Non-linear characteristic correction apparatus and method therefor

{
  "publication_number": "US6166781A",
  "country": "US",
  "kind": "A",
  "title": "Non-linear characteristic correction apparatus and method therefor",
  "abstract": "A non-linear response correction apparatus and method reduce look up table size and output error. In one embodiment, a range of an N-bit input signal is split into two or more sectors, based on a gradient of a non-linear correction curve and an allowable error, and then a N-bit input signal is divided into U upper bits and D lower bits where U and D depend on which sector contains the input signal. First and second look up tables read first and second data stored therein, respectively, using the upper bits of the digital signal as an address. The first data is the difference between a corrected signal and the input signal, and the second data is the gradient of the corrected signal with respect to the gradient of the input signal. The second data read from the second look up table is multiplied by the lower bits, and the first data read from the first look up table is added to the upper bits. The sum is added to the product to produce an N-bit digital corrected signal that compensates for the non-linear characteristics.",
  "claims": [
    "1. An apparatus for correcting non-linear characteristics of a system, comprising: a first look up table for storing first data and outputting the stored first data by using the upper bits of an N-bit digital signal input to the system as an address; a second look up table for storing second data and outputting the stored second data by using the upper bits of the digital signal as an address; a multiplier for multiplying the second data, output from the second look up table, by the lower bits of the digital signal, and outputting the product; and an adder for adding the first data, output from the first look up table, to the product output from the multiplier, wherein the sum output by the adder is an N-bit digital corrected signal for compensating for the non-linear characteristics, used by the system instead of the N-bit digital signal, and the first data is a predetermined number of digital corrected signals, and the second data is the gradient of the digital corrected signal with respect to the gradient of the digital signal.",
    "2. The apparatus of claim 1, wherein the N-bit digital signal is one of red (R), green (G) and blue (B) signals requiring gamma correction.",
    "3. The apparatus of claim 1, wherein the apparatus further comprises: a multiplexer for selecting one of red (R), green (G) and blue (B) color signals to be gamma-corrected in response to a system clock signal and frequency-divided system clock signal, and outputting the selected color signal as the N-bit digital signal to the first look up table, the second look up table and the multiplier; and a demultiplexer for outputting the output from the adder as gamma-corrected R', G' and B' signals, in response to the system clock signal and the frequency-divided system clock signal, wherein the color signals are concurrently gamma-corrected.",
    "4. The apparatus of claim 2, wherein the non-linear characteristic correction apparatus is a gamma correction apparatus included in a transmitter for transmitting the color signals.",
    "5. The apparatus of claim 2, wherein the non-linear characteristic correction apparatus is a gamma correction apparatus included in a receiver for receiving the color signals.",
    "6. The apparatus of claim 1, wherein the first look up table is a writable/readable memory and can use a programmable addressing method.",
    "7. The apparatus of claim 1, wherein the second look up table is a writable/readable memory and can use a programmable addressing method.",
    "8. An apparatus for correcting non-linear characteristics of a system, comprising: a first look up table for storing first data and outputting the stored first data by using the upper bits of an N-bit digital signal input to the system as an address; a second look up table for storing second data and outputting the stored second data by using the upper bits of the digital signal as an address; a multiplier for multiplying the second data, output from the second look up table, by the lower bits of the digital signal, and outputting the product; a first adder for adding the first data, output from the first look up table, to the upper bits of the digital signal, and outputting the sum; and a second adder for adding the output from the multiplier to the output from the first adder, wherein the sum output by the second adder is an N-bit digital corrected signal for compensating for the non-linear characteristics, used by the system instead of the N-bit digital signal, and the first data is the difference between the digital corrected signal and the digital signal, and the second data is the gradient of the digital corrected signal with respect to the gradient of the digital signal.",
    "9. The apparatus of claim 8, wherein the N-bit digital signal is one of red (R), green (G) and blue (B) signals requiring gamma correction.",
    "10. The apparatus of claim 8, wherein the apparatus further comprises: a multiplexer for selecting one of red (R), green (G) and blue (B) color signals to be gamma-corrected in response to a system clock signal and frequency-divided system clock signal, and outputting the selected color signal as the N-bit digital signal to the first look up table, the second look up table and the multiplier; and a demultiplexer for outputting the output from the adder as gamma-corrected R', G', and B' signals, in response to the system clock signal and the frequency-divided system clock signal, wherein the color signals are concurrently gamma-corrected.",
    "11. The apparatus of claim 9, wherein the non-linear characteristic correction apparatus is a gamma correction apparatus included in a transmitter for transmitting the color signals.",
    "12. The apparatus of claim 9, wherein the non-linear characteristic correction apparatus is a gamma correction apparatus included in a receiver for receiving the color signals.",
    "13. The apparatus of claim 8, wherein the first look up table is a writable/readable memory and can use a programmable addressing method.",
    "14. The apparatus of claim 8, wherein the second look up table is a writable/readable memory and can use a programmable addressing method.",
    "15. An apparatus for correcting non-linear characteristics of a system, comprising: a sector classifier for classifying range of an N-bit digital signal into two or more sectors, based on a predetermined gradient and a predetermined allowable error, and outputting a control signal indicating the respective sectors; a bit divider for dividing the N-bit digital signal into upper and lower bits in response to the control signal; a first look up table for storing first data and outputting the stored first data by using the upper bits as an address; a second look up table for storing second data and outputting the stored second data by using the upper bits as an address; a multiplier for multiplying the second data, output from the second look up table, by the lower bits, and outputting the product; and an adder for adding the first data, output from the first look up table, to the product output from the multiplier, wherein the sum output by the adder is an N-bit digital corrected signal for compensating for the non-linear characteristics, used by the system instead of the N-bit digital signal, and the first data is a predetermined number of digital corrected signals, and the second data is the gradient of the digital corrected signal with respect to the gradient of the digital signal, and the control signal is generated such that more bits of the digital signal are allocated as upper bits, in a sector having a steeper gradient.",
    "16. The apparatus of claim 15, wherein the bit divider outputs the entire N-bit digital signal as upper bits when the digital signal is included in a sector having a predetermined level of gradient, in response to the control signal.",
    "17. The apparatus of claim 15, wherein the N-bit digital signal, is one of red (R), green (G) and blue (B) signals requiring gamma correction.",
    "18. The apparatus of claim 15, wherein the apparatus further comprises: a multiplexer for selecting one of red (R), green (G) and blue (B) color signals to be gamma-corrected in response to a system clock signal and frequency-divided system clock signal, and outputting the selected color signal as the N-bit digital signal to the sector classifier and the bit divider; and a demultiplexer for outputting the output from the adder as gamma-corrected R', G', and B' signals, in response to the system clock signal and the frequency-divided system clock signal, wherein the color signals are concurrently gamma-corrected.",
    "19. The apparatus of claim 17, wherein the non-linear characteristic correction apparatus is a gamma correction apparatus included in a transmitter for transmitting the color signals.",
    "20. The apparatus of claim 17, wherein the non-linear characteristic correction apparatus is a gamma correction apparatus included in a receiver for receiving the color signals.",
    "21. The apparatus of claim 15, wherein the first look up table is a writable/readable memory and can use a programmable addressing method.",
    "22. The apparatus of claim 15, wherein the second look up table is a writable/readable memory and can use a programmable addressing method.",
    "23. An apparatus for correcting non-linear characteristics of a system, comprising: a sector classifier for classifying range of an N-bit digital signal into two or more sectors, based on a predetermined gradient and a predetermined allowable error, and outputting a control signal indicating the respective sectors; a bit divider for dividing the N-bit digital signal into upper and lower bits in response to the control signal; a first look up table for storing first data and outputting the stored first data by using the upper bits as an address; a second look up table for storing second data and outputting the stored second data by using the upper bits as an address; a multiplier for multiplying the second data, output from the second look up table, by the lower bits, and outputting the product; a first adder for adding the first data, output from the first look up table, to the upper bits, and outputting the sum; and a second adder for adding the output from the multiplier to the output from the first adder, wherein the sum output by the adder is an N-bit digital corrected signal for compensating for the non-linear characteristics, used by the system instead of the N-bit digital signal, and the first data is the difference between the digital corrected signal and the digital signal, and the second data is the gradient of the digital corrected signal with respect to the gradient of the digital signal, and the control signal is generated such that more bits of the digital signal are allocated as upper bits, in a sector having a steeper gradient.",
    "24. The apparatus of claim 23, wherein the bit divider outputs the entire N-bit digital signal as upper bits when the digital signal is included in a sector having a predetermined level of gradient, in response to the control signal.",
    "25. The apparatus of claim 23, wherein the N-bit digital signal is one of red (R), green (G) and blue (B) signals requiring gamma correction.",
    "26. The apparatus of claim 23, wherein the apparatus further comprises: a multiplexer for selecting one of red (R), green (G) and blue (B) color signals to be gamma-corrected in response to a system clock signal and frequency-divided system clock signal, and outputting the selected color signal as the N-bit digital signal to the sector classifier and the bit divider; and a demultiplexer for outputting the output from the adder as gamma-corrected R', G', and B' signals, in response to the system clock signal and the frequency-divided system clock signal, wherein the color signals are concurrently gamma-corrected.",
    "27. The apparatus of claim 25, wherein the non-linear characteristic correction apparatus is a gamma correction apparatus included in a transmitter for transmitting the color signals.",
    "28. The apparatus of claim 25, wherein the non-linear characteristic correction apparatus is a gamma correction apparatus included in a receiver for receiving the color signals.",
    "29. The apparatus of claim 25, wherein the first look up table is a writable/readable memory and can use a programmable addressing method.",
    "30. The apparatus of claim 25, wherein the second look up table is a writable/readable memory and can use a programmable addressing method.",
    "31. A method for correcting non-linear characteristics of a system, using look up tables, the method comprising the steps of: (a) setting a predetermined gradient and a predetermined allowable error; (b) classifying range of an N-bit digital signal by sector, based on the predetermined gradient and the predetermined allowable error; (c) dividing the N-bit digital signal into upper and lower bits, according to the gradient of the sector including the current digital signal to be corrected, and the predetermined allowable error; (d) reading the first and second data stored in a look up table, according to the upper bits; (e) multiplying the second data by the lower bits; and (f) adding the first data to the product of the multiplication, wherein the sum of the addition is an N-bit digital corrected signal for compensating for the non-linear characteristics, used by the system instead of the N-bit digital signal, and the first data is a predetermined number of digital corrected signals, and the second data is the gradient of the digital corrected signal with respect to the gradient of the digital signal, and the control signal is generated such that more bits of the digital signal are allocated as upper bits in a sector having a steeper gradient.",
    "32. The method of claim 31, wherein in the step (c), the entire N-bit digital signal is divided as upper bits, when the gradient of the sector including the current N-bit digital signal to be corrected is greater than a predetermined level.",
    "33. The method of claim 31, wherein the N-bit digital signal is one of red (R), green (G) and blue (B) signals requiring gamma correction.",
    "34. The method of claim 31, wherein the method further comprises the steps of: (g) selecting one of red (R), green (G) and blue (B) color signals to be gamma-corrected in response to a system clock signal and frequency-divided system clock signal, and performing the steps (a) through (f); and (h) determining the sum obtained in the step (f) as being one of gamma-corrected R', G', and B' signals, in response to the system clock signal and the frequency-divided system clock signal, wherein the color signals are concurrently gamma-corrected.",
    "35. The method of claim 33, wherein the non-linear characteristic correction method is performed in a transmitter for transmitting the color signals.",
    "36. The method of claim 33, wherein the non-linear characteristic correction method is performed in a receiver for receiving the color signals.",
    "37. The method of claim 31, wherein the first data is written to/read from a look up table using a programmable addressing method.",
    "38. The method of claim 31, wherein the second data is written to/read from a look up table using a programmable addressing method.",
    "39. A method for correcting non-linear characteristics of a system, using look up tables, the method comprising the steps of: (a) setting a predetermined gradient and a predetermined allowable error; (b) classifying range of an N-bit digital signal by sector, based on the predetermined gradient and the predetermined allowable error; (c) dividing the N-bit digital signal into upper and lower bits, according to the gradient of the sector including the current digital signal to be corrected, and the predetermined allowable error; (d) reading the first and second data stored in a look up table, according to the upper bits; (e) multiplying the second data by the lower bits; (f) adding the first data to the upper bits; and (g) adding the sum of the addition of step (f) to the product of the multiplication, wherein the sum of the addition of step (g) is an N-bit digital corrected signal for compensating for the non-linear characteristics, used by the system instead of the N-bit digital signal, and the first data is the difference between the digital corrected signal and the digital signal, and the second data is the gradient of the digital corrected signal with respect to the gradient of the digital signal, and the control signal is generated such that more bits of the digital signal are allocated as upper bits in a sector having a steeper gradient.",
    "40. The method of claim 39, wherein in the step (c), the entire N-bit digital signal is divided as upper bits, when the gradient of the sector including the current N-bit digital signal to be corrected is greater than a predetermined level.",
    "41. The method of claim 39, wherein the N-bit digital signal is one of red (R), green (G) and blue (B) signals requiring gamma correction.",
    "42. The method of claim 39, wherein the method further comprises the steps of: (h) selecting one of red (R), green (G) and blue (B) color signals to be gamma-corrected in response to a system clock signal and frequency-divided system clock signal, and performing the steps (a) through (g); and (i) determining the sum obtained in the step (f) as being one of gamma-corrected R', G', and B' signals, in response to the system clock signal and the frequency-divided system clock signal, wherein the color signals are concurrently gamma-corrected.",
    "43. The method of claim 41, wherein the non-linear characteristic correction method is performed in a transmitter for transmitting the color signals.",
    "44. The method of claim 41, wherein the non-linear characteristic correction method is performed in a receiver for receiving the color signals.",
    "45. The method of claim 39, wherein the first data is written to/read from a look up table using a programmable addressing method.",
    "46. The method of claim 39, wherein the second data is written to/read from a look up table using a programmable addressing method."
  ],
  "description_excerpt": "1. Field of the Invention\n\nThe present invention relates to systems having non-linear characteristics such as gamma characteristics, and more particularly, to an apparatus and method for converting input data so that a system having a non-linear response generates output that is linearly related to the input data.\n\n2. Description of the Related Art\n\nIn general, many systems exhibit some type of non-linear characteristics or responses. Particularly, many home appliances, computers, and communication systems, which are familiar in our daily life, have non-linear characteristics. For example, t display device, such as a cathode ray tube (CRT) in a television (TV) or a computer monitor, or a charge coupled device (CCD) in a camera, shows a gamma intensity distribution caused by non-linearity of phosphorescence in the device. In a CRT, the gamma characteristics cause output brightness to have a non-linear relationship with an input luminance signal. This can distort the image on the CRT if the input signal is generated under the assumption of a linear response. Thus, it is necessary to apply gamma correction such input signals to ensure a linear relationship between the input signal and the output luminance.\n\nFIG. 1 is a graph illustrating gamma correction for a CRT of a TV. Here, the X-axis represents the normalized voltage of a video signal input to the CRT, and the Y-axis represents the normalized intensity of the light emitted from the CRT. If the input voltage of the CRT and the intensity of the emitted light are normalized, the CRT has non-linear characteristics 14 as shown in FIG. 1.",
  "cpc": [
    "H04N 1/407",
    "H04N 1/401",
    "H04N 9/69"
  ],
  "ipc": [
    "H04N 1/401",
    "H04N 1/407",
    "H04N 9/69"
  ],
  "assignees": [
    "Samsung Electronics Co Ltd"
  ],
  "inventors": [
    "Mal-seob Kwak",
    "Jun Sunwoo",
    "In-jun Hwang",
    "Bong-Soon Kang"
  ],
  "filing_date": "1997-10-03",
  "publication_date": "2000-12-26",
  "grant_date": "2000-12-26",
  "priority_date": "1996-10-04",
  "application_number": "US-94398297-A",
  "family_id": "27349399",
  "cited_by_count": 71,
  "citations": [
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    "US5175621A",
    "US5196924A",
    "US5282036A",
    "US5408267A",
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    "US5706058A"
  ]
}