Development of an Electro-Optic Scanner for Potential Endoscope Application

Technological advancements in endoscopy design are in current development due to the increased demand for minimally invasive medical procedures. One such advancement is reducing the overall size of the endoscope system while maintaining the resolution and field-of-view (FOV). Reduction of size results in less tissue damage and trauma during operation as well as faster recovery times for patients. Additionally, areas that are inaccessible by today's endoscope designs will be possible to examine. Current endoscopes use either a bundle of optical fibers (optical waveguides) and/or one or more cameras having an array of detectors to capture an image. Thus, the diameter of these devices employed for remote imaging cannot be reduced to smaller than the image size. Even if one ignores additional optical fibers used for illumination of a region of interest, the scope diameter is therefore limited by the individual pixel size of a camera or by the diameter of optical fibers used to acquire the image. Therefore, it is apparent to achieve scopes with less than 3 mm overall diameter using current technologies, resolution and/or FOV must be sacrificed by having fewer pixel elements. All commercially available scopes suffer from this fundamental tradeoff between high image quality and small size. More recently, our research has been working on developing a 2-D electro-optic scanner potentially be implemented for clinical endoscopic imaging application. The proposed optical device has several unique advantages. Electro-optical scanning offers a sensitive, facile, accurate, and superb quality method to capture images of physical and biological tissues. In addition, the minute physical size of the imaging system has a much needed advantage over conventional imaging systems. The proposed design is based on the fact that the propagation direction of a light beam can be changed when the index of refraction of an electro-optic medium is altered by the application of an external electric field. The basic design of the system consists of a thin film electro-optic polymer waveguide with built-in cascaded prisms structure for horizontal beam deflection and an electro-optic grating structure for vertical beam deflection. The cascaded prisms are combined with the electro-optic polymer to create a voltage-controlled horizontal beam deflection. A grating coupler, a structure that is commonly used as light coupling device for dielectric waveguide, is combined with the EO polymer to create the vertical controlled beam deflection. A collimated light beam coupled into the waveguide by a mechanical coupler via an optical fiber cascaded down these two deflection stages. When the beam exits, the emitted light beam is displaced along two orthogonal directions in a raster pattern. A photodetector array integrated in the same substrate captured the reflected intensity. The scanned imaged is then analyzed and reconstruct based on the received signal.