Field Type: Real Image Height

This notebook demonstrates the RealImageHeightField type, where fields are defined by the intersection height of the real chief ray at the image plane. This differs from the paraxial image height, which uses linear paraxial approximations.

import optiland.backend as be
from optiland.optic import Optic

class CookeTriplet(Optic):
    """A Cooke triplet lens design."""

    def __init__(self):
        super().__init__()

        self.surfaces.add(index=0, radius=be.inf, thickness=be.inf)
        self.surfaces.add(index=1, radius=22.01359, thickness=3.25896, material="SK16")
        self.surfaces.add(index=2, radius=-435.76044, thickness=6.00755)
        self.surfaces.add(index=3, radius=-22.21328, thickness=0.99997, material=("F2", "schott"))
        self.surfaces.add(index=4, radius=20.29192, thickness=4.75041, is_stop=True)
        self.surfaces.add(index=5, radius=79.68360, thickness=2.95208, material="SK16")
        self.surfaces.add(index=6, radius=-18.39533, thickness=42.20778)
        self.surfaces.add(index=7)

        self.set_aperture(aperture_type="EPD", value=10)

        # Set Field Type to RealImageHeightField
        self.fields.set_type(field_type="real_image_height")

        # Add fields at specific real image heights (mm)
        self.fields.add(y=0)
        self.fields.add(y=12)
        self.fields.add(y=18)

        self.wavelengths.add(value=0.48)
        self.wavelengths.add(value=0.55, is_primary=True)
        self.wavelengths.add(value=0.65)

lens = CookeTriplet()
_ = lens.draw()

# Verify Real Image Heights
print("Verifying Real Image Heights...")
max_field = lens.fields.max_field
print(f"Max Field: {max_field} mm")

# Normalized field coordinates for the added fields
Hx = be.array([0, 0, 0])
Hy = be.array([0, 12/max_field, 18/max_field])

# Trace chief rays (Pupil = 0,0) at primary wavelength
rays = lens.trace_generic(Hx, Hy, Px=0, Py=0, wavelength=0.55)

print("\nTarget Height vs Actual Image Height:")
for target, actual in zip(Hy * max_field, rays.y):
    print(f"Target: {target:.4f} mm, Actual: {actual:.4f} mm, Error: {abs(target - actual):.4e} mm")

Verifying Real Image Heights...
Max Field: 18.0 mm

Target Height vs Actual Image Height:
Target: 0.0000 mm, Actual: 0.0000 mm, Error: 0.0000e+00 mm
Target: 12.0000 mm, Actual: 12.0000 mm, Error: 1.2434e-14 mm
Target: 18.0000 mm, Actual: 18.0000 mm, Error: 2.4869e-14 mm