JPH11160753A - Diaphragm device for camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain stable aperture accuracy regardless of a diaphragm blade driving method with respect to a diaphragm device where a step motor is set as a driving source and the opening direction of a diaphragm blade is not limited to one direction. SOLUTION: The rotation of the step motor 11 is transmitted to a diaphragm ring 10 through gears 12 and 10h, and the diaphragm blades 14a to 14g opens or closes an aperture for exposure AP in accordance with the rotating direction of the ring 10. The real apertures of the diaphragm blades are made coincident by controlling the overshoot amount of each diaphragm blade by changing the rate of pulses supplied to the motor according to data in a data table between the case that the diaphragm blade is stopped down from a large diaphragm side to reach an aimed aperture value and the case that it is opened from a small diameter side to reach the aimed aperture.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aperture device for a camera using a stepping motor as a drive source for a digital camera, a silver halide film camera, and the like. The present invention relates to a diaphragm device capable of obtaining aperture accuracy.

[0002]

2. Description of the Related Art Conventionally, there has been known an aperture device for driving an aperture ring for driving an iris aperture blade using a stepping motor as a drive source. As is well known, in this type of aperture device, a plurality of aperture blades of the same shape are arranged so as to be rotatable at the same angular interval around the aperture, and the rotation of the step motor is transmitted by a gear to rotate around the aperture. In the moving aperture ring, the same number of cam grooves as the plurality of aperture blades are formed in the same shape at the same angular interval around the aperture, and the cam followers planted on each aperture blade are provided in each cam groove. The cam is connected. Therefore, when the rotation of the stepping motor is transmitted to the cam ring by a gear and the aperture ring is rotated about the aperture, the cam followers formed on the respective aperture blades rotate in accordance with the respective cam grooves to rotate the shaft. By controlling the step rotation position, the aperture diameter of the aperture can be controlled.

[0003]

However, when the above-described gear transmission mechanism is used, a so-called backlash occurs between the gear on the step motor side and the gear on the aperture ring side, and the aperture is restricted. It goes without saying that there is some play between the cam edge formed on the ring and the cam follower formed on the diaphragm blade. It is also well known that the step motor pulsates every step rotation. FIG.
10 is an enlarged view of a joint portion between the gear 1 on the stepping motor side and the gear 2 on the drawing ring side. FIG. 9 shows a case where the gear 1 on the stepping motor side is rotated counterclockwise.
0 indicates a case where the gear 1 on the step motor side is rotated clockwise.

When the gear 1 on the stepping motor side is rotated counterclockwise, the gear 2 on the aperture ring rotates clockwise while being pressed by the gear 1, and the rotation of the gear 1 is stopped. The rotation of the gear 2 also stops, but the gear 1 does not stop instantaneously at the same time as the stepping stop of the driving pulse, but overshoots counterclockwise to the position 1 'as shown by the dotted line due to the pulsation, and then changes to the solid line. It returns to the indicated position 1 and stops. Therefore, the gear 2 on the aperture ring side stops in a state where it is rotated clockwise to the position where the gear 1 overshoots. Conversely, when the gear 1 on the step motor is rotated clockwise, the gear 2 on the aperture ring rotates counterclockwise while being pressed by the gear 1, and the rotation of the gear 1 is stopped. The rotation of the gear 2 also stops, but the gear 1 does not stop instantaneously at the same time as the stepping stop of the drive pulse. It returns to the position shown in 1 and stops.
The gear 2 on the aperture ring side stops while rotating counterclockwise to the position where the gear 1 overshoots.

FIG. 11 is an opening characteristic curve showing this state, and a curve 3 shows the running characteristic of the gear 1 on the step motor side when the gear 1 rotates counterclockwise as shown in FIG. Thus, the gear 1 rotates from the large diameter to the small diameter side as shown by the solid line 3 and stops at the target position shown by 5 after the overshoot shown by 4. The dotted line 6 indicates the position of the gear 2 on the aperture ring side at this time, and the gear 2 on the aperture ring side moves to the smaller aperture side than the original middle aperture position and stops due to the effect of overshoot. . The curve 7 shows the running characteristics of the gear 1 on the stepping motor side when the gear 1 rotates clockwise as shown in FIG. 10, and the gear 1 has a small diameter to a large diameter as shown by a solid line 7. Rotate to the side,
After the overshoot indicated by 8, the motor stops at the target position indicated by 5. The dotted line 9 indicates the position of the gear 2 on the aperture ring side at this time, and the gear 2 on the aperture ring side moves to a larger aperture side than the original middle aperture position and stops due to the effect of overshoot. . Therefore, even when trying to obtain the same aperture, an aperture error corresponding to the interval between the dotted line 6 and the dotted line 9 in FIG. 11 occurs when the aperture is narrowed down from the large aperture and when the aperture is opened from the small aperture. Although the caliber error between the gear 1 on the step motor side and the gear 2 on the aperture ring side has been described here, the play between the cam groove formed on the aperture ring and the cam follower formed on the aperture blade is described. Causes the exact same reduction. When the aperture is reduced from the large aperture, the aperture becomes smaller than the target aperture, and when the aperture is opened from the small aperture, the aperture becomes larger than the target aperture. .

In order to solve such a problem, it is conceivable to provide a spring for absorbing gear backlash or to provide a spring for absorbing play between the cam groove and the cam follower for each aperture blade. In particular, extending the springs to all the aperture blades has a problem that the storage space for the springs becomes large and these springs impose a large load on the stepping motor. For this reason, in many cases, the aperture value is stabilized by generally unifying the operation direction of the step motor at the time of the aperture control operation, for example, from a fully opened state to a narrowed down direction.

In recent years, so-called digital cameras, which project an optical image onto an image pickup device in addition to a silver halide film and output the optical image as a digital signal, have become widespread. Some types of digital cameras are known so that a photographed image can be viewed on a liquid crystal finder instead of a so-called optical finder. However, when such a liquid crystal finder is used, the aperture device is either forward or reverse. It is desirable to be able to operate in both directions, and a diaphragm device that can operate only in one direction in controlling the aperture value hinders the use of a liquid crystal finder. However, as described above, when the aperture blade is operated bidirectionally, an error occurs in the actual aperture value when the aperture is stopped down and when the aperture is opened.
Since the latitude of the CD imaging device is extremely narrow as compared with the silver halide film, there is a problem that the error of the aperture value is at a level that cannot be ignored.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and provides a diaphragm apparatus for a camera capable of obtaining a stable aperture accuracy regardless of the operation direction of a step motor. The purpose is to: In summary, a camera shutter device according to claim 1 includes: a step motor (11) rotatable in both forward and reverse directions by advancing a forward rotation pulse or a reverse rotation pulse; and one or more step motors A driving member (10) gear-coupled through the gear trains (12, 10h) and operable in both forward and reverse directions according to the rotation direction of the step motor: an opening for exposure corresponding to the operating position of the driving member One or a plurality of aperture blades (14a to 14g) for regulating the opening diameter of the step motor: forward or reverse rotation of the step motor by stepping forward or reverse rotation pulses supplied to the step motor. Thus, a motor control means (for example, CPU 3) for driving the driving member to a position corresponding to a target opening diameter by forward operation or reverse operation of the driving member.
6) The motor control means rotates the step motor to a target position by a forward rotation pulse and rotates the step motor to a target position by a reverse rotation pulse. The pulse rate (t1, t2, t3) of the forward rotation pulse and / or the reverse rotation pulse is changed so that the overshoot amount when the stepping motor stops is different from the time when the stepping motor is stopped. A camera shutter device according to a second aspect of the present invention is based on the premise that the shutter device for a camera according to the first aspect is used. During the final stop pulse time finally supplied, energization (t3) of the phase immediately before the final stop pulse is performed, and the energization time of the immediately preceding phase is determined between the forward rotation operation and the reverse rotation operation of the step motor. Is changed. The camera diaphragm device according to claim 3 is as follows:
Assuming the camera shutter device according to claim 2, the motor control means changes a change amount (t3) of the energization time of the immediately preceding phase according to a target stop position of the driving member. Things. Further, the camera aperture device according to claim 4 is based on the camera aperture device according to claim 1, claim 2 or claim 3: the motor control means is configured to supply a direct current to the step motor. The pulse time (t1) of the immediately preceding pulse supplied immediately before the final stop pulse finally supplied in the diversion pulse or the reverse rotation pulse is changed between the forward rotation operation and the reverse rotation operation of the step motor. It is characterized by the following. Further, the camera shutter device according to claim 5 is:
Assuming the camera shutter device described above, the motor control means changes the amount of change in the pulse time (t1) of the immediately preceding pulse in accordance with a target stop position of the driving member. .

According to the first aspect of the present invention, the stepping motor is rotated forward or backward by supplying a forward rotation pulse or a reverse rotation pulse.
The drive member operates in the forward or reverse direction. The one or more aperture blades regulate the opening diameter of the exposure opening in accordance with the operating position of the driving member, so that the operating position of the driving member can be controlled by a forward or reverse rotation pulse supplied to the stepping motor. For example, it is possible to control the diameter of the aperture formed by the aperture blade. The motor control means changes the pulse rate so that the amount of overshoot when the step motor stops during the forward rotation and the reverse rotation of the step motor changes. Therefore, the forward rotation operation is performed by appropriately adjusting the pulse rate. Accordingly, it is possible to eliminate an error in the aperture value between when the target aperture diameter is obtained and when the target aperture diameter is obtained by the reversing operation.

According to a second aspect of the present invention, the pulse rate change is more concretely performed during the final stop pulse time finally supplied during the forward rotation pulse or the reverse rotation pulse supplied to the stepping motor. By performing the energization of the phase immediately before the stop pulse, the motor torque at the time of the step rotation to the final stop position is reduced, and the overshoot amount is correspondingly reduced. Since the amount of decrease in motor torque fluctuates by changing the energization time of the previous phase,
If the energization time of the immediately preceding phase is changed between the forward rotation and the reverse rotation, the amount of overshoot at the stop position can be changed between the forward rotation and the reverse rotation. It is possible to eliminate the caliber value error.

According to a third aspect of the present invention, the amount of change in the energization time of the immediately preceding phase is changed in accordance with the stop position of the driving member, and the load applied to the step motor varies depending on the stop position of the driving member. Is assumed. For example, when a spring for absorbing backlash is stretched over the driving member, the load applied to the step motor also changes because the tension of the spring changes according to the position of the driving member. Also, when there is no spring for backlash absorption, for example, especially when there are a large number of diaphragm components such as an iris diaphragm, the aperture is narrowed down.
The load applied to the step motor increases due to the frictional force and elastic force between the respective aperture blades. The overshoot generated with respect to the step motor has a property that fluctuates according to the load fluctuation when the motor torque is fixed. Therefore, in order to compensate for such a variation in overshoot caused by a load variation caused by the operating position of the driving member, the energizing time of the immediately preceding phase is changed according to the stop position of the driving member.

Claim 4 shows another form of the change of the pulse rate. According to the fourth aspect, the pulse time of the immediately preceding pulse supplied immediately before the finally supplied final stop pulse in the forward rotation pulse or the reverse rotation pulse supplied to the step motor is increased or decreased. The motor torque during step rotation to the stop position is increased or decreased, and the amount of overshoot is also increased or decreased. If the pulse time of the immediately preceding pulse is extended beyond the standard, the holding force of the motor in the immediately preceding step increases, so that the torque when stepping to the final stop position decreases and the amount of overshoot also decreases. . Conversely, if the pulse time of the immediately preceding pulse is shortened from the standard, the holding force of the motor in the immediately preceding step decreases, so that the torque when stepping to the final stop position increases and the overshoot amount also increases. Therefore, if the pulse time of the immediately preceding pulse is changed between the forward rotation and the reverse rotation, the overshoot amount at the stop position can be changed between the forward rotation and the reverse rotation. Can be eliminated. Claim 4
Is a modification of the second aspect in terms of changing the pulse rate, but can be used in combination with the second aspect.

According to a fifth aspect of the present invention, based on the premise of the fourth aspect, the amount of change in the pulse time of the immediately preceding pulse is changed in accordance with the stop position of the driving member. It is assumed that it fluctuates. The fifth aspect is also for compensating the variation of the overshoot due to the load variation caused by the operating position of the driving member, and changes the amount of change of the pulse time of the immediately preceding pulse according to the stop position of the driving member. .

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a plan view of a camera shutter device according to an embodiment of the present invention as viewed from a subject side, and shows an aperture ring as an example of a driving member. An aperture ring 10 is arranged around an optical axis of a photographic lens (not shown). It is formed in a rotatable ring shape, and an exposure opening AP is formed in the center. Since the present embodiment assumes an iris diaphragm having seven blades, the cam ring 1 having the same shape is formed on the diaphragm ring 10 at angular intervals obtained by equally dividing one circumference around the exposure opening AP.
0a to 10g are formed. Reference numeral 11 denotes a step motor, 12 denotes an output pinion of the step motor 11, and the output pinion 12 meshes with a rack 10h formed on a part of the outer edge of the aperture ring 10. Output pinion 12 and rack 1
0h to the aperture ring 10 and the aperture ring 1
0 rotates stepwise in the opposite direction to the output pinion 12.
In the illustrated embodiment, the output pinion 12 is connected to the rack 10.
Although an example is shown in which the gear is directly meshed with the gear h, a gear train may be interposed therebetween. Reference numeral 13 denotes a backlash absorbing spring provided as required.
Reference numeral 3 denotes a spring hook 1 protruding from an outer edge of the drawing ring 10.
0i, which gives the aperture ring 10 a right-handed turning property. Note that the spring 13 indicates only the biasing direction by an arrow.

Reference numerals 14a to 14g denote diaphragm blades having the same shape, respectively. The diaphragm blades 14a to 14g are rotating shafts 15a which are planted at angular intervals obtained by equally dividing one circumference around the exposure opening AP. From 15g (1 from the rotating shaft 15a)
5g is provided on a base plate (not shown) provided on the front side of the aperture blades 14a to 14g. ) Is rotatably supported. Cam followers 16a to 16g are provided upright on the back surfaces of the aperture blades 14a to 14g, respectively.
Each of these cam followers 16a to 16g has a cam groove 1
It is inserted from 0a to 10g. In the drawings, cam grooves 10a to 10g, aperture blades 14a to 14g, rotating shafts 15a to 15g, and cam followers 16a to 16g.
Are paired if they share the same alphabetic code.

The state shown in FIG. 1 shows the fully opened state of the exposure opening. The aperture blade 10 is rotated counterclockwise by rotating the output pinion 12 clockwise from the state shown in FIG. 14a to 14g narrow the aperture AP for exposure. FIG. 2 shows a state in which the exposure aperture AP is narrowed down to the intermediate aperture, and FIG. 3 shows a state in which the exposure aperture AP is narrowed down to the minimum aperture. That is, the output pinion 12 is rotated clockwise from the state shown in FIG.
Is rotated counterclockwise, the cam followers 16a to 16g erected on the respective aperture blades 14a to 14g follow the corresponding cam grooves 10a to 10g to operate, so that each of the aperture blades 14a to 14g is connected to the respective rotating shaft. Rotate counterclockwise around 15a to 15g to narrow down the exposure aperture AP.

Considering now the case of obtaining the intermediate aperture shown in FIG. 2, when the current aperture state is the fully open state shown in FIG. 1, the aperture ring 10 is rotated counterclockwise, and the current aperture state is obtained. When the aperture ring 10 is in the small aperture state shown in FIG. 3, the aperture ring 10 is rotated clockwise. However, when the step ring 11 is driven at a common pulse rate regardless of the rotation direction. It is known that an error occurs in the aperture value obtained depending on the rotation direction of the step motor 11 due to backlash between the output pinion 12 and the rack 10h and play between the cam followers 16a to 16g and the cam grooves 10a to 10g. It is as pointed out in detail as a problem.

Therefore, in the present invention, when a predetermined aperture is obtained, the pulse rate of a driving pulse supplied to the step motor 11 is changed according to the rotation direction of the step motor 11, thereby controlling the rotation direction of the step motor 11. And stable caliber accuracy can be obtained. FIG. 4 is a block diagram of a control system for controlling the rotation direction of the step motor 11. In the figure, reference numerals 17 and 18 denote coils 19 and 20 of the step motor 11, transistors for supplying a current in the forward direction to the coil 17, 21, 22 transistors for supplying a current in the reverse direction to the coil 17, 23, 2
Reference numeral 4 denotes each inverter. Similarly, transistors 25 and 26 supply a positive current to the coil 18, and transistors 27 and 26.
Reference numeral 28 denotes a transistor for supplying a current in the reverse direction to the coil 18, and reference numerals 29 and 30 denote inverters. Reference numeral 31 denotes a motor control circuit for controlling the conduction of the transistor. Since the drive circuits for the coils 17 and 18 have basically the same configuration, the operation will be described on behalf of the coil 17 side. When the A-phase pulse generated by the motor control circuit 31 becomes H level, the transistors 19 and 18 20 is turned on, and a current flows in a positive direction (from top to bottom in the drawing) through the coil 17,
When the negative A-phase pulse goes to the H level, the transistor 21,
22 turns on and a current flows in the coil 17 in the opposite direction.

Reference numerals 32 and 33 denote switches interlocked with the shutter button, and reference numeral 36 denotes a CPU for performing overall control.
When the switch 32 is made in the half stroke of the shutter button, the divided voltage levels of the resistors 34 and 35 are applied to the CPU 36, and in the full stroke of the shutter button, the switch 33 is made and the power supply level is applied to the CPU 36. Reference numeral 37 denotes a data table formed of, for example, an EEPROM in which control data, particularly data relating to a pulse rate, is stored; 38, a counter indicating the current position;
Reference numeral 39 denotes an interrupt timer for periodically generating an interrupt, and reference numeral 40 denotes a luminance input unit for inputting the field luminance.

The purpose of increasing or decreasing the overshoot is to obtain a stable aperture value regardless of the direction of operation of the diaphragm blade.
(1) When the overshoot in the one traveling direction is set as specified and the stop position is matched by suppressing the overshoot in the other traveling direction, (2) When the overshoot is suppressed in both cases, (3) When suppressing one overshoot and emphasizing the other overshoot,
Basically, the amount of overshoot should be controlled so that the same diameter is finally obtained when the specified aperture is obtained by narrowing the aperture and when the aperture is obtained by opening the aperture. It will be good.

FIG. 5 is a characteristic curve showing this overshoot state. From the large-diameter side, narrow down along the curve of 41 and after overshooting 42, step motor 1
When the control is performed so that 2 converges to the position 43, the aperture value obtained by the narrowing is the position indicated by the line 44. Therefore, in this case, in order to obtain the same aperture value by opening along the curve of 45 from the small aperture side, the overshoot amount may be suppressed by the line of 46. Conversely, an aperture is opened along line 45 from the small aperture side,
After 47 overshoots, the step motor 12
When the control is performed so as to converge to the position 3, the aperture value obtained by the opening becomes the position indicated by the line 48. Therefore, in this case, in order to obtain the same aperture value by narrowing down along the line 41 from the large aperture side, the overshoot amount may be suppressed by the line 49. Further, the overshoot amount when narrowing down from the large-diameter side is suppressed as shown by a line 50 and the overshoot amount when opening from the small-diameter side is suppressed as shown by a line 51, so that both overshoot positions can be completely set. The center point may be matched, and in any case, if the backlash between the pinion 12 and the rack 10h or the play between the cam grooves 10a to 10g and the cam followers 16a to 16g is within the range, the overshoot at the time of both operations may occur. It suffices if the peak positions match.

Next, the operation of this embodiment will be described with reference to the above items, the flowchart of FIG. 6, and the time charts of FIGS. Note that these flowcharts and time charts assume a case where overshoot is suppressed when narrowing down from the large-diameter side and overshoot is emphasized when opening down from the small-diameter side. I have.

When the main switch (not shown) is turned on, the program starts, and the CPU 36
From time 9, every time a periodic interrupt is input, the aperture control program characterizing the present invention is executed. Each time an interrupt is received from the interrupt timer 39, the CPU 36 monitors the switch 32 which makes a half stroke of the shutter button. When the switch 32 is making the make, the CPU 36 reads the subject brightness from the brightness input unit 40 and sets the read brightness to the read brightness. Aperture value N based on
Is calculated. On the other hand, an up-down type counter 38
Indicates the current aperture value, and the CPU 36 determines the rotation direction of the step motor 11 based on the count value of the counter 38 and the target aperture value N.

First, the case where the rotation direction is opposite (that is, the case where the target aperture value is reached by opening the exposure opening AP from the small aperture side) will be described. A time chart in the case of the reverse rotation is shown in FIG. If it is determined that the rotation is in the reverse direction, the CPU 36 reads the step time t1 of the (N + 1) th stage from the data table 37, and
The reverse pulse is incremented in the cycle of ms, and the counter 38 is decremented every increment of the reverse pulse. Incidentally, the meaning of t1 will become clear with the explanation of the operation. The reverse rotation pulse is advanced so that the phase of the A-phase pulse precedes the phase of the B-phase pulse by 90 degrees. By this pulse increment, the pinion 12 rotates counterclockwise, and the rotation is transmitted to the rack 10h, and the aperture ring 10 rotates clockwise. Accordingly, the cam followers 16a to 16g formed on the respective blades 14a to 14g rotate clockwise around the respective shafts 15a to 15g while following the cam grooves 10a to 10g formed on the aperture ring 10, respectively. Opening. Since the increment of the reverse rotation pulse is performed with the subtraction of the counter 38 toward the target N-th stage, the N + 1-th stage immediately before the target N-th stage.

The CPU 36 determines that the value of the counter 38 is N + 1.
At the stage, the pulse time of the (N + 1) th stage (the number of stages in which the A phase and the B phase become HL in FIG. 7) is set to t1 seconds, and after the elapse of t1 seconds, the HH, which is the Nth phase, is output, and If the contact 33 that operates at the full stroke of the shutter button is made to stop and the pulse 33 is stopped, the photographing process is executed, and if the contact 33 is not made, the next interruption is performed.

Now, as described above, N +
When the pulse time t1 of the first stage is shortened, the stop holding force of the (N + 1) th stage (attraction force generated between the rotor and the stator of the stepping motor 11 at the (N + 1) th stage) becomes relatively small, so that N + 1 The torque at the time of step rotation from the step N to the step N becomes relatively large.
The overshoot when rotating from the first stage to the Nth stage is large. Accordingly, the data table 3 is set by setting the time t1 so that a preferable overshoot amount is obtained.
7 in advance, the aperture blades 14a to 14g
Thus, it is possible to finely adjust the opening diameter obtained.

Next, the case where the rotation direction is the forward direction (that is, the case where the target aperture value is reached by narrowing the exposure aperture AP from the large aperture side) will be described. FIG. 8 shows a time chart in the case of the forward rotation. If it is determined that the rotation is the forward opening rotation, the CPU 36 determines from the data table 37 the step time t2 for energizing the Nth stage and the step time t3 for energizing the (N-1) th stage, which is the immediately preceding stage. The reading and the increment of the normal rotation pulse are performed at a period of 4 ms, and the counter 38 is added for each increment of the normal rotation pulse. The normal rotation pulse is advanced so that the phase of the B-phase pulse precedes the phase of the A-phase pulse by 90 degrees. By this pulse increment, the pinion 12 rotates clockwise, and the rotation is transmitted to the rack 10h, and the aperture ring 10 rotates counterclockwise. Therefore, the cam followers 16a to 16g formed on the respective blades 14a to 14g rotate counterclockwise around the respective shafts 15a to 15g while following the cam grooves 10a to 10g formed on the aperture ring 10, respectively. I will narrow down the AP. The increment of the forward rotation pulse is performed while adding the counter 38 to the target N-th stage.

When the value of the counter 38 reaches the N-th stage, the CPU 36 sets the pulse time of this N-th stage (the number of stages in which the phase A and the phase B become HH in FIG. 8) to t2 seconds, and after the elapse of t2 seconds, the N After outputting HL, which is the phase of the first stage, and then outputting HH, which is the phase of the Nth stage again, the stepping of the pulse for normal rotation is stopped, and the contact 33 which operates with the full stroke of the shutter button is made. If the contact has been made, the photographing process is executed. If the contact 33 has not been made, the next interruption is performed.

As described above, the N-th stage HH is energized for a pulse time of t2, and the immediately preceding N-1th phase HL is energized for a pulse time of t3. When energization of HH, which is the phase of the stage, is performed, the overshoot at the Nth stage is relatively small because a torque is generated in the direction of canceling the overshoot of the Nth stage during the time of the pulse energization at t3. Becomes At this time, the decrease in the amount of overshoot is determined by the combination of the time of t2 and the time of t3.
If the time of 2, t3 is set and stored in advance in the data table 37, the aperture diameter obtained by the aperture blades 14a to 14g can be finely adjusted.

In the description of the operation with reference to the flowchart, the overshoot is suppressed when the target N-th stage is reached by narrowing down from the large-diameter side to the small-diameter side, and the aperture is narrowed down from the small-diameter side to the large-diameter side. Although the case where the overshoot is emphasized when reaching the target N-th stage by clarity has been described, as described with reference to FIG. What is necessary is just to determine suitably according to it. In the above, t
The respective times 1, 1, t2, and t3 have been described without being specified, but it is needless to say that these pulse times are values that should be appropriately determined by tests or the like depending on the type of equipment. Further, these times are not of a nature that must be fixed within the entire movable range, but are set to t1, t2, t3 for each target numerical value of N for each of various load fluctuation factors caused by the setting position of the aperture. Can be measured by a test or the like and stored in the data table 31 of the EEPROM configuration as appropriate.

[0031]

As described above, according to the present invention, when the aperture blades are set to the same aperture, an aperture setting error according to the driving direction of the motor does not occur. Thus, when applied to a still camera that does not require the user to specify the drive direction of the aperture blade when setting the aperture, the aperture blade can be driven from the current aperture position to the target aperture position via the shortest path. Also, there is no setting error caused by the driving direction at this time.

[Brief description of the drawings]

FIG. 1 is a plan view of a diaphragm device of the present invention in a fully opened state.

FIG. 2 is a plan view of the aperture device according to the present invention in a medium diameter state.

FIG. 3 is a plan view of the aperture device of the present invention in a small diameter state.

FIG. 4 is a block diagram of a control system of the diaphragm device of the present invention.

FIG. 5 is an explanatory diagram showing the opening and closing characteristics of the aperture device of the present invention.

FIG. 6 is a flowchart of a control operation according to the present invention.

FIG. 7 is a time chart of the reverse rotation operation of the aperture device of the present invention.

FIG. 8 is a time chart of the normal rotation operation of the aperture device of the present invention.

FIG. 9 is an explanatory diagram of an error factor due to gear backlash.

FIG. 10 is an explanatory diagram of an error factor due to gear backlash.

FIG. 11 is an explanatory diagram showing the opening and closing characteristics of a conventional diaphragm device.

[Explanation of symbols]

Reference Signs List 10 aperture ring 10h rack 11 step motor 12 pinion 14a, 14b, 14c, 14d, 14e, 14g aperture blade 31 motor control circuit 36 CPU 37 data table 38 counter

Claims (5)

[Claims] 1. A stepping motor that can be rotated in both forward and reverse directions by stepping forward or reverse rotation pulses, and the stepping motor is connected to the stepping motor through one or more gear trains. A driving member operable in both forward and reverse directions in accordance with the rotation direction of the motor, one or a plurality of aperture blades for regulating the opening diameter of the exposure opening corresponding to the operating position of the driving member, The stepping motor is rotated forward or backward by feeding the supplied forward rotation pulse or reverse rotation pulse, so that the drive member corresponds to a target opening diameter by forward or reverse operation of the drive member. A motor control means for driving the stepping motor to a target position by a forward rotation pulse. The pulse rate of the forward rotation pulse and / or the reverse rotation pulse is changed so that the amount of overshoot when the step motor is stopped differs between when the rotation is performed and when the stepping motor is rotated to the target position by the reverse rotation pulse. An aperture device for a camera, characterized in that the aperture stop is performed. 2. The stop device for a camera according to claim 1, wherein said motor control means includes a final stop pulse time finally supplied during a forward rotation pulse or a reverse rotation pulse supplied to said step motor. Wherein the energization of the phase immediately before the final stop pulse is performed, and the energization time of the immediately preceding phase is changed between the forward rotation operation and the reverse rotation operation of the step motor. 3. The shutter device for a camera according to claim 2, wherein the motor control means changes the amount of change in the energizing time of the immediately preceding phase according to a target stop position of the driving member. Aperture device for camera. 4. A diaphragm apparatus for a camera according to claim 1, wherein said motor control means determines a final one of a forward rotation pulse and a reverse rotation pulse supplied to said step motor. A shutter device for a camera, wherein a pulse time of a pulse immediately before a last stop pulse supplied to the step motor is changed between a forward rotation operation and a reverse rotation operation of the stepping motor. 5. The camera shutter device according to claim 4, wherein said motor control means changes a change amount of a pulse time of said immediately preceding pulse according to a target stop position of said driving member. Aperture device for camera.