Development of a flexible variable-view angioscopy system using face-angled GRIN lenses to enhance field of vision

A novel flexible variable-view angioscopy (VVA) system developed in a very simple way to enhance field of vision, using two face-angled graded-index (GRIN) lenses, a coherent image guide, and a complementary metal-oxide-semiconductor camera module. The two face-angled GRIN lenses are arranged in a line to change the visual field, thus enhancing the field of vision. In addition, this flexible angioscope can be miniaturized and inserted in a confined space such as a blood vessel. In order to evaluate the performance of this VVA system, we obtain optical images using a USAF 1951 target according to the variation of the visual field by simply rotating one GRIN lens without moving the distal end. From the images, we also measure the spatial resolutions of this system for each group and element of the USAF 1951 target and through calculation of the modulation transfer functions. Although the spatial resolution decreases slightly as the difference in rotation angle increases, we can enhance the field of vision by ∼23.2% using this VVA system.