JPS60260909A - Photographing lens driving circuit - Google Patents

Abstract

PURPOSE:To eliminate the necessity of the resetting operation after photographing, by returning again a cam member which has been moved to a prescribed position in accordance with distance information outputted from a distance measuring circuit to its initial position by supplying electricity to a movable coil member. CONSTITUTION:When a distance signal from the distance measuring circuit of a camera main body is converted into a pulse number at a control section, electricity supply of the pulse number corresponding to the detected distance is performed to the 1st movable coil member of an electromagnetic driving device 100 from a driving circuit. As a result, the movable coil member and also a notched gear plate 220 simultaneously start swinging motions and, in the clockwise forward motion, the notched gear plate 220 turns a click 227 clockwise. In the returning motion, the gear plate 220 turns another click 228 clockwise, and thus a cam member 230 is advanced clockwise by a quantity corresponding to one tooth of a ratchet 232. Therefore, a lens frame 240 is pushed linearly in the advancing direction by the cam face 231 of the cam member 230 and, when the electricity supply of the prescribed pulse is terminated and the cam member 230 is stopped from the rotating condition, a photographing lens 241 is set to its focussing position at the position where the cam member 230 is stopped.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a driving circuit for a photographing lens that is moved by an electromagnetic driving device.

[Prior art]

Conventionally, when driving a lens unit attached to a camera for focusing operations, etc., there have been two types: one that uses a motor as the driving source, and the other that uses electromagnetic force as the driving source. In the former case, as is the case with lens-shutter cameras, after shooting is complete, a motor drives the shooting lens to a close-up position when the film is advanced, and the camera takes pictures up to the position determined by the ratiometric signal at the time of shooting. There were two methods: one method used spring bias to return the lens, and the other method used in the AF system of eye-reflex cameras, where the distance measurement signal was used to change the rotation amount and direction of the motor to drive the photographic lens, but both methods used gear reduction. Since it is necessary to add a device or a device to convert rotational action to linear action, it has become difficult to incorporate it into modern cameras, which are becoming smaller and lighter.

Therefore, the latter electromagnetic drive method has come to be adopted, but as an electromagnetic drive device used for focusing operations such as photographic lenses, the gap between opposing fixed permanent magnets is narrowed (
Based on the premise of reducing the loss in the magnetic circuit,
] movable coil members are disposed within the gear knob,
The rotating or rectilinear movement of this movable coil member was used to drive a photographic lens to the in-focus position.

Therefore, there is a restriction that only two stages of control can be selected depending on the direction of the applied current, that is, from infinite distance to close range or from close range to infinite distance.

Furthermore, two movable coil members are disposed within the gear, one of which converts a cam surface that regulates the position of the photographic lens, and the other of which moves the photographic lens into contact with the cam surface. Focusing operations have also been attempted, but even in this case, control from infinite distance to close range is limited to about 6 steps, and the electromagnetic drive device has problems such as a complicated structure and a large volume. There's more C.

One of the ways to solve these functional and structural defects is to convert the signal from the distance measuring device into a pulse current, energize the moving coil member to make it swing, and install the coil outside the electromagnetic drive device. A method has been proposed in which the signal is transmitted to a cam member that moves the cam member.

One of them is a proposal in Japanese Patent Publication No. 58-43434, and according to Part 1+, the number of pulse energizations to the moving coil member and the number of steps of the cam member are adjusted appropriately. : By setting combinations, it is possible to control the photographic lens to more (focus positions).

However, the cam member must be returned to its initial position each time a photograph is completed, which makes the structure somewhat complicated, and since the cam member's stepping mechanism is provided within the electromagnetic drive device, it takes up less space. There are restrictions, and therefore, the cam surface cannot have a sufficient length, making it difficult to achieve high accuracy in the focusing position.

[Purpose of the invention]

The present invention controls pulse energization to the electromagnetic drive device based on distance information from a distance measuring circuit to set the photographic lens to the in-focus position7, and returns the photographic lens to the initial position without requiring a reset operation after photographing. The object of this invention is to provide a photographing lens drive circuit that can be restored.

[Structure of the invention]

The present invention causes a cam member rotating around an optical axis to step in one direction and rotate by energizing an electromagnetic drive device according to distance information from a drive circuit, thereby causing a photographic lens to rotate. The device is configured to set the camera to the in-focus position and return to the initial position again.In particular, it is an electromagnetic drive system in which a movable coil member is provided between the ranging circuit and the fixed permanent magnet and the opposing yoke. and a lens unit that is capable of moving the lens unit in the optical axis direction by driving the cam member step by step by the movable coil member that is reciprocated by a drive current in which distance information output from the distance measuring circuit is pulse-exchanged. In the driving device, the cam member is returned to its initial position by energizing the movable coil member again after the cam member has moved to a predetermined position based on the distance information output from the distance measuring circuit. This is achieved by a photographic lens drive circuit featuring:

〔Example〕

One embodiment according to the present invention is shown in FIGS. 1-5.

FIG. 1 shows an expanded view of a photographic lens focusing device equipped with a photographic lens driving circuit according to the present invention.
00 is attached to the lens barrel (not shown) of the camera, and furthermore, on the front side, there is a lens drive base plate 110 that holds each member constituting the focusing device, and its flange portion 111 is attached with screws 1):, The installation is leaked by doing so.

As shown in FIGS. 2 to 4, the electromagnetic drive device 100 includes a holding frame 4 integrally connected to the outer periphery of the body l, permanent magnets 5 equally distributed in the circumferential direction with respect to the ribs, and the holding frame 4. 4, and a photographing lead having a coil pattern 6a in the gap between the permanent magnet 5 and the second yoke 3. A first movable coil member 6 which is a movable coil member for drive control.
and a second movable coil member 7, which is a light quantity control movable coil member having a coil pattern 7a, are separated from each other by ring-shaped spacers lla and hinb of two sizes as shown in FIG. 4 so as not to interfere with each other. They are arranged in a layered manner. The spacers 11a and llb may be fixed or movable relative to the holding frame 4.

The first movable coil member (6 movable coil members) repeats small reciprocating rotations in response to pulse signals from a distance measuring circuit built into the camera body, and powers a member of a focusing device (described later) via a pin 10 implanted thereon. It is designed to convey.

In addition, the second movable coil member 7 is rotated back and forth when energized by the light amount control circuit, and a pair of pins 18 installed in the ribs are connected to a pair of pins 18 installed between the second yoke 3 and the main plate 15. Exposure is performed by opening and closing the shutter blade 14 about a shaft 16 as a fulcrum.

On the other hand, a notched gear plate 220 and a cam member 230 are rotatably fitted in the base of the outer periphery of the body 112 of the lens drive base plate 110 attached to the front surface of the electromagnetic drive device 100; A lens unit incorporating a photographic lens 241, ie, a lens frame 240, is slidably fitted to the inner surface.

The lens frame 240 has three pins 242 on its outer periphery.
The lens frame 240H1 of the lens drive base plate 110 is inserted through three straight grooves 113 provided in the body 112 of the lens drive base plate 110, and can slide only in the optical axis direction. Since the pin 242 is constantly pressed in the direction of the lens driving base plate 110 by the three legs 251 of the leaf spring 250 integrated with the presser metal fitting 260 attached to the front surface, the pin 242 is divided into three parts of the cam member 230. It comes into contact with the cam surface 23 and stops, thereby determining the position of the photographing lens 241.

On the other hand, the swing pin lO of the first movable coil member 6 in the electromagnetic drive device 110 passes through the elongated hole 114 provided in the flange portion 111 of the lens drive base plate 110 and engages with the bifurcated portion 221 of the notched gear plate 220. The notched gear plate 22 () that meets the flange portion 1 of the lens drive base plate 110
Through a gear 222 that rotates at a fixed position on the gear plate 11 and a gear 223 that meshes with the gear plate 223, the pin 224 also connects to a pair of pins 224 on the notched gear plate 220, and can rotate in the circumferential direction around the optical axis. It is connected to the arc gear 225 so as to be able to transmit uniform rotation.

Furthermore, elastic members (not shown) are provided at the protrusion 226 of the notched gear plate 220 and the end of the arcuate gear 225, respectively.
The cam member 23 is provided with claws 227 and 228 that are biased clockwise by
It occupies a position where it engages with a mold wheel 232 formed on the circumferential surface of 0.

Next, its effect will be explained.

When the distance signal from the distance measuring circuit of the camera body shown in FIG. 5 is converted into a pulse number in the control section, the drive circuit sends a pulse corresponding to the detected distance to the first movable coil member 6 of the electromagnetic drive device 100. A number of energizations are performed.

As a result, the movable coil member 6 and the notched gear plate 220 simultaneously undergo a rocking motion, and the mold 227 is moved during the forward movement in the clockwise direction, while the mold 227 is moved during the backward movement in the counterclockwise direction. 228 in the clockwise direction, and the cam member 230 is moved clockwise by steps corresponding to one tooth of the die wheel 232.

Therefore, the lens frame 240 is attached to the cam surface 2 of the cam member 230.
31, and when the cam member 2:30 stops rotating after a predetermined pulse energization ends, the photographing lens 24+ is set at the focusing position at that position.

In this state, the control section energizes the second movable coil member 7 for a time appropriate to the exposure amount based on a signal from the exposure section, and the shutter blade 14 opens and closes. Pulse energization starts to be applied to the movable coil member 6, and the cam member 230 starts rotating clockwise again.

In this case, the number of pulses for re-energizing the first movable coil member 6 is also determined based on the distance signal from the distance measuring circuit described above.
- Move the cam surface 2:31 of the cam member 230 from its initial position, that is, the highest position on the cam surface 23].
The number of pulses sufficient to complete a cycle, that is, one-third rotation in this embodiment, is energized by the control section to the drive circuit.

As described above, according to the photographic lens drive circuit of the present invention, both the function of controlling the photographic lens to the in-focus position and the function of returning the photographic lens to its initial position after photographing are performed by pulse energization from the drive circuit. It can be driven by a cam member that is stepped in the same direction and rotates endlessly.

[There is no need for a complicated charging mechanism to reset the photographic lens, and the cam member rotates only in the same direction to drive the photographic lens in one direction, making it possible to set the focus position with high precision.

Note that in this embodiment, as described above, the first movable coil member moves forward with each pulse of energization from the drive circuit.
Since it has a reciprocating structure in which the photographic lens is driven two steps in a backward motion, the current direction of energization when returning the photographic lens to its initial position is the final pulse when the photographic lens is controlled to the in-focus position. It is sufficient if the current direction is started in the opposite direction to the signal energization. For the same reason, if the first movable coil member has a single-feed configuration in which the photographing lens is driven one step only during one of its forward or backward movements, the current flow starts in the same direction. It will be necessary to do so.

〔Effect of the invention〕

The present invention eliminates the need for a reset mechanism for the focusing device to return the photographing lens to its initial position after shooting, thus simplifying the mechanism of the focusing device and useful for improving focusing function and accuracy. Take a picture 210, □Oh. 8. More. （・：

[Brief explanation of drawings]

FIG. 1 is an exploded perspective view of a focusing device equipped with a photographing lens drive circuit according to the present invention. 2 to 4 are plan, cross-sectional, and perspective views of the electromagnetic drive device used in the device. FIG. 5 is a block circuit diagram. 100... Electromagnetic drive device 10... Swinging bin 11 (1
... Lens drive base plate 220 ... Notched gear plate 225
...Arc-shaped gears 227, 228...Claws 230...
・Cam part paulownia 232...windmill 240...lens frame 2
41... Photographing lens 250... Leaf spring 260...
・Presser metal agent Patent attorney No 1) Father-in-law Figure 2 Figure 3

Claims (1)

[Scope of Claims] (]) An electromagnetic drive device having a moving coil member provided between a distance measuring path and a yoke facing a fixed permanent magnet, and distance information outputted from the distance measuring circuit. In the lens driving device, the lens unit can be moved in the optical axis direction by driving the cam member step by step by the movable coil member that reciprocates using a drive current obtained by pulse-converting the distance information outputted from the distance measuring circuit. 1. A photographing lens driving circuit, wherein the cam member is returned to its initial position by energizing the movable coil member again after the cam member has moved to a predetermined position. (2) The photographing lens drive according to claim 1, characterized in that the cam member returns to the initial position by a pulse number that is a predetermined pulse number minus a pulse number based on distance information. circuit. (3) The lens according to claim 1 or 2, wherein the current direction when energizing the movable coil member again is opposite to the energization direction during the previous final drive. drive circuit. (4) The lens drive according to claim 1 or 2, wherein the current direction when the movable coil member is energized again is the same direction as the energization direction during the previous final drive. circuit.