Abstract: A reference surface is used to develop an empirical plot between a parameter of interest, such as roughness or modulation, and the position of the reference mirror in an interferometer by repeating measurements of the reference surface at different positions of the reference mirror so as to identify the in-focus position of the reference mirror. Serial quality-control measurements of samples of interest are carried out with the reference mirror in such in-focus position until a predetermined quality-control event triggers an automated system re-calibration by re-measuring the reference surface and, if the result does not correspond to the in-focus position of the reference mirror according to the plot, by finding a new in-focus position for the reference mirror using the same plot or, alternatively, a new similarly produced plot. Sample measurements are then resumed with the mirror placed at that new position.

Abstract: A reference surface is used to develop an empirical plot between a parameter of interest, such as roughness or modulation, and the position of the reference mirror in an interferometer by repeating measurements of the reference surface at different positions of the reference mirror so as to identify the in-focus position of the reference mirror. Serial quality-control measurements of samples of interest are carried out with the reference mirror in such in-focus position until a predetermined quality-control event triggers an automated system re-calibration by re-measuring the reference surface and, if the result does not correspond to the in-focus position of the reference mirror according to the plot, by finding a new in-focus position for the reference mirror using the same plot or, alternatively, a new similarly produced plot. Sample measurements are then resumed with the mirror placed at that new position.

Abstract: A reference surface is used to develop an empirical plot between a parameter of interest, such as roughness or modulation, and the position of the reference mirror in an interferometer by repeating measurements of the reference surface at different positions of the reference mirror so as to identify the in-focus position of the reference mirror. Serial quality-control measurements of samples of interest are carried out with the reference mirror in such in-focus position until a predetermined quality-control event triggers an automated system re-calibration by re-measuring the reference surface and, if the result does not correspond to the in-focus position of the reference mirror according to the plot, by finding a new in-focus position for the reference mirror using the same plot or, alternatively, a new similarly produced plot. Sample measurements are then resumed with the mirror placed at that new position.

Abstract: A side camera is combined with a conventional optical metrology system to image the object during the focusing scan performed in normal focusing procedures. The camera is positioned in fixed spatial relation to the objective and with its focal plane in substantial alignment with the optical axis of the objective so as to image the object during the scan. The camera is used to monitor the illumination spot formed on the object by the beam projected through the system's objective. The in-focus position is found by moving the object such that the illumination spot coincides with the objective's focus seen through the camera.

Abstract: The power input to the light source of a microscope is varied as necessary to maintain a constant degree of detector saturation as the objective is moved toward a best-focus position. Focus is found by tracking the source's intensity necessary to maintain the detector irradiance at a constant level. The in-focus position is reached when the power input (and correspondingly the intensity of the light emitted by the source) reaches a minimum. The concept can be applied in a similar manner to minimize or eliminate tilt in a sample.

Abstract: The power input to the light source of a microscope is varied as necessary to maintain a constant degree of detector saturation as the objective is moved toward a best-focus position. Focus is found by tracking the source's intensity necessary to maintain the detector irradiance at a constant level. The in-focus position is reached when the power input (and correspondingly the intensity of the light emitted by the source) reaches a minimum. The concept can be applied in a similar manner to minimize or eliminate tilt in a sample.

Abstract: The power input to the light source of a microscope is varied as necessary to maintain a constant degree of detector saturation as the objective is moved toward a best-focus position. Focus is found by tracking the source's intensity necessary to maintain the detector irradiance at a constant level. The in-focus position is reached when the power input (and correspondingly the intensity of the light emitted by the source) reaches a minimum. The concept can be applied in a similar manner to minimize or eliminate tilt in a sample.

Abstract: An illumination system for an interferometer combines a white-light source and a green source with a reflective green dichroic filter. When the green source alone is energized for PSI measurements, the output of the illumination system is green only. When a white-light output is desired for VSI measurements, both sources are energized and the intensity of the green light is judiciously calibrated to match the spectral band filtered out by the dichroic mirror. Therefore, the system can switch between green and white light simply by changing the selection of energized sources, without any mechanical switching and attendant delays and vibrations. Multiple narrowband sources may be combined with white light in a similar manner.

Abstract: An illumination system for an interferometer combines a white-light source and a green source with a reflective green dichroic filter. When the green source alone is energized for PSI measurements, the output of the illumination system is green only. When a white-light output is desired for VSI measurements, both sources are energized and the intensity of the green light is judiciously calibrated to match the spectral band filtered out by the dichroic mirror. Therefore, the system can switch between green and white light simply by changing the selection of energized sources, without any mechanical switching and attendant delays and vibrations. Multiple narrowband sources may be combined with white light in a similar manner.