JP2017017901A - Stepping motor drive state detector, optical apparatus and stepping motor drive state detection program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid false detection of the out-of-tune of a stepping motor.SOLUTION: A stepping motor drive state detector 115 acquires first positional information of a driven member 112 based on a signal from position detection means 121 for detecting the position of the driven member driven by a stepping motor 113, and acquires second positional information of the driven member based on the count of the drive pulse signals applied to the stepping motor. The device detects the out-of-tune of the stepping motor by comparing the first positional information and second positional information. Detection of the out-of-tune is restricted when the stepping motor is in a specific drive state.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a technique for controlling the driving of a stepping motor, and more particularly to a technique for detecting step-out of a stepping motor.

  When the driving of the stepping motor is controlled by the open loop system, the stepping motor is likely to be out of step. When step-out occurs, the actual position of the driven member driven by the stepping motor deviates from the control target position.

  Patent Document 1 discloses an optical device that detects a stepping motor step-out using the number of drive pulses applied to a stepping motor after detecting that a driven member is positioned at a reference position by a reset sensor. . Specifically, it is possible to detect that the driven member is located at different reference positions by two reset sensors. Then, if the cumulative value of the number of drive pulses actually applied to the stepping motor between the two reference positions is different from the predetermined number of pulses (threshold value) stored in advance as the original number of drive pulses between the two reference positions, it is lost. Detects the occurrence of a key.

Japanese Patent No. 2633129

  However, the stepping motor may rotate slightly (unnecessary reversing operation) in the direction opposite to the original driving direction in terms of control depending on the detent torque and vibration characteristics. For this reason, in the optical device disclosed in Patent Document 1, the driven member detected by one reset sensor is reset again without being detected by another reset sensor by an unnecessary reversing operation of the subsequent stepping motor. It may be detected by a sensor. In the optical device of Patent Document 1 in which the two reset sensors detect the driven member sequentially to detect step-out, the detection of the driven member by the same reset sensor may be treated as the detection by another reset sensor. . As a result, even though the stepping motor has not stepped out, the difference between the cumulative value of the number of drive pulses applied to the stepping motor and the threshold value becomes large, and stepout is erroneously detected.

  The present invention provides a stepping motor drive state detection device and the like that can avoid erroneous detection of step-out due to the influence of detent torque or the like of a stepping motor.

  A stepping motor drive state detection device according to one aspect of the present invention acquires first position information of a driven member based on a signal from a position detection unit that detects the position of the driven member driven by the stepping motor. First position acquisition means; second position acquisition means for acquiring second position information of the driven member based on a count value of the number of pulses of the drive pulse signal applied to the stepping motor; and first position Step-out detecting means for detecting step-out of the stepping motor by comparing the information with the second position information is provided. The step-out detection means limits detection of step-out when the stepping motor is in a specific drive state.

  An optical device that includes the stepping motor drive state detection device and whose driven member is an optical member also constitutes another aspect of the present invention.

  A stepping motor drive state detection program according to another aspect of the present invention is a computer program that causes a computer to execute processing for detecting stepping motor step-out. The processing includes processing for obtaining first position information of the driving member based on a signal from a position detecting means for detecting the position of the driven member driven by the stepping motor, and a driving pulse signal applied to the stepping motor. Detection for detecting step-out of the stepping motor by comparing the first position information and the second position information with the process of acquiring the second position information of the driven member based on the count value of the number of pulses of Processing. In the detection process, detection of step-out when the stepping motor is in a specific drive state is limited.

  According to the present invention, the step-out determination is limited when the stepping motor is in the specific drive state, so that erroneous detection of the occurrence of step-out can be avoided.

1 is a block diagram showing a configuration of a camera system including an interchangeable lens provided with a stepping motor drive state detection device that is Embodiment 1 of the present invention. FIG. 3 is a perspective view showing a drive system for a focus lens including a stepping motor in Embodiment 1. FIG. 6 is a diagram illustrating an ideal output change of the reset sensor group in the first embodiment. FIG. 6 is a diagram illustrating output changes of the reset sensor group in consideration of various errors in the first embodiment. FIG. 6 is a diagram illustrating a step-out determination invalid section in focus search driving according to the first embodiment. The figure which shows the time change of the reset sensor group at the time of driving the focus in Example 1, and step-out determination valid / invalid. 5 is a flowchart illustrating focus drive processing according to the first exemplary embodiment. 5 is a flowchart illustrating step-out determination permission / prohibition setting processing according to the first embodiment.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 shows a lens constituted by an interchangeable lens 110 as an optical device having a step-out detection unit 115 as a stepping motor driving state detection device according to an embodiment of the present invention, and a camera body 130 as an imaging device. 1 shows a configuration of a replaceable camera system 100. The interchangeable lens 110 is detachably attached to the camera body 130.

  The camera body 130 is provided with an image sensor 136, a camera CPU 131, a control system power supply 132, a drive system power supply 133, a camera communication unit 134, and a focus detection unit 135. The image sensor 136 photoelectrically converts a subject image formed by the imaging optical system in the interchangeable lens 110 and outputs an electrical signal. An image processing circuit (not shown) generates a video signal using the electrical signal output from the image sensor 136.

  The camera CPU 131 controls all operations in the camera main body 130 and incorporates memories such as RAM, ROM, and EEPROM. The control system power supply 132 supplies power to a control system circuit that consumes relatively little power and requires a stable power supply, such as the image sensor 136, the image processing circuit, the focus detection unit 135, and a photometric unit (not shown). The drive system power supply 133 detects the voltage (or power) of the control system power supply 132 and supplies power to a drive system circuit that consumes a relatively large amount of power, such as an external accessory including the interchangeable lens 110 and a shutter drive unit (not shown). To do.

  The camera communication unit 134 has a plurality of communication terminals for communicating with a lens CPU 111 described later, and transmits focus detection information and photometry information to the lens CPU 111 and receives information from the lens CPU 111. The focus detection unit 135 detects the focus state of the photographic optical system with respect to the subject using a phase difference detection method using the light beam from the photographic optical system in the interchangeable lens 110.

  The interchangeable lens 110 includes a lens CPU 111, a focus lens (focus element) 112, a stepping motor 113 that drives the focus lens 112, a focus drive circuit 114, a step-out detection unit 115, and a lens communication unit 116. It has been. The lens CPU 111 controls the operation of the interchangeable lens 110 based on the command signal, request signal, and various information from the camera CPU 131. The lens CPU 111 includes a memory such as a RAM, a ROM, and an EEPROM, and a drive control unit for controlling the driving of the stepping motor 113.

  The stepping motor 113 includes a rotatable rotor and an exciting coil as a stator, and rotates the rotor in response to a drive pulse signal applied to the exciting coil. If the step-out described later does not occur, the rotor (stepping motor 113) rotates by the amount of rotation corresponding to the number of drive pulse signals applied to the exciting coil (hereinafter referred to as the number of drive pulses).

  The focus drive circuit 114 applies a drive pulse signal to the stepping motor 113 in accordance with a focus drive command from the lens CPU 111. Thereby, the focus lens 112 as a driven member is driven in the optical axis direction of the photographing optical system, and the focus state of the photographing optical system is adjusted. Note that the imaging element 136 may be used as a focus element that is driven to adjust the focus state, and the imaging element 136 may be driven in the optical axis direction by a stepping motor.

  The lens communication unit 116 has a plurality of communication terminals for communicating with the camera CPU 131 and receives the above-described focus detection information and the like from the camera CPU 131. The lens communication unit 116 transmits lens ID information, which is identification information unique to the interchangeable lens 110, to the camera CPU 131.

  In this embodiment, a stepping motor 113 is used as a drive actuator for the focus lens 112, and a drive control process including a step-out detection process described later is performed on the stepping motor 113. However, the step-out detection process can also be applied to a stepping motor that drives a variable power lens, a diaphragm, or the like as a driven member (optical member) other than the focus lens.

  Next, a configuration for detecting step-out of the stepping motor 113 in this embodiment will be described with reference to FIG. FIG. 2 shows a focus drive system that drives the focus lens 112. The focus drive system includes a lead screw 117 integrated with the rotor wall of the stepping motor 113, a rack 118, a lens holding member 119 that holds the focus lens 112, and three reset sensors (position detection means) 121a, 121b, 121c. In the following description, the three reset sensors 121a, 121b, and 121c are collectively referred to as a reset sensor group 121. The lens holding member 119 is provided with a plurality of light shielding walls 120.

  When the stepping motor 113 is driven and the lead screw 117 rotates, the rotational force is converted into a driving force in the axial direction of the lead screw 117, that is, in the optical axis direction by the rack 118 engaged with the lead screw 117. Since the rack 118 is attached to the lens holding member 119, the lens holding member 119 (that is, the focus lens 112) is driven in the optical axis direction together with the rack 118. In the following description, the position of the focus lens 112 and the lens holding member 119 that holds the focus lens 112 is referred to as a focus lens position.

  The reset sensor group 121 is fixed to a lens barrel (not shown) that houses the photographing optical system. In this embodiment, a transmissive photo interrupter is used as each reset sensor. The photo interrupter outputs a high level signal when the light receiving unit detects light, and outputs a low level signal when the light receiving unit does not detect light. The plurality of light shielding walls 120 provided on the lens holding member 119 enter between the light emitting unit and the light receiving unit of the reset sensors 121a to 121c according to the focus lens position, and block light from the light emitting unit toward the light receiving unit. Therefore, the output patterns of High (hereinafter abbreviated as H) and Low (hereinafter abbreviated as L) from the reset sensors 121a to 121c change according to the focus lens position. The lens CPU 111 and the step-out detection unit 115 can detect the focus lens position based on the output patterns of the reset sensors 121a to 121c.

  In this embodiment, a case where a transmissive photo interrupter is used as a reset sensor will be described. However, other position detecting means such as a reflective photo interrupter or a magnetic sensor may be used. In addition, the number and arrangement of the reset sensor group 121 and the light shielding walls 120 in the present embodiment are merely examples, and the position detection means may be provided in other numbers and arrangement.

  FIG. 3 shows an output pattern of the reset sensor group 121 according to the focus lens position in the present embodiment. The horizontal axis is the focus lens position, which indicates the position from the image side to the subject side from left to right. The vertical axis represents the output (H, L) of each reset sensor. The output of the photo interrupter PI-a as the reset sensor 121a, the photo interrupter PI-b as the reset sensor 121b, and the photo interrupter PI-c as the reset sensor 121c is shown in order from the top of FIG.

  In this embodiment, since three binary output photo interrupters are used, there are eight output patterns of the reset sensor group 121. From the output pattern of the reset sensor group 121, the focus lens position at that time can be narrowed within a predetermined range. Furthermore, the focus lens position can be specified by moving the focus lens 112 to a position where the output of any one of the photo interrupters is switched.

  For example, when the outputs of the photo interrupters PI-a, PI-b, and PI-c are in L, L, and L states, from the output edge position FP_PI1 of the photo interrupter PI-a to the output edge position FP_PI2 of the photo interrupter PI-b The focus lens position is within the range. When the focus lens 112 moves to the subject side from this state, the photo interrupter PI-b outputs H by exiting from the light shielding wall 120 between the light emitting portion and the light receiving portion. Thereby, the focus lens position (absolute position) at this time can be specified as FP_PI2.

  If the absolute position detection mechanism is not provided, the camera CPU 131 issues a reset processing command to the lens CPU 111 in order to specify the focus lens position. The lens CPU 111 that has received the reset processing command performs a reset process for moving the focus lens 112 to any one of the output edge positions FP_PI1 to FP_PI7. The lens CPU 111 stores the focus lens positions (absolute positions) corresponding to the output edge positions FP_PI1 to FP_PI7 in advance. When the lens CPU 111 detects that the focus lens 112 is positioned at any one of the output edge positions FP_PI1 to FP_PI7 by the reset process, the lens CPU 111 sets the absolute position corresponding to the output edge position as the reset position. When the reset process is completed, the lens CPU 111 receives a focus drive command issued from the camera CPU 131 after transmitting a reset completion status to the camera CPU 131. The lens CPU 111 causes the focus drive circuit 114 to apply a drive pulse signal having a pulse number corresponding to the drive amount of the focus lens 112 included in the focus drive command to the stepping motor 113.

  Then, the lens CPU 111 adds or subtracts the drive pulse number applied to the stepping motor 113 at this time to the drive pulse number corresponding to the reset position. In this way, the lens CPU 111 manages the focus lens position as an accumulated count value of the number of drive pulses from the reset position.

  Next, the step-out detection unit 115 will be described. The step-out detection unit 115 according to the present embodiment uses the output of the reset sensor group 121 to detect (determine) step-out of the stepping motor 113 after completion of the reset process described above. Specifically, the step-out detection unit 115 performs step-out determination at the seven output edge positions FP_PI1 to FP_PI7 shown in FIG. The step-out detection unit 115 functions as a first position acquisition unit, a second position acquisition unit, and a step-out detection unit.

  For example, the number of drive pulses of the stepping motor 113 corresponding to the output edge position FP_PI4 is 8000 pulses, and the number of drive pulses corresponding to the output edge position FP_PI5 is 9000 pulses. Assume that reset processing is performed at the output edge position FP_PI4, and then the stepping motor 113 for 1200 pulses is driven from the output edge position FP_PI4 to the subject side. During the 1200 pulse drive, the output pattern of the reset sensor group 121 changes from H, L, H to L, L, H corresponding to the output edge position FP_PI5 when the stepping motor 113 is driven for 1004 pulses. Suppose it has changed.

  At this time, the focus lens position (second position information: hereinafter referred to as a drive pulse cumulative value) managed as a cumulative count value of the number of drive pulses in the lens CPU 111 is 8000 + 1004 = 9004 pulses. On the other hand, the original number of drive pulses (first position information: hereinafter referred to as determination reference pulse number) at the output edge position FP_PI5 is the aforementioned 9000 pulses, and the difference from the 9004 pulse is 4 pulses. The lens CPU 111 determines that the stepping motor 113 has stepped out when the difference between the number of determination reference pulses and the cumulative drive pulse value is greater than a preset threshold value. If it is determined that a step-out has occurred, the reset process is performed again to reacquire the absolute position of the focus lens position.

  In the focus drive system as in this embodiment, the drive is performed even if no step-out occurs due to the delay of signal output from the reset sensor group 121 and the expansion and contraction due to the temperature change of each member constituting the focus drive system. The accumulated pulse value may not match the number of determination reference pulses. However, when a step-out occurs, the difference between the number of determination reference pulses and the accumulated drive pulse value is greatly different from the difference when no step-out occurs. Therefore, it is preferable to use a difference larger than the difference not due to step out as a step out determination threshold (step out determination threshold). For example, in consideration of tooth skipping between the lead screw 117 and the rack 118, if the number of pulses corresponding to the number of drive pulses for one rotation of the stepping motor 113 is used as the step-out determination threshold value as a predetermined value, the step-out determination threshold value is set. In addition to the tone, the occurrence of tooth skipping can also be detected.

  Further, if each of the eight output patterns of the reset sensor group 121 appears only once within the movable range in which the focus lens 112 can move, the step-out determination by the above-described method is sufficient. However, the interchangeable lens 110 has a variation in the shape of the light shielding wall 120, a difference in elongation due to temperature, an error in the mounting position of each reset sensor, a difference in aging characteristics of the light emission efficiency of the light emitting part, There are individual differences such as differences in sensitivity characteristics. Due to such individual differences, an ideal output pattern as shown in FIG. 3 may not be obtained. For example, an output pattern as shown in FIG. 4 may be obtained.

  FIG. 4 shows changes in the output (vertical axis) of the reset sensor group 121 according to the focus lens position when the photo interrupter PI-b is mounted closer to the photo interrupter PI-a than in the case shown in FIG. Show. The horizontal axis is the focus lens position. In FIG. 4, there are two regions each where the output pattern of the reset sensor group 121 is H, H, and L, and two regions where H, L, and L are present. In this case, in order to specify one of the output edge positions FP_PI1 to FP_PI7, in addition to the output pattern of the reset sensor group 121, it is necessary to detect the driving direction of the stepping motor 113 (hereinafter referred to as the motor driving direction). . In the following description, the motor driving direction for driving the focus lens 112 toward the subject side is referred to as the subject direction, and the motor driving direction for driving the focus lens 112 toward the opposite side (image plane side) from the subject side is the image. It is called the surface direction.

  For example, in order to detect the output edge position FP_PI1, if the motor driving direction is the subject direction, the output of the photointerrupter PI-a is changed from H to L while the outputs of the photointerrupters PI-b and PI-c are both L. It is only necessary that the changed timing can be detected. Further, in order to detect the output edge position FP_PI4, if the motor driving direction is the image plane direction, the output of the photointerrupter PI-b is maintained while the output of the photointerrupter PI-a is H and the output of the photointerrupter PI-c is L. It is only necessary to detect the timing at which is changed from L to H. Thus, even if there is an individual difference in the reset sensor group 121, one output edge position can be specified from the output pattern of the reset sensor group 121 and the motor driving direction.

However, in a stepping motor, an unintended reversing operation (hereinafter referred to as an unnecessary reversing operation) may occur due to the influence of detent torque and vibration characteristics. If this unnecessary reversal operation occurs in the vicinity of the output edge position of the photo interrupter, the lens CPU 111 detects an incorrect focus lens position, and as a result, there is a risk of making an erroneous step-out determination. For example, the driving of the stepping motor 113 in the direction of the subject from the state where the focus lens 112 is stopped at a position close to the subject side with respect to the output edge position FP_PI1 in FIG. Shall start. At this time, it is assumed that the output of the photointerrupter PI-a, which should not change immediately by the unnecessary reversing operation of the stepping motor 113, has changed from L to H. However, in terms of control, the motor driving direction is the subject direction, and the output of the photo interrupter PI-c is L. Therefore, the output edge position FP_PI3 is detected when the output of the photo interrupter PI-a changes from L to H. That's right. That is, it is detected that the focus lens 112 is positioned at the output edge position FP_PI3 even though it is positioned at the output edge position FP_PI1. For this reason,
The number of drive pulses at FP_PI3−the number of drive pulses at FP_PI1> the step-out determination threshold value, and it is erroneously determined to be out of step.

  As described above, the step-out detection unit 115 according to the present embodiment detects step-out of the stepping motor 113 (step-out determination) except for a specific drive state that is affected by detent torque such as unnecessary reversal operation. In other words, the step-out determination in the specific drive state of the stepping motor 113 is limited (prohibited).

  As a specific drive state in which an unnecessary reversal operation may occur, the drive before and after the time point when the energization to the excitation coil of the stepping motor 113 is switched on / off, such as when the drive of the stepping motor 113 is started and when the drive is stopped, is performed. States. That is, it includes a driving state from the start of driving of the stepping motor 113 (start of energization to the exciting coil) until a driving pulse signal having a predetermined number of pulses is applied to the stepping motor 113. Further, the specific drive state includes a drive state from when application of a drive pulse signal of a predetermined number of pulses before driving of the stepping motor 113 is stopped to when energization holding to the exciting coil is finished. The predetermined number of pulses (predetermined value) may be, for example, 4 pulses (1-2 phase excitation conversion). Note that the stepping motor 113 is not rotated in a state where the energization to the excitation coil is held, but since the energization to the excitation coil is performed, it is a part of the driving state of the stepping motor 113.

  Another specific driving state is a driving state at a speed lower than a predetermined speed at which so-called intermittent driving due to the detent torque of the stepping motor 113 is likely to occur. For example, the driving state is lower than 200 pps. The predetermined number of pulses and the predetermined speed may be appropriately set according to the characteristics of the stepping motor 113 and the reset sensor group 121.

  Still another specific driving state includes a wobbling driving state in which intentional reverse driving (reciprocating driving) is repeated. The wobbling driving state is a driving state in which the focus lens 112 is repeatedly reciprocated with a small predetermined driving amount in order to detect the direction in which the contrast evaluation value increases in contrast type focus control. Since the inversion operation is frequently repeated in the wobbling driving state, the driving direction of the focus lens 112 may already have changed depending on the timing at which the output edge position is detected due to the output delay of the reset sensor group 121. Furthermore, vibrations due to frequent stops may occur. For this reason, it is preferable that the step-out determination is prohibited even in the wobbling driving state, although the driving state is not affected by the detent torque.

  Each of the specific drive states described above may be changed according to the zooming state of the imaging optical system or the position where the focus lens 112 moves.

  A specific drive state from when the stepping motor 113 is driven to stop through the acceleration drive, the constant speed drive and the deceleration drive to drive the focus lens 112 will be described with reference to FIG. In FIG. 5, the horizontal axis represents time, and the vertical axis represents the angular velocity of the stepping motor 113. First, energization of the exciting coil (hereinafter referred to as coil energization) is started simultaneously with the start of driving of the stepping motor 113 (start of the driving sequence). Thereafter, acceleration is driven stepwise up to 1000 pps through acceleration stages of 100 pps and 300 pps, and constant speed driving is performed at 1000 pps. Thereafter, the stop sequence is entered from before the stop position of the focus lens 112. In the stop sequence, the motor is decelerated stepwise through the deceleration stages at 300 pps and 100 pps, and the coil energization is held for a predetermined time in order to suppress the vibration of the stepping motor 113 in a state where the stop position is reached. In FIG. 5, the section in the specific drive state in which the step-out detection unit 115 prohibits the step-out determination is the section IHBT1 in which the coil energization is started to accelerate to the 300 pp acceleration stage and the stop state after decelerating to the 100 pp speed reduction stage. This is the section IHBT2 until the coil energization is completed.

  FIG. 6 shows changes in the output (vertical axis) of the reset sensor group 121 and step-out detection when an unnecessary reversal operation of the stepping motor 113 occurs when the output of the reset sensor group 121 changes as shown in FIG. The relationship with prohibition of the step-out determination by the part 115 is shown. The horizontal axis indicates time. In FIG. 6, the focus lens 112 moves from a position close to the output edge position FP_PI1 on the subject side (indicated by a star in FIG. 4) to a stop position close to the output edge position FP_PI4 on the image plane side (* in FIG. 4). Drive). The upper part of FIG. 6 shows the change of the focus lens position. A solid line indicates an actual focus lens position, and a broken line indicates a focus lens position as a target position given by the lens CPU 111 (hereinafter referred to as a target focus lens position). In addition, three changes in the middle stage of FIG. 6 show changes in the output of the reset sensor group 121 (photo interrupters PI-a, PI-b, and PI-c). Furthermore, the lower part of FIG. 6 shows switching between non-prohibition (non-limitation, permission) / prohibition (limitation) of the step-out determination of the step-out detection unit 115.

  At time T0, coil energization to the stepping motor 113 is started. At this time, when the exciting coil having a phase delayed from the rotor in the motor driving direction is excited, the rotor is pulled back in the direction opposite to the motor driving direction. This phenomenon occurs when a stable phase of the rotor exists in the vicinity of the stop position at the time of the previous drive.If the power is turned off after reaching the stop position, the rotor is attracted to the stable phase, and the position is shifted from the stop position. This is due to the phenomenon of minute rotation. As a result, the focus lens 112 moves in the direction opposite to the original driving direction and passes through the output edge position FP_PI1 of the photo interrupter PI-a at time T1. For this reason, the output of the photo interrupter PI-a changes from L to H.

  Subsequently, when the rotor starts to rotate in the motor driving direction, the focus lens 112 passes through the output edge position FP_PI1 again at time T2, so that the output of the photo interrupter PI-a changes from H to L.

  Thereafter, the focus lens 112 is further driven to the subject side, passes the output edge position FP_PI3 of the photo interrupter PI-a at time T4, and further reaches the stop position at time T5, the driving of the stepping motor 113 is stopped. The During time T5 to T10, the coil energization is held to stabilize the rotor in this stopped state. Although application of the drive pulse signal to the exciting coil is completed at time T5, the rotor is vibrated by the inertial force and detent torque of the rotor. Due to this vibration, the focus lens 112 temporarily moves further to the subject side than the stop position, and passes the output edge position FP_PI4 of the photo interrupter PI-b at time T6. Further, at time T7, the output edge position FP_PI4 'of the photo interrupter PI-c is passed. Since the coil energization is maintained, the focus lens 112 is pulled back to the stop position side, passes through the output edge position FP_PI4 ′ again at time T8, and passes again through the output edge position FP_PI4 at time T9. . At the subsequent time T10, the holding of the coil energization ends.

  The step-out detection unit 115 takes off the drive section (time T0 to T3) from the drive start position where the coil energization to the stepping motor 113 is started until the coil energization for the four pulses, which is the predetermined number of pulses described above, is completed. Prohibits key judgment. Further, the step out determination is also prohibited in the drive section (time T5 to T10) from when the coil energization of the four drive pulse signals before the stop position is started until the coil energization is stopped. That is, for the stepping motor 113, the driving state at times T0 to T3 and the driving state at times T5 to T10 are specific driving states.

  The focus lens position is estimated based on the output pattern of the reset sensor group 121 at this time. Since the output pattern at time T0 is L, H, and L, the focus lens position is considered to be between the output edge positions FP_PI2 to FP_PI3.

  At time T1, the output pattern changes to H, H, and L, and at time T2, the output pattern returns to L, H, and L. The output pattern changes to H, H, and L at time T4, changes to H, L, and L at time T6, and further changes to H, L, and H at time T7. Thereafter, the output pattern changes to H, L, L at time T8, and then returns to H, H, L at time T9.

  Here, a method of specifying the output edge position where the focus lens 112 is actually positioned when the motor driving direction is the subject direction will be described. The output of the photo interrupter PI-a changes from L to H when the focus lens position reaches the output edge position FP_PI3 or FP_PI7. At this time, if the output of the photo interrupter PI-c is L, the focus lens 112 is positioned at the output edge position FP_PI3, and if the output of the photo interrupter PI-c is H, the focus lens 112 is positioned at the output edge position FP_PI7.

  The output of the photo interrupter PI-a changes from H to L when the focus lens position reaches the output edge position FP_PI1 or FP_PI5. At this time, if the output of the photo interrupter PI-c is L, the focus lens 112 is positioned at the output edge position FP_PI1, and if the output of the photo interrupter PI-c is H, the focus lens 112 is positioned at the output edge position FP_PI5.

  The output of the photo interrupter PI-b changes from L to H when the focus lens position reaches the output edge position FP_PI2 or FP_PI6. At this time, if the output of the photo interrupter PI-c is L, the focus lens 112 is positioned at the output edge position FP_PI2, and if the output of the photo interrupter PI-c is H, the focus lens 112 is positioned at the output edge position FP_PI6.

  Further, when the output of the photo interrupter PI-b changes from H to L, the focus lens 112 is positioned at the output edge position FP_PI4. Similarly, when the output of the photo interrupter PI-c changes from L to H, the focus lens 112 is positioned at the output edge position FP_PI4 ′.

  From the above, the focus lens position (first position information) specified (detected) at times T1 to T9 is as follows.

  At time T1, since the motor drive direction is the subject direction, the detected focus lens position is FP_PI3 (however, it is actually located at FP_PI1). At time T2, since the output of the photo interrupter PI-a changes from H to L and the motor driving direction is the subject direction, the focus lens position is FP_PI1 or FP_PI5. However, since the output of the photo interrupter PI-c is L, the detected focus lens position is FP_PI1.

  At time T4, since the output of the photo interrupter PI-a changes from L to H, the detected focus lens position is FP_PI3. At time T6, since the output of the photo interrupter PI-b changes from H to L, the detected focus lens position is FP_PI4. At time T7, since the output of the photo interrupter PI-c changes from L to H, the detected focus lens position is FP_PI4 ′.

  At time T8, since the output of the photo interrupter PI-c changes from H to L, the detected focus lens position is FP_PI4 ′. At time T9, the output of the photo interrupter PI-b changes from L to H and the motor driving direction is the subject direction, so the focus lens position is FP_PI2 or FP_PI6. However, since the output of the photo interrupter PI-c is L, the detected focus lens position is FP_PI2 (however, it is actually FP_PI4).

  Thus, the focus lens position is erroneously detected at time T1 and time T9. For this reason, when the step-out determination is performed based on the focus lens position erroneously detected at the time T1 and the time T9, a determination result that the step-out has occurred is obtained even though the step-out has not occurred. However, in this embodiment, the time T1 and the time T9 are included in the drive section in the specific drive state described above. That is, step-out determination based on the focus lens position erroneously detected at time T1 and time T9 is not performed. For this reason, erroneous determination of step-out can be prevented.

  FIG. 7 shows a focus drive process performed by the lens CPU 111 that has received a focus drive command issued by the camera CPU 131. The lens CPU 111 executes this processing in accordance with a focus drive program that is a computer program. The focus drive program includes a stepping motor drive state detection program for performing step-out determination of the stepping motor 113.

  In step S101, the lens CPU 111 receives a focus drive command from the camera CPU 131. The lens CPU 111 performs the following various settings in accordance with the received focus drive command and the current drive state of the focus lens 112, and controls the drive of the stepping motor 113 via the focus drive circuit 114.

  In step S102, the lens CPU 111 sets the drive speed of the stepping motor 113 in accordance with the focus drive command. For example, the drive speed is set so that the image plane moving speed due to the movement of the focus lens 112 during moving image capturing is constant.

  Next, in step S103, the lens CPU 111 sets the power rate of the drive pulse signal applied to the stepping motor 113. When the load torque applied to the stepping motor 113 changes according to the focus lens position, the speed fluctuation due to the load torque does not occur, and the driving sound does not become loud in moving image capturing that wants to suppress the driving sound. The power rate is set according to the imaging conditions.

  In step S104, the lens CPU 111 sets the drive amount of the stepping motor 113. In this embodiment, since the relative position of the focus lens 112 is driven, the lens CPU 111 sets a drive amount (target drive pulse number of the stepping motor 113) from the focus lens position when the focus drive command is issued. When absolute position driving of the focus lens 112 is performed, the driving amount is set so that the focus lens 112 moves to a designated position.

  Next, in step S <b> 105, the lens CPU 111 starts driving of the stepping motor 113 by giving a control signal to the focus driving circuit 114 and applying a driving pulse signal to the stepping motor 113.

  Next, in step S <b> 200, the lens CPU 111 sets permission (non-restriction) / prohibition (restriction) of step-out determination by the step-out detection unit 115. Details of the processing here will be described later. The lens CPU 111 having set permission / prohibition of the step-out determination proceeds to step S106.

  In step S <b> 106, the lens CPU 111 determines whether an output edge of the reset sensor group 121 (hereinafter referred to as a sensor output edge) is detected by the movement of the focus lens 112. If a sensor output edge is detected, the process proceeds to step S110, and if not detected, the process proceeds to step S107. In the following description, a focus lens position where a sensor output edge is detected is referred to as a sensor output edge position.

  In step S107, the lens CPU 111 determines whether or not the focus lens 112 has reached the stop position. In this embodiment, there is no means for detecting the absolute position of the focus lens 112 except for the reset position detectable by the reset sensor group 121. Therefore, the lens CPU 111 counts the number of driving pulses applied to the stepping motor after starting the driving of the stepping motor 113 in step S105, and stops when the count value matches the target driving pulse number up to the stop position. Judgment of reaching position. If the stop position has been reached, the process proceeds to step S109. If not, the process proceeds to step S108.

  In step S108, the lens CPU 111 updates the driving information of the stepping motor 113. Here, the drive amount of the stepping motor 113 is updated. If the driving requires acceleration / deceleration, the speed change timing is determined and the driving speed of the stepping motor 113 is changed. Furthermore, the lens CPU 111 also changes the power rate according to the changed drive information. Thereafter, the lens CPU 111 returns to step S200.

  In step S <b> 109, since the focus lens 112 has reached the stop position, the lens CPU 111 performs energization holding for the excitation coil of an arbitrary phase in the stepping motor 113. Then, after the energization holding is performed for a predetermined time, the energization is stopped and the present process is terminated.

  In step S110, the lens CPU 111 acquires the output pattern of the reset sensor group 121 and the motor drive direction, and specifies the sensor output edge position reached by the focus lens 112.

  In step S111, the lens CPU 111 causes the step-out detection unit 115 to perform calculation for step-out determination. That is, the difference value between the number of drive steps (first position information) corresponding to the sensor output edge position specified in step S110 and the current drive pulse accumulated value (second position information) managed by the lens CPU 111 is obtained. Let it be calculated.

  In step S112, the lens CPU 111 causes the step-out detection unit 115 to compare the difference value calculated in step S111 with the step-out determination threshold value. The step-out detection unit 115 determines that step-out has occurred if the difference value is greater than the step-out determination threshold. If step out determination is prohibited in step S200, the step out detection unit 115 does not determine that step out has occurred even if the difference value is greater than the step out determination threshold. The lens CPU 111 proceeds to step S113 if the step-out detection unit 115 determines that step-out has occurred, and proceeds to step S107 otherwise.

  In step S113, the lens CPU 111 discards the current focus drive command. Since the position of the focus lens 112 cannot be managed because the stepping motor 113 has stepped out, the current focus driving command is discarded and the stepping motor 113 is stopped.

  In step S <b> 114, the lens CPU 111 issues a reset processing request to the camera CPU 131. The camera CPU 131 that has received the reset processing request issues a reset processing command to the lens CPU 111, and the lens CPU 111 that has received this request performs reset processing again as recovery processing for the step-out. Thereafter, the lens CPU 111 ends the process through step S114.

  Next, the step-out determination permission / prohibition setting process performed by the lens CPU 111 in step S200 in FIG. 7 will be described with reference to the flowchart in FIG.

  In step S201, the lens CPU 111 determines whether the reset process has been completed. Since the position of the focus lens 112 cannot be managed unless the reset process is completed, the process proceeds to step S207, and step-out determination is prohibited. On the other hand, if the reset process is completed, the process proceeds to step S202.

In step S202, the lens CPU 111 calculates the number of driven pulses that is the difference between the current focus lens position and the focus lens position at the start of driving the focus lens 112 (stepping motor 113). Then, it is determined whether or not the number of driven pulses is equal to or greater than the threshold Th ₁ (= 4 pulses) as the predetermined number of pulses described above. Here, it is determined whether or not it is in a drive section (that is, a specific drive state) where an unnecessary reversal operation occurs when the stepping motor 113 starts to be driven. Lens CPU111, the step as a number of drive already pulse proceeds to step S203 if not effect of unwanted inversion operation if the threshold value Th ₁ or more, there may be effects of unwanted inversion operation if the number of drive already pulses is smaller than the threshold value Th ₁ Proceeding to S207, step-out determination is prohibited.

In step S203, the lens CPU 111 determines that the difference between the current focus lens position and the target focus lens position that is the stop position, that is, the number of undriven pulses is equal to or greater than the threshold Th ₂ (= 4 pulses) as the predetermined number of pulses described above. Determine if there is. Here, it is determined whether or not it is in a drive section (that is, a specific drive state) in which an unnecessary reverse operation occurs before the stepping motor 113 stops driving. Lens CPU111, the step as the non-driving pulse number proceeds to step S204 if not effect of unwanted inversion operation if the threshold value Th ₂ or more, there may be effects of unwanted inversion operation if undriven pulse number is smaller than the threshold value Th ₂ Proceeding to S207, step-out determination is prohibited.

In step S204, the lens CPU 111 determines whether or not the driving speed of the stepping motor 113 is equal to or higher than the predetermined speed Spd _th (= 200 pps) described above. Here, it is determined whether or not the low-speed driving state (that is, the specific driving state) in which intermittent driving due to the detent torque of the stepping motor 113 is likely to occur. Lens CPU111, the drive speed of the step S205 if the predetermined speed _{Spd th} or more, the process proceeds to step S207 as easily intermittent driving occurs if slower than the predetermined speed _{Spd th,} prohibits the step-out determination.

  In step S205, the lens CPU 111 determines whether or not the current driving of the focus lens 112 is in the wobbling driving state (specific driving state). Then, if the current driving state is not the wobbling driving state, the lens CPU 111 proceeds to step S206. On the other hand, if the current driving state is the wobbling driving state, the process proceeds to step S207 because it is not suitable for the step-out determination, and the step-out determination is prohibited.

  In step S <b> 206, the lens CPU 111 permits the step-out determination in the step-out detection unit 115. That is, when the step-out is detected in step S112 in FIG. 7, the lens CPU 111 is notified of the step-out. Then, this process ends.

  As described above, in this embodiment, the step-out determination is limited when the stepping motor 113 is in the specific drive state, so that it is possible to avoid erroneous detection (error determination) of the occurrence of step-out.

In the present embodiment, the case where the step-out detection unit 115 as the stepping motor driving state detection device is provided in the interchangeable lens 110 of the interchangeable lens camera system has been described. However, the stepping motor driving is performed in the lens-integrated camera (optical device). A state detection device may be provided.
(Other examples)
The present invention supplies a program that realizes one or more functions of the above-described embodiments to a system or apparatus via a network or a storage medium, and one or more processors in a computer of the system or apparatus read and execute the program This process can be realized. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

  Each embodiment described above is only a representative example, and various modifications and changes can be made to each embodiment in carrying out the present invention.

112 Focus lens 113 Stepping motor 115 Step-out detection unit 121 Reset sensor

Claims (10)

First position acquisition means for acquiring first position information of the driven member based on a signal from a position detection means for detecting the position of the driven member driven by the stepping motor;
Second position acquisition means for acquiring second position information of the driven member based on a count value of the number of pulses of the drive pulse signal applied to the stepping motor;
A step-out detecting means for detecting step-out of the stepping motor by comparing the first position information and the second position information;
The step-out detection means limits the detection of the step-out when the stepping motor is in a specific drive state.   The said specific drive state is a state driven by application of the drive pulse signal of a predetermined number of pulses at least one of when the stepping motor starts driving and before driving stops. Stepping motor drive state detection device.   3. The stepping motor drive state detection device according to claim 1, wherein the specific drive state is a state in which a reversal operation in a direction opposite to a drive direction occurs due to a detent torque in the stepping motor.   The stepping motor drive state detection device according to claim 1, wherein the specific drive state is a state in which a drive speed of the stepping motor is lower than a predetermined speed.   The stepping motor drive state detection device according to claim 1, wherein the specific drive state is a state in which energization of the stepping motor is maintained in a stop sequence of the stepping motor. The stepping motor drive state detection device according to any one of claims 1 to 5,
An optical apparatus, wherein the driven member is an optical member.   The optical apparatus according to claim 6, wherein the optical member is a focus element that adjusts a focus state of an optical system.   The optical apparatus according to claim 7, wherein the specific drive state is a state in which the stepping motor repeats reciprocating drive of the focus element by a predetermined drive amount.   The optical apparatus according to claim 7, wherein the specific drive state is changed according to a position of the focus element or a zooming state of the optical system. A computer program for causing a computer to execute processing for detecting stepping motor step-out,
The process is
Processing for obtaining first position information of the driven member based on a signal from a position detecting means for detecting the position of the driven member driven by the stepping motor;
A process of obtaining second position information of the driven member based on a count value of the number of pulses of the driving pulse signal applied to the stepping motor;
A detection process for detecting step-out of the stepping motor by comparing the first position information and the second position information;
The detection process restricts detection of the step-out when the stepping motor is in a specific driving state.