Two coherent LiDAR modulation formats are compared by the minimum required number of photons per pixel. Phase-coded and linear frequency chirp modulations are found to result in similar sensitivity of a few photons per pixel.

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There are many different LiDARs on the market today. They have a variety of specifications, and standards are yet to be developed. On a very fundamental level LiDARs can be classified by how they transmit (modulation format) and how they receive (detection method) light. Most commercial LiDARs use high power amplitude-modulated lasers and direct detection.

In coherent detection LiDAR, a low power frequency modulated continuous wave (FMCW) laser source is commonly used. Such LiDARs are gaining industry attention due to their ability to measure radial velocity directly, quantum-limited sensitivity and immunity to interference. The two most popular modulation formats of coherent LiDAR are linear frequency modulation (LFM) and phase shift keying (PSK, phase-coded LiDAR). …

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