JPS6169048A - Electronic flash device - Google Patents

Abstract

PURPOSE:To obtain always a correct exposure independently of the distance to an object by providing a switching circuit which is turned on a prescribed time after light emission of a flash discharging tube and connecting first a small-capacity capacitor in the initial stage of light emission. CONSTITUTION:When a signal which is in the high level for a certain time is outputted from a timer circuit 28 to a trigger circuit 21 by turning-on of a synchronizing contact 29, a flash discharging tube 27 starts light emission, and the rise characteristic of light emission is slow because a large-capacity inductance 19 is connected in series to a discharging course including a small- capacity capacitor 16. When a delay circuit which receives the high-level signal turns on a switching circuit 6 after a prescribed time, a discharging course including a large-capacity capacitor 15 is added, but the rise characteristic of light emission is sharp till reaching the peak value because a small-capacity inductance 20 is connected, and light emission falls slowly thereafter.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Application of the Invention) The present invention relates to an improvement in an electronic flash device that stops emitting light from a flash discharge tube when the integrated value of reflected light from a subject reaches a predetermined value.

(Background of the Invention) Conventionally, this type of device has a light emission characteristic with an extremely rapid rise up to the peak value as shown in FIG. When this occurs, the timing of stopping the light emission is delayed and proper exposure cannot be obtained. In other words, during close-range shooting, the light emission is stopped at any point in the sharp rising part A (see Fig. 5).For example, point 1! , 4 If you try to stop the light emission at position a, there will be a time delay (
If the time delay is t, as shown in Table 1-r), the exposure will shift to the position indicated by the dotted line a, resulting in overexposure. Note that in cases other than close-range photography, the light emission is stopped at some point in the gradual falling curve section B, so even if the time delay t occurs, the exposure is not so adversely affected (dotted line b in Figure 5, bl),.

Therefore, an inductance with a large capacity is connected in series with the flash discharge tube, and an effort is made to make the sudden rise part a gentle rise. However, there is a considerable amount of resistance in the inductance, and the capacitance If a large inductance is used, energy will be lost due to its resistance, resulting in a light emitting characteristic as shown in Figure 6. If an inductance with such a large capacity is connected, there will be an insufficient amount of light when shooting at long distances. .

(Object of the Invention) An object of the present invention is to provide an electronic flash device that solves the above-mentioned problems and can always provide appropriate exposure regardless of the distance to the subject.

(Features of the Invention) In order to achieve the above object, the present invention includes a switching means that is turned on after a predetermined time elapses from the start of light emission of the flash discharge tube, in a circuit connecting the first capacitor and the flash discharge tube. Insert the small volume “” @cr＞＊□,) or
24□, 8 lights, connect to the flash discharge tube through an inductance with a large capacity that makes the characteristics loose, and then supply luminous energy to the flash discharge tube through an inductance with a larger capacity than a small capacitor. The present invention is characterized in that after a predetermined period of time, emitted light energy is additionally supplied from the first capacitor having a large capacity via a switch 7'' means.

(Embodiments of the Invention) The present invention will be explained in detail below based on illustrated embodiments.

FIG. 1 is a circuit diagram showing an embodiment of the present invention. 1 is a power supply battery, 2 is a power switch, and 3 is a D that boosts the DC voltage.
C-DC converter, 4° 5 is a diode, 6 is a thyristor 7, capacitor 8. Pulse transformer9. Diode 10. A switching circuit consisting of a thyristor 11 and resistors 12, 13, and 14; 15 a large-capacity capacitor for causing the flash discharge tube to emit light; and 16 a small capacitor connected at the initial stage of light emission of the flash discharge tube (described later); A capacitor 17, 18 is a diode, 19 is an inductance with a large capacitance connected in series to the capacitor 16 with a small capacitance, 20 is an inductance with a small capacitance, 21 is a resistor 22. Trigger capacitor 23.
Trigger transformer 24, trigger thyristor 25 and resistor 2
27 is a flash discharge tube; 28 is a timer circuit that outputs a high-level signal for a certain period of time when the synchro contact 29 is turned on; 30 is a high-level signal input from the timer circuit 28; A delay circuit 31 is a commutating capacitor 32 that operates the switching circuit 6 and turns on the thyristor 7 after a predetermined period of time.
, charging resistance 33, 34° resistance 35 of commutation capacitor 32
．． Main thyristor 36. Main thyristor 3 via resistor 35
capacitor 37.6 connected to the gate of capacitor 37.6. A light amount control circuit composed of a sub-thyristor 38 and a resistor 39.40,
41 is a light receiving element that receives reflected light from a subject, and 42 is a known dimming circuit.

Next, the operation will be explained. When the synchro contact 29 is turned on (see PfJZ diagram), a high level signal is output from the timer circuit 28 to the trigger circuit 21 for a certain period of time. Then, the trigger circuit 21 operates and the flash discharge tube 27 starts emitting light (see FIG. 3). At this time, capacitor 16, diode 17, inductance 19.20. Flash discharge tube27. The discharge path of the main thyristor 36 is opened, but since the inductance 19 with a large capacity is connected in series to this path, the rise characteristic of the light emission of the flash discharge tube 27 is a gentle curve C (Fig. 3). ). still,
In normal close-range photography, the light falls within the range of this light t (the amount of light in the section C). In addition, the timer circuit 28
The high-level signal output from the switching circuit 6 is also input to the delay circuit 30, and in response to this, the delay circuit 30 switches the switching circuit 6 to the switching circuit 6 after a predetermined period of time has passed since the input of the high-level signal.
Outputs a high level signal (see Figure 2). This causes the switching circuit 6 to operate and the thyristor 11 to turn on. When the thyristor 11 is turned on, the capacitor 15, the thyristor 11, the inductance 20. Flash discharge tube27. When the main thyristor 36 is released, a path is opened in addition to the previously described path. In this case, only the inductance 20 with a small capacity is connected, so the curve D (see Figure 3) rises sharply until it reaches its peak value, and then falls slowly. .

If we are currently shooting at close range, the light control circuit 42 will also send a light emission stop signal to the light amount control circuit 31 at the position of, for example, dotted line C on the curve C shown in FIG. At this time, even if an electrical delay occurs in the above-mentioned dimmer circuit 42, light amount control circuit 31, etc., and the timing at which the flash discharge tube 270 stops emitting light is delayed, the curve C will rise gradually due to the action of the inductance 190 having a large capacity. Therefore, even if an electrical delay occurs in the light control circuit 42 or the like, overexposure will not occur.

r4Wr"K'[""1°1・l010・Example 7°1
A light emission stop signal will be generated at position 47d,
In this case as well, since the fall is gentle as described above, overexposure will not occur.

Furthermore, since the capacitor 15 with a large capacitance is connected at this point, only the inductance 20 with a small capacitance acts on the light emission of the flash discharge tube 270, so that there is no shortage of light quantity.

FIG. 4 is a circuit diagram showing another embodiment of the present invention. 1st
The same parts as in the figure are represented by the same symbols.

43 is a pre-emission flash discharge tube that emits infrared light depending on the charge M of the capacitor 16 and voltage; 44 is a resistor 45; a trigger transformer 46. A known trigger circuit including a trigger capacitor 47, a trigger thyristor 48 and a resistor 49, 5
0 is a switch that is turned on when the first stage of the shirt release button is suppressed, T+ is a pre-emission timer circuit, T2 is a timer circuit, and G+ is a switch that turns off transistor 51 when a high level signal is input from timer circuit T+ or T2. 52 is a light receiving element that receives reflected light from the subject; 53 is an integral capacitor charged by the photocurrent from the light receiving element 52; 54 to 58 are voltage dividing resistors; 59
61 is a comparator 1M, which is a storage circuit, 62 to 64 are transistors, 65 to 67 are integral capacitors, Gy is a gate circuit, 68 is a transistor that is turned on and off by the output of the gate circuit G, and 69.70 is a voltage dividing resistor.

71 is a comparator, and OP is an aperture control signal generation circuit.

72 is a terminal for outputting an aperture control signal to the camera side.

Next, the operation will be explained. When the power switch 2 is turned on, the capacitor 16 is
7, which is sufficient for the pre-flash flash discharge tube 43 to emit light.
pressure is charged. Next, when the switch 50 is turned on,
Timer circuit T.

A high level signal is output from each terminal t, ts for a certain period of time. When a high level signal is output from the terminal t3, the trigger circuit 44 is activated and the flash discharge tube 4 for pre-emission is activated.
3 starts emitting light. On the other hand, from terminal t, gate circuit G
, when a high level signal is input to the terminal t of the gate circuit Gl.

A lower level signal is output to the transistor 51,
Transistor 51 is turned off to allow charging of integration capacitor 53. The light receiving element 52 photoelectrically converts the reflected light from the subject to charge the integral capacitor 53.

The charging voltage of the integral capacitor 53 is proportional to the integrated value of the reflected light from the subject. Voltage dividing resistor 55-58
0 partial pressure point a = c f) The potential is determined corresponding to the short distance, middle distance, and long distance to the subject.

For example, in the case of a long distance, the charging voltage of the integrating capacitor 53 becomes higher than the potential at the 1-division voltage point C and lower than the potential at the voltage-division point S at the time when the pre-emission is completed. Therefore, in this case, if the distance is short, all of the comparators 59 to 61
Each outputs a high level signal. After a certain period of time, the output of the terminal t2 of the pre-emission timer circuit T is inverted to a low level signal, and when this signal is input to the terminal t7 of the memory circuit M, the memory circuit M outputs the current terminal 1. -1.0 input level is memorized and one of the five transistors 62 to 64 is turned on based on the input level.For example, if the outputs of the comparators 59 to 61 are all high level signals, the transistor 64 is turned on. is turned on and the short-range integrating capacitor 67 is selected. Further, the aperture control signal generation circuit OP generates an aperture control signal in response to turning on of any one of the transistors 62 to 64, sends the aperture control signal to the camera side from the terminal 72, and adjusts the aperture of the lens according to the subject distance. and change it.

When the synchro contact 29 is turned on, the terminals 12, 1 . A continuous signal is output for a certain period of time. When a high level signal is output from the terminal t2, the trigger circuit 21 is activated and the flash discharge tube 27 starts emitting light. At this time, capacitor 16. diode 1
7, inductance 19, 20, flash discharge tube 27. Since the opening force of the discharge path of the main cylinder 27 is applied, the rising characteristic of light emission from the flash discharge tube 270 becomes gentle due to the action of the inductance 19.

Further, when a high-level signal is output from the terminal t3 of the timer circuit T to the delay circuit 30, the delay circuit 30 outputs a high-level signal to the switching circuit 6 after a predetermined period of time has elapsed since the input of the high-level signal. , this turns on the thyristor 11, so that the capacitor 15, the thyristor 11 . The inductance 20, the flash discharge tube 27° and the discharge path of the main thyristor 36 are opened, and the flash discharge tube 27
0 light emission has a light emission curve as shown in FIG. 3 due to the effect of the inductance 200 as described above.

On the other hand, when a high level signal is output from the terminal 11 of the timer circuit -, the terminal t of the gate circuit G2 is output.

The output becomes a high level signal, and the transistor 68 is turned off. As a result, one of the integral capacitors 65 to 67 selected by the memory circuit M can be charged. When the flash light from the flash discharge tube 27 is reflected on the subject and received by the light receiving element 52, it is converted into a current, and one of the integrating capacitors 65 to 67 selected by the memory circuit M is charged with the current. When the charging voltage of one of the integrating capacitors 65 to 67 becomes higher than the voltage dividing point of the voltage dividing resistors 69 and 70, the comparator 71 outputs a light emission stop signal to the sight control circuit 31.

That is, the comparator 71 outputs a light emission stop signal depending on the distance to the subject (for example, at the position indicated by the dotted line C or dotted line d in FIG. 3).

According to the embodiment shown in FIG. 1.4, at the initial stage of light emission of the flash discharge tube 270, that is, within the short-distance shooting range, the small capacity capacitor 1
6 and a large-capacitance inductance 19, the rise characteristic of light emission from the flash discharge tube 270 is made gentle, and thereafter, a large-capacity capacitor 15 and a small-capacity inductance 200 are combined to cause light emission.
Overexposure will no longer occur when photographing close-up shadows, and insufficient scenery will no longer occur when photographing from a long distance. In addition, since the inductance 19 with a large capacity is connected only in the initial stage of light emission of the flash discharge tube 270, and the inductance 20 with a small capacity is connected thereafter, the energy loss due to the resistance to the ihentaritan can be minimized. I can do it. 4. For example, the energy ratio of the small capacity capacitor 16 and the large capacity capacitor 15 is 1=
9, and assuming that the energy loss due to the small capacitance inductance 20 is 0% and the energy loss due to the large capacitance inductance 19 is 50%, the energy given to the flash discharge tube 27 is 0.5 x 1/10 + I x 9 /10 = 0
．． 95, and 95% of the total energy can be used. If this was done using the inductance 19 with a large capacity for the entire light emission time, only 50% would be available, resulting in a light emission characteristic as shown in FIG. 6, for example.

Furthermore, in the embodiment shown in FIG. 4, the small capacity capacitor 16 used when the flash discharge tube 270 emits light can also be used as a pre-flash capacitor, so there is no need to newly arrange a pre-flash capacitor. It also has the advantage of being good. Moreover, since the flashlight discharge tube 270 light emission time during close-range photography is shortened (see FIG. 3), color balance will not be disrupted.

(Correspondence between the invention and the embodiments) In FIG. 1.4, the capacitor 15 is the first capacitor of the present invention, and the light amount control circuit 31 is the first capacitor of the present invention. 11 In the control circuit, the +j iris register 11 serves as the switching means, and the capacitor 16 serves as the second capacitor.

Inductance 19 becomes an inductance with a large capacity,
They correspond to each other.

(Modification) In the embodiments shown in FIGS. 1 and 4, the thyristor 11
Although the delay circuit 30 is used to turn on the thyristor 6, the present invention is not limited to this, and the circuit configuration may be such that the thyristor 6 is turned on by detecting that the energy of the small capacity medium capacitor 16 has decreased below a certain value. It's okay.

(Effects of the Invention) f As explained above, according to the present invention, a switching means that is turned on after a predetermined time elapses from the start of light emission of the flash discharge tube is provided in the circuit connecting the first capacitor and the flash discharge tube. , and connect a small capacity @2 capacitor to the flash discharge tube through an inductance with a large capacity that makes the light emission rise characteristic loose, and then a flash discharge occurs through an inductance with a larger capacity than the small capacity capacitor. Since luminous energy is supplied to the tube and, after a predetermined period of time, additional luminous energy is supplied from the first large-capacity capacitor via the switching means, appropriate exposure can always be obtained regardless of the distance to the subject. You can do it like this.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing one embodiment of the present invention, Fig. 2 is a time chart of the synchronizing contact and delay circuit, Fig. 3 is a waveform diagram showing the light emission characteristics of the flash discharge tube, and Fig. 4 is the main circuit diagram. A circuit diagram showing another embodiment of the invention, FIG. 5 is a diagram showing an example of the light emission waveform of a conventional flash discharge tube, and FIG. 6 is a diagram showing the light emission characteristics of a flash discharge tube when a large capacitance inductance is connected in series. FIG. DESCRIPTION OF SYMBOLS 1... Power supply battery, 6... Switching circuit, 15°16... Capacitor, 19.20... Inductance, 21... Trigger circuit, 27... Flash discharge tube. 29... Synchro contact, 30... Delay circuit, 31...
...Light amount control circuit, 42...Dimmer circuit, 41...Light receiving element, '43...Flash discharge tube for pre-emission, 44...
- Trigger circuit, 52... Light receiving element, 53... Integrating capacitor, 71... Comparator, T+, Tz... Timer circuit, OP... Aperture control circuit.

Claims (1)

[Claims] 1. A flash discharge tube, a large-capacity first capacitor for causing the flash discharge tube to emit light, a trigger circuit that starts emitting light from the flash discharge tube by turning on a synchronizing contact, and integration of reflected light from the subject. In an electronic flash device comprising: a control circuit that stops light emission of the flash discharge tube when a value reaches a predetermined value, the flash discharge tube is included in a circuit connecting the first capacitor and the flash discharge tube; A switching means that is turned on after a predetermined time elapses from the start of light emission is inserted, and a second capacitor with a small capacity is connected to the flash discharge tube through an inductance with a large capacity enough to make the light emission start-up characteristics gentle. Electronic flash device.