Disposable low cost video endoscopes for straight and oblique viewing direction with simplified integration

摘要

Video endoscopes with an imager located at the distal end possess a simplified opto-mechanical layout compared to classical setups since an optical relay system is not required. Together with the availability of low price miniature CMOS imagers, this enables for building low cost devices for single usage avoiding the necessity of withstanding autoclaving which is one of the major drivers in both, system fabrication and operating cost. The optical layout has to take into account geometrical as well as opto-electronic aspects and is therefore a trade-off between system diameter, sensitivity and resolution. Consequently, the image circle should be as close as possible to the outer diameter for optimum performance in terms of resolution and sensitivity which goes along with large pixel size. We propose systems designs and prototypes for f/4, 3mm outer diameter endoscopes with 70° and 110° field of view using a CMOS imager with 650x650 pixels of 2.8um pitch. The final systems are based on a simplified and rugged integration using a single polymer lens made by injection molding, a GRIN lens and a dispensed lens made of UV curing material allowing for high performance paired with low fabrication cost. Additionally, a side view system angled at 30° is presented based on a tilting reflection prism requiring minimum construction space allowing for an outer diameter of 3mm.