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Light Modulation With The Supersonic Cell

The Jeffree cell, ~85 years ago, an early acousto-optic modulator that could be constructed in the home workshop using water or kerosene.

From US Patent 2,155,659 (Filed Feb. 27, 1935), Light Modulating Device, “This invention relates to light modulating devices such as may be used in television, sound recording and for other purposes. The present invention makes use of the principle that when high frequency mechanical waves are caused to traverse a body forming part of an optical system, they bring about general retardations and accelerations of the wave front of a beam of light passing through or reflected from the body, these retardations and accelerations corresponding to the regions of compression and rarefaction or of varying displacement of the body produced by the waves. Owing to the regular spacing of these regions, corresponding to the wavelength employed, there can be produced optical effects similar to those caused by a diffraction grating.”

“I Claim: 1. Apparatus for controlling the intensity of a beam of light in accordance with a plurality of mechanical carrier waves of different frequencies, said apparatus comprising a body capable of transmitting mechanical waves to produce diffraction grating effects, means for applying to said body a complex mechanical vibration comprising a mixture of carrier waves to cause said complex mechanical vibration to traverse said body, means for acting selectively on carrier waves of different frequencies in said mixture traversing said body to cause each of said carrier waves to follow a path in said body which is spatially separated from the paths of the others of said carrier waves and means for directing light of a beam upon the carrier waves in each of said paths to control simultaneously and independently of one another the intensity of spatially separated parts of said light beam.”

This early acousto-optic modulator technology was used in the Scophony system of mechanical television.

Just add a proper transducer and driver to the cell and begin scanning.

References:

[1] Editor, “Light modulation with the supersonic cell: a simple explanation,” Television and Short-Wave World Magazine, No. 126, Vol. 11, p. 461, August 1938.

[2] J.H. Jeffree, “The Scophony Light Control,” Television and Short-Wave World Magazine, No. 99, Vol. 9, p. 260, May 1936; British Patent 439,236 (1934).

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Pre-War Optical Transceiver: Lichtsprechgerät 80

Probably the best modern interpretations of the 1930’s free space optical communications device Lichtsprechgerät 80 are by Helge Fykse and by Dirk Rollema.[1] Rollema’s article goes into excellent detail on the transmitter, receiver, optics and electronics. Here is a link to a recent youtube video on the Li Spr 80 photophone in operation.

The interface between the “Small prism” and “Large prism” effects modulation (see Rollema for details).

These light-beam voice communications devices were in operation by Germany in 1935 and the range was 2-4km, depending on conditions. The Lichtsprechgerät 80 was developed and manufactured by Carl Zeiss. The RX used three RV2P800 pentodes and the TX used two RV2P800 pentodes, where the filament voltage was 2v and B+ was 60v. The filament batteries would last 20 hours and the B battery could last up to 100 operating hours.

The Li Spr 80 had a big brother, the “250/130” and it was said to have a range of >30km, again depending on conditions.

Li Spr 250/130 Optics

Here is a link to another interesting page on the LiSpr80.

Remarkable for 1935. There are indications that these sets were made in large quantities, and I have yet to see one in person.

[1] Dirk W. Rollema, PA0SR, “Optical Communications – 1935 Style,” Electronics and Wireless World, p.46-49, August 1985. NB that his amateur radio call sign was PA0SE, not PA0SR. Looks like a typo. Unfortunately, Dirk is SK (2016).

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First Mass-Produced Asphere?

According to the Navitar website, “1955: World’s first mass-produced aspheric lens element used in the Elgeet Golden Navitar 12mm f/1.2 wide angle lens developed for 16mm movie cameras. [The asphere is the last optical element in the lens.(1)]. I suspect it depends on the definition of “mass-produced” since we have this mass-produced asphere from the 1940’s: RCA Projection Televisions. Given the broad definition of “asphere,” I’m sure that there are other examples that came earlier.

According to Dr. Rudolf Kingslake, “The Elgeet Optical Company was founded by three young men who had been boyhood friends: Mortimer A. London, then a lens inspector at Kodak, with David L. Goldstein and Peter Terbuska of Ilex. (The firm’s name is an acronym of L, G. and T). In 1946 they began by leasing some machine tools to make lens-polishing machinery, and with this they set up shop in an Atlantic Avenue loft (Rochester, NY), where they did all their own lens manufacture, packaging, and selling.

By 1952 the firm had grown sufficiently to enable them to purchase a former clothing plant at 838 Smith Street (Rochester, NY). At that time Goldstein was president, Terbuska was secretary, and London treasurer. The company prospered and with nearly 300 employees they manufactured thousands of lenses for small movie cameras and many other applications.

Clean, but incomplete.

London left in 1960, and in 1962 the firm acquired ownership of the ancient establishment of Steinheil in Munich, but they soon sold this, I believe to Lear Siegler. In 1964 there were difficulties at stock-holder’s meetings, and the firm was reorganized with Alfred Watson as president. Two years later the assets of the company were acquired by MATI (Management and Technology Inc.), who acquired Turner Bellows at the same time. MATI survived only until 1969, when they disappeared. Goldstein purchased the remaining assets of the former Gundlach Manufacturing Company in Fairport (NY) and reorganized it under the name “Dynamic Optics Incorporated,” but this also ceased operations in 1972.”

Clean, but incomplete.
Clean, but incomplete.
Not complete.
  1. P.A. Merigold, “Aspheric Optical Systems,” unknown reference (CIA?).