Research On The Measurement System Of Transparent Material’s Thickness Based On Polychromatic Confocal Technology

In recent years, with the rapid development of optical fabrication, optical fiber and Pharmaceuticals industry, the demand for transparent materials productions such as small glass tube and glass container increases rapidly. Because of the productive technology and equipments lags in domestic companies, the qualities of their products are worse than the similar products of developed countries. It is deeply affecting the high-end product. The transparent materials productions need high precise parameters of small precise glass containers, especially the containers’wall thickness and demand for the measure velocity seriously in the producing process. Meanwhile, there are characteristics of hyperthermia, red heat, brittleness and difficult to use contact measurement, so we must research for the non-contact online detecting technology to achieve the parameters’measuring. Using photoelectric can solve the detecting problems of transparent materials productions meanwhile significant to assure the productions’qualities and improve their international competitive abilities.Polychromatic confocal technique has characteristics of multiple surface chromatographic.-Because of the performance of high quality measurement, it is the latest research in the field of photoelectric detection. This thesis researches on the thickness detecting of related products of transparent material such as the plate glass manufacture, optical parts processing and so on. It is to solve the high precision detecting problem of transparent material thickness by utilizing especial optical system, high speed data acquisition technology and advanced analysising and processing technology of optical spectrum. Based on the characteristic that different wavelength optical spectrum produce axial dispersion through optical system, detector accepts axial dispersion echo signal of continous spectrum and then it realizes transparent material thickness detecting by analyzing wavelength data returned from the upper and lower two surfaces. This method overcomes the problem that last method could only get the relative result so that the absolute measurement can be realized. The main contents of study include four aspects. Firstly, it researches the theory of polychromatic confocal. Analyzing the signal characteristics of polychromatic confocal surface and then the wavelength signals and the dimension model of thickness for transparent material in the continuous spectrum are derived, which base on the polychromatic illumination beam and make use of the dispersion characteristic on asis. After that, the confocal’optical system is designed to research the relationship of optical parameters in axial dispersion optical system. The design of optical system is optimized theoretically. Then, we research spectral signal differential acquisiting processing principle and design the spectral signal acquisition system based on CCD according to it. The acquisited spectrum signal is converted digital signal and then delivered from acquisiting card to PC by interface circuit. At last, LabVIEW was used to analysis spectrum and construct software system, and after the wavelength peak value correspounding the upper and lower surfaces being found, it is converted to thickness with math model. At last, The principle prototype of transparent material confocal measurement is constructed by polychromatic confocal optical system combination with optical fiber transmission, optical splitting system and acquisiting and analyzing system of spectrum signal. According to experimental result, the principle scheme of the measurement system is put forward completely.Polychromatic confocal measurement method, utilizing axial dispersion characteristic of focusing light beam by bringing in polychromatic light beam, extend the range to20mm with absolute distinguishability. Confocal transparent material thickness’ measurement method, based on polychromatic lighting, can make distinguishability at±0.005mm. In conclusion, using polychromatic measurement method proposed by this paper to measure extensiveness and successive thickness-changing transparent material at a high speed and high precision online is feasible and meaningful actually and has better practical value.