US Army MILES Photodiode  
Written by AnubisTTP on 2023-10-02  



This large photodiode has a more interesting pedigree than one would expect... it was built to take part in the planet's most sophisticated game of laser tag. The Multiple Integrated Laser Engagement System, or MILES, was a program started in 1978 by the United States Army with the goal of using lasers for simulated combat exercises. Soldiers would wear special attachments on their helmets that were ringed with these photodiodes, which could detect bursts of laser light from modules that could be attached to the barrel of an M16 rifle. As would be expected from the US Army, this photodiode looks like something the Klingon Empire would build if it developed a sudden interest in optoelectronics. The large diode die is encased in a heavy three piece metal enclosure with a glass cavity window. The cavity window is traced with a fine grid of wires, most likely to provide an extra layer of electromagnetic shielding to the semiconductor within. In operation the entire diode would be covered with a dark plastic dome, which would filter out ambient light and prevent false positives. We have been unable to date this part; the MILES system underwent many revisions over the years and is still in use today.

Early MILES battle simulations were allegedly fraught with the types of problems familiar to anyone who played laser tag in the 1980's, including 'zombie' soldiers, who could continue to fight after being killed. By the mid 1980s a loud alarm was added to the sensor system to prevent this, which could only be silenced by inserting a key into the control box for the sensors. The same key was also required to activate the laser on the soldier's rifle; when a soldier was 'killed', the key would have to be removed from the rifle to deactivate the buzzer on the sensor control unit, rendering the rifle inoperative in the process.


US Army MILES Photodiode
US Army MILES photodiode. The MILES system was a form of laser tag used by the US Army for training and battle simulations.

US Army Multiple Integrated Laser Engagement System Photodiode
This MILES photodiode contians a protective screen embedded in it's glass window.

US Army Multiple Integrated Laser Engagement System Abrams Computer
The MILES system was also designed to be used with vehicles. Shown here is a MILES photodiode next to the control display unit for a US Army Abrams tank.

US Army MILES Control Indicator
First-generation vehicle mount MILES control display unit, shown with several PCBs removed. This unit was produced by Xerox in 1979.

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