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ST VL53L1X Manual

ST VL53L1X Manual

Counting people with long-distance ranging time-of-flight sensor
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UM2600
User manual
Counting people with the VL53L1X long-distance ranging Time-of-Flight sensor
Introduction
This user manual explains how to use a VL53L1X long-distance ranging Time-of-Flight (ToF) sensor to count people crossing a
specific predefined area, like a meeting room entrance or a particular location in a corridor. It also describes an algorithm used
to count the people. The algorithm is provided as an example and can be downloaded from st.com, in the VL53L1X embedded
SW section, under the reference STSW-IMG010.
In addition, this document presents the details of a counting application where a sensor is set on the top, not the side, of the
area to be tracked.
UM2600 - Rev 1 - June 2019
www.st.com
For further information contact your local STMicroelectronics sales office.

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Summary of Contents for ST VL53L1X

  • Page 1 It also describes an algorithm used to count the people. The algorithm is provided as an example and can be downloaded from st.com, in the VL53L1X embedded SW section, under the reference STSW-IMG010.

  • Page 2: Acronyms And Abbreviations

    UM2600 Acronyms and abbreviations Acronyms and abbreviations Table 1. Acronyms and abbreviations Acronym/abbreviation Definition field of view SPAD single photon avalanche diode software Time-of-Flight UM2600 - Rev 1 page 2/14...

  • Page 3: Overview

    Overview Overview Counting people with the VL53L1X consists of using the multiple zones of the sensor receiving SPAD area, and of configuring it with two distinct fields of view (FoV), to alternatively get a ranging distance from them and consequently recognize the movements of a person. Using this method, the number of people occupying a meeting room, accessible from a reasonably narrow access, is known at all times by detecting the entrances and exits of the attendees.

  • Page 4: Algorithm Description

    UM2600 Algorithm description Algorithm description The counting algorithm example relies on a list of states that have to occur in a certain order to detect if a person has crossed the specified area and in which direction this area has been crossed. These states are stored in a list and compared to two default lists of states that represent how the area is crossed in two different directions.

  • Page 5: Hysteresis

    UM2600 Hysteresis Hysteresis The algorithm validates a crossing event only when a person has fully crossed the two zones. It does not validate the event when the person remains for a long time under the FoV or when the person decides to return from the place he came from.

  • Page 6: Vl53L1X Sensor And Algorithm Configuration

    VL53L1X sensor and algorithm configuration It is sufficient to set the two FoVs by dividing the 16*16 SPAD array of the VL53L1X sensor into two sub N*16 arrays. For example, N can be chosen within the interval [4, 8]. This means that it is not necessary to use the same SPADs for front and back ranging.

  • Page 7: Software And Board Package

    The serial speed is set at the 460800 bauds per second. The figure below shows the captured distances from two zones, where the VL53L1X is set at 2600 mm from the floor. The black arrows correspond to the times when a person was detected entering or exiting the area being tracked.
  • Page 8 UM2600 Software and board package Figure 8. Example of captured distances UM2600 - Rev 1 page 8/14...

  • Page 9: Setup Reliability

    UM2600 Setup reliability Setup reliability Ranging on the floor Reliability of the algorithm relies on the accuracy of the setup which detects the distance between the sensor and the floor. This can be ensured only if nothing (e.g. no obstacle or static object) blocks the front and back FoVs. The two figures below illustrate two cases where the distance to the floor is measured over many measurements.
  • Page 10 UM2600 Ranging on the floor Figure 10. Unreliable setup, the mean of the measured distances from the two zones is significantly different and the minimum measured distance is greater than the distance between the sensor and the floor (2600 mm) minus 700 mm.

  • Page 11: Ensure Overlap In The Two Detection Zones

    UM2600 Ensure overlap in the two detection zones The figure below shows a trimming procedure example in which a significant number of distances have been extracted by ranging with the SPADs enabled within the red rectangle (10 SPADs lines). The red rectangle can be moved by one line or more between each test.

  • Page 12: Revision History

    UM2600 Revision history Table 2. Document revision history Date Version Changes 26-Jun-2019 Initial release UM2600 - Rev 1 page 12/14...

  • Page 13: Table Of Contents

    VL53L1X sensor and algorithm configuration ........
  • Page 14 ST’s terms and conditions of sale in place at the time of order acknowledgement. Purchasers are solely responsible for the choice, selection, and use of ST products and ST assumes no liability for application assistance or the design of Purchasers’...

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