Currently, there is a discussion about constructing a new large optical-infrared telescope, in which the diameter of the primary mirror is 12m (Su et al., 2016). Su et al. (2016) propose an innovative design (SYZ design) which consists of three mirrors with non-zero power, including a relay mirror below the primary mirror. This design yields a good imaging quality and a relatively flatten field curvature at Nasmyth focus. To evaluate the science compatibility of this three-mirror telescope, we compare the system performance of SYZ design with conventional two-mirror telescope designs such as Ritchey–Chrétien (RC) design and Aplanatic Gregorian (AG) design available in the world in this report. We found that SYZ telescope yield a superb imaging quality. Nevertheless, RC and AG designs has a higher total throughput which translate to smaller equivalent-noise-area (ENA).
In tactile scanning profiler, the measuring force would change in a wide range when it was used for profile measurement in a large range, which could possibly destroy the measured surface. To solve the problem, measuring force control system for tactile scanning profiler was needed. In the paper, a voice coil motor-based measuring force control system for tactile scanning profiler was designed. In the design, a low stiffness coefficient spring was used to provide contact force, while a voice coil motor (VCM) to balance the spring force so that the contact force could be kept for constant measuring force. A VCM was designed specially, and for active measuring force control, a precision current source circuit under the control of a DSP unit was designed to drive the VCM. The performance of voice coil motor based measuring force control system had been tested, and its good characteristics were verified.
Piezoelectric ceramics with a flexible hinge guide was used for fine positioning at nanometer level, while a stepping motor was used for coarse positioning with a resolution at micrometer level, and their combination helped fulfillment of vertical scanning positioning with large range and nanometer resolution. A grating sensor was used for the real-time measurement of scanning displacement for close-loop positioning control. The properties of the flexible hinge guide was analyzed using ANSYS. Experimental results indicated the performance of the system was good. The system had a good application prospect in an optical profiler for surface measurement.
White light interference (WLI) optical profiler had been used widely for structured surface measurement. To achieve high measuring accuracy, piezoelectric ceramic (PZT) was usually used as the vertical scanning unit, which was normally less than 100um and only for small range structured surface measurement. With the development of advanced manufacturing technology, precision structured surfaces with large step height were appearing. To satisfy the measurement requirements of this kind of precision structured surfaces, WLI optical profiler with large range had to be developed. In this paper, an optical profiler was proposed, in which a coarse-fine vertical scanning system was adopted to expand its measurement range to 10mm while its resolution still at nanometer level.
Small angle measurement has been widely use for the alignment or error compensation of a mechanical system. In this paper a small angle dynamic measurement device based on laser interference technique is introduced, which consists of a reference module and a measuring module. The measuring module is fixed on the measured object. With the variation of the small tilt angle of the measured object, the phase difference between the two beams from prism1 and prism2 changes according to it. By analyzing the interference patterns, the variation of the small tilt angle can be obtained dynamically. Experimental setup has been established and the results show that the measurement range is 15' with the resolution of 0.08", the measurement error is less than 8″.
Non-contact three-dimension (3D) measurement technology has developed rapidly. Digital grating projection is regarded as the best prospect one. There are many problems, such as low accuracy, which have not been solved yet. Based on digital grating phase-shift, and combed with height-phase mapping and self lattice calibrating, a new 3D measurement method has been proposed. With little geometric constraints to digital grating and CCD, the measurement system is more feasible, which can be used to realize the accurate measurement and reconstruction according to the 3D information from measured object. By applying the method proposed to a reference object, the experience has lead to good result which shows that the new method is efficient and precision.