Aiming at the wide-spectrum chromatic aberration problem of membrane diffractive lenses, the concept of the digital chromatic aberration correction infrared imaging system was proposed. The principle of digital chromatic aberration correction was given, and the chromatic aberration correction of this system was completed on a computer, which is based on a wavelength-tunable laser local oscillator coherent detection detector. Compared with the chromatic aberration correction method for traditional lenses, this membrane diffractive optical system exhibited characteristics of small size, low weight, and low complexity. The digital chromatic aberration correction application conditions of this membrane diffractive optical system were analyzed. In addition, the main parameters and imaging simulation results were given. The center wavelength of this membrane diffractive optical system is 1.55 µm, and its spectral range is 1.50-1.60 µm. The application of autocorrelation processing to infrared complex images after digital chromatic aberration correction followed by incoherent accumulation of the received corrected complex images based on multiple stepping wavelengths could significantly improve the imaging signal-to-noise ratio.

Digital infrared chromatic aberration correction algorithm for a membrane diffractive lens based on coherent imaging.

The projection of fringes plays an essential role in many applications, such as fringe projection profilometry and structured illumination microscopy. However, these capabilities are significantly constrained in environments affected by optical scattering. Although recent developments in wavefront shaping have effectively generated high-fidelity focal points and relatively simple structured images amidst scattering, the ability to project fringes that cover half of the projection area has not yet been achieved. To address this limitation, this study presents a fringe projector enabled by a neural network, capable of projecting fringes with variable periodicities and orientation angles through scattering media. We tested this projector on two types of scattering media: ground glass diffusers and multimode fibers. For these scattering media, the average Pearson's correlation coefficients between the projected fringes and their designed configurations are 86.9% and 79.7%, respectively. These results demonstrate the effectiveness of the proposed neural network enabled fringe projector. This advancement is expected to broaden the scope of fringe-based imaging techniques, making it feasible to employ them in conditions previously hindered by scattering effects.

Neural network enabled fringe projection through scattering media

Structured light beams have played important roles in the fields of optical imaging and optical manipulation. However, light fields scatter when they encounter highly anisotropic scattering media, such as biological tissue, which destroys their original structured fields and turns them into speckle fields. To reconstruct structured light beams through highly anisotropic scattering media, we present a method based on intensity transmission matrix which only relates the input and output light intensity distributions. Compared with the conventional method which relies on the measurement of complex-valued transmission matrix, our scheme is easy to implement, fast and stable. With the assistance of spatial filters, three kinds of structured light beams, Bessel-like beams, vortex beams and cylindrical vector beams, were constructed experimentally through a ZnO scattering layer. The present method is expected to promote optical applications through highly anisotropic scattering media.

/pdf/experimental-generation-of-structured-light-beams-through-1wdaxc6k.pdf

Experimental Generation of Structured Light Beams through Highly Anisotropic Scattering Media with an Intensity Transmission Matrix Measurement

Turbulence in complex environments such as the atmosphere and biological media has always been a great challenge to the application of beam propagation in optical communication, optical trapping and manipulation. To overcome this challenge, this study comprehensively investigates the robust propagation of traditional Gaussian and autofocusing beams in turbulent environments. In order to select stable beams that exhibit high intensity and high field gradient at the focal position in complex environments, Kolmogorov turbulence theory is used to simulate the propagation of beams in atmospheric turbulence based on the multi-phase screen method. We systematically analyze the intensity fluctuations, the variation of the coherence factor and the change in the scintillation index with propagation distance. The analysis reveals that the intensity fluctuations of autofocusing beams are significantly smaller than those of Gaussian beams, and the coherence of autofocusing beams is better than that of Gaussian beams under turbulence. Moreover, autofocusing beams exhibit less oscillation than Gaussian beams, indicating that autofocusing beams propagate in complex environments with less distortion and intensity fluctuation. Overall, this work clearly demonstrates that autofocusing beams exhibit higher stability in propagation compared with Gaussian beams, showing great promise for applications such as optical trapping and manipulation in complex environments.

Robust autofocusing propagation in turbulence

With the advent of computing power and higher resolution CMOS sensor, imaging camera for mobile phone application has become very common in consumer portable product such as mobile phone, tablet or even wearable devices and head mount devices . Higher resolution image sensor, on the other hand, will suffer chromatic aberration (CA) where the colour channel appears shifted. Better lens design with more lens elements may be required. However, this will add more cost and manufacturing challenges. Many studies and methods have been proposed for CA correction through post image processing and those methods required calibration or post image process before correction factor can be applied. In this paper, we propose a new algorithm that will pre-defined the CA correction factor through lens design simulation.

Self-image correction for low-cost imaging optic

Optical tweezers can manipulate tiny particles. However, the distortion caused by the scattering medium restricts the applications of optical tweezers. Wavefront shaping techniques including the transmission matrix (TM) method are powerful tools to achieve light focusing behind the scattering medium. In this paper, we propose a new kind of TM, named intensity transmission matrix (ITM). Only relying on the intensity distribution, we can calculate the ITM with only about 1/4 measurement time of the widely used four-phase method. Meanwhile, ITM method can avoid the energy loss in diffraction introduced by holographic modulation. Based on the ITM, we have implemented particle manipulation with a high degree of freedom on single and multiple particles. In addition, the manipulation range is enlarged over twenty times (compared with the memory effect) to 200 μm.

/pdf/particle-manipulation-behind-turbid-medium-based-on-3klrx8c5.pdf

Particle manipulation behind turbid medium based on intensity transmission matrix

Optical design and implementation of a compact and long focal length imaging system

The large-diameter diffractive telescope has the advantage of observing space debris. Some of the key issues are the design and tolerance analysis of the telescope with the segmented primary lens. In this paper, we design a space large-diameter sub-aperture stitching diffractive telescope that can achieve a large diameter of 1438 mm, a long focal length of 2000 mm, and a full field of view (FOV) of 0.34°. Considering the manufacturing and stitching errors of the sub-aperture can affect the telescope’s image quality, we provide a tolerance analysis method based on Monte Carlo analysis, which makes the consequence of the tolerance analysis nearly reality. The tolerance ranges are proposed not only for the segmented primary lens but also for the whole telescope system.

Design and tolerance analysis of a large-diameter diffractive telescope


 Real-time polarization medium-wave infrared (MIR) optical imaging systems enable the acquisition of infrared and polarization information of a target. At present, real-time polarization middle-infrared devices mainly face the following problems: poor real-time performance, low transmission, and high requirements for fabrication and integration. Herein, we need to improve the performance of the real-time polarization imaging system in the MIR waveband and solve the above-mentioned defects. Therefore, we propose an MIR polarization imaging system for achieving real-time polarization-modulated imaging with high transmission as well as improved performance based on a pixel-wise metasurface micro-polarization array (PMMPA). The PMMPA element comprises several linear polarization (LP) filters with different polarization angles. The optimization results demonstrate that the transmittance of the LP filters is up to 77% at a wavelength of 4.0 μm and an extinction ratio of 88 dB. In addition, a near-diffraction-limited real-time MIR imaging optical system is designed with a field of view (FOV) of 5ºand an F-number of 2. The simulation results show that an MIR polarization imaging system with excellent real-time performance and high transmission is achieved by using an optimized PMMPA element. Therefore, the method is compatible with the available optical system design technologies and provides a way to realize real-time polarization imaging in mid-infrared wavebands.

Real-time and high-transmitted middle-infrared optical imaging system based on pixel-wise metasurface micropolarization array

By combining optical systems and image processing, wavefront coding can greatly expand the depth of focus and depth of field of optical systems. It has been widely used in iris detection, high-power microscopic objective lens, infrared optical system athermalized, and so on. At present, the image restoration algorithms commonly used in wavefront coding are based on deconvolution, Wiener filtering, and so on. Although these algorithms can achieve an excellent image restoration effect, they will also bring boundary ringing effects and artifacts to the image. When the image is disturbed by strong noise, the restoration effect will also be seriously affected. To solve these problems, a wavefront coded image restoration algorithm based on compressed sensing is proposed in this paper. The strong data reconstruction ability of the compressed sensing restoration algorithm is used to restore the encoded image obtained by the wavefront coding system. This method can effectively suppress noise and reconstruct the image without artifact and boundary ringing effect. Through the comparison of simulation results, the effectiveness of the proposed method is verified.

Wavefront coded image restoration algorithm based on compressed sensing for off-axis mirror system

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