Tachometer for aircraft or spacecraft - with precise measurement of effective speed of craft by craft itself used beam of light passed through optically dense medium

摘要

Tachometer for aircraft or spacecraft comprises a moving optically dense medium (M) through which two interference beams (A, B; C, D; D', C', B', A') are passed in opposite directions, which provide direct indications or, when the arrangement is reversed, shifts which are measured by electronic or other sensing means and which can be converted to direct speed values by automatic means on the basis of experimental values. If the assembly moves at a speed of 'v', according to the Fizeau test the beam CD is delayed and the beam D'C' is accelerated, causing an interference shift which doubles on rotation of the apparatus.