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Proceedings Paper

Small form-factor VGA camera with variable focus by liquid lens
Author(s): Kari A. Oikarinen; Mika Aikio
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Paper Abstract

We present the design of a 24 mm long variable focus lens for 1/4" sensor. The chosen CMOS color sensor has VGA (640×480) resolution and 5.6 μm pixel size. The lens utilizes one Varioptic Arctic 320 liquid lens that has a voltage-controllable focal length due to the electrowetting effect. There are no mechanical moving parts. The principle of operation of the liquid lens is explained briefly. We discuss designing optical systems with this type of lens. This includes a modeling approach that allows entering a voltage value to modify the configuration of the liquid lens. The presented design consists only of spherical glass surfaces. The choice to use spherical surfaces was made in order to decrease the costs of manufacturing and provide more predictable performance by the better established method. Fabrication tolerances are compensated by the adjustability of the liquid lens, further increasing the feasibility of manufacturing. The lens is manufactured and assembled into a demonstrator camera. It has an f-number of 2.5 and 40 degree full field of view. The effective focal length varies around 6 millimeters as the liquid lens is adjusted. In simulations we have achieved a focus distance controllable between 20 millimeters and infinity. The design differs from previous approaches by having the aperture stop in the middle of the system instead of in front.

Paper Details

Date Published: 5 May 2010
PDF: 8 pages
Proc. SPIE 7723, Optics, Photonics, and Digital Technologies for Multimedia Applications, 772316 (5 May 2010); doi: 10.1117/12.851142
Show Author Affiliations
Kari A. Oikarinen, VTT Technical Research Ctr. of Finland (Finland)
Mika Aikio, VTT Technical Research Ctr. of Finland (Finland)

Published in SPIE Proceedings Vol. 7723:
Optics, Photonics, and Digital Technologies for Multimedia Applications
Peter Schelkens; Touradj Ebrahimi; Gabriel Cristóbal; Frédéric Truchetet; Pasi Saarikko, Editor(s)

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