A doublet lens has four surfaces with radii R 1 to R 4.
2.
It was first completed in 1910, but unsatisfactory optics caused a two-year delay before a suitable doublet lens was installed.
3.
Development of the doublet lens by Churchill at Corning Glass Works allowed an electric light source to be more effective than with previous daytime colorlight signal designs.
4.
The original General Railway Signal ( GRS ) Type " G " design consisted of a cast iron box containing three doublet lens units in a triangular arrangement.
5.
They differed little from the popular Brownie cameras, the only technical difference being the introduction of a new doublet lens, allowing the same picture to be projected on a film plate over a shorter distance, making the Beau Brownies nearly 2 " shorter than their conventional counterparts.
6.
As early as 1915, the technological push by-such intellectual giants as A . H . Rudd of the Pennsylvania R . R . and his concept of speed signalling combined with his development of the Position Light signal and the concurrent color-light signals using William Churchill's doublet lens combination in practical terms made the semaphore technically obsolete.
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