Equivalent Calibration Method Based on a Blackbody Baffle Substitution for a Large External Surface-Source Blackbody

Area of Science:

• Optics and Photonics
• Infrared Technology
• Radiometry

Background:

• Precise radiometric calibration is essential for accurate infrared system measurements.
• Periodic calibration of infrared cameras is necessary for image interpretation and performance monitoring.
• Existing field calibration methods for large-aperture equipment often require large external blackbody sources.

Purpose of the Study:

• To propose and validate an equivalent calibration method using an internal blackbody baffle.
• To enable field calibration of large-aperture infrared equipment without external sources.
• To derive and experimentally verify the equivalent calibration conversion function (ECCF).

Main Methods:

• Development of an equivalent calibration method utilizing an internal blackbody baffle.
• Derivation of the equivalent calibration conversion function (ECCF) based on camera grayscale response and calibration models.
• Experimental validation using a cooled mid-wave infrared camera and target imaging experiments.

Main Results:

• The derived functional form of the ECCF aligns with physical principles.
• Inversion results using ECCF closely match direct external blackbody calibration (average error 0.198%, max error <1%).
• Radiation brightness inversion accuracy meets radiometric measurement requirements (max error 6.29%).

Conclusions:

• The proposed equivalent calibration method provides a viable alternative to traditional external blackbody calibration.
• The ECCF accurately converts grayscale response to radiometric values for infrared systems.
• This method enhances the practicality and accuracy of radiometric calibration for large-aperture infrared equipment.