CN117782524A - Device and method for measuring beam divergence angle - Google Patents
Device and method for measuring beam divergence angle Download PDFInfo
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- CN117782524A CN117782524A CN202211155300.8A CN202211155300A CN117782524A CN 117782524 A CN117782524 A CN 117782524A CN 202211155300 A CN202211155300 A CN 202211155300A CN 117782524 A CN117782524 A CN 117782524A
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Abstract
The application discloses a device for measuring a beam divergence angle, which is characterized by comprising a laser, an optical lens and a photoelectric detector, wherein the laser is used for emitting detection light, and the detection light is received by the photoelectric detector through the optical lens; thus, the measuring problem of the divergence angle of the low-power light beam can be solved.
Description
Technical Field
The present disclosure relates to the field of optical technologies, and in particular, to a device and a method for measuring a beam divergence angle.
Background
The beam divergence angle refers to the degree that the beam width or the beam diameter increases along with the increase of the beam propagation distance, reflects the divergence characteristics of the beam when transmitted at different distances, and can intuitively evaluate the focusable degree of the beam or the quality of a transmission system of the beam. The small beam divergence angle can effectively utilize the beam energy, so that the beam achieves good directivity and high signal-to-noise ratio, thereby realizing the requirements of reducing the receiving sensitivity of the system and the like. The divergence angle of the light beam can be accurately measured and detected, and technical support can be provided for optical design and parameter evaluation of the whole system.
The traditional methods for measuring the divergence angle of the light beam include a trepanning method and a knife edge method, but the traditional methods need to accurately measure the divergence angle of the light beam at the back focal plane of the lens, and the testing error caused by the system debugging error is larger. The existing common methods such as Jiao Changfa, far-field wide-angle method, far-field double-point method and the like greatly improve the precision of a measuring system, but still have the defects of larger measuring error, complex measuring mode, huge measuring structure and difficulty in realizing portable measurement. For far-field double-point measurement, the distance between the beam and the detector needs to be moved, and the divergence angle of the beam is obtained by precisely fitting the value to the diameter change of the detection distance and the light spot. The structure not only needs to have accurate measurement distance, but also needs to have accurate moving guide rail to change the distance between the detection light spot and the detector. This method, although achieving high measurement accuracy of beam parameters (divergence angles), makes the structure complicated. Jiao Changfa the divergence angle of the measuring beam requires that the detector receiving surface be located at the back focal plane of the lens system, which requires not only precise tuning accuracy, but also large measurement errors. While far field wide angle measurement assumes that the beam is transmitted as a point source, which is unsuitable in most beam transmissions, the approximate assumption necessarily causes large errors.
Disclosure of Invention
The present invention provides a device for measuring beam divergence angle, so as to solve the technical problem that the beam divergence angle cannot be obtained because the corresponding optical power value of the detection surface is lower than the background optical power when the detector moves far along the beam direction, so that the spot size at the detection position cannot be measured effectively, and the beam divergence angle cannot be obtained.
In order to achieve the above purpose, the technical solution adopted in the embodiment of the present application is as follows:
in a first aspect, an embodiment of the present application provides an apparatus for measuring a divergence angle of a light beam, including a laser, an optical lens, and a photodetector, where the laser is configured to emit a probe light, and the probe light is received by the photodetector through the optical lens.
Optionally, the photodetector moves in a plane.
Optionally, the light divergence angle is related to a distance between the light lens and the laser, a spherical radius of curvature of the light lens, and a refractive index of the light lens.
1. In a second aspect, an embodiment of the present application provides a method for measuring a divergence angle of a light beam, including the steps of:
the laser emits detection light;
the detection light passes through an optical lens;
the photodetector receives the detection light passing through the optical lens.
Optionally, the divergence angle of the light velocity is obtained according to a tangential angle of an intersection point of the probe beam and the front surface of the optical lens, a refractive index of the optical lens, and an outgoing angle of the probe beam passing through the rear surface of the lens.
Optionally, the outgoing angle of the probe beam passing through the rear surface of the lens is obtained by measurement.
Optionally, the tangential angle of the intersection point of the probe beam and the front surface of the optical lens is obtained by the coordinate position of the laser, the coordinate position of the tangential angle of the intersection point of the probe beam and the front surface of the optical lens, and the distance between the laser and the optical lens.
The beneficial effects of this application are:
an apparatus for measuring a divergence angle of a light beam, comprising a laser for emitting a probe light, an optical lens, and a photodetector, the probe light being received by the photodetector through the optical lens; thus, the measuring problem of the divergence angle of the low-power light beam can be solved.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the embodiments will be briefly described below, it being understood that the following drawings only illustrate some embodiments of the present application and therefore should not be considered limiting the scope, and that other related drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of a system for measuring beam divergence angle in accordance with the prior art;
FIG. 2 is a schematic diagram of a system for measuring beam divergence angle according to an embodiment of the present application;
fig. 3 is a schematic diagram of a process for obtaining a beam divergence angle according to an embodiment of the present application.
Detailed Description
For the purposes of making the objects, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions of the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is apparent that the described embodiments are some embodiments of the present application, but not all embodiments. The components of the embodiments of the present application, which are generally described and illustrated in the figures herein, may be arranged and designed in a wide variety of different configurations.
Thus, the following detailed description of the embodiments of the present application, as provided in the accompanying drawings, is not intended to limit the scope of the application, as claimed, but is merely representative of selected embodiments of the application. All other embodiments, which can be made by one of ordinary skill in the art based on the embodiments herein without making any inventive effort, are intended to be within the scope of the present application.
It should be noted that: like reference numerals and letters denote like items in the following figures, and thus once an item is defined in one figure, no further definition or explanation thereof is necessary in the following figures.
Fig. 1 is a schematic diagram of a system for measuring beam divergence angle according to the prior art, and as shown in fig. 1, includes a laser for emitting a laser beam, and a photodetector. In fig. 1, the displacement platform is used to scan the photodetectors in the xy plane, and fig. 1 shows the positions of three photodetectors for illustration only and is not particularly limited. Finding 1/e of peak power from signals received by photodetectors 2 Or half-width position to determine spot radius d 1 Then the detector is moved along the luminous direction by a certain distance l, the scanning test flow is repeated, and the corresponding light spot size d is calculated 2 According to the formulaThe far-field divergence angle of the beam can be obtained. In the embodiment shown in fig. 1, the photodetector is moved by two distances to determine the two distances l 1 Distance l 2 The two beam divergence angles are summed and averaged to obtain a quasi-beamHigh-definition beam divergence angle. Similarly, the obtained beam divergence angles of more than two can be summed and averaged when the moved position is more than 2.
The method shown in fig. 1 has a certain defect that the divergence angle of the low-power beam cannot be measured, because when the photoelectric detector moves far along the beam direction, the corresponding optical power value of the detection surface is lower than the background optical power, so that the size of the light spot at the detection position cannot be effectively measured, and then the divergence angle of the beam cannot be obtained.
Fig. 2 is a schematic diagram of a system for measuring beam divergence angle according to an embodiment of the present application. As shown in fig. 2, includes a laser emitting detection light, an optical lens, and a photodetector. The optical lens in fig. 2 can increase the effective moving distance of the detector, thereby improving the test accuracy of the divergence angle of the low-power light beam.
Fig. 3 is a schematic diagram of a process for obtaining a beam divergence angle according to an embodiment of the present application. The embodiment shown in fig. 3 is suitable for use in the system shown in fig. 2. As shown in fig. 3, the detection light emitted from the laser at point a passes through the optical lens and the photodetector. The probe light emitted from the laser at point a shown in fig. 3 reaches point B of the optical lens where a portion of the light is reflected off the lens and a portion of the light is refracted. Wherein, the angle 1 is an auxiliary angle made by the incident angle of the light beam at the point A entering the front surface of the lens;
the angle 2 is an included angle between an incident light beam entering the front surface of the lens at the point A and the reverse extension line of the refraction light beam; θ is the divergence angle of the beam to be measured; θ in An incident angle for the light beam to enter the front surface of the lens; θ out The outgoing included angle of the light beam passing through the rear surface of the lens;the tangential included angle is the intersection point B of the light beam to be measured and the front surface of the lens; p (P) ⊥ An included angle is formed between the light beam to be measured and the front surface of the lens along the normal direction of the incident direction; n is the refractive index of the optical lens; the angle 3 is the angle of incidence of the beam into the rear surface of the lens. From fig. 3, it can be derived that:
/>
that is, after the light beam with the divergence angle of 2 theta passes through the lens, the divergence angle of the emergent light beam is 2 theta out And theta and the divergence angle of the emergent beam,The refractive index of the lens is related.
As can be seen from FIG. 3, the two coordinate positions of A, B are (0, 0), (x) B ，y B ) The distance between the point A and the lens is L, and the spherical curvature radius of the lens is R, namelyThe calculation is shown in formula (4):
y B 2 ＝R 2 -[x B -(R+L)] 2
from the following components
(1+tan 2 θ)x 2 -2(R+L)x+L 2 +2RL＝0
From the formulas (1) to (4), the divergence angle θ of the outgoing beam after passing through the lens is measured out The beam divergence angle 2 theta can be obtained by the distance L between the lens and the light emitting surface, the refractive index n of the lens and the curvature radius R.
The embodiment of the application can measure the spot size at the position where the corresponding light power value of the detection surface is lower than the background light power when the photoelectric detector moves far along the light beam direction by arranging the optical lens in the system for measuring the light beam divergence angle, so that the light beam divergence angle is obtained. The technical problem of large measuring error of the beam divergence angle can be solved.
It should be noted that in this document, relational terms such as "first" and "second" and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises an element.
The foregoing description is only of the preferred embodiments of the present application and is not intended to limit the same, but rather, various modifications and variations may be made by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application should be included in the protection scope of the present application. It should be noted that: like reference numerals and letters denote like items in the following figures, and thus once an item is defined in one figure, no further definition or explanation thereof is necessary in the following figures. The foregoing description is only of the preferred embodiments of the present application and is not intended to limit the same, but rather, various modifications and variations may be made by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application should be included in the protection scope of the present application.
Claims (7)
1. An apparatus for measuring a divergence angle of a light beam, comprising a laser for emitting a probe light, an optical lens, and a photodetector, the probe light being received by the photodetector through the optical lens.
2. The apparatus for measuring beam divergence angle as recited in claim 1 wherein said photodetector moves in a plane.
3. The apparatus for measuring beam divergence angle as set forth in claim 1 wherein said beam divergence angle is related to a distance between said optical lens and said laser, a spherical radius of curvature of said optical lens, and a refractive index of said optical lens.
4. A method of measuring the divergence angle of a beam, comprising the steps of:
the laser emits detection light;
the detection light passes through an optical lens;
the photodetector receives the detection light passing through the optical lens.
5. The method of measuring beam divergence as set forth in claim 4 wherein said speed of light divergence angle is obtained from a tangential angle of intersection of said probe beam with said front surface of said optical lens, a refractive index of said optical lens, and an exit angle of said probe beam through said rear surface of said lens.
6. The method of measuring the divergence angle of a beam of light of claim 4 wherein the angle of exit of said probe beam through the rear surface of the lens is obtained by measurement.
7. The method of measuring beam divergence as set forth in claim 4 wherein the tangential angle of the probe beam at the intersection with the front surface of the optical lens is obtained by the coordinate position of the laser, the coordinate position of the tangential angle of the probe beam at the intersection with the front surface of the optical lens, and the distance between the laser and the optical lens.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211155300.8A CN117782524A (en) | 2022-09-21 | 2022-09-21 | Device and method for measuring beam divergence angle |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211155300.8A CN117782524A (en) | 2022-09-21 | 2022-09-21 | Device and method for measuring beam divergence angle |
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| CN117782524A true CN117782524A (en) | 2024-03-29 |
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| CN202211155300.8A Pending CN117782524A (en) | 2022-09-21 | 2022-09-21 | Device and method for measuring beam divergence angle |
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