JP3129818B2 - Lens position detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lens position detecting device for a camera in which a lens barrel moves forward and backward.

[0002]

2. Description of the Related Art Variable focus cameras include a camera with a zoom function in which the focal length of a photographing lens changes continuously, and a two-focal point switchable between a short focal length for wide-angle photographing and a long focal length for telephoto photographing. Focus cameras are known, but in most cases, the focal length is changed by moving the photographing lens back and forth.

In recent years, even with a single focus camera, a camera has been developed, which is designed to be thinner by extending a photographic lens forward of the camera when in use and retracting it into the camera body when not in use.

In such a camera in which the photographing lens is moved forward and backward, a lens position detection switch is required to control the position of the lens. Also, if the lens is stopped due to the power being turned off while the lens is being moved, or the battery being removed to replace the battery, if the position of the lens is unknown, then the power will be turned on or the battery will be replaced. When the malfunction is corrected, the movement of the lens cannot be controlled. For that purpose, it is necessary to detect the position of the lens. Further, when the position of the lens can be detected, the lens can be advanced to the photographing preparation position before photographing.

Therefore, as a method of retaining lens position information even when the power is turned off, there is known a method of detecting lens position information and storing the information in a memory in which the written contents are not erased even when the power is turned off. Expensive. Therefore, as a simple and inexpensive part configuration, a contact piece is attached to the lens barrel, and a slider attached to the camera body is brought into contact with the contact piece to electrically detect the position of the lens barrel. Although a detection method is also known, it may be difficult to employ this method in a helicoid lens forward / rearward movement mechanism described later.

As a mechanism for moving the photographing lens back and forth, there is known a system in which a lens barrel is fitted to a guide shaft extending in the optical axis direction provided on the camera body and moved.
If the length of the lens barrel in the axial direction is shortened to make the camera thinner, the fitting portion between the lens barrel and the guide shaft becomes shorter, which makes it difficult to always maintain the straightness of the lens barrel. Verticality cannot be secured.

Therefore, a helicoid type lens forward / backward mechanism is known as a lens forward / backward mechanism which can secure the straightness of the lens barrel and is effective for downsizing the camera. A thread groove is provided on one of the inner and outer peripheral surfaces of the cylinder. There are a single helicoid method with a cut and a double helicoid method with a thread groove on both the inner and outer peripheral surfaces. The latter double helicoid method is an intermediate helicoid that has a double helicoid that meshes on both sides with a screw groove cut on the inner circumference of the fixed barrel of the camera body and a screw groove cut on the outer circumference of the lens barrel that moves forward and backward inside the fixed barrel. When the intermediate helicoid is rotated from the outside using the (intermediate cylinder), the intermediate helicoid advances while rotating, and the lens barrel only moves straight inside the intermediate helicoid because the rotation is prevented. By setting the pitch of the inner circumferential groove of the intermediate helicoid to be larger than the pitch of the outer circumferential groove, the amount of extension of the lens barrel can be increased, which is an extremely effective method for making the camera thinner and smaller.

[0008]

However, in a camera employing such a double helicoid type lens forward / backward movement mechanism, a contact piece is provided on a lens barrel in order to use an intermediate helicoid (intermediate barrel), and the camera body is provided. If a slider is provided on the side and the above-mentioned lens position detection method of detecting the position information of the photographing lens by contact between them is adopted, the number of components is large, the mechanism becomes complicated, and it is very difficult to realize.

Therefore, it is conceivable to turn on / off the lens position detection switch using the rotation of the intermediate helicoid. As one of the methods, a projection is provided on the intermediate helicoid, and a lever is operated by the projection. A method of turning on / off the position detection switch can be considered. However, in this method, when the lens is moved, the intermediate helicoid moves forward and backward, so that the lever and the thread groove on the outer peripheral surface of the intermediate helicoid interfere with each other. There is a problem that a space is needed for the protrusion to move, which is not preferable for downsizing the camera.

The present invention has been made in view of the above points, and in the above-described double helicoid type lens moving device, the information on the lens position is accurately and quickly detected by a mechanism having as few components as possible and having a simple structure. The purpose is to do so.

[0011]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention comprises a lens barrel for holding a taking lens and an inner helicoid coupled with a helicoid, and an outer surface which is helicoidally coupled with a fixed cylinder fixed to a camera body. A helicoid, an intermediate body having a gear portion, and a pinion gear for transmitting rotation from a drive source provided in the camera body, meshing the pinion gear and the gear portion of the intermediate body, and To the intermediate cylinder, the intermediate cylinder is moved in the optical axis direction relative to the fixed cylinder based on the coupling between the fixed cylinder and the outer helicoid of the intermediate cylinder, and the lens barrel and the intermediate cylinder are moved. In a lens moving device that moves the lens barrel in the optical axis direction with respect to the intermediate cylinder based on coupling with an inner helicoid, a gear portion provided on an outer periphery of the intermediate cylinder has a part. A moving member that forms a notched defect portion and that is displaced by climbing from the defect portion to a non-defective portion by rotation of the intermediate cylinder and movement in the optical axis direction, and a switch that is turned on / off by displacement of the moving member; Is provided on the main body.

[0012]

In a camera having a double helicoid type lens moving device using an intermediate cylinder having helicoids on the inner surface and the outer surface, a moving member attached to the main body has a missing portion formed in a part of a gear provided around the intermediate cylinder. By operating on the switch by getting on and off the defective portion, on / off information can be generated to quickly and accurately detect the lens position.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.

FIG. 1 is a partially cutaway front view of a camera provided with a lens position detecting device according to an embodiment of the present invention.

At the front of the camera, a lens barrel 1 having a taking lens 4, a window 30 for flash emission, a finder window 31,
A light emitting and receiving window 32 for autofocus, a lamp 33 for displaying a self-timer, and an AE light receiving window 34 are arranged. Although not shown, a power switch and a release button are provided on the upper surface of the camera.

FIG. 2 is a sectional view showing a main part of the lens moving device of the present invention, FIGS. 3 (a) and 3 (b) are diagrams showing a main part of the lens position detecting device, and FIG. 4 is a perspective view of the intermediate helicoid. FIG.

The lens barrel 1 is connected to an intermediate cylinder, ie, an intermediate helicoid 3 provided so as to surround the outer periphery thereof, by a helicoid consisting of several precision screw grooves. The intermediate helicoid 3 is also helicoidally connected to the fixed barrel 2 fixed to the camera body by a screw groove provided on the outer peripheral surface. The helicoid provided on the inner and outer surfaces of the intermediate helicoid 3 is called a double helicoid. The intermediate helicoid 3 transmits the driving force of the driving motor 8 through an intermediate gear such as a pinion gear 13 to a driving gear 9 described later.
, The lens barrel 1 rotates in the fixed barrel 2 and moves forward and backward, but since the lens barrel 1 cannot be rotated by the rectilinear guide plate 12, it only moves forward and backward in the intermediate helicoid 3. I have.

Referring back to FIG. 1, a four-blade rotating blade 21 is attached to the lower part of the front of the camera body so as to be rotated by the drive motor 8 of the camera. The rotation speed is the same as that of the motor pinion 13. A photo interrupter 22 is attached so as to sandwich the rotating blade 21, and the rotating blade 21
When rotated, the photo interrupter 22 outputs four pulse signals. The count value of this pulse signal becomes information on the moving distance of the photographing lens 4. The rotating blades 21 and the photo interrupter 22 constitute pulse generating means.

With such a double helicoid type lens forward / backward movement mechanism, the lens barrel 1 and thus the photographing lens 4 move forward by a certain distance from the most retracted position, that is, the retracted position with respect to the camera body, and go through the reference position to the photographing preparation position To the close-up position, which is the most protruding position, and can retreat from that position. When the lens barrel 1 is at the photographing preparation position, the photographing lens 4 starts from the photographing preparation position and uses the pulse signal output from the photo interrupter 22 according to the autofocus sequence.
The lens can be moved to a certain lens position to perform focusing.

As shown in FIGS. 3A, 3B and 4, on the outer periphery of the intermediate helicoid 3, there is provided a drive gear 9 which meshes with a pinion 13 connected to a drive motor 8. The drive gear 9 has a narrow portion (deleted portion) 10 ′ in which the tooth width is narrowed by being cut out over a certain length in the circumferential direction, and a cam portion (remaining wide) in which the tooth width remains wide. Non-defective portion) 10 and the cam portion 10
Steps 14 and 15 are formed between the first and second narrow portions 10 ′. In other words, the portion between the step portion 14 and the step portion 15 is a wide portion and forms the cam portion 10 (FIG. 4). The cam or non-defective portion 10 acts not only as a toothed gear but also as a cam. As shown in FIG. 4, the pinion gear 13 has a long tooth width in the axial direction, and has a size that can sufficiently cope with the movement of the intermediate helicoid 3 in the optical axis direction.

A switch 7 operated by the cam portion 10 is provided near the drive gear 9 of the intermediate helicoid 3,
The entire switch 7 can be moved in the circumferential direction with respect to the fixed barrel 2 for fine adjustment of the mounting position.
The switch 7 includes a fixed contact 5 attached to a substrate 16 provided on a base plate 24 (shown in FIG. 2) fixed to the camera body,
A signal corresponding to the position of the intermediate helicoid 3 is extracted from the fixed contact 5. The sliding piece 6 is a base plate 24
Moving member 18 rotatably fitted on a shaft 17 fixed to the
That is, one end is fixed to the follower plate 18 and the other end is movably in contact with the upper surface of the fixed contact 5. Follower plate 1
A spring 19 (see FIG. 2) is provided between the shaft 8 and the substrate 16 so as to be fitted on the shaft 17, and the follower plate 18 is urged clockwise by the spring 19 so that its end face 2
0 is elastically pressed against the cam portion 10 of the intermediate helicoid 3. When the protruding piece 26 fixed to the follower plate 18 comes into contact with the stopper pin 25 fixed to the base plate 24 (shown in FIG. 3A), the follower plate 18 further rotates clockwise (FIG. 3A). At).

Next, the operation of the switch 7 will be described with reference to FIGS. 3 (a) and 3 (b).

When the power switch is turned on during photographing, the drive motor 8 rotates, and the intermediate helicoid 3 is pointed by an arrow A.
Rotate in the direction of. As a result, the lens barrel 1 moves forward, and the photographing lens 4 moves in the optical axis direction (perpendicular to the drawing). Lens barrel 1
3A, the end surface 20 of the follower plate 18 of the switch 7 contacts the step 14 of the drive gear 9 on the outer periphery of the intermediate helicoid 3 at the position shown in FIG. At this time, the sliding contact piece 6 of the switch 7 and the fixed contact 5
Are off because they do not touch.

When the intermediate helicoid 3 further rotates in the direction A and the lens barrel 1 moves forward, the step 14 of the drive gear 9 pushes the side surface 20 of the follower plate 18, and the follower plate 18 3B, the movable member, that is, the side surface 23 of the follower plate 18 rides on the cam portion (non-deficient portion) 10 as shown in FIG. The contact is made over at least two or more teeth, and slides smoothly without generating vibration. In this state, the sliding contact piece 6 of the switch 7 comes into contact with the fixed contact 5 to be turned on. This position where the switch is turned on is the reference position of the taking lens. While the intermediate helicoid 3 is rotating and the lens barrel 1 is further advanced, the cam portion 10 has a constant length, so that this ON state is continued. When the number of pulse signals output from the photo-interrupter 22 is counted a predetermined number (for example, 20 pulses), the drive motor 8 and the lens barrel 1 are stopped. This position is the photographing preparation position.

When the intermediate helicoid 3 rotates in the direction opposite to the direction A, the follower plate 18 moves from the state shown in FIG.
Returning to the state of (a), at this time, the follower plate 18 of the switch 7 is urged clockwise by the spring 19, so that the switch 7 returns to the off state.

Next, the lens movement control using the signal of the switch 7 will be described.

When the power switch of the camera is turned on, the CPU, which is a part of the control device inside the camera, judges whether the switch 7 is on or off. As a result, (1) when the switch 7 is off, the lens barrel 1 is at a position before reaching the reference position. (2) When the switch 7 is on The lens barrel 1 is at a position extended from the reference position.

Therefore, in the state (1) (OFF), the lens barrel 1 is advanced until the switch 7 changes from OFF to ON, and after the lens barrel 1 turns from OFF to ON (this position is the reference position). The CPU starts counting the number of pulse signals output from the photo-interrupter 22, and when counting twenty, brakes the drive motor 8 and stops the lens barrel 1. This position is the photographing preparation position. After that, the user presses the release button to start a series of shooting operations such as distance measurement, photometry, and shutter drive.

On the other hand, in the above state (2) (on), the drive motor 8 is rotated in the reverse direction to retract the lens barrel 1 once toward the retracted side, and when the switch 7 changes from on to off (this state). The lens barrel 1 is stopped (the position is the reference position). Thereafter, the drive motor 8 is rotated forward, the lens barrel 1 is moved forward, and when the switch 7 changes from off to on again (this position is the reference position), counting of pulse signals is started.
By counting 0, the drive motor 8 is braked, and the lens barrel 1 is stopped. This position is the photographing preparation position. Thereafter, a series of shooting operations is started.

As described above, the reference position of the lens barrel 1 can be known from the on / off state of the switch 7, and the lens barrel 1 can be determined by the number of pulse signals output from the photointerrupter 22.
You can know the exact location of.

When the release button is pressed lightly one step at the beginning of a series of photographing operations, distance measurement and photometry are performed, and the photographing lens 4 is controlled in 24 positions based on the distance measurement information.

In the above embodiment, the cam switch is constituted by the fixed contact 5 provided on the substrate 16 and the sliding contact piece 6 which is rotated by the cam 10 with the rotation of the intermediate helicoid 3. May be configured by a spring switch that turns on when contacted with and turns off when the cam portion 10 separates.

[0033]

As described above, according to the present invention,
In a double helicoid lens moving device using an intermediate helicoid (intermediate cylinder) having helicoids on the inner surface and the outer surface, a part of a gear portion on an outer periphery of the intermediate cylinder is cut out to form a missing portion, and rotation and light of the intermediate cylinder are controlled. A moving member which is displaced by moving from a defective portion to a non-defective portion by moving in the axial direction is provided, and the position of the lens barrel can be detected by outputting on / off information by a switch displaced by the moving member.
Therefore, even in the double helicoid type lens moving device, an extremely excellent effect that the lens position can be detected by a mechanism having a very simple structure can be obtained.

[Brief description of the drawings]

FIG. 1 is a front view of a camera provided with a lens position detecting device according to the present invention, showing a part of the camera cut away.

FIG. 2 is a sectional view showing a main part of a lens moving mechanism of the lens position detecting device according to the present invention.

FIG. 3A is a front view showing a main part of the lens position detecting device according to the present invention in a state immediately before a switch is turned on.
(B) is a front view showing a main part of the lens position detecting device in a state immediately after a switch is turned on.

FIG. 4 is a perspective view of an intermediate helicoid, that is, an intermediate cylinder used in the lens position detecting device of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Lens barrel 2 Fixed torso 3 Intermediate helicoid (intermediate torso) 4 Shooting lens 5 Fixed contact 6 Sliding contact piece 7 Switch 8 Drive motor 9 Drive gear 10 Cam part (non-deletion part) 10 'Narrow part (deletion part) 12 Straight guide plate 13 Pinion gear 14, 15 Step 16 Substrate 17 Shaft 18 Follower plate 19 Spring 20 Side surface 21 AF propeller 22 Photo interrupter 30 Flash 31 Finder window 32 Auto focus window 33 Self-timer lamp 34 AE light receiving window

Claims (1)

(57) [Claims] An intermediate cylinder having an inner helicoid coupled to a lens barrel holding a taking lens and a helicoid, an outer helicoid coupled to a fixed cylinder fixed to the camera body, an outer helicoid coupled to the helicoid, and a gear portion, and a camera body. A pinion gear for transmitting rotation from a drive source, meshing the pinion gear with a gear portion of the intermediate cylinder, and transmitting the rotation of the pinion gear to the intermediate cylinder, whereby the fixed cylinder and the intermediate cylinder are rotated. The intermediate cylinder is moved in the optical axis direction with respect to the fixed cylinder based on the coupling with the outer helicoid, and the lens barrel is moved relative to the intermediate cylinder based on the coupling between the lens barrel and the inner helicoid of the intermediate cylinder. In the lens moving device that moves in the optical axis direction, a partially cutout portion is formed in a gear portion provided on the outer periphery of the intermediate cylinder, and the rotation of the intermediate cylinder and the optical axis direction are performed. A lens position detecting device for a camera, comprising: a moving member which is displaced by climbing from the defective portion to a non-defective portion by moving in a direction, and a switch which is turned on / off by the displacement of the moving member.