JP2003035860A - Optical equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve space efficiency in optical equipment as much as possible by using a sheet type light shielding member as a fixed diaphragm. SOLUTION: The optical equipment is provided with a lens holding member 2 holding a lens unit L2 and a ring sheet type light shielding member 2d intercepting unnecessary light at the outermost position in the optical axis direction of the lens unit, and the light shielding member is fixed on the lens holding member in a state where it is deformed from plate ring shape to nearly truncated cone ring shape which is rotationally symmetric with respect to an optical axis so that its outer peripheral side part may be positioned on the more inside in the optical axis direction of the lens holding member than its inner periphery side part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical device such as a lens barrel and an image pickup device such as a still camera or a video camera equipped with the lens barrel.

[0002]

2. Description of the Related Art As a zoom lens for a video camera, for example, there is a zoom lens composed of four lens groups in order from the subject side: a fixed convex lens, a movable concave lens, a fixed convex lens, and a movable convex lens group.

FIGS. 6A and 6B show a lens barrel structure of a general zoom lens having a four-group lens structure. In addition, (B) has shown the AA line cross section in (A).

The four lens groups 201a to 201d constituting this zoom lens are fixed front lens 201.
a, a variator lens group 201b that performs a magnification change operation by moving along the optical axis, a fixed afocal lens 201c, and a focal plane maintenance and focusing at the time of magnification change by moving along the optical axis. The focusing lens group 201d is used.

The guide bars 203, 204a, 204b are arranged parallel to the optical axis 205, and guide the moving lens group and prevent rotation. The DC motor 206 serves as a drive source for moving the variator lens group 201b.

The front lens 201a is held by the front lens barrel 202, and the variator lens group 201b is a V moving ring 21.
It is held at 1. In addition, the afocal lens 201
c is the intermediate frame 215, and the focusing lens group 201d
Are held by the RR moving ring 214.

The front lens barrel 202 is positioned and fixed to the rear lens barrel 216, the guide bar 203 is positioned and supported by both lens barrels 202 and 216, and the guide screw shaft 208 is rotatably supported. There is.
The guide screw shaft 208 is rotationally driven by the rotation of the output shaft 206a of the DC motor 206 being transmitted via the gear train 207.

The V moving ring 211 for holding the variator lens group 201b includes a pressing spring 209 and the pressing spring 20.
9 has a ball 210 that engages with a screw groove 208a formed in the guide screw shaft 208 by a force of 9 and the guide screw shaft 20 is driven by the DC motor 206.
When 8 is driven to rotate, it is moved forward and backward in the optical axis direction while being guided by the guide bar 203 and restricted in rotation.

The rear lens barrel 216 and the intermediate frame 215 positioned on the rear lens barrel 216 have guide bars 204a, 2a.
04b is fitted and supported. The RR moving ring 214 can be moved back and forth in the optical axis direction while being guided and restricted in rotation by the guide bars 204a and 204b.

The RR moving ring 214 for holding the focusing lens group 201d is provided with guide bars 204a, 204.
a sleeve portion slidably fitted in b is formed, and the rack 213 has an RR moving ring 2 in the optical axis direction.
It is assembled so as to be integrated with 14.

The stepping motor 212 rotatably drives a lead screw 212a formed integrally with its output shaft. The RR moving ring 21 is attached to the lead screw 212a.
The rack 213 assembled to the No. 4 is engaged, and the lead screw 212a rotates to move the RR moving ring 214 in the optical axis direction while being guided by the guide bars 204a and 204b.

As the driving source for the variator lens group, a stepping motor may be used as in the focusing lens group.

The front lens barrel 202, the intermediate frame 215, and the rear lens barrel 216 form a lens barrel main body for substantially hermetically accommodating lenses and the like.

Further, when the lens group holding frame is moved by using such a stepping motor, after detecting that the holding frame is located at one reference position in the optical axis direction by using a photo interrupter or the like, The absolute position of the holding frame is detected by continuously counting the number of drive pulses given to the stepping motor.

FIG. 7 shows an electrical structure of a camera body in a conventional image pickup apparatus. In this figure,
Constituent elements of the lens barrel described in 1 are given the same reference numerals as in FIG.

Reference numeral 221 denotes a solid-state image pickup device such as CCD, and 222.
Is a drive mechanism of the variator lens group 201b, and includes a motor 206 (or stepping motor) and a gear train 207.
And a guide screw shaft 208 and the like.

223 is a focusing lens group 201d.
And a stepping motor 212, a lead screw shaft 212a, a rack 213, and the like.

Reference numeral 224 is a drive mechanism of a diaphragm device 235 arranged between the variator lens group 201b and the afocal lens 201c.

Reference numeral 225 is a zoom encoder and 227 is a focus encoder. These encoders respectively detect the absolute positions of the variator lens group 201b and the focusing lens group 201d in the optical axis direction. When a DC motor is used as a variator drive source as shown in FIG. 6, an absolute position encoder such as a volume is used, or a magnetic type is used.

When a stepping motor is used as a drive source, a method is used in which the holding frame is arranged at the reference position as described above and then the number of operation pulses input to the stepping motor is continuously counted. It is common.

Reference numeral 226 denotes a diaphragm encoder, which has a structure in which a Hall element is arranged inside a diaphragm driving source 224 such as a motor to detect the rotational positional relationship between the rotor and the stator.

A CPU 232 controls the camera. A camera signal processing circuit 228 subjects the output of the solid-state image sensor 221 to predetermined amplification and gamma correction. The contrast signal of the video signal subjected to these predetermined processes passes through the AE gate 229 and the AF gate 230. That is, the optimum signal extraction range for determining the exposure and focusing is set at this gate within the entire screen. The size of this gate is variable,
There may be more than one.

An AF signal processing circuit 231 processes an AF signal for AF (autofocus), and generates one or a plurality of outputs related to high frequency components of a video signal. 233 is a zoom switch and 234 is a zoom tracking memory. Zoom tracking memory 234
Stores information on the focusing lens position to be set in accordance with the subject distance and the variator lens position during zooming. In addition, as a zoom tracking memory, C
The memory in PU232 may be used.

For example, the zoom switch 23 is selected by the photographer.
3 is operated, the CPU 232 causes the current variator to be the detection result of the zoom encoder 225 so that the predetermined positional relationship between the variator lens and the focusing lens calculated based on the information in the zoom tracking memory 234 is maintained. The absolute position in the optical axis direction of the lens and the calculated position where the variator lens should be set, and the absolute position in the optical axis direction of the current focus lens that is the detection result of the focus encoder 227 and the calculated focus lens should be set The zoom drive mechanism 222 and the focussing drive mechanism 223 are drive-controlled so that their positions match each other.

Further, in the autofocus operation, the CPU 2 is controlled so that the output of the AF signal processing circuit 231 shows a peak.
Reference numeral 32 drives and controls the focusing drive mechanism 223.

Further, in order to obtain proper exposure, the CPU 2
32 sets the average value of the output of the Y signal that has passed through the AE gate 229 as a predetermined value, and drives and controls the aperture drive mechanism 224 so that the output of the aperture encoder 226 becomes this predetermined value, and controls the aperture diameter.

Here, a method of cutting a harmful light beam (unnecessary light) that enters from outside the effective diameter and causes flare and ghost in the lens optical system of the conventional video camera will be described with reference to FIG.

In order to cut off the unnecessary light, in most cases, as shown in FIG. 8A, the innermost diameter 211b of the lens holding member 211a for holding the lens is made equal to the effective diameter of the optical system. A sheet member 211c having an opening having the same diameter as the effective diameter is arranged.

Then, as shown in FIG. 8A, when the sheet member 211c is fixed in a lens group composed of two or more lenses, a sheet of adjacent lenses called a marginal contact is used. A method of sandwiching and fixing the member 211c is adopted.

In this case, as shown in FIG. 8B, the sheet member 211c is deformed into a substantially truncated cone shape along the lens surface due to its flexibility or elasticity.

Further, when the unnecessary light is cut on the most image plane side or the most object side of the lens group, the above-mentioned marginal contact method cannot be adopted. Therefore, a light shielding member 211d having a certain thickness other than the sheet member is used. A method of fitting into the lens holding member or fixing to the lens barrel main body (202) by a bayonet or a helicoid is adopted.

[0032]

However, in a situation where there is a strict internal space margin, such as a lens barrel which has been downsized in recent years, when a member having a certain thickness other than the sheet member is used, the lens barrel However, there is a problem that it becomes large.

For this reason, it is desirable to use a sheet member even when unnecessary light is cut on the most image plane side or the most object side of the lens group.

However, if the sheet member is used as it is in a flat plate shape, the space efficiency can only be improved due to the reduced thickness, and further the space efficiency can be improved by utilizing the flexibility of the sheet member. It should be planned.

[0035]

In order to solve the above problems, in the optical device of the present invention, unnecessary light is generated at the lens holding member for holding the lens unit and the outermost position of the lens unit in the optical axis direction. A light-shielding member in the form of a ring sheet for blocking is provided, and the light-shielding member is rotationally symmetrical with respect to the optical axis so that the outer peripheral side portion is located inside the lens holding member in the optical axis direction from the inner peripheral side portion from the flat plate ring shape. Is fixed to the lens holding member in a state of being deformed into a substantially truncated cone ring shape.

In this way, the ring-sheet-shaped light-shielding member arranged at the outermost position (the most image plane side or the object side) in the optical axis direction of the lens unit holds the lens on the outer peripheral side than on the inner peripheral side. By transforming it into a substantially truncated cone ring shape so that it is located on the inner side in the optical axis direction of the member, it is not possible to place the light shielding member on the plane orthogonal to the optical axis while keeping the flat plate ring shape, so that the surface of the conical inclined surface of the light shielding member is not possible. It is possible to newly create a space to be used, and it is possible to improve the space efficiency in the optical device.

Therefore, for example, in the case where the lens holding member is movable in the optical axis direction, when the optical unit such as the light quantity adjusting unit is arranged near the moving end of the lens holding member, the above-mentioned new It is possible to make a part of the optical unit enter into such a space (beyond the position of the inner peripheral side portion of the light shielding member and approach the outer peripheral side portion). Therefore, the space required for moving the lens holding member (necessary for moving without interfering with the optical unit) can be reduced, and the entire optical device can be made compact.

Further, by forming a notch in the light shielding member so as to prevent unnecessary deformation (wrinkles or the like) in the inner peripheral side portion due to the deformation of the substantially frustoconical ring shape, this light shielding member is used. It becomes possible to block unnecessary light evenly in the circumferential direction.

In order to prevent the wrinkles and the like as described above from occurring, it is conceivable that the sheet member may be drawn into a truncated cone shape from the beginning, but the processing man-hour increases correspondingly,
It is not preferable because it leads to cost increase.

By fixing the light shielding member to the lens holding member by welding, it is possible to eliminate the risk of soiling the lens surface as in the case of using an adhesive.

[0041]

1 and 2 show the configuration of a lens barrel (optical device) according to an embodiment of the present invention. This lens barrel is used for an imaging device (optical device including the lens barrel) such as a still camera or a video camera.

Further, this lens barrel has a variable power optical system having a four-group structure of convex, concave and convex in order from the object side.

In these figures, L1 is a first lens group, L2 is a second lens group that performs a zooming operation by moving in the optical axis direction, and L3 is an image due to camera shake caused by shifting in a plane orthogonal to the optical axis. A third lens unit L4 for correcting shake is a fourth lens unit L4 for performing a focusing operation by moving in the optical axis direction.

Reference numeral 1 is a front lens barrel unit holding the first lens group L1, 2 is a second lens group moving frame holding the second lens group L2, and 3 is movable the third lens group L3 in a plane orthogonal to the optical axis. Is a shift unit, 4 is a fourth group moving frame for holding the fourth lens group L4, and 5 is a rear lens barrel to which an image pickup device (not shown) such as a CCD is attached.

Numerals 6 and 7 are guide bars, both ends of which are positioned and fixed by the front lens barrel unit 1 and the rear lens barrel 5. Further, 8 is a guide bar 8, both ends of which are positioned and fixed by the shift unit 3 and the rear lens barrel 5. The front lens barrel unit 1 and the rear lens barrel 5 constitute a lens barrel body.

The second group moving frame 2 is guided in the optical axis direction by the guide bars 6 and 7, and the fourth group moving frame 4 is guided by the guide bars 6 and 7.
8 is guided in the optical axis direction. The moving frames 2 and 4 are prevented from rotating around the other guide bar by one of the two guide bars.

The shift unit 3 is positioned on the front lens barrel unit 1, and then the rear lens barrel 5 and the front lens barrel unit 1 are positioned.
It is sandwiched and fixed by.

Reference numeral 9 denotes a light quantity adjusting unit (optical unit) for changing the quantity of light incident on the optical system, which is a so-called iris diaphragm for changing the aperture diameter by moving six diaphragm blades around the optical axis. In addition, the light quantity adjusting unit 9 includes
An ND filter 20 having three types of densities is attached to the optical path so that it can move forward and backward. The light amount adjustment unit 9 is fixed to the shift unit 3 from the front by three screws. The light amount adjusting unit 9 will be described in detail later.

The rear lens barrel 5 is positioned on the front lens barrel unit 1, and at the same time, as described above, the shift unit 3 is sandwiched and fixed together from behind by three screws.

Reference numeral 10 denotes a lead screw for moving the fourth lens unit L4 in the optical axis direction, which has a bearing shape before and after the lead screw, and has a rotor magnet 10a magnetized in multiple poles at its rear end. There is.

Reference numeral 11 is a stepping motor stator unit for rotating the rotor magnet 10a, and the lead screw 10 is rotatably supported by the shift unit 3 and a bearing portion provided in the stepping motor stator unit 11. The lead screw 10 meshes with a rack 4 a attached to the fourth group moving frame 4. Therefore, the stepping motor stator unit 1
When the rotor magnet 10a and the lead screw 10 are driven to rotate by the motor 1, the lead screw 10a
The fourth group moving frame 4 and the fourth lens group L4 are driven in the optical axis direction by the meshing action of the rack and the rack 4a.

The fourth group moving frame 4, the guide bars 6, 8,
The rack 4a and the lead screw 10 are biased by the biasing force of the torsion coil spring 4b, and the rattling between them is removed.

Reference numeral 12 denotes a lead screw for moving the second lens unit L2 in the optical axis direction, which has a bearing shape in the front and rear thereof and has a rotor magnet 12a magnetized in multiple poles fixed to its rear end. There is.

Reference numeral 13 is a stepping motor stator unit for rotating the rotor magnet 12a, and the lead screw 12 is rotatably supported by the shift unit 3 and a bearing portion provided in the stepping motor stator unit 13. The lead screw 12 meshes with a rack 2 a attached to the second group moving frame 2. Therefore, the stepping motor stator unit 1
When the rotor magnet 12a and the lead screw 12 are rotationally driven by 3, the lead screw 12a
The second group moving frame 2 and the second lens group L2 are driven in the optical axis direction by the meshing action of the rack and the rack 2a.

The second group moving frame 2, the guide bars 6, 7,
The rack 2a and the lead screw 12 are biased by the biasing force of the torsion coil spring 2b, and rattling between them is removed.

The stepping motor stator units 11 and 13 are fixed to the rear lens barrel 5 with two screws.

Reference numeral 14 denotes a focus reset switch composed of a photo interrupter, which optically detects the switching between light blocking and light transmitting due to the movement of the light blocking portion 4c formed in the fourth group moving frame 4 in the optical axis direction, and outputs an electrical signal. Is output. The control circuit (not shown) uses the focus reset switch 14
Whether or not the fourth lens unit L4 is located at the reference position is detected based on the signal from. The focus reset switch 14 is fixed to the rear barrel 5 with one screw through the substrate.

Numeral 15 is a zoom reset switch composed of a photo interrupter, which optically detects switching between light blocking and light transmitting due to the movement of the light blocking portion 2c formed on the second group moving frame 2 in the optical axis direction, and outputs an electrical signal. Is output. The control circuit detects, based on the signal from the zoom reset switch 15, whether or not the second lens unit L2 is located at the reference position. The zoom reset switch 15 is fixed to the front lens barrel unit 1 with one screw through the board.

Here, the structure of the shift unit 3 that makes the third lens unit L3 movable in the plane orthogonal to the optical axis will be described in more detail. The third lens unit L3 has a vertical direction to correct image shake in the PITCH direction (angle change in the vertical direction of the camera) and a YAW direction (angle change in the horizontal direction of the camera).
In order to correct the image blurring of the image, it is held so that it can be shifted in the horizontal direction, and has a drive system and a position detection system independent in the vertical direction and the horizontal direction. By these drive system and position detection system, the third lens unit L3 can be shifted to any position in the plane orthogonal to the optical axis.

Since the vertical drive system and the horizontal drive system and the position detection system have the same configuration with an angle of 90 degrees, the vertical drive system and the position detection system whose cross section is shown in FIG. 2 are shown here. Only the system will be explained.

Reference numeral 3b is a shift base which is a base of a fixed portion of the shift unit 3 and which is integrated with the body of the lens barrel. Reference numeral 3d is a compression coil spring, which is made of a material such as phosphor bronze wire so as not to be attracted by a magnet for position detection and driving, which will be described later, arranged near the compression coil spring.

Reference numeral 3a is a shift lens barrel for holding the third lens group L3. The front portion of the compression coil spring 3d is provided on the outer periphery of the holding portion of the shift lens barrel 3a for holding the third lens group L3. It is fitted so as to be substantially coaxial with the optical axis of L3. The front end of the compression coil spring 3d is fitted into a V-shaped groove (not shown) formed in the shift barrel 3a and positioned and fixed to the shift barrel 3a.

3l is a shift base 3b and a shift lens barrel 3a.
A ball which is disposed between the shift base 3b and the shift base 3b and comes into rolling contact with the shift lens barrel 3a. Although only one ball 3l is shown in the figure, in reality, it is arranged at three locations around the optical axis at substantially equal intervals. The balls 3l are made of a material such as SUS304 (austenitic stainless steel) so as not to be attracted by a driving magnet, which will be described later, disposed in the vicinity thereof.

There are three surfaces on which the balls 3l are in contact, on the shift base 13 side and on the shift lens barrel 15 side, and each contact surface is a surface orthogonal to the optical axis of the optical system. Has become. When the nominal diameters of the three balls are the same, holding and moving the third lens unit L3 while keeping the posture perpendicular to the optical axis by suppressing the mutual difference between the positions of the three surfaces in the optical axis direction. Guidance is possible.

3c is a sensor base which is a fixed member on the rear side, the position of which is determined by two positioning pins, and which is connected to the shift base 3b by three screws.

The rear portion of the compression coil spring 3d is fitted into the sensor base 3c so as to be substantially coaxial with the optical axis of the lens barrel. The compression coil spring 3d is compressed between the shift barrel 3a and the sensor base 3c and presses the shift barrel 3a against the shift base 3b via the ball 3l.

Even if the three balls 3l are not sandwiched between the shift base 3b and the shift lens barrel 3a between the three balls 3l and the respective contact surfaces, the balls 3l can be easily contacted from the contact surfaces. By applying the lubricating oil having a viscosity that does not drop off, an inertial force that exceeds the urging force of the compression coil spring 3d acts on the shift barrel 3a, and the balls 3l
It is possible to prevent the position of the ball from being easily displaced even when the ball is in the non-sandwiched state.

Next, the drive system of the shift barrel 3a will be described. Reference numeral 3j denotes a driving magnet which is magnetized into two poles in a radial direction with respect to the optical axis, 3k a yoke for closing a magnetic flux on the front side in the optical axis direction of the driving magnet 3j, and 3i fixed to the shift lens barrel 3a by adhesion. The formed coil 3h is a yoke for closing the magnetic flux on the rear side in the optical axis direction of the driving magnet 3j. The yoke 3h is fixed to the shift base 3b by the magnetic force of the magnet so as to form a space in which the coil 3i moves between the yoke 3h and the driving magnet 3j, and constitutes a magnetic circuit.

When a current is passed through the coil 3i, the driving magnet 3
Lorentz force is generated due to mutual repulsion of magnetic force lines generated in the magnet and the coil in a direction substantially perpendicular to the magnetization boundary of the two-pole magnetization of j, and the shift barrel 3a moves. That is, this drive system is a so-called moving coil type drive system.

Since the drive systems thus configured are arranged in the vertical and horizontal directions, respectively, the shift lens barrel 3
It is possible to drive a in two substantially orthogonal directions. At this time, as described above, the shift barrel 3a is urged by the compression coil spring 3d with respect to the shift base 3b with the three balls 3l interposed therebetween, and thus becomes a load when the shift barrel 3a is driven. The frictional force is only rolling friction of the ball 3l. Since this rolling friction is extremely small,
The shift lens barrel 3a can be minutely drive-controlled.

Next, the position detection system of the shift barrel 3a will be described. Reference numeral 3f is a detection magnet that is magnetized into two poles in the radial direction with respect to the optical axis, and reference numeral 3g is a yoke that closes the magnetic flux on the front side in the optical axis direction of the detection magnet 3f. These are fixed to the shift barrel 3a. 3e is a Hall element for converting the magnetic flux density into an electric signal, which is positioned and fixed to the sensor base 3c.

In the position detecting system configured as described above, when the shift lens barrel 3a is driven in the vertical direction or the horizontal direction, the magnetic flux density detected by the Hall element 3e changes, and this change in magnetic flux density is appropriate. The position of the shift barrel 3a can be detected by detecting the electric signal from the Hall element 3e by various signal processing.

Here, the positional relationship between the second lens group moving frame 2 holding the second lens group L2 and the light amount adjusting unit 9 located on the image plane side with respect to the second lens group moving frame 2 will be described with reference to FIGS. 4 will be described.

FIG. 4 is an exploded perspective view showing the structure of the light quantity adjusting unit 9. The second lens group L2 is a lens group that performs the zooming operation by moving in the optical axis direction as described above, but FIG. 3 shows the second lens group L2 during the zooming operation.
2 is a cross-sectional view showing a positional relationship when 2 is moved to the most image plane side. FIG.

The light amount adjusting unit 9 located on the image side of the second lens unit L2 adjusts the light amount by rotating the six diaphragm blades 9e around the optical axis and changing the aperture diameter. . Actually, the diaphragm driving lever 9c connected to the output shaft of the diaphragm driving actuator 9b rotates, and the diaphragm driving windmill 9d connected to the driving lever 9c rotates to rotate each of the six diaphragm blades 9e. Then, the aperture diameter is changed and the amount of light is adjusted. A diaphragm pressing metal plate 9f for preventing the diaphragm blade 9e from floating is arranged further on the object side than the diaphragm blade 9e.

The second group moving frame 2 is a mold member mainly made of polycarbonate, and deforms the annular projection 2e of the second group moving frame 2 by heating on the image side of the second lens group L2 (heat). Hold the second lens unit L2. The inner diameter of the caulked portion after the second lens unit L2 is fixed by the thermal caulking is φ2h. In this optical system, the effective diameter of the second lens unit L2 is φ2i, and φ2h> φ2i.

However, in this relationship, the caulking portion cannot cut off harmful light coming from outside the effective diameter,
Ghosts and flares will occur.

In FIG. 3, the fixed diaphragm (light-shielding member) 2d plays a role of cutting harmful light.

The fixed diaphragm 2d is a sheet-like member having a thickness of about 50 μm, and originally has a flat plate ring shape. Then, at the time of assembly, it is on the object side with respect to the plane orthogonal to the optical axis (that is, the outer peripheral side of the fixed aperture stop 2d is located on the inner side in the optical axis direction of the second group moving frame 2 than the inner peripheral side).
A holding portion of the second lens group (lens unit) L2 in the second lens group moving frame 2 is deformed into a substantially circular truncated cone ring rotationally symmetric with respect to the optical axis having a certain angle 2f, and is formed in a hole formed on the outer peripheral side thereof. After inserting the protrusions 2g provided at eight locations in the circumferential direction on the outer side in the radial direction, the protrusions 2g are fixed to the second group moving frame 2 by being deformed by heat (caulking).

The inner diameter of the fixed aperture stop 2d is substantially the same as the above-mentioned effective diameter φ2i, so that harmful light entering from outside the effective diameter can be reliably cut.

In FIG. 3, assuming that the fixed diaphragm is fixed on the plane orthogonal to the optical axis without making an angle 2f with respect to the plane orthogonal to the optical axis, the second group moving frame 2 moves toward the image plane side. When it moves to the end, it interferes with the diaphragm pressing metal plate 9f of the light amount adjusting unit 9. Therefore, in order to avoid such interference, it is necessary to dispose the light amount adjustment unit 9 closer to the image surface side (that is, to expand the space required for moving the second lens unit moving frame), which leads to an increase in the size of the lens barrel. Connect

On the other hand, in this embodiment, the fixed diaphragm 2
By deforming d as described above, it is possible to create a new space facing the conical inclined surface of the fixed aperture stop 2d on the radially outer side of the lens holding portion of the second group moving frame 2. For this reason, as shown in FIG. 3, when the second group moving frame 2 moves to the moving end on the image plane side, the diaphragm pressing metal plate 9f of the light amount adjusting unit 9 exceeds the inner peripheral side portion of the fixed diaphragm 2d and the outer periphery. It is possible to enter into this space to a position close to the side part.

Therefore, the space required for moving the second lens unit moving frame 2 in the lens barrel can be reduced, and the lens barrel can be downsized accordingly.

Next, a method of fixing the fixed diaphragm 2d to the second group moving frame 2 will be described with reference to FIG. 5 is 2
The state immediately before fixing the fixed diaphragm 2 to the group moving frame 2 is shown.

The second group moving frame 2 is provided with a positioning pin 2j and a rotation stopping pin 2k for positioning the center of the aperture diameter (diameter φ2i) of the fixed diaphragm 2d at the optical axis center. By fitting the positioning pin 2j and the positioning hole 2d2 of the fixed diaphragm 2d and fitting the rotation stopping pin 2k and the rotation stopping elongated hole 2d3, the center of the opening diameter of the fixed diaphragm 2d is the same as the optical axis center. Becomes

The annular slant surface 2l of the second lens unit moving frame 2 is a conical slant surface which is rotationally symmetric with respect to the optical axis center, and the angle of this slant surface with respect to the optical axis orthogonal plane is the angle 2f shown in FIG.
Is the same as.

When fixing the fixed diaphragm 2d to the second-group moving frame 2, the flat diaphragm 2d fixed diaphragm 2d is deformed into a substantially truncated cone shape, and holes are formed at eight locations in the circumferential direction of the fixed diaphragm 2d. The portion 2d1 is fitted to the projecting portions 2g provided at eight positions in the circumferential direction of the second group moving frame 2, and the object-side surface of the fixed aperture stop 2d is brought into contact with the annular inclined surface 2l of the second group moving frame 2.

After that, by heating and crushing the portion of the protrusion 2g of the second-group moving frame 2 that protrudes from the hole 2d1 of the fixed aperture 2d, the fixed aperture 2d remains deformed into a truncated cone shape. It is fixed to the group moving frame 2.

Here, in the outer peripheral side portion of the fixed diaphragm 2d,
Cutouts 2d4 are formed at eight locations in the circumferential direction. Without this notch, when the fixed diaphragm 2d is deformed into a truncated cone shape so as to abut the slope 2l, the fixed diaphragm 2
Stress concentrates on the inner diameter side portion of d, and unnecessary deformation such as wrinkles occurs, and the desired aperture inner diameter 2i is not formed.
It causes ghost and flare. In the present embodiment, the notch 2d4 is formed in advance on the outer peripheral side portion of the fixed diaphragm 2d to avoid such unnecessary deformation and obtain a desired diaphragm inner diameter 2i.

In the above embodiment, in addition to the projections 2g at the eight positions of the second group moving frame 2 and the holes 2d1 at the eight positions of the fixed aperture stop 2d, positioning and deflection of the fixed aperture stop 2d with respect to the second group movement frame 2 are performed. For stopping, positioning pins 2i and 2k are formed on the second group moving frame 2, and a hole 2d27 and an elongated hole 2d3 which are fitted to these are formed on the fixed diaphragm 2d. Of the above-mentioned eight sets of protrusions 2g and holes 2d1, two sets may have a shape suitable for positioning and steadying.

[0091]

As described above, according to the present invention,
A ring-sheet-shaped light-shielding member arranged at the outermost position in the optical axis direction of the lens unit is formed into a substantially truncated cone ring shape so that the outer peripheral side portion is located inside the lens holding member in the optical axis direction relative to the inner peripheral side portion. By transforming it into a new shape, it is possible to create a new space facing the conical slope of the light blocking member, which was not possible when the light blocking member was placed on the plane orthogonal to the optical axis as it was in the shape of a flat plate ring. The efficiency can be improved.

Therefore, for example, when the lens holding member is movable in the optical axis direction, when the optical unit such as the light quantity adjusting unit is arranged near the moving end of the lens holding member, the above new A part of the optical unit can be made to enter the space (beyond the position of the inner peripheral side portion of the light shielding member and approach the outer peripheral side portion). Therefore, the space required for moving the lens holding member (necessary for moving without interfering with the optical unit) can be reduced, and the entire optical device can be made compact.

Further, if a notch is formed in the light shielding member so as to prevent unnecessary deformation (wrinkles or the like) in the inner peripheral side portion due to the deformation of the shape of the truncated cone ring, the light shielding member will form a circle. Unnecessary light can be blocked evenly around the circumference, and flare and ghosts caused by the unnecessary deformation can be reliably prevented.

Furthermore, by fixing the light shielding member to the lens holding member by welding, it is possible to eliminate the risk of soiling the lens surface as in the case of using an adhesive.

[Brief description of drawings]

FIG. 1 is an exploded perspective view of an entire lens barrel that is an embodiment of the present invention.

FIG. 2 is a sectional view of the entire lens barrel.

FIG. 3 is a sectional view showing a positional relationship between a variable power lens group and a light amount adjustment unit in the lens barrel.

FIG. 4 is an exploded perspective view of the light amount adjustment unit.

FIG. 5 is an exploded perspective view showing a method of fixing a fixed diaphragm to a moving frame holding the variable power lens group.

FIG. 6 is a sectional view of a conventional lens barrel for a video camera.

FIG. 7 is a block diagram of an electric circuit of a conventional lens barrel for a video camera.

FIG. 8 is a configuration diagram of a conventional fixed aperture.

[Explanation of symbols]

1 Front lens barrel unit 2 2nd group moving frame 2d fixed aperture 2d4 cutout 3 shift units 4 4 group moving frame 5 Rear lens barrel 6, 7, 8 guide bar 9 Light intensity adjustment unit 10 lead screw 11 Stepping motor stator unit 12 lead screw 13 Stepping motor stator unit 14, 15 Photo interrupter

Claims (5)

[Claims] 1. A lens holding member for holding a lens unit, and a ring sheet-shaped light blocking member for blocking unnecessary light at an outermost position in the optical axis direction of the lens unit, wherein the light blocking member comprises: In the state of being deformed from the flat plate ring shape to a substantially frustoconical ring shape that is rotationally symmetric with respect to the optical axis so that the outer peripheral side portion of the light shielding member is located on the inner side in the optical axis direction of the lens holding member than the inner peripheral side portion. An optical device fixed to the lens holding member. 2. The optical device according to claim 1, wherein the light shielding member is formed with a notch for preventing unnecessary deformation of an inner peripheral side portion due to the deformation. 3. The optical device according to claim 1, wherein the light shielding member is fixed by welding an outer peripheral side portion of the light shielding member to the lens holding member. 4. The optical device according to claim 1, wherein the lens holding member is movable in the optical axis direction. 5. When the lens holding member is located at a moving end of the lens holding member, a part of another optical unit arranged near the moving end is located at an inner peripheral side portion of the light shielding member. The optical device according to claim 4, wherein the optical device approaches the outer peripheral side portion beyond the position in the optical axis direction.