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As the national metrology institute (NMI), we are focusing on the development and dissemination of measurement standards, promotion of measurement standards utilization, development of measurement technologies related to measurement standards, legal metrology work and training of experts. Our activity covers engineering, physical, material, and chemical measurement standards. It also covers development of measurement and analytical instrumentation. We also coordinate international activities on metrology standards as a national representative.
Researchers at AIST, in collaboration with Panasonic Production Engineering Co., Ltd., have developed a sphere diameter measurement technology that achieves the world's highest level of accuracy. In recent years, in fields where high-definition images are essential, such as in-vehicle cameras and endoscopes, optical components increasingly adopt free-form geometries to enhance optical performance. For free-form lenses and mirrors, it is crucial not only to minimize surface profile deviation to the nano-level but also to ensure that the absolute shape, including the radius of curvature, aligns with the design shape at the nano-level. Achieving this requires not only nano-level processing technology but also shape measurement technology that matches or surpasses the precision of nano-level processing. The accuracy of absolute shape measurement in profilometers of optical components such as free-form lenses and mirrors, depends on the calibration accuracy of the sphere diameter used as a reference for the measuring instrument. Until now, the calibration accuracy of sphere diameter has had an uncertainty of approximately 100 nm to 200 nm, which is not superior to the measurement resolution and repeatability of free-form surface profilometers. In this study, we developed a sphere diameter calibration method using a micro-coordinate measuring machine (µ-CMM) equipped with a low-contact force probe system and a silicon gauge block as the reference. This method enabled measurement of sphere diameters with an uncertainty of 15 nm. By using this sphere as a reference for free-form surface profilometers, it is expected to improve the accuracy of free-form surface measurements. Details of this research were published in Precision Engineering on December 7, 2024.
Researchers at AIST have developed a high-precision sphericity calibration system of reference spherical lenses with an uncertainty of 4.3 nm. High-precision compact lenses are indispensable for cameras used in smartphones, endoscopes, etc. to obtain high-definition images. To achieve high precision in optical elements such as lenses and mirrors, it is necessary to fabricate the absolute profile of the element with the designed profile at the nanometer level. Therefore, it is necessary to precisely and accurately measure the processed surface profile and evaluate the deviation from the designed profile. The high-precision profile measuring apparatus measures the sample profile by referring to the reference spherical lens with a high sphericity. The sphericity of the reference spherical lens determines the accuracy of the measurement. In the sphericity calibration system using laser interferometer, we have established a system to easily calibrate reference spherical lenses of any f-number used in the industry by a practical method called the random ball test. We have also established an uncertainty evaluation method based on a detailed analysis of measurement errors caused by misalignment of the optical system. By adopting the random ball test and the uncertainty evaluation method, we have realized a calibration system for user's reference spherical lens of any f-number with a measurement uncertainty of 4.3 nm. Through the calibration system for reference spherical lenses used in industry, we will contribute to the development of high-precision optical elements and the advancement of product quality control.
Relation between AIST's sphericity calibration system and reference spherical lenses used in production sites
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