Patent Application
20180226030
The present invention relates to a light source apparatus, an image display apparatus and a control method for a light source apparatus.
There are color image display apparatuses including a color liquid-crystal panel having a color filter and a light source apparatus (backlight apparatus) which irradiates white light onto the rear surface of the color liquid-crystal panel. Conventionally, a fluorescent lamp, such as a cold-cathode fluorescent lamp (CCFL), or the like, is mainly used as a light source for a light source apparatus. However, in recent years, light-emitting diodes (LED), which are excellent in terms of power consumption, lifespan, color reproduction and environmental burden, have come to be used as a light source for light source apparatuses.
A light source apparatus which uses an LED as a light source (LED backlight apparatus) generally has a plurality of LEDs. Japanese Patent Application Publication No. 2001-142409 discloses an LED backlight apparatus having a plurality of light-emitting blocks. The light-emitting blocks each have one or more LED. Furthermore, Japanese Patent Application Publication No. 2001-142409 indicates that the light emission brightness of each of the plurality of light-emitting blocks is controlled individually.
By reducing the light emission brightness of light-emitting blocks which irradiate light onto a low-brightness display region of the screen of the color image display apparatus, it is possible to reduce the power consumption and to improve the contrast of the display image (the image displayed on the screen). A low-brightness display region is a region where a dark image is displayed. Furthermore, by increasing the light emission brightness of the light-emitting blocks which irradiate light onto a high-brightness display region of the screen, it is possible to improve the contrast of the display image, and it becomes possible to portray glare and sparkle that could not be portrayed conventionally. A high-brightness display region is a region where a bright image is displayed. By reducing the light emission brightness of the light-emitting blocks which irradiate light onto the low-brightness display region and raising the light emission brightness of the light-emitting blocks which irradiate light onto the high-brightness display region, it is possible to further improve the contrast of the display image. The light emission control of the respective light-emitting blocks corresponding to the characteristics of the image is called “local dimming control”. Furthermore, local dimming control which raises the light emission brightness of the light-emitting blocks that irradiates light onto the high-brightness display region is called “high dynamic range (HDR) control”.
In general, it is desirable for the power consumption of the apparatus to be small. As described above, there is local dimming control which is capable of reducing the power consumption. However, light source apparatuses are not necessarily capable of carrying out local dimming control of this kind. Furthermore, the user may not necessarily want local dimming control. Therefore, a new method is required which is capable of reducing the power consumption even when local dimming control is not carried out.
The present invention provides technology capable of reducing the power consumption of a light source apparatus, without carrying out local dimming control.
The present invention in its first aspect provides a light source apparatus, comprising:
a light-emitting unit having a plurality of light-emitting diodes having mutually different light emission colors;
a setting unit configured to set any of a plurality of drive modes including a first drive mode and a second drive mode having mutually different drive methods for the light-emitting unit; and
a control unit configured to drive the light-emitting unit in such that each of the plurality of light-emitting diodes emits light periodically, by a drive method corresponding to the drive mode set by the setting unit, wherein
in a case where the light-emitting unit is lit with a predetermined light emission brightness, in a light-emitting diode from among the plurality of light-emitting diodes, a drive current value during a lighting period is lower and a lighting period during one cycle is longer in the second drive mode than those in the first drive mode.
The present invention in its second aspect provides an image display apparatus, comprising:
a light source apparatus; and
a display unit configured to display an image on a screen by modulating light from the light source apparatus on the basis of input image data, wherein
the light source apparatus comprises
in a case where the light-emitting unit is lit with a predetermined light emission brightness, in a light-emitting diode from among the plurality of light-emitting diodes, a drive current value during a lighting period is lower and a lighting period during one cycle is longer in the second drive mode than those in the first drive mode.
The present invention in its third aspect provides a control method for a light source apparatus including a light-emitting unit having a plurality of light-emitting diodes having mutually different light emission colors, comprising:
setting any of a plurality of drive modes including a first drive mode and a second drive mode having mutually different drive methods for the light-emitting unit; and
driving the light-emitting unit in such that each of the plurality of light-emitting diodes emits light periodically, by a drive method corresponding to the drive mode set by the setting, wherein
in a case where the light-emitting unit is lit with a predetermined light emission brightness, in a light-emitting diode from among the plurality of light-emitting diodes, a drive current value during a lighting period is lower and a lighting period during one cycle is longer in the second drive mode than those in the first drive mode.
The present invention in its fourth aspect provides a non-transitory computer readable medium that stores a program, wherein
the program causes a computer to execute a control method for a light source apparatus including a light-emitting unit having a plurality of light-emitting diodes having mutually different light emission colors;
the control method comprises
in a case where the light-emitting unit is lit with a predetermined light emission brightness, in a light-emitting diode from among the plurality of light-emitting diodes, a drive current value during a lighting period is lower and a lighting period during one cycle is longer in the second drive mode than those in the first drive mode.
According to the present invention, it is possible to reduce the power consumption of a light source apparatus, without carrying out local dimming control.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
Below, a light source apparatus, a display apparatus and a control method for same relating to a first embodiment of the present invention will be described.
In the present embodiment, an example of a light source (backlight apparatus) for a color image display apparatus is described, but the liquid source apparatus is not limited to this. The light source apparatus may be a lighting apparatus, such as a street lamp, indoor lighting, microscope illumination, or the like.
Furthermore, in the present embodiment, an example is described in which the image display apparatus is a transmission-type liquid-crystal display apparatus, but the image display apparatus is not limited to this. The image display apparatus may have a light source apparatus and a display unit which displays an image on a screen by modulating light from the light source apparatus on the basis of input image data (image data input to the image display apparatus). For example, the image display apparatus may be a reflection-type liquid-crystal display apparatus. Furthermore, the image display apparatus may be a display using a MEMS shutter method which employs a microelectromechanicalsystem (MEMS) shutter, ratherthan liquid-crystal elements. The image display apparatus may be a monochromatic image display apparatus.
The LED substrate 101 emits light (for example, white light) which is irradiated onto the rear surface of the color liquid-crystal panel 105. There are no particular restrictions on the light emission color of the LED substrate 101. A plurality of light-emitting diodes (LEDs) are provided on the LED substrate 101. The diffusion plate 102, the condensing sheet 103 and the reflection-type polarizing film 104 are provided at positions opposing the LED. The diffusion plate 102, the condensing sheet 103 and the reflection-type polarizing film 104 are arranged substantially in parallel (or completely in parallel) with the LED substrate 101, and apply optical changes to the light from the LED substrate 101 (more specifically, from the LEDs). More specifically, the diffusion plate 102 causes the LED substrate 101 to function as a surface light source, by diffusing the light from the plurality of LEDs. The condensing sheet 103 improves the front surface brightness (the brightness in the front surface direction), by condensing, in the front surface direction (the side of the color liquid-crystal panel 105), the light that has been diffused by the diffusion plate 102 and which is incident on the condensing sheet 103 at various angles of incidence. The reflection-type polarizing film 104 improves the front surface brightness by efficiently polarizing the incident light.
The diffusion plate 102, condensing sheet 103 and reflection-type polarizing film 104 are used in superimposed fashion. Below, these optical members are jointly referred to as an optical sheet 106. The optical sheet 106 may include members other than the optical members described above, and furthermore, may omit at least one of the optical members described above. Moreover, the optical sheet 106 and the color liquid-crystal panel 105 may be configured in an integrated fashion.
The color liquid-crystal panel 105 is a display unit which displays an image on the screen by modulating light from the backlight apparatus. More specifically, the color liquid-crystal panel 105 has a plurality of R sub-pixels which transmit red light, G sub-pixels which transmit green light, and B sub-pixels which transmit blue light. The color liquid-crystal panel 105 controls the transmissivity of the irradiated light, respectively in each sub-pixel. Therefore, the brightness of irradiated light is controlled respectively in each sub-pixel and a color image is displayed.
The backlight apparatus having the configuration described above (a configuration such as that shown in
A plurality of LEDs 112 having mutually different light emission colors are provided in the light-emitting blocks 111. In the example in
In the present embodiment, an indium-gallium-aluminum-phosphorous type (InGaAlP-type) semiconductor LED is used as the R-LED, and a gallium nitride type (GaN-type) semiconductor LED is used as the G-LED and B-LED.
An optical sensor 113 (detection unit) is provided in each of the light-emitting blocks 111. The optical sensor 113 detects light from the light-emitting block 111 and outputs the detection value (light detection value). A portion of the light from the light-emitting block 111 is reflected by the optical sheet (the diffusion plate and/or reflection-type polarizing film), etc. and returned to the light-emitting block 111 side. The optical sensor 113 detects, for example, synthesized light made up of light that is directly incident from the light-emitting block 111 (direct light) and light that is reflected by the optical sheet 106 and returned to the LED substrate 101 side (reflected light). It is possible to use a brightness sensor (photodiode, phototransistor, etc.) which detects the brightness of the light, as the optical sensor 113. Furthermore, it is also possible to use as the optical sensor 113 a color sensor which detects the color of the light. It is also possible to use an optical sensor which detects both the brightness and the color of the light, as the optical sensor 113. From the detection value of the optical sensor 113, it is possible determine change in at least one of the light emission color and the light emission brightness of the light-emitting block 111 due to deterioration of the LEDs 112 and/or temperature variations.
There are no particular restrictions on the number, shape and arrangement of the light-emitting blocks 111. One light-emitting block may be used as the LED substrate 101. For instance, on the LED substrate 101, the abovementioned 35 light-emitting blocks 111 may be used as one light-emitting block. Furthermore, the plurality of light-emitting blocks 111 may be arranged in a staggered matrix configuration. In the example in
Similarly, there are no particular restrictions on the number, shape and arrangement of the partial regions. For example, a plurality of split regions configuring the region of the screen may be used as a plurality of partial regions. The plurality of partial regions may be separated from each other, at least a portion of one partial region may overlap with at least a portion of another partial region.
Similarly, there are no particular restrictions on the number and arrangement of the LEDs 112. Furthermore, there are no particular restrictions on the type (light emission color) of the LEDs 112. For example, LEDs which emit yellow light may be used. It is also possible to omit at least one of R-LEDs and B-LEDs.
Similarly, there are no particular restrictions on the number and arrangement of the optical sensors 113. For example, it is also possible to provide one optical sensor 113 for two or more light-emitting blocks 111.
The mode setting unit 170 sets the image processing unit 160 to anyone of a plurality of drive modes, each having mutually different methods for driving the LED substrate 101 (plurality of LEDs 112). More specifically, the mode setting unit 170 outputs a mode signal 171 indicating anyone of the plurality of drive modes, to the image processing unit 160. Consequently, the drive mode indicated by the mode signal 171 is set in the image processing unit 160. In the present embodiment, the plurality of drive modes include an LD mode (first mode) and a non-LD mode (second mode). The LD mode is a drive mode which adaptively changes at least one of the light emission brightness and the light emission color of the LED substrate 101. Furthermore, the LD mode is a drive mode which changes at least one of the light emission brightness and the light emission color of the LED substrate 101, individually, in each of the plurality of partial regions (execution of local dimming control). In other words, the LD mode is a drive mode which individually changes at least one of the light emission brightness and the light emission color of the plurality of light-emitting blocks 111. The non-LD mode is a drive mode which does not change the light emission brightness or the light emission color of the LED substrate 101. Furthermore, the non-LD mode is a drive mode which causes the light emission brightness and the light emission color of the LED substrate 101 to coincide substantially (or completely) between the plurality of partial regions. In other words, the non-LD mode is a drive mode which causes the light emission brightness and the light emission color of the light-emitting blocks 111 to coincide substantially in each of the plurality of light-emitting blocks 111 (local dimming control not executed).
The image processing unit 160 carries out processing corresponding to the set drive mode.
Firstly, a case where the non-LD mode is set will be described. In this case, the image processing unit 160 determines a common LD correction value 162 for each of the plurality of the light-emitting blocks 111, and the determined LD correction value 162 is output to a microcomputer 125. The LD correction value 162 is determined for each light emission color of the LED 112. Furthermore, the image processing unit 160 generates display image data 161 by applying predetermined image processing to the input image data 150. The predetermined image processing involves general image processing, for example, resolution conversion processing, sharpness processing, color conversion processing, gamma conversion, and the like. The image processing unit 160 outputs the generated display image data 161 to the color liquid-crystal panel 105. The input image data may be used as display image data.
Next, a case where the LD mode is set will be described. In this case, the image processing unit 160 determines an LD correction value 162 individually for each of the plurality of the light-emitting blocks 111, and the determined LD correction values 162 are output to a microcomputer 125. The LD correction values 162 are determined for each combination of the light-emitting block 111 and light emission color of the LEDs 112. Furthermore, the image processing unit 160 generates display image data 161 by applying non-uniformity reduction processing and the abovementioned predetermined image processing to the input image data 150. In a case where local dimming control is implemented to change the light emission of the plurality of light-emitting blocks 111, individually, unwanted non-uniformity (brightness non-uniformity (halo effect) and/or color non-uniformity) may occur in the display image (the image display on the screen), due to differences in the light emission between the plurality of light-emitting blocks 111. The non-uniformity reduction processing is image processing for reducing the non-uniformities of this kind. The image processing unit 160 outputs the generated display image data to the color liquid-crystal panel 105. The predetermined image processing described above does not have to be carried out.
A concrete example of the determination method of the LD correction value 162 in a case where the LD mode has been set will now be described. The image processing unit 160 determines the brightness of the image data that is to be displayed on the partial region, by analyzing the input image data 150, for each of the plurality of partial regions. For each of the plurality of partial regions, the image processing unit 160 determines the LD correction value 162 for the light-emitting block 111 corresponding to that partial region, in accordance with the brightness of the image data that is to be displayed in that partial region. For example, the LD correction value 162 is determined in such a manner that the light emission brightness of a light-emitting block 111 where the brightness of the image data to be displayed in the partial region is low is controlled to a higher value than the light emission brightness of a light-emitting block 111 where the brightness of the image data to be displayed in the partial region is high.
Light emission change correction values 163 determined for each of the plurality of light-emitting blocks 111 are recorded in a non-volatile memory 126. The light emission change correction values 163 are determined for each combination of the light-emitting block 111 and light emission color of the LEDs 112. The microcomputer 125 reads out the light emission change correction values 163 determined for each of the plurality of the light-emitting blocks 111, from the non-volatile memory 126. The microcomputer 125 generates an LED driver control signal 127 for each of the plurality of light-emitting blocks 111, on the basis of the LD correction values 162 output from the image processing unit 160 and the light emission change correction values 163 which have been read out. Subsequently, the microcomputer 125 outputs the LED driver control signal 127 generated for the light-emitting block 111, to the LED driver 120 corresponding to that light-emitting block 111. In
Next, one example of the operation of the color image display apparatus in a case of generating the light emission change correction values 163 is described. If there is change in the temperature and deterioration over time of the plurality of LEDs 112, the light emission characteristics of the plurality of LEDs 112 change. As a result of this, unwanted change in the light emission brightness and/or light emission color of the LED substrate 101 occurs. Furthermore, in a case where there is fluctuation in the temperature and deterioration over time of the plurality of LEDs 112, the light emission characteristics of the plurality of LEDs 112 also fluctuate. As a result of this, light having unwanted non-uniformity (brightness non-uniformity and/or color non-uniformity) is emitted from, the LED substrate 101. The light emission change correction value 163 is a correction value for reducing the unwanted variation and/or non-uniformity in the light emitted from the LED substrate 101. In the present embodiment, the following processing (processing for generating light emission change correction values 163; light emission adjustment processing) is carried out periodically or at specific timings. The light emission adjustment process may be carried out during free time when the user is not using the color image display apparatus, but does not necessarily have to be carried out in this way. The adjustment process may also be carried out in a short period of time such that variation in the quality of the display image due to the execution of light emission adjustment processing is not noticeable to the user while the user is using the color image display apparatus.
In the light emission adjustment process, only the light-emitting block 111 that is the object of processing (object block) is lit, and the other light-emitting blocks 111 are extinguished. In this state, the light emitted from the object block is detected using the optical sensor 113. Then, a light emission change correction value 163 is determined on the basis of the detection value of the optical sensor 113, and the light emission brightness and light emission color of the object block are adjusted using the determined light emission change correction value 163. Furthermore, the determined light emission change correction value 163 is recorded in the non-volatile memory 126. Processing of this kind is carried out respectively for each of the plurality of light-emitting blocks 111. Below, an example where the light-emitting block 111 (3,4) is the object block is described. Furthermore, below, an example where the light emission brightness of the light-emitting block 111 is adjusted is described.
In the optical sensor 113, the light 121 (3,4) emitted from the light-emitting block 111 (3,4) is detected. The optical sensor 113 outputs an analogue value 122 (detection value) which represents the brightness, in accordance with the brightness of the detected light 121 (3,4). In
The brightness reference value (reference detection value) for each light-emitting block 111 determined at the time of manufacture of the color image display apparatus is recorded previously in the non-volatile memory 126. The microcomputer 125 compares the detection value of the object block with the brightness reference value of the object block. The microcomputer 125 determines the light emission change correction value 163 of the object block in accordance with the result of the abovementioned comparison, in such a manner that the detection value of the object block matches the brightness reference value of the object block. The light emission change correction value 163 is a correction value for adjusting the LED driver control signal 127. The light emission brightness of the light-emitting block 111 can be adjusted by adjusting the pulse width or pulse amplitude of the pulse signal (current or voltage pulse signal) which is applied to the light-emitting block 111. The light emission change correction value 163 may be a correction value which modifies the pulse width, or a correction value which modifies the pulse amplitude, or a correction value which modifies both the pulse width and the pulse amplitude.
A light emission change correction value 163 which adjusts the light emission brightness of the light-emitting blocks 111 in such a manner that the detection value becomes the reference value is determined, and unwanted change and/or non-uniformity in the light emitted from the LED substrate 101 can be reduced by using the determined light emission change correction value 163.
Firstly, the mode setting unit 170 sets a drive mode (S101). In a case where the LD mode has been set, the processing advances to S102, and in a case where the non-LD mode has been set, the processing advances to S112. The mode setting unit 170 sets the drive mode in accordance with a user operation. The user operation is a user operation for selecting one drive mode from a list of a plurality of drive modes, for example. An on screen display (OSD) image, for example, is used for the list. There are no particular restrictions on the method for setting the drive mode. For example, the mode setting unit 170 may set (change) the drive mode automatically in accordance with the input image data 150. In a case where it is sought to raise the contrast of the display image, the LD mode is set.
In S102, the microcomputer 125 sets a reference current value, which is a reference for the current (drive current value) supplied to the light-emitting blocks 111 while the light-emitting blocks 111 are lit. In the present embodiment, in the LD mode, the pulse width of the pulse current supplied to the light-emitting blocks 111 is controlled in accordance with the input image data 150. Control of the pulse width is called “PWM control”. Therefore, the processing in S102 is a process for determining the current to be supplied to the light-emitting blocks 111 in a case where the light-emitting blocks 111 are lit.
In the present embodiment, the light-emitting blocks 111 emit light cyclically. After S102, the microcomputer 125 sets a reference duty ratio, which is a reference value of the duty ratio that indicates the length of the lighting period of the light-emitting block 111 in one cycle of light emission by the light-emitting block 111 (S103). In the present embodiment, the duty ratio is the ratio of the length of the lighting period to the length of one cycle. The microcomputer 125, for example, determines the reference duty ratio in accordance with the reference brightness, which is the reference value of the display brightness (on-screen brightness). In the present embodiment, the reference brightness is 100 (cd/m2). The display brightness is dependent on the drive current value and the duty ratio. In a case where it is sought to reduce the display brightness to ½, the duty ratio should be halved, for instance.
The reference brightness may be a predetermined fixed value, or a value that can be changed by the user. The reference brightness may also be higher or lower than 100 (cd/m2). Furthermore, there are no particular restrictions on the definition of the duty ratio. For example, the ratio of the length of the extinction period to the length of one cycle may be used as the duty ratio.
In the example in
In the case of the LD mode, the light emission brightness and light emission color of the light-emitting blocks 111 are changed in accordance with the input image data 150. Therefore, it is necessary to provide a margin for increase in the light emission brightness of the light-emitting block 111, and the reference duty ratio is set to a low ratio. For example, the reference duty ratio is set to approximately 25% of the upper limit of the duty ratio. On the other hand, the reference current value is set to a high level in order to enable a display with the reference brightness that has been set. For example, the reference current value is set to 100 (mA) approximately. Furthermore, in a case of determining the reference current value and the reference duty ratio, the light emission change correction value 163 is used.
The description now returns to
The processing in S104 and S105 is carried out repeatedly with each frame of the input image data 150, for instance. After S105, the processing returns to S101. The processing in S102 to S105 is carried out repeatedly while the LD mode is set, and in a case where the non-LD mode is set, the processing advances to S112.
In S112, the microcomputer 125 sets the drive current value for non-LD mode. Next, the microcomputer 125 sets the duty ratio for non-LD mode (S113). In S112 and S113, the drive current value and duty ratio are set for each of the plurality of LEDs 112, similarly to S102 to S104. In S112 and S113, the drive current value and the duty ratio are set in such a manner that the light emission brightness and the light emission color of the light-emitting block 111 substantially match those in a case where the LD mode is set. Then, the microcomputer 125 drives the LED substrate 101 in accordance with the drive current value set in S112 and the duty ratio set in S113.
Below, the improvement in power efficiency achieved by carrying out the processing in S112 to S115 will be described.
In the R-LEDs, as shown by the solid line 301, the reduction in the forward voltage Vf due to reduction in the drive current value If is not particularly large. On the other hand, in the G-LEDs and the B-LEDs, as shown by the broken line 302, the reduction in the forward voltage Vf due to reduction in the drive current value If is large. The power consumed by the LEDs is calculated by multiplying the forward voltage Vf by the drive current value If. Therefore, in the G-LEDs and the B-LEDs, the forward voltage Vf is reduced greatly and the power consumption is reduced significantly, by the reduction in the drive current value If.
In the R-LEDs and the B-LEDs, there is a large reduction in the light emission intensity due to reduction in the drive current value If. Therefore, in the R-LEDs and the B-LEDs, along lighting period is required in order to suppress reduction in the light emission brightness due to reduction in the drive current value If. On the other hand, in the G-LEDs, the reduction of the light emission intensity due to reduction in the drive current value If is not particularly large. This is because the quantum efficiency is improved by the reduction in the drive current value If. Therefore, in the G-LEDs, it is possible to suppress reduction in the light emission brightness due to reduction in the drive current value If, without increasing the lighting period to a great extent.
From
The solid line 331 shows the characteristics of the R-LEDs. As shown in
The single-dotted line 332 shows the characteristics of the B-LEDs. As shown in
The broken line 333 shows the characteristics of the G-LEDs. As shown in
From the above, as shown in
The reduction in the light emission brightness of the LED that occurs with the passage of time is largely dependent on the light emission color and/or use conditions of the LED. The thick solid line 341 in
The deterioration over time of an LED is dependent on the light emission wavelength (the wavelength of the light emitted by the LED), the duty ratio and the chip temperature (LED temperature). The shorter the light emission wavelength, the faster the deterioration over time. The higher the duty ratio, the faster the deterioration over time. The higher the chip temperature, the faster the deterioration over time. Since the light emission wavelength of the B-LEDs is short, the rate of deterioration over time is extremely fast, as indicated by the thick solid line 341, and the thin solid line 342. Furthermore, the deterioration over time is accelerated by the process of reducing the drive current value and raising the duty ratio. From these factors, it can be seen that in a case where a process is carried out to reduce the drive current value of the B-LEDs and also raise the duty ratio of the B-LEDs, the resulting acceleration of the deterioration over time of the B-LEDs is greater than the effect in improving the power efficiency. The light emission wavelength of the G-LEDs is longer than that of the B-LEDs, and therefore the deterioration over time is relatively slower, as indicated by the thick broken line 343 and the thin broken line 344. There is a possibility that the deterioration over time of the G-LEDs will be accelerated by a process of reducing the drive current value of the G-LEDs and raising the duty ratio of the G-LEDs. However, the power efficiency is improved significantly by a process of this kind. As a result of this, reduction in the temperature of the G-LEDs can be expected and there are few concerns over accelerating the deterioration over time of the G-LEDs.
As described above, according to the present embodiment, based on the following assumption, the drive current value of the G-LEDs is lower and the lighting period of the G-LEDs is longer in the second mode (non-LD mode) than in the first mode (LD mode). Therefore, it is possible to reduce the power consumption of the light source apparatus, without carrying out local dimming control. The circumstances of the following assumption are, for example, that “the G-LEDs are driven with the reference current value and reference duty ratio shown in
Assumption: The G-LEDs are driven in such a manner that the light emission brightness of the G-LEDs substantially coincides between the first mode and the second mode.
In the present embodiment, an example was described in which the first mode is the LD mode, but the invention is not limited to this. For example, the first mode may be a drive mode which always uses the reference current value and the reference duty ratio in
Below, alight source apparatus, a display apparatus and a control method for same relating to a second embodiment of the present invention will be described. In the first embodiment, the first mode was LD mode and the second mode was non-LD mode. In the present embodiment, a case is described in which the first mode is non-boost mode and the second mode is boost mode. The non-boost mode according to the present embodiment is the same as the LD mode of the first embodiment. The boost mode is a drive mode which causes the LED substrate 101 to emit light with a light emission brightness that is higher than the upper limit of the light emission brightness of the LED substrate 101 in a case where the non-boost mode is set. By setting the boost mode, it is possible to improve the display brightness. In a case where the display brightness is improved, the visibility of the display image is improved in bright environments (such as a sunlit living room, or outdoors, etc.). Furthermore, by setting the boost mode, the number of identifiable gradations is increased, and therefore the boost mode is desirable in medical applications, such as mammography. Below, the functions and/or processing which are different to the first embodiment are described in detail, and the functions and/or processing which are the same as the first embodiment are not described.
A drive mode which does not change the light emission brightness or the light emission color of the LED substrate 101 may also be used as the non-boost mode. In this case, the boost mode can be regarded as a drive mode which causes the LED substrate 101 to emit light with a light emission brightness that is higher than the light emission brightness of the LED substrate 101 in a case where the non-boost mode is set.
Firstly, the mode setting unit 170 sets the drive mode (S201). In a case where the non-boost mode has been set, the processing advances to S202, and in a case where the boost mode has been set, the processing advances to S212. The mode setting unit 170 sets the drive mode in accordance with a user operation. The user operation is a user operation for selecting one drive mode from a list of a plurality of drive modes, for example. There are no particular restrictions on the method for setting the drive mode. For example, the mode setting unit 170 may set the drive mode in accordance with a user operation other than a user operation for selecting one of a plurality of drive modes. More specifically, the mode setting unit 170 may switch the drive mode between non-boost mode and boost mode depending on whether or not the reference brightness input by the user is equal to or greater than a threshold value (for example, 100 (cd/m2)). In a case where it is required to raise the upper limit value of the light emission brightness of the LED substrate 101 and/or the upper limit value of the display brightness, the boost mode is set.
There are no particular restrictions on the light emission brightness of the LED substrate 101 in a case where the non-boost mode is set and the light emission brightness of the LED substrate 101 in a case where the boost mode is set. For example, the upper limit of the light emission brightness of the LED substrate 101 in a case where the non-boost mode is set is 100 (cd/m2), and the light emission brightness of the LED substrate 101 in a case where the boost mode is set is twice that (200 (cd/m2)). The (upper limit) of the light emission brightness of the LED substrate 101 in each of the drive modes may be a predetermined fixed value, or may be a value that can be changed by the user.
In S202 to S205, the same processing as S102 to S105 of the first embodiment (
In S212, the microcomputer 125 sets the drive current value for boost mode. Next, the microcomputer 125 sets the duty ratio for boost mode (S213). In the present embodiment, the drive current value and the duty ratio for boost mode are set from a similar perspective to the first embodiment. In the present embodiment, at least one of the drive current value and the duty ratio is set to a value higher than
As described above, according to the present embodiment, similarly to the first embodiment, based on the assumption described in the first embodiment, the drive current value of the G-LEDs is lower and the lighting period of the G-LEDs is longer in the second mode (boost mode) than in the first mode (non-boost mode). Therefore, it is possible to reduce the power consumption of the light source apparatus, without carrying out local dimming control.
Below, alight source apparatus, a display apparatus and a control method for same relating to a third embodiment of the present invention will be described. In the first and second embodiments, an example is described in which the power consumption of the whole apparatus is reduced by modifying the drive current value and duty ratio of the G-LEDs. However, the light emission wavelength (main wavelength d) of an LED changes with the drive current value of the LED. Consequently, in the first embodiment in which the balance of the drive current value is changed between the G-LEDs and the other LEDs, a change in the light emission color of the LED substrate 101 (color deviation) occurs. In the present embodiment, an example is described in which color deviation of this kind can be reduced. Below, the functions and/or processing which are different to the first embodiment are described in detail, and the functions and/or processing that are the same as the first embodiment are not described. Below, the first embodiment is described as a basis, but the processing in the present embodiment can also be applied to the second embodiment.
The three vertices of the triangles 401, 402 are the red chromaticity point, the green chromaticity point and the blue chromaticity point. Here, the pixel values of the image data are RGB values (R value, G value, B value), and the gradation values (R value, G value and B value) are values from 0 to 255. The red chromaticity point is a chromaticity point of the display color having an RGB value (255,0,0), and is a vertex point near (u′,v′)=(0.5,0.5). The green chromaticity point is a chromaticity point of the display color having an RGB value (0,255, 0), and is a vertex point near (u′,v′)=(0.1,0.6). The blue chromaticity point is a chromaticity point of the display color having an RGB value (0,0,255), and is a vertex point near (u′,v′)=(0.2,0.1).
In the non-LD mode of the first embodiment, only the drive current value of the G-LEDs is controlled to a smaller value than the LD mode. Therefore, in the non-LD mode, the light emission wavelength λd of the G-LEDs is displaced to the long wavelength side compared to the LD mode. For example, the light emission wavelength λd of the G-LEDs is displaced by +4 nm. If the light emission wavelength λd of the G-LED is 530 (nm) in a case where the LD mode is set, the light emission wavelength λd of the G-LED in a case where the non-LD mode is set is 534 (nm). As a result of this, a chromaticity point displaced to the long wavelength side from the triangle 401 is obtained as the green chromaticity point, as shown by the triangle 402. Furthermore, the blue chromaticity point is displaced to the short wavelength side by shifting the light emission wavelength λd of the G-LEDs to the long wavelength side. This is because the spectrum of green light that leaks out in a case of displaying a blue color is reduced. In this way, in the method according to the first embodiment, there is a displacement of two points which are the green chromaticity point and the blue chromaticity point, between the LD mode and the non-LD mode. In a case where there is a displacement of the two points in this way, a large variation (error) occurs in the display color and the range thereof.
In the non-LD mode of the present embodiment, the drive current value of the G-LEDs and the B-LEDs is controlled to a smaller value than the LD mode. Therefore, in the non-LD mode, the light emission wavelength λd of the G-LEDs and the B-LEDs is displaced to the long wavelength side compared to the LD mode. For example, the light emission wavelength λd of the G-LEDs is displaced by +4 nm, and the light emission wavelength λd of the B-LEDs is displaced by 2 nm. As a result of this, a chromaticity point displaced to the long wavelength side from the triangle 411 is obtained as the green chromaticity point, as shown by the triangle 412. On the other hand, there is little displacement of the blue chromaticity point. This is because reduction in the spectrum of green light that leaks out during display of a blue color is suppressed by displacing the light emission wavelength λd of both the G-LEDs and the B-LEDs to the long wavelength side. In this way, in the present embodiment, there is little displacement of the chromaticity points apart from the green chromaticity point, between the LD mode and the non-LD mode, and therefore it is possible to reduce error in the display color and the range thereof.
As described above, according to the present embodiment, the light emission of the G-LEDs is controlled similarly to the first embodiment. Therefore, it is possible to reduce the power consumption of the light source apparatus, without carrying out local dimming control. Furthermore, according to the present embodiment, based on the following assumption, the drive current value of the B-LEDs is lower and the lighting period of the B-LEDs is longer in the second mode (non-LD mode) than in the first mode (LD mode). Consequently, it is possible to reduce variation in the light emission color of the LED substrate 101 due to change in the drive current value.
Assumption: The B-LEDs are driven in such a manner that the light emission brightness of the B-LEDs substantially coincides between the first mode and the second mode.
Embodiment(s) of the present invention can also be realized by a computer of a system or apparatus that reads out and executes computer executable instructions (e.g., one or more programs) recorded on a storage medium (which may also be referred to more fully as a ‘non-transitory computer-readable storage medium’) to perform the functions of one or more of the above-described embodiment(s) and/or that includes one or more circuits (e.g., application specific integrated circuit (ASIC)) for performing the functions of one or more of the above-described embodiment(s), and by a method performed by the computer of the system or apparatus by, for example, reading out and executing the computer executable instructions from the storage medium to perform the functions of one or more of the above-described embodiment(s) and/or controlling the one or more circuits to perform the functions of one or more of the above-described embodiment(s). The computer may comprise one or more processors (e.g., central processing unit (CPU), micro processing unit (MPU)) and may include a network of separate computers or separate processors to read out and execute the computer executable instructions. The computer executable instructions may be provided to the computer, for example, from a network or the storage medium. The storage medium may include, for example, one or more of a hard disk, a random-access memory (RAM), a read only memory (ROM), a storage of distributed computing systems, an optical disk (such as a compact disc (CD), digital versatile disc (DVD), or Blu-ray Disc (BD)™), a flash memory device, a memory card, and the like.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2015-064872, filed on Mar. 26, 2015, which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2015-064872 | Mar 2015 | JP | national |
This application is a divisional of application Ser. No. 15/078,145, filed Mar. 23, 2016, the entire disclosure of which is hereby incorporated by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 15078145 | Mar 2016 | US |
| Child | 15946228 | US |
