Lens barrel, lens assembly, and imaging device

Abstract

To provide a lens barrel having a collapsible structure that has good optical performance and is compactly accommodated.SOLUTION: A lens barrel has a base barrel, and a lens holding frame that holds a lens and is movably held in an optical axis direction with respect to the base barrel. The base barrel has a first guaranteed surface, and the lens holding frame has a second guaranteed surface. The first guaranteed surface and the second guaranteed surface are in contact with each other in a photographing state and are separated from each other in the optical axis direction in a collapsed state. The lens barrel has an urging member that urges the base barrel and the lens holding frame in a direction different from the optical axis direction so that the first guaranteed surface and the second guaranteed surface are in contact with each other.SELECTED DRAWING: Figure 13

Description

Technical Field

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[0001] The present invention relates to a lens barrel, a lens device, and an imaging device.

Background Art

[0002] Some optical devices such as digital cameras, video cameras, and interchangeable lenses are equipped with a lens barrel that moves a zoom group and a focus group by zooming. When moving from a shooting state to a state where shooting is restricted, such as a storage state, many devices achieve miniaturization of the lens barrel in the storage state by making the distance between adjacent lens groups smaller. To achieve this, in the shooting state, the lens holding frame is held using a biasing member such as a spring, and in the storage state, it is made to abut against other moving members or fixed members, and the lens holding frame is moved against the biasing force of the biasing member.

[0003] Patent Document 1 discloses a configuration in which a lens holding frame is held movably in the optical axis direction on a base moving cylinder that moves by zooming, and in the shooting state, the lens holding frame is made to abut against the end of the base moving cylinder using a biasing member, thereby integrally holding the base moving cylinder and the lens holding frame. And when moving to the storage state, the lens holding frame is made to abut against a fixed part, and the lens holding frame is moved relative to the base moving cylinder against the force of the spring, and a configuration is disclosed in which the entire lens barrel is made compact by reducing the distance between each group of shooting lenses.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In recent years, there has been a demand for smaller lens barrels. Therefore, conventional compact digital cameras have employed a design that reduces the spacing between lens groups when transitioning from a shooting state to a storage state where shooting is restricted, thereby achieving a smaller size. This type of design is increasingly being adopted for interchangeable lenses in SLR and mirrorless cameras.

[0006] However, maintaining optical performance requires keeping the positional accuracy of each lens group very high. Patent Document 1 describes a mechanism in which, in the shooting state, the contact portion (protruding piece) of the lens holding frame is abutted against the end wall of the base moving cylinder by a biasing member. However, the details of the contact portion are not disclosed, and there is a possibility that the lens holding frame may tilt or become loose relative to the base moving cylinder.

[0007] Furthermore, there is no detailed disclosure regarding the movement guide structure of the lens retaining frame relative to the base moving barrel. Even if the outer diameter of the lens retaining frame and the inner diameter of the base moving barrel are fitted together, a gap is necessary for movement, which may cause eccentricity due to the play in the fitting and potentially degrade optical performance.

[0008] The present invention aims to provide a lens barrel with a compact, retractable structure that has good optical performance. [Means for solving the problem]

[0009] The lens barrel of the present invention is First Hold the lens hand Optical axis direction fart movable Na First lens retaining frame and , a base lens barrel that holds the first lens retaining frame and It has, One of the base lens barrel and the first lens retaining frame is provided with a first guide shaft member extending in the optical axis direction, and the other is provided with two first fitting holes that slidably engage with the first guide shaft member in the optical axis direction, and the other of the base lens barrel and the first lens retaining frame is prevented from rotating around the first guide shaft member by a first rotation prevention mechanism. The aforementioned base lens barrel has a first safety surface implied , the above First The lens retaining frame has a second warranty surface. implied The first and second guarantee surfaces are in contact with each other in the shooting state, and are in contact with each other in the retracted state. light Axial axis fart They are spaced apart so that the first and second guarantee surfaces come into contact with each other.、 A direction different from the optical axis direction fart The base lens barrel and the First A biasing member that biases the lens holding frame Furthermore is provided.

Advantages of the Invention

[0010] According to the present invention, it is possible to provide a lens barrel having a retractable structure that can be compactly housed and has good optical performance.

Brief Description of the Drawings

[0011] [Figure 1] (a) Front perspective view and (b) rear perspective view of the interchangeable lens and digital camera according to Embodiment 1 of the present invention. [Figure 2] Block diagram showing the configuration of the interchangeable lens and digital camera of Embodiment 1. [Figure 3] Cross-sectional view of the interchangeable lens (wide-angle end during shooting) of Embodiment 1. [Figure 4] Cross-sectional view of the interchangeable lens (telephoto end during shooting) of Embodiment 1. [Figure 5] Cross-sectional view of the interchangeable lens (retracted end when not shooting) of Embodiment 1. [Figure 6] Cross-sectional view of the main part showing the state of the interchangeable lens of Embodiment 1 at the closest distance in the wide-angle end. [Figure 7] Cross-sectional view of the main part showing the housed state of the interchangeable lens in FIG. 6. [Figure 8] Perspective view showing the holding structure of the focus group in the state of being closest to the wide-angle end. [Figure 9] Perspective view showing the holding structure of the focus group in the housed state. [Figure 10] Perspective view of the lens mount 102 as viewed from the object side. [Figure 11] Perspective view for explaining the holding structure of the fifth zoom group in the state of being closest to the wide-angle end. [Figure 12] Perspective view for explaining the holding structure of the fifth zoom group in the housed state. [Figure 13] Perspective view showing only the fifth zoom group in the state of being closest to the wide-angle end shown in FIG. 11. [Figure 14] Front view of the rear group base cylinder in the stored state as seen from the object side. [Figure 15] Side view of the rear group base cylinder in the stored state shown in Fig. 14. [Figure 16] Cross-sectional view of the rear group base cylinder cut along line A-A in Fig. 15. [Figure 17] Figure showing the shooting state as a cross-sectional view of the rear group base cylinder cut along line B-B in Fig. 14. [Figure 18] Figure showing the stored state as a cross-sectional view of the rear group base cylinder cut along line B-B in Fig. 14. [Figure 19] Perspective view of the 5-group lens holding frame as seen from the image side. [Figure 20] Figure explaining the guarantee surface in a front view of the 5-group lens holding frame as seen from the image side. [Figure 21] Front view of the rear group base cylinder as seen from the object side. [Figure 22] Figure explaining the biasing force in a front view of the 5-group lens holding frame as seen from the image side. [Figure 23] Front view of the 5-group lens holding frame of Example 2 as seen from the image side.

Mode for Carrying Out the Invention

[0012] [Example 1] Hereinafter, Example 1 of the present invention will be described with reference to the drawings. The same reference numerals throughout the drawings indicate the same or corresponding parts. In Example 1, an interchangeable lens, which is an example of an optical device, will be described. However, the present invention can be variously modified and changed within the scope of its gist, such as in a lens-integrated camera.

[0013] Figures 1(a) and 1(b) show the external appearance of an interchangeable lens 101 and a digital camera (hereinafter referred to as the camera body) 1 to which the interchangeable lens 101 is detachably attached, which are embodiments of the present invention. Figures 1(a) and 1(b) are perspective views showing the front and rear sides, respectively. As shown in Figure 1(a), the direction in which the optical axis of the imaging optical system housing the interchangeable lens 101 extends is defined as the X-axis direction, and the directions perpendicular to this are defined as the Z-axis direction (horizontal direction) and the Y-axis direction (vertical direction). Hereinafter, the Z-axis direction and the Y-axis direction will be collectively referred to as the Z / Y-axis direction. The rotation direction around the Z-axis will be defined as the pitch direction, and the rotation direction around the Y-axis will be defined as the yaw direction. The pitch direction and the yaw direction (hereinafter collectively referred to as the pitch / yaw direction) are the directions of rotation around two axes, the Z-axis and the Y-axis, which are orthogonal to each other.

[0014] The left side of the camera body 1 (when viewed from the front, towards the shooting lens) (right side when viewed from the back) is provided with a grip section 2 for the user to hold the camera body 1 with their hand. A power control unit 3 is located on the top surface of the camera body 1. When the user turns on the power control unit 3 while the camera body 1 is powered off, power is supplied, the camera body 1 powers on, and computer programs such as focus group origin detection are executed, putting the camera into shooting standby mode. Conversely, when the user turns off the power control unit 3 while the camera body 1 is powered on, the camera body 1 powers off.

[0015] Furthermore, the top surface of the camera body 1 is equipped with a mode dial 4, a shutter release button 5, and an accessory shoe 6. The user can switch between shooting modes by rotating the mode dial 4. The shooting modes include a manual still image shooting mode in which the user can arbitrarily set shooting conditions such as shutter speed and aperture value, an auto still image shooting mode that automatically obtains the appropriate exposure amount, and a video shooting mode for shooting videos. In addition, the user can instruct preparatory actions for shooting, such as autofocus and automatic exposure control, by half-pressing the shutter release button 5, and can instruct shooting by fully pressing it. Accessories such as external flashes can be attached to the accessory shoe 6 in a detachable manner.

[0016] The interchangeable lens 101 is mechanically and electrically connected to a camera mount 7 provided on the camera body 1 via a lens mount 102, which is the mounting part for the camera body 1. Inside the interchangeable lens 101 is an imaging optical system that forms an image of the subject by focusing light from the subject. A zoom operation ring 103, which can be rotated around the optical axis by user operation, is provided on the outer circumference of the interchangeable lens 101. When the zoom operation ring 103 is rotated by the user, the zoom group constituting the imaging optical system moves to a predetermined usage position corresponding to the angle of the zoom operation ring 103. In this way, the user can take pictures at the desired angle of view.

[0017] As shown in Figure 1(b), the rear of the camera body 1 is provided with a rear control unit 8 and a display unit 9. The rear control unit 8 includes multiple buttons and dials to which various functions are assigned. When the camera body 1 is powered on and a still image or video shooting mode is set, the display unit 9 displays a through image of the subject being captured by the image sensor, which will be described later. The display unit 9 also displays shooting parameters indicating shooting conditions such as shutter speed and aperture value, and the user can change the settings of the shooting parameters by operating the rear control unit 8 while viewing the display. The rear control unit 8 includes a playback button for instructing playback of recorded images, and when the user operates the playback button, the captured images are displayed on the display unit 9.

[0018] Figure 2 is a block diagram showing the electrical and optical configuration of the interchangeable lens 101 and the camera body 1. The camera body 1 includes a power supply unit 10 that supplies power to the camera body 1 and the interchangeable lens 101, and an operation unit 11 that includes the aforementioned power operation unit 3, mode dial 4, release button 5, rear operation unit 8, and touch panel function of the display unit 9. The overall system control of the camera body 1 and the interchangeable lens 101 is performed by the cooperation of the camera control unit 12 provided in the camera body 1 and the lens control unit 104 provided in the interchangeable lens 101. The camera control unit 12 reads and executes a computer program stored in the memory unit 13. At that time, the camera control unit 12 communicates with the lens control unit 104 via the communication terminal of the electrical contact 105 provided in the lens mount 102, and communicates various control signals and data. The electrical contact 105 includes a power terminal that supplies power from the power supply unit 10 to the interchangeable lens 101.

[0019] The imaging optical system of the interchangeable lens 101 includes a zoom group 110 connected to the zoom operation ring 103, which moves in the optical axis direction to change the angle of view, and a lens vibration damping group 112 including a shift lens as a vibration damping element. The lens vibration damping group 112 reduces image shake by moving (shifting) in the Z / Y axis direction perpendicular to the optical axis. The imaging optical system also includes an aperture 301 that performs light intensity adjustment and a focus group 114 including a focus lens that moves in the optical axis direction to adjust the focus. Furthermore, the interchangeable lens 101 includes a vibration damping drive unit 201 that moves the lens vibration damping group 112, an aperture drive unit 302 that drives the aperture 301, and a focus drive unit 401 that moves the focus group 114.

[0020] The camera body 1 includes a shutter unit 14, a shutter drive unit 15, an image sensor 16, an image processing unit 17, a focus detection unit 18, and the aforementioned camera control unit 12. The shutter unit 14 controls the amount of light that is imaged by the imaging optical system in the interchangeable lens 101 and exposed to the image sensor 16. The image sensor 16 converts the subject image formed by the imaging optical system into an image signal. The image processing unit 17 performs various image processing on the image signal and then generates an image signal. The display unit 9 displays the image signal (through image) output from the image processing unit 17, displays the shooting parameters as described above, and plays back and displays the captured image recorded in the storage unit 13 or a recording medium (not shown).

[0021] The camera control unit 12 controls the focus drive unit 401 in response to shooting preparation operations on the operation unit 11 (such as half-pressing the release button 5). For example, when autofocus operation is instructed, the focus detection unit 18 determines the focus state of the subject image formed by the image sensor 16 based on the image signal generated by the image processing unit 17, generates a focus signal, and transmits it to the camera control unit 12. At the same time, the focus drive unit 401 transmits information regarding the current position of the focus group 114 to the camera control unit 12. The camera control unit 12 compares the focus state of the subject image with the current position of the focus group 114, calculates the focus drive amount from the amount of deviation, and transmits it to the lens control unit 104. The lens control unit 104 then moves the focus group 114 to the target position in the optical axis direction via the focus drive unit 401, and corrects the focus deviation of the subject image.

[0022] As will be explained in more detail later, the focus drive unit 401 includes a focus motor and a photo interrupter that detects the origin position of the focus group 114. Generally, a stepping motor, which is a type of actuator, is often used as the focus motor. However, since a stepping motor can only control the relative amount of drive, the current position of the focus group 114 is uncertain when the camera body 1 is powered off. Also, even if the camera body 1 remains powered on, if the power supply to the interchangeable lens 101 is interrupted, such as by mechanically removing the interchangeable lens 101 from the camera mount 7 of the camera body 1, the focus group 114 will remain in the position it was in when the power was cut off and will become undetectable. When the user turns on the power control unit 3 from this state where the current position of the focus group 114 is uncertain, the focus group 114 must first be moved to the origin position and the origin detection process performed before reaching the shooting standby state. Note that a DC motor equipped with an encoder or an ultrasonic motor may be used as the actuator. Furthermore, while a photointerrupter directly receives light emitted from a light-emitting unit at a light-receiving unit, alternatively, a photoreflector that receives reflected light from a reflective surface or a brush that electrically detects a signal by contacting a conductive pattern may be used.

[0023] Furthermore, the camera control unit 12 controls the driving of the aperture 301 and shutter unit 14 via the aperture drive unit 302 and shutter drive unit 15, according to the aperture value and shutter speed settings received from the operation unit 11. For example, when automatic exposure control is instructed, the camera control unit 12 receives the luminance signal generated by the image processing unit 17 and performs photometric calculations. Based on the results of these photometric calculations, the camera control unit 12 controls the aperture drive unit 302 in response to the shooting instruction operation on the operation unit 11 (such as fully pressing the release button 5). At the same time, the camera control unit 12 controls the driving of the shutter unit 14 via the shutter drive unit 15 and performs exposure processing by the image sensor 16.

[0024] The camera body 1 has a pitch shake detection unit 19 and a yaw shake detection unit 20 as shake detection means capable of detecting image shake caused by user hand shake, etc. The pitch shake detection unit 19 and the yaw shake detection unit 20 each use an angular velocity sensor (vibration gyro) and an angular acceleration sensor to detect image shake in the pitch direction (rotation direction around the Z axis) and yaw direction (rotation direction around the Y axis), and output shake signals. The camera control unit 12 uses the shake signal from the pitch shake detection unit 19 to calculate the shift position of the lens vibration isolation group 112 in the Y axis direction. Similarly, the camera control unit 12 uses the shake signal from the yaw shake detection unit 20 to calculate the shift position of the lens vibration isolation group 112 in the Z axis direction. Then, according to the calculated pitch / yaw direction shift position, the camera control unit 12 moves the lens vibration isolation group 112 to the target position in the Z / Y axis direction via the vibration isolation drive unit 201, thereby reducing image shake during exposure and through-image display.

[0025] The interchangeable lens 101 has a zoom operation ring 103 for changing the angle of view of the imaging optical system, and a zoom detection unit 106 for detecting the angle of the zoom operation ring 103. The zoom detection unit 106 detects the angle of the zoom operation ring 103 operated by the user as an absolute value, and is configured, for example, using a resistive linear potentiometer. The information regarding the angle of view detected by the zoom detection unit 106 is transmitted to the lens control unit 104 and reflected in the various controls performed by the camera control unit 12 described above. On the other hand, some of this information is recorded together with the captured image in the storage unit 13 or a recording medium (not shown).

[0026] Next, the positional relationships of the main components of the interchangeable lens 101 will be explained using Figures 3, 4, and 5. Figures 3, 4, and 5 are cross-sectional views on the XY plane including the optical axis. The center line shown here substantially coincides with the optical axis determined by the imaging optical system, and therefore will be considered synonymous with the optical axis hereafter. Figures 3 and 4 show the wide-angle end on the short-focus side and the telephoto end on the long-focus side of the zoom, respectively, and both are in a state where photography is possible. On the other hand, Figure 5 shows the retracted state (so-called collapsible state) where photography is restricted, and shows the state in which the overall length is shortened in the optical axis direction. As shown in Figure 5, the lens device (lens barrel) of the present invention has a collapsible mechanism and has a configuration that allows the overall length in the optical axis direction to be shortened when not in use, making it compact.

[0027] As shown in Figures 3 and 4, in this embodiment, a six-group configuration is adopted as an example of an imaging optical system. The zoom group 110 moves to different predetermined operating positions at the wide-angle end and the telephoto end to focus light from the subject onto the image sensor 16. The zoom group 110 consists of a first zoom group 111, a lens image stabilization group 112 functioning as a second zoom group, an aperture 301, a third zoom group 113, a focus group 114 functioning as a fourth zoom group, a fifth zoom group 115, and a sixth zoom group 116. It should be noted that the present invention does not limit the configuration of the imaging optical system; for example, the lens image stabilization group 112 and the focus group 114 may function as other zoom groups. Also, some of the lens groups may be fixed rather than movable.

[0028] The straight guide tube 107 is a fixed component that is fixed to the lens mount 102 via the fixed tube 117 (see Figure 6). Cam grooves (not shown) are formed at equal intervals on the outer surface of the straight guide tube 107. On the other hand, a cam follower (not shown) is provided on the inner circumference of the cam tube 108. Furthermore, the cam tube 108 is connected to the zoom operating ring 103 via a key (not shown). When the zoom operating ring 103 is rotated, the cam tube 108 moves back and forth in the direction of the optical axis while rotating around the optical axis due to the engagement of the cam grooves and the cam follower.

[0029] The linear guide cylinder 107 has linear guide grooves formed at equal intervals to restrict the rotational movement of the zoom group 110 and guide it to move in a straight line in the optical axis direction. The cam cylinder 108 also has cam grooves formed at equal intervals, corresponding to the zoom group 110, each having a different angle of trajectory in the rotational direction. On the other hand, the zoom group 110 is provided with multiple cam followers, each cam follower fitted into its corresponding linear guide groove and cam groove. When the user rotates the zoom operating ring 103, the cam cylinder 108 rotates, and the cam followers, through the fitting of the linear guide grooves and cam grooves, restrict rotational movement while moving the zoom group 110 back and forth in the optical axis direction.

[0030] The interchangeable lens 101 in this embodiment has a mechanism (details not shown) for retracting the lens image stabilization group 112 out of the optical axis. This allows the zoom group 110 to be moved further towards the rear (camera body 1 side) when stored, thereby shortening the overall length of the interchangeable lens 101 and improving portability. At the wide-angle end in Figure 3, the distance between the first zoom group 111 and the lens image stabilization group 112 is wide, while at the telephoto end in Figure 4, the distance between the fifth zoom group 115 and the sixth zoom group 116 is wide. In the stored position, the distances between each of these lens groups are narrowed, shortening the overall length in the optical axis direction when stored.

[0031] As shown in Figure 5, in the retracted state, the zoom group 110 moves to a position close to each other. From this state, for example, if the user rotates the zoom operation ring 103 to the wide-angle end, the zoom group 110 moves toward the subject and moves to a predetermined usage position, resulting in the shooting state shown in Figure 3. Since this mechanism is a well-known technology that has been used in many optical instruments to date, a detailed explanation is omitted here.

[0032] Furthermore, in the shooting state shown in Figures 3 and 4, all zoom groups 110 are arranged on the same optical axis, but in the stored state shown in Figure 5, the lens image stabilization group 112 is retracted in a direction perpendicular to the optical axis (radial direction). From the shooting-ready state shown in Figure 3, if, for example, the user rotates the zoom operation ring 103 to the end of the stored state, the zoom groups 110 begin to move toward the camera body 1, and at the same time, the lens image stabilization group 112 retracts from the optical axis position that has moved in a direction perpendicular to the optical axis. Into the space thus created on the image sensor side, the first zoom group 111 moves further and is stored so as not to interfere with each other, resulting in the state with the shortest overall length shown in Figure 5. Since this retraction mechanism of the lens image stabilization group 112 is a well-known technology that has been used in many optical instruments to date, a detailed explanation is omitted here.

[0033] Next, the detailed configuration of the latter group according to the present invention will be described. Figure 6 is a cross-sectional view of the main part showing the wide-angle end close-up of the interchangeable lens embodying the present invention, and Figure 7 is a cross-sectional view of the main part showing the interchangeable lens of Figure 6 moved to the stored position.

[0034] In Figures 6 and 7, the rear group base barrel (base lens barrel) 118 holds an aperture 301 (not shown), a third zoom group 113, a focus group 114, a focus drive unit 401 (not shown), and a fifth zoom group 115, and moves together with these components during zooming. The rear group base barrel 118 has three cam followers 120 at equal positions on its outer circumference. The cam followers 120 engage with tapered inner circumferential cam grooves 108a provided on the inner circumference of the cam cylinder 108, and the engaging portion 120a of each cam follower 120 is conical in shape and configured to make line contact with the inclined surface of the inner circumferential cam groove 108a. In addition, the inner circumferential portion 120b of the cam follower 120 engages with a straight groove 107a provided on the straight guide cylinder 107, and the rear group base barrel 118 moves in the optical axis direction by rotating the cam cylinder 108.

[0035] Figures 8 and 9 are perspective views showing the holding structure of the focus group (second lens) 114. Figure 8 shows the wide-angle end close-up state, and Figure 9 shows the retracted state.

[0036] In Figures 8 and 9, the 4-group lens holder frame (second lens holder frame) 141 holds the lenses constituting the focus group 114. The guide bar 142 (second guide shaft member) is a metal member fixed to the rear group base cylinder 118 and is slidably (movably) engaged with the sliding holes 141a and 141b (two second fitting holes spaced apart in the optical axis direction) provided in the 4-group lens holder frame 141. The guide bar 142, sliding holes 141a and 141b constitute a second guide mechanism that allows the rear group base cylinder 118 and the 4-group lens holder frame 141 to move relative to each other in the optical axis direction. Similarly, the guide bar 143, fixed to the rear group base cylinder 118, engages with the U-shaped groove 141c provided in the 4-group lens holder frame 141. This creates a second anti-rotation mechanism with the guide bar 143 and the U-shaped groove 141c, preventing the rotation of the 4-group lens holding frame 141 around the guide bar 142, and the 4-group lens holding frame 141 is held so as to be movable in the optical axis direction relative to the rear group base barrel 118.

[0037] The rack holder 144 has a through hole into which the guide bar 142 is inserted. The rack holder 144 is held so as to be movable in the axial direction of the guide bar 142, and rotation around the through hole is prevented by the boss 144a engaging with an elongated hole 141d provided in the 4-group lens holding frame 141. The rack holder 144 is biased by a coil spring 145 so that its end 144b is pressed against the sliding hole 141b side of the 4-group lens holding frame 141.

[0038] The rack 146 engages with the lead screw 147a of the stepper motor 147, which constitutes the focus drive unit 401 (see Figure 16). The rack 146 is configured such that its rotating shaft portion 146a engages with the shaft hole 144c of the rack holder 144, allowing rotation only around the shaft hole 144c. This ensures stable engagement even if the lead screw 147a of the stepper motor 147 vibrates due to variations in part precision. With this configuration, the stepper motor 147 can drive the 4-group lens holding frame 141 to move in the optical axis direction.

[0039] In the storage state shown in Figure 9, the rear group base cylinder 118 moves, causing the contact portion 141e on the 4-group lens holding frame 141 to abut against the 4-group contact portion 102a (see Figure 10) on the fixed lens mount 102. As a result, the rack 146 engages with the lead screw 147a and does not move, compressing the coil spring 145, which allows the 4-group lens holding frame 141 to move relative to the rear group base cylinder 118.

[0040] Figure 10 is a perspective view of the lens mount 102 as seen from the object side. Figures 11 and 12 are perspective views illustrating the holding structure of the fifth zoom group 115 according to the present invention. Figure 11 shows the wide-angle end close-up state, and Figure 12 shows the retracted state. Figure 13 is a perspective view showing only the fifth zoom group 115 in the same state as in Figure 11.

[0041] In Figure 11, the 5-group lens holder frame 151 holds the lenses constituting the fifth zoom group 115. The guide bar (guide shaft member) 143 is a metal member fixed to the rear group base cylinder 118 and is slidably (movably) engaged with the sliding holes 151a and 151b (two fitting holes spaced apart in the optical axis direction) provided in the 5-group lens holder frame 151. The guide bar 143, sliding holes 151a and 151b constitute a guide mechanism that allows the rear group base cylinder 118 and the 5-group lens holder frame 151 to move relative to each other in the optical axis direction. Furthermore, a rotation-preventing structure, described later, prevents the 5-group lens holder frame 151 from rotating around the guide bar 143, and the 5-group lens holder frame 151 is held so as to be movable in the optical axis direction relative to the rear group base cylinder 118. The guide bar 143 serves both to prevent the rotation of the 4-group lens retaining frame 141 and to guide the movement of the 5-group lens retaining frame 151 in the optical axis direction.

[0042] The coil spring 153 is a tension coil spring having circular hooks 153a and 153b at both ends. The hook 153a of the coil spring 153 engages with a projection 118a provided on the rear group base cylinder 118, and the hook 153b at the other end engages with a projection 151c provided on the 5-group lens retaining frame 151. Therefore, the 5-group lens retaining frame 151 is always biased toward the image side relative to the rear group base cylinder 118.

[0043] Figure 14 is a front view of the rear group base cylinder 118 as seen from the image side, Figure 15 is a side view of the rear group base cylinder 118 in Figure 14, and Figure 16 shows a cross-sectional view taken along line AA in Figure 15. Figures 17 and 18 are cross-sectional views taken along line BB in Figure 14, with Figure 17 showing the wide-angle end infinity state (shooting state) and Figure 18 showing the retracted state.

[0044] As shown in Figure 14, the outer circumference of the rear group base cylinder 118 has cam followers at three equal points. Two of these cam followers 120 are integrally molded with the rear group base cylinder 118. One movable cam follower 121 is held on the rear group base cylinder 118 so as to be movable in the direction passing through the optical axis (hereinafter referred to as the radial direction) in a plane perpendicular to the optical axis.

[0045] The movable cam follower 121 is always in contact with the inner circumferential cam groove 108a of the cam cylinder 108 with a predetermined biasing force (elastic force) by a compression coil spring (not shown), preventing the rear group base cylinder 118 from tipping over due to rattle.

[0046] As shown in Figures 17 and 18, the three-group lens retaining frame 161 constituting the third zoom group 113 has three eccentric rollers 162 attached by screws at three locations, and the eccentric rollers 162 are rotatably held. The eccentric roller 162 has a small diameter portion 162a that is coaxial with the axis of rotation and an eccentric portion 162b. The small diameter portion 162a engages with a circumferentially long groove 118e provided in the rear group base cylinder 118, and the eccentric portion 162b engages with a straight groove 118f in the optical axis direction. Therefore, by rotating the eccentric roller 162, it is possible to adjust the eccentricity of the three-group lens retaining frame 161 with respect to the optical axis. A tension coil spring, which is a backlash removal spring 163, is attached to the eccentric roller 162. The hook portion of the backlash removal spring 163 is attached to a spring attachment portion 118g provided in the rear group base cylinder 118 (see Figures 11 and 12).

[0047] The sub-biasing spring 164, which is a compression coil spring, is guided by a boss 151f provided on the 5-group lens retaining frame 151, and its tip abuts against the spring receiving portion 161a of the 3-group lens retaining frame 161. The sub-biasing spring 164 biases the 5-group lens retaining frame 151 toward the image side and simultaneously biases the 3-group lens retaining frame 161 toward the object side. Therefore, it is not necessary to attach a backlash spring 163 to the eccentric roller 162 closest to the sub-biasing spring 164.

[0048] As shown in Figures 11 and 12, the play-reducing spring 163 biases the 3-group lens retaining frame 161 and the rear group base cylinder 118 obliquely with respect to the optical axis, thereby biasing both the long groove 118e and the straight groove 118f in one direction and preventing play. In this embodiment, the sub-biasing spring 164 biases the 5-group lens retaining frame 151 and the 3-group lens retaining frame 161 in the direction of the optical axis, but it may also bias them obliquely with respect to the optical axis.

[0049] Figure 19 is a perspective view of the 5-group lens holder frame 151 as seen from the object side, and Figure 20 is a front view of the same 5-group lens holder frame 151 as seen from the image side.

[0050] The sub-biasing spring 164 and the coil spring 153 are positioned opposite each other across the optical axis, and the biasing force of the sub-biasing spring 164 is set to be weaker than that of the coil spring 153. The 5-group lens retaining frame 151 is biased by both the coil spring 153 and the sub-biasing spring 164 (multiple biasing members, multiple elastic members), and the line of action of their resultant force passes through the position indicated by point F in Figure 20 in a plane perpendicular to the optical axis. As a result, point F is located within the triangle connecting the three 5-group guarantee surfaces 151d (second guarantee surfaces), so that when the biasing force of the springs acts, the three guarantee surfaces reliably contact the guarantee surface on the rear group base cylinder 118 side.

[0051] Figure 21 is a front view of the rear group base cylinder 118 as seen from the object side. In the shooting state, the 5-group guarantee surface 151d of the 5-group lens holding frame 151 abuts against the rear group guarantee surface (first guarantee surface) 118d of the flange portion of the rear group base cylinder 118.

[0052] By controlling the precision of each guarantee surface at the component level, the inclination of the 5-group lens retaining frame 151 relative to the rear group base barrel 118 can be maintained with high precision. Specifically, the position tolerance between the cam follower and the rear group guarantee surface 118d in the rear group base barrel 118, and the position tolerance between the 5-group guarantee surface 151d and the lens receiving surface in the 5-group lens retaining frame 151, are set to values ​​that will yield the required image quality.

[0053] Figure 22, like Figure 20, is a front view of the 5-group lens holder frame 151 as seen from the image side. The biasing force of the coil spring 153 acts in an oblique direction indicated by T in the figure with respect to the optical axis. This biases the 5-group lens holder frame 151 toward the image plane. At the same time, in a plane perpendicular to the direction in which the 5-group lens holder frame 151 is movable relative to the guide bar 143 (the optical axis direction) (within the plane of the paper in Figure 22), the coil spring 153 biases the 5-group lens holder frame 151 relative to the guide bar 143 in the direction T shown in Figure 22. This causes the outer diameter of the guide bar 143 and the inner diameter of the sliding hole 151a to be offset to eliminate the diameter play. The guide bar 143 is positioned at a distance indicated by D in the figure from the straight line containing the biasing direction T. As a result, a rotational moment is generated around the guide bar 143 in the 5-group lens retaining frame 151, and the elongated hole 151g is constantly biased in the M direction shown in the figure by the anti-rotation boss 118h (see Figure 21), which is a rotation prevention mechanism provided on the rear group base barrel 118. This maintains a state of being offset to eliminate play.

[0054] The biasing force of the coil spring 153 is set so that the elongated hole 151g is always biased from a constant direction relative to the anti-rotation boss 118h in all positions during shooting. Therefore, the elongated hole 151g may be a flat surface instead of a hole. Alternatively, the anti-rotation boss 118h may be a flat surface, and the 5-group lens retaining frame 151 side may slide as a projection.

[0055] The sliding holes 151a and 151b in the 5-group lens holder frame 151 have a difference in diameter. The sliding hole 151a, which is closer to the lens constituting the fifth zoom group 115, has a gap with the guide bar 143 that is small enough to not cause problems with movement, thereby preventing the fifth zoom group 115 from becoming eccentric relative to the rear group base barrel 118. Conversely, the gap between the sliding hole 151b and the guide bar 143 is made somewhat larger so that, in the shooting state, all 5-group guarantee surfaces 151d on the 5-group lens holder frame 151 make sure to contact the rear group guarantee surface 118d of the rear group base barrel 118. In other words, it allows the 5-group lens holder frame 151 to tilt relative to the guide bar 143. The amount of the gap is set to an appropriate amount by calculating the machining tolerances of the parts so that the guarantee surfaces come into contact with each other even when the guide bar 143 is tilted to its maximum extent.

[0056] As explained above, the positional accuracy of the 5-group lens retaining frame 151 relative to the rear group base barrel 118 is maintained by biasing the coil spring 153 in a direction different from the optical axis. In other words, the play that occurs in the guide bar 143 and the anti-rotation boss 118h as it moves in the optical axis direction is shifted to one side, and lens eccentricity can be suppressed. In addition, by bringing the 5-group guarantee surface 151d and the rear group guarantee surface 118d into contact, it is possible to prevent lens tilting and achieve high-precision positioning.

[0057] In the shooting state, the 5-group guarantee surface 151d of the 5-group lens holding frame 151 contacts the rear-group guarantee surface 118d provided on the flange portion of the rear-group base barrel 118, and the rear-group base barrel 118 and the 5-group lens holding frame 151 move together as a single unit.

[0058] In the storage state shown in Figures 12 to 18, the rear group base barrel 118 moves toward the image side, causing the contact portion 151e provided on the 5-group lens holding frame 151 to abut against the 5-group contact portion 102b (see Figure 10) of the fixed lens mount 102 (a component other than the base lens barrel). This allows the 5-group lens holding frame 151 to move relative to the rear group base barrel 118 against the biasing force of the coil spring 153 and the sub-biasing spring 164.

[0059] Therefore, when transitioning from the shooting state to the retracted state, rotating the cam cylinder 108 and moving the rear group base cylinder 118 toward the image side causes the 4-group lens retaining frame 141 and the 5-group lens retaining frame 151 to come into contact with the lens mount 102, which is a fixing member, or with a member integrally formed with the lens mount. As the rear group base cylinder 118 continues to move toward the image side, the 4-group lens retaining frame 141 and the 5-group lens retaining frame 151 move toward the object side relative to the rear group base cylinder 118. In other words, as the rear group base cylinder 118 continues to move toward the image side, the 4-group lens retaining frame 141 and the 5-group lens retaining frame 151 come into contact with the contact part of the lens mount 102 and become unable to move. The rear group base cylinder 118 continues to move toward the image side until each lens group is at its minimum distance from each other.

[0060] Next, we will describe the contact points between the 4-group lens retaining frame 141 and the 5-group lens retaining frame 151 when moving to the storage position. As shown in Figures 8 and 9, a guide bar 142 is located next to the contact portion 141e of the 4-group lens holding frame 141, and a coil spring 145 is positioned there. In the retracted state, the biasing force of the coil spring 145 is transmitted to the rear group base cylinder 118 via the rack 146 and stepper motor 147.

[0061] Furthermore, as shown in Figures 11 and 12, a guide bar 143 and a coil spring 153 are located next to the contact portion 151e of the 5-group lens holding frame 151, and in the retracted state, the biasing force of the coil spring 153 is applied to the rear group base cylinder 118.

[0062] By positioning contact parts and biasing members for moving the guide bars (which are guide members in the optical axis direction) to their retracted state, the force component perpendicular to the direction of movement acting on the guide bars and sliding holes can be reduced. This reduces the drive load due to friction and makes the movement of each moving group smoother.

[0063] In the description of Embodiment 1 above, the guide bar 143 was described as being fixed to the rear group base cylinder 118, and the sliding holes 151a and 151b that engage with the guide bar 143 were described as being fixed to the 5-group lens holding frame 151. However, the present invention is not limited to this configuration. The effects of the present invention can be similarly obtained even if the guide bar 143 is fixed to one of the rear group base cylinder 118 and the 5-group lens holding frame 151, and the sliding holes 151a and 151b are configured on the other. Furthermore, the effects of the present invention can also be enjoyed for the second guide mechanism if the guide bar 142 is configured on one of the rear group base cylinder 118 and the 4-group lens holding frame 141, and the sliding holes 141a and 141b are configured on the other.

[0064] [Example 2] Next, Example 2 of the present invention will be described. Figure 23 is a front view of the 5-group lens holder frame 151, which is Example 2, as seen from the image plane side. Components with the same function are given the same reference numerals as in Example 1.

[0065] There are three 5-group guarantee surfaces 151h, which are the parts that come into contact with the guarantee surface on the rear group base cylinder 118 side when photographed. The 5-group guarantee surfaces 151h are positioned further outward than in Embodiment 1. The biasing member, the coil spring 153, is positioned inside the triangle formed by the three 5-group guarantee surfaces 151h. In this way, the three guarantee surfaces can be reliably brought into contact with a single coil spring 153 without using a sub-biasing member.

[0066] Thus, depending on the available space, positioning the safety surface further outward offers advantages in improving accuracy against lens tilting and also allows for a reduction in the number of biasing members.

[0067] In this embodiment, a stepper motor is used to drive the focus lens, but the same effect can be achieved by using a friction-contact type drive means such as an ultrasonic motor. Also, although zooming is performed manually, the same effect can be achieved by using an electric zoom.

[0068] Although the examples described relate to interchangeable lenses for still image and video shooting, similar effects may be obtainable in lens barrels used for image recording. Furthermore, it can be applied to miniaturizing lens barrels by contacting fixed parts other than the mount, or by contacting other moving lens groups. [Explanation of Symbols]

[0069] 115. Fifth zoom group (lens) 118 Rear group base tube (base tube) 118d Rear group guarantee surface (first guarantee surface) 151 5-group lens retaining frame (lens retaining frame) 151d Group 5 guaranteed surface (Second guaranteed surface) 151h Group 5 Guaranteed Surface (Second Guaranteed Surface) 153 Coil spring (biasing member) 164 Sub-biasing spring (biasing member)

Claims

1. A first lens holding frame that holds a first lens and is movable in the optical axis direction, It has a base barrel that holds the first lens retaining frame, One of the base lens barrel and the first lens retaining frame is provided with a first guide shaft member extending in the optical axis direction, and the other is provided with two first fitting holes that slidably engage with the first guide shaft member in the optical axis direction. The base barrel and the other of the first lens retaining frame are prevented from rotating around the first guide shaft member by a first rotation prevention mechanism. The base barrel includes a first safety surface, and the first lens retaining frame includes a second safety surface. The first and second safety surfaces are in contact with each other in the shooting state, and are separated from each other in the optical axis direction in the retracted state. A lens barrel further comprising a biasing member that biases the base lens barrel and the first lens holding frame in a direction different from the optical axis direction such that the first guarantee surface and the second guarantee surface come into contact with each other.

2. The lens barrel according to Claim 1, characterized in that the gap between the one of the two first fitting holes that is closer to the first lens in the optical axis direction and the first guide shaft member is smaller than the gap between the other fitting hole and the first guide shaft member.

3. The lens further comprises a second lens holding frame, which is held by the base lens barrel and is movable in the optical axis direction for holding the second lens, One of the base lens barrel and the second lens retaining frame is provided with a second guide shaft member extending in the optical axis direction, and the other is provided with two second fitting holes that slidably engage with the second guide shaft member in the optical axis direction. The lens barrel according to claim 1 or 2, characterized in that the other of the base barrel and the second lens retaining frame is prevented from rotating around the second guide shaft member by a second rotation prevention mechanism.

4. The lens barrel according to claim 3, characterized in that the second guide shaft member constitutes the first rotation prevention mechanism.

5. The lens barrel according to claim 3 or 4, characterized in that the first guide shaft member constitutes the second anti-rotation mechanism.

6. The base barrel includes three of the first safety surfaces, and the first lens retaining frame includes three of the second safety surfaces. The lens barrel according to any one of claims 1 to 5, characterized in that each of the three first safety surfaces and the three second safety surfaces in corresponding pairs are in contact with each other in the shooting state and spaced apart from each other in the optical axis direction in the retracted state.

7. The lens barrel according to claim 6, wherein the biasing member includes a plurality of elastic members, and the line of action of the resultant force of the elastic forces from the plurality of elastic members passes through the triangle formed by the three first safety surfaces.

8. A first lens holding frame that holds the first lens and is movable in the optical axis direction, It has a base barrel that holds the first lens retaining frame, The base lens barrel includes three first safety surfaces, and the first lens retaining frame includes three second safety surfaces. Each of the three first and three second guarantee surfaces, in their corresponding pairs, are in contact with each other in the shooting state and are spaced apart in the optical axis direction in the retracted state. The system further includes a biasing member that biases the base lens barrel and the first lens holding frame in a direction different from the optical axis direction such that each of the corresponding pairs of the three first and three second guarantee surfaces comes into contact with each other. The lens barrel is characterized in that the biasing member includes a plurality of elastic members, and the line of action of the resultant force of the elastic forces from the plurality of elastic members passes through the triangle formed by the three first safety surfaces.

9. The lens barrel according to any one of claims 1 to 8, wherein the biasing member includes a plurality of elastic members, and the direction of the resultant force of the elastic forces from the plurality of elastic members is different from the direction of the optical axis.

10. The lens barrel according to any one of claims 1 to 9, characterized in that the first lens holding frame has a contact portion that, when retracted, contacts a member other than the base lens barrel in the optical axis direction.

11. The lens barrel according to claim 10, characterized in that the member other than the base barrel is a fixing member.

12. The lens barrel according to claim 11, characterized in that the fixing member is a lens mount attached to the camera body, or a member integrally formed with the lens mount.

13. The lens barrel according to any one of claims 1 to 12, characterized in that the base barrel is movable in the direction of the optical axis.

14. A lens device having a lens barrel according to any one of claims 1 to 13.

15. An imaging device characterized by comprising a lens device as described in claim 14 and an image sensor for capturing an image formed by the lens device.

Images