Multiple-wavelength range-gated active imaging principle in the accumulation mode for three-dimensional imaging.

Abstract

Having laid the foundations of the multiple-wavelength range-gated active imaging principle in flash mode in a previous paper, we have been studying its use in accumulation mode. Whatever the mode, the principle consists of restoring the 3D scene directly in a single image at the moment of recording with a camera. Each emitted light pulse with a different wavelength corresponds to a visualized zone with a different distance in the scene. So each of these visualized zones is identified by a different wavelength. In flash mode, the camera shutter opens just once during the emission of light pulses with the different wavelengths. However, the energy constraints to restore scenes in three dimensions can lead to a change in the recording mode when moving from the flash mode to the accumulation mode. In this mode, the cycle, including a series of light pulses with the used wavelengths and an aperture of the camera shutter, is repeated several times for a given image recorded with the intensified camera. Each wavelength always corresponds to a visualized slice with a different distance in the scene. So, the accumulation enables increasing the illumination of every visualized slice. The modeling conducted in the previous paper must be completed to adapt it to this mode. The tests with a multiple-wavelength laser source confirmed the quality improvement of the recorded images for more remote scenes and validated the principle of restoring, directly in a color image, the three dimensions of a scene.