Optical sensor and method of operating the optical sensor

A method of operating an optical sensor comprising a path adjuster having adjustable transmissivity and reflectivity, the method comprising:

• emitting light using a light source;
• selectively controlling a reflectance of the path adjuster to be greater than a transmittance of the path adjuster at a first time to reflect the light;
• selectively controlling the transmittance of the path adjuster to be greater than a reflectance of the path adjuster for the light to pass through the path adjuster and to be incident on a target material in skin or blood of an object at a second time different from the first time;
• receiving light reflected from the path adjuster corresponding to the first time as a reference light;
• and
• receiving the light passing through the path adjuster, reflected by the target material and returning through the path adjuster as a measurement light;
• normalizing the measurement light with a ratio of an intensity of the measurement light to an intensity of the reference light;
• and
• obtaining information of the target material based on the normalized measurement light,
• wherein the measurement light is reflected from the target material among the light passing through the path adjuster and has a same wavelength as the reference light, and
• wherein the reference light and the measurement light correspond to the light emitted from a same light source and are detected by a same light receiver.