optoweleocr trlodnic
Optical measurement head Turbine blade
Fiber for sending light λ2 Experimental setup
(single-mode) + 1 λ1 The laser Doppler measurement sen- λ λ1 sor consists of an optical head, a light- λ1, - 1
2 λ2 λ , source unit, and a detection unit (see λ1 Measurement
DRESDEN UNIVERSITY OF TECHNOLOGY
2 volume figure). The light-source unit contains a 660 and 830 nm fiber-pigtailed laser Fiber for scattering light (multi-mode) diode combined with a 2 × 1 fiberoptic coupler and transmitted through a 25 m Light- 25 m long source fiber patch cables long fiberoptic patch cable to the optical- unit Detection unit sensor head. In the sensor head, the ex- 2× 1 panded fiberoptic beam is collimated coupler λ λ1, λ2 and then focused by a diffractive lens
Photo-
detector 2
2 λ1 optimized for 660 nm with a numerical aperture of 0.2 and a focal length of Laser diode 1 Laser diode 2 To PC 20 mm. Because of the high dispersion 660 nm 830 nm of the lens, the beam waists of the two wavelengths are separated by several
Photo-
detector 1
In an experimental setup for a laser-Doppler tip-clearance probe, a passive optical-mea- millimeters in the axial direction. By
surement head is connected by fiberoptic patch cables to a light source and a detection unit. Outer dimensions of the measurement head are 200 ×
82 ×
54 mm. placing a diffraction grating at the fo-
cal length of the lens, the positive and
time, detector frame rate, and speed of poral and high spatial resolution simul- negative diffraction patterns of the first
mechanical scanning, respectively. taneously, and the passive and flexible diffraction order of the two wavelengths
Compared to these other methods, fiberoptic measurement head is insensi- can be focused by another series of lens-the new laser Doppler tip-clearance tive to temperature variations and elec- es and used as the interfering beams probe based on LDV provides high tem- trical disturbances. crucial to the LDV measurement.
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References:
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