Journal of the Society of Motion Picture Engineers ( Volume: 47, Issue: 6, December 1946)

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An Improved 200-Mil Push-Pull Density Modulator

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Publisher: SMPTE
Doc Type: Journal Article
Article Type: research-article
Abstract: A completely new variable-density modulator utilizing a three ribbon push-pull valve is described. The entire valve is sealed by the force of the Alnico V permanent magnet on the Permendur pole pieces. Signal is applied to the center ribbon and noise-reduction currents are applied to the outer ribbons. True class A push-pull operation is obtained from the two component single ribbon valves by the use of an inverter prism which aligns the modulating and noise-reduction edges of each aperture. An anamorphote condenser lens is used to eliminate lamp filament striations at the valve ribbon plane. An anamorphote objective lens gives a 4:1 reduction of the valve aperture in the vertical plane at the film and a 2:1 reduction along the length of the sound track. A meter is supplied to measure exposure as well as setting up “bias.” A photocell monitor is supplied and a “blooping” light for indicating synchronous start marks. Mathematical analysis of the exposure produced by the modulating ribbon is appended as well as a similar analysis of the four ribbon push-pull valve which the new valve supersedes.
Publication Date: 1946-12-01
DOI: 10.5594/J12752
Link: https://doi.org/10.5594/J12752
Author(s): J. G. Frayne, T. B. Cunningham, V. Pagliarulo

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J. G. Frayne, T. B. Cunningham, and V. Pagliarulo; An Improved 200-Mil Push-Pull Density Modulator, Journal of the Society of Motion Picture Engineers ( Volume: 47, Issue: 6, December 1946); SMPTE, 1946. Available at https://doi.org/10.5594/J12752

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J. G. Frayne, T. B. Cunningham, and V. Pagliarulo; An Improved 200-Mil Push-Pull Density Modulator, Journal of the Society of Motion Picture Engineers ( Volume: 47, Issue: 6, December 1946); SMPTE, 1946. Available at https://doi.org/10.5594/J12752

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<span class="citation">J. G. Frayne, T. B. Cunningham, and V. Pagliarulo; <cite>An Improved 200-Mil Push-Pull Density Modulator</cite>, Journal of the Society of Motion Picture Engineers ( Volume: 47, Issue: 6, December 1946); SMPTE, 1946. Available at <a href="https://doi.org/10.5594/J12752" target="_blank" rel="noopener">https://doi.org/10.5594/J12752</a></span>

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<li>
J. G. Frayne, T. B. Cunningham, and V. Pagliarulo; <cite id="bib-10-5594-j12752">An Improved 200-Mil Push-Pull Density Modulator</cite>, Journal of the Society of Motion Picture Engineers ( Volume: 47, Issue: 6, December 1946); SMPTE, 1946
<span class="doi">10.5594/J12752</span>
</li>