Open architecture time of flight 3D SWIR camera operating at 150 MHz modulation frequency

Abstract

In the past two decades 3-D cameras have proven to be one of the next revolutions in machine vision. However, these devices are still an emerging technology with a particularly narrow set of commercially available devices. In this paper, the concept and execution of the first short wavelength infrared (SWIR) time-of-flight (ToF) 3-D camera system operating at a wavelength of 1550 nm is presented. By decoupling the optical and electrical components of the system in an open architecture we not only surpass many of the limitations of an on-chip integrated solution, but also can easily change the imaging device based on the requirements of the application. We achieve modulation frequencies up to 150 MHz, which exceeds the conventional values currently published for other large format modulators by about five times. This increase in the modulation frequency allows for a TOF camera with significantly higher depth resolution, while the open architecture design allows for a highly reconfigurable device that can be modified for specific working conditions.

Time-of-flight imaging based on resonant photoelastic modulation

“…Electro-absorption in multiple quantum well using an optical cavity can be used to modulate light [33], but this approach has a narrow acceptance angle for light due to the use of an optical cavity in the modulator. Stepped quantum well modulator (SQM) has also been used to modulate light, but this design has limited aperture (∼1 mm) and uses a microscope objective to focus the received light from the scene onto the surface of the SQM [34].…”

Low cost structured-light based 3D surface reconstruction

“…The stereo vision techniques (Wu and Qu, 2007;Chen et al, 2008) are inspired by human vision systems; they use two cameras to capture the images from different perspectives. After identifying the object features in the images, the shape of the object can be reconstructed by standard triangulation techniques.…”

“…However, levelness readings are derived from depth/3D measurements which can be a bottleneck in many industrial processes, due to the high accuracy required, elevated cost, and tedious maintenance of the acquisition systems. Many depth/3D measurement techniques (Fang et al, 2017) have been explored to compute surface levelness such as time of flight (ToF) (Hagebeuker and Marketing, 2007;Lussana et al, 2015;Wheaton et al, 2017), stereo vision (Brown et al, 2003;Sandoz et al, 2010;Zhou et al, 2018), optical fiber sensing (Mohanty and Kuang, 2011;Eznaveh et al, 2017;Wang et al, 2018), and structured light (Huang et al, 2017;Xu et al, 2017;Zhang, 2018). In general, they vary in terms of working distance, image resolution, response speed, cost, and hardware configuration.…”