JP4194199B2 - Light amount adjusting device and imaging device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a light amount adjusting device and an imaging device, and more particularly to a light amount adjusting device used for an imaging device such as a digital camera.
[0002]
[Prior art]
2. Description of the Related Art A light amount adjusting device used in a conventional video camera, digital camera, or the like opens and closes two diaphragm blades that are driven via a rotor magnet that rotates according to the amount of current supplied to a drive coil. A galvano actuator and a Hall element that detects the position of the diaphragm by detecting the magnetic force of the rotor magnet, and controls the diaphragm position by the detection output of the Hall element are widely used as a known technique. Yes.
[0003]
Further, at the time of shutter operation during 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, in the actuator of the above-described conventional example, the Hall element for detecting the position of the diaphragm, the detection circuit for the diaphragm position using the output of the Hall element, the number of parts for circuit adjustment, etc. is large, and the circuit is complicated. Further, in order to realize a high-speed shutter, it is necessary to reduce the resistance value of the drive coil, but there is a drawback that power consumption at the time of normal aperture value setting is also increased.
[0005]
For this reason, in recent years, it is difficult to realize an energy saving, small, and inexpensive light amount adjusting device required for a digital still camera or the like.
[0006]
An object of the invention according to the present application is to provide an inexpensive and highly accurate light amount adjusting device and an imaging device including the light amount adjusting device.
[0007]
[Means for Solving the Problems]
The first configuration of the light amount adjusting device that realizes the object of the invention according to the present application is arranged so as to have a phase difference of 90 degrees in electrical angle with respect to a cylindrical rotor magnet that is multipolarly magnetized on the outer peripheral surface. and had two sets of electromagnets wound coils in the stator, said a PM type stepping motor of two-phase for forward and reverse rotation of said rotor magnet by energizing the alternating current to the coils, the initial position of the rotor magnet And a stopper that limits the mechanical angle of the rotor magnet within the range of mechanical angle <(2 × 360 °) / P, where the number of magnetic poles of the rotor magnet is P, and the stepping motor, There are two states, an open state and a closed state , at the limit position by the stopper , and the light quantity between the open state and the closed state depends on the energization conditions for the two sets of electromagnets. A light amount adjusting member whose adjustment state (aperture state) is variable, and when setting a light amount adjustment value of the light amount adjusting member, the stepping motor is driven at a first drive pulse rate , and a shutter using the light amount adjusting member In the case of performing the operation, there is provided drive means for driving the stepping motor at a second drive pulse rate having a pulse rate larger than the first drive pulse rate.
[0008]
The second configuration of the light amount adjusting device for realizing the object of the invention according to this application, the first configuration, said drive means, which variable corresponds to the second driving pulse rate to the light amount adjustment value It is.
[0009]
The configuration of the imaging device that realizes the object of the invention according to the present application includes the light amount adjusting device having any one of the above configurations .
[0010]
DETAILED DESCRIPTION OF THE INVENTION
(First embodiment)
1, FIG. 2, FIG. 3, and FIG. 6 show a first embodiment of the present invention.
[0011]
In FIG. 1, reference numeral 1 denotes a rotor magnet having four poles magnetized on the outer peripheral surface, 2 a rotating shaft fixed to the rotor magnet 1, and 3 a lever fixed to the rotating shaft 2 and pivoting together with the rotor magnet 1.
[0012]
4 is an A stator that serves as one magnetic pole of the electromagnet, 5 is an A exciting coil that excites the A stator 4 to generate magnetic force, 6 is a B stator that serves as the magnetic pole of the other electromagnet, and 7 is an exciting B stator 6. The two sets of electromagnets are arranged with a phase difference of 90 ° in terms of electrical angle.
[0013]
That is, a two-phase stepping motor in which the rotor magnet 1 rotates in synchronization with the generated rotating magnetic field is configured by flowing an alternating current having a phase difference of 90 ° to the A excitation coil 5 and the B excitation coil 7 . .
[0014]
Reference numerals 8 and 9 denote a first stopper and a second stopper that abut against the turning lever 3 to restrict the turning of the turning lever 3, and the rotor magnet 1 is based on the initial state when the A excitation coil 5 is energized in the ← direction. The mechanical angle is limited to ((2 × 360 °) / P) or less, that is, in the present embodiment, P = 4, so that the mechanical angle is limited to a range of <180 °.
[0015]
FIG. 2 shows an operation that can be set to the initial position by energizing the A excitation coil 5 in the ← direction from the turning restricted state in which the turning lever 3 is in contact with the first stopper 8 and the second stopper 9. In addition, the positional relationship in which the first and second stoppers and the lever 3 abut on the rotor magnet 1 with arrows is substituted.
[0016]
As shown in FIG. 2A, when the turning lever 3 is in contact with the first stopper 8 and the A exciting coil 5 is energized in the → direction, the N and S poles are magnetized in the A stator 4 as shown in the figure. Therefore, a rotational force is generated in the illustrated rotational direction, and the initial state is restored. This relationship is the same from the state in which the lever 3 shown in FIG. 2B is in contact with the second stopper 8.
[0017]
That is, when the mechanical angle of the rotor magnet 1 regulated by the first and second stoppers 8 and 9 is equal to or greater than ((2 × 360 °) / P), even if the A excitation coil 5 is energized in the → direction, 1, since no rotational force is generated in the direction of returning from the state in contact with the second stoppers 8 and 9 to the initial state, and the rotational force is generated in the reverse direction, the mechanical angle of the rotor magnet 1 is set to ((2 × 360 ° ) / P) or less.
[0018]
FIG. 3 shows an operation in which the rotor magnet 1 sets the rotational position by energizing the A excitation coil 5 and the B excitation coil 7 from the initial state.
[0019]
Operation from FIG. 3 (1) to FIG. 3 (2) In order to return the rotor magnet 1 to the initial position, the A excitation coil 5 is energized in the ← direction.
[0020]
Next, when the B excitation coil 7 is energized in the direction shown in FIG. 3 (2) and the A excitation coil 5 is de-energized, the rotor magnet 1 rotates in the arrow direction (right) in FIG. 3 (2). Then, it stops at the position {circle around (1)} where the magnetic pole of the B stator 6 and the magnetic pole of the rotor magnet face each other.
[0021]
Operation from FIG. 3 (1) to FIG. 3 (3) In order to return the rotor magnet 1 to the initial position, the A excitation coil 5 is energized in the direction of ←.
[0022]
Next, when the B exciting coil 7 is energized in the energizing direction shown in FIG. 3 (3) and the energizing of the A exciting coil 5 is turned OFF, the rotor magnet 1 moves in the arrow direction (left) of FIG. 3 (3). It rotates and stops at the position (3) where the magnetic pole of the B stator 6 and the magnetic pole of the rotor magnet 1 face each other. If the position restriction of the rotation angle is set in a range narrower than the positions (1) and (3), the position of the three positions can be determined only by the energization conditions of the A excitation coil 5 and the B excitation coil 7.
[0023]
In the above-described first embodiment shown in FIGS. 1 to 3, the energization of the exciting coil is described by one-phase excitation. However, if it is performed by 1-2-phase excitation, the stop position can be further easily increased. it can.
[0024]
FIG. 4 shows energization waveforms when the control input of the A excitation coil 5 and the B excitation coil 7 of the two-phase stepping motor is a microstep (pseudo sine wave) drive input.
[0025]
The initial position of the lever 3 is when the B excitation coil 7 has an input of SIN 100%.
[0026]
To rotate the electrical angle by 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 A excitation coil 5 and the B excitation coil 7 is
A excitation coil 5 = SIN (θ-90)
B excitation coil 7 = SIN (θ)
If the ratio is set to the ratio obtained in step 1, the stop position of the lever can be substantially controlled.
[0027]
That is, the stop position of the lever can be determined in accordance with the ratio of the energization amounts of the A excitation coil 5 and the B excitation coil 7, so that an arbitrary aperture value can be set.
[0028]
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.
[0029]
FIG. 5 is a schematic configuration diagram when a motor that performs the operation shown in FIG. 3 is applied to a light amount adjusting device.
[0030]
In FIG. 5, 10 is a two-phase stepping motor. Reference numeral 11 denotes a rotating lever fixed to the rotating shaft 2 of the stepping motor 10, and the rotation position of the stepping motor 10 is restricted by contact between the two stoppers 12 a and 12 b provided on the stepping motor 10 and the lever 11. Is done.
[0031]
The restriction range of the rotational position described above is set to the aforementioned mechanical angle <((2 × 360 °) / P).
[0032]
An energization input to the stepping motor 10 is supplied from a terminal (not shown) to the A excitation coil 5 and the B excitation coil 7, and the energization method is performed by a control device (not shown) as described above.
[0033]
The lever 11 is fixed to the rotary shaft 2 of the stepping motor 10 by press-fitting or bonding, and an arm lever portion 11b is formed. Engagement pins 11a provided at both ends of the arm lever portion 11b serve as a light shielding member. The pair of diaphragm blades 13 are engaged with the long grooves 13 c formed respectively, and the pair of diaphragm blades 13 are guided by the guide 15 so that the pair of diaphragm blades 13 can be moved forward and backward by the rotation of the lever 11. It has become.
[0034]
Here, in the small aperture state, the stepping motor determines the state of the initial position based on the energizing condition of FIG.
[0035]
Next, the aperture opening state and the aperture closing state are determined based on the energization conditions of FIGS. 3 (2) and 3 (3).
[0036]
In order to open the diaphragm, the rotating shaft 2 of the motor rotates clockwise according to the energization condition of FIG. 3 (2), and when the rotating shaft 2 rotates clockwise, the aperture blade 13 opens and the lever 11 rotates clockwise. The position is restricted by the stopper 12b, and the open state is set by the aperture opening diameter 14 of the imaging device (not shown).
[0037]
At this time, the opening formed by each opening notch 13a of the pair of diaphragm blades 13 has a larger diameter than the aperture opening diameter.
[0038]
On the other hand, in the closed state, the rotating shaft 2 of the motor rotates counterclockwise according to the energization condition of FIG. 3 (3), and the lever 11 rotates counterclockwise by rotating the rotating shaft 2 counterclockwise. The position is restricted at 12a, and the aperture closed state is determined.
The correspondence between FIG. 3 and FIG. 5 is as follows.
[0039]
[0040]
ST101: After turning on the power supply (camera main power supply), it is determined whether or not the mode SW is in the photographing mode.
[0041]
ST102: If it is the photographing mode, the stepping motor drive pulse rate is set to A [PPS]. It is desirable to set A [PPS] to a low pulse rate in order to guarantee the stop position accuracy of the diaphragm. Here, the pulse rate indicates the number of pulses (steps) by which the motor is moved per second, and PPS indicates pulses (steps) / second. For example, the pulse rate of 480 (PPS) is the number of pulses (steps) that rotate the motor by 480 pulses (steps) per second, and a stepping motor of 20 steps / 1 rotation rotates 24 times.
[0042]
ST103: Set the aperture to the open position.
[0043]
ST104: It is determined whether or not a first release switch (hereinafter abbreviated as SW1), which is a switch for determining exposure that is turned on when the release button is pressed halfway, is turned on.
[0044]
ST105: If SW1 is on, an exposure determination process pre-programmed in the ROM of the microcomputer is executed, and an instruction is given to set the aperture to the optimum aperture position in the open or small aperture direction.
[0045]
ST106: The optimum aperture position is calculated and set to a predetermined aperture position.
[0046]
ST107: The stepping motor drive pulse rate is set to B [PPS]. B [PPS] is set to a higher pulse rate than when the aperture is set, and the closing operation (shutter operation ) is performed at a high speed.
[0047]
ST108: It is determined whether or not a second release switch (hereinafter abbreviated as SW2) that is turned on by further pressing the release button for an exposure operation (shutter operation) is turned on.
[0048]
ST109: An image is captured using an imaging device (CCD) in synchronization with SW2. During this time, the operations of ST110 and ST111 are performed.
[0049]
ST110: Drive the diaphragm to the closed position.
[0050]
ST111: Energize and hold the stepping motor for a predetermined time at the aperture closed position.
[0051]
ST112: The energization of the stepping motor is turned off at the aperture closed position.
[0052]
ST113: The image data stored in the image sensor (CCD) is stored in the memory of the camera circuit.
[0053]
ST114: It is determined whether reading of image data is completed. If completed, the process returns to ST101.
[0054]
(Second Embodiment)
FIG. 7 shows a second embodiment.
[0055]
FIG. 7 shows a flowchart when the light amount adjusting device of the above-described embodiment is applied to a digital camera or the like.
[0056]
ST201: After the power is turned on, it is determined whether or not the mode SW is a photographing mode.
[0057]
ST202: If it is the photographing mode, the stepping motor drive pulse rate is set to A [PPS]. It is desirable to set A [PPS] to a low pulse rate in order to guarantee the stop position accuracy of the diaphragm.
[0058]
ST203: Set the aperture to the open position.
[0059]
ST204: It is determined whether SW1, which is a switch for determining exposure, is turned on.
[0060]
ST205: When SW1 is on, an exposure determination process pre-programmed in the ROM of the microcomputer is executed, and an instruction is given to set the aperture to the optimum aperture position in the open or small aperture direction.
[0061]
ST206: The optimum aperture position is calculated and set to a predetermined aperture position.
[0062]
ST207: It is determined whether there is exposure correction information.
[0063]
ST208: If exposure correction information is present, it is determined whether exposure is + correction.
[0064]
When the exposure correction is (+), the pulse rate BX [PPS] corresponding to the correction amount is set.
[0065]
When the exposure correction is (−), the pulse rate is set to B + X [PPS] corresponding to the correction amount.
[0066]
X is set by storing a value corresponding to the exposure correction amount in a memory in advance and giving an appropriate value.
[0067]
ST209: When there is no exposure correction information, the pulse rate is set to B [PPS].
[0068]
ST210: It is determined whether SW2 (shutter) is turned on.
[0069]
ST 212: synchronization with SW2 capturing an image using an image pickup device (CCD) with. During this time, the operations of ST211 and ST213 are performed.
[0070]
ST 211: drives the aperture in the closed position.
[0071]
ST213: Energize and hold the stepping motor for a predetermined time at the aperture closed position.
[0072]
ST214: The energization of the stepping motor is turned off at the aperture closed position.
[0073]
ST215: Store the image data stored in the image sensor (CCD) in the memory of the camera circuit.
[0074]
ST216: It is determined whether reading of image data is completed. If completed, the process returns to ST201.
[0075]
【The invention's effect】
According to the first aspect of the present invention, a closing speed, that is, a high-speed shutter operation at the time of taking a still image is possible.
[0076]
According to the second aspect of the present invention, since the second drive pulse rate of the stepping motor when the closing operation is performed can be varied corresponding to the exposure control, the aperture priority exposure control is possible.
[0077]
According to the third aspect of the present invention, an inexpensive and highly accurate exposure control system can be constructed by using the light quantity adjusting device according to the first and second aspects of the present invention as an aperture shutter for a digital camera or the like.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a driving principle of a motor of a light amount adjusting device according to a first embodiment.
2 shows the drive position of the motor of FIG. 1, wherein (a) shows the return from the first stopper position to the initial position, and (b) shows the return from the second stopper position to the initial position.
FIGS. 3A to 3C are views showing energization directions and rotation directions of coils of the motor of FIG.
4 is a waveform diagram showing the relationship between the energization waveform to the motor of FIG. 1 and the mechanical angle.
FIG. 5 is a diagram illustrating a diaphragm position of the light amount adjusting device according to the first embodiment.
FIG. 6 is an operation flowchart of the first embodiment.
FIG. 7 is an operation flowchart of the second 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 ... Diaphragm blade 14 ... Diaphragm opening diameter 15 ... Diaphragm blade straight guide

Claims (3)

There are two sets of electromagnets in which a coil is wound around a stator that is disposed opposite to the cylindrical rotor magnet that is multipolarly magnetized on the outer peripheral surface with a phase difference of 90 degrees in electrical angle. and PM-type stepping motor of two-phase for forward and reverse rotation of said rotor magnet by energizing the alternating current,
The mechanical angle of the rotor magnet to the initial position of the rotor magnet based, the magnetized poles number of the rotor magnet as a P, a stopper for limiting the mechanical angle <(2 × 360 °) / P in the range of,
It is driven by the stepping motor and has two states, an open state and a closed state , at a limit position by the stopper , and the light amount adjustment state is between the open state and the closed state according to the energization condition to the two sets of electromagnets A variable light amount adjusting member;
When the light amount adjustment value of the light amount adjustment member is set, the stepping motor is driven at a first drive pulse rate , and when the shutter operation using the light amount adjustment member is performed, it is larger than the first drive pulse rate. And a drive unit for driving the stepping motor at a second drive pulse rate of a pulse rate . Said drive means, the light amount adjusting device according to claim 1, characterized in that the variable corresponding to the second driving pulse rate to the light amount adjustment value. Imaging apparatus characterized by having a light amount adjustment device according to claim 1 or 2.