- Most definations are based on the paraxial optics
- The paraxial image height for optical design is fast for calculation, but inaccuracy for wide angle or big distortion
- The real image height needs to calculate the ray iteration and is inaccuracy.
- We wil use a sample in CAXCAD to show the difference

Double Guass sample will be used for the demonstration.

The default field type is angle in degrees and display in the title of the window.

We changed the field type to paraxial image height

The tiltle will be updated immediately

Input FIR in the command window, we can get the first order data and the paraxial height is 14 lens unit

The 3D layout will be also changed at the same time

We need to know the real image height with the RAYY operand, which is the reay ray height.

The pupil normalized values are 0.1 0.5 1, the results are 1.3886 6.9499 和 13.9422 and the max field is not 14.

The reason of the difference camed from paraxial optics, it can be accepted if the offset is not too big, because the speed will be fast for calculation.

Now we change the field type to real image height.

We got the accurate results and of course the software will take more time to calculate the ray iteration.

We have optimized the calculation for the real image height for CAXCAD, it is the balance between accurate and time.

For more information about CAXCAD, please send email to us.