Parallelism testing device

Abstract

The invention provides a parallelism testing device which is used for testing the parallelism of the surface of an optical wafer, the parallelism testing device comprises a laser light source, a sample table and a reflected light observation plate, the sample table comprises a connecting surface used for positioning the optical wafer to be tested, the reflected light observation plate comprises an observation surface facing the sample table, and the observation surface faces the sample table. The connecting surface and the observation surface are spaced in parallel, the incident angle of incident laser light rays emitted by the laser light source to the optical wafer to be measured on the optical wafer to be measured is smaller than a preset value, and the observation surface is used for receiving reflected light of the incident laser light rays reflected by the optical wafer to be measured. The parallelism testing device only needs to be composed of the laser light source, the sample table and the reflected light observation plate, and is simple in structure and low in manufacturing cost.

Description

Technical Field

[0001] The present application relates to the technical field of testing equipment, and in particular to a parallelism testing device. Background Art

[0002] With the development of technology, augmented reality (AR) display devices, such as AR glasses, can see both the real world outside and virtual images. The augmented reality display device includes a diffraction light waveguide lens with a diffraction grating, and the diffraction light waveguide lens is generally manufactured on an optical wafer by nanoimprinting and other processes. Because light is totally reflected and propagated in the diffraction light waveguide lens, if the surface parallelism of the lens substrate, i.e., the optical wafer, is poor, the total reflection path of light of different colors will gradually deviate, which is reflected in the optical display, that is, the clarity deteriorates or even seriously enough that images of different colors will separate. Therefore, in order to present a better optical effect, the optical wafer needs to have better surface parallelism.

[0003] In order to test the parallelism of the optical wafer surface, a multi-surface simultaneous interferometer such as the Verifire MST device is generally used for testing. Although this type of testing equipment has high accuracy, it requires a large-aperture lens and a precise interference optical path. Therefore, the existing multi-surface simultaneous interferometer has a complex structure and a high manufacturing cost. Summary of the invention

[0004] In order to solve the above problems, the present application provides a parallelism testing device with a simple structure and low manufacturing cost.

[0005] The present application provides a parallelism testing device for testing the parallelism of the surface of an optical wafer, the parallelism testing device comprising a laser light source, a sample stage and a reflected light observation plate, the sample stage comprising a connecting surface for positioning the optical wafer to be tested, the reflected light observation plate comprising an observation surface facing the sample stage, the connecting surface being parallel and spaced apart from the observation surface, the incident angle of the incident laser light emitted by the laser light source to the optical wafer to be tested on the optical wafer to be tested being less than a preset value, and the observation surface being used to receive reflected light of the incident laser light reflected by the optical wafer to be tested.

[0006] The parallelism testing device of the present application only requires three components: a laser light source, a sample stage and a reflected light observation plate. It has a simple structure and low manufacturing cost. The parallelism testing device can quickly test the surface parallelism of the optical wafer to be tested with high sensitivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 It is a structural schematic diagram of a parallelism testing device provided in one embodiment of the present application.

[0008] Figure 2 yes Figure 1 Schematic diagram of the optical principle of the parallelism test device.

[0009] Figure 3 yes Figure 1 A schematic diagram of a parallelism testing device in the figure showing the parallelism of the surface of one of the optical wafers to be tested.

[0010] Figure 4 yes Figure 1 Schematic diagram of the parallelism testing device in testing the parallelism of another optical wafer surface to be tested.

[0011] Main markings:

[0012] 100. Parallelism testing device; 20. Laser light source; 40. Sample stage; 42. Connecting surface; 45. Positioning mechanism; 60. Reflected light observation plate; 62. Observation surface; 621. First laser spot; 623. Second laser spot; 300. Optical wafer to be tested. DETAILED DESCRIPTION

[0013] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0014] It should be noted that the reference to "embodiment" or "implementation method" in this document means that the specific features, structures or characteristics described in conjunction with the embodiment or implementation method may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0015] The terms "first" and "second" appearing in this application are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "plurality" refers to two or more, unless otherwise clearly and specifically defined.

[0016] See also Figure 1 and Figure 2One embodiment of the present application provides a parallelism test device 100 for measuring the parallelism of the surface of an optical wafer 300 to be tested. The parallelism test device 100 includes a laser light source 20, a sample stage 40 and a reflected light observation plate 60. The sample stage 40 includes a connection surface 42 for connecting the optical wafer 300 to be tested. The reflected light observation plate 60 includes an observation surface 62 facing the sample stage 40. The connection surface 42 is parallel to and spaced from the observation surface 62. In this embodiment, the connection surface 42 is parallel to and spaced from the observation surface 62. The incident angle θ of the incident laser light I emitted by the laser light source 20 to the optical wafer 300 to be tested on the optical wafer 300 to be tested is less than a preset value. Optionally, the preset value is 10 degrees. The observation surface 62 is used to receive the reflected light of the incident laser light I reflected by the optical wafer 300 to be tested. Specifically, the incident angle θ is greater than 0 degrees and less than 10 degrees. For example, the incident angle θ can be, but is not limited to, 2 degrees, 3 degrees, 5 degrees, 6 degrees or 8 degrees. In this embodiment, the incident angle θ is 8 degrees.

[0017] When using the parallelism testing device 100, the connection surface of the optical wafer 300 to be tested is connected to the connection surface 42, and the laser light source 20 is turned on to emit incident laser light I to the optical wafer 300 to be tested. The reflected light reflected by the surface of the optical wafer 300 to be tested is emitted to the observation surface 62 to form a laser spot. The parallelism of the optical wafer 300 to be tested is judged by the laser spot on the observation surface 62.

[0018] The parallelism testing device 100 of the present application only requires three components: a laser light source 20, a sample stage 40 and a reflected light observation plate 60. It has a simple structure and low manufacturing cost. The parallelism testing device 100 can quickly test the surface parallelism of the optical wafer 300 to be tested, and has high sensitivity.

[0019] The so-called augmented reality (AR) means that the light to be displayed generated by the image source in the near-eye display device enters the optical waveguide layer through the coupling-in grating, and is then coupled out through the coupling-out grating and emitted to the human eye; the external environment light (for example, outdoor sunlight, light generated by indoor lighting) can also pass through the coupling-in grating to enter the human eye. Therefore, the user can view the image in the image source and the image in the external environment, thereby realizing the augmented reality function that combines virtual and real.

[0020] The so-called diffraction waveguide is a medium device that guides the propagation of light waves therein. The diffraction waveguide layer is also called an optical waveguide layer, a dielectric waveguide layer or a waveguide layer. The optical waveguide layer usually includes two categories: one is an integrated optical waveguide layer, including a planar (thin film) dielectric waveguide layer and a strip dielectric waveguide layer, which are usually part of an optoelectronic integrated device (or system), so they are called integrated optical waveguide layers; the other is a cylindrical waveguide layer, usually called an optical fiber (optical fiber). Under normal circumstances, the optical waveguide layer is a guiding structure for transmitting light (optical frequency electromagnetic waves) composed of a light transparent medium (such as quartz glass). When the light is transmitted in the optical waveguide layer, total reflection will occur in the optical waveguide layer, so that the light is confined to propagate in the optical waveguide layer. As the main technical solution for augmented reality AR glasses at present, the optical waveguide layer can transmit the light projected by the micro projector to the front of the glasses, and superimpose a virtual image on the real image in front of the user's eyes, that is, it has the function of augmented reality.

[0021] Optionally, the optical waveguide layer is a light-transmitting material, and the optical waveguide layer may be, but is not limited to, glass, resin, etc. Optionally, the resin material may be, but is not limited to, an ultraviolet light-curable resin material or a thermally-curable resin material, and the grating structure may be formed on the optical waveguide layer by ultraviolet light curing or thermal curing.

[0022] The so-called coupling-in area has a diffraction grating, that is, the coupling-in area has a surface relief grating, and the so-called coupling-out area has a diffraction grating, that is, the coupling-out area has a surface relief grating; light is emitted from an image source such as a projection light machine, coupled in through the coupling-in area, and is transmitted to the coupling-out area through total reflection in the optical waveguide layer to form an image.

[0023] The optical waveguide layer with a diffraction grating on the surface is generally divided into a reflective array optical waveguide and a diffraction optical waveguide, and the diffraction optical waveguide can be further divided into a surface relief grating and a volume holographic grating. The surface relief grating (i.e., diffraction grating) is a relatively popular technical solution at present, that is, the morphology of the coupling-in area and the coupling-out area is a surface relief grating, and the surface relief grating has a light diffraction function. Optionally, the surface relief grating can be manufactured by nanoimprinting technology at present. Specifically, a mold is made in advance, and then the mold is imprinted on a film layer coated with an imprinting glue (similar to stamping), that is, the structure can be transferred to the imprinting glue to form a surface relief grating. Optionally, the surface relief grating can also be a micro-nano structure formed by nanoimprinting, and the surface relief grating can also be a micro-nano structure formed by etching the substrate.

[0024] Diffractive waveguide lenses are generally manufactured by nanoimprinting on optical wafers. The optical wafers generally include optical glass or optical plastic materials.

[0025] Please also read Figure 1-Figure 4 The optical wafer 300 to be measured includes at least a first surface and a second surface. The incident laser light I of the laser light source 20 is reflected by the first surface and the second surface respectively to generate a first reflected light R1 and a second reflected light R2. The first reflected light R1 and the second reflected light R2 form a first laser spot 621 and a second laser spot 623 on the observation surface 62 respectively. If the first surface is parallel to the second surface, the first reflected light R1 is parallel to the second reflected light R2, and the distance between the first laser spot 621 and the second laser spot 623 on the observation surface 62 remains fixed. If the first surface is not parallel to the second surface, the first reflected light R1 is not parallel to the second reflected light R2, and the distance between the first laser spot 621 and the second laser spot 623 changes with the distance D between the connecting surface 42 and the observation surface 62.

[0026] Specifically, if the first surface and the second surface on the optical wafer 300 to be tested are not parallel, when the laser light source 20 is turned on to emit incident light to the first surface and the second surface of the optical wafer 300 to be tested, the first reflected light R1 and the second reflected light R2 are respectively reflected by the first surface and the second surface, and the first reflected light R1 and the second reflected light R2 respectively form a first laser spot 621 and a second laser spot 623 on the observation surface 62. When the distance D between the connecting surface 42 and the observation surface 62 changes, the distance between the first laser spot 621 and the second laser spot 623 also changes; that is, when the distance D between the connecting surface 42 and the observation surface 62 becomes smaller, the distance between the first laser spot 621 and the second laser spot 623 also becomes smaller, and when the distance D between the connecting surface 42 and the observation surface 62 becomes larger, the distance between the first laser spot 621 and the second laser spot 623 also becomes larger.

[0027] If the first surface and the second surface on the optical wafer 300 to be measured are parallel, when the laser light source 20 is turned on to emit incident light to the first surface and the second surface of the optical wafer 300 to be measured, the first reflected light R1 and the second reflected light R2 are respectively reflected by the first surface and the second surface, and the first reflected light R1 and the second reflected light R2 respectively form a first laser spot 621 and a second laser spot 623 on the observation surface 62. When the distance D between the connecting surface 42 and the observation surface 62 changes, the distance between the first laser spot 621 and the second laser spot 623 does not change; that is, no matter whether the distance D between the connecting surface 42 and the observation surface 62 becomes smaller or larger, the distance between the first laser spot 621 and the second laser spot 623 always remains unchanged.

[0028] When the first surface and the second surface are parallel to each other, the spacing between the first laser spot 621 and the second laser spot 623 on the observation surface 62 depends on the size of the incident angle θ of the laser light source 20 and the thickness of the optical wafer 300 to be measured, and the spacing between the first laser spot 621 and the second laser spot 623 is not changed by the change of the spacing D between the connecting surface 42 and the observation surface 62. Specifically, the smaller the incident angle θ is and the thinner the thickness of the optical wafer 300 to be measured is, the smaller the spacing between the first laser spot 621 and the second laser spot 623 is; the larger the incident angle θ is and the thicker the thickness of the optical wafer 300 to be measured is, the larger the spacing between the first laser spot 621 and the second laser spot 623 is. In this embodiment, the incident angle θ is small (less than 10 degrees), and the thickness of the optical wafer 300 to be tested is less than or equal to 2 mm. When the first surface is parallel to the second surface, the distance between the first reflected light R1 and the second reflected light R2 after being reflected by the first surface and the second surface is very small, and the user will not observe the separation of the laser spots through the eyes, that is, the first laser spot 621 overlaps the second laser spot 623.

[0029] When the first surface is not parallel to the second surface, the first reflected light R1 and the second reflected light R2 reflected by the first surface and the second surface are not parallel, and an angle is generated between the first reflected light R1 and the second reflected light R2. The angle deviation of the angle is:

[0030]

[0031] in, is the angular deviation of the reflected light, n is the refractive index of the optical wafer material, It is the parallelism deviation between the first surface and the second surface of the optical wafer. That is, based on the same type of optical wafer material, the greater the parallelism deviation between the first surface and the second surface, the greater the angle deviation between the first reflected light R1 and the second reflected light R2; when the parallelism deviation between the first surface and the second surface is smaller, the angle deviation between the first reflected light R1 and the second reflected light R2 is smaller; when there is no parallelism deviation between the first surface and the second surface, that is, the first surface is parallel to the second surface, the first reflected light R1 and the second reflected light R2 are parallel to each other.

[0032] The distance deviation between the first laser spot 621 and the second laser spot 623 on the observation surface 62 is:

[0033]

[0034] Wherein, L is the distance deviation between the first laser spot 621 and the second laser spot 623, d is the material thickness of the optical wafer 300 to be measured, θ′ is the refraction angle of the incident laser light I in the material of the optical wafer 300 to be measured, D is the distance between the observation plate 60 and the optical wafer 300 to be measured, n is the refractive index of the material of the optical wafer 300 to be measured, is the parallelism deviation between the first surface and the second surface of the optical wafer 300 to be tested.

[0035] In the present application, since the incident angle θ of the incident laser light I emitted by the laser light source 20 to the optical wafer 300 to be measured is less than 10 degrees, and the material thickness of the optical wafer 300 to be measured is less than or equal to 2 mm, the laser spot separation caused by the material thickness of the optical wafer 300 to be measured can be ignored, and the distance deviation between the first laser spot 621 and the second laser spot 623 on the observation surface 62 can be simplified as:

[0036]

[0037] Wherein, L is the distance deviation between the first laser spot 621 and the second laser spot 623, D is the distance between the observation plate 60 and the optical wafer 300 to be measured, n is the refractive index of the material of the optical wafer 300 to be measured, is the parallelism deviation between the first surface and the second surface of the optical wafer 300 to be measured. That is, in the case of the optical wafer 300 to be measured with the same refractive index, the larger the distance D between the observation surface 62 of the observation plate 60 and the measuring optical wafer 300, and the larger the parallelism deviation between the first surface and the second surface of the measuring optical wafer 300, the larger the distance deviation between the first laser spot 621 and the second laser spot 623; based on the optical wafer 300 to be measured with the same refractive index, the smaller the distance D between the observation surface 62 of the observation plate 60 and the optical wafer 300 to be measured, and the smaller the parallelism deviation between the first surface and the second surface of the optical wafer 300 to be measured, the smaller the distance deviation between the first laser spot 621 and the second laser spot 623; when the parallelism deviation between the first surface and the second surface of the optical wafer 300 to be measured is 0, that is, the first surface is parallel to the second surface, the distance deviation between the first laser spot 621 and the second laser spot 623 is 0, that is, the first laser spot 621 and the second laser spot 623 overlap. The user can measure the parallelism deviation between the first surface and the second surface of the optical wafer 300 to be measured by measuring the separation distance between the first laser spot 621 and the second laser spot 623 on the observation plate 60 .

[0038] When the parallelism test device 100 of the present application is used to test the parallelism of the optical wafer 300 to be tested, the user only needs to measure the separation distance of the two laser spots on the observation plate 60 to determine the parallelism deviation of the two surfaces on the optical wafer 300 to be tested; if the two laser spots overlap, it can be determined that the parallelism of the two surfaces on the optical wafer 300 to be tested meets the requirements; if the two laser spots are separated, it can be determined that the parallelism of the two surfaces on the optical wafer 300 to be tested does not meet the requirements. Therefore, the parallelism test device 100 is simple to operate, easy to use, and has low manufacturing cost.

[0039] like Figure 1 As shown, a positioning mechanism 45 is provided on the connection surface 42, and the positioning mechanism 45 is used to position the optical wafer 300 to be tested. Specifically, the positioning mechanism 45 is a positioning frame convexly provided on the connection surface 42, and a positioning space is provided on the side of the positioning frame facing the observation surface 62, and the positioning space is used to position the optical wafer 300 to be tested. When the optical wafer 300 to be tested is positioned in the positioning space, the optical wafer 300 to be tested is parallel to the observation surface 62.

[0040] In other embodiments, a positioning space can be directly opened on the connecting surface 42 of the sample stage 40, and the positioning space is used to position the optical wafer 300 to be tested; when the optical wafer 300 to be tested is positioned in the positioning space, the optical wafer 300 to be tested is parallel to the observation surface 62; optionally, the connecting surface 42 protrudes from the side of the optical wafer 300 to be tested facing the observation surface 62, or the side of the optical wafer 300 to be tested facing the observation surface 62 is coplanar with the connecting surface 42.

[0041] Optionally, the sample stage 40 can move relative to the laser light source 20, so that the incident laser light I of the laser light source 20 can irradiate different points on the optical wafer 300 to be tested. That is, the sample stage 40 can move relative to the laser light source 20 on a plane parallel to the connecting surface 42, so as to drive the optical wafer 300 to be tested to move on a plane parallel to the connecting surface 42, so that different points of the optical wafer 300 to be tested can be tested under the condition that the laser light source 20 remains stationary.

[0042] Optionally, the sample stage 40 can move relative to the reflected light observation plate 60 in a direction perpendicular to the connection surface 42, that is, the sample stage 40 can move closer to or farther from the observation surface 62, so as to drive the optical wafer 300 to be measured on the sample stage 40 to move closer to or farther from the observation surface 62, thereby changing the distance D between the connection surface 42 and the observation surface 62. Specifically, when the sample stage 40 approaches the observation surface 62 in a direction perpendicular to the observation surface 62, the distance D between the connection surface 42 and the observation surface 62 becomes smaller; when the sample stage 40 moves away from the observation surface 62 in a direction perpendicular to the observation surface 62, the distance D between the connection surface 42 and the observation surface 62 becomes larger.

[0043] Optionally, the distance D between the observation surface 62 and the optical wafer 300 to be measured is greater than or equal to 1 meter, that is, the distance D can be but is not limited to 2 meters, 3 meters, 4 meters, 5 meters, 6 meters, etc. In this embodiment, the observation plate 60 is a flat plate, and the observation surface 62 is arranged on the side of the observation plate 60 facing the optical wafer 300 to be measured, and the observation surface 62 can receive the reflected light spot reflected by the laser light source 20 incident on the optical wafer 300 to be measured. Generally, the parallelism deviation of the surface of the optical wafer 300 to be measured is small. In order to more clearly observe the distance deviation of the reflected laser spot, the distance D between the observation plate 60 and the optical wafer 300 to be measured should be greater than 1 meter.

[0044] In other embodiments, the reflected light observation plate 60 can move relative to the sample stage 40 in a direction perpendicular to the observation surface 62 to change the distance D between the connection surface 42 and the observation surface 62. Specifically, when the reflected light observation plate 60 approaches the connection surface 42 in a direction perpendicular to the observation surface 62, the distance D between the connection surface 42 and the observation surface 62 becomes smaller; when the reflected light observation plate 60 moves away from the connection surface 42 in a direction perpendicular to the observation surface 62, the distance D between the connection surface 42 and the observation surface 62 becomes larger.

[0045] In other embodiments, the reflected light observation plate 60 and the sample stage 40 can move relative to each other in a direction perpendicular to the observation surface 62 to change the distance D between the connection surface 42 and the observation surface 62. Specifically, when the reflected light observation plate 60 and the sample stage 40 approach each other in a direction perpendicular to the observation surface 62, the distance D between the connection surface 42 and the observation surface 62 becomes smaller; when the reflected light observation plate 60 and the sample stage 40 move away from each other in a direction perpendicular to the observation surface 62, the distance D between the connection surface 42 and the observation surface 62 becomes larger.

[0046] Optionally, a ruler is provided on the observation surface 62, and the ruler is used to measure the distance between the first laser spot 621 and the second laser spot 623. The ruler is printed on the observation surface 62, which can facilitate quick testing of the separation distance between the first laser spot 621 and the second laser spot 623.

[0047] Optionally, the laser light source 20 may be a red laser light source, a green laser light source or a blue laser light source. Specifically, the laser light source 20 may be, but is not limited to, a 488nm argon laser (blue light), a 514nm argon laser (green light), a 543nm helium-neon laser (green light), a 633nm helium-neon laser (red light), etc. The smaller the diameter of the laser spot, the higher the test sensitivity of the parallelism testing device 100; preferably, the diameter of the laser spot is <1mm, that is, the diameters of the first laser spot 621 and the second laser spot 623 are <1mm.

[0048] Optionally, the parallelism testing device 100 further includes a diffractive optical element, which is connected to the laser light source 20, so that a beam of incident laser light emitted by the laser light source 20 forms m*n incident laser light beams after passing through the diffractive optical element, and these incident laser light beams form m*n laser spots on the observation surface 62 after being reflected by the optical wafer 300 to be tested; wherein m and n are both positive integers greater than 1. When the m*n incident laser light beams are incident on the optical wafer 300 to be tested at the same time, the parallelism of multiple points on the optical wafer 300 to be tested can be simultaneously observed on the observation surface 62.

[0049] Optionally, the parallelism testing device 100 may further include a camera, which is used to take pictures of the observation surface 62, and then automatically capture the laser spot separation distance by taking pictures; thereby the parallelism of the optical wafer 300 to be tested can be tested more accurately.

[0050] When using the parallelism testing device 100, move the sample stage 40 and / or the observation plate 60 so that the distance D between the connecting surface 42 and the observation surface 62 is at least greater than 1 meter, position the optical wafer 300 to be tested on the positioning mechanism 45 of the sample stage 40, turn on the laser light source 20 to allow the incident laser light I to be incident on the optical wafer 300 to be tested, and form a laser spot on the observation surface 62 after being reflected by the surface of the optical wafer 300 to be tested. By observing the separation distance between the laser spots, the parallelism of the optical wafer 300 to be tested can be obtained.

[0051] After actual verification of the parallelism testing device 100, when the distance D between the observation surface 62 and the optical wafer 300 to be tested is 5 meters, if a laser light source with a laser spot diameter of 0.4 mm is used, the surface parallelism test sensitivity of the optical wafer 300 to be tested with a refractive index of 1.7 is <0.002°; if a laser light source with a laser spot diameter of 0.1 mm is used, the surface parallelism test sensitivity of the optical wafer 300 to be tested with a refractive index of 1.7 is <0.0005°, which meets the testing requirements of the optical wafer.

[0052] This article uses specific examples to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the core idea of ​​the present application. At the same time, for general technical personnel in this field, according to the idea of ​​the present application, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as a limitation on the present application.

Claims

1. A parallelism testing device for testing the parallelism of an optical wafer surface, characterized in that: The parallelism testing device includes a laser light source, a sample stage and a reflected light observation plate, the sample stage includes a connecting surface for positioning the optical wafer to be tested, the reflected light observation plate includes an observation surface facing the sample stage, the observation surface is parallel and spaced from the connecting surface, the incident angle of the incident laser light emitted by the laser light source to the optical wafer to be tested on the optical wafer to be tested is less than a preset value, and the observation surface is used to receive reflected light of the incident laser light reflected by the optical wafer to be tested.

2. The parallelism testing device according to claim 1, characterized in that: The optical wafer to be measured includes at least a first surface and a second surface. The incident laser light of the laser light source is reflected by the first surface and the second surface respectively to generate a first reflected light and a second reflected light. The first reflected light and the second reflected light form a first laser spot and a second laser spot on the observation surface respectively. If the first surface is parallel to the second surface, the first reflected light is parallel to the second reflected light, and the distance between the first laser spot and the second laser spot remains unchanged. If the first surface is not parallel to the second surface, the first reflected light is not parallel to the second reflected light, and the distance between the first laser spot and the second laser spot changes with the distance between the connecting surface and the observation surface.

3. The parallelism testing device according to claim 1, characterized in that: The distance between the observation surface and the optical wafer to be measured is greater than or equal to 1 meter.

4. The parallelism testing device according to claim 1, characterized in that: A positioning mechanism is provided on the connection surface, and the positioning mechanism is used for positioning the optical wafer to be tested.

5. The parallelism testing device according to claim 1, characterized in that: The sample stage can be moved relative to the laser light source so that the incident laser light from the laser light source can illuminate different points on the optical wafer to be measured; the sample stage and / or the reflected light observation plate can be moved in a direction perpendicular to the observation surface to change the distance between the connecting surface and the observation surface.

6. The parallelism testing device according to claim 2, characterized in that: When the first reflected light is not parallel to the second reflected light, the angle deviation between the first reflected light and the second reflected light is: in, is the angular deviation of the reflected light, n is the refractive index of the optical wafer material, is the parallelism deviation between the first surface and the second surface of the optical wafer.

7. The parallelism testing device according to claim 2, characterized in that: The distance deviation between the first laser spot and the second laser spot on the observation surface is: Wherein, d is the thickness of the optical wafer material, θ′ is the refraction angle of the incident laser light in the optical wafer material, D is the distance between the observation plate and the optical wafer to be measured, and n is the refractive index of the optical wafer material. is the parallelism deviation between the first surface and the second surface of the optical wafer.

8. The parallelism testing device according to claim 7, characterized in that: When the thickness of the optical crystal to be measured is less than or equal to 2 mm, the spacing deviation between the first laser spot and the second laser spot on the observation surface is: Wherein, D is the distance between the observation plate and the optical wafer to be measured, n is the refractive index of the optical wafer material, and Φ is the parallelism deviation between the first surface and the second surface of the optical wafer.

9. The parallelism testing device according to claim 1, characterized in that: The parallelism testing device also includes a diffraction optical element, which is connected to the laser light source, so that a beam of incident laser light emitted by the laser light source forms m*n incident laser light beams after passing through the diffraction optical element, and forms m*n laser spots on the observation surface after being reflected by the optical wafer to be tested; wherein m and n are both positive integers greater than 1.

10. The parallelism testing device according to claim 2, characterized in that: A ruler is arranged on the observation surface to measure the distance between the first laser spot and the second laser spot.

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