Patent ID: 6130439
Filing Date: 2000-10-10
Classification: G01N

Abstract:
An instrument for measuring the refractive index of a fluid, comprising:a coherent light source which emits at least one beam of coherent light;a sensor that receives and contains the fluid whose refractive index is to be measured, the sensor being illuminated by the light source and comprising a block of material which is transparent to the light and includes a machined portion which comprises a hole or a groove, the sensor having a surface which is flat and parallel to the hole or the groove;a photodetector that receives the coherent light beam that has been directly transmitted or reflected by the sensor, wherein superimposition of rays of the light beam which have traveled along different optical paths through the walls of the sensor, by transmission and/or reflection of the light beam at various optical interfaces of the sensor, leads to the formation of interference fringes, the photodetector tracking movement of the interference fringes directly from the sensor, the movement of the interference fringes being a function of changes in the refractive index of the fluid contained in the sensor; anda processor that determines the refractive index of the fluid contained in the sensor from the interference fringes tracked by the photodetector.