Optical lens assemblies are composed of a number of lenses mounted for a particular imaging function. These can include telecentric lenses, collimators, beam expanders, zoom lenses, etc. Optical lens assemblies can be used to magnify, expand, collimate, or otherwise alter or condition light.
Telecentric Optical Lenses
Telecentric lenses are compound lens assemblies used to provide images independent of an object’s distance, or to prevent wide ranges of angles of incidence. Applications for telecentric lens assemblies include digital image sensors, machine vision systems, measurement systems that use charged-couple devices (CCDs), metrology equipment, and microlithographic camera systems.
There are three basic types of telecentric optical lens assemblies: object-space, image-space, and double telecentric. With object-space telecentric optical lenses, the entrance pupil is at infinity. With image-space telecentric optical lens assemblies, the exit pupil is at infinity. If both the entrance pupil and the exit pupil are at infinity, then the lens is double telecentric. Specialty telecentric optical lens assemblies are also available.
Collimators are optical lens assemblies that take divergent or convergent incoming light rays and produces parallel light output. There are many types of collimators. Examples include laser collimators, x-ray collimators, and infrared radiometer collimators.
Collimator optical lens assemblies function based on spot size, insertion loss, and working distance. Collimation refers to the adjustment of the position and orientation of optical elements within a telescope and other optical instrument to achieve optimum performance. Barlowed collimation is a technique developed for adjusting the angular alignment of the Newtonian primary mirror.
Beam expanders are another type of optical lens assemblies. Beam expanders are used to increase the diameter of a laser beam or other light beam. There are two types of beam expander optical lens assemblies: Kepler and Galileo. Kepler beam expanders or Keplerian beam expanders have two positive lenses or groups of lenses. Galileo beam expanders or Galilean beam expanders have both negative and positive lenses or lens systems. Zoom systems and modular systems require special beam expander optical lens assemblies.
Optical lens assemblies also include zoom lenses. Zoom lenses are mechanical assemblies of lens elements that provide the ability to vary focal length and angle of view. This type of optical lens assembly is commonly used with still, video, motion picture camera, projectors, microscopes, telescopes, and other optical instruments. True zoom lenses or parafocal lenses maintain their focus when the focal length changes. Varifocal lenses lose their focus during zooming. Other types of optical lens assemblies may also be commonly available.