The invention discloses a
confocal optical path system and method for suppressing
stray light, and belongs to the technical field of optical precision measurement. According to the invention, the
beam expander is moved forwards by 2-5 mm relative to the flat
beam splitter prism, so that the
light beam incident to the core
beam splitter is actively converted into the
Gaussian beam with the specific
divergence angle from the parallel light, and is coupled with the symmetrically arranged
confocal light paths, thereby solving the problem that in the existing
heterodyne laser vibration measurement technology, the parallel light generates multi-path reflection on the surface of a planar optical element, so that the
measurement precision is greatly improved. In the prior art, a stable parasitic interference cavity is formed, high-order and dynamic nonlinear errors and
phase drift are introduced, and the technical problems of
system complexity, high cost and difficult installation and adjustment caused by traditional suppression means (such as off-axis design and an ultrahigh antireflection film) are solved, the
spatial coherence of
stray light and main
signal light is destroyed, the
stray light intensity in the
system is suppressed by about two orders of magnitude, and the
system stability is improved. The non-linear
distortion of a measurement
signal is significantly reduced, and the adjustment tolerance and long-term stability of an
optical path are improved at the same time.