Abstract

A vibrating knife-edge technique is proposed for measuring the focal length of a microlens. The technique is based on the propagation properties of Gaussian beams. A laser beam with a Gaussian intensity profile is focused in front of the microlens under test. After being transmitted through the microlens, the beam propagates toward a detector, which consists of a photodiode that is half blocked by a knife-edge. The photodiode integrates approximately half the intensity of the transmitted beam. The knife-edge vibrates sinusoidally with small amplitude in a plane normal to the direction of propagation. Our analysis shows that the output signal at the photodiode consists of a dc component plus a temporal sinusoidal signal whose amplitude is proportional to the focal length of the microlens. After system calibration, the focal length is measured with an envelope detector or a lock-in amplifier.

© 2001 Optical Society of America

Actual focal length of a symmetric biconvex microlens and its application in determining the transmitted beam waist position

Jian Wang and John P. Barton
Appl. Opt. 49(30) 5828-5836 (2010)

Two-dimensional operation of a scanning optical microscope by vibrating knife-edge tomography

S. Samson and A. Korpel
Appl. Opt. 34(2) 285-289 (1995)

Measurement of Gaussian laser beam radius using the knife-edge technique: improvement on data analysis

Marcos A. de Araújo, Rubens Silva, Emerson de Lima, Daniel P. Pereira, and Paulo C. de Oliveira
Appl. Opt. 48(2) 393-396 (2009)

Knife-edge scanning measurements of subwavelength focused light beams

A. H. Firester, M. E. Heller, and P. Sheng
Appl. Opt. 16(7) 1971-1974 (1977)

Near-field analysis of the knife-edge technique

Abraham Aharoni, Abraham Gover, and Kenneth M. Jassby
Appl. Opt. 24(18) 3018-3027 (1985)