CN217766078U - System for simultaneously measuring thermal expansion coefficient and temperature refractive index coefficient of object - Google Patents
System for simultaneously measuring thermal expansion coefficient and temperature refractive index coefficient of object Download PDFInfo
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- CN217766078U CN217766078U CN202220711264.8U CN202220711264U CN217766078U CN 217766078 U CN217766078 U CN 217766078U CN 202220711264 U CN202220711264 U CN 202220711264U CN 217766078 U CN217766078 U CN 217766078U
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Abstract
The utility model provides a system for simultaneous measurement object coefficient of thermal expansion and temperature refractive index. The system comprises a laser light source system, a Michelson Fizeau interference system, a temperature control system and a data acquisition system which are connected through a light path; the laser light source system comprises a laser, a beam expander or a collimator, and the Michelson Fizeau interference system comprises a 45-degree semi-transparent and semi-reflective mirror, a reflector and an object to be detected; the temperature control system comprises a heat preservation device, a heating device and a quartz material, and the object to be measured is placed in the heat preservation device. The temperature control system, the 45-degree semi-transparent and semi-reflective mirror and the data acquisition system form a light path in the vertical direction, and the laser light source system, the 45-degree semi-transparent and semi-reflective mirror and the reflector form a light path in the horizontal direction. The utility model discloses a combine michelson and fexol interference principle, utilize two surfaces of speculum and sample can be at the same change of intensification in-process simultaneous measurement axial length and refracting index, but simultaneous measurement material coefficient of thermal expansion and temperature coefficient of refraction.
Description
Technical Field
The utility model relates to a material heat altered shape measures technical field, especially relates to a system of simultaneous measurement object thermal expansion coefficient and temperature refractive index coefficient.
Background
After a temperature field is applied to the light-transmitting material, the molecules arranged in order according to the principle in the material change the distance along with the temperature, and the change of the length or the volume is represented in a macroscopic manner. The linear expansion coefficient is defined as the ratio of the relative change of length or volume of the material under the action of temperature fields with different gradients to the length or volume of the material at the original temperature, and is one of the basic characteristic parameters of the material.
The thermal deformation is microscopically manifested in two ways. On one hand, the applied temperature field causes the arrangement structure of the molecules in the light-transmitting material to change; on the other hand, thermal stresses are generated due to the fact that the external constraint and the mutual constraint between the internal parts cannot be completely freely expanded and contracted. Both of which result in a change in certain optical properties of the material, with refractive index being one of the most important optical parameters.
The linear expansion coefficient of the optical lens material is approximately in the order of 10 -7 -10 -5 Within the range, the thermal expansion of the optical material is very small, and the common tool for measuring the length cannot accurately measure the length due to low precision, and cannot simultaneously measure the change of the thermal expansion coefficient and the temperature refractive index of the transparent object when the transparent object is heated.
The experimental device diagram of a prior art scheme for measuring the thermal expansion coefficient and the refractive index temperature coefficient of glass is shown in fig. 1, and the sample and light path design diagram is shown in fig. 2. The samples used in this experiment were made of homogeneous isotropic glass as shown in the left panel of fig. 2. In the figure, A is a glass cylinder with a part cut away, and the upper and lower surfaces are basically parallel; b and B' are 2 circular glass plates also partially cut out, the upper and lower surfaces of each glass plate being non-parallel. The 3 pieces of glass A, B and B' are glued into a whole. The refractive index of the glue is the same as that of glass, and the thickness of the glue can be ignored. The laser was directed to the sample from above as shown in the right hand figure of fig. 2.
When the laser light is reflected from both sides of the sample, 3 reflected spots are visible on the screen, and the intermediate spots have interference fringes. It is formed by the interference of the lower surface of the upper thin glass plate and the upper surface 2 beam reflected light of the lower thin glass plate. The optical path difference of these 2 beams is 2L. When the sample is heated, the interference fringe is observed to move by m, assuming that the sample temperature is increased by Δ L = L β · Δ T (β is the thermal expansion coefficient of glass) 1 And (3) strips.
When the laser light is reflected from a single surface of the sample, only 1 spot with interference fringes, formed by the interference of the reflected light from the upper and lower surfaces of the glass cylinder, is visible on the screen. The optical path difference of these 2 beams is 2nL. Assuming that the interference fringe upon heating has moved by m 2 And (3) strips. Then there are:
knowing L and n, provided that the number of fringe shifts m is measured separately 1 、m 2 In relation to the temperature T, from m 1 -T，m 2 And (4) plotting T, and respectively obtaining the thermal expansion coefficient beta and the refractive index temperature coefficient gamma.
During the experiment, firstly, a sample is carefully slid into a sample cavity in the middle of a large aluminum block, a temperature sensor is inserted, then the large aluminum block is placed on an electric furnace, and the large aluminum block and the electric furnace are placed on a lifting platform. A laser, a lift table, etc. are placed on the optical bench. And (3) turning on a laser power supply, and adjusting the positions of the laser and the sample to ensure that 3 reflection light spots can be seen on the screen when the laser is reflected from the sample, wherein 1 interference fringe is arranged in the middle. Starting the electric furnace, heating the sample, addingHeating to a certain temperature, turning off the electric furnace, and measuring the number m of interference fringes in the process of natural temperature reduction of the sample 1 And the temperature T. After the data is measured, the sample is rotated to the other side, 1 light spot with interference fringes can be seen on the screen, the sample is heated, and the number m of the interference fringes is measured in the sample cooling process 2 And the temperature T.
The technical scheme for measuring the thermal expansion coefficient and the refractive index temperature coefficient of the glass in the prior art has the following defects: the thermal expansion coefficient and the refractive index temperature coefficient can not be measured simultaneously in the same temperature change process, and the change mechanisms of the thermal expansion coefficient and the refractive index temperature coefficient can not be well researched; only the state that the interference pattern with the equal thickness is the fringe is considered, and the state that the interference pattern with the equal inclination is the circular spot is not considered.
SUMMERY OF THE UTILITY MODEL
The utility model provides a system for simultaneous measurement object thermal expansion coefficient and temperature refractive index to realize the thermal expansion coefficient and the temperature refractive index coefficient that can be at same temperature variation in-process simultaneous measurement object.
In order to achieve the purpose, the utility model adopts the following technical scheme.
A system for simultaneously measuring the coefficient of thermal expansion and the temperature index of refraction of an object, comprising: the system comprises a laser light source system, a Michelson Fizeau interference system, a temperature control system and a data acquisition system which are connected through an optical path;
the laser light source system comprises a laser, a beam expander or a collimator, and the Michelson Fizeau interference system comprises a 45-degree semi-transparent and semi-reflective mirror, a reflector and an object to be detected; the temperature control system comprises a heat preservation device, a heating device and a quartz material, the quartz material is used as an experiment reference surface, the heat preservation device is connected with the heating device, the object to be tested is placed in the heat preservation device, the heat preservation device is arranged on a quartz gasket, and the data acquisition system is placed above the 45-degree semi-transparent semi-reflective mirror;
the temperature control system, 45 degrees semi-transparent semi-reflecting mirror and the data acquisition system constitute the light path of vertical direction, the laser instrument, beam expanding mirror or collimater, 45 degrees semi-transparent semi-reflecting mirror with the speculum constitutes the light path of horizontal direction.
Preferably, the distance from the mirror to the 45 ° half mirror is not equal to the distance from the 45 ° half mirror to the reference plane of the quartz material.
Preferably, when the laser system is a laser and a beam expander, the formed light source is a point light source, and the reflector is perpendicular to the surface of the object to be measured;
when the laser system is a laser and a collimator, the formed light source is a parallel light source, and the surface of the reflector and the surface of the object to be measured are not vertical.
Preferably, the heat preservation device is cylindrical and is buckled on a quartz gasket, the surface of the heat preservation device is perforated, and the aperture is close to the size of the light spot.
Preferably, heating device includes heating plate, thermostat and temperature probe, the heating plate pastes on cylindrical stainless steel product, and the card is put in cylindrical shell, the heating plate passes through electric wire connection thermostat, the temperature probe is gone deep into cylindrical shell inside by upper portion aperture.
Preferably, the data acquisition system comprises ground glass, a camera and a processor; or a charge coupled device CCD camera and processor.
Preferably, the system is integrated in an acrylic plate box with an opening on a cuboid to form an integrated system, the lower part of the acrylic plate box is a rectangular bottom support, four acrylic plates which are perpendicular to each other are placed on the rectangular bottom support, and a small hole is formed in the middle of the left side surface of the acrylic plate box at a certain height, so that light emitted by a laser light source system can pass through the hole smoothly; the right side of the acrylic plate box is provided with an integrated reflector at the same height at the center of the structure;
the front acrylic plate and the rear acrylic plate are respectively provided with a rectangular groove which is 45 degrees with the bottom support at corresponding heights, the acrylic plates with 45 degrees of semi-transparent and semi-reflective mirrors are clamped and placed in the centers by adopting a tenon-and-mortise structure, the data acquisition system is positioned at the upper part of the integrated system, the acrylic plates and the horizontal rectangular bottom support are clamped and placed at 45 degrees, a square hole is formed in the light arrival position, and the observation screen is clamped and placed in the square hole; the temperature control system and the object to be measured are arranged on a rectangular bottom support of the integrated system, and the upper part of the temperature control system and the object to be measured are opposite to a 45-degree semi-transparent and semi-reflective mirror clamped on an acrylic plate.
By the foregoing the embodiment of the utility model provides a technical scheme can see out, the embodiment of the utility model provides a scheme has combined the principle and the design that michelson and fexol interfered, can be at the same change of intensification in-process simultaneous measurement axial length and refracting index, has improved device sensitivity simultaneously, has the advantage that the measurement is convenient, the precision is high.
Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to these drawings without creative efforts.
FIG. 1 is a diagram of an experimental setup for measuring the temperature coefficient of thermal expansion and refractive index of glass according to the prior art;
FIG. 2 is a sample and optical path layout of a prior art solution for measuring the temperature coefficient of thermal expansion and refractive index of glass;
fig. 3 is an experimental light path diagram of an apparatus for simultaneously measuring a thermal expansion coefficient and a temperature refractive index of a transparent object according to an embodiment of the present invention;
fig. 4 is a three-dimensional usage state diagram of each device in the experimental optical path of the device for simultaneously measuring the thermal expansion coefficient and the temperature refractive index of the transparent object according to the embodiment of the present invention;
fig. 5 is a schematic diagram of a partial optical path of a system for simultaneously measuring a thermal expansion coefficient and a temperature refractive index coefficient of an object according to an embodiment of the present invention;
fig. 6 is a processing flow chart of a computer image processing algorithm according to an embodiment of the present invention;
fig. 7 is a schematic view illustrating a change of a central circular spot according to an embodiment of the present invention.
In the figure, 1-laser; 2-a beam expander or collimator; 3-an object to be measured; 4-quartz spacers; 5-45 degree semi-transparent semi-reflecting mirror; 6-a viewing screen; 7-a heat preservation device; 8-a heating device; 9-mirror.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below by referring to the drawings are exemplary only for explaining the present invention, and should not be construed as limiting the present invention.
As used herein, the singular forms "a", "an", "the" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. It will be understood that when an element is referred to as being "connected" or "coupled" to another element, it can be directly connected or coupled to the other element or intervening elements may also be present. Further, "connected" or "coupled" as used herein may include wirelessly connected or coupled. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the prior art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
For the convenience of understanding the embodiments of the present invention, the following description will be given by way of example only with reference to the accompanying drawings, and the embodiments are not limited thereto.
The first embodiment is as follows:
the principle of thermal deformation includes: the light transmitting material undergoes a change in its internal molecular arrangement with a change in temperature (rise or fall), which macroscopically exhibits a slight change in length (expansion or contraction) in each direction. When the temperature of the solid material rises, the structural volume thereof increases accordingly. Microscopically, solid molecules are usually tightly packed and as the temperature rises, the molecules begin to vibrate at a faster rate and push against each other. This process increases the distance between adjacent atoms, causing the solid to expand, which increases the volume of the solid structure. The change of the axial length of the solid is a linear function of the temperature, the ratio of the length increment to the original length under the change of unit temperature is called as a linear expansion coefficient, and the calculation formula is as follows:
where l represents the initial length of the solid material and t represents the temperature. α is a solid linear expansion coefficient as a linear expansion coefficient to be measured.
Meanwhile, the refractive index of the material is changed due to the change of the intermolecular structure caused by the increase of the temperature. The refractive index of a material will be affected by two factors that act in opposition: on one hand, due to temperature rise, the density of the glass is reduced by thermal expansion, and the refractive index is reduced; on the other hand, the temperature is increased, resulting in cation pair O 2- The effect of (2) is reduced, the polarizability is increased, and the refractive index is increased. And the eigenfrequency of the electronic vibration is reduced along with the temperature rise, so that the ultraviolet absorption limit caused by the superposition of the eigenfrequency is moved to the long wave direction, and the refractive index is raised. Refractive index and temperature phase of materialIn the case of not causing stress, the amount of change in refractive index per 1 ℃ change in temperature is called the temperature refractive index coefficient of refractive index, and the calculation formula is:
where n represents the refractive index of the solid material and t represents the temperature.
The utility model discloses a measure linear expansion coefficient and temperature refracting index coefficient and explore the heat effect mechanism to be applied to aspects such as administrative affairs, precision instruments are revised.
The principle of measuring the refractive index of the light-transmitting material by Michelson and Fizeau interference comprises the following steps: two rows of coherent light beams with the same frequency, the same vibration direction and constant phase difference have mutual strengthening or weakening phenomena in a space intersection region, namely, the interference phenomenon of the light beams. The micro length change (light wavelength order) and the micro angle change can be deduced according to the relation between the change of the light interference pattern and the optical path difference and wavelength.
When the laser system is a laser and a beam expander, the formed light source is a point light source, and when the reflector is completely vertical to the surface of the sample, the light source is equal-inclination interference, and the interference light can be received as annular equal-inclination interference fringes on a screen; when the laser system is a laser and a collimator, the formed light source is a parallel light source, and when the reflector and the surface of the sample are not vertical, the light source is equal-thickness interference, so that straight stripes which are symmetrical by taking an equal-thickness intersection line as a center can be obtained. The mode for which the interference effect is optimal can be selected for different samples.
The straight stripe can show translation and refractive index variation, angle change direction and size of each point of the object upper surface that awaits measuring more in the ring than comparing, but the measurement degree of difficulty is bigger than the ring. In summary, the anisotropic object has different thermal expansion coefficients and refractive indexes in different directions, and is suitable for observing the thermal expansion coefficients and the temperature refractive index coefficients in different directions by using straight stripes with equal-thickness intersecting lines as central symmetry; an isotropic object has the same thermal expansion coefficient, refractive index, and the like in different directions, and the thermal expansion coefficient and the temperature refractive index coefficient are preferably observed using annular equal-inclination interference fringes.
TABLE 2 comparison of interference circles and fringes
Table 2 above illustrates the following:
when the circular light spot is generated, calculating the translation and refractive index variation of the light beam reflected by the upper surface of the object to be measured according to the throughput of the circular light spot; calculating the angle change direction of the upper surface of the light beam reflected by the upper surface of the object to be measured according to the moving direction of the circle center of the circular light spot; obtaining the angle change of the upper surface of the light beam reflected by the upper surface of the object to be measured according to the calibration data through the circle center moving distance of the circular light spot; the translation and the refractive index change of different positions of the light beam reflected by the object to be measured can be known through the change of the shape of the circular ring light spot.
When the stripe is generated, calculating the change of the stripe level through the translation of the stripe, and calculating to obtain the translation of the upper surface and the refractive index variation; the angle of the light beam reflected by the upper surface of the object to be detected can be known to change through the slope change of the stripes; calculating the size of the angle change of the upper surface of the light beam reflected by the upper surface of the object to be measured through the density change of the stripes; and calculating the angle change size of the upper surface of the object to be measured, the translation of the upper surface and the refractive index change quantity through the change of the stripes at different positions of the stripes.
The embodiment of the utility model provides a pair of simultaneous measurement object thermal expansion coefficient and temperature refractive index device's experiment light path picture is shown in fig. 3, and the three-dimensional use state picture of each device is shown in fig. 4 in the experiment light path, and above-mentioned device includes laser light source system, michelson fizeau interference system, temperature control system and the data acquisition system of connecting through the light path.
The laser light source system comprises a laser, a beam expander or a collimator, and the Michelson Fizeau interference system comprises 1 45-degree semi-transparent and semi-reflective mirror, 2 optical plane reflectors and an object to be measured; the temperature control system comprises a heat preservation device, a heating device and a quartz material, wherein the quartz material is used as an experiment reference surface and is used for heat insulation. The heat preservation device is connected with the heating device, the object to be measured is placed in the heat preservation device, the heat preservation device is arranged on the quartz gasket, and the data acquisition system is placed above the 45-degree semi-transparent and semi-reflective mirror. The data acquisition system comprises ground glass, a camera and a processor; or a charge coupled device CCD camera and processor.
The temperature control system, 45 degrees semi-transparent semi-reflecting mirror and the data acquisition system constitute the light path of vertical direction, the laser instrument, beam expanding mirror or collimater, 45 degrees semi-transparent semi-reflecting mirror with the speculum constitutes the light path of horizontal direction.
The above-mentioned device can be used for the experiment of simultaneous measurement object thermal expansion coefficient and temperature refracting index, based on the light path diagram of fig. 3 and fig. 4, the embodiment of the utility model provides a processing procedure of the method of simultaneous measurement transparent object thermal expansion coefficient and temperature refracting index includes following processing step:
and (1) installing the system on an optical platform. The laser is first mounted and fixed to the optical bench. And opening a power supply of the laser, and adjusting the pitch angle of the laser to enable emergent light of the laser to be parallel to the optical platform.
And (2) installing a reflector in the light path, and adjusting the reflector in the horizontal direction to enable the horizontal incident beam and the reflected beam to coincide, namely, the light emitted by the laser returns through the original path of the reflector. And then blocking the horizontal reflecting mirror, installing a 45-degree semi-transparent semi-reflecting mirror and adjusting the mirror surface angle of the semi-transparent semi-reflecting mirror to ensure that the 45-degree semi-horizontal incident light beam and the reflected light beam can be superposed. And installing a beam expander, adjusting the height and direction of the beam expander, and adjusting the laser to be in a horizontal state. And on the optical platform, adjusting the distance between the beam expander and the laser, and fixing the beam expander after adjusting the light spot to a set size range.
And (3) placing the object to be detected on a quartz gasket, sleeving the quartz gasket in the heat preservation device, embedding the heating sheet in the heat preservation device, connecting the heating box through a circuit, and enabling the heating box to be independent of the optical path.
And (4) building a data acquisition system comprising a camera, installing an observation screen, and erecting the camera so that the camera can clearly shoot images on the observation screen.
Step (5) viewing interference patterns on the observation screen, wherein in order to make imaging clearer, the laser can be finely adjusted to make laser emitted by the laser parallel to a horizontal plane and hit the center of a reserved position of the 45-degree semi-transparent and semi-reflective mirror, and horizontal incident beams and reflected beams of the 45-degree semi-transparent and semi-reflective mirror and the reflecting mirror can be coincided by adjusting the mirror surface angles of the 45-degree semi-transparent and semi-reflective mirror and the reflecting mirror; or finely adjusting the object to be measured, the reflector and the like until the shape of the interference pattern is clear and meets the requirement, and it is worth noting that the distance from the reflector to the 45-degree semi-transparent and semi-reflective mirror is not equal to the distance from the 45-degree semi-transparent and semi-reflective mirror to the reference surface of the quartz material.
And (6) opening the heating device and the camera, raising the temperature in the heat preservation device to a set temperature, preserving the heat, and after the temperature of the heat preservation device is stable, obtaining the image of the throughput change of the interference pattern displayed on the observation screen by the camera in a video recording mode.
And (7) processing data. As a new precise measurement technology, the image measurement technology has many advantages such as high resolution, high speed, large dynamic range, rich information content, and automation, and is now widely used in various industrial measurements. The utility model discloses the experiment combines the high accuracy of michelson interferometer and the above-mentioned advantage of image measurement technique, aims at realizing non-contact, the high accuracy of refracting index, on a large scale, the high automatic real-time measurement.
Opening the video data on a computer, transcoding the video data into an image, performing noise reduction and binarization processing on the image, if the image is a circular spot, finding a circular interference center position and a minimum circle radius under a current frame, and determining the circular spot throughput according to the number of wave crests and wave troughs generated on the radius change image; if the position of the stripe is the stripe, the position variation of the stripe is captured. Thereby obtaining the throughput (fringe movement number) k of the round spot formed by the interference between the upper surface of the object to be measured and the reflecting mirror 1 ′-k 1 Round spot throughput (fringe movement number) formed by interference between the lower surface of the object to be measured and the reflecting mirror)k 2 ′-k 2 。
And (3) changing a light source into collimated light, repeating the steps (2) to (7) under the condition of ensuring that other devices are not changed, and simultaneously measuring the thermal expansion coefficient and the temperature refractive index coefficient of the object through the change of the constant-thickness interference series.
In practical application, a data acquisition system consisting of ground glass and a camera can be built, the interference pattern is reflected on the ground glass through a reflector, and the camera is used for recording.
The observation screen in the data acquisition system can also be set as a CCD, and the interference pattern is converted into a digital signal through the CCD to be displayed on a computer, so that the interference image can be clearly displayed in a computer picture.
And (5) repeating the steps (1) to (7) under the condition of ensuring that other devices are not changed, and still simultaneously measuring the thermal expansion coefficient and the temperature refractive index coefficient of the object.
And respectively calculating the thermal expansion coefficient and the temperature refractive index coefficient of the object made of a single material according to the steps, measuring the sample for multiple times, and solving the average value to reduce the error when solving the result. The thermal expansion coefficient and the temperature refractive index coefficient of the various materials were determined by the above-described methods.
In practical application, the light source can be changed into collimated light, the steps (2) to (7) are repeated under the condition that other devices are not changed, and the thermal expansion coefficient and the temperature refractive index coefficient of the object can be measured simultaneously through the change of the equal-thickness interference series;
in the experimental process, the conditions of fluctuation, continuous swallowing and continuous spitting and the like of the interference circular ring are found, and manual observation is very difficult; in addition, the whole experiment has long duration, so that the manual reading time is long, and the purposes of rapidly and conveniently observing the circular ring throughput and the stripe movement are achieved by adopting a computer image processing technology.
The embodiment of the utility model provides a processing flow of computer image processing algorithm is shown in fig. 6, including following processing step:
step S1: and (5) performing video frame cutting and processing by using opencv. It should be noted that the photographed isocline stripe must be centered and uniformly exposed, otherwise it is not beneficial for subsequent image processing and counting.
Step S2: the picture is mainly denoised so as to identify the image characteristics. In the experiment, the Motion filter is adopted to enhance high-frequency information such as edges, outlines and the like of the images, and retain low-frequency information of image content, so that the definition of boundary stripes is improved.
And step S3: since the brightness of the experimental interference image fluctuates significantly during the imaging process, it is difficult to specify the standard of shape fitting without performing the binarization process, and thus the binarization process is very necessary. In the experiment, the image is subjected to binarization processing by adopting an adaptive threshold algorithm, so that the image becomes an interference background image except for an interference image, wherein the interference image is only an image with 0 gray level and an image with 255 gray levels.
And step S4: and identifying whether the obtained image is a circular spot or a stripe and counting.
If the identification object is the circular spot, after the center coordinates of the interference circular spot are obtained, the average value of 8 point pixel values around the center is taken as the vertical coordinate, the change curve of the change curve along with the frame number is drawn, and the number of wave crests of the curve is calculated to obtain the throughput number of the circular spot.
The final read information yields the round spot throughput by the following criteria:
1. if the fitted curve has smooth peaks and valleys and does not have instantaneous great change, the identified object is not changed and is the central circular spot of the same level, so that the handling of the circular spots is not caused;
2. if the curve after the fitting process has a tendency of instantaneous increase or decrease (ignoring bad values), it indicates that the recognition target is changed and that there is a swallow or a spit of a round spot. When the sudden drop occurs, the radius of the identification object is suddenly reduced, and a new central circular spot appears in the identification object, so that the identification object is spitted out; fig. 7 is a schematic diagram illustrating a change of a central circular spot according to an embodiment of the present invention, wherein when a sudden increase occurs, the radius of the recognition object is suddenly increased, the internal central circular spot disappears, and the original external circular spot is changed into a new central circular spot, so that the recognition object is spitted out.
If the identification object is a stripe, tracking the position of a certain stripe by adopting a depersort tracking algorithm, counting the variation of the stripe, and calculating the number of the stripes passing through the variation. Fitting a curve of the number of the stripes along with the change of the number of the video frames by using a computer, and calculating the number of wave crests of which the curve exceeds a threshold set by an experiment, namely the stripe throughput.
Thereby obtaining the throughput (fringe movement number) k of the round spot formed by the interference between the upper surface of the object to be measured and the reflecting mirror 1 ′-k 1 Round spot throughput (fringe movement number) k formed by interference of lower surface of object to be measured and reflecting mirror 2 ′-k 2 。
The embodiment of the utility model provides a partial light path sketch map of system of simultaneous measurement object coefficient of thermal expansion and temperature refractive index is shown in figure 5. Laser emitted by the laser penetrates through the beam expander to form light spots, so that an interference image is formed and is easier to observe. Then the laser is divided into two beams of light by a 45-degree semi-transparent semi-reflecting mirror, and one beam of light finally reaches the observation screen through a reflecting mirror and the semi-reflecting mirror through a horizontal light path; the other beam of light which passes through the vertical direction is transmitted downwards through the lower surface of the 45-degree semi-transparent semi-reflecting mirror and is respectively reflected by the upper surface and the lower surface of the object to be detected to be divided into two beams of light, and the two beams of reflected light respectively reach the observation screen through the 45-degree semi-transparent semi-reflecting mirror.
The three beams of light generate interference in pairs on the observation screen to generate circular light spots and stripes on the observation screen. Practical experiments show that the interference light intensity generated by the light beams reflected by the upper surface, the lower surface and the surface of the object to be measured is the smallest, the light intensity reflected by the reflector is the second of the light intensity reflected by the lower surface of the object to be measured, and the light intensity reflected by the reflector is the strongest with the light intensity reflected by the upper surface of the object to be measured. The method comprises the following steps of measuring the interference level change generated by light beams reflected by the upper surface and the lower surface of an object, the light beams reflected by a reflector and the interference level change reflected by the lower surface of the object to be measured simultaneously, and obtaining the thermal expansion coefficient and the temperature refractive index coefficient of the object simultaneously; in addition, the thermal expansion coefficient and the temperature refractive index coefficient of the object can be obtained by simultaneously measuring the changes of the interference levels of the light beam reflected by the reflector and the light beam reflected by the upper surface of the object to be measured and the changes of the interference levels of the light beam reflected by the reflector and the light beam reflected by the lower surface of the object to be measured.
When the laser system is a laser and a beam expander, the formed light source is a point light source, and when the reflector is completely vertical to the surface of the sample, the light source is equal-inclination interference, and the interference light can be received as annular equal-inclination interference fringes on a screen; when the laser system is a laser and a collimator, the formed light source is a parallel light source, and when the reflector and the surface of the sample are not vertical, the light source is equal-thickness interference, so that straight stripes which are symmetrical by taking an equal-thickness intersection line as a center can be obtained. The mode for optimizing the interference effect can be selected for different samples.
Straight stripe compares in the ring and can show the translation and the refractive index change amount of each point of the object upper surface that awaits measuring more, angle change direction and size, but measures the degree of difficulty and is bigger than the ring. In summary, the anisotropic object has different thermal expansion coefficients and refractive indexes in different directions, and is suitable for observing the thermal expansion coefficients and the temperature refractive index coefficients in different directions by using straight stripes with equal-thickness intersecting lines as central symmetry; an isotropic object has the same thermal expansion coefficient, refractive index, and the like in different directions, and the thermal expansion coefficient and the temperature refractive index coefficient are preferably observed using circular equi-tilt interference fringes.
TABLE 2 comparison of interference rings and fringes
The upper surface of the quartz gasket at room temperature is taken as a reference surface, and the reference surface is fixed and does not change along with the change of temperature. L in FIG. 3 1 Is the distance from the semi-transparent and semi-reflective mirror to the reflective mirror, l 2 Is the distance from the semi-transparent semi-reflective mirror to the upper surface of the object to be measured, l 3 The distance from the upper surface of the object to be measured to the reference surface is smaller considering that the quartz gasket is heatedIs defined as 4 The distance between the lower surface of the object to be measured and the reference surface is 0 at room temperature.
The interference generated by the light beam reflected by the reflector and the light beam reflected by the upper surface of the object to be measured is as follows:
the optical path difference between the light beam reflected by the reflector and the light beam reflected by the upper surface of the object to be measured and the interference fringe k have the following relationship:
wherein n is 0 Is the refractive index of air, λ is the wavelength of the laser light emitted by the laser, k 1 In the order of stripes.
In the formula, l and k both change with the change of temperature, so that the formula comprises the following components:
wherein l 2 ' is the distance, k, from the heated half-mirror to the upper surface of the object to be measured 1 ' is the striation order after heating.
(5) Subtracting (6) from formula:
2n 0 (l 2 ′-l 2 )＝(k 1 ′-k 1 )λ (7)
here, l can be calculated from the number of circular spots in throughput or the number of stripe shifts k' -k 2 ′-l 2 。
Interference generated by the light beam reflected by the reflector and the light beam reflected by the lower surface of the object to be measured:
firstly, the expansion caused by the heating of the quartz pad under the object to be measured is temporarily not considered, i.e. the lower surface of the object to be measured is considered to be fixed.
The optical path difference between the light beam reflected by the reflector and the light beam reflected by the lower surface of the object to be measured and the interference fringe k have the following relationship:
5＝2n 0 l 2 +2nl 3 -2n 0 l 1 ＝k 2 λ (8)
wherein n is 0 Is the refractive index of air, n is the refractive index of the sample to be measured, and lambda is the wavelength of the laser light emitted by the laser.
In the formula I 2 、n、l 3 And k vary with temperature, so there are:
5′＝2n 0 l 2 ′+2n′l 3 ′-2n 0 l 1 ＝k 2 ′λ (9)
wherein l 2 ' is the distance from the heated semi-transparent semi-reflecting mirror to the upper surface of the object to be measured, /) 3 ' is the distance, k, from the upper surface of the object to be measured to the reference surface after heating 2 ' is the striation order after heating.
(8) Subtracting (9) from formula:
2n 0 (l 2 ′-l 2 )+2n′l 3 ′-2nl 3 ＝(k 2 ′-k 2 )λ (10)
let n' = n + Δ n, one obtains:
2n 0 (l 2 ′-l 2 )+2n(l 3 ′-l 3 )+2Δnl 3 ′＝(k 2 ′-k 2 )λ (11)
is easy to know 2 +l 3 Is constant and is equal to the distance between the half mirror and the reference plane, so 2 ′-l 2 ＝-(l 3 ′-l 3 ). Is shown by the formula (5) 2 ′-l 2 While l 3 Is also easy to obtain and is the thickness corresponding to the initial temperature, so that the throughput k can be obtained only by image processing 2 ′-k 2 The refractive index change Δ n of the object to be measured can be obtained.
Error correction of quartz shim: the quartz wafer is padded under the object to be detected. The linear expansion coefficient of quartz is one to two orders of magnitude smaller than that of the object to be measured, so the influence on the experiment is small but not negligible. This corresponds to considering the distance l of the quartz pad (corresponding to the lower surface of the object to be measured) from the reference plane under the condition that the virtual reference plane is not changed 4 0 at room temperature, with increasing temperature, l 4 Has a value ofCan no longer be 0.
The principle of the correction is similar to the principle of the interference produced by the mirror and the beam reflected by the upper surface, where the formula of the correction based on formula (5) is given directly:
2n 0 (l 2 ′-l 2 )+2n(l 3 ′-l 3 )+2Δnl 3 ′+2n(l 4 -l 4 ′)-2Δnl 4 ′＝(k 2 ′-k 2 )λ (12)
wherein l 4 -l 4 ′、l 4 ′(l 4 0) initially) can be obtained by blank experiments, and n represents the refractive index of the measured sample.
To sum up, it is only necessary to obtain the circular spot throughput (fringe movement number) k 1 ′-k 1 、k 2 ′-k 2 And k in blank experiments 3 ′-k 3 The value of delta n in a certain temperature range can be calculated, and the thermal expansion coefficient and the temperature refractive index coefficient of the object to be measured can be further calculated.
Principle of surface inclination angle of object to be measured: if the interference pattern is a circular spot interference pattern, the movement of the circle center of the light spot represents that the surface of the object to be detected generates a tiny inclination angle, and the relationship between the size of the inclination angle and the movement direction of the circle center of the circular spot on the two-dimensional plane can be obtained through calibration. The angle was calibrated using a micrometer screw. Firstly, horizontally placing the spiral micrometer, placing an object to be measured on the plane of the micrometer, rotating in the same direction (clockwise or anticlockwise) to lift the table top, observing the distance of circle center movement in the observation screen and recording the distance as delta x, recording the difference between two times of vertical height changes before and after as delta h, and recording the distance from the angle change fulcrum of the spiral side micrometer to a lifting point as L s From this, the angle change is calculated, denoted as Δ θ.
If the interference pattern is a fringe interference pattern, the change of the slope of the fringe represents that the surface of the object to be detected generates a tiny inclination angle, and the relation between the size of the inclination angle and the change of the slope can be obtained through calibration. The angle was calibrated using a micrometer screw. Firstly, horizontally placing the micrometer screw, placing the object to be measured on the micrometer plane, and rotating according to the same direction (clockwise or anticlockwise direction)The table top is lifted, the slope change of the stripes in the observation screen can be observed to be delta alpha at the moment, the difference between the two vertical height changes before and after recording is delta h, and the distance from the angle change fulcrum of the spiral lateral micro-meter to the lifting point is recorded as L s From this, the angle change is calculated, denoted as Δ θ.
In order to eliminate the influence of thermal expansion and other factors of the quartz gasket, a blank experiment is firstly carried out, the experimental device is unchanged, the experimental steps are unchanged, and only the object to be tested is taken away. The principle of the blank experiment is similar to that of the interference generated by the mirror and the beam reflected by the upper surface, where the formula is given directly:
2n 0 (l 4 ′-l 4 )＝(k 3 ′-k 3 )λ (13)
from this, it can be obtained 4 ′-l 4 As a known quantity of equation (9).
In order to increase systematicness, easy operation and aesthetic property, the device is integrated in a system made of acrylic plates, and an optical base is fixed on an optical platform. The acrylic is also called organic glass, can replace organic glass, and has the characteristics of good light transmission performance, long service life and the like. The integrated device can realize experimental measurement only by adjusting the positions of the laser and the beam expander to collimate the light, irradiating the light at the center of the semi-transparent semi-reflective mirror and turning on the heating device and the camera. The connection and structural features between the various components of the device are now described as follows:
and integrating the system in an acrylic plate box with an opening on the cuboid to form an integrated system. The whole integrated system is a cuboid upper opening box type, the lower part of the system is a rectangular bottom support which is provided with four acrylic plates which are vertical to each other and enclose the periphery of the box type, and a small hole is arranged in the middle of the left side surface of the acrylic plate box at a certain height so that the light emitted by the laser light source system can smoothly pass through the small hole; the right side of the acrylic plate box is provided with an integrated reflector at the same height at the center of the structure; the front plate and the rear plate are respectively provided with a rectangular groove which is 45 degrees with the bottom support at corresponding heights, and the front plate and the rear plate are connected with an acrylic plate which is clamped at the center and is provided with a 45-degree semi-transparent and semi-reflective mirror by adopting a mortise and tenon structure, so that the thickness of the acrylic plate is ensured to be thinner as far as possible under the condition of ensuring the structural strength and the device stability; the data acquisition system is positioned at the upper part of the integrated system, adopts a structure that an acrylic plate and a horizontal bottom support are clamped at an angle of 45 degrees, and a square hole is formed at the light arrival position to clamp the observation screen; the temperature control system and the object to be measured are arranged on a bottom support of the integrated system, and the upper part of the integrated system is opposite to a 45-degree semi-transparent and semi-reflective mirror clamped on an acrylic plate.
The light path of the integrated system is emitted by a laser light source system, penetrates through an opening of the acrylic plate on the left side, is divided into two paths through a 45-degree semi-transparent semi-reflecting mirror clamped in the middle, one path horizontally emits to a reflecting mirror, and the other path vertically emits downwards and then reflects to a data acquisition system through the upper surface and the lower surface of a temperature control system and a material one by one.
The experimental procedure was as follows:
putting an object to be measured on a quartz gasket of a heating device, turning on a power supply of a helium-neon laser, adjusting a pitch angle of the laser, and adjusting the laser to be horizontal, wherein a light beam is aligned to the center of a 45-degree half-transmitting and half-reflecting mirror.
And (2) finely adjusting the object to be detected, the 45-degree semi-transparent and semi-reflective mirror and the reflector to ensure that the interference pattern has a good shape and is easy to observe.
And (3) opening the heating device and the camera, raising the temperature in the heat preservation device to a set temperature, preserving the heat, and after the temperature of the heat preservation device is stable, obtaining the image of the throughput change of the interference pattern displayed on the observation screen by the camera in a video recording mode.
Opening video data on a computer, transcoding the video data into an image at a speed of 60 frames per second by using related codes of image processing, performing noise reduction and binarization processing on the image, and processing each frame of image to obtain the round spot throughput (fringe throughput) k formed by the interference of the upper surface of the object to be measured and the reflector 1 ′-k 1 And a round spot throughput (fringe throughput) k formed by the interference of the lower surface and the reflecting mirror 2 ′-k 2 。
Step (5) of converting k 1 ′-k 1 Substituting the axial elongation l of the object to be measured into the formula (7) 2 ′-l 2 And then l is obtained by blank experiment 4 ' (blank experiment)Obtained k 3 ′-k 3 Substituting into equation (7) to obtain l 4 ') calculate l 2 ′-l 2 -l 4 ', the thermal expansion coefficient of the object to be measured can be obtained according to the formula (3). Will k 2 ′-k 2 The refractive index change quantity delta n of the object to be measured can be obtained by substituting the formula (12), and the temperature refractive index coefficient of the object to be measured can be obtained by substituting the formula (4).
And (6) replacing different samples, and repeating the steps (3) to (6) to obtain multiple groups of data.
The embodiment of the utility model provides a scheme requires not highly to the sample shape, comparatively level and smooth can, also need not the adhesion. And interference circular spot throughput (or fringe movement) is used to calculate the thermal expansion coefficient and temperature index coefficient, relative to the fringes, which is easily computable.
To sum up, the embodiment of the utility model provides a combine through interfering with michelson and fexol, utilize two surfaces of speculum and sample can be at the change of same intensification in-process simultaneous measurement axial length and refracting index, but simultaneous measurement material coefficient of thermal expansion and temperature refractive index to explore the heat altered shape mechanism, be applied to aspects such as criminal investigation, precision instruments correction. Compared with other technologies, the technology has the advantages that the operation and the device are complex, and the change of the thermal expansion coefficient and the temperature refractive index coefficient when the transparent object is heated can be measured simply and simultaneously.
For guaranteeing the measured accuracy, the utility model discloses abandoned the intensification measurement technique of adopting among the traditional device, adopted cooling process data collection, avoided the influence of air disturbance to the experiment accuracy to very big degree.
The Motion filter and the adaptive threshold algorithm are adopted to binarize and enhance the image information.
Those of ordinary skill in the art will understand that: the figures are schematic representations of one embodiment, and the blocks or processes in the figures are not necessarily required to practice the present invention.
Those of ordinary skill in the art will understand that: the components in the devices in the embodiments may be distributed in the devices in the embodiments according to the description of the embodiments, or may be correspondingly changed in one or more devices different from the embodiments. The components of the above embodiments may be combined into one component, or may be further divided into a plurality of sub-components.
The embodiments in the present specification are described in a progressive manner, and the same and similar parts among the embodiments are referred to each other, and each embodiment focuses on the differences from the other embodiments. In particular, apparatus or system embodiments, which are substantially similar to method embodiments, are described in relative ease, and reference may be made to some descriptions of method embodiments for related points. The above-described embodiments of the apparatus and system are merely illustrative, and the units described as separate parts may or may not be physically separate, and the parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of the present embodiment. One of ordinary skill in the art can understand and implement without inventive effort.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention should be covered by the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (6)
1. A system for simultaneously measuring the coefficient of thermal expansion and the temperature index of refraction of an object, comprising: the system comprises a laser light source system, a Michelson Fizeau interference system, a temperature control system and a data acquisition system which are connected through an optical path;
the laser light source system comprises a laser, a beam expander or a collimator, and the Michelson Fizeau interference system comprises a 45-degree semi-transparent and semi-reflective mirror, a reflector and an object to be detected; the temperature control system comprises a heat preservation device, a heating device and a quartz material, the quartz material is used as an experiment reference surface, the heat preservation device is connected with the heating device, the object to be tested is placed in the heat preservation device, the heat preservation device is arranged on a quartz gasket, and the data acquisition system is placed above the 45-degree semi-transparent semi-reflective mirror;
the temperature control system 45 semi-transparent semi-reflecting mirror with the data acquisition system constitutes the light path of vertical direction, the laser instrument, beam expanding lens or collimater 45 semi-transparent semi-reflecting mirror with the speculum constitutes the light path of horizontal direction.
2. The system for simultaneously measuring the thermal expansion coefficient and the temperature refractive index of an object according to claim 1, wherein the distance from the mirror to the 45 ° half mirror is not equal to the distance from the 45 ° half mirror to the reference plane of the quartz material.
3. The system of claim 1, wherein the thermal insulator is cylindrical and is fastened to a quartz spacer, and the surface of the thermal insulator is perforated to have a diameter close to the size of the light spot.
4. The system for simultaneously measuring the thermal expansion coefficient and the temperature refractive index coefficient of an object according to claim 1, wherein the heating device comprises a heating plate, a temperature controller and a temperature probe, the heating plate is attached to the cylindrical stainless steel product and clamped in the cylindrical shell, the heating plate is connected with the temperature controller through a wire, and the temperature probe extends into the cylindrical shell from the upper small hole.
5. The system for simultaneously measuring the coefficient of thermal expansion and the temperature index of refraction of an object according to claim 1, wherein said data acquisition system comprises ground glass, a camera, and a processor; or a charge coupled device CCD camera and processor.
6. The system for simultaneously measuring the thermal expansion coefficient and the temperature refractive index coefficient of an object according to any one of claims 1 to 5, wherein the system is integrated in an acrylic board box with an opening on a rectangular solid to form an integrated system, the lower part of the acrylic board box is a rectangular base on which four acrylic boards perpendicular to each other are placed, and a small hole is arranged in the middle of the left side surface of the acrylic board box at a certain height so that light emitted by a laser light source system can smoothly pass through the hole; the integrated reflector at the same height is arranged in the center of the right structure of the acrylic plate box;
the front acrylic plate and the rear acrylic plate are respectively provided with a rectangular groove which is 45 degrees with the bottom support at corresponding heights, the acrylic plates with the 45-degree semi-transparent and semi-reflective mirror clamped at the centers are connected by adopting a mortise and tenon structure, the data acquisition system is positioned at the upper part of the integrated system, the acrylic plates and the horizontal rectangular bottom support are clamped at 45 degrees, a square hole is formed at the light arrival position, and the observation screen is clamped in the square hole; the temperature control system and the object to be measured are arranged on a rectangular bottom support of the integrated system, and the upper part of the temperature control system and the object to be measured are opposite to a 45-degree semi-transparent and semi-reflective mirror clamped on an acrylic plate.
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