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.
A concept for a freeform primary lens system (FPLS) is proposed for designing freeform optics in the direct-backlight system of liquid crystal displays. This FPLS has a super small ratio of height of the optics system h to LED source with diameter D by avoiding the use of traditional secondary optics for LED illumination applications. The FPLS is first designed based on energy conservation principles and ray mapping techniques, and improved through feedback optimization algorithms. Both simulation data and experimental data are employed successively to improve the illumination uniformity on the target plane. Meanwhile, the divergence angle of the FPLS is further improved to achieve a more uniform irradiance distribution pattern of the LED luminaire array on the target plane with an ultrashort projection distance between source and target. We demonstrate the concept by designing and manufacturing an FPLS; the experimental data show that, with h / D = 0.98 of the optical system, the relative standard deviation of the target area reaches 0.22 within the divergence angle of 120 deg.
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).
Recently, China is planning to construct a new large optical-infrared telescope (LOT), in which the aperture of the primary mirror is as large as 12m. China’s LOT is a general-purpose telescope, which is aimed to work with multiple scientific instruments such as spectrographs. Based on the requirements of LOT telescope, we have compared the performance of Ritchey–Chrétien (RC) design and Aplanatic-Gregorian (AG) design from the perspective of scientific performance and construction cost. By taking the primary focal ratio, Nasmyth focal ratio, and telescope’s site condition into consideration, we finally recommend a RC f/1.6 design configuration for LOT’s Nasmyth telescope system. Unlike the general identical configuration, we choose a non-identical configuration for the telescope system which has a shorter Cassegrain focal ratio compared to the designed Nasmyth focal ratio. The non-identical design can allow for a shorter back focal distance and therefore a shorter telescope fork to guarantee the gravitational stability of the whole telescope structure, as well as relatively lower construction cost. Detailed analysis for the feasibility of our recommended design is provided in this paper.
To accomplish the interference testing to an off-axis parabolic mirror, we provided a kind of hybrid compensation modal combining compensator with stitching testing. To verify the validity of the above modal, we measured a Φ1450mm off-axis parabolic mirror with the above method. It can be seen from the stitching map that the stitching map is smooth and continuous in the full aperture. At the same time, to evaluate the stitching testing accuracy, we compared the stitching testing map and the subaperture testing map. It shows that the RMS of the residual map between them is 0.003λ, verifying the validity and accuracy of the model.
In this paper, the aperture averaged scintillations of the Bessel beams carrying optical vortices propagating in turbulent atmosphere are evaluated. The multistep form of the propagation algorithm and a numerical phase screen simulation method are applied to the calculations of the aperture averaged scintillation. The results show that the Bessel beam with more topological charges delivers the smaller scintillation. The relation between the aperture averaged scintillation and the size of the beams is investigated. The effect of inner and outer scales of turbulence on the scintillations of the Bessel beams is also studied. These results may be useful in long-distance optical communications in free space or in turbulent atmosphere.
The intensity distributions of some light sources have the rotationally symmetric property. We propose a method to design freeform optics by sampling the source intensity distribution nonuniformly in a modified double‐pole coordinate system to satisfy the circular emission pattern of the light source. We can greatly improve the smoothness of the designed freeform surfaces and maximize the collection efficiency. We demonstrate the design method with two freeform illumination lenses: one for the light from the multimode filter and the other for the light emitting diode with a hemisphere emitting solid angle. We also demonstrate that the nonuniform sampling algorithm has significant advantages for designing freeform reflectors with superlarge collection angle.
In this paper, we propose a new composite ray mapping method to design freeform total internal reflective (TIR) optics for LED illumination. We sample the ray intensity distribution into rectangular grids which have the best topological match to those rectangular grids on the target surface. With the multiple-to-one mapping relationships between the source intensity distribution and target irradiance distribution, we can construct the freeform TIR surfaces and freeform refractive surface using Snell’s law. Compared to our previous design using uv-θϕ composite ray mapping method, this design approach is expected to have much less surface error and improve the illumination uniformity further because of the better topological match. In addition, due to the overlapping mechanism by multiple-to-one (composite) ray mapping, the method could lead to a more robust freeform optics compared to traditional freeform optics designs.
We propose a new method to design freeform reflectors by nonuniformly sampling the source intensity distribution in double pole coordinate system. In double pole coordinate system, there is no pole for the whole hemisphere because both poles of the spherical coordinate system are moved to southernmost point of the sphere and overlapped together. With symmetric definition of both angular coordinates in the modified double pole coordinate system, a better match between the source intensity distribution and target irradiance distribution can be achieved for reflectors with large acceptance solid angle, leading to higher light efficiency and better uniformity on the target surface. With non-uniform sampling of the source intensity, we can design circular freeform reflector to obtain uniform rectangular illumination pattern. Aided by the feedback optimization, the freeform reflector can achieve the collection efficiency for ideal point source over 0.7 and relative standard deviation (RSD) less than 0.1.
This paper reports the design trade off study of the design of an innovative CMOS active pixel sensor (CAPS) based on Silicon-on-Insulator (SOI) technology. The CAPS designs approach provides the flexibility and high-density features of hybrid pixel sensors with photon counting architecture. This sensor is the key component for optimized X-ray Tomosynthesis. A proof-ofprinciple test chip, paying particular attention to the noise performance of the pixel, front-end electronics (FEE) and readout speed, is available for testing in 2008. We present the design of the test chip in this paper.
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