JPS6126200B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an automatic light control type electronic flash device that can constantly perform appropriate light emission control without causing overexposure, especially during close-range photography, with little loss of light emission energy and no unnecessary light emission. .

Camera automation has become remarkable these days, and flash devices, which provide auxiliary light, are now integrated with the camera, and their light emission is controlled in relation to the distance to the subject, shutter speed, etc. There are two methods of controlling this type of automatic dimming type electronic flash device: one is to put a switching element in parallel with the flash discharge tube to short-circuit unnecessary electrical energy, and the other is to put a switching element in series with the flash discharge tube to open the discharge circuit. There is. The so-called parallel method described above consumes unnecessary energy for each control, and the residual charge of the main capacitor becomes close to zero, resulting in large energy loss and a long recharging time to the main capacitor. The drawback is that it takes a long time to reach a state where flash light can be emitted.

On the other hand, _the series method uses a commutating capacitor _C2 to turn off the switching element _SCR1 as shown in Fig. The electric charge of the commutating capacitor _C2 charged with the polarity flows in the direction of the arrow, and the switching element _SCR1 becomes non-conductive due to the reverse voltage. Thereafter, the residual charge in the main capacitor _C1 reversely charges the commutating capacitor _C2 , and at this time the charging current flows through the flash discharge tube T. Therefore, as shown in Figure 1b, the flash discharge tube T emits an extra amount of light B than the desired point A, and for example, when a camera is adjusted to a short distance in preparation for close-up photography, the amount of exposure is reduced. There was a drawback that the amount was too high.

On the other hand, looking at the user's preferences, in response to the automation of cameras as mentioned above, they would like to take pictures of subjects that can be photographed with a camera using an automatic flash electronic flash device, except for those that are far away where the light cannot reach. I have a request. However, when photographing a very close subject using automatic flash control with the lens aperture wide open,
As mentioned above, in the series type, overexposure occurs due to the commutation capacitor. In addition, when the distance to the subject is considerable and a large amount of light is required, the parallel type as described above has a large energy loss and the capacity of the main capacitor is also large, so it takes longer to become ready to emit light. It is inappropriate because it takes time. As described above, both the serial type and the parallel type have drawbacks depending on the type of photography the camera takes, and neither type of control type can satisfy the needs of users.

This invention was made with these points in mind, and it skillfully brings out the advantages of the so-called parallel and series control methods. When shooting, the light rises well and there is no overexposure.
An object of the present invention is to provide an automatic light control type electronic flash device that can always perform accurate and stable control.

The present invention includes first and second main capacitors connected to the flash discharge tube, which are charged in advance before the flash discharge tube emits light, and a first switching element connected in series to the flash discharge tube, The circuit includes a series light amount control circuit that controls the amount of light emitted from the flash discharge tube by the electric charge of the first main capacitor, and a second switching element connected in parallel to the flash discharge tube.
A parallel light intensity control circuit is provided to control the amount of light emitted by the flash discharge tube based on the charge of the main capacitor.When shooting at long distances, that is, when a large amount of light is emitted, the final light amount is controlled by the series light amount control circuit, and when shooting at close distances, the final light amount is controlled by the parallel light amount control circuit. The amount of light emitted is controlled by a light amount control circuit.

More specifically, the second switching element is first turned on by a pulse signal generated when light is reflected from a subject due to light emission from a flash discharge tube, and a flash discharge is caused by the charge in the second main capacitor. The tube stops emitting light, and during close-up photography, the parallel light amount control circuit completes control of the amount of light emitted.

Next, when the pulse signal is not generated after a certain period of time has elapsed since the flash discharge tube was activated, that is, during long-distance photography, the first switching element is further turned on to increase the charge amount of the flash discharge tube. The flash discharge tube continues to emit light due to the large charge of the first main capacitor, and then, when the pulse signal is generated, the first switching element is turned off to cause the flash discharge tube to emit light due to the charge of the first main capacitor. make it stop.

An embodiment of the present invention will be described below with reference to the drawings. First, to explain the schematic configuration with reference to FIG. 2, a first main capacitor is connected between both ends of the DC power supply 11.
C ₁ is connected, and a series circuit of a flash discharge tube 12 and a series light amount control circuit 13 is connected in parallel with this first main capacitor C ₁ . Further, a parallel light amount control circuit 14 and a second main capacitor C ₂ are provided in parallel with the flash discharge tubes 1 and 2, and a resistor 15 is further provided between the second main capacitor C ₂ and the negative terminal of the DC power supply 11. is connected.

A trigger circuit 16 is connected to the trigger electrode of the flash discharge tube 12 and is connected to a trigger circuit 16 that triggers based on a signal generated in response to the shutter operation of the camera, and the output end of this trigger circuit 16 is further connected to a delay circuit 17 and a gate circuit 18. be done. The output terminal of this gate circuit 18 is connected to the series light quantity control circuit 13 and also to one input terminal of an AND circuit 19, and the output terminal of this AND circuit 19 is connected to the series light quantity control circuit 13. The other input terminal of the AND circuit 19 is connected to the output terminal of the pulse generating circuit 20. The output end of this pulse generation circuit 20 is also connected to the parallel light amount control circuit 21, and the input end thereof is connected in series with an integrating circuit 22 and a light receiving section 23.

In such a configuration, the first main capacitor
C ₁ is directly charged by the DC power supply 11 , and the second main capacitor C ₂ is charged by the DC power supply 11 via the resistor 15 . In this state, when a signal is applied to the trigger circuit 16 by the camera shutter, the flash discharge tube 12 is ignited and the second
Due to the charge on the main capacitor C ₂ of the flash discharge tube 12
emits light. This light emission causes reflected light from the subject to enter the light receiving section 22 . This reflected light is converted into an electrical quantity by the light receiving section 22, integrated by the integrating circuit 21, and applied to the pulse generating circuit 20. This pulse generating circuit 20 generates a pulse when a predetermined input reflected light hits, and the pulse is applied to the parallel light amount control circuit 14. This turns on the second switching element in the parallel light amount control circuit 14, short-circuits the second main capacitor _C2 , and stops the flash discharge tube ₁₂ from emitting light due to the charge of the second main capacitor C2. do. On the other hand, if there is no output pulse from the pulse generation circuit 20 after a certain period of time has elapsed after the flash discharge tube 12 is activated by the trigger circuit 16, the serial light amount control circuit 13 The first switching element in the control circuit 13 is turned on, and the flash discharge tube 12 continues to emit light due to the charge of the first main capacitor _C1 . The output pulse of the pulse generating circuit 20 is also applied to the AND circuit 19 and ANDed with the output pulse of the gate circuit 18.
9, the first in the series light amount control circuit 13
The switching element is turned off, and the flash discharge tube 12 stops emitting light due to the charge of the first main capacitor _C1 .

In this way, if a pulse is generated from the pulse generation circuit 20 before the first main capacitor C ₁ starts emitting light, control is performed by the parallel light amount control circuit 14 as described above, and after that, the pulse generation circuit 20 generates a pulse. When a pulse occurs, the series light amount control circuit 1
Control is performed by 3.

Now, to explain a more specific configuration, as shown in FIG. 3, one end of a flash discharge tube 12 such as a xenon flash discharge tube has an inductor 2
3. Power supply circuit 11 via diode 24 in parallel
The other end of the flash discharge tube 12 is connected to a switching element 25 such as a silicon controlled rectifier element.
(first switching element)
Connected to the negative terminal of 1. Further, the secondary side of a trigger coil 26 is connected between the trigger electrode of the flash discharge tube 12 and the anode of the switching element 25, and one end of the primary side of the trigger coil 26 is connected to one end of the switch 28 via a capacitor 27 and It is connected to the connection point between the inductor 23 and the flash discharge tube 12 via a resistor 29, and further connected to the negative terminal of the power supply circuit 11 via a capacitor 30. The other end of the primary side of the trigger coil 26 is connected to the other end of the switch 28, and the other end of the trigger coil 26 is connected to the other end of the switch 28.
It is connected to the gate of the switching element 25 via a switching element 31 having constant voltage characteristics such as a Zener diode or a trigger diode. This gate is connected to the power supply circuit 1 through a resistor 32.
1 and the AND circuit 19
is connected to one input end of the The connection point between the switching element 31 and the resistor 10 is the capacitor 3.
3. Connected to the negative terminal of the power supply circuit 11 via a resistor 34 in parallel. A parallel circuit of an inductor 35 and a diode 36 is connected to the connection point of the flash discharge tube 12 with the inductor 23, and a first main capacitor C ₁ is connected between the other end of this parallel circuit and the negative end of the power supply circuit 11. is connected. Further, a resistor 47 and a switching element 37 such as a silicon-controlled rectifier are connected in series between the connection point of the flash discharge tube 12 with the inductor 35 and the negative terminal of the power supply circuit 11. A capacitor 38 is connected between the anode of this switching element 37 and the anode of the switching element 25.
The gate of the switching element 37 is connected to the negative terminal of the power supply circuit 11 via the resistor 39, and is also connected to the output terminal of the AND circuit 19.

On the other hand, a discharge tube 40 such as a quench tube (second switching element) and a resistor 15 are connected in series between the positive and negative ends of the power supply circuit 11, and a trigger coil 41 is connected to the trigger electrode of the discharge tube 40. be done. One end of the primary side and one end of the secondary side of this trigger coil 41 are commonly connected to the negative terminal of the power supply circuit 11, and one end of the primary side is connected to the anode of a switching element 43 such as a silicon-controlled rectifier element via a capacitor 42. connected to. This switching element 43 and a resistor 44 are inserted and connected in series to both ends of the power supply circuit 11. This resistor 44 and switching element 4
3 is connected to one end of the switching element 31 via a diode 45. Further, the gate of the switching element 43 is connected to the negative terminal of the power supply circuit 11 via the resistor 46, and is also connected to the output terminal of the pulse generating circuit 20.

To explain the correspondence between FIG. 2 and FIG. 3, the series light amount control circuit 13 in FIG. The parallel light amount control circuit 14 in FIG. 2 includes the discharge tube 40, trigger coil 41, capacitor 42, switching element 43, resistors 44, 4 in FIG.
This corresponds to part 6. The trigger circuit 16 in FIG. 2 corresponds to the trigger coil 26, capacitor 27, switch 28, and resistor 29 in FIG.
The delay circuit 17 in FIG. 2 is connected to the resistors 10 and 3 in FIG.
4, corresponding to the capacitors 30 and 33, and the second
The gate circuit 18 in the figure corresponds to the switching element 31 in FIG.

In this configuration, the first main capacitor C 1 is directly connected to the power supply circuit 11 and the second main capacitor C ₁ is directly connected to the power supply circuit 11 .
C ₂ is charged via the resistor 15, and the capacitor 38 is charged via the resistors 15 and 47.
Capacitor 30 is charged via resistor 29, and capacitor 27 is charged via resistors 29, 10, and 34. When the switch 28 is turned on in conjunction with the shutter operation of the camera, the charge in the capacitor 27 flows to the primary side of the trigger coil 26 of the flash discharge tube 12, and a high voltage is generated on the secondary side. Therefore, the gas sealed in the flash discharge tube 12 is ionized, and the charge in the main capacitor _C2 flows into the flash discharge tube 12 via the inductor 23, causing light emission. At the same time, by turning on the switch 28, the electric charge of the capacitor 30 is transferred to the capacitor 33 via the resistor 10.
and this is charged. This capacitor 33
When the voltage reaches a certain value after a certain period of time, the switching element 31 becomes conductive, a voltage is applied to the gate of the switching element 25, and this switching element 2
5 becomes conductive. This switching element 25
Due to the conduction, the charge in the main capacitor _C1 flows to the flash discharge tube 12, and light emission continues with a predetermined time difference from the start of discharge of the main capacitor _C2 .

When reflected light returns from the subject due to such light emission, the reflected light is detected by the light receiving section 22 and a pulse is generated from the pulse generating circuit 20 as described above. This pulse is applied to the gate of switching element 43 and therefore
3 is conductive. Then, the charge of the capacitor 42 flows to the trigger coil 41, generating a high voltage on its secondary side, which is applied to the trigger electrode of the discharge tube 40 as a switching element connected in parallel to the capacitor _C2 . Therefore, it is applied to the trigger electrode of the discharge tube 40. Therefore, the gas inside the discharge tube 40 is ionized, and since the internal impedance of the discharge tube 40 during ionization is sufficiently lower than that of the discharge tube 12, the first main capacitor _C2 is short-circuited. Therefore, the flash discharge tube 12 stops emitting light.

That is, if a pulse is applied to the gate of the switching element 43 during the period when the flash discharge tube 12 is being discharged due to the charge of the second capacitor _C2 , the capacitor 33 is discharged through the diode 45 due to the conduction, so that the switching element 25 does not become a conductive state. Therefore the first main capacitor
C ₁ does not discharge and there is no loss of it.

Next, when a pulse is generated from the pulse generation circuit 20 after the flash discharge tube ₁₂ emits light due to the charge of the second main capacitor C2, and the light emission shifts to light emission due to the charge of the first main capacitor _C1 , the switching element 43 becomes conductive, but the AND circuit 19 is already turned on, and a pulse is applied to the gate of the switching element 37.
conducts. Then, the charge stored in the commutation capacitor 38 flows through the switching element 37, and a reverse voltage is applied to the switching element 25, which becomes non-conductive. Therefore, the flash discharge tube 12 stops emitting light.

When the light is emitted towards a very close subject in this way, the reflected light returns quickly and has a value that can generate pulses in a short time, so the second main capacitor C ₂ for parallel light amount control is used. Light amount control is performed by short-circuiting. Therefore, in this case, unlike serial light amount control, there is no sharpness in the light emission, the rise is good, there is no overexposure, and it is excellent for small light amount and close-range photography.

On the other hand, when photographing a distant subject or in high light,
Light is emitted by the first main capacitor _C1 having a larger charge, and the amount of light is controlled by series control. Therefore, no energy is wasted, the first main capacitor _C1 is quickly charged, and the standby period for repeated use is short, making it convenient to use. In this case, the flash will still stop sharply, but if the subject is far away, there will be little effect.

Incidentally, the discharge tube 40 may be a silicon controlled rectifier element SCR or a thyratron. Further, the switching element 37 may be a thyratron.

Furthermore, the inductors 23 and 35 are for slowing down the discharge of the first and second main capacitors C ₁ and C ₂ , and the diodes 24 and 36 are for preventing the influence of the back electromotive force generated from the inductors 23 and 35. It is for the purpose of

As described above, according to the present invention, when shooting at close range, the light emission can be stopped sharply and properly controlled without overexposure, and when shooting at long distances and with a large amount of light, there is less energy loss and the standby period is shorter. It is possible to provide an automatic dimming type electronic flash device that can perform a flashing operation.

[Brief explanation of the drawing]

Fig. 1a is a wiring diagram showing a conventional series flash control type flash device, Fig. 1b is a light emission characteristic diagram of the circuit shown in Fig. 1a, and Fig. 2 is an automatic light control type electronic flash according to the present invention. A block diagram of the device, FIG. 3 is a wiring diagram of an electronic flash device according to an embodiment of the present invention. DESCRIPTION OF SYMBOLS 11... Power supply circuit, 12... Flash discharge tube, 13... Series light amount control circuit, 14... Parallel light amount control circuit, 15
...Resistor, 16...Trigger circuit, 17...Delay circuit, 1
8... Gate circuit, 19... AND circuit, 20... Pulse generating circuit, 21... Integrating circuit, 22... Light receiving section,
C ₁ , C ₂ ...Main capacitor.

Claims (1)

[Scope of Claims] 1. A flash discharge tube; first and second main capacitors connected to the flash discharge tube and charged in advance before the flash discharge tube emits light; connected in series to the flash discharge tube; a series light amount control circuit including a first switching element and controlling the amount of light emitted from the flash discharge tube by the charge of the first main capacitor; and a second switching element connected in parallel to the flash discharge tube. a parallel light amount control circuit that controls the amount of light emitted by the flash discharge tube based on the charge of the second main capacitor; means for turning on a second switching element to stop the flash discharge tube from emitting light due to the electric charge of the second main capacitor; means for turning on the first switching element to cause the flash discharge tube to emit light by the electric charge of the first main capacitor; and the means for turning on the first switching element; The device further comprises means for turning off the first switching element when the pulse signal is emitted later to stop the flash discharge tube from emitting light due to the electric charge of the first main capacitor. Auto-adjustable electronic flash device.