Fig. 1. Schematic of the experimental setup of quantitative phase imaging based on TIE

Fig. 2. Spectrum of the green and the blue bandpass filters illuminated by halogen lamp

Fig. 3. Phase retrieval procedure of TIE based on fast Fourier transform

Fig. 4. Simulation process of polychromatic intensity at the over-focus，in-focus and over-focus planes

Fig. 5. RMSE variation curve of the green and the blue bandpass filters

Fig. 6. Evolution of optimal mean wavelength and corresponding RMSE with different defocus distance in the absence of noise

Fig. 7. Evolution of optimal mean wavelength and corresponding RMSE with different defocus distance in the presence of noise

Fig. 8. Evolution of optimal mean wavelength and corresponding RMSE with different sampling spacing

Fig. 9. Experimental results of the green bandpass filter with different defocus distances

Fig. 10. Experimental results of the blue bandpass filter with different defocus distances