Point Spread Function (PSF)
Definition
A mathematical description of how the imaging system spreads the light from a single point source across neighbouring pixels. Defocus, diffraction, and motion each produce characteristic PSF shapes.
- Field
- Digital image enhancement
- Describes
- How a point source's light spreads across pixels
- Common causes
- Defocus, diffraction, motion blur
Common questions
How is the PSF used to enhance a blurred forensic image?+
If the PSF that caused the blur can be estimated or measured, a deconvolution filter built from it can be applied to the image to reverse much of the spreading and partially recover detail that was smeared across neighbouring pixels.
Why can PSF-based enhancement not restore detail lost outright?+
Deconvolution can only redistribute information the sensor actually recorded. Where the true detail fell below the sensor's noise floor or resolution limit before capture, no amount of PSF modeling can recreate it, only sharpen what already exists in the data.
Related terms
- CLAHE
- Contrast Limited Adaptive Histogram Equalisation. Divides the image into local tiles, equalises each tile's contrast separately, and blends results. Recovers shadow detail...
- Deconvolution
- A computational technique that estimates the PSF and inverts its effect to recover a sharper image. The quality depends entirely on how...
- Nyquist Limit
- The sampling theorem's constraint: to faithfully record a feature, the sensor must sample it at least twice per cycle. A feature smaller...
- Spatial Resolution
- The finest detail a camera system can record, determined by pixel size and lens quality, measured in line pairs per millimetre or...
- Super-Resolution
- Methods that attempt to produce an image with higher pixel density than the source. Interpolation-based SR fills in values by estimation; learning-based...