Enclosed signal field with level difference and its application to position measurement for multiple objects

A method for two-dimensional position measurement using an enclosed signal field has been studied and is reported here. This method can perform both macro- and micro-measurements, the appropriate combination of these two measurements is called “zooming function”. Macro-measurement is applied to a large area with low sensitivity, while micro-measurement is for measuring a small area with high sensitivity. The purpose of this research is to apply zooming functional measurement to multiple objects. In this type of application, there are several difficulties that must be overcome. First, signals experience interruption mutually by detectors and, second, a multiple zooming procedure is required. To solve the first problem, a novel method is proposed to change the level between LED arrays and photo detectors. The second difficulty is solved using communication between the LED arrays system and the photo sensor systems. The validity of these methods is shown in the experimental results which reveal that multiple object measurement can perform as well as single object measurement, as long as the height of the LED is designed appropriately.