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Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 17, Iss. 22 — Oct. 26, 2009
  • pp: 20051–20062

Laser differential confocal ultra-long focal length measurement

Weiqian Zhao, Ruoduan Sun, Lirong Qiu, and Dingguo Sha  »View Author Affiliations

Optics Express, Vol. 17, Issue 22, pp. 20051-20062 (2009)

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A new laser differential confocal focal-length measurement method is proposed for the measurement of an ultra-long focal-length. The approach proposed uses the property of an axial intensity curve that the absolute zero precisely corresponds to the focus of the objective in a differential confocal focusing system (DCFS) to measure the variation in position of DCFS focus with and without a measured ultra-long focal-length lens (UFL), uses the distance between the two focuses to obtain the UFL focal-length, and thereby achieving the precise measurement of ultra-long focal-length. The method has a high focusing precision, a strong anti-interference capability and a short measurement light-path. The theoretical analyses and preliminary experimental results indicate that the relative measurement error is about 0.01% when the method is used for the measurement of back-focus-distance (BFD).

© 2009 OSA

OCIS Codes
(120.0120) Instrumentation, measurement, and metrology : Instrumentation, measurement, and metrology
(120.3620) Instrumentation, measurement, and metrology : Lens system design
(180.1790) Microscopy : Confocal microscopy
(220.4840) Optical design and fabrication : Testing

ToC Category:
Instrumentation, Measurement, and Metrology

Original Manuscript: July 7, 2009
Revised Manuscript: August 30, 2009
Manuscript Accepted: October 1, 2009
Published: October 20, 2009

Weiqian Zhao, Ruoduan Sun, Lirong Qiu, and Dingguo Sha, "Laser differential confocal ultra-long focal length measurement," Opt. Express 17, 20051-20062 (2009)

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