JP2002090797A - Light amount adjustment device, lens device, and imaging device - Google Patents

Abstract

(57) [Problem] Immediately before an ND filter covers a light passage opening S, a displacement of an image plane occurs due to a thickness and a refractive index of the filter, and the resolution is reduced. SOLUTION: This light amount adjusting device is provided with a neutral density filter 14 at one of a plurality of light shielding blades 131c and 131d that open and close to change an opening area of a light passage opening S, wherein the neutral density filter is reduced. Main filter portion 14a having a light transmittance corresponding to the dimming effect required as an optical filter
And a constant light having a width H in the opening and closing direction necessary to cover the opening area S ′ on the front end side in the closing direction with respect to the area covered by the main filter portion in the light passage port, and having substantially no light dimming effect. It has a main filter part and a non-filter part having substantially the same thickness and refractive index in the optical axis direction and having a transmittance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light amount adjusting device used for an image pickup device such as a video camera or a lens device.

[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 of a fixed convex, a movable concave, a fixed convex, and a movable convex in order from the subject side.

FIGS. 14A and 14B show a lens barrel structure of a general zoom lens having a four-group lens structure. (B) shows a cross section taken along line AA in (A).

The four lens groups 201a to 201d constituting the zoom lens are composed of a fixed front lens 201.
a, a variator lens group 201b that performs a zooming operation by moving along the optical axis, a fixed afocal lens 201c, and a focal plane maintenance and focusing during zooming by moving along the optical axis. And a focusing lens group 201d.

The guide bars 203, 204a, and 204b are arranged in parallel with the optical axis 205, and guide and stop the moving lens group. The DC motor 206 is a driving 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
It is held at 1. Also, the afocal lens 201
c denotes an intermediate frame 215 and a focusing lens group 201d.
Are held by the RR moving ring 214.

The front lens barrel 202 is positioned and fixed to a rear lens barrel 216. A guide bar 203 is positioned and supported by the two lens barrels 202 and 216, and a guide screw shaft 208 is rotatably supported. I have.
The guide screw shaft 208 is driven to rotate by the rotation of the output shaft 206 a of the DC motor 206 being transmitted through a gear train 207.

A V-moving ring 211 for holding the variator lens group 201b includes a pressing spring 209 and the pressing spring 20.
And a ball 210 which engages with a screw groove 208a formed in the guide screw shaft 208 by a force of 9 by the DC motor 206.
By being driven to rotate, 8 moves forward and backward in the optical axis direction while being guided and regulated by the guide bar 203.

Guide bars 204a, 204 are provided on the rear barrel 216 and the intermediate frame 215 positioned in the rear barrel 216.
04b is fitted and supported. The RR moving ring 214 can advance and retreat in the optical axis direction while being guided and rotated by the guide bars 204a and 204b.

Guide bars 204a and 204 are provided on an RR moving ring 214 for holding the focusing lens group 201d.
b is formed with a sleeve portion that is slidably fitted to the RR moving ring 2 in the optical axis direction.
14 and are integrated with each other.

The stepping motor 212 rotationally drives a lead screw 212a formed integrally with its output shaft. The RR moving ring 21 is attached to the lead screw 212a.
The RR moving ring 214 moves in the optical axis direction while being guided by the guide bars 204a and 204b by the rotation of the lead screw 212a with the engagement of the rack 213 assembled to the rack 4.

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

The front lens barrel 202, the intermediate frame 215, and the rear lens barrel 216 form a lens barrel body that substantially accommodates a lens or the like.

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 using a photo interrupter or the like, The absolute position of the holding frame is detected by continuously counting the number of drive pulses applied to the stepping motor.

FIG. 15 shows an electrical configuration of a camera body in a conventional imaging apparatus. In this figure, the same reference numerals as in FIG. 14 denote the components of the lens barrel described in FIG.

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

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

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

Reference numeral 225 denotes a zoom encoder, and 227 denotes a focus encoder. Each of these encoders detects the absolute position of the variator lens group 201b and the focusing lens group 201d in the optical axis direction. When a DC motor is used as the variator driving source as shown in FIG. 11, 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 of continuously counting the number of operation pulses input to the stepping motor after arranging the holding frame at the reference position as described above is used. General.

Reference numeral 226 denotes an aperture encoder, which employs a system in which a Hall element is disposed inside an aperture drive source 224 such as a motor and detects the rotational positional relationship between a rotor and a stator.

A CPU 232 controls the camera. A camera signal processing circuit 228 performs predetermined amplification, gamma correction, and the like on the output of the solid-state imaging device 221. The contrast signal of the video signal that has undergone these predetermined processes passes through the AE gate 229 and the AF gate 230. That is, the optimum signal extraction range for exposure determination and focusing is set by this gate in the entire screen. The size of this gate is variable,
There may be a case where a plurality is provided.

Reference numeral 231 denotes an AF signal processing circuit which processes an AF signal for AF (auto focus), and generates one or a plurality of outputs related to a high frequency component 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. Note that C is used as the zoom tracking memory.
The memory in the PU 232 may be used.

For example, the photographer sets the zoom switch 23
3 is operated, the CPU 232 determines the current variator as a 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 of the zoom tracking memory 234 is maintained. The absolute position in the optical axis direction of the lens and the calculated position of the variator lens to be set, and the current absolute position of the focus lens in the optical axis direction as a detection result of the focus encoder 227 and the calculated focus lens should be set. The drive of the zoom drive mechanism 222 and the focussing drive mechanism 223 is controlled so that the positions match each other.

In the auto focus operation, the CPU 2 sets the output of the AF signal processing circuit 231 to a peak so that
Reference numeral 32 controls the driving of the focusing drive mechanism 223.

Further, in order to obtain an appropriate exposure, the CPU 2
Reference numeral 32 designates the average value of the output of the Y signal passing through the AE gate 229 as a predetermined value, and controls the drive of the aperture driving mechanism 224 so that the output of the aperture encoder 226 becomes the predetermined value, thereby controlling the aperture diameter.

Here, as a diaphragm device mounted on a conventional video camera, there is, for example, one having a configuration shown in FIG. This aperture device is a two-blade type,
The diaphragm blades 23a and 23b are connected to a seesaw drive lever 23 by one rotating electromagnetic actuator (motor) 23c.
It is configured to be driven via d. In addition, 23e is a main plate (namely, a casing) of the expansion device.

In this diaphragm device, an electromagnetic drive having a rotor made of a cylindrical permanent magnet (or a rotor magnetized on the outer peripheral surface of a cylindrical metal body) is used as a drive source of the diaphragm blade. An actuator is used, and the actuator controls a rotation position and a rotation amount (rotation angle) by detecting a change in movement of a magnetic pole on an outer peripheral surface of the rotor by a Hall element.

In addition, there is also a diaphragm device having the structure shown in FIGS. FIG. 17 shows the open state of the diaphragm device.
FIG. 18 shows a fully closed state of the aperture device. FIG.
Reference numeral 9 denotes an arrangement relationship of each component in the aperture device with respect to the optical axis direction.

Reference numeral 13a denotes an actuator for opening and closing the aperture blade 13d. An intermediate portion in the longitudinal direction of the drive lever 13c 'is press-fitted and held on the output shaft 13a1 of the actuator 13a. The drive lever 13
Pin portions 13c1 'and 13c' are formed at both ends of c '. The pin portion 13c1 'is engaged with the long hole portion 13d1 of the first aperture blade 13d.

Further, a guide groove 13d2 is formed on the first diaphragm blade 13d, and a guide pin 13f1 formed on a base member 13f of the diaphragm device is engaged with the guide groove 13d2. I have.

Similarly, the pin portion 13c2 'is engaged with the long hole portion 13e1 of the second diaphragm blade 13e. Also, the second
A guide groove 13e2 is formed on the aperture blade 13e, and the guide member 13e2 has a base member 13e.
The guide pin 13f2 formed in f is engaged.

The aperture blade 13e has an ND so as to cover an aperture of about F5.6 to F8 for small aperture correction.
The filter 14 is attached.

In the aperture device configured as described above,
When the actuator 13a rotates, the drive lever 13c also rotates, so that both the diaphragm blades 13d and 13e are driven in the vertical direction in the figure.

On the other hand, as the ND filter 14, a uniform density filter or a density change type ND filter whose density (light transmittance) gradually increases from the filter tip side as shown in FIGS. I have.

In the case of a uniform density filter, as the sensitivity of the image pickup device increases, the density of the ND filter is increased to reduce the amount of light transmission, and the minimum aperture of the diaphragm can be increased even when the brightness of the subject is the same. I have to.

However, when the density of the ND filter is increased as described above, in the state shown in FIG. 20, the light amount difference between the light a passing through the filter 14 and the light b not passing through is greatly different, and the resolution is reduced. The drawback is that this will happen.

In this regard, the use of the density change type ND filter can reduce the above-described degradation in resolution due to the light amount difference to some extent.

[0039]

However, irrespective of the density change type or the uniform density type, the ND filter is particularly suitable for the Fno. Immediately before covering the aperture opening corresponding to (e.g., F5.6), an optical path length difference occurs due to the thickness of the filter and the refractive index, causing a positional shift of an image forming surface and lowering the resolution. I understand that.

That is, even if the density change type ND filter is used, although the resolution deterioration due to the light amount difference is improved, the image plane displacement due to the thickness of the ND filter and the refractive index remains. In a lens unit in which the pixel pitch of the imaging element is as small as 3.2 to 3.8 μm and the permissible circle of confusion is small, this image plane position shift causes an unacceptable amount of one-sided blurring, thereby deteriorating the image quality.

Accordingly, an object of the present invention is to provide a light quantity adjusting device which can guarantee good image forming performance particularly in an intermediate aperture region, regardless of whether a uniform density type or a density change type ND filter is used.

[0042]

In order to achieve the above object, according to the present invention, a light-attenuating filter is provided on one of a plurality of light-shielding blades for opening and closing to change the opening area of a light passage opening. An adjusting device, wherein the light reducing filter is a main filter portion having a light transmittance corresponding to a light reducing effect required as a light reducing filter or a light transmittance changing to obtain the light reducing effect; It has a width in the opening and closing direction necessary to cover an opening area (for example, an area having an area small enough to cause a small-aperture diffraction phenomenon) in the opening in a direction closer to the front end than the area covered by the main filter portion in the mouth. In addition, the main filter portion and the non-filter portion having substantially the same thickness and refractive index in the optical axis direction have a constant light transmittance substantially free of a dimming effect.

As a result, it is possible to prevent the displacement of the image plane position due to the thickness of the filter and the refractive index, which has conventionally occurred before the neutral density filter covers the light passage opening.

Specifically, the non-filter portion may be formed of the same material as the material of the main filter portion so as to have substantially the same thickness as the main filter portion. Further, when the main filter portion is configured to have a filter layer for obtaining a light-reducing effect on the material, the light transmittance of the non-filter portion is reduced by the light transmission of the material itself having no filter layer. What is necessary is just a rate. The light transmittance of the non-filter portion is 75%
All that is required is the above.

[0045]

FIG. 1 and FIG. 2 show a lens barrel (lens device) provided with an aperture unit (light amount adjusting device) according to an embodiment of the present invention. This lens device is used for a video camera (imaging device) (not shown).

In these figures, 1 is the first lens which is the front lens.
A group lens, 2 is a variator group lens, 3 is a fixed afocal group lens, and 4 is a focusing group lens.

Reference numeral 5 denotes a front lens barrel that holds the first lens unit 1. As shown in FIG. 3, the front lens barrel 5 has openings on the upper surface and the image forming surface side, and has left and right side surfaces and lower surfaces having wall surfaces extended in the image forming surface direction. ing.

A light-shielding line 5a having a matte surface is formed on the inner wall of the lower surface of the front lens barrel 5, and the light-shielding line 5a prevents reflection of light on the inner wall of the lower surface, thereby generating harmful reflection ghosts. Here, the light-shielding line 5a is formed by upward sliding in FIG. 3 in molding the mold. For this reason, the inner wall shape of the front lens barrel 5 has a shape that can be formed by sliding upward in all the parts requiring dimensional accuracy. In other words, among the inner wall shapes of the front lens barrel 5, the lower holes 5b and the like of the fixing screws, which do not require much accuracy, are formed by a molding method such as a slide in a slide. The reference holes 5h and 5g of the guide shafts 6a and 6b cannot be formed.

If the slide-in-slide molding method is used, there is a problem that the molding optical dispersion is too large to guarantee desired optical performance.

For this reason, in the present embodiment, as shown in FIG.
Reference grooves 5g and 5h are formed by forming reference grooves regulated in three directions by 5d, and accurately fitted to four outer diameters of the guide shafts 6a and 6b by reference ribs 5e and 5f regulated in the horizontal direction by sliding upward. Can be formed.

Reference numeral 7 denotes a rear barrel connected to the rear of the front barrel 5. The rear barrel 7 includes a low-pass filter holder 7b and a CCD holder 7c for holding a CCD (not shown).
And As shown in FIG. 5, the rear barrel 7 has an opening surface facing the left and right direction and the direction of the optical axis subject, and is used as a reference for contact with the front lens barrel 5 extended in the direction of the optical axis subject. It has one side surface that supports the surface 7a.

Since the rear barrel 7 in the present embodiment does not have a light shielding means on its inner wall, the configuration of the slide of the die is, as shown in FIG. The guide shaft 6
The reference holes 7d and 7e for positioning and holding a and 6b can be easily and accurately formed by sliding in the forward direction, and their shapes are formed as perfect circles as shown in FIG.

In this embodiment, since the light blocking means is not provided on the inner wall of the rear lens barrel 7, the reference hole is formed by sliding forward. However, when the light blocking means is provided, the above-described front lens barrel is used. As in the case of No. 5, it can be formed with high precision by sliding in the left-right direction.

The guide shafts 6a and 6b are positioned and held by fitting into the reference holes 5g and 5h of the front lens barrel 5 and the reference holes 7d and 7e of the rear lens barrel 7 formed as described above.

The V-moving ring 8 holding the variator group lens 2 has a sleeve 8a fitted on the guide shaft 6a on the reference positioning side and a U-groove 8b fitted on the guide shaft 6b on the steadying side. Thus, the position of the variator group lens 2 on the optical axis is determined, and the rotation of the V moving ring 8 around the guide shaft 6a in a plane orthogonal to the optical axis is prevented. The inclination (falling) of the variator group lens 2 with respect to the optical axis direction is ensured by increasing the fitting length of the sleeve 8a to the guide shaft 6a.

A rack (not shown) is attached to the V-movement ring 8 so as to be rotatable in the optical axis direction without play in the optical axis direction. This rack, as shown in FIG.
It engages with the screw shaft 10a of the motor 10. When the PZ motor 10 rotates and the screw shaft 10a rotates, the V-moving ring 8 is driven forward and backward in the optical axis direction by the engagement between the screw shaft 10a and the rack.

RR for holding focusing lens 4
The movable ring 9 has a sleeve 9a fitted on the guide shaft 6b on the reference positioning side, and has a U groove 9b fitted on the guide shaft 6a on the steadying side. Thus, the optical axis position of the focusing group lens 4 is determined, and the rotation of the RR moving ring 9 around the guide shaft 6b in a plane orthogonal to the optical axis is prevented. The inclination (falling) of the focusing lens unit 4 with respect to the optical axis direction is determined by the guide shaft 6 of the sleeve 9a.
This is ensured by increasing the fitting length for b. Further, the reason why the guide shafts on the reference positioning side of the V moving ring 8 and the RR moving ring 9 are different is to secure the respective moving ranges when the fitting length of each sleeve is increased. is there.

A rack (not shown) is attached to the RR moving ring 9 so as to be rotatable in the optical axis direction and without play in the optical axis direction. This rack is, as shown in FIG.
It meshes with the screw shaft 11a of the F motor 11. AF
When the motor 11 rotates and the screw shaft 11a rotates, the RR moving ring 9 is driven forward and backward in the optical axis direction by the engaging action between the screw shaft 11a and the rack.

The intermediate frame 12 holding the fixed afocal group lens 3 has a reference positioning hole 12 as shown in FIG.
a and the anti-sway slot 12b are formed, and the optical axes of the afocal group lens 3 are positioned by fitting the guide shafts 6a and 6b, respectively. However, the V-moving ring 8 and the RR-moving ring 9 guarantee the fall of the lens held by each by setting the sleeve length on the reference positioning side to be long, whereas the sleeve length of the intermediate frame 12 is 2
Since the length of the sleeve of one moving group lens is long, it is difficult to set it long. For this reason, three engagement portions with the front lens barrel 5 are formed in the intermediate frame 12 to ensure that the afocal group lens 3 falls down. Note that 12c, 12d, 1
Reference numeral 2e denotes a locking portion formed on the intermediate frame 12. The locking portions 12c, 12d, and 12e are respectively engaged with locking grooves 5i and 5j and a long hole-shaped locking groove 5k formed in the front lens barrel 5 corresponding thereto.

First, one of the locking portions 12c and 12d is fitted into one of the locking grooves 5i and 5j of the front lens barrel 5 to define the position of the intermediate frame 12 in the optical axis direction. The engagement of the opposite (other) engaging portion with the other engaging groove prevents the intermediate frame 12 from falling in the X-axis direction in FIG. The engagement of the locking portion 12e with the locking long hole 5k prevents the intermediate frame 12 from falling in the Y-axis direction in FIG. In addition, each of the locking portions may be set to be fitted to the locking groove, or may be set to be lightly press-fitted.

The assembly of the lens barrel constructed as described above is performed in the following procedure. First, two guide shafts 6
With the V moving ring 8, the intermediate frame 12, and the RR moving ring 9 penetratingly held by the a and 6b, the intermediate frame 12 is inserted into the front lens barrel 5 from the direction orthogonal to the optical axis, and the engagement grooves 5i and 5j are formed. , 5k are engaged with the locking portions 12c, 12d, 12e of the intermediate frame 12.

Thereafter, the guide shafts 6a and 6b are
The rear lens barrel 7 is assembled by sliding in the reference holes 5g and 5h from the optical axis direction by the fitting length of these guide shafts, and the rear lens barrel 7 is assembled from the optical axis direction and fixed to the front lens barrel 5. As a result, the outer periphery of the lens barrel is substantially sealed.

After that, the PZ motor 10, the AF motor 11, and the aperture unit 13 are assembled in a direction orthogonal to the optical axis to complete a lens barrel unit.

As another assembling method, the guide shafts 6a and 6b are incorporated into the rear barrel 7 from the optical axis direction, and the RR moving ring 8, the intermediate frame 12 and the V moving ring 9 are sequentially arranged. In the direction of the optical axis. Then, the front frame 5 is dropped from the direction perpendicular to the optical axis until the intermediate frame 12 is at the proper position.
The lens barrel may be completed by being slid for the fitting length of a and 6b and incorporated. The subsequent steps are the same as those described above.

Next, the structure of the aperture unit 13 and the mechanism for opening and closing the aperture blades will be described in detail. In FIG.
FIG. 9 shows the overall configuration of the aperture unit 13.
2 shows an internal configuration of the aperture unit 13.

In FIG. 9, reference numeral 131a denotes a diaphragm actuator. As the diaphragm actuator 131a, any actuator may be used as long as it generates a required torque for opening and closing the diaphragm blades. For example, a galvanometer or a stepping motor may be used.

An intermediate portion of the drive lever 131b is press-fitted and held on the output shaft of the actuator 131a. At both ends of the drive lever 131b, the connecting shaft 13
1b1 and 131b2 are formed respectively.

The connecting shaft 131b1 of the driving lever 131b
Is rotatably and radially fitted into a hole 131c1 formed in the first diaphragm blade (light shielding blade) 131c, whereby the drive lever 131b and the first diaphragm blade 131c are connected. The first diaphragm blade 131c is further formed with a guide groove 131c2 having a curved shape.
A guide shaft 131e1 provided on the base member (apparatus main body) of the aperture unit 13 is engaged with 31c2.

The connecting shaft 13 of the drive lever 131b
1b2 is a hole 13 formed in the second diaphragm blade 131d.
1d1 so as to be rotatable so that the driving lever 1
31b and the 2nd diaphragm blade 131d are connected. The second diaphragm blade 131d has another guide groove 1 having a curved shape.
31d2 is formed, and the guide groove 131d2 is formed.
The guide shaft 131e provided on the base member
2 are engaged.

Here, as shown in FIG.
31d1 and 131d2 each have an arc shape with a radius of curvature R, and are formed in an arc shape that is convex on the side of the light passage opening S formed by the two diaphragm blades 131c and 131d.

In the aperture unit 13 thus configured, when the aperture actuator 131a is driven to rotate the drive lever 131b, the first aperture blade 131c and the second aperture blade 13 connected to the drive lever 131b.
The guides 1d are driven in the vertical direction in the optical axis orthogonal direction while being moved and guided by the engagement between the guide grooves 131c2 and 131d2 and the guide shafts 131e1 and 131e2. Thereby, both diaphragm blades 131
The opening area of the light passage opening S formed by c and 131d changes between the open state and the fully closed state, and the amount of light incident on the CCD through each group lens is adjusted.

In the aperture unit 13 of the present embodiment, the guide grooves 131d1 and 131d2 are formed in the above-described arc shapes, respectively.
When driving 1c and 131d between the open state and the fully closed state, the center (the center of gravity of the opening area) of the light passage S hardly moves, and is maintained at a substantially constant position in the plane orthogonal to the optical axis. You.

The aperture unit 13 is positioned in the lens barrel such that the center position 131f substantially coincides with the optical axis of the lens barrel (or the photographing optical axis of the imaging device). Maintaining the center of the light passage S (the center of gravity of the opening area) at a substantially constant position as described above is effective for making the light amount around the optical axis relative to the CCD uniform.

In the above embodiment, the guide shafts 131e1 and 131e2 are provided on the base member and the diaphragm blades 131e.
Although the case where the guide grooves 131c2 and 131d2 are provided in c and 131d has been described, a guide groove may be provided in the base member and a guide shaft may be provided in the diaphragm blade.

In the above embodiment, the driving lever 13
1b, connecting shafts 131b1 and 131b2 with aperture blades 13
Although the case where the holes 131c1 and 131d1 are provided in 1c and 131d has been described, the holes may be provided in the drive lever and the connecting shafts may be provided in the aperture blades.

On the other hand, as shown in FIGS. 9 to 12, an ND filter (a neutral density filter) 1 is provided on the second diaphragm blade 131d.
4 is pasted. FIG. 11 shows the light passage S
Has shown the state which is an open area, FIG.
The state where the light passage opening S has an opening area corresponding to the intermediate stop area (for example, F5.6) is shown.

The ND filter 14 includes a main filter section 14a having a light transmittance (in this embodiment, a uniform light transmittance of 12.5%) corresponding to the light reduction effect originally required as an ND filter, A band-shaped non-filter portion 14b provided at a tip of the portion 14a with a predetermined height and width and having a light transmittance (light transmittance of about 100 to 75%) having substantially no dimming effect. It is configured.

Here, the ND filter 14 is 100 to 7
It is manufactured based on a filter material such as a nearly colorless and transparent plastic plate having a light transmittance of about 5%. The main filter portion 14a has a light transmittance of 12.5% on the filter material. A filter layer necessary for obtaining the filter layer is formed.

More specifically, after masking a film material having a transmittance of 100%, the film material is vapor-deposited to a thickness of 12.5%.
In the case where a% transmission portion is formed and the density is further increased, masking is also performed on the back surface and vapor deposition is performed so as to support the multi-density. In other words, the back surface of the 12.5% transmission portion is further vapor-deposited to form an approximately 6.3% transmission portion.

The main filter section 14a is connected to the light passage S
Is a predetermined Fno. (For example, F5.6), the size is set such that the light passage opening S can be covered when the opening area corresponds to F5.6.

The filter material itself is used for the non-filter portion 14b.
b has a constant light transmittance among light transmittances of about 100 to 75% which are substantially free of a dimming effect, and have substantially the same thickness and refractive index as the main filter portion 14a. Has become.

Then, the non-filter section 14b is
As shown in (A) and (B), the main filter section 14a is provided with the Fno. Immediately before covering the light passage S corresponding to (for example, F5.6), this filter section 14a
A small opening area present on the tip side in the closing direction of
An opening / closing direction capable of covering an opening area (an opening area having an area equivalent to an opening area corresponding to about F16 in the optical system of the zoom lens according to the present embodiment) having an area where a so-called small-aperture diffraction phenomenon can occur. It has a width (height) H.

As a result, the small opening area S ', which has conventionally been simply open, is now replaced with the non-filter section 1.
4b, it is possible to avoid resolution degradation due to the thickness and refractive index of the filter, which has conventionally occurred immediately before the ND filter covers the light passage opening particularly in the intermediate aperture region.

In this embodiment, the main filter unit 14
Although the case where the ND filter 14 in which a is uniform is used has been described, the present invention is also applicable to a density change type in which the main filter portion gradually increases in density from the front end side in the closing direction. Can be. FIG. 13 shows how the density (light transmittance) of the entire ND filter including the non-filter portion changes in the ND filter in which the main filter portion is a density change type.

The light transmittance of the non-filter portion 14b 'is constant over the entire width thereof, and
The light transmittance of a ′ gradually decreases from the tip side.

In this case as well, it is possible to avoid the degradation of the resolution due to the thickness and the refractive index of the filter, which has conventionally occurred immediately before the ND filter covers the light passage opening, particularly in the intermediate aperture region.

In the above embodiment, a lens barrel for a video camera has been described. However, the present invention can be applied to still image cameras and other image pickup devices, and lens barrels for them.

[0088]

As described above, according to the present invention,
A main filter portion having a light transmittance corresponding to the filter's original dimming effect, and a width necessary to cover an opening region on the front end side in the closing direction with respect to a region covered by the main filter portion in the light passage opening. A light-absorbing filter having a constant light transmittance with substantially no light-attenuating effect, and having a main filter portion and a non-filter portion having substantially the same thickness and refractive index in the optical axis direction. Therefore, it is possible to prevent the shift of the image plane position due to the thickness of the filter and the refractive index, which has conventionally occurred before the neutral density filter covers the light passage opening, and has a good image forming performance. Can be realized.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a lens barrel for a video camera having an aperture unit according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of the lens barrel.

FIG. 3 is a configuration diagram of a mold slide of a front lens barrel constituting the lens barrel.

FIG. 4 is a rear view of the front lens barrel.

FIG. 5 is a configuration diagram of a mold slide of a rear barrel that constitutes the lens barrel.

FIG. 6 is a front view of the rear barrel.

FIG. 7 is an exploded perspective view of the lens barrel.

FIG. 8 is a diagram showing an engagement state between the front lens barrel and an intermediate frame.

FIG. 9 is a configuration diagram (view in the optical axis direction) of the aperture unit.

FIG. 10 is an external view showing the overall configuration of the aperture unit.

FIG. 11 is a diagram showing an internal configuration (open state) of the aperture unit.

FIG. 12 is a diagram illustrating a state immediately before an ND filter attached to a diaphragm blade in the light amount unit covers a light passage opening in an intermediate diaphragm area.

FIG. 13 is a graph showing a change in transmittance of an ND filter provided in a diaphragm unit according to a modification of the embodiment.

FIG. 14 is a sectional view of a conventional lens barrel for a video camera.

FIG. 15 is a block diagram of an electric circuit of a conventional lens barrel for a video camera.

FIG. 16 is a configuration diagram of a conventional diaphragm device.

FIG. 17 is a configuration diagram of a conventional aperture device (open state).

FIG. 18 is a configuration diagram of a conventional aperture device (fully closed state).

FIG. 19 is a side view of a conventional aperture device.

FIG. 20 is a configuration diagram of an optical system of a conventional lens barrel for a video camera.

FIG. 21 is an explanatory diagram of a conventional density change type ND filter.

FIG. 22 is a graph showing a change in light transmittance of a conventional density change type ND filter.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1st group lens 2 Variator group lens 3 Afocal group lens 4 Focusing group lens 5 Front lens barrel 5a Shading line 5b Fixed screw lower hole 5c, 5d Left and right sliding hole 5e, 5f Right and left regulation reference rib 5g 5h Reference hole 5i, 5j, 5k Lock groove 6a, 6b Guide shaft 7 Rear barrel 7a Contact reference surface 7b Low-pass filter holding unit 7c CCD holding unit 7d, 7e Reference hole 8 V moving ring 8a sleeve 8b U groove 9 RR moving ring 9a sleeve 9b U groove 10 PZ motor 10a screw shaft 10b holding member 11 AF motor 11a screw shaft 11b holding member 12 intermediate frame 12a reference positioning hole 12b steady rest long hole 12c, 12d, 12e locking portion 13 aperture unit 131a Blade drive actuator 131b Over 131b1,131b2 connecting shaft 131c first diaphragm blade 131d second diaphragm blade 131c1,131d1 hole 131c2,131d2 guide groove 131e1,131e2 guide shaft portion 14 ND filter 14a, 14a 'main filter portion 14b, 14b' unfiltered portion

Claims (7)

[Claims] 1. A light amount adjusting device comprising: a light-attenuating filter provided on one of a plurality of light-shielding blades for opening and closing to change an opening area of a light-passing opening. A main filter portion having a light transmittance corresponding to the light reduction effect to be obtained or a light transmittance changing to obtain the light reduction effect, and a front end in a closing direction of a light passage opening than a region covered by the main filter portion. Has a width in the opening and closing direction necessary to cover the side opening area, has a constant light transmittance substantially without a dimming effect, and substantially has a thickness and a refractive index in the optical axis direction and the optical axis direction which are different from those of the main filter portion. And a non-filter portion identical to the above. 2. The method according to claim 1, wherein the non-filter portion is formed of the same material as the material of the main filter portion and has substantially the same thickness as the main filter portion. The light amount adjusting device according to the above. 3. The main filter section has a filter layer for obtaining a light-reducing effect on the material, and the light transmittance of the non-filter section has no filter layer. 3. The light amount adjusting device according to claim 2, wherein the light transmittance is the light transmittance of the material itself. 4. The light amount adjusting device according to claim 1, wherein the light transmittance of the non-filter portion is 75% or more. 5. The area of the non-filter portion is an area necessary to cover an opening area where a small aperture diffraction phenomenon can occur in an optical system provided with the light amount adjusting device. Item 5. The light amount adjusting device according to any one of Items 1 to 4. 6. A lens device comprising the light amount adjusting device according to claim 1. Description: 7. An image pickup apparatus comprising the light amount adjusting device according to claim 1.