Research Of Variable Transparence Filters And Control Equipment

Starting from the project origin, this thesis elaborates gradually the significant function of variable transparence filters in many optical instruments, and the profound significance of studying and developing these products to promote our country's technical level in the optics coating domain. We research the realization method in theory and attempt to realize these products in practice, so the key point of this article lies in narrating the realization process of variable transparence filters.Variable transparence filters are made in vacuum coating craft, therefore design of optics thin film must be carried on before manufacture products. The optics film theory is the base of vacuum thin film coating that the formulas of light density inferred from. According to these formulas a computational program is programmed, and the distributing of thin film on the base is obtained. The thin film increases continuously but non-linearity on the base, so a mechanical set must be design to make the film material distribute according to the rule. The only movement part - baffle plate in this mechanical set runs slowly and quickly all along, that a driver motor whose velocity can be modulated in big range is needed. We have referred to many kinds of electrical motor, but a step-motor is used in the mechanical set finally.A special circuit is needed to drive the step-motor. There are so many ways to build such circuit but it may be easier using special chips of step-motor in such circuit. L297 in combination with L298 is a nice solution. MCS-8051 single chip microcomputer is adopted to give out control pulse to L297&L298's driver circuit. Two exterior interrupts formed from two buttons is designed to convenient for user control, and eight 7-segments LED's are used to display some useful data when MCS-8051 is running.A step-motor can but receive digital signal, and the velocity of baffle plate changes continually, so baffle plate's velocity must be done a digital conversion, And furthermore, to avoid losing steps a transition treatment has been done when the step-motor runs at the maximum velocity. All these must be done before composing the control program. The eight 7-segments LED's and tow keys also need been involved in the control program.It is well known that a film coating machine can't plate uniformly in strictly speaking, and it is different between each film coatings, so it is in conflict with the theory base of this thesis——uniform distribution of film material. For that, transparent linearity is too bad to meet the desire. One way to improve the linearity is adjusting the speed of baffle plate.Adjusting the speed of step-motor, line iteration is used, but iteration will be done only when the slope of transparent departure too much. The Microsoft Excell 2003 is efficacious to do this calculation. Multinomial fitting can give out a new smooth delay times curve. By this way, transparent linearity is improved observably.