CN112611464A - Transmission type temperature field measuring device and method based on infrared digital holographic technology - Google Patents
Transmission type temperature field measuring device and method based on infrared digital holographic technology Download PDFInfo
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- G01J5/00—Radiation pyrometry, e.g. infrared or optical thermometry
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Abstract
The invention discloses a transmission-type temperature field measuring device and method based on an infrared digital holographic technology, and belongs to the field of infrared digital holographic application. The device comprises an infrared laser, a beam splitter, a beam expander, a lens, a reflector, a temperature field detection cavity, an infrared focal plane array imaging sensor, an image processing unit and a U-shaped light-tight shell. The device is protected and fixed by the U-shaped light-tight casing, and only two round holes are reserved on the device for embedding the lens III and the lens IV made of germanium materials, so that visible light interference is avoided, and the purpose of improving the measurement precision is achieved. The method calculates the stripe displacement by combining the image subtraction and the pixel point size, and calculates the temperature field variation by the stripe displacement; the infrared digital holographic technology is used for measuring the temperature field, so that the real-time performance of the temperature field detection can be guaranteed, and the resistance of the temperature field detection device to various interferences is improved.
Description
Technical Field
The invention discloses a transmission-type temperature field measuring device and method based on an infrared digital holographic technology, and belongs to the field of infrared digital holographic application.
Background
The existing temperature field measuring means mainly comprise four means, namely probe contact type, schlieren quantitative detection type, infrared thermal imaging detection type and visible light holographic interference detection type, wherein the probe contact type is most commonly used in daily life, has high measuring precision, can monitor the temperature in real time, but cannot realize nondestructive detection during measurement, has limited space range of a detectable temperature field, and cannot be applied to numerous industrial fields; the infrared thermal imaging detection mode is used for detecting the temperature by receiving infrared waves radiated by an object, has high detection speed and limited precision, is easily influenced by a use environment, and has sharply reduced detection precision when facing a detection environment with smoke or flame, so that the actual application value of the infrared thermal imaging detection mode in industrial production is lower; the schlieren quantitative detection method is simple, but the measurement precision is slightly low, and the requirement of high-precision temperature field detection cannot be met.
Generally, the conventional holographic interferometry measures interference fringes generated by interference of two coherent light beams, and when a physical quantity of a region through which object light passes changes, all the changes of the physical quantity are reflected as changes of the fringes, and the changes of the fringes are changes of the wavelength level of the light, so that the holographic interferometry measures very small changes of the physical quantity. When the temperature field changes, the air density changes, the refractive index of the air is further changed, the optical path of light propagating in the air is changed due to the change of the refractive index, after the optical path difference between two beams of coherent light changes, the phenomenon that interference fringes can shift can be observed, and the small change of the temperature field can be calculated by measuring the displacement of the fringes. The temperature field is measured by using the holographic interference measurement method, so that the temperature field detection device and the temperature field detection method based on the holographic interference measurement method have the advantages of nondestructive detection and high-precision detection, but the temperature field detection device and the temperature field detection method based on the holographic interference measurement method, which use visible light as a light source, have higher requirements on environmental stability and are easily interfered by the visible light due to the limitation of the wavelength of the visible light; and because the visible light wavelength is shorter, the space range of the detectable temperature field is also limited, and the range of the detectable temperature field variation is also limited; in addition, the detection accuracy is rapidly reduced when the environment is detected in the presence of smoke or flame, and the device cannot be used in a scene requiring darkness; the above-mentioned disadvantages make the temperature field detection means not applicable in large scale.
In order to solve the defects of the technical means, the infrared digital holography and the holographic interference metering means are combined by considering various excellent characteristics of the infrared digital holography, so that the anti-interference performance of the system can be greatly improved, the requirement of the system on the stability is reduced, the application range of the system is expanded, and the device and the method for measuring and monitoring the high-precision temperature field in real time in multiple scenes are obtained.
Disclosure of Invention
The invention aims to provide a transmission-type temperature field measuring device based on an infrared digital holographic technology, which not only exerts the advantages of high-precision measurement of a holographic interference metering means, but also combines the advantages of strong anti-interference performance of infrared digital holography and real-time detection.
In order to meet the technical requirements, the technical scheme adopted by the invention is as follows:
a transmission-type temperature field measuring device based on an infrared digital holographic technology comprises an infrared laser 1, a beam splitter I2, a beam expander I3, a beam expander II4, a lens I5, a lens II6, a reflector I7, a reflector II8, a lens III9, a lens IV10, a beam splitter II11, an infrared focal plane array imaging sensor 12, a microcomputer 13 and a U-shaped light-tight shell 14.
The infrared focal plane array imaging sensor 12 is arranged inside the U-shaped light-tight casing 14, and the microcomputer 13 is arranged outside the U-shaped light-tight casing; the microcomputer 13 is connected with the infrared focal plane array imaging sensor 12 through a data cable; the side wall of the U-shaped light-tight casing 14 is provided with two round holes for arranging the lens III9 and the lens IV10, the connecting line of the central points of the two round holes is superposed with the light path of the infrared object beam, and the lens III9 and the lens IV10 are fixed in the round holes on the side wall of the U-shaped light-tight casing; the infrared laser 1 emits infrared laser, the infrared laser is split into two beams of infrared laser by a beam splitter I2, one beam of infrared laser is expanded by a beam expander I3 and collimated into a parallel infrared laser beam by a lens I5, the parallel infrared laser beam reaches a reflector I7 and then reaches a lens III9 by reflection, and is emitted out of a U-shaped light-tight shell through a lens III9, then reaches a lens IV10 and then enters the U-shaped light-tight shell through a lens IV10, the beam reaches a beam splitter II11 after passing through the lens IV10, and the beam is called an infrared object beam; the temperature field measurement area is arranged between the lens III9 and the lens IV10 along the optical path direction.
The other infrared laser beam split by the beam splitter I2 is expanded by the beam expander II4 and collimated into a parallel infrared laser beam by the lens II6, and the parallel infrared laser beam reaches the reflector II8, is reflected by the reflector II8 and reaches the beam splitter II11, and is called an infrared reference beam.
The infrared object beam and the infrared reference beam form a series of interference fringes on the beam splitter II11, the series of interference fringes are called as an infrared holographic interference pattern, the infrared holographic interference pattern is received and recorded by the infrared focal plane array imaging sensor 12, the received optical signal is converted into an electric signal, and the electric signal is transmitted to the microcomputer 13 for storage and data processing.
The infrared laser 1 is an infrared laser with the emission laser wavelength of 10.64 mu m, and the attenuation effect of the infrared laser beam with the wavelength in the air is weak, so that the infrared laser beam can be prevented from being attenuated too fast in the air; meanwhile, the infrared laser beam with the wavelength is different from the infrared light with the wavelength of 780nm-7000nm emitted by the flame, and the influence of the infrared light emitted by the flame on the interference pattern can be eliminated by means of image processing, so that the device can accurately measure the temperature field distribution of the flame.
Furthermore, the infrared laser 1 of the present invention selects an infrared laser with a wavelength of 10.64 μm, so that the penetrability of the object light beam and the reference light beam to the particle field such as smoke is greatly improved compared with the laser beam using the visible light band, and the device can accurately measure the temperature field distribution in the environment with the particle field such as smoke.
The inner side of the side wall of the U-shaped light-tight casing 14 is pure black to absorb infrared light entering the U-shaped light-tight casing 14 and prevent the infrared light from reflecting back and forth inside the U-shaped light-tight casing 14 and being received by the infrared focal plane array imaging sensor 12 to affect the reception of the interference fringe pattern by the infrared focal plane array imaging sensor 12.
The lens III9 and the lens IV10 are made of germanium materials, so that the interference pattern is prevented from being influenced by visible light entering an optical path.
The infrared object beam and the infrared reference beam are parallel light after beam expansion, and the maximum difference value of optical paths through which the infrared object beam and the infrared reference beam pass is 1 cm.
The infrared hologram is received by the infrared focal plane array imaging sensor 12, the sensitivity of the infrared focal plane array imaging sensor 12 is selected to match the power of the infrared laser 1, and the sensing waveband needs to match the wavelength of the infrared laser 1, i.e. the waveband of the selected wavelength of the infrared laser 1 can be sensed, so as to achieve a better imaging effect.
The infrared focal plane array imaging sensor 12 is replaced by a CCD image sensor with an induction wave band containing the wavelength wave band of the infrared laser 1, and the function realization of the whole device is not influenced.
The microcomputer 13 can filter the received infrared hologram and redisplay the processed hologram, so that the device can measure the temperature field distribution of flame and can measure the temperature field distribution in the environment with smoke and other particle fields.
A transmission-type temperature field measuring method based on infrared digital holographic technology relies on the basic theory of holographic interference measurement, and can calculate the change value of a temperature field by measuring and calculating the displacement of fringes according to the phenomenon that interference fringes can be displaced caused by the tiny change of the temperature field, and comprises the following steps:
(1) the infrared laser 1 is turned on, the interference pattern generated at this time on the beam splitter II11 is collected by the CCD image sensor, and the collected interference pattern, which is called an initial temperature field infrared hologram, is stored in the microcomputer.
(2) Placing the desired measured temperature field region in a recessed region of a U-shaped light-tight enclosure (14) between lens III9 and lens IV10, and leaving the desired measured temperature field region in the light path; generally, since the optical path used is a transmission type optical path, the region required to measure the temperature field needs to be transparent.
(3) After the placed measured object is stable, the CCD image sensor is used for collecting the interference pattern generated on the beam splitter II11 at the moment, and the collected interference pattern is stored in the microcomputer, wherein the interference pattern is called as a changed temperature field infrared hologram.
(4) And performing image subtraction processing on the initial temperature field infrared hologram and the changed temperature field infrared hologram, and calculating the displacement d of each interference fringe in the infrared holograms before and after the temperature field changes.
(5) The fringe order N of each interference fringe is calculated from the obtained fringe displacement d.
(6) Combining the relationship between the gas refractive index and the gas density described by the combination of the fringe interference level N and the Gradson-Del relationship with an ideal gas state equation to obtain a mathematical relational expression of temperature and fringe level, obtaining the temperature of each point through mathematical calculation, and reconstructing the temperature field distribution of the temperature field measurement area by integrating the temperature information of each point.
Further, the real-time monitoring of the temperature field is realized by repeatedly executing the steps 3 to 6.
Furthermore, the temperature field region to be measured in step 2 may be the interior of a non-solid transparent object such as air, or may be the region above the surface of a solid object; when the temperature field area to be measured contains the solid object, the solid object can not block the transmission of the infrared object beam.
Further, in step 3, when the object to be measured in the temperature field measurement area is a flame, the collected interference pattern needs to be filtered, and the adopted filter is a band-pass filter, so that the influence of infrared light emitted by the flame on the interference pattern is eliminated.
Further, in step 1 and step 3, when smoke exists in the temperature field measurement area, the collected interference pattern needs to be filtered, and the adopted filter is a low-pass filter to remove image noise formed by the smoke.
Further, in step 4, the calculation method for calculating the displacement d of the interference fringes at each point in the infrared hologram before and after the temperature field changes is to count the number of pixels where the fringes move, and combine the width of each pixel to calculate the displacement d of the interference fringes.
Compared with the prior art, the invention has the following advantages:
(1) the invention applies the infrared digital holographic technology to the transmission type temperature field measurement, compared with the temperature field measured by the prior visible light digital holographic interference measurement means, the infrared light wavelength is longer than the visible light wavelength, so that the whole temperature field measurement system can realize the normal measurement of the temperature field under a larger vibration amplitude, and the requirement of the system on the environmental stability is reduced.
(2) Compared with the temperature field measured by the conventional visible light digital holographic interference metering means, the infrared digital holographic technology is applied to the transmission type temperature field measurement, and the penetration force of infrared light to the particle field such as smoke is far stronger than that of visible light, so that the temperature field measurement device and the method can realize accurate measurement of the temperature field in the environment with the particle field such as smoke as interference quantity.
(3) The invention applies the infrared digital holographic technology to the transmission type temperature field measurement, compared with the temperature field measured by the prior visible light digital holographic interference measurement method, because the infrared light with the wavelength of 10.64 mu m is selected as the light source and is different from the infrared light with the wavelength of 780nm-7000nm emitted by the flame, the influence of the infrared light emitted by the flame on the interference pattern can be eliminated by means of image processing, thereby the device can more accurately measure the temperature field distribution of the flame.
(4) According to the transmission type temperature field measuring device based on the infrared digital holographic technology, the whole device is protected and fixed by the U-shaped light-tight shell, the inner side of the side wall of the used U-shaped light-tight shell is pure black, and only two round holes are reserved on the device and are embedded with the lens lll and the lens IV made of germanium materials, so that the interference of visible light is avoided, and the temperature field measuring precision is improved.
(5) The invention relates to a transmission-type temperature field measurement method based on an infrared digital holographic technology, which adopts an image subtraction method to process an initial temperature field infrared hologram and a changed temperature field infrared hologram, takes the number of pixel points as a basic unit of the displacement of stripes, and combines the size of the pixel points to quickly calculate the displacement of the stripes and rebuild the temperature field distribution according to the displacement of the stripes; compared with the temperature field reconstruction method such as the conventional algebraic reconstruction method and the like, the method has the advantages of small operand and high temperature field reconstruction speed.
Drawings
Other features, objects and advantages of the invention will become more apparent upon reading of the detailed description of non-limiting embodiments with reference to the following drawings:
fig. 1 is a schematic overall structure diagram of an embodiment of the present invention:
in the figure: the system comprises an infrared laser 1, a beam splitter 2, a beam expander 3, a beam expander 4, a lens 5, a lens 6, a lens 7, a reflector 8, a reflector II, a lens III9, a lens IV10, a beam splitter 11, an infrared focal plane array imaging sensor 12, a microcomputer 13 and a light-tight shell 14.
Fig. 2 is a schematic three-dimensional view of a U-shaped opaque housing in an embodiment of the invention.
Fig. 3 is a schematic view of the working process of the present invention.
Fig. 4 is a diagram showing the relative positions of the planar heating plate as the target object to be measured and the infrared object beam in embodiment 3 of the present invention, wherein the arrow line is a schematic diagram of the bottom of the propagation range of the infrared object beam, the arrow direction indicates the propagation direction of the infrared object beam, and the three-dimensional coordinate is an indicator of the three-dimensional direction.
FIG. 5 is an example of the initial temperature field infrared hologram recorded in operation step 1 in example 3 of the present invention.
FIG. 6 is an example of the changed temperature field infrared hologram recorded in operation step 3 in example 3 of the present invention.
Detailed Description
The present invention is further described in detail with reference to the following specific examples, but the scope of the present invention is not limited to the above description.
Example 1
As shown in fig. 1, this embodiment provides a transmissive temperature field measuring device based on infrared digital holography, which includes an infrared laser 1, a beam splitter I2, a beam expander I3, a beam expander II4, a lens I5, a lens II6, a mirror I7, a mirror II8, a beam splitter II11, an infrared focal plane array imaging sensor 12, which is disposed inside a U-shaped opaque housing 14, a microcomputer 13 disposed outside the U-shaped opaque housing and connected to the infrared focal plane array imaging sensor 12 through a data cable, and a lens III9 and a lens IV10 disposed on a side wall of the U-shaped opaque housing.
The infrared laser 1 selects an infrared laser with the emission laser wavelength of 10.64 mu m, the attenuation effect of the infrared laser beam with the wavelength in the air is weak, the infrared laser beam can be prevented from being attenuated too fast in the air, meanwhile, the wavelength of the infrared laser beam is different from the wavelength of infrared light emitted by flame and with the wavelength of 780nm-7000nm, the influence of the infrared light emitted by the flame on an interference pattern can be eliminated by means of image processing, and therefore the device can accurately measure the temperature field distribution of the flame. The infrared laser 1 emits infrared laser, and is split into two beams of infrared laser by a beam splitter I2, after being expanded by a beam expander I3, one beam of infrared laser is collimated into one beam of parallel infrared laser beam by a lens I5, the parallel infrared laser beam reaches a reflector I7, reaches a lens III9 after being reflected, and is emitted out of a U-shaped light-tight shell through a lens III9, then reaches a lens IV10, and then enters the U-shaped light-tight shell through a lens IV10, the beam reaches a beam splitter II11 after passing through a lens IV10, and the beam is called an infrared object beam; another infrared laser beam split by the beam splitter I2 is expanded by a beam expander II4 and collimated into a parallel infrared laser beam by a lens II6, and the parallel infrared laser beam reaches a reflector II8, is reflected by a reflector II8 and reaches a beam splitter II11, and is called an infrared reference beam; a temperature field measuring area is arranged between the lens III9 and the lens IV10 along the light path direction; the infrared object beam and the infrared reference beam form a series of interference fringes on the beam splitter II11, and the series of interference fringes is called an infrared holographic interference pattern, and the infrared holographic interference pattern is received and recorded by the infrared focal plane array imaging sensor 12.
The sensitivity of the infrared focal plane array imaging sensor 12 is selected to match the power of the infrared laser 1, and the sensing waveband of the infrared focal plane array imaging sensor needs to match the wavelength of the infrared laser 1, namely, the infrared focal plane array imaging sensor can sense the waveband of the selected wavelength of the infrared laser 1, so that a good imaging effect is achieved. The infrared focal plane array imaging sensor 12 converts the received optical signal into an electrical signal, and then transmits the electrical signal to a microcomputer for storage and data processing. Up to this point, the temperature information of the measured temperature field is stored in the microcomputer.
The infrared laser 1, the beam splitter I2, the beam expander I3, the beam expander II4, the lens I5, the lens II6, the reflector I7, the reflector II8, the beam splitter II11 and the infrared focal plane array imaging sensor 12 are fixed inside the U-shaped light-tight shell 14, so that the stability of the device is enhanced, and the imaging quality is guaranteed.
The model of the infrared laser 1 is CO2-ULR-75, the model of the infrared focal plane array imaging sensor 12 is cube817, and the lens III9 and the lens IV10 are germanium lenses.
The inner side of the side wall of the U-shaped light-tight housing 14 is pure black to absorb infrared light entering the U-shaped light-tight housing 14, and to prevent the infrared light from reflecting back and forth inside the U-shaped light-tight housing 14 to be received by the infrared focal plane array imaging sensor 12 and affecting the reception of the interference fringe pattern by the infrared focal plane array imaging sensor 12.
The infrared focal plane array imaging sensor 12 described in this embodiment may also be replaced by a CCD image sensor whose sensing band includes the wavelength band of the infrared laser 1.
Example 2
The embodiment provides a transmission type temperature field measuring method based on an infrared digital holographic technology, which specifically comprises the following steps:
step 1: the infrared laser 1 is turned on, the interference pattern generated at this time on the beam splitter II11 is collected by the CCD image sensor, and the collected interference pattern, which is called an initial temperature field infrared hologram, is stored in the microcomputer.
Step 2: the desired temperature field measurement area, which in this embodiment is the temperature field distribution of the air in the temperature field measurement area and the slight change in its temperature, is placed in the recessed area of the U-shaped light-tight enclosure 14 between lens III9 and lens IV10, and is in the light path.
And step 3: after the temperature field area to be measured is stable, the CCD image sensor is used for collecting the interference pattern generated on the beam splitter II11 at the moment, and the collected interference pattern is stored in the microcomputer, wherein the interference pattern is called as a temperature field infrared hologram after change.
And 4, step 4: and performing image subtraction processing on the initial temperature field infrared hologram and the changed temperature field infrared hologram, and calculating the displacement d of each interference fringe in the infrared holograms before and after the temperature field changes.
And 5: the fringe order N of each interference fringe is calculated from the obtained fringe displacement d.
The method for calculating the fringe order N is as follows:
taking a certain stripe as an example, when the stripe interval in the initial temperature field infrared hologram is x, the stripe order N satisfies the relationship with the stripe displacement d and the stripe interval x in the initial temperature field infrared hologram: n = d/x. Since the fringe spacing x and the fringe displacement d in the initial temperature field infrared hologram can be calculated by counting the number of pixels and combining the width of each pixel, the fringe order N can be obtained by the relational expression.
Step 6: and calculating the density field of the temperature field measurement area according to the obtained fringe interference level N and the relationship between the gas refractive index and the gas density described by the Gredston-Del relationship, calculating the temperature of each point by an ideal gas state equation, and reconstructing the temperature field distribution of the air in the temperature field measurement area by integrating the temperature information of each point.
The method for calculating the temperature of each point is as follows:
the relationship between the refractive index of a gas and the density of the gas described by the Gredston-Dall relationship is:
the ideal gas state equation is:
the combination of the above two equations yields a refractive index versus temperature relationship:
through mathematical calculations, a mathematical relationship between temperature and fringe order N can be obtained:
wherein K is the fringe order, mu is the air molar mass, R is the gas universal constant, P is the gas pressure, T0 is the ambient temperature of the environment where the device is located, lambda is the wavelength of the light wave, and N is the fringe order obtained in step 5; to this end, the temperature may be calculated.
Further, the real-time monitoring of the temperature field is realized by repeatedly executing the steps 3 to 6.
Furthermore, the distribution of the temperature fields in different time can be compared, so that the tiny change of the air temperature value at each position in the temperature field detection area in a certain time range can be obtained.
Further, when the object to be measured placed in the light-tight enclosure 14 in step 2 is a non-transparent object, the object to be measured cannot block the propagation of the infrared object beam, in which case only the temperature field distribution above the object surface can be measured.
Further, in step 3, when the object to be measured in the temperature field measurement area is a flame, the collected interference pattern needs to be filtered, and the adopted filter is a band-pass filter, so that the influence of infrared light emitted by the flame on the interference pattern is eliminated.
Further, in step 1 and step 3, when smoke exists in the temperature field measurement area, although the infrared light has strong penetrability to the particle field such as smoke, the situation that the infrared light is shielded by the particle field and the temperature field cannot be measured does not occur, the particle field is recorded as image noise together with the interference pattern, the collected interference pattern needs to be filtered, and the adopted filter is a low-pass filter to remove the image noise formed by the smoke.
Example 3
This embodiment provides a transmission type temperature field measuring apparatus based on the infrared digital holography technology in accordance with the embodiment given in embodiment 1 and a transmission type temperature field measuring method based on the infrared digital holography technology in accordance with the embodiment given in embodiment 2, which measure the temperature field distribution above the surface of a flat heating plate. The planar heating plate is placed in the temperature field measurement area according to the requirements of the foregoing specification, and cannot block the propagation of the infrared object beam, as shown in fig. 3, the upper surface of the planar heating plate is tangent to the bottom of the propagation range of the infrared object beam.
The specific measurement steps are as follows:
step 1: the infrared laser 1 is turned on, the CCD image sensor is used to collect the infrared hologram of the initial temperature field generated at this time on the beam splitter II11, and the collected interference pattern is stored in the microcomputer.
Step 2: the flat heated plate is placed in the recessed area of the U-shaped light-tight enclosure 14 between lens III9 and lens IV10 with the upper surface of the flat heated plate tangent to the bottom of the infrared object beam propagation range.
And step 3: after the whole device is stabilized, the CCD image sensor is used for collecting the changed temperature field infrared hologram generated on the beam splitter II11 at the moment, and the collected interference pattern is stored in the microcomputer.
And 4, step 4: and performing image subtraction processing on the initial temperature field infrared hologram and the changed temperature field infrared hologram, and calculating the displacement d of each interference fringe in the infrared holograms before and after the temperature field changes.
And 5: the fringe order N of each interference fringe is calculated from the obtained fringe displacement d.
Step 6: and calculating the density field of the temperature field measurement area according to the obtained fringe interference level N and the relationship between the gas refractive index and the gas density described by the Gredston-Del relationship, calculating the temperature of each point by an ideal gas state equation, and reconstructing the temperature field distribution of the air in the temperature field measurement area by integrating the temperature information of each point.
Further, in the whole temperature field measuring process, the steps 3 to 6 can be automatically repeated, so that the real-time monitoring of the temperature field above the upper surface of the planar heating plate in the heating state is realized.
FIG. 5 is an example of the initial temperature field infrared hologram recorded in operation step 1 in example 3 of the present invention.
FIG. 6 is an example of the changed temperature field infrared hologram recorded in operation step 3 in example 3 of the present invention.
As can be seen from comparing fig. 5 and 6, when the planar heating plate in a heated state is placed in the temperature field measurement area, each interference fringe is obviously displaced, at this time, any point on the fringe in fig. 6 may be selected, and compared with fig. 5, the fringe displacement of the point is obtained by a method of counting pixel points, and the current temperature value of the point is calculated according to the methods of steps 4 to 6, and the point is taken as an example, the same method may be applied to the calculation of the temperature value of any point on fig. 6, thereby realizing the measurement of the entire temperature field in the area photographed in fig. 6.
Claims (10)
1. A transmission-type temperature field measuring device based on infrared digital holographic technology is characterized in that: the infrared laser system comprises an infrared laser (1), a beam splitter I (2), a beam expander I (3), a beam expander II (4), a lens I (5), a lens II (6), a reflector I (7), a reflector II (8), a lens III (9), a lens IV (10), a beam splitter II (11), an infrared focal plane array imaging sensor (12), a microcomputer (13) and a light-tight shell (14);
the infrared focal plane array imaging sensor (12) is arranged inside the U-shaped light-tight casing (14), and the microcomputer (13) is arranged outside the U-shaped light-tight casing; the microcomputer (13) is connected with the infrared focal plane array imaging sensor (12) through a data cable; two round holes for arranging a lens III (9) and a lens IV (10) are arranged on the side wall of the U-shaped light-tight shell (14), the connecting line of the central points of the two round holes is superposed with the light path of the infrared object beam, and the lens III (9) and the lens IV (10) are fixed in the round holes on the side wall of the U-shaped light-tight shell;
the infrared laser (1) emits infrared laser, the beam is split into two beams of infrared laser by a beam splitter I (2), one beam of infrared laser is collimated into a beam of parallel infrared laser beam by a lens I (5) after being expanded by a beam expander I (3), the parallel infrared laser beam reaches a lens III (9) after reaching a reflector I (7) through reflection, and is emitted out of a U-shaped opaque shell through the lens III (9), then reaches a lens IV (10), and then enters the U-shaped opaque shell through the lens IV (10), the beam reaches a beam splitter II (11) after passing through the lens IV (10), and the beam is called as an infrared object beam; a temperature field measurement area is arranged between the lens III (9) and the lens IV (10) along the light path direction;
another infrared laser beam split by the beam splitter I (2) is collimated into a parallel infrared laser beam by the lens II (6) after being expanded by the beam expander II (4), and the parallel infrared laser beam reaches the reflector II (8), is reflected by the reflector II (8) and then reaches the beam splitter II (11), and is called an infrared reference beam;
the infrared object beam and the infrared reference beam form a series of interference fringes on the beam splitter II (11), the series of interference fringes are called as an infrared holographic interference pattern, the infrared holographic interference pattern is received and recorded by an infrared focal plane array imaging sensor (12), received optical signals are converted into electric signals, and then the electric signals are transmitted to a microcomputer (13) for storage and data processing.
2. The transmissive temperature field measuring device based on infrared digital holography as claimed in claim 1, wherein: the infrared laser (1) is an infrared laser with the wavelength of 10.64 mu m.
3. The transmissive temperature field measuring device based on infrared digital holography as claimed in claim 1, wherein: the lens III (9) and the lens IV (10) are germanium lenses; the inner side of the side wall of the U-shaped light-tight casing (14) is pure black.
4. The transmissive temperature field measuring device based on infrared digital holography as claimed in claim 1, wherein: the infrared focal plane array imaging sensor (12) is replaced by a CCD image sensor with an induction waveband containing the wavelength waveband of the infrared laser (1).
5. The transmissive temperature field measuring device based on infrared digital holography as claimed in claim 1, wherein: the infrared object beam and the infrared reference beam are parallel light after beam expansion, and the maximum difference value of optical paths through which the infrared object beam and the infrared reference beam pass is 1 cm.
6. The method for measuring the temperature field by using the device as claimed in any one of claims 1 to 5, which is characterized by comprising the following steps:
(1) turning on an infrared laser (1), collecting an interference pattern generated on a beam splitter II (11) by using a CCD image sensor or an infrared focal plane array imaging sensor (12), and storing the collected interference pattern in a microcomputer, wherein the interference pattern is called as an initial temperature field infrared hologram;
(2) placing the temperature field area to be measured in a concave area of a U-shaped light-tight shell (14) between a lens III (9) and a lens IV (10), and enabling the temperature field area to be measured to be in a light path;
(3) after the temperature field area to be measured is stable, collecting an interference pattern generated on a beam splitter II (11) by using a CCD image sensor or an infrared focal plane array imaging sensor (12), and storing the collected interference pattern in a microcomputer, wherein the interference pattern is called as a changed temperature field infrared hologram;
(4) performing image subtraction processing on the initial temperature field infrared hologram and the changed temperature field infrared hologram, and calculating the displacement d of each interference fringe in the infrared holograms before and after the temperature field is changed;
(5) calculating the fringe order N of each interference fringe according to the obtained fringe displacement d;
(6) combining the relationship between the gas refractive index and the gas density described by the combination of the fringe interference level N and the Gradson-Del relationship with an ideal gas state equation to obtain a mathematical relational expression of temperature and fringe level, obtaining the temperature of each point through mathematical calculation, and reconstructing the temperature field distribution of the temperature field measurement area by integrating the temperature information of each point.
7. The method of claim 6, further comprising: and (5) repeatedly executing the steps (3) to (6) to realize real-time monitoring of the temperature field.
8. The method of claim 6, further comprising: and (3) when the object to be measured in the temperature field measurement area is flame, filtering the acquired interference pattern, wherein the adopted filter is a band-pass filter, and the influence of infrared light emitted by the flame on the interference pattern is eliminated.
9. The method of claim 6, further comprising: in the step (1) and the step (3), when smoke exists in the temperature field measurement area, the collected interference pattern needs to be filtered, the adopted filter is a low-pass filter, and image noise formed by the smoke is removed.
10. The method of claim 6, further comprising: the method for calculating the displacement d of the interference fringes of each point in the infrared hologram before and after the temperature field change comprises the following steps: the number of pixels where the fringe moves is counted, and the width of each pixel is combined, so that the displacement d of the interference fringe is calculated.
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