  A real-time ranging lidar with 0.1 Mega Hertz update rate and few-micrometer
resolution incorporating dispersive Fourier transformation and instantaneous
microwave frequency measurement is proposed and demonstrated. As time-stretched
femtosecond laser pulse passing through an all-fiber Mach-Zehnder
Interferometer, where the detection light beam is inserted into the optical
path of one arm, the displacement is encoded to the frequency variation of the
temporal interferogram. To deal with the challenges in storage and real-time
processing of the microwave pulse generated on a photodetector, we turn to
all-optical signal processing. A carrier wave is modulated by the time-domain
interferogram using an intensity modulator. After that, the frequency variation
of the microwave pulse is uploaded to the first order sidebands. Finally, the
frequency shift of the sidebands is turned into transmission change through a
symmetric-locked frequency discriminator. In experiment, A real-time ranging
system with adjustable dynamic range and detection sensitivity is realized by
incorporating a programmable optical filter. Standard deviation of 7.64 {\mu}m,
overall mean error of 19.10 {\mu}m over 15 mm detection range and standard
deviation of 37.73 {\mu}m, overall mean error of 36.63 {\mu}m over 45 mm
detection range are obtained respectively.
