n every production environment there are numerous factors that can thwart the effectiveness of machine vision systems. Aside from obvious challenges such as ambient lighting, temperature drift, and part positioning variation, vibration is one of the more subtle contributors.
In this blog, we will discuss the advantages of 3D over 2D vision in solving the fundamental challenge of vibration.
The Problem of Object Movement
Vibration most commonly occurs in transport systems such as conveyors. Movement is detrimental to inspection because it results in blurred edges and scaling effects that can have a negative impact on measurement precision (sometimes completely obscuring the edges or surface features of an object).
2D is Sensitive to Vibration
2D solutions are component-based, which means they are made up of several independent products that must tie into a common mounting and calibration process to deliver metrology data. Component design makes 2D vision systems highly sensitive to object movement because any variation in object height changes pixel scaling and therefore measurement accuracy.
System integrators, therefore, must introduce part fixturing along the optical axis (Z-axis), the use of scale-invariant feature detection, or large telecentric optics that have to match the size of the field of view in order to eliminate environmental effects such as vibration.
The Smart 3D Solution
In contrast, 3D smart sensors have a fully integrated optical design for improved stability. All components in a 3D sensor are rigidly mounted on a single “spine” assembly that ensures focal lengths are locked-in relative to emitter and imager planes, and temperature compensation corrects for any drift.
3D vision technology has an integrated optical design that stabilizes the device, resulting in increased measurement accuracy.
Built-In Vibration Correction
In instances where vibration does appear in a height map, 3D smart sensors offer built-in tools for fast and easy correction. Since vibration presents itself as patterns in 3D height variation, the effect is already captured in the height map and can be subsequently processed for removal.
Vibration is captured as line and color patterns in a 3D height map.
Vibration correction results in cleaner 3D data (i.e., removes height variation).
How It's Done - Vibration Correction Tool
The Vibration Correction tool in Gocator® analyzes variation in 3D surface data and removes high-frequency noise. This tool is useful for increasing the repeatability and accuracy of measurements when subtle vibrations in your transport system introduce height variation.
Uncorrected surface vibration (actual scan data)
Surface vibration corrected using the built-in tool (actual scan data)
The Vibration Correction tool also allows you to correct data by selecting a designated region, which is useful when movement occurs regularly in a specific area of your scan data.
The tool can then send corrected or difference (subtracted from original) surface data to other tools for applying measurements. The result is highly repeatable metrology performance that is otherwise difficult to achieve in 2D systems.