Last year, SRI International marked its 70th anniversary as a non-profit research organization. Initially conceived as the Stanford Research Institute with a building in Palo Alto, California, it separated from its university patron in 1970. It hosts an IEEE Milestone for helping to create the first link of the Internet in 1969, and can look forward to at least one more for creating Siri, which it licensed to Apple. Today it employs more than 2,100 people in 19 locations.
One of those locations is in West Windsor, New Jersey. Since 2011, SRI International has run what used to be RCA Laboratories, which is five years older than its owner. Renamed the David Sarnoff Research Center in 1951, and Sarnoff Corporation in 1997, the facility is renowned for its work in video systems and devices, for which it has been awarded ten Emmys and three IEEE Milestones.
Nonetheless, the buildings are the same ones that RCA constructed between 1941 and 1966, and some members of the staff can still recall when they worked for “the most trusted name in electronics.” The site hosts IEEE Milestones for electronic color television, liquid crystal displays, and the TIROS weather satellite, and is eligible for any number of other inventions and innovations, from blue LEDs to combinatorial chemistry. For its diamond anniversary, however, let’s go back to its first five years, when its research staff helped the United States triumph over the totalitarian threats to democracy in Europe and self-determination in Asia.
At the time, RCA Labs already had a government contract for the development of improved sensitivity, resolution and signal-to-noise levels in video cameras. Since 1934, when Vladimir Zworykin first proposed TV-guided aerial weapons using his new Iconoscope video image tube, RCA engineers, in their Camden labs, had been working through the issues associated with transmitting and receiving video signals to and from an airplane. Working with RCA Victor engineers, the fledgling Princeton group refined the camera’s operation using a variety of imagers-both Zworykin’s iconoscope and Albert Rose’s second-generation orthicon. The former offered more resolution, the latter more sensitivity, but neither was very effective amid the atmospheric effects seen during flight.
In 1943, Rose, Paul Weimer, Harold Law, and their technicians at the RCA Labs invented the image orthicon, a 43cm-long vacuum tube imager that was 100 times more sensitive than its predecessors were.
Through the manipulation of electrons stimulated by contact with photons from an image on a sensitized thin glass screen, and their migration to an electrode scanned by an electron beam, an electronic image was amplified before its transfer as a signal to be further amplified in a cascading series of electrodes. The sensitivity was such that Ray Kell, who led the group designing the camera, could be clearly identified by the light of the moon.
RCA delivered 250 image orthicon cameras to the U.S. Navy and Air Force, which tested them on Nazi German targets in France and imperial Japanese targets on southwest Pacific islands. The military effect of TV-guided weapons was not significant for both technical reasons of transmission and political reasons of Air Force identity-who needed heroic pilots if bombs could be controlled remotely? Nonetheless, the TV-guided drones became increasingly effective with pilot experience and technical refinement. By the war’s end, Rose, Weimer, and Law had developed the MIMO, the miniature image orthicon, a version reduced to the size of a fat cigar that, with its electronics, fit in the nose of a 2,000-pound GLOMB, or glider bomb.
The image orthicon had significant technical and social impacts after the war, but not without challenges. In 1946-47, it was the most complex and expensive electron tube for sale, and Otto Schade, working for the labs out of RCA’s electron tube plant in Harrison, New Jersey, had corrected the iconoscope’s major flaws with patents during the war. RCA’s National Broadcasting Company (NBC) was not enthused about paying a premium for the image orthicon tubes, which needed regular replacement, when cheaper iconoscopes got the job done.
Only a decree from above resulted in NBC swallowing the charges and using the new tube “with the eyes of a cat,” as the ad copy from J. Walter Thompson touting RCA’s innovation proclaimed.
The “Immy” – industry shorthand for image orthicon - also became the namesake for the Academy of Television Arts and Sciences’ award, represented by a winged woman, the muse of art, upholding a ball of orbiting electrons. In 1948, film editor and television engineer Louis McManus submitted the winning design for a television award modeled on the Academy of Motion Pictures Association’s Oscar. McManus’ wife, Dorothy, posed for the statuette, but neither her name nor “Dottie” was the right sobriquet for the award. What to call it, then? While the academy’s president lobbied for an “Ike,” in honor of the fading Iconoscope, that nickname was already reserved for General Dwight Eisenhower. On the other hand, for engineers like Harry Lubcke, maintaining the new TV cameras, “gimme an Immy” was a common expression when replacing the tube. “I” soon became “E” and the image orthicon’s legacy in broadcasting looks to continue indefinitely.
Efforts to miniaturize the tube into the MIMO, and the mastery of return-beam scanning aided Paul Weimer and his team in developing the vidicon. This simpler, smaller photoconductive tube relied on extremely thin targets of amorphous selenium for photons, reducing to practice the material that stimulated efforts to invent television cameras in the 1870s. Iterations of and variations on the vidicon, notably Philips’s Plumbicon, ultimately succeeded the Immy in broadcast cameras in the 1960s. Vidicons also enabled the development of portable TV cameras and electronic news gathering in the 1950s, space-based video and reconnaissance in the 1960s, and portable and home video revolutions during the 1970s.
Yet the legacy of RCA Labs’ 1940s video camera tubes persisted well beyond that technology. In 1959, Weimer received RCA’s European fellowship. He chose to spend his year learning semiconductor physics with Pierre Aigrain at the Sorbonne, because he could see that “semiconductors were a coming thing.” On returning to the Labs, Weimer joined the crowd trying to integrate silicon transistors in a circuit, but it soon occurred to him that a thin-film integrated circuit might be a cheaper approach if he could make a thin-film transistor (TFT) to go with the thin-film resistors and capacitors already available.
Weimer’s recent training and his long experience in evaporation techniques for thin films in the both the monochrome and color vidicons made him the ideal person for this task. He and his team used cadmium sulfide, a semiconductor heavily researched for vidicon targets, and the “same stretched-wire masking jig which had been built for producing color filter patterns in the early tricolor vidicon served to define the source, drain, and gate in the TFTs.” Weimer presented his findings at the IRE-AIEE Device Research Conference at Stanford in June 1961, and follow-ups won best papers at the 1963 and 1965 International Solid-State Circuits Conferences. Less publicly, his group received a series of contracts with Wright-Patterson Air Force Base over ten years to develop a solid-state image sensor “using the new integrated circuit techniques.”
In continuing their research on thin-film semiconductors, Frank Shallcross found that cadmium selenide (CdSe) also worked as an n-type transistor, while Weimer found that lead sulfide could be evaporated as a p-type transistor. When he took his complementary insulated gate flip flop to RCA’s relevant patent attorney, Weimer recalled that “his eyes got big and he said, “Make it as big as you can.'” Note that Weimer added silicon as a potential n-type and p-type transistor a day after the initial notebook entry; the disclosure is stapled to the reverse, and the patent issued three years later.
TFTs did not attract much interest until the challenge arose to address liquid-crystal displays in the early 1970s. Weimer actually filed for a patent in 1967 on a flat-panel display using light cells of “any type which emits light under the control of a voltage, e.g. . . . liquid crystal cells which control the passage of light through them” using his CdSe TFTs. Fabricating an integrated circuit large enough to exploit this approach defeated the Labs’ Bernard Lechner, however, who concluded his leadership of the effort to make an LCD television in 1970. He and his team wrote an article on active-matrix addressing that included the use of TFTs before Weimer’s patent issued or Westinghouse’s Peter Brody made public his successful LCD efforts using CdSe TFTs.
Although most TFTs now use amorphous silicon instead of II-VI semiconductors, they persist well into the 21st century. Like the image orthicon behind the Emmy statuette, however, this legacy of RCA Laboratories’ video research lies concealed, under the LCD and OLED panels of our smartphones, monitors, and televisions.
All images courtesy David Sarnoff Library with the exception of the Emmy illustration.
- Cherie Kagan and Paul Andry, eds., Thin-Film Transistors (2003).
- Alexander B. Magoun, David Sarnoff Research Center: From RCA Labs to Sarnoff Corporation (2003).
- Richard C. Webb, Tele-Visionaries: The People Behind the Invention of Television (2005).
- Paul K. Weimer, an oral history conducted in 1975 by Mark Heyer/Al Pinsky, IEEE History Center, Hoboken, NJ, USA.