ImagingPath.chiefRay

raytracing.ImagingPath.chiefRay(self, y=None)

This function returns the chief ray for a height y at object. The chief ray for height y is the ray that goes through the center of the aperture stop.

Parameters:

y (float) – The starting height of the chief ray at the object (default=None) If no height is provided, then the function uses the limit of the field of view.

Returns:

chiefRay – The properties (i.e. height and the angle of the chief ray.)

Return type:

object of Ray class

Examples

>>> from raytracing import *
>>> path = ImagingPath() # define an imaging path
>>> # use append() to add elements to the imaging path
>>> path.append(Space(d=20))
>>> path.append(Lens(f=20,diameter=2,label="f=20"))
>>> path.append(Space(d=30))
>>> path.append(Lens(f=10,diameter=10,label="f=10"))
>>> path.append(Space(d=10))
>>> print(path.chiefRay())
y =  3.333
theta = -0.167
z = 0.000

See also

raytracing.ImagingPath.marginalRays, raytracing.ImagingPath.axialRay, raytracing.ImagingPath.principalRay

Notes

The calculation is simple: obtain the transfer matrix to the aperture stop, then we know that the input ray (which we are looking for) will end at y=0 at the aperture stop. If the element B in the transfer matrix for the imaging path is zero, there is no value for the height and angle that makes a proper chief ray. So the function will return None. If there is no aperture stop, there is no chief ray either. None is also returned.