JP2011203292A - Projection display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a projection display device which generates only a little amount of heat from an LED, achieves an expanded color gamut of an image to be displayed, facilitates the gradation control of the image to be displayed, and provides a bright projected image.SOLUTION: A frequency determination part 33 generates a frequency signal on the basis of a gradation signal extracted from an image signal and a mixture ratio signal set on the basis of chromaticity information and luminance information. An LED driving pulse generation part 31 generates an LED pulse signal on the basis of the frequency signal and a synchronization signal. An LED drive circuit 32 generates an LED driving signal being a pulse signal having a pulse width corresponding to the gradation signal, on the basis of the LED pulse signal and outputs the LED driving signal to LED light sources 2r, 2g and 2b.

Description

  When projecting an image by field sequential driving using a plurality of light sources having different wavelengths and a single light modulation element, the present invention projects an image with little variation in chromaticity regardless of the gradation of the projected image. The present invention relates to a projection display device that can

2. Description of the Related Art As a small-sized device that displays a large screen image, a projection display device that uses a single light modulation element and performs field sequential driving is known.
The projection display device irradiates a liquid crystal display element with illumination light from a light source, and enlarges and projects an image displayed on the liquid crystal display element on a screen.

In recent years, semiconductor light sources such as LEDs and lasers have been increased in luminance, and studies have been conducted on use as light sources for projection display devices.
Semiconductor light sources are actively studied for practical use because they can control the light source at high speed, and are small, light, and have a long life.
In addition, field sequential driving using one light modulation element has been studied using the high-speed controllability of a semiconductor light source.
Patent Document 1 discloses a projection display device that uses an LED light source and displays an image by field sequential driving.

Patent Document 1 generally discloses the following contents.
The display device described in Patent Literature 1 includes red (R), green (G), and blue (B) LEDs, one spatial modulation element, and a light source adjustment unit. One frame of video is divided into three subframes corresponding to R light, G light, and B light, and R, G, and B video signals are supplied to the spatial modulation element in each subframe. The R, G and B LEDs are driven at high speed. The light source adjustment unit determines the mixing ratio of the respective light emission amounts of the R, G, and B LEDs in order to set the image as the target color space, and determines each of the R, G, and B LEDs based on the mixing ratio. Set the LED drive current to flow.
By adjusting the LED drive current that flows to each of the G and B LEDs for each subframe, the color space is set to a desired position, and the color gamut is adjusted, and the luminance of the light irradiated to the spatial modulation element is also adjusted. High bright projection picture can be obtained.

JP 2006-330177 A

By the way, the spatial modulation element used in the display device described in Patent Document 1 uses an analog-driven spatial modulation element that controls the gradation of a displayed image by the amount of voltage or current applied to the spatial modulation element. .
However, the analog-driven spatial modulation element has the following problems. An analog-driven spatial modulation element is liable to cause an alignment defect called disclination, and it is difficult to improve the contrast of an image. In addition, an analog-driven spatial modulation element has a complicated drive circuit structure, making it difficult to increase productivity and increasing the cost. Furthermore, in the analog-driven spatial modulation element, the voltage applied to the liquid crystal is not applied to the target and is biased toward one electrode side, and a direct current component is added to the liquid crystal, which tends to cause a defect called burn-in.

  Furthermore, the LED light source described in Patent Document 1 uses continuous driving in which a voltage is continuously applied as a driving method. In the case of continuous driving, the light emission efficiency is reduced due to heat generation by driving for a long time, and the hue of the displayed image may change because the center wavelength moves.

  Therefore, the present invention uses a driving method with less LED heat generation, improves the problem of the analog-driven spatial modulation element, and facilitates the expansion of the chromaticity of the displayed image and the gradation control of the displayed image. An object of the present invention is to provide a projection display device capable of obtaining a bright projection image.

In order to achieve the above object, the present invention provides the following 1) to 5).
1) A plurality of semiconductor light sources (2r, 2g, 2b) that are driven by pulse driving and emit light having different wavelengths, and the semiconductor light sources (2r, 2g, 2b) that are pulse-driven and incident based on element driving signals. And a spatial modulation element (5) for optically modulating and outputting light from the video signal, and extracting and outputting a synchronization signal from the video signal, and generating the element drive signal from the video signal to generate the spatial modulation element (5). ) And a light source drive pulse generation unit (31) for generating a light source drive pulse signal synchronized with the video signal based on the synchronization signal output from the element drive circuit (21). And a light source drive that outputs a light source drive signal for driving the semiconductor light sources (2r, 2g, 2b) based on the light source drive pulse signal output from the light source drive pulse generator (31). Circuit projection display device, characterized in that it comprises (32), a (1).
2) A plurality of semiconductor light sources (2r, 2g, 2b) that are driven by pulse driving and emit light having different wavelengths, and the semiconductor light sources (2r, 2g, 2b) that are pulse-driven and incident based on element driving signals. A spatial modulation element (5) for optically modulating and outputting the light from the image signal; and a gradation signal extraction unit (22) for extracting the gradation signal from the image signal and outputting the image signal and the gradation signal; The device drive circuit (21) that generates the device drive signal from the video signal and outputs the device drive signal to the spatial modulation device (5) and the light emitted from the plurality of semiconductor light sources (2r, 2g, 2b) are mixed The plurality of semiconductor light sources (2r, 2g, 2b) are pulse-driven based on a mixing ratio signal including information on the mixing ratio at the time of performing and a gradation signal output from the gradation signal extraction unit (22). Determine the pulse information, A frequency determining unit (33) that outputs as a frequency signal, and a light source driving circuit that outputs a light source driving signal for driving the semiconductor light sources (2r, 2g, 2b) based on the frequency signal output from the frequency determining unit (33) (32), and the pulse information includes information on the number of pulses, a pulse frequency, and a pulse width corresponding to each of the plurality of semiconductor light sources (2r, 2g, 2b). A projection type display device (1), which is controlled based on a mixing ratio signal.
3) A mixing ratio setting unit (34) is further provided, and the mixing ratio setting unit (34) is configured to include the plurality of semiconductor light sources (2r) based on chromaticity information regarding a desired color gamut or luminance information regarding target luminance. , 2g, 2b), the projection display device (1) according to 2), wherein a mixture ratio signal including information on a mixture ratio when the light emitted from the mixture is mixed is set.
4) The element driving circuit (21) generates and outputs a synchronization signal from the input video signal, and outputs the frequency signal output from the frequency determining unit (33) and the element driving circuit (21). A light source drive pulse generation unit (31) that generates a light source drive pulse signal based on the synchronization signal, and the light source drive circuit (32) includes the light source generated by the light source drive pulse generation unit (31). A projection display device according to 2) or 3), wherein a light source drive signal is generated based on the drive pulse signal, and the semiconductor light source (2r, 2g, 2b) is caused to emit light in synchronization with the element drive signal. (1).
5) The number of the spatial modulation elements (5) is one, and the element drive signal is divided into a number of subframes in which one frame of the projected image corresponds to the number of the plurality of semiconductor light sources (2r, 2g, 2b). Any one of 2) to 4), wherein the plurality of semiconductor light sources (2r, 2g, 2b) emit light in accordance with corresponding subframes. The projection type display device (1) described.

  According to the present invention, a driving method with less heat generation of the LED is used, the problem of the analog-driven spatial modulation element is improved, the color gamut of the displayed image is enlarged, and the gradation control of the displayed image is facilitated. You can get a bright projected picture.

It is the schematic which shows the structure of the projection type display apparatus of 1st Embodiment. It is explanatory drawing which shows the drive method of the spatial modulation element of the projection type display apparatus of 1st Embodiment. It is explanatory drawing which shows the drive method of the semiconductor light source of the projection type display apparatus of 1st Embodiment. It is a block diagram explaining the detail of the control part of the projection type display apparatus of 1st Embodiment. It is a timing chart explaining the outline of the light source drive signal and element drive signal of the projection type display apparatus of 1st Embodiment. It is a timing chart explaining the outline of the light source drive signal and element drive signal at the time of making it color-mix in the projection type display apparatus of 1st Embodiment. It is explanatory drawing which shows the drive method of the semiconductor light source of the projection type display apparatus of 2nd Embodiment. It is a block diagram explaining the detail of the control part of the projection type display apparatus of 2nd Embodiment. It is a timing chart explaining the outline of the light source drive signal and element drive signal at the time of making it color-mix in the projection type display apparatus of 2nd Embodiment.

Embodiments of a projection display device according to the present invention will be described below with reference to the drawings.
Note that components having common functions are denoted by the same reference symbols throughout the drawings, and repeated descriptions of components once described are omitted.

<First Embodiment>
FIG. 1 is a schematic diagram illustrating a configuration of a projection display device 1 according to the first embodiment.
The projection display device 1 includes a semiconductor light source 2, an illumination optical system 3, a polarization separation element 4, a spatial modulation element 5, a projection optical system 6, and a control unit 7.

The semiconductor light source 2 includes an R light semiconductor light source 2r that emits red (R) light, an R light semiconductor light source 2g that emits green (G) light, and a B light semiconductor light source that emits blue (B) light. 2b and a base 21 having a heat radiating function, and the respective color semiconductor light sources 2r, 2g, 2b are fixed to the base 21. As each color semiconductor light source 2r, 2g, 2b, a light emitting diode (LED) or a semiconductor laser is used. Here, a case where LEDs are used will be described.
The illumination optical system 3 includes a plurality of optical elements. The illumination light of each color light emitted from the semiconductor light source 2 is incident on the illumination optical system 3. The illumination optical system 3 reduces unevenness in illumination intensity of the incident illumination light, and changes the size of the illumination light flux. Adjust to match the size of 5.

  The polarization separation element 4 includes a polarization separation surface 41 that is disposed at an inclination of 45 degrees with respect to an incident light beam. The incident light beam transmits the first linearly polarized light having a predetermined angle on the polarization separation surface 41 and reflects the second linearly polarized light orthogonal to the first linearly polarized light. As the polarization separation element 4, a polarization beam splitter (PBS) or a wire grid polarizer is used. Here, the case where PBS4 is used will be described.

The spatial modulation element 5 optically modulates and reflects the first linearly polarized light incident from the polarization separation element 4 based on the element drive signal input from the control unit 7, and emits the modulated linear light to the polarization separation element 4. To do. As the spatial modulation element 5, a reflective or transmissive liquid crystal element or a digital micromirror device is used. Here, a case where the reflective liquid crystal element 5 is used as the spatial modulation element 5 will be described.
The projection optical system 6 enlarges the incident light and enlarges and projects an image on a screen (not shown).

The control unit 7 includes an element control unit 11, a light source (LED) control unit 12, and a power supply circuit unit 13.
The element control unit 11 outputs an element driving signal for optically modulating the spatial modulation element 5 based on a video signal input from the outside. The LED control unit 12 outputs a light source (LED) driving signal for driving the semiconductor light sources 2r, 2g, and 2b for each color. The power supply circuit unit 13 supplies power for generating an element drive signal and a light source drive signal to the element control unit 11 and the LED control unit 12, respectively.

Next, the path of light emitted from the semiconductor light source 2 will be described.
The respective color semiconductor light sources 2r, 2g, and 2b emit R light, G light, and B light based on the light source driving signal input by the LED control unit 12. Each emitted color light enters the illumination optical system 3 as illumination light.
The illumination light incident on the illumination optical system 3 is adjusted so as to reduce the illuminance unevenness of the illumination light and adjust the size of the luminous flux of the illumination light so as to match the size of the spatial modulation element 5.

  The illumination light emitted from the illumination optical system 3 enters the polarization separation element 4, and the S-polarized light that is the second linearly polarized light is reflected at the polarization separation surface 41 inclined by 45 degrees with respect to the incident illumination light beam, Only the P-polarized light that is the first linearly polarized light is transmitted. Although the case where the P-polarized light is the first linearly polarized light and the S-polarized light is the second linearly polarized light has been described here, the S-polarized light may be the first linearly polarized light and the P-polarized light may be the second linearly polarized light. .

The P-polarized light transmitted through the polarization separation element 4 is incident on the reflective liquid crystal element 5. The reflective liquid crystal element 5 optically modulates P-polarized light with an element drive signal output from the element control unit 11 based on a video signal input from the outside, and reflects and emits the light as modulated light.
The modulated light reflected by the reflective liquid crystal element 5 is incident on the polarization separation element 4 again, and S-polarized light, which is a modulation component of the modulated light, is reflected by the polarization separation surface 41 and is bent by 90 degrees from the polarization separation element 4. Eject.

  The S-polarized light reflected by the polarization separation surface 41 exits from the polarization separation element 4 and enters the projection optical system 6. The S-polarized light incident on the projection optical system 6 is enlarged and projected as image light by the projection optical system 6.

Next, a driving method of the reflective liquid crystal element 5 used in the projection display device 1 of the first embodiment will be described with reference to FIG.
FIG. 2A shows a driving method of the reflective liquid crystal element 5 using general analog driving, in which the liquid crystal is modulated with an alternating voltage of a predetermined period (one frame). The gradation control in the case of analog driving is controlled by the amplitude value of the driving voltage. That is, in FIG. 2A, one frame is driven at 100% (all white) of + V and −V, and two frames are at 50% (halftone) of + V / 2 and −V / 2. The driven state is shown. In this driving method, the gradation characteristic of the displayed image is determined according to the voltage, and thus shows a good characteristic.

  However, the analog-driven reflective liquid crystal element 5 is liable to cause an alignment defect called disclination, and it is difficult to improve the contrast of the image. In addition, the structure of the drive circuit is complicated, and it is difficult to increase productivity, resulting in an increase in cost. Further, the voltage applied to the liquid crystal is not applied to the target but is biased toward one electrode side, and a direct current component is added to the liquid crystal, which tends to cause a defect called burn-in.

As a method for solving these problems, there is a reflective liquid crystal element 5 using digital driving.
As shown in FIG. 2B, the digitally driven reflective liquid crystal element 5 modulates the liquid crystal by a pulse having a constant peak voltage. Image gradation control in the digitally driven reflective liquid crystal element 5 is performed by liquid crystal modulation by the average potential of the digital pulse voltage of the subframe divided into pulses.
Therefore, as shown in FIG. 2B, in order to display 100% all white in one frame, it is sufficient to drive the time t with pulses of + V and −V subframes. On the other hand, in order to display a halftone of 50% in two frames, the time t / 2 is driven with pulses of + V and −V subframes.

Next, as a technique for preventing a decrease in light emission efficiency due to heat generation of the LED light sources 2r, 2g, and 2b and preventing a change in color of an image, there is a pulse drive of the LED light sources 2r, 2g, and 2b.
A method for driving the LED light sources 2r, 2g, and 2b used in the projection display device 1 of the first embodiment will be described with reference to FIG.
FIG. 3A is a diagram illustrating a driving state of the LED light sources 2r, 2g, and 2b by continuous driving described in the related art. In the LED light sources 2r, 2g, and 2b by continuous driving, when outputting the maximum output luminance of 100%, the voltage is continuously oscillated in a + V state. When the luminance is changed, the voltage is changed according to the luminance to continuously oscillate.

On the other hand, in the case of pulse driving, as shown in FIG. 3B, a rectangular wave having a constant peak voltage and a predetermined duty ratio is continuously oscillated and driven.
In the pulse-driven LED light sources 2r, 2g, and 2b used in the projection display device 1 of the first embodiment, the luminance is controlled by the number of pulses.
When the LED light sources 2r, 2g, and 2b output the maximum luminance of 100%, n pulses of the peak voltage + V are oscillated during the time t. Similarly, when 50% luminance is output, n / 2 pulses of peak voltage + V are oscillated during time t. Similarly, when outputting 33% luminance, n / 3 pulses of peak voltage + V are oscillated during time t. In this way, the luminance of the light output from the LED light sources 2r, 2g, 2b is controlled.

Next, details of the element control unit 11 and the LED control unit 12 using the digitally driven reflective liquid crystal element 5 and the pulse-driven LED light sources 2r, 2g, and 2b will be described with reference to FIG.
As shown in FIG. 4, the element control unit 11 includes an element drive circuit 21. The LED control unit 12 includes a light source (LED) drive pulse generation unit 31 and a light source (LED) drive circuit 32. Power is supplied from the power supply circuit unit 13 to the element drive circuit 21, the LED drive pulse generation unit 31, and the LED drive circuit 32.

  The video signal corresponding to the video to be projected is input to the element drive circuit 21 of the element control unit 11. The element drive circuit 21 generates a synchronization signal for controlling the pulse timing when the LED light sources 2r, 2g, and 2b are pulse-driven from the input video signal, and outputs the synchronization signal to the LED drive pulse controller 31. In the LED drive pulse control unit 31, the LED light sources 2r, 2g, and 2b are pulse-driven based on the input synchronization signal, so that an LED drive pulse signal having a constant voltage and a predetermined duty ratio is generated and output.

The LED drive pulse signal output from the LED drive pulse control unit 31 is input to the LED drive circuit 32, and the number of pulses corresponding to the brightness of the output light of the LED is output to the LED light sources 2r, 2g, 2b as the LED drive signal. .
In the element drive circuit 21, an element drive signal having a constant peak voltage for digitally driving the reflective liquid crystal element 5 based on a video signal input from the outside and a synchronization signal input from the LED drive pulse generator 31. And output to the reflective liquid crystal element 5.
As a result, the LED light sources 2r, 2g, and 2b output light having a luminance corresponding to the LED driving signal, and the reflective liquid crystal element 5 optically modulates the illumination light incident at a gradation corresponding to the element driving signal to obtain modulated light. Output.

Next, LED driving signals and element driving signals when driving the LED light sources 2r, 2g, 2b and the reflective liquid crystal element 5 with the circuit of FIG. 4 will be described with reference to the timing chart of FIG. In order to make it easy to understand the portion corresponding to the R color, the portion corresponding to the G color, and the portion corresponding to the B color, the drive signal is separately displayed as three element drive signals of R, G, and B. The first frame is divided into three subframes of R, G, and B. The first subframe corresponds to the R color, the second subframe corresponds to the G color, and the third subframe corresponds to the B color. In the second frame, the fourth subframe is R color, the fifth subframe is G color, and the sixth subframe is B color. In the following frames, three subframes of R, G, and B are repeated. Configured.
FIG. 5B shows an R-color LED drive signal, a G-color LED drive signal, and a B-color LED drive signal corresponding to the three subframes R, G, and B in FIG. .

The first frame shows the case of 100% gradation (all white), and the second frame shows the case of 50% gradation (halftone).
As described above, by using the digitally driven reflective liquid crystal display element 5 and the pulse-driven LED light sources 2r, 2g, and 2b, the projected image can be easily controlled in the gradation of the displayed image with little change in the color of the LED. Can be obtained.

<Second Embodiment>
Next, a configuration capable of enlarging the color gamut of a bright projected image and a projected image in the projection display device 1 of the first embodiment will be described as a second example.
As a technique for brightening a projected image, there are a method of using a plurality of LED light sources having the same wavelength, a method of increasing the amount of light output from the LED light source, and a method of mixing light emitted from the LED light sources of the respective colors. The method of using a plurality of LED light sources and the method of increasing the amount of light output from the LED light sources may increase the cost of the light source and increase the heat generation and shift the wavelength of the output light. On the other hand, the method of mixing the light emitted from the LED light sources of the respective colors does not increase the number of light sources, so that the cost does not increase and heat generation does not increase.

Further, the color gamut of the projected image in the projection display device 1 of the first embodiment depends on the output wavelength of each output light of the LED light sources 2r, 2g, 2b. Therefore, in order to expand the color gamut of the projected image, the output wavelength of the LED light sources 2r, 2g, 2b is varied, the wavelength of the output light from the LED light sources 2r, 2g, 2b is changed by an optical element, and the like. However, in either case, the cost increases and the brightness of the output light decreases.
Also in this case, by mixing the light emitted from the LED light sources 2r, 2g, and 2b of the respective colors, the cost does not increase and the luminance can be increased.

FIG. 6 is a timing chart for explaining a case where light emitted from the LED light sources 2r, 2g, and 2b is mixed using the projection display device 1 of the first embodiment.
In the first sub-frame displaying R color, the LED light source 2r for R light, which is the principal ray of the LED drive signal, continuously emits light, whereas the LED light source 2g for G light is 1 / of the first sub-frame. It emits light only for 4 periods. Further, the LED light source 2b for B light emits light only for 1/8 period of the first subframe.

Similarly, in the second sub-frame displaying G color, the LED light source 2g for G light, which is the principal light, emits light continuously, whereas the LED light source 2r for R light, which is the second light. Emits light only during a quarter period of the second subframe. Further, the LED light source 2b for the B light, which is the third light beam, emits light only for 1/8 period of the first subframe.
Similarly, in the third sub-frame for displaying the B color, the LED light source 2b for B light, which is the main light, emits light continuously, whereas the LED light source 2g for G light, which is the second light. Emits light only during a quarter period of the first subframe. Further, the LED light source 2r for R light, which is the third light beam, emits light only during the 1/8 period of the second subframe.

In the case of the first frame in which the reflective liquid crystal display element 5 modulates with a modulation factor of 100%, the reflective liquid crystal display element 5 is continuously driven in the period of each subframe. Therefore, the driving period of the LED light source corresponding to the principal ray coincides with the driving period of the reflective liquid crystal display element 5.
On the other hand, in the case of the second frame in which the reflective liquid crystal display element 5 modulates with a modulation factor of 50%, the reflective liquid crystal display element 5 is driven for a period that is half of the period of each subframe. For this reason, the driving period of the LED light source corresponding to the principal ray is ½ of the driving period of the reflective liquid crystal display element 5.

Here, even when the chief ray is continuously emitted as in the second frame, if the driving period of the reflective liquid crystal display element 5 is short, light from the LED light source is emitted only during the driving period of the reflective liquid crystal display element 5. Not used.
Therefore, the driving period of the reflective liquid crystal display element 5, the driving period of the LED light source corresponding to the second light beam, and the driving period of the LED light source corresponding to the third light beam are 1: 1/4 in the first frame. However, in the second frame, the ratio is 1/2: 1/4: 1/8, and the ratio of the second and third rays increases. As a result, it is different from the color mixture ratio of the LED light source in the case of the first frame, and the hue changes when the gradation is different as in the first frame and the second frame.

Therefore, a driving method of the LED light sources 2r, 2g, and 2b in which the hue does not change regardless of the gradation of the projected image when the light emitted from the LED light sources 2r, 2g, and 2b is mixed will be described with reference to FIG. .
FIG. 7A shows the driving method of the first embodiment shown in FIG. In this case, the luminance is controlled by the number of pulses. When the LED light sources 2r, 2g, and 2b output the maximum luminance of 100%, n pulses of the peak voltage + V are oscillated during the time t. Similarly, when 50% luminance is output, n / 2 pulses of peak voltage + V are oscillated during time t. Similarly, when outputting 33% luminance, n / 3 pulses of peak voltage + V are oscillated during time t. In this way, the luminance of the light output from the LED light sources 2r, 2g, 2b is controlled.

On the other hand, FIG. 7B shows a driving method of the LED light sources 2r, 2g, and 2b in the second embodiment. The driving method of FIG. 7B is characterized in that the number of pulses in each frame is the same regardless of the luminance of the LED, and the pulse duty ratio is changed for each frame in accordance with the luminance.
Specifically, as shown in FIG. 7B, since the number of pulses is the same, the pulse period is the same, and the pulse width, which is the length of the ON state of the pulse, is proportional to the luminance. . That is, when the pulse width of 100% luminance is x, the pulse width of 50% luminance is x / 2, and the pulse width of 33% luminance is x / 3.

Next, details of the LED control unit 12 that uses the driving method of the LED light sources 2r, 2g, and 2b in FIG. 7B and the element control unit 11 that drives the digitally driven reflective liquid crystal element 5 will be described with reference to FIG. explain.
As shown in FIG. 7, the element control unit 11 includes an element drive circuit 21 and a gradation signal extraction unit 22. The LED control unit 12 includes an LED drive pulse generation unit 31 and an LED drive circuit 32. An element drive circuit 21, an LED drive pulse generation unit 31, an LED drive circuit 32, a frequency determination unit 33, and a mixing ratio setting unit 34 are provided. Further, power is supplied from the power supply circuit unit 13 to each of the element control unit 11 and the LED control unit 12.
The video signal corresponding to the video to be projected is input to the gradation signal extraction unit 22 of the element control unit 11. In the gradation signal extraction unit 22, gradation information of each frame is extracted from the input video signal and is output as a gradation signal, and the input video information is output to the element driving circuit 21.

The element driving circuit 21 extracts and outputs a synchronization signal for controlling the pulse timing when the LED light sources 2r, 2g, and 2b are pulse-driven from the input video signal, and outputs an element based on the input video information. A drive signal is generated and output to the reflective liquid crystal display element 5.
In the LED control unit 12, chromaticity information for setting a color gamut or luminance information for setting luminance is input to the mixing ratio setting unit 34. The chromaticity information or the luminance information may be stored in advance in the projection display device 1 or may be input by the user. In the mixing ratio setting unit 34, based on the input chromaticity information or luminance information, the mixing ratio of the output light output from each of the R light LED light source 2r, the G light LED light source 2g, and the B light LED light source 2b is set. It is determined and output to the frequency determination unit 33 as a mixing ratio signal.

The gradation signal output from the gradation signal extraction unit 22 is input to the frequency determination unit 33. The frequency determination unit 33 determines the duty ratio (pulse width), the number of pulses, and the frequency for driving the LED light sources 2r, 2g, and 2b based on the input gradation signal and the mixing ratio signal, and outputs the frequency signal. It is output to the LED drive pulse controller 31.
In the LED drive pulse control unit 31, an LED drive pulse signal is generated based on the frequency signal and the synchronization signal input from the element drive circuit 21, and is output to the LED drive circuit 32.
In the LED drive circuit 32, the number of pulses corresponding to the brightness of the output light of the LED is output to the LED light sources 2r, 2g, 2b based on the LED drive pulse signal input from the LED drive pulse controller 31 as an LED drive signal.

  With the above configuration, the LED light sources 2r, 2g, and 2b output light with luminance corresponding to the LED drive signal, and the reflective liquid crystal element 5 optically modulates and modulates illumination light incident at a gradation corresponding to the element drive signal. It can be output as light.

Next, the LED drive signal and the element drive signal when the LED light sources 2r, 2g, 2b and the reflective liquid crystal element 5 are driven by the circuit of FIG. 8 will be described with reference to the timing chart of FIG. In order to make it easy to understand the portion corresponding to the R color, the portion corresponding to the G color, and the portion corresponding to the B color, the drive signal is separately displayed as three element drive signals of R, G, and B. The first frame is divided into three subframes of R, G, and B. The first subframe corresponds to the R color, the second subframe corresponds to the G color, and the third subframe corresponds to the B color. In the second frame, the fourth subframe is R color, the fifth subframe is G color, and the sixth subframe is B color. In the following frames, three subframes of R, G, and B are repeated. Configured.
FIG. 9B shows an R color LED drive signal, a G color LED drive signal, and a B color LED drive signal corresponding to the three subframes R, G, and B of FIG. 9A. .

The first frame shows the case of 100% gradation (all white), and the second frame shows the case of 50% gradation (halftone).
In addition, the output light output from the LED light source in each subframe is in order of increasing luminance. The principal ray, the second ray, and the third ray. Specifically, in the case of the first and fourth subframes displaying R color, the principal ray is output light from the LED light source 2r for R light, and the second ray is emitted from the LED light source 2g for G light. The third light beam is output light from the LED light source 2b for B light. In the case of the second and fifth subframes displaying G color, the principal ray is output light from the LED light source 2g for G light, and the second ray is output light from the LED light source 2r for R light. The third light beam is output light from the LED light source 2b for B light. In the case of the third and sixth subframes displaying B color, the principal ray is output light from the LED light source 2b for B light, and the second ray is output light from the LED light source 2g for G light. The third light beam is output light from the LED light source 2r for R light.

When the LED light sources 2r, 2g, and 2b are driven by the pulse of FIG. 7B, the LED light source 2r for R light is driven by a pulse having a pulse width x in the first and fourth subframes, and the G light. The LED light source 2g for driving is driven by a pulse having a pulse width of x / 2, and the LED light source 2b for B light is driven by a pulse having a pulse width of x / 3.
Also,
Further, in the third and sixth subframes, the LED light source 2b for B light is driven by a pulse having a pulse width x, the LED light source 2g for G light is driven by a pulse having a pulse width x / 2, and R The light LED light source 2r is driven by a pulse having a pulse width of x / 3.

In each subframe, the LED light sources 2r, 2g, and 2b are continuously driven in each subframe period although the pulse widths are different.
In the reflective liquid crystal display element 5, the first, second and third subframes having 100% gradation (whole white) and the fourth, fifth and sixth subframes having 50% gradation (halftone). In the second frame, the reflective liquid crystal display element 5 is driven only for half the period of each subframe with respect to the first frame. However, since the LED light sources 2r, 2g, and 2b adjust the luminance not by the number of pulses but by the pulse width, the mixing ratio of the emitted light from the LED light sources 2r, 2g, and 2b in the first frame and the second frame. Does not change, and the hue does not change when the gradation is different.

  In this way, by using the digitally driven reflective liquid crystal display element 5 that controls the gradation with the number of pulses and the pulse-driven LED light sources 2r, 2g, and 2b that control the brightness with the pulse width, the LED generates less heat, The color gamut of the displayed image can be expanded, and a bright projection image can be obtained.

11, 12, 13
DESCRIPTION OF SYMBOLS 1 ... Projection type display apparatus 2, 2r, 2g, 2b ... Semiconductor light source (LED light source), 3 ... Illumination optical system, 4 ... Polarization separation element, 5 ... Spatial modulation element (reflection type liquid crystal display element), 6 ... Projection Optical system 7 ... Control unit 11 ... Element control unit 12 ... Light source (LED) control unit 13 ... Power supply circuit unit 21 ... Element drive circuit 22 ... Gradation signal extraction unit 31 ... Light source (LED) drive Pulse generation unit 32 ... Light source (LED) drive circuit 33 ... Frequency determination unit 34 ... Mixing ratio setting unit 41 ... Polarization separation plane

Claims (5)

A plurality of semiconductor light sources that are driven by pulse driving and emit light having different wavelengths,
A spatial modulation element that is pulse-driven based on an element drive signal and modulates and outputs the incident light from the semiconductor light source;
An element drive circuit that extracts and outputs a synchronization signal from a video signal, generates the element drive signal from the video signal, and outputs the device drive signal to the spatial modulation element;
A light source driving pulse generation unit that generates a light source driving pulse signal synchronized with the video signal based on the synchronization signal output from the element driving circuit;
A light source driving circuit that outputs a light source driving signal for driving the semiconductor light source based on the light source driving pulse signal output from the light source driving pulse generation unit;
A projection type display device comprising: A plurality of semiconductor light sources that are driven by pulse driving and emit light having different wavelengths,
A spatial modulation element that is pulse-driven based on an element drive signal and modulates and outputs the incident light from the semiconductor light source;
A gradation signal extraction unit that extracts a gradation signal from a video signal and outputs the video signal and the gradation signal;
An element driving circuit for generating the element driving signal from the video signal and outputting the generated element driving signal to the spatial modulation element;
Pulse driving the plurality of semiconductor light sources based on a mixing ratio signal including information on a mixing ratio when light emitted from the plurality of semiconductor light sources is mixed and a gradation signal output from the gradation signal extraction unit Determining the pulse information to be output, and outputting a frequency signal as a frequency signal;
A light source driving circuit for outputting a light source driving signal for driving a semiconductor light source based on the frequency signal output from the frequency determining unit;
With
The pulse information includes information on the number of pulses, a pulse frequency, and a pulse width corresponding to each of the plurality of semiconductor light sources, and the pulse width is controlled based on the mixing ratio signal. Type display device. A mixing ratio setting unit;
The mixing ratio setting unit includes a mixing ratio signal including information on a mixing ratio when light emitted from the plurality of semiconductor light sources is mixed based on chromaticity information on a desired color gamut or luminance information on a target luminance. The projection display device according to claim 2, wherein: is set. The element drive circuit generates and outputs a synchronization signal from the input video signal,
A light source drive pulse generation unit that generates a light source drive pulse signal based on the frequency signal output from the frequency determination unit and the synchronization signal output from the element drive circuit;
The light source driving circuit generates a light source driving signal based on the light source driving pulse signal generated by the light source driving pulse generation unit, and causes the semiconductor light source to emit light in synchronization with the element driving signal. The projection display device according to claim 2 or claim 3. The spatial modulation element is one,
The element driving signal is a signal for time division driving in which one frame of a projection image is divided into a number of subframes corresponding to the number of the plurality of semiconductor light sources,
5. The projection display device according to claim 2, wherein the plurality of semiconductor light sources emit light according to a corresponding subframe. 6.

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