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HD LPR System For Toll Gate
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HD LPR System for Toll Gate
Hangzhou Hikvision Digital Technology Co., Ltd.
2015.9
HD LPR System For Toll Gate
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Content
Chapter 1 System Overview ........................................................................................... 3
1.1 Application background .................................................................................... 3
1.2 Demand analysis ............................................................................................... 3
1.2.1 Business analysis ........................................................................... 3
1.2.2 Functional requirements analysis ................................................... 4
1.3 Building Goals .................................................................................................. 4
Chapter 2 System overall design..................................................................................... 5
2.1 System overall structure .................................................................................... 5
2.2 Front end subsystem ......................................................................................... 5
2.2.1 Car-checking unit ........................................................................... 6
2.2.2 HD image acquisition and processing unit .................................... 6
2.2.3 Communication unit....................................................................... 6
2.3 Model Selection ................................................................................................ 7
2.3.1 Car plate recognition and capture unit (PRCU-4101-T) ............. 7
2.3.2 Compensating light ........................................................................ 7
Chapter 3 System installation ......................................................................................... 8
Chapter 4 Functions ...................................................................................................... 10
4.1 Main functions ................................................................................................ 10
4.2 Charging function ........................................................................................... 10
4.2.1 Prevention of cards exchanging ................................................... 10
4.2.2 Vehicle model classification assistance........................................ 12
4.2.3 Toll free vehicle management ...................................................... 13
4.2.4 Blacklist management .................................................................. 13
Chapter5 Performance Index ........................................................................................ 13
Chapter 6 System Features............................................................................................ 15
Chapter 7 Capture Performance .................................................................................... 16
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Chapter 1 System Overview
1.1 Application background
As the economy soars all these years, highway is developing rapidly. With the
increasing of road networks and tolls, many problems emerge in current highway
charging system. These problems are summarized as follows:
1) Car plate number must be entered manually which involves large
workload and thus greatly decreasing passing efficiency.
2) Cars of opposite directions exchange passing card during the journey so
fewer miles will be counted by system, which leads to large toll loss.
3) Toll collector relegates vehicle types deliberately so as to cheat the
charging system and get illegal income. They even buy and sell passing
card illegally.
4) Poor management on charge-free cars and black-listed cars.
5) Isolation between surveillance system and charging system.
It is a waste of money to build two separate systems for surveillance
system and charging system respectively.
1.2 Demand analysis
1.2.1 Business analysis
1) Improve the service quality of toll gate
By capturing plate number automatically, HD car plate recognition system
greatly reduces manual workload. That also helps to lessen the passing time
and enlarge traffic capacity of toll gate.
2) Prevent toll loss
To prevent the toll loss caused by exchanging passing card, the HD car plate
recognition system must be with following functions. The system can
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automatically recognize the car plate, and then extract binary image and write
it into passing card. At the exit toll gate, car plate will be recognized a second
time. System then compares these two pieces of information. Alarm will be
triggered if they are mismatched.
By correlating the car types and image, there is no way for toll collector to
relegate car type for extra illegal income.
3) Surveillance demands for Charging channels of toll gate
To prevent dispute, HD car plate recognition system should also be with
video recording function to keep a log of passing cars for future
investigation.
4) Resource integration needs
Charging system and operating system are both in need of video surveillance
resource. Given the two systems must be physically independent, cameras
used in HD car plate recognition system must be with two independent
network interfaces which provide those two systems with separated video
signals thereby saving cost and protecting network security.
1.2.2 Functional requirements analysis
1) Vehicle-capturing needs
The current needs require that HD car plate recognition system should
capture the passing car automatically and record its image.
2) Car plate recognition needs
HD car plate recognition system must be capable to recognize the
information on the plate such as letter, number and color. Binary image of
car plate is also required.
1.3 Building Goals
Install HD car plate recognition system to highway toll gate so that car plate can
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be captured and recognized automatically. In that way, the operating efficiency of toll
gate is greatly improved especially in terms of more standardized management,
abundant analyzed data brought by system, elimination of cheating behaviors. The
benefit it brings is obvious both in economic and social aspects.
Chapter 2 System overall design
2.1 System overall structure
HD car plate recognition system includes: front ends subsystem, transmission
system and central subsystem which implements the central management to
information collection, transmission and application.
System structure
The main system involves charging system and video surveillance system,
captured data and video stream are transmitted to those two via two physically
separated network interfaces on each capture unit.
2.2 Front end subsystem
Front end subsystem includes car-checking unit, HD image processing unit and
communication unit.
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2.2.1 Car-checking unit
Currently in our country and abroad, the most of road monitoring systems are
mainly based on two working modes: induction coil and video detection。
1. induction coil
Induction coil is the most favorable car-checking method with high precision.
Car-checking unit communicates with HD capture camera through IO control cable.
When a car passes above the induction coil, car-checking unit gets the trigger signal
and control the HD camera to capture image.
2. video detection
Car-checking algorithm is embedded in the capture camera, so it is no need to
underlay the induction coil. It is a good alternative of induction coil which features
long construction period, damage of road and large maintenance workload. But still
its capture rate is lower than induction coil. This shortcoming could be made up
through multi-frame checking method.
2.2.2 HD image acquisition and processing unit
This unit consists of capture unit, fill-flash unit and column unit. Specifically
camera used in capture unit is 3maga pixels and fill flash unit adopts strobe LED
lamp.
Progressive scanning CCD of industrial level and high-speed DSP are integrated
in HD capture camera. Each unit can complete functions such as image capturing, car
plate recognition independently thus enhancing the processing ability of the whole
system. In that way, the system becomes more simple and easy to extend.
2.2.3 Communication unit
Composed by Ethernet switches and transmission link, this unit is mainly
responsible for data transmission and exchanging
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2.3 Model Selection
2.3.1 Car plate recognition and capture unit (PRCU-4101-T)
1/1.8 inch 300maga pixels high definition color camera
2048(H)×1536(V);
Support car plate recognition;
Support LED light compensation;
2.3.2 Compensating light
2.3.2.1 White-light LED compensating lamp (SLU-2100)
16 LED lamps;
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Color temperature:5000-7000K;
Trigger frequency:50Hz~400 Hz;
Response time:≤20us。
Chapter 3 System installation
The following picture shows the typical application of HD Car Plate Recognition
System used in highway toll gate. Equipped with HD plate recognition cameras of 3
mega pixels, the capture unit is mounted on toll island.
On-site mounting
The following picture shows the on-site effect:
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On-site effect
Induction loop is under laid 300mm beside the toll window and the exact
dimensions are as below.
100mm
100mm
2200mm 2400mm
800mm100mm 100mm
1000mm
Dimensions of induction loop
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Chapter 4 Functions
4.1 Main functions
Main functions of HD Car Plate Recognition System include: image capturing,
car plate recognition and video surveillance.
1) Capture and recognition function
This system can capture image of automobiles automatically and recognize
plate number.
Plus: oversea version must be customized according to different areas
2) Data provider function
This system can provide key information of cars to charging system such as
binary plate image and HD car image of frontal view.
3) HD surveillance video stream
4) Capture units provide HD video stream to charging system and surveillance
system.
5) Support Countries and regions: Singapore, Malaysia, Indonesia, Australia,
Korea, Vietnam, Thailand, Hong Kong, Macao, Taiwan, Philippines, Turkey,
United Arab Emirates
4.2 Charging function
4.2.1 Prevention of cards exchanging
1) Implementation principles
For Enclosed highway, drivers get passing card at the entrance and hand in it at
the exit together with passing fee. At entrance, capture cameras read in car plate
number and write its binary image into the passing card. When the car gets to the exit,
the system compares these two pictures. An alarm will be triggered asking for manual
intervention if any differences are found.
2) Processing flow
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Entrance flow Exit flow
There is no charging process at Highway Entrance. Camera in lane controller
reads in plate number, converts it to binary image and writes it into IC card (the same
thing as passing card in preceding paragraph) ,
Drivers carry that card all the way to the exit. After charging process, processing
data(car plate recognizing result, entrance number, vehicle model, processing type,
lane number, toll collector number, passing time ) produced by lane controller will be
saved locally and also uploaded to charging system at the same time.
At the exit, lane controller will compare the plate number with which saved in IC
card. If they are mismatched, the system will invoke the original plate images
captured at entrance and exit respectively and compare them again. If the result is
negative then the plate binary image captured at entrance will be displayed on the
screen of lane controller and also an alarm will be triggered.
In actual implementation, recognition rate cannot get to 100%.In some cases, car
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plate cannot be recognized successfully. To make up that deficiency, binary image
comparison technique is adopted in this system. By using that, stained plate
recognition problem is solved. Data size of binary image is very low and can be easily
saved into IC card. Moreover, internet is not necessary for Data transmission between
entrance and exit so system requirements are not high and data transmission is much
safer, faster and more reliable.
3) Comparison algorithm of binary image of plate
Image comparison is a relatively complex problem. This system mainly adopts
techniques such as revolving correction, sliding matching and elastic matching to
judge two pictures if they are from the same origin.
The matching module is packaged into a dynamic link library, so the lane
controller only needs to invoke interface functions to complete matching process.
In the situation when no reliable plate recognition result is available, this
algorithm perfectly extracts the plate number from binary image. By taking full use of
reflecting light, recognition result can be guaranteed even in some special
circumstances where car plate is seriously stained.
4.2.2 Vehicle model classification assistance
1) Implementation method
First is to set up a library including plate numbers and vehicle models, each
number correspond to a vehicle model. Then when toll collector enters the vehicle
model, the data including plate number will be uploaded into sever and compared in
the library.
2) Processing procedure
Establishing data library automatically
When a car first passes through the toll gate, its relative information such as plate
number and vehicle model will be sent to data server. Among them, plate number is
recognized by lane controller while vehicle model is entered by toll collector
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manually.
Alarming automatically
When the same car passes toll gate again, system will compare the plate number
and model automatically with the record in the library. If they are mismatched, the
system will trigger the alarm to remind auditor.
Audit
Auditor confirms the vehicle model through the car image and record. Then the
correct data will be updated into the library.
4.2.3 Toll free vehicle management
Establishing a database for toll free library and only the vehicles in library can
pass for free.
4.2.4 Blacklist management
Establish a data base for blacklisted vehicles. When the vehicles in the blacklist
pass, alarm will be triggered asking for further handling
Chapter5 Performance Index
Serial
Number
Project Index
1 Capture and recognizing time ≤200ms
2 Plate recognizing rate Customization for different areas
3 Captured image index Definition 2048(H)×1536(V),JPEG,about400KB
4
Binary plate image index
Dimensions (length × width): 112×20pixels(depends
on particular case)
size:≤280byte(depends on particular case)
5 Mean Time Between Failures
MTBF ≥20000h
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Serial
Number
Project Index
6 Shutter speed 1/25s to 1/100,000s ,support continuous adjustment
7 Trigger mode Support on-off external input mode and software
instruction trigger mode.
8 Interface two 10/100/1000Mbps Ethernet interfaces,one RS485
interface ,one RS232 serial port。
9 Column dimensions Height 1300,chassis R150(depends on particular case)
10 IP Grade HD plate recognizer:≥IP55(Compensation LED :IP65)
11 Power source 100VAC~240VAC,48Hz~52Hz
12 Power consumption <50W
13 Operating temperature -10℃~+60℃(without heater and radiator)
14 Operating humidity <95%@40℃,No condensation
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Chapter 6 System Features
1. Intelligent HD cameras integrated with image capture and recognizing
Intelligent HD cameras adopt HD CCD, ISP and high-performance
DSP architecture. It supports JPEG and H.264 video stream output
simultaneously. More importantly, image capture and plate recognition
are both completed in HD cameras. So the system is very simple and
easy to extend.
2. Dual network interfaces and output ports
The two network cards are physically isolated so that data security can
be guaranteed. DSP in the camera generates two copies of original data
and sends them to corresponding network cards whereby the data is then
uploaded to charging network and surveillance network respectively. It is
a very cost-efficient design.
3. High plate recognition rate
The plate recognition technique includes plate locating and character
segmentation and it is in leading level in so many domestic industrial
applications. We also have total property right of his technique.
4. Advanced matching algorithm
In the case where the plate is seriously stained and no clear image can be
acquired, system callouts the original plate image (captured at the
entrance) saved in IC card and compares it to the image captured at exit.
The matching module adopts advanced image matching algorithm which
is able to judge if two images come from the same origin. The
automatically matching algorithm greatly relieves manual workload and
promotes the plate matching rate.