![]() While the thickness of the lens appears reasonable (i.e. Looking at the 3D Layout, though, there appears to be a problem with our lens’ thickness. The values of all three thickness boundary constraint operands have no contribution to the total Merit Function value: Looking at the boundary constraint operands in the Merit Function Editor, it is clear that all of our boundary constraints are being met. OpticStudio adjusts the radius of curvature and r 4 coefficient of the front of our lens to improve image quality. Click Optimize.Optimize! , select “Automatic” for the cycles, and then click “Start”. With our Merit Function setup, we can now optimize our Schmidt camera using the standard (local DLS) optimizer. We will bound a minimum thickness of 1 mm at the center and edge along with a maximum thickness of 5 mm. As such, we will incorporate default boundary constraints on thickness in our Merit Function. While we are not going to optimize the thickness of the lens, changes to the radius of curvature and 4th order aspheric coefficient will change the effective thickness of our lens. Be sure to set the number of “Rings” to 4 given that we are optimizing the r 4 aspheric coefficient. In the Optimize tab, select Optimization Wizard. With variables set, we will now build a default Merit Function for RMS spot radius. ![]() Variables have already been set for the front radius of curvature of the aspheric lens, along with the r 4 coefficient of the asphere: We want to improve the imaging performance of our Schmidt camera so we will optimize for best RMS spot size. It consists of an aspheric lens along with a spherical mirror: This particular Schmidt camera is a standard configuration. While Schmidt cameras are generally used for wide field of view applications, we will just work on-axis for the purposes of this article. This Sequential file provides a model of a Schmidt camera. To examine the thickness boundary constraint capabilities of OpticStudio, please download the file attached to this article. As we will see, polynomial aspheric surfaces generally cannot be successfully bounded using the default constraints. While these default constraints can be useful, there are cases where they will not sufficiently bound the thickness of a given surface. Thickness boundary constraints for glass and air are so common they are built directly into the Optimization Wizard. Unbounded, thickness variables will generally produce either very thin, unmountable lenses or lenses that are unreasonably thick, heavy and expensive. Probably the most common variable type that requires bounding is thickness. Successful optimization usually involves the bounding of variables to ensure that optimized systems are physically realizable. ![]() This article explains how the FTGT and FTLT optimization operands can be used to successfully constrain the thickness of a surface at intermediate aperture locations. ![]() There are some cases in which default thickness boundary constraints are not always sufficient when optimizing aspheric components. ![]()
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