This paper expands on the research presented in 'An Advance in Infrared Lens Characterization: Measurement of the
Lens MTF Using Common Undersampled IR Systems.' This update provides empirical data demonstrating the test
system's performance through experimental modulation transfer function and encircled energy tests. This research also
expands further on the software algorithms, describing the method used to obtain accurate real-time optical performance
analysis. Real-time testing has a number of valuable applications, including focus optimization, prototyping, rapid/high-volume
testing, and testing on-the-fly.
The modulation transfer function (MTF) measurement has been a staple of optics testing for many years. Obtaining a highly accurate measurement of the MTF of a lens, however, has remained a challenge for a number of reasons. Traditional MTF tests give a measure of overall system performance, rather than characterizing individual parts such as the lens. Also, the theoretical performance of the optics generally outstrips FPA/camera performance by a wide margin. This typically requires intricate hardware setups to quantify lens performance, such as specialized single-detector systems. These systems, however, are very difficult to use, have few other applications, and are quite expensive.
This paper will describe an improved technique for measuring the optical quality of infrared optical systems, as well as preliminary research regarding individual component (i.e. - lens) MTF. In particular, the methodology presented will expand upon the traditional "tilted slit" technique and demonstrate an improved test capability for characterization of MTF and other optical unit under test (UUT) performance parameters. We will describe a methodology which uses Gaussian energy profiling and novel collection optics to deliver an MTF measurement capability with resolution and usability superior to that of single point measurement techniques. The paper will also discuss the optical system requirements and mathematical algorithms required to provide a fast, accurate, and high-resolution FFT/MTF capability, and support for a range of other optical UUT characterization modes.