PSF-based radiometry for small targets

The conventional infrared radiometry method can only calculate the irradiance of the extended source, which is no longer applicable when the target size is too small. This paper proposes PSF-based radiometry to realize the infrared radiometry of small targets. From the point spread function (PSF) theory, the relationship between the on-axis irradiance of incoherent light imaging in the image plane and the size of the target is obtained, and then the variance of the PSF is obtained by varying target size. Then, to establish a small-target radiation detection model, the relationship between the variance of the PSF and the target irradiance is obtained by varying the target irradiance. Finally, the experimental results suggest that the measurement error of different irradiance is less than 1.5 %. The error remains within a stable range as the target size decreases and the variance of the error is less than 0.16. Compared with the conventional energy-based method, it proves that the PSF-based method is more accurate and the overall error is lower, which is well suited for the measurement of small-target irradiance. © 2023 Elsevier Science. •This manuscript proposes a mathematical model of the relationship between the on-axis irradiance of incoherent light imaging in the image plane and the size of the target.•The processing process of data obtained by the PSF-based method does not generate additional errors.•The PSF-based method only requires single data processing for small-target radiation measurement, and only requires the target size and the on-axis gray value of the image plane to accurately calculate the target irradiance.•The experimental results suggest that the measurement error of different irradiance is less than 1.5 %. The error is overall small and does not become larger when the target size is too small, making it more suitable and practical for small-target radiation measurement.