Tunable fiber confocal sensor with LED

Chun-Jen Weng; Tzu-Hsien Lan; Chi-Hung Hwang; Nien-Nan Chu; Chien-Yao Huang; Pi-Ying Cheng

doi:10.1117/12.2189154

17 July 2015 Tunable fiber confocal sensor with LED

Chun-Jen Weng, Tzu-Hsien Lan, Chi-Hung Hwang, Nien-Nan Chu, Chien-Yao Huang, Pi-Ying Cheng

Proceedings Volume 9524, International Conference on Optical and Photonic Engineering (icOPEN 2015); 95240Z (2015) https://doi.org/10.1117/12.2189154
Event: International Conference on Optical and Photonic Engineering (icOPEN2015), 2015, Singapore, Singapore

Abstract

A novel concept of confocal sensor based on focal lens is proposed to measure the displacement. The light source is a stabilized fiber coupled LED. A 1x2 graded-index multimode fiber optic coupler is used in this sensor. One port is a LED input port via SMA connector, another port is a LED output port connected to a reflective collimator and the other port is a reflective sensor port connected to a photo detector. The focusing sensor head is the cascade of a focal lens and a 20X objective lens. In this confocal displacement sensor, LED passes through a focal lens and an objective lens so that the LED beam focuses at a fixed focal point. A test target is placed after the objective lens. The displacement between the sensor head and a target can be measured quickly by detecting the reflective power according to the confocal principle. The long-term stability of LED is under 0.5%. The effective back focal length is varied from 5.67mm to 6.57mm by 0-290mA current driving so that the measuring range is about 0.9mm. The FWHM resolution of displacement is about 50μm. This sensor has the features of low cost, high stability, high precision and compact.

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Chun-Jen Weng, Tzu-Hsien Lan, Chi-Hung Hwang, Nien-Nan Chu, Chien-Yao Huang, and Pi-Ying Cheng "Tunable fiber confocal sensor with LED", Proc. SPIE 9524, International Conference on Optical and Photonic Engineering (icOPEN 2015), 95240Z (17 July 2015); https://doi.org/10.1117/12.2189154

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KEYWORDS

Sensors

Light emitting diodes

Confocal microscopy

Fiber optics sensors

Reflectivity

Objectives

Fiber couplers

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