DESIGN AND FABRICATION OF HIGH QUALITY IMAGING OBJECTIVE WORKING IN THE NEAR-INFRARED SPECTRAL REGION FOR VEIN FINDER DEVICES

Abstract

This work demonstrates a new design of an imaging objective operating in the near-infrared spectral region for vein finder devices. The objective has a simple structure, consisting of 6 elements divided into 2 groups and a long-pass optical filter that allows a near-infrared spectrum to pass through. Due to the filter, the objective only creates images in the 850-940 nm spectral region produced by the infrared illuminator and therefore it can eliminate optical noise in the visible region. The objective image quality is very high, suitable for vein imaging: large aperture, f/2.0, allows creating clear vein images from weak signal reflected from the human skin surface; modulation transfer function (MTF) of 0.5 at a frequency of 72.5 lines/mm; field curvature and image distortion less than 50 μm and 0.1%, respectively. The experimental result indicates that the objective can provide clear vein images when combining with a Sony IMX287 CMOS image sensor.