Electronic Television — Invented at 21 by a Farm Boy Who Drew It in a Potato Field
Philo Farnsworth's 1930 patent describes the image dissector — the all-electronic camera tube that captured the first fully electronic television image, invented by a 14-year-old Idaho farm boy who conceived it while plowing rows of potatoes.
Original patent title: “Television system”
What this patent covers
The actual claim
This patent describes an electronic camera tube called an image dissector. A lens focuses an image onto a photosensitive surface (cathode) at one end of a vacuum tube. The photosensitive material emits electrons in proportion to the light intensity at each point — a process called the photoelectric effect. These electrons form an 'electron image' (a spatial pattern of electrons matching the light pattern of the original scene). A magnetic field deflects the entire electron image across a small aperture (the 'dissector aperture') — by varying the magnetic deflection, different points of the image are swept across the aperture sequentially, and a detector behind the aperture produces an electrical current proportional to the brightness at each scanned point. This current, varying over time, is the video signal.
What this patent does NOT cover
The boundaries
- The cathode ray tube (CRT) display — Farnsworth's patent covers the camera pickup tube, not the display
- Vladimir Zworykin's iconoscope (RCA's competing camera tube) — a different all-electronic design that RCA claimed predated Farnsworth's work
- Color television — the image dissector was a black-and-white device; color encoding systems came later
- Modern image sensors (CCD, CMOS) — solid-state electronic successors to vacuum tube camera technology
These exclusions are unique to PatentBrief — derived from the actual claim language, not patent-office boilerplate.
What made this novel
Farnsworth conceived the image dissector at age 14, in 1921, while plowing rows of potatoes on his family's farm in Rigby, Idaho. He realized that an image could be captured and transmitted electronically by scanning it line by line — exactly like the rows of crops he was plowing. He drew diagrams for his high school chemistry teacher, Justin Tolman, who later provided crucial testimony in the patent dispute with RCA. Farnsworth built a working prototype in 1927, at age 21, with funding from San Francisco investors. On September 7, 1927, he transmitted the first fully electronic television image — a single straight line. When his investors asked 'When are we going to see some dollars in this thing?', he transmitted a dollar sign.
Schematic visualization of the patent's claim structure. Hand-drawn diagrams in progress for each landmark patent.
Where you've seen this
Real-world examples
The first fully electronic television image was transmitted by Farnsworth on September 7, 1927, in his lab at 202 Green Street, San Francisco — over 90 years before 4K TVs would display the same scene in 8 million pixels
RCA's David Sarnoff offered to buy Farnsworth's patents for $100,000 and hire him as an employee — Farnsworth refused; RCA instead launched a patent interference challenge that Farnsworth ultimately won based on his teacher's testimony and 1922 drawings
Farnsworth's patent victory forced RCA — the dominant electronics company of the era — to license his technology, one of the few times an independent inventor defeated a major corporation in a patent battle of this scale
Why it matters
The bigger picture
Farnsworth is one of history's most poignant inventor stories. He conceived television at 14, built it at 21, won his patents against RCA, and licensed his technology — then watched as World War II halted commercial television development for six years, causing his patents to expire before he could profit from mass-market TV. He earned less from television than any major inventor of a world-changing technology. He suffered a breakdown in the 1940s and spent his later years working on nuclear fusion. He died in 1971, and his wife Elma ('Pem') said that when he first saw the moon landing on television — the culmination of a medium he invented — he turned to her and said it had all been worth it.
Filed
January 7, 1927
Granted
August 26, 1930
Claim 1 — Plain English
What this patent covers
This patent describes an electronic camera tube called an image dissector. A lens focuses an image onto a photosensitive surface (cathode) at one end of a vacuum tube. The photosensitive material emits electrons in proportion to the light intensity at each point — a process called the photoelectric effect. These electrons form an 'electron image' (a spatial pattern of electrons matching the light pattern of the original scene). A magnetic field deflects the entire electron image across a small aperture (the 'dissector aperture') — by varying the magnetic deflection, different points of the image are swept across the aperture sequentially, and a detector behind the aperture produces an electrical current proportional to the brightness at each scanned point. This current, varying over time, is the video signal.
The clever bit
Farnsworth conceived the image dissector at age 14, in 1921, while plowing rows of potatoes on his family's farm in Rigby, Idaho. He realized that an image could be captured and transmitted electronically by scanning it line by line — exactly like the rows of crops he was plowing. He drew diagrams for his high school chemistry teacher, Justin Tolman, who later provided crucial testimony in the patent dispute with RCA. Farnsworth built a working prototype in 1927, at age 21, with funding from San Francisco investors. On September 7, 1927, he transmitted the first fully electronic television image — a single straight line. When his investors asked 'When are we going to see some dollars in this thing?', he transmitted a dollar sign.
What it does not cover
- The cathode ray tube (CRT) display — Farnsworth's patent covers the camera pickup tube, not the display
- Vladimir Zworykin's iconoscope (RCA's competing camera tube) — a different all-electronic design that RCA claimed predated Farnsworth's work
- Color television — the image dissector was a black-and-white device; color encoding systems came later
- Modern image sensors (CCD, CMOS) — solid-state electronic successors to vacuum tube camera technology
Patent Journey
From filing to expiry
Patent Filed
1927
Patent Granted
1930 · 4yr after filing
Patent Expired
1947
PatentBrief Score
Impact Score
Early stage
Citation count
22/40
Moderately cited
Claim breadth
0/20
Narrow claims
Recency
0/20
Older than 20 years
Assignee scale
0/20
Independent or smaller assignee
PatentBrief Impact Score — based on citation count, claim breadth, recency, and assignee scale. Not a legal assessment.
Glossary
Key terms defined
- electron image
- The spatial pattern of electrons emitted by the photosensitive surface, corresponding to the bright and dark areas of the scene being filmed
- image dissector
- Farnsworth's camera tube — a vacuum tube that converts a focused optical image into an electronic video signal by scanning it with a magnetic field
- dissector aperture
- The small opening through which the electron image is swept sequentially, converting the spatial pattern into a time-varying electrical signal
- photoelectric effect
- The emission of electrons by a material when struck by light — the physical basis of electronic image capture
Citations
Patent lineage
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