CN113992813A

CN113992813A - Prism assembly, periscopic camera module and prism assembly assembling method

Info

Publication number: CN113992813A
Application number: CN202010651516.8A
Authority: CN
Inventors: 裴海鹏; 田中武彦; 蒋伟杰; 孙鑫翔
Original assignee: Ningbo Sunny Opotech Co Ltd
Current assignee: Ningbo Sunny Opotech Co Ltd
Priority date: 2020-07-08
Filing date: 2020-07-08
Publication date: 2022-01-28
Anticipated expiration: 2040-07-08
Also published as: CN113992813B; CN115769124A; WO2022007603A1

Abstract

The invention provides a prism assembly, which comprises a prism; the maximum outer diameter of the first lens is smaller than the diameter of a circumscribed circle of the top surface of the prism and larger than the diameter of an inscribed circle of the top surface of the prism; the composite lens barrel comprises a mounting hole, the mounting hole comprises an upper section and a lower section, the overlooking outline of the upper section is circular with a protruding part, a second mounting groove is formed in the circular section in the overlooking outline, the second mounting groove is provided with a step surface for bearing against the bottom surface of the first lens, a first mounting groove is formed in the protruding part in the overlooking outline, and the first mounting groove is communicated up and down, so that the top surface of the prism can penetrate through the upper section; the lower segment is adapted to bear against and secure the prism. The invention also provides a corresponding periscopic camera module and a prism assembly assembling method. The invention is beneficial to improving the production yield and consistency; helping to reduce device size.

Description

Prism assembly, periscopic camera module and prism assembly assembling method

Technical Field

The invention relates to the technical field of camera modules, in particular to a prism assembly for fixing a prism and a lens together, a corresponding periscopic camera module and a corresponding assembling method.

Background

With the rise of living standard, the requirements of consumers on the camera function of terminal devices such as mobile phones and tablets are higher and higher, so that the effects of background blurring and night shooting are required to be achieved, the requirements on telephoto are also provided, and the consumers need the terminal devices capable of clearly shooting distant pictures. In order to capture a distant picture, the camera module is usually required to have a longer focal length. For the vertical module, it is necessary to increase the height to increase the focal length, however, due to the size limitation (especially the limitation of the device thickness) of the terminal device (such as a mobile phone), the vertical long focus module can only achieve the equivalent focal length of 2X-3X compared to the main camera. The periscopic camera module provides a higher focal length than the main camera, so that the periscopic camera module is usually used for long-distance or super-long-distance shooting. The periscopic type folds the light path through the prism, and the height of the module is changed from the height along the incident direction to the direction perpendicular to the incident direction, so that the thickness increase of the mobile phone (or other terminal equipment) caused by the increase of the multiplying power is avoided. At present, periscopic camera modules in mobile phones have been able to achieve equivalent focal lengths compared to main/wide-angle modules of 5X-10X. Therefore, under the condition that a mobile phone manufacturer ensures that the thickness of the mobile phone is not increased at a mobile phone terminal, the periscopic camera module is a better choice for realizing telephoto shooting.

Periscopic module generally includes prism and a plurality of lens, and wherein the prism possesses the ability with light folding, and the light after the prism reflection need guarantee to pass through each lens as far as stably as possible, just can become comparatively clear image on the chip, because the focus is longer in addition, shoots the main part picture and accounts for than great, in order to reduce because the picture influence of shake, and periscopic module often can be equipped with OIS mechanism for the periscopic module can realize the anti-shake.

In the prior art, for the solution that the front end of the prism (the end close to the object) is provided with the lens, the lens and the prism are usually assembled in one module. However, the shape of the lens is often circular, while the faces of the prism are generally polygonal, which are not identical in shape, which makes assembly more difficult. Because the camera module is a high-precision optical system, the imaging quality can be reduced or even the imaging cannot be realized due to the tiny position deviation of each optical element. Therefore, how to assemble the prism and the lens with high precision enables the obtained prism assembly and the camera module to have better production yield and consistency.

Therefore, there is a need for a new assembly structure and assembly method for prism and lens, so as to improve the production yield and consistency of the prism assembly and periscopic camera module.

Disclosure of Invention

The present invention is directed to overcome the disadvantages of the prior art, and provides a solution for an assembling structure and an assembling method of a prism and a lens, so as to improve the production yield and consistency of a prism assembly and a periscopic camera module.

To solve the above technical problem, the present invention provides a prism assembly, comprising: the prism is provided with two right-angle surfaces and an inclined surface which are perpendicular to each other, the two right-angle surfaces are an incident surface and an emergent surface respectively, and the inclined surface is a reflecting surface; at least one first lens at the incident end of the prism, wherein the maximum outer diameter of the at least one first lens is smaller than the diameter of a circumscribed circle of the top surface of the prism and larger than the diameter of an inscribed circle of the top surface of the prism; the composite lens barrel comprises a mounting hole, the mounting hole comprises an upper section and a lower section, the overlooking outline of the upper section is circular with a protruding part, a second mounting groove is formed in the circular section in the overlooking outline, the second mounting groove is provided with a step surface for bearing against the bottom surface of the first lens, a first mounting groove is formed in the protruding part in the overlooking outline, and the first mounting groove is communicated up and down, so that the top surface of the prism can penetrate through the upper section; the lower segment is adapted to bear against and secure the prism.

The top surface of the prism is rectangular, the first mounting grooves penetrate through four corners of the upper section of the mounting hole, and the first mounting grooves form a rectangular profile in a top view angle to allow the top surface of the prism to penetrate through the upper section.

The inner side surface of the first mounting groove is provided with a plurality of steps so as to bear against a plurality of optical elements, and the optical elements comprise the first lens, the spacing ring or the shading sheet.

And under a overlooking angle, the distance between the side wall of the first mounting groove and the edge of the top surface of the prism is at least 3 mu m.

Wherein the at least one first lens has a positive refractive power.

Wherein the depth of the upper segment is 0.40mm-1.5 mm.

The prism assembly further comprises a light shading sheet or a space ring which is arranged on the upper section and is positioned on the upper surface of the first lens or positioned between two adjacent first lenses; the overlooking shape of the shading sheet or the space ring is a circular ring shape with four protruding parts, and the outer contours of the four protruding parts form a rectangle matched with the shape of the top surface of the prism.

The top view shape of the at least one first lens is a circular ring shape with four protruding parts, and the outer contour of the four protruding parts forms a rectangle matched with the shape of the top surface of the prism.

Wherein, the longitudinal section of the first mounting groove is provided with an inclined edge, and the inclined angle of the inclined edge is 30-45 degrees.

The lower section forms a prism mounting groove which is rectangular in an overlooking visual angle, and the bottom of the prism mounting groove forms an inclined plane to serve as a bottom bearing surface of the prism.

Wherein, the bearing surface is provided with a convex edge, and the top surface of the convex edge is 10-20 μm higher than the surface of the bottom bearing surface.

And the bottom bearing surface is provided with a plurality of strip-shaped grooves which are strip-shaped under the overlooking angle.

Wherein the longitudinal section of the strip-shaped groove is triangular.

And the light outlet side of the composite lens barrel is provided with a light window, and the edge of the light window is provided with a support piece which is suitable for bearing the emergent surface of the prism.

The lower section is provided with two closed side walls, the two closed side walls correspond to the two parallel side faces of the prism respectively, and grooves are formed in the inner side faces of the two closed side walls.

Wherein the prism is made of glass and the first lens is made of plastic.

Wherein the composite lens barrel is integrally formed.

According to another aspect of the application, still provide a periscopic module of making a video recording, it includes: any of the foregoing prism assemblies; a second lens assembly; and a photosensitive assembly; the second lens assembly is fixed at the emergent end of the prism assembly, and the photosensitive assembly is fixed at the rear end of the second lens assembly.

The second lens assembly comprises a second lens barrel and at least one second lens mounted in the second lens barrel; the second lens barrel comprises a first barrel body and a second barrel body, and the inner diameter of the first barrel body is larger than that of the second barrel body; the first cylinder and the second cylinder are integrally formed.

The first cylinder is in a cut cylinder shape, and the second cylinder is in a cylinder shape; the first cylinder and the second cylinder are integrally formed; wherein, the cutting cylinder shape is the shape of cutting surface formed on the top and/or the bottom by cutting the top and/or the bottom of the cylinder.

Wherein the second lens arranged on the first cylinder is in a cutting circle shape.

The periscopic camera module further comprises a motor, and the second lens barrel is mounted in the motor.

The photosensitive assembly comprises a photosensitive chip and an optical anti-shake module for driving the photosensitive chip to move.

According to yet another aspect of the present application, there is also provided a prism assembly assembling method, including: step 1) preparing a composite lens barrel and a prism which are separated from each other, wherein the prism is provided with two right-angle surfaces and an inclined surface which are perpendicular to each other, the two right-angle surfaces are an incident surface and an emergent surface respectively, and the inclined surface is a reflecting surface; the composite lens barrel comprises a mounting hole, the mounting hole comprises an upper section and a lower section, the overlooking outline of the upper section is circular with a protruding part, a circular section in the overlooking outline forms a second mounting groove, the second mounting groove is provided with a step surface, the protruding part in the overlooking outline forms a first mounting groove, and the first mounting groove is communicated up and down so that the top surface of the prism can penetrate through the upper section; the lower segment has an inclined bearing surface; step 2) extending the prism into the mounting hole from the upper part of the composite lens barrel, enabling the prism to penetrate through the upper section and enter the lower section, and bearing and bonding the inclined surface of the prism to the inclined bearing surface; and step 3) mounting at least one first lens on the step surface of the upper section of the composite lens barrel; wherein the maximum outer diameter of the at least one first lens is smaller than the circumscribed circle diameter of the top surface of the prism and larger than the inscribed circle diameter of the top surface of the prism.

In the step 1), the inclined bearing surface is provided with a convex edge, and the top surface of the convex edge is 10-20 μm higher than the surface of the inclined bearing surface; and the step 2) also comprises arranging glue between the convex edge and the side wall of the composite lens barrel so as to enable the inclined surface of the prism to bear against and be bonded with the inclined bearing surface.

In the step 1), the lower section of the composite lens barrel is provided with a light-emitting side, and the light-emitting side is provided with a light window; the lower section of the composite lens barrel is also provided with two closed side walls corresponding to the prisms respectively, and the inner side surfaces of the side walls are provided with grooves for containing glue; the prism assembly assembling method further comprises: and 4) injecting reinforcing glue into the grooves on the inner side surfaces of the side walls from the light emergent side of the lower section, and solidifying the reinforcing glue to bond and reinforce the prism and the composite lens barrel.

In the step 2), the inclined plane of the prism is bonded to the inclined bearing surface through UV glue; in the step 4), the reinforcing glue is UV glue.

Wherein the step 4) is performed between the step 2) and the step 3).

Compared with the prior art, the application has at least one of the following technical effects:

1. the prism assembly structure and the assembling method are beneficial to improving the production yield and consistency.

2. The prism assembly structure and the assembling method can improve the inclination degree of the assembled prism relative to the lens.

3. The utility model provides a prism subassembly structure helps reducing the size of prism and camera lens to reduce periscopic camera module's volume and occupation space.

Drawings

Fig. 1 is a perspective view of a periscopic camera module according to an embodiment of the present disclosure;

FIG. 2a is a schematic optical path diagram of a first lens group and a reflection prism in an embodiment of the present application;

FIG. 2b is a schematic optical path diagram of the first lens set and the reflection prism when the first lens has negative refractive power;

FIG. 3 illustrates a schematic perspective view of a prism assembly in one embodiment of the present application;

fig. 4 shows a longitudinal sectional perspective view of the composite lens barrel in an embodiment of the present application;

fig. 5 illustrates a longitudinal sectional perspective view of a composite lens barrel having a multi-step according to an embodiment of the present application;

FIG. 6a shows a schematic top view of a gobo or spacer ring in an embodiment of the present application;

FIG. 6b shows a perspective view of a gobo or spacer ring in an embodiment of the present application;

FIG. 7 shows a schematic top view of a shaped first lens in an embodiment of the present application;

fig. 8 shows a schematic cross-sectional view of a composite barrel and a prism to be assembled in an embodiment of the present application;

fig. 9 shows a perspective view of a compound lens barrel in an embodiment of the present application at approximately a top view angle;

fig. 10 is a perspective view of a composite lens barrel according to an embodiment of the present application at an approximate side view angle;

fig. 11 illustrates a glue placement position during assembly of a prism assembly in an embodiment of the present application.

Detailed Description

For a better understanding of the present application, various aspects of the present application will be described in more detail with reference to the accompanying drawings. It should be understood that the detailed description is merely illustrative of exemplary embodiments of the present application and does not limit the scope of the present application in any way. Like reference numerals refer to like elements throughout the specification. The expression "and/or" includes any and all combinations of one or more of the associated listed items.

It should be noted that the expressions first, second, etc. in this specification are used only to distinguish one feature from another feature, and do not indicate any limitation on the features. Thus, a first body discussed below may also be referred to as a second body without departing from the teachings of the present application.

In the drawings, the thickness, size, and shape of an object have been slightly exaggerated for convenience of explanation. The figures are purely diagrammatic and not drawn to scale.

It will be further understood that the terms "comprises," "comprising," "includes," "including," "has," "including," and/or "including," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. Moreover, when a statement such as "at least one of" appears after a list of listed features, the entirety of the listed features is modified rather than modifying individual elements in the list. Furthermore, when describing embodiments of the present application, the use of "may" mean "one or more embodiments of the present application. Also, the term "exemplary" is intended to refer to an example or illustration.

As used herein, the terms "substantially," "about," and the like are used as terms of table approximation and not as terms of table degree, and are intended to account for inherent deviations in measured or calculated values that will be recognized by those of ordinary skill in the art.

Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict.

The invention is further described below with reference to the accompanying drawings and specific embodiments.

Fig. 1 is a perspective view of a periscopic camera module according to an embodiment of the present application. Referring to fig. 1, in the present embodiment, the periscopic optical lens includes a prism assembly 100, a second lens assembly 200, and a photosensitive assembly 300. The prism assembly 100 includes a first lens group, a reflective prism, and a compound lens barrel 103 for assembling the first lens group and the reflective prism. Fig. 1 actually shows only the compound lens barrel 103 and the first lens group 102, and the reflecting prism located below the first lens group 102, which is not directly shown in fig. 1 for simplicity. In addition, the first lens group 102 may include one or more first lenses and other auxiliary optical elements (e.g., a light shielding plate or a spacer ring). For clarity, only the first lens element of the first lens group 102 is shown in fig. 1. Further, fig. 2a shows a schematic optical path diagram of the first lens group and the reflection prism in an embodiment of the present application. Referring to fig. 2a, the first lens group 102 includes at least one lens at the incident end of the reflective prism 101. In this embodiment, the top surface 101a of the reflection prism 101 is an incident surface, and the first lens group 102 is located at the top end of the reflection prism 101. In this embodiment, the first lens group 102 has positive refractive power, and can converge light from an object and then enter the top surface 101a of the prism 101. This design allows the area of the entrance surface of the prism 101 to be reduced, thereby ensuring that the size of the prism does not exceed the size of the first lens group (or the size of the top surface of the prism does not exceed the size of the largest lens in the first lens group). The dimensions of the prism and the lens are referred to herein as the dimensions in a top view. Generally, the lens is circular in shape and its size is its diameter. The surface of the prism is square (or rectangular) and its dimension may be the length of its diagonal. The first lens group with positive refractive power is arranged at the front end of the reflection prism 101, so that the aperture of the imaging channel can be reduced, and the areas of the light incident surface, the reflection surface and the light emitting surface of the prism 101 at the rear end of the reflection prism are reduced. Since the aperture of the imaging channel to be provided inside the prism 101 is reduced, the height of the periscopic camera module (the dimension in the light incident direction, that is, the dimension in the normal direction of the prism incident surface) can be reduced by designing a prism with a smaller volume. In contrast, fig. 2b shows a schematic optical path diagram of the first lens group and the reflection prism in the case that the first lens has negative refractive power. It can be seen that, in the comparative example shown in fig. 2b, since the first lens group has negative refractive power and the aperture of the imaging channel is enlarged, the prism 101 needs to provide the imaging channel with a larger aperture, and therefore the prism 101 needs to have a larger volume, which is not beneficial to reducing the height and volume of the periscopic camera module. Further, referring to fig. 1, in the present embodiment, a second lens group 202 is disposed at the exit end of the prism (i.e. the rear end of the prism). The second lens group 202 may be mounted in the second barrel 201 to constitute the second lens assembly 200. In this embodiment, since the prism optical path is folded, the height of the periscopic imaging module (or periscopic optical lens) is not determined by the optical path length. At this moment, the aperture of each lens of the second lens group is well controlled, and the height of the periscopic camera module can not be increased. For example, the maximum height of the second lens assembly 200 is denoted as L2, and the height of the prism assembly 100 is denoted as L1, such that L2 is not greater than L1. In practical design, the diameter of the lens with the largest aperture in the second lens group and the thickness of the cylinder wall of the section corresponding to the second lens barrel are controlled, so that L2 is not more than L1. In the above embodiment, the lens group having positive refractive power is disposed at the front end of the prism, so that the height of the prism can be reduced by about 2-3mm, thereby reducing the height of the periscopic module. Further, in this embodiment, the photosensitive assembly 300 is located at the rear end of the second lens assembly 200. The photosensitive assembly 300 includes a photosensitive chip for receiving light passing through the optical lens and outputting imaged image data.

Further, fig. 3 shows a perspective view of the prism assembly in one embodiment of the present application. Referring to fig. 3, in the present embodiment, the prism assembly 100 has a composite lens barrel 103 for assembling the first lens group 102 and the reflective prism 101 (refer to fig. 2a in combination). In a camera module, a plurality of optical elements need to be assembled together according to the positional relationship determined by the optical design thereof, so as to achieve the desired imaging quality and camera function. In a general vertical camera module, a plurality of lenses are assembled together through a cylindrical lens barrel, and for a periscopic module, the difficulty of assembling is increased due to the addition of a prism which is a special optical element. In some existing solutions, a housing is separately manufactured for the prism as a structural member, and then the housing is assembled with the lens barrel. In the embodiment, the light incident side and the light emitting side of the prism both have lenses, and if the prism, the light incident side lens group (i.e., the first lens group) and the light emitting side lens group (i.e., the second lens group) are respectively and independently manufactured with corresponding structural members, the structural members may be too many. And when multiple structural members are assembled together, it is easy to introduce greater tolerances during the assembly process. Such assembly tolerance stack-up may lead to a reduction in the uniformity of the finished periscope lens or module and may also lead to a reduction in production yield. The embodiment provides a composite lens cone for assembling the first lens group and the reflecting prism group together. Fig. 4 shows a longitudinal sectional perspective view of the composite lens barrel in an embodiment of the present application. Referring to fig. 3 and 4 in combination, in the present embodiment, the composite lens barrel 103 is substantially rectangular parallelepiped, and has a composite mounting hole 106 therein, and the composite mounting hole 106 has an upper section 106a and a lower section 106 b. The first depth D1 in fig. 4 shows the depth of the upper segment 106a and the second depth D2 shows the depth of the lower segment 106 b. That is, in the composite mounting hole 106, the section corresponding to the first depth D1 is the upper section 106a, and the section corresponding to the second depth D2 is the lower section 106 b. Further, the upper section 106a of the composite mounting hole 106 is used to bear against and secure the first lens group 102. The lower section 106b of the compound mounting hole 106 is used to bear against and secure the prism 101 (see also fig. 2 a). Specifically, the upper segment 106a has a step for mounting the individual lenses of the first lens group 102. The step may include a lateral step face and a vertical face. When the first lens group 102 includes a plurality of lenses, the upper section 106a may have a multi-step structure. Fig. 5 illustrates a longitudinal sectional perspective view of a composite lens barrel having a multi-step according to an embodiment of the present application. Referring to fig. 5, in the present embodiment, the upper section 106a of the composite barrel 106 has multiple steps, wherein each step may include a step surface and a vertical surface. For example, the first step may have a first step face 107b and a first vertical face 107a, the second step may have a second step face 108b and a second vertical face 108a, and the third step may have a third step face 109b and a third vertical face 109 a. Still referring to fig. 3, the upper section 106a may include a first mounting slot 104 and a second mounting slot 105 from a top view. The second mounting groove 105 may be a substantially circular through hole, similar to the mounting groove of the inner surface of the general circular barrel. The first mounting groove 104 is a evasion groove which penetrates four corners of the circular through hole provided in the second mounting groove 105 so that the top surface of the square (or rectangular) prism 101 can pass through the upper section 106a and enter the lower section 106 b. Note that since the first mounting groove 104 is provided therethrough, the first mounting groove 104 may not be provided with a step (i.e., the first mounting groove 104 may not have a step surface). Further, in the present embodiment, the first mounting groove 104 is approximately a right angle in a top view, and the right angle can be matched with four corners of the top surface of the prism 101. The depth of the first mounting groove 104 is 1-1.6 mm. In one embodiment, the depth of the first mounting groove is preferably 1.3mm to ensure that two lenses can be disposed at the front end of the prism. The depth of the first mounting groove 104 refers to a distance between the upper surface of the compound lens barrel 103 and the interface of the upper section 106a and the lower section 106 b. The interface of the upper segment 106a and the lower segment 106b may be a step surface (e.g., the third step surface 109b in fig. 5) for bearing against the bottommost first lens. In other embodiments, the interface between the upper section 106a and the lower section 106b may be lower than the step surface of the first bottommost lens, for example, the top surface of the prism may be regarded as the interface. Further, in order to ensure that the prism is not easily interfered when assembled to the lens barrel, in one embodiment, the distance between the side wall of the first mounting groove and the edge of the top surface of the prism is at least 3 μm (i.e., a gap of at least 3 μm is formed between the side wall of the first mounting groove and the edge of the top surface of the prism at the position of any protruding part). In other words, the first mounting groove forms the rectangular profile with an edge length at least 6 μm greater than the corresponding edge length of the top surface of the prism (the first mounting groove forms the rectangular profile with each edge corresponding to two protrusions, at the location of each protrusion, the side walls of the first mounting groove are each at least 3 μm away from the edge of the top surface of the prism, and thus the rectangular profile edge length is at least 6 μm greater than the corresponding edge of the top surface of the prism). In this embodiment, in order to prevent the size of the lens of the first lens group from further increasing, the outer circle of the lens and the rectangular mounting hole of the prism are selected to interfere with each other, so that the outer circle of the lens does not need to be enlarged to allow the prism to pass through. This further controls the size of the lens.

In the above embodiment, the prism may be a triangular prism having two right-angle surfaces and an inclined surface, or may be a deformed triangular prism formed by cutting corners of the triangular prism. Generally, two right-angle surfaces are perpendicular to each other and serve as an incident surface and an exit surface, respectively, and the inclined surface can serve as a reflecting surface.

Further, in an embodiment of the present application, a light shielding sheet (e.g., SOMA) or a spacer ring may be included in the first lens group. Fig. 6a shows a schematic top view of a gobo or spacer ring in an embodiment of the present application. Fig. 6b shows a perspective view of a gobo or spacer ring in an embodiment of the present application. Referring to fig. 6a and 6b, in the present embodiment, the light shielding sheet or the spacer has a circular ring shape with four protruding portions, and the outer contour of the four protruding portions forms a rectangle adapted to the shape of the top surface of the prism. The shape of the through square avoidance through hole formed by the profiles of the four first mounting grooves is adaptive to that of the through square avoidance through hole. Thus, the four protrusions can be arranged at the positions of the four first mounting grooves, and the design can prevent glue leakage in the glue dispensing step of the assembly process. Specifically, due to the arrangement of the SOMA with the protruding portion, glue does not leak directly from the first mounting groove to the lower side (e.g., from the upper section to the lower section of the composite through hole) during the dispensing step, thereby avoiding causing stains on the prism surface or causing other problems. Note that in the present application, the shapes of the light-shielding sheet and the spacer are adapted to the top profile of the upper section of the composite lens barrel. The top profile of the upper section is actually a composite shape formed by the fusion of the first mounting groove and the second mounting groove. Specifically, the complex shape is a shape in which a partial section protrudes outward on the basis of a circle, and thus such a complex shape is sometimes referred to herein as a circle having a protrusion. In this embodiment, since the top surface of the prism is rectangular, the complex shape includes four protrusions each having a right angle, and the four protrusions may form an interrupted rectangular profile so that the top surface of the prism passes through. It should be noted that the top surface of the prism in the present application is not limited to a rectangle, for example, in other embodiments of the present application, the top surface of the prism may be a rectangular deformed body, such as a polygon formed by cutting out four corner blocks of a rectangle, or a rounded rectangle formed by chamfering a rectangle. At this time, the top profile of the upper section of the composite lens barrel can be adjusted accordingly. At the same time, the top profile of the gobos or spacers can be adjusted accordingly, i.e. the top profile of the gobos or spacers can be a compound shape (e.g. a circle with a protrusion) matching the shape of the upper segment.

Further, in an embodiment of the present application, the first lens group includes at least one shaped first lens. Figure 7 shows a schematic top view of a shaped first lens in an embodiment of the present application. Referring to fig. 7, in the present embodiment, the top view shape of the first lens is substantially circular with four protrusions. The four projections form four right angles, and the outer contours of the four projections may substantially form a rectangle. The rectangle can be matched with the shape of the top surface of the prism, namely the shape of a through square avoidance through hole formed by the outlines of the four first mounting grooves. Thus, the four protrusions can be arranged at the positions of the four first mounting grooves, and the design of the first lens with the special shape can prevent glue leakage in the glue dispensing step of the assembly process. That is, since the first lens having the protruding portion is provided, the glue does not directly leak from the first mounting groove to the lower side (e.g., from the upper section to the lower section of the composite through hole) in the dispensing step, thereby preventing stains from occurring on the surface of the prism or causing other problems. It should be noted that the top surface of the prism in the present application is not limited to a rectangle, for example, in other embodiments of the present application, the top surface of the prism may be a rectangular deformed body, such as a polygon formed by cutting out four corner blocks of a rectangle, or a rounded rectangle formed by chamfering a rectangle. At this time, the top profile of the upper section of the composite lens barrel can be adjusted accordingly. At the same time, the top view profile of the first lens can be adjusted accordingly, i.e. the top view profile of the first lens can be a complex shape (e.g. a circle with protrusions) matching the upper segment shape.

Further, in one embodiment of the present application, in the prism assembly, a longitudinal section of the first mounting groove of the compound lens barrel has a slanted side. Fig. 8 is a schematic cross-sectional view illustrating a composite barrel and a prism to be assembled according to an embodiment of the present application. Referring to fig. 8, in the present embodiment, the inclined angle of the inclined side C is 30 to 45 °. The inclination angle of the inclined edge C is the included angle between the inclined edge and the vertical direction. In this embodiment, the inclined edge may be used to guide the prism for assembly, thereby improving the assemblability of the prism. Specifically, when the prism passes through the upper segment during assembly, even if the prism and the lens barrel interfere with each other due to the contact with the inclined edge (or inclined surface), the prism is guided or tends to move obliquely downward, thereby facilitating assembly. Moreover, the design of the inclined edge is also beneficial to improving the demoulding capability of the composite lens cone. Specifically, the composite lens barrel can be manufactured by adopting a plastic forming process such as molding or injection molding, and when the top of the composite lens barrel is provided with the inclined edge, the formed lens barrel can be demoulded, so that the rough demoulding surface of the lens barrel caused by poor demoulding is avoided.

Further, in one embodiment of the present application, the second mounting groove of the composite lens barrel of the prism assembly has three steps. The first step near the object side is used for installing the shading element, the second step is used for installing a first lens, and the third step is used for installing a second first lens. A spacer (or SOMA) may be provided between the first and second first lenses to prevent stray light generated by the first lens from passing through the second first lens. In this embodiment, the first lens may be understood as a lens located on the light incident side of the prism, and may also be referred to as a light incident side lens. In the present embodiment, there are two incident-side lenses. The first and second first lenses are the lens at the light incident side close to the object side and the lens at the light incident side close to the image side (i.e. the prism incident surface), respectively. And the exit end of the prism (i.e. the back end of the prism) may be provided with a second lens group, and the second lens group may include at least one second lens. The second lens may also be referred to as the light exit side lens. The light exit side lens may be plural. In this embodiment, a spacer (or an SOMA) is disposed on the first lens close to the object side, so that the first lens is prevented from having a stray light risk caused by the diaphragm. Further, in this embodiment, the rubber material may be disposed on the spacer (or the SOMA), and the surface of the spacer or the SOMA may be a rough surface, which may not only reduce stray light, but also increase the bonding strength.

In another embodiment of the present application, the second mounting groove may have only one step for mounting the first lens, and the first lens is the only lens in the first lens group. The upper surface of the first lens may be provided with ink to form a diaphragm. In the modified embodiment, the lens barrel can be directly connected with the lens by arranging a sleeve or an SOMA (spin on alumina) mode, so that the step number of the second mounting groove can be reduced, and the design difficulty and the cost of the composite lens barrel are reduced. In addition, the height increase of the first lens group arranged in front of the prism is also reduced. That is, the number of steps of the second mounting groove arranged at the front end of the prism is not limited to the above-mentioned three-step scheme, and a technician can flexibly adjust the second mounting groove according to actual conditions.

Further, referring to fig. 4 and 8 in combination, in an embodiment of the present application, the lower section 106b of the compound lens barrel 103 forms a prism installation groove. The prism mounting groove is square (or rectangular) in a top view. The bottom of the prism mounting groove forms a 45 ° inclined plane 110. The 45 ° inclined surface 110 may be a continuous integral bearing surface, or may be a strip-shaped bearing surface formed by a plurality of strip-shaped grooves 110b (see fig. 4). The bearing surface can have a convex edge 110a, and the top surface of the convex edge 110a is 10-20 μm higher than the surface of the bearing surface (here, the surface of the bearing surface refers to the surface of the region of the bearing surface where the convex edge is not arranged). In actual installation, the inclined surface of the prism is supported by the convex edge 110a, so that the contact between the inclined surface of the prism and the bearing surface of the composite lens barrel is prevented from being too close. In this embodiment, the inclined plane of the prism is a reflecting surface, and the reflecting surface needs to realize the turning of the light path based on the total reflection principle. If the contact between the inclined surface of the prism and the bottom bearing surface of the composite lens barrel is too close, that is, no dielectric layer (for example, air gap) exists between the inclined surface of the prism and the bottom bearing surface of the lens barrel, the refractive index of the lens barrel manufacturing material directly affects the total reflection function of the inclined surface of the prism, and sometimes even the total reflection function may fail. Therefore, in the embodiment, the convex edge is arranged on the 45-degree bearing surface of the lens barrel, so that the inclined surface of the prism can be prevented from being in too close contact with the bearing surface of the composite lens barrel, and the condition that the total reflection function of the prism is invalid is avoided. The convex edges can be two or three or more, so long as the prism can be supported, and a medium layer is arranged between the inclined surface of the prism and the bottom bearing surface of the composite lens cone. Referring to fig. 4, in one embodiment, the convex edge 110a may be disposed near the side wall 111 of the composite lens barrel 103, so that a glue distribution groove is formed between the side wall 111 of the composite lens barrel 103 and the convex edge 110 a. Thus, during assembly, glue may be disposed between the convex edge 110a and the side wall 111 of the composite lens barrel 103, thereby facilitating adhesion of the bottom surface of the prism (i.e., the inclined surface of the prism) to the composite lens barrel 103.

Further, fig. 9 shows a perspective view of the compound lens barrel in an embodiment of the present application at an approximate top view angle. Referring to fig. 9, in this embodiment, a set of grooves 110b is disposed on a bottom bearing surface (i.e., the inclined surface 110) of the prism installation groove of the compound lens barrel 103. That is, the bottom bearing surface of the prism mounting groove is a strip-shaped bearing surface formed by a plurality of strip-shaped grooves (strip-shaped in a top view). The design with the groove can reduce the shape variation of the lens barrel caused by the shrinkage of the molding or injection molding material during the molding process.

Further, still referring to fig. 9, in one embodiment of the present application, the interval distance between the grooves 110b provided on the bottom seating surface of the prism installation groove is 0.5 to 0.8mm, and the width of the single groove 110b is 0.5 to 0.8 mm. In addition, the groove 110b is in the shape of an isosceles right triangle in longitudinal section, and the side length of the right-angle side of the isosceles right triangle is preferably 5.5-6 mm. In a preferred embodiment, the bottom bearing surface can be provided with three grooves 110b, which not only avoids the problem that the lens barrel is not strong enough due to too many grooves, but also solves the problem that the lens barrel is easy to deform during molding.

Further, fig. 10 shows a perspective view of the composite lens barrel in an embodiment of the present application at an approximate side view angle. The side viewing angle here refers to the viewing angle of the light exit side. With combined reference to fig. 9 and 10, in the present embodiment, an optical window 112 is provided on the light exit side of the compound lens barrel 103, so that the light reflected by the prism exits. The four corners of the light window 112 (or other locations of the edges of the light window) may be provided with support members 112a adapted to bear against the prism exit face. The support 112a may be integrally formed with the main body portion of the composite barrel 103. From a side view (i.e. a view of the light emitting side), each of the supporting members 112a may have a substantially triangular shape, which can avoid the light emitted from the prism, so as to prevent a dark corner from occurring due to the supporting members blocking the light. In the present embodiment, there are four supporting members 112a, and each supporting member 112a is disposed at one corner of the light window. In this embodiment, the lower section of the compound lens barrel 103 further has two closed side walls 111, and the two closed side walls 111 correspond to two sides of the prism respectively. The inner side surfaces 111a of the two side walls 111 may be provided with grooves 111b so as to reduce dimensional changes caused by shrinkage of molding materials when the composite barrel 103 is molded. On the other hand, the groove 111b may also accommodate a glue material, so that two parallel side surfaces of the prism are adhered and fixed to the two side walls 111 of the composite lens barrel 103.

Further, in an embodiment, the side wall 111 of the compound lens barrel 103 further has a light exit side surface 111c facing the light exit side, and the light exit side surface 111c is a surface connecting the inner side surface 111a of the side wall 111 and the outer side surface 111d of the side wall 111. In this embodiment, the light-exiting side surface 111c has an inclined angle, that is, the light-exiting side surface 111c is an inclined surface or at least includes an inclined section (refer to fig. 9 and 10 in combination). One end of the groove 111b may communicate with the light exit side surface 111 c. The design can facilitate the demolding and molding of the composite lens barrel on one hand and also facilitate the arrangement of a glue material (the glue material can also be called glue water) on the other hand. Specifically, the composite barrel 103 may be rotated by 90 degrees so that the light exit side surface 111c faces upward, and then a glue material may be disposed on the light exit side surface 111c, and the glue material may flow to the inner side surface 111a side along the inclined direction of the light exit side surface 111c, and then enter the groove 111 b.

Further, in one embodiment of the present application, the reflection prism may be made of glass, and the first mirror and the second mirror may be made of plastic. The height S1 of the prism assembly is below 8.5mm, and preferably, the height S1 of the prism assembly can be 6.5-8.5 mm.

Further, still referring to fig. 1, in an embodiment of the present application, a second lens assembly 200 is further disposed at a rear end (i.e., a light exit side) of the prism. The second lens assembly 200 includes: a second barrel 201 and at least one second lens mounted within the second barrel 201. Wherein the second barrel 201 may include a first cylinder 201a and a second cylinder 201 b. The first cylinder 201a may have a larger inner diameter than the second cylinder 201b for mounting a second lens of a second lens group 202 having a larger outer diameter. The second cylinder 201b may be cylindrical, the first cylinder 201a may be cut cylindrical, and the first cylinder 201a and the second cylinder 201b may be integrally formed. The cutting of the cylinder is to cut the top and/or bottom of the cylinder to form the shape of cut surfaces at the top and/or bottom. Such a design may reduce the height of the second lens assembly 200, thereby helping to reduce the thickness of the terminal device (e.g., a cell phone). Further, the second lens disposed on the first cylinder may also be in a cutting circle shape. The cut portion may be the non-effective diameter of the second lens, or may include both the non-effective diameter and a portion of the effective diameter.

Further, in one embodiment of the present application, the periscopic camera module may include a motor. The second lens assembly may be mounted inside the motor carrier, and the second lens assembly may move relative to the motor housing, so as to implement functions of auto-focusing or optical anti-shake. Further, in an embodiment of the present application, the photosensitive component may also have a chip anti-shake function (for example, an OIS chip or other structures may be used), that is, the photosensitive chip may move relative to a housing (for example, a housing of the camera module) to compensate for shake of the camera module.

In one embodiment of the present application, there is also provided a method for assembling a prism assembly, which includes the following steps S1-S4.

Step S1, the compound barrel and the prism are prepared separately from each other. The structure and shape of the composite lens barrel and the prism can refer to the description of the foregoing embodiments, and are not repeated herein.

Step S2, a prism is picked up (for example, the prism can be picked up by a suction nozzle), and the prism enters the inside of the composite lens barrel from the top surface of the composite lens barrel, passes through the upper section of the composite lens barrel, and is adhered to the lower section of the composite lens barrel. Glue can be firstly drawn on the lower section of the composite lens cone, and the glue material can be UV glue (or UV glue) for pre-fixing. The UV glue may be arranged on a 45 ° bearing surface of the composite barrel. Specifically, fig. 11 shows the glue arrangement position during the assembly of the prism assembly in one embodiment of the present application, and referring to fig. 11, the UV glue 191 (which may also be referred to as pre-fixing glue) may be arranged in the gap 190 (which is substantially in the shape of a bar) between the convex edge 110a of the bearing surface (which may also be referred to as inclined bearing surface) and the side wall 111 of the composite barrel. After the UV glue 191 (i.e., the pre-fixing glue) is arranged, the prism may be inserted from the top surface of the composite barrel, and then enter the lower section of the composite barrel through the upper section of the composite barrel, and the inclined surface of the prism is supported on the 45 ° supporting surface of the lower section of the composite barrel. At this time, the UV glue 191 is cured by UV light irradiation, thereby fixing the prism to the composite barrel. Wherein the UV light may be irradiated from the light exit side of the prism. In this step, the width of the UV glue 191 (i.e. the pre-fixing glue) disposed between the convex edge 110a and the side wall 111 of the composite barrel is 100 μm-300 μm, and the glue width is smaller than the distance from the convex edge to the side wall of the composite barrel to prevent the glue from overflowing. The top surface of the raised edge 110a is 10-20 μm higher than the surface of the bearing surface (here, the surface of the bearing surface refers to the surface of the region of the bearing surface where the raised edge is not arranged). During actual installation, the inclined surface of the prism is supported by the convex edge, so that the contact between the inclined surface of the prism and the bearing surface of the composite lens barrel is prevented from being too tight. In this embodiment, the inclined plane of the prism is a reflecting surface, and the reflecting surface needs to realize the turning of the light path based on the total reflection principle. If the contact between the inclined surface of the prism and the bottom bearing surface of the composite lens barrel is too close, so that no dielectric layer (such as an air gap) exists between the inclined surface of the prism and the bottom bearing surface of the lens barrel, the total reflection function of the inclined surface of the prism is directly influenced by the refractive index of the lens barrel manufacturing material, and sometimes even the total reflection function may fail. Therefore, in this embodiment, the convex edge is disposed on the 45 ° bearing surface of the lens barrel, so that the inclined surface of the prism can be prevented from being too tightly contacted with the bearing surface of the composite lens barrel (for example, an air gap can be formed between the inclined surface of the prism and the bottom bearing surface of the lens barrel), and the occurrence of failure of the total reflection function of the prism can be avoided.

And step S3, after the prism is mounted on the composite lens barrel, sequentially mounting a lens and other optical elements in a second mounting groove of the composite lens barrel. Wherein, the lens is referred to as a light side lens (or referred to as a first lens). After the last lens is installed, the sleeve is installed to ensure that the first lens group is not influenced by stray light. The second mounting groove of the composite barrel may have a plurality of steps. In this step, the plurality of first lenses of the first lens group may be sequentially mounted from small to large according to the outer diameters thereof.

Step S4, fixing glue is disposed on the light exit side of the prism, the glue is preferably disposed in a groove on the inner side of the composite lens barrel, and the groove on the side wall can prevent the glue from overflowing. In addition, the side wall groove can also reduce the shape change caused by shrinkage in the process of forming the side wall of the lens barrel. In step S2, the bottom surface of the prism (i.e., the inclined surface of the prism) is bonded to the bearing surface of the composite barrel using UV glue. However, the bonding reliability and the fastness of UV glues are not sufficient. In this step, the compound barrel 103 may be rotated by 90 degrees, so that the light-emitting side surface 111c faces upward (with respect to the position of the light-emitting side surface 111c, refer to fig. 9, 10 and 11, but it should be noted that the compound barrel 103 in fig. 9, 10 and 11 is not actually rotated to the posture that the light-emitting side surface 111c faces upward), then the reinforcing glue 192 is disposed on the light-emitting side surface 111c, and the reinforcing glue 192 may flow to the inner side surface 111a side along the inclined direction of the light-emitting side surface 111c, and then enter the groove 111b, that is, the reinforcing glue may enter the channel formed by the groove 111b and the prism side wall. And after the reinforcing glue 192 is cured, the prism and the composite lens cone are completely fixed. In this step, the reinforcing glue disposed in the groove of the inner side surface of the composite lens barrel may also be referred to as fixing glue, which is used to reinforce the adhesion of the pre-fixing glue (e.g., the UV glue disposed on the inclined bearing surface of the composite lens barrel in step S1), so that the prism and the composite lens barrel are completely fixed, thereby improving the reliability and the firmness of the prism assembly. In this embodiment, the reinforcing glue may also be a UV glue, and the UV glue may be cured by exposure. The step S4 is performed after the step S2. Specifically, steps S2 and S3 may be executed first, and then step S4 may be executed, or step S4 may be executed between step S2 and step S3. When step S4 is executed between step S2 and step S3, the prism may be firmly bonded to the composite lens barrel, and then the more complex first lens group is assembled (i.e., the optical elements of the first lens group are sequentially assembled into the composite lens barrel).

Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention and are not limited. Although the present invention has been described in detail with reference to the embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

1. A prism assembly, comprising:

the prism is provided with two right-angle surfaces and an inclined surface which are perpendicular to each other, the two right-angle surfaces are an incident surface and an emergent surface respectively, and the inclined surface is a reflecting surface;

at least one first lens at the incident end of the prism, wherein the maximum outer diameter of the at least one first lens is smaller than the diameter of a circumscribed circle of the top surface of the prism and larger than the diameter of an inscribed circle of the top surface of the prism; and

a composite barrel including a mounting hole including an upper section and a lower section, a top view profile of the upper section being circular with a protrusion, a circular section in the top view profile forming a second mounting groove and the second mounting groove having a step surface for bearing against a bottom surface of the first lens, the protrusion in the top view profile forming a first mounting groove, the first mounting groove being perforated up and down so that a top surface of the prism can pass through the upper section; the lower segment is adapted to bear against and secure the prism.

2. The prism assembly according to claim 1, wherein the top surface of the prism has a rectangular shape, the first mounting grooves are provided through four corners of the upper section of the mounting hole, and the first mounting grooves form a rectangular profile in a plan view to allow the top surface of the prism to pass through the upper section.

3. The prism assembly according to claim 2, wherein the inner side of the first mounting groove has multiple steps for bearing against a plurality of optical elements, the optical elements comprising the first lens, spacer ring or gobo.

4. The prism assembly of claim 2, wherein the side wall of the first mounting groove is at least 3 μm from the top edge of the prism from a top view.

5. The prism assembly of claim 2, wherein the at least one first optic has a positive refractive power.

6. The prism assembly according to claim 2, wherein the upper section has a depth of 0.40mm to 1.5 mm.

7. The prism assembly according to claim 2, wherein the prism assembly further comprises a light shield or spacer ring mounted to the upper section and located at an upper surface of the first lens or located between two adjacent first lenses; the overlooking shape of the shading sheet or the space ring is a circular ring shape with four protruding parts, and the outer contours of the four protruding parts form a rectangle matched with the shape of the top surface of the prism.

8. The prism assembly of claim 2, wherein the at least one first mirror has a circular top shape with four protrusions, and the four protrusions are shaped as a rectangle matching the top surface of the prism.

9. The prism assembly according to claim 2, wherein the longitudinal section of the first mounting groove has a slanted side having a slant angle of 30-45 °.

10. The prism assembly according to claim 2, wherein the lower section forms a prism mounting groove that is rectangular in a top view, and a bottom of the prism mounting groove forms a slope to serve as a bottom bearing surface for the prism.

11. The prism assembly according to claim 10, wherein the bearing surface has a convex edge, and the top surface of the convex edge is 10-20 μm higher than the surface of the bottom bearing surface.

12. The prism assembly of claim 10, wherein the bottom bearing surface has a plurality of elongated grooves that are elongated in plan view.

13. The prism assembly of claim 12, wherein the longitudinal cross-section of the strip-shaped groove is triangular.

14. The prism assembly according to claim 2, wherein the light exit side of the compound barrel is provided with a light window, the edge of which is provided with a support adapted to bear against the exit face of the prism.

15. The prism assembly according to claim 14, wherein the lower section further has two closed side walls corresponding to two parallel sides of the prism, respectively, and wherein inner sides of the two closed side walls are recessed.

16. The prism assembly of claim 2, wherein the prism is made of glass and the first lens is made of plastic.

17. The prism assembly of claim 1, wherein the composite barrel is integrally formed.

18. Periscope formula module of making a video recording, its characterized in that includes:

the prism assembly of any one of claims 1 to 17;

a second lens assembly; and

a photosensitive assembly;

the second lens assembly is fixed at the emergent end of the prism assembly, and the photosensitive assembly is fixed at the rear end of the second lens assembly.

19. The periscopic camera module of claim 18, wherein the second lens assembly includes a second barrel and at least one second lens mounted within the second barrel; the second lens barrel comprises a first barrel body and a second barrel body, and the inner diameter of the first barrel body is larger than that of the second barrel body; the first cylinder and the second cylinder are integrally formed.

20. The periscopic camera module of claim 19, wherein the first cylinder is cut cylindrical and the second cylinder is cylindrical; the first cylinder and the second cylinder are integrally formed; wherein, the cutting cylinder shape is the shape of cutting surface formed on the top and/or the bottom by cutting the top and/or the bottom of the cylinder.

21. The periscopic camera module of claim 20, wherein the second lens disposed in the first cylinder is in the shape of a cutting circle.

22. The periscopic camera module of claim 18, further comprising a motor, the second barrel mounted within the motor.

23. The periscopic camera module of claim 18, wherein the photosensitive assembly comprises a photosensitive chip and an optical anti-shake module for driving the photosensitive chip to move.

24. A method of assembling a prism assembly, comprising:

step 1) preparing a composite lens barrel and a prism which are separated from each other, wherein the prism is provided with two right-angle surfaces and an inclined surface which are perpendicular to each other, the two right-angle surfaces are an incident surface and an emergent surface respectively, and the inclined surface is a reflecting surface; the composite lens barrel comprises a mounting hole, the mounting hole comprises an upper section and a lower section, the overlooking outline of the upper section is circular with a protruding part, a circular section in the overlooking outline forms a second mounting groove, the second mounting groove is provided with a step surface, the protruding part in the overlooking outline forms a first mounting groove, and the first mounting groove is communicated up and down so that the top surface of the prism can penetrate through the upper section; the lower segment has an inclined bearing surface;

step 2) extending the prism into the mounting hole from the upper part of the composite lens barrel, enabling the prism to penetrate through the upper section and enter the lower section, and bearing and bonding the inclined surface of the prism to the inclined bearing surface; and

step 3) mounting at least one first lens on the step surface of the upper section of the composite lens barrel; wherein the maximum outer diameter of the at least one first lens is smaller than the circumscribed circle diameter of the top surface of the prism and larger than the inscribed circle diameter of the top surface of the prism.

25. The method according to claim 24, wherein in step 1), the inclined bearing surface has a convex edge, and the top surface of the convex edge is 10-20 μm higher than the surface of the inclined bearing surface;

and the step 2) also comprises arranging glue between the convex edge and the side wall of the composite lens barrel so as to enable the inclined surface of the prism to bear against and be bonded with the inclined bearing surface.

26. The method according to claim 25, wherein in step 1), the lower section of the composite barrel has a light exit side, and the light exit side has a light window; the lower section of the composite lens barrel is also provided with two closed side walls corresponding to the prisms respectively, and the inner side surfaces of the side walls are provided with grooves for containing glue;

the prism assembly assembling method further comprises:

and 4) injecting reinforcing glue into the grooves on the inner side surfaces of the side walls from the light emergent side of the lower section, and solidifying the reinforcing glue to bond and reinforce the prism and the composite lens barrel.

27. The method according to claim 26, wherein in the step 2), the inclined plane of the prism is bonded to the inclined bearing surface by UV glue;

in the step 4), the reinforcing glue is UV glue.

28. The prism assembly assembling method according to claim 27, wherein the step 4) is performed between the step 2) and the step 3).