JPH0368099A - license plate recognition device - Google Patents

Abstract

PURPOSE:To quickly perform the bus arbitration control most suitable for number plate recognition processing by giving a higher priority level to a bus acquisition request and switching the priority between plate segmenting processing and character recognition processing in accordance with the processing condition. CONSTITUTION:A bus permitting signal consists of a whole control card input LWAV1, plate segmenting and character recognizing card inputs LWAV2 to LWAV12, and a monitoring processing card input LWAV13. The highest priority level and the second highest priority level are given to the request from a monitoring processing card (LWRQ13) and that from a whole control processing card (LWRQ1) respectively. Requests in plate segmenting processing cards (LWRQ2 to LWRQ7) and requests in character recognition processing cards (LWRQ8 to LWRQ12) are preferred in the occurrence order; and when they simultaneously occur, the precedence is determined in each highest priority level.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an automatic license plate recognition device that images a traveling vehicle with a television camera and processes the obtained still image to recognize the license plate of the vehicle. .

(Conventional Technique #) Conventionally, in this type of bus right arbitration device, the priority of each line is determined by the connection state of the bus request lines, and a line with a lower priority is determined by a higher request line than the bus request line. The right to use the bus could not be obtained while the bus was being used or requesting bus use.

In this system, the right to use the bus was granted to a bus use request from a line with a lower priority only when the bus was in an unused state and all higher-order lines had not issued use requests.

(Problems to be Solved by the Invention) In the conventional bus use right arbitration device described above, the number of request lines is usually 8 or less, but if the number increases by 1 and the bus usage frequency is high, the request line with low priority is The disadvantage was that it required a long wait to obtain usage rights. For license plate recognition, for example, character recognition of vehicle model code and character recognition of usage code, the recognition result will not be valid unless both recognitions are completed, and there is no priority for each character recognition process. In such a case, due to the limitations of the bus arbitration system, since priority is given, bus access is waited for only one character recognition process, resulting in a delay in the recognition result.

On the other hand, license plate recognition processing requires processing all vehicles that are continuously running, so plate extraction processing and character recognition processing are performed in a pipeline system.
Furthermore, the plate cutting process itself is internally a pipeline process, and candidates for plate existing position address information as a result of plate cutting are sent several times during one image capture, and as soon as the results are determined, they are sent to the character recognition process. In most cases, the first time is the correct plate location address, but as long as there is time, the extraction process is continued, and if there is a candidate, it is sent to the character recognition process to increase the accuracy of plate extraction.For this reason, the bus arbitration method is a method that increases the accuracy of plate extraction. When the request line from the plate cutting process is prioritized, the request line from the character recognition process is prioritized when the first plate existing position address is obtained, and the next vehicle passes and the next vehicle passes. If the image is taken, priority is given to the plate cutting process again, which is desirable. However, the conventional bus right arbitration device cannot switch the priority right.

The present invention solves these conventional drawbacks,
The purpose is to provide a license plate recognition device that prioritizes the order in which bus acquisition requests occur, and also allows the priority of plate cutting processing and character recognition processing to be switched depending on the processing situation. That is.

(Means for Solving the Problems) The license plate recognition device of the present invention includes two or three image memory cards that store still image digital data captured simultaneously by two or three cameras, and refers to the image memory.・Check if there is a car license plate in it, and if it exists, calculate the address of the plate location. An image processing calculation card that cuts out each character position,
Monitoring processing with four character recognition calculation cards that recognize each character from each character position information, an overall control card that controls and manages the entire process, and a monitor function that allows you to refer to data during each process for software debugging and maintenance. Consisting of cards, each processing card has one bus that can read and write to the image memory, and has a high-speed bus usage right arbitration function that is ideal for number recognition processing as a bus arbiter for acquiring the right to use that bus. It is something.

(Function) With the above configuration, the present invention is most suitable for number recognition processing obtained from the bus acquisition request from each processing card this time, the bus acquisition request from the previous processing card, and the previous bus use permission response to each card. By assembling the current bus use permission response for all patterns, it is possible to immediately output a use permission response in response to a change in the bus acquisition input.

Furthermore, since a large number of bus request inputs are internally coded, the above functions can be realized with a small circuit configuration.

(Embodiment) FIG. 1 is a circuit diagram of an express bus control section of a license plate recognition device in an embodiment of the present invention. 1 is a bus use request line latch section from each processing card, and 2 is a bus use permission output section for each processing card. 3 is a part that inputs the previous bus request and current bus request from the plate cutting section, stores it internally, encodes and outputs the current bus request line according to the priority pattern algorithm, and 4 is a character recognition part. This is the part that encodes and outputs requests from the computer using the same algorithm as above. 5 and 6 are parts that latch the requests from 3 and 4 once and store the previous request, and 7 is a part that stores all bus acquisition requests internally and finally acquires the bus according to the priority pattern algorithm. This is the part that outputs the authorization code. Reference numeral 8 denotes a latch section for the previous bus use permission state. In the operation, the priority order at that time is determined in steps 3 and 4.7 in response to the bus acquisition input change in step 1, and the results are outputted to each processing section in step 2. Details are shown below.

The input data for 1 is 14, including 13 bus request signals and one priority mode signal.

The bus request signal is LWRQI, which is the overall control card output.
LWRQ2-72 from the plate cutout card LWRQ8-12 from the character recognition card. and LWRQI3 from the monitoring processing card.

This is the priority mode signal PCORCR signal. When this signal is O, requests from the plate cutout card are given priority over requests from the character recognition card. At 1, the opposite is true.

The output data of No. 2 is 14 lines, including 13 bus grant signals and one path busy status signal corresponding to each request.

The bus permission signal is the overall control card input LWAVI,
Plate cutting/LWAV2-12 to character recognition card
．． and to the monitoring processing card (7) LWAVI3
Consisting of

The priority order shall be as follows.

- Prioritize requests from the monitoring processing card (LWRQI3) first, requests from the overall control processing card (LWRQ) second, and follow the priority mode signal thereafter.

■ Plate cutting processing card (LWRQ2-7) 2
Among the requests in the character recognition processing card (LWRQ8 to LWRQ12), the first occurrence is given priority, and the twelfth occurrence is given second priority. If they occur at the same time, the priority order will be determined based on the highest priority level at that time.

Next, the algorithm for all the patterns stored in 3.4.7 to realize the above priority order will be described.

3.4 Algorithm (1) When all a are OFF
0. Oni O (no request) (2) When Ie 0 & Tsu = 0 ■ When only one of A (let it be α) is ON □→Work = α′,
When two or more of OniO■A (α, β, γ...) are ON, α>β>γ... according to the priority order of AO>AI>A2>A3>A4>A5>A6. 22 α′, O = β′ γ Ignore the following (3) When I≠O & tsu=O, let I = α. ■ When only the internal work book (α) of A is ON, □ → Work = α′, Oni 0 ■ When only one of A (Let's say β, β≠α) is ON - → Engineering: β', Oni 0 ■ When two of A are ON (α, β) □ → Engineering = α' , O;β′■If two of A (β, γ, β・γ≠α) are ON and β>γ, then 1 → Eng: β′, Oniγ
■When three or more of A are ON ■When three of A are ON (β, γ...≠α) (4) B: 0
&tsu ≠ 0 engineering: 0.
Oni 0 Normally this condition does not occur.

(5) When A: 0 & T ≠ O If we set A: α and T: β, ■
When only one of A (γ and O) is ON, −□→Eng = γ',
O = 0 γ can be α, β, or other ■ When two of A (α, β) are ON □ → Eng = α', O = β'■
When two of the wires (β, γ≠α) are ON, −1 → engineering = β′,
When two of oni γ′■a (α, γ≠β) are ON −−→
E = α', O = γ' ■When two of A (γ, δ γ, δ both ≠ α, β) are ON, then α = α' ■ Three or more of A (α, When β, γ, etc.) are ON → E; α', Oni β' ■ Three or more of
When α is 0FF) is ON, 7 shows input/output and internal coding correspondence.

■3 or more of A (α, γ, δ...β are 0FF) are O
When N ■ When three or more of (A) and (γ, δ... α, β are both 0FF) are ON, Algorithm 7 (1) AO = OFF, A1. = OFF, force = 0. When Ki = 0, Ke = 0 (no request) (2) Ri≠0 (set Ri = α) and ■ When the demands of AO, AI, force, and Ki are all different from α -→
Ke=O ■ AO, AI, force, when α exists in the request of Ki - → Ke=α' (3) When R=O, A12=O (priority is given to the plate cut-out part) AO) A1. ) Based on the priority order of force>ki, if the highest priority is α, then
K: α′(4)ri, 0. A12=1. (Character Recognition Unit Priority) Based on the priority order of AO>Al>Force>K, the highest priority is given (Effects of the Invention) According to the present invention, bus arbitration is optimal for license plate recognition processing for a large number of bus input requests. Control can be performed at high speed, and the bus priority order can be changed during the recognition process.Furthermore, by changing the bus priority algorithm, the new algorithm pattern can be memorized and used in another system. It can also be adapted to a suitable method.

Its practical effects are extremely large.

[Brief explanation of drawings]

FIG. 1 shows a circuit section of a high-speed bus control section of a number recognition device with built-in high-speed bus control in one embodiment of the present invention. 1: Bus request input latch unit from each processing card. 2...Decoder unit that outputs bus use permission to each processing card. 3...The current bus acquisition request code output section obtained from the previous and current bus acquisition requests from the plate cutting section. 4: Current bus acquisition request code output unit obtained from the previous and current bus acquisition requests from the character recognition unit. 5... Previous and bus acquisition request latch section from the plate cutout section. 6: Previous and bus acquisition request latch unit from character recognition unit. 7: Current bus use permission code output section obtained from all bus acquisition requests and the previous bus use permission state. 8...Last bus use permission state latch section.

Claims (1)

[Claims] 2 to 3 image memory cards that store still image digital data captured simultaneously by 2 to 3 cameras, refer to and process the image memory, and check whether a vehicle license plate exists in it. Then, use 4 to 6 plate cut-out image processing calculation cards to obtain the plate location address, and the position of each character (land branch code, vehicle type code, usage code, serial number) in the license plate from the plate location address information. An image processing calculation card that cuts out the text, four character recognition calculation cards that recognize each character from the character position information, and controls and controls the entire process.
It consists of an overall control card for management and a monitoring processing card that has a monitor function that allows you to refer to data in progress for software debugging and maintenance, and has one bus on which each of the processing cards can read and write to the image memory. A license plate recognition device, characterized in that it has an express bus usage right arbitration function that is most suitable for number recognition processing as a bus arbiter for acquiring the usage right of the bus.