Abstract: A microscope system moves a target in a first direction relative to a low power objective lens and, during the relative motion, generates and records values of an electronic focus signal that depends on the magnitude of light reflected by the target. Then, a host workstation calculates a first estimate of position ("focus position") of the target at which the microscope system is focused, by a median point method. In the median point method, the host workstation calculates the sum of the recorded values and determines the position along the range of motion at which half of this sum was exceeded, to be a first estimate of the focus position. From the intensity values of the first pass, optimal sensor gain is set for subsequent passes. Second and third estimates of the focus position can be calculated in a similar manner if necessary and the target is moved to the most recent estimate of the focus position.

Abstract: A microscope system moves a target in a first direction relative to a low power objective lens and, during the relative motion, generates and records values of an electronic focus signal that depends on the magnitude of light reflected by the target. Then, a host workstation calculates a first estimate of position ("focus position") of the target at which the microscope system is focused, by a median point method. In the median point method, the host workstation calculates the sum of the recorded values and determines the position along the range of motion at which half of this sum was exceeded, to be a first estimate of the focus position. From the intensity values of the first pass, optimal sensor gain is set for subsequent passes. Second and third estimates of the focus position can be calculated in a similar manner if necessary and the target is moved to the most recent estimate of the focus position.

Abstract: A method for quickly performing an auto-focus operation on a confocal microscope. As a coarse Z-stage moves a target toward an objective lens, a photodetector generates an analog electronic focus signal which exceeds a threshold level during a focused condition. When a focused condition exists, a latching comparator, which is coupled to the electronic focus signal and to a signal representative of the threshold level, trips and the target is stopped. The analog nature of the electronic focus signal assures that the focused condition will be detected. As a result, the target may be moved quickly without missing a focused condition. The target is moved several times at progressively slower velocities to position the target close to the focus position.