Automatic dark level zeroing for an analog video signal
Assignee3M Company
InventorKenneth I. Wolfe
Life of this patent
Estimating the term…
Abstract
An automatic dark level zeroing circuit removes a dark level DC bias from an analog video signal generated by a charge-coupled device (CCD) camera, The automatic dark level zeroing circuit is DC-coupled to the CCD camera such that there is no loss of low frequency information in the analog video signal, The automatic dark level zeroing circuit forms an adaptive feedback loop that removes the dark level DC bias from the analog video signal by using a sampled value of the analog video signal that represents an internally masked pixel to produce a zero correction signal that is then combined with the analog video signal to remove the dark level DC bias without removing any useful video information or otherwise altering the information content of the analog video signal,
Claims13
An automatic dark level zeroing circuit for removing a dark level DC bias from an analog video signal generated by a charge-coupled device (CCD) camera, comprising:
- a summing node that is DC-coupled to the CCD camera and combines the analog video signal and a zero correction signal to produce a zeroed video signal;
- a video gain amplifier connected to the summing node that amplifies the zeroed video signal in response to a user-supplied setting to produce an output video signal;
- a sample/hold circuit that samples the output video signal to produce a sampled video value in response to a sample command indicative of when the output video signal represents the dark level DC bias;
- and
- a difference integrator connected to the sample/hold circuit to subtract the sampled video value from a zero voltage value to produce the zero correction signal,
- such that the automatic dark level zeroing circuit forms an adaptive feedback loop that removes the dark level DC bias from the analog video signal.
An automatic dark level zeroing circuit for removing a dark level DC bias from an analog video signal generated by a charge-coupled device (CCD) camera, comprising:
- a summing node that is DC-coupled to the CCD camera and combines
- the analog video signal and a zero correction signal to produce a zeroed video signal;
- a video gain amplifier connected to the summing node that amplifies the zeroed video signal in response to a user-supplied setting to produce an output video signal;
- means for sampling the output video signal to produce a sampled video value in response to a sample command indicative of when the output video signal represents the dark level DC bias;
- and
- means for averaging the sampled video value over a plurality of scan times for the CCD camera to produce the zero correction signal,
- such that the automatic dark level zeroing circuit forms an adaptive feedback loop that removes the dark level DC bias from the analog video signal.
An automatic dark level zeroing circuit for removing a dark level DC bias from an analog video signal generated by a charge-coupled device (CCD) camera, comprising:
- a summing node that is DC-coupled to the CCD camera and combines the analog video signal and a zero correction signal to produce a zeroed video signal;
- a reference voltage supplied to the summing node, the reference voltage being a fixed voltage value substantially equal to and polarity from the dark level DC bias;
- means for sampling the zeroed video signal to produce a sampled video value in response to a sample command indicative of when the zeroed video signal represents the dark level DC bias:
- and
- means for averaging the sampled video value over a plurality of scan times for the CCD camera to produce the zero correction signal,
- such that the automatic dark level zeroing circuit forms an adaptive feedback loop that removes the dark level DC bias from the analog video signal.
An automatic dark level zeroing circuit for removing a dark level DC bias from an analog video signal generated by a charge-coupled device (CCD) camera, comprising:
- a summing node that is DC-coupled to the CCD camera and combines the analog video signal and a zero correction signal to produce a zeroed video
- means for sampling the zeroed video signal to produce a sampled video value in response to a sample command indicative of when the zeroed video signal represents the dark level DC bias:
- and
- means for averaging the sampled video value over a plurality of scan times for the CCD camera to produce the zero correction signal,
- such that the automatic dark level zeroing circuit forms an adaptive feedback loop that removes the dark level DC bias from the analog video signal and the zeroed video signal is maintained within 0 V, .+-. a nominal voltage variance that is less than a voltage variance of 3 least significant bits (LSB) of a flash analog-to-digital (A/D) converter that receives the zeroed video signal.
Dependencies are inferred from the claim text.