FreeOptical

Free open-source optical design and simulation software for Linux

Design and analyse objectives, refractors, telescopes and spectrographs surface by surface, like with the big commercial packages, with no licence or subscription.

Download version 0.10.0Source code on GitHub

Features

Exact ray tracing

Sequential 3D ray trace: spheres, conics, even aspheres, mirrors, tilted and decentered surfaces (folded systems), central obstructions, diffraction gratings.

Wave analyses

Optical path difference (OPD), wavefront map, 37 Zernike polynomials, Strehl ratio, diffraction PSF and tangential and sagittal MTF.

Aberrations

Spot diagram, ray fans, longitudinal spherical aberration, field curvature, distortion and Seidel coefficients surface by surface.

Real glasses

Sellmeier formulas, built-in Schott glasses, fused silica and fluorite; import of Zemax .agf catalogues (Schott, Ohara, CDGM…).

Optimization

Damped least squares (DLS) over all fields and colours: radii, thicknesses, conics, aspherics, focal length and constraints.

Spectrographs and other instruments

Spectrographs (dispersion, slit image, resolving power R), near objects (microscopes, relays), afocal systems (eyepieces, binoculars), ideal lens.

Mirror testing

Bath interferometer: interferogram of a mirror at its centre of curvature, analysis of interferogram photos, measured conic, surface error and Strehl ratio.

Like professional software

Coordinate breaks for folded systems, solves and pickups (automatic focus, imposed F-number, aplanatic surface), encircled energy, chromatic analyses, beam footprints, tolerancing (sensitivities and Monte Carlo), import of Zemax .zmx files.

Open and scriptable

Graphical interface, terminal interface and MCP server to drive the calculations from an AI agent. Import of TDESIGN, LENSDES and RAYTRACE files (Rutten and van Venrooij).

Screenshots

2D section of a 200 mm F/10 Schmidt-Cassegrain
2D section of a 200 mm F/10 Schmidt-Cassegrain
Wavefront and Zernike coefficients
Wavefront and Zernike coefficients
Modulation transfer function (MTF)
Modulation transfer function (MTF)
Ray fans of an achromatic doublet
Ray fans of an achromatic doublet

Installation

Debian, Ubuntu and derivatives (amd64): download the .deb package of the latest release, then:

sudo apt install ./freeoptical_0.10.0_amd64.deb

Later versions install from the Update button of the program. From source: cargo build --release.

Who is it for?

Amateur astronomers who grind their mirrors or design their instruments, optics students and teachers, engineers looking for a free alternative to commercial optical design software such as Zemax OpticStudio, Code V or OSLO.

Languages

Interface in English, French and German (Language menu).