JPS5917402B2 - Malfunction prevention device for cameras equipped with automatic focus adjustment device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a camera with an automatic focusing device, in particular, a photoelectric distance measuring device having a pair of optical systems, which first scans in the forward direction over a distance measuring range, and The signal value from the photoelectric distance measuring device (hereinafter referred to as a photoelectric signal) when the images of 9 and 9 match is stored, and the photoelectric signal generated at the stage of reverse direction scanning matches the stored photoelectric signal. The present invention relates to an improvement of a camera 5 having an automatic focus adjustment device of the type that stops a photographing lens in a moving state for focus adjustment by using a detection signal when the focus is adjusted.

In this type of camera, in the forward scanning stage, the photoelectric range finder simply determines the peak, for example, the maximum signal value, of the signal value from the photoelectric range finder, which simply represents the subject position, and in the reverse direction scanning stage, the photo is taken. In order to stop the zero-shadow lens, it is necessary to provide an actuation switch at the boundary point between the forward scanning phase and the reverse scanning phase for setting the stopping means of the taking lens into an operative state.

However, if the activation switch is provided in a simple manner, the subject may become flat due to the current fluctuation phenomenon or chattering phenomenon (hereinafter simply referred to as current fluctuation phenomenon, etc.) in the circuit that occurs when the switch is turned on. If the contrast is solidified, there is a risk that the automatic focusing device will not work properly.

The present invention has been made to eliminate this drawback, and its novel features reside in the points described in the claims.

For convenience of explanation, first, an outline of the automatic focus adjustment device shown in FIG. 1 will be explained.

In Fig. 1, the components of the photoelectric distance measuring device are shown. 1 is a fixed mirror, 2 is a movable mirror provided on the base gear 3, and the light flux from the subject is directed to the fixed mirror according to the triangulation principle. 1, and the other distance measuring optical axis B, which is determined by the swinging of the movable mirror 2 provided on the gear 3, reach the surface reflecting prism 4. The light enters the imaging lenses 5, 5' and forms images on the respective light receiving elements 6, 6'.

The light receiving elements 6, 6' are each divided into several sections, and the outputs of the corresponding divided sections are compared. The results of each comparison are then introduced into the addition calculation circuit 7, where they are added together so that the maximum output is achieved when the sum of the comparison values is zero, and the output signal of the photoelectric distance measuring device is output, and the maximum value is detected. A photoelectric signal CO is applied to one input end of the device 8. The maximum detector 8
A grounded capacitor C1 and a resistor R1 are connected in series to the other input terminal of the detector 8, and the output VPD of the maximum value detector 8 is connected to the resistor R1 and the other input terminal of the detector 8 via a diode D1. A known maximum value detection circuit (or maximum value storage circuit) is formed by the maximum value detector 8, the capacitor C1, the resistor R1, and the diode D1, and the addition calculation circuit 7 The maximum value of the outputs is stored as the comparison signal VDT. Now, the output VDT of the maximum value detector 8 is introduced into the AD converter 9, and when the comparison signal VPT and the photoelectric signal VcO match (including some fluctuation range), the A-D converter 9
and both signals V so that the output VAF of is 1101.

If there is a difference between T and VCO of more than a specified value, A-D
The A-D so that the output VAF of the converter 9 is %111.
The converter 9 converts the signal into a digital signal VAF. That is, when the images match, the output VAF of the detection circuit section composed of the maximum value detector 8 and the AD converter 9 becomes a detection signal to that effect. This digital signal VAF is converted into a ground control signal VD by a capacitor C4 and a resistor R2 which are differentiating circuits.
is applied to the switching circuit 10 which controls the excitation/demagnetization of the magnet solenoid 11.

Therefore, the switching circuit 10 is configured to perform a predetermined operation only when the rise regulation signal VD is applied.

Solenoid 11 is used when using the camera (or when starting distance measurement)
The switching circuit 10 is supplied with power from a power source (not shown) and is in an excited state, but if the switching circuit 10 is in an active state, the rising regulation signal V is activated. The positive pulse of the circuit 1
It is controlled by the switching circuit 10 to be demagnetized when the voltage is applied to zero. SW is an operating switch for activating the switching circuit 10. Therefore, a blocking pawl 12 that is guided so as to be movable in a straight line is provided opposite to the solenoid 11 as an armature.
When it is demagnetized, it is configured so that it can move upward in the figure by the force of the spring 13 and engage with the tooth row 15 on the scanning control plate 14.

The running difference control plate 14 is always biased by a strong spring 16 so that it can be displaced to the right. It is configured such that it can be set at the charging position and can be started from the position shown in the figure in conjunction with, for example, a shutter release operation.

The control plate 14 is provided with a V7 reverse for swinging the movable mirror 2 by the same amount first in a counterclockwise direction (hereinafter referred to as the forward direction) and then in a clockwise direction (hereinafter referred to as the reverse direction). Only when the V7-shaped cam groove 14a and the movable mirror 2 are swung in the opposite direction, the photographing lens frame 19 (described later) is rotated so as to move from the closest distance position to the infinity position of the lens. The actuating switch SW is closed at the displacement position of the scanning control plate 14 corresponding to the fork-shaped portions 14b and 14c for rotating the movable mirror 2 and the point in time when the swinging direction of the movable mirror 2 is reversed (changed from the forward direction to the reverse direction). A switch cam 14d is formed whose relative position is determined so that the cam groove 14a is connected to a pin 18 on the interlocking rod 17 which meshes with the base gear 3 of the movable mirror 2 with a lock tooth.
The fork-shaped portions 14b and 14c are precisely engaged with a pin mounted on the outer periphery of the photographing lens frame 19 between them. 20 are sandwiched while maintaining a predetermined time lag gap (corresponding to the forward movement range T1 of the movable mirror 2). The photographic lens barrel 19 is engaged with a fixed lens barrel 21 fixed to the camera body (or an interchangeable lens) using a pin 22 and a becoid 21a mechanism, and there is some vibration between the lens barrel 21 and the fixed lens barrel 21. Frictional force is applied to such an extent that the photographing lens frame 19 does not rotate even when F is the film surface. Now, when the scanning control plate 14 is unlocked and displaced to the right in conjunction with the shutter release operation, for example, in the first half stage T1 of the displacement process, the interlocking rod 17 moves into the cam groove 14a. Since the movable mirror 2 descends according to the action, the movable mirror 2 first scans the field from the infinite position to the closest distance position. This scanning result is obtained from the two light receiving elements 6, 6.
Each corresponding pair of divided sections of introduced at the end. At this time, if the main subject to be photographed has a clear contrast with the field, the photoelectric signal at the scanning point corresponding to the position of the main subject will be larger than the photoelectric signal at other scanning points. Therefore, the photoelectric signal value at the scanning point of the main subject is stored in the maximum value detection circuit 8, R1, C1, D. In this case, the output from the maximum value detector 8 becomes the rise regulation signal VD and is ultimately applied to the switching circuit 10, but since the operating switch SW is not yet closed, the switching circuit 10 does not perform the predetermined operation. without doing it,
Therefore, the solenoid 11 remains energized. That is, the blocking claw 12 and the tooth row 15 of the scanning control plate 14 are not engaged with each other. Now, the running difference control board 14
When it subsequently moves to the latter stage T2, the displacement becomes the interlocking rod 17.
, the movable mirror 2 scans the object in the opposite direction from the closest distance position to the infinite distance position, and converts the scanning results into a photoelectric signal VcO sequentially to the maximum value detection circuit 8, R1.
, C1, and D1.

At the same time, the operating switch SW closes to maintain the switching circuit 10 in the active state. At this time, until the scanning line reaches the scanning point of the main subject, the photoelectric signal VcO is always lower than the comparison signal (memory signal) VDT, so A-
The digital signal VAF 711 continues to be output from the D converter 9, but since this does not become the rising regulation signal D by the differentiating circuit C4 and R2, the switching circuit 10
does not perform the predetermined operation, so the solenoid 11 remains energized.

When the scanning line of the movable mirror 2 reaches the scanning point of the main subject, the photoelectric signal VcO at that time coincides with the comparison signal VDF, and the digital signal lamp of the A-D converter 9 is changed to 1T. When the object's running difference point passes, the digital signal V
Since the AF becomes 1VF1 again, this generates the rising regulation signal D, actuating the switching circuit 10 and demagnetizing the solenoid 11. Therefore, the blocking claw 12
3 engages the tooth row 15 and stops the scanning control plate 14 at the current position. In this case, the photographic lens frame 19 enters the second half scanning stage T2 of the scanning regulating plate 14, and at the same time its pin 20 is pushed by the fork arm 14c of the regulating plate 14, so that it continues to rotate and adjusts the focus toward infinity. The camera, which had been in continuous motion, comes to a halt at its current position, that is, in a state where it is focused on the main subject, as the scanning control plate 14 is stopped. Incidentally, errors due to phenomena such as a delay in the operation of the blocking claw 12 are compensated for by, for example, shifting the starting position of the photographing lens frame 19 by that amount in advance.

A problem arises when the main subject does not have a clear contrast with the field, for example when photographing a landscape at infinity.

In this case, the photographing lens must be focused at an infinite distance position, but an accident occurs in which the lens stops at a finite distance position due to a phenomenon such as a current fluctuation in the circuit that occurs when the operating switch SW is turned on. That is, when the main subject does not have a clear contrast, the relationship between the photoelectric signal VcO and the comparison signal VDT in the first half scanning stage T1 of the movable mirror 2 is always maintained in a substantially coincident state, so that the digital signal generated during this period is As shown in Fig. 2, the VAF continues to be 1"01".In this state, the first half scanning stage T1
When the operating switch SW is closed at the turning point between the second half scanning stage T2 and the second half scanning stage T2, the voltage of the circuit power supply (not shown) decreases due to the current fluctuation phenomenon at the time of switching on, and therefore the photoelectric signal VcO and the comparison signal There is a considerable difference between A- and DT.
The output signal of the D converter 9 changes to "111". Then, this digital signal is converted into a rise regulating signal VD by the differentiating circuits C4 and R2 and activates the switching circuit 10, which is already in the activated state. This may cause an accident, that is, a malfunction, in which the scanning control plate 14 is stopped at the current position due to engagement with the scanning control plate 14. Therefore, in the present invention, as shown in FIG. 3, one input terminal of the maximum value detector 8, which is a detection circuit section, and the circuit of the actuation switch SW are connected through at least a delay capacitor C3. The current fluctuation phenomenon that occurs when the SW is turned on is actively used for the purpose of lowering the photoelectric signal VcO, and the digital signal VAF from the A-D converter 9 is applied to the maximum value detection circuit described above. Therefore, by setting the comparison signal VDT to a higher value after this time, the above-mentioned malfunction is attempted to be prevented.

Now, in the embodiment shown in Figure 3, a capacitor C2 and a diode D2 are provided in the path for introducing the digital signal VAF into the maximum value detection circuit, and a diode D3 is connected in series with the delay capacitor C3. Resistor R3
and a switch 23 are attached.

Now, when the operating switch SW is closed at the turning point of the scanning stages T1 and T2, the voltage of the photoelectric signal VcO at that time temporarily decreases as shown in FIG. 4 due to the current fluctuation phenomenon when it is turned on. A difference exceeding a predetermined amount is generated between the comparison voltage VDT and the comparison voltage VDT.

Therefore, an output VPD is generated in the maximum value detector 8, which becomes a digital signal VAF of "11", which is further applied to the switching circuit 10 via a differentiating circuit, but at this time, the delay capacitor C3 is still being charged. Even if the operating switch SW is turned on, this does not mean that the switch SW is actually closed;
As a result, the switching circuit 10 remains in a state that has not yet been brought into operation. Therefore, the rise regulation signal VD applied as described above has no effect on the switching circuit 10. In this case, the activation switch SW takes the time equivalent to the charging time of the delay capacitor C3 to recover to its original value, and in the process changes the switching circuit 10 to the active state. This is the period after the occurrence of Therefore, unless the rise regulation signal VD is newly applied to the switching circuit 10 thereafter, the excitation state of the remagnet solenoid 11 remains unchanged. Therefore, the digital signal VAF "F" from the A-D converter 9 is introduced into the maximum value detection circuit on the other hand and added to the comparison signal value VDT, so that the value of the comparison signal VDT from this point onwards is is changed to a high value as shown in FIG.

However, in the object field within the distance measurement range, it is absolutely impossible to generate a photoelectric signal VcO comparable to this high voltage comparison signal, so in the second half scanning stage T2, the comparison signal is always higher than the subsequent photoelectric signal. will continue to remain high. That is, the output from the maximum value detector 8 continues to maintain the digital signal VAF at 1V Bi. Therefore, in the process of the second half scanning stage T2, since the rising edge regulation signal VD is not applied to the switching circuit 10, the photographic lens frame 1
9 moves to one of the movement limits (for example, infinite position),
It will be stopped at that position. In other words, in the case of such a main subject with no contrast, it is possible to photograph the subject with focus at infinity. It should be noted that the discharge switch 23, which is provided to speed up the next photographing process, can be configured with appropriate means to close for a predetermined period of time in conjunction with the film winding operation, for example, so that the delay capacitor C3 is closed. The charged charge is discharged when the circuit is closed and is restored to its original state.

In this case, the capacitance of the delay capacitor C3 is set to a small value, and a natural discharge phenomenon of the capacitor that occurs when the operating switch Sw is closed for the next photographing and a discharge phenomenon through the maximum value detector 8 occur. Therefore, if the configuration is such that the charge in the capacitor C3 can be emptied in a short time, or if the time until the next shooting is relatively long,
There is no need to particularly provide a discharge switch. Next, a summary of variations of the present invention will be described. First, regarding the photoelectric distance measuring device, the illustrated embodiment uses a distance measuring device based on the principle of triangulation, which is installed outside the photographic lens. ) The present invention is also applicable to TTL type photoelectric distance measuring devices. In this case, forward scanning and reverse scanning may be performed while reciprocating the photographic lens, or the lens may be moved in one direction. It can also be applied to a photoelectric distance measuring device such as a twin-lens reflex camera in which the finder lens is used as a focusing lens, or to a triangulation principle that uses a photographing lens and a finder lens. Also, the scanning direction for the distance measurement range is reversed from the illustrated embodiment, that is, when scanning in the forward direction, from the closest distance position to the infinity position,
When scanning in the reverse direction, the direction may be set from the infinitely distant position to the closest distance position.

Moreover, in the illustrated embodiment, the maximum value of the photoelectric signal is used as the comparison signal, but the minimum value of the photoelectric signal can also be used as the comparison signal by changing the circuit configuration. In this case, the statement "V7 maximum value 1" in the specification shall be read as "minimum value 1". Furthermore, the activation switch can be applied to circuits in which the switching circuit is put into operation by opening the circuit, and even in the case of a magnet, a type in which the blocking pawl is brought into contact with the teeth when activated is applicable. It can be used. Regarding the means for driving and stopping the photographic lens, it is also possible to drive the lens, including the movable mirror, by a motor, or to stop the motor by cutting off the power supply circuit in response to a command from a switching circuit.

In the illustrated embodiment, the photographing lens is moved to an infinity position when the main subject has low contrast, but the lens is not limited to this, and for example, the lens may be moved to a specific position such as the nearest distance position. Otherwise, depending on the case, a warning may be issued at that time, or the shutter release operation etc. may be changed to a non-operating state to make photography impossible.

As described above, when the present invention is used, it is possible to completely prevent malfunctions due to closing of the operating switch.

It should be noted that the operating switch includes not only a mechanical switch but also an electrical switch such as a transistor.

[Brief explanation of the drawing]

FIG. 1 shows a schematic diagram of an embodiment of a camera with an automatic focus adjustment device, which is a premise for explaining the present invention, and FIG.
The figure shows the operating sequence in this case. FIG. 3 is a schematic diagram of an embodiment of a camera with an automatic focus adjustment device according to the present invention, and FIG. 4 shows an operation sequence in this case. 1...Fixed mirror, 2...
...Movable mirror, 4...Surface reflection prism,
66'-... Light receiving element, 7... Addition calculation circuit, 8... Maximum value detector, 9... A
D converter, 10... Switching circuit, 11.
... Solenoid, 12 ... Blocking claw, 14
...Scanning control plate, 15 ... Teeth row, 17
......Interlocking rod, 19...Photographing lens frame, 21...Fixed lens barrel, 23...Discharge switch, C3...Delay Capacitor, SW...
...Operating switch, VcO...Photoelectric signal, V
DT...Comparison signal, VAF...Digital signal, VD...Rise regulation signal.

Claims (1)

[Claims] 1 First, scan in the forward direction over the distance measurement range with a photoelectric distance measuring device having a pair of optical systems, and measure the signal value from the photoelectric distance measuring device when the images from the pair of optical systems coincide. an automatic focus adjustment device that stops a photographing lens in a moving state for focus adjustment by using a detection signal when a signal value generated in the backward scanning stage matches the stored signal value; In a camera equipped with the above, an activation switch that enables a terminal for inputting the signal value of the detection circuit section that inputs the signal value from the photoelectric distance measuring device and outputs the detection signal, and a means for stopping the photographing lens. A camera equipped with an automatic focus adjustment device that is connected to a terminal of the camera via a capacitor to prevent malfunction when switching the operation switch.