What is different about the Advanced Radiometric Version and the Non-Radiometric Version of Tau2?

Radiometry refers to the estimation of target temperature by measuring the radiation it emits. Advanced Radiometry (AR) means that every pixel in the sensor is calibrated to provide a temperature value, and that image metric features are provided. In standard Tau 2 cameras, radiometry (temperature measurement) is provided via a spot meter, using the center four pixels in the sensor. Accuracy of the spot meter is +20 °C in high-gain state (see 3.3.2.2) and the greater of +20% or +20 °C in low-gain state (Typical performance is on the order of +10 °C in high-gain state). The spot meter value is readable via the serial command bus. Additionally, two user-selectable options for on-screen display of spot-meter data are provided: a numeric value and/or a thermometer-style gauge. The numeric indicator and gauge can be shown in degrees Celsius or Fahrenheit.

A special, additional factory calibration is required for the Advanced Radiometry option during the camera build. AR cannot be retroactively added to an existing Tau2 camera. The Advanced Radiometry features are partially documented at the Knowledge Base. Additional documentation is available to qualified OEM developers.

Advanced Radiometry and TLinear
The Tau2 core provides the option of the following advanced radiometric features:
  • Improved accuracy: typical performance on the order of +5 °C or 5% in high-gain state (varies slightly across the full operating temperature range)
  • Moveable / resizable spot-meter: coordinates user-selectable to any arbitrary location on the array
  • Additional spot-meter data: spot-meter reports average, standard deviation, minimum, and maximum value
  • TLinear: digital data linear in scene temperature, i.e. in real-time operation, the pixel values in the 14-bit digital data correspond to the temperature of the scene.

In normal mode with TLinear disabled, the Tau camera outputs digital data linear in radiometric flux. In TLinear mode, the Tau camera outputs digital data linear in scene temperature. The TLinear feature applies to the 14-bit CMOS and LVDS channels and is user-selectable. Two resolution modes are available and user selectable: high resolution (0.04 Kelvin/count) and low resolution (0.4 Kelvin/count).

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