JPH043858B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an automatic focusing camera that moves a photographic lens to an in-focus position based on the distance measurement result of a distance measurement device that outputs object distance information. be.

[Background technology]

As an automatic focus adjustment device, a stage cam having multiple stages corresponding to multiple focal positions is arranged, and a predetermined stage of the stage cam is selected according to the distance measurement result to the subject. It can be configured such that the photographing lens is moved from the reference position in the optical axis direction and pressed against it.

By the way, in an automatic focus adjustment mechanism in which the taking lens moves from the near-distance side as its home position and comes into contact with a stage cam of the lens positioning member, when the subject is at a far distance, the lens drive that moves the taking lens Since it takes a long time for the member and the lens positioning member, which determines the focusing position of the photographic lens, to rotate together as one unit via the friction engagement member, the lens drive member gains inertia, making it difficult to engage with the friction engagement member. Even after the release, the lens driving member can reliably bring the guide pin into contact with the stepped cam.

However, when the subject is at a short distance, the time for the lens driving member and lens positioning member to rotate as a unit via the friction engagement member is short, so the lens drive member does not have sufficient inertia, and the friction engagement After disengaging from the lens drive member, the force with which the lens drive member presses the guide pin is weak, and the lens drive member cannot be brought into reliable contact with the stepped cam.

In fact, since the position of the photographic lens is determined with an accuracy of several tens of microns, the above problem cannot be ignored.

[Purpose of the invention]

An object of the present invention is to provide an autofocus camera that solves the above-mentioned problems.

[Structure of the invention]

To this end, the present invention provides a photographing lens having a guide pin, and a lens driving member having a grooved cam passing through the guide pin and rotating around an optical axis to move the photographing lens in the optical axis direction. , a lens positioning member that rotates around the optical axis and has a stepped cam that comes into contact with the guide pin in order to restrict the movement stop position of the photographic lens in the optical axis direction; and a friction member that rotates the lens driving member and the lens positioning member. a friction engagement member to be engaged; a locking member to stop the lens positioning member; a motor to drive the lens drive member; The lens driving member and the lens positioning member are rotated as a unit via the friction engagement member, and the locking member is actuated based on object distance measurement information output from the distance measurement device to move the lens positioning member. Then, as only the lens driving member continues to rotate, the friction engagement between the lens driving member and the lens positioning member is released, and the guide pin of the photographic lens is connected to the stepped cam of the lens positioning member. and control means for stopping energization of the motor after the motor is brought into contact, and the control means is configured to control the lens positioning member based on the time required from the start of energization to the motor to the stop of the lens positioning member. In other words, the length of time for rotating only the lens driving member is set.

〔Example〕

Examples of the present invention will be described below. 1st
The figure shows an exploded perspective view of the mechanism of the automatic focus adjustment device, and this mechanism is incorporated into the lens barrel of the camera as a unit.

Reference numeral 10 denotes an electromagnetic unit fixed within the lens barrel, and inside it, in addition to a first movable coil member (not shown) that controls the exposure amount of the photographic lens 50, there is also a second movable coil member (not shown) in which a regulating pin 11 (described later) is installed. Moving coil member 12
is provided so that it can rotate around the optical axis.

A lens guide 20 is attached to the front surface of the optical axis of the electromagnetic unit 10, and is composed of a flange part 21 and a cylindrical part 26. A printed board 22 having a detection pattern for feedback and a stop pawl 24 as a locking member biased clockwise by a tension spring 23 are pivotally mounted. This stop claw 24
The rotation in the clockwise direction is restricted by the locking action of the regulating pin 11 passing through the flange portion 21. On the other hand, the cylindrical portion 26 has three linear grooves 27 formed on its circumferential surface at equal angles. Guide pins 51 of the photographing lens 50 formed at intervals in the optical axis direction and slidably fitted to the inner periphery are guided by the straight grooves 27, thereby making the photographing lens 50 movable in the optical axis direction. There is.

40 is a lens driving member rotatably fitted to the outer periphery of the cylindrical portion 26 of the lens guide 20;
Three diagonal cam grooves 42 provided in the cylindrical portion 41
The guide pin 51 of the photographic lens 50 is inserted through the guide pin 51 and cooperates with the rectilinear groove 27 to regulate the position of the photographic lens 50 in the optical axis direction.

The lens drive member 40 also includes a pinion 6 that meshes with a gear portion 47 provided on the flange portion 46.
1 is rotated by the motor 60, which enables clockwise rotation from the illustrated position and reverse rotation for return.

Reference numeral 30 denotes a lens positioning member that is fitted onto the cylindrical portion 41 of the lens driving member 40. A step cam 31 consisting of a plurality of stages corresponding to a plurality of focusing positions is formed on the end surface of the lens positioning member. By bringing the guide pin 51 of the photographing lens 50 into contact with the lens, the photographing lens 50 is set at a predetermined focusing position. Note that three stepped cams 31 are provided corresponding to the number of guide pins 51.

Lens positioning member 30 and lens driving member 40
means the pressing spring 3 as a friction engagement member attached to the protrusion 32 of the lens positioning member 30.
3 is connected to the flange portion 4 of the lens driving member 40.
They are integrated by engaging with a V-shaped notch 48 provided in the section 6, and are simultaneously rotated by the motor 60.

A contact piece 35 is attached to the other protrusion 34 of the lens positioning member 30, and by sliding the circuit pattern on the printed board 22 of the lens guide 20 as the lens driving member 40 rotates, the photographing lens is moved. A pulse signal corresponding to a movement amount of 50 is sent out. Further, other portions are provided with pawl teeth 36 to engage with the stop pawl 24.

The lens driving member 40 and the lens positioning member 30 are sandwiched between the front surface of the flange portion 21 of the lens guide 20 and the back surface of a presser plate 70 attached via the three pillars 71 of the flange portion 21. , can be rotated freely.

Now, when the distance measuring device detects the distance to the subject in conjunction with the operation of operating the release of the camera, the focusing operation of the photographic lens 50 is started. This operation will be explained with reference to FIGS. 2 and 3.

First, as shown in FIG. 2A, the stepped cam 31 of the lens positioning member 30 and the grooved cam 42 of the lens driving member 40 are substantially parallel to each other, although they are curved with a slight interval between them. At this time, the guide pin 51 of the photographic lens 50 is located on the lower end side of the grooved cam 42 in the figure, that is, on the front end side of the optical axis.

Next, when a positive current is applied to the second movable coil member 12, a clockwise movement torque is applied to the regulating pin 11, and the stop pawl 24 is inadvertently engaged with the pawl 36 of the lens positioning member 30. release it if it is. That is, first of all, the stop claw 24
is unlocked.

Next, with a slight delay from the operation of the regulating pin 11, the motor 60 starts normal rotation, and simultaneously rotates the lens driving member 40 and the lens positioning member 30 clockwise (in the direction of arrow A in FIG. 2).

Along with this operation, the photographing lens 50 recedes linearly, and at the same time, the contact piece 35 starts sliding against the printed board 22, and the number of rotations of the photographing lens 50 corresponds to the amount of rotation, that is, the amount of movement in the optical axis direction. pulses are sent out from the printed board 22.

When the number of pulses matches the number of pulses set in advance in accordance with the distance measurement result, the motor 60
forward rotation stops.

Next, a little later than the stop of this motor 60,
A negative current is applied to the second movable coil member 12, whereby the regulating pin 11 is rotated counterclockwise, the stop pawl 24 engages with the pawl teeth 36, and the rotation of the lens positioning member 30 is locked. Ru.

As described above, the guide pin 51 is guided to the front spaced from any selected stage of the stage cam 31 of the lens positioning member 30 (the stage corresponding to the distance measurement result). Reference numeral 51a in FIG. 2b indicates the position of the guide pin 51. This completes the selection operation of selecting a specific stage corresponding to the distance measurement result of the stage cam 31.

Next, with a slight delay from the locking of the lens positioning member 30, the motor 60 starts rotating forward again.
The lens drive member 40 further rotates clockwise.
At this time, the pressing spring 33 attached to the lens positioning member 30 comes off from the notch 48 of the lens driving member 40, and the lens driving member 40 rotates independently.

With this normal rotation of the lens driving member 40 again,
The guide pin 51 of the photographic lens 50, which was held at a position apart from the stepped cam 31, is shown in FIG.
As shown by reference numeral 51b, the photographic lens 50 is pressed against the step in front of it, and the photographic lens 50 is set at the optical axis position corresponding to the distance measurement result. Thereafter, when a predetermined period of time has elapsed, the motor 60 stops normal rotation.

In this way, the photographic lens 50 is focused on the subject, and exposure is then performed by the operation of the first movable coil member (not shown), completing the shutter operation.

When this shutter operation is completed, a positive current flows through the second movable coil member 12 again, and the regulating pin 11
moves clockwise, and the stop pawl 24 engages the pawl teeth 36.
The lock is released.

Next, the motor 60 starts reverse rotation, first rotating the lens driving member 40 counterclockwise to linearly advance the photographing lens 50, and the notch 48 engages with the pressing spring 33 of the lens positioning member 30. When reaching the position, the lens positioning member 30
The motor 60 further rotates counterclockwise to return to its initial state, and then the motor 60 stops.

By the way, the distance that the guide pin 51 moves to the front of a predetermined stage of the stage cam 31 is a length that corresponds to the distance to the subject. For example, if the distance to the subject is long, it is necessary to send out many pulses. Therefore, the moving distance of the guide pin 51 becomes long.On the other hand, if the distance to the subject is short, fewer pulses need to be sent out, so the moving distance of the guide pin 51 can be shortened.

Therefore, the time required to select a predetermined stage of the stage cam changes depending on the distance measurement result, and this cannot be avoided.

If this is directly reflected in the time for automatic focus adjustment, camera shake and other problems will occur, especially if the time is long, but the present invention aims to solve such problems.

Therefore, in the present invention, the time period during which the guide pin 51 is pressed against the selected stage after the stage selection operation is changed in the opposite manner to the above, depending on the distance measurement result. For example, as shown in FIG. 3, when the number of pulses from the printed board 22 is small, such as five, the selection time is Ta.
If the pressing time at that time is Tb, as shown in Figure 4, if there are 8 pulses, the selected time will be Ta'(>Ta), so the pressing time will be Tb'(<Tb). , "Ta+Tb≒Ta+Tb'", and based on the selection time required from the start of energization to the motor 60 until the stop of the lens positioning member 30,
The longer the selection time, the shorter the pressing time, and the shorter the selection time, the longer the pressing time for rotating only the lens drive member 40 was set.

In this way, when the selection time is short, the pressing time is set long, so the lens drive member 40
has sufficient force to press the guide pin 51 and can reliably contact the step cam 31.

In addition, if the selection time is long, there is no need to increase the pressing time, so it is set short, so even though the guide pin 51 is firmly in contact with the step cam 30, the motor is not energized for an unnecessarily long time. This prevents power consumption from being wasted.

In addition, as a result, the overall focusing time from the start of energization to the motor, including the selection time and pressing time, is almost constant, so the overall focusing time is almost constant regardless of the subject distance measurement, and after the release The time it takes for the shutter to fire is also almost constant, allowing the photographer to know when the shutter will fire regardless of the shooting distance, and eliminating the possibility of camera shake or missed shutter shots.

The camera prototyped by the inventor has distance measurement results of 13
It was divided into stages, and the number of stages of the stage cam was set to 13. If the number of pulses obtained from the distance measurement results is in the range of 1 to 6, the pressing time of the guide pin 51 is
70ms, and when the number of pulses is in the range of 7 to 13, the pressing time is set to 50ms, but due to manufacturing and other reasons, there are only two types of pressing times, and the pressing time is set for each number of pulses. Of course, it is possible to set each of them.

In the above embodiment, the selection mechanism that selects the stage of the stage cam according to the distance measurement result and the pressing mechanism that presses the photographing lens against the selected stage of the stage cam are as follows:
The lens guide 20, the lens positioning member 30, the lens driving member 40, the guide pin 51 of the photographing lens 50, and the pressing spring 33 are commonly configured, and the lens positioning member 30 and the lens driving member 40 are integrated in the step selection operation. The lens positioning member 3 is moved during the pressing operation to the selected stage.
0 is locked and only the lens driving member 40 is moved, but the present invention is not limited to this, and the selection mechanism and the pressing mechanism may be configured as completely independent mechanisms.

〔Effect of the invention〕

From the above, according to the present invention, based on the selection time required from the start of energization to the motor to the stop of the lens positioning member, the longer the selection time is, the shorter the pressing time is, and the shorter the selection time is, the longer the pressing time is set to rotate only the lens driving member. Therefore, it has the following advantages.

When the selection time is short, the pressing time becomes long and the guide pin reliably contacts the stepped cam.

Conversely, if the selection time is long, the pressing time is shortened, and even though the guide pin is in reliable contact with the step cam, the motor is not energized for an unnecessarily long time, thereby preventing waste of power.

The total focusing time, which is the sum of the selection time and the pressing time, is almost constant, and the time from release to shutter release is almost constant, so there is no chance of camera shake or missed shutter shots.

[Brief explanation of drawings]

Figure 1 is an exploded perspective view of the automatic focus adjustment device;
Figures a and b are explanatory diagrams of the operations of the main parts, and Figures 3 and 4 are timing charts of the focusing operation.

Claims (1)

[Scope of Claims] 1. A photographic lens having a guide pin; and a lens drive member having a grooved cam passing through the guide pin and rotating around an optical axis to move the photographic lens in the optical axis direction. , a lens positioning member that rotates around the optical axis and has a step cam that comes into contact with the guide pin to regulate a stop position of the photographing lens in the optical axis direction; and a friction member that rotates the lens driving member and the lens positioning member. a friction engagement member for engaging; a locking member for stopping the lens positioning member; a motor for driving the lens drive member; The lens driving member and the lens positioning member are rotated as a unit via the friction engagement member, and the locking member is actuated based on object distance measurement information output from the distance measurement device to move the lens positioning member. With the subsequent rotation of only the lens driving member,
Control means for stopping energization of the motor after releasing the friction engagement between the lens driving member and the lens positioning member and bringing the guide pin of the photographing lens into contact with the stepped cam of the lens positioning member. and the control means sets a time period for rotating only the lens driving member, such that the longer the time is, the shorter the time is, and the shorter the time is, the longer the time is for rotating only the lens driving member, based on the time required from the start of energization to the motor to the stop of the lens positioning member. Features an autofocus camera.