JPH0462055B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a series dimming type electronic flash device that stops emitting light by cutting off the discharge current of the main capacitor when the integrated value of reflected light from the subject reaches a predetermined value. It is about improvement.

A so-called series dimming type electronic flash device discharges only the charge corresponding to the amount of light necessary and sufficient for photographing from the main capacitor, depending on the photographing distance and the reflectance of the subject. Therefore, in the case of a close-distance object with a high reflectance, only a small amount of charge is discharged, so that the time required to emit light again after emitting light can be significantly shortened. As a result, by using the automatic winding drive device in combination, it becomes possible to perform flash photography repeatedly at high speed.

High-speed continuous shooting with an electronic flash device is only possible with objects that are very close and have a high reflectance. If these conditions are not met, the main capacitor of the flash device will not be able to keep up with the charge and will not be able to obtain a sufficient amount of light. . The conventional device has a drawback in that it cannot be determined whether the charging of the flash device can follow the frame speed of the automatic winding drive device.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks and provide an electronic flash device that can automatically and accurately determine whether or not the charge of the main capacitor can follow continuous shooting by an automatic winding drive device. That's true.

In order to achieve this object, the present invention provides a detection circuit that detects the amount of flash light consumed in one flash light emission, and a detection circuit that detects whether the amount of flash light emission detected by the detection circuit is smaller than a predetermined amount. The present invention is characterized in that it is provided with a determination circuit that determines that continuous flash photography is possible by determining that the amount of flash light emission is smaller than a predetermined amount. Note that the amount of flash light emission is detected in the form of flash duration, amount of discharged charge, etc.

Hereinafter, the present invention will be explained in detail based on illustrated embodiments.

FIG. 1 shows an embodiment of the present invention.
An oscillating booster circuit 5 consisting of a transistor 1, a capacitor 2, an oscillating transformer 3, and a resistor 4 is connected to a power source E. The output of this oscillating booster circuit 5 is supplied to a main capacitor 7 via a diode 6. The main capacitor 7 includes a series circuit of a resistor 8 and a trigger thyristor 9, a series circuit of a flash discharge tube 10 and a main thyristor 11, a series circuit of a resistor 12 and a commutating thyristor 13, and a series circuit of a resistor 14, a neon tube 15, and a resistor 1.
Six series circuits are connected in parallel. A capacitor 17 is connected in parallel to this resistor 16, forming a base circuit of a transistor 18. A series circuit of a trigger capacitor 19 and a primary winding 20a of a trigger transformer 20 is connected in parallel to the trigger thyristor 9.
0b has one end connected to the trigger electrode 1 of the flash discharge tube 10.
0a, the other end is the flash discharge tube 10 and the main thyristor 1.
1 connection point _P1 , respectively. A resistor 21 is connected in parallel to the main thyristor 11,
Further, a series circuit including a commutating capacitor 22, a resistor 23, a capacitor 24, and a resistor 25 are connected in parallel. A connection point P ₂ between the capacitor 24 and the resistor 25 is connected to the gate of the main thyristor 11. Also, the connection point P ₃ between the capacitor 22 and the resistor 23
is connected to the connection point P ₄ between the resistor 12 and the commutating thyristor 13.

The base of a transistor 26 whose emitter is connected to the positive end of the power source E is connected to the negative end of the power source E through a series circuit consisting of a resistor 27, a transistor 18, and a synchro contact 28. A series circuit of a resistor 29 and a constant voltage diode 30 is connected to the collector load of this transistor 26, and the collector is connected to a trigger thyristor 9 via a resistor 31.
connected to the gate. The constant voltage diode 3
0 includes a series circuit of a capacitor 32 and a resistor 33,
A series circuit of resistors 34 and 35, a comparator 36,
Comparator 37, series circuit of light receiving element 38 and integrating capacitor 39, AND gate 40, resistor 41
and a series circuit of thyristor 42, comparator 43
are connected sequentially in parallel. The capacitor 32 is connected to the non-inverting input terminal of the comparator 36.
A connection point P ₅ between the resistor 33 and the resistor 33 is connected to the inverting input terminal, and a connection point P ₆ between the resistor 34 and the resistor 35 is connected to the inverting input terminal.
The output terminal of comparator 36 is connected to one input terminal of AND gate 40.

A connection point P ₇ between the light receiving element 38 and the integrating capacitor 39 is connected to the non-inverting input terminal of the comparator 37.
However, connection point P ₆ is connected to the inverting input terminal, respectively.
The output terminal of this comparator 37 is connected to the other input terminal of the AND gate 40 and also to the gate of the commutating thyristor 13 via a resistor 44. Comparator 36 and comparator 37
AND gate 40 whose input terminal is connected to the output terminal of
The output terminal of is connected to the gate of the thyristor 42 via a resistor 45.

The inverting input terminal of the comparator 43 is connected to the resistor 41.
and the connection point _P8 of the thyristor 42, and the non-inverting input terminal is connected to the connection point _P6 . A capacitor 46 is connected in parallel with the thyristor 42. The output terminal of comparator 43 is connected to the base of transistor 48 via resistor 47.

This transistor 48 has its emitter connected to the positive end of the power source E, and its collector connected to the negative end of the power source E via a diode 49 and a capacitor 50. A series circuit of a resistor 51 and a light emitting display element 52 and a transistor 53 are connected in parallel with the capacitor 50.
The emitter and collector of are connected. The base of the transistor 53 is connected to a resistor 29 and a constant voltage diode 3 through a series circuit of a resistor 54 and a capacitor 55.
0 connection point P ₉ .

In FIG. 1, 56 is a light amount control circuit, 57 is a photometric circuit, and both circuits 56 and 57 form a dimming circuit. The photometry circuit 57 is also used as a circuit for detecting the flash duration in actual light emission. 58 is a setting circuit for setting the maximum flash time for the maximum amount of light emission, and 59 is a display circuit.

An automatic hoisting drive device 60 such as an electric hoisting drive device surrounded by a broken line in FIG. 1 has a changeover switch 61 built therein. Depending on the operating mode of the automatic winding drive device 60, the changeover switch 61 is switched to one contact S side for single-frame shooting and to the other contact C side for continuous shooting. Changeover switch 61
A contact A and one contact S are connected to both ends of the resistor 33.

One embodiment of the present invention is constructed as described above, and its operation will be explained below.

When a power switch (not shown) is turned on, the oscillation booster circuit 5 is activated and charges the main capacitor 7, trigger capacitor 19, and commutating capacitor 22 to the polarities shown in the drawing through the diode 6, respectively. When the charging voltage of the main capacitor 7 reaches a sufficiently high value to cause the flash discharge tube 10 to emit light, the neon tube 15 for indicating completion of charging is lit, and the base potential of the transistor 18 rises.

When the synchro contact 28 turns on in this state,
Transistor 18 turns on, causing base current to flow through transistor 26 .
is turned on, current is supplied to the gate of the trigger thyristor 9 via the resistor 31, and the trigger thyristor 9 is turned on. When the trigger thyristor 9 is turned on, the charge in the trigger capacitor 19 is discharged through the primary winding 20a of the trigger transformer 20, and the secondary winding 20a of the trigger transformer 20 is discharged.
The high voltage induced in b is applied to the trigger electrode 10a of the flash discharge tube 10 to ionize the flash discharge tube 10, and this discharge current is applied to the gate of the main thyristor 11 via the commutating capacitor 22 etc. The thyristor 11 is turned on and the flash discharge tube 10 starts emitting light.

At the same time that the transistor 26 is turned on and a gate signal is given to the trigger thyristor 9, current is supplied to the constant voltage diode 30 through the resistor 29, and the voltage generated across this is applied to the setting circuit 5.
8. Works as a power supply voltage for the photometry circuit 57, AND gate 40, and display circuit 59. When the flash discharge tube 10 emits light and reflected light from the subject enters the light receiving element 38, the integral capacitor 39 is charged by a photoelectric current corresponding to the magnitude of the incident light, and this charging voltage is applied to the voltage regulator diode 30. constant voltage resistor 3
When the voltage at the connection point P ₆ divided by 4 and 35 is reached,
The output of the comparator 37 is inverted from low level to high level, and commutating thyristor 13 is turned on by receiving this high level output at its gate. As a result, commutation capacitor 22 and commutation thyristor 13
A commutating circuit is formed which includes a main thyristor 11 and a commutating circuit, and the main thyristor 11 is turned off by a discharge current caused by the charge of the commutating capacitor 22 flowing through this commutating circuit, thereby stopping the flash discharge tube 10 from emitting light.

If the time from when the flash discharge tube 10 starts emitting light until the commutation circuit operates and stops emitting light, that is, the flash time, is T, then the shorter the flash time T, the less charge will be discharged from the main capacitor 7, and the next time. The time required to complete the flash preparation is short, and it can follow high-speed continuous shooting. Let T _M be the maximum flash duration that can follow continuous shooting when the automatic winding drive device 60 is used.

When continuous photographing is performed using the automatic winding drive device 60, the changeover switch 61 is switched to the other contact C side, so both ends of the resistor 33 are not short-circuited by the changeover switch 61. At this time, the capacitor 32 is charged through the resistor 33 due to the constant voltage generated in the constant voltage diode 30, and the capacitor 32 is charged through the resistor 33.
The non-inverting input of 6 decreases over time.
The non-inverting input is the connection point from the start of power supply to the setting circuit 58.
The output of the comparator 36 is at a high level until the constant voltage of _P6 is reached, and thereafter the output of the comparator 36 is at a low level. Here, the time during which the output of the comparator 36 is at a high level is set as the maximum flash time T _M described above.

Next, we will consider cases in which the flash time T is shorter than the maximum flash time T _M and cases in which it is better, using FIGS. 2 and 3.

() When it is shorter than the maximum flash time T _M (can follow continuous shooting) The waveforms of each part in this case are shown in Figure 2. If the flashing time in this case is _T1 , then since _T1 < _TM , there is a time period _T1 to _TM in which both the outputs of the comparators 36 and 37 are at a high level. Therefore, the output of the AND gate 40 is T ₁ ~
It is at a high level during T _M. This high-level signal turns on the thyristor 42 through the resistor 45, and the charge that had been charged in the capacitor 46 until then is discharged at once through the thyristor 42, and the inverting input of the comparator 43 goes low before reaching the potential at the connection point _P6 . Therefore, the output of the comparator 43 remains at a high level, the transistor 48 remains off, the light-emitting display element 52 does not light up, and continuous shooting is displayed.

() When longer than the maximum flash time T _M (unable to follow continuous shooting) The waveforms of each part in this case are shown in Figure 3. If the flash duration in this case is T ₂ , then T _M <T ₂ , so by the time the output of the comparator 37 is inverted from low level to high level, the output of the comparator 36 is already at the low level.
In other words, the outputs of the comparators 36 and 37 are never at high level, and the AND gate 40
Since the output of the thyristor 42 never becomes high level, a gate signal to the thyristor 42 is not generated, and the thyristor 42 is never turned on. Capacitor 46 connected to the inverting input terminal of comparator 43
is not discharged by the thyristor 42,
It continues to be charged through the resistor 41, and finally reaches the potential of the connection point _P6 , which is a non-inverting input, at time _T3 .
At this point, the output of the comparator 43 is inverted from high level to low level, thereby turning on the transistor 48, charging the capacitor 50 through the diode 49, and charging the capacitor 50 through the resistor 51 and the light emitting display element 52. , by lighting the light-emitting display element 52, it is displayed to the photographer that the flash duration T is longer than the maximum flash duration _TM and that continuous photography is not possible. Normally, the duration of the voltage generated in the voltage regulator diode 30 is about 10 milliseconds, but since the capacitor 50 is instantly charged through the transistor 48 and the diode 49, the time constants of the capacitor 50 and the resistor 51 should be made large. For example, the display time that continuous shooting is not possible can be made long enough for the photographer to be able to sense it. The photographer approaches the subject in accordance with this display and takes pictures from a distance that ensures continuous shooting, thereby avoiding mistakes in shooting due to inability to follow continuous shooting.

Next, let us consider a case where a message indicating that continuous shooting is not possible is displayed after the first light is emitted, and it becomes possible to follow continuous shooting by moving the camera closer. If the next shooting is performed while the display indicating that continuous shooting is not possible is still displayed, the capacitor 5
5. A base current is supplied to the transistor 53 through the resistor 54, and the transistor 53 is turned on, discharging the charge stored in the capacitor 50 at once, and stopping the display indicating that continuous shooting is not possible. If the time constants of the resistor 54 and the capacitor 55 are properly determined, the capacitor 50 can be sufficiently discharged, and the transistor 53 can be turned off by the time the transistor 48 can be turned on.

In the illustrated embodiment, the photometric circuit 57 corresponds to the detection circuit of the present invention, and the AND gate 40 corresponds to the discrimination circuit of the present invention.

In the illustrated embodiment, a light display circuit 59 is provided for simplicity of the circuit, but a sound display circuit may be provided instead. Further, although the light emitting display element 52 is turned on when continuous shooting is not possible, it may be turned on when continuous shooting is possible. Furthermore, without displaying or in combination with display, the high level output of the AND gate 40 is sent to the camera, and the next shutter release is enabled only when the camera side receives the high level output. You can do it like this.

As a physical quantity that is a variable related to the amount of light emitted, the amount of discharged charge of the main capacitor 7 can be used instead of the flash duration. In this case, for example, if a current detection resistor is connected in series to the main thyristor 11 and a capacitor is charged by the voltage generated across the current detection resistor, the charging voltage of this capacitor will be the same as that of the main capacitor 7. Since it is proportional to the amount of discharged charge, it is determined whether or not the charge of the main capacitor can follow continuous shooting by comparing the maximum light emission amount with a reference voltage that is proportional to the maximum amount of discharged charge of the main capacitor 7. I can do it.

As explained above, according to the present invention, the amount of flash light consumed in one flash light emission is detected, it is determined whether the detected flash light amount is smaller than a predetermined amount, and the flash light emission amount is determined. Since it is determined that continuous flash photography is possible by determining that the amount is smaller than a predetermined amount, it is possible to automatically and accurately judge whether or not it is possible to follow continuous flash photography.
It is possible to prevent shooting errors due to inability to follow the image.

[Brief explanation of drawings]

Figure 1 is a circuit diagram showing one embodiment of the present invention, Figure 2 is a circuit diagram showing an embodiment of the present invention.
3 and 3 are output waveform diagrams of various parts in an embodiment of the present invention. 7... Main capacitor, 10... Flash discharge tube, 1
1... Main thyristor, 13... Commutation thyristor,
28... Synchro contact, 38... Light receiving element, 39
... Integral capacitor, 40 ... And gate, 5
6...Light amount control circuit, 57...Photometering circuit, 58...
...setting circuit.

Claims (1)

[Scope of Claims] 1. A series dimming type electronic flash device that stops emitting light by cutting off the discharge current of the main capacitor when the integrated value of reflected light from the subject reaches a predetermined value, A detection circuit that detects the amount of flash light consumed in one flash emission, and a detection circuit that determines whether the amount of flash light emission detected by the detection circuit is smaller than a predetermined amount, 1. An electronic flash device comprising: a determination circuit that determines that continuous flash photography is possible when determining that the size of the electronic flash is small.