Encoder apparatus
AssigneeRenishaw PLC
InventorsJason Kempton SLACK, Theodore Richard REEVE, David John MCCABE, Richard James BALE
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Abstract
A position measurement encoder apparatus, including: a scale comprising a series of features which are readable by a readhead so as to determine a relative position of the scale and the readhead, and which diffract light into multiple diffraction orders; a readhead including a light source for illuminating the scale, and at least a first sensor configured to detect a signal produced thereat by one or more diffraction orders produced by the scale; wherein the readhead further comprises a diffraction order encoder which encodes at least one diffraction order with a different optical state to that of at least one other diffraction order.
Claims17
A position measurement encoder apparatus, comprising:
- a scale comprising a series of position features which are readable by a readhead, the series extending along a measuring dimension, and which diffract light into multiple diffraction orders;
- a readhead comprising a light source for illuminating the scale, and at least a first sensor configured to detect a signal produced thereat by one or more diffraction orders produced by the scale's series of position features which can be used to determine the relative position of the scale and readhead along the measuring dimension;
- wherein the readhead further comprises a diffraction order encoder which encodes at least one diffraction order produced by the scale's series of position features with a different optical state to that of at least one other diffraction order produced by the scale's series of position features.
A position measurement encoder apparatus, comprising:
- a scale comprising a series of periodic features configured to diffract light into multiple diffraction orders, including a 0th diffraction order;
- a readhead comprising a light source for illuminating the scale, and at least one sensor configured to detect an interference fringe pattern/fringe field which moves with relative motion of the scale and readhead, the interference fringe pattern/fringe field being produced by the diffraction orders from the scale at the at least one sensor;
- in which the period of the fringe is M·p/2, where M is the magnification factor of the encoder's optical system, and p is the period of the scale.
A position measurement encoder apparatus, comprising:
- a scale comprising a series of periodic features configured to diffract light into multiple diffraction orders, including a 0th diffraction order;
- a readhead comprising a light source for illuminating the scale, and at least one sensor configured to detect a resultant field which changes with relative motion of the scale and readhead, the resultant field being produced by the diffraction orders from the scale at the at least one sensor;
- in which the readhead is configured such that the 0th diffraction order does not contribute to the production of the resultant field at the at least one sensor.
Dependencies are inferred from the claim text.