CN106931899B - Three-dimensional shape scanning system for inhibiting noise of laser spots and improving stability - Google Patents

Abstract

A three-dimensional topography scanning system for suppressing laser spot noise and improving stability includes a line light source, a rotating mirror and an image capture device. The line light source provides a line light beam. The rotating mirror reflects the line light beam to a surface to be measured to form an irradiation area on the surface to be measured. The rotating mirror rotates so that the irradiation area swings, and the irradiation areas at different times overlap with each other, thereby achieving the effect of blurring the light spot. The image capture device is used to capture the image of the irradiation area on the surface to be measured to calculate the three-dimensional topography. Because the irradiation area formed by the line light beam on the surface to be measured in the three-dimensional topography scanning system swings over time, and the irradiation areas at different times overlap with each other, even if the line light beam forms a light spot on the surface to be measured, the light spot will be blurred due to the swinging irradiation area.

Description

A three-dimensional topography scanning system that suppresses laser spot noise and improves stability

technical field

The invention relates to a three-dimensional topography scanning system.

Background technique

The 3D scanning technology is to analyze the appearance (or geometric shape) of the object, and the scanned signal will carry out 3D reconstruction calculation to obtain the digital information of the actual object. The triangulation method is a kind of three-dimensional scanning technology, which uses a light source to illuminate an object, and then obtains beam information on the object through an image capture device. Since the light source, the light beam on the object and the image capturing device form a triangle, this technique is called triangulation.

On some triangulation systems, a laser can be used as a light source to illuminate the object to be measured. Because the laser has high directivity and high coherence, the characteristics of the object to be tested are easier to identify. However, due to the high coherence of the laser light, it is easy to form a speckle on the rough surface, which comes from the interference effect between the scattered light formed by the laser hitting the rough surface, thereby generating an irregular speckle pattern. These light spots may cause image interference, which may lead to erroneous judgments in subsequent analysis data.

SUMMARY OF THE INVENTION

The present disclosure provides a three-dimensional topography scanning system, which includes a line light source, a rotating mirror and an image capturing device. A line light source provides a line beam. The rotating mirror reflects the line beam to the surface to be measured to form an illuminated area on the surface to be measured. The rotation of the rotating mirror causes the irradiated area to swing, and the irradiated areas at different times overlap each other. The image capturing device is used for capturing images of the irradiation area on the surface to be measured.

In some embodiments, the illuminated area on the surface to be measured has an extension direction. The rotation of the rotating mirror causes the irradiation area to swing substantially along the extending direction.

In some embodiments, the illuminated area on the surface to be measured has an extension direction. The irradiated area has a first length along the extending direction, and the swing of the irradiated area is smaller than the first length of the irradiated area.

In some embodiments, the illuminated area on the surface to be measured has an extension direction. The irradiation area has a first length along the extending direction, and the image capturing device has an imaging area on the surface to be measured, the imaging area has a second length along the extending direction, and the second length is smaller than the first length.

In some implementations, the rotating mirror has a rotation frequency, and the image capturing device has an imaging frequency, and the rotation frequency is equal to the imaging frequency.

In some embodiments, the rotating mirror has a rotation frequency, and the image capturing device has an imaging frequency, and the rotation frequency is greater than the imaging frequency.

In some embodiments, the rotating mirror includes a mirror and a rotating mechanism. The mirror has an axis of rotation that is substantially at the center of the mirror. The rotating mechanism is connected to the mirror so that the mirror rotates along the rotation axis.

In some embodiments, the line light source includes a point light source and a lenticular lens. The point light source provides the first light beam. The cylindrical lens is used to deform the first light beam into a line light beam.

In some embodiments, the line beam is a laser beam.

In the above-mentioned embodiment, the irradiation area formed by the line beam on the surface to be measured in the three-dimensional topography scanning system will swing over time, and the irradiation areas at different times overlap each other, so even if the line beam will form a spot on the surface to be measured , the light spot will also be blurred by the oscillating illuminated area.

Description of drawings

1 is a perspective view of a three-dimensional topography scanning system according to an embodiment of the present invention;

2A is a schematic diagram of an image of an irradiated area;

Fig. 2B is the brightness distribution diagram of the irradiation area along the line segment B-B' when the rotating mirror is not rotated;

And Fig. 2C is the brightness distribution diagram of the irradiation area along the line segment B-B' when the rotating mirror rotates;

3 is a top view of the irradiation area of FIG. 1;

FIG. 4 is a timing chart showing the position of the irradiation area and the image capturing by the image capturing device in FIG. 1;

FIG. 5 is a schematic structural diagram of the line light source of FIG. 1 .

Detailed ways

Several embodiments of the present invention will be disclosed below with the accompanying drawings. For the sake of clarity, many practical details will be described together in the following description. It should be understood, however, that these practical details should not be used to limit the invention. That is, in some embodiments of the invention, these practical details are unnecessary. In addition, for the purpose of simplifying the drawings, some well-known and conventional structures and elements are shown in a simplified and schematic manner in the drawings.

FIG. 1 is a perspective view of a three-dimensional topography scanning system according to an embodiment of the present invention. The three-dimensional topography scanning system includes a line light source 110 , a rotating mirror 120 and an image capturing device 130 . A line light source 110 provides a line light beam 112 . The rotating mirror 120 reflects the line beam 112 to the surface to be measured 910 to form an irradiation area A on the surface to be measured 910 . The rotation of the rotating mirror 120 causes the irradiation area A to swing, and the irradiation areas A at different times overlap each other. The image capturing device 130 is used for capturing an image of the irradiation area A on the surface to be measured 910 . For the sake of clarity, FIG. 1 schematically illustrates three moments, that is, the rotating mirror 120 rotates to three angles to form three irradiation areas on the surface to be measured 910 .

In some embodiments, the surface to be measured 910 may be the surface of a platform 900 . However, in other embodiments, a test object (not shown) can be placed on the platform 900, and the three-dimensional topography scanning system is used to scan the three-dimensional appearance of the test object. If the three-dimensional topography scanning system scans the object to be measured, the surface to be measured is the surface of the object to be measured (and the platform 900 ) irradiated by the line beam 112 . If the three-dimensional topography scanning system scans the surface of the platform 900 , the surface to be measured 910 is the surface of the platform 900 irradiated by the line beam 112 . For the sake of clarity, the surface of the platform 900 irradiated by the line beam 112 is taken as an example of the surface to be measured 910 .

With the three-dimensional topography scanning system of this embodiment, the speckle generated by the line light source 110 can be blurred, so as to reduce the misjudgment caused by the subsequent image analysis. Specifically, the line light source 110 provides a line beam 112 , and the line beam 112 forms a linear irradiation area A on the platform 900 , and the image capturing device 130 can capture the characteristic information reflected by the irradiation area A. If the platform 900 and the three-dimensional topography scanning system move relative to each other (eg, the platform 900 moves), the irradiation area A illuminates different parts of the platform 900 , whereby the image capture device 130 can obtain the overall feature information of the surface of the platform 900 . In this embodiment, the irradiation area A formed by the line beam 112 on the surface to be measured 910 in the three-dimensional topography scanning system will oscillate with time, and the irradiation areas A at different times overlap each other, so even if the line beam 112 will be A light spot is formed on the measuring surface 910, and the light spot will move due to the swinging irradiation area A, and the light spots on the irradiation area A have different distribution patterns. These two factors cause the light spot to be blurred when the irradiation area A swings, thereby Suppresses or eliminates the effect of flare on subsequent image analysis.

For example, please refer to the description of the embodiments of FIGS. 2A to 2C . 2A is a schematic diagram of the image I' of the irradiation area A', FIG. 2B is a luminance distribution diagram of the irradiation area A' along the line segment BB' when the rotating mirror is not rotated, and FIG. 2C is the irradiation area A' along the line when the rotating mirror is rotated Luminance profile of segment BB'. FIG. 2A shows the irradiation area A' where the object to be tested (not shown) is a plane. If the object to be tested has surfaces with different heights, the irradiation area A' will be deformed, that is, the position of each point in the irradiation area A' will shift with the surface features (such as height) of the object to be tested. By analyzing the irradiation area A 'The offset of each point can calculate the surface features of the object to be measured. When the rotating mirror is not rotated, the light spot has obvious brightness, thus generating multiple peaks in the brightness distribution diagram of Fig. 2B. When analyzing the offset there (eg, taking the center of gravity of the luminance distribution curve), these peaks will become noise, making the analyzed offset position inaccurate. However, when the rotating mirror is rotated, the light spot is blurred, and the brightness distribution curve in Figure 2C is smoother, so the analyzed offset position is more accurate. From the above description, it can be proved that the rotation of the rotating mirror can blur the light spot, thereby obtaining more accurate analysis data.

Next, please refer to FIG. 1 and FIG. 3 together, wherein FIG. 3 is a top view of the irradiation area A of FIG. 1 . In this embodiment, the rotating mirror 120 rotates with time, so the line beam 112 forms irradiation areas A1 , A2 , . The irradiation areas A1-An on the surface to be measured 910 have an extending direction D (or more precisely, the lengthwise extending direction of the irradiation areas A1-An), and the rotating mirror 120 rotates so that the irradiation areas A1-An are substantially along the extending direction D swing.

In this article, "substance" is used to modify any relationship that can be slightly changed, but this slight change does not change its essence (in addition, the "substance" mentioned in this article can apply the above interpretation, so it is no longer necessary. repeat). For example, "the rotating mirror 120 rotates so that the irradiation areas A1-An substantially swing along the extending direction D", except that the description means that the rotating mirror 120 rotates so that the irradiation areas A1-An actually swing along the extending direction D, as long as the improvement can be achieved For the purpose of the light spot, the arrangement direction of the irradiation areas A1 to An may be slightly non-parallel to the extending direction D.

Since the irradiation areas A1-An swing with time, the light spot on each of the irradiation areas A1-An also swings accordingly, so that the light spot is blurred. In this way, in the image obtained by the image capturing device 130, the information of the light spot can be suppressed. In addition, since the irradiation areas A1 to An are substantially swung along the extending direction D, while blurring the light spot, the irradiation areas A1 to An can still maintain the accuracy of the scanning direction S (ie, the direction substantially perpendicular to the extending direction D).

Please refer to Figure 3. Each of the irradiation areas A1 to An has a length L1 along the extending direction D, and the swing Δ of the irradiation areas A1 to An is smaller than the length L1 of the irradiation areas A1 to An. In other words, an overlapping area O is formed between the irradiated areas A1 to An, which is represented by dots in FIG. 3 . In some embodiments, the irradiation areas A1 - An are partially located in the overlapping area O no matter how the irradiation areas A1 - An swing. For example, the length L1 of the irradiation areas A1-An can be about 100 mm, and the swing Δ is about 10 mm, so the length L2 of the overlapping area O is about 80 mm, but the invention is not limited to the above-mentioned values.

In some embodiments, the image capturing device 130 of FIG. 1 has an image capturing area I on the surface to be measured 910 . The imaging area I has a length L3 along the extending direction D. The length L3 of the imaging area I is smaller than the length L1 of the irradiation areas A1 to An. In addition, the length L3 of the imaging area I may be substantially equal to or smaller than the length L2 of the overlapping area O. Taking the above example, the length L3 of the imaging area I may be substantially equal to or less than 80 mm, but the present invention is not limited to the above numerical value. In other words, the opposite ends of the image capturing area I in the extending direction D can be located in the overlapping area O, so that the image capturing device 130 will not capture images outside the overlapping area O, thus avoiding capturing the image due to the irradiation area A1 ~An flickering image produced by swinging.

Next, please refer to FIG. 1 and FIG. 4 together, wherein FIG. 4 is a timing chart showing the position of the irradiation area A in FIG. 1 and the image capturing by the image capturing device 130 . In FIG. 4, the line segment 202 represents the position of the irradiation area A. As shown in FIG. In some embodiments, the rotating mirror 120 has a rotation frequency, and the image capturing device 130 has an image capturing frequency. For example, in FIG. 4, the rotating mirror 120 is rotated five times in one second, so the rotation frequency is about 5 Hz. The image capturing device 130 captures an image at times T1 and T2 each, and time T1 is approximately 0.38 seconds, so the frequency of capturing images is approximately (1 second/0.38 seconds) = approximately 2.6 Hz. However, the present invention does not use the aforementioned Values are limited. On the other hand, the image acquired by the image capturing device 130 from time T1 to time T2 (exposure time) includes the cumulative change of the irradiation area A (or light spot) from position P1 to position P2, thereby achieving the effect of blurring the light spot . Therefore, if the rotation frequency of the rotating mirror 120 is equal to the image capturing frequency of the image capturing device 130 , the obtained image may include all position changes from the position P1 to the position P1 ′ (that is, the rotating mirror 120 rotates once). The rotation frequency of the image capture device 130 is greater than the image capture frequency of the image capture device 130 , that is, the image capture device 130 rotates the rotating mirror 120 more than once during one capture period, and the obtained image contains more positional changes. The faster the rotating mirror 120 rotates, the faster the light spot swings, and the more obvious the degree of blurring.

Please refer to FIG. 5 , which is a schematic structural diagram of the line light source 110 of FIG. 1 . In some embodiments, the line light source 110 includes a point light source 114 and a lenticular lens 116 . The point light source 114 provides the first light beam 115 . The cylindrical lens 116 is used to deform the first light beam 115 into a line light beam 112 . Herein, the light spot of the first light beam 115 provided by the point light source 114 is substantially non-linear, such as circular or elliptical. The point light source 114 can be, for example, a laser. The lens surface of the cylindrical lens 116 is curved in a single axial direction, so the first light beam 115 can be deformed in a single axial direction (eg, converged and then diffused), so that the first light beam 115 becomes a line beam 112 . However, the above-mentioned structure of the line light source 110 is only an example, and is not intended to limit the present invention. Those skilled in the present invention can flexibly design the composition structure of the line light source 110 according to actual needs.

Then please go back to Figure 1. In some embodiments, the rotating mirror 120 includes a mirror 122 and a rotating mechanism 124 . The mirror 122 has a rotation axis 123 , and the rotation axis 123 is substantially located at the center of the mirror 122 . The rotation mechanism 124 is connected to the mirror 122 so that the mirror 122 rotates along the rotation axis 123 . The rotation mechanism 124 can be, for example, a stepping motor or a magnet, and uses mechanical force or magnetic force to drive the mirror 122 to rotate.

To sum up the above, the 3D topography scanning system according to the various embodiments of the present invention oscillates with time because the irradiation area formed by the line beam on the surface to be measured, and the irradiation areas at different times overlap each other, so even if the line beam will be on the surface to be measured A light spot is formed on the surface, and the light spot is also blurred by the oscillating illumination area. In this way, there is no need to add an additional diffuser plate to eliminate light spots.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the present invention. Anyone skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the present invention The scope of protection shall be subject to the scope defined by the appended claims.

Claims (9)

1. a kind of three-dimensional appearance scanning system, characterized by comprising:

One linear light source provides a Line beam；

The Line beam is reflexed to a tested surface by one revolving mirror, in forming an irradiation area on the tested surface, the wherein rotation Mirror rotates so that the irradiation area is swung, and the irradiation area of different moments forms an overlapping region, and the irradiated region Domain is positioned partially at except the overlapping region；And

One image capture unit, to capture the image of the irradiation area on the tested surface.

2. three-dimensional appearance scanning system according to claim 1, which is characterized in that the irradiation area tool on the tested surface There is an extending direction, which rotates so that irradiation area essence is swung along the extending direction.

3. three-dimensional appearance scanning system according to claim 1, which is characterized in that the irradiation area tool on the tested surface There is an extending direction, which has one first length along the extending direction, and the amplitude of oscillation which swings is less than First length of the irradiation area.

4. three-dimensional appearance scanning system according to claim 1, which is characterized in that the irradiation area tool on the tested surface There is an extending direction, which has one first length along the extending direction, and the image capture unit is to be measured in this There is a capture region on face, which has one second length along the extending direction, second length be less than this One length.

5. three-dimensional appearance scanning system according to claim 1, which is characterized in that the revolving mirror has a speed, And the image capture unit has a capture frequency, which is equal to the capture frequency.

6. three-dimensional appearance scanning system according to claim 1, which is characterized in that the revolving mirror has a speed, And the image capture unit has a capture frequency, which is greater than the capture frequency.

7. three-dimensional appearance scanning system according to claim 1, which is characterized in that the revolving mirror includes:

One reflecting mirror, has a rotary shaft, which is substantially located at the center of the reflecting mirror；And

One rotating mechanism connects the reflecting mirror, so that the reflecting mirror is rotated along the rotary shaft.

8. three-dimensional appearance scanning system according to claim 1, which is characterized in that the linear light source includes:

One point light source provides one first light beam；And

One cylindrical lenses, to be the Line beam by first light distortion.

9. three-dimensional appearance scanning system according to claim 1, which is characterized in that the Line beam is laser beam.