Design Of Dual-wavelength Industrial Endoscope For The Blast Furnace Burden Surface Monitoring

The operation of blast furnace materials affects the process of ironmaking chemical reactions,and a well-shaped material surface helps to improve the distribution of gas flow,reduce coke consumption,and enhance ironmaking efficiency.However,existing methods for monitoring material surface have issues such as small measurement range,low measurement accuracy,and limited data types.In this paper,a dual-wavelength industrial endoscope that combines visible and long-wavelength infrared is designed.The visible system provides wide-field and high-resolution visual monitoring within a single blast furnace opening,while the infrared system provides stable material surface infrared images and temperature calibration.First,the technical specifications for the dual-wavelength industrial endoscope are proposed based on practical monitoring environments.The optical and mechanical structure of the endoscope is analyzed based on these specifications,and a dual-channel optical structure is selected.A flat reflection mirror turning structure is added to the infrared system to adjust the distribution of the endoscope’s optical path.The low-light CMOS is selected as the image sensor for the visible system,and a non-cooled infrared focal plane is selected for the infrared system.The transmittance of the dual-wavelength industrial endoscope optical system is analyzed,and the detection sensitivity of the endoscope is quantitatively calculated from two perspectives: environmental illumination and radiation source temperature.Then,the imaging principle of the endoscope is introduced,and a dual-element endoscope optical system design method for objective and relay systems is proposed.Using the integrated design concept of the endoscope optical system,the optical system design of the dual-wavelength industrial endoscope for the blast furnace is completed.The design result of the visible industrial endoscope is: optical length of 1040 mm,overall diameter ≤ 26 mm,F number is 6,MTF ≥ 0.2 @ 160 lp/mm;the design result of the long-wavelength infrared endoscope is: optical length of 1060 mm,overall diameter ≤ 16 mm,F number is 5,MTF ≥ 0.1@13lp/mm.The results of image quality analysis and tolerance analysis show that the industrial endoscope designed in this paper has good imaging quality and processability.Finally,the mechanical structure of the industrial endoscope is designed,and the freedom of the turning structure and the overall structure of the dual-channel system are completed.Imaging tests of the visible and long-wavelength infrared industrial endoscopes are performed,where the visible system can distinguish a line width of 10 mm at a distance of 5 m,and the detection sensitivity of the infrared system is better than2℃ at a distance of 30 cm.Moreover,the system has been applied to gas boilers in a certain steel plant.The test results show that the dual-element industrial endoscope optical design scheme proposed in this paper is feasible and reliable,and real-time material surface monitoring using a dual-wavelength industrial endoscope is accurate and efficient.