Probability of Unrecognized LiDAR Interference for TCSPC LiDAR

Abstract

A standard method for distance determination is light detection and ranging (LiDAR), which relies on the emission and detection of reflected laser pulses. When LiDAR systems become common for every vehicle, many simultaneous laser signals will produce mutual LiDAR interference between LiDAR systems. In this paper, we analyze the possibility to recognize mutual interference in time-correlated single photon counting (TCSPC) LiDAR with particular focus on flash systems. We evaluate the LiDAR interference appearance by deriving the expected event distribution for ego and aggressor signal. From that, we calculate the probability of photon detection within each measured signal. This paper shows the high potential of different pulse repetition frequencies to reduce LiDAR interference. Using signal-to-noise ratio (SNR), we define the extinction distance, beyond which the aggressor signal completely extinguishes the ego signal. Applied on different background and laser event rates, we find the connection between ideal LiDAR system designs and lowest probability for unrecognized LiDAR interference. Furthermore, we show the relationship to a specific LiDAR design, which must fulfill eye safety condition and receives lower intensities with increasing target distances. Finally, we present different solutions for the recognition and reduction of LiDAR interference based on our previous results. Index Terms-Light detection and ranging (LiDAR), mutual LiDAR interference, time-correlated single-photon counting (TCSPC), direct time-of-flight (dTOF).

Optimized Interference Suppression for TCSPC LiDAR

“…Small deviations in the PRF e.g. by manufacturing tolerances can already distribute the foreign laser pulse in the histogram, whereas the own laser signal stays accumulated [5]. In this case, the strongly smeared signal width can be distinguished from the own laser pulse form.…”

“…The SNR value of the second lower pulse signature in the histogram is drawn by the equation given in [5]. In contrast to single pulse detections, the second pulse detection of interference is influenced by the first pulse signature in the histogram so that the SNR decreases again for high laser-generated event rates [5]. As seen, the algorithm can be applied for SNR values ≥ 3.…”

“…These event rates produced at the LiDAR detector are proportional to the photon rates of the arriving laser and background photons. The orange contour line illustrates the SNR at value 3 calculated in the histogram by the SNR equation in [5].…”

“…These pulse signatures are generally indistinguishable so that the TOF of the own pulse and hence the target distance cannot be clearly determined. The corresponding PDF for multiple pulse signatures in a histogram is given in [5]. In the following, we only consider detected pulse signatures from real objects of interest.…”

Analysis of interference suppression in single photon lidar

“…However, the laser signals emitted by multiple LiDARs in the same scene can cause mutual interference, also known as crosstalk, which is particularly severe for flash LiDARs. The crosstalk phenomenon will cause LiDAR sensors to be unable to accurately obtain distance information, posing a hidden danger to vehicle driving safety [1] [2] . Therefore, in flash LiDAR, suppressing crosstalk is a crucial issue.…”