Fig. 1. Principle of LRTI

Fig. 2. Optimization method of LRTI based on waveform decomposition

Fig. 3. Noise threshold calculation

Fig. 4. Flow chart of waveform decomposition method

Fig. 5. Schematic diagram of experimental system

Fig. 6. Sinogram of laser echo signal

Fig. 7. Decomposed waveform components. (a) Waveform components when sampling angle is 45° ; (b) waveform components when sampling angle is 90°

Fig. 8. Optimized laser echo signals. (a) Optimized waveform when sampling angle is 45° ; (b) optimized waveform when sampling angle is 90°

Fig. 9. Reconstructed images. (a) Unprocessed reconstructed image; (b) reconstructed image after waveform decomposition

Fig. 10. Reconstructed images. (a), (b) Original reconstructed images when sampling angle intervals are 3° and 5°, respectively; (c), (d) reconstructed images after waveform decomposition when sampling angle intervals are 3° and 5°, respectively