The present application claims priority from Japanese application serial no. 2007-237165 filed on Sep. 12, 2007, the content of which is hereby incorporated by reference into this application.
1. Field of the Invention
The present invention relates to a display device whose luminance is controllable in accordance with a current quantity applied to a display element, or a light emitting time period. More particularly, it relates to a display device which is configured of display elements represented by an emissive type, also termed “organic EL (ElectroLuminescence) or organic light emitting diodes”.
2. Description of the Related Art
Owing to the spread of various information processors, there are various display devices complying with roles. Among them, a display employing organic EL elements (an organic EL display device) has been highlighted as a display device of emissive type. An OLED or the like light emitting element for use in the display device does not require backlight as in a liquid-crystal display (liquid-crystal display device), and it is suited to a lower power consumption. Moreover, as compared with the liquid-crystal display, the organic EL element has merits such as a higher pixel visibility and a higher response rate.
Further, the organic EL element has characteristics similar to those of a diode, and its luminance can be controlled by a current quantity which is caused to flow through the element. Driving methods in such an emissive type display device are disclosed in JP-A-2006-91709, etc. Besides, regarding a configuration in which a touch panel or the like input device is incorporated into such a display device, JP-A-10-49305, etc. can be mentioned.
As the characteristic of the organic EL element (OLED), the internal resistance value of the element changes, depending upon a service period or an ambient environment. Especially, the organic EL element has the property that, when the service period increases, the internal resistance heightens secularly, so a current to flow through the element decreases. Therefore, when the pixels of an identical place within a screen, for example, a menu display are lit up for a long time, an burn-in phenomenon occurs in the place. For coping with the burn-in phenomenon, the state of the pixel needs to be detected. A method for the detection is one in which the pixel state is detected in the blanking period of display data. In the blanking period, the pixel is not caused to emit light, and hence, a displaying voltage is not applied. Therefore, using a power source separate from a power source for the light emission, a certain fixed current is applied to the pixel in the blanking period, and a voltage in this state is detected, whereby a degradation in the burn-in is detected from the change of the voltage. Besides, since the current cannot be applied to the pixel during a display period, a circuit for the above detection is used only in the blanking period.
Meanwhile, in order to detect a temperature characteristic and an ambient brightness and to detect a touch panel or the like input sensor used, similar detection circuits are respectively necessitated. In furnishing the system of the display device with the detection circuits, further controllers or the like control means are necessitated for coping with the burn-in detection, the temperature characteristic detection and the ambient brightness detection, and a circuit scale becomes large.
An object of the present invention is to cope with the detection of the burn-in degradation of an OLED, the detection of the temperature characteristic of the OLED, the detection of a sensor panel, etc. by a circuit of one detection loop, and to share the circuit of one detection loop, thereby to reduce a circuit scale.
According to one aspect of performance of the invention, a display device includes independent power sources for a display use and a detection use, display elements, switches for independently connecting the power sources and the individual elements, a circuit for controlling the switches, and a variable amplifier as detection means, which has the function of reading the state of each pixel and the internal detection function of generating the read result in a controllable shape, and which can change-over a detection result from an external sensor and an internal detection result through a timing control, so as to convert the detection result into a value corresponding to a subject to-be-detected, whereby the detections can performed by the detection circuit of one loop.
In the above configuration, detection devices which are connected to the detection circuit are sequentially changed-over in a display period and a blanking period, and the gain and timing of an adaptive amplifier are controlled in accordance with the subject to-be-detected, thereby to obtain an image display device in which the plurality of detection devices are detectable with the identical detection circuit.
The circuit and controller of the detection loop are shared for a plurality of detection loops, whereby the circuit scale can be reduced.
By way of example, according to the first embodiment of the invention to be described later, an internal pixel state and an external detection device can be detected by an identical detection circuit. Besides, according to the second embodiment of the invention, a plurality of external detection devices and an internal pixel state can be detected by an identical detection circuit. In addition, according to the third embodiment of the invention, an internal pixel state and an external detection device which needs to be regularly detected can be detected by an identical detection circuit.
Now, the best mode for carrying out the present invention will be described in detail with reference to the drawings.
A RAM 5 and a CPU 6 are connected to the display driver 1 through a control bus 4. Although only the RAM 5 and the CPU 6 are mentioned as principal devices here, other devices such as a ROM and various I/O controllers may well be connected. The display driver 1 includes a controller 10, which controls various portions within the display driver 1. Besides, the controller 10 performs the controls of writing detection data from the various sensors, into the RAM 5, and fetching display data to be displayed in the display panel section 2, from the RAM 5.
A data line 11 and a detection line 14 are connected to the controller 10. Although only one data line 11 and only one detection line 14 are shown in
The input line serves to input several sorts of detection results to the controller 10. The detection results are converted into digital values by the A/D converter 15 through the adaptive amplifier 16, and the digital value is inputted to the controller 10. The adaptive amplifier 16 plays the role of clamping detection values of different voltage levels into a certain fixed range. The controller 10 controls the adaptive amplifier 16 and the detecting power source 18 through a control line 17. The driver 1 and the display panel section 2 are connected by a control line 19, while the driver 1 and the sensor section 3 are connected by a control line 20.
The control line 19 is connected with the data line 11 through a switch 21, and with the detection line 14 through a switch 22. The control line 20 is connected with the detection line 14 through a switch 23. The switches 21, 22 and 23 are controlled by a control line 24 led from the controller 10. The control line 24 may control the switches 21, 22 and 23 either independently or collectively, and this control line 24 is configured of a plurality of lines in the case of the independent controls. Various detection devices which include the temperature sensor, an illuminance sensor, a chromaticity sensor and a sound sensor, and the touch panel and other input devices, can be connected in the sensor section 3.
On the other hand,
The display control unit 52 transmission-controls the display data corrected by the correction control unit 51, in agreement with the timing of the display panel. The precharge control unit 53 fixes the voltage of the data line 11 in the detection mode, and it is used for improving a response rate. A changeover control unit 54 adjusts a signal timing within the controller 10 and the timing of an external signal. A signal selection unit 55 changes-over the outputs of the display control unit 52 and the precharge control unit 53 and transmits either output to the data line 11 under the control of the changeover control unit 54. The switch control unit 56 controls the control line 24.
This control line 24 controls the selection switches of lines led to the data line 11 and the detection line 14, and it consists of a single line or a plurality of lines in accordance with the control configuration of the switches. The amplifier control unit 57 controls the state of the adaptive amplifier from the changeover control unit 54, and in the case of employing the setting table in order to set the adaptive amplifier, and this amplifier control unit 57 alters the setting of the adaptive amplifier with the setting information of the table prepared in a memory 58.
Besides, this period corresponds to the temperature detection period 63 in the detection loop. In the control of the detection loop, the switch 23 is turned ON by the control line 32 in order to connect the detection line 14 and the control line 20 for the purpose of the temperature detection. Thus, in these periods, the temperature detection is performed while the display is being presented. Subsequently, in the control of the display loop, in order to connect the detection line 14 and the control line 19 in the blanking period 62, the switch 22 is turned ON by the control line 31, and the switch 21 is turned OFF by the control line 30. This period corresponds to the burn-in detection period 64 in the detection loop. In the control of the detection loop, the switch 23 is turned OFF by the control line 32 in order to disconnect the detection line 14 and the control line 20.
Thus, in such a period, the pixel state (for example, a voltage or current) is detected. Besides, in a case where the setting of the temperature detection state is a setting-A 65 and where the setting of the burn-in detection state is a setting-B 66, the adaptive amplifier is set in the state of the setting-A 65 during the temperature detection period 63, and it is set in the state of the setting-B 66 during the burn-in detection period 64, whereby the state of the amplifier is set. These operations are performed every frame, and the displays and detections are made compatible.
Subsequently, at a step 74, the signal selection unit 55 within the controller 10 is changed-over. At a step 75, the adaptive amplifier is set by the control line 17. At a step 76, the changeover switches are set by the control line 24. A detection flag is reset at a step 77, and a display flag is set at a step 78. The detection flag and the display flag are contained within the controller 10, and they serve to store the state of the display loop. The display period is decided at a step 79. The decision of the display period is rendered by a timer or a counter.
In a case where the display period has ended, it is shifted to the blanking period. The signal selection unit 55 within the controller 10 is changed-over at a step 80. The adaptive amplifier is set by the control line 17 at a step 81. The changeover switches are set by the control line 24 at a step 82. The display flag is reset at a step 83, and the detection flag is set at a step 84. The blanking period is decided at a step 85. The decision of the blanking period is rendered by a timer or a counter. In a case where the blanking period has ended, it is shifted to the display period, and the routine shifts to the step 74. In this example, the display flag and the detection flag are simultaneously changed-over, but they can also be changed-over with a time difference.
In a case where all the detections of one time have ended at the step 104, the routine shifts to a step 105. In a case where the display flag is “1” at the step 105, the routine waits until the display flag becomes “0”. When the display flag changes to “0”, the routine shifts to the step 101. In a case where the display flag is “0” at the step 101, the routine shifts to a step 106. In a case where the detection flag is “0” at the step 106, the routine shifts to the step 101, at which the state of the display flag is monitored. On the other hand, in a case where the detection flag is “1” at the step 106, the routine shifts to a step 107. Detections from the display panel section are performed at the step 107.
If the detection flag is in the state of “1” at a step 108, whether or not all the detections of one time have ended is judged at a step 109. When all the detections have not been ended, the operations from the step 107 are repeated. In a case where the detection flag is “0” at the step 108, it is indicated that the blanking period has ended in the course of the detection. Therefore, the routine shifts to the step 111. In a case where all the detections of one time have ended at the step 109, the routine shifts to a step 110. In a case where the detection flag is “1” at the step 110, the routine waits until the detection flag becomes “0”. When the detection flag changes to “0”, the routine shifts to the step 101. The step 111 executes an error process. As an example of the error process, in a case where the display period or the detection period has timed-out, a procedure is traced in which the interrupted state of the routine is transmitted from the controller 10 to the CPU 6, and in which the CPU 6 having received the signal executes the exceptional process of the operating system.
A control line 121 controls the connection of the control line 19 and the detection line 14 by the switch 22. A control line 122 controls the connection of the detection line 14 and any desired one of control lines 124, 125 and 126 by the corresponding one of the switches 123. Since the control lines 120, 121 and 122 can perform the independent controls, the ON/OFF operations of the switches 21, 22 and 123 can be controlled at any desired timings. Further, the switches 123 have a kind of selector configuration. Therefore, in a case where the control line 122 is formed of a single line, the switches 123 can be sequentially changed-over, and in a case where the control line 122 is formed of a plurality of lines, any desired changeover of the switches 123 becomes possible. The sorts of sensors which are changed-over by the switches 123 may be in any number.
In the control of the display loop, in order to connect the data line 11 and the control line 19 in a display period 61, the switch 21 is turned ON by the control line 120, and the switch 22 is turned OFF by the control line 121. Besides, in such a period, a temperature detection period 130 and an illuminance detection period 132 are alternately set every frame in the detection loop. In the control of the detection loop, accordingly, the switches 123 are selected by the control line 122 in order to connect the detection line 14 and the control line 124 when the temperature is detected, and to connect the detection line 14 and the control line 125 when the illuminance is detected. Thus, in these periods, the detections of the sensor sections are performed while displays are being presented.
Subsequently, in the control of the display loop, in order to connect the detection line 14 and the control line 19 in the blanking period 62, the switch 22 is turned ON by the control line 121, and the switch 21 is turned OFF by the control line 120. This period corresponds to an burn-in detection period 131 in the detection loop. In the control of the detection loop, in order to disconnect the detection line 14 and the control line 124 or 125, all the switches 123 are turned OFF by the control line 122. Thus, a pixel state is detected in such a period.
Besides, in a case where the setting of the temperature detection state is a setting-A 133, where the setting of the burn-in detection state is a setting-B 134, and where the setting of the illuminance detection state is a setting-C 135, the adaptive amplifier is set in the state of the setting-A 133 during the temperature detection period 130, it is set in the state of the setting-B 134 during the burn-in detection period 131, and it is set in the state of the setting-C 135 during the illuminance detection period 132, whereby the state of the amplifier is set. The detection operations by the different sensors are performed in 2-frame units, and the displays and detections are made compatible.
An input device such as the touch panel needs to be accessed at fixed intervals, and when the interval of the access changes, an inconvenience sometimes occurs in a process after the detection. That is, a highest priority level can be set for the specified input device. Reference numeral 60 designates one frame period, which is constituted by a display period and a blanking period in a display loop. In the detection loop, one frame period is constituted by temperature detection periods, touch panel detection periods, and burn-in detection periods.
It is assumed that the display panel, the temperature detection sensor and the touch panel sensor are respectively connected to the control line 19, the control line 124 and the control line 125. In the control of the display loop, in order to connect the data line 11 and the control line 19 in the display period 61, the switch 21 is turned ON by the control line 120, and the switch 22 is turned OFF by the control line 121. Besides, in this period, the temperature detection periods 140 and the touch panel detection periods 141 are alternately set within one frame in the detection loop. In the control of the detection loop, the switches 123 are selected by the control line 122 in order to connect the detection line 14 and the control line 124 when the temperature is detected, and to connect the detection line 14 and the control line 125 when the touch panel is detected. Thus, in such a period, the detections of the sensor sections are performed while the display is being presented.
Subsequently, in the control of the display loop, the switch 21 is turned OFF by the control line 120 during the blanking period 62. In this embodiment, the control line 125 needs to be connected to the control line 14 even during the blanking period. Therefore, in order to alternately connect the control line 19 and the control line 125 to the detection line 14, either of the switch 22 and the switch 123 is turned ON, and the other of them is turned OFF, by the control line 121 and the control line 122. Thus, an burn-in detection period 142 is set in a state where the detection line 14 and the control line 19 are connected, and the touch panel detection period 141 is set in a state where the detection line 14 and the control line 125 are connected.
Besides, in a case where the setting of the temperature detection state is a setting-A 143, where the setting of the touch panel detection state is a setting-B 144, and where the setting of the burn-in detection state is a setting-C 145, the adaptive amplifier is set in the state of the setting-A 143 during the temperature detection period 140, in the state of the setting-B 144 during the touch panel detection period 141, and in the state of the setting-C 145 during the burn-in detection period 142, whereby the state of the amplifier is set. The series of detection operations are performed in single-frame units, and the displays and the detections are made compatible.
The invention is applicable to a simple display device or a panel incorporating the display device, or the display device of an information processing terminal.
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