Ambient light automatic gain control for electronic imaging cameras and the like
First Claim
1. Ambient light automatic gain control apparatus for use with an electronic imaging camera having a multi-element light sensing array and a video amplifier for amplifying signals produced by the array, said apparatus comprising:
- a fiber optic link that collects light from the sky, and couples the light to a predetermined plurality of light sensing elements of the light sensing array that produce a reference voltage in response thereto; and
automatic gain control circuits coupled to the light sensing array for controlling the gain of the video amplifier of the camera as a function of the reference voltage produced by the predetermined plurality of light sensing elements.
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Accused Products
Abstract
Apparatus that performs automatic gain control (AGC) for an electronic imaging camera, especially in outdoor surveillance applications. A fiber optic link is used to collect ambient light and couple this light onto a small portion of a light sensing array of the camera. A reference voltage produced by the light sensing array in response to the light from the fiber is used by AGC circuits in the camera to control the integration time of light sensing elements of the array, the gain of the camera'"'"'s video amplifier, and lens aperture, if necessary. These camera gain controls are adjusted to maintain the reference voltage derived from the light provided by the fiber optic link to be within a predefined range as the ambient light level varies due to weather conditions and time of day. Methods of providing automatic gain control correction are also disclosed.
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Citations
22 Claims
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1. Ambient light automatic gain control apparatus for use with an electronic imaging camera having a multi-element light sensing array and a video amplifier for amplifying signals produced by the array, said apparatus comprising:
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a fiber optic link that collects light from the sky, and couples the light to a predetermined plurality of light sensing elements of the light sensing array that produce a reference voltage in response thereto; and automatic gain control circuits coupled to the light sensing array for controlling the gain of the video amplifier of the camera as a function of the reference voltage produced by the predetermined plurality of light sensing elements. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. Ambient light automatic gain control apparatus for use with an electronic imaging camera having a multi-element light sensing array and a video amplifier for amplifying signals produced by the array, said apparatus comprising:
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a fiber optic link that collects light from the sky, and couples the light to a predetermined plurality of light sensing elements of the light sensing array that produce a reference voltage in response thereto; and automatic gain control circuits coupled to the light sensing array for controlling the integration time of all light sensing elements thereof and gain of the video amplifier of the camera as a function of the reference voltage produced by the predetermined plurality of light sensing elements. - View Dependent Claims (15)
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16. A method of automatically controlling the gain of an electronic imaging camera having a multi-element light sensing array and a video amplifier for amplifying signals produced by the array, said method comprising the steps of:
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collecting light from the sky; coupling the collected light to a predetermined plurality of light sensing elements of the light sensing array; producing a reference voltage in response to the light coupled to the predetermined plurality of light sensing elements; and adjusting the gain of the video amplifier of the electronic imaging camera in response to and as a function of the reference voltage. - View Dependent Claims (17, 18, 19)
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20. A method of automatically controlling the gain of an electronic imaging camera having a multi-element light sensing array and a video amplifier for amplifying signals produced by the array, said method comprising the steps of:
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collecting light from the sky; coupling the collected light to a predetermined plurality of light sensing elements of the light sensing array; producing a reference voltage in response to the light coupled to the predetermined plurality of light sensing elements; adjusting the gain of the video amplifier of the electronic imaging camera in response to and as a function of the reference voltage; and adjusting the integration time of all light sensing elements of the array as a function of the reference voltage produced by the predetermined plurality of light sensing elements. - View Dependent Claims (21, 22)
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Specification