CN113483679B - Contact lens parameter measuring device and method - Google Patents
Contact lens parameter measuring device and method Download PDFInfo
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- CN113483679B CN113483679B CN202110762599.2A CN202110762599A CN113483679B CN 113483679 B CN113483679 B CN 113483679B CN 202110762599 A CN202110762599 A CN 202110762599A CN 113483679 B CN113483679 B CN 113483679B
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- G01B11/00—Measuring arrangements characterised by the use of optical techniques
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- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/002—Measuring arrangements characterised by the use of optical techniques for measuring two or more coordinates
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/02—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness
- G01B11/03—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness by measuring coordinates of points
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- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/24—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures
- G01B11/2441—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures using interferometry
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- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/24—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures
- G01B11/255—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures for measuring radius of curvature
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
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- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/41—Refractivity; Phase-affecting properties, e.g. optical path length
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Abstract
The invention relates to a contact lens parameter measuring device and method, including the low coherent light source, connect sequentially first light splitting component and collimator through the optic fibre, the other side of collimator places the second light splitting component, second lens, reflecting mirror sequentially; the other output end of the first light splitting element is connected with a spectrometer through an optical fiber, and the spectrometer is electrically connected with a computer; an X-Y galvanometer is arranged on one side of the other output end of the second light splitting element, and a first lens and a sample stage are sequentially arranged on the other side of the X-Y galvanometer; light emitted by the low-coherence light source enters the first light splitting element, light output from one end of the first light splitting element is converted into parallel light through the collimator, the parallel light is split into reference light and sample light through the second light splitting element, and the surface of the sample stage is perpendicular to the sample light. The invention realizes the measurement of the parameters of the center thickness, the water content and the curvature radius of the contact lens on one device, avoids the damage to a sample, saves the detection time and reduces the subjective error.
Description
Technical Field
The invention belongs to the technical field of optical interference measurement, and particularly relates to a contact lens parameter measuring device and method.
Background
Contact lenses have the advantages of beautiful wearing, convenient wearing, stable wearing and the like, are increasingly popular with people, and the number of users is greatly increased. With the improvement of living standard and the progress of medical field, the development and application of protective corneal contact lens, cosmetic corneal contact lens and medical corneal contact lens are promoted. The main parameters of contact lenses include: the center thickness, moisture content, and radius of curvature, which are important in the accurate measurement of these parameters of contact lenses, are important in both the preparation and application of contact lenses. However, the current methods for measuring the parameters of the contact lenses have the following defects:
1. measuring the center thickness: the contact lenses are mainly divided into hard lenses and soft lenses, the center thickness measurement of the hard lenses is contact measurement, samples can be contacted during measurement, and particularly, when the hard lenses are measured, a firing pin needs to be placed on the lenses, so that the samples are easily damaged.
2. Measuring the water content: the methods for measuring the water content of contact lenses on the market are mainly oven method and halogen water determination method. One of the test methods specified in GB/T11417.7-2012 is the gravimetric method for determining its water content, i.e. the oven method, which has the following disadvantages: (1) the oven method needs a large amount of samples, usually more than 7-8 samples are needed, which causes certain difficulty in sampling and inspecting the quality of the samples. (2) The oven method is too long in time consumption, and a drying process of 16-18 hours is usually required. (3) The detection process is not easy to operate and complex in operation, the sample needs to be cooled to room temperature in a drying chamber with a drying agent after being dried, and moisture in air is easily absorbed in the cooling process, so that the detection result is influenced. Although the halogen lamp moisture meter method is improved in experimental speed compared with the oven method, the halogen lamp moisture meter method has some disadvantages: (1) the measurement instrument itself contains water which can cause the lens to absorb water during contact with the sample, resulting in inaccurate measurements. (2) The drying time is usually between 1 and 2 hours, and the time is too long. (3) During detection, the temperature of the instrument needs to be raised to more than 100 ℃, the structure of the sample can be damaged, and the sample is damaged.
3. Measuring the curvature radius: the curvature radius determines the fitting relation between the lens and the cornea, so the detection of the lens is an important parameter for detecting the contact lens, at present, a curvature radius determinator is used for detecting the curvature radius, the detection method comprises the steps of firstly cleaning and drying the detection lens, placing the detection lens into a groove to enable the concave surface of the lens to face upwards and keep the concave surface free of any liquid, placing a lens tray at a proper position to observe small green light beams reflected by the lens, observing real images and virtual images in star-shaped patterns through an ocular lens, enabling the real images to be located at the position close to zero and at the center of a dial plate, enabling a pointer to be adjusted to zero and clear by adjusting an objective lens to enable the virtual images to be clear, reading out millimeter close to one percent from the dial plate to be the curvature radius value of the lens, the measurement process is complex and tedious, the image definition needs to be manually judged, subjective errors may be introduced.
In the measurement of the center thickness and the radius of curvature, if the sample vertex is deviated, an error is generated; in addition, the vertex positions are manually determined in the current measurement, and subjective errors exist. Meanwhile, the measurement of the parameters of the contact lenses at present needs different devices to measure different parameters, and cannot be completed on one device.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a contact lens parameter measuring device and a method.
A contact lens parameter measuring device comprises a low-coherence light source, a first light splitting element, a collimator, a second light splitting element, a second lens, a reflector, an X-Y vibrating mirror, a sample stage, a first lens, a spectrometer and a computer, wherein the low-coherence light source is sequentially connected with the first light splitting element and the collimator through optical fibers, and the second light splitting element, the second lens and the reflector are sequentially arranged on the other side of the collimator; the other output end of the first light splitting element is connected with a spectrometer through an optical fiber, and the spectrometer is electrically connected with a computer; an X-Y galvanometer is arranged on one side of the other output end of the second light splitting element, and a first lens and a sample stage are sequentially arranged on the other side of the X-Y galvanometer; the light emitted by the low-coherence light source enters the first light splitting element, and the light output from one end of the first light splitting element is converted into parallel light through the collimator; the parallel light is divided into reference light and sample light by the second light splitting element, and the surface of the sample stage is a reflector and is vertical to the sample light.
The spectrometer comprises a third lens, a grating, a fourth lens and a camera which are sequentially arranged, wherein the other output end of the first light splitting element is connected with the third lens through an optical fiber, the camera is electrically connected with a computer, light sequentially passes through the lens and the grating and is collected by the camera, and then the interference spectrum is transmitted to the computer.
The measuring method of the contact lens parameter measuring device specifically comprises the following steps:
the method comprises the following steps: a sample is not placed on the sample table, an X-Y galvanometer is used for scanning, light emitted by a low-coherence light source enters a first light splitting element, and light output from one end of the first light splitting element is converted into parallel light through a collimator; parallel light is split into reference light and sample light by the second light splitting element, wherein the reference light is focused on the reflecting mirror by the second lens, the sample light irradiates the first lens through an X vibration mirror and a Y vibration mirror of the X-Y vibration mirror, the sample light is focused on the sample table through the first lens, the reflected light on the surface of the sample table and the reference light reflected by the reflecting mirror reversely propagate according to an original path, enter the first light splitting element, enter the spectrometer through the other output end of the first light splitting element to form an interference spectrum, and the interference spectrum is collected by the spectrometer and transmitted to the computer for phase demodulation; the interference spectrum formed by the surface of the sample stage and the reference light is marked as S0(x, y; k), wherein x and y represent the plane coordinates of the scanning point, and k represents the wave number distribution of the spectrometer;
step two: placing a sample to be detected on a sample table, enabling the convex surface to face upwards, scanning by using an X-Y galvanometer, enabling light emitted by a low-coherence light source to enter a first light splitting element, and enabling light output from one end of the first light splitting element to be converted into parallel light through a collimator; the parallel light passes through a second light splitting element which splits the parallel light into reference light and sample light, wherein the reference light is focused on a reflecting mirror through a second lens, the sample light irradiates on the first lens through an X-Y galvanometer and an X-Y galvanometer of the X-Y galvanometer, the sample light is focused on a sample to be measured and a sample stage through the first lens, the reflected light on the upper surface, the reflected light on the lower surface and the reflected light on the sample stage surface of the sample to be measured and the reference light reflected by the reflecting mirror reversely propagate along an original path and enter a spectrometer, the reflected light on the upper surface, the lower surface and the sample stage surface of the sample to be measured respectively form interference spectrums with the reflected reference light, the interference spectrum formed by the upper surface of the sample to be measured and the reference light reflected by the reflecting mirror is marked as S1(X, Y; k), the interference spectrum formed by the lower surface of the sample to be measured and the reference light reflected by the reflecting mirror is marked as S2(X, y; k) the interference spectrum formed by the sample stage surface and the reference light reflected by the mirror is labeled S3(x, y; k) (ii) a
Step three: the computer calculates the surface profile Z0(x, y) of the sample stage according to S0(x, y; k), and the method for calculating Z0(x, y) is as follows: eliminating direct current components from the interference spectrum S0(x, y; k), and carrying out intensity normalization; performing Fast Fourier Transform (FFT) on the preprocessed data, and obtaining dimensionless frequency m0 and phase from the magnitude spectrum
Performing uncoiling treatment to obtain;
wherein: KC represents the central wave number of the spectrometer, delta represents the FFT resolution of the spectrometer, and N0 is the phase winding frequency;
KC can be calibrated through monochromatic light with a known wavelength, delta can be calibrated through a glass sheet with a known thickness and a known refractive index, and N0 is obtained through a unwinding algorithm;
step four: calculating contact lens parameters: in the measurement of step two, the signals of S1(x, y; k), S2(x, y; k) and S3(x, y; k) are added together, S1(x, y; k), S2(x, y; k) and S3(x, y; k) are extracted separately by a band-pass filter, and then a sample upper surface profile Z1(x, y), a sample lower surface profile Z2(x, y), a sample stage surface profile Z3(x, y) after placing the sample are calculated by the method of step three from S1(x, y; k) (x, y; k), S2(x, y; k) and S3(x, y; k);
marking the radius of a sample to be detected as R, marking the spherical center coordinates of the sample to be detected as (a, b, c), and calculating the curvature radius and the spherical center coordinates (a, b, c) of the lens from Z1(x, y) by using a fitting method;
when the sample to be measured is placed, the optical path difference between the reflected light passing through the center point of the sample to be measured and passing through the upper surface of the sample and the reference light reflected by the reflector is d1 ═ Z1(a, b), the optical path difference between the reflected light passing through the center point of the sample to be measured and passing through the lower surface of the sample and the reference light reflected by the reflector is d2 ═ Z2(a, b), and the optical path difference between the reflected light passing through the center point of the sample to be measured and passing through the surface of the sample table and the reference light reflected by the reflector is d3 ═ Z3(a, b); when the sample is not placed, the optical path length difference between the reflected light passing through the (a, b) point and the surface of the sample platform and the reference light reflected by the reflector is d 0-Z0 (a, b);
the center thickness d and the refractive index n0 of the sample are shown by the following formulas (2) to (4):
d＝(d2-d1)-(d3-d0) (2)
n0＝(d2-d1)/(d2-d1-d3+d0) (3)
obtaining the formula (4) of the water content x of the sample according to the calculation formula of the refractive index of the mixture:
x＝100*(n0-m)/(n-m) (4)
wherein: x represents the water content of the sample, n represents the refractive index of the material of the sample to be measured in a dry state, m represents the refractive index of the liquid absorbed by the sample to be measured, and the refractive index of the liquid can be known according to the components of the liquid.
The invention has the beneficial effects that:
1. the measurement of the center thickness, water content and radius of curvature parameters of the contact lens is accomplished in one apparatus.
2. The device provided by the invention is a non-contact method for measuring parameters of the contact lens, and can avoid damage to a sample.
3. When the device is used for measuring the water content of the contact lens, sample dehydration is not needed, the measurement is rapid and convenient, and the detection time is saved.
4. When the device is used for measuring the center thickness and the curvature radius of the contact lens, the curvature radius of the lens can be obtained without searching the vertex of the lens, and the subjective error is reduced.
Drawings
FIG. 1 is a schematic view of a contact lens parameter measuring device according to the present invention;
wherein the content of the first and second substances,
1-a low-coherence light source, 2-a first light splitting element, 3-a collimator, 4-a second light splitting element, 5-an X-vibration mirror, 6-a Y-vibration mirror, 7-a first lens, 8-a sample to be detected, 9-a second lens, 10-a reflector, 11-a third lens, 12-a grating, 13-a fourth lens, 14-a camera, 15-a computer, 16-a sample stage and 17-a spectrometer.
Detailed Description
For better understanding of the present invention, the technical solutions and effects of the present invention will be described in detail by the embodiments with reference to the accompanying drawings.
Example 1:
in this example, the nominal center thickness of the contact lens sample to be tested was 80 μm, the base curve radius was 8.6mm, the wearing method was a year-throw type, and the water content was 40%.
As shown in fig. 1, a contact lens parameter measuring device includes a low coherence light source 1, a first light splitting element 2, a collimator 3, a second light splitting element 4, a second lens 9, a reflector 10, an X-Y galvanometer, a sample stage 16, a first lens 7, a spectrometer 17, and a computer 15, where the low coherence light source 1 is sequentially connected to the first light splitting element 2 and the collimator 3 through an optical fiber, and the second light splitting element 4, the second lens 9, and the reflector 10 are sequentially disposed on the other side of the collimator 3. The other output end of the first light splitting element 2 is connected with a spectrometer 17 through an optical fiber, and the spectrometer 17 is electrically connected with the computer 15. And an X-Y galvanometer is arranged on one side of the other output end of the second light splitting element 4, and a first lens 7 and a sample stage 16 are sequentially arranged on the other side of the X-Y galvanometer. In this embodiment, the central wavelength of the low coherence light source 1 is 1310nm, the bandwidth is 82nm, and the splitting ratio of the first light splitting element 2 is 50: 50, the splitting ratio of the second light splitting element 4 is 50: 50, the focal length of the second lens 9 is 50mm, and the focal length of the first lens 7 is 50 mm.
The light emitted by the low coherence light source 1 enters the first light splitting element 2, and the light output from one end of the first light splitting element 2 is changed into parallel light through the collimator 3; the parallel light passes through the second light splitting element 4, the second light splitting element 4 splits the parallel light into reference light and sample light, the reference light is focused on the reflecting mirror 10 through the second lens 9, the sample light is irradiated on the first lens 7 through the X galvanometer 5 and the Y galvanometer 6 of the X-Y galvanometer, and the sample light is focused on the surface of a sample 8 to be measured on the sample stage 16 through the first lens 7. The sample table 16 is used for placing a sample 8 to be measured, and the surface of the sample table 16 is provided with a reflector 10 which is vertical to the sample light; the reference light reflected by the reflector 10 and the sample light reflected by the sample stage 16 and the sample 8 to be measured are reflected according to the original path to form an interference spectrum, enter the first light splitting element 2, and enter the spectrometer 17 through the other output end of the first light splitting element 2. The spectrometer 17 transmits the collected interference spectrum to the computer 15 for phase demodulation, and calculates the optical path difference by combining the frequency and phase of the fourier transform for demodulation.
The spectrometer 17 comprises a third lens 11, a grating 12, a fourth lens 13 and a camera 14 which are arranged in sequence, the other output end of the first light splitting element 2 is connected with the third lens 11 through an optical fiber, the camera 14 is electrically connected with a computer 15, light passes through the lens and the grating 12 in sequence and is collected by the camera 14, and then the interference spectrum is transmitted to the computer 15. In this embodiment, the focal length of the third lens 11 is 100mm, the grating 12 is a transmission-type grating 12, the model thereof is 1145line/mm, the focal length of the fourth lens 13 is 150mm, the camera 14 is a line CCD camera, and the model is GL 2048. The camera 14 records the interference spectrum of the reflected reference light and the sample light, transmits the interference spectrum to the computer 15 for processing, demodulates the interference spectrum by combining the frequency and the phase of the Fourier transform, and calculates the optical path difference.
The method for measuring the parameters of the contact lens by using the contact lens parameter measuring device specifically comprises the following steps:
the method comprises the following steps: a sample is not placed on the sample table 16, an X-Y galvanometer is used for scanning, light emitted by the low-coherence light source 1 enters the first light splitting element 2, and light output from one end of the first light splitting element 2 is changed into parallel light through the collimator 3; the parallel light passes through the second light splitting element 4, the parallel light is split into reference light and sample light by the second light splitting element 4, the reference light is focused on the reflecting mirror 10 through the second lens 9, the sample light irradiates the first lens 7 through the X-vibration mirror 5 and the Y-vibration mirror 6 of the X-Y vibration mirror, the sample light is focused on the sample stage 16 through the first lens 7, the reflected light on the surface of the sample stage 16 and the reference light reflected by the reflecting mirror 10 reversely propagate according to the original path and enter the first light splitting element 2, and enter the spectrometer 17 through the other output end of the first light splitting element 2 to form an interference spectrum, and the interference spectrum is collected by the spectrometer 17 and transmitted to the computer 15 for phase demodulation. The interference spectrum formed by the surface of the sample stage 16 and the reference light is labeled S0(x, y; k), where x and y represent the planar coordinates of the scanning point and k represents the wavenumber distribution of the spectrometer 17.
Step two: placing a sample 8 to be detected on a sample table 16, wherein the convex surface faces upwards, scanning is carried out by using an X-Y galvanometer, light emitted by a low-coherence light source 1 enters a first light splitting element 2, and light output from one end of the first light splitting element 2 is changed into parallel light through a collimator 3; the parallel light passes through the second light splitting element 4, the second light splitting element 4 splits the parallel light into reference light and sample light, wherein the reference light is focused on the reflecting mirror 10 through the second lens 9, the sample light passes through the X-Y galvanometer 5 and the Y galvanometer 6 of the X-Y galvanometer and irradiates on the first lens 7, the sample light is focused on the sample 8 to be measured and the sample stage 16 through the first lens 7, the reflected light on the upper surface, the reflected light on the lower surface, the reflected light on the surface of the sample 16 and the reference light reflected by the reflecting mirror 10 reversely propagate along the original path and enter the spectrometer 17, the reflected light on the upper surface, the lower surface and the surface of the sample 8 to be measured respectively form interference spectra with the reflected reference light, the interference spectra formed by the upper surface of the sample 8 to be measured and the reference light reflected by the reflecting mirror 10 are marked as S1(X, Y; k), the interference spectra formed by the lower surface of the sample 8 to be measured and the reference light reflected by the reflecting mirror 10 are marked as S2(X, y; k) the interference spectrum formed by the surface of the sample stage 16 and the reference light reflected by the mirror 10 is labeled S3(x, y; k) in that respect
Step three: the computer 15 calculates the surface profile Z0(x, y) of the sample stage 16 according to S0(x, y; k), and the method for calculating Z0(x, y) is as follows: eliminating DC component from interference spectrum S0(x, y; k)Line intensity normalization; performing Fast Fourier Transform (FFT) on the processed data, and obtaining dimensionless frequency m0 and phase from the amplitude spectrum
Performing unwinding treatment to obtain the product;
wherein: KC represents the spectrometer 17 center wave number, Δ represents the FFT resolution of the spectrometer 17, and N0 is the phase wrap times.
KC can be calibrated by a monochromatic light of known wavelength, Δ can be calibrated by a glass sheet of known thickness and refractive index, and N0 is derived by the unwrapping algorithm.
Step four: calculating contact lens parameters: in the measurement of step two, the signals of S1(x, y; k), S2(x, y; k) and S3(x, y; k) are added together, S1(x, y; k), S2(x, y; k) and S3(x, y; k) are first separately extracted through a band-pass filter, and then a sample upper surface profile Z1(x, y), a sample lower surface profile Z2(x, y), a sample stage 16 surface profile Z3(x, y) after placing the sample are calculated from S1(x, y; k) (x, y; k), S2(x, y; k) and S3(x, y; k) using the method shown in step three.
Marking the radius of the sample 8 to be measured as R, marking the sphere center coordinates of the sample 8 to be measured as (a, b, c), calculating the curvature radius R and the sphere center coordinates (a, b, c) of the lens by Z1(x, y) by using a fitting method, wherein the difference value between the calculated value and the actual value of each point is as follows: e (x)0，y0，z0，r)＝(x-x0)2+(y-y0)2+(Z1-z0)2-r2Wherein (x)0，y0，z0R) is the sphere center coordinate and radius to be found, when E (x)0，y0，z0When r) is the minimum, then a is equal to x0，b＝y0，c＝z0And R ═ R. The radius of curvature R in this example is 8.5 mm.
When the sample 8 is placed, the optical path difference between the reflected light passing through the center point of the sample 8 and reflected by the upper surface of the sample and the reference light reflected by the reflecting mirror 10 is d1 (Z1) (a, b), the optical path difference between the reflected light passing through the center point of the sample 8 and reflected by the lower surface of the sample and the reference light reflected by the reflecting mirror 10 is d2 (Z2) (a, b), and the optical path difference between the reflected light passing through the center point of the sample 8 and reflected by the surface of the sample stage 16 and the reference light reflected by the reflecting mirror 10 is d3 (Z3) (a, b). When no sample is placed, the optical path length difference between the reflected light from the sample stage 16 surface passing through the point (a, b) and the reference light reflected by the mirror 10 is Z0(a, b) as d 0.
The center thickness d and the refractive index n0 of the sample are shown by the following formulas (2) to (4):
d＝(d2-d1)-(d3-d0) (2)
n0＝(d2-d1)/(d2-d1-d3+d0) (3)
obtaining the formula (4) of the water content CW of the sample according to the calculation formula of the mixture refractive index:
CW＝100*(n0-m)/(n-m) (4)
wherein: x represents the water content of the sample, n represents the refractive index of the material of the sample 8 to be measured in a dry state, m represents the refractive index of the liquid absorbed by the sample 8 to be measured, and n and m can be measured by the prior art.
The measurement results show that d0 is 1131.471 μm, d1 is 1108.613 μm, d2 is 1200.045 μm, d3 is 1142.9 μm, the center thickness of the sample 8 to be measured is about d 80.003 μm, and the refractive index of the sample is n0 which is 1.423.
In this embodiment, the refractive index of the material of the sample 8 in a dry state is 1.56, the refractive index of the liquid absorbed by the sample 8 is 1.333, and the water content CW of the contact lens sample calculated by the above formula (4) is about 39.6%, which corresponds to the nominal value.
Claims (2)
1. A measuring method of a contact lens parameter measuring device is disclosed, wherein the adopted contact lens parameter measuring device comprises a low-coherence light source, a first light splitting element, a collimator, a second light splitting element, a second lens, a reflector, an X-Y galvanometer, a sample stage, a first lens, a spectrometer and a computer, wherein the low-coherence light source is sequentially connected with the first light splitting element and the collimator through an optical fiber, and the second light splitting element, the second lens and the reflector are sequentially arranged on the other side of the collimator; the other output end of the first light splitting element is connected with a spectrometer through an optical fiber, and the spectrometer is electrically connected with a computer; an X-Y galvanometer is arranged on one side of the other output end of the second light splitting element, and a first lens and a sample stage are sequentially arranged on the other side of the X-Y galvanometer; the light emitted by the low-coherence light source enters the first light splitting element, and the light output from one end of the first light splitting element is converted into parallel light through the collimator; the parallel light is split into reference light and sample light by the second light splitting element, and the surface of the sample stage is a reflector and is vertical to the sample light;
the method is characterized in that: the method specifically comprises the following steps:
the method comprises the following steps: a sample is not placed on the sample table, an X-Y galvanometer is used for scanning, light emitted by a low-coherence light source enters a first light splitting element, and light output from one end of the first light splitting element is converted into parallel light through a collimator; parallel light is split into reference light and sample light by the second light splitting element, wherein the reference light is focused on the reflecting mirror by the second lens, the sample light irradiates the first lens through an X vibration mirror and a Y vibration mirror of the X-Y vibration mirror, the sample light is focused on the sample table through the first lens, the reflected light on the surface of the sample table and the reference light reflected by the reflecting mirror reversely propagate according to an original path, enter the first light splitting element, enter the spectrometer through the other output end of the first light splitting element to form an interference spectrum, and the interference spectrum is collected by the spectrometer and transmitted to the computer for phase demodulation; the interference spectrum formed by the surface of the sample table and the reference light is marked as S0(x, y; k), wherein x and y represent the plane coordinates of the scanning point, and k represents the wave number distribution of the spectrometer;
step two: placing a sample to be detected on a sample table, enabling the convex surface to face upwards, scanning by using an X-Y galvanometer, enabling light emitted by a low-coherence light source to enter a first light splitting element, and enabling light output from one end of the first light splitting element to be converted into parallel light through a collimator; the parallel light passes through a second light splitting element which splits the parallel light into reference light and sample light, wherein the reference light is focused on a reflecting mirror through a second lens, the sample light irradiates on the first lens through an X-vibration mirror and a Y-vibration mirror of an X-Y vibration mirror, the sample light is focused on a sample to be measured and a sample stage through the first lens, the reflected light of the upper surface, the reflected light of the lower surface, the reflected light of the surface of the sample stage and the reference light reflected by the reflecting mirror reversely propagate according to an original path and enter a spectrometer, the reflected light of the upper surface, the lower surface and the surface of the sample stage of the sample to be measured respectively form interference spectrums with the reflected reference light, the interference spectrum formed by the upper surface of the sample to be measured and the reference light reflected by the reflecting mirror is marked as S1(X, Y; k), the interference spectrum formed by the lower surface of the sample to be measured and the reference light reflected by the reflecting mirror is marked as S2(X, y; k) the interference spectrum formed by the sample stage surface and the reference light reflected by the mirror is labeled S3(x, y; k) (ii) a
Step three: the computer calculates the surface profile Z0(x, y) of the sample stage according to S0(x, y; k), and the method for calculating Z0(x, y) is as follows: eliminating direct current components from the interference spectrum S0(x, y; k), and carrying out intensity normalization; performing fast Fourier transform on the preprocessed data, and obtaining dimensionless frequency m0 and phase from the amplitude spectrum
Performing unwinding treatment to obtain the product;
wherein: KC represents the central wave number of the spectrometer, Delta represents the FFT resolution of the spectrometer, and N0 is the phase winding times;
KC is calibrated through monochromatic light with a known wavelength, Delta is calibrated through a glass sheet with a known thickness and a known refractive index, and N0 is obtained through a uncoiling algorithm;
step four: calculating the contact lens parameters: in the measurement of step two, the signals of S1(x, y; k), S2(x, y; k) and S3(x, y; k) are added together, S1(x, y; k), S2(x, y; k) and S3(x, y; k) are extracted separately by a band-pass filter, and then the sample upper surface profile Z1(x, y), the sample lower surface profile Z2(x, y) and the sample stage surface profile Z3(x, y) after the sample is placed are calculated by the method of step three from S1(x, y; k), S2(x, y; k) and S3(x, y; k);
marking the radius of a sample to be detected as R, marking the spherical center coordinates of the sample to be detected as (a, b, c), and calculating the curvature radius R and the spherical center coordinates (a, b, c) of the lens from Z1(x, y) by using a fitting method;
when the sample to be measured is placed, the optical path difference between the reflected light passing through the center point of the sample to be measured and passing through the upper surface of the sample and the reference light reflected by the reflector is d1 ═ Z1(a, b), the optical path difference between the reflected light passing through the center point of the sample to be measured and passing through the lower surface of the sample and the reference light reflected by the reflector is d2 ═ Z2(a, b), and the optical path difference between the reflected light passing through the center point of the sample to be measured and passing through the surface of the sample table and the reference light reflected by the reflector is d3 ═ Z3(a, b); when the sample is not placed, the optical path difference between the reflected light passing through the point (a, b) and the surface of the sample platform and the reference light reflected by the reflector is d0 which is Z0(a, b);
the center thickness d and the refractive index n0 of the sample are shown by the following formulas (2) to (4):
d＝(d2-d1)-(d3-d0) (2)
n0＝(d2-d1)/(d2-d1-d3+d0) (3)
obtaining the formula (4) of the water content x of the sample according to the calculation formula of the refractive index of the mixture:
x＝100*(n0-m)/(n-m) (4)
wherein: x represents the water content of the sample, n represents the refractive index of the material of the sample to be measured in a dry state, m represents the refractive index of the liquid absorbed by the sample to be measured, and the refractive index of the liquid can be known according to the components of the liquid.
2. The method of claim 1, wherein the contact lens parameter measuring device comprises: the spectrometer comprises a third lens, a grating, a fourth lens and a camera which are sequentially placed, wherein the other output end of the first light splitting element is connected with the third lens through an optical fiber, the camera is electrically connected with a computer, light sequentially passes through the lens and the grating and is collected by the camera, and then interference spectrum is transmitted to the computer.
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