Vision inspection systems enable companies to measure parts accurately and quickly, leading to less rejected pieces and increased production.
There are various vision measurement systems on the market, and this article will address several such examples, such as optical comparators, cameras and software solutions.
Optical Comparators
Optic comparators remain one of the most widely used visual measurement systems today, due to their ease of operation and cost-efficiency.
Operatives use a screen overlay or crosshairs to center a workpiece silhouette, then move its stage until hitting prescribed plan points on a display for measuring. A computer then analyzes this image, measuring each edge and computing dimensions based on them.
Modern comparators provide more accurate images through the use of telecentric optical designs that increase depth of field and reduce measurement variation, and feature high-resolution displays and automatic edge detection for fast and precise inspection.
While some have predicted the demise of optical comparators, they continue to prove invaluable in quality control and production environments for an array of purposes. A newer all-in-one vision inspection system such as Hexagon Manufacturing Intelligence’s Optiv Classic 443 brings together both its advantages as an optical comparator with CMM’s automated movement and programming features for more comprehensive solutions that meet most inspection needs while permitting users to easily transfer programs between machines.
Cameras
Cameras use light to convert electric signals into images on an image sensor, as well as capture and deliver these signals to frame grabbers or other sensors in vision systems for processing.
Lenses serve to focus images onto sensors or sensor arrays and are an important element of machine vision systems’ image quality. Their performance can be evaluated during design by comparing it to an objective measurement of target components or features such as size.
As a general guideline for selecting cameras, they should offer at least three-pixel coverage of the dimensions being inspected. Camera resolution depends upon both image sensor size and subpixel pitch size; additionally, cameras must feature a high signal-to-noise ratio so as to accurately record image data for processing and decision making; this measurement is usually expressed as decibels with higher values indicating improved performance.
Optical Sensors
Optic sensors are detectors which respond to changes in the position of a light beam, as well as testing additional properties like its polarization or optical spectrum.
Machine vision systems perform one of the most prevalent functions: presence inspection. This task verifies whether an assembly or part is present on a conveyor belt or production line and helps ensure quality assurance processes continue without failures due to mislabeled bottles or missing screws.
To test this theory, measurements were conducted with various basic sensor sensitivity levels to verify it. As expected, measurement uncertainty usns(x’) increased with an increase in sensor sensitivity due to micro-vibrations and air movements affecting image contour. It is therefore especially essential to use optical sensors with stable and precise constructions.
Optical Software
Vision measurement systems differ from profile projectors/optical comparators and measuring microscopes by requiring software for control and edge detection. This software drives a camera to locate points on edges and surfaces, and then constructs features from these detected points such as lines and diameters. Many vision measuring machine software packages also output ASME or ISO tolerancing (e.g. true position, parallelism), while some even support 3D scanning via focus image stacking.
Optic software programs provide an endless variety of graphics for design, analysis and optimization – from two and three-dimensional views of an optical system through transverse ray-aberration plots, wavefront plots, point-spread function plots, MTF curves; encircled energy plots to lateral chromatic focus plots – that will assist with designing your optical components efficiently and achieving their maximum potential. Be sure to choose one with a damped least squares optimization algorithm as well as tools designed specifically to optimize each component.
An advanced optical design and analysis program offers users a user-friendly experience, with lightning fast simulations. A top custom optical design program, for instance, features an easy drag-and-drop interface that enables them to model any business process with ease.
