Drive control apparatus, and lens apparatus and image pickup system including the drive control apparatus

A drive control apparatus includes a movable member; a driver configured to drive the movable member; a transmission device configured to transmit a driving force of the driver to the movable member; a first detector provided on the movable member side of the transmission device configured to detect a driving state of the movable member; a second detector provided on the driver side of the transmission device configured to detect a driving state of the driver; and a controller configured to control driving of the driver. The controller is configured to select, as information to be fed back, first drive information obtained from the first detector, or second drive information obtained from the second detector, based on the first drive information and the second drive information; and control the driving of the driver based on the selected one of the first drive information and the second drive information.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a drive control apparatus configured to control the driving of a movable member, and more particularly, to a lens apparatus and an image pickup system that include a drive control apparatus configured to control the driving of a movable optical member.

Description of the Related Art

Lens apparatus in which a movable optical member driven by a motor is controlled have employed feedback control to reduce to zero a difference between a control target and the position of the movable optical member, which is detected by a position detector. An example thereof is disclosed in Japanese Patent Application Laid-Open No. 2005-323488.

When a drive transmission mechanism configured to transmit a driving force from the motor to the position detector is, for example, a gear train in the technology of Japanese Patent Application Laid-Open No. 2005-323488, play (clearance, e.g., backlash) between gears of the gear train causes a difference between the driving position of the motor, which is a control target, and the result of position detection by the position detector, and a phase inversion of a control output and the position detection result due to the difference may lead to oscillation phenomena.

The oscillation phenomena are brought about especially when the movable optical member moves under the influence of an external force, e.g., gravity, thereby causing the detected position of the driven member to change (forward with respect to the direction of driving) within the extent of play irrespective of the motor's driving.

SUMMARY OF THE INVENTION

The present invention provides a drive control apparatus capable of drive control that prevents a change in the detected position of a movable optical member under the influence of an external force unrelated to a motor's driving from leading to oscillation phenomena.

According to one embodiment of the present invention, there is provided a drive control apparatus, including: a movable member; a driver configured to drive the movable member; a transmission device configured to transmit a driving force of the driver to the movable member; a first detector provided on a movable member side of the transmission device and configured to detect a driving state of the movable member; a second detector provided on a driver side of the transmission device and configured to detect a driving state of the driver; and a controller configured to control driving of the driver, in which the controller is configured to: select, as information to be fed back, one of first drive information which is obtained from the first detector, and second drive information which is obtained from the second detector, based on the first drive information and the second drive information; select the second drive information as the information to be fed back when the first drive information precedes the second drive information in a driving direction of the controlled driver; and control the driving of the driver based on the selected one of the first drive information and the second drive information.

According to the lens apparatus of the present invention, it is possible to provide the drive control apparatus capable of drive control that prevents a change in the detected position of the movable optical member under the influence of an external force unrelated to the motor's driving from leading to oscillation phenomena.

DESCRIPTION OF THE EMBODIMENTS

The present invention is described in detail by way of embodiments illustrated in the drawings.

First Embodiment

A drive control apparatus according to a first embodiment of the present invention is described with reference toFIG. 1toFIG. 10.

FIG. 1is a function block diagram of a lens apparatus1that includes the drive control apparatus of this embodiment.

The lens apparatus1mainly includes a movable optical member11, a potentiometer12(hereinafter also referred to as “POT12”) configured to detect the position of the movable optical member11and to output position information, a rotating motor13(hereinafter also referred to as “MOT13”) configured to drive the movable optical member11, and a potentiometer14(hereinafter also referred to as “POT14”) configured to detect the rotation position of the MOT13and to output position information. The lens apparatus1further includes a drive transmission device15configured to transmit a driving force of the MOT13to the movable optical member11, a position switcher16configured to switch from one of position information of the POT12and position information of the POT14to the other and to output the switched-to position information, a controller17configured to perform feedback control on the MOT13with the use of position information output by the position switcher16, and a drive circuit18configured to drive the MOT13.

To elaborate, the movable optical member11includes a lens unit having a well-known movable mechanism, which is mounted to the lens apparatus. The lens unit in this embodiment is a zoom lens unit for varying the power of the lens apparatus, and has a gear of the movable optical member11which is used to drive the movable mechanism. The gear of the movable optical member11is engaged with a gear of the POT12. The POT12and the POT14are well-known potentiometers in which a gear is fixed to a rotating shaft.

The gear of the POT12is engaged with the gear of the movable optical member11and one of gears of the drive transmission device15to detect the rotation position of the movable optical member11and to output position information S01. The gear of the POT14is connected to a gear of the MOT13to detect the rotation position of the MOT13and to output position information S02. The MOT13is a well-known DC motor in which a gear is fixed to a rotating shaft, and the gear of the MOT13is engaged with the gear of the POT14and one of the gears of the drive transmission device15.

The drive transmission device15includes a well-known gear train, a connection shaft, and other components. The drive transmission device15connects the gear of the POT12and the gear of the MOT13to transmit a driving force of the MOT13to the movable optical member11via the drive transmission device15. The gear of the movable optical member11and the gear of the POT14may be connected directly to the gears of the drive transmission device15. The POT12is placed on the movable optical member side (movable member side) of the drive transmission device15to detect the driving state of the movable member. The POT14is placed on the motor side (driver side) of the drive transmission device15to detect the driving state (position, speed, and the like) of the motor. The position information S01and the position information S02are input to the position switcher16.

The position switcher16outputs one of the position information S01and the position information S02to the controller17, which is described later, based on switching conditions, which are described later (with reference toFIG. 10). A control target position (control target value) Sct1and position information that is output as a feedback signal by the position switcher16are input to the controller17. The controller17outputs a control signal S03with which feedback control is performed on the MOT13to the drive circuit18, which is described later. The drive circuit18receives the control signal S03input thereto, and outputs a drive signal S04to drive the MOT13.

The control target position Sct1is a position information that indicates a control target of the MOT13(the movable optical member11). The control signal S03is an output signal of the controller17which is obtained by adjusting a difference between the control target position Sct1and the position information with a gain or the like.

Mechanical driving mechanisms generally have various types of play, and also in this embodiment, there is a backlash or other types of play between gears. In this embodiment, the gear of the POT12and the gear of the movable optical member11are arranged next to each other, and the gear of the POT14and the gear of the MOT13are arranged next to each other. The amount of backlash between the POT12and the movable optical member11is smaller than the amount of backlash between the POT14and the movable optical member11. The amount of backlash between the POT14and the MOT13is smaller than the amount of backlash between the POT12and the MOT13.

The movement of the gear of the POT12and the gear of the MOT13in this embodiment is described next with reference toFIG. 2toFIG. 9.

FIG. 2,FIG. 3, andFIG. 7toFIG. 9are schematic diagrams for illustrating an engaged state of the gear of the POT12and the gear of the MOT13, which rotates counter-clockwise (to the left on the paper) and rotates clockwise (to the right on the paper), respectively. Gear teeth A2and A1of the MOT13are arranged in the counter-clockwise direction in the order stated. Gear teeth B2and B1of the POT12are arranged in the clockwise direction in the order stated. Gear of the drive transmission device15that are interposed between the gear of the POT12and the gear of the MOT13are omitted in the description given here for the sake of convenience.

FIG. 2is a diagram for illustrating a normal state in which the gear of the MOT13is driving the gear of the POT12(the movable optical member side), and the gear tooth A1of the MOT13and the gear tooth B1of the POT12are engaged with each other (hereinafter referred to as “State1”).

FIG. 3is a diagram for illustrating a state in which the gear of the POT12alone has suddenly rotated from State1, with the result that the gear tooth A1of the MOT13is engaged with the gear tooth B2of the POT12(hereinafter referred to as “State2”). This is a state in which the gear of the POT12(the movable optical member11) has moved under the influence of, for example, an external force irrespective of the rotation of the MOT13.

The operation in State1and State2and oscillation phenomena are described next with reference toFIG. 4andFIG. 5.

FIG. 4is a graph for showing the tracks of the gears' rotation positions in State1and State2.FIG. 5is a graph for showing the rotation positions of the gears after State2in the case where control according to the present invention is not employed.

First, the rotation position of the gear of the POT12and the rotation position of the gear of the MOT13match with each other in State1, and the controller17controls the MOT13with the use of the position information S01, which is the result of detection executed by the POT12. Next, the gear of the POT12in State2moves in the driving direction and precedes the gear of the MOT13while the rotation position of the gear of the MOT13passes the control target position Sct1as in State1.

The controller17consequently performs feedback control so that the rotation position of the gear of the POT12returns to the control target position Sct1, and a control output is generated in a direction opposite from the gear rotation direction of the POT12with respect to the control target position Sct1. However, the rotation position of the gear of the POT12again falls on a point beyond the control target position Sct1.

The gear rotation position repeatedly overshoots the control target position Sct1in this manner, which leads to oscillation phenomena.

Control according to the present invention which prevents the oscillation phenomena is described next with reference toFIG. 2toFIG. 10.

FIG. 6is a graph for showing the rotation positions of the gears in the case where the control according to the present invention is employed and the gear of the POT12has come to a stop after State2.

First, there is no significant difference between the position information S01of the POT12and the position information S02of the POT14in State1(seeFIG. 2), and the position switcher16ofFIG. 1therefore selects and outputs the position information S01. The controller17uses this position information S01to perform feedback control on the MOT13.

Next, there is a significant difference between the position information S01of the POT12and the position information S02of the POT14in State2(seeFIG. 3), and the position switcher16ofFIG. 1therefore selects and outputs the position information S02. The controller17uses this position information S02to perform feedback control on the MOT13. Through the feedback control, State2ofFIG. 3in which the tooth A1of the MOT13and the tooth B2of the POT12are in contact with each other changes to State3in which the driving of the MOT13is controlled to rotate until the tooth A1of the MOT13comes into contact with the tooth B1of the POT12, which is still at the moment. Also in State3, there is a significant difference between the position information S01and the position information S02(seeFIG. 7), and the controller17therefore uses the position information S02to perform feedback control on the MOT13.

The state in which the tooth A1of the MOT13is brought into contact with the tooth B1of the stationary POT12through the drive control and rotation of the MOT13is followed by State4in which the stationary POT12starts rotating and gear teeth of the MOT13rotate while biasing the gear teeth of the POT12toward the rotation direction. Lastly, the difference between the position information S01of the POT12and the position information S02of the POT14becomes equal to or smaller than a given value in State4(seeFIG. 8andFIG. 9), and the position switcher16ofFIG. 1selects and outputs the position information S01. The controller17uses this position information S01to perform feedback control on the MOT13. During the shifts of control from State1to State4, the control target position Sct1is kept output under constant control (for example, uniform motion shown inFIG. 6) whichever of the position information S01and the position information S02is employed as a signal to be fed back to control.

Details of the control method according to the present invention are described next with reference toFIG. 10.

FIG. 10is a flow chart for illustrating the control method of the present invention.

In Step ST01, the detection result (S01) of the POT12is obtained first. In Step ST02, the detection result (S02) of the POT14is obtained next. In Step ST03, a difference between S01and S02(|S01−S02|) is calculated. The control method proceeds to Step ST04in the case where the difference exceeds a given value Δp, and to Step ST05in the case where the difference is equal to or smaller than the given value Δp. In Step ST04, the position switcher16selects the position information S02out of the position information S01and the position information S02that have been input to the position switcher16, and outputs the position information S02to the controller17. The controller17performs feedback control on the MOT13with the use of the position information S02. In Step ST05, on the other hand, the position switcher16selects the position information S01out of the position information S01and the position information S02that have been input to the position switcher16, and outputs the position information S01to the controller17. The controller17performs feedback control on the MOT13with the use of the position information S01.

The control according to the present invention thus uses in a normal state (State1and State4) the POT12, which is capable of detecting the rotation position of the movable optical member11more accurately (because placed next to the movable optical member11). In a state where the difference between the position information of the POT12and the position information of the POT14is greater than a given value and oscillation is a possibility (State2and State3), the present invention uses position information output from the POT14, which is capable of detecting the rotation position of the MOT13serving as a control target more accurately (because placed next to the MOT13), to control the MOT13.

Configured as described above, the lens apparatus of this embodiment is capable of preventing oscillation phenomena (seeFIG. 5) which is an effect of the present invention, and also has an effect in that the rotation position of the movable optical member can be detected and controlled with precision in a normal state where the chance of oscillation phenomena is small.

Second Embodiment

A lens apparatus according to a second embodiment of the present invention is described with reference toFIG. 1,FIG. 5toFIG. 9, andFIG. 11toFIG. 16.

This embodiment differs from the first embodiment in the movement of the POT12, which is configured to detect the rotation position of the movable optical member11, but has the same basic configuration as that of the lens apparatus1described in the first embodiment. Descriptions on components of the second embodiment that overlap with components of the first embodiment are therefore omitted. The following description about the lens apparatus of this embodiment focuses on the difference from the configuration of the first embodiment.

FIG. 12andFIG. 14toFIG. 16are schematic diagrams for illustrating an engaged state of the gear of the POT12and the gear of the MOT13, and rotation directions, gear teeth names, and the like inFIG. 12andFIG. 14toFIG. 16are the same as in the first embodiment.

FIG. 11is a graph for showing the rotation positions of the gears in the case where control according to the present invention is employed. In the case illustrated inFIG. 11, the gear of the POT12continues to rotate after State2from its position inFIG. 6of the first embodiment, at the same speed as the gear of the MOT13(this state is referred to as “State5”).

In State5(seeFIG. 12), when the difference |S01−S02| exceeds Δp in Step ST03of the processing of the first embodiment that is illustrated in the flow chart ofFIG. 10, the position switcher16selects the position information S02out of the position information S01and the position information S02and outputs the position information S02to the controller17in Step ST04. The controller17uses the position information S02to perform feedback control on the MOT13.

FIG. 12is a diagram for illustrating a case in which the gear of the POT12maintains State5once after State2, and comes to a stop as in the first embodiment.

State6and State7(FIG. 14,FIG. 15, andFIG. 16) inFIG. 13correspond to State3and State4, respectively, of the first embodiment (seeFIG. 6,FIG. 7,FIG. 8, andFIG. 9). In State6, there is a significant difference between the position information S01and the position information S02as in State3. The position switcher16therefore selects the position information S02out of the position information S01and the position information S02, and outputs the position information S02to the controller17. The controller17uses the position information S02to perform feedback control on the MOT13.

In State7, the difference between the position information S01of the POT12and the position information S02of the POT14is equal to or smaller than the given value as in State4(seeFIG. 15andFIG. 16). The position switcher16therefore selects the position information S01out of the position information S01and the position information S02, and outputs the position information S01to the controller17. The controller17uses the position information S01to perform feedback control on the MOT13.

Thus, the chances of the oscillation phenomena described in the first embodiment with reference toFIG. 5are high also when the gear of the POT12accidentally rotates at the same speed as the gear of the MOT13without the MOT13driving the POT12, and some external factor causes sudden acceleration/deceleration of the gear of the POT12because the MOT13is not driving the POT12. However, such oscillation can be prevented in advance by controlling the MOT13with the use of the position information S02in the manner described in this embodiment.

Third Embodiment

A lens apparatus according to a third embodiment of the present invention is described with reference toFIG. 1,FIG. 17, andFIG. 18.

This embodiment differs from the first embodiment in that control using a voltage between terminals of the MOT13is executed in place of control using the position information of the POT14, and in that speed feedback control is executed in place of position feedback control. The rest of the basic configuration of the third embodiment is the same as that of the lens apparatus1described in the first embodiment. Descriptions on components of the third embodiment that overlap with components of the first embodiment are therefore omitted. The following description about the lens apparatus of this embodiment focuses on the differences from the configuration of the first embodiment.

FIG. 17is a function block diagram of a lens apparatus2of this embodiment.

Unlike the lens apparatus1of the first embodiment, the lens apparatus2of this embodiment does not include the POT14configured to detect the position of the MOT13, and includes, in place of the position switcher16, the controller17, and the drive circuit18, a speed switcher26, a controller27, and a drive circuit28, which have different functions from the functions of their counterparts in the lens apparatus1.

Functional differences of those components from the ones in the first embodiment are described below.

The drive circuit28outputs a drive voltage signal (hereinafter referred to as “drive voltage S05”) of the MOT13to the controller27. The position information S01output by the POT12and the drive voltage S05output by the drive circuit28are input to the speed switcher26. The speed switcher26converts the input position information S01and drive voltage S05separately into speeds to generate a speed information S01′ from the position information S01and to generate a speed information S05′ from the drive voltage S05. The speed switcher26outputs to the controller27one of the speed information S01′ and the speed information S05′ based on the difference between the speed information S01′ and the speed information S05′. A control target speed Sct1′ and one of the speed information S01′ and the speed information S05′ are input to the controller27, and the controller27performs speed feedback control on the MOT13.

Details of the control method according to the present invention are described next with reference toFIG. 18.

FIG. 18is a flow chart for illustrating the control method of the present invention.

In Step ST01, the position detection result (S01) of the POT12is obtained first. In Step ST06, the position detection result (S01) of the POT12is converted into the speed information S01′. In Step ST07, a voltage between terminals of the MOT13is detected to obtain the motor drive voltage S05. In Step ST08, the speed information S05′ of the MOT13is calculated from the motor drive voltage S05. In Step ST09, a difference between S01′ and S05′ (|S01′−S05′|) is calculated. The control method proceeds to Step ST10in the case where the difference exceeds a given value Δv, and proceeds to Step ST11in the case where the difference is equal to or smaller than the given value Δv. In Step ST10, the speed switcher26selects the speed information S05′ and outputs the speed information S05′ to the controller27. The controller27uses the speed information S05′ to perform speed feedback control on the MOT13. In Step ST11, the speed switcher26selects and outputs the speed information S01′, and the controller27uses the speed information S01′ to perform speed feedback control on the MOT13.

The third embodiment, where the rotation speed of the MOT13is used in feedback control of the MOT13when there is a significant difference in rotation speed between the MOT13and the POT12, is thus capable of preventing oscillation as the first embodiment and the second embodiment are. In addition, the lens apparatus of the third embodiment which does not need the POT14to detect the rotation position or speed of the MOT13can accordingly be reduced in size, weight, and cost.

The drive voltage and motor rotation speed of the MOT13, which is a DC motor, can generally be expressed in a proportional relationship. However, noise that is generated by a contact between a brush and a commutator inside the motor is often superimposed on the drive voltage. It is therefore more desirable to use an averaged drive voltage in control in the case where a feedback system is built with the use of the drive voltage of the MOT13.

While the third embodiment discusses an example in which the speed information S05′ of the MOT13is obtained from the motor drive voltage S05, the present invention is not limited thereto. For instance, a counter electromotive force may be derived from the drive voltage and drive current of the DC motor to evaluate a load on the DC motor based on the counter electromotive force and to use the load as a signal to be fed back to the drive control of the motor.

Fourth Embodiment

A lens apparatus according to a fourth embodiment of the present invention is described with reference toFIG. 19toFIG. 22.

In the methods described in the first embodiment to the third embodiment, control is executed with the use of position information or the drive voltage of the MOT13(or the POT14placed next to the MOT13), which is a drive target, in order to prevent oscillation phenomena. In the case of making an optical state correction on an image such as a correction of the angle of view, however, more accurate position information of the movable optical member is needed beside position information that is used in the control of the MOT13.

Thus, in this embodiment, a case in which the angle of view is corrected is described below.

The configuration of a lens apparatus3according to this embodiment is outlined inFIG. 19, and differs from the lens apparatus2of the third embodiment in that a movable optical member31and an encoder ENC32(hereinafter referred to as “ENC32”) are included in place of the movable optical member11and the POT12, respectively, and in that an angle-of-view correction arithmetic operator39(a corrector) and a Z controller40are additionally included.

FIG. 21is a function block diagram of an image pickup system6, which includes the lens apparatus3of this embodiment and a camera apparatus5.

The movable optical member31includes a lens unit having a well-known movable mechanism that is mounted to the lens apparatus. The lens unit in this embodiment is a zoom lens unit for varying the power of the lens apparatus, and has a gear used to drive the movable mechanism. The gear is connected to a gear of the ENC32.

The encoder ENC32is a well-known, rotary-type encoder, and has a gear on a rotating shaft. The gear of the ENC32is connected to the gear of the movable optical member31and one of the gears of the drive transmission device15to detect a rotation position, and to output the position information S01.

The position information output by the ENC32is generally in the form of a digital pulse waveform or an analog sine waveform. However, the configuration of the waveform is irrelevant to the essence of the present invention, and the position information of the ENC32is therefore treated as the same as the position information S01of the POT12in the first embodiment to the third embodiment.

The angle-of-view correction arithmetic operator39generates a control for controlling the driving of the zoom lens unit (not shown), which is included in the lens apparatus3, in order to correct a change in the angle of view that is caused by the movement of a focus lens unit for adjusting the focus of the lens apparatus3of this embodiment when the focus lens unit is put into operation. The position of the zoom lens unit and the position of the focus lens unit are necessary to correct a change in the angle of view that is caused when the focus lens unit is put into operation. The position information S01of the zoom lens unit which is output by the ENC32and position information from a position detector (not shown) of the focus lens unit are input to the angle-of-view correction arithmetic operator39. The angle-of-view correction arithmetic operator39outputs a zoom control signal S06to the Z controller40. The zoom control signal S06is input to the Z controller40, and the Z controller40controls the zoom lens unit for varying the power of the lens apparatus3.

The lens apparatus3includes, other than the zoom-system components illustrated inFIG. 21, a drive circuit for focus driving, a focus motor for driving, the position detector configured to detect the position of the focus lens unit, a drive transmission device connecting the focus motor to a movable member of the focus lens unit, and the like. The position of the focus lens unit is input to the angle-of-view correction arithmetic operator39from the position detector to be used in a calculation for the correction of the angle of view.

FIG. 20is a flow chart for illustrating the control method of the present invention.

The flow chart ofFIG. 20differs from the flow chart ofFIG. 18of the third embodiment in that Step ST12is added to use the position information of the ENC32always as the position (optical position G) of the zoom lens unit.

The position information of the ENC32, which is capable of detecting the position of the movable optical member (zoom lenses)31more accurately (because placed next to the movable optical member31), can thus always be used as the position of the zoom lens unit which is used in the correction of the angle of view, even when the drive voltage of the MOT13is selected and used by the speed switcher26in the drive control of the movable optical member31.

The fourth embodiment discusses an example a case in which the lens apparatus uses position information that is provided by an encoder placed next to the movable optical member as a more accurate zoom lens position, which is needed by the angle-of-view correction arithmetic operator in angle-of-view correction necessary for focus operation, even when the driving of the zoom lenses is controlled based on speed information that is provided by the drive motor. Similarly, the configuration described above can be applied as it is to obtain a more accurate focus lens position, which is needed by the angle-of-view correction arithmetic operator in angle-of-view correction necessary for focus operation. In short, one of driver-side drive information (in the form of position or speed) and driven-side drive information (in the form of position or speed) is selected based on the difference between the two, to be used in the drive control of the focus lenses via the drive transmission device that has play in the drive system. In this drive control, focus lens position information that is provided by the encoder placed next to the focus lens unit is used in a calculation for the correction of the angle of view even when the driver-side drive information is used, thereby accomplishing angle-of-view correction that is even higher in precision.

Fifth Embodiment

An image pickup system according to a fifth embodiment of the present invention is described.

FIG. 21is a function block diagram for illustrating the image pickup system6, which includes the lens apparatus3of the fourth embodiment and the camera apparatus5having an aberration correction function.

The camera apparatus5includes an image pickup unit51configured to pick up an optical image formed by the lens apparatus3and to output image pickup data, an aberration correction arithmetic operator52configured to output aberration correction data for correcting various optical aberrations that are contained in the optical image, and an image generator53configured to generate an image based on the image pickup data and the aberration correction data.

The aberration correction arithmetic operator52generates the aberration correction data based on the position information S01output by the lens apparatus3. Other types of information than the position information S01, such as zoom position information and diaphragm position information of the lens apparatus3, may also be taken into consideration in aberration correction.

In this manner, when angle-of-view correction, image correction, or the like is made based on accurate information about the state of optical apparatus (such as the position of the movable optical component) regardless of inside or outside the lens apparatus, one of driver-side drive information (in the form of position or speed) and driven-side drive information (in the form of position or speed) is selected based on the difference between the two, to be used in the drive control of the movable optical member31via the drive transmission device that has play. In this drive control, position information of the ENC32, which is capable of detecting the position of the movable optical member31more accurately (because placed next to the movable optical member31) is used even when the driver-side drive information is used, thereby accomplishing precise angle-of-view correction, image correction, or other similar correction.

An image pickup system that is a derivative of the fifth embodiment of the present invention is described with reference toFIG. 22.

The image pickup system according to an embodiment of the present invention illustrated inFIG. 22has a form in which the lens apparatus3inside the image pickup system of the fifth embodiment which is illustrated inFIG. 21is divided into a lens apparatus7and a drive apparatus8. The lens apparatus7includes the movable optical member31, and the drive apparatus8includes the other components of the lens apparatus3than the movable optical member31. There is no essential difference in overall function as an image pickup system between the image pickup system6ofFIG. 21and the image pickup system ofFIG. 22. The only difference is that the lens apparatus3inside the image pickup system6ofFIG. 21is configured as separate apparatus, the lens apparatus7and the drive apparatus8, in the image pickup system ofFIG. 22to be mounted to each other for use.

In this manner, when angle-of-view correction, image correction, or the like is made based on accurate information about the state of optical apparatus (such as the position of the movable optical component) regardless of inside or outside the lens apparatus, one of driver-side drive information (in the form of position or speed) and driven-side drive information is selected based on the difference between the two, to be used in the drive control of the movable optical member31via the drive transmission device that has play. In this drive control, position information of the ENC32, which is capable of detecting the position of the movable optical member31more accurately (because placed next to the movable optical member31) is used even when the driver-side drive information is used, thereby executing precise angle-of-view correction, image correction, or other similar correction.

In any of the embodiments described above, direct position detection and direct driving of the movable optical member, which is the ultimate control target of the lens apparatus, without an intervening component, e.g., a drive transmission device is desirable in truth.

However, actual lens apparatus need to use a drive transmission device due to difficulties in securing an installation space and the like. The use of a gear train is also necessary in order to secure a speed reduction ratio for reasons such as the drive performance of the motor and the detection precision of the position detector.

In the case where the position of the movable optical member needs to be obtained for optical aberration correction or the like in a camera that is run as a set with lenses, the position of the movable optical member needs to be detected in manual operation of the movable optical member as well, which makes placing the motor and the position detector apart from each other a preferred arrangement. The movable optical member of the lens apparatus, the position detector configured to detect the position of the movable optical member, and the motor configured to drive the movable optical member are therefore put in places apart from one another in many cases, while allowing for mechanical play between the components.

When gravity is applied to the movable optical member in this type of lens apparatus, with a difference in posture created between the components, for example, the movable optical member is moved within the extent of the play irrespective of the motor's driving, which can trigger oscillation phenomena.

The present invention can provide a technology with which oscillation phenomena caused in the manner described above are prevented and the accurate position of the movable optical member can always be detected as well to carry out the optical aberration correction or other similar correction with precision.

Cases that require the detection of the accurate position of the movable optical member include, other than the angle-of-view correction and image correction given as examples, a case in which an image is output to a virtual system configured to composite CG images.

The type of the MOT13is not limited to DC motors. While the embodiments described above discuss as an example a case in which the drive voltage of the MOT13is used to detect speed information, the rotation position or speed of the motor may be detected from the drive current or voltage (waveform) of the motor irrespective of the type of the motor. The speed calculated from the drive voltage in the embodiments may be converted into a position to feed back the position.

The method of controlling the MOT13is also not limited to the control methods of the embodiments, and speed feedback control and position feedback control may be combined.

Other Embodiments

This application claims the benefit of Japanese Patent Application No. 2015-127952, filed Jun. 25, 2015, which is hereby incorporated by reference herein in its entirety.