Anybody here know about IR image converter tubes? - Page 1
Forum section: electronics / general

author: Ben321
author_rank: Frequent Contributor
timestamp: August 03, 2025, 10:08:45 pm
content: Previously I had bought a Find-R-Scope IR viewer on eBay, which should work at up to either 1350nm or 1550nm, depending on the model. Unfortunately the objective lens assembly was missing, and didn't appear to be something I could buy as a replacement part on the FJW website. Eventually I gave up trying to repair it and I took it apart, to see just what was inside.The tube inside is actually not an FJW manufactured part. Instead it seems to come from a company I've never heard of before called Varo Inc. And it has a model number of 6914. Anybody here know anything about this Varo company, or the image converter tubes they make? I couldn't find any info about them online. I've seen similar tubes (nearly identical in structure) on eBay from a different company called Mullard, and they are stated to be from "Mk1 Infrared Binoculars" (which from further research appear to be 1970s night vision equipment), which makes me think Varo may also be a very old company, and that the Varo tubes used in the FJW IR viewers may be equally old, and that FJW was just disassembling old NV equipment to get the tubes (not contracting to Varo to make new tubes, because I can't find anything about that company online).I've attached a photo of my Varo 6914 tube here to this post. Any info you guys could share about these tubes and the Varo company would be nice.

author: Ben321
author_rank: Frequent Contributor
timestamp: August 03, 2025, 10:11:33 pm
content: Uh oh. It seems that the tube photo got autorotated to landscape orientation by the forum website script. My tube photo was taken with my phone in portrait orientation, and needs to be in portrait to be viewed correctly. Even downloading it doesn't fix this, as it seems my photo is processed irreversibly when it's uploaded. I had hoped it was just a viewing issue, that the image viewing in the browser would only be affected, but it seems the image file itself is altered permanently by the image uploading script on this forum.

author: Fraser
author_rank: Super Contributor
timestamp: August 03, 2025, 10:14:41 pm
content: 10 seconds of Googling….https://frank.pocnet.net/sheets/132/6/6914.pdf

author: Fraser
author_rank: Super Contributor
timestamp: August 03, 2025, 10:17:22 pm
content: And another 20 seconds of Googling …..http://lampes-et-tubes.info/ic/MIL-PRF-1-1049H.pdf

author: Fraser
author_rank: Super Contributor
timestamp: August 03, 2025, 10:18:52 pm
content: https://frank.pocnet.net/sheets/049/6/6914.pdfhttp://lampes-et-tubes.info/ic/6914.pdf

author: Fraser
author_rank: Super Contributor
timestamp: August 03, 2025, 10:24:09 pm
content: It looks as if VARO were naughty and got caught supplying “Uncle Sam” with sub standard components for night vision !….The following text was copied from here….https://www.justice.gov/archive/opa/pr/1996/July96/346.civ.htmlFOR IMMEDIATE RELEASE CIVTHURSDAY, JULY 18, 1996 (202) 616-2765TDD (202) 514-1888U.S. SETTLES LAWSUIT FILED AGAINST MILITARY CONTRACTORSWASHINGTON, D.C. -- Varo Inc., a subsidiary of ImoIndustries Inc., will pay the United States $2 million to settleallegations that Varo, its Ni-Tec division, and Optic ElectronicCorporation violated the False Claims Act by delivering to theArmy components for night vision equipment that did not meet thereliability and testing requirements of military contracts, theDepartment of Justice and the Dallas, Texas, U.S. Attorney'soffice announced today.Assistant Attorney General Frank W. Hunger of the CivilDivision and Dallas U.S. Attorney Paul E. Coggins said thesettlement resolves a qui tam false claims lawsuit broughtagainst Varo, Imo Industries Inc., Ni-Tec, Optic-ElectronicCorporation and six former or current Ni-Tec employees in U.S.District Court in Dallas, Texas. The suit was filed by a formeremployee of Ni-Tec, which Optic-Electronic founded in 1961 andVaro later acquired. Varo, Optic-Electronic and Ni-Tec arelocated in Garland, Texas.Varo will pay the United States $2 million to resolve thematter, while Imo, its parent, guaranteed the payment.The Department said the firms manufactured image intensifiertubes used in the Army's night vision goggles and aviator's nightvision imaging systems.A government investigation found that over several years thefirms submitted false quality control reports to the Army,including false failure analysis reports and false productassurance and test reports alleging that the components met allreliability requirements when in fact they did not.Hunger said the firms worked with the Army to recall andretest more than 1,000 image intensifier tubes from the Army'sinventory and replaced non-conforming tubes with those that metmilitary specifications.Night vision goggles are a light-weight night vision systemworn on the head that provides enhanced imagery so the wearer canperform such tasks as walking, driving, weapon firing, shortrange surveillance, map reading, vehicle maintenance andadministering medical aid with light from the moon and stars.The aviator's night vision imaging system is an image intensifiersystem used by military helicopter pilots to aid their visionduring low level flights at night.The qui tam provisions of the False Claims Act permit aprivate citizen to file a suit on behalf of the federalgovernment and collect a portion of the money if the government'saction is successful. The suit was filed in March 1995. Thegovernment intervened and took over the lawsuit on May 31, 1996.The case was jointly investigated by the Federal Bureau ofInvestigation's Dallas, Texas, office and the Defense CriminalInvestigative Service's Southwest Field Office at Fort Worth,Texas.#####96-

author: Ben321
author_rank: Frequent Contributor
timestamp: August 03, 2025, 10:26:33 pm
content: Quote from: Fraser on August 03, 2025, 10:14:41 pmNot the same tube. It has a hard cutoff at 1200nm. The tubes used in FJW equipment are from Varo, and have sensitivity up to either 1350nm or 1550nm (depending on which tube is being used). I'd be curious about the tube maker Varo too, not just this specific tube. Duckduckgo isn't finding anything about the Varo tube making company.

author: Fraser
author_rank: Super Contributor
timestamp: August 03, 2025, 10:30:23 pm
content: IMO Industries…..Public CompanyIncorporated: 1901 as De Laval Steam Turbine CompanyEmployees: 7,400Sales: $928 millionStock Exchanges: New YorkSICs: 3829 Measuring & Controlling Devices Nee; 3511 Turbines & Turbine Generator Sets; 3566 Speed Changers, Drives & Gears; 3826 Analytical Instruments; 3714 Motor Vehicle Parts & AccessoriesImo Industries, Inc. is a leading producer in a number of domestic and international industrial, defense, transportation, commercial aviation and marine, utility, and process, oil, and gas markets. Imo’s Instruments and Controls Business manufactures a wide range of analytical and optical instruments and electronic and mechanical controls, while its Power Systems Business provides an array of engineered power products and services to customers around the globe.Imo Delaval, Inc., renamed Imo Industries, Inc. in 1989, was created as a public company in December 1986, when Trans-america Corporation, which had acquired the De Laval Steam Turbine Company in 1962, distributed Imo stock to its shareholders on a one-for-ten basis. (Since then the stock has been traded on the New York Stock Exchange with the symbol IMD.) In 1986 Imo Delaval, with 21 plants in North America and Europe and close to 3,500 employees, had revenues of $358 million. The newly independent company launched an aggressive strategy on several fronts. Through the late 1980s and early 1990s, Imo actively sought to acquire companies involved in related business areas to strengthen and enhance existing product and service lines. Continuing the company tradition, resources were dedicated to development of engineering applications and solutions in a number of areas, including efforts to respond to worldwide environmental concerns.Imo’s long-established reputation and stability have been grounded in the success of its turbines, compressors, pumps, and motion control equipment, which are still produced by Imo companies, including Delaval Turbine, Imo Pump, Warren Pumps, Boston Gear, and Delroyd Worm Gear, and still account for almost two-thirds of its operations. The energetic acquisitions campaign of the late 1980s has effected a greater diversity in current activities. Revolutionary night vision and laser systems produced by new subsidiaries Baird (acquired in 1987) and Varo (acquired in 1988) have made Imo a major force in electro-optical systems. A one-piece door lock developed by Roltra, a major supplier to Fiat and 100 percent Imo-owned since 1991, has attracted attention in European and other automobile markets. Other products such as sensors and pressure switches from Gems Sensors (acquired in 1969) and Barksdale (acquired in 1964), respectively, have been redesigned for detecting leaks in underground storage tanks and piping systems. A Gems electronic liquid level switch has been instrumental in revolutionizing Freon gas recycling and recovery systems. In the 1990s, with billion dollar sales, Imo Industries management sees its role as providing strategic direction and support for its some two dozen quasi-independent operations.VARO……Beginning in 1987, the newspapers bristled with accounts of Imo acquisitions, large and small. Among the largest were Baird Corporation (1987, $55.8 million), manufacturer of spectrometers and optical systems; Incom International Inc. (1987, $145.8 million), a group of manufacturers of electronic controls and power transmission devices; and Varo (1988, $117 million), a major supplier of night vision equipment to the military. Less costly but important acquisitions included Warren Pumps and Roltra (1989), Quabbin Industries (1990), an aftermarket service company and producer of retractable seals to increase turbine efficiency, and Opto-Electronic Corp., which was merged with Varo.Earnings in the early 1990s were depressed. Gross profit margins slipped from 29.1 percent in 1989 to 25.8 percent in 1991. Paying down accumulated long-term debt from its acquisition program and lessened potential recovery momentum. However, the company expects to offer some long-term protection from up-and-down behavior in various markets with its carefully developed multiple-niche strategy. W. J. Holcombe continues as chief executive officer and chairman of the board.Company-wide efforts remain directed toward increasing the competitive advantage through marketing initiatives and manufacturing efficiencies and diminishing the effects of market fluctuations. The year 1991 saw a nine percent workforce reduction as manufacturing processes designed to increase productivity and reduce lead times were implemented. Streamlining strategies have also resulted in the integration of like operations such as the combining of Varo and OEC (Electro-Optical Systems) and the consolidation of a new Turbo-Care group. Multi-division marketing such as the recent Pacific-area program based in Singapore exemplifies the company’s efforts to reach expanded global markets.One-third of operations are attached to military contracts, including ongoing programs such as night vision and laser equipment. Aerospace product development has been increasingly targeted to commercial aviation customers. And there is a recent focus on products for transportation, industrial, utility and co-generation, and oil, gas, and process markets that stress efficiency and environmental initiatives that may underscore stability and contribute to long-term profitability and recovery.

author: Ben321
author_rank: Frequent Contributor
timestamp: August 03, 2025, 10:33:24 pm
content: Quote from: Fraser on August 03, 2025, 10:30:23 pmWhere did you find that article? Thst also explains why I can't find anything about that company. Apparently they are now owned by Imo, a different company.

author: Fraser
author_rank: Super Contributor
timestamp: August 03, 2025, 10:34:59 pm
content: Ben321,Do not believe everything claimed !For information, small changes in materials can enhance performance but the basic mechanics and needs of the tube made by other manufacturers remain valid.

author: Fraser
author_rank: Super Contributor
timestamp: August 03, 2025, 10:36:27 pm
content: https://www.encyclopedia.com/social-sciences-and-law/economics-business-and-labor/businesses-and-occupations/imo-industries-inc

author: Fraser
author_rank: Super Contributor
timestamp: August 03, 2025, 10:43:42 pm
content: Find-R-Scope are made by FJW not MFJ.I found FJW kit to be marginal in terms of wavelength coverage as performance trailed off rapidly as you approached SWIR.Good kit for up to 1000nm but not great after that in my experience. That tallies with the tube specs I have found. Some tubes might be tweaked or “selected on test” for better coverage but I would not get excited about these FJW units. Better cameras used the SWIR vidicon tubes rather than IR converters like the 6914.

author: Fraser
author_rank: Super Contributor
timestamp: August 03, 2025, 10:49:39 pm
content: From the current FJW web site. Note the description next to the different models, testing method and typical spectrum response plot provided…..https://fjwoptical.com/products/fjw-find-r-scope-infrared-ir-handheld-viewer?variant=45317599363225

author: Fraser
author_rank: Super Contributor
timestamp: August 03, 2025, 10:57:17 pm
content: The choice of lens material may also dictate whether the scope is standard 1350nm, or the enhanced response to 1550nm. The choice of lens is the wavelength limiting factor on the vidicon type SWIR cameras as well.

author: Ben321
author_rank: Frequent Contributor
timestamp: August 03, 2025, 11:04:47 pm
content: Quote from: Fraser on August 03, 2025, 10:43:42 pmOops. Sorry. I was using the wrong name. You're right that it is FJW not MFJ (MFJ makes ham radio stuff).

author: Ben321
author_rank: Frequent Contributor
timestamp: August 03, 2025, 11:15:41 pm
content: Quote from: Fraser on August 03, 2025, 10:57:17 pmSince FJW explicitly has 2 product lines for 1350nm and 1550nm maximum wavelength (and this is for the viewer, indepentent of the lens), I assume this is a tube spec. Either FJW is testing old tubes they got their hands on to see if some of them are better than spec, and then putting those that are significantly better than spec in the 1550nm units, or else they specifically know that different manufacturers made tubes with different compositions of photocathode (even if they have the same part number for the tube), and so FJW is using one manufacturer's tubes for the 1350nm Find-R-Scopes and a different manufacturer's tubes for the 1550nm Find-R-Scopes. For example, Varo may have made tubes with photocathodes made out of one material, but a different company may make their tubes with photo cathodes made out of a different material.Or else FJW has a contract with one company (maybe the successor to the company Varo, but still carrying Varo branding on the tubes) to make 2 different product lines of tubes, and one is explicitly made for up to 1350nm sensitivity and the other is for up to 1550nm sensitivity.

author: Ben321
author_rank: Frequent Contributor
timestamp: August 03, 2025, 11:32:02 pm
content: Quote from: Fraser on August 03, 2025, 10:57:17 pmBut this is usually an issue over about 2000nm, I think. Standard optical glass lenses usually work up to like 1900nm without too much reduction in transparency at that wavelength, right?

author: Fraser
author_rank: Super Contributor
timestamp: August 03, 2025, 11:48:45 pm
content: This RCA document does not really help you determine the exact materials used. But may be of interest to you as it shows the various “S” spectral responses.https://www.worldradiohistory.com/BOOKSHELF-ARH/Technology/RCA-Books/RCA-Tube-Handbook-HB-3-Vol-3-4.pdfhttp://tubes.tubeampdesign.com/sheets/049/suppinfo/rca_hb3_pdg.pdf

author: Fraser
author_rank: Super Contributor
timestamp: August 03, 2025, 11:56:13 pm
content: All references that I can find seem to confirm that he “6914” tube is an S1 spectral response. If it were a different spectral response I would expect it to have either some unusual suffix or a completely different part number. As I said previously, FJW can claim a spectral response but what is the sensitivity at that stated wavelength ? It can be so poor that the manufacturers specifications and spectral plots do not show it. A bit like a paper clip can be used as an antenna on a 50 Ohm HF receiver input …. It functions as an Antenna to some extent at HF, but just not very well !

author: TimFox
author_rank: Super Contributor
timestamp: August 03, 2025, 11:58:19 pm
content: I remember buying high-voltage rectifier stacks from Varo in the 1970s--probably intended for use in night-vision equipment.

author: Fraser
author_rank: Super Contributor
timestamp: August 04, 2025, 12:06:15 am
content: So spectral response compared to FJW plot. Note the relative sensitivity figures on the left scale. The 6914 is supposed to provide peak performance at 800nm and falls off above that. Different scales can make plots look very different so look at the scale and detail contained.

author: OhmBob
author_rank: Newbie
timestamp: September 03, 2025, 07:18:34 am
content: Interesting find! Varo Inc. was indeed a real company — they were active mainly in the 1960s–1980s as a manufacturer of electro-optical components, including image intensifier tubes, photocathodes, and night-vision assemblies. They were eventually acquired (or their product lines absorbed) by EG&G, and later some of that technology ended up under L3 (now L3Harris). Your 6914 tube is very likely a Gen 1 or early Gen 2 image converter, judging by the construction you described.These tubes were common in early IR viewers and night scopes like the Mk1/Mk2 binoculars you mentioned. They’re usually 1st generation electrostatic-focus tubes with S-20 photocathodes, so they work best with IR sources around 800–900 nm, though some were optimized for slightly longer wavelengths. Unfortunately, most of these tubes are no longer made, so sourcing an exact replacement is difficult — you’d need to watch surplus markets or eBay for NOS (new-old-stock).