Simple implementation solution for laser rangefinder

1. Project Overview

1.1 Introduction

Laser ranging has high angular resolution and strong anti-interference ability. It can avoid the multipath effect and ground interference of microwaves close to the ground. It is also light, compact, and easy to install and adjust. It is one of the most ideal instruments for high-precision ranging. After the construction of a railway tunnel is completed, its surrounding rock tends to change slowly, and the rangefinder can measure its convergence.

1.2 Project Background/Motivation for Topic Selection

According to our market research, the price of ordinary handheld laser rangefinders is about 1,000 yuan, and those with serial ports and other communication interfaces are more than 2,000 yuan, and they have single functions and simple interfaces. Therefore, we use the AVR128 processor to construct a new laser rangefinder detection system, which has multi-functions, high precision, automation and price advantages, and is applied to the surrounding rock convergence monitoring of railway tunnels.

2. Demand Analysis

2.1 Functional requirements

The designed distance meter can measure the convergence of railway tunnels around the clock, save the data to SD card and transmit it to the monitoring center.

2.2 Performance requirements

The designed rangefinder has an angle of more than 0.1mm, and the module is stable and reliable.

3. Solution Design

3.1 System Function Implementation Principle

Taking advantage of the extremely short duration and high instantaneous power of laser pulses, even without a cooperating target, the distance can be measured by receiving the diffuse reflection signal of the target. The principle of pulse laser ranging is similar to radar ranging. A pulsed laser is used to emit a single laser pulse or a laser pulse train to the target. The counter measures the round-trip time from the laser pulse to the target and back to the receiver, thereby calculating the distance of the target. The principle of pulse laser ranging is shown in Figure 1, and the ranging formula is: d=ct/2. Among them, d is the measured distance, c is the speed of light, and t is the round-trip time of the ranging signal.

Figure 1 Principle of pulse laser ranging