CN211825691U - Rapid fluorescence lifetime imaging system for flow field diagnostics - Google Patents
Rapid fluorescence lifetime imaging system for flow field diagnostics Download PDFInfo
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Abstract
The utility model provides a quick fluorescence life-span imaging system for flow field diagnosis solves the low and low problem of frame rate of current fluorescence life-span imaging technology imaging time resolution. The system comprises a pulse laser, a sheet light shaping device, a flow field generating device, a filter, a framing camera and a data processing device; the pulse laser simultaneously emits laser pulses and electric signals, and the sheet light shaping device is used for shaping the laser pulses into sheet light; the flow field generating device is used for providing a target flow field to be detected, and the target flow field to be detected emits a fluorescence signal after being irradiated by sheet light; the filter plate is used for transmitting the fluorescence signal and filtering the stray signal; the framing camera comprises a synchronous control device and four gate control cameras, and the synchronous control device controls exposure time gates and time delay of the four gate control cameras; triggering the framing camera to expose by the electric signal to obtain a four-frame image; and the data processing device is used for receiving the four-frame images captured by the frame camera and processing the four-frame images to obtain and display the fluorescence life images.
Description
Technical Field
The utility model relates to a flow field diagnostic technique, concretely relates to quick fluorescence life-span imaging system for flow field diagnosis.
Background
The flow field comprises airflow, combustion, plasma and a multiphase flow field, and experimental research on the flow field diagnosis technology can provide data support for establishment and verification of a flow field model, so that a theoretical basis is provided for application of relevant engineering, such as improvement of engine performance. Most of the traditional flow field diagnosis technologies are intrusive, and the flow field is disturbed, so that errors exist in measurement of flow field parameters.
At present, the most advanced flow field diagnosis technology is an optical diagnosis technology, and non-invasive measurement of a flow field can be realized; the planar laser induced fluorescence lifetime imaging (PLIF) technology is widely applied, and can realize measurement of flow field parameters such as concentration of major/trace components, temperature, pressure, speed and the like. PLIF can carry out two-dimensional slice wide field imaging to the target of treating the detection through shaping exciting light into the piece light, however, in the aspect of concentration measurement, although PLIF fluorescence signal intensity carries fluorescent agent concentration information, because the existence of collision quenching effect makes its qualitative and quantitative measurement that can not realize the concentration, only can realize the visual measurement of component.
In order to realize quantitative measurement of the concentration of the components in the flow field, the collision quenching rate needs to be measured, and the Fluorescence Lifetime Imaging (FLI) technology can obtain the collision quenching rate by measuring the lifetime, so that the quantitative measurement of the concentration of the components is realized.
The traditional Fluorescence Lifetime Imaging (FLI) technology comprises time-dependent single photon counting Technology (TCSPC) and gated fluorescence lifetime imaging (TG-FLI) technology imaging and the like, wherein the time-dependent single photon counting Technology (TCSPC) uses a photomultiplier tube to scan and image a target, the acquisition time of a single fluorescence lifetime image is in the order of minutes, the gated fluorescence lifetime imaging (TG-FLI) uses a single ICCD to perform wide-field imaging on the target, and I is required to be delayed for multiple timesThe time gate of the CCD acquires a plurality of images to calculate the lifetime image, and the acquisition time is in the order of seconds, for example, chinese patent publication No. CN 109253992a, entitled plasma fluorescence lifetime measuring device and method. Two ICCDs are combined with a gated fluorescence lifetime imaging method to realize formaldehyde (CH) in laminar flame for the first time by Ehn2O) (a.ehn, o.johansson, a.arvidsson, m.alden, and j.book, "Single-laser fluorescence lifetime imaging on the nanosecond computer using a Daul Image and ModelingEvaluation algorithm," op.express 20(3), 3044-3056 (2012), which exposes the flow field simultaneously using two ICCDs with different time gates, and from which a fluorescence lifetime Image can be calculated. The method can realize single-fluorescence lifetime imaging of the flow field under a single-exponential decay model, but cannot realize single-fluorescence lifetime imaging of the flow field under a double-exponential decay model and cannot realize fluorescence lifetime imaging with a high frame rate.
Because qualitative and quantitative measurement of component concentration in a high-speed complex flow field requires a rapid fluorescence lifetime imaging technology to realize freezing of a transient flow field and monitoring of the high-speed flow field, a new fluorescence lifetime imaging technology is urgently needed at present to meet the requirements of high time resolution and high imaging frame rate required by complex flow field diagnosis.
SUMMERY OF THE UTILITY MODEL
In order to solve the technical problems that the speed of the existing fluorescence imaging technology is slower, the measurement precision of the fluorescence life is lower, the high time resolution of a complex flow field and the high imaging frame rate cannot be met, the utility model provides a rapid fluorescence life imaging system for flow field diagnosis.
In order to achieve the above purpose, the utility model provides a technical scheme is:
a rapid fluorescence lifetime imaging system for flow field diagnostics, characterized by: the device comprises a pulse laser, a sheet light shaping device, a flow field generating device, a filter, a framing camera and a data processing device;
the pulse laser simultaneously emits laser pulses and electric signals, the laser pulses are picosecond laser pulses with single pulse energy at a millijoule level, and the wavelength of the laser pulses is equal to the excitation wavelength of a component to be detected in a target to be detected in the flow field generating device;
the sheet light shaping device is used for shaping laser pulses into sheet light;
the flow field generating device is used for providing a target flow field to be detected, and components to be detected in the target flow field to be detected emit fluorescence signals after the target flow field to be detected is irradiated by the sheet light;
the filter plate is used for transmitting the fluorescent signal and filtering a stray signal, and the stray signal comprises laser pulse;
the framing camera comprises a synchronous control device and four gated cameras, and the synchronous control device is used for controlling exposure time gates and time delay of the four gated cameras;
the framing camera is connected with a pulse laser, the framing camera is triggered by an electric signal emitted by the pulse laser, the four gating cameras are controlled by the synchronous control device, and the fluorescent signal filtered by the filter plate is exposed to obtain a four-framing image;
the data processing device is connected with the framing camera and used for receiving the four-frame images captured by the framing camera, processing the four-frame images by adopting a fluorescence life algorithm, and obtaining and displaying fluorescence life images;
the fluorescence lifetime algorithm is a fitting algorithm based on a least square method or a maximum likelihood method, or a non-fitting algorithm based on a rapid fluorescence lifetime algorithm.
Further, the framing camera is an aperture-dividing framing camera, an amplitude-dividing framing camera or a rotating mirror framing camera.
Further, the gated camera is an image-enhanced CCD or image-enhanced CMOS camera.
Further, the filter is a band-pass filter or a long-pass filter.
Compared with the prior art, the utility model has the advantages that:
the utility model discloses imaging system uses the framing camera that contains four gate control cameras to carry out four images simultaneous exposure to the fluorescence signal that the target flow field produced, and every image has different exposure time door, reuses four images and carries out the calculation of fluorescence life image, has that imaging speed is fast and the high characteristics of frame rate, has overcome the slow and low defect of frame rate of traditional fluorescence life imaging method imaging speed.
Drawings
FIG. 1 is a schematic diagram of the rapid fluorescence lifetime imaging system for flow field diagnostics of the present invention;
FIG. 2 is a timing diagram of the laser pulses and 4 gated camera time gates in the dual-exponential decay model rapid fluorescence lifetime imaging method for flow field diagnostics of the present invention;
FIG. 3 is a schematic diagram of the fluorescence lifetime image calculation in the fast fluorescence lifetime imaging method using the dual-exponential decay model for flow field diagnosis according to the present invention;
FIG. 4 is a timing diagram of the laser pulses and 4 gated camera time gates in the single exponential decay model high repetition frequency fast fluorescence lifetime imaging method for flow field diagnostics of the present invention;
FIG. 5 is a schematic diagram of the fluorescence lifetime image calculation in the single exponential decay model high repetition frequency fast fluorescence lifetime imaging method for flow field diagnosis of the present invention.
Wherein the reference numbers are as follows:
the device comprises a pulse laser 1, a light shaping device 2, a flow field generating device 3, a filter 4, a framing camera 5 and a data processing device 6.
Detailed Description
The present invention will be described in further detail with reference to the following drawings and specific embodiments.
As shown in fig. 1, a fast fluorescence lifetime imaging system for flow field diagnosis includes a pulse laser 1, a sheet light shaping device 2, a flow field generating device 3, a filter 4, a framing camera 5 and a data processing device 6.
The pulse laser 1 generates picosecond laser pulses with single pulse energy at milli-joule level and wavelength at the absorption peak of a target component, and is used for exciting a target flow field generated by the flow field generating device 3; at the same time, the pulsed laser 1 emits an electrical signal for triggering the framing camera 5 to perform an exposure.
The sheet light shaping device 2 is used for shaping laser pulses into sheet light to realize wide-field imaging of a flow field, and generally comprises a beam expander and a collimating lens, and can also comprise other devices capable of realizing the same function.
The flow field generating device 3 is used for providing a target flow field to be detected, and after the target flow field to be detected is irradiated by sheet light, components to be detected in the target flow field to be detected emit fluorescence signals; the flow field generating device 3 can be a spray pipe, a chamber with an observation window and a wind tunnel, and the generated target flow field to be detected can be airflow, combustion, plasma and a multiphase flow field.
The filter 4 is placed in front of the framing camera 5, is used for transmitting the fluorescent signal and filtering the exciting light, and can be a band-pass filter or a long-pass filter 4, the transmission waveband is determined by the wavelengths of the exciting light and the signal light, and the shortest wavelength of the transmission waveband is not less than the wavelength of the exciting light.
The framing camera 5 comprises a synchronous control device and four gate control cameras, the synchronous control device is used for receiving an electric signal emitted by the laser and controlling exposure time gates and time delay of the four gate control cameras, and the four gate control cameras are used for recording four fluorescence intensity images with different time gates to obtain four framing images; the framing camera 5 is an aperture-dividing framing camera or an amplitude-dividing framing camera or a rotating mirror framing camera, and the gate control camera is an image-enhanced CCD or an image-enhanced CMOS camera.
And the data processing device 6 is connected with the framing camera 5 and is used for receiving the four-frame images captured by the framing camera 5 and processing the four-frame images by adopting a fluorescence life algorithm to obtain and display fluorescence life images. The fluorescence lifetime algorithm employed by the data processing device 6 may be a fitting algorithm based on a least square method or a maximum likelihood method, or may be a non-iterative algorithm such as a fast fluorescence lifetime algorithm.
Based on the above fast fluorescence lifetime imaging system for flow field diagnosis, this embodiment provides a single fluorescence lifetime imaging method for a flow field under a double-exponential decay model, in which a timing diagram of time gates of 4 gated cameras in a laser pulse and framing camera 5 is shown in fig. 2, and a fluorescence lifetime image calculation schematic diagram in the method is shown in fig. 3, and the imaging method includes the following steps:
firstly, a pulse laser 1 emits a picosecond laser pulse with single pulse energy at a millijoule level, and the wavelength of the picosecond laser pulse corresponds to the excitation wavelength of a component to be detected in a target to be detected in a flow field generating device 3;
at the same time, the pulsed laser 1 emits an electrical signal;
secondly, the picosecond laser pulse is shaped into a sheet light by the sheet light shaping device 2, and the size of the sheet light is determined by the observation area of the target to be measured;
irradiating the target flow field to be measured generated by the flow field generating device 3 with sheet light, so that the components to be measured in the target flow field to be measured emit fluorescence signals, and filtering stray signals through the filter 4;
triggering a framing camera 5 by an electric signal emitted by the pulse laser 1 to expose the fluorescence signal filtered by the filter 4, wherein the framing camera 5 comprises four gate-controlled cameras, namely a gate-controlled camera 1, a gate-controlled camera 2, a gate-controlled camera 3 and a gate-controlled camera 4, and acquiring and recording four fluorescence intensity images with different exposure time, namely a gate-controlled image 1, a gate-controlled image 2, a gate-controlled image 3 and a gate-controlled image 4;
fifthly, four fluorescence intensity images (a gate control image 1, a gate control image 2, a gate control image 3 and a gate control image 4) captured by the framing camera 5 are transmitted to the data processing device 6, and fluorescence lifetime images under a double-exponential decay model are calculated and displayed by using a fitting algorithm;
the double-exponential fluorescence intensity attenuation model is as follows:
I＝A1exp(-t/τ1)+A2exp(-t/τ2)；
wherein I is time-varying fluorescence signal intensity, t is time, A1、A2Is 2 pre-exponential factors, tau1、τ 22 different fluorescence lifetimes. It can be seen that at least four sampled images are required to calculate the unknown pre-exponential factor a1And A2And fluorescence lifetime τ1And τ2The utility model can be on the listUnder the condition of the double-exponential fluorescence lifetime image fitting, four sampling images are simultaneously obtained to fit the double-exponential fluorescence lifetime image, a fitting algorithm is a least square method or a maximum likelihood method, and the time resolution of the fluorescence lifetime image is determined by a measurement time window of the framing camera 5.
The fast fluorescence lifetime imaging method of the dual-exponential decay model in the embodiment utilizes a four-frame exposure image of a fluorescence signal under single excitation of a pulse laser, can realize single fluorescence lifetime imaging of a flow field under the dual-exponential decay model, and further realizes fast fluorescence lifetime imaging with high time resolution.
Based on the above fast fluorescence lifetime imaging system for flow field diagnosis, this embodiment further provides a high repetition frequency fast fluorescence lifetime imaging method under a single exponential decay model, in which a timing diagram of time gates of 4 gated cameras in a laser pulse and framing camera 5 is shown in fig. 4, and a fluorescence lifetime image calculation schematic diagram in the method is shown in fig. 5, and the imaging method includes the following steps:
the method comprises the following steps that firstly, a pulse laser 1 continuously emits two picosecond laser pulses with the repetition frequency of KHz-MHz and the energy of millijoule level, and the wavelength of the picosecond laser pulses corresponds to the excitation wavelength of a component to be detected in a target to be detected in a flow field generating device 3;
at the same time, the pulsed laser 1 emits an electrical signal;
secondly, shaping the two picosecond laser pulses into two sheets of light by a sheet light shaping device 2, wherein the size of the sheets of light is determined by an observation area of a target to be measured;
step three, the two sheets of light sequentially irradiate the target flow field to be measured generated by the flow field generating device 3, so that the target component to be measured in the target flow field to be measured emits two fluorescent signals, and stray signals are filtered by the filter 4;
wherein the two fluorescence signals are a first fluorescence signal and a second fluorescence signal respectively;
triggering the framing camera 5 by the electric signal emitted by the pulse laser 1 to expose the first fluorescent signal and the second fluorescent signal filtered by the filter 4;
the framing camera 5 comprises four gate control cameras, wherein two gate control cameras expose the first fluorescence signal to obtain two fluorescence intensity images which record the first fluorescence signal and are provided with gates with different exposure time, namely a gate control image 1 and a gate control image 2;
the other two gating cameras of the framing camera 5 expose the second fluorescence signal to obtain two fluorescence intensity images with different exposure time gates for recording the second fluorescence signal, namely a gating image 3 and a gating image 4;
fifthly, four fluorescence intensity images (a gate control image 1, a gate control image 2, a gate control image 3 and a gate control image 4) collected by the framing camera 5 are transmitted to a data processing device 6, and calculation and display of two high-repetition-frequency fluorescence life images are carried out;
the calculation of the two high repetition frequency fluorescence lifetime images is specifically as follows:
two gated fluorescence intensity images (gated image 1 and gated image 2) of the first fluorescence signal were recorded for calculating a first frame fluorescence lifetime map; two gated fluorescence intensity images (gated image 3 and gated image 4) of the second fluorescence signal were recorded for calculation of the second frame fluorescence lifetime map. Wherein the fluorescence lifetime algorithm is a fast fluorescence lifetime algorithm. Thus, the method obtains two frames of fluorescence lifetime images with high frame rate, and the frame rate is determined by the repetition frequency (KHz-MHz) of the high-repetition-frequency laser.
In the high repetition frequency fluorescence lifetime imaging method of the single exponential decay model, a pulse laser is used for continuously emitting fluorescent signal four-frame exposure images recorded under the excitation of two high repetition frequency (KHz-MHz) pulses, and the high repetition frequency (KHz-MHz) rapid fluorescence lifetime imaging of a flow field can be realized under the single exponential decay model.
The above description is only for the preferred embodiment of the present invention, and the technical solution of the present invention is not limited thereto, and any known modifications made by those skilled in the art on the basis of the main technical idea of the present invention belong to the technical scope to be protected by the present invention.
Claims (5)
1. A rapid fluorescence lifetime imaging system for flow field diagnostics, characterized by: the device comprises a pulse laser (1), a sheet light shaping device (2), a flow field generating device (3), a filter (4), a framing camera (5) and a data processing device (6);
the pulse laser (1) simultaneously emits laser pulses and electric signals, the laser pulses are picosecond laser pulses with single pulse energy at a millijoule level, and the wavelength of the laser pulses is equal to the excitation wavelength of components to be detected in a target to be detected in the flow field generating device (3);
the sheet light shaping device (2) is used for shaping laser pulses into sheet light;
the flow field generating device (3) is used for providing a target flow field to be detected, and components to be detected in the target flow field to be detected emit fluorescence signals after the target flow field to be detected is irradiated by the sheet light;
the filter plate (4) is used for transmitting the fluorescent signal and filtering out a stray signal, and the stray signal comprises laser pulses;
the framing camera (5) comprises a synchronous control device and four gated cameras, and the synchronous control device is used for controlling exposure time gates and time delay of the four gated cameras;
the framing camera (5) is connected with the pulse laser (1), the framing camera (5) is triggered by an electric signal emitted by the pulse laser (1), the four gating cameras are controlled by the synchronous control device, and the fluorescent signal filtered by the filter (4) is exposed to obtain four-frame images;
the data processing device (6) is connected with the framing camera (5) and is used for receiving the four-frame images captured by the framing camera (5), processing the four-frame images by adopting a fluorescence life algorithm, and obtaining and displaying fluorescence life images;
the fluorescence lifetime algorithm is a fitting algorithm based on a least square method or a maximum likelihood method, or a non-fitting algorithm based on a rapid fluorescence lifetime algorithm.
2. The rapid fluorescence lifetime imaging system for flow field diagnostics of claim 1, wherein: the framing camera (5) is a sub-aperture type framing camera or a sub-amplitude type framing camera or a rotating mirror type framing camera.
3. The rapid fluorescence lifetime imaging system for flow field diagnostics of claim 1, wherein: the gated camera is an image-enhanced CCD or image-enhanced CMOS camera.
4. The rapid fluorescence lifetime imaging system for flow field diagnostics as claimed in any one of claims 1 to 3, wherein: the filter is a band-pass filter or a long-pass filter.
5. The rapid fluorescence lifetime imaging system for flow field diagnostics of claim 4, wherein: the sheet light shaping device (2) comprises a beam expander and a collimating lens which are sequentially arranged along the laser transmission direction.
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