In actual applications of three-dimensional (3D) holographic display, the holograms need to be effectively stored and transmitted through the network. Thereby, there is an urgent demand for protecting the ownership of holograms against piracy and malicious manipulation. This paper realizes an ownership protection for holograms by embedding the watermark into the optimized cellular automata (OCA) domains. This work has the advantages of simultaneously improving the imperceptibility by selecting the "best" rule and OCA domains for watermark embedding and increasing robustness via the property of the multiple memory of the plenoptic image. We present experimental results of the visual quality of watermarked holograms and the robustness of 3D watermark to verify the performance of the proposed watermarking method. Experimental results confirm the imperceptibility and robustness of the proposed method.