Quality Scan: Vision Systems are More Capable
By Michael Metzger
Nikon Instruments Inc.
To support continuous improvement of manufacturing technology and quality, optical imaging instrumentation has been standard on the factory floor for more than 60 years. Early on, manufacturing depended on highly skilled technicians to acquire noncontact magnified images to make simple measurements. Optical comparators and microscopes were the primary tools used to inspect and measure the part under review. Today, advances in optical imaging and wireless communications are creating a new digital-to-data revolution, and influencing the way products are manufactured. Cell phones, PDAs, iPODS, and digital cameras are all fueling a growing appetite for products made by manufacturers who can do more and reduce cost. To meet this voracious demand, optical manufacturers are continuously creating new instrumentation that is both easy to use and effective for lean manufacturing.
A new generation of optical instrument is responding to manufacturers' needs with more optical resolution and higher capabilities. Vision systems are evolving from simple video-measuring devices to sophisticated high resolution-scanning instruments. These systems use the newest imaging techniques, such as extended depth of field (DOF) and field-of-view (FOV) stitching.
These innovative techniques are solving one of the biggest problems with video measuring. As magnification increases to improve accuracy, the features to be measured are enlarged so that only a fractional part of the whole feature to be measured can be seen. Therefore, as magnification increases, DOF becomes shallower and FOV significantly smaller. Increasing magnification is one of the key ways to increase accuracy and precision, but it causes conflict for operators, because increasing magnification can reduce the FOV and DOF.
FOV stitching and extended DOF techniques therefore have become two of the most valuable new tools for optical imaging, because the techniques allow the technician to increase resolution, and use the capabilities of ultraprecision Z scanning to stack images for surface profile and form.
High-magnification imaging can be used for better sample characterization because of the built-in mechanical precision of the vision system. Intelligent software adjoins large FOV data files automatically, forming a larger composite image of stitched ultra-high-precision coordinate data. To extend the DOF, the optical instrument acquires a high magnification, ultra thin, DOF image slice at multiple Z height intervals that span the feature from bottom to top. Because these images are taken at the highest magnification and numerical aperture, it's possible to maintain their high pixel-resolution data. The image slices are stacked via the software and recombined to produce an accurate image with 3-D heights.
Vision systems of the future will be ultra-high-quality optical instruments. Their precision and functional value will be derived from superior mechanics, optics, and electronics. This type of product results from the scientific collaboration of several new technologies using sophisticated manufacturing materials and processes. Design and manufacturing experience from the digital camera and semiconductor industries, and lens designs from optical microscopes will provide future vision systems with a cutting-edge-technology toolbox to offer solutions for challenging new measuring applications. These precision optical instruments will integrate computer-aided engineering, design, and manufacturing to produce the high quality necessary to precisely handle multiple lens systems, cameras, lasers, and special illuminators. They also must be hefty and robust enough to remove unwanted vibration if they are to deliver outstanding results.
Things are changing fast in the digital-to-data world. Look at how the cell phone and consumer digital camera have evolved over the past few years. A digital camera from just a few years ago will most likely have limited zoom, be too slow, and not have enough memory to meet current customer needs.
Industrial optical and digital instrumentation is also changing at a phenomenal rate. New capabilities are advancing precision, and speed and imaging are quickly making products obsolete. The technicians using these vision systems understand the power they possess to help their businesses grow by solving problems and measuring things that were once impossible to measure.
These technicians can turn digital image information into usable, actionable data because there is a growing need in manufacturing for automation that leads to better information and solutions. Vision system technology provides the platform needed to literally zoom deeper into processes to better characterize products.
This article was first published in the April 2005 edition of Manufacturing Engineering magazine.