JP2013050499A - Optical image shake correction mechanism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical image shake correction mechanism enabling accurate image shake correction control with small position detection error by securing high linearity.SOLUTION: The optical image shake correction mechanism includes a correction lens group, lens position detection means 10, a permanent magnet 8, angle shake detection means, lens moving means, image shake correction control means, and a yoke. The yoke is composed of two yokes of a first yoke 7 and a second yoke 5. The second yoke 5 has a substantially square hole with one side of 1 to 1.8 times of the position detection range of the lens position detection means 10. The center of the hole is at a position facing the center of the lens position detection means 10 in a state where the correction lens group is not moved by the lens moving means and is at a steady state position.

Description

The present invention relates to an image blur correction mechanism mounted on a single-lens reflex camera or the like, and more particularly to an optical image blur correction mechanism that optically corrects an image blur by shifting a lens or the like.

Some recent imaging apparatuses, particularly single-lens reflex cameras, compact cameras, and video cameras, are equipped with a mechanism for correcting image blur during shooting.

Image blur in shooting occurs, for example, when an image on the imaging plane moves due to camera vibration caused by camera shake of the photographer.

As a correction mechanism for correcting the image blur as described above, there is an optical image blur correction mechanism that performs image blur correction by driving some lens groups of the lens optical system on the optical device side.

In general, an optical image shake correction mechanism is a lens group (hereinafter referred to as a correction lens group) capable of shifting an imaging position by moving in a direction orthogonal to the optical axis in order to correct image shake, and a camera shake. An angular velocity sensor that detects the angular velocity and a Hall element that detects the current position of the correction lens group are provided.

That is, in the optical image blur correction mechanism, the current position of the correction lens group is detected from the output of the Hall element, and the image blur amount is calculated from the output of the angular velocity sensor. The CPU that controls the lens drives and controls the correction lens group in a direction to cancel the image blur based on the current position of the correction lens group detected by the Hall element and the image blur amount calculated from the output of the angular velocity sensor. This adjusts the imaging position.

As described above, in the optical image blur correction mechanism, the Hall element is used to detect the current position of the correction lens group.

The Hall element detects the magnetic flux density and outputs an analog signal proportional to the magnitude. Therefore, the Hall element outputs an analog signal proportional to the amount of movement by designing the arrangement so that the magnetic flux density proportional to the position of the measurement object is applied to the Hall element position, and the control device for the correction lens group The position of the measurement object can be detected from the change in the hall output.

For example, when the moving range of the measurement object is 1 mm, the Hall element as described above can detect the movement distance of the measurement object in units of several μm.

However, the range in which position detection with high accuracy by the Hall element is possible is usually about 1 mm (± 0.5 mm), and the range is narrow.

For this reason, in a lens such as a macro lens that has a large movement amount of the correction lens group, there is a problem that sufficient linearity cannot be ensured by position detection using a Hall element.

Conventionally, in order to cope with the above problems, as a technique for ensuring high linearity, for example, there are those described in the following patent documents.

JP 2005-275379 A

The cited document 1 has two sets of magnets that generate a magnetic field detected by the Hall element in order to detect the horizontal position of the correction lens group, and the two magnets are arranged apart from each other. Similarly, in order to detect the vertical position of the correction lens group, the correction lens unit has a pair of magnets that generate a magnetic field detected by the Hall element, and the two magnets are arranged apart from each other. Thus, a technique for ensuring a highly accurate position detectable range is described.

However, in the invention described in the cited document 1, what is considered for improving linearity is only about the distance between two magnets that are arranged apart from each other, and other The positional relationship, configuration, distance, and position detection accuracy of the components have not been studied.

According to a first aspect of the present invention, there is provided a correction lens group movable in a direction substantially orthogonal to an optical axis, a lens position detection device for detecting a position of the correction lens group, and the lens position detection device determining the position of the correction lens group. Detected by a permanent magnet that generates a magnetic field for detection, an angular shake detection device that detects angular shake, a lens driving device that moves the correction lens group using the magnetic force of the permanent magnet, and the angular shake detection device A difference between the target position of the correction lens group calculated from the shake signal and the current position of the correction lens group detected by the lens position detection device to the target position of the correction lens group; An image blur correction control device for controlling the lens driving device by PID control and first and second yokes constituting a magnetic circuit, wherein the second yoke detects the lens position. A hole having a substantially square shape whose length is 1 to 1.8 times the position detection range of the device, and the center of the hole is not moved by the lens driving device. The optical image blur correction mechanism is characterized by being a position facing the center of the lens position detection device in a state where the lens is in a constant position.

Provided is an optical image blur correction mechanism capable of ensuring high linearity, having a small position detection error, and capable of highly accurate image blur correction control.

The block diagram which shows the camera system in the Example which concerns on this invention. 1 is an exploded perspective view of an image shake correction mechanism of an embodiment according to the present invention. Schematic diagram showing the relationship between thrust acting during image blur correction and the distance between two permanent magnets The perspective view of the 2nd yoke member 5 of the image blur correction mechanism of the Example which concerns on this invention. 1 is a perspective view of an image shake correction mechanism according to an embodiment of the present invention when viewed from the image plane side. The schematic diagram which compares the example of the case where a hole is provided in the 2nd yoke member 5, and the change of the magnetic flux density of the example when a hole is not provided. The schematic diagram which compares the example of the case where a hole is provided in the 2nd yoke member 5, and the position detection error of the example when a hole is not provided. An example in which the hole provided in the second yoke member 5 is an approximately square with one side of 6.5 mm, an example in which the one side is an approximately square with 4.5 mm, and an approximately square with one side of 3 mm The schematic diagram which compares the change of the magnetic flux density of the example in a case. An example in which the hole provided in the second yoke member 5 is an approximately square with one side of 6.5 mm, an example in which the one side is an approximately square with 4.5 mm, and an approximately square with one side of 3 mm The schematic diagram which compares the magnitude | size of the position detection error of the example in a case. Comparison of changes in magnetic flux density between the example in which the second yoke member 5 is provided with a substantially square hole having a side of 4.5 mm and the example in which a substantially square recess having a side of 4.5 mm is provided. Schematic diagram to do. The size of the position detection error in the example in which the second yoke member 5 is provided with a substantially square hole having a side of 4.5 mm and the example in which a substantially square recess having a side of 4.5 mm is provided. The schematic diagram which compares.

First, the configuration of an optical device and an imaging device on which an image blur correction mechanism is mounted will be described. FIG. 1 is a block diagram illustrating a configuration of a camera system (an image pickup apparatus and an optical apparatus) equipped with an image blur correction mechanism.

In FIG. 1, reference numeral 200 denotes an imaging device, and 100 denotes an optical device.

First, components of the optical device 100 will be described.

Reference numeral 101 denotes an optical system, 103 denotes an aperture unit, 105 denotes an aperture drive circuit that drives the aperture unit, 117 denotes a focus lens group, and 119 denotes a focus lens drive device that drives the focus lens group 117.

Further, 121 is a correction lens group, 123 is an angular shake detection device, 125 is a lens position detection device, 127 is a lens driving device, and 129 is an image shake correction CPU.

Two angular shake detection devices 123 are provided in the optical device 100 and detect the rotation of the optical device 100 in the pitch direction and the yaw direction. As described above, information detected from these angular shake detection devices 123 is input to the image shake correction CPU 129. As the angular shake detection device 123, for example, a gyro sensor or the like is used.

The lens driving device 127 is an actuator for moving the correction lens group 121. As the lens driving device 127, a voice coil motor (VCM) is used in this embodiment. Such a VCM is composed of a pair of coils and a permanent magnet. Details of the coil and the permanent magnet in this embodiment will be described later.

In addition, the lens position detection device 125 detects the current position of the correction lens group 121 from the magnetic flux density of the permanent magnet that constitutes the lens driving device 127. As described above, the information output from the lens position detection device 125 is input to the image blur correction CPU 129. In the present embodiment, three Hall elements 10 described later are used as the lens position detection device 125. That is, the lens position detection device 125 in the present embodiment is composed of three Hall elements.

Further, the image shake correction CPU 129 acquires information of the angle shake detection device 123, calculates a target position that is information on a direction and a distance in which the correction lens group 121 is moved using the information, and outputs the target position from the lens position detection device 125. Position information of the correction lens group 121 is acquired, and PID control is performed using the information.

Further, 131 is a lock mechanism, 133 is a lock drive circuit, 135 is a lock detection device, and 137 is an image blur correction switch.

The lock mechanism 131 mechanically captures the correction lens group 121, and the lock drive circuit 133 drives the lock mechanism 131. The lock detection device 135 detects whether or not the lock mechanism normally captures the correction lens group 121. The image blur correction switch 137 is an image blur correction switch that can be operated from the outside, and whether or not to perform image blur correction and which control to use among a plurality of image blur correction control methods is determined by a photographer's operation. Can be switched.

The image shake correction mechanism of the present invention includes a correction lens group 121, an angle shake detection device 123, a lens position detection device 125, a lens drive device 127, an image shake correction CPU 129, a lock mechanism 131, a lock drive circuit 133, a lock detection device 135, An image blur correction switch 137 is provided. A detailed configuration of the image blur correction mechanism of the present invention will be described later.

Further, 139 is a lens CPU, 141 is a lens contact, and 143 is a lens mount.

The lens CPU 139 controls the operation of various circuits in the optical device 100, and when the imaging device 200 is mounted, the lens contact 141 and a camera contact 245 described later are connected to communicate with the camera CPU 201 described later. . Reference numeral 143 denotes a lens mount, which is coupled to a camera mount 243 described later to mechanically connect the imaging device 200 and the optical device 100.

Next, components of the imaging device 200 will be described.

Reference numeral 201 denotes a camera CPU. The camera CPU 201 controls the operation of various circuits in the imaging apparatus 200, and when the optical apparatus 100 is mounted, the lens contact 141 and the camera contact 245 are connected to communicate with the lens CPU 139. A power switch 203 that can be operated from the outside is a switch that activates the camera CPU 201 to enable power supply to each actuator and sensor in the system and operation of the system.

205 is a two-stroke release switch that can be operated from the outside, 207 is a mode dial that switches various settings of the camera body, 209 is a power supply for the operation of the entire camera system, 211 is various settings of the camera body and captured images. A display device having an LCD or the like for displaying.

A focus detection circuit 221 detects a focus from a signal output from the autofocus sensor 219, a mirror unit 225 guides a light beam incident from the optical device 100 to the finder optical system 237, and a drive unit 227 drives the mirror unit. The mirror driving device 229 is a mirror driving circuit for controlling the mirror driving device. Reference numeral 231 denotes a shutter drive circuit that drives the shutter unit 233. A penta roof prism 235 guides the light beam guided by the mirror unit 225 to the finder optical system 237. Reference numeral 239 denotes a photometric sensor. The photometric sensor 239 has a plurality of photometric areas for performing photometry, and outputs photometric data corresponding to the illuminance of the subject light guided to each divided photometric area. The photometry calculation circuit 241 is a photometry calculation circuit that processes photometry data output from the photometry sensor 239. Reference numeral 243 denotes a camera mount. The camera mount 243 is coupled to the lens mount 143 to mechanically connect the imaging device 200 and the optical device 100. Reference numeral 247 denotes an imaging surface on which a film in a film camera or a solid-state imaging device in a digital camera is located.

Next, the image blur correction mechanism in the optical apparatus 100 of the present embodiment will be described in detail.

FIG. 2 is an exploded perspective view of the image blur correction mechanism according to the embodiment of the present invention.

First, each member of the image blur correction mechanism will be described with reference to FIG. Reference numeral 1 denotes a base member, 2 denotes a lens holding member for holding the correction lens group 121, 3 denotes a recess for limiting a range in which a support member 6 described later can move, and attachment of a first flexible printed circuit board 4 described later It is a guide member with the seating surface for.

4 is a first flexible printed circuit board to which a coil 9 and a hall element 10 to be described later are attached, 5 is a second yoke member formed of a steel plate with high magnetic permeability, 6 is a spherical shape made of metal or hard resin, It is a support member that sandwiches and supports the lens holding member 2 from the image plane side and the subject side.

7 is a first yoke member formed of a steel plate having a high magnetic permeability like the second yoke member 5, 8 is six permanent magnets fixed at positions separated from each other, and 9 is formed by winding a conductive wire. Coil. A hall element 10 (not shown) is attached to the surface of the first flexible printed board 4 opposite to the surface to which the coil 9 is attached. The Hall element 10 detects the magnetic flux density of the permanent magnet 8.

11 is a lock member having a lock shaft extending from the lens holding member 2 and a groove for capturing the swing shaft, and 12 is fixed to the base member 1, and is used to limit the movement of the lock member in the optical axis method. It is a cover member.

Reference numeral 13 denotes a motor base member for fixing an actuator 14 and a photo interrupter 15 which will be described later, reference numeral 14 denotes an actuator that normally uses a stepping motor or a DC motor, and an actuator that drives the lock member 11; The photointerrupter 16 is a second flexible printed circuit board for electrically connecting the lens barrel to the actuator 14 and the photointerrupter 15.

Reference numerals 17 to 21 denote fastening members for fastening the above-described members.

Next, the first yoke member 7, the second yoke member 5, the permanent magnet 8, and the coil 9 that generates thrust by the magnetic field generated by the permanent magnet 8, which constitute the magnetic circuit detected by the Hall element 10, will be described. To do.

The permanent magnet 8 generates a magnetic field for detecting the position of the Hall element 10 and coil thrust. As described above, the image shake correction mechanism of this embodiment has six permanent magnets. Two such permanent magnets form a set, and the two permanent magnets are arranged with a certain distance from each other.

The coil 9 and the Hall element 10 are fixed to the first flexible printed board 4 and are electrically connected.

The first yoke member 7 and the second yoke member 5 prevent leakage of magnetic flux to the outside and constitute a magnetic circuit. Moreover, the magnetic flux linked to the coil is increased.

Next, the arrangement interval of the two permanent magnets and the position detection range of the Hall element 10 will be described.

As disclosed in Patent Document 1, the wider the interval between the two permanent magnets, the wider the position detection range. However, if the distance between the two permanent magnets is too large, the size of the image blur correction mechanism is increased, which is not preferable.

In this embodiment, the movement amount of the lens holding member 2, that is, the position detection range of the Hall element 10 is set to 3.2 mm. In response to this, in this embodiment, the interval between the two permanent magnets is set to 2 mm, which is equal to or more than half the amount of movement. This is because when the distance between the permanent magnets 8 is equal to or less than the half value of the movement amount, the thrust is reduced when the movement amount becomes maximum.

A phenomenon in which the thrust decreases because the distance between the two permanent magnets is narrow will be described below with reference to FIG.

FIG. 3 is a schematic diagram showing the relationship between the thrust acting during image blur correction and the distance between two permanent magnets.

FIG. 3B shows a case where the distance between two permanent magnets is sufficiently 1.6 mm or more, and FIG. 3B shows a state where the lens holding member 2 has been moved greatly. As can be seen from (B '), the thrust works normally if the distance between the two permanent magnets is separated.

On the other hand, (A) shows the case where the distance between the two permanent magnets is 1.6 mm or less, and (A ′) shows the case where the lens holding member 2 is largely moved. As can be seen from (A ′), when the lens holding member 2 is moved largely, the coil 9 receives a magnetic field on the opposite side of the shaded portion that is a part of the permanent magnet 8 b, thereby generating a reverse thrust. Thereby, since thrust will fall, it is not preferable even if the space | interval of two magnets is too narrow.

However, this is not the case depending on the size of the coil. For example, when the coil 9 is small, even if the distance between the permanent magnets 8a and 8b is 1.6 mm or more, the hatched line in which the coil 9 is a part of the permanent magnet 8b when the lens holding member 2 is largely moved. It is conceivable that the magnetic field on the opposite side of the portion is not received and the thrust on the opposite side is not generated.

Next, in this embodiment, the holes provided in the second yoke member 5 and their positions will be described.

FIG. 4 is a perspective view of the second yoke member 5 of the image shake correcting mechanism according to the embodiment of the present invention. FIG. 5 is a perspective view of the image shake correcting mechanism according to the embodiment of the present invention as viewed from the image plane side. It is.

As shown in FIGS. 4 and 5, the second yoke member 5 is provided with three holes.

Such holes are provided in order to reduce the influence of the magnetic field that the Hall element 10 receives from the second yoke member 5. Therefore, as shown in FIG. 5, one such hole is provided at a position facing the hall element 10 on the second yoke member 5.

Further, the center of the hole is set to a position facing the center of the Hall element 10 in the optical axis direction in a state where the lens holding member 2 holding the correction lens group is in a normal position where it is not moved by the VCM. Is done.

Next, the necessity of such holes will be described in detail.

First, the change in magnetic flux density will be described with reference to FIG. FIG. 6 is a schematic diagram for comparing changes in magnetic flux density between an example in which a hole is provided in the second yoke member 5 and an example in which no hole is provided. In FIG. 6, the vertical axis represents the magnetic flux density, and the horizontal axis represents the stroke.

Here, since the output of the Hall element is proportional to the magnetic flux density, the value of the magnetic flux density may be considered as the output of the Hall element, that is, the detection position.

As shown in FIG. 6, in the case where the second yoke member 5 is not provided with a hole, the magnetic flux density changes more rapidly and the linearity is lower than in the example where the hole is provided.

Next, the position detection error will be described with reference to FIG. FIG. 7 is a schematic diagram comparing the position detection error between the example in which a hole is provided in the second yoke member 5 and the example in which no hole is provided. In FIG. 7, the vertical axis represents the position detection error, and the horizontal axis represents the stroke. Each unit is μm on the vertical axis and mm on the horizontal axis.

As shown in FIG. 7, the position detection error is smaller when the hole is provided than when the hole is not provided.

Therefore, in this embodiment, by reducing the influence of the magnetic field received by the Hall element 10 from the second yoke member 5, a high linearity is ensured, and a hole is formed in the second yoke member 5 in order to reduce the position detection error. Is provided.

Further, in order to reduce the influence of the second yoke member 5, it is conceivable to dispose the second yoke member 5 and the Hall element separately. In that case, the permanent magnet 8 and the second yoke member 5 are arranged. This causes an increase in the thrust of the VCM and an increase in the size of the shake correction mechanism due to an increase in the gap, which is not desirable.

Next, the size and shape of the hole will be described.

In the present embodiment, the hole is defined as a substantially square having a length of 1 to 1.8 times the position detection range of the Hall element 10 as one side. As described above, in this embodiment, the position detection range of the Hall element 10 is 3.2 mm. Therefore, in this embodiment, the length of one side of the hole is desirably 3.2 mm to 5.76 mm.

This is because the position detection error increases when the size of the hole is too small or too large. This will be described next with reference to FIGS.

FIG. 8 shows an example in which the holes provided in the second yoke member 5 are substantially square with one side of 6.5 mm, an example in which one side is substantially square with one side of 4.5 mm, and one side with 3 mm. It is a schematic diagram which compares the change of the magnetic flux density of the example in the case of a substantially square. In FIG. 8, the vertical axis represents the magnetic flux density, and the horizontal axis represents the stroke.

As shown in FIG. 8, the change in magnetic flux density is an example in the case of a substantially square with one side of 6.5 mm, an example in the case of a substantially square with one side of 4.5 mm, and an example in the case of a substantially square with one side of 3 mm. In order, the linearity is high.

That is, the larger the hole provided in the second yoke member 5, the higher the linearity.

Next, FIG. 9 shows an example in which the holes provided in the second yoke member 5 are substantially square with one side of 6.5 mm, an example in which one side is substantially square with 4.5 mm, and one side. It is a schematic diagram which compares the magnitude | size of the position detection error of the example in the case of a substantially square of 3 mm. In FIG. 9, the vertical axis represents the position detection error, and the horizontal axis represents the stroke. Each unit is μm on the vertical axis and mm on the horizontal axis.

As shown in FIG. 9, the position detection error is an example in the case of a substantially square with one side of 6.5 mm, in the case of an example of a substantially square with one side of 3 mm, and in the case of an example of a substantially square with one side of 4.5 mm. Larger in order.

That is, if the hole provided in the second yoke member 5 is too large or too small, the position detection error becomes large.

Therefore, in this embodiment, the upper limit of the length of one side of the hole provided in the second yoke member 5 is 1.8 times the position detection range of the Hall element 10, and the lower limit is 1 of the position detection range of the Hall element 10. By setting it to be doubled, it is possible to achieve both high linearity and small position detection error.

Further, in this embodiment, by reducing the influence of the second yoke member 5 on the Hall element 10, the linearity is increased, and a hole is formed in the second yoke member 5 in order to reduce the position detection error. Provided. However, in order to reduce the influence of the second yoke member 5, it is also conceivable that the second yoke member 5 is provided with a recess instead of a hole.

In the present embodiment, the reason why the second yoke member 5 is provided with a hole instead of a recess will be described next.

FIG. 10 shows an example in which the second yoke member 5 is provided with a substantially square hole having a side of 4.5 mm, and an example in which a substantially square recess having a side of 4.5 mm is provided. It is a schematic diagram which compares the change of. In FIG. 10, the vertical axis represents the magnetic flux density, and the horizontal axis represents the stroke.

As shown in FIG. 10, the change in the magnetic flux density is more in the case where a substantially square hole having a side of 4.5 mm is provided in the example where a substantially square hole having a side of 4.5 mm is provided. Compared to it, it is moderate and linearity is high.

That is, if it is the same magnitude | size, the direction which provided the hole rather than providing a dent will become high.

Next, FIG. 11 shows an example in which the second yoke member 5 is provided with a substantially square hole having a side of 4.5 mm, and an example in which a substantially square recess having a side of 4.5 mm is provided. It is a schematic diagram which compares the magnitude | size of a position detection error. In FIG. 11, the vertical axis is a position detection error, and the horizontal axis is a stroke. Each unit is μm on the vertical axis and mm on the horizontal axis.

As shown in FIG. 11, the position detection error in the case where a substantially square hole having a side of 4.5 mm is provided is larger than that in the case where a substantially square recess having a side of 4.5 mm is provided. Small.

That is, if the holes have the same size, the position detection error is smaller and the position detection can be performed with higher accuracy when the hole is provided than when the recess is provided.

Based on the above results, in this embodiment, the second yoke member 5 is provided with a hole instead of a recess.

As described above, in this embodiment, in the image blur correction mechanism having three actuators, the yoke constituting the magnetic circuit has a length that is 1 to 1.8 times the position detection range of the Hall element 10 as one side. By providing a substantially square hole, it is possible to provide an optical image blur correction mechanism that has high linearity, small position detection error, and high accuracy image blur correction control.

DESCRIPTION OF SYMBOLS 1 Base member 2 Lens holding member 3 Guide member 4 1st flexible printed circuit board 5 2nd yoke member 6 Support member 7 1st yoke member 8 Permanent magnet 9 Coil 10 Hall element 11 Lock member 12 Cover member 13 Motor base member 14 Actuator 15 Photointerrupter 16 Second flexible printed circuit board 17 Fastening member 18 Fastening member 19 Fastening member 20 Fastening member 21 Fastening member 100 Optical device 200 Imaging device

Claims (1)

A correction lens group movable in a direction substantially orthogonal to the optical axis;
A lens position detection device for detecting the position of the correction lens group;
A permanent magnet for generating a magnetic field for the lens position detection device to detect the position of the correction lens group;
An angular shake detection device for detecting angular shake;
A lens driving device that moves the correction lens group using the magnetic force of the permanent magnet;
From the target position of the correction lens group calculated from the shake signal detected by the angular shake detection device and the current position of the correction lens group detected by the lens position detection device, the target position of the correction lens group An image blur correction control device that calculates the difference up to and controls the lens driving device by PID control, and first and second yokes that constitute a magnetic circuit,
The second yoke has a substantially square hole with one side that is 1 to 1.8 times the position detection range of the lens position detection device;
The center of the hole is a position facing the center of the lens position detecting device in a state where the correction lens group is in a normal position where the correction lens group is not moved by the lens moving device. Formula image shake correction mechanism.

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