| 摘要 |
An optical device having a diffraction grating displaced from the focal point of a converging monochromatic beam of light for encoding the position of or measuring the displacement of an object or the light beam is disclosed. The diffraction grating, disposed a determinable distance in front of or behind the focal point of the converging light beam, generates a diffraction pattern comprising a plurality of amplitude modulated directional light beams which may be imaged with or without the aid of an intermediate lens. The angular change of the directional light beams comprising the diffraction pattern may be visually or electro-optically detected to encode or provide a measure of the relative displacement between the light beam and the grating.
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