Picture signal enhancement circuit includes a non-linear circuit for enhancing the picture signal in dependence of histograms measured at transitions in the picture signal

• US 5,734,746 A
• Filed: 08/27/1996
• Issued: 03/31/1998
• Est. Priority Date: 10/08/1993
• Status: Expired due to Term

• Current Assignee: Entropic Communications Incorporated (Maxlinear Incorporated)
• Original Assignee: US Philips Corporation (Koninklijke Philips N.V.)
• Inventors: Jaspers, Cornelis A. M.
• Primary Examiner(s): Mancuso, Joseph
• Assistant Examiner(s): Johnson, Timothy M.
• Application Number:
  US08/704,401
• Time in Patent Office: 581 Days
• Field of Search: 382/168, 382/169, 382/172, 382/266, 348/672, 348/674, 348/254
• US Class Current: 382/169
• CPC Class Codes: H04N 5/20 Circuitry for controlling amplitude response
• CPC Class Codes: H04N 5/202 Gamma control circuits for controlling camera response irrespective of the scene brightness H04N23/82

Abstract

In a picture signal enhancement circuit having a circuit (3) for measuring a histogram and a non-linear processing circuit (1), coupled to the measuring circuit (3), for enhancing the picture signal in dependence upon the measured histogram, the histogram is measured only at transitions in the picture signal.

Claims

1. A picture signal enhancement circuit comprising means for measuring a histogram, and a non-linear processing circuit, coupled to the measuring means, for enhancing the picture signal in dependence upon the measured histogram, characterized in that the histogram is measured only at transitions in the picture signal, wherein the picture signal has a first number of pixels for which the histogram can be determined, while the histogram is actually determined at the transitions for a second number of pixels, the histogram comprising a predetermined number of histogram segments, and the contents of each of these histogram segments being multiplied by a correction factor which depends on a difference between the first number and the second number of pixels.

2. A picture signal enhancement circuit as claimed in claim 1, wherein the difference is multiplied by a value which decreases with an increase of the difference before the correction factor is determined on the basis of said difference.

3. A picture signal enhancement circuit comprising means for measuring a histogram, and a non-linear processing circuit, coupled to the measuring means, for enhancing the picture signal in dependence upon the measured histogram, characterized in that the histogram is measured only at transitions in the picture signal, wherein the picture signal has a first period of time per picture for which the histogram can be determined, while the histogram is actually determined at the transitions for a total second period of time, the histogram comprising a predetermined number of histogram segments, and the contents of each of these histogram segments being multiplied by a correction factor which depends on a difference between the first period of time and the second period of time, respectively.

4. A picture signal enhancement circuit as claimed in claim 3, wherein the difference is multiplied by a value which decreases with an increase of the difference before the correction factor is determined on the basis of said difference.