CN217542339U - Period measurement device of transmission type grating - Google Patents

Abstract

The present application provides a period measuring apparatus of a transmission type grating, which may include: the base comprises a bearing surface, and the grating to be detected is arranged on the base; the light source is arranged on the base, and the light emitting direction of the light source is parallel to the bearing surface of the base; the arc-shaped guide rail is arranged on the base; and the photoelectric detector is arranged on the arc-shaped guide rail and movably connected with the arc-shaped guide rail. The diffraction light of the specific diffraction order of the grating is detected by the photoelectric detector, the diffraction angle of the diffraction light is recorded, and the grating period of the transmission grating is quickly measured based on the grating diffraction equation, so that a simple, convenient and effective tool is provided for measuring and verifying the grating period of the waveguide design grating. The device is simple to operate, and the grating period is measured quickly, simply and conveniently. Meanwhile, parameters of the device can be adjusted according to actual conditions, and the grating period measuring range is wide.

Description

Period measurement device of transmission type grating

technical field

The present application relates to the technical field of grating period measurement, and in particular, to a transmission-type grating period measurement device.

Background technique

The diffractive optical waveguides of Augmented Reality (AR) glasses often use gratings to realize the coupling in and out of light. The grating period is an important structural parameter of the grating. efficiency) has an important impact, thereby affecting the overall coupling-in-coupling efficiency of the waveguide. When optimizing the performance of the waveguide, the grating period of the waveguide coupled into or out of the area grating is generally set to make the waveguide display the best performance. However, there are errors in the actual grating processing process, resulting in some defects in the coupled-in or out-coupling area of the grating, that is, the actual grating period value may not be consistent with the theoretical value, resulting in problems such as reduced coupling-out efficiency and poor uniformity. Therefore, it is necessary to Measurement Verification.

At present, to measure the grating period of the grating to be measured, the grating structure can be directly observed through a scanning electron microscope, and the value of the grating period can be measured, but the scanning electron microscope is expensive, which increases the production cost of the grating.

Utility model content

The embodiments of the present application propose a period measurement device for a transmission type grating, so as to solve at least one of the above technical problems.

The embodiments of the present application achieve the above objects through the following technical solutions.

A transmission-type grating period measurement device, comprising: a base, including a bearing surface, on which the grating to be measured is arranged; a light source, arranged on the base, and the light emitting direction of the light source is parallel to the bearing of the base an arc-shaped guide rail, arranged on the base; and a photodetector, arranged on the arc-shaped guide rail and movably connected with the arc-shaped guide rail.

In one embodiment, it further includes: a rotating table, which is arranged on the base and is rotatably connected with the base, and the grating to be measured is arranged on the rotating table.

In an embodiment, it further includes: a fixture, the fixture is arranged on the rotating table and is fixedly connected with the rotating table, and the fixture is used for fixing the grating to be measured.

In one embodiment, the arc-shaped guide rail includes: a chute, the extension direction of the chute is consistent with the extension direction of the arc-shaped guide rail, and the photodetector includes: a slider, the slider The block is located at the bottom of the photodetector, and the slider is slidably connected with the chute.

In an embodiment, the device for measuring the period of the transmission grating further comprises: a lifting rod, the lifting rod is arranged on the base, and the light source is arranged on the lifting rod.

In one embodiment, the arc-shaped guide rail is provided with a first scale, and the first scale is arranged along the extending direction of the circumference of the arc-shaped guide rail.

In an embodiment, the arc-shaped guide rail is detachably connected to the base; the bottom end of the arc-shaped guide rail is provided with an external thread, the bearing surface of the base is provided with a threaded hole, and the arc-shaped guide rail is provided with an external thread. The external thread of the shaped guide rail and the threaded hole of the base are threadedly matched with each other.

In one embodiment, a second scale is provided on the circumference of the rotary table, and the second scale is arranged along the extension direction of the circumference of the rotary table.

In one embodiment, the light source is a laser.

In one embodiment, the photodetector is a CCD sensor or a CMOS sensor.

The solution provided by the embodiments of the present application detects the diffracted light of a specific diffraction order of the grating by means of a photodetector, records the diffraction angle, and quickly measures the grating period of the transmission grating based on the grating diffraction equation, thereby providing a method for measuring and verifying the grating period of the waveguide designed grating. A simple and effective tool. The device is simple to operate, fast and easy to measure the grating period, and the parameters of the device can be adjusted according to the actual situation, and the grating period measurement range is wide.

Description of drawings

In order to illustrate the technical solutions in the embodiments of the present application more clearly, the following briefly introduces the drawings that are used in the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application. For those skilled in the art, other drawings can also be obtained from these drawings without creative effort.

FIG. 1 is a schematic structural diagram of a period measuring device for a transmission type grating according to an embodiment of the present application.

FIG. 2 is a schematic diagram of a measuring device for the grating period of the transmission diffraction grating.

FIG. 3 is a schematic diagram of diffraction angle correction of transmitted -1st order light.

Description of the drawings: Period measurement device 10 of transmission grating, base 100, bearing surface 110, rotary table 200, grating to be measured 300, light source 400, arc-shaped guide rail 500, chute 530, photodetector 600, slider 610 , fixture 700, lifting rod 800.

Detailed ways

Embodiments of the present application are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals refer to the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary, only used to explain the present application, and should not be construed as a limitation on the present application.

In order to make those skilled in the art better understand the solutions of the present application, the following will clearly and completely describe the technical solutions in the embodiments of the present application with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, but not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative efforts shall fall within the protection scope of this application.

The diffractive optical waveguides of AR glasses often use gratings to couple in and out light. As an important structural parameter of the grating, the grating period has an important impact on the diffraction characteristics of the grating (such as the direction of the diffraction order and its diffraction efficiency), so It affects the overall coupling-in-coupling efficiency of the waveguide. When optimizing the performance of the waveguide, the grating period of the waveguide coupled into or out of the area grating is generally set to make the waveguide display the best performance. However, there are errors in the actual grating processing process, resulting in some defects in the coupled-in or out-coupling area of the grating, that is, the actual grating period value may not be consistent with the theoretical value, resulting in problems such as reduced coupling-out efficiency and poor uniformity. Therefore, it is necessary to Measurement Verification.

The diffractive optical waveguides of AR glasses often use gratings to couple in and out light. As an important structural parameter of the grating, the grating period d has an important influence on the diffraction characteristics of the grating (such as the direction of the diffraction order and its diffraction efficiency). Thus, the overall coupling-in-coupling-out efficiency of the waveguide is affected. When designing the parameters of the waveguide grating, the grating period of the area grating coupled in or out is generally designed to make the waveguide display performance the best. However, in the actual manufacturing process of the diffraction grating, due to various factors, the grooves of the grating have various Formal errors, such as the non-parallel grating grooves, the spacing error of the grating grooves, and the inconsistency of the groove shapes, etc., cause the actual value of the grating period to deviate from the theoretical design value, resulting in the impact of the spectral quality of the grating. Astigmatism, reduction in reflection-1st order diffraction efficiency, etc., will adversely affect the display performance of the waveguide. At present, to measure the grating period deviation caused by the grating groove error, the grating structure can be directly observed by scanning electron microscope, and the value of the grating period can be measured, but the scanning electron microscope is expensive and will cause damage to the sample.

The present application proposes a period measurement device for a transmission grating, which aims to provide a simple and fast measurement tool for the measurement and verification of the grating period of a waveguide designed grating, which helps to optimize the overall performance of the waveguide, thereby improving the display performance of AR glasses.

Referring to FIG. 1 , the present application provides a transmission grating period measurement device 10 , the device may include: a base 100 , a rotary table 200 , a light source 400 , a circular arc guide 500 and a photodetector 600 .

The base 100 may be a square base 100 or a circular base 100 , and the thickness of the base 100 may be smaller than the length, width or diameter of the base 100 to ensure the stability of the base 100 . The base 100 includes a bearing surface 110 , which is a smooth and flat plane. The base 100 is used to carry other components such as the rotary table 200 , the light source 400 , the arc guide 500 and the photodetector 600 . It can be understood that the base 100 shown in FIG. 1 is only for illustration, and the present application is not limited to the specific shape of the base 100 .

The rotary table 200 is disposed on the bearing surface 110 of the base 100, and the rotary table 200 is rotatably connected to the base 100, and the rotary table 200 is used to carry the grating 300 to be measured; the rotary table 200 may be a cylindrical structure, so as to for the user to rotate it. The bottom of the rotary table 200 can be provided with a rotation groove, and the bearing surface 110 of the base 100 can be provided with a rotating rod. In connection, the rotating stage 200 can be used to adjust the incident angle of the incident light. It can be understood that the rotary table 200 shown in FIG. 1 is only for illustration, and the present application is not limited to the specific shape of the rotary table 200 .

The light source 400 is disposed on the base 100, and the light source 400 is located on one side of the rotating table 200, and the light emitting direction of the light source 400 points to the rotating table 200 to ensure that the light emitted from the light source 400 can pass through the rotating table 200. 200 on the grating 300 to be tested. In addition, the light emitting direction of the light source 400 is parallel to the bearing surface 110 of the base 100 . The light source 400 is used for emitting light beams, and generally a single-wavelength laser or LED light source 400 is used. It can be understood that the light source 400 shown in FIG. 1 is only for illustration, and the present application is not limited to the specific form of the light source 400 .

The arc-shaped guide rail 500 is arranged on the base 100 , and the arc-shaped guide rail 500 is located on the side of the rotary table 200 away from the light source 400 ; The object on the upper part realizes the position change along the plane of the arc-shaped guide rail 500 . Meanwhile, in this solution, the rotary table 200 is arranged at the center of the circular arc guide rail 500 , so that the distance between the photodetector 600 and the rotary table 200 remains unchanged no matter where the photodetector 600 is on the circular arc rail 500 . The setting of the above-mentioned arc-shaped guide rail 500 functions as a control variable.

The photodetector 600 is arranged on the arc-shaped guide rail 500 and is movably connected to the arc-shaped guide rail 500; that is, the photodetector 600 can realize the position along the path of the arc-shaped guide rail 500 on the arc-shaped guide rail 500 Variety. The photodetector 600 is used to collect light signal images in real time and perform data processing.

Wherein, the center of the arc-shaped guide rail 500 is located on the connecting line between the measurement point of the grating 300 to be measured and the light source 400 , and the arc-shaped guide rail 500 may be symmetrical along the connecting line. The position setting of the above-mentioned arc-shaped guide rail 500 can make the area detectable by the photodetector 600 more symmetrical, which helps to improve the detection accuracy of the photodetector 600 .

The working principle of the embodiment of the present application is as follows: turn on the light source 400, so that the incident light of the light source 400 passes through the grating 300 to be measured set on the rotating table 200, adjust the position of the photodetector 600 on the arc-shaped guide rail 500, and the photoelectric detection The device 600 collects and records optical signal images.

可以推导得到待测光栅300的光栅周期d与角度α的对应关系，这里规定T_-1级光线在入射光右侧取+，左侧取-。这样根据d与角度α的对应关系可以在不同α处算出对应光栅周期d数值，从而实现快速测量光栅周期的目的。As shown in FIG. 2 , the light source 400 emits a wavelength of λ and is incident on the surface of the grating to be measured 300 rotated by a certain angle i, by measuring the transmission order diffraction direction of the grating to be measured 300, here the transmission-1(T _-1 ) level angle α (α is the angle of the transmitted light relative to the incident light, point O in the figure is the 0° position in the scale on the circular arc guide 500), according to the diffraction grating equation

The corresponding relationship between the grating period d of the grating to be measured 300 and the angle α can be derived, and it is stipulated here that the light of the T _-1 order takes + on the right side of the incident light and - on the left side. In this way, according to the corresponding relationship between d and the angle α, the value of the corresponding grating period d can be calculated at different α, so as to achieve the purpose of quickly measuring the grating period.

To sum up, the device in the embodiment of the present application detects the diffracted light of a specific diffraction order of the grating through the photodetector, records the diffraction angle, and quickly measures the grating period of the transmission grating based on the grating diffraction equation, so as to design the grating period of the grating for the waveguide. Measurement verification provides a simple and effective tool. The device is easy to operate, and the grating period is measured quickly and easily. At the same time, the parameters of the device can be adjusted according to the actual situation, and the measurement range of the grating period is wide.

In an embodiment, please refer to FIG. 1 again, the period measuring device 10 of the transmission grating may further include a fixture 700, and the fixture 700 is arranged on the rotary table 200 and is fixedly connected to the rotary table 200, For example, welding, screw connection, etc., it is enough to ensure that the clamp 700 does not loosen after clamping the grating 300 to be measured. The fixture 700 is used to fix the grating 300 to be measured. In this embodiment, the clamp 700 may be a spring clamp. It should be noted that, in this embodiment, although the clamp 700 is used to clamp the grating 300 to be measured, it should be able to clamp the grating 300 to be measured during fixing, but it will not damage the grating 300 to be tested. A flexible cushion such as rubber, resin, etc. is arranged on it. At the same time, the clamp 700 itself is fixed on the rotary table 200 and can rotate freely with the rotary table 200 . For example, the clamp 700 can be connected to the rotating shaft provided on the rotating table 200 by providing a rotating shaft hole on the bottom surface of the clamp 700 to realize the rotational connection between the clamp 700 and the rotating table 200 . When the grating 300 to be measured is fixed by the fixture 700 , it is necessary to ensure that the measuring position of the grating 300 to be measured is on the rotation axis of the turntable 200 , so as to ensure that the measurement position does not change due to the rotation of the turntable 200 . The setting of the fixture 700 can ensure the accuracy of the position of the grating 300 to be tested, thereby improving the accuracy of the test.

In one embodiment, the arc-shaped guide rail 500 may include: a chute 530, the extension direction of the chute 530 is consistent with the extension direction of the arc-shaped guide rail 500, and the photodetector 600 includes: The slider 610 is located at the bottom of the photodetector 600 , and the slider 610 is slidably connected with the chute 530 . The above arrangement of the photodetector 600 and the arc-shaped guide rail 500 helps to improve the fault tolerance rate of the device in use.

In an embodiment, the transmission-type grating period measurement device 10 further includes a lift rod 800 , the lift rod 800 is arranged on the base 100 , and the light source 400 is arranged on the lift rod 800 . It can be understood that the lifting rod 800 can not only perform a lifting function to change the height of the light source 400 , but also rotate relative to the base 100 to change the light emitting direction of the light source 400 .

In one embodiment, the arc-shaped guide rail 500 is provided with a first scale, and the first scale is arranged along the extension direction of the circumference of the arc-shaped guide rail 500 , and the measurement point of the grating 300 to be measured is the same as the The intersection point of the connection line of the light source 400 and the circular arc guide rail 500 is 0°, and the angle of one side of the intersection point is +, and the angle of the other side is -. The setting of the above scale can facilitate the user to record the change of the angle. At the same time, the intersection of the connecting line and the arc-shaped guide rail 500 is taken as 0°, so that the scales on both sides of the intersection are symmetrically distributed, and the numerical values on both sides of the intersection can be calculated more conveniently.

In one embodiment, the arc-shaped guide rail 500 is detachably connected to the base 100 . For example, snap joint or tenon joint, etc., the detachable connection can facilitate the disassembly and installation of the period measuring device 10 of the transmission grating. In this embodiment, the bottom end of the circular arc guide 500 is provided with an external thread, so the The bearing surface of the base 100 is provided with threaded holes, and the external threads of the circular arc guide rail 500 and the threaded holes of the base 100 are threadedly matched with each other.

In an embodiment, a second scale is provided on the circumference of the rotating table 200 , the second scale is arranged along the extending direction of the circumference of the rotating table 200 , and the second scale is opposite to the photodetector 600 . , the setting of the second scale can facilitate the acquisition of the rotation amount of the rotary table 200 , thereby facilitating the measurement of the grating period of the grating 300 to be measured.

In one embodiment, the clamp 700 is made of a flexible material, such as rubber, resin, or the like. Using a flexible material to make the fixture 700 can reduce the probability that the fixture 700 damages the grating 300 to be measured, thereby improving the accuracy and efficiency of detection.

In one embodiment, the photodetector 600 is a CCD sensor or a CMOS sensor. The detection incident light passes through the grating 300 to be tested for the stronger diffraction order optical signals except the 0th order diffraction. Generally, the stronger detection signal is the 1st order diffraction. At the same time, the detected light signal can be converted into an electrical signal. Diffracted light has better light sensitivity. Generally, a CCD or CMOS image sensor is used, and a CCD camera is used here, which can be connected to a computer host to collect optical signal images in real time for data processing.

Please combine Figure 1 and Figure 3, the workflow of this device is:

1. Install the grating 300 to be measured on the rotary table 200, turn on the light source 400, and ensure that the light emitted from the light source 400 is vertically incident on the grating;

2. Rotate the rotary table 200 by a certain angle i (i=0° if not rotated) to ensure that when the light passes through the grating, other diffraction orders other than the 0th order of diffraction can be generated, such as transmission 1st order, transmission -1st order;

3. The CCD camera scans from an angle of -90° to an angle of 90° (or from an angle of 90° to an angle of -90°) on the circular arc guide 500. When the other diffraction orders except the transmission 0 order are incident on the photoelectric When the receiving port of the detector 600 (the photodetector 600 used here is a CCD camera), the camera acquisition software will display a light spot, where the transmission-1-level light signal is collected. At this time, the center of the camera is located along the transmission- 1 (T _-1 ) level angle α points to the scale position α ₁ (not shown in the figure) on the circular arc guide rail 500;

4. At the same time, the software analyzes the image collected by the CCD. Assuming that the horizontal distance L from the center of the image spot to the center pixel of the camera is calculated, the diffraction angle of the actual diffracted light is α=α ₁ ±arctan L/R. The selection of the sign here depends on the spot The center deviation of the camera center pixel is a left deviation or a right deviation. As shown in Figure 3, the image spot center deviates from the camera center pixel to the right. At this time, the diffraction angle of the transmitted -1st order light should be corrected as α=α ₁ -arctan L/R;

5. Finally, substitute the wavelength λ of the light source 400, the incident angle i, and the diffraction angle α into the formula:

By calculation, the value of the grating period d of the grating 300 to be measured can be obtained.

where:

d is the grating period of the grating to be measured;

i is the incident angle;

α is the diffraction angle;

λ is the wavelength of the light emitted by the light source.

The present application proposes a period measurement device for a transmission type grating. The device detects the diffracted light of a specific diffraction order of the grating through a photodetector, records its diffraction angle, and quickly measures the grating period of the transmission grating based on the grating diffraction equation, thereby providing a simple and effective tool for the measurement and verification of the grating period of the waveguide design grating . The device is easy to operate, and the grating period is measured quickly and easily. At the same time, the parameters of the device can be adjusted according to the actual situation, and the measurement range of the grating period is wide.

The description of the terms "some embodiments," "other embodiments," etc. means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of this application. In this application, schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the particular features, structures, materials or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, those skilled in the art may combine and combine the different implementations or examples described in this application, as well as the features of the different implementations or examples, without conflicting each other.

The above embodiments are only used to illustrate the technical solutions of the present application, but not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: The recorded technical solutions are modified, or some technical features thereof are equivalently replaced; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the various embodiments of the application, and should be included in this application. within the scope of protection.

Claims (10)

1. A period measuring device of a transmission grating, characterized in that, comprising: the base, including the bearing surface; a light source, which is arranged on the base, and the light emitting direction of the light source is parallel to the bearing surface of the base; an arc-shaped guide rail disposed on the base; and The photodetector is arranged on the arc-shaped guide rail and is movably connected with the arc-shaped guide rail. 2. The period measuring device of the transmission grating according to claim 1, characterized in that, further comprising: The rotary table is arranged on the base and is rotatably connected with the base. 3. The period measuring device of the transmission grating according to claim 2, characterized in that, further comprising: The fixture is arranged on the rotary table and is fixedly connected with the rotary table, and the fixture is used for fixing the grating to be measured. 4 . The period measuring device of transmission grating according to claim 3 , wherein the circular arc guide rail comprises: a chute, and the extension direction of the chute is consistent with the extension direction of the circular arc guide rail. 5 . , the bottom of the photodetector is provided with a slider, and the slider is slidably connected with the chute. 5 . The period measuring device for a transmission grating according to claim 1 , wherein the period measuring device for the transmission grating further comprises: a lifting rod, the lifting rod is arranged on the base, the light source arranged on the lift rod. 6 . The period measuring device for transmission grating according to claim 1 , wherein a first scale is provided on the arc-shaped guide rail, and the first scale extends along the arc-shaped guide rail. 7 . Orientation arrangement. 7 . The period measuring device of transmission grating according to claim 1 , wherein the bottom end of the arc-shaped guide rail is provided with an external thread, the bearing surface of the base is provided with a threaded hole, and the circular arc is provided with an external thread. The external thread of the shaped guide rail and the threaded hole of the base are threadedly matched with each other. 8 . The period measuring device of transmission grating according to claim 2 , wherein a second scale is provided on the circumference of the rotating table, and the second scale is arranged along the extending direction of the circumference of the rotating table. 9 . . 9 . The device for measuring the period of a transmission grating according to claim 1 , wherein the light source is a laser. 10 . 10. The device for measuring the period of a transmission grating according to claim 1, wherein the photodetector is a CCD sensor or a CMOS sensor.

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