JPH03155385A - Variable focus lens drive unit - Google Patents

Abstract

PURPOSE:To set the final stop position at any point without fluctuation by synchronizing cogging period Tm and pulse signal generating period Tp according to a relation Tp/2=n.Tm (n is a natural number). CONSTITUTION:When a front group frame (not shown) moves in WIDE direction and a slide brush contacts with the left end of a WIDE pattern 42, a WIDE position switch SWw produces an ON(Low) signal to rotate a DC motor 33 reversely thus causing inverted displacement of the front ground frame in TELE direction. When the front group frame moves in TELE direction and the slide brush comes to a position separating from the left end of the WIDE pattern 42, a WIDE position switch S'Ww produces an OFF(Hi) signal and a microcomputer 55 executes control to interrupt power supply to the DC motor 33. Since cogging period Tm and pulse signal generating period Tp of a pulse signal generating means are in such relation as Tp/2=n.Tm (n is a natural number), the DC motor 33 always stops at the self-running torque position of the motor.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an improvement of a variable focus lens drive device used, for example, in a camera.

[Conventional technology]

2. Description of the Related Art Conventionally, there are cameras that use the rotational driving force of a motor to change the focal length of a variable focus lens and to perform focusing operations.

For example, in the technique disclosed in Japanese Patent Application Laid-Open No. 60-80812, the amount of movement of the lens necessary for focal length changing operation and focusing operation is set by the number of pulses emitted by the pulse plate 15, and a predetermined number of pulses is set. The lens is configured to stop at the desired position by cutting off the power supply to the motor at the time of counting.

[Problem to be solved by the invention]

By the way, there are usually two ways to stop a motor that is rotating at high speed: allowing it to rotate freely and applying a brake. Even if a high-precision DC motor is used, several residual rotations (free-running rotation) occur between the time when the motor is stopped and the motor stops.

For example, if the number of rotations of a DC motor is detected as the number of pulses on a rotary encoder, and the power supply is cut off and the motor is stopped when a predetermined number of pulses are counted, the actual number of rotations will be detected after a stop signal is issued. Until it stops, it performs several remaining rotations.

The number of rotations of this residual rotation varies greatly even in the absence of cogging (periodic torque fluctuations characteristic of DC motors with a core), but it is usually largely due to the influence of cogging. In this case, there is a high probability that the motor will stop at the cogging position.

However, if the pulse period and the cogging position are not synchronized, the motor's rotation stop position may or may not match the cogging position, which will greatly affect the probability of the motor's final stop position. become. In other words, the rotation stop position of the motor varies by the cogging width.

In other words, as shown in Fig. 5(a) and Fig. 5(b), among the changes in the free-running rotational torque due to cogging, the pulses that occur when there is no synchronized point within one cycle (random state) In this case, if a stop signal is issued to the motor at an arbitrary number of pulses, the final stop position will vary depending on the relationship between the magnitude of the free-running rotational torque and the load.

Such variations in the stop position adversely affect the original performance of the motor and significantly reduce the precision of motor drive control. However, the final stop position of the motor varies, significantly reducing the accuracy of the focal length changing operation and focusing operation of the photographic lens.

In this way, the phenomenon of variation in stopping position due to cogging is
This is not a problem that is unique to variable focus lens drive devices used in cameras, but is widely related to various types of variable focus lens drive devices, and there has been a strong desire for an improvement measure.

The present invention has been made in view of the above circumstances, and provides a novel variable focus lens drive device that can set the final stop position without variation at any position by constantly stabilizing the influence of cogging. The purpose is to

[Means to solve the problem]

The configuration of the present invention for achieving this object is a variable focus lens driving device that uses a DC motor having a core to change the focal length of a variable focus lens and perform focusing operations at each focal length. In the above-mentioned DC
a pulse signal generating means for converting the rotation angle and rotation speed of the motor into pulse signals; a pulse signal detecting means for counting pulse signals emitted by the pulse signal generating means; D.C.
a motor control circuit that controls the rotation angle and rotation speed of the motor, and where Tm is the cogging period of the DC motor and Tp is the pulse signal generation period of the pulse signal generation means, these two periods are The reason is that they are configured to be synchronized using the relational expression -Tp=n-Toboro (where n is a natural number).

[For production]

The variable focus lens drive device configured as above is
By synchronizing the cogging period of the DC motor and the pulse signal generation period of the pulse signal generation means in a predetermined relationship, the rotation of the motor can be stopped with good precision during focal length switching and focusing operations of the photographic lens. Stably set.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The variable focus lens driving device of the present invention will be described in detail below based on illustrated embodiments.

FIG. 1 is a partially exploded perspective view showing the configuration of an embodiment of the variable focus type lens driving device according to the present invention, and shows the state at the time of position E photography.

FIG. 2 is a diagram showing the relationship between the WIDE ID pattern, the E pattern, and the ground pattern, which constitute the WIDE position switch and the E position switch.

A variable focus lens to which this variable focus lens driving device 1 is applied has a main lens system and a sub lens system Ls.

With this variable focus lens, during WIDE (or standard) shooting, the sub lens system Ls is placed in a retracted position off the shooting optical axis O, and only the main lens system is on the shooting optical axis O. Achieve the focal length of time.

Then, when shooting in position E, the sub lens system Ls placed in the retracted position is inserted into the rear optical path (exposure aperture side optical path) of the main lens system as shown in FIG. By the cooperation of the lens system Ls and the sub-lens system Ls, the lens system is configured to realize a focal length at the time of position E photography.

Reference numeral 2 denotes a lens frame of this variable focus type lens, and this lens frame 2 has an exposure aperture 3 located on the photographing optical axis ○, and a portion around the exposure aperture 3, both of which receive photographing light #O. A common ball 41 rotation prevention pawl 5 and a drive lead screw 6 are provided that extend protrudingly toward the subject along the common ball 41 .

Further, a cam plate member 7 is provided on the lens frame 2 near the right end (on the figure) of the common pole 4 in parallel with the common pole 4; A push-down action surface 7a that is inclined with respect to the axial direction of the common pole 4 and a holding action surface 7b that is perpendicular to the axial direction of the common pole 4 are formed.

Note that the lens barrel 2 and the cam plate member 7 can also be formed integrally with a camera fixing section (not shown), if necessary.

Now, the above-mentioned main lens system LM is provided in the front group frame 10 that is slidably provided with respect to the common pole 4, and the sub lens system Ls is provided so that it is slidable and rotatable with respect to the common pole 4. They are configured to be held in the rear group frame 20, respectively.

In this case, the front group frame io includes the frame main body 11, the auxiliary frame part 12, and double steels 13a and 13b that vertically connect the two.
The lower part of the frame body 11 and the auxiliary frame part 12 are provided with a T-N nut 1 which is slidably and precisely fitted to the common pole 4.
4 (only one is shown) is fixed with adhesive.

Furthermore, a notch 11a is formed in the upper corner of the frame 1 main body 11 to precisely engage with the single-rotation blocking pawl 5, thereby preventing the front group frame 10 from rotating around the common pawl 4. are doing.

Further, a driving lead nut 15 is attached to the lower part of the frame body 11 in parallel with the T-N nut 14, and the position of the driving lead nut 15 is fixed by the common pole 4 and the rotation prevention pole 5. The front group frame 10 and the drive lead screw 6 are adjustably attached to the frame body 11 so as not to cause positional interference.

Note that the material of the front group frame 10 is preferably a synthetic resin material from the viewpoint of cost, and the T-N nut 14 and the drive lead nut 15 are both made of a synthetic resin material if accuracy and durability can be obtained. It may be configured integrally with the group frame 10.

Reference numeral 16 denotes an electric sliding brush whose sliding legs are bifurcated, and is attached to the frame body 11 of the front group frame 1o via a suitable insulating material.

In this bifurcated sliding brush 16, one sliding leg portion slides while being intermittently pressed against a WIDE ID-tone 42 and a position E pattern 43 of a position switch board 41, which will be described later.
The other sliding leg is configured to slide in constant pressure contact with the ground pattern 44.

On the other hand, the rear group frame 20 is composed of a tip portion 21 that holds the sub lens system Ls, a base portion 22 formed in a bifurcated state, and a stay 23 that connects both.
is provided to the common pole 4 so as to be located between the frame main body 11 and the auxiliary frame portion 12 of the front group frame 10.

A positioning protrusion 21a that can engage with the outer circumferential surface of the rotation prevention pawl 5 is formed in a part of the tip 21. This is to set the attitude of the rear group frame 20 during position E shooting, that is, the attitude when the sub lens system Ls is accurately positioned on the shooting optical axis 0.

Further, the above-mentioned cam plate member 7 is attached to the base 22 of the rear group frame 20.
A locking pin 24 that can be engaged with the cam plate member 7 is installed, but the relative relationship between the locking pin 24 and the cam plate member 7 is such that when the rear group frame 20 is driven and displaced toward the exposure aperture 3 side during WIDE shooting, , the push-down action surface 7a of the cam plate member 7 is connected to this engagement pin 24.
is set so that the rear group frame 20 can be rotated clockwise by pressing down, and thereafter the rear group frame 20 can be held in the retracted position by the function of the holding action surface 7b.

Therefore, the sub-lens system Ls, which was in the insertion position shown in FIG. 1 at the time of photographing in position E, starts retracting out of the photographing optical axis 0 from the time when the locking/disengaging pin 24 is pressed down by the push-down action surface 7a. After the engaging/disengaging pin 24 comes into contact with the holding surface 7b, the retracted position is maintained as it is.

Note that the rear group frame 20 has a T-N fixedly provided on the base 22.
Although it is slidably and rotatably fitted to the common pole 5 via the nut 22a, its constituent material is preferably a synthetic resin material, and the T-N nut 22a provides precision and durability. Otherwise, it may be configured integrally with the rear group frame 20.

Reference numeral 25 denotes a twisting spring wound around the common pole 4, and its pivoting force is used to apply a counterclockwise pivoting force to the rear group frame 20.

This twisting spring 25 has one end hooked on the lower stay 13b of the double steel of the front group frame 10, and the other end hooked on a push protrusion 26 formed on the base 22 of the rear group frame 20.

Reference numeral 27 denotes a coil-shaped connection spring, which connects the frame body 11 of the front group frame 10.
A hook is provided between the protrusion 11b formed on the rear group frame 20 and the protrusion 22b formed on the base 22 of the rear group frame 20. and,
When the front group frame 10 is displaced toward the subject, the connecting spring 27 is configured to allow the rear group frame 20 to be integrally displaced in the same direction.

However, the amount of displacement of the rear group frame 20 toward the subject is regulated by the tip of the adjustment screw 28 (the right end in the figure), which determines the position of the rear group frame 20 in the optical axis direction during position E shooting. Therefore, even if the front group frame 10 is further displaced toward the subject, the rear group frame 20 will remain at its regulating position.

This means that when shooting at position E, the rear group frame 2° is adjusted by the adjustment screw 2.
8, the position of the rear group frame 20 in the optical axis direction is stabilized.

This adjustment screw 28 is screwed into a support plate 45 that is vertically formed near the left end of a position stand 40 or at an appropriate location on the lens frame 2, which will be described later. The restriction position relative to 2o can be adjusted.

On the other hand, when the front group frame 10 is displaced toward the exposure aperture 3,
The rear group frame 2o is configured to be integrally pushed and displaced in the same direction via a push projection 26 provided on the base 22 of the rear group frame 20.

Reference numeral 29 denotes a compression spring for accurately determining the position of the front group frame 10 by biasing the backlash existing between the front group frame 10 and the drive lead screw 6. It is provided in a winding manner on a common pole 4 between the lens frame 2 and the lens frame 2.

Now, at the left end of the aforementioned drive lead screw 6, a driven gear 31 and a rotary encoder (hereinafter abbreviated as "encoder") 32 are fixedly attached, of which the driven gear 31 is , is connected to a drive gear 34 of a DC motor 33 that can drive the drive screw 6 in a reversible direction via a suitable reduction gear mechanism (not shown).

On the other hand, the encoder 32 is combined with a photointerrupter 35, and a pulse signal generating means 3 for detecting the rotation angle and rotation speed of the drive lead screw 6 as a pulse signal.
6.

The DC motor 33 is configured as a motor having a core, and the cogging period Tm of the DC motor 33 and the pulse signal generation period 'rp of the pulse signal generation means 36 are as follows: Tp=n-TII (where n is It is configured in advance so that it can be synchronized using a relational expression (natural number).

For example, if the DC motor 33 cogs 6 times per rotation, the slit of the encoder 32 is designed so that the pulse signal can be generated only a multiple of 6 times (12 times) per rotation of the DC motor 33. ing.

Reference numeral 40 denotes a position stand made of a suitable insulating material such as a synthetic resin material, and is installed upright on the lens frame 2 with its inner surface parallel to the photographing optical axis O (common pole 4). It is being

And, on the inside surface of this position stand 4o, WIDE
A position switch board 41 is fixed for setting the relative positions of the main lens system LM and the sub lens system Ls during photographing and during position E photographing.

As shown in FIG. 2, this position switch board 41 has three conductive patterns formed thereon: a WIDE ID pattern 42, a position E pattern 43, and a ground pattern 44. The WIDE ID pattern 42 and the position E pattern 43 are as follows.

On the same line with a predetermined interval in the direction of the optical axis O.

Furthermore, the two-sided patterns 42 and 43 are arranged parallel to the ground pattern 44.

In this case, one sliding leg of the aforementioned sliding brush 16 is
The WIDEID-on 42 and the position E pattern 43 are intermittently contacted during zooming, and the other sliding leg is configured to be in constant contact with the ground pattern 44.
Short-circuits are made between the E pattern 42 and the ground pattern 44 and between the E pattern 43 and the ground pattern 44 via the sliding brush 16.

As a result, the WI'DE pattern 42 and the sliding brush 16 constitute the WIDE position switch SW%I, and the position E pattern 43 and the sliding brush 16 constitute the position E position switch SWT. Become.

A sliding brush 16 (i.e., front group frame 10) that is displaced in the front-rear direction on the photographing optical axis O, and a WIDE ID lens 4 are provided.
2 and the position E pattern 43 are set in the following relative positional relationship.

That is, as shown in detail in Figure 2, first, WIDE
At a position close to the exposure aperture 3 on the position switch board 41 located between the ID-on 42 and the E pattern 43,
Set the WIDE preparation position (WIDE reference position) and
Next, on the WIDE ID-on 42, W for focusing is placed.
IDE closest distance, closest distance position top 1 IDE infinity position, IDE infinity position 2 settings respectively.

Similarly, a position E preparation position (position E reference position) T is set at a position close to the subject side on the position switch board 41 located between the WIDEID-on 42 and the position E pattern 43, and the position E pattern 43, a position E closest distance position T1 and a position E infinity position T2 upon focusing are respectively set.

In addition, WIDE preparation position W0 and WIDE ID-42
A slight interval is formed between the left end of the position E preparation position T0 and the right end of the position E pattern 43, respectively.

In FIG. 3, the control section of the variable focus lens driving device 1 is indicated as a whole by 50.

This control unit 5o includes a TW switching operation button 51, a shutter release button 52, an AF (automatic focus adjustment device) IC5
3. Control means such as a motor drive IC 54, a microcomputer (hereinafter referred to as "microcomputer") 55, and a photometry switch 56, and the above-mentioned WIDE position switch SWw
and a position E position switch SWT.

In this case, the microcomputer 55 rotates the DC motor 33 in either direction based on the control signal from each control means and the on/off signal of each position switch,
Then, it is controlled to stop.

Furthermore, the shooting mode of the variable focus lens when the previous shooting was completed, that is, whether the variable focus lens is in the WIDE shooting mode or the TE LE shooting mode is determined by the microcomputer 55 in advance. It is also configured to be remembered.

Hereinafter, the basic operation regarding WIDE-position E switching of the variable focus lens drive device 1 configured as described above will be explained.

When the power switch (not shown) of the varifocal lens drive device 1 or the camera is turned on, the motor drive IC 54 operates to rotate the DC motor 33 in the WIDE direction, and the DC motor 33 is rotated in the WIDE direction through the drive lead screw 6 and drive lead nut 15. , displaces the front group frame 10 in the same direction.

The front group frame 10 moves in the WIDE direction, and the sliding brush 16
When the WIDE position switch SWw comes into contact with the left end of the WIDE ID-on 42, the WIDE position switch SWw turns on (Low).
) signal to reversely rotate the DC motor 33 and displace the front group frame 10 in the right direction.

Then, the front group frame 10 moves to the right from the position E, and the sliding brush 1
6 comes off the left end of the WIDE ID-on 42, the V/4DE position switch SWw turns off (H
i) A signal is output to control the microcomputer 55 to cut off the power supply to the DC motor 33.

In this case, the DC motors 3 and 3 whose power supply is cut off continue to self-propelled rotation, but as described above, the DC motors 3 and 3
Since the synchronization relationship between the cogging period Tow of No. 3 and the pulse signal generation period Tp of the pulse signal generation means 36 is set to the relationship -Tp = n-Tm (where n is a natural number), the DC motor 33 , Figure 5 (Q)
As shown in (d), the motor always stops at the free rotation torque position of the motor.

This is because if the half cycle (1/2) Tp of the pulse is synchronized with the cogging cycle T■, a substantial stop signal of the DC motor 33 is always issued at the same free-running rotational torque position.

The stopping position of this DC motor 33 is slightly off the left end of the WIDE drive turn 42, so prepare for WIDE in advance! ! If W6 is set at this stop position, when the power switch of the variable focus lens drive device 1 or the camera is turned on.

The DC motor 33 always stops the front group frame 10 at the WIDE ready position.

Note that the microcomputer 55 stores the shooting mode of the variable focus lens when the previous shooting was completed, so
The position of the front group frame 10 when the previous shooting was completed is WIDE.
When in the position at the time of photographing, that is, when the sliding brush 16 is located on the WIDE ID-tone 42, the DC
The configuration is such that the initial rotation control of the motor 33 in the WIDE direction is omitted.

Therefore, the DC motor 33 can stop the front group frame 10 at the WIDE preparation position W0 whether the front group frame 10 is in the position for WIDE photography or the position for E photography.

By the way, when the variable focus lens is in the WIDE ready position, the front group frame 10 is displaced from the position shown in the first figure to a position close to the exposure aperture 3, so the rear group frame 2o is moved to the sub lens system Ls. is held in a retracted position away from the photographing optical axis ○.

That is, when the front group frame 10 moves rightward from the position shown in FIG. Since the rear group frame 20 is pushed to the right while resisting, the rear group frame 20
The engagement/disengagement pin 24 implanted in the cam plate member 7 comes into contact with the push-down surface 7a of the cam plate member 7 and is pushed down.

As a result, the rear group frame 2o rotates clockwise against the turning biasing force of the twisting spring 25 and shifts to the above-mentioned retracted position, and the main lens system becomes the focal point during WIDE shooting. It will be set in a relative position that realizes the distance.

Now, when the front group frame 10 is in the WIDE preparation position W0 and the T-W switching operation button 51 is operated to switch the variable focus lens to the E shooting mode, the front group frame 1o and the rear group frame 2o performs the following operation to shift the variable focus lens to the state at the time of T E and L E photography.

That is, when the T-W switching operation button 51 is switched to a state that realizes E photography, the microcomputer 55 switches the motor drive IC.
54 to rotate the DC motor 33 in the right direction, and the front group frame 10 is moved in the same direction via the drive lead screw 6 and drive lead nut 15.

Then, when the sliding brush 16 contacts the right end of the position E pattern 43, the position E position switch SWT outputs an on (Low) signal to reversely rotate the DC motor 33 and move the front group frame 10 in the WIDE direction. Displace it in an inverse manner.

Therefore, the sliding brush 16 is displaced to a position where it deviates from the right end of the position E pattern 43;
The position switch SWT outputs an off (Hi) signal to cut off the power supply to the DC motor 33.

Therefore, the DC motor 33 whose power supply is cut off stops at the free rotation torque position of the motor, which is slightly ahead of the right end of the position E pattern 43, due to the circumstances described above.

That is, if the position E preparation position T0 is set in advance to this stop position, when the T-W switching operation button 51 is switched to the state that realizes position E photography, the DC motor 33 always positions the front group frame 1o. It can be stopped at the E preparation position T0.

Now, when the variable focus lens is set at the E preparation position T0, the front group frame 10 moves from a position close to the exposure aperture 3 to a position shown in the first figure close to the subject.

At this time, the rear group frame 20 held in the retracted position is pulled by the connecting spring 27 and displaced to the left during the movement of the front group frame 10, so that the engagement pin 24 on the rear group frame 20 is moved. It moves away from the push-down action surface 7a of the cam plate member 7.

Therefore, the rear group frame 20 is rotated counterclockwise by the turning force of the twisting spring 25 while moving to the left (toward the subject), and the positioning protrusion 21a formed at the tip 21 of the rear group frame 2o is rotated. Rotation is prevented in a posture in which the sub-lens system Ls is in contact with the outer circumferential surface of the blocking pole 5, that is, in a posture in which the sub-lens system Ls is accurately positioned on the photographing optical axis 0.

However, the front group frame 10 and the rear group frame 20 continue to move integrally to the left, and when the base 22 of the rear group frame 20 comes into contact with the tip of the adjustment screw 28, the rear group frame 20 The main lens system only stops at that position, and the main lens system moves a little further and stops at a predetermined position, and is set at a relative position that realizes the focal length at the time of position E photography.

In this case, the urging force of the connection spring 27 is applied to the rear group frame 20, and the rear group frame 20 is reliably held at the stop position.

Note that when the front group frame 10 is in the E preparation position T0,
- When the W switching operation button 51 is operated to switch to a state in which wrDE photography is realized, the front group frame 10 is set to the WIDE preparation position Wo according to the procedure described above.

This means that by switching the T-W switching operation button 51 to the bidirectional shooting mode, the variable focus lens can be
This means that the mode for DE photography and the mode for E photography can be set alternately.

Next, the focusing operation and photographing operation in each photographing mode will be explained with reference to the WIDE-position E switching control diagram in FIG. 4.

When the variable focus lens is set to WIDE shooting mode, the front group frame 10 is set to WIDE shooting mode, as described above.
The number of DE preparation positions is set to 0, and the rear group frame 20 is placed in the retracted position.

Now, when you turn on the metering switch 56 when taking pictures,
AF distance measurement information during IDE shooting is output from the AF IC 53 to the microcomputer 55, and the amount of extension of the main lens system LM (the amount of displacement of the front group frame 10) is based on this distance information.
is calculated by the microcomputer 55 and set as the pulse count number of the photointerrupter 35.

Note that this pulse count number is a count number set as the WIDE preparation position number 0 standard, and when the DC motor 33 rotates, the pulse signal generation means 36 consisting of the rotary encoder 32 and the photointerrupter 35 By reading this count number, the rotation speed and rotation angle of the drive lead screw 6 are controlled.

In other words, the amount of displacement of the front group frame 10 at the WIDE preparation position number 0 is determined by this pulse count number.

After the number of pulse counts has been set by the photo interrupter 35, when the shutter release button 52 is pressed, the motor drive IC 54 starts operating and drives the DC motor 33 by the number of pulse counts corresponding to the AF distance information. The front group frame 10 is rotated to displace the front group frame 10 in the direction of the exposure aperture 3 (image side) via the drive lead screw 6 and the drive lead nut 15.

Therefore, the front group frame 10 moves to a position after counting the pulse count calculated by the microcomputer 55, which exists within the range of the WIDE nearest distance position W1 and the WIDE infinity position W2, and the rotation of the motor 33 is stopped. Accordingly, the main lens system LM
Set it to the position corresponding to the IAF distance information.

In this case, the DC motor 33 stops with high accuracy at the above-mentioned self-running rotational torque position of the passing motor.

Further, since the rear group frame 2o moves while the engagement pin 24 on the rear group frame 20 comes into contact with the holding surface 7b of the cam plate member 7, the rear group frame 2o can be displaced together with the front group frame 10 while maintaining the retracted position. become.

Then, the shutter is released, and the variable focus lens finishes shooting at the focal length of WIDE shooting, but after shooting is finished, the DC motor 33 rotates in the opposite direction to flip the front group frame 10 toward the subject. When the WIDE position switch SWw changes from an on signal to an off (Hi) signal, the reverse rotation of the DC motor 33 is stopped.

Therefore, the front group frame 10 returns to the WIDE preparation position W0.

On the other hand, when the variable focus lens is set to the E shooting mode, the front group frame 10 is set to the E preparation position T0, and the rear group frame 20 is inserted into the rear optical path. has been done.

When the photometry switch 56 is turned on in this state, the AF distance information during E shooting is transferred from the AF IC 53 to the microcomputer 5.
Based on this distance information, the amount of extension of the main lens system (the amount of displacement of the front group frame 10) is output to the microcomputer 5.
5 and set as the pulse count number of the photointerrupter 35.

The pulse count number in this case is the count number set based on the E preparation position T0, and as in the case of WIDE shooting, this pulse count number allows the front group frame 10 to be moved from the E preparation position T0. The amount of displacement is determined.

The subsequent operation procedure is the same as that for focusing and shooting during WIDE shooting, so a detailed explanation will be omitted. However, at the end of focusing, the front group frame 1o is at E infinity position T. Move to the position corresponding to the AF distance information within the range of the position E nearest distance position 1i'r x, and move the rear group frame 20
remains in the locked position by the tip of the adjustment screw 28. After the photographing is completed, the front group frame 1o returns to the E preparation position T0.

Note that in this case, the DC motor 33 is stopped with high accuracy at the free rotational torque position of the motor, as in the case of WIDE photography.

As explained above, in the above-mentioned variable focus lens drive device 1, when the DC motor 33 performs the focal length switching operation and the focusing operation of the photographing lens,
It becomes possible to set the rotation stop precision of the DC motor 33 favorably and stably.

Note that the free-running rotational torque position of the DC motor 33 does not need to be the peak position of the cogging torque.

Furthermore, in the illustrated embodiment, the lens holding frame (front group frame 10) that needs to be displaced is displaced by the drive lead screw 6, but in cases where the amount of displacement is small, for example, a cam displacement mechanism may also be used. .

Although one embodiment has been described above, the present invention is not limited to this, and can be modified in various ways without changing the gist thereof.

For example, in the illustrated embodiment, a bifocal variable focus lens is described in which a part of the lens system is inserted into and removed from the photographing optical axis, but it is also possible to apply the present invention to a ground type variable focus lens. I would like to add that.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to realize a novel variable focus lens drive device that can set the final stop position without variation at any position by constantly stabilizing the influence of cogging. becomes.

[Brief explanation of the drawing]

FIG. 1 is a partially exploded perspective view showing the configuration of an embodiment of a variable focus lens driving device according to the present invention, and FIG.
FIG. 3 is a layout diagram showing the relationship between the WIDE ID pattern, the position E pattern, and the ground pattern that constitute the IDE position switch and the position E position switch. FIG. 4 is an explanatory diagram of the WIDE-position E switching control of the variable focus lens drive device according to the same embodiment, and FIG. , FIG. 5(b) is a state diagram showing the final stop position of the motor as the free-running rotational torque changes, and FIG. 5(c) and FIG. 5(d) are state diagrams showing the DC motor controlled by the present invention. FIG. 1...Variable focus type lens drive device. 2... Lens barrel, 3... Exposure aperture, 5... Rotation prevention pole, 6... Drive lead screw, 7...・Cam plate member, 7a...Press-down action surface, 7b...Holding action surface, 1o...
・Front group frame, 11... Frame body, 12.
...Auxiliary frame portion, 13a, 13b...Double steel 14...T-N nut, 15...Drive lead nut, 16...Sliding Moving brush, 21... Tip part, 21a... Positioning protrusion, 22... Base part. 24...Latching/disengaging pin, 26...Pushing protrusion, 28...Adjustment screw, 3...Stay 5...Twist it. 7... Connection spring, 9... Compression spring. 2o... Rear group frame, 4... Common pole, 31... Driven gear, 32... Rotary encoder, 33...
...DC motor, 34... Drive gear, 35... Photo interrupter, 36...
・Pulse signal generating means, 40...Position stand, 41...Position switch board, 42...
... WIDEID-on, 43 ... Place E pattern, 44 ... Ground pattern, 45 ... Support plate, 50 ...
・Control unit, 51...T-W switching operation button, 52
・・・・・・Shirt release button, 53・・・・・・A
F IC1 54...Motor drive IC1 55...Microcomputer, 56...
...Metering switch, L++t...Main lens system, Ls...Sub-lens system, ○...Photographing optical axis, SW%l...WIDE position switch. SWT...E position switch, Wo ・
...WIDE preparation position. W work...WIDE closest distance position, W2...
...WIDE infinity position, To...E ready position, T1...E closest distance position, T2...E infinity position. Figure 2

Claims (1)

[Claims] (1) In a variable focus lens driving device that uses a DC motor having a core to change the focal length of a variable focus lens and perform focusing operations at each focal length, the rotation angle and rotation of the DC motor pulse signal generating means for converting the number into a pulse signal; pulse signal detecting means for counting the pulse signals emitted by the pulse signal generating means; and based on the pulse detection signal from the pulse signal detecting means, the rotation angle of the DC motor and and a motor control circuit that controls the number of rotations, and where the cogging period of the DC motor is Tm and the pulse signal generation period of the pulse signal generation means is Tp, these two periods are 1/2Tp=n. - A variable focus type lens driving device characterized in that it is configured to be synchronized using a relational expression of Tm (where n is a natural number).