A solution concentration measuring device and method based on the principle of equal-thickness interference

Abstract

The present application relates to a kind of solution concentration measuring device based on equal-thickness interference principle, including optical guide rail, optical guide rail is equipped with sliding stage, laser, beam expander, polarizer are sequentially arranged on the optical guide rail of one side of sliding stage, optical guide rail is equipped with light screen on the other side of sliding stage, optical guide rail outside is equipped with iron stand, the optical guide rail of the vertical pole of iron stand is clamped spectroscopic device is placed above sliding stage, the vertical pole of iron stand is clamped digital microscope and is placed above spectroscopic device, digital microscope is connected with computer, laser, beam expander, polarizer, light screen are in the light path of same horizontal straight laser beam emitted by laser.The present application device experimental parameter is convenient and dynamic adjustable, applied computer visualization technology directly displays interference image on computer screen, so that equal-thickness interference phenomenon is more intuitive and clear, can be observed the obvious change of interference fringe in the process of adjusting split tip film.

Description

TECHNICAL FIELD

[0001] The present application relates to a device for measuring the concentration of a solution, in particular to a device for measuring the concentration of a solution based on the principle of equal-thickness interference. BACKGROUND

[0002] Liquid concentration is an important parameter for characterizing medium solutions, and plays a very important role in food, chemical industry, medicine, scientific research and other aspects, covering all aspects of daily life.

[0003] On the one hand, the measurement of liquid concentration is an important process. The current mainstream concentration detection methods include evaporation method, titration method, conductivity measurement, optical rotation measurement and light transmittance measurement. However, the above measurement methods have the problems of wasting a large amount of reagents, increasing experimental cost, inconvenient data acquisition and long time consumption. Although the conductivity measurement and optical rotation measurement have a short time consumption, they are often limited to a single type of measurable solution, and the chemical composition of the solution changes after the conductivity measurement, which makes it impossible to continue using the solution, and it is difficult to monitor the concentration of the chemical solution for storage.

[0004] On the other hand, equal-thickness interference and its application are important learning content for students majoring in science and engineering. However, the current mainstream equal-thickness interference experimental instruments have the problems of difficulty in observing interference phenomenon with naked eyes, complex data measurement process, poor applicability and low thinking inspiration to students. SUMMARY

[0005] The technical problem to be solved by the present application is to provide a device for measuring the concentration of a solution based on the principle of equal-thickness interference, which can measure the concentration of a transparent liquid without chemical interference based on the principle of split-beam thin film interference.

[0006] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0007] A device for measuring the concentration of a solution based on the principle of equal-thickness interference, comprising an optical guide rail, a sliding stage is arranged on the optical guide rail, a laser, a beam expander, and a polarizer are arranged in sequence on one side of the optical guide rail, a light screen is arranged on the other side of the optical guide rail, an iron stand is arranged outside the optical guide rail, a light splitting device is clamped on the vertical rod of the iron stand and arranged above the sliding stage, a digital microscope is clamped on the vertical rod of the iron stand and arranged above the light splitting device, the digital microscope is connected to a computer, and the laser, the beam expander, the polarizer and the light screen are arranged on the same horizontal straight line light path of the laser.

[0008] As a further scheme of the present application, the sliding object table comprises a rack, the bottom of the rack is in sliding connection with the optical rail, a slide groove is arranged in the rack, a ground glass plate is placed in the slide groove, one side of the ground glass plate is connected with a tablet clamp, the bottom of the other side of the ground glass plate is connected with a vertical micrometer rod, the rod head of the vertical micrometer rod is exposed from the upper surface of the ground glass plate, the middle part of the rack is connected with a horizontal micrometer rod, the rod head of the horizontal micrometer rod is in abutment with the side surface of the ground glass plate, a cover glass and a glass slide are stacked on the ground glass plate, and the glass slide is tightly pressed on the ground glass plate by the tablet clamp.

[0009] As a further scheme of the present application, the tablet clamp comprises a screw rod, a nut, a tablet and a spring, the screw rod is fixedly connected with the ground glass plate, the spring and the tablet are sleeved on the screw rod, and the top end of the screw rod is connected with the nut.

[0010] As a further scheme of the present application, the laser, the beam expander, the polarizer and the light screen are connected with the optical rail through the support.

[0011] As a further scheme of the present application, the digital microscope is connected with the vertical rod of the iron stand through the hoop support.

[0012] As a further scheme of the present application, the light splitting device is connected with the vertical rod of the iron stand through the universal adjusting positioning support.

[0013] As a further scheme of the present application, the light splitting device is a flat glass.

[0014] As a further scheme of the present application, the light splitting device comprises a light splitting prism and a prism support, and the prism support is clamped on the outside of the light splitting prism.

[0015] As a further scheme of the present application, the light screen is provided with a scale line.

[0016] A measurement method of a solution concentration measuring device based on the principle of equal-thickness interference, and the specific steps are as follows:

[0017] I. Instrument adjustment and determination of the included angle of the wedge

[0018] 1. Turn on the laser power supply and the computer image software;

[0019] 2. Fix the glass slide under the tablet clamp, and place the cover glass on the glass slide, one end of the cover glass is in contact with the left side of the glass slide, and the other end is placed above the rod head of the vertical micrometer rod;

[0020] 3. Adjust the laser light path collimation, the light splitting device, the focal length of the digital microscope, and the S-EYE software on the computer displays the air image taken by the digital microscope as the equal-thickness interference image of the wedge film;

[0021] 4. Adjust the vertical micrometer, make the cover glass and the slide parallel, record the scale value H1 of the vertical micrometer at this time, and then adjust the vertical micrometer to make the cover glass contact the micrometer with one end lifted by 0.1-0.3mm, leaving a gap for dropping liquid;

[0022] 5. Move the cover glass away, drop a drop of pure water on the slide, and then cover the cover glass, keeping one end in contact with the left side of the slide and the other end placed on the head of the vertical micrometer, at this time, the computer screen appears the split tip film interference fringes of water, adjust the vertical micrometer to make the fringes clear, and the number of fringes in the computer screen reaches 10-15, record the scale value H2 of the vertical micrometer at this time, and the split tip film angle at this time is:

[0023] d is the vertical distance from the split tip film angle tip to the contact point of the vertical micrometer and the cover glass;

[0024] II. Fringe spacing and concentration measurement

[0025] 1. Use the water-absorbing paper to wipe the liquid on the slide and the cover glass, drop the solution to be measured on the slide, cover the cover glass, keep one end of the cover glass in contact with the left side of the slide, and the other end placed on the head of the vertical micrometer;

[0026] 2. Record the scale value L1 of the horizontal micrometer;

[0027] 3. Operate the computer to draw two standard lines of cross on the image, parallel and perpendicular to the fringes, and the intersection is at the position of the dark fringe;

[0028] 4. Slowly rotate the horizontal micrometer, so that N fringes pass through the intersection on the image, N is 50-100, and then record the scale value L2 of the horizontal micrometer, and calculate the fringe spacing l=(L1-L2) / N;

[0029] 5. Calculate the solution concentration according to the formula,

[0030] In the formula,

[0031] c is the solution concentration;

[0032] λ is the wavelength of the laser beam;

[0033] θ is the split tip film angle;

[0034] l is the fringe spacing;

[0035] a and b are constants.

[0036] Compared with the prior art, the present application has the beneficial effects that:

[0037] 1. The device of the present application is convenient to obtain experimental parameters and dynamically adjustable, the computer visualization technology is applied to directly display the interference image on the computer screen, the equal-thickness interference phenomenon is more intuitive and clear, the obvious change of the interference fringes can be observed in the process of adjusting the wedge-shaped film, which helps students better understand the nature of the equal-thickness interference, and at the same time, more fun is obtained in the experiment, and has great application prospect.

[0038] 2. The present application measures the refractive index of the solution by the wedge interference method, substitutes the refractive index into the empirical formula to obtain the solution concentration, has novel design, simple structure and convenient operation, and effectively solves the problems of more liquid volume and longer time in the traditional concentration measurement method, and solution chemical pollution.

[0039] 3. The device of the present application has simple design and is convenient to operate and measure and understand, the optical method used has very little liquid volume, waste is effectively avoided, it can be applied to the measurement of various medium solutions, and will not cause chemical interference to most substances, in addition, the carrier glass sheet of the to-be-measured solution has strong corrosion resistance, and can also be applied to the concentration measurement of various acid, alkali, strong oxidizing agent and other corrosive liquids.

[0040] 4. The to-be-measured solution forms a thin film wedge between the glass sheets, the laser emits laser after expansion by the beam expander, interference occurs at the thin film wedge, the interference fringes are observed by the digital microscope, the pitch between the fringes is measured by combining the screw micrometer rod and the computer image recognition technology, and then the solution concentration is obtained according to the refractive index formula and the empirical formula of the material concentration, and by substituting the pitch and the known film wedge angle. This makes the experimental process simple and convenient, and the phenomenon is obvious. As a measuring device, it is simple to operate and the result is reliable; as a teaching instrument, the phenomenon is intuitive and the change is lively, which can greatly enhance the students' understanding of optical knowledge and improve the experimental fun. BRIEF DESCRIPTION OF DRAWINGS

[0041] Figure 1 It is a structural schematic view of the present application.

[0042] Figure 2 It is a top view of the present application.

[0043] Figure 3 It is a top view of the sliding stage.

[0044] Figure 4 It is a side view of the sliding stage.

[0045] Figure 5 It is a structural schematic view of the tablet pressing clamp.

[0046] Figure 6 It is an elevation view of the light splitting prism.

[0047] Figure 7 It is a top view of the light splitting prism.

[0048] Figure 8 Figure 1 is a schematic diagram of the optical path of the light splitting device.

[0049] Figure 9 Figure 2 is a schematic diagram of the interference fringe principle of the present application.

[0050] In the figure: optical rail 1, laser 2, beam expander 3, polarizer 4, iron stand 5, light screen 6, sliding stage 7, digital microscope 8, light splitting device 9, computer 10, support 11, clamp support 12, universal positioning support 13;

[0051] Storage rack 71, chute 72, ground glass plate 73, tablet clamp 74, vertical micrometer rod 75, horizontal micrometer rod 76, glass slide 77, cover glass 78, light splitting prism 91, prism holder 92. DETAILED DESCRIPTION

[0052] In the description of the present application, it is to be understood that the terms "first", "second", etc. are used only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined with "first", "second", etc. can explicitly or implicitly include one or more of the features. In the description of the present application, unless otherwise specified, the meaning of "a plurality of" is two or more.

[0053] In the description of the present application, it is to be understood that, unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connection" should be understood in a broad sense, for example, it can be fixed connection, or detachable connection, or integrally connected; it can be mechanical connection, or electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, or the communication inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0054] As Figures 1-6 A solution concentration measuring device based on the principle of equal thickness interference, comprising an optical rail 1, a sliding stage 7 is arranged on the optical rail 1, a laser 2, a beam expander 3 and a polarizer 4 are arranged in sequence on one side of the optical rail 1 of the sliding stage 7, a light screen 6 is arranged on the other side of the optical rail 1 of the sliding stage 7, an iron stand 5 is arranged outside the optical rail 1, a light splitting device 9 is clamped on the vertical rod of the iron stand 5 and placed above the sliding stage 7, a digital microscope 8 is clamped on the vertical rod of the iron stand 5 and placed above the light splitting device 9, the digital microscope 8 is connected with a computer 10, and the laser 2, the beam expander 3, the polarizer 4 and the light screen 6 are on the optical path of the same horizontal linear laser beam emitted by the laser 2.

[0055] The sliding carrier platform 7 comprises a rack 71, the bottom of which is in sliding connection with the optical guide rail 1, a sliding groove 72 is arranged in the rack 71, a frosted glass plate 73 is arranged in the sliding groove 72, a tablet clamp 74 is connected to one side of the frosted glass plate 73, the bottom of the other side of the frosted glass plate 73 is connected with a vertical micrometer rod 75, the rod head of the vertical micrometer rod 75 can be exposed from the frosted glass plate 73, a horizontal micrometer rod 76 is connected to the middle part of the rack 71, the rod head of the horizontal micrometer rod 76 is in abutment with the side of the frosted glass plate 73, the rotating horizontal micrometer rod 76 can push the frosted glass plate 73 to displace in the sliding groove 72, a cover glass 78 and a glass slide 77 are stacked on the frosted glass plate 73, the glass slide 77 is tightly pressed on the frosted glass plate 73 by the tablet clamp 74, one end of the cover glass 78 is placed on the rod head of the vertical micrometer rod 75 exposed, and the height of the vertical micrometer rod 75 can be adjusted to adjust the size of the included angle between the cover glass 78 and the glass slide 77.

[0056] The tablet clamp 74 comprises a screw rod 741, a nut 742, a tablet 743 and a spring 744, the screw rod 741 is fixedly connected with the frosted glass plate 73, the spring 744 and the tablet 743 are sleeved on the screw rod 741, and the top end of the screw rod 741 is connected with the nut 742.

[0057] The laser 2, the beam expander 3, the polarizer 4 and the light screen 6 are connected with the optical guide rail 1 through the support 11.

[0058] The digital microscope 8 is connected with the vertical rod of the iron stand 5 through the hoop support 12.

[0059] The light splitting device 9 is connected with the vertical rod of the iron stand 5 through the universal adjusting positioning support 13.

[0060] The light splitting device 9 is a flat glass.

[0061] The light splitting device 9 comprises a light splitting prism 91 and a prism holder 92, and the prism holder 92 is clamped outside the light splitting prism 91.

[0062] The light screen 6 is provided with a scale line.

[0063] The working process of the above device is as follows:

[0064] A drop of the solution to be measured is added on the glass slide, the cover glass 78 is orthogonally covered, and the solution to be measured forms a split tip film. One end of the cover glass 78 is placed on the rod head of the vertical micrometer rod 75 exposed, so that an included angle is formed between the cover glass 78 and the glass slide 77, that is, the split tip film angle.

[0065] The light splitting device 9 is adjusted to be directly above the split tip film, the light splitting device 9 forms an included angle with the horizontal plane, and is located on the light path of the laser beam emitted by the laser 2. The digital microscope 8 is adjusted to be directly above the light splitting device 9.

[0066] The laser 2 emits laser beam, the beam expander 3 is used to expand the laser beam diameter, increase the light range on the wedge film, the polarizer 4 uses the laser beam polarization characteristics to adjust the light intensity to avoid the digital microscope damage, the light screen 6 can slide on the optical rail 1, the light screen 6 has scale lines, whether the expanded laser is parallel can be checked.

[0067] The horizontal straight light emitted by the laser 2 is reflected to the wedge film of the solution to be measured on the sliding stage 7 as the interference medium by the light splitting device 9, and the interference light reflected by the wedge film transmits through the flat glass 9 and is photographed by the digital microscope 8.

[0068] The above device measurement method, the specific operation steps are:

[0069] I. Instrument adjustment and determination of wedge angle

[0070] 1. Turn on the laser power supply and the computer image software;

[0071] 2. Place the slide under the slide clamp and fix it, place the cover glass on the slide, one end contacts the left side of the slide, and the other end is placed above the head of the vertical micrometer rod;

[0072] 3. Adjust the laser light path collimation, light splitting device, digital microscope focal length, and the S-EYE software on the computer displays the air as the wedge film equal thickness interference image photographed by the digital microscope;

[0073] 4. Adjust the vertical micrometer rod so that the cover glass and the slide are parallel, record the scale value H1 of the vertical micrometer rod at this time, and then adjust the vertical micrometer rod so that the cover glass contacts the micrometer rod and the one end is lifted by 0.1-0.3mm;

[0074] 5. Move the cover glass, add a drop of pure water on the slide, and then cover the cover glass, keep one end in contact with the left side of the slide, and the other end is placed on the head of the vertical micrometer rod, at this time the computer screen appears the wedge film interference fringes of water, continue to lift the vertical micrometer rod to make the fringes clear, the number of fringes in the computer screen reaches 10-15, record the scale value H2 of the vertical micrometer rod at this time, the wedge film angle at this time is:

[0075] d is the vertical distance from the tip of the wedge film angle to the contact point of the vertical micrometer rod and the cover glass;

[0076] II. Fringe spacing and concentration measurement

[0077] 1. Wipe the liquid off the slide and coverslip with absorbent paper, drop the solution to be tested onto the slide, cover with the coverslip, with one end of the coverslip in contact with the left side of the slide and the other end placed on the head of the vertical micrometer rod;

[0078] 2. Record the scale value L1 of the horizontal micrometer rod;

[0079] 3. Using a computer, draw two standard cross lines on the image, one parallel and one perpendicular to the stripes, with the intersection point at the position of the dark stripe;

[0080] 4. Slowly rotate the horizontal micrometer rod so that N stripes pass through the intersection point on the image. N is 50 to 100 stripes. Then record the scale value L2 of the horizontal micrometer rod and calculate the stripe spacing as l = (L1 - L2) / N.

[0081] 5. Calculate the solution concentration using the formula.

[0082] The calculation formula can be edited in an Excel spreadsheet in advance. When measuring, you only need to enter the stripe spacing value to directly obtain the liquid concentration.

[0083] This process does not involve programming; it only requires mastering the basic applications of Excel to analyze measurement results. The operation is relatively simple and easy to learn and use.

[0084] The formula for solution concentration is derived as follows:

[0085] 1. The generation of stripes and the calculation of stripe spacing

[0086] The coherent beams of two overlapping interference beams satisfy the following optical path difference Δ:

[0087] Bright fringes are produced when Δ = mλ.

[0088] Dark lines appear from time to time

[0089] In thin-film interference, When light is incident perpendicularly, γ = 0. At this point, equal-thickness interference of the thin film occurs.

[0090] like Figures 7-8 As shown: When a beam of light is incident perpendicularly on the wedge film, the reflected light from the upper and lower surfaces of the wedge is coherent, and the optical path difference is... By combining the thin film equal-thickness interference condition and the optical path difference expression at positions with wedge thicknesses h1 and h2, we can obtain:

[0091]

[0092]

[0093] Subtracting the two equations, we get:

[0094]

[0095] The stripe interval:

[0096]

[0097] 2. Conversion relationship between stripe interval and refractive index, concentration

[0098] According to the above formula, the refractive index of the wedge-shaped medium is:

[0099]

[0100] The concentration and refractive index of the solution have a linear function relationship:

[0101] c = an + b —— ⑥

[0102] That is:

[0103]

[0104] In the formula:

[0105] m is the interference order, m = 0, 1, 2, 3, …;

[0106] is the optical path difference corresponding to h2 and h1;

[0107] h1, h2 are the wedge-shaped film thicknesses corresponding to the positions of adjacent interference orders;

[0108] Δh is the difference between h1 and h2;

[0109] λ is the wavelength of the laser beam;

[0110] θ is the wedge angle;

[0111] l is the stripe interval;

[0112] n is the refractive index of the wedge-shaped film medium;

[0113] c is the solution concentration;

[0114] a, b are constants, see Table 1.

[0115] Table 1:

[0116] Sodium chloride Sucrose alcohol (c < 50%) Alcohol (50% < c < 80%) a 532.13 547.21 2054.4 2771.7 b -709.21 -726.84 -2745.1 -3711.4

[0117] In order to make the purpose, technical scheme and technical effect of the present application clearer, the technical scheme in the embodiments of the present application will be described clearly and completely. However, the following described embodiments are only some of the embodiments of the present application, but not all the embodiments. In combination with the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor belong to the protection scope of the present application.

[0118] Embodiment 1

[0119] A solution concentration measuring device based on the principle of equal-thickness interference comprises an optical rail 1, a sliding stage 7 is arranged on the optical rail 1, a laser 2, a beam expander 3 and a polarizer 4 are arranged on the optical rail 1 at one side of the sliding stage 7 in sequence, a light screen 6 is arranged on the optical rail 1 at the other side of the sliding stage 7, an iron stand 5 is arranged outside the optical rail 1, and a flat glass is connected with the vertical rod of the iron stand 5 through a universal adjusting positioning support 13. The flat glass is bonded with the universal adjusting positioning support 13 by glue, and the angle between the flat glass and the horizontal plane is adjusted to be 45°. A digital microscope 8 is arranged above the flat glass and is connected with the vertical rod of the iron stand 5 through a hoop support 12.

[0120] The digital microscope 8 is connected with a computer 10, and the laser 2, the beam expander 3, the polarizer 4 and the light screen 6 are on the light path of the same horizontal straight laser beam emitted by the laser 2. The laser 2, the beam expander 3, the polarizer 4 and the light screen 6 are connected with the optical rail 1 through a support 11. The light screen 6 is provided with a scale line.

[0121] The sliding stage 7 comprises a storage rack 71, the bottom of the storage rack 71 is slidably connected with the optical rail 1, a sliding groove 72 is arranged in the storage rack 71, a ground glass plate 73 is placed in the sliding groove 72, a tablet clamp 74 is connected with one side of the ground glass plate 73, a vertical micrometer rod 75 is connected with the bottom of the other side of the ground glass plate 73, the rod head of the vertical micrometer rod 75 can be exposed from the upper surface of the ground glass plate 73, a horizontal micrometer rod 76 is connected with the middle part of the storage rack 71, the rod head of the horizontal micrometer rod 76 abuts against the side surface of the ground glass plate 73, and rotating the horizontal screw micrometer rod 76 can push the ground glass plate 73 to displace in the sliding groove 72. A cover glass 78 and a glass slide 77 are stacked on the ground glass plate 73, and the glass slide 77 is tightly pressed on the ground glass plate 73 by the tablet clamp 74. One end of the cover glass 78 is placed on the rod head of the vertical micrometer rod 75 exposed, and the height of the vertical micrometer rod 75 can be adjusted to adjust the size of the included angle between the cover glass 78 and the glass slide 77.

[0122] The tablet clamp 74 comprises a screw rod 741, a nut 742, a tablet 743 and a spring 744, the screw rod 741 is fixedly connected with the ground glass plate 73, the spring 744 and the tablet 743 are sleeved on the screw rod 741, and the top end of the screw rod 741 is connected with the nut 742.

[0123] Embodiment 2

[0124] A solution concentration measuring device based on the principle of equal thickness interference, comprising an optical guide rail 1, a sliding stage 7 is arranged on the optical guide rail 1, a laser 2, a beam expander 3 and a polarizer 4 are arranged on the optical guide rail 1 at one side of the sliding stage 7, a light screen 6 is arranged on the optical guide rail 1 at the other side of the sliding stage 7, an iron stand 5 is arranged outside the optical guide rail 1, a light splitting device 9 is clamped on the iron stand 5, the light splitting device 9 comprises a light splitting prism 91 and a prism holder 92, the prism holder 92 is clamped outside the light splitting prism 91.

[0125] A digital microscope 8 is arranged above the light splitting device 9, and the digital microscope 8 is connected with the vertical rod of the iron stand 5 through a hoop support 12.

[0126] The digital microscope 8 is connected with a computer 10, the laser 2, the beam expander 3, the polarizer 4 and the light screen 6 are arranged on the light path of the same horizontal straight laser beam emitted by the laser 2, and the laser 2, the beam expander 3, the polarizer 4 and the light screen 6 are connected with the optical guide rail 1 through a support 11.

[0127] The sliding stage 7 comprises a placing rack 71, the bottom of the placing rack 71 is in sliding connection with the optical guide rail 1, a sliding groove 72 is arranged in the placing rack 71, a ground glass plate 73 is arranged in the sliding groove 72, a pressing clamp 74 is connected with one side of the ground glass plate 73, a vertical micrometer rod 75 is connected with the bottom of the other side of the ground glass plate 73, the rod head of the vertical micrometer rod 75 can be exposed from the upper surface of the ground glass plate 73, a horizontal micrometer rod 76 is connected with the middle part of the placing rack 71, the rod head of the horizontal micrometer rod 76 is in abutment with the side surface of the ground glass plate 73, the rotation of the horizontal screw micrometer rod 76 can drive the ground glass plate 73 to displace in the sliding groove 72, a cover glass 78 and a glass slide 77 are stacked on the ground glass plate 73, and the glass slide 77 is tightly pressed on the ground glass plate 73 by the pressing clamp 74.

[0128] The pressing clamp 74 comprises a screw rod 741, a nut 742, a pressing piece 743 and a spring 744, the screw rod 741 is fixedly connected with the ground glass plate 73, the spring 744 and the pressing piece 743 are sleeved on the screw rod 741, and the top end of the screw rod 741 is connected with the nut 742.

[0129] Taking a sodium chloride solution with a mass fraction of 15% as an example, the device in Example 2 is used for measurement, and the light wave wavelength of the laser beam is 650 nm.

[0130] 1. The instrument is adjusted well, and the included angle of the cleaved tip is determined well.

[0131] 2. Wipe the pure water on the slide and cover glass with the absorbent paper, drop the sodium chloride solution on the slide, cover the cover glass, one end of the cover glass contacts the left side of the slide, and the other end contacts the vertical micrometer rod.

[0132] 3. Record the scale value of the horizontal micrometer rod at this time L1=12.000 mm.

[0133] 4. Operate the computer to draw two standard lines of cross on the image parallel and perpendicular to the stripes, and the intersection is in the middle position of the dark stripes.

[0134] 5. Slowly rotate the horizontal micrometer rod, so that 50 stripes pass through the intersection on the image, and then record the scale value of the horizontal micrometer rod L2=7.916 mm, and calculate the stripe spacing l=(L1-L2) / N=(12.000-7.916) / 50.

[0135] 6. Calculate the concentration of the solution according to the formula, Substitute the data, and take a, b values from Table 1.

[0136]

[0137] Repeat the above method 5 times, and the experimental data of the concentration of the sodium chloride solution are shown in Table 2.

[0138] The calculation formula can be edited in advance in the excel table, and the liquid concentration can be directly obtained by only inputting the stripe spacing value during measurement.

[0139] Take the measurement of the sucrose solution with a mass fraction of 20% as an example: the wavelength of the laser beam is 650 nm;

[0140] 1. Adjust the instrument; the included angle of the wedge is determined;

[0141] 2. Wipe the pure water on the slide and cover glass with the absorbent paper, drop the sodium chloride solution on the slide, cover the cover glass, one end of the cover glass contacts the left side of the slide, and the other end contacts the vertical micrometer rod.

[0142] 3. Record the scale value of the horizontal micrometer rod at this time L1=12.000 mm.

[0143] 4. Operate the computer to draw two standard lines of cross on the image parallel and perpendicular to the stripes, and the intersection is in the middle position of the dark stripes.

[0144] 5. Slowly rotate the horizontal micrometer rod, so that 50 stripes pass through the intersection on the image, and then record the scale value of the horizontal micrometer rod L2=7.927 mm, and calculate the stripe spacing l=(L1-L2) / N=(12.000-7.927) / 50.

[0145] 6. Calculate the concentration of the solution according to the formula, Substitute the data, take a, b value according to table 1.

[0146]

[0147] Repeat the above method 5 times, the concentration of sucrose solution experimental data are shown in table 2.

[0148] The formula can be edited in advance in excel table, and the liquid concentration can be directly obtained by inputting the stripe spacing value during measurement.

[0149] Experimental data:

[0150]

[0151]

[0152] Although the embodiments of the present application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made thereto without departing from the principles and spirit of the application, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for measuring solution concentration using a device based on the principle of equal thickness interference, characterized in that, The device includes an optical guide rail with a sliding stage. A laser, a beam expander, and a polarizer are sequentially arranged on the optical guide rail on one side of the sliding stage. A screen is arranged on the optical guide rail on the other side of the sliding stage. An iron frame is provided outside the optical guide rail. A beam splitter is held on the upright of the iron frame and placed above the sliding stage. A digital microscope is held on the upright of the iron frame and placed above the beam splitter. The digital microscope is connected to a computer. The laser, beam expander, polarizer, and screen are all located on the optical path of the same horizontal straight laser beam emitted by the laser. The sliding stage includes a shelf, the bottom of which is slidably connected to an optical guide rail. The shelf has a groove in which a frosted glass plate is placed. One side of the frosted glass plate is connected to a pressing clamp, and the bottom of the other side is connected to a vertical micrometer rod. The head of the vertical micrometer rod protrudes from the top of the frosted glass plate. A horizontal micrometer rod is connected to the middle of the shelf, and the head of the horizontal micrometer rod abuts against the side of the frosted glass plate. A glass slide and a cover glass are stacked on the frosted glass plate, and the glass slide is pressed tightly onto the frosted glass plate by the pressing clamp. The aforementioned pressure plate clamp includes a screw, a nut, a pressure plate, and a spring. The screw is fixedly connected to the frosted glass plate, and the spring and pressure plate are sleeved on the screw. The top of the screw is connected to the nut. The laser, beam expander, polarizer, and screen are all connected to the optical rail via a bracket; The digital microscope is connected to the uprights of the iron stand via a clamp bracket; The aforementioned beam splitting device is connected to the uprights of the iron frame via a universal adjustable positioning bracket; The aforementioned beam splitter is a flat glass plate; The beam splitting device includes a beam splitting prism and a prism frame, with the prism frame clamped on the outside of the beam splitting prism; The screen is equipped with scale lines; The measurement method and specific steps are as follows: I. Instrument Adjustment and Determination of the Wedge Angle 1) Turn on the laser power and the computer imaging software; 2) Place the glass slide under the slide clamp to fix it, place the coverslip on the glass slide, with one end in contact with the left side of the glass slide and the other end above the head of the vertical micrometer rod; 3) Adjust the laser beam collimation, beam splitting device, and digital microscope focal length. Display the equal-thickness interference image of air as a wedge film taken by the digital microscope using S-EYE software on the computer. 4) Adjust the vertical micrometer rod to make the coverslip and the slide parallel, and record the scale value H1 of the vertical micrometer rod at this time. Then adjust the vertical micrometer rod to raise the end of the coverslip that contacts the micrometer rod by 0.1 to 0.3 mm, leaving a gap for the liquid to be added. 5) Remove the coverslip, add a drop of pure water to the slide, and then replace the coverslip, keeping one end in contact with the left side of the slide and the other end placed on the tip of the vertical micrometer. At this point, water wedge-shaped thin-film interference fringes will appear on the computer screen. Adjust the vertical micrometer until the fringes are clear, reaching 10-15 fringes on the computer screen. Record the scale value H2 of the vertical micrometer at this point. The wedge-shaped thin-film angle at this time is: d is the vertical distance from the apex of the wedge-shaped thin film angle to the contact point between the vertical micrometer rod and the coverslip; II. Stripe Spacing and Concentration Measurement 1) Wipe the liquid off the slide and coverslip with absorbent paper, drop the solution to be tested onto the slide, cover with the coverslip, with one end of the coverslip in contact with the left side of the slide and the other end placed on the head of the vertical micrometer rod; 2) Record the scale value L1 of the horizontal micrometer rod; 3) Using the computer, draw two standard cross lines on the image, one parallel and one perpendicular to the stripes, with the intersection point at the position of the dark stripe; 4) Slowly rotate the horizontal micrometer rod until N fringes pass through the intersection point on the image. N is 50-100 fringes. Record the scale value L2 of the horizontal micrometer rod and calculate the fringe spacing. ; 5) Calculate the solution concentration using the formula. In the formula: c is the solution concentration; λ is the wavelength of the laser beam; θ is the included angle of the wedge-shaped films; l represents the stripe spacing; a and b are constants.

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