200 mm Prime Lens Tutorial (Part A): Load, Inspect, and Run a Baseline Ray Trace

🎯 Learning objectives

Load the 200 mm prime lens example and understand the source–lens–detector layout.
Run a baseline ray trace and locate the key outputs (RAY_image.csv, detector folder).
Inspect ray paths in 3D and identify the main lens group, stop, and detector plane.

📦 Prerequisites

OghmaNano installed and Optical Workbench enabled.
Basic familiarity with geometric optics (rays, focal length, lens surfaces).

⏱ Estimated time

Part A: 10–15 min
Part B: 15–20 min
Total: ~30–35 min depending on exploration depth.

Introduction

3D view of the 200 mm prime lens demo in OghmaNano with rays passing through the lens group. — A 200 mm prime lens demo rendered in the Optical Workbench. This tutorial focuses on geometry-first inspection and ray-path sanity checks (no metrics required).

In this tutorial we use a 200 mm prime lens to demonstrate how to inspect a multi-element photographic lens in 3D, run a baseline ray trace, and interpret the output qualitatively. The goal is not to “score” the lens with a merit function; it is to learn how to read the geometry and ray paths so you can quickly spot clipping, misplacement of the stop, and off-axis sensitivity.

Loading the 200 mm prime lens

From the main window click New simulation, then double-click the Ray tracing icon to open the example library. Locate the entry labelled 200 mm prime lens (or similar) and double-click it. Choose a working directory and click OK.

New simulation dialog showing Ray tracing category. — The **New simulation** dialog. Double-click **Ray tracing**.

Ray tracing example library showing a 200 mm prime lens entry. — The ray-tracing example library. Double-click the **200 mm prime** entry.

Orienting yourself in the 3D scene

After loading, the Optical Workbench view should resemble ??. Identify the light source plane, the lens group, any stop/aperture object, and the detector plane. Rotate the scene and confirm the propagation direction (left → right).

Optical Workbench showing the 200 mm prime lens group, source plane, and detector. — The 200 mm prime lens scene in the Optical Workbench (example view).

Running a baseline ray trace

Click Run simulation (blue triangle). When the run completes you should see a ray bundle passing through the lens group to the detector (example in ??).

Ray trace run for the 200 mm prime lens showing rays through the lens group. — Baseline ray trace for the 200 mm prime lens.

Locating and opening the key outputs

Switch to the Output tab. Open the detector folder (typically detector0) and then open RAY_image.csv to view the detector image. This is the fastest qualitative check that “something sensible” is forming at the image plane.

Output tab showing detector folder. — The **Output** tab. Open the detector folder (e.g. `detector0`).

Detector image for the baseline 200 mm prime lens run. — Detector image (`RAY_image.csv`) for the baseline run.

What you can now do (Part A)

Load and navigate the 200 mm prime lens demo in the Optical Workbench.
Run a baseline ray trace and confirm rays propagate through the full lens group.
Open the outputs and view detector0/RAY_image.csv as a quick sanity check.

Common checks if the output looks “wrong”

Confirm the detector plane is behind the lens group and facing the beam.
Reduce ray density if the 3D view becomes visually cluttered.
Check that you opened the correct detector folder (the magenta plane in the 3D scene).

👉 Next step: Continue to Part B to identify chief and marginal rays, diagnose clipping/vignetting by eye, and build a “pre-metric” lens sanity-check workflow.