JP2006064830A - Lens drive unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lens drive unit which can be made small, and can realize accurate detection of the reference position of a lens even when the unit is abnormally ended. <P>SOLUTION: A DC motor (19) as a lens driving means is driven so that a zoom lens holding frame (15) for holding a zoom lens goes toward a sensor (33), and a focus lens holding frame (13) is moved with the contact of the zoom lens holding frame (15), and the position of the zoom lens when it is detected by the sensor (33) that the focus lens holding frame (13) reaches the reference position is detected as the reference position of the zoom lens. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a lens driving device used in an imaging apparatus such as a digital still camera and a digital video camera, and more particularly to a lens driving device that performs lens position control based on a reference position.

  In general, a zoom function and a focus function of an imaging apparatus such as a digital camera are realized by performing control to move a zoom lens group and a focus lens group arranged in a lens barrel in the optical axis direction. At this time, a predetermined position in the lens barrel of the zoom lens group or the focus lens group is set as a reference position, and lens movement control is performed based on the reference position.

  For this reason, a sensor for detecting a reference position (origin position) of a zoom lens unit or a focus lens unit that moves in the optical axis direction is generally attached in the lens barrel. Conventionally, the output level of the photosensor when the lens unit is driven by a motor using the shielding member attached to the lens unit and the transmission photosensor, and the shielding member moved together with the lens unit crosses the photosensor. A method for detecting a reference position of a lens unit by monitoring a change has been proposed. Such a detection method is disclosed in Patent Document 1, for example.

  Hereinafter, the method disclosed in Patent Document 1 will be described. FIG. 20 is a diagram illustrating a main part of the configuration of the lens driving device disclosed in Patent Document 1. In FIG. This lens driving device has a focus lens unit 111 that carries a focus lens group and a zoom lens unit 115 that carries a zoom lens group, which are driven by motors 117 and 119 via feed screws 118 and 120, respectively. The Shield plates 131 and 132 are attached to the focus lens unit 111 and the zoom lens unit 115, respectively. A photosensor 133 including a light emitting element and a light receiving element is provided in the lens barrel 139, and outputs a detection signal when light propagation from the light emitting element to the light receiving element is interrupted. The photosensor 133 is disposed at a predetermined position in the lens barrel 139 that gives a reference position for each of the focus lens unit 111 and the zoom lens unit 115.

The focus lens unit 111 is moved in the optical axis direction by a motor 117 and a feed screw 118. When the shielding plate 131 passes through the photosensor 133 due to the movement, the photosensor 133 changes its output level. The control device 137 can detect that the focus lens unit 111 has reached the reference position of the focus lens by monitoring the output level of the photosensor 133. Similarly, the zoom lens unit 115 can detect that the reference position of the zoom lens has been reached.
JP-A-4-184309

  In the lens driving device configured as described above, it is necessary to dispose a common photosensor between the zoom lens unit and the focus lens unit, and to provide a shielding member for each lens unit. Further, when the lens unit is stored, the lens units need to be brought close to each other. At this time, in order to prevent the mutual shielding members from coming into contact with each other, it is necessary to take measures such as increasing the size of the photosensor. Such a configuration becomes an obstacle to downsizing the lens driving device in the optical axis direction.

  Further, in the imaging apparatus having the above configuration, when the power supply is interrupted due to an unexpected situation and abnormally ends, and the imaging apparatus is subsequently activated, the reference position detection process of the zoom lens unit is normally performed. However, there is a problem in that a normal reference position cannot be detected if the focus lens unit is abnormally terminated while the photo sensor is blocked.

  SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and the object of the present invention is to enable downsizing of the lens driving device and to accurately detect the reference position of the lens even in the case of abnormal termination. An object of the present invention is to provide a lens driving device that can be used.

  The lens driving device according to the present invention includes a first lens holding frame that holds the first lens, first lens driving means that drives the first lens holding frame, and the first lens holding frame that is a predetermined reference. A sensor for detecting that the position has been reached; a second lens holding frame that holds the second lens and can directly or indirectly contact the first lens holding frame; and a second lens holding frame And a second lens driving means for driving the first and second lens driving means, and a control means for determining a reference position of each of the first and second lenses. The control means drives the second lens driving means so that the second lens holding frame faces the sensor, and moves the first lens holding frame by direct or indirect contact with the second lens holding frame. The position of the second lens holding frame when the first lens holding frame reaches the reference position is detected as the reference position of the second lens.

  The control means determines whether or not the lens driving device has ended normally last time. If it is determined that the lens driving device has not ended normally, the control means further detects the reference position of the second lens before detecting the first lens holding frame. The following control may be performed by determining whether the sensor has detected that has reached the reference position. That is, when the sensor detects that the first lens holding frame has reached the reference position, the control means moves the first lens holding frame in the direction toward the sensor, while the first lens If the sensor does not detect that the holding frame has reached the reference position, the first lens holding frame may be moved away from the sensor.

  In the above case, the control means determines that the sensor has detected that the first lens holding frame has reached the reference position before detecting the reference position of the second lens without completing the normal end. In this case, it is more preferable that the first lens driving unit is driven with a smaller power than that in the normal operation to move the first lens holding frame in the direction toward the sensor.

  The control means applies the power equivalent to the first lens holding frame reaching the reference position to the first lens driving means, but the first lens holding frame is the reference position of the first lens. If the sensor does not detect that it has reached the value, it may be determined that there is an error state, and the first lens driving unit may be driven with greater power than during normal operation.

  When the first lens driving unit is a stepping motor, the control unit changes the current applied to the stepping motor from a sine wave to a rectangular wave and determines the phase of the current when the first lens driving unit is determined to be in an error state. It is more preferable to set the phase at which the torque of the stepping motor is maximum in the moving direction of one lens holding frame.

  The reference position of the first lens may be detected after detecting the reference position of the second lens.

  The sensor may include a light emitting element and a light receiving element, and may output signals having different levels according to transmission and blocking of light from the light emitting element to the light receiving element. At this time, the control means determines that the first lens has reached the reference position when the output of the sensor indicates a change from the light shielding state to the light transmitting state.

  The first lens driving means includes urging means for urging the first lens holding frame in a direction away from the sensor, and means for transmitting power in a direction toward the sensor side to the first lens holding frame. But you can.

  Further, the control means determines whether or not the normal end has been completed last time, and if it is determined that the normal end has not been completed, the control unit further includes the first lens holding frame before detecting the reference position of the second lens. It may be determined whether the sensor has detected that the reference position has been reached, and the following control may be performed. That is, when the sensor does not detect that the first lens holding frame has reached the reference position, the control means moves the first lens holding frame by a predetermined amount in a direction away from the sensor, and When the sensor detects that the holding frame has reached the reference position, the first lens holding frame may be moved larger than a predetermined amount in a direction away from the sensor.

  According to the present invention, since the reference position of the zoom lens is detected using the shielding plate attached to the focus lens holding frame while the focus lens holding frame is pushed down by the zoom lens holding frame, the shielding plate is attached to each lens. Therefore, it is not necessary to provide the device, and the device can be downsized. Further, at the time of startup after abnormal termination, the reference position detection operation is performed after the lens is moved to a position suitable for the reference position detection, so that the reference position can be normally detected.

  Embodiments of a lens driving device according to the present invention will be described with reference to the accompanying drawings.

1. Configuration of Apparatus FIG. 1 is a diagram showing a configuration of a main part of an imaging apparatus such as a digital still camera or a digital video camera to which the technical idea of the present invention is applied.

  The focus lens holding frame 13 holding the focus lens 11, the zoom lens holding frame 15 holding the zoom lens (not shown), the focus lens and the zoom lens have reached the reference position in the lens barrel of the image pickup apparatus. A photo sensor 33 for detecting this and a CCD image sensor 35 for converting optical information input via a lens into an electrical image signal are provided.

  The photosensor 33 includes a light emitting element and a light receiving element, and outputs signals having different levels according to transmission / blocking of light from the light emitting element to the light receiving element. A light shielding plate 31 is attached to the focus lens holding frame 13. When the focus lens holding frame 13 reaches a predetermined position, the light in the photosensor 33 is blocked by the light shielding plate 31 and output from the photosensor 33. The signal level to be changed changes.

  The focus lens holding frame 13 and the zoom lens holding frame 15 are attached to the guide pole 21 so as to be slidable in the axial direction (optical axis direction). The zoom lens holding frame 15 is driven by a DC motor 19. The focus lens holding frame 13 is biased by a spring 23 along the guide pole 21 toward the subject (A direction). The focus lens holding frame 13 receives an elastic force from the spring 23 and tries to move upward (direction A), but its position can be regulated by the regulating member 29. The regulating member 29 is screwed with the rotating shaft 27 of the stepping motor 17 and moves in the optical axis direction as the rotating shaft 27, that is, the stepping motor 17 rotates.

  The CCD image sensor 35 is attached to a lens barrel outer frame 39. The lens barrel outer frame 39 is provided with a stopper 25 for preventing collision between the focus lens holding frame 13 and the CCD image sensor 35.

  A pressing member 18 is attached to the focus lens side of the zoom lens holding frame 15. The pressing member 18 can come into contact with the focus lens holding frame 13, and can push the focus lens holding frame 13 toward the CCD image sensor 35 (B direction) in the contacted state. The focus lens holding frame 13 of the zoom lens holding frame 15 may be brought into direct contact without using the pressing member 18.

  The lens driving device further includes a microcomputer 37 for operation control. The microcomputer 37 is composed of, for example, a semiconductor integrated circuit. The microcomputer 37 includes a signal processing unit 37a that processes an image signal from the CCD image sensor 35, and a control unit 37b that drives the stepping motor 17 and the DC motor 19 to control lens driving and lens reference position detection processing. .

  In the imaging apparatus, the position of the focus lens holding frame 13 in the optical axis direction is controlled by the elastic force of the spring 23 and the regulating member 29 driven by the stepping motor 17. The zoom lens holding frame 15 is moved to a desired position in the optical axis direction by a DC motor 19.

  The rotation angle of the stepping motor 17 is determined according to the number of applied pulses. The amount of movement of the lens 11 is proportional to the rotation angle of the stepping motor 17. Therefore, if the number of pulses applied to the stepping motor 17 is counted, the position of the focus lens holding frame 13 can be grasped by referring to the count value. 2A is a diagram showing a drive current waveform applied to the stepping motor 17, and FIG. 2B is a diagram showing the movement of the lens holding frame 13 at that time. (C) is a view showing a state of rotation of the stepping motor 17. As shown in FIG. 2A, two-phase drive currents X1 and X2 that are 90 degrees out of phase are applied to the stepping motor 17. By applying this drive current, the stepping motor 17 rotates as shown in FIG. 2C, and the frame lens holding frame 13 is sent to the photosensor 33 side as shown in FIG.

  For a DC motor, generally, a rotary encoder for detecting the rotor position is used to extract a position detection signal, and the rotation angle of the motor can be recognized and controlled by counting the number of pulses of the position detection signal. Also in the present embodiment, the position detection signal of the DC motor 19 is obtained using a rotary encoder (not shown), and the number of pulses of the position detection signal is detected (counted), whereby the movement amount of the zoom lens holding frame 15, that is, The position is controlled.

2. Reference position detection processing The reference position (origin) detection processing of each lens of the imaging apparatus configured as described above will be described. FIG. 3 is a flowchart showing the overall flow of the lens reference position detection processing of the imaging apparatus. The reference position detection process is executed when the imaging apparatus is turned on. This process is executed by the control unit 37b of the microcomputer 37.

(2.1 Overall flow)
In FIG. 3, when the power of the image pickup apparatus is turned on, first, it is determined whether the image has ended normally or abnormally at the end of the previous time (S11). The normal end / abnormal end can be determined by, for example, storing a flag indicating the previous end state in the memory of the microcomputer 37 and referring to the flag. The case where the power supply is not normally terminated (that is, the case where the power supply is abnormally terminated) may be a case where the power supply is forcibly cut off due to, for example, the battery being removed during the operation of the imaging apparatus or the remaining amount of the battery becomes zero. It is done.

  When the imaging apparatus ends normally, the imaging apparatus performs a predetermined end process, and places the focus lens holding frame 11 and the zoom lens holding frame 13 at predetermined positions. For example, each lens is controlled to a state as shown in FIG. This state is a light shielding state, in which the zoom lens holding frame 15 pushes down the focus lens holding frame 13. In this case, since the lens position at the end is fixed, the next control is performed according to the predetermined lens position when it is started next time. On the other hand, when the process ends abnormally, the end process is not executed, so the positions of the focus lens holding frame 11 and the zoom lens holding frame 13 at the end are indeterminate, and the lens reference position is accurately set when it is next started. It may not be detected. Therefore, if the previous abnormal end has occurred, a lens movement process is performed as a return process after the abnormal end (S12). By the lens movement process, the zoom lens or the focus lens is moved to a position suitable for the reference position detection. Details of this processing will be described later.

  Thereafter, a reference process for detecting the reference position of the zoom lens is performed (S13), followed by a process for detecting the reference position of the focus lens (S14). Specific contents of these processes will also be described later.

  When the reference position detection process for each lens is completed, it is determined whether or not the zoom lens reference position has been detected in the previous zoom lens reference position detection process (S13). Depending on the arrangement state of the lens, since the reference position may not be detected accurately in the process of detecting the reference position of the zoom lens only once, the success or failure of detection of the reference position of the zoom lens is determined.

  If detection is not possible in the first zoom lens reference position detection process, a second zoom lens reference position detection process is performed (S16). The procedure of the second zoom lens detection process is the same as the procedure of the first zoom lens detection process.

  The zoom lens holding frame 15 is not in contact with the focus lens holding frame 13 by continuously performing the focus lens reference position detecting process (S14) after the zoom lens reference position detecting process (S13). Thus, the lens is moved to the subject side (A direction side) in the optical axis direction, and the focus lens holding frame 15 is also moved to the A direction side from the reference position. If the detection operation is started from such a state, the reference position of the zoom lens can be reliably detected. Therefore, even if the detection process is not successful in the first zoom lens reference position detection process (S13), the zoom lens reference position can be reliably detected by the second process (S16).

  As described above, when the detection of the reference position of the zoom lens and the focus lens is completed, the present process is terminated. Note that the zoom lens detection process is performed before the focus lens detection process because the zoom lens is positioned above after the zoom lens detection process is completed. It is because it can move smoothly to.

(2.2 Zoom lens reference position detection process)
Detailed contents of the above-described zoom lens reference position detection process (S13) will be described.

  The reference position of the zoom lens is detected by controlling the focus lens holding frame 13 and the zoom lens holding frame 15 to a state as shown in FIG. That is, when the DC motor 19 is driven and the zoom lens holding frame 15 is pushed down to the photosensor 33 side (B direction) in the optical axis direction, the pressing portion 18 of the zoom lens holding frame 15 eventually becomes the focus lens holding frame 13. Abut. When the zoom lens holding frame 15 is further pushed down in this state, the focus lens holding frame 13 is pushed down by the pressing portion 18. When the shielding plate 31 is lowered to the position of the photosensor 33, the photosensor 33 changes the light transmitting / shading state, and the reference position is detected by detecting this change. Hereinafter, this process will be described in more detail with reference to the flowchart of FIG.

  First, the DC motor 19 is driven to move the zoom lens holding frame 15 to the photosensor 33 side (B side in FIG. 4) (S31). When the zoom lens holding frame 15 is moved to the B side in this way, the pressing member 18 eventually comes into contact with the focus lens holding frame 13. If the zoom lens holding frame 15 is further moved to the photosensor 33 side in this state, the focus lens holding frame 13 is pushed down by the zoom lens holding frame 15, and the light shielding plate 31 is also lowered accordingly. When the light shielding plate 31 is lowered to the position of the photosensor 33, the photosensor 33 detects light shielding.

  It is determined whether or not light shielding is detected by the photosensor 33 (S32). When the light shielding is not detected, the zoom lens holding frame 15 is considered to be above the photosensor 33, so that the zoom lens holding frame 15 needs to move further downward.

  Therefore, if no light shielding is detected, it is first determined whether or not a voltage necessary to move the zoom lens holding frame 15 by the predetermined distance L5 is applied to the DC motor 19 (S33). This is possible by counting the number of pulses of the position detection signal of the DC motor 19. That is, it is possible by determining whether or not the count value is the number of pulses corresponding to the distance L5. Here, the distance L5 is the maximum movable distance of the zoom lens holding frame 15 (see FIG. 4).

  If the voltage necessary for moving the distance L5 has not been applied yet, the process returns to step S31 to perform control for moving the zoom lens holding frame 13 further downward.

  When the voltage necessary for moving the distance L5 is already applied to the DC motor 19, an error recovery process is performed (S34). In this case, since the DC motor 19 may be idling, in the error recovery process, to prevent idling, the motor current set value is increased and the torque of the DC motor 19 is increased. Returning, the zoom lens holding frame 13 is controlled to move further downward.

  In step S32, when the photo sensor 33 detects light shielding, the moving direction of the zoom lens is reversed and moved to the subject side (A side) (S35). Thereafter, it is determined whether or not light transmission is detected by the photosensor 33 (S36). If transmission is detected, the position of the zoom lens at that time is determined as the reference position (S39). When the reference position is detected, the number of pulses of the position detection signal output from the DC motor 19 since the start of the reference position detection operation of the zoom lens is stored as information corresponding to the reference position of the zoom lens holding frame 15.

  On the other hand, if the transmission of light is not detected in step S36, it is determined whether or not the voltage necessary for moving the zoom lens holding frame 15 by the predetermined distance L3 is applied to the DC motor 19 (S37).

  If the voltage necessary for moving the distance L3 has not been applied yet, the process returns to step S35, and control is performed to move the zoom lens holding frame 13 further to the subject side. Here, the distance L3 is a distance such that the photosensor 33 reliably changes from the light shielding detection state to the transmission detection state when the light shielding plate 33 moves at least by that distance (see FIG. 4).

  If the photosensor 33 does not detect transmission (YES in step S37) even though the voltage required to move the distance L3 has already been applied, an error signal is output (S38), and the process is performed. finish.

  As described above, in the present embodiment, the zoom lens holding frame 15 is moved to the photosensor 33 side while being in contact with the focus lens holding frame 13. When light shielding is detected by the photosensor 33, the moving direction is reversed, and a position where the detection state of the photosensor 33 changes from “light shielding” to “transmission” is detected. The detected position is determined as the reference position of the zoom lens. As described above, the position when the detection state of the photosensor 33 changes from “light shielding” to “transmission” is to make it possible to detect the reference position of the zoom lens more reliably. For example, when the focus lens holding frame 13 is pressed by the regulating member 29 and the photo sensor 33 detects the light shielding, the reference position is determined only by whether or not the photo sensor 33 detects the light shielding. This is because even if the zoom lens is far from the reference position, it may be erroneously determined that the zoom lens holding frame 15 has reached the reference position.

(2.3 Focus lens reference position detection processing)
The detailed contents of the focus lens reference position detection process (S14) will be described with reference to the flowchart of FIG.

  First, the stepping motor 17 is driven to move the restricting member 29, and the focus lens holding frame 13 is moved to the photosensor 33 side (B side) (S51).

  It is determined whether or not light shielding is detected by the photosensor 33 (S52). If the light shielding is not detected, it is determined whether or not the number of pulses necessary to move the focus lens holding frame 13 by the predetermined distance L1 is applied to the stepping motor 17 (S53). Here, the distance L1 is the maximum movable distance of the focus lens holding frame 15a when the focus lens holding frame 15a is closest to the subject (see FIG. 1). If the number of pulses necessary for the movement of the distance L1 has not yet been applied, the process returns to step S51, and control is performed to move the focus lens holding frame 13 further to the photosensor 33 side.

  In step S53, if the number of pulses necessary to move the distance L1 has already been applied to the stepping motor 17, after performing the error recovery process 1 (S54), the process returns to step S51 and the focus lens holding frame 13 is moved. Furthermore, the control which moves to the photosensor 33 side (B side) is performed. In the error recovery process 1, control is performed to increase the torque of the stepping motor 17 and move the focus lens holding frame 13 to the photo sensor side (B side). Details thereof will be described later.

  In step S52, when light shielding is detected by the photosensor 33, the moving direction of the focus lens holding frame 13 is reversed and moved to the subject side (A side) (S55). It is determined whether or not transmission is detected by the photosensor 33 (S56). If transmission is detected, the position of the focus lens 11 at that time is determined as a reference position (S59). As described above, when the photo sensor 33 detects light shielding when the focus lens holding frame 13 is lowered, the moving direction is reversed, and then the position where the photo sensor 33 is changed from the light shielding state to the transmission state is detected. Is the reference position. When the reference position is detected, the number of pulses applied to the stepping motor 17 since the start of the reference position detection operation of the zoom lens is stored as information related to the reference position of the focus lens 11.

  On the other hand, if transmission is not detected in step S56, it is determined whether or not the number of pulses necessary to move the focus lens holding frame 13 by the predetermined distance L3 is applied to the stepping motor 17 (S57), and the movement is performed by the distance L3. If the number of pulses necessary for this is not applied, the process returns to step S55, and control is performed to move the focus lens holding frame 11 further to the subject side (A side).

  If the photosensor 33 does not detect transmission despite the number of pulses necessary to move the distance L3 (YES in step S57), error recovery processing 2 is performed (S58), and the process returns to step S55. In the error recovery process 2, control is performed to increase the torque of the stepping motor 17 and move the focus lens holding frame 13 to the subject side (A side). Details thereof will be described later.

(2.3.1 Error recovery process)
Details of the error recovery process 1 (step S54) will be described with reference to the flowchart of FIG. In this process, control is performed to increase the torque of the stepping motor 17 and move the focus lens holding frame 13 to the photosensor 33 side (B side).

  First, the set value of the current phase of the drive current of the stepping motor 17 is changed (S71). Specifically, the phase is set so that the phase upon error recovery is a phase that gives the maximum torque of the motor. The setting of the phase will be specifically described with reference to FIG. In FIG. 8, error recovery is performed at time T′2.

  FIG. 8A shows a current waveform at the time of normal setting (during sine waveform driving). The solid line shows the drive current waveform before error determination (before time T′2), and the broken line shows the drive current waveform assumed when no error has occurred. FIG. 8B shows a current waveform when the phase is set so that the torque becomes maximum at the time of error recovery (T′2). In FIG. 8A, the phase that gives the maximum torque is a point (for example, times T′1 and T′3) at which the two-phase drive currents intersect. Since the motor torque becomes maximum at the motor times T′1 and T′3, the phase of the times T′1 and T′3 in the direction in which the motor is to be advanced, that is, the phase at the time T′3 is an error Select as the phase setting value at the time of return.

  Returning to FIG. 7, after the phase adjustment, the setting of the current waveform of the drive current of the stepping motor 17 is changed from a sine wave to a rectangular wave (S72). By setting the rectangular wave, the torque of the stepping motor 17 increases. However, the amplitude A1 of the rectangular wave is preferably greater than or equal to the amplitude A2 of the sine wave. 8C and 8D show current trajectories when the sine wave after the phase change is changed to a rectangular wave for each of the first phase current and the second phase current.

  FIGS. 8E and 8F show the current trajectories before and after the error determination for the two-phase drive current whose current setting has been changed as described above. As shown in the figure, the drive current waveform is changed from a sine waveform to a rectangular waveform before and after time T′2.

  The stepping motor 17 is driven with the above current setting, and the focus lens 11 is moved to the photosensor 33 side (B side) (S73). Thereafter, the setting of the drive current of the stepping motor 17 is returned to the normal set value (S74), and the return process is terminated.

  FIG. 9 is a view showing a flowchart of the error recovery process 2 (step S58). The error recovery process 2 is basically the same as the error recovery process 1 described above, but differs from the error recovery process 1 in that the moving direction of the focus lens 11 is the subject side (A side) in step S93. .

(2.4 Lens movement processing when the previous abnormal end)
Details of the lens movement process (step S12) in the flowchart of FIG. 3 will be described. In the lens movement process, a process for moving the lens to a position suitable for the reference position detection is performed.

  For example, as shown in FIG. 10B, when the focus lens 11 after abnormal termination is in the vicinity of the reference position, the reference position may not be detected accurately. For example, when the focus lens 11 is in the vicinity of the reference position, the guide pole 21 vibrates with the movement of the zoom lens during the reference position detection operation of the zoom lens, which causes the focus lens 11 to vibrate. This is because it may be detected.

  Further, it is assumed that the lens position when the imaging apparatus is abnormally ended is in any of the states shown in FIGS. 13, 15, 17, and 19. FIG. 13 shows a state in which the photo sensor 33 is in a light-shielding state and the focus lens holding frame 13 is pressed by the regulating member 29. FIG. 15 shows a state in which the photosensor 33 is in a light shielding state and the focus lens holding frame 13 is pressed by the zoom lens holding frame 15. FIG. 17 shows a state in which the photosensor 33 is in a light-transmitting state and the focus lens holding frame 13 is pressed by the regulating member 29. FIG. 19 shows a state in which the photosensor 33 is in a light-transmitting state and the focus lens holding frame 13 is pressed by the zoom lens holding frame 15. When the lens position is in the above state, it cannot be detected accurately even if the lens reference position detection operation is performed according to the procedure shown in FIGS. For example, even if the reference position detection operation of the zoom lens is performed in the state shown in FIG. 13, the focus lens holding frame 13 is pressed by the restricting member 29, so that the photosensor 33 is not in the translucent state and the reference position is set. It cannot be detected.

  In order to solve the problem at the time of abnormal termination as described above, in the present embodiment, when the previous abnormal termination is completed, a process for moving the lens to a position where the reference position can be stably detected at the start after the abnormal termination is performed. Is going. The procedure of lens movement processing will be specifically described with reference to the flowcharts of FIGS.

  First, it is determined whether or not light transmission is detected by the photosensor 33 (S101). If transmission is not detected, a process of moving the focus lens 11 to the photosensor 33 side (B side) is performed (S102). Specifically, the process shown in FIG. 12 is performed. First, the drive current of the stepping motor 17 is set to a small current value (S111). For example, as shown in FIG. 2, the current set value is changed from the sine wave X to the sine wave X2. By reducing the current value, the force for pushing the focus lens holding frame 13 can be weakened, so that the focus lens holding frame 13 is fixed to the stopper 25 and the like and cannot be pulled back upward. it can. Next, the number of pulses necessary to move the focus lens 11 to the photosensor 33 side (B side) by a predetermined distance L1 is applied to the stepping motor 17 (S112). Thereafter, the drive current setting of the stepping motor 17 is returned to the normal set value (S113).

  On the other hand, when light transmission is detected by the photosensor 33, a process of moving the focus lens 11 to the subject side (A side) is performed (S103). The specific processing is the same as the procedure of the flowchart shown in FIG. 12 except that the moving direction of the focus lens is the subject side (A side).

  In the present embodiment, as a lens movement process at the time of abnormal termination last time, when the transmission is not detected, the focus lens 11 is moved to the photosensor 33 side (B side) to ensure a light shielding state. Although this is done (S102 in FIG. 11), the present invention is not limited to this, and even when transmission is not detected, the focus lens 11 may be moved to the subject side (A side) as in step S103. . However, in such a configuration, it is preferable that the amount of movement of the focus lens 11 when transmission is not detected be larger than the amount of movement when transmission is detected. By doing in this way, even if it is a case where transmission is not detected, it can be made into a transmission state reliably.

  Even when the initial state at the time of starting the reference position detection operation is in each state shown in FIGS. 13, 15, 17, and 19, it will be specifically described in each case that the reference position can be correctly detected after the lens movement process. To do.

i) In the case where the initial state is the state shown in FIG. 13 In this case, in order to ensure the light-shielding state by the lens moving process (S12), the restricting member 29 is first moved to the photosensor side (B side) to focus. Press the lens 11 down. At this time, the torque of the stepping motor 17 is made smaller than usual. This is to prevent problems such as the focus lens holding frame 13 sticking to the stopper 25 and the like and cannot be pulled back.

  FIG. 14 is a view showing a state after the restricting member 29 is moved to the photosensor 33 side by the lens moving process (S12) from the state of FIG. When the reference position detection operation (S13) of the zoom lens is started in this state, no matter how the zoom lens is moved, the light shielding state does not change to the transmission state, and the correct zoom lens reference position cannot be obtained.

  Next, the focus lens reference position detection process (S14) is performed in the state shown in FIG. When the reference position detection operation of the focus lens is finished, the state shown in FIG. 1 is obtained. In this state, the reference position detection operation of the zoom lens can be normally performed. Therefore, if the state after the abnormal end is restarted is the state shown in FIG. 13, the reference position of the zoom lens is accurately detected by performing the second zoom lens reference position detection process (S16). be able to.

ii) In the case where the initial state is the state shown in FIG. 15 In this case, in order to ensure the light shielding state by the lens moving process (S12), first, the regulating member 29 is moved to the photosensor 33 side (B side), The focus lens holding frame 13 is pressed down. The torque of the motor at this time is also made smaller than usual. The state at that time is the state shown in FIG.

  Next, the reference position detection operation (S13) of the zoom lens is started in the state shown in FIG. In this case, no matter how the zoom lens is moved, the light shielding state does not change to the transmission state. Therefore, the state shown in FIG. 16 is changed to the state shown in FIG. 14, and then the reference position detection operation (S14) of the focus lens 11 is started. When the reference position detection operation of the focus lens 11 is finished, the state shown in FIG. 1 is obtained. In this state, the reference position detection operation of the zoom lens can be normally performed. Therefore, if the initial state is the state shown in FIG. 15, the reference position of the zoom lens can be normally detected by performing the reference position detection operation of the zoom lens twice.

iii) In the case where the initial state is the state shown in FIG. 17 In this case, the restricting member 29 is moved to the subject side (A side) in order to ensure the light transmitting state by the lens moving process (S12), and the focus lens 11 Lift up. The torque of the motor at this time remains normal. The state at that time is shown in FIG. The reference position detection operation (S13) of the zoom lens is started in the state shown in FIG. In this operation, since the focus lens holding frame 13 can be pressed by the zoom lens holding frame 15, the transmission state can be changed to the light blocking state, and the reference position detection operation of the zoom lens can be normally terminated. Thereafter, a focus lens reference position detection operation (S14) is performed. Therefore, if the detection operation is started in the state of FIG. 18, it is not necessary to perform the reference position detection operation of the zoom lens twice.

iv) In the case where the initial state is the state shown in FIG. 19 In this case, the lens 29 is moved to the subject side (A side) and the focus lens 11 is moved in order to ensure the light transmitting state by the lens moving process (S12). Although the focus lens holding frame 13 is restricted by the zoom lens holding frame 15, the focus lens holding frame 13 cannot be lifted. Therefore, the reference position detection operation (S13) of the zoom lens holding frame 15 is started in the state shown in FIG. At this time, since the light shielding plate 31 may be located in the vicinity of the light shielding detection position, at first glance, it seems that the light transmission / light shielding state becomes unstable. However, since the focus lens holding frame 13 is sandwiched between the zoom lens holding frame 15 and the spring 23, the light shielding plate 31 does not vibrate, and the reference position of the zoom lens can be normally detected in a stable state. Can do. When the operation of detecting the reference position of the zoom lens is completed, the state shown in FIG. 1 is obtained. Thereafter, a focus lens reference position detection operation (S14) is performed. Therefore, when the reference position detection operation is started from the state of FIG. 19, it is not necessary to perform the reference position detection operation of the zoom lens twice.

  As described above, according to the imaging apparatus of the present embodiment, the reference position of the zoom lens is detected using the shielding plate attached to the focus lens holding frame while the focus lens holding frame is pushed down by the zoom lens holding frame. . For this reason, it is not necessary to provide a shielding plate for each lens, and downsizing of the apparatus can be realized. Further, at the time of activation after abnormal termination, the reference position detection operation is performed after the lens is moved to a position suitable for the reference position detection. For this reason, the reference position of the lens can be reliably detected.

  The present invention can realize downsizing in the lens barrel and is useful for an imaging apparatus such as a digital still camera or a digital video camera.

The figure which showed the structure of the principal part of imaging devices, such as a digital still camera and a digital video camera, based on this invention (A) The figure which showed the two-phase current waveform applied to a stepping motor, (b) The figure explaining the movement of a focus lens holding frame with a stepping motor, (c) The figure explaining the mode of rotation of a stepping motor Flowchart showing the overall flow of lens reference position detection processing in the imaging apparatus The figure explaining the state of the focus lens holding frame and the zoom lens holding frame in the reference position detection operation of the zoom lens Flowchart of zoom lens reference position detection processing Flow chart of focus lens reference position detection processing Flow chart of error recovery process 1 (A) The figure which shows the drive current locus of the stepping motor before error detection, (b) The figure which shows the drive current locus after phase adjustment from the time of error occurrence, (c) It converts into the rectangular wave regarding the 1st phase The figure which shows a drive current locus after, (d) The figure which shows the drive current locus after converting into the rectangular wave about the 2nd phase, (e) The figure which shows the drive current locus of the 1st phase before and after an error, (f) The error The figure which shows the drive current locus of the 2nd phase before and behind Flow chart of error recovery process 2 The figure which shows an example of the arrangement state of each lens after a normal end The figure which shows an example of the arrangement state of each lens after abnormal termination Lens movement process flowchart Flow chart of movement processing of focus lens to photo sensor side (B side) The figure which shows the arrangement | positioning state of each lens assumed when it completes abnormally (example 1) The figure which showed the state after moving a control member to the photosensor side by the lens movement process from the state of FIG. FIG. 4 is a diagram illustrating an arrangement state of each lens that is assumed in the case of abnormal termination (example 2). The figure which showed the state after moving a control member to the photosensor side by the lens movement process from the state of FIG. FIG. 4 is a diagram illustrating an arrangement state of each lens that is assumed in the case of abnormal termination (Example 3). The figure which showed the state after moving a control member to the photographic subject side by the lens movement process from the state of FIG. FIG. 4 is a diagram illustrating an arrangement state of each lens assumed in the case of abnormal termination (example 4). The figure which shows the principal part of the conventional lens drive device

Explanation of symbols

11 Focus lens 13 Focus lens holding frame 15 Zoom lens holding frame (zoom lens)
17 Stepping motor 18 Pressing member 19 DC motor 21 Guide pole 25 Stopper 27 Rotating shaft 29 Restricting member 31 Shading plate 33 Photo sensor 37 Microcomputer 37a Signal processing unit 37b Control unit 39 Lens barrel outer frame

Claims (10)

A first lens holding frame for holding a first lens;
First lens driving means for driving the first lens holding frame;
A sensor for detecting that the first lens holding frame has reached a predetermined reference position;
A second lens holding frame that holds a second lens and is capable of directly or indirectly contacting the first lens holding frame;
Second lens driving means for driving the second lens holding frame;
Control means for controlling the first and second lens driving means, and further for determining a reference position of each of the first and second lenses,
The control means drives the second lens driving means so that the second lens holding frame faces the sensor, and the first lens holding frame is directly or indirectly brought into contact with the first lens holding frame. Moving the lens holding frame to detect the position of the second lens holding frame when the first lens holding frame reaches the reference position as the reference position of the second lens;
A lens driving device. When the control means determines whether or not it ended normally last time, and determines that it did not end normally,
Further, before detecting the reference position of the second lens, it is determined whether or not the sensor detects that the first lens holding frame has reached the reference position;
When the sensor detects that the first lens holding frame has reached the reference position, the first lens holding frame is moved in a direction toward the sensor,
If the sensor does not detect that the first lens holding frame has reached the reference position, the first lens holding frame is moved away from the sensor;
The lens driving device according to claim 1.   When it is determined that the first lens holding frame has reached the reference position before detecting the reference position of the second lens and the control unit has not normally ended last time, 3. The lens driving device according to claim 2, wherein the first lens driving unit is driven with smaller power to move the first lens holding frame in a direction toward the sensor. 4.   The control means supplies the first lens driving means with power corresponding to the first lens holding frame reaching the reference position, but the first lens holding frame reaches the reference position. 2. The lens driving device according to claim 1, wherein if the sensor does not detect this, it is determined that there is an error state, and the first lens driving unit is driven with a larger power than during normal operation. .   The first lens driving means is a stepping motor, and the control means changes the current applied to the stepping motor from a sine wave to a rectangular wave and determines the current when The lens driving device according to claim 4, wherein the phase is set to a phase at which the torque of the stepping motor is maximized in the moving direction of the first lens holding frame.   The lens driving device according to claim 1, wherein the reference position of the first lens is detected after the reference position of the second lens is detected. The sensor includes a light emitting element and a light receiving element, and outputs a signal having a different level according to transmission and blocking of light from the light emitting element to the light receiving element.
2. The control unit according to claim 1, wherein the first lens determines that the first lens has reached the reference position when the output of the sensor indicates a change from a light shielding state to a light transmitting state. Lens drive device.   The driving means for the first lens biases the first lens holding frame in a direction away from the sensor, and power in a direction toward the sensor against the force of the biasing means. The lens driving apparatus according to claim 1, further comprising a restricting unit that transmits the first lens holding frame.   The lens driving apparatus according to claim 1, wherein the first lens is a focus lens, and the second lens is a zoom lens. When the control means determines whether or not it ended normally last time, and determines that it did not end normally,
Further, before detecting the reference position of the second lens, it is determined whether or not the sensor detects that the first lens holding frame has reached the reference position;
If the sensor does not detect that the first lens holding frame has reached the reference position, move the first lens holding frame by a predetermined amount in a direction away from the sensor,
When the sensor detects that the first lens holding frame has reached the reference position, the first lens holding frame is moved larger than the predetermined amount in a direction away from the sensor.
The lens driving device according to claim 1.

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