Cylindrical mirrors, as an important optical element, have various types, and different types of cylindrical mirrors play unique roles in optical systems.
Aluminum alloy cylindrical surface mirror:
Characteristics: With good optical performance, especially some aspheric surfaces are more outstanding after enhancement, they are widely used in many optical systems. However, for some complex mirrors, it is difficult to obtain higher accuracy by single point diamond turning (SPDT) technique alone, and the residual periodic diamond turning structure causes scattering loss at shorter wavelengths, so additional polishing steps are usually required.
Applications: Single-point diamond turning technology can be used directly in Infrared optics applications, and its accuracy can be improved by combining it with processes such as magnetorheological polishing (MRF), which provides a reference for the fabrication of aluminum alloy mirrors with complex surfaces.
High precision cylindrical mirror:
Requirements: Not only is it required to have extremely low surface roughness, no surface/subsurface damage and low residual stress, etc., but also the parallelism and perpendicularity of its cylindrical busbar need to be ensured.
Traditional Processing Methods: Traditional grinding and polishing technology and computer-controlled optical surface molding (CCOS) have their own advantages and disadvantages in terms of surface roughness, face shape accuracy and busbar error after processing of cylindrical mirrors.
New process: Aiming at the problems of low efficiency, high roughness and surface/subsurface damage of the existing processing methods, a new process of magnetorheological polishing of aspherical cylindrical mirrors with symmetric structure is proposed. This process reduces the surface roughness of the cylindrical mirrors and improves the profile accuracy. At a polishing time of 40 min, the surface roughness Ra is reduced from 1.84 μm to 0.36 μm, the local profile accuracy RMS1 is reduced from 1.91 μm to 0.24 μm, and the busbar cross-section profile accuracy RMS2 is reduced from 4.1 μm to 0.68 μm.
Monocrystalline silicon cylindrical mirror:
Processing method: In order to obtain high-precision monocrystalline silicon cylindrical surface optical elements, the coordinate transfer function model of the diamond grinding wheel in the process of parallel grinding of cylindrical surfaces was established, and the forming process scheme was proposed based on the dressing accuracy of the grinding wheel and the grinding accuracy of the elements.
Experimental results: The experiments were carried out on the monocrystalline silicon cylindrical mirror with the size of 440mm×50mm, and the shape error PV value after grinding was about 2.7μm, which proved the correctness of the transfer function of the monocrystalline silicon cylindrical optical element and the molding process scheme.
Half parabolic cylindrical mirror:
Role: It is an important part of the missile laser fuze receiver, and reducing its imaging line width on the detector can improve the detection sensitivity and field of view edge sharpness.
Analysis method: The geometrical-optical mathematical model of half-amplitude parabolic-cylindrical mirror is established, the imaging characteristics of its focal plane are analyzed by the method of translating the light section near the focal plane, the concept of optimal image plane is put forward based on the principle of the minimum imaging linewidth and the convergence of the near-axis light rays in the focal plane and the inclined focal plane are compared. The simulation results show that the imaging linewidth of the off-axis parallel rays on its tilted focal plane is significantly reduced.
Variable-section compression-bending ellipsoidal cylindrical reflector:
Design scheme: According to the needs of the synchrotron radiation beam in the project of building line station, the scheme of variable cross-section bent ellipsoidal cylindrical reflector is proposed. The program is based on the design theory of variable-width curved ellipsoid cylindrical focusing mirror, deriving the formula for calculating the slope error of variable cross-section (with arc-vector focusing) mirrors, and optimizing the design.
The design is based on the optical parameters of the focusing mirror (object distance p, image distance q and grazing incidence angle θ), and the design error of the mirror is finally calculated with the help of finite element analysis software. The results show that, under this requirement, the optimal widths of the two ends of the mirror are 49.5mm and 90.5mm, respectively. After calculating, simulating and optimizing the bending moments of the mirror at both ends of the compression bending, the root-mean-square value of the slope error is reduced from ∼5.1368 μrad to ∼0.0636 μrad (1m length), which is close to the systematic error (∼0.0407 μrad), and meets the design requirements (＜0.1 μrad). 0.1μrad).
Hyper-elliptic cylindrical surface gradient coil design in the hyper-elliptic column:
Role: The super-elliptic cylindrical design surface can reduce the distance between the coil and the target, improve the space utilization, and expand the effective range of the imaging area.
DESIGN METHOD: The flow function method and the extensibility of the column surface are utilized to design the gradient coils in the MRI system on the super-elliptic cylindrical surface. The expressions of magnetic field strength and stream function are established according to the Biot-Savart law, and the least-squares method and Tikhonov regularization method are used to construct the dual-objective design function, and the optimization problem of the gradient coil is transformed into a direct solution problem of a suitable linear system of equations through the introduction of appropriate boundary constraints of the stream function.
Aspherical columnar microlens:
FUNCTION: Aspherical cylindrical microlens is an important micro-optical element with laser collimation, focusing, homogenization, etc. It has a wide range of applications in laser communication, fiber optic sensing, LIDAR ranging, laser pumping and other systems.
Preparation method: In order to reduce the size of the optoelectronic system and improve the performance of the fiber, increasing the numerical aperture of the lens is a common solution. It is proposed to use silicon with larger refractive index as an alternative material to quartz substrate with low refractive index, so that the numerical aperture of the microlens can be greatly increased under the same volume, and at the same time, the processing volume can be reduced to improve the preparation efficiency. In view of the traditional quartz microlens preparation method is no longer applicable to the silicon microlens, we propose to prepare photoresist aspheric patterns based on the mask-shift exposure method, using multiple coating and cyclic exposure methods to solve the problems of poor uniformity of thick adhesive coating and obvious traces of exposure mask, and finally using plasma etching technology for pattern transfer to realize the preparation of microlenses.
Silicon lens preparation process
Convex and flat cylindrical mirrors for beam shaping in laser-induced breakdown spectroscopy:
Role: In order to improve the problem of uneven distribution of laser energy in the laser-induced breakdown spectroscopy (LIBS) technique, a plano-convex cylindrical mirror is utilized to shape the laser beam. Through the simulation software, the optical path imaging simulation of different focal lengths of plano-convex cylindrical mirrors is carried out to determine the optimal focal length of 100mm to meet the conditions of the laser, and the shaping system based on LIBS beam is constructed on the basis of the simulation software.
Experimental results: The experiments show that compared with the shaping without plano-convex cylindrical mirrors, the average coefficient of variation of the focal spot intensity of strontium in the samples is reduced by 41.91%, the average coefficient of peak-to-valley ratio of the focal spot intensity is reduced by 41.27%, and the uniformity of the energy is increased by 17.23%, and the coefficient of determination of the fit is increased from 0.860 to 0.914. The results show that the use of plano-convex cylindrical mirrors can increase the beam energy uniformity, and the results validate that the use of plano-convex cylindrical mirrors can increase the energy uniformity. The results show that the use of plano-convex cylindrical mirrors can improve the uniformity of the beam energy, which verifies that plano-convex cylindrical mirrors are an effective method for laser beam shaping.
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