JPS5953525B2 - Exposure time control device for flash photography - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an exposure time control circuit that provides an exposure time suitable for flash photography in response to a flash emission ready signal from a flash discharge lamp control circuit during flash photography. Japanese Patent Application Publication No. 5
As disclosed in No. 3-1528, during flash photography, shutter closing is inhibited while a flash light emission ready signal is being received, and the flash light emission ready signal disappears when the flash discharge lamp emits light. and an improvement in an exposure time control circuit of the type that initiates shutter closing.

With this type of exposure time control circuit, the exposure time is automatically selected according to the flashlight preparation state of the flashlight emitter, so flash photography can be performed simply by opening and closing the flashlight emitter's power switch or the flashlight readiness detection circuit switch. In addition to being able to select the appropriate exposure time, the shutter is closed in response to the light emitted from the flashlight discharge lamp, so exposure by flashlight discharge lamp illumination can be obtained without waste, making it convenient and rational. It is.

However, for example, when the main subject is illuminated with a flash discharge lamp, and the background is not illuminated or is not sufficiently illuminated, a long exposure is used to take a well-balanced photograph, or the background is illuminated with a slow shutter speed. It was not possible to take pictures with special intentions, such as when the camera was washed away by a camera. The purpose of the present invention is to
It is an object of the present invention to enable photographing with such a special intention to be performed using the exposure time control circuit as described above.

For shooting with such special intentions, it is sufficient to perform flash photography at a shutter speed slower than the flash synchronization limit speed, and flash photography at a shutter speed that is faster than the flash synchronization limit speed is difficult, for example, for focal plane shutters. In this case, the flash discharge lamp emits light while a part of the screen remains obscured by the shutter curtain, resulting in so-called slit exposure, which is undesirable.

Therefore, in the present invention, when the desired exposure time based on a manual setting value or photometric value is longer than a predetermined exposure time that allows flash synchronization, such as the flash synchronization limit speed, flash photography can be performed with the desired exposure time, and when it is short, flash synchronization can be performed. It is configured to provide a possible predetermined exposure time. The present invention will be explained in more detail with reference to illustrated embodiments. Ru.

FIG. 1 is a circuit diagram of the first embodiment of the present invention, and this circuit is as follows:
In order to control the exposure time of a single-lens reflex camera, photometric output and the like are stored prior to the start of exposure, and the exposure time is controlled based on the stored values. In the figure, 1 is a photometric light-receiving element such as a photodiode, which is placed, for example, on the pentaprism roof of a single-lens reflex camera or near the eyepiece, and is designed to receive light from a subject through a photographic lens. . 2 logarithmically compresses the photoelectric output of the light-receiving element 1, and electrically performs photographic calculations on it according to the set exposure conditions such as the set aperture value and film sensitivity, and obtains the appropriate exposure according to the subject brightness and set exposure conditions. This is a photometric calculation circuit that outputs a signal corresponding to time.

4 is a signal corresponding to the exposure time according to the resistance value of the variable resistor 3 which is set by operating an exposure time setting manual operation member (not shown), in other words, a signal corresponding to the exposure time set by the manual operation member. A manual exposure time signal generation circuit outputs a corresponding signal, which signal corresponds to the output signal of the photometry calculation circuit and takes the same level for the same exposure time.

S1 is a manual/automatic selection switch, and automatic exposure contact A or manual exposure contact M is selected by operating a selection operation member (not shown). Note that this selection operation member may be integrated with the exposure time setting manual operation member or may be separate from it. S3 is a memory switch that is opened before the camera's reflection mirror retreats from the photographing optical path, and when it is opened, , the output of the photometric calculation circuit 2 or the manual exposure time signal generation circuit 4 selected by the selection switch S1, that is, the potential at point (a) is stored in the storage capacitor 5.

6 is a logarithmic expansion transistor, and an output current proportional to the inverse logarithm of the storage voltage of the storage capacitor 5 flows through its collector.

S4 is a trigger switch, and S5 is a short-circuit switch for the integrating capacitor 7.
is closed and S5 is opened to start charging the integrating capacitor 7 by the output current of the transistor 6. Reference numeral 8 denotes a switching circuit which inverts the output from "high 7" to "gate-7" and cuts off the transistor 9 when the charging voltage of the integrating capacitor 7 reaches a predetermined value.

An electromagnet 10 prevents the shutter from closing while it is energized, and allows the shutter to close when it is demagnetized.

Jll is connected to the flash discharge lamp control circuit described below, and when it is ready to emit a flash, such as when its main capacitor is fully charged, it becomes extremely high and has low impedance.
After firing the flash or while preparing to fire the flash, the flash signal input terminal becomes extremely high impedance.

Transistor 11 is connected to electromagnet 1 in parallel with transistor 9.
0, and becomes conductive when the potential of the input terminal Jll is high 7. Transistors 12, 13 and resistors 14, 15
is a circuit that level-shifts the potential at point (a) to a level corresponding to an exposure time shorter than the flash tuning limit speed according to the potential of the input terminal Jll, and when the input terminal Jll becomes x high 7, the transistors 12, 13 becomes conductive and performs a level shift effect. S2 is a control switch that connects the input terminal Jll to the base of the transistor 12 only when manual exposure control is selected, and is interlocked with the manual/automatic selection switch S. No. 17 is a constant voltage circuit that generates a voltage corresponding to the flash tuning limit speed (for example, 1/60 second).

16, the potential at the upper end point (b) of this constant voltage circuit 17 is applied to the non-inverting input terminal, and the potential at the above-mentioned point (a) is applied to the inverting input terminal, and when the latter is higher than the former, the output is Mail
[When the voltage becomes 7, the P-channel MOS-FET 19 becomes conductive, and the N-channel MOS-FET 18 is cut off.In the opposite case, the output becomes ＼7 and the FET 18 becomes conductive.
This is a comparator that cuts off 19.

20 is sent through FET 18 or 19 (a
A-D converting the voltage at point ) or point (b), that is, the analog signal as a voltage representing the exposure time, into a digital signal.
The converter 21 is a display circuit that displays the exposure time based on the digital signal.

The potential of the input terminal Jll is also input to the display circuit 21,
When this terminal Jll becomes very high, the display element blinks, for example, to indicate that the flash discharge lamp is ready to emit light. Transistors 22, 23, 24 are input terminals Jll
This is to control the potential at the upper end point (b) of the constant voltage circuit 17 according to the potential of
, 24 are conductive, and the potential at point (b) is set to the power supply voltage level +V
When the input terminal Jll becomes high 7, the transistor 22 becomes conductive, and therefore the transistors 23 and 2
4 becomes non-conductive, and the voltage at point (b) becomes a predetermined voltage from the constant voltage circuit 17. The constant voltage circuit 17 and the transistors 22 to 24 are, for example, a constant current circuit 25 as shown in FIG.
and the resistor 26 are connected in series so that a constant voltage is generated across the resistor 26, and the emitter collector of the transistor 24 is connected in parallel with the constant current circuit 25. When the transistor 24 becomes conductive, the point (b) The potential should be set to +V. FIG. 3 shows an example of a flash discharge lamp control circuit that can be combined with the circuit shown in FIG.
31 is a DC power source 30 when the power switch S6 is closed.
This is a booster circuit that boosts the output of the oscillator, and is composed of a blocking oscillation circuit and the like as is known in the art.

Reference numeral 33 denotes a main capacitor that stores electrical energy at high voltage for the flash discharge tube 46 to emit light, and the output current of the booster circuit 31 flows into the main capacitor via the backflow prevention diode 32.

44 is a trigger capacitor, and 45 is a trigger transformer. When the thyristor 43 becomes conductive, a high voltage is applied to the trigger electrode of the flash discharge tube 46 via the secondary coil of the trigger transformer 45 by the discharge current of the trigger capacitor 44. The flash discharge tube 46 is made conductive and emit light.

A neon tube 34 connected in series with a Zener diode 35 that generates a constant voltage between the terminals is for detecting the voltage of the main capacitor 33, and works in conjunction with the power switch S6 to detect the voltage of the main capacitor 33 when the switch S7 is closed. When charged to a predetermined level or higher, it lights up, supplies current to the Zener diode 35, and generates a constant voltage between its terminals.

36 and 37 divide the voltage of the Zener diode 35,
applied to the base of transistor 38 to make it conductive;
Connection midpoint C of resistors 39 and 40 connected to its collector
This is a voltage dividing resistor that generates a predetermined voltage.

The connection middle point C is connected to the camera side input terminal Jll via the flash discharge lamp side connection terminal Jl2, and is also connected to the base of the transistor 41. The collector of the transistor 41 is connected to the base of the transistor 42, and the emitter of the transistor 41 and the base of the transistor 42 are connected to each other.
2 collector is the flash discharge lamp side connection terminal J22, J32
It is connected to the synchro switch S8 in the camera through the camera-side connection terminals J2l and J3l, and when the synchro switch JS8 is closed in synchronization with the fully open shutter, the emitter of the transistor 41 is closed. When grounded, the neon tube 34 lights up at this time, and if a predetermined voltage is generated across the Zener diode 35, the transistors 41 and 42 become conductive and the thyristor 43 becomes conductive. Next, the operation of the above configuration will be explained.

First, if the flash discharge lamp control circuit shown in FIG. 3 is not connected to the camera-side exposure time control circuit shown in FIG. When required, the output of the photometry calculation circuit 2 or the manual exposure time signal generation circuit 4 is memorized through the selection switch S1 and the memory switch S3, and the voltage of the capacitor 7 charged by the output current based on the memorized value is When the predetermined seven levels are reached, the transistor 9 becomes non-conductive through the switching circuit 8, demagnetizing the electromagnet 10 and closing the shutter.

At this time, the power terminal Jll is in the state of low 7, so the transistor 11 remains non-conductive and does not take part in controlling the shutter, and the transistor 12 is also non-conductive, so the transistor 13 is also non-conductive. , (a) The level of point is not shifted. On the other hand, in the display system, due to the 10-7 state of the input terminal Jll, the transistor 22 becomes non-conductive, and the transistor 23 becomes non-conductive.
. The voltage at point (a) is A-
The exposure time is input to the D converter 20, and the corresponding exposure time is digitally displayed by the display circuit 21. next,
The selection switch S1 and the control switch S2 are respectively connected to the automatic exposure contact A side, and the circuits of FIGS. 1 and 3 are connected to the connection terminals Jll, Jl2, J2l, J22, J3l, J3.
A case will be described in which flash photography is performed in a state in which the light beams are connected by 2.

The power switch S6 in FIG. 3 is closed, and the main capacitor 3
3 is charged to a predetermined level and the neon tube 34 lights up, point (c) becomes high 7, and therefore the input terminal Jll
becomes high 7, and transistors 1L12 and 22 become conductive. Due to conduction of the transistor 11, the electromagnet 10
is excited regardless of the state of transistor 9. Due to the conduction of the transistor 12, the transistor 13 becomes conductive,
The potential at point (a) is level-shifted by the voltage drop caused by the resistor 15, and no matter what level the output of the photometry calculation circuit 2 is, the potential at point (a) is level-shifted by the voltage drop caused by the resistor 15. The voltage reaches a level corresponding to the time, and this potential is stored in the storage capacitor 5. When the shutter is released in this state, the transistor 9 becomes non-conductive at a relatively early stage, the synchro switch S8 is closed in synchronization with the fully opening of the shutter, and when the flash discharge tube 46 emits light,
The voltage of the main capacitor 33 suddenly drops, and the neon tube 34
As a result, the point (c), that is, the input terminal Jll becomes the opening -7, the transistor 11 is cut off, and the electromagnet 10
Demagnetize and close the shutter. On the other hand, in the display system, the transistor 22 becomes conductive due to the high voltage of the input terminal Jll, and as a result, the transistors 23 and 24 are cut off, and the non-inverting input terminal of the comparator 16 is supplied with the flash synchronization limit speed. A corresponding voltage is applied from the constant voltage circuit 17.

As mentioned above, the inverting input terminal of the comparator 16 has
The voltage at point (a) whose level has been shifted by the voltage drop across the resistor 15 is input. Therefore, since the input on the inverting input terminal side of the comparator 16 is higher, it produces an output of 0-7, conducts the P channel FET 19, and connects the constant voltage circuit 17.
The output of . The directly applied high 7 signal causes, for example, an active exposure time display element to blink, indicating that the main capacitor has been charged, that is, the flash discharge lamp is ready to emit light. Selection switch S1 and control switch S2
is connected to the manual exposure contact M, and when flash photography is performed, the level shift circuit 12 is controlled by the control switch S2.
.about.15 is disconnected from the input terminal Jll.

Therefore, even if the input terminal Jll becomes high 7, the transistors 12 and 13 do not conduct, and the level at point (a) is not shifted. On the other hand, transistor 11. and 22 are connected to the input terminal Jll regardless of the state of the control switch S2. Therefore, while this terminal Jll is at high 7, that is, from the completion of charging of the main capacitor 33 of the flash discharge lamp control circuit until the flash discharge tube 46 emits light, the transistor 11 is conductive, exciting the electromagnet 10 and , the voltage of the constant voltage circuit 17 is directly input to the non-inverting input terminal of the comparator. Therefore, when the exposure time set by the variable resistor 3 is shorter than the flash tuning limit speed, the exposure time is controlled by the transistor 11, since the transistor 9 becomes non-conductive earlier than the transistor 11.
Immediately after the flash discharge tube 46 emits light in synchronization with the full opening of the shutter, shutter closing is started. At this time, since the potential at point (a) is higher than the output voltage of the constant voltage circuit 17, the output of the comparator 16 is -7, and the P channel FET
19 is made conductive, the display circuit 21 displays the exposure time of the flash synchronization limit speed, and at the same time, the completion of charging of the main capacitor is also indicated by its blinking. When the manually set exposure time is longer than the flash synchronization limit speed, when the transistor 11 becomes non-conductive due to the light emission of the flash discharge tube 46, the transistor 9 is still in the conductive state, and the manually set exposure time is After a certain period of time, it becomes non-conductive and starts closing the shutter.

That is, the exposure time is controlled by a conventional control circuit.
In this case, since the level of the non-inverting input terminal of the comparator 16 is higher than that of the inverting input terminal, it produces an output of ``high 7'' and conducts the N-channel FET 18, so that the display circuit changes the potential at point (a). Displays the set exposure time according to the FIG. 4 is a circuit example of a camera and a flash emitter showing a second embodiment of the present invention. The same circuit parts as in FIGS. Circuit components such as the booster circuit, neon tube, trigger section, and flash discharge tube of the lamp control circuit are omitted.

In the first embodiment, the selection and control switch Sl on the camera side
, S2 was used to switch the flash photography mode, but in this second embodiment, the flash photography mode is changed by a changeover switch S on the flash discharge lamp side. The switch S is a changeover switch provided on the flash discharge lamp control circuit side. When the switch S is connected to the F side, the potential at the connection point between the resistors 36 and 371 is changed, and when it is connected to the H side, the potential at the connection point between the resistors 371 and 371 is changed.
The potential at the connection point of No. 2 is transmitted to the camera side via terminals J2l and Jll.

Comparators 52, 53, constant current source 54, resistor 55,
Are 56 and 57 flash lights? This is a circuit that determines the level of the signal from. The transistor 50 and the resistor 51 are circuits for increasing the charging current of the integrating capacitor 7 and advancing the switching timing of the switching circuit 8, and are used for the same purpose as the level shift circuit shown in FIGS. The constant current source 100 and the resistors 101 to 10n have n reference potentials (1) to (Vn).
The circuits 201 to 20n are the reference potentials (V1) to (
Comparators 301 to 30n- that compare Vn) with the potential (V1) corresponding to the shutter speed from switch S1;
1 is for adjacent comparators (e.g. 20k and 20k+1
A circuit that outputs a negative signal of the exclusive OR of the outputs of ゛,
Connected to the output of this circuit are LEDs 4Ol to 40n-1 whose illumination is visible, for example, next to the corresponding exposure time scale or number on an exposure time scale or column of exposure time numbers. Depending on which LED lights up, the set or calculated exposure time is displayed.

When LED4OO lights up, it indicates that the calculated exposure time corresponding to the potential at point (a) has exceeded the control limit on the high-speed side that can be controlled by the camera, and when LED4On starts to light up, it indicates that the calculated exposure time corresponding to the potential at point (a) has exceeded the control limit on the high-speed side that can be controlled by the camera. This indicates that the limit has been exceeded. LED4Ok indicates that the set or calculated exposure time is at the flash synchronization limit speed (for example, 1/60 second). 64 is an oscillation device that outputs a signal that always makes the transistor 65 conductive when the transistor 61 is non-conductive, and allows the transistor 65 to repeat the conductive and non-conductive states while the transistor 61 is conductive. It can be implemented with a circuit, for example, a circuit as shown in FIG.

In Fig. 5, transistors 641, 642, capacitor 6
43, 644 and resistors 645 to 648 constitute an astable multivibrator, and when the transistor 61 is non-conducting, the astable multivibrator is inoperative.
Transistor 641 remains conductive, and transistor 65 is enabled to conduct. When the transistor 61 becomes conductive, the astable multivibrator becomes operational, the transistors 641 and 642 alternately become conductive and non-conductive, and the transistor 65 becomes able to repeat the conductive and non-conductive states. It is also possible to provide this oscillation circuit on the flashlight emitter side and input the oscillating signal as the light emission preparation completion signal. Next, the operation shown in FIG. 4 will be explained. First, when flash photography is not being performed, the signal from the photometry calculation circuit 2 or the manual exposure time signal generation circuit 4 is stored in the capacitor 5, and this stored value is converted into an output current logarithmically expanded by the transistor 6. The current is integrated by a capacitor 7, and when this integrated voltage reaches a predetermined value, the output of the switching circuit is inverted to make the transistor 9 non-conductive, the electromagnet 10 is demagnetized, and the shutter starts closing. The display at this time is that the potential (Vi) at point (a) is compared with the reference potentials (V1) to (Vn), and for example, (Vk)
When <(Vi) <(Vk-1), the comparator 201
~20k-1 output becomes high 7, 20k~20n
The output becomes low 7, and the comparators 20k-1 and 2
Only the output of the exclusive OR 30k-1 that inputs the output of 0k becomes low 7, all other circuits become high 7, LED 4Ok-1 lights up continuously, and the voltage changes according to the potential at point (a). Exposure time is displayed digitally.

Next, a case will be described in which the switch S9 of the flash discharge lamp control circuit is connected to the F side and flash photography is performed.

At this time, the outputs of the comparators 52 and 53 are both high 7. Therefore, transistors 11 and 50 become conductive, and switching circuit 8 switches at a higher speed than the flash tuning limit speed, but since transistor 11 is still conducting at that time, shutter closure does not start and the flash discharge continues. When the tube emits light and the input terminal Jll becomes 40-1'', the outputs of the comparators 52 and 53 are inverted to low 7, and the transistor 11 becomes non-conductive and the shutter close is activated.The display at this time First, due to the high 7 of the comparator 52, the transistor 67 becomes conductive, and the potential at point (a) (
Vi) is dropped to ground potential, and comparators 20-1~
All outputs of 20n become high 7, and transistor 6
8 becomes conductive, making it impossible to light up the LED 4On, and enabling the transistors 61 and 66 to become conductive, so that the oscillation circuit 6
4 outputs an oscillation signal to blink an LED 4Ok corresponding to, for example, 1/60 second of the flash synchronization limit speed, indicating that flash photography will be performed at the flash synchronization limit speed.

Next, the operation when the changeover switch of the flash discharge lamp control circuit is connected to the H side will be explained.

At this time, the output of the comparator 52 is ``1'', and the output of the comparator 53 is ``high 2'', and the transistors 11, 60, 61
is conductive, and 50, 66, 67, and 68 are non-conductive. (a
) When the potential (i) at point (i) is higher than the potential corresponding to the flash tuning limit speed, the switching circuit 8 inverts the output at a faster rate than 1/60 seconds, but since the transistor 11 is still conducting, the shutter is closed. However, when the flash discharge tube emits light, the light emission ready signal disappears, the comparator 53 is inverted to 0 low 2, and shutter closing starts. Furthermore, when the output potential (Vi) is lower than the potential corresponding to the flash tuning limit speed, the switching circuit 8 outputs (
a) When the exposure time corresponding to the potential at the point has elapsed, the transistor 9 is turned off, the electromagnet 10 is demagnetized, and the shutter is closed. Therefore, it is possible to perform flash photography in which the shutter is controlled at a speed lower than the flash synchronization limit speed.

In this case, the display is as shown below when the potential (Vi) at point (a) is higher than the potential corresponding to the flash tuning limit speed.

This signal is inverted to high 2 by the inverting circuit 62, making the transistor 63 conductive and turning off the LEDs 4OO to 40k-1.At the same time, the LED 4Ok is made to blink using the output signal of the oscillation circuit 64 at the flash synchronization/limit speed. Displays that flash photography will be performed. (a) When the potential (Vi) at point (a) is lower than the potential corresponding to the flash tuning limit speed, (a)
) LED 4 indicating the exposure time corresponding to the potential (Vi) of the point
One of the LEDs Ok to 40n is blinked by a signal from the oscillation circuit 64 to indicate that flash photography will be performed at an exposure time corresponding to the blinking LED. As described in detail above, according to the present invention, a flash photography can be performed using a simple structure of simply adding a manual operation member to an exposure control device for flash photography as proposed in Japanese Patent Application Laid-open No. 53-1528. , the shutter closes in response to the flash discharge tube's light emission, and in addition to the mode that allows shooting with the minimum necessary exposure time, if the planned exposure time is shorter than the flash synchronization limit speed, the flash synchronization limit speed is selected. If the exposure time is long, a mode in which flash photography is performed with the scheduled exposure time can be selectively performed by manual operation of the manual operation member, and special modes such as balancing the exposure by using the flash and a slow shutter speed or long exposure are available. It becomes possible to take pictures as intended.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of an embodiment of the present invention, Fig. 2 is a partial circuit diagram showing an example of the constant voltage circuit of Fig. 1, and Fig. 3 is a circuit diagram of a flash discharge lamp control circuit to be combined with the circuit of Fig. 1. FIG. 4 is a circuit diagram showing an example, FIG. 4 is a circuit diagram of another embodiment, and FIG. 5 is a circuit diagram showing a specific example of an oscillation circuit used in the circuit of FIG. 1 to 9: first deterrent circuit, Jll,ll, 53: second deterrent circuit, 10: electromagnet, 13, 15, 50, 51: auxiliary control circuit, S2, S,, l2, 52: switch means.

Claims (1)

[Claims] 1. In a flash photography device that emits flash light when the shutter is fully open, a first suppression circuit outputs a suppression signal for suppressing shutter closing operation for a period of scheduled exposure time based on a manually set value or a measured value of subject brightness. and a second control signal that outputs a suppression signal for suppressing the closing operation of the shutter during the generation period of the light emission preparation completion signal which is generated when the flashlight emission preparation of the flashlight emitter is completed and disappears when the flashlight emission is completed.
an electromagnet that releases the inhibition of shutter closing operation when the inhibition signals from both the first and second inhibition circuits disappear; and an electromagnet that is activated by the light emission ready signal and is activated at the scheduled exposure time Regardless, an auxiliary control circuit that controls the first suppression circuit so as to cause the suppression signal from the first suppression circuit to disappear in a shorter period from when the shutter is opened until the light emission ready signal disappears; and a manual operation. a first state in which the operation of the auxiliary control circuit is permitted; and a second state in which the operation of the auxiliary control circuit is prohibited and the inhibition signal from the first inhibition circuit is output as is for the period of the scheduled exposure time; 1. An exposure time control device for flash photography, comprising: a switch means that is selectively switched in response to manual operation of the manual operation member.