A DMD-based molecular tagging velocimetry system

Abstract

The application relates to a DMD-based molecular marker velocimetry system, comprising an MTV marker grid generation module and a camera module and a computer connected with the MTV marker grid generation module, the MTV marker grid generation module comprising two groups of symmetrically arranged DLP units which are orthogonal to a measuring fluid region, each of the DLP units being connected with a UV LED light source, the DLP unit comprising a DMD chip which converts the UV LED light source into a modulated light beam with stable intensity, spatially uniform distribution and time stability under the control of the computer, forms a marker grid in the measuring fluid region, excites a tracer, and realizes velocity field construction based on two shooting images collected by the camera module. Compared with the prior art, the application can greatly improve the grid thickness and light intensity stability of the molecular marker velocimetry marker grid, thereby improving the precision, and can reduce the number of optical elements used in the traditional molecular marker velocimetry technology, thereby reducing the measurement cost.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of molecular tagging velocimetry, and particularly to a molecular tagging velocimetry system based on DMD. BACKGROUND

[0002] Molecular tagging velocimetry (MTV) is a full-field optical technique. This technique relies on the fact that molecules can be transformed into long-lived tracers upon excitation by photons of appropriate wavelength, while the measurement region is tagged using a pulsed laser. The tagging information of the measurement region is recorded twice in succession using a camera within the lifetime of the tracers. The motion of the tracers is extracted from the two recorded images based on image processing algorithms, and an approximation of the fluid spatial velocity is obtained. The key of the MTV technique lies in the selection of the tracers and the pulsed laser tagging method. The tracers are generally selected to be molecular reagents that can be easily excited to undergo energy transition in the wavelength range of 200-500 nm, and have a long light-emitting lifetime. In velocity measurement, the pulsed laser is used to tag the measurement region to generate "line tag" and "tag grid" fringes. By comparing the Lagrangian displacement of the "line tag" and "tag grid" fringes recorded by the camera twice, the fluid spatial motion velocity is obtained.

[0003] Most of the existing methods for generating "line tag" and "tag grid" fringes are to place optical elements such as gratings or prisms between the laser exit and the measurement region, so as to generate parallel light sources with equal thickness. However, the intensity distribution of the generated parallel light sources along the thickness generally satisfies the Gaussian distribution. However, the "line tag" and "tag grid" fringes obtained by such parallel light sources have relatively obvious contrast and chromatic aberration, which affects the intersection angle of the tag fringes in the MTV image pair, and has a great influence on the accuracy of velocity measurement. SUMMARY

[0004] The purpose of the present application is to solve the measurement error caused by the original laser tagging method of MTV, and to provide a molecular tagging velocimetry system based on DMD. The original laser tagging method of MTV is changed by using a DMD chip, so as to improve the accuracy of velocity measurement by MTV, and to provide a basis for the wide application of MTV.

[0005] The purpose of the present application can be achieved by the following technical solutions:

[0006] A molecular tagging velocimetry system based on DMD, comprising an MTV tag grid generation module, a camera module and a computer connected with the MTV tag grid generation module, the MTV tag grid generation module comprising two groups of DLP units symmetrically arranged and orthogonal to the measurement fluid region, each DLP unit being connected with a UV LED light source,

[0007] The DLP unit comprises a DMD chip which converts the UV LED light source into a modulated light beam with stable intensity, spatial uniform distribution and time stability under the control of a computer, forms a marker grid in the measurement fluid region, excites the tracer, and realizes velocity field construction based on two captured images collected by a camera module.

[0008] Further, the DMD chip comprises a plurality of micro-mirrors, and the modulated light beam is obtained by:

[0009] changing the PWM value of each micro-mirror under the control of a computer;

[0010] selecting two DMD micro-mirror arrays with a fixed number of columns, adjusting them to an open state, and adjusting the remaining micro-mirrors to a closed state to obtain a sheet light with stable light intensity;

[0011] blocking the DMD micro-mirror array in the row direction with a fixed number of micro-mirrors and intervals to obtain a plurality of beams of square cross-section reflected illumination light beams with a determined number and fixed size, i.e., the modulated light beam.

[0012] Further, the changing of the PWM value of each micro-mirror is specifically:

[0013] adjusting the PWM value based on the minimum actual light intensity received by the camera module to obtain a PWM value that makes the light intensity of all micro-mirrors spatially uniformly distributed;

[0014] correcting the PWM value of the micro-mirror in real time to obtain time-stable illumination.

[0015] Further, the fixed number of columns is 1 to N, and N is the maximum number of micro-mirror columns contained in the DMD chip.

[0016] Further, the excitation wavelength range of the tracer is 400-700 nm.

[0017] Further, the lifetime of the tracer is calibrated according to the intensity of the two captured images.

[0018] Further, the lifetime of the tracer is greater than the time interval between the two captured images.

[0019] Further, cross-correlation calculation is performed on the two captured images collected by the camera module to realize velocity field construction.

[0020] Further, the diagnostic window size in the cross-correlation calculation is not more than 32x32.

[0021] Further, the camera module comprises a CCD camera and a light filter arranged in sequence, the CCD camera is installed in the normal direction of the mark grid.

[0022] Further, the position of the selected DMD micromirror array is changed to realize the construction of the three-dimensional velocity field of the measured fluid region.

[0023] Compared with the prior art, the present application has the following beneficial effects:

[0024] 1. The present application is based on DMD chip optical modulation, through the adjustment of PWM value, the sheet light with stable light intensity, uniform distribution and fixed thickness can be generated, so as to generate the molecular marker velocity measurement mark grid, reduce the influence of the mark grid stripe on the accuracy of velocity measurement, improve the accuracy of velocity measurement of MTV, provide the basis for the wide application of MTV technology in the field of velocity measurement, and also have important significance for accelerating the experimental fluid research;

[0025] 2. The present application can generate illumination light with a wide excitation wavelength range through the optical modulation of DMD chip, which can be used for most tracer excitation and has wide applicability.

[0026] 3. The present application is based on DMD chip optical modulation, which reduces the number of optical elements used in the traditional molecular marker velocity measurement technology, greatly reduces the cost. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 It is a structural schematic diagram of the present application;

[0028] Figure 2 It is a mark grid generation schematic diagram in the embodiment of the present application;

[0029] Figure 3 It is the mark grid generated at the first time in the embodiment of the present application;

[0030] Figure 4 It is the mark grid generated at the second time in the embodiment of the present application;

[0031] Figure 5 It is the two-dimensional velocity field result obtained by calculation in the embodiment of the present application;

[0032] In the figure: 1-CCD camera, 2-light filter, 3-data transmission cable, 4-signal synchronization cable, 5-computer, 6-measured fluid region, 7-UV LED light source, 8-optical fiber, 9-DMD chip, 10-DLP unit, 11-modulated light beam, 12-mark grid. DETAILED DESCRIPTION

[0033] The application will be described in detail below with reference to the drawings and specific embodiments. The embodiments are implemented on the premise of the technical solutions of the application, and detailed implementation modes and specific operation processes are given, but the protection scope of the application is not limited to the following embodiments.

[0034] The digital light processing technology (DLP) with a digital micromirror (DMD) as a control core is the most representative product of the existing digital light modulation technology. The DMD chip is a two-dimensional programmable array with high flexibility, and a sheet light with a relatively concentrated light intensity distribution can be obtained through programming modulation. The application is realized based on the DMD.

[0035] Reference Figure 1 As shown in the figure, the embodiment provides a DMD-based molecular marker velocimetry system, which comprises an MTV marker grid generation module and a camera module and a computer connected with the MTV marker grid generation module, the MTV marker grid generation module comprises two groups of symmetrically arranged DLP units 10 orthogonally arranged to the measuring fluid region, each DLP unit 10 is connected with a UV LED light source 7, the DLP unit 10 comprises a DMD chip 9, the computer 5 is installed with DMD chip data input and programming software and DLP control software, the DMD chip 9 converts the UV LED light source 7 into a modulated light beam 11 with stable intensity, spatial uniform distribution and time stability under the control of the computer 5, forms a marker grid 12 in the measuring fluid region 6, excites the tracer, and realizes velocity field construction based on two shooting images collected by the camera module.

[0036] The DMD chip comprises a plurality of micromirrors, and the DMD micromirror array at different positions can be selected to be turned on under the control of the computer 5, so as to realize acquisition of a two-dimensional velocity field or a three-dimensional velocity field.

[0037] The camera module comprises a CCD camera 1 and a light filter 2 arranged in sequence, and the CCD camera 1 is installed in the normal direction of the marker grid.

[0038] In the above system, the computer 5 is connected with the CCD camera 1 and the DLP unit 10 through a data transmission cable respectively, the CCD camera 1 is connected with the DLP unit 10 through a signal synchronization cable 4, and the UV LED light source 7 is connected with the DLP unit 10 through an optical fiber 8.

[0039] The tracer used in the above system has an excitation wavelength range of 400-700 nm, and the lifetime is calibrated according to the intensity of the two images, but the lifetime must be greater than the time interval of the two shooting times of the camera.

[0040] As Figure 1 and Figure 2As shown, the specific process of molecular marker velocimetry grid generation and velocity field calculation using the above DMD-based molecular marker velocimetry system is as follows:

[0041] (1) Operate two DMD chips and modify the reflection intensity of the micromirrors to obtain stable and spatially uniformly distributed illumination;

[0042] In this embodiment, in order to keep the light intensity of all micromirrors consistent, the actual minimum light intensity received by the camera is taken as a reference, and the PWM values of the micromirrors on the two DMD chips are changed through the DLP control software on the computer to obtain all the PWM values of the spatially uniformly distributed light intensity of all micromirrors.

[0043] (2) Real-time control of two DMD chips to obtain illumination with time stability;

[0044] In this embodiment, the temporal instability of the UV LED light source will cause temporal instability of the reflected light of the DMD micromirrors, so the PWM values of the DMD micromirrors are changed in real time through the DLP control software on the computer for correction to obtain illumination with time stability.

[0045] (3) Select two DMD micromirror arrays with a fixed number of columns, adjust them to the open state, and adjust the remaining micromirrors to the closed state to obtain a light intensity stable sheet light, the fixed number of columns is 1-N, and N is the maximum value of the number of micromirror columns contained in the DMD chip;

[0046] In this embodiment, the DMD chip of the DLP4500 series is used, and the micromirror array is 1140x912. Five columns of micromirrors at the center are selected with a fixed number of columns of 5, and the number of rows remains unchanged at 1140 rows. The 1140x5 micromirrors are turned on, and the remaining micromirrors are turned off.

[0047] (4) According to the sheet light obtained by adjusting step (3), the sheet light is blocked in the row direction with a fixed number of micromirrors and an interval to obtain a number of determined and fixed size square column cross-section reflected illumination beams;

[0048] In this embodiment, the 1140x5 micromirror array obtained by adjusting step 3) is blocked with 5x5 and an interval of 45 to obtain a total of 22 fixed-size multi-beam square column cross-section reflected illumination beams, i.e. the modulated light beam 11. The illumination beams of the two DMD chips are orthogonal to the same plane to obtain the "marker grid" as shown in Figure 3 .

[0049] (5) Use the multi-beam square column cross-section reflected illumination obtained in step (4) to form an orthogonal "marker grid" in the flow field to excite the tracer; the camera continuously takes two images in a short time;

[0050] In this embodiment, the excited tracer molecule reagent is imaged at two time instants using a CCD camera during its lifetime, and the two time instants are Figure 3 and Figure 4 as shown, with an image size of 500x500 pixels.

[0051] (6) Based on the two images obtained in step (5), a two-dimensional cross-correlation calculation is performed on the images to obtain a two-dimensional velocity field, and the diagnostic window size in the cross-correlation calculation is not more than 32x32.

[0052] In this embodiment, the diagnostic window with a size of 25x25 pixels is selected for Figure 3 and Figure 4 the diagnostic window data is subjected to FFT transformation to obtain the frequency domain transformation results of the two diagnostic windows; then the frequency domain transformation results of the two diagnostic windows are subjected to FFT convolution calculation to obtain the energy spectrum of the particle field of the two diagnostic windows; the energy spectrum is subjected to one inverse Fourier transform to obtain a cross-correlation function; and the average speed of the tracer in the diagnostic window is calculated according to the peak value of the cross-correlation function and the two-dimensional index where the peak value is located; when all the diagnostic windows are processed in the loop, the global velocity field can be obtained, as shown in Figure 5 .

[0053] (7) The position of the sheet light in step (3) is changed, and steps (4), (5) and (6) are repeated to obtain a three-dimensional velocity field in the fluid measurement region.

[0054] The preferred embodiments of the present application are described in detail above. It should be understood that those skilled in the art can make many modifications and changes to the present application without creative efforts based on the concept of the present application. Therefore, any technical solutions obtained by logical analysis, reasoning or limited experiments based on the prior art according to the concept of the present application shall be within the protection scope defined by the claims.

Claims

1. A DMD-based molecular marker velocimetry system, characterized by, The application relates to a kind of MTV mark grid generation module, and camera module and computer are connected with the MTV mark grid generation module, the MTV mark grid generation module includes two groups of symmetrically arranged DLP units, and the modulated light beam is orthogonal to the measuring fluid region, The DLP unit includes a DMD chip, which converts the UV LED light source into a modulated light beam with stable intensity, spatially uniform distribution and temporal stability under the control of the computer, forms a mark grid in the measuring fluid region, excites the tracer, and realizes velocity field construction based on two captured images collected by the camera module, The DMD chip includes a plurality of micromirrors, and the modulated light beam is obtained by: Changing the PWM value of each micromirror under the control of the computer; Selecting two DMD micromirror arrays with a fixed number of columns, adjusting them to an open state, and adjusting the remaining micromirrors to a closed state to obtain a sheet light with stable light intensity; In the row direction, the DMD micromirror array is blocked with a fixed number of micromirrors and intervals to obtain a plurality of beams of square column cross-section reflected illumination light beams with a fixed size, i.e., the modulated light beam, The excitation wavelength range of the tracer is 400-700 nm.

2. The DMD-based molecular beacon velocimetry system of claim 1, wherein, The PWM value of each micromirror is changed as follows: Adjust the PWM value based on the minimum actual light intensity received by the camera module to obtain a PWM value that allows all micromirror light intensities to be spatially uniformly distributed; Real-time correction of the PWM value of the micromirror to obtain time-stable illumination.

3. The DMD-based molecular beacon velocimetry system of claim 1, wherein, The fixed number of columns is 1-N, and N is the maximum number of micromirror columns included in the DMD chip.

4. The DMD-based molecular beacon velocimetry system of claim 1, wherein, The lifetime of the tracer is calibrated based on the intensity of the two captured images.

5. The DMD-based molecular beacon velocimetry system of claim 4, wherein, The lifetime of the tracer is greater than the time interval between the two captured images.

6. The DMD-based molecular beacon velocimetry system of claim 1, wherein, Cross-correlation calculation is performed on the two captured images collected by the camera module to realize velocity field construction.

7. The DMD-based molecular beacon velocimetry system of claim 1, wherein, The camera module includes a CCD camera and a light filter arranged in sequence, and the CCD camera is installed in the normal direction of the mark grid.

8. The DMD-based molecular beacon velocimetry system of claim 1, wherein, Changing the position of the selected DMD micromirror array realizes the construction of the three-dimensional velocity field of the measuring fluid region.

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