Human eye The upper end of the range is given in terms of normal visual performance as 10 cd/m (100,000,000 or one hundred million candelas per square meter). The eye includes a lens similar to lenses found in optical instruments such as cameras and the same physics principles can be applied. The pupil of the human eye is its aperture; the iris is the diaphragm that serves as the aperture stop. Refraction in the cornea causes the effective aperture (the entrance pupil) to differ slightly from the physical pupil diameter. The entrance pupil is typically about 4 mm in diameter, although it
Diaphragm compressor properties and sufficient temperature resistance. A diaphragm compressor is the same as a membrane compressor. In the late 19th century William Burton started a workshop building pumps and air compressors at Nogent-sur-Oise, 60kM north of Paris, France. Henri Corblin, generally recognised as the inventor of the metallic diaphragm compressor, was based nearby in Paris itself and in 1923 he received a US patent for his invention and design work. The photograph included in this section depicts a three-stage diaphragm compressor used to compress hydrogen gas to 6,000 psi (41 MPa) for use in a prototype hydrogen and compressed natural gas