Multiple-wavelength range-gated active imaging applied to the evaluation of simultaneous movement of millimeter-size objects moving in a given volume

Time dilation and time reversal with the multiple-wavelengths range-gated active imaging principle

The possibility of realizing time dilation and time reversal of events taking place in a scene by using the multiple-wavelengths range-gated active imaging (WRAI) principle in superimposed style was studied. Both temporal behaviors could be analyzed as a function of time since the WRAI principle allows different positions of the object in the image to be frozen at different moments according to the wavelengths. As the speed of the photons varies in the function of the refraction law of the crossed medium, different media were used to intervene in the time of the events recorded by the camera. Different wavelengths were used to select these media. By increasing the refractive index of the crossed medium as a function of time, the scene events arrived chronologically with an increasing delay compared to the events seen in the open, giving the impression of slowing down time. Similarly, by decreasing the refractive index of the crossed medium as a function of time, the scene events arrived chronologically in the opposite direction compared to the events seen in the open, giving the impression of going back in time. Experimental test results validated the theoretical part and the possibility of observing these different temporal behaviors with the multiple-wavelengths range-gated active imaging principle in superimposed style.

Multiple-wavelength range-gated active imaging principle integrating spectral information for five-dimensional imaging

The combined multiple-wavelength range-gated active imaging (WRAI) principle is able to determine the position of a moving object in a four-dimensional space and to deduce its trajectory and its speed independently of the video frequency. By combining two wavelength categories, it determines the depth of moving objects in the scene with the warm color category and the precise moment of a moving object's position with the cold color category. Therefore, since each object had the ability to transmit information from different wavelengths, related to the spectral reflectances, it became interesting to identify their spectral signatures from these reflectances. Using a conventional method of spectral classification, it was shown that it is possible to identify objects in a 3D scene from their a priori known spectral signatures and, thanks to this, to reveal especially the fifth dimension in the imaging of the WRAI principle. The experimental tests confirmed that it is possible to record moving objects in a five-dimensional space represented by a single image, thus validating this multi-wavelength imaging method.