Position detecting apparatus

• US 6,070,132 A
• Filed: 10/28/1997
• Issued: 05/30/2000
• Est. Priority Date: 10/28/1996
• Status: Expired due to Fees

• Current Assignee: Sony Precision Technology, Inc. (Sony Group Corp.)
• Original Assignee: Sony Precision Technology, Inc. (Sony Group Corp.)
• Inventors: Ishimoto, Shigeru
• Primary Examiner(s): SHAH, KAMINI S
• Application Number:
  US08/959,467
• Time in Patent Office: 945 Days
• Field of Search: 702/158, 73/650, 73/660, 73/657, 73/659, 324/309, 324/319, 359/824, 359/823, 359/694, 359/698
• US Class Current: 702/158
• CPC Class Codes: G01B 7/02 for measuring length, width or thickness G01B7/004, G01B7/12 take precedence

Abstract

A displacement detecting apparatus includes a scale having a graduation of predetermined pitches, a sensor which is displaceable with respect to the scale and detects a period signal corresponding to the pitch. Interpolating sections interpolate the periodic signal from the sensor by different resolutions. One of the interpolating sections outputs a first interpolation signal of m (positive integer) phases shifted by a phase difference θ1, and the other interpolating sections outputs a second interpolation signal of n (positive integer) phases shifted by a phase difference θ2.

Claims

1. A position detecting apparatus comprising:

a single scale having graduation lines marked at predetermined pitches;

a sensor displaceable with respect to said single scale and detecting periodic signals indicative of cycles corresponding to the pitches of the graduation lines; and

a plurality of interpolating means for interpolating the periodic signals, the plurality of interpolation means including a first interpolation means for outputting a first integer number of first interpolation signals, and a second interpolation means for outputting a second integer number of second interpolation signals, the first interpolation signals differing in phase from each other by a first predetermined angle, the second interpolation signals differing in phase from each other by a second predetermined angle.

2. A position detecting apparatus as claimed in claim 1, wherein each of said plural interpolating means includes phase shifting means for phase-shifting the periodic signals by means of the vector adding method.

3. A position detecting apparatus as claimed in claim 1, wherein each of said plural interpolating means includes an analog-to-digital converter for converting the periodic signals into digital signals and a conversion table for converting an output signal of the analog-to-digital converter to the interpolation signals.

4. A position detecting apparatus as claimed in claim 1, wherein said first interpolating means includes phase shifting means for phase-shifting the periodic signals by means of the vector adding method, and said second interpolating means includes an analog-to-digital converter for converting the periodic signals into digital signals and a conversion table for converting an output signal of the analog-to-digital converter to the second interpolation signals.

5. A position detecting apparatus as claimed in claim 1, wherein each of said plural interpolating means has a different resolution with respect to each other.

6. A position detecting apparatus as claimed in claim 1, wherein the plural interpolating means further includes a third interpolation means, wherein said first interpolating means outputs three-phase signals, and said second interpolating means outputs two-phase signals which are different in division number from two-phase signals outputted by said third interpolating means.

7. A position detecting apparatus as claimed in claim 1, wherein said single scale and said sensor are of a magnetic type for generating periodic signals according to a displacement of said sensor with respect to said single scale.

8. A position detecting apparatus as claimed in claim 1, wherein the first and second interpolation signals respectively outputted from said first and second interpolating means are supplied to a servo mechanism including a servomotor.

9. A position detecting apparatus as claimed in claim 1, wherein said sensor is constituted by a pair of magnet resistor heads each of which includes a pair of magnetic resistor elements arranged into a bridge structure.