07 Jan 2019 Near Infrared 3D Sensing
Three-dimensional sensing technology is the foundation of multiple new applications, such as:
- Facial and gesture recognition
- Eye tracking and iris detection
- Automotive LiDAR for autonomous vehicle sensing
- Multimodal sensing for vehicle gesture and motion control
- Other near-infrared 3D sensing applications
Measurement techniques such as Time-of-Flight (ToF) and Diffractive Optical Elements (DOE) are being used with NIR LEDs and lasers. To ensure performance, accuracy, and safety of devices and systems that use NIR sensing, an effective test and measurement solution is needed.
Near Infrared Intensity Lens Solution
The Radiant Vision Systems Near-Infrared (NIR) Intensity Lens system is an integrated camera/lens solution that measures the angular distribution and radiant intensity of 940 nm near-infrared (NIR or near-IR) emitters. The NIR Intensity Lens system utilizes Fourier optics to capture a full cone of data in a single measurement to ±70 degrees, giving you extremely fast, accurate results ideal for in-line quality control.
Manufacturers of three-dimensional sensing technology can apply the NIR Intensity Lens solution for angular measurement of NIR LEDs, lasers, and Diffractive Optical Elements (DOE). The lens mounts directly to a Radiant Vision Systems ProMetric® Y16 Imaging Radiometer, and features ProMetric or TrueTest™ Software for intuitive system setup and customizable automated measurement sequences. Additional tests specific to NIR emission measurement are available.
Example of NIR Intensity Lens positioned above a NIR-emitting light source to analyze the complete angular distribution.
High-Resolution Angular Measurement
The NIR Intensity Lens captures the complete angular distribution of a NIR light source (to ±70 degrees) in a single image, and achieves an angular resolution of 0.05 degrees per CCD pixel. Paired with the ProMetric® Y16 Imaging Radiometer featuring a 16-megapixel CCD sensor, the NIR Intensity Lens has the capability to measure radiant intensity, power, and radiant flux with a high degree of accuracy at each view angle. This ensures both accurate distribution and intensity of NIR emissions for object sensing, and safe levels of NIR output for use in human-machine interface applications such as eye and facial sensing.
Safety Considerations
The human eye does not respond to invisible wavelengths of NIR light the same way it does to bright visible light, and therefore can be damaged by NIR emissions. The NIR Intensity Lens enables you to ensure device safety and comply with industry standards such as:
Cross-section radar plot showing radiant intensity (as a function of angle) of a near-infrared LED, captured by the NIR Intensity Lens and output by TrueTest Software.
Diffractive Optical Elements
 Diffractive Optical Elements (DOE) distribute NIR laser emissions in a dot pattern (often tens of thousands of dots) over a wide spatial area. This array provides NIR sensors with a grid map used to detect 3D surfaces with varying shapes, curvatures, and depths, such as the human face. A single beam of NIR laser light is emitted through a DOE “screen”, which splits it into multiple emission points, creating a complex pattern of dots. This pattern is cast on the 3D surface of a target object, such as a face. As the laser light interacts with the object, each of the dots in the array is reflected back to the device’s NIR sensor at a different angular location, size, and intensity, indicating depth and curvature. Calculating the deviation of distributed light versus received reflected light, the sensing device can construct a 3D “map” of the object.
Each dot in a facial recognition DOE array must be accurately positioned (correct angle, inclination, azimuth) to ensure it is properly reflected back and “understood” by the emitting device’s infrared sensor. Manufacturers need to control the position and output of each dot for the device to correctly map the contours of the target object. It is also important to control the radiant intensity (W/sr) intensity of each point to ensure safe levels of NIR output in applications—such as facial recognition and iris tracking—where the human eye is exposed to NIR emissions.
Diffractive Optical Element (DOE) emissions captured by the Radiant NIR Intensity Lens solution and analyzed for angular location, maximum radiant intensity, uniformity, and flux.
Radiant’s NIR Intensity Lens can identify points of interest across the image, measuring point-by-point values for maximum peak (strongest emitter), location at x,y, maximum peak inclination/azimuth, maximum peak averages, maximum peak solid angle, number of pixels as maximum peak point, spot power uniformity (between dots), total flux, and DOE flux (subtracting the background peak).
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