JPH05107440A - Optical apparatus - Google Patents

Abstract

PURPOSE:To provide an optical apparatus that is suitable for miniaturizing the lens unit as a lens driving device such as a video camera, and by which fine lens positioning can be enabled. CONSTITUTION:The one end of a laminated piezoelectric element 3 is fixed to a projection 2a provided on the outer circumferential surface of a lens-retaining frame 2 in which a focusing lens 10 is contained, and to the other end 7 thereof, the one end of a bimorph piezoelectric element 6 is fixed. On the opposite side of the projection 2, a similar bimorph piezoelectric element 4 is fixed. The outer circumferential surface of a lens-retaining-frame supporting member 9 and the inner wall surface of a lens- barrel 1 are machined so as to be easily slidable to each other and are in contact with each other. When voltage is turned ON, the bimorph piezoelectric elements 4, 6 bend and the clamp between the engaging member 8 at the end thereof and the inside surface of the lens-barrel 1 is disconnected; on the other hand, when voltage is turned OFF, they are returned to their initial shape and are clamped by the lens- barrel 1. The laminated piezo-electric element 3 extends when voltage is turned ON; while it returns to its initial length when it is turned OFF. Thus, fine positioning is carried out by alternately clamping the bimorph piezoelectric elements 4, 6, and by combining the extension and recovery of the laminated piezoelectric element 3 with a good timing for moving the lens 10 backward and forward.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical device such as a video camera.

[0002]

2. Description of the Related Art As a zoom lens for photographing generally used in an optical device such as a video camera, a first lens group (focus lens) is used for focus adjustment.
And the second group is a variator lens for zooming,
A front-lens focus type zoom lens, such as a compensator lens for keeping the image forming position constant even when the third lens unit performs zooming, and a relay lens for the fourth lens member, is used. Be done. On the other hand, a so-called inner focus or rear focus type zoom lens that performs focusing using a lens group behind the variator lens is known and is also used in products. Various types of such zoom lens are known, but here, the configuration of a zoom lens unit using a zoom lens using the rearmost lens group for focusing is shown in FIG.
Shown in.

In the figure, 101 is a fixed front lens group, 102 is a variator lens group, 103 is a fixed lens group, and 104 is a focusing (compensator) lens group. 105 is a guide rod for preventing rotation,
106 is a variator feed rod, 107 is a fixed lens barrel, and 10
Reference numeral 8 is an aperture unit (inserted here at right angles to the paper surface), reference numeral 109 is a step motor, which is a focus motor, and reference numeral 110 is an output shaft of the step motor, which is provided with an external thread for moving the lens. 111
Is a female screw portion that meshes with this male screw, and is integral with the moving frame 112 of the lens 104. Reference numerals 113 and 114 are guide rods for the moving frame of the lens 104, 115 is a rear plate for positioning and pressing the guide rods, and 116 is a relay holder. 117 is a zoom motor, 118 is a reduction unit 119 and 120 of the zoom motor, and 1 is an interlocking gear.
The gear 20 is fixed to the zoom feed rod 106.

With the above configuration, the step motor 10
When 9 is driven, the focus lens 104 moves in the optical axis direction by screw feeding. Also, the zoom motor 117
When is driven, the gears 119 and 120 are interlocked and the shaft 106 rotates, so that the variator 102 moves in the optical axis direction.

FIG. 9 shows the positional relationship between the variator lens and the focusing lens in such a lens according to some distances. Here, as an example,
The in-focus positional relationships for infinite, 2 m, 1 m 80 cm, and 0 cm subjects are shown. In the case of inner focus,
Thus, the positional relationship between the variator and the focus lens differs depending on the subject distance.

Therefore, if the zoom motor 117 is simply driven under the structure shown in FIG. 8, defocusing will occur.

Since the inner focus lens has the above-mentioned characteristics, the inner focus lens is practically used in addition to the above-mentioned advantage of "excellent close-up photographing ability" and "small number of lens components". The conversion was delayed.

However, in recent years, a technique for optimally controlling the lens positional relationship as shown in FIG. 10 in accordance with the subject distance is being developed and commercialized.

For example, JP-A-1-280709, JP-A-1-321416, and JP-A-2-144509 present a method of tracing a locus of the positional relationship between both lenses according to such a distance. In Japanese Patent Laid-Open No. 1-280709, FIGS.
The positional relationship between the variator and the compensator (focus lens) is maintained by the method shown in FIG.

FIG. 10 shows a block diagram. 101-
Reference numeral 104 denotes the same lens group as that shown in FIG. The position of the variator lens group 102 is the zoom encoder 1
The position is detected by 21. Here, as the type of encoder, for example, a volume encoder configured such that a brush integrally attached to a variator moving ring slides on a substrate on which a resistance pattern is printed can be considered. A diaphragm encoder 122 detects the diaphragm value, and uses, for example, a Hall element output provided in the diaphragm meter 137. Reference numeral 123 is an image pickup device such as a CCD, and 124 is a camera processing circuit, and the Y signal is taken into the AF circuit 125. The AF circuit determines whether it is in-focus or out-of-focus, and when it is out-of-focus, it is determined whether it is mae pin or at-pin, and the degree of out-of-focus. These results are CPU
It is captured in 126.

A power-on reset circuit 127 performs various reset operations when the power is turned on. A zoom operation circuit 128 notifies the CPU 126 of the contents when the operator operates the zoom switch 129. 130-1
A memory 32 stores the trajectory data shown in FIG. 11 and includes direction data 130, velocity data 131, and boundary data 132. 133 is a zoom motor driver, 134 is a step motor driver, 135 is a step motor, 136 is a zoom motor, the number of input pulses of the step motor 135 is continuously counted in the CPU 126, and is used as an encoder of the absolute position of the focus lens 104. There is. In such a configuration, the variator position and the focus lens position are determined by the zoom encoder 121 and the step motor input pulse number, respectively, so that one point on the map shown in FIG. 11 is determined. On the other hand, the map shown in FIG. 11 is divided by the boundary data 132 into tanzaque small areas I, II, III ... As shown in FIG. Here, the shaded area is an area where the lens is prohibited from being positioned. When one point on the map is determined in this way, it is possible to determine the area to which the one point belongs in the small area.

For the speed data and direction data, the rotation speed and direction of the step motor obtained from the locus passing through the center of each area are stored in each area. For example, in the example of FIG. 11, the horizontal axis (variator position) is divided into 10 zones. Assuming that the zoom motor speed is set to move T-W in 10 seconds, the transit time for one zone in the zoom direction is 1 sec.
Is. 12 is an enlarged view of block III in FIG.
Then, there is a locus 138 in the center of this block, 139 in the lower left, and 140 in the upper right, and the inclinations are slightly different. Here, the center locus can be traced with almost no error if it moves at a speed of X mm / 1 sec.

The speed thus obtained will be referred to as "area representative speed". The speed memory stores as many values as the number of small areas in accordance with the area. If this speed is shown as 141, it will be 14 depending on the AF detection result.
The step motor speed is set by finely adjusting the typical speed like 2,143. In the direction data, the code data is stored because the rotation direction of the step motor changes depending on the area even when the zoom is T → W (W → T).

As described above, the step motor speed determined by correcting the area representative speed obtained from the position of the variator and the focus lens by the detection result of the AF circuit is used to step the zoom motor. By controlling the position of the focus lens by driving the motor, it becomes possible to prevent out-of-focus blur during zooming even with the inner focus lens. Such a cam tracing method is called an electronic cam.

Here, in addition to the "representative speed" of 141 in FIG. 12, speeds such as 142 and 143 are stored for each block, and three speeds are selected according to the AF distance measurement result. Is also presented.

As described above, a DC motor, a step motor, an ultrasonic motor, a voice coil motor, etc. are used as the conventional actuator for driving the lens, and the driving force of the motor is a reduction gear or a timing belt. It is transmitted via a transmission mechanism such as a feed screw mechanism or directly. However, there are problems that noise and vibration are large, loss torque and backlash are large, and it is difficult to reduce size and weight.

Further, with the main problems of downsizing and weight saving and minute positioning, a driving source and a fine movement mechanism utilizing minute deformation of an object or substance have come to be used. Of these drive sources, the most widely used recently is a piezoelectric element, and various types of piezoelectric motors have been proposed so far. The fine linear movement mechanism disclosed in JP-A-55-100059 is one application example of a piezoelectric linear motor configured by using a piezoelectric element.

FIG. 13 shows a schematic structure of the linear fine movement mechanism or the piezoelectric linear motor disclosed in the above publication. In the figure, 144, 145a, 145b, 1
Both 46a and 146b are laminated piezoelectric elements. These piezoelectric elements are held by a pair of holding members 147 and 148 having a T-shaped vertical cross-sectional shape as shown in the drawing, and the first laminated piezoelectric element 144 expands and contracts in the direction A of travel along the guide rail 149. Further, the second laminated piezoelectric elements 145a, 145b and the third laminated piezoelectric elements 146a, 146b are arranged in a direction perpendicular to the traveling direction A, that is, toward both wall surfaces of the guide rail 149 facing each other. It can be expanded and contracted. The piezoelectric linear motor includes the first to third laminated piezoelectric elements 14
When the timing of voltage application to 4, 145a, 145b, 146a, 146b is sequentially switched according to a predetermined pattern, the worm moves in the advancing direction A or in the opposite direction while performing a worming action. Therefore, if the length of the guide rail 149 is increased, it is possible to move a long distance.

[0019]

In an image pickup apparatus such as a video camera which employs a rear focus type zoom lens, an electromagnetic motor such as a step motor or a voice coil motor is used as a focus motor. However, when the step motor is adopted, the lens position is detected by counting the drive input pulses, and it is not necessary to provide a separate position detecting device, but the step motor itself is large and the lens unit cannot be downsized. Further, if another electromagnetic motor is adopted, the motor itself can be miniaturized, but a position detection device must be separately provided, and again there is a problem that the lens unit cannot be miniaturized. Further, with the miniaturization of the image pickup device (CCD), minute lens positioning is required, but the required accuracy cannot be achieved with a combination of an electromagnetic motor such as a step motor and a mechanical transmission mechanism such as a feed screw mechanism. There is.

Therefore, an object of the present invention is to reduce the size of a lens unit as a lens driving device for a video camera,
Another object of the present invention is to provide an optical device that can perform minute lens positioning.

[0021]

According to the present invention, as a driving means for moving a movable lens in an optical axis direction, at least two first actuators for switching between contact and non-contact with a reference member, and the first actuator. A second actuator for changing the interval between the actuators is provided, and at least one of the first actuators is formed of a bimorph type piezoelectric body. As a result, according to the present invention, it is possible to provide a small-sized optical device capable of minute lens positioning.

[0022]

EXAMPLE An example will be described with reference to FIGS. In the embodiment, a piezoelectric motor is applied to a focus motor of an image pickup device such as a video camera.

FIG. 1A is a sectional view of the focus lens portion of the lens barrel incorporating the piezoelectric linear motor of the embodiment of the present invention in the optical axis direction, and FIG. 1B is the same as FIG. 1A. FIG. 6 is a cross-sectional view taken along line BB of FIG. In the figure, 1 is a lens barrel as a member that serves as a movement reference, and 2 is a cylindrical lens holding frame holding a lens 15. A protrusion 2a is provided on the outer peripheral surface of the lens holding frame 2, and a laminated piezoelectric element 3 extending in a direction parallel to the optical axis (that is, the moving direction of the movable portion) is provided at one end of the rear end face of the protrusion 2a. It is cantilevered. Also, the protrusion 2
A piezoelectric element mounting member 5 is fixed to the front end surface of a, and a bimorph type piezoelectric element 4 extending parallel to the optical axis is cantileveredly bonded to the front end surface of the member 5. ..

On the other hand, the same piezoelectric element mounting member 7 as the member 5 is fixed to the rear end surface of the laminated piezoelectric element 3 by adhesion or the like, and the same bimorph type piezoelectric element 6 as the piezoelectric element 4 is attached to the member 7. Is cantilevered on its front end face. An engaging member 8 such as felt, which is pressed against the inner peripheral surface of the lens barrel 1, is fixed to each of the upper surface of the front end portion of the piezoelectric element 4 and the upper surface of the rear end portion of the piezoelectric element 6.

A lens holding frame support member 9 made of, for example, iron, which constitutes the sliding surface of the lens holding frame 2, is fitted and fixed to the inner peripheral surface of the lens barrel 1, and the inner peripheral surface of the member 9 (that is, the lens). The surface of the holding frame 2 that contacts the outer peripheral surface) is coated with a fluororesin in order to reduce friction with the lens holding frame 2. The member 9 does not have to be a cylindrical body, and in this embodiment, as shown in FIG. 1B, three fan-shaped segment blocks spaced from each other on the circumference centered on the axial center of the lens barrel 1 are used. And two blocks of them function as guide members for guiding the above-mentioned protrusion 2a so as to move only along the optical axis direction (that is, not to rotate the lens holding frame 2). Have

Next, the operating principle and operating state of the piezoelectric linear motor of this embodiment will be described with reference to FIGS.

Note that FIG. 2 is a schematic view showing each operation state, and FIG. 3 is an example of an applied voltage pattern for performing the shingling insect operation.

(A) No voltage is applied to each piezoelectric actuator, and the bimorph type piezoelectric actuators 4, 6
(Hereinafter, the piezoelectric body 4 is described as C ₁ and the piezoelectric body 6 is described as C _2. )

[0029] (ii) C ₂ is bent a voltage is applied, the clamp is released by C _2, only C ₁ is clamped.

While holding the states of (c) and (b), by applying a piezoelectric force to the laminated piezoelectric actuator 3 for straight movement (hereinafter, the piezoelectric body 3 is indicated by M), M is expanded and installed on this. The C ₂ that has been moved also moves in the x direction.

[0031] By releasing the applied voltage (D) C _2, the shape of the C ₂ restores, C ₂ again clamps.

[0032] By applying a voltage to the (e) then C _1, C ₁ is clamped by the bent C ₁ is released, only the C ₂ is clamped.

By releasing the applied voltage of M in the clamped state of (f) and (e), M restores and shortens its entire length, and C ₁ and the movable part 11 move in the x direction.

[0034] (g) finally by releasing the applied voltage C _1, the shape of C ₁ is restored, returns to the initial state (a).

Each of the piezoelectric bodies and the movable portion 11 moves in the x direction by the amount of extension of the piezoelectric body M for rectilinear movement, with one cycle consisting of the steps (a) to (g). (A) ~ (g)
If the applied voltage pattern of 1 is reversed, it will move in the -x direction. The amount of movement per cycle can be adjusted by adjusting the magnitude of the voltage applied to the straight-moving piezoelectric body M.

FIG. 4 shows a block diagram of this embodiment. 1
Reference numeral 2 is a fixed front lens group, 13 is a variator lens group for zooming, 14 is a fixed lens group, and 15 is a focusing function and a function of correcting a displacement of an image plane caused by the movement of the variator lens group 13. Share with
It is a focusing (compensator) lens group located closest to the image plane. The position of the variator lens group 13 is detected by the zoom encoder 16. Here, the zoom encoder 16 is, for example, a volume encoder configured to slide a brush integrally attached to the variator moving ring on the substrate on which the resistance pattern is printed. Reference numeral 17 denotes an aperture encoder for detecting an aperture value, which uses a Hall element output provided in an aperture meter, for example. Reference numeral 18 is an image pickup device such as CCD, and 19 is a camera processing circuit, and the Y signal is taken into the AF signal 20. The AF circuit determines whether the object is in-focus or out-of-focus, and when it is out of focus, determines whether it is the front focus or the rear focus, and how much the focus is out of focus. These results are CPU2
Taken in 1. 22 is a power-on reset circuit,
Performs various reset operations when the power is turned on. A zoom operation circuit 23 notifies the CPU 21 of the contents when the operator operates the zoom switch 24. Numerals 25 to 27 are memory portions for the movement locus data of the focusing lens 15, which are composed of direction data 27, velocity data 26, and boundary data 25. Reference numeral 28 denotes a zoom motor driver, and 29 denotes a focus motor driver, which continuously counts the number of cycles of the applied voltage described above in the CPU 21 and serves as an absolute position encoder of the focus lens. 30 is a zoom motor, for example, a DC motor. Reference numeral 31 is a focus motor, which is the above-described piezoelectric linear motor.

The automatic focus detection method of the lens driving device of this embodiment will be described with reference to FIG. Reference numeral 41 shows the entire screen of the video camera, and 42 shows the distance measuring area therein. In principle, this is a method of detecting the contrast of the image, and the blur amount is detected by processing the output of the image having the contrast indicated by 43, for example. 5A shows a video signal of the image 43 from the image sensor, and FIG. 5B shows a differential waveform thereof. (C) shows a waveform obtained by converting the differentiated waveform into an absolute value, and (d) shows a signal level (evaluation value) A obtained by integrating and holding the absolute value-converted waveform. That is, a high signal level is obtained when the image 43 is sharp, and a low signal level is obtained when the image 43 is not sharp, that is, when the image is blurred. Therefore, basically, as shown in FIG. 5C, the position B of the focus lens group which should be in focus can be determined by detecting the position where the signal level A is the highest.

In the optical system according to the present embodiment, that is, in the so-called rear focus zoom lens system in which the focusing function and the compensator function are performed by one correction lens group, the conventional general zoom lens system, that is, Unlike a lens system in which a focusing lens group and a compensator lens group exist respectively, and the movement locus of the compensator lens group can be uniquely determined, the movement locus of the correction lens group differs depending on the subject distance. Draw a trajectory. This state is shown in FIG. The horizontal axis represents the position of the variator lens group 13, that is, the focal length, and the vertical axis represents the position of the focus lens group 15. Incidentally, W on the left end indicates the wide end, and T on the right end indicates the tele end. As is clear from this figure, the movement locus of the focus lens group 15 differs depending on the subject distance. For continuous movement of the variator lens group 13 during zooming, the focus lens group 15
In order to track the subject while maintaining the in-focus state in real time, the focal lengths are divided into a plurality of zones as shown in FIG. 6B according to the characteristic diagram shown in FIG. The speed (reference measure) of the focus lens group 15 is stored in advance. In this embodiment, it is premised that the moving speed of the variator lens group 13 during zooming is constant. With the above configuration, if the in-focus state is maintained before the start of zooming, after that, the focus lens group 1 is moved from the position of the variator lens group 13 and the focus lens group 15 and the zoom direction.
The moving speed and moving direction of 5 are determined, and the focus lens group can be moved without a response delay.

Next, the operation procedure of the lens drive control by the CPU 21 will be described based on the flowchart shown in FIG.

When the zoom button or the like is operated in step 51, this routine is entered. This routine is, for example, 1
At / 60 sec, the steps from step 52 onward are repeated. Also,
If the operation of the zoom button or the like is stopped or the variator lens group position reaches the end of the movement range area, this routine is stopped.

When this routine is entered in step 51, it is determined in step 52 whether the AF device 20 is in the operating state. When the AF device 20 is not operating, step 5
At 3, the zoom operation is prohibited. Therefore, when the AF device is not operating, zooming is not performed even if the zoom button or the like is operated. Step 5 when the AF is in operation
Go to 4.

In step 54, the previous blur evaluation value A ₀ is stored in A ₂ . In this case, since the previous blur evaluation has not been performed at the start of the zoom operation, the value of A ₀ = 0 is stored in A ₂ .

At step 55, the current blur evaluation value A is set to A.
Store in ₁ . In step 56, (A ₁ -A ₂ ) is stored in Ad. In step 57, A is stored in A ₀ for use as the previous blur evaluation value in the next routine.

Next, at step 58, points (V, R) in the map of FIG. 5A are calculated from the current position (V) of the variator lens group 13 and focus lens group 15 position (RR).
R) is detected. In step 59, the area to which the (V, RR) point detected in 58 belongs is detected. Step 6
At 0, the speed that becomes the front pin and the speed that becomes the rear pin are read from the area representative speed and the area representative data stored for each area. Next, at step 61, the CPU 21 takes in whether the operation of the zoom switch (T, W) is from wide to tele or from tele to wide.

Next, at step 62, the CPU 21 reads the contents read from these data and the AF device 20.
Focus lens group 15 based on the read out blur information
The moving direction of the focus motor 31 for driving is determined, and the driving direction of the motor 30 for driving the variator lens group is determined according to the operation result of the zoom switch.
After that, output to the focus motor drive circuit 29 and output to the zoom motor driver 28 are performed so that the two motors move at substantially the same time. The above-mentioned piezoelectric motor is configured to change the voltage applied to the piezoelectric body M and the driving step.
Movement speed changes. That is, as the speed data 26, the voltage value applied to the piezoelectric body M and the driving step may be stored in memory.

In this embodiment, the sliding system is used as the moving mechanism, but a moving mechanism such as a bar sleeve system may be used.

In the present embodiment, the DC motor is used as the zoom motor and the volume encoder is used as the zoom encoder. However, the encoder function is obtained by using the piezoelectric linear motor used as the focusing motor as the zoom motor and counting the drive pulses. It is also possible to provide.

[0048]

As described above, by using an actuator using a bimorph type piezoelectric body as a lens driving means for a video camera or the like, it is possible to downsize an optical device and to perform minute lens positioning. It can be performed.

[Brief description of drawings]

FIG. 1 is a diagram showing a lens barrel incorporating a piezoelectric linear motor according to an embodiment of the present invention,

FIG. 2 is a diagram for explaining the operation of the linear motor,

FIG. 3 is a diagram showing an applied voltage pattern for a piezoelectric linear motor,

FIG. 4 is a block diagram of a video camera as an embodiment,

FIG. 5 is an operation explanatory view of the AF device,

FIG. 6 is a diagram showing a cam locus,

FIG. 7 is an operation flowchart of the CPU,

FIG. 8 is a configuration diagram of a zoom lens unit using a rear focusing zoom lens,

FIG. 9 is a diagram showing a focusing position relationship between a variator lens and a focusing lens;

FIG. 10 is a block diagram of a conventional video camera,

FIG. 11 is a diagram showing an example of cam locus division,

12 is an enlarged view of block III in FIG. 11,

FIG. 13 is a schematic diagram of a conventional piezoelectric linear motor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Lens barrel 2 Lens holding frame 10 Focusing lens 9 Lens holding frame support member 4, 6 Bimorph type piezoelectric body 3 Laminated piezoelectric body

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical display location H02N 2/00 B 8525-5H H04N 5/232 A 9187-5C (72) Inventor Hiroyuki Takahara Tokyo 3-30-2 Shimomaruko, Ota-ku Canon Inc.

Claims (3)

[Claims] 1. A movable lens which is movable in the optical axis direction, and a drive means for moving the movable lens in the optical axis direction, wherein the drive means switches between contact and non-contact with a reference member. A plurality of first actuators and a second actuator that is arranged between the first actuators and has a different distance, and at least one of the first actuators is formed of a bimorph type piezoelectric body. And optical equipment. 2. A first movable lens which is movable in the optical axis direction for zooming, and a second movable lens which also functions as a compensator in focusing and zooming and which is movable in the optical axis direction. , The first or second
Driving means for moving at least one of the movable lenses in the optical axis direction, the driving means switching between contact and non-contact with a reference member and at least two first actuators, and the first actuator. An optical device comprising a second actuator disposed between the two and changing a distance, wherein at least one of the first actuators is formed of a bimorph type piezoelectric body. 3. The optical apparatus according to claim 2, wherein both the first movable lens and the second movable lens are moved in the optical axis direction by the drive means.