Multilevel holographic encryption based on the Tiger Amulet concept.

Optical holographic encryption (OHE) has been extensively researched in the field of information security due to its parallel and multi-dimensional characteristics. However, although some progress in OHE has been made in recent years, inherent security flaws resulting from the robust nature of holograms persist. In this study, we propose a multilevel holographic encryption method based on the Tiger Amulet (TA) concept. Compared with the normal OHE, our method employs two ciphertexts. It strategically utilizes the low-level plaintext as intentional deceptive content to confound the potential eavesdroppers. Furthermore, we ingeniously exploit the hologram's robustness in reverse, thereby establishing an additional protection mechanism to enhance the security of the middle-level plaintext. Leveraging the TA concept, the high-level plaintext can only be decrypted when two matched ciphertexts are combined and collimated. The TA based decryption mechanism enhances the security and sensitivity deciphering high-level plaintext. Benefiting from the security mechanisms above, our proposed method demonstrates promising applicability across diverse scenarios and holds the potential to redefine the landscape of multilevel OHE design.

DBPFNet: a dual-band polarization image fusion network based on the attention mechanism and atrous spatial pyramid pooling.

In the current image fusion techniques, typically dual-band images are fused to obtain a fused image with salient target information, or intensity and polarization images are fused to achieve an image with enhanced visual perception. However, the current lack of dual-band polarization image datasets and effective fusion methods pose significant challenges for extracting more information in a single image. To address these problems, we construct a dataset containing intensity and polarization images in the visible and near-infrared bands. Furthermore, we propose an end-to-end image fusion network using attention mechanisms and atrous spatial pyramid pooling to extract key information and multi-scale global contextual information. Moreover, we design efficient loss functions to train the network. The experiments verify that the proposed method achieves better performance than the state-of-the-art in both subjective and objective evaluations.

Multi-key optical encryption based on two-channel incoherent scattering imaging.

Optical encryption has been extensively researched in the field of information security due to its characteristics of being parallel and multi-dimensionsal. However, most of the proposed multiple-image encryption systems suffer from a cross-talk problem. Here, we propose a multi-key optical encryption method based on a two-channel incoherent scattering imaging. In the encryption process, plaintexts are coded by the random phase mask (RPM) in each channel and then coupled by an incoherent superposition to form the output ciphertexts. In the decryption process, the plaintexts, keys, and ciphertexts, are treated as a system of two linear equations with two unknowns. By utilizing the principles of linear equations, the issue of cross-talk can be mathematically resolved. The proposed method enhances the security of the cryptosystem through the quantity and order of the keys. Specifically, the key space is significantly expanded by removing the requirement of uncorrected keys. This approach provides a superior method that can be easily implemented in various application scenarios.

Construction method for designing a spectrometer with variable spectral resolution and wide bandwidth using multiple off-axis convex gratings.

The classic Offner spectrometer has the advantages of having a simple structure, light weight, and high imaging quality. It is easily to achieve a fixed spectral resolution but cannot meet usage requirements. Therefore, we present a practical method for designing a spectrometer with variable spectral resolution. Multiple off-axis convex (OAC) gratings are used to replace the convex grating in the classic Offner spectrometer. We derive the principle through ray tracing and establish an optimization process for the basic parameters of multiple OAC gratings. To demonstrate this method, a corresponding system is designed. The results show that a variable spectral resolution, with a variation ratio close to 4, of 0.45-1.91 nm is achieved over a wide bandwidth of 460-900 nm. Additionally, the smile and keystone of the system are well corrected.

Algorithm based on the optimal block zonal strategy for fast wavefront reconstruction.

Fast wavefront reconstruction is crucial for improving the temporal frequency of adaptive optics systems, in which a mass of subapertures is used. In this paper, we present a novel block zonal reconstruction algorithm based on Southwell geometry to speed up the wavefront reconstruction from Shack-Hartmann wavefront sensor measurements. Therein, we use the theory of computational complexity to install a novel optimal block zonal strategy to get the best size of the subwavefront and give the verification through simulations. Compared with the classical Southwell entire wavefront reconstruction algorithm, the algorithm based on the optimal block zonal strategy needs only a few milliseconds to finish the reconstruction process from 100×100 subapertures. Moreover, we analyze the superiority to use our algorithm to realize the phase reconstruction of the unconnected subwavefront, which cannot be reconstructed via traditional methods. Further, the simulation and experiments show that the precision of the algorithm based on the proposed optimal block zonal strategy is comparable with the commercial wavefront sensor HASO, the time consumption is much less than that of the traditional zonal reconstruction, and it is applicable to the square wavefront, circular wavefront, and local unconnected wavefront. Our proposed algorithm can be widely utilized in astronomical observation, laser transmission, and remote sensing.