JP5901429B2 - Image display device - Google Patents

Description

  The present invention relates to an image display device that displays an image by modulating light from a plurality of light sources for each pixel.

  In recent years, LEDs featuring low power consumption and high contrast, and liquid crystal display devices using a laser as a light source are rapidly spreading. Furthermore, as in Patent Document 1, a light source combining an LED and a laser has been devised. These light sources are composed of light emitters of each color such as red, green, and blue, for example, and white light is generated over the entire screen by arranging a plurality of light sources in the vertical direction.

  Since each luminous body changes its luminous efficiency and wavelength according to its temperature characteristics, its chromaticity and luminance change due to changes in temperature conditions. Therefore, conventionally, a technique for correcting changes in chromaticity and luminance has been devised. For example, in Patent Document 2, a color sensor and a temperature sensor for detecting chromaticity and luminance are provided in the vicinity of each of a plurality of light sources, and a light emitter of each light source is driven based on a detection value of the color sensor and a detection temperature of the temperature sensor. An image display device that corrects the amount has been proposed.

  In Patent Document 3, a color detection value is detected that is related to the chromaticity of a light source using a color sensor, and the drive control amount of each light source is set so that the color detection value approaches a color reference value that is a control target. An image display device that corrects the secular change of the light source by correcting the above has been proposed.

JP 2005-64163 A JP 2005-331644 A JP 2010-66465 A

  In an image display apparatus that uses a combination of a plurality of light sources in the vertical direction of the apparatus, color irregularities and luminance irregularities occur on the screen due to changes in chromaticity and luminance due to temperature differences between the light sources. Since the laser has a large change in chromaticity and luminance due to temperature, the above phenomenon appears remarkably when a laser is used as a light source. In order to suppress such a phenomenon in the image display devices of Patent Documents 2 and 3, it is necessary to provide a color sensor, a temperature sensor, and a detection unit of these sensors corresponding to each light source. It was.

  An object of the present invention is to provide an image display device that suppresses color unevenness and luminance unevenness at low cost in view of the above-described problems.

  An image display device according to the present invention includes a plurality of light sources, an illumination unit that mixes and outputs light from the plurality of light sources, and an image display unit that modulates light from the illumination unit for each pixel to form an image. A light source temperature detection unit that detects a light source temperature, a color sensor that detects a color detection value related to the chromaticity of the output light of the illumination unit, and a color reference value. A color reference value storage unit, a light source temperature, a color detection value, a color reference value, a first light source control amount calculation unit that calculates a drive control amount of one light source, and a plurality of light sources Based on the temperature difference detection unit between the light sources that acquires the temperature difference between the other light source other than the one light source and the one light source, the drive control amount of the one light source, the light source temperature, and the temperature difference, A second light source control amount calculation unit for calculating a drive control amount, a drive control amount of one light source, and a drive control of another light source Based on, and a light source driver for driving a plurality of light sources.

  An image display device according to the present invention is provided in the vicinity of one light source among a plurality of light sources, and detects a color detection value related to the chromaticity of output light from a light source temperature detection unit and an illumination unit. A first light source control amount calculation that calculates a drive control amount of one light source based on a color sensor, a color reference value storage unit that stores a color reference value, a light source temperature, a color detection value, and a color reference value A light source temperature difference detection unit that obtains a temperature difference between a light source other than the one light source and the one light source, a drive control amount of the one light source, a light source temperature, and a temperature difference And a light source drive unit for driving a plurality of light sources based on a drive control amount for one light source and a drive control amount for another light source. With. With the above configuration, color unevenness and luminance unevenness due to temperature and secular change can be suppressed without providing a light source temperature detection unit corresponding to all light sources.

1 is a block diagram illustrating a configuration of an image display device according to Embodiment 1. FIG. 6 is a block diagram illustrating a configuration of an image display apparatus according to Embodiment 2. FIG.

<A. Embodiment 1>
<A-1. Configuration, operation>
FIG. 1 is a block diagram showing a configuration of an image display apparatus 100 according to Embodiment 1 of the present invention. The image display device 100 includes a light source group L, a light source driving unit 7 that drives the light source group L, an illumination unit 8, and an image display unit 9.

  The light source group L includes n light sources (light source L1, light source L2,..., Light source Ln). The light sources L <b> 1 to Ln have red, blue, and green light emitters such as LEDs and lasers, and are driven by the light source driving unit 7.

  Light from the light source group L is mixed by the illumination unit 8 to become white light, and illuminates the image display unit 9. The image display unit 9 modulates the output light of the illumination unit 8 for each pixel according to the content of image data input from the outside, and displays an image. This image display apparatus is configured as a direct-view image display apparatus such as a liquid crystal display. In that case, the illumination unit 8 is configured by, for example, a light guide plate, and the image display unit 9 is configured by, for example, a liquid crystal panel.

  The image display apparatus 100 further includes a color sensor 1, a light source temperature detection unit 2, a color reference value storage unit 3, and a light source control amount calculation unit 4.

  The color sensor 1 is normally installed at a position that does not hinder image display in the image display unit 9, detects the chromaticity of the output light of the illumination unit 8, and outputs the detection result as a color detection value. For example, the color sensor 1 detects the intensity Rs of red light, the intensity Bs of blue light, and the intensity Gs of green light. These Rs, Bs, and Gs are used as color detection values as they are or after processing such as normalization. When the chromaticity of the illumination light changes, the ratio of Rs, Bs, and Gs also changes, so that the color detection value is an amount related to the chromaticity of the illumination light.

  The light source temperature detection unit 2 is a temperature sensor provided in the vicinity of one light source L1 in the light source group L, and detects the temperature of the light source L1. In this specification, in addition to the temperature of the light source itself, the temperature in the vicinity of the light source is also referred to as the temperature of the light source (light source temperature). The image display device 100 does not include a temperature sensor for measuring the temperatures of the light sources L2 to Ln, and estimates the temperatures of the light sources L2 to Ln from the measured temperature of the light source L1. Therefore, the number of temperature sensors may be one and the configuration is simple. In addition, although the light source temperature detection part 2 was provided with respect to the light source L1, the light source in which the light source temperature detection part 2 is provided is not limited to the light source L1, but may be provided for any one light source in the light source group L. Is possible.

  The color reference value storage unit 3 stores a color reference value that is a reference value to be compared with a color detection value when adjusting the chromaticity of the illumination light. If the color reference value is data in the same format as the color detection value, the comparison with the color detection value is easy. In addition, if the light source L1 to Ln is adjusted so as to have a predetermined chromaticity under a specific temperature condition and the color detection value of the color sensor 1 in that state is used as a color reference value, the color sensor 1 Variations in color detection values due to individual differences can be excluded from the comparison results with color reference values. Further, considering that the spectral distribution of the light sources L1 to Ln changes when the temperature condition changes and the sensitivity of the color sensor 1 changes, a value obtained by correcting the color detection value according to the temperature condition acquired from the light source temperature detection unit 2 is obtained. You may employ | adopt as a color reference value. The correction of the color detection value according to the temperature condition is performed by a known technique disclosed in Patent Documents 2 and 3, for example.

  The light source control amount calculation unit 4 includes a first light source control amount calculation unit 41 and a second light source control amount calculation unit 42. The first light source control amount calculation unit 41 acquires a color detection value from the color sensor 1, a color reference value from the color reference value storage unit 3, and a temperature of the light source L1 from the light source temperature detection unit 2, respectively. The first light source control amount calculation unit 41 corrects the color detection value based on the temperature of the light source L1 to obtain a correction color detection value, and then performs drive control of the light source L1 so that the correction color detection value approaches the color reference value. Correct the amount. More specifically, the drive current value for each light emitter of the light source L1 is corrected. The operation of the second light source control amount calculation unit 42 will be described later.

  Furthermore, the image display apparatus 100 includes a light emission period control unit 6 and a temperature difference detection unit 5 between light sources. The light emission period control unit 6 generates a light emission drive signal that determines the light emission period of each light source, and outputs the light emission drive signal to the light source drive unit 7. The light source drive unit 7 controls the light emission periods of the light sources L1 to Ln according to the light emission drive signal. In the following description, as an example, the light emission drive signal is a PWM signal synchronized with image processing. When the ratio of the High period in the PWM signal is increased according to the content of the image, the luminance of the light source increases and the power consumption increases, so the temperature around the light source increases. The light emission period control unit 6 outputs the ratio of the high period of the light emission drive signal or a value proportional thereto to the light source temperature difference detection unit 5 as information on the light emission period.

  The inter-light source temperature difference detection unit 5 acquires information on the light emission periods of the light sources L1 to Ln from the light emission period control unit 6, and further acquires the temperature of the light source L1 from the light source temperature detection unit 2. And based on these, the temperature difference with respect to the light source L1 of the light sources L2-Ln is calculated, and a calculation result is output to the light source control amount calculating part 4 as a temperature difference calculated value. One method for calculating the temperature difference is to obtain the relationship between the light emission period information and the temperature difference as a table or an approximate expression in advance by a technique such as experiment or simulation.

  An approximate expression for calculating the temperature difference with respect to the light source L1 is shown below. The temperature difference between the light sources L2 to Ln with respect to the light source L1 is approximated to be proportional to the ratio of the high period of the light emission drive signal (hereinafter referred to as Duty1 (%)). If the temperature difference between the light source Ln and the light source L1 when the duty 1 is the maximum is ΔT0 (n), the temperature difference ΔT (n) between the light source calculated from the duty 1 and the light source Ln is expressed by the following equation.

  The second light source control amount calculation unit 42 receives the drive control amount of the light source L1 from the first light source control amount calculation unit 41, the temperature of the light source L1 from the light source temperature detection unit 2, and the light source temperature difference detection unit 5 from the light source temperature difference detection unit 5. A temperature difference between the light source Ln and the light source L1 is acquired. Based on these, the drive control amounts of the light sources L2 to Ln are calculated so that the light sources L2 to Ln have the same luminance and chromaticity as the light source L1, and are output to the light source drive unit 7. The drive control amount of the light sources L2 to Ln is expressed by the following equation.

  Here, the correction coefficient (n) is a function having the temperature difference ΔT (n) and the temperature of the light source L1 as parameters, and is expressed by the following equation.

  The function F1 can be obtained by tabulating data acquired in advance through experiments or simulations or by using an approximate expression. By the above formulas (1) to (3), the drive control amounts of the light sources L2 to Ln are calculated from the information on the light emission periods of the light sources L2 to Ln and the temperature of the light source L1.

  The light source drive unit 7 drives the light source L1 based on the drive control amount of the light source L1 acquired from the first light source control amount calculation unit 41, and the drive control amounts of the light sources L2 to Ln acquired from the second light source control amount calculation unit 42. The light sources L2 to Ln are driven based on the above. Moreover, a light emission drive signal is acquired from the light emission period control part 6, and the light sources L1-Ln are driven based on these.

<A-2. Effect>
The image display apparatus according to the present embodiment includes a plurality of light sources L1 to Ln, an illumination unit 8 that mixes and outputs light from the plurality of light sources L1 to Ln, and modulates light from the illumination unit 8 for each pixel. The image display unit 9 for forming an image, the light source temperature detection unit 2 for detecting the light source temperature provided in the vicinity of one light source L1 among the plurality of light sources L1 to Ln, and the chromaticity of the output light of the illumination unit Based on the color sensor 1 for detecting the color detection value related to the color, the color reference value storage unit 3 for storing the color reference value, the light source temperature, the color detection value, and the color reference value, the driving of one light source L1 A first light source control amount calculation unit 41 that calculates a control amount, and an inter-light source temperature that acquires a temperature difference between one light source L1 and other light sources L2 to Ln other than one light source L1 among the plurality of light sources L1 to Ln. Based on the difference detection unit 5, the drive control amount of one light source L1, the light source temperature, and the temperature difference, etc. The plurality of light sources L1 to Ln are driven based on the second light source control amount calculation unit 42 that calculates the drive control amounts of the light sources L2 to Ln, the drive control amount of one light source L1, and the drive control amounts of the other light sources L2. A light source driving unit 7. Therefore, it is possible to suppress color unevenness and brightness unevenness with an image display device having a simple configuration in which one temperature sensor is provided as the light source temperature detection unit 2 and one color sensor 1 is provided.

  Moreover, since the temperature difference detection part between light sources calculates the temperature difference with the light source L1 based on the light emission period of the light sources L2-Ln, even if it does not provide a temperature sensor with respect to the light sources L2-Ln, the light source L2-Ln. It is possible to adjust chromaticity and luminance based on temperature change.

<B. Second Embodiment>
<B-1. Configuration, operation>
FIG. 2 is a block diagram illustrating a configuration of the image display apparatus 101 according to the second embodiment. In addition to the configuration of the image display apparatus 100 according to the first embodiment, the image display apparatus 101 cools the light sources L1 to Ln and adjusts the temperature in the apparatus, and fan control for controlling the fan 11 A part 10 is further provided. 2 that are the same as those in FIG. 1 are the same as those in the image display apparatus 100 according to the first embodiment, and thus the description thereof is omitted.

  The fan control unit 10 generates fan rotation speed information of the fan 11 and outputs it to the fan 11. The fan 11 rotates according to the fan rotation speed information acquired from the fan control unit 10, and cools the light sources L1 to Ln.

  The inter-light source temperature difference detection unit 5 acquires the temperature of the light source L1 from the light source temperature detection unit 2, acquires fan rotation speed information from the fan control unit 10, and relates to the light emission periods of the light sources L2 to Ln from the light emission period control unit 6. Information is acquired, and based on these, a temperature difference between the light sources L2 to Ln and the light source L1 is detected.

  Alternatively, the inter-light source temperature difference detection unit 5 detects the temperature difference from the temperature of the light source L1 and the light emission periods of the light sources L2 to Ln, and then the second light source control amount calculation unit 42 detects the light source L2 as in the first embodiment. In calculating the drive control amount of .about.Ln, fan rotational speed information may be taken into consideration. If the fan rotation speed is reduced, the light source temperature is increased, so that the temperature difference between the light sources due to the difference in the light emission period is considered to increase.

  That is, when the speed ratio with respect to the maximum rotational speed of the fan is Duty2 (%) as the fan rotational speed information, the correction coefficient (n) of Expression (2) is expressed by the following expression.

  Here, the function F2 is a function of the temperature of the light source L1, ΔT (n), and Duty2, and is obtained by tabulating the results of experiments and simulations in advance or by creating an approximate expression from the results. If the effect on the correction coefficient due to the rotational speed of the fan and the effect on the correction coefficient due to the temperature difference between the light sources can be approximated as independent (orthogonal), the correction coefficient can be expressed as It may be expressed.

<B-2. Effect>
The image display device according to the present embodiment further includes a fan 11 that cools the plurality of light sources L1 to Ln, and the inter-light source temperature difference detection unit 5 determines the rotation speed of the fan 11 in addition to the light emission period of the light sources L2 to Ln. Also, the temperature difference between the light sources L2 to Ln and the light source L1 is calculated. Thereby, the temperature difference can be accurately calculated in consideration of the change in the temperature difference due to the rotation speed of the fan 11. Therefore, the chromaticity and luminance of the light sources L2 to Ln can be adjusted based on the temperature change without providing a temperature sensor for the light sources L2 to Ln.

<C. Embodiment 3>
In the first and second embodiments, the temperature difference between the light sources L2 to Ln and the light source L1 is estimated based on the information on the light emission period and the information on the rotation speed of the fan 11. However, when there is a margin in cost, the light source temperature detector 2 may directly measure the temperatures of the light sources L2 to Ln. That is, the light source temperature detector 2 (temperature sensor) is also provided in the vicinity of the light sources L2 to Ln, and by directly measuring the temperatures of the light sources L2 to Ln, from the measured temperature of the light source L1 and the measured temperatures of the light sources L2 to Ln, The temperature difference may be calculated more accurately.

  In the image display device according to the present embodiment, the light source temperature detection unit 2 is also provided in the vicinity of the other light sources L2 to Ln, and the inter-light source temperature difference detection unit 5 includes the light source temperature corresponding to the one light source L1 and the other. Since the temperature difference is calculated from the light source temperatures corresponding to the light sources L2 to Ln, the temperature difference between the light source L1 and the light sources L2 to Ln can be calculated more accurately, and the chromaticity based on the temperature change of the light sources L2 to Ln can be calculated. The brightness can be adjusted with high accuracy.

  It should be noted that the present invention can be freely combined with each other within the scope of the invention, and each embodiment can be appropriately modified or omitted.

  DESCRIPTION OF SYMBOLS 1 Color sensor, 2 Light source temperature detection part, 3 Color reference value memory | storage part, 4 Light source control amount calculating part, 5 Light source temperature difference detection part, 6 Light emission period control part, 7 Light source drive part, L Light source group, L1, L2 , Ln light source, 8 illumination unit, 9 image display unit, 10 fan control unit, 11 fan, 41 first light source control amount calculation unit, 42 second light source control amount calculation unit.

Claims (3)

Multiple light sources;
An illumination unit that mixes and outputs light from the plurality of light sources;
An image display unit that modulates light from the illumination unit for each pixel to form an image;
A light source temperature detecting unit provided in the vicinity of one of the plurality of light sources and detecting a light source temperature;
A color sensor for detecting a color detection value related to the chromaticity of the output light of the illumination unit;
A color reference value storage unit for storing color reference values;
A first light source control amount calculation unit that calculates a drive control amount of the one light source based on the light source temperature, the color detection value, and the color reference value;
A temperature difference detection unit between light sources that obtains a temperature difference between another light source other than the one light source and the one light source among the plurality of light sources;
A second light source control amount calculation unit that calculates a drive control amount of the other light source based on the drive control amount of the one light source, the light source temperature, and the temperature difference;
A light source drive unit that drives the plurality of light sources based on the drive control amount of the one light source and the drive control amount of the other light source,
Image display device. The inter-light source temperature difference detection unit calculates the temperature difference based on a light emission period of the light source.
The image display device according to claim 1. A fan for cooling the light sources;
The temperature difference detection unit between the light sources calculates the temperature difference based on the rotational speed of the fan,
The image display device according to claim 2.

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