AIt is difficult for Murata ultrasonic sensors to determine the size of the object. If multiple sensors are used in an array, we assume it is possible to determine object size from differences in echo arrival time at individual sensors, however this is unrealistic in terms of both technical and cost efficiency. (For recognition of plane surface size, it is far more inexpensive to use a CCD camera.) To recognize object size, it is necessary to use an array of sensors and intelligent image processing, as in ultrasonic diagnosis equipment for medical use. It is also necessary to limit the range of sensing reflections. Therefore we believe it is not a realistic solution to recognize object size using ultrasonic sensors.)