Video processing apparatus, video processing method, and computer program

A holding type display such as a liquid-crystal display for controlling motion blur is disclosed. A step edge detector detects an edge portion of a moving step edge in video data in an input frame or an input field. A corrector corrects a pixel value of a pixel at the edge portion of the step edge detected by the step edge detector, based on a spatial amount of motion of the corresponding pixel supplied by a motion detector.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a video processing apparatus, a video processing method, and a computer program and, in particular, to a video processing apparatus, a video processing method, and a computer program for controlling motion blur of a moving picture in a holding type display device such as a liquid-crystal display device.

2. Description of the Related Art

Cathode-ray tubes (CRTs) are in widespread use as a display for displaying a moving picture. Liquid-crystal displays working in a display method different from the CRT are also widely used (see Japanese Patent Application No. 2001-118396, for example).

When a predetermined one of a plurality of frames or fields forming a moving picture is addressed on a CRT, a built-in electron gun successively scans each of horizontal lines (scanning lines) forming the screen of the CRT. The addressed frame or field is thus displayed on the screen of the CRT.

Each of a plurality of pixels forming the addressed frame or field is displayed in an impulsive manner along time axis. In other words, a pixel is displayed at the corresponding location thereof only at the moment the electron gun scans and hits. Display devices adopting the same display method as the CRT are generally referred to as an impulsive type display.

In contrast, liquid-crystal displays hold the display of all liquid crystals forming the entire screen from when a predetermined one of a plurality of frames or fields forming a moving picture is addressed until when the displaying of a next frame or field is addressed. The addressed frame or field is thus displayed on the screen.

It is assumed that one pixel corresponds to a respective liquid crystal. A frame or a field is addressed, and the pixel value of each pixel forming the addressed frame or the addressed field is addressed in the liquid-crystal display device. The liquid-crystal display device applies a voltage, at a level corresponding to the addressed pixel value, to a respective liquid crystal (corresponding to the respective pixel), each pixel forming the screen of the liquid-crystal display device. In response, each liquid crystal emits light at intensity responsive to the level of the applied voltage. Each liquid crystal is continuously supplied with the voltage of the same level and emits light at the same level at least until a next frame or a next field is addressed for displaying. In other words, a pixel having an addressed pixel value is continuously displayed in a respective liquid crystal.

When the pixel value of a predetermined pixel needs to be updated with the next frame or the next field addressed for displaying, the liquid crystal corresponding to the pixel is supplied with the voltage at the level responsive to the updated pixel value (in other words, the applied voltage changes in level). The output level (light intensity) of the corresponding liquid crystal also changes.

The liquid-crystal display device, adopting the display method different from the impulsive type display device such as the CRT, has advantages such as small mounting space requirement, low power consumption, and display relatively free from distortion.

However, the liquid-crystal display device has a drawback that the occurrence of motion blur is more frequent than in the impulsive type display device when a moving picture is displayed.

It has been considered that the generation of motion blur in the liquid-crystal display device is caused by a slow response of the liquid crystal. Image blurring has been considered to take place in the liquid-crystal display device, because it takes time for each liquid crystal to reach an addressed target level (namely, to a level corresponding to the addressed pixel value if one liquid crystal corresponds to a respective pixel).

To overcome this drawback, namely, to control the generation of motion blur, Japanese Patent Application No. 2001-118396 discloses the following technique. In accordance with the disclosed technique, a voltage at a level higher than the level responsive to a target level (namely, to a level corresponding to the addressed pixel value if one liquid crystal corresponds to a respective pixel) is applied. This technique is referred to as an overdrive method, hereinafter. The overdrive method sets, as a target level, a level higher than a normal level, in other words, corrects a target level.

FIG. 1illustrates the principle of the overdrive method and more specifically, illustrates waveforms in time response of the output level of the liquid crystal with the overdrive method used and unused (normal operation).

As shown, the horizontal axis is time axis, and the vertical axis is an output level of the liquid crystal (intensity of light). A curve1represents the waveform of the time response of the output level of the liquid crystal with the overdrive method unused (the normal operation mode). A curve2represents the waveform of the time response of the output level of the liquid crystal with the overdrive method used. Here, T represents display time of one frame or one field, namely, time from when one frame or one field is addressed for displaying to when a next frame or a next field is addressed for displaying. Hereinafter, time T is referred to as frame time T or field time T. In the liquid-crystal display device, the frame time T or the field time T is typically 16.6 ms.

As shown inFIG. 1, an output level of a liquid pixel of interest (hereinafter referred to as a target pixel) from among pixels forming the screen of the liquid-crystal display device is a level Yb immediately prior to time zero. When a given frame or field is addressed at time zero, it is assumed that the addressed level of the target liquid crystal (a target level) is a level Ye.

In the ordinary liquid-crystal display device with the overdrive method used, the target liquid crystal is supplied with the voltage at the level corresponding to the target level Ye at time zero. If the target liquid crystal is an ideal one (with response speed at infinity), the output level thereof immediately changes to the target level Ye from the level Yb at the moment the voltage at the level corresponding to the target level Ye is applied. In practice, however, the output level of the target liquid crystal gradually changes from the level Yb to the target level Ye as represented by the curve1. The response waveform (the waveform of the curve1) of the output level of the target liquid crystal becomes a delayed waveform.

More specifically, the output level of the target liquid crystal reaches a level Yt1lower than the target level Ye even at time t1which is the frame time or the field time T later than time zero (even when the next frame or the next field is addressed for displaying).

It is now assumed that the target level of the target liquid crystal is still the level Ye when the next frame or the next field is addressed at time t1.

In the curve1ofFIG. 1, the output level of the target liquid crystal gradually rises toward the target level Ye from the level Yt1. Even at time t2that is the frame time T or the field time T later than time t1(namely, even when another next frame or another next field is addressed), the output level of the target liquid crystal reaches only a level Yt2lower than the target level Ye.

In the overdrive method, the target liquid crystal is supplied with a voltage at a level higher than the target level Ye (a level corresponding to a level Ylck as shown inFIG. 1) during a period of time from when one frame or one field is addressed (at time zero inFIG. 1) to when a next frame or a next field is addressed (at time t1inFIG. 1) so that the output level reaches the target level Ye.

As represented by the curve2, the output level of the target liquid crystal reaches the target level Ye at time t1that is the one frame time T or the one field time T later than time zero.

In other words, the target level is modified from the level Ye to the level Ylck higher than the level Ye at time zero in the overdrive method ofFIG. 1. The target liquid crystal is supplied with a voltage at the modified target level Ylck. As a result, the output level of the target liquid crystal reaches the unmodified target level Ye (namely, the actually desired level Ye) at time t1that is one frame time T or one field time T later than application of the voltage.

When the next frame or the next field is addressed at time t1, the target level of the target pixel remains the level Ye in that addressing. Since the output level of the target liquid crystal already reaches the level Ye at time, t1, the target level remains unmodified at the level Ye, and the voltage at the level corresponding to the level Ye is continuously supplied to the target liquid crystal. In this way, the output level of the target liquid crystal is maintained at the target level Ye from time t1to time t2.

FIG. 2illustrates a visual change in the output level of the liquid crystal (light intensity) corresponding to the curves ofFIG. 1with the overdrive method in operation and not in operation.

As shown inFIG. 2, the left-hand vertical axis is time axis corresponding to the time axis ofFIG. 1. The change in the output level of the liquid crystal with time (the change in the curve1ofFIG. 1) is shown on the right of the time axis with the overdrive method not in operation. The change in the output level of the liquid crystal with time (the change in the curve2) is shown on the right hand sideFIG. 2with the overdrive method in operation. As shown inFIG. 2, the output level of the liquid crystal is shown in density of gray tone. The densest gray tone represents the level Yb inFIG. 1, and the lightest gray tone represents the level Ye inFIG. 1.

Even with the overdrive method in operation, the generation of motion blur is not controlled. Currently, no effective method for controlling the motion blur is available in the liquid-crystal display device. The liquid-crystal display device is not free from the above drawback.

The motion blur has been discussed in connection with the liquid-crystal display device. However, this drawback affects not only the liquid-crystal display device, but also any type of display device that includes a plurality of display elements, each of which takes a predetermined time to-reach an output target level from the addressing of the target level, and is associated with at least a portion of a predetermined one of pixels forming a frame or a field.

Many of such display devices adopt a display method in which at least part of display elements forming the screen holds display for a predetermined period of time from the addressing of a predetermined frame or field to the addressing of a next frame or field. Hereinafter, the liquid-crystal display device and the display device adopting such a display method are collectively referred to as a holding type display device. A display state of a display element (a liquid crystal in the liquid-crystal display device) forming the screen of the holding type display device is referred to as a hold display. The above-referenced drawback is a common problem of the holding type display device.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide a video processing apparatus that controls the generation of motion blur in a moving image.

A first video processing apparatus of the present invention includes a unit for detecting motion in a video based on input video data and reference video data immediately prior to the input video data, a video processing unit for processing a pixel value in the video data based on the result of the motion detection of the motion detecting unit, and a display unit for displaying the result of the process of the pixel value provided by the video processing unit. The video processing unit includes a step edge detector for detecting an edge portion in response to the result of the motion detection of the motion detecting unit, and a corrector for correcting the result of the step edge detection of the step edge detector.

Preferably, the motion detecting unit detects the motion in the video by comparing an object moving in the video data with an object moving in the reference video data.

Preferably, the corrector performs correction by changing the edge height in the edge portion detected by the step edge detector depending on the motion detected by the motion detecting unit.

Preferably, the corrector performs correction by changing the edge height in the edge portion of the step edge detected by the step edge detector depending on the display characteristics of the display unit.

A first video processing method of the present invention includes the steps of detecting motion in a video based on input video data and reference video data immediately prior to the input video data, processing a pixel value in the video data based on the result of the motion detection in the motion detecting step, and displaying the result of the process of the pixel value provided in the video processing step. The video processing step includes detecting an edge portion of a step edge in response to the result of the motion detection in the motion detecting step, and correcting the result of the step edge detection.

A first computer program of the present invention for causing a computer to perform a video processing method, includes program code for performing the steps of detecting motion in a video based on input video data and reference video data immediately prior to the input video data, processing a pixel value in the video data based on the result of the motion detection in the motion detecting step, and displaying the result of the process of the pixel value provided in the video processing step. The video processing step includes detecting an edge portion of a step edge in response to the result of the motion detection in the motion detecting step, and correcting the result of the step edge detection.

In accordance with the first video processing apparatus, the first video processing method, and the first computer program, the motion in the video data is detected from the input video data and the reference video data immediately prior to the input video data. The pixel value of at least one portion of the video data is processed in response to the result of motion detection. The result of the process of the pixel value is displayed. The edge portion in the video data is detected and is then corrected based on the result of the motion detection.

A second video processing apparatus of the present invention commands a display device to display each of a plurality of access units constituting a moving picture. The display device includes a plurality of display elements that take a predetermined period of time to reach an output target level from the moment the target level is addressed, each of the plurality of display elements corresponding to at least a portion of a predetermined one of pixels forming the access unit. The video processing apparatus includes a motion detecting unit for detecting an object that has moved to a spatial location in a first access unit from a spatial location in a second access unit prior to the first access unit and a spatial amount of motion of the object, an edge detecting unit for detecting an edge portion of the object detected by the motion detecting unit, a correcting unit for correcting a pixel value of a pixel, positioned at the edge portion of the object detected by the edge detecting unit, from among a plurality of pixels forming the first access unit, based on the spatial amount of motion of the object detected by the motion detecting unit, and a display commanding unit for commanding the display device to display the first access unit by addressing the pixel values of the plurality of pixels forming the first access unit, containing the pixel value corrected by the correcting unit, as the target levels of the corresponding display elements to the display device.

Preferably, the object includes pixels which, having a first pixel value, are consecutively aligned in the direction of motion, and beyond a predetermined pixel thereof as a border, pixels which, having a second pixel value different from the first pixel value, are consecutively aligned in the direction of motion, and the edge detecting unit detects, as a pixel corresponding to the edge portion of the object, a pixel having the first pixel value bordering the pixel having the second pixel value.

Preferably, the edge detecting unit further calculates the difference value between the first pixel value of the first pixel detected as the edge portion of the object and the second pixel value of a second pixel adjacent to the first pixel in the direction of motion. The correcting unit determines, regarding the first pixel detected by the edge detecting unit, a first gain depending on the amount of motion detected by the motion detecting unit, calculates the product between the determined first gain and the difference value detected by the edge detecting unit so as to determine a correction value, and adds the determined correction value to the pixel value of the first pixel so as to determine a corrected pixel value of the first pixel.

Preferably, the correcting unit further determines, regarding the first pixel, a second gain depending on the time response characteristics of the display element corresponding to the first pixel of the display device, and calculates the product of the first gain, the determined second gain, and the difference value so as to determine the correction value.

Preferably, the correcting unit further sets, as a target pixel to be corrected, two or more pixels including the first pixel, of pixels consecutively lined in the direction opposite to the direction of motion of the object, beginning at the first pixel, distributes the correction value to the two or more pixels to be corrected, adds the distributed correction value to the pixel values corresponding to the two or more pixels to be corrected so as to determine the corrected pixel value of the two or more pixels to be corrected.

A second video processing method of the present invention commands a display device to display each of a plurality of access units constituting a moving picture. The display device includes a plurality of display elements that take a predetermined period of time to reach an output target level from the moment the target level is addressed, each of the plurality of display elements corresponding to at least a portion of a predetermined one of pixels forming the access unit. The video processing method includes a motion detecting step for detecting an object that has moved to a spatial location in a first access unit from a spatial location in a second access unit prior to the first access unit and a spatial amount of motion of the object, an edge detecting step for detecting an edge portion of the object detected in the motion detecting step, a correcting step for correcting the pixel value of a pixel, positioned at the edge portion of the object detected in the edge detecting step, from among a plurality of pixels forming the first access unit, based on the spatial amount of motion of the object detected in the motion detecting step, and a display commanding step for commanding the display device to display the first access unit by addressing the pixel values of the plurality of pixels forming the first access unit, containing the pixel value corrected in the correcting step, as the target levels of the corresponding display elements to the display device.

A second computer program of the present invention causes a computer to perform a video processing method for commanding a display device to display each of a plurality of access units constituting a moving picture. The display device includes a plurality of display elements that take a predetermined period of time to reach an output target level from the moment the target level is addressed, each of the plurality of display elements corresponding to at least a portion of a predetermined one of pixels forming the access unit. The computer program includes program code for performing a motion detecting step for detecting an object that has moved to a spatial location in a first access unit from a spatial location in a second access unit prior to the first access unit and a spatial amount of motion of the object, an edge detecting step for detecting an edge portion of the object detected in the motion detecting step, a correcting step for correcting the pixel value of a pixel, positioned at the edge portion of the object detected in the edge detecting step, from among a plurality of pixels forming the first access unit, based on the spatial amount of motion of the object detected in the motion detecting step, and a display commanding step for commanding the display device to display the first access unit by addressing the pixel values of the plurality of pixels forming the first access unit, containing the pixel value corrected in the correcting step, as the target levels of the corresponding display elements to the display device.

In accordance with the second video processing apparatus, the second video processing method, and the second computer program, the display device is commanded to display each of a plurality of access units constituting a moving picture, wherein the display device includes a plurality of display elements that take a predetermined period of time to reach an output target level from the moment the target level is addressed, each of the plurality of display elements corresponding to at least a portion of a predetermined one of pixels forming the access unit. More specifically, the object that has moved to a spatial location in the first access unit to a spatial location in the second access unit prior to the first access unit is detected. The amount of motion of the object and the edge portion of the object are detected. The pixel value of the pixel, positioned at the edge portion of the detected object, from among the plurality of pixels forming the first access unit, is corrected based on the spatial amount of motion of the detected object. The display device is commanded to display the first access unit by addressing the pixel values of the plurality of pixels forming the first access unit, containing the pixel value corrected in the correcting step, as the target levels of the corresponding display elements to the display device.

A third video processing apparatus of the present invention includes a motion detecting unit for detecting motion in a video based on input video data and reference video data immediately prior to the input video data, a first video processing unit for performing a first video process on the video data based on the result of the motion detection of the motion detecting unit, a second video processing unit for performing a second video process other than the first video process on the video data based on the result of the motion detection of the motion detecting unit, and a display unit for displaying at least one of the results of the first and second video processes of the first and second video processing units based on the result of the motion detection of the motion detecting unit.

Preferably, the motion detecting unit detects the motion in the video by comparing an object moving in the video data with an object moving in the reference video data.

Preferably, the second video processing unit includes a step edge detector for detecting an edge portion in accordance with the result of the motion detection of the motion detecting unit, and a corrector for correcting the result of the step edge detection of the step edge detector.

Preferably, the display unit includes a switch for switching between the result of the video process of the first processing unit and the result of the video process of the second video processing unit, based on the result of motion detection of the motion detecting unit, a display controller for converting the result selected by the switch to a signal having a predetermined format responsive to the target level of a display element of each pixel, and a hold unit for holding the result of the conversion of the display controller for each of all display elements.

Preferably, the corrector performs correction by changing the edge height in the edge portion detected by the step edge detector depending on the motion detected by the motion detecting unit.

Preferably, the corrector performs correction by changing the edge height in the edge portion detected by the step edge detector depending on the display characteristics of the display unit.

A third video processing method of the present invention includes a motion detecting step for detecting motion in a video based on input video data and reference video data immediately prior to the input video data, a first video processing step for performing a first video process on the video data based on the result of the motion detection in the motion detecting step, a second video processing step for performing a second video process other than the first video process on the video data based on the result of the motion detection in the motion detecting step, and a display step for displaying at least one of the results of the first and second video processes of the first and second video processing steps based on the result of the motion detection in the motion detecting step.

A third computer program of the present invention causes a computer to perform a video processing method, and includes program code for performing a motion detecting step for detecting motion in a video based on input video data and reference video data immediately prior to the input video data, a first video processing step for performing a first video process on the video data based on the result of the motion detection in the motion detecting step, a second video processing step for performing a second video process other than the first video process on the video data based on the result of the motion detection in the motion detecting step, and a display step for displaying at least one of the results of the first and second video processes of the first and second video processing steps based on the result of the motion detection in the motion detecting step.

In accordance with the third video processing apparatus, the third video processing method, and the third computer program, the motion in a video is detected based on the input video data and the reference video data immediately prior to the video data. The first video process and the second video process are performed in accordance with the results of the motion detection. Depending on the result of the motion detection, at least one of the results of the first video process and the second video process is displayed.

A fourth video processing apparatus of the present invention includes a motion detecting unit for detecting motion in a video based on input video data and reference video data immediately prior to the input video data, a video processing unit for performing a video process on pixel values in the video data based on the result of the motion detection of the motion detecting unit, and a display controlling unit for controlling a predetermined display device to display the result of the video processing unit. The video processing unit includes a correcting unit for subjecting a block formed of two pixels values corresponding to two pixels to be disposed consecutively in a predetermined direction of the video data to an asymmetric high-pass filter process, taking advantage of the result of the motion detecting unit, thereby correcting one of the pixel values included in the block.

A fourth video processing method of the present invention includes the steps of detecting motion in a video based on input video data and reference video data immediately prior to the input video data, processing a pixel value in the video data based on the result of the motion detection in the motion detecting step, and controlling a predetermined display device to display the result of the process of the pixel value provided in the video processing step. The video processing step includes a correcting step for subjecting a block formed of two pixels values corresponding to two pixels to be disposed consecutively in a predetermined direction of the video data to an asymmetric high-pass filter process, taking advantage of the result of the motion detecting step, thereby correcting one of the pixel values included in the block.

A fourth computer program of the present invention includes program code for performing the steps of detecting motion in a video based on input video data and reference video data immediately prior to the input video data, processing a pixel value in the video data based on the result of the motion detection in the motion detecting step, and controlling a predetermined display device to display the result of the process of the pixel value provided in the video processing step. The video processing step includes a correcting step for subjecting a block formed of two pixels values corresponding to two pixels to be disposed consecutively in a predetermined direction of the video data to an asymmetric high-pass filter process, taking advantage of the result of the motion detecting step, thereby correcting one of the pixel values included in the block.

In accordance with the fourth video processing apparatus, the fourth video processing method, and the fourth computer program, the motion in a video is detected based on the input video data and the reference video data immediately prior to the video data. The pixel values in the video data are processed in accordance with the detected motion, and the video of which the pixel values are processed is displayed on a predetermined display device. More specifically, the process of pixel values includes at least a process for subjecting a block formed of two pixels values corresponding to two pixels to be disposed consecutively in a predetermined direction of the video data to an asymmetric high-pass filter process, taking advantage of the detected motion, thereby correcting one of the pixel values included in the block.

The video processing apparatus may be a standalone apparatus separate from a display device, or may contain the display device as an element. Alternatively, the video processing apparatus may be contained as a unit in the display device.

The present invention is applicable to a recording medium that stores the computer program of the present invention.

The present invention thus controls the holding type display device such as the liquid-crystal display device in the display function thereof. The present invention controls the motion blur of a moving picture in the holding type display device such as the liquid-crystal display device.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

According to the present invention, a first video processing apparatus is provided. This first video processing apparatus includes a unit (for example, a motion detector24ofFIG. 7) for detecting motion in a video based on input video data (for example, video data currently input to a video processing apparatus11ofFIG. 7) and reference video data (for example, video data output from a reference video storage unit23ofFIG. 7) immediately prior to the input video data, a video processing unit (for example, a video processor22ofFIG. 7) for processing a pixel value in the video data based on the result of the motion detection of the motion detecting unit, and a display unit (a holding type display unit12ofFIG. 7) for displaying the result of the process of the pixel value provided by the video processing unit. The video processing unit includes a step edge detector (for example, a step edge detector31ofFIG. 7) for detecting an edge portion in response to the result of the motion detection of the motion detecting unit, and a corrector (for example, a corrector32ofFIG. 7) for correcting the result of the step edge detection of the step edge detector.

According to the present invention, a second video processing apparatus is provided. This second video processing apparatus (for example, the video processing apparatus11ofFIG. 7) commands a display device (for example, the holding type display unit12ofFIG. 7) to display each of a plurality of access units constituting a moving picture. The display device includes a plurality of display elements (for example, display elements providing the response waveform like the curve1ofFIG. 1) that take a predetermined period of time (for example, twice as long as the frame time T or field time T as shown inFIG. 1) to reach an output target level (for example, the level Ye ofFIG. 1) from the moment the target level is addressed, each of the plurality of display elements corresponding to at least a portion of a predetermined one of pixels forming the access unit. The video processing apparatus includes a motion detecting unit (for example, a motion detector24ofFIG. 7) for detecting an object (for example, a step edge moving as shown fromFIG. 3toFIG. 4) that has moved to a spatial location in a first access unit from a spatial location in a second access unit prior to the first access unit and a spatial amount of motion of the object, an edge detecting unit (for example, a step edge detector31of a video processor22ofFIG. 7, or a difference value computing unit81of the video processor22ofFIG. 23) for detecting an edge portion of the object detected by the motion detecting unit, a correcting unit (for example, a corrector32ofFIG. 7, or a difference value-dependent gain Ge decision unit82through an adder87) for correcting (in a manner shown inFIG. 11throughFIG. 13, for example) the pixel value of a pixel (for example, a pixel n+4 at the edge portion of the step edge ofFIG. 4andFIG. 12, or a pixel n+5 ofFIG. 13), positioned at the edge portion of the object detected by the edge detecting unit, from among a plurality of pixels forming the first access unit, based on the spatial amount of motion of the object detected by the motion detecting unit, and a display commanding unit (for example, a display controller26ofFIG. 7) for commanding the display device to display the first access unit by addressing the pixel values of the plurality of pixels forming the first access unit, containing the pixel value corrected by the correcting unit, as the target levels of the corresponding display elements to the display device.

In this second video processing apparatus, the object includes pixels (for example, pixels n−8 through n+4 ofFIG. 4) which, having a first pixel value (for example, a pixel value E ofFIG. 4), are consecutively aligned in the direction of motion (for example, the direction X represented by the arrow ofFIG. 4), and beyond a predetermined pixel (for example, the pixel n+4 ofFIG. 4) thereof as a border, pixels (for example, the pixel n+5 and more rightward pixels ofFIG. 4) which, having a second pixel value (for example, a pixel value B ofFIG. 4) different from the first pixel value, are consecutively aligned in the direction of motion, and the edge detecting unit detects, as the edge portion of the object, a pixel (for example, the pixel n+4 ofFIG. 4) having the first pixel value bordering the pixel having the second pixel value.

In this second video processing apparatus, the edge detecting unit further calculates the difference value between the first pixel value of the first pixel detected as a pixel corresponding to the edge portion of the object, and the second pixel value of the second pixel adjacent to the first pixel in the direction of motion of the object. The correcting unit determines a first gain (for example, a motion speed-dependent gain Gv ofFIG. 17) depending on the amount of motion detected by the motion detecting unit with regard to the first pixel detected by the edge detecting unit, calculates the product between the determined first gain and the difference value detected by the edge detecting unit so as to determine a correction value (for example, a correction value decision unit86ofFIG. 23determines a later-described correction value R=Gv×(Nr−Nrn)), and adds the determined correction value to the pixel value of the first pixel so as to determine a corrected pixel value of the first pixel (for example, and an adder87ofFIG. 23outputs an added value Nr+R between a correction value R and the pixel value Nr of a target pixel).

In this second video processing apparatus, the correcting unit determines a second gain depending on the time response characteristics of the display element corresponding to the first pixel of the display device (for example, a difference value-dependent gain Ge decision unit82ofFIG. 23determines a difference value-dependent gain Ge ofFIG. 22, and also a target level-dependent gain Gl decision unit84determines a target level-dependent gain Gl ofFIG. 20), and calculates the product between the first gain, the determined second gain, and the difference value so as to determine the correction value (multipliers83and85calculate Ge×Gl×(Nr−Nrn), further, a correction value decision unit86calculates Gv×Ge×Gl×(Nr−Nrn), and then the calculated result is determined as a correction value R).

The correcting unit further sets, as a target pixel to be corrected, two or more pixels including the first pixel of pixels consecutively lined in the direction opposite to the direction of motion of the object, beginning at the first pixel (for example, a pixel n+4 and a pixel n+3 ofFIG. 25are set as a target pixel), distributes the correction value to the two or more target pixels thus set (for example, as shown inFIG. 25, a correction value R is distributed in the proportion of 2:1), and adds the distributed correction value to the pixel values corresponding to the two or more target pixels so as to determine the corrected pixel values of the corresponding target pixels (for example, as shown inFIG. 25, the correction value of the pixel n+4 is determined as 2/3R, and the correction value of the pixel n+3 is determined as R/3).

According to the present invention, a third video processing apparatus is provided. This third video processing apparatus includes a motion detecting unit (for example, the motion detector24ofFIG. 7) for detecting motion in a video based on input video data (for example, video data currently input to the video processing apparatus11ofFIG. 7)and referencevideo data (for example, the video data output from the reference video storage unit23ofFIG. 7) immediately prior to the input video data, a first video processing unit (for example, a video processor21ofFIG. 7) for performing a first video process on the video data based on the result of the motion detection of the motion detecting unit, a second video processing unit (for example, a video processor22ofFIG. 7) for performing a second video process other than the first video process on the video data based on the result of the motion detection of the motion detecting unit, and a display unit (as will be discussed later, a switch25, the display controller26, and the holding type display unit12, shown inFIG. 7, may be considered as a single display unit) for displaying at least one of the results of the first and second video processes of the first and second video processing units based on the result of the motion detection in the motion detecting unit.

In the third video processing apparatus, the second video processing unit includes a step edge detector (for example, the step edge detector31ofFIG. 7) for detecting an edge portion in accordance with the result of the motion detection of the motion detecting unit, and a corrector (for example, the corrector32ofFIG. 7) for correcting the result of the step edge detection of the step edge detector.

In the third video processing apparatus, the display unit includes a switch (for example, the switch25ofFIG. 7) for switching between the result of the video process of the first processing unit and the result of the video process of the second video processing unit, based on the result of the motion detection of the motion detecting unit, a display controller (for example, the display controller26ofFIG. 7) for converting the result selected by the switch to a signal (for example, a voltage signal at a voltage level corresponding to the target level) having a predetermined format responsive to the target level of a display element of each pixel, and a hold unit (for example, the holding type display unit12ofFIG. 7) for holding the result of the conversion of the display controller for each of all display elements.

According to the present invention, a fourth video processing apparatus is provided. This fourth video processing apparatus includes a motion detecting unit (for example, a motion detector24ofFIG. 7) for detecting motion in a video based on input video data and reference video data immediately prior to the input video data, a video processing unit (for example, a video processor22ofFIG. 14provided instead of a video processor22ofFIG. 7) for performing a video process on pixel values in the video data based on the result of the motion detection of the motion detecting unit, and a display controlling unit (for example, a display controller26ofFIG. 7) for controlling a predetermined display device to display the result of the video processing unit. The video processing unit includes a correcting unit (for example, an asymmetric coefficient filter62through a multiplier66of the video processor22ofFIG. 14) for subjecting a block formed of two pixels values corresponding to two pixels to be disposed consecutively in a predetermined direction of the video data to an asymmetric high-pass filter process, taking advantage of the result of the motion detecting unit, thereby correcting one of the pixel values included in the block.

The inventors of this invention have analyzed the cause why the overdrive method is still unable to overcome the conventional drawback, namely, the cause why the motion blur is not controlled in the holding type display device, and have developed a video processing apparatus free from the drawback based on the results of analysis.

The results of analysis is now discussed before the discussion of the video processing apparatus of the preferred embodiments of the present invention free from the drawback.

One of the causes for the generation of motion blur is slow response speed of the liquid crystal (pixel) in the liquid-crystal display device. The overdrive method is a solution taking into consideration the slow response.

The slow response of the liquid crystal is not the only cause for the motion blur in the liquid crystal. The retinal after-image of the human who views the liquid-crystal display device is also one of the causes. The inventors of this invention have considered that the overdrive method fails to take into consideration the retinal-after image, and that for this reason, the motion blur is not effectively eliminated. The retinal after-image refers to the phenomenon that the eyes of the human unconsciously track an object if the object is moving.

The retinal after-image and the motion blur in the liquid-crystal display device will now be discussed in detail with reference toFIGS. 3 through 6.

It is assumed in the following discussion that each display element (a liquid crystal in the liquid-crystal display device) forming the screen of the holding type display device corresponds to a predetermined one of a plurality pixels forming one frame or one field.

FIG. 3illustrates a step edge contained in a predetermined frame or a predetermined field.

As shown, the horizontal axis represents a position of each pixel (in a spatial direction X), and the vertical axis represents a pixel value. Located at positions n−8 through n+4 are respective pixels associated with the respective numbers. Hereinafter, a pixel numbered k is referred to as a pixel k (k is any integer number).

One spatial direction in which pixels forming a frame or a field are consecutively lined is referred to as a spatial X direction, and a spatial direction perpendicular to the spatial direction X is referred to a spatial direction Y. As shown inFIG. 3, the pixels n−8 through n+4 are consecutively lined in the spatial direction X.

Pixels having a first pixel value (a pixel value E inFIG. 3) are consecutively lined in a predetermined direction (the spatial direction X inFIG. 3), and beyond a predetermined pixel (the pixel n inFIG. 3), pixels having a second pixel value (a pixel value B inFIG. 3) different from the first pixel value are consecutively lined in the spatial direction X. A set of these pixels is referred to a step edge.

An object having a constant pixel value E is displayed on a background having a constant pixel value B in a predetermined frame or a predetermined field. From among a plurality of pixels forming the frame or the field, a set of pixels consecutively lined in a predetermined direction in the vicinity of a border (edge) between the object and the background is a step edge. If the step edge moves in a predetermined direction, the object must move in the same direction. In other words, as will be discussed later, the object is decomposed into step edges, and a step edge itself may be regarded as an object.

For example, it is assumed that the step edge is now moving at a constant velocity in the spatial direction X as shown inFIG. 3, and the amount of motion across frames or fields is 4 pixels/frame or 4 pixels/field. The step edge reaches the position in the next frame or the next field as shown inFIG. 4.

If the frame or the field containing the step edge ofFIG. 4is a frame of interest or a field of interest to be displayed (hereinafter referred to as a display target frame or a display target field),FIG. 3shows the step edge contained in the frame or the field immediately prior to the display target frame or the display target field. If the step edge is moving at a constant velocity of 4 pixels/frame or 4 pixels/field,FIG. 4shows the step edge contained in the display target frame or the display target field.

FIG. 5illustrates the relationship between a hold display of each liquid crystal (each pixel) forming the screen of the liquid-crystal display device and the retinal after-image with the previously discussed overdrive method in operation.

The output level of the liquid crystal changes with time as shown when the liquid-crystal display device displays the step edge ofFIG. 4.

The top horizontal axis ofFIG. 5represents a pixel position (the spatial direction X) and the vertical axis represents time axis. As previously discussed, one pixel corresponds to one liquid crystal, and the horizontal axis represents the position of each of the pixels n−9 thought n+8. A liquid crystal corresponding to a pixel k is referred to as a liquid crystal k. In the upper portion ofFIG. 5, the density of gray tone represents the output level of the liquid crystals (liquid crystals n−7 through n+4). The densest tone of gray represents a level corresponding to the pixel value B ofFIG. 4, and the lightest tone of gray represents a level corresponding to the pixel value E ofFIG. 4. With reference toFIGS. 6 and 11, as will be discussed later, a lighter tone of gray is shown, and represents a level corresponding to a pixel value higher than the pixel value E ofFIG. 4.

Shown in the lower portion ofFIG. 5is the amount of light picked up by the retina of a human user when the human user views the step edge ofFIG. 4appearing on the screen of the liquid-crystal display device. More specifically, the vertical axis represents the amount of light picked up by the retina of the user. The horizontal axis represents the position of the retina of the user (in the spatial direction X) at time point tb on the upper portion ofFIG. 5.

As shown in the upper portion ofFIG. 5, immediately prior to time ta, the liquid-crystal display device displays the frame or the field containing the step edge ofFIG. 3(respectively immediately prior to the display target frame or the display target field), and the liquid-crystal display device is commanded to display the display target frame or the display target field containing the step edge ofFIG. 4at time ta.

Each of the liquid crystals (pixels) n−7 through n outputs light at a level corresponding to the pixel value E at time ta. The liquid-crystal display device applies a voltage at a level corresponding to the pixel value E to each of the liquid crystals (pixels) n−7 through n at time ta thereafter. Each of the liquid crystals (pixels) n−7 through n continuously emits light at a level corresponding to the pixel value E (presenting a hold display).

In contrast, each of the liquid crystals (pixels) n+1 through n+4 outputs light at a level corresponding to the pixel value B at time ta. The liquid-crystal display device supplies each of the liquid crystals (pixels) n+1 through n+4 with a voltage at a level (corresponding to the level Ylck ofFIG. 1) higher than the level of the pixel E immediately subsequent to time ta. From a period of time immediately subsequent to time ta to time tb at which the liquid-crystal display device is commanded to display a next frame or a next field (during the frame time T of the display target frame or frame field T of the display target field), the output level of each of the liquid crystals n+1 through n+4 gradually approaches to the level corresponding to the pixel value E from the level corresponding to the pixel level B.

Since the user continuously views the step edge displayed on the liquid-crystal display device with the retinal after-image from before time ta, the user continuously views the step edge in accordance with the arrow in shown in the upper portion ofFIG. 5(in step with the movement of the step edge) even during the period of time from time ta at which the liquid-crystal display device is commanded to display the display target frame or the display target field to time tb at which the liquid-crystal display device is commanded to display the next frame or the next field (namely, during the frame time T of the display target frame or the field time T of the display target field).

More specifically, a point i+1 on the retina of the human user, looking at a border between the liquid crystal n+1 and the liquid crystal n+2 at time tb, moves along a left-most arrow-headed line as shown. The left-most arrow-headed line extending from time ta to time tb represents a trajectory of the point i+1 of the retina.

At each time point between time ta and time tb, the point i+1 of the retina receives light at a predetermined level emitted from the liquid crystal at a position where the leftmost arrow-headed line passes. As a result, light incident at successive points of time is accumulated on the point i+1 of the retina. At time tb, the storage amount of light (integral of incident light), namely, the amount light accumulated along the left-most arrow-headed line on the upper portion ofFIG. 5is picked up. An image responsive to the amount of light is thus focused on the point i+1 of the retina.

Likewise, at each time point between time ta and tb, each remaining point k (k is any value among i−8 through i+8 except i+1) of the retina receives light at a predetermined level output from the liquid crystal at a position corresponding to the point k, and successively accumulates received light. At time tb, the amount of light shown on the lower portion ofFIG. 5(the integral of the incident light) is captured at each point k of the retina. An image responsive to the amount of captured light is thus focused on each point k of the retina.

As shown in the lower portion ofFIG. 5, at time tb, the amount of captured light is not constant but is gradually reduced within a range of points i through i+8 in response to locations of eight pixels from liquid crystals n+1 through n+8. In response to the amount of light, the image formed within the range of the retina from points i through i+8 becomes blurred as if the image gradually varies from the pixel value E to the pixel value B. A motion blur occurs within the range of the retina from points i through i+8.

To compensate for a lack of amount of light captured within the retinal range of points i through i+4 in response to the output from the location of four pixels of liquid crystals n+1 through n+4 (where the actual step edge ofFIG. 4is present) at time tb, the voltage level applied to each liquid crystal may be heightened (the target level of each liquid crystal is further heightened). In contrast toFIG. 5,FIG. 6illustrates a resulting image in such a case.

Referring toFIG. 6, the overdrive method is also in operation as inFIG. 5. However,FIG. 6illustrates the relationship between a hold display and an after-image in the liquid-crystal display device that displays the step edge with a voltage higher in level than inFIG. 5(with the target level corrected to be even higher).

As shown in the upper portion ofFIG. 6, the frame or the field (immediately prior to the display target frame or the display target field) containing the step edge ofFIG. 3is displayed on the liquid-crystal display device immediately prior to time ta. At time ta, the liquid-crystal display device is commanded to display the display target frame or the display target field containing the edge frame or field ofFIG. 4.

Each of the liquid crystals (pixels) n−7 through n−4 outputs light at a level corresponding to the pixel value E at time ta. The liquid-crystal display device applies a voltage at a level corresponding to the pixel value E to each of the liquid crystals n−7 through n−4 at time ta thereafter. Each of the liquid crystals n−7 through n−4 continuously holds the output level thereof at a level corresponding to the pixel value E.

Each of the liquid crystals (pixels) n−3 through n outputs light at a level higher than a level corresponding to the pixel value E at time ta. The liquid-crystal display device applies a voltage at a level corresponding to the pixel value E to each of the liquid crystals n−3 through n at time ta thereafter. The output of each of the liquid crystals n−3 through n gradually drops. Each of the liquid crystals n−3 through n drops down to the level corresponding to the pixel value E, and maintains the same level.

In contrast, each of the liquid crystals (pixels) n+1 through n+4 outputs light at a level corresponding to the pixel value B at time ta. The liquid-crystal display device supplies each of the liquid crystals n+1 through n+4 with a voltage at a level higher than the level of the pixel E (at a level even higher than inFIG. 5) at time immediately subsequent to time ta. From a period of time immediately subsequent to time ta to time tb at which the liquid-crystal display device is commanded to display a next frame or a next field (during the frame time T of the display target frame or frame field T of the display target field), the output level of each of the liquid crystals n+1 through n+4 approaches the level corresponding to the pixel value E from the level corresponding to the pixel level B (at a rate faster than inFIG. 5), reaches a level corresponding to the pixel E prior to time tb, and then further continuously rises until time tb.

Since the user continuously views the step edge displayed on the liquid-crystal display device with the retinal after-image from before time ta, the user continuously views the step edge in accordance with the arrow in the upper portion ofFIG. 6(in step with the movement of the step edge) even during the period of time from time ta at which the liquid-crystal display device is commanded to display the display target frame or the display target field to time tb at which the liquid-crystal display device is commanded to display the next frame or the next field (namely, during the frame time T of the display target frame or the field time T of the display target field).

At each time point between time ta and time tb, each of the points i−8 through i+8 of the retina of the human user successively accumulates light at a predetermined level output from the corresponding location of the liquid crystal. As a result, at time tb, the storage amount of light (integral of incident light) shown in the lower portion ofFIG. 6is captured at each of the points i−8 through i+8 of the retina. An image responsive to the amount of captured light is focused on each of the points i−8 through i+8 of the retina.

A comparison of the lower portion ofFIG. 5with the lower portion ofFIG. 6shows that the slope of the curve representing the amount of light shown inFIG. 6is steeper than inFIG. 5within a range of points i through i+8 on the retina corresponding to locations of eight pixels of n+1 through n+8. The step edge becomes more sharply focused on the retina of the human than inFIG. 5.

As already discussed with reference toFIG. 6, the output level of each liquid crystal is sometimes higher than the level corresponding to the pixel value E of the step edge. As a result, at points i−4 through i+4 corresponding to the liquid crystals n−3 through n+4, the amount of actually captured light becomes larger than the amount of light (equal to the amount of light captured at the points i−8 through i−4 of the retina corresponding to the locations of liquid crystals n−7 through n−4) that should be captured.

More specifically, an image responsive to a pixel value higher than the pixel value E is formed within a range of points i−4 through i+4 of the retina (a whitened image is displayed). Such an image is far from a solution to the motion blur. The image formed within the range of points i−4 through i+4 of the retina may be considered a sort of blurred image. If considered so, the range of motion blur extends to the range of points i−4 through i+8 of the retina corresponding to the locations of 12 pixels of liquid crystals n−3 through n+8.

Since the human eyes have the retinal after-image characteristic, the motion blur is not eliminated even if all pixel values of the liquid crystals (pixels) corresponding to the moving object (namely, the level of the voltage applied to each of the liquid crystals) are corrected, in other words, even if only the response speed of the output level of the liquid crystal is improved.

The inventors of this invention have developed a video processing apparatus that processes video taking into consideration not only the slow response of the liquid crystal but also the after-image that has not been accounted for in the known overdrive method. Such a video processing apparatus may be carried out in various embodiments, a specific example being the structure shown inFIG. 7.

FIG. 7illustrates the structure of the video processing apparatus in accordance with one preferred embodiment of the present invention.

As shown, a video processing apparatus11controls a holding type display unit12as a liquid-crystal display device in the displaying of a moving picture. The video processing apparatus11commands the holding type display unit12to successively display a plurality of frames or fields forming a moving picture. As previously discussed, the holding type display unit12displays display elements (not shown) corresponding to a plurality of pixels forming a first frame or field for a predetermined period of time from when the holding type display unit12is commanded to display the first frame or field. The holding type display unit12holds display on at least part of the display elements. In other words, at least part of the display elements maintains a hold display for a predetermined period of time.

The holding type display unit12causes the display elements (not shown) corresponding to all pixels forming the first frame or field to display a video from when the holding type display unit12is commanded to display the first frame or field until when the holding type display unit12is commanded to display the second frame or field. All display elements thus hold display.

More specifically, the video processing apparatus11successively receives video data of a plurality of frames or fields forming a moving picture. In other words, the video processing apparatus11receives the video data of the display target frame or field (for example, pixel values of all pixels forming the display target frame or field). The video data of the display target frame or field is input to each of a video processor21, a video processor22, a reference video storage unit23, and a motion detector24.

The video processor21performs a predetermined video process on the video data of the input display target frame or field on a per pixel basis, and outputs the processed video data to a switch25. More specifically, the video processor21corrects the pixel values of the pixels by performing the predetermined video process on each of a plurality of pixels forming the display target frame or field, and successively outputs the corrected pixel values to the switch25in a predetermined order.

The video process performed by the video processor21is not limited to any particular one. As shown inFIG. 7, the video processor21receives a reference video (a frame or field immediately prior to the display target frame or field) output from the reference video storage unit23, and results of motion detection provided by the motion detector24to be discussed later. The video processor21may use both the reference video and the motion detection result, one of both, or neither of both. For example, the video processor21may have a predetermined rule table (not shown), and may perform the video process to correct the pixel values of the pixels forming the display target frame or field.

The video processor21is not an element essential to the video processing apparatus11, and may be dispensed with. Without the video processor21, the video data of the display target frame or field is input to each of the video processor22, the reference video storage unit23, the motion detector24, and the switch25.

The video processor22corrects the pixel values of the pixels at the edge portion of a moving object (the moving object is the one shifted from the location thereof in the frame or field immediately prior to the display target frame or field) detected by the motion detector24from the input display target frame or field, and outputs the corrected pixel values to the switch25.

As will be discussed later, the video processor22may capture an image corresponding to a real thing as an object, and may perform the video process on the captured object. The video processor22here captures the step edge ofFIG. 3orFIG. 4as one object, and performs the above video process on a per step edge basis.

InFIG. 7, the video processor22is made up of a step edge detector31and a corrector32. However, the embodiment is not restricted to the arrangement shown inFIG. 7; rather, various embodiments may be made. More specifically, for example, the video processor22may be configured such as shown inFIG. 14orFIG. 23described later.

However, these preferred embodiments of the video processor22(description of the preferred embodiments shown inFIG. 7,FIG. 14, andFIG. 23) will be discussed in detail later.

The reference video storage unit23stores the video data of the input display target frame or field as the video data of the reference video for a frame or field subsequent to the display target frame or field. When the video data of a new frame or field is input as the video data of the display target frame or field, the reference video storage unit23thus stores the new video data. The reference video storage unit23continuously stores the video data of the frame or field (which was the display target frame or field immediately before the newly entered display target frame or field) as the video data of the reference video for the newly entered display target frame or field.

When the video data of the display target frame or field is input, the motion detector24acquires the video data of the reference video (of the frame or field immediately prior to the display target frame or field) stored in the reference video storage unit23. The motion detector24detects, on a per pixel basis, a moving object (with the location thereof shifted from the location thereof in the reference video) by comparing the video data of the display target frame or field with the video data of the reference video frame. The motion detector24further detects, on a per pixel basis, the spatial amount of motion of the object. Here, the amount of motion contains information relating to the direction of motion, and may be represented by plus or minus information.

The motion detector24detects motion in the video by comparing the moving object in the input video data with the moving object in the reference video output from the reference video storage unit23.

The motion detector24can separately detect an object moving in a spatial direction X and a spatial direction Y. In the discussion that follows, the object moving in the spatial direction X only is detected.

The motion detector24detects, by pixel, the object that has moved in the spatial direction X. The motion detector24determines whether a pixel of interest to be processed (hereinafter referred to as a target pixel) from among a plurality of pixels forming the display target frame or field is a pixel of the object that has moved in the spatial direction X.

If the motion detector24determines that the target pixel is not the pixel of the object that has moved in the spatial direction X, the motion detector24notifies the switch25(and the video processor21as necessary) of the result of determination. As will be discussed later, the switch25switches the input thereof to the video processor21.

If the motion detector24determines that the target pixel is the pixel of the object that has moved in the spatial direction X, the motion detector24notifies the step edge detector31, the corrector32, and the switch25(and the video processor21as necessary) of the result of determination. The switch25switches the input thereof to the video processor22(the corrector32), as will be discussed later. The motion detector24further detects the spatial amount of motion of the object corresponding to the target pixel (between frames or fields), and supplies the step edge detector31and the corrector32with the spatial amount of motion.

As previously discussed, the switch25switches the input thereof in response to the determination result of the motion detector24.

If the motion detector24determines that the target pixel is not a pixel corresponding to the moving object (here, a step edge), the switch25switches the input thereof to the video processor21to supply the display controller26with data (pixel value) of the target pixel from the video processor21.

If the motion detector24determines that the target pixel is a pixel corresponding to the moving object (here, a step edge), the switch25switches the input thereof to the corrector32in the video processor22to supply the display controller26with data (pixel value) of the target pixel from the corrector32.

The display controller26converts the data (pixel value) of each pixel forming the display target frame or field successively supplied from the switch25to a signal in a predetermined format as a target level of corresponding element, and outputs the signal to the holding type display unit12. By performing this process, the display controller26commands the holding type display unit12to display the display target frame or field.

The video processor22inFIG. 7will now be discussed in detail.

The video processor22includes the step edge detector31and the corrector32inFIG. 7.

The step edge detector31detects the edge portion from the moving object detected by the motion detector24, from the video data of the input display target frame or field, and supplies the corrector32with the results of detection.

More specifically, if an image of a real thing with color or density thereof changing in gradation is present in the display target frame or field, the step edge detector31captures the image of the real thing as an object, and detects the edge of the captured object.

The step edge detector31generates a function representing a change in the pixel value in the direction of motion of the object (in the spatial direction X), and calculates the first derivative of the function at each pixel. The first derivative of a predetermined pixel thus calculated shows the degree of difference between the pixel value of one pixel and the pixel value of another pixel adjacent to the one pixel. The step edge detector31thus detects a pixel having a first derivative (not zero) as a pixel corresponding to the edge portion of the object.

The generation of the function and the calculation of the first derivative of the function are too heavy for the step edge detector31to perform. As previously discussed, the step edge detector31captures the step edge as an object, and decomposes the video data of the input display target frame or field into a set of video data of a plurality of step edges formed in the spatial direction X, detects the edge portion of each of the plurality of step edges, and supplies the corrector32with the results of detection.

It is now assumed that the video data ofFIG. 8is contained in the display target frame or field. As shown inFIG. 8, the horizontal axis represents a pixel position (in the spatial direction X), and the vertical axis represents a pixel value. The video data ofFIG. 8thus contains a pixel value L2at a pixel X1, a pixel value L3at a pixel X2, and a pixel value L1at a pixel X3.

The step edge detector31decomposes the video data ofFIG. 8into two step edges, namely, a step edge in the left portion ofFIG. 9(present between the pixel value L2at the pixel X1and the pixel value L3at the pixel X2thereafter) and a step edge in the right portion ofFIG. 9(present between the pixel value L3through to the pixel X2and the pixel value L1at the pixel X3thereafter). The step edge detector31thus detects each of the two step edges ofFIG. 9.

The step edge is composed of a group of pixels having a first pixel value (a first pixel group lined in the spatial direction X) and a group of pixels having a second pixel value (a second pixel group lined in the spatial direction X). The step edge detector31finds a pixel different in pixel value from a pixel adjacent thereto, and detects the edge portion of the step edge by determining that the location of that pixel corresponds to the edge portion of the step edge.

Like the motion detector24, the step edge detector31regards, as a target pixel, a predetermined one of a plurality of pixels forming the display target frame or field, and detects the step edge by target pixel by target pixel. The step edge detector31detects the edge portion of the step edge by calculating a difference between the pixel value of a target pixel and the pixel value of a predetermined pixel adjacent to the target pixel (in the spatial direction X).

The step edge detector31calculates the difference between the pixel value of the target pixel and the pixel value of the adjacent pixel. If a difference results, in other words, if the result (difference) is not zero, the target pixel is detected as being a pixel corresponding to the edge portion of the step edge.

Returning toFIG. 7, the step edge detector31supplies the corrector32with the pixel value of the target pixel and the calculated value (the difference between the pixel value of the target pixel and the pixel value of the adjacent pixel).

The pixel with respect to which the difference is calculated may be any one of the two pixels adjacent to the target pixel (in the spatial direction X). Since the motion detector24supplies the step edge detector31with the amount of motion of the object in the spatial direction X (the amount of motion information containing the direction of motion represented in plus or minus information), the pixel with respect to which the difference is calculated may be a pixel present in the direction of movement of the step edge or in the opposite direction of movement of the step edge.

The corrector32corrects the pixel value of the target pixel corresponding to the edge portion of the step edge detected by the step edge detector31, based on the spatial amount of motion of the step edge of the target pixel (in the spatial direction X), and the height of the step edge (the difference at the edge portion of the step edge between the pixel value of the target pixel and the pixel value of the pixel adjacent to the target pixel).

The corrector32receives the pixel value of the target pixel and the difference thereof from the step edge detector31, and the spatial amount of motion of the step edge of the target pixel (in the spatial direction X) from the motion detector24. If the supplied difference is not zero, and the supplied amount of motion is not zero, the corrector32determines that the target pixel is the pixel corresponding to the edge portion of the moving step edge. Based on the supplied difference and amount of motion, the corrector32corrects the pixel value of the target pixel.

The present invention is not limited to any particular correction method. It is important that the pixel value is corrected based on the amount of motion of the step edge. The following correction method may be used.

FIG. 10illustrates a correction method of the pixel value in accordance with one preferred embodiment of the present invention.FIG. 10illustrates the relationship between a hold display of liquid crystals (pixels) forming the screen of a liquid-crystal display device (one embodiment of the holding type display unit12ofFIG. 7) and the after-image in the normal operation (such as in the known overdrive method or in the operation not using any of techniques of the preferred embodiments of the present invention to be discussed later).

As shown in the upper portion ofFIG. 10, a change occurs in the output level of the liquid crystal corresponding to the location of the step edge with respect to time with the step edge ofFIG. 4appearing on the liquid-crystal display device asFIGS. 5 and 6. Like inFIGS. 5 and 6, the amount of light picked up by the retina of the user is shown in the lower portion ofFIG. 10when the user views the step edge ofFIG. 4displayed on the liquid-crystal display device.

For example, the frame or field (namely, the frame or field immediately prior to the display target frame or field) containing the step edge ofFIG. 3was displayed on the liquid-crystal display device immediately prior to time ta as shown in the upper portion ofFIG. 10, and at time ta, the liquid-crystal display device is commanded to display the display target frame or field containing the step edge ofFIG. 4.

The liquid-crystal display device supplies each of the liquid crystals (pixels) n−7 through n+4 with a voltage at a level corresponding to the pixel value E from time ta thereafter. The output level of the liquid crystals n−7 through n+4 changes as shown in the upper portion ofFIG. 10.

The user has tracked the step edge, viewing the step edge displayed on the liquid-crystal display device as the after-image from before time ta. The user thus continuously views the step edge in accordance with the arrow-headed lines shown on the upper portion ofFIG. 10(in step with the motion of the step edge) during a period of time from time ta at which the liquid-crystal display device is commanded to display the display target frame or the display target field to time tb at which the liquid-crystal display device is commanded to display the next frame or the next field (namely, during the frame time T of the display target frame or the field time T of the display target field).

The amount S of light shown in the lower portion ofFIG. 10is accumulated within a range of the retina from points i−8 through i+8 corresponding to an area of liquid crystals n−7 through n+8 (the actual location of the step edge ofFIG. 4and the area surrounding the step edge) is accumulated, and an image corresponding to the accumulated light thus develops. Motion blur is thus generated.

In contrast, if the amount of light S and the amount of light R are accumulated within the range of the retina from points i−8 through i+8 as shown in the lower portion ofFIG. 10, the generation of the motion blur is controlled. The lacking amount of light is here designated R.

The corrector32corrects the amount of light, compensating for the amount R of light in the preferred embodiment of the present invention. However, if the corrector32uniformly corrects the amount of light for each of the pixels n+1 through n+4, the liquid-crystal display device presents the same result as the known overdrive method, thereby still suffering from motion blur. In accordance with the preferred embodiment of the present invention, the corrector32corrects only the pixel value of a pixel (the pixel n+4 inFIG. 10) corresponding to the edge portion of the step edge taking into consideration the after-image.

More specifically, if a command to change the pixel in level from the pixel value B to the pixel value E is issued on the assumption that time response of each of the liquid crystals is a primary delay factor of a predetermined time constant τ (in other words, the time response of all liquid crystals is always the same), the output level (in pixel value) Y(t) is represented by equation 1. Here, t represents time with the command provided to the liquid crystal being at time zero.

The lacking amount R of light shown inFIG. 10, if converted into a pixel value, is expressed by equation 2.

The corrector32thus corrects the pixel value of the pixel (the pixel n+4 ofFIG. 10) corresponding to the edge portion of the step edge by adding the (pixel value converted) lacking amount R of light represented by equation (2), as a correction value, to the pixel value.

FIG. 11illustrates the relationship between the hold display of each liquid crystal (pixel) forming the screen of the liquid-crystal display device and the after-image with only the pixel value of the pixel corresponding to the edge portion of the step edge corrected (namely, the preferred embodiment of the present invention applied).FIG. 11illustrates the result of the preferred embodiment of the present invention in contrast with the results of the known techniques illustrated inFIGS. 5,6, and10.

As shown in the upper portion ofFIG. 11, the pixel value is corrected by adding the (pixel value converted) lacking amount R of light represented by equation 2 to the pixel value of the pixel corresponding to the edge portion of the step edge. More specifically, at time point earlier than time ta by T (at time point the liquid-crystal display device is commanded to display the frame or field containing the step edge ofFIG. 3), the pixel value of the pixel (liquid crystal) n is corrected. At time ta (at the moment the liquid-crystal display device is commanded to display the frame or field containing the step edge ofFIG. 4), the pixel value of the pixel (liquid crystal) n+4 is corrected.

From time ta thereafter, the liquid-crystal display device (the holding type display unit12) supplies each of the liquid crystals n−7 through n+3 with a voltage corresponding to the pixel value E as a target level. The target level for the liquid crystal n+4 is a corrected pixel value (namely, a sum of the pixel value E and the correction value R represented by equation 2). The liquid-crystal display device supplies only the liquid crystal n+4 with the corrected pixel value. The output level of the liquid crystals n−7 through n+4 changes as shown in the upper portion ofFIG. 11.

The user has tracked the step edge, viewing the step edge displayed on the liquid-crystal display device as the after-image. The user thus continuously views the step edge in accordance with the arrow-headed lines shown on the upper portion ofFIG. 11(in step with the motion of the step edge) during a period of time from time ta at which the liquid-crystal display device is commanded to display the display target frame or the display target field to time tb at which the liquid-crystal display device is commanded to display the next frame or the next field (namely, during the frame time T of the display target frame or the field time T of the display target field).

More specifically, the point i+1 of the retina of the user continuously views the step edge along an arrow-headed line41from time ta to time tb. In the meantime, the retina point i+1 passes the liquid crystal (pixel) n that was to be corrected previous time (in the correction performed at time point earlier than time ta by period T). When passing the liquid crystal n, the lacking amount of light is picked up, and as a result, the target amount of pixel is captured at time tb.

During the period of time from ta to tb, another point k of the retina (any one of points i−8 through i+8 except i+1) similarly passes at least one of the liquid crystals to be corrected (the liquid crystals respectively corresponding to the pixels n−4, n, and n+4). When the liquid crystal is passed by the point k, a lacking amount of light (for correction) is picked up. As a result, a target amount of light is captured at time tb.

An ideal amount of light (the sum of the amount S of light and the lacking amount R of light as shown inFIG. 10) is captured within the range of the point i−8 through the point i+8 of the retina of the user as shown in the lower portion ofFIG. 11. An image responsive to the amount of light is thus formed.

Referring to the lower portion ofFIG. 11, the image responsive to a substantially uniform amount of light free from an overshoot is generated within range of the point i−8 through the point i+8 of the retina of the user, and the range of motion blur is limited to the point i+4 through the point i+8 of the retina corresponding to the location of the pixel n+5 to the pixel n+8. The preferred embodiment of the present invention thus controls the motion blur more than any of the known cases (shown inFIGS. 5,6, and10).

In the above discussion, the pixel value is corrected when the step edge moves at a rate of 4 pixels/frame or 4 pixels/field in the spatial direction X. Even if the step edge moves at a different rate, the corrector32corrects the pixel value of the pixel corresponding to the edge portion of the step edge in the same way as discussed above, thereby controlling the motion blur.

If the amount of motion is changed from 4 pixels/frame or 4 pixels/field to an amount of motion of v pixels/frame or v pixels/field in equation 2, the correction value R is expressed by equation 3.

If the step edge moves at a uniform velocity, the amount of motion v between frames or fields expresses a motion speed. If the step edge moves at a uniform velocity between frames or fields, the amount of motion v of the step edge between frames or fields is a motion velocity v of the step edge between frames or fields.

In the above example, description has been made regarding the step edge inFIG. 4as an example, and accordingly, the target pixel is a pixel n+4, and consequently, the pixel value of the target pixel n+4 is E; on the other hand, the pixel value of the pixel (a pixel n+5 not shown inFIG. 4) adjacent to the target pixel in the spatial direction X is B. However, the pixel values of the target pixel and the pixel adjacent to the target pixel are not restricted to these values, rather, various values may be adopted. Accordingly, if it is assumed that the pixel value of the target pixel is Nr, and the pixel value of the pixel adjacent to the target pixel in the spatial direction X is Nrn, the above equation 3 becomes a further generalized equation such as the following equation 4.

In equation 4, if the target pixel is not a pixel at the edge portion of the step edge, the difference value Nr−Nrn becomes zero, and consequently, the correction value R also becomes zero. For example, in equation 4, if the target pixel is a pixel n, both Nr−Nrn and E−E become zero. Thus, equation 4 is conceived as a generalized correction equation that can be applied to all pixels, including zero correction (prohibition of correction).

Returning toFIG. 7, the motion detector24supplies the corrector32with the amount of motion v of the step edge corresponding to the target pixel, as described above. The step edge detector31supplies the corrector32with the pixel value Nr of the target pixel (the pixel value E in a case that the target pixel is the pixel n+4 inFIG. 4) and the difference value Nr−Nrn (the difference value E−B in a case that the target pixel is the pixel n+4 inFIG. 4). Accordingly, for example, the corrector32substitutes the supplied amount of motion v, the pixel value Nr of the target pixel, and the difference value Nr−Nrn for in equation 4 (equation 3 in a case that the target pixel is the pixel n+4 inFIG. 4), and determines the correction value R by calculating the right-hand side of equation 4. The corrector32updates the pixel value of the target pixel with the pixel value Nr+R (the pixel value E+R in a case that the target pixel is the pixel n+4 inFIG. 4), and supplies the display controller26with the pixel value Nr+R through the switch25.

As described above, the display controller26addresses the pixel values of a plurality of pixels forming a display target frame or field to the holding type display unit12, including the corrected pixel value Nr+R (the pixel value E+R in a case that the target pixel is the pixel n+4 inFIG. 4), serving as target levels corresponding to display elements of the holding type display unit12. The display controller26thus commands the holding type display unit12to display the display target frame or field.

Note that it has been assumed here that the time constant τ in the above equations 1 through 4 is uniform for facilitation of explanation, however, in practice, the time constant τ differs.

More specifically, as a command toward the target liquid crystal corresponding to the target pixel (the target display element of the holding type display unit12ofFIG. 7), if a command for changing from the original pixel value Nrn (hereafter, this is referred to as the old pixel value Nrn as well) to the pixel value Nr (hereafter, this is referred to as the target pixel value Nr or the new pixel value Nr as well) is given, i.e., if the input voltage of the target liquid crystal changes from the voltage level corresponding to the old pixel value Nrn to the voltage level corresponding to the new pixel value Nr, the time required for the intensity of output light of the target liquid crystal to change from the intensity of light corresponding to the old pixel value Nrn to the intensity of light corresponding to the new pixel value Nr, i.e., the response time (response speed) of the target liquid crystal differs depending on the values of the old pixel value Nr−1 and the new pixel value Nr. Accordingly, it is needless to say that the time constant τ of the target liquid crystal differs depending on the values of the old pixel value Nr−1 and the new pixel value Nr.

Accordingly, in the event that it is necessary to perform more precise correction, taking the difference of the time constant τ into consideration, a table (for example, a later-described table such as shown inFIG. 18, hereafter, referred to as a panel table) on which the response speed of liquid crystal corresponding to the values of the old pixel value Nr−1 and the new pixel value Nr is described should be retained by the corrector32, and the like. Thus, the corrector32identifies the time constant τ with reference to the panel table, substitutes the above-described amount of motion v, pixel value Nr of the target pixel, and difference value Nr−Nrn as well as the time constant τ in equation 4 so as to calculate the right-hand side of equation 4, whereby the correction value R can be calculated more precisely. The corrector32then updates the pixel value of the target pixel with the pixel value Nr+R, and supplies the display controller26with the updated pixel value through the switch25.

Description has been made regarding an example of the correction method of the pixel value of the target pixel.

Note that the correction method of the pixel value of the target pixel is not restricted to the above-described example, rather, various methods may be adopted.

Hereafter, description will be made regarding other examples of the correction method of the pixel of the target pixel.

Assuming that the time constant τ is uniform as with the above example, the correction value R of equation 4 is expressed such as in the following equation 5.

Note that C represents a predetermined fixed value (the proportional coefficient of v) in equation 5.

Regarding the portion C×v in the right-hand side of equation 5 as a gain depending on (proportionate to) the amount of motion (speed) v, represented by G, equation 6 is expressed as the following equation 7.

Accordingly, instead of the video processor22inFIG. 7, the video processor22which provides a high-pass filter process equivalent to calculating the following equation 7, i.e., the video processor22configured as an asymmetric high-pass filter may be adopted.

Nr′ represents the output value of this asymmetric high-pass filter, i.e., the corrected pixel value of the target pixel in equation 7.

Note that the asymmetric high-pass filter means such as the following filter.

In the video process, if a block (hereafter, referred to as the target block (Nr, Nrn)) made up of the pixel value Nr of the target pixel and the pixel value Nrn of the pixel adjacent to the target pixel (in this case, in the spatial direction X) is subjected to generalized high-pass filtering, this target block (Nr, Nrn) is updated such as a block (Nr+ΔN, Nrn−ΔN). Note that ΔN represents the amount of correction (value). Such a filter for subjecting the two pixel values Nr and Nrn to a high-pass filtering process, i.e., a generalized high-pass filter for subjecting the two pixel values Nr and Nrn to a filtering process such that the amount of correction ΔN is line-symmetric over the border between the two pixels is referred to as a symmetric high-pass filter in the present specification. Examples of the symmetric high-pass filter include a filter (hereafter, referred to simply as sharpness) for adding so-called sharpness effects to a video (so-called picture formation).

On the other hand, a filter for outputting a block (Nr+ΔN, Nrn) or a block (Nr, Nrn−ΔN) as the result of a filtering process if the target block (Nr, Nrn) is input, i.e., a filter for subjecting only one of the two pixel values Nr and Nrn to a high-pass filtering process is referred to as an asymmetric high-pass filter in the present specification.

More specifically, for example, it is assumed that a pixel n+4 is the target pixel inFIG. 12on which the same step edge as that inFIG. 4is drawn. In this case, the pixel value Nr of the target pixel n+4 is equal to E, the pixel value Nrn of the pixel n+5 adjacent to the target pixel n+4 in the spatial direction X is equal to B.

In this case, if the two pixel values Nr and Nrn are subjected to sharpness that is a symmetric high-pass filtering such that the amount of correction ΔN becomes a value R equivalent to the result of the above equation 6, the pixel value Nr of the target pixel n+4 is updated (corrected) from the pixel value E to the pixel value E+R, and the pixel value Nrn of the pixel n+5 adjacent to the target pixel n+4 is updated from the pixel value B to the pixel value B−R. As mentioned above, if so-called picture formation is an object, there is no problem even if sharpness is used, whereby the object can be achieved.

However, if the object of the present invention, i.e., correction for suppressing motion blur is an object, there is no need to correct the pixel value Nrn of the pixel n+5 adjacent to the target pixel n+4 (the pixel value B does not need to be changed), and the object cannot be achieved even if sharpness is used.

To achieve the object of the present invention, i.e., correction for suppressing motion blur, as shown inFIG. 12, it is preferable to use an asymmetric high-pass filter such that only the pixel value Nr of the target pixel can be updated from the pixel value E to the pixel value E+R (namely, the pixel value Nr′ following correction of the left-hand side of equation 7).

As shown inFIG. 12, description has been made wherein the direction of motion of the step edge is the spatial direction X, and accordingly, the pixel to be corrected is the pixel n+4 of the two pixels n+4 and n+5 forming the edge portion of the step edge.

In contrast, as shown inFIG. 13, if the direction of motion of the step edge is the direction opposite to the spatial direction X, the pixel to be corrected needs to be the pixel n+5 of the two pixels n+4 and n+5 forming the edge portion of the step edge.

In this case, the pixel value B of the pixel n+5 is updated to a pixel value B′ such as shown in the following equation 8.

Generalizing the above description, consequently, if the direction of motion of the step edge corresponding to the target block (Nr, Nrn) is positive, i.e., the spatial direction X, only the pixel value Nr of the target pixel is updated to a pixel value Nr′ in accordance with equation 7.

In contrast, if the direction of motion of the step edge corresponding to the target block (Nr, Nrn) is negative, i.e., the direction opposite to the spatial direction X, only the pixel value Nrn of the pixel adjacent to the target pixel in the spatial direction X is updated to a pixel value Nrn′ in accordance with the following equation 9.

As mentioned above, one of the pixel values of the target pixel and the pixel adjacent to the target pixel in the spatial direction X at the edge portion of the step edge is updated depending on the direction of motion of the step edge. Therefore, the following description will be made on the assumption that the edge portion of the step edge formed in the spatial direction X expresses not a single target pixel as mentioned above but a pair (block) of two pixels consecutively lined in the spatial direction X each of which has a different pixel value.

More specifically, in the following description, not the single pixel value Nr of the target pixel but a pair of the pixel value Nr and the pixel value Nrn of the pixel adjacent to the target pixel in the spatial direction X (or in the direction opposite to the spatial direction X), i.e., the above-mentioned target block (Nr, Nrn) will be treated as a unit. In this case, it is necessary to determine whether the input target block (Nr, Nrn) is output as an updated target block (Nr′, Nrn) or as an updated target block (Nr, Nrn′) depending on the direction of motion of the step edge. Namely, it is necessary to switch which of the target block (Nr, Nrn) is corrected, the pixel value Nr or the pixel value Nrn. In the present embodiment, as shown in later discussedFIGS. 15 and 16, a filter coefficient is used to be switched depending on the direction of motion of the step edge. Description will be made later regarding the switching of this filter coefficient in detail, and so forth.

As is evident from the above description, the video processor22for performing a high-pass filtering process equivalent to calculating equation 7 or equation 9, i.e., the video processor22configured as an asymmetric high-pass filter may be adopted instead of the video processor22having the configuration inFIG. 7.

For example, the video processor22may be configured as an asymmetric high-pass filter such as shown inFIG. 14.FIG. 14illustrates a configuration example of the video processor22which is configured as an asymmetric high-pass filter.

More specifically, the video processor (asymmetric high-pass filter)22inFIG. 14is made up of a switch61, an asymmetric coefficient filter62, an asymmetric coefficient filter63, a coefficient selecting unit64, a gain G decision unit65, a multiplier66, and an adder67.

As shown inFIG. 14, the video data of an input video is input to the video processor22on a per the target block (Nr, Nrn) basis. More specifically, the target block (Nr, Nrn) is supplied to the switch61and the adder67.

The switch61switches the output destination to one of the asymmetric coefficient filter62side and the asymmetric coefficient filter63side under control of the coefficient selecting unit64.

The asymmetric coefficient filter62retains a filter coefficient (weighted value) such as shown inFIG. 15for example, and subjects the input target block (Nr, Nrn) to an asymmetric filtering process, using this filter coefficient.

Note that inFIG. 15, the “1” within the square to the left indicates a filter coefficient corresponding to the pixel value Nr, and “−1” within the square to the right indicates a filter coefficient corresponding to the pixel value Nr−1. Of the filter coefficients 1 and −1, it is assumed that the pixel value side (namely, the pixel value Nr inFIG. 15, and the pixel value Nr−1 inFIG. 16mentioned later) corresponding to the filter coefficient 1 is subjected to a filtering process.

More specifically, for example, the asymmetric coefficient filter62calculates the following equations 10 and 11, and supplies a pair of the results Nr62and Nrn62, i.e., (Nr62, Nrn62)=(Nr−Nrn,0) to the multiplier66.

In contrast, the asymmetric coefficient filter63retains a filter coefficient (weighted value) such as shown inFIG. 16for example, and subjects the input target block (Nr, Nrn) to an asymmetric filtering process, using this filter coefficient.

Note that inFIG. 16, “−1” within the square to the left side indicates a filter coefficient corresponding to the pixel value Nr, and “1” within the square to the right indicates a filter coefficient corresponding to the pixel value Nr−1.

More specifically, for example, the asymmetric coefficient filter63calculates the following equations 12 and 13, and supplies a pair of the results Nr63and Nrn63, i.e., (Nr63, Nrn63)=(0, Nrn−Nr) to the multiplier66.

The coefficient selecting unit64detects the direction of motion of the target pixel based on the amount of motion (vector) v of the target pixel (the pixel having the pixel value Nr) supplied from the motion detector24.

The coefficient selecting unit64, in a case that the detected direction of motion is positive, i.e., in a case that the direction of motion of the step edge is the spatial direction X as shown inFIG. 12, switches the output destination of the switch61to the asymmetric coefficient filter62side.

Thus, while the target block (Nr, Nrn) is supplied to the asymmetric coefficient filter62, the target block (Nr, Nrn) is prohibited from being supplied to the asymmetric coefficient filter63.

Therefore, the asymmetric coefficient filter62may be referred to as a filter used in a case that the direction of motion of the target pixel (step edge) is positive (spatial direction X), i.e., a filter for correcting the pixel value Nr (the pixel value E of the pixel n+4 inFIG. 12) of the target pixel.

In contrast, in a case that the detected direction of motion is negative, i.e., in a case that the direction of motion of the step edge is the direction opposite to the spatial direction X as shown inFIG. 13, the coefficient selecting unit64switches the output destination of the switch61to the asymmetric coefficient filter63side.

Thus, while the target block (Nr, Nrn) is supplied to the asymmetric coefficient filter63, the target block (Nr, Nrn) is prohibited from being supplied to the asymmetric coefficient filter62.

Therefore, the asymmetric coefficient filter63may be referred to as a filter used in a case that the direction of motion of the target pixel (step edge) is negative (the direction opposite to the spatial direction X), i.e., a filter for correcting the pixel value Nrn (the pixel value B of the pixel n+5 inFIG. 13) of the pixel adjacent to the target pixel in the spatial direction X.

The gain G decision unit65determines the gain G used in equations 7 and 9 based on the amount of motion v (absolute value) of the target pixel (step edge) supplied from the motion detector24, and supplies the gain G to the multiplier66.

More specifically, the gain G, as described in equation 5, is a variable gain changing the value thereof in proportion to the amount of motion v (absolute value). The gain G decision unit65may retain a proportionality constant C such as shown in equation 5, substitute the amount of motion v supplied from the motion detector24in the following equation 14, calculate equation 14, determine the obtained result as the gain G, and output the determined gain G to the multiplier66.

Alternatively, the gain G decision unit65may retain a table such as shown inFIG. 17, i.e., a table expressing the relationship between the amount of motion v and the gain G (a gain Gv in the example inFIG. 17instead of the gain G, which will be explained later), determine the gain G with reference to this table, and output the determined gain G to the multiplier66.

As mentioned above, in a case that the direction of motion of the target pixel (step edge) is positive (spatial direction X), a block (Nr−Nrn,0) that is output of the filtering process by the asymmetric coefficient filter62is supplied to the multiplier66, and also the gain G determined by the gain G decision unit65are supplied to the multiplier66. The multiplier66calculates the following equations 15 and 16, and a pair of the calculated results Nr66+ and Nrn66+, i.e., (Nr66+, Nrn66+)=(R,0) is supplied to the adder67.

In contrast, in a case that the direction of motion of the target pixel (step edge) is negative (the direction opposite to the spatial direction X), a block (0, Nrn−Nr) that is output of the filtering process by the asymmetric coefficient filter63is supplied to the multiplier66, and also the gain G determined by the gain G decision unit65are supplied to the multiplier66. The multiplier66calculates the following equations 17 and 18, and a pair of the calculated results Nr66− and Nrn66−, i.e., (Nr66−, Nrn66−)=(0, −R) is supplied to the adder67.

Summarizing the above description, consequently, the switch61through the multiplier66determine the amount of correction of the target block (Nr, Nrn), and then supply this to the adder67inFIG. 14.

The adder67adds the block expressing the amount of correction output from the multiplier66to the target block (Nr, Nrn), and then outputs this result to the external switch25.

In other words, in a case that the direction of motion of the target pixel (step edge) is positive (spatial direction X), a block (R(=(Nr−Nrn)×G),0) expressing the amount of correction is output from the multiplier66to the adder67. The adder67adds this block (R,0) to the target block (Nr, Nrn), and outputs this result, i.e., a block (Nr+R, Nrn) to the switch25as the corrected target block.

In other words, in this case, the adder67substitutes the pixel value Nr of the target pixel of the target block (Nr, Nrn) and the correction value R(=(Nr−Nrn)×G) of the block (R,0) supplied from the multiplier66in equation 7, calculates equation 7, and then outputs the result as a corrected pixel value Nr′ of the target pixel.

In contrast, in a case that the direction of motion of the target pixel (step edge) is negative (the direction opposite to the spatial direction X), a block (0, −R) expressing the amount of correction is output from the multiplier66to the adder67. The adder67adds this block (0, −R) to the target block (Nr, Nrn), and outputs this result, i.e., a block (Nr, Nrn−R) to the switch25as the corrected target block.

In other words, in this case, the adder67substitutes the pixel value Nrn of the pixel adjacent to the target pixel of the target block (Nr, Nrn) in the spatial direction X and the correction value −R(=−(Nr−Nrn)×G) of the block (0, −R) supplied from the multiplier66in equation 9, calculates equation 9, and then outputs the result as a corrected pixel value Nrn′ of the pixel adjacent to the target pixel in the spatial direction X.

Description has been made so far regarding a preferred embodiment of the video processor22based on the assumption that the response speed of the display elements (liquid crystal in a case that the holding type unit12inFIG. 7is formed of a liquid crystal display device) of the holding type display unit12inFIG. 7and the time constant τ are both uniform.

However, as mentioned above, the time constant τ varies depending on the old pixel value and the new pixel value (target pixel value) in reality. To identify the time constant τ, a panel table such as shown inFIG. 18may be adopted, for example.

In the panel table inFIG. 18, in a case that a command for changing from the corresponding old pixel value to the corresponding target (new) pixel value is issued, the time (msec) required for the intensity of light of liquid crystal to reach from the intensity of light corresponding to the old pixel value to the intensity of light corresponding to the new pixel value, i.e., an example of response time (msec) is within each square.

For example, 20 is in the square of the first column of the second line, which expresses that the response time of liquid crystal required for changing from the light level corresponding to a pixel value192to the light level corresponding to a pixel value64is 20 msec.

On the other hand, 12 is in the square of the second column of the first line, which expresses that the response time of liquid crystal required for changing from the light level corresponding to a pixel value64to the intensity of light corresponding to a pixel value192is 12 msec.

As mentioned above, in general, the frame time T (seeFIG. 2etc.) is 16.6 msec, in a case that a pixel value changes from64to192(corresponding to the intensity of light thereof), the response time of liquid crystal is faster than the frame time T, so that the intensity of light of liquid crystal can reach the target level (corresponding to a pixel value192) faster than the frame time.

On the other hand, in a case that a pixel value changes from192to64(corresponding to the intensity of light thereof), the response time of liquid crystal is slower than the frame time T, so that the intensity of light of the liquid crystal cannot reach the target level (corresponding to a pixel value64) even if the frame time elapses, i.e., even if a command for a new target pixel value corresponding to the next frame is issued.

Thus, so long as the video processor22retains the panel table regarding the holding type display unit12, correction of pixel values can be performed more precisely, while taking the time τ constant into consideration.

However, while only the relationship between the two pixel values64and192is included in the panel table inFIG. 18to facilitate explanation, a real panel table further includes relationship (information) between a great number of pixel values. Accordingly, adapting a panel table including such a great amount of information causes a drawback that the circuit scale of the video processor22increases in order to calculate the correction value of pixel values.

On the other hand, one of the advantages of the video processor22being configured of an asymmetric high-pass filter such as shown inFIG. 14is that the circuit scale thereof can be reduced.

Accordingly, if the video processor22is configured of both an asymmetric high-pass filter and a calculating unit (not shown) using a panel table, the drawback caused by the panel table reduces the advantage of the asymmetric high-pass filter. Consequently, the reduction level of the circuit scale of the video processor22stays in a small range.

In other words, it is difficult to configure the video processor22capable of correcting pixel values, taking account of the influence of the response speed (time constant τ) of liquid crystal, as an asymmetric high-pass filter, simply by adapting a known panel table.

The inventors of this invention have conceived an idea wherein the relationship between the time response of liquid crystal (time constant τ), the old pixel value, and the new pixel value based on this panel table are subjected to functional approximation, the output values of these approximate functions are regarded as a variable gain, and the characteristics of the high-pass filter are changed using these variable gains, thereby enabling correction of pixel values to be performed, taking account of the response speed of liquid crystal (time constant τ).

The inventors of this invention have devised an asymmetric high-pass filter capable of correcting pixel values, taking account of the influence of the real response speed of liquid crystal (time constant τ) based on such an idea, i.e., the video processor22capable of markedly reducing the circuit scale thereof.

The inventors of this invention have devised the video processor22configured of the asymmetric high-pass filter such as shown inFIG. 14, for example. Moreover, the inventors of this invention have devised the gain G decision unit65having the configuration shown inFIG. 19to correct pixel values taking account of the influence of the real response speed of liquid crystal (time constant τ).

As shown inFIG. 19, this gain G decision unit65is made up of a target level-dependent gain Gl decision unit71, a difference value-dependent gain Ge decision unit72, a multiplier73, a motion speed-dependent gain Gv decision unit74, and a multiplier75.

The target level-dependent gain Gl decision unit71has retained the approximate function itself expressing the relationship between the response speed of liquid crystal (time constant τ) and the target pixel value (new pixel value), and information such as the panel table expressing the approximate function beforehand, and determines a first gain based on the information.

Note that the target pixel value (new pixel value) is any one of the pixel values Nr and Nrn of the target block (Nr, Nrn) in an input video. The target block (Nr, Nrn) indicates the target levels (new pixel values) corresponding to the target liquid crystal corresponding to the target pixel (the target display element of the holding type display unit12inFIG. 7) and the liquid crystal adjacent to the target liquid crystal in the spatial direction X respectively.

While an input video input to the gain G decision unit65is not shown inFIG. 17, an input video input to the target level-dependent gain Gl decision unit71is shown inFIG. 19.

As can be understood from the above description, the first gain is a gain depending on the response speed of liquid crystal (time constant τ) and the target pixel value (new pixel value). Hereafter, the first gain is referred to as a target level-dependent gain Gl.

More specifically, the target level-dependent gain Gl decision unit71can retain a table such as shown inFIG. 20, for example.FIG. 20is an example of the table generated based on the panel table inFIG. 18(in practice, based on a panel table further including a great amount of information).

As shown inFIG. 20, the target level-dependent gain Gl corresponding to a new pixel value192expresses a lower value. This is because, in a case that a pixel value changes from64to192(in a case of changing to the intensity of light corresponding thereto) in the panel table ofFIG. 18, the response time of liquid crystal is faster than the frame time T, and accordingly, there is no need to increase the amount of correction so much. In other words, the table shown inFIG. 20approximately expresses the relationship between the response speed of liquid crystal (time constant τ) and the target pixel value (new pixel value).

The target level-dependent gain Gl decision unit71extracts the pixel value Nr or the pixel value Nrn of the input target block (Nr, Nrn) as a target (new) pixel value, immediately determines the target level-dependent gain Gl thereof with reference to a table such as shown inFIG. 20, and then outputs the determined gain Gl to the multiplier73.

As shown inFIG. 12, in a case that the step edge is moving in the spatial direction X, the target pixel n+4 at the edge portion becomes a pixel to be corrected. In this case, in the pixel n+4 to be corrected, the pixel value E expresses a new pixel value (target pixel value) prior to correction, the pixel value B expresses an old pixel value (seeFIG. 3). In other words, in this case, the next command for the liquid crystal (the display element of the holding type display unit12) corresponding to the pixel n+4 addresses a shift from the small pixel value B to the large pixel value E (the input voltage of the liquid crystal corresponding to the pixel n+4 changes from the voltage level corresponding to the pixel value B to the voltage level corresponding to the pixel value E).

In contrast, as shown inFIG. 13, in a case that the step edge is moving in the direction opposite to the spatial direction X, the pixel n+5 adjacent to the target pixel n+4 in the spatial direction X at the edge portion becomes a pixel to be corrected. In this case, in the pixel n+5 to be corrected, the pixel value B expresses a new pixel value (target pixel value) prior to correction, the pixel value E expresses an old pixel value. In other words, in this case, the next command for the liquid crystal corresponding to the pixel n+5 addresses a shift from the large pixel value E to the small pixel value B (the input voltage of the liquid crystal corresponding to the pixel n+5 changes from the voltage level corresponding to the pixel value E to the voltage level corresponding to the pixel value B).

Thus, even if the new pixel value is the same as the previous one (the new input voltage level of liquid crystal is the same as the previous one), the direction of the shift from the old pixel value to the new pixel value thereof (the direction of the shift from the old input voltage level of liquid crystal to the new input voltage level) differs. InFIG. 12, the direction of the shift is the direction from the small old pixel value to the large new pixel value. In contrast, inFIG. 13, the direction of the shift is the direction from the large old pixel value to the small new pixel value.

On the other hand, even if the new pixel value is the same as the previous one, the response speed of liquid crystal (time constant τ) is not always the same depending on the direction of the shift thereof. More specifically, the response speed of liquid crystal (time constant τ) in a case of the direction of the shift from the large old pixel value to the small new pixel value (in a case of changing an input voltage from the large old voltage level to the small new voltage level), and the response speed of liquid crystal (time constant τ) in a case of the direction of the shift from the small old pixel value to the large new pixel value (in a case of changing an input voltage from the small old voltage level to the large new voltage level) are not always the same.

This is because the holding type display unit12configured as a liquid crystal display device inFIG. 7has so-called γ characteristics. More specifically, the holding type display unit12has characteristics wherein the shift of output light (brightness) is mild when the pixel value (the voltage level of an input voltage) addressing the target pixel (target liquid crystal) of the next display target frame is small, however, the greater the pixel value (the voltage level of an input voltage) becomes, the rapidly greater the shift of output light (brightness) becomes. Also, this is because the holding type display unit12is sometimes subjected to γ correction due to this.

Accordingly, even if the new pixel value is the same as the previous one, a different value is preferably applied to the target level-dependent gain Gl depending on the direction of the shift from the old pixel value to the new pixel value in some cases.

In this case, the target level-dependent gain Gl decision unit71preferably retains not a single table such as shown inFIG. 20but two kinds of tables, for example, the table inFIG. 20for the shift from the small old pixel value to the large new pixel value, and the table inFIG. 21for the shift from the large old pixel value to the small new pixel value.

Note that the horizontal axes of the table inFIG. 20and the table inFIG. 21, i.e., the axial scale (coordinates positions) of the target (new) pixel value are not matched in particular.

The target level-dependent gain Gl decision unit71inFIG. 19monitors the output from the asymmetric coefficient filters62and63respectively, in a case of the output from the asymmetric coefficient filter62, regards the pixel value Nr of the input target block (Nr, Nrn) as a target (new) pixel value, the pixel value Nrn as an old pixel value, determines the target level-dependent gain Gl with reference to the table inFIG. 20when Nr>Nrn, or with reference to the table inFIG. 21when Nr<Nrn, and then outputs the determined gain Gl to the multiplier73.

In contrast, if there is output from the asymmetric coefficient filter63, the target level-dependent gain Gl decision unit71regards the pixel value Nrn of the input target block (Nr, Nrn) as a target (new) pixel value, the pixel value Nr as an old pixel value, determines the target level-dependent gain Gl with reference to the table inFIG. 21when Nr>Nrn, or with reference to the table inFIG. 20when Nr<Nrn, and then outputs the determined gain Gl to the multiplier73.

While an input video input to the gain G decision unit65from the asymmetric coefficient filter62or the asymmetric coefficient filter63is not shown inFIG. 17, an input video input to the target level-dependent gain Gl decision unit71from the asymmetric coefficient filter62or the asymmetric coefficient filter63is shown inFIG. 19.

Thus, the target level-dependent gain Gl, which is a variable gain expressing the relationship between the response speed of liquid crystal (time constant τ) and the new pixel value, is determined by the target level-dependent gain Gl decision unit71. The rest is to determine a variable gain expressing the approximation of the relationship between the response speed of liquid crystal (time constant τ) and the old pixel value. InFIG. 19, the difference value-dependent gain Ge decision unit72is provided as a block for determining such a variable gain.

However, as mentioned above, the difference value-dependent gain Ge decision unit72treats not the old pixel value itself but information corresponding to the old pixel value such as the difference value (primary differential value) between the new pixel value and the old pixel value. More specifically, for example, as mentioned above, the value Nr−Nrn of a block (Nr−Nrn,0) output from the asymmetric coefficient filter62expresses the difference value between the new pixel value and the old pixel value in the target pixel. In the same way, the value Nrn−Nr of a block (0, Nrn−Nr) output from the asymmetric coefficient filter63expresses the difference value between the new pixel value and the old pixel value in the pixel adjacent to the target pixel in the spatial direction X. The difference value-dependent gain Ge decision unit72uses the output from the asymmetric coefficient filter62or the asymmetric coefficient filter63as information corresponding to the old pixel value, for example.

While an input video input to the gain G decision unit65from the asymmetric coefficient filter62or the asymmetric coefficient filter63is not shown inFIG. 17, an input video input to the difference value-dependent gain Ge decision unit72from the asymmetric coefficient filter62or the asymmetric coefficient filter63is shown inFIG. 19.

In this case, the difference value-dependent gain Ge decision unit72has retained the approximate function itself expressing the relationship between the response speed of liquid crystal (time constant τ) and the difference value between the target pixel value (new pixel value) and the old pixel value, and information such as the panel table expressing the approximate function beforehand, and determines a second gain based on the above information, and the output from the asymmetric coefficient filter62or the asymmetric coefficient filter63.

Thus, the second gain is a gain depending on the response speed of liquid crystal (time constant τ) and the difference value between the target pixel value (new pixel value) and the old pixel value. Hereafter, the second gain is referred to as a difference value level-dependent gain Ge.

More specifically, the difference value-dependent gain Ge decision unit72can retain a table such as shown inFIG. 22, for example.

In this case, the difference value-dependent gain Ge decision unit72extracts the value Nr−Nrn of a block (Nr−Nrn,0) output from the asymmetric coefficient filter62or the value Nrn−Nr of a block (0, Nrn−Nr) output from the asymmetric coefficient filter63as a difference value, immediately determines the difference value-dependent gain Ge with reference to the extracted difference value and the panel table ofFIG. 22and so forth, and then supplies the determined gain Ge to the multiplier73.

The multiplier73multiplies the target level-dependent gain Gl supplied from the target level-dependent gain Gl decision unit71by the difference value-dependent gain Ge supplied from the difference value-dependent gain Ge decision unit72, and then supplies the result, i.e., a value Ge×Gl to the multiplier75.

A motion speed-dependent gain Gv decision unit74determines the above-mentioned gain used in a case that the response speed of liquid crystal (time constant τ) is not taken into consideration, i.e., a gain depending on the amount of motion (speed) v of the step edge (target pixel) supplied from the motion detector24as a third gain, and then supplies the third gain to the multiplier75. Thus, the third gain is a gain depending on the amount of motion (speed) v of the step edge (target pixel). Hereafter, the third gain is referred to as a motion speed-dependent gain Gv.

In other words, the motion speed-dependent gain Gv decision unit74retains a proportionality constant C shown in equation 14 beforehand, substitutes the amount of motion v supplied from the motion detector24in equation 14, calculates equation 14, determines the result as the motion speed-dependent gain Gv, and then outputs the determined gain Gv to the multiplier75.

Alternatively, the motion speed-dependent gain Gv decision unit74may retain a table such as shown inFIG. 17, i.e., the table expressing the relationship between the amount of motion v and the motion speed-dependent gain Gv beforehand, determine the motion speed-dependent gain Gv with reference to this table, and then output the determined gain Gv to the multiplier66.

The multiplier75multiplies the value Ge×Gl supplied from the multiplier73by the motion speed-dependent gain Gv supplied from the motion speed-dependent gain Gv decision unit74, and then outputs the result to the multiplier66as a final gain G.

Consequently, the gain G decision unit65inFIG. 19determines a value equivalent to the result of the right-hand side of the following equation 19 as a final gain G, and then outputs the final gain G to the external multiplier66.

Thus, in a case that the response speed of liquid crystal (time constant τ) is not taken into consideration (in a case of assuming that the response speed is constant), the final gain G becomes simply the motion speed-dependent gain Gv itself; on the other hand, in a case that the response speed of liquid crystal (time constant τ) is taken into consideration, the final gain G becomes a value obtained by multiplying the motion speed-dependent gain Gv by the value Ge×Gl (the product between the target level-dependent gain Gl and the difference value-dependent gain Ge) expressing the approximation of the response speed of liquid crystal (time constant τ).

Description has been made as a preferred embodiment of the video processor22, regarding the video processor22inFIG. 14which is configured as an asymmetric high-pass filter for subjecting pixel values to high-pass filtering equivalent to calculating equation 7 or equation 9, as well as the above-mentioned video processor22inFIG. 7.

Furthermore, description will be made regarding an arrangement wherein the gain G decision unit65inFIG. 14is configured such as shown inFIG. 19, as a preferred embodiment of the video processor22made up of an asymmetric high-pass filter capable of correcting pixel values taking account of the influence of the real response speed of liquid crystal (time constant τ).

However, the video processor22is not restricted to the preferred embodiments inFIGS. 7,14, and19; rather, various embodiments can be realized. In other words, as long as the video processor22is configured as an asymmetric high-pass filter for subjecting pixel values to high-pass filtering equivalent to calculating equation 7 or equation 9, any embodiment may be adopted as the video processor22. However, in a case of correcting a pixel value taking account of the influence of the real response speed of liquid crystal (time constant τ), the asymmetric high-pass filter needs to determine the gain G equivalent to calculating equation 19.

More specifically, for example, the video processor22may be configured as an asymmetric high-pass filter such as shown inFIG. 23.

The video processor22inFIG. 23is made up of a difference value computing unit (coefficient filtering unit)81, a difference value-dependent gain Ge decision unit82, a multiplier83, a target level-dependent gain Gl decision unit84, a multiplier85, a correction value decision unit86, and an adder87.

The difference value computing unit (coefficient filtering unit)81includes each function of the switch61, the asymmetric coefficient filter62, the asymmetric coefficient filter63, and the coefficient selecting unit64inFIG. 14. More specifically, the difference value computing unit81supplies the difference value-dependent gain Ge decision unit82and the multiplier83with a block (Nr−Nrn,0) or a block (0, Nrn−Nr).

The difference value-dependent gain Ge decision unit82basically includes the same function as the difference value-dependent gain Ge decision unit72inFIG. 19. More specifically, the difference value-dependent gain Ge decision unit82supplies the multiplier83with the difference value-dependent gain Ge.

The multiplier83multiplies a block (Nr−Nrn,0) or a block (0, Nrn−Nr) supplied from the difference value computing unit (coefficient filtering unit)81by the difference value-dependent gain Ge supplied from the difference value-dependent gain Ge decision unit82, and then supplies the multiplier85with the result, i.e., a block (Ge×(Nr−Nrn),0) or a block (0, Ge×(Nrn−Nr)).

The target level-dependent gain Gl decision unit84basically includes the same function as the target level-dependent gain Gl decision unit71inFIG. 19. More specifically, the target level-dependent gain Gl decision unit84supplies the multiplier85with the target level-dependent gain Gl.

InFIG. 23, the block (Gl×Ge×(Nr−Nrn),0) and the block (0, Gl×Ge×(Nrn−Nr)) input to the correction value decision unit86are blocks in which the response speed of liquid crystal (time constant τ) has already been taken into consideration. In other words, the characteristics of the asymmetric high-pass filter22has already been changed until the process of the correction value decision unit86in accordance with the response speed of liquid crystal (time constant τ).

Accordingly, the correction value decision unit86can obtain a correction value by further changing the characteristics of the asymmetric high-pass filter22in accordance with the motion speed v supplied from the motion detector24.

More specifically, the correction value decision unit86includes each function of the motion speed-dependent gain Gv decision unit74and the multiplier75inFIG. 19, and the multiplier66inFIG. 14, generates a block (R(=Gv×Gl×Ge×(Nr−Nrn)),0) or a block (0, −R(=Gv×Gl×Ge×(Nrn−Nr))), and then supplies the generated block to the adder87.

The adder87basically has the same function and configuration as the adder67inFIG. 14. Moreover, information input to the adder87is the same information as the information input to the adder67inFIG. 14. Namely, a block (R,0) or a block (0, −R), and the target block (Nr, Nrn) output from the correction value decision unit86are input to the adder87, as mentioned above.

Accordingly, the output from the adder87inFIG. 23, i.e., the output from the video processor (asymmetric high-pass filter)22inFIG. 23becomes a block (Nr+R, Nrn) or a block (Nr, Nrn−R), which is basically the same as the output from the adder67inFIG. 14, i.e., the output from the video processor (asymmetric high-pass filter)22inFIG. 14(however, in a case that the gain G decision unit65inFIG. 14has the configuration inFIG. 19).

Accordingly, in a case that the video processor22is configured as an asymmetric high-pass filter, the configuration therein is not restricted to any particular one as long as the output thereof is the same. Accordingly, various kinds of configuration may be adopted as well as the configurations shown inFIGS. 14 and 23, though not shown in the drawing.

As mentioned above, the greater the amount of motion v supplied from the motion detector24is, the greater the correction value R of the pixel value is. In accordance with this, the pixel value following correction is also increased. For example, in a case that the pixel value Nr of the target pixel is corrected (see equation 7), the greater the correction value R is, the greater the pixel value Nr+R of the target pixel following correction is.

On the other hand, the holding type display unit12configured as a liquid crystal display device or the like includes a predetermined dynamic range. Note that the term “dynamic range” means a numerical value expressing signal reproducibility, and in general, means a ratio between the maximal value and the minimal value expressed in dB, or expressed by the number of bits. However, hereinafter, a pixel value converted from the maximal value of signal reproducibility is referred to as a dynamic range for the sake of facilitating explanation (readily comparable with others).

Accordingly, as shown inFIG. 24, the greater the correction value R is, the pixel value following correction (inFIG. 24, the pixel value E+R following correction of the target pixel n+4) sometimes exceeds the dynamic range.

In this case, the holding type display unit12cannot reproduce a pixel value beyond the dynamic range, i.e., can reproduce a pixel value up to the dynamic range (up to the intensity of light corresponding to the dynamic range). Accordingly, even if a pixel value beyond the dynamic range is commanded (for example, inFIG. 24, as a command for the pixel n+4, even if the pixel value E+R beyond the dynamic range is commanded), consequently, the result is the same in a case of commanding the pixel value corresponding to the dynamic range. In other words, as marked by an “X” inFIG. 24, the portion corresponding to (pixel value E+R)−(dynamic range) of the correction value R cannot be corrected.

As mentioned above, the correction value R is the amount of correction for eliminating motion blur caused by the retinal after-image of the human. Moreover, as mentioned inFIG. 10, the correction value R is the difference value between the original amount of light to be accumulated on the retina of the human and the real amount of light to be accumulated, i.e., the value corresponding to the lacking amount of light. Accordingly, the amount of light corresponding to (pixel value E−R)−(dynamic range) of the correction value R is not accumulated on the human retina, resulting in a problem wherein effects for eliminating motion blur is reduced.

To solve this problem, it is necessary that the number of pixels to be corrected be not one pixel at the edge portion of the step edge (inFIG. 24, pixel n+4 alone) but two or more pixels, i.e., for example, inFIG. 25, two or more pixels (pixels n+4 and n+3) of pixels (pixels n+4 through n−8) consecutively lined in the direction opposite to the direction of motion of the step edge beginning at the pixel n+4.

However, in this case, if the video processors22inFIGS. 7,14, and23are made up of a simple filter, it is difficult to realize correction of two or more pixels to be corrected since the amount of motion v (detected by the motion detector24) in each of two or more pixels sometimes differs.

Accordingly, for example, in a case that the video processor22is configured such as shown inFIG. 7, the corrector32should perform a process for propagating the correction value R in the direction opposite to the direction of motion of the step edge (inFIG. 25, the direction opposite to the spatial direction X) from the pixel at the edge portion of the step edge (inFIG. 25, pixel n+4). In other words, the corrector32should distribute and add the correction value R to two or more pixels (inFIG. 25, pixel n+4 and pixel n+3) consecutively lined in the direction opposite to the direction of motion of the step edge, beginning at one pixel (inFIG. 25, pixel n+4) at the edge portion of the step edge.

The method itself for distributing and processing the correction value R is not restricted to any particular method, for example, an arrangement may be made wherein the corrector32obtains the final correction value R, and then determines distribution values as respective correction values obtained by the distribution process wherein the final correction value R is distributed in a predetermined proportion to two or more pixels to be corrected, so as to add the distributed correction values to the pixel values of corresponding pixels respectively.

The correction results in a case that the corrector32has performed such a process are shown inFIG. 25, for example. InFIG. 25, the pixel n+4 and the pixel n+3 are regarded as a pixel to be corrected, the correction value R is distributed in the proportion of (correction value of pixel n+4: correction value of pixel n+3=2:1), and consequently, correction value of pixel n+4=2R/3 and correction value of pixel n+3=R/3 are determined respectively.

Alternatively, for example, in a case that the video processor22is configured such as shown inFIG. 23, the correction value decision unit86has a table for determining the motion speed-dependent gain Gv such as shown inFIG. 26, determines the motion speed-dependent gain Gv of each of two or more pixels to be corrected with reference to the table inFIG. 26, obtains each gain G of the two or more pixels to be corrected using the determined two or more motion speed-dependent gain Gvs, and then obtains each correction value of the two or more pixels to be corrected based on the obtained two or more gain Gs.

More specifically, for example, as shown inFIG. 25, in a case that the step edge moves in the spatial direction X, and the edge portion of the step edge corresponds to the pixel n+4, the correction decision unit24acquires the amount of motion v at the pixel n+4 from the motion detector24, and determines the motion speed-dependent gain Gv at the pixel n+4 based on the relationship between the amount of motion v and a line Gvnr of the table inFIG. 26. In the same way, the correction value decision unit24determines the motion speed-dependent gain Gv at the pixel n+3 based on the relationship between the amount of motion v and a line Gvnr−1 of the table inFIG. 26.

Note that the motion speed-dependent gain Gv at the pixel n+4 is referred to as a motion speed-dependent gain Gvn+4, and the motion speed-dependent gain Gv at the pixel n+3 is referred to as a motion speed-dependent gain Gvn+3, hereinafter.

Next, the correction value decision unit86calculates the following equations 20 and 21, determines the correction value at the pixel n+4 (hereinafter, referred to as a correction value Rn+4) and the correction value at the pixel n+3 (hereinafter, referred to as a correction value Rn+3) respectively, and then supplies the determined correction values to the adder87.

Thus, the correction value Rn+4 at the pixel n+4 and the correction value Rn+3 at the pixel n+3 are supplied to the adder87. In this case, the pixel value Nr (pixel value E, inFIG. 25) of the pixel n+4 and the pixel value Nrn (pixel value E, inFIG. 25) of the pixel n+3 are also supplied to the adder87as an input video.

Accordingly, the adder87adds the pixel value E of the pixel n+4 and the correction value Rn+4 at the pixel n+4, and then supplies the result (E+Rn+4) to the switch25as the corrected pixel value of the pixel n+4. In the same way, the adder87adds the pixel value E of the pixel n+3 and the correction value Rn+3 at the pixel n+3, and then supplies the result (E+Rn+3) to the switch25as the corrected pixel value of the pixel n+3.

Note that in a case that the step edge moves in the direction opposite to the spatial direction X, the pixels to be corrected are the pixel n+5 and the pixel n+6, and basically the same process as mentioned above is performed except that the difference value output from the difference value computing unit81is difference value (Nrn−Nr)=(B−E). Accordingly, detailed description thereof will be omitted here.

Referring to the flowchart inFIG. 27, the video processing of the video processing apparatus (seeFIG. 7) of the preferred embodiment of the present invention will now be discussed.

In step S1, the video processing apparatus11receives the video data of the display target frame or field. More specifically, the video data of the display target frame or field is input to each of the video processor21, the video processor22, the reference video storage unit23, and the motion detector24.

In step S2, the video processing apparatus11(including the video processor21, the video processor22, the motion detector24, etc.) sets one of a plurality of pixels forming the display target frame or field as a target pixel.

In step S3, the motion detector24compares the video data of the display target frame or field with the video data of the reference video (of the frame or field immediately prior to the display target frame or field) stored in the reference video storage unit23, thereby determining whether there is a motion in the target pixel.

If it is determined in step S3that no motion is detected in the target pixel, the result of the determination is fed to the switch25, and the switch25switches the input thereof to the video processor21. In step S4, the video processor21performs the predetermined process on the target pixel, thereby correcting the pixel of the target pixel. The video processor21outputs the corrected pixel value to the display controller26through the switch25.

If it is determined in step S3that there is a motion in the target pixel, the result of the determination is supplied to the switch25, and the switch25switches the input thereof to the video processor22(the corrector32).

In step S5, the motion detector24calculates the amount of motion of the target pixel (the amount of motion of the object corresponding to the target pixel between frames or fields), thereby supplying the result of the calculation to each of the step edge detector31and the corrector32.

In step S6, the step edge detector31calculates the difference between the pixel value of the target pixel and the pixel value of the pixel adjacent in the predetermined direction (in this case, one of the spatial directions X determined based on the amount of motion (direction of motion) supplied from the motion detector24) The step edge detector31supplies the corrector32with the calculated difference and the pixel value of the target pixel.

In step S7, the corrector32corrects the pixel value of the target pixel based on the amount of motion and the difference of the target pixel, and supplies the display controller26with the corrected pixel value through the switch25.

As previously discussed, the amount of motion v of the target pixel (the amount of motion v of the step edge corresponding to the target pixel) is fed from the motion detector24to the corrector32in step S5. The pixel value E of the target pixel and the difference (E−B) are fed from the step edge detector31to the corrector32in step S6. In step S7, the corrector32substitutes the supplied amount of motion v, the pixel value E of the target pixel, and the difference (E−B) in equation 3, and calculates the right-hand side of equation 3, thereby calculating the correction value R and updating the pixel value of the target pixel with the pixel value E+R. The updated pixel value E+R is then fed to the display controller26through the switch25.

If the difference is zero, in other words, if the target pixel is not a pixel corresponding to the edge portion of the step edge, the correction value R becomes zero from equation 3. If the difference is zero, the pixel value of the target pixel is not corrected, and is fed to the display controller26through the switch25as is.

Alternatively, the video processor22having the configuration example inFIG. 14or the video processor22having the configuration example inFIG. 23may perform the above-described process, thereby enabling the processes in steps S6and S7to be performed.

In step S8, the display controller26outputs the pixel value of the target pixel, supplied from the video processor21or the video processor22through the switch25, to the holding type display unit12. Before being fed to the holding type display unit12, the pixel value may be converted into a signal compatible with the holding type display unit12as necessary. In other words, the display controller26output the pixel of the target pixel at the target level of the display element corresponding to the target pixel, from among the display elements of the holding type display unit12to the holding type display unit12.

In step S9, the video processing apparatus11determines whether or not the pixel values of all pixels are output.

If it is determined in step S9that the pixel values of all pixels are not yet output, the algorithm loops to step S2to repeat the above process. More specifically, the unprocessed pixels out of the plurality of pixels forming the display target frame or field are successively set as a target pixel and the pixel value of the target pixel is corrected. The corrected pixel value (including a zero value) is output to the holding type display unit12.

When the holding type display unit12is supplied with the pixel values of all pixels forming the display target frame or field after repeating the above process, it is determined that the pixel values of all pixels are processed. The algorithm proceeds to step S10.

The holding type display unit12supplies each of the display elements forming the screen thereof with the voltage at the level corresponding to the supplied pixel value (the target level). The holding type display unit12continuously supplies the display element with the voltage at that level until the display of the next frame or field is addressed (in other words, until the pixel values of all pixels forming the next frame or field are supplied). Each display element continuously holds the display thereof.

In step S10, the video processing apparatus11determines whether all frames or fields forming a moving picture are processed.

If it is determined in step S10that not all frames or fields are processed, the algorithm loops to step S1. The next frame or field is input as a display target frame or field, and subsequent steps are repeated.

If the pixel values of all pixels forming last frame or field are corrected (including a zero value) out of the plurality of frames or fields forming the moving picture, and output to the holding type display unit12, it is determined in step S10that all frames or fields are processed. The video processing apparatus11thus ends the video processing.

The video processing apparatus11ofFIG. 27individually outputs the corrected pixel values of the pixels forming the display target frame or field to the holding type display unit12. Alternatively, the video processing apparatus11may output the pixel values as the video data of the display target frame or field at a time after correcting the pixel values of all pixels forming the display target frame or field.

As described above, the video processing apparatus of the preferred embodiment of the present invention corrects an edge or texture, moving in space contained in a moving picture, in not only time axis such as time response characteristics of the holding type display unit12but also spatial direction such as the motion direction of the edge or texture. The video processing apparatus of the present invention thus provides a sharp edge without excessive correction in comparison with the known video processing apparatus, which performs the overdrive method correcting the pixel value in the time axis only. More specifically, in comparison with the known video processing apparatus, the video processing apparatus of the preferred embodiment of the present invention controls the frequency of occurrence of motion blur and the degree of motion blur of the edge or texture moving in space.

In other words, the video processing apparatus of the preferred embodiment of the present invention provides the advantages of the correction, namely, controls the frequency of occurrence of and the degree of motion blur of the edge or texture moving in space regardless of the time response characteristics of the holding type display unit12.

The video processing apparatus of the preferred embodiment of the present invention decomposes the video data corresponding to the edge or texture moving in space into a set of video data of the step edge, and corrects each piece of the video data of the step edge. The correction is thus appropriately performed and the workload involved in the correction process is lightened.

In the above discussion, the motion direction of the step edge is in the spatial direction X. Even the motion direction of the step edge is in the spatial direction Y, the video processing apparatus11corrects the pixel value in the same manner as discussed above. The preferred embodiment of the present invention corrects the motion blur not only in the spatial direction X but also in the spatial direction Y.

The preferred embodiment of the present invention performs the correction in the video processing, thereby providing the above-mentioned advantages regardless of the response characteristics of a display panel.

The preferred embodiment of the present invention is not limited to the arrangement shown inFIG. 7.

The video processing apparatus11and the holding type display unit12, shown inFIG. 7, may be combined as one video processing apparatus. In this case, the switch25, the display controller26, and the holding type display unit12may be combined as a display unit.

Such a video processing apparatus includes a reference video storage unit23, a motion detector24for detecting a motion in a video based on input video data and reference video data (video data output from the reference video storage unit23) immediately prior to the input video data, a video processor21for performing a first video process on the video data based on the result of the motion detection provided by the motion detector24, a video processor22for performing, on the video data, a second video process other than the first video process based on the result of the motion detection provided by the motion detector24, and a display device for displaying at least one of the outputs of the video processor21and the video processor22based on the result of the motion detection provided by the motion detector24.

The display device includes a switch25that switches between the output from the video processor21and the output from the video processor22, based on the result of the motion detection provided by the motion detector24, a display controller26for converting the output provided by the switch25into a signal (a voltage signal at a voltage level corresponding to the target level), in accordance with the target level of the display element corresponding to each pixel, and a holding type display unit12for holding the result of the display controller26at the display elements thereof.

The video processing apparatus of the present invention may be arranged as shown inFIG. 28.

FIG. 28illustrates another structure of the video processing apparatus of the present invention. InFIG. 28, elements identical to those described with reference toFIG. 7are designated with the same reference numerals.

A video processing apparatus51ofFIG. 28is substantially identical in structure and function to the video processing apparatus11ofFIG. 7. The video processing apparatus51includes a video processor21through a display controller26, and the interconnection of these elements is basically identical to that of the video processing apparatus11ofFIG. 7.

In the video processing apparatus11ofFIG. 7, the output of the motion detector24is fed to the step edge detector31. In the video processing apparatus51ofFIG. 28, the output of the motion detector24is not fed to the step edge detector31. Conversely, the output of the step edge detector31is fed to each of the motion detector24and the video processor21.

The video processing apparatus51thus enjoys a small amount of process in comparison with the video processing apparatus11(FIG. 7). The operation of the video processing apparatus51will now be discussed.

In the video processing apparatus11ofFIG. 7, each of the video processor21and the video processor22performs the correction process on all pixels forming a predetermined frame or field. In other words, the video processing is performed on each frame or field twice.

In contrast, in the video processing apparatus51ofFIG. 28, the step edge detector31detects a pixel corresponding to a step edge from among a plurality of pixels forming a predetermined frame or field, and supplies each of the corrector32, the motion detector24, and the video processor21with the result of the detection.

The motion detector24thus detects motion in only the pixel (the pixel corresponding to the step edge) detected by the step edge detector31. In other words, the motion detector24determines whether or not the step edge detected by the step edge detector31is moving.

The video processor21inhibits the processing of the pixel, from which the motion detector24detects motion, from among the pixels (corresponding to the step edge) detected by the step edge detector31. In other words, the video processor21inhibits the processing of the pixel corresponding to the moving step edge, and processes the remaining pixels.

In the video processing apparatus51ofFIG. 28, the processing of one pixel is performed by either the video processor21or the video processor22. In other words, the video processing is performed on a given frame or field, one time only. The motion detector24thus detects the pixel corresponding to the step edge only. The amount of process is thus smaller in the video processing apparatus51ofFIG. 28than in the video processing apparatus11ofFIG. 7.

The above series of process steps may be performed using hardware or software.

The video processing apparatus11ofFIG. 7and the video processing apparatus51ofFIG. 28may be constructed of a personal computer ofFIG. 29, for example.

Referring toFIG. 29, a central processing unit (CPU)101performs a variety of processes in accordance with a program stored in a read-only memory (ROM)102, or the program loaded from a storage unit108to a random-access memory (RAM)103. The RAM103stores data the CPU101needs to perform various processes.

The CPU101, the RAM102, and the RAM103are interconnected through an internal bus104. The internal bus104is connected to an input/output interface105.

Also connected to an input/output interface105are an input unit106including a keyboard, a mouse, etc., an output unit107including a display, the storage unit108including a hard disk, and a communication unit109including a modem, a terminal adapter, etc. The communication unit109performs a communication process with another information processing apparatus through a variety of networks including the Internet.

Also connected to the input/output interface105is a drive110as necessary. A removable medium111, such as a magnetic disk, an optical disk, a magneto-optical disk or a semiconductor memory, is loaded onto the drive110, as necessary. A computer program read from one of such media is installed to the storage unit108as necessary.

If the series of process steps is performed using software, a computer program of the software may be installed from a network or a recording medium to a memory of a computer assembled into dedicated hardware, or into a general-purpose computer that performs a variety of functions by installing various programs thereon.

As shown inFIG. 29, the recording medium may be not only a package medium such as removable storage media (package medium)11including a magnetic disk (including a floppy disk), optical disks (including a compact-disk read-only memory (CD-ROM), digital versatile disk (DVD), electro-optical disks (including Mini-Disk (MD)), or a semiconductor memory storing the program and supplied separately from the computer to a user to provide the program, but also the ROM102and a hard disk such as the storage unit108, each storing the program.

The process steps discussed in this specification are sequentially performed in the time series order as stated. Alternatively, the steps may be performed in parallel or separately.

The moving picture handled by the video processing apparatus of the preferred embodiment of the present invention may be processed on a per frame basis or on a per field basis. The unit of process is also referred to as an access unit in this specification.

In the above discussion, each display element forming the screen of the holding type display unit12(the display element is a liquid crystal in this liquid-crystal display device) corresponds to a respective one of a plurality of pixels forming the frame or field. A plurality of display elements may correspond to a single pixel. In other words, a plurality of elements may display a single pixel.