Distance measurement device

The distance measurement device comprising:

• a signal generator configured to generate a first signal having a first repetition frequency and a second signal having a second repetition frequency higher than the first repetition frequency;
• a light source configured to generate light whose wavelength is modulated with time through internal modulation based on the first signal, and output resultant light;
• a modulator configured to further modulate, with time, the wavelength of the light output from the light source using a Doppler effect through external modulation based on the second signal, and output resultant light;
• a splitter configured to divide the light output from the modulator into measurement light and reference light;
• an irradiator configured to irradiate a target object with the measurement light;
• a detector configured to detect interference light between reflected light obtained by the measurement light being reflected by the target object and the reference light;
• and
• a calculator configured to calculate a distance to the target object on the basis of an output signal from the detector.