JP2009151081A - Imaging device - Google Patents

Abstract

Provided is an imaging device that can mount an ultrasonic motor as a focus motor to improve movement accuracy and quietness, can drive a focus lens minutely, and can drive a focus lens with high accuracy. .
An imaging apparatus including an ultrasonic motor 35 that moves a focus lens 24, a focus ring 67 that receives a manual focus operation by a photographer, and a focus ring sensor 30 that detects an operation amount of the focus ring 67. And a lens microcomputer 20 that controls the drive voltage of the ultrasonic motor 35 in accordance with the operation amount detected by the focus ring sensor 30. If the operation amount in the focus ring 67 is less than a predetermined value, the lens microcomputer 20 At the start of driving the ultrasonic motor 35, the drive voltage of the ultrasonic motor 35 is increased stepwise.
[Selection] Figure 1

Description

  The present invention relates to an imaging apparatus such as a digital still camera.

  In recent years, digital single-lens reflex cameras are rapidly spreading. In this digital single-lens reflex camera, when an object is observed using an optical viewfinder, light incident on the imaging optical system is reflected by a reflecting mirror disposed on the optical path and guided to the viewfinder optical system. As a result, the subject image is converted into an erect image via a pentaprism or the like and guided to the optical viewfinder. Thus, the photographer can observe the subject image formed by the imaging optical system from the optical viewfinder. As described above, the reflection mirror is usually arranged on the optical path.

  A general digital single-lens reflex camera has an autofocus (hereinafter referred to as AF) function and a manual focus (hereinafter referred to as MF) function capable of focusing a subject image on an imaging surface of an image sensor. There are many. The AF function operates the focus motor in the interchangeable lens by half-pressing the release button on the camera body, and moves the focus lens in the direction of the optical axis to automatically focus. It is a function. In the MF function, when the photographer rotates the focus ring arranged on the interchangeable lens, the focus motor in the interchangeable lens is driven, the focus lens is moved in the optical axis direction, and manually focused. It is a function that can perform the operation. The focus motor that can move the focus lens in this way is often composed of a DC motor.

However, it is difficult for the DC motor to move the focus lens with high accuracy, and the DC motor lacks silence. Therefore, Patent Document 1 discloses a configuration in which an ultrasonic motor excellent in movement accuracy and quietness is adopted as a focus motor.
Japanese Patent Laid-Open No. 11-356071

  However, in the configuration disclosed in Patent Document 1, during MF, the drive voltage of the ultrasonic motor is turned on / off at a predetermined cycle according to the rotation angle of the focus ring, and the speed is increased by intermittently driving the ultrasonic motor. Because of the control, it is difficult to drive the focus lens with high accuracy. Therefore, it takes time for the photographer to move the focus lens to a desired position, and the operability is lowered.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an imaging apparatus that can mount an ultrasonic motor as a focus motor to improve movement accuracy and quietness, and can perform fine drive of the focus lens and can drive the focus lens with high precision. Is to provide.

  An imaging apparatus according to the present invention is an imaging apparatus that includes a focus lens and an ultrasonic motor that moves the focus lens, an operation unit that receives a manual focus operation by a photographer, and an operation amount of the operation unit. Detection means for detecting, and control means for controlling the drive voltage of the ultrasonic motor in accordance with the operation amount detected by the detection means, wherein the control means has an operation amount in the operation means less than a predetermined value. For example, when the driving of the ultrasonic motor is started, the driving voltage of the ultrasonic motor is increased stepwise.

  According to the present invention, it is possible to mount an ultrasonic motor as a focus motor to improve movement accuracy and quietness, and to perform highly accurate minute driving of the focus lens.

(Embodiment)
Hereinafter, embodiments of the imaging apparatus of the present invention will be described. Note that “front” in the text refers to the subject side of the camera body, and corresponds, for example, to the left in FIG. Further, “rear” means the side opposite to the subject of the camera body, that is, the imaging element side with respect to the imaging optical system, and corresponds to the right direction in FIG. The “upper side” refers to a direction corresponding to the upper vertical direction of the captured image when the long side direction of the captured image is horizontal, and corresponds to the upward direction in FIG. Usually, the side on which the release button is arranged in the camera body corresponds to the upper side. Further, the “lower side” means a direction opposite to the upper side, and corresponds to a downward direction in FIG. In each part, front, back, upper, and lower surfaces are referred to as a front surface, a back surface, an upper surface, and a lower surface, respectively.

[1. Overall configuration of camera system)
FIG. 1 is a block diagram showing the overall configuration of the camera system 1.

  As shown in FIG. 1, the camera system 1 is a system used for an interchangeable lens type digital single-lens reflex camera. The camera system 1 includes a camera body 3 and an interchangeable lens 2 that is detachably attached to the camera body 3. The interchangeable lens 2 is attached to a lens mount 70 provided on the front surface of the camera body 3.

[1-1. Configuration of camera body)
The camera body 3 includes an image capturing unit 71 that captures an image of a subject, a body microcomputer 12 (main body control unit) that controls the operation of each unit such as the image capturing unit 71, and an image display unit 72 that can display captured images and various types of information. An image storage unit 73 capable of storing image data, a viewfinder optical system 19 for observing a subject, a release button 50 for accepting an operation by a photographer during photographing and AF, a power switch 51, and a nonvolatile memory 53.

  The imaging unit 71 includes a quick return mirror 4 that guides incident light to the finder optical system 19 and the focus detection unit 5, an imaging sensor 11 such as a charge coupled device (CCD) image sensor that performs photoelectric conversion, and an exposure state of the imaging sensor 11. A shutter unit 10 that adjusts the image, a shutter control unit 14 that controls driving of the shutter unit 10 based on a control signal from the body microcomputer 12, an image sensor control unit 13 that controls the operation of the image sensor 11, and a focus mode selection Part 34.

  The body microcomputer 12 controls various sequences. Specifically, the body microcomputer 12 is equipped with a central processing unit (CPU), a read-only memory (ROM), and a random access memory (RAM), and a program stored in the ROM is read into the CPU. Thus, the body microcomputer 12 can realize various functions. For example, the body microcomputer 12 has a function of detecting that the interchangeable lens 2 is attached to the camera body 3. As shown in FIG. 1, the body microcomputer 12 is configured to be able to communicate with each part provided in the camera body 3.

  The image display unit 72 includes a liquid crystal monitor 16 and an image display control unit 15 that controls the operation of the liquid crystal monitor 16. In the present embodiment, the liquid crystal monitor 16 is provided as a display element for displaying an image. However, the display element is not limited to the liquid crystal monitor, and may be composed of at least an image display element such as an organic EL display. Good.

  The image storage unit 73 is, for example, an image recording / reproducing unit 18 capable of recording and reproducing image data of a captured image on a card-type recording medium (not shown), and an image recording for controlling the operation of the image recording / reproducing unit 18 And a control unit 17. In this embodiment, the medium for recording image data is a card-type recording medium having a semiconductor memory, but it may be a disk-type or tape-type recording medium.

  The quick return mirror 4 includes a main mirror 4a that can reflect and transmit incident light, and a sub mirror 4b that is provided on the back side of the main mirror 4a and reflects transmitted light from the main mirror 4a. The click return mirror 4 can be jumped out of the optical path X by a quick return mirror control unit (not shown) that operates under the control of the body microcomputer 12. Incident light is split into two light fluxes, a reflected light flux and a transmitted light flux, by the main mirror 4a. The reflected light beam is guided to the finder optical system 19. On the other hand, the transmitted light beam is reflected by the sub mirror 4b and used as a light beam for autofocusing by the focus detection unit 5 described later. During normal shooting, the quick return mirror control unit causes the quick return mirror 4 to jump out of the optical path X, and the shutter unit 10 is opened to form a subject image on the imaging surface of the imaging sensor 11. When not photographing, the quick return mirror 4 is disposed on the optical path X as shown in FIG. 1, and the shutter unit 10 is closed.

  The finder optical system 19 includes a finder screen 6 on which a subject image is formed, a pentaprism 7 that converts the subject image into an erect image, an eyepiece 8 that guides the erect image of the subject to the finder eyepiece window 9, and a photographer. A viewfinder eyepiece window 9 through which a subject image can be observed is provided.

  The power switch 51 is an operation unit that allows the photographer to turn on / off the power of the camera system 1. The power switch 51 controls a power supply circuit (not shown) to supply power to each part of the camera body 3 and the interchangeable lens 2 when turned on by the photographer.

  The release button 50 is an operation unit that can be operated by the photographer during focusing and release. The release button 50 is a button that can be pressed halfway and fully. In the release button 50, a first switch that is turned on when the release button 50 is pressed halfway and a second switch that is turned on when the release button 50 is fully pressed are arranged. Yes. The body microcomputer 12 determines a half-pressed state and a fully-pressed state based on a control signal sent from the release button 50. For example, the body microcomputer 12 outputs a control signal to the lens microcomputer 20 to execute the focusing operation when the half-pressed state of the release button 50 is detected, and the camera to execute the photographing operation when the full-pressed state of the release button 50 is detected. Each part of the main body 3 is controlled.

  The nonvolatile memory 53 stores various types of information (main body information) regarding the camera main body 3. This body information includes, for example, the model name for identifying the camera body 3 such as the manufacturer name, date of manufacture, model number, version of software installed in the body microcomputer 12 and information on firmware upgrade. Information (main body identification information) and the like are included. These pieces of information may be stored in the memory in the body microcomputer 12 instead of the nonvolatile memory 53.

  The focus mode selection unit 34 is an operation unit for selecting three types of modes, an auto focus mode (AF mode), a manual focus mode (MF mode), and an auto / manual focus mode (AF + MF mode). It is provided in the housing of the camera body 3 so that it can be operated. The AF mode is a mode for automatically adjusting the focus. The MF mode is a mode for the photographer to manually operate the focus ring 67 to move the focus lens 24 to a desired focus position. The AF + MF mode is a mode in which both the AF mode and the MF mode can be used. The focus can be finely adjusted manually by operating the focus ring 67 while automatically adjusting the focus by half-pressing the release button 50. it can. The focus mode selection unit 34 is connected to the body microcomputer 12, and the body microcomputer 12 determines which focus mode is selected. The body microcomputer 12 transmits information related to the focus mode to the lens microcomputer 20. The lens microcomputer 20 switches control of the ultrasonic motor 35 (described later) based on the received information regarding the focus mode.

[1-2. Interchangeable lens configuration)
As shown in FIG. 1, the interchangeable lens 2 includes an imaging optical system 21 that forms an optical image of a subject, a lens barrel 45 that supports the imaging optical system 21, a focus adjustment unit 40 that performs focusing, and an incident light amount. Aperture adjustment unit 41 that adjusts, lens microcomputer 20 (lens control unit) that controls the operation of the interchangeable lens 2, a non-volatile memory 52, a temperature sensor 39 that can detect environmental temperature, and a lens mount 70 that can be attached and detached. A body mount 80 is provided.

  The focus adjustment unit 40 is a unit for adjusting the focus of the optical image formed by the imaging optical system 21. The focus adjustment unit 40 includes an ultrasonic motor 35, a motor drive circuit 37, and a position sensor 25.

  The lens barrel 45 includes a support frame 33 that holds the focus lens 24 and other frames. The support frame 33 is rotationally driven by the ultrasonic motor 35. When the support frame 33 rotates with respect to another frame, the support frame 33 moves in a direction along the optical axis X by a cam groove (not shown) formed in the support frame 33 and a pin fixed to the other frame. Moving.

  The ultrasonic motor 35 is a motor for driving the focus lens 24 included in the imaging optical system 21 and can rotate the support frame 33. The ultrasonic motor 35 has a built-in piezoelectric element that vibrates when a voltage is supplied. The piezoelectric element is provided with a comb-shaped stator (not shown). When a voltage is supplied to the piezoelectric element, the piezoelectric element vibrates, and this vibration causes elliptical vibration in the stator. As a result, a rotor (not shown) in frictional contact with the stator rotates, and a rotational driving force can be obtained. The rotational driving force of the rotor is transmitted to the support frame 33 through a gear and a drive ring (not shown). The ultrasonic motor 35 is driven through a motor drive circuit 37. As shown in FIG. 2, the motor drive circuit 37 includes, for example, a step-up transformer 37a, a field effect transistor (FET) 37b, a control IC (Integrated Circuit) 37c, and a DC-DC converter 37d. . In addition, since the operating characteristics of the ultrasonic motor 35 change depending on the environmental temperature, a temperature sensor 39 is provided to measure the environmental temperature of the ultrasonic motor 35. The temperature sensor 39 is mounted on or built in the motor drive circuit 37. Usually, since the ultrasonic motor 35 is disposed near the motor drive circuit 37, the environmental temperature of the ultrasonic motor 35 and the temperature of the motor drive circuit 37 can be measured by the temperature sensor 39.

  The position sensor 25 is a sensor for detecting the position of the focus lens 24 in the movable range in the direction along the optical axis X, and a variable resistor or a magnetoresistive effect element (MR sensor) is used. The position sensor 25 can acquire the position information of the focus lens 24 by using the output voltage with respect to the change in resistance value.

  The focus ring 67 is disposed on the cylindrical surface of the substantially cylindrical lens barrel 45 so as to be rotatable in the circumferential direction of the lens barrel 45. The photographer rotates the focus ring 67 when manually adjusting the focus.

  The focus ring sensor 30 is a sensor for detecting the rotation of the focus ring 67 included in the operation unit (not shown), and is composed of, for example, a rotation pulse encoder. The focus ring sensor 30 detects the rotation angle (operation amount) and rotation direction of the focus ring 67 and outputs focal length information to the lens microcomputer 20. Specifically, the focus ring 67 has protrusions (not shown) provided at equal pitches in the rotation direction. The focus ring sensor 30 includes two sets of sensor units including a light emitting unit that continuously emits light and a light receiving unit (not shown) that can receive light emitted from the light emitting unit. When the focus ring 67 rotates, the projection passes between the light emitting unit and the light receiving unit, light incident on the light receiving unit is periodically blocked by the projection, and light is incident on the light receiving unit intermittently. The light receiving unit converts the incident light into an electrical signal, thereby generating a pulse corresponding to the rotation of the focus ring 67. The focus ring sensor 30 can detect the rotation angle (operation amount) of the focus ring 67 based on the number of generated pulses, and the rotation of the focus ring 67 based on the phase of the pulses output from each of the two sets of sensor units. The direction can be detected. The focus ring sensor 30 outputs information on the detected rotation angle and rotation direction to the lens microcomputer 20. The lens microcomputer 20 temporarily stores rotation angle information including information about the received rotation angle and rotation direction in the nonvolatile memory 52. Further, the rotation speed of the focus ring 67 can be obtained based on the rotation angle of the focus ring 67 and the time during which the rotation operation is performed (operation time). The operation time and rotation speed of the focus ring 67 are calculated by the lens microcomputer 20, for example.

  The aperture adjustment unit 41 includes an aperture unit 26 that adjusts the aperture or opening, and an aperture control unit 27 that controls the operation of the aperture unit 26.

  The lens microcomputer 20 is connected to each part mounted on the interchangeable lens 2. Specifically, the lens microcomputer 20 is equipped with a CPU, a ROM, and a RAM, and various functions can be executed by reading a program stored in the ROM into the CPU. In addition, the body microcomputer 12 and the lens microcomputer 20 can be electrically connected via electrical contacts (not shown) provided on the lens mount 70 and the body mount 80, respectively, and information can be transmitted and received between them. ing. The communication between the body microcomputer 12 and the lens microcomputer 20 may be performed by optical communication or wireless radio waves.

  The nonvolatile memory 52 stores various information (lens information) regarding the interchangeable lens 2. The lens information includes, for example, a model for specifying the interchangeable lens 2 such as a manufacturer name, date of manufacture, model number, software version installed in the lens microcomputer 20 and information on firmware upgrade. Information (lens specifying information), information regarding whether or not the focus adjustment unit 40 is compatible with the contrast detection method, and the like are included. The nonvolatile memory 52 can store information transmitted from the body microcomputer 12. These pieces of information may be stored in the memory unit in the lens microcomputer 20 instead of the nonvolatile memory 52.

  The rotation amount detection unit 47 can detect the rotation amount of the ultrasonic motor 35. Specifically, the rotation amount detection unit 47 includes an encoder that detects the movement amount of the focus lens 24, and detects the rotation amount of the ultrasonic motor 35 based on the detected movement amount of the focus lens 24. Information on the detected rotation amount is sent to the lens microcomputer 20 as a detection signal (MR signal). In the present embodiment, the rotation amount detection unit 47 is configured as a block independent of the lens microcomputer 20, but may be provided in the lens microcomputer 20.

[2. Driving characteristics of ultrasonic motor)
The rotation speed of the ultrasonic motor 35 is generally controlled by changing the frequency, amplitude, and phase difference of the drive voltage. FIG. 3 is a frequency characteristic showing the relationship between the drive frequency (input) and speed characteristic (output) of the ultrasonic motor 35 at the rated voltage V1.

  When the rated voltage V1 is supplied to the ultrasonic motor 35, as shown in FIG. 3, the rotational speed of the rotor is fastest at the resonance frequency F0, and the rotational speed of the rotor decreases as the drive frequency becomes higher than the resonance frequency F0. To do. Further, in a frequency region lower than the resonance frequency F0, vibrations are not transmitted to the rotor and the rotor rotates while sliding with respect to the stator, so that the rotational speed becomes low and abnormal noise is generated. For this reason, generally, when speed control (frequency control) is performed using the drive frequency, a frequency region higher than the resonance frequency F0 is used. For example, when the ultrasonic motor 35 is driven in the range of the drive frequencies F1 to F2 in FIG. 3, the rotational speed of the rotor changes from R1 to R2, and the rotational speed of the rotor decreases as the drive frequency increases. Thus, the ultrasonic motor 35 can control the rotation speed (frequency control) by changing the input drive frequency.

  FIG. 4 shows frequency characteristics when the drive voltage of the ultrasonic motor 35 is changed. As shown in FIG. 4, when a voltage V2 lower than the voltage V1 is supplied to the ultrasonic motor 35, if the drive frequency is F3, the rotation speed is driven at a rotation speed R4 lower than the rotation speed R3 at the voltage V1. To do. As described above, the ultrasonic motor 35 can control the rotation speed (voltage control) by changing the drive voltage. However, voltage control has a smaller change rate of the rotation speed relative to the voltage change range than frequency control, so when speed control in a wide range from low speed to high speed is required, the voltage is constant and the frequency is changed. It is easier to control the rotational speed of the ultrasonic motor 35.

[3. Camera system operation)
As shown in FIG. 1, in the finder photographing mode in which the photographer takes a picture through the finder eyepiece window 9, the main mirror 4a is disposed on the optical path. For this reason, light from a subject (not shown) passes through the imaging optical system 21 and enters the main mirror 4a, which is a semi-transmissive mirror. Part of the light incident on the main mirror 4a is reflected by the main mirror 4a and incident on the finder screen 6, and the remaining light is transmitted through the main mirror 4a and incident on the sub mirror 4b. The light incident on the finder screen 6 is formed as a subject image. This subject image is converted into an erect image by the pentaprism 7 and enters the eyepiece 8. Thereby, the photographer can observe an erect image of the subject through the viewfinder eyepiece window 9. Further, the light incident on the sub mirror 4 b is reflected by the reflecting surface of the sub mirror 4 b and enters the focus detection unit 5.

[3-1. basic action〕
FIG. 5 shows an operation flow of the camera system 1 until the photographing operation is executed. When shooting, the body microcomputer 12 first determines the focus mode. Specifically, the body microcomputer 12 determines the mode selected by the focus mode selection unit 34. When the AF mode is selected in the focus mode selection unit 34 (S1), the body microcomputer 12 monitors the state of the release button 50 (S2). When the release button 50 is half-pressed, the body microcomputer 12 transmits half-press operation information to the lens microcomputer 20. The lens microcomputer 20 controls the drive frequency of the ultrasonic motor 35 based on the half-press operation information sent from the body microcomputer 12 to start the focus adjustment operation (S3).

  On the other hand, when the MF mode is selected in the focus mode selection unit 34 (S4), the body microcomputer 12 transmits MF mode information to the lens microcomputer 20. The lens microcomputer 20 monitors the rotation state of the focus ring 67 based on the MF mode information sent from the body microcomputer 12 (S5). When the focus ring 67 is rotated by the photographer, the focus ring sensor 30 detects the rotation of the focus ring 67. Specifically, the focus ring sensor 30 detects the rotation angle and rotation direction of the focus ring 67 based on a pulse generated as the focus ring 67 rotates, and sends information on the detection result to the lens microcomputer 20. . Based on the information sent from the focus ring sensor 30, the lens microcomputer 20 controls the drive voltage of the ultrasonic motor 35 to start the focus adjustment operation (S6).

  Further, when the AF + MF mode is selected in the focus mode selection unit 34 (S7), the body microcomputer 12 monitors the state of the release button 50 (S8). When the body microcomputer 12 detects that the release button 50 is half-pressed, the body microcomputer 12 controls each part of the lens microcomputer 20 and the like, and controls the driving frequency of the ultrasonic motor 35 as in the AF mode to perform the focus adjustment operation. Control to start (S9). When the release button 50 is not pressed halfway, the focus mode monitoring is continued (S1 to S8).

  After the focus adjustment operation is completed, the body microcomputer 12 detects again the operation state of the release button 50 (S10), and at the same time, the lens microcomputer 20 detects the operation state of the focus ring 67 again (S11). When the half-press operation of the release button 50 is continued and the focus ring 67 is rotated, the lens microcomputer 20 controls the drive voltage of the ultrasonic motor 35 as in the MF mode, and performs the focus adjustment operation. Control is performed (S12).

  On the other hand, when the half-press operation of the release button 50 is continued, but the focus ring 67 is not rotated, or when the half-press operation of the release button 50 is stopped after step S9, the body microcomputer 12 When the full pressing operation of the release button 50 is detected (S13), the process proceeds to the photographing operation (S14). If the release button 50 has not been fully pressed, it may be possible to further adjust the focus or switch the focus mode. Therefore, the process returns to step S1, and monitoring of the focus mode is repeated thereafter.

[3-2. Operation in MF mode]
In the AF mode, since the focus lens 24 is driven to the in-focus position by the ultrasonic motor 35, the continuous drive time of the ultrasonic motor 35 is short (for example, 1 second or less).

  However, in the MF mode, since the driving time of the ultrasonic motor 35 is determined by the time during which the photographer operates the focus ring 67, there can be a situation where continuous driving is performed at a low speed for a long time.

  For example, as shown in FIG. 6, in the MF mode, the focus lens 24 is driven at three speeds according to the rotation speed of the focus ring 67. Specifically, when the rotation speed Rf of the focus ring 67 is Rf2 <Rf ≦ Rf1, the rotation speed of the ultrasonic motor 35 is set to a rotation speed Rm1 corresponding to the average rotation speed Rf5 of the rotation speeds Rf1 and Rf2. . Similarly, when the rotational speed Rf of the focus ring 67 is speed Rf3 <Rf ≦ Rf2, the ultrasonic motor 35 is set to a rotational speed Rm2 corresponding to the rotational speed Rf6. When the rotation speed Rf of the focus ring 67 is Rf4 ≦ Rf ≦ Rf3, the ultrasonic motor 35 is set to the rotation speed Rm3 corresponding to the rotation speed Rf7. Here, the rotational speed Rm1 is set lower than the rotational speed R1, and the rotational speed Rm3 is set higher than the rotational speed R2.

  However, when the ultrasonic motor 35 is continuously driven for a long time, as shown in FIG. 7, the step-up transformer 37a itself generates heat due to the influence of the iron loss of the step-up transformer 37a (see FIG. 2) of the motor drive circuit 37, and time elapses. At the same time, power loss increases. Also, the ultrasonic motor 35 itself generates heat if it continues to supply voltage for a long time. For this reason, when the ultrasonic motor 35 is operated with the drive frequency F2 (see FIG. 3) in a state where a relatively high voltage is supplied, the power consumption increases with time as shown by the power consumption curve C1 in FIG. There is a possibility that the allowable power consumption Wa assigned to drive the focus lens 24 may be exceeded. A power consumption curve C2 in FIG. 7 shows a change in power consumption when the ultrasonic motor 35 is driven at an intermediate voltage between the maximum voltage and the minimum voltage.

  As described above, in the MF mode, a control method capable of continuously driving for a long time while reducing power consumption is required.

[3-3. Micro drive of ultrasonic motor in MF mode]
Next, control for moving the focus lens 24 by a minute distance in the MF mode will be described.

  FIG. 8 shows a flow of basic operation in the MF mode. As described with reference to FIG. 5, the body microcomputer 12 detects the focus mode selection state in the focus mode selection unit 34 (S21), and if the MF mode is selected, the body microcomputer 12 transmits the MF mode selection information to the lens microcomputer. 20 is transmitted.

  The lens microcomputer 20 detects the rotation operation of the focus ring 67 based on the MF mode selection information sent from the body microcomputer 12. That is, when the pulse based on the rotation of the focus ring 67 is output from the focus ring sensor 30, the lens microcomputer 20 detects that the focus ring 67 has been rotated (S22).

  Next, the lens microcomputer 20 shifts to the minute drive mode or the normal drive mode based on the pulse output from the focus ring sensor 30 (S23). That is, the number of pulses output from the focus ring sensor 30 in a predetermined period is counted. If the rotation angle of the focus ring 67 is large and the number of pulses is equal to or greater than a predetermined value, the normal drive mode is entered (S25). If the rotation angle is small and the number of pulses is less than the predetermined value, the mode is shifted to the minute drive mode (S24).

  The determination of the drive mode in the present embodiment is controlled so as to shift to the minute drive mode when only one pulse is output from the focus ring sensor 30 during the sampling interval of 16 msec. Further, when two pulses are output from the focus ring sensor 30 during the sampling interval of 16 msec, control is performed so as to shift to the normal drive mode. The sampling time and the number of pulses are examples.

  Next, the operation in the minute drive mode will be described.

[3-3-1. (Basic control of minute drive)
FIG. 9 shows an outline of control of drive voltage and drive frequency in the minute drive mode in the present embodiment. FIG. 9A shows a pulse output from the focus ring sensor 30. FIG. 9B shows the drive voltage of the ultrasonic motor 35. FIG. 9C shows the driving frequency of the ultrasonic motor 35.

  When the focus ring 67 is slightly rotated by the photographer, the focus ring sensor 30 transmits a pulse shown in FIG. 9A to the lens microcomputer 20. When the first pulse (timing t1) is sent from the focus ring sensor 30, the lens microcomputer 20 shifts to the minute driving mode. When the lens microcomputer 20 shifts to the minute drive mode, the drive voltage of the ultrasonic motor 35 is increased stepwise (hereinafter referred to as a sweep) as shown in FIG. 9B. In the example shown in FIG. 9, the initial driving voltage is 50 V, and is increased by 0.87 V every 1 msec after timing t1.

  When driving is started when the ultrasonic motor 35 sweeps the drive voltage to the voltage V10 (for example, timing t2), the drive voltage is maintained at the voltage V10 as shown by the characteristic VA1 after the timing t2, and the focus lens 24 is slightly changed. It can be moved a distance.

  On the other hand, as shown in the characteristic VA2, even when the driving voltage of the ultrasonic motor 35 reaches the maximum voltage (70V in the example shown in FIG. 9) (timing t3), the driving of the ultrasonic motor 35 has not started. The drive frequency is swept while keeping the drive voltage at the maximum voltage. Thereby, the ultrasonic motor 35 can be driven, and the focus lens 24 can be moved by a minute distance.

  In the above control, when the focus lens 24 is slightly driven, the drive voltage is swept with the drive frequency fixed, and the ultrasonic motor 35 is driven. Therefore, since the ultrasonic motor 35 can be driven with a driving voltage that is equal to or lower than the maximum voltage, power consumption can be reduced. Further, since the resolution of the voltage control is high, the rotational speed control of the ultrasonic motor 35 can be performed with higher accuracy than the control in which the drive voltage is set to a fixed value and the drive frequency is swept.

  The minimum voltage (50V), the maximum voltage (70V), the amount of voltage increase (0.87V), and the time interval (1 msec) at the time of voltage increase are examples.

[3-3-2. (Specific control of minute drive)
FIG. 10 shows a specific example of control of the drive voltage and drive frequency in the minute drive mode in the present embodiment. FIG. 10A shows a pulse output from the focus ring sensor 30. FIG. 10B shows the drive voltage of the ultrasonic motor 35. FIG. 10C shows the drive frequency of the ultrasonic motor 35. FIG. 10D shows a pulse (MR signal) output from the rotation amount detection unit 47 when the ultrasonic motor 35 is rotating.

  When the focus ring 67 is slightly rotated by the photographer, the focus ring sensor 30 transmits a pulse shown in FIG. When the first pulse (timing t11) is sent from the focus ring sensor 30, the lens microcomputer 20 shifts to the minute driving mode.

  Next, the lens microcomputer 20 sweeps the drive voltage applied to the ultrasonic motor 35 from the lowest voltage V11 as shown in FIG. The lens microcomputer 20 monitors the MR signal shown in FIG. 10D while sweeping the drive voltage. During the period t11 to t12 in FIG. 10, since the MR signal is not output, the ultrasonic motor 35 is not driven.

  When the lens microcomputer 20 sweeps the drive voltage of the ultrasonic motor 35 to the drive start voltage value (for example, at timing t12), the ultrasonic motor 35 starts driving and the focus lens 24 starts minute driving. At this time, the lens microcomputer 20 detects the MR signal output from the rotation amount detection unit 47, stops the drive voltage increase control, and maintains the voltage V12 when the ultrasonic motor 35 starts to be driven.

  Next, the lens microcomputer 20 starts counting the number of pulses of the MR signal from timing t12. When the number of pulses of the MR signal reaches the number of pulses corresponding to the amount of movement of the focus lens 24 to the target stop position (stop target pulse number), the lens microcomputer 20 stops the application of the drive voltage, and the ultrasonic motor The drive of 35 is stopped. As a result, the focus lens 24 stops moving.

  In the above control, when the focus lens 24 is slightly driven, the drive voltage is swept in a state where the drive frequency is fixed, and the ultrasonic motor 35 is driven with the drive voltage when the MR signal is detected. Therefore, since the ultrasonic motor 35 is driven with a driving voltage equal to or lower than the maximum voltage, power consumption can be reduced. Further, since the resolution of the voltage control is high, the rotational speed control of the ultrasonic motor 35 can be performed with higher accuracy than the control in which the drive voltage is set to a fixed value and the drive frequency is swept.

[3-3-3. (Reversal control of minute drive)
Normally, mechanical parts called backlash are provided in mechanical parts that operate while being fitted such as gears and cams that couple the ultrasonic motor 35 and the focus lens 24, so as to operate smoothly. ing. Therefore, if the ultrasonic motor 35 is always rotated in one rotation direction, there is no relative deviation between the rotation of the ultrasonic motor 35 based on backlash and the movement of the focus lens 24, but the ultrasonic wave When the motor 35 is rotated in the first rotation direction and then reversed to the second rotation direction opposite to the first rotation direction, the rotation operation is started in the second rotation direction. At this time, a relative deviation occurs between the rotation of the ultrasonic motor 35 based on the backlash and the movement of the focus lens 24. For example, when the ultrasonic motor 35 is rotated in the first rotation direction and then rotated in the second rotation direction, the rotational force of the ultrasonic motor 35 is not transmitted to the focus lens 24 due to backlash, and the focus lens 24 is A period during which no moving operation is performed occurs. The backlash in such a mechanical component is adjusted to a predetermined amount before the camera system 1 is shipped from the factory. Therefore, the backlash generated when the rotation direction of the ultrasonic motor 35 is reversed as described above. Based on this, the time during which the focus lens 24 does not move (hereinafter referred to as hiss time) can also be grasped. Information on the hysteresis time adjusted before factory shipment is written in the memory in the lens microcomputer 20 or the nonvolatile memory 52.

  In the present embodiment, since the ultrasonic motor 35 has a structure that moves the focus lens 24 via the transmission gear, there is a backlash of the transmission gear. Therefore, between the actual rotation amount of the ultrasonic motor 35 and the rotation amount detected by the rotation amount detection unit 47 (the rotation amount of the ultrasonic motor 35 detected based on the movement amount of the focus lens 24). Deviation based on backlash may occur. For example, immediately after the direction of rotation of the ultrasonic motor 35 is reversed, the rotational force is not transmitted to the focus lens 24 due to backlash in the transmission gear even though the ultrasonic motor 35 is rotating. Does not move, and there is a period in which no MR signal is output from the rotation amount detection unit 47.

  FIG. 11 shows a specific example of inversion control when the ultrasonic motor 35 is rotated in the first rotation direction and then rotated in the second rotation direction in the minute drive mode in the present embodiment. FIG. 11A shows a pulse output from the focus ring sensor 30. FIG. 11B shows the drive voltage of the ultrasonic motor 35. FIG. 11C shows the driving frequency of the ultrasonic motor 35. FIG. 11D shows a pulse (MR signal) output from the rotation amount detection unit 47 when the ultrasonic motor 35 is rotating.

  The focus ring 67 is rotated in the first rotation direction by the photographer and, for example, the focus lens 24 is moved in the first direction based on the control shown in FIG. When the rotation operation is slightly performed in the second rotation direction opposite to the rotation direction, the focus ring sensor 30 transmits a pulse shown in FIG. When the first pulse (timing t21) is sent from the focus ring sensor 30, the lens microcomputer 20 shifts to the minute driving mode.

  Next, the lens microcomputer 20 sweeps the drive voltage applied to the ultrasonic motor 35 from the lowest voltage V21 as shown in FIG. The lens microcomputer 20 monitors the MR signal shown in FIG. 11D while sweeping the drive voltage.

  When the lens microcomputer 20 sweeps the drive voltage to the maximum voltage V22 (timing t22), the maximum voltage is at least from t22 to t24 corresponding to the hysteresis time based on the hysteresis time information read from the memory in the lens microcomputer 20. V22 is maintained. In this period t22 to t24, the drive voltage and the drive frequency are constant.

  Here, when the ultrasonic motor 35 starts to rotate during the period t22 to t24 (timing t23), the lens microcomputer 20 maintains the driving voltage (maximum voltage V22) and the driving frequency at that time, and from the timing t23. The counting of the number of pulses of the MR signal is started. When the number of pulses of the MR signal reaches the number of pulses corresponding to the amount of movement of the focus lens 24 to the target stop position (stop target pulse number), the lens microcomputer 20 stops the application of the drive voltage, and the ultrasonic motor The drive of 35 is stopped. As a result, the focus lens 24 stops moving (t25).

  When the ultrasonic motor 35 does not start rotating during the period t22 to t24 (when no MR signal is output), the lens microcomputer 20 sweeps the drive frequency after the timing t24 (for example, the timing shown in FIG. 9). Control after t3).

  In the above control, when the focus lens 24 is slightly driven, the drive voltage is swept with the drive frequency fixed, and the ultrasonic motor 35 is driven. Therefore, since the ultrasonic motor 35 is driven with a driving voltage equal to or lower than the maximum voltage, power consumption can be reduced. Further, since the resolution of the voltage control is higher than the control in which the drive voltage is set to a fixed value and the drive frequency is swept, the rotational speed control of the ultrasonic motor 35 can be performed with high accuracy.

  In this embodiment, the backlash of the mechanical parts for driving the focus lens 24 is measured in advance, and the premeasured backlash is removed when the rotation direction of the ultrasonic motor 35 is reversed. In this case, the drive voltage and drive frequency of the ultrasonic motor 35 are not swept, and the rotational speed of the ultrasonic motor 35 can be prevented from increasing excessively. That is, since the focus lens 24 does not start during the period in which the ultrasonic motor 35 is driven and the backlash is removed, after the drive voltage is swept to the maximum voltage, the control is performed to sweep the drive frequency. There is a possibility that the rotational speed of 35 increases too much. In the present embodiment, when the rotation direction of the ultrasonic motor 35 is reversed, the rotation speed of the ultrasonic motor 35 is not excessively increased by controlling the drive voltage and the drive frequency not to sweep for a predetermined hysteresis time after the voltage sweep. I am doing so.

  The minimum voltage V21 (50V) and the maximum voltage V22 (70V) are examples.

  Further, the reversing operation in the present embodiment is not limited to the operation for removing the backlash between the ultrasonic motor 35 and the focus lens 24, but for removing the backlash between the ultrasonic motor 35 and the position sensor 25. It is also applicable to the operation of

[3-3-4. Temperature correction)
In the ultrasonic motor 35, the friction coefficient of the ultrasonic motor 35 and the mechanical parts varies depending on the temperature of the use environment. When the usage environment is low temperature, a large torque is required to activate the ultrasonic motor 35, and the drive voltage also increases. Therefore, in the micro drive mode, in the case of controlling the voltage to sweep at a constant increase regardless of the temperature of the usage environment, if the temperature of the usage environment is lower than the normal temperature, the voltage reaches the voltage at which the ultrasonic motor 35 starts operating. It takes time to do so, and the startup response decreases. Therefore, in the present embodiment, control according to the environmental temperature is performed using information on the environmental temperature obtained from the temperature sensor 39 (see FIG. 1).

  FIG. 12 shows a specific example of control of drive voltage and drive frequency in the minute drive mode in the present embodiment. FIG. 12A shows a pulse output from the focus ring sensor 30. FIG. 12B shows the drive voltage of the ultrasonic motor 35. FIG. 12C shows the driving frequency of the ultrasonic motor 35.

  When the focus ring 67 is slightly rotated by the photographer, the focus ring sensor 30 transmits a pulse shown in FIG. When the first pulse (timing t31) is sent from the focus ring sensor 30, the lens microcomputer 20 shifts to the minute driving mode.

  Next, the lens microcomputer 20 acquires environmental temperature information from the temperature sensor 39 and compares it with a reference temperature (5 ° C. in the present embodiment). If the environmental temperature is higher than the reference temperature as a result of the comparison, it is determined that the ambient temperature is normal, and if the environmental temperature is lower than the reference temperature, it is determined that the ambient temperature is low. When the lens microcomputer 20 determines that the environmental temperature is normal temperature, it sweeps the drive voltage based on the characteristic H1 in FIG. 12B, and when it determines that the environmental temperature is low, FIG. The drive voltage is swept based on the characteristic L1 in FIG. The characteristic H1 is a characteristic in which the voltage is increased by 0.87 V, for example, at a time interval of 1 msec from the lowest voltage V31 (for example, 50 V) and increased to the maximum voltage V32 (for example, 70 V). The characteristic L1 is a characteristic in which the voltage is increased by 2.54 V, for example, at a time interval of 1 msec from the lowest voltage V31 and increased to the maximum voltage V33 (for example, 80 V). That is, when the environmental temperature is low, the drive voltage sweep amount is larger and the maximum voltage is higher than the normal temperature. Hereinafter, a specific operation at each temperature will be described.

  When the lens microcomputer 20 determines that the environmental temperature is normal temperature, the drive voltage of the ultrasonic motor 35 is swept by 0.87 V every 1 msec as shown by the characteristic H1 in FIG. When the drive voltage is swept to the drive start voltage value, the ultrasonic motor 35 starts to rotate, and the focus lens 24 can be moved by a minute distance.

  After timing t31, the lens microcomputer 20 monitors the driving voltage and operating state of the ultrasonic motor 35, and the ultrasonic motor 35 rotates even when reaching the maximum voltage (70V in the example shown in FIG. 12) (timing t33). If not, the drive frequency is swept while keeping the drive voltage at the maximum voltage (characteristic H2). Thereby, the ultrasonic motor 35 can be driven, and the focus lens 24 can be moved by a minute distance.

  If the lens microcomputer 20 determines that the environmental temperature is low, the driving voltage of the ultrasonic motor 35 is swept by 2.54 V every 1 msec as shown by the characteristic L1 in FIG. When the drive voltage is swept to the drive start voltage value, the ultrasonic motor 35 starts to drive, and the focus lens 24 can be moved by a minute distance.

  After timing t31, the lens microcomputer 20 monitors the driving voltage and the operating state of the ultrasonic motor 35, and the ultrasonic motor 35 is driven even when the maximum voltage (80 V in the example shown in FIG. 12) is reached (timing t32). If not started, the drive frequency is swept while keeping the drive voltage at the maximum voltage (characteristic L2). Thereby, the ultrasonic motor 35 can be driven, and the focus lens 24 can be moved by a minute distance.

  In the above control, when the focus lens 24 is slightly driven, the drive voltage is swept with the drive frequency fixed, and the ultrasonic motor 35 is driven. Therefore, since the ultrasonic motor 35 can be driven with a driving voltage that is equal to or lower than the maximum voltage, power consumption can be reduced. Further, since the resolution of the voltage control is high, the rotational speed control of the ultrasonic motor 35 can be performed with higher accuracy than the control in which the drive voltage is set to a fixed value and the drive frequency is swept.

  When it is determined that the environmental temperature is low based on the environmental temperature obtained from the temperature sensor 39, the ultrasonic motor 35 is increased by increasing the sweep amount of the drive voltage and increasing the maximum voltage as compared with the normal temperature. The starting torque can be made higher than that at room temperature, and the starting response can be improved. Moreover, since the maximum voltage is lower than that at low temperatures at room temperature, power consumption can be suppressed.

  The minimum voltage V31 (50V), the maximum voltage V32 (70V), V33 (80V), the drive voltage sweep amount at room temperature (0.87V), the drive voltage sweep amount at low temperature (2.54V), The time interval (1 msec) and the reference temperature (5 ° C.) during the voltage sweep are examples.

[3-3-5. Overall flow of micro drive mode)
FIG. 13 shows the overall flow in the minute drive mode.

  First, when the camera system 1 enters the micro drive mode of the MF mode (see FIG. 8 for the flow until entering the micro drive mode), the drive voltage of the ultrasonic motor 35 is swept (S31). The lens microcomputer 20 monitors the MR signal while sweeping the drive voltage of the ultrasonic motor 35 or while driving at the maximum voltage (S32). Here, when the lens microcomputer 20 detects the MR signal, the ultrasonic motor 35 is driven while maintaining the drive voltage and drive frequency of the ultrasonic motor 35 at that time (S38). On the other hand, if the lens microcomputer 20 does not detect the MR signal, it is determined whether the drive voltage of the ultrasonic motor 35 has reached the maximum voltage (upper limit value) (S33). If the maximum voltage has not been reached, the drive voltage is swept. (S31), and if the maximum voltage is reached, the reversal operation is determined (S34).

  If the lens microcomputer 20 does not detect the reversing operation of the focus ring 67, the lens microcomputer 20 sweeps the drive frequency of the ultrasonic motor 35 (S36). On the other hand, if a reversing operation of the focus ring 67 is detected, control is performed so that a constant maximum voltage is applied to the ultrasonic motor 35 for a hysteresis time based on a preset backlash amount (S35). Thus, by applying a constant maximum voltage to the ultrasonic motor 35, backlash can be eliminated. When the hysteresis time has elapsed, the lens microcomputer 20 sweeps the drive frequency of the ultrasonic motor 35 (S36).

  The lens microcomputer 20 monitors the MR signal while sweeping the drive frequency of the ultrasonic motor 35 (S37). If the MR signal is detected, the driving voltage and driving frequency of the ultrasonic motor 35 at that time are maintained (S38).

  The lens microcomputer 20 counts the number of MR signal pulses after detecting the MR signal in step S32 or S37. The lens microcomputer 20 monitors whether or not the counted pulse number has reached a preset stop target pulse number (S39), and if the stop target pulse number is reached, the drive voltage to the ultrasonic motor 35 is reached. Is stopped, and the driving of the ultrasonic motor 35 is stopped (S40).

[3-3-6. Other configuration examples and control examples]
In the present embodiment, the lens microcomputer 20 counts the number of MR signal pulses after the ultrasonic motor 35 starts rotating, and when the number of MR signal pulses reaches the target stop pulse number, the lens microcomputer 20 drives the ultrasonic motor 35. Although it is configured to stop, the target stop pulse number can be switched based on the current focus position. For example, when the focus position is near the infinite end, the stop target pulse number is 70 pulses, and when the focus position is near the near end, the stop target pulse number is 16 pulses. In the case of a camera system having a zoom function, the stop target pulse number can be switched based on both the focus position information and the current zoom position information.

  Further, in the present embodiment, when the ultrasonic motor 35 is driven minutely and the focus ring 67 is rotated by the photographer and a pulse is newly transmitted from the focus ring sensor 30 to the lens microcomputer 20, the pulse is very small. As long as the drive mode is not exited, the pulse transmitted from the focus ring sensor 30 is ignored, and the ultrasonic motor 35 is driven and controlled. In addition to this configuration, when a new pulse is transmitted from the focus ring sensor 30, the drive control of the ultrasonic motor 35 may be performed again at the timing when the new pulse is transmitted.

  In this embodiment, the minute driving in the MF mode has been described. However, the minute driving in the AF mode can also be handled. In the AF mode, the lens microcomputer 20 shifts to the micro drive mode in the AF mode when the body microcomputer 12 sends a drive command with an MR signal pulse number of 71 pulses or less to the lens microcomputer 20. In this case, the lens microcomputer 20 sets the number of pulses (10 to 71 pulses) sent from the body microcomputer 12 to the target stop pulse number, and performs drive control of the ultrasonic motor 35.

[4. Effects of the embodiment, etc.]
According to the present embodiment, when the focus lens 24 is slightly driven, the drive voltage is swept in a state where the drive frequency is fixed, and the ultrasonic motor 35 is driven. Therefore, since the ultrasonic motor 35 can be driven with a driving voltage that is equal to or lower than the maximum voltage, power consumption can be reduced.

  Further, since the resolution of the voltage control is higher than the control in which the drive voltage is set to a fixed value and the drive frequency is swept, the rotational speed control of the ultrasonic motor 35 can be performed with high accuracy.

  In addition, if the rotational speed of the ultrasonic motor 35 (drive speed of the focus lens 24) is increased too much during the minute drive, the focus lens 24 is likely to overrun the target lens stop position. There is a problem that it takes time to move the lens 24 to the target stop position, or the position accuracy is lowered. Since the drive voltage is swept as in the present embodiment and the ultrasonic motor 35 starts to rotate (when the focus lens 24 starts moving), the ultrasonic motor 35 is driven with the drive voltage and the drive frequency. The ultrasonic motor 35 can be driven at the minimum rotational speed (the minimum moving speed of the focus lens 24). Therefore, the phenomenon that the focus lens 24 overruns the target lens stop position can be greatly reduced, and high-speed and highly accurate position control can be performed. In the present embodiment, since the ultrasonic motor 35 is driven with the lowest voltage, power consumption can be suppressed.

  In this embodiment, the backlash of the mechanical parts for driving the focus lens 24 is measured in advance, and the premeasured backlash is removed when the rotation direction of the ultrasonic motor 35 is reversed. In this case, the drive voltage and drive frequency of the ultrasonic motor 35 are not swept, and the rotational speed of the ultrasonic motor 35 can be prevented from increasing excessively. That is, since the focus lens 24 does not start during the period in which the ultrasonic motor 35 is driven and the backlash is removed, after the drive voltage is swept to the maximum voltage, the control is performed to sweep the drive frequency. There is a possibility that the rotational speed of 35 increases too much. In the present embodiment, when the rotation direction of the ultrasonic motor 35 is reversed, the rotation speed of the ultrasonic motor 35 is not excessively increased by controlling the drive voltage and the drive frequency not to sweep for a predetermined hysteresis time after the voltage sweep. I am doing so.

  Further, in the present embodiment, at the time of minute driving, based on the environmental temperature information obtained from the temperature sensor 39, if the environmental temperature is equal to or lower than (or lower than) the predetermined temperature, the drive voltage increase amount and the maximum voltage are increased. Thus, the torque at the start of the minute operation of the ultrasonic motor 35 can be increased. Therefore, it is possible to improve the response at the start of the minute operation of the ultrasonic motor 35.

  Further, in the present embodiment, by adopting a configuration in which the stop target pulse number is changed according to the focus position and zoom position, it is possible to perform highly accurate lens driving according to the focus position and zoom position.

  In the present embodiment, in order to perform MF, the focus ring 67 is rotatably provided on the cylindrical surface of the lens barrel 45. However, at least if the photographer can manually perform MF operation, the rotation is performed. It is not limited to the ring type operation means. For example, it can be realized by lever type or button type operation means.

  In this embodiment, the lens interchangeable digital camera is described as an example, but the present invention can also be applied to a lens integrated digital camera.

[Appendix 1]
An imaging apparatus according to the present invention is an imaging apparatus that includes a focus lens and an ultrasonic motor that moves the focus lens, an operation unit that receives a manual focus operation by a photographer, and an operation amount of the operation unit. An operation amount detection means for detecting; and a control means for controlling a drive voltage of the ultrasonic motor in accordance with the operation amount detected by the operation amount detection means, wherein the control means has a predetermined operation amount in the operation means. If the value is less than the value, the driving voltage of the ultrasonic motor is increased stepwise when the driving of the ultrasonic motor is started.

  According to this configuration, since the ultrasonic motor can be driven with a driving voltage that is equal to or lower than the maximum voltage, power consumption can be reduced.

  Further, since the resolution of the voltage control is higher than the control in which the drive voltage is set to a fixed value and the drive frequency is swept (stepped down), the rotational speed control of the ultrasonic motor 35 can be performed with high accuracy. it can.

  Note that the focus ring 67 in the present embodiment is an example of the operating means in the present invention. The focus ring sensor 30 is an example of an operation amount detection unit. The lens microcomputer 20 is an example of a control unit.

[Appendix 2]
In the imaging apparatus according to the aspect of the invention, when the focus lens starts moving when the drive voltage of the ultrasonic motor is increased stepwise, the control unit determines the drive voltage when the focus lens starts to move. It can be set as the structure maintained.

  According to this configuration, at the time of minute driving, the ultrasonic motor can be driven at the minimum rotation speed, and the phenomenon that the focus lens overruns the target lens stop position can be greatly reduced, and high speed can be achieved. In addition, highly accurate position control can be performed. In this embodiment, since the ultrasonic motor is driven at the lowest voltage that can be driven, power consumption can be suppressed.

[Appendix 3]
In the imaging apparatus of the present invention, the control means controls the drive frequency of the ultrasonic motor stepwise when the ultrasonic motor does not operate when the drive voltage of the ultrasonic motor reaches a maximum voltage. can do.

  According to this configuration, when the ultrasonic motor does not operate by sweeping the driving voltage, the ultrasonic motor can be reliably operated by sweeping the driving frequency of the ultrasonic motor.

[Appendix 4]
The imaging apparatus according to the present invention further includes a storage unit, and the storage unit includes the ultrasonic motor, which is necessary for removing backlash of a mechanical component that couples the focus lens and the ultrasonic motor. When the drive time information is written and the control means detects that the rotation direction of the operation means is reversed and the operation amount in the operation means is less than a predetermined value, the control means steps the drive voltage of the ultrasonic motor. The driving voltage of the ultrasonic motor can be set to the maximum voltage based on the driving time.

  According to this configuration, it is possible to prevent the rotational speed of the ultrasonic motor from being excessively increased. In other words, the focus lens does not start during the period when the ultrasonic motor is driven and the backlash is removed. Therefore, after the drive voltage is swept to the maximum voltage, the drive frequency is swept and the ultrasonic motor is rotated. The speed may increase too much. In the present invention, when the rotation direction of the ultrasonic motor is reversed, control is performed so that the drive voltage and the drive frequency are not swept for a predetermined hysteresis time after the voltage sweep, so that the rotation speed of the ultrasonic motor is not excessively increased. .

  The memory in the lens microcomputer 20 and the nonvolatile memory 52 in the present embodiment are an example of the storage unit of the present invention.

[Appendix 5]
The imaging apparatus according to the present invention further includes a temperature measuring unit capable of measuring an environmental temperature, and the control unit per unit time of the driving voltage of the ultrasonic motor according to the temperature measured by the temperature measuring unit. It can be set as the structure which changes the raise amount of.

  With this configuration, it is possible to increase the torque at the start of the minute operation of the ultrasonic motor when the environmental temperature is low, and improve the response at the start of the minute operation of the ultrasonic motor.

  The temperature sensor 39 according to the present embodiment is an example of a temperature measuring unit according to the present invention.

[Appendix 6]
The imaging apparatus according to the present invention further includes a rotation amount detection unit that detects a rotation amount of the ultrasonic motor and outputs a detection signal, and the control unit rotates the rotation amount when driving the ultrasonic motor. The number of pulses of the detection signal output from the detection means is counted, and when the number of pulses reaches the target number of pulses, the driving of the ultrasonic motor is stopped and the number of target pulses is changed according to the position of the focus lens. It can be configured.

  With this configuration, highly accurate lens driving can be performed according to the focus position.

  In the present embodiment, the rotation amount detection unit 47 is an example of a rotation amount detection means in the present invention.

[Appendix 7]
The imaging device of the present invention may further include a zoom lens, and the control unit may change the target pulse number according to the position of the zoom lens.

  With this configuration, highly accurate lens driving can be performed in accordance with the focus position and zoom position.

  The present invention is useful for an imaging apparatus such as a digital still camera.

1 is a block diagram illustrating a configuration of an imaging device in an embodiment Block diagram showing the configuration of the motor drive circuit Characteristic chart showing characteristics of drive frequency of ultrasonic motor Characteristic diagram showing the characteristics of the driving frequency of the ultrasonic motor when the voltage changes Flow chart showing the flow of operations during shooting Characteristic diagram showing the relationship between the rotational speed of the focus ring and the rotational speed of the rotor of the ultrasonic motor Characteristic diagram showing temporal change of power consumption of ultrasonic motor A flowchart showing a flow of switching between the normal drive mode and the minute drive mode in the MF mode. Timing chart showing control of drive voltage and drive frequency of ultrasonic motor in minute drive mode Timing chart showing control of drive voltage and drive frequency of ultrasonic motor in minute drive mode Timing chart showing control of drive voltage and drive frequency of ultrasonic motor in minute drive mode Timing chart showing control of drive voltage and drive frequency of ultrasonic motor in minute drive mode Flow chart showing the overall operation flow in the minute drive mode

Explanation of symbols

1 Camera system (imaging device)
2 Interchangeable lens 3 Camera body 20 Lens microcomputer (control means)
30 Focus ring sensor (operation amount detection means)
35 Ultrasonic motor 39 Temperature sensor (temperature measuring means)
67 Focus ring (operating means)

Claims (7)

An imaging apparatus comprising a focus lens and an ultrasonic motor that moves the focus lens,
Operation means for accepting manual focus operation by the photographer;
An operation amount detection means for detecting an operation amount of the operation means;
Control means for controlling the drive voltage of the ultrasonic motor according to the operation amount detected by the operation amount detection means,
The control means includes
An imaging apparatus that increases the driving voltage of the ultrasonic motor stepwise when the driving of the ultrasonic motor is started if the operation amount in the operating means is less than a predetermined value. The control means includes
The imaging apparatus according to claim 1, wherein when the focus lens starts moving while the drive voltage of the ultrasonic motor is gradually increased, the drive voltage when the focus lens starts to move is maintained. The control means includes
The imaging apparatus according to claim 1, wherein when the ultrasonic motor does not operate when the driving voltage of the ultrasonic motor reaches a maximum voltage, the driving frequency of the ultrasonic motor is controlled stepwise. A storage means,
The storage means
Information on the driving time of the ultrasonic motor necessary for removing backlash of a mechanical component that couples the focus lens and the ultrasonic motor is written,
The control means includes
When detecting that the rotation direction of the operation means is reversed and that the operation amount in the operation means is less than a predetermined value, the drive voltage of the ultrasonic motor is increased stepwise,
The imaging apparatus according to claim 1, wherein the driving voltage of the ultrasonic motor is set to a maximum voltage based on the driving time. A temperature measuring means capable of measuring the environmental temperature is further provided,
The control means includes
The imaging apparatus according to claim 1, wherein an increase amount per unit time of the driving voltage of the ultrasonic motor is changed according to the temperature measured by the temperature measuring unit. A rotation amount detecting means for detecting a rotation amount of the ultrasonic motor and outputting a detection signal;
The control means includes
When driving the ultrasonic motor, the number of pulses of the detection signal output from the rotation amount detection means is counted, and when the pulse number reaches the target pulse number, the driving of the ultrasonic motor is stopped,
The imaging apparatus according to claim 1, wherein the target pulse number is changed according to a position of the focus lens. A zoom lens,
The control means includes
The imaging apparatus according to claim 6, wherein the target pulse number is changed according to a position of the zoom lens.

Images