# Patent

## Title
Image displaying device and method and image processing device and method for preventing image deterioration due to motion-compensated rate conversion processing

## Abstract

It is an object to prevent the image quality deterioration of a moving image likely to include a plurality of the same consecutive images such as 2-3 or 2-2 pulldown video due to the motion-compensated frame rate conversion (FRC) processing. An image displaying device is provided with an FRC portion (10) for converting the number of frames in an input image signal by interpolating an image signal to which a motion compensation processing has been given between the frames in the input image signal, a pulldown detecting portion (14) for detecting whether the input image signal is an image signal to which pulldown conversion has been performed, and a controlling portion (15). The FRC portion (10) includes a motion vector detecting portion (11e) for detecting a motion vector between the frames of the input image signal, an interpolating vector evaluating portion (11f) for allocating an interpolating vector between the frames based on the motion vector information, and an interpolating frame generating portion (12d) for generating an interpolating frame from the interpolating vector. In the case that the input image signal is an image signal to which pulldown conversion has been performed, the controlling portion (15) set the motion vector detected by the motion vector detecting portion (11e) to zero-vector to make the motion compensation processing of the FRC portion (10) ineffective.

## Background
TECHNICAL FIELD
The present invention relates to an image displaying device and method and an image processing device and method having a function of converting a frame rate or field rate, and more particularly, to an image displaying device and an image displaying method of the device and an image processing device and an image processing method of the device, which include preventing the image quality deterioration of a moving image likely to include a plurality of the same consecutive images due to a motion-compensated rate conversion processing.
BACKGROUND OF THE INVENTION
As compared to conventional cathode-ray tubes (CRTs) primarily used for realizing moving images, LCDs (Liquid Crystal Displays) have a drawback, so-called motion blur, which is the blurring of outline of a moving portion perceived by a viewer when displaying a moving image. It is pointed out that this motion blur arises from the LCD display mode itself (see, e.g., Specification of Japanese Patent No. 3295437; “Ishiguro Hidekazu and Kurita Taiichiro, “Consideration on Motion Picture Quality of the Hold Type Display with an octuple-rate CRT”, IEICE Technical Report, Institute of Electronics, Information and Communication Engineers, EID96-4(1996-06), p.19-26”).
Since fluorescent material is scanned by an electron beam to cause emission of light for display in CRTs, the light emission of pixels is basically impulse-like although slight afterglow of the fluorescent material exists. This is called an impulse display mode. On the other hand, in the case of LCDs, an electric charge is accumulated by applying an electric field to liquid crystal and is retained at a relatively high rate until the next time the electric field is applied. Especially, in the case of the TFT mode, since a TFT switch is provided for each dot composing a pixel and each pixel normally has an auxiliary capacity, the ability to retain the accumulated charge is extremely high. Therefore, the light emission is continued until the pixels are rewritten by the application of the electric field based on the image information of the next frame or field (hereinafter, represented by the frame) . This is called a hold display mode.
Since the impulse response of the image displaying light has a temporal spread in the above hold display mode, spatial frequency characteristics deteriorate along with temporal frequency characteristics, resulting in the motion blur. Since the human eye can smoothly follow a moving object, if the light emission time is long as in the case of the hold type, the movement of image seems jerky and unnatural due to the time integration effect.
To improve the motion blur in the above hold display mode, a frame rate (number of frames) is converted by interpolating an image between frames in a known technology. This technology is called FRC (Frame Rate Converter) and is put to practical use in liquid crystal displaying devices, etc.
Conventionally known methods of converting the frame rate include various techniques such as simply repeating read-out of the same frame for a plurality of times and frame interpolation using linear interpolation between frames (see, e.g., Yamauchi Tatsuro, “TV Standards Conversion”, Journal of the Institute of Television Engineers of Japan, Vol. 45, No. 12, pp.1534-1543 (1991)). However, in the case of the frame interpolation processing using the linear interpolation, unnaturalness of motion (jerkiness, judder) is generated due to the frame rate conversion, and the motion blur disturbance due to the above hold display mode cannot sufficiently be improved, resulting in inadequate image quality.
To eliminate effects of the jerkiness, etc., and improve quality of moving images, a motion-compensated frame interpolation processing using motion vectors is proposed. Since a moving image itself is captured to compensate the image movement in this processing, highly natural moving images may be acquired without deteriorating the resolution and generating the jerkiness. Since interpolation image signals are generated with motion compensation, the motion blur disturbance due to the above hold display mode may sufficiently be improved.
Above Specification of Japanese Patent No. 3295437 discloses a technology of motion-adaptively generating interpolating frames to increase a frame frequency of a display image for improving deterioration of spatial frequency characteristics causing the motion blur. In this case, at least one interpolation image signal interpolated between frames of a display image is motion-adaptively generated from the previous and subsequent frames, and the generated interpolation image signals are interpolated between the frames and are sequentially displayed.
FIG. 1 is a block diagram of a schematic configuration of an FRC drive display circuit in a conventional liquid crystal displaying device and, in FIG. 1, the FRC drive display circuit includes an FRC portion 100 that converts the number of frames of the input image signal by interpolating the image signals to which the motion compensation processing has been given between frames of the input video signal, an active-matrix liquid crystal display panel 104 having a liquid crystal layer and an electrode for applying the scan signal and the data signal to the liquid crystal layer, and an electrode driving portion 103 for driving a scan electrode and a data electrode of the liquid crystal display panel 104 based on the image signal subjected to the frame rate conversion by the FRC portion 100.
The FRC portion 100 includes a motion vector detecting portion 101 that detects motion vector information from the input image signal and an interpolating frame generating portion 102 that generates interpolating frames based on the motion vector information acquired by the motion vector detecting portion 101.
In the above configuration, for example, the motion vector detecting portion 101 may obtain the motion vector information with the use of a block matching method and a gradient method described later or if the motion vector information is included in the input image signal in some form, this information may be utilized. For example, the image data compression-encoded with the use of the MPEG format includes motion vector information of a moving image calculated at the time of encoding, and this motion vector information may be acquired.
FIG. 2 is a diagram for explaining a frame rate conversion processing by the conventional FRC drive display circuit shown in FIG. 1. The FRC portion 100 generates interpolating frames (gray-colored images in FIG. 2) between frames with the motion compensation using the motion vector information output from the motion vector detecting portion 101 and sequentially outputs the generated interpolation signals along with the input frame signals to perform processing of converting the frame rate of the input image signal from 60 frames per second (60 Hz) to 120 frames per second Hz).
FIG. 3 is a diagram for explaining an interpolating frame generation processing of the motion vector detecting portion 101 and the interpolating frame generating portion 102. The motion vector detecting portion 101 uses the gradient method to detect a motion vector 105 from, for example, a frame #1 and a frame #2 shown in FIG. 3. The motion vector detecting portion 101 obtains the motion vector 105 by measuring a direction and an amount of movement in 1/60 second between the frame #1 and the frame #2. The interpolating frame generating portion 102 then uses the obtained motion vector 105 to allocate an interpolating vector 106 between the frame #1 and the frame #2. An interpolating frame 107 is generated by moving an object (in this case, an automobile) from a position of the frame #1 to a position after 1/120 second based on the interpolating vector 106.
By performing the motion-compensated frame interpolation processing with the use of the motion vector information to increase a display frame frequency in this way, the display state of the LCD (the hold display mode) can be made closer to the display state of the CRT (the impulse display mode) and the image quality deterioration can be improved which is due to the motion blur generated when displaying a moving image.
In the motion-compensated frame interpolation processing, it is essential to detect the motion vectors for performing the motion compensation. For example, the block matching method and the gradient method are proposed as representative techniques for the motion vector detection. In these methods, the motion vector is detected for each pixel or small block between two consecutive frames and this motion vector is used to interpolate each pixel or small block of the interpolating frame between two frames. An image at an arbitrary position between two frames is interpolated at an accurately compensated position to convert the number of frames.
Since the frames are highly correlated in moving images and has continuity in the time axis direction, a pixel or a small block moving in one frame tends to move with the same movement amount in the subsequent frame or the previous frame. For example, in the case of a moving image of a ball rolling from the right to the left of a screen, the ball area moves with similar movement amounts in every frame. Consecutive frames tend to have the continuity of motion vectors.
Therefore, the motion vector in the next frame may more easily or more accurately be detected by reference to a motion vector detection result of preceding frames. For example, in the iterative gradient method, which is an improved gradient method, a motion vector of a neighboring block already detected in the previous frame or the current frame is defined as an initial deflection vector, which is used as a starting point to repeat calculations of the gradient method for a detected block. With this method, a substantially accurate movement amount can be acquired by repeating the gradient method about two times.
A motion vector may also efficiently be detected in the block matching method in such a way that a reference is made to the motion vector detection result of the previous frame to change the search order. When detecting a motion vector, for example, the frame rate conversion may be processed in real time by utilizing the motion vector already detected.
DISCLOSURE OF THE INVENTION
Problems to be Solved by the Invention
Video signals may be sourced from videos from movie films and videos from computer graphics (CG) in addition to videos shot by normal television video cameras. Therefore, television broadcast signals and video disc reproduction signals in the NTSC mode or the PAL mode often include video signals from movie films or CG. Due to the recent development in storage capacity of recording medium (e.g., DVD (digital versatile disc), HD (hard disc)) and the digitization of transmission methods, video signals from various sources may be mixed.
For example, a normal movie film has 24 frames per second and, when this film is output to a display having a frame rate of 60 Hz, the video having a frame rate of 24 Hz is to which the 2-3 pull-down processing has been given and is converted into and output as video signals having a frame rate of 60 Hz by outputting the same images for every two or three frames.
When a film movie or a CG animation video having 30 frames per second is output to a display having a frame rate of 60 Hz, the video having a frame rate of 30 Hz is subjected to the 2-2 pull-down processing and is converted into and output as video signals having a frame rate of 60 Hz by outputting the same images for every two frames. When a film movie having 24 frames per second is output to a display having a frame rate of 50 Hz, the video having a frame rate of 24 Hz is to which the 2-2 pull-down processing has been given and the same images are output for every two frames.
Film movies or CG animation videos often have original images having a frame rate equal to 60 Hz or less and are displayed and output as 60-Hz video signals by consecutively outputting a plurality of the same images as above.
The case of a film movie having 24 frames per second described above will be described with reference to FIG. 4. Frame #1 to #10 of FIG. 4 represents an image sequence converted into 60 Hz from a 24-Hz movie video through the 2-3 pull-down processing. The frames #1 and #2, the frames #3 to #5, the frames #6 and #7, and the frames #8 to #10 are the same images, respectively.
In a video likely to include a plurality of the same output images, the continuity of motion vectors becomes impaired between frames. For example, it is assumed that some kind of a moving object is shot in the video of FIG. 4. Although a motion vector is detected between the frames #5 and #6 since these frames are different images, a motion vector to be detected should completely be zero between the next frames #6 and #7 since these frames are the same images. Since the next frames #7 and #8 are different images, a motion vector is detected between these frames.
With regard to the motion vectors of the successive frames from the frame #5 to the frame #7 of FIG. 4, no continuity of the motion vectors exists between adjacent frames since “motion vector exists”, “motion vector is zero”, and “motion vector exists” are mixed in this order.
If the processing for detecting the motion vector in the next frame is executed by referring to the motion vector detection result of the previous frame as above for such a video likely to include a plurality of the same output images, it is problematic that the motion vector is erroneously detected since no continuity of the motion vector exists between the frames.
In the above example, although a motion vector to be detected should completely be zero between the frames #6 and #7 since these frames are the same images, a motion vector between the previous frames #5 and #6 is not zero and, therefore, a vector other than zero may erroneously be detected by referring to this vector.
Although a motion vector should be detected between the frames #7 and #8 since these frames are different images, a motion vector between the previous frames #6 and #7 is zero and, therefore, a zero vector may erroneously be detected by referring to this vector. It is problematic that such an erroneous detection of the motion vector may cause the image quality deterioration in the displayed video.
The present invention was conceived in view of the above problems and it is therefore the object of the present invention to provide an image displaying device and method and an image processing device and method capable of preventing the image quality deterioration of a moving image likely to include a plurality of the same consecutive images such as 2-3 pulldown video and 2-2 pulldown video due to the motion-compensated frame rate conversion (FRC) processing.
Means for Solving the Problems
A first invention of the present application is an image displaying device having a rate converting portion that interpolates an image signal to which a motion compensation processing has been given between frames or fields of an input image signal to convert and output the number of frames or fields of the input image signal to a display panel, wherein a determining portion that determines whether the input image signal is an image signal to which pulldown conversion has been performed is included, and when the input image signal is determined to be an image signal to which pulldown conversion has been performed by the determining portion, image interpolation by the motion compensation processing is not performed.
A second invention of the present application is the image displaying device, wherein the rate converting portion includes a portion that generates an interpolation image signal to which a motion compensation processing has been given based on motion vector information between consecutive frames or fields included in the input image signal, and when the input image signal is determined to be an image signal to which pulldown conversion has been performed, a motion compensation processing in the interpolation image signal generating portion is made ineffective.
A third invention of the present application is the image displaying device, wherein the rate converting portion includes: a motion vector detecting portion that detects motion vector information between consecutive frames or fields included in the input image signal; an interpolating vector allocating portion that allocates an interpolating vector between the frames or the fields based on the detected motion vector information; an interpolation image generating portion that generates an interpolation image signal from the input image signal, using the allocated interpolating vector; and an image interpolating portion that interpolates the generated interpolation image signal between the frames or the fields.
A fourth invention of the present application is the image displaying device, wherein when the input image signal is determined to be an image signal to which pulldown conversion has been performed, the motion vector detected by the motion vector detecting portion is set to zero-vector to make the motion compensation processing ineffective.
A fifth invention of the present application is the image displaying device, wherein when the input image signal is determined to be an image signal to which pulldown conversion has been performed, the interpolating vector allocated by the interpolating vector allocating portion is set to zero-vector to make the motion compensation processing ineffective.
A sixth invention of the present application is the image displaying device, wherein the input image signal is output to the display panel without converting the number of frames or fields of the input image signal when the input image signal is determined to be an image signal to which pulldown conversion has been performed.
A seventh invention of the present application is The image displaying device, wherein a drive frequency of a display panel that displays an image signal is variable, and wherein the drive frequency of the display panel displaying the image signals is variable and the drive frequency of the display panel is varied in accordance with the frame frequency or the field frequency of the input image signal when the input image signal is determined to be an image signal to which pulldown conversion has been performed.
A eighth invention of the present application is the image displaying device, wherein another rate converting portion that inserts an image signal to which the motion compensation processing has not been given between frames or fields of the input image signal to convert the number of frames or fields of the input image signal is also included, and the image signal with the number of frames or fields converted by the another rate converting portion is output to the display panel when the input image signal is determined to be an image signal to which pulldown conversion has been performed.
A ninth invention of the present application is the image displaying device, wherein the another rate converting portion inserts an image signal of the frames or fields between frames or fields of the input image signal to convert the number of frames or fields of the input image signal.
A tenth invention of the present application is the image displaying device, wherein the another rate converting portion interpolates an image signal to which a linear interpolation processing has been given between frames or fields of the input image signal to convert the number of frames or fields of the input image signal.
A eleventh invention of the present application is the image displaying device, wherein the another rate converting portion inserts a predetermined monochromatic image signal between frames or fields of the input image signal to convert the number of frames or fields of the input image signal.
A twelfth invention of the present application is an image displaying method having a step of interpolating an image signal to which a motion compensation processing has been given between frames or fields of an input image signal to convert the number of frames or fields of the input image signal, wherein it is determined whether the input image signal is an image signal to which pulldown conversion has been performed, and image interpolation by the motion compensation processing is not performed when it is determined that the input image signal is an image signal to which pulldown conversion has been performed.
A thirteenth invention of the present application is the image displaying method, wherein the step of converting the number of frames or fields of the input image signal includes a process of generating an interpolation image signal to which a motion compensation processing has been given based on motion vector information between consecutive frames or fields included in the input image signal, wherein when the input image signal is determined to be an image signal to which pulldown conversion has been performed, a motion compensation processing in the process of generating the interpolation image signal is made ineffective.
A fourteenth invention of the present application is the image displaying method, wherein a drive frequency of a display panel is changed in accordance with the frame frequency or the field frequency of the input image signal when it is determined that the input image signal is an image signal to which pulldown conversion has been performed.
A fifteenth invention of the present application is the image displaying method, wherein an image signal of the frames or fields of the input image signal is inserted between these frames or fields to convert the number of frames or fields of the input image signal when it is determined that the input image signal is an image signal to which pulldown conversion has been performed.
A sixteenth invention of the present application is the image displaying method, wherein an image signal to which a linear interpolation processing has been given is interpolated between frames or fields of the input image signal to convert the number of frames or fields of the input image signal when it is determined that the input image signal is an image signal to which pulldown conversion has been performed.
A seventeenth invention of the present application is the image displaying method, wherein a predetermined monochromatic image signal is inserted between frames or fields of the input image signal to convert the number of frames or fields of the input image signal when it is determined that the input image signal is an image signal to which pulldown conversion has been performed.
A eighteenth invention of the present application is an image processing device having a rate converting portion that interpolates an image signal to which a motion compensation processing has been given between frames or fields of an input image signal to convert the number of frames or fields of the input image signal, wherein a determining portion that determines whether the input image signal is an image signal to which pulldown conversion has been performed is included, and when the input image signal is determined to be an image signal to which pulldown conversion has been performed by the determining portion, image interpolation by the motion compensation processing is not performed.
A nineteenth invention of the present application is the image processing device, wherein the rate converting portion includes a portion that generates an interpolation image signal to which a motion compensation processing has been given based on motion vector information between consecutive frames or fields included in the input image signal, and when the input image signal is determined to be an image signal to which pulldown conversion has been performed, a motion compensation processing in the interpolation image signal generating portion is made ineffective.
A twentieth invention of the present application is the image processing device, wherein another rate converting portion that inserts an image signal to which the motion compensation processing has not been given between frames or fields of the input image signal to convert the number of frames or fields of the input image signal is also included, an the image signal with the number of frames or fields converted by the another rate converting portion is output to the display panel when the input image signal is determined to be an image signal to which pulldown conversion has been performed.
A twenty-first invention of the present application is the image processing device, wherein the another rate converting portion inserts an image signal of the frames or fields between frames or fields of the input image signal to convert the number of frames or fields of the input image signal.
A twenty-second invention of the present application is the image processing device, wherein the another rate converting portion interpolates an image signal to which a linear interpolation processing has been given between frames or fields of the input image signal to convert the number of frames or fields of the input image signal.
A twenty-third invention of the present application is the image processing device, wherein the another rate converting portion inserts a predetermined monochromatic image signal between frames or fields of the input image signal to convert the number of frames or fields of the input image signal.
A twenty-fourth invention of the present application is an image processing method having a step of interpolating an image signal to which a motion compensation processing has been given between frames or fields of an input image signal to convert the number of frames or fields of the input image signal, wherein it is determined whether the input image signal is an image signal to which pulldown conversion has been performed, and image interpolation by the motion compensation processing is not performed when it is determined that the input image signal is an image signal to which pulldown conversion has been performed.
A twenty-fifth invention of the present application is the image processing method, wherein the step of converting the number of frames or fields of the input image signal includes a process of generating an interpolation image signal to which a motion compensation processing has been given based on motion vector information between consecutive frames or fields included in the input image signal, wherein when the input image signal is determined to be an image signal to which pulldown conversion has been performed, a motion compensation processing in the process of generating the interpolation image signal is made ineffective.
A twenty-sixth invention of the present application is the image processing method, wherein an image signal of the frames or fields of the input image signal is inserted between these frames or fields to convert the number of frames or fields of the input image signal when it is determined that the input image signal is an image signal to which pulldown conversion has been performed.
A twenty-seventh invention of the present application is the image processing method, wherein an image signal to which a linear interpolation processing has been given is interpolated between frames or fields of the input image signal to convert the number of frames or fields of the input image signal when it is determined that the input image signal is an image signal to which pulldown conversion has been performed.
A twenty-eighth invention of the present application is the image processing method, wherein a predetermined monochromatic image signal is inserted between frames or fields of the input image signal to convert the number of frames or fields of the input image signal when it is determined that the input image signal is an image signal to which pulldown conversion has been performed.
A twenty-ninth invention of the present application is an image displaying device having a rate converting portion that interpolates an image signal to which a motion compensation processing has been given between frames or fields of an input image signal to convert and output the number of frames or fields of the input image signal to a display panel, wherein a determining portion that determines whether the input image signal is an image signal to which pulldown conversion has been performed is included, and when the input image signal is determined to be an image signal to which pulldown conversion has been performed by the determining portion strength of the motion compensation processing is reduced.
A thirty invention of the present application is the image displaying device, wherein the rate converting portion includes an interpolation image generating portion that performs weighted addition of the image signal to which the motion compensation processing has been given and an image signal to which a linear interpolation processing has been given at a predetermined rate to generate an interpolation image signal and the weighted addition rate is reduced when the input image signal is determined to be an image signal to which pulldown conversion has been performed.
A thirty-first invention of the present application is the image displaying device, wherein when the input image signal is determined to be an image signal to which pulldown conversion has been performed, the interpolation image generating portion defines the image signal to which the linear interpolation processing has been given as the interpolation image signal, and when the input image signal is determined not to be an image signal to which pulldown conversion has been performed, the interpolation image generating portion defines the image signal to which the motion compensation processing has been given as the interpolation image signal.
A thirty-second invention of the present application is An image displaying method having a step of interpolating an image signal to which a motion compensation processing has been given between frames or fields of an input image signal to convert the number of frames or fields of the input image signal, wherein it is determined whether the input image signal is an image signal to which pulldown conversion has been performed, and strength of the motion compensation processing is reduced when the input image signal is determined to be an image signal to which pulldown conversion has been performed.
A thirty-third invention of the present application is an image processing device having a rate converting portion that interpolates an image signal to which a motion compensation processing has been given between frames or fields of an input image signal to convert the number of frames or fields of the input image signal, wherein a determining portion that determines whether the input image signal is an image signal to which pulldown conversion has been performed is included, and when the input image signal is determined to be an image signal to which pulldown conversion has been performed by the determining portion, strength of the motion compensation processing is reduced.
A thirty-fourth invention of the present application is an image processing method having a step of interpolating an image signal to which a motion compensation processing has been given between frames or fields of an input image signal to convert the number of frames or fields of the input image signal, wherein it is determined whether the input image signal is an image signal to which pulldown conversion has been performed, and strength of the motion compensation processing is reduced when the input image signal is determined to be an image signal to which pulldown conversion has been performed.
Effect of the Invention
According to the present invention, the image quality deterioration of displayed images may effectively be prevented by not executing the interpolation processing through motion compensation if an image signal to which 2-3 pulldown conversion or 2-2 pulldown conversion has been given is input.



BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a block diagram of a schematic configuration of an FRC drive display circuit in a conventional liquid crystal displaying device.
FIG. 2 is a diagram for explaining a frame rate conversion processing by the conventional FRC drive display circuit shown in FIG. 1.
FIG. 3 is a diagram for explaining an interpolating frame generation processing of a motion vector detecting portion and an interpolating frame generating portion.
FIG. 4 is a diagram for explaining an image sequence when a 24-Hz film movie is converted by the 2-3 pulldowm processing into 60 Hz.
FIG. 5 is a block diagram of an exemplary configuration of a frame rate converting portion included in an image displaying device of the present invention.
FIG. 6 is a diagram for explaining an example of an interpolating frame generating processing of a frame generating portion.
FIG. 7 is a block diagram of an exemplary main configuration of a liquid crystal displaying device according to a first embodiment of the present invention.
FIG. 8 is a block diagram of an exemplary main configuration of a liquid crystal displaying device according to a second embodiment of the present invention.
FIG. 9 is a block diagram of an exemplary main configuration of a liquid crystal displaying device according to a third embodiment of the present invention.
FIG. 10 is a diagram of a relationship between input data and output data according to the third embodiment of the present invention.
FIG. 11 is a block diagram of an exemplary main configuration of a liquid crystal displaying device according to a fourth embodiment of the present invention.
FIG. 12 is a diagram of a relationship between input data and output data according to the fourth embodiment of the present invention.
FIG. 13 is a block diagram of an exemplary main configuration of a liquid crystal displaying device according to a fifth embodiment of the present invention.
FIG. 14 is a diagram of a relationship between input data and output data according to the fifth embodiment of the present invention.
FIG. 15 is a block diagram of an exemplary main configuration of a liquid crystal displaying device according to a sixth embodiment of the present invention.
FIG. 16 is a diagram of a relationship between input data and output data according to the sixth embodiment of the present invention.
FIG. 17 is a block diagram of an exemplary main configuration of an FRC portion according to a seventh embodiment of the present invention.
FIG. 18 is a flowchart for explaining an example of an image displaying method by the image displaying device of the present invention.
FIG. 19 is a flowchart for explaining another example of the image displaying method by the image displaying device of the present invention.
FIG. 20 is a flowchart for explaining another example of the image displaying method by the image displaying device of the present invention.



EXPLANATION OF REFERENCE NUMERALS
10, 100 . . . frame rate converting (FRC) portion; 11 . . . vector detecting portion; 11a . . . luminance signal extracting portion; 11b . . . preprocessing filter; 11c . . . motion detection frame memory; 11d . . . initial vector memory; 11e, 101 . . . motion vector detecting portion; 11f . . . interpolating vector evaluating portion; 12 . . . frame generating portion; 12a . . . interpolating frame memory; 12b, 102 . . . interpolating frame generating portion; 12c . . . time base conversion frame memory; 12d . . . time base converting portion; 12e . . . compensation intensity varying portion; 14 . . . pulldown detecting portion; 15 . . . controlling portion; 16 . . . switching portion; 17 . . . zero vector; 18, 103 . . . electrode driving portion; 19, 104 . . . liquid crystal display panel; 20 . . . path; 21 . . . memory; 22 . . . linear interpolation processing portion; 23 . . . black-level signal insertion processing portion; 105 . . . motion vector; 106 . . . interpolating vector; and 107 . . . interpolating frame.
PREFERRED EMBODIMENT OF THE INVENTION
A preferred embodiment of an image displaying device of the present invention will now be described referring to the accompanying drawings. Although the present invention is applicable to either field signals and interpolation field signals or frame signals and interpolating frame signals, the frame signals and the interpolating frame signals will be described as a representative example since both (field and frame) are in a similar relationship with each other.
FIG. 5 is a block diagram of an exemplary configuration of a motion compensated frame rate converting portion included in the image displaying device of the present invention, in FIG. 5, reference numeral 10 denotes a frame rate converting portion (hereinafter, FRC portion), and the FRC portion 10 corresponds to a rate converting portion of the present invention and is comprised of a vector detecting portion 11 that detects a motion vector between two consecutive frames included in an input image signal and a frame generating portion 12 that generates an interpolating frame (interpolation image) based on the detected motion vector. Although the iterative gradient method is used for the motion vector detection in the description of the vector detecting portion 11, the method is not limited to the iterative gradient method and may be the block matching method.
A feature of the iterative gradient method is that several types of movement amounts may be detected, and a motion vector may be detected even from a moving object having a small region since a motion vector may be detected for each block. The circuit configuration thereof may be realized in a smaller scale than other modes (such as the block matching method). In the iterative gradient method, an already detected motion vector of a neighboring block is defined as an initial deflection vector, which is used as a starting point to repeat calculations of the gradient method for a detected block. With this method, a substantially accurate movement amount may be acquired by repeating the gradient method about two times.
In FIG. 5, the vector detecting portion 11 includes a luminance signal extracting portion 11a that extracts a luminance signal (Y signal) from an input image signal (RGB signal), a preprocessing filter 11b that limits a high bandwidth by applying LPF to the extracted Y signal, a motion detection frame memory 11c, an initial vector memory lid that accumulates initial vector candidates, a motion vector detecting portion 11e that detects motion vectors between frames with the use of the iterative gradient method, and an interpolating vector evaluating portion 11f that allocates an interpolating vector between the frames based on the detected motion vectors.
The FRC portion 10 corresponds to the rate converting portion of the present invention; the motion vector detecting portion 11e corresponds to a motion vector detecting portion of the present invention; and the interpolating vector evaluating portion 11f corresponds to an interpolating vector allocating portion of the present invention.
Since a differential component of a pixel is used for the calculations of the above iterative gradient method, the method is easily affected by noises and calculation errors are increased if large gradient variations exist in a detected block and, therefore, the LPF is applied by the preprocessing filter 11b to limit the high bandwidth. In the initial vector memory 11d, motion vectors (initial vector candidates) already detected in a frame immediately before the previous frame are accumulated as initial vector candidates.
The motion vector detecting portion 11e selects a motion vector closest to the motion vector of the detected block for an initial vector from the initial vector candidates accumulated in the initial vector memory 11d. The initial vector is selected by the block matching method from the already detected motion vectors (initial vector candidates) in neighboring blocks of the detected block. The motion vector detecting portion 11e uses the selected initial vector as a starting point to detect a motion vector between a previous frame and a current frame through the calculations of the gradient method.
The interpolating vector evaluating portion 11f evaluates the motion vectors detected by the motion vector detecting portion 11e, allocates an optimum interpolating vector to an interpolation block between frames based on the evaluation result, and outputs the vector to the frame generating portion 12.
The frame generating portion 12 includes an interpolating frame memory 12a that accumulates two input frames (previous frame and current frame), an interpolating frame generating portion 12b that generates an interpolating frame based on the two input frames from the interpolating frame memory 12a and the interpolating vector from the interpolating vector evaluating portion 11f, a time base conversion frame memory 12c for accumulating the input frames (previous frame and current frame), and a time base converting portion 12d that inserts the interpolating frame from the interpolating frame generating portion 12b into the input frames from the time base conversion frame memory 12c to generate an output image signal (RGB signal).
The interpolating frame generating portion 12b corresponds to an interpolation image generating portion of the present invention and the time base converting portion 12d corresponds to an image interpolating portion of the present invention.
FIG. 6 is a diagram for explaining an example of the interpolating frame generating processing of the frame generating portion 12. The interpolating frame generating portion 12b stretches an interpolating vector V allocated to the interpolation block into the previous frame and the current frame and uses pixels located adjacent to the intersecting points with the frames to interpolate the pixels in the interpolation block. For example, in the previous frame F1, the luminance of a point A is calculated from three adjacent points. In the current frame F2, the luminance of a point B is calculated from three adjacent points. In the interpolating frame F12, the luminance of a point P is interpolated using the luminance of the points A and B. The luminance of the point P may be an average of the luminance of the point A and the luminance of the point B, for example.
The interpolating frame F12 generated as above is sent to the time base converting portion 12d. The time base converting portion 12d sandwiches the interpolating frame F12 between the previous frame F1 and the current frame F2 to perform processing of converting a frame rate. In this way, the FRC portion 10 may convert the input image signal (60 frames/sec) into a motion-compensated output image signal (120 frames/sec), which may be output to a display panel to reduce the motion blur and improve the moving image quality. Although the 60-frame/sec input image signal is converted into the 120-frame/sec (double) output image signal in the frame rate conversion of this description, this is obviously applicable to the case of acquiring 90-frame/sec (1.5 times) and 180-frame/sec (three times) output image signals, for example.
The image displaying device of the present invention includes the FRC portion 10 shown in FIG. 5 and the main object thereof is to make the motion compensation processing of the FRC portion 10 ineffective over the entire screen (full screen) to prevent the image quality deterioration due to the FRC processing if the input image signals are image signals likely to include a plurality of the same consecutive images such as an image signal processed by 2-3 pulldown conversion or 2-2 pulldown conversion. Although the present invention is applicable to general image displaying devices having the hold-type display characteristics such as liquid crystal displays, organic EL displays, and electrophoretic displays, a representative example described in the following embodiments will be the case of applying the present invention to a liquid crystal displaying device using a liquid crystal display panel for a display panel.
In a first embodiment of the present invention, when the input image signal is, for example, an image signal to which 2-3 pulldown conversion or 2-2 pulldown conversion was performed, the output of the motion vector detecting portion 11e is forced to be zero-vector to make the motion compensation processing of the FRC portion 10 ineffective.
FIG. 7 is a block diagram of an exemplary main configuration of a liquid crystal displaying device according to the first embodiment of the present invention and the liquid crystal displaying device includes the FRC portion 10, a pulldown detecting portion 14, a controlling portion 15, a switching portion 16, a zero-vector portion 17, an electrode driving portion 18, and a liquid crystal display panel 19. The switching portion 16 is disposed between the motion vector detecting portion 11e and the interpolating vector evaluating portion 11f within the FRC portion 10 and switches over the motion vector from the motion vector detecting portion 11e to the zero-vector 17 in accordance with the instruction from the controlling portion 15.
The pulldown detecting portion 14 detects whether an input image signal is, for example, an image signal to which 2-3 pulldown or 2-2 pulldown conversion was performed. Various methods of detecting a video signal to which pulldown conversion (telecine signal) was performed have been suggested (and are referred to as telecine detection) , and various known techniques are available for the methods. For example, in one method, a difference between frames (fields) is determined and an image signal to which 2-3 pulldown or 2-2 pulldown conversion was performed can be detected based on a period of output of a signal that indicates the largeness of the difference.
When an identification signal capable of identifying an image signal as pulldown video is added to the image signal and is transmitted together, whether an input image signal is an image signal generated by pulldown conversion processing may be detected by using this identifying signal.
The liquid crystal display panel 19 is an active-matrix liquid crystal display that has a liquid crystal layer and electrodes for applying scan signals and data signals to the liquid crystal layer. The electrode driving portion 18 is a display driver for driving the scan electrodes and the data electrodes of the liquid crystal display panel 19 based on the image signal to which the frame rate conversion by the FRC portion 10 has been given. The controlling portion 15 includes a CPU for controlling the above portions and performs control such that the motion compensation processing of the FRC portion 10 is made ineffective when the pulldown detecting portion 14 detects that the input image signal is an image signal to which pulldown conversion has been performed.
The drive frequency of the liquid crystal display panel 19 is a frame frequency converted by the FRC portion 10. Therefore, if an image signal input with a frame frequency of 60 Hz is converted by the FRC portion 10 into a frame frequency of 120 Hz, the drive frequency of the liquid crystal display panel 19 is 120 Hz. However, if the frame frequency conversion of the FRC processing is not performed and the input image signal is directly displayed and output, the drive frequency of the liquid crystal display panel 19 is the frame frequency of the input image signal.
If the pulldown detecting portion 14 detects that the input image signal is an image signal to which pulldown conversion has been performed, the controlling portion 15 switches the switching portion 16 to the zero-vector 17 to forcibly replace the motion vector detected by the motion vector detecting portion lie with the zero-vector. If the pulldown detecting portion 14 does not detect that the input image signal is an image signal to which pulldown conversion has been performed, the switching portion 16 is switched to the motion vector detecting portion lie to input the motion vector detected by the motion vector detecting portion lie to the interpolating vector evaluating portion 11f. 
Therefore, the moving image quality may be improved by the motion-compensated FRC processing at the time of the normal moving image display and, when a moving image processed by pulldown conversion, namely, a moving image likely to include a plurality of the same consecutive images is input, the detection errors, the motion compensation errors, etc., of the motion vector due to the discontinuity of the image movement are eliminated and the image quality may effectively be prevented from deteriorating due to the motion-compensated FRC processing by making the motion compensation processing ineffective with the motion vector set to zero-vector.
In a second embodiment of the present invention, when an input image signal is, for example, an image signal to which 2-3 pulldown conversion or 2-2 pulldown conversion has been performed, the interpolating vector from the interpolating vector evaluating portion 11f is set to zero-vector to make the motion compensation processing of the FRC portion 10 ineffective so that no interpolation can occur between pixels located at different positions.
FIG. 8 is a block diagram of an exemplary main configuration of a liquid crystal displaying device according to the second embodiment of the present invention and the liquid crystal displaying device includes the FRC portion 10, the pulldown detecting portion 14, the controlling portion 15, the switching portion 16, the zero-vector portion 17, the electrode driving portion 18, and the liquid crystal display panel 19. The switching portion 16 is disposed between the interpolating vector evaluating portion 11f and the interpolating frame generating portion 12b within the FRC portion 10 and switches the interpolating vector from the interpolating vector evaluating portion 11f to the zero-vector 17 in accordance with the instruction from the controlling portion 15.
If the pulldown detecting portion 14 detects an input image signal is an image signal to which pulldown conversion has been performed, the controlling portion 15 switches the switching portion 16 to the zero-vector 17 to set the interpolating vector allocated by the interpolating vector evaluating portion 11f to zero-vector. If the pulldown detecting portion 14 does not detect that an input image signal is an image signal to which pulldown conversion has been performed, the switching portion 16 is switched to the interpolating vector evaluating portion 11f to input the interpolating vector allocated by the interpolating vector evaluating portion 11f to the interpolating frame generating portion 12b. 
When a moving picture processed by pulldown conversion, namely, a moving picture likely to include a plurality of the same consecutive images is input, the detection errors, the motion compensation errors, etc., of the motion vector due to the discontinuity of the image movement are eliminated in the same was as described in the first embodiment and the image quality may effectively be prevented from deteriorating due to the motion-compensated FRC processing by making the motion compensation processing ineffective with the interpolating vector forcibly set to zero-vector.
In a third embodiment of the present invention, a path is provided to bypass the FRC portion 10 and, when the input image signal is, for example, an image signal to which 2-3 pulldown conversion or 2-2 pulldown conversion has been performed, the input image signal to which pulldown conversion has been performed is input to the bypass to change the drive frequency of the liquid crystal display panel 19 in conformity with the frame frequency of the input image signal. When an image signal to which pulldown conversion has been performed is input, the switching is performed such that the input image signal to which pulldown conversion has been performed is directly output and displayed on the liquid crystal display panel 19 without performing the frame rate conversion.
FIG. 9 is a block diagram of an exemplary main configuration of a liquid crystal displaying device according to the third embodiment of the present invention and the liquid crystal displaying device includes the FRC portion 10, the pulldown detecting portion 14, the controlling portion 15, the switching portion 16, the electrode driving portion 18, the liquid crystal display panel 19, and a path 20 for bypassing the FRC portion 10. The switching portion 16 is disposed on the previous stage of the FRC portion 10 and switches the input image signal to input whether to the FRC portion 10 or to the path 20 in accordance with the instruction from the controlling portion 15.
When the pulldown detecting portion 14 detects that the input image signal is an image signal to which pulldown conversion has been performed, the controlling portion 15 shifts the switching portion 16 to the path 20 to bypass the FRC portion 10. When the pulldown detecting portion 14 does not detect that the input image signal is an image signal to which pulldown conversion has been performed, the switching portion 16 is shifted to the FRC portion 10 to perform the FRC processing (motion-compensated frame interpolation processing) for the input image signal. The switching portion 16 may be disposed on the subsequent stage of the FRC portion 10 such that the output signal of the FRC portion 10 and the output signal of the path 20 are switched over to output to the liquid crystal display panel 19.
In this embodiment, the controlling portion 15 may change the drive frequency of the liquid crystal display panel 19, and when an image signal to which pulldown conversion has been performed (telecine signal) is input, the input image signal is input to the path 20 to change the drive frequency of the liquid crystal display panel 19 in conformity with the frame frequency of the input image signal.
FIG. 10 is a diagram of a relationship between input data and output data according to the third embodiment of the present invention. FIG. 10 (A) depicts the input data to the path 20 and FIG. 10(B) depicts the output data from the path 20. As shown in FIG. 10(A), if the input image signal (input data) is input to the path 20 with a frame frequency of 60 Hz, the display time per frame is about 16.7 ms. The controlling portion 15 controls the electrode driving portion 18, which is the display driver, to change the drive frequency of the liquid crystal display panel 19 from 120 Hz to 60 Hz and causes the input data to be output from the path 20 at 60 Hz without performing the frame rate conversion as shown in FIG. 10(B).
Since the liquid crystal display panel 19 displays the frame output from the path 20 without the frame rate conversion at the drive frequency of 60 Hz, the display time per frame is still about 16.7 ms.
Therefore, the moving image quality may be improved by the motion-compensated FRC processing at the time of the normal moving image display and, when the moving image processed by pulldown conversion, namely, a moving image likely to include a plurality of the same consecutive images is input, the detection errors, the motion compensation errors, etc., of the motion vector due to the discontinuity of the image movement are eliminated and the image quality may effectively be prevented from deteriorating due to the motion-compensated FRC processing by prohibiting the frame rate conversion itself with the FRC processing bypassed.
In a fourth embodiment of the present invention, a path is provided to bypass the FRC portion 10 and, when the input image signal is, for example, an image signal to which 2-3 pulldown conversion or 2-2 pulldown conversion has been performed, the input image signal to which pulldown conversion has been performed is input to the bypass to accumulate the input image signal in a memory on the path and the frame rate is converted by rapidly and repeatedly reading the image signal of the same frame from the memory more than once. When the image signal to which pulldown conversion has been performed is input, the switching is performed such that the input image signal is rapidly and sequentially output to convert the frame rate and is output and displayed on the liquid crystal display panel 19 without performing the motion-compensated frame rate conversion.
FIG. 11 is a block diagram of an exemplary main configuration of a liquid crystal displaying device according to the fourth embodiment of the present invention and the liquid crystal displaying device includes the FRC portion 10, the pulldown detecting portion 14, the controlling portion 15, the switching portion 16, the electrode driving portion 18, the liquid crystal display panel 19, the path 20 for bypassing the FRC portion 10, and a memory 21 on the path 20. The switching portion 16 is disposed on the previous stage of the FRC portion 10 and switches the input image signal to input whether to the FRC portion 10 or to the path 20 in accordance with the instruction from the controlling portion 15.
When the pulldown detecting portion 14 detects that the input image signal is an image signal to which pulldown conversion has been performed, the controlling portion 15 shifts the switching portion 16 to the path 20 to bypass the FRC portion 10 and to accumulate the input image signal in the memory 21. The frame insert processing is subsequently performed by repeatedly reading the same frame from the memory 21 more than once. When the pulldown detecting portion 14 does not detect that the input image signal is an image signal to which pulldown conversion has been performed, the switching portion 16 is switched to the FRC portion 10 to perform the FRC processing (motion-compensated frame interpolation processing) for the input image signal. The switching portion 16 may be disposed on the subsequent stage of the FRC portion 10 such that the output signal of the FRC portion 10 and the output signal of the memory 21 are switched over to output to the liquid crystal display panel 19.
In this embodiment, the drive frequency of the liquid crystal display panel 19 is not changed and is maintained at 120 Hz. When the image signal to which pulldown conversion has been performed (telecine signal) is input, the controlling portion 15 and the memory 21 comprise a portion for converting the number of frames of the input image signal by inserting an image signal of the previous or subsequent frame between the frames of the input image signal. The frame rate (the number of frames) of the display image signal input to the electrode driving portion 18 is always the same.
FIG. 12 is a view of a relationship between input data and output data according to the fourth embodiment of the present invention. FIG. 12(A) shows the input data to the path 20 and FIG. 12(B) shows the output data from the path 20. As shown in FIG. 12(A), if the input image signal (input data) is input to the path 20 with a frame frequency of 60 Hz, the display time per frame is about 16.7 ms. The input data are temporarily accumulated in the memory 21, and an image signal of the frame (in FIG. 12, frame A) is output which is repeatedly read from the memory 21 at double speed as shown in FIG. 12(B).
The liquid crystal display panel 19 displays the output data into which the image signal of the same frame has been inserted, at the drive frequency of 120 Hz. Since the number of frames is converted by repeatedly reading the same frame twice, the display time per frame is about 8.3 ms in this case.
When the moving image processed by pulldown conversion, namely, a moving image likely to include a plurality of the same consecutive images is input, the detection errors, the motion compensation errors, etc., of the motion vector due to the discontinuity of images are eliminated and the image quality may effectively be prevented from deteriorating due to the motion-compensated FRC processing by not performing the interpolation processing through motion compensation for the input image signal. Since the frame rate is converted by repeatedly reading the same frame in this case, the drive frequency of the liquid crystal display panel 19 does not need to be changed.
In a fifth embodiment of the present invention, a path is provided to bypass the FRC portion 10 and, when the input image signal is, for example, an image signal to which 2-3 pulldown conversion or 2-2 pulldown conversion has been performed, the input image signal to which pulldown conversion has been performed is input to the bypass and the input image signal is input to a linear interpolation processing portion on the path to interpolate an image signal to which the linear interpolation has been performed. When the image signal to which pulldown conversion has been performed is input, the switching is performed such that the frame rate is converted by performing the linear interpolation processing rather than the interpolation processing through motion compensation.
FIG. 13 is a block diagram of an exemplary main configuration of a liquid crystal displaying device according to the fifth embodiment of the present invention and the liquid crystal displaying device includes the FRC portion 10, the pulldown detecting portion 14, the controlling portion 15, the switching portion 16, the electrode driving portion 18, the liquid crystal display panel 19, the path 20 for bypassing the FRC portion 10, and a linear interpolation processing portion 22 on the path 20. The switching portion 16 is disposed on the previous stage of the FRC portion 10 and switches the input image signal to input whether to the FRC portion 10 or to the path 20 in accordance with the instruction from the controlling portion 15.
When the pulldown detecting portion 14 detects that the input image signal is an image signal to which pulldown conversion has been performed, the controlling portion 15 shifts the switching portion 16 to the path 20 to bypass the FRC portion 10 and the input image signal is input to the linear interpolation processing portion 22. The linear interpolation processing portion 22 inserts an interpolating frame to which the linear interpolation processing has been given between frames. When the pulldown detecting portion 14 does not detect that the input image signal is an image signal to which pulldown conversion has been performed, the switching portion 16 is switched to the FRC portion 10 to perform the FRC processing (motion-compensated frame interpolation processing) for the input image signal. The switching portion 16 may be disposed on the subsequent stage of the FRC portion 10 such that the output signal of the FRC portion 10 and the output signal of the linear interpolation processing portion 22 are switched over to output to the liquid crystal display panel 19.
In this embodiment, the drive frequency of the liquid crystal display panel 19 is not changed and is maintained at 120 Hz. The frame rate (the number of frames) of the display image signal input to the electrode driving portion 18 is always the same. When the image signal to which pulldown conversion has been performed (telecine signal) is input, the linear interpolation processing portion 22 comprises a portion for converting the number of frames of the input image signal by interpolating an image signal to which the linear interpolation processing has been given between the frames of the input image signal. In the linear interpolation processing, as described in the above document (Yamauchi Tatsuro, “TV Standards Conversion”, Journal of the Institute of Television Engineers of Japan, Vol. 45, No. 12, pp.1534-1543 (1991)), an interpolating frame is acquired through linear interpolation using a frame interpolation ratio α from the signal of the previous frame and the signal of the current frame.
FIG. 14 is a view of a relationship between input data and output data according to the fifth embodiment of the present invention. FIG. 14(A) shows the input data to the path 20 and FIG. 14 (B) shows the output data from the path 20. As shown in FIG. 14(A), if the input image signal (input data) is input to the path 20 with a frame frequency of 60 Hz, the display time per frame is about 16.7 ms. The input data are input to the linear interpolation processing portion 22, and the image signal to which the linear interpolation processing has been given (in FIG. 14, frame A+B) is interpolated and output between the frames (in this case, between frames A and B) as shown in FIG. 14(B).
The liquid crystal display panel 19 displays the output data into which the image signal to which the linear interpolation processing has been given, is interpolated at the drive frequency of 120 Hz. Since the number of frames is converted by interpolating the image signal to which the linear interpolation processing has been given, the display time per frame is about 8.3 ms in this case.
When the moving image processed by pulldown conversion, namely, a moving image likely to include a plurality of the same consecutive images is input, the detection errors, the motion compensation errors, etc., of the motion vector due to the discontinuity of images are eliminated and the image quality may effectively be prevented from deteriorating due to the motion-compensated FRC processing by not performing the interpolation processing through motion compensation for the input image signal. Since the frame rate is converted by interpolating the image signal to which the linear interpolation processing has been given in this case, the drive frequency of the liquid crystal display panel 19 does not need to be changed.
In a sixth embodiment of the present invention, a path is provided to bypass the FRC portion 10 and, when the input image signal is, for example, an image signal to which 2-3 pulldown conversion or 2-2 pulldown conversion has been performed, the input image signal to which pulldown conversion has been performed is input to the bypass and the input image signal is input to a black-level signal insertion processing portion on the path to insert a predetermined monochromatic image signal such as a black-level signal. When the image signal to which pulldown conversion has been performed is input, the switching is performed such that the frame rate is converted by performing the monochromatic image insertion processing rather than the interpolation processing through motion compensation.
FIG. 15 is a block diagram of an exemplary main configuration of a liquid crystal displaying device according to the sixth embodiment of the present invention and the liquid crystal displaying device includes the FRC portion 10, the pulldown detecting portion 14, the controlling portion 15, the switching portion 16, the electrode driving portion 18, the liquid crystal display panel 19, the path 20 for bypassing the FRC portion 10, and a black-level signal insertion processing portion 23 on the path 20. The switching portion 16 is disposed on the previous stage of the FRC portion 10 and switches the input image signal to input whether to the FRC portion 10 or to the path 20 in accordance with the instruction from the controlling portion 15.
When the pulldown detecting portion 14 detects that the input image signal is an image signal to which pulldown conversion has been performed, the controlling portion 15 shifts the switching portion 16 to the path 20 to bypass the FRC portion 10 and the input image signal is input to the black-level signal insertion processing portion 23. The black-level signal insertion processing portion 23 performs the time scale compression (frame rate conversion) for the input image signal, for example, with the use of a memory to insert the predetermined monochromatic image signal such as a black-level signal between the input frames. When the pulldown detecting portion 14 does not detect that input image signal is an image signal to which pulldown conversion has been performed, the switching portion 16 is shifted to the FRC portion 10 to perform the FRC processing (motion-compensated frame interpolation processing) for the input image signal. The switching portion 16 may be disposed on the subsequent stage of the FRC portion 10 such that the output signal of the FRC portion 10 and the output signal of the black-level signal insertion processing portion 23 are switched over to output to the liquid crystal display panel 19.
In this embodiment, the drive frequency of the liquid crystal display panel 19 is not changed and is maintained at 120 Hz. The frame rate (the number of frames) of the display image signal input to the electrode driving portion 18 is always the same. When the image signal to which pulldown conversion has been performed (telecine signal) is input, the black-level signal insertion processing portion 23 comprises a portion for converting the number of frames of the input image signal by inserting the predetermined monochromatic image signal such as a black-level signal between the frames of the input image signal. Another embodiment of the black-level signal insertion processing may be configured such that the electrode driving portion 18 applies a voltage for writing black to the liquid crystal display panel 19 for a predetermined period (in the case of this example, 1/120 second).
FIG. 16 is a view of a relationship between input data and output data according to the sixth embodiment of the present invention. FIG. 16 (A) shows the input data to the path 20 and FIG. 16(B) shows the output data from the path 20. As shown in FIG. 16(A), if the input image signal (input data) is input to the path 20 with a frame frequency of 60 Hz, the display time per frame is about 16.7 ms. The input data are input to the black-level signal insertion processing portion 23, and a black-level signal (in FIG. 16, black-colored frame) is inserted and output between the frames (in this case, between the frames A and B) as shown in FIG. 16(B).
Although the image quality deterioration due to the motion blur is improved and the image quality deterioration due to the motion compensation error is not generated by inserting the black image signal between the frames of the input image signal in this way, the emission luminance must be increased in a backlight (not shown) disposed on the backside of the liquid crystal display panel 19 to compensate the reduction of the display luminance due to the shortening of the image display period.
The liquid crystal display panel 19 displays the output data, into which the black-level signal has been inserted, at the drive frequency of 120 Hz. Since the number of frames is converted by inserting the black-level signal, the display time per frame is about 8.3 ms in this case.
When a moving image processed by pulldown conversion, namely, a moving image likely to include a plurality of the same consecutive images is input, the detection errors, the motion compensation errors, etc., of the motion vector due to the discontinuity of images are eliminated and the image quality may effectively be prevented from deteriorating due to the motion-compensated FRC processing by not performing the interpolation processing through motion compensation for the input image signal. Since the frame rate is converted by inserting the monochromatic image signal in this case, the drive frequency of the liquid crystal display panel 19 does not need to be changed. The moving image quality improving effect may also be maintained in this case.
Other than the above embodiment, when the input image signal is, for example, an image signal to which 2-3 pulldown conversion or 2-2 pulldown conversion has been performed, the image quality may be prevented from deteriorating due to the motion-compensated FRC processing and the moving image quality improving effect may be maintained at the same time by dividing the original image of the input frame into a plurality of frame images at a predetermined luminance ratio for the frame rate conversion.
In a seventh embodiment of the present invention, when the input image signal is, for example, an image signal to which 2-3 pulldown conversion or 2-2 pulldown conversion has been performed, the compensation intensity of the motion compensation processing may be varied in the interpolating frame generating portion. Specifically, the weighted addition rate may be varied when the pull-down converted image signal is input by providing the interpolating frame generating portion that performs weighted addition of the image signal to which the motion compensation processing has been given and the image signal to which the linear interpolation processing has been given at a predetermined rate to generate an interpolating frame.
FIG. 17 is a block diagram of an exemplary main configuration of the FRC portion 10 according to the seventh embodiment of the present invention, and the frame generating portion 12 of the FRC portion 10 includes the interpolating frame memory 12a, the interpolating frame generating portion 12b, and a compensation intensity varying portion 12e that may vary the compensation intensity of the motion compensation processing in the FRC portion 10. In FIG. 17, V denotes an interpolating vector; α denotes a frame interpolation ratio; and β denotes interpolation intensity (weighted addition rate).
Generally, for example, the frame interpolation through the linear interpolation between two frames and the frame interpolation using motion vectors (motion compensated interpolation) are known as methods of the frame interpolation processing. In the former case, an interpolating frame is acquired by the linear interpolation from the signal of the previous frame and the signal of the current frame at a frame interpolation ratio α. Therefore, using this linear interpolation may prevent the image quality deterioration due to the motion compensation errors in the FRC processing.
On the other hand, to acquire an interpolating frame from the previous frame and the current frame in the latter case, the interpolating vector V is detected from the motion vectors between the previous frame image and the current frame image, and the interpolating frame is acquired from the weighted addition of a signal of the previous frame image shifted by a degree of αV obtained by dividing the value (interpolating vector V) by the frame interpolation ratio α and a signal of the current frame image shifted by (1−α)V. Although good image quality may be acquired without deteriorating the resolution since a moving image itself is captured and compensated by using this motion-compensated interpolation, the image quality may be deteriorated in the pulled-down video due to this processing.
Therefore, in this embodiment, the compensation intensity varying portion 12e is disposed in the frame generating portion 12. When the pulldown detecting portion 14 detects that the input image signal is an image signal to which pulldown conversion has been performed, the compensation intensity varying portion 12e varies the weighted addition rate β. The weighted addition rate β is a rate for performing the weighted addition of the image signal to which the motion compensation processing has been given and the image signal to which the linear interpolation processing has been given. The interpolating frame generating portion 12b of this embodiment performs the weighted addition of the linear interpolation and the motion-compensated interpolation in accordance with the weighted addition rate D to generate the interpolating frame.
For example, when the input image signal is an image signal to which pulldown conversion has been performed, the compensation intensity varying portion 12e sets the weighted addition rate β=0 and defines the image signal to which the linear interpolation processing has been given as the interpolating frame to prevent the image deterioration. On the other hand, when the input image signal is not an image signal to which pulldown conversion has been performed, the weighted addition rate β=1 is set to define the image signal to which the motion compensation processing has been given as the interpolating frame to achieve better image quality for the moving image.
Since the weighted addition rate β may arbitrarily and variably be set, the rate may be set to a substantially intermediate value between zero and one. This enables to control the deterioration of the image quality and to perform the motion compensation in the interpolating frame image at the same time, and this may appropriately improve both the image quality deterioration due to the motion blur and the image quality deterioration due to the motion compensation errors.
Since the compensation intensity may be varied (weakened) in the motion compensation processing in the FRC when the moving image processed by pulldown conversion, namely, a moving image likely to include a plurality of the same consecutive images is input, the image quality deterioration due to the motion-compensated FRC process may effectively be controlled by reducing the effects of the detection errors, the motion compensation errors, etc., of the motion vector due to the discontinuity of images.
FIG. 18 is a flowchart for explaining an example of an image displaying method carried out by the image displaying device of the present invention. An example of the image displaying method in the first embodiment will be described. First, the image displaying device determines whether an input image signal is an image signal to which pulldown conversion has been performed (telecine signal) (step 1), and if it is determined that the input image signal is an image signal to which pulldown conversion has been performed (in the case of YES), the motion vector or the interpolating vector is set to zero-vector to make the motion compensation processing of the FRC portion 10 ineffective (step S2). If it is determined at step SI that the input image signal is not an image signal to which pulldown conversion has been performed (in the case of NO), the motion compensation processing by the FRC portion 10 is executed as usual (step S3). The image signal with the frame frequency converted in this way is displayed and output from the liquid crystal display panel 19 (step S4).
FIG. 19 is a flowchart for explaining another example of the image displaying method by the image displaying device of the present invention. An example of the image displaying method in the second to sixth embodiments will be described. First, the image displaying device determines whether the input image signal is an image signal to which pulldown conversion has been performed (telecine signal) (step S11), and if it is determined that the input image signal is an image signal to which pulldown conversion has been performed (in the case of YES), the motion-compensated frame interpolation processing of the FRC portion 10 is bypassed and the input image signal is input to the other path 20 (step S12). On the bypassing path 20, the image signal is output after the frame rate is converted by executing any one of the inter-frame interpolation of the image signal to which the linear interpolation processing has been given, the inter-frame interpolation of the image signal of the same frame, and the inter-frame interpolation of the predetermined monochromatic image signal such as a black-level signal, or the input image signal is directly output to execute processing such as changing the drive frequency of the liquid crystal display panel 19.
If it is determined at step S11 that the input image signal is not an image signal to which pulldown conversion has been performed (in the case of NO), an image signal to which the interpolation processing through motion compensation was executed is output from the FRC portion 10 (step S13). Finally, the image is displayed and output from the liquid crystal display panel 19 (step S14).
FIG. 20 is a flowchart for explaining another example of the image displaying method by the image displaying device of the present invention. An example of the image displaying method in the seventh embodiment will be described. First, the image displaying device determines whether the input image signal is an image signal to which pulldown conversion has been performed (telecine signal) (step S21) , and if it is determined that the input image signal is an image signal to which pulldown conversion has been performed (in the case of YES), the compensation intensity is varied (weakened) in the motion compensation processing of the FRC portion 10 (step S22). If it is determined at step S21 that the input image signal is not an image signal to which pulldown conversion has been performed (in the case of NO), the compensation intensity is increased as usual in the motion compensation processing of the FRC portion 10 (step S23). The image signal with the frame frequency converted in this way is displayed and output from the liquid crystal display panel 19 (step S24).
According to the present invention, when a moving image signal likely to include a plurality of the same consecutive images, such as 2-3 pulldown video or 2-2 pulldown video, is input, display and output may be performed by making the motion compensation processing in the frame rate converting (FRC) portion ineffective and, therefore, the image quality may effectively be prevented from deteriorating due to the motion compensation errors. It is needless to say that the image signal is not limited to the television image signal and may be an image signal reproduced from an external medium.
Although the exemplary embodiments related to the image processing device and method of the present invention have been described as above, the above description will facilitate understanding of an image processing program operable to drive a computer to execute the image processing method as a program and a program recording medium, which is a computer-readable recording medium having the image processing program recorded thereon.
Although the image processing device of the present invention is integrally disposed within the image displaying device in the form described in the above embodiments, the image processing device of the present invention is not limited to this form and it is needless to say that the image processing device may be disposed in video output devices such as various recording medium reproducing devices, for example.

## Claims

1. An image displaying device having a rate converting portion that interpolates an image signal to which a motion compensation processing has been applied between frames or fields of an input image signal to convert and output the number of frames or fields of the input image signal to a display panel, further comprising
a determining portion that determines whether the input image signal is an image signal to which pulldown conversion has been performed, wherein
when the determining portion determines that the input image signal is an image signal to which pulldown conversion has been performed, image interpolation by the motion compensation processing is not performed by the rate converting portion, wherein
the rate converting portion includes a portion that generates an interpolation image signal to which a motion compensation processing has been applied based on motion vector information between consecutive frames or fields included in the input image signal, and
when the input image signal is determined to be an image signal to which pulldown conversion has been performed, a motion compensation processing in the interpolation image signal generating portion is made ineffective, wherein
the rate converting portion includes:
a motion vector detecting portion that detects motion vector information between consecutive frames or fields included in the input image signal;
an interpolating vector allocating portion that allocates an interpolating vector between the frames or the fields based on the detected motion vector information;
an interpolation image generating portion that generates an interpolation image signal from the input image signal, using the allocated interpolating vector; and
an image interpolating portion that interpolates the generated interpolation image signal between the frames or the fields.

2. The image displaying device as defined in claim 1, wherein
when the input image signal is determined to be an image signal to which pulldown conversion has been performed, the motion vector detected by the motion vector detecting portion is set to zero-vector to make the motion compensation processing ineffective.

3. The image displaying device as defined in claim 1, wherein
when the input image signal is determined to be an image signal to which pulldown conversion has been performed, the interpolating vector allocated by the interpolating vector allocating portion is set to zero-vector to make the motion compensation processing ineffective.

4. An image displaying device having a rate converting portion that interpolates an image signal to which a motion compensation processing has been applied between frames or fields of an input image signal to convert and output the number of frames or fields of the input image signal to a display panel, further comprising
a determining portion that determines whether the input image signal is an image signal to which pulldown conversion has been performed, wherein
when the determining portion determines that the input image signal is an image signal to which pulldown conversion has been performed, image interpolation by the motion compensation processing is not performed by the rate converting portion, wherein
the input image signal is output to the display panel without converting the number of frames or fields of the input image signal when the input image signal is determined to be an image signal to which pulldown conversion has been performed, wherein
a drive frequency of a display panel that displays an image signal is variable, and wherein
the drive frequency of the display panel displaying the image signals is variable and the drive frequency of the display panel is varied in accordance with the frame frequency or the field frequency of the input image signal when the input image signal is determined to be an image signal to which pulldown conversion has been performed.

5. An image displaying device having a rate converting portion that interpolates an image signal to which a motion compensation processing has been applied between frames or fields of an input image signal to convert and output the number of frames or fields of the input image signal to a display panel, further comprising
a determining portion that determines whether the input image signal is an image signal to which pulldown conversion has been performed, wherein
when the determining portion determines that the input image signal is an image signal to which pulldown conversion has been performed, image interpolation by the motion compensation processing is not performed by the rate converting portion, further comprising
another rate converting portion that inserts an image signal to which the motion compensation processing has not been applied between frames or fields of the input image signal to convert the number of frames or fields of the input image signal, wherein
the image signal with the number of frames or fields converted by the another rate converting portion is output to the display panel when the input image signal is determined to be an image signal to which pulldown conversion has been performed.

6. The image displaying device as defined in claim 5, wherein
the another rate converting portion inserts an image signal of the frames or fields between frames or fields of the input image signal to convert the number of frames or fields of the input image signal.

7. The image displaying device as defined in claim 5, wherein
the another rate converting portion interpolates an image signal to which a linear interpolation processing has been applied between frames or fields of the input image signal to convert the number of frames or fields of the input image signal.

8. The image displaying device as defined in claim 5, wherein
the another rate converting portion inserts a predetermined monochromatic image signal between frames or fields of the input image signal to convert the number of frames or fields of the input image signal.

9. An image displaying method having a step of interpolating an image signal to which a motion compensation processing has been applied between frames or fields of an input image signal to convert the number of frames or fields of the input image signal, the method further comprising
determining whether the input image signal is an image signal to which pulldown conversion has been performed, wherein
image interpolation by the motion compensation processing is not performed in the step of interpolating an image signal when it is determined that the input image signal is an image signal to which pulldown conversion has been performed; and
displaying the image signal to which image interpolation by the motion compensation processing has not been performed, wherein
a drive frequency of a display panel is changed in accordance with the frame frequency or the field frequency of the input image signal when it is determined that the input image signal is an image signal to which pulldown conversion has been performed.

10. An image displaying method having a step of interpolating an image signal to which a motion compensation processing has been applied between frames or fields of an input image signal to convert the number of frames or fields of the input image signal, the method further comprising
determining whether the input image signal is an image signal to which pulldown conversion has been performed, wherein
image interpolation by the motion compensation processing is not performed in the step of interpolating an image signal when it is determined that the input image signal is an image signal to which pulldown conversion has been performed; and
displaying the image signal to which image interpolation by the motion compensation processing has not been performed, wherein
an image signal to which a linear interpolation processing has been applied is interpolated between frames or fields of the input image signal to convert the number of frames or fields of the input image signal when it is determined that the input image signal is an image signal to which pulldown conversion has been performed.

11. An image displaying method having a step of interpolating an image signal to which a motion compensation processing has been applied between frames or fields of an input image signal to convert the number of frames or fields of the input image signal, the method further comprising
determining whether the input image signal is an image signal to which pulldown conversion has been performed, wherein
image interpolation by the motion compensation processing is not performed in the step of interpolating an image signal when it is determined that the input image signal is an image signal to which pulldown conversion has been performed; and
displaying the image signal to which image interpolation by the motion compensation processing has not been performed, wherein
a predetermined monochromatic image signal is inserted between frames or fields of the input image signal to convert the number of frames or fields of the input image signal when it is determined that the input image signal is an image signal to which pulldown conversion has been performed.

12. An image processing device having a rate converting portion that interpolates an image signal to which a motion compensation processing has been applied between frames or fields of an input image signal to convert the number of frames or fields of the input image signal, further comprising
a determining portion that determines whether the input image signal is an image signal to which pulldown conversion has been performed, wherein
when the determining portion determines the input image signal is an image signal to which pulldown conversion has been performed, image interpolation by the motion compensation processing is not performed by the rate converting portion, wherein
another rate converting portion that inserts an image signal to which the motion compensation processing has not been applied between frames or fields of the input image signal to convert the number of frames or fields of the input image signal is also included, and
the image signal with the number of frames or fields converted by the another rate converting portion is output to the display panel when the input image signal is determined to be an image signal to which pulldown conversion has been performed.

13. The image processing device as defined in claim 12, wherein
the another rate converting portion inserts an image signal of the frames or fields between frames or fields of the input image signal to convert the number of frames or fields of the input image signal.

14. The image processing device as defined in claim 12, wherein
the another rate converting portion interpolates an image signal to which a linear interpolation processing has been applied between frames or fields of the input image signal to convert the number of frames or fields of the input image signal.

15. The image processing device as defined in claim 12, wherein
the another rate converting portion inserts a predetermined monochromatic image signal between frames or fields of the input image signal to convert the number of frames or fields of the input image signal.

16. An image processing method having a step of interpolating an image signal to which a motion compensation processing has been applied between frames or fields of an input image signal to convert the number of frames or fields of the input image signal, the method further comprising
determining whether the input image signal is an image signal to which pulldown conversion has been performed, wherein
image interpolation by the motion compensation processing is not performed in the step of interpolating an image signal when it is determined that the input image signal is an image signal to which pulldown conversion has been performed, wherein
an image signal to which a linear interpolation processing has been applied is interpolated between frames or fields of the input image signal to convert the number of frames or fields of the input image signal when it is determined that the input image signal is an image signal to which pulldown conversion has been performed.

17. An image processing method having a step of interpolating an image signal to which a motion compensation processing has been applied between frames or fields of an input image signal to convert the number of frames or fields of the input image signal, the method further comprising
determining whether the input image signal is an image signal to which pulldown conversion has been performed, wherein
image interpolation by the motion compensation processing is not performed in the step of interpolating an image signal when it is determined that the input image signal is an image signal to which pulldown conversion has been performed, wherein
a predetermined monochromatic image signal is inserted between frames or fields of the input image signal to convert the number of frames or fields of the input image signal when it is determined that the input image signal is an image signal to which pulldown conversion has been performed.

18. An image displaying device having a rate converting portion that interpolates an image signal to which a motion compensation processing has been applied between frames or fields of an input image signal to convert and output the number of frames or fields of the input image signal to a display panel, further comprising:
a determining portion that determines whether the input image signal is an image signal to which pulldown conversion has been performed, wherein
when the input image signal is determined to be an image signal to which pulldown conversion has been performed by the determining portion, strength of the motion compensation processing is reduced, wherein
the rate converting portion includes
an interpolation image generating portion that performs weighted addition of the image signal to which the motion compensation processing has been applied and an image signal to which a linear interpolation processing has been applied at a predetermined rate to generate an interpolation image signal, wherein
the weighted addition rate is reduced when the input image signal is determined to be an image signal to which pulldown conversion has been performed.

19. The image displaying device as defined in claim 18, wherein
when the input image signal is determined to be an image signal to which pulldown conversion has been performed, the interpolation image generating portion defines the image signal to which the linear interpolation processing has been applied as the interpolation image signal, and
when the input image signal is determined not to be an image signal to which pulldown conversion has been performed, the interpolation image generating portion defines the image signal to which the motion compensation processing has been applied as the interpolation image signal.