JP4875374B2 - Light control device - Google Patents

Description

  The present invention relates to a light amount adjusting device having a step motor used in an optical apparatus such as a digital still camera or a video camera.

  2. Description of the Related Art Conventionally, a light amount adjusting device such as an optical device used in a digital still camera, a video camera, or the like has been used in many cases using a so-called galvanometer as a driving source.

  In this diaphragm mechanism, the position of a rotor, which is a permanent magnet of a galvanometer, is detected using a Hall element, and the detection result is feedback-controlled to operate the rotor to a target position, thereby performing diaphragm control.

  In addition, digital still cameras and other devices that require a shutter mechanism repel and apply the excitation magnetic field generated by the permanent magnet and coil of the galvanometer from the above-mentioned aperture control position, and rotate the rotor by suction to open and close the aperture control blade. The shutter operation is performed.

  However, when the galvanometer is used as a drive source in the aperture mechanism in this way, the speed is slow even when the shutter operation is performed, and it is not suitable for high-speed time-setting.

  Therefore, a diaphragm mechanism using a stepping motor instead of a galvanometer as a drive source can be considered.

  In a diaphragm mechanism using a stepping motor, for example, a linear drive lever is press-fitted on a rotating shaft of the stepping motor, and a drive pin is provided on the drive lever. Each of the drive pins is engaged with two diaphragm blades through a long hole. In such a diaphragm mechanism, a predetermined pulse is applied to the stepping motor to rotate it, thereby causing the two diaphragm blades to linearly move in directions opposite to each other. The amount of light is adjusted by changing the size of the aperture of the two diaphragm blades according to their positional relationship.

  During the shutter operation, pulses are sequentially applied to the stepping motor in the direction in which the two diaphragm blades are closed, and the motor is rotated to fully close the diaphragm blades at high speed.

  However, in an aperture shutter mechanism using a stepping motor, when the shutter is fully closed, there may be a case where the aperture shutter mechanism deviates from a predetermined position due to bounce of an aperture shutter blade. When charge is transferred from an image sensor such as a CCD in this state, noise is placed on the transfer signal due to light leakage, or the aperture for the given pulse is shifted during the next aperture operation, making normal aperture control impossible. Or

In order to avoid these problems, for example, in Patent Document 1, the initial position of the stop is detected by a photocoupler to guarantee the home position. Patent Document 2 discloses a method of performing an initialization operation in which a pulse signal is given to a motor and an aperture shutter blade stopped after shifting from a predetermined position is returned to a predetermined position.
JP 6-59309 JP JP 2004-109531 JP

  However, all of the above-mentioned methods detect or reset the aperture shutter blade when it stops at a position other than the predetermined position due to the bounding of the aperture shutter blade. It is not a countermeasure against light leakage during charge transfer immediately after full closure.

  The present invention has been made in view of such problems, and has a simple configuration without adding a special member to increase the shutter speed and stop the stable blades, in particular, bounce (re-exposure) of the aperture shutter blades. It is an object of the present invention to provide a light amount adjusting device realized by control.

According to a first configuration for realizing the object of the present invention, as described in claim 1, a ground plate in which an opening for transmitting light is formed and a plurality of support guides capable of parallel reciprocation with respect to the ground plate. A light shielding member, a light shielding member driving unit that engages with the plurality of light shielding members and rotates by energizing a stepping motor driven by a plurality of pulses, and the parallel reciprocating motion A stopper provided on the light shielding member for stopping the light shielding member in a fully closed state by contacting the ground plate at an angle with respect to the direction of the parallel reciprocation after the light shielding member to fully close the opening. includes a part, and the stepping motor is two-phase driven, from the fully opened state to fully open the opening of the base plate to the fully closed state is controlled with a predetermined pulse, mutually phase at least two of said light shielding member In the light amount adjustment device for adjusting the amount of light by parallel reciprocated in the direction of, the light shielding member by driving the stepping motor by a predetermined pulse after moving the fully closed, further one pulse extra two-phase drive The stepping motor is energized, and energized and held for a predetermined time in the excitation phase, and thereafter the operation is returned to the excited state with a predetermined pulse .

  According to a second configuration for realizing the object of the present invention, as described in claim 2, in the first configuration described above, the stopper portion of the light shielding member that reciprocates in parallel is 25 degrees with respect to the reciprocating motion direction. It contacts the ground plane at an angle of 65 degrees.

  According to a third configuration for realizing the object of the present invention, as described in claim 3, in any one of the above configurations, the at least two light shielding members that reciprocally move in parallel with each other are one light shielding member. The stopper portion of the other light-shielding member abuts on the ground plate after the timing when the one light-shielding member abuts on the ground plate.

  As described above, according to the light quantity adjusting device of the present invention, in order to stop the re-exposure due to the bounce of the aperture shutter blade that is a light shielding member, for example, a blade stopper portion is formed on each aperture shutter blade. The blade stopper portion disperses the energy of contact with the blade shape of the inclined surface that contacts the stopper portion of the main plate at an angle of 25 degrees to less than 65 degrees with respect to the operation direction of the aperture shutter blade. Due to the dispersion of energy, the bounce force applied to the aperture shutter blades that perform parallel reciprocating motion is directed in the turning direction, and the bounce force in the swiveling direction is applied to, for example, a plurality of guide pins that guide the parallel reciprocating motion of the aperture shutter blades. Acting in different directions, the bounce force is cancelled, the bounce of the aperture shutter blade after the shutter operation is suppressed, the shutter speed is increased and the stable stop is realized, and the durability of the blade is also improved.

  In addition, for example, two diaphragm shutter blades that are light shielding members reciprocate in parallel in opposite directions due to rotation of the light shielding member driving means such as a drive lever, so that the stopper portion of one diaphragm shutter blade contacts the ground plane. After the contact, the stopper portion of the other aperture shutter blade is brought into contact with the base plate after the timing at which the one aperture shutter blade contacts, so that the bounce force of one aperture shutter blade is It acts as a braking force immediately before coming into contact with the stopper, and can stop the bounce more effectively.

  Further, in the control of the motor, when the shutter blade comes into contact with the mechanical end position on the closing side, it is pressed against the stopper at the two-phase excitation position where the torque of the motor is large. Then, after controlling the drive from the open state to the closed state with 3 pulses of 2-phase drive, hold the energized phase at the 72 ° (+ A phase, -B phase) position of plus 1 pulse for 15 ms or longer. By using together with the means to stop the motor bounce by securely pressing the motor attenuation bounce to the mechanical end position, the bounce of the aperture shutter blade after the shutter closing operation is suppressed and the shutter speed is increased and the aperture shutter blade A stable stop makes it possible to mitigate the impact of the aperture shutter blade and stop re-exposure.

  Furthermore, since the behavior of the blades can be suppressed, durability can be improved.

Hereinafter, the present invention will be described based on embodiments shown in the drawings.
First Embodiment FIG. 1 is an exploded perspective view showing a configuration of a light amount adjusting apparatus according to a first embodiment of the present invention. FIG. 2 is a plan view of the light amount adjusting device. FIG. 2A shows a state in which the opening of the base plate is fully opened by the aperture shutter blade, and FIG. 2B shows a state in which the opening is fully closed.

This light amount adjusting device is provided with a stepping motor 6 that is a light shielding member drive source, a blade drive lever 2 that is a blade drive means that is rotated by the stepping motor 6, and both ends of the blade drive lever 2. The drive pins 2a and 2b, the pair of diaphragm blades 3 and 4 that are light shielding members with which the drive pins 2a and 2b are respectively engaged, and the movement of the pair of diaphragm blades 3 and 4 in the optical axis direction are regulated and stored. The blade cover 5 and the base plate 1 are provided. The aperture shutter blades 3 and 4 are formed with aperture portions 3 b and 4 b , and two elongated holes 3 c, 3 d, 4 c, and 4 d are formed on the same side along the moving direction. One diaphragm shutter blade 3 has a stopper portion 3a formed on the side connected to the drive pin 2a, and the other diaphragm blade 4 has a stopper portion 4a formed at the end of the long hole 4c. The base plate 1 is connected in the moving direction of the pair of aperture shutter blades 3, 4, and engages with each of the two elongated holes 3 c, 4 c, 3 d, 4 d so as to form a pair of aperture shutter blades 3, 4. Guide pins 1a and 1b for projecting parallel motion are provided.

  In this light quantity adjusting device, the pair of aperture shutter blades 3 and 4 are reciprocated in parallel in opposite directions by the rotation of the blade drive lever 2, thereby opening the aperture 10 by the aperture portions 3 b and 4 b of the aperture shutter blades 3 and 4. Is formed. The amount of light is adjusted by changing the size of the opening 10 depending on the positional relationship between the aperture shutter blades 3 and 4, but the number of blades is not limited to two, and the opening is formed by three or more blades. You may do it. Moreover, it can also be set as the structure which contains an ND filter in them.

  The stepping motor 6 includes a rotor (not shown) in which, for example, 10 poles are alternately magnetized on the outer peripheral surface of a cylinder, a rotating shaft 6a provided on the rotor, and a rotor magnet (not shown) outer periphery. And two electromagnets composed of exciting coils (not shown) having an electrical phase difference of 90 degrees. The stepping motor 6 is a two-phase stepping motor that rotates forward and backward by supplying current to two electromagnets having a phase difference of 90 degrees in two excitation coils by a stepping motor drive circuit (not shown). The stepping motor 6 is fastened to the base plate 1 with fixing screws 7 and the blade cover 5 is fixed to the upper surface of the base plate 1 with fixing screws 8 to prevent the diaphragm shutter blades 3 and 4 from coming off.

  In order to perform light amount adjustment by the light amount adjusting device of the present embodiment, the blade driving lever 2 is rotated forward and backward by forward and reverse rotation of the stepping motor 6. Since the pair of aperture shutter blades 3 and 4 are engaged with the drive pins 2a and 2b projecting from the blade drive lever 2 and in the direction of reciprocating the aperture shutter blades 3 and 4 in opposite directions, The aperture shutter blades 3 and 4 slide and move in opposite directions, and the aperture 10 is formed by the aperture portions 3b and 4b of the aperture shutter blades 3 and 4. Then, when the area of the opening 10 changes depending on the positional relationship between the diaphragm portions 3b and 4b, the amount of light passing through the opening 10 changes, and light amount adjustment is performed.

  Further, after the pair of aperture shutter blades 3 and 4 are reciprocated in parallel in opposite directions to change the area of the aperture 10 to adjust the amount of light passing through the aperture 10, the stepping motor 6 operates the aperture in the closing direction. The shutter is closed by exciting driving.

  At this time, the blade stopper portions 3 a and 4 a of the blades 3 and 4 come into contact with the stopper portions 1 c and 1 d of the base plate 1.

  On the other hand, in the present embodiment, the blade drive lever 2 performs drive control from the fully open state to the fully closed state of the opening 10 with 54 ° rotation corresponding to 3 pulses in the two-phase drive. Further, the stepping motor 6 can be stopped at an arbitrary position by performing microstep driving, for example, and the area of the opening 10 can be continuously changed.

  In the embodiment shown in FIG. 1, the blade stopper portions 3a, 4a are in contact with the stopper portions 1c, 1d provided on the base plate 1 in the closed state of the pair of aperture shutter blades 3, 4, but are further opened. However, a similar blade stopper portion may be provided on the aperture shutter blade, and the base plate 1 may be provided with a stopper portion.

  Further, FIG. 2 shows positions where the blade stopper portions 3a and 4a and the stopper portions 1c and 1d are provided, and a specific shape thereof is shown in FIG.

  In FIG. 3, a blade stopper portion 3a provided on one of the aperture shutter blades 3 is provided inside a right side portion where an engagement hole for engaging with the drive pin 2a is formed. It is formed in the inclined surface of angle (theta) with respect to the rectilinear movement direction. Further, on one short side of the base plate 1, a stopper portion 1 c having an inclination angle θ that contacts the blade stopper portion 3 a is formed.

Further, the blades stopper portion 4a formed at the tip of the left side portion of the other aperture shutter blade 4 is formed on the inclined surface of the angle θ with respect to the rectilinear direction of movement of the diaphragm shutter blade 4, of the base plate 1 other A stopper portion 1d having an inclination angle θ that contacts the blade stopper portion 4a is formed on the side side.

  In FIG. 3, the drive pins 2 a and 2 b projecting from the blade drive lever 2 and the pair of aperture shutter blades 3 and 4 reciprocate in parallel with the opposite directions of the aperture shutter blades 3 and 4 by the rotation of the blade drive lever 2. Since they are engaged so as to move, when the blade drive lever 2 is rotated forward and backward by forward and reverse rotation of the stepping motor 6, the aperture shutter blades 3 and 4 slide and move horizontally in the opposite directions. Due to this horizontal movement of the slide, the aperture 10 is formed by the aperture portions 3b and 4b of the pair of aperture shutter blades 3 and 4.

  Then, when the area of the opening 10 changes depending on the positional relationship between the diaphragm portions 3b and 4b, the amount of light passing through the opening 10 changes, and light amount adjustment is performed. Thereafter, the shutter is closed by the excitation drive of the stepping motor 6 that operates the pair of blades in the closing direction.

  At this time, the blade stopper portions 3 a and 4 a set on the blades 3 and 4 come into contact with the stopper portions 1 c and 1 d of the base plate 1.

  The inclination angle θ of the stopper portions 3a and 4a formed respectively on the pair of aperture shutter blades 3 and 4 is arranged to be in contact with the stopper portion of the base plate 1 at an angle of 25 degrees to less than 65 degrees, preferably about 45 degrees. Yes.

  The reason why the desirable angle of the inclination angle θ is 45 degrees is to distribute the force when the aperture shutter blade contacts the base plate as evenly as possible in the direction perpendicular to the travel direction of the aperture shutter blade and the travel direction. is there. If it is smaller than this, the effect of reducing the bounce is reduced, and if it is larger, the load applied to the long hole engaged with the driving pins 2a and 2b of the aperture shutter blade is increased, which may cause a problem in durability. The range of 25 to 65 degrees should be tolerated by play due to play of the processing holes of the parts, the slotted holes that engage with the drive pins of the aperture shutter blades, and the drive pins. there is no problem.

  Thereby, the repulsive force (bound force) due to the contact of the aperture shutter blade with the base plate is dispersed in the moving direction of the blade and in the direction substantially perpendicular to the moving direction of the blade. As a result, the force that bounces in the direction in which the elongated holes 3c, 3d, 4c, and 4d of the aperture shutter blades are guided to the guide pins 1a and 1b provided on the base plate 1 is reduced, and the aperture shutter blades bounce (re-exposure). Can be prevented.

  This is particularly effective when the aperture shutter blade is guided by the two guide pins 1a and 1b and is opened and closed linearly as in the present embodiment.

  That is, since the aperture shutter blades 3 and 4 come into contact with the stopper portions 1c and 1d of the base plate 1 at the inclination angle θ, the aperture shutter blades 3 and 4 have a bound component in the moving direction of the blades and the moving direction of the blades. Bound component force in a direction perpendicular to the direction acts, and the resultant resultant force acts in a direction perpendicular to the inclined surface. Since the aperture shutter blades 3 and 4 are guided by the two guide pins 1a and 1b in the two long holes 3c, 3d, 4c, and 4d that are continuous in the moving direction, this bound resultant force is applied to the aperture shutter blades 3 and 4. Will act as a turning force.

  When a turning force as a bound resultant force acts on the aperture shutter blades 3 and 4, for example, in the aperture shutter blade 4, when the guide pin 1 a is turned as a starting point, the elongated hole 4 c has an inner periphery on the left side with respect to the guide pin 1 a. The surface abuts, and the elongated hole 4d abuts the right inner peripheral surface against the guide pin 1b. Since the direction of the two points at which the aperture shutter blades 3 and 4 act on the guide pins 1a and 1b are different depending on the bound force, the force acting on these two points is canceled out, and the bounce can be further suppressed. .

  In the case of an aperture shutter blade of the type that pivots around a single guide pin, the bounce force is controlled by the aperture shutter blade if the shutter blade is brought into contact with the stopper to suppress the bounce. As with this drive, the blades turn as they are, and the bounce force cannot be canceled out. However, as in this embodiment, the diaphragm shutter blades are reciprocated in the direction opposite to each other, guided by the two guide pins. In the type that moves, the bounce force acts on the aperture shutter blade as a turning force and is canceled.

Second Embodiment FIG. 4 shows a second embodiment of the present invention.

  In the embodiment shown in FIG. 4, at least one of the stopper portions 3a, 4a formed on the pair of aperture shutter blades 3, 4 is 25 to 65 degrees with respect to the operation direction of the pair of blades 3, 4. It arrange | positions so that it may contact | abut to the stopper parts 1c and 1d of the baseplate 1 at an angle below, and the blade | wing 3 is set in that way in this Embodiment. Here, the contact surface of the stopper portion 4a of the aperture shutter blade 4 and the stopper portion 1d of the base plate 1 has a structure along the direction orthogonal to the moving direction of the aperture shutter blade 4, but the embodiment shown in FIG. Similarly, an inclined surface having an inclination angle θ may be used.

  In this embodiment, after the stopper portion 3a of the aperture shutter blade 3 abuts against the stopper portion 1c of the base plate 1, the stopper portion 4a of the other aperture shutter blade 4 becomes the stopper portion of the base plate 1 with a delay of 1 ms or less. In 1d, the timing is shifted and contact is made.

  In the present embodiment, the blade stopper portion 3a of the aperture shutter blade 3 is first brought into contact with the stopper portion 1a of the base plate 1, and the blade stopper portion 4a of the aperture shutter blade 4 has a delay of 1 ms or less. The stopper portion that is in contact with the portion 1d has a phase shift that causes a shift in the contact timing.

  For this reason, the aperture shutter blade 3 is in contact with the aperture shutter blade 3 when the blade stopper portion 3a of the aperture shutter blade 3 abuts against the stopper portion 1c of the base plate 1 and the bound resultant force converted into the turning force acts on the aperture shutter blade 3 as described above. The blade stopper portion 4a is not yet in contact with the stopper portion 1d of the base plate 1, and at this time, a rotational force in the direction opposite to the drive direction is applied to the drive lever 2 by the bound force of the aperture shutter blade 3.

  That is, a force in the direction opposite to the moving direction is applied to the aperture shutter blade 4 from the aperture shutter blade 3 via the drive lever 2, so that the bound force of the aperture shutter blade 3 and the aperture shutter blade 4 are shifted during this phase shift. Works so that the moving force immediately before coming into contact with the stopper portion 1d of the base plate 1 cancels each other, and the bounce of the aperture shutter blades 3 and 4 can be eliminated. As a result, blade bounding during high-speed shutter operation is suppressed, and shutter speed is increased and blades are stably stopped.

Third Embodiment FIG. 5 shows a third embodiment of the present invention.

FIG. 5 shows the relationship between the energized states of the two phases of the stepping motor 6, the A phase and the B phase, the rotation angle of the blade driving lever 2, and the blade operation.
In order to change the diaphragm by continuously changing the area of the opening 10 from the fully opened state of the opening 10 as shown in FIG. 2A to the fully closed state of the opening 10 as shown in FIG. From the energized state 0 ° (+ A phase, -B phase) in which 10 is fully open to the energized state 9 ° (+ A phase), energized state 18 ° (+ A phase, + B phase), energized state 27 ° (+ B phase), Energized state 36 ° (-A phase, + B phase), energized state 45 ° (-A phase), and energized state 54 ° (-A phase, -B phase) where the opening 10 is in the fully closed mechanical end state, Excitation energization of the A phase and B phase of the stepping motor 6 is performed.

  For example, in the above embodiment, the diaphragm control is continuously changed by 1-2 phase driving.

  In the light quantity adjusting device controlled as described above, the stepping motor can be operated from the fully open state to the fully closed state by performing the above-described energization operation regardless of the position within the rotation control range of the stepping motor 6. The electrical angle of 6 is set to be driven within 360 degrees.

  This is because it is possible to omit the position detecting means of the stepping motor 6 or the blade drive lever 2 by performing energization control that does not repeat the same excitation phase in the energization pattern during the 1-2 phase driving of the stepping motor.

  Further, a circuit for driving the position detecting means is not required. For this reason, size reduction and cost reduction of the light quantity adjusting device can also be realized.

  Further, in the control during the closing operation of the shutter, the operation of the drive pulse is controlled by the two-phase drive. This is because the stop time is shorter when the blade is pressed against the stopper portion at the two-phase excitation position where the torque of the motor is large when the blade comes into contact with the closing mechanical end position.

  On the other hand, in the present embodiment, after the drive from the open state to the closed state is controlled to 54 ° (−A phase, −B phase) of the three-phase energized phase of the two-phase drive, a plus one pulse is further added. The energized phase at 72 ° (+ A phase, -B phase) is kept energized for 15 ms or longer.

  In other words, in a 3-pulse energized phase of 54 ° for two-phase driving, the aperture shutter blade abuts on a mechanical stop end (abbreviated as a mechanical end) that is a stopper portion of the main plate 1 and further energizes one pulse for two-phase driving. However, the aperture shutter blades are stopped at a stop position where they do not move further straight, but a large force in the closing direction is applied to the drive lever 2 by the excitation force of the motor, so that the aperture shutter blades are pressed to the stop position. Furthermore, the motor can be prevented from bouncing to the aperture shutter blade due to the attenuation bounce of the motor caused by stopping energization after energizing the energized phase 54 ° of 3 pulses of 2-phase drive, and the aperture shutter blade is moved to the mechanical end position. It can be pressed down securely and the motor bounce can be stopped to achieve a stable stop.

  In this state, the motor may be de-energized. However, since the plus one pulse is energized to the predetermined closed position, the aperture shutter blade is located at the position of the blade stopper and the stopper (mechanical end) of the main plate. Depending on the relationship, it may stop at a position slightly overrun from a predetermined stop position.

  In this case, since there is a possibility of malfunction during the next aperture operation, the pulse corresponding to the predetermined stop position is energized again after the plus one pulse is energized to return to the predetermined position.

  That is, after exciting with a pulse corresponding to a predetermined stop position, the blade is prevented from bouncing by energizing and holding for one plus pulse, and then returned by one pulse in the direction in which the motor reverses to ensure that the blade is in the proper stop position. To stop.

  Although the present invention has been described with reference to the embodiment, the present invention is not limited to the above embodiment, and various controls are possible.

  For example, in the above embodiment, the driving method of the stepping motor 6 is 1-2 phase excitation or 2-phase excitation driving. However, a driving method such as microstep driving may be used.

  In addition, although each embodiment is effective when implemented alone, in recent years, there has been an increasing demand for higher shutter speeds for the purpose of camera shake prevention. Then, the purpose can be achieved more reliably.

It is a disassembled perspective view showing the structure of the light quantity adjustment apparatus which concerns on the 1st Embodiment of this invention. The top view of the light quantity adjustment apparatus of FIG. 1 is shown, (a) shows a fully open state of an opening, (b) shows a fully closed state. It is a figure showing the structure of the wing stopper part of the aperture shutter blade | wing of the light quantity adjustment apparatus shown in FIG. 2, and the stopper part of a ground plane. It is a figure showing the top view of the light quantity adjustment apparatus which shows the 2nd Embodiment of this invention. The 3rd Embodiment of this invention is shown and represents the relationship between the energized state of the A phase and B phase which are two phases of the stepping motor with which a light quantity adjustment apparatus is equipped, the rotation angle of a blade drive lever, and a blade | wing operation | movement.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Base plate 1a, 1b ... Guide pin 1c, 1d ... Stopper part 2 of base plate ... Blade drive lever 2a, 2b ... Drive pin 3, 4 ... Diaphragm shutter blade 3a, 4a ... Blade stopper part 3b, 4b ... Diaphragm part 3c, 3d, 4c, 4d ... slot 5 ... blade cover,
6 ... Stepping motor,
7 ... Motor fixing screw, 8 ... Bane cover fixing screw, 10 ... Opening

Claims (3)

A ground plate with an opening that transmits light;
A plurality of light shielding members supported and guided so as to be capable of reciprocating in parallel with the base plate;
A light shielding member driving means for driving the plurality of light shielding members by engaging with the plurality of light shielding members and rotating by energizing a stepping motor driven by a plurality of pulses ;
After the light shielding member that reciprocates in parallel reciprocates the opening, the light shielding member contacts the ground plane at an angle with respect to the direction of the reciprocating motion, and stops the light shielding member in a fully closed state. The stopper part provided in
Have
The stepping motor is driven in two phases, and is controlled with a predetermined pulse from a fully open state in which the opening of the ground plate is fully opened to a fully closed state, and at least two of the light shielding members are reciprocated in parallel in mutually opposite directions. In the light amount adjustment device that adjusts the light amount by
After driving the stepping motor with a predetermined pulse and moving the light-shielding member to the fully closed state, the stepping motor is further excited by one pulse by two-phase driving and energized and held for a predetermined time in the excitation phase. Then, an operation for returning to the excited state at a predetermined pulse is performed .   The light amount adjusting device according to claim 1, wherein the stopper portion of the light shielding member that reciprocates in parallel makes contact with the ground plane at an angle of 25 to 65 degrees with respect to the reciprocating direction.   The at least two light shielding members that reciprocate in parallel with each other in the opposite directions are such that after the stopper portion of one light shielding member comes into contact with the ground plate, the stopper portion of the other light shielding member is disposed on the ground plate. The light amount adjusting device according to claim 1, wherein the light amount adjusting device is in contact with the ground plate with a delay from a timing of contact with the base plate.

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