Composite video signal correction unit for video imaging and video recording systems

• US 7,652,723 B1
• Filed: 03/16/2005
• Issued: 01/26/2010
• Est. Priority Date: 04/19/2004
• Status: Expired due to Fees

• Current Assignee: Video Accessory Corporation
• Original Assignee: Video Accessory Corporation
• Inventors: Brannan, Edward, Frey, Richard, Patton, David
• Primary Examiner(s): Tran; Trang U
• Application Number:
  US11/082,370
• Time in Patent Office: 1,777 Days
• Field of Search: 348/691, 348692-698, 348/525, 348/521, 348526-527, 348/689, 348/673, 348/677, 348/572
• US Class Current: 348/691
• CPC Class Codes: H04N 5/16 Circuitry for reinsertion of dc and slowly varying components of signal; Circuitry for preservation of black or white level

Abstract

In one embodiment, a signal processing system is provided that includes:

• • (a) a video input 400 operable to receive a first analog video signal and remove the DC voltage offset component from the video signal to form a DC-adjusted analog video signal; and
  • (b) DC restore circuitry 416 operable to set an average DC voltage of a first portion of the DC-adjusted analog video signal to a ground reference voltage to yield a DC-adjusted analog video signal. The DC-restored analog video signal is then provided to an Analog-to-Digital or A/D converter 112 for conversion into a digital video signal.

Claims

1. A signal processing system, comprising:

(a) a video input operable to receive at least a first composite analog video signal, the first composite analog video signal comprising a Direct Current or DC voltage offset component, the video input including Analog Circuit or A/C coupling operable to remove at least most of the DC voltage offset component from the first composite video signal to form a DC-adjusted composite analog video signal;

(b) DC restore circuitry operable to set an average DC voltage of at least a first portion of the DC-adjusted composite analog video signal to a reference voltage, the reference voltage being equal to ground to output a DC-restored composite analog video signal, the DC restore circuitry including a Sync Separator operable to send a hold signal during a color burst portion of the DC-adjusted composite analog video signal, and including said Sync Separator coupled to a buffered logic device operable to set an average voltage during the color burst portion of the DC-adjusted composite analog video signal; and

(c) an Analog-to-Digital or A/D converter operable to convert the DC-restored composite analog video signal into a composite digital video signal.

2. The system of claim 1, wherein, in the removing step (b), the DC voltage offset component is removed by capacitive coupling.

3. The system of claim 1, wherein the at least a first portion of the DC-adjusted composite analog video signal is the color burst of the video signal.

4. The system of claim 3, wherein the DC restore circuitry comprises an amplifier to amplify the DC-adjusted composite analog video signal, a time-gated sample-hold switch circuit to sample the DC-adjusted composite analog video signal, a switch controller to control the switch setting in the sample-hold switch circuit, and a coupling capacitor to provide level shifting of the DC-restored composite analog video signal, wherein, during a first time interval, the sample-hold circuit samples the DC-adjusted composite analog video signal, wherein the average DC voltage of the sample-hold circuit'"'"'s sample of the at least a first portion of the DC-adjusted composite analog video signal is set to the reference voltage, and wherein, during a second non-overlapping time interval, the sample-hold circuit is set to hold.

5. The system of claim 1, wherein the DC-adjusted composite analog video signal comprises ground loop interference and further comprising between the video input and DC restore circuitry:

(d) a differential input to remove at least most of the ground loop interference from the DC-adjusted composite analog video signal.

6. The system of claim 5, further comprising between the differential input and DC restore circuitry:

(e) adjustable gain circuitry operable to amplify at least a first part of the DC-adjusted composite analog video signal to a selected level, the at least a first part of the DC-adjusted composite analog video signal comprising a sync tip.

7. The system of claim 6, further comprising after the adjustable gain circuitry and before the DC restore circuitry:

(f) an adjustable equalizer to amplify at least a second part of the DC-adjusted composite analog video signal only at frequencies above a selected frequency.

8. The system of claim 7, wherein the average DC voltage is set during a first time interval and the DC restore circuitry is further operable during a second non-overlapping time interval, to stabilize at least a second portion of the DC-adjusted composite analog video signal, whereby the DC restore circuitry provides a DC-restored composite analog video signal in which the at least a first portion of the DC-restored composite analog video signal is at DC ground potential and at least a second portion of the DC-restored composite analog video signal is not at DC ground potential.

9. A signal processing system, comprising:

(a) video input means for receiving at least a first composite analog video signal, the first composite analog video signal comprising a Direct Current or DC voltage offset component, and removing at least most of the DC voltage offset component from the video signal to form a DC-adjusted composite analog video signal;

(b) DC restoring means for setting an average DC voltage of at least a first portion of the DC-adjusted composite analog video signal to a reference voltage, the reference voltage being equal to ground and the at least a first portion comprising at least one of the front porch, breezeway, color burst, and back door to yield a DC-restored composite analog video signal, the DC restore circuitry including a Sync Separator operable to send a hold signal during a color burst portion of the DC-adjusted composite analog video signal, and including said Sync Separator coupled to a buffered logic device operable to set an average voltage during the color burst portion of the DC-adjusted composite analog video signal; and

(c) an Analog-to-Digital or A/D converter operable to convert the DC-restored composite analog video signal into a composite digital video signal.

10. The system of claim 9, wherein the DC-adjusted composite analog video signal comprises ground loop interference and further comprising between the video input and DC restoring means:

(d) differential input means for removing at least most of the ground loop interference from the DC-adjusted composite analog video signal.

11. The system of claim 10, further comprising between the differential input and DC restore circuitry:

(e) adjustable gain means for amplifying at least a first part of the DC-adjusted composite analog video signal to a selected level, the at least a part of the DC-adjusted composite analog video signal comprising the sync tip.

12. The system of claim 11, further comprising after the adjustable gain means and before the DC restoring means:

(f) adjustable equalizer means for amplifying at least a second part of the DC-adjusted composite analog video signal only at frequencies above a selected frequency, wherein the at least a second part comprises the color burst but excludes the sync tip.

13. The system of claim 9, wherein the DC-restoring means stabilizes at least a second portion of the DC-adjusted composite analog video signal, the at least a second portion comprising the sync tip, whereby the DC restoring means provides a DC-restored composite analog video signal in which at least a first portion of the DC-restored composite analog video signal is at DC ground potential and at least a second portion of the DC-restored composite analog video signal is not at DC ground potential.