Zero reference generating method and apparatus for optical encoders

Claim 2

An encoder for providing positional information about a moveable member comprising code member means couplable to the moveable member for movement with the moveable member; reference member means positioned to be stationary relative to the code member; an index sequence positioned at a single zero position on the code member means and on the reference member means comprising a plurality of index patterns, wherein each of the plurality of index patterns comprises a mask component positioned on the reference member means and a corresponding code disk component positioned on the code member means, and wherein for each of the plurality of index patterns the mask component includes a plurality of unit width indicia and the code disk component includes a different plurality of unit width indicia, and further wherein the mask components of each of the plurality of index patterns are separated from one another, and the code disk component of each of the plurality of index patterns are separated from one another, by predetermined spacings; and means for detecting the degree of registration between the mask and code disk components of the index sequence.

Claim 3

The encoder of claim 1 wherein the plurality of index patterns comprise a repeated first index pattern.

Claim 4

The encoder of claim 2 wherein the mask component of the first index pattern is selected so that, for the zero position of the reference member means, the degree of registration between the code disk component and the mask component is a maximum, and so that for all other positions the degree of registration is no greater than a background level greater than zero.

Claim 5

The encoder of claim 2 wherein the mask component of the first index pattern is selected so that, for the zero position of the reference member means and the code member means, the degree of registration between the code disk component and the mask component is at a maximum, and so that for all other positions the degree of registration is no greater than a background level.

Claim 6

The encoder of claim 1 wherein the plurality of index patterns include a first index pattern, and a second index pattern in which the unit indicia therein are arranged in reverse order from the unit indica in the first index pattern.

Claim 7

The encoder of claim 5 wherein the first index pattern is repeated in the index sequence.

Claim 8

An encoder for providing positional information about a moveable member comprising code member means coupled to the moveable member for movement with the moveable member; reference member means positioned to be stationary relative to the code member means; position indicia positioned on the code member means along a position indica track; reference indicia positioned on the reference member means along a reference indicia track so that said reference indicia track is in registration with said position indicia track; means for determining the degree of registration between the reference indicia and the position indicia; an index sequence positoned at single a zero position on the code member means and reference member means said index sequence including a plurality of the same index pattern, wherein the index pattern comprises a mask component positioned on the reference member means and a code disk component positioned on the code member means, wherein the mask component and the code disk component each include a plurality of unit width indicia, and further wherein the mask components of each of the plurality of the same index pattern are separated from one another, and the code disk components of each of the plurality of the same index pattern, are separated from one another by predetermined spacings; and wherein said determining means further determines the degree of registration between the mask and code disk components of the index sequence.

Claim 9

An encoder for providing positional information about a moveable member comprising code member means coupled to the moveable member for movement with the moveable member; reference member means positioned to be stationary relative to the code member means; position indicia positioned on the code member means along a position indica track; reference indicia positioned on the reference member means along a reference indicia track so that said reference indicia track is in registration with said position indicia track; means for determining the degree of registration between the reference indicia and the position indicia; an index sequence positoned at single a zero position on the code member means and reference member means said index sequence including a plurality of the same index pattern, wherein the index pattern comprises a mask component positioned on the reference member means and a code disk component positioned on the code member means, wherein the mask component and the code disk component each include a plurality of unit width indicia, and further wherein the mask components of each of the plurality of the same index pattern are separated from one another, and the code disk components of each of the plurality of the same index pattern, are separated from one another by predetermined spacings; and wherein said determining means further determines the degree of registration between the mask and code disk components of the index sequence.

Claim 12

The encoder of claim 2 wherein the code disk component of the first index pattern comprises three abutted indicia and the mask component thereof comprises two indicia spaced apart by a unit length.

Claim 13

The encoder of claim 9 wherein the spacings between the index patterns are according to the series of integers 2, 3, 4, 5 . . . , N-1, N, where each integer represents a multiple of a unit space.

Claim 14

The encoder of claim 2 wherein the code disk component of the first index pattern comprises three indicia, the first of which is spaced from the other two by two unit widths and the second and third of which are spaced from one another by a unit width, and further wherein the mask component thereof comprises four indicia, the first of which is spaced from the other three by two unit widths and the other three are abutted against each other.

Claim 15

The encoder of claim 11 wherein the index patterns are spaced from one another according to the integer series 3, 5, 8, 9, where each integer represents a multiple of a unit space.

Claim 16

The encoder of claim 2 wherein the code disk component of the first index pattern comprises four indicia, the first of which is spaced from the second by six unit widths, the second and third of which are spaced from one another by two unit widths, and the fourth of which is spaced from the third by a unit with, and further wherein the mask component thereof comprises five indicia, the first of which is spaced from the second by six unit widths, the second and third of which are separated by two unit widths, and the third, fourth and fifth of which are abutted together.

Claim 17

The encoder of claim 13 wherein the index patterns are repeated twice and the spacing between the index patterns is five unit widths.