Radiation sensitive automatic focus system

Claim 1

A system for automatically keeping a light image in sharp focus, comprising: means for deflecting a representative portion of an image forming main beam of light to form a sample beam producing a sample image; means for altering the focus of the sample image to simulate adjustment of the focus of the light image formed by said main beam; means for sensing the sharpness of focus of said sample image; comparing means for determining whether said sample image is in sharper focus when the focus of said sample image is altered to simulate adjustment or when it is not so altered; and actuating means for automatically adjusting the focus of said light image formed by said main beam when said sample image is in sharper focus in its altered form; the altering means including a plurality of optical elements having mutUally different focal lengths, means for blanking off said optical elements from light from said sample beam and unblanking means for allowing light from said sample beam to pass through each of said optical elements in sequence to form successive images simulating different conditions of focus of the light image formed by the main light beam; the sensing means including means for producing electrical signals indicative of the sharpness of focus of each of said successive images; and the comparing means including a differentiating circuit for selecting the maximum signal from among the signals produced by the sensing means.

Claim 2

A system for automatically keeping a light image in sharp focus, comprising: means for deflecting a representative portion of an image forming main beam of light to form a sample beam producing a sample image; means for altering the focus of the sample image to simulate adjustment of the focus of the light image formed by said main beam; means for sensing the sharpness of focus of said sample image; comparing means for determining whether said sample image is in sharper focus when the focus of said sample image is altered to simulate adjustment or when it is not so altered; and actuating means for automatically adjusting the focus of said light image formed by said main beam when said sample image is in sharper focus in its altered form; the altering means including a plurality of optical elements having mutUally different focal lengths, means for blanking off said optical elements from light from said sample beam and unblanking means for allowing light from said sample beam to pass through each of said optical elements in sequence to form successive images simulating different conditions of focus of the light image formed by the main light beam; the sensing means including means for producing electrical signals indicative of the sharpness of focus of each of said successive images; and the comparing means including a differentiating circuit for selecting the maximum signal from among the signals produced by the sensing means.

Claim 3

A system for automatically keeping a projected film image in sharp focus on a screen by adjustment of the projection apparatus comprising: beam divider means for deflecting a representative portion of a projected main light beam to form a sample beam; a plurality of lenses positioned for intercepting and transmitting light from said sample beam, said lenses having different focal lengths to form a sample image in sharp focus for different conditions of focus of the film image formed by said projected main light mean; means for blanking off said lenses from light from said sample beam and unblanking means cooperating with said lenses to unblank each lens in sequence while keeping the other lenses blanked off; a television pickup tube so positioned that successive sample images will be formed at the pickup tube by light transmitted through each of the lenses as the lenses are sequentially unblanked; means for scanning the television pickup tube whereby corresponding electrical signals proportional to the sharpness of focus of the sample images on the tube are produced; means for amplifying and differentiating said electrical signals; means for integrating the amplified and differentiated electrical signals corresponding to each of the successive sample images; a scanner switch device cooperating with said unblanking means for sequentially passing the electrical signal corresponding to the sample image produced by each lens to the integrating means while said lens is unblanked; differential relay means for comparing the integrated signals and selecting the strongest of said integrated signals; and a reversible motor actuated by said differential relay means to cause a focus adjusting means to adjust the focus of the projecting apparatus in the direction indicated by said strongest signal.

Claim 4

A system for automatically keeping a projected film image in sharp focus on a screen by adjustment of the projection apparatus comprising: beam divider means for deflecting a representative portion of a projected main light beam to form a sample beam; a plurality of lenses positioned for intercepting and transmitting light from said sample beam, said lenses having different focal lengths to form a sample image in sharp focus for different conditions of focus of the film image formed by said projected main light mean; means for blanking off said lenses from light from said sample beam and unblanking means cooperating with said lenses to unblank each lens in sequence while keeping the other lenses blanked off; a television pickup tube so positioned that successive sample images will be formed at the pickup tube by light transmitted through each of the lenses as the lenses are sequentially unblanked; means for scanning the television pickup tube whereby corresponding electrical signals proportional to the sharpness of focus of the sample images on the tube are produced; means for amplifying and differentiating said electrical signals; means for integrating the amplified and differentiated electrical signals corresponding to each of the successive sample images; a scanner switch device cooperating with said unblanking means for sequentially passing the electrical signal corresponding to the sample image produced by each lens to the integrating means while said lens is unblanked; differential relay means for comparing the integrated signals and selecting the strongest of said integrated signals; and a reversible motor actuated by said differential relay means to cause a focus adjusting means to adjust the focus of the projecting apparatus in the direction indicated by said strongest signal.

Claim 6

A method for automatically keeping a projected light image in sharp focus comprising: projecting an image forming light beam, separating a representative sample portion of light from said image forming light beam; optically, sequentially altering said sample portion of light to simulate different conditions of focus of the light image formed by said beam; imaging the optically altered sample portion of light to produce sequential sample images and electronically producing an electrical signal which is proportional to the degree of contrast in each of the sample images; comparing said electrical signals and causing the focus of the light image formed by said light beam to be corrected whenever the strongest of the electrical signals compared corresponds to simulation of a condition of focus which differs from the actual condition of focus of the image formed by the light beam.

Claim 7

A method for automatically keeping a projected light image in sharp focus comprising: projecting an image forming light beam, separating a representative sample portion of light from said image forming light beam; optically, sequentially altering said sample portion of light to simulate different conditions of focus of the light image formed by said beam; imaging the optically altered sample portion of light to produce sequential sample images and electronically producing an electrical signal which is proportional to the degree of contrast in each of the sample images; comparing said electrical signals and causing the focus of the light image formed by said light beam to be corrected whenever the strongest of the electrical signals compared corresponds to simulation of a condition of focus which differs from the actual condition of focus of the image formed by the light beam.