日本語
HOME > National Metrology Institute of Japan
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.
The National Institute of Advanced Industrial Science and Technology (AIST) and Nichia Corporation have developed a light source with light-emitting diodes (LEDs) that replaces existing luminous intensity standard lamps by reproducing the standard spectrum of incandescent lamps as defined by the International Commission on Illumination (CIE). The comfortable lighting level in living and working spaces is evaluated by an illuminance meter. Illuminance meters (illuminance sensors) are familiar measuring instruments that are incorporated into smartphones and used for dimming displays, etc. It is mandatory for new automobiles sold after April 2020 to have automatic headlights in order to avoid no lights at dusk hours for a safety reason. The system is equipped with a function that automatically turns on the headlights when the ambient light level is less than 1 000 lx. In order to properly use illuminance meters from the viewpoint of safety management, it is important to measure and control illuminance accurately, for example, by having them calibrated traceable to the national measurement standards. Manufacturers and testing laboratories calibrate illuminance meters using "luminous intensity standard lamps," which are incandescent lamps calibrated to be traceable to national measurement standards. However, incandescent lamps are no longer produced worldwide, and as a result of this phase-out, the discontinued luminous intensity standard lamps have become a global concern. In response, AIST and Nichia Corporation have developed a light source (Illuminant A standard LED) that provides the standard spectrum (CIE standard illuminant A) using LEDs. The Illuminant A standard LED not only meets the specifications for spectrum and illuminance values required for calibration of illuminance meters, but also improves the aging rate to about 1/20 of a luminous intensity standard lamp by an appropriate seasoning process of the LED package. As a result, it is expected to extend the recalibration periods and improve the measurement uncertainty in manufacturers and testing laboratories. Details of this technology were published in Measurement on August 16, 2024.
Researchers at AIST, in collaboration with researchers at Yokohama National University, have succeeded in generating a highly accurate time scale for 230 consecutive days by using an optical lattice clock. Currently, a redefinition of the second is being discussed so that the optical frequency obtained using an optical clock will be used as the standard. Once the second is redefined, it is expected that a "graduated scale" tens of thousands of times finer than the current definition will be established, and that highly accurate time and frequency can be supplied to society. Many issues remain to be addressed in order to redefine the second, such as ensuring that the new definition is accurate and realized robustly over a long period compared with the current definition. Among them, the generation of a highly accurate and stable time scale by adjusting the frequency of an atomic clock based on an optical clock is considered as one of the conditions that are desired to be achieved for the redefinition of the second, and so research to incorporate an optical clock into a time scale is underway in many countries. AIST has been generating a time scale by manually adjusting the frequency of a hydrogen maser atomic clock, which is an atomic clock capable of continuous operation, but an even more accurate time scale can be expected to be generated by using an optical lattice clock. However, it has been difficult to accurately adjust the frequency of the atomic clock during the shutdown period of the optical lattice clock because the optical lattice clock could only be operated at a low uptime. Using previously obtained data from an optical lattice clock that had been successfully operated at high uptime, the frequency of the hydrogen maser atomic clock was adjusted in a postprocessing analysis to generate a time scale based on the optical lattice clock. This time scale achieved the world's highest level of synchronization accuracy of within ±1 ns (one billionth of a second) from UTC, the international time standard, over a 230-day period. This achievement is expected to accelerate the consideration of the redefinition of the second. Details of this technology have been published in Physical Review Applied on June 7, 2024 (EST).
Conceptual diagram of the generation of the current Time Frequency National Standard UTC (NMIJ) (top) and the future National Standard UTC (NMIJ) (bottom) using an optical lattice clock
▲ ページトップへ
Copyright © National Institute of Advanced Industrial Science and Technology （AIST） （Japan Corporate Number 7010005005425）. All rights reserved.