Importance

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Abstract

A method of initializing the position of an optical shaft encoder without having to precisely index the encoder with respect to its shaft. The optical encoder includes an optical shutter mounted for rotation with the shaft and light emitters and light detectors associated with the optical shutter for respectively illuminating and detecting a predetermined pattern of code markings formed on the optical shutter. An electrical circuit, such as a suitably programmed microprocessor, is responsive to the status of the light emitters and light detectors for determining the angular position of the optical shutter and shaft relative to the light emitters and detectors from the detected predetermined pattern. The optical shutter is mounted to the shaft in some arbitrary position and the code pattern associated with this position is detected by the electrical circuit. This position is then used as the 'zero' or index position and all other angular positions of the optical shutter and shaft are thereafter indexed to this initial position. This eliminates the need to align the optical shutter with some indexing mark on the shaft or with a shaft driven pointer, such as utilized in the dial-type register display commonly used in gas, water or electric meters.

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First Claim