JPS6217209B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power switch for a distance measuring circuit for a camera, which is equipped with a distance measuring circuit for detecting and displaying the in-focus position of a focusing lens of the camera.

Distance measuring circuits of conventional cameras are configured using various focus detection methods. For example, there is a method to detect the in-focus position using the characteristic that the CdS resistance value shows an extreme value when the image is most clearly projected on the CdS surface, or a method that uses the principle of a double image matching type rangefinder. There are methods such as photoelectrically detecting the subject distance and determining the in-focus position. Since these distance measuring circuits are configured to visually display whether or not the object is in focus, the rotation of the distance ring can be stopped to determine the position of the focusing lens. A camera that simplifies focusing by electrically detecting the suitability of focusing and displaying it within the viewfinder's field of view, etc., allows the camera to simply connect and disconnect the power supply to the distance measuring circuit. This is done by pressing a button halfway or using a separate open/close switch. However, focusing by rotating the distance ring while pressing the release button halfway and moving the focusing lens to the in-focus position is unstable and difficult to operate. Even if a separate open/close switch is used, it is inconvenient to operate the distance ring while pressing the button because the operation is duplicated. In this case, using an open/close switch would make operation easier, but it would be necessary to open the switch after use, and if this was forgotten, the battery would be wasted, causing inconvenience. In the case of a camera that incorporates a fully automatic focusing mechanism, this problem does not occur because the focusing operation is performed automatically by the drive motor, but in the case of a manual type camera, focusing is performed in the same way as a conventional camera. Although it has the advantage of being able to be performed naturally and according to the operator's will while checking with visual indicators etc., on the other hand,
This caused the above-mentioned inconvenience.

This invention uses a switch means that can easily connect the power to the distance measuring circuit when rotating the distance ring, thereby improving the operability of the camera and preventing unnecessary power consumption when not in use. The purpose is to extend the life of the battery.

The present invention will be described below with reference to the accompanying drawings.
FIG. 1 is a schematic diagram of a single-lens reflex camera to which the present invention is applied. The focusing lens 1 is moved out and returned from the camera body A by rotation of the distance ring 2, and is operated. By this operation, the focus display signal X is sent to the visual indicator 31 of the distance measuring circuit 3, and when the focus is displayed, it is sufficient to stop rotating the distance ring 2, and the focusing lens 1 detects the in-focus position. At the same time, the operator can confirm. This distance measuring circuit 3 is connected to a power source E via a switching circuit 4, and an input terminal 41 of this switching circuit 4 is connected to rotation detection means 5 which outputs a rotation detection signal I.
In the embodiment shown in FIG. 1, this rotation detection means 5 includes a rotation detection member 51 that outputs a rectangular wave Y when the distance ring 2 rotates, and a rotation detection signal that outputs the output rectangular wave Y of the rotation detection member 51. Rotation detection circuit 5 that compensates for I
It is composed of 2.

As shown in FIG. 2, the switching circuit 4 includes a switching element, here a switch transistor 4.
It is opened and closed by the operation of 2. The base end of this switch transistor 42 is connected to the collector end of an NPN type transistor 43, and the base end of this transistor 43 is located at the input end 41 of the switch circuit 4. Therefore, when a predetermined current is applied to the input terminal 41, the transistor 43 is turned on, and this causes a voltage drop at the base terminal of the switch transistor 42, so that the switch transistor 42 is turned on. Therefore, the power source E is connected to the distance measuring circuit 3. This switch circuit 4 uses a switch transistor 42 as an NPN
It may be replaced with a type transistor. In this case, the base end of the switch transistor 42 can directly serve as the input end 41. This switch element 4
2 can also be replaced with a relay.

As shown in FIG. 3, the rotation detection member 51 has a brush 51a fixed to the distance ring 2, and the contact end of this brush is slidably in contact with the rectangular wave pattern 51b of the fixed ring 6. As shown in FIG. 4, this pattern 51b is made of a pair of comb-shaped electrodes 51c and a guide electrode 51d as an output end, and has a cylindrical shape as a whole. A voltage Vc is applied between the pair of electrodes, and as the brush slides, a rectangular wave of a constant voltage Vc is sequentially applied to the guide electrode 51d.
(See Figure 6). As shown in FIG. 5a, this rotation detection member 51 is provided with a magnetic coating band 51e on the inner circumferential surface 21 of the distance ring, a rectangular wave Y is magnetically recorded on this coating band 51e, and this is magnetically detected. It may also be configured to be detected by the head 51f. Magnetic detection head 51f
is attached to the fixed ring 6 side, thereby making it possible to output the rectangular wave Y to point a. Furthermore, it may be constructed as shown in FIG. 5b. distance ring 2
A rotary pressing piece 22 is provided on the side of the camera body A that is tapered toward the direction of rotation of the ring, and a sliding rod 23 that is constantly pressed toward the tapered surface by a spring is attached to the tapered surface of this pressing piece 22. It is in contact. This sliding rod 23 is slidably attached to the camera body A, and also has a brush 51a fixed thereto. The contact end of this brush is in slidable contact with the rectangular wave forming pattern 51b. The structure of the pattern 51b and the brush 51a is almost the same as that of the embodiment shown in FIG.
The only difference is that a operates in the reciprocating direction.

The rotation detection circuit 52 consists of a differentiating circuit 52a and a smoothing circuit _52b as shown in FIG. ₁
The waveform at point b becomes the waveform b representing the voltage at the portion where the input signal changes largely (see FIG. 6). This is connected to a smoothing circuit 52b consisting of a diode D ₁ , a protective resistor R ₂ , and a capacitor C ₂
Enter. As a result, the waveform at point c becomes a DC waveform, which is applied as the rotation detection signal I to the input end 41 of the switching circuit 4. This causes the switching circuit 4 to operate. In this rotation detection circuit 52, the power E is input only when the distance ring 2 is rotated, and the distance measurement circuit 3 is activated. However, as soon as the distance ring stops rotating relative to the camera body, the visual indicator light 31 becomes invisible.
This may cause anxiety to the operator, so
It is desirable to provide the rotation detection circuit 52 with a hold circuit 52d that continues outputting for a certain period of time. Thereby, the visual indicator light 31 can be operated for a certain period of time even after the rotation has stopped. In FIG. 7, a hold circuit 52 is shown.
A rotation detection circuit 52 with d added is shown. That is, a voltage follower using an operational amplifier 52c may be provided between the differentiating circuit 52a and the smoothing circuit 52b, or the capacitance of the capacitor _C2 may be increased. The rotation detection member 51 described above includes the variable resistor 5
It may be formed with 1 g. As shown in Figure 8, the cylindrical resistor winding of the variable resistor 51g is connected to the distance ring 2.
The brush 51a is provided on the fixing ring 6 side. The pulsating output signal Ya thus output is:
It passes through a differentiation circuit 52a and is then connected to a known rectification circuit 52e.
Full-wave rectification is performed at , and a rotation detection signal I is further output from a smoothing circuit 52b.

Since this invention is as described above, it has the following effects.

The power source E can be connected to the distance measuring circuit 3 by rotating the distance ring. In other words, when performing a focusing operation, the visual indicator light 3 indicates the focusing state at the same time as the distance ring 2 is rotated and for a certain period of time thereafter.
Since 1 is displayed by lighting, focusing operability is good. In particular, the visual indicator 31 continues to illuminate for a certain period of time after the distance ring stops rotating, that is, for a period of time that allows the operator to easily reconfirm the in-focus state, giving the operator a sense of security. can.
Since the distance ring 2 is rotated only when focusing, the power source E can be reliably released from the distance measurement circuit 3 when the camera is not in use, eliminating unnecessary power consumption and extending battery life. There are also advantages.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a single-lens reflex camera to which this invention is applied, FIG. 2 is an electric circuit diagram of the embodiment shown in FIG.
FIG. 3 is a front view of the distance ring used in the embodiment shown in FIG. 1, FIG. 4 is a partially enlarged plan view of the rotation detection member used in this invention, and FIG. FIG. 5b is a side view showing another embodiment of the distance ring, and FIG.
FIG. 2 is an explanatory diagram showing waveforms at each point in the electric circuit, and FIGS. 7 and 8 are electric circuit diagrams showing different embodiments of the rotation detection circuit. DESCRIPTION OF SYMBOLS 1... Focusing lens, 2... Distance ring, 3... Distance measuring circuit, 4... Switching circuit, 41... Switching element, 5... Rotation detection means, 51... Rotation detection member, 52 ...Rotation detection circuit, A...Camera body, I...Rotation detection signal, E
...Power supply, 52d...Hold circuit.

Claims (1)

[Claims] 1. In the power switch of the distance measuring circuit, which is configured so that the focusing lens detects the in-focus position based on manual rotation of the distance ring provided on the camera body and displays this, the distance measuring circuit and the power source are connected to each other. A switching circuit having a switch element is provided between the switching circuit and the switching circuit, and rotation detection means for detecting relative rotation of the distance ring with respect to the camera body and outputting a rotation detection signal is connected to the switching circuit. The rotation detection means is provided with a hold means for continuing to output the rotation detection signal for a certain period of time after the distance ring stops rotating, and the rotation detection signal outputted by the rotation of the distance ring is used to control the switching circuit. A power switch for a distance measuring circuit configured to close the circuit and connect a power source to the distance measuring circuit.