JPH0381138B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an interchangeable lens camera system having an automatic focus detection function, and more particularly to a power sustaining method for the system.

In recent years, the development of cameras with automatic focus detection function has become active, and it is already well known that many types of AF (autofocus) cameras with non-interchangeable lenses have appeared on the market. Interchangeable lenses have also gone beyond prototype announcements to commercially available products. In all of these announced lenses, the so-called in-lens autofocus (LAF) is equipped with everything including a focus detector, a motor as a drive source, and a battery for power supply inside the mirror body of the interchangeable lens. ) method is adopted. This LAF method allows the use of a conventional camera body, but has the disadvantage that the interchangeable lens body is extremely large, impairing operability. On the other hand, when looking at camera bodies, even among interchangeable lens cameras, cameras with exposure meters and cameras with electronic shutters are popular, and many have a power battery inside the camera body. Furthermore, there are many devices that are built into the camera body, such as automatic winding devices, and devices that are attached as accessories to the camera body. Therefore, when using the above-mentioned LAF type interchangeable lens, it becomes a so-called dual power system with power batteries on both the lens side and the camera body side, which is extremely inefficient in terms of energy efficiency.

SUMMARY OF THE INVENTION The present invention aims to solve the above-mentioned drawbacks, reduce the size of the interchangeable lens body, and provide a power connection method for a single-lens reflex autofocus camera system that is energy efficient and electrically stable. shall be.

In order to achieve the above object, the present invention provides the following steps when connecting the motor provided inside the interchangeable lens body to a power source outside the mirror body in order to move the photographing lens in the optical axis direction and adjust the focus. A connector dedicated to the power supply line for driving the motor is provided in the lens mount of the interchangeable lens, and the motor is connected to the power supply through this connector, so that at least a closed loop independent of the focus detection control circuit is constructed. This is a characteristic feature. Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.

FIG. 1 is a sectional view for explaining an embodiment of the present invention, in which fixed lenses 1, 2, and 3 and movable lenses 4, 5, and 6, which constitute a photographing lens optical system, are respectively arranged in an interchangeable lens body A. A fixed lens barrel 7 and a movable lens barrel 8 are provided, and the movable lens barrel 8 is screwed and held by a helicoid screw 7' of the fixed lens barrel 7. Further, a gear 8' with a wide tooth width is provided on the outer periphery of the movable lens barrel 8, and meshes with a small gear 10 provided on the drive shaft of a reversible motor 9 fixedly installed in the fixed lens barrel 7.
The rotational driving force rotates the movable lens barrel 8 via the gears 10 and 8', and the movable lens barrel 8 is further rotated and moved in the optical axis direction in accordance with the lead of the helicoid 7' that is screwed together. Reference numeral 11 denotes a motor drive circuit for driving the motor 9 in forward and reverse rotation, and is configured to switch the direction of rotation of the motor 9 by a transistor switching circuit as shown in FIG. This second figure will be described in detail later.

At the right end of the fixed lens barrel 7, there is a camera body B (including the replaceable viewfinder part B') and a photographic lens A.
A bayonet type lens mount 12 is fixedly installed to detachably hold the lens mount 1.
Connector contact 13A, 1 provided on the inner surface of 2
3B, and the motor 9 is directly connected to a power supply battery 14 provided in the camera body B via a motor drive circuit 11 and connector contacts 13A and 13B. 15A and 15B are connector contacts provided on the camera side mount, and when the photographic lens A is attached to the camera body, the contact 13A
contacts contact 15A, and contact 13B contacts contact 15B.
come into contact with. 16 is a sliding knob for opening and closing switch SW ₁ provided in the power line between motor drive circuit 11 and connector contact 13A.

Inside the camera body B is a swinging mirror 21 that directs a portion of the light that has passed through the photographic lens optical systems 1 to 6 toward a viewfinder optical system consisting of a focusing plate 17, a condenser lens 18, a penta roof prism 19, and an eyepiece 20. is provided, and this swinging mirror 2
1 is reflected downward by a submirror 22 that swings together with the swinging mirror 21, and is guided to a light receiving element 23 disposed at the bottom of the camera body. The light-receiving surface of the light-receiving element 23 is provided at a position conjugate with the film plane F or the focal plane of the focusing plate 17, and the output from the light-receiving element 23 is calculated by the arithmetic circuit 24 and becomes an output indicating the in-focus position of the photographic lens. . This output is input to the control circuit 25, and the control signal is input to the motor drive circuit 11 via the connector contact section 27 provided on the camera body side mount and the connector contact section 26 provided on the lens mount 12. Ru.

FIG. 2 is a wiring diagram of the motor drive circuit 11, in which the control signal connector contact section 26 has two contacts 26A,
26B, when switch SW ₁ is turned on, the signal of contact 26A is H level and contact 26B is L level, the power supply 14 - contact 13A - transistor
T ₂ - Motor 9 - Transistor T ₈ - Contact 13B
- A power supply line for driving the motor of the power supply 14 is configured, and the power supply line for driving the motor is configured by a signal of L level at contact 26A and H level at contact _{26B .} - Contact 13B - Power supply 14
The situation is reversed. Further, when an L level signal is input to both contacts 26A and 26B, both _T4 and _T8 are turned on, forming a closed circuit and forming a motor brake circuit, so that the motor suddenly stops. To explain this circuit operation in more detail, if contact 26A receives an H level signal and contact 26B receives an L level signal, T ₁ is OFF, T ₂ and T ₃ are ON, and T ₈ is also ON.
becomes. On the other hand, since T ₅ is ON, T ₆ is OFF,
Since T ₇ is also OFF, T ₄ is also OFF. Therefore, the current flows in the direction of _T2-9 - _T8 and the motor rotates in the normal direction. When the contact 26A receives an L level signal and the contact 26B receives an H level signal, since this switching circuit is symmetrical with respect to the motor 9, the current becomes T ₆
The flow motor reverses in the direction of -9-T ₄ . Next, when both contacts 26A and 26B are both at L level, both T ₁ and T ₅ are ON, so both T ₂ and T ₆ are
OFF, the power supply to the motor from contact 13A is cut off, and the motor stops. At that time, T ₃ ,
Since T ₇ is both turned on, both T ₈ and T ₄ are turned on, forming a motor brake circuit and stopping the motor suddenly. When both contacts 13A and 13B are at H level, this switching circuit does not operate at all and the motor stops, but since no brake circuit is formed, it is impossible to stop the motor suddenly.

Returning again to the electrical equipment inside the camera body, the control circuit 25 includes not only a motor drive control circuit but also a display circuit 28 including a display element, which controls the image formed by the photographing lens on the light receiving surface of the light receiving element 23. Detects whether the focus is in the front position or the rear position,
Alternatively, a display signal circuit is added that sends a signal to display the status, such as whether the camera is accurately focused. Further, the exposure value is displayed on a display element in the display circuit 28 by a signal from an exposure control circuit 29 which includes a photometry circuit and automatically controls the aperture and/or shutter speed. A power supply circuit 30 is used as a drive source for the light receiving element 23, the arithmetic circuit 24, the control circuit 25, the display circuit 28, the exposure control circuit 29, and the aperture device or electronic shutter device controlled by the exposure control circuit 29. Power is supplied from the battery 14 via a separate circuit that is completely independent of the aforementioned motor drive power supply line. Note that the power supply circuit 30 includes circuits for timing control, voltage detection, and the like.

When the camera according to the embodiment shown in FIG.
3, and the arithmetic circuit 29 calculates the focal position of the photographing lens with respect to the subject. The calculated result becomes a control signal by the control circuit 25 and is transmitted to the motor drive circuit 11 via the connectors 27 and 26. At this time, the sliding knob 16
When switch SW ₁ is turned on, power for driving the motor is supplied from the power battery 14 provided in the camera body B to the connector contacts 13A and 13B.
Since the motor 9 is supplied to the motor drive circuit 11 through the Rotation is performed by moving lens barrel 8 via gears 11 and 8'.
, the movable lens barrel 8 is moved back and forth along the optical axis by the lead of the helicoid screw 7', and the object image is also transferred to the light receiving element 23 accordingly.
When the movable lens barrel 8 reaches the calculated focusing position, the control circuit 25
When a motor stop signal is sent from (in FIG. 2, an L level signal is input to both contacts 26A and 26B), the motor 9 suddenly stops. When starting the motor, the load is large, so the current increases, but since the motor drive power line is installed independently from other circuits, the voltage drop in the motor drive power line due to contact resistance at the connector is reduced. The stability of other circuits is maintained without affecting the other circuits.

SW ₂ in Figure 1 is a limit switch that is turned on when the movable lens barrel of the photographic lens reaches the infinite (∞) or shortest photographing distance position. A detection circuit 31 provided in the motor detects the ON state of the switch SW ₂ and controls the motor 9 via the control circuit 25 and the motor drive circuit 11 based on the signal.
For example, even if the movable lens barrel of the photographing lens moves to the ∞ position, if no focus detection signal is output, the control circuit 25
reverses the output level at contacts 26A and 26B when SW ₂ is ON, and the motor drive circuit 11
The motor 9 is reversed by the signal. In this case, the switch SW ₂ and the detection circuit 31 are connected to the connectors 32A and 32 provided on the lens and camera body.
B, 33A, and 33B to form a switch circuit. This circuit is independent of the motor power supply loop.

Here, the significance of making the closed loop for supplying motor power independent from other circuits will be further explained with reference to FIG. As shown by the dotted line in the figure, 33
B is grounded, and using this potential as a reference, SW ₂
Assume that the detection circuit 31 detects that 33A becomes the same potential level by turning ON. At this time, if the point P is connected to the terminal 32B as shown by the dotted line, the threshold level of the detection circuit 31 may become high, making it difficult to detect the potential of 32B. This will be understood from the explanation below.

Assuming that starting current IM flows through motor 9,
The potential VA at point P is as follows, where R is the resistance value between contacts 13B and 15B.

VA=IM×R Assuming that VCC was present at contact 13A. (RM is the internal resistance of motor 9) IM=VCC/RM Therefore, VA=VCC×R/RM.

As an example, if VCC=3.5V, RM=5Ω, and R=0.5Ω, VA=3.5×0.5/5=0.35(Volt).

The threshold level of the detection circuit 31 is 0.3V,
In other words, when SW ₂ is turned ON, the potential of contact 33B is 0.3V.
If the condition is as follows, if the configuration is such that it is determined that SW ₂ is ON, it will be difficult to determine in the above example. This means that the greater the value of R, that is, the resistance of the connector, the greater the VA, that is, the higher the threshold level, and the detection of ON of SW ₂ of the detection circuit 31 becomes unstable or impossible. It shows. In other words,
This defect occurs because a part of the motor drive power supply line in the signal system circuit is shared, or in other words, the motor drive power supply line is not independent from other circuits. In the embodiment shown in FIG. 1, the motor drive circuit 11 is provided on the photographing lens A side, but
Even if this is provided on the camera body B side, there is no problem as long as the motor drive power supply line is configured to be separate and independent from other circuits. In addition, the power supply battery 14
In Fig. 1, the circuit device including the camera body B
For example, this can be used as a viewfinder.
B' may be installed inside the camera body B', or from the attached power supply battery for the motor drive (not shown), the camera body B'
The motor drive power supply line may be configured to independently supply drive power to the motor in the photographic lens A via the motor.

Furthermore, the control circuit 25 has a built-in circuit that emits a motor drive control signal and a circuit that sends a signal to the display circuit 28, but if the display circuit is not required, the motor drive control signal Needless to say, it is sufficient to have only a circuit that emits .

As described above, according to the present invention, there is no power supply battery on the photographing lens side, and the motor drive power line connected to the power supply via the connector with extremely low contact resistance at the lens mount is isolated from other circuits. Since it is constructed with an independent closed loop, it is possible to provide a compact and space-efficient interchangeable lens for an autofocus camera system. Moreover, according to the present invention, since the power source is unified, the energy efficiency is extremely high, and the power supply voltage supply can be stabilized by a simple method.

[Brief explanation of drawings]

Fig. 1 is a sectional view showing an embodiment of the present invention, Fig. 2 is a wiring diagram of the motor drive circuit shown in Fig. 1, and Fig. 3 is an explanatory diagram of a motor control circuit including switch SW ₂ shown in Fig. 1. . 1, 2, 3, 4, 5, 6... Photographing lens optical system, 9... Motor, 11... Motor drive circuit, 12... Lens mount, 13A, 13B...
... Connector contact, 14 ... Power supply, 23, 24,
25... Focus detection control circuit, A... Interchangeable lens,
B...Camera body.

Claims (1)

[Claims] 1. One power source, two camera-side power supply terminals connected to the positive and negative electrodes of the power source, a camera-side circuit that is supplied with power from the power source and controls the camera, and the camera. An automatic focusing interchangeable lens that can be attached to a camera having two camera-side signal terminals connected to a side circuit, comprising: a motor for moving at least a part of a photographing lens optical system in the optical axis direction; two lens-side power supply terminals that are respectively connected to the two camera-side power supply terminals when attached to the camera; Two power supply lines that supply power to the motor, a lens-side signal circuit that emits signals for the interchangeable lens, and a lens-side power supply terminal that are provided separately from the two lens-side power supply terminals, so that when the interchangeable lens is attached to the camera, the 2
two lens-side signal terminals each connected to one camera-side signal terminal, and two signal lines that transmit signals of the lens-side signal circuit to the two lens-side signal terminals; An interchangeable lens characterized in that the signal line and the two power supply lines are electrically independent.