JP3389276B2 - Camera positioning device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a positioning device for positioning a lens, an aperture blade, and the like used in a still camera or the like by using a step motor as a driving source, and more particularly to a step motor. The present invention relates to a positioning device capable of obtaining a positioning resolution further subdivided within a step rotation angle. 2. Description of the Related Art In recent years, a position member such as a distance ring or an aperture blade is step-driven by a step rotation of a step motor, and the position member is locked at a target position by a locking mechanism such as a ratchet. A positioning device using a step motor as a drive source has been widely used. As is well known, a stepping motor rotates stepwise due to a change in a magnetized state between a rotor and a stator accompanying the advancement of a driving pulse. The step rotation angle of the member is the minimum unit. On the other hand, with today's camera lenses, there is an increasing demand for finer focusing steps with zooming and multi-focus including a long focal length region. Therefore, conventionally, a method has been generally proposed in which the reduction ratio of the reduction gear is increased or the excitation method of the motor is a 1-2-phase excitation method. Although the resolution can be improved by increasing the reduction ratio of the reduction gear, this method inevitably involves a decrease in the speed of the position member, so that the sequence time becomes longer. The problem arises. Further, the resolution of the 1-2-phase excitation method can be doubled as compared with the 2-phase excitation method, but the torque is only about 70% of that of the 2-phase excitation method, and the power supply voltage is particularly limited. In the case of a compact camera, a decrease in torque causes many problems such as a decrease in the number of shots. [0005] The present invention has been made in view of such problems, and can increase the resolution without causing an increase in the sequence time and a decrease in the torque. It is an object of the present invention to provide a camera positioning device as described above. In summary, a camera positioning device according to the present invention includes a step motor capable of rotating forward and backward, a driving member that is rotated by the rotation of the step motor and rotates stepwise, and is driven by the driving member when the step motor rotates forward. Assuming a camera positioning device having a position member that rotates step by step and a locking member that locks the position member, the locking member is moved by 1 / n (n: In addition to a configuration in which n locking levers each having a locking position difference of (an integer of 2 or more) pitch are provided, the position member is rotated by 1 / n during one step.
When locking in the position, the last pulse of the forward drive pulse
Rotation time of the position member by 1 / n step or more.
And rotate it to the next locking position.
The position member is controlled so as to be shortened within a range not to be turned, and the position member is locked by any one of the n locking levers. That is, according to the camera positioning device of the present invention, when the stepping motor rotates forward, the position member runs in the first direction following the drive member. When the rotation direction of the step motor is reversed, the running direction of the driving member is also reversed, and the motor driving force is not transmitted to the position member. At this time, the position member is locked by the locking member and stopped at that position. . Up to this point, the operation is the same as that of the conventional mechanism, but in the case of the present invention, the locking member has a locking position at a pitch of 1 / n (n is an integer of 2 or more) of the one-step movement amount of the position member. It is composed of n locking levers each having a difference.
Now, the stepping motor does not instantaneously rotate stepwise at the same time as stepping the drive pulse, but rotates stepwise with a transient time due to the torque generated by the stepping of the drive pulse. Therefore, if the supply of the final pulse is discontinued before the stepping motor rotates to the position corresponding to the final pulse of the series of forward rotation driving pulses , the stepping motor will stop immediately before the stepping position corresponding to the final pulse. It returns to the step rotation position. According to the present invention, as described above, the locking member is constituted by n locking levers having a locking position difference of 1 / n pitch of the one-step movement of the position member. A series of forward drive supplied to
If the time of the final pulse of the dynamic pulse is appropriately controlled, the position member can be set to the above n according to the timing at which the final pulse is terminated.
It is locked by any one of the locking levers, and the resolution within n steps within the step rotation angle unique to the motor can be obtained. An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a plan view showing an initial state of a camera positioning device according to one embodiment of the present invention. In the figure, reference numeral 1 denotes a shutter base plate, and an aperture 1a for exposure is formed at the center of the shutter base plate 1. Reference numeral 2 denotes a drive ring. The drive ring 2 is supported on the near side of the shutter base plate 1 so as to be rotatable around an aperture 1a. A rack 2 a is formed at a part of the outer edge of the drive ring 2. Reference numeral 3 denotes a step motor, and the rotation of the output gear 3a is transmitted to the rack 2a via gears 4a and 4b constituting a two-stage gear. Reference numeral 5 denotes a lens drive ring which is an example of a position member. The lens drive ring 5 is supported on the front side of the drive ring 2 so as to be rotatable around the aperture 1a. The front surface of the lens drive ring 5 is spaced apart by 120 degrees to drive an unillustrated photographing lens group.
, Three tilt cams 5a are formed, and the lens drive ring 5 is turned leftward from the state shown in the figure, so that the photographing lens group (not shown) is extended toward the subject (the front side in the figure) . The left-handed power of the lens drive ring 5 is supplied from the step motor 3 via the drive ring 2. That is, the driving ring 2 is formed with the projection 2b,
A pin 5b located on the left-handed path of the projecting piece 2b is implanted on the back surface of the lens driving ring 5. During the left-handed rotation process of the driving ring 2, the lens driving ring starts from the time when the projecting piece 2b engages the pin 5b. 5 is therefore left-handed to the driving ring 2
Can be Reference numeral 6 denotes a locking member for locking a ratchet gear 5c formed on a part of the outer edge of the lens driving ring 5. As shown in FIGS. 7 and 8 in an enlarged manner, the locking member has two ratchet levers 6a and 6b (n = 2) , and the locking point of the ratchet gear 5c by the ratchet levers 6a and 6b is It is shifted by a half step angle. Each of the ratchet levers 6a, 6b is coaxially supported on a shaft 1b on the main plate 1 and is given a left turning force by springs 7, 8 (only the biasing direction is indicated by an arrow). However, in the initial state, the ratchet lever 6a is formed by the curved portion 2 formed on the drive ring 2.
c, and the ratchet lever 6b has a pin 6c implanted in the ratchet lever 6b.
The left rotation is regulated in the state shown in FIG. The power for right-handed rotation of the lens drive ring 5 is given from a return spring 9. That is, a return arm 5d is formed on the lens drive ring 5, and this return arm 5d
One end of a return spring 9 is locked to the upper pin 5e. The other end of the return spring 9 is locked by a pin 1c planted on the shutter base plate 1, and the return spring 9 is charged in the process of turning the lens drive ring 5 counterclockwise. When the lens drive ring 5 is rotated counterclockwise to the target in-focus position, the step motor 3 reverses to rotate the drive ring 2 clockwise, but at this point, any one of the claws of the ratchet gear 5 c is connected to the ratchet lever 6.
a, 6b, and remains at the extended position. Immediately before the drive ring 2 returns to the initial position, the ratchet lever 6 is bent by the curved portion 2c of the drive ring 2.
a rotates clockwise, and when the ratchet lever 6b rotates clockwise, the ratchet gear 5c turns the ratchet lever 6a.
Alternatively, the lens drive ring 5 is released from 6b and returns rightward to the initial position due to the elasticity charged in the return spring 9. Reference numeral 10 denotes a blade opening / closing lever. The blade opening / closing lever 10 is swingably supported by a shaft 1d on the shutter base plate 1. Reference numeral 11 denotes a shutter blade swingably supported by a shaft 1e planted on the back surface of the shutter base plate 1, and an engaging pin 10a planted on the back surface of the blade opening / closing lever 10 penetrates the shutter base plate 1. (The through hole is omitted in the drawing , but is formed in an arc shape centered on the axis 1d.
You . ), And is engaged with a long hole 11 a formed in the shutter blade 11. Accordingly, when the blade opening / closing lever 10 rotates clockwise from the state shown in FIG. 1, the engagement pin 10a rotates the shutter blade 11 clockwise about the shaft 1e while opening the aperture 1a while engaging the elongated hole 11a. Although only one shutter blade 11 is shown to avoid complication of the drawing, it is needless to say that another shutter blade 11 having a symmetrical shape is provided. The blade opening / closing lever 10 always has a spring 12
The right and left rotation is given by
The cam follower 10b formed on the driving ring 5 comes into contact with the protruding pieces 5f formed on the lens driving ring 5, the protruding pieces 2d and 2e formed on the driving ring 2, and the V-shaped cam 2f formed on the driving ring 2 to make the blade. The right turning angle of the opening / closing lever 10 is controlled. FIG. 2 is a block diagram of a control system for controlling the stepping motor in accordance with the photographing distance. Reference numerals 3b and 3c denote coils of the stepping motor 3.
Reference numerals 20 and 21 denote motor drivers for supplying a drive current to the coils 3b and 3c , and reference numeral 22 denotes a pulse generation circuit for generating A-phase and B-phase drive pulses for controlling the motor drivers 20 and 21. [0016] Since the motor driver 20, 21 have the same configuration, it will be explained as a representative in the motor driver 20, motor driver 20, the transistor 20a supplies the forward drive current to the coil 3b, 20b, the coil 3b Transistors 20c and 20 for supplying a driving current in the reverse direction
d, and a bridge circuit having inverters 20e and 20f. The positive-phase A-phase pulse generated by the pulse generation circuit 22 is applied to the transistor 20b and the inverter 20e.
, The transistors 20a and 20b are turned on, and a positive drive current is supplied to the coil 3b . When the opposite A-phase pulse generated by the pulse generation circuit 22 is supplied to the transistor 20c via the transistor 20d and the inverter 20f,
The transistors 20c and 20d are turned on, and a driving current in the opposite direction is supplied to the coil 3b . Reference numeral 23 denotes a known distance measuring circuit for measuring a subject distance, and reference numeral 24 denotes a CPU for controlling the pulse generating circuit 22 in accordance with the output of the distance measuring circuit 23. Details of the control operation are shown in FIG. This is shown in the flowchart. In addition, 25
Is a counter for storing the lens extension position, and 26 is a flag register. Next, the operation of the present embodiment will be described with reference to the above items and FIGS. In the initial state, all the mechanisms are in the state shown in FIG. In this state, when a shutter button (not shown) is pressed, the CPU 24 causes the distance measurement circuit 23 to operate.
, The extension position of the photographing lens is calculated, and if the extension position is N steps (N is a natural number), 0 is set in the flag register 26, and the extension position is N-1 / 2 steps. In the case, the flag register 26
Is set to 1. While incrementing the counter 25, the CPU 24 applies a command for generating a forward rotation drive pulse to the pulse generation circuit 22 at a period of, for example, 4 ms. The pulse generation circuit 22 outputs the forward rotation drive pulse (when the phase of the A phase is B phase). Is supplied to the motor drivers 20 and 21). The coils 3b and 3c follow the step of the forward rotation drive pulse.
, The output gear 3a rotates counterclockwise, the rotation of the output gear 3a is transmitted to the two-stage gear including the gears 4a and 4b and the rack 2a, and the drive ring 2 is moved around the aperture 1a. Turns counterclockwise. In the process of driving the drive ring 2 counterclockwise in this manner, the projection 2b formed on the drive ring 2 engages the pin 5b implanted on the back surface of the lens drive ring 5 from the time when the lens drive ring 5 is engaged. Is rotated counterclockwise around the aperture 1a while charging the spring 9 following the drive ring 2, and the cam 5a extends an unillustrated focus adjusting lens toward the subject. Also, as described above,
In the stage where the lens drive ring 5 starts to follow,
Is located at the position of the protrusion 5f of the lens drive ring 5.
, So the cam follower 10b is
It is sequentially engaged with the protruding piece 2e and falls into the V-shaped cam 2f.
And not. FIGS. 4 and 5 show the A-phase pulse, the B-phase pulse and the rotational position of the step motor 3, respectively.
FIG. 4 corresponds to the case where the target focus position is the Nth step, and FIG. 5 corresponds to the case where the target focus position is the N-th step. 4 and 5, A indicates an A-phase pulse, B indicates a B-phase pulse, and a broken line C that changes stepwise indicates the count value of the counter 25, and a curve D that follows the broken line C indicates a transient characteristic. 3 shows the actual position of the step motor 3 including the position. The CPU 24 sets the step motor 3 to 1
The counter value of the counter 25 is monitored every time the step is rotated forward, and when the count value of the counter 25 indicating the rotational position of the step motor 3 becomes the value immediately before the target step (that is, N-1), the flag register 26 is checked. . First, when the flag register 26 is 0 (ie, when the target in-focus position is the Nth step), one more step of the forward rotation driving pulse is supplied to the stepping motor 3 and the counter 25 is turned on. After the addition of 1 and the lapse of Tms, a reverse rotation pulse is supplied to the step motor 3. T described above
Within a time period of ms, the lens driving ring 5 moves to the value described above,
That is, the motor rotates counterclockwise one step further from the N-1 step . Thereafter, the stepping motor 3 rotates in the reverse direction, and the driving ring 2 rotates clockwise. At this time, since the ratchet lever 6a is released from the curved portion 2c of the driving ring 2, the ratchet gear 6 turns leftward by the spring 7 and the ratchet gear 5
The claw at the Nth step of c is locked. FIG. 6 shows a state in which the lens drive ring 5 is locked at a target in-focus position in this manner, and FIG. 7 shows an enlarged view of the ratchet mechanism at this time. The time Tms described above is set in advance as a time sufficient for the lens drive ring 5 to be able to reliably rotate for one step even if the response delay of the mechanical member is taken into consideration. Is rotated to the Nth step by the rotation of the next one step, and the Nth step claw of the ratchet gear 5c is locked by the ratchet lever 6a. On the other hand, when the flag register 26 is 1 (that is, when the target focus position is the N-1 / 2 step), the value described above, that is, the N-1 step is further changed. The forward drive pulse for one step is supplied to the step motor 3.
And the counter 25 is incremented by 1 and a reverse rotation pulse is supplied to the step motor 3 after elapse of (T−t) ms. In consideration of the response delay of the mechanical member, the time of (T−t) ms is such that the lens drive ring 5 cannot be rotated for one step, but can be reliably rotated for one half step. Is set in advance.
Therefore, the time of (T−t) ms elapses and N− (n−1)
/ N) After the stepping motor rotates counterclockwise, the stepping motor 3 starts reverse rotation and the driving ring 2 turns clockwise . At this time, the lens driving ring 5 has the ratchet of the ratchet gear 5c at the Nth step. Since the lens drive ring 5 does not rotate leftward until it is locked by the lever 6a, the lens drive ring 5 slightly rotates leftward following the drive ring 2, and the pawl at the (N-1) th step of the ratchet gear 5c is engaged with the ratchet lever 6b. Stop left-handed rotation when stopped. FIG. 8 shows that the ratchet lever 6b is connected to the ratchet gear 5 in this manner.
13C illustrates a state where the claw at the (N-1) th step is locked. In this embodiment, since a position difference corresponding to 1/2 step is formed between the ratchet lever 6a and the ratchet lever 6b, the lens driving ring 5 is substantially at the Nth step and the N-th step. The locking is performed at the intermediate position of the first step, that is, at the position of the (N-1 / 2) th step, so that the positioning resolution can be doubled. After locking the lens drive ring 5 at any position in this manner, the CPU 24
The stepping motor 3 is rotated clockwise while subtracting 1 from the above, and the exposure control sequence is executed. That is, when the stepping motor 3 is rotated clockwise as described above and the driving ring 2 is rotated clockwise accordingly, the cam follower 10b of the blade opening / closing lever 10 is moved from the projecting piece 2e of the driving ring 2 It falls on the V-shaped cam 2f. Therefore, the blade opening / closing lever 10 is
With the urging force of 2, the shutter blade 11 is turned clockwise about the shaft 1e while the pin 10a planted on the back surface of the blade opening / closing lever 10 is engaged with the elongated hole 11a. To open the aperture 1a. FIG. 9 shows a state in which the shutter blade 11 is opened in this manner. When the desired exposure time has elapsed from the state shown in FIG. 9, the step motor 3 is further rotated clockwise and the drive ring 2 is further rotated clockwise, and the cam follower 10b of the blade opening / closing lever 10 is rotated. The V-shaped cam 2f of the drive ring 2 rides on the projection 2d, and the spring 1
Turn left against 2. Accordingly, the blade opening / closing lever 10 is configured such that the pin 10a engages with the slot 11a while the shutter blade 1
1 is turned left around the axis 1e to close the aperture 1a. When the stepping motor 3 further rotates clockwise, the drive ring 2 further rotates clockwise, and the local portion 2b formed on the drive ring 2 eventually causes the ratchet lever 6 to rotate.
a and ratchet lever 6 against spring 7
Turn a clockwise. In addition, at the same time the ratchet lever 6a La
The pin 6c implanted in the ratchet lever 6b is pressed, and the ratchet lever 6b is turned clockwise against the spring 8.
Therefore, the ratchet gear 5c of the lens driving ring 5 is released from both the ratchet lever 6a and the ratchet lever 6b , and the lens driving ring 5 is turned clockwise by the urging force of the spring 9 to return to the initial position, and one shooting operation is performed. To end. In the above description, the case where the photographing lens is driven has been described as an example. However, by replacing the lens driving ring 5 with an aperture ring, the present invention can be applied to the driving of aperture blades. [0030] In the above the example in which the manner divided into two within one step angle, but with further increase the number of the ratchet lever, in particular for adjusting the time of the above t
It is also possible to further subdivide the more one step angle within. As described above, according to the present invention, the positioning resolution can be improved without causing a decrease in motor torque or an increase in sequence time on the premise of a camera positioning device using a stepping motor as a drive source. It can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a mechanism diagram showing an initial state of a camera positioning device according to an embodiment of the present invention. FIG. 2 is a block diagram of a control system of the embodiment. FIG. 3 is a flowchart showing a control operation of the embodiment. FIG. 4 is a time chart in the case where the apparatus of the embodiment is locked in N steps. FIG. 5 is a time chart in a case where the apparatus of the embodiment is locked in N-1 / 2 steps. FIG. 6 is a mechanism diagram of a conventional example apparatus in a lens extended state. FIG. 7 is an enlarged view of a case where the apparatus of the embodiment is locked in N steps. FIG. 8 is an enlarged view of the case where the device of the embodiment is locked in N-1 / 2 steps. FIG. 9 is a mechanism diagram of the apparatus of the embodiment in a shutter open state. [Description of Signs] 2 Drive ring 3 Step motor 5 Lens drive ring 5c Ratchet gear 6a Ratchet lever 6b Ratchet lever

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G02B ^7/ 02-7/10 G03B 9/08

Claims (1)

(57) [Claim 1] A step motor capable of forward / reverse rotation, a drive member that rotates stepwise by transmitting the rotation of the step motor, and a drive member that rotates when the step motor rotates forward. A positioning device for a camera having a position member that rotates stepped following and a locking member that locks the position member, wherein the locking member is moved by 1 / step of a one-step movement amount of the position member.
It is composed of n locking levers each having a locking position difference of n (n is an integer of 2 or more) pitch, and the position member is subdivided into 1 / n for one step.
When locking at the rotation position, the last drive pulse for forward rotation
Rotate the position member by 1 / n step or more for pulse time
And rotate it to the next locking position.
A positioning device for controlling the camera so that the position member is locked by any one of the n locking levers.