Wavefront-coding technique for inexpensive and robust retinal imaging

Extended depth-of-field infrared imaging with deeply learned wavefront coding

Wavefront coding (WFC) techniques, including optical coding and digital image processing stages, enable significant capabilities for extending the depth of field of imaging systems. In this study, we demonstrated a deeply learned far-infrared WFC camera with an extended depth of field. We designed and optimized a high-order polynomial phase mask by a genetic algorithm, exhibiting a higher defocus consistency of the modulated transfer functions than works published previously. Additionally, we trained a generative adversarial network based on a synthesized WFC dataset for the digital processing part, which is more effective and robust than conventional decoding methods. Furthermore, we captured real-world infrared images using the WFC camera with far, middle, and near object distances. Their results after wavefront coding/decoding showed that the model of deeply learned networks improves the image quality and signal-to-noise ratio significantly and quickly. Therefore, we construct a novel artificial intelligent method of deeply learned WFC optical imaging by applying infrared wavelengths, but not limited to, and provide good potential for its practical application in "smart" imaging and large range target detection.

Wavefront coding with Jacobi-Fourier phase masks for retinal imaging

Wavefront coding is a technique that combines optical phase elements and digital signal processing in order to increase the effective depth of focus of optical systems. The success of wavefront coding lies in the design of a suitable phase mask placed at the system's aperture. This element allows for image formation invariant under the effects of different second-order optical aberrations. In optical systems limited by temporally or spatially varying high-order aberrations, the use of wavefront coding has not been fully demonstrated. Here we propose the choice of Jacobi-Fourier shaped phase masks to produce sharp and clear retinal images of living eyes. To demonstrate the potential use of the technique, we analyze the performance of the Jacobi-Fourier phase masks through experimental simulations to alleviate aberrations for different eye aberrations. We will show that the best mask choice is robust to noise while keeping acceptable resolution and reducing image artefacts.

Experimental analysis of a wavefront coding system with a phase plate in different surfaces

The application of an integrated phase plate can greatly simplify an optical system structure due to the defocus insensitivity and aberration inhibition of the wavefront coding imaging technology. In addition, the development of free-form surface technology promotes the application of integrated phase plates. In order to view the imaging characteristics of the integrated wavefront coding system, we built two kinds of wavefront coding systems with the phase plate integrated in different surfaces of the optical system. Simulation results show that phase plates with the same parameters but in different surfaces can realize consistent results. For further observation, two separated phase plates with the same parameters are processed, and, correspondingly, experiments of microscopic objective imaging are carried out. Experimental results confirm that the phase plate can be successfully applied to increase the design flexibility of wavefront coding, leading to a potential mass application solution.

Imaging and image restoration of lens-combined modulated wavefront coding

In this paper, it presents a new wavefront coding (WFC) technology that we call lens-combined modulated wavefront coding (LM-WFC). Based on the LM-WFC design method, we establish a large depth of field and large aperture system. Simulation results indicate that the modulation transfer function of the system has a defocus invariant characteristic, which all typical WFC systems have, with a large depth of field. Experimental results for comparing the LM-WFC imaging system and a traditional imaging system are presented. The comparative results demonstrate that the LM-WFC system has an imaging performance invariant over a wide depth of field range.

Interferometric Local Measurements of High-Order Aberrations in Progressive Addition Lenses

PURPOSE

The main goal of this work is to show the principles, design, and performance of a modified point diffraction interferometer (PDI) for evaluating the local higher-order aberrations of progressive addition lenses (PALs). Because aberrations have different impacts in visual perception, we propose a device to provide a customized solution with the best permissible amounts and combinations of aberrations for improving a subject's vision.

METHODS

A PDI has been adapted to measure local high-order aberrations in PALs.

RESULTS

High-order aberrations in three different PALs within four relevant circular regions of interest (ROIs) with a radius ranging from 0.4 to 2.4 mm were measured with an accuracy of λ/10 within the ROI using the tailored PDI. The interferometer also allows for easily choosing the position and number of the ROIs.

CONCLUSIONS

The interferometric device is compact, robust, and accurate. The operational principle is very simple, and it provides the local high-order aberrations directly without adding additional parts to the interferometer. As expected, the amount of high-order aberrations depends on the chosen ROI of the PAL; the corridor is the more critical region. We found, in accordance with the literature, that, in the corridor, second- and third-order aberrations are dominant and spherical aberration is negligible.