Fig. 1. TSOM based on interferometric signal center positioning

Fig. 2. Stack interferometric TSOM image

Fig. 3. HDVSI algorithm

Fig. 4. Ideal interferometric signal and its envelope

Fig. 5. Near-field and far-field simulation area division

Fig. 6. Light field of Gaussian source. (a) Light field distribution in plane of focus; (b) ideal and actual focal planes

Fig. 7. Simulation of TSOM scanning process using FDTD. (a) Set simulation area and adjust light source and FPM parameters; (b) scanning-spot; (c) through-focus scanning

Fig. 8. 3D-PSF consists of direct current term and alternating current term

Fig. 9. Effects of spectral bandwidth and NA on direct current and alternating current terms in 3D-PSF. (a) Direct current terms in 3D-PSF; (b) alternating current terms in 3D-PSF

Fig. 10. Experimental TSOM images under different NA. (a) NA=0.8; (b) NA=0.55

Fig. 11. Low-coherence interferometry of microstructural groove. (a) Mirau-type low-coherence micro-interference system; (b) surface structure of sample to be tested

Fig. 12. Low-coherence micro-interferometer

Fig. 13. Restoration results of groove topography with linewidth of 10 μm and depth of 100 μm. (a) Result of topography restoration; (b) cross-section view with y=0

Fig. 14. Restoration results of groove topography with linewidth of 2 μm and depth of 10 μm. (a) Result of topography restoration; (b) cross-section view with y=0

Fig. 15. Scanned images in depth-of-focus range. (a) +0.95 μm; (b) 0 μm; (c) -0.95 μm

Fig. 16. Stacked TSOM images with different planes within depth of focus as centers. (a) +0.95 μm; (b) +0.48 μm; (c) 0 μm; (d) -0.48 μm; (e) -0.95 μm

Fig. 17. Comparison of experimental and simulated TSOM images for groove sample with linewidth of 2 μm. (a) Experimental TSOM image; (b) simulation TSOM image

Fig. 18. Measurement results of TSOM images stacked with different planes as centers

Fig. 19. Interference fringe change during TSOM scanning

Fig. 20. Vertical scanning to locate focus plane. (a) Low coherent interferometric signal contrast envelope; (b) experimental image and ROI corresponding to peak of contrast envelope

Fig. 21. Low-coherence interference TSOM image. (a) Light field distribution in focal plane; (b) stacked axial scanning light fields

Fig. 22. Extraction of TSOM textures. (a) Raw TSOM image for experiment; (b) raw TSOM image for simulation; (c) extracted experiment TSOM texture; (d) extracted simulation TSOM texture

Fig. 23. Measurement result of low-coherence interference TSOM image

Fig. 24. Measurement repeatability