  LiDAR, using a laser-based ranging method for precise environmental 3D
sensing, has numerous scientific and industrial applications. However, the
challenge lies in simultaneously enhancing precision and update rate, hinders
its application in more unexpected scenarios. To this end, an optical frequency
comb with a stable repetition frequency and femtosecond pulse width was used as
an advanced laser source. The LiDAR performance significantly improved in the
micrometer and megahertz regimes using an asynchronous sampling ranging method
of electrical pulses based on a single femtosecond laser. This overcame the
limitation of traditional optical sampling approaches, achieving a 38.8
${\mu}$m Allan deviation at an update rate of 1 MHz and 8.06 ${\mu}$m after 2
ms time-averaging. The proposed method used a single laser for fast metrology
monitoring, 1 megapixel/s 3D imaging at the meter-level non-ambiguous range and
contactless vital sign detection at the hundred-micrometer scale.
