CN103913288A - Rainbow schlieren measurement imaging system and method - Google Patents

Abstract

A rainbow schlieren measurement imaging system and method, the system includes a light source for outputting optical signals; and a first focusing lens, a slit stop, a first collimating lens, Flow field observation area, second focusing lens, rainbow filter, second collimating lens, digital microarray mirror, converging lens and three-color single-point photodetector; compression connected with electrical signal of three-color single-point photodetector The algorithm module is used for reconstructing the color image, and calculates the density change distribution of the observed flow field according to the rainbow schlieren calculation method of the image. The present invention combines compressed sensing theory with rainbow schlieren measurement, and creatively proposes a sparse rainbow schlieren measurement method, which has the characteristics of high throughput, high signal-to-noise ratio, fast and flexible, and is suitable for conventional light intensity, weak light, and weak light , ultra-weak light and single-photon rainbow schlieren measurement method, which is a sparse rainbow schlieren measurement method with a large dynamic range.

Description

Rainbow schlieren measurement imaging system and method

technical field

The invention relates to the field of rainbow schlieren measurement and imaging, in particular to a system and method for rainbow schlieren measurement and imaging based on compressed sensing.

Background technique

Since Topler first used the schlieren measurement technique to quantitatively measure the flow field, the schlieren has gradually become a routine measurement instrument in wind tunnel tests. Fluids are measured using schlieren, which offers high sensitivity and image resolution compared to shadow measurement techniques. The disadvantage is that it is difficult to eliminate the optical path error, the image contrast is poor, and it is difficult to quantitatively measure the airflow. However, color schlieren imaging systems and analysis methods are being developed as a measurement technique for schlieren deficiency. In 1952, British Holder, D.W. and North, R.J. first invented the color schlieren measurement method. Compared with the schlieren measurement technology, it has high sensitivity and high image contrast; in the schlieren field, the solid appears black, and the gas flow appears colorful. Boundary conditions simplify post-measurement and analysis; color schlieren makes image recording easier. After a long period of development, Holder and North proposed a color schlieren measurement method based on prisms, slits and three-color filters; Cords proposed a color schlieren measurement method based on filters and slits; Kaspar proposed a multicolor filter color schlieren measurement method. Schlieren measurement method. In the last century, NASA in the United States, ESA in Europe and JAXA in Japan have used the rainbow schlieren method to measure flame structures in short-term microgravity environments such as Lewis drop towers, Japanese microgravity falling wells, and free-falling objects. In recent years, my country has also carried out research work on the measurement of flame structure by rainbow schlieren method. The Institute of Mechanics of the Chinese Academy of Sciences has cooperated with Polish scientists to carry out related research. Interference methods are often used to obtain flow field density in wind tunnel tests. Interferometry is a strict quantitative measurement technique. The refractive index distribution of the flow field can be strictly calculated from the flow field interferogram, and the flow field density and other hydrodynamic and aerodynamic parameters can be calculated from the Gladstone-Dell constant formula. In terms of shock wave wind tunnel and ballistic target tests, technologies such as Mach interference, holographic interference and rainbow schlieren interference have been applied. In these methods, the rainbow schlieren optical path is used, and this optical path is used as the optical path of the object beam. Experimental interferograms were obtained by these methods and quantitative values of the density of the flow field were obtained.

Rainbow schlieren imaging technology also has wide application value in the field of combustion. Combustion is a phenomenon in which a fuel and an oxidant undergo a strong chemical reaction, and the process involves complex interactions such as chemical reaction, flow, heat and mass transfer. The diagnostic technology in the microgravity combustion experiment requires qualitative or quantitative measurement of the temperature, flow field, gas composition and concentration, and solid particle composition and concentration of the combustion process, and analyzes the combustion phenomenon through data processing. When processing the data obtained by the rainbow schlieren method, the illuminance or contrast of the rainbow schlieren image is calculated from the light field distribution image, and the laser deflection angle is obtained, and the refractive index distribution of the flow field is calculated, and then the flow field is calculated. Density change or density value, left after calculating the temperature distribution of the flow field.

Rainbow schlieren imaging technology uses the disturbance of airflow to light waves to convert airflow changes into images. With the development of wind tunnel airflow research, especially the research of high-speed shock waves, rainbow schlieren imaging technology has been widely used. In the application of anti-stealth aircraft imaging, the combination of infrared rainbow schlieren imaging and passive optical ranging technology can realize the imaging and positioning of stealth aircraft. The vortex with a huge range and a long retention time can indirectly measure the stealth aircraft by measuring the airflow trajectory disturbed by the stealth aircraft.

Compressed sensing was proposed by researchers such as E.J.Candes, J.Romberg, T.Tao and D.L.Donoho in 2004. As early as the last century, the French mathematician Prony proposed a sparse signal recovery method. This method is to estimate the sparseness by solving the eigenvalue problem. The non-zero amplitude and corresponding frequency of the triangular polynomial; B. Logan first proposed a sparse constraint method based on the minimization of the L1 norm. The subsequently developed compressed sensing theory is to combine the L1 norm minimization sparse constraints with random matrices to obtain the best results of sparse signal reconstruction performance. Compressed sensing is based on the compressibility of signals, through low-dimensional space, low resolution, under Nyquist samples uncorrelated observations of data to realize the perception of high-dimensional signals. It is widely used in information theory, image processing, earth science, optical/microwave imaging, pattern recognition, wireless communication, atmospheric science, earth science, physical astronomy, high-precision optical measurement and other disciplines.

Compressed sensing theory is to perform sampling and compression at the same time, making good use of the prior knowledge that natural signals can be represented under a certain sparse basis, and can achieve sub-sampling far below the Nyquist/Shannon sampling limit, and can Nearly perfect reconstruction of signal information. Its most widely used is single-pixel camera technology, which can use a point detector instead of an area array detector to complete all detection tasks. If this technology is applied in the field of optical rainbow schlieren measurement, it will definitely reduce the detection dimension , to avoid the optical noise and electrical noise brought by the area array detector, and to use the digital micromirror device DMD, which is a passive optical component, which will not bring any noise to the signal, and the detector does not need a preamplifier any more , In addition, the system can also achieve high-speed sampling of 23kHz, which is beyond the reach of traditional area array detectors. In addition, the robust reconstruction algorithm will surely lead to more potential applications.

Contents of the invention

The purpose of the present invention is to apply the compressed sensing theory to the field of fluid rainbow schlieren measurement, thereby providing a rainbow schlieren measurement imaging system and method based on compressed sensing.

In order to achieve the above object, the present invention provides a rainbow schlieren measurement and imaging system, which includes: a light source for outputting optical signals; and a first focusing lens and a slit diaphragm sequentially arranged along the output optical signal path of the light source , a first collimating lens, a second focusing lens, a rainbow filter, a second collimating lens, a digital microarray mirror, a converging lens and a three-color single-point photodetector, and the flow field observation area is located between the first collimating lens and Between the second focusing lens; the compression algorithm module, which is connected to the three-color single-point photodetector with electrical signals, is used to reconstruct the color image, and calculates the density change distribution of the observed flow field according to the rainbow schlieren calculation method of the image.

Further, the slit diaphragm includes a slit and a pinhole diaphragm, and the diaphragm is a diaphragm part that can be adjusted or replaced manually or electrically, or a standard diaphragm with a fixed size.

To achieve the above object, the present invention provides a rainbow schlieren measurement imaging system, which includes: a light source for outputting optical signals; and a first focusing lens, a dispersion prism, a second A collimating lens, a second focusing lens, a slit, a second collimating lens, a digital microarray mirror, a converging lens and a three-color single-point photodetector, the flow field observation area is located between the first collimating lens and the second focusing between the lenses;

The compression algorithm module is electrically connected with the three-color single-point photodetector, and is used to reconstruct the color image, and calculates the density change distribution of the observed flow field according to the rainbow schlieren calculation method of the image.

Further, it also includes a reflector unit, which includes a first reflector and a second reflector, the first reflector is arranged between the first collimator lens and the flow field observation area, and is used to align the first The outgoing light of the collimating lens is reflected into the flow field observation area; the second reflector is arranged between the flow field observation area and the second focusing lens, and is used to reflect the outgoing light of the flow field observation area to the second focusing lens.

Further, the reflectors in the reflector unit are broadband dielectric film reflectors, metal film reflectors, dielectric laser line reflectors or cold and heat reflectors.

Further, the light source is a white light source.

Further, the white light source is a white light source composed of a xenon lamp or a halogen lamp, or an ultra-broadband light source using laser-driven light source technology, with a wavelength range of 170nm-2100nm, or a light source that uses multiple excitation sources to drive a light guide to emit light.

Further, the digital microarray reflector adopts reflective and transmissive liquid crystal spatial light modulators.

Further, the three-color single-point photodetector is a visible light photodetector or a single photon detector.

Further, the three-color single-point photodetector is a single-photon detector, and the single-photon detector is an optical avalanche diode, a solid-state photomultiplier tube or a superconducting single-photon detector.

Further, the three-color single-point detector includes three independent photodetection elements, and a microlens and a red, blue, and green three-color filter are installed at the front end of each photoelectric detection element to detect light of three wavelengths of red, blue, and green respectively. Then the color image is reconstructed by the three-color palette algorithm.

Further, the digital microarray reflector is synchronized with the three-color single-point photodetector, and each time the micromirror array in the digital microarray reflector is flipped, the three-color single-point photodetector is Accumulate and detect all light intensities within the flipping time interval to realize photoelectric signal acquisition and conversion, and then transmit the electrical signal to the compression algorithm module.

In order to solve the above problems, the present invention also provides a rainbow schlieren measurement imaging method, which includes:

Step 1. The light source outputs an optical signal, and after being focused by the first focusing lens, the stray background light is filtered through the slit diaphragm;

Step 2, after being collimated by the first collimator lens, the beam is incident on the flow field observation area;

Step 3, after the light beam emitted from the flow field observation area is converged by the second focusing lens, the deflected light is converted into a color image of different colors at the focal point of the lens through a rainbow filter;

Step 4, after being collimated by the second collimating lens, it is incident on the digital microarray reflector, and the light field is randomly modulated;

Step 5, after being converged by the converging lens, it is incident on the three-color single-point photodetector, and the three-color single-point photodetector sends the converted electrical signal to the compression algorithm module;

In step 6, the color image is reconstructed through the compression algorithm module, and the density change distribution of the observed flow field is calculated by the rainbow schlieren calculation method on the image.

Further, in the step 2, the light beam collimated by the first collimating lens beam expander is reflected by the first mirror and then enters the flow field observation area.

Further, in the step 3, the light beam emitted from the flow field observation area is reflected by the second mirror to the second focusing lens for convergence.

The present invention combines compressed sensing theory with rainbow schlieren measurement, and creatively proposes a sparse rainbow schlieren measurement method, which has the characteristics of high throughput, high signal-to-noise ratio, fast and flexible, and is suitable for conventional light intensity, weak light, and weak light , ultra-weak light and single-photon rainbow schlieren measurement method, which is a sparse rainbow schlieren measurement method with a large dynamic range.

The combination of compressed sensing and rainbow schlieren measurement can realize high-throughput rainbow schlieren measurement. The classic rainbow schlieren measurement technology has a low signal-to-noise ratio in the measurement process of flame, wind tunnel, air flow, etc., especially in high-speed, ultra- In the measurement of high-speed flow field, the environmental background interference is relatively large. Using this high-throughput feature, the signal-to-noise ratio of rainbow schlieren measurement can be improved.

Through this method, the combination of single-photon detector and sparse undersampling is used to realize the quantum rainbow schlieren measurement method, and the physical characteristics of the long-distance flow field can be obtained.

Sparse rainbow schlieren measurement is an important development direction in the field of high-precision optical measurement. It has significant advantages in heat flow and gas flow, and is a non-contact high-precision optical measurement technology.

Description of drawings

FIG. 1 is a schematic structural diagram of the rainbow schlieren measurement imaging system of the present invention.

FIG. 2 is a structural schematic diagram of the rainbow schlieren measurement and imaging system based on the compressive sensing of the prism and slit structure of the schlieren measurement and imaging system of the present invention.

Among them: light source 1; first focusing lens 2; slit stop 3; first collimating lens 4; first mirror 5; smooth observation area 6; second mirror 7; second focusing lens 8; rainbow filter 9; second collimating lens 10; digital microarray mirror 11; converging lens 12; three-color single-point photodetector 13; compression algorithm module 14; dispersion prism 15; slit 16.

Detailed ways

Embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings. It should be noted that, in the case of no conflict, the embodiments in the present application and the features in the embodiments can be combined arbitrarily with each other.

The present invention combines compressed sensing theory with rainbow schlieren measurement, and creatively proposes a sparse rainbow schlieren measurement method, which has the characteristics of high throughput, high signal-to-noise ratio, fast and flexible, and is suitable for conventional light intensity, weak light, and weak light , ultra-weak light and single-photon rainbow schlieren measurement method, which is a sparse rainbow schlieren measurement method with a large dynamic range. The rainbow schlieren measurement imaging system and method based on compressed sensing of the present invention adopts the principle of compressed sensing (Compressive Sensing, referred to as CS), which can be randomly sampled with fewer data samples (far lower than Nyquist / the limit of Shannon's sampling theorem) perfectly recovers the original signal. First, use prior knowledge to select a suitable sparse basis Ψ, so that the point spread function x is transformed by Ψ to obtain x' which is the most sparse; under the condition of known measured value vector y, measurement matrix A and sparse basis Ψ, establish Starting from the mathematical model y=AΨx'+e, the convex optimization is carried out through the compressed sensing algorithm, and after obtaining x', the Invert x; then calculate the deflection angle through the offset, and then calculate the flow field density, and then calculate the temperature distribution of the flow field; at present, the rainbow schlieren measurement is based on the prism slit method and the filter slit method , three-color filter hair, multi-color filter and other methods.

The above is the description of the compressive sensing theory algorithm and the rainbow schlieren measurement method, and the imaging measurement system of the present invention will be described in detail below in combination with the compressive sensing principle.

The first embodiment of the rainbow schlieren measurement imaging system

Referring to Fig. 1, the rainbow schlieren measurement and imaging system of this embodiment includes a light source 1 and a first focusing lens 2, a slit stop 3, a first collimating lens 4, a first Two focusing lenses 8 , a rainbow filter 9 , a second collimating lens 10 , a digital microarray mirror 11 , a converging lens 12 and a three-color single-point photodetector 13 . The smooth viewing area 6 is located between the first collimating lens 4 and the second focusing lens 8 . The compression algorithm module 14 is electrically connected with the three-color single-point photodetector 13, and is used for reconstructing the color image, and calculates the density change distribution of the observed flow field according to the rainbow schlieren calculation method of the image.

As shown in FIG. 1 , in order to adjust the path of the optical signal output by the light source 1, a reflector unit is also included in this embodiment. The reflector unit includes a first reflector 5 and a second reflector 7, and the first reflector 5 is arranged on the second reflector 7. Between a collimating lens 4 and the flow field observation area 6, it is used to reflect the outgoing light of the first collimating lens 4 into the flow field observation area 6; the second reflector 7 is arranged at the flow field observation area 6 and the second focusing Between the lenses 8 , it is used to reflect the outgoing light of the flow field observation area 6 to the second focusing lens 8 .

The optical signal is output by the light source 1, after being focused by the first focusing lens 2, the stray background light is filtered by the slit diaphragm 3, and then the beam is expanded and collimated by the first collimating lens 4, and then reflected by the first reflector 5 After entering the flow field observation area 6, it is reflected by the second mirror 7 and input to the second focusing lens 8. After converging, the deflected light is converted into a color image of different colors at the focal point of the lens by the rainbow filter 9 , and then collimated by the second collimating lens 10, it is incident on the digital microarray reflector 11, after the light field is randomly modulated, it is converged by the converging lens 12 and then incident on the three-color single-point photodetector 13, and then through the compression algorithm Module 14 reconstructs the image, the color image, and finally calculates the distribution of density changes in the observed flow field through the rainbow schlieren calculation method on the image.

In this embodiment, the light source 1 is a white light source. After being focused by the first focusing lens 2, it is irradiated onto the slit diaphragm 3 to form a white light point source. The white light source can be composed of a xenon lamp, a halogen lamp, etc.; it can also be Ultra-broadband light source using laser-driven light source technology, the wavelength range can include 170nm-2100nm, high output optical power, high luminous stability, and long working life; in addition, multi-wavelength solid-state light sources can also be used, that is, driven by multiple excitation sources A light source that emits light from the light pipe.

The slit diaphragm 3 obtains the white light point light source required for rainbow schlieren measurement, and the white light point light source formed by the slit diaphragm is expanded and collimated by the beam expander and collimator lens 4, and then input to the mirror 5 and reflected to the flow field In the observation area; among them, the slit aperture 3 realizes the point light source required for rainbow schlieren measurement, eliminates background stray light at the same time, and improves the signal-to-noise ratio of the optical path system; the slit aperture includes a slit and a pinhole aperture, and the aperture It can be a diaphragm part that can be adjusted or replaced manually or electrically, or a standard diaphragm with a fixed size, etc.

The first reflector 5 and the second reflector 7, the white light after beam expansion passes through the reflector 5, passes through the flow field observation area 6, then irradiates the second reflector 7, and then reflects to the second focusing lens 8; , the mirrors used include broadband dielectric film mirrors, metal film mirrors, dielectric laser line mirrors, cold and hot mirrors, etc., and also include ultra-fast, back-polished, round and square, D-shaped, concave, cylindrical Concave surface, Lizhou paraboloid, elliptical mirror, etc., in addition, it also includes passive or active optical components such as beam splitters and prisms for reflection; these optical components must be wide wavelength range components, which can make all white light sources enter optical system.

Flow field observation area 6 is the area where light and flow field interact, and can be used for microgravity flame combustion flow field measurement, wind tunnel flow field measurement, drop tower combustion flow field measurement, rocket combustion flow field measurement, liquid flow field measurement, Blade swirl measurement, gas jet measurement and other fields; can be applied to symmetric flow field, asymmetric flow field, supersonic flow field, gas mixing flow field, two-dimensional unsteady flow field, three-dimensional flow field measurement, etc. The rainbow filter 9 passes through the reflector 7, and the light deflected by the flow field is focused by the focusing lens 8, and the rainbow filter is placed at the focal point of the focusing lens to convert the deflected light into color images of different colors. The different colors of the color image represent different offsets of light deflection. According to the focal length and offset of the focusing lens, the deflection angle of light can be calculated, thereby calculating the density gradient and then calculating the density field; the rainbow filter is made by using The film SLR camera shoots the designed filter on the film negative, and uses the developed film negative as the rainbow filter. During the experiment, choose the appropriate exposure time according to the actual light intensity. In addition, according to the light flow The maximum deflection angle in the field determines the actual length of the rainbow filter; in order to accurately measure the parameters of the flow field, the rainbow filter needs to be calibrated, and the curve is drawn according to the obtained chromaticity value at a fixed deflection displacement Fitting, and then compare the calibrated fitting curve parameters with the actual measured data to obtain the light deflection offset with high accuracy; in addition, nonlinear gradient rainbow filters and two-dimensional chromaticity changes can also be used Rainbow filter.

The digital microarray mirror 11, the light collimated by the collimating lens 10 is irradiated onto the digital microarray mirror 11, and then the deflected color image is subjected to random spatial light modulation, and the randomly modulated The coded image is imaged, and then input to the three-color single-point photodetector 13; the digital array mirror can also use other adjustable spatial light modulators such as reflective and transmissive liquid crystal spatial light modulators.

The converging lens unit converges the image modulated by the digital microarray reflective lens 11 to one point by the converging lens 12, and then enters the corresponding three-color single-point photodetector 13, and realizes high-throughput imaging through the converging lens 12, which can be applied In weak light, ultra-weak photosynthetic single-photon rainbow schlieren measurement and imaging.

The three-color single-point photodetector 13 receives the optical signal converged by the converging lens 12, and then inputs it to the corresponding compression algorithm module 14, wherein the three-color single-point photodetector can be a visible light photodetector or a single-photon detector; wherein Single-photon detectors can be visible light avalanche diodes, solid-state photomultiplier tubes, superconducting single-photon detectors, etc.; the three-color single-point detector contains three independent photodetection elements, each element is equipped with a microlens and red and blue The green three-color filter detects the light of three wavelengths of red, blue and green respectively, and then uses the three-color palette algorithm to reconstruct a color image.

The compression algorithm module 14 adopts any of the following algorithms to realize compressed sensing: greedy reconstruction algorithm, matching tracking algorithm MP, orthogonal matching tracking algorithm OMP, base tracking algorithm BP, LASSO, LARS, GPSR, Bayesian estimation algorithm, magic, IST , TV, StOMP, CoSaMP, LBI, SP, l1_ls, smp algorithm, SpaRSA algorithm, TwIST algorithm, l0 reconstruction algorithm, l1 reconstruction algorithm, l2 reconstruction algorithm, etc. The sparse base can use discrete cosine transform base, wavelet base, Fourier Transformation basis, gradient basis, gabor transformation basis, etc.; by using the above-mentioned compression algorithm module to reconstruct the image of the three wavelengths of red, blue and green, and then reconstruct the color image through the red, blue and green three-color color algorithm.

Synchronization is required between the digital microarray reflector 11 and the three-color single-point photodetector 13. Every time the micromirror array in the digital microarray reflector 11 is flipped over, the three-color single-point photodetector 13 accumulates a total amount of time in the flip time interval. All light intensities are detected to realize photoelectric signal acquisition and conversion, and then sent to the corresponding compression algorithm module 14 .

The second embodiment of the rainbow schlieren measurement imaging system

As shown in Figure 2, the rainbow schlieren measurement and imaging system of this embodiment adopts the prism slit method. A dispersion prism 15 is placed between the straight lenses 4, and a slit 16 is placed between the second focusing lens 8 and the second collimating lens 10 to form a compressed sensing rainbow schlieren measurement imaging system and method based on the prism slit method.

Embodiment of Rainbow Schlieren Measurement and Imaging Method

The imaging method for rainbow schlieren measurement in this embodiment includes:

Step 1, the light signal is output by the light source 1, and after being focused by the first focusing lens 2, the stray background light is filtered through the slit diaphragm 3 to form a point light source;

Step 2: After the beam is expanded and collimated by the first collimating lens 4, it is reflected by the first mirror 5 and then incident on the flow field observation area 6;

Step 3, after the input is reflected by the second mirror 7 and converged by the second focusing lens 8, the deflected light is converted into a color image of different colors at the focal point of the second focusing lens 8 through the rainbow filter 9;

Step 4, after being collimated by the second collimating lens 10, it is incident on the digital microarray reflector 11, and the light field is randomly modulated;

Step 5, after being converged by the converging lens 12, it is incident on the three-color single-point photodetector 13, and the three-color single-point photodetector 13 sends the converted electrical signal to the compression algorithm module 14;

In step 6, the compression algorithm module 14 reconstructs the color image, and calculates the density change distribution of the observed flow field through the rainbow schlieren calculation method on the image.

In the above step 2, the beam expanded and collimated by the first collimating lens 4 is reflected by the first mirror 5 and then enters the flow field observation area 6 .

In the above step 3, the light beam emitted from the flow field observation area 6 is reflected by the second mirror 7 to the second focusing lens 8 for convergence.

The digital microarray mirror unit can load information on a one-dimensional or two-dimensional optical data field, and is a key device in modern optical fields such as real-time optical information processing, adaptive optics and optical computing. Under the control of changing electrical driving signals or other signals, the amplitude or intensity, phase, polarization state and wavelength of the light distribution in space are changed, or incoherent light is converted into coherent light. There are many types, mainly including digital micro-mirror device (Digital Micro-mirror Device, referred to as DMD), frosted glass, liquid crystal light valve, etc. The modulation used here is light intensity modulation including amplitude modulation.

The DMD used in this embodiment is an array containing tens of thousands of micromirrors mounted on hinges (mainstream DMDs are composed of 1024×768 arrays, up to 2048×1152), and the size of each lens It is 14μm×14μm (or 16μm×16μm) and can turn on and off the light of a pixel. These micromirrors are all suspended. A lens is electrostatically tilted to both sides by about 10-12° (in this embodiment, +12° and -12° are taken), and these two states are recorded as 1 and 0, corresponding to "on" and "off", respectively. When the lenses are not operating, they are in a "parked" state of 0°.

The present invention combines compressed sensing theory with rainbow schlieren measurement, and creatively proposes a sparse rainbow schlieren measurement method, which has the characteristics of high throughput, high signal-to-noise ratio, fast and flexible, and is suitable for conventional light intensity, weak light, and weak light , ultra-weak light and single-photon rainbow schlieren measurement method, which is a sparse rainbow schlieren measurement method with a large dynamic range.

1) The combination of compressed sensing and rainbow schlieren measurement can realize high-throughput rainbow schlieren measurement. The classic rainbow schlieren measurement technology has a low signal-to-noise ratio in the measurement process of flame, wind tunnel, air flow, etc., especially at high speed 1. The environmental background interference is relatively large in ultra-high-speed flow field measurement. Using this high-throughput feature can improve the signal-to-noise ratio of rainbow schlieren measurement.

2) Through this method, the combination of single photon detector and sparse undersampling is used to realize the quantum rainbow schlieren measurement method, which can realize the physical characteristics of the long-distance flow field.

3) Sparse rainbow schlieren measurement is an important development direction in the field of high-precision optical measurement. It has significant advantages in heat flow and gas flow, and is a non-contact high-precision optical measurement technology.

Professionals should further realize that the units and algorithm steps described in conjunction with the embodiments disclosed herein can be implemented by electronic hardware, computer software, or a combination of the two. In order to clearly illustrate the relationship between hardware and software Interchangeability. In the above description, the composition and steps of each example have been generally described according to their functions. Whether these functions are executed by hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art may use different methods to implement the described functions for each specific application, but such implementation should not be regarded as exceeding the scope of the present invention.

The steps of the methods or algorithms described in connection with the embodiments disclosed herein may be implemented by hardware, software modules executed by a processor, or a combination of both. Software modules can be placed in random access memory (RAM), internal memory, read-only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, removable disk, CD-ROM, or any other Any other known storage medium.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (15)

1. a rainbow schlieren measure imaging system, is characterized in that, comprising:

Light source, for output optical signal; And the first condenser lens setting gradually along described light source output optical signal path, slit diaphragm, the first collimation lens, the second condenser lens, rainbow filter plate, the second collimation lens, digital microarray catoptron, plus lens and three look single-point photodetectors, flow observation region is between the first collimation lens and the second condenser lens;

Compression algorithm module, it is connected with three look single-point photodetector electric signal, and for reconstruct coloured image, the variable density that calculates observation flow field according to the rainbow schlieren computing method of image distributes.

2. rainbow schlieren measure imaging system as claimed in claim 1, is characterized in that, described slit diaphragm comprises slit and pinhole diaphragm, and this diaphragm is by the diaphragm parts of manual or motorized adjustment or replacing, or the standard form diaphragm of fixed measure.

3. a rainbow schlieren measure imaging system, is characterized in that, comprising:

Light source, for output optical signal; And the first condenser lens setting gradually along described light source output optical signal path, dispersing prism, the first collimation lens, the second condenser lens, slit, the second collimation lens, digital microarray catoptron, plus lens and three look single-point photodetectors, flow observation region is between the first collimation lens and the second condenser lens;

Compression algorithm module, it is connected with three look single-point photodetector electric signal, and for reconstruct coloured image, the variable density that calculates observation flow field according to the rainbow schlieren computing method of image distributes.

4. the rainbow schlieren measure imaging system as described in claim 1 or 3, it is characterized in that, also comprise mirror unit, it comprises the first catoptron and the second catoptron, described the first catoptron is located between described the first collimation lens and described flow observation region, for the emergent light of the first collimation lens is reflected into into observation area, flow field; Described the second catoptron is located between described flow observation region and described the second condenser lens, for the emergent light in described flow observation region is reflexed to the second condenser lens.

5. rainbow schlieren measure imaging system as claimed in claim 4, is characterized in that, the catoptron in described mirror unit is broadband deielectric-coating catoptron, metal film catoptron, dielectric laser line reflection mirror or cold and hot catoptron.

6. the rainbow schlieren measure imaging system as described in claim 1 or 3, is characterized in that, described light source is white light source.

7. rainbow schlieren measure imaging system as claimed in claim 6, it is characterized in that, described white light source is xenon lamp, Halogen lamp LED composition white light source, or the super broadband light source of employing laser driven light source technology, wavelength coverage is 170nm-2100nm, or utilizes multiple driving source to drive the luminous light source of photoconductive tube.

8. the rainbow schlieren measure imaging system as described in claim 1 or 3, is characterized in that, described digital microarray catoptron adopts reflective and transmission-type LCD space light modulator.

9. the rainbow schlieren measure imaging system as described in claim 1 or 3, is characterized in that, described three look single-point photodetectors are visible ray photodetector or single-photon detector.

10. rainbow schlieren measure imaging system as claimed in claim 9, is characterized in that, described three look single-point photodetectors are single-photon detector, and described single-photon detector is light avalanche diode, solid-state photomultiplier or superconducting single-photon detector.

11. rainbow schlieren measure imaging systems as described in claim 1 or 3, it is characterized in that, in described three look single-point detectors, comprise three independent optical detection devices, each optical detection device front end is installed a lenticule and red bluish-green three-colour filter, survey respectively the light of red bluish-green three wavelength, then adopt three-primary colours palette algorithm to reconstruct coloured image.

12. rainbow schlieren measure imaging systems as described in claim 1 or 3, it is characterized in that, between described digital microarray catoptron and described three look single-point photodetectors, synchronize, the every upset of micro mirror array in described digital microarray catoptron once, described three look single-point photodetectors add up to survey all light intensity of arrival in interval in this flip-flop transition, realize photoelectric signal collection conversion, then by extremely described compression algorithm module of electric signal transmission.

13. 1 kinds of rainbow schlieren measure formation methods, is characterized in that, described method comprises:

Step 1, light source output optical signal, after the first condenser lens focuses on, by the spuious bias light of slit diaphragm filtering;

Step 2, after the first collimation lens beam-expanding collimation, incides flow observation region;

Step 3, after the second condenser lens converges, is converted to the light after deviation at lens focus place the coloured image of different colours by the light beam of described flow observation region outgoing through rainbow optical filter;

Step 4 incides digital microarray catoptron after the second collimation lens collimation, and light field is carried out to Stochastic Modulation;

Step 5 incides three look single-point photodetectors after plus lens converges, and the electric signal being converted to is delivered to compression algorithm module by described three look single-point photodetectors;

Step 6, through compression algorithm Restructuring Module coloured image, the variable density that calculates observation flow field by the rainbow schlieren computing method to image distributes.

14. rainbow schlieren measure formation methods as claimed in claim 13, is characterized in that, in described step 2, the light beam after the first collimation lens beam-expanding collimation incides flow observation region after the first catoptron reflection.

15. rainbow schlieren measure formation methods as claimed in claim 13, is characterized in that, in described step 3, reflex to described the second condenser lens converge by the light beam of described flow observation region outgoing through the second catoptron.