This PDF file contains the front matter associated with SPIE Proceedings Volume 12070, including the Title Page, Copyright information, and Table of Contents.

As an important technology for realizing national strategies such as intelligent manufacturing and industrial 4.0, digital twin (DT) has received great attention from scholars and enterprises. At present, it has been applied to vehicles, ships, spacecraft, satellite, machining process and other fields, but there is no research report in the field of optical manufacturing. Aiming at this problem, and taking the reflective optical systems as the object, the applications of DT were discussed from the lifecycle dimension, including design and development, manufacturing and assembly, operation, and maintenance, et al. On this basis, taking the construction of the optical DT model as an example, the modelling methods of machining error and assembly error were mainly studied, the applications of the DT in computer-aided alignment and active optics were discussed, which demonstrate the importance of DT technology in the manufacturing process of reflective optical systems.

Optical sparse aperture systems often need to correct the piston error between sub-apertures to obtain high-resolution imaging quality. This paper constructs a deep convolutional neural network via transfer learning to perform piston error sensing on a single focal plane image. First, a batch of data sets that introduce piston error generates according to the principle of sparse aperture imaging. The image features are extracted through the pre-training network, and the mapping relationship between the features and the corresponding piston error values is established. When a given single image is sent to the network for processing, then get corresponding piston error value via search with the nearest neighbors. The simulation results verify the method's effectiveness and measure the piston error of the 1λ dynamic range. Because this detection method can perform piston error sensing tasks without introducing additional measuring equipment, it dramatically reduces the complexity and hardware cost of the optical system. It may be used as a new piston error detection technology in the future.

The 1.2-m primary mirror supporting systems are composed of axial support system with whiffletree structure and lateral support system with 6 tangent links. With the simulation based on the finite element analysis (FEA), the 18 points positions of the axial support are determined and the bottom chamber structure of the primary mirror is improved. In order to reduce the mirror surface deformation, the assembly stress on the primary mirror is reduced by optimizing the lateral support structure. The analysis results demonstrated that the root-mean-square (RMS) of the surface deformation is 10.9nm when the primary mirror points vertically. Meanwhile the RMS of the surface deformation is 10.3nm when the primary mirror points horizontally.

In order to deal with the threat of space debris to space experiment platforms and equipment, three-mirror anastigmatic system, which has the characteristics of light weight, small size and good optical performance, are used for space debris detection and detailed imaging. With the development of freeform surfaces, this article shows a new type of structure which has good optical performance and simple complexity of assembly and adjustment. The first step is to analyze the calculation method of the initial structure parameters of TMA system, and then the secondary mirror adopts the XY polynomial freeform surface. The primary mirror is reused as tertiary mirror, and the design of a new type TMA system is finally completed. Its effective focal length is 400 mm, the field of view (FOV) is 2°×4°, F/# is 5. At the Nyquist frequency 108lp/mm, the MTF value of this system is greater than 0.588. The maximum distortion is less than 0.80%. The results show that the imaging quality of the system meets the design requirements in the effective field of view.

With the widening of the application scenarios for target observation, the traditional ground-based fixed LAT system has been unable to meet the requirement of high precision tracking ，the LAT need to be installed on different motion platforms. In this case, a series of photoelectric tracking systems based on motion platforms have been derived. The combination of LAT and moving platform brings a new problem--Disturbance such as braking, vibrating, and shaking of the platform will cause the deflection and shaking of the LAT imaging screen, which will have a great impact on the LAT tracking. In this paper, a method to determine the change of the attitude angle θ of the target in the field of view caused by the movement of a moving platform is proposed to suppressed overcome the disturbance introduced caused by the application of LAT in moving platform carrier. According to the angular position data of the target tracking point acquired by the CCD system and the attitude information of the motion platform in the geodetic coordinate system provided by the inertial navigation system, the attitude angle of the target can be calculated by applying the proposed attitude estimation algorithm. This method not only, provides a specific estimation process of target attitude angle, but also offers principle information for tracking state decision, image processing, and fiducial direction calculation.

This paper designs an integrated optical system for detection and recognition. The system combines the R-C (Ritchey-Chretien optics) system and the zoom structure. The R-C mirror design of the initial structure of the system is completed by calculation of theory. Then, use the zoom theory to complete the design of the two zoom positions. The two zoom positions respectively realize the detection and identification of space debris. The F numbers are 5.86 and 11. The field of view angles are 2.83°and 0.6°. It works in band of 400-750nm. The system has an entrance pupil diameter of 300mm. The detection position can detect space debris with a brightness of 13 magnitude stars, with focal length of 1760mm; the recognition position’s modulation transfer function is greater than 0.6 at the Nyquist frequency of 33.33lp/mm, with the focal length of 3300mm. The zoom theory is well applied in the integrated detection and recognition system.

Compound axis servomechanism (CAS) is the most popular form of structure used in the large aperture telescope (LAT) system in the last few decades. In the control system of the CAS, the sub-axis which is driven by a fast-steering mirror (FSM) plays a decisive role in observation target tracking. In this paper, the kinetic dynamic of fast observation target (FOT) is analyzed by the time-frequency spectrum method. A sub-axis controller base on the FOT’s kinetic dynamic is proposed to improve the tracking performance of the CAS system. Traditional double-loop control is applied in sub-axis control. The inner loop is designed to provide a large bandwidth to cope with the FOT. As for the outer loop, a new control approach that is PIPI double integrations control is introduced to achieve a better tracking performance for the FOT. Additionally, the relationship between time delay and bandwidth of the LAT system is analyzed to demonstrate that the time delay is the main restriction to further improve the bandwidth of a CCD-based sub-axis controller. The theory and the simulation result indicate the proposed approach can improve the tracking performance of the LAT system to a certain extent, but still not sufficient when it comes to the FOT.

Synthetic aperture is the mainstream structure of current astronomical telescopes. However, after the synthetic aperture telescope is deployed in orbit, there will remain tilt and piston error between adjacent segments, which will sharply deteriorate the imaging quality of the optical system. The traditional piston error detection method based on dispersed fringe sensor has the question that it is difficult to detect the piston error within one wavelength, and the detection accuracy is restricted by the detection range. The method in this paper constructs multiple monochromatic light channels by opening windows in different areas on the dispersed fringe pattern, calculating and obtaining the feature value in each window to form a feature vector. Then, the convolutional neural network is introduced to distinguish the feature vector to detect piston error. Among them, the training set construction method adopted in this paper only needs raw data in one wavelength to construct a training set covering the entire detection range. Through simulation, the method proposed in this paper achieves the detection range of [-208λ, 208λ] (λ=720nm), and regardless of the presence of noise, the root mean square value of the detection error does not exceed 17.7nm (0.027λ_min, λ_min=660nm).

The Southern Spectroscopic Survey Telescope (SSST) is a planned multi-wavelength sky survey telescope. The main scientific instrument of the telescope is an astronomical spectrometer. In this paper, we present a feasible optic system design based on wide-field Cassegrain corrector configuration for the telescope and related multi-object and fiber-fed spectrograph (MOFFS) system. The latest telescope design has a large field of view (FOV) of 2.6°×2.6° with its image spot size less than 0.3 arcsec in diameter for its full FOV in 80% encircled energy with the atmospheric dispersion effect taken into consideration. The MOFFS system based on the Volume Phase Holographic Gratings (VPHG) has an RMS radius of less than 12μm from center to edge of the fiber slit and the working band from 360nm to 1100nm while having the VPHG diameters less than 120mm. The camera group lens exhibited a transmittance higher than 88% at the whole working waveband.

We briefly report on the development of a 50 mm balloon-borne coronagraph and its recent ground experiment results made at the high altitude (4800 m above the sea level) site of Mt. Wumingshan in Daocheng, Sichuan of China. The main scientific purpose for developing this coronagraph is to investigate the morphology and dynamics of low-layer coronal structures before and during solar eruptions by observing at a float altitude of about 30 km from 1.08 R_sun to 1.5 R_sun at white light wavelength (centered at 550.0 nm, bandwidth 5 nm). The instrument is an internally occulted Lyot coronagraph developed by Yunnan Observatories in collaboration with Shangdong University (in Weihai) and Changchun Institute of Optics, Fine Mechanics and Physics. The coronagraph was designed with scattered light intensity level of better than 1×10-5 I_sun in the inner field of view. A filter wheel system with linear polarizers and an sCMOS camera provided polarization and total brightness images of size 2048 x 2048 pixels. The first successful results were taken on February 27, 2021 in the Daocheng site. This coronagraph experiment obtained coronal images only showing obvious coronal structures very near limb. Furthermore, during the end of March and early April, after improving the polarizer filter system, higher-quality coronal images with pB coronal structures appeared in the full field of view were obtained in our ground-based experiments. Comparison between our results and the other coronal data in the world are discussed. The success of the 50 mm coronagraph in ground experiments is a milestone for us to develop the next-generation large-aperture coronagraph, as well as for future near space projects.

According to the assembly requirements of the space camera's primary and secondary mirror system, this paper proposes the assembly process of carbon fiber truss fuselage's primary and secondary mirror system based on adhesive error compensation technology. The process starts from a system point of view, the adhesive bonding of the truss fuselage was unified with the assembly of the primary and secondary mirror system. The adhesive technology was used to compensate the machining errors of the structural parts, and the adhesive bonding of the truss fuselage and the optical axis consistency assembly of primary and secondary mirror system are realized in the process of one adjustment. According to this assembly process idea, the assembly process of primary and secondary mirror system was designed. Firstly, the optical axis of the primary mirror and the optical axis of the secondary mirror were calibrated by the principle of autocollimation, and the optical axis was guided to the cross reticule as the reference for subsequent installation and adjustment. Secondly, in order to realize this process method, the assembly and adjustment platform of the primary and secondary mirror was designed and built. In addition, the factors that affect the assembly precision of the primary and secondary mirror system are analyzed one by one, and the calculation method of system assembly error is obtained. This assembly method has been successfully applied to a space camera. After assembly, the coaxiality between the optical axis of the primary mirror and the optical axis of the secondary mirror is better than 0.02mm, the Angle between the optical axis is better than 10 ", and the wavefront of the primary and secondary mirror system is close to the optical design index. The assembly method presented in this paper provides a technical reference for the assembly of similar large aperture optical machine system.

LINC-NIRVANA is a near-infrared image-plane beam combiner with advanced layer-oriented multi-conjugated adaptive optics (MCAO) for the Large Binocular Telescope. The instrument will combine the lights from the two 8.4 m primary mirrors in “Fizeau” mode in which the wavefronts will interfere in the focal plane, not in the pupil plane, so it is a true imaging instrument. The field of view can be several arcminutes, only limited by the performance of the adaptive optics (AO) system to obtain near-zero aberration wavefronts over large sky angles. However, if the secondary mirrors of the MCAO system have mechanical displacement in a way that would make the plate scale of the two systems change and then may cause variant PSFs and a degradation of the image quality which may affect the fringe tracking performance. Thus it is very important to know whether the plate scale of LN changes or not. To try to compensate for this problem, a plate scale variation detecting method is proposed. The useful information is gotten from the un-overlapping wavefront which is measured by the high wave-front sensor (HWS), and then processed by an algorithm to extract the long-time exposure average value of wavefront tip and tilt which is related to and response to the plate scale change. The simulation study shows that the method is feasible, and the paper gives practical guidelines for the application of plate scale variation detecting for LINC-NIRVANA.

In recent years, X-ray phase sensing technology has been widely used in at-wavelength metrology and optical characterization. One of the latest developments is the technology based on X-ray speckle. It has attracted wide attention because of its simple and flexible experimental arrangement, high-cost performance, multi-mode, and high angular sensitivity. The speckle-based technique can precisely measure the wavefront and associated aberrations and is therefore a suitable device for in-situ metrology. Shanghai Synchrotron Radiation Facility (SSRF) has been implemented and further improved such a technique. We have demonstrated that the speckle-based technique can be used in the wavefront measurement of the reflective and transmissive optics and diffraction optics such as mirrors, lens, and crystals. This paper will introduce the latest developments in speckle-based wavelength measurement technology and some application examples at SSRF.

Segmented telescope is an effective way to realize high-resolution observations in astronomy. An important work for high-resolution observations using segmented telescopes is phasing the segmented primary mirror. Modified Shack-Hartmann sensor. Is proposed for piston error detection. The interference pattern created by a circular lens placed across two adjacent mirrors in exit pupil plane is used as the signal of the modified Shack-Hartmann sensor. Piston errors need to be extracted from the interference pattern. The offset of lens and gap error of adjacent mirrors causes the distortion of interference pattern, and leads to a reduction in the detection accuracy of existing piston error extraction techniques. In this paper, we propose to replace the circular lens with a square lens and the mathematical model of the corresponding interference pattern is modeled by Fourier optics, including the one-dimensional and two-dimensional analytical solution of the interference pattern. The simulation results show that the proposed analytical solution can effectively characterize the interference pattern in the ideal situation and in the presence of lateral offset of the lens and the gap error of the adjacent mirrors situation. The results presented here give a deeper insight into the interference pattern of modified Shack-Hartmann sensor, and are of great help for developing new piston error detection techniques based on modified Shack-Hartmann sensor.

A Φ1400mm silicon carbide (SiC) mirror assembly was designed according to the requirement of the mass and the optical surface distortion. The parameters of the light-weighted open-back primary mirror were optimized by finite element analysis. Six flexure bipods were designed to support the mirror edge in 12 points evenly. 12 floating anti-gravity supports were used to Minimize the optical surface distortion caused by gravity effect to obtain the real optical surface during polishing. The mirror was precisely assembled with the bipods supports and the Carbon fiber reinforcement plastic (CFRP) chamber. The optical test with interferometer showed that the surface distortion was less than 0.03λ (λ=632nm) RMS with ±5°C temperature variation and 1g gravity condition, and the mass was 145kg, which coincided with the FEA results.

With the rapid progress of technology and manufacture, the number of telescopes in space is mounting dramatically. Considering launch cost, more and more engineers nowadays pursue lightweight and compact design of telescope in space. Traditional design scheme usually has a support plate for primary reflective mirror. It will take some space for other parts. The paper, taking a primary reflective mirror with 600mm in diameter as an example, put forward a novel design of circle support component instead of traditional support plate. It utilized a special structural layout to save more space. The paper specified this design scheme and made comparison between these two design schemes. The paper also gave the assembling method of the primary reflective mirror and circle support component, which would verify its feasibility in engineering practice in a virtual way. The novel structure design in this paper will give some guidance to engineers and designers, who are devoting themselves to designing space telescopes.

An efficient orthogonal velocity polishing tool (OVPT) was developed. The OVPT was installed on the end flange of an industry robot. The movement range of the industry robot reaches φ 1000 millimeter. The robot OVPT is a highly efficiency processing method for aspheric precision optics manufacturing. In this paper, a 360 mm diameter fused silica parabolic mirror was polished by the robot OVPT. The convergence of OVPT based on an industry robot is outstanding. After 4 times of polishing, a final surface error RMS 16.6nm was achieved, and the initial surface error RMS was 69.5nm. A polished surface roughness Ra 1.5nm was achieved by robot OVPT.

The deformable mirrors are becoming more and more important in laser systems. As the laser power increases, the deformation of the thin mirror also increases under laser irradiation. In this paper, to reduce the temperature rising, several cooling methods were proposed. These methods include air knife cooling, pole heads cooling, PZTs + pole heads cooling, Cu columns implanted around PZTs cooling, and PZTs inter-infill cooling. This paper mainly calculated the cooling effect of these cooling methods on the deformable mirrors under laser irradiation. In addition, the different cooling media such as water and air was also studied. Based on the results, we found the air cooling effect is poor, and water cooling effect is obvious. The cooling effect of adding heat-conducting sheets and Cu columns is not obvious. It has a good cooling effect when adding a heat-conducting Cu block with the same honeycomb shape as PZTs on the back of the mirror, and the temperature rising can be reduced from 7.46 °C to 2.96 °C. These calculations are valuable for the application of deformable mirror cooling.

This paper focuses on the optimization of heat dissipation efficiency in heat-stop of large ground-based solar telescope. The cooling structure of multi-channel loop cooling system for solar telescope CLST with 1.8 meters’ aperture is designed and built in Ansys-CFX software based on computational fluid dynamics. During the optimized simulation of the models, number and position of inlets, coolant flow rate and maximum temperature are taken as variables, constraint and objective respectively. In case of same coolant flow rate, more numbers of inlets and position of inlets are closer to the axis of heat-stop, the maximum temperature on the heat-stop decreases. In the design of CLST heat-stop cooling structure, after arrangement of the number and position of inlets in heat-stop cooling structure, its cooling efficiency increases by 35 percent.

Laser projectors are more and more widely used because of their large screen, and high brightness. However, the stray light outside the screen affects the user's viewing effect dramatically. In some cases, it looks like there's a halo on the top, or loos like some light outside the picture in the black. Since the stray light comes from the reflection of mechanical structural parts in the lens, and some stray light is launched by the light on digital micromirror device (DMD) off state in the illumination system, how to carry out theoretical analysis effectively is a difficult problem. On the other hand, how to trace stray light back to the source after it hits the screen and reduce it is also a challenge. Herein, some effective theoretic analysis methods and practical analysis methods are put forward, and effective countermeasures are given. Through experiments, the stray light situation is effectively improved.

In recent years, with the development of ultra-smooth surface polishing technology and extremely low-loss coating technology, the reflectivity of high-reflectivity mirror has become higher and higher, and the loss has become lower and lower. The high-reflectivity mirrors with total loss below 10^-5 Even 10^-6 have been commercialized. At the same time, measurement methods for the loss of high-reflectivity mirrors are constantly evolving. This article summarizes the loss measurement methods for high-reflectivity mirrors and the latest research progress at home and abroad, gives the principle of mainstream methods for high-reflectivity mirrors loss measurement, and introduces the measurement method for total loss and the various individual loss which make up it, including scatter, absorption and transmissions loss. What’s more, corresponding advantages and disadvantages are summarized.

The large solar telescope is automatic equipment for observing the sun. The primary mirror of the equipment can concentrate solar energy, and, the accumulation of such energy, if not effectively controlled during the equipment application, will be prone to lead to the deviation of the sunlight focus, which can damage the equipment itself and the surrounding equipment, or even threat people's lives. Therefore, sound safety protection strategies with multiple working scenarios and details taken into account are required in the process of installation, debugging, maintenance and application of the large adaptive solar telescope to effectively ensure the equipment safety.