Structured light pattern projection device and projection method

Abstract

The application discloses a structured light pattern projection device and a projection method, which comprises a point laser, a diffractive optical element lens, a polarizer, a mirror, a polarizer motor and a mirror motor; the diffractive optical element lens is used for converting the point laser emitted by the point laser into linear laser; the linear laser is projected onto the mirror after being processed by the polarizer; the mirror reflects the processed linear laser to the target object surface; the polarizer motor is used for driving the polarizer to rotate around the central axis of the polarizer; the central axis is the central axis perpendicular to the polarizer; the mirror motor is used for driving the mirror to rotate around the vertical axis of the mirror; the vertical axis is the central axis along the axial direction of the mirror; and the linear laser projected onto the mirror coincides with the vertical axis of the mirror. The structured light pattern projection device has simple structure, large depth of field and can form clear patterns in a wide range; the structured light pattern projection method is simple; the synchronous rotation of the polarizer and the mirror under a certain rule can realize the projection of the structured light pattern.

Description

Technical Field

[0001] This invention belongs to the field of structured light measurement technology, specifically relating to a structured light pattern projection device and projection method. Background Technology

[0002] In the field of structured light measurement, in order to acquire the three-dimensional shape of the object being measured, it is necessary to project a specific pattern onto the surface of the object. This pattern is usually a sinusoidal stripe pattern in which the gray level changes sinusoidally along the length of the image. When using a conventional projector to project such a pattern, due to the limitation of the depth of field range of the lens of the conventional projector, it is impossible to form a clear pattern over a wide range, which affects the measurement range of the structured light measurement system. At the same time, the complex internal structure of conventional projectors makes it difficult to reduce the size of the structured light measurement system. Summary of the Invention

[0003] The purpose of this invention is to provide a structured light pattern projection device and projection method, which solves the problems of shallow depth of field and complex internal structure of conventional projectors.

[0004] This invention is achieved through the following technical solution:

[0005] A structured light pattern projection device includes a point laser, a diffractive optical element lens, a polarizer, a mirror, a polarizer motor, and a mirror motor;

[0006] The diffractive optical element lens is used to convert the point laser emitted by the point laser into a line laser. The line laser is processed by a polarizer and then projected onto a reflector. The reflector reflects the processed line laser onto the surface of the target object.

[0007] The polarizer motor is used to drive the polarizer to rotate around the central axis of the polarizer, which is the central axis perpendicular to the polarizer.

[0008] The reflector motor is used to drive the reflector to rotate around the vertical axis of the reflector. The vertical axis is the central axis along the axial direction of the reflector, and the linear laser projected onto the reflector coincides with the vertical axis of the reflector.

[0009] In some embodiments, a projection window is provided between the reflector and the target object to allow linear laser light reflected from the reflector to pass through.

[0010] In some embodiments, the projection window is a flat plate with a rectangular window, and the plane where the projection window is located is parallel to the axis of the reflector motor.

[0011] In some embodiments, photosensitive elements are respectively installed on the side edges of the projection window.

[0012] This invention also relates to a structured light pattern projection method, which uses the above-mentioned structured light pattern projection device to project a structured light pattern onto the surface of a target object, and includes the following steps:

[0013] S1. Turn on the point laser;

[0014] S2. The polarizer is driven to rotate continuously in one direction by a polarizer motor; the mirror is driven to rotate continuously in one direction by a mirror motor, so as to project linear light rays onto the target object.

[0015] In some embodiments, step S2 further includes the step:

[0016] S21. Obtain the sweep angle of the reflector when the linear laser reflected by the reflector reaches the right boundary of the projection window from the left boundary.

[0017] S22. Obtain the rotation speed of the polarizer and the mirror based on the sweep angle of the mirror, the projection frame rate of the structured light pattern, and the number of cycles of light intensity change of the structured light pattern.

[0018] In some embodiments, step S22 includes:

[0019] S221. Determine the rotational speed of the reflector based on the frame rate of the structured light pattern projection;

[0020] S222. Obtain the time it takes for the linear laser reflected by the mirror to pass through the projection window based on the sweeping angle and rotation speed of the mirror.

[0021] S223. The rotational speed of the polarizer is obtained based on the time it takes for the linear laser to pass through the projection window and the number of cycles of light intensity change of the required structured light pattern.

[0022] In some embodiments, step S21 includes:

[0023] S211. Obtain the time difference between the feedback signals from the photosensitive elements set on both sides of the projection window;

[0024] S212. Obtain the sweep angle of the reflector based on the time difference and the rotation speed of the reflector.

[0025] In some embodiments, it also includes:

[0026] The angle difference of the polarizer is obtained for each phase shift step when the structured light pattern is projected; the projection of the structured light pattern is completed according to the phase shift step and the angle difference of the polarizer.

[0027] After the previous structured light pattern is projected and the reflected linear laser sweeps across the right boundary of the projection window, the speed of the polarizer is changed so that the mirror rotates to the point where the linear laser sweeps across the left boundary of the projection window again. At this point, the polarizer returns to the rotation speed required for projection, and the angle of the polarizer at this moment is the difference between the angle of the polarizer at the time of the previous structured light image projection and the angle of the polarizer obtained.

[0028] In some embodiments, the polarizer rotation speed is re-acquired based on the number of light intensity change cycles of the next desired structured light pattern, and the structured light pattern is projected until the number of light intensity change cycles of all desired structured light patterns has been projected.

[0029] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0030] 1. This invention achieves the projection of structured light patterns by synchronously rotating a polarizer and a reflector under certain rules. Different structured light patterns can be obtained by changing the rotation speed of the polarizer and the reflector. The control method is simple, the implementation is convenient, and the structure is simple. Only a few components are needed to achieve the projection of structured light stripe patterns.

[0031] 2. This invention uses diffractive optical elements, lenses, and polarizers, which makes the depth of field of the structured light pattern projection device deeper than that of conventional projectors. It can form clear patterns over a wider range, resulting in a wide projection range and good projection effect. It does not rely on lenses during the imaging process and can clearly image within the range where the laser beam can be clearly displayed.

[0032] 3. The sweeping angle of the reflector is determined by using a projection window, thereby determining the rotation speed of the reflector and polarizer, which makes the projection effect of the structured light stripe pattern on the surface of the target object better and easier to control.

[0033] 4. Photosensitive elements are installed on the sides of the projection window. When the linear laser sweeps across the two photosensitive elements, feedback signals are generated respectively. The sweeping angle of the reflector is obtained based on the time difference of the feedback signals of the two photosensitive elements and the rotation speed of the reflector. This facilitates the rapid adjustment of the rotation speed of the polarizer and the reflector, and can better realize the projection of structured light stripe patterns. Attached Figure Description

[0034] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 This is a schematic diagram of a structured light pattern projection device according to an embodiment of the present invention.

[0036] Wherein: 1-point laser, 2-diffractive optical element (DOE) lens, 3-polarizer, 4-reflector, 5-projection window, 6-reflector motor, 7-projection line, 8-target object. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments.

[0038] Example 1

[0039] A preferred embodiment of a structured light pattern projection device, referring to Figure 1 A structured light pattern projection device includes a point laser 1, a diffractive optical element (DOE) lens 2, a polarizer 3, a reflector 4, a polarizer motor, and a reflector motor 6.

[0040] The diffractive optical element (DOE) lens 2 is used to convert the point laser emitted by the point laser 1 into a line laser. The line laser is processed by the polarizer 3 and then projected onto the reflector 4. The reflector 4 reflects the processed line laser onto the surface of the target object 8.

[0041] By employing diffractive optical element (DOE) lens 2 and polarizer 3, the depth of field of the structured light pattern projection device is greater than that of conventional projectors, enabling the formation of clear patterns over a wider range. This results in a wide projection range and good projection effect. The imaging process does not rely on lenses, and clear imaging can be achieved within the range where the laser beam can be clearly displayed.

[0042] The polarizer motor is used to drive the polarizer 3 to rotate around the central axis of the polarizer 3. The central axis is a central axis perpendicular to the polarizer 3. As the polarizer motor rotates, the intensity of the linear laser passing through the polarizer 3 can be controlled, thereby changing the brightness of the projection line 7.

[0043] The reflector motor 6 is used to drive the reflector 4 to rotate around the vertical axis of the reflector 4. The vertical axis is the central axis along the axial direction of the reflector 4, and the linear laser projected onto the reflector 4 coincides with the vertical axis of the reflector 4. As the reflector 4 rotates with the reflector motor 6, the linear laser projection line 7 forms a sweeping pattern on the surface of the target object 8.

[0044] A projection window 5 is provided between the reflector 4 and the target object 8 to allow the linear laser reflected from the reflector 4 to pass through; the projection window 5 is a flat plate with a rectangular window, the plane where the projection window 5 is located is parallel to the axis of the reflector motor, and the upper and lower sides of the projection window 5 are parallel to the central axis of the point laser 1; photosensitive elements are respectively installed on the sides of the projection window 5.

[0045] When the reflector 4 is parallel to the central axis of the laser 1, it cannot reflect light effectively. When it is nearly parallel, the reflection effect is poor. When it is perpendicular, the light is reflected back along the original path. Therefore, the effective reflection range is when the reflector 4 and the central axis of the laser 1 form an angle of 90° to 180°. The middle range of 135°±22.5° is taken as an optimal range. The angle between the projection window 5 and the central axis of the laser 1 is 0°, which is the best. When the reflector 4 is rotated to 135°-22.5°, the reflected beam passes through the left side of the projection window. When the reflector 4 is rotated to 135°+22.5°, the reflected beam passes through the right side of the projection window.

[0046] The sweep angle of the reflector is determined by the projection window 5, thereby determining the rotation speed of the reflector 4 and the polarizer 3, which improves the projection effect of the structured light stripe pattern on the surface of the target object 8. Photosensitive elements are installed on the sides of the projection window 5. When the linear laser sweeps across the two photosensitive elements, feedback signals are generated respectively. The sweep angle of the reflector is obtained based on the time difference between the two feedback signals and the rotation speed of the reflector 4, which facilitates the rapid adjustment of the rotation speed of the polarizer 3 and the reflector 4, and can better realize the projection of the structured light stripe pattern.

[0047] The structured light pattern projection device described above has a simple structure and requires only a few components to project structured light stripe patterns.

[0048] The present invention also relates to a preferred embodiment of a structured light pattern projection method, referring to... Figure 1 The structured light pattern is projected onto the surface of the target object 8 using the aforementioned structured light pattern projection device, comprising the following steps:

[0049] S1. The point laser 1 is turned on by an electrical signal; the point laser emitted by the point laser 1 is transformed into a line laser by the diffractive optical element (DOE) lens 2, the line laser passes through the polarizer 3 and reaches the reflector 4, the reflector 4 reflects the line laser, the reflected line laser passes through the projection window 5 and reaches the target object 8, forming a line laser projection line 7 on the surface of the target object 8, realizing the projection of the structured light stripe image on the surface of the target object 8.

[0050] S2. The polarizer 3 is continuously rotated in one direction by the polarizer motor; the reflector 4 is continuously rotated in one direction by the reflector motor 6, so that the linear laser projection line 7 is projected onto the target object.

[0051] S3. Obtain the rotational speed R of the reflector based on the projection frame rate F of the structured light pattern, denoted as R (revolutions / minute) = 60 * F (frames / second);

[0052] One rotation of the reflector produces one scanning pattern, so the projection frame rate F of the structured light pattern is the number of patterns generated per second.

[0053] S4. Based on the time it takes for the linear laser to generate feedback signals when it sweeps across the two photosensitive elements, obtain the time difference between the feedback signals of the photosensitive elements set on both sides of the projection window; then obtain the sweeping angle α of the reflector based on the time difference between the feedback signals of the two photosensitive elements and the rotational speed R of the reflector.

[0054] S5. Based on the sweep angle α and the rotational speed of the mirror, obtain the time it takes for the line laser reflected by mirror 4 to pass through the projection window. The time required to rotate by angle α is α / 360 of the time required for one revolution, and the time required for one revolution is 60 / R (seconds). Therefore, the time it takes for the line laser reflected by mirror 4 to pass through the projection window is denoted as...

[0055] S6. Obtain the rotational speed R′ (revolutions / minute) of the polarizer based on the time it takes for the linear laser to pass through the projection window and the number of cycles N of the light intensity change in the desired structured light pattern, denoted as...

[0056] In this process, the light intensity changes for one cycle for every 90° rotation of the polarizer 3; the number of cycles of light intensity change that the polarizer 3 needs to achieve in the time it takes for the linear laser reflected by the mirror 4 to pass through the projection window is denoted as N.

[0057] S7. Obtain the angle difference of the polarizer during each phase shift step S; complete the projection of the structured light pattern according to the phase shift step S and the angle difference of the polarizer.

[0058] After the previous structured light pattern is projected and the reflected linear laser sweeps across the right boundary of the projection window 5, the speed of the polarizer is changed so that the reflector 4 rotates to the point where the linear laser sweeps across the left boundary of the projection window 5 again. At this point, the polarizer 3 returns to the rotation speed required for projection, and the angle of the polarizer 3 at this moment is the difference between the angle of the polarizer 3 at the previous structured light image projection and the angle of the polarizer 3.

[0059] S8. Based on the number of light intensity change cycles N′ of the next required structured light pattern, re-obtain the rotation speed of the polarizer and project the structured light pattern until the projection of the light intensity change cycles of all required structured light patterns is completed.

[0060] By synchronously rotating the polarizer 3 and the reflector 4 under certain rules, the projection of structured light patterns can be achieved. Different structured light patterns can be obtained by changing the rotation speed of the polarizer and the reflector. The control method is simple, easy to implement, and the structure is simple. Only a few components are needed to achieve the projection of structured light stripe patterns. The rotation speed of the polarizer can be adjusted according to the phase shift step S and the number of light intensity change cycles of the desired structured light pattern to improve the effect of projecting the structured light stripe pattern onto the target object.

[0061] Example 2

[0062] Reference Figure 1 A preferred embodiment of projecting a structured light pattern onto the surface of a target object using the aforementioned structured light pattern projection device is as follows:

[0063] A 650mm point laser 1 is used. A diffractive optical element (DOE) lens 2 corresponding to the point laser 1 is set in front of the point laser 1. A polarizer 3 with a central hole is set in front of the diffractive optical element (DOE) lens 2. The polarizer 3 is set on a polarizer motor. The central hole of the polarizer is coaxial with the polarizer motor. The axis of the central hole of the polarizer is parallel to the axis of the point laser 1.

[0064] By adjusting the focal length of the point laser 1, the point laser emitted by the point laser 1 is transformed into a relatively parallel line laser after passing through the diffractive optical element (DOE) lens 2 and the polarizer 3 in sequence. This results in a linear pattern for the structured light projection, and the thickness of the line laser does not change significantly within a certain distance. The adjusted point laser 1, diffractive optical element (DOE) lens 2, and polarizer motor are then fixedly mounted on the bracket in sequence. When viewed from the axial direction of the point laser 1, the polarizer 3 can completely cover the window area of ​​the point laser 1.

[0065] The polarizer motor drives the polarizer 3 to rotate continuously in one direction around the central axis of the polarizer 3, which can control the intensity of the linear laser transmitted through the polarizer 3 and realize the change of the brightness of the projection line 7.

[0066] A reflector 4 is placed at a certain distance in front of the polarizer 3; a reflector 4 is mounted on a reflector motor 6, and the reflector motor 6 is fixedly mounted on a bracket; the reflector motor 6 is used to drive the reflector 4 to rotate around the vertical axis of the reflector, the vertical axis being the central axis along the axial direction of the reflector, and the linear laser projected onto the reflector 4 coincides with the vertical axis of the reflector; the reflector 4 rotates continuously in one direction at a uniform speed with the reflector motor 6.

[0067] The linear laser beam after passing through polarizer 3 reaches mirror 4, which reflects the linear laser beam. The reflected linear laser beam passes through projection window 5 and reaches target object 8, forming linear laser projection line 7 on the surface of target object. As mirror 4 rotates with mirror motor 6, the linear laser projection line 7 forms a sweeping pattern on the surface of target object.

[0068] A projection window 5 is provided between the reflector 4 and the target object 8 to allow the linear laser reflected from the reflector 4 to pass through. The projection window 5 is a rectangular frame. The plane of the projection window 5 is parallel to the axis of the reflector motor. The upper and lower sides of the projection window 5 form a 45° angle with the central axis of the point laser 1. Photosensitive elements are installed on the two sides of the projection window 5 respectively. When the linear laser sweeps across the two photosensitive elements, feedback signals can be generated respectively.

[0069] The laser 1, polarizer motor, and mirror motor 6 are started by an electrical signal. The sweeping angle range of the mirror is obtained based on the time difference of the feedback signals of the two photosensitive elements and the rotation speed of the mirror.

[0070] The rotation angle of polarizer 3 determines the light intensity, and the rotation angle of reflector 4 determines the position of the light stripe. The matching rotation speeds of the two generate a structured light pattern with periodic brightness changes in the scanning direction. Based on the light intensity change parameters of the structured light pattern, the rotation speeds of polarizer 3 and reflector 4 are adjusted so that the pattern projected from projection window 5 is consistent with the preset structured light pattern. After the previous structured light pattern is projected and the reflected linear laser sweeps across the right boundary of projection window 5, the speed of polarizer is changed so that the reflector rotates to the point where the linear laser sweeps across the left boundary of projection window 5 again. At this point, polarizer 3 returns to the rotation speed required for projection.

[0071] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications or equivalent changes made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A structured light pattern projection device, characterized in that: Includes point lasers, diffractive optical elements, lenses, polarizers, mirrors, polarizer motors, and mirror motors; The diffractive optical element lens is used to convert the point laser emitted by the point laser into a line laser. The line laser is processed by a polarizer and then projected onto a reflector. The reflector reflects the processed line laser onto the surface of the target object. The polarizer motor is used to drive the polarizer to rotate around the central axis of the polarizer, which is the central axis perpendicular to the polarizer. The reflector motor is used to drive the reflector to rotate around the vertical axis of the reflector. The vertical axis is the central axis along the axial direction of the reflector, and the linear laser projected onto the reflector coincides with the vertical axis of the reflector.

2. The structured light pattern projection device according to claim 1, characterized in that: A projection window is provided between the reflector and the target object to allow the linear laser reflected from the reflector to pass through.

3. The structured light pattern projection device according to claim 2, characterized in that: The projection window is a flat plate with a rectangular window, and the plane where the projection window is located is parallel to the axis of the reflector motor.

4. The structured light pattern projection device according to claim 3, characterized in that: Photosensitive elements are installed on the sides of the projection window.

5. A method for projecting structured light patterns, characterized in that, Projecting a structured light pattern onto the surface of a target object using any one of the structured light pattern projection devices of claims 1-4 includes the following steps: S1. Turn on the point laser; S2. The polarizer is driven to rotate continuously in one direction by a polarizer motor; the mirror is driven to rotate continuously in one direction by a mirror motor, so as to project linear light rays onto the target object.

6. The structured light pattern projection method according to claim 5, characterized in that, Step S2 also includes the following steps: S21. Obtain the sweep angle of the reflector when the linear laser reflected by the reflector reaches the right boundary of the projection window from the left boundary. S22. Obtain the rotation speed of the polarizer and the mirror based on the sweep angle of the mirror, the projection frame rate of the structured light pattern, and the number of cycles of light intensity change of the structured light pattern.

7. The structured light pattern projection method according to claim 6, characterized in that, Step S22 includes: S221. Obtain the rotational speed of the reflector based on the frame rate of the structured light pattern projection; S222. Obtain the time it takes for the linear laser reflected by the mirror to pass through the projection window based on the sweeping angle and rotation speed of the mirror. S223. The rotational speed of the polarizer is obtained based on the time it takes for the linear laser to pass through the projection window and the number of cycles of light intensity change of the required structured light pattern.

8. The structured light pattern projection method according to claim 6, characterized in that, Step S21 includes: S211. Obtain the time difference between the feedback signals from the photosensitive elements set on both sides of the projection window; S212. Obtain the sweep angle of the reflector based on the time difference and the rotation speed of the reflector.

9. A structured light pattern projection method according to claim 6, characterized in that, Also includes: The angle difference of the polarizer is obtained for each structured light pattern projection based on the set number of phase shift steps; The structured light pattern is projected based on the phase shift step and the angle difference of the polarizer. After the previous structured light pattern is projected and the reflected linear laser sweeps across the right boundary of the projection window, the speed of the polarizer is changed so that the mirror rotates to the point where the linear laser sweeps across the left boundary of the projection window again. At this point, the polarizer returns to the rotation speed required for projection, and the angle of the polarizer at this moment is the difference between the angle of the polarizer at the time of the previous structured light image projection and the angle of the polarizer obtained.

10. A structured light pattern projection method according to claim 9, characterized in that: It also includes re-acquiring the rotation speed of the polarizer based on the number of light intensity change cycles of the next required structured light pattern, and projecting the structured light pattern until the projection of the light intensity change cycles of all required structured light patterns is completed.

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