Thin film multivariate optical element and detector combinations, thin film optical detectors, and downhole optical computing systems

A method to obtain downhole properties of a downhole sample, comprising:

• deploying a thin film multivariate optical element and detector combination into a wellbore, the thin film multivariate optical element and detector combination comprising:
• at least one layer of multivariate optical element having patterns that manipulate
• at least one spectrum of optical signals;
• at least one layer of detector film;
• and
• a substrate, wherein the at least one layer of multivariate optical element and the
• at least one layer of detector film are deposited on the substrate;
• transmitting optical signals downhole to the at least one layer of multivariate optical element;
• and
• manipulating at least one spectrum of optical signals by the patterns to improve at least one correlation between the at least one spectrum of optical signals and at least one property of a downhole sample.