Summary on Calibration Method of Line-Structured Light

No.	Calibration target	Type	Manufacturing method	Calibration characteristic
1	2000,zigzag block^[23]	3D	Computer numericalcontrol cutting	High-precision auxiliary servo deviceis required. Measuring coordinate systemis set along the light plane. Using directlinear transform (DLT) method tocomplete the calibraion. Calibrationaccuracy is 0.048 mm^[23].
2	1999,target with twoperpendicularplanes^[24-25]			Customized three-dimensional target, highmanufacturing costs. Occlusion existing inimaging process. Use principle of crossratio of invariance for calibration.Calibration accuracy is 0.145 mm^[24].
3	2014,gauge block^[12]			Grinding	Gauge block are standard parts with highprecision. But calibration process requireshigh precision auxiliary servo device.Calirbation accuracy is 0.0279 mm^[12].
4	2015,ball target^[29]		Ball target are standard parts with highprecision. Space cone fitting and spacesphere fitting is used for calibration.Calibration accuracy is 0.04 mm^[29].
5	2016,chessboard^[32]			Easy for feature extraction. Camera and lightplane could be calibrated simultaneouslywith only one target. But it's difficult tomanufacture a large scale target.Calibration accuracy is 0.09 mm^[32].
6	2006,array targetwith circles^[33]	2D		Easy for feature extraction. Camera and lightplane could be calibrated simultaneously withonly one target. But it's difficult tomanufacture a large scale target. Calibrationaccuracy is 0.107 mm^[33].
7	2014,parallel straightlines^[30]		Photpetching /printing	Useparrallel straight lines constraints forcalibration.The calibration method isnovel. Calibration accuracy is 0.134 mm^[30].
9	2012,single circularring target^[34]			Camera and light plane could be calibratedsimultaneously. Operation is flexibleand easy for site calibration.Calibration accuracy is 0.0368 mm^[34].
10	2010,one-dimensionaltarget^[27]	1D		Easy for manufacturing large size target, andfit for site calibration in larget FOV. Useprinciple of vanishing point for calibration.Calibration accuracy is 0.102 mm^[27].
11	2016,linear scale^[35]			Calibration accuracy is high, but it needshigh-precision auxiliary device. The target isparticularly fit for applications of small FOVand high accuracy. Calibration accuracyis 0.013 mm^[35].

Table 2. Evaluation of calibration accuracy of commonly used line structured light

View table

Table 2. Evaluation of calibration accuracy of commonly used line structured light

No.	Evaluation indicator	Evaluation object	Evaluation method
1	Plane fittingaccuracy	Lightplane	Average or maximum of the distance fromcontrol points to fitting plane is computed asthe accuracy results^[40].
2	Repeatability	Single lineardimension	A fixed dimension would be measured formany times, and the maximum, minimum and variancewill be used as the accuracy indicator for repeatability ^[41].
3	Light-planecompositeaccuracy	Dimensions fromany directionin light plane	Based on cross ratio, distance between two control pointsin local world frame would be obtained as the true value,then the corresponding control points would be measuredin 3D coordinate. Finally, the RMS will be computedas the evaluation results^[30].
4	Light-planeseparatingaccuracy	Dimensions alongwith coordinate axesin light plane	The measurement results with gauge block would betaken as the accuracy in vertical direction, and themeasurement results with linear scale could be treatedas the accuracy in horizontal direction^[35].
5	Surfacereconstructionaccuracy	Point cloudafter curveaccumulation	The reconstructed curves would be accumulated alongthe motion direction, and the comparison ofpoint cloud and CAD model will be taken as thesurface reconstruction accuracy^[42].