An adaptive optical system comprising: a wavefront sensor configured to observe a wavefront of a reference light received from a target and generate a wavefront observation information signal indicating an observation result of the wavefront; a controller comprising a processor and configured to calculate a Zernike polynomial on a basis of the wavefront observation information signal and generate m control signals (m is an integer) on a basis of a plurality of Zernike coefficients up to n-th order in the calculated Zernike polynomial, wherein n is an integer equal to or more than three and m satisfies n ≥ m ≥ 3; a light source configured to generate laser light; and an optical system configured to receive the laser light from the light source to optically process so that the laser light has a conjugate wavefront to the wavefront of the reference light in response to the m control signals from the controller and emit the processed laser light to the target; an illuminance sensor configured to observe an illuminance of the reference light and generate an illuminance observation information signal indicating an observation result of the illuminance; a storage device configured to store a plurality of threshold values, wherein two among the m control signals are a first control signal and a second control signal generated on a basis of a first order Zernike coefficient and a second order Zernike coefficient, respectively; wherein the processor is configured to perform a comparison between a rate of change of an illuminance indicated by the illuminance observation information signal and the plurality of the threshold values and to increase or decrease a total number of the Zernike coefficients to calculate among the plurality of Zernike coefficients in response to a result of the comparison. a wavefront sensor configured to observe a wavefront of a reference light received from a target and generate a wavefront observation information signal indicating an observation result of the wavefront; a controller comprising a processor and configured to calculate a Zernike polynomial on a basis of the wavefront observation information signal and generate m control signals (m is an integer) on a basis of a plurality of Zernike coefficients up to n-th order in the calculated Zernike polynomial, wherein n is an integer equal to or more than three and m satisfies n ≥ m ≥ 3; a light source configured to generate laser light; and an optical system configured to receive the laser light from the light source to optically process so that the laser light has a conjugate wavefront to the wavefront of the reference light in response to the m control signals from the controller and emit the processed laser light to the target; an illuminance sensor configured to observe an illuminance of the reference light and generate an illuminance observation information signal indicating an observation result of the illuminance; a storage device configured to store a plurality of threshold values, wherein two among the m control signals are a first control signal and a second control signal generated on a basis of a first order Zernike coefficient and a second order Zernike coefficient, respectively; wherein the processor is configured to perform a comparison between a rate of change of an illuminance indicated by the illuminance observation information signal and the plurality of the threshold values and to increase or decrease a total number of the Zernike coefficients to calculate among the plurality of Zernike coefficients in response to a result of the comparison.