Leitz Periplan Red Dot Eyepiece For High Contrast Views

[j.gardavsky]

Hello friends of fine eyepieces,

about 2 weeks ago, I have retrieved a pair of these eyepieces both for the microscopy and for my 6” F/5 achromatic refractor, and that’s the good reason for this short technical review.
This eyepiece has been originally designed before 1990 as the CVD (Chromatische Vergrösserungsdifferenz, chromatic magnification difference) compensating eyepiece for the microscopes with achromatic eyepieces, to control their chromatic aberration. This is also the last eyepiece in the Leitz Periplan series.
The main characteristics:
Manufacturer’s specifications: PERIPLAN 10x/18 [glasses symbol] red dot, LEITZ WETZLAR GERMANY, item 519749
Focus length and field: f=25mm , AFOV = 40°
Lenses sequence: (field stop – 1 – 2), eye lens in doublet concave out
Coatings: blue single
Eye relief: estimated 16mm
Diameters: insert 23.2mm, maximum out 33mm, eyeguard thread 28mm
Length and weight: 56mm (without eyeguard), 51.6g (without eyeguard)

The CVD correction is revealed as a red ring, visible around the field stop, when the eyepiece is mounted on a microscope or telescope.

Laser tracing the eyepieces lenses reveals a minimum of scattering along the laser ray. One lens may be a high grade BK7 (or a similar high refractive index crown), the other lenses are nearly crystal clear high refractive index and lower dispersion (high Abbe) lens materials, abandoned since 1990 due to the new environment protection regulations.
The closest eyepiece in the highest contrast class is the slightly wider Leica HC Plan 10x/20 (507802), which looks like an inverted version (field stop – 2 - 1) but with no red fringe, followed by the new Leica HC Plan S 10x/22 (507807) with the lenses sequence (1 - field stop – 1 – 1 - 2) again with no red fringe, which can be otherwise viewed as a remake of the old legendary Leitz Periplan GF (1 - field stop – 1 - 2).
All these eyepieces offer the highest contrast views on my 6” F/5 achromatic refractor, the Periplan Red Dot is at the moment on service with my Leitz microscope, performing great both on the Leitz achromatic, Fluoride, and full APO microscope eyepieces.
Other known CVD compensating eyepieces with the red fringe at the field stop are the Carl Zeiss Jena PK, which are the planar and compensating Abbe orthos, and similar compensating eyepieces from Zeiss West.

Thank you for reading,
JG

[j.gardavsky]

Hello all,

here is a pic of the red fringe, taken on a microscope,

Best,
JG