Applications of a laser radar system with depth accuracy down to 0.2 mm for high accuracy 3-D imaging are described.
The system is based on a green pulsed laser triggering a picosecond ICCD camera with data recording of only a few
seconds. The submillimeter accuracy gradually degrades at ranges above a few hundred meters due to turbulence,
vibrations, etc. As a specific example, we show 3-D accuracy for surface tile inspection of a miniature space shuttle and
the resolution of cracks and defects is demonstrated, which is relevant for the planned laser radar inspections from the
space shuttle boom and the longer range survey from the International Space Station. By coupling the laser light through
a Raman fiber we also demonstrate multispectral 3-D imaging.
Results from our fast and high accuracy 3-D laser radar are given at distances up to 500 m. The system is based on gated viewing with range accuracy below 1 mm under optimal circumstances. It consists of a high sensitivity, fast, intensified CCD camera, and an Nd:YAG passively Q-switched 32.4 kHz pulsed green laser at 532 nm. The CCD has 752×582 pixels. Camera shutter and delay steps are controlled in steps of 100 ps. Each laser pulse triggers the camera delay and shutter. A 3-D image is constructed from a sequence of 50-100 2-D reflectivity images, where each frame integrates ~700 laser pulses on the CCD. In 50 Hz video mode we record a 2-D sequence in a second and process a 3-D image in a few seconds. We compare 3-D images at short to long distances and quantify the degree of person identification in 3-D. Turbulence, vibrations and system errors are found to limit a successful PID to distances shorter than ~500m for our prototype system.