Multi-band laser combined laser negative schlieren system

Abstract

The invention discloses a multi-band laser combined laser negative schlieren system. The system is characterized in that convex lenses are arranged on the outer sides of two optical windows; the plurality of lasers emit lasers with different wave bands, the lasers are combined into a beam of transmission laser through the light combining device, the beam of transmission laser enters the test area from the convex lens and the optical window on one side of the test area after being expanded and penetrates out of the optical window and the convex lens on the other side of the test area, and the laser penetrating out is condensed to form a beam of projection laser; and the plurality of light splitting sheets are in one-to-one correspondence with the plurality of laser devices and are arranged on a light path of one beam of projected laser, and the lasers emitted by the plurality of laser devices in different wavebands are respectively separated from the beam of projected laser through reflection and enter the acquisition camera for imaging. According to the invention, a pair of optical windows uses the same optical path to integrate a plurality of negative schlieren systems which have different performances and work independently, images with different characteristics at the same moment and with the same optical phenomenon can be obtained, and multi-type data acquisition of experiments is realized.

Description

Technical Field

[0001] The invention relates to the technical field of laser schlieren systems, and in particular to a laser schlieren system of a multi-band laser combination. Background Art

[0002] The shadow / schlieren system is an optical measurement technology commonly used in high-speed wind tunnels and ballistic targets. The airflow passing through the optical path is compressed by the model, and the density changes, causing the light to be deflected, producing corresponding light and dark images in the image.

[0003] The existing shadow / schlieren technology is limited by space. There is only one pair of optical windows available in the experimental cabin. Usually, a shadow / schlieren system can be set up, but it is difficult to meet different test requirements. For example, for a test section with a sub-meter length, the experimental test time window is tens of microseconds, which is difficult to meet the test requirements for high spatial / temporal resolution and local / overall flow structure observation. Although the optical path multiplexing of the same pair of optical windows can be achieved through spatial separation technology, it is currently impossible to achieve complete overlap of the optical paths of different shadow / schlieren systems. When only one shadow / schlieren system can be set up, it is obviously necessary to conduct detection step by step. At the same time, there are differences in the images formed by light sources at different spatial positions during the optical path multiplexing process.

[0004] In summary, the existing schlieren system cannot meet the requirements of simultaneously capturing images of lasers with different characteristics. Summary of the invention

[0005] The object of the present invention is to provide a laser schlieren system of a multi-band laser combination to solve the technical problem in the prior art that the existing schlieren system cannot realize the image acquisition requirements of lasers with different characteristics at the same time.

[0006] In order to solve the above technical problems, the present invention specifically provides the following technical solutions:

[0007] A laser schlieren system with a multi-band laser combination, comprising:

[0008] Two optical windows, convex lenses are arranged outside the two optical windows, and a test area is arranged between the two optical windows for the fluid light beam to pass through;

[0009] A plurality of lasers are used to emit lasers of different wavelength bands. The lasers emitted by the plurality of lasers are combined into a beam of transmitted lasers by a light combining device. The beam of transmitted lasers enters the test area through the convex lens and the optical window on one side of the test area after beam expansion, and passes through the optical window and the convex lens on the other side of the test area. The lasers that pass through are focused to form a beam of projected lasers.

[0010] A plurality of beam splitters, which correspond one to one with the plurality of lasers, are arranged on the optical path of the one projected laser beam, and separate the lasers emitted by the plurality of lasers of different wavelength bands from the one projected laser beam through reflection and enter the acquisition camera for imaging.

[0011] As a preferred solution of the present invention, the light combining device includes multiple light combining plates, and the multiple light combining plates correspond one-to-one to the multiple lasers. The multiple light combining plates combine the lasers emitted by the corresponding multiple lasers into a beam of transmitted laser through reflection.

[0012] As a preferred solution of the present invention, a collimating lens is arranged between the laser and the light combining plate, and the laser light generated by the laser is projected onto the light combining plate through the collimating lens.

[0013] As a preferred solution of the present invention, a narrow-band filter is provided between the beam splitter and the acquisition camera, and the wavelength of the laser light generated by the laser is the same as the central wavelength of the corresponding narrow-band filter.

[0014] As a preferred solution of the present invention, a focusing lens is arranged between the beam splitter and the narrow-band filter.

[0015] As a preferred solution of the present invention, a splitter concave lens is arranged on the optical path of the transmitted laser beam entering the convex lens, and the splitter concave lens is used to expand the transmitted laser beam and then project it to the convex lens;

[0016] A light-combining concave lens is provided on the optical path between the convex lens and the one beam of projected laser light. The light-combining concave lens is used to focus the laser light refracted by the convex lens to form the one beam of projected laser light.

[0017] As a preferred solution of the present invention, the central wavelength of the laser is the same as that of the corresponding narrow-band filter.

[0018] As a preferred solution of the present invention, the beam splitter and the light combiner are both dichroic filters, and the reflection wavelengths of the beam splitter and the light combiner include the working wavelengths of the corresponding lasers.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The present invention realizes the installation of multiple sets of independently working schlieren systems with different performances using the same optical path on the same pair of optical windows, which can achieve the acquisition of images with different characteristics and the same optical path for the same optical phenomenon at the same time without affecting the imaging. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the implementation methods of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the implementation methods or the description of the prior art. Obviously, the drawings in the following description are only exemplary, and for ordinary technicians in this field, other implementation drawings can be derived from the provided drawings without creative work.

[0022] Figure 1 A schematic diagram of a laser schlieren system according to an embodiment of the present invention;

[0023] Figure 2 Schematic diagram of a light combiner and a light splitter according to an embodiment of the present invention.

[0024] The numbers in the figure represent the following:

[0025] 10-optical window; 20-convex lens; 30-laser; 40-light combining device; 50-testing area; 60-beam splitter; 70-collimating lens; 80-collection camera; 90-narrow-band filter; 100-condensing lens; 110-beam splitting concave lens; 120-light combining concave lens. DETAILED DESCRIPTION

[0026] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] like Figure 1 and Figure 2 As shown, the present invention provides a laser schlieren system of a multi-band laser combination, comprising:

[0028] Two optical windows 10, convex lenses 20 are arranged outside the two optical windows 10, and a test area is set between the two optical windows 10 for the fluid light beam to pass through;

[0029] Multiple lasers 30 are used to emit lasers of different wavelength bands. The lasers emitted by the multiple lasers are combined into a beam of transmitted laser through a light combining device 40. After beam expansion, the beam of transmitted laser enters the test area from the convex lens 20 and the optical window 10 on one side of the test area 50, and passes through the optical window 10 and the convex lens 20 on the other side of the test area 50. After passing through, the laser is focused to form a beam of projected laser.

[0030] Multiple beam splitters 60 correspond to multiple lasers 30 one by one and are arranged on the optical path of a projected laser beam. Lasers emitted by multiple lasers 30 of different wavelength bands are separated from the projected laser beam by reflection and enter the acquisition camera for imaging.

[0031] In terms of specific implementation, this embodiment is mainly aimed at optical measurement images in high enthalpy wind tunnels or when there is combustion flow, and at the situation of shadow / schlieren image acquisition when one observation window is needed to simultaneously obtain different measurement requirements (imaging band, spatial resolution, exposure time, frame interval and number of frames).

[0032] In the existing shadow / schlieren device, affected by the light source and forming equipment, usually a set of shadow / schlieren device can only meet part of the measurement requirements. In addition, when the existing spatial separation technology reuses the optical path, there is an angle between the main optical axes of the optical paths of different shadow / schlieren systems, the optical paths do not overlap, and there are differences in the imaging areas.

[0033] In the present embodiment, a light combining device is provided in a classic lens-type shadow / schlieren system composed of a laser beam to combine multiple lasers into the same optical path, and a light splitting device is provided to separate lasers of corresponding wavelength bands from one laser optical path, thereby realizing multiplexing of multiple optical paths by a pair of optical windows. The same window can realize multiple shadow / schlieren systems working simultaneously without interfering with each other, and images with different characteristics and the same optical path can be obtained for the same phenomenon at the same time in two optical observation windows.

[0034] In this embodiment, a basic optical path is first constructed, and the laser light emitted by one laser is combined into a beam of transmitted laser light through the light combining device 40. After beam expansion, the transmitted laser light enters the test area 50 from the convex lens 20 and the optical window 10 on one side of the test area 50, and passes through the optical window 10 and the convex lens 20 on the other side of the test area 50. The laser light after passing through is focused to form a beam of projected laser light, in which the laser light emitted by the laser 30 is directly opposite to the center position of the two convex lenses 20, and then the laser light emitted by other multiple lasers 30 is refracted into the basic optical path through the light combining device 40.

[0035] Specifically, the light combining device 40 includes a plurality of light combining plates, and the plurality of light combining plates correspond one-to-one to the plurality of lasers. The plurality of light combining plates combine the lasers emitted by the corresponding plurality of lasers 30 into a beam of transmitted laser by reflection.

[0036] This embodiment is an optical measurement technology for measuring density changes of a fluid passing between two optical observation windows. The test area between the two optical windows 10 is the area where the light beam in the fluid measured by the shadow system passes.

[0037] When light passes through this area, the change in density within the area will refract the light in the direction of lower density, thereby changing the light intensity at different positions in the image and showing the change in density.

[0038] Optical windows confine the fluid while allowing light to pass through it. Optical windows are installed in wind tunnels to keep the experimental chamber sealed.

[0039] A collimating lens 70 is disposed between the laser 30 and the light combining plate. The laser light generated by the laser 30 is projected onto the light combining plate through the collimating lens 70. The collimating lens 70 can adjust the laser beam emitted by the corresponding laser 30 into parallel light.

[0040] A narrowband filter 90 is provided between the spectrometer 60 and the acquisition camera 80. The wavelength of the laser light generated by the laser 30 is the same as the central wavelength of the corresponding narrowband filter 90. The narrowband filter 90 can filter out stray light in the laser beam separated by the spectrometer.

[0041] In the present embodiment, in the separation of light beams after combining light of different wavelength bands, a focusing lens 100 is provided between the beam splitter 60 and the narrow-band filter 90. The focusing lens 100 can converge the parallel light separated by the beam splitter 60, so that the acquisition camera 80 can obtain accurate imaging.

[0042] A beam splitting concave lens 110 is arranged on the optical path of a beam of transmitted laser light entering the convex lens. The beam splitting concave lens 110 is used to expand the beam of transmitted laser light and then project it to the convex lens.

[0043] A light-combining concave lens 120 is provided on the optical path between the convex lens and a beam of projected laser light. The light-combining concave lens 120 is used to focus the laser light refracted by the convex lens to form a beam of projected laser light.

[0044] The center wavelength of the laser 30 and the corresponding narrow band filter are the same.

[0045] The beam splitter 60 and the light combiner are both dichroic filters, and the reflection wavelengths of the beam splitter 60 and the light combiner include the working wavelengths of the corresponding lasers.

[0046] The above embodiments are only exemplary embodiments of the present application and are not intended to limit the present application. The protection scope of the present application is defined by the claims. Those skilled in the art may make various modifications or equivalent substitutions to the present application within the essence and protection scope of the present application, and such modifications or equivalent substitutions shall also be deemed to fall within the protection scope of the present application.

Claims

1. A laser schlieren system with a multi-band laser combination. It is characterized in that include, Two optical windows (10), convex lenses (20) are arranged outside the two optical windows (10), and a test area is arranged between the two optical windows (10) for a fluid light beam to pass through; A plurality of lasers (30) are used to emit lasers of different wavelength bands. The lasers emitted by the plurality of lasers are combined into a beam of transmitted laser light through a light combining device (40). The beam of transmitted laser light enters the test area from the convex lens (20) and the optical window (10) on one side of the test area (50) after beam expansion, and passes through the optical window (10) and the convex lens (20) on the other side of the test area (50). The laser light that passes through is focused to form a beam of projected laser light. A plurality of beam splitters (60) are provided, each corresponding to the plurality of lasers (30) on a one-to-one basis, and are arranged on the optical path of the one beam of projected laser light. The laser lights emitted by the plurality of lasers (30) of different wavelength bands are separated from the one beam of projected laser light by reflection, and enter the acquisition camera (80) for imaging.

2. The laser schlieren system of a multi-band laser combination according to claim 1, It is characterized in that The light combining device (40) comprises a plurality of light combining plates, and the plurality of light combining plates correspond one-to-one to the plurality of lasers. The plurality of light combining plates combine the lasers emitted by the corresponding plurality of lasers (30) into a beam of transmitted laser through reflection.

3. The laser schlieren system of a multi-band laser combination according to claim 2, It is characterized in that A collimating lens (70) is provided between the laser (30) and the light combining plate, and the laser light generated by the laser (30) is projected onto the light combining plate through the collimating lens (70).

4. The laser schlieren system of a multi-band laser combination according to claim 3, It is characterized in that A narrowband filter (90) is provided between the beam splitter (60) and the acquisition camera (80), and the wavelength of the laser light generated by the laser (30) is the same as the central wavelength of the corresponding narrowband filter (90).

5. The laser schlieren system of a multi-band laser combination according to claim 4, It is characterized in that A condenser lens (100) is provided between the beam splitter (60) and the narrow-band filter (90).

6. The laser schlieren system of a multi-band laser combination according to claim 1, It is characterized in that A beam splitting concave lens (110) is arranged on the optical path of the transmitted laser beam entering the convex lens, and the beam splitting concave lens (110) is used to expand the transmitted laser beam and then project it onto the convex lens; A light-combining concave lens (120) is provided on the optical path between the convex lens and the one beam of projected laser light, and the light-combining concave lens (120) is used to focus the laser light refracted by the convex lens to form the one beam of projected laser light.

7. The laser schlieren system of a multi-band laser combination according to claim 4, It is characterized in that The central wavelength of the laser (30) is the same as that of the corresponding narrow-band filter.

8. The laser schlieren system of a multi-band laser combination according to claim 4, It is characterized in that The beam splitter (60) and the light combiner are both dichroic filters, and the reflection wavelengths of the beam splitter (60) and the light combiner include the working wavelengths of the corresponding lasers.

Images