JP2005333740A - Control method of stepping motor, control device of stepping motor, focus position control method of lens and focus position control device of lens - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control method of a stepping motor which can control an excitation voltage at phase excitation changing time, which does not have a torque loss, and which suppresses generation of a vibration or a noise and to provide a controller of the stepping motor, a focus position control method of a lens and a focus position controller of the lens. <P>SOLUTION: The excessive response of the rotor or the stepping motor is suppressed by controlling an excitation voltage at the duty ratio at standing up or falling of the excitation voltage of the stepping motor. The rotation of the stepping motor can be controlled smoothly controllable, and silencing at the rotation drive time can be performed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a stepping motor control method, a stepping motor control device, a lens focal position control method, and a lens focal position control device.

  In general, in an imaging apparatus such as a digital camera equipped with a zoom lens, the variable power lens is driven by a DC motor, and the focus lens is driven by a stepping motor. In a digital camera having a recording function, the driving of the stepping motor is controlled in order to reduce the vibration and noise of the stepping motor during focusing.

With respect to a method for controlling the driving of such a stepping motor, a technique is disclosed in which a multistage step control is possible by applying a sine waveform excitation voltage to each phase of the stepping motor to smooth the rotor transition (see FIG. For example, see Patent Document 1).
In addition, a technique has been disclosed that realizes noise reduction by applying an excitation voltage with a trapezoidal waveform when driving a stepping motor at a low speed, and applying an excitation voltage with a rectangular waveform when driving at a high speed (for example, , See Patent Document 2).
Japanese Patent Publication No. 52-24649 Japanese Patent Publication No.53-25085

However, according to the method for controlling the driving of the stepping motor disclosed in Patent Document 1, the output torque of the stepping motor is reduced as compared with the case where the excitation voltage is applied with a rectangular waveform, and thus a larger motor is required. This hinders downsizing of the apparatus.
Further, according to the method for controlling the driving of the stepping motor disclosed in Patent Document 2, although there is an effect of noise reduction in the low speed range, there is a problem that vibration and noise cannot be prevented in the high speed range.

  In order to solve the above problems, the invention according to claim 1 is a method of controlling a stepping motor driven by a pulsed excitation voltage, wherein the excitation voltage at the time of rising or falling of the excitation voltage is represented by a duty ratio. Control is performed by a control method.

  According to a second aspect of the present invention, in the stepping motor control method of the first aspect, the excitation voltage is controlled by a duty ratio control method in which the duty ratio gradually increases with time when the excitation voltage rises. The excitation voltage control at the fall of the excitation voltage is performed by a duty ratio control method in which the duty ratio gradually decreases with time.

  According to a third aspect of the present invention, in the stepping motor control method according to the first or second aspect, the pulse frequency during the duty ratio control is higher than the self-starting frequency.

  According to a fourth aspect of the present invention, in the stepping motor control method according to any one of the first to third aspects, the excitation voltage is applied continuously for a self-start limit pulse period.

  According to a fifth aspect of the present invention, in the control device for the stepping motor driven by the pulsed excitation voltage, the control means for controlling the excitation voltage at the rise or fall of the excitation voltage by a duty ratio control method. It is provided with.

  According to a sixth aspect of the present invention, in the stepping motor control device according to the fifth aspect of the present invention, the control means controls the excitation voltage when the excitation voltage rises, and the duty ratio gradually increases with time. The control is performed using a ratio, and the excitation voltage is controlled at a duty ratio that gradually decreases with time when the excitation voltage falls.

  A seventh aspect of the present invention is the stepping motor control device according to the fifth or sixth aspect, further comprising means for setting a pulse frequency higher than a self-starting frequency when the excitation voltage is duty ratio controlled. Features.

  An eighth aspect of the present invention is the stepping motor control device according to any one of the fifth to seventh aspects, further comprising means for applying an excitation voltage continuously for a self-start limit pulse period. Features.

  According to a ninth aspect of the present invention, in the lens focal position control method using a stepping motor driven by a pulsed excitation voltage, the excitation voltage at the rise or fall of the excitation voltage is represented by a duty ratio control system. It is controlled by.

  According to a tenth aspect of the present invention, in the lens focal point position control method according to the ninth aspect, the excitation voltage is controlled by a duty ratio control method in which the duty ratio gradually increases with time when the excitation voltage rises. The excitation voltage is controlled at the fall of the excitation voltage by a duty ratio control method in which the duty ratio gradually decreases with time.

  According to an eleventh aspect of the present invention, in the lens focus position control method according to the ninth or tenth aspect, a pulse frequency during the duty ratio control is higher than a self-starting frequency.

  A twelfth aspect of the present invention is the lens focal point position control method according to any one of the ninth to eleventh aspects, wherein the excitation voltage is applied continuously for a self-start limit pulse period. To do.

  According to a thirteenth aspect of the present invention, in the lens focal position control device driven by a pulsed excitation voltage, the excitation voltage is controlled by a duty ratio control method when the excitation voltage rises or falls. Means are provided.

  According to a fourteenth aspect of the present invention, in the lens focal position control device according to the thirteenth aspect, the control means controls the excitation voltage when the excitation voltage rises, and the duty ratio gradually increases with time. Control is performed with a duty ratio, and control of the excitation voltage at the fall of the excitation voltage is performed with a duty ratio that gradually decreases with time.

  According to a fifteenth aspect of the present invention, in the lens focus position control device according to the thirteenth or fourteenth aspect, the pulse frequency when the duty ratio of the excitation voltage is controlled is set to be higher than the self-starting frequency. It is characterized by.

  According to a sixteenth aspect of the present invention, in the lens focus position control device according to any one of the thirteenth to fifteenth aspects, the lens focal position control device further comprises means for applying an excitation voltage continuously for a self-start limit pulse period. It is characterized by.

  According to the first and second aspects of the present invention, since the excitation voltage is controlled by the duty ratio control method at the time of rising or falling of the excitation voltage, the rising characteristic or the falling of the excitation voltage can be adjusted by adjusting the duty ratio. The characteristics can be smoothed. Therefore, it is possible to suppress a steep change in the rise or fall of the excitation voltage, and it is possible to suppress the generation of vibration and noise caused by the stepping motor.

  According to the third aspect of the present invention, the rotation of the stepping motor at the specified rotation angle accompanying the change in the excitation voltage is suppressed. Therefore, an excessive transition response of the rotor can be prevented to enable smooth rotation, and generation of vibration and noise due to the stepping motor can be suppressed.

  According to the fourth aspect of the present invention, the excitation voltage application time is a time required for the control by the duty ratio control method and a time required for the rotation by the specified rotation angle of the stepping motor. Therefore, it is possible to suppress the occurrence of torque loss when the excitation voltage changes, and the drive control of the stepping motor can be performed without attenuation.

  According to the fifth and sixth aspects of the present invention, since the excitation voltage is controlled by the duty ratio control method at the rising or falling of the excitation voltage, the rising characteristic or the falling of the excitation voltage can be adjusted by adjusting the duty ratio. The characteristics can be smoothed. Therefore, it is possible to suppress a steep change in the rise or fall of the excitation voltage, and it is possible to provide a device that suppresses the generation of vibration and noise caused by the stepping motor.

  According to the seventh aspect of the present invention, the rotation of the stepping motor at the specified rotation angle accompanying the change in the excitation voltage is suppressed. Therefore, an excessive shift response of the rotor can be prevented to enable smooth rotation, and a device that suppresses generation of vibration and noise caused by the stepping motor can be provided.

  According to the eighth aspect of the present invention, the excitation voltage application time is the time required for control by the duty ratio control method and the time required for rotation by the specified rotation angle of the stepping motor. Therefore, it is possible to suppress the occurrence of torque loss even when the excitation voltage changes, and the control device for the stepping motor can be reduced in size.

  According to the ninth and tenth aspects of the present invention, since the excitation voltage is controlled by the duty ratio control method at the time of rising or falling of the excitation voltage, the rising characteristic or the falling of the excitation voltage is adjusted by adjusting the duty ratio. The characteristics can be smoothed. Therefore, it is possible to suppress a steep change in the rise or fall of the excitation voltage, and it is possible to control the lens focus position in which the generation of vibration and noise due to the stepping motor is suppressed.

  According to the eleventh aspect of the present invention, the rotation of the stepping motor at the specified rotation angle accompanying the change of the excitation voltage is suppressed. Therefore, it is possible to smoothly rotate the rotor by preventing an excessive shift response of the rotor, and it is possible to control the lens focus position in which generation of vibration and noise due to the stepping motor is suppressed.

  According to the twelfth aspect of the invention, the excitation voltage application time is a time required for the control by the duty ratio control method and a time required for the rotation by the specified rotation angle of the stepping motor. Accordingly, it is possible to suppress the occurrence of torque loss when the excitation voltage changes, and it is possible to control the lens focal position by controlling the driving of the stepping motor without attenuation.

  According to the invention described in claims 13 and 14, since the excitation voltage is controlled by the duty ratio control method at the time of rising or falling of the excitation voltage, the rising characteristic or the falling of the excitation voltage is adjusted by adjusting the duty ratio. The characteristics can be smoothed. Therefore, it is possible to provide a lens focus position control device that can suppress a steep change in the excitation voltage rise or fall, and that suppresses the occurrence of vibration and noise caused by the stepping motor.

  According to the fifteenth aspect of the present invention, the rotation of the stepping motor at the specified rotation angle accompanying the change in the excitation voltage is suppressed. Therefore, it is possible to provide a lens focal position control device that prevents an excessive displacement response of the rotor and enables smooth rotation and suppresses the generation of vibration and noise caused by the stepping motor.

According to the sixteenth aspect of the present invention, the excitation voltage application time is the time required for control by the duty ratio control method and the time required for rotation by the specified rotation angle of the stepping motor. Therefore, even if the excitation voltage changes, it is possible to suppress the occurrence of torque loss, and it is not necessary to increase the size of the stepping motor, so that the lens focal position control device can be reduced in size.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
First, the configuration of the lens focal position control device according to the present invention will be described.
FIG. 1 shows an example of the overall configuration of a lens focal position control apparatus 1 according to the present embodiment.

  As shown in FIG. 1, the lens focal position control device 1 includes a microcomputer 2 and a motor drive IC 3 that outputs a pulsed excitation voltage based on a signal input via an output control unit 24 of the microcomputer 2. The image is formed through the stepping motor 4 driven by the magnetic field generated by the excitation voltage input from the motor drive IC 3, the focusing lens 51 that moves linearly by the rotation of the stepping motor 4, and the focusing lens 51. An image sensor 6 such as a CCD (Charge Coupled Devices) that converts the subject image into an electrical signal, and a lens focus position detector 7 that detects the lens focus position by detecting the image formation state of the image sensor 6. Composed.

  The microcomputer 2 includes a CPU 21 having an arithmetic unit 211, an input control unit 22, a memory 23, an output control unit 24, and the like. In the CPU 21, based on the lens focal position data input from the input control unit 22, the duty ratio at the rise or fall of the excitation voltage is calculated in cooperation with the application program stored in the memory 23. The A pulsed excitation voltage based on the calculated value is output from the output control unit 24, and input terminals in1, in2, and in3 of the motor drive IC 3 connected to the output terminals a, b, c, and d of the output control unit 24, respectively. , In4.

  The motor drive IC 3 and the stepping motor 4 will be described later with reference to FIGS.

  The lens unit 5 includes a focusing lens 51 provided facing the light receiving surface of the image sensor 6. The focusing lens 51 is supported by a lens support 52 so as to be linearly movable in the optical axis direction. At the upper end of the lens support 52, there is a slider 54 that fits into a slide bar 53 disposed in the optical axis direction of the focusing lens 51. A screwing portion 55 is provided at the lower end portion of the lens support 52, and this screwing portion 55 is screwed to a lead screw portion formed on the rotor output shaft 41 of the stepping motor 4, and as the stepping motor 4 rotates. Thus, the focusing lens 51 is linearly moved in the optical axis direction of the focusing lens 51 to adjust the focus.

  The lens focal position detection unit 7 calculates a contrast value based on the electric signal input from the image sensor 6 and detects the lens position. The position where the contrast value is the highest is the lens focal position of the focusing lens. The calculated contrast value is input to the input control unit 22.

  FIG. 2 shows a circuit configuration diagram of the motor drive IC 3 and the stepping motor 4. FIG. 3 is a truth table of the motor drive IC 3. The transistors Q1, Q2, Q3, Q4 are turned on or off corresponding to the signal logic of the input signals inputted to the input terminals in1, in2, in3, in4 of the motor drive IC3, and the control unit 31 corresponding to the state. The control unit 32 operates, and a signal due to the operation is applied to the bases of the transistors TR11, TR12, TR21, TR22, TR31, TR32, TR41, and TR42 of the inverter to perform switching control. As a result, as shown in the truth table of FIG. 3, the excitation voltage is output from the output terminals out1, out2, out3, and out4.

  FIG. 4 shows an excitation pattern and a waveform diagram in the rotation direction when the stepping motor 4 is driven by two-layer excitation. A state in which High (logic 1), Low (logic 0), Low (logic 0), and High (logic 1) are input to the terminals A +, A−, B +, and B− of the coil A phase and B phase, respectively, is digital. This is represented by (1001) as a signal string, which is an excitation pattern P1. Similarly, the excitation pattern P2 is (1010), the excitation pattern P3 is (0110), and the excitation pattern P4 is (0101). Each excitation pattern is stored in the memory 23. When the stepping motor 4 changes the excitation state in the order of the excitation pattern P1, the excitation pattern P2, the excitation pattern P3, the excitation pattern P4, the excitation pattern P1,..., The rotor rotates in the forward rotation direction, and the excitation pattern P1, When the excitation state changes in the order of excitation pattern P4, excitation pattern P3, excitation pattern P2, excitation pattern P1,..., The rotor rotates in the reverse direction.

  Each time the excitation pattern changes once, such as the excitation pattern P1 to the excitation pattern P2 in FIG. 4, the rotor of the stepping motor 4 rotates by a specified rotation angle. The reciprocal of the time interval of rotation for the specified rotation angle is set as the driving frequency of the stepping motor 4. In addition, PPS is displayed as a pulse rate indicating that the change of the excitation state is one pulse and the drive frequency is represented by the number of pulses per second.

Next, a lens focal position control method according to the present embodiment will be described.
5, 6 and 7 show examples of lens focal position control algorithms.

As shown in FIG. 5, when the lens position of the focusing lens 51 is detected by the lens focus position detection unit 7 and the detected value is input to the input control unit 22 (step S1), the input control unit 22 It is determined from the contrast value whether the aligning lens 51 is at the lens focal position (step S2). If the focusing lens 51 is at the lens focal position (S2: Yes), the process proceeds to step S28, and since the focusing lens 51 is at the lens focal position, the driving of the stepping motor 4 is stopped, and the algorithm ends.
If it is not at the focal position (S2: No), the process proceeds to step S3. In step S3, the rotation direction of the stepping motor 4 necessary for moving the focusing lens 51 to the focal position is determined. If forward rotation is necessary (S3: Yes), the process proceeds to step S4. If reverse rotation is necessary (S3: No), the process proceeds to step S16.

  In step S4, focusing is started, and the microcomputer 2 reads the excitation pattern P1 and the excitation pattern P2 from the memory 23, and sets O1 = P1 and O2 = P2 in the output information O1 and O2 to the output terminal, respectively. The stepping motor 4 is in the excitation state of the excitation pattern P1 when O1 is output, and is in the excitation state of the excitation pattern P2 when O2 is output.

  When the phase excitation changes, the excitation voltage is duty ratio controlled at the time of rising or falling (step S5).

Before describing the duty ratio control of the excitation voltage, the relationship between the torque and the pulse rate in the stepping motor will be described with reference to FIG. A pulse rate capable of starting the rotation of the rotor completely in a one-to-one correspondence under a certain use load is defined as a self-start limit pulse rate, and a region inside the self-start limit pulse rate curve is set as a self-start region.
Also, the use pulse rate for starting the rotor at a certain use load is generally set to 50 to 80% of the self-start range pulse rate, but after the stepping motor starts rotating, the pulse rate is bypassed. The rotor can be driven at a high pulse rate by increasing to the region.

  In FIG. 8, the use condition of the motor according to the present invention is exemplified by the use condition of the motor in which the self-start limit pulse rate at a certain use load is x (PPS) and the use pulse rate is 50% (0.5x) of the self-start limit pulse rate. A method for switching the phase excitation will be described.

If the time per pulse of the self-start limit pulse rate (the time of the self-start limit pulse period) is T1, Tl = 1 / x, and if the time per pulse of the used pulse rate is Tu, Tu = 1 / 0.5x.
In order to generate a torque that satisfies the use load by starting the stepping motor, it is necessary to apply excitation for a minimum Tl time, and there is a margin of (Tu−Tl) compared to the excitation time of the use pulse. In the present invention, using this time, phase excitation is switched step by step using the duty ratio, and then the Tl time excitation voltage is continuously applied to switch the phase excitation of the stepping motor.

  Next, the duty ratio control of the excitation voltage will be described with reference to FIGS. FIG. 9 shows an excitation pattern and an excitation voltage waveform diagram when the duty ratio of the excitation voltage is controlled. In addition, the subroutine shown by step S5, step S8, step S11, step S14, step S17, step S20, step S23, step S26 shown in FIG. 5, FIG. 6 is the algorithm shown in FIG. Hereinafter, a method of stepwise switching the phase excitation using the duty ratio will be described by taking the duty ratio to be changed nine times from 10% to 10% as an example. The time T per pulse of the pulses used at this time is T = (Tu−Tl) / 10. During this time per pulse, the phase excitation of the stepping motor can be switched, but the rotation at the specified rotation angle does not occur.

  In step S51, n (n = T / 10) is set in the counter C. Subsequently, D1 = C is set as the delay time D1 (step S52), and D2 = (TC) is set as the delay time D2 (step S53). Subsequently, O2 is output by the microcomputer 2 (step S54), and the excitation voltage is applied with the excitation pattern of O2 during the delay time D1 (step S55). In step S4, since the excitation pattern P2 is set in O2, the excitation pattern P2 is applied for 10% of the time T per pulse.

  In step S56, O1 is output by the microcomputer 2 (step S56), and the excitation voltage is applied in the excitation pattern of O1 during the delay time D2 (step S57). In step S4, since the excitation pattern P1 is set in O1, the excitation pattern P1 is applied for 90% of the time T per pulse.

  In step S58, (C + n) is set in the counter C. As a result, a value that increases 10% of the time T per pulse is set in the counter C. In step S59, the value of C is compared with the value of (T−n). If C is large, the process proceeds to step S60, and if C is small, the process returns to step S52.

  When returning to step 52, 20% of the time T per pulse is set as the delay time D1 (step S52), and 80% of the time T per pulse is set as the delay time D2 (step S52). S53). Therefore, the excitation pattern P2, which is the previous phase excitation pattern that changes in step S55, is applied for 20% of the time T per pulse, and the excitation pattern P1, which is the phase excitation pattern before the change in step S57, is 1. It is applied for 80% of the time T per pulse.

  By repeating step 52 to step 59 in this manner, the application time of the previous phase excitation pattern to be changed increases from 10% to 90% in 10% increments, and the application time of the phase excitation pattern before the change is from 90%. Decrease in increments of 10% to 10%. This corresponds to the first half of the excitation pattern P2 in FIGS. 9 (a) and 9 (b). By controlling the excitation pattern with the duty ratio, the rising characteristic or falling characteristic of the excitation voltage becomes smooth.

  In step S60, the microcomputer 2 outputs O2. Since the excitation pattern P2 is set in O2 in step S4, the excitation pattern P2 set in O2 in step S61 is applied for a delay time Tl. This corresponds to the self-start limit pulse cycle time, and after the phase excitation switching is completed, the process proceeds to step S6 (FIG. 5). This corresponds to the latter half of the excitation pattern P2 in FIGS. 9 (a) and 9 (b).

  In step S6, it is determined whether or not the focusing lens 51 is in the focal position. If it is determined that it is not in the focal position, the process proceeds to step S7. If it is determined that it is in the focal position, the process proceeds to step S28, and the driving of the stepping motor 4 is stopped.

  In step S7, the microcomputer 2 reads the excitation pattern P2 and the excitation pattern P3 from the memory 23, and sets O1 = P2 and O2 = P3 in the output information O1 and O2 to the output terminal, respectively. Steps S7 to S9 are the same as steps S4 to S6 except that the phase excitation patterns are different. Similarly, Step S10 to Step S12 and Step 13 to Step S15 correspond to Step S7 to Step S9, except that the phase excitation pattern is different.

  Steps S16 to S27 when reverse rotation is necessary also correspond to steps S4 to S15, except that the phase excitation patterns set in the output information O1 and O2 to the output terminal are different.

  FIG. 10 is a characteristic diagram of the time change of the specified rotation angle θ when the phase excitation of the stepping motor is switched.

  When the phase excitation is switched by a rectangular wave, the rotor overshoots after the rising time t when the rotor reaches the specified rotation angle θ, as indicated by the solid line R, and stops by repeating the inherent damping vibration. As the rise time t is shorter and the step angle θ is larger, a reaction force accompanying the rotation of the rotor is generated in the stepping motor, so that vibration and noise are generated. In particular, when the stepping motor is driven at a low speed, the reaction force generated each time the rotation and stop of the rotor are repeated increases, and the generation of vibration and noise also increases.

  However, according to the present invention, the excitation voltage is the time per pulse when the phase excitation is switched but the specified rotation angle of the rotor does not rotate, and the duty ratio is changed stepwise. Accumulated in stages and released in stages at the time of falling, excessive response of the rotor can be suppressed, and a transition indicated by a broken line S can be realized. Therefore, the rotation of the stepping motor 4 can be controlled smoothly, and noise reduction during rotation driving can be achieved.

  In addition, since the excitation voltage is applied continuously for the self-start limit pulse period, a sufficient torque can be generated for the load used.

  Further, since no special circuit configuration or IC is required when carrying out the control of the present invention, it is possible to reduce the size and cost of the apparatus.

The embodiment of the present invention has been described above. However, the description in the above embodiment is an example of the lens focal position control method according to the present invention, and the present invention is not limited to this.
For example, in the present invention, the case of two-phase excitation has been described, but similar control is possible even in the case of 1-2 phase excitation. In this case, since the transition angle per pulse is half that of the two-phase excitation, further noise reduction of the stepping motor can be achieved.

  After the rotation of the stepping motor is started, the duty ratio control is thinned out from every 10% to every 20% or 30%, etc., and the drive is shifted to high speed rotation in the through region, and the self-start limit pulse cycle It is also possible to shorten the time Tl.

1 is an overall configuration diagram of a lens focal position control apparatus to which the present invention is applied. FIG. It is a motor drive IC and a stepping motor circuit block diagram to which the present invention is applied. It is a truth table of a motor drive IC to which the present invention is applied. It is a wave form diagram which shows the excitation pattern and rotation direction of the stepping motor to which this invention is applied. It is a flowchart of the control algorithm of the lens focus position to which the present invention is applied. It is a flowchart of the control algorithm of the lens focus position to which the present invention is applied. It is a flowchart of the control algorithm of the lens focus position to which the present invention is applied. It is a characteristic view which shows the relationship between the torque of the stepping motor to which this invention is applied, and a pulse rate. It is a waveform diagram of an excitation pattern and an excitation voltage when phase excitation to which the present invention is applied changes. It is a characteristic view which shows the time change of the prescription | regulation rotation angle (theta) when the excitation state of the stepping motor to which this invention is applied changes.

Explanation of symbols

1 Lens focus position control device 1
2 Microcomputer 2
21 CPU21
211 arithmetic unit 211
22 Input control unit 22
23 Memory 23
24 Output control unit 24
3 Motor drive IC3
4 Stepping motor 4
41 Rotor output shaft 41
5 Lens unit 5
51 Focusing lens 51
52 Lens support 52
53 Slide bar 53
54 Slider 54
55 Threaded portion 55
6 Image sensor 6
7 Lens focus position detector 7

Claims (16)

In a control method of a stepping motor driven by a pulsed excitation voltage,
Controlling the excitation voltage at the rise or fall of the excitation voltage by a duty ratio control method;
Stepping motor control method characterized by the above. The stepping motor control method according to claim 1,
Control of the excitation voltage at the rise of the excitation voltage is performed by a duty ratio control method in which the duty ratio gradually increases with time,
The control of the excitation voltage at the fall of the excitation voltage is performed by a duty ratio control method in which the duty ratio gradually decreases with time,
Stepping motor control method characterized by the above. In the stepping motor control method according to claim 1 or 2,
The pulse frequency during the duty ratio control is higher than the self-starting frequency;
Stepping motor control method characterized by the above. In the control method of the stepping motor according to any one of claims 1 to 3,
Apply excitation voltage continuously for the self-start limit pulse period,
Stepping motor control method characterized by the above. In a stepping motor control device driven by a pulsed excitation voltage,
A control means for controlling the excitation voltage at the time of rising or falling of the excitation voltage by a duty ratio control method;
Stepping motor control device characterized by the above. In the control device of the stepping motor according to claim 5,
The control means controls the excitation voltage when the excitation voltage rises at a duty ratio that gradually increases with time, and controls the excitation voltage when the excitation voltage falls. Control with a duty ratio that gradually decreases with time,
Stepping motor control device characterized by the above. The stepping motor control device according to claim 5 or 6,
The pulse frequency when the duty ratio of the excitation voltage is controlled is provided with means for setting higher than the self-starting frequency,
Stepping motor control device characterized by the above. In the control device of the stepping motor according to any one of claims 5 to 7,
Provided with means for applying the excitation voltage continuously for the self-start limit pulse period,
Stepping motor control device characterized by the above. In the method for controlling the lens focal position using a stepping motor driven by a pulsed excitation voltage,
Controlling the excitation voltage at the rise or fall of the excitation voltage by a duty ratio control method;
A method for controlling the focal position of a lens. The method of controlling a lens focal position according to claim 9,
Control of the excitation voltage at the rise of the excitation voltage is performed by a duty ratio control method in which the duty ratio gradually increases with time,
The control of the excitation voltage at the fall of the excitation voltage is performed by a duty ratio control method in which the duty ratio gradually decreases with time,
A method for controlling the focal position of a lens. The method of controlling a lens focal position according to claim 9 or 10,
The pulse frequency during the duty ratio control is higher than the self-starting frequency;
A method for controlling the focal position of a lens. The method for controlling the focal position of a lens according to any one of claims 9 to 11,
Apply excitation voltage continuously for the self-start limit pulse period,
A method for controlling the focal position of a lens. In a lens focal position control device driven by a pulsed excitation voltage,
Comprising a control means for controlling the excitation voltage at the rise or fall of the excitation voltage by a duty ratio control method;
A lens focal position control device. The lens focal position control device according to claim 13,
The control means controls the excitation voltage when the excitation voltage rises at a duty ratio that gradually increases with time, and controls the excitation voltage when the excitation voltage falls. Control with a duty ratio that gradually decreases with time,
A lens focal position control device. The lens focal position control device according to claim 13 or 14,
The pulse frequency when the duty ratio of the excitation voltage is controlled is provided with means for setting higher than the self-starting frequency,
A lens focal position control device. The lens focal position control device according to any one of claims 13 to 15,
Provided with means for applying the excitation voltage continuously for the self-start limit pulse period,
A lens focal position control device.

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