ABSTRACT
A dual aspheric integrated beam shaper suitable for a high-power laser situation has been designed and realized. The model for this lens was derived theoretically and the performance was evaluated using a detailed simulation. The ultrasonic vibration assisted cutting and the high-precision grinding and polishing technology were used for the processing. The surface accuracy was less than 200 nm measured with a profiler, and the roughness was smaller than 20 nm with the help of the white light interferometer. Shaping experiments were carried out, which verified that the Gaussian beam has uniform intensity distribution with a uniformity of 85.13% in the near field and converges to a point in the far field, which is exactly as expected. It thus provides an actual selection for high-power laser shaping.
ABSTRACT
To realize the flow visualization of shock train structures by Schlieren measurements in a square-to-circular transition isolator, a high-precision conformal optical window was manufactured by fly-cutting technology. According to the light refraction principle, the window's outer surface was iteratively optimized based on the super-elliptic curves of the internal flow channel. Through tolerance analysis and processing parameter optimization, the transmitted wavefront error (RMS value) of the finished window was 0.823λ (λ=632.8n m). Based on a z-type Schlieren apparatus, the high-precision Schlieren measurements were conducted through the window and processed by an image filtering process method. The results promote high-precision Schlieren observation towards square-to-circular transition isolators.
ABSTRACT
In order to perform the flow visualization of a shock train structure by the schlieren imaging method in the cylindrical isolator, to the best of our knowledge, a novel integrative design and processing scheme of an aluminum alloy pipe with an acrylic conformal optical window pair are proposed. The optical ray tracing and wavefront correction methods were applied to design the inner cylindrical surfaces and outer aspherical cylindrical surfaces of the optical window pair for parallel light correction based on the conjoint analysis with the processing capability. Under the tolerance analysis and the optimization of the machining path, the integrative model was fabricated on a three-axis computer numerical control machine using two-axis turning and fast tool servo machining. The wavefront aberration (peak-to-valley value) and wavefront aberration (RMS) of the optical window pair were corrected within 12.189 and 2.658λ (λ=632.8nm) in the observation area which met the requirements of high-precision schlieren observation.
ABSTRACT
The NiP coating has excellent wear and corrosion resistance, and electroless nickel-phosphorus coating is one of the best measures for surface modification of metal optical devices. The NiP layer could be processed by single-point diamond turning (SPDT). However, the periodic marks on the surface of the NiP coating processed by SPDT will lead to diffraction and stray light, which will reduce the reflectivity and image quality of the mirror. This paper studied smoothing polishing based on chemical mechanical polishing to remove turning periodic marks efficiently. Firstly, we studied the chemical corrosion and mechanical removal mechanism of smoothing polishing of the NiP coating through theoretical analysis. Then, the influencing factors of processing the quality of smoothing polishing are analyzed, and the optimal machining parameters and polishing slurry formula are formulated. Finally, through the developed process, the surface roughness of Root Mean Square (RMS) 0.223 nm is realized on the NiP coating, and an ultra-smooth surface that can meet the service accuracy of a hard X-ray mirror is obtained. Our research simplifies the high-precision machining process of the NiP coating and improves the machining efficiency. Therefore, it can be used as a new high-precision manufacturing NiP coating method.
ABSTRACT
A three-step quasi-absolute testing method for optical cylinders is proposed in this Letter. Three measurements are taken at the so-called cat's eye position and confocal null testing positions with a computer-generated hologram (CGH) rotated around the axis parallel to that of the cylinder. The quasi-absolute surface error of the cylinder is obtained by simple operations including addition/subtraction and flip of the datasets. The uncertainty is traceable to an optical flat. Two different CGHs are used for a convex cylinder and give consistent quasi-absolute testing results of the surface error, which experimentally validates the method.
ABSTRACT
The surface of metal mirrors is often polished by electroless coating with a Ni-P modified layer after single-point diamond turning. In practice, however, improvements in mirror quality are closely related to the polishing environment, polishing medium, and polishing force. If not adequately controlled, processing defects such as visible scratches can lead to the deterioration of surface roughness. Based on the Ni-P modified surface of a metal reflector mirror, this study optimizes the configuration of magnetorheological figuring (MRF) fluid and polishing process parameters so that MRF high-efficiency surface modification can be realized and the scratch problem can be resolved. The processing method of a high-performance metal mirror is developed by studying the high-efficiency and high-precision processing technology based on small head smoothing. The surface roughness achieved by the proposed method was better than Ra = 0.39 nm. The ultrasonic cleaning process effectively improved the surface roughness after processing. According to the combined processing technology developed in this study, the modified layer of the parabolic mirror with a diameter of 370 mm was processed, and the surface quality was increased from RMS = 338.684 nm to RMS = 21.267 nm.
ABSTRACT
All-reflective coaxial visible/infrared imaging systems based on monolithic multisurface optics have been a hot point of research in recent years. Since multiple surfaces share a single substrate, their relative positions are fundamentally guaranteed as fabricated without any alignment. In this paper, the coaxial system is designed with multifolded ideas. Both the visible subsystem and the infrared subsystem are comprised of two monolithic optical modules, which are machined by single-point diamond turning (SPDT). A novel method based on a computer-generated hologram (CGH) is then proposed to simultaneously measure the shape and position of monolithic multisurface optics. The effects of surface shape and position error on the wavefront aberration of the system are also discussed with the help of Zernike annular polynomials. Then the wavefront aberration of the system is measured, from which we subtract the contribution of surface shape and position error. The aberration induced by misalignment of the two monolithic modules is then estimated. It indicates that the concentricity is about 3 µm. Finally, two similar systems with different clear apertures are assembled as a coaxial visible/infrared imaging system. Coaxial visible and infrared images are captured and fused to show clearer details.