Display, control method, and program

Abstract

To achieve a technique to prevent the generation of heat in and a deterioration in the display quality of a display.SOLUTION: A display comprises a light-emitting device that is driven by current, and voltage control means that controls drive voltage for driving the light-emitting device based on the temperature of the display. The voltage control means controls the amount of change in the drive voltage per unit time so as not to exceed a predetermined limit range. The predetermined limit range is determined based on the relationship between a change in the drive voltage and a change in the light emission luminance of the light-emitting device.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a technique for driving a light-emitting element. [Background technology]

[0002] Organic EL (Electro Luminescence) displays have higher contrast than liquid crystal displays and do not require backlighting, so they are used in mobile devices such as smart devices. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2007-101951 A Summary of the Invention [Problem to be solved by the invention]

[0004] In an organic EL display, the light emission brightness is controlled by the amount of current passed through a light emitting element such as an organic light emitting diode (OLED), and the more the amount of current passed through the light emitting element, the higher the light emission brightness becomes, but the more power consumption and heat generation increase. Furthermore, if the driving voltage applied to the light emitting element is significantly changed in order to increase the amount of current passed through the light emitting element, the light emission brightness also changes significantly, resulting in a deterioration in display quality.

[0005] The present invention has been made in view of the above-mentioned problems, and has an object to realize a technique for suppressing heat generation and deterioration of display quality in a display device. [Means for solving the problem]

[0006] In order to solve the above problems and achieve the object, the display device of the present invention comprises a light-emitting element driven by a current, and a voltage control means for controlling a drive voltage for driving the light-emitting element based on the temperature of the display device, wherein the voltage control means controls the amount of change in the drive voltage per unit time so as not to exceed a predetermined limit range, and the predetermined limit range is determined based on the relationship between the change in the drive voltage and the change in the luminance of the light-emitting element.

[0007] In addition, the display device of the present invention comprises a light-emitting element driven by a current, and a voltage control means for controlling a driving voltage for driving the light-emitting element based on the temperature of the display device, and the voltage control means changes the driving voltage when the display brightness of the display device is changed. Effect of the Invention

[0008] According to the present invention, heat generation in a display device and deterioration of display quality can be suppressed. [Brief description of the drawings]

[0009] [Figure 1] FIG. 2 is a block diagram showing a hardware configuration of the display device according to the embodiment. [Diagram 2] FIG. 2 is a circuit diagram showing a configuration of a unit pixel according to the present embodiment. [Diagram 3] FIG. 4 is a graph showing the relationship between the driving voltage and temperature of the light-emitting element of the present embodiment. [Figure 4] 5 is a diagram for explaining a method of setting the drive voltage of a light-emitting element when the temperature of the display device of the first embodiment increases. FIG. [Diagram 5] 5 is a diagram for explaining a method of setting the drive voltage of a light-emitting element when the temperature of the display device of the first embodiment is decreased. FIG. [Figure 6] FIG. 11 is a schematic cross-sectional view showing the hardware configuration of an imaging apparatus according to a second embodiment. [Figure 7] 10 is a flowchart for explaining the photographing operation of the imaging apparatus according to the second embodiment. [Figure 8] 11 is a diagram for explaining a method for setting a driving voltage for a light-emitting element of the display device of the third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, the embodiments will be described in detail with reference to the attached drawings. Note that the following embodiments do not limit the invention according to the claims. Although the embodiments describe a number of features, not all of these features are essential to the invention, and the features may be combined in any manner. Furthermore, in the attached drawings, the same reference numbers are used for the same or similar configurations, and duplicated descriptions are omitted.

[0011] Hereinafter, an embodiment in which a display device of the present invention is applied to an organic EL (Electro Luminescence) display mounted on an imaging device such as a digital camera, and a light-emitting element such as an organic light emitting diode (OLED) is driven will be described in detail with reference to the accompanying drawings.

[0012] The display device of the present invention is not limited to organic EL displays, but can be widely applied to display devices equipped with current-driven light-emitting elements. Also, the imaging device to which the display device of the present invention is applied is not limited to digital cameras, but can also be applied to mobile devices such as smartphone devices and tablet devices, personal computers (PCs), and displays of TV receivers.

[0013] [Embodiment 1] First, a display device 1 of the present embodiment will be described with reference to FIGS.

[0014] FIG. 1 is a block diagram showing the hardware configuration of a display device according to the present embodiment.

[0015] The display device 1 has a pixel array 100 including a plurality of pixels 101. The pixel array 100 has a plurality of pixels 101 arranged two-dimensionally in a plurality of row directions (horizontal or crosswise direction) and a plurality of column directions (vertical or lengthwise direction) that are orthogonal to each other. A control signal is input to each pixel (unit pixel) 101 from a vertical scanning circuit 200 via a scanning line 210, and a luminance signal Vsig, which is an image signal, is input from a signal output circuit 300 via a signal line 310.

[0016] The vertical scanning circuit 200 is controlled by a control signal output from the control circuit 400 via a control line 410. The signal output circuit 300 is controlled by a control signal output from the control circuit 400 via a control line 420. The unit pixel 101 includes a light emitting diode (light emitting element) and emits light with an amount of light corresponding to a luminance signal Vsig input to the unit pixel 101. Each pixel 101 may have a plurality of sub-pixels arranged for each of the RGB colors. In this case, the signal lines 310 are arranged for each column based on each sub-pixel. For example, when one pixel includes three sub-pixels, three signal lines 310 are arranged for one pixel column.

[0017] The signal output circuit 300 includes a horizontal scanning circuit 301, a column DAC circuit 302 provided corresponding to pixels in a plurality of columns, and a column driver circuit 303 provided corresponding to pixels in a plurality of columns. In this embodiment, one column DAC circuit 302 corresponds to one column driver circuit 303. An image signal scanned by the horizontal scanning circuit 301 and input in each column direction is converted into an analog signal by the column DAC circuit 302, and output as a luminance signal Vsig from the column driver circuit 303 to the pixels in each column direction. The reference voltage generation circuit 500 generates analog voltages Vref (for example, 256 analog voltages when the image signal is 8 bits) in number according to the image signal in each column direction, and supplies them to the column DAC circuit 302.

[0018] The control circuit 400 controls a second voltage VCAT for setting a drive voltage Vdf for causing a light emitting element 110 (described later) to emit light, based on the temperature of the display device 1 acquired from the temperature detection unit 600. The second voltage VCAT corresponds to a voltage on the cathode (negative) side of the light emitting element 110 of a unit pixel 101 (described later in FIG. 2). The temperature detection unit 600 detects the temperature of the display device 1. The temperature of the display device 1 is, for example, the temperature of the light emitting element 110 inside the display device 1, the temperature of the substrate of the pixel array 100, or the temperature of at least one location in the vicinity of either of them.

[0019] FIG. 2 is a circuit diagram showing a configuration of a unit pixel 101 of this embodiment.

[0020] The light emitting element 110 is an organic light emitting diode (OLED) that emits light with an amount of light corresponding to the amount of current flowing through the light emitting element 110. The amount of light emitted by the light emitting element 110 increases as the amount of current flowing through the light emitting element 110 increases, and decreases as the amount of current flowing through the element decreases.

[0021] The driving element 112 is a transistor that supplies a driving current to the light emitting element 110 to cause the light emitting element 110 to emit light.

[0022] The signal voltage holding element 113 is a transistor that applies a signal voltage to the gate of the driving element 112 .

[0023] The first capacitive element 108 and the second capacitive element 109 are capacitors that hold the gate voltage of the driving element 112 at the signal voltage when the signal voltage holding element 113 is in the on state. Even if the signal voltage holding element 113 is in the off state, the first capacitive element 108 and the second capacitive element 109 hold the gate voltage of the driving element 112 at the signal voltage, so that the driving element 112 can operate with a constant current.

[0024] The light emission control element 106 is a transistor that supplies current from the first voltage VDD to the drive element 112 in order to perform light emission control by passing a drive current from the drive element 112 to the light emitting element 110. The reset element 107 is a transistor that cuts off the power supply to the light emitting element 110 and stops light emission by bypassing the drive current flowing from the drive element 112 to the light emitting element 110 to the voltage VCAT in the previous stage of the light emitting element 110.

[0025] The scanning line 210 applies a signal voltage for controlling the on / off timing of the switch elements 106, 107, and 113 to the gates of the switch elements 106, 107, and 113. The scanning line 210 includes a first scanning line 2101 for controlling the on / off timing of the light emission control element 106, a second scanning line 2102 for controlling the on / off timing of the signal voltage holding element 113, and a third scanning line 2103 for controlling the on / off timing of the reset element 107.

[0026] The unit pixel 101 operates the drive element 112 as a current source due to the potential difference Vdf between the first voltage VDD on the anode (plus) side of the light emitting element 110 and the second voltage VCAT (<VDD) on the cathode (minus) side. The light emitting element 110 emits light when current flows through the light emitting element 110 due to the potential difference Vdf between the first voltage VDD and the second voltage VCAT. Also, the light amount of the light emitting element 110 changes when the second voltage VCAT is changed while the first voltage VDD is in a constant state. Therefore, by limiting the change amount of the potential difference Vdf between the first voltage VDD and the second voltage VCAT, it is possible to suppress the luminance variation caused by the current variation flowing through the light emitting element 110 and the power consumption of the light emitting element 110.

[0027] However, due to the parasitic capacitance between the wiring on the drain side (VCAT side) of the drive element 112 and the gate of the drive element 112, when the change amount of the second voltage VCAT is increased, the luminance signal Vsig, which is the gate voltage of the drive element 112, transiently varies. As a result, the emission luminance of the light emitting element 110 greatly varies, deteriorating the display quality.

[0028] Therefore, in this embodiment, as described later with reference to Figures 3 to 5, the driving voltage Vdf (second voltage VCAT) of the light-emitting element 110 is appropriately controlled in accordance with the luminance setting (screen brightness setting) of the display device 1 and temperature changes, thereby suppressing the power consumption, heat generation, and deterioration of display quality of the display device 1.

[0029] Fig. 3 illustrates the relationship between the driving voltage Vdf of the light emitting element 110 and temperature. In Fig. 3, the horizontal axis illustrates the temperature of the display device 1, and the vertical axis illustrates the driving voltage. In the example of Fig. 3, three types of luminance settings are illustrated as the luminance of light emission: high luminance, medium luminance, and low luminance. The luminance settings indicate the relationship between the driving voltage Vdf capable of displaying 255 gradations and the temperature, with high luminance being 1000 cd, medium luminance being 800 cd, and low luminance being 500 cd, for example. The temperature corresponds to the temperature of the display device 1.

[0030] As shown in Fig. 3, the lower the temperature of the display device 1, the higher the drive voltage Vdf of the light emitting element 110 becomes, and therefore the higher the emission luminance of the light emitting element 110 becomes, the higher the voltage required becomes. In other words, it can be said that the relationship in Fig. 3 shows the relationship between the change in drive voltage of the light emitting element 110 and the change in emission luminance. Note that, when the display device 1 starts displaying (when the light emitting element 110 starts emitting light), the light emitting element 110 emits light at the maximum voltage required to make the light emitting element 110 emit light, based on the maximum luminance of the light emitting element 110 and the displayable temperature range, as the initial setting of the drive voltage Vdf of the light emitting element 110.

[0031] In this embodiment, the amount of change in the drive voltage Vdf of the light emitting element 110 per unit time is limited according to the brightness setting and temperature change of the display device 1. The amount of change in the drive voltage Vdf of the light emitting element 110 per unit time includes at least one of the amount of change in the drive voltage Vdf per time and the period (update frequency) for changing the drive voltage Vdf. In detail, when the temperature of the display device 1 drops, the drive voltage Vdf becomes insufficient if it does not follow the temperature change, and an image cannot be displayed, so the update frequency is increased (the period is shortened) and the drive voltage Vdf is changed quickly. Also, when the temperature of the display device 1 rises, the display is possible even if the drive voltage Vdf does not follow the temperature change, so the update frequency is decreased (the period is lengthened) and the drive voltage Vdf is changed as slowly as possible to reduce the brightness fluctuation.

[0032] FIG. 4 is a diagram for explaining a method of setting the drive voltage Vdf of the light emitting element 110 when the temperature of the display device 1 rises.

[0033] In Fig. 4, the horizontal axis represents the temperature of the display device 1, and the vertical axis represents the second voltage VCAT. When the drive voltage Vdf is low, the second voltage VCAT is high, which is the opposite characteristic to that in Fig. 3. The temperature of the display device 1 is detected at a predetermined cycle.

[0034] 4 illustrates the relationship between the temperature of the light emitting element 110 during light emission and the second voltage VCAT. The second voltage VCAT is set so as not to exceed the upper limit range of the second voltage VCAT shown by the solid line 401 with respect to the temperature of the display device 1. In reality, since there are manufacturing variations in the light emitting element and temperature detection errors, the second voltage VCAT is set according to the dashed line 402 that is shifted downward from the solid line 401 by a margin Δvh.

[0035] In FIG. 4, at temperature t1 at the start of light emission, the second voltage VCAT is set to v1 according to the dashed line 402.

[0036] Next, at temperature t2 (>t1) after a certain time has elapsed since the start of light emission, v2 is the optimal value for the second voltage VCAT according to the broken line 402, but when the voltage changes from v1 to v2, the amount of change in the second voltage VCAT exceeds the limit voltage vlimit_h. As described above, when the amount of change in the second voltage VCAT is large, the display brightness fluctuates transiently. Therefore, by controlling the voltage fluctuation of the second voltage VCAT to within vlimit_h and setting the second voltage VCAT to v2', the brightness fluctuation can be suppressed.

[0037] Furthermore, at temperature t3 (>t2) after a predetermined time has elapsed from temperature t2, v3 is the optimal value for the second voltage VCAT according to the dashed line 402, but as with temperature t2, the amount of change in the second voltage VCAT is controlled to within the limit voltage vlimit_h, and the second voltage VCAT is set to v3'.

[0038] Furthermore, at temperature t4 (>t3) after a predetermined time has elapsed from temperature t3, v4 is the optimal value for the second voltage VCAT according to the dashed line 402, and the difference with v3' is within the limit voltage vlimit_h, so the second voltage VCAT is set to v4.

[0039] FIG. 5 is a diagram for explaining a method of setting the drive voltage Vdf of the light emitting element 110 when the temperature of the display device 1 drops.

[0040] In Fig. 5, the horizontal axis represents the temperature of the display device 1, and the vertical axis represents the second voltage VCAT. When the drive voltage Vdf is low, the second voltage VCAT is high, which is the opposite characteristic to the relationship in Fig. 3. The temperature of the display device 1 is detected at a predetermined cycle.

[0041] The solid line 501 in Fig. 5 illustrates the relationship between the temperature at the time of light emission of the light-emitting element 110 and the second voltage VCAT. Note that the solid line 501 in Fig. 5 is the same as the solid line 401 in Fig. 4. The second voltage VCAT is set so as not to exceed the limit range which is the upper limit of the second voltage VCAT indicated by the solid line 501 with respect to the temperature of the display device 1. In reality, due to manufacturing variations of the light-emitting element and detection errors of the temperature, the second voltage VCAT is set according to the broken line 502 which is shifted in the downward direction by a margin Δvl (>Δvh) with respect to the solid line 501.

[0042] In Fig. 5, at the temperature t5 at the start of light emission, the second voltage VCAT is set to v5 according to the broken line 502.

[0043] Next, at the temperature t6 (<t5) after a predetermined time has elapsed from the start of light emission, v6 is the optimum value as the second voltage VCAT according to the broken line 502. However, if the change from v5 to v6 occurs, the change amount of the second voltage VCAT will exceed the limit voltage vlimit_l. As described above, when the change amount of the second voltage VCAT is large, the display luminance will transiently fluctuate. Therefore, by controlling the voltage fluctuation of the second voltage VCAT within vlimit_l and setting the second voltage VCAT to v6´, the luminance fluctuation can be suppressed.

[0044] Furthermore, at the temperature t7 (<t6) after a predetermined time has elapsed from the temperature t6, v7 is the optimum value as the second voltage VCAT according to the broken line 502. However, similar to the temperature t6, the change amount of the second voltage VCAT is controlled within the limit voltage vlimit_l, and the second voltage VCAT is set to v7´.

[0045] Furthermore, at the temperature t8 (<t7) after a predetermined time has elapsed from the temperature t7, v8 is the optimum value as the second voltage VCAT according to the broken line 502. Since the difference from v7´ is within the limit voltage vlimit_l, the second voltage VCAT is set to v8.

[0046] In this embodiment, the limited ranges in FIGS. 4 and 5 are set to a range in which the change in the light amount of the light emitting element 110 caused by the change in the drive voltage Vdf of the light emitting element 110 falls within 3%.

[0047] In this embodiment, the limit range of the second voltage VCAT is different between when the temperature is decreasing and when the temperature is increasing. That is, the limit voltage vlimit_l when the temperature is decreasing is set to a value larger than the limit voltage vlimit_h when the temperature is increasing, and the margin Δvl when the temperature is decreasing is set to a value larger than the margin Δvh when the temperature is increasing. This makes it possible to control the second voltage VCAT so that it does not exceed the solid lines 401 and 501 in FIG. 4 and FIG. 5.

[0048] In this embodiment, the amount of change in the second voltage VCAT that is changed at one time is smaller when the temperature of the display device 1 is rising (Figure 4) than when the temperature is decreasing (Figure 5). However, the period for changing the second voltage VCAT may be shorter when the temperature of the display device 1 is rising (Figure 4) than when the temperature is decreasing (Figure 5).

[0049] In addition, in the first embodiment, a method for setting the second voltage VCAT when the temperature rises and when the temperature falls has been described. However, when the temperature rises from the temperature t1 at the start of light emission in FIG. 4, the second voltage VCAT does not exceed the solid line 401. Therefore, the second voltage VCAT may be controlled only when the temperature falls from the temperature t1.

[0050] Also, after setting the drive voltage Vdf based on the temperature at the start of light emission of the light emitting element 110, the drive voltage Vdf may not be changed when the temperature of the display device 1 rises, and the drive voltage Vdf may be changed when the temperature of the display device 1 drops. Similarly, after setting the drive voltage Vdf based on the temperature at the start of light emission of the light emitting element 110, the drive voltage Vdf may not be changed until a predetermined time has elapsed since the start of light emission of the light emitting element 110, because the temperature of the display device 1 is not stable. In this case, the temperature of the display device 1 after the start of light emission of the light emitting element 110 is higher than before light emission, so the drive voltage Vdf will not be insufficient.

[0051] The control of the second voltage VCAT in this embodiment may be performed by the control circuit 400 of the display device 1, or may be performed by the control unit 2 of the imaging device 10 in which the display device 1 is mounted, as in the second embodiment. The control of the second voltage VCAT in this embodiment may be performed during a blanking period. In this case, the control may be based on a lookup table that stores the relationship between the temperature of the display device 1 and the second voltage VCAT. A plurality of lookup tables may be prepared according to the temperature at the start of light emission of the light-emitting element 110.

[0052] According to the above-described first embodiment, when the drive voltage Vdf of the light emitting element 110 is controlled in response to the luminance setting of the display device 1 and the temperature change of the light emitting element 110, the amount of change in the drive voltage Vdf of the light emitting element 110 per unit time is controlled so as not to exceed a predetermined limit range. This makes it possible to suppress the power consumption and heat generation of the display device 1 and the deterioration of the display quality.

[0053] In the first embodiment, the second voltage VCAT may be controlled based on at least one of the temperature and the luminance setting of the display device 1. In this case, the drive voltage Vdf of the light-emitting element 110 may be controlled so that the higher the temperature of the display device 1 is, the lower the drive voltage Vdf of the light-emitting element 110 is, and the lower the luminance setting is, the lower the drive voltage Vdf of the light-emitting element 110 is.

[0054] [Embodiment 2] In embodiment 2, an example is described in which the display device 1 of embodiment 1 is mounted on an imaging device 10, and the control of the driving voltage Vdf of the light-emitting element 110 described in embodiment 1 is performed at the timing when the display luminance of the display device 1 changes.

[0055] FIG. 6 is a schematic cross-sectional view showing a hardware configuration of an imaging device 10 including the display device 1 of the first embodiment.

[0056] The imaging device 10 is a digital camera with interchangeable lenses to which a lens device 20 can be attached or detached. The imaging device 10 captures an image of a subject transmitted through the lens device 20 to generate image data. The lens device 20 is mechanically and electrically connected to the imaging device 10 via a lens mount 9, and is controlled by the imaging device 10.

[0057] The housing of the imaging device 10 is provided with a display device 1, a control unit 2, an imaging unit 3, a storage unit 4, a display drive unit 5, an eyepiece unit 6, a shutter button 7, and a function button 8.

[0058] The control unit 2 is a controller including a calculation processor that controls the components of the imaging device 10, a ROM, a RAM, and the like.

[0059] The imaging unit 3 has a global electronic shutter type CMOS image sensor. The imaging unit 3 is disposed on a planned imaging plane of the lens device 20, and is electrically exposure-controlled.

[0060] The storage unit 4 is a recording medium such as a memory card for recording captured image data.

[0061] The display drive unit 5 is a driver circuit that drives the display device 1 described with reference to FIGS. 1 and 2 under the control of the control unit 2 to display an image.

[0062] The eyepiece unit 6 has an eyepiece lens for observing the subject image displayed on the display device 1.

[0063] The shutter button 7 is turned on during operation by pressing it halfway (instruction to prepare for shooting) and generates a first shutter switch signal SW1. In response to the first shutter switch signal SW1, the control unit 2 starts preparation operations for shooting, such as AF (autofocus) processing, AE (auto exposure) processing, AWB (auto white balance) processing, and EF (pre-flash) processing.

[0064] Furthermore, the shutter button 102 is turned on when the operation is completed, that is, when the button is fully pressed (photographing instruction), and generates a second shutter switch signal SW2. The control unit 2 starts a series of operations for photographing processing, from reading out a signal from the imaging unit 3 to writing captured image data to the storage unit 4, in response to the second shutter switch signal SW2.

[0065] The function button 15 is an operating member that accepts user operations for changing the operation mode of the imaging device 10, changing the display brightness of the display device 1, displaying a menu screen for various settings, etc. The operation modes of the imaging device 10 include a shooting mode (live view mode) and a playback mode.

[0066] The housing of the lens device 20 is provided with lenses 21 and 22 for zooming and focusing, an aperture 23, an aperture drive section 24, a lens drive mechanism 25, a rotation detection section 26, a pulse plate 27, and an AF drive section 28. Although the lens device 20 is composed of two lenses 21 and 22 in the example of Fig. 6, it goes without saying that in practice it is composed of two or more lenses.

[0067] The aperture drive unit 24 has an actuator that drives the aperture 23 under the control of the control unit 2, a driver circuit, and the like.

[0068] The lens drive mechanism 25 includes a motor, gears, driver circuits, etc. for moving the lenses 21 and 22 forward or backward.

[0069] The rotation detection unit 26 is a photocoupler that detects the rotation of the pulse plate 27 that is linked to the lens drive mechanism 25. The rotation detection unit 26 notifies the AF drive unit 29 of the detection result of the rotation of the pulse plate 27. The AF drive unit 28 drives the lens drive mechanism 25 based on the rotation of the pulse plate 27 and the lens drive information received from the imaging device 10, and moves the lenses 21 and 22 to the in-focus position.

[0070] Based on the photometric signal obtained from the imaging unit 3, which also functions as a photometric sensor, the control unit 2 amplifies, logarithmically compresses, and A / D converts the luminance signal corresponding to the brightness of the field, and calculates the field luminance information to determine shooting information such as the luminance setting and exposure time of the display device 1 (AE processing).

[0071] In addition, the control unit 2 performs A / D conversion of the signal voltage from the phase difference detection pixels included in the image sensor of the imaging unit 3, and performs image plane phase difference AF (AF processing) to calculate the distance to the subject corresponding to the focus detection position from the obtained signal.

[0072] 7, the control unit 2 controls the drive voltage Vdf of the light emitting element 110 in accordance with the timing at which the display luminance of the display device 1 changes. In this case, the timing at which the display luminance of the display device 1 changes is as follows. (1) The timing when the display target of the display device 1 is changed Display targets include live view images, menu screens, playback images, etc. (2) Timing when the brightness setting of the display device 1 is changed Timing when the user changes the brightness setting, when the brightness adjustment function automatically changes the brightness setting according to the surrounding brightness, when the exposure is automatically changed, etc. In addition, when the driving voltage Vdf of the light-emitting element 110 falls below the voltage required to cause the light-emitting element 110 to emit light, the control unit 2 changes the driving voltage Vdf to a voltage that allows the light-emitting element 110 to emit light within the limited range, regardless of whether the display brightness has changed or not.

[0073] FIG. 7 is a flowchart illustrating the photographing operation of the imaging device 10 of the second embodiment.

[0074] The process in FIG. 7 is realized by the control unit 2 executing a program stored in the ROM or storage unit 4 and controlling each component of the imaging device 10, and the operation mode of the imaging device 10 is started in the shooting mode.

[0075] In step S701, the control unit 2 sets, to an initial value, a second voltage VCAT for setting the drive voltage Vdf of the light-emitting element 110 of the display device 1. The initial value of the second voltage VCAT is set to a maximum voltage necessary for causing the light-emitting element 110 to emit light, based on the maximum luminance of the light-emitting element 110 and the displayable temperature range, as described in FIG.

[0076] In step S702, the control unit 2 starts an imaging operation by the imaging unit 3, and displays an image (live view image) captured by the imaging unit 3 on the display device 1. The user can observe the image displayed on the display device 1 through the eyepiece unit 6.

[0077] In step S703, the control unit 2 determines whether or not the luminance setting of the display device 1 is changed. If the control unit 2 determines that the luminance setting of the display device 1 is changed, the process proceeds to step S704. If the control unit 2 determines that the luminance setting of the display device 1 is not changed, the process proceeds to step S705. The control unit 2 makes the determination based on whether or not the timing is the timing when the user has changed the luminance setting, the timing when the luminance setting has been automatically changed by the brightness adjustment function, or the timing when the exposure has been automatically changed. For example, the control unit 2 measures the brightness of the live view image, determines a corresponding luminance setting from the three types of luminance settings in FIG. 3 based on the metering result, and determines whether or not the luminance setting is changed based on the determined result.

[0078] In step S704, the control unit 2 changes the luminance setting of the display device 1 to the luminance setting determined in step S703, and sets the second voltage VCAT according to the temperature of the display device 1 in FIG. 4 or FIG. 5 so that the driving voltage Vdf is such that the light emitting element 110 emits light at an emission luminance corresponding to the changed luminance setting. Then, the control unit 2 outputs a control signal for controlling the second voltage VCAT to the control circuit 400 of the display device 1. In this case, since the luminance setting of the display device 1 is changed, it is not necessary to consider a transient luminance fluctuation caused by the change in the second voltage VCAT. Therefore, there is no need to limit the amount of change in the second voltage VCAT as in the first embodiment, and it is changed all at once.

[0079] In step S705, the control unit 2 determines whether or not the display target of the display device 1 will be changed. If the control unit 2 determines that the display target of the display device 1 will be changed, the process proceeds to step S706. If the control unit 2 determines that the display target of the display device 1 will not be changed, the process proceeds to step S708. For example, the control unit 2 determines whether or not the display target can be switched from a live view image to a menu screen or a playback image by the user operating the function button 8.

[0080] In step S706, the control unit 2 changes the luminance setting of the display device 1 according to the brightness of the display object determined in step S705, and sets the second voltage VCAT according to the temperature of the display device 1 in FIG. 4 or FIG. 5 so that the driving voltage Vdf is such that the light emitting element 110 emits light at an emission luminance corresponding to the changed luminance setting. In this case, since the entire display object of the display device 1 is changed, it is not necessary to consider a transient luminance fluctuation caused by the change in the second voltage VCAT. Therefore, there is no need to limit the amount of change in the second voltage VCAT as in the first embodiment, and the second voltage VCAT is changed all at once. After that, if the control unit 2 determines that the user has finished operating the function button 8, the process proceeds to step S707.

[0081] In step S707, the control unit 2 restarts the imaging operation by the imaging unit 3, and displays on the display device 1 an image captured by the imaging unit 3 (a live view image).

[0082] In step S708, the control unit 2 determines whether or not to end the shooting operation due to a change in the operating mode of the imaging device 10, etc., and if it is determined that the shooting operation should be ended, it ends the processing, and if it is not determined that the shooting operation should be ended, it proceeds to step S709.

[0083] In step S709, the control unit 2 performs processing to detect a main subject from an image (live view image) captured by the imaging unit 3. The control unit 2 determines the position of the main subject in the image displayed on the display device 1 by performing face detection of a person or the like from the image captured by the imaging unit 3.

[0084] In step S710, the control unit 2 determines whether the shutter button 7 has been pressed halfway (instruction to prepare for shooting) and the first shutter switch signal SW1 has been turned on. If the control unit 2 determines that the first shutter switch signal SW1 has been turned on, the process proceeds to step S711. If the control unit 2 does not determine that the first shutter switch signal SW1 has been turned on, the process returns to step S702. The control unit 2 executes AF (autofocus) processing and AE (autoexposure) processing on the main subject determined in step S709 using the first shutter switch signal SW1.

[0085] In step S711, the control unit 2 determines whether the shutter button 7 is fully pressed (photographing instruction) and the second shutter switch signal SW2 is turned on. If the control unit 2 determines that the second shutter switch signal SW2 is turned on, the process proceeds to step S712. If the control unit 2 does not determine that the second shutter switch signal SW2 is turned on, the process returns to step S702.

[0086] In step S712, the control unit 2 executes a photographing process in which image data captured by the imaging unit 3 is written into the storage unit 4 in response to the second shutter switch signal SW1, and the process returns to step S702.

[0087] In addition, if the temperature of the display device 1 drops without the brightness setting or the display target being changed in steps S703 and S705, and the second voltage VCAT is about to exceed the limit range shown in Figure 5, the second voltage VCAT is controlled to an appropriate level while limiting the amount of change in the second voltage VCAT, as described in embodiment 1.

[0088] The above-mentioned operations described as being performed by the control unit 101 of the imaging device 10 may be performed by a single piece of hardware, or the entire device may be controlled by multiple pieces of hardware (e.g., multiple processors or circuits) sharing the processing.

[0089] According to the above-mentioned embodiment 2, the driving voltage Vdf of the light-emitting element 110 of the display device 1 can be appropriately controlled at the timing when the display luminance of the display device 1 changes, as in embodiment 1, so that the power consumption, heat generation, and deterioration of the display quality of the display device 1 can be suppressed.

[0090] [Embodiment 3] In embodiment 3, when controlling the driving voltage Vdf of the light-emitting element 110 described in embodiment 2, an example is described in which the driving voltage Vdf is set by predicting the temperature change of the light-emitting element 110 after the display luminance of the display device 1 changes, thereby reducing the frequency of updating the driving voltage Vdf.

[0091] FIG. 8 is a diagram for explaining a method for setting the driving voltage of the light emitting element 110 of the third embodiment.

[0092] In FIG. 8, the horizontal axis represents time, and the vertical axis represents the second voltage VCAT.

[0093] Straight lines 800, 801, and 802 indicate voltages set as the second voltage VCAT. Solid lines 803, 804, and 805 illustrate the relationship between the temperature of the light-emitting element 110 during light emission and the second voltage VCAT. The second voltage VCAT is set so as not to exceed the upper limit range of the second voltage VCAT indicated by the solid lines 803, 804, and 805 with respect to the temperature of the display device 1. In reality, there are manufacturing variations in the light-emitting element and temperature detection errors, so the second voltage VCAT is set according to the broken lines 806, 807, and 808 that are shifted in a direction that is lower by the margin Δvh with respect to the solid lines 803, 804, and 805. Δvh and Δvl are the same as the margin Δvh when the temperature rises and the margin Δvl when the temperature falls, described in FIG. 4 or FIG. 5 of the first embodiment.

[0094] First, when a shooting operation starts from time a1 and a live view image is displayed on the display device 1, the second voltage VCAT is set to v1 (straight line 800) at temperature t1 at time a1. In this case, since the display object is a high-luminance live view image, the temperature of the display device 1 rises, but the second voltage VCAT is not changed and remains constant at v1 (straight line 800) until the display object is changed.

[0095] Next, when the display target is changed to the menu screen at time a2, the second voltage VCAT at temperature t2 at time a2 becomes v2', which is shifted from the solid line 803 by the margin Δvh. However, since it is known that the menu screen to be displayed is low brightness, it can be predicted that the temperature t2 after the menu screen is displayed will drop from the temperature t1 when the live view image is displayed. Therefore, the second voltage VCAT is set to v2, which is shifted from the solid line 803 by the margin Δvl when the temperature drops, at time a2. In this way, by setting the second voltage VCAT to v2 when the temperature drops from t2, rather than v2' at the temperature t2 immediately after the display brightness is changed, it is possible to reduce the update frequency of the second voltage VCAT when the temperature drops after the display brightness is changed. Then, since the temperature drops from time a2 to time a3 after the display brightness is changed, the second voltage VCAT is controlled while limiting the change amount of the second voltage VCAT, as in FIG. 5 of the first embodiment, so that the second voltage VCAT does not exceed the solid line 804.

[0096] Next, when the display object is switched to a live view image at time a3, the second voltage VCAT at temperature t3 at time t3 becomes v3', which is shifted by the margin Δvl from the solid line 804. However, the display brightness of the live view image of the display object can be predicted to be the same as before it is switched to the menu screen, and the temperature after the live view image is displayed can be predicted to rise from the temperature t3 when the menu is displayed. Therefore, at the temperature t3 at time a3, v3 shifted by the margin Δvh at the time of temperature rise from the solid line 804 is set as the second voltage VCAT. In this way, by setting the second voltage VCAT to v3 when the temperature rises from the temperature t3, rather than v3' at the temperature t3 immediately after the display brightness is changed, the second voltage VCAT after the display brightness is changed can be brought closer to the optimal value after the temperature rise, and the frequency of updating the second voltage VCAT can be reduced and power consumption can be suppressed.

[0097] In the third embodiment, a method for setting the second voltage VCAT that predicts both a temperature rise and a temperature drop has been described. However, the second voltage VCAT may be controlled either when the temperature rises or when the temperature drops.

[0098] According to the above-described embodiment 3, in addition to the effects of embodiment 2, by predicting the temperature change of the light-emitting element 110 after the display luminance of the display device 1 changes and setting the driving voltage Vdf, the frequency of updating the driving voltage Vdf can be reduced, thereby enhancing the effect of reducing the power consumption and heat generation of the display device 1.

[0099] The present invention is not limited to the above-described embodiment, and can be applied to a case where a plurality of display devices are provided, such as a head-mounted display. When a plurality of display devices are provided, the drive voltage supplied to all the display devices may be commonly controlled. When the voltage control is common, the drive voltage is controlled based on the lowest temperature of all the display devices.

[0100] [Other embodiments] The present invention can also be realized by supplying a program that realizes one or more functions of each embodiment to a system or device via a network or a storage medium, and having one or more processors of a computer in the system or device read and execute the program. The present invention can also be realized by a circuit (e.g., ASIC) that realizes one or more functions.

[0101] The invention is not limited to the above-described embodiments, and various modifications and variations are possible without departing from the spirit and scope of the invention. Accordingly, the following claims are appended to apprise the public of the scope of the invention.

[0102] The disclosure of this specification includes the following display device, control method, and program. [Configuration 1] A light emitting element driven by an electric current; a voltage control means for controlling a drive voltage for driving the light emitting element based on a temperature of the display device; the voltage control means controls the amount of change in the drive voltage per unit time so as not to exceed a predetermined limit range; The display device according to claim 1, wherein the predetermined limit range is determined based on a relationship between a change in the drive voltage and a change in the luminance of the light emitting element. [Configuration 2] 2. The display device according to configuration 1, wherein the amount of change in the drive voltage per unit time includes at least one of an amount of change in the drive voltage at one time and a period for changing the drive voltage. [Configuration 3] 3. The display device according to configuration 1 or 2, wherein the predetermined limit range is different when the temperature of the display device is increasing and when the temperature is decreasing. [Configuration 4] 4. The display device according to any one of configurations 1 to 3, wherein the predetermined limit range is determined based on a relationship between a change in temperature of the display device and a change in the drive voltage. [Configuration 5] A temperature detection means for detecting a temperature of the display device, 5. The display device according to any one of configurations 1 to 4, wherein the voltage control means controls the drive voltage based on a temperature detected by the temperature detection means at a predetermined cycle. [Configuration 6] The display device according to configuration 2, wherein an amount of change in the driving voltage during a temperature rise of the display device is smaller than an amount of change in the driving voltage during a temperature drop of the display device. [Configuration 7] 3. The display device according to configuration 2, wherein a period for changing the drive voltage when the temperature of the display device is increasing is shorter than a period for changing the drive voltage when the temperature of the display device is decreasing. [Configuration 8] The display device described in any one of configurations 1 to 7, characterized in that the voltage control means controls the drive voltage based on at least one of a temperature and a display brightness of the display device, so that the drive voltage becomes lower as the temperature of the display device increases and the drive voltage becomes lower as the display brightness decreases. [Configuration 9] 2. The display device according to configuration 1, wherein the voltage control means does not change the drive voltage, which is set based on the temperature at the start of light emission of the light-emitting element, when the temperature of the display device increases. [Configuration 10] The display device according to configuration 1, wherein the voltage control means does not change the drive voltage, which is set based on the temperature at the start of light emission of the display device, for a predetermined period of time from the start of light emission of the light-emitting element. [Configuration 11] 11. The display device according to any one of configurations 1 to 10, wherein the voltage control means controls the drive voltage based on a look-up table that stores a relationship between a temperature of the display device and the drive voltage. [Configuration 12] 12. The display device according to any one of configurations 1 to 11, wherein the predetermined limited range is a range in which a change in the amount of light of the light-emitting element due to a change in the drive voltage is within 3%. [Configuration 13] The light-emitting element emits light when a current flows due to a potential difference between a first voltage and a second voltage, 13. The display device according to any one of configurations 1 to 12, wherein the voltage control means controls the drive voltage by changing the second voltage while the first voltage is kept constant. [Configuration 14] A light emitting element driven by an electric current; a voltage control means for controlling a drive voltage for driving the light emitting element based on a temperature of the display device; The display device according to claim 1, wherein the voltage control means changes the drive voltage when the display luminance of the display device is changed. [Configuration 15] The display brightness is a setting of the brightness of the screen, 15. The display device according to configuration 14, wherein the brightness of the screen is set by a user operation or automatically. [Configuration 16] the change in the display luminance is a change in a display target, 15. The display device according to configuration 14, wherein the display object is at least one of a live view image, a menu screen, and a playback image. [Configuration 17] The voltage control means predicts a temperature change of the display device after a display luminance of the display device is changed, controlling the amount of change in the drive voltage per unit time based on the predicted temperature so as not to exceed a predetermined limit range; 17. The display device according to any one of configurations 14 to 16, wherein the predetermined limit range is determined based on a relationship between a change in the drive voltage and a change in the luminance of the light emitting element. [Configuration 18] 18. The display device according to configuration 17, wherein the amount of change in the drive voltage per unit time includes at least one of the amount of change in the drive voltage at one time and a period for changing the drive voltage. [Configuration 19] 19. The display device according to configuration 17 or 18, wherein the predetermined limit range is different when the temperature of the display device is rising and when the temperature is falling. [Configuration 20] 20. The display device according to any one of configurations 17 to 19, wherein the predetermined limit range is determined based on a relationship between a change in temperature of the display device and a change in the drive voltage. [Configuration 21] 19. The display device according to configuration 18, wherein the amount of change in the driving voltage during a temperature rise of the display device is smaller than the amount of change in the driving voltage during a temperature drop of the display device. [Configuration 22] 19. The display device according to configuration 18, wherein a period for changing the drive voltage when the temperature of the display device is increasing is shorter than a period for changing the drive voltage when the temperature of the display device is decreasing. [Configuration 23] The light-emitting element emits light when a current flows due to a potential difference between a first voltage and a second voltage, 23. The display device according to any one of configurations 14 to 22, wherein the voltage control means controls the drive voltage by changing the second voltage while the first voltage is kept constant. [Configuration 24] The display device described in any one of configurations 17 to 22, characterized in that when the driving voltage falls below a voltage required to make the light-emitting element emit light, the voltage control means changes the driving voltage to a voltage at which the light-emitting element can emit light within the specified limit range, regardless of whether the display brightness of the display device changes. [Configuration 25] A method for controlling a display device including a light-emitting element driven by a current, comprising the steps of: a voltage control step of controlling a drive voltage for driving the light-emitting element based on a temperature of the display device; In the voltage control step, a change amount of the driving voltage per unit time is controlled so as not to exceed a predetermined limit range; The control method according to claim 1, wherein the predetermined limit range is determined based on a relationship between a change in the drive voltage and a change in the light emission luminance of the light emitting element. [Configuration 26] A method for controlling a display device including a light-emitting element driven by a current, comprising the steps of: a voltage control step of controlling a drive voltage for driving the light-emitting element based on a temperature of the display device; The control method, wherein the voltage control step changes the drive voltage when the display luminance of the display device is changed. [Configuration 27] A program for causing a computer to function as a voltage control means for a display device according to any one of configurations 1 to 24. [Explanation of symbols]

[0103] 1...display device, 2...control section, 3...imaging section, 4...storage section, 10...imaging device, 101...unit pixel, 110...light emitting element, 600...temperature detection section

Claims

1. A light-emitting element driven by current, voltage control means for controlling a driving voltage for driving the light-emitting element based on at least one of the temperature and the display luminance of the display device, the driving voltage decreasing as the temperature of the display device increases, and the driving voltage decreasing as the display luminance of the display device decreases; the voltage control means controls such that a change amount of the driving voltage per unit time does not exceed a predetermined limit range; The display device according to claim 1, wherein the predetermined limit range is determined based on a relationship between a change in the driving voltage and a change in the light emission luminance of the light-emitting element.

2. The display device according to claim 1, wherein the change amount of the driving voltage per unit time includes at least one of a change amount of the driving voltage at one time and a period of changing the driving voltage.

3. The display device according to claim 1, wherein the predetermined limit range is different when the temperature of the display device rises and when it falls.

4. The display device according to claim 1, wherein the predetermined limit range is determined by a relationship between a change in the temperature of the display device and a change in the driving voltage.

5. having temperature detection means for detecting the temperature of the display device; The display device according to claim 1, wherein the voltage control means controls the driving voltage based on the temperature detected by the temperature detection means at a predetermined period.

6. The display device according to claim 2, wherein the change amount of the driving voltage at one time when the temperature of the display device rises is smaller than the change amount of the driving voltage at one time when the temperature of the display device falls.

7. The display device according to claim 2, wherein a period of changing the driving voltage when the temperature of the display device rises is shorter than a period of changing the driving voltage when the temperature of the display device falls.

8. The display device according to claim 1, wherein the voltage control means does not change the driving voltage set based on the temperature at the start of light emission of the light-emitting element when the temperature of the display device rises.

9. The display device according to claim 1, wherein the voltage control means does not change the driving voltage set based on the temperature at the start of light emission of the display device for a predetermined time from the start of light emission of the light-emitting element.

10. The display device according to claim 1, wherein the voltage control means controls the drive voltage based on a look-up table storing the relationship between the temperature of the display device and the drive voltage.

11.

12. The display device according to claim 1, wherein the predetermined limit range is a range in which the change in the amount of light of the light-emitting element due to the change in the drive voltage is within 3%.

13. The light-emitting element emits light when current flows due to the potential difference between a first voltage and a second voltage.

14. The display device according to claim 1, wherein the voltage control means controls the drive voltage by changing the second voltage while the first voltage is constant.

15. A light-emitting element driven by current, and voltage control means for controlling the drive voltage for driving the light-emitting element based on the temperature of the display device, wherein the voltage control means changes the drive voltage when the display target of the display device is changed,

16. The display device, wherein the display target includes at least one of a live view image, a menu screen, and a playback image.

17. The light-emitting element emits light when current flows due to the potential difference between a first voltage and a second voltage.

18. The display device according to claim 17, wherein the voltage control means controls the drive voltage by changing the second voltage while the first voltage is constant.

19. A control method for a display device including a light-emitting element driven by current, comprising a voltage control step of controlling the drive voltage for driving the light-emitting element based on at least one of the temperature of the display device and the display luminance, and controlling such that the drive voltage decreases as the temperature of the display device increases and the drive voltage decreases as the display luminance of the display device decreases, wherein in the voltage control step, the change amount of the drive voltage per unit time is controlled not to exceed a predetermined limit range,

20. The control method, wherein the predetermined limit range is determined based on the relationship between the change in the drive voltage and the change in the emission luminance of the light-emitting element.

21. A control method for a display device including a light-emitting element driven by current, comprising a voltage control step of controlling the drive voltage for driving the light-emitting element based on the temperature of the display device, wherein in the voltage control step, the drive voltage is changed when the display target of the display device is changed. The control method is characterized in that the display target includes at least one of a live view image, a menu screen, and a playback image.

17. A program for causing a computer to function as the voltage control means of the display device according to any one of claims 1 to 14.

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