JPH08101334A - Servo mechanism for film surface moving type automatic focusing camera - Google Patents

Abstract

PURPOSE: To provide a servo mechanism of a film surface moving type automatic focusing camera constituted so that an optical axis unit being a movable part can be controlled to be moved at a higher speed as to a back focusing control type automatic focusing camera obtained by arranging a film chamber on the fixed side of a camera main body. CONSTITUTION: A holding member 30 fixing the hollow coil 37 of a voice coil- shaped linear actuator is fixed to the side surface of a mirror box 5. Then, mutually crossed levers 32 and 33 are fitted between a camera fixing side and the optical axis unit 1 side. By making a current flow, the coil 37 is linearly moved along a U-shaped yoke 38 so as to move the unit 1 in parallel along an optical axis. Since the linear actuator is used, a focusing speed is increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photographic lens interchangeable camera, and more particularly to a servo mechanism for adjusting the focus of an optical axis unit which is a movable part of a back focus control type auto focus camera.

[0002]

2. Description of the Related Art Generally, when an AF is applied to a single-lens reflex camera, a method of automating an operation of focusing a subject by adjusting a distance ring of a lens is adopted. As the driving method, there are an in-body motor and an in-lens motor, which have been put into practical use. All of them are AF dedicated lenses, and it has been impossible to convert conventional lenses into AF.

In order to enable AF operation with a conventional MF lens based on a lens mount on which a conventional lens can be mounted and exchanged, the main body is divided into front and rear parts and the so-called rear film surface position control is performed. The present inventor has already proposed a back focus control method. This method uses ABF (Autom) to distinguish it from conventional autofocus.
atic Back Focusing) System
Advocated to call. In this back focus control, the rear unit, which is a movable unit, has a photographing function including a film chamber and includes many of the functions of the camera, and therefore has a considerable weight and volume. On the other hand, in order to perform AF, it is necessary to control this movable part at high speed and precisely. In order to control this movable part at high speed and with precision, it is necessary to reduce the volume and reduce the weight.

[0004]

Therefore, in consideration of the popular type that prioritizes small size and light weight of the entire camera within the range that does not impair the idea of the ABF, the movable range of the lens flange back is set to 5 mm or less. However, it is stated in the patent application (film surface moving type autofocus camera) dated September 13, 1994 that there is no change in the product concept that adheres to this idea. Therefore, when considering only models that do not have a large movable range, the cartridge chambers and spool chambers (film chambers) located on the left and right of the camera body are located on the fixed side of the camera body, and the AF sensor module and finder mechanism are used as the movable side. A method of adjusting the back focus by moving the film parallel to the optical axis while holding the film in a center unit (optical axis unit) having a function of photographing the optical axis including a mirror box mechanism having a shutter, a film opening and a film pressure plate. Proposed.
With this method, it is possible to achieve a further reduction in the weight of the movable part, and it is possible to control the speed even faster than in the past. An object of the present invention is to provide a servo mechanism of a film surface moving type autofocus camera capable of controlling the movement of the optical axis unit at a higher speed in the backfocus control autofocus camera in which the film chamber is arranged on the camera fixed side. To do.

[0005]

In order to achieve the above object, a servo mechanism of a film surface moving type autofocus camera according to the present invention is a camera appearance having a lens mount for a photographing lens and a back cover for loading and unloading a film. And a finder mechanism, a distance measuring mechanism, an exposure mechanism and a film opening portion which are arranged at the center of the optical axis passing through the lens, and have a predetermined distance in the optical axis direction with respect to the camera appearance fixing section. Equipped with a movable optical axis unit,
A film surface moving type autofocus camera in which a film winding side and a rewinding side film chambers arranged on the left and right sides of the film opening portion and a film feeding mechanism for feeding the film are arranged in the camera appearance fixing portion. Then, the optical axis unit is configured to move in the optical axis direction and perform a focusing operation in accordance with the linear movement of the moving portion of the linear driving means.

According to the present invention, in addition to the above structure, a lever is provided so as to cross over the side surface of the optical axis unit and the camera appearance fixing section, and the optical axis unit and the camera appearance fixing section are connected to the camera appearance fixing section. The connecting portion with the end portion of the lever and the intersecting portion of the intersecting lever are configured to be rotatable, and by providing this crossing lever mechanism on both side surfaces of the optical axis unit, the above-mentioned camera exterior fixing portion is provided with The optical axis unit is held and configured to be movable in parallel with the optical axis.

[0007]

According to the above construction, the movable part can be limited to only the photographing mechanism unit centering on the optical axis, the weight can be reduced, and the voice coil type linear actuator installed parallel to the optical axis can be directly driven and servo-controlled. Thus, high speed control can be achieved.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in more detail below with reference to the drawings. FIG. 1 is a plan sectional view for explaining the basic structure of a film surface moving type autofocus camera according to the present invention, showing an optical axis unit as a movable part and a state of film surface movement. This figure shows a state in which the focus can be adjusted only by moving the optical axis unit B having a photographing function. The movable amount of the flange back is reduced and the cartridge 36 and the spool 4 arranged on both sides of the aperture 4 are shown.
A film chamber accommodating 2 is provided in the camera exterior fixing section A. The optical axis unit B is a portion surrounded by a two-dot chain line, and has a mirror 63 and a mirror box mechanism 4 as a photographing function.
5, the shutter mechanism 16, the pressure plate 61 and the like.

In this example, the fitting portions 71a, 71b, 72 are attached to the side surface of the optical axis unit B, and the optical axis unit is guided by the guide rods 69, 70 whose ends are fixed to the camera appearance fixing portion A. B can move while being held parallel to the optical axis direction. FIG. 1A shows a state in which the optical axis unit B is moved to a film winding position, that is, a maximum movable position, and FIG. 1B shows that the optical axis unit B is brought to the minimum movable position for focusing. It shows the state. By adopting such a configuration, the movable part is further reduced in weight and focus control becomes easier. FIG. 2 proposes a servo mechanism for driving and controlling the optical axis unit based on this optical axis unit.

FIG. 2 is a perspective view showing an embodiment of a servo mechanism of a film surface moving type autofocus camera according to the present invention. A voice coil type linear actuator is used as a linear driving mechanism. FIG. 3 is a perspective view showing an example of a linear actuator using a flat coil based on the same principle. FIG. 4 is a principle diagram for explaining the operation of the linear actuator used in the present invention. In FIG. 2, the mount base 3 that corresponds to the front surface of the camera serves as a camera appearance fixing portion (hereinafter referred to as “fixing portion”), and this fixing portion serves as a reference. A mount is installed on the mount base 3 so that the interchangeable lens 2 can be mounted.
A base plate 43 is fixed to the mount base 3 with screws 50. The cross lever 3 is attached to the bent portion 43a below the main plate 43.
3 is rotatably connected by a pin 34, and the upper bent portion 43
A pin 44 fixed to the end of the cross lever 32 is slidably coupled to the long groove 43c of b.

These crossing levers 32 and 33 are crossed in an X shape, and the crossing point is rotatably connected by a pin 35. On the other hand, the main plate 27 is fixed to the side surface of the movable mirror box 5, and the cross lever 32 is provided below the main plate 27.
The lower end of is attached rotatably by a pin 31. In addition, the cross lever 3 is inserted into the long groove 27a above the main plate 27.
A pin 29 fixed to the upper end of 3 is slidably connected. This crossing lever mechanism is also installed on the opposite side (invisible part) of the mirror box 5, and the mount base 3 holds the movable optical axis unit 1 so that it can move in parallel to the optical axis by this mechanism. it can.

The optical axis unit 1 includes a viewfinder mechanism including a mirror, a quick return mechanism, and a pentaprism 4, an AF module including an auxiliary mirror, an AF sensor, a lens, and the like, including a portion that cannot be seen in this figure, and a shutter mechanism 2.
6 and inner rails 21, 2 for holding the film
4, the outer rails 20 and 25, and the aperture plate 22 composed of the film opening 23 are the main components, and these are integrated into a unit. Film opening 2
The film is held on the aperture plate 22 by holding the film on
And a film pressure plate (not shown).
Although not shown in the figure, the film pressure plate can be held by being attracted to the aperture plate 22 by a magnet or the like. Therefore, after the film is loaded, the focus can be adjusted while the film is held on the optical axis unit 1 by the pressure plate.

Next, a linear drive mechanism for driving the optical axis unit 1 with respect to the mount base 3 of the fixed portion will be described. As described above, the control is performed using the voice coil type linear actuator. In this actuator, U-shaped yokes 38 and 40 are arranged side by side and magnets 39 and 41 are adhered and fixed inside the U-shape. This cross section is shown in FIG. Magnets 39 and 41
The pole on the side facing the yoke is the N pole, which is the same pole. Therefore, a magnetic circuit is formed so that the magnetic fields of the magnets 39 and 41 both flow toward the central yoke, pass through each yoke, and return to the S pole of each magnet.

A rectangular hollow coil (moving coil) 37 is inserted into this central yoke, and when a current in the direction shown in FIG. 4 (A) is passed through the coil 37, the magnetic lines of force by the magnets 39 and 41 and the coil are generated. Since it intersects with the flowing current, a force is generated in the coil based on the principle known as Fleming's law. In the figure, the force acting on the coil 37 is in the right direction. If a current is applied to the coil 37 in the direction opposite to that shown in the figure, the force naturally acts to the left. In FIG. 2, the U-shaped yokes 38 and 40 are fixed to the base plate 43 fixed to the mount base 3 with screws, and the yokes 38 and 4 are fixed.
The inner yoke of 0 is glued to form a double layer.
The coil 37 fixed by being sandwiched between the arms 30a and 30b of the holding member 30 with respect to the central yoke plate having the two-layered structure.
Is inserted so that you can move in and out. Holding member 3
Since 0 is fixed to the base plate 27 of the mirror box 5, if a current is applied to the coil 37, the optical axis unit 1 can be moved in parallel with the optical axis by the force acting on the coil.

Although an example of the structure of the moving coil of the linear drive mechanism has been shown above, various other structures are possible. FIG. 3 shows an example in which a flat coil is used as the moving coil of the linear drive mechanism. The flat magnets 52 and 53 are arranged side by side and bonded and fixed to the inner surface of the yoke plate 56.
The magnetic poles of the flat magnets 52 and 53 are placed so as to have opposite poles as shown in the figure. A gap is secured between the surfaces of the flat magnets 52, 53 to secure the yoke plate 5
1 is arranged. In this gap, the coil end 54a of the flat coil 54 is located almost directly above the flat magnet 52, and one coil end 54b is located almost directly above the flat magnet 53.

FIG. 4B is a sectional view of this moving coil. When a current is applied to the coil 54 in the direction shown in the figure, the flat magnets (permanent magnets) 52, 53
The magnetic lines of force act on the coil ends 54a and 54b, respectively, and a driving force is generated in the coil by the same principle as described above. Therefore, similarly, if the flat coil 54 shown in FIG. 3 is sandwiched between the U-shaped portions of the tip 55a of the holding member 55 and adhesively fixed, the force acting on the flat coil 54 can be changed depending on the direction of the current. Can be controlled arbitrarily. From this, it is understood that the optical axis unit can be arbitrarily driven and controlled by the coil current. In addition, FIG.
It is obvious that the same effect can be obtained with such a configuration.

The linear drive mechanism is constructed as described above, and the optical axis unit 1 can be moved in parallel with the optical axis. Figure 2
In the upper right position of the fixed portion, the photo interrupters 11 and 7 for detecting the movement amount and the position of the optical axis unit 1 are installed by the holder 8. The encoder plate 10 in which the slit 18 is engraved is fixed to the optical axis unit 1,
The slit 18 is configured to move in the photo interrupters 11 and 7 via the masks 19 and 6. The encoder plate 10 also moves together with the optical axis unit 1, and the moving position of the optical axis unit 1 can be measured. The drive speed of this voice coil type linear motor is drastically increased, so there is an undesirable phenomenon that an appropriate position is difficult to determine due to overshoot or oscillation caused by a sudden start or sudden stop. May occur.

Therefore, in order to suppress this, the auxiliary actuator 28 is provided at a position opposite to the linear motor. The auxiliary actuator 28 is also of voice coil type. Magnet 1 magnetized axially in the center
5, the center yoke 13 is connected to one magnetic pole of the magnet 15 to form a central magnetic pole. The other magnetic pole of the magnet 15 is connected to the cylindrical yoke 14 that covers the outer periphery of the central magnetic pole, and the cylindrical yoke 14 forms the other magnetic pole. The damper coil 12 is inserted between the cylindrical yoke 14 and the central magnetic pole, and the damper coil 12 can be linearly moved back and forth along the central magnetic pole. The end portion of the damper coil 12 is attached to the fixed portion, and the cylindrical yoke 14 is fixed to the holding member 17 attached to the optical axis unit 1.

The operating principle of this actuator is as shown in FIG. This auxiliary actuator 2
Reference numeral 8 is used for braking, and is operated so as to suppress sudden movement of the optical axis unit 1. For example, when the optical axis unit 1 tries to move abruptly, an electromotive force is generated in the damper coil 12 in proportion to the amount of change in the magnetic field that cuts the coil in a certain short unit time. It is well known that this coil acts as a braking force in proportion to the electromotive force generated when the coil ends are short-circuited. As a result, the auxiliary actuator 28
Plays a role as a damper that keeps the driving of the optical axis unit 1 at a constant speed. Also, it is possible to cancel the driving force of the main actuator by passing a current in the opposite direction. Further, by controlling the current of the main actuator used for detecting the moving speed, the speed of the optical axis unit 1 can be controlled, and the finer servo control can be performed.

FIG. 5 is a circuit diagram showing a control circuit of a camera for operating the servo mechanism according to the present invention. Generally, in response to a signal from the first step of the release button operation, the AF circuit including the AFCPU 65 etc. starts up and the AF is performed through the interchangeable lens.
An AF signal is sent to the AFCPU 65 according to the amount of light of the subject incident on the sensor 66, and distance measurement calculation is performed. As a result, the defocus amount from the current position is calculated, and the film surface of the optical axis unit is moved to adjust the back focus in that direction. Therefore, AFCPU
Reference numeral 65 controls the driver circuit 64 to pass an electric current through the hollow coil 37 so as to act in the focusing direction. As a result, a driving force is generated in the linear actuator and the hollow coil 37 begins to move, but the damper coil 12 is short-circuited or a reverse current is made to flow in response to abrupt movement to suppress abrupt changes.

During the movement, the linear encoder 67 composed of a photo interrupter, an encoder plate, etc. is moved to a position near the in-focus position while counting the amount of movement, and a necessary amount of braking is applied to the damper coil 12 while an appropriate stop position is applied. Can be brought to. Since the damper coil 12 can also serve as a sensor for detecting acceleration as described above, the damper coil 12 feeds back the current of the hollow coil 37 in response to a sudden movement to control the movement of the hollow coil itself to control the proper movement and position. You can also do When the AF circuit is not activated, the light axis unit can always bring the optical axis unit to the reference position.

[0022]

As described above, according to the present invention, the film chamber mounted on the movable portion side and the feeding mechanism thereof are provided on the fixed portion side, and the structure of the optical axis unit as the movable portion is changed to the photographing mechanism unit. Further, by directly driving the optical axis unit by the linear driving means and performing servo control, it is possible to achieve higher-speed focusing control. Moreover, if a crossing lever mechanism is used as a mechanism for smoothly guiding the optical axis unit parallel to the optical axis, the number of points where the optical axis unit itself directly contacts the fixed side can be minimized, which is further advantageous for high-speed control. become. When shooting, it is required that the photographer can focus on the subject from the moment he looks into the viewfinder without any time difference.However, the back focus control method is much heavier and more movable than the lens ring drive method, so it is called focusing speed. It's a disadvantage. However, according to the present invention, the weight of the optical axis unit can be further reduced and high-speed control can be achieved, and the concept of the film surface moving type autofocus camera can be expanded.

[Brief description of drawings]

FIG. 1 is a plan sectional view for explaining the basic structure of a film surface moving type autofocus camera according to the present invention, showing an optical axis unit as a movable part and a state of film surface movement.

FIG. 2 is a perspective view showing an embodiment of a servo mechanism of a film surface moving type autofocus camera according to the present invention.

FIG. 3 is a perspective view showing another embodiment of a linear actuator using a flat coil.

FIG. 4 is a principle diagram for explaining the operation of each linear actuator.

FIG. 5 is a circuit diagram showing a control circuit of a camera for operating the servo mechanism according to the present invention.

[Explanation of symbols]

 1 ... Optical axis unit 2 ... Interchangeable lens 3 ... Mount base 4 ... Penta prism 5 ... Mirror box 6,19 ... Mask 7,11 ... Photointerrupter 8 ... Holder 9,18 ... Slit 10 ... Encoder plate 12 ... Damper coil 13 ... Center Yoke 14 ... Cylindrical yoke 15 ... Magnet 16, 26 ... Shutter mechanism 17, 30, 55 ... Holding member 20, 25 ... Outer rail 21, 24 ... Inner rail 22 ... Aperture 27, 43 ... Main plate 28 ... Auxiliary actuator 29, 31 , 34, 35 ... Pins 32, 33 ... Cross lever 37 ... Hollow coil (moving coil) 38, 40 ... U-shaped yoke 39, 41, 60 ... Magnet (permanent magnet) 51, 56, 57 ... Yoke 52, 53 ... Flat magnet 54 ... Flat coil 58 ... Moving magnet 59 ... Fixed coil Le 64 ... driver circuit 65 ... AF CPU 66 ... AF sensor 67 ... movable position detection linear encoder

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location G03B 13/32 G03B 3/04

Claims (2)

[Claims] 1. A fixing portion mainly having an outer appearance of a camera, which has a lens mount for a photographing lens and a back lid for taking in and out a film, a finder mechanism, a distance measuring mechanism arranged at the center of an optical axis passing through the lens, An optical axis unit that has an exposure mechanism and a film opening, and is movable in the optical axis direction by a predetermined distance with respect to the camera appearance fixing section, and is arranged on the camera appearance fixing section to the left and right of the film opening. A film surface moving type autofocus camera in which a film winding side and a rewinding side film chamber and a film feeding mechanism for feeding the film are arranged, wherein the optical axis unit is a moving unit of a linear driving unit. A servo mechanism for a film surface moving type autofocus camera, which moves in the optical axis direction to perform a focusing operation according to a linear movement. 2. A lever is provided so as to cross between a side surface of the optical axis unit and the camera appearance fixing portion, and a connecting portion between the optical axis unit and the camera appearance fixing portion and an end portion of the lever, The intersecting portion of the intersecting levers is configured to be rotatable, and by providing the crossing lever mechanism on both side surfaces of the optical axis unit, the optical axis unit is held with respect to the camera appearance fixing section while holding the optical axis unit. The servo mechanism of the film surface moving type autofocus camera according to claim 1, wherein the servo mechanism is capable of moving in parallel with respect to the above.