JP5058775B2 - Optical apparatus having vibration wave actuator - Google Patents

Description

  The present invention relates to an optical apparatus having a vibration wave actuator as autofocus means for focusing on a subject.

  2. Description of the Related Art Conventionally, a vibration wave motor that represents a vibration wave actuator is set so that an alternating electric field applied to a vibrating body rotates in two A and B phases with a certain phase difference. The phase difference between the A phase and the B phase is ± 90 °, and the rotation direction is determined by this positive / negative. In addition, the rotation speed is generally controlled to a desired speed by changing the voltage applied to the motor and the frequency of the A phase and the B phase.

  The vibration wave motor is usually coupled with a mechanical rotating body or moving body, and generally performs speed feedback control in order to stabilize the rotational speed of the rotating body.

  FIG. 12 shows an FN characteristic diagram of the relationship between the frequency and the rotational speed of the vibration wave motor. It can be seen that the rotational speed of the vibration wave motor can be changed by changing the frequency applied to the motor. When the frequency applied to the motor is high, the number of rotations is slow. By decreasing the frequency, the number of rotations gradually increases, and when it passes a certain point, it tends to decrease again. This is called the resonance frequency of the wave motor.

  As a feature of such a vibration wave motor, the frequency range higher than the resonance frequency has a longer base of the rotation speed characteristic with respect to the frequency, and the rotation speed changes rapidly with respect to the frequency at a frequency lower than the resonance frequency. . Therefore, when speed feedback control as described above is performed, it is common to use a frequency band higher than the resonance frequency. Further, it can be seen that the control near the resonance frequency has a large change in the rotational speed with respect to the applied frequency, and it is difficult to perform the speed control.

  As a control method using this vibration wave motor, Patent Document 1 describes that the start frequency of the vibration wave motor is stored and the frequency at the next drive is set in order to shorten the start time of the vibration wave motor. Is described. Patent Document 2 describes a control method for focusing on a subject in an optical apparatus using a vibration wave motor. For example, in a control method generally referred to as TVAF, a wobbling drive that detects a change in focus is performed by slightly driving a part of a photographing lens within a predetermined time. That is, it is described that a vibration wave motor is used.

JP 2002-281769 A JP 2003-279846 A

  As a feature of the vibration wave motor, since the driving torque is large and the rotation speed is low, a reduction mechanism such as that used in a conventional DC motor is unnecessary, and therefore, the operating noise can be reduced. Therefore, this vibration wave motor is used for interchangeable lenses of single-lens reflex cameras, but in recent years, digitalization of cameras has progressed, and it is possible to shoot not only still images but also simple moving pictures such as video cameras. Yes.

  In order to perform moving image shooting with a single-lens reflex camera, a mirror unique to a single-lens reflex camera cannot be used because it prevents light from entering the image sensor. Therefore, it is necessary to always shoot with the mirror in the retracted state, but since this mirror is also used to detect the focus of the subject's autofocus, there may be a problem that autofocus cannot be performed during movie shooting.

  For this reason, the steel video wobbling method disclosed in Patent Document 2 is conceivable. However, an interchangeable lens using a vibration wave motor has the following problems in motor control.

  (A) Since the driving lens is larger than that of the video camera, the load fluctuation is large. (B) The frequency-speed characteristics of the vibration wave motor differ depending on the temperature. (C) In order to perform low-speed driving, it is necessary to use the high frequency side, but the high frequency side is susceptible to load fluctuations because the torque fluctuation of the vibration wave motor itself is large.

  Due to these problems, the following can be cited as items to be noted when performing minute driving with a vibration wave motor.

  (1) Since it is necessary to apply a voltage to the vibration wave motor in advance from the high frequency side due to the difference in temperature characteristics, it takes time to start the vibration wave motor.

  (2) Even if the vibration wave motor is started, since the subsequent speed fluctuation is large, the stop position accuracy at the end of the minute driving varies.

  With regard to the above (1), it is possible to relax to some extent by storing the startup frequency introduced in Patent Document 1. However, it does not take measures against the long driving time until storage and the speed fluctuation in (2).

  An object of the present invention is to provide an optical apparatus having a vibration wave actuator capable of solving the above-described problems and shortening focus detection and focusing time when a lens is driven using the vibration wave actuator. is there.

  To achieve the above object, an optical apparatus having a vibration wave actuator according to the present invention includes a vibration wave actuator, frequency changing means for changing the frequency of a voltage applied to the vibration wave actuator, and time measuring means for measuring elapsed time. And a rotation amount detection means for detecting the rotation amount of the vibration wave actuator, and a control means for controlling the vibration wave actuator. The control means has a predetermined frequency when the vibration wave actuator is activated. Is measured by the time measuring means, and the next activation frequency is determined according to the rotation amount detected by the rotation amount detecting means after a predetermined time has elapsed. Features.

  Further, an optical apparatus having a vibration wave actuator according to the present invention includes a driven member, a vibration wave actuator that drives the driven member, and a frequency changing unit that changes a frequency of a voltage applied to the vibration wave actuator; Timing means for measuring the elapsed time, rotation amount detection means for detecting the rotation amount of the vibration wave actuator, and control means for controlling the vibration wave actuator, the control means comprising the vibration wave actuator When starting, an elapsed time after applying a predetermined frequency to the vibration wave actuator is measured by the time measuring means, and information from the rotation amount detecting means after a predetermined time has passed and the driven member The next activation frequency is determined according to the amount of play.

  According to the optical apparatus having the vibration wave actuator according to the present invention, it is possible to alleviate the difficulty of control unique to the vibration wave actuator, and to quickly focus regardless of the difference in the shooting mode of the camera or the detection mode of the autofocus. Detection and focusing time can be shortened.

  The present invention will be described in detail based on the embodiment shown in FIGS.

  FIG. 1 is a block circuit configuration diagram of an interchangeable lens and an autofocus single-lens reflex digital camera. The lens body 1 is attached to the camera body 20 in a replaceable manner. The lens body 1 is provided with a focus unit 3 which is a driven member having a focus lens 2. The lens body 1 incorporates a lens microcomputer 4 having an internal timer 4a as a timekeeping means, and an internal memory 4b composed of ROM, RAM and the like.

  The output of the lens microcomputer 4 is connected to a driver circuit 5 and a booster circuit 6, and the output of the driver circuit 5 is connected to a vibration wave motor 7 that is a vibration wave actuator that drives the focus unit 3. The output of the booster circuit 6 is connected to the driver circuit 5. Outputs of a rotation amount detection unit 8 that detects the rotation amount of the vibration wave motor 7 and a phase difference detector 9 that detects a phase difference between the vibration wave motor 7 are connected to the lens microcomputer 4. Further, the output of the absolute position detector 10 that detects the position of the focus unit 3 is connected to the lens microcomputer 4.

  In the camera body 20, an image sensor 21 made of, for example, a CCD is disposed on the optical axis of the focus lens 2. An image sensor 21, an AF start switch 23, and a distance measuring unit 24 are connected to the camera microcomputer 22 in the camera body 20. The lens microcomputer 4 and the camera microcomputer 22 are connected via a contact unit 25.

  A booster circuit 6 that is a driving power source of the vibration wave motor 7 is a circuit (DC / DC converter) that generates a reference voltage to be applied and boosts the battery voltage to about five times. The driver circuit 5 performs power amplification for driving the vibration wave motor 7. The lens microcomputer 4 is equipped with a serial communication controller, a DAC function, and an input / output port for controlling all of the lens body 1 and communicating with the camera body 20 via the contact unit 25.

  The rotation amount detection unit 8 detects the rotation amount of the vibration wave motor 7 and is composed of a small disk that rotates in synchronization with the rotation of the vibration wave motor 7 and a photo interrupter element. The circular plate is cut off at the same pitch on the circumference, and a signal change is detected depending on whether the light projected from the LED of the photo interrupter element reaches the light receiving element or is blocked. Further, the time interval of one pitch of the signal from the photo interrupter element described above is measured, and the speed of the vibration wave motor 7 and the focus unit 3 is detected.

  In the lens microcomputer 4, the unit of movement is a signal from the photo interrupter element, and each control constant is determined with one signal change as one pulse. Since the movement amount of the focus unit 3 is mechanically proportional to the rotation amount of the vibration wave motor 7, the movement amount of the focus unit 3 is also detected by counting the number of pitches described above. The phase difference detector 9 detects the phase difference between the AC voltage applied to the vibration wave motor 7 and the S phase described above.

  The distance measuring unit 24 measures the current position of the focus unit 3 with respect to the distance to the subject and the amount of focus deviation at the image sensor 21. In an image pickup element of an autofocus camera, a method of detecting a phase difference using a plurality of line sensors using a CCD is generally used. As another method for detecting a focus shift, in the case of a moving image, there is a wobbling method for driving the focus lens described above. This wobbling method is a method in which the focus lens is driven with such a small amount of movement that the camera photographer cannot recognize the focus shift.

  In this embodiment, a minute focus shift due to the wobbling is detected as a contrast change by the image sensor 21 to detect a focus state. If the subject is not in focus, the focus unit 3 is driven at an extremely low speed in the in-focus direction based on the detection result. The camera microcomputer 22 performs all control of the camera, and the photographer instructs the focus and release using the mechanical AF start switch 23.

  The contact unit 25 has a plurality of metal contacts for performing communication with the camera body 20, and a plurality of metal protrusions are provided on the camera body 20 side. On the lens body 1 side, a plurality of metal pieces to be brought into contact with the protrusions are embedded, and the camera microcomputer 22 and the lens microcomputer 4 are electrically connected through the respective metals. Since the metal contact is only in mechanical contact, the lens body 1 can be removed. The position detector 10 is for detecting the absolute position of the focus unit 3, and has a method of forming a specific electrical pattern on a copper foil substrate and reading the pattern with a metal brush.

  An operation when the camera shooting mode is the still image shooting mode or the autofocus detection method is the phase difference method will be described. The camera microcomputer 22 detects the AF start switch 23 and waits until an instruction to start autofocus is received from the photographer. When the instruction is received, the data from the distance measuring unit 24 is captured. The distance measuring unit 24 measures the amount of focus deviation from the distance to the subject and the current position of the focus unit 3 through the position detector 10 of the focus unit 3. The camera microcomputer 22 calculates the amount of movement of the focus unit 3 for focusing from the measured focus shift amount, and communicates with the lens microcomputer 4 through the contact unit 25.

  The lens microcomputer 4 activates the booster circuit 6 and applies a voltage of about 30 V to the driver circuit 5. When a voltage is applied to the driver circuit 5, the lens microcomputer 4 outputs a drive waveform in which the A phase and the B phase are shifted by 90 ° at a predetermined frequency using the internal timer 4 a to drive the vibration wave motor 7. Then, the movement of the focus unit 3 is started. The lens microcomputer 4 gradually decreases the frequency and increases the rotational speed of the vibration wave motor each time a predetermined time elapses in the internal timer 4a. The lens microcomputer 4 always monitors the rotation amount detection unit 8 and compares it with the movement amount transmitted from the camera microcomputer 22. If they match as a result of the comparison, it is determined that the focus unit 3 has moved by a predetermined movement amount, and the drive of the vibration wave motor 7 is stopped.

  Further, the output change of the rotation amount detection unit 8 is measured for time by the internal timer 4a of the lens microcomputer 4, and compared with a time value corresponding to the target speed, that is, the target rotation speed, which is set in the internal memory 4b of the lens microcomputer 4 in advance. To do. As a result, if there is a difference, the frequency is changed, and the rotational speed control of the vibration wave motor 7, that is, the moving speed control of the focus unit 3 is performed.

  When the camera shooting mode is a moving image shooting mode for continuously shooting a subject, or when the autofocus detection method is a TVAF method using wobbling driving, the camera microcomputer 22 always performs an operation of taking a subject image into the image sensor 21. Is going. The moving image shooting mode or wobbling drive instruction is transmitted to the lens microcomputer 4 through the contact unit 25 to the lens microcomputer 4. The focus state of the subject is detected from the imaging data from the image sensor 21, and the direction and speed of movement of the focus lens 2 for focusing on the subject are determined. Next, the determined moving direction and moving speed are transmitted to the lens microcomputer 4.

  The lens microcomputer 4 determines a frequency to be applied to the vibration wave motor 7 in order to perform wobbling driving. When the lens microcomputer 4 receives an instruction of the moving direction and moving speed from the camera microcomputer 22, the lens microcomputer 4 starts up the booster circuit 6 and applies a voltage of about 30 V to the driver circuit 5. When a voltage is applied to the driver circuit 5, the lens microcomputer 4 outputs a drive waveform in which the A phase and the B phase are shifted by 90 ° at a predetermined frequency, and drives the vibration wave motor 7 to move the focus unit 3. To start.

  Every time a predetermined time elapses in the internal timer 4a, the lens microcomputer 4 reverses the 90 ° phase of the A phase and the B phase applied to the vibration wave motor 7 and reverses the moving direction, which becomes the wobbling drive. The focus can be detected. In order to perform focus correction, the focus unit 3 is moved slightly by increasing the wobbling drive time only in the moving direction. The lens microcomputer 4 measures the output change of the rotation amount detection unit 8 with the internal timer 4a of the lens microcomputer 4 and controls the movement speed of the focus unit 3 with the movement speed instructed from the camera microcomputer 22.

  FIG. 2 is a drive circuit diagram of a driver circuit 5, a phase difference detector 9, a booster circuit 6 and a lens microcomputer 4 for operating the vibration wave motor 7. This drive circuit has a method of controlling the speed of the vibration wave motor 7 by changing the frequency.

  As a function of the lens microcomputer 4 for controlling the vibration wave motor 7, a frequency generator function for generating a frequency to be applied to the vibration wave motor 7 and a timer counter function with a signal capture function for detecting the phase of the vibration wave motor 7 It has. The step-up DCDC converter unit 31 is a power supply circuit applied to the vibration wave motor 7, and the operation / non-operation of this circuit is controlled by the converter unit 31. The regulator 32 stably supplies a power source 33, is supplied to the lens microcomputer 4, and is also used as a reference power source for phase detection. The NPN transistor 34 is supplied with power by the inverter 35 on the A phase side of the vibration wave motor 7, and the NPN transistor 36 is supplied with power by the inverter 37 on the B phase side of the vibration wave motor 7.

  The input of the A-phase side inverter 35 and the base of the A-phase side NPN transistor 38 are respectively connected to the A-phase side frequency generator output terminal of the lens microcomputer 4. Further, the output of the inverter 35 is connected to the base of the NPN transistor 34 through the resistor 39, and the power is sinked / sourced to the A phase side of the vibration wave motor 7 by the output logic of the lens microcomputer 4.

  Similarly, the input of the B-phase side inverter 37 and the base of the B-phase side NPN transistor 40 are respectively connected to the B-phase side frequency generator output terminal of the lens microcomputer 4. Further, the output of the inverter 37 is connected to the base of the NPN transistor 36 through the resistor 41, and the power is sinked / sourced to the B phase side of the vibration wave motor 7 by the output logic of the lens microcomputer 4.

  By connecting the A-phase side coil 42 and the A-phase side capacitor 43 in series with the power source, a boosted voltage corresponding to the applied frequency is applied to the A-phase of the vibration wave motor 7. Similarly, by connecting the B-phase side coil 44 and the B-phase side capacitor 45 in series with the power source, a boosted voltage corresponding to the applied frequency is applied to the B phase of the vibration wave motor 7.

  The piezoelectric element 50 is distorted by applying a voltage to the A phase and the B phase by the A phase side electrode 46, the B phase side electrode 47, the S phase electrode 48 and the GND electrode 49 of the vibration wave motor 7. As a result, the phase of the B phase with respect to the A phase is changed by ± 90 °, an elliptical motion is generated on the contact surface with the rotating portion of the vibration wave motor 7 and the rotating portion rotates.

  The voltage dividing circuit 51 halves the voltage of the regulator 32 to form the threshold voltage of the comparators 52 and 53. The high pass filters 54 and 55 are for the S phase of the vibration wave motor 7, and the high pass filters 56 and 57 are for the B phase of the vibration wave motor 7. The comparator 52 is for the B phase of the vibration wave motor 7, and performs waveform shaping of the B phase for level shifting to the voltage of the regulator 32. The comparator 53 is for the S phase of the vibration wave motor 7 and performs S phase waveform shaping in order to shift the level to the voltage of the regulator 32.

  The lens microcomputer 4 detects the phase difference output of the comparators 52 and 53, and controls the phase by limiting the change in frequency so that the control does not exceed the resonance frequency shown in FIG.

  As shown in FIG. 12, unlike the DC motor, the vibration wave motor 7 exhibits non-linear characteristics in which the amount of change in frequency and the rotational speed are not simply proportional. As described above, since the rotation speed is low and the torque is small on the high frequency side, the rotation speed changes with load fluctuation. Since the low frequency side has a high rotational speed and a large torque, the rotational speed does not change with a slight load fluctuation.

  In order to perform the wobbling drive using the vibration wave motor 7 described above, the wobbling drive is preferably a minute drive, and therefore it is desirable to drive using the high frequency side as the control. This is because the high-frequency side is considered to be suitable for fine driving because the rotation speed is slower.

  FIG. 3 is a temperature characteristic diagram of the FN characteristic of the vibration wave motor 7 using the temperature as a parameter. The FN characteristic shifts with the temperature as a whole, shifts to the high frequency side when the temperature is low, and changes when the temperature is high. Shifts to the low frequency side. FIG. 4 is an enlarged view of a portion surrounded by an alternate long and short dash line in FIG. When the frequency of the voltage applied to the vibration wave motor 7 is moved from a high frequency to a low frequency, the rotation starts suddenly from a certain frequency as shown in FIG. The frequency at which this rotation starts is called the starting frequency, and this offset itself has no problem.

  However, this starting frequency changes due to load fluctuations and temperature characteristics, or the slope on the low frequency side after that changes somewhat. When the high frequency side as shown in FIG. 4 is used for wobbling driving, it is considered that the start-up time of the vibration wave motor 7 is delayed depending on the load, which is not suitable for wobbling driving in which the driving time is determined. . Furthermore, since the vibration wave motor 7 also has different temperature characteristics, measures such as temperature detection are required to perform stable wobbling driving.

  In this embodiment, attention is paid to wobbling driving when moving image shooting is performed using the vibration wave motor 7, and the above-described points weak against temperature characteristics and torque fluctuations are improved. For this reason, for torque fluctuations, the driving frequency on the lower frequency side is used for moving image shooting than for still image shooting, and the current characteristics of the vibration wave motor 7 are detected by the initial operation before shooting for temperature changes. It can respond by doing.

  In the initial operation, when the lens main body 1 incorporating the vibration wave motor 7 is attached to the camera main body 20, power is supplied from the camera main body 20 through the contact unit 25, and the lens microcomputer 4 executes a reset operation. In this reset operation, a specific frequency is applied for a predetermined time in order to determine the current characteristics of the vibration wave motor 7. For example, assuming that the applied frequency is 30.0 KHz and the predetermined time is 100 ms, the average speed after the vibration wave motor 7 is started (to be precise, it is the average of the driving time, but in this specification it is easy to understand the speed) is detected. To do. As an average speed detection method, calculation is performed based on the movement amount output from the internal timer 4a of the lens microcomputer 4 and the rotation amount detection unit 8. For example, when the movement amount in 100 ms is 50 pulses, 100/50 = 2.0 ms / pulse is an average value.

  It is conceivable that the calculation result of the average speed can be earlier or slower than 50 pulses even if the same frequency is applied due to the difference in motor characteristics, torque fluctuation, and ambient temperature as described above. Therefore, since it is necessary to detect this motor characteristic at the time of mounting on the camera and determine the starting frequency at the time of wobbling driving, such an operation process is performed in the reset process of the lens microcomputer 4.

  Table 1 shows the table data of the starting frequency at the time of moving mode or wobbling driving at the infinite focus position stored in the internal memory 4b of the lens microcomputer 4 when the amount of mechanical play is small.

Table 1
Applied frequency Speed information Starting frequency 30.0KHz 1-2ms 31.0KHz
2-3ms 30.5KHz
3-4ms 30.0KHz
Applied frequency Speed information Starting frequency 29.5KHz 1-2ms 30.5KHz
2-3ms 30.0KHz
3-4ms 29.5Hz
Applied frequency Speed information Starting frequency 30.5KHz 1-2ms 31.5KHz
2-3ms 31.0KHz
3-4ms 30.5KHz

  When the average value calculated above is applied to Table 1, since the average speed when applying 30 KHz is 2 ms, the starting frequency at the time of wobbling driving in the middle of the top table is 30.5 KHz. First, as a precondition for determining the values in Table 1, the required movement amount in wobbling driving is 25 pulses and the driving time is 80 ms. This value means that the time allowed for the autofocus system in the wobbling operation for detecting the focus as a moving image is 80 ms. In addition, in order to detect a change in the focus of the subject, it means that 25 pulses of vibration wave drive are required, and the focus must be changed by 25 pulses in 80 ms. From these values, it can be determined that 80 ms / 25 pulses = 3.2 ms is the drive time per pulse, and the required average speed is 3.2 ms / pulse.

  In Table 1, this 3-4 ms is the average speed required for wobbling. For example, when the applied frequency is 30 KHz and the average speed is 2.5 ms, if the wobbling operation is performed at 30 KHz, the driving speed is fast, resulting in a driving amount of 25 pulses or more, and the user can see the variation in focus. A malfunction occurs.

  Therefore, in Table 1, the applied frequency in the wobbling drive is selected to be 30.5 KHz, and the frequency is set so that the drive is slower than 30 KHz. Further, for example, when the applied frequency is 30 KHz and the average speed is 5 ms, the driving amount is less than 25 pulses, and it is conceivable that problems such as inability to detect a focus change may occur. In such a case, faster start-up must be performed, and the re-driving and re-measurement are performed at an applied frequency of 29.5 KHz earlier. This is the same even when it is too early. If it is outside the range of the table data in Table 1, the applied frequency is changed and remeasurement is performed, and the frequency applied during the wobbling drive is determined by these operations.

  In this embodiment, the applied frequency is set to the center of the three measurement frequency ranges in FIG. 3 is set on condition that the vibration wave motor 7 can be started under all temperature conditions. In addition, the vibration wave motor 7 can be started from a substantially constant speed at the same time when the frequency is applied regardless of the load by setting the relatively low frequency side so that it is hardly affected by the load fluctuation factor.

  That is, based on the average speed described above, the necessary start-up frequency is changed from Table 1, and when the wobbling drive is performed, the above-described invention is to be solved by applying the changed start-up frequency to the vibration wave motor 7. Therefore, the control corresponding to the condition (1) described in the problem to be performed can be performed.

  In Table 1, the speed information is the average speed. However, if the condition (1) is always constant, the table of the movement amount and the starting frequency may require fewer calculations. However, since the amount of movement for detection is considered to be not constant depending on various conditions of the lens body 1, the average speed is used in this embodiment.

  Table 1 shows that the applied frequencies are different, but this is for determining the starting frequency by changing the applied frequency when the condition is not satisfied. For example, when the applied frequency is too high at 30 KHz, stable control can always be performed by changing to 30.5 KHz when the applied frequency is too slow and changing to 29.5 KHz when the applied frequency is too slow.

  Table 1 shows the average speed. If the table is based on the drive amount after a predetermined time, or the table based on the elapsed time when the predetermined drive amount is driven, the average speed is shown. Since the arithmetic processing can be reduced, the processing of the lens microcomputer 4 can be accelerated.

  FIG. 5 is a flowchart showing the operation by the program in the serial communication processing of the lens microcomputer 4 of the present embodiment. The program analyzes the communication sent from the camera body 20 through the contact unit 25 and performs necessary processing. is there. The processing of the lens microcomputer 4 is performed in the interrupt processing of the serial communication unit.

  (Step S102) The lens microcomputer 4 analyzes the communication sent from the camera microcomputer 22 and determines whether it is related to a focus drive command.

  (Step S103) If the communication sent from the camera microcomputer 22 is other than the focus drive command, other processing is performed. Since only the focus drive command is related to the present embodiment, description of other processing is omitted.

  (Step S104) If the communication sent from the camera microcomputer 22 is a focus drive command, the current camera shooting mode is confirmed. This discriminates whether it is a still image shooting mode which is a single shooting mode or a moving image shooting mode by continuous shooting mode. As a determination method, shooting mode information is transmitted from the camera microcomputer 22 in advance, and is temporarily stored and determined. This storage process is performed in the other process of step S103.

  In this processing, determination of an autofocus detection method may be performed in addition to the shooting mode. In this case, the determination is a wobbling operation for a moving image and a phase difference for a still image. That is, the camera microcomputer 22 sends in advance information on either a still image, a moving image, phase difference AF, TVAF, or a normal operation or a wobbling operation.

  (Step S105) If the shooting mode of the camera body 20 is the moving image shooting mode, the wobbling operation is started by applying the starting frequency determined from Table 1 to the vibration wave motor 7, and the internal timer 4a of the lens microcomputer 4 is simultaneously started. Start.

  (Step S106) If the shooting mode of the camera body 20 is the still image shooting mode, the activation frequency for still image shooting is applied to the vibration wave motor 7 to start the focus drive. The start-up frequency for still image shooting is exactly the same as the conventional interchangeable lens control technique using the vibration wave motor 7.

  The outline is to store the starting frequency of the vibration wave motor 7 introduced in the background art and set the starting frequency at the next driving. Further, a movement amount for focusing on the subject is transmitted from the camera microcomputer 22 in advance, and the focus unit 3 is controlled to stop according to the movement amount.

  (Step S107) An end process of the camera communication process is performed. The interrupt processing for serial communication is mainly completed, and the next communication is set to be received.

  FIG. 6 is a flowchart showing the program operation in the reset processing and normal processing of the lens microcomputer 4 of this embodiment.

  (Step S <b> 201) This process is performed mainly when the lens body 1 is attached to the camera body 20 in the reset process of the lens microcomputer 4. That is, basically, the lens microcomputer 4 performs processing only once when the power is turned on.

  (Step S202) In order to determine the current characteristics of the vibration wave motor 7 described in Table 1, a specific frequency is applied for a predetermined time. For example, in Table 1, the applied frequency is first described as 30.0 KHz as an intermediate frequency. Simultaneously with the application, the internal timer 4a of the lens microcomputer 4 is started.

  (Step S203) The timer value started in Step S202 is read to determine whether a predetermined time has elapsed, and wait until the time has elapsed. The predetermined time is, for example, 100 ms described in Table 1.

  (Step S204) When 100 ms elapses in step S203, the average speed is calculated based on the relationship between the result of reading the signal from the rotation amount detection unit 8 and the time of 100 ms. For example, when the applied frequency is 30.0 KHz and the movement amount is 50 pulses when the predetermined time is 100 ms, 100/50 = 2.0 ms / pulse is an average value.

  Table 1 is stored in advance as table data in the internal memory 4b of the lens microcomputer 4, and the average value is compared with the table data. The result is stored in the internal memory 4b as the next activation frequency.

  (Step S205) As a result of comparing the average speed calculated in Step S204 with the table data, if the activation frequency cannot be derived, the process returns to Step S202 again. The applied frequency at this time is other than 30.0 KHz. In this step, this series of processing is repeated until the activation frequency is determined.

  (Step S206) When it is determined in step S205 that the activation frequency has been determined, the subsequent processing is normal lens processing.

  (Step S207) The lens microcomputer 4 detects the state of various switches and writes the detection result in the internal memory 4b of the lens microcomputer 4. The switch is equipped with an auto focus / manual focus switching switch, a zoom position detection switch in the case of a zoom lens, and many other switches, but the description is omitted because it is not related to this embodiment.

  The position detector 10 detects the absolute position of the focus unit 3. The lens microcomputer 4 stores various optical data based on the absolute position of the focus unit 3 in the internal memory 4b, and changes the control based on the position information.

  (Step S <b> 208) The lens microcomputer 4 determines in sequence whether the focus unit 3 is currently driven based on whether or not a voltage is simply applied to the vibration wave motor 7. If the focus unit 3 is not being driven, the process proceeds to step S207. The lens microcomputer 4 performs various other processes, but since it is not related to the present embodiment, the description other than when driving the lens is omitted.

  (Step S209) If the focus unit 3 is being driven in step S208, the shooting mode of the camera is confirmed. In this processing, determination of an autofocus detection method may be performed in addition to the shooting mode, and a wobbling operation is determined for a moving image, and a phase difference is determined for a still image. In other words, the camera microcomputer 22 sends in advance information on either a still image, a moving image, phase difference AF, TVAF, normal operation of focusing, or wobbling operation, and makes a determination accordingly.

  As a result, if all are the former, the process proceeds to the flowchart of FIG. 7 described later as still image processing, and if the latter, the process proceeds to the flowchart of FIG. When one process ends, the process proceeds to step S207.

  FIG. 7 is a flowchart of the program processing operation by the lens microcomputer 4 when the shooting mode of the camera body 20 is the still image shooting mode, the phase difference AF mode, or the normal operation of the focus.

  (Step S301) Since it is determined that the focus is being driven in Step S208 of FIG. 6, the current moving speed of the focus unit 3 is detected. As a speed detection method, the lens microcomputer 4 recognizes the time per pulse by measuring the pitch interval of the pulse output from the rotation amount detection unit 8 with the internal timer 4a. In the still image shooting mode, since the focus unit 3 is controlled to move at a preset speed, the application to the vibration wave motor 7 is performed so that the predetermined speed is obtained based on the speed information. The frequency has been changed.

  (Step S302) Since the movement amount of the focus unit 3 for focusing on the subject has been transmitted from the camera microcomputer 22 in advance, the movement detection is performed to determine whether or not the movement amount has been reached. If the amount of movement has not been reached, the process proceeds to step S304 and the process is terminated.

  (Step S303) Since the predetermined amount of movement has been reached, the voltage application to the vibration wave motor 7 is stopped and the focus drive is stopped.

  (Step S304) The processing of this routine is terminated.

  FIG. 8 is a flowchart of the program processing operation by the lens microcomputer 4 when the shooting mode of the camera body 20 is the moving image shooting mode, the TVAF mode, or the focus wobbling operation.

  (Step S401) The value of the internal timer 4a of the lens microcomputer 4 started in Step S105 of FIG. 5 is confirmed. This waits for a time until the movement of the focus unit 3 is reversed by the wobbling drive. At this time, the time is fixed at 80 ms, for example.

  (Step S402) Since the internal timer 4a has reached 80 ms, the two phases of the A phase and the B phase applied to the vibration wave motor 7 are reversed by 90 °. As a result, the vibration wave motor 7 is driven in the direction opposite to the previous rotation direction, and the moving direction of the focus unit 3 is also reversed.

  (Step S403) When the camera body 20 is set to prohibit autofocus and the shooting mode is set to other than moving image, it is necessary to prohibit the wobbling operation, so it is determined whether or not the communication is transmitted from the camera microcomputer 22. If no stop command has been sent, the process proceeds to step S405, and the process ends.

  (Step S404) When a command to stop the wobbling drive is transmitted from the camera microcomputer 22, the voltage application to the vibration wave motor 7 is stopped and the focus drive is stopped.

  (Step S405) The processing of this routine is terminated.

  FIG. 9 is a flowchart of the operation on the program in the processing for the lens microcomputer 4 of the camera microcomputer 22 of the present embodiment, and only the portion related to the present embodiment will be described.

  (Step S501) The camera microcomputer 22 confirms the state of the AF start switch 23. In this state, in S1, the photographer mainly instructs the start of autofocus. The camera microcomputer 22 determines whether this state S1 is on.

  (Step S502) Since the photographer is not instructed to start autofocus, other processing is performed. The contents of the other processes are irrelevant to the present embodiment, and the description is omitted. The present embodiment relates to the case where the state S1 is OFF, and only transmits a wobbling operation stop command to the lens microcomputer 4.

  (Step S503) Since the start of autofocus is instructed by the photographer, the current shooting mode of the camera body 20 is transmitted to the lens microcomputer 4. The contents include information on either a still image, a moving image, phase difference AF, TVAF, focus normal operation, or wobbling operation.

  (Step S504) Since auto-focusing is started, when the shooting mode of the camera body 20 is a still image, the movement amount of the focus unit 3 for focusing on the subject is set to the lens microcomputer 4 based on the output from the distance measuring unit 24. Send. When the camera mode is a moving image, a wobbling start command is transmitted to the lens microcomputer 4. Thereafter, the process proceeds to step S501.

  In the first embodiment, the ideal lens body 1 has been described. However, there is actually a problem to be considered. This is a mechanical ratchet at the part where the vibration wave motor 7 and the focus unit 3 are coupled, that is, backlash. In the first embodiment, it is assumed that the amount of play is 0 or always constant. However, in practice, this amount of movement cannot be ignored in relation to the amount of focus movement (sensitivity) at the image sensor 21 with respect to the amount of movement of the focus lens 2.

  When the moving amount of the focus lens 2 is larger than the actual moving amount of the lens having high sensitivity, the focus of the subject is changed by the wobbling drive, so that the photographed image looks worse. On the other hand, if the moving amount of the focus lens 2 is smaller than the actual lens with low sensitivity, the amount of change in the contrast of the subject during TVAF is small, resulting in an obstacle such as being out of focus. Therefore, it is necessary to perform control in consideration of the amount described above. In the second embodiment, this is a countermeasure and is intended to minimize the problem.

  FIG. 10 is a characteristic diagram showing the time from when the vibration wave motor 7 is driven until the focus unit 3 reaches a predetermined movement amount. In FIG. 10, there is a portion that has not moved despite the passage of time, but this is because it takes some time for the vibration mode to stabilize even when the vibration wave motor 7 is started. ing. However, it is negligible in terms of time and can be almost ignored.

  The time A represents a state in which there is almost no mechanical backlash between the vibration wave motor 7 and the focus unit 3 described above. In this case, it can be determined that the focus unit 3 is immediately moving at the same time as the motor is started. The time B represents a state in which there is mechanical backlash between the vibration wave motor 7 and the focus unit 3. In this case, even if the vibration wave motor 7 is started, the focus unit 3 does not move until it becomes clogged, so that there is a time difference between the A time and the B time.

  Normally, this rattling state can be created by reversing the previous driving direction of the vibration wave motor 7. Since reversal is always repeated with wobbling drive in TVAF, by setting this amount to a constant amount, if it is added to the motor drive time by the delay time, a stable stop position can be obtained. However, it is difficult to keep the amount of blurring constant. Particularly, in recent years, the mechanical configuration of the interchangeable lens has become complicated, and the amount of blurring differs depending on the position of the focus unit 3 or the zooming position having a zooming function. It has become common. Therefore, it is necessary to change the control state based on the position information.

  Table 1 described in the first embodiment assumes a case where the absolute position of the focus unit 3 is on the infinite side and the amount of backlash is relatively small. However, in the following Table 2, the absolute position of the focus unit 3 is on the near side. Suppose that the amount of rattle is large.

  Compared with Table 1, the starting frequency is set lower in the moving image mode or the wobbling drive starting frequency at the focus closest side position when the amount of play in Table 2 is large.

Table 2
Applied frequency Speed information Start frequency 30.0KHz 1-2ms 30.5KHz
2-3ms 30.0KHz
3-4ms 29.5KHz
Applied frequency Speed information Starting frequency 29.5KHz 1-2ms 30.0KHz
2-3ms 29.5KHz
3-4ms 29.0Hz
Applied frequency Speed information Starting frequency 30.5KHz 1-2ms 31.0KHz
2-3ms 30.5KHz
3-4ms 30.0KHz

  As a result, the vibration wave motor 7 can be moved faster than the infinite position, and the amount of rotation of the vibration wave motor 7 can be increased within the time limit for wobbling driving, thereby reducing the influence of rattling. Therefore, in Table 2, since the vibration wave motor 7 moves faster as the frequency is lower than in Table 1, the starting frequency is set lower by 0.5 KHz under the same conditions.

  In summary, Table 1 is used when the focus unit 3 is located on the infinite side, and Table 2 is used when the focus unit 3 is located on the closest side. That is, since the amount of play differs depending on the position of the focus unit 3, the absolute position detector 10 detects the position information of the focus unit 3 and decides which table to use.

  Table 2 shows the average speed. If the table is based on the drive amount after the predetermined time has elapsed, or the table is based on the elapsed time when the predetermined drive amount is driven, the average speed is shown. Since the arithmetic processing can be reduced, the processing of the lens microcomputer 4 can be accelerated.

  FIG. 11 is an operation flowchart according to the program in the reset process and the normal process by the lens microcomputer 4 of the second embodiment.

  (Step S601) The lens microcomputer 4 is reset mainly when the lens body 1 is attached to the camera body 20. Basically, the lens microcomputer 4 performs processing only once when the power is turned on.

  (Step S602) In order to determine the current characteristics of the vibration wave motor 7 described in Table 1 or 2, a specific frequency is applied for a predetermined time. For example, in Table 1 or Table 2, the applied frequency is first described as 30.0 KHz as an intermediate frequency. Simultaneously with the application, the internal timer 4a of the lens microcomputer 4 is started.

  (Step S603) The value of the internal timer 4a started in Step S602 is read to determine whether a predetermined time has elapsed, and wait until the time has elapsed. The predetermined time is, for example, 100 ms described in Table 1 or 2.

  (Step S604) The lens microcomputer 4 reads the signal from the position detector 10 and detects the absolute position of the focus unit 3. In this embodiment, there are only two types, the closest side or the infinite side, but the absolute position that can be detected can be increased in accordance with the allowable amount.

  (Step S605) When the elapsed time by the internal timer 4a is 100 ms in step S603, the average speed is calculated based on the relationship between the result of reading the signal from the rotation amount detection unit 8 and the time of 100 ms. For example, when the applied frequency is 30.0 KHz and the movement amount is 50 pulses when the predetermined time is 100 ms, 100/50 = 2.0 ms / pulse is an average value.

  Based on this average value and the position information detected in step S604, the data stored in advance in the internal memory 4b of the lens microcomputer 4 as Table data 1 or 2 is compared. If the position information is infinite, the activation frequency is small when the amount of play is small, and if the position information is close, the activation frequency is when the amount of play is large, and the result is the next activation frequency and the result is the internal memory 4b of the lens microcomputer 4. To remember.

  (Step S606) As a result of comparing the average speed calculated in Step S605 with the table data, if the activation frequency cannot be derived, the process proceeds to Step S602 again. The applied frequency at this time is other than 30.0 KHz. In this step S606, this series of processing is repeated until the activation frequency is determined.

  (Step S607) If it is determined in step S606 that the activation frequency has been determined, normal lens processing is performed thereafter.

  (Step S608) The lens microcomputer 4 detects the state of various switches and writes the detection result in the internal memory 4b of the lens microcomputer 4.

  The lens microcomputer 4 stores various optical data based on the absolute position of the position detector 10 in the internal memory 4b, and changes the control based on the position information.

  (Step S609) The lens microcomputer 4 determines whether or not the focus unit 3 is currently being driven. If it is not being driven, the process proceeds to step S608.

  (Step S610) If the focus unit 3 is being driven in step S609, the shooting mode of the camera body 20 is confirmed.

  From the camera microcomputer 22, information on either a still image, a moving image, normal operation of phase difference AF, TVAF or focus, or a wobbling operation is sent in advance, and a determination is made accordingly. As a result, if all are the former, the process proceeds to the flowchart of FIG. 7 as still image processing, and if the latter, the process proceeds to the flowchart of FIG. 8 as moving image processing. When one process ends, the process proceeds to step S608.

1 is a block circuit configuration diagram of a single-lens reflex digital camera of Embodiment 1. FIG. It is a drive circuit diagram of a vibration wave motor. It is a temperature characteristic figure of a vibration wave motor. FIG. 4 is an FN characteristic diagram of a vibration wave motor showing a partial enlargement of FIG. 3. It is a processing flowchart figure. It is a flowchart figure of a reset process. It is a flowchart figure of a motor control process. It is a flowchart figure of a motor control process. It is a flowchart figure of a camera process. FIG. 6 is a characteristic diagram of time and focus movement amount. FIG. 10 is a flowchart of reset processing according to the second embodiment. It is a FN characteristic view of a vibration wave motor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Lens main body 2 Focus lens 3 Focus unit 4 Lens microcomputer 4a Internal timer 4b Internal memory 5 Driver circuit 6 Booster circuit 7 Vibration wave motor 8 Rotation amount detection unit 9 Phase difference detector 10 Absolute position detector 20 Camera main body 21 Imaging element 22 Camera microcomputer 23 AF start switch 24 Ranging unit 25 Contact unit

Claims (6)

A vibration wave actuator; a frequency changing means for changing a frequency of a voltage applied to the vibration wave actuator; a time measuring means for measuring an elapsed time; a rotation amount detection means for detecting a rotation amount of the vibration wave actuator; Control means for controlling the wave actuator, and when the vibration wave actuator is activated, the control means measures an elapsed time after applying a predetermined frequency to the vibration wave actuator by the time measuring means. , optical science apparatus and determines the next starting frequency according to the rotation amount detected by the rotation amount detecting means after a predetermined time has elapsed. A driven member, a vibration wave actuator that drives the driven member, a frequency changing unit that changes a frequency of a voltage applied to the vibration wave actuator, a time measuring unit that measures an elapsed time, and a rotation of the vibration wave actuator A rotation amount detecting means for detecting the amount; and a control means for controlling the vibration wave actuator, wherein the control means applies a predetermined frequency to the vibration wave actuator when the vibration wave actuator is activated. The elapsed time after the measurement is measured by the time measuring means, and the next starting frequency is determined according to the information from the rotation amount detecting means after a predetermined time has elapsed and the amount of play of the driven member. light science equipment and features. Information on the applied frequency, the speed when the vibration wave actuator is applied at the applied frequency, and the activation frequency of the vibration wave actuator is acquired in advance, and the previously acquired information and the vibration wave actuator are acquired at the predetermined frequency for the predetermined time. The optical apparatus according to claim 1 or 2, wherein a next activation frequency is determined by comparing with information obtained from a rotation amount detected by the rotation amount detection means when driven. It said control means lights Studies device according to any one of claims 1 to 3, characterized in that use is switched next time the starting frequency by a camera shooting mode. Light Studies device according to claim 4, characterized in that it comprises a moving image shooting mode for continuously shooting a subject image, the two cameras photographing mode of the still image shooting mode is a single shot. Light Science apparatus according to claim 4 by the difference autofocus detection system for focusing on the subject, and having a camera shooting mode for switching the starting frequency.

Images