Developments in MTF Testing

Modulation transfer function (MTF) testing is employed to test the resolution of imaging optics.

Some recent developments in MTF testing include extremely high spatial frequency (>3000 lp/mm) measurements, real-time testing in the thermal infrared, measurement of systems with recessed focal planes, and characterization and impact of stray light on MTF measurements.

MTF testing is an objective and quantitative measure of image quality and is valuable for cascade systems, while also allowing for evaluation of full system performance. According to Daniel Orband of Optikos Corp., who discussed the system in a talk at Optifab 2009, these features make it ideal for night-vision goggles.

Advantages include its testing versatility and its ability to easily measure imaging characteristics such as distortion, astigmatism, field curvature, axial color and more.

In an ultrahigh spatial frequency measurement, the MTF system scans in the near-UV spectrum at a measurement of 5000 lp/mm utilizing source scanning. The system provides full lens characterization of distortion, field curvature and astigmatism, with a 4-mm effective focal length (EFL) and f/0.55 lens tested at 350 nm.

MTF instrumentation equipment is typically priced at $30,0000 and generally accommodates smaller-scale lenses. The mechanism can also assist in automotive testing and military applications.

Optikos, located in Wakefield, Mass., manufactures measurement instrumentation equipment for optical image quality and provides optical engineering and product development services. As an MTF testing facility, the company offers solutions for component- and system-level tests on imaging systems operating in the UV and far-IR spectrums.

Amanda D. Francoeur
amanda.francoeur@laurin.com