Polarimeter calibration method and apparatus

A method of calibrating a saccharimeter to work at an unknown wavelength in the near infra-red, comprising calibrating the saccharimeter at a standard known wavelength, using the calibrated saccharimeter to measure a sugar sample, measuring the same sugar sample at the unknown wavelength, and setting the saccharimeter to give the same measurement at the said unknown wavelength as at the known wavelength.

A polarimeter adapted to operate at a known wavelength and at another, unknown wavelength, wherein the polarimeter has an optical system comprising a light source, means for collimating light from the source, a pair of interference filters arranged such that they can be introduced alternately into the collimated light beam to produce two different wavelengths, one of which passes light at a known wavelength and the other of which passes light at an unknown wavelength, a polariser for polarising the light beam, means for introducing a sample to be tested into the polarised light beam, an analyser for receiving light transmitted through the sample and a light detection system, electrical means operatively connected to the analyser and detection system for producing an output representative of the optical activity of the sample and calibration means for adjusting the output whereby the same output can be achieved when measuring the sample using the two different wavelengths.

A saccharimeter adapted to operate at a known wavelength and at another unknown, wavelength in the near infra-red, wherein said saccharimeter has an optical system comprising a light source, means for collimating light from the source, a pair of interference filters arranged such that they can be introduced alternately into the collimated light beam to produce two different wavelengths, one of which passes light at a known wavelength and the other of which passes light at an unknown wavelength in the near infra-red, a polariser for polarising the light beam, means for introducing a sample to be tested into the polarised light beam, an analyser for receiving light transmitted through the sample and a light detection system, electrical measurement means operatively connected to the analyser and detection system for producing output representative of the optical activity of the sample and calibration means for adjusting the measurement means whereby the same output can be achieved when measuring the sample using the two different wavelengths.