JP4962318B2 - Zoom lens and image pickup apparatus including the same - Google Patents

Description

  The present invention relates to a zoom lens and an image pickup apparatus including the same, and more particularly to a technique for reducing ghost and flare caused by reflection on an inner surface of a lens barrel.

As a zoom lens used for a video camera or the like, for example, a four-group zoom lens is known.
In this four-group zoom lens, when the movable second lens group for zooming, which is the second lens group from the subject side, is located on the TEL side far from the subject, a ghost caused by reflection on the inner surface of the lens barrel・ Flare is likely to occur, and it is a problem to suppress this occurrence.

An example of the suppression technique is described in Patent Document 1.
This Patent Document 1 describes a zoom lens having a second lens group having a light blocking means for blocking ghost light.

JP 2004-170857 A

  The technique described in Patent Document 1 can effectively shield ghost light generated by reflection on the inner wall of the lens barrel.

However, even with this technology, in recent zoom lenses, in the remarkable F-number (bright lens), high zoom ratio (high magnification zoom) and ultra-miniaturization (with downsizing of the video camera). However, there are situations where further improvements are desired.
Specifically, the effective pixel area corresponds to a diagonal 1 / 6-type compact image sensor, the open F value is F1.8, and the wide-end equivalent focal length is 36 mm (16: 9/35 mm equivalent). In the zoom lens, the zoom magnification is actually 35 times.

  That is, in order to obtain a high magnification, the moving distance of the second lens group moves to a position farther from the first lens group, and the inner wall is disposed closer to the optical axis in order to reduce the size of the zoom lens unit itself. It has become so.

For this downsizing, there is a strong demand for reducing the lateral width (so-called thickness) in the left-right direction with respect to a video camera on which a zoom lens unit is mounted.
For this reason, it is necessary to design the left and right side walls closer to the optical axis than the upper and lower side walls.

This will be described with reference to FIGS.
FIG. 10 is a schematic layout diagram seen from the front side of the conventional video camera, and FIG. 11 is a schematic layout diagram seen from the front side of the desired video camera.

  In FIG. 10, a conventional video camera 101-1 has a recording medium unit 101 (such as a hard disk drive), a circuit board unit 102, a zoom lens unit ZL-1 having a lens 105, and an image display unit (LCD unit) GH. They were arranged in this order in the direction.

  In FIG. 11, the desired video camera 101-2 also includes a recording medium unit 101, a circuit board unit 102, a zoom lens unit ZL-2 having a lens 105, and an image display unit (LCD unit) GH in this order in the left-right direction. Although arranged, the width Wz2 of the zoom lens unit ZL-2 is set much narrower than the width Wz1 of the zoom lens unit ZL-1.

To realize this, a pair of guide shafts (not shown) that support the movable lens is changed from the conventional diagonal position to the upper and lower parallel arrangement and position, and the lead screw (not shown) It is arranged very close.
As a result, the width W2 of the video camera 101-2 is also much narrower and slimmer than in the past.

  And this video camera 101-2 is miniaturized so that it is easier to grip, and a sense of stability during gripping can be obtained better.

  When the above situation is embodied, as shown in FIG. 12, the second lens group moves to a position about 20 mm away from the first lens group as the distance between the lens surfaces at the TEL position. As an example, the effective diameter of the third lens closest to the second lens group is 19 mm, and the surfaces of the left and right side walls of the lens barrel are close to the position of 7.5 mm from the optical axis. It is.

  FIG. 13 is a schematic optical path diagram of the first lens group and the second lens group in this configuration.

In FIG. 13, the first lens group LG1 is composed of three lenses, a first lens 1, a second lens 2, and a third lens 3, from the subject side. The second lens group is schematically described as one LG2.
Further, the second lens group LG2 is provided with a light shielding part 106 similar to the light shielding means described in Patent Document 1.

  Here, the light enters the first lens 1 at an angle of 25 ° to 30 ° with respect to the optical axis CL, is reflected by the inner wall surface 107 of the lens barrel, and the reflected light enters the effective screen area, causing flare and ghost. Possible light is shielded by the light shielding unit 106.

  However, the second lens group LG2 can be moved to the right in FIG. 13 in order to increase the zoom, and is incident on the first lens at an incident angle of 30 ° to 45 ° with respect to the optical axis CL. The light is reflected near the first lens group LG1 on the inner wall surface 107 of the lens barrel by the incident position on the first lens 1 and is incident on the second lens group at an angle not shielded by the light shielding unit 106.・ It became clear that there was something that caused ghost.

FIG. 13 shows an example of incident angles of 35 °, 40 °, and 45 ° with respect to the optical axis CL that causes the flare ghost.
In either case, it can be seen that although the light is reflected from the inner wall of the lens barrel, the light enters the second lens group 2LG without being shielded by the shield 106.

  If the light is strong light such as sunlight, the image quality of the captured image is significantly degraded as flare and ghost light. Even if there is no obvious flare or ghost, the contrast is lowered.

Therefore, the problem to be solved by the present invention is to provide a zoom lens that suppresses the occurrence of flare and ghost even when the pair of opposed inner walls of the lens barrel is close to the optical axis and the magnification is increased. is there.
Also provided is an imaging device capable of obtaining high-quality captured images by suppressing the occurrence of flare and ghost even when a pair of opposed inner walls of a lens barrel is provided with a zoom lens having a high magnification close to the optical axis. There is to do.

In order to solve the above problems, the present invention has the following configurations 1) to 3) as means.
1) The lens barrel (50k), the first lens group (LG1) fixed to one end of the lens barrel (50k) on the subject side, and the optical axis (CL) of the first lens group (LG1) on the optical axis (CL) In a zoom lens comprising: a second lens group for zooming (LG2) that moves so as to be separated from and in contact with the first lens group (LG1);
Before Symbol inner wall of the first lens group (LG1) near said barrel (50k), the optical axis of the first recess scooped away from (CL) (11) and the second recess (12), In this order from the first lens group (LG1) side,
The outer shape of the zoom lens protrudes in a direction in which a portion corresponding to the first recess is further away from the optical axis than other portions,
The relationship between the depth t1 of the first recess (11), the depth t2 of the second recess (12), and the thickness t of the inner wall in the direction away from the optical axis is t1>t> t2. A connecting surface (11c) having a distance from the optical axis substantially equal to the distance from the optical axis of the inner wall is provided between the first concave portion and the second concave portion. The zoom lens (50).
2) The inner wall has two pairs of opposed surfaces, and the other pair of surfaces (50f, 50g) is located closer to the optical axis (CL) than the one pair of surfaces. The zoom lens (50) according to 1), wherein the first and second recesses (11, 12) are provided on the other pair of surfaces (50f, 50g). .
3) Image pickup comprising the zoom lens (50) according to 1) or 2) and an image pickup element (6) for converting a subject image formed by the zoom lens (50) into an image signal and outputting the image signal. Device (51).

According to the present invention, even if the pair of opposed inner walls of the lens barrel is close to the optical axis and the magnification is increased, the effect of suppressing the occurrence of flare and ghost is achieved.
In addition, even if the pair of opposed inner walls of the lens barrel are provided with a zoom lens with a high magnification close to the optical axis, the occurrence of flare and ghost is suppressed, and a high-quality captured image can be obtained. Play.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described with reference to FIGS.

  As an embodiment of the zoom lens of the present invention and an image pickup apparatus including the zoom lens, a zoom lens 50 and a video camera 51 as an image pickup apparatus including the zoom lens 50 will be described in detail below.

FIG. 1 is an external perspective view of a video camera 51 provided with a zoom lens 50.
FIG. 1A is a perspective view of the embodied product, and FIG. 1B is a schematic diagram for explanation thereof, showing a state in which an image display unit 4 described later is opened.

  The video camera 51 includes a circuit board unit 2, a zoom lens 50, a recording medium unit 3, and an image sensor 6 inside the main body unit 1.

The recording medium unit 3 records information on the hard disk HD and reads information recorded on the hard disk HD using the hard disk HD as a recording medium.
The circuit board unit 2 includes a circuit such as an image processing circuit that processes an image signal from the image sensor 6 and a control unit that controls the entire camera.

  Further, the right side surface (the right side surface in FIG. 1) of the main body portion 1 is provided with an image display portion 4 that can be opened and closed in a range of 0 ° to 90 ° with respect to the main body portion 1, and the left side surface has a grip. Part 5 is provided. FIG. 1B shows a state in which the image display unit 4 is opened by about 90 °.

FIG. 2 is a front view of the video camera 51 as seen from the subject side, and shows the internal layout.
In FIG. 2, a recording medium section 3, a circuit board section 2, and a zoom lens 50 are arranged in parallel in the main body section 1 from the grip 5 side.

FIG. 3 is an external perspective view of the zoom lens 50.
In FIG. 3, the main body size of the zoom lens 50 is a width Wz2: 17 mm, a height Hz2: 35 mm, a depth Dz2: 54 mm in the optical axis CL direction, and an aspect ratio (Hz2 / Wz2) of about 2 Having a cross section.
The diameter φL1 of the foremost lens (first lens L1) is φ23 mm, and the portion that holds the first lens L1 protrudes in the left-right direction from the other body part.

  FIG. 4 is a diagram illustrating the inside of the zoom lens 50 shown in FIG.

FIG. 4 shows a state in which the lid 50b that covers the opening of the box-shaped housing 50a of the zoom lens 50 is on the opposite side and the bottom of the housing 50a is removed. A lens barrel 50k is configured having a housing 50a and a lid 50b.
The housing 50a and the lid 50b are formed by injection molding of resin. Polycarbonate (PC) or the like can be used as this resin. Glass fibers may be included.

In the housing 50a, a pair of guide shafts 50c and 50d are disposed in parallel with the optical axis CL on the upper and lower sides. A lead screw 50e is disposed in the vicinity of the lower guide shaft 50d in parallel therewith.
The first lens group LG1 is fixed to the left end portion of the housing 50a.
A third lens group LG3, which is a fixed lens group, is fixed near the center of the housing 50a.
The iris unit 7 is fixed immediately before the third lens group LG3 (on the first lens group LG1 side).

Between the first lens portion LG1 and the iris unit 7, a second lens group LG2 supported by guide shafts 50c and 50d is disposed so as to be movable in the optical axis direction.
The second lens group LG2 is moved by the rotation of a lead screw 50e driven by a motor (not shown).

A fourth lens group LG4 is disposed on the rear side of the optical axis CL of the third lens group LG3.
The fourth lens group LG4 is supported by the pair of guide shafts 50c and 50d and is movable in the direction of the optical axis CL by the rotation of a lead screw (not shown).

  Behind the fourth lens group LG4, an element mounting portion 8 for mounting the imaging element 6 is provided.

  In the above configuration, the magnification is changed by the movement of the second lens group LG2, and focusing is performed by the movement of the fourth lens group LG4.

  FIG. 5 shows the lens configuration of the zoom lens 50. This is an example, and the present invention is not limited to this.

The first lens group LG1 includes a first lens L1, a second lens L2, and a third lens L3, and has a positive refractive power. The first lens L1 is a negative lens, and the second and third lenses L2 and L3 are positive lenses.
The second lens group LG2 includes a fourth lens L4, a fifth lens L5, and a sixth lens L6, and has negative refractive power. The fourth lens L4 and the fifth lens L5 are negative lenses, and the sixth lens L6 is a positive lens.

  In FIG. 5, the second lens group LG2 is located at the telephoto end (TEL end) farthest from the first lens group on the optical axis CL.

The third group lens LG3 includes a seventh lens L7.
The fourth group lens LG4 includes eighth to eleventh lenses L8 to L11.

  As described above, the iris unit 7 is disposed immediately before the third lens group LG3, and the shielding unit 9 (corresponding to the shielding unit 106 described above) is provided in the second lens group LG2.

  An imaging element 6 is disposed behind the fourth lens group.

  As described above, the bottom surface 50f of the housing 50a on the right side of the zoom lens 50, that is, the surface facing the lid 50b and the inner surface 50g of the lid 50b on the left side are on the optical axis CL. The left and right sides are approaching.

  FIG. 6 is a view including a horizontal cross section and a vertical cross section of the zoom lens 50. Specifically, FIG. 6 (a) is a right side view of the zoom lens 50, FIG. 6 (b) is an AA longitudinal sectional view as seen from the lower surface side, and FIG. 6 (c) is seen from the front side. It is a BB cross-sectional view. In these drawings, the second to fourth lens groups are omitted.

  In FIG. 6B, the distance α from the optical axis CL to the bottom surface 50f and the inner surface 50g is 7.5 mm.

  In FIG. 6B, the inner surface of the bottom surface 50f and the inner surface 50g on the first lens group LG1 side (M portion in the figure) and in the vicinity of the first lens group LG1 is arranged in the thickness direction (light Two recesses are provided in the direction away from the shaft. This will be described in detail next.

FIG. 7 is an enlarged view of the M portion of the bottom surface 50f in FIG. 6B, and also shows the main optical paths.
Further, FIG. 7 shows the first lens group LG1, the bottom surface 50f of the housing 50a, the second lens group LG2, and the shielding portion 9 provided in the second lens group LG2. Here, the second lens group LG2 is located at the telephoto end (TEL end) farthest from the first lens group on the optical axis CL.

In FIG. 7, a concave portion 11 is formed on the bottom lens 50f on the third lens L3 side, which is located farther from the optical axis than other portions.
Further, on the side opposite to the first lens group LG1 with respect to the concave portion 11, a concave portion 12 is formed with a depth t2 within the range of the thickness t forming the bottom surface 50f.
The concave portion 11 is hereinafter referred to as the first concave portion 11 and the concave portion 12 is hereinafter also referred to as the second concave portion 12.
That is, the first concave portion 11 and the second concave portion 12 are formed in this order from the first lens group LG1 side.

  Due to the first and second recesses 11 and 12, 30 to 35 of the light incident on the first lens L1 at an incident angle of 30 to 45 with respect to the optical axis CL as described in FIG. When the light is incident at an incident angle of ° and does not have the concave portions 11 and 12, the light that has entered the effective screen without being shielded by the shielding portion 9 hits the rising surface 12 a of the second concave portion 12, and the first Reflected back to the lens group LG1.

  Further, the light that has entered the first lens L1 at an incident angle of 35 ° to 45 ° with respect to the optical axis CL and has entered the effective screen without being shielded by the shielding portion 9 when there is no concave portion 11, 12. Hits the rising surface 11a of the first recess 11 and reflects back to the first lens group LG1.

  The first concave portion 11 and the second concave portion 12 are provided on the inner surface 50g as well as the bottom surface 50f.

  Therefore, the light incident on the first lens L1 at an incident angle of 30 ° to 45 ° with respect to the optical axis by the first concave portion 11 and the second concave portion 12 can be easily entered into the effective screen. There is no entry.

Therefore, in the zoom lens 50, the pair of opposed inner walls of the lens barrel 50k, that is, the bottom surface 50f and the inner surface 50g are located closer to the optical axis CL than the other pair of opposed inner walls, and the moving distance of the second lens group LG2 is set. Even if the magnification is increased by increasing the length, generation of flare and ghost is suppressed.
Further, the imaging device 51 has a pair of opposed inner walls 50f and 50f of the lens barrel 50k positioned closer to the optical axis CL than the other pair of opposed inner walls, and increases the moving distance of the second lens group LG2. Even if a zoom lens with a high magnification is provided, the occurrence of flare and ghost is suppressed, and a high-quality captured image can be obtained.

  The bottom surface (surface parallel to the optical axis CL) 11b of the first recess 11 shown in FIG. 7 and the connecting surface 11c that connects both the recesses between the first recess 11 and the second recess 12 are shown in FIG. As shown in c), it is formed as a plane.

These surfaces are not limited to flat surfaces, and may be formed as peripheral surfaces centered on the optical axis CL.
In particular, it is more preferable to use the connecting surface 11c as a peripheral surface because generation of flare and ghost can be effectively suppressed over a predetermined angle range.

Here, the 1st recessed part 11 is utilized when fixing each lens L1-L3 of the 1st lens group LG1 to the lens-barrel 50k.
Specifically, each of the lenses L1 to L3 is fixed to the casing 50a by caulking, but is used as a jig escape portion into which a receiving jig is inserted. This portion is a portion provided for caulking, and in the embodiment, this portion is also used for suppressing the occurrence of flare and ghost caused by reflection of the inner wall surface of light having an incident angle of 35 ° to 45 °. -ing
Accordingly, the depth t1 of the first concave portion 11 is deeper than the thickness t of the portion of the bottom surface 50f, and the portion corresponding to the first concave portion 11 as the outer shape of the zoom lens 50 is the other portion. It protrudes outward.
That is, the relationship between the depths t1 and t2 of the first and second recesses 11 and 12 and the wall thickness t is t1>t> t2.

  In addition, the first recess 11 and the second recess 12 are formed continuously or intermittently on the surface of the mountain-shaped projection 13 having a fine triangular section.

  FIG. 8 is a diagram illustrating a state in which the mountain-shaped protrusions 13 are continuously formed. Further, in FIG. 8, the second lens L2 and the third lens L3 are omitted.

  Similar mountain-shaped protrusions 13 are provided on the bottom surface 50f and the inner surface 50g on the third lens group side with respect to the second recess 12.

FIG. 9 shows an example in which the mountain-shaped protrusions 13 are formed intermittently.
In this figure, a flat portion 14 is formed between adjacent mountain-shaped protrusions 13.

  By forming the mountain-shaped protrusion 13, it is possible to further reduce the above-described 30 ° to 45 ° light that has been suppressed in the first and second recesses 11 and 12 from entering the effective screen. .

Specific dimensions of the first and second recesses 11 and 12 and the like are set to optimum dimensions corresponding to the optical path of each lens group. An example is shown in FIG. In this example,
t = 1.0, t = 1.1, t2 = 0.5
Optical axis direction width of the first recess 11: 3.3
Wall thickness in the first recess 11: 1.0
It is.

  As shown in FIG. 8, the above-described depths t1 and t2 and the thickness t when the mountain-shaped protrusion 13 is formed are each defined with reference to the tip position of the protrusion.

  The embodiment of the present invention is not limited to the configuration and procedure described above, and it goes without saying that modifications may be made without departing from the scope of the present invention.

It is a perspective view which shows the Example of the imaging device of this invention. It is the front view explaining the Example of the imaging device of this invention. It is a perspective view which shows the Example of the zoom lens of this invention. It is a perspective view for demonstrating the internal structure in the Example of the zoom lens of this invention. It is a figure for demonstrating the lens structure in the Example of the zoom lens of this invention. It is a figure for demonstrating the lens barrel in the Example of the zoom lens of this invention. FIG. 6 is an optical path diagram for explaining the operation in the embodiment of the zoom lens according to the present invention. It is a partial expanded sectional view for demonstrating the principal part in the Example of the zoom lens of this invention. It is a typical fragmentary sectional view explaining the modification of the principal part in the Example of the zoom lens of this invention. It is a figure for demonstrating the layout of the internal structure of the conventional video camera. It is a figure for demonstrating the example of the layout desired with respect to the internal structure of a video camera. It is a figure for demonstrating the principal part in the Example of the zoom lens of this invention. It is an optical path diagram for demonstrating the conventional zoom lens.

DESCRIPTION OF SYMBOLS 1 Main-body part 2 Circuit board part 3 Recording-medium part 4 Image display part 5 Grip part 6 Image pick-up element 7 Iris unit 8 Element attachment part 9 (106) Shielding part 11 1st recessed part 11a Starting surface 11b Bottom face 11c Connection surface 12 1st 2 concave portion 12a rising surface 13 mountain-shaped protrusion 14 flat portion 50 zoom lens 50a housing 50b lid portion 50c, 50d guide shaft 50e lead screw 50f bottom surface (opposite inner wall)
50g inner surface (opposite inner wall)
50k housing (barrel)
51 Video Camera CL Optical Axis L1 to First Lenses LG1 to LG4 First to Fourth Lens Groups

Claims (3)

A lens barrel,
A first lens group fixed to one end of the lens barrel on the subject side ;
A zoom lens comprising: a second lens group for zooming that moves so as to be separated from and in contact with the first lens group on the optical axis of the first lens group;
Before Symbol inner wall of the first lens near group of the lens barrel, a first recess and a second recess scooped in a direction away from the optical axis, it has in this order from the first lens group side,
The outer shape of the zoom lens protrudes in a direction in which a portion corresponding to the first recess is further away from the optical axis than other portions,
The relationship between the depth t1 of the first recess, the depth t2 of the second recess, and the thickness t in the direction away from the optical axis of the inner wall is t1>t> t2.
A zoom lens comprising a connecting surface between the first concave portion and the second concave portion, wherein a distance from the optical axis is substantially equal to a distance from the optical axis of the inner wall. The inner wall has two pairs of opposed surfaces and is configured such that the other pair of surfaces is located closer to the initial optical axis than the one pair of surfaces.
The zoom lens according to claim 1, wherein the first and second recesses are provided on the other pair of surfaces. A zoom lens according to claim 1 or 2,
An image pickup device comprising: an image pickup device that converts an object image formed by the zoom lens into an image signal and outputs the image signal.