JP2006010892A - Imaging optical unit and imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an imaging optical unit comprising an imaging optical system including movable lens groups and a movable member for restricting an amount of light, with which a size reduction is achieved in the direction along the optical axis of an imaging optical system. <P>SOLUTION: A digital camera (1) comprises: the imaging optical system including a fixed lens group (21) having a prism (25), the movable lens groups (22 and 23), and a fixed lens group (24); an imaging device (26); and a movable shutter unit (50). The lens groups (22 and 23) and the shutter unit (50) are independently driven by motors (42, 43, and 44). A guide shaft (36) supports the lens groups (22 and 23) so that the lens groups (22 and 23) freely move, and prevents the lens groups (22 and 23) from inclining. A guide shaft (37) prevents the lens groups (22 and 23) from rotating. Conversely, the guide shaft (37) supports the shutter unit (50) so that the shutter unit (50) freely moves, and prevents the shutter unit (50) from inclining. The guide shaft (36) prevents the shutter unit (50) from rotating. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an imaging optical unit including an imaging optical system and a light amount regulating member such as a shutter, and more particularly to an imaging optical unit in which a part of a lens group of the imaging optical system and the light quantity regulating member are movable in the optical axis direction.

  The camera is equipped with several lens groups to form an image of light from the object to be photographed, and prevents unnecessary external light from being mixed into the light from the object to be photographed and facilitates handling as a unit. Therefore, the lens group is housed in the lens barrel. Some lens groups are fixed, while others are movable in the optical axis direction, such as for focus adjustment and zoom.

  Conventionally, a spiral screw is provided on the inner surface of the lens barrel, a screw that engages with the lens barrel screw is provided on the lens frame that holds the lens group, and the lens group is rotated in the optical axis direction by rotating the lens barrel. Had to be moved to. Thus, in the configuration in which the lens group is moved by the rotation of the lens barrel, the rotating lens barrel is inevitably formed in a cylindrical shape, which is limited in shape and sufficient to accommodate the entire lens frame of the movable lens group. It must have a size, and miniaturization is difficult.

  Furthermore, if a drive source such as a motor for driving the movable lens group is arranged in the lens barrel, the size of the lens barrel is further increased. Therefore, it is necessary to arrange the drive source outside the lens barrel. At this time, if the drive source is arranged on the side of the lens barrel, the total size of the lens barrel and the drive source increases in the direction perpendicular to the optical axis of the lens group, and the drive source is connected to the lens barrel. If arranged on the extension, the overall size increases in the optical axis direction of the lens group.

  Therefore, a rod-shaped drive shaft provided with a helical screw on the outer peripheral surface is arranged in parallel to the optical axis of the lens group, and a screw that engages with the screw of the drive shaft is provided on the lens frame. The lens group is moved by rotation. In this case, it is necessary to prevent tilting and displacement of the optical axis. For this purpose, at least two guide shafts parallel to the optical axis of the lens group are provided, and a through hole through which one guide shaft passes and the other guide shaft In general, the lens frame is provided with a portion sandwiching the lens group, and the lens group is movably supported by one guide shaft to prevent tilting, and the other guide shaft prevents rotation. In this configuration, there is no restriction on the shape of the lens barrel, and a driving source for rotating the driving shaft can be arranged in the lens barrel together with the driving shaft and the guide shaft, so that the overall size can be easily suppressed. Become.

  Cameras include a diaphragm that blocks the peripheral part of the light beam and regulates the amount of light, and in many cases, a camera that includes a shutter that blocks the entire light beam for exposure only for a predetermined time. In addition, there is a camera that includes an ND filter that transmits light at a predetermined transmittance and regulates the amount of light.

In general, these light quantity regulating members are fixedly arranged at predetermined positions. However, when the imaging optical system is a zoom optical system, it is sometimes easier to reduce the overall size if the light amount regulating member is made movable rather than fixed. Japanese Patent Application Laid-Open No. 2003-43359 discloses a diaphragm. An optical system that moves differently from any movable lens group is disclosed.
JP 2003-43359 A

  Although the above publication does not mention a configuration for moving the diaphragm, in a configuration in which the movable lens group is movably supported by two guide shafts while being prevented from rotating, the guide shafts of the light quantity regulating member are used. It is preferable to use both for supporting and moving in order to reduce the overall size. However, if one of the guide shafts prevents both the movable lens group and the light quantity regulating member from tilting, and the other guide shaft prevents both the movable lens group and the light quantity regulating member from rotating, the movable lens group and the light quantity As a result, the movement range of the restricting member is restricted or the entire size in the direction along the guide shaft is increased. This is due to the following reason.

  That is, in order to prevent the tilting of the movable lens group and the light quantity regulating member accurately, the lens frame of the movable lens group and the holding frame of the light quantity regulating member must be in contact with the guide shaft over a wide range. A portion of the holding frame that contacts the guide shaft (hereinafter referred to as a contact portion) must be elongated in the direction along the guide shaft. On the other hand, since the contact part of the lens frame and the contact part of the holding frame are in contact with the same guide shaft, they cannot be closer than the position where they abut each other. Therefore, if the contact part of the lens frame or the holding frame is lengthened, the shortest distance between the movable lens and the light amount regulating member tends to be restricted.

  If the contact part of the lens frame is provided in a part far from the light amount regulating member and the contact part of the holding frame is provided in a part far from the movable lens, the problem that the shortest distance between the movable lens and the light quantity regulating member is avoided is avoided. Can do. However, in this configuration, the length of the guide shaft greatly exceeds the sum of the moving range of the movable lens and the moving range of the light amount restricting member, and an increase in size along the guide shaft is unavoidable.

  The present invention has been made in view of such problems, and is an imaging optical unit including an imaging optical system including a movable lens group and a movable light amount regulating member, and a direction along the optical axis of the imaging optical system. It aims at providing a small thing about. It is another object of the present invention to provide a small image pickup apparatus including such an image pickup unit.

  In order to achieve the above object, the present invention comprises an imaging optical system that includes a plurality of lens groups and guides light to an external imaging device, and a light amount regulating member that regulates the amount of light guided to the imaging device. In the imaging optical unit in which a part of the lens group and the light quantity regulating member are movable in a direction along the optical axis of the imaging optical system, a first holding member that holds the movable lens group, and a first light quantity regulating member that holds the light quantity regulating member. 2 holding members, and a first axis and a second axis parallel to the optical axis of the imaging optical system. The first axis is in contact with the first holding member, and the first holding member is freely movable. The first holding member is prevented from tilting with respect to the optical axis of the imaging optical system while the second axis is in contact with the first holding member, and the first holding member is centered on the first axis. The second shaft is in contact with the second holding member and movably supports the second holding member. The second holding member is prevented from tilting with respect to the optical axis of the imaging optical system, and the first shaft is in contact with the second holding member and prevents the second holding member from rotating about the second axis. The configuration is as follows.

  In this imaging optical unit, the light quantity regulating member is movable on a first axis for supporting the movable lens group so as to be movable and preventing its tilting and a second axis for preventing the rotation of the movable lens group. It is also used to support and prevent tilting and rotation. However, instead of supporting both the movable lens group and the light quantity regulating member on the same axis to prevent them from tilting, the first axis is used to support the movable lens group and prevent tilting. The second shaft is used to support the regulating member and prevent tilting.

  In this configuration, the contact portion of the first holding member that holds the movable lens group (the portion that makes contact with the first shaft) and the contact portion of the second holding member that holds the light amount regulating member (which makes contact with the second shaft). There is no possibility of contact with the part. Accordingly, the length of the first axis or the second axis is suppressed to a value slightly exceeding the sum of the moving range of the movable lens and the moving range of the light amount regulating member, and the contact portion of the first holding member and the second axis are reduced. The length of the contact portion of the holding member that is necessary and sufficient for preventing tilting and the shortest distance between the movable lens group and the light amount regulating member can be shortened.

  Here, a first drive unit that engages with the first holding member and moves the first holding member, and a second drive unit that engages with the second holding member and moves the light amount regulating member are provided. Provided, and the engagement site between the first drive unit and the first holding member and the engagement site between the second drive unit and the second holding member are located on substantially opposite sides with respect to the optical axis of the imaging optical system. It can be set as the structure to do. In this configuration, it is easy to provide the two drive units so as not to interfere with each other.

  In a state in which the movable lens group and the light amount regulating member are closest, the portion of the first holding member that is in contact with the first axis and the portion of the second holding member that is in contact with the second axis are imaging optics. It is also possible to overlap them when viewed from a direction perpendicular to the optical axis of the system. In this way, it becomes very easy to make each of the contact portions of the first holding member and the contact portion of the second holding member as long as necessary to prevent the tilt, and the movable lens and the light amount regulation It is also easy to shorten the shortest distance of the members.

  The first holding member that holds the movable lens group, the second holding member that holds the light amount regulating member, the first shaft, and the second shaft are accommodated, and the first shaft and the second shaft are accommodated. A lens barrel supporting the shaft may be provided, and the second holding member may have a plate-like portion along the inner surface of the lens barrel at the edge thereof. In order to move the light quantity regulating member smoothly, it is necessary that the second holding member that holds the light quantity regulating member does not come into contact with the lens barrel. In this case, the edge of the second holding member There is a possibility that a gap is formed between the lens barrel and the lens barrel, and unnecessary light passes through the gap to cause flare. However, by providing a plate-like portion along the inner surface of the lens barrel at the edge of the second holding member, the light passing through the gap between the plate-shaped portion and the inner surface of the lens barrel is reflected many times to attenuate. It is possible to prevent flare from occurring.

  In order to achieve the above object, according to the present invention, an imaging apparatus includes any one of the imaging optical units described above and an imaging device that captures an image by receiving light guided by the imaging optical unit.

  In the imaging optical unit of the present invention, since both the movable lens group and the light amount regulating member are movably supported to prevent the tilting and rotation of the movable lens group and the light quantity regulating member, the structure is simplified. In addition, since different axes are used for supporting and tilting the movable lens group and preventing and tilting the light quantity regulating member, the contact portions of the holding members with the shaft are tilted without lengthening the two axes. It is possible to make the length necessary and sufficient for prevention, and it is possible to shorten the shortest distance between the movable lens group and the light amount regulating member. Therefore, it becomes a highly accurate and compact imaging optical unit capable of providing a high-quality image.

  Hereinafter, a digital camera according to an embodiment of the present invention will be described with reference to the drawings. An appearance of the digital camera 1 of the present embodiment is schematically shown in FIG. In FIG. 1, (a) is a front view, (b) is a rear view, and a dotted line represents an internal lens barrel described later.

  The digital camera 1 has a substantially rectangular parallelepiped housing 10 whose shortest side is about a fraction of the other side. During normal shooting, the direction of the shortest side of the housing 10 ( 1 is the front-rear direction, the longest side direction (left-right direction in FIG. 1) is left-right direction, and the side direction between them (up-down direction in FIG. 1) is up-down direction. It is set to be gripped by the user in a state of facing. Hereinafter, the front and rear, left and right, and top and bottom directions are determined based on this state.

  The digital camera 1 has an objective window 11, a finder front window 12a, a flash light emitting unit 13, a self-timer lamp 14 on the front, a finder rear window 12b, a display unit 15, a mode setting switch 16, a cursor button 17, and a plurality of buttons. The operation key 18 has a release button 19 on the upper surface.

  The objective window 11 can be opened and closed. When the objective window 11 is opened, a first lens group included in an imaging optical system described later appears. The finder windows 12a and 12b provide an optical image of the shooting target, and the flash light emitting unit 13 emits flash light that illuminates the shooting target. The self-timer lamp 14 is lit to indicate that preparation for self-timer shooting is in progress.

  The display unit 15 includes a liquid crystal display, and displays various information such as the setting status of the digital camera 1 and operation guidance in addition to the photographed image. The mode setting switch 16 is a slide type and is used for setting an operation mode of the digital camera 1. The digital camera 1 has a still image shooting mode for shooting and recording a still image, a moving image shooting mode for shooting and recording a movie, and a playback mode for playing back and displaying the recorded image. In the vicinity of the switch 16, marks representing the respective modes are marked.

  The cursor button 17 has four contacts on the top, bottom, left, and right, and is used to move the cursor displayed on the display unit 15. The digital camera 1 includes a zoom lens as an imaging optical system, and the cursor button 17 is also used for adjusting the focal length. The operation keys 18 are used for settings related to functions of the digital camera 1 such as switching of items to be displayed on the display unit 15 and selection of displayed items. The release button 19 operates in two stages, and is used for an instruction for preparing to shoot an image to be recorded and an instruction to shoot an image to be recorded. The digital camera 1 has automatic focusing (AF) and automatic exposure control (AE) functions, and performs AF and AE in preparation for shooting.

  The internal configuration of the digital camera 1 is schematically shown in FIGS. FIG. 2 is a front perspective view of the entire imaging optical system. FIG. 3 is a side perspective view of the image pickup optical system. FIGS. 3A and 3B show a vicinity of a shutter unit and a second lens group, which will be described later.

  The digital camera 1 includes an imaging optical system including a first lens group 21, a second lens group 22, a third lens group 23, and a fourth lens group 24, a CCD area sensor, and the like in a housing 10. The image pickup device 26 and the optical low-pass filter 27 are provided. The light from the subject is imaged on the image pickup device 26 by the image pickup optical system, and the light is converted into an electric signal by the image pickup device 26. Take a picture. The imaging optical system and the imaging element 26 are disposed near the center of the casing 10 in the vertical direction.

  A signal output from the image sensor 26 is processed by a circuit (not shown) to be image data representing a captured image. Image data can be recorded on a removable recording medium (not shown).

  The image sensor 26 is fixed to a support substrate 10 a provided in the housing 10, and the low pass filter 27 is fixed to the image sensor 26. The first lens group 21 includes two lenses 21 a and 21 b and a prism 25. The lens 21 b, the second lens group 22, the third lens group 23, and the fourth lens group 24 of the first lens group 21 are housed in a lens barrel 70. The second lens group 22 is disposed between the first lens group 21 and the image sensor 26, and the third lens group 23 is disposed between the second lens group 22 and the image sensor 26. The fourth lens group 24 is disposed between the third lens group 23 and the image sensor 26. In FIG. 2, the second lens group 22 and the third lens group 23 are each represented as one lens, but the lens groups 22, 23, and 24 are each composed of a single lens or a plurality of lenses.

  One lens 21a of the first lens group 21 is set so that its optical axis faces the front-rear direction, and the other lens 21b of the first lens group 21 has its optical axis as the optical axis of the lens 21a. It is set to be orthogonal to the left and right direction.

  The prism 25 is a triangular prism having a right-angled isosceles triangle, and one of two surfaces orthogonal to each other faces the lens 21a, the other faces the lens 21b, and a slope is formed with the optical axis of the lens 21a. It is located on the intersection of the lens 21b and the optical axis of the lens 21b, and is arranged at 45 ° to the optical axis of the lens 21a and the optical axis of the lens 21b. The lens 21 a and the prism 25 are fixed to the prism holder 71, and the prism holder 71 is fixed to the lens barrel 70.

  The second lens group 22, the third lens group 23, and the fourth lens group 24 are set so that their optical axes coincide with the optical axis of the lens 21b. Therefore, the optical axis of the entire image pickup optical system is bent 90 ° by the prism 25 in the middle, and most of the optical axis is set to face in the left-right direction. In addition, the prism 25 totally reflects the light from the photographing target incident through the lens 21a by the inclined surface and guides it to the lens 21b. A reflective film may be provided on the slope of the prism 25.

  The first lens group 21 and the fourth lens group 24 are fixed. Both the second lens group 22 and the third lens group 23 are movable in the optical axis direction. The movement of the second lens group 22 performs zooming, that is, the change of the focal length, and the movement of the third lens group 23 performs focusing, that is, the adjustment of the focus on the object to be imaged. The second lens group 22 is held by a lens frame 32, and the third lens group 23 is held by a lens frame 33.

  The digital camera 1 includes a motor 42 for moving the second lens group 22 together with the lens frame 32, and a motor 43 for moving the third lens group 23 together with the lens frame 33. Are provided with guide shafts 36 and 37 for supporting the lens group 22 and the third lens group 23 and guiding their movement in the optical axis direction. The guide shafts 36 and 37 have a cylindrical shape with a smooth outer peripheral surface, and are parallel to the optical axis of the second lens group 22 and the optical axis of the third lens group 23. The ends of the guide shafts 36 and 37 are fixed to the lens barrel 70, and the guide shaft 37 is located on the opposite side of the guide shaft 36 with respect to the second lens group 22 and the third lens group 23.

  The lens frame 32 that holds the second lens group 22 penetrates the guide shaft 36 and comes into contact with the guide shaft 37 and a tilt prevention portion 32 a that prevents the lens frame 32 from tilting with respect to the guide shaft 36. An anti-rotation portion 32 b that prevents the lens frame 32 from rotating around 36 is provided.

  The tilt prevention portion 32a has a cylindrical shape having an inner diameter slightly larger than the outer diameter of the guide shaft 36, and the inner peripheral surface thereof is smooth. The tilt prevention portion 32 a is configured such that the entire inner peripheral surface thereof is in contact with the outer peripheral surface of the penetrating guide shaft 36 and allows the lens frame 32 to move smoothly in a direction parallel to the guide shaft 36. The tilt of the lens frame 32 with respect to the shaft 36 is prevented. Thus, the posture of the second lens group 22 is always kept constant, and its optical axis is always parallel to the guide shaft 36. In addition, in order to reduce the friction with the guide shaft 36 and to simplify the structure of the mold used for molding, a long window is formed in the tilt prevention portion 32a in a direction parallel to the guide shaft 36. Yes.

  The rotation preventing portion 32b is obtained by cutting out the edge of the lens frame 32 into a substantially rectangular shape, and has parallel inner surfaces and smooth inner surfaces. The anti-rotation portion 32b is in contact with the guide shaft 37 at two points on the inner surface, and allows the lens frame 32 to move smoothly in a direction parallel to the guide shaft 37, while attempting to rotate around the guide shaft 36. The movement of the frame 32 is restricted. Thus, the optical axis of the second lens group 22 always coincides with the optical axis of the lens 21b of the fixed first lens group 21.

  The tilt prevention portion 32 a that is in sliding contact with the guide shaft 36 is made as long as possible along the guide shaft 36 within a range that does not restrict the movement range of the second lens group 22. Therefore, even if a slight error occurs in the outer diameter of the guide shaft 36 and the inner diameter of the tilt preventing portion 32a, the tilt of the optical axis of the second lens group 22 can be suppressed to a slight extent. In addition, the guide shaft 36 and the guide shaft 37 (the tilt prevention portion 32a and the rotation prevention portion 32b) are located on opposite sides of the second lens group 22, and the distance between them is long. Therefore, even if a slight error occurs in the outer diameter of the guide shaft 37 or the separation width of the inner surface of the rotation preventing portion 32b, the positional deviation of the optical axis of the second lens group 22 is suppressed to a slight extent.

  The lens frame 33 that holds the third lens group 23 is also provided with a tilt prevention portion 33 a that contacts the guide shaft 36 and a rotation prevention portion 33 b that contacts the guide shaft 37. The configurations and functions of the tilt preventing unit 33a and the rotation preventing unit 33b are the same as those of the tilt preventing unit 32a and the rotation preventing unit 32b.

  A rotating shaft of a motor 42 that moves the lens frame 32 that holds the second lens group 22 is coupled to a cylindrical drive shaft 47 having a helical screw formed on the outer peripheral surface thereof. A cylindrical drive shaft 48 having a spiral screw formed on the outer peripheral surface is also coupled to the rotation shaft of the motor 43 that moves the lens frame 33 that holds the group 23. These drive shafts 47 and 48 are parallel to the guide shafts 36 and 37 and are located on the same straight line. The lens frame 32 is provided with an engagement portion 32c having a substantially U-shaped cross section in a direction perpendicular to the drive shaft 47 and having a semi-circular deepest portion formed with a screw that engages with the screw of the drive shaft 47. The lens frame 33 also has a substantially U-shaped cross section in the direction perpendicular to the drive shaft 48, and a screw that engages with the screw of the drive shaft 48 is formed in the semicircular deepest portion. A portion 33c is provided.

  The drive shaft 47 rotates with the rotation of the rotation shaft of the motor 42, and the rotation is transmitted to the engaging portion 32 c via the screw, and the lens frame 32 moves along the guide shafts 36 and 37. Similarly, the drive shaft 48 rotates with the rotation of the rotation shaft of the motor 43, the rotation is transmitted to the engaging portion 33 c via the screw, and the lens frame 33 moves along the guide shafts 36 and 37.

  A projection 32 d is provided on the lens frame 32, and a tension spring (not shown) parallel to the guide shaft 36 is provided between the projection 32 d and the lens barrel 70. The lens frame 32 is always urged in one direction by the tension spring, so that the drive shaft 47 does not rattle when moving in the direction of increasing the focal length or when reducing the focal length. Engage.

  In the digital camera 1, the tip of the lens frame 32 that holds the second lens group 22 protrudes inward to have a circular opening, and this is used as the diaphragm 41. Accordingly, the aperture of the diaphragm 41 is fixed, and the diaphragm 41 moves together with the second lens group 22 that controls zooming.

  The digital camera 1 includes a shutter unit 50 that blocks light from a subject to be imaged and controls exposure of the image sensor 26. The shutter unit 50 includes a plurality of movable sectors 51, circular openings 52a and 53a, a substrate 52 and a pressing plate 53 sandwiching the sector 51 therebetween, and a sector in a direction parallel to the substrate 52. By opening 51, the openings 52a and 53a are opened and closed. The substrate 52 and the pressing plate 53 are perpendicular to the optical axis of the second lens group 22, and the optical axis passes through the centers of the openings 52a and 53a.

  The imaging optical system has a configuration in which the position where the shutter unit 50 should be set changes by zooming, and the ideal position of the shutter unit 50 changes according to the focal length. Therefore, in the digital camera 1, the shutter unit 50 is movable in the optical axis direction of the imaging optical system so that the shutter unit 50 is always set to the ideal position.

  In the digital camera 1, the first lens group 21 has negative power, the second lens group 22 has positive power, the third lens group 23 has positive power, and the fourth lens group 24 has negative power. Optical setting. FIG. 4 shows a zoom curve connecting the positions of the first to fourth lens groups 21 to 24 during zooming. In FIG. 4, the upper end is the wide end, ie, the shortest settable distance, and the lower end is the tele end, ie, the longest settable focal length.

  Since the first lens group 21 and the fourth lens group 24 are fixed and the imaging element 26 is also fixed, their positions do not change. The second lens group 22 linearly moves from the imaging element 26 side to the first lens group 21 side while changing from the shortest focal length to the longest focal length. While the third lens group 23 changes from the shortest focal length to the longest focal length, the third lens group 23 first moves from the first lens group 21 side to the image sensor 26 side, and then moves to the first lens group 21 side. Moving.

  The positions of the shutter unit 50 during zooming are shown in a dotted line in FIG. The position of the shutter unit 50 forms a curve that swells toward the image sensor 26. This curve is different from the zoom curve of the second lens group 22 that controls focusing, and the shutter unit 50 moves separately from the second lens group 22.

  As shown in FIG. 2, the shutter unit 50 includes a drive unit 54 that drives the sector 51 in addition to the sector 51, the substrate 52, and the pressing plate 53. The drive unit 53 includes a moving magnet and a coil that generates a magnetic field and moves the moving magnet. A flexible wiring board 59 for supplying power and control signals is connected to the drive unit 54 from the outside of the lens barrel 70. The flexible wiring board 59 is provided in a spiral shape along the inner peripheral surface of the lens barrel 70 so as not to block light and to absorb the force accompanying the movement of the shutter unit 50.

  The shutter unit 50 supports the second lens group 22 and the third lens group 23 movably, and is movably supported by guide shafts 36 and 37 that prevent them from tilting and rotating, and also rotates and tilts. Is prevented. However, it is the guide shaft 37 that prevents the lens groups 22 and 23 from rotating by supporting the shutter unit 50 movably, and the lens group 22 and the rotation that prevents the shutter unit 50 from rotating. This is a guide shaft 36 that movably supports 23 and prevents tilting.

  The substrate 52 that holds the sector 51, the pressing plate 53, and the drive unit 54 penetrates the guide shaft 37 to prevent the substrate 52 (shutter unit 50) from tilting with respect to the guide shaft 37, and the guide. An anti-rotation portion 50 b that prevents the substrate 52 (shutter unit 50) from rotating about the guide shaft 37 is provided in contact with the shaft 36.

  The tilt preventing portion 50a has a cylindrical shape having an inner diameter slightly larger than the outer diameter of the guide shaft 37, and the inner peripheral surface thereof is smooth. The tilt preventing portion 50a is configured so that the entire inner peripheral surface thereof is in contact with the outer peripheral surface of the penetrating guide shaft 37 and allows the substrate 52 to move smoothly in a direction parallel to the guide shaft 37. Inclination of the substrate 52 with respect to 37 is prevented. Thus, the posture of the shutter unit 50 is always kept constant, and the substrate 52 is always perpendicular to the guide shaft 37. Although not shown, the tilt prevention portion 50a has a window that is long in a direction parallel to the guide shaft 37 in order to reduce friction with the guide shaft 37 and to simplify the configuration of the mold used for molding. Is formed.

  The rotation preventing part 50b is obtained by cutting out the edge of the substrate 52 into a substantially rectangular shape, and has parallel inner surfaces and smooth inner surfaces. The rotation prevention unit 50b contacts the guide shaft 36 at two points on the inner surface, and allows the substrate 52 to move smoothly in a direction parallel to the guide shaft 36, while rotating around the guide shaft 37. Regulate the movement of Thus, the centers of the openings 52a and 53a of the substrate 52 and the pressing plate 53 are always located on the optical axis of the imaging optical system.

  The tilt preventing portion 50 a that is in sliding contact with the guide shaft 37 is made as long as possible along the guide shaft 37 within a range that does not restrict the movement range of the shutter unit 50. Therefore, even if some errors occur in the outer diameter of the guide shaft 37 and the inner diameter of the tilt prevention portion 50a, the tilt of the shutter unit 50 can be suppressed to a slight extent. Further, since the guide shaft 37 and the guide shaft 36 (the tilt prevention portion 50a and the rotation prevention portion 50b) are located on opposite sides of the shutter unit 50 and the distance between them is long, the outer diameter and rotation of the guide shaft 36 are long. Even if a slight error occurs in the separation width of the inner surface of the prevention portion 50b, the positional deviation of the openings 52a and 53a can be suppressed to a slight extent.

  When the shutter unit 50 and the second lens group 22 are closest to each other, the tilt preventing unit 50a of the shutter unit 50 and the tilt preventing unit 32a of the lens frame 32 holding the second lens group 22 are provided with imaging optics. They overlap each other when viewed from a direction perpendicular to the optical axis of the system. By doing so, the shortest distance between the shutter unit 50 and the second lens group 22 can be shortened regardless of the lengths of the tilt prevention portions 50a and 32a.

  The digital camera 1 includes a motor 44 for moving the shutter unit 50, and a cylindrical drive shaft 49 having a spiral screw formed on the outer peripheral surface thereof is coupled to the rotation shaft of the motor 44. . The drive shaft 49 is parallel to the guide shafts 36 and 37 and is located in the vicinity of the guide shaft 37. The substrate 52 of the shutter unit 50 has a substantially U-shaped cross section in a direction perpendicular to the drive shaft 49, and an engagement portion in which a screw that engages with the screw of the drive shaft 49 is formed in the semicircular deepest portion. 50c is provided. The drive shaft 49 rotates with the rotation of the rotation shaft of the motor 44, the rotation is transmitted to the engaging portion 50c through the screw, and the shutter unit 50 moves along the guide shafts 37 and 36.

  The main purpose of the shutter unit 50 is to control the exposure time of the image sensor 26, but the shutter unit 50 largely inclines from outside the imaging target range and blocks light entering the lens barrel 70 to generate flare. It also has a function to prevent. The surface of the pressing plate 53 of the shutter unit 50 on the first lens group 21 side is provided with an antireflection coating, and the entire inner surface of the lens barrel 70 is also provided with an antireflection coating.

  However, if antireflection coatings are provided on the surfaces of the guide shafts 36, 37 and the drive shafts 47, 48, 49, the tilt prevention portions 32a, 33a, 50a, the rotation prevention portions 32b, 33b, 50b, the engagement portions 32c, 33c, These surfaces are not provided with an anti-reflection coating because they may be worn by contact with 50c and the accuracy may decrease. Moreover, the antireflection coating is not applied to the surfaces of the motors 42, 43, and 44 from the viewpoint of suppressing the decrease in manufacturing efficiency and the increase in cost.

  On the other hand, in order to allow the shutter unit 50 to move smoothly, the edge of the substrate 52 does not contact the inner surface of the lens barrel 70, and there is a gap between them. Therefore, when there is a bright light source such as the sun or a lighting fixture outside the imaging target range, the light from the light source is greatly inclined and enters the lens barrel 70, and is reflected by the guide shafts 36, 37, etc. There is a risk of flare passing through the gap between 52 and the lens barrel 70 and reaching the image sensor 26.

  In order to prevent this, in the digital camera 1, a plate-like portion 50 d along the inner surface of the lens barrel 70 is provided at the edge of the substrate 52. As shown in FIG. 3A, the plate-like portion 50d has a cylindrical shape over the entire circumference of the substrate 52, and as shown in FIG. 2, the width (guide shaft) is several times the thickness of the substrate 52 or more. 37 in the direction along 37).

  There is still a gap between the plate-like portion 50d and the lens barrel 70. However, light from outside the imaging target range is greatly inclined and enters the lens barrel 70, and is reflected by the surface of the guide shaft 37 and the like, and enters the gap. Even if it reaches, the light is reflected a plurality of times by the outer surface of the plate-like portion 50d and the inner surface of the lens barrel 70. Therefore, even if the intensity of the light is so high that it does not disappear with a single incidence on the inner surface of the lens barrel 70, it can be attenuated during multiple reflections, and flare is prevented. If the movement of the shutter unit 50 is restricted when the width of the plate-like portion 50d is increased, the width of the plate-like portion 50d may be suppressed to some extent and an antireflection coating may be applied to the outer surface thereof.

  In this example, the aperture diameter is fixed. However, it is also possible to provide an aperture unit with a variable aperture composed of a plurality of rotatable aperture sectors, and to move the aperture unit in the optical axis direction. Further, a filter unit including a rotatable ND filter can be provided, and the filter unit can be made movable in the optical axis direction. In either case, the guide shaft that prevents the rotation of the lens group supports the diaphragm (filter) unit movably and prevents tilting, and the guide shaft that supports the lens group movably and prevents tilting, Prevent rotation of the aperture (filter) unit.

BRIEF DESCRIPTION OF THE DRAWINGS The front view (a) and back view (b) which show typically the external appearance of the digital camera of one Embodiment of this invention. FIG. 3 is a front perspective view schematically showing the internal configuration (around the imaging optical system) of the digital camera. FIG. 6 is a side perspective view showing the vicinity of the shutter unit (a) and the vicinity of the second lens group (b) of the digital camera. The figure which shows typically the position of each lens group and shutter unit during zooming of the said digital camera.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Digital camera 10 Case 10a Board | substrate 11 Objective window 12a Finder front window 12b Finder rear window 13 Flash light emission part 14 Self-timer lamp 15 Display part 16 Mode setting switch 17 Cursor button 18 Operation key 19 Release button 21 1st lens group 21a , 21b First lens group lens 22 Second lens group 23 Third lens group 24 Fourth lens group 25 Prism 26 Image sensor 27 Optical low-pass filter 32, 33 Lens frame 32a, 33a Tilt prevention part 32b, 33b Rotation Prevention part 32c, 33c Engagement part 32d Protrusion 36, 37 Guide shaft 41 Aperture 42, 43, 44 Motor 47, 48, 49 Drive shaft 50 Shutter unit 50a Tilt prevention part 50b Anti-rotation part 50c Engagement part 50d Plate-like part 51 Shatter Sector 52 substrate 52a opening 53 pressing plate 53a opening 54 driver 59 flexible wiring board 70 barrel 71 prism holder

Claims (5)

An image pickup optical system that includes a plurality of lens groups and guides light to an external image sensor, and a light amount restriction member that restricts the amount of light guided to the image pickup element. In the imaging optical unit movable in the direction along the optical axis of the imaging optical system,
A first holding member for holding a movable lens group;
A second holding member for holding the light amount regulating member;
A first axis and a second axis parallel to the optical axis of the imaging optical system;
The first shaft is in contact with the first holding member to prevent the first holding member from being tilted with respect to the optical axis of the imaging optical system while movably supporting the first holding member. In contact with the first holding member to prevent rotation of the first holding member about the first axis;
The second shaft is in contact with the second holding member and prevents the second holding member from tilting with respect to the optical axis of the imaging optical system while movably supporting the second holding member. An imaging optical unit that prevents the second holding member from rotating about the second axis in contact with the second holding member. A first drive unit that engages with the first holding member and moves the first holding member; and a second drive unit that engages with the second holding member and moves the light amount regulating member;
The engagement site between the first drive unit and the first holding member and the engagement site between the second drive unit and the second holding member are located approximately on opposite sides with respect to the optical axis of the imaging optical system. The imaging optical unit according to claim 1. In a state in which the movable lens group and the light amount regulating member are closest, the portion of the first holding member that is in contact with the first axis and the portion of the second holding member that is in contact with the second axis are imaging optics. The imaging optical unit according to claim 1, wherein the imaging optical unit overlaps when viewed from a direction perpendicular to the optical axis of the system. The first holding member that holds the movable lens group, the second holding member that holds the light amount regulating member, the first shaft, and the second shaft are accommodated, and the first shaft and the second shaft are accommodated. A lens barrel that supports the shaft,
The imaging optical unit according to claim 1, wherein the second holding member has a plate-like portion along the inner surface of the lens barrel at an edge thereof.   An image pickup apparatus comprising: the image pickup optical unit according to claim 1; and an image pickup element that receives light guided by the image pickup optical unit and picks up an image.

Images