CN102853918A - Pneumatic optical wavefront ultra-high frequency measurement system and method - Google Patents

Abstract

The invention provides an aero-optical wavefront ultra-high frequency measurement system, which includes a first dual-cavity laser, a second dual-cavity laser, a first half-transparent mirror facing the light outlet of the first dual-cavity laser, and a The first reflector of the light outlet of the second double-cavity laser, the first CCD camera and the second CCD camera that are arranged side by side, the synchronous controller, the computer system that is connected to the first and the second CCD camera and the synchronous controller, facing The second half-mirror of the lens of the second CCD camera, the second reflector facing the lens of the first CCD camera, the background image, the convex lens and the small hole respectively positioned on the opposite sides of the wind tunnel experiment cabin. The background image is on the same side as the second dual-cavity laser; the first and second CCD cameras and the first and second dual-cavity lasers are connected to a synchronous controller. The invention also relates to a measurement method, which uses a computer to analyze and calculate the photographed background image, so as to realize the ultra-high frequency measurement of the full-field aero-optical wavefront distortion.

Description

Aero-optical wavefront UHF measurement system and method

technical field

The invention relates to the field of aerospace, in particular to an aero-optical wavefront ultra-high frequency measurement system used in the fields of supersonic imaging guidance, aerial photography, airborne telescope and the like. Furthermore, the invention also relates to a method comprising the above-mentioned measuring system.

Background technique

The aero-optical wavefront measurement technique can be used to study the aero-optical effects encountered in the fields of supersonic imaging guidance, aerial photography and airborne telescopes. There are many existing measurement methods, such as: interferometry, small aperture beam technology and Malley probe measurement method. The commonly used Malley probe measurement method uses a position sensor to measure the deflection of the beam at a very high frequency, which can only measure a single point wavefront and cannot perform full-field measurement. The Malley probe measurement method is based on the frozen flow hypothesis. The frozen flow hypothesis believes that when the airflow passes through the beam, the refractive index of the flow field only shifts along the direction of the airflow, but there is no change in the spatial distribution. However, in the actual flow field, the convective velocity is unsteady, and the flow field structure also develops and changes, so the assumption of frozen flow is not strictly correct. Especially for the aero-optics research of supersonic flow, there is an urgent need for a high-frequency, full-field measurement of wavefront distortion technology and equipment.

Contents of the invention

The purpose of the present invention is to provide a system and method capable of measuring full-field aero-optical wavefronts with a time interval of microsecond level, so as to obtain data on the time history of supersonic turbulent aero-optical wavefronts and realize ultra-high frequency measurement. Moreover, the equipment of the aero-optical wavefront measurement system of the present invention is simple and easy to operate.

In order to achieve the above object, according to one aspect of the present invention, an aero-optical wavefront ultra-high frequency measurement system is provided, which is used for ultra-high-frequency measurement of the aero-optic wavefront distortion of the laser beam passing through the supersonic wind tunnel experimental cabin , the supersonic wind tunnel experimental cabin produces a supersonic flow field, including the first dual-cavity laser and the second dual-cavity laser arranged side by side; the first half-mirror, the first half-mirror facing the first dual-cavity laser Light outlet; the first mirror, the first mirror is facing the light outlet of the second dual-cavity laser; the first CCD camera and the second CCD camera arranged side by side; the synchronization controller, the first and second CCD cameras and the first and the second dual-cavity laser are connected to the synchronous controller; the computer system, the computer system is connected to the first and second CCD cameras and the synchronous controller; the second half-mirror, the second half-mirror is facing the first The lens of two CCD cameras; the second reflecting mirror, the second reflecting mirror is facing the lens of the first CCD camera; the background image and the convex lens which are respectively positioned at the opposite sides of the wind tunnel experiment cabin, the background image and the first and second double cavity The laser is located on the same side, adjacent to the first half mirror; and the small hole between the convex lens and the second half mirror.

Further, both the first and second CCD cameras are frame-spanning cameras.

Further, the first dual-cavity laser and the first CCD camera are used simultaneously; the second dual-cavity laser and the second CCD camera are used simultaneously.

Further, each laser beam emitted by the first or second dual-cavity laser is exactly within the exposure time range of the corresponding first or second CCD camera, respectively.

Furthermore, the wind tunnel experiment cabin is provided with an optical window, and both the background image and the convex lens are facing the optical window.

According to another aspect of the present invention, there is also provided a method for an aero-optic wavefront UHF measurement system, which includes the above-mentioned aero-optic wavefront measurement system, the computer system sends a first instruction to the synchronous controller, and the synchronous controller After receiving the first instruction, send the first control signal to the first dual-cavity laser and the first CCD camera; after receiving the first control signal, the first dual-cavity laser follows the first predetermined pulse timing predetermined by the computer system Sequentially emit the laser beam that illuminates the flow field in the wind tunnel experiment cabin; the first CCD camera takes pictures of the background image illuminated by the laser in turn according to the second predetermined pulse timing predetermined by the computer system; the computer system stores the first CCD camera every time The photographed background image illuminated by the laser; the computer system sends a second command to the synchronous controller, and the synchronous controller sends a second control signal to the second dual-cavity laser and the second CCD camera after receiving the second command; After receiving the second control signal, the second dual-cavity laser sequentially emits a laser beam that illuminates the flow field in the wind tunnel experimental cabin according to the third predetermined pulse sequence predetermined by the computer system; the second CCD camera follows the predetermined pulse sequence predetermined by the computer system. The fourth predetermined pulse time sequence sequentially takes pictures of the background image illuminated by the laser; the computer system stores the background image illuminated by the laser every time taken by the second CCD camera; the computer performs cross-correlation calculations on the background image and the reference image it stores Obtain the image displacement of the background image, and then calculate the aero-optical wavefront distortion at different times through the relationship between the image displacement and the aero-optic wavefront, wherein, in the above process, the first predetermined pulse timing, the second predetermined pulse timing, the third predetermined The pulse timing and the time interval between every two adjacent pulse timings of the fourth predetermined pulse timing are less than or equal to 0.2 microseconds to 10 microseconds.

Further, after the first dual-cavity laser receives the first control signal, each laser cavity of the first laser emits laser beams according to the first predetermined pulse timing, and each laser beam passes through the first half-mirror, the background Image, wind tunnel experiment cabin, convex lens, small hole, second half mirror and second reflector, the first CCD camera exposes according to the second predetermined pulse time sequence, and is reflected by the second reflector respectively by each The background image after the laser beam is illuminated is taken.

Further, when the first dual-cavity laser and the first CCD camera are working, the second dual-cavity laser and the second CCD camera are turned off.

Further, after the second dual-cavity laser receives the second control signal, each laser cavity of the second dual-cavity laser emits laser beams according to the third predetermined pulse timing, and each laser beam passes through the first mirror in turn, and the first half The half-mirror, the background image, the wind tunnel experiment cabin, the convex lens, the small hole, the second half-mirror, and the second CCD camera is exposed to the second half-mirror according to the second predetermined pulse time sequence. The background images illuminated by each laser beam are captured.

Further, when the second dual-cavity laser and the second CCD camera are working, the first dual-cavity laser and the first CCD camera are turned off.

The present invention has the following beneficial effects: the present invention utilizes the first and second double-cavity lasers to reduce the interval time between every two adjacent laser beams, thereby effectively reducing the time between two adjacent aero-optical wavefront images. Then, the displacement of the background image at different times is used to calculate the aero-optic wavefront distortion at different times, so as to realize the ultra-high frequency measurement of the full-field aero-optic wavefront distortion.

In addition to the objects, features and advantages described above, the present invention has other objects, features and advantages. Hereinafter, the present invention will be described in further detail with reference to the drawings.

Description of drawings

The accompanying drawings constituting a part of this application are used to provide further understanding of the present invention, and the schematic embodiments and descriptions of the present invention are used to explain the present invention, and do not constitute an improper limitation of the present invention. In the attached picture:

Fig. 1 is the schematic diagram of the aero-optical wavefront UHF measurement system of the preferred embodiment of the present invention; And

FIG. 2 is a schematic diagram of a method using an aero-optical wavefront UHF measurement system according to a preferred embodiment of the present invention.

Detailed ways

The embodiments of the present invention will be described in detail below with reference to the accompanying drawings, but the present invention can be implemented in many different ways defined and covered by the claims.

Referring to FIG. 1 , the aero-optical wavefront UHF measurement system of a preferred embodiment of the present invention is used for UHF measurement of the aero-optical wavefront distortion of a laser beam passing through a wind tunnel experiment cabin 10 . The wind tunnel experiment cabin 10 includes an optical window 12 , so that the background image light illuminated by the laser beam passes through the optical window 12 of the wind tunnel experiment cabin 10 . During the aero-optic wavefront test, a supersonic flow field is generated in the wind tunnel experiment cabin 10 .

The aero-optic wavefront measurement system includes a first dual-cavity laser 20 and a second dual-cavity laser 26 arranged side by side, a first half mirror 30, a first mirror 36, a background image 40, a convex lens 50, a small hole 55, The second half mirror 60 , the second mirror 66 , the first CCD camera 70 , the second CCD camera 72 , the synchronization controller 80 and the computer system 90 . Both the first CCD camera 70 and the second CCD camera 72 are frame-spanning cameras. In other embodiments, multiple dual cavity lasers can also be used side by side.

Preferably, the first and second dual-cavity lasers 20, 26 emit a single pulse laser beam with a width of 6 ns, an energy of the single pulse laser beam up to 500 mJ, and a wavelength λ equal to 532 nm. The light outlet of the first dual-cavity laser 20 faces the first half-mirror 30 . The light outlet of the second dual-cavity laser 26 faces the first mirror 36 . Obviously, in other implementation manners, the first dual-cavity laser 20 and the second dual-cavity laser 26 may also be multi-cavity lasers; multiple dual-cavity lasers may also be used side by side.

The background image 40 is located on one side of the wind tunnel experiment cabin 10 and faces the optical window 12 on the side wall of the wind tunnel experiment cabin 10 . The background image 40 is facing the first half mirror 30 . The laser beam emitted by the first dual-cavity laser 20 or the second dual-cavity laser 26 illuminates the background image 40 after being combined by the first half mirror 30 and the first reflector 36, and the background image is illuminated The emitted light passes through the optical window 12 .

The convex lens 50 is located on the other side of the wind tunnel experiment chamber 10 opposite to the background image 40 , and faces the optical window 12 , for receiving the laser beam passing through the optical window 12 .

The small hole 55 is located between the second half mirror 60 and the convex lens 50 . The laser beam passing through the convex lens 50 passes through the small hole 55 to form an image, and then is transmitted and reflected by the second half mirror 60 and the second mirror 66 to be imaged by the first or second CCD cameras 70 and 72 .

The first CCD camera 70 and the second CCD camera 72 are arranged side by side. Wherein, the lens of the first CCD camera is facing the second mirror 66 ; the lens of the second CCD camera 72 is facing the second half mirror 60 . Both the first CCD camera 70 and the second CCD camera 72 are dual-exposure high-resolution CCD cameras consistent with the first dual-cavity laser 20 and the second dual-cavity laser 26, and the shortest time interval between two adjacent exposures can reach 200ns , with a resolution of 2Kx2K. The first CCD camera 70 and the second CCD camera 72 are also connected to the computer system 90 so as to store the images of the background image 40 captured by the first CCD camera 70 and the second CCD camera 72 each time through the computer system 90 .

The synchronization controller 80 is respectively connected to the first CCD camera 70 , the second CCD camera 72 , the first dual-cavity laser 20 , the second dual-cavity laser 26 and the computer system 90 . The computer system 90 sends instructions to the synchronous controller 80, and then the synchronous controller 80 controls the first CCD camera 70 and the first dual-cavity laser 20 respectively, and the second CCD camera 72 and the second dual-cavity laser 26 work synchronously to ensure the first The background image 40 illuminated by the laser beam of a dual-cavity laser 20 is captured by the first CCD camera 70 ; the background image 40 illuminated by the laser beam of the second dual-cavity laser 26 is captured by the second CCD camera 72 .

Please refer to Fig. 2, the method utilizing the aero-optical wavefront measurement system of the present invention comprises the following steps:

S1: The computer system 90 sends a first instruction to the synchronization controller 80 .

After receiving the first instruction, the synchronization controller 80 sends a first control signal to the first dual-cavity laser 20 and the first CCD camera 70 to make the first dual-cavity laser 20 and the first CCD camera 70 work synchronously. At this point, the second dual cavity laser 26 and the second CCD camera 72 are turned off.

S2: After receiving the first control signal from the synchronous controller 80, each laser cavity of the first dual-cavity laser 20 sequentially emits a laser beam that illuminates the background image 40 according to the first predetermined pulse timing predetermined by the computer system 90 ; The first CCD camera 70 sequentially takes pictures of the background image 40 illuminated by the laser according to the second predetermined pulse timing predetermined by the computer system 90 .

The specific process is as follows: the first dual-cavity laser 20 emits laser light from one of the laser cavities after its own laser delay, and the laser beam is combined into a laser beam through the optical components of the first dual-cavity laser 20 to irradiate the first semi-transparent semi-transparent laser beam. Mirror 30. Part of the light source of the laser beam passes through the first half mirror 30 to illuminate the background image 40 , and the light of the background image passes through the optical window 12 . The light beam passing through the optical window 12 passes through the convex lens 50 and then passes through the small hole 55 to form an image. The image formed through the small hole 55 is reflected by the second mirror 66 and falls into the shooting range of the first CCD camera 70 . At this time, the first CCD camera 70 is just in the shooting and exposure stage after a camera delay, so as to realize shooting the background image 40 illuminated by the laser light at this moment. The first CCD camera 70 saves the background image 40 photographed at the above moment to the buffer memory of the first CCD camera 70 after the exposure is completed.

At this time, another laser cavity of the first dual-cavity laser 20 emits laser light, and based on the same process as above, the first CCD camera 70 takes a picture of the background image 40 illuminated by the laser beam generated by the other laser cavity at this moment , and save the captured background image 40 to the cache memory of the first CCD camera 70 . Afterwards, the first dual cavity laser 20 and the first CCD camera 70 are turned off.

In this step, the laser delay time for emitting each laser beam is generally determined by the first dual-cavity laser 20, so the camera delay time of the first CCD camera 70 can be adjusted to ensure that the first dual-cavity laser 20 Each emitted laser beam is just within the corresponding exposure time range of the first CCD camera 70 .

S3: The photos of the background image 40 illuminated by the laser at the two moments in the buffer memory of the first CCD camera 70 are transmitted to the computer system 90 and stored by the computer system 90 .

S4: The computer system 90 sends a second command to the synchronization controller 80 .

After receiving the second instruction, the synchronization controller 80 sends a second control signal to the second dual-cavity laser 26 and the second CCD camera 72 to make the second dual-cavity laser 26 and the second CCD camera 72 work synchronously.

S5: After receiving the second control signal from the synchronous controller 80, each laser cavity of the second dual-cavity laser 26 sequentially emits a laser beam that illuminates the background image 40 according to the third predetermined pulse timing predetermined by the computer system 90 ; The second CCD camera 72 sequentially takes pictures of the background image 40 illuminated by the laser according to the fourth predetermined pulse timing predetermined by the computer system 90 .

The specific process is as follows: the second dual-cavity laser 26 emits laser light from one of the laser cavities after its own laser delay. The laser beam is irradiated to the first half mirror 30 after being reflected by the first mirror 36 . Part of the light source of the laser beam passes through the first half mirror 30 to illuminate the background image 40 , and the light of the background image passes through the optical window 12 . The light passing through the optical window 12 passes through the convex lens 50 and then passes through the small hole 55 to form an image. The image formed through the small hole 55 passes through the second half mirror 60 and partially transmits to the lens of the second CCD camera 72 . At this time, the second CCD camera 72 is just in the shooting and exposure stage after a camera delay, so as to realize shooting the background image 40 illuminated by the laser light at this moment. After the exposure is completed, the second CCD camera 72 saves the background image 40 taken at the above moment to the buffer memory of the second CCD camera 72 .

At this time, another laser cavity of the second dual-cavity laser 26 emits laser light, and based on the same process as above, the second CCD camera 70 takes a picture of the background image 40 illuminated by the laser beam generated by the other laser cavity at this moment. , and save the captured background image 40 to the buffer memory of the second CCD camera 70 .

In this step, the laser delay time of emitting each laser beam is generally determined by the second dual-cavity laser 26, so the camera delay time of the second CCD camera 72 can be adjusted to ensure that the second dual-cavity laser 26 Each emitted laser beam is just within the corresponding exposure time range of the second CCD camera 72 .

In the above steps S2 and S5, the time interval between every adjacent two pulse timings of the first predetermined pulse timing, the second predetermined pulse timing, the third predetermined pulse timing and the fourth predetermined pulse timing is less than or equal to 0.2 Microseconds to 10 microseconds, that is, the frequency between every two adjacent pulse sequences can be as high as 160MHz, so as to realize ultra-high frequency measurement of aero-optical distortion.

S6: The background image in the cache of the second CCD camera 72 is transmitted to the computer system 90 and stored by the computer system 90 .

S7: According to the schlieren principle, the computer system 90 performs cross-correlation calculation on the image of the background image stored in the computer system 90 and the reference image to obtain the displacement of the background image 40 at different times, and then through the displacement of the background image 40 at different times The displacement can then be used to calculate the aero-optical wavefront distortion at different times, and realize the measurement of UHF wavefront distortion.

The present invention utilizes the dual-cavity first and second lasers 20, 26 to reduce the interval time between every two adjacent laser beams, thereby effectively reducing the time interval between taking two adjacent aero-optical wavefront images , which ensures that the time interval between two adjacent aero-optical wavefront images can reach the order of microseconds.

Obviously, in other implementation manners, the first and second lasers 20 and 26 in the above method can also use multi-cavity lasers to take multiple pictures of the background image 40 with very short time intervals.

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 (10)

1. Pneumatic optical wavefront ultrahigh frequency measuring system, being used for that ultrahigh frequency is carried out in the Pneumatic optical wavefront distortion of the laser beam by the supersonic wind tunnel Laboratory Module measures, described supersonic wind tunnel Laboratory Module produces supersonic flow field, it is characterized in that, described Pneumatic optical wavefront measurement system comprises:

At least one that is arranged side by side the first dual-cavity laser and at least one the second dual-cavity laser;

The first semi-transparent semi-reflecting lens, described the first semi-transparent semi-reflecting lens is over against the light-emitting window of described the first dual-cavity laser;

The first catoptron, described the first catoptron is over against the light-emitting window of described the second dual-cavity laser;

A CCD camera that is arranged side by side and the 2nd CCD camera;

Isochronous controller, described first and second CCD camera and described first and second dual-cavity laser all are connected in described

Isochronous controller;

Computer system, described computer system are connected in described first and second CCD camera and described isochronous controller;

The second semi-transparent semi-reflecting lens, described the second semi-transparent semi-reflecting lens is over against the camera lens of described the 2nd CCD camera;

The second catoptron, described the second catoptron is over against the camera lens of a described CCD camera;

Lay respectively at background image and the convex lens of the relative both sides in described wind tunnel experiment cabin, described background image and described first and second dual-cavity laser are positioned at the same side, and contiguous described the first semi-transparent semi-reflecting lens; And

Aperture between described convex lens and described the second semi-transparent semi-reflecting lens.

2. Pneumatic optical wavefront ultrahigh frequency measuring system according to claim 1 is characterized in that,

Described first and second CCD camera is frame straddling cameras.

3. Pneumatic optical wavefront ultrahigh frequency measuring system according to claim 2 is characterized in that,

Described the first dual-cavity laser and a described CCD camera use simultaneously;

Described the second dual-cavity laser and described the 2nd CCD camera use simultaneously.

4. Pneumatic optical wavefront ultrahigh frequency measuring system according to claim 3 is characterized in that,

Every a branch of laser beam of the described first or second dual-cavity laser emission just in time is in respectively within the time shutter scope of the first or the 2nd corresponding CCD camera.

5. Pneumatic optical wavefront ultrahigh frequency measuring system according to claim 4 is characterized in that,

Described wind tunnel experiment cabin is provided with optical window, and described background image and described convex lens are all over against described optical window.

6. a method of using the Pneumatic optical wavefront ultrahigh frequency measuring system of described claim 1 to 5 any one is characterized in that, comprises the steps:

Described computer system is sent first instruction to described isochronous controller, and described isochronous controller receives that backward described the first dual-cavity laser of described first instruction and a CCD camera send first control signal;

After receiving first control signal, the first predetermined pulse sequential that described the first dual-cavity laser is reserved in advance according to described computer system is launched the laser beam that illuminates described wind tunnel experiment cabin flow field successively; The second predetermined pulse sequential that a described CCD camera is reserved in advance according to described computer system is successively to being taken pictures by the described background image of illuminated with laser light;

The described CCD camera of described computer system stores take each time by the described background image of illuminated with laser light;

Described computer system is sent second instruction to described isochronous controller, and described isochronous controller receives that backward described the second dual-cavity laser of described second instruction and the 2nd CCD camera send second control signal;

After receiving second control signal, the 3rd predetermined pulse sequential that described the second dual-cavity laser (a plurality of dual-cavity lasers and so that every group of result's the time interval can be very little under sequential control) is reserved in advance according to described computer system is launched the laser beam that illuminates described wind tunnel experiment cabin flow field successively; The 4th predetermined pulse sequential that described the 2nd CCD camera is reserved in advance according to described computer system is successively to being taken pictures by the described background image of illuminated with laser light;

Described the 2nd CCD camera of described computer system stores take each time by the described background image of illuminated with laser light;

Described computing machine carries out cross-correlation calculation to described background image and the reference picture of its preservation, obtain the picture displacement of described background image, relation by described picture displacement and Pneumatic optical wavefront calculates Pneumatic optical wavefront distortion OPD again, wherein, in the said process, described the first predetermined pulse sequential, described the second predetermined pulse sequential, described the 3rd predetermined pulse sequential all are less than or equal to 0.2 microsecond ~ 10 microseconds according to the time interval between every adjacent two pulse sequences that reach described the 4th predetermined pulse sequential.

7. Pneumatic optical wavefront ultrahigh frequency measuring method according to claim 6 is characterized in that,

After described the first dual-cavity laser is received described first control signal, each laser cavity of described the first laser instrument gives off laser beam according to described the first predetermined pulse sequential, each laser beam is passed through described the first semi-transparent semi-reflecting lens, described background image, described wind tunnel experiment cabin, described convex lens, described aperture, described the second semi-transparent semi-reflecting lens and described the second catoptron successively, a described CCD camera according to the exposure of described the second predetermined pulse sequential respectively to being taken by the background image after being illuminated by each laser beam after described the second mirror reflects.

8. Pneumatic optical wavefront ultrahigh frequency measuring method according to claim 7 is characterized in that,

When described the first dual-cavity laser and the work of a described CCD camera, described the second dual-cavity laser and the 2nd CCD camera are closed.

9. Pneumatic optical wavefront ultrahigh frequency measuring method according to claim 6 is characterized in that,

After described the second dual-cavity laser is received described the second control signal, each laser cavity of described the second dual-cavity laser gives off laser beam according to described the 3rd predetermined pulse sequential, each laser beam is passed through described the first catoptron successively, described the first semi-transparent semi-reflecting lens, described background image, described wind tunnel experiment cabin, described convex lens, described aperture, described the second semi-transparent semi-reflecting lens, described the 2nd CCD camera according to the exposure of described the second predetermined pulse sequential respectively to seen through by described the second semi-transparent semi-reflecting lens illuminated by each laser beam after background image take.

10. Pneumatic optical wavefront ultrahigh frequency measuring method according to claim 9 is characterized in that,

When described the second dual-cavity laser and the work of described the 2nd CCD camera, described the first dual-cavity laser and a CCD camera are closed.

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