In Zemax OpticStudio, Geometric Image Analysis is an effective method for studying the behavior of optical systems governed by geometric optics. This blog article explains how to utilize the Geometric Image Analysis feature to create cross-section plots and obtain optical performance data for an extended source. The Geometric Image Analysis tool also enables the examination of point or extended source objects in systems effectively described by geometric optics.
Geometric Image Analysis is a valuable tool for assessing the image quality of an aberrated beam on any given surface. It allows the object to be modeled as either a point source (by setting the Field Size to zero) or an extended source (with a non-zero Field Size). The tool also provides options to define the size and pixel resolution of the detector used to capture the image on the surface of interest.
Here we use a Double Gauss with 28-degree field lens as an example in Zemax installation folder. The lens structure is shown below:
The Geometric Image Analysis setting can be found at the path below: Analysis - Extended Scene Analysis - Geometric Image Analysis. Below shows an input of 0-, 10-, and 14-degrees input in small image scale in 0.1 mm.
0 degree
10 degrees
14 degrees
With Field setting, the image file is centered on defined field position. This permits a small target such as a bar chart to be moved to any location in the field of view. The resulting image is then centered on the chief ray coordinate of this field position.
If Cross Section at “Show” is selected, the X or Y cross-section of intensity along the center row is shown below:
0 degree
10 degrees
14 degrees
The operand IMAE shows image analysis data. This operand returns fractional efficiency, centroid, or RMS data as computed by the geometric image analysis feature, using whatever the current default settings are. To use this operand, first define the settings on the geometric image analysis feature as desired, then press Save on the settings box. The operand IMAE will return the desired data as computed by the image analysis feature.
The merit function below presents using IMAE operand to do image analysis, with return of estimates of the efficiency of an optical system. Such estimates are made by launching many rays into the entrance pupil; computing the fraction of rays that pass through all surface apertures to any surface.
If we enlarge field size to 1 and image size to 3, with an original file input of Grid, the image result shows as below.
The cross-section view in X is shown below:
The cross-section view in Y is shown below:
In summary, Geometric Image Analysis provides a quick tool in Zemax sequential mode to illustrate presence at image plane, with overall defined field, aperture and wavelength. Compared to nonsequential mode, it provides limited source shape in “File” tab but provides quick overall light distribution show without converting to nonsequential mode.