Embodiments of the disclosure provide a transmitter containing a divergence adjustment device, and an optical sensing method using the same. For example, the optical sensing method includes emitting, by an optical source of an optical sensing system, optical signals. The optical sensing method further includes dynamically collimating, by a tunable collimation lens of the optical sensing system, the emitted optical signals to varying divergences. The method additionally includes steering, by a steering device of the optical sensing system, the tuned optical signals toward an environment surrounding the optical sensing system. The method additionally includes receiving, by a receiver of the optical sensing system, the optical signals returning from the environment.