This paper presents a review of modern-day schlieren optics system and its application. Schlieren imaging systems provide a powerful technique to visualize changes or nonuniformities in refractive index of air or other transparent media. For over two centuries, schlieren systems were typically implemented for a wide variety of non-intrusive real-time fluid dynamics studies. With the popularizat...

Schlieren imaging in wind-tunnels is extensively utilized to study the effects of air on an airplane surface. One of the interesting subjects for research is to study the effects of speed change on the airplane surface. Speed change results in occurrence of shock waves, which are visualized as lines on Schlieren images. In this paper, we study the problem of detecting speed of a plane after occ...

Schlieren imaging enables real-time visualization of airflow through refraction of light. The potential of schlieren imaging for speech research was first proposed nearly 40 years ago [1]. A recent study tested this proposal [2]. Phonetically trained raters coded schlieren recordings of French vowels as oral versus nasal [2] (Figure 1). Although raters discriminated between the oral and nasal v...

A review is given of outdoor schlieren and shadowgraph imaging, beginning with an historical perspective. The optical principles of the sunlight shadowgraph method and schlieren observation by background distortion are discussed. Examples and illustrations are given of the visualization of outdoor thermal convection, combustion, and explosion phenomena. Jet aircraft and high-speed flight are fe...

A very large schlieren optical system (2.3x2.9m field-of-view) and its applications in thermal airflow visualization, high-speed imaging of shock waves, and full-scale equipment studies are described. In order to have such a large field-of-view this is a lens-and-grid-type schlieren system using a very large grid as a light source, as first described at the 7 ISFV. It is currently the largest i...

An effective yet simple quantitative synthetic Schlieren imaging technique is presented in this paper. A multiplexed fringe pattern displayed on a common laptop screen observed through disturbed medium resulting change of the pattern. Fourier analysis such provides high-resolution and almost real time measurement rays’ deflection due to refractive index variation. The developed was applied for ...

We demonstrate a simple phase-sensitive microscopic technique capable of imaging the phase gradient of a transparent specimen, based on the Schlieren modulation and confocal laser scanning microscopy (CLSM). The incident laser is refracted by the phase gradient of the specimen and excites a fluorescence plate behind the specimen to create a secondary illumination; then the fluoresence is modula...

This work presents the use of the schlieren imaging to quantify the salinity gradients in a microfluidic device. By partially blocking the back focal plane of the objective lens, the schlieren microscope produces an image with patterns that correspond to spatial derivative of refractive index in the specimen. Since salinity variation leads to change in refractive index, the fluid mixing of an a...