Distance measurement system

A distance measurement system that measures a distance to a measurement object in a non-contact manner, the distance measurement system comprising:

• a light source configured to output FM light whose optical frequency is periodically swept;
• a beam splitter configured to split the FM light into two beams;
• a measurement optical system configured to further split one beam of the two beams, which are obtained by the beam splitter splitting the FM light, into two beams, and output a measurement beat signal based on a frequency difference between one beam of FM light and reflected light occurring when the measurement object is irradiated with the other beam of FM light;
• a reference optical system configured to further split the other beam of the two beams, which are obtained by the beam splitter splitting the FM light, into two beams, input both beams of FM light obtained by the further splitting to an interferometer having a known optical path length difference, and output a reference beat signal based on a frequency difference between both beams of FM light output by the interferometer;
• and
• a calculation device configured to perform calculation processing on the measurement beat signal and the reference beat signal, wherein
• the calculation device includes
• a distance measurement unit configured to calculate a distance to the measurement object based on the measurement beat signal,
• a beat signal processing unit configured to process the reference beat signal to generate a desired signal, and
• a determination processing unit configured to determine an abnormality of the light source by comparing the desired signal with a reference value.