Conformal window is a protective and imaging element in the optical system of high speed flying missile. Its surfaces are required to have the ultra-precision level of surface finish and profile accuracy to ensure good imaging quality and excellent aerodynamic. The large size and high steepness of conformal window bring great challenges to the high- precision manufacturing of inside and outside surfaces. In this paper, an ultra-precision grinding process was designed for conformal window with high steepness. The problems existing in the process of machining the inner and outer surfaces of the window were analyzed, and the most suitable grinding methods for the inner and outer surfaces were determined respectively. Furthermore, the ultra-precision grinding process of conformal window were designed and verified in detail. The research of this paper can be used as a guideline for ultra-precision manufacturing of large-size optical components with high steepness.
BK7 optical glass is widely used as aerospace optical window. Precision grinding is a common method for machining BK7 optical elements. CVD diamond grinding wheel is a cutting tool with excellent wear resistance, which can realize high efficiency grinding for BK7. However, due to its small chip space, the surface quality will be affected by the large grinding force and difficult chip removal. In this paper, micro-grooves with different angles and widths were fabricated on CVD diamond grinding wheel surfaces by picosecond laser to improve the chip space. The grinding experiments of BK7 were carried out using these micro-structured wheels. The results show that the grinding force was reduced by 80% at most compared with the unstructured wheel, and the machined surface roughness was also decreased by up to 85%. The grinding force of structured CVD diamond grinding wheel decreases with the increase of the surface micro-structure groove angle. With the increase of groove width on the surface of structured CVD diamond grinding wheel, the surface roughness of the workpiece decreases first and then increases. When the groove width is 80μm, the surface roughness of the workpiece reaches the minimum value.
KEYWORDS: Silica, Optics manufacturing, Surface roughness, Optical components, Photovoltaics, Diamond, Spindles, Laser systems engineering, High power lasers, 3D metrology
Hard-brittle thin-walled tubular optics are widely used in the field of high-power solid-state lasers. The 3D accuracy requirement and the clamping deformation of the hard and brittle thin-walled structure pose a great challenge for ultra-precision manufacturing. In this paper, fused silica thin-walled tubular optics with the length of 100mm, the inner diameter of 42mm and the outer diameter of 50mm were fabricated successfully through ultra-precision grinding. The profile accuracy of PV1.6μm, the surface roughness of Ra10nm, the straightness of 1.64μm, the roundness of 1.62μm and the cylindricity of 2.13μm were achieved through in-place dressing of grinding wheel, on-machine measurement, off-line measurement, and the iterative compensation machining. The technical difficulties of ultra-precision manufacturing of hard brittle thin-walled optics have been overcome.
Cylindrical optical element is a common type of aspheric lens, which can realize the transmission, shaping and amplification of the beam in the optical system. It has a wide range of applications, such as linear detector illumination, holographic illumination, optical information processing, strong laser system and synchrotron radiation beamline. In this paper, an efficient robot-assisted rotation-revolution ultra-precision belt grinding technology was presented for cylindrical optical element. First, the structure of device and processing principle of the rotation-revolution belt grinding device was introduced. Then, based on the generalized Preston equation and Hertz contact theory, the removal function of the ultra-precision belt grinding was established. Finally, the cylindrical element of optical glass with a diameter of 50.09mm was ground. After 6 hours of processing, the cylindricity accuracy of the element was decreased from original 112.4μm to 4.6μm, and the surface roughness was decreased from 2.631μm to 3.085nm.
A series of ultra-precision grinding experiments were carried out on transparent AlON ceramic. The grinding parameters (wheel speed, workpiece speed, feedrate and depth of grinding) were optimized by studying the influence of process parameters on surface quality. Comprehensive consideration of surface quality and machining efficiency, the grinding process parameters selected for finishing are as bellow: the wheel speed is 6000rpm, the workpiece speed is 39rpm, the feedrate is 5mm/min and the depth of grinding is 3μm. A grinding verification experiment was carried out after optimization. According to the optimized process parameters, the AlON optical window (the diameter is 120mm, the length-diameter ratio is 1.08, the thickness is 3mm) was processed by ultra-precision grinding. The form accuracy, surface roughness and infrared transmittance of the AlON optical window were tested and discussed.
Compared with conventional grinding tools, the chemical vapor deposition (CVD) diamond grinding tools have lots of advantages. However, the practical application of CVD grinding tools is limited, because of the small chip-holding space of abrasive layer. Based on the previous research, the structured grinding tools identified as an available method to improve grinding performance. Therefore, the micro-structured CVD diamond tools were invented. In this paper, the picosecond pulse laser was adopted to machine the micro-structures on CVD diamond. The ablation threshold of CVD diamond film was obtained with picosecond pulse laser. And then, the micro-grooves were machined on diamond film surface with different laser machining parameters. The effects of defocus, laser power, scanning speed, scanning times and machining offset on groove width and depth were analyzed respectively.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.