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Tech Papers

Ahead of the Competition: The Benefits of Using a Zoom Lens

by William Bridson, Director of Research and Development - Navitar Inc.

Global competition and rising product development costs are key issues for today's manufacturing companies. More and more organizations are realizing lower overall production costs by implementing vision system designs that are modular and flexible in nature. Incorporating a zoom lens, versus fixed, into a machine vision system will give your organization the edge it needs to stay ahead of the competition. The benefits of zoom lenses range from flexibility and precision performance to cost effectiveness and adaptability. These and other benefits are outlined below.

Modular Design 
Perhaps the largest benefit of the zoom lens is its modular design. Selecting from a range of models and accessories, building the perfect custom zoom system is simple. Due to its sophisticated construction, many zoom lenses offer true coaxial illumination, which is the most efficient means of illuminating a flat specular object. Ring illuminators may be added as required. Attachments at each end of the zoom allow simple variation of working distances and magnifications. It is also possible to work with polarization, inject a laser, superimpose a reticule, delve into the increasingly popular field of fluorescence, and simultaneously view with different types of cameras. With the addition of detents, or motors and software, zoom settings may be calibrated and reliably repeated for measurements of various sized objects.

Flexibility
A key benefit of using zoom lenses in the product development process is the opportunity to build flexibility into automated equipment. When product design changes are expected or if certain assembly processes have not been proven, the machine builder can incorporate a zoom lens with a modular design providing the flexibility for an easy change. Vision engineers and imaging equipment manufacturers are already thinking about their next generation equipment before their first product generations are even shipped out the door. An automated vision system incorporating the right modular zoom optics will result in vision equipment that can be easily rearranged, retooled and reused for changing production items.

Performance 
Utilizing a precision zoom lens, which offers continuously changing focal lengths to adjust magnification while maintaining focus, is typically preferred over using a fixed telecentric lens which may offer only one magnification. The Metrology industry has always demanded the highest level of precision and measurement accuracy and has relied on the flexibility of zoom lens designs for years. Automated metrology systems typically utilize a zoom lens that is designed to calibrate itself at every magnification change in order to achieve consistent measurement accuracy.

Reduce Development Time 
Decisions made during product development determine a significant proportion of product costs and ultimately determine the portion of profits that a product will generate over its life. During the product development stage, the organization designs the features that give the product an edge over competing offerings and affect the costs that will shape profit margins. As a rule of thumb, eighty percent of the costs are engineered during product development (Blanchard 1978; Cooper and Slagmulder 1997).

Zoom lenses, with their inherent multi-magnification design, enable flexibility to be designed into new automation equipment. It is very common for customers to want changes made to a static design that was originally using a fixed lens. The flexibility of the zoom lens helps you move ahead with development work despite customer changes and uncertainty about specific imaging requirements - all while keeping costs low.

Adaptability 
An inherent capability of the zoom lens is adjusting to match changing workplace conditions. With the addition of a quality zoom lens, companies can inspect a wide range of parts without the hassle of performing advance measurements and calculations or stocking an assortment of fixed lenses. For example in the die bonding industry, the chips to be bonded can vary from a fraction of a millimeter to over ten millimeters every few days. The goal is to have the chip cover as much of the sensor as possible to facilitate accurate placement. To minimize confusion and number of on-board setup personnel, zooms are now supplied with motors and software that permit keying in a code for the particular work piece to automatically set the zoom lens for the optimum conditions. Other applications may include keying in two numbers, the first being a low magnification condition for location and the second permitting identification at a higher magnification.

The benefits of zoom lenses go beyond equipment manufacturers and are also realized directly on the industrial machine vision factory floor. Many companies integrate inspection systems for use on a production line. Quite often, different, yet similar, production lines in a factory will have distinct requirements and constraints such as field of view (FOV) or working distance (WD).

Cost Effective 
One approach to managing costs during product development is to incorporate modular features into the design process. This modularity allows you to increase your product offerings without increasing the number of products developed. Zoom lenses permit easy system customization and provide multiple configuration options without changing anything in the bill of materials (BOM) or the assembly procedure, thus keeping costs down.

Quality 
The optical goal of machine vision is to spread the object in question over the entire sensor, while maintaining a maximum of edge 'crispness.' A zoom lens provides the field expansion, and a well-designed zoom system provides the crispness. With the appropriate accessories, a high magnification zoom will offer fields from five inches to 1/4 millimeter.

Size 
While the invention of the Stereozoom Microscope allowed operators to handle ever-shrinking electronic components, the Videozoom, with its compact size and modular design flexibility, is ideal for use in a number of OEM applications.

Variety 
There are many different types of zoom lenses available. Navitar offers a diverse selection of lenses that deliver unbeatable accuracy and repeatability. High magnification zooms, similar to the Navitar 12X (55 to 667 mm) and Zoom 6000 (6X) lenses (69 to 442 mm focal length), are used in many semiconductor, electronic, bioscience, and life science applications. Large field of view zooms, like the Navitar Zoom 7000 (18-108 mm focal length) and Varifocal zooms (6-13 mm), are ideal for a large variety of factory floor inspection system production lines. With the wide selection available the possibilities are almost limitless.

When designing your next machine vision system, consider the benefits of incorporating a zoom lens. A customized modular zoom system can help speed up product development, reduce costs, and simplify system customization and configuration - to help you zoom ahead of your competition.

About the Author
William Bridson leads the new product development initiatives for Navitar, Inc. He has over forty years experience in the field of imaging systems design and has held positions including Vice President of Engineering and Director of Microscope Development.

About Navitar, Inc. 
Navitar, Inc., established in 1972 and based in Rochester, New York, first introduced precision zoom optics to the machine vision industry in 1984. Today, they are recognized as the leading manufacturer of superior quality optical lenses and complete customized optical solutions for the machine vision and electronic imaging markets. Supporting the semiconductor, electronics, life sciences, biosciences, metrology, military, R&D, and nanotechnology markets around the globe, Navitar optics are used in a variety of applications ranging from flat panel display inspection, drug discovery, laboratory-on-a-chip reading, and high speed factory automation applications. Navitar, Inc. has offices and subsidiaries in the U.S., Europe, the Middle East, and Asia. For more information about Navitar, Inc. and their innovative products, visit the company's web site at www.navitar.com or contact Navitar, Inc. at 200 Commerce Drive, Rochester, NY 14623. Phone 585-359-4000, Fax 585-359-4999.

References 
Blanchard, Benjamin S., Design and Manage to Life Cycle Cost (1978) M/A Press, Portland, Ore.
Cooper, Robin and Regine Slagmulder (1997) Target Costing and Value Engineering, Productivity Press, Portland, OR

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