An optical analysis system for measuring compositions of a sample includes a light source radiating a first light. A modulator disposed in a ray path of the light modulates the light to a desired frequency. A spectral element filters the light for a spectral range of interest of the sample. An optical filter receives a first light beam split from the light reflecting from the sample and optically filters data carried by the first light beam into at least one orthogonal component of the first light beam. A first detector measures a property of the orthogonal component. A second detector receives a second light beam split from the light reflecting from the sample for comparison of the property of the orthogonal component to the second light beam. An accelerometer senses when to acquire data from the sample.