How to minimise distortion

Question

Hi everybody,I have come across an impass in zemax. My problem statement says that I have three lenses separated by some distances. I have to move the distance between these lenses. The problem that is occurring is "distortion aberration" in the system. I've tried to  use some operand to reduce distortion by making the radius of curvature variables and now the distortion is absent in the system for a particular set of distances between the lenses. Now, when I am trying to move the lenses again, the distortion increases again. Pictures are attached for your reference. One where distortion is zero and other when the distance between lenses have increased and the distortion increases simultaneously.I request you to guide me so that I can move my lenses without getting distortion in the system.Any help will be appreciated.ThanksFig.1: Distortion is 0 for a particular distance (10mm distance between lens 1 and lens 2, and lens 2 and lens 3) Fig.2: Distortion increases when the distance between Lenses increses (Distance between lens 1 and lens 2 is 20mm & lens 2 and lens 3 is 14mm)

Michael.Young · Accepted Answer

Hi @Shivam,I would like to follow up on your problem to see how things are going.Originally, the question sounded like it was a homework assignment that was intended to demonstrate the methods to reduce the 3rd-order aberration of distortion (W400). However, given your comment about the image not being clear towards the edges, makes me think that may not have been the intent of the original question.To reduce 3rd-order distortion, symmetry about the stop is the most straightforward way doing so. This means the stop should be placed near or inside of the biconvex lens. To control distortion, the DIST operand can be used.To control for “clarity” or contrast/resolution. Use the default merit function to build the merit function and use the spot optimization at this point.Perhaps these resources may shed some light on the design process,https://support.zemax.com/hc/en-us/articles/1500005576302-How-to-design-a-singlet-lens-Part-1-Setuphttps://support.zemax.com/hc/en-us/articles/1500005577942-How-to-design-a-singlet-lens-Part-2-Analysishttps://support.zemax.com/hc/en-us/articles/1500005577962-How-to-design-a-singlet-lens-Part-3-Optimization

Michael.Young · Answer

Hi@Shivam,Where have you placed your stop in the example provided?What is the purpose of the paraxial lens after L3?What is the threshold value for too much distortion? In your second example, it is only 0.005%.How are you supposed to vary the distances between L1, L2, and L3?

How to minimise distortion

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