Method and apparatus for automatic optical focusing on an optically discernible feature on an object

Claim 3

The method claimed in claim 1 including the further step of adjusting the distance between said instrument and said object to said optimum focal distance.

Claim 4

The method claimed in claim 1 where the step of determining the values of the coefficients is made by the least squares best fit method.

Claim 5

The method claimed in claim 1 wherein said optical instrument is a microscope, and wherein said image scanning means includes a photodetector behind a slit for measuring light intensities across a magnified image of a specimen mounted on a stage having adjustment means for focusing said microscope.

Claim 6

The method claimed in claim 4 wherein the microscope image scanning means and stage adjustment means is controlled by a digital processor.

Claim 7

The method claimed in claim 5 wherein the steps of noting the variations in measured light intensities, determining an edge value, and determining optimum focal distance is performed by said digital processor.

Claim 8

The method claimed in claim 3 wherein said optical instrument is a camera.

Claim 9

The method claimed in claim 7 wherein said camera is a television camera.

Claim 10

Apparatus for automatically adjusting an associated optical system to optimum focus upon an object after an initial focus upon a fixed feature on said object, said apparatus comprising: first electrical driving means for varying the focal distance between the optical system and the fixed feature on said object; scanning means located at the focal plane of said optical system, said scanning means including second electrical driving means for scanning a narrow transparent slit across an image of said fixed feature on said object; detecting means responsive to the illumination transmitted by said transparent slit for measuring variations in illumination intensities as said slit is scanned across said image, and for generating electrical output signals indicative of said measured variations; and processing means responsive to said electrical output signals for controlling the operation of said first and said second electrical driving means, said processing means determining edge values (E.V.) of a scan made at the initial focus and at each of a plurality of scans taken at differing focal distances different from that of said initial scan, a plot of said edge values as a function of said focal distances being a curve of the form, E.V.=ae 2 +be+c, said processing means determining therefrom the optimum focal distance, e best , by first determining the values of the coefficients, "a" and "b", by the least squares best fit method then determining focal distance from the equation, e best =-b/2a, and then adjusting said first electrical driving means to the point of said optimum focal distance.

Claim 11

Apparatus for automatically adjusting an associated optical system to optimum focus upon an object after an initial focus upon a fixed feature on said object, said apparatus comprising: first electrical driving means for varying the focal distance between the optical system and the fixed feature on said object; scanning means located at the focal plane of said optical system, said scanning means including second electrical driving means for scanning a narrow transparent slit across an image of said fixed feature on said object; detecting means responsive to the illumination transmitted by said transparent slit for measuring variations in illumination intensities as said slit is scanned across said image, and for generating electrical output signals indicative of said measured variations; and processing means responsive to said electrical output signals for controlling the operation of said first and said second electrical driving means, said processing means determining edge values (E.V.) of a scan made at the initial focus and at each of a plurality of scans taken at differing focal distances different from that of said initial scan, a plot of said edge values as a function of said focal distances being a curve of the form, E.V.=ae 2 +be+c, said processing means determining therefrom the optimum focal distance, e best , by first determining the values of the coefficients, "a" and "b", by the least squares best fit method then determining focal distance from the equation, e best =-b/2a, and then adjusting said first electrical driving means to the point of said optimum focal distance.

Claim 12

The apparatus claimed in claim 9 wherein said optical system is part of a camera.

Claim 13

The apparatus claimed in claim 9 wherein said optical system is part of an optical microscope.

Claim 14

The apparatus claimed in claim 9 where said optical system is part of a scanning densitometer.

Claim 15

Apparatus for automatically adjusting the optical system of an associated television camera to optimum focus upon an object after an initial focus upon a feature on said object, said apparatus comprising: electrical driving means coupled to the optical system for varying the focus between the television camera and the object; digitizing circuitry coupled to the output of the television camera for converting television synchronizing signals and detected image signals into corresponding digital signals; digital processing means coupled to the output of said digitizing circuitry for controlling the operation of said electrical driving means, said processing means determining from said digitizing synchronizing signals and from the intensity of said detected image signals edge values of television raster scans made substantially at the initial focus and at each of a plurality of raster scans taken at differing focal distances different from that of said initial focus, a plot of said edge values as a function of said focal distances being a curve of the form, edge value (E.V.)=ae 2 +be+c, said digital processing means determining therefrom the optimum focal distance, e best , by first determining the values of the coefficients, "a" and "b", by the least squares best fit method then determining focal distance from the equation, e best =-b/2a, and adjusting said electrical driving means to the point of said optimum focal distance.

Claim 16

Apparatus for automatically adjusting the optical system of an associated television camera to optimum focus upon an object after an initial focus upon a feature on said object, said apparatus comprising: electrical driving means coupled to the optical system for varying the focus between the television camera and the object; digitizing circuitry coupled to the output of the television camera for converting television synchronizing signals and detected image signals into corresponding digital signals; digital processing means coupled to the output of said digitizing circuitry for controlling the operation of said electrical driving means, said processing means determining from said digitizing synchronizing signals and from the intensity of said detected image signals edge values of television raster scans made substantially at the initial focus and at each of a plurality of raster scans taken at differing focal distances different from that of said initial focus, a plot of said edge values as a function of said focal distances being a curve of the form, edge value (E.V.)=ae 2 +be+c, said digital processing means determining therefrom the optimum focal distance, e best , by first determining the values of the coefficients, "a" and "b", by the least squares best fit method then determining focal distance from the equation, e best =-b/2a, and adjusting said electrical driving means to the point of said optimum focal distance.