Xingtao Yan

Optical system design of subminiature endoscope with imaging fiber bundle

A new subminiature endoscope which used for reconnaissance and diagnosis has been designed. This subminiature endoscope is designed based on imaging fiber bundle and consist of the front object lens whose aperture is only 0.5mm, imaging fiber bundle and the post coupling lens. It realized by using subminiature optical systems . The FOV(field of view) and the focal length of the front object lens are 50° and 0.59mm. And the object distance, F number and detected imaging high of the front object lens are 3mm, 6 and 0.5mm. The total number of the imaging fiber bundle are 10000 and it’s pixel cell size is 5 μm. The effective aperture of the imaging fiber bundle is 0.46mm. The post coupling lens has a reduction ratio of 1.73. It’s object distance and imaging height are 5mm and 0.8mm. The Numerical Aperture (NA) of the front object lens, imaging fiber bundle and the post coupling lens are matching will. The coupling efficiency of the imaging fiber bundle is above 93% and the system’s design result can meet the need of the limit resolution of the imaging fiber. This kind of the fiber endoscope has the peculiarity of wide FOV, fine imaging quality, compact configuration, low finished cost and etc. It is meaningful to realize the objective of miniaturization, batch-type production and high imaging quality of the endoscope.

Study of imaging fiber bundle coupling technique in IR system

Due to its advantageous imaging characteristic and banding flexibility, imaging fiber bundle can be used for line-plane-switching push-broom infrared imaging. How to precisely couple the fiber bundle in the optics system is the key to get excellent image for transmission. After introducing the basic system composition and structural characteristics of the infrared systems coupled with imaging fiber bundle, this article analysis the coupling efficiency and the design requirements of its relay lenses with the angle of the numerical aperture selecting in the system and cold stop matching of the refrigerant infrared detector. For an actual need, one relay coupling system has been designed with the magnification is -0.6, field of objective height is 4mm, objective numerical aperture is 0.15, which has excellent image quality and enough coupling efficiency. In the end, the push broom imaging experiment is carried out. The results show that the design meets the requirements of light energy efficiency and image quality. This design has a certain reference value for the design of the infrared fiber optical system.

Experimental study on the push-broom infrared imaging system based on line-plane-switching fiber bundle

The use of line-plane-switching infrared fiber bundle to achieve wide field of view push-broom infrared imaging has been studied with experiment. In this technology, the linear array end of the imaging fiber bundle is used as a long-linear array infrared detector, and the plane array end of the bundle is coupled by a mature small scale Infrared Focal Plane Array (IRFPA). It can evade the difficulty of getting the long-linear array infrared detector directly, and has a signally significance to the development of internal infrared imaging technology. Based on the introduction of the composition, working principle of this novel infrared optical system, the system principle-demonstrating experiment has been accomplished. The line-plane-switching fiber bundle used in this experiment is 64×9 format plane array and 192×3 format linear array. It is made from chalcogenide glass fibers, possessing core (As40S59.5Se0.5) of 45 μm, cladding (As40S60) of 5 μm, and error of 1% in diameter. Perfect imaging results prove that this novel technology is feasibility and superiority. The analysis of the experiment makes a foundation for the subsequent further verification experiments.

Design of the relay lens for infrared system coupled with imaging fiber bundle

Relay lens is an important element for infrared system coupled with imaging fiber bundle. According to the basic composition and structural characteristics of infrared system coupled with imaging fiber bundle, this paper put forward the general principle and method of its relay lens design, then a material relay lens has been designed by ZEMAX with definite performance index. It has a working spectral coverage from 3.7μm to 4.8μm, focal length of 33.5mm, magnification of -0.6, linear field of view of 12mm, objective numerical aperture of 0.15. It is objective telecentric and is adapted to the relay of infrared detector and imaging fiber bundle. The total lens has two aspheric surfaces and only four pieces of singlet. Its MTF value is 0.7@17 lp/mm, and distortion is -0.19%. After necessary tolerance analysis and structural design, this relay lens has been fabricated. The optical performances fulfill the design requirements and clear images have been got by this lens. These prove the validity and rationality of the design method. It gives a foundational guidance for such relay lens design.

Research on color constancy computation based on YCbCr color space and gray surface

Color constancy is of important for many computer vision applications, such as image classification, color object recognition, object tracking and so on. But unlike the human visual system, imaging device cannot be able to compute color constant descriptors which do not vary with the color of the illuminant, so solving color constancy problem is necessary. In the calculation of color constancy, illuminant estimation is the key. Because grey surfaces can perfectly reflect the color of the scene illumination, many methods have been proposed to identify grey surfaces to estimate the illuminant. But they either rely on the camera’s parameters, lacking universality, or work inaccurate in worse conditions. In order to solve these problems, in this paper, an iterative method is proposed. The quality of the proposed method is tested and compared to the previous color constancy methods on the Macbeth Chart and two data sets of synthetic and real images. Through MATLAB simulation, experimental pictures and quantitative data for performance evaluation were gotten. The simulated results show that the proposed algorithm is accurate and efficient in identification of the grey surfaces, even in worse condition. And it performs well in color constancy computation on both synthetic and real images.

Optical System Design of Full-Disc Magnetic Field Telescope

Full-Disc magnetic field telescope is an important instrument for astronomical observations. In order to meet the optical performance of the full-Disc magnetic field Telescope and the harsh coupling conditions of its filters, determined the optical parameters of the optical system by calculation. According to the calculation of the optical parameters, we puts forward a feasible optical structure which can make the system more compact under the premise of meeting the telescope in optical properties and filters coupling conditions. for the system, we have adopted the basic idea of modular design, and the overall system is divided into several subsystems were designed. the results show that the maximum wave front distortion(pv) of the system of all field of view is 0.1327? the value of MTF at the spatial frequency of 67 lp/mm is higher than 0.45 in every field. the image quality of the system approximates to the diffractive limit.