Four-reflector single-camera double-view-angle high-speed imaging method used under underwater explosion impact

Abstract

The invention discloses a four-reflector single-camera double-view-angle high-speed imaging method under underwater explosion impact, and the method comprises the following specific steps: S1, independently packaging a high-speed camera in a waterproof cylinder which is cylindrical on the whole, and enabling an observation window of the waterproof cylinder to be circular transparent flat explosion-proof glass, the optical axis of the high-speed camera passes through the center of the observation window and is perpendicular to the observation window plane; s2, two inner side reflecting mirror groups are symmetrically placed right in front of the observation window, and two outer side reflecting mirror groups are symmetrically placed on the two sides of the inner side reflecting mirror groups; s3, adjusting the positions, sizes and inclination angles of the two outer side reflectors; judging whether the camera equivalent included angle and the system compactness of the adjusted measurement system meet design requirements or not, and if the design requirements are met, executing the step S4; and S4, recording the measured object on the left side and the right side of the imaging plane of the camera respectively, and segmenting the image into a left image and a right image along the vertical center line to complete underwater double-view imaging.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of underwater three-dimensional vision, and in particular to a four-mirror single-camera dual-view high-speed imaging method under underwater explosion impact. TECHNICAL BACKGROUND

[0002] Underwater explosion and the physical phenomena such as shock wave and bubble pulsation generated thereby are important research objects in the fields of ship and ocean engineering, weapon damage effect, underwater structure protection, etc. Accurate capture of the propagation of explosion shock wave front, formation and evolution of cavitation zone, and dynamic response process of structure is of great importance to understanding damage mechanism, verifying numerical model and evaluating protection performance. These phenomena have the characteristics of transient, high speed, three-dimensional and asymmetry, and the characteristic time scale is usually in the order of microseconds to milliseconds, and the spatial scale changes dramatically, which puts forward very high requirements on observation technology.

[0003] Traditional high-speed imaging technology faces two major challenges in such applications: first, single view, a single camera can only provide two-dimensional plane information, and cannot restore the three-dimensional spatial structure of the shock wave and the stereoscopic information of the object deformation, making it difficult to analyze asymmetric phenomena. Second, time synchronization and cost. Although multiple high-speed cameras can solve the problem of stereoscopic observation, the system is extremely expensive, and the high-precision synchronization trigger between multiple cameras in nanoseconds, subsequent strict registration and calibration of images put forward strict requirements, and the system complexity and failure rate are significantly increased. SUMMARY

[0004] The present application provides a four-mirror single-camera dual-view high-speed imaging method under underwater explosion impact, which uses a single high-speed camera and multiple plane mirrors to observe and record images during the deformation process of the structure under underwater explosion impact from dual views, providing a tool for underwater transient three-dimensional deformation measurement.

[0005] Technical scheme, in order to achieve the above-mentioned application purpose, the present application provides a four-mirror single-camera dual-view high-speed imaging method under underwater explosion impact, which comprises the following steps:

[0006] S1, the high-speed camera is individually packaged in a waterproof cylinder, the waterproof cylinder is in the form of a cylinder as a whole, the observation window of the waterproof cylinder is a circular transparent flat explosion-proof glass, and the optical axis of the high-speed camera passes through the center of the observation window and is perpendicular to the plane of the observation window;

[0007] S2, two inner mirror groups are symmetrically placed in front of the observation window, and two outer mirror groups are symmetrically placed on both sides of the inner mirror groups, together forming a dual-view imaging light path;

[0008] S3, adjust the position, size and tilt angle of the two outer mirrors according to different measurement requirements; and determine whether the camera equivalent angle and system compactness of the adjusted measurement system meet the design requirements; if the design requirements are met, proceed to step S4;

[0009] S4, using the four-mirror single-camera double-view high-speed imaging system, the measured object is recorded on the left and right sides of the camera imaging plane respectively, and the image is divided into left and right images along the vertical center line, and the underwater double-view imaging is completed.

[0010] Further, in step S2, the specific positional relationship of the camera, transparent observation window and mirror is as follows:

[0011] 2.1, establish the imaging system coordinate system O-XY: take the camera optical center as the origin O, take the high-speed camera optical axis direction as the positive direction of Y axis, and take the direction parallel to the observation window plane and horizontal as the X axis;

[0012] 2.2, the distance from the camera optical center to the inner surface of the observation window is defined as d0, and the thickness of the observation window is defined as t;

[0013] 2.3, the two inner mirrors are rectangular plane mirrors, which are placed in the water in front of the observation window, the two inner mirrors are mirror-symmetric about the Y axis, and the included angle between the two mirrors is fixed at a right angle of 90°, that is, the included angle between the two mirror surfaces and the X axis is 45°, the distance between the bottom edge of the two mirrors and the outer surface of the observation window is d1, and the two mirrors are connected with the camera waterproof cylinder by bolts;

[0014] 2.4, the two inner mirrors are rectangular plane mirrors, which are placed in the water in front of the observation window, the two inner mirrors are mirror-symmetric about the Y axis, and are symmetrically placed on the two sides of the two inner mirrors, and the bottom edge of the inner mirror is on the same horizontal line with the bottom edge of the inner mirror, the distance between the bottom edges of the inner and outer mirrors on the Y axis is d2, and the acute angle between the plane of the outer mirror and the X axis is , the two inner mirrors are connected with the camera waterproof cylinder by bolts.

[0015] Further, the range of the acute angle is greater than 45° and less than 90°.

[0016] Further, in step S3, the method for meeting different measurement requirements is:

[0017] The following parameters are fixed: the distance d0 from the camera optical center to the inner surface of the observation window, the thickness t of the observation window, and the distance d1 between the bottom edge of the inner mirror and the outer surface of the observation window, that is, the camera and the waterproof cylinder, the transparent observation window and the two inner mirrors are fixedly connected, and the following parameters are changed to meet different measurement requirements: the distance d2 between the bottom edges of the inner and outer mirrors, and the acute angle between the plane of the outer mirror and the X axis , i.e. the outer mirror can be detached and replaced.

[0018] Further, in step S3, the specific method for judging whether the equivalent camera included angle and the system compactness meet the requirements is as follows:

[0019] 4.1, define the equivalent camera included angle: underwater single camera double view angle imaging can be regarded as left and right two virtual underwater cameras imaging the object from different positions. Assuming that the imaging light paths of the left and right two endpoints in the measured field of view are P l , Q l at the reflection points of the left outer mirror, and P r , Q r at the reflection points of the right outer mirror. The position of the light center of the left virtual camera is determined by the intersection of the extension lines of the left and right two endpoints in the field of view along P l , Q l direction, and the position of the light center of the right virtual camera is determined by the intersection of the extension lines of the left and right two endpoints in the field of view along P r , Q r direction. Assuming that the coordinates of the light centers of the left and right virtual cameras in the real imaging system coordinate system O-XY are O l , O r , and the coordinates of the light center of the right virtual camera are (O rx , O ry ):

[0020]

[0021] The light centers of the left and right virtual cameras are symmetrical about the Y axis, and in the O-XY coordinate system, the distance of the measured plane from the coordinate origin is defined as the system object distance H, and the equivalent camera included angle θ is defined as:

[0022]

[0023] 4.2, define the system compactness η:

[0024] .

[0025] Further, η is between 0.6 and 0.8.

[0026] Further, θ is between 15° and 30°.

[0027] Beneficial effects, compared with the prior art, the technical scheme of the present application has the following beneficial technical effects:

[0028] The application provides a single-camera double-view high-speed imaging method based on a four-mirror optical system. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 The application is a method flowchart.

[0030] Figure 2 The application is a measurement parameter schematic diagram.

[0031] Figure 3 The application is a three-dimensional structure diagram of a measurement device.

[0032] Label explanation, 1, 4 - outer mirror, 2, 3 - inner mirror, 5 - flat transparent observation window, 6 - waterproof housing, 7 - high-speed camera, 8, 9 - outer mirror support. DETAILED DESCRIPTION

[0033] The application will be further described below in combination with specific implementation cases.

[0034] As shown in the drawings, the application provides a four-mirror single-camera double-view high-speed imaging method under underwater explosion impact, which comprises the following steps: Figure 1

[0035] S1, the high-speed camera is individually packaged in a waterproof cylinder, the waterproof cylinder is in a cylindrical shape as a whole, the observation window of the waterproof cylinder is a circular transparent flat explosion-proof glass, the optical axis of the high-speed camera passes through the center of the observation window and is perpendicular to the plane of the observation window;

[0036] S2, two inner mirror groups are symmetrically placed in front of the observation window, and two outer mirror groups are symmetrically placed on the two sides of the inner mirror group, to jointly form a double-view imaging light path;

[0037] S3, according to different measurement requirements, the positions, sizes and inclination angles of the two outer mirrors are adjusted; and whether the camera equivalent angle and the system compactness of the measurement system after adjustment meet the design requirements are judged, if the design requirements are met, step S4 is performed;

[0038] S4, using the four-mirror single-camera double-view high-speed imaging system, the measured object is recorded on the left and right sides of the camera imaging plane respectively, and the image is divided into a left image and a right image along the vertical center line, to complete underwater double-view imaging.

[0039] Further, in step S2, the specific positional relationship of the camera, the transparent observation window and the mirror is as follows:

[0040] ​2.1, Establishing the imaging system coordinate system O-XY: taking the camera optical center as the origin O, taking the high-speed camera optical axis direction as the positive direction of the Y axis, and taking the direction parallel to the observation window plane and horizontal as the X axis;

[0041] 2.2, The distance from the camera optical center to the inner surface of the observation window is defined as d0, and the thickness of the observation window is defined as t;

[0042] 2.3, The two inner mirrors are rectangular plane mirrors placed in the water in front of the observation window, and the two inner mirrors are mirror-symmetric about the Y axis, and the included angle between the two inner mirrors is fixed at a right angle of 90°, that is, the included angle between the two mirror surfaces and the X axis is 45°, the distance between the bottom edge of the two mirrors and the outer surface of the observation window is d1, and the two mirrors are connected by a connecting device and bolted to the camera waterproof cylinder;

[0043] 2.4, The two inner mirrors are rectangular plane mirrors placed in the water in front of the observation window, and the two inner mirrors are mirror-symmetric about the Y axis, and the two inner mirrors are symmetrically placed on both sides of the two inner mirrors, and the bottom edge of the inner mirror is on the same horizontal line as the bottom edge of the inner mirror, the distance between the bottom edges of the inner and outer mirrors on both sides of the Y axis is d2, and the acute angle between the plane of the outer mirror and the X axis is , and the two inner mirrors are connected by a connecting device and bolted to the camera waterproof cylinder.

[0044] Further, the range is greater than 45° and less than 90°.

[0045] Further, the method for meeting different measurement requirements in step S3 is:

[0046] The following parameters are fixed: the distance d0 from the camera optical center to the inner surface of the observation window, the thickness t of the observation window, and the distance d1 from the bottom edge of the inner mirror to the outer surface of the observation window, that is, the camera and the waterproof cylinder, the transparent observation window, and the two inner mirrors are fixed, and the following parameters are changed to meet different measurement requirements: the distance d2 between the bottom edges of the inner and outer mirrors, and the acute angle between the plane of the outer mirror and the X axis, that is, the outer mirror can be detached and replaced.

[0047] Further, in step S3, the specific method for determining whether the equivalent camera angle and the system compactness meet the requirements is as follows:

[0048] 4.1, Defining the equivalent camera angle: underwater single-camera double-view imaging can be regarded as two virtual underwater cameras imaging the object from different positions. Assuming that the imaging light paths of the left and right two endpoints in the measured field of view are P l , Q l at the reflection points of the left outer mirror, and P r , Qr The position of the left virtual camera optical center is determined by the intersection of the extension lines of the left and right end points in the field of view along P l , Q l direction. The position of the right virtual camera optical center is determined by the intersection of the extension lines of the left and right end points in the field of view along P r , Q r direction. Let the coordinates of the optical centers of the left and right virtual cameras in the real imaging system coordinate system O-XY be O l , O r , and the coordinates of the right virtual camera optical center be (O rx , O ry ):

[0049]

[0050] The left and right virtual camera optical centers are symmetric about the Y axis. In the O-XY coordinate system, define the distance of the measured plane from the coordinate origin as the system object distance H, and define the equivalent camera included angle θ as:

[0051]

[0052] 4.2, define the system compactness η:

[0053] .

[0054] Further, η is between 0.6 and 0.8.

[0055] Further, θ is between 15° and 30°.

[0056] The specific structural dimensions are shown in Figure 2 .

[0057] 1. The high-speed camera is individually packaged in a waterproof cylinder, the waterproof cylinder is in the shape of a cylinder as a whole, the observation window of the waterproof cylinder is a circular transparent glass with parallel upper and lower surfaces, and the optical axis of the high-speed camera passes through the center of the observation window and is perpendicular to the plane of the observation window;

[0058] 2. Install the inner mirrors: place two mirrors symmetrically in front of the observation window, the two mirrors are mirror-symmetric about the Y axis, and the bottom edges close to the camera are in close contact. The distance from the camera optical center to the inner surface of the observation window is 50 mm, the thickness of the observation window is 20 mm, the distance from the bottom edge of the inner mirror to the outer surface of the observation window is 12 mm, and the included angle between the two mirror surfaces is fixed at a right angle of 90°, i.e. the included angle between the two mirror surfaces and the X axis is 45 degrees. The two mirrors are fixed to the camera waterproof cylinder by bolts through a connecting device. After installation and manufacturing are completed, this part is fixed and does not move.

[0059] 3、Install the outer mirrors: two mirrors are mirror-symmetrical about the Y-axis, and are placed on both sides of the two inner mirrors, and the bottom edges of the outer mirrors close to the camera are on the same horizontal line with the bottom edges of the inner mirrors. The distance between the bottom edges of the inner and outer mirrors on the right side of the Y-axis is defined as 120 mm, and the angles between the planes of the two outer mirrors and the X-axis are both 54°. The two mirrors are connected with the camera waterproof cylinder by connecting devices and bolts, and can be replaced according to different measurement scenes.

[0060] 4、The equivalent camera angle θ is calculated according to the formula, which should be between 15° and 30°. The system compactness η is, which should be between 0.6 and 0.8.

[0061] 5、Using the four-mirror single-camera dual-view high-speed imaging system, the measured object is recorded on the left and right sides of the camera imaging plane, and the image is divided into left and right images along the vertical center line, and underwater dual-view imaging is completed.

Claims

1. A four-mirror single-camera dual-view high-speed imaging method under underwater explosion impact, characterized in that, The method comprises the following steps: S1, the high-speed camera is individually packaged in a waterproof cylinder, the waterproof cylinder is in a whole cylindrical shape, the observation window of the waterproof cylinder is a circular transparent flat plate explosion-proof glass, the optical axis of the high-speed camera passes through the center of the observation window and is placed vertically to the plane of the observation window; S2, two sets of inner mirrors are symmetrically placed in front of the observation window, and two sets of outer mirrors are symmetrically placed on both sides of the inner mirror set, together forming a double-view imaging light path; S3, according to different measurement requirements, the positions, sizes and inclination angles of the two outer mirrors are adjusted, and whether the camera equivalent angle and the system compactness of the measurement system after adjustment meet the design requirements are judged, if they meet the design requirements, step S4 is performed; S4, using the four-mirror single-camera double-view high-speed imaging system, the measured object is recorded on the left and right sides of the camera imaging plane, and the image is divided into left and right images along the vertical center line to complete the underwater double-view imaging.

2. The method for four-mirror single camera dual-view high-speed imaging under underwater explosion impact according to claim 1, characterized in that, In step S2, the specific positional relationship of the high-speed camera, the transparent observation window and the mirrors is as follows: 2.1, an imaging system coordinate system O-XY is established: taking the camera optical center as the origin O, taking the high-speed camera optical axis direction as the positive direction of Y axis, and taking the direction parallel to the observation window plane and horizontal as the X axis; 2.2, the distance from the camera optical center to the inner surface of the observation window is defined as d0, and the thickness of the observation window is defined as t; 2.3, the two inner mirrors are rectangular plane mirrors, the two inner mirrors are fixedly connected with the camera waterproof cylinder by a connecting device and bolts, are placed in the water in front of the observation window, are symmetrically placed about the Y axis, and the included angle between the two inner mirrors is fixed at a right angle of 90°, that is, the included angle between the two mirror surfaces and the X axis is 45°, and the distance from the bottom edge to the outer surface of the observation window is d1; 2.4, the two inner mirrors are rectangular plane mirrors, the two inner mirrors are bolted with the camera waterproof cylinder through the connecting device, are placed in the water in front of the observation window, the two inner mirrors are mirror symmetrical about the Y axis, are symmetrically placed on the two sides of the two inner mirrors respectively, and the bottom edges of the inner mirrors are on the same horizontal line as the bottom edges of the outer mirrors, the distance between the bottom edges of the inner and outer mirrors on the two sides of the Y axis is d2, and the acute angles between the planes of the outer mirrors and the X axis are both .

3. The method for four-mirror single camera dual-view high-speed imaging under underwater explosion impact according to claim 2, characterized in that, the range of greater than 45° and less than 90°.

4. The method according to claim 2 or 3, wherein, The method for meeting different measurement requirements in step S3 is as follows: Fix the following parameters: the distance d0 from the camera optical center to the inner surface of the observation window, the thickness t of the observation window, the distance d1 from the bottom edge of the inner mirror to the outer surface of the observation window, that is, the camera is fixed with the waterproof cylinder, the transparent observation window and the two inner mirrors, change the following parameters to meet different measurement requirements: the distance d2 between the bottom edges of the inner and outer mirrors, the acute angle between the plane of the outer mirror and the X axis , that is, the outer mirror can be detached and replaced.

5. The method according to claim 4, wherein, In step S3, the specific method for judging whether the camera equivalent angle and the system compactness meet the requirements is as follows: 5.1, Definition of equivalent camera angle: underwater single camera dual view imaging is regarded as imaging of object by two virtual underwater cameras from different positions, assuming that the imaging light paths of the left and right endpoints in the measured field of view are reflected at the reflection points P l , Q l of the left outer mirror and P r , Q r of the right outer mirror respectively, the position of the optical center of the left virtual camera is determined by the intersection of the extension lines of the left and right endpoints in the field of view along the P l , Q l direction respectively, the position of the optical center of the right virtual camera is determined by the intersection of the extension lines of the left and right endpoints in the field of view along the P r , Q r direction respectively, assuming that the coordinates of the optical centers of the left and right virtual cameras in the real imaging system coordinate system O-XY are O l , O r respectively, and the coordinates of the optical center of the right virtual camera are represented as (O rx , O ry ): ； The left and right virtual camera optical centers are symmetric about the Y axis, in the O-XY coordinate system, the distance from the measured plane to the coordinate origin is defined as the system object distance H, and the equivalent camera included angle θ is defined as: ； 5.2, the system compactness η is defined as: 。 6. The method according to claim 5, wherein, η is between 0.6 and 0.

8.

7. The method according to claim 5, wherein, The equivalent camera included angle θ is between 15° and 30°.

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