JP2937723B2 - Light control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light amount control device mounted on a photographing device such as a video camera.

[0002]

2. Description of the Related Art As shown in FIG. 8, for example, a light quantity control device mounted on a photographing device such as a video camera has a rotor magnet 82 composed of permanent magnets and having two poles, for example.
A rotor magnet 82 and a yoke 83 forming a magnetic circuit are provided on the outer periphery of the rotor, and a drive coil 81 and a braking coil 85 for detecting the rotation speed of the rotor magnet are installed in a gap between the rotor magnet 82 and the yoke 83. The light amount control member 86 composed of a light shielding member is driven by a motor that is a driving source of the mold. Reference numeral 84 denotes the rotational position of the rotor magnet 82.
A Hall element 87 is detected from the magnetic flux of the light.
6 is a return spring that urges 6 in the closing direction.

FIG. 9 is a block diagram of a light quantity control device using an inner magnet type motor driving source. A is a lens unit of a video camera, B is a control circuit unit of the camera, and a lens unit A is a zoom motor 100. A braking coil 101 integrated with the driving source 102 of the light amount control device, a detection device (Hall element 84) 103a of the position detection means 103, an autofocus motor 104, and a light amount detection device 105 for detecting the light amount of the subject passing through the photographing optical system. The control circuit B of the camera processes a signal from the light amount detection device 105 into a video signal and outputs the video signal as a video signal.
6. A control circuit 107 for controlling the drive of the autofocus motor 104 for focusing based on a signal from the light amount detection device 105, and a drive amount setting means 108 for setting a drive amount for opening and closing the aperture. And an amplifier 110 for amplifying the speed information from the braking coil 101, and driving a motor for driving the light amount control member 86 based on a comparison between the speed information from the amplifier 110 and the information from the drive amount setting means 108. Comparison means 111 for controlling energization of the coil
And an amplifier 1 for amplifying position information detected by the detection device (Hall element 84) 103a of the detection means 103
03b, and the position information from the amplifier 103b is input to the drive amount setting means 108.

A conventional light quantity control device having such a configuration is as follows.
In order to open and close the light amount control member 86 gently and smoothly, the rotation speed of the rotor magnet 82 is detected by the braking coil 101, and the speed is controlled to a position where the optimum light amount is obtained. The light amount control member 86 is driven by the urging force of the spring 87.

On the other hand, a mechanical drive mechanism constituting the light quantity control device and an electrical control circuit are separately disposed separately, and the control circuit is connected to a control circuit section of the camera, and the drive mechanism is connected to a lens section. The printed circuit board 88, which is an interface on which the Hall element 84 and the connector are mounted, is connected therebetween by a flexible printed circuit board (not shown) for connecting the printed circuit board to a camera control circuit.

[0006]

However, the above-mentioned conventional light quantity control device is mounted because the drive source of the light quantity control member uses an inner magnet type motor whose structure is formed in a cylindrical shape. It jumped out of the lens barrel and hindered downsizing of the lens barrel, and thus downsizing of the camera as a whole.

Further, since the light quantity control member is driven to rotate by a motor, the following drawbacks have been pointed out.

(1) The frictional load of the light quantity control member is enlarged and amplified in the end direction of the rotation, and a large driving torque is required, resulting in an increase in the size of the apparatus.

(2) The guide bar of the lens must be arranged on the outer periphery of the rotation space for the rotation space of the light amount control member, which leads to an increase in the size of the camera.

(3) In particular, when an attempt is made to use two light amount control members, the aperture becomes a shape far from a perfect circle, which causes image deterioration.

[0011]

Means for Solving the Problems The invention described in claim 1
And a rotor made of a permanent magnet and facing the rotor
A stator yoke in which a plurality of magnetic poles are formed at positions,
Coil wound on stator yoke, perpendicular to optical axis
Two light-amount joint members that slide in the
And a transmission member for transmitting power to the two light amount adjustment members.
A light amount control device having the transmission member.
Formed with two arms that respectively engage with two light intensity members
And the angle between the two arms is less than 180 °
It is characterized in that the angle is set .

[0012]

[0013]

[0014]

1 to 3 show a first embodiment of the present invention. FIG. 1 is a block diagram of a light quantity control device, and FIG. 2 is a block diagram of a video camera using the light quantity control device of FIG. 3 is an exploded perspective view of the light quantity control device of FIG.

The light quantity control device shown in FIG. 3 is a light quantity control device using a so-called external magnet type motor as a drive source. Reference numeral 3 denotes a two-part stator yoke which is arranged in the circumferential direction with respect to the optical axis 12. The coil bobbin 1a around which the coil 1 is wound is mounted on one yoke. Reference numeral 2 denotes a rotor magnet disposed with a gap in a circumferential portion formed at the tip of the stator yoke 3, and is magnetized to two poles in the radial direction. In the circumferential portion of the stator yoke 3, a pair of opposed main magnetic poles 3a and 3c having a large opening angle and a pair of opposed auxiliary poles 3b and 3d having a small opening angle are formed. The one-way detent torque is generated for the rotor magnet 2 by the difference in the opening angle between the main magnetic pole and the auxiliary pole. In this embodiment, the detent torque causes the rotor magnet 2 to close in the direction in which the light amount control members 6 and 7 close. , Thus eliminating the need for a return spring as in the prior art.

Reference numeral 9 denotes a pair of arm portions 9a, 9
b is a transmission member integrally formed with the rotor magnet 2.
The rotation shaft 9c is fixed to a shaft hole of the pair of arm portions 9
Actuation pins formed at the tips of a and 9b respectively engage with the respective engagement holes of the light quantity control members 6 and 7, and the light quantity control held by the rotation of the rotor magnet 2 so as to be slidable in a direction orthogonal to the optical axis. The aperture diameter is reduced by moving the members 6 and 7 straight in the direction facing each other, and the aperture diameter is increased by moving the members 6 and 7 straight in the direction away from each other, thereby adjusting the amount of light incident on the lens. .

Reference numeral 8 denotes a base plate, an opening 8a, an engaging claw for engaging and holding the stator yoke 3, a bearing 8b for supporting one end of a rotating shaft 9c fixed to the rotor magnet 2, and a Hall element 4. , A guide pin or the like into which a long groove for supporting and guiding formed in the light quantity control members 6 and 7 is fitted, the motor part is fitted into the circular arc part on one side, and the light quantity control member 6 is formed. , 7 are also mounted from the same direction as the motor unit. The case 10 has an opening 10a, a bearing 10b for supporting the other shaft end of the rotary shaft 9c, and the like, and a case 10 for holding the light quantity control members 6, 7 and preventing ingress of dust and the like from the outside. Opening is closed.

A printed circuit board, for example, a flexible printed circuit board 11 is mounted on the back side of the base plate 8 with respect to the arc portion of the base plate 8, and the flexible printed circuit board 11 including the hall element 4 is shown in FIG. A motor drive circuit is mounted to transmit and receive signals to and from a control circuit unit of the camera. The magnetism of the rotor magnet 2 is detected from the thrust direction by the Hall element 4 facing the Hall element opening 8c.

As shown in FIG. 3B, the center position of the rotor magnet 3 with respect to the yoke 3 is shifted in the axial direction, so that a magnetic imbalance occurs in the rotor magnet 2, An urging force is generated downward in the axial direction. As a result, the occurrence of blurring in the axial direction of the rotor magnet 2 due to external vibration is suppressed, and the occurrence of an error in the detection of magnetism by the Hall element 4 or the detection of magnetism is prevented.

As shown in FIG. 3 (c), the angle δ between the two arms 9a and 9b of the transmission member 9 is smaller than 180 degrees and has a fan-like shape folded toward the opening 8a. The transmission member 9 can be effectively arranged within a narrow range.

FIG. 7 shows a state in which the light amount control device is attached to the lens barrel. FIG. 7A shows a state in which the light amount control device of the above-described embodiment is installed, and FIG. An example in which a control device is provided is shown, where L is an optical space, D is a lens barrel space, 71 is a conventional inner magnet type motor, 72 is a guide bar for movably supporting a lens, and 73 is a light amount control of the present embodiment. The device 74 is a guide bar that movably supports the lens.

In the case of the lens barrel equipped with the light amount control device of the present embodiment shown in FIG. 7A, since the outer magnet type motor can freely set the coil space, as shown in FIG. The drive unit can be accommodated in a dead space between the optical space L and the lens barrel space. Further, since the light amount control members 6 and 7 move straight in the direction facing each other, the guide bar can be provided in the space inside the lens barrel.
That is, the lens barrel can be made more compact, and can be incorporated into the lens barrel later, thereby facilitating maintenance, correction, replacement, assembly work, and the like.

On the other hand, as shown in FIG. 3 (c), by making the transmission member 9 sector-shaped, the outer periphery of the drive unit for linearly moving the light amount control members 6, 7 is formed into an arc shape as shown in FIG. And can be accommodated in the dead space of the arc-shaped lens barrel.

Next, a video camera equipped with the light amount control device having the above-described configuration will be described with reference to a block diagram shown in FIG. Note that the same units as those in the block diagram of FIG. 9 are denoted by the same reference numerals, and description thereof will be omitted.

The light incident on the taking lens is a light amount controlling member 6,
An image is formed on the light amount detection device 105 composed of a CCD through the opening formed by the optical signal 7, and the optical signal is converted into an electric signal to output a video signal YS.

In response to the video signal YS, the drive amount setting means 108 changes the drive amount information VP of the light amount control members 6 and 7 based on the table set in the memory 109 together with the operation amount information of the detection means 200. The incident light quantity is set to an appropriate value, and is output to the comparison means 202.

The comparison means 202 excites the drive coil 1 of the drive source 201 based on the drive amount information VP, and drives the rotor magnet 2 to rotate by the attracting action and repulsive action of the rotor magnet 2 through the stator yoke 3. When the rotor magnet 2 rotates, the light amount control members 6 and 7 move straight in directions facing each other via the transmission member 9,
The lens operates so as to adjust the light incident on the lens to obtain an appropriate exposure amount. The rotation range of the transmission member 9 is regulated by the base plate 8, and the rotor magnet 2 has a rotation angle of 360 degrees / P (P is the number of poles: 2
In this embodiment, since the rotor magnet 2 is magnetized to two poles, rotation within a range of 180 degrees is permitted.

When the rotor magnet 2 rotates, the detecting means 200 comprising the Hall element 4 detects the rotational position of the rotor magnet 2 from the output change.

The position information VF from the detection means 200 is position information and can be used to control the rotation range of the rotor magnet 2 as it is. It cannot be used to rotate at slow speeds. Therefore, in the present embodiment, the position information VF is output to the correction means 203, corrected to drive speed information VS by the differentiating circuit of the correction means 203, and output to the comparison means 202.

The comparing means 202 feeds back the driving speed information VS proportional to the rotation speed of the rotor magnet 2 to the driving amount information VP output from the driving amount setting means 108 in response to the input of the position information VF, and uses the difference as a difference. A certain drive control information VD is output to the drive coil 1 of the drive source 201. The output of the detecting means 200, the rotor magnet 2 is being two-pole magnetized, and a benzalkonium be rotated within an angular range of 180 degrees, for example substantially linear signal between the peak and the peak of the sine wave Changes to

FIG. 1 shows a specific drive circuit configuration of the comparing means 202, the driving source 201, the detecting means 200, and the correcting means 203 shown in FIG.

The driving circuit performs feedback control of negative feedback. The detecting means 200 has an amplifier for amplifying and adjusting the output of the Hall element 4 and outputting operation amount information VF which is also position information. Has a differentiating circuit for differentiating the operation amount information VF and converting it into drive speed information VS, and VR is a reference voltage. The comparing means 202 has an integration circuit that compares the drive speed information VS with the drive amount information VP and outputs the difference to the drive coil 1 as drive control information VD.

The operation of the driving circuit will be described with reference to FIG. 13 which shows a change in a signal of each circuit in a correlated manner.

FIG. 13A shows drive amount information VP.
In accordance with the change in the light amount, the drive amount information V around the value of the reference voltage VR is set so that the light amount YS always approaches the set target value or the operation amount information VF approaches the target value.
Change P. Here, the light amount control member is stopped at the level of the reference voltage VR, and a close signal for closing the light amount control member is output when the voltage is equal to or higher than the reference voltage VR. Therefore,
The greater the difference between the control amount such as the light amount YS and the target value, the greater the level difference between the reference voltage VR and the drive amount information VP.

FIG. 13B shows the drive control information VD. The drive control information VD obtained by integrating the difference between the drive amount information VP and the drive speed information VS is applied to the drive coil 1. L ₀
Represents a voltage level corresponding to a return torque by di dent torque, drive control information VD is stopped if consistent with L _0, the open side if exceeds, or drives the light amount control member in the closing direction if Sagare.

FIG. 13C shows the operation amount information VF, in which the operation amount of the rotor magnet 2 is linearly and directly detected by the Hall element 4 in accordance with the drive control information VD. The voltage is adjusted to 1 volt (V) at the open end of the control member and to 3 V at the closed end, and the voltage level corresponds to the rotational position of the rotor magnet 2 and the opening diameter (aperture value) of the light amount control member.

FIG. 13D shows the driving speed information VS outputted from the correction means.
This is a signal obtained by differentiating the operation information VF. The output becomes larger as the change speed of the operation information VF becomes faster (as the inclination of the operation information VF becomes larger), and thus becomes a signal proportional to the rotation speed of the rotor magnet 2. Here, when the drive speed information VS matches the reference signal VR, the speed is 0 and the reference signal V
When the speed is larger than R, the speed in the opening direction is detected, and when the level is lower than the reference signal VR, the speed in the closing direction is detected.

[0038] In this driving circuit, drive control information VD accordance open signal of the driving amount information VP rises, from where exceeding the voltage level L _0, the rotor magnet 2 is initially rotated and accelerated. In this state, it reaches the open end, which is a slight rotation range, at a stroke in a few milliseconds.
It passes the target value. On the other hand, with the close signal of the drive amount information VP, a step operation in which the target value is not approached, such as up to the close end, is performed.

Then, the drive speed information VS proportional to the change speed of the operation amount information VF is negatively fed back to the drive amount information VP,
The difference is used as drive control information VD.

When the rotor magnet 2 is accelerated for the first time, the operation amount information VF changes abruptly, and accordingly, the drive speed information VS rises abruptly. As a result of comparing the driving speed information VS and operation amount information VP, drops the start of the driving amount information VD, the level of the driving amount information VD is lowered than L ₀ generates a closing direction of the torque. For this reason, the rotation speed of the rotor magnet 2 slows down and attempts to stop, but the change speed of the operation amount information VF also becomes slow, so that the drive speed information VS also approaches the reference signal VR.

However, as a result of comparing the drive speed information VS with the drive amount information VP, the drive control information VD rises,
Uplink, also the rotor magnet 2 start acceleration than the level L _0.

By such a negative feedback operation, a one-phase excitation type motor that causes a step operation can be controlled at a very low speed and stably.

Accordingly, the operation of the present embodiment allows the rotor magnet 2 to operate smoothly and slowly even in a slight rotation range, and the unstable operation of light quantity control such as hunting is improved. As a result, an outer-magnet-type light quantity control device capable of fine and smooth light quantity control is obtained.

In this embodiment, the rotor magnet 2 is spring-biased in the direction in which the light quantity control members 6 and 7 are closed by an appropriate detent torque set by the magnetic pole canceling means of the stator yoke 3. In a state where power is not supplied, an auto-closed system is adopted in which the light amount control member automatically returns to the closed position by this spring urging force. Of course, the present invention is not limited to this method, and may be a method of almost completely canceling the detent torque.

The principle of the above-described detent torque setting and canceling means will now be described with reference to FIGS.
2 will be described.

FIG. 5 shows that the polarity of the detent torque is opposite to each other due to the opening angle of the magnetic pole. The number of magnetic poles magnetized on the rotor magnet is represented by P (P = 2 in this embodiment). In this case, the magnitude θ of the opening angle of the magnetic pole becomes θ
_{If 1} <360 ° / 2P, as shown in FIG. 5A, a detent torque acts on the polarity of the SN pole facing the yoke, and if θ ₂ > 360 ° / 2P,
As shown in FIG. 5B, the detent torque acts on the polarity of the magnetic pole of SN in the direction perpendicular to the opposing portion of the yoke. Note that x indicates a stable point and O indicates an unstable point.

FIG. 10 shows this torque characteristic with respect to the rotation angle. FIG. 10 (a) shows the torque characteristic in FIG. 10 (a), and FIG. 5 (b) shows the torque characteristic in FIG. 10 (b)
5, the counterclockwise direction is positive (open direction), and the NS position of the rotor magnet in FIG. 5 is 0 °. FIG.
In (a), (b), and (c), a, c, and e indicate detent torques, and b, d, and f indicate exciting torques due to the coil current I.

Using the characteristics of the detent torque,
FIG. 6 shows a method for canceling the detent torque.

FIG. 6A shows that the opening angle of the magnetic pole A is 360 ° /
In the example in which the opening angle of the magnetic pole B is set to 360 ° / 2P or more below 2P, the detent torque of each magnetic pole A is shown in FIG.
A shown in FIG. 10A and the magnetic pole B shown in FIG.
Therefore, the detent torque shown in FIG. 6A can be almost canceled out as e shown in FIG. 10C. At this time, with a small excitation torque as shown by b and d in FIG. 10, the range that can be driven against the detent torque as shown by a and c is a very small range shown by oblique lines. In (c), the motor can be driven in a range of 360 ° / P with a very small exciting torque for the same purpose indicated by f.

FIG. 6B shows that the main magnetic pole M is 360
The same effect as that of FIG. 6A is obtained by providing an auxiliary pole having the same opening angle by shifting the angle of the magnetic pole of ° / 2P, and the detent torque by the main magnetic pole M is shown in FIG. ), And the complementary pole c is shown in FIG.
, And as a result, e in FIG.
, And can be almost completely canceled out.

FIGS. 6C and 6D show a method in which the detent torque is set by using the above two canceling means.

FIG. 6C shows the model of the above-described embodiment. Since the opening angles of the magnetic poles M1 and M2 are set to 360 ° / 2P or more, the generated detent torque is shown in FIG.
(A), and the opening angles of the supplementary poles C1 and C2 are set to 360 ° / 2P or less, and the facing poles C1 and C2 are opposed to the main poles M1 and M2. Since the magnets are arranged out of phase in the positive rotation direction, the generated detent torque becomes a curve h shown in FIG. 11B, and the resultant force becomes a curve i shown in FIG. 11C. The phase is shifted so that the magnitude of the curves g and h is about 1/3 by canceling the detent torque, and the peak of the exciting torque j and the peak of the opposite polarity of the detent torque i substantially coincide. This excitation torque j is determined by the auxiliary pole C1 and the main pole M1 formed on one and the same yoke.
And the auxiliary pole C2 and the main magnetic pole M formed on the other same yoke.
The phase shifts due to the shift of the facing angle with the second.

The usable range of the motor is a range in which the detent torque i is used as the return torque and the drive can be performed by overcoming the detent torque i by the excitation torque j. The resultant force k of the detent torque i and the excitation torque j is open. The torque i is the closing torque. In this case, it is desirable that the excitation torque j is set to about twice the detent torque i.

In particular, the light amount control device for moving images does not require high-speed operation and requires power saving for continuous operation.
The required minimum drive torque is sufficient. For this reason, an exciting torque twice as large as the detent torque which causes a large load is required, and the conventional detent torque setting means cannot be expected to be as small, light and power-saving as the present embodiment.

FIG. 6D is a model diagram of another embodiment shown in FIG. 4 to be described later. As in the case of FIG. 6C, the opening angle of the main magnetic pole M is set to 360 ° / 2P or less. As a result, the detent torque of the main magnetic pole M becomes a curve 1 shown in FIG. 12A, and the opening angle of the auxiliary pole C is set to 360 ° / 2P or less. 12B, the detent torque of the auxiliary pole C becomes a curve n shown in FIG. 12B. Then, the resultant force of the two detent torques becomes a curve q shown in FIG. 12C, and cancels out the detent torque, and is の of the curves l and n.
The phases are shifted so that the magnitude of the excitation torque r and the peak of the opposite polarity of q substantially coincide with each other.

The usable range indicates the range in which the detent torque q is used as the return torque and the drive can be performed by overcoming the detent torque q by the excitation torque r. r is the closed torque.

The means for setting the detent torque using the means for canceling the detent torque is such that the center of the opening angle of the auxiliary pole is α = 360 with respect to the center of the opening angle of the main pole in the two embodiments. Being shifted from the angle of ° / 2P in the rotation direction in which the return force is generated and arranged at an angle position of β = 360 ° / 2P or less, it has a magnitude required for the return force and a phase matching the exciting torque. A desired detent torque is set. In the above-described embodiment,
The main magnetic pole refers to the magnetic pole of the stator yoke having a large open angle among the magnetic poles of the stator yoke around which the drive coil is wound, and the auxiliary pole is the magnetic pole of the stator yoke without the drive coil being wound, or the magnetic pole of the drive coil being wound. Out of the magnetic poles of the stator yoke.

The detent torque setting means increases the opening angle of the magnetic pole from 360 ° / 2P,
The detent torque, which has been offset by means such as reducing the area of the rotor magnet facing the rotor, or changing the air cap of the rotor magnet, etc., can be adjusted to be unbalanced, and the polarity, phase, and magnitude of the detent torque can be adjusted. Can be set freely.

In the light amount control devices of the above-described embodiment and the embodiment described later, the detent torque is used for the return force of the light amount control member, but FIGS. 6 (a) and 6 (b).
A method in which the detent torque is completely canceled as described above may be applied. In this case, since the drive can be performed with a lower excitation torque, the size, weight, and power consumption can be further reduced.

Thus, it is possible to freely provide a magnetically equivalent return spring in place of the mechanical return spring of the light amount control member used conventionally.

The detent torque is a huge load with respect to the drive control force of the drive coil. However, since the means for canceling the detent torque is provided magnetically, it can be rotationally driven with a small drive control force. A light amount control device can be realized, which is effective in reducing the size, weight, cost, and power consumption. In particular, since there is no large change in detent torque that causes disturbance, good, fine, and smooth control characteristics can be obtained.

FIG. 4 shows a second embodiment of the present invention. Only parts different from those of the first embodiment shown in FIG. 3 will be described, and description of the other parts will be omitted.

Numeral 43 denotes a stator yoke comprising stator yoke portions 43-1 and 43-2 having a two-part structure having main magnetic poles 43b and 43c and a complementary yoke portion 49 having auxiliary poles 49b and 49c. 43-1 and 43-2
A bobbin around which a drive coil 41 is wound is mounted on a portion where the rotor magnet 42 is engaged in the optical axis direction, and a rotor magnet 42 is arranged with a certain gap between these magnetic poles and auxiliary poles. -2 and bearing holes 43a, 49 for supporting the shaft of the rotor magnet in the auxiliary pole yoke 49.
a is formed. Since the operation of the auxiliary pole yoke portion 49 has been described above, the description is omitted here. However, the rotor magnet 42 is urged in the closing direction with the detent torque set and canceled together with the auxiliary pole 49. .

Reference numeral 44 denotes a Hall element, which is mounted on a substrate 51 on which a drive circuit as shown in FIG. 1 is mounted so as to extend in the optical axis direction.

The rotor magnet 42 is composed of a plastic magnet in which a transmission member 42a and a rotating shaft 42b are integrally formed, and is magnetized to two poles in the radial direction.

[0066]

As described above, according to the first aspect of the present invention, there is provided a rotor comprising a permanent magnet, a stator yoke having a plurality of magnetic poles formed at positions opposed to the rotor, and a winding around the stator yoke. A light quantity control device comprising: a coil to be turned; two light quantity adjustment members that slide in a direction orthogonal to an optical axis; and a transmission member that transmits a driving force of the rotor to the two light quantity adjustment members. The member is formed with two arms that respectively engage with the two light amount adjustment members, and the angle between the two arms is 18.
By setting the angle to be smaller than 0 °, the transmission member can be accommodated along the outer shape of the drive source, and the size of the light amount control device can be reduced.

[0067]

[0068]

[0069]

[0070]

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing details of a driving circuit according to a first embodiment of the present invention.

FIG. 2 is a block diagram of a video camera equipped with the drive circuit of FIG.

FIG. 3 is an exploded perspective view of the light quantity control device according to the first embodiment of the present invention.

FIG. 4 is an exploded perspective view of a light amount control device according to a second embodiment of the present invention.

FIG. 5 is a diagram showing the principle of generation of detent torque.

FIG. 6 is a view showing the principle of canceling and setting detent torque.

7A and 7B are cross-sectional views of a lens barrel having a light amount control device, wherein FIG. 7A shows a case where the light amount control device of the first embodiment is mounted, and FIG. 7B shows a conventional example.

FIG. 8 is a plan view of a light quantity control device driven by a conventional inner magnet type motor.

FIG. 9 is a block diagram of a video camera having the lens barrel of FIG. 8;

FIG. 10 is a diagram showing a relationship between a detent torque and a rotation angle.

FIG. 11 is a diagram showing a relationship between detent torque and rotation angle.

FIG. 12 is a diagram showing a relationship between detent torque and rotation angle.

FIG. 13 is a view showing output waveforms of respective signals in the block of FIG. 1;

FIG. 14 is a plan view of an assembled state of the light amount control device of FIG. 3;

FIG. 15 is a plan view of the light amount control device in FIG. 4 in an assembled state.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 drive coil 2 rotor magnet 3 stator yoke 4 hall element 6, 7 light quantity control member 200 detection means 201 drive source 202 comparison means 203 correction means

Claims (1)

(57) [Claims] 1. A scan of the row data consisting of a permanent magnet, a plurality of magnetic poles in a position facing the rotor are formed
A data yoke, a coil wound around the stator yoke,
And a driving force of the rotor is transmitted to the two light quantity adjusting members.
A light transmission control device having a transmission member connected to the two light amount adjustment members.
Two arm portions are formed, and the two arm portions
The light amount control device, wherein the angle is set to an angle smaller than 180 ° .