JP2002107792A - Light quantity adjusting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light quantity adjusting device capable of adjusting the quantity of light without using a sensor or detection circuit for detecting the position of a diaphragm. SOLUTION: The light quantity adjusting device is provided with a light quantity adjusting member, a stepping motor, in which a pair of stators 4, 6 provided with exciting coils 5, 7 are arranged oppositely to a rotor magnet 1 moltipolar-magnitized on its outer peripheral surface with a phase difference of an electric angle 90 deg. and by which the adjusting member is opened/closed by positively/reversely rotating the magnet 1 by allowing an alternate current to flow through the coils 5, 7, and stoppers 8, 9 for limiting the mechanical angle of the magnet 1 within a prescribed range with the initial position of the magnet 1 determined by power supply to the prescribed exciting coil as reference. When the number of magnetic poles of the magnet 1 is defined as P, the stoppers 8, 9 are limited so that mechanical angle is less than (2×360 deg.)/P.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image recording device such as a light amount adjusting device and a digital camera.

[0002]

2. Description of the Related Art A conventional light amount adjusting device used in a video camera or the like includes a galvano-type actuator for opening and closing two aperture blades according to the amount of current supplied to a driving coil, and a Hall element for detecting the position of the aperture. With
A device provided with a circuit for outputting a control signal for an aperture position is widely used as a known technique.

Further, at the time of a shutter operation at the time of capturing an image, it is necessary to obtain a high-speed closing operation characteristic by supplying a reverse current to a driving coil.

[0004]

However, in the above-described conventional actuator, however, the number of components is large, such as a hole element for detecting the position of the diaphragm, a circuit for detecting the diaphragm position using the output of the hall element, and circuit adjustment, and the circuit is complicated. In order to realize a high-speed shutter, it is necessary to reduce the resistance value of the drive coil, but there is a disadvantage that power consumption when setting an ordinary aperture value increases.

Further, in such a configuration, it is difficult to realize an energy-saving, small-sized and inexpensive light amount adjusting device required for a digital still camera or the like in recent years.

A first object of the present invention is to provide a light amount adjusting device and an image recording apparatus capable of adjusting the light amount without using a sensor for detecting the position of the diaphragm and a detecting circuit.

A second object of the invention according to the present application is to provide a light amount adjusting device and an image recording device which can save energy at the time of controlling the aperture value and at the time of setting the aperture value and can speed up the closing operation. Things.

[0008]

According to a first aspect of the present invention, a pair of stators provided with an exciting coil are attached to a light amount adjusting member and a rotor magnet multi-polarized on an outer peripheral surface by an electric angle of 90 degrees.
A stepping motor that is disposed opposite to each other with a phase difference of a degree and rotates forward and reverse by applying an alternating current to each of the coils to open and close the light amount adjusting member, and is determined by energizing the predetermined exciting coil. And a stopper that limits the mechanical angle of the rotor magnet to a predetermined range based on the initial position of the rotor magnet, wherein the mechanical angle <P when the number of magnetized poles of the rotor magnet is P. (2.times.360.degree.) / P.

According to a second aspect of the present invention, in the first aspect, the two restricting positions regulated by the stopper are a first opening position and a second opening position having different opening areas, and the initial position is fully closed. It is characterized by the position.

A third invention is characterized in that, in any one of the above inventions, one of the exciting coils is used for setting the initial position.

According to a fourth aspect, in the third aspect, the resistance value of the one excitation coil is smaller than the resistance value of the other excitation coil.

According to a fifth aspect of the present invention, in any one of the above aspects, a control input to the one exciting coil is smaller than a control input to the other exciting coil.

According to a sixth aspect of the present invention, in any one of the first to fourth aspects, the control input of the stepping motor is:
It is characterized in that the energization waveform at the time of setting the aperture value is a PWM input, and the energization waveform at the time of the closing operation is a rectangular wave input.

According to a seventh aspect of the present invention, there is provided an image recording apparatus including any one of the above-described light amount adjusting devices.

In an eighth aspect based on the seventh aspect, the image recording apparatus is a digital camera.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) FIGS. 1 to 5 show the principle of operation of a light quantity adjusting device according to a first embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a cylindrical rotor magnet having four poles magnetized on the outer peripheral surface, 2 denotes a rotating shaft fixed to the rotor magnet 1, and 3 denotes a lever fixed to the rotating shaft 2 and rotates together with the rotor magnet 1. .

Reference numeral 4 denotes an A-stator serving as one magnetic pole of the electromagnet, 5 denotes an A-excitation coil for exciting the A-stator 4 to generate a magnetic force, 6 denotes a B stator serving as a magnetic pole of the other electromagnet, and 7 denotes a B stator 6 The two sets of electromagnets are arranged with a phase difference of 90 ° in electrical angle.

That is, a two-phase PM type stepping motor in which the rotor magnet 1 rotates in synchronization with a rotating magnetic field generated by passing an alternating current having a phase difference of 90 ° to the A excitation coil 5 and the B excitation coil 7 is used. Make up.

8 and 9 show that the mechanical angle of the rotor magnet 1 is not more than ((2 × 360 °) / P), that is, P = 4, based on the initial state when the A exciting coil 5 is energized in the ← direction. A first stopper and a second stopper that limit the mechanical angle to a range of <180 °.

FIG. 2A shows an operation that can be set to the initial position by energizing the A exciting coil 5 in the ← direction from the positions of the first stopper 8 and the second stopper 9. Here, the positional relationship in which the first stopper 8, the second stopper 9 and the lever 3 are in contact with each other is represented by an arrow shown in FIG. The first stopper position shown in FIG. 2A and the second stopper position shown in FIG. 2B are moved, for example, by applying a drive signal to the A excitation coil or the B excitation coil, and the energization is performed at those positions. It shall be stopped.

When the A excitation coil 5 is energized in the → direction while the lever 3 is in contact with the first stopper 8, the magnetic pole of the A stator 4 becomes N × as shown in FIG.
The S pole is magnetized, and a rotational force is generated in the illustrated rotation direction to return to the initial state.

This relationship is the same when the lever 3 returns to the initial state from the state in which the lever 3 is in contact with the second stopper 9, as shown in FIG. 2B.

Therefore, the mechanical angle of the rotor magnet 1 regulated by the first stopper 8 and the second stopper 9 is
When [(2 × 360 °) / P] or more, even if the A exciting coil 5 is energized in the → direction, no rotational force is generated in the direction of returning to the initial state from the first stopper 8 and the second stopper 9,
Since a rotational force is generated in the opposite direction, the mechanical angle of the rotor magnet 1 shown in the present embodiment needs to be set to [(2 × 360 °) / P] or less.

FIG. 3 shows the A, B excitation coils 5, 7 from the initial state.
The operation of setting the rotational position of the rotor magnet 1 by supplying power to the rotor magnet 1 will be described.

FIG. 3 (a) → FIG. 3 (b) As described above, when the A exciting coil 5 is energized in the ← direction (first direction), the rotor magnet 1 returns to the initial position.

Next, as shown in FIG. 3 (b), the B magnetizing coil 7 is energized in the ← direction (second direction) and the energizing of the A magnetizing coil 5 is turned off.
Rotates in the direction of the arrow (right) in FIG. 3B and stops at the position indicated by the magnetic pole of the B stator 6 and the magnetic pole of the rotor magnet 1 facing each other.

FIG. 3 (a) → FIG. 3 (c) In order to return the rotor magnet 1 to the initial position, the A excitation coil 5 is energized in the ← direction (first direction) as described above.

Next, as shown in FIG. 3 (c), when the B excitation coil 7 is energized in the → direction (the direction opposite to the second direction) and the A excitation coil 5 is turned off, the rotor magnet 1 rotates in the direction of the arrow (left) in FIG.
It stops at the position shown by the magnetic pole of the B stator 6 and the magnetic pole of the rotor magnet 1 facing each other.

In other words, if the position of the rotation angle is restricted in a range narrower than the position indicated by the position shown in the figure, the position of the three positions can be determined only by the energizing conditions of the A and B excitation coils 5 and 7. .

In the first embodiment shown in FIGS.
Although the energization of the excitation coil has been described with one-phase excitation, 1-2
If phase excitation is used, the number of stop positions can be easily increased.

FIG. 4 shows A and B of a two-phase stepping motor.
7 shows an energization waveform when the control input of the excitation coils 5 and 7 is a microstep drive input by a pseudo sine wave.

The initial position of the lever 3 is such that the B excitation coil is
It is when the input of N 100% is input.

In order to rotate by an electrical angle of θ ° with respect to the initial position, as can be seen from the conduction waveforms in FIG.
By setting the ratio of the energization amount of the B excitation coil 7 to the ratio obtained by A excitation coil = SIN (θ−90) B excitation coil = SIN (θ), the stop position of the lever 3 can be substantially controlled. .

The number of divisions of the microstep drive waveform may be selected and determined according to the use state of the device.

FIG. 5 is a schematic diagram showing a case where the present invention is applied to a light amount adjusting device corresponding to the description of the operation in FIG.

In FIG. 5, reference numeral 10 denotes a two-phase stepping motor, and reference numeral 11 denotes a lever fixed to the rotating shaft 2 of the stepping motor 10, and two stoppers 12 and the lever 11 provided on the stepping motor 10. Thus, the rotational position of the stepping motor 10 is regulated.

The above-mentioned position restriction range is the aforementioned mechanical angle <[(2
× 360 °) / P].

The energizing input of the stepping motor 10 is supplied from the terminal 10a to the A and B exciting coils 5, 7, and the energizing method is the same as that described above, so that the detailed description will be omitted.

The lever 11 is fixed to the rotary shaft 2 of the stepping motor 10 by press-fitting or bonding or the like, and is provided in two long grooves 13c protruding from shoulders of a pair of diaphragm blades 13 which move relatively. The protrusions 11a of the lever 11 projecting from the left and right of the rotating shaft 2 are engaged with each other.
By rotating the aperture blade 13 itself can be moved forward and backward along the linear movement guide 15.

In the closed state, the state of the initial position of the stepping motor 10 is determined by the energizing condition shown in FIG.

Next, FIGS. 3B and 3C of the B excitation coil 7 are shown.
The aperture open state or the small aperture state is determined according to the energization conditions shown in FIG.

Opening of the aperture is performed by opening the aperture blade 13 under the energizing conditions shown in FIG. 3B, whereby the lever 11 rotates counterclockwise and the position is regulated by the stopper 12, and the aperture of the optical device (not shown) is opened. An open state is set with a diameter of 14.

At this time, the opening of the opening 13 a of the diaphragm blade 13 is larger in diameter than the diaphragm opening diameter 14.

The aperture state (small aperture) between the open state of the aperture and the fully closed state of the aperture (small aperture) is such that the lever 11 is rotated clockwise by the energizing condition shown in FIG. Determines the shape of the small stop aperture. At this time, the correspondence between FIG. 3 and FIG. 5 is as follows.

FIG. 3 ⇔ FIG. 5 Initial Position 閉 Closed Position Position ⇔ Aperture Open Position ⇔ Aperture Small Aperture (Second Embodiment) In this embodiment, the energization to the excitation coil is pulsed. Numeral 6 indicates the waveform of the current supplied to the exciting coil of the light amount adjusting device.

FIG. 6 (a) shows the waveforms of current supplied to the exciting coils when the aperture value is set. At this time, approximately duty
If it is set to 50%, the power consumption can be reduced to about 1/2 as compared with the case of the rectangular wave input shown in FIG. The PWM frequency at this time is set at a frequency at which the waveform of the energizing current becomes substantially a direct current.

FIG. 6B shows an energization waveform during the closing operation (shutter operation). Since a high closing speed is required, a rectangular wave is the optimum condition.

(Third Embodiment) In the above-described embodiment, the condition of the energization input to the exciting coils is optimized when the resistance values of the respective exciting coils are equal. Set the resistance of the drive coil to A excitation coil <
If the B excitation coil is used, power consumption can be reduced at least when setting the aperture value.

(Fourth Embodiment) FIG. 7 shows a fourth embodiment of the present invention.
An embodiment will be described.

FIG. 7 is a flowchart in the case where each of the above embodiments is applied to an image recording apparatus such as a digital camera.

ST101: After turning on the power, it is determined whether or not the mode SW is in the photographing mode.

ST102: If the mode is the photographing mode, the aperture drive circuit is set to the PWM drive shown in FIG.

ST103: The aperture is set to open.

ST104: It is determined whether or not a first release switch for starting an operation for determining exposure when the release button provided on the camera is half-pressed to be turned on has been turned on.

ST105: If the first release switch is on, an exposure determination process pre-programmed in the ROM of the microcomputer is executed, and an instruction to set the aperture to open or small is issued.

ST106: It is determined whether or not an instruction to open the aperture has been issued.

ST107: In the case of (N) in ST106,
Set to small aperture.

ST108: When the aperture is open or S
When the aperture is set at T107, the aperture drive circuit is set to rectangular drive.

ST109: It is determined whether or not the release button is further pressed and the second release switch for performing the shutter release is on.

ST110: When the second release switch is turned on, the diaphragm is driven to the closed position and held.

ST111: Capture an image.

ST112: It is determined whether or not the image capture has been completed, and if completed, the process returns to ST101.

[0063]

According to the first to third aspects of the present invention, the control input of the stepping motor is configured such that the control input for setting the aperture value is smaller than the control input for the closing operation. The amount of light can be easily adjusted without using a position detection sensor or a detection circuit.

According to the fourth and fifth aspects of the present invention, the coil resistance value of the stepping motor is smaller than the other coil resistance value of the phase determining the closing operation. In addition, energy can be saved at the time of setting the aperture value, and the speed of the closing operation can be increased.

According to the sixth aspect of the present invention, the control input of the stepping motor is such that an energization waveform at the time of setting an aperture value is a PWM input to a predetermined coil, and an energization waveform at the time of closing operation is applied to a predetermined coil. Since the rectangular wave input is used, energy can be saved during aperture value control, and the closing operation can be speeded up.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a stepping motor of a light amount adjusting device according to a first embodiment of the present invention.

2 (a) and 2 (b) are diagrams showing energizing directions for setting an initial position of the light amount adjusting device shown in FIG.

FIGS. 3A, 3B, and 3C are explanatory diagrams of the operation of the first embodiment.

FIG. 4 is a diagram showing a conduction waveform in the first embodiment.

FIG. 5 is a diagram showing an operation state of the light amount adjusting device according to the first embodiment.

FIG. 6 is a diagram showing an energization waveform according to the second embodiment.

FIG. 7 is a flowchart illustrating a fourth embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Rotor magnet 2 ... Rotating shaft 3, 11 ... Lever 4 ... A stator 5 ... A excitation coil 6 ... B stator 7 ... B excitation coil 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 (8)

[Claims] A pair of stators provided with excitation coils having a phase difference of 90 degrees in electrical angle with respect to a light amount adjusting member and a rotor magnet multi-polarized on an outer peripheral surface; A stepping motor for rotating the light amount adjusting member in forward and reverse directions by applying an alternating current to each coil, and the rotor based on an initial position of the rotor magnet determined by energizing a predetermined exciting coil; A stopper for limiting the mechanical angle of the magnet within a predetermined range, wherein the stopper has a mechanical angle <(2 × 360) where P is the number of magnetized poles of the rotor magnet.
°) / P. 2. The control device according to claim 1, wherein the two restricting positions regulated by the stopper are a first opening position and a second opening position having different opening areas, and the initial position is a fully closed position. The light amount adjusting device according to 1. 3. The light amount adjusting device according to claim 1, wherein one of the exciting coils is used for setting the initial position. 4. The light amount adjusting device according to claim 3, wherein a resistance value of the one excitation coil is smaller than a resistance value of the other excitation coil. 5. The light quantity adjusting device according to claim 1, wherein a control input to the one excitation coil is smaller than a control input to the other excitation coil. 6. The control input of the stepping motor includes:
The light amount adjusting device according to any one of claims 1 to 4, wherein the energization waveform at the time of setting the aperture value is a PWM input, and the energization waveform at the time of the closing operation is a rectangular wave input. 7. An image recording apparatus comprising the light amount adjusting device according to claim 1. 8. The image recording device according to claim 7, wherein the image recording device is a digital camera.