System4f.focusPositions

raytracing.System4f.focusPositions(self, z)

Positions of both focal points on either side of the element.

The front and back focal spots will be different if the index of refraction is different on both sides.

Parameters:: z (float) – Position from where the positions are calculated
Returns:: focusPositions – An array of front focal position and the back focal position.
Return type:: array

Examples

>>> from raytracing import *
>>> # M1 is an ABCD matrix of a lens (f=5)
>>> M1= Matrix(A=1,B=0,C=-1/5,D=1,physicalLength=4,frontVertex=-1,backVertex=5,label='Lens')
>>> Position0=M1.focusPositions(z=0)
>>> print('focal positions (F,B):' , Position0)
focal positions (F,B): CardinalPoint(z1=-5.0, z2=9.0)

And if we move object 2 units:

>>> Position2=M1.focusPositions(z=2)
>>> print('focal positions (F,B):' , Position2)
focal positions (F,B): CardinalPoint(z1=-3.0, z2=11.0)