JP2009204890A - Zoom lens device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form a cam on a cam cylinder of small diameter at a moderate inclination, and to prevent a power variable driving ring from moving in the optical axial direction. <P>SOLUTION: The cam cylinder 19 is rotated unidirectionally, to move four lens holding frames 23-26 in the same direction by displacements of four cam apertures 33-36, when varying power. A cam follower 48 for the cam cylinder 19 is provided in an outer circumference of the cam cylinder 19. The cam follower 48 is engaged with an optical-axis-directionally long groove part 20a of the variable power driving ring 20, arranged in the outer circumference of a fixed cylinder 18, through a cam aperture 47 for the cam cylinder, provided in the fixed cylinder 18 arranged in the outer circumference of the cam cylinder 19. The variable power driving ring 20 rotates the cam cylinder 19 to move the lens-holding frames 23-26, and moves the cam cylinder optical axially by a displacement of the cam aperture 47 for the cam cylinder, while holding the lens-holding frames 23-26. The cam follower 48 for the cam cylinder is moved in the optical axis direction, in accompaniment thereto in the inside of the groove part 20a, and movement of the variable power driving ring 20 does not occur the optical axis direction. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a zoom lens device that simultaneously moves a plurality of lens holding frames in an optical axis direction by rotating a cam cylinder with respect to a fixed cylinder.

  As a conventional zoom lens device, for example, when zooming, the cam cylinder is rotated with respect to the fixed cylinder, and the lens is held at the intersection of the cam surface spirally provided on the cam cylinder and the rectilinear guide surface provided on the fixed cylinder. A device using a cam mechanism that moves a lens group held on a lens holding frame in the optical axis direction by guiding a cam follower provided on the frame is known (Patent Document 1).

  There is an increasing demand for a compact zoom lens device that has a large zoom magnification. However, if the zoom magnification is increased, the amount of movement of the lens group for zooming increases, and unless the cam barrel diameter is increased, the cam barrel is increased. The inclination angle of the cam groove formed on the cam cylinder with respect to the rotation direction of the cam cylinder is increased. When the inclination angle of the cam groove increases, a large torque is required to rotate the cam cylinder, and it becomes difficult to smoothly move the cam follower.

In order to solve such problems, the applicant of the present application not only rotates the cam barrel in accordance with the magnification operation for rotating the magnification driving ring (zoom ring) in the circumferential direction, but also moves it in the optical axis direction. In addition, it is not necessary to increase the inclination angle of the cam groove by allowing the lens group for zooming to be displaced by the combined movement amount of the movement by the cam groove and the movement of the cam cylinder in the optical axis direction. A zoom lens apparatus as described above was proposed (Patent Document 2).
JP-A-4-57007 JP 2007-264220 A

  However, in the zoom lens device described in Patent Document 2, when the variable magnification drive ring is rotated in the circumferential direction in order to perform variable magnification, the variable magnification drive ring simultaneously moves in the optical axis direction, resulting in poor operability. I understood. In addition, this means that when the variable magnification drive ring is rotated by a machine, the meshing position between the gear for transmitting the drive from the variable magnification motor to the variable magnification drive ring and the gear formed on the outer peripheral surface of the variable magnification drive ring. Means that the lens is always displaced in accordance with the zooming operation, so that the zooming operation may not be stable.

  The present invention has been made in consideration of the above-described problems, and can smoothly move each lens group and can prevent movement of the zooming drive ring in the optical axis direction accompanying zooming operation. An object is to provide a zoom lens device.

  In order to achieve the above object, a zoom lens apparatus according to the present invention holds a fixed cylinder having a rectilinear guide opening and a lens group that is moved by different moving amounts at the time of zooming. A plurality of lens holding frames provided with outer cam followers are supported on the outer periphery, and are rotatably supported in the fixed cylinder and movable in the direction of the optical axis. A cam cylinder that is movably held in the axial direction, and is provided on the cam cylinder, is engaged with each of the cam followers, and rotates the cam cylinder toward one of the circumferential directions around the optical axis. A zoom lens device comprising: a cam that is tilted in a direction to move all of the lens holding frames toward one of the optical axis directions with respect to the fixed cylinder; Provided on the fixed cylinder A cam cylinder cam opening, a cam cylinder cam follower that protrudes from the cam cylinder and engages with the cam cylinder cam opening, and is rotatably attached to the outer circumference of the fixed cylinder, A variable power drive in which a long groove portion is formed in the optical axis direction that engages with the tip of the cam follower for the cam barrel and applies a rotational force to the cam barrel and allows the cam follower for the cam barrel to move in the optical axis direction And the cam opening for the cam cylinder is the same as the direction in which the cams move the lens holding frames due to the rotation of the zoom drive ring to the one of the circumferential directions around the optical axis. The cam cylinder is formed so as to be inclined in the direction in which the cam cylinder is moved.

  According to the zoom lens device of the present invention, each lens holding frame is arranged in the optical axis direction with respect to the fixed cylinder by an amount corresponding to the displacement of each cam provided on the cam cylinder plus the displacement of the cam cylinder itself. Since the movement of the cam follower for the cam cylinder in the optical axis direction along with the movement of the cam cylinder is performed inside the groove portion long in the optical axis direction formed in the variable magnification drive ring, the variable magnification drive ring Each lens group can be smoothly moved without being moved in the optical axis direction.

  As shown in FIGS. 1 and 2, the projector zoom lens device 10 according to the embodiment of the present invention includes first to sixth lens groups 11 to 16 in order from the screen side (object side). At the time of focusing, the first lens group 11 that is the front lens is moved in the optical axis direction, and at the time of zooming, the second to fifth lens groups 12 to 15 are respectively moved in the optical axis direction. The sixth lens group 16 is fixed. Reference numeral 17 denotes a surface on which a document to be projected is placed. For example, in a liquid crystal projector, a surface on which a liquid crystal panel is placed.

  The lens barrel of the zoom lens device 10 includes a fixed barrel 18, a cam barrel 19, a zoom drive ring 20, a focus drive ring 21, and first to sixth lens holding frames 22 that hold the first to sixth lens groups, respectively. ~ 27. The fixed cylinder 18 has a sixth lens holding frame 27 fixed to the rear end, a cam cylinder 19 on the inner periphery, a focus drive ring 21 on the outer periphery of the tip, and a zoom drive ring 20 on the outer periphery of the center. ing.

  The fixed cylinder 18 has a long cylindrical shape that covers the entire outer periphery of the cam cylinder 19 and extends in both directions in the optical axis direction than the cam cylinder 19. The first lens holding frame 22 is fixed to the tip of the focus drive ring 21, and the rear end of the focus drive ring 21 is fitted on the outer periphery of the fixed cylinder 18.

  The fixed cylinder 18 and the focus drive ring 21 are coupled by male / female helicoids 30 and 31. The focus drive ring 21 is rotated in the optical axis direction according to the leads of the male and female helicoids 30 and 31 while being rotated with respect to the fixed cylinder 18 by inputting the drive from the focus motor 29 to the gear train 32 provided on the outer periphery. Move to move the first lens holding frame 22 together.

  The cam cylinder 19 houses therein second to fifth lens holding frames 23 to 26 so as to be movable in the optical axis direction, and four cam openings 33 to 36 are formed on the outer periphery. The cam openings 33 to 36 are for individually moving the second to fifth lens holding frames 23 to 26 in the optical axis direction by the rotation of the cam cylinder 19. Cam openings 33 to 36 corresponding to the second to fifth lens holding frames 23 to 26 are respectively provided at three divided positions in the circumferential direction.

  The second to fifth lens holding frames 23 to 26 are respectively provided with cam followers 38 to 41 at the outer periphery divided into three positions. The cam followers 38 to 41 are engaged with the cam openings 33 to 36, respectively. Further, straight guide openings 45 are respectively formed in the fixed cylinder 18 at three circumferential positions. The rectilinear guide opening 45 is formed to extend long in the optical axis direction, and the cam followers 38 to 41 engage with each other to prevent the second to fifth lens holding frames 23 to 26 from rotating.

  In addition to the rectilinear guide opening 45, the fixed cylinder 18 is formed with a cam cylinder cam opening 47 having a cam surface for moving the cam cylinder 19 in the optical axis direction. This cam cylinder cam opening 47 is also provided at each of the three divided positions in the circumferential direction. A cam cylinder cam follower 48 fixed to the outer periphery of the cam cylinder 19 is engaged with the cam surface of the cam cylinder cam opening 47.

  The variable magnification drive ring 20 is attached to the outer periphery of the fixed cylinder 18 so as to be rotatable in the circumferential direction. The variable magnification drive ring 20 is formed with a groove portion 20a with which the tip of the cam follower 48 for cam cylinder is engaged. The groove 20a has an elongated linear shape extending in the optical axis direction so that the shaft of the cam cylinder cam follower 48 is loosely fitted, and the cam cylinder cam follower 48 is not allowed to rotate around the optical axis. However, the cam cylinder cam follower 48 is allowed to move in the optical axis direction.

  In other words, the variable power drive ring 20 and the cam cylinder 19 are rotated together by the cam cylinder cam follower 48 via the cam cylinder cam opening 47 of the fixed cylinder 18, and the cam cylinder cam follower 48 accompanying this rotation. Is moved in the groove 20a, and the movement of the variable magnification drive ring 20 in the optical axis direction does not occur. The length of the groove 20a is a value obtained by adding the thickness (diameter) of the cam follower 48 for the cam cylinder to the moving amount L (see FIG. 4) of the cam cylinder 19 in the optical axis direction.

  A gear train 50 is formed on the outer periphery of the variable power drive ring 20. The gear train 50 is inputted with driving from the zooming motor 51. When driving is input, the variable magnification driving ring 20 rotates with respect to the fixed cylinder 18. At this time, since the zoom drive ring 20 does not move in the optical axis direction due to the action of the groove 20a described above, the drive input position from the zoom motor 51 to the gear train 50 is displaced in the optical axis direction. There is nothing. For this reason, rotation driving of the variable magnification drive ring 20 is performed stably.

  Since the cam cylinder 19 is connected to the variable magnification drive ring 20 via the cam cylinder cam follower 48 and the groove 20a as described above, when the variable magnification drive ring 20 is rotated, the cam cylinder 19 rotates together with the variable magnification drive ring 20. However, the cam cylinder cam follower 48 moves in the optical axis direction according to the displacement of the cam cylinder cam follower 48. Further, as described above, when the cam cylinder 19 rotates, the second to fifth lens holding frames 23 to 26 move in the optical axis direction according to the displacement of the cam openings 33 to 36, respectively.

  3 and 4 show development views of the cam cylinder 19. Each of the cam openings 33 to 36 is inclined so as to move the second to fifth lens holding frames 23 to 26 toward the screen side in the optical axis direction when the magnification is changed from the wide end toward the tele end. Is formed. The cam cylinder cam opening 47 moves the cam cylinder 19 in the same direction as the direction in which the second to fifth lens holding frames 23 to 26 move when the magnification is changed from the wide end to the tele end. It is formed to be inclined. Here, the wide end of the zoom lens device 10 is a high magnification side with a high projection magnification that increases the screen size projected on the screen, and the tele end is a low magnification with a low projection magnification that reduces the screen size. On the side.

  When the magnification driving ring 20 is rotated to change the magnification from the wide end to the tele end, the cam cylinder cam follower 48 moves from the one end 47a to the other end 47b of the cam cylinder cam opening 47 by a length W1. Along with this, the cam cylinder 19 moves in the optical axis direction. This movement amount is the length L shown in FIG. Note that the one end 47a and the other end 47b of the cam cylinder cam opening 47 are restriction portions that regulate the rotation range of the variable power drive ring 20 by the cam cylinder cam follower 48 coming into contact therewith.

  When the cam cylinder cam follower 48 moves from one end 47 a to the other end 47 b of the cam cylinder cam opening 47, the cam cylinder 19 rotates in the tele end direction of the rotation direction of the variable power drive ring 20, and each cam The openings 33 to 36 also rotate. The cam followers 38 to 41 engaged with the cam openings 33 to 36 do not rotate because the cam followers 38 to 41 are engaged with the rectilinear guide opening 45, and the cam openings 33 to 36 and the rectilinear guide opening 45 It will move following the intersection.

  As a result, the second lens holding frame 23 is screened relative to the fixed cylinder 18 by the sum of the displacement amount L1 of the cam opening 33 along the optical axis direction and the movement amount L of the cam barrel 19 in the optical axis direction. Move towards the side. Similarly, the third lens holding frame 24 is screened with respect to the fixed cylinder 18 by the sum of the amount of displacement L2 of the cam opening 34 along the optical axis direction and the amount of movement L of the cam cylinder 19 in the optical axis direction. Move towards the side. Similarly, the fourth lens holding frame 25 also has a screen side relative to the fixed cylinder 18 by the sum of the displacement amount L3 of the cam opening 35 along the optical axis direction and the movement amount L of the cam barrel 19 in the optical axis direction. Move towards Similarly, the fifth lens holding frame 26 is also relative to the fixed cylinder 18 by the sum of the displacement amount L4 of the cam opening 36 along the optical axis direction and the movement amount L of the cam barrel 19 in the optical axis direction. Move toward the screen.

  That is, the amount of movement for moving the second to fifth lens holding frames 23 to 26 at the time of zooming is determined by the displacement along the optical axis direction of each cam opening 33 to 36 and the optical axis direction of the cam barrel 19. Since the cam cylinder 19 is moved in the same direction as the movement direction of the second lens holding frames 23 to 26, the cam openings 33 to 36 are arranged in the optical axis direction. The cam cylinder 19 can be formed in a spiral shape with a short displacement, that is, a shape with a reduced inclination. For this reason, even if the diameter of the cam cylinder 19 is reduced, each of the cam openings 33 to 36 can be formed with a gentle inclination. Therefore, even one small diameter cam cylinder 19 has four lens holding frames 23 to 26. Can be moved smoothly.

  In the embodiment described above, the second to fifth lens holding frames 23 to 25 are moved in the same direction as the moving direction of the cam cylinder 19 in conjunction with the rotation of the cam cylinder 19 in one direction. However, the configuration is not limited to these four lens holding frames, and two or more lens holding frames may be moved. Further, the number of cam followers 38 to 41, 48 and cams 33 to 36, 47 is not limited to five and may be any number.

  In each of the embodiments described above, the zoom drive ring 20 is automatically driven by driving the zoom motor 51. However, the zoom motor 51 may be omitted and rotated manually.

  In each of the above embodiments, the zoom lens device used in the projector has been described. However, the present invention is not limited to this, and the present invention is also applied to an optical apparatus using an optical system such as a photographic camera, an electronic camera, and a copying machine. Can be applied.

It is sectional drawing which shows the state in the wide end of the zoom lens apparatus of this invention. It is sectional drawing which shows the state in the tele end of the zoom lens apparatus of this invention. It is an expanded view which shows the state in the wide end of a cam cylinder. It is an expanded view which shows the state in the tele end of a cam cylinder.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Zoom lens apparatus 18 Fixed cylinder 19 Cam cylinder 20 Variable magnification drive ring 20a Groove part 22-27 Lens holding frame 33-36 Cam opening 38-41 Cam follower 47 Cam cylinder cam opening 48 Cam cylinder cam follower

Claims (1)

A fixed cylinder having a straight guide opening;
A plurality of lens holding frames each holding a lens group that is moved by a different amount of movement at the time of zooming, and having cam followers that engage with the linear guide openings;
A cam cylinder that is rotatably supported in the fixed cylinder and movably in the optical axis direction, and that holds the plurality of lens holding frames movably in the optical axis direction inside;
Provided on the cam cylinder, engaged with each of the cam followers, and rotating the cam cylinder toward one of the circumferential directions centered on the optical axis, to In a zoom lens device comprising: a cam that is tilted in a direction to be moved toward one direction of the optical axis with respect to the fixed cylinder;
A cam cylinder cam opening provided in the fixed cylinder;
A cam follower for a cam cylinder that protrudes from an outer periphery of the cam cylinder and engages with the cam cylinder cam opening;
The cam cylinder is rotatably mounted on the outer periphery of the fixed cylinder, engages with the tip of the cam cylinder cam follower to give a rotational force to the cam cylinder, and allows the cam cylinder cam follower to move in the optical axis direction. A variable magnification drive ring in which a long groove is formed in the optical axis direction;
With
The cam cylinder cam opening is formed in the same direction as a direction in which the cams move the lens holding frames by the rotation of the zoom driving ring to the one of the circumferential directions around the optical axis. A zoom lens device, wherein the zoom lens device is formed so as to be inclined in the direction in which the lens is moved.

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