Nitewalker
Feb 17, 2020
Updated: Jan 18, 2021
There have been and still are rumors being spread that modern L3Harris unfilmed image tubes wear out faster than thin filmed. I've heard this directly from reputable dealers and people in the industry, however, these sources sell thin filmed tubes that compete against filmless. Recently, a well known dealer put an actual number on it, saying they lose 20% of their performance after 500 hours. That is highly unlikely as the Omnibus contracts (Mil-Spec) call for 10,000 hour usable life. These tubes are ultimately made for the military and L3 MUST meet that requirement. In the very early days of unfilmed they did have a significantly shortened lifespan and this is where these rumors originate from.
I heard how awesome unfilmed white phosphor was when I first got into night vision, however, I avoided it because of what I was told. Fast forward to 2019 and after speaking to several people in the industry, including someone at L3Harris, I decided to buy high spec unfilmed white phosphor. The image quality and performance blows away every thin filmed tube I'd used thus far. Looking back at it, I'm pretty pissed at myself for not doing it sooner.
Anyways, this came up recently on the AR-15 night vision forum, and TNVC got a written statement from L3. Technically, they are L3Harris since merging with Harris. For those not familiar, Harris had to sell their night vision division (former ITT) to Elbit Systems of America, in order for the merger to happen. So, Harris night vision tubes are now Elbit Systems of America, and L3 is L3Harris.
Publicly shared statement from L3Harris to Sam Houston of TNVC:
Sam,
The engineers we sent to SHOT were hearing similar BS.
1) As you know, we are required to run sample units on lifetime reliability. The reliability requirement is 1500 hours on “accelerated reliability”. The accelerated profile is supposed to represent 10x acceleration over typical real-world use. This is possibly one source of mis-information. Each hour on the test box is supposed to be equivalent to ~10 hours of “real world” use. The profile is in the various MIL-PRFs. Note: the US Army designed the test, not the manufacturers.
I pulled the last three months of complete data for the unfilmed product. On average, gain INCREASED 18% at 1500 hours, and SNR went down 1.2%. That’s only 15 tubes, because we only run 5 a month, and even the accelerated test takes around 3 months to complete. Next time you or anyone else from TNVC is in the factory, I will be happy to show you the equipment, as well as share some of the performance graphs.
Now, the original unfilmed tubes from the late 90s early 2000s had serious lifetime issues. I remember ITT built some that lasted around 200 hours. The early Litton/L-3 ones were better, but honestly not by much. I’m told we got 500 hours, but the yield to get there was terrible. That was 15-20 years ago though. The tech is completely different now, and has been for many years.
Also, the US Air Force would not have given us a $93 million contract for high-FOM unfilmed tubes if they had lifetime reliability problems.
Contracts are public record, but just in case you need a link here is a news article:
Mark E. Horning
Sr. Engineer – Integrated Vision Solutions
Electron Tube Operations
COMMUNICATION SYSTEMS / L3HARRIS TECHNOLOGIES
1215 S. 52nd St / Tempe, AZ 85281/ USA