Research Of The Online Laser-scanned Measuring For The Thickness

The thesis researches and studies the thickness measurement method based onthe principle of laser differential scanning measurement. Including a series of keytechnologies such as optical system structure and mechanical structure, beam receivermodule, amplification and filter circuit, conjugate boundary detection circuit, timeinterval measurement circuit, MCU control circuit and software and so on.The main contents in the project:1. It analyzes and investigates the optical system structure of laser differentialscanning measurement in thickness, and compares the characteristics of commonlyused lasers. The characteristics laser was selected as a system light source. Getting thegeneral design principles of the structure of extension and collimation beam byanalyzing the beam size of system measurement field in theoretical; Analyzing thecharacteristics of the differential scanning rotating mirror structure, which gives theconclusion that the selection of differential characteristic quantities affects themeasurement result.2. The optical system of mechanical parts and separately carried on the design.Optical system selection of semiconductor laser light source as a system, and thescanning laser collimator’s the correction; The scanning system design of receivingthe objective; Select silicon photoelectric diode as the photoelectric signal changedevice. Mechanical system design selection of stepping motor for scanning motor; thedesign of a new type of differential scanning turn mirror and analyzes the differentialscanning turn the structure characteristics of the lens.3. Aims to the specific requirements for this system, the design use twodifferential amplification and filter circuit to change the light current signal intovoltage signal. This can eliminate the noise impact caused by a number ofphotodiodes in parallel. The project researches and implements a new detectionmethod of the boundary signal-conjugate boundary detection. The online simulationon PSPICE software and hardware verification shows the method has good stabilityand environmental adaptability. 4. The time interval of several common measurement methods (direct pulsecount method and simulation method and simulation interpolation) for comparisonand analysis, select simulate interpolation as the system time interval measurements.And the hardware circuit and single-chip microcomputer interface design, through thesimulation results prove the time interval measured the correctness of the circuitdesign and has higher precision.5. Design the MCU control circuit and peripheral circuit (stepping motor drive,74LS221delay controller, digital pipe display, etc.). Finally to the actualmeasurement system of experimental data and on the error of the comprehensiveanalysis, points out the main cause of the error caused by system, and puts forwardthe measures to further improve the precision of the system.