High-precision grating period measuring device and method
By forming reference light with a beam returner and achieving self-collimation of the grating period measuring device through a focusing lens, the problem of large grating period measurement error in the prior art is solved, and high-precision grating period measurement is achieved.
Patent Information
- Application Number
- CN202510204410.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-24
- Publication Date
- 2025-06-06
AI Technical Summary
The existing method of measuring the grating period by self-climbing the grating is difficult to determine whether the self-climbing diffraction light and incident light completely overlap, resulting in large measurement errors.
The return incident light characteristics of the beam returner are used to form the reference light, and the high-precision alignment of the self-collective diffraction light and the incident light is achieved through the focusing lens, thereby improving the grating period measurement accuracy.
High precision for grating period measurement is achieved, alignment accuracy no longer depends on increasing propagation length, and measurement accuracy is further improved by using a focus lens.
Smart Images
Figure CN120102093A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the field of grating period measurement, in particular to a device and method for measuring grating period by utilizing grating self-collimation angle. Technical Background
[0002] As an important dispersive element, diffraction grating is widely used in high-energy lasers, spectral analysis, integrated circuits, optical communications, optical precision measurement and other fields. One of the most basic and important indicators of a grating is the period value, which is often called the grating constant. Nowadays, people have higher and higher performance requirements for precision instruments, and thus the requirements for the error of the grating period are becoming more and more stringent. Therefore, the invention of a high-precision grating period measurement device and method is of great significance to the realization of high-performance gratings.
[0003] At present, the methods of measuring grating period using grating self-collimation angle at home and abroad generally encounter the problem of difficulty in judging whether the self-collimated diffracted light and the incident light completely overlap. This leads to a large error in the measured grating period. The commonly used method to reduce the measurement error is to increase the propagation distance of the measuring beam, but this not only makes the measurement system too long, but also causes the light spot to diverge too large and difficult to align. As far as we know, no one has proposed using the reference light formed by the characteristics of the incident light returned by the beam reflector and the focusing lens to achieve the alignment of the self-collimated diffracted light and the incident light, thereby improving the measurement accuracy of the grating period. Summary of the invention
[0004] In order to accurately measure the grating period, the present invention provides a high-precision grating period measurement device and method.
[0005] The technical solution of the present invention is as follows:
[0006] A high-precision grating period measurement device, characterized in that it includes a laser light source, an aperture, a beam splitter, a beam returner, a high-precision turntable, a grating to be measured, a focusing lens and a detector.
[0007] The laser light source emits a light beam which passes through an aperture and then is incident on a beam splitter, which splits the incident light beam into a reference light beam and a measurement light beam. The beam returner is placed in the propagation direction of the reference light beam, and the reference light beam is returned along the original path after being incident on the beam returner. The reference light beam returned along the original path passes through the beam splitter and then is incident on a focusing lens, which focuses the incident reference light beam onto a detector. The high-precision turntable and the grating to be measured are placed in the propagation direction of the measurement light beam, and the measurement light beam is incident on the grating to be measured, and the grating to be measured diffracts the incident measurement light beam and returns it to the beam splitter, and the measurement light beam returned by diffraction is reflected by the beam splitter and then is incident on the focusing lens, which focuses the incident measurement light beam onto the detector.
[0008] The grating to be measured is placed on a high-precision turntable.
[0009] The light beam returner is a component or device that can return the incident light to its original path under any incident angle.
[0010] The beam splitter is a beam splitting wedge or other components that can transmit and reflect the incident light intensity in a certain proportion.
[0011] The detector is an industrial camera or other components that can display and read the position of the incident light spot.
[0012] The method for measuring grating period by a high-precision grating period measuring device is characterized in that the method comprises the following steps:
[0013] ① Move the detector position so that the focus of the reference beam after being focused by the focusing lens (7) is irradiated on the detector (8), and mark or record the focus position (x 0 ,y 0 );
[0014] ② Rotate the high-precision turntable (5) so that the positive m-order diffracted light of the measuring beam incident on the grating to be measured (6) is reflected by the beam splitter (3) and focused by the focusing lens (7) and then irradiated on the detector (8) and aligned with the focal position (x 0 ,y 0 ) overlap, record the high-precision turntable angle θ at this time 1 ;
[0015] ③ Rotate the high-precision turntable (5) so that the negative m-order diffracted light of the measuring beam incident on the grating to be measured (6) is reflected by the beam splitter (3) and focused by the focusing lens (7) and then irradiated on the detector (8) and aligned with the focal position (x 0 ,y 0 ) overlap, record the high-precision turntable angle θ at this time 2 ;
[0016] ④ Use the following formula to calculate the grating period d:
[0017] Where: λ is the wavelength of the laser light source (1), m is the diffraction order of the grating, m is an integer, θ 1 and θ 2 High-precision turntable angles recorded for steps ② and ③.
[0018] The present invention has the following advantages and outstanding effects:
[0019] Compared with the method of measuring grating period by grating self-collimation angle at home and abroad, the present invention uses the reference light formed by the characteristics of the incident light returned by the beam returner to achieve high-precision alignment of the self-collimated diffracted light and the incident light, thereby improving the measurement accuracy of the grating period. In addition, the present invention is easy to operate and has low adjustment difficulty. It does not need to increase the propagation length to improve the alignment accuracy, and the period measurement accuracy is further improved by using a focusing lens. BRIEF DESCRIPTION OF THE DRAWINGS
[0020] Figure 1 It is a structural schematic diagram of a high-precision grating period measurement device of the present invention.
[0021] Figure 2 Schematic diagram of the diffraction light of the grating to be measured when the third diffraction order is adopted in Example 2.
[0022] In the figure:
[0023] 1-Laser light source, 2-Aperture, 3-Beam splitter, 4-Beam returner, 5-High-precision turntable, 6-Grating to be measured, 7-Focusing lens, 8-Detector. DETAILED DESCRIPTION
[0024] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments, but the protection scope of the present invention shall not be limited thereto.
[0025] Example 1:
[0026] Figure 1 It is a structural schematic diagram of a high-precision grating period measurement device of the present invention. As shown in the figure, a high-precision grating period measurement device includes a laser light source 1, an aperture 2, a beam splitter 3, a beam returner 4, a high-precision turntable 5, a grating to be measured 6, a focusing lens 7 and a detector 8.
[0027] The laser light source uses a 532nm semiconductor laser. The aperture uses a variable aperture. The beam splitter uses a beam splitting wedge, and the transmittance and reflectivity ratio of the beam splitting is 90:10. The beam returner is realized by two apertures and a reflector. The high-precision turntable uses a turntable with a minimum resolution of 1″. The grating to be measured uses a 4μm (250l / mm) grating prepared by laser direct writing technology. The focusing lens uses a plano-convex lens with a focal length of 1000mm. The detector uses an industrial camera with a minimum pixel size of 4μm.
[0028] The semiconductor laser emits 532nm wavelength laser, and the aperture is adjusted to about 1mm to reduce the diameter of the incident laser beam. After passing through the splitter wedge, the laser is split into a reference beam and a measurement beam by the beam splitter film on the rear surface. The position of the beam returner is adjusted to make the reference grating return along the original path, and the position of the focusing lens is adjusted to make the reference beam and the focusing lens coaxial. A high-precision turntable and the grating to be measured are placed so that the position where the measurement beam is incident on the grating to be measured coincides with the rotation axis of the turntable.
[0029] The method for period measurement according to a high-precision grating period measurement device provided by this patent includes the following steps:
[0030] ① Move the detector so that the focus of the reference beam after being focused by the focusing lens is irradiated on the detector, and mark the focus position with a cross mark;
[0031] ② Rotate the high-precision turntable so that the positive 7th order diffracted light of the measuring beam incident on the grating to be measured is reflected by the beam splitter and focused by the focusing lens in turn, then irradiated on the detector and coincides with the focal position of the reference beam. Record the high-precision turntable angle θ at this time. 1 =47°7′13″;
[0032] ③ Rotate the high-precision turntable so that the negative 7th order diffraction light of the measuring beam incident on the grating to be measured is reflected by the beam splitter and focused by the focusing lens, and then irradiates the detector and coincides with the focal position of the reference beam (x 0 ,y 0 ) overlap, record the high-precision turntable angle θ at this time 2 =102°36′8″;
[0033] ④ Use the following formula to calculate the grating period d:
[0034] Where: λ is the wavelength of the semiconductor laser 532nm, m is the 7th diffraction order of the grating. After calculation, the grating period d = 4000.214nm is obtained. The converted line density is 249.987l / mm.
[0035] Example 2:
[0036] This embodiment 2 uses the same elements and steps as the embodiment 1, the only difference being that the grating to be tested is a grating with a period of 2 μm (500 l / mm) prepared by holographic interference exposure technology.
[0037] The same as in Example 1, the only difference is that steps ② and ③ use m=3rd order diffracted light incident to measure the angle θ of the high-precision turntable respectively. 1 =51°31′19″ and θ 1=98°33′42″. After calculation, the grating period d=1999.664nm. Converted into a line density of 500.083l / mm.
[0038] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.
Claims
1. A high-precision grating period measurement device, characterized in that: It comprises a laser light source (1), an aperture (2), a beam splitter (3), a beam returner (4), a high-precision turntable (5), a focusing lens (7) and a detector (8); The monochromatic laser light emitted by the laser light source (1) is limited by an aperture (2) and then split into a reference beam and a measurement beam by a beam splitter (3); The beam returner (4) is arranged in the propagation direction of the reference beam and is coaxial with the focusing lens (7), and is configured to make the incident reference beam return to the beam splitter along the original path, and be transmitted to the focusing lens (7) by the beam splitter (3); The high-precision turntable (5) carries the grating to be measured (6), and its rotation axis coincides with the incident position of the measuring light beam; After being diffracted by the grating to be measured (6), the measuring light beam returns to the beam splitter (3), is reflected by the beam splitter (3) to the focusing lens (7), and is co-focused with the reference light beam on the detector (8); The angle data of the high-precision turntable (5) is linked with the focus position signal of the detector (8) to calculate the grating period.
2. A high-precision grating period measurement device as claimed in claim 1, characterized in that: The light beam returner (4) is a component or device that can return the incident light along its original path under any incident angle.
3. A high-precision grating period measurement device as claimed in claim 1, characterized in that: The beam splitter (3) is a beam splitting wedge or other components that can transmit and reflect incident light intensities in a certain proportion.
4. A high-precision grating period measurement device as claimed in claim 1, characterized in that: The detector (8) is an industrial camera or other components capable of displaying or reading the position of the incident light spot.
5. A method for measuring grating period using the high-precision grating period measurement device according to claim 1, characterized in that: The method comprises the following steps: ① Move the detector position so that the focus of the reference beam after being focused by the focusing lens (7) is irradiated on the detector (8), and mark or record the focus position (x0, y0); ② Rotate the high-precision turntable (5) so that the positive m-order diffracted light of the measuring light beam incident on the grating to be measured (6) is reflected by the beam splitter (3) and focused by the focusing lens (7) and then irradiated on the detector (8) and coincides with the focal position (x0, y0) of the reference light beam, and record the high-precision turntable angle θ1 at this time; ③ The high-precision turntable (5) is rotated in the opposite direction, so that the negative m-order diffracted light of the measuring light beam incident on the grating to be measured (6) is reflected by the beam splitter (3) and focused by the focusing lens (7) and then irradiated on the detector (8), and coincides with the focal position (x0, y0) of the reference light beam, and the high-precision turntable angle θ2 at this time is recorded; ④ The formula for calculating the period d of the grating to be measured is as follows: Wherein: λ is the wavelength of the laser emitted by the laser light source (1), m is the grating diffraction order, and m is an integer.