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Time-of-flight sensing with single-photon sensitivity enables new approaches for the localization of objects outside a sensor's field of view by analyzing backscattered photons. In this Letter, the authors have studied the application of Geiger-mode avalanche photodiode arrays and eye-safe infrared lasers, and provide experimental data of the direct visualization of backscattering light in flight, and direct vision and indirect vision of targets in line-of-sight and non-line-of-sight configurations at shortwave infrared wavelengths.

In the present paper we discuss the method of image coding by multiple exposure of range-gated images. This method enlarges the depth mapping range of range-gated imaging systems exponentially with the number of utilized images. We developed a theoretical model to give a precise prediction of the number of permutations that can be used for image coding. For what we believe is the first time, we realized an image coding sequence for three range-gated images to enlarge the depth mapping range by a factor of 12. We demonstrate three-dimensional imaging in a range of 460 to 1000 m using a laser pulse width of 300 ns. Because of the impact of noise, a critical linking error occurs during the encoding of the intensity images. It is possible to reduce this error by the application of effective noise reduction strategies and the use of a threshold value to the tolerance drift of intensity levels.

Range-gated active imaging is a well-known technique used for night vision or for vision enhancement in scattering environments. A lot of papers have been published, in which the performance enhancement of range gating has been demonstrated. However, there are no studies which systematically investigate and quantify the real gain brought by range gating, in comparison with a classical imaging system, in controlled smoke densities. In this paper, a systematic investigation of the performance enhancement of range-gated viewing is presented in comparison with a color camera representing the human vision. The influence of range gating and of the gate shape is studied. We have been able to demonstrate that a short-wave infrared (SWIR) range-gated active imaging system can enhance by a factor of 6.9 the penetration depth in dense smoke. On the other hand, we have shown that the combination of a short pulse with a short integration time gives better contrasted images in dense scattering media.

Range-gated viewing is a prominent technique for night vision, remote sensing and vision trough obstacles (fog, smoke, camouflage netting ). Furthermore, range-gated images reflect not only the scene reflectance but also contain depth information. The whole depth information can be calculated from a minimum number of two range-gated images via the super-resolution depth mapping technique. For the first time, this method is applied to range-gated viewing at infrared wavelengths. An EBCMOS camera and a solid sate laser illumination in the 1.5 μm wavelength scale were used to depth-map a scene with minimal laser activity of 9 ns per image.