JP2510143Y2 - Focus position adjustment mechanism of zoom lens - Google Patents

Description

[Detailed Description of the Invention] [Industrial field of application] The present invention is a focus for adjusting a focus back position by a photographing lens system in a zoom type photographing lens capable of telephoto / wide-angle photographing (hereinafter referred to as a zoom lens). Position adjustment mechanism.

[Conventional technology]

As a part of multifunctionalization in recent cameras, zoom lenses that can freely shoot from telephoto to wide-angle have come to be used. Moreover, the zooming operation of this zoom lens can be used for quick shooting and operability. From the aspect, it is general that an electric motor incorporated in the camera body is used as a drive source.

By the way, this type of zoom lens has at least two or more lens groups in its lens barrel, and the focal length is changed by changing the interval between these lens groups to obtain a desired image magnification. It is structured so that you can shoot. An important requirement for such a zoom lens is that the position of the focus surface (focus back) must be constant at any position during zooming operation. To be

Therefore, in this type of zoom lens, the lens barrel is configured to change the focal length by changing the interval between the plurality of lens groups with a cam or the like.
It is designed so that the focus back position is always constant.
Then, in such a zoom lens, conventionally, as a general adjustment method for adjusting the relative positional relationship between the lens barrel, each lens group inside thereof, and the camera body side,
First, by changing the focal length, the phase of the cam that controls the interval between each lens group is adjusted so that the focus back becomes constant, and then the focus back position on the camera body side is adjusted without shifting the adjusted phase. Insert a washer, spacer, shim or other inclusion between the zoom lens barrel and the reference surface on the camera body side where this lens barrel is attached while measuring the specified thickness so that it matches the film surface. Alternatively, a method of holding the zoom lens barrel on the fixed side member by a straight-moving helicoid mechanism and transmitting the rotation through this helicoid mechanism to move the entire zoom lens barrel back and forth in the optical axis direction is used for adjustment. Was there.

[Problems to be solved by the device]

However, in the former case described in the above-mentioned conventional adjustment method, continuous adjustment is difficult because the types of washers that can be prepared are limited when the zoom lens barrel is assembled to the camera body. In addition to lacking in mass productivity, this adjustment work itself is extremely troublesome, such as checking the amount of focus back deviation, determining the thickness of the washer to be inserted and incorporating it, and checking the amount of focus back deviation multiple times. It was complicated.

On the other hand, in the case of the latter described in, although the advantages of workability and the like can be obtained as compared with the former case described above, it is possible to incorporate a special mechanical component in the camera body only for the purpose of focusing back adjustment. It is necessary to increase the number of parts and increase the manufacturing cost.

In particular, the focus back adjustment as described above is performed only once when the assembly is once performed and then when the parts are replaced or disassembled during maintenance. The frequency thereof is not so high, and the mechanism for only the focus back adjustment is used. It is desired to take some measures to minimize the addition of parts and to easily perform simple and continuous adjustment.

[Means for solving the problem]

In order to meet such a demand, the focus position adjusting mechanism of the zoom lens according to the present invention has a rear end side of the holding barrel 4 that holds the first lens group 5 that is moved back and forth as the rotary barrel 3 rotates. A second lens group 12 biased to one end side by a spring 13 is held in a guide tube 10 fixedly mounted on the guide tube 10 so as to be movable back and forth by engaging a cam pin 14 with a straight cam groove 10a of the guide tube 10. At the same time, the cam pin 14 moves the rectilinear cam groove so as to move the second lens group 12 forward and backward with respect to the first lens group 5.
A camming cylinder 16 for zooming having a circumferential cam groove 16a engaged through 10a is connected to the rotary cylinder 3 by a connector (clutch plate 1
It is provided so as to rotate in conjunction with the rotation by connecting via 7), and the orientation of the cam groove 16a is outside the normal use area of the circumferential cam groove 16a formed in the cam barrel 16. Are formed with extension grooves 20 in different directions and in a direction in which the acting force of the spring 13 on the cam pin 14 is locked.

[Action]

According to the present invention, when the focus position adjustment, that is, the focus back adjustment is performed in the zoom lens, the cam barrel is rotated to the outside of the normal use area via the rotary barrel.
The cam pin on the lens group side of is exposed in the extended groove portion formed continuously outside the normal use area of the circumferential cam groove of the cam barrel,
The spring for urging the lens group locks the acting force on the cam pin to fix the phase by the cam means, and thereafter cuts off the rotation transmission between the cam barrel and the rotary barrel by the connector, and relatively By making it rotatable, the entire shooting lens group may be moved back and forth with respect to the film surface while maintaining a constant distance between both lens groups. It becomes possible to adjust to the state.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to the embodiments shown in the drawings.

1 (a), (b), (c) to FIG. 5 show an embodiment of a focus position adjusting mechanism for a zoom lens according to the present invention. A schematic configuration of a zoom lens as a photographing lens mechanism portion shown by 1 will be briefly described with reference to FIGS. 3 to 5, and reference numeral 2 in the drawings constitutes a part of a camera main body whose entire illustration is omitted. The front body 3 is a rotary cylinder that is rotatably fitted and held in a holding hole of the front body 2, and the movement of the rotary cylinder 3 with respect to the front body 2 in the optical axis direction is as follows.
It is regulated by a rotary cylinder retainer 2a which is screwed to the front body 2. The rotary cylinder 3 is rotationally driven by a predetermined angle in an appropriate direction by transmitting rotation from a zooming drive mechanism (not shown).

Further, an inner peripheral helicoid groove 3a forming a straight-moving helicoid mechanism is formed on the inner peripheral portion of the rotary cylinder 3, and an outer peripheral helicoid groove 4a meshing with the inner peripheral helicoid groove 3a is provided on the rear end side outer peripheral portion to function as a lens barrel. The holding cylinder 4 is fitted and held,
The holding cylinder 4 is moved back and forth in the optical axis direction as the rotary cylinder 3 rotates. Reference numeral 5 in FIG. 4 denotes a first lens group held by a lens frame 5a in the front end side small diameter portion of the holding cylinder 4, and further, on the front end side small diameter outer peripheral side of the holding cylinder 4, a cylindrical cover 4b. In the annular space covered by
Various mechanical components such as the shutter drive mechanism 6 are provided. Further, as shown in FIG. 4, a lens shutter mechanism section 7 is arranged at the rear end side portion of the first lens group 5 in the holding cylinder 4. Further, reference numeral 8 in the drawing is a straight line extending in the optical axis direction in the rotary cylinder 3 in a state where a base end portion bent in a substantially L shape is screwed to the rear end side of the front body 2. With the key, the rotation of the holding cylinder 4 is restricted by engaging the tip end side of the key with a part of the holding cylinder 4.

It is to be noted that the reference numeral 9 in FIG.
Of the zoom encoder board wound around the outer peripheral portion of the disk, a contact pattern or the like (not shown) serving as a rotational position indicating means is circumferentially formed on the board 9, and a signal extraction is provided on the front body 2 side. By contacting the encoder brush 9a, which is the means, the position of the rotary cylinder 3 in the rotational direction is detected, and the zooming position in the zoom lens 1 associated with the rotation is described above. The configuration is such that feedback control is performed to a controller (not shown) that controls driving (for example).

Reference numeral 10 is a guide cylinder which is arranged in the large diameter portion on the rear end side of the holding cylinder 4 in a loosely fitted state and whose front end side flange is integrally fixed by a set screw 11 (see FIG. 4, etc.). A straight-ahead guide groove 10a extending in the optical axis direction is formed at three locations evenly distributed in the circumferential direction. The second member 12 is held in the guide cylinder 10 so as to be movable back and forth in the optical axis direction, and is given a biasing force to the rear end side by a rattling prevention spring 13.
In the lens group, the three outer circumferential portions of the lens frame 12a are equally arranged in the circumferential direction, and the guide tube 10 projects in the radial direction.
A cam pin 14 that is engaged so as to pass through each of the linear guide grooves 10a is screwed. It should be noted that, as is apparent from FIG. 5, the straight advance key 8 is provided at a part of the outer peripheral portion of the guide cylinder 10 which holds the second lens group 12 so as to be movable back and forth.
A roller that is arranged so that it can roll while sandwiching the
15 and 15 are assembled with the stop screws 15a and 15a, whereby the guide cylinder 10 can be moved only in the optical axis direction by the straight key 8 together with the holding cylinder 4, and the movement in the rotation direction is restricted. There is. In addition, the above-mentioned second lens group 12 is a spring.
The cam pin 14 is pressed against the rear end side end portion of the forward cam groove 10a by the urging force of 13, and is movably held in the guide cylinder 10 without rattling.

Reference numeral 16 denotes a cam cylinder that constitutes a cylindrical cam mechanism together with the guide cylinder 10 by being rotatably fitted and held on the inner peripheral portion of the rear end side of the holding cylinder 4 on the outer peripheral side of the guide cylinder 10. The second lens group 12 is made the first by the 10 and the cam barrel 16.
By making the lens group 5 move forward and backward, as is well known, it is possible to change the combined focal length of these lens groups 5 and 12 and perform the required zooming operation. A circumferential cam groove into which the tip of the cam pin 14 from the side of the second lens group 12 penetrating the straight cam grooves 10a of the guide cylinder 10 is engaged with the outer peripheral portion of the cam cylinder 16. 16a
However, it is formed so as to be inclined with respect to the optical axis direction.

17 is a fixing screw on a part of the rear end side end surface of the cam cylinder 16 described above.
A clutch plate which is fixed by 18 and is a connector for connecting the cam cylinder 16 to the rotary cylinder 3 side in the rotational direction and rotating integrally and synchronously. A projecting piece protruding from the clutch plate 17 in the outer peripheral direction. As is apparent from FIGS. 4 and 5, 17a engages with an engaging groove 3b recessed in a part of the inner peripheral portion of the rotary cylinder 3 along the optical axis direction, When the clutch is engaged, the cam barrel 16 is coupled to the rotary barrel 3 so as to be movable in the optical axis direction, and the holding barrel 4, which is fed by the rotation of the rotary barrel 3 through a straight helicoid mechanism, is fed in. It is configured so that it can rotate independently of the side of the guide tube 10 and can operate in conjunction with each other in the optical axis direction. Reference numeral 17b in the drawing denotes an arc groove for screw fixing of the clutch plate 17, and when the screw 18 is loosened to release the clutch engagement state, the rotation transmission from the rotary cylinder 3 to the cam cylinder 16 is separated, and these are made relative to each other. It is configured to be rotatable. That is, the relative rotation range of the arc groove 17b and the screw 18 described above serves as an adjustment allowance at the time of adjusting the focus back position described later.

In the zoom lens 1 having such a configuration, when the rotary cylinder 3 is rotated in a predetermined direction by the rotation transmission from the zooming drive mechanism such as an electric motor provided on the camera body side, the linear helicoid mechanism causes the rotary cylinder 3 to move inside the holding cylinder 4. While the first lens group 5 is extended or retracted in the optical axis direction,
Due to the relationship between the circumferential cam groove 16a, which is relatively displaced by the rotation of the cam cylinder 16 connected by the clutch plate 17, and the straight-moving cam groove 10a of the guide cylinder 10, via the cam pin 14 engaged with them. The second lens group 12 also moves back and forth while changing the distance from the first lens group 5, and as a result, zooming photography with a predetermined image magnification becomes possible. The zooming position is sent to the controller side when the rotary position of the rotary cylinder 3 is detected by the encoder (9, 9a).

In the cylindrical cam mechanism described above, when the cam barrel 16 is rotated by the rotation of the rotary barrel 3, the circumferential cam groove 16a of the cam barrel 16a is rotated.
The rotational force is transmitted to the cam pin 14 engaged with the cam pin 14, but the cam pin 14 is also engaged with the linear cam groove 10a of the guide cylinder 10 whose rotation is restricted and only linear motion is allowed. The rotational movement is restricted to, and as a result, the rotational force is converted into a moving force in the optical axis direction, the second lens group 12 moves back and forth along the movement of the circumferential cam groove 16a, and both lens groups 5, It is well known that the interval between 12 is changed to a desired state and the zooming operation is performed. At this time, the cam pin 14 on the second lens group 12 side is always urged toward the rear end side by the spring 13 and is pressed against the groove side edge of the cam groove, so that the cam groove and the cam pin 14 are Even if there is a rattling between them, there is no problem in operation.

Now, according to the present invention, in the zoom lens 1 having the above-described configuration, the rotary cylinder 3 is always provided via the clutch plate 17.
The circumference of the cam barrel 16 for zooming that changes the focal length by changing the distance between the second lens group 12 and the first lens group 5 by being connected to the side and being rotated along with the rotation. Outside the normal use area of the cam groove 16a, as is clear from FIGS. 1 (a), (b) and FIG. 2, the direction of the cam groove 16a is different from that of the cam groove 14a to the cam pin 14. This is characterized in that the extension groove portion 20 that extends in the direction in which the acting force P is locked is formed continuously through the bent portion.

That is, in performing the focus position adjustment, that is, the focus back adjustment in the zoom lens 1 described above, the clutch plate 17 is stopped in order to keep the distance between the first lens group 5 and the second lens group 12 constant. It is preferable to loosen the screw 18 (the clutch plate 17 may be removed) and separate the cam barrel 16 from the rotary barrel 3 side to make it relatively rotatable. With this arrangement, by rotating the rotary barrel 3 while keeping the cam barrel 16 side stopped, the holding barrel 4 is moved in the optical axis direction while keeping the distance between both lens groups 5 and 12 constant. It is possible to move back and forth in this way, which allows the distance between the first and second lens groups 5 and 12 and the film surface (not shown) to be adjusted arbitrarily, and the focus position to be adjusted appropriately. And it can be done reliably, but in this case there are some problems.

This will be described in detail with reference to FIGS. 1 (a), (b), (c), etc. First, the cam barrel 16 will be as shown in FIG. 1 (a) when unfolded. When the focus back position is adjusted in the cylinder 16, when the cam pin 14 releases the coupling of the clutch plate 17 within the normal use range of the circumferential cam groove 16a as shown in FIG. Due to the relationship between the urging force P that acts and the inclination of the cam surface 16b in the circumferential cam groove 16a of the cam barrel 16, the cam barrel 16 that is no longer restricted in the rotation direction rotates in the direction indicated by arrow A in the figure. As a result, the phase of the cam barrel 16 (positional relationship of the second lens group 12 with respect to the position of the first lens group 5) that is positioned during assembly or in the previous process is displaced. Therefore, according to the present invention, as shown in FIG. 1B, the cam extension groove portion 20 is formed in the cam groove 16a of the cam barrel 16 in addition to the normal use range, and the cam pin 14 is formed in the extension groove portion 20.
The force P applied to the cam pin 14 by the spring 13 is used as a force for restricting the rotation of the cam barrel 16 in reverse.

FIG. 2 shows the relationship between the respective parts, in which the horizontal axis represents the rotation angle of the rotary cylinder 3, and the vertical axis represents the first lens group 5, the second lens group 12, and the focus back. It is a graph of the positions. Here, the position of the first lens group 5 may be considered as the position of the protective cylinder 4 in the configuration of the zoom lens 1 described above. In this figure, the first lens group 5 is extended and retracted by a rectilinear helicoid mechanism in proportion to the rotation angle of the rotary cylinder 3. On the other hand, in the second lens group 12, as the cam barrel 16 rotates in synchronization with the rotary barrel 3, the circumferential cam groove 16a of the cam barrel 16 causes the cam surface 16b and the straight guide groove 10a of the guide barrel 10 to move. , Move the focus back position to be constant while changing the focal length.

By the way, when the cam pin 14 is dropped to the focus back adjustment position beyond the normal zooming range, that is, the normal use range of the cam, the cam surface in the cam extension groove portion 20 of the cam barrel 16 keeps the focus back position constant. As shown in FIG. 2, the focus back position is Δb because it is not
However, if the cam barrel 16 is accurately formed,
This value of Δb can be suppressed to a slight amount of displacement.
That is, this Δb is set at the original focus back adjustment target position.
If you adjust it while keeping the margin in advance, the focus back will be
When the rotary cylinder 3 is rotated and the cylindrical cam mechanism or the like is returned to the normal use range, it substantially matches the predetermined adjustment target value.

It should be noted that the rotary cylinder 3 is rotated to the focus back adjustment position so that the cam pin 14 is dropped into the extension groove portion 20 continuous with the circumferential cam groove 16a of the cam cylinder 16, and the screw 18 of the clutch plate 17 is loosened to release the second lens. The first lens group 5 and the second lens 5 when the rotary cylinder 3 is rotated with the acting force on the cam pin 14 being locked by the spring 13 for biasing the group 12 and the phase being fixed by the cam means. The movement of the group 12 and the focus back position is indicated by broken lines a, b, and c in FIG. As is apparent from the broken lines a, b, and c, when the rotary cylinder 3 is rotated in this state, the first and second lens groups 5 and 12 can be moved back and forth without changing their intervals. Therefore, the focus back position can be freely moved and adjusted to an appropriate position.

Then, as described above, the focus back is adjusted to the target adjustment position with a margin for the displacement of Δb, and then the corresponding position of the circular arc groove 17b of the clutch plate 17 is tightened and fixed with the screw 18, and the rotary cylinder 3 is further fixed. The adjustment is completed by returning to the normal use range again. That is, after fixing the clutch plate 17 with the screw 18, the rotary cylinder 3 may be rotated so that the cam pin 14 faces the normal circumferential cam groove 16a from the extension groove portion 20. Here, during normal use, the signal from the encoder (9, 9a) accompanying the rotation of the rotary cylinder 3 is constantly monitored,
It is recommended that the is not rotated to the focus back adjustment position.

Further, according to the above-described configuration, as the components for focus back adjustment, the clutch plate 17 for connecting and disconnecting the transmission of the driving force to the cylindrical cam mechanism and fixing the clutch plate 17 within a predetermined angle range. Only the screw 18 is required, and the shooting optical lens system (first and second lens groups 5 and 12) is continuously moved back and forth simultaneously in the optical axis direction by using a helicoid mechanism equipped as a part of the zooming mechanism. Since it is sufficient to adjust the focus back position, it is possible to adjust to the adjustment target value while checking the focus back position. Therefore, such a configuration has an advantage that the number of constituent parts can be minimized and workability can be significantly improved.

Further, in the above-mentioned cam mechanism, when the cam pin 14 follows the cam surface 16b of the circumferential cam groove 16a via the straight-moving cam groove 10a, the urging force of the spring 13 acts on the cam pin 14. Due to the relationship between the urging force of the cam groove 16 and the slope of the cam groove 16, the acting force in the direction opposite to the direction in which the cam pin 14 is always moved acts on the cam surface 16b. Therefore, conventionally, by separating the driving force to the cam mechanism by the clutch plate 17, the cam barrel 16 that has lost its support is pushed back by the urging force to the cam pin 14, and is adjusted in the previous step at the time of assembling the bending angle. The problem of phase shift is eliminated. In particular, according to the present invention, the clutch plate 17 is disengaged with the cam pin 14 facing the extension groove 20 of the cam groove 16a, and the clutch plate 17 is disengaged so that the cam pin 14 is urged by the extension groove 20. It can be used as a fixing force within 20 and can eliminate conventional problems such as phase shift.

It should be noted that the present invention is not limited to the structure of the embodiment described above, and the shape, structure, etc. of each part of the zoom lens 1 can be freely modified or changed, and various modifications can be considered. Also,
In the above-described embodiment, the case where the extension groove portion 20 which is inclined in the opposite direction through the bent portion is formed outside the normal use range of the circumferential cam groove 16a in the cam barrel 16 has been exemplified. It is not limited, and it will be easily understood that it may be, for example, an extension groove portion extending from the end portion of the circumferential cam groove 16a in the direction orthogonal to the optical axis direction, that is, in the circumferential direction. The point is that the extension groove portion may be in a direction different from the direction of the cam groove 16a and in the direction in which the acting force of the spring 13 on the cam pin 14 is locked.

[Effect of device]

As described above, according to the focus position adjusting mechanism of the zoom lens of the present invention, the first lens group is held by being biased toward the one end side by the spring in the guide tube attached to the holding tube side of the first lens group. The second lens group is moved back and forth by engagement of the cam pin with the straight cam groove of the guide cylinder and engagement of the cam pin with the circumferential cam groove of the cam cylinder, and rotation associated with the rotary cylinder of the cam cylinder. The cam barrel in the zoom lens that changes the combined focal length of is connected so that it is always rotated in conjunction with the rotary barrel, and the connector that makes it rotatable relative to the rotary barrel during focus back adjustment is used. An extension groove portion that is provided and extends outside the normal use area of the circumferential cam groove formed in the cam barrel, in a direction different from the direction of the cam groove and in a direction for locking the acting force of the spring on the cam pin. To form Therefore, despite the simple and inexpensive structure, it requires complicated work such as interposing a washer and other inclusions for the focus back adjustment, and it is a component used only during the focus back adjustment. There is no need to attach a special mechanical component as a part of the above, and since the focus back position can be adjusted continuously by a simple operation, it is possible to shorten the time required for adjustment, etc. There is an effect.

[Brief description of drawings]

FIG. 1 shows an embodiment of a focus position adjusting mechanism for a zoom lens according to the present invention, and FIGS. 1 (a), (b) and (c) show a cam pin, a circumferential cam groove and a cam pin for adjusting a focus back position. Exploded view and operation explanatory view showing the relationship with the straight cam groove,
FIG. 2 is an explanatory view showing the movement of the first and second lens groups and the focus back position during zooming and focus back adjustment, FIG. 3 is a schematic perspective view showing the components of the zoom lens, and FIG. FIG. 5 is a cross-sectional view of the main part, and FIG.
It is a -V line sectional view. 1 ... Zoom lens, 2 ... Front body, 3 ... Rotating cylinder, 4 ... Holding cylinder, 5 ... First lens group, 8 ... Straight guide, 10 ... Guide cylinder, 10a ... Straight cam Groove, 12 ……
2nd lens group, 13 ... rattling prevention spring, 14 ... cam pin, 16 ... cam barrel, 16a ... circumferential cam groove, 17 ... clutch plate (connector), 17a ... projecting piece , 17b …… Arc groove for screw fixing, 18 …… Screw, 20 …… Extension groove.

Claims (1)

(57) [Scope of utility model registration request] 1. A first lens group held in a holding barrel that is moved back and forth in the optical axis direction as the rotating barrel rotates, and a guide barrel fixedly mounted on the rear end side of the holding barrel. A second lens group that is moved back and forth in the optical axis direction by the engagement of the cam pin with the straight-moving cam groove and is held by being biased toward one end side in the optical axis direction by a spring; and a guide tube in the holding tube. The second lens group is attached to the outer peripheral side of the second lens group by a cam pin that is rotatably fitted to the outer peripheral side and is engaged with the circumferential cam groove through the rectilinear cam groove by being rotated in association with the rotation of the rotary cylinder. A cam barrel for moving the first lens group forward and backward to change the combined focal length of these two lens groups, and this cam barrel is connected to the rotary barrel so as to be movable in the optical axis direction at all times. Adjust the distance to the film surface by moving both lens groups back and forth in the optical axis direction. The cam is provided with a connector that is relatively rotatable, and the direction is different from the direction of the cam groove outside the normal use area of the circumferential cam groove formed in the cam barrel. A focus position adjusting mechanism for a zoom lens, wherein an extension groove portion is formed in a direction in which an acting force of the spring on the cam pin is locked.