Application of TDC-GP2 in Laser Range Sensor
Laser range finder sensor can get the distance between sensor and detecting target by measuring flight time of laser pulse. The designed laser pulse measurement sensor use FPGA EP2C20F as the control core of system. In order to improve measurement precisi
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School of Mechatronics Engineering and Automation, Shanghai University, China 2 The Third Research Institute of Ministry of Public Security, China
Abstract. Laser range finder sensor can get the distance between sensor and detecting target by measuring flight time of laser pulse. The designed laser pulse measurement sensor use FPGA EP2C20F as the control core of system. In order to improve measurement precision of laser flight time interval, we have designed a time interval measurement module by using a special high precision time to digital converter TDC-GP2. The testing resolution is up to 65ps. This sensor is low power dissipation and high measuring accuracy. Keywords: TDC-GP2, time interval measurement, laser ranging, time delay channel.
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Introduction
The pulsed laser ranging is widely used in industry, aerospace, geodesy and robot for its high peak power`[1], long detection distance and high range measuring accuracy. It get the distance between sensor and detecting target by analyzing the round trip time of transmitted pulse and echo pulse. In order to realize high precision measurement, we need to measure the laser flight time interval [2]l accurately. The TDC_GP2 which is a high precision time to digital converter, use the delay line insertion method [3]. It reached the picosecond level by quantifying time interval accurately using transmission delay of simple logic portal. It can measure the time interval between two or more pulses . It has two measurement range, 0-1.8us (0270m) and 2Tref-4ms (75m-25km). The typical resolution of two channels is 65ps. Every single channel can response three or four stops pulse signal and filter noise in two measurement mode [4, 5]. So this chip is not only measurement accurately, but also very large range. We have designed a time interval measurement module by one channel based on TDC-GP2 chip [6]. This circuit is high integration, low power dissipation, system stable and beneficial to improve measurement accuracy.
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Principal Structure of TDC
The pulsed laser calculates distance by measure the time between emission and return [7]. So the time measurement step is very important. For the speed of laser is especially fast, the time interval between laser pulses is very small. For example, if we need to James J. (Jong Hyuk) Park et al. (eds.), Future Information Technology, Lecture Notes in Electrical Engineering 309, DOI: 10.1007/978-3-642-55038-6_49, © Springer-Verlag Berlin Heidelberg 2014
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Y. Xian, Z. Tang, and B. Li
calculate distance of 1 kilometer and the resolution require 1cm, the resolution of time interval is up to 67ps. TDC-GP2 is the next generation of ACAM general purpose TDCs [8]. Higher resolution and smaller package size make it ideal for cost sensitive industrial applications. With special functional blocks like a fire-pulse generator, stop-enable, temperature measurement, and clock control it is perfectly suited for ultrasonic flow-meter and heat meter applications. It has two measurement ranges [9]. In range one, TDC has 2 channels with
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