Stereo comparator
The stereo comparator is a measuring device for determining image coordinates on photographic plates or films . It is used in astronomy and photogrammetry .
The device invented by Carl Pulfrich is based on binocular vision ( stereoscopy ) and, in its simple design, is a table-top device. The blink comparator marks the astronomer's point of view where a star has moved or is only contained in one of the two images ( asteroid , comet, etc.). There is a monocomparator for evaluating individual plates .
For the evaluation of aerial photos of the map production and for higher accuracies (up to 0.001 mm = 1 µm), some global companies produced large floor-standing devices. The observer operates the image coordinates x, y with handwheels and the height or parallax with a foot disk.
Since the visual evaluation of detailed aerial or star photographs took up to several hours, the analog (photographic) method of recording and evaluation was replaced by digital methods.
literature
- Lieuwe Evert Willem van Albada: Stereophotography - Astrophotography - The projection system . In: Scientific Applications of Photography . Part 1. Verlag der H. Lindemanns Buchhandlung, Stuttgart 1992, ISBN 3-928126-24-5 , p. 87 f .