Image processing device, image display device, and image processing method

Abstract

The image processing device comprises a target correction amount calculating unit operable to calculate target correction amount based on input image signals, a frame memory operable to store the input image signals, a scene change amount calculating unit operable to calculate scene change amount based on an input image signal of the present frame and an input image signal of the previous frame, a correction amount calculating unit operable to calculate correction amount for the input image signal of the present frame, based on the target correction amount and the scene change amount, and a correcting unit operable to perform image quality correction to the input image signal of the present frame to generate a corrected input image signal, thereby outputting the corrected input image signal as an output image signal.

1 . An image processing device operable to correct image quality of input image signals, the image processing device comprising: 
 an image signal storing unit;    a target correction amount calculating unit;    a scene change amount calculating unit;    a correction amount calculating unit; and    a correcting unit,    wherein said image signal storing unit is operable to store the input image signals,    wherein said target correction amount calculating unit is operable to calculate target correction amount from an input image signal of a present frame,    wherein said scene change amount calculating unit is operable to calculate scene change amount, based on the input image signal of the present frame and an input image signal of a previous frame existing previous to the present frame, the input image signal of the previous frame being stored in said image signal storing unit;    wherein said correction amount calculating unit is operable to calculate correction amount for the input signal of the present frame, based on the target correction amount and the scene change amount; and    wherein said correcting unit is operable to correct the input image signal of the present frame using the correction amount to generate a corrected input image signal, thereby outputting the corrected input image signal as an output image signal.    
     
     
         2 . An image processing device operable to correct image quality of input image signals, the image processing device comprising: 
 a target correction amount calculating unit;    a scene change amount calculating unit;    a correction amount calculating unit comprising a correction amount storing memory; and    a correcting unit,    wherein said target correction amount calculating unit is operable to calculate target correction amount from an input image signal of a present frame,    wherein said scene change amount calculating unit is operable to calculate scene change amount for the input image signal of the present frame, based on the target correction amount calculated by said target correction amount calculating unit and correction amount for an input image signal of a previous frame existing previous to the present frame, the correction amount being stored in said correction amount storing memory;    wherein said correction amount calculating unit is operable to calculate correction amount for the inputted image signal of the present frame to yield a calculated correction amount, based on the target correction amount calculated by said target correction amount calculating unit and the scene change amount calculated by said scene change amount calculating unit and operable to output the calculated correction amount as well as to store the calculated correction amount into said correction amount storing memory; and    wherein said correcting unit is operable to correct the input image signal of the present frame using the correction amount outputted by said correction amount calculating unit to generate a corrected input image signal, thereby outputting the corrected input image signal as an output image signal.    
     
     
         3 . An image processing device operable to correct image quality of input image signals, the image processing device comprising: 
 an image signal storing unit;    a characteristic amount extracting unit;    a target correction amount calculating unit;    a scene change amount calculating unit;    a correction amount calculating unit; and    a correcting unit,    wherein said image signal storing unit is operable to store the input image signals,    wherein said characteristic amount extracting unit is operable to extract characteristic amount from an input image signal of a present frame,    wherein said target correction amount calculating unit is operable to calculate target correction amount, based on the characteristic amount extracted by said characteristic amount extracting unit,    wherein said scene change amount calculating unit is operable to calculate scene change amount based on the input image signal of the present frame and an input image signal of a previous frame existing previous to the present frame, the input image signal being stored in said image signal storing unit,    wherein said correction amount calculating unit is operable to calculate correction amount for the input image signal of the present frame based on the target correction amount and the scene change amount, and    wherein said correcting unit is operable to correct the input image signal of the present frame using the correction amount to generate a corrected input image signal, thereby outputting the corrected input image signal as an output image signal.    
     
     
         4 . The image processing device as defined in  claim 3 , wherein the characteristic amount extracted by said characteristic amount extracting unit includes at least one of a brightness average value, a brightness maximum value, a chroma average value, and a chroma maximum value of the input image signal of the present frame.  
     
     
         5 . The image processing device as defined in  claim 1 , wherein when the scene change amount is smaller than a predetermined threshold value, said correcting unit calculates correction amount for the input image signal of the present frame, based on the target correction amount obtained from the input image signal of the present frame and the correction amount for the input image signal of the previous frame, and 
 wherein when the scene change amount is greater than the predetermined threshold value, said correcting unit calculates correction amount for the input image signal of the present frame, based on only the target correction amount obtained from the input image signal of the present frame.    
     
     
         6 . The image processing device as defined in  claim 2 , wherein said correcting unit comprises a function generator, a maximum change amount calculating unit, a comparing unit, and a correction amount storing memory, 
 wherein said function generator is operable to generate a function,    wherein said maximum change amount calculating unit is operable to calculate maximum change amount of the correction amount using the function generated by said function generator with the inputted scene change amount as a variable, and    wherein said comparing unit is operable to calculate correction amount for the input image signal of the present frame, using the inputted target correction amount, the maximum change amount of the correction amount, and the correction amount for the input image signal of the previous frame stored in said correction amount storing memory.    
     
     
         7 . The image processing device as defined in  claim 6 , wherein the function generated by said function generator is a first-order differentiable-monotonically increasing-continuous function with one variable, and 
 wherein, assuming an interval between “0” and “N” (N>0) for the variable to exist, and defining as a linear slope a slope of a line connecting a point of coordinates given by “0” and a value of the function for “0” and a point of coordinates given by “N” and a value of the function for “N”, and further assuming “α” and “β” (α<β) as certain variables existing in the interval between “0” and “N”; then, a first derivative of the function for “α” is smaller than the linear slope and a first derivative of the function for “β” is greater than the linear slope.    
     
     
         8 . The image processing device as defined in  claim 6 , wherein the function generated by said function generator is a positive-continuous function with one variable, and 
 wherein, assuming an interval between “−N” and “N” (N>0) for the variable to exist, and further assuming “α” (0<α<N) as a certain variable; then, a value of the function for “−α” is smaller than a value of the function for “α”.    
     
     
         9 . The image processing device as defined in  claim 6 , wherein the function generated by said function generator is given by a first-order differentiable polynomial.  
     
     
         10 . The image processing device as defined in  claim 6 , wherein the function generated by said function generator is approximated by a polygonal line composing a plurality of connected lines.  
     
     
         11 . The image processing device as defined in  claim 1 , wherein said correction amount calculating unit comprises: 
 a correction amount storing memory operable to store a correction amount of the input image signal;    a constant setting unit operable to set a plurality of constants to define a maximum change amount of the correction amount in each of a plurality of small segments that divide a whole region of the scene change amount;    a maximum change amount selector operable to select, as the maximum change amount of the correction amount, one of the plurality of constants that corresponds to the scene change amount inputted; and    a comparing unit operable to calculate correction amount of the input image signal of the present frame, based on the target correction amount inputted, the maximum change amount of the correction amount, and the correction amount of the input image signal of the present frame stored in said correction amount storing memory.    
     
     
         12 . The image processing device as defined in  claim 11 , wherein the plurality of constants set by said constant setting unit are greater-than-zero real numbers and a series of differences between neighboring constants of the plurality of constants makes a series of progressively increasing numbers.  
     
     
         13 . An image processing device operable to correct image quality of input image signals, the image processing device comprising: 
 a function generator operable to generate a function y=f(x) with a variable x, the variable x being an input difference value defined as difference between an input image signal of a present frame and an input image signal of a previous frame existing previous to the present frame, and a functional value y being an output difference value defined as difference between an output image signal of the present frame and an output image signal of the previous frame; and    a correcting unit operable to correct the input image signal of the present frame using the functional value generated by said function generator to generate a corrected input image signal, thereby outputting the corrected input image signal as an output image signal,    wherein the function y=f(x) includes a first portion for the variable x smaller than a value of “N” and a second portion for the variable x equal to or greater than the value of “N”, the value of “N” being a certain available value for the input difference value.    
     
     
         14 . The image processing device as defined in  claim 13 , wherein the function y=f(x) is downward convex in the first portion.  
     
     
         15 . The image processing device as defined in  claim 13 , wherein the function y=f(x) satisfies in the first portion a condition that f(x/s)<f(x)/s, for a positive constant “s”.  
     
     
         16 . The image processing device as defined in  claim 13 , wherein the function f(x) is downward convex in the first portion and includes at least one linear segment with a non-zero slope different from a slope of the second portion.  
     
     
         17 . The image processing device as defined in  claim 13 , wherein, when the input image signal having same values for all pixels of a frame changes to a new value at the present frame from a value of the input image signal that has continuously been fed until the previous frame, the input difference value as the variable x is defined as difference between the input image signal of the present frame and the input image signal of the previous frame, and the output difference value as the functional value y is defined as difference between the output image signal of the present frame and the output image signal of the previous frame.  
     
     
         18 . An image processing device operable to correct image quality of input image signals, the image processing device comprising: 
 a function generator operable to generate a function y=g(x) with a variable x, the variable x being an input difference value defined as difference between an input image signal of a present frame and an input image signal of a previous frame existing previous to the present frame, and a functional value y being an output difference value defined as difference between an output image signal of the present frame and an output image signal of the previous frame; and    a correcting unit operable to correct the input image signal of the present frame using the functional value generated by said function generator to generate a corrected input image signal, thereby outputting the corrected input image signal as an output image signal,    wherein the function y=g(x) includes at least two sets of combination that yield a same functional value y for different variables x.    
     
     
         19 . The image processing device as defined in  claim 18 , wherein the function y=g(x) includes a first portion for the variable x smaller than a value of “N” and a second portion for the variable x equal to or greater than the value of “N”, the value of “N” being a certain available value for the input difference value, and wherein a curve connecting points is downward convex in the first portion, each of the points being defined by coordinates of a smallest variable x among the variables that yield a same functional value y and the functional value y.  
     
     
         20 . The image processing device as defined in  claim 18 , wherein in the first portion of the function g(x), a curve y=h(x) connecting points, each of the points being defined by coordinates of a smallest variable x among the variables that yield a same functional value y and the functional value y, satisfies a condition that h(x/s)<h(x)/s, for a positive constant “s”.  
     
     
         21 . The image processing device as defined in  claim 18 , wherein, when the input image signal having same values for all pixels of a frame changes to a new value at the present frame from a value of the input image signal that has continuously been fed until the previous frame, the input difference value as the variable x is defined as difference between the input image signal of the present frame and the input image signal of the previous frame, and the output difference value as the functional value y is defined as difference between the output image signal of the present frame and the output image signal of the previous frame.  
     
     
         22 . An image display device comprising an image processing device and an image display unit, 
 wherein the image processing device comprises:    an image signal storing unit operable to store input image signals;    a target correction amount calculating unit operable to calculate target correction amount from an input image signal of a present frame;    a scene change amount calculating unit operable to calculate scene change amount, based on the input image signal of the present frame and an input image signal of a previous frame existing previous to the present frame, the input image signal of the previous frame being stored in said image signal storing unit;    a correction amount calculating unit operable to calculate correction amount for the input signal of the present frame, based on the target correction amount and the scene change amount; and    a correcting unit operable to correct the input image signal of the present frame using the correction amount to generate a corrected input image signal, thereby outputting the corrected input image signal as an output image signal,    wherein said image processing device is, in accordance with the scene change, operable to correct an externally fed input image signal to generate a corrected input image signal and operable to output the corrected input image signal as an output image signal, and    wherein said image display unit is operable to display the output image signal outputted by said image processing device.    
     
     
         23 . The image display device as defined in  claim 22 , wherein said image display unit includes at least one of a liquid crystal display and a plasma display.  
     
     
         24 . An image processing method to correct image quality of input image signals, the image processing method including: 
 storing the input image signals,    calculating target correction amount based on an input image signal of a present frame,    calculating scene change amount, based on the input image signal of the present frame and an input image signal of a previous frame existing previous to the present frame, the input image signal of the previous frame being stored in said storing input image signals,    calculating correction amount for the input image signal of the present frame, based on the target correction amount and the scene change amount, and storing the calculated correction amount, and    correcting the input image signal of the present frame using the correction amount to generate a corrected input image signal, thereby outputting the corrected input image signal as an output image signal.    
     
     
         25 . The image processing method as defined in  claim 24 , wherein said calculating scene change amount includes calculating scene change amount for the input image signal of the present frame, based on the target correction amount calculated in said calculating target correction amount and the correction amount for the input image signal of the previous frame stored in said calculating correction amount, and 
 wherein said calculating correction amount includes calculating correction amount for the input image signal of the present frame, based on the target correction amount calculated in said calculating target correction amount and the scene change amount calculated in said calculating scene change amount, and outputting and storing the calculated correction amount.    
     
     
         26 . The image processing method as defined in  claim 24 , the image processing method further including extracting characteristic amount from the input image signal of the present frame, wherein said calculating target correction amount includes calculating the target amount based on the characteristic amount extracted in said extracting characteristic amount.  
     
     
         27 . The image processing method as defined in  claim 26 , wherein the characteristic amount extracted in said extracting characteristic amount includes at least one of a brightness average value, a brightness maximum value, a chroma average value, and a chroma maximum value of the inputted signal of the present frame.  
     
     
         28 . The image processing method as defined in  claim 24 , wherein said calculating correction amount includes: 
 comparing the scene change amount calculated in said calculating scene change amount with a predetermined threshold value,    calculating correction amount for the input image signal of the present frame, based on the target correction amount calculated from the input image signal of the present frame and the correction amount for the input image signal of the previous frame in a case when, according to the compared result in said comparing, the scene change amount is smaller than the predetermined threshold value, and    calculating correction amount for the input image signal of the present frame, based on only the target correction amount calculated from the input image signal of the present frame in a case when, according to the compared result in said comparing, the scene change amount is greater than the predetermined threshold value.    
     
     
         29 . The image processing method as defined in  claim 24 , wherein said calculating correction amount further includes: 
 generating a function,    storing correction amount,    calculating a maximum change amount of the correction amount using the function generated in said generating a function with the inputted scene change amount as a variable, and    calculating the correction amount for the input image signal of the present frame, based on the inputted target correction amount, the maximum change amount of the correction amount, and the correction amount for the input image signal of the previous frame stored in said storing correction amount.    
     
     
         30 . The image processing method as defined in  claim 24 , wherein the function generated in said generating a function is a first-order differentiable-monotonically increasing-continuous function with one variable, and 
 wherein, assuming an interval between “0” and “N” (N>0) for the variable to exist, and defining as a linear slope a slope of a line connecting a point of coordinates given by “0” and a value of the function for “0” and a point of coordinates given by “N” and a value of the function for “N”, and further assuming “α” and “β” (α<β) as a certain variables existing in the interval between “0” and “N”; then, a first derivative of the function for “α” is smaller than the linear slope and a first derivative of the function for “β” is greater than the linear slope.    
     
     
         31 . The image processing method as defined in  claim 29 , wherein the function generated in said generating a function is a positive-continuous function with one variable, and 
 wherein, assuming an interval between “−N” and “N” (N>0) for the variable to exist, and further assuming “α” (0<α<N) as a certain variable; then, a value of the function for “−α” is smaller than a value of the function for “α”.    
     
     
         32 . The image processing method as defined in  claim 29 , wherein the function generated in said generating a function is given by a first-order differentiable polynomial.  
     
     
         33 . The image processing method as defined in  claim 29 , wherein the function generated in said generating a function is approximated by a polygonal line composing a plurality of connected lines.  
     
     
         34 . The image processing method as defined in  claim 24 , wherein said calculating correction amount includes: 
 storing a correction amount of the input image signal,    setting a plurality of constants to define the maximum change amount of the correction amount, in each of a plurality of small segments that divide a whole region of the scene change amount,    selecting, as the maximum change amount of the correction amount, one of the plurality of constants that corresponds to the inputted scene change amount, and    calculating correction amount for the input image signal of the present frame, based on the target correction amount inputted, the maximum change amount of the correction amount, and the correction amount of the input image signal of the previous frame stored in said storing correction amount.    
     
     
         35 . The image processing method as defined in  claim 34 , wherein the plurality of constants set in said setting a plurality of constants are greater-than-zero real numbers and a series of differences between neighboring constants of the plurality of constants makes a series of progressively increasing numbers.