A telecentric lens is a specialized optical lens designed to have its entrance or exit pupil at infinity. This unique design makes the image magnification insensitive to the distance between the object and the lens or the distance between the image plane and the lens. Telecentric lenses are crucial in applications requiring precise two-dimensional measurements, such as industrial machine vision, metrology, and photolithography. There are three main types of telecentric lenses: object-space, image-space, and bi-telecentric. Object-space telecentric lenses are commonly used in measurement tasks where the object's height or position varies. Image-space telecentric lenses deliver near-normal chief-ray incidence on the sensor, reducing vignetting and color shifts. Bi-telecentric lenses combine the benefits of both, offering the highest measurement stability.
Key features of telecentric lenses include low distortion, constant magnification, and the elimination of perspective errors. These lenses provide orthographic projection, ensuring that objects maintain the same size regardless of their distance from the lens. Telecentric lenses are larger, heavier, and often more expensive than standard lenses due to the additional components required to achieve telecentricity. Prominent manufacturers include Edmund Optics, Carl Zeiss AG, Jos. Schneider Optische Werke GmbH, Mitutoyo Corporation, Navitar, Inc., Kowa Company, Ltd., Tamron Co., Ltd, VicoImaging and Sill Optics. The price range for telecentric lenses can vary significantly based on specifications and features, with some available from around $740 to $3,800, while others can cost upwards of $4,571. Telecentric lenses are widely available from various suppliers, including Edmund Optics and Opto Engineering.
