Resources - FAQs

Your one-stop destination for everything you need to kickstart your journey with LightWare’s microLiDAR®.

Frequently asked questions

LightWare Studio

Learn how to download and use LightWare Studio in the video below.

Learn how to upgrade the firmware on your LightWare sensor in the video below:

Technical information

LightWare’s products use lasers that emit light with a wavelength of 905 nm. This wavelength has been chosen to provide a good balance between reliability and eye safety. Shorter wavelengths are more hazardous and lasers with longer wavelengths are less reliable.

All LightWare products use the “direct time-of-flight” principle to measure distance. This works by timing how long it takes for a flash of laser light to travel to the surface being measured and back again. The distance is calculated using the equation:

distance-to-surface = speed-of-light x time-of-flight / 2

What makes the beam spread analysis difficult is that there is an “actual” beam spread and an “effective” beam spread.

The “actual” beam spread is an optical phenomena caused by the geometry of the lenses. This is a diverging cone that increases linearly in size as the distance increases.

The “effective” beam divergence is a measure of what the detector sees when a target is in the beam. At close distances the “effective” and “actual” beam divergence are similar. As soon as the edge of the target enters the beam it is detected making the apparent position of the edge of the beam match with the theoretical position.

As the distance increases the signal gets weaker so more of the target needs to be directly in the beam before the return signal can be detected. In other words the apparent edge of the beam no longer matches with the theoretical edge. This makes the beam appear to be smaller than the “actual” beam diameter and the “effective” beam divergence reduces as the distance increases.

As an example, a field-test with an LW20/C provided the following results:

at 10 m distance – beam spread of approx. 4.5 cm
at 45 m distance – beam spread of 19.0 cm
at 91 m distance – beam spread of 20.3 cm

The PLD (Pulsed Laser Diode) and APD (Avalanche Photo Diode) LightWare uses in their Laser Rangefinders have a lifespan of 100 000 hours.

The other electronic components have a much longer lifespan.

Caution: Electronics may degrade if subjected to high temperatures. We recommended keeping the products well within the specified operating temperatures.

The mean time between failure (MTBF) of mechanical components inside scanning devices are as follows:

– motors: approximately 6 000 hours

– slip rings: approximately 2 000 hours

In case of failure or maintenance please contact LightWare for our RMA procedure.

The SF 22 is a great tool for hobbyists who want to get their hands on a long range LiDAR at low cost. This unit has 100 m range and is able to connect via Serial UART or I2C. This amazing little unit has a resolution of 1 cm, thus it also has high precision. In this article we will connect to the SF 22 using a Serial UART connection.

In this application guide:

We will look at the difference between first and last return signals
How knowing this information will allow you to set up the device more optimally
All libraries used in this document can be found in the Quickstart & API reference guide

When a LiDAR unit measures range, generally it is a solid surface that the return signal is received from. But what happens to light that passes through a surface that light is able to pass through such as glass or perspex? The result is you get two signals back. This is not apparent at close range, this is due to the wavelength of the laser. Depending on the wavelength of the sensor you are using, there will be a range where the first and last return data will appear to be the same. This is because the “length” of the light pulse is of a certain distance and at a short distance the two return signals are seen as one continuous return by the APD sensor. Both instances will be shown below, the first image shows what happens at close range. The second image shows what happens at long range.

Short Distance Return Signal

Definition

First return – simply put is the light signal that the SF 22 receives as the first strong light signal back from the single pulse.
Second return – is the second light signal that the SF 22 receives as the second strong signal back from a single pulse.

Connecting the Arduino for Serial UART communication:

SF 22 Serial UART connection to Arduino

Arduino Code

The code given below is available in the quick start guide (Quickstart & API reference guide), a slight addition to the code needs to be made to access the second return information.

The following lines of code were added to the code:

(sf22.lastRaw_cm,DEC) … ( access the last return distance in centimeters.)

(sf22.lastStrength_cm,DEC) …( access the last return signal strength in centimeters.)

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Code:

// www.Lightware.co.za Oct 2019

// Lightware example code using the lw_sf22.h library

// This library enables the use of the I2C and Serial Interface

// This library is designed to use 2 Serial ports on the Arduino

#include <lw_sf22.h>

#include <Wire.h>

LW_SF22 sf22(Serial1, Serial);

void setup() {

//this is the serial port for the terminal window

Serial.begin(115200);

// Setup the Serial port for the SF22 interface

Serial1.begin(115200);

// Disable any possible streaming data

sf22.writeDataStreamType(0);

delay(100);