Fig. 1. Filtering template. (a) Structural diagram; (b) image patches in scope of template

Fig. 2. Cross-section of damage

Fig. 3. Segmentation results before and after improvement of LASSR algorithm. (a) Original damage image; (b) three-dimensional intensity distribution of original damage image; (c) result after improvement; (d) result before improvement

Fig. 4. Enlarged view of rectangular area in Fig. 3(a)

Fig. 5. Signal images. (a) Before adaptive local enhancement; (b) after adaptive local enhancement; (c)(d) three-dimensional morphologies corresponding to (a) and (b), respectively

Fig. 6. Intensity distributions of signal images before and after adaptive local enhancement. (a)-(d) Corresponding to damages numbered by 1-4 in Fig. 4

Fig. 7. Original damage image and its segmentation result.(a) Original damage image; (b) segmentation result

Fig. 8. Measurement results under microscope. (a) Local area of optical element; (b) - (f) corresponding to measurement results of damage points numbered by 1-5 under high magnification microscope