Simple implementation solution for laser range finder

I. Project Overview

1.1 Introduction

Laser ranging has high angular resolution and strong anti-interference ability. It can avoid the multipath effect and ground object interference problem of microwave close to the ground, and has the advantages of light weight, compact structure, convenient installation and adjustment, etc. One of the ideal instruments. After the construction of the railway tunnel, the surrounding rock has a slow trend, and the rangefinder can measure its convergence.

1.2 Project Background / Motivation

According to our research market, the price of ordinary handheld laser range finder is about 1000 yuan, with other communication interfaces such as serial port being more than 2000 yuan, and the function is single and the interface is simple. Therefore, we use AVR128 processor to construct a new laser ranging detection system, which has multi-function, high-precision, automation and price advantages, and is applied to the surrounding rock monitoring of railway tunnels.

Second, the demand analysis

2.1 Functional requirements

The designed range finder is capable of 24/7 measurement of the convergence of the railway tunnel and is capable of saving data to the SD card and transmitting it to the monitoring center.

2.2 Performance requirements

Designed range finder, the angle is above 0.1mm, the module is stable and reliable.

Third, the program design

3.1 System function realization principle

Taking advantage of the extremely short duration of the laser pulse and the large instantaneous power, even if there is no cooperation target, the distance measurement can be performed by receiving the diffuse reflection signal of the measured object. The principle of pulsed laser ranging is similar to radar ranging. A pulse laser is used to transmit a single laser pulse or laser pulse train to a target. The counter measures the round trip time when the laser pulse reaches the target and returns to the receiver by the target, thereby calculating the target. distance. The principle of pulsed laser ranging is shown in Figure 1. The ranging formula is: d = ct/2. Where d is the measurement distance, c is the speed of light, and t is the round trip time of the ranging signal.