CN114355620A - Laser speckle suppression device and method for 3D vision - Google Patents
Laser speckle suppression device and method for 3D vision Download PDFInfo
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Abstract
The invention relates to a laser speckle suppression device and a method for 3D vision, the laser speckle suppression device comprises a laser, a first optical element for collimating the line width direction of the laser, a second optical element for collimating the long direction of the laser line, and a movement mechanism for driving the whole or part of the second optical element to generate relative displacement relative to the first optical element in the line length direction and/or in the direction of transmitting the laser to a working surface, so that the laser generates relative movement along the long direction of the working surface, the position of the laser emitted from the laser emitting surface of the second optical element is changed, the laser generates relative movement along the long direction of the working surface, the position and the shape of speckles on the working surface are changed, the speckle effect is suppressed, the line width of the laser line is not changed, and the beam quality of the laser in the line width direction is not deteriorated, the measurement accuracy is not affected.
Description
Technical Field
The invention relates to the technical field of 3D vision, in particular to a laser speckle suppression device and method for 3D vision.
Background
Laser light is widely used in various fields due to its high coherence, high collimation, and high brightness. These properties of the laser do not produce a positive effect in all applications. As in the field of 3D measurement using laser triangulation, the high coherence of the laser light leads to a reduction in measurement accuracy. The reason is that after laser light irradiates a rough surface, countless independent scattering surface elements are formed after the laser light is reflected, and due to the high correlation of the laser light, the scattered light generates an interference phenomenon in the space transmission process to form a granular speckle pattern, namely laser speckle. The principle of the laser triangulation method is to determine the height information of the measured object by using the position of the laser on the target surface of the camera, and the position of the laser in the camera is determined by the energy distribution of the laser. The irregular speckles affect laser energy distribution, thereby causing fluctuation of the position of the lifting point and further affecting the measurement precision. This is therefore an urgent problem to be solved in high-precision measurement.
The existing laser speckle suppression methods have two types: one is a static speckle elimination method, for example, the method has complex operation, large volume and poor stability by splitting and combining laser beams; the other method is a dynamic speckle elimination method, for example, the output wavelength of the laser is changed by changing the temperature of the laser, on one hand, the change range of the laser wavelength along with the temperature is small, the speckle elimination effect is not added, on the other hand, the light source wavelength FHWM is increased, so that the FHWM of the optical filter is increased, and the environmental light resistance of the shooting system is not facilitated. Some manufacturers adopt a scheme of rotating or vibrating a diffuser (ground glass), for example, a low speckle laser transmitter device disclosed in patent CN 211904057U, in which a diffuser (diffuser) in the laser transmitter device is driven by a motor and rotates around a central axis during operation, but this method also deteriorates the quality of a laser beam in a laser direction when suppressing speckle, thereby deteriorating measurement accuracy, and although this patent adopts a diaphragm to reduce the influence of laser in a line width direction, laser energy loss is also caused. Therefore, it is necessary to design a new speckle suppression device and a new speckle suppression method for laser light.
Disclosure of Invention
The technical problem to be solved by the present invention is to overcome the defects in the prior art, and thus to provide a laser speckle suppression device and method for 3D vision.
In order to achieve the purpose, the invention adopts the following technical scheme:
a laser speckle suppression apparatus for 3D vision, comprising:
a laser for emitting laser light;
the first optical element is used for collimating the line width direction of the laser;
the second optical element is used for collimating the long direction of the laser line;
and the movement mechanism is connected with the whole or part of the second optical element and drives the whole or part of the second optical element to generate relative displacement relative to the first optical element in the linear length direction and/or the direction of transmitting the laser to the working surface, so that the laser generates relative movement on the working surface along the linear length direction.
Preferably, the line width direction is defined as an X-axis direction, the line length direction is defined as a Y-axis direction, and the direction of laser transmission to the working surface is defined as a Z-axis direction;
the second optical element comprises a first lens and a random phase plane;
the first lens is provided with a first surface facing the laser, and the diopter direction of the first surface is the Y-axis direction; the first lens is provided with a second surface facing to the working surface, and the random phase surface is positioned on one side where the second surface of the first lens is positioned;
the random phase surface is arranged towards the working surface and provided with a plurality of one-dimensional steps with random height and width, and the one-dimensional steps with different heights are randomly distributed along the Y-axis direction.
Preferably, the random phase surface is disposed on the phase plate and fixedly connected to the first lens, or the first lens and the random phase surface are integrated, and the moving mechanism is a vibrator that drives the entire second optical element to reciprocate along the Y-axis direction and/or the Z-axis direction.
Preferably, the random phase surface is disposed on the phase plate and fixedly connected to the first lens, or the first lens and the random phase surface are of an integrated structure, the moving mechanism is a rotator connected to the second optical element, a rotation axis of the rotator is disposed along a line width direction, and a rotation center of the rotator and a center of a circle of a curved surface of the first surface are eccentrically disposed, so that the rotator drives the second optical element to swing in a Y axis direction and a Z axis direction, and the second optical element is relatively displaced with respect to the first optical element in the Y axis direction and the Z axis direction.
Preferably, the random phase surface is arranged on the phase plate, the first lens is arranged separately from the phase plate, the movement mechanism is a vibrator, and the vibrator drives the random phase surface to reciprocate along the Y-axis direction and/or the Z-axis direction.
Preferably, the laser speckle suppression device further comprises a third optical element, which is located between the second optical element and the working surface, the diopter direction of the third optical element is a linear length direction, and the third optical element is randomly eccentric along the linear length direction; the third optical element is a cylindrical mirror array or a single cylindrical mirror.
Preferably, the cylindrical mirror array comprises a plurality of unit lenses, and curved edges of adjacent unit lenses are connected;
the parameters of the cylindrical mirror array are obtained by the following relational expression:
In order to achieve the purpose, the invention also adopts the following technical scheme:
a laser speckle suppression method for 3D vision adopts the laser speckle suppression device for 3D vision, and comprises the following steps:
emitting laser;
the laser is collimated in the line width direction through the first optical element;
the laser passes through the second optical element, and the laser is collimated in the linear direction;
the moving mechanism drives the whole or part of the second optical element to move, so that the second optical element generates relative displacement relative to the first optical element in the linear length direction and/or the direction of transmitting the laser to the working surface, the angle of the laser which is incident into the second optical element and the position of the laser which is incident into the emitting surface of the second optical element are changed, the polarization direction and the phase of the laser which is emitted from the second optical element are changed, the laser generates relative movement along the linear length direction on the working surface, the position and the shape of speckles on the working surface are changed, but the line width of the laser is not changed, and linear laser is formed on the working surface.
Preferably, the line width direction is defined as an X-axis direction, the line length direction is defined as a Y-axis direction, and the direction of laser transmission to the working surface is defined as a Z-axis direction;
the method comprises the following steps:
the second optical element includes a first lens and a random phase surface,
setting the motion mechanism as a vibrator, and controlling the motion mechanism to drive the first lens and/or the random phase surface to reciprocate in the Y-axis direction and/or the Z-axis direction;
alternatively, the first and second electrodes may be,
the movement mechanism is set to be a rotator, a rotating shaft of the rotator is set to be along the line width direction, and the rotating center of the rotator and the center of the curved surface circle of the first surface of the first lens are eccentrically arranged; and controlling the rotator to drive the first lens and the random phase plane to swing in the Y-axis direction and the Z-axis direction, and generating relative displacement in the Y-axis direction and the Z-axis direction relative to the first optical element.
Preferably, the method comprises: and setting the frequency of the vibrator to be more than 100 times of the frequency corresponding to the exposure time.
Compared with the prior art, the invention has the beneficial effects that:
the laser speckle suppression device and the method for 3D vision provided in the technical scheme do not have a scatterer, do not cause divergence and energy loss to laser in the line width direction, but utilize the whole or part of the second optical element to generate relative displacement in the line length direction of the light path relative to the first optical element, thereby changing the position of laser emitted from the laser emitting surface of the second optical element, causing the laser to generate relative motion in the long direction of the working surface along the line, changing the position and shape of speckles on the working surface, while suppressing the speckle effect, but not changing the line width of the laser line, not causing the quality of the laser beam in the line width direction to be deteriorated, and not affecting the measurement accuracy, and after the light beams changing along with time are accumulated in the exposure time of the camera, obtaining an image with obviously reduced speckle effect. The technical scheme of the invention has lower requirements on the performance of the motion mechanism and the assembly of the whole or partial second optical element and the motion mechanism, has simple structure and relatively smaller volume, and is suitable for being applied to miniaturized 3D visual products.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.
Fig. 1 is a schematic diagram of a laser speckle suppression apparatus provided in a first embodiment of the present invention.
Fig. 2 is a schematic diagram of a laser speckle reduction apparatus provided in a second embodiment of the present invention.
Fig. 3 is a schematic diagram of a laser speckle reduction apparatus provided in a third embodiment of the present invention.
Fig. 4 is a schematic structural diagram of a random phase plane according to an embodiment of the present invention.
Fig. 5 is a schematic diagram of the third optical element according to the embodiment of the invention being a single cylindrical mirror.
Fig. 6 is a schematic diagram illustrating a third optical element according to an embodiment of the invention being a cylindrical mirror array.
Fig. 7 is a schematic structural diagram of a third optical element according to an embodiment of the invention in the case of a cylindrical mirror array of a normal array.
Fig. 8 is a schematic structural diagram of a third optical element according to an embodiment of the invention, which is an optimized cylindrical mirror array.
Description of reference numerals:
1. a laser;
2. a first optical element; 21. a second cylindrical mirror;
3. a second optical element; 31. a first cylindrical mirror; 311. a first side; 312. a second face; 32. a phase plate; 321. a random phase plane; 322. a one-dimensional step;
4. a vibrator; 41. a rotator;
5. a third optical element; 51. a unit lens;
6. a working surface.
Detailed Description
The technical solutions of the present invention will be described clearly and completely with reference to the accompanying drawings, and it should be understood that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description and simplicity of description, but do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.
The high coherence of the laser light leads to a reduction in the measurement accuracy. The reason is that after laser light irradiates a rough surface, countless independent scattering surface elements are formed after the laser light is reflected, and due to the high correlation of the laser light, the scattered light generates an interference phenomenon in the space transmission process to form a granular speckle pattern, namely laser speckle. The intensity of laser speckle is generally characterized by the speckle contrast, which can be expressed as:
According to the speckle theory, if the incoherent superposition of N independent speckle patterns (in China for 3D vision, N patterns are superposed within the exposure time of a camera), the speckle contrast becomes the original one
Based on the principle, the laser speckle suppression device is adopted in the application to decompose laser into N mutually irrelevant light sources on a time sequence within the exposure time t of the camera, and the effect can be obtained.
Based on this, as shown in fig. 1 to fig. 3, an embodiment of the present invention provides a laser speckle suppression device for 3D vision, which includes a laser 1, a first optical element 2, a second optical element 3, and a movement mechanism, wherein laser light is emitted from the laser 1, passes through the first optical element 2 and the second optical element 3 in sequence, forms linear laser light on a working surface 6, and in order to decompose the laser light into N mutually unrelated light sources in time series, the movement mechanism drives the whole or a part of the second optical element 3 to generate relative displacement in a linear length direction and/or a direction in which the laser light is transmitted to the working surface 6 relative to the first optical element 2, and a position at which the laser light is emitted from the second optical element 3 changes, so that the laser light generates corresponding movement on the working surface 6 along the linear length direction of the laser light, and changes a position and a shape of a speckle on the working surface 6, but the line width of the laser line is not changed, the measurement precision is not influenced, and the laser changing along with the time is accumulated in the exposure time of the camera to obtain an image with obviously reduced speckle effect.
Specifically, the laser 1 is used for emitting laser, the laser used in the laser triangulation method is generally a semiconductor laser 1, the semiconductor laser 1 is generally divided into a fast axis and a slow axis, the fast axis divergence angle is large, and the airy disk formula is used for knowing that the laser is more beneficial to focusing into a small light spot, so that the fast axis direction is used as the line width direction of the line laser, the fast axis direction is defined as the X axis direction for convenient description, the slow axis direction is used as the line length direction of the line laser, the Y axis direction is defined for convenient description, and meanwhile, the direction of transmitting the laser to the working surface 6 is defined as the Z axis direction based on the X axis direction and the Y axis direction; the first optical element 2 is used for collimating the line width direction of the laser, namely, after the laser passes through the first optical element 2, the light path in the X-axis direction is collimated, and the second optical element 3 is used for collimating the line length direction of the laser, namely, after the laser passes through the second optical element 3, the light path in the Y-axis direction is collimated.
It should be noted that, in some embodiments, the second optical element 3 is a split structure, the first optical element 2 may be combined with a part of the second optical element 3 as a whole, and the other part of the second optical element 3 is connected to a moving mechanism, and the moving mechanism drives the part of the second optical element 3, so that the laser emitting surface of the second optical element 3 is displaced relative to the first optical element 2 in the linear length direction and/or the direction in which the laser is transmitted to the working surface 6.
In some embodiments, the second optical element 3 includes a first lens, such as a cylindrical mirror with a single diopter in the Y-axis direction, the first lens has a first surface 311 (laser incident surface) facing the laser 1, the diopter direction of the first surface 311 is the Y-axis direction, i.e. the convex surface of the cylindrical mirror faces the laser 1; the first lens has a second surface 312 (laser light exit surface) facing the working surface 6, i.e., the plane of the cylindrical mirror.
In other embodiments, the second optical element 3 includes a first lens and a random phase surface 321, the first lens is a cylindrical lens with a diopter direction being the Y-axis direction, the first lens has a first surface 311 (laser incident surface) facing the laser 1, the diopter direction of the first surface 311 is the Y-axis direction, i.e. the convex surface of the cylindrical lens faces the laser 1; the first lens has a second surface 312 (laser emitting surface) facing the working surface 6, i.e., the plane of the cylindrical mirror; the random phase plane 321 is located on the side of the first lens where the second plane 312 is located, and is fixed on the plane of the cylindrical mirror, or is close to the plane of the cylindrical mirror but is located separately from the cylindrical mirror. The random phase surface 321 is fixed on the first lens in various ways, for example, the random phase surface 321 is disposed on the phase plate 32 and fixedly connected to the first lens, or the first lens and the random phase surface 321 are integrated and directly formed on the second surface 312 of the first lens.
In other embodiments, the second optical element 3 may also be a combination of a portion of the spherical lens with the refractive power in the Y-axis direction and a split phase plate 32, and a random phase surface 321 is disposed on a side of the phase plate 32 facing the working surface 6; at this time, the first optical element 2 may be a portion of the spherical lens whose diopter direction is the X-axis direction, a portion of the second optical element 3 and the first optical element 2 form an integral body and is a spherical lens, the phase plate 32 is disposed separately from the spherical lens, and the moving mechanism drives the phase plate 32 to move.
The random phase plane 321 in the above embodiment functions to further reduce the speckle effect, and the principle is as follows: the random phase surface 321 is arranged toward the working surface 6, and laser passes through the first optical element 2 and part of the second optical element 3 and then exits from the random phase surface 321, as shown in fig. 4, a plurality of one-dimensional steps 322 with random height and width are arranged on the random phase surface 321, the one-dimensional steps 322 with different heights are randomly distributed along the Y-axis direction, and the one-dimensional steps 322 change the polarization direction and the phase of the laser 1, so that the position of speckle on the working surface 6 is changed, and the speckle effect is reduced. The random phase plane 321 may be made of a birefringent material, such as quartz crystal, mica crystal, magnesium fluoride crystal, etc., and for the convenience of manufacturing the second optical element 3, the random phase plane 321 on the phase plate 32 is generally directly used and combined with a spherical lens or a cylindrical lens. In order not to affect the line width of the laser in the X-axis direction, the height of the one-dimensional step 322 should not be too high, for example, not exceed 50um, and the step width should be smaller than the displacement amplitude related to the displacement amplitude of the motion mechanism.
When the second optical element 3 is a cylindrical lens with a single diopter in the Y-axis direction, the movement mechanism drives the whole second optical element 3 to move or rotate in the Y-axis direction and/or the Z-axis direction, and the second optical element and the first optical element 2 are displaced relatively.
When the second optical element 3 is a combination of a cylindrical mirror and the random phase surface 321, the diopter direction of which is the Y-axis direction, the cylindrical mirror and the random phase surface 321 may be an integrated structure or a split structure; when the cylindrical mirror and the random phase plane 321 are in an integrated structure, the motion mechanism drives the whole second optical element 3 to move or rotate in the Y-axis direction and/or the Z-axis direction, and to generate relative displacement with the first optical element 2; when the cylindrical mirror and the random phase plane 321 are in a split structure, the motion mechanism drives the cylindrical mirror to move or rotate in the Y-axis direction and/or the Z-axis direction, and may also drive the random phase plane 321 to move in the Y-axis direction. Since the cylindrical mirror and the random phase plane 321 whose diopter direction is the Y-axis direction do not change the laser line width, even if the second optical element 3 generates displacement in the X-axis and Z-axis directions due to the installation accuracy or the characteristics of the movement mechanism itself, the performance of the laser in the line width direction is not affected, the measurement accuracy is not affected, and the requirements for the installation process and the movement mechanism are reduced.
When the second optical element 3 is a combination of the part of the spherical lens with the diopter direction being the Y-axis direction and the split phase plate 32, at this time, part of the second optical element 3 and the first optical element 2 form a whole body which is the spherical lens, and the phase plate 32 and the spherical lens are separately arranged, the motion mechanism drives the random phase plane 321 to move in the Y-axis direction, at this time, because the phase plate 32 does not change the laser line width, even if the displacement in the X-axis direction and the Z-axis direction is generated due to the installation accuracy or the characteristics of the motion mechanism itself, the performance of the laser in the line width direction is not affected, and the measurement accuracy is not affected.
Based on the above description, the technical solution of the present invention will be briefly described below with reference to several specific embodiments.
In the first embodiment shown in fig. 1, the first optical element 2 is a second lens, such as a second cylindrical lens 21, and the second cylindrical lens 21 may have two cylindrical surfaces, or one cylindrical surface and the other planar surface, and the diopter direction of the second cylindrical lens 21 is the X-axis direction and functions to control the line width of the line laser, and the second optical element 3 includes a first lens and a random phase surface 321, the first lens is a first cylindrical lens 31, and the random phase surface 321 is disposed on the phase plate 32, as described above. The second optical element 3 of the present embodiment is a bonded body of a first cylindrical mirror 31 and a phase plate 32, the first cylindrical mirror 31 has a first surface 311 (laser incident surface) whose diopter direction is the Y-axis direction, the first surface 311 is disposed facing the laser 1 and is used for collimating laser light in the linear length direction, the phase plate 32 is fixed to a second surface 312 facing the first cylindrical mirror 31 and is operative, and a random phase surface 321 (laser emitting surface) faces the working surface 6 and is used for randomly changing the polarization and phase of the laser light emitted from the second optical element 3 along the Y-axis direction. The motion mechanism is a vibrator 4, because the first cylindrical mirror 31 has a larger volume and the phase plate 32 is fixedly connected with the first cylindrical mirror 31, the vibrator 4 is connected to the first cylindrical mirror 31 to drive the first cylindrical mirror 31 and the phase plate 32 thereon to reciprocate along the Y-axis direction, so as to change the incidence angle of the laser beam from the laser incidence surface, the emission angle of the laser beam from the laser emission surface and the position of the laser beam incident on the laser emission surface, and change the polarization direction and phase of the laser beam emitted by the laser beam in cooperation with the movement of the phase surface 321 of the random phase, thereby leading the laser falling on the working surface 6 to generate corresponding movement along the long direction (Y-axis direction) and changing the position and the shape of the speckle on the working surface 6 without changing the line width of the laser line and influencing the measurement precision, and after the lasers changing along with the time are accumulated in the exposure time of the camera, an image with obviously reduced speckle effect is obtained. Assuming that the exposure time is t and the vibration frequency of the first cylindrical mirror 31 following the vibrator 4 is f, the speckle contrast is reduced to the original one
. Even if the second optical element of this embodiment generates displacements in the X-axis direction and the Z-axis direction due to the mounting accuracy or the characteristics of the movement mechanism itself, the performance of the laser in the line width direction is not affected, and the measurement accuracy is not affected.
Preferably, in this embodiment, the laser speckle suppression device further includes a third optical element 5, which is located between the second optical element 3 and the working surface 6, the diopter direction of the third optical element 5 is a line length direction (Y-axis direction), and the third optical element 5 diverges the laser line length direction to form a line laser on the working surface. And the third optical element 5 is randomly decentered in the linear direction; the third optical element 5 is a cylindrical mirror array or a single cylindrical mirror. The third optical element 5 serves to further reduce the speckle contrast. As shown in fig. 1, in the specific embodiment, taking the third optical element 5 as a cylindrical lens array as an example, the cylindrical lens array is formed by arranging a plurality of unit lenses 51 along the Y-axis direction, and the eccentric direction of each unit lens 51 is randomly eccentric along the Y-axis direction, the angle of the collimated laser emitted from the second optical element 3, which is diverged by each column of the cylindrical lens array, can cover the requirement of the system on the length of the laser line, so that the obtained line laser is the superposition of the line laser generated by each unit lens 51, and the random eccentricity of the unit lenses 51 makes each unit line laser have random dislocation along the length direction on the working surface 6, so that the local correlation of the light generated by each cylindrical surface can be reduced, and the speckle contrast can be further reduced. Compared with a single cylindrical mirror, as shown in fig. 5, a common cylindrical mirror or a powell prism is adopted, adjacent light comes from adjacent points of the working surface 6, the incident angle of the laser passing through the cylindrical mirror array at each point on the working surface 6 is increased, as shown in fig. 6, the cylindrical mirror array is the superposition of different cylindrical mirror units, so the beam angle is larger, and the speckle contrast can be better reduced by the cylindrical mirror array based on the speckle theory. The cylindrical lens array comprises a plurality of unit lenses, each unit lens is a cylindrical lens, and one side facing the working surface is provided with diopter.
Parameters of the cylindrical mirror array as shown in FIGS. 1 and 8Obtained from the following relation:
wherein n is the refractive index of the cylindrical mirror array, r is the curvature radius of the unit lens 51, and D is the length of the unit lens along the diopter direction; l is the required line length of the line laser on the working surface 6; h is the distance from the cylindrical mirror array to the working surface and is called the working distance, the closer the working distance is, the better the speckle suppression effect is, and considering that the size of the cylindrical mirror array is far smaller than the working distance, the working distance is the distance from the central point of the cylindrical mirror array to the working surface for convenient calculation. It should be noted that although the speckle effect of the cylindrical mirror array is better, in some embodiments, the third optical element 5 may be a single cylindrical mirror, which satisfies the requirement of use.
In order to avoid the stray light that is easily generated in the high-low gap between the unit lenses 51 in the cylindrical mirror array, as shown in fig. 7, it is preferable that, when designing the cylindrical mirror array, the unit lenses 51 are moved in the Z-axis direction so that the curved edges of the adjacent unit lenses are in contact with each other, and there is no step between the adjacent unit lenses 51, as shown in fig. 8, in this case, one surface of the cylindrical mirror array facing the second optical element 3 is a flat surface, and the laser light incident on the cylindrical mirror array is collimated light.
Preferably, the vibrator 4 in this embodiment may be a piezoelectric ceramic or other micro vibrator 4, and the frequency thereof needs to be significantly larger than the frequency corresponding to the exposure time, for example, more than 100 times, and assuming that the exposure time is 10ms, the vibration frequency needs to be more than 10 kHz. Because the second optical element 3 driven by the vibrator 4 aligns the line length direction of the laser, and the first optical element 2 remains still, the vibrator 4 is not strictly required to drive the second optical element 3 to vibrate along the Y-axis direction, and can also properly vibrate along the Z-axis direction, and as long as the vibrator 4 does not rotate along the Z-axis direction, the line width of the line laser is not affected, so the requirements for mounting the second optical element 3 and the vibrator 4 and the requirements for the vibrator 4 per se are lower, and the implementation is easier.
In the second embodiment shown in fig. 2, the first optical element 2 is a second lens, such as a second cylindrical lens 21, and the second cylindrical lens 21 may have two cylindrical surfaces, or one cylindrical surface and the other planar surface, and the diopter direction of the second cylindrical lens 21 is the X-axis direction, which functions to control the line width of the line laser, and the second optical element 3 includes a first lens and a random phase surface 321, the first lens is a first cylindrical lens 31, and the random phase surface 321 is disposed on the phase plate 32, as described above. The second optical element 3 of the present embodiment is a bonded body of a first cylindrical mirror 31 and a phase plate 32, the first cylindrical mirror 31 has a first surface 311 (laser incident surface) whose diopter direction is the Y-axis direction, the first surface 311 is disposed facing the laser 1 and is used for collimating laser light in the linear length direction, the phase plate 32 is fixed to a second surface 312 facing the first cylindrical mirror 31 and is operative, and a random phase surface 321 (laser emitting surface) faces the working surface 6 and is used for randomly changing the polarization and phase of the laser light emitted from the second optical element 3 along the Y-axis direction. The movement mechanism is a rotator 41, because the volume of the first cylindrical mirror 31 is large, and the phase plate 32 is fixedly connected with the first cylindrical mirror 31, the rotator 41 is connected with the first cylindrical mirror 31 to drive the first cylindrical mirror 31 and the phase plate 32 thereon to swing together, the rotation axis of the rotator 41 is arranged along the line width direction, and the rotation center of the rotator and the center of the curved circle of the first surface are eccentrically arranged, so that points which do not generate relative displacement are prevented from being arranged on the first surface when the second optical element 3 swings relative to the first optical element; the rotator 41 drives the whole second optical element 3 to swing in the Y-axis direction and the Z-axis direction, so that the second optical element 3 generates relative displacement in the Y-axis direction and the Z-axis direction relative to the first optical element 2, the incident angle of the laser from the laser incident surface, the incident angle of the laser from the laser emergent surface and the position of the laser emergent surface are changed, and the polarization direction and the phase of the laser when the laser is emitted are changed by matching with the movement of the phase plane 321 of the random phase, so that the laser falling on the working surface 6 generates corresponding movement along the long direction (Y-axis direction) to change the position and the shape of speckles on the working surface 6, but the line width of the laser line is not changed, the measurement accuracy is not affected, and the lasers changing along the time are accumulated in the exposure time of the camera to obtain an image with obviously reduced speckle effect. Even if the second optical element of this embodiment generates displacements in the X-axis and Z-axis directions simultaneously due to the mounting accuracy or the characteristics of the movement mechanism itself, the performance of the laser in the line width direction is not affected, and the measurement accuracy is not affected.
Preferably, the laser speckle suppression device of this embodiment further includes a third optical element 5, as shown in the first embodiment, which is not described herein again.
In the third embodiment shown in fig. 3, the first optical element 2 is a second lens, such as a second cylindrical lens 21, and the second cylindrical lens 21 may have two cylindrical surfaces, or one cylindrical surface and the other planar surface, the diopter direction of the second cylindrical lens 21 is the X-axis direction and functions to control the line width of the line laser, and the second optical element 3 includes a first lens and a random phase surface 321, the first lens is a first cylindrical lens 31, and the random phase surface 321 is disposed on the phase plate 32, as described above. The second optical element 3 of the present embodiment is a split combination of the first cylindrical mirror 31 and the phase plate 32. The first cylindrical mirror 31 has a first surface 311 (laser incident surface) having a diopter direction in the Y-axis direction, the first surface 311 being provided facing the laser 1 for collimating the laser light in the linear length direction, the phase plate 32 being provided close to the plane (second surface 312) of the first cylindrical mirror 31 but apart from the first cylindrical mirror 31, the laser light being emitted from the first cylindrical mirror 31, incident on the phase plate 32, and emitted from the phase plate 32 toward the random phase surface 321 (laser emitting surface) of the working surface 6 for randomly changing the polarization and phase of the laser light emitted from the second optical element 3 in the Y-axis direction. The movement mechanism is a vibrator 4 which is directly connected with the phase plate 32 to drive the phase plate 32 to reciprocate along the Y-axis direction, so that the incident position and the emergent position of laser on the phase plate 32 are changed, the polarization direction and the phase position of the laser during the laser emitting are changed, the laser falling on the working surface 6 generates corresponding movement along the long direction (Y-axis direction) of the line, the position and the shape of speckles on the working surface 6 are changed, but the line width of the laser line is not changed, the measurement precision is not influenced, and after the lasers changing along with time are accumulated in the exposure time of the camera, an image with obviously reduced speckle effect is obtained.
At this time, since the phase plate 32 does not change the line width of the laser light, the first optical element 2 collimating the laser light in the X-axis direction and the first cylindrical mirror 31 collimating the laser light in the Y-axis direction (part of the second optical element 3) remain stationary, even if displacements in the X-axis and Z-axis directions are generated due to the mounting accuracy or the characteristics of the movement mechanism itself, the performance of the laser light in the line width direction is not affected, and the measurement accuracy is not affected.
Preferably, the laser speckle suppression device of this embodiment further includes a third optical element 5, as shown in the first embodiment, which is not described herein again.
In a fourth embodiment, which is not shown, the difference is that the second optical element 3 is a combination of a portion of the spherical lens with the diopter direction being the Y-axis direction and the split phase plate 32, in this case, the first optical element 2 can be a portion of the spherical lens with the diopter direction being the X-axis direction, a portion of the second optical element 3 and the first optical element 2 form an integral body, which is a spherical lens, and the phase plate 32 is disposed separately from the spherical lens, the movement mechanism is a vibrator 4, which drives the phase plate 32 to move in the Y-axis direction, changes the incident position and the emergent position of the laser light on the phase plate 32, changes the polarization direction and the phase when the laser light is emitted, so that the laser light falling on the working surface 6 generates corresponding movement along the long direction (Y-axis direction), changes the position and the shape of the speckle on the working surface 6, but the line width of the laser line is not changed, and the measurement precision is not influenced.
Based on the laser speckle suppression device for 3D vision of the above embodiment, the invention also provides a laser speckle suppression method for 3D vision, which includes the following steps:
emitting laser;
the laser passes through the first optical element 2, and the laser is collimated in the line width direction;
the laser passes through the second optical element 3, and the laser is collimated in the linear direction;
the moving mechanism drives the whole or part of the second optical element 3 to move, so that the second optical element 3 generates relative displacement in the linear length direction and/or the direction of transmitting the laser to the working surface 6 relative to the first optical element 2, the angle of the laser which is incident into the second optical element 3 and the position of the laser which is incident into the emitting surface of the second optical element 3 are changed, the polarization direction and the phase of the laser which is emitted from the second optical element 3 are changed, the laser generates relative movement in the linear length direction on the working surface 6, the position and the shape of speckles on the working surface 6 are changed, the line width of the laser is not changed, and linear laser is formed on the working surface 6.
Specifically, for convenience of description, the line width direction is defined as an X-axis direction, the line length direction is defined as a Y-axis direction, and the direction in which the laser is transmitted to the working surface 6 is defined as a Z-axis direction.
Based on the laser speckle suppression device of the first embodiment, the laser 1 emits laser, the laser passes through the first optical element 2 (the second cylindrical mirror 21) and is collimated in the line width direction, the laser passes through the first cylindrical mirror 31 in the second optical element 3 and is collimated in the line length direction, and then is emitted from the random phase plane 321, meanwhile, the moving mechanism (the vibrator 4) drives the second optical element 3 (the first cylindrical mirror 31 and the phase plate 32) to vibrate along the Y-axis direction, so that the second optical element 3 generates relative displacement in the Y-axis direction relative to the first optical element 2, and certainly, the mounting accuracy or the characteristics of the vibrator 4 itself cause the second optical element 3 to generate relative position in the Z-axis direction relative to the first optical element 2, but does not affect the line width of the line laser; at this time, the frequency of the oscillator 4 is controlled to be 100 times or more higher than the frequency corresponding to the exposure time, the angle at which the laser light enters the second optical element 3 and the position of the exit surface of the second optical element 3 are changed by the movement of the second optical element 3, the polarization direction and the phase of the laser light exiting from the second optical element 3 are changed, the laser light is relatively moved in the longitudinal direction on the working surface 6, the position and the shape of the speckle on the working surface 6 are changed, and the linear laser light is formed on the working surface 6 without changing the line width of the laser light.
Based on the laser speckle suppression device of the second embodiment, the laser 1 emits laser, the laser passes through the first optical element 2 (the second cylindrical mirror 21) and is collimated in the line width direction, the laser passes through the first cylindrical mirror 31 in the second optical element 3 and is collimated in the line length direction, and then is emitted from the random phase plane 321, meanwhile, the moving mechanism (the rotator 41) drives the second optical element 3 (the first cylindrical mirror 31 and the phase plate 32) to swing along the axis which is eccentric to the center of the curved surface of the first cylindrical mirror 31 in the X-axis direction, so that the second optical element 3 is displaced in the Y-axis direction and the Z-axis direction relative to the first optical element 2, and due to the movement of the second optical element 3, the angle of the laser emitted from the second optical element 3 and the position of the incident surface of the second optical element 3 are changed, the polarization direction and the phase of the laser emitted from the second optical element 3 are changed, the laser generates relative motion along the long direction of the line on the working surface 6, the position and the shape of the speckle on the working surface 6 are changed, but the line width of the laser is not changed, and the line laser is formed on the working surface 6.
Based on the laser speckle suppression device of the third embodiment, the laser 1 emits laser, the laser passes through the first optical element 2 (the second cylindrical mirror 21) and is collimated in the line width direction, the laser passes through the first cylindrical mirror 31 in the second optical element 3 and is collimated in the line length direction, the laser is incident into the phase plate 32, at this time, because of the vibration of part of the second optical element 3 (the phase plate 32) in the Y axis direction, the incident position and the emergent position of the laser on the phase plate 32 are changed, the polarization direction and the phase when the laser is emitted are changed, so that the laser falling on the working surface 6 generates corresponding movement along the long direction (the Y axis direction) of the line, the position and the shape of the speckle on the working surface 6 are changed, but the line width of the laser line is not changed, the measurement accuracy is not affected, and the lasers changing along with time are accumulated in the exposure time of the camera, an image with obviously reduced speckle effect is obtained, the vibration amplitude of the vibrator 4 is related to the width of the one-dimensional step 322 of the random phase plane 321, the vibration frequency needs to be obviously greater than the frequency corresponding to the exposure time, for example, more than 100 times, and if the exposure time is 10ms, the vibration frequency needs to be more than 10 kHz.
The above embodiments are only preferred embodiments of the present invention, and the protection scope of the present invention is not limited thereby, and any insubstantial changes and substitutions made by those skilled in the art based on the present invention are within the protection scope of the present invention.
Claims (10)
1. A laser speckle suppression device for 3D vision, comprising:
a laser for emitting laser light;
the first optical element is used for collimating the line width direction of the laser;
the second optical element is used for collimating the long direction of the laser line;
and the movement mechanism is connected with the whole or part of the second optical element and drives the whole or part of the second optical element to generate relative displacement relative to the first optical element in the linear length direction and/or the direction of transmitting the laser to the working surface, so that the laser generates relative movement on the working surface along the linear length direction.
2. The laser speckle suppression apparatus for 3D vision according to claim 1,
defining the line width direction as an X-axis direction, the line length direction as a Y-axis direction, and the direction of transmitting laser to a working surface as a Z-axis direction;
the second optical element comprises a first lens and a random phase plane;
the first lens is provided with a first surface facing the laser, and the diopter direction of the first surface is the Y-axis direction; the first lens is provided with a second surface facing to the working surface, and the random phase surface is positioned on one side where the second surface of the first lens is positioned;
the random phase surface is arranged towards the working surface and provided with a plurality of one-dimensional steps with random height and width, and the one-dimensional steps with different heights are randomly distributed along the Y-axis direction.
3. The laser speckle suppression device for 3D vision according to claim 2, wherein the random phase plane is disposed on the phase plate and fixedly connected to the first lens, or the first lens and the random phase plane are integrated, and the moving mechanism is a vibrator, and the vibrator drives the whole second optical element to reciprocate along the Y-axis direction and/or the Z-axis direction.
4. The laser speckle suppression apparatus for 3D vision according to claim 2,
the random phase surface is arranged on the phase plate and fixedly connected with the first lens, or the first lens and the random phase surface are of an integrated structure, the moving mechanism is a rotator, the rotator is connected with the second optical element, the rotating shaft of the rotator is arranged along the line width direction, the rotating center of the rotator is eccentrically arranged with the center of the curved surface of the first surface, so that the rotator drives the second optical element to swing in the Y-axis direction and the Z-axis direction, and the second optical element is opposite to the first optical element to generate relative displacement in the Y-axis direction and the Z-axis direction.
5. The laser speckle suppression apparatus for 3D vision according to claim 2,
the random phase surface is arranged on the phase plate, the first lens is separated from the phase plate, the moving mechanism is a vibrator, and the vibrator drives the random phase surface to reciprocate along the Y-axis direction and/or the Z-axis direction.
6. The laser speckle suppression apparatus for 3D vision according to any one of claims 1 to 5,
the second optical element is positioned between the first optical element and the working surface, the diopter direction of the second optical element is a linear length direction, and the second optical element is randomly eccentric along the linear length direction; the third optical element is a cylindrical mirror array or a single cylindrical mirror.
7. The laser speckle suppression apparatus for 3D vision according to claim 6,
the cylindrical mirror array comprises a plurality of unit lenses, and the curved surface edges of the adjacent unit lenses are connected;
the parameters of the cylindrical mirror array are obtained by the following relational expression:
8. A laser speckle reduction method for 3D vision, which employs the laser speckle reduction apparatus for 3D vision according to any one of claims 1 to 7, comprising the steps of:
emitting laser;
the laser is collimated in the line width direction through the first optical element;
the laser passes through the second optical element, and the laser is collimated in the linear direction;
the moving mechanism drives the whole or part of the second optical element to move, so that the second optical element generates relative displacement in the linear length direction and/or the direction of transmitting the laser to the working surface relative to the first optical element, the angle of the laser which is incident into the second optical element and the position of the laser which is incident into the emitting surface of the second optical element are changed, the laser generates relative movement in the linear length direction of the working surface, the position and the shape of speckles on the working surface are changed, the line width of the laser is not changed, and linear laser is formed on the working surface.
9. The laser speckle suppression method for 3D vision according to claim 8,
defining the line width direction as an X-axis direction, the line length direction as a Y-axis direction, and the direction of transmitting laser to a working surface as a Z-axis direction;
the second optical element includes a first lens and a random phase surface,
setting the motion mechanism as a vibrator, and controlling the motion mechanism to drive the first lens and/or the random phase surface to reciprocate in the Y-axis direction and/or the Z-axis direction;
alternatively, the first and second electrodes may be,
the movement mechanism is set to be a rotator, a rotating shaft of the rotator is set to be along the line width direction, and the rotating center of the rotator and the center of the curved surface circle of the first surface of the first lens are eccentrically arranged; and controlling the rotator to drive the first lens and the random phase plane to swing in the Y-axis direction and the Z-axis direction, and generating relative displacement in the Y-axis direction and the Z-axis direction relative to the first optical element.
10. The laser speckle suppression method for 3D vision according to claim 9,
and setting the frequency of the vibrator to be more than 100 times of the frequency corresponding to the exposure time.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN114696193A (en) * | 2022-06-02 | 2022-07-01 | 杭州灵西机器人智能科技有限公司 | Multi-line laser system for 3D measurement, generation and scanning method |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110057318A (en) * | 2018-01-19 | 2019-07-26 | 康耐视股份有限公司 | It is used to form the system that can be imaged as the uniform irradiation line of small speckle line |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN110057318A (en) * | 2018-01-19 | 2019-07-26 | 康耐视股份有限公司 | It is used to form the system that can be imaged as the uniform irradiation line of small speckle line |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114696193A (en) * | 2022-06-02 | 2022-07-01 | 杭州灵西机器人智能科技有限公司 | Multi-line laser system for 3D measurement, generation and scanning method |
| CN114696193B (en) * | 2022-06-02 | 2022-11-01 | 杭州灵西机器人智能科技有限公司 | Multi-line laser system for 3D measurement, generation and scanning method |
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