JPS6227369B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an auto-fading diaphragm control device.

Aperture control devices that operate an aperture member according to changes in subject brightness to always obtain an appropriate exposure amount are already known, and there have also been improvements to drive means that operate the aperture member according to changes in subject brightness. Motors using motors called ping motors, pulse motors, etc. (hereinafter referred to as stepping motors) are known. As is well known, the operation of the stepping motor is controlled by a pulse signal, and its driving speed is determined by the frequency of the pulse signal. Therefore, in an aperture control device using such a stepping motor, it is necessary to operate the aperture member at high speed in accordance with the ever-changing subject brightness. It can be said that the pulse signal for controlling the operation needs to be of high frequency. The present invention relates to an aperture control device configured as described above in which fading is performed using the aperture member.

As is well known, when fading is performed using an aperture member, unless there is a high-brightness object in the subject that is significantly different from other objects, the appropriate exposure aperture value and an aperture value approximately 4 to 5 steps below this aperture value are necessary. Substantial fading occurs within this range. Therefore, the desirable operation of the aperture member during fading is such that it operates at a low speed within the above range and changes the aperture value. However, if the aperture member operates at a low speed over the entire fading range, for example, if there is a high-brightness object that is significantly different from others in the subject, the high-brightness object will remain in the image forever. , or may appear from an early stage, so it is desirable that the aperture member operates at a high speed in a range outside the actual fading range.

Therefore, the present invention provides an diaphragm capable of automatic fading, in which, although approximate, at least during fade-in photography, the diaphragm member is operated at a high speed for a certain period of time at the beginning of the fade-in photography, and then operated at a low speed. A control device is provided.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an auto-fading diaphragm control device according to the present invention will be described in detail below with reference to the accompanying drawings.

In the drawing, Rx indicates a photoreceptor such as CdS for well-known TTL photometry, which is placed behind the aperture member 10 operated by a stepping motor, which will be described later. Together with a variable resistor Rv set according to the photosensitivity and fixed resistors R ₁ to R ₃ , a bridge circuit for photometry is connected to the power supply E via the main switch SW ₀ as shown in the figure, and the photoreceptor Rx It is configured to output an unbalanced signal to the next-stage first and second comparators COM ₁ and COM ₂ according to the brightness of the subject light incident thereon. The respective output terminals of the first and second comparators COM ₁ and COM ₂ are connected to one input terminals a and c of the first and second NAND gate circuits NG ₁ and NG ₂ forming the next stage flip-flop circuit. There is. Note that resistors _R4 and _R5 are pull-up resistors. The respective output terminals of the first and second NAND gate circuits NG ₁ and NG ₂ are connected to the first and second inverters INV ₁ and
It is connected to one input terminal e and g of the third and fourth NAND gate circuits NG ₃ and NG ₄ via INV ₂ . Furthermore, in the drawing, reference numeral 20 indicates a stepping motor drive section, which operates when one output of the third and fourth NAND gate circuits _NG3 and _NG4 becomes " ₀ ". It is configured to sequentially excite drive coils represented by _L4 to drive the stepping motor in forward and reverse rotation.
Furthermore, this driving section 20 is configured to drive and control the stepping motor in response to a pulse signal applied via one of the third and fourth NAND gate circuits NG ₃ and NG ₄ . The pulse signal is
It is supplied by a first pulse signal oscillator OSC ₁ that oscillates a high frequency pulse signal and a second pulse signal oscillator OSC ₂ that oscillates a low frequency pulse signal, and these first and second pulse signal oscillators
OSC ₁ and OSC ₂ are connected to the other input terminals f and h of the third and fourth NAND gate circuits NG ₃ and NG ₄ via the fifth and sixth NAND gate circuits NG ₅ and NG ₆ .
are commonly connected. The other input terminals i and j of the fifth and sixth NAND gate circuits NG ₅ and NG ₆ are connected to the respective output terminals of the third and fourth inverters INV ₃ and INV ₄ connected in series, which operate as described below. has been done. The fourth inverter INV ₄ is connected to the output terminal of a monostable multivibrator consisting of transistors Tr ₁ and Tr ₂ and capacitors C and R ₆ to R ₉ , etc., and when the monostable multivibrator is in an operating state, the input is "1"
and is set to become "0" after a predetermined time. The triggering of the monostable multivibrator is based on the switching operation of the first mode changeover switch _SW1 . the first mode changeover switch;
SW ₁ is another second mode changeover switch SW ₂
, and is switched by a single switching operation member (not shown), and the switching operation member can be set to a normal shooting position, a fade-out shooting position rotated counterclockwise from this position, and a fade-out shooting position rotated counterclockwise from this position, and a fade-out shooting position rotated counterclockwise from this position. The rotated fade-in photographing position is taken, and the first and second mode changeover switches _SW1 and _SW2 are changed over by this changeover operation member as follows. That is, when the switching operation member is in the normal shooting position, the first mode changeover switch SW ₁ switches the movable contact A connected to the trigger capacitor of the monostable multivibrator to the open terminal B, and then to the fade-out shooting position. At one time, the movable contact piece A is switched to the grounded fixed terminal C, and when the camera is at the fade-in photographing position, the movable contact piece A is switched to the output terminal D of a third comparator COM ₃ , which will be described later. The other second mode changeover switch SW2 is set to the first mode changeover switch _SW2 when the changeover operation member is in the normal photographing position.
The movable terminal E connected to the output terminal of the NAND gate circuit NG ₁ and the input terminal d of the second NAND gate circuit NG ₂ is connected to the open terminal, and when it is in the fade-out shooting position, the movable terminal E is connected to the grounded fixed terminal G. , and when in the fade-in photographing position, the movable terminal E is switched and connected to a fixed terminal H which is connected to a time setting circuit to be described later via a diode D. The third comparator COM ₃ has its positive input terminal connected to voltage dividing resistors R ₁₀ and R ₁₁ ,
The negative side input terminal is connected to a time circuit including a resistor _R12 and a capacitor _C0 , and is configured to be inverted after a certain period of time determined by the time circuit. Note that SW ₃ is a fade-in start switch that is turned on when the operating member is set to the fade-in photographing position and turned off when the film is started.

The aperture control device configured as described above operates as follows during normal photography, fade-out photography, and fade-in photography.

First, the operation of the aperture control device in normal shooting will be described.
The aperture control device operates as a so-called EE by switching SW ₁ and SW ₂ to connect the movable contact pieces A and E to the open terminals B and G with the operation members in the normal photographing position.

In other words, during normal shooting, this aperture control device changes the output of the first comparator COM ₁ to "1" and the output of the second comparator when the subject brightness increases.
The output of the comparator COM ₂ is "0", the output of the first NAND gate circuit NG ₁ is "0", the output of the second NAND gate circuit NG ₂ is "1", the first inverter INV ₁
The output of the second inverter INV 2 becomes "1", and the output of the second inverter INV ₂ becomes "0". Furthermore, at this time, the monostable multivibrator is not triggered, the input of the fourth inverter INV ₄ is "0", and therefore the input signal of "0" is input to one input terminal i of the fifth NAND gate circuit NG ₅ . , and since the input signal "1" is applied to one input terminal j of the sixth NAND gate circuit NG ₆ , the pulse signal "1" of the first pulse signal oscillator OSC ₁ is applied to the third and fourth NAND gate circuits. It is applied to the other input terminals f and h of NG ₃ and NG ₄ .
Therefore, when the subject brightness becomes high, this aperture control device causes the input of the third NAND gate circuit NG ₃ to become "1, 1", and the stepping motor drive unit 2
0 operates the aperture member 10 toward the closing side using a stepping motor. In addition, when the subject brightness becomes lower than the balanced state, the output of the first comparator COM ₁ becomes "0", and the output of the second comparator
COM ₂ output is "1", first NAND gate circuit
The output of NG ₁ is "1", the second NAND gate circuit NG ₂
The output of the first inverter INV ₁ becomes "0", and the output of the second inverter INV ₂ becomes "1". Therefore, when the subject brightness becomes low, this aperture control device uses the fourth NAND gate circuit.
The input of NG ₄ becomes "1.1", and the stepping motor drive unit 20 uses the stepping motor to drive the aperture member 10 toward the open side.

Next, a case in which this diaphragm control device performs an auto-fading operation will be described below.

First, let's talk about the case where auto-fade-out photography is performed following normal photography. In this case, by rotating the operating member counterclockwise and setting it to the fade-out photography position, the first and second mode selection switches SW ₁ and SW are switched. ₂ is switched, the first mode changeover switch SW ₁ grounds the trigger capacitor C ₁ of the monostable multivibrator,
In addition, the second mode changeover switch _SW2 is switched to ground the output terminal of the first NAND gate circuit _NG1 . Therefore, the first NAND gate circuit NG ₁
The output of becomes “0” and the third NAND gate circuit NG ₃
A signal "1" is applied to one input terminal e of the fourth inverter INV 4, and the monostable multivibrator is in the operating state for a certain period of time determined by the monostable multivibrator, and the fourth inverter INV ₄ input is "1". The signal from the second pulse signal oscillator OSC ₂ is input to the other input terminal f of the third NAND gate circuit NG ₃ via the sixth NAND gate circuit NG ₆ . Therefore, this diaphragm control device sets the operating member to the fade-out photographing position, so that the third
After the operating member is positioned at the fade-out photographing position by the signal from the NAND gate circuit NG ₃ , the aperture member 10 is operated toward the close side at a low speed for a certain period of time based on the low frequency pulse signal from the second pulse signal oscillator OSC ₂ . After the predetermined time has elapsed, the diaphragm member 10 is continued to be moved toward the close side at high speed again based on the high frequency pulse signal from the first pulse signal oscillator OSC ₁ to effect a fade-out.

Next, when performing fade-in photography, the diaphragm control device rotates the operating member clockwise to bring it to the fade-in photography position and turns on the main switch _SW0 , thereby performing fade-in photography. That is, the first mode changeover switch is activated by the above operation.
SW ₁ switches the connection of the trigger capacitor C ₁ to the output terminal of the third comparator COM ₃ , and the second mode changeover switch SW ₂ switches the connection of the trigger capacitor C 1 to the output terminal of the third comparator COM ₃ .
One input terminal d of is connected to the terminal of a capacitor _C0 forming a time constant circuit, and the fade-in start switch _SW3 is turned on.

This aperture control device set as above is
When the main switch SW ₀ is turned on, the output of the third comparator COM ₃ is "1", and the output of the first NAND gate circuit NG ₁ is "0", so that high speed is achieved as described above. The diaphragm member 10 is operated until it is closed, and the shutter release operation turns off the feedback start switch SW ₃ , and the output of the second NAND gate circuit NG ₂ becomes "0", causing the diaphragm member 10 to operate at high speed. As described above, it is operated to the open side. Along with this operation, capacitor C ₀ is charged, and as the terminal voltage of capacitor C ₀ reaches a certain value, the third comparator COM ₃ is inverted and the monostable multivibrator becomes operational. From this point on, the monostable multivibrator is activated at low speed. During the time determined by the vibrator, the aperture member 10 is operated to the open side, that is, to the proper exposure aperture value.

Therefore, during fade-in photography, this aperture control device operates to operate the aperture member 10 at high speed toward the open side for a certain period of time after the fade-in start, and then at low speed.

As is clear from the above description, according to the present invention, when performing fade-in, after the fade-in start, the diaphragm member is operated by switching from high speed to low speed, so that the actual range of fade-in photography is limited. This makes it possible to perform ideal fade-in photography.

[Brief explanation of the drawing]

The drawing is a main circuit diagram of an embodiment of an autofading diaphragm control device according to the present invention. OSC ₁ ...First pulse signal (high frequency pulse signal) oscillator, OSC ₂ ...Second pulse signal (low frequency pulse signal) oscillator, 10...Aperture member, C ₀
...Capacitor, R ₁₂ ...Resistor, COM ₃ ...Third comparator, SW ₁ ...First mode selection switch, SW ₂ ...Second mode selection switch, SW ₃ ...
Fade in-start switch.

Claims (1)

[Claims] 1. A stepping motor driven by a pulse signal in response to a change in subject brightness is configured to control the operation of an aperture member to obtain an appropriate exposure aperture value, and the stepping motor is forcibly driven. a pulse signal oscillation means capable of oscillating the pulse signal into two types of high and low frequency pulse signals in an auto-fading diaphragm control device configured to perform fading by operating the diaphragm member; a pulse signal switching means for switching so that a pulse signal of one of the frequencies of the pulse signal oscillation means can be applied to the stepping motor; and control means for controlling the operation of the pulse signal switching means so that a high frequency pulse signal is applied to the diaphragm and a low frequency pulse signal is applied after the elapse of the predetermined period of time. Control device.