Laser monitoring of the coal level of coal silo by depth pre-calibration

A novel contact-free laser triangulation method for measuring the coal level of coal silo was presented under harsh environmental conditions such as dense dust,high humidity and low illumination in coal mines.A laser source and a camera were mounted on the top of the coal silo where the laser spot projected into the coal silo was imaged by the camera.Using the pinhole imaging model,the lateral shift of the spot image was calculated to determine the coal level,which is by use of a pre-calibrated look-up table of the coal depth and shifts.The precise of measurement relies on the step size of pre-calibration.A measurement device was devised according to this principle and the field application shows that the proposed method is easy to implement to detect the coal level of coal silo at the condition of low illumination in coal mines.