JPH0112250Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention is an automatic focusing camera that determines the position of the photographing lens based on a focus detection signal detected by an automatic focus detector. It concerns the method of determination.

First, an autofocus detector that can be applied to the present invention will be explained using FIGS. 1 and 2.

FIG. 1 is a principle diagram showing the optical conditions of an automatic focus detector. In FIG. 1, object light is focused by a movable lens 1 and imaged on the surface of a small lens 2, and the small lens 2 directs the exit pupil of the movable lens 1 to a pair of light receiving elements A ₁ , B ₁ ; A ₂ , Image is formed on B ₂ . That is, the light receiving elements A ₁ (or A ₂ ) and B ₁ (or B ₂ ) receive only the light that has passed through the A section and the B section of the movable lens 1, respectively. If the subject image 0 is currently in focus, the light receiving elements A ₁ and B ₁ are sensing the same area portion 0 ₁ of the subject, and the illuminance will be the same. When the subject moves to the 0' position, area 0 ₁ is divided into two parts, one of which is used by photodetector A ₁ , and the other by photodetector A1.
B ₁ respectively, and the illuminance of both elements is no longer the same. In other words, it shows that the image is out of focus.

FIG. 2 is a block diagram of the focus detection circuit. The received illuminance, that is, the current of the light receiving element (light receiving diode) is converted into voltage by the log diode, and the channel amplifiers C ₁ and C ₂ detect this potential difference. When in focus, that is, light receiving element A ₁
When the illuminances of C 1 and B ₁ and A ₂ and B ₂ are equal, the outputs of the channel amplifiers C ₁ and C ₂ are at 0 (zero) level. Summary amplifier 3 is both channel amplifier C ₁ ,
Detects the potential difference between C _{and 2} , and generates an output of 0 (zero) if there is no difference. When the output of the summary amplifier 3 is 0 (zero), the detector 4 outputs a focusing signal (hereinafter referred to as AF).
Synchro switch S
When is ON, the AF signal is latched,
The AF signal is not transmitted to the solenoid drive amplifier 5, but is transmitted when the synchro switch S is OFF. When the camera is not in focus, that is, when there is a potential difference between both channel amplifiers, the output of the summary amplifier 3 is not 0 (zero), so the detector 4 does not generate an AF signal.

In the autofocus detector described above, it is a prerequisite that there is sufficient contrast in subject brightness. However, even if the brightness of the subject does not have sufficient contrast, both channel amplifiers
There is no potential difference between C ₁ and C ₂ , so even in this case, that is, when focus detection is impossible.
This will generate an AF signal. In order to avoid misunderstandings in the following explanation, we will distinguish it from a correct AF signal, which occurs when focus detection is impossible.
The AF signal will be called the default signal.

Scenes when the contrast of the subject brightness is insufficient are: (1) Even if the subject brightness is bright, the subject is on the same brightness surface (in the case of a subject at infinity,
(2) When the brightness of the subject is too dark and the contrast is insufficient (that is, when flash photography is required). In cases where focus detection is impossible, it is preferable to set the photographic lens at infinity in cases such as Scene 1 above, and to the normal focal position (for example, 3 m) in cases such as Scene 2. , it is the purpose of the present invention to solve this problem. In the present invention, the above object is achieved by variously switching the OFF position of the synchro switch S of the above-mentioned automatic focus adjuster, and will be explained in more detail below with reference to FIG.

FIG. 3 shows the state before the automatic focus detection operation, and the same parts as the automatic focus detector described in FIGS. 1 and 2 are given the same numbers. Reference numeral 6 denotes an AF drive lever, which is biased leftward by a spring 7 and whose left end is locked by a release plate 8. The AF drive lever 6 has a cam groove 6 that associates and drives the photographing lens 9 and the movable lens 1 respectively.
a, 6b, and a pawl portion 6c that is regulated by the solenoid 10. In the state shown in the figure,
The photographing lens 9 and the movable lens 1 are located further back than the infinity position. The release plate 8 has a cam portion 8a and protrusions 8b, 8c, and is urged upward by a spring 11. Reference numeral 12 denotes a switching plate for switching between normal photography and flash photography, and when flash photography is to be performed, it is manually adjusted to the flash mark. Both S ₁ and S ₂ are synchro switches, and both switches are connected in parallel. The synchro switch S ₁ is controlled by the protrusion 8b of the release plate 8. The synchro switch S ₂ is connected to the switching plate 12.
When the AF drive lever 6 moves to the left and the photographing lens 9 reaches the normal focal position, it is turned OFF by the protrusion 6d. It's becoming like that. S _M is a main switch, which is regulated by a protrusion 8c of the release plate 8. E is a power supply, and the automatic focus detector and each switch are connected as shown in the figure. 13 is a film.

Next, the operation will be explained.

First of all, for normal shooting without flash shooting,
Therefore, the case where the synchro switch _S2 is in the OFF state will be explained. When the release plate 8 is pressed down for photographing, the main switch S _M is turned on in the first stage and the focus detection circuit begins to operate. The release plate 8 is further pushed down, and just before the AF drive lever 6 enters the slope of the cam 8a of the release plate 8 and begins to move, the synchro switch _S1 is activated.
OFF, and by continuing to press down, the AF drive lever 6
moves to the left along the cam 8a. When the AF drive lever 6 moves to the left, the photographing lens 9 and movable lens 1
is moved from the above-mentioned position to an infinity position and further to a short distance side via the cam portions 6a and 6b.

If there is sufficient contrast in the subject brightness, both synchro switches S ₁ and S ₂ are turned OFF.
During the movement of the movable lens 1, an AF signal is generated when the subject position is in focus, driving the solenoid 10, and at that point the claw 6c of the AF drive lever 6 is locked and the movement is stopped. let me,
The photographing lens 9 is positioned.

If the subject brightness does not have sufficient contrast, a default signal will be generated as soon as the main switch _SM is turned on, and therefore the solenoid 10 will be driven when the synchro switch _S1 is turned off. AF by successively pressing the release button
The drive lever 6 moves to the left, and the first claw portion 6c of the drive lever 6 moves to the left.
The solenoid 10 locks the position (that is, corresponding to the infinite position of the photographing lens 9).

Next, a case will be described in which the synchro switch _S2 is initially turned on when performing flash photography. Generally, when performing flash photography, the subject brightness is often so dark that focus detection is impossible. In this case, a default signal will be generated as soon as the main switch _SM is turned on.
Synchro switch S ₁ is activated by pressing down the release button.
It turns off, but the only synchro switch S ₂
Since it is ON, at this point solenoid 10
is not driven. Further, the AF drive lever 6 moves to the left due to the subsequent depression of the release, and in the middle of this movement, that is, when the photographic lens 9 reaches the normal focal position (for example, 3 m), the protrusion 6d turns off the synchro switch _S2 ,
Therefore, the default signal is transmitted to the solenoid 10, the claw portion 6c is locked, and the AF drive lever 6 is stopped moving at the common focal point position of the photographing lens 9.

Next, even in the case of flash photography such as backlight photography, if there is sufficient contrast in the brightness of the subject, an AF signal can be generated instead of a default signal.
In other words, the AF before synchro switch S ₂ was turned off
The signal cannot be transmitted to the solenoid 10, and the AF signal will be transmitted to the solenoid only after the synchro switch _S2 is turned off. However, in this case, it is almost impossible for the subject position to be on the infinity side from the normal focal position, considering the intention of flash photography, and in most cases it is located on the short distance side from around the normal focal position. Therefore, there is no problem when it comes to actual shooting.

In the embodiment described above, the synchro switch
S ₁ was controlled by operating the release plate 8, but it goes without saying that this can be done as long as the movement of the photographing lens 9 reaches infinity, and therefore it is turned OFF at the starting point where the AF drive lever 6 starts moving. It may be controlled.
Needless to say, the shutter is released after the position of the photographic lens 6 is determined.

As explained above, according to the device of the present invention, it is possible to control the settings of the photographing lens with both the AF signal and the default signal, and in the case of the default signal, two types of setting conditions can be satisfied, which is the essential feature of an automatic focusing device. It is effective enough to compensate for the shortcomings.

[Brief explanation of drawings]

FIG. 1 is a principle diagram showing the optical conditions of an automatic focus adjuster. FIG. 2 is a block diagram of the focus detection circuit. FIG. 3 is a diagram showing a specific embodiment of the device of the present invention. 1...Movable lens, 2...Small lens, 3...Summary amplifier, 4...Detector, 5...Solenoid drive amplifier, 6...AF drive lever, 8...
...Release plate, 9...Photographing lens, 10...Solenoid, 12...Switching plate, _A1 , _A2 , _B1 , _B2 ...
Light receiving element, S, S ₁ , S ₂ ... synchro switch,
S _M ...Main switch, E...Power supply.

Claims (1)

[Scope of utility model registration request] An automatic focus detector includes a movable lens and a focus detection circuit, and generates a focus signal when the light receiving elements of the focus detection circuit detect the same illuminance; and an automatic focus detector that generates a focus signal when the light receiving elements of the focus detection circuit detect the same illuminance; A driving member that integrally drives the lens from the infinity side of the photographing lens, a first synchronizer switch that is opened and closed by operating the release member, and a normal photographing position in which no flash is used and a flash photographing position. a switching member that is movable; and a second switching member that is opened and closed by movement of the switching member, and which is opened and opened by movement of the drive member during flash photography.
The focus signal generated from the automatic focus detector is latched by the opening/closing operation of the first and second synchro switches, and the first synchro switch latches the focusing signal generated from the automatic focus detector by operating the release member. When the switch starts operating, the release member releases the latch, and the second synchro switch constantly releases the switch when the switching member is in the normal shooting position, and when it is in the flash shooting position. The latch is held, but the latch is released when the driving member reaches a position corresponding to the normal focal point of the photographic lens, and the focus signal is released only when both synchro switches are released. A security device in an automatic focus detection device for a camera, characterized in that it enables transmission.