JPS63163311A - Automatic focusing device and its lens driving mechanism - Google Patents

Abstract

PURPOSE:To attain size reduction and to improve a response speed by storing constituent components including a lens driving mechanism constituted so as to move and control a focus lens directly in the directions of the optical axis in a lens main body. CONSTITUTION:This device is equipped with a linear motor which is stored in the lens main body 33 and has an electromagnet 36 and a permanent magnet 35 so that one is provided movably to and away from the other in the optical axis directions (A-B directions), the focus lens supported by the former between the electromagnet 36 and permanent magnet 35, and the lens driving mechanism which has a driving means for moving and controlling the focus lens 32 in the AB directions by driving and controlling the linear motor. Then this lens driving mechanism is controlled according to the input image information of an image pickup element 37 provided to the lens main body 33. Consequently, constituent components such as a speed reduction mechanism, etc., are reduced to reduce the size and weight, and the operation is speeded up to improve the response speed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an autofocus Btl used in, for example, a video camera or a single-lens reflex camera, and its lens mechanism.

(Prior Art) Generally, as shown in FIG. 14, an autofocus device for a video camera uses infrared rays emitted from an infrared light emitting element 2 in a lens body 1 to pass through a total reflection mirror 3 to a subject 4 (a 15th
A so-called infrared distance measuring method is known in which the distance is measured by irradiating the object (see figure) and detecting the reflected infrared rays with an infrared light receiving element 5. In this case, a lens drive mechanism L1 including a drive motor 6 for focus adjustment, an infrared light receiving element 5, and a light receiving lens 8 are arranged outside the lens body 1, and an infrared light emitting element 2 and a total reflection mirror 3 are placed inside the lens body 1. will be placed. That is, the infrared light emitting element 2
As shown in FIG. 15, only the infrared rays of a certain wavelength are reflected by the total reflection mirror 3 and the dynamic mirror 9, and then reflected by the lens group 10 and the focus lens 1.
The object 4 is irradiated via the light beam 1. Here, the angle of incidence of this infrared rays upon the infrared light receiving element 5 differs depending on the distance of the subject 4. As a result, the infrared receiving element 5 is moved so that the incident light is irradiated onto its center, and in response to this movement, the drive motor 6 is controlled by a control section (not shown) to move the focus lens 11 in the optical axis direction. to adjust the focus.

In recent years, as shown in FIG. 16, an autofocus detection section is provided in which an image element 12 such as a COD is disposed on the back surface of a lens section 13 via a mask lens 15 having a piezoceramic diaphragm 14, and this imaging An autofocus device configured to adjust the focus by detecting the position with respect to the subject from the video signal input to the element 12 has also been realized.

That is, incident light from an object (not shown) that has passed through the lens unit 13 is transmitted to the image sensor 1 via the focus lens 16.
2, a subject image is formed on its image plane, and converted into a video signal. At the same time, this video signal is minutely captured by a mask lens 15 having a piezoceramic diaphragm 14 along the optical path length, so that it does not affect the image depending on the depth of field and is sufficiently detected as a signal. controlled and modulated. The modulated components of this video signal are guided to the AF signal processing section 19 via a band pass filter (BPF) 17 and a BPF switching section 18, where they are synchronously detected using the reference frequency of the reference frequency generation section 20, and then synthesized. A focal signal is formed and guided to the control port 2). Then, the control unit 2) drives and controls the focus adjustment drive motor 23 via the lens information detection unit/lens drive unit 22 in accordance with the focus signal to move the focus lens 16 in the optical axis direction to bring the focus into focus. to be adjusted.

However, regardless of the configuration of the autofocus device described above, a deceleration mechanism or the like is required to decelerate the rotational motion of the drive motor 6.23 and convert it into linear motion. The problem was that it was very complicated and its response speed was slow. Further, according to these, all of them include a drive motor 6.23, and the lens drive mechanism (I) must be disposed outside the lens body 1 (see FIG. 14), which makes them larger and larger. Moreover, it has the problem that @Shibu becomes bulky. In particular, the autofocus device shown in FIG. 14 requires the infrared light receiving element 5 and the light receiving lens 8 to be provided together with the lens drive mechanism 7, so that the autofocus device shown in FIG.
As it became larger than @, it caused more commotion.

(Problems to be Solved by the Invention) This invention was made to solve the above-mentioned problems of response speed and the problem of large-sized and heavy-duty companies. , and 1. It is an object of the present invention to provide an autofocus device and its lens drive mechanism that can improve response speed as much as possible.

[Structure of the Invention] (Means for Solving the Problems) The present invention includes an electromagnet and a permanent magnet housed in a lens body and disposed opposite to each other such that one of the magnets is movable in the optical axis direction. A lens drive 8 mechanism is gradually provided, which includes a linear motor, a focus lens supported by the other of the electromagnet and the permanent magnet, and a drive means for controlling the drive of the linear motor to control the movement of the focus lens in the optical axis direction. Moreover, this lens driving mechanism is controlled in accordance with input image information from an R image element provided in the lens body.

<Function> With the above configuration, the components including the lens drive mechanism configured to directly control the movement of the focus lens in the optical axis direction are accommodated within the lens body, improving response speed and reducing size. This achieved an improvement in

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows the main parts of an autofocus device and its lens drive mechanism according to an embodiment of the present invention.
．． Reference numerals 31 and 32 denote first to third lens groups constituting the imaging lens arranged at a predetermined interval on the lens body 33 (however, in the figure, for convenience of illustration, one convex lens is shown). figure)
It is. Of these, the third lens group 32 constitutes a focus lens, and is disposed so as to be movable in the optical axis direction (in the direction of arrows A and B) via a slider member 34 formed of, for example, a permanent magnet. This third lens group 32
A stator 35 made of, for example, a permanent magnet and an electromagnet 36 formed by winding a magnetic core are arranged opposite to the lens body 33 so as to sandwich the magnets, thereby forming a so-called linear motor.

Furthermore, an image pickup device 37 such as a COD is disposed in the lens body 33 corresponding to the first to third lens groups 30, 31, and 32. As shown in FIG. 2, this image sensor 37 has an output terminal connected to a camera circuit 38 and a bandpass filter (
PF) 39. This BPF 39 is connected to a linear motor drive section 44 via a bell ringer 43 that is connected to an AF signal processing section 40, a control section 41, and a reference frequency generation section 42.

In the above configuration, the first to third lens groups 30 to 32
The captured object 45 is input as a video signal to the layer detector 37 via the first to third lens groups 30 to 32. At the same time, the third lens group 32
4, the image sensor 3 is subjected to minute vibrations at a reference frequency.
The video signal imaged on 7 is modulated. As the 8 frequency components of this video signal increase as shown in FIG. The optical path length corresponds to the high frequency component, and the focus is shifted in the direction of the arrow in the so-called 2-focus state, and the focus is shifted in the direction of the arrow B in the so-called back-bin state. change like this. At the same time, the level fluctuations of the high frequency components are 18% higher than each other in the forward bin state and the rear bin state, as shown in parts a' and c' in the figure.
A phase difference of 0° occurs, and the amplitude b' in the figure becomes the minimum in the focused state. Then, this modulated video signal is processed by BPF
At 39, the modulated component is extracted and guided to the AF signal processing section 40, where it is synchronously detected at the reference frequency of the reference frequency generation section 42, and a focusing signal is formed and guided to the control section 41. This control section 41 operates a linear motor drive section 44 in response to the focusing signal.
A predetermined current is supplied to the electromagnet 36 through the electromagnet 36. As a result, the electromagnet 36 exerts a repulsive force fl between the stator 35 and the slider member 34, as shown in FIG.

r2 is generated and the slider member 34 is moved in the optical axis direction to control the third lens group 32 to the in-focus position.

Note that the slider member 34 is positioned by the electromagnet 36 when the slider member 34 and the N and SIn poles of the fixed portion are opposed to each other as shown in FIG. As shown in FIG. 6, when the S magnetic pole is made to correspond to the Nfa pole, it will be positioned on the stator 35. When a predetermined level of current is supplied to the electromagnet 36 at the initial position of the slider member 34, the slider member 34 moves in the optical axis direction to a position where the distance between the electromagnet 36 and the stator 35 is fl-f2. will be moved.

In this manner, the autofocus device includes a lens piiilJm side in which a linear motor is disposed inside the lens body 33, and the slide member 34 to which the third lens group 32 is attached is disposed opposite to the electromagnet 36. By configuring the lens drive mechanism to perform drive control 11''tj according to the image information of the 1-image element 37 provided in the lens body 33, the conventional components of the reduction gear are omitted, resulting in a reduction in size and weight. It is possible to improve the speed of response, as well as to speed up the operation and achieve an improvement in response speed.

In the above embodiment, the third lens group 32 is configured to constantly vibrate minutely in order to detect the focusing signal, but the configuration is not limited to this, and for example, as shown in FIG. 7, the gate circuit 46 and It is also possible to provide a gated t2'lI signal generating section 47 and to divide the focus shift detection and focusing operations into time series. That is, as shown in FIG. 8, when the gate control signal generation section 47 is at O (L), the reference frequency of the reference frequency generation section 42 is applied as a drive section input signal to the linear motor drive section 44, and the third lens The group 32 is slightly vibrated to modulate the video signal of the vaSS element 37. The modulated component of this modulated video signal is extracted by the BPF 39 and guided to the AF signal processing section 40 where it is synchronously detected at the reference frequency of the reference frequency generation section 42 to form a focusing signal and guided to the control section 41. . When the gate control signal generating section 47 is high (H), the reference frequency is turned off by the gate circuit 46, and the control section 41 operates the linear motor driving section 44 to supply a predetermined current to the electromagnet 36. do. - Also, in the above embodiment, the stator 35 formed of a permanent magnet
．． Slider member 34 and electromagnet 36 formed of permanent magnets
Although the explanation has been given on the case where the linear motor is configured using the linear motor, it is also possible to configure the linear motor as shown in FIGS. 9 to 13, for example, and the same effects can be expected.

In FIG. 9, a slider member 34a made of a permanent magnet is attached to a stator 35a made of a metal or resin material via a spring member 48a, and a winding is connected to the magnetic core corresponding to the slider member 34a. The electromagnets 36a are arranged in the same manner as shown in FIG.

In FIG. 10, a slider member 34b formed of an electromagnet is arranged movably in the optical axis direction in correspondence with a stator 35b formed of a permanent magnet.
It is supported by a holding member 49 fixed to 3 through a spring member 48b.

FIG. 11 shows an electromagnet 36b fixed to the lens body 33 so as to sandwich a slider member 34c formed of a permanent magnet.
, 36c are arranged and connected to each other via a spring member 48C.

FIG. 12 shows the second and third lens groups 31, 32 permanently
Slider portion 034d formed by E.

A stator 35clR formed of a permanent magnet is disposed between the slider members 34d and 346 so as to be movable in the optical axis direction via the slider member 34e. The lens body 33 is provided with core magnets 36d and 36e whose magnetic cores are wound with wire so as to sandwich both the slider members 34d and 34e, and the second and third lens groups 31. 32 are arranged so as to be movable in the optical axis direction.

FIG. 13 shows a slider member 34f in which the first and third lens groups 30 and 32 are formed of permanent magnets.

A stator 35d formed of a permanent magnet is disposed so as to be movable in the optical axis direction via the slider member 34Q, and is formed between the slider members 34f, 34Q and the second lens group 31.

35e are provided respectively. The lens body 33 is provided with electromagnets 36f and 30g having wires wound around magnetic cores so as to sandwich both the slider members 34f and 34Q, and the first and third lens groups 30, 32 Both are arranged so as to be movable in the optical axis direction.

Therefore, it goes without saying that the present invention is not limited to the above embodiments, and that various modifications can be made without departing from the spirit of the invention.

[Effects of the Invention] As detailed above, according to the present invention, there is provided an autofocus device that has a simple configuration, can be miniaturized, and can improve response speed as much as possible. and its lens drive mechanism.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the main parts of an autofocus device and its lens driving mechanism according to an embodiment of the present invention, FIG. 2 is a circuit configuration diagram showing the control system of FIG. 1, and FIG. Figure 1 is a diagram shown to explain the operating principle, Figures 4 to 6 are sectional views shown to explain the #JJ work in Figure 1, Figure 7
8 is a circuit configuration diagram showing a control system according to another embodiment of the present invention, FIG. 8 is a timing chart showing the operating state of FIG. 7, and FIGS. 9 to 13 are respectively other embodiments of the present invention. Cross-sectional views showing examples, FIGS. 14 to 16, are diagrams shown for explaining conventional autofocus devices, respectively. 30 to 32...first to third lens groups, 33...
・Lens body, 34...Slider member, 35° 35a
, 35b, 35c, 35d, 35e--Stator, 36
．． 36a, 36b, 36c, 36d. 36e, 36f, 36G... Electromagnet, 37-111 element, 38... Camera circuit, 39... BPF, 40.
...AF (No. A processing section, 41...control m+ section, 42...
- Reference frequency generation section, 43... Sieve device, 44... Linear motor drive section, 45... Subject, 46... Gate circuit, 47... Gate control signal generation section, 48a, 4
8b, 48c... Spring portion 4'A, 49... Holding member. Patent attorney Takehiko Suzue Focus position: Figure 3, Figure 4, then move to Figure 5, Figure 6 AB, Figure 9 AB, Figure 10, Figure 11, Figure 12, Figure 13.

Claims (2)

[Claims] (1) A linear motor that is housed in the lens body and has an electromagnet and a permanent magnet, the other of which is disposed so as to be movable in the optical axis direction, and which is supported by the other of the electromagnet and the permanent magnet. A focus lens, an image sensor provided in the lens body corresponding to the focus lens, and drive control of the linear motor according to image information input to the image sensor via the focus lens, and a focus lens. An autofocus device comprising: a control means for moving a lens in an optical axis direction to adjust focus. (2) A linear motor having an electromagnet and a permanent magnet housed in the lens body, the other of which is movably movable in the optical axis direction, and which is supported by the other of the electromagnet and the permanent magnet. 1. A lens drive mechanism for an autofocus device, comprising: a focus lens; and a drive means for driving and controlling the linear motor to control movement of the focus lens in an optical axis direction.