Plasmat lens

The Plasmat has been developed by Paul Rudolph in 1918 and in the 1920s, high-performance lens of Hugo Meyer ( " Meyer -Optik " ), Görlitz.

The Plasmat goes back to the so-called Dagor - type lenses. The Dagor was a sechslinsiger Double Anastigmat Goerz of Berlin. The Dagor consists of two three-lens cemented lens groups are symmetrically disposed about the aperture. In otherwise good optical performance but remained a significant spherical aberration. Due to the disentanglement of the inner two lenses from the two cemented lens groups, additional degrees of freedom were to correct this optical aberration. Particularly successful sat Paul Rudolph with the Plasmat this design principle to. The immediate predecessor of the Plasmats was calculated by Ernst work Euryplan 1:6. First built by Schulze & Billerbeck, and later by Hugo Meyer. Hence Rudolph first developed the (double) Plasmat with a light intensity of almost 1:4.

The Plasmat consists essentially of two opposing doublet, inside which a further curved converging lens ( meniscus ) is assigned. There is an air gap between the doublet and the menisci; between the menisci the aperture. Instead of the four air-glass interfaces of the Dagor Plasmat thus has eight such surfaces. Since the coating of optical surfaces had not been invented in the 1920s, the Plasmat for internal reflections was vulnerable.

The first so-called double - or phrase - Plasmat had a maximum aperture of 1:4.5. In addition to use in the "normal " photography Plasmate were often used in devices for copying documents.

Cinema Plasmat 1:1.5 / 16 mm, serial number 782 339

Cinema Plasmat 1:1.5 / 40 mm, serial number 500 385, as a projection lens

The cinema Plasmat consists of two nearly symmetric lens groups

An important further reached Rudolph 1922. Inspired by the very high required light intensity of film cameras, he constructed the cinema Plasmat. Here the two inner lenses were the other way around and bent the front doublet increased. With this design, light intensities of 1:2 (1924 ), and finally 1:1.5 (1926) were achieved. These were then the most light-sensitive photographic lenses in the world.

The London Camera Company A.O. Roth vermarktere mid - late 1920s, a " Meyer Speed ​​Camera " ( 4.5 cm × 6 cm), which was equipped with a 1:2 / ~ 90 mm ​​cinema Plasmat as a lens. Due to the high light intensity, the lens has also been used scientifically. Thus was the beginning of the 1930s a cinema Plasmat 1:1.5 / 50 mm use in the photographic and spectrographic study of the aurora. There are also variants that can be used as a projection lens (see picture).