Laser interferometry systems and methods

Abstract

Systems and methods for measuring moving objects using laser interferometry are provided, including a laser interferometry system including a laser emitter configured to emit a laser beam, a beam splitter configured to split the emitted laser beam into a first split beam and a second split beam directed toward a deflector, the first split beam having a first beam diameter and a second beam diameter, the first beam diameter being larger than the second beam diameter, and the second split beam having a third beam diameter and a fourth beam diameter, the third beam diameter being larger than the fourth beam diameter, and a deflector configured to deflect the first split beam to intersect with the second split beam, the first beam diameter and the third beam diameter being parallel.

Description

[Technical field]

[0001] (CROSS REFERENCE TO RELATED APPLICATIONS) This application claims the benefit of U.S. Provisional Application No. 62 / 903,310, filed September 20, 2019, the entire contents of which are incorporated herein by reference.

[0002] (Field) The present disclosure relates to methods for measuring moving objects using laser interferometry, and more particularly, to methods for obtaining reliable and accurate measurements of moving objects using laser interferometry. [Background technology]

[0003] (background) Laser interferometry may be used to measure the speed or length of a moving object. Laser interferometry uses two laser beams that converge on the surface of the moving object, forming an intersection region. The moving object reflects light within the intersection region (or depth of field). This reflected light is detected by a photodetector, and the Doppler effect may be used to determine the speed and / or length of the moving object. The exact measurement may depend on one or more of the following characteristics: color of the object, texture of the object, presentation angle, reflectivity or absorption properties of the object, cleanliness of the laser path between the laser surface velocimeter and the object, composition of the object, etc.

[0004] A laser surface velocimeter is an instrument that uses the Doppler shift of a laser beam (i.e., the light reflected from the surface of the moving object) to measure the speed of a moving object. Specifically, a laser surface velocimeter intersects two beams of collimated, monochromatic, coherent laser light at the moving object to be measured. Transmission optics direct the beams to intersect at a predetermined distance, and the two beams interfere, producing a set of interference fringes. As the moving object passes through the interference fringes, it reflects the light, which is then collected by receiving optics and focused onto a photodetector. Summary of the Invention [Means for solving the problem]

[0005] (overview) Laser interferometry systems and methods are provided that use laser interferometry to measure moving objects. The systems and methods provided herein can measure various characteristics of a moving object, such as its speed. To obtain more accurate measurements, the systems and methods provided herein can include an effective measurement area that is larger than that of the conventional laser interferometry systems and methods described above. In particular, a larger measurement area can be achieved by rotating the orientation of an elliptical laser beam profile, elongating one or more axes of the elliptical profile, and / or using a smaller convergence angle.

[0006] Conventional methods using laser interferometry as described above are deficient in capturing accurate measurements of moving objects, particularly those with small cross-sectional areas. Such objects have very small reflective areas (e.g., the top of an object with a circular cross-sectional area) to produce good measurements, so the precise position of the laser is important to achieve accurate measurements. Thus, it is often difficult to receive enough light reflected back from the moving object to obtain accurate measurements. In particular, objects with small cross-sectional areas, objects that change position rapidly (in a direction other than the velocity direction), and objects that cannot be guided by the nature of the manufacturing process are typically difficult to measure accurately using conventional laser interferometry.

[0007] Disclosed herein are methods for accurately measuring such objects (e.g., objects with small cross-sectional areas, objects that change position rapidly, and objects that cannot be steered by the nature of the manufacturing process). In particular, the methods provided herein include (1) rotating the laser to increase the effective measurement area, (2) expanding the laser beam along one or more axes, and (3) minimizing the convergence angle to obtain a longer depth of field. Each of these features is described in detail below.

[0008] In some embodiments, a laser interferometry system is provided, the system comprising: a laser emitter configured to emit a laser beam; a beam splitter configured to split the emitted laser beam into a first split beam and a second split beam directed to a deflector, the first split beam having a first beam diameter and a second beam diameter, the first beam diameter being larger than the second beam diameter, the second split beam having a third beam diameter and a fourth beam diameter, the third beam diameter being larger than the fourth beam diameter; and a deflector configured to deflect the first split beam to intersect with the second split beam, the first beam diameter and the third beam diameter being parallel.

[0009] In some embodiments of the system, the first beam diameter and the third beam diameter are equal, and the second beam diameter and the fourth beam diameter are equal.

[0010] In some embodiments of the system, the first split beam and the second split beam intersect at an angle less than 60 degrees.

[0011] In some embodiments of the system, the emitted laser beam comprises a fifth beam diameter and a sixth beam diameter, the fifth beam diameter being greater than the sixth beam diameter, and at least one of the fifth beam diameter or the sixth beam diameter is increased by passing the emitted laser beam through a cylindrical lens.

[0012] In some embodiments of the system, the first beam diameter is at least three times larger than the second beam diameter and the third beam diameter is at least three times larger than the fourth beam diameter.

[0013] In some embodiments of the system, the system comprises a processor, a memory, and instructions stored on the memory, the instructions configured to cause the system to calculate a velocity of an object moving through the intersection region.

[0014] In some embodiments of the system, the calculated velocity is in a direction orthogonal to the first beam diameter and the third beam diameter.

[0015] In some embodiments of the system, the object comprises a cord, wire, rod, or a flat sheet of paper or plastic.

[0016] In some embodiments, a laser interferometry system is provided, the system comprising: a laser emitter configured to emit a laser beam; a beam splitter configured to split the emitted laser beam into a first split beam and a second split beam directed to a deflector, the first split beam having a first beam diameter and a second beam diameter, the first beam diameter being larger than the second beam diameter, the second split beam having a third beam diameter and a fourth beam diameter, the third beam diameter being larger than the fourth beam diameter; and a deflector configured to deflect the first split beam to intersect with the second split beam, the emitted laser beam having a fifth beam diameter and a sixth beam diameter, the fifth beam diameter being larger than the sixth beam diameter, and at least one of the fifth beam diameter or the sixth beam diameter is increased by passing the emitted laser beam through a cylindrical lens.

[0017] In some embodiments of the system, the first beam diameter and the third beam diameter are parallel.

[0018] In some embodiments of the system, the first beam diameter and the third beam diameter are equal, and the second beam diameter and the fourth beam diameter are equal.

[0019] In some embodiments of the system, the first split beam and the second split beam intersect at an angle less than 60 degrees.

[0020] In some embodiments of the system, the first beam diameter is at least three times larger than the second beam diameter and the third beam diameter is at least three times larger than the fourth beam diameter.

[0021] In some embodiments of the system, the system comprises a processor, a memory, and instructions stored on the memory, the instructions configured to cause the system to calculate a velocity of an object moving through the intersection region.

[0022] In some embodiments of the system, the calculated velocity is in a direction orthogonal to the first beam diameter and the third beam diameter.

[0023] In some embodiments of the system, the object comprises a cord, wire, rod, or a flat sheet of paper or plastic.

[0024] In some embodiments, a laser interferometry system is provided, the system comprising: a laser emitter configured to emit a laser beam; a beam splitter configured to split the emitted laser beam into a first split beam and a second split beam directed to a deflector, the first split beam having a first beam diameter and a second beam diameter, the first beam diameter being larger than the second beam diameter, and the second split beam having a third beam diameter and a fourth beam diameter, the third beam diameter being larger than the fourth beam diameter; and a deflector configured to deflect the first split beam to intersect with the second split beam, wherein the first split beam and the second split beam intersect at an angle less than 60 degrees.

[0025] In some embodiments of the system, the first beam diameter and the third beam diameter are equal, and the second beam diameter and the fourth beam diameter are equal.

[0026] In some embodiments of the system, the first split beam and the second split beam intersect at an angle of less than 20 degrees.

[0027] In some embodiments of the system, the first beam diameter and the third beam diameter are parallel.

[0028] In some embodiments of the system, the emitted laser beam comprises a fifth beam diameter and a sixth beam diameter, the fifth beam diameter being greater than the sixth beam diameter, and at least one of the fifth beam diameter or the sixth beam diameter is increased by passing the emitted laser beam through a cylindrical lens.

[0029] In some embodiments of the system, the first beam diameter is at least three times larger than the second beam diameter and the third beam diameter is at least three times larger than the fourth beam diameter.

[0030] In some embodiments of the system, the system comprises a processor, a memory, and instructions stored on the memory, the instructions configured to cause the system to calculate a velocity of an object moving through the intersection region.

[0031] In some embodiments of the system, the calculated velocity is in a direction orthogonal to the first beam diameter and the third beam diameter.

[0032] In some embodiments of the system, the object comprises a cord, wire, rod, or a flat sheet of paper or plastic. The present invention provides, for example: (Item 1) 1. A laser interferometry system, comprising: a laser emitter configured to emit a laser beam; a beam splitter configured to split the emitted laser beam into a first split beam and a second split beam directed toward a deflector, the first split beam having a first beam diameter and a second beam diameter, the first beam diameter being larger than the second beam diameter, and the second split beam having a third beam diameter and a fourth beam diameter, the third beam diameter being larger than the fourth beam diameter; a deflector configured to deflect the first split beam to intersect with the second split beam; Equipped with The first beam diameter and the third beam diameter are parallel. (Item 2) 2. The system of claim 1, wherein the first beam diameter and the third beam diameter are equal, and the second beam diameter and the fourth beam diameter are equal. (Item 3) 3. The system of claim 1, wherein the first split beam and the second split beam intersect at an angle of less than 60 degrees. (Item 4) 4. The system of any one of claims 1 to 3, wherein the emitted laser beam comprises a fifth beam diameter and a sixth beam diameter, the fifth beam diameter being greater than the sixth beam diameter, and at least one of the fifth beam diameter or the sixth beam diameter is increased by passing the emitted laser beam through a cylindrical lens. (Item 5) 5. The system of any one of items 1 to 4, wherein the first beam diameter is at least three times larger than the second beam diameter, and the third beam diameter is at least three times larger than the fourth beam diameter. (Item 6) 6. The system of any one of claims 1 to 5, comprising a processor, a memory, and instructions stored on the memory, the instructions configured to cause the system to calculate a velocity of an object moving through an intersection region. (Item 7) 7. The system of claim 6, wherein the calculated velocity is in a direction orthogonal to the first beam diameter and the third beam diameter. (Item 8) 7. The system of claim 6, wherein the object comprises a cord, wire, rod, or flat sheet of paper or plastic. (Item 9) 1. A laser interferometry system, comprising: a laser emitter configured to emit a laser beam; a beam splitter configured to split the emitted laser beam into a first split beam and a second split beam directed toward a deflector, the first split beam having a first beam diameter and a second beam diameter, the first beam diameter being larger than the second beam diameter, and the second split beam having a third beam diameter and a fourth beam diameter, the third beam diameter being larger than the fourth beam diameter; a deflector configured to deflect the first split beam to intersect with the second split beam; Equipped with the emitted laser beam comprises a fifth beam diameter and a sixth beam diameter, the fifth beam diameter being greater than the sixth beam diameter, and at least one of the fifth beam diameter or the sixth beam diameter is increased by passing the emitted laser beam through a cylindrical lens. (Item 10) Item 10. The system of item 9, wherein the first beam diameter and the third beam diameter are parallel. (Item 11) Item 11. The system of item 9 or item 10, wherein the first beam diameter and the third beam diameter are equal, and the second beam diameter and the fourth beam diameter are equal. (Item 12) 12. The system of any one of claims 9 to 11, wherein the first split beam and the second split beam intersect at an angle of less than 60 degrees. (Item 13) 13. The system of any one of items 9 to 12, wherein the first beam diameter is at least three times larger than the second beam diameter and the third beam diameter is at least three times larger than the fourth beam diameter. (Item 14) 14. The system of any one of claims 9 to 13, comprising a processor, a memory, and instructions stored on the memory, the instructions configured to cause the system to calculate a velocity of an object moving through an intersection region. (Item 15) Item 15. The system of item 14, wherein the calculated velocity is in a direction orthogonal to the first beam diameter and the third beam diameter. (Item 16) Item 15. The system of item 14, wherein the object comprises a cord, wire, rod, or flat sheet of paper or plastic. (Item 17) 1. A laser interferometry system, comprising: a laser emitter configured to emit a laser beam; a beam splitter configured to split the emitted laser beam into a first split beam and a second split beam directed toward a deflector, the first split beam having a first beam diameter and a second beam diameter, the first beam diameter being larger than the second beam diameter, and the second split beam having a third beam diameter and a fourth beam diameter, the third beam diameter being larger than the fourth beam diameter; a deflector configured to deflect the first split beam to intersect with the second split beam; Equipped with The first split beam and the second split beam intersect at an angle of less than 60 degrees. (Item 18) Item 18. The system of item 17, wherein the first beam diameter and the third beam diameter are equal and the second beam diameter and the fourth beam diameter are equal. (Item 19) Item 19. The system of item 17 or item 18, wherein the first split beam and the second split beam intersect at an angle of less than 20 degrees. (Item 20) 20. The system of any one of items 17 to 19, wherein the first beam diameter and the third beam diameter are parallel. (Item 21) 21. The system of any one of items 17-20, wherein the emitted laser beam comprises a fifth beam diameter and a sixth beam diameter, the fifth beam diameter being greater than the sixth beam diameter, and at least one of the fifth beam diameter or the sixth beam diameter is increased by passing the emitted laser beam through a cylindrical lens. (Item 22) 22. The system of any one of items 17 to 21, wherein the first beam diameter is at least three times larger than the second beam diameter and the third beam diameter is at least three times larger than the fourth beam diameter. (Item 23) 23. The system of any one of claims 17 to 22, comprising a processor, a memory, and instructions stored on the memory, the instructions configured to cause the system to calculate a velocity of an object moving through an intersection region. (Item 24) 24. The system of claim 23, wherein the calculated velocity is in a direction orthogonal to the first beam diameter and the third beam diameter. (Item 25) 24. The system of claim 23, wherein the object comprises a cord, wire, rod, or flat sheet of paper or plastic. [Brief description of the drawings]

[0033] BRIEF DESCRIPTION OF THE DRAWINGS Various embodiments are described with reference to the accompanying drawings.

[0034] [Figure 1] 1A and 1B each depict a laser beam reflecting off a moving object according to some embodiments.

[0035] [Diagram 2] 2A and 2B each depict a schematic of a laser beam orientation used to measure a moving object according to some embodiments.

[0036] [Diagram 3] FIG. 3 illustrates a top view of a laser surface velocimeter according to some embodiments.

[0037] [Figure 4] FIG. 4 illustrates features of a laser surface velocimeter according to some embodiments.

[0038] [Diagram 5] FIG. 5 illustrates features of a laser surface velocimeter according to some embodiments.

[0039] [Figure 6] FIG. 6 illustrates a laser beam configuration according to some embodiments.

[0040] [Figure 7] FIG. 7 shows a focused laser beam that creates an interference fringe pattern according to some embodiments.

[0041] [Figure 8] 8A and 8B each depict an interference fringe pattern according to some embodiments. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0042] (Detailed Description) Described herein are laser interferometry systems and methods for measuring moving objects using laser interferometry. In particular, the methods described herein are used to obtain more reliable and accurate measurements of such objects. For example, measurements that may be obtained using the systems and methods described herein may include measurements related to the movement of such moving objects for purposes of process control, speed monitoring, cut length control and verification, and thickness control.

[0043] Laser interferometry obtains measurements by using the separation of laser energy into two beams using a beam splitter. The split beams are then recombined or crossed. The object being measured reflects light within the area where the split beams cross (called the depth of field). The exact measurement may depend on one or more of the following characteristics: the color of the object, the texture of the object, the presentation angle, the reflectivity or absorption properties of the object, the cleanliness of the laser path between the laser surface velocimeter and the object, and the composition of the object.

[0044] Traditional methods of measuring moving objects have difficulty in obtaining reliable and accurate measurements due to the small reflective area on the surface of the object. In addition, these methods are designed such that the laser surface velocimeter is stationary and measures the speed of the object moving in the X-axis direction. However, even if the object is moving in the X-axis direction, the position of the moving object also constantly fluctuates in the Y and Z-axis directions. Therefore, this small reflective area, coupled with the object's movement in the Y and Z-axis directions, can lead to inaccurate or uncertain measurements, or missing measurements.

[0045] 1A and 1B illustrate the difficulty of measuring a moving object with conventional methods. Both figures show a cross section of an object 102 traveling in a direction extending into and out of the page. As shown in FIG. 1A, the laser beam 104 is directed just on top of the object 102 such that the reflected or scattered light 106 is directed back into the path of the laser beam 104. However, FIG. 1B illustrates the case where the object 102 has moved slightly to the left, causing the laser beam 104 to be directed to the side of the object 102 rather than the top of the object 102. Thus, the reflected or scattered light 106 is directed outward at an angle that does not intersect with the path of the laser beam 104. Thus, the scattered light 106 in FIG. 1B cannot be received / detected to obtain an accurate measurement, assuming that the scattered light 106 needs to be directed back in the direction of the laser beam 104 to be detected by the detector. Thus, even a slight movement of the object 102 can prevent the laser surface velocimeter from obtaining a reliable and accurate measurement.

[0046] 2A and 2B also illustrate how uncertain a conventional laser surface velocimeter (particularly the effective measurement area of ​​a conventional laser surface velocimeter) can be. Specifically, FIG. 2A illustrates a moving object 204 configured to move linearly in the X-axis direction (i.e., side to side). Laser beam profile 202A illustrates a laser beam profile consistent with the systems and methods described herein. Laser beam profile 202B illustrates a non-rotating laser beam profile consistent with a conventional metrology system. When the moving object 204 is centered with respect to the laser beam profiles 202A and 202B, both the conventional system (i.e., laser beam profile 202B) and the system described herein (i.e., laser beam profile 202A) can obtain accurate measurements.

[0047] However, Figure 2B illustrates the difficulties that arise when using conventional metrology methods. As shown, the moving object is shifted slightly in the Y-axis direction such that it is not perfectly centered with respect to the laser beam profiles 202A and 202B. Thus, the conventional metrology method (i.e., laser beam profile 202B) is unable to take this shift into account and obtain an accurate measurement. However, the system and method provided herein (i.e., laser beam profile 202A) is more able to obtain an accurate measurement because the laser beam profile 202A is still directed to the top of the moving object 204 even when the object shifts.

[0048] The systems and methods described herein include a larger intersection or effective measurement area (i.e., the area where two laser beams intersect) that allows for more reliable and accurate measurement of moving objects. The systems and methods described herein utilize a laser surface velocimeter for measurement. Specific features of the systems and methods provided that can be implemented to create a larger effective measurement area include (1) rotating the laser beam profile, (2) expanding the laser beam in one or more axial directions, and (3) creating a longer depth of field. In addition to a detailed description of each of the features of the measurement methods described herein listed above, a description of the laser surface velocimeter used for the systems and methods provided herein is provided below.

[0049] (Laser Surface Speed ​​Meter) In addition to methods of measuring moving objects, laser surface velocimeters (i.e., laser interferometry systems) are also provided that may be used with the measurement methods provided herein. A description of the laser surface velocimeter is provided below.

[0050] 3 provides a top-down view of a laser surface velocimeter 300 according to some embodiments provided herein. As shown in the figure, the laser surface velocimeter 300 may include a laser diode 302, a collimating lens 304, an emitted laser beam 306, a cylindrical lens 308, a beam splitter 310, a transmitted laser beam 312, a deflected laser beam 314, and a mirror 316.

[0051] In some embodiments, the laser diode 302 may be rotated relative to the laser diode of a conventional laser surface velocimeter to generate a rotated laser beam profile. For example, Figure 4 shows a conventional laser beam diode 402, a conventional laser beam profile 404, and a moving object 406. In this conventional configuration, the length of the laser beam profile 404 is parallel to the direction of motion of the moving object 406.

[0052] In contrast, Figure 5 shows the configuration of a laser surface velocimeter 500 according to some embodiments. The laser surface velocimeter 500 may include a laser diode 502, a laser beam profile 504, and a moving object 506. A cylindrical lens 508 may also be included to expand the length or width of the laser beam profile 504, as described in more detail below.

[0053] As shown in Figure 5, the laser diode 502 is rotated 90 degrees relative to the laser diode 402 of Figure 4. Rotating the laser diode 502 rotates the laser beam profile 504. By rotating the laser diode 502 to produce a rotated laser beam profile 504, the effective measurement area of ​​the laser beam can be increased.

[0054] The laser surface velocimeter 300 of Figure 3 also includes a collimating lens 304. The collimating lens 304 is an optical lens that helps narrow the laser beam and / or align the beam as desired.

[0055] In some embodiments, the laser surface velocimeter 300 may also include a cylindrical lens 308 (or any other means of expanding the laser beam diameter). A cylindrical lens, such as the cylindrical lens 308 of FIG. 3, is a lens that may expand or compress light in one or more directions. In some embodiments, the cylindrical lens 308 may be used to expand the laser beam profile 304 in a particular direction. For example, the cylindrical lens 308 may be used to expand the laser beam profile 304 in a direction along the Y-axis. Further details related to cylindrical lenses and expanding the laser beam profile are provided below.

[0056] In some embodiments, the laser surface velocimeter 300 may include a beam splitter 310. A beam splitter is an optical device that can split a beam of light into two. As shown in FIG. 3, the beam splitter 310 may split the collimated laser beam 306 into two separate laser beams, i.e., a transmitted laser beam 312 and a deflected laser beam 314. In some embodiments, the transmitted laser beam 312 and the deflected laser beam 314 may diverge from the beam splitter 310 at an angle of 30 to 90 degrees. In some embodiments, the size and / or shape of the profile of the transmitted laser beam 312 and the deflected laser beam 314 may be the same.

[0057] In some embodiments, the laser surface velocimeter 300 may include a mirror 316. The mirror 316 may be used to deflect the deflected laser beam 314. Specifically, the mirror 316 may be configured to deflect the deflected laser beam 314 such that the transmitted laser beam 312 and the deflected laser beam 314 converge at the surface of the moving object. In some embodiments, the laser surface velocimeter 300 may include two mirrors 316, one to redirect the deflected laser beam 314 and the second to redirect the transmitted laser beam 312. In some embodiments, the mirror 316 may redirect the transmitted laser beam 312 and / or the deflected laser beam 314 such that the two laser beams converge downstream. In some embodiments, the transmitted laser beam 312 and the deflected laser beam 314 may converge at the location of the object to be measured (such as the surface of the moving object). In some embodiments, the laser surface velocimeter 300 may include a polarizer.

[0058] (Rotated Laser) Compared with the laser beam profile of conventional measurement methods, a system and method for measuring moving objects that includes a rotated laser beam profile is described below.For example, a laser emitter can be rotated so that the laser beam profile of the emitted laser beam is oriented so that its length is perpendicular to the moving direction of the moving object (the length of the laser beam profile is greater than the width of the laser beam profile).As used herein, the term "profile" for a laser beam (e.g., laser beam profile) refers to the cross-sectional area of ​​the laser beam, which is a plane with the diameter of the beam, and the diameter is perpendicular to the beam axis of the laser beam.

[0059] A beam of light (e.g., a laser beam) can be defined by a beam axis, a first beam diameter (BD1), and a second beam diameter (BD2). As used herein, BD1 and BD2 are perpendicular to the beam axis of the beam of light, and BD1 and BD2 are perpendicular to each other.

[0060] In some embodiments, rotating the laser beam profile can produce a larger effective measurement area (i.e., the area where the transmitted and deflected beams intersect at the surface of the moving object). In some embodiments, the laser beam profile can be elliptical in shape. In some embodiments, the laser beam can be rotated such that the major axis of the ellipse of the elliptical profile (i.e., BD1 or BD2 of the beam) is perpendicular to the direction of travel of the moving object to be measured.

[0061] 6 depicts a configuration 600 that includes a laser beam profile 602 that has been rotated such that the major axis (BD1) of the elliptical profile is perpendicular to the direction of object motion. The laser beam profile 602 is shown with its major axis (BD1) in the vertical (Y-axis) direction and its minor axis (BD2) in the horizontal (X-axis) direction. A moving object 604 is shown having a horizontal (X-axis) length and horizontal (X-axis) motion. Thus, the rotated laser produces a beam profile 602 with its major axis (BD1) perpendicular to the motion of the moving object 604.

[0062] (Expanded laser beam profile) The methods of measuring a moving object provided herein can include expanding a profile of a laser beam along one or more beam diameters. In some embodiments, the expanding of the laser beam profile is accomplished by using a cylindrical lens.

[0063] The broadening of the laser beam profile can be accomplished without degrading the quality of the collimated light received from the laser, which would result in less consistent accuracy throughout the depth of field of the laser surface velocimeter if the quality of the collimated light was degraded.

[0064] In some embodiments, magnification of the laser beam profile does not impair the accuracy of measurements taken using the laser surface velocimeter, specifically, when properly performed, magnification of the profile does not alter the depth of field fringe pattern (compared to an otherwise unmagnified laser beam profile).

[0065] In some embodiments, the laser beam profile may be expanded 1.5 to 10 times or 2 to 5 times its initial length. In some embodiments, the laser beam profile may be expanded more than 1.5 times, more than 2 times, more than 3 times, more than 4 times, more than 5 times, or more than 6 times its initial length. In some embodiments, the laser beam profile may be expanded less than 10 times, less than 8 times, less than 6 times, less than 5 times, less than 4 times, or less than 3 times its initial length. In some embodiments, the laser beam profile may be expanded in a single dimension. In some embodiments, the laser beam profile may be expanded in two or more dimensions.

[0066] 5 shows a laser surface velocimeter 400 including an expanded laser beam profile according to some embodiments. As described above, the laser surface velocimeter 500 may include a laser diode 502, a laser beam profile 504, a moving object 506, and a cylindrical lens 508.

[0067] The laser diode 502 may be rotated as described in detail above, or the laser diode 502 may be configured to emit a (non-rotated) laser beam consistent with the prior art.

[0068] 5, the moving object 506 may have a velocity direction along the horizontal or X-axis. Thus, to avoid compromising the accuracy of the measurements, the laser beam profile 504 may be magnified in the Y and / or Z dimensions. In some embodiments, a cylindrical lens 508 may be used to magnify the laser beam profile 504 in one or more dimensions. For example, as shown in FIG. 5, the cylindrical lens 508 magnifies the laser beam profile 504 at least vertically or along the Y-axis.

[0069] (depth of field) In some embodiments, the methods of measuring moving objects provided herein may include a longer depth of field. In some embodiments, the depth of field may be extended in a direction that is not the same as the velocity direction in which the material to be measured is moving. For example, if the material to be measured has a velocity direction along the X-axis, the depth of field may be extended in the Y-axis and / or Z-axis directions. As used herein, "depth of field" and "effective measurement area" (or "measurement area") may be used interchangeably. This area (i.e., depth of field, effective measurement area, or measurement area) is generated when the transmitted laser beam and the deflected laser beam partially or completely converge and intersect.

[0070] At the depth of field, an interference fringe pattern is created. For example, the light waves of the transmitted laser beam interfere with the light waves of the deflected laser beam, creating interference fringes (e.g., alternating light and dark bands). This redistribution of light intensity creates an interference pattern. When these interference patterns are reflected off the surface of a material (e.g., the material to be measured), the reflected light creates high and low intensity levels of energy. These various levels of energy are reflected into the laser surface velocimeter and used to measure a feature (more specifically, the movement of the material). For example, the reflected energy may be received by the laser surface velocimeter and directed to a photodiode. The photodiode converts the energy from light energy to electrical energy. The electrical energy is also known as a Doppler signal because its frequency varies with the speed of movement of the material from which the laser energy is reflected. This Doppler signal is converted to a velocity based on the geometry of a known, calibrated interference fringe pattern and compared in relation to the time between the electrical intersection patterns received by the laser surface velocimeter.

[0071] 7 shows a schematic of converging laser beams. As shown, laser beam 720 converges with laser beam 722 to intersect, creating a depth of field / effective measurement area 724. This depth of field / effective measurement area 724 includes an interference fringe pattern produced by the intersecting laser beams at the convergence point. In some embodiments, the object or material to be measured is placed within this depth of field / effective measurement area 724. As shown, the laser beam profile has been rotated to be consistent with laser beam profile 502 of FIG. 5.

[0072] Each of Figures 8A and 8B shows an interference fringe pattern produced by the intersection of two laser beams. In Figure 8A, laser beam 820 and laser beam 822 converge at an angle greater than the convergence angle depicted in Figure 8B. As shown in Figure 8A, a larger intersection angle (i.e., convergence angle) creates a smaller interference fringe pattern or a shorter depth of field. Conversely, Figure 8B shows a smaller intersection angle (i.e., convergence angle) creating a larger interference fringe pattern or a larger depth of field.

[0073] In some embodiments, the depth of field may be increased to accommodate a reduction in depth of field created by rotating the laser beam profile and / or magnifying the laser beam profile. For example, rotating the laser beam profile as described above may reduce the intersection range in the Z-axis direction due to a vertical laser beam profile (e.g., laser beam profile 504 of FIG. 5) rather than the horizontal laser beam profile (e.g., laser beam profile 404 of FIG. 4) of the prior art.

[0074] In some embodiments, to accommodate this shorter depth of field created by the rotated laser beam profile, a smaller angle may be used between the two laser beams to recover at least a portion of the depth that would otherwise be lost due to the rotation of the laser beam profile. For example, a smaller angle between the two laser beams may be achieved to minimize the distance between the transmitted laser beams (e.g., the distance between the transmitted laser beam 312 and the deflected laser beam 314 in FIG. 3). Minimizing the distance between the transmitted laser beam and the deflected laser beam may minimize the convergence angle of the two laser beams.

[0075] In some embodiments, the convergence angle between the transmitted and deflected laser beams can be between 5 and 40 degrees, or between 10 and 30 degrees. In some embodiments, the convergence angle between the transmitted and deflected laser beams can be greater than 5 degrees, greater than 10 degrees, greater than 15 degrees, greater than 20 degrees, greater than 25 degrees, or greater than 30 degrees. In some embodiments, the convergence angle between the transmitted and deflected laser beams can be less than 40 degrees, less than 35 degrees, less than 30 degrees, less than 25 degrees, less than 20 degrees, less than 15 degrees, or less than 10 degrees.

[0076] Unless otherwise defined, all technical terms, notations, and technical and scientific terms or terminology used herein are intended to have the same meaning as commonly understood by one of ordinary skill in the art to which the claimed subject matter pertains. In some cases, terms with commonly understood meanings are defined herein for clarity and / or ready reference, and the inclusion of such definitions herein should not necessarily be construed as representing a substantial difference beyond what is commonly understood in the art.

[0077] As used herein, the singular forms "a", "an", and "the" are intended to include the plural forms unless the context clearly dictates otherwise. It should also be understood that the term "and / or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items. It should further be understood that the terms "includes," "including" and / or "comprises," "comprising" as used herein specify the presence of stated features, integers, steps, operations, elements, components, and / or units, but do not negate the presence or addition of one or more other features, integers, steps, operations, elements, components, units, and / or groups thereof.

[0078] This application discloses several numerical ranges in the text and figures. The disclosed numerical ranges inherently support any range or value within the disclosed numerical ranges, including the endpoints, since the disclosure can be practiced throughout the disclosed numerical ranges, even if precise range limitations are not literally stated in the specification.

[0079] The foregoing description has been described with reference to specific embodiments for purposes of explanation. However, the illustrative discussion above is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many modifications and variations are possible in light of the above teachings. The embodiments were chosen and described in order to best explain the principles of the technology and their practical application, thereby enabling others skilled in the art to best utilize the technology and various embodiments with various modifications as suitable for the specific use contemplated.

[0080] Although the present disclosure and examples have been fully described with reference to the accompanying drawings, it should be noted that various changes and modifications will become apparent to those skilled in the art, and such changes and modifications should be understood to be included within the scope of the present disclosure and examples as defined by the claims.

Claims

1. 1. A laser interferometry system, comprising: a laser emitter configured to emit a laser beam, the laser emitter being a rotating laser diode having a rotating laser beam profile; a beam splitter configured to split the emitted laser beam into a first split beam and a second split beam directed toward a single deflector, the first split beam having a first beam diameter and a second beam diameter, the first beam diameter being larger than the second beam diameter, and the second split beam having a third beam diameter and a fourth beam diameter, the third beam diameter being larger than the fourth beam diameter; the single deflector configured to deflect the first split beam to intersect with the second split beam; Equipped with The first beam diameter and the third beam diameter are parallel.

2. The system of claim 1 , wherein the first beam diameter and the third beam diameter are equal and the second beam diameter and the fourth beam diameter are equal.

3. 3. The system of claim 1 or claim 2, wherein the first split beam and the second split beam intersect at an angle of less than 60 degrees.

4. 4. The system of claim 1, wherein the emitted laser beam comprises a fifth beam diameter and a sixth beam diameter, the fifth beam diameter being greater than the sixth beam diameter, and at least one of the fifth beam diameter or the sixth beam diameter is increased by passing the emitted laser beam through a cylindrical lens.

5. The system of any one of claims 1 to 4, wherein the first beam diameter is at least three times larger than the second beam diameter and the third beam diameter is at least three times larger than the fourth beam diameter.

6. 6. The system of claim 1, comprising a processor, a memory, and instructions stored on the memory, the instructions configured to cause the system to calculate a velocity of an object moving through an intersection region.

7. The system of claim 6 , wherein the calculated velocity is in a direction orthogonal to the first beam diameter and the third beam diameter.

8. The system of claim 6 , wherein the object comprises a cord, wire, rod, or flat sheet of paper or plastic.

9. 1. A laser interferometry system, comprising: a laser emitter configured to emit a laser beam, the laser emitter being a rotating laser diode having a rotating laser beam profile; a beam splitter configured to split the emitted laser beam into a first split beam and a second split beam directed toward a single deflector, the first split beam having a first beam diameter and a second beam diameter, the first beam diameter being larger than the second beam diameter, and the second split beam having a third beam diameter and a fourth beam diameter, the third beam diameter being larger than the fourth beam diameter; the single deflector configured to deflect the first split beam to intersect with the second split beam; Equipped with the emitted laser beam comprises a fifth beam diameter and a sixth beam diameter, the fifth beam diameter being greater than the sixth beam diameter, and at least one of the fifth beam diameter or the sixth beam diameter is increased by passing the emitted laser beam through a cylindrical lens.

10. The system of claim 9 , wherein the first beam diameter and the third beam diameter are parallel.

11. 11. The system of claim 9 or claim 10, wherein the first beam diameter and the third beam diameter are equal and the second beam diameter and the fourth beam diameter are equal.

12. The system of any one of claims 9 to 11, wherein the first split beam and the second split beam intersect at an angle of less than 60 degrees.

13. The system of any one of claims 9 to 12, wherein the first beam diameter is at least three times larger than the second beam diameter and the third beam diameter is at least three times larger than the fourth beam diameter.

14. 14. The system of any one of claims 9 to 13, comprising a processor, a memory, and instructions stored on the memory, the instructions configured to cause the system to calculate a velocity of an object moving through an intersection region.

15. The system of claim 14 , wherein the calculated velocity is in a direction orthogonal to the first beam diameter and the third beam diameter.

16. The system of claim 14 , wherein the object comprises a cord, wire, rod, or flat sheet of paper or plastic.

17. 1. A laser interferometry system, comprising: a laser emitter configured to emit a laser beam, the laser emitter being a rotating laser diode having a rotating laser beam profile; a beam splitter configured to split the emitted laser beam into a first split beam and a second split beam directed toward a single deflector, the first split beam having a first beam diameter and a second beam diameter, the first beam diameter being larger than the second beam diameter, and the second split beam having a third beam diameter and a fourth beam diameter, the third beam diameter being larger than the fourth beam diameter; the single deflector configured to deflect the first split beam to intersect with the second split beam; Equipped with The system wherein the first split beam and the second split beam intersect at an angle of less than 60 degrees.

18. 20. The system of claim 17, wherein the first beam diameter and the third beam diameter are equal and the second beam diameter and the fourth beam diameter are equal.

19. 19. The system of claim 17 or claim 18, wherein the first split beam and the second split beam intersect at an angle of less than 20 degrees.

20. The system of any one of claims 17 to 19, wherein the first beam diameter and the third beam diameter are parallel.

21. 21. The system of any one of claims 17 to 20, wherein the emitted laser beam comprises a fifth beam diameter and a sixth beam diameter, the fifth beam diameter being larger than the sixth beam diameter, and at least one of the fifth beam diameter or the sixth beam diameter is increased by passing the emitted laser beam through a cylindrical lens.

22. The system of any one of claims 17 to 21, wherein the first beam diameter is at least three times larger than the second beam diameter and the third beam diameter is at least three times larger than the fourth beam diameter.

23. 23. The system of any one of claims 17 to 22, comprising a processor, a memory, and instructions stored on the memory, the instructions configured to cause the system to calculate a velocity of an object moving through an intersection region.

24. 24. The system of claim 23, wherein the calculated velocity is in a direction orthogonal to the first beam diameter and the third beam diameter.

25. 24. The system of claim 23, wherein the object comprises a cord, wire, rod, or flat sheet of paper or plastic.

26. The system described in claim 1, wherein the beam splitter is a single beam splitter.

27. ​​The system described in claim 1, further comprising a single cylindrical lens.

28. The system described in claim 1, wherein the beam splitter is a single beam splitter and the system further comprises a single cylindrical lens.

29. The system of claim 1, wherein the laser beam profile is expanded 1.5 to 10 times its initial length.

30. The system of claim 1, wherein the laser beam profile can be expanded in a single dimension.

31. The system of claim 1, wherein the laser beam profile can be expanded in two or more dimensions.

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