http://www.usa.canon.com/cusa/semiconductor/products/encoder_optolectronic_components/laser_rotary_encoder/k_1?pageKeyCode=writeReviewPage
K-1
3333342
Features
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Extremely High Precision and Accuracy: 81,000 Sine waves per revolution.
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Very compact and lightweight.
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Maximum frequency response of 500kHz (360rpm).