Search

With the rapid development of digital image processing and recognition, the intelligent grid wins a great opportunity. We could be able to get the information from digital images quickly based on computer analysis, algorithms of deep learning and machine learning, grid data extraction, model training and image recognition. The article firstly reviewed the current status of traditional grid, including a broad overview of the specific strengths and weaknesses, secondly analyzed the intelligence algorithms of deep learning and machine learning based on neural network, then achieved the recognition and reconstruction of wiring diagram through image recognition based on neural network, lastly showed the prospects of image recognition in power system.

The Gerchberg–Saxton (GS) algorithm is widely used in various disciplines of modern sciences and technologies where phase retrieval is required. However, this legendary algorithm most likely stagnates after a few iterations. Many efforts have been taken to improve this situation. Here we propose to introduce the strategy of gradient descent and weighting technique to the GS algorithm, and demonstrate it using two examples: design of a diffractive optical element (DOE) to achieve off-axis illumination in lithographic tools, and design of a computer generated hologram (CGH) for holographic display. Both numerical simulation and optical experiments are carried out for demonstration.

In this paper, we propose a simple method for realizing color holographic imaging using one thin diffractive optical element (DOE), which can reconstruct a two-dimensional color image with one phase plate at a user defined distance from phase plate. The phase plate is optimized by combining Gerchberg–Saxton algorithm and compensation algorithm for improving the resolution ratio of reproduced color images. For accelerating the computational time, the Graphic Processing Unit (GPU) is used for saving time costs. In the end, the simulation experiments verified our method.

We experimentally demonstrate a light-field moment microscopy (LFMM). The proposed technique employs a better estimation of the intensity derivative in solving the Poisson equation and therefore can significantly reduce the noise and error in the reconstructed light-field moment. The light field can be reconstructed then by using the moment, enabling the perspective view and depth estimation of the object. The proposed LFMM can be simply implemented using a standard commercial light microscope. This will open up new possibility for standard microscopes in high-resolution light-field observations.

We propose an iterative algorithm by introducing the strategy of gradient decent and magnitude modification into the Gerchburg-Saxton (GS) algorithm. Simulations and experimental results demonstrate its better performance for holographic display comparing with the GS.

It is well known that holographic display can provide 3D scenes with continuous viewpoints and is free of accommodation-convergence conflict. So far most of the research in this area focuses on the display end, leaving the acquisition end merely explored. For holographic content acquisition, one needs to capture the scene in 3D. Ways to do this include the traditional optical holography and integral imaging. However, optical holography suffers from serious speckle while integral imaging has a long march to increase the resolution. In this paper, we propose a technique based on a variation of the transport of intensity equation to calculate the “phase” information of a scene from its defocusd intensity captured by a color camera under white light illumination. With the defocused phase and intensity data at hand, we can calculate the infocused wavefront of the scene, and further encode it into a computer generated hologram for subsequent holographic display. We demonstrate the proposed technique by simulation and experimental results. Compared with existing 3D acquisition techniques for holographic display, our method may provide better viewing experience due to the free of speckle in the acquisition stage, as well as the fact that the resolution does not limited by the microlenslet.

One method of realizing color holographic imaging using one thin diffractive optical element (DOE) is proposed. This method can reconstruct a two-dimensional color image with one phase plate at user defined distance from DOE. For improving the resolution ratio of reproduced color images, the DOE is optimized by combining Gerchberg-Saxton algorithm and compensation algorithm. To accelerate the computational process, the Graphic Processing Unit (GPU) is used. In the end, the simulation result was analyzed to verify the validity of this method.

Phase contains important information about the diffraction or scattering property of an object, and therefore the imaging of phase is vital to many applications including biomedicine and metrology, just name a few. However, due to the limited bandwidth of image sensors, it is not possible to directly detect the phase of an optical field. Many methods including the Transport of Intensity Equation (TIE) have been well demonstrated for quantitative and non-interferometric imaging of phase. The TIE offers an experimentally simple technique for computing phase quantitatively from two or more defocused images. Usually, the defocused images were experimentally obtained by shifting the camera along the optical axis with slight intervals. Note that light field imaging has the capability to take an image stack focused at different depths by digital refocusing the captured light field of a scene. In this paper, we propose to combine Light Field Microscopy and the TIE method for phase imaging, taking the digital-refocusing advantage of Light Field Microscopy. We demonstrate the propose technique by simulation results. Compare with the traditional camera-shifting technique, light-field imaging allows the capturing the defocused images without any mechanical instability and therefore demonstrate advantage in practical applications.

In general, Fourier transform lenses are considered as ideal in the design algorithms of diffractive optical elements (DOEs). However, the inherent aberrations of a real Fourier transform lens disturb the far field pattern. The difference between the generated pattern and the expected design will impact the system performance. Therefore, a method for modifying the Fourier spectrum of DOEs without introducing other optical elements to reduce the aberration effect of the Fourier transform lens is proposed. By applying this method, beam shaping performance is improved markedly for the optical system with a real Fourier transform lens. The experiments carried out with a commercial Fourier transform lens give evidence for this method. The method is capable of reducing the system complexity as well as improving its performance.

Off axis illumination (OAI) is one of the key resolution enhancement technologies in projection lithography system. Recently, phase type diffractive optical elements (DOEs) are adopted by most of the lithography machine manufactures to realize OAI. In general, the efficiency of the OAI unit is the main consideration compared with uniformity. However, the main goal of the traditional constraint of iterative Fourier transformation algorithm (IFTA) is used to optimize the SNR, while diffraction efficiency is the secondary consideration. Therefore a constraint for IFTA is well designed to increase the efficiency of DOE in this paper. This constraint can guarantee the pole balance at the same time. The main idea of this constraint is to apply amplitude and phase freedoms in the signal window and to control the total energy of each pole. Based on the proposed constraint several DOEs are designed for high NA lithography illumination system. And remarkable improvement in the efficiency is observed compared with the traditional constraint. Furthermore, the efficiency and uniformity could be weighted by adjusting the parameter with extending this constraint to general case. To demonstrate the proposed constraints, experiments are carried out where a spatial light modulator is utilized to represent DOEs.