CN104154870B - A kind of method of bi-coloured light interferometry oil film thickness - Google Patents

Abstract

The invention belongs to field of optical measuring technologies, a kind of method relating to bi-coloured light interferometry oil film thickness, the red and green color interference of light tristimulus values of oil film thickness between steel ball and glass plate first calculated by meter, the optical interference picture that surveying record difference sliding speed and the different steel ball added under the conditions of load and glass plate contact area lubricating oil film thickness cause again, the G R analyzing the nearest darkened features striped in distance contact center modulates light intensity curve, determine streaky concrete progression in whole interference image, it is calculated concrete film thickness distribution, realize the measurement of oil film thickness；It is simple that it measures process, measures efficiency high, gets the range of big 3 times than white light interference, it is simple to measures the oil film thickness distribution of whole contact area under different sliding speed and different loads.

Description

A kind of method of bi-coloured light interferometry oil film thickness

Technical field:

The invention belongs to field of optical measuring technologies, relate to the side of a kind of bi-coloured light interferometry oil film thickness Method, particularly one utilize bi-coloured light interfere and Relative light intensity principle measure machinery Contact Pair between nanometer to sub-micro Rice magnitude oil film thickness method, it is adaptable to measure elastohydrodynamic lubrication, hydrldynamic pressure lubrication and Film thickness distribution in the contact area of friction speed, load under his lubricating status.

Background technology:

Between mechanical operating part, form the oil film of adequate thickness, two surface segmentation are come, be to reduce to rub Wipe, it is to avoid the important means of abrasion.At present, optical interferometry be measure oil film thickness most efficient method it One, it utilizes the interference fringe formed to calculate oil film thickness and shape.Nineteen sixty-five, Cameron etc. People proposes the measurement structure of ball-dish contact, utilizes Optical interference techniques first observed to the warp with outlet constriction Allusion quotation shape of a hoof oil film shape, has opened up photoelastic stream (Optical Elastohydrodynamics) research field, after Improved, it is determined that glass plate, beam splitter layer (Cr film), bed course (SiO₂), lubricating oil and the light of steel ball Learning and measure configuration, wherein the introducing of light splitting Cr film greatly improves the contrast of interference fringe, cushion layer technique Propose to reduce to survey thickness lower limit.According to use light source difference, optical interferometry be divided into monochromatic light interferometric method and White Light Interferometer, monochromatic light interferometric method is by interference fringe level time counting and analyzes the change of light intensity between light and shade striped Judging oil film thickness, the relative light intensity method (ROII) and the Qingdao science and engineering that propose in conjunction with Huangping, Luo Jianbin etc. are big Learning the MBI measurement scheme that Guo Feng proposes, resolution is 0.85nm, and range reaches 5 μm；But need in the measurements From speed be 0 time serialograph, from image history, count order of interference, the most not only efficiency is low Under, and often can lose level time in high speed kinetic measurement, cause thickness to be judged by accident；White Light Interferometer utilizes interferes In image, the change of hue coordinate calculates oil film thickness, it is not necessary to determine interference fringe level time；But the increasing with thickness Adding, the wave-length coverage forming constructive interference increases, and the contrast of interference fringe and color saturation decay are serious, For white light interference, its highest thickness of surveying is usually no more than 1 μm, and the precision measured depends on strict Calibration process, the several factors of calibration process, as static demarcating is different with the curvature of contact surface in kinetic measurement Etc. the error that will cause measurement.Maximum oil film thickness can be surveyed in order to improve under the conditions of ensureing certainty of measurement, grind Studying carefully personnel to be also adopted by double-colored or three coloured light and measure, really monochromatic light is interfered and white light interference compromise, Lord etc. propose pseudo-phase stepping measurement method based on the trichroism interference of light, but due to technical sophistication, not It is promoted；Qingdao Technological University Guo Feng, State of Zhao build at its paper " bi-coloured light interference light that oil film thickness is measured Modulation method " in G-R bi-coloured light modulation technology is proposed, attempt with an Image Information Processing thickness, Avoiding the monochromatic light dependence to history image level time, but clap the cycle merely with a modulating wave, range is only 1 μm, it is impossible to meet the measurement demand of high thickness, the more crucially pole of the adjustment curve of dual-beam Theoretical Calculation In value point and actual measurement, extreme point size deviation is relatively big, causes the method cannot apply in reality is measured.Cause This, explore a kind of wide range, in high precision, facilitate feasible method to nano/submicron lubricating oil film thickness It is necessary for measuring.

Summary of the invention:

It is an object of the invention to overcome the order of interference that in existing measuring method, monochromatic light is loaded down with trivial details to count and other The shortcoming that interference technique range is little, seeking design provides the side of a kind of bi-coloured light interferometry oil film thickness Method, can expand to 4 μm by optics range, can be accurately judged to the dry of fixing point by a width dichromatic interference image Relating to level time, then the monochromatic HONGGUANG light distribution of recycling realizes varying load or change between Contact Pair according to relative light intensity method The efficient measurement of dynamic nano/submicron oil film thickness under speed operating mode.

To achieve these goals, the present invention uses bi-coloured light film lubrication testing stand to realize oil film thickness Measure, bi-coloured light film lubrication testing stand is provided with the oil film between captured in real time steel ball and glass plate Contact Pair and does Relating to the 3CCD color camera of image, be transferred to Computer display and storage through image card, it specifically measures step Suddenly include:

(1) oil film thickness between steel ball and glass plate, is calculated corresponding red green from 1nm to 4500nm Bi-coloured light interferes the red green RG relative intensity distribution of tristimulus values, i.e. oil film interference system；Color is utilized to be added former Reason and color reproduction equation, be respectively f to sensitive property of spectrum_R(λ)、f_G(λ)、f_B(λ) 3CCD is color The color tristimulus values that 3CCD (RGB) color camera of form and aspect machine obtains is

$C=\underset{\mathrm{\λ}}{\∫}\mathrm{kS}\left(\mathrm{\λ}\right)I_h\left(\mathrm{\λ}\right)f_C\left(\mathrm{\λ}\right)\mathrm{d\λ},$ C=R, G, B

Wherein, C represents R (red), G (green), B (blue) tristimulus values, and S (λ) is red and green color light source used Spectral power distribution function, k is adjustment factor, and the span of k is between 0 to 1, it is therefore intended that make The equal normalization of tristimulus values, I_h(λ) it is that on each wave band λ, thickness is the interference light intensity at h, glass plate interface Interference light intensity I is according to formula

$I={\left|{\stackrel{\‾}{E}}_0^{-}\right|}^2={|{\stackrel{\‾}{E}}_0^{-1}+{\stackrel{\‾}{E}}_0^{-2}+{\stackrel{\‾}{E}}_0^{-3}+{\stackrel{\‾}{E}}_0^{-4}+\·\·\·|}^2={\left|\underset{m=1}{\overset{\∞}{\mathrm{\Σ}}}{\stackrel{\‾}{E}}_0^{-m}\right|}^2$ Calculate, whereinRepresent reflection light electricity to Amount, m=1,2 ..., subscript 0 represents glass medium,Directly glass plate interface reflection, other are anti- Penetrate light all through reflection and the projection of glass plate layers below；Then increase to along oil film thickness from 0nm 4500nm, the normalization light intensity that the normalization light intensity of green glow deducts HONGGUANG obtains bi-coloured light modulation light intensity G-R, And draw out thickness variation relation curve chart corresponding with G, R, G-R relative light intensity with this；G-R modulates light Strong curve presents the feature of modulating wave to the change of thickness, and the size of this Curve Maximization point exists 1 a pair with thickness The relation answered, corresponding bi-coloured light interference image is clapped boundary at each modulating wave and is presented darkened features bar Stricture of vagina；The centre wavelength used is respectively the red and green color LASER Light Source of 653nm and 532nm, result of calculation In display G-R modulation light intensity curve, each ripple claps corresponding optical thickness is 1408nm, and each ripple is clapped and all comprised 10 extreme points, adjacent ripple is clapped the most identical, to bi-coloured light in the 4500nm film thickness range calculated The darkened features fringe position of interference image is made G-R and is modulated light intensity curve after calculating normalization red-green glow intensity values After, take each ripple of curve and clap absolute value sum SUM of upper 8th and the 9th extreme point light intensity value as sentencing Clapping according to distinguishing first three ripple, find that SUM value is clapped for first wave between 1.0 to 1.8, SUM value is 1.8 Then belonging to the second ripple between 2.8 to clap, SUM value is that the 3rd ripple is clapped between 2.5 to 3.2, and wherein first three is individual Ripple claps order of interference respectively (4,4), (8,8), (12,12) that the 8th extreme point correspondence monochrome HONGGUANG is interfered；

(2), surveying record sliding speed is more than steel ball during 0mm/s and glass plate contact area lubricating oil film thickness The optical interference picture caused, the G-R modulation light intensity analyzing the nearest darkened features striped in distance contact center is bent Line, calculate simultaneously the 8th and the 9th extreme point light intensity value absolute value sum and with calculated SUM value Wave band, and the order of interference of the 8th extreme point position correspondence HONGGUANG is clapped belonging to contrasting；Then with meter The thickness relative light intensity curve control of the 0～4500nm HONGGUANG obtained, show that the center under this sliding speed is done Relate to the concrete interference level in district, so that it is determined that streaky concrete progression in whole interference image, then utilize Principle of interference is calculated concrete film thickness distribution；Same procedure is utilized to record the steel ball of different sliding speed continuously The interference of light image caused with glass plate contact area lubricating film, thus the center obtained under different sliding speed connects Touch district's order of interference and film thickness distribution；

(3) under the conditions of, surveying record loads lever imposed load, steel ball and glass plate contact area lubricating film cause Interference image, measure draw the darkened features striped that center, distance contact area is nearest under this load G-R adjust Light intensity curve processed, utilizes the 8th simultaneously and the 9th extreme point light intensity value absolute value sum judges the 8th pole The order of interference of value point position correspondence HONGGUANG；Then with calculated 0～4500nm HONGGUANG thickness- Relative light intensity curve comparison draws the concrete interference level in the center interference district under this speed, may thereby determine that whole Streaky concrete progression in individual interference image, then utilizes principle of interference to be calculated concrete thickness and divides Cloth, it is achieved the measurement of oil film thickness.

The acquisition process of double-colored modulation light intensity G-R of the present invention specifically includes: first pass through 3CCD colour phase Machine storage interference image；Re-record rotating speed and/or load, then obtain interference image specify region HONGGUANG and Green glow light intensity value also stores, and exports HONGGUANG and the maximum of green glow light intensity and minima respectively；Utilize formula

$G-R=\frac{{2I}_G-(I_{G\max }+I_{G\min })}{I_{G\max }-I_{G\min }}-\frac{{2I}_R-(I_{R\max }+I_{R\min })}{I_{R\max }-I_{R\min }}$

Calculate double-colored difference light intensity G-R in described region.

In G-R of the present invention modulation light intensity curve, the determination methods of the 8th and the 9th extreme point is specifically wrapped Include: first obtain the G-R at interference image darkened features interference fringe and modulate the change of light intensity pixel coordinate Change；Then the light intensity absolute value all extreme points less than 0.5 on the extreme point of G-R modulation light intensity curve are found out Position, i.e. 0 district, comprise and represent a ripple and clap the position terminated；Secondly, from 0th district to contact center position, I.e. Contact Pair gap and the relatively reduced direction of thickness, the order of magnitude approximately equalised nearest near 0th district Group adjacent extreme point is the 8th and the 9th extreme point, wherein G-R value be less than 0 for the 8th extreme point, greatly In 0 for the 9th extreme point.

Bi-coloured light of the present invention interferes the agent structure of film lubrication testing stand to include testing stand base, red green double Color LASER Light Source, rotating ground glass, optical fiber, computer, 3CCD color camera, coaxial-illuminating microscope, Glass plate, steel ball, loading lever, spring tension meter, ball torr and servomotor, testing stand base is installed and puts Having glass plate, load lever and servomotor, glass plate is transparent circular structure；Load above one end of lever It is equipped with ball torr, is connected with spring tension meter below the other end；Be fixed with in ball torr steel ball, steel ball and glass plate it Between raceway on add lubricating oil formed lubricating oil film；Red and green color LASER Light Source is placed on testing stand base, The front side of red and green color LASER Light Source is placed with rotating ground glass, between rotating ground glass and coaxial-illuminating microscope It is provided with optical fiber, after the light that red and green color LASER Light Source sends filters through rotating ground glass, imports through optical fiber coaxial Illumination microscope, the final vertical microscopical viewing area of directive coaxial-illuminating；By spring tension meter to loading Lever imposed load realizes the measurement of oil film thickness under different loads；Servomotor carries on testing stand base Dynamic glass plate rotates, and corresponding experiment contact area rotating speed is 0mm/s to 1.5m/s, it is achieved glass plate different rotating speeds The measurement of lower thickness；Connect directly over coaxial-illuminating microscope and have 3CCD color camera, 3CCD color camera Captured in real time interference image, and interference image is transferred to equipped with the computer of image pick-up card showing or protecting Deposit.

The present invention is compared with the measuring method of other optical interference oil film thicknesses, special by a dichromatic interference image The G-R levying striped modulates Intensity Analysis, is accurately judged to the interference level at lubricating contact district minimum thickness, And then directly can calculate thickness h according to monochromatic multiple-beam interference principle, it is simple that it measures process, measures Efficiency is high, it is to avoid monochromatic light relies on the order of interference counting loss of accelerator picture record under high-speed working condition and asks Topic, gets the range of big 3 times than white light interference, can reach 4 μm；It is easy to measure different sliding speed and not It is distributed with the oil film thickness of contact area whole under load, for lubricating oil between Contact Pair in Study on Lubrication and engineering reality Film thickness measurement provides a kind of new method.

Accompanying drawing illustrates:

Fig. 1 is bi-coloured light film lubrication testing stand package assembly principle schematic used in the present invention, wherein wraps Include testing stand base 101, red and green color LASER Light Source 102, rotating ground glass 103, optical fiber 104, computer 105,3CCD color camera 106, coaxial-illuminating microscope 107, glass plate 108, steel ball 109, loading Lever 110, spring tension meter 111, ball torr 112 and servomotor 113.

Fig. 2 is present invention sensitive property of spectrum response curve of 3CCD color camera used when realizing, wherein 21 is the spectral response curve f of blue light_B(λ), 22 is the spectral response curve f of green glow_G(λ), 23 is HONGGUANG Spectral response curve f_R(λ)。

Fig. 3 is present invention spectral power distribution function of red and green color LASER Light Source used when realizing.

Fig. 4 is that the present invention calculates data base's thickness and normalization red-green glow strong R, G and relative modulation light when realizing The graph of a relation of strong G-R.

Fig. 5 be the bat ripple that the 0-4500nm thickness wedge gap that the present invention calculates when realizing produces terminate place in The red and green color optical interference picture of existing darkened features striped.

Fig. 6 is the static interference image of embodiment of the present invention 3CCD color camera shooting.

Fig. 7 is surveyed ball dish Hertz contact interference image with center as starting point by the embodiment of the present invention, along steel ball radius Increase the relative modulation light intensity G-R scattergram in direction.

Fig. 8 is ball dish Hertz contact measurement result of the present invention and classical Hertzian contact theory comparison diagram, wherein 71 For Hertzian contact theory curve, 72 record curve for the test of bi-coloured light interference technique.

Fig. 9 is the dynamic oil film interference image of embodiment of the present invention 3CCD color camera shooting.

Figure 10 is that the embodiment of the present invention adjusts the distance the nearest first group of darkened features striped in contact center along image slices The radius of element coordinate representation increases the G-R relative modulation Intensity Analysis figure in direction.

Figure 11 is the multiple-beam interference generation schematic diagram that multilayer film used by the present invention measures system.

Detailed description of the invention:

Below by embodiment and combine accompanying drawing the invention will be further described.

Embodiment:

The bi-coloured light that the present embodiment uses interferes the agent structure of film lubrication testing stand to include testing stand base 101, red and green color LASER Light Source 102, rotating ground glass 103, optical fiber 104, computer 105,3CCD Color camera 106, coaxial-illuminating microscope 107, glass plate 108, steel ball 109, loading lever 110, bullet Spring strain gauge 111, ball torr 112 and servomotor 113, on testing stand base 101 install be equipped with glass plate 108, Loading lever 110 and servomotor 113, glass plate 108 is transparent circular structure；Load the one of lever 110 It is equipped with ball torr 112 above end, is connected with spring tension meter 111 below the other end；It is fixed with steel in ball torr 112 Ball 109, the raceway between steel ball 109 and glass plate 108 adds 30ml lubricating oil to form lubricating oil film； Red and green color LASER Light Source 102 is placed on testing stand base 101, the front side of red and green color LASER Light Source 102 It is placed with rotating ground glass 103, between rotating ground glass 103 and coaxial-illuminating microscope 107, is provided with optical fiber 104, after the light that red and green color LASER Light Source 102 sends filters through rotating ground glass 103, through optical fiber 104 Import coaxial-illuminating microscope 107, the viewing area of final vertical directive coaxial-illuminating microscope 107；Pass through Spring tension meter 111 realizes the measurement of oil film thickness under different loads to loading lever 110 imposed load； Servomotor 113 drives the axle of glass plate 108 to rotate on testing stand base 101, and corresponding experiment contact area turns Speed is 0mm/s to 1.5m/s, it is achieved the measurement of thickness under glass plate different rotating speeds；Coaxial-illuminating microscope 107 Surface connects 3CCD color camera 106,3CCD color camera 106 captured in real time interference image, and Interference image is transferred to equipped with the computer 105 of image pick-up card showing or preserving.

The experimental situation temperature of the present embodiment is 20 ± 1 DEG C, and relative humidity is 50% ± 5%；Glass plate 108 is K9 glass plate, the surface of glass plate 108 adds chromium plating film, and reflectance is 20%, and roughness Ra is 4nm； A diameter of 25.4mm of steel ball 109, the sphere of steel ball 109 is the accurate polishing surface of high reflectance, surface Roughness Ra is less than 8nm；The centre wavelength of red and green color LASER Light Source 102 is respectively 653nm and 532nm； Composite lubricating film is air, and refractive index is 1.0；3CCD color camera 106 captures steel ball 109 and glass plate 108 Interference image between Contact Pair, is transferred to computer 105 through image card and shows and store, concrete measuring process Including:

S101: calculate and lubricate air film thickness between steel ball 109 and glass plate 108 from 1nm to 4500nm couple The red green RG relative intensity distribution of the red and green color interference of light tristimulus values answered, i.e. oil film interference system；Utilize face Form and aspect add principle and color reproduction equation, and sensitive property of spectrum shown in Fig. 2 is respectively f_R(λ)、f_G(λ)、 f_B(λ) color tristimulus values that 3CCD (RGB) color camera 106 obtains is

$C=\underset{\mathrm{\λ}}{\∫}\mathrm{kS}\left(\mathrm{\λ}\right)I_h\left(\mathrm{\λ}\right)f_C\left(\mathrm{\λ}\right)\mathrm{d\λ},$ C=R, G, B

Wherein, C represents that R, G, B tristimulus values, S (λ) are the spectrum energy of red and green color LASER Light Source 102 used Amount distribution function (as shown in Figure 3), k is adjustment factor, and the span of k is between 0 to 1, and purpose exists In making the equal normalization of tristimulus values, I_h(λ) it is the interference light intensity that on each wave band λ, thickness is corresponding when being h, because of many The high reflectance of tunic medium and steel ball surface causes multiple-beam interference, the interference light intensity of final glass interface according to $I={\left|{\stackrel{\‾}{E}}_0^{-}\right|}^2={|{\stackrel{\‾}{E}}_0^{-1}+{\stackrel{\‾}{E}}_0^{-2}+{\stackrel{\‾}{E}}_0^{-3}+{\stackrel{\‾}{E}}_0^{-4}+\·\·\·|}^2={\left|\underset{m=1}{\overset{\∞}{\mathrm{\Σ}}}{\stackrel{\‾}{E}}_0^{-m}\right|}^2$ Calculate, wherein(m=1,2 ...) represent reflection light Electricity vector, subscript 0 represents glass medium, onlyDirectly from chromium-glass interface reflection, other are anti- Penetrate light all through reflection and the projection of chromium-glass layers below；Thus on the basis of multiple-beam interference, it is considered to Red and green color optical source wavelength, bandwidth and the response of 3CCD color camera, generate the oil film thickness of complete set The color shades computational algorithm that bi-coloured light is interfered；4500nm is increased to from 0nm, by green glow along air thickness Normalization light intensity deducts the normalization light intensity of HONGGUANG and obtains double-colored difference light intensity G-R, with this draw out thickness with The corresponding variation relation curve chart of G, R, G-R relative light intensity, as shown in Figure 4；G-R curve is to thickness Change presents the feature of modulation, and in certain film thickness range, the size of the extreme point of this curve exists one with thickness One-to-one correspondence, the interference image of corresponding bi-coloured light is clapped boundary at each modulating wave and is presented black Feature striped, as shown in Figure 5；Centre wavelength for using is respectively the red green double of 653nm and 532nm Color LASER Light Source 102, the optical thickness that in result of calculation display G-R modulation light intensity curve, the bat of each ripple is corresponding is 1408nm, the bat of each ripple all comprises 10 extreme points, and adjacent ripple is clapped the most identical, to 4500nm The darkened features fringe position of bi-coloured light interference image in film thickness range, makes after calculating normalization red-green glow intensity values G-R modulates light intensity curve, take each ripple of curve clap upper 8th and the 9th extreme point light intensity value absolute value it Distinguish first three ripple with SUM as criterion to clap, it is contemplated that in model color calculation error and actual measurement application Image noise problem, have all the time SUM value between 1.0 to 1.8 for first wave clap, SUM value is 1.8 Then belonging to the second ripple between 2.8 to clap, SUM value is that the 3rd ripple is clapped between 2.5 to 3.2, and first three ripple Clap order of interference respectively (4,4), (8,8), (12,12) that the 8th extreme point correspondence monochrome HONGGUANG is interfered；

S102: loaded loading lever 110 by spring tension meter 111, keeps steel ball 109 and glass plate Load between 108 is 2N, and coaxial-illuminating microscope 107 is focused after understanding to image, colored with 3CCD Camera 106 shoots and preserves interference image such as Fig. 6, analyzes first group of darkened features that distance contact center is nearest The G-R that striped increases direction along radius modulates light intensity, as it is shown in fig. 7, calculate the 8th and the 9th simultaneously Extreme point light intensity value absolute value sum is 1.52, and the SUM value criterion contrast gone out with Theoretical Calculation, because 1.52 are situated between Between 1.0 and 1.8, therefore learn that this region belongs to first and claps wave band, and the 8th extreme point position The order of interference of coordinate correspondence HONGGUANG is (4,4)；Then along half radial direction contact area center position according to HONGGUANG Light intensity changes, and has 4 to interfere long point mutually to interfere cancellation point with 4, therefore draws the concrete interference at contact center Progression is (0,0), may thereby determine that streaky concrete progression in whole interference image, then utilizes Monochromatic light Relative light intensity principle is calculated concrete film thickness distribution as shown in Figure 8, and Fig. 8 shows proposed method Measurement result have, with classical Hertzian contact theory value of calculation, property of well coincideing；

S103: adding 30ml PB1300 lubricating oil on glass plate 108, the density of this lubricating oil is 896 kg·m^-3, when 20 DEG C, dynamic viscosity is 117Pa s, and refractive index is 1.502；Continue to add with spring tension meter 111 Carrying, making the load between steel ball 109 and glass plate 108 is 10N, regulates coaxial-illuminating microscope 107 focal length To image clear after, start servomotor 113, setting speed is 2.22mm/s；Use 3CCD color camera 106 shoot and preserve interference image as it is shown in figure 9, analyze first group of darkened features that distance contact center is nearest The G-R that striped increases direction along radius modulates light intensity, sees Figure 10, calculates the 8th extreme point A and the simultaneously 9 extreme point B light intensity value absolute value sums are 2.25, and its size is between 1.8 and 2.8, therefore learns this Region belongs to second count wave band, thus knows the order of interference of the 8th extreme point position coordinate correspondence HONGGUANG For (8,8), because of thickness consecutive variations, to center, contact area, the light intensity according to HONGGUANG changes, and has counted dry Relate to Xiang Changdian and interfere the number of cancellation point i.e. to can get the concrete interference level in center interference district, and then can be true Streaky concrete progression in fixed whole interference image, then utilizes monochromatic light Relative light intensity principle to be calculated The film thickness value of any Region Of Interest in image.

Normalization red-green glow strong R, G described in the present embodiment and the acquisition of red and green color relative difference light intensity G-R Journey specifically includes:

S201: store interference image by 3CCD color camera 106；

S202: obtain and store rotating speed and load to file；

S203: the HONGGUANG in acquisition image appointment region and green glow light intensity value are also saved in file；

S204: HONGGUANG and the maximum of green glow light intensity and minima in output specified region；

S205: utilize formula

$G=\frac{{2I}_G-(I_{G\max }+I_{G\min })}{I_{G\max }-I_{G\min }},R=\frac{{2I}_R-(I_{R\max }+I_{R\min })}{I_{R\max }-I_{R\min }}$ With

$G-R=\frac{{2I}_G-(I_{G\max }+I_{G\min })}{I_{G\max }-I_{G\min }}-\frac{{2I}_R-(I_{R\max }+I_{R\min })}{I_{R\max }-I_{R\min }}$

Calculate normalization red-green glow strong R, the G in described region and double-colored relative difference light intensity G-R.

In G-R of the present invention modulation light intensity curve, the determination methods of the 8th and the 9th extreme point is specifically wrapped Include: first obtain the G-R at interference image darkened features interference fringe and modulate the change of light intensity pixel coordinate Change；Then the light intensity absolute value all extreme points less than 0.5 on the extreme point of G-R modulation light intensity curve are found out, The position of the point that these G-R light intensity values are the least, i.e. 0 district, comprise and represent a ripple and clap the position terminated； Secondly, from 0th district to the direction that contact center position, i.e. Contact Pair gap and thickness are relatively reduced, near 0 The nearest approximately equalised one group of adjacent extreme point of order of magnitude in district is the 8th and the 9th extreme point, wherein G-R value less than 0 for the 8th extreme point, more than 0 for the 9th extreme point.

Calculating list of references " Guo Feng, the Cortex Phellodendri woods of the multiple-beam interference light intensity that the present embodiment relates to；Micro-nano profit The large range measuring system that synovial membrane is thick, tribology journal 2004, volume 17, the third phase, page 521；I.e. Guo F.and Wong P.L.,A wide range measuring system for thin lubricating film: From nano to micro thickness, Tribology Letters, 2004, Vol.17, No.3.521 ", such as Figure 11 Shown in, optics measuring of oil film system is the 4 layers of dielectric optical system being made up of glass, chromium, oil and steel, respectively Dielectric layer is labeled as q=0～3, at the boundary of q and q+1, all of luminous reflectance electric vector and light transmission electricity Vector synthesizes two classes by incident and the reflection direction of propagation, is denoted as respectivelyWithSubscript plus sige or minus sign represent The direction of propagation, subscript represents that light is propagated in medium number therein (as 0 is glass),It is that oil is demarcated with steel The electric vector that place propagates to steel,Represent the electric vector of incident illumination,Represent the electric vector of emergent light；Medium The refractive index of q is designated as

${\stackrel{\‾}{n}}_q=n_q-{\mathrm{ik}}_q,$ Q=0～3

Wherein n_qIt is real part refractive index, k_qBeing attenuation quotient, for optically transparent medium, attenuation quotient is zero；? The intersection of dielectric layer q and q+1, effective reflection coefficient is write

${\stackrel{\‾}{R}}_q=\frac{{\stackrel{\‾}{E}}_q^{-}}{{\stackrel{\‾}{E}}_q^{+}},$ Q=0～3

Reflection coefficientWithThere is following relation:

${\stackrel{\‾}{R}}_{q-1}=\frac{{\stackrel{\‾}{r}}_{q-1}+{\stackrel{\‾}{R}}_q\exp (-{i2\stackrel{\‾}{\mathrm{\δ}}\mathrm{}}_q)}{1+{\stackrel{\‾}{r}}_{q-1}{\stackrel{\‾}{R}}_q\exp (-{i2\stackrel{\‾}{\mathrm{\δ}}}_q)}$

WhereinQ is the thickness of dielectric layer q, and λ is the wavelength of incident illumination,It is Fei Nier Reflection coefficient, because not having transmission only reflection at steel ball surface, therefore hasCan obtain successively according to above formulaThe reflectivity of hierarchical system or interference strength are defined as reflected light radiation can be to incident radiation The ratio of energy, or the reflection light strength ratio to incident illumination, by formulaCalculate and obtain multi-beam interference Strong or reflectance, starts to oil film thickness d from 0nm₂Assignment successively, i.e. obtains thickness and multi-beam interference Strong relation.

The order of interference of any point in the interference image that the present embodiment relates to is defined as (δ, β), wherein n-th grade Between dark fringe and (n+1)th grade of dark fringe, the dark order of interference of point is δ=n, n-th grade of bright fringes and (n+1)th Between level bright fringes, the bright order of interference of point is β=n；If going out, with bi-coloured light checking interference, the interference that HONGGUANG is corresponding The order of interference (δ, β) of certain reference point in image, because of thickness consecutive variations, order of interference is interfered along with HONGGUANG Growth and decline be also consecutive variations, therefore can determine in interference image order of interference of other point.

The monochromatic light multiple-beam interference Relative light intensity principle that the present embodiment relates to measures thickness list of references " Wang Xue Cutting edge of a knife or a sword, Guo Feng, Yang Peiran；Nano/micron bullet stream oil film thickness measurement system, tribology journal 2006, the 26th Volume, the 2nd phase, page 150～154 ", in the interference of light, interference strength with thickness with λ/(2n) as cycle Change, λ is wavelength, and n is medium refraction index, and to arbitrary oil film thickness h, all unique corresponding order of interference is (β =0, δ=0) or the oil film thickness h of (β=0, δ=1)₀(being defined as 0 grade of oil film thickness at this), both have phase With interference strength, and its relation meets following formula

$h=h_0+\mathrm{\β}\frac{\mathrm{\λ}}{2n}$

In formula: h is oil film thickness, h₀Being 0 grade of oil film thickness, i.e. oil film thickness during β=0, λ is wavelength, n Being the refractive index of lubricating oil, β is the bright order of interference of point between n-th grade of bright fringes and (n+1)th grade of bright fringes； 0 grade of thickness h₀Can be calculated by multiple-beam interference light intensity with the relation curve of normalized interference strength.So Calculating thickness by multiple-beam interference is exactly the normalization light intensity extracting image, goes out correspondence according to increasing range lookup 0 grade of thickness, then class obtains final thickness plus the number of cycles thickness of β λ/2n；Wherein measure point to interfere The acquisition of level time β is crucial, measures monochromatic light, by gradually starting to increase Entrainment Velocity from 0 and increase film Thickness obtains, and needs whole process under cameras record, but oil film change at a high speed is it may happen that the loss of level time, Cause thickness mistake in computation；The present embodiment goes out any point in interference image by the feature fringe analysis of bi-coloured light Order of interference, and do not rely on historical record, thus avoid interference with level time counting loaded down with trivial details and be likely to occur Level time is lost.

The present embodiment is according to interference of light principle, when the idol that optical path difference Δ is incident illumination half-wavelength of two bundle coherent lights During several times, strengthen after two light wave superpositions, bright fringes occurs；When the optical path difference Δ of two bundle coherent lights is incident illumination half During the odd-multiple of wavelength, weaken after two light wave superpositions, dark fringe occurs；If optical path difference increases continuously from 0, just Light and dark interference fringe can be produced, the degree of light and shade light strong representation, it can be appreciated that fixing thickness pair Should unique light intensity value, but the fixing the most corresponding periodic multiple thickness of light intensity value, it is proposed that interference order Secondary concept is distinguish between；Membrane thickness measuring system reflects from steel ball 109 surface and glass plate 108 surface Two-beam, from a branch of incident illumination, meets between the coherent condition of light, and steel ball 109 and glass plate 108 Thickness consecutive variations, therefore can produce light and dark interference fringe.

The accounting equation of color reproduction described in the present embodiment sees " Yu Daoyin, Tan Hengying；China Machine Press 2006, page 80 "；Utilize " Red-Green-Blue " model and color reproduction equation, quick to spectrum Sense characteristic is respectively f_R(λ)、f_G(λ)、f_B(λ) color tristimulus values that camera sensor obtains is

$C=\underset{\mathrm{\λ}}{\∫}\mathrm{kS}\left(\mathrm{\λ}\right)I_h\left(\mathrm{\λ}\right)f_C\left(\mathrm{\λ}\right)\mathrm{d\λ},$ C=R, G, B

Wherein, C represents that R, G, B color tristimulus values, S (λ) are that the spectral energy of red and green color light source used divides Cloth function, k is normalization coefficient, the span of k between 0 to 1, I_h(λ) it is on each wave band λ Thickness is the interference light intensity of h height.

Color described in the present embodiment is added principle and sees " Yu Daoyin, Tan Hengying；China Machine Press 2006 Year, page 79 "；The RGB tristimulus values of secondary colour is each component color corresponding tristimulus values sum, then color F matching equation is expressed as F=R+G+B；Replacement rate according to Jim Glassman color mixture, if there being two face Color lights R 1, G1, after B1 and R2, G2, B2 are added mixing, then the tristimulus values of mixed light is

$\left\{\begin{array}{c}R=R_1+R_2\\ G=G_1+G_2\\ B=B_1+B_2\end{array}\right.$

The tristimulus values of secondary colour is each component color tristimulus values sum.

Described in the present embodiment, color computer reproducing method sees " Zhou Guangmei, Guo Feng, Li Hongsheng；Lubricating oil film is double The characteristic research of coloured light interferometer measuration system, Acta Optica 2012, volume 32, the 3rd phase, article is numbered 0312006 ", color reproduction uses " RGB " color system, is arranged a kind of mixed during mapping by trichromatic value Conjunction color value is pattern coloring, and form is as follows:

Blend color value=RGB (red value, green value, blue valve)

Here " red value ", " green value ", " blue valve " are integer, and span is 0～255, represent The intensity of each color in blend color.When computer color reappears, need by tristimulus values R, G, B carries out linear process, becomes the color code that can be accepted by computer.

Hertz contact deformation used by the present embodiment sees: Yang Peiran；Fluid lubrication numerical analysis, national defense industry goes out Version society 1998, page 49, in the contact area of hertz point cantact, two surfaces mutually compress, and gap is 0, Outside contact area, increasing centrally along radius x from contact, deformation post gap H is

$H=\frac{4W}{\mathrm{\π}{E}^{\′}}[\frac{\left|x\right|}{b}\sqrt{\frac{x^2}{b^2}-1}-\ln (\frac{\left|x\right|}{b}+\sqrt{\frac{x^2}{b^2}-1})]$

Wherein, E' is the equivalent elastic modulus on two surfaces, and b is contact area half-breadth, calculates according to the following formula

$\frac{1}{E^{\′}}=\frac{1}{2}(\frac{1-v_1^2}{E_1}+\frac{1-v_2^2}{E_2})$

$b=\sqrt{\frac{8\mathrm{WR}}{\mathrm{\π}{E}^{\′}}}$

Wherein, R is steel ball radius, v₁、v₂For the Poisson's ratio of upper and lower contact surface, E₁、E₂For connecing up and down Touch the elastic modelling quantity on surface, all can obtain by tabling look-up.

The obtaining step of interference image described in the present embodiment is as follows:

(1). open bi-coloured light film lubrication testing stand place room air conditioner, regulation temperature for for 20 ± 1 DEG C, phase To humidity 50% ± 5%, after temperature and humidity is constant, start experiment；

(2). open computer 105, red and green color LASER Light Source 102, servomotor 113 and 3CCD colour phase The power supply of machine 106；

(3). at 30 milliliters of lubricating oil of glass plate 108 surface smear, apply predetermined load loading on lever 101 Lotus, makes steel ball 109 contact with glass plate 108 surface, increases direction, steel ball from contact area centrally along steel ball radius Gap between 109 and glass plate 108 is being gradually increased, and when coherent light incidence, meets principle of interference, will produce Raw interference fringe；

(4). start the computer 105 equipped with 3CCD color camera 106 matching Image Acquisition Board, open image Acquisition software, clicks on real-time image acquisition, after allowing two-color laser pass rotating ground glass 103 filtering, through optical fiber 104 incide in coaxial-illuminating microscope 107, by coaxial-illuminating microscope 107 alignment with the ball dish contact area, regulation Focal length is clear to image；

(5). starting servomotor 113, servomotor 113 drives glass plate 108 to rotate, and regulates To the rotating speed of needs test, preserve the required image that gathers with image capture software, and analysis needs to measure thickness figure As the rgb light intensity values in region, calculate normalization relative light intensity value R, G and the relative modulation needing measured zone Light intensity difference G-R；

(6). to same loaded load, the rotating speed of regulation glass plate 108；Or the rotating speed of same glass plate 108, Regulation loaded load, all can capture interference image and analyze the G-R relative modulation light of required film thickness measured zone Strong difference.

Claims (3)

1. the method for a bi-coloured light interferometry oil film thickness, it is characterised in that use bi-coloured light to interfere Film lubrication testing stand realizes the measurement of oil film thickness, and its concrete measuring process includes:

(1) oil film thickness between steel ball and glass plate, is calculated corresponding red green from 1nm to 4500nm Bi-coloured light interferes the red green RG relative intensity distribution of tristimulus values, i.e. oil film interference system；Color is utilized to be added former Reason and color reproduction equation, be respectively f to sensitive property of spectrum_R(λ)、f_G(λ)、f_B(λ) 3CCD is color The color tristimulus values that form and aspect machine obtains is

$C=\underset{\mathrm{\λ}}{\∫}kS\left(\mathrm{\λ}\right)I_h\left(\mathrm{\λ}\right)f_C\left(\mathrm{\λ}\right)d\mathrm{\λ},C=R,G,B$

Wherein, C represents R (red), G (green), B (blue) tristimulus values, and S (λ) is red and green color light source used Spectral power distribution function, k is adjustment factor, and the span of k is between 0 to 1, it is therefore intended that make The equal normalization of tristimulus values, I_h(λ) it is that on each wave band λ, thickness is the interference light intensity at h, glass plate interface Interference light intensity I is according to formula

Calculate, whereinRepresent reflection light electricity to Amount, m=1,2 ..., subscript 0 represents glass medium,Directly reflected by glass plate interface, other Reflection light is all through reflection and the projection of glass plate layers below；Then increase along oil film thickness from 0nm To 4500nm, the normalization light intensity that the normalization light intensity of green glow deducts HONGGUANG obtains double-colored modulation light intensity G-R, And draw out thickness variation relation curve chart corresponding with G, R, G-R relative light intensity with this；G-R modulates light Strong curve presents the feature of modulating wave to the change of thickness, and the size of this Curve Maximization point exists 1 a pair with thickness The relation answered, corresponding bi-coloured light interference image is clapped boundary at each modulating wave and is presented darkened features bar Stricture of vagina；The centre wavelength used is respectively the red and green color LASER Light Source of 653nm and 532nm, result of calculation In display G-R modulation light intensity curve, each ripple claps corresponding optical thickness is 1408nm, and each ripple is clapped and all comprised 10 extreme points, adjacent ripple is clapped the most identical, to bi-coloured light in the 4500nm film thickness range calculated The darkened features fringe position of interference image is made G-R and is modulated light intensity curve after calculating normalization red-green glow intensity values After, take each ripple of curve and clap absolute value sum SUM of upper 8th and the 9th extreme point light intensity value as sentencing Clapping according to distinguishing first three ripple, find that SUM value is clapped for first wave between 1.0 to 1.8, SUM value is 1.8 Then belonging to the second ripple between 2.8 to clap, SUM value is that the 3rd ripple is clapped between 2.5 to 3.2, and wherein first three is individual Ripple claps order of interference respectively (4,4), (8,8), (12,12) that the 8th extreme point correspondence monochrome HONGGUANG is interfered；

(2), surveying record sliding speed is more than steel ball during 0mm/s and glass plate contact area lubricating oil film thickness The optical interference picture caused, the G-R modulation light intensity analyzing the nearest darkened features striped in distance contact center is bent Line, calculate simultaneously the 8th and the 9th extreme point light intensity value absolute value sum and with calculated SUM value Contrast affiliated ripple and clap section, and the order of interference of the 8th extreme point position correspondence HONGGUANG；Then with meter The thickness relative light intensity curve control of the 0～4500nm HONGGUANG obtained, show that the center under this sliding speed is done Relate to the concrete interference level in district, so that it is determined that streaky concrete progression in whole interference image, then utilize Principle of interference is calculated concrete film thickness distribution；Same procedure is utilized to record the steel ball of different sliding speed continuously The interference of light image caused with glass plate contact area lubricating film, thus the center obtained under different sliding speed connects Touch district's order of interference and film thickness distribution；

(3) under the conditions of, surveying record loads lever imposed load, steel ball and glass plate contact area lubricating film cause Interference image, measure draw the darkened features striped that center, distance contact area is nearest under this load G-R adjust Light intensity curve processed, utilizes the 8th simultaneously and the 9th extreme point light intensity value absolute value sum judges the 8th pole The order of interference of value point position correspondence HONGGUANG；Then with calculated 0～4500nm HONGGUANG thickness- Relative light intensity curve comparison draws the concrete interference level in the center interference district under this speed, so that it is determined that whole dry Relate to streaky concrete progression in image, then utilize principle of interference to be calculated concrete film thickness distribution, real The measurement of existing oil film thickness；

Described bi-coloured light interferes the agent structure of film lubrication testing stand to include testing stand base, red and green color laser Light source, rotating ground glass, optical fiber, computer, 3CCD color camera, coaxial-illuminating microscope, glass plate, Steel ball, load lever, spring tension meter, ball torr and servomotor, testing stand base is installed be equipped with glass plate, Loading lever and servomotor, glass plate is transparent circular structure；Load and be equipped with ball torr above one end of lever, It is connected with spring tension meter below the other end；Steel ball it is fixed with, on the raceway between steel ball and glass plate in ball torr Add lubricating oil and form lubricating oil film；Red and green color LASER Light Source is placed on testing stand base, and red and green color swashs The front side of radiant is placed with rotating ground glass, is provided with optical fiber between rotating ground glass and coaxial-illuminating microscope, After the light that red and green color LASER Light Source sends filters through rotating ground glass, import coaxial-illuminating through optical fiber micro- Mirror, the final vertical microscopical viewing area of directive coaxial-illuminating；Applied loading lever by spring tension meter Load realizes the measurement of oil film thickness under different loads；Servomotor drives glass plate on testing stand base Rotating, corresponding experiment contact area rotating speed is 0mm/s to 1.5m/s, it is achieved thickness under glass plate different rotating speeds Measure；Connect directly over coaxial-illuminating microscope and have 3CCD color camera, 3CCD color camera captured in real time Interference image, and interference image is transferred to equipped with the computer of image pick-up card showing or preserving.

The method of bi-coloured light interferometry oil film thickness the most according to claim 1, its feature exists Acquisition process in described double-colored modulation light intensity G-R specifically includes: first pass through the storage of 3CCD color camera dry Relate to image；Re-record rotating speed and/or load, then obtain interference image and specify HONGGUANG and the green glow light intensity in region Value also stores, and exports HONGGUANG and the maximum of green glow light intensity and minima respectively；Utilize formula

$G-R=\frac{2I_G-(I_{Gmax}+I_{Gmin})}{I_{Gmax}-I_{Gmin}}-\frac{2I_R-(I_{Rmax}+I_{Rmin})}{I_{Rmax}-I_{Rmin}}$

Calculate double-colored modulation light intensity G-R in described region.

The method of bi-coloured light interferometry oil film thickness the most according to claim 1, its feature exists In described G-R modulation light intensity curve, the determination methods of the 8th and the 9th extreme point specifically includes: first Obtain the G-R at interference image darkened features interference fringe and modulate the change of light intensity pixel coordinate；Then Find out the position of the light intensity absolute value all extreme points less than 0.5 on the extreme point of G-R modulation light intensity curve, i.e. 0th district, comprises and represents a ripple and clap the position terminated；Secondly, from 0th district to contact center position, i.e. contact Auxiliary air gap and the relatively reduced direction of thickness, the order of magnitude nearest near 0th district approximately equalised one group adjacent Extreme point is the 8th and the 9th extreme point, wherein G-R value less than 0 for the 8th extreme point, more than 0 It it is the 9th extreme point.