JPS6227699B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an automatic exposure amount control device capable of auto-fading, and more particularly to an automatic exposure amount control device in which an aperture member for controlling the exposure amount is driven using a stepping motor. It is related to the device.

As is well known, an automatic exposure amount control device called TTL metering uses a photoreceptor to measure the light of the subject that has passed through the aperture of the aperture member, and adjusts the brightness of the subject to be measured by the photoreceptor. The aperture member is configured to actuate a driving means for driving the aperture member accordingly to perform feedback control of the aperture member, and also utilizes an aperture member (on a child aperture portion of the aperture called a parent and child aperture) that is linked to the aperture member for the photographic lens. Even those that do have almost the above configuration.
Further, in such an automatic exposure amount control device, the driving means is forcibly operated to drive the diaphragm member between a proper exposure aperture value state and a closed state to perform fade-out or fade-in. It is well known that automatic exposure control devices capable of autofading have also been proposed and put into practical use.

However, the automatic exposure amount control device capable of auto-fading with the above-mentioned configuration is put into a closed state by the fade-in shooting preparation setting operation at the time of fade-in, so no subject light enters the photoreceptor at all. When fade-in is started, the rise characteristics of the photoreceptor are extremely poor, and there is a strong possibility that, for example, the aperture member may overshoot when the fade-in is completed.

Incidentally, in recent years, an automatic exposure amount control device has been proposed that uses a motor called a pulse motor, a stepping motor, or the like (hereinafter referred to as a stepping motor) as the driving means. The advantage of an automatic exposure amount control device using such a stepping motor is that the speed of the stepping motor is determined by the frequency of the pulse signal that drives and controls it, and the operation can be reliably stopped depending on the presence or absence of the pulse signal. Therefore, it is possible to control the aperture at a predetermined speed and set the aperture value to a predetermined value.

SUMMARY OF THE INVENTION In view of the above-mentioned problems, the present invention provides an automatic exposure amount control device capable of auto-fading, which takes full advantage of the advantages of a stepping motor and solves the above-described drawbacks.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an automatic exposure control device capable of auto-fading according to the present invention will be described in detail based on an embodiment shown in the accompanying drawings.

In the drawings, reference numeral 10 indicates an aperture member for controlling exposure amount, Rx indicates a photoreceptor such as a CDS that receives the subject light incident through the aperture member 10, and this photoreceptor Rx includes first and second variable resistors. vessel RV ₁ and
Main switch with RV ₂ and fixed resistors R ₁ and R ₂
Configures a photometric bridge circuit connected to power supply E via SW ₀ , and connects to the first and second comparators in the next stage.
An unbalanced output signal based on changes in subject brightness is provided to COM ₁ and COM ₂ . First and second comparators with pull-up resistors designated R ₃ and R ₄
The output terminals of COM ₁ and COM ₂ are the first and second NAND gate circuits that constitute a flip-flop circuit.
It is connected to one input terminal a and c of each of NG ₁ and NG ₂ . The first and second NAND gate circuits NG ₁ and NG ₂ have their output terminals connected to the third and fourth NAND gate circuits NG 3 and _{NG 4 via} the first and second inverters INV ₁ and INV ₂ , respectively.
are connected to one input terminal e and g of the. Furthermore, the bridge circuit including the photoreceptor Rx is
The third comparator COM ₃ has one input terminal connected to the midpoint between the photoreceptor Rx and the first variable resistor RV ₁ , which is set according to the sensitivity of the film used, and the other input terminal connected to the third comparator COM 3. 2 variable resistor RV ₂
It is connected to the slider of. Said second
The variable resistor RV ₂ is set to correspond to an aperture value approximately 4 to 5 steps below the proper exposure aperture value, taking into consideration the balance of the bridge circuit. The output terminal of the third comparator COM ₃ is connected to one input terminal i of the next fifth NAND gate circuit NG ₅ . Said fifth NAND gate circuit NG ₅
is the output terminal of the 6th NAND gate circuit in the next stage.
It is connected to one input terminal k of NG ₆ and also to the first mode changeover switch SW ₁ .
Furthermore, these fifth and sixth NAND gate circuits NG ₅ and NG ₆ are provided such that their respective other input terminals j and l are grounded via a fade-in setting switch SW ₃ and a second mode changeover switch SW _{2 .} It is connected to the. Said first and second
Mode selection switches SW ₁ and SW ₂ are configured to be externally operable by a single operating member (not shown), and when the operating member is in the neutral position, they are in the normal shooting state and rotated counterclockwise. The photographing mode is switched so that fade-out photographing is performed when the position is rotated in the clockwise direction, and fade-in photographing is performed when the position is rotated clockwise. To illustrate this in terms of the switch configuration, when the operating member of the first mode changeover switch _SW1 is in the neutral position, the movable contact piece A is opened, and when the operating member is in the counterclockwise position, the movable contact piece A is opened.
The movable contact piece A is connected to the ground terminal B, and when the operating member is in the clockwise direction, the movable contact piece A is connected to the fixed terminal C connected to the output terminal of the fifth NAND gate circuit _NG5 . has been done.
Further, the movable terminal 2 of the second mode changeover switch SW ₂ , which is grounded, is commonly connected to one of the input terminals j and l of the fifth and sixth NAND gate circuits when the operating members are sequentially operated as described above. It is configured to be switched and connected to the fixed terminals E and H and then to the fixed terminal G via the fade-in start switch _SW4 . The fade-in setting switch SW ₃ is interlocked with the operating member,
It is configured so that it is turned on when the operating member is rotated clockwise to enter the fade-in shooting state, and is turned off by the second step press operation of the shutter release operation, which turns on the main switch SW ₀ with the first press operation. has been done. Also fade in start switch
SW ₄ is configured to be turned on together with the fade-in setting switch SW ₃ and turned off when the photographing operation, that is, film advance, shutter, etc., starts. The above photographing operation is performed using a thyristor whose gate terminal is connected to the output terminal of the sixth NAND gate circuit _NG6 via the third inverter _INV3 .
This is done by turning on and off the electromagnetic release circuit 30, which includes the SCR, a photographing mode changeover switch _SW5 , and a switch _SW6 connected in parallel with the thyristor SCR. Above shooting mode switch SW ₅
are the first and second changeover switches _SW1 and
Switches in conjunction with SW _2. Normal shooting occurs when the movable contact piece is connected to terminal R, fade-out when it is connected to terminal N, and fade-in shooting when it is connected to terminal L. be. Switch SW ₅ is a normally open switch that is turned on when the shutter release is operated.

Furthermore, in the drawing, Tr ₂ and Tr ₃ indicate transistors that constitute a monostable multivibrator together with a capacitor C and resistors R ₁ to R ₉ , and this monostable multivibrator is connected to a second mode changeover switch SW ₂ . There is. Further, the output terminal of this monostable multivibrator is connected to the seventh NAND gate circuit NG 7 through the fifth and sixth inverters INV ₅ and INV ₆ or _the eighth inverter INV ₅ through the fifth and sixth inverters INV 5 and INV 6.
It is connected to one input terminal n and o of each NAND gate circuit _NG8 . Said seventh and eighth
NAND gate circuits NG ₇ and NG ₈ have 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 connected to their other input terminals m and p, respectively. The respective output terminals are connected to the other input terminals f and h of the third and fourth NAND gate circuits NG ₃ and NG ₄ , respectively. Furthermore, the third and fourth NAND gate circuits NG ₃
and _NG4 , the input terminals f and h are connected to the output terminal of the third inverter _INV3 via a fourth inverter _INV4 . The third and fourth NAND gate circuits NG ₃ and NG ₄ to which input signals are applied as described above have their output terminals connected to a stepping motor drive circuit 20 that sequentially excites drive coils represented by L ₁ to L ₄ . The stepper motor that drives the aperture member 10 is controlled.

The exposure amount control device capable of auto-fading configured as described above is as follows.
Activates during normal auto-fade-out shooting and auto-fade-in shooting.

That is, when performing normal photography, the exposure amount control device operates so that an appropriate amount of exposure is always obtained by setting the operating member to the neutral position and operating the shutter release. By setting this to the neutral position with respect to the operating member, the movable contact A of the first mode changeover switch _SW1 is at the open end, the movable contact D of the second mode changeover switch _SW2 is at the fixed terminal H, Since the movable contact of the photographing mode switch SW ₅ is located at the terminal, the first and second NAND gate circuits NG ₁ and NG ₂ are ready to operate as flip-flop circuits, and the fifth and sixth NAND gates The other input terminals j and l of circuits NG ₅ and NG ₆ are grounded. Therefore, by closing the main switch SW ₀ ,
This exposure amount control device is the 6th NAND gate circuit NG ₆
Even though the output is "1", the electromagnetic release circuit 30 is turned on and the shooting operation is started,
In addition, since the monostable multivibrator is also inactive and the input of the fifth inverter INV ₅ is "0", the high frequency pulse signal from the first pulse signal oscillator osc ₁ is transmitted through the seventh NAND gate circuit NG ₇ to "0". 1” is the third and fourth NAND gate circuit NG ₃ and
The respective input terminals f and h of NG ₄ are applied. In such a situation, if the exposure amount is excessive, the output of the first comparator COM ₁ is "1", the output of the second comparator COM ₂ is "0",
The output of the first NAND gate circuit NG ₁ is “0”, the output of the second
The output of the NAND gate circuit NG ₂ is "1", the output of the first inverter INV ₁ is "1", the second inverter INV ₂
output becomes "0", and as described above, the input of the third NAND gate circuit _NG3 becomes "1, 1", operating the stepping motor drive circuit 20, and the stepping motor moves the aperture member 10 to the close side. Works to drive. In addition, when the amount of exposure is insufficient, the above circuit element is reversed, and the input of the fourth NAND gate circuit NG ₄ becomes "1, 1" and the aperture member 1
0 to the open side.

Therefore, in the exposure amount control device during normal shooting, the stepping motor is driven and controlled by the high frequency pulse signal from the first pulse signal oscillator _OSC1 , so the aperture is adjusted at high speed to follow the change in subject brightness. It is possible to move the member.

Next, the operation of the exposure amount control device during auto-fading will be described assuming that normal photography is now performed and then fade-out photography is performed.

For fade-out photography, turn the operating member counterclockwise to select the first and second mode selection switch _SW1.
This is done by switching SW ₂ and shooting mode changeover switch SW ₅ . That is, in this exposure amount control device, by connecting the movable contact A of the first mode changeover switch _SW1 to the ground terminal B, the output of the first NAND gate circuit _NG1 becomes "0", and the stepping motor is forced to operate. It is driven to the close side. At the same time, by connecting the movable contact 2 of the second mode changeover switch SW ₂ to the fixed terminal, the monostable multivibrator becomes operational, and the input of the fifth inverter INV ₅ is determined by the monostable multivibrator. During this time, the input terminal f of the third NAND gate circuit _NG3 is connected to the second pulse signal oscillator.
A low frequency pulse signal from osc ₂ is applied through an eighth NAND gate circuit NG ₈ . Therefore, during fade-out photography, this exposure amount control device operates to stop down from the appropriate exposure aperture value to achieve fade-out, but at this time, it stops down at a low speed for a certain period of time from the start of fade-out, and after a certain period of time has elapsed, It operates to narrow down the image at high speed again.
Next, the operation of the exposure amount control device during fade-in photography will be described.

In order to perform fade-in photography, first, the operating member is rotated clockwise to set the first and second mode changeover switches _SW1 and _SW2 and the photography mode changeover switch _SW5 to the fade-in photography position. That is, by the above operation, the movable contact A of the first mode changeover switch _SW1 connects with the fixed terminal C, and the movable contact of the second mode changeover switch _SW2 connects with the fixed terminal G. Mode changeover switch
Set the movable contact of SW ₅ to connect to the open terminal, and turn on the fade-in setting switch SW ₃ .

As described above, when the exposure control device that has been operated and set is turned on with the main switch SW ₀ in the first step of the shutter release operation, the third comparator
Since the output of COM ₃ is "1", the outputs of the first and second NAND gate circuits NG ₁ and NG ₂ are "1", and the fade-in start switch SW ₄ is turned off, it is a monostable multivibrator. does not operate and operates in the same way as in normal shooting mode. Here, when the shutter release operation is further performed and the fade-in setting switch SW ₃ is turned off in the second stage operation, this exposure amount control device will cause the output of the first NAND gate circuit NG ₁ to be "0" and the output of the second NAND gate circuit NG to be "0". Since the output of ₂ becomes "1", the aperture member 10 is operated to be driven toward the closing side at high speed as described above. Then, in the above-described operation, the exposure amount control device inverts the output of the third comparator COM ₃ from "1" to "0" when the aperture is narrowed down to the aperture value determined by the second variable resistor RV ₂ . The output of the fifth NAND gate circuit NG ₅ becomes "1" and the first
The output of NAND gate circuit NG ₁ is “1” and the second
When the output of the NAND gate circuit NG ₂ becomes "0", the operating state in which the aperture member 10 is moved toward the closing side as described above is canceled, and when the output of the sixth NAND gate circuit NG ₆ becomes "0", the third and the input terminals f and h of the third and fourth NAND gate circuits NG ₃ and NG ₄ via the fourth inverters INV ₃ and INV ₄ .
The above-mentioned output of "0" is input to , and the signal from the first pulse signal oscillator osc ₁ that has been applied via the seventh NAND gate circuit NG ₇ is stopped.
Therefore, at this time, the diaphragm member 10 performs a diaphragm operation to a state corresponding to an aperture value approximately 4 to 5 steps below the proper exposure aperture value, and then stops. However, in this exposure amount control device, when the output of the sixth NAND gate circuit NG ₆ becomes "0", the thyristor SCR is turned on and the photographing operation is started, so the fade-in start switch SW ₄ is turned off. The monostable multivibrator operates, and as mentioned above, the pulse motor is operated by the low frequency pulse signal from the second pulse signal oscillator OSC ₂ .
Based on the output of the second NAND gate circuit NG ₂ being "1", the aperture member 10 is operated to the open side.

As described above, when fade-in, this exposure amount control device operates at high speed to reduce the aperture value to an aperture value that is approximately 4 to 5 steps under from the appropriate exposure aperture value before photographing, and then at low speed when photographing starts. It operates wide open until the appropriate exposure aperture value is reached, allowing for fade-in photography.

As is clear from the above, according to the automatic exposure control device capable of auto-fading according to the present invention, fade-in photography is started immediately after the aperture is stopped down to an aperture value at which no image substantially appears before fade-in photography starts. Therefore, the response characteristics of the photoreceptor are good, and a stable appropriate exposure value can be obtained without overshooting of the diaphragm member before and after completion of fade-in.

[Brief explanation of the drawing]

The drawings relate to an automatic exposure amount control device capable of auto-fading, which is an embodiment of the present invention. Rx...Photoreceptor, RV ₂ ...Second variable resistor, 10...
Aperture member, 20... stepping motor drive circuit,
SW ₁ ...First mode selection switch, SW ₂ ...Second mode selection switch, osc ₁ ...First pulse signal oscillator,
osc ₂ ...Second pulse signal oscillator, _SW5 ...Photographing mode selection switch, 30...Electromagnetic release circuit.

Claims (1)

[Scope of Claims] 1. An automatic exposure amount control device that operates a driving means in accordance with the brightness of a subject to control the operation of an aperture member, and also forcibly drives the driving means to enable automatic fading by the aperture member. , Prior to fade-in photography, the driving means is driven to reduce the aperture to an aperture value approximately 4 to 5 steps below the appropriate exposure aperture value, and when photography starts, the driving means is driven to open the diaphragm member. An automatic exposure amount control device capable of auto-fading, characterized in that it comprises a fade-in setting means for setting so that fade-in photography is performed. 2. The automatic exposure amount control device capable of auto-fading according to claim 1, wherein a stepping motor is used as the driving means. 3. The stepping motor is provided so that its operation is controlled by a high-frequency pulse signal during driving prior to fade-in imaging by the fade-in setting means, and by a low-frequency pulse signal during fade-in imaging. An automatic exposure amount control device capable of auto-fading as claimed in claim 2.