, and the light source as described above is within the range of the integrated light quantity set in this way. 10G drive control is performed. That is, by extending the light emission time while reducing the light emission amount Pg1, the integrated light amount can be brought close to or equal to the above value, and the light emission efficiency can be improved while maintaining a desired white balance. Become.

  Thereby, the total light emission amount in the light sources 10R, 10G, and 10B in one frame period can be increased. FIG. 5 shows the relationship between the light emission time and the brightness in the light source 10G. That is, by controlling the drive current, the brightness reduced by controlling the drive current can be complemented by controlling the length of the light emission period while maintaining good light emission efficiency. As a result, it is possible to perform control for suppressing power consumption while maintaining brightness. Further, since the total light emission amount increases as the light emission period tg1 is set longer, control for improving the brightness is also possible. That is, the total light emission amount can be increased and the brightness can be improved without significantly increasing the power consumption. Alternatively, it is possible to improve only the brightness while keeping the power consumption constant.

  In other words, in the light emitting diode, the brightness (illumination luminance and display luminance) is determined by the area of the figure surrounded by the light emission amount and the light emission period in the drive sequence. Therefore, if the figure obtained by the light emission amount Pg and the light emission period tg in the comparative example and the figure obtained by the light emission amount Pg1 and the light emission period tg1 in the present embodiment are set to have the same area, in both cases Equivalent brightness can be obtained. However, in the latter case (light emission amount Pg1, light emission period tg1) in which the drive current (light emission amount) is lowered and the light emission period is made longer, the power consumption can be reduced because the light emission efficiency is higher.

(About color reproducibility)
FIG. 6 shows the color reproduction range (CIE 1931 chromaticity) in the present embodiment. In the present embodiment, a green LED is used as the light source 10G, and a red LD and a blue LD are used as the light sources 10R and 10B. In this case, the color reproduction range is as shown in FIG. Specifically, in the light sources 10R, 10G, and 10B, when the light emission period of the light source 10G is lengthened, the vertex coordinates of G remain at a fixed position (square points in the figure), but R and B The vertex coordinates are shifted inward (shifted sequentially from the round point to the triangular point and the square point in the figure).

  Here, considering the comparison with the color reproduction range of the NTSC standard (a range surrounded by a broken line in the figure) which is a standard color space, it is sufficient if the color reproducibility of this NTSC standard can be secured. In other applications, the coordinates of each vertex showing monochromaticity may be shifted to the other color light side so as to approach the NTSC standard area. Strictly speaking, this means color mixture within the subframe period, but the effect of the color mixture can be reduced by appropriately setting the length of the light emission period while maintaining white balance throughout the entire frame period. Can be reduced. Further, by including at least one laser diode in the light sources 10R, 10G, and 10B, the color reproduction range can be easily expanded due to the monochromaticity of the laser diode. The color reproduction range can be an arbitrary color reproduction range by adjusting each video section of RGB.

  As described above, in the present embodiment, among the light sources 10R, 10G, and 10B that are time-division driven, a light emitting diode is used for the light source 10G, and the light source control unit 14 controls the drive current of the light source 10G. Therefore, the light emission efficiency in the light source 10G can be improved using the relationship between the drive current and the light emission efficiency in the light emitting diode. In addition, since the length of the light emission period tg1 is set according to the drive current, it is possible to reduce power consumption while maintaining brightness, or to improve brightness without increasing power consumption. It becomes possible. Therefore, desired power consumption and brightness can be realized when a plurality of light sources including light emitting diodes are driven in a time-sharing manner.

  Next, modified examples (modified examples 1 to 4) of the drive sequence of the light source control unit 14 according to the above embodiment will be described. In the following, the same components as those in the above embodiment are denoted by the same reference numerals, and description thereof will be omitted as appropriate.

<Modification 1>
7A to 7D are timing diagrams for explaining the time-division driving operation of the R, G, and B light sources according to the first modification. 7A to 7C schematically show the drive sequence in each light source, with the vertical axis representing the light emission amount P and the horizontal axis representing time t. FIG. 7D schematically shows the modulation operation for each color light in the light modulation element 12. This modification is an example of a drive sequence in the case where a green LED is used as the light source 10G and red LD and blue LD are used as the light sources 10R and 10B, respectively, as in the above embodiment. Also in this modified example, as in the above embodiment, in each drive sequence of the light sources 10R and 10B as laser diodes, the light emission amount (Pr, Pb) is the height and the light emission period (tr, tb) is the width. Represented by a square wave.

  Further, in the drive sequence of the light source 10G as a light emitting diode, the drive current is reduced to a value corresponding to the light emission amount Pg1, and control for improving the light emission efficiency is performed. In accordance with this drive current, the light emission period tg2 is set over not only the subframe period fg but also the subframe periods fr and fb that are temporally continuous.

  However, in this modification, the light emission period tg2 of the light source 10G is different from the light emission period tg1 of the light source 10G in the above embodiment in the timing of the light emission start and light emission end. In other words, in this modification, for example, in the subframe periods fr and fb that are temporally continuous with the subframe period fg, the temporal period between the light emission period tg2 of the light source 10G and the light emission periods tr and tb of the light sources 10r and 10B. The start and end timings of the light emission period tg2 are set so that the overlap is reduced.

  Specifically, the light source driving unit 14 sets the end timing of the light emission period tg2 so that the light emission period tg2 of the light source 10G and the light emission period tb of the light source 10B do not overlap in the subframe period fb. Shift from t1 (end timing of the light emission period tg1 in the above embodiment) to t2. Here, in the subframe period fr, the light emission start timing is shifted by the same time as the light emission end timing shift time. That is, since the length of the light emission period tg2 (light emission time) is equivalent to the length of the light emission time tg1 in the above embodiment, the brightness and power consumption are equivalent to those in the above embodiment.

  Also in this modification, by controlling the drive current of the light source 10G as a light emitting diode, while maintaining good light emission efficiency, the power consumption can be reduced while maintaining brightness by controlling the length of the light emission period tg2. Suppressing control is possible. It is also possible to increase the total amount of light emission without significantly increasing power consumption and improve brightness. Therefore, an effect equivalent to that of the above embodiment can be obtained.

  In addition, the light emission start timing and the light emission end timing of the light emission period tg2 of the light source 10G are shifted as described above, so that the temporal overlap between the light emission period tg2 and the light emission period tb is reduced in the subframe periods fr and fb. By so doing, it is possible to suppress the occurrence of color mixing between the subframe periods. Therefore, the color order can be easily adjusted as compared with the above embodiment.

<Modification 2>
8A to 8D are timing charts for explaining the time-division driving operation of the R, G, and B light sources according to the second modification. FIGS. 8A to 8C schematically show the driving sequence in each light source, with the vertical axis representing the light emission amount P and the horizontal axis representing time t. FIG. 8D schematically shows a modulation operation for each color light in the light modulation element 12. This modification is an example of a drive sequence in the case where a green LED is used as the light source 10G and red LD and blue LD are used as the light sources 10R and 10B, respectively, as in the above embodiment. Also in this modification, as in the above-described embodiment, the light emission amount (Pr, Pb) is the height and the light emission period (tr, tb) is the width for each drive sequence of the light sources 10R and 10B as the laser diodes. Represented by a square wave.

  Further, in the driving sequence of the light source 10G as a light emitting diode, the driving current is controlled, and in accordance with this driving current, the light emitting period tg1 is not only the subframe period fg but also the subframe periods fr, It is set over fb.

  However, in the present modification, in the light emission period tg1 of the light source 10G, the value of the drive current of the light source 10G is different between the subframe period fg and the subframe periods fr and fb. Specifically, the light source driving unit 14 sets the driving current of the light source 10G to a value larger than the subframe periods fr and fb in the subframe period fg. For example, during the period corresponding to the subframe periods fr and fb in the light emission period tg1, the drive current is set to be the light emission amount Pg1 (Pg1 <Pr, Pb), and during the subframe period fg, the light emission amount Pg2 (Pg1 The drive current is set to satisfy <Pg2 ≦ Pr, Pb).

  As in this modification, by setting the light emission amount Pg2 in the subframe period fg to be higher than the light emission amount Pg1 in the subframe periods fr and fb, the light emission period set over the subframe periods fr, fg, and fb. For example, when the brightness is insufficient at tg1, the brightness can be improved without significantly increasing the power consumption. Therefore, an effect equivalent to that of the above embodiment can be obtained.

<Modification 3>
9A to 9D are timing charts for explaining the time-division driving operation of the R, G, and B light sources according to the third modification. FIGS. 9A to 9C schematically show a driving sequence in each light source, with the vertical axis representing the light emission amount P and the horizontal axis representing time t. FIG. 9D schematically shows the modulation operation for each color light in the light modulation element 12. This modification is an example of a drive sequence in the case where a green LED is used as the light source 10G and red LD and blue LD are used as the light sources 10R and 10B, respectively, as in the above embodiment. Also in this modified example, as in the above embodiment, in each drive sequence of the light sources 10R and 10B as laser diodes, the light emission amount (Pr, Pb) is the height and the light emission period (tr, tb) is the width. Represented by a square wave.

  Further, in the drive sequence of the light source 10G as a light emitting diode, the drive current is reduced to a value corresponding to the light emission amount Pg1, and control for improving the light emission efficiency is performed. In accordance with this drive current, the light emission period is set not only in the subframe period fg but also in the subframe periods fr and fb that are temporally continuous.

  However, in this modification, the light emission period of the light source 10G is provided with a period tga that does not overlap in time with the light emission periods tr and tb of the light sources 10R and 10B, and a period tgb that overlaps in time. The drive current differs between the periods tga and tgb.

  Specifically, the light source driving unit 14 sets the driving current of the light source 10G in the period tga to a value larger than the driving current in the period tgb. Here, only the period tga is the light emission period of the light source 10G (the drive current in the period tgb is 0 (zero)). In other words, the light emission periods tr, tga, and tb are set so as not to overlap each other. Note that the values of the drive currents in these periods tga and tgb are not limited to those described above, and it is only necessary that the drive current in the period tga is relatively larger than the drive current in the period tgb.

  Also in this modification, by controlling the drive current of the light source 10G as a light emitting diode, while maintaining good light emission efficiency, the power consumption is suppressed while maintaining brightness by controlling the length of the light emission period. Control is possible. It is also possible to increase the total amount of light emission without significantly increasing power consumption and improve brightness. Therefore, an effect equivalent to that of the above embodiment can be obtained.

  In the light emission period of the light source 10G, the driving current is set to a larger value in the time period tga that does not overlap in time with the light emission periods tr and tb of the light sources 10R and 10B. Accordingly, it is possible to ensure brightness while suppressing color mixing between the subframe periods. Therefore, the color order can be easily adjusted and brightness can be easily obtained as compared with the above embodiment.

<Modification 4>
10A to 10D are timing charts for explaining the time-division driving operation of the R, G, and B light sources according to the fourth modification. FIGS. 10A to 10C schematically show the driving sequence of each light source, with the vertical axis representing the light emission amount P and the horizontal axis representing time t. FIG. 10D schematically shows the modulation operation for each color light in the light modulation element 12. This modification is an example of a drive sequence in the case where light emitting diodes are included in the three light sources R, G, and B, as in the above embodiment.

  However, in this modified example, two light emitting diodes are included. For example, a green LED is used as the light source 10G and a red LED is used as the light source 10R, and only the light source 10B is a blue LD. In this modification as well, in the driving sequence of the light source 10B as a laser diode, the light emission amount (Pb) is represented by a rectangular wave having a height and a light emission period (tb) as a width, as in the above embodiment. .

  In this modification, in each drive sequence of the light sources 10R and 10G as light emitting diodes, control is performed to reduce the drive currents to values corresponding to the light emission amounts Pr1 and Pg1 to improve the light emission efficiency. In accordance with these drive currents, the light emission periods tr1, tg1 of the light sources 10R, 10G are set over subframe periods fr, fg, fb that are temporally continuous.

  Also in this modification, brightness is maintained by controlling the length of the light emission periods tr1 and tg1, while maintaining good light emission efficiency by controlling the drive currents of the light sources 10R and 10G as light emitting diodes. In addition, it is possible to control to reduce power consumption. It is also possible to increase the total amount of light emission without significantly increasing power consumption and improve brightness. Therefore, an effect equivalent to that of the above embodiment can be obtained. Thus, it is sufficient that each of the R, G, and B light sources includes one or more light emitting diodes, and the light emitting diodes may be used for all three light sources.

  Here, FIG. 11 shows a color reproduction range in a case where light emitting diodes are used for all three light sources, and control is performed such that the drive currents of these light sources are lowered and the light emission periods are lengthened. Thus, when light emitting diodes are used for all three light sources, the vertex coordinates of R, G, and B shift inward (in order from the round point in the figure to the triangular point and the square point in order. However, as described above, the influence of the color mixture can be reduced by appropriately setting the length of the light emission period while maintaining the white balance in the entire one frame period.

  While the present invention has been described with reference to the embodiments and modifications, the present invention is not limited to these embodiments and the like, and various modifications can be made. For example, in the above-described embodiment, when a plurality of light sources are three light sources of R, G, and B, a case where a light emitting diode is used as the G light source (or the G light source and the R light source) among them is described. However, the light source used as the light emitting diode is not limited to this. However, the effect of the present invention is more effective when an LED of a color that exhibits a larger reduction rate of light emission efficiency due to an increase in drive current is selected as the LED to be controlled. In the said embodiment etc., green LED is used as an example of such LED.

  Furthermore, in the above-described embodiment, the transmissive liquid crystal panel is exemplified as the light modulation element. However, the present invention is not limited to this. For example, a reflective liquid crystal panel, DMD (Digital Micromirror Device), or the like may be used. .

  In addition, in the above-described embodiment and the like, each component (optical system) of the illumination device and the display device has been specifically described, but it is not necessary to include all the components, and other components are not included. Furthermore, you may provide.

  In the above-described embodiments and the like, a projector (particularly a microprojector) is given as an example of the display device of the present invention. However, the present invention is not limited to this. For example, the present invention is also applicable to a direct-view display device and an exposure device such as a stepper. Is possible.

  DESCRIPTION OF SYMBOLS 1 ... Display apparatus, 1A ... Illuminating device, 10R, 10G, 10B ... Light source, 11 ... Optical path composition element, 12 ... Light modulation element, 13 ... Projection lens, 14 ... Light source control part, 15 ... Irradiated surface, Z ... Light Axis, fr, fg, fb ... subframe period, Pr, Pg, Pg1, Pg2, Pb ... emission amount, tr, tr1, tg, tg1, tg2, tb ... emission period.

Claims (14)

A plurality of light sources including at least one light emitting diode and emitting two or more kinds of colored lights;
A light source controller that drives the plurality of light sources to emit light in a time-sharing manner,
The light source control unit controls a drive current of the light emitting diode and sets a length of a light emission period according to the drive current. The light source control unit includes a light emitting period of the light emitting diode, a first unit period assigned to the light emitting diode in time-division driving, and a second unit period that is temporally continuous with at least the first unit period. The lighting device according to claim 1, wherein the lighting device is set over a wide range. The lighting device according to claim 1, wherein the light source control unit performs control to reduce a drive current of the light emitting diode. The lighting device according to claim 3, wherein the light source control unit sets a light emission period of the light emitting diode to be longer. The light source control unit sets the light emission start and light emission end timings of the light emitting diodes so that temporal overlap between the light emission periods of the light emitting diodes and the other light sources is reduced. Lighting equipment. The lighting device according to claim 4, wherein the light source control unit sets a driving current of the light emitting diode to a value larger than the second unit period in the first unit period. The light emitting period of the light emitting diode has a first period that does not overlap in time with the light emitting period of the other light source, and a second period that overlaps in time.
The lighting device according to claim 4, wherein the light source control unit sets a driving current of the light emitting diode to a value larger than that of the second period in the first period. The lighting device according to claim 1, wherein the plurality of light sources are light sources that emit red light, green light, and blue light, respectively. The lighting device according to claim 8, wherein the plurality of light sources include a light emitting diode and a laser diode. The lighting device according to claim 8, wherein all of the plurality of light sources are light emitting diodes. The illuminating device according to claim 8, further comprising an optical path combining element that combines optical paths of colored lights emitted from the plurality of light sources. An illumination device; and a light modulation element that modulates light emitted from the illumination device based on a video signal;
The lighting device includes:
A plurality of light sources including at least one light emitting diode and emitting two or more kinds of colored lights;
A light source controller that drives the plurality of light sources to emit light in a time-sharing manner,
The light source control unit controls a drive current of the light emitting diode and sets a length of a light emission period according to the drive current. The display device according to claim 12, further comprising a projection optical system that projects light modulated by the light modulation element onto a projection surface. The plurality of light sources are light sources that emit red light, green light, and blue light, respectively.
The light modulation element modulates each color light emitted from the plurality of light sources in accordance with control of the light source control unit for each subframe period corresponding to a period obtained by dividing one frame period into three. Display device.

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