JPH0640907U - Lens frame drive mechanism - Google Patents

Abstract

(57) [Abstract] [Purpose] A driving mechanism for a plurality of lens holding frames, in which sliding resistance acting on a lens frame driving system is reduced, the structure is simple, the optical precision is high, and the mirror Provided is a lens frame drive mechanism capable of downsizing a cylinder. A rib cam 5 fixed to a cam shaft 4 and having a relatively long transfer span is provided so as to be positioned on the peripheral surface of a cylindrical body for driving the second group lens holding frame 1. ,
An end surface cam 6 having a relatively short transfer span in a spiral shape having a cam surface on the end surface side of the tubular body for driving the third group lens holding frame 2.
The holding frames 1 and 2 are displaced along different feeding curves.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a lens frame driving mechanism, and more particularly, to a lens frame driving mechanism suitable for a lens lens frame that can drive zooming of a camera.

[0002]

[Prior art]

 Conventionally, in a zoom lens frame, the number of lens frames driven to perform a zoom operation may be one or more depending on the type of lens. In a recent zoom lens for a video camera, a lens type having a four-group structure, which is a plural-group lens structure as shown in FIG. 6, is general. As will be described later, basically, the second lens group, which is a zoom lens, is driven in order to perform zooming, and the fourth lens group, which is a focus lens, is also driven at the same time for focus shift correction. The method of driving the second lens group often employs a feed screw driving mechanism, which has a simple structure and is advantageous in terms of control and space.

In the four-group lens barrel shown in FIG. 6, the first group lens 102 and the third group lens 104 are fixedly held on the lens frame 100. A second group lens holding frame 108 that holds the second group lens 103 that is a zoom lens and a fourth group lens holding frame 109 that holds the fourth group lens 105 that is a focus lens are provided on the lens frames 100 and 101, respectively. It is held by the supported guide shafts 112 and 113 so as to be movable back and forth in the optical axis direction. An optical filter 106 and a CCD 107 are arranged behind the fourth lens group 105.

As for the second group lens holding frame 108, a nut 125 is screwed into the feed screw 111 as shown in the “D” partial sectional view of FIG. Axial positioning is done. During the zooming operation, the feed screw 111 is rotationally driven by the zoom motor 121 via the gear train 123 to move the lens holding frame forward and backward. On the other hand, in the fourth group lens holding frame 109, a nut 134 is screwed onto the feed screw 115, and positioning is performed in the optical axis direction through the nut, and the feed screw 115 is used during focusing operation or during zooming focus correction. The focus motor 131 causes the focus motor 131 to rotate to move back and forth.

In the zoom lens barrel having the four-group configuration, as described above, the drive control of the fourth-group lens 105 for correcting the focus shift due to the focus movement during zooming drive becomes complicated, and troublesome control is performed. Had to do. Further, when the zoom ratio is increased, the problem of aberration arises only by such correction movement of the fourth lens group. In addition, there is a problem that it is difficult to reduce the focal length on the wide side to obtain a wide angle of view.

Therefore, in order to solve the problems of the zoom ratio, widening of the angle of view, and simplification of drive control, a zoom for moving two zoom lens groups as shown in FIG. 7 during zooming. A lens barrel has been put to practical use. These two sets of zoom lenses are moved along independent extension curves in response to zooming, thereby satisfying the above-mentioned high magnification and wide angle of view in the zoom lens barrel.

The zoom lens barrel shown in FIG. 7 is a zoom lens barrel having a five-group configuration, and includes a first group lens holding frame 142 for holding the first and fourth group lenses in the lens frames 140 and 150, respectively. The fourth group lens holding frame 145 is fixedly supported. In addition, the second group lens holding frame 143 and the third group lens holding frame 144, which individually hold the second and third group lenses that form the zoom lens, respectively, are guided by the guide shaft 144 supported by the lens frame 140. It is supported so that it can move back and forth in the axial direction. A fifth lens group holding frame 146, which holds the fifth lens group, which is a focus lens, is supported by a guide shaft 154 supported by the rear lens frame 150 so as to be movable back and forth in the optical axis direction. An optical filter 147 and a CCD 148 are arranged behind the fifth lens group. A diaphragm 155 driven by a diaphragm motor 156 is arranged in the fourth lens group holding frame 145. The fifth lens group holding frame 146 is driven back and forth by a focus motor 157 during focusing operation.

Then, the second group lens holding frame 143 and the third group lens holding frame 144 are moved along different predetermined extension curves during the zooming operation. The driving is performed by rotating a cam ring 151 by a zoom motor (not shown) and via a cam groove provided in the cam ring 151. A lens frame drive mechanism using the cam ring is disclosed in, for example, Japanese Patent Laid-Open No. 60-112008.

It can be said that the lens barrel shown in FIG. 7 described above satisfies the zoom function. However, since a ring-shaped cam ring is used for driving a plurality of lens holding frames, there is a problem that the outer shape of the lens barrel becomes large. Furthermore, when applied to a lens barrel of a type in which the lens holding frame is arranged across the diaphragm mechanism, the diameter of the cam ring must be increased in order to avoid interference with the diaphragm mechanism. In addition, I had no choice but to enlarge the outer shape of the lens barrel. This has been an obstacle to providing a compact camera that is easy to handle and has high performance, especially in a situation where image pickup devices such as CCDs are downsized in video cameras and the like.

Therefore, in place of the cam ring described above, a long span cam having a relatively long transfer span for driving the lens frame and a short span cam having a relatively short transfer span for driving the other lens frame are provided. However, a lens frame drive mechanism having a linkage mechanism for transmitting displacement by rotating the long span cam coaxially with the rotation of the short span cam at least within a predetermined range is conceivable.

FIG. 8 is a vertical cross-sectional view of a main mechanical portion of a zoom lens barrel having the lens frame driving mechanism. The zoom lens barrel is a five-group zoom lens, and the first group lens 162 is supported by the outer frame 161 which is a tubular body, and the second group lens 163 and the second group lens 163 which constitute the zoom lens. The third group lens 164 is held by a second group lens holding frame 165 and a third group lens holding frame 166, which are lens frames, respectively, and is supported by the outer frame 161. A supporting guide shaft 167 and a rotation stopping guide. It is supported by a shaft 168 (see FIG. 9) so as to be movable back and forth in the optical axis O direction. Although not shown in FIG. 8, behind the third lens group 164, like the lens barrel shown in FIG. 7, the fourth lens group, which is a fixed lens group, and the focus driven focusing in the optical axis O direction. A fifth lens group of lenses, an optical filter, and a CCD are arranged along the optical axis O. The present lens frame driving mechanism can be applied to a lens barrel in which a diaphragm is arranged between the second group lens holding frame 165 and the third group lens holding frame 166.

The second group lens holding frame 165 and the third group lens holding frame 166 are driven in the optical axis O direction by a convex rib having a predetermined lead angle, which is a long span cam having a long transfer distance. It is performed by rotating the rib cam 172 having the cam surface 172a and the end cam 173 which is a short span cam having a short transfer distance. The rib cam 172 and the end face cam 173 are coaxially fixed to the cam shaft 170, and the cam shaft 170 is rotatably supported by the outer frame 161 in the vicinity of the supporting guide shaft 167 and is supported by the zoom motor 175. A gear 171 driven via a gear train 176 is fixed.

FIG. 9 is a perspective view showing a main part of the lens frame driving mechanism. In the second group lens holding frame 165 and the third group lens holding frame 166, the rib cam 172 and the cam end surface cam 173 can be brought into contact with the cam surfaces in the vicinity of the fitting holes 165a and 166a into the supporting guide shaft 167, respectively. The driven pins 165c and 166c are fixed. The driven pin 165c is in contact with the rib-shaped cam surface 172a of the rib cam 172 by the biasing force of the leaf spring portion 165b formed integrally with the holding frame 165. The driven pin 166c is in contact with the cam surface of the end cam 173 by the urging force of the tension spring 174 suspended between the holding frames 166 and 165.

The rib-shaped cam surface 172a provided on the rib cam 172 is a cam surface having a predetermined lead in the range of a movable rotation angle of 320 °. The cam surface provided on the end surface cam 173 also has a cam surface in the range of a rotation angle of 320 °. FIG. 10 shows the relationship between the rotation angles of the cams, that is, the zoom positions W (wide) to T (tele), and the movement amounts of the holding frames 165 and 166, that is, the lens extension amounts. As shown in the figure, between the zoom positions W to T, the second group lens 163 extended by the rib cam 172 linearly extends a long distance, but the third group lens 163 extended by the end face cam 173 does not. , A relatively short distance. These characteristics are determined by the optical design requirements of the lens.

The present drive mechanism configured as described above includes the second and third group lenses 163, which are two zoom lenses, by the rib cam 172 and the end face cam 173, which are provided in the vicinity of the guide shaft 167 and have a relatively small diameter. , 164 can be moved along a desired locus, and a zoom lens can have a high magnification, a wide angle of view, and easy control, and at the same time, a small diameter rib cam 172 can be mounted on a single cam shaft 170. Since the upper end surface cam 173 is provided, the conventional large-diameter cam ring is not required, and the enlargement of the outer shape of the lens barrel can be avoided.

However, in the present drive mechanism, the rib cam 172 and the end face cam 173 have an integral structure, and the operating rotation angle needs to be within 360 degrees because of the cam structure of the end face cam 173. As a result, the rib cam 172 requires a long-distance feeding action, so that the lead of the rib-shaped cam surface 172a stands up, the pressure angle of the cam contact portion increases, the load resistance also increases, and in driving, It becomes an unfavorable state.

The present invention has been made to solve the above-mentioned problems, and in a lens frame driving mechanism that drives a plurality of lens lens frames, the sliding resistance acting on the lens frame driving system is reduced, and a simple structure is achieved. It is an object of the present invention to provide a lens frame drive mechanism that has a high optical accuracy and is capable of reducing the size of the lens barrel.

[0018]

[Means for Solving the Problems]

 The lens frame drive mechanism of the present invention is designed to drive the lens frame by driving a long span cam having a relatively long transfer span, which is provided so as to be located on the peripheral surface of the cylindrical body, and another lens frame. It is characterized by having a short span cam having a relatively short transfer span in a spiral shape having a cam surface on the end face side of the tubular body.

[0019]

[Action]

 The long-span cam and the short-span cam are coaxially driven to rotate, and the long-span cam displaces the corresponding lens frame along the cam surface of the span cam and the short-span cam along the spiral cam surface.

[0020]

【Example】

 An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view of a lens frame driving mechanism according to an embodiment of the present invention. Further, FIG. 2 is a side view of the above-mentioned lens frame drive mechanism section. Further, FIG. 3 is a longitudinal sectional view of a main part of the lens frame drive mechanism section. The zoom lens barrel to which this drive mechanism is applied has the same configuration as the lens barrel shown in FIG. This lens frame drive mechanism is characterized in that the spiral end face cam 6 for driving the third lens group holding frame 1 has a spiral end face cam face 6a having an operating rotation angle of one rotation or more. . The same components as those applied to the lens barrel shown in FIG. 8 or the lens frame driving mechanism shown in FIG. 9 are designated by the same reference numerals as those shown in FIGS. explain.

The configuration of the drive mechanism of this embodiment will be described in detail. As shown in FIGS. 1 and 2, the cam shaft 4 that is rotationally driven during zooming operation includes a spiral end surface cam 6 that is a short span cam, A rib cam 5, which is a long-span cam having a rib-shaped cam surface 5a, is integrally fixed. Then, the cam shaft rotates once or more between the zoom positions W to T during the zooming operation. The driven pinch 1a arranged near the fitting portion of the supporting guide shaft 167 of the second group lens holding frame 1 is fitted into the rib-like cam surface 5a which is a convex lead for one rotation or more. . Further, as shown in FIG. 2, the spiral cam surface 6a of the end surface cam 6 can freely project to a holding portion 2b arranged in the vicinity of the fitting portion of the supporting guide shaft 167 of the third group lens holding frame 2. The tip end of the L-shaped driven pin 3 that has been fitted is in contact. Although not shown in FIG. 2, a tension spring is suspended between the holding frame 2 and the holding frame 1.

As shown in the vertical sectional view of FIG. 3, the driven pin 3 is biased in the protruding direction toward the center of the cam shaft 4 by the compression spring 7 built in the holding portion 2b. Therefore, as the end cam 6 rotates, the tip of the driven pin 3 slides on the spiral cam surface 6a. Further, the fitting gap with the holding portion 2b is set as small as possible in order to secure the positional accuracy of the driven pin 3 in the advancing / retreating direction. Therefore, in order to reduce the resistance when the driven pin 3 moves in and out, it is necessary to bleed the air inside the holding portion 2b, and the holding portion 2b is provided with an air port 2c for that purpose (see FIG. 3).

In the zooming drive by the lens frame drive mechanism of the present embodiment configured as described above, when the cam shaft 4 is rotated in correspondence with the zoom positions W to T, the driven clamping piece on the holding frame side is moved. 1a and the driven pin 3 move along the rib-shaped cam surface 5a or the spiral cam surface 6a, respectively, and the holding frames 1 and 2 move forward and backward.

The lens frame driving mechanism of this embodiment has a structure in which the rib cam 5 and the spiral end surface cam 6 for driving the holding frame are integrally fixed to the cam shaft 4, and the cam shaft 4 is rotatable for one rotation or more. From this, the lead angle of the rib-shaped cam surface 5a of the rib cam 5 can be set smaller and more gradual. Therefore, the pressure angle of the cam contact portion is reduced and the load resistance is also reduced. Then, the driven part is smoothly driven. Further, even if the present drive mechanism is applied to a lens barrel in which the lens holding frame is arranged across the diaphragm mechanism, there is an effect that the lens barrel outer shape does not become large.

FIG. 4 is a vertical sectional view of a lens frame drive mechanism of a modified example of the above embodiment. The lens frame drive mechanism of this modified example uses a projection for guiding the driven pin of the spiral cam surface of the spiral cam instead of the spiral end surface cam 6 (see FIGS. 2 and 3) in the lens frame drive mechanism of the above embodiment. It is arranged spirally along the surface, and the compression spring 7 for urging the protrusion of the driven pin shown in FIG. 3 is unnecessary.

That is, as shown in FIG. 4, the spiral end surface cam 16 fixed to the cam shaft 14 is formed with a spiral cam surface 16a, and further extends spirally along the cam surface 16a. The guide protrusion 16b is formed. A driven pin 13 is fitted in a holding portion 12b provided on the third group lens holding frame 12 in a state of being retractable in the cam shaft center direction. The tip of the driven pin 13 is fitted into the guide projection 16b, and the tip of the driven pin 13 is in contact with the spiral cam surface 16a. A tension spring 17 is suspended between the third lens group holding frame 12 and a second lens group holding frame (not shown) in order to bring the driven pin 13 into contact with the spiral cam surface 16a.

Further, an air hole 12c is provided in the upper portion of the holding portion 12b of the holding frame 12 to reduce the withdrawal resistance of the driven pin 13. A rib cam for driving the second lens group holding frame is not shown in FIG. 4, but is fixed to the cam shaft 14 as in the embodiment of FIGS. 1 and 2, and is integrated with the spiral end surface cam 16 during zooming. It can be rotated.

In the mechanism of the present modification configured as described above, by rotating the cam shaft 14, the driven pin 13 slides in a state of contacting the spiral cam surface 16a while moving in and out along the spiral. Move. Then, the lens holding frame 12 is driven back and forth in the optical axis direction. Further, according to the drive mechanism of this modification, since the compression spring for urging the driven pin applied in the embodiment of FIGS. 1 and 2 is omitted, the sliding resistance of the driven pin 13 is also small. , Smooth lens driving is performed.

FIG. 5 is a vertical sectional view of a lens frame drive mechanism of another modification of the embodiment of FIGS. The lens frame drive mechanism of this modification is different from the lens frame drive mechanism of the modification shown in FIG. 4 in that a concave spiral groove is provided instead of the guide projection 16b for the driven pin guide on the spiral cam surface. Characterized by points. Therefore, similarly, the compression spring 7 (see FIG. 3) for urging the protrusion of the driven pin is unnecessary.

That is, as shown in FIG. 5, the spiral end surface cam 26 fixed to the cam shaft 24 is formed with a guide spiral groove 26 b, and the bottom surface of the spiral groove 26 b becomes the spiral cam surface 26 a. Further, an L-shaped driven pin 23 is fitted in a holding portion 22b provided in the third group lens holding frame 22 in a state of being retractable in the cam shaft center direction. The tip of the driven pin 23 is fitted in the guide spiral groove 26b, and the tip is in contact with the spiral cam surface 26a. In order to bring the tip of the driven pin 23 into contact with the spiral cam surface 26a, a tension spring (not shown) is suspended between the third group lens holding frame 22 and the second group lens holding frame (not shown). There is.

An air hole 22c is provided in the upper portion of the holding portion 22b of the holding frame 22 to reduce the withdrawal resistance of the driven pin 23. Although the rib cam for driving the second lens group holding frame is not shown in FIG. 5, it is fixed to the cam shaft 24 like the embodiment of FIGS. It can be rotated integrally.

Also in the lens frame drive mechanism of the present modified example configured as described above, by rotating the cam shaft 24 in the same manner as in the modified example, the driven pin 23 spirals in and out along the spiral. It slides while being in contact with the cam surface 26a. Then, the lens holding frame 22 is driven back and forth in the optical axis direction. Also in this modification, the sliding resistance of the driven pin 23 is small and a smooth lens drive can be obtained.

[0033]

[Effect of device]

 As described above, the lens frame drive mechanism of the present invention rotationally drives the long span cam and the short span cam coaxially, the long span cam follows the cam surface of the span cam, and the short span cam follows the spiral cam surface. Since each of the lens barrels is displaced by the above, the movable rotation angle of the cam can be set to one rotation or more, and the cam surface of the span cam can be formed in a reasonable shape. The sliding resistance acting on the lens frame drive system is reduced, the optical accuracy is high, and the lens barrel can be downsized.

[Brief description of drawings]

FIG. 1 is a perspective view of a main part of a lens frame drive mechanism showing an embodiment of the present invention.

FIG. 2 is a side view of the lens frame driving mechanism of FIG.

3 is a longitudinal sectional view of a main part of the lens frame driving mechanism of FIG.

FIG. 4 is a longitudinal sectional view of a main part of a lens frame drive mechanism of a modified example of the embodiment of FIG.

5 is a longitudinal sectional view of a main part of a lens frame drive mechanism of another modified example with respect to the embodiment of FIG.

FIG. 6 is a vertical cross-sectional view of a lens barrel having a four-group configuration including a conventional lens frame driving mechanism.

FIG. 7 is a vertical cross-sectional view of a lens barrel having a five-group configuration that incorporates another conventional lens frame driving mechanism.

FIG. 8 is a vertical cross-sectional view of a lens barrel that incorporates still another conventional lens frame driving mechanism.

9 is a perspective view of a main part of the lens frame driving mechanism of FIG.

10 is a lens extension amount diagram in the lens frame drive mechanism of FIG. 8;

[Explanation of symbols]

5 …………………… Rib cam (long span cam with long transfer span) 6,16,26 …… End face cam (short span cam with short transfer span)

Claims (1)

[Scope of utility model registration request] 1. A long-span cam having a relatively long transfer span, which is provided so as to be positioned on the peripheral surface of a tubular body for driving the lens frame, and a tubular body for driving the other lens frame. A lens frame drive mechanism, comprising: a spiral short cam having a relatively short transfer span, the end surface of which is a cam surface.