Sample holder

A computer implemented method of using a spectrophotometer to analyse a measurement sample disposed in a sample holder including:

• a first surface having a first predetermined geometry, and
• a second surface having a second predetermined geometry, the first surface being opposite the second surface,
• the sample holder being configured to hold a measurement sample between the first surface and the second surface such that a distance between the first surface and the second surface defines an optical pathlength of the sample holder,
• wherein the predetermined geometries of the first surface and the second surface provide a continuously variable cross-section across the sample holder so as to provide a continuous range of optical pathlengths,
• the spectrophotometer having a light source for emitting light through the measurement sample, and a detector for detecting light intensity transmitted through the measurement sample, the method comprising:
• measuring, by the detector, one or more light intensities,
• obtaining a detected transmission value corresponding to each optical pathlength of the sample holder, the detected transmission value being based on the one or more light intensity measurements from the detector,
• calculating an estimated transmission value corresponding to each optical pathlength of the sample holder, and
• determining an attenuation coefficient of the measurement sample that minimizes an error between the detected transmission values and the estimated transmission values.

A method of manufacturing a sample holder including:

• a first surface having a first predetermined geometry defined by a smooth aspheric surface, and
• a second surface having a second predetermined geometry, the first surface being opposite the second surface,
• the sample holder being configured to hold a measurement sample between the first surface and the second surface such that a distance between the first surface and the second surface defines an optical pathlength of the sample holder,
• wherein the predetermined geometries of the first surface and the second surface provide a continuously variable cross-section across the sample holder so as to provide a continuous range of optical pathlengths,
• the method comprising:
• forming a first portion of the sample holder to provide the first surface,
• forming a second portion of the sample holder to provide the second surface, and
• attaching the first portion to the second portion such that the first portion is movable relative to the second portion between
• an open position to allow placement or removal of the measured sample, and
• a closed position in which the first surface is in a fixed position relative to the second surface to provide the continuously variable cross-section across the sample holder.