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Optical autofocus for high resolution laser photoplotting

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Alonso Fernández, José and Crespo Vázquez, Daniel and Jiménez Castillo, Isidoro and Bernabeu Martínez, Eusebio (2005) Optical autofocus for high resolution laser photoplotting. In Photonic Materials, Devices, and Applications. Proceedings of The Society Of Photo-Optical Instrumentation Engineers (SPIE), 1-2 (5840). SPIE--The International Society for Optical Engineering, pp. 871-878. ISBN 0-8194-5835-X

Official URL: http://dx.doi.org/10.1117/12.628138




Abstract

An all optical autofocus has been designed and tested for tight line width control in a high NA laser photoplotter system. The laser system is based in a GaN semiconductor laser with power 30 mW and wavelength 405 nm. The advantage of using this laser, despite the relatively long wavenlength, is compactness and easy for high frequency modulation. The autofocus system is based in a secondary 635 nm GaAlAs laser without need for wavelength, neither power stabilization. The two beams are delivered coaxially through the focusing lens by means of a dichroic beamsplitter. Focusing lens need no correction for chromatic aberration, as this is compensed by appropriate autofocus beam divergence. After reflection in the sample, the autofocus beam is separated from the returning writing beam and then guided to a collimation sensor, in which defocus of about 1/20 of the Rayleigh range of the writing beam can be detected and compensated by an analogue PID electronic control. Stable linewidth within 5% is achieved with different numerical aperture focusing lenses.


Item Type:Book Section
Additional Information:

© (2005) SPIE--The International Society for Optical Engineering.
Conference on Photonic Materials, Devices and Applications (2005. Sevilla, España)

Uncontrolled Keywords:System
Subjects:Sciences > Physics > Optics
ID Code:26745
Deposited On:25 Sep 2014 10:46
Last Modified:25 Sep 2014 10:46

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