An optical sensor (100, 400, 510, 610, 710) comprising: a light source (110, 410, 711) configured to emit light; a photodetector array (120, 420, 712) comprising a plurality of photodetectors positioned at different distances from the light source, each photodetector being configured to detect an optical signal returning from an object irradiated by the light emitted by the light source, and to measure a light intensity of the detected optical signal; and a processor (130, 430, 520, 620, 713) configured to determine a correlation coefficient between (i) In ρ 2 R ρ S 0 and ρ, or (ii) R ( p) and ρ -2, based on the measured light intensity, wherein ρ denotes a distance between the light source and a photodetector of the plurality of photodetectors, R ( ρ) denotes a light intensity measured by the photodetector positioned away from the light source by the distance ρ, and S 0 denotes a light intensity emitted by the light source, and wherein the processor is further configured to compare the determined correlation coefficient with a predetermined threshold, wherein, based on the determined correlation coefficient exceeding a threshold, the processor is further configured to determine that a quality of the optical signal is the acceptable level or higher, and, based on the determination that the quality of the optical signal is the acceptable level or higher, the processor is further configured to provide the measured light intensity to an apparatus for measuring optical characteristics of the object; and based on the determined correlation coefficient being less than or equal to the threshold, the processor is further configured to determine that the quality of the optical signal is less than the acceptable level, and based on the determination that the quality of the optical signal is less than the acceptable level, the processor is further configured to discard the measured light intensity, and to control the light source and the photodetector array to repeatedly perform the emitting of the light and to measure the light intensity. a light source (110, 410, 711) configured to emit light; a photodetector array (120, 420, 712) comprising a plurality of photodetectors positioned at different distances from the light source, each photodetector being configured to detect an optical signal returning from an object irradiated by the light emitted by the light source, and to measure a light intensity of the detected optical signal; and a processor (130, 430, 520, 620, 713) configured to determine a correlation coefficient between (i) In ρ 2 R ρ S 0 and ρ, or (ii) R ( p) and ρ -2, (i) In ρ 2 R ρ S 0 and ρ, or (ii) R ( p) and ρ -2, based on the measured light intensity, wherein ρ denotes a distance between the light source and a photodetector of the plurality of photodetectors, R ( ρ) denotes a light intensity measured by the photodetector positioned away from the light source by the distance ρ, and S 0 denotes a light intensity emitted by the light source, and wherein the processor is further configured to compare the determined correlation coefficient with a predetermined threshold, wherein, based on the determined correlation coefficient exceeding a threshold, the processor is further configured to determine that a quality of the optical signal is the acceptable level or higher, and, based on the determination that the quality of the optical signal is the acceptable level or higher, the processor is further configured to provide the measured light intensity to an apparatus for measuring optical characteristics of the object; and based on the determined correlation coefficient being less than or equal to the threshold, the processor is further configured to determine that the quality of the optical signal is less than the acceptable level, and based on the determination that the quality of the optical signal is less than the acceptable level, the processor is further configured to discard the measured light intensity, and to control the light source and the photodetector array to repeatedly perform the emitting of the light and to measure the light intensity.