Perfectly aligned lenses and prisms in binocular barrels produce a crisp merged image that is said to be collimated rough handling can knock binoculars out of collimation leading to fuzzy or overlapping images and possibly cat s eye shaped images in each eyepiece.
Roof prism binocular collimation.
Provided the binoculars are not severely out of collimation the collimation is accomplished using the porro prisms housed just in front of the eyepieces.
This can cause eyestrain headaches and a degraded user experience.
Roof prism binocular roof prism binocular is more streamlined as the glasses are in line with one another.
Contain 2 prisms called dach or dachkanten prism and derive their name from abbe koenig ak prism design.
These are easy to hold for you are more compact and more expensive than porro prism binoculars.
In a roof prism binocular the prisms reflective surfaces resemble those of a rooftop hence the name.
The arrowed screws in the images are the collimation screws that pass to the outside through the housing.
The system used in binoculars consists of two prisms with at least one prism having a roof edge.
Normally the collimation is adjusted by screws on porro prism bins which i assume that 20x60s will be.
Aligning the prisms the typical cause of porro prism binoculars losing collimation is being dropped or receiving a knock that shifts one of the prisms.