Image processing device, image display system, image processing method and program therefor

The present invention contains subject matter related to Japanese Patent Application JP 2007-326342 filed in the Japan Patent Office on Dec. 18, 2007, the entire contents of which being incorporated herein by reference.

1. Field of the Invention

The present invention relates to an image processing device which processes externally input image data and outputs it to a hold-type display device, an image display system including the processing device, an image processing method and a program therefor.

2. Description of the Related Art

In recent years, flat panel displays like LCDs (Liquid Crystal Display) have widely been spread, in place of CRTs (Cathode Ray Tube).

In motion display, unlike an impulse-type display device, such as a CRT, a hold-type display device, such as LCD, keeps displaying all pixels constituting an image page, for a period of time since an instruction of displaying a predetermined one of a plurality of frames or fields (hereinafter referred to as a “field”) constituting a motion image is issued until an instruction of displaying a next frame is issued. Thus, in the hold-type display device, an issue is the occurrence of motion blur, such as blurring in the leading edge, tailing in the trailing edge, delay in a perception position, in the moving object, by an Eye-Trace Integration effect (an afterglow characteristic on human retina, when following a motion picture). Specifically, in the LCD, it is considered that this motion blur can easily occur due to a delay in the response speed of the liquid crystal.

For this issue, an overdrive technique is provided for restraining the motion blur by improving the response characteristic of the LCD. To improve the response characteristic in response to a step input in the LCD, in the overdrive technique, for example, a voltage greater than a target voltage corresponding to a specified brightness value is applied so as to accelerate a brightness transition, in a frame where an input signal variation first occurs. With the utilization of this overdrive technique, the response speed of the liquid crystal can increase in a half-tone region, and attaining a restraining effect of the motion blur. A proposed technique is provided for restraining the motion blur more effectively, by changing a waveform of a voltage applied in accordance with a motion vector in each frame, using the overdrive technique (see, for example, JP-A No. 2005-43864).

However, an issue in the overdrive technique is that a sufficiently high voltage for accelerating the response speed of the liquid crystal may not be applied, because of the limit of the applicable voltage range in the liquid crystal. As a result, the motion blur restraining effect may not sufficiently be attained, for example, when a target voltage for a black display or a white display is near the limit of the voltage range (in the case of the tone variation in a high tone range or a low tone range).

In the liquid crystal display driving in a VA-mode, different characteristics show at between the rise and the decay of the liquid crystal. It takes much time for the variation of molecular alignments, when rise from a level “0” (e.g. black). Thus, an issue is that a specified brightness transition may not be attained within one frame in consideration of the response speed of the liquid crystal using only the overdrive technique.

Recently, a double-speed operation technique has been developed for displaying image data on the LCD, by time-dividing a frame to be displayed in order to reduce the Eye-Trace Integration effect, and obtaining an interpolated image between frames based on a motion vector of an input image in order to increase the motion picture display frequency using a plurality of sub-fields.

However, if the display frequency is increased, the driving frequency of a display driver which drives the display device increases as well. This may result an issue of an insufficient charge, an increase in the number of terminals of IC or connector, an increase in the substrate area, heat generation, an increase in EMI (Electro Magnetic Interference), an increase in cost.

The present invention has been made in consideration of the above issues. It is desirable to restrain an increase in cost, to reduce an Eye-Trace Integration effect, to improve a response characteristic of image display in all tone variations, and to restrain the motion blur, in an image processing device which processes externally input image data and outputs it to a hold-type display device, an image display system including the processing device, an image processing method and a program therefor.

According to an embodiment of the present invention, there is provided an image processing device which processes externally input image data and outputs the display image data to a hold-type display device, including: a motion vector detecting unit which detects a motion vector of the input image data; a response time information storage unit which stores response time information representing a time since a driving voltage is applied to the display device until the display device displays an image with a tone corresponding to the driving voltage, in association with a tone variation value; a compensation processing unit which compensates a pixel value in the image data for each pixel, in a frame which is one frame ahead of a frame to be displayed by the display device, based on the image data, the motion vector and the response time information; and an output unit which outputs the image data after compensated by the compensation processing unit to the display device.

The image processing device may further include an edge detecting unit which detects an edge from the input image data, based on the motion vector.

The compensation processing unit may determine whether to perform a compensation process for the pixel value, in accordance with a detection result of the edge detecting unit.

The compensation processing unit may decide whether to perform the compensation process in accordance with an edge direction of an edge part detected by the edge detecting unit.

Further, at this time, the compensation processing unit may decide to perform the compensation process, when it is determined that the edge part detected by the edge detecting unit is in a rise area from a low tone to a high tone based on the edge direction, and may decide not to perform the compensation process, when it is determined that the edge part is in a decay area from a high tone to a low tone based on the edge direction.

The compensation processing unit may include: a compensation range setting unit which sets a compensation range for compensating a pixel value in the image data based on the motion vector; a filter setting unit which sets a characteristic of a filter for compensating the pixel value in the image data so as to display an image with a tone corresponding to a tone set based on the image data when the display device displays the frame to be displayed, based on the image data, the motion vector and the response time information; and a filter processing unit which compensates a pixel value of the pixel within the compensation range by filtering the image data with a filter having the characteristic set by the filter setting unit, in the frame that is one frame ahead of the frame to be displayed by the display device.

The image processing device having the compensation processing unit may further include an edge detecting unit which detects an edge from the input image data based on the motion vector.

At this time, the compensation processing unit may further include a selecting unit which selects either one of the image data whose pixel value has been compensated by the filter processing unit and the image data whose pixel value has not been compensated by the filter processing unit, in accordance with a detection result of the edge detecting unit.