"""Reciprocal Radius Variable Module
This module contains the ReciprocalRadiusVariable class, which represents a variable for
the reciprocal of the radius of a surface in an optic. The transformation is useful
because a nearly flat surface (with a very large positive or negative radius) has a
reciprocal near zero, which makes the optimization around a nearly flat surface
continuous. The reciprocal radius provides a continuous transition when surface changes
from convex to concave (when the radius changes sign).
Daniel Miranda, 2025
ALL rights ceded to Kramer Harrison
"""
from __future__ import annotations
import optiland.backend as be
from optiland.optimization.scaling.linear import LinearScaler
from optiland.optimization.variable.base import VariableBehavior
[docs]
class ReciprocalRadiusVariable(VariableBehavior):
"""Represents a variable for the reciprocal of the radius of a surface in an optic.
Args:
optic (Optic): The optic object that contains the surface.
surface_number (int): The index of the surface in the optic.
scaler (Scaler): The scaler to use for the variable. Defaults to
a linear scaler with factor=10.0.
**kwargs: Additional keyword arguments.
Attributes:
optic (Optic): The optic object that contains the surface.
surface_number (int): The index of the surface in the optic.
Methods:
get_value(): Returns the current value of the reciprocal radius.
update_value(new_value): Updates the value via the reciprocal, converting back
to radius.
"""
def __init__(self, optic, surface_number, scaler=None, **kwargs):
if scaler is None:
scaler = LinearScaler(factor=10.0)
super().__init__(optic, surface_number, scaler=scaler, **kwargs)
[docs]
def get_value(self):
"""Returns the current value of the reciprocal of the radius.
Returns:
float: The current reciprocal radius.
"""
radius = self._surfaces.radii[self.surface_number]
# Avoid division by zero
if radius != 0:
reciprocal = 1.0 / radius if be.isfinite(radius) else 0.0
else:
reciprocal = be.inf
return reciprocal
[docs]
def update_value(self, new_value):
"""Updates the surface radius based on the new reciprocal variable value.
Args:
new_value (float): The new reciprocal radius value.
"""
# Allow zero but handle appropriately
new_radius = be.inf if new_value == 0 else 1.0 / new_value
self.optic.updater.set_radius(new_radius, self.surface_number)
def __str__(self):
"""Return a string representation of the variable.
Returns:
str: A string representation of the reciprocal radius variable.
"""
n = self.surface_number
v = self.get_value()
return f"Reciprocal Radius of Curvature - Surface {n} - value: {v}"