Device and method for testing diffraction efficiency of large-aperture grating

Abstract

The invention belongs to the technical field of machining, and particularly relates to a large-aperture grating diffraction efficiency testing device and method.The testing device comprises a laser, a beam splitter, a beam expanding lens set, a rotating table, a collecting lens, a testing table and an optical power meter; light emitted by the laser is divided into two beams of laser L1 and L2 with equal energy after passing through the beam splitter, wherein L1 is directly collected by the first optical power meter; a light spot formed after the L2 is processed by the beam expanding lens group directly enters the grating to be tested on the rotating table, and a second optical power meter is arranged on the testing table and used for collecting light processed by the grating. According to the testing device and method for the diffraction efficiency of the grating, the rotating table and the testing table are of a coaxial and independent rotating structure, the testing device and method are suitable for testing transmission type grating and diffraction type grating products at the same time, and the diffraction efficiency of different levels can be tested; before the actual test, the device is calibrated, so that the accuracy of the measurement result is higher.

Description

Technical Field

[0001] The present invention relates to the technical field of optical device testing, and particularly to a testing device and method for the diffraction efficiency of a large-aperture grating. Background Art

[0002] As an important spectroscopic element, the grating works based on the diffraction effect of light, separating the polychromatic light according to different wavelengths to form a clear spectrum. The diffraction efficiency of the grating is the core index to measure its performance. The grating diffraction efficiency directly reflects the diffraction ability of the grating for light waves of different wavelengths and directly determines the working performance of the product. Therefore, the testing of the grating diffraction efficiency has become one of the key means to evaluate the quality of grating products.

[0003] The existing grating diffraction efficiency testing methods mainly focus on the measurement of the zero-order and first-order diffraction efficiencies in the continuous wavelength range. However, in practical applications (such as in the fields of optical communication and lidar in the 850 nm band), the diffraction efficiencies of higher-order diffraction orders (such as the second order, third order, etc.) also have extremely important application values. Unfortunately, due to the relatively weaker intensity of the higher-order diffracted light and the significantly increased testing difficulty, most of the existing measurement means often cannot effectively measure the diffraction efficiencies of higher-order diffraction orders, which makes the performance optimization of the grating in higher-order diffraction applications lack effective data support, thus restricting to a certain extent the wide application of grating products in some specific fields. At the same time, the general grating diffraction efficiency testing device can only measure one of the transmissive grating and the reflective grating, and has poor versatility. Therefore, it is necessary to invent a new grating diffraction efficiency testing device and method. Summary of the Invention

[0004] The purpose of the present invention is to overcome the above deficiencies of the prior art and provide a testing device and method for the diffraction efficiency of a large-aperture grating, which can achieve the accurate measurement of the diffraction efficiency of the higher-order diffraction order of the grating; and has strong versatility.

[0005] The technical solution of the present invention is: The present invention first provides a testing device for the diffraction efficiency of a large-aperture grating, which successively includes a laser, a beam splitter, an expander lens group, a rotating table, a condenser lens, a test table, and an optical power meter; the light emitted by the laser is divided into two equal-energy laser beams L1 and L2 by the beam splitter, wherein L1 is directly collected by the first optical power meter; after being processed by the expander lens group, L2 forms a light spot and directly enters the grating to be tested on the rotating table. The rotating table is used to realize the angle adjustment of the grating to be tested. A second optical power meter is arranged on the test table, and the second optical power meter is used to collect the light after being processed by the grating. The test table rotates independently relative to the rotating table, and the rotation axis of the test table coincides with the rotation axis of the rotating table.

[0006] Further, the test bench is a rotating arm coaxially arranged with the rotating table.

[0007] Further, a condenser lens is arranged on the test bench, so that the light after grating processing passes through the condenser lens and then is collected by the second optical power meter.

[0008] Further, a diaphragm is provided in the beam expander lens group, and the diaphragm is used to adjust the diameter of the outgoing light spot so that the diameter of the light spot is adapted to the grating to be measured.

[0009] Further, the rotating table adopts a high-precision rotating platform, such as the RAuK series ultra-high precision electric rotating table, the Jingcui Optics high-precision rotating displacement table, and the manual rotating table SXZA series.

[0010] Further, there are multiple test benches, and an optical power meter is arranged on each test bench. The rotation axis of each test bench is the same as the rotation axis of the rotating table, and each test bench can rotate freely and independently.

[0011] Further, there are two test benches. During use, the movements of the two test benches can be symmetric about the 0th-order diffraction light of the grating. In this case, the optical power meters on the test benches can simultaneously measure the ±m-order diffraction lights respectively, improving the efficiency.

[0012] The present invention also provides a method for testing the diffraction efficiency of a large-aperture grating. The above device is adopted, and specifically includes the following steps:

[0013] S1. Device calibration

[0014] After assembling the large-aperture grating diffraction efficiency test device, first do not install the grating. Adjust the diaphragm in the beam expander lens group to ensure that the size of the light spot after passing through the beam expander lens group is adapted to the grating to be measured; then turn on the laser, collect the data of the first optical power meter and the second optical power meter respectively, and calculate the calibration factor through formula (1):

[0015]

[0016] In the formula: η is the calibration factor, w is the value of the first optical power meter, and w′ is the value of the second optical power meter;

[0017] S2. Start measurement

[0018] S2-1. After obtaining the calibration factor, install the grating to be measured on the rotating table;

[0019] S2-2. Keep the rotating table stationary, and adjust the angles of the test benches to the 0th order, +1st order, -1st order, +2nd order, -2nd order,

[0020] +3rd order, -3rd order positions respectively, and the optical powers corresponding to the corresponding orders can be obtained, which are w′0, w′ +1, w′ -1 , w′ +2 , w′ -2 , w′ +3 , w′ -3 .

[0021] S2-3. Calculate the diffraction efficiency

[0022]

[0023] Where: m is the diffraction order, m = 0, ±1, ±2, ±3...

[0024] Advantages of the present invention compared with the prior art: The test device and method for the diffraction efficiency of the grating proposed by the present invention, through the structure that the rotating table and the test table are coaxially centered and rotate independently, are applicable to the tests of both transmissive gratings and diffractive grating products, and can test the diffraction efficiencies of different orders; before the actual test, the present invention also performs a calibration operation to obtain a real-time calibration factor, and the measurement results are calibrated, with higher accuracy. Brief description of the drawings

[0025] Figure 1 is a schematic structural diagram of the device in Embodiment 1 of the present invention;

[0026] Figure 2 is a schematic optical path diagram of the present invention. Detailed implementation manners

[0027] To make the purpose, technical solutions and advantages of the present invention clearer, in the following description, the descriptions of well-known structures and technologies are omitted to avoid unnecessarily confusing the concepts in the present invention.

[0028] Embodiment 1

[0029] As Figure 1-2 shown, the test device for the diffraction efficiency of the large-aperture grating in this embodiment successively includes a laser, a beam splitter, an expander lens group, a rotating table, a condenser lens, a test table and an optical power meter; the light emitted by the laser is divided into two equal-energy laser beams L1 and L2 by the beam splitter, where L1 is directly collected by the first optical power meter; after being processed by the expander lens group, L2 forms a light spot and directly enters the grating to be tested on the rotating table. The rotating table is used to adjust the angle of the grating to be tested. A second optical power meter is arranged on the test table, and the second optical power meter is used to collect the light after being processed by the grating. The test table rotates independently relative to the rotating table, and the rotation axis of the test table coincides with the rotation axis of the rotating table.

[0030] In this embodiment, the test table is a rotating arm coaxially centered with the rotating table. A condenser lens is arranged on the test table, so that the light after being processed by the grating passes through the condenser lens and then is collected by the second optical power meter.

[0031] In this embodiment, the beam expander lens group adopts a Galilean beam expander, which is provided with a diaphragm. The diaphragm is used to adjust the diameter of the outgoing light spot so that the diameter of the light spot is adapted to the grating to be measured. The rotary table adopts the RAuK series of ultra-high-precision electric rotary tables.

[0032] The specific usage method of the test device in this embodiment is as follows:

[0033] S1. Device calibration

[0034] After assembling the large-aperture grating diffraction efficiency test device, first do not install the grating. Adjust the diaphragm in the beam expander lens group to ensure that the size of the light spot after passing through the beam expander lens group is adapted to the grating to be measured; then turn on the laser, collect the data of the first optical power meter and the second optical power meter respectively, and calculate the calibration factor through formula (1):

[0035]

[0036] In the formula: η is the calibration factor, w is the value of the first optical power meter, and w′ is the value of the second optical power meter;

[0037] S2. Start measurement

[0038] S2-1. After obtaining the calibration factor, install the grating to be measured on the rotary table;

[0039] S2-2. Keep the rotary table stationary, and adjust the angle of the test bench to the 0th order, +1st order, -1st order, +2nd order, -2nd order,

[0040] +3rd order, -3rd order positions respectively, and the optical powers corresponding to the respective orders can be obtained, which are w′0, w′ +1 , w′ -1 , w′ +2 , w′ -2 , w′ +3 , w′ -3 .

[0041] S2-3. Calculate the diffraction efficiency

[0042]

[0043] Where: m is the diffraction order, m = 0, ±1, ±2, ±3...

[0044] In some other embodiments, two test benches can be set up simultaneously. A condenser lens and a optical power meter are provided on each test bench; and the movements of the two test benches are symmetric left and right, that is, when one test bench is rotated, the other test bench can rotate synchronously in the opposite direction. In this way, in practical applications, the two test benches are symmetric about the zero-order diffraction. In this way, the optical power meters on the two test benches can simultaneously measure the ±m-order diffracted light respectively, improving the efficiency; at the same time, the values of the optical power meters on the two test benches can be compared in a timely manner, which is particularly suitable for the detection of symmetric gratings. The specific implementation method of the symmetric movement of the two test benches can adopt a gear transmission mechanism, which will not be elaborated here. In some embodiments, the length of the test bench is less than the distance from the beam expander lens group to the rotating table, so that the test bench can rotate freely 360 degrees without being affected by the beam expander lens group, which is beneficial to the test of reflective gratings.

[0045] The above are only some embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have combinations and variations of the foregoing various technical features. Without departing from the spirit and scope of the present invention, improvements, variations, equivalent replacements made by those skilled in the art, or the use of the structure or method of the present invention in other fields to achieve the same effect all fall within the protection scope of the present invention.

Claims

1. A test device for the diffraction efficiency of a large-aperture grating, comprising a laser, a beam splitter, a beam expansion lens group, a rotating table, a condenser, a test table and an optical power meter; characterized in that: The light emitted by the laser is divided into two laser beams L1 and L2 with equal energy after passing through a beam splitter, wherein L1 is directly collected by a first optical power meter; the light spot formed by L2 after being processed by a beam expansion lens group is directly shot into the grating to be measured on the rotating table, and the rotating table is used to realize the angle adjustment of the grating to be measured. A second optical power meter is arranged on the test table, and the second optical power meter is used to collect the light processed by the grating. The test table rotates independently relative to the rotating table, and the rotation axis of the test table coincides with the rotation axis of the rotating table.

2. The device for testing the diffraction efficiency of a large aperture grating according to claim 1, characterized in that: The test bench is a rotating arm coaxially arranged with the rotating table.

3. The device for testing the diffraction efficiency of a large aperture grating according to claim 1, characterized in that: The test bench is also provided with a condenser, so that the light after grating processing passes through the condenser and is then collected by the second optical power meter.

4. The device for testing the diffraction efficiency of a large aperture grating according to claim 1, characterized in that: The beam expanding lens group is provided with an aperture, and the aperture is used to adjust the diameter of the emergent light spot so that the diameter of the light spot is adapted to the grating to be measured.

5. The device for testing the diffraction efficiency of a large aperture grating according to claim 1, characterized in that: The rotating table adopts a high-precision rotating platform.

6. The device for testing the diffraction efficiency of a large aperture grating according to claim 1, characterized in that: There are multiple test benches, each of which is provided with an optical power meter, and the rotating axis of the test bench is aligned with the rotating axis of the rotating table.

7. The device for testing the diffraction efficiency of a large aperture grating according to claim 6, characterized in that: Each test stand rotates independently.

8. The device for testing the diffraction efficiency of a large aperture grating according to claim 6, characterized in that: There are two test benches, and the movements of the two test benches are symmetrical. In this way, under certain circumstances, the optical power meters on the two test benches are used to simultaneously measure ±m-order diffraction lights, where m is the diffraction order, m=0, ±1, ±2, ±3...

9. A method for testing the diffraction efficiency of a large aperture grating, using the device as claimed in any one of claims 1 to 9, characterized in that: The following steps are involved: S1. Device calibration After assembling the test device, do not install the grating first, adjust the aperture in the beam expansion lens group to ensure that the spot size after passing through the beam expansion lens group is compatible with the grating to be tested; then turn on the laser, collect data from the first optical power meter and the second optical power meter respectively, and calculate the calibration factor using formula (1): Where: η is the calibration factor, w is the value of the first optical power meter, and w′ is the value of the second optical power meter; S2, start measuring S2-1. After obtaining the calibration factor, install the grating to be measured on a rotating platform; S2-2. Keep the rotating table still and adjust the test table angle to level 0, +1, -1, +2, -2, +3, -3 respectively, and you can get the corresponding optical power, which are w′0, w′ +1 , w′ -1 , w′ +2 , w′ -2 , w′ +3 , w′ -3 . S2-3. Calculation of diffraction efficiency Wherein: m is the diffraction order, m = 0, ±1, ±2, ±3...

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