Fig. 1. Schematic diagram of equally spaced fan beam rearrangement

Fig. 2. Schematic diagram of cone beam CT imaging

Fig. 3. Comparison of projection surfaces by algorithms

Fig. 4. Schematic diagram of reconstruction of using variable filter path algorithm. (a) Schematic of x‑y plane geometry; (b) arc curves with different parameter combinations; (c) section view of ray SβD perpendicular to x‑y plane

Fig. 5. Reconstruction flow of the proposed algorithm combined with CLRP approach

Fig. 6. Schematic diagram of projection conversion parameters. (a) Schematic diagram of CL projection transformation geometry; (b) converted equivalent CT projection

Fig. 7. Schematic diagram of focus coordinate conversion. (a) Before conversion; (b) after conversion

Fig. 8. Reconstructed images at y=-32 mm for different parameter combinations. (a) Ideal image; (b)-(d) reconstructed images when the parameter condition is k2<k1; (e) reconstructed image when the parameter condition is k2=k1; (f)-(h) reconstructed images when the parameter condition is k2>k1

Fig. 9. Gray scale value comparison of the center sequence of y=-32 mm reconstructed images under different parameter combinations

Fig. 10. Plots of mean square error surfaces reconstructed using different parameter combinations for each cone angle. (a) 15° cone angle; (b) 23° cone angle; (c) 30° cone angle; (d) 40° cone angle; (e) 50° cone angle

Fig. 11. Comparison of reconstructed images for each algorithm. (a) Ideal image; (b) FDK; (c) P-FDK; (d) T-FDK; (e) proposed algorithm

Fig. 12. Gray scale value comparison of reconstructed images at different locations for each algorithm. (a) x=32 mm; (b) y=-32 mm; (c) z=70 mm

Fig. 13. Comparison of reconstructed images for every algorithm at different cone angles. (a) 15° cone angle; (b) 23° cone angle; (c) 40° cone angle; (d) 50° cone angle

Fig. 14. Projection schematic before and after CLRP conversion and data rearrangement. (a) Multilayer PCB model; (b) CL projection; (c) CT projection after CLRP conversion; (d) projection after data rearrangement

Fig. 15. Comparison of reconstructed images for each layer of multilayer PCB model. (a) Layer 6; (b) layer 24; (c) layer 42; (d) layer 60; (e) layer 78; (f) layer 96

Fig. 16. Comparison of detailed parts of multilayer PCB model reconstruction. (a) FDK reconstruction; (b) reconstruction by proposed algorithm; (c) ROI-I comparison; (d) ROI-II comparison

Fig. 17. CL scanning system and sample. (a) CL scanning system; (b) sample to be reconstructed

Fig. 18. Comparison of actual PCB reconstruction results. (a) Component layer reconstructed by FDK algorithm; (b) component layer reconstructed by the proposed algorithm; (c) built line layer reconstructed by FDK algorithm; (d) built line layer reconstructed by the proposed algorithm