Optical multiple-reflection arrangement

An optical multiple-reflection arrangement having first and second reflection devices at respective ends of a measurement path and having a light source at one end of the measurement path, the light source and the reflection devices being so constructed and arranged that a light beam starting from the light source passes at least four times through the measurement path before it passes out of the latter, the first reflection device disposed at the end of the measurement path remote from the light source comprising a lens having a focal length equal to its distance from the light source, behind this lens a first retroreflecting element which reflects an incoming light beam in the same direction but offset laterally, and light beam deflection means which impart to at least one of the incoming and outgoing beams of the retroreflecting element a deflection such that the image made of the light source by the reflection device lies at the side of the light source;

• the second reflection device being a second retroreflector disposed near, and outside the plane of the image made of the light source by the first reflection device.