Near-Field Holographic Display for In-Situ Merger of Real-Time Tomographic Data with Direct Vision

Abstract

Real Time Tomographic Reflection (RTTR) is a technique developed by our laboratory that permits in situ visualization of near-field tomographic images, enabling natural hand-eye coordination to guide invasive procedures. Originally developed for the Sonic Flashlight, RTTR uses a half-silvered mirror to merge the direct view of a patient with a real-time tomographic image from within the patient by reflecting a viewpoint-independent virtual image precisely into its actual anatomic location. For example, the Sonic Flashlight displays a real-time virtual image of an ultrasound data slice at its real location inside the patient. This work presents a derivative concept that replaces the half-silvered mirror with a Flolographic Optical Element (HOE). This new technique, called Real Time Tomographic Holography (RTTH), eliminates a disadvantage of RTTR, namely, that the virtual image is restricted to the size and shape of the source display. RTTH enables the tomographic projection of a large virtual image using a small LCD image source, as required for many medical and non-medical applications. The perceived location of the projected virtual image is essentially independent of viewpoint. There are no optical elements between the HOE and the virtual image, allowing unobstructed viewing of—and interaction with—both the virtual image and the patient or physical object(s) within which the virtual image may be located. This dissertation presents the design and construction of the first RTTH optical system. It also presents alignment and validation methods for the RTTH system to evaluate its inevitable distortions, in particular the blur and positional instability that must be present, to some degree, in any non-trivial RTTH system.