ENCODER

• US 20120085897A1
• Filed: 10/05/2011
• Published: 04/12/2012
• Est. Priority Date: 10/08/2010
• Status: Active Grant

• Current Assignee: Mitutoyo Corporation
• Original Assignee: Mitutoyo Corporation
• Inventors: Kato, Yoshiaki
• Granted Patent: US 8,729,458 B2
• Time in Patent Office: Days
• US Class Current: 250/231.1
• CPC Class Codes: G01D 5/24476 Signal processing G01D5/2448 - G01D5/24495 take precedence

Abstract

A detection head includes a plurality of detection array portions that are arranged in a direction along which the head is relatively displaceable. Position signals indicating a position of the detection head are calculated from output signals output from the detection array portions. In order to combine the position signals with one another and determine the position of the detection head with respect to the scale, weighting according to a level of the output signal is performed on the position signal of each of the detection array portions, and the weighted position signals are averaged.

Claims

1. An encoder comprising:

a scale; and

a detection head which is relatively displaceable with respect to the scale,

wherein the detection head includes

a plurality of detection array portions that are arranged in a direction along which the detection head is relatively displaceable,

a processor configured to calculate position signals indicating a position of the detection head from output signals output from the detection array portions, and to combine the position signals with one another and determine the position of the detection head with respect to the scale, and

wherein the processor is configured to perform weighting according to a level of the output signal on the position signal of each of the detection array portions, and to average the weighted position signals.

2. The encoder according to claim 1, wherein

the weighting on the position signal is performed by setting a total sum of absolute values of differences of adjacent ones of signal strength data of the output signals output from individual detection elements constituting the detection array portions, or square values of the differences, as a coefficient of the position signal.

3. The encoder according to claim 1, wherein

the weighting on the position signal is performed by performing sinusoidal curve fitting on signal strength data of the output signals output from individual detection elements constituting the detection array portions, and setting a product of an amplitude of a sinusoidal wave obtained by the fitting, and an array width of the detection array portions, as a coefficient of the position signal.

4. An encoder according to claim 1, wherein

the weighting on the position signal is performed by setting a product of a diameter of a Lissajous waveform obtained from a two-phase sinusoidal signal which is the output signal, and an array width of the detection array portions, as a coefficient of the position signal.