JP2010057308A - Drive device and image capturing apparatus with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drive device, the number of components of which can be reduced than in the prior art. <P>SOLUTION: An auto-focus camera 10 includes a moving section 13c for moving a focus lens 11, a protrusion 14 and a machine end 15, a microcomputer 24, and a counter 28. The microcomputer 24 has a movement control mode for moving the moving section 13c and an initialization mode to be executed before the movement control mode, as operation modes. In the initialization mode, the machine end is moved by moving the moving section 13c so that the protrusion 14 may abut against any position of the machine end 15 to set the counter 28 to a predetermined value. Thereafter, the moving direction is reversed and the moving section 13c is moved at a predetermined power supply time to reach a position which is used as the origin for the movement control mode. In the movement control mode, positioning the moving position 13c is controlled based on a counter value of the counter 28. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a driving device having a piezoelectric element and an imaging device including the driving device.

  In recent years, small camera modules equipped with an autofocus function that automatically detects the focus of a photographic lens have been adopted in portable devices and the like. Furthermore, various devices have been sought for the lens driving device in order to reduce the size of the camera module.

  A conventional driving device uses, for example, a photo interrupter detection sensor in order to obtain a moving origin of a moving unit that moves a lens (see, for example, Patent Document 1). A sensor using a magnetic sensor such as a Hall element as a detection sensor is also known (see, for example, Patent Document 2). Hereinafter, a conventional driving apparatus will be described with reference to FIG. FIG. 18 shows an autofocus camera provided with a conventional driving device described in Patent Document 1.

  A conventional autofocus camera 310 in FIG. 18 includes a focus lens 311, a lens barrel 312 having a shielding plate 312 a that shields light, and an impact-type piezoelectric actuator that drives the lens barrel 312 in the optical axis direction of the focus lens 311. 313, a base end sensor 315 disposed at the base end position 315a of the movable range of the shielding plate 312a, a distal end sensor 316 disposed at the distal end position 316a of the movable range of the shielding plate 312a, and the focus lens 311. A CCD (Charge Coupled Device) 317 that converts the imaged subject light into a video signal, a drive circuit 318 that supplies power to the impact piezoelectric actuator 313, and an image processing IC that performs image processing based on the video signal output from the CCD 317 (Integrated Circuit) 320. The proximal sensor 315 includes a photo interrupter that detects the presence of the shielding plate 312a on the proximal end position 315a side when the light path is blocked by the shielding plate 312a. The distal sensor 316 has a light path that is blocked by the shielding plate 312a. It is composed of a photo interrupter that detects that the shielding plate 312a is present on the tip end position 316a side by being blocked.

  Here, the impact-type piezoelectric actuator 313 extends in the direction indicated by the arrow 310a and contracts in the direction indicated by the arrow 310b opposite to the direction indicated by the arrow 310a, and the piezoelectric element 313a is coupled to the piezoelectric element 313a. The driving shaft 313b driven in the direction indicated by arrows 310a and 310b by 313a and the lens barrel 312 are fixed and frictionally engaged with the driving shaft 313b to move in the direction indicated by arrows 310a and 310b with respect to the driving shaft 313b. Moving part 313c.

In the conventional autofocus camera 310 in FIG. 18, when the shielding plate 312 a moves with the movement of the focus lens 311, and the light in the proximal sensor 315 is shielded at a position where the focus lens 311 is focused at infinity, Since the voltage of the output signal of the end sensor 315 changes from the high level to the low level, the lens position at the infinity side origin can be detected. Similarly, when the light in the tip sensor 316 is blocked at a position where the focus lens 311 is focused at a predetermined object distance on the near side, the voltage of the output signal of the tip sensor 316 changes from a high level to a low level. As a result, the position of the nearest origin can be detected.
JP 2007-37337 A JP 2007-41387 A

  However, in order to obtain the position information of the base end and the distal end, which is the reference for the position information of the moving unit, the conventional driving device uses a position detecting sensor such as an optical sensor such as a photo interrupter or a magnetic sensor such as a Hall element. In addition, it is necessary to increase the number of parts and secure the part placement space because the object to be detected such as a shielding plate and magnet is placed on the moving part while maintaining the necessary positional relationship. Thus, it has been difficult to reduce the size and weight.

  The present invention has been made to solve the conventional problems, and can reduce the number of parts compared to the conventional one without impairing positioning accuracy, and can achieve a reduction in size and weight, and a driving device thereof. An object of the present invention is to provide an imaging apparatus provided.

  The drive device of the present invention is engaged with the drive unit by a frictional force between the piezoelectric element, the drive unit driven by the piezoelectric element, and the drive unit, and according to the expansion and contraction operation of the piezoelectric element. A moving part, a mechanical end part that mechanically limits a start point and an end point of a moving range of the moving part, a supply control unit that controls supply of electric power to the piezoelectric element, and the piezoelectric element A counter that stores a counter value corresponding to position information of the moving unit based on a power supply time and a moving direction of the moving unit, and the supply control unit performs the control to move the moving unit The control mode and an initialization mode performed before the movement control mode are provided as operation modes, and in the initialization mode, the moving unit is moved to any one of the start point and the end point. After performing the machine end moving operation to set the unter to a predetermined value, the position where the moving unit is moved in a predetermined power supply time by reversing the moving direction is the origin of the moving unit in the movement control mode. In the movement control mode, positioning control of the moving unit is performed based on the counter value of the counter.

  With this configuration, the drive device of the present invention resets the counter to a predetermined value, and then reverses the moving direction and moves the moving unit for a specific power supply time as the origin of the moving unit in the movement control mode. Since the positioning can be performed based on the counter information in the movement control mode, the driving device using the piezoelectric actuator can be controlled without using the position detection sensor. Therefore, the drive device of the present invention can reduce the number of parts as compared with the conventional one without impairing positioning accuracy, and can achieve a reduction in size and weight.

  The image pickup apparatus of the present invention further includes a drive device, a lens supported by the moving unit, and an image pickup device that picks up an image of the subject, and the movement control mode automatically transfers the image of the subject to the image pickup device. The supply control means starts moving the lens position to the start point position where the autofocus control is started based on the position of the origin determined in the initialization mode. And a focal point search operation mode for performing a focal point search operation for starting a focal point search from the start point. A plurality of means for moving the position of the lens to a position of a search start point for starting a search by different methods, and performing the autofocus control. To time, in response to said operation performed autofocus control previously has selectively those switching configure the operation at the start of the movement operation mode by said plurality of means.

  With this configuration, the imaging apparatus of the present invention refers to the lens movement history before executing autofocus, determines the degree of error between the logical position and the physical position, and based on the result, the search start point of autofocus By selecting from a plurality of movement methods, unnecessary time can be saved, so that the time required for the autofocus operation can be shortened.

  Furthermore, in the imaging apparatus according to the present invention, the supply control unit stores power supply time data specific to the driving device for moving the position of the lens from one of the start point and the end point to a predetermined position. A memory for storing, reverse the moving direction after performing the machine end moving operation, and the position where the lens position is moved during the power supply time unique to the driving device as the origin, the counter value at this time And a first start point moving means for moving the lens position to the search start point based on the first counter movement direction, and the moving direction is reversed after the machine end moving operation is performed based on the current counter value. The position where the position of the lens is moved during the power supply time is set as the origin, and the position of the lens is moved to the search start point based on the counter value at this time. At least two start points of start point moving means and third start point moving means for directly moving the position of the lens to the search start point based on the counter value of the origin obtained in the initialization mode The moving means is provided as the plurality of means.

  With this configuration, the imaging apparatus of the present invention can perform more appropriate control by increasing the choices of the starting point moving means.

  Furthermore, in the imaging apparatus of the present invention, during the autofocus control, the supply control unit is set to a value that is predetermined from the position of the origin indicated by the counter value in a direction opposite to the direction in which the in-focus search operation is performed. The position where the lens is moved is used as the search start point.

  With this configuration, the imaging apparatus of the present invention can reliably capture a search range to which autofocus should be applied.

  Furthermore, in the imaging apparatus of the present invention, after the supply control unit performs focus adjustment during the autofocus control, the lens is always set to the origin after finishing a predetermined imaging operation including still image imaging. It has a configuration that controls positioning so as to move to a position.

  With this configuration, the imaging apparatus of the present invention can quickly start the focus search operation when the next autofocus is started, so that the time required for the autofocus operation can be shortened.

  The present invention provides a driving device that can reduce the number of parts as compared with the conventional one without impairing positioning accuracy, and can be reduced in size and weight, and an imaging device including the driving device. It can be done.

  Hereinafter, a driving apparatus and an imaging apparatus according to the present invention will be described with reference to the drawings. Note that an embodiment will be described by taking an autofocus camera as an example of an imaging apparatus provided with a drive device according to the present invention.

  FIG. 1 is a block diagram showing a configuration of an autofocus camera in the present embodiment. As shown in FIG. 1, the autofocus camera 10 according to the present embodiment limits the movement range of the focus lens 11, the lens barrel 12, the piezoelectric actuator 13 that drives the lens barrel 12, and the lens barrel 12. The convex portion 14 and the machine end portion 15, the EEPROM (Electronically Erasable and Programmable Read Only Memory) 16 that stores adjustment value data unique to the driving device, and the subject light imaged by the focus lens 11 are converted into video signals. An image sensor 17, a drive circuit 18 that supplies power to the piezoelectric actuator 13, and an image processing IC 20 that performs image processing based on a video signal output from the image sensor 17 are provided.

  Here, the piezoelectric actuator 13 extends in the direction indicated by the arrow 10a and contracts in the direction indicated by the arrow 10b opposite to the direction indicated by the arrow 10a, and the piezoelectric element 13a coupled to the piezoelectric element 13a. A direction indicated by arrows 10a and 10b with respect to the drive shaft 13b by fixing the lens barrel 12 and frictionally engaging the drive shaft 13b as a drive unit driven in a direction indicated by arrows 10a and 10b. And a moving portion 13c that moves to the position. The moving unit 13c is configured to move the focus lens 11 along the optical axis of the optical system in parallel with the expansion / contraction direction of the piezoelectric element 13a, that is, the axial direction of the drive shaft 13b.

  The mechanical end 15 is provided on a fixed lens frame (not shown), and the infinity-side mechanical end 15 a that restricts the movement of the focus lens 11 in the retracting direction via the convex 14, and the focus lens 11. And a macro-side machine end 15b for restricting movement in the feeding direction.

  The image processing IC 20 includes an input / output circuit 21 that exchanges adjustment value data and the like unique to the driving device with the EEPROM 16, an image sensor control circuit 22 that controls the operation of the image sensor 17, and a video signal output by the image sensor 17. An image signal processing unit 23 for generating a focus evaluation value from the high-frequency component of the image, and an image contrast by controlling the operation of the drive circuit 18 via the input / output circuit 21 based on the focus evaluation value obtained by the image signal processing unit 23 A microcomputer unit 24 for performing auto-focusing of the system, a ROM (Read Only Memory) 25 for storing an operation program of the microcomputer unit 24, a RAM (Random Access Memory) 26 as a work area of the microcomputer unit 24, and mainly video The memory controller 27 that controls signal input / output and the counter value corresponding to the position information of the focus lens 11 are counted and stored. And a counter 28.

  The microcomputer unit 24 controls the power supply to the piezoelectric element 13a by the drive circuit 18, and constitutes a supply control means. Specifically, for example, when the microcomputer unit 24 supplies voltage to the piezoelectric element 13a by the drive circuit 18, the supply time of the voltage to the piezoelectric element 13a is set to an integral multiple of the control unit time. Yes. The counter 28 counts a counter value according to, for example, the voltage supply time to the piezoelectric element 13a, and the counter value is an integer that is an integer multiple of the above, for example. Therefore, the counter value of the counter 28 corresponds to the position information of the focus lens 11.

  The ROM 25 is a signal that gives the waveform shape of the voltage that the drive circuit 18 supplies to the piezoelectric element 13a, that is, a signal that determines the contraction / extension speed and drive frequency of the piezoelectric element 13a. 2A used when the moving unit 13c is moved in the direction indicated by 10a, and when the moving unit 13c is moved in the retraction direction of the focus lens 11, that is, the direction indicated by the arrow 10b. The signal shown in FIG. 2B is stored. Here, the signals shown in FIG. 2 include, for example, inertial masses of the focus lens 11, the lens barrel 12, and the moving unit 13c, and loads such as dynamic friction force and static friction force generated between the drive shaft 13b and the moving unit 13c. The autofocus camera 10 is set to operate stably based on the thrust of the piezoelectric element 13a and the moving speed of the moving unit 13c. Note that the cycle of the signal shown in FIG. 2A is equal to the cycle of the signal shown in FIG. The control unit time may be set in the cycle shown in FIG. 2, and in this case, the distance that the focus lens 11 moves is determined in the time corresponding to the cycle shown in the figure.

  The driving device 30 that drives the focus lens 11 includes the lens barrel 12, the piezoelectric actuator 13, the EEPROM 16, the driving circuit 18, the input / output circuit 21, the microcomputer unit 24, the ROM 25, the RAM 26, and the memory controller 27.

  Next, the case where the driving device 30 shown in FIG. 1 is a driving device that drives a lens mechanism for portable equipment will be described as an example.

  The autofocus camera 10 has an initialization mode when the camera is activated and a movement control mode for moving the focus lens 11. First, when the camera is activated, if the position of the focus lens 11 is initialized in the initialization mode (lens position initialization), the position of the focus lens 11 before the automatic focusing is automatically performed and an object at infinity is imaged. At this time, the position is set so as to satisfy a predetermined level of resolution, and the focus lens 11 is moved to an appropriate position in the subsequent movement control mode.

  Hereinafter, the operation of the autofocus camera 10 will be described. FIG. 3 is a flowchart showing processing in the initialization mode when the camera is activated.

  In the initialization mode when the camera is activated, the microcomputer unit 24 sufficiently moves the focus lens 11 in any direction of the machine end 15 in order to move the focus lens 11 to the target stop position that is the origin of the movement control mode. It moves and presses against one of the machine end parts 15 (step S1). After step S1, the microcomputer unit 24 initializes a counter 28 that acquires position information of the focus lens 11 to a predetermined value (step S2).

  Next, the microcomputer unit 24 reverses the moving direction to give a predetermined power supply time, extends the focus lens 11 to a range that satisfies a predetermined resolution on the display screen of the portable device, and controls it to be the origin of the movement control mode. (Step S3). Thereafter, the counter 28 counts according to the power supply time and the moving direction, and the count value is stored as position information of the focus lens 11.

  In the present embodiment, a predetermined power supply time is provided so that the position of the focus lens 11 at the time of starting the camera is positioned within a focal depth range in which a predetermined resolution can always be obtained by the display device of the camera. The focus lens 11 is moved with the infinity side reference position (or pan focus position and optical macro side reference position) as the origin of the movement control mode. As a result, the positioning range of the focus lens 11 is far ( Alternatively, an object having a target subject distance) is always accommodated within a focal depth range in which a predetermined resolution can be obtained by a camera display device.

  In the initialization mode of the present embodiment, the microcomputer unit 24 reverses the movement direction after pressing the focus lens 11 against the machine end 15 (the infinity side machine end 15a or the macro side machine end 15b). The EEPROM 16 uses the power supply time when moving to the origin of the movement control mode as an adjustment value based on a power supply time that is a lens position that focuses at infinity (or target subject distance) in advance for each individual camera. To record.

  Hereinafter, an adjustment procedure for acquiring the adjustment value will be described with reference to FIGS. 4 to 7 are flowcharts showing the adjustment procedure of the optical position (optical infinity side reference position, optical macro side reference position). 8-10 is explanatory drawing of the adjustment procedure of an optical position.

  First, the adjustment procedure from the infinity side machine end 15a to the optical infinity side reference position will be described with reference to the flowchart shown in FIG. 4 and FIG.

  The microcomputer unit 24 moves the focus lens 11 to the infinity side machine end 15a by driving the piezoelectric actuator 13 with a power supply time that can sufficiently reach the infinity side machine end 15a (step S11). Here, as shown in FIG. 8, the microcomputer unit 24 captures a curve indicating the relationship between the lens extension amount and the contrast of the image by photographing the autocollimator on the infinity side as the adjustment chart (step S12). The subsequent steps are executed to obtain the power supply time corresponding to the lens position of the curve vertex.

  The microcomputer unit 24 drives the piezoelectric actuator 13 to reverse the focus lens 11 from the infinity side machine end 15a to the direction of the optical infinity side reference position (step S13). Is moved in the macro direction (step S14), and the power supply time accumulated from the infinity side machine end 15a is updated (step S15).

  Here, the microcomputer unit 24 acquires the focus evaluation value from the image signal processing unit 23 (step S16), and determines whether or not the focus lens 11 has already passed the position corresponding to the above-described curve vertex (step S17). ). The passage of the curve vertex is determined by the negative variation between the acquired focus evaluation value and the previous acquired value. If it is determined in step S17 that the focus lens 11 has passed the position corresponding to the curve vertex, the microcomputer unit 24 drives the piezoelectric actuator 13 to once move the focus lens 11 to the infinity side machine end 15a. (Step S18). On the other hand, if it is not determined in step S17 that the focus lens 11 has passed the position corresponding to the curve vertex, the process returns to step S14.

  Next, as shown in FIG. 8, the microcomputer unit 24 obtains a function approximated by a polynomial on the basis of three or more focus evaluation values before and after the apex and the power supply time corresponding to each, and is derived from this function. The power supply time corresponding to the top of the curve is calculated, and the focus lens 11 is moved by the calculated power supply time (step S19).

  The microcomputer unit 24 temporarily stores the calculated power supply time in the RAM 26 as an adjustment value (step S20). Before step S20, a focus evaluation value is acquired from the image signal processing unit 23 at a position where the focus lens 11 is moved by the power supply time calculated by the microcomputer unit 24, and the acquired focus evaluation value corresponds to the apex. A step of confirming whether or not may be added.

  Next, the adjustment procedure from the macro side machine end 15b to the optical infinity side reference position will be described with reference to the flowchart shown in FIG. 5 and FIG.

  The microcomputer unit 24 drives the piezoelectric actuator 13 with a power supply time that can sufficiently reach the macro machine end 15b to move the focus lens 11 to the macro machine end 15b (step S31). As shown in FIG. 8, the microcomputer unit 24 captures a curve indicating the relationship between the lens extension amount (step) and the contrast of the image by photographing the autocollimator on the infinity side as an adjustment chart (step S32). Then, the following steps are executed in order to obtain the power supply time corresponding to the lens position at the vertex of the curve.

  The microcomputer unit 24 drives the piezoelectric actuator 13 to invert the focus lens 11 from the macro-side machine end 15b toward the optical macro-side reference position (step S33), and moves the focus lens 11 infinitely for a specified amount of power supply time. While moving in the far direction (step S34), the power supply time for the amount of movement accumulated from the macro-side machine end 15b is updated (step S35).

  Here, the microcomputer unit 24 acquires the focus evaluation value from the image signal processing unit 23 (step S36), and determines whether or not the focus lens 11 has passed the position corresponding to the above-described curve vertex (step S37). . The passage of the curve vertex is determined by the negative variation between the acquired focus evaluation value and the previous acquired value. If it is determined in step S37 that the focus lens 11 has passed the position corresponding to the curve vertex, the microcomputer unit 24 drives the piezoelectric actuator 13 to once move the focus lens 11 again to the macro side machine end 15b. (Step S38). On the other hand, if it is not determined in step S37 that the focus lens 11 has passed the position corresponding to the curve vertex, the process returns to step S34.

  Next, the microcomputer unit 24 obtains a function approximated by a polynomial based on three or more focus evaluation values before and after the vertex and the power supply time corresponding to each of the focus evaluation values, and the power corresponding to the vertex of the curve derived from this function. The supply time is calculated, and the focus lens 11 is moved by the calculated power supply time (step S39).

  The microcomputer unit 24 temporarily stores the calculated power supply time in the RAM 26 as an adjustment value (step S40). Before step S40, the focus evaluation value is acquired from the image signal processing unit 23 at the position where the focus lens 11 is moved by the power supply time calculated by the microcomputer unit 24, and the acquired focus evaluation value corresponds to the apex. A step of confirming whether or not may be added.

  Next, the adjustment procedure from the infinity side machine end 15a to the optical macro side reference position will be described with reference to the flowchart shown in FIG. 6 and FIG.

  The microcomputer unit 24 moves the focus lens 11 to the infinity side machine end 15a by driving the piezoelectric actuator 13 with a power supply time that can sufficiently reach the infinity side machine end 15a (step S51). Here, as shown in FIG. 9, the microcomputer section 24 captures a curve indicating the relationship between the lens feed amount and the image contrast by photographing the macro adjustment chart (step S52), and the lens at the curve apex. The following steps are executed to obtain the power supply time corresponding to the position.

  The microcomputer unit 24 drives the piezoelectric actuator 13 to invert the focus lens 11 from the infinity side machine end 15a toward the optical infinity side reference position (step S53), and the focus lens 11 for a specified amount of power supply time. Is moved in the macro direction (step S54), and the power supply time for the amount of movement accumulated from the infinity side machine end 15a is updated (step S55).

  Here, the microcomputer unit 24 acquires the focus evaluation value from the image signal processing unit 23 (step S56), and determines whether or not the focus lens 11 has passed the position corresponding to the above-described curve vertex (step S57). . The passage of the curve vertex is determined by the negative variation between the acquired focus evaluation value and the previous acquired value. If it is determined in step S57 that the focus lens 11 has passed the position corresponding to the curve vertex, the microcomputer unit 24 drives the piezoelectric actuator 13 to once move the focus lens 11 to the infinity-side machine end 15a. (Step S58). On the other hand, if it is not determined in step S57 that the focus lens 11 has passed the position corresponding to the curve vertex, the process returns to step S54.

  Next, the microcomputer unit 24 obtains a function approximated by a polynomial based on three or more focus evaluation values before and after the vertex and the power supply time corresponding to each of the focus evaluation values, and the power corresponding to the vertex of the curve derived from this function. The supply time is calculated, and the focus lens 11 is moved by the calculated power supply time (step S59).

  The microcomputer unit 24 temporarily stores the calculated power supply time in the RAM 26 as an adjustment value (step S60). Before step S60, a focus evaluation value is acquired from the image signal processing unit 23 at a position where the focus lens 11 is moved by the power supply time calculated by the microcomputer unit 24, and the acquired focus evaluation value corresponds to the apex. A step of confirming whether or not may be added.

  Next, the adjustment procedure from the macro side machine end 15b to the optical macro side reference position will be described with reference to the flowchart shown in FIG. 7 and FIG.

  The microcomputer unit 24 drives the piezoelectric actuator 13 with a power supply time that can sufficiently reach the macro machine end 15b to move the focus lens 11 to the macro machine end 15b (step S71). Here, as shown in FIG. 9, the microcomputer unit 24 captures a curve indicating the relationship between the lens extension amount and the contrast of the image by photographing the macro adjustment chart (step S <b> 72). The following steps are executed to obtain the power supply time corresponding to the lens position.

  The microcomputer unit 24 drives the piezoelectric actuator 13 to invert the focus lens 11 from the macro-side machine end 15b in the direction of the optical macro-side reference position (step S73), and makes the focus lens 11 infinite for a predetermined amount of power supply time. In addition to moving in the far direction (step S74), the power supply time for the amount of movement accumulated from the macro side machine end 15b is updated (step S75).

  Here, the microcomputer unit 24 acquires the focus evaluation value from the image signal processing unit 23 (step S76), and determines whether or not the focus lens 11 has passed the position corresponding to the above-described curve vertex (step S77). . The passage of the curve vertex is determined by the negative variation between the acquired focus evaluation value and the previous acquired value. When it is determined in step S77 that the focus lens 11 has passed the position corresponding to the curve vertex, the microcomputer unit 24 drives the piezoelectric actuator 13 to once move the focus lens 11 again to the macro side machine end 15b. (Step S78). On the other hand, if it is not determined in step S77 that the focus lens 11 has passed the position corresponding to the curve vertex, the process returns to step S74.

  Next, the microcomputer unit 24 obtains a function approximated by a polynomial based on three or more focus evaluation values before and after the vertex and the power supply time corresponding to each of the focus evaluation values, and the power corresponding to the vertex of the curve derived from this function. The supply time is calculated, and the focus lens 11 is moved by the calculated power supply time (step S79).

  The microcomputer unit 24 temporarily stores the calculated power supply time in the RAM 26 as an adjustment value (step S80). Before step S80, a focus evaluation value is acquired from the image signal processing unit 23 at a position where the focus lens 11 is moved by the power supply time calculated by the microcomputer unit 24, and the acquired focus evaluation value corresponds to the apex. A step of confirming whether or not may be added.

  Finally, the microcomputer unit 24 acquires a total of four adjustment values temporarily stored in the RAM 26 and records them in the EEPROM 16 (step S81).

Further, the microcomputer unit 24 knows the distances of a plurality of different objects serving as subjects, and when obtaining adjustment values corresponding to these object distances from the same mechanical end point, it calculates the difference between the adjustment values to the middle of the object. You may obtain | require the electric power supply time to the located object as an adjustment value. For example, the relationship between the defocus Ld of the focus lens 11 and the object distance L can be expressed as Ld = f ^{2 / (L−f)} where the focal distance f of the focus lens 11 is the same. The defocus (lens extension amount) for an arbitrary subject distance is obtained from the difference between the two adjustment values acquired from 15, and the power supply time proportional to the defocus is obtained. Therefore, the microcomputer unit 24 moves the focus lens 11 to a target object distance position, or temporarily replaces the focus lens 11 with an intermediate value between the adjustment values calculated by complementing the above-described equations. It is possible to change the range.

  Further, as shown in FIG. 10, based on the difference between the two adjustment values acquired from one of the machine end portions 15 and the difference between the two adjustment values acquired from the other of the machine end portions 15, The moving speed ratio k according to the moving direction shown can be obtained. In FIG. 10, the adjustment value from the infinity side machine end to the optical infinity side reference position is (a), the adjustment value from the infinity side machine end to the optical macro side reference position is (d), the macro side machine When the adjustment value from the end to the optical macro side reference position is (c) and the adjustment value from the macro side machine end to the optical infinity side reference position is (b), when driving in the direction of the arrow 10a, The moving speed ratio k is obtained by the following equation.

k = ((d)-(a)) / ((b)-(c))
The data of the moving speed ratio k is calculated by the microcomputer unit 24 and stored in the RAM 26. The microcomputer unit 24 can be driven in a time obtained by multiplying a normal moving time by k by using the moving speed ratio k.

  Next, the movement control mode will be described. FIG. 11 is a flowchart showing processing when the focus lens 11 is moved in the movement control mode.

  When the focus lens 11 is moved by a time N times the control unit time of the voltage to the piezoelectric element 13a, the microcomputer unit 24 determines whether or not the direction in which the focus lens 11 is moved is the direction indicated by the arrow 10a (step). If it is determined in step S91 that the movement is to be performed in the direction indicated by the arrow 10a in step S91, the movement is performed for a time obtained by multiplying N times the control unit time Bc by the movement speed ratio k stored in the RAM 26 (step S92). On the other hand, if it is determined in step S91 not to move in the direction indicated by the arrow 10a, the focus lens 11 is moved in the retracting direction, that is, the direction indicated by the arrow 10b for N times the control unit time Bc (step S93). When the counter 28 is moved in the direction indicated by the arrow 10a, the counter 28 counts the amount multiplied by the moving speed ratio k.

  Next, the start point moving operation for moving the focus lens 11 to the position where the search is started when performing autofocus in the movement control mode will be described. As described above, the video contrast autofocus employed in the present embodiment changes the focus distance by changing the feed amount of the focus lens 11, and the focus evaluation value obtained from the high-frequency component of the video signal is changed. This is a control for searching for the maximum (vertex) lens position and converging and stopping the focus lens 11 in the vicinity thereof. At this time, in order to reliably establish the autofocus without missing the vertex position information, it is necessary to reliably capture the search range. In this respect, the position at which the autofocus search operation is started is important.

  In order to detect a vertex, a method of once passing the vertex and detecting from the increase / decrease of the focus evaluation value at this time is generally known, and this method is also adopted in this embodiment. Therefore, the focus lens 11 is moved in a region slightly wider than the extension range of the focus lens 11 corresponding to the target close distance from the optical infinity. Furthermore, when a positioning error is expected with respect to the absolute position on the optical infinity side, which is defined as the origin in the present embodiment, the search is performed by enlarging the movement range in a region corresponding to the deviation amount.

  Positioning to the optical infinity immediately after the lens position initialization is performed by the same operation as that at the time of adjustment, and since there is no subsequent movement, the position accuracy is high. Compared to this, when the lens is moved and stopped, the true optical infinity reference position is obtained when the lens is returned to the internal counter position defined as optical infinity based on the grasp value of the internal counter inside the camera. The deviation will increase. In particular, when autofocus is executed, the actuator is repeatedly started, stopped, and reversed in the direction of movement, and therefore the error between the lens position grasped by the internal counter and the physical lens position tends to increase gradually. become. On the other hand, when auto-focusing is performed, if the search is started after always performing the same procedure as the lens position initialization as the starting point movement operation, the drive time of the piezoelectric actuator becomes longer, and the time required for the entire auto-focus process It is not a good idea to always use this method.

  Therefore, in the present embodiment, a plurality of methods for moving to the starting point for starting autofocus are provided, and by appropriately managing according to the movement history of the focus lens 11, unnecessary movement time is reduced to reduce autofocus. The autofocus is established without impairing the accuracy of focusing while suppressing an increase in the time required for focusing. Hereinafter, the method of the starting point moving operation in the present embodiment will be specifically described.

  First, the related camera initialization operation will be described. Since the current position of the focus lens 11 is not grasped in the camera initialization operation, first, the drive time to the machine end 15 on the reference side is changed from the arbitrary lens position to the machine end 15 on the reference side. The power supply time is set and driven with a predetermined value that can be reached and pressed against the machine end 15 on the reference side, and the counter 28 is set to a predetermined value. The lens moving direction is reversed, and the focus lens 11 is moved to the optical infinity side reference position that is the origin of the movement control mode by driving with the power supply time based on the adjustment value read from the EEPROM 16.

  Here, the moving distance for calculating the power supply time to the machine end 15 is assumed to be a full stroke from the infinity side machine end 15a to the macro side machine end 15b as described above, and the piezoelectric actuator The moving speed of 13 is calculated using a value derived from the adjustment value described above. That is, when the moving speed varies depending on the moving direction, the correction is made by the above-described moving speed ratio k. At this time, the absolute value of the moving speed is based on a value measured by, for example, a laser displacement meter and stored in the EEPROM 16 when the distance between the optical infinity side reference position and the optical macro side reference position is adjusted. .

  Next, the first to third start point movement operations in the movement control mode will be described. These first to third start point moving operations are respectively executed by the microcomputer unit 24 as first to third start point moving means. In addition, it is preferable to set it as the structure provided with at least 2 start point moving means among the 1st-3rd starting point moving means.

  FIG. 12 shows a first starting point moving method in the movement control mode. This method takes the offset into account when calculating the power supply time after direction reversal with respect to the above-described camera initialization operation immediately after the camera is activated. That is, the drive time is calculated on the assumption of the entire span from the infinity side machine end 15a to the macro side machine end 15b, the focus lens 11 is moved (step S101), and the counter 28 is set to a predetermined value (step S101). S102). Next, the direction is reversed, and the focus lens 11 is moved by the power supply time based on the read adjustment value and the set offset value (step S103), and the search is started with the moved position as the search start point of autofocus. (Step S104).

  As shown in FIG. 13, in the second starting point moving method, at any lens position where the counter value is known, the current position is first grasped based on the value read from the counter 28, and the current position is determined. The theoretical power supply time required to reach the machine end 15 on the reference side is derived and multiplied by a predetermined coefficient in the direction of the machine end 15 on the side using the focus lens 11 as a reference. It moves to the machine end 15 on the side to be driven and pressed (step S111), and the counter 28 is set to a predetermined value (step S112). Next, the direction is reversed, and the focus lens 11 is moved by the power supply time based on the read adjustment value and the set offset value (step S113), and the search is started with the moved position as the search start point of autofocus. (Step S114).

  As shown in FIG. 14, the third start point moving method first grasps the current position based on the value read from the counter 28, and directly corresponds to the target autofocus search start point from that position. (Step S121), and the search is started as an autofocus search start point (step S122).

  The first to third methods described above are methods for selectively switching the method of moving to the position where the search starts at the time of autofocusing according to the operation history of the focus lens 11, As a separately selectable function, the control method shown in FIG. 15 may be executed. This control method performs an autofocus operation without referring to the operation history of the focus lens 11 and a series of accompanying operations such as still image capturing, and the position of the focus lens 11 is changed after a predetermined time has elapsed. By moving (step S131) to a predetermined reference position (for example, optical infinity side reference position) recorded as an adjustment value, the position at which the search operation is started the next time autofocus is executed The focus lens 11 is moved directly based on the logical value of the counter 28 (step S132) so that the autofocus search operation can be started (step S133), and the time spent for autofocus control is reduced. This is a control method that can be shortened.

  When the camera is activated and the lens position initialization operation is performed, and this control method is selected, when the autofocus command is executed, the search operation is immediately started based on the grasped value of the counter 28. The focus lens 11 is directly moved to start a search operation, and autofocus is executed. After the autofocus is completed, if still image capturing or focus lock extension operation is not performed within a predetermined time, the lens position initialization operation is automatically performed, and the position of the focus lens 11 is determined based on the optical infinity side reference. Move to position.

  Next, a determination method for selecting the start point movement operation will be described. Note that a cumulative AF command counter is provided on the firmware of the microcomputer unit 24. The cumulative AF command counter is incremented each time an AF command is issued, and the start point moving operation or initialization is performed by the first start point moving method. It is assumed that the cumulative AF command counter is cleared to zero.

  In FIG. 16, when an autofocus command is issued and the microcomputer unit 24 receives the autofocus command (step S <b> 141), the start point for starting the search for autofocus is started when the microcomputer unit 24 starts the start point moving operation. The moving operation is selected from the first to third methods based on the selection procedure (step S142) described later, and the mode is selected and set based on the selected starting point moving operation method (step S143). By executing the start point moving operation (step S144), the focus lens 11 is moved to the start point and the movement is completed (step S145), and the autofocus search is started (step S146).

  FIG. 17 specifically shows the selection procedure (step S142) in FIG. 16 when selecting the starting point movement operation. When the selection is started, the microcomputer unit 24 determines whether or not the previously executed command is a lens position initialization command (step S151), and the operation performed immediately before is a lens position initialization command. If it is determined, the third start point moving method is selected as the search start point moving operation (step S152). If the previously executed command is other than the lens position initialization command, it is determined whether or not the predetermined number of times has been reached by referring to the value of the cumulative AF command counter (step S153). Selects the second starting point moving method (step S154), and if the number of times is equal to or greater than the predetermined number of times, selects the first starting point moving method (step S155).

  In the present embodiment, the firmware stored in the microcomputer unit 24 and the ROM 25 in the imaging apparatus is provided with a lens operation history reference unit and a start point moving operation determination unit, and the control is completed within the camera module. Although an example is shown, the present invention is not limited to this. For example, the number of executions of a command related to lens movement, such as an autofocus command, is used as a reference means for the lens operation history, and the determination is based on the data. The means may be configured to be stored and controlled in a host system in which both camera modules are mounted, for example, software on a portable terminal.

  In the autofocus camera 10, the entire lens system is the focus lens 11. However, the present invention is not limited to this, and a plurality of lens groups are divided into a fixed lens and a moving lens, and Of these, the focus lens may be moved to adjust the focus.

  As described above, the drive device according to the present invention and the image pickup apparatus including the drive device can perform positioning control without losing positioning accuracy without requiring a means such as a position detection sensor, and can reduce the number of parts. It can be reduced more than before and is useful for mounting on small electronic devices.

Block diagram of an autofocus camera in one embodiment of the present invention (1) A diagram showing an example of a voltage waveform supplied to the piezoelectric element when the focus lens is moved in the extending direction of the focus lens in one embodiment of the present invention. b) A diagram showing an example of a voltage waveform supplied to the piezoelectric element when the focus lens is moved in the retraction direction of the focus lens. The flowchart which shows the process of the initialization mode at the time of starting in one embodiment of this invention The flowchart which shows the adjustment procedure from an infinity side machine end part to an optical infinity side reference position in one embodiment of this invention. The flowchart which shows the adjustment procedure from a macro side machine edge part to an optical infinity side reference position in one embodiment of this invention. The flowchart which shows the adjustment procedure from the infinity side machine end part to the optical macro side reference position in one embodiment of this invention The flowchart which shows the adjustment procedure from a macro side machine end part to an optical macro side reference position in one embodiment of the present invention. The figure which shows a mode that an infinite autocollimator is image | photographed as an adjustment chart in one embodiment of this invention. The figure which shows a mode that the chart for macro adjustment is image | photographed in one embodiment of this invention. Explanatory drawing of moving speed ratio in one embodiment of this invention Flowchart showing processing when moving the focus lens in the movement control mode in one embodiment of the present invention The figure explaining the 1st start point movement method among the individual operation | movement of the start point movement operation | movement of an autofocus search in one embodiment of this invention. The figure explaining the 2nd start point movement method among the individual operation | movement of the start point movement operation | movement of an autofocus search in one embodiment of this invention. The figure explaining the 3rd start point movement method among the individual operations of the start point movement operation of an autofocus search in one embodiment of the present invention. The figure explaining the different method different from the 1st-3rd starting point movement method in one embodiment of this invention. The flowchart which shows the procedure of starting point movement operation | movement selection in one embodiment of this invention. The flowchart which shows the selection procedure in one embodiment of this invention. Block diagram of an autofocus camera equipped with a drive unit that realizes a conventional autofocus function

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Autofocus camera 10a, 10b Arrow which shows moving direction 11 Focus lens 12 Lens barrel 12a Shielding plate 13 Piezoelectric actuator 13a Piezoelectric element 13b Drive shaft 13c Moving part 14 Convex part 15 Machine end part 15a Infinity side machine end part 15b Macro Side machine end 16 EEPROM
17 Image sensor 18 Drive circuit 20 Image processing IC
21 I / O circuit 22 Image sensor control circuit 23 Image signal processing unit 24 Microcomputer unit 25 ROM
26 RAM
27 Memory Controller 28 Counter 30 Drive Device

Claims (5)

A piezoelectric element, a driving unit driven by the piezoelectric element, a moving unit that is engaged with the driving unit by a frictional force between the driving unit and moves according to an expansion / contraction operation of the piezoelectric element; A mechanical end for mechanically limiting a start point and an end point of a moving range of the moving unit; supply control means for controlling supply of electric power to the piezoelectric element; power supply time for the piezoelectric element; and the moving unit A counter that stores a counter value according to position information of the moving unit based on the moving direction of
The supply control means has, as operation modes, a movement control mode for performing the control to move the moving unit and an initialization mode performed before the movement control mode, and in the initialization mode, the start point And moving the moving unit to any one of the end points and performing a machine end moving operation for setting the counter to a predetermined value, then reversing the moving direction and moving the moving unit for a predetermined power supply time. The position where the part is moved is used as the origin of the moving part in the movement control mode, and positioning control of the moving part is performed based on the counter value of the counter in the movement control mode. A drive device characterized by the above. The driving apparatus according to claim 1, a lens supported by the moving unit, and an image sensor that images a subject, wherein the movement control mode automatically focuses the image of the subject on the image sensor. Including autofocus function
The supply control means includes a start point moving operation mode in which the position of the lens is moved to a position of a start point at which autofocus control is started based on the position of the origin determined in the initialization mode, and from the start point And an in-focus search operation mode in which an in-focus search operation for starting an in-focus search is performed as an operation mode, and the search start point position at which the search for the in-focus point is started in the start point movement operation mode. A plurality of means for moving the position of the lens by mutually different methods, and when performing the autofocus control, a start point moving operation mode by the plurality of means according to an operation performed before the autofocus control. An image pickup apparatus that selectively switches the operation in the above. The supply control means includes a memory for storing data of a power supply time unique to the driving device for moving the position of the lens from any position of the start point and the end point to a predetermined position.
After performing the machine end moving operation, the moving direction is reversed, and the position where the lens position is moved during the power supply time specific to the driving device is defined as the origin, and the position of the lens is determined based on the counter value at this time. First start point moving means for moving the search point to the search start point;
After performing the machine end moving operation based on the current counter value, the moving direction is reversed, and the position where the lens position is moved during the power supply time specific to the driving device is the origin, and the counter value at this time Second starting point moving means for moving the position of the lens to the search starting point based on
A plurality of at least two start point moving means out of third start point moving means for directly moving the position of the lens to the search start point based on the counter value of the origin obtained in the initialization mode; The imaging apparatus according to claim 2, wherein the imaging apparatus is provided. In the autofocus control, the supply control means moves the lens in a direction opposite to the direction in which the in-focus search operation is performed by a predetermined value from the position of the origin indicated by the counter value. The imaging apparatus according to claim 2, wherein the imaging apparatus is a search start point. The supply control means performs positioning control so that the lens always moves to the position of the origin after completing a predetermined imaging operation including still image imaging after performing focus adjustment during the autofocus control. The imaging device according to any one of claims 2 to 4, wherein the imaging device is any one of the above.