Research on a Handheld 3D Laser Scanning System for Measuring Large-Sized Objects

Abstract

A handheld 3D laser scanning system is proposed for measuring large-sized objects on site. This system is mainly composed of two CCD cameras and a line laser projector, in which the two CCD cameras constitute a binocular stereo vision system to locate the scanner’s position in the fixed workpiece coordinate system online, meanwhile the left CCD camera and the laser line projector constitute a structured light system to get the laser lines modulated by the workpiece features. The marked points and laser line are both obtained in the coordinate system of the left camera in each moment. To get the workpiece outline, the handheld scanner’s position is evaluated online by matching up the marked points got by the binocular stereo vision system and those in the workpiece coordinate system measured by a TRITOP system beforehand; then the laser line with workpiece’s features got at this moment is transformed into the fixed workpiece coordinate system. Finally, the 3D information composed by the laser lines can be reconstructed in the workpiece coordinate system. A ball arm with two standard balls, which is placed on a glass plate with many marked points randomly stuck on, is measured to test the system accuracy. The distance errors between the two balls are within ±0.05 mm, the radius errors of the two balls are all within ±0.04 mm, the distance errors from the scatter points to the fitted sphere are distributed evenly, within ±0.25 mm, without accumulated errors. Measurement results of two typical workpieces show that the system can measure large-sized objects completely with acceptable accuracy and have the advantage of avoiding some deficiencies, such as sheltering and limited measuring range.

Flexible Three-Dimensional Reconstruction via Structured-Light-Based Visual Positioning and Global Optimization

“…From the above comparison we can see that the accuracy of the method in this paper is close to that of the method in [1], but much higher than the method in [25]. However, the method in [1] needs to post artificial markers on the surface of the object to expand the measurement range, the operation process is complicated. In comparison, our proposed method is easier to operate.…”

“…To demonstrate the advantages of this method more clearly, a comparative analysis is conducted with the existing method. Wang et al [1] used standard industrial 3D scanners called TRITOP for three-dimensional reconstruction. Since the measurement range of the scanner is small, some artificial marked points are attached on measured object to expand the scanning range.…”

“…Vision measurement is widely used in the field of industrial measurement [1,2,3,4,5]. Vision-based structured light measurement methods can effectively improve the precision of the measurement.…”

Portable System for Box Volume Measurement Based on Line-Structured Light Vision and Deep Learning

“…Fernandes et al [14] presented an approach that is based on projective geometry; they computed the box dimensions by using data that were extracted from the box silhouette and the projection of two parallel laser beams on one of the imaged faces of the box. Wang et al [15] proposed a handheld 3D laser scanning system that consists of a binocular stereovision and line laser projector for measuring large-sized objects on site. Pan et al [16] proposed a wheel size measurement framework that is based on a structured-light vision sensor, which has high precision and reliability and is suitable for highly reflective conditions.…”

Structured Light Three-Dimensional Measurement Based on Machine Learning

“…Structured light three-dimensional measurement technology is an active optical measurement technology with the characteristics of small volume, low price, and easy installation and maintenance [1]. Therefore, this technology exhibits a wide range of applications in actual industrial fields, such as vision inspection [2,3], face profilometry [4,5,6], and robots [7,8,9]. The light source projects the structured light with a certain shape pattern, such as a light spot, a light strip or a light surface structure, and the structured pattern reflected by the object is obtained using an image sensor, such as a charge-coupled device (CCD).…”