Anywhere Light Goes™ Blog
A blog about optical design, build, test and more.
Why Doesn’t My Calculated EFL Match My Test Results?
A key part of validating optical hardware is reconciling differences between design simulations and hardware test results. Understanding the subtleties of how simulation and test results are produced, and why differences may exist, can avoid potential frustrations and delays in the hardware testing process. Many optical parameters such as effective focal length (EFL), distortion, and field curvature, can be simulated in a lens design by tracing the chief ray through the system and evaluating its location in the image plane. When measuring real optical systems, measuring these parameters requires evaluating a focused spot in the image plane. That spot is formed by a ray bundle that fills the system’s pupil. It is often impractical, or impossible, to restrict the optical...
Some Overlooked Thermal Considerations When Mounting Lenses For Aerial Imaging Applications
Aerial imaging applications present a unique challenge when considering thermal environmental changes. A system can experience extremely low temperatures while at altitude and extremely hot temperature while waiting and taxiing on hot tarmac. If the environmental changes are not fully considered early in the design phase, then the system is likely to suffer from performance degradation, reduction of service life and possibly structural failure of optical elements. The effects on the system from thermal changes may seem obvious at first, but there are some key areas that are often overlooked. These areas include survival of bonded optical elements and thermally-induced lens deformation. Survival of the optical elements seems straight forward, but thermal stress induced in bonded doublets raises issues of...
Pitfalls in Selecting LEDs for Quantitative Devices
In the world of visible light sources, it’s hard to beat light emitting diodes (LEDs). These tiny emitters are mass produced in countless varieties of color and intensity, making them the obvious choice for a device that requires a lot of light at specific wavelengths. Often there are dozens of candidates that would produce acceptable performance. Some applications, however, push the envelope either by maximizing throughput, multiplexing via coexisting spectral channels, or coupling the light into finicky optical elements. In these cases, the LED can become a performance limiter, making it critical to select the best LED for the device. Now we have a problem: LEDs are advertised primarily for the enormous market of general lighting. This use case has...
Lensless Imaging – Hype or the Future?
Optikos touts ourselves as the Optical Engineering Experts™, so it’s always interesting when a customer approaches us to remove optics from their system! We’ve had a variety of interested parties engage Optikos about lensless imaging. This is a novel approach to imaging that removes the optical lens, while still generating high quality images using computational photography. So how does this work? Lensless imaging seeks to collect phase and amplitude information from an object or scene, and then recreate the scene from that information. The most approachable method may be digital holographic imaging. In this scheme a coherent optical beam is reflected off of, or passes through, an object of interest. The incident beam diffracts off the object and interferes with...
Don’t Multiply MTFs (Unless You Know What You’re Doing)
If you have two optical systems and you’ve measured their individual MTFs, it can be tempting to think you can calculate the combined MTF of the two together. Unfortunately, that doesn’t always work. The modulation transfer function (MTF) of an image-forming optical system is a measure of how well that system transfers the contrast of an object to the contrast of an image. And, there are many situations in optical design where the object of one sub-system is the image formed by another. A common example is a telescope with an eyepiece. So, why not measure their MTFs individually to get the full system MTF? Have a look at the 10 mm focal length singlet in Figure 1. This lens...
