Apparatus and method for automatically focusing an interference microscope

Claim 1

A method of automatically focusing an optical instrument onto a sample surface, comprising the steps of: (a) moving an objective of the optical instrument to a position between the sample surface and a fringe window at a first speed by operating a position sensor to sense when the objective is a predetermined safe distance from the sample surface and turning off a motor moving the objective in response to such sensing; (b) moving the objective away from the sample surface at a second speed; (c) illuminating the sample surface with broad bank light through an interferometer in the optical instrument, splitting off a part of a resulting interference beam, and sensing intensities of the split off part of the interference beam by means of a first detector; (d) stopping movement of the objective in response to sensing of a change in a variable which is a function of sensed intensities, the change indicating presence of fringes in the interference beam; (e) moving the objective in the fringe window at a third speed, sensing a change in the variable, and recording values of the variable being produced in response to the first detector, and determining and storing a maximum value of the variable; (f) moving the objective in the fringe window at a fourth speed, sensing intensities of signals being produced by the first detector, and comparing corresponding values of the variable to the stored maximum value; (g) stopping the objective in response to the comparing when a value of the variable being produced by the first detector is equal to a preselected percentage of the maximum value.

Claim 2

A method of automatically focusing an optical instrument onto a sample surface, comprising the steps of: (a) moving an objective of the optical instrument to a position between the sample surface and a fringe window at a first speed by operating a position sensor to sense when the objective is a predetermined safe distance from the sample surface and turning off a motor moving the objective in response to such sensing; (b) moving the objective away from the sample surface at a second speed; (c) illuminating the sample surface with broad bank light through an interferometer in the optical instrument, splitting off a part of a resulting interference beam, and sensing intensities of the split off part of the interference beam by means of a first detector; (d) stopping movement of the objective in response to sensing of a change in a variable which is a function of sensed intensities, the change indicating presence of fringes in the interference beam; (e) moving the objective in the fringe window at a third speed, sensing a change in the variable, and recording values of the variable being produced in response to the first detector, and determining and storing a maximum value of the variable; (f) moving the objective in the fringe window at a fourth speed, sensing intensities of signals being produced by the first detector, and comparing corresponding values of the variable to the stored maximum value; (g) stopping the objective in response to the comparing when a value of the variable being produced by the first detector is equal to a preselected percentage of the maximum value.

Claim 6

An apparatus for automatically focusing an optical instrument onto a sample surface, comprising in combination: (a) an objective of the optical instrument; (b) means for moving the objective to a position between the sample surface and a fringe window at a first speed, wherein the moving means includes means for moving the objective of the optical instrument to the position between the sample surface and the fringe window by operating a position sensor to sense when the objective is a predetermined safe distance from the sample surface and means for turning off a motor moving the objective in response to such sensing when the objective is the predetermined safe distance from the sample surface; (c) means for moving the objective away from the sample surface at a second speed; (d) means for illuminating the sample surface with broad band light through an interferometer in the optical instrument, splitting off a part of a resulting interference beam; (e) a first detector; (f) means for sensing intensities of the split off part of the interference beam by means of the first detector; (g) means for stopping movement of the objective in response to sensing of a change in a variable which is a function of sensed intensities, the change indicating presence of fringes in the interference beam; (h) means for moving the objective in a fringe window at a third speed and sensing a resulting change in the variable; (i) means for recording values of the variable being produced in response to the first detector; (j) means for determining and storing a maximum value of the variable; (k) means for moving the objective in the fringe window at a fourth speed and sensing intensities of signals being produced by the first detector; (l) means for comparing corresponding values of the variable to the stored maximum value; and (m) means for stopping the objective in response to the comparing when a value of the variable being produced by the first detector is equal to a preselected percentage of the maximum value.

Claim 7

An apparatus for automatically focusing an optical instrument onto a sample surface, comprising in combination: (a) an objective of the optical instrument; (b) means for moving the objective to a position between the sample surface and a fringe window at a first speed, wherein the moving means includes means for moving the objective of the optical instrument to the position between the sample surface and the fringe window by operating a position sensor to sense when the objective is a predetermined safe distance from the sample surface and means for turning off a motor moving the objective in response to such sensing when the objective is the predetermined safe distance from the sample surface; (c) means for moving the objective away from the sample surface at a second speed; (d) means for illuminating the sample surface with broad band light through an interferometer in the optical instrument, splitting off a part of a resulting interference beam; (e) a first detector; (f) means for sensing intensities of the split off part of the interference beam by means of the first detector; (g) means for stopping movement of the objective in response to sensing of a change in a variable which is a function of sensed intensities, the change indicating presence of fringes in the interference beam; (h) means for moving the objective in a fringe window at a third speed and sensing a resulting change in the variable; (i) means for recording values of the variable being produced in response to the first detector; (j) means for determining and storing a maximum value of the variable; (k) means for moving the objective in the fringe window at a fourth speed and sensing intensities of signals being produced by the first detector; (l) means for comparing corresponding values of the variable to the stored maximum value; and (m) means for stopping the objective in response to the comparing when a value of the variable being produced by the first detector is equal to a preselected percentage of the maximum value.

Claim 11

A method of automatically focusing an optical instrument onto a sample surface, comprising the steps of: (a) moving an objective of the optical instrument to a position between the sample surface and a fringe window at a first speed; (b) moving the objective away from the sample surface at a second speed; (c) illuminating the sample surface with broad band light through an interferometer in the optical instrument, splitting off a part of a resulting interference beam, and sensing intensities of the split off part of the interference beam by means of a first detector; (d) stopping movement of the objective in response to sensing of a change in a variable which is a function of sensed intensities, the change indicating presence of fringes in the interference beam; (e) moving the objective in the fringe window at a third speed, sensing a change in the variable, and recording values of the variable being produced in response to the first detector, and determining and storing a maximum value of the variable; (f) moving the objective in the fringe window at a fourth speed, sensing intensities of signals being produced by the first detector, and comparing corresponding values of the variable to the stored maximum value; (g) stopping the objective in response to the comparing when a value of the variable being produced by the first detector is equal to a preselected percentage of the maximum value.

Claim 12

A method of automatically focusing an optical instrument onto a sample surface, comprising the steps of: (a) moving an objective of the optical instrument to a position between the sample surface and a fringe window at a first speed; (b) moving the objective away from the sample surface at a second speed; (c) illuminating the sample surface with broad band light through an interferometer in the optical instrument, splitting off a part of a resulting interference beam, and sensing intensities of the split off part of the interference beam by means of a first detector; (d) stopping movement of the objective in response to sensing of a change in a variable which is a function of sensed intensities, the change indicating presence of fringes in the interference beam; (e) moving the objective in the fringe window at a third speed, sensing a change in the variable, and recording values of the variable being produced in response to the first detector, and determining and storing a maximum value of the variable; (f) moving the objective in the fringe window at a fourth speed, sensing intensities of signals being produced by the first detector, and comparing corresponding values of the variable to the stored maximum value; (g) stopping the objective in response to the comparing when a value of the variable being produced by the first detector is equal to a preselected percentage of the maximum value.

Claim 13

An apparatus for automatically focusing an optical instrument onto a sample surface, comprising in combination: (a) an objective of the optical instrument; (b) means for moving the objective to a position between the sample surface and a fringe window at a first speed; (c) means for moving the objective away from the sample surface at a second speed; (d) means for illuminating the sample surface with broad band light through an interferometer in the optical instrument, splitting off a part of a resulting interference beam; (e) a first detector; (f) means for sensing intensities of the split off part of the interference beam by means of the first detector; (g) means for stopping movement of the objective in response to sensing of a change in a variable which is a function of sensed intensities, the change indicating presence of fringes in the interference beam; (h) means for moving the objective in a fringe window at a third speed and sensing a resulting change in the variable; (i) means for recording values of the variable being produced in response to the first detector; (j) means for determining and storing a maximum value of the variable; (k) means for moving the objective in the fringe window at a fourth speed and sensing intensities of signals being produced by the first detector; (l) means for comparing corresponding values of the variable to the stored maximum value; and (m) means for stopping the objective in response to the comparing when a value of the variable being produced by the first detector is equal to a preselected percentage of the maximum value.

Claim 14

An apparatus for automatically focusing an optical instrument onto a sample surface, comprising in combination: (a) an objective of the optical instrument; (b) means for moving the objective to a position between the sample surface and a fringe window at a first speed; (c) means for moving the objective away from the sample surface at a second speed; (d) means for illuminating the sample surface with broad band light through an interferometer in the optical instrument, splitting off a part of a resulting interference beam; (e) a first detector; (f) means for sensing intensities of the split off part of the interference beam by means of the first detector; (g) means for stopping movement of the objective in response to sensing of a change in a variable which is a function of sensed intensities, the change indicating presence of fringes in the interference beam; (h) means for moving the objective in a fringe window at a third speed and sensing a resulting change in the variable; (i) means for recording values of the variable being produced in response to the first detector; (j) means for determining and storing a maximum value of the variable; (k) means for moving the objective in the fringe window at a fourth speed and sensing intensities of signals being produced by the first detector; (l) means for comparing corresponding values of the variable to the stored maximum value; and (m) means for stopping the objective in response to the comparing when a value of the variable being produced by the first detector is equal to a preselected percentage of the maximum value.