METROLOGICAL APPARATUS

摘要

Metrological apparatus and a confocal sensor for use in such apparatus are described. The confocal sensor (1) has an optical pinhole (11) adapted for letting through a light beam (2). An optical assembly of the sensor has a first lens (12) having a refractive profile (121) and a diffractive profile (122) and a second lens (13) having at least a refractive profile (131). The refractive profile (121) of the first lens (12) and the refractive profile (131) of the second lens (13) focus the light beam (2) into a focused beam (21). The diffractive profile (122) of the first lens (12) creates longitudinal chromatic aberration so that the focused beam (21) has a focal zone with a longitudinal depth (R).

主权项

1. A confocal sensor having an optical assembly for directing light from a light source towards a surface having a characteristic to be measured and for supplying light reflected from the surface to a detector, the optical assembly comprising:
first and second lenses positioned in series along an optical path of the sensor, the first and second lenses each having a refractive profile to focus light from the light source into a focussed beam, at least one of the first and second lenses also having a diffractive profile to introduce chromatic aberration to cause different wavelengths to focus at different focal points along the optical path thereby resulting in a focal zone having a longitudinal depth along the optical axis, the confocal sensor having an optical aperture to inhibit light other than light reflected from a focus point passing to the detector.