Scanning optical point- and line-sensor (SOS)

Project focus

  • Development of scanning systems with different optical sensors for 3D imaging
  • High-speed, high-precision motion control of scanners for imaging
  • Data acquisition system to accurately reconstruct 3D images


In order to optimize production settings and inspect products at factories for high productivity and reliability, surface properties of the products can be evaluated by three dimensional (3D) measurements. For these applications, optical sensors are ideal for their high-speed non-contact and accurate measurements, such as laser triangulation sensors and polychromatic confocal sensors for displacement measurement, as well as colorimeters and spectrophotometers for color sensing, as shown in Fig. 1. To generate 3D measurement data, such sensors are moved with respect to the products for scanning. However, currently used methods have limited performance on measurement rage, scanning speed, motion precision, or flexibility.

Different types of optical sensors targeted for the scanning optical-point and -line systems.

To overcome the limitation for better productivity and reliability of production in this project, a rotating or steering mirror scans the sensor’s optical point or line over a product surface, as shown in Fig.2, targeting triangulation, confocal, and color sensors.

In the development of the measurement systems, methods and principles for a systematic approach towards the holistic system integration of the optical metrology sensors and the mechatronic scanning systems are developed and validated, enabling fast and precise 3D measurements of surfaces. The system development also focuses on yielding the highest performance and evaluating critical system parameters such as the distance to the measurement object, the achievable steering angle for the applied sensing method, the measurement principle itself and measurement modes, as well as environmental influences. Trade-offs between and the influence of critical system parameters such as the alignment accuracy that may cause a potential crosstalk due to misalignment are to be investigated in detail.

Depending on the targeted application, control methods are applied and tested on the implemented systems. To control the motion of the integrated opto-mechatronic components for more generic applications with arbitrary scan-patterns, modern control techniques such as model-based control and two-degree-of-freedom control are to be applied. To reduce measurement uncertainty by highly precise scanning, ILC or RC techniques will also be investigated to improve the tracking performance for repeated scanning patterns. There are also different types of scanning patterns, and most suitable one for a targeted application is adopted in the same manner as the system integration and control design to achieve the highest performance as the measurement system for the in-line metrology.

Representative configuration of a scanning optical-point & -line system with a confocal displacement sensor.


  • In-line metrology
  • Product inspection
  • 3D imaging

Related publications

  • S. Ito, H. W. Yoo, and G. Schitter, Comparison of Modeling-free Learning Control Algorithms for Galvanometer Scanner’s Periodic Motion, in Proceedings of the IEEE/ASME International conference on advanced intelligent mechatronics, 2017.
    Title = {Comparison of Modeling-free Learning Control Algorithms for Galvanometer Scanner's Periodic Motion},
    Author = {Ito, Shingo and Yoo, Han Woong and Schitter, Georg},
    Booktitle = {Proceedings of the IEEE/ASME International conference on advanced intelligent mechatronics},
    Year = {2017},
    Doi = {10.1109/AIM.2017.8014207},

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