Signal level control for video system
AssigneeWelch Allyn, Inc.
InventorAndrew Longacre, Jr.
Life of this patent
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Abstract
An automatic signal level control for use in a video system using a solid state imager capable of integrating pulsed light images of a target imaged thereon. An automatic gain control is used to adjust the gain of a variable gain amplifier in the output circuit of the image sensor. A strobe lamp is used to illuminate the target during each imaging sequence. The feedback signal to the amplifier is compared to an upper and lower threshold and, in response thereto, the number of pulses generated during each illumination sequence are adjusted to maintain the video signal levels within a desired operating range.
Claims12
An automatic signal level control for use in a video system wherein a solid state image sensor records light images of a remote target and provides video signals indicative of the target information that includes
- a variable gain amplifier for adjusting the level of the video signal delivered to the video processor,
- an automatic gain control circuit for sensing the level of the video signal output of the amplifier and providing a feedback signal to the amplifier for maintaining the level of the said video signal within an optimum range,
- a strobe lamp for illuminating a target within the viewing range of the sensor, said lamp having a programmable lamp drive for adjusting the pulse rate of the lamp to control the amount of illumination falling on the target during each imaging sequence,
- a comparator means for sensing the level of the feedback signal in the gain control circuit and providing a first output signal when the gain level falls below a lower threshold level and a second output signal when the gain level rises above an upper threshold level, and
- control means responsive to the comparator means output for programming the lamp drive to increase the pulse rate when the gain exceeds the upper threshold level and to decrease the pulse rate when the gain falls below the lower threshold level whereby the video signal level is maintained within the desired optimum range.
A method of controlling a video signal level that includes the steps of
- providing a solid state image sensor for integrating light images of a target recorded thereon and providing a video signal of the recorded image data,
- illuminating the target with a series of light pulses during each imaging sequence,
- passing the video output signals from the imager through a variable gain amplifier,
- controlling the gain of the amplifier to maintain signal level of the video output thereof within a given range,
- changing the number of light pulses from the lamp during each illumination sequence when the gain of the amplifier falls above or below the given range.
Dependencies are inferred from the claim text.