• 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

  • Sensitivity to tolerances is a well-known problem in optical design.
  • CAXCAD allow user to reduce general tolerance sensitivity to improve the manufacturability of the optimized lens
  • The SSN2 is as the  “sensitivity” parameter to the merit function.

  • The Cooke triplet is a photographic lens designed and patented (patent number GB 22,607) in 1893 by Dennis Taylor who was employed as chief engineer by T. Cooke & Sons of York. It was the first lens system that allowed elimination of most of the optical distortion or aberration at the outer edge of lenses. The Cooke triplet is noted for being able to correct the Seidel aberrations. It is recognized as one of the most important objective designs in the field of photography. The lens designed, invented by Dennis Taylor but named for the firm he worked for, consists of three separated lens elements. It has two biconvex lenses on the outer and a biconcave lens in the middle.
  • The design took a new approach to solving the optical design issues.

  • Multi-Start in DLS Optimization
  • Fast Engine in Global Optimization
  • Fast Ray Aiming:three modes can be selected and the CX Ray Aiming don't need the iteration of raytracing
  • Automatic Design: user don't need to remember the MF operate any more
  • Derivative Increments Data help user to know effective vaviables
  • Fast MTF calculation
  • Automaticly MTF Targets tool
  • Eyes Care Mode
  • Fast Graphics Drawing
  • Quickly Command Window

  • Doublet with BK7 and F2
  • The chromatic aberration will be minized
  • There are three sphere surface, so the SPHA will be also corrected. 
  • The optimization will silde to the local vellay, but we can use the multi-start to find a better solution.
  • MF target: EFL=100mm and RMS Spot Radius for all F D C wavelength 

  • Surface type: Asphere with even terms Coeff.
  • Seidel Aberration Coeff. to know the SPHA.
  • Multi-Start to find the initial data
  • MF Target: RMS Spot Radius with more real rays

    • EPD 25mm
    • EFL 100mm
    • Field: 0 Angle
    • Wavelength: 0.55um
    • MF Target: RMS Spot Radius


The five basic types of aberration which are due to the geometry of lenses or mirrors, and which are applicable to systems dealing with monochromatic light, are known as Seidel aberrations, from an 1857 paper by Ludwig von Seidel. These are the aberrations that become evident in third-order optics, also known as Seidel optics.



The Optical Path Difference  or OPD  is core parameter of optical system.

Wavefront Map shows all the OPD distribution.

CAXCAD Provides theWavefront Map Analysis Function as the following introduction. 

Graphics Window

CAXCAD uses the exit pupil as the position of reference sphere. 



If this is the first time you have got CAXCAD, please follow this article to install the software.

The latest version of the software was named with the date information.

Paraxial ray tracing assumes that the tangent and sine of all angles are equal to the angles themselves (in other words, tan(u)=u ⁡ and sin(u)=u ⁡ ). This approximation is valid for small angles but can lead to the propagation of error as ray angles increase.