Special issue—Advanced design and manufacturing of optical system
2021, 50(10): 20210311.
doi: 10.3788/IRLA20210311
An prototype of imaging spectrometer for the remote sensing of solar induced chlorphyll fluorescence of vegetation was researched to satisfy the scientific requirements of high SNR and high spectral resolution for the weak fluorescence observation. Based on the principle of relationship between the fluorescence and solar Fraunhofer lines, the optimization of the optical system with high performance was completed. It covered the visible-near infrared working waveband of 670-780 nm, which also covered the special wavelengths of the solar induced fluorescence. The numerical aperture was 0.25 which ensured the enough SNR of the system. The imaging spectrometer also owned spectral resolution better than 0.3 nm and excellent imaging quality. The performance tests of the prototype were studied. The research will supply an excellent engineering application in the further solar induced chlorophyll fluorescence high spectral imaging observation.
2021, 50(10): 20210520.
doi: 10.3788/IRLA20210520
To solve the problem of high-precision testing of large-diameter plane mirrors, a mathematical model of subaperture stitching testing based on global optimization was established, and a stitching factor was proposed for overlapping area values. Based on the above method, combined with engineering examples, the stitching testing of a plane mirror was completed with a diameter of 120 mm, and four subapertures to be tested were planned. In order to compare the stitching performance of the algorithm described in this paper with the traditional least-squared fitting stitching algorithm, two algorithms were used to complete the surface reconstruction of the plane mirror to be measured. The experimental results show that the stitching results obtained by the two algorithms are smooth, continuous, no "stitch marks". At the same time, the results of the two algorithms are also compared with the full-aperture testing results. In this paper, obvious "stitch marks" can be seen in the residual map of the traditional splicing algorithm, and the stitching results obtained by the algorithm method in this paper are smooth and continuous, while the PV and RMS values of the residual graph are 0.012λ and 0.002λ, respectively, which are less than the PV and RMS values of the traditional algorithm residuals chart, which verifies the reliability and accuracy of the algorithm.
2021, 50(10): 20210224.
doi: 10.3788/IRLA20210224
In order to ensure the imaging quality of large-aperture survey telescope under dramatic changes of external environment and realize fast alignment, the wavefront sensing system was required to cover a large dynamic range while maintaining the aberration detection accuracy. First, a set of large dynamic range alignment technology was established based on the light intensity distribution of the single-sided defocus image and curvature sensing. Both analytical formulas and machine learning methods were used to figure out the defocusing and other low-order aberrations. Then, theoretical analysis was made on the resolution accuracy of different types of aberrations. Finally, experimental verification was carried out. The results show that the defocusing detection error (take wavefront RMS variation as the criterion) is less than 5%, while the misalignment detection error is less than 15%, which meets the alignment and adjustment requirements.
2021, 50(10): 20210476.
doi: 10.3788/IRLA20210476
High-resolution space optical camera defocused in orbit due to the change of space operational environment, which would affect the image quality. Therefore, refocusing were required by the camera in orbit. In order to meet the requirements of high resolution and lightweight space optical camera, a main support structure with both support and refocusing function was designed. The position of the secondary mirror assembly was adjusted along the optical axis by the precise temperature control of the supporting structure, then the camera can be refocused by the thermal control of the supporting structure. Firstly, the refocusing accuracy was analyzed according to the optical system parameters to determine the design requirements of the support structure; Then, the global optimization of the supporting structure was performed based on the variable density of continuous topology optimization (SIMP); Finally, the thermal optical test was performed to verify the thermal refocusing function and measure the thermal refocusing parameters of the apace camera. The experimental results show that the thermal refocusing parameter of the supporting structure is 0.071 mm/℃, the refocusing accuracy and range are 0.014 mm and ±0.385 mm respectively. The proposed method had been used in the design of "Jilin-1"gf03 satellite which had been tested in orbit, and the focusing accuracy and focusing range meet the design expectations.
2021, 50(10): 20210213.
doi: 10.3788/IRLA20210213
Variable intelligent trusses have great advantages in optical equipment and on-orbit assembly. The relevant applications and the development of variable intelligent trusses on large-aperture optical equipment were summarized. Firstly, for serial configuration with less degrees of freedom, the design and application of variable intelligent trusses applied on telescopes were discussed; then, the application of the variable intelligent trusses in the on-orbit assembly, service and adjustment of the telescope were introduced. In view of its high degree of freedom and high positioning accuracy, the feedback methods that could be used in the adjustment of the trusses were summarized, the structure and control algorithm of the trusses were discussed as well. Finally, the technologies currently applied to smart trusses were summarized and the development trend was summarized.
2021, 50(10): 20210265.
doi: 10.3788/IRLA20210265
Laser guidance is one of the most commonly used guidance methods nowadays, and the performance of laser semi-active optical system directly affects its guidance accuracy. The method for the aberration optimization design of laser semi-active optical system was discussed, the initial structure of the optical system was realized by giving different spherical aberration and defocus values, and the spot uniformity design was realized by controlling the asymmetric aberration. A refractive laser semi-active lens was designed and fabricated, in 1064 nm working wavelength, with ± 9.2° field of view, 5 mm spot size, uniform energy distribution. In order to solve the problem that laser semi-active lens can not be detected separately, the principle of a low-cost visual testing of lens was proposed, which based on the chromatic aberration characteristics, and the visual testing system for laser semi-active optical lens was built. Test results of the lens show that the spot size satisfies the design requirements, and the low-cost visual testing system significantly improves the efficiency of lens testing and is easy to engineering and mass-produce.
2021, 50(10): 20210477.
doi: 10.3788/IRLA20210477
The design, assembly and experiment of the optomechanical system of a compact spaceborne video camera developed for the 20 kg micro-nano optical remote sensing satellite were introduced, and the integrated optimization method was also proposed. The camera was a Cassegrain optical system including two mirrors and one corrector assembly. In order to obtain the best thermal stability, the mirrors were made of silicon carbide. Firstly, based on the task and overall design of 20 kg micro-nano video satellite, the requirements of video camera were proposed; Then, the optical and optomechanical structure system of the video camera were introduced respectively; In order to further improve the lightweight rate, while meeting the requirements of optical performance, the optomechanical integration optimization method was used to the lightweight design. After optimization, the mass of the optomechanical system was only 3.03 kg, the weight of the whole camera was only 4.76 kg, and the 1st mode was larger than 120 Hz; Finally, the assembly and ground mechanical experiments of the camera were summarized. The results showed that the camera had very dynamic properties and stability.
2021, 50(10): 20210527.
doi: 10.3788/IRLA20210527
With the development of advanced optical system design and manufacturing, large aperture optical system has been widely used. However, the lack of high precision surface shape detection means limits the manufacture and application of large aperture plane mirrors. In order to detect the surface shape of large aperture planar mirror with high precision, a Shack-Hartmann scanning and stiching detection method was proposed. The scanning and stiching principle and wavefront reconstruction algorithm were studied, and the mathematical model of microlens array imaging was established to verify the feasibility of Shack-Hartmann scanning and stiching detection principle. A scanning and stiching test experiment was carried out for a 150 mm aperture plane mirror, the full aperture surface shape 0.019λ RMS(λ=635 nm) was obtained. Compared with the results of interference detection, the detection accuracy was 0.008λ RMS. The results show that the method can realize the high precision detection of large aperture planar mirror.
2021, 50(10): 20210294.
doi: 10.3788/IRLA20210294
To solve the problem of the large amount of noise in the event stream output by the event camera, an event stream denoising algorithm based on the probability undirected graph model was introduced. Due to the imaging principle of the camera, the change of the target had certain regularity and correlation in time and space. By mapping the event to the polar coordinate space-time neighborhood, the local correlation of the event was established to build a complete probability graph model. In addition, the improved conditional iterative mode algorithm was used to optimize the iterative solution of model. The experimental results of simulated data generated by the event camera simulator and the real data recorded by DAVIS346 show that the proposed algorithm can effectively remove noise events. Finally, the comparison with the filtering algorithm proves that the algorithm is superior to the filtering algorithm.
2021, 50(10): 20210091.
doi: 10.3788/IRLA20210091
The relay optical system was widely used in optical systems such as infrared spectral imaging system, light field imaging system, optical microscopy system, polarization interference imaging system, compound eye imaging system, ring-belt panoramic optical system, multi-scale imaging system and head-mounted enhanced display system, etc, which can link up, match pupil and deflect optical systems. The structures of the existing relay optical system were studied. The design method of telecentric off-axis three-mirror optical system with front aperture and the description method of free-form surface were introduced. According to the design parameters, the telecentric relay optical system with broadband and real entrance pupil was completed. The system was an off-axis three-mirror optical system structure, and each mirror was a free-form surface described by XY polynomial. The results of CODEV software simulation show that the MTF of the system is close to the diffraction limit, the distortion is less than 1%, and the imaging quality is good with the working spectral range of 0.4-5.0 μm, f'=400 mm, F/3 and 2ω=8°.
2021, 50(10): 20210118.
doi: 10.3788/IRLA20210118
A bi-axial half-butterfly flexure hinge for an fast steering mirror （FSM） was presented to adapt high stability accuracy of beam-pointing control performance in laser weapon systems. According to the requirements of reciprocating movements and high bandwidth provided for the FSM, the solid model of the bi-axial half-butterfly flexure hinge was designed. By applying Castigliano’s displacement theorem, the numerical model was simplified and deduced. Furthermore, to quantify the numerical model, natural frequencies of the finite-element analysis and experiments were carried out, of which the results were compared with the analytic solutions. The experiment results show that the in-plane natural frequency is 165.29 Hz. The comparison shows that the error between numerical analytic and experimentation is 1.3%, and the error between FEA and experimentation is 3.2%. It is proven that the bi-axial half-butterfly flexure hinge is an appropriate structure as a guide mechanism for an FSM system.
