Beam path in lens systems
This program can be used to calculate the ray path through individual or multiple lenses. The actual refraction at the interfaces is calculated so that lens errors (e.g. spherical aberration) and thick lenses can also be examined. The lenses can be easily moved with the mouse so that the effect on the beam path can be observed directly. If you know the parameters of the lenses in a lens (e.g. the Carl Zeiss Tessar), you can easily calculate the ray path through the entire lens and thus its imaging properties(Tessar lens parameters).
Downloads
Strahlengang.exe
(old version)
Strahlengang.exe
Tessar.dat
(lens data for Tessar lens with approx. 500mm focal length)
Operation
After calling up the program, insert a lens by clicking on "Insert lens" and entering the parameters of the lens. For each lens, the radius of curvature of the left and right surfaces, the intersection points of the surfaces with the optical axis, the refractive index and the size of the lens (outer radius) are entered. The characterization of the lenses with radius of curvature and refractive index allows a flexible selection of different lens types. By creating additional lenses, lens systems with several (maximum 100) lenses can be calculated. Existing lenses can be moved with the mouse by pressing and holding the left mouse button on the lens and moving the lens along the optical axis. You can even change the order of the lenses in this way. The program does not check whether lenses overlap. If overlaps occur, the displayed beam path is nonsensical. To change the parameters of a lens, click on it with the right mouse button. A window opens with the current parameters of the selected lens. You can also remove the lens by clicking on the corresponding button in this window. The object parameters can also be changed, e.g. to set an object point away from the optical axis. In the beam path display, the location coordinates are displayed at the mouse cursor so that you can easily read the locations of the focal points.
Numerical realization
The ray path is calculated using Snellius' law of refraction and simple geometry. To do this, the intersection of a straight light beam with the nearest surface is calculated piece by piece and the direction of the beam is changed there using the law of refraction. Reflections on the lens surfaces are not taken into account.
Remark
The focal length of a thin lens is calculated approximately from the radii of curvature(R1, R2) and the refractive index(n) with 1/f =(n-1)*(1/R1-1/R2). The sign of the radii must be taken into account.