JP2012247630A - Image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image display device which reduces the consumption power of a light source, even in the case of having a plurality of light sources with different luminous efficiency for a drive current value.SOLUTION: A projection image display device 100 includes a control part 220 which controls a first light source and a second light source. The first light source and the second light source has a predetermined reference light emission period. The control part 220 controls the fist light source such that the light emission period of the first light source is shorter than the reference light emission period, and controls the second light source such that the light emission period of the second light source is longer than the reference light emission period.

Description

  The present invention relates to an image display apparatus including a plurality of light sources having different light emission efficiency with respect to a drive current value.

  2. Description of the Related Art Conventionally, an image display device that displays an image using light emitted from a light source is known. The video display device is, for example, a liquid crystal monitor, a television, a projector, or the like. The light source is an LED (Light Emitting Diode), an LD (Laser Diode), or the like.

  Here, a technique for reducing the power consumption of the light source by increasing the light emission efficiency of the light source has been proposed. Specifically, the light emission efficiency of the light source is enhanced by controlling the light source with a drive current value close to the maximum drive current value. Further, in order to suppress the heat generation of the light source, the light source is controlled by pulse driving (for example, Patent Document 1).

JP 2009-295571 A

  By the way, as a result of intensive studies, the inventors have found that not only a light source having a higher light emission efficiency as the drive current value is higher, but also a light source having a higher light emission efficiency as the drive current value is lower. In other words, the inventors have found that there are cases where the above-described technique cannot reduce the power consumption of the light source.

  Therefore, the present invention has been made to solve the above-described problem, and reduces power consumption of a light source even when there are a plurality of types of light sources having different light emission efficiencies with respect to a drive current value. It is an object of the present invention to provide a video display device that can be used.

  The video display device according to the first feature includes a first light source (for example, the light source 10G and the light source 10B) having higher light emission efficiency as the drive current value is higher, and a second light source (for example, higher light emission efficiency as the drive current value is lower). And a light source 10R). The video display device includes a control unit (control unit 220) that controls the first light source and the second light source. A reference light emission period is defined for the first light source and the second light source. The control unit controls the first light source so that a light emission period of the first light source is shorter than the reference light emission period, and the light emission period of the second light source is longer than the reference light emission period. Control the second light source.

  In the first feature, the control unit determines a light emission period of the second light source after determining a light emission period of the first light source.

  In the first feature, a reference drive current value is defined for the first light source and the second light source in addition to the reference light emission period. The control unit is configured such that a light emission period of the first light source is shorter than the reference light emission period according to a required light amount of light emitted from the first light source, and a drive current value of the first light source is the reference drive current. The first light source is controlled to be larger than the value. The control unit is configured such that a light emission period of the second light source is longer than the reference light emission period according to a required light amount of light emitted from the second light source, and a drive current value of the second light source is the reference drive current. The second light source is controlled to be smaller than the value.

  In the first feature, the control unit determines a required light amount of light emitted from the first light source and a required light amount of light emitted from the second light source based on a video input signal.

  In the first feature, the control unit determines a light emission period of the first light source according to a degree of bias of a signal value of a video signal corresponding to the first light source.

  According to the present invention, it is possible to provide an image display apparatus that can reduce the power consumption of a light source even when there are a plurality of types of light sources having different light emission efficiencies with respect to a drive current value.

FIG. 1 is a diagram showing a projection display apparatus 100 according to the first embodiment. FIG. 2 is a diagram illustrating the control unit 200 according to the first embodiment. FIG. 3 is a diagram illustrating a characteristic curve of the first light source according to the first embodiment. FIG. 4 is a diagram illustrating a characteristic curve of the second light source according to the first embodiment. FIG. 5 is a diagram for explaining a light emission period and a drive current value according to the first embodiment. FIG. 6 is a diagram for explaining the light emission period and the drive current value according to the first embodiment. FIG. 7 is a diagram for explaining a light emission period and a drive current value according to the first modification. FIG. 8 is a diagram for explaining the light emission period and the drive current value according to the first modification. FIG. 9 is a diagram illustrating a characteristic curve of the second light source according to the third modification.

  Hereinafter, an image display apparatus according to an embodiment of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals.

  However, it should be noted that the drawings are schematic and ratios of dimensions and the like are different from actual ones. Therefore, specific dimensions and the like should be determined in consideration of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

[Outline of Embodiment]
The video display apparatus according to the embodiment includes a first light source having a higher light emission efficiency as the drive current value is higher, and a second light source having a higher light emission efficiency as the drive current value is lower. The video display device includes a control unit that controls the first light source and the second light source. A reference light emission period is defined for the first light source and the second light source. The control unit controls the first light source so that a light emission period of the first light source is shorter than the reference light emission period, and the light emission period of the second light source is longer than the reference light emission period. Control the second light source.

  According to the embodiment, the control unit controls the first light source so that the light emission period of the first light source is shorter than the reference light emission period, and the first light source so that the light emission period of the second light source is longer than the reference light emission period. Two light sources are controlled. Therefore, even when there are a plurality of types of light sources having different light emission efficiency with respect to the drive current value, the power consumption of the light source can be reduced.

[First Embodiment]
(Configuration of video display device)
The video display device according to the first embodiment will be described below. FIG. 1 is a diagram showing a projection display apparatus 100 according to the first embodiment. In the first embodiment, the projection display apparatus 100 is merely exemplified as the image display apparatus. The video display device may be a liquid crystal monitor or a television.

  As shown in FIG. 1, the projection display apparatus 100 includes a light source 10 (light source 10R, light source 10G, and light source 10B), a mirror 20, a mirror 30, a mirror 40, a rod integrator 50, and a reflection mirror 60. DMD 70 and projection unit 80. The projection display apparatus 100 has a necessary lens group.

  The light source 10R is a light source that emits red component light R, and is, for example, a red LED (Light Emitting Diode) or a red LD (Laser Diode). The light source 10G is a light source that emits green component light G, and is, for example, a green LED or a green LD. The light source 10B is a light source that emits blue component light B, and is, for example, a blue LED or a blue LD.

  The mirror 20 is a mirror that reflects the red component light R. The mirror 30 is a dichroic mirror that reflects the green component light G emitted from the light source 10 </ b> G and transmits the red component light R reflected by the mirror 20. The mirror 40 is a dichroic mirror that transmits the blue component light B emitted from the light source 10 </ b> B and reflects the red component light R and the green component light G synthesized by the mirror 30.

  In the first embodiment, the mirror 30 and the mirror 40 constitute a color combining unit that combines the red component light R, the green component light G, and the blue component light B.

  The rod integrator 50 is an example of a uniformizing unit that uniformizes the light emitted from the light source 10. Specifically, the rod integrator 50 has a light incident surface, a light emitting surface, and a light reflecting side surface provided from the outer periphery of the light incident surface to the outer periphery of the light emitting surface. Specifically, the rod integrator 50 makes the color component light uniform by reflecting the color component light on the light reflection side surface. The rod integrator 50 may be a solid rod made of glass or the like, or a hollow rod having an inner surface constituted by a mirror surface.

  The reflection mirror 60 is a mirror that guides the light emitted from the rod integrator 50 to the DMD 70.

  The DMD 70 is composed of a plurality of minute mirrors, and the plurality of minute mirrors are movable. The DMD 70 switches whether to reflect the light combined by the mirror 30 and the mirror 40 to the projection unit 80 by changing the angle of each micromirror.

  The projection unit 80 projects the image light emitted from the DMD 70 onto the projection surface.

(Configuration of control unit)
The control unit according to the first embodiment will be described below with reference to the drawings. FIG. 2 is a block diagram showing the control unit 200 according to the first embodiment. The control unit 200 is provided in the projection display apparatus 100 and controls the projection display apparatus 100.

The control unit 200 converts the video input signal into a video output signal. The video input signal includes a red input signal R _in , a green input signal G _in, and a blue input signal B _in . The video output signal includes a red output signal _Rout , a green output signal _Gout, and a blue output signal _Bout . The video input signal and the video output signal are signals input for each pixel constituting one frame. For example, the maximum value of the video input signal and the video output signal is “255”, and the minimum value of the video input signal and the video output signal is “0”.

  As shown in FIG. 2, the control unit 200 includes a video signal acquisition unit 210 and a control unit 220.

The video signal acquisition unit 210 receives video input signals (red input signal R _in , green input signal G _in , and blue input signal B _in ) from an external device (not shown) such as a DVD or a TV tuner.

  The control unit 220 controls the projection display apparatus 100. For example, the control unit 220 controls the light source 10 and the DMD 70.

  Here, in the first embodiment, the light source 10 (the light source 10R, the light source 10G, and the light source 10B) is a first light source having a higher light emission efficiency as the drive current value is higher, and a second light source having a higher light emission efficiency as the drive current value is lower. Including a light source.

  First, the first light source has, for example, a characteristic curve shown in FIG. As shown in FIG. 3, when the drive current value is equal to or less than the threshold Th, the light emission amount of the first light source is “0”. When the drive current value is larger than the threshold value Th, the light emission amount of the first light source is larger as the drive current value is larger. For example, the drive current value and the light emission amount of the first light source have a proportional relationship. As a whole, it should be noted that the larger the drive current value, the higher the luminous efficiency of the first light source.

  Here, a reference drive current value is determined for the first light source. The reference drive current value is a drive current value used in a general state, and is determined by, for example, the manufacturer of the first light source.

  An upper limit drive current value is determined for the first light source. The upper limit drive current value is a value that the drive current value must not exceed, and is determined by the manufacturer of the first light source, for example. It should be noted that the first light source may be destroyed when the drive current value exceeds the upper limit drive current value.

  The first light source has a reference light emission period. The reference light emission period is, for example, a period in which one frame period is equally divided by the number of reference colors for reproducing an image. For example, when the reference colors are red, green, and blue, the reference light emission period is 1/3 of one frame period. However, the reference light emission period may be determined in advance and does not necessarily have to be a period in which one frame period is equally divided.

  Second, the second light source has, for example, a characteristic curve shown in FIG. As shown in FIG. 4, the larger the drive current value, the smaller the light emission amount of the second light source. Thus, as a whole, it should be noted that the light emission efficiency of the second light source is higher as the drive current value is smaller.

  Here, as with the first light source, a reference drive current value, an upper limit drive current value, and a reference light emission period are determined for the second light source.

  Note that the first light source is, for example, an LD (Laser Diode), and the second light source is, for example, an LED (Light Emitting Diode). However, depending on the materials of the first light source and the second light source, the first light source may be an LED and the second light source may be an LD. Alternatively, both the first light source and the second light source may be LEDs, and both the first light source and the second light source may be LDs.

  In such a case, the control unit 220 controls the first light source such that the light emission period of the first light source is shorter than the reference light emission period, and the light emission period of the second light source is longer than the reference light emission period. Control the second light source.

  For example, in the case where the luminance of the image is uniformly reduced, the first light source is controlled such that the light emission period of the first light source is shorter than the reference light emission period, and the light emission period of the second light source is longer than the reference light emission period. Thus, the second light source is controlled.

  It is preferable that the control unit 220 determines the light emission period of the second light source (that is, the extendable period) after determining the light emission period of the first light source (that is, the shortenable period). Specifically, the light emission period (extendable period) of the second light source can be easily determined by first determining the light emission period (period that can be shortened) of the first light source. Conversely, it should be noted that if the light emission period (extendable period) of the second light source is determined first, it is not possible to determine the period during which the light emission period of the second light source can be extended.

  For example, a case where the light source 10R is the second light source and the light source 10G and the light source 10B are the first light source is illustrated.

  In the normal state, as shown in FIG. 5, the drive current values of the light source 10R, the light source 10G, and the light source 10B are reference drive current values, and the light emission periods of the light source 10R, the light source 10G, and the light source 10B are reference light emission periods. It is.

  On the other hand, when the amount of light emitted from the light source 10R, the light source 10G, and the light source 10B is halved uniformly, as shown in FIG. 6, the light emission periods of the light source 10G and the light source 10B are longer than the reference light emission period. The light source 10G and the light source 10B are controlled to be shorter, and the light source 10R is controlled so that the light emission period of the light source 10R is longer than the reference light emission period.

  Since the light amount of the red component light R is relatively larger than the light amounts of the green component light G and the blue component light B, the light source 10R is controlled with a drive current value smaller than the reference drive current value.

(Function and effect)
According to the first embodiment, the control unit 220 controls the first light source such that the light emission period of the first light source is shorter than the reference light emission period, and the light emission period of the second light source is longer than the reference light emission period. The second light source is controlled as described above. Therefore, even when there are a plurality of types of light sources having different light emission efficiency with respect to the drive current value, the power consumption of the light source can be reduced.

[Modification 1]
Hereinafter, Modification Example 1 of the first embodiment will be described. In the following, differences from the first embodiment will be mainly described.

  In the first modification, the control unit 220 determines that the light emission period of the first light source is shorter than the reference light emission period and the drive current value of the first light source is the reference drive current according to the required light amount of light emitted from the first light source. The first light source is controlled to be larger than the value. Further, the controller 220 determines that the light emission period of the second light source is longer than the reference light emission period and the drive current value of the second light source is greater than the reference drive current value according to the required light amount of light emitted from the second light source. The second light source is controlled to be small.

  Here, it should be noted that the necessary light amount is determined by the light amount emitted from the light source 10 and the video input signal. The amount of light emitted from the light source 10 is determined by the drive current value and the light emission period.

  It is preferable that the control unit 220 determines the light emission period of the second light source (that is, the extendable period) after determining the light emission period of the first light source (that is, the shortenable period).

  For example, a case where the light source 10R is the second light source and the light source 10G and the light source 10B are the first light source is illustrated.

  In the normal state, as shown in FIG. 7, the drive current values of the light source 10R, the light source 10G, and the light source 10B are reference drive current values, and the emission periods of the light source 10R, the light source 10G, and the light source 10B are the reference emission period. It is.

  On the other hand, when the drive current value and the light emission period are controlled according to the required light amount, the light emission periods of the light source 10G and the light source 10B are shorter than the reference light emission period as shown in FIG. The light source 10G and the light source 10B are controlled so that the drive current values of 10G and the light source 10B are larger than the reference drive current value. On the other hand, the light source 10R is controlled so that the light emission period of the light source 10R is longer than the reference light emission period and the drive current value of the light source 10R is smaller than the reference drive current value.

  In such a case, the drive current value and the light emission period multiplication result (that is, the amount of light emitted from the light source 10) are not different from the reference drive current value and the reference light emission period multiplication result. The light emission period may be determined.

  Alternatively, the video input signal may be expanded to maintain the color balance of red, green and blue. In other words, the signal expansion amount, the drive current value, and the light emission period are determined according to the multiplication result (required light amount) of the video input signal, the reference drive current value, and the reference light emission period.

  In the first modification, the drive current value is controlled to be larger than the reference drive current value, but the drive current value does not exceed the above-described upper limit drive current value. The lower limit of the light emission period is a minimum period necessary to maintain the number of gradations to be expressed by the DMD 70. For example, as shown in Modification Example 2 described later, the lower the number of gradations to be expressed by the DMD 70, the smaller the lower limit of the light emission period.

[Modification 2]
Hereinafter, Modification Example 2 of the first embodiment will be described. In the following, differences from the first embodiment will be mainly described.

  In the second modification, the control unit 220 determines the light emission period (that is, the shortenable period) of the first light source according to the degree of deviation of the signal value of the video signal (video input signal) corresponding to the first light source. .

  Specifically, a case will be described in which an element (for example, DMD 70) that expresses the gradation of an image by reflecting light in a time division manner is provided as a light modulation element. In such a case, when the light emission period of the first light source becomes shorter than the reference light emission period, the number of gradations that can be expressed by the DMD 70 decreases.

  Therefore, in the second modification, the light emission period (that is, the shortenable period) of the first light source is determined according to the degree of deviation of the signal value of the video input signal.

  Note that the degree of bias of the signal value of the video input signal is the variance of the signal value of the video input signal of 1 frame, the difference between the maximum value and the minimum value of the video input signal of 1 frame, The number of gradations actually used.

  The control unit 220 shortens the light emission period of the first light source as the degree of bias of the signal value of the video input signal is larger.

  However, in the case where it is essential to maintain color balance, it is a condition that the drive current value does not exceed the upper limit drive current value and that signal expansion is possible. In other words, the control unit 220 shortens the light emission period of the first light source as the degree of bias of the signal value of the video input signal increases within a range where the color balance can be maintained by increasing the drive current value or signal expansion.

[Modification 3]
Hereinafter, Modification 3 of the first embodiment will be described. In the following, differences from the first embodiment will be mainly described.

  In the third modification, a case where the light source 10 (the light source 10R, the light source 10G, and the light source 10B) is a light source array including a plurality of light sources will be described.

  In such a case, the control unit 220 decreases the drive current value in order from the light source having the largest drive current value to be decreased in order to decrease the unit light quantity.

  Here, a case where the light source 10 is the second light source is illustrated. For example, as shown in FIG. 9, a case where light sources A to C are provided as the second light source will be described.

  The control unit 220 decreases the drive current value in order from the light source having the largest drive current value to be decreased in order to reduce the unit light amount among the light sources A to C. In other words, the control unit 220 decreases the drive current value in order from the light source with the gentle slope of the characteristic curve shown in FIG.

  For example, in the state shown in FIG. 9, when the drive current values of the light sources A to C are the reference drive current values, first, since the characteristic curve of the light source C is the most gradual, the drive current value of the light source C Decrease. When the drive current value of the light source C decreases, the characteristic curve of the light source B becomes gentler than the characteristic curve of the light source C. In such a case, the drive current value of the light source B is decreased.

  As a result, when the light emission amount of the second light source is reduced, the drive current value of the second light source can be efficiently reduced.

[Other Embodiments]
Although the present invention has been described with reference to the above-described embodiments, it should not be understood that the descriptions and drawings constituting a part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

  In the embodiment, the DMD 70 is exemplified as the light modulation element. However, the embodiment is not limited to this. The light modulation element may be a transmissive liquid crystal panel or a reflective liquid crystal panel.

  In the first modification, the case where the color balance is maintained by increasing the driving current value of the first light source and expanding the signal when the light emission period of the first light source is shortened is illustrated. However, the embodiment is not limited to this. For example, the control unit 220 may compensate for the amount of light that is insufficient depending on the light emission period of the first light source only by signal expansion.

  DESCRIPTION OF SYMBOLS 10 ... Light source, 20 ... Mirror, 30 ... Mirror, 40 ... Mirror, 50 ... Rod integrator, 60 ... Reflecting mirror, 70 ... DMD, 80 ... Projection unit, 100 ... Projection type image display apparatus, 200 ... Control unit, 210 ... Video signal acquisition unit, 220... Control unit

Claims (5)

A video display device comprising a first light source having a higher light emission efficiency as the drive current value is higher, and a second light source having a higher light emission efficiency as the drive current value is lower,
A controller for controlling the first light source and the second light source;
A reference light emission period is defined for the first light source and the second light source,
The control unit controls the first light source so that a light emission period of the first light source is shorter than the reference light emission period, and the light emission period of the second light source is longer than the reference light emission period. An image display device that controls a second light source.   The video display apparatus according to claim 1, wherein the control unit determines a light emission period of the second light source after determining a light emission period of the first light source. In addition to the reference emission period, a reference drive current value is defined for the first light source and the second light source,
The control unit is configured such that a light emission period of the first light source is shorter than the reference light emission period according to a required light amount of light emitted from the first light source, and a drive current value of the first light source is the reference drive current. Controlling the first light source to be greater than the value;
The control unit is configured such that a light emission period of the second light source is longer than the reference light emission period according to a required light amount of light emitted from the second light source, and a drive current value of the second light source is the reference drive current. The video display device according to claim 1, wherein the second light source is controlled to be smaller than a value.   The said control part determines the required light quantity of the light radiate | emitted from the said 1st light source, and the required light quantity of the light radiate | emitted from the said 2nd light source based on a video input signal. Video display device.   The video display apparatus according to claim 1, wherein the control unit determines a light emission period of the first light source according to a degree of bias of a signal value of a video signal corresponding to the first light source.

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