Three dimensional FMCW scanless imaging: optical challenges and solutions

Laurent Frey; Anis Daami; Florence Rigal; Desire Muhire

doi:10.1117/12.2578121

5 March 2021 Three dimensional FMCW scanless imaging: optical challenges and solutions

Laurent Frey, Anis Daami, Florence Rigal, Desire Muhire

Proceedings Volume 11693, Photonic Instrumentation Engineering VIII; 116930P (2021) https://doi.org/10.1117/12.2578121
Event: SPIE OPTO, 2021, Online Only

Abstract

Three dimensional (3D) sensing has recently been introduced in mobile devices for mass-market applications such as facial or gesture recognition. The two technologies widely used in smartphones, structured light and time of flight, are based on active imaging and enable operating in darkness. Nevertheless, ocular security constraints limit the accessible outdoor range in sunlight conditions. In contrast, immunity to ambient light is a natural advantage of Frequency Modulated Continuous Wave (FMCW) LIght Detection And Ranging (LIDAR), which is also an active technique, using the coherent nature of the laser source, through a reference arm to amplify the signal from the scene. However, the FMCW LIDAR potentially requires complex opto-electronic components for sequential scanning of the scene. Therefore, obtaining high resolution images at video rate becomes a real issue. In this paper, we investigate low power FMCW imaging (~1mW) with instantaneous active illumination of the scene and heterodyne detection with an image sensor, to combine the advantages of previous techniques with each other. We consider several configurations for the optical system, common to the scene and reference beams. Ideal criteria include uniform illumination of the image sensor by the reference arm, wavefront matching of the scene and reference beams for an optimal heterodyne yield at every pixel location, and minimization of optical loss. Moreover, the average speckle size, with regards to the pixel size and numerical aperture influences the statistical performance of the whole sensor. Finally, the optimal system choice is reinforced by experimental results on a bench setup built in the visible range.

Conference Presentation

Citation Download Citation

Laurent Frey, Anis Daami, Florence Rigal, and Desire Muhire "Three dimensional FMCW scanless imaging: optical challenges and solutions", Proc. SPIE 11693, Photonic Instrumentation Engineering VIII, 116930P (5 March 2021); https://doi.org/10.1117/12.2578121

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