The multispectral high-resolution imaging system is composed of four wide-spectrum cameras, which can detect targets in the visible, short-wave infrared, medium-wave infrared and long-wave infrared spectrum simultaneously. In order to reduce the size of the system, the four wide-spectrum cameras use the same telescope. To achieve operating wavelengths covering four wavebands, the telescope uses a fully reflective design with a coaxial aspherical surface with a hole in the center of the primary mirror. If aberration-free testing is used, the central aperture will occur, resulting in incomplete aperture of surface shape detection. Thus, in this paper, a compensator is designed which can achieve the whole aperture of surface testing without centralized obscuration. At the same time, the impact of the misalignment of compensator in the optical path during the test is analyzed. The optical testing path adopts infinite conjugate working distance to reduce one adjustment amount of compensator. And the first surface of compensator is coordinated with the interferometer to adjust the angle of compensator quickly and accurately, which further reduces the measurement error introduced by the optical testing path. The design of the compensator can realize the control of sensitive misalignment, reduce the surface measuring error caused by the compensator misalignments, and eventually reduce the precise processing error.
UlE, as a kind of ultra-low thermal expansion glass, has been widely applied in large-aperture optical mirrors and space telescopes. However, hard-brittle material feature of ULE brings certain difficulty for machining. In this paper, rotary ultrasonic vibration-assisted peripheral grinding (RUPG), combining rotary ultrasonic vibratio (UV) and conventional grinding (CG) is proposed, and grinding process and quality characteristic are investigated in terms of surface morphology, grinding force, surface roughness, subsurface damage depth, and subsurface morphology. A serious of comparative experiments for between RUPG and CG were conducted. The results show that rotary UV in RUPG can markedly decrease the grinding force with a factor of 46.78%. The change rule of grinding force with the varying of grinding parameters in RUPG is consistent with that in CG, i.e., grinding force increases as the increasing of grinding depth and feed rate, while it decreases with the growth of spindle speed. Grinding surface marks were found to be obviously weakened by UV and surface consistency was accordingly improved. Besides, measurement results of surface roughness also real that UV plays a positive role in diminishing surface roughness by almost 23.01%, and reducing the subsurface damage depth by a factor of 17.19%.
Most of the existing defect detectors focus on the size, location, depth and number of defects of the tested components. The instrument is usually large in size and requires high accuracy for the environment and motion devices. In contrast, the direct random bed motion, which aims at finding and locating defects, is highly efficient, low-cost and environmentally practical, while the research on vibration-resistant defect tester is rare.In order to solve this problem, based on the principle of micro-scattering imaging in dark field, a set of optical component surface defect detection device is built, and the influence factors of light intensity, illumination angle, wavelength and other defect detection factors are experimentally studied, in order to provide design basis for the follow-up development of on-line defect detection instrument. The experimental results show that the most important factor affecting the sensitivity is the azimuth angle and pitch angle of the incident light, which is more than 30 degrees between the incident light and the scratch direction. When the pitch angle is between 60 degrees and 70 degrees, the higher detection sensitivity can be obtained. In addition, improving the illumination intensity can help to improve the detection of defects. In the visible range, the wavelength has little effect on the sensitivity.
Nowadays, many optical elements are fabricated by means of glass molding using hard and brittle inserts such as Silicon Carbide (SiC) and Silicon Nitride (Si3N4). However, for those hard-to-machine materials, the most feasible solution is still with ultra-precision grinding and following polishing. Hence, it is necessary and meaningful to study their plastic properties for the development of optical fabrication and ultra-precision manufacturing process. However, the conventional methods including compression test and indentation fracture mechanics are not sufficient to obtain the accurate parameters and still lack of reliable supporting of the machining process. To solve this problem, this paper presents a novel way to correlate the plastic properties to the indentation data using dimensional analysis for the two sorts of hard and brittle materials of SiC and Si3N4. Through integrating the data obtained by the indentation tests and the modeling method presented in this paper, stress-strain behavior, yield stress σy, yield strain epsilony and strain hardening exponent n could be determined. The processing performance of these two materials reflected by the above parameters are consistent with the conclusions drawing from the indentation crack development under varying loads during the indentation test, which verifies the effectiveness and feasibility of the presented modeling method.
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