A laser wavelength measurement device and method based on an interference method

Abstract

The present invention relates to a laser wavelength measuring device and method based on an interference method, comprising: a laser source to be measured, which is used to emit a laser beam to be measured; a beam splitter, which is used to receive the laser beam to be measured, transmit the laser beam to be measured to a wedge-shaped reflector, and reflect it to a lens; the wedge-shaped reflector, which is used to reflect the laser beam to be measured transmitted by the beam splitter to the lens; the lens, which is used to receive the laser beams to be measured reflected by the beam splitter and the wedge-shaped reflector, and transmit the laser beam to be measured to a photodetector; the photodetector, which is used to receive the laser beam to be measured transmitted by the lens; and a processor, which is electrically connected to the photodetector and is used to detect the interference phenomenon generated on the photodetector. In the present invention, the optical devices used in the measuring device are simple, and there is no need for a standard wavelength laser source to participate in the measurement, which greatly reduces the complexity of the measuring device and also improves the measurement accuracy of the device for the wavelength of the laser to be measured.

Description

Technical Field

[0001] The present invention relates to the technical field of laser wavelength measurement, and particularly to a laser wavelength measurement device and method based on an interference method. Background Art

[0002] The accurate measurement of laser wavelength is crucial for the field of optical precision measurement. Taking a laser interferometer as an example, its measurement accuracy is directly related to the accuracy of the laser wavelength. How to improve the measurement accuracy of the laser wavelength and reduce the complexity and cost of the laser wavelength measurement device has become an important research content in the related field. Summary of the Invention

[0003] The purpose of the present invention is to improve the deficiencies existing in the prior art and provide a laser wavelength measurement device and method based on an interference method.

[0004] In order to achieve the above-mentioned invention purpose, the embodiments of the present invention provide the following technical solutions:

[0005] A laser wavelength measurement device based on an interference method, comprising:

[0006] A laser source to be measured, for emitting a laser beam to be measured;

[0007] A beam splitter, for receiving the laser beam to be measured, transmitting the laser beam to be measured to a wedge-shaped reflector, and reflecting it to a lens;

[0008] A wedge-shaped reflector, for reflecting the laser beam to be measured transmitted by the beam splitter to the lens;

[0009] A lens, for receiving the laser beam to be measured reflected by the beam splitter and the wedge-shaped reflector, and transmitting the laser beam to be measured to a photodetector;

[0010] A photodetector, for receiving the laser beam to be measured transmitted by the lens;

[0011] A processor, electrically connected to the photodetector, for detecting the interference phenomenon generated on the photodetector.

[0012] Furthermore, in order to better implement the present invention, the wedge-shaped reflector is connected with a precision displacement device for driving the wedge-shaped reflector to move in its horizontal direction.

[0013] Furthermore, in order to better implement the present invention, the precision displacement device is a piezoelectric ceramic motor without a guide rail.

[0014] Furthermore, in order to better implement the present invention, the wedge-shaped reflector includes a reflecting surface, and the beam splitter is arranged parallel to the reflecting surface of the wedge-shaped reflector.

[0015] Furthermore, in order to better implement the present invention, the lens is a convex lens.

[0016] Furthermore, to better implement the present invention, the photodetector is disposed at the focal point of the convex lens.

[0017] Furthermore, to better implement the present invention, it further includes a housing. The laser wavelength measuring device based on the interference method is disposed in the housing, and the laser source to be measured, the beam splitter, the lens, the photodetector, and the precision displacement device are fixedly disposed relative to the housing respectively.

[0018] A laser wavelength measuring method based on the interference method includes the following steps:

[0019] Step S1: Fix the laser source to be measured, the beam splitter, the lens, the photodetector, and the precision displacement device in the housing;

[0020] Step S2: Turn on the laser source to be measured, and move the position of the wedge-shaped reflector so that the wedge-shaped reflector can receive the laser beam to be measured;

[0021] Step S3: Control the precision displacement device to drive the wedge-shaped reflector to move in the horizontal direction so that constructive interference / destructive interference occurs on the photodetector, and the processor records the displacement X1 of the wedge-shaped reflector;

[0022] Step S4: Continue to control the precision displacement device to drive the wedge-shaped reflector to move in the horizontal direction until the next constructive interference / destructive interference occurs on the photodetector, and the processor records the displacement X2 of the wedge-shaped reflector;

[0023] Step S5: The processor calculates the wavelength of the laser beam to be measured according to the displacement of the two horizontal movements of the wedge-shaped reflector, the angle between the reflecting surface of the wedge-shaped reflector and the horizontal direction, and the angle between the laser beam to be measured incident on the reflecting surface and the reflecting surface.

[0024] Furthermore, to better implement the present invention, in step S1, the beam splitter is arranged parallel to the reflecting surface of the wedge-shaped reflector.

[0025] Furthermore, to better implement the present invention, in step S1, the photodetector is disposed at the focal point of the lens.

[0026] Compared with the prior art, the beneficial effects of the present invention are:

[0027] The optical devices used in the measuring device of the present invention are simple, without the need to add a standard wavelength laser source to participate in the measurement, greatly reducing the complexity of the measuring device, and also improving the measurement accuracy of the device for the laser wavelength to be measured.

[0028] The precision displacement device of the present invention is a piezoelectric ceramic motor without a guide rail, which avoids the influence of guide rail machining errors on wavelength measurement and improves the accuracy of wavelength measurement results.

[0029] The present invention can use the precision displacement device to drive the wedge-shaped reflector to move in its vertical direction, eliminating the small vertical displacement generated by the influence of gravity when the precision displacement device and the wedge-shaped reflector move, making the accuracy of the optical path difference measurement more accurate, that is, improving the accuracy of the laser wavelength measurement result. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for use in the embodiments. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings.

[0031] Figure 1 It is a schematic structural diagram of the measurement device according to Embodiment 1 of the present invention;

[0032] Figure 2 It is a schematic diagram of the measurement device after movement according to Embodiment 1 of the present invention;

[0033] Figure 3 It is a schematic diagram of the included angle calculation according to Embodiment 1 of the present invention;

[0034] Figure 4 It is a schematic diagram of the calculation of the optical path difference change amount according to Embodiment 1 of the present invention;

[0035] Figure 5 It is a schematic structural diagram of the measurement device according to Embodiment 2 of the present invention;

[0036] Figure 6 It is a schematic diagram of the measurement device after movement according to Embodiment 2 of the present invention;

[0037] Figure 7 It is a schematic diagram of the calculation of the optical path difference change amount according to Embodiment 2 of the present invention;

[0038] Figure 8 It is a schematic structural diagram of the measurement device according to Embodiment 3 of the present invention.

[0039] MAIN ELEMENT SYMBOL DESCRIPTION

[0040] Laser source to be measured 100, beam splitter 200, wedge-shaped reflector 300, reflecting surface 301, lens 400, photodetector 500, precision displacement device 600. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0041] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. The components of the embodiments of the present invention usually described and illustrated in the accompanying drawings here can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed present invention, but merely represents the selected embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0042] It should be noted that similar reference numerals and letters indicate similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0043] Embodiment 1:

[0044] The present invention is implemented through the following technical solutions. A laser wavelength measurement device based on an interference method, as Figure 1 shown, includes a laser source 100 to be measured, a beam splitter 200, a wedge-shaped reflector 300, a lens 400, a photodetector 500, a processor, and a precision displacement device 600, where:

[0045] The laser source 100 to be measured is used to emit a laser beam to be measured to the beam splitter 200.

[0046] The beam splitter 200 is disposed between the laser source 100 to be measured and the wedge-shaped reflector 300, and is used to transmit the received laser beam to be measured to the wedge-shaped reflector 300 and reflect it to the convex lens. For the sake of easy distinction, the laser beam to be measured transmitted by the beam splitter 200 to the wedge-shaped reflector 300 is defined as the transmitted laser beam to be measured, and the laser beam to be measured reflected by the beam splitter 200 to the lens 400 is defined as the reflected laser beam to be measured.

[0047] The wedge-shaped reflector 300 is used to receive the transmitted laser beam to be measured transmitted by the beam splitter 200 and reflect the transmitted laser beam to be measured to the lens 400. The wedge-shaped reflector 300 includes a reflecting surface 301, and the laser beam to be measured transmitted by the beam splitter 200 enters the reflecting surface 301 and is then reflected from the reflecting surface 301 to the lens 400. The beam splitter 200 is arranged parallel to the reflecting surface 301 of the wedge-shaped reflector 300, so that the reflected laser beam to be measured reflected by the beam splitter 200 to the lens 400 is parallel to the transmitted laser beam to be measured reflected by the wedge-shaped reflector 300 to the lens 400.

[0048] A lens 400 is configured to receive the reflected laser beam to be measured reflected by the beam splitter 200 and the transmitted laser beam to be measured reflected by the wedge reflector 300, and transmit these two laser beams to the photodetector 500.

[0049] The photodetector 500 is disposed at the focal point of the lens 400 and is configured to receive the reflected laser beam to be measured and the transmitted laser beam to be measured transmitted by the lens 400.

[0050] A processor is configured to record the horizontal displacement of the wedge reflector 300, detect the constructive interference or destructive interference phenomenon generated on the photodetector 500, and finally calculate the wavelength of the laser beam to be measured.

[0051] A precision displacement device 600 is connected to the wedge reflector 300 and is configured to drive the wedge reflector 300 to move in its horizontal direction.

[0052] It should be noted that the lens 400 is a convex lens. According to the transmission principle of the convex lens, the light rays perpendicular to the convex lens will all pass through the focal point of the convex lens. In order to make the two beams of light transmitted to the photodetector 500 fall on the same point, the photodetector 500 is disposed on the focal plane of the lens 400. However, when the parallel light rays incident on the lens 400 are not perpendicular to the lens 400, the photodetector 500 is disposed at the secondary focal point of the lens 400 so that the two laser beams that are not perpendicular to the lens 400 can fall on the same point of the photodetector 500 after passing through the lens 400. This embodiment is described by taking the parallel reflected laser beam to be measured and the transmitted laser beam to be measured perpendicular to the lens as an example.

[0053] The precision displacement device is a piezoelectric ceramic motor without a guide rail, so that when the precision displacement device drives the wedge reflector to move, it is a non-guided movement, which avoids the influence of the guide rail processing error on the wavelength measurement and improves the accuracy of the wavelength measurement result.

[0054] The laser wavelength measurement device based on the interference method is disposed in a housing, that is, the laser source to be measured, the beam splitter, the lens, the photodetector, and the precision displacement device are respectively fixedly disposed relative to the housing. At the start of the measurement, the precision displacement device controls the wedge reflector to move in its horizontal direction.

[0055] Such as Figure 1As shown, the laser source 100 to be measured emits a laser beam to be measured to the beam splitter 200. After receiving the laser beam to be measured, the beam splitter 200 divides the laser beam to be measured into a reflected laser beam to be measured and a transmitted laser beam to be measured. The reflected laser beam to be measured is directly reflected to the lens 400, and the transmitted laser beam to be measured is transmitted to the reflecting surface 301 of the wedge-shaped reflector 300. The reflecting surface 301 reflects the transmitted laser beam to be measured to the lens 400. The lens 400 transmits the received reflected laser beam to be measured and the transmitted laser beam to be measured to the photodetector 500. A processor electrically connected to the photodetector 500 can detect the interference phenomenon generated on the photodetector 500.

[0056] As Figure 2 shown, before the measurement starts, finely adjust the positions of each optical element so that the reflected laser beam to be measured and the transmitted laser beam to be measured can be received on the photodetector 500. When the measurement starts, control the precision displacement device 600 to drive the wedge-shaped reflector 300 to move in its horizontal direction, so that a constructive interference or destructive interference phenomenon appears on the photodetector 500. In this embodiment, only constructive interference is taken as an example. The processor records the displacement X1 of the precision displacement device 600 driving the wedge-shaped reflector 300 to move horizontally this time; continue to control the precision displacement device 600 to drive the wedge-shaped reflector 300 to move in the same direction as the previous time in its horizontal direction until a constructive interference phenomenon is generated on the photodetector 500 again. The processor records the total displacement X2 of the precision displacement device 600 driving the wedge-shaped reflector 300 to move horizontally twice. The processor can calculate the increment or decrement of the optical path difference between the two laser beams after two movements and the optical path difference between the two laser beams after one movement according to the displacement difference X between the two recorded displacements, the angle α between the reflecting surface 301 of the wedge-shaped reflector 300 and the horizontal plane, and the angle β between the transmitted laser beam to be measured incident on the reflecting surface 301 and the transmitted laser beam to be measured reflected from the reflecting surface 301. According to the relationship between the wavelength and the optical path difference, the optical path difference is equal to an integer multiple of the wavelength. Then, in this embodiment, only one constructive interference is separated, and the optical path difference is equal to the wavelength of the laser beam to be measured.

[0057] It should be noted that no matter how the wedge-shaped reflector 300 moves, the optical path of the laser beam to be measured emitted from the laser source 100 to be measured to the beam splitter 200 remains unchanged all the time, and the optical path of the reflected laser beam to be measured reflected by the beam splitter 200 until it enters the photodetector 500 also remains unchanged all the time. Therefore, when the wedge-shaped reflector 300 is moved, only the optical path of the transmitted laser beam to be measured can be changed. Then, the change amount of the optical path difference between the reflected laser beam to be measured and the transmitted laser beam to be measured is the change amount of the optical path of the transmitted laser beam to be measured before and after moving the wedge-shaped reflector 300.

[0058] As Figure 3As shown, when it is known that the angle between the reflecting surface 301 of the wedge-shaped reflector 300 and the horizontal line is α, that is, ∠OAB=α, and ∠AOC=∠OBA=∠OBC=90°, then ∠AOB=∠OCB, then ∠COB=∠OAB=α, therefore ∠DOE=2∠COB=2α=β, then the angle between the measured transmitted laser beam incident on the reflecting surface 301 and the measured transmitted laser beam reflected from the reflecting surface 301 is β=2α.

[0059] Specifically, it is known that when there is a constructive interference on the photodetector 500, the displacement amount of the wedge-shaped reflector 300 driven by the precision displacement device 600 is X=X2-X1, and it is known that the angle between the reflective surface 301 of the wedge-shaped reflector 300 and the horizontal line is α, and the angle between the measured transmission laser beam incident on the reflective surface 301 and the measured transmission laser beam reflected from the reflective surface 301 is 2α. Figure 4 As shown, point O is the incident point of the laser beam to be measured falling on the reflective surface 301 before the wedge-shaped reflector 300 moves, point O' is the incident point of the transmitted laser beam to be measured falling on the reflective surface 301 after the wedge-shaped reflector 300 moves by a displacement of X, and point O'' is the foot of the perpendicular between point O and the optical path of the transmitted laser beam to be measured reflected from the reflective surface 301 after the wedge-shaped reflector 300 moves by a displacement of X. It is easy to understand that the optical path increment of the transmitted laser beam to be measured after the wedge-shaped reflector 300 moves by a displacement of X is L=OO'+O'O'', that is, the change in the optical path difference between the reflected laser beam to be measured and the transmitted laser beam to be measured is:

[0060] L = xtan(x) + xtan(x)cos(x)

[0061] Right now:

[0062]

[0063] Therefore, the optical path difference variation L can be obtained, thereby obtaining the wavelength of the laser beam to be measured.

[0064] Assuming that the angle between the wedge-shaped reflector 300 and the horizontal line is α=0.1°, and X=1000 nm, then it is calculated that L=3.4907 nm, and the wavelength of the laser beam to be measured is λ=3.4907 nm.

[0065] Based on the above measurement device, a laser wavelength measurement method based on interference is proposed, which includes the following steps:

[0066] Step S1: The laser source to be tested, the beam splitter, the lens, the photoelectric detector, and the precision displacement device are fixedly arranged in the housing; the beam splitter is arranged parallel to the reflective surface of the wedge-shaped reflector, and the photoelectric detector is arranged at the focus of the lens;

[0067] Step S2: Turn on the laser source to be measured, and move the position of the wedge-shaped reflector so that the wedge-shaped reflector can receive the laser beam to be measured;

[0068] Step S3: Control the precision displacement device to drive the wedge-shaped reflector to move horizontally so that constructive interference / destructive interference occurs on the photodetector, and the processor records the displacement X1 of the wedge-shaped reflector;

[0069] Step S4: Continue to control the precision displacement device to drive the wedge-shaped reflector to move horizontally until the next constructive interference / destructive interference occurs on the photodetector, and the processor records the displacement X2 of the wedge-shaped reflector;

[0070] Step S5: The processor calculates the wavelength of the laser beam to be measured based on the displacement of the wedge-shaped reflector during two horizontal movements, the angle between the reflecting surface of the wedge-shaped reflector and the horizontal direction, and the angle between the laser beam to be measured incident on the reflecting surface and the reflecting surface.

[0071] To improve the measurement accuracy of the laser wavelength, in this embodiment, N laser constructive interference / destructive interference phenomena can be measured to further reduce the influence of the displacement accuracy of the precision displacement device on the measurement of the laser wavelength.

[0072] Embodiment 2:

[0073] As another implementable manner, to avoid the angle between the reflecting surface 301 of the wedge-shaped reflector 300 and the horizontal line being too small, so that the laser beam incident on the reflecting surface 301 is reflected by the reflecting surface 301 and then enters the beam splitter 200 again, as Figure 5 shown, tilt the laser beam to be measured emitted by the laser source 100 to the beam splitter 200. At this time, the angle between the transmitted laser beam to be measured incident on the reflecting surface 301 and the transmitted laser beam to be measured reflected from the reflecting surface 301 is no longer 2α. As Figure 6 、 7 shown, but when tilting the laser source 100 to be measured, the angle α` between the laser beam to be measured and the vertical direction is known. Then, the angle between the transmitted laser beam to be measured incident on the reflecting surface 301 and the reflecting surface 301 is β` = 90° - α - α`. When the wedge-shaped reflector 300 moves a displacement X, the optical path difference between the two laser beams is:

[0074]

[0075] Other parts of this embodiment are the same as those of the above embodiment, so they will not be described in detail.

[0076] Embodiment 3:

[0077] As another implementable manner, the precision displacement device drives the wedge-shaped reflector to move in its vertical direction, as Figure 8As described above, the measuring principle is the same as that of the first embodiment, that is, when constructive interference or destructive interference occurs twice, the wedge-shaped reflector moves a displacement X in its vertical direction. The processor can calculate the increment or decrement of the optical path difference between the two laser beams after two movements and the optical path difference between the two laser beams after one movement according to the displacement X, the angle α between the reflective surface 301 of the wedge-shaped reflector 300 and the horizontal plane, and the angle β between the transmitted laser beam to be measured incident on the reflective surface 301 and the transmitted laser beam to be measured reflected from the reflective surface 301. According to the relationship between the wavelength and the optical path difference, the optical path difference is equal to an integer multiple of the wavelength. Then, in this embodiment, only one constructive interference is separated, and the optical path difference is equal to the wavelength of the laser beam to be measured. By moving the wedge-shaped reflector in its vertical direction, it is possible to eliminate the small displacement in the vertical direction caused by the influence of gravity when the precision displacement device and the wedge-shaped reflector are moved, thereby reducing the accuracy of the optical path difference measurement.

[0078] Based on the above measurement device, a laser wavelength measurement method based on interference is proposed, which includes the following steps:

[0079] Step S1: The laser source to be tested, the beam splitter, the lens, the photoelectric detector, and the precision displacement device are fixedly arranged in the housing; the beam splitter is arranged parallel to the reflective surface of the wedge-shaped reflector, and the photoelectric detector is arranged at the focus of the lens;

[0080] Step S2: turning on the laser source to be measured, and moving the position of the wedge-shaped reflector so that the wedge-shaped reflector can receive the laser beam to be measured;

[0081] Step S3: Control the precision displacement device to drive the wedge-shaped reflector to move in the vertical direction, so that constructive interference / destructive interference occurs on the photodetector, and the processor records the displacement X1 of the wedge-shaped reflector;

[0082] Step S4: Continue to control the precision displacement device to drive the wedge-shaped reflector to move in the vertical direction until the next constructive interference / destructive interference phenomenon occurs on the photodetector, and the processor records the displacement X2 of the wedge-shaped reflector;

[0083] Step S5: The processor calculates the wavelength of the laser beam to be measured according to the displacement of the wedge-shaped reflector in two vertical movements, the angle between the reflective surface of the wedge-shaped reflector and the horizontal direction, and the angle between the laser beam to be measured incident on the reflective surface and the reflective surface.

[0084] In order to improve the measurement accuracy of the laser wavelength, this embodiment can measure the constructive interference / destructive interference phenomena of N lasers, and further reduce the influence of the displacement accuracy of the precision displacement device on the laser wavelength measurement.

[0085] The present invention can use a precision displacement device to drive a wedge-shaped reflector to move in its vertical direction, eliminating the tiny displacement in the vertical direction caused by the influence of gravity when the precision displacement device and the wedge-shaped reflector are moving, making the accuracy of the optical path difference measurement more accurate, that is, improving the accuracy of the laser wavelength measurement result.

[0086] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of changes or substitutions, which should all be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A method for measuring the wavelength of a laser based on an interference method, characterized in that: It is realized by a laser wavelength measuring device based on an interference method, and the device includes: A laser source to be measured, which is used to emit a laser beam to be measured; A beam splitter, which is arranged between the laser source to be measured and the wedge-shaped reflector, and is used to receive the laser beam to be measured, transmit the laser beam to be measured to the wedge-shaped reflector, and reflect it to the lens; A wedge-shaped reflector, which is used to reflect the laser beam to be measured transmitted by the beam splitter to the lens; A lens, which is used to receive the laser beam to be measured reflected by the beam splitter and the wedge-shaped reflector, and transmit the laser beam to be measured to the photodetector; A photodetector, which is arranged at the focal point of the lens and is used to receive the laser beam to be measured transmitted by the lens; A processor, which is electrically connected to the photodetector and is used to detect the interference phenomenon generated on the photodetector; The wedge-shaped reflector is connected with a precise displacement device, which is used to drive the wedge-shaped reflector to move in its horizontal direction / vertical direction; the wedge-shaped reflector includes a reflecting surface, and the beam splitter is arranged parallel to the reflecting surface of the wedge-shaped reflector; The method includes the following steps: Step S1: Fix the laser source to be measured, the beam splitter, the lens, the photodetector and the precise displacement device in the housing; Step S2: Turn on the laser source to be measured, and move the position of the wedge-shaped reflector so that the wedge-shaped reflector can receive the laser beam to be measured; Step S3: Control the precise displacement device to drive the wedge-shaped reflector to move in the horizontal direction / vertical direction, so that a constructive interference / destructive interference phenomenon is generated on the photodetector, and the processor records the displacement X1 of the wedge-shaped reflector; Step S4: Continue to control the precise displacement device to drive the wedge-shaped reflector to move in the horizontal direction / vertical direction until the next constructive interference / destructive interference phenomenon is generated on the photodetector, and the processor records the displacement X2 of the wedge-shaped reflector; Step S5: The processor calculates the wavelength of the laser beam to be measured according to the displacement of the wedge-shaped reflector during two horizontal / vertical movements, the angle between the reflecting surface of the wedge-shaped reflector and the horizontal direction, and the angle between the laser beam to be measured incident on the reflecting surface and the reflecting surface.

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