The success of VCSEL technology has led to their use in a wide range of sensing, imaging, scanning and ranging applications across multiple fields - machine vision, automotive, scientific and medical.
Many consumers are familiar with gesture recognition as part of a user interface that senses touch or finger motion, such as is used in devices with touchscreens like tablets. 3D sensing allows the same basic detection and interpolation of place and movement in three dimensions. The full range of applications possible with 3D sensing has not been fully explored yet.
By passing an infrared light source through an optical element to spread the light either into a structured pattern or a sheet of light, systems are able to capture depth information across an entire room by measuring the light reflected off of objects. This enables, for example, consumers to control games or their entire entertainment center with gestures without the need for a physical remote or even getting up. Gesture recognition can also enhance touchscreen capabilities in cars by allowing users to make gestures a foot or more away from the dashboard without having to touch or block the screen. In future mobile devices, 3D sensing will augment camera capabilities to enable object recognition, depth data, greater precision, and object placement.
To be able to detect movement across a living room, however, the detection system needs high power and precision: it is one thing to track a finger on a touchscreen and altogether another to detect a slight finger movement six feet away. Time-of-Flight tracking techniques, for example, flash a light pulse and track depth and motion by measuring the travel time of the light pulse from an object to an individual pixel on an image sensor. In some cases, phase differences are used to calculate depth and motion. Wavelength stability over the entire operating temperature range of the optical source is critical to maintaining tracking precision as filters are typically applied in the receive path to minimize noise in the received signal. Electrical efficiency may further be improved by optimizing the pulse width and duty cycle at which the system must flash to achieve sufficient resolution. This directly impacts battery life in portable systems and minimizes how much heat the system will need to dissipate.
Time-of-Flight benefits include, but are not limited to:
- Measures distance via photon time or phase difference
- Can also measure photon count
- Very fast and accurate under all conditions
- Highly integrated, simple, low cost
- Uses high-resolution detector-array to provide depth ‘map’
- ‘Global Shutter’ Rx allows full-frame capture in one shot