PHOTOELECTRIC ENCODER

Abstract

In a photoelectric encoder (incremental encoder and absolute encoder) having a detector that is displaceable relative to a scale having a predetermined pattern (incremental pattern and pseudorandom pattern) formed thereon, the detection range, to be simultaneously detected, of the pattern is divided in at least the detection direction, and a plurality of light-receiving systems are provided to detect each of the respective detection areas, whereby measurement of a wide detection range is enabled by using a small-sized and simple optical system and light-receiving system.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The preferred embodiments will be described with reference to the drawings, wherein like elements have been denoted throughout the figures with like reference numerals, and wherein;

FIG. 1 is a perspective view showing an optical system based on a lens array described in Patent Document 3;

FIG. 2 is an optical path diagram thereof;

FIG. 3 is an optical path diagram, partially including a plan view, which schematically shows the major parts of Embodiment 1 of the present invention that is applied to an incremental encoder;

FIG. 4 is a block diagram showing a signal processing circuit thereof;

FIG. 5 is a block diagram showing a signal processing circuit according to Embodiment 2 of the present invention;

FIG. 6 is a plan view including a block diagram, which shows the major parts of Embodiment 3 of the present invention;

FIG. 7 is an optical path diagram, partially including a plan view, which schematically shows the major parts of Embodiment 4 of the present invention;

FIG. 8 is an optical path diagram, partially including a plan view, which schematically shows the major parts of Embodiment 5 of the present invention that is applied to an absolute encoder;

FIG. 9 is a block diagram showing a signal processing circuit thereof;

FIG. 10 is a view showing detailed processing thereof;

FIG. 11 is a view showing a case where the correlation peak is made low due to a stain in Embodiment 5;

FIG. 12 is a view showing detailed processing in Embodiment 6 of the present invention;

FIG. 13 is an optical path diagram, partially including a plan view, which schematically shows the major parts of Embodiment 7 of the present invention;

FIG. 14 is an optical path diagram, partially including a plan view, which schematically shows the major parts of Embodiment 8 of the present invention;

FIG. 15 is an optical path diagram, partially including a plan view, which schematically shows the major parts of Embodiment 9 of the present invention;

FIG. 16 is an optical path diagram, partially including a plan view, which schematically shows the major parts of Embodiment 10 of the present invention;

FIG. 17 is an optical path diagram, partially including a perspective view, which schematically shows the major parts of Embodiment 11 of the present invention;

FIG. 18 is an optical path diagram, partially including a perspective view, which schematically shows the detection portion of Embodiment 12 of the present invention;

FIG. 19 is a plan view showing a cut-off position of individual detection patterns according to Embodiment 12;

FIG. 20 is a block diagram showing a signal processing circuit according to Embodiment 12;

FIG. 21 is a view showing one example of individual correlation peaks according to Embodiment 12;

FIG. 22 is a plan view showing a case where a stain is taken, according to Embodiment 12;

FIG. 23 is a view showing a correlation peak in the case where a stain is taken, according to Embodiment 12; and

FIG. 24 is a plan view showing a process according to Embodiment 13 of the present invention.

Claims

1. A photoelectric encoder having a detector that is displaceable relative to a scale having a predetermined pattern formed thereon, in which a detection range, to be simultaneously detected, of the pattern is divided in at least a detection direction, and comprising a plurality of light-receiving systems to detect the respective divided areas.

2. The photoelectric encoder according to claim 1, wherein a light-shielding plate is disposed between the light-receiving systems.

3. The photoelectric encoder according to claim 1, wherein an imaging optical system is provided for each of the light-receiving systems.

4. The photoelectric encoder according to claim 3, wherein the imaging optical system is a single-side or a double-side telecentric optical system.

5. The photoelectric encoder according to claim 1, wherein the detection range is divided in a direction perpendicular to the detection direction.

6. The photoelectric encoder according to claim 1, wherein partial staining of the detection range is detected by an amplitude of outputs of divided and detected points.

7. The photoelectric encoder according to claim 6, wherein an output of points other than the point where staining is detected is used for detection of displacement.

8. The photoelectric encoder according to claim 1, wherein the pattern is an incremental pattern.

9. The photoelectric encoder according to claim 8, wherein an amount of movement is detected by averaging the outputs of the divided and detected points.

10. The photoelectric encoder according to claim 8, wherein posture detection of the detector is carried out by relative comparison of outputs of the divided and detected points.

11. The photoelectric encoder according to claim 1, wherein the pattern is a pseudorandom pattern.

12. The photoelectric encoder according to claim 11, wherein the divided and detected patterns are individually subjected to correlation calculations, and a position at which an order of the correlation peaks is accurate and an interval between the respective correlation peaks is within a predetermined range is judged to be an absolute position.

13. The photoelectric encoder according to claim 12, wherein the corresponding individual detection pattern where a height of the correlation peak is lower than a threshold value, is not used for correlation calculations.

14. The photoelectric encoder according to claim 12, wherein a correlation calculation is carried out in an entire area of the periodic cycle with respect to one of a plurality of individual detection patterns to obtain a highest correlation peak, and the correlation calculation is carried out only in the surrounding thereof.