Method and equipment based on multi-core fiber Bragg grating probe for measuring structures of a micro part

Patent metadata

Field	Value
Publication number	US-10060723-B2
Application number	US-201415112179-A
Country	US
Kind code	B2
Filing date	Dec 25, 2014
Priority date	Jan 17, 2014
Publication date	Aug 28, 2018
Grant date	Aug 28, 2018

Abstract

A method and equipment based on multi-core fiber Bragg grating (FBG) probe for measuring structures of a micro part are provided. The provided method relates to how to accomplish measuring structures of a micro part by transforming two or three-dimensional contact displacements into spectrum shifts of the multi-core FBG probe, and to reconstruct the structure geometry of a micro part. The provided equipment can be used to bring the spherical tip of the multi-core FBG probe into contact with a micro part, to determine coordinates of contact points, and to reconstruct the structure geometry of a micro part. The provided method and equipment feature high sensitivity, low probing force, high inspecting aspect ratio and immunity to environment interference.

First claim

What is claimed is:

1. A method based on multi-core FBG probe for measuring structures of a micro part includes following steps:
Step 1. Providing a multi-core FBG probe, which comprises a spherical tip and a multi-core fiber stylus inscribed FBGs in its cores; the multi-core fiber stylus, cantilevered at one end and with the spherical tip fixed on the other, serves as the multi-core FBG probe; the multi-core fiber utilized to fabricate the multi-core fiber stylus should have one or more cores located out of the center of the multi-core fiber;
Step 2. Providing a photoelectric probing system, which consists of the multi-core FBG probe mentioned in step 1, an optical path for the operation of the multi-core FBG probe, and an interrogation unit (consisting of a demodulation unit and a signal processing unit) for detecting and processing the sensing signal of the multi-core FBG probe; when a micro part is measured, the spherical tip of the multi-core FBG probe is brought into contact with a micro part and the spectra of FBGs comprised in the multi-core fiber stylus shift accordingly; the optical path supplies the multi-core FBG probe with energy and ensures the sensing signal containing spectrum shifts of FBGs in the multi-core fiber stylus and the reference FBG can reach the interrogation unit; the interrogation unit detects the sensing signal, transforms it into spectrum shifts of FBGs, and then calculates contact displacements of the spherical tip of the multi-core FBG probe relative to its zero-force position;
Step 3. Combining the photoelectric probing system mentioned in step 2 with a coordinate measuring instrument system to form an equipment based on multi-core FBG probe for measuring structures of a micro part, contact displacements of the spherical tip of the multi-core FBG probe and coordinates of the multi-core FBG probe relative to the coordinate measuring instrument system are acquired in real time and are processed by a measurement computer, wherein coordinates of contact points can be calculated from coordinates of the multi-core FBG probe relative to the coordinate measuring instrument system and contact displacements of the spherical tip of the multi-core FBG probe relative to its zero-force position measured directly using the photoelectric probing system;
Step 4. A micro part measured is fastened to a measurement table of the equipment based on multi-core FBG probe for measuring structures of a micro part mentioned in step 3; the motion of the measurement table and the multi-core FBG probe fixed on the sleeve of the equipment is controlled by manual operation or a measurement program; relative motion between the multi-core FBG probe and a micro part occurs and the motion track is accurately designed to bring the spherical tip of the multi-core FBG probe into contact with a certain point of a micro part, coordinates of a contact point can be calculated in the measurement computer mentioned in step 3;
Step 5. Repeat the measurement process in step 4 to obtain coordinates of more contact points and the structure geometry of a micro part measured can be reconstructed from coordinates of these contact points.

2. The equipment based on multi-core FBG probe 519 for measuring structures of a micro part comprises:
a photoelectric probing system 58 consists of:
a multi-core FBG probe 519 for sensing contact displacements consisting of a multi-core fiber stylus 514 inscribed FBGs in its cores and a spherical tip 515 fixed on the top of the multi-core fiber stylus 514 ,
a light source 59 for supplying light energy for the multi-core FBG probe 519 ,
an optical circulator 510 ,
a multi-channel optical switch 511 for switching optical paths to measure the spectra of FBGs in a time-division-multiplexing way,
a multi-core fiber fan-out 512 for making single mode fiber access to every core of the multi-core fiber stylus 514 ,
a multi-core fiber 513 for connecting the multi-core fiber fan-out 512 with the multi-core fiber stylus 514 ,
a reference FBG 516 for compensating environment temperature drifts,
a demodulation unit 517 for detecting spectrum signal and transforming it into electric signal,
a signal processing unit 518 for processing electric signal and calculating contact displacements ΔX 1 , ΔY 1 and ΔZ 1 of the spherical tip 515 of the multi-core FBG probe 519 relative to its zero-force position;
wherein, the photoelectric probing system 58 makes the multi-core FBG probe 519 working, demodulates the sensing signal and extracts contact displacements ΔX 1 , ΔY 1 and ΔZ 1 of the spherical tip 515 of the multi-core FBG probe 519 relative to its zero-force position, and
the light source 59 and the optical circulator 510 , the optical circulator 510 and the multi-channel optical switch 511 , the multi-channel optical switch 511 and the multi-core fiber fan-out 512 , the multi-channel optical switch 511 and the reference FBG 516 , and the optical circulator 511 and the demodulation unit 517 are linked with single mode fiber, respectively; the multi-core fiber fan-out 512 and the multi-core fiber stylus 514 of the multi-core FBG probe 519 are linked with the multi-core fiber 513 ; the demodulation unit 517 and the signal processing unit 518 are linked with electric cable;

a coordinate measuring instrument system 51 consists of:
a crosspiece 52 ,
a sleeve 53 adjustable in the X and Z direction with the multi-core FBG probe 519 fixed on it,
a measurement table 54 movable in the Y direction with a micro part being measured fastened to it for motion in axis y,
an instrument basement 55 for supporting and driving the measurement table 54 and the sleeve 53 through the crosspiece 52 ,
a XYZ-counter 56 for determining coordinate values X, Y, Z of the coordinate measuring instrument system 51 ,
a Computer Numerical Controller (CNC) controller 57 for controlling the motion of the sleeve 53 and the measurement table 54 ;
wherein, the coordinate measuring instrument system 51 is controlled by the CNC controller 57 to implement the whole measuring process, and accurate coordinates of the multi-core FBG probe 519 relative to the coordinate measuring instrument system 51 are determined by the CNC controller 57 , and
the crosspiece 52 and the sleeve 53 adjustable in the X and Z direction, the crosspiece 52 and the instrument basement 55 , the measurement table 54 movable in the Y direction and the instrument basement 55 are linked with mechanical structures, respectively; the sleeve 53 adjustable in the X and Z direction and the XYZ-counter 56 , the measurement table 54 movable in the Y direction and the XYZ-counter 56 , the instrument basement 55 and the CNC controller 57 are linked with electric cable, respectively;

a measurement computer 520 which is utilized to calculate coordinates of a micro part measured using results of the coordinate measuring instrument system 51 and the photoelectric probing system 58 , and plan the measuring process and send motion signal to the CNC controller 57 of the coordinate measuring instrument system 51 ,
wherein, the multi-channel optical switch 511 is controlled by the measurement computer 520 for switching optical paths to measure FBGs comprising in the multi-core fiber stylus 514 of the multi-core FBG probe 519 and the reference FBG 516 , and
the XYZ-counter 56 and the measurement computer 520 , and the CNC controller 57 and the measurement computer 520 , the multi-channel optical switch 511 and the measurement computer 520 , and the signal processing unit 518 and the measurement computer 520 are linked with electric cable, respectively.

3. The equipment based on multi-core FBG probe 519 for measuring structures of a micro part of claim 2 , wherein the

Assignees

• Harbin Inst Technology

Inventors

• Cui Jiwen
• Feng Kunpeng
• Li Junying
• Tan Jiubin

Classifications

• G01D5/35316

  using a Bragg gratings · CPC title

• G01D5/3538

  using a particular type of fiber, e.g. fibre with several cores, PANDA fiber, fiber with an elliptic core or the like · CPC title

• G01B11/007 Primary

  feeler heads therefor · CPC title

• G01B11/18

  using photoelastic elements · CPC title

• G01B5/012 Primary

  Contact-making feeler heads therefor · CPC title