DISPLACEMENT MEASURING APPARATUS

• US 20120069323A1
• Filed: 03/07/2011
• Published: 03/22/2012
• Est. Priority Date: 09/16/2010
• Status: Active Grant

• Current Assignee: Canon Ayutthaya Limited (Canon Inc.)
• Original Assignee: Canon Ayutthaya Limited (Canon Inc.)
• Inventors: Miyaoka, Yasuyuki, Arimitsu, Yasumichi
• Granted Patent: US 9,116,163 B2
• Time in Patent Office: Days
• US Class Current: 356/28
• CPC Class Codes: G01D 5/2451 Incremental encoders G01D5/2454 takes precedence
• CPC Class Codes: G01D 5/34746 Linear encoders
• CPC Class Codes: G01P 3/486 delivered by photo-electric detectors
• CPC Class Codes: G01P 3/68 using optical means, i.e. using infrared, visible, or ultraviolet light G01P3/80 takes precedence ; by reflection of waves G01S17/58
• CPC Class Codes: G03G 15/5054 by measuring the characteristics of an intermediate image carrying member or the characteristics of an image on an intermediate image carrying member, e.g. intermediate transfer belt or drum, conveyor belt
• CPC Class Codes: G03G 2215/0158 Colour registration

Abstract

A displacement measuring apparatus including: a first light detector including a first emitter illuminating optically identifiable marks disposed on a moving body, and a first light receiver detecting light through the marks; a second light detector including a second emitter illuminating the marks and a second light receiver detecting light through the marks, wherein the second light detector is arranged at a predetermined interval from the first light detector in a moving direction of the moving body; an identical point detecting unit detecting a first timing at which the first and second light detector detecting an identical mark among the marks, and a second timing; a velocity calculating unit calculating a velocity of the moving body by using the first and second timing determined by the identical point detecting unit; and a time-sharing light emitting unit allowing the first and second emitter to emit the light in a time-sharing manner.

Claims

1. A displacement measuring apparatus, comprising:

a first light detector including a first emitter that illuminates optically identifiable marks disposed on a moving body, and a first light receiver that detects light from the optically identifiable marks;

a second light detector including a second emitter that illuminates the optically identifiable marks and a second light receiver that detects light from the optically identifiable marks, wherein the second light detector is arranged at a predetermined interval from the first light detector in a moving direction of the moving body;

an identical point detecting unit that determines a first time at which the first light detector detects a first mark among the optically identifiable marks, and a second time different from the first time at which the second light detector detects the first mark;

a velocity calculating unit that calculates a moving velocity of the moving body by using the first time and the second time determined by the identical point detecting unit; and

a time-sharing light emitting unit that allows the first emitter and the second emitter to emit light in a time-sharing manner.

2. A displacement measuring apparatus according to claim 1, further comprising:

a reference signal generating unit that generates a reference signal having a predetermined frequency;

an energization control unit that controls energization states of the first emitter and the second emitter in synchronism with the reference signal; and

a sampling unit that samples outputs of the first light detector and the second light detector in synchronism with the reference signal, wherein the time-sharing light emitting unit allows the first emitter and the second emitter to emit light in a time-sharing manner based on signals from the reference signal generating unit and the energization control unit, and

wherein the identical point detecting unit determines a detection time of the first mark for each of the first light detector and the second light detector through interpolating computation by using output values of the respective first light detector and second light detector sampled by the sampling unit.

3. A displacement measuring apparatus according to claim 2, wherein the identical point detecting unit determines a time at which signal output from each of the first light detector and the second light detector has a predetermined threshold voltage through the interpolating computation based on at least two sampled values in a vicinity of the predetermined threshold voltage, the at least two sampled values being sampled by the sampling unit from the signal.

4. A displacement measuring apparatus according to claim 2, wherein the predetermined frequency of the reference signal is an integral multiple of a center frequency of a signal output from the first light detector and a signal output from the second light detector.

5. A displacement measuring apparatus according to claim 2,

wherein each of signals output from the first light detector and the second light detector includes signals different in phase by 90 degrees, and

wherein in each of the first light detector and the second light detector, the identical point detecting unit samples the signals different in phase by 90 degrees at least two sampling points through the sampling unit, and calculates a phase of a signal to be detected from the sampled signals through arctangent computation, to thereby determine a time at which the phase of the signal to be detected has a predetermined threshold phase through interpolating computation of the at least two sampling points.

6. A displacement measuring apparatus according to claim 1, wherein the time-sharing light emitting unit and the identical point detecting unit repeat a series of operation of illuminating the optically identifiable marks on the moving body with the light from the first emitter, detecting the light from the optically identifiable marks by the first light receiver, then turning off the first emitter, then turning on the second emitter, detecting the light from the optically identifiable marks by the second light receiver, turning off the second emitter after detecting the identical mark among the optically identifiable marks, and then turning on the first emitter.

7. A displacement measuring apparatus according to claim 1, wherein the first light detector and the second light detector are arranged on the same substrate so that, when a direction from the first emitter to the first light receiver in the first light detector and a direction from the second emitter to the second light receiver in the second light detector, forms an angle of 180 degrees.

8. A displacement measuring apparatus according to claim 1, wherein the first light detector and the second light detector are arranged so that a line connecting a midpoint of a segment connecting centers of the first emitter and the first light receiver and a midpoint of a segment connecting centers of the second emitter and the second light receiver is parallel to a velocity detecting direction.

9. A displacement measuring apparatus according to claim 1, wherein the first light detector and the second light detector are arranged so that a distance between center lines of the first light receiver and the second light receiver perpendicular to a velocity detecting direction is equal to a distance between center lines of the first emitter and the second emitter perpendicular to the velocity detecting direction.

10. A displacement measuring apparatus according to claim 9, wherein the first light detector and the second light detector are arranged so that the center lines of the first light receiver and the second light receiver perpendicular to the velocity detecting direction are identical with the center lines of the first emitter and the second emitter perpendicular to the velocity detecting direction, respectively.

11. A displacement measuring apparatus according to claim 1, wherein the first light receiver and the second light receiver are alternately arranged on a semiconductor, and with a set of four alternately arranged light receivers as a minimum unit, at least one set is cyclically arranged.

12. A displacement measuring apparatus according to claim 11, wherein each of the first light receiver and the second light receiver alternately arranged comprises a light receiving element array including multiple light receiving elements.

13. A displacement measuring apparatus according to claim 4, further comprising:

a second velocity calculating unit for calculating a second velocity information based on a signal from one of the first light detector and the second light detector; and

a velocity combining unit for calculating a velocity by calculating of a combination of detection velocity bands of a first velocity information calculated by the velocity calculating unit and the second velocity information,

wherein the first light detector and the second light detector each have a pitch detector for detecting an array pitch of marks,

wherein the second velocity information is a velocity information calculated from passing time information obtained under the marks passing by the first light detector or the second light detector, and information of a time length of the array pitch of the marks.

14. A displacement measuring apparatus according to claim 4, further comprising:

a second velocity calculating unit for calculating a second velocity information based on a signal from one of the first light detector and the second light detector; and

a velocity combining unit for calculating a velocity by calculating of a combination of detection velocity bands of a first velocity information calculated by the velocity calculating unit and the second velocity information,

wherein the first light detector and the second light detector each have a pitch detector for detecting an array pitch of marks,

wherein each of the signals from the first light detector and the second light detector include signals having a phase difference of an angle of 90 degrees, and

wherein the second velocity information comprises a velocity information calculated from a time difference information corresponding to the phase difference between the signals obtained under the marks passing by the first light detector or the second light detector, and information of a length of the array pitch of the marks corresponding to the phase difference.

15. A displacement measuring apparatus, comprising:

a first light detector including a first emitter that illuminates optically identifiable marks disposed on a moving body, and a first light receiver that detects light from the optically identifiable marks; and

a second light detector including a second emitter that illuminates the optically identifiable marks and a second light receiver that detects light from the optically identifiable marks, wherein the second light detector is arranged at a predetermined interval from the first light detector in a moving direction of the moving body,

wherein assuming that a first array direction be a direction from the first emitter to first light receiver and a second array direction be a direction from the second emitter to the second light receiver, the first array direction and the second array direction are opposite to each other.

16. A displacement measuring apparatus according to claim 15, wherein the first array direction and the second array direction form an angle of 180 degrees.