Infrared technique: period 1934 – 1959
In 1934, the Commission for Physical Armorment of the Ministry of War was requested to conduct experiments with invisible rays. They wanted a means of detection to be able to observe enemy ships by night and in mist. This could activate the river barriers with ground mines. In 1936, the first tests were taken with an infrared flashing light (see also: “Background: what is infrared?” at the bottom of this page). The receiver used a so-called talloid cell.
A period of trials and improvements followed between 1937 and 1939. Among other things, experiments were done with multiple infrared beams across the river so that the right mine of the barrier would explode at the right time. In 1939, the Artillery Establishments commissioned the manufacturing of the system by with NV Nederlandsche Instrumentenfabriek Waldorp in The Hague. The system was used by the Corps Pontoon laying and Torpedoists. In the May days of 1940, the system was used as a river barrier across the river Merwede (without connected mines).
In 1935, experiments with infrared photography were carried out for a short period for the Royal Netherlands Navy. A limited improvement in vision was observed as compared to ordinary photography in the event of a clearing.
In July 1938, initial tests were conducted with an infrared viewer developed by Philips. The tests were not convincing although the importance of the invention was recognised. Immediately after the liberation of the Netherlands, new experiments with the improved infrared viewer were carried out in 1946 – 1947. In 1948, a device for detection at night was developed using a searchlight. All the light from the visible spectrum was filtered out while maintaining the infrared spectrum. The idea was very sound, and a lot of the research was spent to optimising the design, by researching the needed filters, tubes for image conversion, types of searchlights etc. The Royal Netherlands East Indies Army (KNIL) needed such equipment to track down people in the jungle.
After WWII, the infrared investigations for the Navy were picked up again, especially to be able to determine the detection distance to ships at sea using passive means at night. In 1947, ships at Scheveningen were detected up to a few kilometres away with infrared observation using a platinum bolometer and an old German 60 cm diameter searchlight mirror. The conclusion was that infrared scanning would work fine ashore, but on a floating platform stability issues would arise given the long processing time.
In 1957, with a self-developed highly sensitive Golay detector (wiki: Golay), the observation distance of ships was increased to 15 kilometres as was evident from experiments at Kijkduin.
In 1957, work started on the development of semiconductor bolometers and photocells based on PbSe, PbS, CdSe and InSb.
T. Nooijen (2015), Physics Research at RVO-TNO during the early cold war, Univ. of Utrecht (pdf)