Fig 1.
The workflow of the proposed automatic detection and reproduction of NHP.
Lower left: The digital mesh model of the reference board was recorded. True horizontal vx and vertical vy axes were detected and saved. Then, patients’ face models (upper left) were corrected (right) according to the transformation T.
Fig 2.
Set up of the reference board.
The reference board was taped with color patterns on the front side facing the SP device cameras. Side grooves were crafted by using surface gauge at the side and top edge. Short paper tags were taped near the edges for angulation matching with laser beams. It was held by a vice clamp, connected to a two-way focusing slider for fine horizontal positional adjustments; and 3D geared head for angulation adjustments. Laser beams A (bottom right) and B1–B2 were projections from V2 which was aligned to be parallel to the mirror plane. Laser beam C1–C2 and D1–D2 were projections from front alignment lasers. Yaw angle was aligned with A-B1 (right) and top board edge; pitch angle was aligned with B1–B2 and side groove; roll angle was aligned with C1–C2, D1–D2 and dotted lines on card paper.
Fig 3.
The reference board was placed at the capturing position which was aligned with laser beams. The vertical laser plane V2 from side laser was aligned with side wall landmarks (dotted lines marked with pencil) which indicate the mirror plane (pitch and yaw). Another vertical laser plane V2’ and V2” from front lasers indicate true verticals on the reference board pattern (roll). Two front alignment lasers offer cross validation of the angulation adjustments.
Fig 4.
The side laser was elevated to a higher position than the reference board such that the laser plane V2 can beam up the side (pitch) and top edge (yaw) of the board. It was aligned to the side wall landmarks such that V2 was parallel to the NHP mirror plane. Another alignment lasers were placed next to the 3D camera rig for projecting laser beam indicating true verticals for roll angle.
Fig 5.
Flowchart of computing the orientation correction matrix T from laser aligned reference board.
Fig 6.
Validation of the automatic orientation method on a plastic head.
The alignment laser was placed at the center of SP device (which was perpendicular to the NHP mirror) and were indicated with the arrow stickers. Top row: frontal, top and left lateral views of reconstructed facial surface from 3dMD. Bottom row: corrected surfaces with the proposed method.
Table 1.
Descriptive statistics of angulation deviations of the detected axes of still reference board for 3dMD (M = 60) and DI3D (M = 30).
Fig 7.
Reference board angulation deviations for using one front alignment laser (3dMD).
75 trails were performed by 3 investigators, 8 were excluded due to bad exposures and apparent misalignment.
Table 2.
Descriptive statistics of angulation deviations of reference board alignment for 3dMD, N = 67.
Table 3.
One sample t tests to determine whether the angulation deviation in pitch, roll and yaw from the three operators were different to 0°.
Fig 8.
Reference board angulation deviations for using two front alignment lasers on 3dMD with 5 shots for each trail averaged.
Fig 9.
Reference board angulation deviations for using two front alignment lasers on DI3D with 5 shots for each trail averaged.
Table 4.
Descriptive statistics of angulation deviations of reference board alignment for 3dMD (N = 30, M = 5) and DI3D (N = 33, M = 5) respectively.