Patent ID: 8040498

Claim:
An optical arrangement for identification of a changed state of a fluid with respect to a reference state of said fluid, the fluid having a refraction index that changes with the change of the state of said fluid, said arrangement comprising a) a transparent enclosure adapted to be filled with at least a portion of said fluid; b) an object observable through said enclosure; c) an optical system having an optical axis and enabling the observation of said object when illuminated by diffuse light, via said enclosure filled with said fluid; the optical arrangement being designed such that an image of said object observed in the changed state of the fluid is optically distinctive from an image of said object observed in said reference state of the fluid due to a change of the refraction index, at least one of said reference image and said changed image being predetermined, so that said identification can be performed by comparing a current image of said object to the predetermined image, and wherein a polarization angle of said fluid also changes with the change of the state of the fluid, and said optical arrangement includes two polarization filters, one at each side of said enclosure.