Korean J Orthod.  2011 Apr;41(2):76-86. 10.4041/kjod.2011.41.2.76.

Influence of the angles and number of scans on the accuracy of 3D laser scanning

• Lee KM
• Song HY
• Lee KH
• Hwang HS

• KMID: 2274244
• DOI: http://doi.org/10.4041/kjod.2011.41.2.76

Abstract

OBJECTIVE
To investigate whether the accuracy of 3D laser scanning is influenced by the angles and number of scans.
METHODS
Using a 3D laser scanner, 10 manikins with facial markers were scanned at 7 horizontal angles (front view and at 20degrees, 45degrees, and 60degrees angles on the right and left sides). Three-dimensional facial images were reconstructed by 6 methods differing in the number and angles of scans, and measurements of these images were compared to the physical measurements from the manikins.
RESULTS
The laser scan images were magnified by 0.14 - 0.26%. For images reconstructed by merging 2 scans, excluding the front view; and by merging 3 scans, including the front view and scans obtained at 20degrees on both sides; several measurements were significantly different than the physical measurements. However, for images reconstructed by merging 3 scans, including the front view; and 5 scans, including the front view and scans obtained at 20degrees and 60degrees on both sides; only 1 measurement was significantly different.
CONCLUSIONS
These results suggest that the number and angle of scans influence the accuracy of 3D laser scanning. A minimum of 3 scans, including the front view and scans obtained at more than 45degrees on both sides, should be integrated to obtain accurate 3D facial images.

Keyword

3D laser scanner; Scan angle; Number of scans

MeSH Terms

Manikins

Figure

• 

  Fig. 1 The positions of the facial markers used in this study: FRt, right area of forehead; FLt, left area of forehead; Fm, middle area of forehead; G, glabella; N', soft tissue nasion; Pn, pronasale; ExRt, right exocanthion; ExLt, left exocanthion; ZyRt, right zygion; ZyLt, left zygion; CkRt, right cheek; CkLt, left cheek; ChRt, right cheilion; ChLt, left cheilion; UL, upper lip; LL, lower lip; Go'Rt, right soft tissue gonion; Go'Lt, left soft tissue gonion; Pg', soft tissue pogonion; TraRt, right tragus; TraLt, left tragus.

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  Fig. 2 The laser scanner and rotator used in this study. A, Vivid 910 3D laser scanner (Minolta, Tokyo, Japan); B, rotator fabricated for this study. Protractor is attached at the base of the rotator.

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  Fig. 3 Linear measurements used in this study: 1, Pn-Fm; 2, Pn-FRt; 3, Pn-FLt; 4, Pn-G; 5, Pn-N'; 6, Pn-ExRt; 7, Pn-ExLt; 8, Pn-ZyRt; 9, Pn-ZyLt; 10, Pn-CkRt; 11, Pn-CkLt; 12, Pn-ChRt; 13, Pn-ChLt; 14, Pn-UL; 15, Pn-LL; 16, Pn-Pg'; 17, Pn-Go'Rt; 18, Pn-Go'Lt; 19, Pn-TraRt; 20, Pn-TraLt; 21, FRt-FLt; 22, ExRt-ExLt; 23, ZyRt-ZyLt; 24, CkRt-CkLt; 25, ChRt-ChLt; 26, Go'Rt-Go'Lt

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  Fig. 4 Integrated 3D laser scan images were created in RapidForm software, and measurements were obtained using the 3D measure function.

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  Fig. 5 Bland-Altman plots for variations in (Pn-Pg') of Methods 4, 5, and 6. The x-axis shows the average of each integrated 3D laser scan image with physical measurements of manikins, whereas the y-axis represents the difference between the 2 measurements. The limits of agreement are indicated by horizontal lines.

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  Fig. 6 Differences between each integrated 3D laser scan image and the physical measurements of the manikins (mm).

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