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Advanced Design

Multi-Configuration Zoom Lens

Learn how to handle lenses that change their state and geometry.

AdvancedAdvanced Optical DesignNumPy backend20 min read

Introduction

This example demonstrates how to create, visualize, and optimize a multi-configuration zoom lens system using the MultiConfiguration class.

Core concepts used

MultiConfiguration(lens)
The manager class that holds a base 'Optic' and tracks variations of that optic across different states.
mc.set_thickness(surface_index=5, value=2.4)
Overrides a specific thickness for one or more configurations. This is how 'zoom groups' are modeled.
mc.set_optic_property(...)
Allows you to change any property (like Field or F-number) for specific configurations.
problem.add_operand(..., input_data={'optic': mc.configurations[1]})
Binds an optimization target to a specific configuration's state.

Step-by-step build

1

Import NumPy and the Optic class

python
import numpy as np
from optiland.optic import Optic
from optiland.multiconfig import MultiConfiguration
from optiland.optimization import OptimizationProblem
from optiland.optimization import LeastSquares
2

Define the Base Optical System

First, we define the base optical system (Configuration 0). This system represents the first zoom position.

Design reference: Milton Laikin, Lens Design, 2007, Pg. 362. Note this design is in inches = 25.4 mm.

python
# Initialize the Optic
lens = Optic()

# Define Wavelengths (Standard Visible)
lens.add_wavelength(value=0.4861)  # F
lens.add_wavelength(value=0.5876, is_primary=True)  # d
lens.add_wavelength(value=0.6563)  # C

# Define Fields (On-axis and Edge)
lens.set_field_type("angle")
lens.add_field(y=0)
lens.add_field(y=14.93)
lens.add_field(y=28.07)

# Define Aperture
lens.set_aperture("imageFNO", 2.4)

# --- Surface Definition ---
# Note: Base configuration uses values for the first zoom position (EFL 0.591)

lens.add_surface(index=0, radius=np.inf, thickness=np.inf)
lens.add_surface(
 index=1, radius=10.0697, thickness=1.2211, material="N-LAK9", aperture=5.8
)
lens.add_surface(
 index=2, radius=-6.2327, thickness=0.2360, material="SF5", aperture=5.8
)
lens.add_surface(index=3, radius=15.1603, thickness=0.0150, aperture=5.38)
lens.add_surface(
 index=4, radius=6.0741, thickness=0.4336, material="N-LAF21", aperture=5.26
)
lens.add_surface(index=5, radius=12.9033, thickness=0.0903, aperture=5.2) # Variable T
lens.add_surface(
 index=6, radius=41.2877, thickness=0.1400, material="N-LAK9", aperture=2.42
)
lens.add_surface(index=7, radius=1.7269, thickness=0.4613, aperture=2.0)
lens.add_surface(
 index=8, radius=-3.8953, thickness=0.1400, material="N-LAK9", aperture=2.0
)
lens.add_surface(
 index=9, radius=1.2599, thickness=0.5386, material="SF5", aperture=1.96
)
lens.add_surface(
 index=10, radius=-43.9995, thickness=5.7197, aperture=1.96  # Variable T
)
lens.add_surface(
 index=11, radius=3.4298, thickness=0.3125, material="N-LAK9", aperture=1.8
)
lens.add_surface(index=12, radius=-4.9794, thickness=0.0150, aperture=1.8)
lens.add_surface(
 index=13, radius=1.6004, thickness=0.1698, material="SF1", aperture=1.68
)
lens.add_surface(
 index=14, radius=0.7220, thickness=0.4947, material="N-LAK9", aperture=1.38
)
lens.add_surface(index=15, radius=6.9314, thickness=0.0090, aperture=1.38) # Variable T
lens.add_surface(index=16, radius=np.inf, thickness=0.2934, is_stop=True)
lens.add_surface(
 index=17, radius=-1.2083, thickness=0.1191, material="N-LAK8", aperture=0.66
)
lens.add_surface(
 index=18, radius=-2.8138, thickness=0.0984, material="SF1", aperture=0.7
)
lens.add_surface(index=19, radius=1.9740, thickness=0.0659, aperture=0.7)
lens.add_surface(
 index=20, radius=-2.5527, thickness=0.3367, material="N-SF8", aperture=0.7
)
lens.add_surface(index=21, radius=-0.8716, thickness=0.0200, aperture=0.86)
lens.add_surface(
 index=22, radius=1.9698, thickness=0.2970, material="N-BAK4", aperture=0.88
)
lens.add_surface(
 index=23, radius=-0.7692, thickness=0.1000, material="SF1", aperture=0.88
)
lens.add_surface(index=24, radius=-3.7908, thickness=0.9232, aperture=0.88)
lens.add_surface(index=25, radius=np.inf, thickness=0.0)

lens.set_ray_aiming("iterative", cache=True)
3

Create Multi-Configuration Setup

We now initialize the MultiConfiguration object. The base optic is automatically assigned as Configuration 0. We then add three additional configurations for different zoom positions. Both zoom positions and fields are defined for each additional configuration. In general, any property of the optic can be defined for any configuration.

python
# Multi-Configuration Setup
mc = MultiConfiguration(lens)

# Configuration 0 is the base (lens)
# Values are already set for Config 0 (EFL 0.591)

# Configuration 1 (EFL 1.272)
mc.add_configuration()
mc.set_thickness(surface_index=5, value=2.4124, configurations=[1])
mc.set_thickness(surface_index=10, value=3.2501, configurations=[1])
mc.set_thickness(surface_index=15, value=0.1566, configurations=[1])
# Update fields for configuration 1
mc.set_optic_property(
 attribute_path="fields.fields[1].y", value=7.05, configurations=[1])
mc.set_optic_property(
 attribute_path="fields.fields[2].y", value=13.9, configurations=[1])

# Configuration 2 (EFL 2.741)
mc.add_configuration()
mc.set_thickness(surface_index=5, value=4.0081, configurations=[2])
mc.set_thickness(surface_index=10, value=1.4376, configurations=[2])
mc.set_thickness(surface_index=15, value=0.3733, configurations=[2])
# Update fields for configuration 2
mc.set_optic_property(
 attribute_path="fields.fields[1].y", value=3.288, configurations=[2])
mc.set_optic_property(
 attribute_path="fields.fields[2].y", value=6.555, configurations=[2])

# Configuration 3 (EFL 5.905)
mc.add_configuration()
mc.set_thickness(surface_index=5, value=5.1199, configurations=[3])
mc.set_thickness(surface_index=10, value=0.0100, configurations=[3])
mc.set_thickness(surface_index=15, value=0.6891, configurations=[3])
# Update fields for configuration 3
mc.set_optic_property(
 attribute_path="fields.fields[1].y", value=1.528, configurations=[3])
mc.set_optic_property(
 attribute_path="fields.fields[2].y", value=3.053, configurations=[3])

for config in mc.configurations:
 config.scale_system(25.4)  # Scale each config to metric
4

Visualize the Configurations

We can visualize all configurations side-by-side using the draw method.

python
_ = mc.draw()
Visualize the Configurations
5

Optimization

We can optimize the system by defining variables and operands. In a multi-configuration system, variables can be applied to common surfaces (affecting all configurations due to pickups) or to specific independent parameters.

Here, we demonstrate a simple optimization setup.

python
problem = OptimizationProblem()

# 1. Add Variables
# Optimize radius of surface 1. Since other configurations are linked to this surface
# by default (via pickups), optimizing the base optic affects all configurations.
problem.add_variable(
 optic=mc.configurations[0], variable_type='radius', surface_number=1
)

# Optimize the spacing after surface 5 for Configuration 1
problem.add_variable(
 optic=mc.configurations[1], variable_type='thickness', surface_number=5
)

# 2. Add Operands
# Target EFL for Config 0
problem.add_operand(
 operand_type='f2', target=0.591*25.4, weight=1.0,
 input_data={'optic': mc.configurations[0]}
)
# Target EFL for Config 1
problem.add_operand(
 operand_type='f2', target=1.272*25.4, weight=1.0,
 input_data={'optic': mc.configurations[1]}
)

# 3. Run Optimization
optimizer = LeastSquares(problem)
optimizer.optimize(maxiter=5)

# Check results
problem.info()
6

Draw the final optimized configuration

python
# View the final design for configuration 3
_ = mc.configurations[3].draw()
Step
Show full code listing
python
import numpy as np
from optiland.optic import Optic
from optiland.multiconfig import MultiConfiguration
from optiland.optimization import OptimizationProblem
from optiland.optimization import LeastSquares

# Initialize the Optic
lens = Optic()

# Define Wavelengths (Standard Visible)
lens.add_wavelength(value=0.4861)  # F
lens.add_wavelength(value=0.5876, is_primary=True)  # d
lens.add_wavelength(value=0.6563)  # C

# Define Fields (On-axis and Edge)
lens.set_field_type("angle")
lens.add_field(y=0)
lens.add_field(y=14.93)
lens.add_field(y=28.07)

# Define Aperture
lens.set_aperture("imageFNO", 2.4)

# --- Surface Definition ---
# Note: Base configuration uses values for the first zoom position (EFL 0.591)

lens.add_surface(index=0, radius=np.inf, thickness=np.inf)
lens.add_surface(
  index=1, radius=10.0697, thickness=1.2211, material="N-LAK9", aperture=5.8
)
lens.add_surface(
  index=2, radius=-6.2327, thickness=0.2360, material="SF5", aperture=5.8
)
lens.add_surface(index=3, radius=15.1603, thickness=0.0150, aperture=5.38)
lens.add_surface(
  index=4, radius=6.0741, thickness=0.4336, material="N-LAF21", aperture=5.26
)
lens.add_surface(index=5, radius=12.9033, thickness=0.0903, aperture=5.2) # Variable T
lens.add_surface(
  index=6, radius=41.2877, thickness=0.1400, material="N-LAK9", aperture=2.42
)
lens.add_surface(index=7, radius=1.7269, thickness=0.4613, aperture=2.0)
lens.add_surface(
  index=8, radius=-3.8953, thickness=0.1400, material="N-LAK9", aperture=2.0
)
lens.add_surface(
  index=9, radius=1.2599, thickness=0.5386, material="SF5", aperture=1.96
)
lens.add_surface(
  index=10, radius=-43.9995, thickness=5.7197, aperture=1.96  # Variable T
)
lens.add_surface(
  index=11, radius=3.4298, thickness=0.3125, material="N-LAK9", aperture=1.8
)
lens.add_surface(index=12, radius=-4.9794, thickness=0.0150, aperture=1.8)
lens.add_surface(
  index=13, radius=1.6004, thickness=0.1698, material="SF1", aperture=1.68
)
lens.add_surface(
  index=14, radius=0.7220, thickness=0.4947, material="N-LAK9", aperture=1.38
)
lens.add_surface(index=15, radius=6.9314, thickness=0.0090, aperture=1.38) # Variable T
lens.add_surface(index=16, radius=np.inf, thickness=0.2934, is_stop=True)
lens.add_surface(
  index=17, radius=-1.2083, thickness=0.1191, material="N-LAK8", aperture=0.66
)
lens.add_surface(
  index=18, radius=-2.8138, thickness=0.0984, material="SF1", aperture=0.7
)
lens.add_surface(index=19, radius=1.9740, thickness=0.0659, aperture=0.7)
lens.add_surface(
  index=20, radius=-2.5527, thickness=0.3367, material="N-SF8", aperture=0.7
)
lens.add_surface(index=21, radius=-0.8716, thickness=0.0200, aperture=0.86)
lens.add_surface(
  index=22, radius=1.9698, thickness=0.2970, material="N-BAK4", aperture=0.88
)
lens.add_surface(
  index=23, radius=-0.7692, thickness=0.1000, material="SF1", aperture=0.88
)
lens.add_surface(index=24, radius=-3.7908, thickness=0.9232, aperture=0.88)
lens.add_surface(index=25, radius=np.inf, thickness=0.0)

lens.set_ray_aiming("iterative", cache=True)

# Multi-Configuration Setup
mc = MultiConfiguration(lens)

# Configuration 0 is the base (lens)
# Values are already set for Config 0 (EFL 0.591)

# Configuration 1 (EFL 1.272)
mc.add_configuration()
mc.set_thickness(surface_index=5, value=2.4124, configurations=[1])
mc.set_thickness(surface_index=10, value=3.2501, configurations=[1])
mc.set_thickness(surface_index=15, value=0.1566, configurations=[1])
# Update fields for configuration 1
mc.set_optic_property(
  attribute_path="fields.fields[1].y", value=7.05, configurations=[1])
mc.set_optic_property(
  attribute_path="fields.fields[2].y", value=13.9, configurations=[1])

# Configuration 2 (EFL 2.741)
mc.add_configuration()
mc.set_thickness(surface_index=5, value=4.0081, configurations=[2])
mc.set_thickness(surface_index=10, value=1.4376, configurations=[2])
mc.set_thickness(surface_index=15, value=0.3733, configurations=[2])
# Update fields for configuration 2
mc.set_optic_property(
  attribute_path="fields.fields[1].y", value=3.288, configurations=[2])
mc.set_optic_property(
  attribute_path="fields.fields[2].y", value=6.555, configurations=[2])

# Configuration 3 (EFL 5.905)
mc.add_configuration()
mc.set_thickness(surface_index=5, value=5.1199, configurations=[3])
mc.set_thickness(surface_index=10, value=0.0100, configurations=[3])
mc.set_thickness(surface_index=15, value=0.6891, configurations=[3])
# Update fields for configuration 3
mc.set_optic_property(
  attribute_path="fields.fields[1].y", value=1.528, configurations=[3])
mc.set_optic_property(
  attribute_path="fields.fields[2].y", value=3.053, configurations=[3])

for config in mc.configurations:
  config.scale_system(25.4)  # Scale each config to metric

_ = mc.draw()

problem = OptimizationProblem()

# 1. Add Variables
# Optimize radius of surface 1. Since other configurations are linked to this surface
# by default (via pickups), optimizing the base optic affects all configurations.
problem.add_variable(
  optic=mc.configurations[0], variable_type='radius', surface_number=1
)

# Optimize the spacing after surface 5 for Configuration 1
problem.add_variable(
  optic=mc.configurations[1], variable_type='thickness', surface_number=5
)

# 2. Add Operands
# Target EFL for Config 0
problem.add_operand(
  operand_type='f2', target=0.591*25.4, weight=1.0,
  input_data={'optic': mc.configurations[0]}
)
# Target EFL for Config 1
problem.add_operand(
  operand_type='f2', target=1.272*25.4, weight=1.0,
  input_data={'optic': mc.configurations[1]}
)

# 3. Run Optimization
optimizer = LeastSquares(problem)
optimizer.optimize(maxiter=5)

# Check results
problem.info()

# View the final design for configuration 3
_ = mc.configurations[3].draw()

Conclusions

  • The MultiConfiguration class was used to model a real zoom lens (from Milton Laikin's reference design) across four distinct focal-length positions by overriding variable airspaces and field angles per configuration.
  • Scaling the system from inches to millimetres with scale_system(25.4) demonstrated that Optiland's multi-configuration framework is unit-agnostic and integrates seamlessly with published lens data.
  • The mc.draw() method rendered all four zoom configurations side-by-side in a single call, making it straightforward to verify layout continuity across zoom positions.
  • Optimization variables and operands were bound to specific configurations, showing how shared (pickup) parameters and configuration-independent parameters can coexist in the same OptimizationProblem.
  • Viewing the final telephoto configuration individually confirmed that the optimized shared surface radius propagated correctly through the configuration pickup mechanism, validating the multi-configuration constraint system.

Next tutorials

NextTolerancing, Sensitivity AnalysesAnalyze how small manufacturing errors impact the performance of your design.RelatedGlass ExpertUse auto-material selection to refine your zoom lens's color correction.

Original notebook: Tutorial_7f_Multi_Configuration_Zoom_Lenses.ipynb on GitHub · ReadTheDocs