Automatic light control system

An electro-optical system comprising:

• a lens system having an iris diaphragm,
• a television camera to convert light energy to video output signals,
• said television camera further comprising a gain determining element,
• a first feedback loop responsive to said video output signals to stably control said gain determining element to provide optimum operation below overloading of said camera,
• a second feedback loop responsive to said video output signals to adjust said iris diaphragm to admit an amount of light energy for optimum video output signals below overloading of said camera,
• a first concentrically graded neutral density filter,
• a second neutral density filter having a transmission of the order of negative powers of ten, and
• means to mechanically couple said second neutral density filter for insertion into and out of the light path of said lens system.

A television system comprising:

• a. a first optical variable attenuation element,
• b. an image intensifier coupled to intensify the images passing through said optical variable attenuation element,
• c. an electronic variable gain element coupled to said image intensifier to convert the images from said image intensifer to electrical signals,
• d. means to detect said electrical signals to provide an automatic light control voltage,
• e. a first feedback loop comprising means rapidly responsive to said automatic light control voltage to control said electronic variable gain element to effect optimum gain operation below overloading of said gain element, and
• f. a second feedback loop comprising means less rapidly responsive to said automatic light control voltage than said first feedback loop to control said optical variable gain element to provide in conjunction with said first feedback loop a constant optimum illumination on said electronic variable gain element.

In a television system having a television camera tube to produce video output:

• a. a camera tube gain determining electrode,
• b. a source of camera tube operating voltage,
• c. means to couple said source to said electrode,
• d. means responsive to the video output to generate corresponding level signals,
• e. non-linear control function means saturable at low video output levels to regulate said source to provide rapid increase of source voltage coupled to said electrode so that maximum system gain is achieved before target current from said camera tube is reduced to low levels.

In a television system having a television camera tube to produce video output:

• a camera tube gain determining electrode,
• a source of camera tube operating voltage,
• means to couple said source to said electrode,
• means responsive to the video output to generate the corresponding level signals, and
• non-linear control function means saturable at low video output levels to regulate said source to provide an increase of source voltage coupled to said electrode so that maximum system gain is achieved before target current from said camera tube is reduced to low levels.