An optical axis adjusting mechanism, comprising: a first adjusting plate which is rotatably connected to a mounting bracket, an axis around which the first adjusting plate is rotated relative to the mounting bracket being a first rotation axis; and a second adjusting plate which has a connecting part for fixedly connecting with an imaging unit housing, the second adjusting plate being rotatably connected with the first adjusting plate, and an axis around which the second adjusting plate is rotated relative to the first adjusting plate being a second rotation axis, wherein the first rotation axis is at an angle to the second rotation axis, wherein, the first adjusting plate and the second adjusting plate are located outside the imaging unit housing, wherein the first rotation axis is a first revolving axis, and the second rotation axis is a second revolving axis, the optical axis adjusting mechanism further comprising: a first rotation shaft, wherein the axis of the first rotation shaft is the first revolving axis, and the first rotation shaft comprises a shaft rod section and a thread section which are connected to each other, wherein the shaft rod section is engaged with a corresponding shaft hole in the mounting bracket, and the thread section is screwed into a corresponding threaded hole in the first adjusting plate, wherein a plurality of circular-arc through holes are provided in the mounting bracket, the circular-arc through holes extend in a circular arc shape with the axis of the first rotation shaft as a center, a plurality of connecting threaded holes are provided in the first adjusting plate, the first adjusting plate and the mounting bracket are fixedly connected by screwing fastening screws into corresponding connecting threaded holes through the circular-arc through holes, and the first revolving axis extends vertically. a first adjusting plate which is rotatably connected to a mounting bracket, an axis around which the first adjusting plate is rotated relative to the mounting bracket being a first rotation axis; and a second adjusting plate which has a connecting part for fixedly connecting with an imaging unit housing, the second adjusting plate being rotatably connected with the first adjusting plate, and an axis around which the second adjusting plate is rotated relative to the first adjusting plate being a second rotation axis, wherein the first rotation axis is at an angle to the second rotation axis, wherein, the first adjusting plate and the second adjusting plate are located outside the imaging unit housing, wherein the first rotation axis is a first revolving axis, and the second rotation axis is a second revolving axis, the optical axis adjusting mechanism further comprising: a first rotation shaft, wherein the axis of the first rotation shaft is the first revolving axis, and the first rotation shaft comprises a shaft rod section and a thread section which are connected to each other, wherein the shaft rod section is engaged with a corresponding shaft hole in the mounting bracket, and the thread section is screwed into a corresponding threaded hole in the first adjusting plate, wherein a plurality of circular-arc through holes are provided in the mounting bracket, the circular-arc through holes extend in a circular arc shape with the axis of the first rotation shaft as a center, a plurality of connecting threaded holes are provided in the first adjusting plate, the first adjusting plate and the mounting bracket are fixedly connected by screwing fastening screws into corresponding connecting threaded holes through the circular-arc through holes, and the first revolving axis extends vertically.