Pure red color detection circuit and color compensation circuit using the same

Abstract

Red color saturation is increased and red color with higher purity can be reproduced by composing: a red color detection circuit 1 for detecting a red color signal having higher purity by inputting color differential signals (R-Y) and (B-Y) modulated by color subcarrier, subtracting the absolute value of the (B-Y) signal from the positive polarity component of the (R-Y) signal and removing the negative part of the subtracted signal; Y signal compensation block including: first gain controller 50 b for controlling the output signal amplitude of red color detection circuit 1 and a subtracter 50 a for subtracting the output signal of first gain controller 50 b from a luminance signal Y; an (R-Y) signal compensation block including: second gain controller 51 b for controlling the output signal amplitude of red color detection circuit 1 and an adder 51 a for adding the output signal of second gain controller 51 b and the input (R-Y) signal; and a (B-Y) signal compensation block including: third gain controller 52 b for controlling the output signal amplitude of red color detection circuit 1, a polarity inverter 52 c for inverting the output signal polarity of third gain controller 52 b, a switch circuit 52 d for selecting either input signal or output signal of polarity inverter 52 c, a polarity discriminator 52 e for discriminating the polarity of the input (B-Y) signal and controlling switch circuit 52 d and an adder 52 e for adding the output signal of switch circuit 52 d and the input (B-Y) signal.

What is claimed is:  
     
       1. A pure red color detection circuit comprising: 
       a slice meanscircuit for inputtingreceiving a color demodulated color-difference signal (R-Y) and for extractingoutputting an (R-Y) signal component at a slice level (Ls);  
       absolute value means for inputting a color demodulated color-difference signal (B-Y) and for outputting an absolute value component of said inputted  color-difference signal (B-Y);  
       subtraction means for subtracting the absolute value component of the (B-Y) signal output from said absolute value means , from the (R-Y) signal sliced at said slice level (Ls) and output from said slice means ; and  
       limited meansa limiter for removing a negative component of thea signal output from said subtraction means and for outputting a red color component having an (R-Y) signal component in a first andor a second quadrantsin a Cartesian plane.  
     
     
       2. A color compensation circuit comprising: 
       red color detection means for detecting a red component, using color difference signals (R-Y) and (B-Y); and  
       Y signal compensation means for compensating a Y signal, using the  which receives an output signal of said red color detection means; and  wherein  
       said Y signal compensation means comprises:  
       first  gain control means for decreasing the  an output signal amplitude of said red color detection means; and  
       second  subtraction means for subtracting the  an output signal of said first  gain control means from the Y signal.  
     
     
       3. A color compensation circuit comprising: 
       red color detection means for detecting a red component, using color difference signals (R-Y) and (B-Y); and  
       (R-Y) signal compensation means for compensating said (R-Y) signal, using the  which receives an output signal of said red color detection means; and  wherein  
       said (R-Y) signal compensation means comprises:  
       second  gain control means for controlling the  an output signal amplitude of said red color detection means; and  
       first  addition means for adding said (R-Y) signal and the  an output signal of said second  gain control means.  
     
     
       4. A color compensation circuit comprising: 
       pure red color detection means for inputting  receiving color demodulated (R-Y) and (B-Y) signal  signals and detecting a red color from the (R-Y) and (B-Y) signals;  
       gain control means for controlling gain of a red detecting  detection signal detected as  at said pure red color detection means and outputted from said pure red color detection means; and  
       addition means inputting  for receiving an output signal from said gain control means and the (B-Y) signal, and outputting a compensated (B-Y) signal as a (B-Y)′ signal.  
     
     
       5. A color compensation circuit comprising: 
       pure red color detection means for inputting  receiving  color demodulated (R-Y) and (B-Y) signals and for detecting a red color from the (R-Y) and (B-Y) signals;  
       first and second gain control means for controlling gain of a red detecting  detection signal detected at said pure red color detection means and outputted from said pure red color detection means;  
       first addition means for inputting the  receiving an output signal from said first  a third gain control means and the (B-Y) signal, and for outputting a compensated (B-Y) signal as a (B-Y)′ signal; and  
       second addition means for inputting the  receiving an output signal from said second gain control means and the (R-Y) signal, and for outputting a compensated (R-Y) signal as a (R-Y)′ signal.  
     
     
       6. A color compensation circuit comprising: 
       pure red color detecting  detection means for detecting a red color component, using color-difference signals (R-Y) and (B-Y);  
       first, second and third gain control means for independently controlling gain of a signal detected at said pure red color detection means;  
       secondfirst subtraction means for inputting thereceiving a signal output from said first gain control means and a Y signal, and for subtracting the signal output from said second  first gain control means from said Y signal;  
       first addition means inputting the  for receiving a signal output from said second gain control means and the (R-Y) signal; and  
       second addition means inputting the  for receiving a signal output from said third gain control means and the (B-Y) signal; and  wherein  
       said pure red color detection means includes:  
       slice means for inputting  receiving a color demodulated color-difference signal (R-Y) and for extracting  outputting an (R-Y) signal component at a slice level;  
       absolute value means for inputting a color demodulated color-difference signal (B-Y) and for outputting an absolute value component of said inputted  color-difference signal (B-Y);  
       firstsecond subtraction means for subtracting the absolute value component of the (B-Y) signal output from said absolute value means,  from the (R-Y) signal at said slide level and output from said slice means ; and  
       limiter means for removing a negative component of the  a signal output from said second subtraction means and for outputting a red color component having an (R-Y) signal component in first and second quadrants.  
     
     
       7. A color compensation circuit comprising: 
       red color detection means for detecting a red component, using color differential signals (R-Y) and (B-Y); and  
       (B-Y) signal compensation means for decreasing an absolute value of said color differential signal (B-Y), using the  an output signal of said red color detection means, ; wherein said (B-Y) signal compensation means includes:  
       third  gain control means for decreasing the amplitude of the  an output signal of said red color detection means;  
       polarity discrimination means for judging an output signal polarity of said color difference signal (B-Y);  
       polarity inverting means for inverting the output  a signal polarity of an output signal from said third  gain control means;  
       signal selection means for outputting an output signal of said polarity inverting means if said color differential signal (B-Y) has a positive polarity and outputting an output signal of said third  gain control means if said color difference signal (B-Y) has a negative polarity; and  
       third  addition means for adding the  an output signal of said signal selection means and said color difference signal (B-Y).  
     
     
       8. A color compensation circuit comprising: 
       red color detection means for detecting a red component, using color differential signals (R-Y) and (B-Y); and  
       (B-Y) signal compensation means for decreasing an absolute value of said color differential signal (B-Y), using the  an output signal of said red color detection means, ; wherein said (B-Y) signal compensation means comprises:  
       third  gain control means for decreasing the  an amplitude of the output signal of said red color detection means;  
       polarity discrimination means for judging the  a polarity of said color difference signal (B-Y) and outputting a + 1 if said color difference signal  ( B - Y )  has a negative polarity  or a − 1 signal  if said color difference signal  ( B - Y )  has a positive polarity ;  
       multiplication means for multiplying the  an output signal of said third  gain control means by the  an output signal of said polarity discrimination means; and  
       third  addition means for adding the  an output signal of said multiplication means and said (B-Y) signal.  
     
     
       9. A color compensation circuit as defined in  claim 2 , further including a pure  wherein said red color detection circuit which  means comprises: 
       slice means for slicing a color difference signal (R-Y) with a designated slice level and outputting a sliced signal;  
       absolute value means for outputting an absolute value of a color difference signal (B-Y);  
       firstsecond subtraction means for subtracting thean output signal of said absolute value means from the outputsliced signal of said slice means; and  
       limiter means for removing a negative polarity part of the  an output signal of said first  second subtraction means.  
     
     
       10. A color compensation circuit as defined in  claim 3 , further including a pure  wherein said red color detection circuit which  means comprises: 
       slice means for slicing a color difference signal (R-Y) with a designated slice level and outputting a sliced signal;  
       absolute value means for outputting an absolute value of a color difference signal (B-Y);  
       first  subtraction means for subtracting the  an output signal of said absolute value means from the output  sliced signal of said slice means; and  
       limiter means for removing a negative polarity part of the  an output signal of said first  subtraction means.  
     
     
       11. A color compensation circuit as defined in  claim 4 , further including a pure  wherein said red color detection circuit which  means comprises: 
       slice means for slicing a color differential signal (R-Y) with a designated slice level and outputting a sliced signal;  
       absolute value means for outputting an absolute value of a color difference signal (B-Y);  
       first  subtraction means for subtracting the  an output signal of said absolute value means from the output  sliced signal of said slice means; and  
       limiter means for removing a negative polarity part of the  an output signal of said first  subtraction means.