Conception of a C-Arm Parametrization Device Evaluated by an Inverse Registration Approach: An application for 2D/3D Registration in Minimally Invasive Surgery

Camera resectioning is the process of finding the intrinsic and extrinsic parameters of the pinhole camera model. A mobile X-ray device (C-arm) can be represented with the pinhole camera model. The C-arm parameters can be determined with a parametrization device and the direct linear transformation (DLT) algorithm. We present the conception process of a parametrization device and further optimizations of the DLT algorithm. The evaluation of the parametrization quality is carried out with an inverse registration approach on a testing device. The seven landmarks in the testing device are compared on an X-ray image and a digitally reconstructed radiograph (DRR). The average distance of the corresponding landmarks between imaging modalities is 2.5 pixels. This deviation indicates an adequate design of the parametrization device for a 2D/3D registration in minimally invasive surgery.

Constraints for Time-Multiplexed Structured Light with a Hand-held Camera

Multi-frame structured light in projector-camera systems affords high-density and non-contact methods of 3D surface reconstruction. However, they have strict setup constraints which can become expensive and time-consuming. Here, we investigate the conditions under which a projective homography can be used to compensate for small perturbations in pose caused by a hand-held camera. We synthesize data using a pinhole camera model and use it to determine the average 2D reprojection error per point correspondence. This error map is grouped into regions with specified upper-bounds to classify which regions produce sufficiently minimal error to be considered feasible for a structured-light projector-camera system with a hand-held camera. Empirical results demonstrate that a sub-pixel reprojection accuracy is achievable with a feasible geometric constraints

Ancestral Light Capture: Camera Obscura

Ancestral Light Capture: Camera Obscura -...light rays entering the eye and light rays entering the glass globe placed inside a small camera obscura - Codex Atlanticus, fol 337, ca 1500 Leonardo Da Vinci..".I select cast off materials to create my cameras, and with them, construct an imagery that interprets the humanity of a cast off people". "A Second of Your Time" Prospect 1.5 Biennial 2010, New Orleans. I found fragments of glass bottles and glass shards, through wanderings in the back spaces of buildings behind the town square in Marion, Alabama and in the East Smithfield community in Birmingham. a community erased through highway construction. Those glass fragments (Da Vinci's" Glass Globe"), functioned as a lens for allowing the light to pass through, capturing the spiritual memories of those black folks who last touched the glass. The passage of the light from the glass fragments was embedded onto the film, which had been placed inside my small camera obscura/pinhole camera.