Simulation of ghost images in zoom system by ASAP

The stray light which is generated by the residual multi-reflection on the surfaces in optical system easily forms ghost images near the image plane and they influence the acuity and contrast gradient of images, decrease the resolution of lens, and disturb the target discrimination. It is difficult to be simulated and analyzed due to the excessive surfaces, complex structure and locomotory parts in zoom lens. All the transmission planes taken as the partial reflection and partial transmission planes were simulated with ASAP（advanced system analysis program）and the stray rays on dangerous surfaces which easily generate the ghost images in zoom lens were analyzed. Based on it, the zoom lens was optimized and the quality of image was improved by changing the curvature and refractive index of the second reflection planes.