Schmidt system

The Schmidt system was popular, used in reverse, for television projection systems.

Most water-tube railway locomotives, especially in Europe, used the Schmidt system.

The Schmidt system used a sealed ultra-high-pressure circuit that simply transferred heat to a high-pressure circuit, by means of heating coils inside a high-pressure boiler.

In other designs, such as the Schmidt systems, the aspheric corrector plate can be made by using a vacuum to distort an optically parallel plate into a curve which is then polished "flat" on one side.

However, the report stated that both superheater types had serious drawbacks, with the Schmidt system featuring a damper control on the superheater header that caused hot gases to condense into sulphuric acid, which caused pitting and subsequent weakening of the superheater elements.

Also, as the system of Mersenne + Schmidt is the sum of two anastigmats: the Mersenne system is an anastigmat, and so is the Schmidt system, the resultant system is also an anastigmat, as third-order aberrations are purely additive.

The HP cylinder exhaust passed through an LP feed heater, and then the tubes of an LP boiler; this was roughly equivalent to the LP boiler in the Schmidt system, but was heated by HP exhaust steam not combustion gases.