Research On Real-time And Online Linear CCD Caliper Measure System

The development of modern industrial technology puts forward new requirementsfor measuring technology. It needs to measure the workpiece fast and accurate in time,and in order to avoid the workpiece being damaged by the contact of the measuringinstrument in the measuring process, it needs to measure without contact. Based on theresearch of non-contact measurement technology and CCD application technology, thistopic designed an online real-time non-contact measurement system with CCD as theimage sensor, and STM32as the main control chip.This system is designed from two parts, optical and circuit parts. In the design ofoptical path, the system chooses imaging amplifying light path to convert the size of themeasured workpiece to the CCD photo surface, and through CCD photoelectricconversion, the size information is transferred to electrical signal, and it will beprocessed by the circuit part. The circuit part mainly includes power supply module,CCD module, data processing module and USB data transfer module. Power supplymodule in this system using the booster and power conversion chips to satisfy thedifferent voltage requirements of the power supply via a USB cable. In CCD module, bymaking use of control function and timers of STM32, a very good drive sequence isobtained. In data processing, it chooses AD9945, a high-precision and high-speed12bitsanalog to digital converter to convert the CCD signal, and it can eliminate the resetpulse signal of the CCD signal, and inhibit the dark current noise inherent to the CCDsignal, also it can convert the CCD signal from analog to digital. In data transitionmodule, digital data is transferred by USB, which supports hot plug and use and morefast and convenient than serial port. The data is transferred to computer for saving anddisplaying.Finally do binarization processing to the acquired data and extract the data of theleft and right edges to curve fitting, then derivate the curve to get the left and rightboundary points. Through get the difference of the abscissa boundary points to obtainthe size of the image shadow. Then according to the magnification of optical systemand the measured value of the workpiece, the size of the workpiece is obtained.