CN210005208U - high-uniformity high-resolution schlieren optical system using aspheric surface - Google Patents

Abstract

The utility model relates to a highly uniform and high-resolution schlieren optical system using an aspheric surface, which solves the problems of low uniformity and low resolution of the existing schlieren system. The system includes a light source system, a sealed front observation window, a collimating main reflector, a schlieren system, a schlieren main reflector, a sealed back observation window and an imaging system; cabin, the schlieren lens barrel after sealing; the observation window before sealing is set on the side of the schlieren lens barrel before sealing, and the observation window after sealing is set on the side of the schlieren lens barrel after sealing; the collimating main reflector and the schlieren main reflector All use aspheric mirrors; the imaging system is a telephoto imaging system; the light emitted by the light source system passes through the observation window before sealing and enters the collimating main mirror, and the light after passing through the collimating main mirror passes through the sealing front schlieren tube. Enter the test chamber and enter the schlieren main reflector, the schlieren main reflector reflects the light, and then enters the imaging system after passing through the sealed observation window.

Description

A Highly Uniform and High Resolution Schlieren Optical System Using Aspheric Surfaces

technical field

The utility model relates to a schlieren optical system, in particular to a high-uniform and high-resolution schlieren optical system using an aspheric surface.

Background technique

In a schlieren imaging system, uniformity and resolution are important indicators for evaluating the quality of schlieren images. In the development process of the traditional schlieren system, the grasp of the above two indicators usually relies on past experience, or it is necessary to set up simple experiments to verify the design results. For the schlieren system of the order of 1 meter, the previous experience is limited, and the cost of the simple experiment method is huge. Therefore, the traditional method is not suitable for the schlieren system of the order of 1 meter. How to ensure the uniformity of the schlieren system of the order of 1 meter? And the resolution index meets the design requirements, which puts forward higher requirements for the design of the entire system.

Existing schlieren imaging systems generally include three pairs of conjugation relationships, the first pair of conjugation relationships is to image the light source surface on the slit, the second pair of conjugation relationships is to image the slit on the knife edge, and the third pair of conjugation relationships. The yoke relationship is to image the object surface of the test area on the camera receiving screen. Among them, the first pair of conjugate relationship is used to obtain a regular and uniform secondary light source; the second pair of conjugate relationship is mainly used to form a slit image at the knife edge; the third pair of conjugate relationship is mainly used to obtain the pattern of the test area. shadow image. Therefore, the uniformity affecting the schlieren system mainly depends on the second pair of conjugation relations, and the resolution of the schlieren system mainly depends on the third pair of conjugation relations. The size of the main mirror and the schlieren mirror of the existing schlieren system is in the order of meters, and it is difficult to ensure the processing size of the main mirror and the schlieren mirror and the uniformity of the refractive index, which leads to a decrease in the uniformity and resolution of the schlieren system. .

Utility model content

The purpose of the utility model is to solve the problems of low uniformity and low resolution of the existing schlieren system, and provides a high-uniform and high-resolution schlieren optical system using an aspheric surface.

The technical scheme of the present utility model is:

A highly uniform and high-resolution schlieren optical system using an aspheric surface, comprising a light source system, a sealed front observation window, a collimating main reflector, a schlieren system, a schlieren main reflector, a sealed rear observation window and an imaging system; the The schlieren system includes a schlieren lens barrel before sealing, a test chamber, and a schlieren lens barrel after sealing, which are arranged in sequence; the observation window before sealing is arranged on the side of the schlieren lens barrel before sealing, and the observation window after sealing is arranged on the side of the schlieren lens barrel before sealing. The side surface of the rear schlieren lens barrel; the collimating main reflector and the schlieren main reflector are both aspherical reflectors; the imaging system is a telephoto imaging system; the light emitted by the light source system is incident through the observation window before sealing After reaching the collimating main reflector, the light collimated by the collimating main reflector enters the test chamber through the schlieren tube before sealing, and enters the schlieren main reflector after passing through the air flow of the test chamber through the after-sealing schlieren tube. The primary reflector reflects the light and enters the imaging system after passing through the sealed rear viewing window.

Further, the collimating main reflection mirror and the schlieren main reflection mirror are coaxial parabolic main reflection mirrors, and are placed symmetrically with respect to the test chamber, with an off-axis angle of 1.6°.

Further, the reflecting surfaces of the collimating main reflecting mirror and the schlieren main reflecting mirror are provided with protective films.

Further, the sealed observation window is a small-sized sealed observation window, and its diameter is smaller than 1/10 of the effective flow field display range. The sealing front observation window is a small-sized sealing front observation window, and its diameter is smaller than 1/10 of the effective flow field display range.

Further, the schlieren lens barrel before sealing and the test chamber are connected by a sealing bellows, and the test chamber and the schlieren lens barrel after sealing are connected by a sealing bellows.

Further, the light source system includes an ultra-high-brightness LED lamp, a condensing lens group, a slit, and a first plane reflector, which are arranged in sequence.

Further, the optical axis of the condenser lens group, the center of the slit, and the center of the first plane mirror are coaxially arranged.

Further, the slits are "mouth"-shaped slits.

Further, the imaging system includes a second plane mirror, a knife edge, a focusing lens group and a schlieren camera arranged in sequence, and a knife edge controller for controlling the knife edge.

Further, the schlieren lens barrel before sealing and the schlieren lens barrel after sealing are cylindrical structures.

Compared with the prior art, the utility model has the following technical effects:

1. The schlieren system of the present utility model adopts the design of an aspherical reflector, and the aspherical reflector is an off-axis paraboloid design, which avoids aberrations such as spherical aberration of the spherical reflector, ensures the uniformity of the image, and greatly improves the The uniformity and resolution of the schlieren system are improved.

2. The imaging system of the present invention adopts a telephoto imaging system, which ensures the resolution of the schlieren system. The resolution of the system is proportional to the aperture of the system and inversely proportional to the focal length of the system, and the telephoto system has a higher resolution.

Description of drawings

Figure 1 is a schematic diagram of the high-uniform and high-resolution schlieren optical system of the present invention using an aspheric surface.

Reference numerals: 1- super bright LED lamp, 2- condenser lens group, 3- slit, 4- first plane mirror, 5- sealed front viewing window, 6- collimating main mirror, 7- sealed Front Schlieren Tube, 8-Test Chamber, 9-Sealed Back Schlieren Tube, 10-Schlieren Primary Reflector, 11-Sealed Back Observation Window, 12-Second Plane Reflector, 13-Knife Edge, 14-Knife Edge Controller, 15- Focusing Lens Group, 16- Schlieren Camera, 17- Sealed Bellows.

Detailed ways

The content of the present utility model will be described in further detail below in conjunction with the accompanying drawings and specific embodiments.

As shown in Figure 1, the present utility model proposes a highly uniform and high-resolution schlieren optical system using an aspheric surface, including a light source system, a sealed front observation window 5, a collimating main reflector 6, a schlieren system, and a schlieren main reflection Mirror 10, sealed rear viewing window 11 and imaging system.

The light source system includes an ultra-high-brightness LED lamp 1 , a condensing lens group 2 , a "mouth"-shaped slit 3 , and a first plane reflection mirror 4 , which are arranged in sequence. The ultra-high brightness LED lamp 1 should have a large luminous flux value. The optical axis of the condenser lens group 2 , the center of the "mouth"-shaped slit 3 , and the center of the first plane mirror 4 are the same. The "mouth"-shaped slit is composed of four narrow slits in the "mouth" shape and a combined color filter formed by splicing four colored glasses of red, yellow, green and blue.

The imaging system includes a knife edge controller 14 , a knife edge 13 , a second plane mirror 12 , a focusing lens group 15 , and a schlieren camera 16 . The knife edge 13 is four narrow slits in the "mouth" shape, and the knife edge controller 14 can respectively control the positions of the four narrow slits 3 in the "mouth" shape, so that all light can pass through the knife edge 13 . The optical axes of the second plane mirror 12, the focusing lens group 15, and the schlieren camera 16 are kept the same. The schlieren camera 16 is located at the focal position of the focusing lens group 15 . The light passes through the sealed observation window 11 and is reflected to the knife edge 13 by the second plane mirror 12. The knife edge controller 14 controls the position of the four "mouth"-shaped slits 3 in the knife edge 13, so that the light enters the focusing lens group through the knife edge 13. 15. The focusing lens group 15 focuses the light on the photosensitive surface of the schlieren camera 16, and the schlieren camera 16 images the outgoing light to obtain a schlieren image of the high-speed airflow in the test chamber 8.

The schlieren system includes a schlieren lens barrel 7 before sealing, a test chamber 8 and a schlieren lens barrel 9 after sealing. The schlieren lens barrel 7 before sealing and the schlieren lens barrel 9 after sealing are fixed at both ends of the test chamber 8, and the test chamber 8 is placed in a high-speed wind tunnel. The collimated optical axis of the collimating main reflection mirror 6 is consistent with the main axis of the schlieren system, and the center of the schlieren main reflection mirror 10 is consistent with the center of the collimating main reflection mirror 6 . The schlieren lens barrel 7 before sealing and the test chamber 8 are connected by an airtight bellows, the schlieren lens barrel 7 before sealing and the schlieren lens barrel 9 after sealing can be welded on both sides of the test chamber 8, and the test chamber 8 and the schlieren after sealing can be welded on both sides. The lens barrels 9 are connected through an airtight bellows. The schlieren lens barrel 7 before sealing and the schlieren lens barrel 9 after sealing can be cylindrical, and are formed by crimping and welding stainless steel plates. The outgoing light of the collimating main reflector 6 is parallel light, and the parallel light passes through the central axis of the schlieren lens barrel 7 before sealing, the test chamber 8 and the schlieren lens barrel 9 after sealing.

The observation window 5 before the sealing is arranged on the side of the schlieren lens barrel 7 before the sealing, and the observation window 11 after the sealing is arranged on the side of the schlieren lens barrel 9 after the sealing; It is less than 1/10 of the effective flow field display range, and does not block the effective passage aperture of light. The sealed observation window 11 is a small-sized sealed observation window 11, and its aperture is smaller than 1/10 of the effective flow field display range, and does not block the effective passage of light through the aperture.

Both the collimating main reflection mirror 6 and the schlieren main reflection mirror 10 are aspherical reflection mirrors, which ensures the uniformity of the imaging of the schlieren system. The aspheric mirror is an off-axis paraboloid design, which avoids the spherical aberration and other aberrations of the spherical mirror and ensures the uniformity of the image.

In the imaging system, the focusing lens group 15 adopts a telephoto imaging system, which ensures the resolution of the schlieren system. The resolution of the system is proportional to the aperture of the system and inversely proportional to the focal length of the system, and the telephoto system has a higher resolution.

The utility model forms a slit conjugate image at the knife edge 13, which can improve the uniformity of the schlieren system, improve the schlieren image of the schlieren camera 16, and improve the resolution of the schlieren system. Through the setting of the aspherical mirror, the imaging quality of the conjugate image of the slit formed at the knife edge 13 is improved, and the uniformity of the schlieren system is improved. The schlieren image of the schlieren camera is improved by the setting of the long focal length focusing lens group 15, and the resolution of the schlieren system is improved.

The light emitted by the ultra-high-brightness LED lamp 1 is condensed by the condenser lens group 2, and after being condensed by the condenser lens group 2, the light passes through the "mouth"-shaped slit 3, and is installed in the "mouth"-shaped slit. , yellow, green, blue four kinds of colored glass "mouth" shaped four narrow slit filter. The filtered light is reflected by the first plane reflection mirror 4 to the observation window 5 before the small size sealing, and the light enters the collimating main reflection mirror 6 through the small size sealing front observation window 5, and the collimating main reflection mirror 6 collimates the light. , and reflect the light to the schlieren lens barrel 7 before sealing, the light reaches the test chamber 8 through the schlieren lens barrel 7 before the seal, the test chamber 8 is placed in the high-speed wind tunnel, and the light passes through the high-speed wind tunnel in the test chamber 8 After sealing, the schlieren barrel 9 is incident on the schlieren main reflector 10, and the schlieren main reflector 10 reflects the light through the small-sized sealed observation window 11 to reach the second plane reflector 12, and the second plane reflector 12 reflects the light. To the knife edge 13, the knife edge controller 14 controls the four slit positions of the "mouth" shape in the knife edge 13, so that the light reaches the focusing lens group 15 through the knife edge 13, and the focusing lens group 15 focuses the light on the photosensitive surface of the schlieren camera 16, The schlieren camera 16 images the outgoing light to obtain a schlieren image of the high-speed airflow in the test chamber 8 .

The system of the utility model adopts two symmetrically distributed large-diameter (1-meter-level) aspherical reflection mirrors as the optical elements of the collimating light path and the imaging system, respectively. Optimized simulation with optical design ensures high illumination uniformity of the system. The utility model successfully realizes the aspherical surface of the schlieren primary mirror with a diameter of 1 meter, and obtains a schlieren pattern with high uniformity and high resolution, which can be used as a reference and promotion for the design and promotion of a larger diameter schlieren optical system in the future.

Before the system of the present invention is designed, a simulation environment is established, that is, no object is placed in the experimental cabin, and the image received by the schlieren camera 16 is simulated. Since the four color lights emitted by the "mouth"-shaped slit correspond to one slit of the knife edge respectively , respectively simulate the uniformity of each color light on the image plane after being cut by the knife edge. In the schlieren system, the uniformity of the image surface is closely related to the shape of each mirror in the system. Considering the processing error of the main mirror, the shape error of the main mirror caused by the support of the main mirror under different working conditions, the shape error of the plane mirror, the beam in and out The schlieren tube is affected by the sealed observation window, simulates the schlieren system, analyzes the uniformity of the image surface, and then superimposes the results of the four colors of light to obtain the uniformity of the image surface of the schlieren system.

The third pair of conjugate relations of the schlieren system, that is, from the object plane of the test area to the image plane of the schlieren camera, determines the resolution of the system. The original images with different stripe widths are placed at the object surface, and the schlieren main mirror, slit and schlieren imaging system are respectively set up by CODE V software, and the system comprehensive error is considered, and the transfer function of the system from the object surface to the image surface is given. and the contrast result of the output image at the required resolution. Design the parameters of each optical element in the schlieren system, set the parameters of the collimating main mirror and the schlieren main mirror in CODE V, simulate the imaging quality of the schlieren main system, and calculate the resolution and aberration of the image, etc. parameters, according to the obtained image information, determine the specific parameters of the focusing lens group in the imaging system, and obtain an image with good high resolution rate and uniformity.

The collimating main mirror and the schlieren main mirror are placed symmetrically about the test chamber, with an off-axis angle of 1.6°. The collimating main mirror 6 and the schlieren main mirror 10 are coaxial parabolic main mirrors, and their design parameters are:

Wavelength range: 435nm～700nm;

Entrance pupil diameter: Φ1200mm;

Focal length: 12000mm;

Linear expansion coefficient: 0±1.5×10-7/℃;

Diameter Φ1250mm;

Center thickness 175mm;

After the mirror is processed, a film with high reflection coefficient and a protective film should be coated. The protective film is a durable SiO2 film to prevent the oxidation of the high-reflection silver film and protect the high-reflection film. The reflectivity of the film is above 90% and uniform. Sex > 97%.

According to the above parameters, the parameters of the optical path of the system are set in the CODE V software, and the imaging quality of the system is simulated.

Claims (10)

1. a highly uniform high-resolution schlieren optical system that adopts aspheric surface, it is characterized in that: comprise light source system, sealing front observation window (5), collimation main reflector (6), schlieren system, schlieren main reflection a mirror (10), a sealed rear viewing window (11) and an imaging system; The schlieren system comprises a schlieren lens barrel (7) before sealing, a test chamber (8), and a schlieren lens barrel (9) after sealing, which are arranged in sequence; the observation window (5) before sealing is arranged in the schlieren before sealing. the side of the lens barrel (7), the observation window (11) after the sealing is arranged on the side of the schlieren lens barrel (9) after the sealing; Both the collimating main reflection mirror (6) and the schlieren main reflection mirror (10) are aspherical reflection mirrors; The imaging system is a telephoto imaging system; The light emitted by the light source system passes through the observation window (5) before sealing and is incident on the collimating main reflector (6), and the light after being collimated by the collimating main reflector (6) passes through the pre-sealing schlieren lens barrel (7). ) into the test chamber (8), and after passing through the test chamber (8), the air flow passes through the sealed schlieren lens barrel (9) and enters the schlieren main reflector (10), which reflects the light and passes through the schlieren main reflector (10). After sealing, the observation window (11) is incident on the imaging system. 2. The highly uniform high-resolution schlieren optical system according to claim 1, characterized in that: the collimating main reflection mirror (6) and the schlieren main reflection mirror (10) are coaxial paraboloid main mirrors. The reflector is placed symmetrically with respect to the test chamber (8), with an off-axis angle of 1.6°. 3. The highly uniform and high-resolution schlieren optical system using aspherical surfaces according to claim 2, characterized in that: the reflection surfaces of the collimating main reflection mirror (6) and the schlieren main reflection mirror (10) are provided with protective film. 4. The highly uniform high-resolution schlieren optical system using aspheric surface according to claim 3, characterized in that: the observation window (5) before sealing is a small-sized observation window before sealing, and its aperture is smaller than the effective flow field display 1/10 of the range, the sealed rear observation window (11) is a small-sized sealed rear observation window, and its diameter is smaller than 1/10 of the effective flow field display range. 5. The high-uniform high-resolution schlieren optical system using aspheric surface according to any one of claims 1 to 4, characterized in that: the schlieren lens barrel (7) and the test chamber (8) before the sealing pass through the sealing corrugations The tube (17) is connected, and the test chamber (8) and the sealed schlieren lens barrel (9) are connected through the sealing bellows (17). 6. The highly uniform and high-resolution schlieren optical system using aspherical surfaces according to claim 5, wherein the light source system comprises an ultra-high-brightness LED lamp (1) and a condensing lens group (2) arranged in sequence. , a slit (3), and a first plane mirror (4). 7. The high-uniform and high-resolution schlieren optical system using an aspheric surface according to claim 6, wherein the optical axis of the condenser lens group (2), the center of the slit (3), the first plane The center of the reflector (4) is coaxially arranged. 8. The highly uniform and high-resolution schlieren optical system using an aspheric surface according to claim 7, wherein the slit (3) is a "mouth"-shaped slit. 9. The highly uniform and high-resolution schlieren optical system using an aspheric surface according to claim 8, wherein the imaging system comprises a second plane mirror (12), a knife edge (13), a focusing lens arranged in sequence A group (15) and a schlieren camera (16), and a knife edge controller (14) for controlling the knife edge (13). 10 . The high-uniform and high-resolution schlieren optical system according to claim 9 , wherein the schlieren lens barrel ( 7 ) before sealing and the schlieren lens barrel ( 9 ) after sealing are cylindrical structures. 11 .