KR100823280B1 - Image display apparatus - Google Patents

Abstract

An image display device is disclosed. The disclosed image display device includes a light source unit having a plurality of light emitting elements having different wavelengths and provided with at least one light emitting element having n wavelengths (n is an integer of 2 or more), and the light emitting elements having different wavelengths within a predetermined time period. And a lighting control unit for time division driving, wherein the lighting control unit divides n of the light emitting elements having the at least one wavelength into m lighting groups having the same lighting timing (m is an integer of 2 ≦ m ≦ n), and By alternately lighting the m lighting groups at a frequency of 1 / m in the periodic constant time periods, the lighting groups of any one of the m lighting groups can be turned on in each of the predetermined time periods.

According to this, the temperature rise due to self-heating of the light emitting device can be suppressed, and the lifespan of the light emitting device can be extended, and the decrease in luminance due to the thermal effect can be reduced.

Description

Image display apparatus

1 is a timing chart showing a drive signal of a light source unit generated by a lighting control unit of an image display apparatus according to the prior art.

2 is a schematic diagram showing a schematic configuration of an image display device according to a first embodiment of the present invention.

3 is a functional block diagram for explaining a schematic configuration of a light source unit and a lighting control unit used in the image display device according to the first embodiment of the present invention.

4 is a timing chart showing a drive signal of a light source unit generated by a lighting control unit of the image display device according to the first embodiment of the present invention.

5 is a schematic graph for explaining the light output temperature dependency of the LED. The horizontal axis represents lighting time and the vertical axis represents light output relative value.

6 is a timing chart showing a drive signal of a light source unit generated by a lighting control unit of an image display device according to a second embodiment of the present invention.

Fig. 7 is a schematic graph for explaining the change in luminance in the operation of the image display device according to the second embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

1, 50..projector (image display device) 2, 60..lighting unit

3. Condenser lens 4. Spatial modulation device

5. Projection lens 6. Reflective screen

10. Control part 20. LED light source part (light source part)

21. LED driver circuit (lighting control part) 22. Power supply

23, 27. Waveform pattern generator (lighting controller) 25. Temperature detector

26..Lighting mode selection part R1, R2, G1, G2, B1, B2.LED

The present invention relates to an image display apparatus employing a plurality of light emitting elements having different wavelengths as light sources.

Background Art [0002] Conventionally, an image display device that enlarges and projects an image onto a reflective or transmissive screen, such as a projector, a rear projection television, or the like is known. In these image display apparatuses, the image color-separated into red (R), green (G), and blue (B), which are the three primary colors of light, is displayed sequentially in color to display a full color image.

In such an image display apparatus, it is necessary to have a high-brightness light source for enlarged projection. Therefore, when employing a light emitting device such as an LED as a light source, it is often necessary to provide a plurality of light emitting devices for each light emission wavelength and simultaneously turn on the light. many.

The timing chart shown in FIG. 1 is an example of the timing chart of the drive signal in the case of using two LEDs for each color in such a conventional image display apparatus. Reference numerals 200 and 201 denote driving signals of LEDs R1 and R2 having R wavelengths, reference numerals 202 and 203 denote driving signals of LEDs G1 and G2 having G wavelengths, and reference numerals 204 and 205 denote B LEDs. The drive signals of (B1, B2) are shown respectively. Each signal is a square wave whose constant frequency f ₀ = 1 / T ₀ is the fundamental frequency of lighting. The lighting duty of each signal is t _R / T ₀ , t _G / T ₀ and t _B / T ₀ for R, G, and B, respectively. LEDs for each wavelength are time-divisionally driven in the order of R, G, and B according to each signal. Here, t _R , t _G , t _B are set to appropriate values in a range satisfying t _R + t _G + tB = T ₀ , respectively. In addition, the amplitude of each signal has the magnitude of I _R , I _G , and I _B depending on the magnitude of each required driving current.

On the other hand, as a technique related to the lighting control of a plurality of LEDs, Japanese Patent Laid-Open No. 2002-319707 is provided with at least two or more LEDs in order to reduce power consumption per LED, and at least one of them blinks periodically. An LED driving circuit capable of driving an LED without causing a decrease in luminance due to a decrease in the total amount of light by blinking by driving is described.

The image display device using a light emitting element such as a conventional LED as a light source has the following problems.

In a configuration in which a plurality of LEDs are simultaneously lit, a high brightness light source can be realized. However, for example, when a multi-chip LED light source unit is used for miniaturization of a device, a plurality of LED chips are arranged in close proximity, so that the temperature rises according to the lighting time. And shortens the lifetime of the LED or decreases the luminance due to the effect thereof.

On the other hand, in the technique described in Japanese Patent Laid-Open No. 2002-319707, a means for periodically blinking a plurality of LEDs is described, but it is adopted for the purpose of reducing power consumption, and it is possible to reduce the luminance caused by the self-heating of the LED. In this regard, no means or method for periodically blinking a plurality of LEDs is described, and there is no suggestion. Therefore, even if this LED drive circuit is employ | adopted for an image display apparatus, the problem of the said image display apparatus could not be solved immediately.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and when the plurality of light emitting elements are sequentially turned on to project light onto a screen to display an image, the temperature rise due to self-heating of the light emitting elements is suppressed and the life of the light emitting elements is maintained. It is an object of the present invention to provide an image display device capable of extending the time and at the same time reducing the luminance decrease due to the thermal effect.

In order to achieve the above object, the image display device according to the present invention includes a light source unit having a plurality of light emitting elements having different wavelengths and provided with n light emitting elements having at least one wavelength among them (n is an integer of 2 or more), and An image display device having a lighting control unit for time-divisionally driving the light emitting elements having different wavelengths within a predetermined time period, wherein the lighting control units control n light emitting elements having the at least one wavelength by m (m is By dividing the lighting groups into a lighting group of 2? M? N, and lighting the m lighting groups alternately at a frequency of 1 / m in the periodic constant time zones, thereby selecting any one of the m lighting groups in the respective constant time zones. It is set as one structure which can light one lighting group.

According to the present invention, n light emitting elements having at least one wavelength are divided into m lighting groups within each predetermined time period, and each of the lighting groups is alternately lit at a frequency of 1 / m, and the light emitting elements of each lighting group Since the individual lighting frequencies are each 1 / m, the temperature rise of the light emitting element can be reduced.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In all drawings, even if the embodiment is different, the same or corresponding members are denoted by the same reference numerals, and common descriptions are omitted.

[First Embodiment]

The image display device according to the first embodiment of the present invention will be described.

2 is a schematic diagram showing a schematic configuration of an image display device according to a first embodiment of the present invention. 3 is a functional block diagram for explaining a schematic configuration of a light source unit and a lighting control unit employed in the image display device according to the first embodiment of the present invention. 4 is a timing chart showing a drive signal of a light source unit generated by a lighting control unit of the image display device according to the first embodiment of the present invention.

The projector 1 of this embodiment is an image display apparatus for projecting a full color image according to an external signal, for example, on the reflective screen 6.

The schematic configuration of the projector 1 is composed of an illumination unit 2, a condenser lens 3, a spatial modulation element 4, a projection lens 5 and a control unit 10 which controls the entire apparatus.

The illumination unit 2 sequentially generates light of wavelengths corresponding to at least three primary colors R, G, and B of light at time-divisional timing to display a full color image.

The condenser lens 3 is an optical element that condenses the light generated by the illumination unit 2 in the modulation region on the spatial modulation element 4.

The spatial modulation element 4 spatially modulates the light collected by the condenser lens 3 in accordance with an image signal of wavelength light corresponding to the irradiation timing, and displays a color-separated image. As the spatial modulation element 4, a transmissive element or a reflective element can be employed. For example, a transmissive element includes a liquid crystal display device (LCD), and a reflective element includes a micro mirror array (DMD, Digital Micromirror Device) or a reflective liquid crystal panel (LCOS). Etc.

The projection lens 5 is an optical element which enlarges and projects the image displayed by the spatial modulation element 4 onto the reflective screen 6.

The detailed structure of the lighting unit 2 is demonstrated.

As shown by a solid line in FIG. 2, the lighting unit 2 includes an LED light source unit 20, an LED driver circuit unit 21, a power supply unit 22, and a waveform pattern generator 23.

The LED light source unit 20 includes first and second red LEDs R1 and R2, first and second green LEDs G1 and G2 that emit light of wavelengths R, G and B, which are three primary colors of light, respectively. The first and second blue LEDs B1 and B2 (hereinafter, collectively referred to as respective LEDs) are light emitting elements disposed on the base member 20a. The LEDs R1, R2, G1, G2, B1, and B2 are examples of light emitting devices emitting monochromatic wavelength light, but are not limited thereto. For example, an organic light emitting diode (OLED) may be employed as the light emitting device. The LEDs R1, R2, G1, G2, B1, and B2 may be mounted to the base member 20a in a chip state that is not packaged for miniaturization.

2 does not show an actual arrangement position in a schematic diagram. In this embodiment, each LED is appropriately two-dimensionally arranged on the base member 20a so that the light emitted from the condenser lens 3 is easily collected.

The base member 20a also serves as a heat radiating member for each LED, and at least the vicinity of each LED exhibits a temperature change following each temperature change.

The LED driver circuit unit 21 controls the driving current supplied from the power supply unit 22 according to the driving signals of the LEDs R1, R2, G1, G2, B1, and B2 transmitted from the waveform pattern generator 23. It is a drive circuit for independently driving LEDs R1, R2, G1, G2, B1, and B2.

The waveform pattern generation unit 23 is, for example, a signal obtained by pulse-width modulating or delaying the lighting clock based on control information such as the lighting clock supplied from the control unit 10, the lighting duty, amplitude of R, G, and B, and the like. Is appropriately arithmetic processed to generate a drive signal having a predetermined waveform pattern synchronized with the lighting clock, and to select an LED to turn on.

In this embodiment, a drive signal having a waveform pattern as shown in Fig. 4 is generated. For comparison with the prior art, the lighting clock frequency fundamental f ₀ = 1 / T ₀ and the lighting duty of each color t _R / T ₀ , t _G / T ₀ , t _B / T ₀ (where t _R + t _G + t _B = T ₀ ) is the same as in FIG. 1. For example, depending on the luminance characteristics of each color, set the lighting duty of each color to values such as t _R / T ₀ = 20%, t _G / T ₀ = 40%, t _B / T ₀ = 40%, and so on. Can be.

A first signal 100 to drive a red LED (R1) is the frequency, the disclosed light at time _{t 1 f = f 0/2} , the amplitude 2 · I _R, light duty t _R / (2 · T ₀ ) Is a pulse signal. A first signal (102) for driving the green LED (G1) is a time t ₂ = t frequencies, _one disclosed light in + t _R is f = f _0/2, the amplitude 2 · I _G, light duty t _G It is a pulse signal of / (2 · T ₀ ). First blue LED (B1) signal 104 for driving the time t ₃ = t ₁ + t _R + t is _G frequency, the disclosed light at f = f _0/2, the amplitude 2 · I _B, light duty Is a pulse signal of t _B / (2 · T ₀ ). The signals 101, 103, and 105 driving the second red, second green, and second blue LEDs R2, G2, and B2 are respectively the first red, first green, and first blue LEDs R1, G1, and B1. ) Is delayed by T ₀ , which is one period of the fundamental frequency of lighting. That is, the timing at which the first red, first green, and first blue LEDs R1, G1, and B1 light up, and the second red, second green, and first periods between the cycles T ₀ for replacing R, G, and B, respectively. The timing at which the two blue LEDs R2, G2, and B2 are turned on is a drive signal to be replaced. Here, I _R , I _G , and I _B are amplitude values of the signal giving the magnitude of the driving current required in the lighting mode as shown in FIG. 1.

The operation of the projector 1 will be described centering on the operation of the lighting unit 2 of the present embodiment.

5 is a schematic graph for explaining the light output temperature dependency of the LED. The horizontal axis indicates lighting time, and the vertical axis indicates light output relative value.

The projector (1) control unit 10 for, as shown in Figure 2, from the outside of the R, G, receive the respective color-decomposing the image signal to the B, R, G, lights up the fundamental frequency f ₀ that is lit in order to B The lighting clock and control information for controlling the lighting start timing of each color are sent to the lighting unit 2 and the spatial modulation element 4.

In the lighting unit 2, signals 100 to 105 are generated by the waveform pattern generator 23, and the signals 100 to 105 are sent to the LED driver circuit 21 so that each LED of the LED light source 20 is light. (R1, R2, G1, G2, B1, B2) are driven, and wavelength light of R, G, B is time-division driven. On the other hand, the spatial modulation element 4 is time-divisionally driven in synchronization with the timing at which the wavelength light of R, G, B is emitted according to the control information transmitted from the control part 10 and the color-decomposed image signal. Accordingly, the light of R, G, and B emitted from the illumination unit 2 is collected by the condensing lens 3, and spatially modulated by the spatial modulation element 4 to display a color separation image corresponding to each color. . The image displayed on the spatial modulation element 4 is then enlarged in the projection lens 5 and projected onto the reflective screen 6. Since this color separation image looks visually mixed, an observer can observe the full color image by seeing the color-sequential reflection light in the reflective screen 6.

When the LED is driven with a constant current, the LED has a temperature characteristic that the light output decreases as the temperature increases. For example, as shown in FIG. 5, when the same LED is continuously lit in a room temperature environment (see curve 120) and a higher temperature environment (see curve 121), the effect of self-heating is remarkable depending on the lighting time in a high temperature environment. As shown in the curve 121, the luminance decreases with time. On the other hand, in the case of room temperature environment, since heat is radiated even by self-heating, as shown in the curve 120, the ratio of the decrease in brightness becomes gentle compared to the curve 121.

In the present embodiment, as shown in Fig. 4, the prior art of simultaneously lighting two LEDs R1, R2, G1, G2, B1, and B2 of each color as shown in Fig. 1 shows each LED (R1, R2). The lighting time is halved by setting the individual lighting frequencies of G1, G2, B1, and B2 to 1/2 of the lighting fundamental frequency. By doubling the amplitude of each drive signal and doubling the luminance of each LED (R1, R2, G1, G2, B1, B2) per lighting time, the luminance equivalent to that of the prior art can be obtained.

When the light emission luminance is doubled, twice as much power is consumed per unit pulse. However, since the time for heat dissipation is doubled, heat dissipation is efficiently performed, and the amount of self-heating heat storage is reduced.

Therefore, when such lighting is repeated for a long time, the temperature rise is reduced and the life of the LED is improved as compared with the prior art as shown in FIG. In addition, the decrease in luminance due to the effect of temperature rise is reduced.

 Second Embodiment

An image display device according to a second embodiment of the present invention will be described.

6 is a timing chart showing a drive signal of a light source unit generated by a lighting control unit of an image display device according to a second embodiment of the present invention.

As shown in Figs. 2 and 3, the projector 50 of this embodiment includes an illumination unit 60 instead of the illumination unit 2 of the first embodiment.

The lighting unit 60 has a waveform pattern generator 27 instead of the waveform pattern generator 23 of the illumination unit 2 of the first embodiment, and includes a temperature detector 25 and a lighting mode selector 26. (See 2-dot dashed line). Hereinafter, description will be focused on the differences from the above embodiment.

The waveform pattern generator 27 generates a simultaneous lighting mode for generating driving signals corresponding to the signals 200 to 205 of FIG. 1 for each of the LEDs R1, R2, G1, G2, B1, and B2, and FIG. The distributed lighting mode for generating the signals 110, 111, 112, 113, 114, and 115 shown in Fig. 1 is provided interchangeably.

Reference numerals 110, 112, and 114 denote signals for driving the first red, first green, and first blue LEDs R1, G1, and B1, and indicate periods of the signals indicated by reference numerals 200, 202, and 204 of FIG. This is a drive signal of 2 · T ₀ . Reference numerals 111, 113, and 115 denote signals for driving the second red, second green, and second blue LEDs, and signals for driving the first red, first green, and first blue LEDs R1, G1, and B1. Delay (110, 112, 114) by the time T ₀ , respectively.

That is, the signals 110 to 115 for driving the LEDs R1, R2, G1, G2, B1, and B2 are drive signals in which the amplitudes of the signals 100 to 105 of the first embodiment are 1/2 in each color. It is.

The temperature detector 25 is a temperature detector that detects the temperature of each of the LEDs R1, R2, G1, G2, B1, and B2, and sends a detection signal to the light mode selector 26. In this embodiment, the base member 20a having good thermal conductivity is employed, and the LEDs R1, R2, G1, G2, B1, and B2 are detected by detecting the temperature by a temperature sensor contacted or embedded in the base member 20a. The temperature of is indirectly detected. The kind of temperature sensor is not specifically limited, A suitable thing can be employ | adopted as needed.

In addition, when the base member 20a has nonuniform temperature distribution by its structure, material, etc., each temperature sensor is installed in the position which is adjacent to each LED (R1, R2, G1, G2, B1, B2), and each A configuration for detecting the temperature of the LEDs R1, R2, G1, G2, B1, B2 may be employed.

When it is determined that the temperature corresponding to the detection signal sent from the temperature detector 25 is equal to or less than the predetermined threshold value, the lighting mode selector 26 sets the control signal for setting the simultaneous lighting mode to a predetermined threshold value. When it is determined as high, the control signal for setting to the distributed lighting mode is sent to the waveform pattern generator 27, respectively.

The predetermined threshold value can be set, for example, by obtaining a luminance reduction allowable value according to the temperature condition through experiment or the like in advance.

Moreover, when the temperature detection part 25 is made to perform temperature detection of each LED (R1, R2, G1, G2, B1, B2), the temperature of each LED (R1, R2, G1, G2, B1, B2). Since it can be detected separately, it is possible to set the optimum threshold value for each of the predetermined threshold value according to the temperature characteristics of each LED (R1, R2, G1, G2, B1, B2).

The operation of the projector 50 of the present embodiment will be described focusing on the lighting control operation of the LED light source unit 20 different from the projector 1 of the first embodiment.

Fig. 7 is a schematic graph illustrating the change in luminance in the operation of the image display device according to the second embodiment of the present invention. The horizontal axis indicates lighting time, and the vertical axis shows relative luminance.

In this embodiment, the temperature detection unit 25 monitors the temperature of each LED based on the temperature of the base member 20a, and the lighting mode selection unit 26 simultaneously monitors the lighting mode and the distributed lighting mode according to the detection signal. Is optionally set.

At the start of normal operation, since there is no temperature rise due to self-heating of the LED light source unit 20 initially, the detection temperature does not exceed the threshold value and is driven in the simultaneous lighting mode. That is, it is driven by the signals 200-205 shown in FIG.

When the simultaneous lighting mode is continued, the temperature of the LED light source unit 20 is increased by repeated lighting, and the light emission luminance with respect to the constant drive current is lowered, for example, according to the individual temperature characteristics as shown in FIG. For example, as shown by the curve 130a in FIG. 7, the luminance decreases at the initial value P ₀ with the increase of the lighting time over time.

If the simultaneous lighting mode is maintained as it is, as indicated by the curve 130b of the two-dot chain line, the luminance is further lowered and the LED light source unit 20 reaches temperature equilibrium, thereby equilibrating at a constant luminance P ₃ .

On the other hand, in this simultaneous lighting mode, taking into account the case where the number of LEDs turns on is 1/2 for each color, the initial value of the luminance becomes 1/2 of P ₀ in proportion to the number of lighting times. In the same tendency, the luminance decreases, and since the heat generation amount is also halved, the luminance decreases more slowly, and the luminance may be maintained higher than P ₃ when the temperature equilibrium is reached depending on the use environment.

According to such a consideration, it can be seen that when one long LED is turned off rather than performing two simultaneous lighting modes, high brightness can be realized as a result when comparing the lighting after a long time.

In the distributed lighting mode of this embodiment, as shown in FIG. 6, in the RGB lighting 1 cycle T ₀ , the first red, first green, and first blue LEDs R1, G1, B1, and the second red, first Since the green and the second blue LEDs R2, G2, and B2 light up alternately, the number of lightings is counted, and the number of lightings of the LEDs is halved within one cycle of the lighting fundamental frequency. the lighting frequency is f _0/2, so this is, that it is only the temporal LED lighting load per one half compared to when the light-off one LED. Therefore, in the distributed lighting mode of this embodiment, twice as much heat dissipation time can be taken as compared with the case where one LED is lit at the frequency f ₀ . Therefore, the self-heating accumulation amount of each LED is certainly reduced.

Therefore, it is more advantageous for the luminance to be lowered alternately as in the present embodiment, rather than halving only the number of lighting.

For example, considering the case where the temperature detected by the temperature detection unit 25 exceeds the threshold at time t _Q , and the lighting mode selection unit 26 changes from the simultaneous lighting mode to the distributed lighting mode, the curve 130c is plotted. The same change as shown takes place. Here, as a comparative example, the luminance change in the case where the number of lighting is halved is shown by the curve 131.

That is, from the luminance P _Q of the end of the curve 130a, the luminance decreases more slowly than the change rate of the curve 130a. However, as shown in the curve 130c, in the distributed lighting mode, the luminance reduction rate is always lower than that of the comparative example. The temperature equilibrium is reached at, and luminances P ₁ and P ₂ (where P _Q > P ₁ > P ₂ > P ₃ ) are reached, respectively.

By changing from the simultaneous lighting mode to the distributed lighting mode in this manner, the decrease in luminance can be suppressed more favorably than when the simultaneous lighting mode is continued.

In addition, since the temperature rise of each LED is suppressed as a whole by performing the switching control of the lighting mode, it is possible to prevent the deterioration of the life due to the temperature rise.

As described above, the image display device of the present embodiment includes a temperature detector which detects the temperature of the LED of the at least one wavelength, a simultaneous lighting mode in which n lights of the LEDs of the at least one wavelength are simultaneously emitted, and A lighting mode selector for selectively dividing n LEDs of at least one wavelength into m lighting groups, and selectively switching the distributed lighting modes each of which is alternately lit, and the simultaneous lighting mode according to the temperature detected by the temperature detector. It has a structure which changes the said distributed lighting mode. In addition, the above-described embodiment includes n LEDs for each of three wavelengths R, G, and B, and illustrates an example in which n = 2 and m = 2.

According to this, when the temperature of the LED rises by the simultaneous lighting mode, the temperature detecting unit detects the increased temperature, and the lighting mode selection unit changes to the distributed lighting mode to suppress the temperature rise of the LED of each lighting group, and the simultaneous lighting mode In comparison with this, the luminance reduction rate can be reduced.

In addition, although the above description demonstrated the example which applied the drive signal of this invention with respect to all of R, G, and B, what is necessary is just to apply to at least one according to the self-heating amount and the mutual influence degree.

In the above description, the LED has been described as an example in which two types of three different wavelengths are provided, respectively, but the present invention can be implemented for two or more types, and the number n is two or more suitable numbers.

In addition, the n LEDs may be LEDs of at least one wavelength. For example, when one LED having a wavelength other than the at least one wavelength can supply the required amount of light, and there is no fear of lowering the luminance due to temperature rise, or the temperature rise of the LED having at least one wavelength is reduced. When there is no fear of lowering the luminance, the LEDs having wavelengths other than at least one wavelength can be configured as one.

In the case of dividing n LEDs into m lighting groups, in the above embodiment, m = 2 because n = 2. However, when n≥3, a method of dividing m lighting groups into appropriate combinations is necessary. Can be used. For example, if possible, n pieces may be divided into m lighting groups, or n lights may be divided into light lighting groups. In the case of dividing by inequality, it is a matter of course that the amplitude of the drive signal of the LED in each lighting group is appropriately set as needed, and the light emission luminance in each fixed time is adjusted.

In addition, in the above description, the case where each LED is disposed on the base member 20a has been described as an example. However, when each LED is arranged close enough to be thermally affected by each other, each LED is disposed on the plurality of base members. You may be.

In the above description, the case where one cycle of the lighting fundamental frequency coincides with the periodic constant time zone is described as an example, but a plurality of visible light LEDs may have a timing of simultaneous lighting in one cycle of the lighting fundamental frequency. For example, in order to raise the apparent luminance of the image, timings for simultaneously lighting R, G, and B can be provided.

In the above description, as an image display device, a projector for displaying an image on a reflective screen is described as an example. However, the projector may be a projector for displaying an image by projecting light onto a transmissive screen. For example, it may be a rear projection television. In addition, as long as light is projected onto a display medium such as a reflective or transmissive screen, it is not limited to a device that projects an image, and can be used as a suitable lighting device or part of a light transmitting device.

In addition, the component described in each said embodiment can be implemented in combination suitably in the range of the technical idea of this invention, if technically possible.

Here, the case where a name differs about the relationship of the term of each said Example and the term of a claim is demonstrated.

The projector 1 is an embodiment of an image display device. The LED light source unit 20 is an embodiment of the light source unit. LEDs R1, R2, G1, G2, B1, and B2 are exemplary embodiments of light emitting devices. The LED driver circuit 21 and the waveform pattern generator 23 are one embodiment of a lighting controller. The temperature detector 25 and the lighting mode selector 26 together with the LED driver circuit 21 and the waveform pattern generator 27 constitute an embodiment of the lighting controller. In the above embodiment, each LED of R, G, and B wavelengths is divided into two lighting groups. For example, in the LED of the R wavelength, the first red LED R1 and the second red LED R2 are respectively. Each lighting group is comprised.

According to the image display device of the present invention, the temperature rise of the light emitting element can be reduced by dividing the n light emitting elements having at least one wavelength into m lighting groups and setting the individual lighting frequencies of each lighting group to 1 / m. Therefore, the life of the light emitting element can be improved and the effect of suppressing the luminance decrease due to the thermal effect can be obtained.

Such an image display device of the present invention has been described with reference to the embodiments shown in the drawings for clarity, but this is merely an example, and those skilled in the art may have various modifications and other equivalent embodiments therefrom. Will understand. Therefore, the true technical protection scope of the present invention will be defined by the appended claims.

Claims (7)

A light source unit having a plurality of light emitting elements having different wavelengths and having at least one light emitting element having n (n is an integer of 2 or more), and a lighting control unit for time-divisionally driving the light emitting elements having different wavelengths within a predetermined time period An image display device having: The lighting control unit divides the n lighting groups of the at least one wavelength into m lighting groups having the same lighting timing (m is an integer of 2 ≦ m ≦ n), and divides the m lighting groups into the periodic groups. And lighting one by one of the m lighting groups in each of the predetermined time periods by alternately lighting at a frequency of 1 / m each at a predetermined time period. The method of claim 1, The lighting control unit, A temperature detector detecting a temperature of the light emitting device having at least one wavelength; A simultaneous lighting mode for simultaneously emitting n light emitting elements of the at least one wavelength and a distributed lighting mode for lighting each of the n lighting groups of the at least one wavelength in turn by dividing the n lighting groups, respectively. The lighting mode selection unit for changing; And the lighting mode selecting unit changes the simultaneous lighting mode and the distributed lighting mode according to the temperature detected by the temperature detecting unit. The method of claim 2, The lighting mode selection unit selects a simultaneous lighting mode when the temperature detected by the temperature detector is less than or equal to a predetermined threshold value, and selects a distributed lighting mode when the temperature detected by the temperature detector is higher than the threshold value. Image display device. The method of claim 3, And said threshold value is an allowance for decreasing the brightness of said light source portion. The method according to any one of claims 2 to 4, The light source unit includes a base member on which the light emitting element is mounted. And the temperature detector includes a temperature sensor provided in the base member. The method according to any one of claims 2 to 4, The light source unit includes a base member on which the light emitting element is mounted. And the temperature detector includes a plurality of temperature sensors provided in the base member in proximity to each of the light emitting elements. The method according to claim 1 or 2, And the light emitting element is an LED.

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