Fig. 1. Recording geometry of scattered beams by photorefractive volume grating. Volume gratings 1 and 2 represent the signal volume grating and the photorefractive volume grating with high spatial frequency. ${\mathit{E}}_r$, ${\mathit{E}}_o$, and ${\mathit{E}}_{\mathrm{os}}$ represent the reference beam, signal beam, and scattered noise beam, respectively. θ is the recording angle, $W_R$ and $W_S$ are the widths of ${\mathit{E}}_r$ and ${\mathit{E}}_o$, respectively. $\alpha$ is the angle between ${\mathit{E}}_{\mathrm{os}}$ and the $x$ axis.

Fig. 2. Effective wave vector ratio of photorefractive volume grating with high spatial frequency and diffraction efficiency of the traditional volume grating in different recording angles.

Fig. 3. Experimental setup of analog OPC. M1–M5 are reflecting mirrors, SPF represents the spatial filter, and A1, A2 are the beam attenuators. BS1–BS3 are beam splitters, and L1–L7 are the lenses. A, $\mathrm{a}$, and ${\mathrm{A}}^{*}$ represent the reference beam, the object beam, and the conjugate reference beam of A.

Fig. 4. Experimental results of the USAF target (left column) and normalized one-dimensional intensity distribution (right column). The horizontal axis in the right column represents the coordinate value corresponding to the length of the red line, and the middle position of the red line is 0 μm. (a) Image without ground grass. (b) Conjugate reconstructed image without ground grass. (c) Image with the ground grass. (d)–(f) Images after OPC compensation in recording angles of 45°, 30°, and 7.5°, respectively.

Fig. 5. Numerical fitting SNR and diffraction efficiency in different recording angles. The error bar shows the standard deviation of three experimental measurements.