## 1550-nm time-of-flight ranging system employing laser with multiple repetition rates for reducing the range ambiguity |

Optics Express, Vol. 22, Issue 4, pp. 4662-4670 (2014)

http://dx.doi.org/10.1364/OE.22.004662

Acrobat PDF (901 KB)

### Abstract

We demonstrated a time-of-flight (TOF) ranging system employing laser pulses at 1550 nm with multiple repetition rates to decrease the range ambiguity, which was usually found in high-repetition TOF systems. The time-correlated single-photon counting technique with an InGaAs/InP avalanche photodiode based single-photon detector, was applied to record different arrival time of the scattered return photons from the non-cooperative target at different repetition rates to determine the measured distance, providing an effective and convenient method to increase the absolute range capacity of the whole system. We attained hundreds of meters range with millimeter accuracy by using laser pulses of approximately 10-MHz repetition rates.

© 2014 Optical Society of America

## 1. Introduction

7. K. Y. Shrestha, K. C. Slatton, W. E. Carter, and T. K. Cossio, “Performance metrics for single-photon laser ranging,” IEEE Geosci. Remote Sens. Lett. **7**(2), 338–342 (2010). [CrossRef]

10. R. Hadfield, “Single-photon detectors for optical quantum information applications,” Nat. Photonics **3**(12), 696–705 (2009). [CrossRef]

11. A. McCarthy, N. J. Krichel, N. R. Gemmell, X. Ren, M. G. Tanner, S. N. Dorenbos, V. Zwiller, R. H. Hadfield, and G. S. Buller, “Kilometer-range, high resolution depth imaging via 1560 nm wavelength single-photon detection,” Opt. Express **21**(7), 8904–8915 (2013). [CrossRef] [PubMed]

5. R. E. Warburton, A. McCarthy, A. M. Wallace, S. Hernandez-Marin, R. H. Hadfield, S. W. Nam, and G. S. Buller, “Subcentimeter depth resolution using a single-photon counting time-of-flight laser ranging system at 1550 nm wavelength,” Opt. Lett. **32**(15), 2266–2268 (2007). [CrossRef] [PubMed]

11. A. McCarthy, N. J. Krichel, N. R. Gemmell, X. Ren, M. G. Tanner, S. N. Dorenbos, V. Zwiller, R. H. Hadfield, and G. S. Buller, “Kilometer-range, high resolution depth imaging via 1560 nm wavelength single-photon detection,” Opt. Express **21**(7), 8904–8915 (2013). [CrossRef] [PubMed]

12. Z. Yuan, A. Sharpe, J. Dynes, A. Dixon, and A. Shields, “Multi-gigahertz operation of photon counting InGaAs avalanche photodiodes,” Appl. Phys. Lett. **96**(7), 071101 (2010). [CrossRef]

17. M. Ren, X. Gu, Y. Liang, W. Kong, E. Wu, G. Wu, and H. Zeng, “Laser ranging at 1550 nm with 1-GHz sine-wave gated InGaAs/InP APD single-photon detector,” Opt. Express **19**(14), 13497–13502 (2011). [CrossRef] [PubMed]

17. M. Ren, X. Gu, Y. Liang, W. Kong, E. Wu, G. Wu, and H. Zeng, “Laser ranging at 1550 nm with 1-GHz sine-wave gated InGaAs/InP APD single-photon detector,” Opt. Express **19**(14), 13497–13502 (2011). [CrossRef] [PubMed]

*d*can be calculated by,where

_{Rep}*c*is the speed of light in the vacuum,

*n*is the refractive index of air and

*f*is the repetition frequency of the periodic laser source. Here,

_{Rep}*n*is set to be 1, regardless of the different refractive indexes in the testing condition. For instance,

*d*is just 15 meters while

_{Rep}*f*is set to be 10 MHz. The higher the repetition rate is, the shorter absolute range could be determined. To increase the range,

_{Rep}*f*has to be further reduced. However, the acquisition time for valid data should be increased with the laser pulse of low repetition frequency, reducing the efficiency of the whole system. Thus far, many methods have been invented to solve this harsh issue, such as random pattern technique in [18

_{Rep}18. P. A. Hiskett, C. S. Parry, A. McCarthy, and G. S. Buller, “A photon-counting time-of-flight ranging technique developed for the avoidance of range ambiguity at gigahertz clock rates,” Opt. Express **16**(18), 13685–13698 (2008). [CrossRef] [PubMed]

19. N. J. Krichel, A. McCarthy, and G. S. Buller, “Resolving range ambiguity in a photon counting depth imager operating at kilometer distances,” Opt. Express **18**(9), 9192–9206 (2010). [CrossRef] [PubMed]

*s*was determined by where

*n*are the cycle numbers for laser pulses with different repetition rates in the round-way flight,

_{1}, n_{2}……n_{n}*d*are the maximum unambiguous distances for each and

_{Rep1}, d_{Rep2}……d_{Rep3}*t*are the flight time recorded by the TCSPC. By this means, the eventual

_{1}, t_{2}……t_{n}*d*of the ranging system was determined bywhere

_{Rep}*1/F*is the least common multiple of

_{Rep}*1/f*We could increase the

_{Rep1}, 1/f_{Rep2}……1/f_{Repn}.*d*simply by increasing the number of different repetition rates. In our experiment, the repetition rates of the laser pulse were 10 MHz and 9.7 MHz, respectively, increasing the

_{Rep}*d*from ~15 meters to 1455 meters with ease.

_{Rep}## 2. System description

^{−5}/gate, and the timing jitter was about 76 ps. The InGaAs/InP APD was Peltier cooled to 240 K. However, the target was non-cooperative, making the arrival time of the return photons an unknown parameter. In order to detect the return photons to obtain the distance information, the single-photon detector should be operated in the free-running mode, meaning that the laser pulse and the gating pulse had to be set unsynchronized. In that case, the detection efficiency was about 3.9%, and the timing jitter was only 240 ps, as shown in Fig. 2(b).

## 3. Experiment and results

*E*is the single-pulse energy of the laser,

_{out}*μ*is the surface reflectivity of the target,

*D*is the diameter of the telescope,

*T*is the total optical loss of the receiving system (including the loss of the telescope, the focusing lens, the optical filter and fiber coupling),

_{Opt}*T*is the transmission efficiency in the air at 1550 nm. The experimental measurements agreed well with the calculations. By analyzing the different arrival times of the return photons with the two different repetition rates, we could get the exact distance of the target. As mentioned above, the absolute range has been increased from ~15 m to 1455 m. The frequency has a high precision at mHz level (tested by Agilent 53131A). We carried out this experiment in a tall building under daylight condition, utilizing other surrounding buildings which had no significant specular reflection as targets. After spectral filtering of the return photons by the OBPF, the dark count rate was reduced to be about 25 kHz, enabling the ranging system work under daylight conditions. Limited by alternative targets around for test, the actual longest distance we measured was ~460 meters. Note that the ranging limit is much longer than 460 m.

_{Trans}^{6}. And when the measured distance rose to 460 m, the return photon number dropped to be 5 × 10

^{4}. Meanwhile as shown in inset, the valid signal containing the distance message stood out against the background noise level. It could be thus found that longer distance could be measured with the ranging system of the same average laser power. The photon counting peak was centered at 59.580 ns with 10.0-MHz laser pulses, and at 63.644 ns with 9.7-MHz laser pulses. According to Eq. (3), the target was calculated to be at ~460 m away.

20. S. Pellegrini, G. Buller, J. Smith, A. Wallace, and S. Cova, “Laser-based distance measurement using picosecond resolution time-correlated single-photon counting,” Meas. Sci. Technol. **11**(6), 712–716 (2000). [CrossRef]

21. I. Coddington, W. Swann, L. Nenadovic, and N. Newbury, “Rapid and precise absolute distance measurements at long range,” Nat. Photonics **3**(6), 351–356 (2009). [CrossRef]

20. S. Pellegrini, G. Buller, J. Smith, A. Wallace, and S. Cova, “Laser-based distance measurement using picosecond resolution time-correlated single-photon counting,” Meas. Sci. Technol. **11**(6), 712–716 (2000). [CrossRef]

20. S. Pellegrini, G. Buller, J. Smith, A. Wallace, and S. Cova, “Laser-based distance measurement using picosecond resolution time-correlated single-photon counting,” Meas. Sci. Technol. **11**(6), 712–716 (2000). [CrossRef]

*d = ct/2*. As shown in Fig. 4(a), the experimental data fitted well with the simulated one. When the integrated number was 5 × 10

^{4}, the actual time resolution was about 25 ps, while the simulated one was ~22 ps. Considering that the stamping resolution of the TCSPC used in the experiment was set to be 4 ps, the gap between the two time resolutions was quite small. When the distance was 7.5 m away, we could get the minimum distance resolution approximate 1.2 mm. In view of the timing jitter of the TCSPC, 1.2 mm almost reached the limits of the whole system.

^{5}per second. Since we used pulsed laser with two different repetition frequencies, the influence of this surveying method on the distance resolution should be taken into account. In Fig. 4(b), it could be found that the distance resolution was enhanced with the increase of the acquisition time. Moreover, the distance resolution was barely affected by the different repetition rates employed, the two curves almost keeping the same. When the integral acquisition time was 0.01 s, the distance resolution was about 7 mm. In contrast, when the time was increased to 5 s, the total counts were accumulated to be 1 × 10

^{6}and the resolution was about 1.7 mm.

^{6}, 2 × 10

^{5}, and 5 × 10

^{4}to test the performance. At the same distance, the distance resolution was improved with more counts. When the distance was 180 m, the resolution was ~1.6 mm with the count of 1 × 10

^{6}, and 3.4 mm with the count of 5 × 10

^{4}, matching with the results in Fig. 4(b). In the meantime, the depth resolution got worse when the distance increased, and the slope of the curve increased steadily with the decline of the total counts. Under this condition, the only varying factor was the SNR, so we could deduce that the decline of the distance resolution was caused by the growth of the SNR following the increase of the measured distance. Figure 5 shows that the resolution was approximately 2.6 mm at the distance of 7.5 m and increased to 3.7 mm at 460 m with the total photon-count of 5 × 10

^{4}. The distance resolution would get worse with the increase of the measured distance, partly determining the maximum range capability of the whole system.

## 4. Conclusion

## Acknowledgments

## References and links

1. | J. Degnan, “Satellite laser ranging: current status and future prospects,” IEEE Trans. Geosci. Remote Sens. |

2. | J. Degnan, “Photon-counting multikilohertz microlaser altimeters for airborne and spaceborne topographic measurements,” J. Geodyn. |

3. | F. Chen, G. Brown, and M. Song, “Overview of three dimensional shape measurement using optical methods,” Opt. Eng. |

4. | M. A. Albota, R. M. Heinrichs, D. G. Kocher, D. G. Fouche, B. E. Player, M. E. O’Brien, B. F. Aull, J. J. Zayhowski, J. Mooney, B. C. Willard, and R. R. Carlson, “Three-dimensional imaging laser radar with a photon-counting avalanche photodiode array and microchip laser,” Appl. Opt. |

5. | R. E. Warburton, A. McCarthy, A. M. Wallace, S. Hernandez-Marin, R. H. Hadfield, S. W. Nam, and G. S. Buller, “Subcentimeter depth resolution using a single-photon counting time-of-flight laser ranging system at 1550 nm wavelength,” Opt. Lett. |

6. | G. Buller and A. Wallace, “Recent advances in ranging and three-dimensional imaging using time-correlated single-photon counting,” IEEE J. Sel. Top. Quantum Electron. |

7. | K. Y. Shrestha, K. C. Slatton, W. E. Carter, and T. K. Cossio, “Performance metrics for single-photon laser ranging,” IEEE Geosci. Remote Sens. Lett. |

8. | G. Buller, R. Harkins, A. McCarthy, P. Hiskett, G. MacKinnon, G. Smith, R. Sung, A. Wallace, R. Lamb, K. Ridley, and J. Rarity, “Multiple wavelength time-of -flight sensor based on time-correlated single-photon counting,” Rev. Sci. Instrum. |

9. | M. Albota, B. Aull, D. Fouche, R. Heinrichs, D. Kocher, R. Marino, J. Mooney, N. Newbury, M. O’Brien, B. Player, B. Willard, and J. Zayhowski, “Three-dimensional imaging laser radars with Geiger-mode avalanche photodiode arrays,” Lincoln Lab. J. |

10. | R. Hadfield, “Single-photon detectors for optical quantum information applications,” Nat. Photonics |

11. | A. McCarthy, N. J. Krichel, N. R. Gemmell, X. Ren, M. G. Tanner, S. N. Dorenbos, V. Zwiller, R. H. Hadfield, and G. S. Buller, “Kilometer-range, high resolution depth imaging via 1560 nm wavelength single-photon detection,” Opt. Express |

12. | Z. Yuan, A. Sharpe, J. Dynes, A. Dixon, and A. Shields, “Multi-gigahertz operation of photon counting InGaAs avalanche photodiodes,” Appl. Phys. Lett. |

13. | X. Chen, E. Wu, G. Wu, and H. Zeng, “Low-noise high-speed InGaAs/InP-based single-photon detector,” Opt. Express |

14. | N. Namekata, S. Adachi, and S. Inoue, “1.5 GHz single-photon detection at telecommunication wavelengths using sinusoidally gated InGaAs/InP avalanche photodiode,” Opt. Express |

15. | J. Zhang, R. Thew, C. Barreiro, and H. Zbinden, “Practical fast gate rate InGaAs/InP single-photon avalanche photodiodes,” Appl. Phys. Lett. |

16. | Y. Liang, E. Wu, X. Chen, M. Ren, Y. Jian, G. Wu, and H. Zeng, “Low-timing-jitter single-photon detection using 1-GHz sinusoidally gated InGaAs/InP avalanche photodiode,” IEEE Photonics Technol. Lett. |

17. | M. Ren, X. Gu, Y. Liang, W. Kong, E. Wu, G. Wu, and H. Zeng, “Laser ranging at 1550 nm with 1-GHz sine-wave gated InGaAs/InP APD single-photon detector,” Opt. Express |

18. | P. A. Hiskett, C. S. Parry, A. McCarthy, and G. S. Buller, “A photon-counting time-of-flight ranging technique developed for the avoidance of range ambiguity at gigahertz clock rates,” Opt. Express |

19. | N. J. Krichel, A. McCarthy, and G. S. Buller, “Resolving range ambiguity in a photon counting depth imager operating at kilometer distances,” Opt. Express |

20. | S. Pellegrini, G. Buller, J. Smith, A. Wallace, and S. Cova, “Laser-based distance measurement using picosecond resolution time-correlated single-photon counting,” Meas. Sci. Technol. |

21. | I. Coddington, W. Swann, L. Nenadovic, and N. Newbury, “Rapid and precise absolute distance measurements at long range,” Nat. Photonics |

**OCIS Codes**

(030.5260) Coherence and statistical optics : Photon counting

(040.3780) Detectors : Low light level

(280.3400) Remote sensing and sensors : Laser range finder

(280.3640) Remote sensing and sensors : Lidar

(040.1345) Detectors : Avalanche photodiodes (APDs)

**ToC Category:**

Instrumentation, Measurement, and Metrology

**History**

Original Manuscript: December 19, 2013

Revised Manuscript: February 4, 2014

Manuscript Accepted: February 4, 2014

Published: February 20, 2014

**Citation**

Yan Liang, Jianhua Huang, Min Ren, Baicheng Feng, Xiuliang Chen, E Wu, Guang Wu, and Heping Zeng, "1550-nm time-of-flight ranging system employing laser with multiple repetition rates for reducing the range ambiguity," Opt. Express **22**, 4662-4670 (2014)

http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-22-4-4662

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### References

- J. Degnan, “Satellite laser ranging: current status and future prospects,” IEEE Trans. Geosci. Remote Sens. GE-23(4), 398–413 (1985). [CrossRef]
- J. Degnan, “Photon-counting multikilohertz microlaser altimeters for airborne and spaceborne topographic measurements,” J. Geodyn. 34(3-4), 503–549 (2002). [CrossRef]
- F. Chen, G. Brown, M. Song, “Overview of three dimensional shape measurement using optical methods,” Opt. Eng. 39(1), 10–22 (2000). [CrossRef]
- M. A. Albota, R. M. Heinrichs, D. G. Kocher, D. G. Fouche, B. E. Player, M. E. O’Brien, B. F. Aull, J. J. Zayhowski, J. Mooney, B. C. Willard, R. R. Carlson, “Three-dimensional imaging laser radar with a photon-counting avalanche photodiode array and microchip laser,” Appl. Opt. 41(36), 7671–7678 (2002). [CrossRef] [PubMed]
- R. E. Warburton, A. McCarthy, A. M. Wallace, S. Hernandez-Marin, R. H. Hadfield, S. W. Nam, G. S. Buller, “Subcentimeter depth resolution using a single-photon counting time-of-flight laser ranging system at 1550 nm wavelength,” Opt. Lett. 32(15), 2266–2268 (2007). [CrossRef] [PubMed]
- G. Buller, A. Wallace, “Recent advances in ranging and three-dimensional imaging using time-correlated single-photon counting,” IEEE J. Sel. Top. Quantum Electron. 13, 1006–1015 (2007). [CrossRef]
- K. Y. Shrestha, K. C. Slatton, W. E. Carter, T. K. Cossio, “Performance metrics for single-photon laser ranging,” IEEE Geosci. Remote Sens. Lett. 7(2), 338–342 (2010). [CrossRef]
- G. Buller, R. Harkins, A. McCarthy, P. Hiskett, G. MacKinnon, G. Smith, R. Sung, A. Wallace, R. Lamb, K. Ridley, J. Rarity, “Multiple wavelength time-of -flight sensor based on time-correlated single-photon counting,” Rev. Sci. Instrum. 76(8), 083112 (2005). [CrossRef]
- M. Albota, B. Aull, D. Fouche, R. Heinrichs, D. Kocher, R. Marino, J. Mooney, N. Newbury, M. O’Brien, B. Player, B. Willard, J. Zayhowski, “Three-dimensional imaging laser radars with Geiger-mode avalanche photodiode arrays,” Lincoln Lab. J. 13, 351–370 (2002).
- R. Hadfield, “Single-photon detectors for optical quantum information applications,” Nat. Photonics 3(12), 696–705 (2009). [CrossRef]
- A. McCarthy, N. J. Krichel, N. R. Gemmell, X. Ren, M. G. Tanner, S. N. Dorenbos, V. Zwiller, R. H. Hadfield, G. S. Buller, “Kilometer-range, high resolution depth imaging via 1560 nm wavelength single-photon detection,” Opt. Express 21(7), 8904–8915 (2013). [CrossRef] [PubMed]
- Z. Yuan, A. Sharpe, J. Dynes, A. Dixon, A. Shields, “Multi-gigahertz operation of photon counting InGaAs avalanche photodiodes,” Appl. Phys. Lett. 96(7), 071101 (2010). [CrossRef]
- X. Chen, E. Wu, G. Wu, H. Zeng, “Low-noise high-speed InGaAs/InP-based single-photon detector,” Opt. Express 18(7), 7010–7018 (2010). [CrossRef] [PubMed]
- N. Namekata, S. Adachi, S. Inoue, “1.5 GHz single-photon detection at telecommunication wavelengths using sinusoidally gated InGaAs/InP avalanche photodiode,” Opt. Express 17(8), 6275–6282 (2009). [CrossRef] [PubMed]
- J. Zhang, R. Thew, C. Barreiro, H. Zbinden, “Practical fast gate rate InGaAs/InP single-photon avalanche photodiodes,” Appl. Phys. Lett. 95(9), 091103 (2009). [CrossRef]
- Y. Liang, E. Wu, X. Chen, M. Ren, Y. Jian, G. Wu, H. Zeng, “Low-timing-jitter single-photon detection using 1-GHz sinusoidally gated InGaAs/InP avalanche photodiode,” IEEE Photonics Technol. Lett. 23(13), 887–889 (2011). [CrossRef]
- M. Ren, X. Gu, Y. Liang, W. Kong, E. Wu, G. Wu, H. Zeng, “Laser ranging at 1550 nm with 1-GHz sine-wave gated InGaAs/InP APD single-photon detector,” Opt. Express 19(14), 13497–13502 (2011). [CrossRef] [PubMed]
- P. A. Hiskett, C. S. Parry, A. McCarthy, G. S. Buller, “A photon-counting time-of-flight ranging technique developed for the avoidance of range ambiguity at gigahertz clock rates,” Opt. Express 16(18), 13685–13698 (2008). [CrossRef] [PubMed]
- N. J. Krichel, A. McCarthy, G. S. Buller, “Resolving range ambiguity in a photon counting depth imager operating at kilometer distances,” Opt. Express 18(9), 9192–9206 (2010). [CrossRef] [PubMed]
- S. Pellegrini, G. Buller, J. Smith, A. Wallace, S. Cova, “Laser-based distance measurement using picosecond resolution time-correlated single-photon counting,” Meas. Sci. Technol. 11(6), 712–716 (2000). [CrossRef]
- I. Coddington, W. Swann, L. Nenadovic, N. Newbury, “Rapid and precise absolute distance measurements at long range,” Nat. Photonics 3(6), 351–356 (2009). [CrossRef]

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