Fig. 1. Optical layout of autofocus microscope

Fig. 2. Relationship between clear position and defocus degree of A and B two-path optical imaging. (a)(b) Far focus; (c) focal plane; (d)(e) near focus

Fig. 3. Photo of optical platform of autofocus microscope

Fig. 4. Acquisited image from area-array CCD

Fig. 5. Plots of grating acquisited from line-array CCD in different positions. (a) Far focus; (b) focal plane; (c) near focus

Fig. 6. Equal-period fringes

Fig. 7. Focusing results of equal-period digital grating. (a) Focusing curves of different period gratings; (b) focus ranges of different period gratings

Fig. 8. Focusing error of equal-period fringes

Fig. 9. Variable-period digital grating

Fig. 10. Focusing results of variable-period digital grating. (a) Focusing curve; (b) focusing error

Fig. 11. Focusing results for objective lenses with different magnifications. (a) Five times; (b) ten times; (c) twenty times

Fig. 12. Focusing of defective liquid crystal. (a) Scratched glass substrate; (b) acquisited image from area-array CCD; (c) focusing curve of scratched glass substrate