4/7/2023 0 Comments Stereo imaging geometry x y z![]() The pixel index and coordinates in the tile memory block of size 185×388 can be evaluated as This "native" sensor frame is initially aligned with the global coordinate system the sensor is then positioned by applying translations and rotations relative to that native frame. Note that a right-handed rule is used for the coordinate system, so the z-axis is coming out of the page. “natural” matrix-style pixel numeration is preferable for simplicity of the tile description but is not necessarily requiredįor example, CSPAD 2x1 tile pixel geometry is schematically shown in Fig.2.įIG.each tile is represented in data as a minimal solid block of memory,.pixel center (x, y, z) coordinates in each tile can be defined as a look-up table for all pixels,.by design each tile has well defined geometry of pixels which does not need in calibration,.all tiles of the same type have identical geometry,.tiles may be of different types even in a single detector,.tiles, segments, pixel arrays/matrix etc. On the very bottom level of hierarchy structure there should be self-sufficient components of the detector - sensors a.k.a. In this frame photon-hit pixel coordinates (x, y, z) can be easily transformed to the photon diffraction angle θ, 1: Tentative coordinate frame of experimental setup. Z axis pointing from IP along the photon beam propagation direction,įIG.Y axis pointing from IP to the top, and.In some of LCLS experiments Cartesian coordinate system of the setup is defined by the three mutually orthogonal right-hand-indexed axes with origin in the IP: Choice of axes directions depends on experimental preferences. In diffraction experiments origin of the coordinate frame is usually associated with IP. All other setup components are defined relative to the global coordinate frame. On the very top level of hierarchical structure there should be a global coordinate frame associated with entire experimental setup. In this section we list tentative objects and associated coordinate frames which may be involved in typical LCLS experimental setup and explain how they can be inscribed in the hierarchical model. This note contains description of the implemented hierarchical geometry model, coordinate transformation algorithms, tabulation of the hierarchical objects and calibration file format, description of software interface in C++ and Python, details of calibration, etc. Relevant parts of the hierarchical table can be calibrated and updated whenever new geometry information is available, for example from optical measurement or dedicated runs with images of bright diffraction rings or Bragg peaks. All constants for detector/experiment geometry description can be saved in a single file. The last feature is practically useful for calibration purpose. ![]() Tree-like structure can be kept in form of table saved in and retrieved from file. Each child object location and orientation can be described in the parent frame. Nodes/objects of this hierarchical model form the tree which is convenient for navigation and recursion algorithms. To take into account this structure we may consider a variable length series of hierarchical objects like sensor -> sub-detector -> detector -> setup, where lower-level child object(s) is(are) embedded in its higher-level parent object. final level sub-detector is represented by precisely engineered sensor(s) of particular type(s) which geometry needs to be tabulated.sub-detectors of each layer may have stable positions or be moved by stepping motor relative to each other,.in some cases detector is a composition of other sub-detectors arranged together and consisting of other sub-detectors and so on,.position of the detector sensors relative to interaction point (IP) of the photon beam with target is not well known,.In pixel array detectors photon energy is usually deposited in a single pixel and hence a description of the experimental geometry should aim to provide the pixel location to a precision comparable with or better than its size, for the CSPAD about 100μm.ĭetermination of the experimental geometry to such a precision is a challenging task for many reasons: ![]() Nearly all imaging experiments conducted at LCLS require a precise description of the experimental geometry, especially how one or more area detectors are arranged with respect to the x-ray beam and interaction site. ![]() Note that public detector geometry data can be found here. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |