SAG Calculator

Helpful for calculating SAG of spherical optics. Input diameter and radius to automatically calculate SAG, input diamter and SAG to automatically calculate radius, or input SAG and radius to automatically calculate diameter.

The sag directly influences the focal length of a lens or mirror. By manipulating the sag, we can control how light converges or diverges, thus dictating the focusing behavior. This is vital for designing lenses for telescopes, cameras, eyeglasses, and other optical instruments. The sag of a spherical optic is the depth of the curve measured from the vertex (highest point) to the surface of the sphere. It is an important parameter in determining the optical properties of the lens, such as its focal length and aberration.

Spherical optic sag

SAG = R - sqrt(R^2 - (D/2)^2)

where:

• • SAG is the sag of the optic

• • R is the radius of curvature of the optic

• • D is the diameter of the optic

Once you have calculated the sag of your optic, you can use it to calculate other optical properties, such as the focal length and aberration.

Here are some additional things to keep in mind when calculating the sag of a spherical optic:

• • The sag is usually measured in millimeters.

• • The radius of curvature is also usually measured in millimeters.

• • The diameter of the optic can be measured in any unit, but it is typically measured in millimeters or inches.

• The formula assumes that the optic is a perfect sphere. In reality, most optics are not perfect spheres, so the calculated sag may not be exact.