In real optical systems, image quality is often limited not by diffraction alone but by optical aberrations arising from lens geometry, alignment, and field dependence.
Among third-order Seidel aberrations, coma aberration plays a crucial role in degrading off-axis image quality, producing comet-shaped blur patterns that are especially noticeable in imaging, astronomy, and automotive vision systems.
Modern optical design tools such as Ansys Zemax OpticStudio allow engineers to quantify, visualize, and correct coma efficiently during the design stage—reducing costly physical iterations.
Instead of a sharp spot, the image appears:
This distortion reduces spatial resolution, contrast, and measurement accuracy in imaging systems.
Coma arises primarily due to:
One of the strongest advantages of Zemax is its ability to directly visualize aberrations through multiple analysis tools.
This provides immediate confirmation of coma presence.
The tangential and sagittal ray fans in Zemax reveal:
Zemax expresses coma via Zernike polynomial coefficients:
Monitoring these values during optimization enables quantitative coma reduction.
Stars near the edge of the field appear stretched into comets, reducing observation clarity.
Edge-field blur degrades:
Measurement errors increase due to asymmetric point spread.
Hence, coma control is critical in wide-field imaging design.
Proper stop placement can significantly suppress coma.
Observe the geo radius values for off-axis field spot, you can see that spot size as well as coma spread is less of OS 2 optical system compared to OS 1 despite having the same configurations & start design, OS 2’s lens curvatures were optimized a bit more.
This is one of the most effective classical corrections.
Compared to OS 2 system, OS 3 system is way better performing in terms of spot & coma spread. Also, the primary coma aberration (in waves) is quiet a low value. This tells us that a doublet lens pair is far superior to a singlet lens pair for coma correction.
OS 2 & OS 4 are same configuration optical system, but OS 4’s performance in terms spot & coma spread is far less than the OS 2’s performance.
Further if we look at the primary coma using full field aberration plot, it indicates that OS 4 system has less coma aberration (in waves) compared to OS 2
Coma aberration is one of the most important factors affecting off-axis image quality in wide-field optical systems. Its presence can significantly degrade resolution and introduce distortions that impact applications ranging from astronomy to machine vision and automotive sensing.
Through advanced optical design software such as Ansys Zemax OpticStudio, engineers can perform detailed optical aberration analysis, identify the sources of coma, and implement systematic coma aberration correction strategies.
