Optical encoder unit, and optical encoder

Patent metadata

Field	Value
Publication number	US-2016282149-A1
Application number	US-201415034076-A
Country	US
Kind code	A1
Filing date	Oct 31, 2014
Priority date	Nov 5, 2013
Publication date	Sep 29, 2016
Grant date	—

Abstract

An optical encoder unit includes: a light source having a predetermined light distribution; an optical scale having a polarizer whose polarization direction on a plane is along a predetermined direction, and whose polarization direction is changed according to rotation; and an optical sensor unit including a first photoreceiver, a second photoreceiver, a third photoreceiver, and a fourth photoreceiver for receiving incident light that is light source light from the light source made incident on the respective photoreceivers by passing through or being reflected by the optical scale. An emitting surface of the light source and the optical sensor unit are arranged at positions so as to receive a light intensity that is predetermined times greater or more than that corresponding to dark current of the optical sensor.

First claim

1 . An optical encoder unit comprising:
a light source having a predetermined light distribution; an optical scale having a polarizer whose polarization direction on a plane is along a predetermined direction, and whose polarization direction is changed according to rotation; and an optical sensor unit including a first photoreceiver, a second photoreceiver, a third photoreceiver, and a fourth photoreceiver for receiving incident light that is light source light from the light source made incident on the respective photoreceivers by passing through or being reflected by the optical scale, wherein an emitting surface of the light source and the optical sensor unit are arranged at positions so as to receive a light intensity that is predetermined times greater or more than that corresponding to dark current of the optical sensor.

2 . The optical encoder unit according to claim 1 , wherein the emitting surface of the light source and the optical sensor unit are arranged at positions so as to receive a light intensity that is 100 times greater or more than that corresponding to the dark current of the optical sensor unit.

3 . The optical encoder unit according to claim 2 , wherein the emitting surface of the light source and the optical sensor unit are arranged at positions so as to receive a light intensity that is 1000 times greater or more than that corresponding to the dark current of the optical sensor unit.

4 . The optical encoder unit according to claim 1 ,
wherein the first photoreceiver, the second photoreceiver, the third photoreceiver, and the fourth photoreceiver are respectively arranged at an equal distance from an arrangement center, and wherein the first photoreceiver, the second photoreceiver, the third photoreceiver, and the fourth photoreceiver are arranged within a range in which the light distribution of the light source is uniform and receive light.

5 . The optical encoder unit according to claim 1 , wherein the first photoreceiver, the second photoreceiver, the third photoreceiver, and the fourth photoreceiver receive light by polarizing layers that split the incident light in different polarization directions.

6 . The optical encoder unit according to claim 1 , further comprising a cylindrical cover, and a shaft that is capable of freely rotating by being supported by a bearing attached inside the cover,
wherein the cover encloses the optical scale attached to the shaft, the light source, and the optical sensor unit.

7 . The optical encoder unit according to claim 1 , further comprising:
a first bare chip including the first photoreceiver, the second photoreceiver, the third photoreceiver, and the fourth photoreceiver; and
an amplifier circuit for amplifying signals of the first photoreceiver, the second photoreceiver, the third photoreceiver, and the fourth photoreceiver,
wherein the first bare chip and the amplifier circuit are fixed at positions so as to overlap each other in a plan view and are electrically connected to each other.

8 . The optical encoder unit according to claim 1 , further comprising a bare chip that includes the first photoreceiver, the second photoreceiver, the third photoreceiver, and the fourth photoreceiver, and on which an amplifier circuit for amplifying signals of the first photoreceiver, the second photoreceiver, the third photoreceiver, and the fourth photoreceiver are integrated.

9 . An optical encoder comprising:
an optical encoder unit according to claim 1 ; and a calculation processing device that calculates an amount of relative movement between the optical scale and the optical sensor unit from light intensities detected by the first photoreceiver, the second photoreceiver, the third photoreceiver, and the fourth photoreceiver.

10 . The optical encoder according to claim 9 , wherein the calculation processing device calculates an amount of absolute movement between the optical scale and the optical sensor unit by storing in a storage device, and reading from the storage device at a time of activation, whether a rotation position of the optical scale is in a range equal to or more than zero degrees and less than 180 degrees, or in a range equal to or more than 180 degrees and less the 360 degrees.

Assignees

• Nsk Ltd

Inventors

• Oguchi Toshiaki

Classifications

• G01D5/34715

  Scale reading or illumination devices · CPC title

• G01D5/34707

  Scales; Discs, e.g. fixation, fabrication, compensation · CPC title

• G01D5/345

  Polarising encoders · CPC title

• G01D5/3473 Primary

  Circular or rotary encoders · CPC title

• G01D5/344

  using polarisation (G01D5/35303 takes precedence) · CPC title