Kenji Kanayama

Development of vehicle-license number recognition system using real-time image processing and its application to travel-time measurement

In order to recognize vehicle license numbers in real time, a CCD (charge-coupled device) camera with electronic shutter and a hierarchical computer system with a general-purpose microprocessor and pipelined image processors have been developed. Much quicker extraction of the vehicle-license plate on the front-view image is realized by optimization of parameters using Taguchis method. Distinct images outdoors can be obtained using a suitable control of the lens-diaphragm and continuous lighting via floodlight equipment. The results of field tests show that recognition rates of about 90% in the daytime and about 65% at night were attained. The processing time per vehicle is about 150 ms on average.<<ETX>>

Application of fuzzy theory to handwritten character recognition

There has been much research in recent decades on character recognition methods, and some methods have already been put into practical use. There are many unresolved problems, however, with respect to handwritten character recognition as composed with printed character recognition. The authors considered discriminant functions, which constitute the most important part of a character recognition method. As a result of considering problems of conventional statistical discriminant functions, the authors propose applying the fuzzy theory to discriminant functions. The so-called fuzzy discriminant function is capable of representing a data distribution in a more flexible manner because it consists of membership functions on the principal axes of learning samples. The authors conducted recognition experiments for handwritten characters with two types of membership functions. In one type the membership values are directly tuned based on human experiences; in the other they are derived from histograms or statistical data. With the former membership function, the recognition rate of 99.0 percent is achieved for [numeric] characters from the handwritten alphanumeric data base ETL6, and with the latter, the rate of 96.0 percent for [hiragana] characters from handwritten educational [kanji] data base ETL8. This result proves the effectiveness of the fuzzy discriminant function. It also indicates that a dynamic combination of human experiences and statistical techniques is a key to practical systems.

Development and application of vehicle-license number recognition system using real-time image processing

The authors have proposed a system architecture and a high-speed method to extract characters (a four-digit vehicle number) on a vehicle license plate for a realtime vehicle license number recognition system. This paper describes the results of field tests of a system which is based on the previous work but with some further developments. To identify characters on a vehicle license plate, a template-matching method is used which compares the skeleton pattern of characters and its background pattern. To use the system at night, a continuous illumination with two light sources is employed. The experiments including simulations confirm the usefulness of the proposed method at night. The field tests show that about 75 percent of all passing vehicles were recognized successfully in the daytime and about 55 percent at night. The average processing time is about 150 ms, and the 98 percentile value is about 410 ms. These values are sufficient for practical measurements of a vehicle traveling time (between two points). This paper describes also a system to give traveling information to vehicle users, by employing message boards as an example of application of the proposed system.

The Development of a CCD Camera with External Trigger Shutter Function and the Applications

High-speed shutter function is indispensable to obtain a still image for the image processing of rapid moving objects. We propose a new video camera with the electronic shutter function using a frame transfer type CCD (FT-CD), and a new external trigger shutter function which enables to operate the shutter without transient image distortion at any external timing. The electronic shutter function is realized by such a method that stores necessary charges only for the duration of shutter timing by controlling directly FT-CD. As to “smear” which is likely to make a problem to FT-CCD, we confirmed by detailed analysis that “smear” provides no problem in practical uses. To prove the usefulness of this camera, we applied this to the vehicle-license number recognition unit and the automatic defect picture recording system of the paper manufacturing line. These results show that the use of this camera can be expanded to various fields.