High-speed Imaging Technical Papers

The video engineering community strategically uses four terms to describe some fundamental specifications for digital camera performance: signal-to-noise ratio, dynamic range, stops and bit depth. Producers of digital video cameras often cite these terms on data sheets and web sites to provide simplistic metrics for the evaluation and comparison of camera performance by consumers, without explanation. This paper provides explanations of these four terms, what they are measuring, how they can be used and how they are related.

High-speed video, and high-speed imaging in general, are notorious for being processes where the limiting reagent is most often light. Sensor light sensitivity is often the second most sought after quality of a high-speed imaging setup, after speed, and sometimes before resolution. This paper provides an overview of many of the ways an image can be brightened, from the lens, to how manufacturers make sensors, to the many interpretations of the word “gain.” For the sake of focus, this paper will not cover how to better illuminate a subject but will only discuss how to make the most of the light provided.

This work evaluated the iX Cameras i-Speed 727, a commercial CMOS-based continuous recording high-speed camera. Various parameters of importance in the scheme of accurate time-resolved measurements and photonic quantification have been measured under controlled conditions on the bench, using state-of-the-art instrumentation. We will detail the procedures and results of the tests laid out to measure sensor sensitivity, linearity, signal-to-noise ratio and image lag. We also looked into the electronic shutter performance and accuracy, as exposure time is of particular interest to high-speed imaging. The results of the tests show that this camera matches or exceeds the performance of competing units in most aspects, but that, as is the case for other high-speed camera systems, corrections are necessary to make full use of the image data from a quantitative perspective.

Schlieren and related techniques have found many applications in the centuries since they were discovered. Today these methods are used heavily in aerodynamics, ballistics, and fluid dynamics studies in order to aid the researcher in accentuating subtle changes to the medium being studied due to pressure, density, and temperature inhomogeneities. The aim of this paper is to give the reader a small but versatile set of knowledge, tools, and methods, and enable them to effectively employ Schlieren and shadowgraph imaging in their studies, with a special implementation emphasis on high-speed imaging using the i-SPEED cameras from iX Cameras.

Bayer filters are the most popular type of color filter array used by camera manufacturers to produce color images. This paper will describe how we perceive color, how a Bayer filter utilizes this information to detect colors, the common artifacts that may result, and methods to reduce these artifacts.