Design Of High-Speed Transmission And Control For CCD Photoelectric Measurement Signal

Charge Coupled Device(CCD) is a device of photoelectric conversion of the solid imaging, It has many advantages such as smaller pixel size, geometric accuracy, stable performance and strong self-scanning ability, configure the appropriate optical system and the suitable external drive and control processing circuit, can achieve high spatial resolution, especially suitable for various precision image sensor and non-contact photoele-ctric measuring field, for example, the train wheel irregularities detection, the bridge and railway track vibration measurements.In this paper, the CCD photoelectric signal data acquisition system,which is used in non-contact measuring field, is designed based on analysis the CCD working principle and characteristics. We adopted the ADC+CPLD+FIFO+USB digital processing scheme to achieve high-speed CCD optical measuring signal transmission and control function, analyzes the changes of CCD signal under various light intensity.The charge-coupled device (CCD) TCD1703C is used as photosensitive component in the system, the main control unit is accomplished by CPLD (EPM240). The drive timing of linear array CCD and the initialization and sampling control signal of high-speed A/D chip are generated by using VHDL hardware description language, the FIFO reset signal also is generated by VHDL, simulated by QuartusⅡmade of Altera, in the same time, display the output waveform by digital oscilloscope. In view of the chip's features of TCD1703C, the differential amplification and low-pass filter is designed to pre-processing its output signal; The CY7C68013A of Cypress's EZ-USB FX2LP series USB interface chip is developed, the USB drivers and firmware are programmed, to achieved the control signal and the high-speed data transmission between the acquisition system and computer by the GPIF interface mode using USB2.0, and displayed in the host computer.The experimental results show that the system has stable performance, can pinpoint the CCD signal peak position with changing the light position. The speed and accuracy of system has to meet requirements of the hardware data acquisition card in a variety of non-contact measurement, combined with optical technology and the signal processing technology, the CCD data acquisition system has been applied to a laser triangulation displacement measurement.