Fig 1.
Laser scanner design and depiction with 4” cylinder model in scanning area for reference.
Laser scanner, linear and rotary stages, and motion tracking hardware identified. Note that the inertial reference frame used for reconstruction of the limb is shown in the diagram on the right in green. The linear stage in the y-direction is adjusted to the height of the residual limb and the linear stage in the z-direction provides translation along the residual limb as the rotation stage (i.e. Rotation Hub) rotates the laser line sensor around the residual limb. The two-camera motion capture system measure sagittal plane limb motion during the scan to minimize motion artifacts.
Fig 2.
Miniature linear stage, “ministage”, mechanism used to translate and rotate the laser scanner toward distal end of the limb.
A) Diagram of scanner in initial orientation when laser was scanning along length of limb. B) Diagram of scanner in rotated orientation when laser was over distal end of the limb. Red lines indicate the surface of the limb scanned by the laser.
Fig 3.
Path of laser scanner during scan as it translates in the -z direction (from right to left in the diagram).
Note that at the maximum and minimum z-locations the laser completes at least one full revolution about the limb.
Fig 4.
Depiction of captured motion data over scan duration.
Note that, at any given time, motion data is captured for at least one camera.
Fig 5.
First frame view of dot tracking with green regions indicating pixels that are tracked over each dot.
The labelled bounding boxes identify each dot location on the cylinder. (A) Camera 1 view. (B) Camera 2 view. Bounding boxes are defined in each image to uniquely identify the dots from one another, where the green dots indicate those to be tracked and the red areas are not tracked.
Fig 6.
Coordinate frames of the linear stages (green), rotation hub and laser, motion tracking cameras, and the limb.
Note that the center of rotation of the limb is at the knee and is indicated here by C.
Fig 7.
Depictions of the two calibration objects in the laser scanner with relevant misalignment and calibration parameters for each case.
(A) Flat calibration object, used to estimate the two misalignment angles of the laser, ϕM and ψM, and one misalignment translation, ΔRM. (B) Flat plate calibration object, used to further estimate the laser angle, θL, radial distance, RL, and the two frame misalignment angles, ϕf and θf.
Fig 8.
Laser scanner data with regions of missing data corresponding to dot locations highlighted.
Fig 9.
Depiction of method to identify location of surface point on limb, (Ri, θi), in an inertially fixed cylindrical coordinate frame of the linear stages.
Here the z-axis lies on the center of rotation for the laser scanner.
Fig 10.
Projected distance of surface point, , from laser head.
Fig 11.
Calibrated initial laser angle for three performed calibrations.
A, B, and C plots results for calibrations 1,2, and 3, respectively. Black line plots mean value of each parameter, averaged over θR, with a grey corridor plotting minimum and maximum values over five flat plate scans.
Fig 12.
Calibrated initial laser head radius for three performed calibrations.
A, B, and C plots results for calibrations 1,2, and 3, respectively. Black line plots mean value of each parameter, averaged over θR, with a grey corridor plotting minimum and maximum values over five flat plate scans.
Fig 13.
Calibrated change in laser angle for three performed calibrations.
A, B, and C plots results for calibrations 1,2, and 3, respectively. Black line plots mean value of each parameter, averaged over θR, with a grey corridor plotting minimum and maximum values over five flat plate scans.
Fig 14.
Calibrated change in laser head radius for three performed calibrations.
A, B, and C plots results for calibrations 1,2, and 3, respectively. Black line plots mean value of each parameter, with great corridor plotting minimum and maximum values.
Table 1.
Laser calibration parameters for each of three calibrations, with values averaged over θR and standard deviations reported.
Fig 15.
Sampled and meshed static cylinder.
(A) Down sampled points cloud data from scan. (B) Corresponding meshed surface. (C) Meshed surface from subsequent scan. (D) Overlay of two scans, demonstrating repeatability of reconstructed surface.
Fig 16.
Mean static cylinder diameter profiles as a function of position along length of body.
Black dashed line and green window plots the mean and standard deviation of the hand measured diameter. Plots A, B, and C plot the results for calibrations 1, 2, and 3, respectively.
Table 2.
Computed accuracy measures for static cylinder scans across three calibrations.
Fig 17.
Rigid body displacements and rotations for example 2 Hz excitation on 101.6 mm cylinder model.
The vertical red line indicates the start of the scanning data collection. (A) Estimated rigid body translations, and (B) Estimated rigid body rotations of model about the limb z-axis.
Fig 18.
Cylinder diameter profiles using scanner data during 2 Hz excitation with motion correction.
A,B,C plotted for scans from calibrations 1,2, and 3, respectively.
Table 3.
Errors in cylinder diameter, volume, and surface area from dynamic scans after motion correction.
Table 4.
Changes in volumetric and surface area percent errors of dynamic cylinder scans, relative to the initial static scans.
Fig 19.
Displacements of the cylinder during dynamic tests.
(A) Uncorrected meshed scan. (B) Corrected meshed scan. (C) Overlay of A and B, with red bands indicating large positive displacements, and orange bands indicating negative or neutral displacements.
Fig 20.
(A) Down sampled point cloud data. (B) meshed limb surface for human participant. Note in (B) the scanned surface of a dot tracking sticker.
Fig 21.
Human participant limb volume time history over the three scanning phases.
Phase 1 results are combined and reported with error bars. (A) Measured limb volume between scan sets. (B) Measured percent limb volume change relative to Phase 1 results.