JP2015118144A - Video display device - Google Patents

Abstract

Backlight control is performed in consideration of the remaining lifetime of the backlight. A remaining life time calculation unit calculates a remaining life time, which is a remaining life time of the backlight, based on a temperature of the backlight and a cumulative lighting time of the backlight. The backlight control unit 17 controls the backlight 8 based on the remaining life time and the target remaining life time. [Selection] Figure 1

Description

  The present invention relates to a video display device that controls a backlight according to the state of the backlight.

  2. Description of the Related Art Conventionally, in video display devices, control for improving video display performance such as video contrast and brightness, control for improving visual motion blur, and the like have been performed. The control for improving the video display performance is, for example, control of the light emission amount of the backlight adapted to the video. The control for improving the motion blur is backlight emission control.

  Patent Document 1 discloses a technique for controlling light emission of a backlight (hereinafter also referred to as related technique A).

Japanese Patent No. 4644345

  The backlight has a predefined product life. The product life of the backlight is, for example, the total time that the backlight is used until the light emission luminance of the backlight used for the first time is halved. Since the backlight is mass-produced, the product life of each mass-produced backlight is not uniform due to, for example, manufacturing variations.

  Hereinafter, the average product life of each backlight is also referred to as a target life time. The target lifetime is the standard product lifetime of each backlight. In the following, the time that the backlight can be used until the lifetime of the backlight is reached is also referred to as the lifetime. Here, the state where the lifetime of the backlight has been reached is, for example, a state where the light emission luminance of the backlight used for the first time is halved.

  The lifetime of the backlight varies depending on the intensity of light emitted from the backlight. That is, the lifetime of the backlight varies depending on the temperature of the backlight. In the following, the remaining lifetime of the backlight is also referred to as the remaining lifetime. That is, the remaining lifetime of the backlight also changes depending on the control state of the backlight. Note that when the backlight is used for the first time, the remaining lifetime is approximately equal to the target lifetime. Hereinafter, the light having the maximum luminance that can be emitted from the backlight is also referred to as the maximum luminance light.

  Here, it is assumed that the target lifetime is defined by, for example, a condition that the backlight emits light having a luminance lower than the luminance of the maximum luminance light (hereinafter also referred to as condition N). In this case, when the backlight is controlled so that the backlight continuously emits the maximum luminance light, the remaining lifetime of the backlight is longer than the remaining lifetime of the backlight used based on the condition N. There is a problem of shortening. Therefore, it is necessary to control the backlight in consideration of the remaining lifetime of the backlight.

  In Related Art A, backlight control in consideration of the remaining lifetime of the backlight is not disclosed.

  The present invention has been made to solve such a problem, and an object of the present invention is to provide a video display apparatus capable of controlling the backlight in consideration of the remaining lifetime of the backlight.

  In order to achieve the above object, an image display device according to one embodiment of the present invention displays an image using emitted light which is light emitted from a backlight. The video display device includes a backlight control unit that controls the backlight to control the luminance of the emitted light, a temperature detection unit that detects a temperature of the backlight, a temperature of the backlight, and the backlight A calculation unit that calculates a remaining lifetime that is a remaining lifetime of the backlight based on the cumulative lighting time of the backlight, and the backlight control unit includes the remaining lifetime and the use of the backlight The backlight is controlled based on a target remaining life time that is a target for continuing the operation.

  According to the present invention, the calculation unit calculates a remaining lifetime, which is the remaining lifetime of the backlight, based on the temperature of the backlight and the cumulative lighting time of the backlight. The backlight control unit controls the backlight based on the remaining life time and a target remaining life time.

  Thereby, it is possible to control the backlight in consideration of the remaining lifetime of the backlight.

It is a block diagram which shows the structure of the video display apparatus concerning Embodiment 1 of this invention. It is a figure which shows the relationship between temperature and lifetime. It is a figure which shows the state of backlight temperature and lighting time. It is a figure for demonstrating transition of remaining lifetime. It is a block diagram which shows the structure of the video display apparatus concerning Embodiment 2 of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same components are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof may be omitted.

<Embodiment 1>
FIG. 1 is a block diagram showing a configuration of video display apparatus 100 according to Embodiment 1 of the present invention. Referring to FIG. 1, video display device 100 includes superimposition unit 2, display unit 3, video information detection unit 4, correction signal generation unit 5, correction coefficient generation unit 6, backlight 8, backlight A light control unit 17, a temperature detection unit 10, a lighting time measurement unit 13, a remaining life time calculation unit 11, and a remaining life correction coefficient generation unit 12 are provided.

  The video display device 100 receives a video signal VSG from the outside. The video signal VSG indicates video brightness and the like. The superimposing unit 2 receives the video signal VSG. The display unit 3 is a device that displays an image. The display unit 3 displays an image using light emitted from the backlight 8.

  The video information detector 4 receives the video signal VSG. The video information detection unit 4 detects video information from the video signal VSG. The video information is, for example, a video average brightness level, a histogram representing a video brightness level distribution, and the like. The video information detection unit 4 transmits the video information to the correction signal generation unit 5 and the correction coefficient generation unit 6.

  The correction signal generation unit 5 generates a correction signal for correcting the video signal based on the received video information. The correction signal is, for example, a signal for correcting the contrast and signal level of the video signal. The correction signal generation unit 5 transmits the correction signal to the superimposition unit 2.

  The superimposing unit 2 generates a corrected video signal VSG1 obtained by correcting the video signal VSG by superimposing the received correction signal on the video signal VSG. The corrected video signal VSG1 is not always a signal changed from the video signal VSG. The corrected video signal VSG1 may be the same as the video signal VSG depending on the content of the video information.

  Then, the superimposing unit 2 transmits the corrected video signal VSG1 to the display unit 3. The display unit 3 displays a video based on the corrected video signal VSG1.

  The correction coefficient generation unit 6 generates a correction coefficient HK corresponding to the corrected video signal VSG1 based on the received video information. The correction coefficient HK is also a coefficient for improving, for example, video display performance and moving image blur. The initial value of the correction coefficient HK is 1. The correction coefficient generation unit 6 transmits the correction coefficient HK indicating 1 to the backlight control unit 17 and the remaining life correction coefficient generation unit 12 in the initial state or when the correction video signal VSG1 is the same as the video signal VSG. To do.

  If the level (average level) of the corrected video signal VSG1 is, for example, 0.8 times the level (average level) of the video signal VSG, the correction coefficient HK generated by the correction coefficient generation unit 6 is 1 ×. It is 0.8 from 0.8. The correction coefficient generation unit 6 transmits the latest correction coefficient HK to the backlight control unit 17 and the remaining life correction coefficient generation unit 12 every time the value of the correction coefficient HK changes.

  The backlight 8 emits light. The backlight 8 is composed of, for example, an LED (Light Emitting Diode). Hereinafter, the light emitted from the backlight 8 is also referred to as emitted light. The backlight 8 is not limited to the LED, and may be a light using another light source (for example, a cold cathode tube).

  Hereinafter, the period during which the backlight 8 is lit is also referred to as a lighting period. In the following, the period during which the backlight 8 is off is also referred to as the extinguishing period.

  The backlight control unit 17 controls the backlight 8 in order to control the luminance of the emitted light. The backlight control unit 17 generates a control signal CSG for controlling the backlight 8. The backlight control unit 17 controls the backlight 8 by continuously transmitting the control signal CSG to the backlight 8.

  The control signal CSG is a signal for repeatedly generating a lighting period and an extinguishing period in the backlight 8. Hereinafter, a time (cycle) constituted by one continuous lighting period and one light-off period is also referred to as one cycle. One cycle is, for example, less than 1/120 (second).

  The lighting period is a period in which the level of the control signal CSG is H level. The extinguishing period is a period in which the level of the control signal CSG is L level. In the following, the ratio of the lighting period to the lighting period is also referred to as a duty ratio. The duty ratio is represented by 0 to 100 (%).

  The backlight control unit 17 sets the duty ratio of the control signal CSG to the latest control coefficient K1 as needed. The control coefficient K1 is calculated using a backlight setting value BLK, a correction coefficient HK, and a remaining life correction coefficient JHK described later.

  The backlight setting value BLK is a value set in advance by a user or the like. As the backlight setting value BLK, for example, a value in the range of 0 to 1 is set. The backlight setting value BLK is stored in, for example, a memory (not shown).

  Specifically, the control coefficient K1 is calculated by the backlight control unit 17 using the following formula 1.

K1 = K0 × JHK (Formula 1)
(K0 = BLK × HK)
The control coefficient K1 is calculated using the latest correction coefficient HK every time the value of the correction coefficient HK received by the backlight control unit 17 changes. The control coefficient K1 is calculated using the latest remaining life correction coefficient JHK every time the value of the remaining life correction coefficient JHK received by the backlight control unit 17 changes. The initial value of the remaining life correction coefficient JHK is 1.

  The backlight set value BLK corresponds to the duty ratio. As the backlight setting value BLK increases, the luminance of the emitted light from the backlight 8 increases. The luminance of the emitted light is expressed by the length of the lighting period in one cycle. That is, the luminance of the emitted light increases as the duty ratio increases.

  For example, when the backlight setting value BLK is 0.1, the duty ratio is 0.1. For example, when the backlight setting value BLK is 1, the duty ratio is 1. When the backlight setting value BLK is 1, the luminance of the emitted light from the backlight 8 is the highest luminance.

  The backlight 8 repeats lighting and extinguishing according to the control signal CSG continuously received from the backlight control unit 17.

  The temperature detection unit 10 has a function of detecting the temperature of the backlight 8. Hereinafter, the temperature of the backlight 8 is also referred to as a backlight temperature. The temperature detector 10 is provided in the backlight 8 so that the backlight temperature can be detected. For example, the temperature detection unit 10 is provided on the surface of the backlight 8. The backlight temperature is, for example, the junction temperature of the PN junction of the LED. In the following, the junction temperature is also expressed as temperature Tj.

  Note that the backlight temperature is detected by using the following Equation 2 as an example. Here, it is assumed that the temperature detection unit 10 is configured to be able to measure the ambient temperature of the LED (hereinafter also referred to as Ta) and the heat generation amount of the LED.

Tj = Ta + Rθja × P (Formula 2)
In Equation 2, Rθja is a coefficient indicating the thermal resistance from the PN junction to the temperature detection unit 10, that is, the thermal resistance coefficient (° C. · W ⁻¹ ). Rθja is a known value. P is the calorific value (W) of the LED.

  The temperature detector 10 detects (calculates) the temperature Tj by substituting the measured ambient temperature Ta and the heat generation amount P of the LED into Equation 2. The temperature detection unit 10 transmits the latest backlight temperature (temperature Tj) to the remaining lifetime calculation unit 11 as needed.

  As described above, the backlight temperature is not limited to the junction temperature of the LED. For example, when the backlight 8 is configured by a laser light source, the backlight temperature is the temperature of the laser light source.

  It is generally known that reducing the backlight temperature can extend the lifetime of the backlight. Next, the relationship between the backlight temperature and the backlight lifetime will be described.

  Here, as an example, the relationship between the lifetime of the LED used in the backlight 8 and the temperature of the LED will be described. The relationship between the LED lifetime and the LED temperature can be expressed by the Arrhenius equation. The Arrhenius equation predicts the rate of chemical reaction. The Arrhenius equation is expressed by the following equation 3.

K = A × exp (−Ea / kT) (Formula 3)
In Equation 3, K is the reaction rate. A is a constant. Ea is the activation energy. k is the Boltzmann constant. T is temperature (absolute temperature). Hereinafter, the lifetime of the LED is also referred to as the lifetime L.

  The life time L when the light emission luminance of the LED decreases is inversely proportional to K. Therefore, the lifetime L is expressed by the following formula 4.

L = B × exp (Ea / kT) (Formula 4)
In Equation 4, B and activation energy Ea are intrinsic constants of the LED. By transforming Equation 4 using the natural logarithm, the following Equation 5 is derived.

lnL = (Ea / k) × (1 / T) + lnB (Formula 5)
In Equation 5, “ln” is “log”. Expression 5 is expressed as a characteristic line CL1 in the logarithmic graph as shown in FIG. The characteristic line CL1 is, for example, a linear function y = ax + b. In FIG. 2, the lifetime is the lifetime of the LED. The temperature is the aforementioned backlight temperature.

  Since the backlight 8 is mass-produced, the product life of each mass-produced backlight 8 is not uniform due to, for example, manufacturing variations. Specifically, the product lifetimes of the respective backlights 8 are not uniform even when they have the same structure and are used under the same conditions.

  Hereinafter, the product life of the backlight 8 is also referred to as a target life time. Specifically, the target life time is an average product life of each backlight 8 that is mass-produced. That is, the target life time is a standard product life of each backlight. The target life time is a life time of the backlight 8 defined in advance.

  The target life time is a time when the backlight 8 is continuously controlled by the control signal CSG whose duty ratio is the rated value D1. The rated value D1 is, for example, 0.8. The rated value D1 is not limited to 0.8, and may be 1, 0.5, for example.

  Hereinafter, the backlight temperature in a state where the backlight 8 is controlled by the control signal CSG whose duty ratio is the rated value D1 is also referred to as a rated temperature. The target life time is also a time when the backlight 8 is continuously controlled by the control signal CSG so that the backlight temperature maintains the rated temperature.

  Here, referring to FIG. 2, it is assumed that the target lifetime of the backlight 8 driven at the backlight temperature T1 is L1. The target lifetime of the backlight 8 that is driven at the backlight temperature T2 is L2. T1 is larger than T2.

  In the following, the time that the backlight 8 can be used until the lifetime of the backlight 8 is reached is also referred to as the lifetime. Here, the state where the lifetime of the backlight 8 has been reached is, for example, a state where the light emission luminance of the backlight 8 used for the first time is halved. That is, the lifetime is, for example, a luminance half time required for the emission luminance of the backlight 8 used for the first time to be halved.

  In the following, the remaining lifetime of the backlight 8 is also referred to as a remaining lifetime or a remaining lifetime tbn. Note that n in tbn is a natural number. The remaining lifetime is shortened when the backlight 8 continues to be controlled in a state where the backlight temperature is higher than the rated temperature. That is, the remaining life time is shortened when the duty ratio of the control signal CSG is larger than the rated value D1.

  On the other hand, in the state where the backlight temperature is lower than the rated temperature, the remaining lifetime can be extended by controlling the backlight 8. Moreover, the power consumption of the backlight 8 can be reduced by reducing the backlight temperature. Reduction of the power consumption of the backlight 8 is realized by reducing the luminance of the light emitted from the backlight 8.

  When the backlight 8 is used for the first time, the remaining life time is approximately equal to the target life time.

  The target life time can be calculated from the cumulative lighting time of the backlight 8. Here, it is assumed that the backlight 8 is configured by, for example, an LED as a light emitting element. In this case, the target life time is determined by parameters specific to the light emitting elements (LEDs) constituting the backlight 8. For example, the parameters include the characteristics of the fluorescent material used for light emission, the amount of the fluorescent material, the heat dissipation characteristics of the light emitting element, and the structural heat dissipation characteristics surrounding the backlight. The target life time is determined for each backlight structure.

  Referring again to FIG. 1, the lighting time measurement unit 13 measures the cumulative lighting time ta of the backlight 8. The cumulative lighting time ta is the total time of all the times when the backlight 8 is lit. The lighting time measuring unit 13 includes, for example, a memory (not shown). The accumulated lighting time ta is stored in the memory of the lighting time measuring unit 13. The initial value of the cumulative lighting time ta is 0.

  For example, the lighting time measuring unit 13 measures the time during which the backlight 8 is continuously lit every time the backlight 8 is lit. Then, when the lighting of the backlight 8 ends, the lighting time measuring unit 13 adds the time during which the backlight 8 has been continuously lit to the cumulative lighting time ta. Thereby, the cumulative lighting time ta is updated. That is, the cumulative lighting time ta indicates the cumulative time when the backlight 8 is turned on. The lighting time measuring unit 13 transmits the latest accumulated lighting time ta to the remaining life time calculating unit 11 as needed.

  As a result, the remaining life time calculation unit 11 always keeps track of the time during which the backlight 8 has been turned on and the backlight temperature at the time that the backlight 8 has been turned on.

  The remaining life time calculation unit 11 calculates the remaining life time using the backlight temperature received from the temperature detection unit 10 and the latest accumulated lighting time ta received from the lighting time measurement unit 13. That is, the remaining life time calculation unit 11 is a calculation unit that calculates a remaining life time that is the remaining life time of the backlight 8 based on the temperature of the backlight 8 and the cumulative lighting time of the backlight 8.

  Further, every time the remaining lifetime calculation unit 11 calculates the remaining lifetime, the remaining lifetime calculation unit 11 transmits the remaining lifetime to the remaining lifetime correction coefficient generation unit 12.

  Although the details will be described later, the remaining life correction coefficient generation unit 12 calculates the remaining life correction coefficient JHK using the remaining life time every time the remaining life time is received. The remaining life correction coefficient JHK is a coefficient for the backlight control unit 17 to perform control based on the remaining life time. The remaining life correction coefficient JHK is also a parameter for changing the remaining life time.

  As described above, the remaining life time is shortened when the duty ratio of the control signal CSG is larger than the rated value D1. The remaining life correction coefficient JHK is also a coefficient for extending the shortened remaining life time. The remaining life correction coefficient generation unit 12 transmits the remaining life correction coefficient JHK to the backlight control unit 17 every time the remaining life correction coefficient JHK is calculated.

  The remaining life correction coefficient generation unit 12 calculates the control coefficient K0 from time to time using BLK × HK using the backlight setting value BLK and the latest correction coefficient HK. Further, the remaining life correction coefficient generation unit 12 has a function of calculating a time during which the value of the control coefficient K0 has not changed (hereinafter also referred to as an accumulated time Ktm).

  Hereinafter, the target time for continuing the use of the backlight 8 is also referred to as a target remaining life time. The target remaining life time is calculated by the following formula 6.

Target remaining life time = Target life time−Cumulative lighting time ta (Formula 6)
That is, the target remaining life time is a time obtained by subtracting the cumulative lighting time ta from the target life time. In other words, the target remaining life time is a time required for continuing the use of the backlight 8.

  Although described in detail later, the backlight control unit 17 controls the backlight 8 based on the calculated remaining lifetime and the target remaining lifetime. More specifically, the backlight control unit 17 controls the backlight 8 so that the calculated remaining lifetime is equal to or longer than the target remaining lifetime.

  Specifically, as described above, the backlight control unit 17 calculates the control coefficient K1 using the backlight setting value BLK, the correction coefficient HK, and the remaining life correction coefficient JHK. The remaining life correction coefficient JHK is a coefficient for making the remaining life time calculated by the remaining life time calculating unit 11 equal to or more than the target remaining life time.

  Hereinafter, a value indicating the lifetime of the backlight 8 as an index is also referred to as a lifetime value JD. The life value JD is expressed by the following formula 7.

JD = target life time / D1 (Expression 7)
In the following, a numerical value that affects the life value JD is also referred to as a life influence value JE. The life influence value JE is calculated by the following formula 8.

JE = Ktm / (K0 / D1) (Formula 8)
In Equation 8, Ktm is the accumulated time during which the value of K1 has not changed. In addition, the value calculated by the following formula 9 is defined as the remaining life influence value NJE.

NJE = JD−JE (Formula 9)
Next, a process for controlling the backlight 8 in the present embodiment (hereinafter also referred to as a light control process A) will be described. Specifically, the write control process A under the condition A will be described. Here, as an example, it is assumed that the write control process A is performed at time tm11 after time t0.

  Condition A is a condition that target life time = 1000 hours and rated value D1 = 0.5. Condition A is a condition that K0 = 0.6 and JKH = 1 over time tm11. That is, over time tm11, the duty ratio (0.6) of the control signal CSG is a value larger than the rated value D1. That is, the backlight 8 is controlled in a state where the backlight temperature is higher than the rated temperature over the time tm11. For this reason, the remaining lifetime is shorter than the initial value. As described above, since K0 = 0.6 over the time tm11, the accumulated time Ktm = tm11.

  The condition A is a condition that HK = 1 over time tm11. That is, for example, the average luminance level of the video is assumed to be constant over time tm11.

  Condition A is a state in which the backlight 8 is lit with the backlight temperature at T2 over time tm11. As described above, the target life time of the backlight 8 driven at the backlight temperature T2 is L2. From the above conditions, L2 = 1000. Condition A is a condition that the cumulative lighting time ta is time tm11. Further, it is assumed that the time tm11 is 100 hours.

  Next, the write control process A will be described. In the light control process A under the condition A, the remaining lifetime calculation unit 11 uses the received backlight temperature T2 and the latest accumulated lighting time ta (tm11) received from the lighting time measurement unit 13. The remaining life time tbn is calculated. The remaining lifetime tbn is calculated as L2-tm11, that is, 1000-100 = 900. Then, the remaining life time calculation unit 11 transmits the remaining life time tbn to the remaining life correction coefficient generation unit 12.

  The remaining life correction coefficient generation unit 12 calculates the life value JD by the above-described equation 7. The lifetime value JD is 1000 / 0.5 = 2000. Next, the remaining life correction coefficient generation unit 12 calculates the life influence value JE by the above-described equation 8. That is, the lifetime influence value JE is 100 / (0.6 / 0.5) = 83. That is, as described above, since the duty ratio (0.6) of the control signal CSG is larger than the rated value D1 (0.5) over the time tm11, the life value JD is the life influence value JE (83). Only less. That is, the remaining life influence value NJE is 2000−83 = 1919 from the above-described equation 9.

  Hereinafter, the control coefficient K0 for making the remaining life time equal to or longer than the target remaining life time is also referred to as a corrected control coefficient K01. The correction control coefficient K01 is a coefficient used by the backlight control unit 17 as the control coefficient K1.

  Next, the remaining life correction coefficient generation unit 12 calculates the correction control coefficient K01 by the following expression 10 obtained by modifying (target life time−cumulative lighting time ta) / K01 = NJE.

K01 = (Target life time−Cumulative lighting time ta) / NJE (Equation 10)
The correction control coefficient K01 is (1000−100) /1917=0.47 by substituting the above values into Equation 10. That is, if the control signal CSG is generated using K01 (0.47) as K1, the backlight 8 is controlled so that the remaining lifetime is equal to or longer than the target remaining lifetime.

  Therefore, the remaining life correction coefficient generation unit 12 calculates the remaining life correction coefficient JHK by the following expression 11 in which K1 in expression 1 is replaced with K01.

JHK = K01 / K0 (Formula 11)
From Equation 11, the remaining life correction coefficient JHK is 0.47 / 0.6 = 0.78. The remaining life correction coefficient JHK is also a coefficient for lowering the backlight temperature below the rated temperature.

  Then, the remaining life correction coefficient generation unit 12 transmits the calculated remaining life correction coefficient JHK (0.78) to the backlight control unit 17.

  The backlight control unit 17 calculates a new control coefficient K1 (0.6 × 0.78 = 0.47) from the received remaining life correction coefficient JHK, K0 (0.6), and Equation 1. . Then, the backlight control unit 17 sets the duty ratio of the control signal CSG continuously transmitted to the backlight 8 to a new control coefficient K1 (0.47).

  The value set for the duty ratio of the control signal CSG may be a value less than the new control coefficient K1 (0.47) and a value greater than zero. In this case, the remaining lifetime is longer than the target remaining lifetime.

  By the control of the backlight control unit 17 described above, the emission luminance and temperature of the backlight 8 are reduced, and the remaining lifetime becomes equal to or longer than the target remaining lifetime.

  The remaining life correction coefficient JHK is a value calculated using a control coefficient K0 for making the remaining life time equal to or longer than the target remaining life time. That is, the remaining life correction coefficient JHK is a value based on the remaining life time and the target remaining life time.

  The backlight control unit 17 controls the duty ratio of the control signal CSG that is continuously transmitted to the backlight 8 by using the control coefficient K1 calculated using the remaining life correction coefficient JHK. That is, the backlight control unit 17 controls the backlight 8 based on the remaining life time and the target remaining life time. Specifically, the backlight control unit 17 controls the backlight 8 so that the remaining lifetime is equal to or longer than the target remaining lifetime. The write control process A is performed as described above.

  In the light control process A, the process when the average brightness level of the video is constant has been described. However, the light control process A can be applied even when the average brightness level changes at any time. In this case, for example, the remaining life correction coefficient JHK is calculated using the average value of the average luminance level that changes in a predetermined time.

  Next, the transition of the remaining life time in the condition B will be described with an example. FIG. 3 is a diagram illustrating states of backlight temperature and lighting time. Specifically, FIG. 3 is a diagram illustrating states of backlight temperature and lighting time based on the following condition B. The backlight temperature is the junction temperature (Tj) described above.

  The condition B is a condition that the correction coefficient HK = 1 and the rated value D1 = 0.5. The condition B is a condition that the state in which the value of K0 in Expression 1 is 0.5 lasts for the time tm11. The time tm11 is 100 hours. Condition B is a condition that the state in which the value of K0 in Expression 1 is 0.6 continues for a time tm12. The time tm12 is 100 hours.

  The condition B is a condition that the backlight setting value BLK is changed by a user operation so that the state of the backlight 8 changes from the state ST1 to the state ST2.

  As shown in FIG. 3, the state ST1 is a state in which the backlight 8 is lit while the backlight temperature is T2 over time tm11. State ST2 is a state in which the backlight 8 is lit while the backlight temperature is T1 over time tm12.

  The condition B is a condition that the light control process A described above is performed immediately after the period in which the backlight 8 is in the state ST2.

  As described above, the target life time of the backlight 8 driven at the backlight temperature T1 is assumed to be L1. The target lifetime of the backlight 8 that is driven at the backlight temperature T2 is L2. T1 is larger than T2.

  FIG. 4 is a diagram for explaining the transition of the remaining life time. Specifically, FIG. 4 is a diagram for explaining the transition of the remaining lifetime in the condition B. In FIG. 4, the vertical axis indicates the remaining life time represented by an exponential function. The horizontal axis indicates the cumulative lighting time. In FIG. 4, time tm20 is the target life time.

  In FIG. 4, a point P <b> 0 corresponds to a state where the backlight 8 starts to be lit. Point P1 is a point corresponding to the state immediately after the state of the backlight 8 maintains the state ST1. Point P2 is a point where the state of the backlight 8 corresponds to a state immediately after maintaining the state ST2.

  First, the remaining life time tb2 at the point P1 will be described. The remaining life time tb2 at the point P1 is the remaining life time immediately after the backlight 8 is controlled so that the backlight 8 is lit in the state where the backlight temperature is T2 over the time tm11. The remaining life time tb2 is calculated by the following equation 12. Here, the target life time when the backlight temperature is T2 is L2, as described above.

tb2 = L2-tm11 (Formula 12)
Next, the remaining life time tb1 at the point P2 will be described. The remaining life time tb1 at the point P2 is the remaining life time immediately after the backlight 8 is controlled so that the backlight 8 is lit in the state where the backlight temperature is T1 over the time tm12. The remaining life time tb1 is calculated by the following equation (13). Here, as described above, the target lifetime when the backlight temperature is T1 is L1.

tb1 = L1- (tm11 + tm12) (Formula 13)
In Expression 13, tm11 + tm12, that is, tm10 in FIG. 3 is the cumulative lighting time ta of the backlight 8. Note that the target remaining life time is calculated by Equation 6 described above. Further, the above-described write control process A is performed at the time corresponding to the point P2.

  In the write control process A, the remaining life correction coefficient generation unit 12 calculates the remaining life correction coefficient JHK and transmits the remaining life correction coefficient JHK to the backlight control unit 17 as described above.

  As described above, the backlight control unit 17 controls the backlight 8 using the remaining life correction coefficient JHK so that the remaining life time becomes equal to or longer than the target remaining life time. Detailed processing is the same as the above-described processing, and is therefore omitted.

  In the above process, the write control process A is performed at one point P2, but the present invention is not limited to this. The write control process A may be performed a plurality of times, for example, every predetermined time. The write control process A may be performed a plurality of times irregularly.

  In the above processing, the processing when the remaining lifetime is shortened by controlling the backlight 8 in the state where the backlight temperature is higher than the rated temperature has been described.

  Note that the light control process A can be applied even when the remaining lifetime is increased by controlling the backlight 8 in a state where the backlight temperature is lower than the rated temperature. In this case, in the light control process A, the backlight 8 is controlled in a state where the luminance of the emitted light from the backlight 8 is improved, that is, in a state where the backlight temperature is higher than the rated temperature.

  As described above, according to the present embodiment, the remaining lifetime calculation unit 11 is the remaining lifetime of the backlight 8 based on the temperature of the backlight 8 and the cumulative lighting time of the backlight 8. Calculate the remaining life time. The backlight control unit 17 controls the backlight 8 based on the remaining life time and the target remaining life time.

  Thereby, it is possible to control the backlight in consideration of the remaining lifetime of the backlight.

  Further, according to the present embodiment, the backlight control unit 17 uses the remaining life correction coefficient JHK obtained from the backlight temperature so that the remaining life time becomes equal to or longer than the target remaining life time. The light 8 is controlled. As a result, the remaining lifetime of the backlight can be extended.

  Further, according to the present embodiment, the luminance of the emitted light from the backlight 8 is controlled in consideration of the characteristics of the backlight 8.

  As described above, according to the present embodiment, it is possible to suppress significant performance deterioration of the backlight 8. Moreover, the target remaining lifetime can be obtained.

  Related technology A is control aimed at improving video display performance and moving image blur. For this reason, the related art A is not a technique that takes into account the deterioration of the backlight performance, that is, the reduction in the luminance of the backlight over time. Therefore, the related art A has a problem that it is not possible to reduce the deterioration in performance of the backlight over time.

  On the other hand, since the present embodiment is configured as described above, the above problem can be solved.

<Embodiment 2>
FIG. 5 is a block diagram showing a configuration of video display apparatus 100A according to Embodiment 2 of the present invention. Referring to FIG. 5, video display device 100 </ b> A is different from video display device 100 in that it further includes an illuminance detection unit 15 and an illuminance correction coefficient generation unit 16. Since the other configuration of video display device 100A is the same as that of video display device 100, detailed description will not be repeated.

  Hereinafter, the illuminance around the video display device 100A is also referred to as ambient illuminance SD. The ambient illuminance SD is, for example, the illuminance of light applied to the housing (not shown) of the video display device 100A.

  The illuminance detection unit 15 is a sensor that detects illuminance. The illuminance detection unit 15 detects the peripheral illuminance SD as needed. The illuminance detection unit 15 transmits the ambient illuminance SD to the illuminance correction coefficient generation unit 16 as needed.

  The remaining life correction coefficient generation unit 12 according to the present embodiment calculates a remaining life correction coefficient JHKA instead of the remaining life correction coefficient JHK, as compared with the first embodiment. The remaining life correction coefficient JHKA is a coefficient considering the ambient illuminance SD with respect to the characteristics of the remaining life correction coefficient JHK.

  The remaining life correction coefficient generation unit 12 generates an illuminance correction coefficient SHK based on the peripheral illuminance SD every time the peripheral illuminance SD is received. The remaining life correction coefficient generation unit 12 transmits the generated illuminance correction coefficient SHK to the backlight control unit 17 and the remaining life correction coefficient generation unit 12 as needed. The value of the illuminance correction coefficient SHK is set in consideration of the reference illuminance BSD. The reference illuminance BSD is, for example, general illuminance of a room illuminated by illumination.

  When the value of the ambient illuminance SD is the same as the value of the reference illuminance BSD, the illuminance correction coefficient SHK is 1. The illuminance correction coefficient SHK is set to a smaller value as the value of the ambient illuminance SD is smaller. For example, when the value of the ambient illuminance SD is 0.8 times the reference illuminance BSD, the illuminance correction coefficient SHK is set to 1 × 0.8 = 0.8.

  The illuminance correction coefficient SHK is set to a larger value as the value of the ambient illuminance SD is larger. For example, when the value of the ambient illuminance SD is 1.2 times the reference illuminance BSD, the illuminance correction coefficient SHK is set to 1 × 1.2 = 1.2.

  In the present embodiment, the backlight control unit 17 controls the backlight 8 so that the remaining lifetime is equal to or longer than the target remaining lifetime, as in the first embodiment. Although described in detail later, the backlight control unit 17 controls the backlight 8 based on the remaining life time, the target remaining life time, and the ambient illuminance SD.

  The backlight control unit 17 uses the illuminance correction coefficient SHK having the above properties. Therefore, the backlight control unit 17 controls the backlight 8 so that the luminance of the emitted light from the backlight 8 decreases as the ambient illuminance SD decreases. In addition, the backlight control unit 17 controls the backlight 8 so that the luminance of the emitted light from the backlight 8 increases as the ambient illuminance SD increases.

  Hereinafter, differences from the first embodiment will be mainly described. The backlight control unit 17 sets the duty ratio of the control signal CSG to the latest control coefficient K11 as needed. The control coefficient K11 is calculated using the backlight setting value BLK, the correction coefficient HK, the remaining life correction coefficient JHKA, and the illuminance correction coefficient SHK.

  The control coefficient K11 is calculated by the backlight control unit 17 using the following formulas 14 and 15.

K11 = K2 × JHKA (Formula 14)
K2 = K0 × SHK (Formula 15)
In Equation 14, K2 is a control coefficient. K0 in Expression 15 is a value obtained by BLK × HK.

  The control coefficient K11 is calculated using the latest correction coefficient HK every time the value of the correction coefficient HK received by the backlight control unit 17 changes. The control coefficient K11 is calculated using the latest illuminance correction coefficient SHK every time the value of the illuminance correction coefficient SHK received by the backlight control unit 17 changes. The control coefficient K11 is calculated using the latest remaining life correction coefficient JHKA every time the value of the remaining life correction coefficient JHKA received by the backlight control unit 17 changes. The initial value of the remaining life correction coefficient JHKA is 1.

  In addition, the remaining life correction coefficient generation unit 12 calculates the control coefficient K2 from time to time using Expression 15 using the backlight setting value BLK, the correction coefficient HK, and the illuminance correction coefficient SHK. In addition, the remaining life correction coefficient generation unit 12 has a function of calculating a time during which the value of the control coefficient K2 has not changed (hereinafter also referred to as an accumulated time Ktma).

  Next, processing for controlling the backlight 8 in the present embodiment (hereinafter also referred to as light control processing A1) will be described. Specifically, the write control process A1 under the condition A1 will be described. Here, as an example, it is assumed that the write control process A1 is performed at the time when the time tm11 has elapsed from the time t0.

  The condition A1 is a condition that the target life time = 1000 hours and the rated value D1 = 0.5, as in the first embodiment. The condition A1 is a condition that SHK = 1.2 over time tm11. That is, it is assumed that the video display device 100A is installed in an environment with an illuminance greater than the reference illuminance BSD.

  The condition A1 is a condition that K2 = 0.6 and JKHA = 1 over time tm11. That is, over time tm11, the duty ratio (0.6) of the control signal CSG is a value larger than the rated value D1. That is, the backlight 8 is controlled in a state where the backlight temperature is higher than the rated temperature over the time tm11. For this reason, the remaining lifetime is shorter than the initial value. Further, as described above, since K2 = 0.6 over the time tm11, the accumulated time Ktma = tm11.

  The condition A1 is a condition that HK = 1 over the time tm11 as in the first embodiment. That is, for example, the average luminance level of the video is assumed to be constant over time tm11.

  Further, the condition A1 is a state in which the backlight 8 is turned on in the state where the backlight temperature is T2 over the time tm11, as in the first embodiment. As described above, the target life time of the backlight 8 driven at the backlight temperature T2 is L2. From the above conditions, L2 = 1000. The condition A1 is a condition that the cumulative lighting time ta is the time tm11, as in the first embodiment. Further, it is assumed that the time tm11 is 100 hours.

  Next, the write control process A1 will be described. In the following, differences from the write control process A will be mainly described.

  First, the remaining life time calculation unit 11 calculates the remaining life time tbn (900) by the same process as the write control process A, and transmits the remaining life time tbn to the remaining life correction coefficient generation unit 12.

  The remaining life correction coefficient generation unit 12 calculates a life value JD (2000), a life effect value JE (83), and a remaining life effect value NJE (1917) by the same process as the write control process A.

  Hereinafter, the control coefficient K2 for making the remaining life time equal to or longer than the target remaining life time is also referred to as a corrected control coefficient K02. The correction control coefficient K02 is a coefficient used by the backlight control unit 17 as the control coefficient K11.

  Next, the remaining life correction coefficient generation unit 12 calculates the correction control coefficient K02 by the following equation 16 obtained by modifying (target life time−cumulative lighting time ta) / K02 = NJE.

K02 = (Target life time−Cumulative lighting time ta) / NJE (Expression 16)
The correction control coefficient K02 is (1000−100) /1917=0.47 by substituting the above values into Expression 16. That is, if the control signal CSG is generated using K02 (0.47) as K11, the backlight 8 is controlled so that the remaining lifetime is equal to or longer than the target remaining lifetime.

  Therefore, the remaining life correction coefficient generation unit 12 calculates the remaining life correction coefficient JHKA by the following Expression 17 in which K11 in Expression 14 is replaced with K02.

JHKA = K02 / K2 (Formula 17)
From Equation 17, the remaining life correction coefficient JHKA is 0.47 / 0.6 = 0.78. The remaining life correction coefficient JHKA is also a coefficient for lowering the backlight temperature below the rated temperature.

  Then, the remaining life correction coefficient generation unit 12 transmits the calculated remaining life correction coefficient JHKA (0.78) to the backlight control unit 17.

  The backlight control unit 17 calculates a new control coefficient K11 (0.6 × 0.78 = 0.47) from the received remaining life correction coefficient JHKA, K2 (0.6), and Expression 14. . Then, the backlight control unit 17 sets the duty ratio of the control signal CSG that is continuously transmitted to the backlight 8 to a new control coefficient K11 (0.47).

  The value set for the duty ratio of the control signal CSG may be a value less than the new control coefficient K11 (0.47) and a value greater than zero. In this case, the remaining lifetime is longer than the target remaining lifetime.

  By the control of the backlight control unit 17 described above, the emission luminance and temperature of the backlight 8 are reduced, and the remaining lifetime becomes equal to or longer than the target remaining lifetime.

  The remaining life correction coefficient JHKA is a value calculated using the control coefficient K2 for making the remaining life time equal to or longer than the target remaining life time. Here, the control coefficient K2 is a value based on the illuminance correction coefficient SHK corresponding to the ambient illuminance SD, as shown in Expression 15. That is, the remaining life correction coefficient JHKA is a value based on the remaining life time, the target remaining life time, and the ambient illuminance SD.

  The backlight control unit 17 controls the duty ratio of the control signal CSG that is continuously transmitted to the backlight 8 by using the control coefficient K1 calculated using the remaining life correction coefficient JHKA. That is, the backlight control unit 17 controls the backlight 8 based on the remaining lifetime, the target remaining lifetime, and the ambient illuminance SD. Specifically, the backlight control unit 17 controls the backlight 8 so that the remaining lifetime is equal to or longer than the target remaining lifetime. The write control process A1 is performed as described above.

  In the light control process A1, the process when the average luminance level of the video is constant has been described. However, the light control process A1 can be applied even when the average luminance level or the like changes at any time. In this case, for example, the remaining life correction coefficient JHKA is calculated using the average value of the average luminance level that changes in a predetermined time.

  As described above, according to the present embodiment, the backlight control unit 17 controls the backlight 8 so that the remaining life time is equal to or longer than the target remaining life time even in the configuration in which the ambient illuminance is taken into consideration. be able to.

  In the present embodiment using ambient illuminance, the same effect as in the first embodiment can be obtained.

(Other variations)
As described above, the video display device according to the present invention has been described based on the embodiments. However, the present invention is not limited to these embodiments. The present invention also includes modifications made to the present embodiment by those skilled in the art without departing from the scope of the present invention. In other words, 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.

  Further, the video display device 100 or the video display device 100A may not include all the components shown in FIG. 1 or FIG. That is, the video display device 100 or the video display device 100A may include only the minimum components that can realize the effects of the present invention.

  In addition, the present invention may be realized as a backlight control method in which the operation of a characteristic component included in the video display device 100 or the video display device 100A is a step. In the present invention, the computer may execute each step included in the backlight control method. The present invention may also be realized as a program that causes a computer to execute each step included in such a backlight control method. Further, the present invention may be realized as a computer-readable recording medium that stores such a program. The program may be distributed via a transmission medium such as the Internet.

  All the numerical values used in the above-mentioned embodiment are examples of numerical values for specifically explaining the present invention. That is, the present invention is not limited to the numerical values used in the above embodiments.

  The backlight control method according to the present invention corresponds to the light control process A or the light control process A1. The order in which each process in the backlight control method is executed is an example for specifically explaining the present invention, and may be in an order other than the above. Also, part of the processing in the backlight control method and other processing may be executed in parallel independently of each other. 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.

  For example, the backlight control unit 17 is configured to control the backlight 8 using a control coefficient, but is not limited thereto. For example, the backlight control unit 17 may control the backlight 8 using the remaining lifetime.

  Further, although the backlight 8 is controlled by changing the duty ratio of the control signal CSG, the present invention is not limited to this. For example, the backlight 8 may be controlled by changing the power supplied to the backlight 8.

  8 Backlight, 10 Temperature detection unit, 15 Illuminance detection unit, 17 Backlight control unit, 11 Remaining life time calculation unit, 100, 100A Video display device.

Claims (3)

An image display device that displays an image using emitted light that is emitted from a backlight,
A backlight control unit for controlling the backlight to control the luminance of the emitted light;
A temperature detector for detecting the temperature of the backlight;
A calculation unit that calculates a remaining lifetime that is a remaining lifetime of the backlight based on the temperature of the backlight and the cumulative lighting time of the backlight; and
The backlight control unit controls the backlight based on the remaining lifetime and a target remaining lifetime that is a target for continuing use of the backlight. The target remaining life time is a time obtained by subtracting the cumulative lighting time from a predetermined life time of the backlight,
The video display device according to claim 1, wherein the backlight control unit controls the backlight such that the remaining lifetime is equal to or longer than the target remaining lifetime. The video display device further includes:
An illuminance detection unit that detects ambient illuminance that is the illuminance around the video display device,
The video display device according to claim 1, wherein the backlight control unit further controls the backlight based on the ambient illuminance.

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