Meaning
Analytical models describe the response of an imaging system to a single point source of light or radiation. The point spread function represents the degree of blurring that occurs as an infinitely small point is captured by a detector or passed through an optical lens. It is the spatial domain equivalent of the modulation transfer function and provides a direct way to understand the resolution limits of the hardware.
Any image produced by the system is effectively the mathematical convolution of the true object and this blurring function.
Blurring Characterization
Light or X-rays are scattered by the sample and the detector, causing a single point to appear as a broader spot. The width of the point spread function determines the smallest feature that can be clearly resolved. A narrower function indicates a higher quality system that can distinguish between objects that are very close together.
Resolution Decay
Performance often varies across the field of view due to lens aberrations or detector geometry. In many systems, the point spread function is sharpest at the center and becomes wider and more distorted near the edges. Regular testing with a pinhole target allows technicians to map these variations and correct for them during image processing.
System Linearity
Reliable deconvolution requires that the blurring effect remains constant regardless of the intensity of the light. If the point spread function changes with the brightness of the source, the system is non-linear and much harder to calibrate. Maintaining a stable response is essential for quantitative analysis of density and material composition.
