A novel anti-cat-eye effect imaging technique based on wavefront coding is proposed as a solution to the problem of previous anti-cat-eye effect imaging techniques where imaging quality was sacrificed to reduce the retroreflection from the photoelectric imaging equipment. With the application of the Fresnel–Kirchhoff diffraction theory, and the definition of generalized pupil function combining both phase modulation and defocus factors, the cat-eye echo formation of the wavefront coded imaging system is theoretically modeled. Based on the physical model, the diffracted spot profile distribution and the light intensity distribution on the observation plane are further simulated with the changes in the defocus parameter and the phase modulation coefficient. A verification test on the cat-eye laser echo power of the wavefront coded imaging system and that of the conventional imaging system at a 20 m distance are conducted, respectively. Simulations and experiment results show that compared with conventional imaging systems, the wavefront coding imaging system can reduce the retroreflection echo by two orders of magnitude while maintaining better imaging quality through defocusing.

Photoelectric imaging systems typically employ a focal plane detector structure, rendering them vulnerable to laser damage. Laser damage can severely impair or even completely deprive the information acquisition capability of photoelectric imaging systems. A laser damage protection method based on a microlens array light field imaging system is proposed to prevent photoelectric imaging systems from laser damage. The technique utilizes the light field modulation effect of the microlens array to homogenize the spot energy, thereby reducing the maximum single-pixel receiving power at the image sensor. The method's effectiveness has been verified through numerical simulations and experimental validation. First, the laser transmission theoretical model of light field imaging is proposed. Then an experimental setup is established, and measurements are conducted to capture the spot profiles and intensity distributions on the imaging plane across various defocus distances. Finally, the impact of the propagation distance on the maximum single-pixel receiving power and suppression ratio of the light field imaging system is experimentally measured. The simulation and experimental results indicate that, with the proposed method, the energy suppression ratio can easily reach two orders of magnitude, significantly reducing the probability of laser damage in photoelectric imaging systems. (c) 2023 Optica Publishing Group

In order to predict infrared image super-resolution (SR) quality under conditions of no SR image generation and no high-resolution reference image, this article proposes a fully connected neural network model for infrared image SR quality prediction driven by wavelet domain energy features. Utilizing the multiresolution and scale-invariant properties of undecimated wavelets, our model separates low-frequency information component and three high-frequency information components from a low-resolution image. Our model achieves decorrelation of image pixel information and generates wavelet domain energy normalization features. Utilizing a fully connected neural network, we construct a wavelet-based image SR quality prediction network. This neural network combines four subnetworks to enhance the network representation and learning capabilities. The network is trained using wavelet domain energy normalization features, while autonomously learning the mapping relationship between input data and evaluation metric. This model is validated on infrared image data sets. The experimental results indicate that the proposed model can accurately predict SR image quality metrics by utilizing frequency-domain energy features of a low-resolution image.

Optical vortices have drawn extensive research interests due to their widespread applications in various fields. Therefore, it is of great significance to modulate optical vortices to endow them with more properties. Herein, the autofocusing and self-healing properties are introduced to optical vortices via implementing circular cubic phase modulation. The propagation dynamics of the modulated optical vortex is analyzed, and the experimental results match well with the simulations. Moreover, the autodefocusing optical vortices can also be generated, and the flexible switching between the autofocusing state and autodefocusing state can be easily realized by adjusting the helicity of the incident circular polarization. Besides, the topological charges of the two states are also experimentally verified. Our study provides a novel way to modulate optical vortices, which may enrich their applications in optics and photonics.

Laser blindness can reduce or disable the information acquisition ability of photoelectric imaging systems. In this paper, numerical simulation and experimental verification are both performed to systematically study the laser protection performance of the vortex phase mask. First, the imaging model and laser transmission model of the vortex wavefront coding imaging system are introduced in detail. Then, the experimental setup of the imaging system is built, and the imaging result of the imaging system is obtained. Finally, the influence of propagation distance on the maximum single-pixel receiving power and suppression ratio of the imaging system is measured experimentally. The simulation and experimental results both show that the energy suppression ratio of this method can reach more than two orders of magnitude compared with the conventional imaging system, and the probability of laser blindness can be effectively reduced.

The propagation characteristics of a single Airy beam in nonlinear Kerr media were numerically investigated by utilizing the split-step Fourier transform method. We show that in addition to normal breathing solitons, the anomalous bound states of Airy spatial solitons can also be formed, which are similar to the states formed in the interaction between two Airy beams in nonlinear media. This quasi-equilibrium state is formed by the interaction of the main soliton beam and side lobes of Airy beam due to their different propagation trajectories in the nonlinear media. Moreover, it has been shown the Airy spatial solitons in tree structure can be formed by adjusting the initial parameters in the interaction between the Airy beam and Kerr media.