Device for water examination

A water examination method comprising:

• measuring, by a detector, an intensity of light irradiated from a wave source;
• determining, by a calibration unit, whether the intensity of light measured by the detector is equal to or greater than a first reference value;
• when the intensity of light measured by the detector is not equal to or greater than the first reference value, controlling, by the calibration unit, the intensity of light incident in the detector to be decreased;
• determining, by the calibration unit, whether the intensity of light measured by the detector is equal to or less than a second reference value;
• when the intensity of light measured by the detector is not equal to or less than the second reference value, controlling, by the calibration unit, the intensity of light incident in the detector to be increased;
• and
• estimating, by the controller, existence of impurities in the fluid by using a laser speckle detected by the detector in real-time.