Advanced NIR Lens for Precision Radiant Intensity Analysis

Many novel applications, including the following, are based on three-dimensional (3D) sensing technology:

Iris recognition and eye tracking

Recognition of faces and gestures

Multimodal sensing for vehicle motion and gesture control

Automotive LiDAR to detect self-driving cars

Additional uses for near-infrared 3D sensing

Measurement techniques for NIR LEDs and lasers ensure the performance of Time-of-Flight (ToF) light-based proximity sensing and 3D sensing using dot patterns produced by Diffractive Optical Elements (DOE). An efficient test and measurement solution is needed to ensure the precision and functionality of systems and devices that use NIR sensing.

Near-Infrared Intensity Lens Solution

Radiant Vision Systems offers an integrated camera/lens solution called the Near-Infrared (NIR) Intensity Lens system that measures the angular distribution and radiant intensity of near-infrared (NIR or near-IR) emitters at 850 or 940 nm.

Utilizing Fourier optics, the NIR Intensity Lens system records an entire cone of data in a single measurement up to ±70°, providing customers with quick, accurate findings appropriate for in-line quality control.

Manufacturers of 3D sensing technologies can use the NIR Intensity Lens solution to assess the angular response of lasers, NIR LEDs, and structured light patterns created by DOE.

Direct lens alignment with a ProMetric^® Imaging Radiometer from Radiant Vision Systems is possible. Thanks to ProMetric or TrueTestTM software, it offers configurable automated measurement sequences and intuitive system arrangement. Assays specifically for measuring NIR emissions are also available.

Example of NIR Intensity Lens positioned above an NIR-emitting light source to analyze the complete angular distribution. Image Credit:Radiant Vision Systems

High-Resolution Angular Measurement

Radiant Vision Systems' NIR Intensity Lens achieves an angular resolution of approximately 0.05° per image sensor pixel. It records the whole angular distribution of a NIR light source (to ±70°) in a single image.

The NIR Intensity Lens can accurately measure radiant flux, radiant intensity, and power at all view angles when used with the ProMetric^® Imaging Radiometer.

This ensures acceptable levels of NIR output for use in human-machine interface applications such as facial and eye sensing, as well as correct intensity and distribution of NIR emissions for object sensing.

Image Credit:Radiant Vision Systems

Safety Considerations

NIR emissions have the potential to cause harm to the human eye because they differ from intense visible light in how it reacts to invisible wavelengths of NIR light. For example:

IEC 60825-1 laser standard, which includes all NIR lasers

The IEC 62471 standard is required for all light sources throughout America, Europe, and Asia.

According to the American Conference of Governmental Industrial Hygienists (ACGIH). TLVs (threshold limit values) for physical agents, such as “light, near-infrared radiation, and lasers”

Radiant Vision Systems' near-infrared measuring solutions characterize the output of the NIR source, providing producers with useful information for testing these standards.

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.Image Credit:Radiant Vision Systems

Structured Light Dot Pattern Analysis

DOE dispersed NIR laser outputs over a large spatial region in a structured light pattern, primarily consisting of tens of thousands of dots. When a single NIR laser beam passes through a DOE “screen,” it splits into several emission points, typically forming hundreds of dots, creating this pattern. Like a face, a target object's 3D surface is covered with this pattern.

Image Credit:Radiant Vision Systems

When the laser light interacts with the object, each dot in the pattern represents curvature and depth and is reflected to the device's near-infrared sensor at a distinct angular location, intensity, and size. Using the difference between disseminated and received reflected light, the sensing device creates a three-dimensional “map” of the object.

To ensure that a structured light pattern is appropriately reflected and "understood" by the infrared sensor in the emitting device, every dot in the pattern must be positioned precisely (at the right angle, azimuth, and inclination). Manufacturers must control the location and output of each dot on the gadget to precisely map the contours of the target item.

In applications such as iris tracking and facial identification, where the human eye is exposed to NIR emissions, it is imperative to control individual points' radiant intensity (W/sr) to guarantee precise NIR output levels.

Dot emissions created using a diffractive optical element (DOE) are captured by the Radiant NIR Intensity Lens solution and analyzed for angular location, maximum radiant intensity, uniformity, and flux. Image Credit:Radiant Vision Systems

Using point-by-point measurements for maximum peak inclination/azimuth, maximum peak solid angle, location at x, y, spot power uniformity (between dots), maximum peak (strongest emitter), maximum peak averages, number of pixels as maximum peak point, total flux, and DOE flux (subtracting the background peak), Radiant Vision Systems' NIR Intensity Lens can identify points of interest throughout the image.

“Flood” Source Analysis

A strong NIR light burst, sometimes called a “flood” distribution, may be necessary for object sensing to determine closeness using a ToF measurement. Flood emitters, for example, can be used in facial recognition applications to detect the presence of a face and determine focus distance even in low light.

The NIR Intensity Lens provides Flood Source Analysis to evaluate diffuse NIR sources to ensure they meet suggested performance standards and to find and address anomalies like hot spots or intensity fall-off.

Analyze flood distributionof diffuse NIR light sources to evaluate uniformity across angular emissions (in terms of intensity at each degree), center values, angular fall-off, or hot spots.Image Credit:Radiant Vision Systems

Complete Measurement Solution

For comprehensive NIR source characterization and emission measurement, the NIR Intensity Lens provides an application-specific solution. The NIR Intensity Lens provides a turnkey radiometric imaging solution that meets the measurement efficiency, form factor, and cost criteria for many applications when combined and calibrated with a ProMetric Y Imaging Radiometer.

Image Credit:Radiant Vision Systems

The software Radiant NIR solution provides tests for evaluating NIR light angular distributions and DOE-created dot patterns. By applying specific tests to a single camera-captured image, users can quickly and efficiently evaluate all relevant display elements by sequencing tests in seconds.

Tests that are exceptional for NIR analysis include:

POI Total Power

Dot Source Analysis

Total Flux (mW or W)

Image Export

Max Power

Pixel Solid Angle

Flood Source Analysis

Points of Interest

Radiant solutions are hardware/software hybrid systems created to meet specific application needs. They enable producers to implement more effective measurement procedures while utilizing a single supplier for end-to-end assistance.

Key Features and Highlights of NIR Intensity Lens

Small form factor

High angular resolution with 0.05° per pixel of the image sensor

Accurate and trustworthy radiant intensity measuring to ±70° angle

Effective functioning, simultaneously recording data from all angles. Faster at analyzing angular data than goniometric systems

Combination of flexibility, affordability, and great performance

Software for measurement, control, and analysis that is easy to use

Typical Applications

The NIR intensity lens provides an effective measurement option for NIR sources such as lasers and LEDs. This camera/lens combination provides high-resolution imagery for both online and offline applications.

NIR LED, laser, and structured light pattern measurement created by DOE

Angular measurement for 3D sensing devices: Automotive LiDAR, gesture recognition, facial identification, eye tracking, and multimodal human-machine interface (HMI)

Fast operation for in-line measurement to ensure production process quality control

Evaluation of light sources at 850 or 940 nm for accurate production of radiant intensity from all angles