Three-dimensional imaging lidar is a new type of active detection technology, which can obtain target spatial information accurately and quickly. It has a wide application in the fields of target detection and recognition, scientific research detection, mapping and navigation, etc. Three-dimensional imaging lidar has many modulation modes, among which the non-scanning three-dimensional imaging lidar based on polarization modulation has the advantages of long measurement range, high measurement accuracy, fast imaging speed and no motion artifacts, which is one of the hot research directions in this field. In view of this technology, this paper analyzes the principle of polarization modulation imaging by Jones matrix calculation, and obtains the geometric relationship between the imaging illumination values in four polarization directions and the polarization modulation phase delay of Pockels Box. Then, a set of laser radar optical system based on polarization modulation imaging is designed by using optical software. The analysis results show that the designed optical system has good imaging quality, clear target edge imaging and can distinguish independent square targets with a diameter of 1m; The light outside the field of view of the strip light source does not enter the detector, so the system has less stray light and less imaging distortion; At last, the input phase delay δ of the Pockels box in the simulation model is randomly set to different values, and the illumination values of four polarization directions are obtained by imaging simulation, so that the phase delay δ′ of the Pockels box is inverted. The results show that | δ′-δ | ≤ 5.2× 10-6 λ, which proves that the polarization modulation method is correct.
All optical systems are affected by aberrations, and optical encryption systems with lens are no exception. In order to improve the practicality of the optical encryption system, the influences of aberration on the double random phase encoding (DRPE) system are studied. In this paper, Zernike polynomials are used to express the aberration of the lens. Simulation has been carried out. The influences of different types, coefficients, and combinations of aberrations on DRPE system are analyzed. The results of the study indicate that some Zernike polynomials(such as the 4th Zernike polynomial, etc.)will have a greater impact on DRPE system, while some combinations, such as the combination of the 4th and 9th Zernike polynomials, will reduce the influences of aberrations on DRPE system. Besides, the degree to which DRPE system is affected by aberrations is evaluated by the correlation coefficient between the decrypted image and the plaintext. In order to solve the problem of aberration, two solutions are proposed.
In this paper, a temperature control method of flexible composite film was proposed based on porous adsorption principle and phase change materials blending technology, the flexible composite film samples were developed accordingly, and the temperature control performance was tested experimentally. It was shown by the test results, the phase change of flexible composite film can be applied to a wide temperature range of 23-55 ℃, and also conducted heat well.
Polarized LIDAR is defined as radar system which uses the polarization state of the laser to carry information. According to the different features, this paper divides the polarized LIDAR into non-imaging polarized LIDAR and imaging polarized LIDAR. The non-imaging polarized LIDAR can distinguish spherical particles and non-spherical particles by using the particle back polarization,which is used to study dust, haze, fog and other atmospheric phenomena. The imaging polarized LIDAR can instantly obtain the three-dimensional image of the target, which has many advantages such as high resolution, fast imaging speed and simple structure. Subsequently, the polarized LIDAR developed as an independent branch of the study, and a lot of excellent research results have been achieved. This paper mainly introduces the basic principle of polarization LIDAR, the realization way, the research progress at home and abroad.
Fundus camera is widely used in screening and diagnosis of retinal disease. It is a simple, and widely used medical equipment. Early fundus camera expands the pupil with mydriatic to increase the amount of the incoming light, which makes the patients feel vertigo and blurred. Nonmydriatic fundus camera is a trend of fundus camera. Desktop fundus camera is not easy to carry, and only suitable to be used in the hospital. However, portable nonmydriatic retinal camera is convenient for patient self-examination or medical stuff visiting a patient at home. This paper presents a portable nonmydriatic fundus camera with the field of view (FOV) of 40°, Two kinds of light source are used, 590nm is used in imaging, while 808nm light is used in observing the fundus in high resolving power. Ring lights and a hollow mirror are employed to restrain the stray light from the cornea center. The focus of the camera is adjusted by reposition the CCD along the optical axis. The range of the diopter is between -20m-1 and 20m-1.
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