This paper demonstrates a new tolerancing technique that allows the prediction of microlens optical performance based on metrology measurements taken during the fabrication process. NOTE (May 21, 2020): An extension of this work that corrects primary color and oblique astigmatism may be found HERE.Tolerancing microlenses using ZEMAX Tolerancing microlenses using ZEMAX
ZEMAX 14 CHANGE POSITION OF OPTICS DOWNLOAD
And you may also download a more technical version of this article HERE. If you wish, you may download my Zemax OpticStudio model of the above lens by clicking HERE. Thanks for stopping by to read this article. And you know what's cool? Both patents mentioned at the beginning of this article have expired. But modern imaging systems would use electronic image sensors (e.g., CCDs or CMOS sensors), so one can imagine calibrating the system such that the position of the image is measured and computationally accounted for when displaying the image on a digital display screen. You might have noticed that the image shifts as the stop is shifted above the optic axis (because, clearly, the local optic axis at any position on the aspheric surface is a function of the slope at its local curvature). By time multiplexing the digital stops and synchronizing the capture of the images with an appropriate 3D display platform, we can have a 3D machine vision system (with variable focus, and no moving parts). Note that even if we have a symmetric lens, we could program the LCD to have two digital aperture stops such that we now have parallax, hence, achieving a pair of stereo images with variable focus. In fact, there's a neat Zemax knowledge base article written by Mark Nicholson describing a simple approach to design a freeform ophthalmic lens. We could design a completely freeform surface across the entire lens's aperture such that there is variable focal length from edge to edge. With today's freeform manufacturing capabilities, we need not restrict ourselves to such symmetry. The current model is that of an asphere with symmetry about the optic axis, hence, wasting much of the other side (because the stop only has to shift from the center to the edge of one side). You'd then have a variable focus lens with absolutely no moving parts.Īnd that's not all. By programming the LCD to have a digital circular window of 3 mm diameter (with the rest of the LCD screen in opaque mode), one has a digital aperture stop that can be programmed to shift to any location above the optic axis. Such a shutter could be, say, a programmable transmissive liquid crystal display (LCD) whose screen size covers the entire lens's aperture. Now, imagine if we place a liquid crystal shutter at the stop's location. At any object distance between 250 mm and infinity, the stop could be made to be somewhere between the axial position and 12 mm above the optic axis to focus the image (note that you could set up a default merit function to optimize RMS spot size for all the fields and set the stop's vertical position to be variable). Well, almost, but good enough for some large objects. The image is now pretty much back in focus. Consider, for example, a plano-convex lens whose convex surface is described by the following well-known expression for its surface sag: If you think about it, a simple asphere lens actually possesses continuous local variable power across its surface. Here's what I came up with as a rough initial concept.
![zemax 14 change position of optics zemax 14 change position of optics](https://uploads-us-west-2.insided.com/zemax-en/attachment/200506-155809-image.png)
So it occurred to me recently to wonder how one might integrate a freeform lens with a liquid crystal shutter to provide variable focus in the simplest way possible. Ophthalmic progressive power lenses (aka "progressive addition lenses" or simply "progressive lenses") are indeed examples of such lenses. Today, with the advent of modern techniques to design and manufacture freeform surfaces, we wouldn't need lenses with discrete steps in optical surface power.
![zemax 14 change position of optics zemax 14 change position of optics](https://support.zemax.com/hc/article_attachments/1500007436622/KA-01344_1_Three_Lens_System.png)
Almost two decades ago, a number of inventions described techniques to use a liquid crystal display shutter placed behind a lens, whose surface curvature varies in discrete steps across its aperture, to produce variable focus.