JPS58118630A - Electronic flashing device - Google Patents

Abstract

PURPOSE:To judge the possiblity of continuous photographing, by detecting a value of a fixed physical quantity at the time of actual light emission as a variable related to the amount of light emission and comparing the maximum value of the fixed physical quantity to the maximum amount of light emission at which the charging of the main capacitor can follow continuous photographing. CONSTITUTION:At the time when the charge voltage of a main capacitor 7 becomes so high as to let a flash discharge tube 10 emit the light, a neon tube for displaying the completion of charging lights, a thyristor 9 is turned on, a discharge current flows to the primary side winding of a transformer 20, and the flash dischage tube 10 starts the light emission at the high voltage induced at the secondary side. When reflected lights from an object come into a photoreceptor element 38, a capacitor 39 is charged with a photocurrent corresponding to the reflected light, and this charging voltage reaches the voltage at a point P6 which is obtained by dividing the constant voltage of a diode 30, the output of a comparator 37 is inverted into a high level and a thyristor is turned off, and then, the light emission of the discharge tube 10 is stopped. When the time at which the output of the comparator 36 is at a high level is represented as TM (maximum flashing time) and the flashing time is represented as T, continuous photographing is possible when TM>T.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a series dimming type electronic flash device that stops emitting light by cutting off the discharge current of a main capacitor when a fixed value is reached.

A so-called serial dimming type electronic flash device discharges only the charge corresponding to the amount of light necessary and sufficient for photographing from a main capacitor, depending on the photographing distance and the reflectance of the subject. Therefore, in the case of a close-distance subject with a high reflectance, only a small amount of charge is discharged, and the time required for light emission to become possible again can be significantly shortened. As a result, high-speed flash photography is possible by using an automatic winding drive device.

High-speed continuous shooting with an electronic flash device is only possible with very close-distance, highly reflective objects; if these conditions are not met, the main capacitor of the flash device will not be able to keep up with the charge, making it impossible to obtain a sufficient amount of light. . In the conventional device, there was a drawback that it was not possible to judge whether the charging of the flash device could follow the frame speed of the automatic hoisting drive device or whether it was released.The present invention eliminates the above-mentioned drawbacks, An object of the present invention is to provide an electronic flash device that can automatically and accurately judge whether or not the charging of a main capacitor can follow continuous photographing.

In order to achieve this object, the present invention includes a detection means for detecting a value in actual light emission of a predetermined amount of $11 as a variable related to light emission amount, and a detection means for detecting a value in actual light emission of a predetermined amount of $11 as a variable related to light emission amount, and a detection means for detecting a value in actual light emission of $ 11 amount determined in advance as a variable related to light emission amount, and a detection means that detects the value of actual light emission of $11 amount that is predetermined as a variable related to light emission amount. a setting means for setting a maximum value of the physical quantity for the actual light emission, and a determining means for determining that charging of the main capacitor can follow continuous shooting based on the fact that the value of the physical quantity in actual light emission is smaller than the maximum value. It is characterized in that the physical quantities include flash duration, amount of discharged charge, and the like.

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

FIG. 1 shows an embodiment of the present invention, in which the flash duration is taken as a variable related to the amount of light emitted. 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 flash discharge tube 10 and a main thyristor 11.
A series circuit 1 of a resistor 12 and a commutating thyristor 13, and a series circuit of a resistor 14, a neon tube 15, and a resistor 16 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, and one end of the secondary winding 20b of the trigger transformer 20 is connected to the trigger electrode 10a of the flash discharge tube 10. The other end is connected to the connection point between the flash discharge tube 10 and the main thyristor 11, respectively. The main thyristor 1
A resistor 21 is connected in parallel to 1, and a series circuit of a commutating capacitor 22, a resistor 23, a capacitor 24, and a resistor 25 is further connected in parallel. and the capacitor 24
The connection point between the resistor 25 and the resistor 25 is connected to the gate of the main thyristor 11. Further, the connection point aK between the capacitor 22 and the resistor 23 is connected to the connection point aK between the resistor 12 and the commutating thyristor 13.

The base of the transistor 260, whose emitter is connected to the positive terminal of the power source E, is connected to the negative terminal of the power source E via 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 the transistor 26, and the collector is connected to the trigger thyristor 9 via a resistor 31. The constant voltage diode 3
0 has a series circuit of a capacitor 32 and a resistor 33, and a resistor 3
4.35 series circuit, comparator 36, comparator 37, 5Thf, series circuit of element 38 and integrating capacitor 39, antgame) 40. A series circuit of a resistor 41 and a thyristor 42, and a comparator 43 are connected sequentially in parallel. The non-inverting input terminal of this comparator 36 is connected to the connection point Ps between the capacitor 32 and the resistor 33, the inverting input terminal is connected to the connection point between the resistor 34 and the resistor 35, and the output terminal of the comparator 36 is connected to the connection point Ps between the capacitor 32 and the resistor 33. It is connected to one input end of the spike) 40.

The non-inverting input terminal of the comparator 37 is connected to the connection point P7 between the light-receiving element 38 and the component capacitor 39, and the connection point Pa is connected to the inverting input terminal, and the output 1 of the comparator 37 The terminal is connected to the other input terminal of the AND gate 40, and is also connected to the commutating thyristor 13I7) gate via a resistor 44. The output terminal of an AND gate 40 whose input terminal is connected to the output terminals of the converter 36 and the comparator 37 is connected to the gate of the thyristor 42 via a resistor 45.

The inverting input end of the comparator 43 is connected to the connection point a between the resistor 41 and the thyristor 42, and the non-inverting input end is connected to the connection point P6. A capacitor 46 is connected in parallel with the capacitor 42. The output terminal of the comparator 43 is connected to the base of a capacitor transistor 480 via a resistor 47.

This transistor 48 has its emitter connected to the positive terminal of the power supply E, and its collector connected to a diode 49 and a capacitor 50.
It is connected to the negative terminal of the power supply E via. capacitor 5o
A series circuit of a resistor 51 and a light-emitting shallow hydrogen element 52 as well as the emitter-collector of a transistor 53 are connected in parallel. The base of the transistor 530 is connected to a resistor 29 and a constant voltage diode 3 through a series circuit of a resistor 54 and a capacitor 55.
Connected to connection point F% of 0.

In FIG. 81, 56 is a light amount control circuit, 57 is a photometry 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 includes a changeover switch 61 therein.

Depending on the operating mode of the automatic winding drive device 60, the changeover switch 61 is switched to one contact S side when one frame is being manipulated, and K is switched to the other contact C side when continuous shooting is being performed. A contact A and one contact S of the changeover switch 61 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 supply switch (not shown) is turned on, the oscillation booster circuit 5 is activated and the main capacitor 7,
Trigger capacitor] 9 and commutating capacitor 22 are charged to the polarities shown.

When the charging voltage of the main capacitor 70 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 pace potential of the transistor 18 increases.

When the synchro contact 28 is turned on in this state, the transistor 18 is turned on, a pace current flows through the transistor 26, the 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 turns on, the trigger capacitor 19
The charging charge is the primary winding of the trigger transformer 20 @ 20a
The secondary winding 20b of the trigger transformer 20
The high voltage generated by KH is applied to the trigger electrode 10 of the flash discharge tube 10.
aK is applied to ionize the flash discharge tube IO, and this discharge current flows through the commutation capacitor 22 and the like to the main thyristor 11.
The main thyristor 11 is turned on, and the flash discharge tube 10 starts emitting light.

Transistor 26 turns on and triggers thyristor 9
At the same time, a current is supplied to the constant voltage diode 30 through the resistor 29, and the voltage generated across this serves as the power supply voltage for the setting circuit 58, photometry circuit 57, AND gate 40, and indication circuit 59. . The flash discharge tube 10 emits light, and the reflected light from the subject is reflected by the light receiving element 38.
When the photoelectric current corresponds to the magnitude of the incident light, the integrating capacitor 39 is charged, and this charging voltage becomes the '-voltage at the connection point, which is the constant voltage of the constant voltage diode 30 divided by the resistor 34.35. When the voltage is reached, the output of the comparator 37 is inverted from a low level to a high level, and the commutating thyristor 13 is turned on by receiving this high level output at its gate. As a result, a commutating circuit consisting of the commutating capacitor 22, the commutating thyristor 13, and the main thyristor 11 is formed, and the main thyristor 11 is turned off by the discharge current caused by the charged charges of the commutating capacitors 2, 2 flowing through this commutating circuit, and the flashing light is emitted. The discharge tube 10 stops emitting light.

Assuming that T is 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, the discharge charge from the Fussa capacitor 7 with a short flash time T is small, and the next time The time required to complete the flash preparation is short, and it can also follow high-speed continuous shooting. Automatic winding drive system fM60
TM is the maximum flash duration that can follow busy continuous shooting when using TM.

When shooting continuously with the automatic winding drive device 60, the other contact C of the changeover switch 61 is switched to IIK, so the resistor 3
Both ends of 30 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.
The non-inverting input of comparator 36 decreases over time. During the period from the start of power supply to the setting circuit 58 until the non-inverting input reaches a constant voltage at the connection point, the comparator L'-36
The output of the comparator 36 becomes a high level, and after that, the output of the comparator 36 becomes a low level. Here, the time during which the output of the comparator 36 is at a high level is the maximum flash time TM mentioned above.
Set K.

Next, the case where the flash time T is shorter than the maximum flash time TM and the case where it is longer will be considered using FIGS. 2 and 3.

(1) When it is shorter than the maximum flash time TM (can follow continuous shooting) The waveforms of various parts in this case are shown in FIG. If the flash duration in this case is T1, since T+<TM, there is a period (Tl to TM) when both the outputs of the comparators 36 and 37 are at a high level. Therefore, the output of the computer game 40 is at a high level during ('n to 'rM). This high-level signal turns on the thyristor 42 through the resistor 45, and the charge that has been charged in the capacitor 46 up to that point is discharged at once through the thyristor 42, and the inverting input of the converter 43 goes low before reaching the potential at the connection point B. The output of the microcomputer 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.

(11) When longer than the maximum flash time TM (unable to follow continuous shooting) The waveforms of various parts in this case are shown in FIG. In this case, the flash time is T! Then, since TM('I'?), by the time the output of the comparator 37 is inverted from low level to high level, the output of the comparator L/-36 is already at the low level. Since the outputs of the AND gate 40 will never reach a high level, the gate signal to the thyristor 42 will be generated and the photographer will move closer to the subject, ensuring that continuous shooting can be done at a distance. By taking pictures from the beginning, it is possible to avoid mistakes in taking pictures due to the inability to follow continuous shots.

Next, let us consider a case where a message indicating that continuous shooting is not possible is displayed when 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 base current flows to the transistor 53 through the capacitor 55 and the resistor 54 at the rising edge of the voltage being applied to the constant voltage diode 30 during light emission. When the power is supplied, the transistor 53 turns on and discharges the charge stored in the capacitor 5o all at once, stopping the display indicating that continuous photographing is not possible. resistance 54
, if the time constant of the capacitor 55 is set well, the capacitor 50 can be sufficiently discharged, and the transistor 4 can be sufficiently discharged.
By the time transistor 8 can turn on, transistor 53 can be turned off.

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

In the illustrated embodiment, an optical display circuit 5 is used due to the simplicity of the circuit.
9 is provided, but a sound display circuit may be provided instead.

Further, although the light emitting display element 52 is turned on at 5KL when continuous shooting is not possible, it may be turned on when continuous shooting is possible. Furthermore, without displaying 1 or in combination with display,
Send the high level output of AND gate 40 to the camera,
K may be configured to enable the next shutter release only when a high level output is received on the camera side.

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 equal to the discharge charge of the main capacitor 7. Since it is proportional to the amount of light emitted, it can be determined whether the charging of the main capacitor can follow continuous shooting by comparing it with a reference voltage that is proportional to the maximum amount of discharged charge of the main capacitor with respect to the maximum amount of light emission.

As explained above, according to the present invention, the value of a predetermined physical quantity in actual light emission is detected as a variable related to the amount of light emission, and the maximum value of the physical quantity is Since the value of the physical quantity in actual light emission is smaller than the maximum value, it is determined that the charging of the main capacitor can follow continuous shooting. This allows accurate judgment and prevents photographing errors due to inability to follow.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIGS. 2 and 3 are output waveform diagrams of various parts in the embodiment of the present invention. 7. Exposure/main capacitor, 10-.-flash discharge tube, 11.
・Q main thyristor, 13... Commutation thyristor, 28・
Fist/synchro contact, 3g--Ukemoto Takako, 39... Integral capacitor, 40... AND gate, 56... Light amount control circuit, 57... m optical circuit, 58... Setting circuit . Patent applicant: Canon Co., Ltd. Agent Minoru Nakamura Figure 2 Figure 3

Claims (1)

[Claims] 1. In a serial leg 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 predetermined variable related to the amount of emitted light is used. a detection means for detecting the value of the physical quantity in actual light emission; a setting means for setting the maximum value of the physical quantity with respect to the maximum light emission amount at which the main capacitor charge can follow continuous shooting; and a setting means for detecting the value of the physical quantity in actual light emission; 1. An electronic flash device comprising a determining means for determining that charging of a main capacitor can follow continuous shooting based on a value smaller than a maximum value.