A distance calculator for an imaging system having a first imaging device and a second imaging device, the distance calculator comprising: a monocular distance calculation section adapted to calculate monocular distance to a target based on image information captured by one of the first and second imaging devices (101, 102); a stereo distance calculation section adapted to calculate stereo distance to the target based on image information captured by the first imaging device and the second imaging device; a blurriness level calculation section adapted to calculate a first blurriness level of the image information captured by the first imaging device and a second blurriness level of the image information captured by the second imaging device; a distance estimation section adapted to estimate a distance to the target at the time of current detection from a previously determined distance and a previously detected position; and an output distance calculation section adapted to calculate distance to the target to be output, characterized in that the output distance calculation section selects the stereo distance calculated by the stereo distance calculation section as the distance to be output when the distance estimated by the distance estimation section is lower than a predetermined distance threshold and when the first blurriness level and the second blurriness level calculated by the blurriness level calculation section are lower than a predetermined blurriness threshold; the output distance calculation section selects the monocular distance calculated by the monocular distance calculation section as the distance to be output when the distance estimated by the distance estimation section is lower than the predetermined distance threshold and when the first blurriness level or the second blurriness level calculated by the blurriness level calculation section is higher than the predetermined blurriness threshold; and the output distance calculation section selects the monocular distance calculated by the monocular distance calculation section as the distance to be output when the distance estimated by the distance estimation section is higher than the predetermined distance threshold. a monocular distance calculation section adapted to calculate monocular distance to a target based on image information captured by one of the first and second imaging devices (101, 102); a stereo distance calculation section adapted to calculate stereo distance to the target based on image information captured by the first imaging device and the second imaging device; a blurriness level calculation section adapted to calculate a first blurriness level of the image information captured by the first imaging device and a second blurriness level of the image information captured by the second imaging device; a distance estimation section adapted to estimate a distance to the target at the time of current detection from a previously determined distance and a previously detected position; and an output distance calculation section adapted to calculate distance to the target to be output, characterized in that the output distance calculation section selects the stereo distance calculated by the stereo distance calculation section as the distance to be output when the distance estimated by the distance estimation section is lower than a predetermined distance threshold and when the first blurriness level and the second blurriness level calculated by the blurriness level calculation section are lower than a predetermined blurriness threshold; the output distance calculation section selects the monocular distance calculated by the monocular distance calculation section as the distance to be output when the distance estimated by the distance estimation section is lower than the predetermined distance threshold and when the first blurriness level or the second blurriness level calculated by the blurriness level calculation section is higher than the predetermined blurriness threshold; and the output distance calculation section selects the monocular distance calculated by the monocular distance calculation section as the distance to be output when the distance estimated by the distance estimation section is higher than the predetermined distance threshold.