A dual-detection chromatic confocal probe employing a mode-locked femtosecond laser (Invited Paper)

Confocal probes, which consists of a point light source and a point detector, have been widely used in the manufacturing industry for a surface profile measurement of a measurement target object. In recent years, a mode-locked laser, which has advantages; high-stable optical frequency and wide-range optical frequency, and high-stable intensity, has been employed as a light source of the confocal probes, enabling to non-scanning and precise height measurement. However, a non-smoothness of the optical spectrum of the mode-locked laser affects a confocal response curve, which is utilized for the target position measurement, and leads to loss of the measurement accuracy. Therefore, a dual-detection chromatic confocal probe has been proposed and researched to reduce the effects of the non-smoothness optical spectra. In this paper, a review about the dual-detection chromatic confocal probe is summarized.