|
Optical Design Data
Lens Formulae & Design Aids
General
guidelines for choosing a particular lens type for a specific application
are given along with the standard part tables in the followings
sections. Complete detailed optical design service for complex optics
or systems is available from Janos Technology. Fees are often waived
for products we manufacture. Below we show calculations to determine
radii of curvature for a given spherical or cylindrical lens type.
Shown on these sketches are the Effective Focal Length
(EFL), the Back Focal Length (BFL), the Center Thickness (CT), [and the
locations of the element’s Principle Points (P1 and P2)].
The
radii of curvature R1 and R2 refer to the left and right surfaces
respectively. R1 or R2 is positive (negative) if the center of curvature
is to the right (left) side of the lens. The EFL is positive (negative)
if the focal point is to the right (left).
The
lensmaker's equation for a single element in air is:
Here's
the index of refraction for the material at the design wavelength.
In most cases this can be approximated by the Thin Lens Formula:
The
BFL (the distance from the center of the second surface to the focal
point) may be found from:
|
