Projection lens
A projection lens is a lens that is used for projection . The development of projection lenses follows two different lines. The traditional projection lenses are used to depict a template on a screen using light. These projection lenses are - with all their constructive peculiarities - closely related to the lenses for photography. Modern projection lenses are highly corrected anastigmats with luminous intensities of up to f1.4 and higher.
New types of projection lenses have been developed for photolithography (semiconductor technology) .
Areas of application for optical projection lenses
In addition to slide and film projectors, enlargers for photography also use projection lenses. Optical projection lenses are also used in episcopes , epidiascopes and antiscopes , film projectors , video projectors and beamers .
Mechanical construction
The lenses of projection objectives are fitted into metal or plastic cylinders; an adjustable aperture is missing (except with magnifying lenses ). The metal cylinders are often widened on the image side because larger lenses are attached there.
Optical structure
The optical projection leads to a linear enlargement of the original, often several hundred times, of a 24 × 36 mm small picture slide or a 35 mm normal film. The requirements for the achievable image brightness, the resolution and the contrast performance are therefore high. Lenses with a larger focal length (and correspondingly smaller angle of view) are often used for projection than for recording.
Petzval type
Petzval-type lenses have been used since the early days of slide and film projection . The Petzval lens was the first portrait lens because of its light intensity, unmatched in the middle of the 19th century . It is precisely this high light intensity that makes it a suitable projection lens with an acceptable correction of the image errors for small image angles. Petzval lenses consist of a cemented achromatic lens on the image side and two free-standing individual lenses at the rear (diverging lens, converging lens).
A common projection lens of this type is the Kiptar from ISCO Göttingen. Kiptars for the projection of 35 mm normal films were produced in the mid-1950s with light intensities from f2 to f2.9 and focal lengths from 90 to 170 mm. There was a Kiptar f1.6 / 20–85 for Nizo projectors for 8 mm cine film .
A modification of the Petzval lens is followed by the Ocellar II from Agfa (f1.6; 20 and 22 mm) for the Movector 8 narrow film projector. The order of the rear lenses is reversed here, based on a form of portrait lens developed by John Henry Dallmeyer in 1866 .
It is also possible to arrange all four lenses of a Petzval lens in two groups individually free-standing. This is the case with the Askinar f1.9 / 90 to f1.9 / 120 mm from Askania Werke . The Askinar is a cinematographic projection lens that first builds in the converging lens and then the negative meniscus. The opposite way was taken with the Emostar (f1.5; 25, 35 and 50 mm for the narrow film) (f1.5 / 65 to f1.8 / 120 mm for normal film) the emo optics. This also applies to the Kinon (f1.4 / 25 mm) from Meyer-Optik calculated by Roeschlein and the Kipronar from Carl Zeiss Jena (f1.4 / 70 to f1.9 / 250 mm; also in f2.2). Zeiss held the German Imperial Patent 544 429 on the Kipronar design. As with the original Petzval lens, the field curvature for off-axis points is also noticeable in these derived developments.
Triplet type
Most projection lenses in miniature - slide projectors are used are of structurally close relatives of Cooke triplets . As with taking lenses, a good optical result for light intensities between f4 and f2.8 can be achieved with a simple and therefore inexpensive design. Well-known producers in the classic era of slide photography were
- Agfa ( Agomar : f2.5 / 100 to f2.8 / 150 and f3.5 / 85 mm; e.g. for Karator U ),
- Enna Werk ( projection Ennar : 2.8 / 100 to f3.5 / 150 mm for example at Braun-Paximat ),
- ISCO Göttingen ( Projar : f2.8 / 100 mm),
- Leitz ( Dimaron : f2.8 / 85 to f2.8 / 150 mm; Dimar : f4.0 / 200 and f4.0 / 250 mm),
- Ed. Liesegang ( Patrinast : e.g. f2.8 / 85 mm for Liesegang Fantax )
- Meyer optics ( Diaplan : f3 / 100 to F3.5 / 140 mm, for example, Filmosto Jubilar and Filius )
- Wilhelm Will (Wetzlar) ( Maginon : f2.5 / 25 to f3.5 / 127 mm; up to 100 mm focal length for the Braun Paximat)
- Rodenstock ( Splendon , Splendar : f3.5 / 200 to f4 / 250 mm, for example on Agfa Karator U ),
- Staeble-Werk ( Kata : f2.8 / 35 to f3.5 / 150 mm, for example on Braun-Paximat ) and
- CA Steinheil & Sons ( P-Cassar : f2.8 / 80 mm on the Dunco 56 and f3.5 / 150 mm on the Noris Trumpf 250 ).
While most of the companies were simultaneously producing taking lenses, Wilhelm Will (Wetzlar) and Ed. Liesegang oHG (Düsseldorf) largely specialized in projection equipment and lenses.
Classic triplets are also used in the large-format projection lenses for episcopes and epidiascopes (e.g. Isco- Epinar , Leitz- Epnor , Meyer-Epidon ). The light intensity starts here with f3.6. The Meyer- Trioplan was used as a projection lens by the readers.
There are a number of lenses with an extended four-lens structure. Here is part Leitz - Hector for small picture slides having as the taking lens of the same cemented intermediate links. The bright version with f2.5 was produced in focal lengths of 85, 100, 120, 180 and 200 mm. The angle of view was reduced from 28.5 ° to 12 °. These lenses were available for the series of Leitz Prado projectors 150, 250 and 500. The f2.5 / 85 mm Liesegang- Sankar is also a triplet with a lens.
Gaussian type
Since the imaging of off-axis image points caused problems with the Petzval type at very high light intensities, Carl Zeiss Jena developed a series of projection lenses of the Gaussian double lens type in 1953 . This five-lens prokinar was available for the cine film from f1.4 / 35 to f1.4 / 70 mm. The procinar f1.9 / 90 and 105 mm was intended for normal film. The front part consists of two free-standing lenses, the (first) diffusing element of the rear part consists of two cemented lenses with a cemented surface that is curved towards the front part.
Other derived Gauss types can contain six or more lenses ( Super-Kiptar from ISCO or Cinema-Raptar from Wollensack ).
Zoom lenses
Modern zoom lenses for projection (e.g. Schneider-Kreuznach Vario-Cine-Xenon AV MC f3.9 / 85–210) have up to 15 mostly free-standing lenses.
Photolithography
In the last few decades, new technical tasks for projection have developed. The photolithographic structuring of integrated circuits , which requires highly specialized optical systems, plays a special role . The projection takes place here with lasers , for which lenses with the highest imaging performance were created. In order to be able to image ever finer structures, lasers of short wavelengths are used (2008: 193 nm), for whose light only quartz glass is sufficiently transparent . These lenses achieve a resolution of 45 nm on an area of several square centimeters.
Individual evidence
- ↑ a b c d Hans-Martin Brandt (1956) The Photo Lens. Structure and mode of operation of the most important lenses in world production. Friedr. Vieweg & Sohn, Braunschweig. P. 104
- ↑ Gottfried Kindler (no year) History of the MEYER-OPTIK company as a precision optical factory in Görlitz after the Second World War. With addendum: Chronicle of the company Lederwaren Görlitz. 2nd Edition. Society for the Museum of Photography in Görlitz eV p. 10
- ^ Hans-Martin Brandt: The photo lens. Structure and mode of operation of the most important lenses in world production. Friedr. Vieweg & Sohn, Braunschweig 1956, p. 103f.
- ^ Hans-Martin Brandt: The photo lens. Structure and mode of operation of the most important lenses in world production. Friedr. Vieweg & Sohn, Braunschweig 1956, p. 189.
- ^ Hans-Martin Brandt: The photo lens. Structure and mode of operation of the most important lenses in world production. Friedr. Vieweg & Sohn, Braunschweig 1956, pp. 104, 186.
- ^ Hans-Martin Brandt: The photo lens. Structure and mode of operation of the most important lenses in world production. Friedr. Vieweg & Sohn, Braunschweig 1956, pp. 104f, 187ff.
- ^ Hans-Martin Brandt: The photo lens. Structure and mode of operation of the most important lenses in world production. Friedr. Vieweg & Sohn, Braunschweig 1956, pp. 104, 187ff.
- ^ Hans-Martin Brandt: The photo lens. Structure and mode of operation of the most important lenses in world production. Friedr. Vieweg & Sohn, Braunschweig 1956, p. 192.
- ^ Hans-Martin Brandt: The photo lens. Structure and mode of operation of the most important lenses in world production. Friedr. Vieweg & Sohn, Braunschweig 1956, pp. 104, 191.
- ^ A b Hans-Martin Brandt: The Photo Lens. Structure and mode of operation of the most important lenses in world production. Friedr. Vieweg & Sohn, Braunschweig 1956, p. 105.
- ^ Hans-Martin Brandt: The photo lens. Structure and mode of operation of the most important lenses in world production. Friedr. Vieweg & Sohn, Braunschweig 1956, p. 105 in connection with p. 113 image 89/19 and p. 198.
- ↑ Schneider company brochure; Retrieved February 10, 2012 ( Memento of the original from October 11, 2011 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
