Measurement of focal points and other features in optical systems

1. A method of identifying a location of a focal point of an optical system, the method comprising:

using a sensor system to detect light that passed through the optical system, the optical system forming part of an optical device in which the optical system includes a stack of lenses and/or prisms, and the sensor system including a polychromatic confocal sensor;

directing light of different wavelengths from the confocal sensor through the optical system;

detecting in the confocal sensor system light that was reflected back through the optical system; and

determining the focal point of the optical system based on the wavelength of light detected by the sensor system.

2. The method of claim 1 including:

adjusting a position of an objective lens of the confocal sensor along an optical axis of the optical system;

using the sensor system to make a respective measurement while the objective lens is at different positions along the optical axis of the optical system; and

determining the focal point of the optical system based on the measurement at a particular one of the positions at which light is detected by the confocal sensor.

3. The method of claim 1 further including using the confocal sensor to measure a distance to a reference surface associated with the optical system.

4. The method of claim 3 further including using the location of the focal point of the optical system and the distance to the reference surface to obtain a flange focal length.

5. The method of claim 1 wherein the confocal microscope performs first and second measurements from a single position, wherein the position at which the focal point of the optical system matches the focal point of the confocal microscope is determined from one of first or second measurements, and wherein the distance from the reference surface is determined from the other one of the first or second measurements.