Video signal processor

• US 4,811,097 A
• Filed: 10/29/1987
• Issued: 03/07/1989
• Est. Priority Date: 10/29/1987
• Status: Expired due to Term

• Current Assignee: Harris Corporation (L3Harris Technologies, Inc.)
• Original Assignee: Videotek Incorporated (L3Harris Technologies, Inc.)
• Inventors: Ritter, David W., Zortea, Anthony
• Primary Examiner(s): Groody, James J.
• Assistant Examiner(s): NOT, DEFINED
• Application Number:
  US07/114,685
• Time in Patent Office: 495 Days
• Field of Search: 358/36, 358/160, 358/167, 358/139, 375/11, 375/12, 375/13, 375/118, 455/296, 455/306, 455/307, 333/28 R, 333/28 T, 364/572, 364/576, 364/724, 364/726, 364/825, 364/827
• US Class Current: 348/608
• CPC Class Codes: H04N 5/21 Circuitry for suppressing or minimising disturbance, e.g. moiré or halo

Abstract

In one embodiment, the video signal generator outputs a standardized analog video signal. The signal generator includes a clock controlling a sequential address generator. The address generator activates a memory device that is, for example, a ROM. A distortion conditioned standardized digital video signal is stored in the ROM. This distortion conditioned signal has distortion correction characteristics matching an output filter. Following the ROM is a D to A converter that converts the conditioned digital video signal into a conditioned analog video signal. A simple filter follows the D to A converter. The filter introduces distortion into the signal applied at its input but since that signal already has distortion correction characteristics therein, the distortion correction characteristics of the input signal match and substantially cancel the distortion introduced into that signal by the filter. Therefore, a standardized analog video signal is produced at the output of the filter. The real time video signal processor, in another embodiment of the present invention, utilizes a distortion correction operator in conjunction with a memory that introduces into the digital video signal distortion correction characteristics. As with the signal generator, the distortion correction characteristics match and cancel the distortion introduced into the analog signal by the output filter.

Claims

1. A video signal generator for generating a standardized video signal in analog form comprising:

controller means;

means for storing a distortion conditioned standardized digital video signal having distortion correction characteristics, said means for storing coupled to and controlled by said controller means to output said conditioned standardized video signal;

a digital to analog converter means for receiving said conditioned standardized video signal and for converting the same into a distortion conditioned analog signal representative thereof;

a filter means for receiving said conditioned analog signal and for filtering the same;

wherein said filter means introduces distortion into said conditioned analog signal and wherein said distortion correction characteristics of said distortion conditioned standardized video signal substantially match and cancel the distortion introduced by said filter means thereby producing said standardized analog video signal at an output of said filter means.

2. A video signal generator as claimed in claim 1 wherein said distortion introduced by said filter means is a phase distortion of said analog signal and said distortion correction characteristics cancel said phase distortion.

3. A video signal generator as claimed in claim 2 wherein said filter means is a six pole filter.

4. A video signal generator as claimed in claim 1 wherein said means for storing is a read only memory device.

5. A real time video signal processor for processing an analog video signal comprising:

an analog to digital converter means for converting said analog video signal into a representative digital video signal;

means for introducing into said digital video signal distortion correction characteristics and producing a distortion conditioned digital video signal;

a digital to analog converter means for converting said distortion conditioned digital video signal and producing a representative distortion conditioned analog video signal;

a filter means for receiving said distortion conditioned analog video signal and for filtering the same;

wherein said filter means introduces distortion into said conditioned analog signal and wherein said distortion correction characteristics of said distortion conditioned video signal match and cancel the distortion introduced by said filter means thereby producing said analog video signal at an output of said filter means.

6. A real time video signal processor as claimed in claim 5 wherein said means for introducing includes a memory means for storing said digital signal, a means for dynamically modifying said stored digital analog signal and incorporating said distortion correction characteristics therein, and means for outputting the distortion conditioned video signal from said memory means.

7. A real time video signal processor as claimed in claim 5 wherein said memory means is a digital storage device.

8. A real time video signal processor as claimed in claim 6 wherein said means for modifying is at least one digital finite impulse response filter.

9. A method of producing a standardized, analog video signal via a filter that introduces a substantially known distortion into analog video signals passing therethrough comprising the steps of:

obtaining distortion correction factors for said filter based upon said known distortion;

generating a standardized, digital video signal;

transforming said standardized digital video signal, with a known mathematical operation, into a series of mathematical waveform representative functions;

modifying said waveform representative functions to correspond to said distortion correction factors;

inversely transforming the modified waveform representative functions to obtain a distortion conditioned standardized digital video signal;

storing said distortion conditioned standardized digital video signal;

converting said distortion conditioned standardized digital video signal into a distortion conditioned analog video signal; and

passing said distortion conditioned analog video signal through said filter wherein the distortion conditioning characteristics of said signal substantially cancel said known distortion of said filter thereby producing said standardized analog video signal.

10. A method of producing a standardized analog video signal as claimed in claim 9 wherein said known mathematical operation is a Fourier transform and said inverse transformation is an inverse Fourier transform.

11. A method of producing a standardized analog video signal as claimed in claim 10 wherein said storing is digital in nature.

12. A method producing a standardized analog video signal as claimed in claim 9 wherein said distortion correction factors represent correction factors for phase errors in said filter.

13. A method of producing a standardized analog video signal via a filter that introduces a substantially known distortion into analog video signals passing therethrough comprising the steps of:

generating a distortion conditioned standardized digital video signal having distortion correction characteristics that substantially match and cancel said distortion contributed to signals passing through said filter;

converting said distortion conditioned digital video signal into a distortion conditioned, standardized analog video signal;

passing said conditioned analog video signal through said filter wherein the distortion correction characteristics of the conditioned analog signal substantially match and cancel the distortion introduced therein by said filter thereby generating a substantially distortion free, standardized analog video signal.