Diode-laser-based high-precision absolute distance interferometer of 20 m range

Abstract

We present a hybrid absolute distance measurement method that is based on a combination of frequency sweeping, variable synthetic, and two-wavelength, fixed synthetic wavelength interferometry. Both experiments were realized by two external cavity diode lasers. The measurement uncertainty was experimentally and theoretically demonstrated to be smaller than 12 microm at a measurement distance of 20 m.

Optical Sensors for Multi-Axis Angle and Displacement Measurement Using Grating Reflectors

“…However, it is a time-consuming task to carry out precision alignments of the multiple laser beams and the reflective mirrors in a positioning system. Furthermore, a well-controlled environment for suppressing the refractive index error is necessary for accurate measurement [22,23,24,25,26,27]. On the contrary, optical angle sensors, in which the angular displacement of a target of interest is measured by detecting the angle of reflectance of the reflected light, can carry out high precision angular displacement measurement by using a simple optical setup.…”

“…However, on the other hand, displacement measurement based on laser interferometers can be affected by the change of the refractive index of air caused by environmental disturbances such as the changes in temperature, humidity, and air pressure [21]. Although many efforts have been made so far [4,22,23,24,25,26,27], the influence of the refractive index error is a major concern when employing laser interferometers in a multi-axis measurement system. In addition, the alignment of the multiple laser beams is a time-consuming task.…”

Measurement technologies for precision positioning

“…Otherwise, the uncertainty in the synthetic wavelength increases as does the measurement uncertainty. In general, the NAR of two-wavelength interferometry can be extended to several hundreds of millimeters with resolution of 10 mm [174,235].…”

Increasing the operating distance of a phase-shift laser range-finding system by using an active reflector

“…By comparison, better resolutions can be achieved by using the other three methods based on continuous-wave (CW). More precisely, FMCW [4,[7][8][9] and phase-shift ranging [4,[10][11][12][13] can be used to achieve a resolution of several tens of microns or even several microns, while a nanometer-level resolution can be achieved by using interferometry [14,15]. However, long distance (4 1 km) measurement is still a great challenge to a CW ranging system, because of the very low returned light power which is inversely proportional to the 4th power of the distance being measured [1,16].…”