CN101666685B - Device and method for extracting low coherence interference center fringe based on two-dimensional image - Google Patents

Abstract

The invention discloses a device and a method for extracting a low coherence interference center fringe based on a two-dimensional image. The device comprises a low coherence light source, a 3dB optical fibre coupler, a first single mode fiber, a second single mode fiber, a CMOS camera and a computer. Light emitted from the low coherence light source is divided into two beams of light through the 3dB optical fibre coupler; one beam of light irradiates a lens of the CMOS camera through the first single mode fiber; the other beam of light irradiates the lens of the CMOS camera through the second single mode fiber; the two beams of light generate interference in the CMOS camera to form a low coherence interference fringe image; and the low coherence interference fringe image is output to an extraction module of the low coherence interference center fringe in the computer. The invention adopts the CMOS camera to acquire light information, thereby changing the traditional form of the light signal conversion by a photodetector.

Description

A kind of extraction element and method of the low coherence interference center striped based on two dimensional image

Technical field

The present invention relates to the extraction element and the method for a kind of low coherence interference center stripe information, more particularly say, be meant that a kind of CMOS of utilization camera carries out image acquisition, adopt the extraction element of the low coherence interference center striped that the striped contour area relatively carries out then.

Background technology

Interference of light test essence is that the wavelength with light wave measures as unit, and what traditional interferometry mainly detected is interference fringe, by the variation of detection fringe position, shape, spacing etc., accurately measures the small value of some physical quantitys.In these measuring systems, the most normal use is with all kinds of single modes or the narrow-band coherent laser equipment measuring system as light source; Wherein, laser requires optical element to have high accuracy, often makes system more complicated; So this type systematic requires harsh to external environments such as temperature, humidity, pressure, when above condition can't satisfy, can make precision, repeatability and the long-time stability etc. of measurement be difficult to guarantee.

Now, in the low-coherence measuring system, mainly utilize photodetector to carry out the collection of interference signal, the interference signal that promptly collects is an one-dimension information.So in the low-coherence measuring system based on photodetector, mainly be processing to one-dimension information to the processing of interference signal.

Summary of the invention

One of purpose of the present invention provides a kind of extraction element of simple in structure, the low coherence interference center striped that is easy to realize, and this device is made of low-coherence light source, 3dB fiber coupler, first single-mode fiber, second single-mode fiber, CMOS camera and computer system.This computer system stores low coherence interference center striped extraction module and forms by computing machine and in computing machine.

Two of purpose of the present invention is the extracting method that propose a kind of low coherence interference center striped based on two dimensional image, this method at first adopts approach method to obtain the striped profile information of two dimensional image, then the striped profile information is carried out area relatively, and application profile coordinate relational expression finally obtains low coherence interference center stripe information.

In the present invention, described low coherence interference center striped extraction module includes binary image unit, profile extraction unit, contour area comparing unit and reference point coordinate resolution unit.

The advantage of apparatus of the present invention is:

(A) adopt the CMOS camera to carry out obtaining of optical information, changed the transition form that traditional employing photodetector carries out light signal.

(B) utilize the computing power of active computer maturation and be embedded in low coherence interference center striped extraction module in the hard disc of computer, can extract effectively, the center striped in the trackbar print image, can obtain coordinates of reference points simultaneously and show.

(C) adopt the CMOS camera to combine with computing machine (this calculator memory contains low coherence interference center striped extraction module), anti-electromagnetic interference capability is strong, because circuit such as signal amplification, filtering are not contained in interference fringe collection, processing section, so anti-electromagnetic interference capability is more intense.

The advantage of the extracting method of low coherence interference of the present invention center striped is:

(1) obtain more simple, economical with the traditional optical information that utilizes photodetector to carry out.

(2) utilize computing machine to combine and carry out the striped extraction of low coherence interference center with low coherence interference center striped extraction module, its measuring accuracy height, intensity information is converted into the monochrome information of image, is easy to tell center striped and ± 1 grade of striped, thereby than being easier to extract the center striped; The interference signal processing procedure is simple more, directly perceived, quick simultaneously, has improved efficiency of measurement effectively.

Description of drawings

Fig. 1 is the extraction element that the present invention is based on the low coherence interference center striped of two dimensional image.

Fig. 2 is the spacing synoptic diagram of the camera lens of two optical fiber of the present invention and CMOS camera.

Fig. 3 is the interface synoptic diagram of low coherence interference of the present invention center striped extraction module.

Fig. 4 is the black white image with center stripe information of the present invention after binary conversion treatment.

Fig. 5 is the black white image that the present invention obtains to have the profile information striped.

Fig. 6 is the black white image that the present invention has the fringe center point identification.

Among the figure: 1. low-coherence light source 2.3dB fiber coupler 3. first single-mode fibers 4. second single-mode fiber 5.CMOS cameras 6. computing machines

Embodiment

The present invention is described in further detail below in conjunction with accompanying drawing.

Referring to Fig. 1, shown in Figure 2, the present invention is a kind of extraction element of the low coherence interference center striped based on two dimensional image, this device is made of low-coherence light source 1,3dB fiber coupler 2, first single-mode fiber 3, second single-mode fiber 4, CMOS camera 5 and computing machine 6, wherein, low-coherence light source 1,3dB fiber coupler 2, first single-mode fiber 3 and second single-mode fiber 4 form the optical fiber Young's interferometer, and this optical fiber Young's interferometer is measurand; Store low coherence interference center striped extraction module in the hard disk of described computing machine 6, this low coherence interference center striped extraction module is write under VC 6.0 translation and compiling environments, realizes based on OpenCV (opensource computer vision library).In the present invention, the low coherence interference striped of being write based on this low coherence interference signal two dimensional image disposal route is gathered, the process software interface as shown in Figure 3, it is under VC 6.0 translation and compiling environments, realizes based on OpenCV (open source computer vision library).The left-half at interface can show the stripe pattern (as shown in Figure 6) that collects in real time, and right-hand part part can show the interference fringe image that CMOS camera 5 is captured and preserve.After collecting interference fringe image, can extract, identify, follow the tracks of the center striped in the low coherent fringe image, can obtain the reference point coordinate figure, this reference point is the circle among Fig. 6.In addition, this system can also be provided with the size, brightness of image and a stripe pattern that collects is preserved into video.

In the present invention, the minimalist configuration of computing machine 6 is CPU 2GHz, internal memory 2GB, hard disk 180GB; Operating system is windows 2000/2003/XP.

Being connected to of each parts (referring to Fig. 1, shown in Figure 2) in the extraction element of the present invention: the A end of 3dB fiber coupler 2 is connected with low-coherence light source 1, the B end of 3dB fiber coupler 2 is connected with an end of first single-mode fiber 3, leaves gap d between the camera lens 51 of the other end of first single-mode fiber 3 and CMOS camera 5 ₃(d ₃=2cm～4cm), the C of 3dB fiber coupler 2 end is connected with an end of second single-mode fiber 4, leaves gap d between the camera lens 51 of the other end of second single-mode fiber 4 and CMOS camera 5 ₄(d ₄=2cm～4cm), the usb data transmission line that adopts CMOS camera 5 to carry between CMOS camera 5 and the computing machine 6 is connected on the USB interface of computing machine 6.The spacing d of first single-mode fiber 3 and second single-mode fiber 4 ₀≤ 0.5mm.

The light path of extraction element of the present invention is: the centre wavelength of low-coherence light source 1 outgoing is 820nm, the live width spectrum is 39.6nm, luminous power is that the light of 14mW is divided into two-beam behind 3dB fiber coupler 2, a branch of light is through being radiated at behind first single-mode fiber 3 on the camera lens 51 of CMOS camera 5, be radiated on the camera lens 51 of CMOS camera 5 behind another Shu Guangjing second single-mode fiber 4, described two-beam interferes in CMOS camera 5, form the low coherence interference stripe pattern and export to computing machine 6, the low coherence interference center striped extraction module in the computing machine 6 carries out the center striped to the described low coherence interference stripe pattern that receives and extracts.

In the present invention, low coherence interference center striped extraction module includes binary image unit, profile extraction unit, contour area comparing unit and reference point coordinate resolution unit.

The binary image unit obtains bianry image and exports to the profile extraction unit after the image employing binarization method of CMOS camera 5 outputs is handled; Described bianry image is the black white image that contains part center stripe information, as shown in Figure 4.

The profile extraction unit adopts function cvFindContours to seek profile in bianry image, then the striped profile (as shown in Figure 5) that searches out is exported to the contour area comparing unit;

The contour area comparing unit compares the size that all the striped profiles in the bianry image carry out two-dimensional areas, thereby obtains the profile S of area maximum;

Reference point coordinate resolution unit adopts the two-dimensional silhouette relational expression $\begin{array}{c}x=\frac{x_1+x_2+\&CenterDot;\&CenterDot;\&CenterDot;+x_{N-1}+x_N}{N}\\ y=\frac{{\mathrm{<figure-callout\; id="1"\; label="y"\; filenames="H200910092494XE00011.png"\; state="\{\{state\}\}">y</figure-callout>}}_1+y_2+\&CenterDot;\&CenterDot;\&CenterDot;+y_{N-1}+y_N}{N}\end{array}$ Profile S to the area maximum carries out the reference point Coordinate Calculation, thereby obtains the center stripe information of low coherence interference striped, and as shown in Figure 6, circle is the sign of the center striped of low coherence interference striped among the figure.

In the two-dimensional silhouette relational expression $\begin{array}{c}x=\frac{x_1+x_2+\&CenterDot;\&CenterDot;\&CenterDot;+x_{N-1}+x_N}{N}\\ y=\frac{{\mathrm{<figure-callout\; id="1"\; label="y"\; filenames="H200910092494XE00011.png"\; state="\{\{state\}\}">y</figure-callout>}}_1+y_2+\&CenterDot;\&CenterDot;\&CenterDot;+y_{N-1}+y_N}{N}\end{array}$ In:

X represents the horizontal ordinate in the center of circle;

Y represents the ordinate in the center of circle;

N represents the sum of the point among the profile S of area maximum;

x ₁Be illustrated in the horizontal ordinate of the 1st point in the point of profile S of area maximum;

y ₁Be illustrated in the ordinate of the 1st point in the point of profile S of area maximum;

x ₂Be illustrated in the horizontal ordinate of the 2nd point in the point of profile S of area maximum;

y ₂Be illustrated in the ordinate of the 2nd point in the point of profile S of area maximum;

x _N-1Be illustrated in the horizontal ordinate of N-1 point in the point of profile S of area maximum;

y _N-1Be illustrated in the ordinate of N-1 point in the point of profile S of area maximum;

x _NBe illustrated in the horizontal ordinate of N point in the point of profile S of area maximum;

y _NBe illustrated in the ordinate of N point in the point of profile S of area maximum.

The extraction element and the method for a kind of low coherence interference center striped based on two dimensional image of the present invention, the inventor adopts the CMOS camera to carry out obtaining of optical information, has changed the transition form that traditional employing photodetector carries out light signal.Utilize the computing power of active computer maturation and be embedded in low coherence interference center striped extraction module in the hard disc of computer, can extract effectively, the center striped in the trackbar print image, can obtain coordinates of reference points simultaneously and show.Adopt the CMOS camera to combine with computing machine (this calculator memory contains low coherence interference center striped extraction module), anti-electromagnetic interference capability is strong, because circuit such as signal amplification, filtering are not contained in interference fringe collection, processing section, so anti-electromagnetic interference capability is more intense.

Claims (2)

1. extraction element based on the low coherence interference center striped of two dimensional image is characterized in that: this device by low-coherence light source (1), 3dB fiber coupler (2), first single-mode fiber (3), second single-mode fiber (4),

CMOS camera (5) and computing machine (6) constitute;

Store low coherence interference center striped extraction module in the hard disk of described computing machine (6); Described low coherence interference center striped extraction module includes binary image unit, profile extraction unit, contour area comparing unit and reference point coordinate resolution unit; The binary image unit obtains bianry image and exports to the profile extraction unit after the image employing binarization method of CMOS camera (5) output is handled; Described bianry image is the black white image that contains part center stripe information; The profile extraction unit adopts function cvFindContours to seek profile in bianry image, then the striped profile that searches out is exported to the contour area comparing unit; The contour area comparing unit compares the size that all the striped profiles in the bianry image carry out two-dimensional areas, thereby obtains the profile S of area maximum; Reference point coordinate resolution unit adopts the two-dimensional silhouette relational expression

Profile S to the area maximum carries out the reference point Coordinate Calculation, thereby obtains the center stripe information of low coherence interference striped;

The A end of 3dB fiber coupler (2) is connected with low-coherence light source (1), and the B end of 3dB fiber coupler (2) is connected with an end of first single-mode fiber (3), leaves gap d between the camera lens (51) of the other end of first single-mode fiber (3) and CMOS camera (5) ₃=2cm～4cm, the C end of 3dB fiber coupler (2) is connected with an end of second single-mode fiber (4), leaves gap d between the camera lens (51) of the other end of second single-mode fiber (4) and CMOS camera (5) ₄=2cm～4cm, the usb data transmission line that adopts CMOS camera (5) to carry between CMOS camera (5) and the computing machine (6) is connected on the USB interface of computing machine (6);

The spacing d of first single-mode fiber (3) and second single-mode fiber (4) ₀≤ 0.5mm.

2. extracting method based on the low coherence interference center striped of two dimensional image, it is characterized in that: from the centre wavelength of low-coherence light source (1) outgoing is 820nm, the live width spectrum is 39.6nm, luminous power is that the light of 14mW is divided into two-beam behind 3dB fiber coupler (2), on the camera lens (51) of a branch of light through being radiated at CMOS camera (5) behind first single-mode fiber (3), be radiated at behind another Shu Guangjing second single-mode fiber (4) on the camera lens (51) of CMOS camera (5), described two-beam interferes in CMOS camera (5), the low coherence interference center striped extraction module that formation low coherence interference stripe pattern is exported in the computing machine (6) carries out center striped extraction to the described low coherence interference stripe pattern that receives, and the extraction step of center striped is:

The binary image unit obtains bianry image and exports to the profile extraction unit after the image employing binarization method of CMOS camera (5) output is handled; Described bianry image is the black white image that contains part center stripe information;

The profile extraction unit adopts function cvFindContours to seek profile in bianry image, then the striped profile that searches out is exported to the contour area comparing unit;

The contour area comparing unit compares the size that all the striped profiles in the bianry image carry out two-dimensional areas, thereby obtains the profile S of area maximum;

Reference point coordinate resolution unit adopts the two-dimensional silhouette relational expression

Profile S to the area maximum carries out the reference point Coordinate Calculation, thereby obtains the center stripe information of low coherence interference striped.

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