Fig. 1. Schematic of a conventional 4f coherent imaging measurement system and results of theoretical fitting. (a) Experimental setup diagram of the 4f coherent imaging system; (b) Schematic of the diaphragm with phase object; (c) Spatial distribution of intensity in the output plane of the 4f system; (d) Profile of Fig. (c)

Fig. 2. Schematic diagram of the 4f coherent imaging measurement system with an improved MIPO

Fig. 3. Schematic diagram of an improved MIPO

Fig. 4. (a) Phase shift of PO as a function of laser wavelength; (b) ∆T as a function of when L_p/R_a=0.1 (a) PO相移随入射波长变化曲线；(b) 当L_p/R_a=0.1时，∆T随 的变化曲线

Fig. 5. (a) Variation curves of with L_p/R_a under the action of beams of different shapes when ; (b) Variation curves of peak light intensity I₀ on the spectral plane with L_p/R_a under the action of beams of different shapes when (a) 时，不同形状的光束作用下， 随L_p/R_a的变化曲线；(b) 时，不同形状的光束作用下，频谱面上峰值光强I₀随L_p/R_a的变化曲线

Fig. 6. Spot image obtained by adjusting Michelson interferometer

Fig. 7. Profile fitting of optical nonlinear image of copper sulfate aqueous solution measured using two phase objects with phase different. (a) Fitted plot of the nonlinear spot image with the phase difference of 2kπ−0.43π; (b) Fitted plot of the nonlinear spot image with the phase difference of 2kπ+0.46π