LED Location Beacon System Based on Processing of Digital Images

1
CSCI 6602 Digital Image Processing
Topic LED Location Beacon System Based on
Processing of Digital
Images
Presented by Pradeep Monga
2
Background

• TRANSPORTATION is an important aspect in modern
  human lives, which makes Intelligent
  Transportation Systems (ITS) very crucial in any
  highly urbanized city in the world.
• Presented here, is a novel idea on the dual use
  of the LED-based traffic light, which can
  transmit information wirelessly and optically.
• The aim is to develop an Intelligent
  Transportation System.

3
Introduction

• A digital camera is used to capture images
  contained in the LED beacon signal.
• The examined issues are
• structure of the transmitter and the receiver,
• signaling method,
• transmission protocol of the LED panel,
• relationship between the camera capturing rate
  and the LED pattern update rate,
• digital camera exposure technology, and
• efficiency of the image processing algorithms.

4
Intelligent LED Traffic Light
5
Problem Definition

• Digital Camera as an LED Beacon Signal Receiver
• LOS problem
• Signal not received if receiver displaced by
  few degrees.
• Capturing Frame Rate
• 400 frames / sec.
• Communication Protocols
• No synchro between camera frame rate and LED
  flashing frequency.
• Exposure Technology
• Electronic rolling shutter technology
• Image Processing for the LED Beacon Signal
• Time consuming, Signal head detection task

6
Analysis of the LOS problem

• Digital Camera as a receiver
• provides a wider Field-of-View focal length 7.4
  mm and sensor width of 4.2 mm gives horizontal
  FOV close to 30o, while in the photodiode based
  receiver FOV is 5o when radius of photodiode is
  4 mm and focal length is 50 mm,
• low-cost and small in size,
• traffic condition detection,
• collision avoidance,
• rear viewer,
• lane keeping, etc

7
Block Diagram
8
A real life scenario
9
Signalling method of the Intelligent LED Traffic
Light

• LED panel is divided into 9 partitions.
• More partitions (16 or 25) will give larger
  channel capacity but with poorer resolution.
• Within each partition, all the LEDs are either
  On or OFF. In a specified period, some
  partitions are ON and some are OFF in the LED
  panel and this gives a specific pattern.
• Each unique pattern and its complement are used
  to represent a location code.
• The principle is just like pasting a bar code on
  a signpost which tells its location.

10
Examples of the LED panel patterns
There could be 512 different patterns like this
11
Transmission Protocol

• Criteria for the Transmission Protocol Design
• Intelligent LED traffic light acts as a signaling
  device for traffic control as well as a location
  beacon to transmit position information to
  vehicles,
• LED panel should be capable of transmitting
  information wirelessly and optically,
• Minimizing the number of image frames for faster
  extraction of location code,
• The location beacon is a simplex communication
  link, thus the protocol design should prevent
  the need for synchronization between the
  transmitter and receiver.

12
A-On-A-Off protocol
The LED patterns A, On, A and Off are displayed
sequentially for a short period. This sequence is
repeated periodically. The switching is
undetectable to human eye but is captured on the
camera. The differencing helps in extraction of
location code.
13
Recovery of Location Code

• Follow the process of
• Differencing
• Row-Column projection
• Feature Extraction
• Pattern Classification

14
Row-Column Projection
15
Experiments Results for Beacon System
16
Conclusion

• These ideas and designs can be an alternative to
  the existing location beacon systems for vehicle
  positioning and related applications.
• Experiments using prototype transmitter and
  prototype receiver gave a good demonstration of
  the viability of the ideas and methodologies
  developed.
• The performance of the system depends on the
  structure of LED panel, the resolution of the
  camera, the exposure technology of the camera,
  the speed of the image processor, movement of the
  camera and surrounding objects.
• The methodologies developed blend several
  technologies like active pixel CMOS vision
  sensor, high brightness LEDs, and digital image
  processing technique.

17
References

• LED location beacon system based on processing of
  digital imagesPang, G.K.H. Liu,
  H.H.S.Intelligent Transportation Systems, IEEE
  Transactions on , Volume 2 , Issue 3 , Sept.
  2001 Pages135 150
• Optical wireless based on high brightness visible
  LEDsPang, G. Kwan, T. Liu, H. Chi-Ho
  ChanIndustry Applications Conference, 1999.
  Thirty-Fourth IAS Annual Meeting. Conference
  Record of the 1999 IEEE , Volume 3 , 3-7 Oct.
  1999 Pages1693 - 1699 vol.3
• The Benefits Of Led Traffic Lights In London And
  The Pilot Test SitesIbrahim, D. Beasley,
  M.Road Transport Information and Control, 1998.
  9th International Conference on (Conf. Publ. No.
  454) , 21-23 Apr 1998 Pages172 - 176

18
Thanx ! Any Comments or Suggestions are Welcome