Design of an illumination technique to improve the identification of surface flaws on optics

Rahul R. Prasad; Michael Bernacil; John Halpin; John Peterson; Steven Mills; Richard P. Hackel

doi:10.1117/12.585551

21 February 2005 Design of an illumination technique to improve the identification of surface flaws on optics

Rahul R. Prasad, Michael Bernacil, John Halpin, John Peterson, Steven Mills, Richard P. Hackel

Proceedings Volume 5647, Laser-Induced Damage in Optical Materials: 2004; (2005) https://doi.org/10.1117/12.585551
Event: Boulder Damage Symposium XXXVI, 2004, Boulder, Colorado, United States

Abstract

An edge illumination technique has been designed using a monochromatic light source that improves the identification of surface flaws on optics. The system uses a high-resolution CCD camera to capture images of the optics. Conventional edge illumination methods using white light sources have been plagued by light leaking around the optics causing high background levels. The background combined with lower resolution cameras has made it difficult to determine size and intensity characteristics of the flaws. Thus photographs taken of the optics are difficult to analyze quantitatively and do not allow for the detection of small, faintly illuminated sites. Infrared diodes have been utilized to illuminate large-scale (43 cm x 43 cm) fused silica optics, and a two-dimensional array CCD camera has been used to collect the image data. Flaw sizes as small as ~10 μm have been detected. A set of frames has been built to support the infrared sources where one diode array per side is magnetically attached to the frame. The diodes inject light into the optic causing the sites to illuminate, which can be detected by the camera. A customized mounting design has been implemented to secure the frames to the stage, or base, for image acquisition. The design uses a dual bracket assembly to support the frames. With this design for optical illumination, quantitative data has been obtained of the surface flaws. A comparison of the peak intensity, total integrated intensity and size of the flaws measured in these images and the size of the flaws as measured using a microscope will be presented.

Citation Download Citation

Rahul R. Prasad, Michael Bernacil, John Halpin, John Peterson, Steven Mills, and Richard P. Hackel "Design of an illumination technique to improve the identification of surface flaws on optics", Proc. SPIE 5647, Laser-Induced Damage in Optical Materials: 2004, (21 February 2005); https://doi.org/10.1117/12.585551

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