Intensity correction device for providing a correction signal for automatically correcting an intensity of a video signal

• US 5,315,389 A
• Filed: 06/25/1992
• Issued: 05/24/1994
• Est. Priority Date: 06/28/1991
• Status: Expired due to Term

• Current Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Izawa, Yosuke, Okumura, Naoji
• Primary Examiner(s): Groody, James J.
• Assistant Examiner(s): GRANT, CHRISTOPHER C
• Application Number:
  US07/904,214
• Time in Patent Office: 698 Days
• Field of Search: 358/168, 358/169, 358/163, 358/160, 358/166, 382/51, 382/18
• US Class Current: 348/672
• CPC Class Codes: G06T 5/40 using histogram techniques
• CPC Class Codes: G06T 5/92 based on global image properties
• CPC Class Codes: H04N 5/20 Circuitry for controlling amplitude response

Abstract

The invention relates to an intensity correction device for automatically adjusting an intensity of an input video signal by detecting luminance characteristics of the input signal, and provide intensity correction with maintaining clear image by reducing magnitude of the correction signal or by not effecting correction when the luminance level of the input luminance signal is concentrated to a certain luminance level. The intensity correction device includes a histogram memory, a look-up table operating circuit, a look-up table, a maximum value detecting circuit, and an inverter and a multiplier, limiter, or a gain control circuit. By this, when a luminance level of the input video signal is concentrated to a certain luminance level, magnitude of the correction signal can be reduced or made zero. Therefore, by detecting the characteristics of the input image, the intensity of the input video signal can be automatically corrected to the optimal image for providing better picture quality.

Claims

1. An intensity correction device comprising:

a histogram memory for forming a histogram of an input luminance signal;

a look-up table operating circuit for accumulating the histogram and normalizing the accumulated histogram so that a maximum cumulative frequency of occurrence of the input luminance signal becomes a maximum value of an output luminance signal;

a look-up table memory for storing the normalized data and outputting a correction signal in response to the input luminance signal;

a maximum value detecting circuit for detecting a maximum value of the histogram; and

a multiplier for multiplying an inverse value of the maximum value detected by said maximum value detecting circuit and the correction signal.

2. An intensity correction device comprising:

a histogram memory for forming a histogram of an input luminance signal;

a look-up table operating circuit for accumulating the histogram and normalizing the accumulated histogram so that the maximum cumulative frequency of occurrence of the input luminance signal becomes a maximum value of an output luminance signal;

a look-up table memory for storing the normalized data and outputting a correction signal in response to the input luminance signal;

a maximum value detecting circuit for detecting a maximum value of differences of the normalized data; and

a multiplier for multiplying an inverse value of the maximum value detected by said maximum value detecting circuit and the correction signal.

3. An intensity correction device comprising:

a histogram memory for forming a histogram of an input luminance signal;

a look-up table operating circuit for accumulating the histogram and normalizing the accumulated histogram so that a maximum cumulative frequency of occurrence of the input luminance signal becomes a maximum value of an output luminance signal;

a look-up table memory for storing the normalized data and outputting a correction signal in response to the input luminance signal;

a maximum value detecting circuit for detecting a maximum value of differences of the normalized data; and

a limiter for setting the correction signal to zero when said maximum value detected by the maximum value detecting circuit exceeds a predetermined value.

4. An intensity correction device comprising:

a histogram memory for forming a histogram of an input luminance signal;

a look-up table operating circuit for accumulating the histogram and normalizing the accumulated histogram so that a maximum cumulative frequency becomes a maximum value of an output luminance signal;

a look-up table memory for storing the normalized data and outputting a correction signal in response to the input luminance signal;

a maximum value detecting circuit for detecting a maximum value of differences of the normalized data; and

a gain control circuit for varying gain of said correction signal depending upon said maximum value detected by said maximum value detecting circuit.