Measuring device and measuring method

A measuring method for measuring at least any one of a separation displacement that is a displacement of a target to be measured that is moved in a predetermined direction and a moving velocity that is a relative velocity in a direction orthogonal to the predetermined direction, the method comprising:

• a splitting step of splitting laser light that is modulated with respect to time y a predetermined frequency modulation velocity into reference light and measurement light;
• an irradiation and light receiving step of irradiating a surface of the target to be measured with the measurement light from an irradiation and light receiving surface and of receiving reflection light obtained by the measurement light that is reflected on the surface of the target to be measured with the irradiation and light receiving surface, by using one or two or more measuring heads in which an optical axis of the laser light that is irradiated from the irradiation and light receiving surface is disposed to be inclined with respect to the predetermined direction, wherein a number of measuring heads is i, i being an integer greater than or equal to 1;
• a light detecting step of outputting a beat signal by light interference between the reflection light and the reference light;
• and
• an arithmetic processing step of performing arithmetic processing with an arithmetic processing unit by inputting the beat signal into the arithmetic processing unit,
• wherein in the arithmetic processing step,
• a beat frequency based on the beat signal is detected,
• a frequency difference that is a difference between the beat frequency at the time of measurement and a reference frequency that is a beat frequency in a predetermined reference state is calculated, and
• at least any one of the moving velocity and the separation displacement is calculated on the basis of a relationship of the following expression:
• Δfi=k(d/cos θi)+((2V cos α cos Φi sin θi)/λ)+((2V sin α sin Φi sin θi)/λ)
• where Δfi, is the frequency difference, d is the separation displacement, V is the moving velocity, θ is an optical axis angle being an angle of the optical axis relative to a normal direction of the target surface to be measured, Φ is a projection angle, λ is a wavelength of the laser, k is a constant number, and α is a moving direction angle of the target to be measured.

A measuring method for measuring an inclination angle of an optical axis of laser light, that is applied toward a target to be measured that is moved, the method comprising:

• a splitting step of splitting the laser light that is modulated with respect to time by a predetermined frequency modulation velocity into reference light and measurement light;
• an irradiation and light receiving step of irradiating a surface of the target to be measured with the measurement light from an irradiation and light receiving surface and of receiving reflection light obtained by the measurement light that is reflected on the surface of the target to be measured with the irradiation and light receiving surface, by using one or two or more measuring heads in which the optical axis of the laser light that is irradiated from the irradiation and light receiving surface is disposed to be inclined with respect to a predetermined direction of the target to be measured that is moved;
• a light detecting step of outputting a beat signal by light interference between the reflection light and the reference light;
• and
• an arithmetic processing step of performing arithmetic processing with an arithmetic processing unit by inputting the beat signal into the arithmetic processing unit,
• wherein in the arithmetic processing step,
• a calibration data acquiring step of acquiring a velocity difference that is measured by changing a moving velocity of the target to be measured, as a calibration velocity difference, is provided,
• a difference in a beat frequency based on the beat signal at the time of changing the moving velocity of the target to be measured in order to acquire the calibration velocity difference is acquired as a calibration frequency difference, and
• the inclination angle of the optical axis of the laser light is calculated by using a wavelength of the laser light, the calibration velocity difference, and the calibration frequency difference.