Advanced Imaging


Advanced Imaging Magazine

Updated: July 8th, 2008 05:26 PM CDT

Concave Spherical Mirrors For Schlieren Imaging Systems


Schlieren optics are used to record inhomogeneities within a transparent medium (air, water, glass etc.) by detecting the energy refracted by that portion of the medium in which the inhomogeneity occurs. Typical applications include visualisation of airflow turbulence, gas leaks and various thermal phenomena. In a schlieren imaging set-up a source directs light onto a spherical mirror, which collimates the light and redirects it onto a second identical mirror. The resultant image may be captured by an imaging camera or on a screen.

With workshops and test facilities deep underground where temperatures remain constant and vibration is practically non-existent Optical Surfaces Ltd. routinely produces concave spherical mirrors (up to 800 mm in diameter) for Schlieren imaging systems in a range of materials including Pyrex, Zerodur and ULE. Experienced optical craftsmen routinely produce spherical mirrors with surface accuracy of better than lambda/10 with particular emphasis on smoothness of the profile. Final characterisation of surface smoothness is undertaken using the knife edge test which is highly sensitive to slope errors. High precision optical surfaces and durable optical coatings (Au, Al/MgF2, AlSiO) combine to provide superior Schleiren image quality.

Optical Surfaces ISO 9001-2000 approved manufacturing facility provides the flexible resources to supply from single specialist requirements to OEM quantities. Benefiting from its stable environment, quality testing becomes quantifiable and reliable.

Optical Surfaces Ltd. Kenley, Surrey, UK (

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