In the automotive and electronics industries, parts with complicated shapes must be imaged with high accuracy. When using machine vision to inspect three-dimensional parts, this is especially important. In such applications, conventional lenses may produce distorted images. To overcome such distortion, systems integrators must use telecentric lenses. Often telecentric lenses are required because conventional lenses cannot accurately portray objects that are off-axis to the lens or are at different distances from the lens. Viewing-angle error and magnification error are inherent in conventional lenses, and these perspective distortions can create significant interpretation problems for software. If, on one hand, an image of connector pins is captured with a camera fitted with a conventional lens, the area of the tops of the pins that are farther from the lens will appear smaller. Telecentric lenses, on the other hand, maintain a constant viewing angle at any point across the aperture of the objective lens. If the same image of connector pins is captured with a camera fitted with a telecentric lens, the area of the tops of the pins will remain constant. Because of this, machine-vision systems fitted with telecentric lenses can acquire images of objects that appear dimensionally accurate, regardless of viewing angle or proximity to the lens.
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