A field-sequential color system (FSC) is a color television system in which the primary color information is transmitted in successive images and which relies on the human vision system to fuse the successive images into a color picture. One field-sequential system was developed in 1940 by Guillermo González Camarena (US2296019A patent). The Federal Communications Commission adopted it on October 11, 1950, as the standard for color television in the United States. Its regular broadcast debut was on June 25, 1951. However, a few months later, CBS ended color broadcasting on October 20, 1951. In March 1953, CBS withdrew its color system as a standard, creating an opening for all-electronic color systems from other manufacturers.
In the late 1960s, NASA revived the Goldmark-CBS system to broadcast color video from Project Apollo Command Modules, using a camera developed by Westinghouse Electric Corporation. The Westinghouse color camera was adapted to eventually broadcast from the lunar surface itself. Starting with Apollo 10, in May 1969, sequential color TV cameras flew on all NASA human spaceflight missions until the late 1980s, when CCD-based cameras replaced them. After the turn of the 21st century, consumer Digital Light Processing (DLP) projectors use a single chip and produce color by the sequential color process, using a color wheel for both front and rear projectors.
According to television historian Albert Abramson, A. A. Polumordvinov invented the first field-sequential color system. Polumordvinov applied for his Russian patent 10738 in 1899. This system scanned images with two rotating cylinders. A later German patent by A. Frankenstein and Werner von Jaworski described another field-sequential system. Like the CBS System, this patent included a color wheel. Frankenstein and Jaworski applied for their patent 172376 in 1904.
John Logie Baird demonstrated a version of field-sequential color television on July 3, 1928, using a mechanical television system before his use of cathode ray tubes, and producing a vertical color image about 4 inches (10 cm) high. It was described in the journal Nature:
The process consisted of first exploring the object, the image of which is to be transmitted, with a spot of red light, next with a spot of green light, and finally with a spot of blue light. At the receiving station a similar process is employed, red, blue and green images being presented in rapid success to the eye. The apparatus used at the transmitter consists of a disc perforated with three successive spiral curves of holes. The holes in the first spiral are covered with red filters, in the second with green filters and in the third with blue. Light is projected through these holes and an image of the moving holes is projected onto the object. The disc revolves at 10 revolutions per second and so thirty complete images are transmitted every second—ten blue, ten red, and ten green.
At the receiving station a similar disc revolves synchronously with the transmitting disc, and behind this disc, in line with the eye of the observer, are two glow discharge lamps. One of these lamps is a neon tube and the other a tube containing mercury vapor and helium. By means of a commutator the mercury vapor and helium tube is placed in circuit for two-thirds of a revolution and the neon tube for the remaining third. The red light from the neon is accentuated by placing red filters over the view holes for the red image. Similarly, the view holes corresponding to the green and blue images are covered by suitable filters. The blue and green lights both come from the mercury helium tube, which emits light rich in both colors.
Baird demonstrated a modified two-color version in February 1938, using a red and blue-green filter arrangement in the transmitter; on July 27, 1939 he further demonstrated that colour scanning system in combination with a cathode ray tube with filter wheel as the receiver. By December 1940 he had publicly demonstrating a 600 line version of the system.
Goldmark-CBS field-sequential color system
The CBS field-sequential system was an example of a mechanical television system because it relied in part on a disc of color filters rotating at 1440 rpm inside the camera and the receiver, capturing and displaying red, green, and blue television images in sequence. The field rate was increased from 60 to 144 fields per second to overcome the flicker from the separate color images, resulting in 24 complete color frames per second (each of the three colors was scanned twice, double interlacing being standard for all electronic television: 2 scans × 3 colors × 24 frames per second = 144 fields per second), instead of the standard 30 frames/60 fields per second of monochrome. If the 144-field color signal were transmitted with the same detail as a 60-field monochrome signal, 2.4 times the bandwidth would be required. Therefore, to keep the signal within the standard 6-MHz bandwidth of a channel, the image's vertical resolution was reduced from 525 lines to 405. The vertical resolution was 77% of monochrome, and the horizontal resolution was 54% of monochrome.
Because of these variances in resolution and frame rate from the NTSC standards for television broadcasting, field-sequential color broadcasts could not be seen on existing black and white receivers without an adapter (to see them in monochrome), or adapter-converter (to see them in color).
The CBS Sequential Color TV system was first demonstrated to the press on September 4, 1940. A color 16mm film was telecined to a color TV set and shown to the gathered press in Peter Goldmark's New York CBS lab. Live color from television cameras in a studio was first demonstrated to the press in 1941. The system was first shown to the general public on January 12, 1950.
The Federal Communications Commission adopted the CBS color system as the standard for color television in the United States on October 11, 1950. Public tests started in November 1950. CBS Television began regular, seven-day-a-week color broadcasting on June 25, 1951, in the New York City area, with a one-hour variety show hosted by Arthur Godfrey.
In June 1951, Philco offered 11 television models that could show CBS color broadcasts in black and white. CBS purchased its own television manufacturer in April 1951 when no other company would produce color sets using the system. Production of CBS-Columbia color receivers began in September and were first offered for retail sale in October. Field-sequential color broadcasts were suspended by CBS on October 20, 1951 after showing the University of North Carolina versus the University of Maryland college football game.
The cessation of color broadcasts and selling color TV sets came about mostly by the request of the National Production Authority (NPA), which prohibited the manufacture of color sets for the general public during the Korean War. Allen B. DuMont, owner of the DuMont Television Network, suspected that the reason CBS capitulated so easily was because of the complete lack of public interest in non-compatible color TV, and the NPA being a good excuse to cut costs and end what was a money-losing business.
Only 200 color sets had been manufactured for commercial sale, and only 100 of those had shipped, when CBS suspended its color broadcasts. CBS announced in March 1953 that it had abandoned any further plans for its color system.
Meanwhile, RCA continued working on and improving its NTSC compatible color television system, first demonstrated in 1949. By spring 1953, RCA developed an all-electronic color TV system that the NTSC adopted. NTSC compatible color superseded the field-sequential system as the color TV standard for the United States when the FCC approved it for public use on December 17, 1953.
Westinghouse lunar color camera
Color broadcast studio television cameras in the 1960s, such as the RCA TK-41, were large, heavy and high in energy consumption. They used three imaging tubes to generate red, green and blue (RGB) video signals which were combined to produce a composite color picture. These cameras required complex optics to keep the tubes aligned. Since temperature variations and vibration would easily put a three-tube system out of alignment, a more robust system was needed for lunar surface operations.