Device for accurately measuring thickness of transparent film

Abstract

The utility model relates to the technical field of film thickness measurement, in particular to a device for accurately measuring the thickness of a transparent film, which comprises a spectrum system and a spectrum detection circuit, the spectrum system is composed of a light source, two convex lenses, two adjustable slits, a blazed grating and other optical components, the spectrum detection circuit is composed of a photoelectric induction module, a voltage amplifier, a sliding potentiometer, a universal circuit board and other electronic components, compared with the prior art, the spectrum detection device has the advantages of being scientific and reasonable in design, easy to manufacture, low in cost, easy to operate and high in measurement accuracy, and most importantly, the surface of a measured material is not damaged in the measurement process; moreover, the device can be used for actually measuring the thickness of the transparent film in daily production, can also be applied to the field of teaching experiments, and has a prospect of large-scale popularization and application.

Description

TECHNICAL FIELD

[0001] The utility model relates to thin film thickness measurement technical field, concretely is a kind of device for accurately measuring the thickness of transparent film. BACKGROUND

[0002] Measuring thin film thickness is crucial in industrial production and scientific research. Currently, contact measurement is commonly used, mainly using high-precision mechanical film thickness testers to measure the thickness of thin film materials. However, this measurement method has the following obvious shortcomings: first, the working principle of mechanical film thickness testers determines that the tester must physically contact the surface of the measured material during the test to accurately measure the material thickness. However, physical contact will inevitably cause some damage to the surface of the measured material, especially for soft and easily scratched thin film materials such as optical thin films. Long-term use will accumulate this damage into significant wear, affecting the performance and lifespan of the material. Second, high-precision mechanical film thickness testers require professional operation and maintenance, which requires a high level of technical skill from the operator. In addition to proper operation of the instrument and correct parameter setting, the operator must also correctly analyze and process the measurement results. However, in actual operation, there are often cases where the operator's technical level is not sufficient or the operation is not reasonable, ultimately leading to large measurement result errors or even damage to the instrument. Third, this type of tester is expensive and can only be used in professional institutions. Since the tester is a sealed and complete machine, the entire testing process cannot be displayed for the user to view, making it difficult to interact with the user, and thus it cannot be applied in the teaching field. SUMMARY

[0003] To address the above issues, the utility model provides a device for accurately measuring the thickness of transparent film. The principle is based on the cosine function relationship between transmittance and light wave frequency caused by multi-beam interference of thin film. By measuring the transmission spectrum of the measured transparent film, the thickness of the transparent film is calculated based on the periodic fluctuation of transmittance. The entire measurement process does not require physical contact with the surface of the measured material, thus ensuring the performance and lifespan of the measured material. The device is easy to operate and requires a lower level of technical skill from the operator, reducing human interference factors and significantly improving measurement accuracy. During measurement, the change process of the light beam can be completely displayed, making the students' perception of optical phenomena such as interference and diffraction more intuitive and interactive with the students. Therefore, it can be applied in the teaching field, effectively solving the above problems.

[0004] The utility model employs the technical scheme of:

[0005] The application discloses a device for accurately measuring the thickness of a transparent film, which comprises a spectrum system and a spectrum detection circuit, wherein the spectrum system comprises a light source (1), the light source (1) is horizontally arranged, and a first convex lens (2), a first adjustable slit (3), a second convex lens (5), a dry plate holder (6) and a blazed grating (7) are vertically arranged in sequence in the horizontal light emitting direction of the light source (1), the center point of the light source (1), the optical center of the first convex lens (2), the diaphragm center point of the first adjustable slit (3), the optical center of the second convex lens (5) and the center point of the blazed grating (7) are located on the same horizontal line, a ground glass sheet (4) is pasted on the diaphragm on the light emitting side of the first adjustable slit (3), the distance between the first convex lens (2) and the first adjustable slit (3) is 5 cm, the distance between the first adjustable slit (3) and the second convex lens (5) is 3.5 cm, a third convex lens (8) is arranged in the vertical direction of the first-order diffraction light of the blazed grating (7), a second adjustable slit (9) is arranged in parallel with the third convex lens (8), the diaphragm (14) center point of the second adjustable slit (9), the optical center of the third convex lens (8) and the center point of the blazed grating (7) are located on the same straight line, the straight line distance between the center point of the blazed grating (7) and the optical center of the third convex lens (8) is 9-10 cm, the distance between the optical center of the third convex lens (8) and the diaphragm (14) center point of the second adjustable slit (9) is 17.5 cm, a universal circuit board (10) is further arranged in parallel on the back of the second adjustable slit (9), the second adjustable slit (9) and the universal circuit board (10) are covered by a light shielding box (11), a circular window (13) with the same size as the diaphragm (14) of the second adjustable slit (9) is further arranged on the side of the light shielding box (11) close to the second adjustable slit (9), and the circular window (13) is opposite to the diaphragm (14) of the second adjustable slit (9).

[0006] The spectrum detection circuit includes a photoelectric response module D, the photoelectric response module D is composed of n light emitting diodes D1-Dn in parallel, n is an integer and 1≤n≤6, the cathode end of the photoelectric response module D is connected with an external power supply end VCC, one way of the external power supply end VCC is grounded through a first capacitor C1, the other way of the external power supply end VCC is grounded through a second capacitor C2, the anode end of the photoelectric response module D is grounded through a first resistor R1, the anode end of the photoelectric response module D is also connected with the positive input end of a first voltage amplifier U1 through a second resistor R2, the negative input end of the first voltage amplifier U1 is grounded through a third resistor R3 in one way, the other way of the negative input end of the first voltage amplifier U1 is connected with the output end of the first voltage amplifier U1 through a first sliding potential meter R7, the sliding end of the first sliding potential meter R7 is connected with the output end of the first voltage amplifier U1, the output end of the first voltage amplifier U1 is also connected with the positive input end of a second voltage amplifier U2 through a fourth resistor R4, the negative input end of the second voltage amplifier U2 is grounded through a fifth resistor R5 in one way, the other way of the negative input end of the second voltage amplifier U2 is connected with the output end of the second voltage amplifier U2 through a second sliding potential meter R8, the sliding end of the second sliding potential meter R8 is connected with the output end of the second voltage amplifier U2, the output end of the second voltage amplifier U2 is also grounded through a sixth resistor R6, the rest of the electronic components of the spectrum detection circuit are welded on the universal circuit board (10) except the photoelectric response module D;

[0007] The focal length of the first convex lens (2) is 5 cm, the focal length of the second convex lens (5) is 3.5 cm, the focal length of the third convex lens (8) is 17.5 cm, the blaze angle of the blaze grating (7) is 17.46°, and the slit adjustment range of the first adjustable slit (3) and the second adjustable slit (9) is 180 μm-220 μm.

[0008] The photoelectric response module D (12) is arranged in the diaphragm (14) of the second adjustable slit (9), and the second adjustable slit (9) is fixed on the manual linear displacement translation stage (16).

[0009] When light of different wavelengths is shot into the diaphragm of the second adjustable slit, the photoelectric response module receives the light signal and converts it into an electric signal which is output through the first voltage amplifier, at this time, the operator can measure the voltage signal with a multimeter and record it, which is prepared for calculating the transmittance, at the same time, the operator rotates the knob of the translation stage so that the translation stage moves 1 mm each time, that is, the second adjustable slit moves 1 mm each time, so that the photoelectric response module can sense the spectral signal of different wavelengths at different positions.

[0010] Further, the light source (1) includes a white LED lamp or a halogen lamp, and a sodium-mercury lamp, a sodium lamp, and a He-Ne polarization laser.

[0011] Furthermore, the light-shielding box (11) is a black cardboard box.

[0012] It acts as a darkroom, reducing the impact of ambient light.

[0013] Furthermore, the displacement stroke of the manual linear displacement translation stage (16) is -60mm to 60mm.

[0014] Furthermore, the center point of the light source (1) is 14.5 cm above the horizontal plane when the device is laid flat.

[0015] Furthermore, the slit size of both the first adjustable slit (3) and the second adjustable slit (9) is 200 μm.

[0016] Furthermore, the external power supply terminal VCC is a 12V DC power output circuit.

[0017] The optical theoretical basis of this device:

[0018] In an ideal situation, such as Figure 7 As shown, when light rays l1 and l2 enter the blazed grating horizontally, each incident ray is split into two beams by the blazed grating: a first-order diffraction ray and a second-order diffraction ray. The two first-order diffraction beams are... Figure 7 The two blue lines in the image converge at the focal plane x0 after passing through the convex lens L, forming two second-order diffracted rays. Figure 7 The two red lines in the image converge at the focal plane x through the convex lens L.

[0019] From the grating equation, we can obtain:

[0020] d·sin(2θ)=Kλ0 (1)

[0021] d·sin(2θ+Δθ)=Kλ (2)

[0022] x - x0 = f·tanΔθ (3)

[0023] Where K is the diffraction order and K = 1, d is the grating constant and λ0 is the wavelength of the first-order diffracted light, λ is the wavelength of the second-order diffracted light, θ is the blaze angle of the blazed grating, the diffraction angle of the first-order diffracted ray is 2θ, the diffraction angle of the second-order diffracted ray is 2θ+Δθ, Δθ is the angle between the first-order and second-order diffracted rays after the same beam is split, and f is the focal length of the convex lens L.

[0024] By combining formulas (1), (2), and (3), we can derive:

[0025]

[0026] Since f = 175 mm, the value of x corresponds to one of the scales on the manual linear displacement translation stage, which ranges between -50 mm and 50 mm, and thus f >> x satisfies the paraxial approximation, and formula (4) can be simplified as:

[0027]

[0028] However, there is a certain error in actual diffraction, and thus, as shown in Figure 8

[0029] Let x0 = 0, and the diffraction angle is θ', and then formulas (1) and (2) become:

[0030] d·sinθ’+d·sinθ1=λ0 (6)

[0031] d·sin(θ’+Δθ)+d·sinθ1=λ (7)

[0032] where θ1 is the deviation angle between the actual incident light ray l1 and the horizontal direction,

[0033] By combining formulas (6) and (7), the following formula can be obtained:

[0034] λ=λ0+d·[sin(θ’+Δθ)-sinθ’] (8)

[0035] When f >> x, the paraxial approximation is satisfied, and formula (8) can be simplified as:

[0036] λ=λ0+d·[sin(θ’+x / f)-sinθ’] (9)

[0037] In formula (9), only λ0 and θ' are to be determined parameters, and can be obtained by fitting the measured calibration position values through Origin software. Formulas (4) and (9) are derived by the present inventor based on common formulas in the field of optics, and are also the optical theoretical basis of the device.

[0038] ​The working principle of the device is as follows: the light source emits a collimated parallel light beam to the surface of the film, the light beam transmitted through the film is vertically incident into the blazed grating, the diffracted light is focused on the photodiode on the focal plane through the convex lens, the light of different wavelengths is incident on different positions on the focal plane, then the position of the photodiode is translated by moving the linear displacement translation stage, and the light of different wavelengths is sensed. The spectral detection circuit converts the light signals of different wavelengths collected by the photodiode into electrical signals, and a signal amplification circuit is specially designed to increase the intensity and signal-to-noise ratio of the electrical signals. Finally, the light intensity received by the photodiode at different positions is measured, and the transmission spectrum of the transparent film is obtained after calculation. Before measuring the measured film, the measuring device is calibrated by using a sodium mercury lamp, a mercury lamp and a He-Ne polarized laser, and then the position data of the calibration is fitted by using Origin software to obtain the function relationship between the position of the photodiode and the wavelength of the light. After calculation, the relationship curve of the film transmittance and the light wave frequency is obtained, and finally the position data of the wave peak and the wave trough of the transmission spectrum curve are fitted, and the film thickness is calculated according to the film interference formula.

[0039] In summary, due to the adoption of the above scheme, the device has the following advantages:

[0040] (1) The device for accurately measuring the thickness of a transparent film is provided with a spectrum system and a spectrum detection circuit. The principle that the transmittance and the light wave frequency have a cosine function relationship due to the multi-beam interference of the film is utilized, the transmission spectrum of the measured transparent film is measured, the thickness of the transparent film is calculated according to the periodic fluctuation of the transmittance, and compared with the prior art, the device has zero contact with the surface of the measured material in the whole measurement process, so that no damage is caused to the surface of the measured material, and the performance and the service life of the measured material are effectively ensured.

[0041] (2) The device is simple and convenient to operate and maintain, and has a lower requirement on the operation level of the test personnel. It is only required to judge whether the incident light is parallel light and manually adjust the translation table to record data, so that the human interference factors are reduced, and the measurement accuracy is improved.

[0042] (3) Compared with the complete high-precision mechanical film thickness tester on the market, the device is composed of each independently displayable component, and the change process of the light beam during measurement is completely presented. The device is applied to the teaching and experimental research fields, can enable students to more deeply understand important optical concepts such as interference and diffraction, and fully exercises the practical ability of students by enabling the students to independently build the device, and has high interactivity.

[0043] (4) The utility model discloses scientific and reasonable design, simple production, and the required electronic components, optical element, light source and its power supply and other parts can be bought through market conventional channel, and the cost is low, can be used in daily production to measure transparent film thickness also can be applied to teaching, scientific experiment field, has the prospect of large-scale popularization and application. BRIEF DESCRIPTION OF DRAWINGS

[0044] In order to more clearly illustrate the example of the utility model or the technical scheme in prior art, the following will briefly introduce the drawing needed in the implementation example or prior art description, obviously, the drawing in the following description is only some examples of the utility model, and other drawings can also be obtained according to these drawings without the premise of creating for the ordinary skilled in the art.

[0045] Figure 1 The whole schematic diagram of the utility model;

[0046] Figure 2 Spectrum detection circuit diagram;

[0047] Figure 3 Light shielding box structure diagram;

[0048] Figure 4 Second adjustable slit is installed on the front surface schematic diagram of manual linear displacement translation stage;

[0049] Figure 5 Second adjustable slit is installed on the back surface schematic diagram of manual linear displacement translation stage;

[0050] Fig. 612V DC power supply output circuit principle diagram;

[0051] Figure 7 Ideal grating diffraction principle diagram;

[0052] Figure 8 Actual grating diffraction principle diagram;

[0053] Figure 9 Spectrum calibration data fitting result diagram;

[0054] Figure 10 Sample 1 and sample 2 transmission spectrum diagram (T-λ);

[0055] Figure 11 Sample 1 and sample 2 transmission spectrum diagram (T-v);

[0056] Figure 12 Sample 1 transmission spectrum part data fitting result diagram;

[0057] Figure 13 Sample 2 transmission spectrum part data fitting result diagram;

[0058] In the drawing, 1-light source, 2-first convex lens, 3-first adjustable slit, 4-frosted glass sheet, 5-second convex lens, 6-dry plate holder, 7-bright grating, 8-third convex lens, 9-second adjustable slit, 10-universal circuit board, 11-black light shield box, 12-optoelectronic sensing module D, 13-circular window, 14-diaphragm, 15-knob, 16-manual linear displacement translation stage. DETAILED DESCRIPTION

[0059] The technical solutions in the embodiments of the utility model will be described clearly and completely below in conjunction with the drawings in the utility model examples. Obviously, the described embodiments are only part of the embodiments of the utility model, rather than all the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the utility model.

[0060] Embodiment:

[0061] A device for accurately measuring the thickness of a transparent film, as shown in Figure 1 The device comprises a spectrum system and a spectrum detection circuit. The spectrum system comprises a light source 1. The light source 1 is horizontally arranged. A first convex lens 2, a first adjustable slit 3, a second convex lens 5, a dry plate holder 6 and a bright grating 7 are vertically arranged in sequence in the horizontal light emission direction of the light source 1. The center point of the light source 1, the optical center of the first convex lens 2, the diaphragm center point of the first adjustable slit 3, the optical center of the second convex lens 5 and the center point of the bright grating 7 are located on the same horizontal line. The vertical height of the center point of the light source 1 from the horizontal plane when the device is placed horizontally is 14.5 cm. The frosted glass sheet 4 is pasted on the diaphragm on the light emission side of the first adjustable slit 3. The focal length of the first convex lens 2 is 5 cm. The distance between the first convex lens 2 and the first adjustable slit 3 is 5 cm. The focal length of the second convex lens 5 is 3.5 cm. The distance between the first adjustable slit 3 and the second convex lens 5 is 3.5 cm. The third convex lens 8 is arranged in the vertical direction of the first-order diffraction light of the bright grating 7, Figure 2J1 and Q1 in the formula are first order diffraction light, a second adjustable slit 9 is arranged in parallel with the third convex lens 8, the center point of the diaphragm 14 of the second adjustable slit 9, the optical center of the third convex lens 8 and the center point of the blaze grating 7 are located on the same straight line, the straight line distance between the center point of the blaze grating 7 and the optical center of the third convex lens 8 is 10 cm, the focal length of the third convex lens 8 is 17.5 cm, the distance between the optical center of the third convex lens 8 and the center point of the diaphragm 14 of the second adjustable slit 9 is 17.5 cm, the back of the second adjustable slit 9 is further provided with a universal circuit board 10 in parallel, the second adjustable slit 9 and the universal circuit board 10 are covered by a black hard paper box 11, the side of the black hard paper box 11 close to the second adjustable slit 9 is further provided with a circular window 13 consistent with the size of the diaphragm 14 of the second adjustable slit 9, as shown in Figure 3 , the circular window 13 corresponds to the diaphragm 14 of the second adjustable slit 9, the second adjustable slit 9 is fixed on a manual linear displacement translation stage 16, as shown in Figure 5 , the displacement stroke of the manual linear displacement translation stage 16 is -60 mm to 60 mm, the slit size of the first adjustable slit 3 and the second adjustable slit 9 is 200 μm.

[0062] As shown in Figure 2 , the spectral detection circuit includes a photoelectric sensing module D, the photoelectric sensing module D is composed of four light-emitting diodes D1-D4 in parallel, the cathode end of the photoelectric sensing module D is connected with an external power supply end VCC, one way of the external power supply end VCC is grounded through a first capacitor C1, the other way of the external power supply end VCC is grounded through a second capacitor C2, the anode end of the photoelectric sensing module D is grounded through a first resistor R1, the anode end of the photoelectric sensing module D is also connected with the positive input end of a first voltage amplifier U1 through a second resistor R2, the negative input end of the first voltage amplifier U1 is grounded through a third resistor R3 in one way, the other way of the negative input end of the first voltage amplifier U1 is connected with the output end of the first voltage amplifier U1 through a first sliding rheostat R7, the sliding end of the first sliding rheostat R7 is connected with the output end of the first voltage amplifier U1, the output end of the first voltage amplifier U1 is also connected with the positive input end of a second voltage amplifier U2 through a fourth resistor R4, the negative input end of the second voltage amplifier U2 is grounded through a fifth resistor R5 in one way, the other way of the negative input end of the second voltage amplifier U2 is connected with the output end of the second voltage amplifier U2 through a second sliding rheostat R8, the sliding end of the second sliding rheostat R8 is connected with the output end of the second voltage amplifier U2, the output end of the second voltage amplifier U2 is also grounded through a sixth resistor R6, as shown in Figure 4As shown, the photoelectric sensing module D is arranged in the diaphragm 14 of the second adjustable slit 9, and the rest of the electronic components are welded on the universal circuit board 10. Figure 6 As shown, the external power supply end VCC is a 12V DC power output circuit, and

[0063] In this embodiment, the light source 1 is a white LED lamp with a power of 10 watts, a sodium lamp, a sodium-mercury lamp and a He-Ne polarization laser, the white LED lamp is directly powered by a DC stabilized power supply VICTOR3005, the sodium lamp is a complete device with a model of low-voltage sodium lamp and a power supply GP20Na-II, the sodium-mercury lamp is also a complete device with a model of sodium-mercury lamp source GP20Na-Hg, the He-Ne polarization laser has a model of DH-HN250P and is powered by a DH-HN250 laser power supply, the blaze grating 7 has a model of Daguangguangdian GCG-1200-0.5-25, a ruling period of 1200 lines / mm, a blaze angle of 17.46° ≈ 0.305 rad, and a blaze wavelength of 500 nm, each photodiode of the photoelectric sensing module D is a patch silicon PIN photodiode with a model of PD70-01C / TR7, the first voltage amplifier U1 and the second voltage amplifier U2 both have a model of LM358, and the thin film sample 1 and the thin film sample 2 are both zinc oxide ZnO but have different thicknesses.

[0064] The working process of the utility model is as follows:

[0065] (1) According to the height, distance, direction and position required by the above scheme, each optical component is fixed on the flat base, without placing the test sample, a white LED lamp is used as the light source first, the output voltage of the direct current stabilized power supply VICTOR3005 is adjusted to 4V, then it is judged whether the incident light is parallel light, that is, a paperboard with parallel position marks is placed near and far from the light transmitted through the second convex lens, when the spot sizes of the two places are equal, it is determined that the incident light beam is parallel light, if not, it means that the components of the spectral system are not set correctly according to the scheme, the size of the first adjustable slit or the position of the second convex lens needs to be fine-tuned until the incident light is parallel light, then the spectral line data of sodium mercury lamp, sodium lamp and laser are measured for calibration, that is, the light source is replaced by sodium mercury lamp, low-pressure sodium lamp and polarized laser in turn, the sodium mercury lamp emits purple light, green light and yellow light, the sodium lamp emits yellow light, and the laser emits red light, when the light beams of the above colors are respectively shot into the diaphragm window of the second adjustable slit, the operator records the position value of the light beam, that is, the scale value x of the manual straight-line displacement translation table directly below the light beam, in order to fit the values of the to-be-determined parameters λ0 and θ' of formula (9), and also to verify the accuracy of formula (9), the wavelengths λ of the five color light beams emitted by the above different light sources are known, and the corresponding scale values x are shown in Table 1,

[0066] Table 1

[0067]

[0068] Finally, the five groups of values in Table 1 and formula (4), formula (9) are input into Origin software to obtain the spectral calibration data fitting result graph, as shown in Figure 9 The red line is the fitting data line of formula (4), and the blue line is the fitting data line of formula (9), from the five black square positions of the grating diffraction calibration data, it can be seen that the fitting data line of formula (9) is more accurate, so it can be known that formula (9) derived by the inventor is more in line with the actual situation of grating diffraction, then the wavelength of unknown light wave can be calculated by substituting the scale value x into formula (9), and the wavelength of unknown light wave can also be found according to the fitting data line by reading the x value. After fitting, the values of the to-be-determined parameters λ0 and θ' of formula (9) are λ0=560.58085nm and θ'=0.61rad respectively;

[0069] (II) After the calibration step, the light source is replaced by a white LED lamp without placing the test sample, and preheated for ten minutes. After preheating, the light beam of the light source is irradiated on the light-emitting diode to change the output voltage of the first voltage amplifier U1 by rotating the adjusting knob from left to right within the scale range of -50mm-50mm of the manual linear displacement translation table. Therefore, the voltage value of the first voltage amplifier U1 is measured by the multimeter every 1mm and recorded in Table 2. After the measurement, the thin film sample 1 is placed on the dry plate holder, and the above measurement steps are repeated within the scale range of -50mm-50mm, and the measurement data is recorded in Table 2. Finally, the thin film sample 1 is removed and replaced by the thin film sample 2, and the above measurement steps are repeated, and the measurement data is recorded in Table 2. This is the spectral data of the incident light, and there are three groups of data respectively without sample, thin film sample 1 and thin film sample 2, as shown in Table 2.

[0070] Table 2

[0071]

[0072]

[0073]

[0074]

[0075] (III) The x value in Table 2 is substituted into formula (9) to calculate the corresponding light wavelength λ, and then the x value and the corresponding voltage value without sample, sample 1 or sample 2 are substituted into formula (10) to calculate the transmittance T of sample 1 or sample 2 and draw the T-λ graph, as shown in Figure 10

[0076] Transmittance T = Transmitted light intensity / Incident light intensity = Sample voltage / No sample voltage (10)

[0077]

[0078] In formula (11), c is the speed of light, and v is the light frequency. The calculated light wavelength λ is substituted into formula (11) to calculate the light frequency v and draw the T-v graph, as shown in Figure 11

[0079] (IV) According to the multi-beam interference light intensity formula

[0080]

[0081] In formula (11), c is the speed of light, and v is the light frequency. The calculated light wavelength λ is substituted into formula (11) to calculate the light frequency v and draw the T-v graph, as shown in T ​​For the transmission intensity, I0 is the incident light intensity, R is the intensity reflectivity, t is the film thickness, λ is the light wave length, n is the film refractive index, and from formula (12), the transmission intensity I T is linearly related to the cosine of 1 / λ, and the transmission intensity I T is linearly related to the cosine of frequency v, and the transmission rate can be derived from formula (13):

[0082]

[0083] From Figure 11 it can be seen that the sample transmission rate T has a decreasing trend with the increase of the incident light frequency v, which is caused by the change of reflectivity with the change of frequency due to medium dispersion, so formula (13) is changed into the following formula according to the formula of the intensity of multi-beam interference light and the dispersion properties of the transmission rate

[0084] T=y0*x^a-2R{1-cos[2π(x-xc) / w]} (14)

[0085] In formula (14), a is the Cauchy dispersion coefficient, w is the angular frequency, and y0 and xc are fitting parameters. The transmission spectrum of sample 1 and sample 2 is fitted by Origin software combined with formula (14), and the fitting results of part of the data of the transmission spectrum of sample 1 are shown in Figure 12 , the fitting results of part of the data of the transmission spectrum of sample 2 are shown in Figure 13 , Figure 12 the blue line is the fitting curve of part of the spectral data, and the black line is the actual measured spectral data curve, Figure 13 the green line is the fitting curve of part of the spectral data, and the red line is the actual measured spectral data curve, and the values of y0, R, xc, w, and a are shown in the table above the figure, from Figure 12 and Figure 13 it can be seen that the fitting results are basically consistent with the measured data.

[0086] (Five) According to the fitting results of the transmission spectrum T-v graph, the trough and peak of sample 1 and sample 2 are determined, that is, the red dots in Figure 12 and the black dots in Figure 13 , and the data corresponding to the peak and trough are shown in Table 3,

[0087] Table 3

[0088]

[0089] The refractive index of the film sample material ZnO is 2, the substrate is quartz, and there is no half-wave loss between the transmission lights. For Figure 12 and Figure 13 , the film interference satisfies the equation group Wherein t is the film thickness, n is the film refractive index, k is the interference order, λ 峰 is the wavelength when the wave peak, λ 谷 is the wavelength when the wave trough, then:

[0090] Sample 1:

[0091] Wherein λ 峰 = 491nm, λ 谷 = 549.45nm, t1=576.92nm, k1=4.6999592668024 is obtained, since k1 is the interference order and belongs to integer, therefore k1 value is approximate integer 5, sample 2:

[0092] Wherein λ 峰 = 597.61nm, λ 谷 = 574.71nm, t2=1875.19nm, k2=12.551262529074 is obtained, since k2 is the interference order and belongs to integer, therefore k2 value is approximate integer 13, k1 and k2 appear decimal is due to the manual test exists a little error, but the device is specially designed for measuring transparent film material thickness t, as long as the transparent film material thickness can be measured accurately.

[0093] The above only for the preferred embodiment of the present application has, and not to limit the present application, any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application, should be included in the protection scope of the present application.

Claims

1. A device for accurately measuring the thickness of a transparent film, characterized by: The application relates to a spectrum system and a spectrum detection circuit, which comprises a light source (1), a first convex lens (2), a first adjustable slit (3), a second convex lens (5), a dry plate holder (6), a blazed grating (7) arranged vertically in sequence in the horizontal light emitting direction of the light source (1), the center point of the light source (1), the optical center of the first convex lens (2), the diaphragm center point of the first adjustable slit (3), the optical center of the second convex lens (5) and the center point of the blazed grating (7) are located on the same horizontal line, a frosted glass sheet (4) is pasted on the diaphragm on the light emitting side of the first adjustable slit (3), the first convex lens (2) is 5 cm away from the first adjustable slit (3), the first adjustable slit (3) is 3.5 cm away from the second convex lens (5), a third convex lens (8) is arranged in the vertical direction of the first-order diffraction light of the blazed grating (7), a second adjustable slit (9) is arranged in parallel with the third convex lens (8), the diaphragm (14) center point of the second adjustable slit (9), the optical center of the third convex lens (8) and the center point of the blazed grating (7) are located on the same straight line, the straight line distance between the center point of the blazed grating (7) and the optical center of the third convex lens (8) is 9-10 cm, the optical center of the third convex lens (8) is 17.5 cm away from the diaphragm (14) center point of the second adjustable slit (9), a universal circuit board (10) is further arranged in parallel on the back of the second adjustable slit (9), the second adjustable slit (9) and the universal circuit board (10) are covered by a light shielding box (11), a circular window (13) with the same size as the diaphragm (14) of the second adjustable slit (9) is arranged on the side of the light shielding box (11) close to the second adjustable slit (9), and the circular window (13) is opposite to the diaphragm (14) of the second adjustable slit (9). The spectrum detection circuit includes a photoelectric response module D, the photoelectric response module D is composed of n light emitting diodes D1-Dn in parallel, n is an integer and 1≤n≤6, the cathode end of the photoelectric response module D is connected with an external power supply end VCC, one way of the external power supply end VCC is grounded through a first capacitor C1, the other way of the external power supply end VCC is grounded through a second capacitor C2, the anode end of the photoelectric response module D is grounded through a first resistor R1, the anode end of the photoelectric response module D is also connected with the positive input end of a first voltage amplifier U1 through a second resistor R2, the negative input end of the first voltage amplifier U1 is grounded through a third resistor R3 in one way, the other way of the negative input end of the first voltage amplifier U1 is connected with the output end of the first voltage amplifier U1 through a first sliding potential meter R7, the sliding end of the first sliding potential meter R7 is connected with the output end of the first voltage amplifier U1, the output end of the first voltage amplifier U1 is also connected with the positive input end of a second voltage amplifier U2 through a fourth resistor R4, the negative input end of the second voltage amplifier U2 is grounded through a fifth resistor R5 in one way, the other way of the negative input end of the second voltage amplifier U2 is connected with the output end of the second voltage amplifier U2 through a second sliding potential meter R8, the sliding end of the second sliding potential meter R8 is connected with the output end of the second voltage amplifier U2, the output end of the second voltage amplifier U2 is also grounded through a sixth resistor R6, the rest of the electronic components of the spectrum detection circuit are welded on a universal circuit board (10) except the photoelectric response module D; The focal length of the first convex lens (2) is 5 cm, the focal length of the second convex lens (5) is 3.5 cm, the focal length of the third convex lens (8) is 17.5 cm, the blaze angle of the blaze grating (7) is 17.46°, and the slit adjustment range of the first adjustable slit (3) and the second adjustable slit (9) is 180 μm-220 μm. The photoelectric response module D (12) is arranged in the diaphragm (14) of the second adjustable slit (9), and the second adjustable slit (9) is fixed on the manual linear displacement translation stage (16).

2. The device for precisely measuring the thickness of a transparent film according to claim 1, wherein: The light source (1) includes a white LED lamp or a halogen lamp, and a sodium-mercury lamp, a sodium lamp, and a He-Ne polarization laser.

3. The device for precisely measuring the thickness of a transparent film according to claim 1, wherein: The light-shield box (11) is a black hardboard box.

4. The device for precisely measuring the thickness of a transparent thin film according to claim 1, wherein: The displacement stroke of the manual linear displacement translation stage (16) is -60 mm-60 mm.

5. The device for precisely measuring the thickness of a transparent film according to claim 1, wherein: The vertical height of the center point of the light source (1) from the horizontal plane when the device is placed horizontally is 14.5 cm.

6. The device for precisely measuring the thickness of a transparent thin film according to claim 1, wherein: The slit size of the first adjustable slit (3) and the second adjustable slit (9) is 200 μm.

7. The device for precisely measuring the thickness of a transparent thin film according to claim 1, wherein: The external power supply end VCC is a 12 V DC power supply output circuit.

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