Determination of three-dimensional BP lattice constants using in situ measurements.

In this paper, we propose a method to increase the robustness of 2D/3D optical image encryption using the dilated deep convolutional neural network (CNN). In order to solve the problem that encrypted images suffer from some attacks in practical application, we utilize a fast and effective CNN denoiser based on the principle of deep learning. The CNN improves the robustness of the algorithm by improving the resolution of the reconstructed images. Besides, CNN has a high performance against blur and occlusion attacks. We introduce the pixel scrambling method to enhance the security level of the encryption by the private key of pixel scrambling operation. The proposed method can not only realize the encryption of a two-dimensional image but also implement three-dimensional image encryption by combining the integral imaging technology. Double random phase encoding in the fractional Fourier domain is selected for experimental verification, and the results show the capability for robustness, noise immunity, and security of the proposed method. INDEX TERMS Optical image encryption, integral imaging, fractional Fourier transform, convolutional neural network.

The electro-optic effect is the working principle of blue phase (BP) liquid crystals, and it describes the relationship between the field-induced birefringence of BPs and the field strength. Due to the electrostriction of BP crystals under the electric field, an orthorhombic or tetragonal crystal is usually obtained when the field is applied along one of the twofold axes of a BP crystal, leading to the optical biaxiality under electric field. Such field-induced optical biaxiality of BPs has been predicted and observed, but its dependence on the field strength has not been investigated. In this research, we analyze the electro-optics in the field-perpendicular direction by measuring the birefringence in highly ordered BP I(110) crystals perpendicular to the electric field. Results reveal that BP I crystals in the field-perpendicular direction show an electro-optic coefficient of the order of 10−10 m/V2 that may result from the large lattice deformation of BP crystals perpendicular to the electric field. Our research provides important experimental evidence for the tensorial properties of BP Kerr effect and may have important implications on the engineering of BP electro-optical devices in practical applications.

Bessel vortex beams (BVBs) are endowed with non-diffracting properties and carry specific orbital angular momentum, which adds a new degree of freedom in the manipulation of light. A patterned liquid crystal polymer (LCP)-based optical anisotropic film is proposed and demonstrated for generation of non-diffracting BVBs. The optical axis distribution is induced by the functionalized film, which can simultaneously modulate the amplitude and phase of the wavefront. Different BVB modes can be obtained in this manner. The topological charges and non-diffracting properties of the BVBs are experimentally verified. The multifunctional LCP film exhibits the merits of low power consumption, low cost, and easy fabrication. It may provide a new strategy for beam shaping and planar optics.

Integral imaging has three display modes including real mode, virtual mode, and focused mode, and each mode has unique display characteristics. In this paper, the accommodation responses to the three-dimensional (3-D) targets reconstructed by each mode of the integral imaging display were measured and statistically analyzed. Through the least square method, standard deviation analysis, and t-test analysis, we found that the accommodation responses to the 3-D target reconstructed by the focused mode was more similar to that of the real target on the same depth position. Moreover, the closer to the central depth plane was, the steadier accommodation response 3-D targets could provide. These statistical analysis results are helpful to the design of integral imaging display device.