Development of ultra-high dynamic range one-shot three-dimensional imaging method using high repetition rate optical frequency comb

2020 Fiscal Year Final Research Report

• Project/Area Number: 19K15464
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 30020:Optical engineering and photon science-related
• Research Institution: The University of Electro-Communications
• Principal Investigator: Kato Takashi 電気通信大学, 大学院情報理工学研究科, 特任助教 (20795926)
• Project Period (FY): 2019-04-01 – 2021-03-31
• Keywords: 光周波数コム / 3次元計測 / 光演算 / 干渉計測

Outline of Final Research Achievements

By using a chirped high-repetition Yb fiber laser, we have achieved one-shot 3D measurement with a high dynamic range that is continuous and has a long measurable range. In this study, the Yb optical comb with a repetition rate of 750 MHz is used as a light source to generate a pulse train with a pulse interval of 40 cm. The pulse length was increased to 40 cm by applying high chirp using a high-dispersion optical system with diffraction grating pairs, and dead-zone-free measurement was achieved. As a result, an ultra-wide dynamic range measurement with infinite measurement range and depth resolution of 31µm was achieved, and the surface profile of three mirrors 40 cm apart was successfully measured by one-shot.

Free Research Field

光周波数コム

Academic Significance and Societal Importance of the Research Achievements

本研究は、高繰り返し光コム光源を形状計測へ応用する世界で初めての試みである。高い繰り返し周波数を利用した連続かつ長大な計測可能範囲を有する瞬時3次元計測手法を確立する。これは、単なる光源の置き換えではなく、“高繰り返し”の性質を積極的に利用したものであり、高繰り返し光コムの光源としての価値を新たに見出す研究と言える。
また、実質的に計測範囲が無限大といえる超広ダイナミックレンジ計測は、任意の物体が任意の位置に不意に出現したとしても必ず計測することが出来る。特に超短パルスを用いることで実質的な露光時間もフェムト秒となり、超高速現象も測定可能な時空間的な広ダイナミックレンジ計測も達成できる。