In the micro-nano structure manufacturing field, large field of view, flexibility, and single exposure are the advantages of laser interference lithography. However, this method can only produce periodic patterns. In this paper, laser interference lithography and optical field modulation techniques are combined. By adjusting the parameters such as the phase and amplitude of the incident light beam, a light field modulation interference model was constructed to study the relationship between the parameters of the incident light beam and the intensity distribution of the interference light field. We verified the feasibility of the method through simulation. Considering the performance of existing optical modulation devices such as the pixel size of spatial light modulators, we discuss the challenges of this approach and the actual resolution that can be achieved. There is no doubt that this provides a new direction for the preparation of multiscale, variable period micro-nano patterns.
With the improvement of the performance of electro-optical sensors and computer performance, lensless digital in-line holography has been studied and applied widely. However, the resolution of the digital in-line holography system are limited by pixel size and influenced by the twin image. To solve the problem, we proposed a resolution enhancement method, which collects two holograms with different sample-to-sensor distance. The reconstruction is based on Gerchberg–Saxton iteration algorithm, using two normalized and interpolated holograms. We used two prior constraints in the iteration process according to the iteration algorithm for phase retrieval: intensity of the two normalized holograms and the non-negative absorption of the sample. In this method, the interpolation operation before phase retrieval can digitally reduce the sampling interval, and the interpolation point will be optimized with the iteration process. We simulated the resolution enhancement method, and the results of the simulation show that the resolution and image quality of lensless digital in-line holography can be effectively improved.
KEYWORDS: 3D image processing, 3D metrology, Image processing, Optical testing, Imaging systems, Sensors, Cameras, 3D acquisition, Digital image processing, Calibration
Unlike traditional imaging, the light field imaging can obtain location and direction information by one shot, which makes the dynamic three-dimensional shape measurement possible. Firstly, this paper establishes a pixel light field model, and calibrates the measurement system, which lays the foundation for light field refocus. Then proposes light field 3-D shape measurement method based on digital focus distance measurement and appropriate sharpness evaluation function. Meanwhile, hardware module used in dynamic three-dimensional shape measurement based on light field imaging is designed, which is responsible for real-time collection and processing of the light field images and greatly improves the reconstruction speed of the images. Finally achieve light field 3-D shape measurement. The experimental results are present to demonstrate the feasibility of this technique.
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