CN101532825B - Method for measuring thickness of sea surface spilled oil film based on differential laser triangulation method - Google Patents

Abstract

The invention relates to a method for measuring thickness of sea surface spilled oil film based on differential laser triangulation. The method uses dual laser triangulation ranging system, and laser beams emitted by two lasers are respectively irradiated to the upper and the lower surfaces of an oil film to be measured in any vertical direction; the off-plane displacements of the upper and the lower surfaces can be obtained simultaneously according to the size of image drift and configuration parameters of imaging system; the thickness of the measured oil film can be determined by subtracting; and the thickness distribution of oil film in spilled oil area can be obtained by multi-point sampling. The non-contact measuring method has the characteristics of simple theory, convenient measurement, low cost, high precision, small volume and the like, and can be applied to dynamic on-line measurement of oil film thickness at the surface of aqueous solution.

Description

Based on the trigon method for measuring thickness of sea surface spilled oil film of differential laser

[technical field]: the invention belongs to the three-dimensional monitoring technology of marine environment field, particularly a kind of thickness of sea surface spilled oil film measuring technique.

[background technology]: the slick thickness measure is one of indispensable work of marine environmental management, is important problem very in the fields such as environmental protection, chemical analysis, oil film dynamics research.Marine monitoring department and expert are seeking a kind of method of measure water face oil film thickness always, but also fail to find a kind of believable water-surface oil film method for measuring thickness up to now.Oil film thickness is that oil spilling improvement (as the hold water use and the on-the-spot burning etc. of spreading agent) provides effective rational guidance, expand dynamic (dynamical) basic theories important scientific basis is provided for understanding oil reservoir, weather, weather and marine environment are handled all important meaning.Proposed at present and be used for the different oil products on aqueous solution surface and common methods that different oil film thicknesses are measured has following several:

Water Raman back scattering method, UV-irradiation fluorescent spectrometry based on spectral analysis, this method is the spectral intensity under fluorescence lifetime and the different oil film thicknesses by analyzing different oil products, can realize simultaneously that oil product is differentiated and the measurement of oil film thickness, be applicable to the measurement of oil sheet thickness.

Microwave radiometer is to obtain core intersection information by comparing and measuring the bright temperature that obtains, but this method need pre-determine some environmental parameters and oil property parameter.

Multiple beam interferometry, oil film form oil/G﹠O/two plane-parallel layers of water across the sea.Light incident oil gas interface, part light is reflected to air, and the part transmittance enters oil reservoir.The light beam that enters oil reservoir is at water-oil interface generation reflection/transmission, and folded light beam is returned oil reservoir through the water-oil interface reflection, turns back to air through transmission again.Aerial these light wave stacks interfere, and calculate oil film thickness by intervention phase difference.

Scanning white light interferometric method, the method are by analyzing the peakedness ratio of different oil products at the interference envelope of the water surface and air interface formation, carry out oil product and identify, calculating oil film thickness by oil gas interface and the formed separately two groups of interference fringe peak separations of water-oil interface.This technology based on interference technique is applicable to core intersection measurement transparent, that water-oil interface are smooth.

Laser acoustics/laser-ultrasound wave technology, its basic mechanism is based on laser radar and ultrasound wave principle, utilizes acoustic-pulse propagation to return the time of oil gas interface again and the acoustic wave propagation velocity in oil reservoir calculates core intersection through oil reservoir.Developed a kind of laser ultrasonic remote sensing oil film thickness survey sensor, this sensor measurement precision height has very big potentiality in aviation oil overflowing remote sense fields of measurement, but needs three laser instruments: a CO ₂Pulsed laser, a Nd:YAG laser instrument and a He-Ne laser instrument, and volume is very big.

[summary of the invention]: the purpose of this invention is to provide a kind of based on the trigon method for measuring thickness of sea surface spilled oil film of differential laser, to solve the thickness of sea surface spilled oil film problems of measurement, fill up the blank of this technical research of China marine oil overflow monitoring aspect, advance the development of the existing spilled oil monitoring level of China, for thickness of sea surface spilled oil film is measured, oil reservoir is expanded dynamics and marine environment science provides technical foundation.

The present invention proposes thickness measurement technology with laser triangulation first and is applied to the oil spilling oil film thickness and measures, and considers the fluctuation of seawater and oil film, adopts the double light path differential system, promptly adopts the two laser triangulation system of the oblique fire formula of symmetry.The laser beam that laser instrument sends is assembled oblique incidence oil film upper and lower surface through convergent lens, and the incidence point place on the oil film upper and lower surface forms an oval-shaped LASER SPECKLE.Imaging system images in optical receiver CCD with this hot spot and goes up the formation picture point.Utilize two Laser Triangulation Measurement System Based of upper and lower surface,, can obtain this point acoplanarity displacement on two surfaces up and down simultaneously, by subtracting each other the oil film thickness that to determine the measured point according to the structural parameters k of image drift size h and imaging system.In light path system, guarantee that laser beam, imaging len optical axis, CCD are in same plane, angle is 90 ° between strict guarantee laser beam optical axis and the imaging len optical axis, angle between CCD and the imaging len optical axis is 90 °, object distance is constant after just can guaranteeing the measured surface position change, with guarantee measured point in certain field depth can both focal imaging on detector, guaranteed measuring accuracy.

The concrete measuring process of measuring method of the present invention comprises:

The first, light path system is built

Build the two laser triangulation system of the oblique fire formula of symmetry according to Fig. 1, each laser triangulation system comprises the Lights section that laser instrument and convergent lens are formed, and the reception imaging system of being made up of imaging len, detector C CD or position sensor PSD (PositionSensitive Detector) and data acquisition and processing module; Parts identical in the accompanying drawing are represented with identical mark;

The second, light spot image collection

The laser beam that first via laser instrument sends is assembled oblique incidence oil film upper surface to be measured through convergent lens, incidence point place on the oil film upper surface forms an oval-shaped LASER SPECKLE and (regulates lens position, focus is positioned near the upper surface of tested oil film, then this moment, hot spot had very strong brightness and very little radius, form a bright spot), the imaging len that receives in the imaging system images in this hot spot on the CCD; The laser beam that the second road laser instrument sends is assembled by air oblique incidence seawater through convergent lens, reflection and refraction take place at the gas-water interface place, refract light oblique incidence oil film lower surface, incidence point place on the oil film lower surface also forms an oval-shaped LASER SPECKLE and (regulates lens position, focus is positioned near the lower surface of tested oil film, then this moment, hot spot had very strong brightness and very little radius, form a bright spot), imaging system images in this hot spot on the CCD, and makes up and down two lighting points corresponding to the upper and lower surface on the testee any point vertical direction.Gather the hot spot picture point of two-way system on CCD.Reference plane is made as virtual reference plane, and choosing in theory can be any;

Three, image displacement measurement amount

The filtering techniques such as light spot image employing shape filtering that collect are carried out Flame Image Process, utilize methods such as centroid method, Hough conversion to obtain the barycenter of last two picture points of CCD, utilize the range formula between 2 again and then can obtain the image displacement amount h of two hot spot picture point relative datum plane hot spot picture points up and down ₁And h ₂=h ' ₁-h ' ₂

Four, set up the acoplanarity displacement calculation mathematic model

The hot spot that obtained according to the last step is corresponding displacement h on CCD ₁And h ₂, set up the acoplanarity displacement calculation mathematic model, calculate through data processing module, can obtain this point acoplanarity displacement d of the reference plane of two surface distance supposition up and down ₁And d ₂(sense of displacement as shown in the figure, the arrow that makes progress is a positive dirction, to next be negative direction).Wherein first light path system is adopted d ₁=k ₁h ₁Formula is calculated, k in the formula ₁=(u-f) cos α/f.To the second light path system d ₂=l ₁-l ₂=k ' ₁H ' ₁-k ' ₂H ' ₂, k ' in the formula ₁=(a-f) cos θ ₁/ f, U, a are the object distance of two-way imaging system, and α is the angle of laser beam optical axis and tested surface normal, θ ₁Be the incident angle of laser beam incident in the air seawater interface, n ₀Be air refraction, n ₁Be the seawater refractive index, f is the focal length of imaging len;

Five, data processing and output

To two acoplanarity displacement d that obtain ₁And d ₂, subtract each other the oil film thickness d=d that can obtain this point ₁-d ₂

The measuring principle of the inventive method:

Fig. 2 is ultimate principle figure.In the oblique fire formula shown in Fig. 2 (a), laser beam is incident in measurement point A place and forms an oval hot spot at this place with the α angle.At the opposite side of A place normal, the imaging len optical axis becomes the β angle with its normal, and the image of video camera picked-up hot spot also images in a place on the CCD.When launching spot is shifted to the M point along laser beam by the A point, camera absorbs laser radiation at the laser facula at tested object plane M place and image in the m place of CCD under the situation of not doing any change.Laser beam optical axis, CCD are vertical with the imaging len optical axis.According to the structural parameters k of image drift size h and imaging system, can determine the displacement of tested object plane.

If the displacement of luminous point on imaging surface is h ₁, then the displacement of tested object plane is

${\mathrm{<figure-callout\; id="1"\; label="d"\; filenames="H200910068627XE00011.png,H200910068627XE00012.png"\; state="\{\{state\}\}">d</figure-callout>}}_1=\frac{(u-f)h_1}{f}\cos \mathrm{\&alpha;}=k_1{h}_1---\left(1\right)$

U is the object distance of imaging system in the formula, and f is the focal length of imaging len.As long as in following formula, recorded h ₁, can try to achieve d ₁

To Fig. 2 (b), the laser beam that laser instrument sends is with incident angle θ ₁By the A point place of air oblique incidence on the air seawater interface, reflection and refraction take place at the gas-water interface place.Video camera absorbs the image of this flare and images in D point place on the CCD.Refract light oblique incidence oil film lower surface, the incidence point B place on the oil film lower surface also forms an oval-shaped LASER SPECKLE, and video camera absorbs the image of this hot spot and images in C point place on the CCD.If C point and the displacement of D point on imaging surface are h ' ₂, the angle between CCD and the imaging len optical axis is 90 °, then

${\mathrm{<figure-callout\; id="2"\; label="l"\; filenames="H200910068627XE00011.png,H200910068627XE00021.png"\; state="\{\{state\}\}">l</figure-callout>}}_2=\frac{(a-f)\sqrt{{\mathrm{<figure-callout\; id="1"\; label="n"\; filenames="H200910068627XE00011.png,H200910068627XE00012.png"\; state="\{\{state\}\}">n</figure-callout>}}_1^2-n_0^2{\sin }^2{\mathrm{\&theta;}}_1}}{n_0\mathrm{<figure-callout\; id="2"\; label="f\; h"\; filenames="H200910068627XE00011.png,H200910068627XE00021.png"\; state="\{\{state\}\}">f</figure-callout>}}{h}_{}^{}{}_2^{\&prime;}={\mathrm{<figure-callout\; id="2"\; label="k"\; filenames="H200910068627XE00011.png,H200910068627XE00021.png"\; state="\{\{state\}\}">k</figure-callout>}}_2^{\&prime;}{\mathrm{<figure-callout\; id="2"\; label="h"\; filenames="H200910068627XE00011.png,H200910068627XE00021.png"\; state="\{\{state\}\}">h</figure-callout>}}_2^{\&prime;}$

N in the formula ₀Be air refraction, n ₁Be the seawater refractive index, a is the object distance of imaging system, and f is the focal length of imaging len.

When launching spot is shifted to the M point by the A point, imaging point is done corresponding moving on CCD.Analyze as can be known the displacement of tested object plane by Fig. 2 (a)

${\mathrm{<figure-callout\; id="1"\; label="l"\; filenames="H200910068627XE00011.png,H200910068627XE00012.png"\; state="\{\{state\}\}">l</figure-callout>}}_1=\frac{(a-f){\mathrm{<figure-callout\; id="1"\; label="h"\; filenames="H200910068627XE00011.png,H200910068627XE00012.png"\; state="\{\{state\}\}">h</figure-callout>}}_1^{\&prime;}}{f}\cos {\mathrm{\&theta;}}_1={\mathrm{<figure-callout\; id="1"\; label="k"\; filenames="H200910068627XE00011.png,H200910068627XE00012.png"\; state="\{\{state\}\}">k</figure-callout>}}_1^{\&prime;}{\mathrm{<figure-callout\; id="1"\; label="h"\; filenames="H200910068627XE00011.png,H200910068627XE00012.png"\; state="\{\{state\}\}">h</figure-callout>}}_1^{\&prime;}$

H ' wherein ₁Be the image drift size.

Then, the oil film lower surface with respect to the displacement of a M is

${\mathrm{<figure-callout\; id="2"\; label="d"\; filenames="H200910068627XE00011.png,H200910068627XE00021.png"\; state="\{\{state\}\}">d</figure-callout>}}_2=l_1-{\mathrm{<figure-callout\; id="2"\; label="l"\; filenames="H200910068627XE00011.png,H200910068627XE00021.png"\; state="\{\{state\}\}">l</figure-callout>}}_2={\mathrm{<figure-callout\; id="1"\; label="k"\; filenames="H200910068627XE00011.png,H200910068627XE00012.png"\; state="\{\{state\}\}">k</figure-callout>}}_1^{\&prime;}{\mathrm{<figure-callout\; id="1"\; label="h"\; filenames="H200910068627XE00011.png,H200910068627XE00012.png"\; state="\{\{state\}\}">h</figure-callout>}}_1^{\&prime;}-{\mathrm{<figure-callout\; id="2"\; label="k"\; filenames="H200910068627XE00011.png,H200910068627XE00021.png"\; state="\{\{state\}\}">k</figure-callout>}}_2^{\&prime;}{\mathrm{<figure-callout\; id="2"\; label="h"\; filenames="H200910068627XE00011.png,H200910068627XE00021.png"\; state="\{\{state\}\}">h</figure-callout>}}_2^{\&prime;}=\frac{(a-f)\cos {\mathrm{\&theta;}}_1}{\mathrm{<figure-callout\; id="1"\; label="f\; h"\; filenames="H200910068627XE00011.png,H200910068627XE00012.png"\; state="\{\{state\}\}">f</figure-callout>}}{h}_{}^{}{}_1^{\&prime;}-\frac{(a-f)\sqrt{{\mathrm{<figure-callout\; id="1"\; label="n"\; filenames="H200910068627XE00011.png,H200910068627XE00012.png"\; state="\{\{state\}\}">n</figure-callout>}}_1^2-n_0^2{\sin }^2{\mathrm{\&theta;}}_1}}{n_0\mathrm{<figure-callout\; id="2"\; label="f\; h"\; filenames="H200910068627XE00011.png,H200910068627XE00021.png"\; state="\{\{state\}\}">f</figure-callout>}}{h}_{}^{}{}_2^{\&prime;}---\left(2\right)$

In formula (2) if in recorded h ' ₁And h ' ₂, can try to achieve d ₂

Advantage of the present invention and beneficial effect:

The present invention is to provide a kind of non-contact measurement method, this method have principle simple, measure convenient, cost is low, volume is little, can eliminate the error of introducing by imaging system, level change, oil film surface gloss and color, external environment, and effectively overcome the characteristics such as influence of bias light to measuring accuracy, can be used for the on-line dynamic measurement of aqueous solution sea surface oil slick thickness.

This measuring method can realize the dynamic on-line automatic measurement of thickness of sea surface spilled oil film fast, accurately, quantitatively, for detecting, marine oil spill provides reliable survey instrument, advance the development of the existing spilled oil monitoring level of China, oil spilling is administered provides important evidence and technical support.

[description of drawings]:

Fig. 1 is two laser triangulation light path systems of the oblique fire formula of symmetry of the present invention;

Fig. 2 is a laser triangulation schematic diagram of the present invention, and Fig. 2 (a) is an oblique fire formula first via monochromatic light road system, and Fig. 2 (b) is oblique fire formula the second road monochromatic light road system;

Fig. 3 is two laser triangulation system experimentation index paths of the oblique fire formula of symmetry.

The instance graph of the laser image spot that Fig. 4 obtains for the two laser triangulation system of the oblique fire formula of symmetry, Fig. 4 (1) is the image of first via system acquisition, Fig. 4 (2) is the image of the second tunnel system acquisition.

Wherein, 1 is laser instrument, and 2 is convergent lens, and 3 is imaging len, and 4 is CCD, and 5 is virtual reference plane, and 6 are data acquisition and processing module, and 7 is sample cell, and 8 is spectroscope, and 18,19,28,29 are catoptron.

[embodiment]:

Embodiment 1

Be example with experiment light path shown in Figure 3 below, set forth the concrete measuring process of measuring method of the present invention;

1. light path system is built

Build the two laser triangulation system of the oblique fire formula of symmetry shown in Figure 3, system source partly comprises laser instrument 1, convergent lens 2, spectroscope 3, catoptron 18,19,28,29.Laser instrument 1 is the He-Ne laser instrument of wavelength X=632.8nm, and convergent lens 2 is the convergent lens of focal distance f=300mm.(imaging) system of reception is made up of imaging len 3, detector C CD 4 and data acquisition and processing module 6.Imaging len 3 is the imaging len of f=250mm, and detector C CD 4 is an area array CCD, and data acquisition and processing module 6 comprise image pick-up card and computing machine.Sample cell 7 is the aquarium of transparent uncovered, fills water in the pond, and oil float is on the water surface.In light path system, guarantee laser beam, imaging len optical axis, CCD in same plane, strict guarantee laser beam optical axis is vertical with the imaging len optical axis, and CCD is vertical with the imaging len optical axis.Regulate light path first via light beam and the second road light beam intersected in air, and about making two lighting points corresponding to the upper and lower surface on any point vertical direction of testee;

2. light spot image collection

The laser beam that He-Ne laser instrument 1 sends is behind spectroscope 3, and respectively through catoptron 18,19 and 28,29 reflections, scattering and refraction take place at the gasoil horizon place point S place through the convergent lens 2 of the first via is assembled by air oblique incidence oil film upper surface to be measured.Regulate the position of convergent lens 2, make focus be positioned at the near surface of tested oil film, then this moment, hot spot had very strong brightness and very little radius, formed a bright spot.The scattered light at some S place forms an oval-shaped LASER SPECKLE, and imaging len 3 images in this hot spot on the CCD 4.Reflected light is assembled through the second tunnel convergent lens 2 and is entered water by the air oblique incidence through glass (container bottom surface), reflection and refraction take place at air and glass interface point A place, refract light is in reflection of bath of glass interface point C place and refraction, the reflected light at some A, C place respectively forms an oval-shaped LASER SPECKLE, and imaging len 3 images in this hot spot on the CCD 4.Scattering takes place in refract light oblique incidence oil film following table millet cake B place at the water-oil interface place.Regulate the position of convergent lens 2, focus is positioned near the lower surface of tested oil film, the incidence point B place on the oil film lower surface also forms an oval-shaped LASER SPECKLE, and imaging system images in this hot spot on the CCD.Gather the hot spot picture point of two-way system on CCD, as shown in Figure 4.Testing used oil is oil, and the image that the first via is gathered is shown in Fig. 4 (1), and the second tunnel image of gathering is shown in Fig. 4 (2).The picture point of corresponding air-glass interface shown in a among the figure, the picture point of corresponding water-oil interface shown in the b, the picture point that c is depicted as the bath of glass interface (does not mark in Fig. 1 and Fig. 2, if the refractive index and the water/seawater of selected sample cell material are approaching, then putting A overlaps with some C), the picture point of corresponding oil gas interface shown in the s, reference plane is selected in the M point in the oil reservoir, being virtual reference plane, is to obtain by the demarcation to experimental system.In measuring process, fix two range measurement system relative tertiary locations and remain unchanged simultaneously;

3. image displacement is measured

The filtering techniques such as light spot image employing shape filtering that collect are carried out Flame Image Process, utilize centroid method to obtain the center-of-mass coordinate that CCD goes up picture point.The center-of-mass coordinate of the hot spot at the some S place that Fig. 4 (1) gathers is (1896.9,1186.2), and the center-of-mass coordinate of the hot spot at the reference plane point M place of Biao Dinging is (1581.1,1127.6) in advance.The center-of-mass coordinate point B place of the hot spot that Fig. 4 (2) gathers is that (941.1,1302.1), some A place are (1669.3,1352.1), and some C place is (1511.1,1321.2), and the center-of-mass coordinate of the hot spot at calibration point M place is (205.0,1159.3).Utilize the range formula between 2 and then can obtain up and down two hot spot picture points with respect to the image displacement amount of reference point h respectively ₁=2.3768mm and h ₂=h ' ₁-h ' ₂=10.9293mm-1.1928mm-4.2204mm=5.5161mm (h ' ₂=h ' _Bc+ h ' _Ac).

4. data processing

According to hot spot corresponding displacement h on CCD that the last step obtains, data processing module utilizes formula d=kh to calculate, and can obtain the displacement d of oil film upper and lower surface with respect to a M ₁And d ₂, d in the formula ₁=(u-f) h ₁Cos α/f=k ₁h ₁, d ₂=l ₁-l ₂=k ' ₁H ' ₁-k _BcH ' _Bc-k _AcH ' _Ac, wherein, l ₁=k ' ₁H ' ₁=(a-f) cos θ ₁H ' ₁/ f, By demarcate obtaining the object distance a=u=508.38mm of imaging system, α=44.24 °, θ ₁=44.45 °, f=250mm, air refraction n ₀=1, the refractive index of water is n ₁=1.33, glass refraction is n ₃=1.5, calculate and definition obtains d among Fig. 4 according to sense of displacement ₁=1.7599mm, d ₂=-1.4963mm, oil oil film thickness d=3.26mm.

Claims (2)

1. one kind based on the trigon method for measuring thickness of sea surface spilled oil film of differential laser, it is characterized in that this method comprises:

The first, select the two laser triangulation system of the oblique fire formula of symmetry, each laser triangulation system comprises the Lights section that laser instrument and convergent lens are formed, and the reception imaging system of being made up of imaging len, detector C CD or position sensor PSD (PositionSensitive Detector) and data acquisition and processing module;

The second, oil film thickness is measured the design of light path system, the laser beam that makes first via laser instrument send is assembled oblique incidence oil film upper surface to be measured through convergent lens, incidence point place on the oil film upper surface forms an oval-shaped LASER SPECKLE, receives imaging system this hot spot is imaged on the CCD; The laser beam that makes the second road laser instrument send is assembled by air oblique incidence seawater through convergent lens, reflect/scatter and refraction take place at the gas-water interface place, refract light oblique incidence oil film lower surface, incidence point place on the oil film lower surface also forms an oval-shaped LASER SPECKLE, imaging system images in this hot spot on the CCD, and makes up and down two incidence points corresponding to the upper and lower surface on the tested oil film any point vertical direction; Reference plane is made as virtual reference plane, and it is chosen in theory can be any;

Three,, determine the image displacement amount h of these two hot spot picture point relative datum plane hot spot picture points up and down according to the hot spot picture point of above-mentioned two-way system on CCD ₁And h ₂=h ' ₁-h ' ₂

Four, the hot spot corresponding displacement h on CCD that obtained according to the last step ₁And h ₂, digital sampling and processing calculates, and can obtain this point acoplanarity displacement d of the reference plane of two surface distance supposition up and down ₁And d ₂Wherein to the first light path system d ₁=k ₁h ₁, k in the formula ₁=(u-f) cos α/f, α is the angle of laser beam optical axis and tested surface normal, and u is the object distance of imaging system, and f is the focal length of imaging len; To the second light path system d ₂=l ₁-l ₂=k ' ₁H ' ₁-k ' ₂H ' ₂, k ' in the formula ₁=(a-f) cos θ 1/f,

A is the object distance of imaging system, θ ₁Be the incident angle of laser beam incident in the air seawater interface, n ₀Be air refraction, n ₁Be the seawater refractive index;

Five, obtained two acoplanarity displacement d according to the last step ₁And d ₂, subtract each other the oil film thickness d=d that can obtain this point ₁-d ₂

2. measuring method according to claim 1 is characterized in that for the first via light path system angle between laser beam optical axis and the imaging len optical axis is 90 °, and CCD is vertical with the imaging len optical axis; For the second road light path system, the laser beam optical axis is vertical with the imaging len optical axis, and CCD and imaging optical axis angulation are 90 °.

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