JP2004012938A - Light quantity control device and image pickup device provided with light quantity control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light quantity control device capable of performing an inexpensive and quick shutter operation by using a stepping motor as a driving source and to provide an image pickup device provided with the light quantity control device. <P>SOLUTION: As to an energizing phase to coils of the stepping motor when the coils are driven to closed states by current supply to the coils, an energizing phase advanced to the closing direction at an 90° electrical angle from an energizing phase to the coils in a light quantity control state which is determined by an energizing condition to be applied to two sets of electromagnets is used as an initial energizing phase for driving the coils in the closed states to drive the coils to the closing direction. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a light amount adjustment device and an imaging device such as a digital camera including the same.
[0002]
[Prior art]
A conventional light control device used in a video camera or the like includes a galvano-type actuator that opens and closes two aperture blades according to the amount of current supplied to a drive coil, and a hall element for detecting the position of the aperture, and controls the aperture position. Those having an output are widely used as known techniques.
[0003]
At the time of shutter operation at the time of image capture, it is necessary to obtain high-speed closing operation characteristics by means such as reversely energizing the drive coil.
[0004]
[Problems to be solved by the invention]
However, the above-mentioned conventional actuator requires a diaphragm position detection circuit and circuit adjustment using the Hall element for detecting the diaphragm position and the output of the Hall element, the number of components is large, the circuit is complicated, and a high-speed shutter operation is required. To realize this, it is necessary to lower the drive coil resistance value, but the power consumption when setting the normal aperture value may increase. For these reasons, it has been difficult to realize an energy-saving, small-sized, and inexpensive light amount adjusting device required for a digital still camera or the like.
[0005]
The present invention has been made in view of such a problem, and has as its object to provide an inexpensive and high-speed shutter operation using a stepping motor as a driving source and an imaging apparatus including the same. Things.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, according to the present invention, a coil is wound around a cylindrical rotor magnet multipolarly magnetized on an outer peripheral surface and a stator arranged opposite to the rotor magnet with a phase difference of 90 degrees in electrical angle. A two-phase PM type stepping motor having two sets of rotated electromagnets for rotating the rotor magnet forward and reverse by applying an alternating current to each of the coils, and a predetermined energization to the coils. The mechanical angle (rotation angle) of the rotor magnet is defined based on the initial position of the rotor magnet, and the mechanical angle <(2 × 360 °) / P, where P is the number of magnetized poles of the rotor magnet. The stepping motor is driven by a restricting stopper and the open state and the closed state are positioned by the stopper. A light-amount adjusting member that is driven to be in a predetermined light-amount adjusting state according to the power supply condition, and the energizing phase to the coil when the stepping motor is driven to the closed state by energizing the coil is: An initial energizing phase when driving the energizing phase advanced in the closing direction by 90 degrees in electrical angle to the closed state from the energizing phase to the coil in the light quantity adjustment state determined by the energizing conditions for the two sets of electromagnets. It is configured to be driven in the closing direction.
[0007]
Further, an imaging device including the above-described light amount adjusting device may be configured.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
1 to 6 show a first embodiment of the present invention.
[0009]
In FIG. 1, reference numeral 1 denotes a rotor magnet having four poles magnetized on the outer peripheral surface, 2 denotes a rotating shaft fixed to the rotor magnet, 3 denotes a lever fixed to the rotating shaft 2 and rotates together with the rotor magnet 1, and 4 denotes one of the electromagnets. The stators A and 5, which are magnetic poles, are exciting coils A for exciting the stator A to generate a magnetic force, the stators B, 6 are magnetic poles for the other electromagnet, and the exciting coil B for exciting the stator B to generate a magnetic force. The two sets of electromagnets are arranged with a phase difference of 90 ° in electrical angle.
[0010]
That is, a two-phase stepping motor in which a rotor magnet rotates in synchronization with a rotating magnetic field generated by passing an alternating current having a phase difference of 90 ° between the exciting coil A and the exciting coil B is configured.
[0011]
8 and 9, the mechanical angle of the rotor magnet 1 is equal to or less than ((2 × 360 °) / P), that is, P = 4, based on the initial state when the exciting coil A5 is energized in the ← direction. The first stopper and the second stopper are limited to the ranges described above.
[0012]
FIG. 2 shows an operation that can be set to the initial position by applying a current to the exciting coil A in the ← direction from the first and second stoppers. (The positional relationship where the first and second stoppers and the lever 3 are in contact with the rotor magnet 1 is substituted by arrows.) When the exciting coil A is energized in the → direction from the state where the lever 3 is in contact with the first stopper 8, the stator When A is magnetized into the N and S poles as shown in the figure, a rotational force is generated in the illustrated rotating direction, and the state returns to the initial state. This relationship is the same even when the lever 3 is in contact with the second stopper 8. That is, when the mechanical angle of the rotor magnet regulated by the first and second stoppers is equal to or more than ((2 × 360 °) / P), the first and second stoppers return to the initial state even when the exciting coil A is energized in the → direction. Since the rotational force in the returning direction is not generated but the rotational force is generated in the reverse direction, the mechanical angle of the rotor magnet 1 according to the present invention needs to be ((2 × 360 °) / P) or less.
[0013]
FIG. 3 shows an operation of setting the rotational position of the rotor magnet 1 by energizing the exciting coils A / B from the initial state.
[0014]
(1) → (2)
In order to return the rotor magnet 1 to the initial position, the exciting coil A is energized in the ← direction. Next, when the excitation coil B is energized in the direction (2) shown and the excitation coil A is de-energized, the rotor magnet 1 rotates in the direction of the arrow (right) in the illustration (2) and the magnetic pole of the stator B and the magnetic pole of the rotor magnet are rotated. Stop at the opposing (1) position.
[0015]
(1) → (3)
In order to return the rotor magnet 1 to the initial position, the exciting coil A is energized in the ← direction. Next, when the excitation coil B is energized in the direction of (3) and the energization of the excitation coil A is turned off, the rotor magnet 1 rotates in the direction of the arrow (left) in the illustration (3), and the magnetic pole of the stator B and the magnetic pole of the rotor magnet are rotated. Stops at the position (2) that opposes. If the rotation angle position regulation is provided in a range narrower than the (1) position (2) position, the three positions can be determined only by the energizing conditions of the exciting coils A and B.
[0016]
In the first embodiment shown in FIGS. 1 to 3, the energization of the excitation coil is described as one-phase excitation. However, if the excitation is performed with one-two-phase excitation, the stop position can be further increased.
[0017]
FIG. 4 shows an energization waveform when the control input of the excitation coils A and B of the two-phase stepping motor is a microstep (pseudo sine wave) drive input.
[0018]
The initial position of the lever 3 is when the exciting coil B has an input of SIN 100%.
[0019]
In order to rotate by an electrical angle of θ ° with respect to the initial position, as can be seen from the energization waveform in the figure, the ratio of the energization amounts of the excitation coil A and the excitation coil B is determined by the excitation coil A = SIN (θ−90)
Excitation coil B = SIN (θ)
If the ratio is set to the value obtained in (1), the stop position of the lever can be substantially controlled. That is, since the position of the lever can be determined according to the ratio of the amount of current flowing between the exciting coil A and the exciting coil B, an arbitrary aperture value can be set.
[0020]
If the number of divisions of the microstep drive waveform is selected and determined according to the required accuracy of the device, an optimum aperture value can be selected. Also, the number of poles of the magnet rotor of the stepping motor, which is the driving source, may be selected and determined according to the required accuracy and conditions of the device.
[0021]
FIG. 5 is a schematic configuration diagram of a case where the present invention is applied to a light amount adjusting device in accordance with the operation description of FIG. In FIG. 5, reference numeral 10 denotes a two-phase stepping motor. Reference numeral 11 denotes a lever fixed to the rotating shaft 2 of the stepping motor, and two stoppers 12 provided on the stepping motor 10 and the lever 11 regulate the rotational position of the stepping motor.
[0022]
The position restriction range is set to the aforementioned mechanical angle <((2 × 360 °) / P). The energizing input of the stepping motor 10 is supplied from the terminal 10a to the exciting coils A and B, and the energizing method is as described in detail above.
[0023]
The lever 11 is fixed to the rotary shaft 2 of the stepping motor 10 by press-fitting or bonding, and engages with two long grooves 13c of the aperture blade 13 so that the lever 11 is rotated by the linearly moving guide 15 for the aperture blade 13 to rotate the aperture blade 13 Can move forward and backward.
In the closed state, the stepping motor determines the state of the initial position according to the energizing condition (1) shown in FIG.
[0024]
Next, the aperture open state and the aperture closed state are determined based on the energizing conditions (2) and (3) shown in FIG. In opening the aperture, the lever 11 rotates counterclockwise by opening the aperture blade 13 under the energizing condition (2), the position is regulated by the stopper 12, and the aperture is set by the aperture opening diameter 14 of the optical device (not shown). . At this time, the opening formed by the aperture blade 13a has a larger diameter than the aperture opening diameter. In the closed state, the lever 11 rotates clockwise according to the energizing condition (3), the position of the lever 11 is regulated by the stopper 12, and the aperture closed state is determined.
[0025]
The correspondence between FIG. 3 and FIG. 5 is as follows. The initial position in FIG. 3 corresponds to the small aperture stop position in FIG. 5, the one position in FIG. 3 corresponds to the aperture open position in FIG. 5, and the two positions in FIG. 3 correspond to the aperture closed position in FIG. .
[0026]
FIG. 6 is a flowchart when the first embodiment is applied to a digital camera or the like.
ST101: After turning on the power, it is determined whether or not the mode SW is in the photographing mode.
ST102: In the case of the photographing mode, the drive pulse rate of the stepping motor is set to A [PPS]. A [PPS] is set to an arbitrary pulse rate that can guarantee the stop position accuracy of the aperture. Here, the pulse rate indicates the number of pulses (steps) for moving the motor in one second, and PPS indicates pulses / second. For example, the pulse rate of 480 [PPS] is the number of pulses (steps) that rotates the motor 480 pulses (steps) per second. In the case of a stepping motor of 20 steps / 1 rotation, 24 rotations are performed at a mechanical angle of 18 degrees / 1 step.
ST103: Set the aperture to the open position.
ST104: It is determined whether or not the release 1, which is a switch for determining an exposure, is turned on.
ST105: It is determined whether the maximum aperture is sufficient.
ST106: In the case of the release 1on, an exposure determination process programmed in advance in the ROM of the microcomputer is executed, and an instruction is issued to open the aperture or set an optimal aperture position in the small aperture direction.
ST107: The optimum aperture position is held until the aperture closing operation starts.
ST108: The control input to the coil is advanced by 90 electrical degrees in electrical angle while the aperture position is held.
ST109: It is determined whether or not the release 2 (shutter) has been turned on.
ST110: If the release is 2 (on), a current advanced by 90 electrical degrees from the aperture setting position is applied to the coil as an initial current. Here, from the basic principle of a two-phase stepping motor, applying a current advanced by 90 degrees in electrical angle to the coil means that the motor has the highest rotational torque, so that the motor rotates in the closing direction. This is the most suitable condition for initial energization of the coil when driving at high speed.
ST111: Drive the aperture to the closed position at a predetermined pulse rate.
ST112: If release 2 (on), the image pickup device (CCD) starts accumulating images.
ST113: The stepping motor is kept energized for a predetermined time at the aperture closing position.
ST114: It is determined whether or not image capturing is completed. If completed, go to ST115.
ST115: Store the image data stored in the image sensor (CCD) in the memory of the camera circuit.
ST116: Determine whether or not the storage of the image data is completed.
[0027]
If completed, go to ST117.
ST117: After the reading of the image data is completed, the power supply to the coil is turned off at the aperture closing position, and the process proceeds to ST101.
[0028]
【The invention's effect】
As described above, according to the present invention, a coil is wound around a cylindrical rotor magnet multipolarly magnetized on the outer peripheral surface and a stator arranged to face the rotor magnet with a phase difference of 90 degrees in electrical angle. A two-phase PM type stepping motor for rotating the rotor magnet forward and reverse by applying an alternating current to each of the coils, and a predetermined electric current to the coil. The mechanical angle (rotation angle) of the rotor magnet is limited based on the initial position of the rotor magnet such that the mechanical angle <(2 × 360 °) / P is satisfied, where P is the number of magnetized poles of the rotor magnet. And a stopper that is driven by the stepping motor, and is positioned between an open state and a closed state by the stopper. And a light-amount adjusting member that is driven so as to be in a predetermined light-amount adjusting state according to the following. When the stepping motor is driven to the closed state by energizing the coil, the energizing phase of the coil is 2 The energization phase of the coil in the light quantity adjustment state determined by the energization conditions for the set of electromagnets is 90 degrees in electrical angle, and the energization phase advanced in the closing direction is closed as the initial energization phase when driving to the closed state. The sensor is driven in the direction, so no sensor or detection circuit for detecting the position of the diaphragm is used, and the stepping motor can be driven with a high torque during the closing operation, so the closing speed, that is, high speed when capturing a still image Shutter operation is possible.
[0029]
As described above, according to the present invention, it is possible to provide an inexpensive and high-speed shutter operation using a stepping motor as a drive source and an imaging apparatus including the same.
[Brief description of the drawings]
FIG. 1 is a diagram showing a principle diagram of a first embodiment; FIG. 2 is an explanatory diagram of an initial position setting of the first embodiment; FIG. 3 is an operation explanatory diagram of the first embodiment; FIG. FIG. 5 is a configuration diagram of a light amount adjusting device. FIG. 6 is a flowchart of an operation when the first embodiment is applied to a digital camera.
DESCRIPTION OF SYMBOLS 1 Rotor magnet 2 Rotating shaft 3, 11 Lever 4 Stator A
5 Excitation coil A
6 Stator B
7 Excitation coil B
8 1st stopper 9 2nd stopper 10 Stepping motor 12, 16 Stopper 13 Aperture blade 14 Aperture opening diameter 15 Aperture blade straight guide

Claims (2)

A cylindrical rotor magnet multi-polarized on the outer peripheral surface;
The rotor magnet has two phases of electromagnets each of which has a coil wound around a stator disposed opposite to the rotor magnet with a phase difference of 90 degrees in electrical angle, and an alternating current is applied to each of the coils to reverse the rotor magnet. A two-phase PM type stepping motor to be rotated;
The mechanical angle (rotation angle) of the rotor magnet is defined based on the initial position of the rotor magnet determined by the predetermined energization of the coil, and the mechanical angle <(2 × 360 °) where P is the number of magnetized poles of the rotor magnet. ) / P
A stopper that restricts the conditional expression of
A light amount adjusting member driven by the stepping motor, the open state and the closed state are positioned by the stopper, and driven to be in a predetermined light amount adjusting state according to a condition for energizing the two sets of electromagnets. ,
The energization phase to the coil when the stepping motor is driven to the closed state by energization to the coil is smaller than the energization phase to the coil in the light amount adjustment state determined by the energization conditions to the two sets of electromagnets. A light amount adjusting device that drives in the closing direction as an initial energizing phase when the energizing phase advanced in the closing direction by 90 electrical degrees in the closing direction is driven to the closed state. An imaging apparatus comprising the light amount adjusting device according to claim 1.

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