We review some usual laser range finding techniques for in- dustrial applications. After outlining the basic principles of triangulation and time of flight (pulsed, phase-shift and frequency modulated continu- ous wave (FMCW)), we discuss their respective fundamental limitations. Selected examples of traditional and new applications are also briefly presented. © 2001 Society of Photo-Optical Instrumentation Engineers.

Laser ranging: a critical review of usual techniques for distance measurement

This paper describes the theoretical and experimental study of a new technique for optical frequency domain ranging (OFDR) by a frequency-shifted feedback (FSF) laser. In conventional OFDR, a frequency chirped single-mode laser is used as a light source to convert a distance into a beat frequency, and a tradeoff exists between measurement range and resolution. The FSF laser output consists of periodically generated chirped frequency components whose chirp rate is faster than 100 PHz/s (P=10/sup 15/), By use of the FSF laser, the tradeoff is removed and long-distance high-resolution OFDR is realized In the experiment, a distance of 18.5 km was measured with a resolution of 20 mm.

Optical frequency domain ranging by a frequency-shifted feedback laser

Optically pumped planar waveguide lasers: Part II: Gain media, laser systems, and applications

The recent progress in the field of Ti:Er:LiNbO 3 waveguide lasers with emission wavelengths in the range 1530 nm < λ < 1603 nm is reviewed. After a short discussion of the relevant fabrication methods concepts and properties of different types of lasers with grating resonator, acoustooptically tunable Fabry Perot type lasers and new ring laser structures are presented.

Erbium-Doped Lithium Niobate Waveguide Lasers

Doppler laser radar can improve the precision of speed measurement by about two orders of magnitude compared with time-of-flight range finders, which obtain target speeds by range differentiation. However, in a car environment, the usage of traditional Doppler laser radar schemes is limited, because they do not satisfy the requirement of simultaneously measuring the target range together with speed with high precision. First, in this paper, we describe a new in-car laser radar system and show a new modulation scheme that enables the in-car laser radar to simultaneously measure the target range and speed with high precision. Then, we perform simulations and experiments to verify the accuracy of the proposed method. In the Appendix, a brief review of current widely used laser radar schemes is given. The limitations of these schemes to their employment in car applications are also discussed.

Amplitude-Modulated Laser Radar for Range and Speed Measurement in Car Applications

A laser cavity closed via the first-order diffracted light of an acoustooptic modulator is referred to as a frequency-shifted feedback laser (FSF laser). This laser exhibits outstanding features in its oscillation spectrum. We previously demonstrated the first oscillation of an all solid-state FSF laser, and it turned out experimentally that the oscillation spectrum consists of a continuously chirped comb of frequency components. Furthermore, we have been investigating oscillation dynamics both experimentally and analytically for a better understanding of FSF laser. Here experimental results and analyses on the spectral characteristics of the laser are discussed.

T. Hara

Papers

Optical frequency domain ranging by a frequency-shifted feedback laser

Spectral characteristics of an all solid-state frequency-shifted feedback laser