Inner pitching angle adjusting mechanism and photoelectric pod

Abstract

The utility model discloses an inner pitching angle adjusting mechanism and a photoelectric pod, and relates to the photoelectric pod control technical field, the inner pitching angle adjusting mechanism comprises an inner pitching frame and a driving portion, an optical bench is rotatably connected in the inner pitching frame, the inner pitching frame is provided with a mounting arm in an outward extending manner around a connecting axis of the inner pitching frame and the optical bench, and the mounting arm is connected with the driving portion. The driving part is fixedly connected with the mounting arm and located on the side, away from the rotation axis of the optical bench, of the mounting arm, and the driving end of the driving part is fixedly connected with the optical bench and used for driving the optical bench to rotate relative to the inner pitching frame; by adopting the mounting arm, the driving part is far away from the connecting axis of the optical bench and the inner pitching frame, namely the driving part is far away from the crowded central area of the inner pitching frame, so that a space is reserved for the installation of other equipment, the maintenance is convenient, and the heat dissipation efficiency is improved; secondly, due to offset installation of the driving part, model selection and installation positions of the driving part are more flexible and diversified; the driving part can adjust the position according to the gravity center to improve the stability and accuracy of equipment.

Description

TECHNICAL FIELD

[0001] The utility model relates to photoelectric pod control technical field, especially to a kind of inner pitch angle adjusting mechanism and photoelectric pod. BACKGROUND

[0002] Photoelectric pod as the key component of modern photoelectric detection and tracking system plays an important role in many fields such as military reconnaissance, aerial surveying and mapping, security monitoring and the like, and its internal inner pitch shaft system is the core mechanism for realizing target observation angle adjustment and accurate positioning, and motor installation mode is directly related to the performance, reliability and maintenance cost of the whole system.

[0003] Currently, the motor installation mode of inner pitch shaft system mainly adopts two kinds of ways, i.e. two-side installation and shaft end installation. The two-side installation mode drives pitch frame or inner pitch frame by installing motors at symmetrical positions. Although this mode can provide stable driving force, it has the risk of large space occupation and uneven weight distribution, and also needs complex synchronous control to ensure the coordinated work of two-side motors. In addition, the installation and maintenance cost of two-side installation mode is relatively high, which is not conducive to the long-term stable operation of the system.

[0004] The shaft end installation mode directly connects the output shaft of motor with the end of driven shaft. Although this mode simplifies transmission structure, it has high requirements for the strength and precision of shaft, and is easily affected by shaft deformation. Once the shaft is deformed or damaged, it will directly affect the driving effect of motor and the stability of system. In addition, the fault maintenance of shaft end installation mode is relatively complex. SUMMARY

[0005] The main purpose of the utility model is to provide an inner pitch angle adjusting mechanism and photoelectric pod, which aims to solve the problem of inconvenient assembly and maintenance of two-side installation and shaft end installation.

[0006] To achieve the above purpose, the inner pitch angle adjusting mechanism provided by the utility model comprises:

[0007] Inner pitch frame, the inner pitch frame is rotationally connected with optical instrument seat, and the inner pitch frame is provided with mounting arm extending outward around the connecting axis of the optical instrument seat;

[0008] Driving part, the driving part is fixedly connected with the mounting arm, and located at the side of the mounting arm away from the rotation axis of the optical instrument seat;

[0009] Wherein, the driving end of the driving part is fixedly connected with the optical instrument seat, to drive the optical instrument seat to rotate relative to the inner pitch frame.

[0010] In an embodiment, the driving part comprises a stator and a rotor, the stator is fixedly connected with the mounting arm, and the stator is located at a bias position of the inner tilt frame;

[0011] The rotor is rotationally connected with the inner tilt frame and coaxial with the rotation axis of the optical bench, and the rotor is fixedly connected with the optical bench to drive the optical bench to rotate relative to the inner tilt frame.

[0012] In an embodiment, the optical bench comprises a mounting frame and a first connecting piece, the first connecting piece is fixedly connected with the mounting frame, and the first connecting piece is rotationally connected with the inner tilt frame;

[0013] The first connecting piece is fixedly connected with the rotor, and the rotor drives the mounting frame to rotate through the first connecting piece.

[0014] In an embodiment, the first connecting piece comprises an extension part, the extension part extends to a side away from the rotation axis of the first connecting piece, and the extension part is fixedly connected with the rotor.

[0015] In an embodiment, the optical bench further comprises a second connecting piece, the second connecting piece is fixedly connected with the mounting frame, and the second connecting piece is rotationally connected with the inner tilt frame;

[0016] The second connecting piece and the first connecting piece are respectively located at opposite sides of the mounting frame, and the second connecting piece and the first connecting piece are coaxially arranged.

[0017] In an embodiment, a plane formed by rotation of the extension part is perpendicular to the rotation axis of the first connecting piece.

[0018] In an embodiment, the optical bench is provided with a limiting buckle near one side of the inner tilt frame, and the inner tilt frame is provided with a limiting part corresponding to the limiting buckle to limit the rotation angle of the limiting buckle.

[0019] In an embodiment, the driving part is a flat voice coil motor.

[0020] The utility model also proposes a kind of photoelectric pod, and the photoelectric pod includes above-mentioned inner tilt angle adjusting mechanism.

[0021] In an embodiment, the photoelectric pod comprises an outer tilt frame, and the outer tilt frame is rotationally connected with the inner tilt frame;

[0022] The rotation axis of the optical bench relative to the inner tilt frame is defined as a first axis, and the rotation axis of the outer tilt frame relative to the inner tilt frame is defined as a second axis;

[0023] The first axis is perpendicular to the second axis.

[0024] The technical scheme of the utility model discloses the mounting arm, makes the drive portion away from the connecting axis of the optical bench and the inner tilt frame, i.e. the drive portion is away from the crowded central region of the inner tilt frame, leaves the space for the installation of other equipment, can also reduce the risk of electromagnetic interference to the sensitive equipment in the central region, and the drive portion is exposed separately, is convenient for maintenance and improves the heat dissipation efficiency, the bias installation of the drive portion makes the selection and installation position of the drive portion more flexible, improves the layout flexibility, and finally, the drive portion can be adjusted according to the gravity center position, improves the equipment stability and accuracy. BRIEF DESCRIPTION OF DRAWINGS

[0025] In order to more clearly illustrate the technical scheme in the embodiments of the utility model or the prior art, the drawings needed to be used in the embodiment or the prior art description will be briefly introduced below, and obviously, the drawings in the following description are only some embodiments of the utility model, and for those skilled in the art, other drawings can also be obtained according to the structure shown in the drawings without creative labor.

[0026] Figure 1 The structural schematic diagram of an embodiment of the inner tilt angle adjusting mechanism provided by the utility model is shown in the figure.

[0027] Figure 2 The structural schematic diagram of an embodiment of the photoelectric pod provided by the utility model is shown in the figure.

[0028] Figure 3 The structural schematic diagram of the optical bench is shown in the figure.

[0029] Figure 4 The structural schematic diagram of the first connecting piece and the drive portion is shown in the figure.

[0030] Figure 5 The structural schematic diagram of the first connecting piece and the drive portion is shown in the figure. Figure 4 The enlarged schematic diagram of the structure at A in the figure.

[0031] EXPLANATION OF DRAWINGS:

[0032] 100, inner tilt angle adjusting mechanism, 1, inner tilt frame, 11, limiting portion, 2, optical bench, 21, mounting bracket, 22, first connecting piece, 221, extension portion, 23, second connecting piece, 24, limiting buckle, 3, mounting arm, 4, drive portion, 41, stator, 42, rotor, 5, outer tilt frame.

[0033] The realization of the utility model, functional characteristics and advantages will be further explained by combining with the embodiments and referring to the drawings. DETAILED DESCRIPTION

[0034] The technical solutions in the embodiments of the utility model will be clearly and completely described below with reference to the drawings in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, rather than all the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the utility model.

[0035] It should be noted that if the embodiments of the utility model involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative positional relationship, movement condition, etc. between components in a certain posture, and if the certain posture changes, the directional indications also change accordingly.

[0036] In addition, if the embodiments of the utility model involve descriptions such as "first", "second", etc., the descriptions of "first", "second", etc. are only for description purposes and cannot be understood as indicating or implying the relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features limited by "first" and "second" can explicitly or implicitly include at least one of the features. In addition, "and / or" or "and / or" appearing throughout the text means that the three parallel solutions are included, for example, "A and / or B" includes A solution, or B solution, or A and B solution. In addition, the technical solutions of each embodiment can be combined with each other, but it must be based on the fact that a person skilled in the art can realize it, and when the combination of technical solutions appears contradictory or unachievable, it should be considered that the combination of technical solutions does not exist and is not within the scope of protection required by the utility model.

[0037] As a key component of modern photoelectric detection and tracking systems, the electro-optical pod plays an important role in many fields such as military reconnaissance, aerial surveying and mapping, security monitoring, etc. The internal inner pitch axis system is the core mechanism for adjusting the target observation angle and accurately positioning, and the motor installation method directly affects the performance, reliability and maintenance cost of the entire system.

[0038] Currently, the motor installation method for the inner pitch axis system mainly adopts two kinds of methods, i.e. two-side installation and shaft end installation. The two-side installation method drives the pitch frame or inner pitch frame by installing motors at symmetrical positions. Although this method can provide stable driving force, it has the risk of large space occupation and uneven weight distribution, and also needs complex synchronous control to ensure the coordinated work of the two-side motors. In addition, the installation and maintenance cost of the two-side installation method is relatively high, which is not conducive to the long-term stable operation of the system.

[0039] The shaft end mounting mode is to connect the output shaft of the motor directly with the end of the driven shaft, which simplifies the transmission structure, but has higher requirements for the strength and precision of the shaft, and is easily affected by the deformation of the shaft, once the shaft is deformed or damaged, the driving effect of the motor and the stability of the system will be directly affected, and the fault maintenance of the shaft end mounting mode is also relatively complex.

[0040] The utility model provides a kind of inner pitch angle adjusting mechanism 100.

[0041] Please refer to Figures 1 to 5 In an embodiment of the utility model, the inner pitch angle adjusting mechanism 100 includes:

[0042] The inner pitch frame 1 is rotatably connected with the optical bench 2, and the installation arm 3 is arranged outside the inner pitch frame 1 around the connection axis of the optical bench 2.

[0043] The driving part 4 is fixedly connected with the installation arm 3 and located on the side of the installation arm 3 away from the rotation axis of the optical bench 2.

[0044] The driving end of the driving part 4 is fixedly connected with the optical bench 2 to drive the optical bench 2 to rotate relative to the inner pitch frame 1.

[0045] It can be understood that the two-side mounting mode needs to reserve enough space on both sides of the pitch frame to place the motor, which may limit the layout of other components in the case of limited internal space of the photoelectric pod. For example, for some pods that need to install large optical sensors or complex signal processing circuit boards inside the frame, the space occupation on both sides may make the installation position of these devices cramped, or even impossible to install.

[0046] It should be noted that because the driving part 4 is exposed separately inside the pod, when the driving part 4 is removed, the connection between the shafting and other parts does not need to be released, the space limitation is greatly reduced, and it is convenient for technicians to troubleshoot and handle faults.

[0047] In addition, the offset mounting mode provides more flexibility for the selection and layout of the driving part 4. Different sizes and powers of the driving part 4 can be selected according to specific performance requirements and installed in the most suitable position. This flexibility is conducive to the upgrading and expansion of the system.

[0048] For example, when the pitch speed or torque of the pod needs to be increased, a larger power drive unit 4 can be replaced, and the size and weight of the new drive unit 4 can be adjusted by adjusting the bias position, without being restricted by the space and layout of the traditional center-mounted method. At the same time, when new auxiliary equipment (such as cooling devices, auxiliary sensors, etc.) is added, the layout of the bias-mounted drive unit 4 is more easily coordinated with the installation position of the new equipment, facilitating the integration and expansion of the system.

[0049] In addition, the drive unit 4 generates heat during operation, and if the drive unit 4 is centrally mounted in the center of the inner pitch frame 1 or other enclosed and crowded areas, heat dissipation may be affected. Bias-mounted drive unit 4 can place the drive unit 4 in a relatively open and well-ventilated location, improving the heat dissipation conditions of the drive unit 4.

[0050] For example, mounting the drive unit 4 on the outer edge of the inner pitch frame 1 provides enough space around it to set up heat sinks or ventilation channels, which facilitates heat dissipation, thereby improving the working efficiency and reliability of the drive unit 4, prolonging the service life of the drive unit 4, and reducing the risk of performance degradation or failure of the drive unit 4 due to overheating.

[0051] Secondly, in actual application, the pod may have changes in center of gravity and unbalanced load due to the installation of different optical lenses, additional equipment, or in different mounting attitudes. The bias-mounted drive unit 4 can be flexibly adjusted according to the center of gravity position, with a balance accuracy of kilograms, so that the driving force of the drive unit 4 can better adapt to these changes.

[0052] For example, when a heavy telephoto lens is installed on one side of the pod, biasing the drive unit 4 to the opposite side of the heavy load can effectively keep the center of gravity of the pod from changing too much, reducing the counterweight, and thus improving the stability and accuracy of the pod during operation.

[0053] Finally, in the pod, the drive unit 4 may generate electromagnetic interference during operation, affecting the normal operation of surrounding electronic equipment (such as imaging sensors, signal processing circuits, etc.). Bias-mounted drive unit 4 can keep the drive unit 4 at a certain distance from sensitive electronic equipment, reducing the risk of electromagnetic interference.

[0054] For example, mounting the motor on the side away from the imaging system, an electromagnetic shielding layer can be placed in between or the distance between them can be increased, thereby reducing the adverse effects of motor electromagnetic radiation on imaging quality and signal transmission, and improving the overall performance of the pod.

[0055] The technical solution of this utility model, by employing the mounting arm 3, allows the drive unit 4 to be located away from the connecting axis between the optical bench 2 and the inner pitch frame 1, that is, away from the crowded central area of ​​the inner pitch frame 1, leaving space for the installation of other equipment and reducing the risk of electromagnetic interference to sensitive equipment in the central area; furthermore, the drive unit 4 is exposed separately, facilitating maintenance and improving heat dissipation efficiency; secondly, the offset installation of the drive unit 4 makes the selection and installation position of the drive unit 4 more flexible and diverse, improving layout flexibility; finally, the drive unit 4 can adjust its position according to the center of gravity, improving equipment stability and accuracy.

[0056] Optionally, the drive unit 4 includes a stator 41 and a rotor 42, the stator 41 is fixedly connected to the mounting arm 3, and the stator 41 is located at an offset position of the inner pitch frame 1;

[0057] The rotor 42 is rotatably connected to the inner pitch frame 1 and is coaxial with the rotation axis of the optical bench 2. The rotor 42 is fixedly connected to the optical bench 2 so as to drive the optical bench 2 to rotate relative to the inner pitch frame 1.

[0058] like Figure 1 As shown, it can be understood that by fixing the stator 41 to the mounting arm 3 and positioning it at an offset position on the inner pitch frame 1, this layout not only saves space and makes the overall structure more compact, but also effectively utilizes space and avoids energy loss during transmission. Simultaneously, the coaxial rotation design of the rotor 42 and the optical bench 2 ensures the accuracy and efficiency of transmission, reducing unnecessary friction and wear.

[0059] Furthermore, the mounting arm 3 can extend the lever arm. When the optical bench 2 is under a large load, the driving part 4 can apply a certain driving force to drive the optical bench 2 to rotate, which can reduce the requirements on the driving part 4. Secondly, by extending the lever arm, the rotation angle of the optical bench 2 can be controlled more precisely, and it is easier to achieve small angle adjustments.

[0060] In some embodiments, the end of the rotor 42 is rotatably connected to the inner pitch frame 1 via a bearing, and the rotation of the rotor 42 drives the optical bench 2 to rotate, thereby realizing the adjustment of the inner pitch angle.

[0061] Optionally, the optical bench 2 includes a mounting frame 21 and a first connector 22, wherein the first connector 22 is fixedly connected to the mounting frame 21 and rotatably connected to the inner pitch frame 1;

[0062] The first connector 22 is fixedly connected to the rotor 42, and the rotor 42 drives the mounting frame 21 to rotate through the first connector 22.

[0063] Understandably, the first connector 22 serves both as a rotating connection and a fixed connection, making the installation process simpler. In addition, when maintenance or replacement of parts is required, the relevant components can be accessed and disassembled more easily, reducing maintenance costs and time costs.

[0064] For example, when the drive unit 4 needs to be replaced or repaired, it can be removed by disconnecting the rotor 42 from the first connector 22, without having to operate on the components on the optical bench 2 shaft system, thus improving maintenance efficiency.

[0065] Optionally, the first connector 22 includes an extension 221 that extends away from the rotation axis of the first connector 22 and is fixedly connected to the rotor 42.

[0066] like Figure 4 As shown, the extension 221 can extend the distance between the rotor 42 and the rotation axis of the optical bench 2 and the inner pitch frame 1, thereby increasing the lever arm length;

[0067] Furthermore, by rationally designing the shape and size of the extension 221, limited space resources can be fully utilized and interference with other components can be avoided. This design helps to optimize the overall layout and structural compactness of the pod.

[0068] In some embodiments, the extension 221 is provided with multiple connecting through holes so that the rotor 42 can be adjusted in installation position according to different usage scenarios, and the installation position can be adjusted without replacing the first connector 22.

[0069] Optionally, the optical bench 2 further includes a second connector 23, which is fixedly connected to the mounting bracket 21 and rotatably connected to the inner pitch frame 1;

[0070] The second connector 23 and the first connector 22 are located on opposite sides of the mounting bracket 21, and the second connector 23 and the first connector 22 are coaxially arranged.

[0071] like Figure 3As shown, it can be understood that the second connector 23 and the first connector 22 form a symmetrical layout, which greatly enhances the connection stability between the mounting bracket 21 and the inner pitch frame 1. With two-point fixation, the mounting bracket 21 can maintain a more stable posture during rotation, reducing swaying or wobble that may be caused by a single-point connection, and improving the load-bearing capacity of the mounting bracket 21.

[0072] Secondly, the coaxial arrangement of the second connector 23 and the first connector 22 helps to optimize torque balance. During rotation, the second connector 23 and the first connector 22 can evenly distribute torque, avoiding system vibration or instability caused by torque imbalance. This design helps to improve the dynamic response speed and stability of the system.

[0073] Optionally, the plane formed by the rotation of the extension 221 is perpendicular to the rotation axis of the first connector 22.

[0074] It should be noted that when the plane formed by the rotation of the extension 221 is perpendicular to the rotation axis of the first connector 22, the smoothness and consistency during rotation are ensured. The rotation trajectory of the extension 221 remains perpendicular to the rotation axis of the first connector, reducing vibration and instability caused by tilting or swaying.

[0075] Furthermore, it can improve the precision control of the rotation angle of the optical bench 2 by the drive unit 4, thereby improving accuracy.

[0076] Optionally, the optical bench 2 is provided with a limiting buckle 24 on the side near the inner pitch frame 1, and the inner pitch frame 1 is provided with a limiting part 11 corresponding to the limiting buckle 24, so as to limit the rotation angle of the limiting buckle 24.

[0077] like Figure 5 As shown, it can be understood that when the optical bench 2 rotates, it will cause the limiting buckle 24 to rotate. The limiting part 11 restricts the movement angle of the limiting buckle 24. The cooperative design of the limiting buckle 24 and the limiting part 11 can precisely control the rotation range of the optical bench 2 relative to the inner pitch frame 1. This ensures that the optical bench 2 will not exceed the predetermined rotation angle during pitch movement, thereby guaranteeing the stability and safety of the system.

[0078] In some embodiments, the limiting part 11 protrudes from the inner pitch frame 1 and is located on opposite sides of the limiting buckle 24 to limit the movement angle of the optical bench 2.

[0079] In some embodiments, the limiting buckle 24 is detachably connected to the second connecting piece 23, the second connecting piece 23 is partially arranged in the inner tilt frame 1, and the limiting buckle 24 is connected to the outer end of the second connecting piece 23 and located on the outer side wall of the inner tilt frame 1, and the outer side wall of the inner tilt frame 1 is provided with the limiting portion 11.

[0080] Further, the first connecting piece 22 is also provided with the limiting buckle 24 to further limit the rotation angle of the optical bench 2.

[0081] Optionally, the driving portion 4 is a flat voice coil motor.

[0082] It should be noted that the driving motor usually adopts a brushless direct current motor, a direct current frameless torque motor, and a stepping motor as a driving unit, and the flat voice coil motor can effectively avoid the crowded central area of the pod and better utilize the space inside the frame by replacing the traditional driving motor.

[0083] The utility model discloses still propose a kind of photoelectric pod, which includes inner tilt angle adjusting mechanism 100, and the specific structure of the inner tilt angle adjusting mechanism 100 refers to the above embodiment, since the photoelectric pod adopts all technical solutions of the above all embodiments, at least has all beneficial effects brought by the technical solutions of the above embodiments, which will not be repeated here.

[0084] As shown in Figure 2 Optionally, the photoelectric pod includes an outer tilt frame 5, which is rotatably connected to the inner tilt frame 1.

[0085] The rotation axis of the optical bench 2 relative to the inner tilt frame 1 is defined as the first axis, and the rotation axis of the outer tilt frame 5 relative to the inner tilt frame 1 is defined as the second axis.

[0086] Among them, the first axis is perpendicular to the second axis.

[0087] It can be understood that the photoelectric pod can be precisely rotated and adjusted in two independent dimensions through the outer tilt frame 5, which not only improves the accuracy of aiming, but also greatly enhances the flexibility of the photoelectric pod, enabling it to quickly respond and lock the target.

[0088] The above is only an exemplary embodiment of the utility model, and does not limit the patent scope of the utility model, and any equivalent structural transformation made by using the utility model specification and drawings, or direct / indirect application in other related technical fields is included in the patent protection scope of the utility model.

Claims

1. An internal pitch angle adjustment mechanism, characterized in that, include: An inner pitch frame, in which an optical bench is rotatably connected, and an mounting arm extends outward from the inner pitch frame around the connection axis with the optical bench; A drive unit is fixedly connected to the mounting arm and is located on the side of the mounting arm away from the rotation axis of the optical bench. The drive end of the drive unit is fixedly connected to the optical bench, which drives the optical bench to rotate relative to the inner pitch frame.

2. The internal pitch angle adjustment mechanism as described in claim 1, characterized in that, The drive unit includes a stator and a rotor, the stator is fixedly connected to the mounting arm, and the stator is located at an offset position of the inner pitch frame; The rotor is rotatably connected to the inner pitch frame and is coaxial with the rotation axis of the optical bench. The rotor is fixedly connected to the optical bench to drive the optical bench to rotate relative to the inner pitch frame.

3. The internal pitch angle adjustment mechanism as described in claim 2, characterized in that, The optical bench includes a mounting frame and a first connector, the first connector being fixedly connected to the mounting frame and rotatably connected to the inner pitch frame; The first connector is fixedly connected to the rotor, and the rotor drives the mounting frame to rotate through the first connector.

4. The internal pitch angle adjustment mechanism as described in claim 3, characterized in that, The first connector includes an extension that extends toward a side away from the rotation axis of the first connector and is fixedly connected to the rotor.

5. The internal pitch angle adjustment mechanism as described in claim 3, characterized in that, The optical bench also includes a second connector, which is fixedly connected to the mounting bracket and rotatably connected to the inner pitch frame; The second connector and the first connector are located on opposite sides of the mounting bracket, and the second connector and the first connector are coaxially arranged.

6. The internal pitch angle adjustment mechanism as described in claim 4, characterized in that, The plane formed by the rotation of the extension is perpendicular to the rotation axis of the first connector.

7. The internal pitch angle adjustment mechanism as described in any one of claims 1 to 6, characterized in that, The optical bench is provided with a limiting buckle on the side near the inner pitch frame, and the inner pitch frame is provided with a limiting part corresponding to the limiting buckle to limit the rotation angle of the limiting buckle.

8. The internal pitch angle adjustment mechanism as described in claim 7, characterized in that, The drive unit is a flat voice coil motor.

9. A photoelectric pod, characterized in that, The optoelectronic pod includes the internal pitch angle adjustment mechanism as described in any one of claims 1 to 8.

10. The photoelectric pod as described in claim 9, characterized in that, The optoelectronic pod includes an outer pitch frame, which is rotatably connected to the inner pitch frame. The rotation axis of the optical bench relative to the inner pitch frame is defined as the first axis, and the rotation axis of the outer pitch frame relative to the inner pitch frame is defined as the second axis. The first axis is perpendicular to the second axis.

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