JP2006518480A - Image signal processing for color sequential displays - Google Patents

Abstract

The present invention relates to a method for processing an image signal representing a series of images to be displayed on a color sequential display device. In order to enable the presentation of high quality images using a color sequential display device at a reduced cost, it is proposed that the received image signal is separated into at least three color components for each image, at least 3 The two color components are sequentially displayed on the display device 16. Further, a movement from one image to the next image is detected in the received image signal. Motion compensation 15 for at least two color components of the image is performed at the same time instant, and the color components are displayed one after the other. Finally, at least three color components are provided for display. The present invention relates to an apparatus and system having means for implementing the proposed method.

Description

  The present invention relates to processing of an image signal representing a series of images to be displayed on a color sequential display type display device. The invention also relates to a system for displaying a series of images on a color sequential display device.

  It is known from the prior art to display images of an image series by individually displaying the color components of each image, typically red, green and blue. There are different approaches for displaying such individual color components. In essence, generating color is a trade-off between the spatial and temporal resolution of the display.

  A first type of display device, such as a CRT (Cathode Ray Tube) or LCD (Liquid Crystal Display) device, generates and displays all color components simultaneously. In the case of red, green and blue color components, for example, red, green and blue colored dots are simultaneously projected onto the screen, thereby adding the spatial resolution of the display. For simultaneous display, a dedicated hardware part needs to be utilized for each color component.

  In contrast, the second type of display, such as LCoS (Liquid Crystal on Silicon), in contrast, sequentially converts the color components of each image, first the red component of each image, then the green component and finally the blue component. indicate. LCoS displays generate three times as much light for each single dot, thereby adding temporal resolution to the display. The picture rate of the color component is typically three times the picture rate of the series of images to be displayed. This approach has the advantage that very high resolution can be achieved at a relatively limited cost because the same hardware can be used sequentially for each color component.

  Conventionally, a color component signal for sequential display of color components is generated directly from an input signal. However, sequential display of color components introduces artifacts due to moving objects in the video scene. Since individual color components are displayed at different time instants, only one color component can be displayed according to the activation of the original motion. For example, the deviation of the green and blue signals from the original motion trajectory when the Red signal is displayed according to the activation of the original motion, i.e. at the correct image position at the time of display, is known as "color breakup". Create artifacts.

  In order to avoid such artifacts, it has been proposed to perform motion prediction on image sequences and to apply corresponding motion compensation to color components for color sequential display applications. Similar techniques have been applied to “natural motion” TV sets and are well suited for use in color sequential displays. In a direct realization, two of the three color components each need to be motion compensated at their own time instant.

  Motion compensation for at least one color component is described, for example, in WO01 / 10131. The provided compensation scheme determines the motion vector for an area or object in the image stream and predicts the position of the object for each number of presentations of each color component, for example by interpolation or extrapolation. Each color brain representing an area or object at the predicted position is sequentially displayed. Also, it is proposed that the number of times of reference is determined for the most important color component, for example, green, at a temporal moment when motion compensation interpolation is required.

  The cost of implementing a function that compensates for two of the three color components is significant, with a high picture rate of typically 180 Hz and a high spatial resolution of normal displays. The only color component motion compensation, on the other hand, may not lead to a satisfactory reduction in artifacts.

  An object of the present invention is to enable the presentation of high quality images using a display device that follows a color sequential display scheme at a reduced cost. The invention is defined by the independent claims. The dependent claims define advantageous embodiments. The first two steps of the proposed method can be performed in either order or even simultaneously.

  In a system where at least three color components are to be displayed sequentially, i.e. not at the same time instant, motion compensation interpolation is performed at the same time instant for at least two of the three color components. Proceeding from the consideration that, when implemented, satisfactory motion compensation can be achieved. Consequently, motion compensation is not only optimal for one color component, but other color components are also at least partially compensated. The advantage of the present invention is that it is in its own time instant, i.e. not the same moment for at least two of the three color components, but compared to motion compensation with motion vectors dedicated to each color component. , Enabling motion compensation with reduced throughput. This provides a significant cost reduction while maintaining the perceived image quality advantage almost completely.

  Advantageously, the color component with the highest contribution to perceived brightness is not motion compensated and all other color components are motion compensated. This minimizes perceived motion compensation artifacts due to the fact that luminance artifacts are more visible than chrominance artifacts. Since motion compensation always introduces artifacts in different image parts, it is best to concentrate on the primary colors that contribute the least to luminance. In the case of two other color components, motion compensated interpolation should display the color component that contributes second to the perceived brightness than the moment of time when the third color component should be displayed. It is preferably performed at a time instant close to the time instant. In the case of RGB color components, for example, the green component may be considered to be the color component that has the highest contribution to perceived brightness, and the red component has the second highest contribution to perceived brightness. It can be considered that the color component has. Thus, the green component is preferably not motion compensated, and the motion compensation interpolation of the red and blue components is calculated at the time instant of the red component display.

  In a preferred embodiment of the invention, at least two color components are motion compensated in their entirety as this yields the best results. In the case where the color components are calculated from the luminance and chrominance signals of the received image signal (Y / U / V), for example, interpolation of motion compensation of the luminance and chrominance components of each of the at least two color components is It is executed at the same time.

  For a particularly economical alternative, at least two color component non-motion compensated chrominance components are utilized, while only at least two color component luminance components are motion compensated based on motion compensated interpolation.

  The present invention can be used in any apparatus or system that utilizes a color sequential display, for example, in a television set. The color sequential display need not be part of the device according to the present invention. These and other aspects of the invention will be apparent with reference to the embodiments described herein after consideration of the drawings.

  FIG. 1 is a conceptual block diagram of a color sequential display system such as a TV set in which an embodiment of the present invention is implemented. The system has a receiving part 11, which is connected on the one hand to the separating part 12 and on the other hand to the motion prediction part 13. The separation part 12 is further connected to a motion compensation part 15 via a time-based correction part 14. The motion prediction portion 13 is also connected to this motion compensation portion 15. The motion compensation part 15 is finally connected to the display part 16 of the system.

  The receiving part 11 receives an interlaced video signal representing an image sequence. The images of the image sequence are displayed on the screen at a predetermined first time interval, i.e. at a given picture rate.

  The received signal is then supplied to the separation part 12. Separation portion 12 can apply a deinterlacing process to the received video signal, thereby generating a progressive image signal that is separated into red, green and blue (RGB) color components of the respective images. The color components of each image are displayed continuously with an equal, predetermined second time interval, which is typically 1/3 of the first time interval. Furthermore, the display order of the color components is typically green-red-blue for each image. Accordingly, each of the RGB color components is time compressed in the time-based correction portion 14 and delayed accordingly, and the corrected color components are sent to the motion compensation portion 15.

  At the same time, the receiving part 11 provides the received video signal to the motion prediction part 13. The motion prediction portion 13 detects motion from each picture to the next picture, that is, between picture n-1 and picture n. Here, n is the number of each image in the image series. Information regarding any detected motion is provided to the motion compensation portion 15 by the motion prediction portion 13.

  In the motion compensation portion 15, the moment of time when the green component of the image series is displayed is selected as the reference time. Therefore, the motion compensation portion 15 does not perform any compensation for the green component of the image. Each green component sent by the motion compensation portion 15 to the display portion 16 is simply a time-compressed and delayed copy from either picture n-1 or picture n.

  The motion compensation portion 15 is determined by interpolation motion vectors for all portions of the image in which motion is detected by the motion prediction portion 13. The motion vector represents the motion in different parts of the image that takes place when going from picture n-1 to a specific time instant between the two picture n-1 and n time instants in which each motion is detected. Show. More specifically, the motion vector at the instant of time when the red component is delayed is determined. These motion vectors are then used to motion compensate the red component as well as the blue component of the current picture n-1. Thus, the red and blue components are calculated from the input pictures n and n-1 which are time compressed and delayed. The instant of time at which the red component is delayed is chosen to determine the motion vector because it may be advantageous to have a somewhat larger timing error in blue than in red. The motion-compensated red and blue components are supplied to the display portion 16. The display part 16 continuously projects the received RGB color components on the screen.

  2-4 illustrate the differences between the display of uncompensated color components, the display of color components compensated in a known manner, and the display of color components compensated according to the present invention by the system of FIG. is doing.

  2a and 2b relate to the display of the color components of the image sequence without compensation. FIG. 2a shows the position of the object in the image over picture number n. An arrow 21 in the figure indicates the movement of the white ball in the image series. The ball is split for each image into a green component, a red component and a blue component, displayed in sequence. As can be seen, the green component is always displayed at the correct position of the white ball. Since there is no motion compensation, the red and blue components are provided for each image at the same image location as the green component, but at a later moment in time, as a “color breakup” in the displayed video Can see.

  FIG. 2b is a further diagram related to the same situation, having a line representing picture number n. In this figure, the arrows indicate that each color component is effective at the instant of time. All the color components R, G and B (red, green and blue) are valid at the time instant when the green component is displayed. None of these color components are motion compensated.

  3a and 3b relate to the display of color components of an image sequence by motion compensation as known from the art. FIG. 3a is a diagram in which the arrow 31 gives the position of the object in the image over the number n of pictures indicating the movement of the white ball. The ball is split into a green component, a red component and a green component for each image displayed in sequence. The green component is always displayed at the correct position of the white ball without motion compensation. The red and blue components are given for each image at a time instant later than the green component. In this case, the red component is motion compensated with the motion vector determined for each moment of time when the red component is to be displayed, and the blue component is determined for the moment of time when the respective blue component is to be displayed. Motion compensation is performed using a motion vector. Each motion vector is determined, for example, by interpolating the ball position at the moment of presentation of the green component. As a result, the red and blue components are always displayed at the correct position of the white ball, which means the case of movement in which the respective color components are displayed at different image positions.

  FIG. 3b is a further diagram related to the same situation, with a line representing the number n of pictures as in FIG. 2b. In this figure, the arrow G represents the moment of time when the green component is displayed. Arrows R and B represent instants of time when the respective red and blue components are valid. In this case, the time instants are the same as the time instants at which these components are displayed. As a result, the “color breakup” artifact is resolved. In order to derive these R and B components from the input image, these components are motion compensated at their respective optical time instants. Each of the color components is motion compensated with the motion vector required for optimal compensation and no motion compensation is required for the green component. Since dedicated motion vectors are determined for the red and blue components, the processing effort is significant.

  4a and 4b relate to the display of color components of an image sequence by motion compensation according to the present invention. FIG. 4a is similar to FIGS. 2a and 3a, giving the position of the object in the image over the number n of pictures, with the arrow 31 indicating the movement of the white ball. The ball is divided into a green component, a red component and a green component for each image, which are displayed sequentially. The green component is always displayed at the correct position of the white ball without motion compensation. A red component and a blue component are provided for each image at a time instant later than the green component. Each red component is motion compensated with a motion vector approximately determined for each moment of time when the red component is to be displayed, and each blue component is determined for each moment of time that the red component is to be displayed Motion compensation is performed using a motion vector. The motion vector is determined by interpolating the position of the ball at each of the two closest time instants of the green component display. As a result, the red component is essentially always displayed at the position of the white ball that is accurate for the moment of time of their presentation. This approximates the position of the blue component to the position of each white ball that is accurate at the moment of time of their presentation.

  FIG. 4b is a further diagram related to the same situation, with a line representing the number n of pictures as in FIGS. 2b and 3b. In this figure, the arrow G represents the moment of time when the green component is displayed. Arrows R and B are located at a single time instant. This represents the instant of time when each red and blue component is valid. Since these R and B components are derived from the input image, these components are motion compensated at the same instant.

  Only the green component is shown at the right time instant, and small timing errors are allowed in the red and blue components. Timing errors decrease as each primary color contributes to perceived brightness.

  Even when the blue component is not optimally motion compensated, perceived artifacts in the displayed video are minimized.

  In the first embodiment of the present invention implemented in the system of FIG. 1, the determined motion vectors are applied globally to the red and blue components.

  In the second embodiment of the present invention implemented in the system of FIG. 1, the separation portion 12 calculates RGB color components from the luminance Y signal and the chrominance U / Y signal for each image. The motion compensation portion 15 compensates both the luminance component Y and the chrominance component U / V, the red and blue components having the same motion vector.

  Also, in the third embodiment of the present invention implemented in the system of FIG. 1, the separation portion 12 calculates RGB color components from the luminance Y signal and chrominance U / V signal in each image. In this embodiment, motion compensation is performed in the motion compensation portion 15 only for the luminance I components of the red and blue components. The chrominance components U / V of the red and blue components are treated like the green component. That is, no motion compensation is performed on them.

  In the second and third embodiments, the motion compensated Y / U / V signal is extracted, the matrix is subjected to RGB conversion, the result is used to display, for example, a red signal first, and a blue signal is also displayed. It is possible to reuse it by delaying it.

  The described embodiment of the present invention constitutes a selected embodiment of several possible embodiments of the present invention, the previously described embodiment being It is intended to be illustrative rather than to limit the invention, and one of ordinary skill in the art will be able to design many alternative embodiments without departing from the scope of the claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word “comprising” does not exclude the presence of elements or steps other than those listed in a claim. The word “a” or “an” preceding a component does not exclude the presence of a plurality of components. The present invention can be implemented by hardware having several individual elements and a suitably programmed computer. In the device claim enumerating several means / parts, several of these means / parts may be implemented with the same hardware. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used.

1 is a block diagram of a system in which an embodiment of the present invention is realized. It is a figure which illustrates the display of the color component without motion compensation. It is a figure which illustrates the display of a color component by well-known motion compensation. It is a figure which illustrates display of a color component by motion compensation concerning the present invention.

Claims (10)

A method of processing an image signal representing a series of images displayed in a color sequential manner,
Separating the received image signal into at least three color components displayed sequentially for each image;
Detecting movement from one image to the next in the received image signal;
Performing motion compensated interpolation of at least two color components of an image at the same time instant, wherein the color components are displayed one after the other;
Providing the at least three color components;
A method characterized by comprising: The at least three color components have at least red, green and blue images;
The method of claim 1. Of the at least three color components, the color component having the highest contribution to the perceived brightness is provided for display without motion compensation.
The method of claim 1. The at least two color components for which motion compensated interpolation is performed at the same time instant have color components that have the second highest contribution to perceived brightness, and the time instant is Determined to compensate for the motion closest to the moment of time in which the color component having the second highest contribution to perceived brightness is displayed;
The method of claim 1. The at least three color components are calculated from the luminance signal and the chrominance signal in the received image signal, and the motion compensated interpolation of the at least two color components of the image at the same temporal instant is the same temporal instant. Performing a motion compensated interpolation of the respective luminance and chrominance components of each of the at least two color components;
The method of claim 1. The at least three color components are calculated from a luminance signal and a chrominance signal in the received image signal, and the motion compensated interpolation of at least two color components of the image at the same time instant is the at least two color components. Each chrominance component of each of the at least two color components performed by performing motion compensation interpolation at the same temporal instant of each luminance component of the component, wherein motion compensation interpolation is performed at the same temporal instant Is provided for display without motion compensation,
The method of claim 1. Further comprising performing a time based correction to time compress or delay each of the at least three color components.
The method of claim 1. The received image signal comprises an interlaced video signal, and the step of separating the received image signal into at least three color components for each image is for generating a signal for separate successive images. Deinterlacing the received image signal;
The method of claim 1. An apparatus for processing an image signal representing a series of images displayed by a color sequential method,
A receiving portion for receiving an image signal representing a series of images;
A separation portion for separating the received image signal into at least three color components displayed sequentially for each image;
A motion prediction portion for detecting motion from one image to the next in the received image signal;
A motion compensation portion for performing motion compensation interpolation of at least two color components of the image, displayed one after another, at the same time instant;
A device characterized by comprising: A system for displaying a series of images,
An apparatus according to claim 9;
A color sequential display device for displaying at least three received color components of an image in a series of images;
The system characterized by having.

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