Constructing Embedded Car License Plate Recognition System Computer Science and Information Engineering, Tamkang University I-Chih, Chen Advisor: Prof. Wen-Bing, Horng
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Constructing Embedded Car License Plate Recognition System
Computer Science and Information Engineering, Tamkang University
I-Chih, ChenAdvisor: Prof. Wen-Bing, Horng
03/17/15 WISE Lab.
Outline
Introduction Car License Plate Recognition Embedded System
Embedded System Limits Embedded Linux: uClinux
Develop Method Verification Experiment Conclusion
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Introduction Embedded system
To perform specific function Work in time constrained
environment Simple architecture
Low cost Low energy consumption Smaller size
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Introduction Application of car license
plate recognition Law enforcement Security
Parking management Porting car license plate
recognition system to embedded system environment
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Target Board : Creator
Creator is an embedded system target board, contributed by Microtime (新華電腦公司 )
Samsung S3C4510B, ARM7 2MB Flash Memory 16MB SDRAM CMOS(320x240) LCD(160x120) Ethernet
RS-232
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Target Board: Creator
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Outline
Introduction Car License Plate Recognition Embedded System
Embedded System Limits Embedded Linux: uClinux
Develop Method Verification Experiment Conclusion
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Car License Plate Recognition
Image acquisition Car license plate
locating Character segmentation Character recognition Output result
Character segmentation
Character recognition
License display module
Car license plate locating
Display car number
Image capture module
Input vehicle image
Car license plate recognition
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Image Acquisition
CMOS is composed of photodiode
Photodiode captures the intensity of light
Red light was filtered
through red color filter Color Filter Array, CFA
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Color Filter Array, CFA CFA format will decrease
2/3 light intensity Transform four CFA pixels
to one RGB pixel Convert CFA to gray level
Recover light intensity smoothing
BGRY ×+×+×= 114.0587.0299.0
10)117)'(301234(1024
)114)'(5.293229(024.11000
114)'(5875.0229
>>×++×+×=
×++×+××=
×++××+×=
BGGR
BGGR
BGGRY
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Color Filter Array, CFA
Before Convert After Convert
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Locate Car License Plate
Vertical edge is a significant feature of car license plate
Sobel filter enhances edges in the image
edge of levelgray :),(
windowsliding ofboundary right andleft :,
windowsliding ofboundary topand buttom:,
),(__
yxf
rwlw
thbh
yxfedgesofsumbh
thy
rw
lwx∑ ∑
= =
=
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Character Segmentation
Gray level stretching Enhance contrast
K-mean algorithm Threshold
Vertical projection Character
segmentation
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Character Recognition
Character features is extracted by Kirsch Mask
Horizontal feature Vertical feature Left diagonal feature Right diagonal feature
Training neuron network with those features as input
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Horizontal Vertical Left diagonal
Right diagonal
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Outline
Introduction Car License Plate Recognition Embedded System
Embedded System Limits Embedded Linux: uClinux
Develop Method Verification Experiment Conclusion
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Embedded System Limits Processor power
The clock rate of ARM7 is between 80~133Mhz
Floating number operation is slow
Memory capacity 16MB SDRAM PC has 256MB SDRAM
Storage capacity 2MB flash memory PC has 40GB hard driver
Hardware control Driver, ARM tool chain
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PC Creator
Processor 1.2 GHz 100 MHz
Memory 256 MB 16 MB
Storage 40 GB 2 MB
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Embedded Linux: uClinux Without operating system
Follow the hardware spec. and set all flags Hard to handle complicated process
With operating system Hardware control Process scheduling Easy to handle complicated process
uClinux helps development Support TCP/IP Support network file system Basic control interface
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Outline
Introduction Car License Plate Recognition Embedded System
Embedded System Limits Embedded Linux: uClinux
Develop Method Verification Experiment Conclusion
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Develop Method
When developing an embedded program, we usually…
Modify source code Recompile source code Burn program and uClinux
into flash memory. It takes almost 5~10 minutes
Network file system, NFS Access remote hard driver Reduce burning time
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Directory /mnt mounts remote hard driver
Car license plate recognition algorithm
Car license plate recognition algorithm
/nfsProgram
/nfsProgram
/mnt/mnt
Network file system
CFA Image
Commands
Load program
HV- 5597
Image capture
Development
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Outline
Introduction Car License Plate Recognition Embedded System
Embedded System Limits Embedded Linux: uClinux
Develop Method Verification Experiment Conclusion
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Verification Car license plate
recognition system PC version Embedded version
Input same image to both versions
Run car license plate recognition program in both platforms
Compare car license plate recognition results
HV-5597HV-5597 HV-5597HV-5597
EmbeddedVersion
EmbeddedVersion
PCversion
PCversion
Client Server
Compare
PCCreator
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Outline
Introduction Car License Plate Recognition Embedded System
Embedded System Limits Embedded Linux: uClinux
Develop Method Verification Experiment Conclusion
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Experiment
CMOS
Car image
Recognition result
Ethernet
RS-232
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Experiment
Car license plate recognition system
PC version
Car license plate recognition system
Embedded version
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Experiment
GA-3705 EX-7625 HX-6580P7-5250
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Outline
Introduction Car License Plate Recognition Embedded System
Embedded System limits Embedded Linux: uClinux
Develop Method Verification Conclusion
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Conclusion Car license plate recognition algorithm
Covert CFA to grey level Avoid floating number
Response time: from 1 minute to 6 second Software porting procedure
From pc to embedded system uClinux helps hardware control and development
Using NFS to debug saves 5~10 minutes burning time Verification
The accuracy is suffered from Light CMOS resolution Processor power
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Thanks
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