Optical measurement device and optical measurement method
An optical measurement device ( 10 ) according to the present disclosure includes a light-transmitting unit ( 11 ) that transmits ranging light for Time of Flight (ToF) ranging, a light-receiving unit ( 12 ) that receives reflection light reflected from a measurement object by the ranging light transmitted by the light-transmitting unit ( 11 ), a Doppler shift amount calculation unit ( 13 ) that calculates a Doppler shift amount of a frequency of the reflection light, based on a phase change amount of the reflection light received by the light-receiving unit ( 12 ), and a relative speed calculation unit ( 14 ) that calculates a relative speed of the measurement object, based on the Doppler shift amount calculated by the Doppler shift amount calculation unit ( 13 ).
1 . An optical measurement device comprising:
a light-transmitter configured to transmit ranging light for Time of Flight (ToF) ranging;
a light-receiver configured to receive reflection light that is reflected from a measurement object by the transmitted ranging light;
a Doppler shift amount calculator configured to calculate a Doppler shift amount of a frequency of the reflection light, based on a phase change amount of the received reflection light; and
a relative speed calculator configured to calculate a relative speed of the measurement object, based on the calculated Doppler shift amount,
wherein the ranging light to be transmitted has a frequency component of a first frequency offset being an offset in a positive direction with respect to a frequency of a reference light source, and a frequency component of a second frequency offset being an offset in a negative direction with respect to the frequency of the reference light source, and
the Doppler shift amount calculator calculates the Doppler shift amount, based on a value acquired by adding a phase change amount of the frequency component in the positive direction included in the reflection light and a phase change amount of the frequency component in the negative direction included in the reflection light and dividing by 2.
2 . The optical measurement device according to claim 1 , wherein the Doppler shift amount calculator calculates the Doppler shift amount, based on a difference between a phase change amount of reflection light when there is no Doppler shift and a phase change amount of the received reflection light.
3 . The optical measurement device according to claim 1 , further comprising a light pulse generator configured to generate a light pulse having a phase change point between a first phase modulation portion of the first frequency offset and a second phase modulation portion of the second frequency offset,
wherein the light-transmitter transmits the ranging light including the generated light pulse.
4 . The optical measurement device according to claim 3 , further comprising a distance calculator configured to calculate a distance to the measurement object, based on a phase change point of a light pulse included in the transmitted ranging light and a phase change point of a light pulse included in the received reflection light.
5 . The optical measurement device according to claim 1 , wherein the light-transmitter transmits a wavelength-multiplexing signal acquired by wavelength-multiplexing the frequency component of the first frequency offset and the frequency component of the second frequency offset as the ranging light.
6 . The optical measurement device according to claim 5 , further comprising:
a light pulse generator configured to generate a first light pulse having the frequency component of the first frequency offset and a second light pulse having the frequency component of the second frequency offset; and
a wavelength multiplexer configured to wavelength-multiplex the generated first and second light pulses,
wherein the light-transmitter transmits the ranging light including the wavelength-multiplexed first and second light pulses.
7 . The optical measurement device according to claim 5 , further comprising an amplitude modulator configured to generate an amplitude modulation signal having a frequency component of the first frequency offset and a frequency component of the second frequency offset,
wherein the light-transmitter transmits the generated amplitude modulation signal as the ranging light.
8 . The optical measurement device according to claim 5 , further comprising a distance calculator configured to calculate a distance to the measurement object, based on a first peak point of the transmitted ranging light and the first peak point of the received reflection light.
9 . The optical measurement device according to claim 8 , wherein the distance calculator calculates the distance, based on a plurality of peak points of the transmitted ranging light and the plurality of peak points of the received reflection light.
10 . The optical measurement device according to claim 9 , wherein the distance calculator calculates the distance, based on an average of time differences between a plurality of peak points of the transmitted ranging light and the plurality of peak points of the received reflection light.
11 . An optical measurement method comprising:
transmitting ranging light for Time of Flight (ToF) ranging;
receiving reflection light that is reflected from a measurement object by the transmitted ranging light;
calculating a Doppler shift amount of a frequency of the reflection light, based on a phase change amount of the received reflection light; and
calculating a relative speed of the measurement object, based on the calculated Doppler shift amount,
wherein the ranging light to be transmitted has a frequency component of a first frequency offset being an offset in a positive direction with respect to a frequency of a reference light source, and a frequency component of a second frequency offset being an offset in a negative direction with respect to the frequency of the reference light source, and
the calculating of the Doppler shift amount includes calculating the Doppler shift amount, based on a value acquired by adding a phase change amount of the frequency component in the positive direction included in the reflection light and a phase change amount of the frequency component in the negative direction included in the reflection light and dividing by 2.
12 . The optical measurement method according to claim 11 , wherein the calculating the Doppler shift amount includes calculating the Doppler shift amount, based on a difference between a phase change amount of reflection light when there is no Doppler shift and a phase change amount of the received reflection light.