Optics — 3D Geometric Ray Tracer (Spherical Optics)

A lightweight 3D geometric optics ray tracer for planar / spherical optical elements, built for quantitative lens performance analysis (spot diagrams, RMS spot size) and simple lens design comparisons.

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Key features

• Generalized optical surfaces

  • Planar and spherical geometry
  • Refraction and reflection
  • Output plane for spot evaluation

• Physics-correct propagation

  • Snell’s law refraction
  • Handles total internal reflection (TIR) cases
  • Optional consideration of Fresnel loss (kept small for this project)

• Robust ray–surface intersection

  • Plane intersection (z = z0)
  • Spherical intersection via quadratic solve
  • Physically valid root selection + aperture checking

• Quantitative evaluation

  • 3D track plots (ray trajectories)
  • 2D spot diagrams at a chosen plane (typically focal plane)
  • RMS spot size to quantify spherical aberration
  • Comparison against diffraction scale (Δx = λ f / D)

• Lens experiments included

  • Plano-convex (PC) vs convex-plano (CP) orientation comparison
  • Thick-lens / principal-plane shift correction (for finite thickness)
  • Simple biconvex optimization exploration

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Repository structure

• raytracer (core library: rays, surfaces, optics, analysis)
• tests (pytest)
• README.md
• report
• graph (result from tasks)

Playbook: tweak parameters to get different behaviours

Most experiments in this repo reduce to:

(1) ray bundle (input) + (2) lens geometry + (3) observation plane (where you measure the spot)

Below is a practical “change X → you get Y” cheat sheet.

A) Ray bundle (input rays)

Typical parameters you will see in raytracer/analysis.py (names may vary):

• bundle_radius / r_max / radius
  Increase → includes more marginal rays → spherical aberration increases → RMS spot grows faster.

• nrings, rays_per_ring (sampling density)
  Increase → smoother spot/RMS curves and less sampling noise, but slower runtime.

• wavelength / lambda
  Controls the diffraction scale (e.g. ( \Delta x \approx \lambda f / D )).
  Increase → diffraction-limited spot size increases.

Try this: keep the lens fixed and sweep bundle_radius from small → large, then plot RMS spot radius.

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B) Lens geometry (surfaces + material)

Common lens parameters:

• R1, R2 / curvature1, curvature2
  Stronger curvature (smaller (|R|) / larger (|1/R|)) → shorter focal length.
  Curvature distribution affects aberrations (PC vs CP orientation).

• thickness
  Increase → principal plane shift matters more (thick-lens behaviour).

• aperture / D (clear aperture diameter)
  Decrease → reduces aberration contribution (smaller RMS), but increases diffraction limit (larger ( \Delta x )).

• n_lens (refractive index)
  Increase → stronger refraction → shorter focal length (for the same curvatures).

Try this: flip a plano-convex lens orientation (PC ↔ CP) and compare RMS / spot diagrams.

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C) Observation plane (where you evaluate the spot)

Typical parameters:

• z_image / z_screen / output plane position
  Moving the plane changes the measured spot:
  sweep around the expected focus → find minimum RMS (best focus).

Try this: scan z_image around the expected focus and plot RMS vs z_image to locate best focus numerically.

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Quickstart (run locally)

Clone the repo and create a virtual environment:

git clone https://github.com/cid02391689/Optics.git
cd Optics

python3 -m venv .venv
source .venv/bin/activate
python -m pip install -U pip
pip install numpy matplotlib pytest