A projected focusing schlieren system with a programmable grid

Abstract

The present invention proposes a projected focused schlieren system with a programmable grid, wherein the flow field test area is located between the projection lens and the reflective screen; the camera and light source are arranged on the same side of the flow field test area, and the reflective screen is located on the other side of the flow field test area, resulting in a larger imaging field of view for the focused schlieren system. The present invention utilizes the programmable capabilities of digital micromirror devices and has the function of adjusting the schlieren sensitivity online in real time. Specifically, the arrangement of the micromirrors in the "on" and "off" states can be precisely controlled directly through a controller to achieve online, real-time adjustment of the schlieren sensitivity. The adjustment of the schlieren sensitivity is more convenient and has a wider adjustment range. The present invention can greatly reduce the difficulty of using focused schlieren technology in actual scenarios.

Description

Technical Field

[0001] The present invention mainly relates to the field of focusing schlieren technology, in particular to a projection-type focusing schlieren system with a programmable grid. Background Art

[0002] A projected focusing schlieren system with a programmable grid requires a light source and source grid on one side of the test area, while a lens, knife-edge grid, and camera are placed on the other side. This results in a bulky focusing schlieren system. Furthermore, the parameters and relative positions of these components are directly coupled and affect each other, making setting up the focusing schlieren system and adjusting its schlieren sensitivity in real-world scenarios inconvenient and limited in adjustment range, making it extremely time-consuming and labor-intensive. Summary of the Invention

[0003] In view of the problems that the schlieren sensitivity of a current projection-type focusing schlieren system with a programmable grid is inconvenient to adjust and the adjustment range is limited, the present invention proposes a projection-type focusing schlieren system with a programmable grid.

[0004] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0005] A projected focusing schlieren system with a programmable grid includes an integrated module and a reflective screen, wherein a flow field test area is located between the integrated module and the reflective screen;

[0006] The integrated module includes a light source, a condenser lens, a beam splitter prism, a relay lens, a first aperture, a first prism, a digital micromirror device, a second prism, a second aperture, a projection lens, a reflective screen, a focusing lens, and a camera. The flow field test area is located between the projection lens and the reflective screen. The camera and the light source are arranged on the same side of the flow field test area, and the reflective screen is located on the other side of the flow field test area.

[0007] The light source is used to emit schlieren background light. After being emitted from the light source, the schlieren background light is converged by a condenser lens, sequentially passes through a beam splitter prism, a relay lens, and a first aperture, and is then totally reflected by the first prism to the surface of a digital micromirror device. By programming and controlling the digital micromirror device, uniform schlieren background light is reflected by the surface of the digital micromirror device to form a series of strip light sources. The strip light sources reflected by the surface of the digital micromirror device pass through the first prism, the second prism, and the second aperture, and are projected by the projection lens, pass through the flow field test area, and reach the surface of a reflective screen, wherein the surface of the digital micromirror device and the surface of the reflective screen are conjugate with respect to the projection lens. Reflected return light from the surface of the reflective screen returns through the projection lens, the second aperture, the second prism, and the first prism, and is imaged on the surface of the digital micromirror device. The reflected return light reflected by the surface of the digital micromirror device passes through the first prism, the first aperture, the relay lens, the beam splitter prism, and the focusing lens, and is captured and photographed by a camera.

[0008] The digital micromirror device described in the present invention includes a controller and a plurality of micromirrors arranged in an array on the surface of the digital micromirror device. The plurality of micromirrors arranged in an array constitute a micromirror array. The angle of each micromirror is adjustable, corresponding to two states of "on" or "off". The controller is connected and used to control each micromirror in real time to be placed in the "on" or "off" state, thereby controlling the arrangement of the micromirrors in the "on" and "off" states on the surface of the digital micromirror device, thereby realizing online real-time adjustment of the schlieren sensitivity.

[0009] If a single integrated module cannot cover the entire flow field test area, multiple integrated modules can be set up. Multiple integrated modules are distributed side by side on one side of the flow field test area, and the reflective screen is located on the other side of the flow field test area. This makes it convenient to use multiple modules and splice the field of view.

[0010] On the other hand, the present invention also provides a projected focusing schlieren system with a programmable grid, comprising an integrated module and a reflective screen, wherein a flow field test area is located between the integrated module and the reflective screen;

[0011] The integrated module includes a light source, a condenser lens, a first linear polarizer, a first prism group, a digital micromirror device, a polarization beam splitter, a quarter-wave plate, a projection lens, a second linear polarizer, a second prism group, a reflective screen, a focusing lens, and a camera. The flow field test area is located between the projection lens and the reflective screen. The camera and the light source are arranged on the same side of the flow field test area, and the reflective screen is located on the other side of the flow field test area. The digital micromirror device includes two devices, a first digital micromirror device and a second digital micromirror device.

[0012] The light source is used to emit schlieren background light. After being emitted from the light source, the schlieren background light is converged by a condenser lens and then sequentially passes through a first linear polarizer and a first prism group before being incident on the surface of a first digital micromirror device. By programming and controlling the first digital micromirror device, uniform schlieren background light is reflected from the surface of the first digital micromirror device to form a series of strip light sources. The strip light sources reflected from the surface of the first digital micromirror device pass through a polarizing beam splitter prism and a quarter-wave plate and are then projected through a projection lens, passing through a flow field test area, and reaching the surface of a reflective screen. Reflected return light from the surface of the reflective screen sequentially passes through a projection lens, a quarter-wave plate, a polarizing beam splitter prism, a second linear polarizer, and a second prism group before being incident on the surface of a second digital micromirror device. The reflected return light reflected from the surface of the second digital micromirror device passes through a focusing lens and is captured by a camera.

[0013] Through the above technical solution, the present invention can produce the following technical effects:

[0014] The flow field test area of ​​the present invention is located between the projection lens and the reflective screen; the camera and light source are arranged on the same side of the flow field test area, and the reflective screen is located on the other side of the flow field test area, thereby expanding the imaging field of the focused schlieren system. The present invention utilizes the programmable capabilities of digital micromirror devices to provide real-time online adjustment of schlieren sensitivity. Specifically, the arrangement of the micromirrors in both "on" and "off" states can be precisely controlled directly through a controller (such as a computer), achieving online, real-time adjustment of schlieren sensitivity. This makes adjustment of schlieren sensitivity more convenient and extends the adjustment range.

[0015] The present invention can greatly reduce the difficulty of using the focused schlieren technology in actual scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0017] Figure 1 1 is a schematic structural diagram of a projected focusing schlieren system with a programmable grid provided in one embodiment;

[0018] Figure 2 1 is a schematic structural diagram of a projected focusing schlieren system with a programmable grid provided in one embodiment;

[0019] Figure 3 Schematic diagram of three Schlieren sensitivities adjusted in one embodiment, wherein (a) shows the first Schlieren sensitivity, (b) shows the second Schlieren sensitivity, and (c) shows the third Schlieren sensitivity;

[0020] Figure 4 Schematic diagrams of three refractive index sensitivity directions obtained by adjustment in one embodiment, wherein (a) shows the horizontal direction, (b) shows the vertical direction, and (c) shows the 45-degree oblique direction;

[0021] Description of the numbers in the figure:

[0022] 1. Light source, 2. Condensing lens, 3. Beam splitter, 4. Relay lens, 5. First aperture, 6. First prism, 7. Digital micromirror device, 8. Second prism, 9. Second aperture, 10. Projection lens, 11. Flow field test area, 12. Reflection screen, 13. Focusing lens, 14. Camera, 15. First linear polarizer, 16. First prism group, 17. First digital micromirror device, 18. Polarization beam splitter, 19. Quarter wave plate, 20. Second linear polarizer, 21. Second prism group, 22. Second digital micromirror device. DETAILED DESCRIPTION

[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clearly understood, the following drawings and detailed descriptions clearly illustrate the spirit of the present invention. After understanding the embodiments of the present invention, any person skilled in the art will be able to make changes and modifications based on the techniques taught by the present invention without departing from the spirit and scope of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to illustrate the present invention and are not intended to limit the present invention.

[0024] In one embodiment, referring to Figure 1 , providing a projected focusing schlieren system with a programmable grid, comprising an integrated module and a reflective screen 12, wherein a flow field test area 11 is located between the integrated module and the reflective screen 12;

[0025] The integrated module includes a light source 1, a condenser lens 2, a beam splitter prism 3, a relay lens 4, a first aperture 5, a first prism 6, a digital micromirror device 7, a second prism 8, a second aperture 9, a projection lens 10, a reflective screen 12, a focusing lens 13, and a camera 14. The flow field test area 11 is located between the projection lens 10 and the reflective screen 12. The camera 14 and the light source 1 are arranged on the same side of the flow field test area 11, and the reflective screen 12 is located on the other side of the flow field test area 11.

[0026] The light source 1 is used to emit Schlieren background light. After the Schlieren background light is emitted from the light source 1, it is converged by the condenser lens 2, passes through the dichroic prism 3, the relay lens 4, and the first aperture 5 in sequence, and then is totally reflected by the first prism 6 to the surface of the digital micromirror device 7. By programming and controlling the digital micromirror device 7, the uniform Schlieren background light is reflected by the surface of the digital micromirror device to form a series of strip light sources. The strip light sources reflected from the surface of the digital micromirror device 7 pass through the first prism 6, the second prism 8, and the second aperture 9 and are projected through the lens. The mirror 10 projects light, passes through the flow field test area 11, and reaches the surface of the reflective screen 12, where the surface of the digital micromirror device and the surface of the reflective screen are conjugate with respect to the projection lens 10; the reflected light from the surface of the reflective screen 12 is returned through the projection lens 10, the second aperture 9, the second prism 8, and the first prism 6, and is imaged on the surface of the digital micromirror device 7. The reflected light reflected from the surface of the digital micromirror device 7 passes through the first prism 6, the first aperture 5, the relay lens 4, the dichroic prism 3, and the focusing lens 13, and is captured by the camera 14.

[0027] The digital micromirror device 7 in the above embodiment includes a controller and a plurality of micromirrors arranged in an array on the surface of the digital micromirror device. The plurality of micromirrors arranged in an array constitute a micromirror array. The angle of each micromirror is adjustable, corresponding to the two states of "on" or "off". The controller is connected and used to control each micromirror in real time to be placed in the "on" or "off" state, thereby controlling the arrangement of the micromirrors in the "on" and "off" states on the surface of the digital micromirror device, thereby realizing online real-time adjustment of the schlieren sensitivity.

[0028] Since the surface of the digital micromirror device and the surface of the reflective screen are conjugate with respect to the projection lens 10, the reflected light from the reflective screen 12 is collected by the projection lens and imaged on the surface of the digital micromirror device 7. When there is no refractive index change in the flow field test area 11, the vast majority of the reflected light will still fall on the micromirror in the "on" state, then enter the first prism 6, and then be reflected to the relay lens 4 and the dichroic prism 3, and finally pass through the focusing lens 13 and be captured by the camera 14. If there is a certain refractive index change in the flow field test area 11, when the reflected light from the reflective screen 12 reaches the surface of the digital micromirror device 7, part of the light will fall on the micromirror in the "off" state, which will form stray light and most of which will be blocked by the first aperture 5. By adjusting the focusing lens 13, the camera 14 is focused on the flow field test area 11. When there is no refractive index change in the flow field test area 11, the camera 14 captures an image with uniform brightness; when there is a refractive index change in the flow field test area 11 causing light deflection, the camera 14 captures a focused schlieren image with light and dark changes that reflects the flow field structure.

[0029] In one embodiment, referring to Figure 2, providing a projected focusing schlieren system with a programmable grid, comprising an integrated module and a reflective screen 12, wherein a flow field test area 11 is located between the integrated module and the reflective screen 12;

[0030] The integrated module includes a light source 1, a focusing lens 2, a first linear polarizer 15, a first prism group 16, a first digital micromirror device 17, a polarization beam splitter prism 18, a quarter-wave plate 19, a projection lens 10, a second linear polarizer 20, a second prism group 21, a second digital micromirror device 22, a reflective screen 12, a focusing lens 13 and a camera 14. The flow field test area 11 is located between the projection lens 10 and the reflective screen 12; the camera 14 and the light source 1 are arranged on the same side of the flow field test area 11, and the reflective screen 12 is located on the other side of the flow field test area 11.

[0031] The light source 1 is used to emit schlieren background light. After being emitted from the light source 1, the schlieren background light is converged by the condenser lens 2, and then passes through the first linear polarizer 15 and the first prism group 16 in sequence before being incident on the surface of the first digital micromirror device 17. By programming and controlling the first digital micromirror device 17, the uniform schlieren background light is reflected by the surface of the digital micromirror device to form a series of strip light sources. The strip light sources reflected from the surface of the first digital micromirror device 17 pass through the polarization beam splitter prism 18 and the 1 / 4 wave plate 19, and are projected out through the projection lens 10, pass through the flow field test area 11, and reach the surface of the reflection screen 12. Among them, the surface of the first digital micromirror device 17 and the surface of the reflective screen 12 are conjugate with respect to the projection lens 10; the reflected return light from the surface of the reflective screen 12 is incident on the surface of the second digital micromirror device 22 in sequence through the projection lens 10, the 1 / 4 wave plate 19, the polarization beam splitter prism 18, the second linear polarizer 20, and the second prism group 21. The reflected return light reflected from the surface of the second digital micromirror device 22 is captured and photographed by the camera 14 after passing through the focusing lens 13.

[0032] The digital micromirror device 7 in the above embodiment includes a controller and a plurality of micromirrors arranged in an array on the surface of the digital micromirror device. The plurality of micromirrors arranged in an array constitute a micromirror array. The angle of each micromirror is adjustable, corresponding to the two states of "on" or "off". The controller is connected and used to control each micromirror in real time to be placed in the "on" or "off" state, thereby controlling the arrangement of the micromirrors in the "on" and "off" states on the surface of the digital micromirror device, thereby realizing online real-time adjustment of the schlieren sensitivity.

[0033] The Schlieren sensitivity of a projected focusing Schlieren system with a programmable grid in any of the above embodiments is mainly determined by the width of the bright stripes on the strip light source. With the programmable capability of the digital micromirror device, the arrangement of the micromirror array in the "on" and "off" states on the micromirror array can be adjusted online to change the Schlieren sensitivity in real time, such as Figure 3As shown, Figure 3 The dark black stripes are made up of micro-mirrors in the "off" state, and the bright white stripes are made up of micro-mirrors in the "on" state. Figure 3 (a), (b), and (c) show three types of Schlieren sensitivity, respectively. Figure 3 The width of the white bright stripe in (a) is the narrowest. Figure 3 (b) The width of the white bright stripe is in the middle. Figure 3 The width of the white bright stripe in (c) is the widest. Figure 3 The Schlieren sensitivity of (a) is higher than that of (b), and the Schlieren sensitivity of (b) is higher than that of (c). Figure 3 The three types of Schlieren sensitivity shown in the figure can also be flexibly adjusted online as needed. The arrangement of the micro-mirror array in the "on" and "off" states on the micro-mirror array can be adjusted online to change the Schlieren sensitivity in real time. The width of the specific white bright stripes and black dark stripes is not limited.

[0034] The refractive index sensitive direction of a projected focusing schlieren system with a programmable grid refers to the arrangement direction of the light and dark stripes on the strip light source. Benefiting from the programmable capability of the digital micromirror device, the two states of "on" and "off" of each micromirror on the micromirror array can be directly controlled to change the refractive index sensitive direction arbitrarily and quickly, realizing the refractive index sensitivity direction adjustment function, such as Figure 4 As shown, Figure 4 The dark black stripes are made up of micro-mirrors in the "off" state, and the bright white stripes are made up of micro-mirrors in the "on" state. Figure 4 (a), (b), and (c) show three refractive index sensitive directions, where Figure 4 (a) shows the horizontal direction, Figure 4 (b) shows the vertical direction, Figure 4 (c) shows the direction of 45 degrees. In practical applications, it is not limited to Figure 4 The adjustments of the three refractive index sensitivity directions shown in the figure can also be flexibly adjusted as needed. The arrangement of the micro-mirror array in the "on" and "off" states on the micro-mirror array can be adjusted online to change the refractive index sensitivity direction in real time. The specific arrangement direction and angle are not limited.

[0035] A projected focusing schlieren system with a programmable grid. If a single integrated module cannot cover the entire flow field test area, multiple integrated modules can be set up. The multiple integrated modules are distributed side by side on one side of the flow field test area, and the reflective screen is located on the other side of the flow field test area. In this way, multiple modules can be used together and the field of view can be spliced ​​conveniently.

[0036] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0037] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present application, and such modifications and improvements are intended to fall within the scope of protection of the present application. Therefore, the scope of protection of the present application shall be determined by the appended claims.

[0038] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that the present invention is susceptible to various modifications and variations. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A projected focusing schlieren system with a programmable grid, characterized in that: It includes an integrated module and a reflection screen, and the flow field test area is located between the integrated module and the reflection screen; The integrated module includes a light source, a condenser lens, a beam splitter prism, a relay lens, a first aperture, a first prism, a digital micromirror device, a second prism, a second aperture, a projection lens, a reflective screen, a focusing lens, and a camera. The flow field test area is located between the projection lens and the reflective screen. The camera and the light source are arranged on the same side of the flow field test area, and the reflective screen is located on the other side of the flow field test area. The light source is used to emit schlieren background light. After being emitted from the light source, the schlieren background light is converged by a condenser lens, sequentially passes through a beam splitter prism, a relay lens, and a first aperture, and is then totally reflected by the first prism to a surface of a digital micromirror device. The digital micromirror device is programmed and controlled so that uniform schlieren background light is reflected by the surface of the digital micromirror device to form a series of strip light sources. The strip light sources reflected from the surface of the digital micromirror device pass through the first prism, the second prism, and the second aperture, and are then projected by a projection lens, pass through a flow field test area, and reach a surface of a reflective screen, wherein the surface of the digital micromirror device and the surface of the reflective screen are conjugate with respect to the projection lens. The reflected light from the surface of the reflective screen returns through the projection lens, the second aperture, the second prism, and the first prism, and is imaged on the surface of the digital micromirror device. The reflected light reflected from the surface of the digital micromirror device passes through the first prism, the first aperture, the relay lens, the dichroic prism, and the focusing lens, and is captured by the camera.

2. The projected focusing schlieren system with a programmable grid according to claim 1, characterized in that: The digital micromirror device includes a controller and a plurality of micromirrors arranged in an array on the surface of the digital micromirror device. The plurality of micromirrors arranged in an array constitute a micromirror array. The angle of each micromirror is adjustable, corresponding to two states of "on" or "off". The controller is connected and used to control each micromirror in real time to be placed in the "on" or "off" state, thereby controlling the arrangement of the micromirrors in the "on" and "off" states on the surface of the digital micromirror device, thereby realizing online real-time adjustment of the schlieren sensitivity.

3. The projected focusing schlieren system with a programmable grid according to claim 2, characterized in that: The Schlieren background light reflected by the micro-reflector in the "on" state will pass through the first prism, the second prism, and the second aperture, and then be projected out by the projection lens, pass through the flow field test area, and reach the surface of the reflection screen, while the Schlieren background light reflected by the micro-reflector in the "off" state will be blocked by the second aperture.

4. A projected focusing schlieren system with a programmable grid according to claim 1, 2 or 3, characterized in that: There are multiple integrated modules, which are distributed in parallel on one side of the flow field test area, and the reflective screen is located on the other side of the flow field test area.

5. A projected focusing schlieren system with a programmable grid, characterized in that: It includes an integrated module and a reflection screen, and the flow field test area is located between the integrated module and the reflection screen; The integrated module includes a light source, a condenser lens, a first linear polarizer, a first prism group, a digital micromirror device, a polarization beam splitter, a quarter-wave plate, a projection lens, a second linear polarizer, a second prism group, a reflective screen, a focusing lens, and a camera. The flow field test area is located between the projection lens and the reflective screen. The camera and the light source are arranged on the same side of the flow field test area, and the reflective screen is located on the other side of the flow field test area. The digital micromirror device includes two devices, a first digital micromirror device and a second digital micromirror device. The light source is used to emit schlieren background light. After being emitted from the light source, the schlieren background light is converged by a condenser lens and then sequentially passes through a first linear polarizer and a first prism group before being incident on the surface of a first digital micromirror device. By programming and controlling the first digital micromirror device, uniform schlieren background light is reflected from the surface of the first digital micromirror device to form a series of strip light sources. The strip light sources reflected from the surface of the first digital micromirror device pass through a polarizing beam splitter prism and a quarter-wave plate and are then projected through a projection lens, passing through a flow field test area, and reaching the surface of a reflective screen. Reflected return light from the surface of the reflective screen sequentially passes through a projection lens, a quarter-wave plate, a polarizing beam splitter prism, a second linear polarizer, and a second prism group before being incident on the surface of a second digital micromirror device. The reflected return light reflected from the surface of the second digital micromirror device passes through a focusing lens and is captured by a camera.

6. The projected focusing schlieren system with a programmable grid according to claim 5, characterized in that: The first digital micromirror device surface is conjugate with the reflective screen surface with respect to the projection lens.

7. The projected focusing schlieren system with a programmable grid according to claim 5, characterized in that: The digital micromirror device includes a controller and a plurality of micromirrors arranged in an array on the surface of the digital micromirror device. The plurality of micromirrors arranged in an array constitute a micromirror array. The angle of each micromirror is adjustable, corresponding to two states of "on" or "off". The controller is connected and used to control each micromirror in real time to be placed in the "on" or "off" state, thereby controlling the arrangement of the micromirrors in the "on" and "off" states on the surface of the digital micromirror device, thereby realizing online real-time adjustment of the schlieren sensitivity.

8. The projected focusing schlieren system with a programmable grid according to claim 7, characterized in that: The schlieren sensitivity of a projected focusing schlieren system with a programmable grid is determined by the width of the bright stripes on the strip light source. By leveraging the programmable capability of a digital micromirror device (DMD), the schlieren sensitivity can be changed in real time by online adjusting the arrangement of the micromirror array on the DMD surface in the "on" and "off" states.

9. The projected focusing schlieren system with a programmable grid according to claim 8, characterized in that: The refractive index sensitive direction of a projected focusing schlieren system with a programmable grid refers to the arrangement direction of the light and dark stripes on the strip light source. By controlling the "on" and "off" states of each micro-mirror on the micro-mirror array, the refractive index sensitive direction can be changed arbitrarily and quickly, realizing the refractive index sensitivity direction adjustment function.

10. A projected focusing schlieren system with a programmable grid according to any one of claims 5 to 9, characterized in that: There are multiple integrated modules, which are distributed in parallel on one side of the flow field test area, and the reflective screen is located on the other side of the flow field test area.

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