Related Experiment Video
Updated: Jan 25, 2026

A Random-displacement Measurement by Combining a Magnetic Scale and Two Fiber Bragg Gratings
Published on: September 30, 2019
Improved chromatic confocal displacement-sensor based on a spatial-bandpass-filter and an X-shaped fiber-coupler
Abstract:
To improve the positioning capabilities of a chromatic confocal displacement measurement system, we introduce a super-resolving pupil filtering element (referred to as spatial-bandpass-filter), an X-shaped fiber-coupler, and a modified peak-extraction algorithm. The spatial-bandpass-filer decreases the spherical aberration of conventional refractive lenses and transmission loss, without changing the dispersion range. The new optical design minimizes the effect of light-source-variation as well as reflectance-variation of the sample surface against the wavelength by adding a reference arm with an X-shaped fiber-coupler and normalization algorithm. This enables rapid re-purposing to obtain data for crosstalk, reference and measurement signals. A prototype setup was built and the experimental results show that the new chromatic dispersion system can reach a position stability of ± 0.36 μm using a commercial cost-effective white-light source. It reaches an axial displacement resolution of up to 1 μm and a peak-fit error below ± 0.2% for a range of 1.05 mm.
Related Concept Videos
Bandpass Sampling
A bandpass signal has a spectrum with a lower frequency limit, denoted as ω1, and an upper frequency limit, denoted as ω2....
Position and Displacement
Displacement Current
Passive Filters
Low-Pass Filters
Low-pass filters are designed to transmit signals with frequencies lower than the cutoff frequency, ωc, and attenuate those above it. The cutoff...
Active Filters
Position and Displacement Vectors
Further, several important kinds of...

