An optical measurement device includes a light source, a first detector, and a second detector. The light source emits light to a measurement site of a patient and one or more detectors detect the light from the light source. At least a portion of a detector is translucent and the light passes through the translucent portion prior to reaching the measurement site. A detector receives the light after attenuation and/or reflection or refraction by the measurement site. A processor determines a light intensity of the light source, a light intensity through a tissue site, or a light intensity of reflected or refracted light based on light detected by the one or more detectors. The processor can estimate a concentration of an analyte at the measurement site or an absorption or reflection at the measurement site.