JP4518872B2 - Lens driving device, moving body driving device, and reference position detection method - Google Patents

Description

  The present invention relates to a lens driving device for controlling the position of a lens in an imaging apparatus such as a digital still camera or a digital video camera, and more particularly to a lens driving device that performs position control based on a reference position. The present invention also relates to a moving body driving apparatus that moves a general object while performing position control.

  In general, a focus lens and a zoom lens are driven using a stepping motor or a DC motor in a lens barrel of an imaging apparatus such as a digital still camera. These lens drive controls are performed based on the reference position of the lens in the lens barrel. The reference position of the lens is detected every time the camera power is turned on. After the reference position is detected, the focus lens and the zoom lens are controlled based on the reference position. If the reference position is inaccurate, accurate control cannot be realized, and problems such as out-of-focus blur occur. Therefore, high reference position accuracy is desired.

There is a method disclosed in Patent Document 1 as a reference position detection method. In this document, an example in which the initial position of a lens group such as an electronic still camera as a moving body is detected using a photo interrupter provided on the lens barrel side and a light shielding plate attached on the lens group side is described as `` It is described as “prior art”. According to this, the photo interrupter includes a light emitting element and a light receiving element. When the light shielding plate passes through the photo interrupter, the propagation of light from the light emitting element to the light receiving element is interrupted, so that the output voltage level of the light receiving element changes. The initial position of the lens group can be detected from the output voltage of the light receiving element by setting the position of the lens frame, that is, the lens group at that time as the initial position in advance.
JP-A-6-174999

  In the above example, the lens group (moving body) is moved from a certain position toward the reference position, and the light shielding plate attached to the lens group side blocks the propagation of light between the light emitting element and the light receiving element in the photo interrupter. The reference position of the lens group is detected by detecting a change in the output voltage level of the light receiving element when the lens group reaches such a position.

  Since there is no specific description of the detection timing of the change in the output voltage level of the light receiving element from Patent Document 1, it is estimated that the output voltage level of the light receiving element is constantly monitored and the change point is detected. The

  However, in this method, when the output voltage level of the light receiving element is constantly monitored, processing for that is necessary, and the control means such as an electronic camera is burdened accordingly.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to reduce the control load relating to the reference position detection of the lens (moving body) and to improve the accuracy of the reference position detection. The object is to provide a lens driving device (moving body driving device).

  The lens driving device according to the present invention moves the lens using a motor whose rotational position is controlled based on the number of pulses as a driving source, and controls the absolute position of the lens based on the number of pulses according to the distance from the reference position. This is a lens driving device. The lens driving device detects that the lens has reached the reference position and notifies it, a timer for measuring an elapsed time from a predetermined time point, a memory for storing the elapsed time measured by the timer, and a predetermined The number of pulses of the motor is detected at time intervals, and the elapsed time indicated by the timer when the notification from the sensor is received is stored in the memory, and the elapsed time stored in the memory is used for the time received from the sensor. And control means for calculating the number of pulses when interpolating the number of pulses detected before and after and receiving a notification as the number of pulses corresponding to the reference position.

  The predetermined time interval may be given in synchronization with a vertical synchronization signal for an image sensor that converts optical information into an image signal.

  The motor is a stepping motor, and the number of pulses may be the number of pulses applied to the stepping motor. Alternatively, the motor may be a DC motor, and the number of pulses may be the number of pulses of a position detection signal indicating the rotor position of the DC motor.

  The moving body drive device according to the present invention moves the moving body using a motor whose rotation is controlled based on the number of pulses as a driving source, and determines the absolute position of the moving body based on the number of pulses corresponding to the distance from the reference position. It is the moving body drive device to control. The mobile body drive device detects that the mobile body has reached the reference position and notifies it, a timer that measures the elapsed time from a predetermined time point, a memory that stores the elapsed time measured by the timer, The number of pulses of the motor is detected at a predetermined time interval, and the elapsed time indicated by the timer when the notification from the sensor is received is stored in the memory, and the notification from the sensor is received using the time stored in the memory. Control means for calculating the pulse number corresponding to the reference position by interpolating the number of pulses detected before and after the time and receiving the notification.

  In the reference position detection method according to the present invention, the moving body is moved using a motor whose rotation is controlled based on the number of pulses as a driving source, and the absolute position of the moving body is determined based on the number of pulses corresponding to the distance from the reference position. This is a reference position detection method in the case of control. The method detects and notifies that the moving body has reached the reference position, detects the number of motor pulses at a predetermined time interval, measures the elapsed time from a predetermined time point, The step of storing the elapsed time measured when receiving the notification from the sensor and the number of pulses when receiving the notification by interpolating the number of pulses detected before and after the notification time using the stored time Calculating as the number of pulses corresponding to the reference position.

  According to the present invention, it is possible to reduce the load of the detection operation of the reference position of the lens and to detect the reference position with high accuracy.

  Embodiments of a lens driving device (moving body driving device) according to the present invention will be described below 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 imaging apparatus includes a lens barrel 5 that includes a lens driving mechanism and a microcomputer 30 that controls the lens driving mechanism and performs image signal processing.

  In the lens barrel 5, the focus lens 11 is held by a lens holding frame 13. The lens holding frame 13 is screwed with a rotary shaft 15 having a feed screw formed on the surface thereof, and is slidably attached to the guide pole 16.

  Further, the photosensor 21 is disposed at a predetermined position in the lens barrel 5. The photosensor 21 is an element for detecting that the focus lens 11 has reached its reference position (origin), and includes a light emitting element that outputs light and a light receiving element that receives the light. The photosensor 21 outputs a detection signal whose signal level changes when light propagation between the light emitting element and the light receiving element is interrupted. The photosensor 21 outputs a “High” signal when light is transmitted from the light emitting element to the light receiving element, and outputs a “Low” signal when light is blocked between the light emitting element and the light receiving element.

  A light shielding plate 19 is attached to the lens holding frame 13. The light shielding plate 19 moves together with the lens holding frame 13, that is, the lens 11, and blocks light propagating through the photosensor 21 when the lens 11 reaches a predetermined reference position.

  Further, a CCD image sensor 23 for taking an image is attached in the lens barrel 5. The CCD image sensor 23 is an image sensor that converts optical information input through the lens 11 into an image signal and outputs the image signal.

  The microcomputer 30 is a control means for processing an image signal picked up by the CCD image sensor 23 and performing lens movement control, and is constituted by, for example, a semiconductor integrated circuit. The microcomputer 30 includes a system control unit 31 that controls the operation of the microcomputer 30, an image processing unit 33 that processes an image signal from the CCD image sensor 23, and a vertical synchronization that generates a vertical synchronization signal (VD) for the CCD image sensor 23. A signal generation unit 35, a timer 37 for measuring time, a storage unit 39 for storing various information used for control, and an interrupt port 41 for inputting a detection signal from the photosensor 21 as an interrupt control signal.

2. The basic operation of the imaging apparatus having the above configuration will be described.
The focus lens 11 is driven by the rotation shaft 15. The rotation shaft 15 receives power from the stepping motor 17 and rotates to slide the lens holding frame 13, that is, the focus lens 11 along the axial direction (A or B direction in FIG. 1) of the guide pole 16.

  In general, the rotation angle of the stepping motor 17 is determined according to the number of applied pulses (number of steps). Further, the rotation angle of the stepping motor 17 and the movement amount of the lens 11 are proportional. Therefore, if the number of pulses applied to the stepping motor 17 is counted, the position (movement amount) of the focus lens 11 can be grasped by referring to the count value. In the present embodiment, the system control unit 31 counts the number of pulses applied to the stepping motor 17 as a “lens position counter”, and controls the lens position based on the value. The lens position counter value when the lens is at the reference position is reset to zero. In this state, the focus lens 11 can be moved to the position indicated by the lens position counter value by applying a pulse number equal to the lens position counter value counted up or down to the stepping motor 17.

  When the focus lens 11 is driven by the stepping motor 17 and reaches the reference position, the light shielding plate 19 blocks the propagation of light from the photosensor 21, so that the output of the photosensor 21 changes from “High” to “Low”. . The system control unit 31 receives an output signal from the photosensor 21 via the interrupt port 41. Thus, when the system control unit 31 detects that the focus lens 11 has reached the reference position, the system control unit 31 can immediately execute a predetermined process related to the detection.

  The CCD image sensor 23 acquires image information based on the vertical synchronization signal (VD) output from the vertical synchronization signal generator 35. The image signal from the CCD image sensor 23 is processed by the image processing unit 33, and is displayed on a display unit (not shown) of the image pickup apparatus or subjected to compression processing.

3. Reference Position Detection Operation Next, the reference position detection operation of the focus lens 11 will be described in detail. The reference position detection operation is performed when the imaging apparatus is powered on.

  FIG. 2 is a flowchart of the reference position detection operation of the focus lens 11. FIG. 3 is a diagram showing output signal waveforms of the respective processing units of the microcomputer 30 during the reference position detection operation. FIG. 3A shows a vertical synchronization signal (VD) used for controlling the CCD image sensor 23. The CCD image sensor 23 captures image information for each frame in synchronization with this signal. FIG. 3B shows changes in the lens position counter value. The lens position counter value is a value obtained by counting the number of pulses applied to drive the stepping motor 17. FIG. 3C is a diagram showing changes in the timer value.

  First, a vertical synchronizing signal for the CCD image sensor 23 is generated (S101). Next, movement of the focus lens 11 in the reference position direction (B direction in the example of FIG. 1) is started (S102). Once the movement of the focus lens 11 is started, the movement continues until the reference position is detected. That is, until the reference position is detected, the system control unit 31 sequentially changes the lens position counter value as shown in FIG. 3B, for example, and applies the corresponding number of pulses to the stepping motor 17.

  Thereafter, the timer 37 is reset and a time measuring operation (counting operation) is started (S103). When the falling edge of the vertical synchronizing signal of the CCD image sensor 23 is detected (S104), an imaging process is executed (S105). Here, a process of displaying an image captured by the CCD image sensor 23 through the lens 11 on a display unit (not shown) of the digital still camera is performed.

  Until the vertical synchronizing signal of the CCD image sensor 23 rises next (NO in S108), it is determined whether or not the reference position has been detected, that is, whether or not the reference position detection signal has been interrupted (S106). When the reference position is detected, that is, when the reference position detection signal is interrupted, the value of the timer 37 at that time is stored in the storage unit 39 (S107).

  When the vertical synchronizing signal rises (YES in S108), the value of the lens position counter at that time is stored in the storage unit 39 (S109). Thereafter, it is determined whether or not the reference position is detected in the above process (S110). If it is detected, the reference position is calculated based on the timer value and the lens position counter value stored in the storage unit 39 (S111). .

The reference position is obtained as follows. As shown in FIG. 3, it is assumed that the reference position is detected at time T3 between time T2 and time T4. If the timer value and lens position counter value at time T2 are C2 and L2, respectively, the timer value and lens position counter value at time T4 are C4 and L4, respectively, and the timer value at time T3 is C3, the reference position is detected at time T3. The lens position counter value L3 is obtained by the following equation.

  In step S110, if the reference position has not been detected yet, the process returns to step S103, and the above processing is repeated until the reference position is detected (S103 to S110).

  As described above, the lens position counter value L3 at the reference position is obtained. Based on this value L3, the lens position counter at the reference position is reset.

  As described above, according to the present embodiment, in synchronism with the vertical synchronization signal, the lens position counter value and the timer value are taken in every predetermined time interval, and at the generation timing of the reference position detection signal generated in an interrupt manner, Captures the timer value when the reference position is detected. Then, the lens position counter value captured at the time before and after the timing at which the reference position is detected is complemented by using the timer value at the time of detecting the reference position to calculate the lens position counter value at the time of detecting the reference position. That is, the lens position counter value corresponding to the reference position is obtained by complementing the lens position counter value acquired periodically. As described above, the counter value of the stepping motor is monitored periodically and interrupted, and is not always monitored, so the burden on the system control unit is reduced. For this reason, the load on the system can be reduced. In addition, other processes can be executed until the reference position detection signal is interrupted. Therefore, the imaging operation can be performed without waiting for the reference position detection operation. Can be realized.

  Note that one of the lens position counter values periodically acquired before and after interruption of the reference position detection signal may be used as the reference position. However, as in this embodiment, it is possible to detect the reference position with higher accuracy by obtaining the reference value by complementing the two lens position counter values acquired before and after the interruption of the reference position detection signal. Therefore, it is possible to more reliably prevent problems such as defocusing in the imaging apparatus.

  In the above description, the focus lens 11 is driven by the stepping motor 17, but a DC motor can be used instead of the stepping motor 17. In this case, as shown in FIG. 4 (a), the system control unit 31 detects the position where the 90 ° phase is different as shown in FIG. 4 (b) from the rotary encoder 18a for detecting the position of the rotor of the DC motor 18. By inputting the signals P1 and P2 and counting the number of pulses of one position detection signal, the rotation angle of the rotor can be recognized and controlled. Therefore, by using a value obtained by counting the pulses of the position detection signal in the DC motor instead of the lens position counter value in the stepping motor 17 described above, the reference position detection similar to that in the case of the stepping motor is performed even in the case of the DC motor. Operation is possible.

  In the above description, the focus lens is described as an example of the moving body, but a zoom lens may be used. Needless to say, the idea of the present invention can be applied not only to an imaging apparatus but also to other apparatuses that drive an object other than a lens. Although the vertical synchronization signal is used, other signals can be used as long as they have a constant period.

  The present invention is useful for a driving device that controls the position of a moving body based on the number of pulses. For example, the present invention can be applied to an imaging device such as a digital still camera or a digital video camera that controls the lens position based on the number of pulses.

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 Flow chart for detecting the reference position of the focus lens (A) The figure which shows the vertical synchronizing signal (VD) used for control of a CCD image sensor, (b) The figure which shows the change of a lens position counter value, (c) The figure which shows the change of a timer value (A) The figure which shows the structure in the case of driving a focus lens with a DC motor, (b) The figure which shows the position detection signal (position detection pulse) of two phases of a DC motor

Explanation of symbols

DESCRIPTION OF SYMBOLS 5 Lens tube 11 Focus lens 13 Lens holding frame 15 Rotating shaft 16 Guide pole 17 Stepping motor 19 Shading plate 21 Photo sensor 23 CCD image sensor 30 Microcomputer 31 System control part 33 Image processing part 35 Vertical synchronous signal generation part 37 Timer 39 Storage part 41 Interrupt port

Claims (6)

A lens driving device that moves a lens using a motor whose rotational position is controlled based on the number of pulses as a driving source, and controls the absolute position of the lens based on the number of pulses corresponding to a distance from a reference position,
A sensor for detecting and notifying that the lens has reached the reference position;
A timer that measures the elapsed time from a given point in time;
A memory for storing an elapsed time measured by the timer;
The number of pulses of the motor is detected at a predetermined time interval, and the elapsed time indicated by the timer when receiving a notification from the sensor is stored in the memory, and from the sensor using the elapsed time stored in the memory Control means for interpolating the number of pulses detected before and after the time of receiving the notification and calculating the number of pulses when the notification is received as the number of pulses corresponding to the reference position Drive device.   The lens driving device according to claim 1, wherein the predetermined time interval is given in synchronization with a vertical synchronization signal for an image sensor that converts optical information into an image signal.   The lens driving device according to claim 1, wherein the motor is a stepping motor, and the number of pulses is the number of pulses applied to the stepping motor.   The lens driving device according to claim 1, wherein the motor is a DC motor, and the number of pulses is a number of pulses of a position detection signal indicating a rotor position of the DC motor. A moving body drive device that moves a moving body using a motor whose rotation is controlled based on the number of pulses as a driving source, and controls the absolute position of the moving body based on the number of pulses according to the distance from a reference position. ,
A sensor for detecting and notifying that the moving body has reached the reference position;
A timer that measures the elapsed time from a given point in time;
A memory for storing an elapsed time measured by the timer;
The number of pulses of the motor is detected at a predetermined time interval, the elapsed time indicated by the timer is stored in the memory when receiving a notification from the sensor, and the time from the sensor is stored using the time stored in the memory. And a control unit that calculates the number of pulses when the notification is received by interpolating the number of pulses detected before and after the time of receiving the notification as the number of pulses corresponding to the reference position. Drive device. When the moving body is moved using a motor whose rotation is controlled based on the number of pulses as a driving source, and the absolute position of the moving body is controlled based on the number of pulses corresponding to the distance from the reference position, A detection method,
Detecting and notifying that the moving body has reached the reference position; and
Detecting the number of pulses of the motor at a predetermined time interval;
Measuring the elapsed time from a predetermined time;
Storing the measured elapsed time when receiving a notification from the sensor;
Interpolating the number of pulses detected before and after the time when the notification is received using the stored time, and calculating the number of pulses when the notification is received as the number of pulses corresponding to the reference position; A reference position detection method comprising:

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