How to capture cross-section ray distribution of an optical system

How to find the (x,y) coordinates of individual rays, or to view their cross-section ray distribution, this article will share its tips.

Geometric Image Analysis is a very useful feature for characterizing the image quality of an aberrated beam on an arbitrary surface. This feature can be used to model the object as a point source (by setting the Field Size input equal to zero) or an extended source (non-zero for the Field Size). The size and pixelation of the detector used to record the image on the surface of interest may also be specified.

Open the example attached, and use the following settings in the Geometric Image Analysis tool

Field Size: This value defines the full width of the square image file in field coordinates, which may be either lens units or degrees, depending upon the current field definition (heights or angles, respectively).

Image Size: If “Show” is selected as a spot diagram, this value sets the size of the scale bar which is superimposed on the image. It has no effect on the actual size of the image. The image size is set by the object scale and the magnification and aberrations of the system. If “Show” is selected as any other option, this value sets the size of the detector used to capture rays. Rays landing outside of the image size are ignored, and are not included in the total detected rays, which will decrease the computed efficiency.

Let’s see how to check the (x,y) coordinates for each launched ray distribution on the surface of interest.

Input the field to 0 and image size 0.05.

The resultant image will look very similar to the Spot Diagram for the same field point:

The image above is the spot diagram. This is expected since the GIA tool uses a zero input for the Field Size.

Click the text bottom, you could see the data of each ray. One advantage of using GIA in this case is that when the “Show: ” input is set to “Spot Diagram” the text listing of the GIA provides the (x,y) coordinates for each launched ray on the surface of interest. Something which is not available with the Spot Diagram directly.

Let’s view cross-section data of the intensity.

Let’s check the moment data ( intermediate ray distribution) of the optical system.

The IMAE optimization operand can be used to obtain the fractional efficiency of the system for propagation of light from the object plane to a surface of interest. This operand may also be used to generate values for the centroid and width of the intensity pattern.

Then add four IMAE operands to the merit function editor to calculate the fractional efficiency, intensity X- and Y-centroids, and the radial RMS width.

Data = 0: Fractional efficiency

Data = 1: Intensity X-Centroid

Data = 2: Intensity Y-Centroid

Data = 3: Intensity X-direction RMS width (i.e. X^2 intensity moment)

Data = 4: Intensity Y-direction RMS width (i.e. Y^2 intensity moment)

Data = 5: Intensity R-direction RMS width (i.e. R^2 intensity moment)

Then the IMAE operand can be added to the Merit Funtion Editor as below:

The agreement (shown in the Value column) is quite good, as expected. Hope it will help you.

The design file used in this particle is attached, please download it here. example file: cross section moment data of an optical system example

Reference  Source:

  1. Laikin, Milton. Lens Design. CRC Press, 2007.
  3. Zemax Optical Design Program User’s Guide, Zemax Development Corporation


    The material used in this knowledge sharing, is only for research, academic, non-profit educational or personal use, the blog owner has strived to credit the original sources, but cannot warrant the accuracy of copyrights or completeness of the information sources.