Smart glasses and temple grip force calculation method thereof

Abstract

This application provides a smart glasses and a method for calculating the clamping force of the temples. The smart glasses include a first fixing member, which includes a first fixing plate and a sleeve portion; a second fixing member, which is used to connect with the main body of the glasses; a movable shaft and an elastic member. One end of the movable shaft is movably inserted through the through hole, and the other end of the movable shaft is rotatably connected to the second fixing member. The elastic member is disposed on the movable shaft and located between the sleeve portion and the second fixing member. When the temples rotate outward relative to the main body of the glasses, the first fixing plate drives the sleeve portion to compress the elastic member. The elastic member in the compressed state can generate a reaction force on the sleeve portion and the first fixing plate, so as to provide clamping force on the temples through the elastic member, thereby ensuring the stability of wearing the smart glasses.

Description

Technical Field

[0001] This application belongs to the field of wearable device technology, specifically, this application relates to a smart pair of glasses and a method for calculating the clamping force of the temples. Background Technology

[0002] In the prior art, the temples and frames of eyeglasses are generally connected by mechanical connection structures such as hinges to facilitate rotation between the temples and the frames. At the same time, the connection structure can also provide clamping force for the temples to hold the wearer's head.

[0003] However, due to the large weight of the VR headset's main unit, the traditional connection structure cannot provide a clamping force that matches the weight of the VR headset's main unit when the wearer wears it, affecting the stability of wearing the VR headset. Summary of the Invention

[0004] One objective of this application is to provide a new technical solution for calculating the clamping force of smart glasses and their temples.

[0005] According to a first aspect of the embodiments of this application, a smart pair of glasses is provided, comprising:

[0006] The first fixing member includes a first fixing plate and a sleeve portion. The first fixing plate is used to connect with the temple of the mirror, and the sleeve portion is movably connected to the first fixing plate. The sleeve portion has a through hole.

[0007] The second fastener is used to connect to the main body of the glasses;

[0008] A movable shaft and an elastic element are provided. One end of the movable shaft is movably inserted through the through hole, and the other end of the movable shaft is rotatably connected to the second fixing element. The elastic element is disposed on the movable shaft and located between the sleeve and the second fixing element.

[0009] When the temple rotates outward relative to the eyeglass body, the first fixing plate drives the sleeve portion to compress the elastic member, so that the elastic member provides a clamping force on the temple.

[0010] Optionally, the second fixing member includes a second fixing plate and a pushing part. The second fixing plate is used to connect with the main body of the glasses. One end of the pushing part is rotatably connected to the other end of the movable shaft, and the other end of the pushing part is rotatably connected to the second fixing plate.

[0011] Optionally, the pushing part includes a push plate and a rotating shaft, and the second fixing plate has a protrusion;

[0012] The rotating shaft is fixed to one end of the push-stop part, and the other end of the movable shaft is rotatably sleeved on the rotating shaft.

[0013] When the temple rotates outward relative to the main body of the glasses, the protrusion abuts against the pusher.

[0014] Optionally, it also includes a retaining cap, which is connected to one end of the movable shaft and stops the sleeve portion away from the elastic member.

[0015] Optionally, the elastic element is a spring, which is sleeved on the movable shaft.

[0016] Optionally, the spring stiffness coefficient ranges from 0.2 to 2 N / mm.

[0017] Optionally, the first fixing plate has a first connecting arm facing the second fixing plate, the second fixing plate has a second connecting arm facing the first fixing plate, and the other end of the pushing part is coaxially and movably connected to the first connecting arm and the second connecting arm.

[0018] Optionally, the rotation angle between the movable shaft and the pusher plate is in the range of 60°-150°;

[0019] The rotation angle between the first fixing plate and the second fixing plate ranges from 90° to 210°.

[0020] According to a second aspect of the embodiments of this application, a method for calculating the temple clamping force of the smart glasses described in the first aspect is provided, including:

[0021] Calculate the length compression ΔA of the elastic element, where the elastic force F = K * ΔA:

[0022] When the temple rotates outward relative to the main body of the glasses, the included angle B between the movable axis and the push-stop part is obtained, and the clamping force F2 = F*cos(180-B);

[0023] Where K is the stiffness coefficient of the elastic element.

[0024] Optionally, the movable shaft and the push-stop portion form a triangle, and the end of the movable shaft away from the push-stop portion and the end of the push-stop portion away from the movable shaft form an expansion gap L, the length of the elastic element is A, and the included angle between the push-stop portion and the expansion gap is C;

[0025] When the temple switches from the initial state to the outward rotation state, L increases from L1 to L2, A decreases from A1 to A2, the included angle B increases from B1 to B2, and the included angle C decreases from C1 to C2.

[0026] △A=A1-A2

[0027] =Sin(C1)*L1 / Sin(B1)-Sin(C2)*L2 / Sin(B2).

[0028] One technical advantage of this application is:

[0029] The smart glasses provided in this application embodiment include a first fixing member, which includes a first fixing plate and a sleeve portion; a second fixing member, which is used to connect with the main body of the glasses; a movable shaft and an elastic member, one end of the movable shaft is movably inserted through the through hole, and the other end of the movable shaft is rotatably connected to the second fixing member. The elastic member is disposed on the movable shaft and located between the sleeve portion and the second fixing member. When the temple rotates outward relative to the main body of the glasses, the first fixing plate drives the sleeve portion to compress the elastic member. The elastic member in the compressed state can generate a reaction force on the sleeve portion and the first fixing plate, so as to provide a clamping force on the temple through the elastic member, thereby ensuring the stability of wearing the smart glasses.

[0030] Other features and advantages of this application will become clear from the following detailed description of exemplary embodiments with reference to the accompanying drawings. Attached Figure Description

[0031] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments of the present application and, together with their description, serve to explain the principles of the present application.

[0032] Figure 1 A schematic diagram of the connection between the first and second fixing members of smart glasses provided in an embodiment of this application. Figure 1 ;

[0033] Figure 2 An exploded view of the connection structure between the first and second fasteners of smart glasses provided in an embodiment of this application;

[0034] Figure 3 A schematic diagram of the connection between the first and second fixing members of smart glasses provided in an embodiment of this application. Figure 2 ;

[0035] Figure 4 A schematic diagram of the connection between the first and second fixing members of smart glasses provided in an embodiment of this application. Figure 3 ;

[0036] Figure 5 A schematic diagram of the connection between the first and second fixing members of smart glasses provided in an embodiment of this application. Figure 4 ;

[0037] Figure 6This is a schematic diagram illustrating the connection between the temples and the main body of smart glasses, as provided in an embodiment of this application.

[0038] Figure 7 This is a schematic diagram of a smart glasses in its initial state, provided as an embodiment of this application.

[0039] Figure 8 This is a schematic diagram of a smart glasses in an outward rotation state provided in an embodiment of this application;

[0040] Figure 9 This is a schematic diagram of the forces acting on a smart pair of glasses when they are rotated outwards, as provided in an embodiment of this application.

[0041] Wherein: 1. First fixing member; 11. First fixing plate; 111. First connecting arm; 12. Sleeve part; 13. Fixing cap; 2. Second fixing member; 21. Second fixing plate; 211. Protrusion; 212. Second connecting arm; 22. Pushing part; 221. Push piece; 222. Rotating shaft; 3. Movable shaft; 31. Baffle; 4. Elastic member;

[0042] 100. Temples; 200. Eyeglasses body. Detailed Implementation

[0043] Various exemplary embodiments of the present application will now be described in detail with reference to the accompanying drawings. It should be noted that, unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the present application.

[0044] The embodiments of this application will now be described in detail, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0045] The terms "first" and "second" in the specification and claims of this application may explicitly or implicitly include one or more of the features. In the description of this application, unless otherwise stated, "multiple" means two or more. Furthermore, "and / or" in the specification and claims indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0046] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0047] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0048] It should be noted that similar labels and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be discussed further in subsequent figures.

[0049] Reference Figure 1 and Figure 2 This application provides a smart glasses embodiment, which can be AR glasses or VR glasses, and the smart glasses include:

[0050] The first fixing member 1 includes a first fixing plate 11 and a sleeve part 12. The first fixing plate 11 is used to connect with the temple 100. The sleeve part 12 is movably connected to the first fixing plate 11. The sleeve part 12 has a through hole.

[0051] The second fastener 2 is used to connect with the eyeglass body 200;

[0052] The movable shaft 3 and the elastic element 4 are provided. One end of the movable shaft 3 is movably inserted through the through hole, and the other end of the movable shaft 3 is rotatably connected to the second fixing element 2. The elastic element 4 is disposed on the movable shaft 3 and located between the sleeve part 12 and the second fixing element 2.

[0053] See Figure 7 and Figure 8When the temple 100 rotates outward relative to the eyeglass body 200, the first fixing plate 11 drives the sleeve portion 12 to compress the elastic member 4, so that the elastic member 4 provides a clamping force on the temple.

[0054] Specifically, see Figure 4 and Figure 5 A baffle 31 is provided at one end of the movable shaft 3 near the second fixing member 2, and the elastic member 4 is sandwiched between the sleeve part 12 and the baffle 31; the sleeve part 12 is rotatably connected to the first fixing plate 11 by two screws; when the temple 100 rotates outward relative to the eyeglass body 200, the first fixing plate 11 drives the sleeve part 12 to move, so that the sleeve part 12 moves towards the second fixing member 2. At this time, the space for the elastic member 4 is reduced, and the sleeve part 12 compresses the elastic member 4 so that it has a restoring elastic force.

[0055] The elastic element 4, in its compressed state, can generate a reaction force on the sleeve portion 12 and the first fixing plate 11, thereby providing a clamping force on the temples. The smart glasses provided in this embodiment utilize a simple assembly of the elastic element 4 and the movable shaft 3. The compression deformation of the elastic element 4 provides a clamping force that matches the weight of the temples 100 and the glasses body 200, ensuring the stability of the smart glasses during wear and improving the consistency of the feel when wearing them.

[0056] The smart glasses provided in this application embodiment include: a first fixing member 1, which includes a first fixing plate 11 and a sleeve portion 12; a second fixing member 2, which is used to connect with the glasses body 200; a movable shaft 3 and an elastic member 4, one end of the movable shaft 3 is movably inserted through the through hole, and the other end of the movable shaft 3 is rotatably connected to the second fixing member 2; the elastic member 4 is disposed on the movable shaft 3 and located between the sleeve portion 12 and the second fixing member 2; when the temple 100 rotates outward relative to the glasses body 200, the first fixing plate 11 drives the sleeve portion 12 to compress the elastic member 4. The elastic member 4 in the compressed state can generate a reaction force on the sleeve portion 12 and the first fixing plate 11, so as to provide a clamping force on the temple through the elastic member 4, thereby ensuring the stability of wearing the smart glasses.

[0057] Optionally, see Figure 5 and Figure 6The second fixing member 2 includes a second fixing plate 21 and a pushing part 22. The second fixing plate 21 is used to connect with the main body of the glasses. One end of the pushing part 22 is rotatably connected to the other end of the movable shaft 3, and the other end of the pushing part 22 is rotatably connected to the second fixing plate 21.

[0058] Specifically, the first fixing plate 11 has a plurality of first mounting holes for connecting to the temple 100, and the second fixing plate 21 has a plurality of second mounting holes for connecting to the eyeglass body 200. The first fixing plate 11 and the temple 100, and the second fixing plate 21 and the eyeglass body 200 can be fixed by a plurality of screws respectively.

[0059] One end of the push-stop part 22 is rotatably connected to the other end of the movable shaft 3, which facilitates the retraction of the first fixing plate 11 and the push-stop part 22 together when the temple 100 is retracted; while the other end of the push-stop part 22 is rotatably connected to the second fixing plate 21, which can form a stable clamping force on the temple 100 after the push-stop part 22 abuts against the second fixing plate 21 when the temple 100 rotates outward relative to the eyeglass body 200.

[0060] In one embodiment, see Figure 1 and Figure 2 The pushing part 22 includes a pusher 221 and a rotating shaft 222, and the second fixing plate 21 has a protrusion 211;

[0061] The rotating shaft 222 is fixed to one end of the push-stop part 22, and the other end of the movable shaft 3 is rotatably sleeved on the rotating shaft 222;

[0062] When the temple 100 rotates outward relative to the eyeglass body 200, the protrusion 211 abuts against the pusher 221.

[0063] Specifically, the two ends of the rotating shaft 222 are pre-fixed by embedding into the mounting groove on the push-stop part 22, and glue or spot welding is performed at the installation position to ensure the stability of the rotating shaft 222 fixed to one end of the push-stop part 22; while the other end of the movable shaft 3 is clearance-fitted with the rotating shaft 222 so that the movable shaft 3 can rotate smoothly relative to the rotating shaft 222.

[0064] When the temple 100 rotates outward relative to the glasses body 200, the pusher 221 is pressed against the protrusion 211 of the second fixing plate 21, and the sleeve 12 compresses the elastic member 4, causing the length of the elastic member 4 to shorten. The elastic member 4 has a restoring elastic force when compressed, and the reaction force of the elastic member 4 can provide a clamping force that matches the weight of the temple 100 and the glasses body 200, ensuring the stability of wearing the smart glasses.

[0065] Optionally, see Figure 1 and Figure 2 The smart glasses also include a fixing cap 13, which is connected to one end of the movable shaft 3 and stops the sleeve portion 12 on the side away from the elastic member 4.

[0066] Specifically, when the temple 100 rotates outward relative to the eyeglass body 200, the first fixing plate 11 drives the sleeve part 12 to move, causing the sleeve part 12 to move closer to the second fixing member 2; while when the temple 100 retracts inward relative to the eyeglass body 200, the first fixing plate 11 drives the sleeve part 12 to move away from the second fixing member 2. In order to prevent the sleeve part 12 from dislodging from the movable shaft 3, the fixing cap 13 at one end of the movable shaft 3 can be used to stop the sleeve part 12 on the side away from the elastic member 4, so as to ensure stable contact between the sleeve part 12 and the elastic member 4.

[0067] In one embodiment, the elastic element 4 is a spring, which is sleeved on the movable shaft 3.

[0068] Specifically, when the spring is sleeved on the movable shaft 3, the movable shaft 3 can guide the spring when it is compressed or reset, preventing the spring from deflecting during deformation and ensuring the stability and service life of the spring deformation.

[0069] Optionally, the spring stiffness coefficient ranges from 0.2 to 2 N / mm.

[0070] Specifically, since the reaction force generated by the spring on the sleeve 12 and the first fixing plate 11 when compressed is proportional to the spring's stiffness coefficient and the amount of compression, when the stiffness coefficient of the spring is in the range of 0.2-2 N / mm, for example, the stiffness coefficient of the spring is selected as 0.4 N / mm, 0.6 N / mm, 0.8 N / mm, 1.2 N / mm or 1.5 N / mm, so as to provide the clamping force to the temple in time when the spring is compressed.

[0071] In addition, depending on the weight of the different glasses body 200, the spring stiffness coefficient can be selected accordingly; for example, when the weight of the glasses body 200 is large, the spring stiffness coefficient can be selected as 2N / mm, and when the weight of the glasses body 200 is small, the spring stiffness coefficient can be selected as 0.2N / mm, so that the compression deformation of the elastic element 4 can provide the temple 100 with a clamping force that matches the weight of the glasses body 200, thus ensuring the stability of the smart glasses when worn.

[0072] Optionally, see Figure 3 and Figure 4 The first fixing plate 11 has a first connecting arm 111 facing the second fixing plate 21, and the second fixing plate 21 has a second connecting arm 212 facing the first fixing plate 11. The other end of the pushing part 22 is coaxially and movably connected to the first connecting arm 111 and the second connecting arm 212.

[0073] Specifically, see Figure 3 The second connecting arm 212 on the second fixing plate 21, the first connecting arm 111 on the first fixing plate 11, and the lower end of the push plate 221 can be rotatably connected together by two screws, ensuring that the second fixing plate 21, the first fixing plate 11, and the push stop 22 can rotate between each other without loosening, thus ensuring the connection stability of the temple 100 when it rotates outward relative to the eyeglass body 200.

[0074] Optionally, the rotation angle between the movable shaft 3 and the push plate 221 is in the range of 60°-150°;

[0075] The rotation angle between the first fixing plate 11 and the second fixing plate 21 is in the range of 90°-210°.

[0076] Specifically, the included angle between the movable shaft 3 and the pusher piece 221 of the push stop 22 includes B1 and B2. Specifically, in the initial state, the rotational included angle between the movable shaft 3 and the pusher piece 221 of the temple is B1, such as... Figure 7 As shown; when the temple is rotated outward, the rotation angle between the movable shaft 3 and the pusher 221 increases to B2, as... Figure 8 As shown.

[0077] To facilitate the wearing of smart glasses and adapt to wearers with different head circumferences, thereby improving the applicability of the smart glasses, the elastic element 4 can maintain a clamping force on the temples when the rotation angle between the movable shaft 3 and the push plate 221 is in the range of 60°-150°, thus ensuring the stability of wearing the smart glasses.

[0078] When the smart glasses are in the storage state, the temples 100 can rotate and retract relative to the glasses body 200, at which time the rotation angle between the first fixing plate 11 and the second fixing plate 21 can be 90°; when the smart glasses are in the wearing state, the temples 100 can unfold relative to the glasses body 200, so that the rotation angle between the first fixing plate 11 and the second fixing plate 21 can reach 180° or greater.

[0079] Furthermore, in order to make the smart glasses adaptable to wearers with larger head circumferences and provide effective clamping for the wearer, the rotation angle between the first fixing plate 11 and the second fixing plate 21 can be 190°, 200° or even 210°.

[0080] This application embodiment also provides a method for calculating the temple clamping force of the smart glasses, including:

[0081] S101, calculate the length compression ΔA of the elastic element, where the elastic force F = K * ΔA:

[0082] S102, when the temple rotates outward relative to the main body of the glasses, the included angle B between the movable axis and the push-stop part is obtained, and the clamping force F2 of the elastic member on the temple is F*cos(180-B).

[0083] Where K is the stiffness coefficient of the elastic element.

[0084] Specifically, see Figure 9 Utilizing the principle of force decomposition, the elastic force F of the elastic element includes F1 and F2. The direction of F1 is perpendicular to the clamping direction, while the direction of F2 is along the clamping direction. The clamping force F2 can ensure that the first fixing member 1 and the second fixing member 2 are rotatably connected in a small space, while the elastic element provides the wearer with a large clamping force.

[0085] Furthermore, the clamping torque applied to the wearer is M = R * F2, where R is the distance from the pushing part to the point of contact between the head and the temple of the glasses, in order to ensure the stability of the smart glasses when worn.

[0086] Optionally, see Figures 7 to 9 The movable shaft and the push-stop portion form a triangle. The end of the movable shaft away from the push-stop portion and the end of the push-stop portion away from the movable shaft form an expansion gap L. The length of the elastic element is A, and the included angle between the push-stop portion and the expansion gap is C.

[0087] When the temple switches from the initial state to the outward rotation state, L increases from L1 to L2, A decreases from A1 to A2, the included angle B increases from B1 to B2, and the included angle C decreases from C1 to C2.

[0088] Then △A=A1-A2

[0089] =Sin(C1)*L1 / Sin(B1)-Sin(C2)*L2 / Sin(B2).

[0090] Specifically, when the temple switches from the initial state to the outward rotation state, the length compression amount ΔA of the elastic element can be calculated based on the distance between the far end of the movable axis and the far end of the push part, as well as the changes in the included angles B and C. This allows for the quantification of the greater clamping force provided by the elastic element to the wearer, thereby improving the clamping accuracy of the smart glasses.

[0091] While specific embodiments of this application have been described in detail by way of examples, those skilled in the art should understand that the above examples are for illustrative purposes only and are not intended to limit the scope of this application. Those skilled in the art should understand that modifications can be made to the above embodiments without departing from the scope and spirit of this application. The scope of this application is defined by the appended claims.

Claims

1. A smart glass, characterized by, include: The first fixing member (1) includes a first fixing plate (11) and a sleeve part (12). The first fixing plate (11) is used to connect with the temple of the mirror. The sleeve part (12) is movably connected to the first fixing plate (11). The sleeve part (12) has a through hole. The second fastener (2) is used to connect with the main body of the glasses; The movable shaft (3) and the elastic element (4) are provided. One end of the movable shaft (3) is movably inserted through the through hole, and the other end of the movable shaft (3) is rotatably connected to the second fixing element (2). The elastic element (4) is provided on the movable shaft (3) and located between the sleeve part (12) and the second fixing element (2). When the temple rotates outward relative to the main body of the glasses, the first fixing plate (11) drives the sleeve (12) to compress the elastic member (4) so ​​that the elastic member (4) provides a clamping force on the temple; The second fixing member (2) includes a second fixing plate (21) and a push-stop part (22). The second fixing plate (21) is used to connect with the main body of the glasses. One end of the push-stop part (22) is rotatably connected to the other end of the movable shaft (3), and the other end of the push-stop part (22) is rotatably connected to the second fixing plate (21). The push-stop part (22) includes a push plate (221) and a rotating shaft (222), and the second fixing plate (21) has a protrusion (211). The rotating shaft (222) is fixed to one end of the push-stop part (22), and the other end of the movable shaft (3) is rotatably sleeved on the rotating shaft (222); When the temple rotates outward relative to the main body of the glasses, the protrusion (211) abuts against the pusher (221).

2. The smart glasses of claim 1, wherein, It also includes a fixing cap (13), which is connected to one end of the movable shaft (3) and stops the sleeve (12) away from the elastic member (4).

3. The smart glasses of claim 1, wherein, The elastic element (4) is a spring, which is sleeved on the movable shaft (3).

4. The smart glasses according to claim 3, characterized in that, The spring has a stiffness coefficient ranging from 0.2 to 2 N / mm.

5. The smart glasses according to claim 1, characterized in that, The first fixing plate (11) has a first connecting arm (111) facing the second fixing plate (21), and the second fixing plate (21) has a second connecting arm (212) facing the first fixing plate (11). The other end of the pusher (22) is coaxially and movably connected to the first connecting arm (111) and the second connecting arm (212).

6. The smart glasses according to claim 1, characterized in that, The rotation angle between the movable shaft (3) and the push plate (221) is in the range of 60°-150°; The rotation angle between the first fixing plate (11) and the second fixing plate (21) ranges from 90° to 210°.

7. A method for calculating the temple clamping force of smart glasses according to any one of claims 1-6, characterized in that, include: Calculate the length compression ΔA of the elastic element, where the elastic force F = K * ΔA: When the temple rotates outward relative to the main body of the glasses, the angle B between the movable axis and the push-stop part is obtained, and the clamping force F2 = F*cos(180-B). Where K is the stiffness coefficient of the elastic element.

8. The method for calculating the temple clamping force according to claim 7, characterized in that, The movable shaft and the push-stop portion form a triangle. The end of the movable shaft away from the push-stop portion and the end of the push-stop portion away from the movable shaft form an expansion gap L. The length of the elastic element is A, and the included angle between the push-stop portion and the expansion gap is C. When the temple switches from the initial state to the outward rotation state, L increases from L1 to L2, A decreases from A1 to A2, the included angle B increases from B1 to B2, and the included angle C decreases from C1 to C2. △A = A1 - A2 =Sin(C1)*L1 / Sin(B1)-Sin(C2)*L2 / Sin(B2).

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