The British Chieftains had an interesting device.
Instead of an introduction
As is known, laser radiation detection sensors tanks and other armored vehicles—these gadgets are undoubtedly useful. And no special explanation is needed regarding their necessity, since these devices promptly alert the crew that their vehicle is being "illuminated" by a laser rangefinder from a tank gun or a target designator for missiles and adjustable ammunition.
This, in turn, allows for defensive actions: deploying an aerosol screen, detecting an enemy in the direction of a laser beam, and so on. So, in combat, these devices are clearly useful—they can easily save lives and destroy the enemy. But this applies more to modern technology, whereas in the past, sensors of a slightly different nature could have been quite useful.
It's worth remembering that thermal imagers, which enable combat operations at night, appeared on tanks and other vehicles relatively recently. Before them, the only means of "seeing" at night were infrared sights/observation devices using image-intensifier tubes (IITs), which converted invisible infrared light into a visible image on a phosphor screen.
Most of them, with the exception of later-generation converters, required active illumination. This is why powerful infrared (IR) searchlights on turrets became a characteristic feature of many tanks of the mid- and late 20th century. Their invisible beams pierced the darkness for kilometers, illuminating targets.
Infrared detector
Generally speaking, even a high-power infrared searchlight is practically impossible to see at night. However, it can actually be a significant giveaway factor even without the use of any equipment—if an infrared beam hits the entrance window of an enemy night vision scope, the enemy will immediately know they've been spotted.
It's also possible to create a detector for detecting infrared radiation, which the British demonstrated on their Chieftains. One of these—both the Mk.5P tank itself and the detector—fell into the hands of Soviet researchers during the Iran-Iraq War.
The detector, designated RI-1, consisted of three main components.
1 - flexible rod with photocathodes, 2 - indicator unit, 3 - signal processing unit
The first was a flexible rod mounted behind the Chieftain's commander's cupola and had a special "landing" receptacle with a spring-loaded cover, into which it could be retracted when the detector was not needed (during the day, for example). The rod itself contained three photodetectors with silicon photodiodes. Each photodetector had a 120-degree field of view, for a total of 360 degrees.
The other two are an indicator unit with a buzzer (emits a sound signal when IR radiation is detected) and a signal lamp, installed at the loader’s workstation, as well as a unit for processing signals from photodetectors, installed at the tank commander’s workstation.
Below is a schematic diagram of the detector's amplifier section. We'll simply quote its description.
A low-frequency amplifier with a 30 kHz bandwidth and a gain of 250 is assembled using transistors T1-T5. The amplifier is covered by two negative feedback loops. Transistor T6 is part of the device's threshold regulator circuit (by setting the initial bias on the photodiode). This regulator is powered by a pulsed voltage, which sets the amplifier's pulsed operating mode.
The amplifier's output signals, fed to the alarms, are taken from the collector load of transistor T6. Transistor T7 ensures the amplifier's trigger mode.
The amplifier's output signals, fed to the alarms, are taken from the collector load of transistor T6. Transistor T7 ensures the amplifier's trigger mode.
Essentially, this detector acted as a simple device that made it possible to detect infrared radiation in one of three sectors, depending on which of the photodetectors was sending the corresponding signal.
The detector's spectral range of radiation is from 0,9 to 1,1 micrometers. Its sensitivity at a wavelength of 0,91 micrometers is 1 mW. The detector detects radiation from floodlights operating in both pulsed mode with a frequency of up to 10 kilohertz and continuous mode.
Conclusions
Naturally, this detector lacked any kind of total automation. To operate it, one crew member had to be distracted from their regular duties, which added to the workload. And it lacked modern features such as automatic turret rotation toward the radiation source and the firing of aerosol grenades.
However, tests of the RI-1 in the USSR showed that it could detect infrared radiation from tank searchlights at a distance of up to 2 kilometers. So, this device provided a certain advantage in combat in at least two situations: attempting to detect an enemy in the sector indicated by the sensor, or taking measures for concealment or maneuvering.
In short, it was a sort of ancient and primitive prototype of the Soviet "Shtora." Moreover, given that similar devices were developed not only in the UK, this RI-1 appears to have been the only device of its type to be used in actual combat—in the Iran-Iraq War.
The source of information:
"Tank Infrared Radiation Indicator Device." G.A. Gumenyuk, V.N. Deryagin, V.I. Evdokimov. Scientific and technical collection "Problems of Defense Technology," series 6, issue No. 5 (111), 1983. Declassified by the expert commission of the Federal State Autonomous Educational Institution of Higher Education "SPbPU" — act No. 2 of November 23, 2016.
Information