1. A magnetic encoder including plural rows of annular magnetic encoder tracks arranged adjacent to each other, each of the plural rows of magnetic encoder tracks being configured to be read by a corresponding sensor, comprising:
an AB magnetic encoder track including a magnetic pattern having N poles and S poles arranged in alternate fashion magnetized thereto to generate magnetic signals for detection of rotation; and
a Z magnetic encoder track that is different from the AB magnetic encoder track, the Z magnetic encoder track being adjacent to the AB magnetic encoder track and the Z magnetic encoder track providing a reference position for rotation,
each of the AB magnetic encoder track and the Z magnetic encoder track being configured to be employed spaced through an air gap from the corresponding sensors that read magnetic signals of each of the respective magnetic encoder tracks,
the magnetic pattern magnetized to the AB magnetic encoder track being configured to have an unequal pitch such that a magnetic pattern of the magnetic signal acting on and read by the corresponding sensor is, under an interference of magnetisms of the AB magnetic encoder track and the Z magnetic encoder track, detected by the corresponding sensor as an equal pitch magnetic pattern.
2. The magnetic encoder as claimed in claim 1, wherein a magnetic pattern magnetized to the Z magnetic encoder track has the same number of magnetic poles as the AB magnetic encoder track, and a phase offset with respect to the magnetic pattern magnetized to the AB magnetic encoder track, and
the Z magnetic encoder track is configured to provide, by the use of the phase offset with respect to the magnetic pattern magnetized to the AB magnetic encoder track, the reference position for rotation.
3. The magnetic encoder as claimed in claim 1, wherein a magnetic pattern magnetized to the Z magnetic encoder track has an N or S magnetic pole at a certain circumferential location with the remaining circumferential portion being not magnetized.
4. The magnetic encoder as claimed in claim 1, wherein a magnetic pattern magnetized to the Z magnetic encoder track includes an N or S magnetic pole at a certain circumferential location as well as a magnetic pole, which is an opposite magnetic pole to the magnetic pole on the certain circumferential location, at a different circumferential location.
5. The magnetic encoder as claimed in claim 1, wherein each of the magnetic encoder tracks is formed to have a track width, as measured along arrangement direction of the magnetic encoder tracks, in the range of 1 mm to 5 mm.
6. The magnetic encoder as claimed in claim 1, wherein the plural rows of magnetic encoder tracks are adjacent through a boundary line, the magnetic encoder being configured to be employed spaced from the sensors through an air gap that is more than 0.3 mm and is less than 4 mm, the sensors having respective detector portions positioned over the respective magnetic encoder tracks at locations spaced from the boundary line towards the respective magnetic encoder tracks by respective distances in the range of 0.5 mm to 3 mm.
7. The magnetic encoder as claimed in claim 1, wherein at least one of the magnetic encoder tracks includes a ferrite sintered magnet or a magnet containing a ferrite power mixed in a rubber or a resin, and has a thickness that is more than 0.5 mm and is less than 4 mm.
8. The magnetic encoder as claimed in claim 1, wherein the magnetic pattern magnetized to the AB magnetic encoder track includes magnetic poles, each having a length L as measured along a circumferential direction of the magnetic encoder track, the length L being in the range of 0.3 mm to 5 mm, and
wherein each of the magnetic encoder tracks is so formed that the length L has a relationship with a track width W, as measured along arrangement direction of the magnetic encoder tracks, of W>L.
9. The magnetic encoder as claimed in claim 1, further comprising a magnetic material interposed between the plural rows of the adjacent magnetic encoder tracks.
10. The magnetic encoder as claimed in claim 1, further comprising a core having the plural rows of magnetic encoder tracks disposed thereon, the plural rows of the adjacent magnetic encoder tracks having a gap interposed therebetween.
11. The magnetic encoder as claimed in claim 1, wherein the AB magnetic encoder track has a track width as measured along arrangement direction of the magnetic encoder tracks, and the Z magnetic encoder track has a track width, as measured along an arrangement direction of the magnetic encoder tracks, different from the track width of the AB magnetic encoder track.
12. The magnetic encoder as claimed in claim 1, wherein the plural rows of the adjacent magnetic encoder tracks include respective to-be-detected surfaces extending on different planes.
13. A magnetic encoder including plural rows of linear magnetic encoder tracks arranged adjacent to each other, each of the plural rows of magnetic encoder tracks being configured to be read by a corresponding sensor, comprising:
an AB magnetic encoder track including a magnetic pattern magnetized thereto to generate magnetic signals for detection of position, the magnetized magnetic pattern including N poles and S poles arranged in alternate fashion; and
a Z magnetic encoder track that is different from the AB magnetic encoder track, the Z magnetic encoder track being adjacent to the AB magnetic encoder track and the Z magnetic encoder track providing a reference position,
each of the AB magnetic encoder track and the Z magnetic encoder track being configured to be employed spaced through an air gap from the corresponding sensors that read magnetic signals of each of the respective magnetic encoder tracks,
the magnetic pattern magnetized to the AB magnetic encoder track being configured to have an unequal pitch such that a magnetic pattern of the magnetic signal acting on and read by the corresponding sensor is, under the interference of magnetisms of the AB magnetic encoder track and the Z magnetic encoder track, detected by the corresponding sensor as an equal pitch magnetic pattern.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A method of processing an optical device wafer, for dividing an optical device wafer which has optical devices formed in a plurality of regions demarcated by a plurality of streets formed in a grid pattern on a face-side surface thereof, along said plurality of streets into the individual optical devices, said method comprising:
a laser beam processing step of irradiating said optical device wafer with a laser beam along said streets so as to perform laser beam processing on the face side of said optical device wafer, thereby forming breakage starting points along said streets;
a protective plate bonding step of bonding the face side of said optical device wafer having been subjected to said laser beam processing step to a surface of a rigid protective plate with a bonding agent permitting peeling;
a back side grinding step of grinding a back side of said optical device wafer adhered to said protective plate to form said optical device wafer to a finished thickness of said optical devices;
a dicing tape adhering step of adhering the back-side surface of said optical device wafer having been subjected to said back side grinding step to a surface of a dicing tape;
a cut groove forming step of cutting said protective plate bonded to the face side of said optical device wafer having been subjected to said dicing tape adhering step, along said streets formed on said optical device wafer, thereby to form cut grooves not reaching said face-side surface of said optical device wafer;
a wafer dividing step of exerting an external force on said optical device wafer through said protective plate having been subjected to said cut groove forming step, so as to break up said optical device wafer along said breakage starting points formed along said streets, thereby dividing said optical device wafer into the individual optical devices;
a protective plate peeling step of peeling said protective plate bonded to the face side of said optical device wafer having been subjected to said wafer dividing step; and
a picking-up step of picking up the individually divided optical devices adhered to said dicing tape.
2. The method of processing the optical device wafer according to claim 1, wherein said laser beam processing step comprises irradiating said optical device wafer with a laser beam having such a wavelength as to be transmitted through said optical device wafer while adjusting a focal point position of said laser beam to the inside of said optical device wafer, thereby to form an altered layer as said breakage starting points inside said optical device wafer along said streets.
3. The method of processing the optical device wafer according to claim 1, wherein said laser beam processing step comprises irradiating said optical device wafer with a laser beam having such a wavelength as to be absorbed in said optical device wafer, thereby to form laser beam-machined grooves as said breakage starting points in said face-side surface of said optical device wafer along said streets.