JP4722430B2 - Zoom lens barrel cam mechanism - Google Patents

Description

  The present invention relates to a cam mechanism used in a zoom lens barrel, and more particularly, to a cam mechanism of a type in which two or more cam grooves for a rectilinear member are formed in a single cam ring.

  In a zoom lens barrel, two or more types of cam grooves having different basic trajectories are formed in a single cam ring, and followers provided on two or more movable members that are guided straight in the direction of the optical axis are respectively engaged with these cam grooves. It is done. When the cam ring rotates, the movable member moves according to the cam groove basic locus.

  Conventionally, two or more types of cam grooves on a single cam ring are crossed or open at the front and rear ends for follower assembly, but are basically provided independently of each other. This has been considered indispensable to ensure the movement trajectory of the movable member. However, according to the inventor, forming all of the two or more types of cam grooves independently reduces the degree of freedom in arranging the cam grooves and hinders shortening of the axial length.

  It is an object of the present invention to obtain a cam mechanism for a zoom lens barrel that can shorten the axial length of a cam ring that forms two or more types of cam grooves and can increase the degree of freedom of cam groove arrangement.

The cam mechanism of the zoom lens barrel of the present invention has two or more types of cam grooves having different basic loci, each having a start region and an end region spaced apart in the rotational direction of a single cam ring that is rotationally driven. In the zoom lens barrel in which the cam followers of the two rectilinear members guided linearly in the optical axis direction are engaged with the two types of cam grooves, respectively, the two types of cam grooves are respectively a zoom section, The zoom section has a non-zoom section before and after the zoom section, and the start area of one cam groove and the end area of the other cam groove of the two types of cam grooves are the non-zoom sections of the two types of cam grooves. It is characterized by overlapping and sharing in the zoom section .

  The non-zoom section of the two types of cam grooves is located at one of the front and rear of the zoom section, the introduction groove section for introducing the corresponding follower, the storage position and storage section following the introduction groove section, and the front and rear of the zoom section. The over tele section located on the other side is set, and the area including the introduction groove portion and the storage position of one cam groove is set as the start area, and the over tele section of the other cam groove overlaps the start area of the one cam groove. It can be set as the end region.

The form of two types of cam grooves is not ask | required. For example, when one of the two types of cam grooves is composed of a complete cam groove having the same basic locus and an entire basic locus, and an incomplete cam groove having only a portion of the basic locus, this incomplete cam groove An overlap region of a start region and an end region can be formed between the first cam groove and the other cam groove.

  The other cam groove that sets the over tele section as the end region can be an incomplete cam groove in which only a part of the storage section, a part of the tele section of the zoom section, and the over tele section are formed on the cam ring.

  The present invention can be applied to a zoom lens barrel having a four-group configuration, for example, and the two types of cam grooves can be used for a two-group lens and a three-group lens.

  According to the cam mechanism of the present invention, the axial length of the cam ring that forms two or more types of cam grooves can be shortened, and the degree of freedom in arranging the cam grooves can be increased.

  First, the overall structure of a zoom lens barrel to which the present invention is applied will be described with reference to FIGS. The optical system of the zoom lens barrel is a four-group zoom lens system having a first lens unit L1, a second lens unit L2, a third lens unit L3, and a fourth lens unit L4 in order from the object side. The group L1 to the third lens group L3 are lens groups that are involved in zooming, and the fourth lens group L4 is a focus lens group that compensates for focal movement accompanying zooming and is involved in focusing.

  The stationary (fixed) members of the zoom lens barrel are a CCD holder 11, a housing 12 fixed in front of the CCD holder 11, and a rotation restricting ring 13 fixed at the tip of the housing 12. In addition to the CCD, a low-pass filter 11a and a fourth group rectilinear guide 11b are fixed to the CCD holder 11. A fourth group frame 14 with a fourth lens group L4 fixed to the fourth group rectilinear guide 11b goes straight in the optical axis direction. Guided.

  The housing 12 is formed with a female helicoid 12a and a rectilinear guide groove 12b parallel to the optical axis on the inner peripheral surface thereof. The male helicoid 15a on the outer periphery of the rear end of the cam ring 15 is screwed into the female helicoid 12a. A flat gear 15b is formed on the mountain of the male helicoid 15a, and this flat gear 15b meshes with a pinion (not shown) of a forward / reverse drive motor 12c fixed to the housing 12. Accordingly, the cam ring 15 advances and retreats in the optical axis direction according to the helicoids 12a and 15a while the cam ring 15 rotates forward and backward by forward and reverse rotation of the forward and reverse drive motor 12c. In the zoom lens barrel, the cam ring 15 is the only rotating member.

  On the outer periphery of the cam ring 15, a straight guide ring 16 is bayonet-coupled so as to be relatively rotatable and move together in the optical axis direction. A rectilinear guide protrusion 16a that engages with the rectilinear guide groove 12b of the housing 12 is formed on the outer peripheral surface of the rectilinear guide ring 16. When the cam ring 15 rotates and advances and retracts in the optical axis direction, the rectilinear guide ring 16 is formed. While moving relative to the cam ring 15, it moves straight in the optical axis direction.

  A rectilinear guide groove 16b is formed on the inner peripheral surface of the rectilinear guide ring 16, and a rectilinear guide protrusion 17a formed on the rear end of the outer peripheral surface of the first group moving cylinder 17 is engaged with the rectilinear guide groove 16b. The first group moving cylinder 17 is composed of an inner / outer double cylinder whose front end is joined by a radial wall, and the cam ring portion of the cam ring 15 is located between the inner cylinder and the outer cylinder. Further, a barrier support cylinder 18 is located between the linear guide ring 16 and the first group moving cylinder 17, and a linear guide protrusion (not shown) protruding from the inner peripheral surface of the barrier support cylinder 18 is provided. The first group moving cylinder 17 is fitted in the straight guide groove 17b. A barrier block 18 a is fitted and supported at the tip of the barrier support cylinder 18.

  A second group moving frame 19 is linearly guided in the optical axis direction on the inner peripheral surface of the first group moving cylinder 17, and the third group that supports the third lens group L3 and the shutter block 20a on the second group moving frame 19 is supported. The moving frame 20 is guided straight ahead. A first group frame 17x that fixes the first lens group L1 is screwed and fixed to the first group moving cylinder 17, and a second group frame 19a that fixes the second lens group L2 is screwed and fixed to the second group moving frame 19. ing.

  The linear guide relation described above is such that the linear guide ring 16 is linearly guided to the housing 12, the first group moving cylinder 17 is guided linearly to the linear guide ring 16, the barrier support cylinder 18 and the second group moving frame 19 are guided to the first group movable cylinder 17. Is guided in a straight line, and the third group moving frame 20 is guided to the second group moving frame 19 in a straight line.

  On the outer peripheral surface of the cam ring portion of the cam ring 15, a first group cam groove C1 for the first group moving cylinder 17 and a barrier cam groove C2 for the barrier support cylinder 18 are formed. A second group cam groove C3 for the moving frame 19 and a third group cam groove C4 for the third group moving frame 20 are formed. The first group moving cylinder 17, the barrier support cylinder 18, the second group moving frame 19, and the third group moving frame 20 are respectively provided with followers 17f, 18f, 19f, and 20f that engage with the cam grooves C1, C2, C3, and C4. 20ff and 20fr) are fixed or formed. In this embodiment, all the cam grooves and followers are provided in groups of three in a circumferentially spaced manner.

  As described above, the first group moving cylinder 17, the barrier support cylinder 18, the second group moving frame 19 and the third group moving frame 20 are all guided in a straight line. When the cam ring 15 rotates, the light follows the respective cam profiles and followers. By moving linearly in the axial direction, a zooming operation and a storing operation are performed. The fourth group frame 14 (fourth lens group L4) is driven in the optical axis direction by a stepping motor 12d fixed to the housing 12 based on focal point movement information and subject distance information accompanying zooming.

  The cam mechanism of the zoom lens barrel of the present embodiment is applied to the cam ring 15 described above. As described above, the cam ring 15 has the first group cam groove C1 and the barrier cam groove C2 formed on the outer peripheral surface thereof, and the second group cam groove C3 and the third group cam groove C4 formed on the inner peripheral surface thereof. ing. All of these cam grooves have different basic trajectories, and each has a start region (start end) and an end region (end end) that are separated in the rotational direction of the cam ring 15. FIG. 1 and FIG. 2 are expanded views showing cam groove shapes on the inner and outer peripheral surfaces of the cam ring 15.

  The first group cam groove C1 and the barrier cam groove C2 project the barrier support cylinder 18 forward with respect to the first group moving cylinder 17 at the storage position compared to the photographing position (zoom area), and the barrier block 18a barrier. And the first lens unit L1 are set with slightly different shapes so as to prevent interference. The cam groove C1 for the first group and the cam groove C2 for the barrier are respectively assembled positions C11 and C21 parallel to the optical axis direction of the front end, over tele sections C12 and C22, zoom sections C13 and C23, storage sections C14 and C24, And storage positions C15 and C25. The storage positions C15 and C25 exist in the circumferential grooves C16 and C26, and the groove width of the circumferential groove C16 is formed wide as an assembly adjustment margin in the optical axis direction of the first lens unit L1 with respect to the first group moving cylinder 17. Has been. The assembly positions C11 and C21 of the first group cam groove C1 and the barrier cam groove C2 have different circumferential phases (the lengths of the over tele sections C12 and C22 are different in order to enable assembly). ).

  The three second group cam grooves C3 are formed with introduction grooves C31 parallel to the optical axis and opened at the rear ends at the rear ends. The second group cam groove C3 has a storage position C32, a storage section C33, a zoom section C34, and an over tele section C35 following the introduction groove C31. Here, for convenience, an area including the introduction groove C31 and the storage position C32 is defined as a start area of the second group cam groove C3, and an over tele section C35 is defined as an end area. Of course, the over tele section C35 may be considered as the start area, and the area including the introduction groove C31 and the storage position C32 may be considered as the end area.

  On the other hand, the third group cam groove C4 includes a front complete cam groove C4F and a rear incomplete cam groove C4R located behind the front complete cam groove C4F in the optical axis direction. Both ends of the front complete cam groove C4F are closed, and a front follower 20ff that is positioned at one end of the front complete cam groove C4F and fixed to the third group moving frame 20 is inserted into the cam ring 15. Through-holes (introducing groove portions) 15h are formed. The front complete cam groove C4F has an assembly section (introduction groove portion) C41, a storage position C42, a storage section C43, a zoom section C44, and an over tele section C45 following the through hole 15h. Here, for convenience, the assembly section C41 and the storage section C43 from the through hole 15h are set as a start area, and the over tele section C45 is set as an end area.

  On the other hand, the basic locus of the rear incomplete cam groove C4R is the same as the front complete cam groove C4F as shown by a two-dot chain line C4RR in FIG. 1, but is actually formed on the cam ring 15. Are a part (start area) of the storage section C43, a part on the tele side of the zoom section C44, and an over tele section C45 (end area). The over tele section C45 overlaps (is shared) with the storage section C33 (start area) of the second group cam groove C3. The rear incomplete cam groove C4R has a rear end portion opened in both the storage section C43 and the zoom section C44 formed on the cam ring 15, and the three-group movement that engages with the rear incomplete cam groove C4R. The rear follower 20fr of the frame 20 is integrally formed (molded) in advance on the third group moving frame 20.

  As described above, the start region and the end region of the two types of cam grooves formed on the cam ring 15, that is, the end portion (start region) of the storage section C33 of the second group cam groove C3, and the rear incomplete cam groove C4R. By overlapping with the over tele section C45 (end region), the axial length of the cam ring 15 can be shortened, and the lens barrel can be downsized.

  In the above embodiment, in the overlap section of the storage section C33 of the second group cam groove C3 and the over tele section C45 of the rear imperfect cam groove C4R, the circumferential groove width is set to the diameter of the follower 19f and the rear follower 20fr. It is set larger than This ensures an assembly adjustment allowance in the optical axis direction of the second lens unit L2 with respect to the second group moving frame 19, similarly to the circumferential groove width of the storage position C15 (circumferential groove C16) of the first group cam groove C1. It is to do.

  In the zoom lens barrel having the above structure, the follower is assembled (assembled) into each cam groove of the cam ring 15 as follows. First, the follower 17f of the first group moving cylinder 17 is fitted into the cam groove C1 from the assembling position C11, and the cam ring 15 and the first group moving cylinder 17 are relative to each other by a predetermined distance with the follower 17f positioned at the end of the over tele section C12. By rotating, the positions where the follower 18f of the barrier support cylinder 18 and the barrier cam groove C2 are assembled are matched.

  Next, the follower 18f of the barrier support cylinder 18 is inserted into the barrier cam groove C2 from the assembly position C21 and positioned at the end of the over tele section C22, and the cam ring 15 is moved to the first group moving cylinder 17 and the barrier support cylinder 18. The followers 17f and 18f are positioned in the storage positions C15 and C25 (circumferential grooves C16 and C26) by relative rotation.

  In this state, the second group moving frame 19 and the third group moving frame 20, which are separately sub-assembled, are placed in the cam ring 15, and the through hole 15h of the cam ring 15 matches the front follower 20ff screwing position of the third group moving frame 20. Let Then, the front follower 20ff is inserted from the through hole 15h and fixed to the third group moving frame 20. Next, when the follower 19f of the second group moving frame 19 is inserted into the introduction groove C31 of the second group cam groove C3, the front follower 20ff enters the storage position C42 from the assembly section C41, and then the cam ring 15 is moved. The storage section C43 is entered by rotating.

  The rear follower 20fr fixed in advance (integrally formed) with the cam ring 15 engages with the rear follower 20fr in the storage section C43 and the zoom section C44, and stably guides the cam ring 15. That is, as shown in FIG. 6, when the cam ring 15 reaches the vicinity of the front moving end and the front follower 20ff engages with the storage section C43 and the zoom section C44, the three-group moving frame in both the front follower 20ff and the rear follower 20fr. 20 is guided so that the third group moving frame 20 is not inclined.

  In the above embodiment, the present invention is applied between the second group cam groove C3 and the rear incomplete cam groove C4R of the third group cam groove C4. The present invention can be applied to a complete cam groove such as the complete cam groove C4F. Even in this case, if the end of the storage section C33 of the second group cam groove C3 is arranged in parallel without overlapping with the over tele section C45 of the third group cam groove C4, the shaft of the cam ring 15 is compared. It is understood that the direction length can be shortened. Or, compared with the case where the end of the storage section C33 and the end of the over tele section C45 are separated from each other in the circumferential direction, the cam ring 15 can have a small diameter, or the inclination angle of the cam groove can be reduced.

  In the above embodiment, the start region of the two types of cam grooves to be overlapped is a part of the storage section C43, and the end region is the over tele section C45, but regardless of the function (name) of the cam groove, The present invention is established.

  The zoom lens barrel described with reference to FIGS. 3 to 6 is an example to which the zoom lens cam mechanism of the present invention is applied, and it is apparent that the cam mechanism of the present invention can be applied to other lens barrels.

FIG. 5 is a development view showing a cam groove shape on the inner peripheral surface of the cam ring, showing an embodiment of a cam mechanism of the zoom lens barrel according to the present invention. It is an expanded view which shows the cam groove shape of the cam ring outer peripheral surface. It is a disassembled perspective view which shows an example of the zoom lens barrel which applies the cam mechanism by this invention. FIG. 4 is an upper half sectional view of the zoom lens barrel of FIG. 3 in a stored state. FIG. 4 is an upper half sectional view at a short focal length end of the zoom lens barrel of FIG. 3. FIG. 4 is an upper half sectional view at a long focal length end of the zoom lens barrel of FIG. 3.

Explanation of symbols

C1 Group 1 cam groove C2 Barrier cam groove C3 Group 2 cam groove C4 Group 3 cam groove C11 C21 Mounting position C12 C22 Over tele section C13 C23 Zoom section C14 C24 Storage section C15 C25 Storage position C16 C26 Circumferential groove C31 Introduction groove C32 storage position (starting area)
C33 storage section (starting area)
C34 Zoom section C35 Over tele section C4F Front complete cam groove (cam groove for 3 groups)
C4R rear incomplete cam groove (cam groove for 3 groups)
C41 Assembly section (introduction groove)
C42 Storage position C43 Storage section C44 Zoom section C45 Over tele section (end section)
15 Cam ring 15h Through hole (introduction groove)
17 1st group moving cylinder 17f 18f 19f 20ff 20fr Follower 18 Barrier support cylinder 20 3rd group moving frame

Claims (5)

Two or more types of cam grooves with different basic trajectories are formed in a single cam ring that is rotationally driven and has a start region and an end region that are spaced apart in the rotational direction of the cam ring. In the zoom lens barrel that engages the cam followers of the two rectilinear members guided linearly in the optical axis direction,
Each of the two types of cam grooves has a zoom section and a non-zoom section before and after the zoom section.
The start region of one cam groove and the end region of the other cam groove of the two types of cam grooves overlap in the non-zoom section of the two types of cam grooves and are shared. The zoom lens barrel cam mechanism. 2. The zoom lens barrel cam mechanism according to claim 1, wherein the non-zoom section of the two types of cam grooves is disposed on one of the front and rear sides of the zoom section, and the introduction groove section for introducing a corresponding follower, The following storage position and storage section, and an over tele section located on the other side before and after the zoom section, an area including the introduction groove portion of one cam groove and the storage position is set as the start area, and the other cam A zoom lens barrel cam mechanism in which the over tele section of the groove overlaps with the start region of the one cam groove. 3. The zoom lens barrel cam mechanism according to claim 1 or 2, wherein one of the two types of cam grooves has a complete cam groove having the same basic locus and an entire basic locus, and only a part of the basic locus. A zoom lens barrel cam mechanism comprising an incomplete cam groove, wherein an overlap region of the start region and the end region is formed between the incomplete cam groove and the other cam groove. 4. The zoom lens barrel cam mechanism according to claim 3, wherein the other cam groove has a part of the storage section, a part of a tele side of the zoom section, and an over tele section formed on the cam ring. A zoom lens barrel cam mechanism that is a cam groove. 5. The zoom lens barrel cam mechanism according to claim 1, wherein the zoom lens barrel has a four-group configuration, and the two types of cam grooves are for a second group lens and a third group lens. A zoom lens barrel cam mechanism.

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