JP2006138962A - Imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an imaging apparatus surely setting the initial position of a lens without using position detecting components. <P>SOLUTION: The imaging apparatus 1 is provided with: an imager 3; the lens 11 for forming an image in the imager, and a lens holding member for holding the lens, and is shifted in the optical axis direction in contact with a cam member with the drive of the cam member. The lens holding member is energized toward the cam member, and also, the lower limit position of the lens holding member coming close to the imager is controlled by a position control member. The cam member has: a contact part which comes in contact with the lens holding member located in the lower limit position; and a non-contact part adjacent to the contact part and which does not come in contact with the lens holding member located in the lower limit position. The apparatus 1 is also provided with an initial position setting means 51 for setting the position of the lens obtained when it is detected that the lens holding member is positioned in the non-contact position based on the image output signal of the imager 3 as an initial position. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an imaging apparatus having a lens initial setting function.

  In general, a focus adjustment mechanism for focusing a lens at the time of photographing is incorporated in an imaging apparatus such as a camera. In particular, in recent years, imaging apparatuses that perform automatic focusing using a driving means such as a step motor have become widespread. For example, in an imaging apparatus using a step motor, the lens is moved to a predetermined reference position (hereinafter referred to as an initial position), and the lens moving position is managed by the number of pulses from the initial position, thereby performing focus adjustment at the time of shooting. . Therefore, it is important to accurately detect the initial position of the lens and to perform initial setting so that the driving force is accurately transmitted to the lens when the step motor is driven. For example, in the automatic focusing device disclosed in Patent Document 1, a lens that has moved to an initial position (reset position) is confirmed using a photo interrupter.

JP-A-8-160287

  However, when the focusing device disclosed in Patent Document 1 is used for the imaging device, it is necessary to arrange a photo interrupter that is a sensor for detecting an initial position, which increases the number of parts and the number of assembly steps. There is a problem that costs increase. Conventionally, a structure in which a switch is arranged to detect the initial position of the lens is also known, but in this case as well, the same problem as in the case of arranging a photo interrupter occurs.

  Further, when position detection sensor parts such as photo interrupters are arranged inside, there arises a problem that the image pickup apparatus becomes large and the structure becomes complicated. Further, as described above, it is necessary to separately make an initial setting so that the driving force is accurately transmitted to the lens when the step motor is driven.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an imaging apparatus that can reliably set the initial position of a lens without using position detection components.

  The object is to provide an image sensor, a lens for forming a subject image on the image sensor, and a lens holder that holds the lens and contacts the cam member and is moved in the optical axis direction by driving the cam member. A lower limit of the lens holding member in which the lens holding member is biased toward the cam member, and the lens holding member approaches the image pickup device by a position regulating member. A contact portion where the position is regulated and the cam member is in contact with the lens holding member at the lower limit position, and a non-contact portion that is not in contact with the lens holding member at the lower limit position following the contact portion The position of the lens when it is detected that the lens holding member is located on the non-contact portion based on the image output signal of the image sensor is set as an initial position. Initial position setting means for can be achieved by an imaging device provided with a.

  In addition, it is desirable to further include storage means for storing the initial position information of the lens set by the initial position setting means. The lens holding member includes a lens holder that holds the lens, and an engaging portion that is relatively movable in the optical axis direction of the lens holder and the lens, and a contact portion that contacts the cam member. A structure including a focus adjusting member may be used.

  According to the present invention, it is possible to reliably set the initial position of the lens without arranging a position detecting component. Therefore, the cost of the imaging device can be reduced and the structure can be simplified.

  Hereinafter, an embodiment according to the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a configuration of an imaging apparatus 1 according to the present invention. The imaging apparatus 1 includes a lens 11 that forms an image of the subject BJ on the imaging element 3. The lens 11 is moved forward and backward in the optical axis direction by a lens driving device 10 to be described later, and focus adjustment is performed. In FIG. 1, a step motor 8 is illustrated as a driving source of the lens driving device 10. In addition, the imaging apparatus 1 includes a control unit 50. The controller 50 controls the driving of the step motor 8.

  The control unit 50 includes a signal processing circuit 52 that processes an image detection signal from the image sensor 3, a motor drive circuit 53 that controls driving of the step motor 8, a control circuit 51 that controls these as a whole, a control program, A memory 54 for storing a series of data related to control is included. The signal processing circuit 52 can be formed by a DSP (Digital Signal Processor), for example. The control circuit 51 is formed by a CPU (Central Processing Unit), for example, and functions as an initial position setting means for setting an initial position of the lens as will be described later. The memory 54 is a means for storing the initial lens position information.

  With reference to FIG.2 and FIG.3, the detailed mechanical structure of the imaging device 1 is demonstrated in detail. FIG. 2 is a plan view showing the configuration of the image pickup apparatus 1, and FIG. 3 is a side view thereof. In FIG. 3, a part is hatched so that the configuration can be easily confirmed.

  The imaging device 1 includes a lens driving device 10 that advances and retracts the printed circuit board 2, the imaging device 3, the base plate 4, the optical filter 5, and the lens 11 in the optical axis direction LA. A CCD, CMOS, or the like as the image sensor 3 is disposed at a predetermined position on the substrate 2. A base plate 4 is disposed so as to surround the imaging element 3. The base plate 4 is made of a resin such as plastic, and serves as a base member that supports a plurality of components described later. An opening 4HL is formed in the base plate 4 at a position facing the imaging device 3, and an optical filter 5 such as an IR cut filter is disposed so as to close the opening 4HL.

  A lens driving device 10 is mounted on the top of the base plate 4. The lens driving device 10 includes a lens 11, a lens holder 12, an adjustment ring 13 as a focus adjustment member, a pair of guide shafts 7A and 7B, the step motor 8, the worm gear 9, the cam gear 30 as a cam member, and the like. It is configured.

  The lens 11 is fixed and held in a cylindrical lens holder 12. A cylindrical adjustment ring 13 is disposed so as to surround the outer periphery of the lens holder 12. Threaded portions that mesh with each other are formed on the outer periphery of the lens holder 12 and the inner periphery of the adjustment ring 13. The lens holder 12 and the adjustment ring 13 are engaged with each other at a portion indicated by reference numeral SG, and can be moved relative to the adjustment ring 13 in the optical axis direction LA by rotating the lens holder 12. A lens holding member is formed by the lens holder 12 and the adjustment ring 13.

  A pair of guide shafts 7A and 7B are raised from the base plate 4 in parallel with the optical axis direction LA. The adjustment ring 13 has a pair of guide receiving portions 14A and 14B formed so as to protrude in the radial direction from the outer periphery. The guide receiving portions 14A and 14B are engaged with the guide shafts 7A and 7B, respectively. More specifically, one guide receiving portion 14A is formed in a forked shape so as to sandwich the guide shaft 7A from both sides, and the other guide receiving portion 14B is formed in a hole shape so as to be fitted to the guide shaft 7B. ing. With such a configuration, the adjustment ring 13 can be slid with respect to the guide shafts 7A and 7B and moved in the optical axis direction LA. As described above, the lens holder 12 holding the lens 11 is engaged in the adjustment ring 13. Therefore, it is possible to adjust the focus of the lens 11 by moving the lens holder 12 forward and backward in the optical axis direction LA with respect to the adjustment ring 13.

  The adjustment ring 13 has a spring locking portion 13a on a part of the outer periphery. One end of a coil spring 20 described later is locked to the spring locking portion 13a. The adjustment ring 13 has a cam follower 15 so as to protrude downward (from the printed circuit board 2 side) from a part of the outer periphery. The cam follower 15 extends downward along the optical axis direction LA. A tip portion (abutting portion) 15a of the cam follower 15 is formed in a hemispherical shape so as to easily move to a cam surface 32 of a cam gear 30 described later.

  A step motor 8 is fixed on the base plate 4 so that the rotation axis is orthogonal to the optical axis direction LA. A worm gear 9 is fixed to the step motor 8. The worm gear 9 meshes with a tooth row 35 formed on the outer periphery of the cam gear 30. The cam gear 30 is pivotally supported on a support shaft 31 fixed to the base plate 4 in parallel with the optical axis direction LA, and receives a driving force from the worm gear 9 and rotates in both directions as described above. A cam surface 32 is formed on the upper surface of the cam gear 30. This cam surface is a spiral inclined surface. The cam follower 15 of the adjustment ring 13 is in contact with the cam surface 32. A pedestal 36 is formed below the cam gear 30, and the height is adjusted so that the tooth row 35 meshes with the worm gear 9.

  Further, a coil spring 20 that urges the adjustment ring 13 in a predetermined direction is disposed. One end of the coil spring 20 is locked to a spring locking portion 13a on the adjustment ring 13 side, and the other end is locked to a spring locking portion 4a formed on the base plate 4 side. The coil spring 20 is stretched so as to generate a biasing force that draws the spring locking portion 13a and the spring locking portion 4a. Further, as shown in FIG. 3, the coil spring 20 is disposed in an inclined state with respect to the optical axis direction LA. This state is formed by disposing the spring locking portion 4a of the base plate 4 outside the spring locking portion 13a on the adjustment ring 13 side as viewed from the center of the lens 11.

  If the coil spring 20 is disposed so as to be inclined with respect to the optical axis direction LA as described above, the biasing force of the coil spring 20 is efficiently used for stable movement of the lens 11 when the lens 11 is moved in the optical axis direction LA. Can be used well. When the coil spring 20 is tilted with respect to the optical axis direction LA, the urging force based on the coil spring 20 is divided into a force acting in a direction parallel to the optical axis direction LA and a force acting in a direction perpendicular to the optical axis direction LA. Available. The first component force acting in a direction parallel to the optical axis direction LA acts as a force for urging (pressing) the cam follower 15 provided on the adjustment ring 13 toward the cam surface 32. Therefore, the adjustment ring 13 can be moved to a predetermined position in the optical axis direction LA according to the rotation state of the cam gear 30 (change in the position of the cam surface 32). That is, the lens 11 can be accurately moved to a predetermined position in the optical axis direction LA.

  Then, the second component force acting in the direction perpendicular to the optical axis direction LA acts as a force that urges (presses) the adjustment ring 13 against a part of the guide shaft 7B as a backlash. As a result, the adjustment ring 13 can move smoothly without rattling in the optical axis direction LA. Therefore, the lens 11 can be moved to a desired position in the optical axis direction LA while suppressing the displacement of the lens 11.

  As shown in FIG. 3, in the structure shown in this embodiment, the guide receiving portion 14A of the adjustment ring 13 that engages with the guide shaft 7A has a bifurcated shape, and the adjustment ring 13 that engages with the guide shaft 7B. The guide receiving portion 14B has a hole shape. The lens-side inner surface Wa (see FIG. 2) of the guide receiving portion 14B is pressed against the guide shaft 7A in a state where the urging force (force pulled forward) of the coil spring 20 is applied. Further, with respect to the guide receiving portion 14A, the urging force of the coil spring 20 is adopted as a clockwise force, so that the inner surface Wb (see FIG. 2) is pressed against the guide shaft 7B. Thus, since the adjustment ring 13 is supported at three places, the position in the plane perpendicular to the optical axis direction LA is stabilized. The guide receiving portion 14A and the guide receiving portion 14B are set to be substantially symmetrical with respect to the center of the lens 11, and the cam follower 15 and the spring locking portion 13a are set to be substantially symmetrical about the guide receiving portion 14B. Has been. Further, the guide receiving portion 14A may not have a bifurcated shape but may have a hole shape like the guide receiving portion 14B.

  As described above, the cam surface 32 formed on the cam gear 30 has a spiral shape. Therefore, the start end portion and the end end portion of the cam surface 32 are inclined slopes 32t. 2 and 3 illustrate a state in which the cam follower 15 is in contact with a high position of the cam surface 32 formed in a spiral shape. 4 and 5 are views corresponding to FIGS. 2 and 3, in which the cam surface 32 of the cam gear 30 is located at a position lower than the cam follower 15. In particular, as can be confirmed from FIG. 5, the cam follower 15 is designed so as not to contact a predetermined region (a non-contact portion described later) of the cam surface 32. The setting will be described.

  On the side of the guide shaft 7A, a position restricting member 6 that comes into contact with the lower surface of the guide receiving portion 14 is raised from the base plate 4. The position where the lower surface of the guide receiving portion 14 abuts against the position regulating member 6 is the lower limit position of the adjustment ring 13, and this lower limit position is the initial position of the lens 11. Thus, when the adjustment ring 13 is in the lower limit position and the cam gear 30 is rotated and the cam surface 32 comes to the low non-contact portion, a state where the cam follower 15 does not contact the cam surface 32 can be formed. At this time, the lens holder 12 is rotated with respect to the adjustment ring 13 and moved relative to the optical axis direction LA, thereby adjusting the focus of the lens 11 during assembly.

  Further, a configuration for setting the initial position of the lens 11 provided in the imaging apparatus 1 will be described. As described above, the lens 11 is set to the initial position when the adjustment ring 13 reaches the lower limit position. The cam surface 32 of the cam gear 30 is formed with a contact portion that contacts the cam follower 15 and a non-contact portion that does not contact when the adjustment ring 13 is at the lower limit position. The adjustment ring 13 receives a biasing force directed toward the cam surface 32 by the coil spring 20 as described above. Therefore, in this state, when the cam follower 15 faces the non-contact portion of the cam surface 32, the lens 11 is set to the initial position by the urging force. Then, when the cam gear 30 is rotated and the contact portion of the cam surface 32 is positioned below the cam follower 15 and comes into contact therewith, the cam follower 15 is then pushed upward.

  As described above, the cam surface 32 is formed in a spiral shape. Consider a state in which the boundary between the non-contact portion and the contact portion is located directly below the cam follower 15. From this state, when the cam gear 30 is driven so that the contact portion comes under the cam follower 15, the lens 11 starts to move upward from the initial position. That is, in the imaging apparatus 1, when it is detected that the non-contact portion of the cam surface 32 is directly below the cam follower 15, it can be confirmed that the lens 11 is in the initial position, and the lens 11 is moved according to the movement of the cam gear 30. It can also be confirmed that the preparation for accurately moving the lens is completed, that is, the initial position setting of the lens is completed. The configuration for setting the initial position of the lens 11 of the imaging device 1 is designed based on the viewpoint described here. Furthermore, it demonstrates in detail with reference to figures.

  FIG. 6 is a diagram illustrating a cam curve CM that defines the cam surface 32 by developing the outer peripheral surface of the cam gear 30. A focus adjustment region PT used for focus adjustment at the time of photographing is set in a part of the contact portion where the cam follower 15 contacts the cam surface 32. A non-contact area NT is continuously present on the left side (the side on which the cam curve is lowered) of the focus adjustment area PT. This non-contact area NT corresponds to the non-contact part described above. That is, the cam follower 15 does not come into contact even when the adjustment ring 13 comes into contact with the position regulating member 6 and reaches the lower limit position. The cam follower 15 that is easy to understand the relationship with the cam surface 32 is illustrated by a dotted line.

  The contact state and non-contact state of the cam follower 15 are switched at the boundary portion BD between the focus adjustment region PT and the non-contact region NT. When the cam follower 15 is in contact with the focus adjustment region PT when the cam gear 30 is driven, the position of the lens 11 is changed, so that the image of the subject imaged on the image sensor 3 changes. That is, the image detection signal output from the image sensor 3 changes. On the other hand, since the position of the lens 11 does not change when the cam follower 15 is opposed to the non-contact area NT, the image formed on the image sensor 3 does not change. As a result, the image detection signal output from the image sensor 3 is constant without changing. In this way, by monitoring the image detection signal of the image sensor 3, it is possible to confirm which region of the cam gear 30 the cam follower 15 is facing.

  In particular, when the image detection signal has changed from the changed state and when the image detection signal that has been constant has changed, the boundary BD has passed under the cam follower 15. Will show that. Therefore, when the time when the state of the image detection signal changes is detected, the boundary portion BD located immediately below the cam follower 15 can be detected. When the boundary BD is located just below the cam follower 15, the cam surface 32 and the cam follower 15 do not exert a force on each other, that is, the state immediately before the cam surface 32 pushes the cam follower 15 upward. is there. If the drive control of the cam gear 30 is started with this state as the initial position of the lens 11, the adjustment ring 13 can be accurately moved to a desired position in the optical axis direction. Note that the boundary portion BD is an end portion of the focus adjustment region PT, and the boundary portion BD can be set to infinity (∞) or a region for performing macro photography.

  The control circuit 51 shown in FIG. 1 functions as an initial position setting unit to set the initial position of the lens 11. As described above, the control circuit 51 performs the initial position setting by detecting the boundary portion BD between the contact portion and the non-contact portion based on the image detection signal from the image sensor 3. FIG. 7 is a flowchart illustrating an example of processing executed when the control circuit 51 performs initial setting of the lens 11. In the processing shown here, the control circuit 51 compares the contrast value obtained from the image detection signal and confirms the change in the captured image. With reference to FIG. 7 and FIGS. 1 to 6 described above, the control circuit 51 will explain the process of setting the initial position of the lens 11.

  The control circuit 51 sets the count at the current position of the cam gear 30 to P = 0 and starts the initial position setting process (S101). First, the control circuit 51 calculates the contrast value A based on the image detection signal from the image sensor 3 (S102).

  Next, the control circuit 51 supplies one pulse to the step motor 8 to drive the cam gear 30 in the direction of returning one step (the direction in which the height position of the cam follower 15 is lowered) (S103). The control circuit 51 resets the count P = P-1 here (S104), and calculates the contrast value B based on the image detection signal from the image sensor 3 at this time (S105).

  Next, the control circuit 51 compares the contrast value A with the contrast value B (S106). If it is determined in step 106 that the contrast value A and the contrast value B are not equal, it is determined that the cam follower 15 is in contact with the focus adjustment region PT of the cam surface 32. In this case, the processing from step 102 to step 106 is repeated until it is determined that the contrast value A and the contrast value B are equal. By repeating this process, the cam gear 30 is driven so that the boundary portion BD moves below the cam follower 15.

  On the other hand, if the control circuit 51 determines in step 106 that the contrast value A and the contrast value B are equal, it is estimated that the cam follower 15 is in the non-contact area NT after the boundary BD. Therefore, the control circuit 51 resets the count P = 0 here (S107), and calculates the contrast value A based on the image detection signal from the image sensor 3 (S108). Then, the control circuit 51 supplies the step motor 8 with one pulse for driving the cam gear 30 in the reverse direction to drive the cam gear 30 in the direction in which the cam gear 30 is advanced by one step (the direction in which the height position of the cam follower 15 is increased) (S109). ). The control circuit 51 resets the count P = P + 1 here (S110), and calculates the contrast value B based on the image detection signal from the image sensor 3 at this time (S111).

  Next, the control circuit 51 compares the difference between the contrast value A and the contrast value B (S112). If it is determined in step 112 that the contrast value A and the contrast value B are equal, it is determined that the cam follower 15 is in the non-contact area NT, so that it is determined that the contrast value A and the contrast value B are different. Steps 108 to 112 are repeated. By repeating this process, the cam gear 30 is driven so that the boundary portion BD moves below the cam follower 15.

  On the other hand, if the control circuit 51 determines that the contrast value A and the contrast value B are different in step 112, it can be estimated that the cam follower 15 has entered the focus adjustment region PT by one step from the boundary portion BD. Therefore, in the next step 113, the control circuit 51 reversely drives the cam gear 30 in the direction of returning by one step, resets the count P = P-1 (S114), and ends the processing according to this flowchart. When the initial position setting process by the control circuit 51 shown in FIG. 6 is completed, the boundary portion BD is located immediately below the cam follower 15. Therefore, the initial position setting of the lens 11 is completed. In addition, you may add to the determination element the total pulse number which drives the cam gear 30 once in the process in the said flowchart. For example, when it is determined that the cam gear 30 is driven in one direction at a number exceeding the total number of pulses, the process may be stopped.

  The image pickup apparatus 1 described above includes a control circuit 51 as an initial position setting unit for setting the initial position of the lens 11. Since the control circuit 51 sets the initial position of the lens 11, the initial position of the lens is detected as in the conventional apparatus. Therefore, the initial lens position can be reliably set without using components such as sensors and switches. Further, if the information obtained when the initial position setting is executed by the control circuit 51 is stored in the memory 54 shown in FIG. 1, the initial position of the lens 11 can be set in a short time thereafter. become able to.

  In the above-described embodiment, a structure example in which the lens holding member is formed by the lens holder 12 and the adjustment ring 13 is shown as a more preferable structure. However, the guide shafts 7A and 7B are engaged with the lens holder 12 and the biasing force of the coil spring is obtained. You may comprise so that it may act.

  The preferred embodiment of the present invention has been described in detail above, but the present invention is not limited to the specific embodiment, and various modifications can be made within the scope of the gist of the present invention described in the claims.・ Change is possible.

It is the block diagram shown about the structure of the imaging device which concerns on this invention. It is the top view which showed the structure of the imaging device shown in FIG. It is the side view shown so that the structure of the imaging device shown in FIG. 1 could be confirmed. FIG. 3 is a diagram corresponding to FIG. 2 and showing a state where cam surfaces are at different positions. FIG. 4 is a view corresponding to FIG. 3 and showing a state where cam surfaces are at different positions. It is the figure which showed the cam curve which expand | deploys the outer peripheral surface of the cam gearwheel arrange | positioned at an imaging device, and prescribes | regulates a cam surface. 6 is a flowchart illustrating an example of processing executed when the control circuit of the imaging apparatus performs initial lens position setting.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image pick-up device 2 Board | substrate 3 Image pick-up element 6 Position control member 7A, 7B Guide shaft 8 Step motor 10 Lens drive device 11 Lens 12 Lens holder 13 Adjustment ring (focus adjustment member)
14A, 14B Guide receiving portion 15 Cam follower 15 Contact portion 30 Cam gear (cam member)
32 Cam surface 51 Control circuit (initial setting output means)
BD boundary PT focus adjustment area NT non-contact area LA optical axis direction

Claims (3)

An image pickup device, a lens for forming a subject image on the image pickup device, and a lens holding member that holds the lens and contacts the cam member and is moved in the optical axis direction by driving the cam member. An imaging device comprising:
The lens holding member is urged toward the cam member, and a lower limit position of the lens holding member at which the lens holding member approaches the imaging element is regulated by a position regulating member,
A contact portion where the cam member contacts the lens holding member at the lower limit position, and a non-contact portion which does not contact the lens holding member at the lower limit position continuously to the contact portion;
An initial position setting unit configured to set the position of the lens as an initial position when it is detected that the lens holding member is positioned in the non-contact portion based on an image output signal of the image sensor; An imaging device. The imaging apparatus according to claim 1, further comprising storage means for storing initial position information of the lens set by the initial position setting means. The lens holding member includes a lens holder that holds the lens, and an engagement portion that is relatively movable in the optical axis direction of the lens holder and the lens, and has a contact portion that contacts the cam member. The imaging apparatus according to claim 1, further comprising an adjustment member.

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