Fig. 1. Focus evaluation curve

Fig. 2. Implementation block diagram of focus evaluation method

Fig. 3. Figures of object model. (a) Bar; (b) Trapezoid; (c) Circle

Fig. 4. Object scanning imaging model

Fig. 5. Simulated defocused sequence images. (a) Bar; (b) Trapezoid; (c) Circle

Fig. 6. Simulated focus evaluation curves. (a) A (136, 92); (b) B (61, 61); (c) C(126, 48)

Fig. 7. Figures of experimental device. (a) Target scanning experiment device figure with lens of f=8 mm; (b) sensor scanning experiment device figure with lens of f=8 mm; (c) sensor scanning experiment device figure with microscope lens of NA=0.65

Fig. 8. Partial defocused images. (a) Defocused image obtained by moving the target under the imaging lens; (b) defocused image obtained by moving the sensor under the imaging lens; (c) defocus image obtained by moving the sensor under the microscope lens; (d) defocused images obtained through lens zoom

Fig. 9. Focus evaluation curves of experimental defocused image. (a) A(222,333); (b) B(380,310); (c) C(290,240); (d) D (180,90)

Table 1. Parameter definitions and description

Table 2. Calculation results of simulated defocus image

Table 3. Device parameters used in the experiment

Table 4. Calculation results of experimental defocus image