Display device, image signal processing method, and program

There is provided a display device equipped with a display unit, the display device including a receiving part for receiving a difference signal of a plurality of channels including an image signal and content identification information inserted in a blanking period and outputting the image signal and the content identification information; a light emission amount regulation part for setting a reference duty according to image information of the image signal; an adjustment part for adjusting so that an actual duty is within a predetermined range based on the reference duty and an adjustment signal and adjusting a gain of the image signal so that a light emission amount defined by the actual duty and the gain of the image signal becomes the same as the light emission amount defined by the reference duty; and an adjustment signal generation part for generating the adjustment signal based on the content identification information.

CROSS REFERENCES TO RELATED APPLICATIONS

The present invention contains subject matter related to Japanese Patent Application JP 2007-298618 filed in the Japan Patent Office on Nov. 16, 2007, the entire contents of which being incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a display device, an image signal processing method, and a program.

2. Description of the Related Art

In recent years, various display devices such as organic EL display (organic Electro-Luminescence display; or also referred to as OLED display (Organic Light Emitting Diode display)), FED (Field Emission Display), LCD (Liquid Crystal Display), PDP (Plasma Display Panel), and projector are being developed as the display device replacing the CRT display (Cathode Ray Tube display).

Among the various display devices, the organic EL display is a self-light emitting display device that utilizes electroluminescence phenomenon, and is being given particular attention as a display device of the next generation as it excels in moving image characteristic, field angle characteristic, color reproducibility, and the like compared to the display device that desirably additionally includes a light source such as the LCD. The electroluminescence phenomenon is a phenomenon in which when the electron state of a substance (organic EL element) changes from a ground state to an excited state by electric field and returns from an unstable excited state to a stable ground state, the difference energy is released as light.

In the related art, various techniques related to the self-light emitting display device are being developed. The technique related to a light emission time control per unit time in the self-light emitting display device is disclosed in Japanese Patent Application Laid-Open No. 2006-38967 and the like.

Furthermore, in recent years, HDMI (High-Definition Multimedia Interface) is being widely used as a communication interface for connecting an image reproducing device such as DVD recorder, set-top box or a game machine including Play Station (registered trademark) series, and the display device described above for displaying the image reproduced by the image reproducing device.

The HDMI is the communication interface for transmitting at high-speed a non-compressed digital image signal and a digital audio signal associated with the relevant image signal. More specifically, the HDMI is defined with TMDS (Transition Minimized Differential signaling) channel for transmitting at high speed the image signal and the audio signal in one direction from an HDMI source to an HDMI sink, a CEC line (Consumer Electronics Control Line) for enabling bidirectional communication between the HDMI source and the HDMI sink, and the like, where the digital image signal, the audio signal, and various control signals can be transmitted and received together on one cable.

SUMMARY OF THE INVENTION

The technique of the related art related to the light emission time control per unit time detects information indicating whether the image represented by the image signal in frame units is a moving image or a still image based on the externally input image signal, and adjusts a maximum signal tolerance level and a duty ratio of the image signal based on the detected information. Specifically, the technique of the related art related to the light emission time control per unit time reduces the duty ratio which defines the light emission time per frame and raises the maximum signal tolerance level when the detected information indicates moving image. The technique of the related art related to the light emission time control per unit time increases the duty ratio which defines the light emission time per frame and lowers the maximum signal tolerance level when the detected information indicates still image.

However, if the image represented by the image signal transmitted through the high-speed communication interface such as HDMI is an image of high-definition HD (High Definition) resolution, an enormous signal processing is carried out to detect the information indicating whether the image represented by the image signal in frame units is a moving image or a still image. Thus, if the image represented by the image signal is an image of high-definition HD (High Definition) resolution, the possibility of occurrence of mistaken detection and delay in processing is high. In this case, the change in discontinuous brightness and flickers of the image displayed at a timing of switching of the display control may be visually recognized by the user as an uncomfortable feeling. Therefore, higher image quality may not be achieved in the technique of the related art related to the light emission time control per unit time.

In view of the above issues, it is desirable to provide a novel and improved display device, an image signal processing method, and a program capable of achieving higher image quality by controlling the light emission time in which the light emitting element emits light per unit time according to the type of content of the input image signal and also controlling the gain of the image signal.

According to an embodiment of the present invention, there is provided a display device equipped with a display unit in which light emitting elements which self-emits light according to current amount are arranged in a matrix form, the display device including a receiving part for receiving a difference signal of a plurality of channels including an image signal and content identification information for defining a type of content inserted in a blanking period of at least one channel, and outputting the image signal and the content identification information; a light emission amount regulation part for setting a reference duty for defining a light emission amount per unit time in the respective light emitting element according to image information of the image signal; an adjustment part for adjusting so that an actual duty defining a light emission time for light emitting the light emitting element per unit time is within a predetermined range based on the reference duty and an adjustment signal, and adjusting a gain of the image signal so that a light emission amount defined by the actual duty and the gain of the image signal becomes the same as the light emission amount defined by the reference duty; and an adjustment signal generation part for generating the adjustment signal for setting a lower limit value of the actual duty based on the content identification information.

According to such configuration, higher image quality can be achieved by controlling the light emission time in which the light emitting element emits light per unit time according to the type of content of the input image signal, and also controlling the gain of the image signal.

The adjustment part may include a light emission time adjustment part for setting a lower limit value according to the adjustment signal, and adjusting the reference duty to the set lower limit value or an upper limit value defined in advance to output as the actual duty when the reference duty set by the light emission amount regulation part is outside the predetermined range; and a gain adjustment part for adjusting the gain of the image signal based on the reference duty set by the light emission amount regulation part and the actual duty output from the light emission time adjustment part.

According to such configuration, higher image quality can be achieved by setting the lower limit value of the actual duty according to the adjustment signal and also controlling the light emission time per unit time and the gain of the image signal.

The gain adjustment part may attenuate the gain of the image signal according to an increase ratio of the actual duty with respect to the reference duty when the light emission time adjustment part outputs the actual duty adjusted to the lower limit value.

According to such configuration, the light emission time and the image signal both can be adjusted while maintaining the light emission amounts the same.

The gain adjustment part may amplify the gain of the image signal according to a decrease ratio of the actual duty with respect to the reference duty when the light emission time adjustment part outputs the actual duty adjusted to the upper limit value.

According to such configuration, the light emission time and the image signal both can be adjusted while maintaining the light emission amounts the same.

The gain adjustment part may include a first gain correction portion for multiplying the input image signal and the reference duty; and a second gain correction portion for dividing the corrected image signal output from the first gain correction portion with the actual duty output from the light emission time adjustment part.

According to such configuration, the light emission time and the image signal both can be adjusted while maintaining the light emission amounts the same.

The adjustment signal generation part may generate the adjustment signal according to information of the content represented by the content identification information when the information of the content represented by the content identification information represents the same content continuously for a predetermined number of times.

According to such configuration, lowering in image quality originating from the generation of the adjustment signal/control signal over a plurality of times in a short period of time such as one second can be prevented.

An average luminance calculation part for calculating an average of luminance in a predetermined period of the image signals may be further arranged; where the light emission amount regulation part may set the reference duty according to the average luminance calculated in the average luminance calculation part.

According to such configuration, overcurrent is prevented from flowing to the light emitting element by controlling the light emission time per unit time.

The light emission amount regulation part may store a lookup table in which the luminance of the image signal and the reference duty are corresponded, and uniquely sets the reference duty according to the average luminance calculated in the average luminance calculation part.

According to such configuration, the light emission amount per unit time can be regulated.

The predetermined period for the average luminance calculation part to calculate the average of the luminance may be one frame.

According to such configuration, the light emission time in each frame period can be more finely controlled.

The average luminance calculation part may include a current ratio adjustment part for multiplying a correction value for every primary color signal based on a voltage—current characteristic for the every primary signal of the image signal, and an average value calculation part for calculating the average of the luminance in the predetermined period of the image signal output from the current ratio adjustment part.

According to such configuration, an image faithfully following the input image signal can be displayed.

A linear conversion part for gamma correcting the image signal to correct to a linear image signal may be further arranged; wherein the image signal to be input to the light emission amount regulation part may be the corrected image signal.

According to such configuration, overcurrent is prevented from flowing to the light emitting element by controlling the light emission time per unit time.

A gamma conversion part for performing gamma correction corresponding to a gamma characteristic of the display unit on the image signal may be further arranged.

According to such configuration, an image faithfully following the input image signal can be displayed.

According to the embodiments of the present invention described above, there is provided an image signal processing method in a display device equipped with a receiving part for receiving a difference signal of a plurality of channels including an image signal and content identification information for defining a type of content inserted in a blanking period of at least one channel and outputting the image signal and the content identification information, and a display unit in which light emitting elements which self-emits light according to current amount are arranged in a matrix form, the image signal processing method including the steps of generating an adjustment signal for setting a lower limit of an actual duty defining a light emission time for light emitting the light emitting element per unit time based on the content identification information; setting a lower limit value of the actual duty according to the adjustment signal generated in the generating step; setting a reference duty for defining a light emission amount per unit time in the respective light emitting element according to image information of the image signal; and adjusting so that the actual duty is within a predetermined range based on the reference duty and the lower limit value set in the setting step, and adjusting a gain of the image signal so that a light emission amount defined by the actual duty and the gain of the image signal becomes the same as the light emission amount defined by the reference duty.

Through the use of such method, higher image quality can be achieved by controlling the light emission time in which the light emitting element emits light per unit time according to the type of content of the input image signal, and also controlling the gain of the image signal.

According to the embodiments of the present invention described above, there is provided a program used in a display device equipped with a receiving part for receiving a difference signal of a plurality of channels including an image signal and content identification information for defining a type of content inserted in a blanking period of at least one channel and outputting the image signal and the content identification information, and a display unit in which light emitting elements which self-emits light according to current amount are arranged in a matrix form, the program causing a computer to execute the steps of generating an adjustment signal for setting a lower limit of an actual duty defining a light emission time for light emitting the light emitting element per unit time based on the content identification information; setting a lower limit value of the actual duty according to the adjustment signal generated in the generating step; setting a reference duty for defining a light emission amount per unit time in the respective light emitting element according to image information of the image signal; and adjusting so that the actual duty is within a predetermined range based on the reference duty and the lower limit value set in the setting step, and adjusting a gain of the image signal so that a light emission amount defined by the actual duty and the gain of the image signal becomes the same as the light emission amount defined by the reference duty.

According to such program, higher image quality can be achieved by controlling the light emission time in which the light emitting element emits light per unit time according to the type of content of the input image signal, and also controlling the gain of the image signal.

According to the embodiments of the present invention described above, higher image quality can be achieved by controlling the light emission time in which the light emitting element emits light per unit time according to the type of content of the input image signal, and also controlling the gain of the image signal.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereafter, preferred embodiments of the present invention will be described in detail with reference to the appended drawings. Note that in this specification and the appended drawings, structural elements that have substantially the same functions and structures are denoted with the same reference numerals and a repeated explanation of these structural elements is omitted.

(Configuration Example of Image Display System According to an Embodiment of the Present Invention)

First, one example of a configuration of an image display system according to the embodiment of the present invention will be described.FIG. 1is an explanatory view showing one example of a configuration of the image display system according to the embodiment of the present invention. With reference toFIG. 1, the image display system according to the embodiment of the present invention includes image reproducing devices200,300, . . . for reproducing image data and outputting an image signal representing the reproduced image, and a display device100for displaying the image based on the image signal output from the image reproducing device. The image reproducing devices200,300, . . . and the display device100are connected with communication interfaces50,60, . . . .

An organic EL display, which is a self-light emitting display device, will be hereinafter described by way of example as the display device100. The HDMI will be hereinafter described by way of example as communication interfaces50,60, . . . , but the communication interface in the image display system according to the embodiment of the present invention is not limited to the HDMI, and may be a communication interface using D terminal, and the like.

The outline of the configuration of the image reproducing devices200,300, . . . , and the display device100will be described below.FIG. 2is a block diagram showing an outline of the configuration of the image reproducing device and the display device according to the embodiment of the present invention. InFIG. 2, the image reproducing device200will be described by way of example, but the image reproducing device300, . . . can also have a similar configuration.

With reference toFIG. 2, the image reproducing device200includes a storage202, a reproduction part204, and an HDMI source206.

The image reproducing device200is configured to have an MPU (Micro Processing Unit), and the like, and may include a control part (not shown) for performing various calculation processes using a control program etc. and controlling the entire image reproducing device200, a ROM (Read Only Memory; not shown) recorded with program and control data such as calculation parameter used by the control part (not shown), a RAM (Random Access Memory; not shown) for primary storing the program etc. to be executed by the control part (not shown), an operation part (not shown) operable by the user, and the like. The image reproducing device200connects each configuring elements with a bus serving as a data transmission path.

The operation part (not shown) may be an operation input device such as keyboard and mouse, a button, a direction key, a rotatable selector such as jog-dial, or a combination thereof, but is not limited thereto.

The storage202is a storage member arranged in the image reproducing device200, and stores image data and various files such as application and application data. The image data includes data (indicate still image) recorded in a still image format such as JPEG (Joint Photographic Experts Group), bitmap, and the like, and data (indicate moving image) recorded in a moving image format such as WMV (Windows Media Video), H.264/MPEG-4 AVC (H.264/Moving Picture Experts Group phase-4 Advanced Video Coding), and the like, but is not limited thereto.

The storage202includes a magnetic recording medium such as hard disc, and a non-volatile memory such as EEPROM (Electrically Erasable and Programmable Read Only Memory), flash memory, MRAM (Magnetoresistive Random Access Memory), FeRAM (Ferroelectric Random Access Memory), PRAM (Phase change Random Access Memory) and the like, but is not limited thereto.

InFIG. 2, a configuration in which the image reproducing device200includes the storage202is shown, but the image reproducing device according to the embodiment of the present invention is not limited to the configuration including the storage. The image reproducing device according to the embodiment of the present invention includes an optical disc drive for reading the image data recorded in the still image format or the moving image format from an optical disc serving as an external recording medium, and a slot for accommodating an external memory serving as the external recording medium, and is capable of reading the image data from the optical disc and the external memory. The optical disc may be DVD disc, Blu-Ray disc, HD DVD disc, and the like, but is not limited thereto. The external memory may be memory stick, SD memory card, and the like, but is not limited thereto. Needless to say, the image reproducing device according to the embodiment of the present invention may include the storage, and/or, the optical disc drive, and/or the slot.

The reproduction part204decodes the image data and the audio data associated with the image data read from the storage202and the external recording medium in MPEG (Moving Picture Experts Group) method and the like. The reproduction part204then transmits the image signal (image signal corresponding to the image represented by the image data) and the audio signal (audio signal corresponding to the audio represented by the audio data) of baseband to an external device such as display device100via the HDMI source206.

According to the communication complying with the HDMI, the HDMI source206transmits the image signal and the audio signal of the baseband transmitted from the reproduction part204in one direction to the display device100in a difference signal of a plurality of channels. That is, the HDMI source206functions as a transmission part.

The HDMI source206inserts the content type of the image represented by the image signal to transmit, that is, the content identification information for identifying to what content the image represented by the image signal is related during a blanking period of the image signal to transmit. In other words, the HDMI source206functions as an identification information insertion part. The HDMI source206can transmit the content identification information using at least one channel of the plurality of channels. The HDMI source206is not limited to the content identification information, and various control data can be transmitted using one of the plurality of channels. The details of the HDMI source206and the content identification information will be hereinafter described.

According to the configuration shown inFIG. 2, the image reproducing device200reproduces the image data, and can output the image signal representing the reproduced image etc. in the difference signal of a plurality of channels.

The display device100includes an HDMI sink102, a control part104, a signal processing part106, and a panel108.

The display device100may include a ROM (not shown) recorded with program and control data such as calculation parameter used by the control part104, a RAM (not shown) for primary storing the program etc. to be executed by the control part104, an operation part (not shown) operable by the user, a recordation part130, a storage132, an overcurrent detection part134, a data driver136, a gamma circuit138, and the like. The display device100connects each configuring elements with a bus serving as a data transmission path.

The operation part (not shown) may be an operation input device such as keyboard and mouse, a button, a direction key, a rotatable selector such as jog-dial, or a combination thereof, but is not limited thereto.

According to the communication complying with the HDMI, the HDMI sink102receives the difference signal of a plurality of channels transmitted in one direction from the HDMI source206of the image reproducing device200, and outputs image signal, audio signal, and various control data such as content identification information. In other words, the HDMI sink102functions as a receiving part. InFIG. 2, an example where the image signal and the control data are output from the HDMI sink is shown. The audio signal received by the HDMI sink102is output to an audio signal processing circuit (not shown) and the like, and after being subjected to a predetermined signal processing such as gain adjustment, the audio is output from an audio reproduction part (not shown) such as speaker.

The control part104is configured to have MPU and the like, and is capable of controlling the entire display device100.

The control part104processes the control data transmitted from the HDMI sink102, and transmits an adjustment signal (to be hereinafter described) and a control signal (to be hereinafter described) for controlling various processes in the signal processing part106based on the control data to the signal processing part106. The control part104generates the control signal (to be hereinafter described) and the adjustment signal (to be hereinafter described) based on the content identification information. Therefore, the control part104functions as an adjustment signal generation part and a control signal generation part.

The control part104may perform signal processing on the signal transmitted from the signal processing part106, and forward the processing result to the signal processing part106.

The signal processing part106performs a predetermined process on the image signal transmitted from the HDMI sink102, and transmits the processed image signal to the panel108. The details of the signal processing part106will be hereinafter described.

The panel108is a display unit arranged in the display device100. The panel108includes a plurality of pixels arranged in a matrix form (rows and columns). The panel108includes a data line to be applied with an electric signal corresponding to the image signal corresponding to each pixel, and a scan line to be applied with a selection signal. For instance, the panel108for displaying an image of SD (Standard Definition) resolution has at least 640 I·480=307200 (data line I·scan line) pixels, and has 640 I·480 I·3=921600 (data line I·scan line I·number of sub-pixels) sub-pixels if the relevant pixel includes sub-pixels of red (hereinafter referred to as “R”), green (hereinafter referred to as “G”), and blue (hereinafter referred to as “B”) for color display. Similarly, the panel108for displaying the image of HD resolution has 1920 I·1080 pixels, and has 1920 I·1080 I·3 sub-pixels in the case of color display.

When the light emitting element configuring the sub-pixel of each pixel is an organic EL element, The IL characteristic (current-light emission amount characteristic) becomes linear. The display device100includes a gamma conversion part162(to be hereinafter described), where the relationship between the light quantity of a subject represented by the image signal and the current amount to be applied to the light emitting element can become linear by performing gamma correction. Therefore, the display device100can display a moving image or a still image faithfully following the image signal since the relationship between the light quantity of the subject represented by the image signal and the light emission amount is linear.

Furthermore, the panel108includes a pixel circuit (not shown) for controlling the current amount to be applied for every pixel. The pixel circuit is configured to have a switch element and a drive element for controlling the current amount by the scan signal and the voltage signal to be applied, and a capacitor for holding the voltage signal. The switch element and the drive element are configured to have a thin film transistor and the like. Since the respective VI characteristic differs in the transistor arranged in the pixel circuit, the VI characteristic of the panel108as a whole differs from the VI characteristic of the panel of another display device having the same configuration as the display device100. Therefore, the display device100performs gamma correction corresponding to the panel108so as to cancel out the VI characteristic of the panel108in the gamma conversion part162(to be hereinafter described) and obtain a linear relationship between the light quantity of the subject represented by the image signal and the current amount to be applied to the light emitting element.

According to the configuration shown inFIG. 2, the display device100according to the embodiment of the present invention receives the difference signal of a plurality of channels transmitted from the image reproducing device200, and can display the moving image or the still image corresponding to the image signal contained in the difference signal. The configuration of the signal processing part106of the display device100will be hereinafter described.

According to the configuration shown inFIG. 2, the image display system according to the embodiment of the present invention can display the moving image or the still image corresponding to the image signal contained in the difference signal of a plurality of channels transmitted from the image reproducing device200in the display device100.

(Example of Communication Interface According to the Embodiment of the Present Invention)

The communication interface according to the embodiment of the present invention will be described below in more detail.

[Outline of Communication Interface]

First, the outline of the communication interface according to the embodiment of the present invention will be shown.FIG. 3is an explanatory view showing one example of the communication interface according to the embodiment of the present invention, and specifically shows a configuration example of the HDMI source206and the HDMI sink102shown inFIG. 2.

In effective image period (hereinafter referred to as “active video period”), which is a period excluding a horizontal blanking period and a vertical blanking period from a period (hereinafter referred to as “video field”) from a certain vertical synchronous signal to a next vertical synchronous signal, the HDMI source206transmits a difference signal corresponding to the image signal of a baseband worth one screen to the HDMI sink102in one direction in a plurality of channels.

In the horizontal blanking period and the vertical blanking period, the HDMI source206transmits a difference signal corresponding to auxiliary data such as audio signal and control packet associated with the image signal of the baseband to the HDMI sink102in one direction in a plurality of channels.

The HDMI source206includes a source signal processing part210and an HDMI transmitter212. The source signal processing part210transmitted with the image signal and the audio signal of the baseband from the reproduction part204transmits the image signal (video) and the audio signal (audio) to the HDMI transmitter212after performing a predetermined process. The source signal processing part210can also exchange control information, information notifying status (control/status), and the like as necessary with the HDMI transmitter212.

The HDMI transmitter212converts the image signal of the baseband transmitted from the source signal processing part210to the corresponding difference signal, and transmits the relevant difference signal in one direction to the HDMI sink102connected by way of a cable using three TMDS channels0to2(one example of the plurality of channels).

The HDMI transmitter212converts the auxiliary data such as audio signal and control packet of the baseband, and the control data such as vertical synchronous signal (VSYNC), the horizontal synchronous signal (HSYNC), the content identification information, and the like transmitted from the source signal processing part210to the corresponding difference signal, and transmits the relevant difference signal in one direction to the HDMI sink102using the TMDS channels0to2. InFIG. 3, three TMDS channels0to2are shown, but the number of TMDS channels in the embodiment of the present invention is not limited to three.

Furthermore, the HDMI transmitter212transmits to the HDMI sink102in a TMDS clock channel synchronized with the image signal to be transmitted using the TMDS channels0to2.

The HDMI sink102receives the difference signal corresponding to the image signal of the baseband transmitted from the HDMI source206by the plurality of channels in the active video period. The HDMI sink102receives the audio signal and the difference signal corresponding to the control data transmitted from the HDMI source206by the plurality of channels in the horizontal blanking period and the vertical blanking period.

The HDMI sink102includes a HDMI receiver110and a sink signal processing part112. The HDMI receiver110receives the difference signal corresponding to the image signal, the difference signal corresponding to the audio signal, and the difference signal corresponding to the control data transmitted using the TMDS channels0to2from the HDMI source206in synchronization with a pixel clock transmitted on a TMDS clock channel from the HDMI source206.

The HDMI receiver110converts the received difference signals respectively to the corresponding image signal, the audio signal, and the control data, and appropriately transmits the same to the sink signal processing part112.

The sink signal processing part112performs a predetermined process on various signals transmitted from the HDMI receiver110. The sink signal processing part112transmits the control data to the control part104, the image signal to the signal processing part106, and the audio signal to the audio signal processing circuit (not shown) and the like. The sink signal processing part112can exchange control information, information notifying status (control/status), and the like as necessary with the HDMI receiver110.

As described above, the communication interface according to the embodiment of the present invention can transmit the image signal, the audio signal, the control data, and the like from the HDMI source206to the HDMI sink102using the plurality of TMDS channels and the TMDS clock channel.

The transmission channel of the communication interface (HDMI) according to the embodiment of the present invention may also include transmission channels referred to as DDC (Display Data Channel) and CEC line in addition to the TMDS channels0to2, and the TMDS clock channel.

The DDC is used by the HDMI source206to read out E-EDID (Enhanced Extended Display Identification) from the HDMI sink102connected by way of a cable. E-EDID is performance information related to self performance (configuration/capability), and such E-EDID is stored in a ROM (not shown) arranged in the HDMI sink102.

When the HDMI source206reads out the E-EDID from the HDMI sink102using the DDC, the HDMI source206can recognize the format (profile) of the image corresponding to the HDMI sink102such as RGB, YCbCr 4:4:4, YCbCr 4:2:2 etc., that is, the format (profile) of the image corresponding to the display device100based on the E-EDID.

Similar to the HDMI sink102, the HDMI source206stores the E-EDID indicating the performance of the HDMI source206, and can transmit the relevant E-EDID appropriately to the HDMI sink102.

The CEC line is used in bidirectional communication of control data etc. between the HDMI source206and the HDMI sink102.

[Details of Communication Interface]

The communication interface according to the embodiment of the present invention will be described in more detail below.

FIG. 4is an explanatory view showing a configuration example of the HDMI transmitter212and the HDMI receiver110according to the embodiment of the present invention.

The HDMI transmitter212includes encoder/serializers212A,212B, and212C respectively corresponding to the TMDS channels0to2. The encoder/serializers212A,212B, and212C encode the transmitted image signal, the auxiliary data, the control data and the like, convert parallel data to serial data, and transmit the data by a difference signal.

If the image signal has three components of RGB, the B component is transmitted to the encoder/serializer212A, the G component is transmitted to the encoder/serializer212B, and the R component is transmitted to the encoder/serializer212C.

The auxiliary data includes audio signal and control packet. The control packet is transmitted to the encoder/serializer212A, and the audio signal is transmitted to the encoder/serializers212B,212C.

The control data includes one bit of vertical synchronous signal (VSYNC), one bit of horizontal synchronous signal (HSYNC), and one bit of control bits CTL0, CTL1, CTL2, and CTL3.

The vertical synchronous signal and the horizontal synchronous signal are transmitted to the encoder/serializer212B etc. The control bits CTL0and CTL1are transmitted to the encoder/serializer212B, and the control bits CTL2, CTL3are transmitted to the encoder/serializer212C.

The encoder/serializer212A transmits the various transmitted signals in time division. For example, if the B component of the image signal is transmitted, the encoder/serializer212A divides the B component to parallel data of eight bit units, which is a predetermined number of bits, and encodes the same, and then converts the parallel data to serial data and transmits the data to the HDMI receiver110using the TMDS channel0.

If the vertical synchronous signal and the horizontal synchronous signal are transmitted, for example, the encoder/serializer212A encodes the same to two bits of parallel data, converts the parallel data to the serial data, and transmits the data to the HDMI receiver110using the TMDS channel0.

Furthermore, if the auxiliary data is transmitted, the encoder/serializer212A divides the auxiliary data to parallel data of four bit units, encodes the same, coverts the parallel data to the serial data and transmits the data to the HDMI receiver110using the TMDS channel0.

Similar to the encoder/serializer212A, the encoder/serializer212B transmits the various transmitted signals in time division. For example, if the G component of the image signal is transmitted, the encoder/serializer212B divides the G component to parallel data of eight bit units, which is a predetermined number of bits, and encodes the same, and then converts the parallel data to serial data and transmits the data to the HDMI receiver110using the TMDS channel1.

If the control bits CTL0, CTL1are transmitted, for example, the encoder/serializer212B encodes the same to two bits of parallel data, converts the parallel data to the serial data, and transmits the data to the HDMI receiver110using the TMDS channel1.

Furthermore, if the auxiliary data is transmitted, the encoder/serializer212B divides the auxiliary data to parallel data of four bit units, encodes the same, coverts the parallel data to the serial data and transmits the data to the HDMI receiver110using the TMDS channel1.

Similar to the encoder/serializer212A, the encoder/serializer212C transmits the various transmitted signals in time division. For example, if the R component of the image signal is transmitted, the encoder/serializer212C divides the R component to parallel data of eight bit units, which is a predetermined number of bits, and encodes the same, and then converts the parallel data to serial data and transmits the data to the HDMI receiver110using the TMDS channel2.

If the control bits CTL2, CTL3are transmitted, for example, the encoder/serializer212C encodes the same to two bits of parallel data, converts the parallel data to the serial data, and transmits the data to the HDMI receiver110using the TMDS channel2.

Furthermore, if the auxiliary data is transmitted, the encoder/serializer212C divides the auxiliary data to parallel data of four bit units, encodes the same, coverts the parallel data to the serial data and transmits the data to the HDMI receiver110using the TMDS channel2.

The HDMI receiver110includes recovery/decoders110A,110B, and110C respectively corresponding to the TMDS channels0to2. The recovery/decoders110A,110B, and110C respectively receive the image signal, the auxiliary data, and the control data transmitted by the difference signal from the HDMI transmitter212. The recovery/decoders110A,110B, and110C respectively convert the received image signal, the auxiliary data, and the control data from serial data to parallel data, decodes the data and outputs the data.

The recovery/decoder110A receives, for example, the B component of the image signal, the vertical synchronous signal and the horizontal synchronous signal, and the auxiliary data transmitted on the TMDS channel0from the HDMI transmitter212. The recovery/decoder110A converts each of the various received signals from serial data to parallel data, decodes the data and outputs the data.

The recovery/decoder110B receives, for example, the G component of the image signal, the control bits CTL0and CTL1, and the auxiliary data transmitted on the TMDS channel1from the HDMI transmitter212. The recovery/decoder110B converts each of the various received signals from serial data to parallel data, decodes the data and outputs the data.

The recovery/decoder110C receives, for example, the R component of the image signal, the control bits CTL2and CTL3, and the auxiliary data transmitted on the TMDS channel2from the HDMI transmitter212. The recovery/decoder110C converts each of the various received signals from serial data to parallel data, decodes the data and outputs the data.

[One Example of Transmission Period in Each TMDS Channel]

FIG. 5is an explanatory view showing one example of a transmission period in which various signals are transmitted in each TMDS channel of the HDMI according to the embodiment of the present invention. Here,FIG. 5shows a transmission period of various signals when an image signal indicating a progressive image having a resolution of 720 I·480 is transmitted on the TMDS channels0to2. The various signals transmitted on each TMDS channel are collectively termed as “transmission data” below.

The video field in which the transmission data is transmitted on the TMDS channels0to2of the HDMI can be divided into three periods, the video data period, the data island period, and the control period, depending on the type of transmission data.

The video field period is a period from an active edge of a certain vertical synchronous signal to an active edge of the next vertical synchronous signal. The video field frame can be divided to a horizontal blanking period, a vertical blanking period, and an active video period, which is a period excluding the horizontal blanking period and the vertical blanking period from the video field period.

The video data period is assigned to the active video period. In the video data period, the signal of an active pixel worth 720 pixels I·480 lines configuring the image signal for one uncompressed screen is transmitted.

The data island period and the control period are assigned to the horizontal blanking period and the vertical blanking period. The auxiliary data is transmitted in the data island period and the control period. The data island period is assigned to one portion of the horizontal blanking period and the vertical blanking period. Data not relevant to control of the auxiliary data such as packet of the audio data are transmitted in the data island period.

The control period is assigned to other portions of the horizontal blanking period and the vertical blanking period. Data relevant to control of the auxiliary data such as vertical synchronous signal, the horizontal synchronous signal, the control packet, and the like are transmitted in the control period.

The frequency of the pixel clock transmitted on the TMDS clock channel in the HDMI according to the embodiment of the present invention may be 165 MHz, in which case the transmission rate of the data island period is about 500 Mbps.

As described above, the auxiliary data is transmitted in both the data island period and the control period, and the distinction thereof is made by the control bits CTL0, CTL1.FIG. 6is an explanatory view showing one example of a relationship between the control bits CTL0, CTL1and the data island period and the control period according to the embodiment of the present invention.

As shown inFIG. 6A, the control bits CTL0, CTL1represent two states of a device enable state and a device disable state. The device enable state is represented as high level (High) and the device disable state is represented as low level (Low) inFIG. 6A, but are not limited thereto.

The control bits CTL0, CTL1are in the device disable state in the data island period and in the device enable state in the control period. Therefore, the data island period and the control period can be distinguished.

In the data island period in which the control bits CTL0, CTL1are at low level, that is, the control bits CTL0, CTL1indicate the device disable state, the data not relevant to the control of the auxiliary data such as the audio data are transmitted, as shown inFIG. 6B.

In the control period in which the control bits CTL0, CTL1are at high level, that is, the control bits CTL0, CTL1indicate the device enable state, the data relevant to the control of the auxiliary data such as the control packet an preamble are transmitted, as shown inFIG. 6C. The vertical synchronous signal and the horizontal synchronous signal are also transmitted in the control period, as shown inFIG. 6D.

The image display system according to the embodiment of the present invention can display the image signals transmitted from the image reproducing devices200,300, . . . by the communication interface shown inFIGS. 3 to 6on the display device100.

(Content Identification Information According to the Embodiment of the Present Invention)

The content identification information according to the embodiment of the present invention will now be described. As described above, the content identification information is inserted in the blanking period of the image signal at the HDMI source206.

FIG. 7is an explanatory view showing one example of a data structure of an AVI (Auxiliary Video Information) InfoFrame packet arranged in the data island period according to the embodiment of the present invention. In the HDMI according to the embodiment of the present invention, the supplementary information related to the image represented by the image signal can be transmitted from the image reproducing devices200,300, . . . to the display device100by the AVI InfoFrame packet.

With reference toFIG. 7, the content identification information according to the embodiment of the present invention is arranged hierarchically in one bit of ITC in the sixth byte (Data Byte3) and in two bits of CT1, CT0in the eighth byte (Data Byte5).

For instance, the ITC, which is one bit of data, identifies whether or not the image represented by the image signal is a moving image content. The content represents a normal moving image content if ITC=0, and represents not a normal moving image content if ITC=1. The CT1, CT0, which are two bits of data, become effective when ITC=1. That is, CT1, CT0are further used when determined as not the normal moving image content by the ITC.

[Example of Content Identification Information]

FIG. 8is an explanatory view showing one example of the content identification information according to the embodiment of the present invention.

With reference toFIG. 8, the content identification information according to the embodiment of the present invention identifies four contents of “text” content, “photograph” content, “cinema” content, and “game” content. The “text” content represents the general IT (Information Technology” content. The “photograph” content represents the content of still pictures. The “cinema” content represents the content of moving images such as movie and home video. The “game” content represents the content of a PC (Personal Computer) and a game console video.

InFIG. 8, an example where “text” content is represented if CT1=0 and CT0=0, “photograph” content is represented if CT1=0 and CT0=1, “cinema” content is represented if CT1=1 and CT0=0, and “game” content is represented if CT1=1 and CT0=1 is shown, but is should be noted that the content identification information according to the embodiment of the present invention is not limited thereto.

The control part104of the display device100generates the adjustment signal and the control signal based on the content identification information transmitted from the HDMI sink102, and transmits the signals to the signal processing part106. The adjustment signal and the control signal generated by the control part104are signals for controlling the processes in the signal processing part106, where the signal processing part106transmitted with the adjustment signal and the control signal skips a process, changes the setting, and the like in response to the transmitted adjustment signal and the control signal. The display device100according to the embodiment of the present invention will be described in more detail below.

(Display Device100According to the Embodiment of the Present Invention)

FIG. 9is an explanatory view showing one example of a configuration of the display device100according to the embodiment of the present invention. With reference toFIG. 9, the display device100includes the HDMI sink102, the control part104, the signal processing part106, and the panel108, as shown inFIG. 2.

The signal processing part106includes a chroma decoder120, a DRC part122, an enhancer124, and a panel driver126.

The chroma decoder120performs a process related to color such as changing of color space on the image signal transmitted from the HDMI sink102. The chroma decoder120switches the color space to change in response to the control signal transmitted from the control part104. For instance, the chroma decoder120can switch “sRGB (standard RGB)” and “Adobe RGB (registered trademark)” in response to the control signal, but is not limited thereto.

The DRC part122improves the image quality by regenerating the image signal corresponding to the pixel of interest, for example according to the image signal corresponding to the pixel of interest and the image signal corresponding to the surrounding pixels of the relevant pixel of interest with respect to the image signal transmitted from the chroma decoder120. The DRC part122also appropriately can make a switch on whether or not to perform the process according to the control signal transmitted from the control part104.

The enhancer124performs a process of edge enhancement on the image signal transmitted from the DRC part122. The enhancer124also appropriately can make a switch on whether or not to perform the process according to the control signal transmitted from the control part104.

The panel driver126performs various processes such as gamma correction within a linear space, control of a ratio of the light emission time of the light emitting element on the unit time (i.e., ratio of light emission and image erasure in unit time; hereinafter referred to as “duty”), and the like on the image signal transmitted from the enhancer124. The panel driver126can change the set value related to the control of duty in response to the adjustment signal transmitted from the control part104. The detailed configuration example of the panel driver126will be hereinafter described.

According to the above-described configuration, the signal processing part106can perform various processes on the image signal received by the HDMI sink102, and transmit the processed image signal to the panel108.

The control part104generates the adjustment signal and the control signal corresponding to the content identification information based on the content identification information of the control data received by the HDMI sink102, and transmits the same to each part of the signal processing part106.

The control part104can generate the adjustment signal and the control signal corresponding to the information of the content represented by the content identification information when the information of the content represented by the content identification information represents the same content continuously over a predetermined number of times, but is not limited thereto. For instance, the control part104can also generate the adjustment signal and the control signal corresponding to the information of the content represented by the content identification information every time the content identification information is transmitted.

[Process of Control Part104Based on Content Identification Information]

FIG. 10is a flowchart describing one example of a signal generating method based on the content identification information in the control part104of the display device100according to the embodiment of the present invention. A case where the signal processing part106of the display device100includes the chroma decoder120, the DRC part122, the enhancer124, and the panel driver126as shown inFIG. 9will be described below by way of example.

The control part104determines whether or not the ITC of the content identification information transmitted from the HDMI sink102is ITC=1 (S100).

If determined that ITC is not ITC=1 in step S100, the control part104generates a standard adjustment signal/control signal (S102), and outputs the generated adjustment signal/control signal (S118). The standard adjustment signal is a signal for setting the set value related to the control of duty to a prescribed standard set value in the panel driver126of the signal processing part106. The standard control signal is a signal for causing the chroma decoder120, the DRC part122, and the enhancer124of the signal processing part106to perform the prescribed standard process.

The control part104can perform the process of step S102when “ITC=0” is input as the content information, but is not limited thereto. For instance, the control part104can perform the process of step S102when “ITC=0” is transmitted from the HDMI sink102continuously over a predetermined number of times. As the control part104generates the adjustment signal/control signal when the information of the content represented by the content identification information represents the same content continuously over a predetermined number of times, lowering in image quality due to generation of the adjustment signal/control signal over plural times in a short period of one second and the like can be prevented. The control part104may hold the value of the ITC for a predetermined number of times and use the value of the ITC being held to determine whether or not the value of the ITC has been input continuously over a predetermined number of times, but is not limited thereto. Similarly in other determination processes (steps S104, S106, S112to be hereinafter described) shown inFIG. 10, the control part104can perform the process corresponding to the determination result when the value of the content identification information used in the determination is input continuously over a predetermined number of times.

If determined as ITC=1 in step S100, the control part104determines whether or not the CT1of the content identification information transmitted from the HDMI sink102is CT1=0 (S104).

[1] If Determined as CT1=0

If determined as CT1=0 in step S104, the control part104determines whether or not CT0=0 (S106).

If determined as CT0=0 in step S106, the control part104generates the adjustment signal/control signal for “text” content (S108), and outputs the generated adjustment signal/control signal (S118).

The adjustment signal for “text” content is a signal for setting the set value related to the control of duty to a predetermined first value (hereinafter described) for making adjustment such that the duty becomes larger in the panel driver126of the signal processing part106. The generation of flickers can be suppressed, that is, the occurrence of an event that lowers the image quality is suppressed, and higher image quality can be achieved by setting the set value related to the control of duty to the first value.

The control signal for “text” content is a signal for causing the chroma decoder120and the DRC part122to perform the process and not causing the enhancer124to perform the process (i.e., skip the process) with respect to the chroma decoder120, the DRC part122, and the enhancer124of the signal processing part106. If the image signal received by the HDMI sink102is related to the “text” content, the edge enhancement process is not performed in the enhancer124, so that the visibility of text information such as characters contained in the image represented by the image signal improves, and difficulty in reading the characters can be prevented.

If determined as not CT0=0 in step S106, the control part104generates the adjustment signal/control signal for “photograph” content (S110), and outputs the generated adjustment signal/control signal (S118).

The adjustment signal for “photograph” content is a signal for setting the set value related to the control of duty to a predetermined second value (hereinafter described) for making adjustment such that the duty becomes larger in the panel driver126of the signal processing part106. The generation of flickers can be suppressed, and higher image quality can be achieved by setting the set value related to the control of duty to the second value.

The control signal for “photograph” content is a signal for causing the DRC part122and the enhancer124to perform the process and switching the color space to change in the chroma decoder120with respect to the chroma decoder120, the DRC part122, and the enhancer124of the signal processing part106. When the control signal for “photograph” content is input, the chroma decoder120can switch from “sRGB” to “Adobe RGB (registered trademark)”. If the image signal received by the HDMI sink102is related to “photograph” content, the chroma decoder120switches the color space to change to the color space for still image, so that the display device100can display the image (i.e., still image) represented by the image signal at a higher image quality.

[2] If determined as not CT1=0

If determined as not CT1=0 in step S104, the control part104determines whether or not CT0=0 (S112).

If determined as CT0=0 in step S112, the control part104generates the adjustment signal/control signal for “cinema” content (S114), and outputs the generated adjustment signal/control signal (S118).

The adjustment signal for “cinema” content is a signal for setting the set value related to the control of duty to a predetermined third value (hereinafter described) for making adjustment such that the duty becomes smaller in the panel driver126of the signal processing part106. The generation of movement blurs can be suppressed, that is, the occurrence of an event that lowers the image quality can be suppressed, and higher image quality can be achieved by setting the set value related to the control of duty to the third value.

The control signal for “cinema” content is a signal for causing each of the chroma decoder120, the DRC part122, and the enhancer124of the signal processing part106to perform the prescribed standard process, similar to step S102.

If determined as not CT0=0 in step S112, the control part104generates the adjustment signal/control signal for “game” content (S114), and outputs the generated adjustment signal/control signal (S118).

The adjustment signal for “game” content is a signal for setting the set value related to the control of duty to a predetermined fourth value (hereinafter described) for making adjustment such that the duty becomes smaller in the panel driver126of the signal processing part106. The generation of movement blurs can be suppressed, and higher image quality can be achieved by setting the set value related to the control of duty to the fourth value.

The control signal for “game” content is a signal for causing the chroma decoder120and the enhancer124to perform the process and not causing the DRC part122to perform the process (i.e., skip the process) with respect to the chroma decoder120, the DRC part122, and the enhancer124of the signal processing part106. If the image signal received by the HDMI sink102is related to the “game” content, the image quality improvement process is not performed in the DRC part122, so that the delay in image to be displayed with respect to the reproduced audio that occurs by the image quality improvement process can be alleviated, and occurrence of an uncomfortable feeling due to mismatch of the audio and the image felt by the user can be prevented.

The control part104generates the adjustment signal and the control signal based on the content identification information, and can transmit the same to each part of the signal processing part106by using the signal generating method shown inFIG. 10. InFIG. 10, an example where four contents of “text” content, “photograph” content, “cinema” content, and “game” content are used as targets for the content identification information has been described by way of example, but it should be recognized that the control part of the display device according to the embodiment of the present invention is not limited to targeting the four contents.

The configuration of the panel driver126configuring the signal processing part106according to the embodiment of the present invention will be described in more detail below.

FIG. 11is a block diagram showing a configuration example of the panel driver126of the display device100according to the embodiment of the present invention. InFIG. 11, the control part104, the recordation part130, the storage part132, the overcurrent detection part134, the data driver136, the gamma circuit138, and the panel108configuring the display device100are also shown in addition to the panel driver126.

The recordation part130is one storage member arranged in the display device100, and can hold information for controlling the panel driver126in the control part104. The information held in the recordation part130includes a table set in advance with parameters for the control part104to perform signal processing on the signal transmitted from the panel driver126. The recordation part130may be a magnetic recording medium such as hard disc, a non-volatile memory such as EEPROM and flash memory, and the like but is not limited thereto.

The panel driver126can perform signal processing on the input image signal. The panel driver126can perform signal processing with hardware (e.g., signal processing circuit) and/or software (signal processing software). One example of a configuration of the panel driver126will be shown below.

[Configuration Example of Panel Driver126]

The panel driver126includes, for example, an edge grading part140, an I/F part142, a linear conversion part144, a pattern generating part146, a color temperature adjustment part148, a still image detection part150, a long-term color temperature correction part152, a light emission time control part154, a signal level correction part156, a long-term color temperature correction detecting part158, a blur correction part160, a gamma conversion part162, a dither processing part164, a signal output part166, a gate pulse output part168, and a gamma circuit control part170.

The edge grading part140performs signal processing to blur the edges with respect to the input image signal. Specifically, the edge grading part140blurs the edges by intentionally shifting the image represented by the image signal, and suppresses burn-in phenomenon of the image at the panel108. The burn-in phenomenon of the image refers to a degrading phenomenon of the light emission characteristic that occurs when the light emission frequency of a specific pixel of the panel108is higher than other pixels. The luminance of the pixel degraded by the burn-in phenomenon of the image lowers compared to other pixels that are not degraded. Thus a luminance difference between the degraded pixel and the non-degraded portion at the periphery of the relevant pixel becomes large. Due to such difference in luminance, the characters appear to be burnt in the screen to the user of the display device100looking at the video or the image displayed on the display device100.

The I/F part142is an interface for transmitting and receiving signals with components exterior to the panel driver126such as control part104.

The linear conversion part144performs gamma correction on the input image signal to correct to a linear image signal. For instance, if the gamma value of the image signal to be input is “2.2”, the linear conversion part144corrects the image signal so that the gamma value becomes “1.0”.

The pattern generating part146generates a test pattern to be used in the signal processing in the display device100. The test pattern to be used in the signal processing in the display device100includes a test pattern used in display test of the panel108, but is not limited thereto.

The color temperature adjustment part148adjusts the color temperature of the image represented by the image signal, and adjusts the color to be displayed on the panel108of the display device100. The display device100may include a color temperature adjustment member (not shown) enabling the user using the display device100to adjust the color temperature. The user can adjust the color temperature of the image to be displayed on the screen by arranging the color temperature adjustment member (not shown) in the display device100. The color temperature adjustment member (not shown) that may be arranged in the display device100includes button, direction key, rotatable selector such as jog dial, or a combination thereof, but is not limited thereto. The color temperature adjustment member (not shown) may be a member integrated with the operation part (not shown).

The still image detection part150detects time-series difference of the input image signal and determines that the image signal represents still image if a predetermined time difference is not detected. The detection result of the still image detection part150can be used to prevent burn-in phenomenon of the panel108, and to suppress degradation of the light emitting element.

The long-term color temperature correction part152corrects change over time of the R, G, B sub-pixels configuring each pixel of the panel108. The light emitting element (organic EL element) of each color configuring the sub-pixels of the pixel respectively have different LT characteristic (luminance-time characteristic). Thus, the color when displaying the image represented by the image signal on the panel108becomes unbalanced with degradation of the light emitting element over time. Therefore, the long-term color temperature correction part152performs compensation of degradation over time of the light emitting element (organic EL element) of each color configuring the sub-pixel.

The light emission time control part154controls the light emission time per unit time of each pixel of the panel108. More specifically, the light emission time control part154can control the ratio of the light emission time of the light emitting element on the unit time, that is, the duty. The display device100selectively applies current to the pixels of the panel108based on the duty to display the image represented by the image signal for a desired time. The “unit time” according to the embodiment of the present invention may be “periodically repeated unit time”. The “unit time” is described as “one frame period” in the following description, but it should be noted that the “unit time” according to the embodiment of the present invention is not limited to “one frame period”.

The light emission time control part154can control the light emission time (duty) so as to prevent overcurrent from flowing to each pixel (more precisely, light emitting element of each pixel) of the panel108. The overcurrent prevented by the light emission time control part154mainly refers to the flow of current larger than the amount of current allowed by the pixel of the panel108to the pixel (overload).

Furthermore, the light emission time control part154can control the gain of the image signal in addition to the control of the light emission time (duty). As the light emission time control part154controls the light emission time (duty) and the gain of the image signal, overcurrent is prevented, occurrence of an event that lowers the image quality such as flickers and movement blur is suppressed, and higher image quality can be achieved.

The configuration of the light emission time control part154according to the embodiment of the present invention, and the control of the light emission time and the gain of the image signal in the display device100according to the embodiment of the present invention will be hereinafter described in detail.

The signal level correction part156determines the risk of occurrence of the burn-in phenomenon of the image to prevent occurrence of the burn-in phenomenon of the image. The signal level correction part156corrects the signal level of the image signal to prevent burn-in phenomenon of the image when the risk becomes greater than or equal to a predetermined value to adjust the luminance of the image to be displayed on the panel108.

The long-term color temperature correction detecting part158detects information used to compensate the degradation over time of the light emitting element in the long-term color temperature correction part152. The information detected in the long-term color temperature correction detecting part158is sent to the control part104via the I/F part142, and recorded in the recordation part130through the control part104.

The blur correction part160corrects blur of horizontal lines, vertical lines, patches of the entire screen and the like that may occur when the image represented by the image signal is displayed on the panel108. The blur correction part160can make corrections with the level and the coordinate position of the input image signal as references.

The gamma conversion part162performs gamma correction on the image signal (more precisely, image signal output from the blur correction part160) gamma corrected so as to be a linear image signal in the linear conversion part144, and corrects the image signal so as to have a predetermined gamma value. The predetermined gamma value is a value that can cancel out the VI characteristic (voltage—current characteristic, specifically, VI characteristic of the transistor in the pixel circuit) of the pixel circuit arranged in the panel108of the display device100. When the gamma conversion part162performs gamma correction so that the image signal has the predetermined gamma value, the relationship between the light quantity of the subject represented by the image signal and the current amount applied to the light emitting element can be handled as a linear form.

The dither processing part164performs dithering on the image signal gamma corrected in the gamma conversion part162. Dithering is when displaying the displayable colors in combination to represent an intermediate color in an environment with small number of usable colors. The color that originally may not be displayed on the panel108then can be created on appearance and displayed on the panel108by performing dithering process in the dither processing part164.

The signal output part166outputs the image signal subjected to the dithering process in the dither processing part164to the outside of the panel driver126. The image signal output from the signal output part166may be an independent signal for each color of R, G, and B.

The gate pulse output part18outputs a selection signal for controlling the light emission and the light emission time of each pixel of the panel108. The selection signal is based on the duty output from the light emission time control part154, and the light emitting element of the pixel may emit light when the selection signal is at high level, and the light emitting element of the pixel may not emit light when the selection signal is at low level.

The gamma circuit control part170outputs a predetermined set value to the gamma circuit138(to be hereinafter described). The predetermined set value output to the gamma circuit138by the gamma circuit control part170may be a reference voltage to apply to a rudder resistor of a D/A converter (Digital-to-Analog Converter) of the data driver136(to be hereinafter described).

The panel driver126can perform various signal processing on the input image signal according to the above-described configuration.

The storage part132is another storage member arranged in the display device100. The information held by the storage132includes information associating the information on the pixel or the pixel group emitting light exceeding a predetermined luminance and information on the exceeding amount, which are preferable when correcting the luminance in the signal level correction part156, but is not limited thereto. The storage132includes a volatile memory such as SDRAM (Synchronous Dynamic Random Access Memory) and SRAM (Static Random Access Memory), but is not limited thereto, and may be a magnetic recording medium such as hard disc, and a non-volatile memory such as flash memory.

The overcurrent detection part134detects overcurrent and notifies the occurrence of overcurrent to the gate pulse output part168when overcurrent occurs from short-circuit of wiring at a base (not shown) on which the configuring elements of the display device100are arranged. The gate pulse output part168notified of the notification of occurrence of overcurrent from the overcurrent detection part134does not apply the selection signal to each pixel of the panel108, so that overcurrent can be prevented from being applied to the panel108.

The data driver136converts the image signal output from the signal output part166to a voltage signal to be applied to each pixel of the panel108, and outputs the voltage signal to the panel108. The data driver136thus includes a D/A converter for converting the image signal serving as a digital signal to the voltage signal serving as an analog signal.

The gamma circuit138outputs a reference voltage to apply to the rudder resistor of the D/A converter of the data driver136. The reference voltage output to the data driver136by the gamma circuit138can be controlled by the gamma circuit control part170.

The display device100according to the embodiment of the present invention includes the panel driver126having the configuration shown inFIG. 11, so that the image corresponding to the image signal received by the HDMI sink102can be displayed. InFIG. 11, the panel driver126including the pattern generating part146at the post-stage of the linear conversion part144has been shown, but the configuration is not limited thereto, and the panel driver according to the embodiment of the present invention may include the pattern generating part at the pre-stage of the linear conversion part.

(Outline of Transition of Signal Characteristic in Display Device100)

The outline of the transition of the signal characteristic in the display device100according to the embodiment of the present invention will now be described.FIGS. 12A to 12Fare explanatory views showing an outline of the transition of the signal characteristic in the display device100according to the embodiment of the present invention.

Each graph ofFIGS. 12A to 12Fshows the process in the panel driver126of the display device100in time-series, where the left view ofFIGS. 12B to 12Eshows the signal characteristic of the processing result of the pre-stage such as “signal characteristic of the processing result inFIG. 12Acorresponds to the left view of FIG.12B”. The right view ofFIGS. 12A to 12Eshows the signal characteristics used as a coefficient in the process.

[i] Transition of First Signal Characteristic: Transition by Processing of Linear Conversion Part144

As shown on the left view ofFIG. 12A, the image signal received by the HDMI sink102and input to the panel driver126has a predetermined gamma value (e.g., “2.2”). The linear conversion part144of the panel driver126multiplies a gamma curve (linear gamma, right view ofFIG. 12A) opposite to the gamma curve (left view ofFIG. 12A) represented by the image signal input to the panel driver126so as to cancel out the gamma value of the image signal input to the panel driver126to correct the image signal having a characteristic in which the relationship between the light quantity of the subject represented by the image signal and the output B is linear.

[ii] Transition of Second Signal Characteristic: Transition by Processing of Gamma Conversion Part162

The gamma conversion part162of the panel driver126multiplies a gamma curve (panel gamma, right view ofFIG. 12B) opposite to the gamma curve unique to the panel108in advance so as to cancel out the VI characteristic of the transistor (right view ofFIG. 12D) arranged in the panel108.

[iii] Transition of Third Signal Characteristic: Transition by D/A Conversion in Data Driver136

FIG. 12Cshows a case where the image signal is D/A converted in the data driver136. As shown inFIG. 12C, the relationship between the light quantity of the subject represented by the image signal in the image signal and the voltage signal D/A converted from the image signal becomes as shown on the left view ofFIG. 12Dby D/A converting the image signal in the data driver136.

[iv] Transition of Fourth Signal Characteristic: Transition in Pixel Circuit of Panel108

FIG. 12Dshows a case where the voltage signal is applied to the pixel circuit arranged in the panel108by the data driver136. As shown inFIG. 12B, the gamma conversion part162of the panel driver126multiplies in advance the panel gamma corresponding to the VI characteristic of the transistor arranged in the panel108. Therefore, when the voltage signal is applied to the pixel circuit arranged in the panel108, the relationship between the light quantity of the subject represented by the image signal in the image signal and the current applied to the pixel circuit becomes linear as shown on the left view ofFIG. 12E.

[v] Transition of Fifth Signal Characteristic: Transition in Light Emitting Element (Organic EL Element)

As shown on the right view ofFIG. 12E, the IL characteristic of the organic EL element (OLED) becomes linear. Therefore, in the light emitting element of the panel108, the relationship between the light quantity of the subject represented by the image signal shown in the image signal and the light emission amount light emitted from the light emitting element also has a linear relationship by multiplying those having linear signal characteristics as shown inFIG. 12E(FIG. 12F).

As shown inFIGS. 12A to 12F, the display device100can have a linear relationship between the light quantity of the subject represented by the image signal received by the HDMI sink102and the light emission amount light emitted from the light emitting element. Therefore, the display device100can display an image faithfully following the image signal.

(Control of Light Emission Time and Gain of Image Signal in One Frame Period)

The control of the light emission time (duty) and the gain of the image signal in one frame period according to the embodiment of the present invention will now be described. The control of the light emission time and the gain of the image signal in one frame period according to the embodiment of the present invention can be carried out in the light emission time control part154of the panel driver126.

FIG. 13is a block diagram showing one example of the light emission time control part154according to the embodiment of the present invention. The following description will be made assuming the image signal input to the light emission time control part154is a signal independent for each color of R, G, and B corresponding to the image of every one frame period (unit time).

With reference toFIG. 13, the light emission time control part154includes an average luminance calculation part400, a light emission amount regulation part402, and an adjustment part404.

The average luminance calculation part400calculates an average value of the luminance in a predetermined period based on the input image signals of R, G, and B. The predetermined period is one frame period herein, but is not limited thereto, and may be a two-frame period.

The average luminance calculation part400can calculate the average value of the luminance for every predetermined period (i.e., calculate the average value of the luminance in a constant cycle), but is not limited thereto, and the predetermined period may be a varying period.

The following description will be made with the predetermined period being one frame period, and the average luminance calculation part400calculating the average value of the luminance for every one frame period.

[Configuration of Average Luminance Calculation Part400]

FIG. 14is a block diagram showing the average luminance calculation part400according to the embodiment of the present invention. With reference toFIG. 14, the average luminance calculation part400includes a current ratio adjustment part450and an average value calculation part452.

The current ratio adjustment part450adjusts the current ratio of the input image signals of R, G, and B by multiplying a predetermined correction coefficient for each color with respect to each input image signals of R, G, and B. The predetermined correction coefficient is a value that differs for each color in correspondence to the respective VI ratio (voltage—current ratio) of the light emitting element of R, the light emitting element of G, and the light emitting element of B configuring the pixels of the panel108.

FIG. 15is an explanatory view showing one example of the VI ratio of the light emitting element of each color configuring the pixels according to the embodiment of the present invention. As shown inFIG. 15, the VI ratio of the light emitting element of each color configuring the pixel differs for every color such that “light emitting element of B>light emitting element of R>light emitting element of G”. As described above, the display device100multiplies the gamma curve opposite to the gamma curve unique to the panel108in the gamma conversion part162to cancel the gamma value unique to the panel108and perform the process in a linear region. Therefore, the respective VI ratio of the light emitting element of R, the light emitting element of G, and the light emitting element of B can be obtained in advance by deriving in advance the relationship of VI as shown inFIG. 15with the duty fixed at a predetermined value (e.g., “0.25”).

The current ratio adjustment part450may include a storage member, and the predetermined correction coefficient used by the current ratio adjustment part450may be held in the storage member. The storage member of the current ratio adjustment part450includes a non-volatile memory such as EEPROM and flash memory, but is not limited thereto. The predetermined correction coefficient used by the current ratio adjustment part450may be held in a storage member of the display device100such as the recordation part130or the storage132, and appropriately read by the current ratio adjustment part450.

The average value calculation part452calculates an average luminance (APL, average picture level) in one frame period from the image signals of R, G, and B adjusted by the current ratio adjustment part450. A method of calculating the average luminance in one frame period calculated by the average value calculation part452includes using arithmetic average, but is not limited thereto, and the average luminance may be calculated using geometric average or weighted average.

The average luminance calculation part400calculates the average luminance in one frame period as described above, and outputs the average luminance.

Again with reference toFIG. 13, the light emission amount regulation part402sets a reference duty corresponding to the average luminance in one frame period calculated by the average luminance calculation part400. The reference duty is a duty that becomes a reference for regulating the light emission amount for light emitting the pixel (light emitting element) in unit time (e.g., one frame period).

The light emission amount in one frame period (unit time) can be represented with the following equation 1. Here, Lum indicates light emission amount, Sig indicates signal level, and Duty indicates light emission time.
Lum=(Sig)×(Duty)  (Equation 1)

As expressed in equation 1, the light emission amount depends only on the signal level of the input image signal, that is, the gain of the image signal by setting the reference duty.

The setting of the reference duty in the light emission amount regulation part402can be performed using a lookup table in which the average luminance in one frame period and the reference duty are associated. The light emission amount regulation part402may store the lookup table in a storage member including a non-volatile memory such as EEPROM and flash memory, and a magnetic recording medium such as hard disc.

[Method of Obtaining Value Held in the Lookup Table According to the Embodiment of the Present Invention]

The method of obtaining the value held in the lookup table according to the embodiment of the present invention will now be described.FIG. 16is an explanatory view describing a method of obtaining the value held in the lookup table according to the embodiment of the present invention, and shows a relationship of the average luminance (APL) in one frame period and the reference duty (Duty). FIG. shows a case where the average luminance in one frame period is represented with digital data of ten bits by way of example, but it should be noted that the average luminance in one frame period according to the embodiment of the present invention is not limited to digital data of ten bits.

The lookup table according to the embodiment of the present invention is obtained with the light emission amount when the luminance is a maximum (in this case, “white” image is displayed on the panel108) at a predetermined duty as a reference.

An area S shown inFIG. 16shows the light emission amount when the luminance is a maximum with 25% set as the predetermined duty. The predetermined duty according to the embodiment of the present invention is not limited to 25%, and can be set in accordance with the characteristics (e.g., characteristics of light emitting element etc.) of the panel108arranged in the display device100, the MTBF (Mean Time Between Failure) of the display device100, and the like.

A curve a shown inFIG. 16is a curve that passes a value at which the product of the average luminance (APL) in one frame period and the reference duty (Duty) becomes equal to the area S when the reference duty is greater than 25%.

A line b shown inFIG. 16is a line that defines an upper limit value L of the reference duty with respect to the curve a. As shown inFIG. 16, an upper limit value can be provided to the reference duty in the lookup table according to the embodiment of the present invention. The reason for providing the upper limit value in the reference duty in the embodiment of the present invention is to solve the issue originating from the trade off relationship of the “luminance” related to the duty and the “movement blur” when the moving image is displayed. The issue originating from the trade off relationship of the “luminance” related to the duty and the “movement blur” includes the following.

Movement blur: larger

Movement blur: smaller

Therefore, in the lookup table according to the embodiment of the present invention, the issue originating from the trade off relationship of the luminance and the movement blur is solved by setting the upper limit value L in the reference duty and obtaining a constant balance between the “luminance” and the “movement blur”. The upper limit value L of the reference duty can be set in accordance with the characteristics (e.g., characteristics of the light emitting element, and the like) of the panel108arranged in the display device100.

The light emission amount regulation part402can set the reference duty corresponding to the average luminance in one frame period calculated by the average luminance calculation part400by using the lookup table in which the average luminance in one frame period and the reference duty are associated so as to take a value on the curve a and the line b shown inFIG. 16. An example where the upper limit value L is set in the reference duty in the light emission amount regulation part402as shown inFIG. 16has been described above by way of example, but the embodiment of the present invention is not limited thereto. For instance, a light emission time adjustment part406(to be hereinafter described) of the adjustment part404may provide a predetermined upper limit value in the duty.

The light emission time control part154will be described with reference again toFIG. 13. The adjustment part404includes the light emission time adjustment part406and a gain adjustment part408, and adjusts the reference duty and the gain of the image signal output from the light emission amount regulation part402.

The light emission time adjustment part406adjusts the reference duty output from the light emission amount regulation part402, and outputs an actual duty for substantially regulating the light emission time for light emitting the respective light emitting element of the panel108per unit time. Outputting of the actual duty by adjusting the reference duty in the light emission time adjustment part406is referred to as “adjustment of actual duty”. An adjustment example of the actual duty in the light emission time adjustment part406will be described below.

[I] First Adjustment Example of Actual Duty: Setting of Lower Limit Value

FIG. 17is an explanatory view describing a first adjustment example of the actual duty in the light emission time adjustment part406according to the embodiment of the present invention.FIG. 17shows a relationship between the reference duty (Duty) output from the light emission amount regulation part402and the actual duty (Duty′) output from the light emission time adjustment part406.

With reference toFIG. 17, the reference duty (Duty) output from the light emission amount regulation part402and the actual duty (Duty′) output from the light emission time adjustment part406are basically in a proportionality relation of slope1, but it can be seen that the lower limit value L1is provided in the actual duty (Duty′).

As described above, a merit in that the “movement blur” becomes smaller is obtained but a demerit in that the “luminance” becomes lower arises when the duty is small. When the duty becomes short to a curtain extent, a demerit in that flickers occur (stand out) arises. The light emission time adjustment part406thus outputs the reference duty as the actual duty when the reference duty (Duty) output from the light emission amount regulation part402is L1┘·Duty (within regulated range), and outputs the lower limit value L1as the actual duty when the reference duty (Duty) is L1>Duty (outside regulated range) by providing the lower limit value L1to the actual duty (Duty′). The rise in demerits is suppressed and lowering in image quality is prevented by adjusting the actual duty as described above in the light emission time adjustment part406.

When the light emission time adjustment part406adjusts the actual duty as shown inFIG. 17, lowering in image quality of the image to be displayed by the display device100can be prevented, and higher image quality can be achieved.

The actual duty can be adjusted by having the light emission time adjustment part406store the lower limit value L1in the storage member (not shown) in advance, and comparing the reference duty output from the light emission amount regulation part402and the lower limit value L1, but is not limited thereto. The light emission time adjustment part406may include a storage member, and the lower limit value L1may be held in the storage member. The storage member of the light emission time adjustment part406may be a non-volatile memory such as EEPROM and flash memory, but is not limited thereto. The lower limit value L1used by the light emission time adjustment part406may be held in the storage member arranged in the display device100such as the recordation part130or the storage132, and appropriately read out by the light emission time adjustment part406.

The lower limit value L1can be set to a value at which the flickers do not stand out when a video is displayed on the panel108, and may be set in accordance with the characteristics of the panel108(e.g., characteristics of the light emitting element etc.).

[II] Second Adjustment Example of Actual Duty: Setting of Upper Limit Value

FIG. 18is an explanatory view describing a second adjustment example of the actual duty in the light emission time adjustment part406according to the embodiment of the present invention. Similar toFIG. 17,FIG. 18shows a relationship between the reference duty (Duty) output from the light emission amount regulation part402and the actual duty (Duty′) output from the light emission time adjustment part406.

With reference toFIG. 18, the reference duty (Duty) output from the light emission amount regulation part402and the actual duty (Duty′) output from the light emission time adjustment part406are basically in a proportionality relation of slope1, but it can be seen that the upper limit value L2is provided in the actual duty (Duty′).

As described above, a merit in that the “luminance” becomes higher is obtained but a demerit in that the “movement blur” becomes larger arises when the duty is large. The light emission time adjustment part406thus outputs the reference duty as the actual duty when the reference duty (Duty) output from the light emission amount regulation part402is Duty ┘·L2(within regulated range) and outputs the upper limit value L2as the actual duty when the reference duty (Duty) is Duty>L2(outside regulated range) by providing the upper limit value L2to the actual duty (Duty′). The rise in demerits is suppressed and lowering in image quality can be prevented by adjusting the actual duty as described above in the light emission time adjustment part406.

When the light emission time adjustment part406adjusts the actual duty as shown inFIG. 18, lowering in image quality of the image to be displayed by the display device100can be prevented, and higher image quality can be achieved.

The actual duty can be adjusted by having the light emission time adjustment part406store the upper limit value L2in the storage member (not shown) in advance, and comparing the reference duty output from the light emission amount regulation part402and the upper limit value L2, but is not limited thereto. The light emission time adjustment part406clips the value of the reference duty output from the light emission amount regulation part402, so that the actual duty set with the upper limit value L2can be output.

The upper limit value L2can be set to a value at which the movement blurs do not stand out when a video is displayed on the panel108, and may be set in accordance with the characteristics of the panel108(e.g., characteristics of the light emitting element etc.).

[III] Third Adjustment Example of Actual Duty: Setting of Lower Limit Value/Upper Limit Value

Examples of providing the lower limit value L1or the upper limit value L2to the actual duty have been described in the first and second adjustment examples of the actual duty. However, the adjustment of the actual duty in the light emission time adjustment part406is not limited to the first and second adjustment examples.FIG. 19is an explanatory view describing a third adjustment example of the actual duty in the light emission time adjustment part406according to the embodiment of the present invention. Similar toFIG. 17,FIG. 19shows a relationship between the reference duty (Duty) output from the light emission amount regulation part402and the actual duty (Duty′) output from the light emission time adjustment part406.

With reference toFIG. 19, the reference duty (Duty) output from the light emission amount regulation part402and the actual duty (Duty′) output from the light emission time adjustment part406are basically in a proportionality relation of slope1, but it can be seen that the lower limit value L1and the upper limit value L2are provided in the actual duty (Duty′). That is, the light emission time adjustment part406outputs the reference duty as the actual duty when the reference duty (Duty) output from the light emission amount regulation part402is L1┘·Duty ┘·L2(within regulated range). The light emission time adjustment part406outputs the lower limit value L1when L1>Duty (outside regulated range), and outputs the upper limit value L2as the actual duty when the reference duty (Duty) is Duty>L2(outside regulated range).

The light emission time adjustment part406suppresses the demerits (demerits mentioned in the first and second adjustment examples) originating from the trade off relationship of the luminance and the movement blur, and prevents lowering in image quality by providing the lower limit value L1and the upper limit value L2to the actual duty (Duty′). When the light emission time adjustment part406adjusts the actual duty as shown inFIG. 19, lowering in image quality of the image to be displayed by the display device100can be prevented, and higher image quality can be achieved.

[IV] Fourth Adjustment Example of Actual Duty: Setting of Lower Limit Value Based on Adjustment Signal

A configuration of providing the predetermined lower limit value L1and/or the predetermined upper limit value L2to the actual duty has been shown in the first to third adjustment examples of the actual duty described above. However, the adjustment of the actual duty in the light emission time adjustment part406is not limited to the first to third adjustment examples, and the value of the lower limit value can be changed according to the adjustment signal transmitted from the control part104.FIG. 20is an explanatory view describing a fourth adjustment example of the actual duty in the light emission time adjustment part406according to the embodiment of the present invention. Similar toFIG. 17,FIG. 20shows a relationship between the reference duty (Duty) output from the light emission amount regulation part402and the actual duty (Duty′) output from the light emission time adjustment part406.

With reference toFIG. 20, the reference duty (Duty) output from the light emission amount regulation part402and the actual duty (Duty′) output from the light emission time adjustment part406are basically in a proportionality relation of slope1, but it can be seen that the lower limit value L1and the upper limit value L2are provided in the actual duty (Duty′), similar to the third adjustment example shown inFIG. 19.

InFIG. 20, a lower limit value L3and a lower limit value L4with larger actual duty (Duty′) than the lower limit value L1, and a lower limit value L5and a lower limit value L6with smaller actual duty (Duty′) than the lower limit value L1are further set as the lower limit values.

In the fourth adjustment example, the light emission time adjustment part406sets the lower limit value corresponding to the adjustment signal shown in (i) to (v) below based on the adjustment signal transmitted from the control part104.

(i) When “Text” Content Adjustment Signal is Transmitted

For example, when the “text” content adjustment signal is transmitted from the control part104, the light emission time adjustment part406sets the lower limit value L3to the actual duty (Duty′). The lower limit value L3corresponds to the predetermined first value. The light emission time adjustment part406outputs the reference duty as the actual duty when the reference duty (Duty) output from the light emission amount regulation part402is L3┘·Duty ┘·L2(within regulated range). The light emission time adjustment part406outputs the lower limit value L3as the actual duty when L3>Duty (outside regulated range), and outputs the upper limit value L2when Duty>L2(outside regulated range).

(ii) When “Photograph” Content Adjustment Signal is Transmitted

For example, when the “text” content adjustment signal is transmitted from the control part104, the light emission time adjustment part406sets the lower limit value L4to the actual duty (Duty′). The lower limit value L4corresponds to the predetermined second value. The light emission time adjustment part406outputs the reference duty as the actual duty when the reference duty (Duty) output from the light emission amount regulation part402is L4┘·Duty ┘·L2(within regulated range). The light emission time adjustment part406outputs the lower limit value L4as the actual duty when L4>Duty (outside regulated range), and outputs the upper limit value L2when Duty>L2(outside regulated range).

(iii) When “Cinema” Content Adjustment Signal is Transmitted

For example, when the “cinema” content adjustment signal is transmitted from the control part104, the light emission time adjustment part406sets the lower limit value L5to the actual duty (Duty′). The lower limit value L5corresponds to the predetermined third value. The light emission time adjustment part406outputs the reference duty as the actual duty when the reference duty (Duty) output from the light emission amount regulation part402is L5┘·Duty ┘·L2(within regulated range). The light emission time adjustment part406outputs the lower limit value L5as the actual duty when L5>Duty (outside regulated range), and outputs the upper limit value L2when Duty>L2(outside regulated range).

(iv) When “Game” Content Adjustment Signal is Transmitted

For example, when the “game” content adjustment signal is transmitted from the control part104, the light emission time adjustment part406sets the lower limit value L5to the actual duty (Duty′). The lower limit value L6corresponds to the predetermined fourth value. The light emission time adjustment part406outputs the reference duty as the actual duty when the reference duty (Duty) output from the light emission amount regulation part402is L6┘·Duty ┘·L2(within regulated range). The light emission time adjustment part406outputs the lower limit value L6as the actual duty when L6>Duty (outside regulated range), and outputs the upper limit value L2when Duty>L2(outside regulated range).

(v) When Standard Adjustment Signal is Transmitted

For example, when the standard adjustment signal shown inFIG. 10is transmitted from the control part104, the light emission time adjustment part406sets the lower limit value L1to the actual duty (Duty′). The lower limit value L1corresponds to the standard set value. The light emission time adjustment part406outputs the reference duty as the actual duty when the reference duty (Duty) output from the light emission amount regulation part402is L1┘·Duty ┘·L2(within regulated range). The light emission time adjustment part406outputs the lower limit value L1as the actual duty when L1>Duty (outside regulated range), and outputs the upper limit value L2when Duty>L2(outside regulated range).

The light emission time adjustment part406suppresses demerits originating from the trade off relationship of the luminance and the movement blur and prevents lowering in image quality by providing the lower limit values L1to L6and the upper limit value L2to the actual duty (Duty′). The light emission time adjustment part406appropriately changes the lower limit value of the actual duty (Duty′) according to the adjustment signal transmitted from the control part104to adjust the duty according to the content of the content of the image represented by the image signal received by the HDMI sink102. Therefore, the light emission time adjustment part406adjusts the actual duty as shown inFIG. 20to prevent lowering in image quality of the image to be displayed by the display device100, and achieve higher image quality.

The control part104can generate the adjustment signal and the control signal corresponding to the information of the content represented by the content identification information when the information of the content represented by the content identification information represents the same content continuously over a predetermined number of times. Therefore, the display device100can suppress the setting frequency of the lower limit value of the actual duty set according to the adjustment signal in the light emission time adjustment part406and prevent lowering in image quality caused by the change in lower limit value of the actual duty over plural times in one second.

A configuration in which the lower limit value and the upper limit value are provided to the actual duty (Duty′) (i.e., configuration corresponding to third adjustment example) is described as the fourth adjustment example, but the adjustment of the actual duty according to the embodiment of the present invention is not limited to the above. For instance, the adjustment of the actual duty according to the embodiment of the present invention can appropriately change the lower limit value of the first adjustment example shown inFIG. 17according to the adjustment signal transmitted from the control part104.

An example where one of the “text” content adjustment signal, the “photograph” content adjustment signal, the “cinema” content adjustment signal, the “game” content adjustment signal, or the standard adjustment signal is transmitted from the control part104has been described as the fourth adjustment example, but the adjustment signal according to the embodiment of the present invention is not limited thereto. When the adjustment signal transmitted from the control part104differs from the above, the lower limit value of the number corresponding to the number of adjustment signals to be transmitted is set. Furthermore, an example of appropriately changing the lower limit value of the actual duty (Duty′) based on the adjustment signal transmitted from the control part104has been described as a fourth adjustment example, but is not limited thereto, and the upper limit value of the actual duty (Duty′) may be changed based on the adjustment signal.

As shown in first to fourth adjustment examples of the actual duty, the light emission time adjustment part406provides the lower limit value and/or the upper limit value to the actual duty to be output and adjusts the actual duty to prevent lowering in image quality of the image to be displayed by the display device100and achieve higher image quality. The lower limit values L1to L6and the upper limit value L2of the actual duty shown inFIGS. 17 to 20can be set in advance according to the characteristic (e.g., characteristic of light emitting element etc.) of the panel108arranged in the display device100, but is not limited thereto. For instance, the lower limit values L1to L6and the upper limit value L2of the actual duty may be changed according to the user input from the operation part (not shown).

With reference again toFIG. 13, the light emission time control part154will be described. A gain adjustment part408includes a first gain correction portion410and a second gain correction portion412. The gain adjustment part408adjusts the gain of the input image signals of R, G, and B in correspondence to the adjustment of the actual duty in the light emission time adjustment part406. As expressed with equation 1, the light emission amount can be expressed by a product of the signal level and the light emission time. The gain adjustment part408adjusts the gain of the image signal so that the light emission amount defined by the reference duty and the gain of the image signal is maintained the same even after the adjustment of the actual duty.

The first gain correction portion410multiplies the reference duty output from the light emission amount regulation part401with respect to each input image signals of R, G, and B.

The second gain correction portion412divides each R, G, and B image signals corrected by the first gain correction portion410with the actual duty (Duty′) output from the light emission time adjustment part406.

As a result of the correction in the first gain correction portion410and the second gain correction portion412, the adjusted R image signal (R′), the adjusted G image signal (G′) and the adjusted B image signal (B′) output from the gain adjustment part408can be expressed with the following equations 2 to 4.
R′={(R)×™(Duty)}/(Duty′)
R′=(R)×·{(Duty)/(Duty′)}  (Equation 2)
G′={(G)×·(Duty)}/(Duty′)
G′=(G)×·{(Duty)/(Duty′)}  (Equation 3)
B′={(B)×·(Duty)}/(Duty′)
B′=(B)×·{(Duty)/(Duty′)}  (Equation 4)

It is apparent with reference to equations 2 to 4 that the image signals (R′, G′, B′) output from the gain adjustment part408correspond to the adjustment ratio ((Duty)/(Duty′)) of the duty in the light emission time adjustment part406.

The relationship between the adjustment ratio of the duty in the light emission time adjustment part406, and the adjustment of the gain of the image signal in the gain adjustment part408can be expressed as (1) to (3) below.

(1) When adjustment ratio of duty=1

The image signals (R′, G′, B′) output from the gain adjustment part408=input image signals (R, G, B): no change in gain of image signal

(2) When adjustment ratio of duty<1 (when actual duty is set to lower limit values L1to L6)

The image signals (R′, G′, B′) output from the gain adjustment part408<input image signals (R, G, B): attenuation in gain of image signal

(3) When adjustment ratio of duty>1 (when actual duty is set to upper limit value L2)

The image signals (R′, G′, B′) output from the gain adjustment part408>input image signals (R, G, B): amplification in gain of image signal

As expressed with equations 1, and 2 to 4, the light emission amount in one frame period (unit time) defined by the actual duty (Duty′) and the image signals (R′, G′, B′) output from the adjustment part404does not change at before and after the adjustment in the adjustment part404. Therefore, the adjustment part404can adjust the actual duty and the gain of the image signals while maintaining the same light emission amount.

As described above, the display device100according to the embodiment of the present invention calculates the average luminance from the R, G, and B image signals input in one frame period (unit time: predetermined period), and sets the reference duty corresponding to the calculated average luminance. The reference duty according to the embodiment of the present invention is set to a value the largest light emission amount in the predetermined duty and the light emission amount defined by the reference duty and the average luminance in one frame period (unit time: predetermined period) become the same. The display device100can adjust the actual duty and the gain of the image signal so that the light emission amount defined by the reference duty and the gain of the image signal is maintained the same. Therefore, in the display device100, the light emission amount in one frame period (unit time) will not be larger than the largest light emission amount in the predetermined duty, and thus the display device100can prevent overcurrent from flowing to each pixel (more precisely, light emitting element of each pixel) of the panel108.

The display device100adjusts the actual duty by providing the lower limit value L1and/or the upper limit value L2to the actual duty to suppress the rise in demerits (demerits explained in the first and second adjustment examples) originating from the trade off relationship of the luminance and the movement blur and prevent lowering in image quality. Therefore, the display device100can achieve higher image quality of the image to be displayed on the panel108.

The display device100generates the adjustment signal and the control signal based on the content information received by the HDMI sink102, and transmits the generated adjustment signal and the control signal to each part of the signal processing part106for processing the image signal received by the HDMI sink102. The display device100can appropriately change the lower limit value of the actual duty (Duty′) according to the adjustment signal by inputting the adjustment signal based on the content information to the panel driver126of the signal processing part106. As the control signal based on the content information is transmitted to the chroma decoder120, the DRC part122, and the enhancer124of the signal processing part106, the display device100can perform processing of the image signal corresponding to the content of the content of the image represented by the input image signal (image signal received by the HDMI sink102). Therefore, the display device100can adjust the duty and process the image signal according to the content of the content of the image represented by the input image signal, thereby preventing lowering in image quality of the image to be displayed on the panel108and achieving higher image quality.

Furthermore, the display device100generates the adjustment signal and the control signal based on the content information received by the HDMI sink102, and thus information representing a moving image or a still image is not detected based on the image represented by the image signal as in the display device of the related art. Therefore, the display device100can lower the possibility of occurrence of mistaken detection and delay in processing compared to the display device of the related art, and can achieve higher image quality than the display device of the related art.

[Variant of Display Device100According to the Embodiment of the Present Invention]

[a] First Variant

As shown inFIG. 13, the light emission time control part154includes the average luminance calculation part400and the light emission amount regulation part402, and can set the reference duty based on the average luminance calculated in the average luminance calculation part400. However, the light emission time control part according to the embodiment of the present invention is not limited to such configuration. The light emission time control part according to the embodiment of the present invention may include a histogram calculation part for calculating the histogram value of the video as a component replacing the average luminance calculation part400, and the light emission amount regulation part may set the reference duty based on the histogram value. In this configuration as well, the light emission amount in one frame period (unit time) will not be larger than the largest light emission amount in the predetermined duty in the display device according to the first variant, and thus the display device according to the first variant can prevent overcurrent from flowing to each pixel (more precisely, light emitting element of each pixel) of the panel108. The display device according to the first variant can have effects similar to the display device100in addition to the effect of preventing overcurrent.

[b] Second Variant

In the display device100shown inFIG. 13, a configuration in which the adjustment signal is transmitted to the light emission time adjustment part406of the light emission time control part154, and the lower limit value of the actual duty (Duty′) is appropriately changed according to the adjustment signal has been described, but the display device according to the embodiment of the present invention is not limited thereto. For instance, the display device according to the embodiment of the present invention may have the adjustment signal transmitted to the light emission amount regulation part402of the light emission time control part154, and the upper limit value of the reference duty (Duty) shown inFIG. 16may be appropriately changed according to the adjustment signal. The display device according to the second variant controls the light emission time per unit time to prevent overcurrent from flowing to the light emitting element and can change the image quality according to the content of the content of the image represented by the image signal by changing the upper limit value of the reference duty (Duty) according to the adjustment signal.

[c] Third Variant

The display device according to the embodiment of the present invention may arbitrarily combine the configuration of the display device100, the display device according to the first variant, and the display device according to the second variant.

The image reproducing devices200,300, . . . have been described by way of example as components configuring the image display system according to the embodiment of the present invention, but the embodiment of the present invention is not limited thereto. For instance, the embodiment of the present invention may be applied to computers such as PC (Personal Computer), disc reproduction devices such as Blu-Ray disc reproduction device (or Blu-Ray recorder) and DVD recorder, game machines such as Play station (registered trademark), and the like.

The display device100has been described by way of example as a component configuring the image display system according to the embodiment of the present invention, but the embodiment of the present invention is not limited to such mode. For instance, the embodiment of the present invention may be applied to television receivers for receiving television broadcast and displaying pictures, computers such as PC having a display member on the exterior or the interior thereof, and the like.

(Program According to Embodiment of the Present Invention)

According to a program for causing a computer to function as the display device100according to the embodiment of the present invention, higher image quality can be achieved by controlling the light emission time for the light emitting element to emit light per unit time according to the type of content of the input image signal, and also controlling the gain of the image signal.

(Image Signal Processing Method According to the Embodiment of the Present Invention)

The image signal processing method according to the present invention will now be described.FIG. 21is a flowchart showing one example of the image signal processing method according to the embodiment of the present invention, and shows one example of a method related to the control of the light emission time per unit time in the display device100. The following description is made with unit time as one frame period, and the image signals to be input as independent signals for each color of R, G, and B corresponding to the image for every one frame period (unit time).

The display device100calculates the average luminance of the image signal in a predetermined period from the input image signals of R, G, and B (S200). The method of calculating the average luminance in step S200includes arithmetic average, but is not limited thereto. The predetermined period can be assumed as one frame period.

The display device100sets the reference duty based on the average luminance calculated in step S200(S202). The setting of the reference duty in step S202can be carried out using a lookup table in which the average luminance and the reference duty are associated, for example. The lookup table holds the reference duty such that the largest light emission amount in the predetermined duty and the light emission amount defined by the reference duty and the average luminance become the same. The upper limit value may be provided to the reference duty in the lookup table.

The display device100adjusts the gain of the respective input image signals of R, G, and B based on the reference duty set in step S202(S204; first gain adjustment). The adjustment of the gain in step S204can be carried out by multiplying the respective input image signals of R, G, and B and the reference duty set in step S202.

The display device100then determines whether or not the reference duty set in step S202is within a defined range (S206). In step S206, determination is made as within the defined range in one of the following (A) to (E) cases.

(A) When reference duty is larger than the predetermined lower limit value (correspond to first adjustment method)

(B) When reference duty is smaller than the predetermined upper limit value (correspond to second adjustment method)

(C) When reference duty is greater than or equal to the predetermined lower limit value and lower than or equal to the predetermined upper limit value (correspond to third adjustment method)

(D) When reference duty is greater than or equal to the lower limit value appropriately changed according to the adjustment signal and lower than or equal to the predetermined upper limit value (correspond to fourth adjustment method)

(E) When reference duty is larger than the lower limit value appropriately changed according to the adjustment signal (correspond to variant of fourth adjustment method)

The adjustment signals represented in (D) and (E) are generated by the control part104using the signal generating method shown inFIG. 10. The adjustment signals generated by the control part104are transmitted to the light emission time adjustment part406of the light emission time control part154, so that the light emission time adjustment part406can appropriately set the lower limit value corresponding to the adjustment signal.

When determined that the reference duty is within the defined range in step S206, the display device100outputs the reference duty set in step S202as the actual duty (S208).

When determined that the reference duty is not within the defined range in step S206, the display device100adjusts (adjustment of actual duty) the reference duty set in step S202, and outputs the actual duty (S210). The adjustment of the actual duty in step S210can be carried out as below (a) to (c) in each cases of (A) to (E).

(a) In the cases of (A) and (E): output lower limit value as actual duty

(b) In the case of (B): output upper limit value as actual duty

(c) In the cases of (C) and (D): output lower limit value or upper limit value as actual duty

The display device100adjusts the gain of the image signal adjusted in step S204based on the actual duty output in step S208or step S210(S212: second gain adjustment). The adjustment of the gain of the image signal in step S212can be carried out according to the adjustment ratio of the actual duty with respect to the reference duty, as expressed in equations 2 to 4. Therefore, three types of adjustment of “attenuate”, “amplify”, or “no change” can be performed on the gain of the image signal in step S212.

As expressed in equations 1 and 2 to 4, the light emission amount defined by the actual duty output in step S208or step S210and the gain of the image signal adjusted in step S212becomes the same as the light emission amount before adjustment.

The display device100can output the reference duty according to the average luminance in one frame period (unit time) of the input image signals by using the image signal processing method shown inFIG. 21. The reference duty is set to a value the largest light emission amount in the predetermined duty and the light emission amount defined by the reference duty and the average luminance in one frame period (unit time: predetermined period) become the same.

The display device100can suppress rise in demerits (demerits described in first and second adjustment examples described above) originating from the trade off relationship of the luminance and the movement blur and prevent lowering in image quality by providing the lower limit value and/or upper limit value to the actual duty and adjusting the actual duty using the image signal processing method shown inFIG. 21. Furthermore, since the display device100can change the lower limit value of the actual duty according to the adjustment signal generated based on the content identification information, the display device100can control the actual duty according to the content of the content of the image represented by the input image signal.

Moreover, the display device100can adjust the actual duty and the gain of the image signal so that the light emission amount defined by the reference duty and the gain of the image signal is maintained the same by using the image signal processing method shown inFIG. 21.

Therefore, the display device100can achieve higher image quality by controlling the light emission time for the light emitting element to emit light per unit time according to the type of content of the input image signal and also controlling the gain of the image signal using the image signal processing method shown inFIG. 21.

For instance, in the display device100according to the embodiment of the present invention shown inFIG. 9, a configuration in which the display device100includes the HDMI sink102, and the image signal and control data such as content identification information are received using HDMI has been described, but the embodiment of the present invention is not limited to such configuration. In place of the HDMI, the display device according to the embodiment of the present invention may include a receiving member of the image signal such as D terminal and component terminal, and a separate control data receiving member for receiving the control data such as content identification information. In such configuration as well, the display device according to the embodiment of the present invention can generate adjustment signals based on the content identification information, and thus can have effects similar to the display device100described above.

The above-described configuration shows one example of the embodiment of the present invention, and obviously falls within the technical scope of the present invention.