This page is not fully translated, yet. Please help completing the translation.
(remove this paragraph once the translation is finished)
Spatial Frequency Units
Units and Applications of Spatial Frequency
Conversion Formulas
Different units can be converted using parameters such as image height and focal length. The conversion formulas are as follows:
| Unit | Conversion Formula |
|---|---|
| Cycles / Pixel (C/P) | |
| Cycles / Distance (cycles / mm or cycles / inch) | $\frac{MTF(C/P)}{\text{pixel pitch}}$ |
| Line Widths / Picture Height (LW / PH) | $2 \times MTF\left(\frac{LP}{PH}\right)$ ; $2 \times MTF\left(\frac{C}{P}\right) \times PH$ |
| Line Pairs / Picture Height (LP / PH) | $MTF\left(\frac{LW}{PH}\right)/2$ ; $MTF\left(\frac{C}{P}\right) \times PH$ |
| Angular Frequency (Cycles / milliradian) | $0.001 \times MTF\left(\frac{\text{cycles}}{\text{mm}}\right) \times FL(\text{mm})$ |
| Cycles / Degree | $\frac{\pi}{180} \times MTF\left(\frac{\text{cycles}}{\text{mm}}\right) \times FL(\text{mm})$ |
| Cycles / Object mm | $MTF\left(\frac{\text{Cycles}}{\text{Distance}}\right) \times |\text{Magnification}|$ |
| Line Widths / Feature Height (Px) | $2 \times MTF\left(\frac{C}{P}\right) \times \text{Feature Height}$ |
| Line Pairs / Feature Height (Px) | $MTF\left(\frac{C}{P}\right) \times \text{Feature Height}$ |
where PH = picture height (in pixels); FL (mm) = lens focal length in mm; Pixel pitch = distance per pixel = 1 / (pixels per distance).
How to Change the Result Units in RIQA Software?
Open the RIQA software, click “Settings”, select “Global Settings”, and then modify the “Display Unit” according to your needs to change the units of the output results.
