JPH09115682A - Stroboscope device provided with automatic dimming function - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve dimming precision at a short distance. SOLUTION: A device is provided with a flash pulse generating circuit 7 of a pulse width set to generate smaller light quantity than the minimum light quantity to be set in a dimming circuit 6 in a flash tube 2, lighting of the flash tube 2 after starting operation is performed by a starting circuit 5 is discontinuously performed by an output from the flash pulse generating circuit 7, and when prescribed exposure light quantity is accumulated in the dimming circuit 6, emission of light is stopped. Light emission is thus performed by plural times of smaller light quantity than the prescribed exposure light quantity, and a pure light emission part before the prescribed exposure light quantity is reached is accumulated with a residual light emission part in the dimming circuit 6, thereby exclusion of the residual light emission part from accumulation in the dimming circuit 6 can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a strobe device for photographing, and more specifically, it is called an auto strobe or the like, and light from a flash tube turned on for illumination is reflected on a subject. The present invention relates to a strobe device with an automatic light control function, which integrates light returning in a shooting direction and stops light emission of a flash tube when the integrated amount reaches a predetermined value.

[0002]

2. Description of the Related Art FIG. 6 shows an example of the configuration of a conventional strobe device 90 with an automatic light control function of this kind. When taking a picture, it is connected in series to a flash tube 91 such as a xenon discharge tube. A potential is applied to the gate G of the semiconductor switch 92 such as a GTO or IGBT that is present so as to be conductive, and
A trigger voltage is applied to the flash tube 91 by the starting circuit 93,
The electric charge stored in the capacitor 94 is transferred to the flash tube 91.
The inside of the lamp is discharged to emit light.

At this time, the strobe device 90 with the automatic light control function is provided with a light control circuit 95, and the flash tube 91 is provided.
The light reflected from the object is reflected by the light receiving element 95a such as a photodiode and integrated by the integrating circuit 95b.
When the exposure comparator 95c detects that the integrated amount has reached a predetermined value determined by film sensitivity or the like, a signal is sent from the dimming circuit 95 to the gate G of the semiconductor switch 92, and the semiconductor switch 92 is turned on. The light is turned off to stop the emission of the flash tube 91.

By doing so, within the range of the distance where the amount of light from the flash tube 91 is sufficient to illuminate the subject, the photographer stops the lens aperture according to the distance to the subject each time the photograph is taken. Appropriate exposure can be obtained without any troublesome work such as setting a value.

[0005]

However, in the conventional strobe device 90 with an automatic light control function described above,
As shown in FIG. 7, the residual light emitting portion HB is generated in the flash tube 91 even when the potential V applied to the gate G disappears and the semiconductor switch 92 is turned off.
Excessive exposure is caused by the remaining light emitting portion HB.

Especially when the distance to the subject is short,
Since the amount of light required to illuminate the subject is small, the ratio of the remaining light emitting portion HB to the regular light emitting portion HA is high, and as shown in FIG. 8, the dimming accuracy curve A1 shows that the distance to the subject is shorter. In particular, overexposure becomes remarkable, which causes a problem that the conventional strobe device 90 with an automatic light control function lacks the light control accuracy at a short distance, which reduces the practicality.
The solution of this point is an issue.

[0007]

As a concrete means for solving the above-mentioned conventional problems, the present invention provides a starting circuit for starting a flash tube and lighting it, and an object for light of the flash tube. A strobe device with an automatic dimming function, comprising a dimming circuit for receiving reflected light, integrating it, and stopping the emission of the flash tube when a prescribed exposure amount is reached. The device is provided with a flashing pulse generation circuit having a pulse width that causes the flash tube to generate a light quantity smaller than the minimum light quantity set in the dimming circuit, and the flash tube after being started by the starting circuit. Flashing is intermittently performed by the output from the flashing pulse generating circuit, and when the specified exposure amount is integrated in the dimming circuit, the flash tube is stopped from emitting light. Provide equipment Doing, solves the problems as high dimming accuracy in the near is obtained.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described in detail based on the embodiments shown in the drawings. 1 shows a first embodiment of the present invention, and a reference numeral 1 in the drawing is a strobe device with an automatic light control function (hereinafter abbreviated as strobe device 1). Is provided with a flash tube 2 such as a xenon discharge lamp and a condenser 3,
The semiconductor switch 4 such as O or IGBT is connected in series, which is the same as the conventional example.

Further, the strobe device 1 has a starting circuit 5
And a dimming circuit 6 are provided. The starting circuit 5 causes the flash tube 2 to start discharging the electric charge of the capacitor 3, and dimming the reflected light of the light of the flash tube 2 to the subject. Light is received by the light receiving element 6a of the circuit 6 and integrated by the integrating circuit 6b. When the exposure comparator 6c detects that the integrated amount has reached a predetermined value, the semiconductor switch 4 receives a signal from the dimming circuit 6. Is also turned off and the light emission of the flash tube 2 is stopped to perform light control, which is also similar to the conventional example.

In the present invention, the strobe device 1 is provided with a blinking pulse generating circuit 7. The blinking pulse generating circuit 7 continuously generates a plurality of pulses, and the flashing light has a width of each pulse. By lighting the tube 2, the purpose is to make the lighting state of the flash tube 2 intermittent.

Next, the structure of the blinking pulse generating circuit 7 will be described.
A width setting comparator 71 to which the output from the light receiving element 6a of the light control circuit 6 is input, a timer circuit 72 connected to the output of the width setting comparator 71, an output of the width setting comparator 71, and a timer. It is composed of a gate control circuit 73 to which the output of the circuit 72 is input and also the outputs of the starting circuit 5 and the dimming circuit 6.

With the above-described structure, the strobe device 1 of the present invention is configured such that the gate control circuit 7 is activated when photographing is started.
The semiconductor switch 4 is turned on by 3 and the flash tube 2 is triggered at the same time by the starting circuit 5 to discharge the electric charge of the capacitor 3 to emit light.
a produces an output in response to the reflected light, and gives a signal to the integrating circuit 6b and the width setting comparator 71.

Here, the light control performed by the light control circuit 6 will be described in more detail. In the light control, the proper light amount is determined by the aperture value of the lens and the film sensitivity. The semiconductor switch 4 is turned off when the light amount set in the power comparator 6c and integrated in the integrating circuit 6b reaches the appropriate light amount.

The strobe device 1 has, for example, a lens aperture value of F = 2 to 16 and a film sensitivity of ISO2.
5 to 400 can be set with a dial or the like, and the light quantity corresponding to the setting is set in the exposure comparator 6c. Therefore, in the above example, when the aperture value of the lens is set to F = 2 and the film sensitivity is set to ISO400, the light amount set in the exposure comparator 6c becomes the minimum light amount. The operating point set at 71 is set as a brightness value with which the light quantity is smaller than the above-mentioned minimum light quantity.

FIG. 2 is a schematic graph showing the operating state of the strobe device 1. The operation of the strobe device 1 of the present invention will be described below in conjunction with FIG. First, when the synchronizing contact S of the camera is turned on and the flash tube 2 is turned on, the width setting comparator 71 generates the turn-off pulse X before the exposure comparator 6c as described above. This extinguishing pulse X is applied to the OFF terminal of the gate control circuit 73 to turn off the semiconductor switch 4 to extinguish the flash tube 2.

Therefore, the flash light waveform H1 from the flash tube 2 is composed of the pure light emitting portion H1A and the remaining light emitting portion H1B until the turn-off pulse X is output, as shown in FIG. Also,
The extinguishing pulse X of the width setting comparator 71 is also input to the timer circuit 72, and the timer circuit 72 restarts to the ON terminal of the gate control circuit 73 after a predetermined time period after receiving the output of the width setting comparator 71. A pulse Y is applied to turn on the semiconductor switch 4.

At this time, since the flash tube 2 has just been extinguished, the ionization of the gas in the tube remains, and the semiconductor switch 4 is turned on again to be turned on. In this way, the flash tube 2 is repeatedly turned on and off to obtain a flash light waveform H1 having a substantially triangular wave shape. However, since the light quantity of each triangular wave is integrated in the integrating circuit 6b, The exposure comparator 6c outputs a stop pulse Z to the STOP terminal of the gate control circuit 73 at the time when the specified exposure amount is reached (the time when the fifth triangular wave is emitted and reaches the peak in FIG. 2), and the subsequent light emission is performed. To stop.

In the configuration of the present invention, the integrating circuit 6 is used.
b is a pure light emitting part H1 for each triangular wave in the flash waveform H1.
All the light amounts are integrated without distinguishing between A and the remaining light emitting portion H1B. Therefore, if it is assumed that the ratio of the light amounts of the pure light emitting portion H1A and the remaining light emitting portion H1B is 1: 1 and the prescribed exposure amount is reached at the peak of the fifth triangular wave, overexposure is performed. The part that becomes the quantity is the remaining light emitting part H1 of the fifth triangular wave.
It is the portion B, and the excess amount with respect to the appropriate exposure amount is about 10% at most, and the influence in practical use can be ignored.

Further, when the prescribed exposure amount is reached at the extinguished portion of the flash waveform H1, the subsequent lighting is not performed, and at this time, no error occurs. Therefore, according to the configuration of the present invention, as shown in FIG. 3, the dimming accuracy curve A2 is much less likely to be overexposed as compared with the conventional example (see FIG. 8) even when shooting at a short distance, That is, the strobe device 1 can obtain accurate exposure at all distances.

FIGS. 4 and 5 show the second embodiment of the present invention. In the first embodiment described above, a proper exposure amount is certainly obtained, but on the other hand, the flash waveform H1 is Since each of them has a substantially triangular waveform with a small amount of light, the total light emission time T1 becomes long, and for example, when synchronized with a high-speed shutter, there is a concern that light emission will not end within the shutter open time. Occurs.

The second embodiment is carried out in order to cope with the above. In this embodiment, the blinking pulse generating circuit 8 has a width setting comparator 81 similar to that of the first embodiment. Timer circuit 82 and gate control circuit 83
Is provided, and the output of the integrating circuit 6b is connected to the pre-stage light emission comparator 84 in parallel with the exposure comparator 6c. The first turn-off pulse W which is the output of the front stage light emission comparator 84 and the width setting comparator 8
The turn-off pulse X of 1 is input to the OFF terminal of the gate control circuit 83 via the light emission control circuit 85.

At this time, the total light emission amount including the pure light emission portion H2A and the remaining light emission portion H2B in the pre-light emission comparator 84 is also explained in the previous embodiment, as shown by the flash waveform H2 in FIG. A light amount (for example, 80%) that is slightly smaller than the minimum light amount during dimming is set. Further, the light emission control circuit 85 basically performs a switch action, and the first first time light emission control circuit 85 has a light emission control circuit 84 for the preceding light emission.
The first stop pulse W from is selected, and the extinction pulse X from the width setting comparator 81 is selected from the second time onward.

By doing so, when the flash tube 2 is turned on in the strobe device 1 of the second embodiment, first,
The width setting comparator 81 outputs an extinguishing pulse X, but this output is blocked by the light emission control circuit 85 and the gate control circuit 83 does not operate. The gate control circuit 83 operates to turn off the flash tube 2.

Therefore, at this time, the film is 80%
The exposure is performed in such a manner that the exposure amount is almost close to the prescribed exposure amount, and subsequently, the timer circuit 82 relights the flash tube 2. At this time, the light emission control circuit 85 is switched to the width setting comparator 81 side, and the flash tube 2 is extinguished by the extinguishing pulse X from the width setting comparator 81 from the second time onward, and the light amount of one triangular wave is Compared to the first time, it will be significantly less.

However, since the exposure is performed up to almost the specified exposure amount in the first light emission as described above, the specified exposure amount can be reached with a small number of repetitions even after the second light amount. Therefore, the total light emission time T2 is shorter than that in the first embodiment, and can be substantially the same as the light emission time in the conventional example.

[0026]

As described above, according to the present invention, the blinking pulse generating circuit having the pulse width for causing the flash tube to generate a light amount smaller than the minimum light amount that the dimming circuit can control is provided, and the starter circuit After the start-up, the flash tube is turned on intermittently by the output from the flashing pulse generation circuit, and when the specified exposure amount is accumulated in the dimming circuit, the flash tube is stopped from emitting light. By using a strobe device with a light function, light emission is performed multiple times with a light amount smaller than the specified exposure amount, and both the pure light emission part and the remaining light emission part of the light emission before reaching the specified exposure amount are dimmed. As the circuit integration, the entire remaining light emission part is prevented from being excluded from the integration in the dimming circuit, improving the dimming accuracy at short distances, and this type of strobe device with automatic dimming function Extremely excellent in performance improvement It is intended to achieve the effect.

[Brief description of the drawings]

FIG. 1 is a schematic circuit diagram showing a first embodiment of a flash device with an automatic light control function according to the present invention.

FIG. 2 is also a graph schematically showing the operating state of the first embodiment.

FIG. 3 is a graph showing a dimming state of the first embodiment as well.

FIG. 4 is a schematic circuit diagram showing a second embodiment of a strobe device with an automatic light control function according to the present invention.

FIG. 5 is a graph schematically showing the operating state of the second embodiment.

FIG. 6 is a schematic circuit diagram showing a conventional example.

FIG. 7 is a graph showing an operating state of a conventional example.

FIG. 8 is a graph showing a dimming state of a conventional example.

[Explanation of symbols]

 1 ... Strobe device with automatic light control function 2 ... Flash tube 3 ... Capacitor 4 ... Semiconductor switch 5 ... Start-up circuit 6 ... Light control circuit 6a ... Light receiving element 6b ... Integration circuit 6c ... For exposure Comparator 7, 8 ...... Blinking pulse generation circuit 71,81 ...... Width setting comparator 72,82 ...... Timer circuit 73,83 ...... Gate control circuit 84 ...... Previous stage light emission comparator 85 ...... Light emission control circuit X ...... Extinguishing pulse Y ... Relighting pulse Z ... Stop pulse HI, H2 ... Flash waveform

Claims (3)

[Claims] 1. A start-up circuit for starting a flash tube and lighting it, and emitting light of the flash tube when the light reflected by the subject of the flash tube is received and integrated to reach a prescribed exposure amount. In a strobe device with an automatic dimming function provided with a dimming circuit for stopping, the strobe device with an automatic dimming function provides the flash tube with a light amount less than a minimum light amount set in the dimming circuit. A blinking pulse generation circuit having a pulse width to be generated is provided, and the flash tube after being activated by the activation circuit is intermittently lit by the output from the blinking pulse generation circuit, and is defined in the dimming circuit. A strobe device with an automatic light control function, which stops the flash tube from emitting light when the exposure amount is accumulated. 2. The blinking pulse generating circuit sets a pulse width by the time until the light from the flash tube is reflected by a subject reaches a predetermined peak value, and the lighting time is determined by the pulse width. The strobe device with an automatic light control function according to claim 1, wherein the strobe device is set. 3. The blinking pulse generating circuit is continuously turned on until the initial light amount value set in the strobe device with the automatic light control function is reached, and the blinking pulse generating circuit intermittently starts from the time when the initial light amount value is exceeded. The strobe device with an automatic light control function according to claim 1, wherein the strobe device is automatically turned on.