JP4724479B2 - Lens barrel and imaging device - Google Patents

Description

  The present invention relates to a lens barrel and an imaging apparatus that are mounted on an imaging apparatus such as a digital camera, a silver salt camera, and a video camera.

  Conventionally, a technique relating to countermeasures against static pressure of a lens barrel that moves through a guide shaft has been proposed (see, for example, Patent Document 1). In this proposal, when the screw is rotated by the driving force of the motor, the rack meshing with the screw moves in the axial direction. At this time, the rack is biased (biased) with respect to the lens holding member by a spring, so that the lens and the rack can move relative to each other when the lens receives a static pressure from the front. The lens is configured to receive a static pressure when the stopper of the lens holding member abuts against the fixing member.

In addition, another technique relating to countermeasures against static pressure of the lens barrel has been proposed (see, for example, Patent Document 2). In this proposal, a nut plate that moves in the optical axis direction by the rotation of the lead screw is provided, and the lens holding frame that can move along the guide shaft extending in the optical axis direction is urged from one side by the urging means against the nut plate. Has been. When the lens barrel is shortened and retracted into the camera body, the lens holding frame stops at a predetermined retracted position. The stop position of the lens holding frame when retracted is set by bringing the lens holding frame into contact with the nut plate and separating it from the nut plate. Since the lens holding frame is separated from the nut plate, the static pressure on the lens at this time is not applied to the nut plate.
JP 2000-180693 A US 6650488

  However, in the prior art described in Patent Document 1, the rack does not move when the lens is subjected to static pressure, but a charged biasing spring force is applied to the rack. Therefore, even if the rack is not pushed directly, there is a possibility that the thread portion of the rack is damaged or the teeth are missing.

  When a nut plate that can move in the optical axis direction is used as in the prior art described in Patent Document 2, the rotation stop of the nut plate also serves as a guide shaft for the lens. Therefore, since the guide shaft and the nut plate overlap in the optical axis direction, there is a problem that the lens barrel cannot be thinned.

  In addition, it is difficult to make the lens to fall easily by lengthening the sleeve of the lens holding frame, and it is difficult to obtain the accuracy of the lens.

  If the guide shaft on the non-rotating side is set to stop the rotation of the nut plate, the nut plate is now far from the sleeve side, so that it is easy to turn. For this reason, there is a problem that the stability of the operation is deteriorated and the accuracy is liable to occur.

  Moreover, even if the rotation stop of the nut plate is provided separately, a space for passing the shaft for the stroke is required. Further, as the number of axes increases, the parts are required to have high accuracy in order to achieve parallelism of a plurality of axes. Therefore, problems such as troublesome parts processing, an increase in cost, and a decrease in assemblability occur.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a lens barrel and an imaging apparatus that can prevent the accuracy of a lens from being distorted due to damage or deformation of a screw shaft or nut as in the prior art.

In order to achieve the above-described object, a lens barrel of the present invention includes a lens holding member that holds a lens, a biasing unit that biases the lens holding member in a subject direction, and a driving unit that generates a rotational driving force. And a nut that is arranged in parallel with the optical axis and that is rotated by the rotational driving force of the driving means, a groove portion, and a butting portion, and is screwed into the screw shaft to rotate the screw shaft. Accordingly, a nut that moves on the screw shaft and the lens holding member is engaged with the groove portion of the nut to prevent rotation, and the length of the nut that can be engaged in the moving direction is A first rotation restricting portion which is set shorter than the movable stroke of the nut and has a taper at the tip, and is disposed on the lens holding member, and is applied to the nut by the urging force of the urging means. A restricting portion which movement of the lens holding member from one side to the contact object direction is restricted, and the barrel member comprising the lens holding member therein, provided in the barrel member, and the abutment portion of the nut A second rotation restricting portion provided with a predetermined gap, wherein the nut is moved over the entire screw shaft or in a section wider than the restriction range of the first rotation restricting portion. A second rotation restricting portion that prevents rotation of the nut, and the lens holding member moves in the optical axis direction following the movement of the nut.

According to the present invention, since the force is not transmitted to the nut even when the lens is subjected to static pressure, it is possible to prevent the accuracy of the lens from being distorted due to damage or deformation of the screw shaft or nut as in the prior art. It becomes possible. In addition, the lens barrel can be thinned without taking a space in the optical axis direction, and a lens barrel that can be driven smoothly while maintaining accuracy can be realized. In particular, the length in which the rotation restricting portion can be engaged in the moving direction of the nut is set to be shorter than the movable stroke of the nut, so that the lens barrel can be reduced in size. Further, by providing a taper at the tip of the rotation restricting portion, even if the contact between the rotation restricting portion and the nut is removed, the nut can return to its original position, which is an unprecedented effect.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is an exploded perspective view showing a configuration of a lens barrel according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view showing an internal structure of the lens barrel in an assembled state.

  1 and 2, the lens barrel includes a first group lens 1, a lens moving frame 2, a first group barrel 3, a barrier driving unit 6, a second group lens 11, a second group barrel 12, a rectilinear barrel 16, A movable cam ring 17, a fixed cam cylinder 19, a CCD holder 20, a nut 27, a screw shaft 28, and the like are provided.

  The first group lens 1 is composed of a focus lens (hereinafter referred to as a focus lens 1). The lens moving frame 2 has a cylindrical shape into which the focus lens 1 can be fitted, and holds the focus lens 1, and includes a detent 2 a, a bearing portion 2 b, a support portion 2 c, and a restriction portion. The lens moving frame 2 is urged toward the subject (upward in FIG. 2) by the urging force of the compression spring 26.

The detent 2a engages with a U groove 27a (see FIG. 7) of the nut 27. The bearing portion 2b slides with respect to the guide bar 25 when the lens moving frame 2 moves in the optical axis direction. The support portion 2c slides with respect to the rotation stop guide 5a of the base plate 5 when the lens moving frame 2 moves in the optical axis direction. The restricting portion 2d abuts against one surface of the nut 27 (the lower surface of the nut 27 in FIGS. 2 and 6) from one side by the urging force of the compression spring 26 and restricts it in the direction of the subject. That is, the regulating portion 2d is regulated by contacting one surface of the nut 27, and the other surface of the nut 27 (the upper surface of the nut 27 in FIGS. 2 and 6) is not regulated.

  The first group barrel 3 supports the lens moving frame 2 so as to be movable only in the optical axis direction and accommodates the lens moving frame 2, and includes a rotation restricting portion 3a, a supporting portion 3b, a supporting portion 3c, A cam pin seat 3d is provided. The rotation restricting portion 3 a restricts the rotation of the nut 27. Further, the rotation restricting portion 3a prevents the rotation of the nut 27 in the entire section where the nut 27 moves on the screw shaft 28 described later, or in a section wider than the restricting range of the rotation stopper 2a of the lens moving frame 2. The support portion 3b supports the guide bar 25. The support part 3 c supports the ground plane 5. The cam pin 4 is press-fitted into a cam pin seat portion 3d on the outer peripheral portion of the first group barrel 3, and is movable along a cam (described later) of the movable cam ring 17.

  The base plate 5 has lens barrier blades (hereinafter abbreviated as barrier blades) 7 and 8 and a barrier cover 9 fixed thereto, and a detent guide 5a is integrally formed. The barrier drive unit 6 is a unit for moving the barrier blades 7 and 8. The barrier cover 9 is a member that presses the barrier blades 7 and 8, and has an opening 9a. The exterior cap 10 is a member that presses the barrier cover 9. The guide bar 25 is a member that guides the focus lens 1 in the optical axis direction. The focus lens 1 can be moved along the optical axis direction by sliding the guide bar 25 and the bearing portion 2b of the lens moving frame 2 with the anti-rotation guide 5a of the base plate 5 and the support portion 2c of the lens moving frame 2, respectively. To support.

  An AF (Auto Focus) motor 31 generates a driving force for moving the focus lens 1 in the optical axis direction via the lens moving frame 2. A gear 30 meshes with the rotation shaft of the AF motor 31, and a gear 29 meshes with the gear 30. Further, the gear 29 is engaged with a gear formed integrally with the screw shaft 28, and a nut 27 is screwed onto the screw shaft 28. The screw shaft 28 is disposed in parallel with the optical axis. The lens moving frame 2 is biased toward the nut 27 by the action of the compression spring 26, and the position thereof is regulated.

  Here, the stroke when performing the focusing operation by the focus lens 1 is determined by the gap L1 on the subject side in the optical axis direction and the gap L2 on the image plane side in the optical axis direction. The guide bar 25 is not used to prevent the nut 27 from rotating, and therefore it is not necessary to take a length corresponding to the thickness of the mechanism such as the nut 27. Therefore, the stroke of the focus can be taken to the full with respect to the stroke mechanism full length La.

  The stroke mechanism total length La is the sum of the length L0 of the bearing portion 2b of the lens moving frame 2, the gap L1, and the gap L2. For this reason, the length L0 of the bearing portion 2b can be set to the full length other than the necessary focus stroke with respect to the stroke mechanism full length La. Accordingly, by increasing the length L0 of the bearing portion 2b, the inclination of the lens moving frame 2 caused by the backlash of the sliding portion of the guide bar 25 and the bearing portion 2b is reduced, so that the lens moving frame 2 moves the lens. It is possible to reduce the tilt of the focus lens 1 that occurs when the focus lens 1 is fitted to the frame 2 and is tilted by backlash.

  The second group lens 11 is arranged coaxially with the focus lens 1. The second group lens barrel 12 has an inner diameter portion into which the second group lens 11 can be fitted, and holds the second group lens 11. A unit (actuator 13, shutter blade 14 a, aperture blade 14 b, aperture plate 15) including an aperture shutter is attached to the second group lens barrel 12 so as to move integrally with the second group lens barrel 12. By energizing the actuator 13, the shutter blade 14a and the diaphragm blade 14b can be driven. The aperture plate 15 is a member for determining the opening of the second group lens 11.

  The fixed cam cylinder 19 has a cylindrical shape, and a cam groove 19a is formed in the inner diameter portion. A movable cam ring 17 is fitted inside the fixed cam cylinder 19. The moving cam ring 17 has a cylindrical shape and includes a gear portion 17a, a groove 17b, a cam 17c, and a cam 17d. The gear portion 17 a meshes with the Naruto gear 21. A claw 16c (described later) of the straight cylinder 16 is engaged with the groove 17b. A rectilinear cylinder 16 is fitted inside the moving cam ring 17. The cam pin 18 is press-fitted into the outer peripheral portion of the moving cam ring 17. The cam pins 18, the cams 17 c, and the cams 17 d are arranged in the same shape at three locations at 120 ° intervals in the circumferential direction with respect to the moving cam ring 17.

  The rectilinear barrel 16 has a cylindrical shape and is a member for causing the first group barrel 3 and the second group barrel 12 to travel straight in the optical axis direction, and includes a cam groove 16a, a cam groove 16b, and a claw 16c. The cam pin seat 3d of the first group barrel 3 is engaged with the cam groove 16a. The cylindrical portion 12a of the cam pin of the second group barrel 12 is engaged with the cam groove 16b. The claw 16 c is engaged with the groove 17 b of the moving cam ring 17.

  The cam pin 4 of the first group barrel 3 and the cam pin 12b of the second group barrel 12 are engaged with a cam 17c and a cam 17d, respectively. Since these cam pins and cams are equally spaced at 120 degree intervals, the positions of the first lens barrel 3 and the second lens barrel 12 in the direction perpendicular to the optical axis are determined. The cylinder 3 and the second group barrel 12 move only in the optical axis direction.

  A shaft 22 is press-fitted into the inner diameter of the Naruto gear 21, and a rotational driving force of a zoom motor (not shown) is transmitted through the shaft 22.

  When the Naruto gear 21 is rotated by the drive by the zoom motor, the Naruto gear 21 and the gear portion 17a of the moving cam ring 17 are engaged with each other, so that the moving cam ring 17 is rotated. Accordingly, since the cam pin 18 press-fitted into the outer peripheral portion of the moving cam ring 17 moves along the cam groove 19a inside the fixed cam cylinder 19, the moving cam ring 17 moves in the optical axis direction.

  Further, the claw 16c of the rectilinear cylinder 16 is caught in the groove 17b on the inner side of the movable cam ring 17, and the rectilinear cam groove 16b is not rotated inside the fixed cam cylinder 19 by the rectilinear cam groove 16b. Moves straight in the axial direction. As the movable cam ring 17 moves in the optical axis direction, the cam pin 4 and the cam pin 12b move along the cam grooves 17c and 17d of the movable cam ring 17, respectively, so that the first group barrel 3 and the second group barrel 12 respectively. Moves in the direction of the optical axis.

  The CCD holder 20 is fixed to one end face of the fixed cam cylinder 19 and holds an LPF (Low Pass Filter) 23 and a CCD (Charge Coupled Device) 24 inside the holder. By driving the movable cam ring 17 by the zoom motor, the positional relationship among the CCD 24, the second group lens 11 and the focus lens 1 is changed. Thereby, a zoom operation is performed.

  FIG. 3 is a diagram showing an internal configuration of the first group barrel 3.

  In FIG. 3, the barrier blade 7 and the barrier blade 8 are meshed with each other through gears formed at the respective rotation shaft portions. When the barrier blade 8 rotates, the barrier blade 8 and the barrier blade 8 are opposite to the rotation direction of the barrier blade 8. The barrier blades 7 are configured to rotate in the direction. Inside the barrier drive unit 6, an opening spring (not shown) for applying a load in the opening direction of the barrier blades 7 and 8 and a closing spring 34 for applying a load in the closing direction are disposed.

  The closing spring 34 is composed of a torsion spring. Both end portions of the closing spring 34 are fixed to spring-hanging projections 32a and 33a formed on the upper portions of the barrier lever 32 and the barrier lever 33, each of which is composed of two parts. The barrier lever 33 is not shown because it is located on the back side (the back side of the paper in FIG. 3) of the protrusion 33a. By applying a load between the barrier lever 32 and the barrier lever 33 by the force of the closing spring 34, the barrier blades 8 are offset in the closing direction.

  When the barrier blades 7 and 8 are opened, the operation is as follows. When the barrier lever 33 rotates clockwise by the opening spring (not shown), the barrier blade 8 is pushed by the protrusion 32a and rotates counterclockwise. Due to the meshing of the gears of the barrier blades 7, 8, the barrier blade 7 rotates in the clockwise direction opposite to the barrier blade 8. Thereby, the barrier blades 7 and 8 are opened.

  When the barrier blades 7 and 8 are closed, the operation is as follows. The barrier lever 33 rotates counterclockwise against the opening spring by being pressed against the cam surface of the cam portion protruding from the CCD holder 20. At this time, since the protrusion 32a is lowered by the rotation, the barrier blade 8 simultaneously rotates clockwise by the action of the closing spring 34. Due to the meshing of the gears of the barrier blades 7 and 8, the barrier blade 7 rotates counterclockwise. This stops and closes where the barrier blades 7 and 8 meet. The barrier lever 33 further rotates and pulls the closing spring 34 even when the barrier blade 8 stops, thereby further charging the closing force of the barrier blades 7 and 8.

  As described above, the barrier driving unit 6 is coupled to the first group lens unit (focus lens 1, first group barrel 3) and integrally moves back and forth in the optical axis direction, whereby the two barrier blades 7 and 8. Has a mechanism that opens and closes.

  4 is a diagram showing an internal configuration of the first group barrel 3 on the back side of FIG. 3, and FIG. 5 is a perspective view showing an internal configuration in which a part of the first group barrel 3 is cut away. is there.

  4 and 5, the nut 27 shown in FIG. 2 includes a U groove 27a and an abutting portion 27b. A rotation stopper 2 a formed integrally with the lens moving frame 2 is engaged with the U groove 27 a of the nut 27. By driving the AF motor 31, the gear 30 connected to the rotation shaft of the AF motor 31 and the gear 29 meshing with the gear 30 are sequentially rotated, and the screw shaft 28 having the gear meshing with the gear 29 is rotated.

  Since the rotation of the nut 27 is stopped by the rotation stopper 2 a of the lens moving frame 2, the nut 27 moves on the axis of the screw shaft 28. Further, as described above, the lens moving frame 2 that holds the focus lens 1 is displaced to the nut 27 by the action of the compression spring 26 and the position thereof is regulated. Thereby, the position of the focus lens 1 can be moved in the optical axis direction following the movement of the nut 27.

  In this case, the detent 2 a of the lens moving frame 2 is set so that the length in which the nut 27 can be engaged in the moving direction is shorter than the movable stroke of the nut 27. Further, the rotation stopper 2a of the lens moving frame 2 is formed with a tapered portion (see FIG. 6) at a part of the engageable length in the moving direction of the nut 27. The nut 27 can be removed from the rotation stopper 2a of the lens moving frame 2.

  FIG. 6 is a diagram showing the positional relationship between the nut 27 and the lens moving frame 2.

  In FIG. 6, the state A is a state where the nut 27 and the rotation stopper 2a of the lens moving frame 2 are in contact with each other and meshed with each other. When the focus lens 1 is pushed from the front (upward in FIG. 2), the lens moving frame 2 that is biased by the compression spring 26 moves in the direction of the CCD 24 while charging the compression spring 26. The states are shown as B state and C state.

  In the state B, since the position where the nut 27 and the rotation stopper 2a of the lens moving frame 2 abut is the position where the rotation stopper 2a is tapered, the nut 27 can be rotated to some extent. The rotation is restricted at a position corresponding to the taper portion of the detent 2a of the frame 2. Further, due to the action of the taper portion of the detent 2a of the lens moving frame 2, the nut 27 can return to the state A while returning to the original phase if there is no external force at the position corresponding to the taper portion of the detent 2a. .

  FIG. 7 is an enlarged view of a part of FIG. 4 showing the positional relationship of the nut 27 in the C state.

  In FIG. 7, two abutting portions 27 b and 27 b are provided on the side of the nut 27 facing the first group barrel 3. Further, a rotation restricting portion 3a (wall surface) is provided on the side facing the nut 27 in the first group barrel 3, and restricts the rotation when the nut 27 rotates. The rotation restricting portion 3a of the first group barrel 3 is configured so that the U-groove 27a of the nut 27 does not come off from the taper portion of the detent 2a of the lens moving frame 2 no matter which direction the nut 27 rotates. The positional relationship is set such that the rotation is restricted within a predetermined rotation angle.

  In this case, the rotation restricting portion 3a of the first lens barrel 3 is spaced from the nut 27 with a predetermined gap in a state where the rotation stopper 2a of the lens moving frame 2 and the U groove 27a of the nut 27 are engaged. It is set to face each other.

  In the present embodiment, the rotation restricting portion 3a of the first group barrel 3 covers the entire stroke of the nut 27 (the entire range in which the nut 27 moves via the screw shaft 28). However, since the nut 27 does not come off from the rotation stopper 2a of the lens moving frame 2 in the vicinity of the end portion of the nut 27 in the stroke direction side of the CCD 24, the rotation restricting portion 3a of the first group barrel 3 is omitted. It is also possible to do.

  Here, when the external force with respect to the nut 27 is lost, the lens moving frame 2 is pushed and moved by the urging force of the compression spring 26 toward the subject side (upper side in FIG. 2) in the optical axis direction. The taper portion of the rotation stopper 2a and the U groove 27a of the nut 27 abut against each other. As a result, the nut 27 changes from the C state to the B state. Thereafter, in the same manner as described above, the nut 27 returns from the B state to the A state.

  Therefore, when the nut 27 receives an external force from the state A and becomes the C state and the nut 27 is rotated, the nut 27 is in the range restricted by the rotation restricting portion 3a of the first group barrel 3 in the C state. When the state returns, the phase of rotation of the nut 27 also returns. Thereby, the nut 27 and the focus lens 1 can be returned to their original positions in the optical axis direction.

  When an external force is applied to the focus lens 1, the lens moving frame 2 is finally pushed to the most retracted position (the lower side in FIG. 2), and the bearing portion 2b and the support portion 2c of the lens moving frame 2 are moved. In this case, they abut against the support portion 3b and the support portion 3c of the first group barrel 3, respectively.

  As described above, when the lens moving frame 2 is manually retracted to the image plane side (the lower side in FIG. 2) in the optical axis direction, subjected to static pressure at the retracted position, and released, the focus lens 1 is restored. It can be returned to the position. Further, in the state of A, that is, in the state where the rotation stopper 2a of the lens moving frame 2 is engaged with the U groove 27a of the nut 27, the abutting portion 27b of the nut 27 is the rotation restricting portion 3a of the first group barrel 3. It is set not to hit. Thereby, when the nut 27 moves in the direction of the optical axis with the lens moving frame 2, it can move smoothly without causing extra friction.

  FIG. 8 is a block diagram showing a configuration of a digital camera to which the lens barrel shown in FIGS. 1 to 7 is attached.

  8, the digital camera includes a CPU 501, a signal processing circuit 502, an LCD 504, a speaker 506, a signal output terminal 507, a memory 508, a recording unit 509, a microphone 510, a communication terminal 511, a power control unit 512, a strobe 513, and an operation unit 514. The imaging system 505 is provided.

  In the image pickup system 505, the image pickup element 503 includes a CCD that photoelectrically converts an image formed by a lens and outputs the image signal. The shutter drive unit 520 opens and closes the shutter. The aperture driving unit 519 drives the aperture mechanism. The AF reset unit 517 resets the AF operation. The AF motor 518 drives the focus lens and corresponds to the AF motor 31 in FIG. The PZ reset unit 515 resets the zoom operation. The PZ motor 516 performs rotation (forward rotation) / reverse rotation driving of the movable cam ring 17 in FIG.

  The CPU 501 controls the entire digital camera. The signal processing circuit 502 performs various processes such as amplification, A / D conversion, γ processing, compression, D / A conversion, and AF evaluation value generation on the video signal output from the image sensor 503. A microphone (MIC) 510 converts sound into an electrical signal and inputs the signal to the signal processing circuit 502. The LCD 504 displays a captured image. The signal output terminal 507 is a terminal for outputting an image or sound to a device such as a monitor outside the digital camera.

  The speaker 506 outputs sound. The signal processed by the signal processing circuit 502 is reproduced and output as an image / audio output from the LCD 504, the speaker 506, and the signal output terminal 507, respectively. The operation unit 514 includes various operation members such as a power switch, a zoom key, and a release button for operating the digital camera. The memory 508 temporarily stores still image data. The recording unit 509 is an exchangeable memory medium that records still image data.

  The communication terminal 511 is a terminal for communicating with an external device. The power control unit 512 includes a battery, a DC / DC converter, a control circuit, a battery check circuit, and the like. The battery supplies power to the entire digital camera. The DC / DC converter converts and generates a voltage supplied to each part. The control circuit controls the voltage / current supplied to each unit. The battery check circuit performs voltage measurement for battery check.

  The digital camera of the present embodiment is of a retractable type in which the lens barrel is shortened and stored in the digital camera body when the user turns off the power from the operation unit 514.

  When the power is turned on, the PZ motor 516 rotates and is decelerated by a speed reduction mechanism (not shown), and then the moving cam ring 17 rotates to enter a wide (wide angle side) extended state. During the feeding, the zoom is reset by the PZ reset unit 515. Thereby, the CPU 501 can always grasp the position of the lens by counting the energization pulses of the PZ motor 516 thereafter.

  When the power is turned off, the PZ motor 516 reversely rotates and the moving cam ring 17 reverses and retracts, contrary to the above. In the extended state, when a wide (wide angle side) or telescope (telephoto side) operation is performed with the zoom key of the operation unit 514, the PZ motor 516 rotates and the movable cam ring 17 is wide (wide angle side) -tele. Rotates between scopes (telephoto side). Thereby, the zoom operation of the digital camera is performed.

  When shooting a moving image, the CPU 501 determines exposure by performing AE (Auto Exposure) processing based on a signal obtained by processing the video signal from the image sensor 503 by the signal processing circuit 502, and drives the aperture driving unit 519. To determine the aperture value. At the same time, the CPU 501 checks the AF evaluation value. If the AF evaluation value is low, the CPU 501 drives the AF motor 518 at a low speed, moves the focus lens 1 to a position where the AF evaluation value is high, and stops it. These operations may be performed during moving image shooting, and each actuator does not necessarily have to be stopped.

  When shooting a still image, when the user presses the release button of the operation unit 514, the CPU 501 first drives the AF reset unit 517 and the AF motor 518 so that the subject image passing through the lens is in focus. Control. Next, the CPU 501 performs AE processing based on the output of the image sensor 503, determines an aperture value and a shutter speed at which an appropriate exposure amount is obtained, and drives the aperture drive unit 519 so that an appropriate exposure amount is obtained. Control the aperture.

  Next, the CPU 501 resets the image sensor 503, starts accumulating charges by photoelectric conversion, and controls the shutter driving unit 520 to close the shutter so that the shutter speed determined by the AE process is reached. When the exposure amount is insufficient, the CPU 501 causes the strobe 513 to emit light within the time when the shutter is open from the start of charge accumulation. The CPU 501 processes the captured video signal by the signal processing circuit 502, temporarily stores the processed still image data in the memory 508, and then records the data in the recording unit 509.

  As described above, according to the present embodiment, when the lens moving frame 2 is pushed and moved by an external force, the nut 27 is not subjected to the external force and the urging force of the compression spring 26. Further, when the positional relationship between the nut 27 and the lens moving frame 2 is changed, the nut 27 and the rotation stopper 2a of the lens moving frame 2 are engaged in a predetermined range, and are not engaged in other ranges. When the external force applied to the lens moving frame 2 is eliminated, the nut 27 and the rotation stopper 2a of the lens moving frame 2 are engaged so as to have the same positional relationship as described above. As a result, even when the focus lens 1 is subjected to a static pressure, for example, for lens cleaning work, the force is not transmitted to the nut 27. It becomes possible to prevent the accuracy from going wrong.

  Further, while preventing deformation of the lens barrel and damage to the feeding mechanism of the lens barrel, the lens barrel can be thinned without taking a space in the optical axis direction, and the length of the bearing portion 2b of the lens moving frame 2 can be reduced. L0 can be secured as much as possible. By disposing the nut 27 in the vicinity of the bearing portion 2b of the lens moving frame 2, it becomes possible to realize a lens barrel that can be driven smoothly while maintaining accuracy.

  Further, the rotation stopper 2a of the lens moving frame 2 for preventing the rotation of the nut 27 is disposed separately from the guide bar 25 for moving the focus lens 1 in the optical axis direction. Thereby, the sleeve member (bearing portion 2b) of the lens moving frame 2 can be taken as long as possible, and the tilt of the focus lens 1 can be suppressed.

  Further, as described above, the detent 2a of the lens moving frame 2 is arranged separately from the guide bar 25, so that the degree of freedom of arrangement is increased and the lens mechanism in the optical axis direction is as much as the nut 27 and the sleeve member do not overlap. It becomes possible to shorten the whole. This makes it possible to reduce the thickness of a camera equipped with a lens barrel.

  In particular, since the nut 27 can be removed from the rotation stopper 2a of the lens moving frame 2, the length of the nut 27 can be made shorter than the stroke of the focus lens 1. Thereby, the space in the lens barrel can be effectively used, and the lens barrel and the camera to which the lens barrel is attached can be downsized.

  Further, the rotation angle of the nut 27 is kept within a certain range throughout the stroke of the nut 27 by the rotation restricting portion 3 a of the first group barrel 3. Thereby, even when the nut 27 is rotated when the nut 27 is removed from the detent 2a of the lens moving frame 2, the position of the nut 27 in the optical axis direction does not move greatly. In addition, the nut 27 is guided to the original phase by forming a tapered portion in the detent 2a of the lens moving frame 2. Thereby, the position of the nut 27 and the focus lens 1 can be returned to the original position.

[Other embodiments]
In the above embodiment, the case where the lens barrel of the present invention is mounted on a digital camera has been described as an example. However, the present invention is not limited to this, and the lens barrel of the present invention is mounted on a silver salt camera or a video camera. It is also applicable to

It is a disassembled perspective view which shows the structure of the lens barrel which concerns on embodiment of this invention. It is sectional drawing which shows the internal structure in the assembly completion state of a lens-barrel. It is a figure which shows the structure inside a 1st group lens-barrel. It is a figure which shows the structure inside the back side of a 1st group barrel. It is a perspective view which shows the internal structure which notched a part of 1st group lens-barrel. It is a figure which shows the positional relationship of a nut and a lens moving frame. It is the figure which expanded the nut vicinity shown in FIG. It is a block diagram which shows the structure of the digital camera with which a lens barrel is mounted | worn.

Explanation of symbols

1 Focus lens (lens)
2 Lens movement frame (lens holding member)
2a Non-rotating (Rotation restricting portion, first rotation restricting portion)
3 Group 1 barrel (housing member)
3a Rotation restriction part (second rotation restriction part)
26 Compression spring (biasing means)
27 Nut 27a U groove 28 Screw shaft 29, 30 Gear 31 AF motor (drive means)

Claims (4)

A lens holding member for holding the lens;
Biasing means for biasing the lens holding member toward the subject;
Driving means for generating a rotational driving force;
A screw shaft that is arranged in parallel with the optical axis and that is rotated by the rotational driving force of the driving means;
A nut having a groove and a butting portion , screwed into the screw shaft, and moved on the screw shaft as the screw shaft rotates;
Disposed on the lens holding member and engaged with the groove portion of the nut to prevent rotation, and the engageable length in the moving direction of the nut is set to be shorter than the movable stroke of the nut. A first rotation restricting portion having a taper
A restricting portion that is disposed on the lens holding member and is in contact with the nut from one side by the urging force of the urging means, and the movement of the lens holding member in the direction of the subject is restricted;
A lens barrel member having the lens holding member therein;
A second rotation restricting portion provided on the lens barrel member and provided with a predetermined gap from the abutting portion of the nut , wherein the nut moves over the screw shaft; A second rotation restricting portion for preventing rotation of the nut in a section or a section wider than the restriction range of the first rotation restricting portion,
The lens barrel, wherein the lens holding member moves in the optical axis direction following the movement of the nut. In a state in which said said first rotation restricting portion nut is engaged, the second rotation restricting portion, the lens according to claim 1, wherein the opposed with a predetermined gap with respect to the nut A lens barrel. Said second rotation restricting portion, the lens holding member is disposed in the housing member to be accommodated, the lens barrel according to claim 1, wherein the restricting rotation of the nut within a predetermined rotational angle . An imaging apparatus comprising the lens barrel according to any one of claims 1 to 3 .

Images