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From 2015, NSPO (National Space Organization) began to develop off-axis Korsch telescope system for next generation earth observation mission. The experimental Korsch telescope system is consist of five mirrors, including: (1) M1: 550mm diameter clear aperture concave primary mirror, (2) M2: Convex secondary mirror, (3) M3: Off-axis concave tertiary mirror with rectangular aperture, (4) FM1 & FM2: Two folding mirrors with rectangular aperture and flat surface. All the experimental mirrors are designed with lightweight structure and made of fused silica. Since early 2016, we collaborated with Taiwanese domestic company and manufactured all the mirrors for the experimental Korsch telescope. Moreover, we not only accomplished the assembly of M1 but also implemented the form error metrology technique to measure the surface error of M1 with high repeatability in 2017. Recently, in order to validate the structural and athermal design of opto-mechanical structures, several vibration tests and thermal experiments have been accomplished in 2018. The experimental data could not only help us to enhance the analysis accuracy of the finite element model but also benefit to our automated opto-mechanical design system. For next developed phase, the aspheric polishing and reflective coating will be achieved till 2021.

This paper describes superior candidate substrate material- aluminum nitride (AlN), for the cost-effective and high-performance requirements for aerospace mirrors. In fact, high specific stiffness and thermal stability are not only two major considerations to select ideal material but also machinability, dimensional stability, and cost. Silicon carbide shows the best figure of merits 12627, but it has extremely low remove rate and expensive raw material properties. Extremely low expansion ceramics such as Zerodur may be difficult to obtain in large quantities and its figure of merit is 1151. On the contrary, AlN has outstanding thermal conductivity (~170 W/m°C) and maintain high figure of merit 2222 without compromise. In our fabrication processes, the AlN substrate can be easily polished to 53±1nm Ra surface texture and 66.4±2nm RMS surface form. Its unique thermal stability, specific stiffness, and good figure of merits, associated with its easy machinability and low-cost raw materials, makes AlN an ideal selection for superior mirror substrate in the future space mirror optics.

The main purpose of this paper is to develop an automatic print head alignment algorithm for a material jetting-based color 3D additive manufacturing system. This printing system has six print heads, respectively, filled with six different photocurable resin (C, M, Y, K, W) and support. Start of all, the printing system with initial parameters prints a standard platform, which is used to confirm whether the print head is aligned well or not. Next, a scanner is used to gain the printed image. An image processing algorithm is used to get the characteristic points of the capture image and calculate the compensation parameters, which will be imported to the printing system and make the system aligned well. This paper proposed an automatic smart print head alignment algorithm, which can be used on multiple print head based- 3D additive manufacturing system. Replacing of human alignment, this technology can save more time and reduce the error. It also can automatically work and oversee the system in real-time, which will improve the quality and the color performance of the printed products.

For the earth observation mission, there are some critical environmental requirements including low-light condition, fast moving objects, high scanning rate. In order to meet these requirements, the Time-Delay-and-Integration (TDI) technique is critical and essential for the sensor part to improve the Signal to Noise Ratio (SNR) performance. National space organization (NSPO) collaborates with National Chip Implementation Center (CIC) on the next generation image sensor. In order to increase SNR under the light-starved condition, a 32-stages digital-accumulator Time-Delay-and-Integration (TDI) CMOS image sensor is adapted to improve the image quality. Besides, it could successfully take several pictures under different TDI stages on a dynamic test bench. The experimental results verified that the 32-stage TDI CMOS image sensor could function well.

Large mirrors with lightweight structure, such as those used in the telescope system of astronomy or spaceborne applications, are susceptible to stress caused by fabrication process. Furthermore, both the residual stress and subsurface damage are critical for the lightweight tooling of glass materials. In order to figure out the stress distribution on glass substrate, the photoelastic method has been applied to not only the astronomical optics but also the industrial optics of semiconductor equipment. However, there are several influence factors in photoelasticity measurement, including the structure of mirror, fabrication process, and metrology technique. The above factors may affect to the retardation result of photoelasticity measurement and cause the error of stress calculation. Therefore, it is important to clarify the retardation difference contribution to the corresponding influence factors. In this study, we attempted to use photoelastic instrument to investigate the relationship between the photoelastic effect and stress of several kinds of lightweight mirrors. There are three different lightweight mirrors were adapted to the photoelasticity measurement, including: (1) GSO 12” Mirror with 12 inches diameter made by fused silica, (2) Primary Mirror (M1-B) of Formosat-5 with 450 mm diameter made by ZERODUR® , (3) Primary Mirror (M1) of Mircrosat with 380 mm diameter made by CLEARCERAM®-Z. The experimental results depict some obvious retardation differences caused by the certain influence factors and the details will be discussed below.

This article presents the opto-mechanical design of a primary mirror assembly of a ground-based telescope with optimization algorithm. The prototype of ground-based telescope – GSO RC16 with 16 inches diameter blank primary mirror had been manufactured in 2016. However, a telescope with a blank primary mirror is too heavy to carry on for the stargazer. Besides, deformations caused by temperature difference and gravity will do significant effect to the large aperture mirrors with high optical performance requirements. In order to reduce the weight and maintain the stiffness simultaneously, the lightweight design and mounting interface design are critical and important. There are four types of system architectures in this project, including (1) two types of lightweight mirror designs - honeycomb type segments and sector type segments; (2) two types of mounting interface designs - retainer type support and CFRP type support. The optimization results showed that (1) the lightweight ratio of the primary mirrors are greater than 70%; and (2) the PV value of the mirrors supported by optimal mounting interfaces with gravity effect as a tilt of about 45 degrees and ±20°C temperature difference effectively less than 1/4 λ.

The concentrated local electric field on a substrate surface is very helpful to enhance the signal for surface-enhanced Raman scattering (SERS) and surface plasmon resonance (SPR) techniques. In this research, the metallic nano-cylinder, the nano-hole, and nano-annular aperture structures on the glass have been simulated by the finite difference time domain method (FDTD) first to understand the localized surface plasmon resonance (LSP) of them. The simulations for different inner diameters, outer diameters and thickness of the gold film have been done and the better dimension and film thickness which can induce the largest electric field concentration have been chosen. We coated 2 nm and 5 nm thick chromium(Cr), and 50nm and 60nm thick gold(Au) films on SF2 glass substrate, respectively. The different nanoannular aperture structures were successfully patterned on them by using focus ion beam (FIB) to etching gold film surface. Using the OB Morph measurement to observe the structure caused by the SPR shifted. The transmission spectrometer has been adapted to measurement the substrate to observe the spectrum of them. Different concentrations of sodium chloride(NaCl) solutions also have been measured on the different substrates, and the shift of the transmission light wave peak was detected.