An optical system comprising: a first light-projecting system for irradiating a surface with first light from a light source; a second light-projecting system , different from the first light-projection system , for irradiating the surface with second light from a light source; a first light-receiving system including a first lens for focusing first reflected light generated by reflecting light incident on the surface from the first light-projecting system with a first angle of reflection by the surface , and a deflector for deflecting the first reflected light toward the photodetector ; and a second light-receiving system, different from the first light-receiving system, including a second lens for focusing second reflected light generated by reflecting light incident on the surface from the second light-projecting system with a second angle of reflection, different from the first angle of reflection, by the surface ; wherein the first reflected light includes specular reflected light of light incident on the surface from the first light-projecting system ; wherein the second reflected light includes specular reflected light of light incident on the surface from the second light-projecting system ; wherein a first light-receiving area of the photodetector arranged to receive the first reflected light from the first lens and the deflector is spaced apart from a second light-receiving area of the photodetector arranged to receive the second reflected light from the second lens , a direction of an optical axis of the first lens is different from a direction of an optical axis of the second lens . a first light-projecting system for irradiating a surface with first light from a light source; a second light-projecting system , different from the first light-projection system , for irradiating the surface with second light from a light source; a first light-receiving system including a first lens for focusing first reflected light generated by reflecting light incident on the surface from the first light-projecting system with a first angle of reflection by the surface , and a deflector for deflecting the first reflected light toward the photodetector ; and a second light-receiving system, different from the first light-receiving system, including a second lens for focusing second reflected light generated by reflecting light incident on the surface from the second light-projecting system with a second angle of reflection, different from the first angle of reflection, by the surface ; wherein the first reflected light includes specular reflected light of light incident on the surface from the first light-projecting system ; wherein the second reflected light includes specular reflected light of light incident on the surface from the second light-projecting system ; wherein a first light-receiving area of the photodetector arranged to receive the first reflected light from the first lens and the deflector is spaced apart from a second light-receiving area of the photodetector arranged to receive the second reflected light from the second lens , a direction of an optical axis of the first lens is different from a direction of an optical axis of the second lens . <EOS>