Patent ID: 7658884

Claim:
Apparatus for deriving at least one property of a sample liquid from measuring emitted light emitted from said sample liquid upon irradiation of said sample liquid with a probe light beam, said apparatus having a preselected plane and an operable state in which the apparatus contains said sample liquid and is aligned such that a sample surface formed by said sample liquid is at least substantially horizontal and substantially coincides with said preselected plane, said apparatus comprising: a container adapted for containing said sample liquid and comprising a main section containing, when in said operable state, at least a portion of said sample liquid, and a beam trap located and arranged, when in said operable state, below said preselected plane and adapted for trapping light of said probe light beam underneath said preselected plane; and each arranged in a defined position relative to said container: a light source adapted and arranged for generating said probe light beam to be directed, when in said operable state, from above said preselected plane in an angle β 1 ≠0° with respect to a surface normal of said preselected plane, along a path at said sample surface in said main section of said container; a first detector adapted to detect, when in said operable state, an intensity of said emitted light emitted out of said sample liquid through said sample surface in said main section generally along a first detection axis, said first detection axis forming an angle γ 1 ≠0° with a surface normal of said preselected plane; and an optical barrier arranged between a spot at which, when in said operable state, the path of said probe light beam and said preselected plane intersect, and a spot at which, when in said operable state, said first detection axis and said preselected plane intersect, and adapted to block, when in said operable state, a propagation of light originating from reflection or scattering of said probe light beam at said sample surface towards and into said first detector.