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Sequential ray tracing · 15+ Sellmeier glasses · Spot diagrams · ABCD matrix · Chromatic aberration
| # | R (mm) | Aper | Thick | Material | K |
|---|
Rays are traced surface-by-surface using the exact ray-conic intersection equation. At each interface, Snell's law in vector form computes the refracted direction. This handles spherical, parabolic, hyperbolic, and elliptical surfaces via the conic constant K.
Refractive index varies with wavelength: n²(λ) = 1 + Σ Biλ² / (λ² − Ci). Each glass type (N-BK7, N-SF11, F2, etc.) has unique B,C coefficients from measured dispersion curves. This is essential for chromatic aberration analysis.
The system matrix multiplies refraction and transfer matrices for each surface. The equivalent focal length is 1/B where B is the top-right element. This paraxial approximation gives quick focal length, principal planes, and the condition for imaging.
A grid of rays across the entrance pupil is traced to the image plane. The scatter pattern reveals aberration types: spherical (symmetric ring), coma (comet tail), astigmatism (two line foci). RMS spot size compared to the Airy disk indicates diffraction-limited performance.
R > 0: Center of curvature to the right (convex to incoming light).
R < 0: Center of curvature to the left (concave).
R = Inf: Flat (plane) surface.
Measured in millimeters.
K = 0: Sphere
K = −1: Paraboloid
K < −1: Hyperboloid
−1 < K < 0: Prolate ellipsoid
K > 0: Oblate ellipsoid
Axial distance from this surface vertex to the next surface vertex (mm). The last surface's thickness is the back focal distance โ the gap from the last surface to the image plane. Autofocus adjusts this automatically.
The medium after this surface. Set to a glass type (N-BK7, F2, etc.) for the first surface of a lens element, then Air for the last surface of that element. This defines which medium the refraction goes into.
Use this Optical Designer: choose a preset (achromatic doublet, Cooke triplet, Petzval lens) or add surfaces manually. Set radius, aperture, thickness, and glass material for each surface. The tool instantly traces rays and shows focal length, spot diagram, and aberrations. No download or signup needed.
Ray tracing follows light rays surface-by-surface through lenses using Snell's law. This tool uses sequential ray tracing with exact ray-conic intersection math, supporting spheres, parabolas, and aspherical surfaces. It traces up to 13 surfaces in real time, showing 2D cross-section diagrams, spot diagrams, and ray aberration plots.
This tool calculates focal length automatically using the ABCD ray transfer matrix method. Each surface contributes a refraction matrix and each air gap a transfer matrix. The system focal length equals 1/B of the combined matrix. Results update in real time as you edit surface parameters.
Chromatic aberration occurs because glass bends different wavelengths by different amounts, causing color fringing. Pair a low-dispersion crown glass (N-BK7) with a high-dispersion flint glass (N-SF2) in an achromatic doublet. Switch to the Chromatic Aberration view to see EFL at three wavelengths and axial CA.
A spot diagram shows where rays from a point source land on the image plane. A tight cluster means low aberration. The RMS spot radius measures the spread. If RMS is smaller than the Airy disk (1.22 × λ × f/#), the lens is diffraction-limited. Switch to Spot Diagram view to analyze your design.
15+ optical materials with Sellmeier dispersion: Schott glasses (N-BK7, N-SF11, N-SF2, F2, N-FK51A, N-LAK9), fused silica, crystals (CaF₂, BaF₂, MgF₂, sapphire, diamond), and plastics (PMMA, polycarbonate). Each uses the 3-term Sellmeier equation for accurate wavelength-dependent refractive index.
Yes, completely free with no signup. Runs entirely in your browser. Students can learn lens design with presets. Engineers can prototype systems, analyze aberrations, and export as JSON or PNG. Covers undergraduate optics through professional engineering.
This is a free browser-based alternative for sequential ray tracing fundamentals: Sellmeier materials, conic surfaces, spot diagrams, ABCD matrix, chromatic analysis. Ideal for learning and quick prototyping. Zemax/Oslo add tolerancing, MTF, coating design, and non-sequential tracing for production work.
Single lens focal length from R1, R2, and refractive index. Combined and double lens systems.
Thin lens / mirror equation solver with interactive ray diagrams for 7 optical element types.
Refraction calculator with Snell's law, critical angle, prism deviation, and interactive diagrams.