JP3742667B2 - Strobe light emitting device - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a strobe light emitting device, and more particularly to a strobe light emitting device that performs automatic light control at a low cost.
[0002]
BACKGROUND OF THE INVENTION
Photographing with a camera is performed by collecting reflected light from a subject with a lens and forming an image on a film. For this reason, for example, when taking pictures at night or in the daytime in a room or in a dim place, the reflected light from the subject is insufficient, and the subject imaged on the film is underexposed and the image quality deteriorates. .
[0003]
In order to solve such an underexposure, the above camera is usually equipped with an artificial light-emitting device called a strobe light-emitting device, or can be attached as an option, and as described above, it tends to be underexposed. Even at night or in the daytime, when taking a picture in a room or in a dim place, the strobe light emitting device emits light, thereby eliminating the shortage of exposure.
[0004]
In order to obtain an optimum exposure state, for example, it is necessary to determine the aperture value by sufficiently considering various conditions such as the illuminance of ambient light, the distance to the subject, and the illuminance of light emitted from the strobe light emitting device. Therefore, some strobe light emitting devices perform automatic light control by controlling the amount of light emitted from the strobe light emitting device.
[0005]
In addition, it is known that a better picture can be obtained by using irradiation light from the strobe light emitting device as auxiliary light even during daytime shooting that does not use the light emitted by the strobe light emitting device during normal shooting. For this reason, there is also an idea that the strobe light emitting device is always used. In this case, the strobe light emitting device requires dimming control in order to obtain optimal auxiliary light that matches the photographing conditions.
[0006]
In general, dimming control circuits using thyristors (SCRs) are generally used. Recently, however, voltage controlled elements are used because of their features such as high speed, high voltage resistance, and large current. IGBTs (Insulated Gate Bipolar Transistors) are becoming mainstream.
[0007]
[Prior art]
2. Description of the Related Art Conventionally, strobe light emitting devices that perform automatic dimming generally perform dimming by reducing a predetermined amount of energy (charge) when the arc tube emits light with a maximum light amount. For example, a silicon photodiode ( Reflected light from a subject is received by a light receiving element such as SPD (Silicon Photo Diode) or a phototransistor (PT: Photo Transister), and the above-described thyristor, IGBT, or the like is controlled based on the received light amount. In the strobe light emitting device having the light emission pattern as shown in FIG. 5A, as shown in FIG. 5B, the light emission is stopped in a short time during short distance shooting and longer than that during short distance shooting in long distance shooting. The amount of luminescence was controlled by emitting light for a period of time.
[0008]
However, stopping light emission in a short time during short-distance shooting makes it difficult to control the light emission stop time because the time until the light emission stops is very short, resulting in an increase in the cost of the device. As shown in FIG. 6, a diffuser as a neutral density filter is provided in front of the strobe light emitting unit, and the light emission energy is diffused by emitting light through the diffuser at the time of short-distance shooting, and the light emission amount is controlled as shown in FIG. 6. .
[0009]
FIG. 6A shows a light emission pattern at the time of close-up shooting without a diffuser, and FIG. 6B shows a light emission pattern at the time of close-up shooting with a diffuser.
[0010]
[Problems to be solved by the invention]
However, the conventional strobe light emitting device having a diffuser is configured to determine whether to use short-distance shooting or long-distance shooting and to perform switching control of whether to use the diffuser. There was a problem like this.
[0011]
That is, in order to use the diffuser, since the switching mechanism is required, the apparatus itself becomes large, and since the switching time is required, the shutter cannot be released at a desired photo opportunity (that is, There was a problem that photography was not possible.
[0012]
In addition, there is a problem that the cost increases as the number of parts related to the diffuser and the switching mechanism increases.
[0013]
〔the purpose〕
In view of the above problems, an object of the present invention is to provide a strobe light emitting device that performs light emission control at a short distance shooting at low cost.
[0014]
[Means for Solving the Problems]
The invention described in claim 1
A light emitting means for discharging the charge accumulated in advance at a predetermined timing and emitting light based on the generated discharge voltage;
Photometric means for measuring the illuminance of the reflected light from the subject when light is emitted by the light emitting means;
A light emission amount control means for controlling a light emission amount by the light emission means based on a photometric result of the light measurement means;
In the strobe light emitting device having
A distance measuring means for measuring a distance to the subject ;
The light emission amount control means suppresses the light emission amount of the main light emission of the light emission means synchronized with the opening of the shutter of the photographing apparatus when the distance measurement by the distance measurement means is less than a predetermined distance. Before the shutter is opened, a part of the charge storage capacitor that supplies charges to the light emitting unit is discharged to pre-emit the light emitting unit, and then the charge storage capacitor is synchronized with the opening of the shutter. The above-mentioned object is achieved by discharging the remaining electric charge to cause the light emitting means to emit light .
[0017]
[Action]
According to invention of Claim 1,
As a result of distance measurement by the distance measuring means, if the distance is less than a predetermined distance, it is regarded as short-distance shooting, and the light emission control means suppresses the light emission amount of the main light emission synchronized with the shutter opening. Therefore, after the shutter is opened, a part of the charge storage capacitor that supplies charges to the light emitting means is discharged and the light emitting means is pre-lighted, and then the remaining charge storage capacity is synchronized with the shutter opening. Is discharged, and the light emitting means emits light, so that light emission control for suppressing the light emission amount of the main light emission at short distance photographing is performed at low cost, and red-eye prevention can be achieved by pre-light emission before photographing.
[0021]
【Example】
Hereinafter, a preferred embodiment of the present invention will be described with reference to FIG. In FIG. 2, the same parts as those in FIG.
[0022]
First, the configuration of the present embodiment will be described.
[0023]
FIG. 2 is a block diagram showing a main configuration of the present embodiment.
[0024]
In FIG. 2, the strobe light emitting device 1 is roughly divided into a light emitting circuit 2 as a light emitting means, a photometric circuit 3 as a photometric means, a light emission amount control circuit 4 as a light emission amount control means, and a distance measuring circuit 5 as a distance measuring means. The light emission amount suppression circuit 6 is a light emission amount suppression means.
[0025]
The light emitting circuit 2 includes a light emitting tube Xe that emits light based on a discharge voltage of charges accumulated in a main capacitor Cm, which is a charge storage capacitor, and a main capacitor Cm is connected in parallel to both ends of the light emitting tube Xe. Has been. The main capacitor Cm is a large-capacity capacitor that accumulates electric charge for obtaining a discharge voltage necessary for light emission in the arc tube Xe.
[0026]
The arc tube Xe of the light emitting circuit 2 includes a booster circuit (not shown) that oscillates and boosts a power supply voltage supplied from a power supply circuit (not shown) to a predetermined voltage and supplies a charge to the main capacitor Cm. A trigger circuit (not shown) for supplying a voltage boosted to a predetermined voltage by the booster circuit to the arc tube Xe at a predetermined timing is connected.
[0027]
The photometric circuit 3 receives reflected light from the subject S based on the light emitted from the light emitting circuit 2 and measures the illuminance of the reflected light, and includes a phototransistor PT as a light receiving element, a capacitor C1, and a comparator CP. The output terminal of the comparator CP is connected to the base of a bipolar transistor Q1 of a light emission amount control circuit 4 described later.
[0028]
The light emission amount control circuit 4 is composed of bipolar transistors Q1, Q2, Q3, Q4, resistors R2, R3 and IGBT, and a control signal line from the CPU 12 of the distance measuring circuit 5 described later is connected to the base of the bipolar transistor Q3. When the on signal (“H”) is output as a control signal from the CPU 12, the bipolar transistor Q3 is turned on, and a low potential level (“L”) voltage is applied to the base of the bipolar transistor Q4. The bipolar transistor Q4 is turned on, a high potential level (“H”) voltage is applied to the gate of the IGBT to turn on the IGBT, and light emission by the arc tube Xe is performed.
[0029]
When the voltage potential level based on the amount of light received by the phototransistor PT of the photometry circuit 3 exceeds the reference voltage value Vref of the comparator CP, a low potential level (“” is applied to the base of the bipolar transistor Q1 of the light emission amount control circuit 4. L ") voltage is applied to turn on the bipolar transistor Q1, whereby a high potential level (" H ") voltage is applied to the base of the bipolar transistor Q2 to turn on the bipolar transistor Q2 and to the gate of the IGBT. A low potential level (“L”) voltage is applied, the IGBT is turned off, and light emission by the arc tube Xe is stopped.
[0030]
The distance measuring circuit 5 includes, for example, a distance measuring unit 11 using an infrared sensor, and a CPU 12 that calculates the distance from the arc tube Xe to the subject S based on a detection signal from the distance measuring unit 11. The control signal line is connected to the base of the bipolar transistor Q3 of the light emission amount control circuit 4 and to the base of a bipolar transistor Q5 of the light emission amount suppression circuit 6 described later.
[0031]
The light emission amount suppression circuit 6 includes a bipolar transistor Q5, a resistor R1, and a Zener diode Z1, and is turned off as a control signal from the CPU 12 when it is determined that the measurement distance is longer than a predetermined distance as a result of the above-described calculation by the CPU 12. A signal ("L") is output, the bipolar transistor Q5 is turned off, and the arc tube Xe emits a maximum light of, for example, about 330 V by the main capacitor Cm.
[0032]
On the other hand, when it is determined that the measurement distance is shorter than the predetermined distance, an ON signal (“H”) is output as a control signal from the CPU 12, the bipolar transistor Q5 is turned on, and the Zener of the light emission amount suppression circuit 6 is turned on. The discharge of the main capacitor Cm is suppressed by the diode Z1, and, for example, light emission of about 270V is performed.
[0033]
Therefore, if the distance measured by the distance measuring circuit 5 is equal to or less than the predetermined distance, it is regarded as short-distance shooting, and the light emission amount suppression circuit 6 suppresses the light emission amount by the arc tube Xe. Strobe light can be emitted with the amount of light emitted.
[0034]
For this reason, it is possible to perform light emission control at the time of short-distance shooting at a lower cost compared to the conventional example having the diffuser described above.
[0035]
In this case, the light emission amount suppression circuit 6 is constituted by a constant voltage circuit including a Zener diode Z1 connected in parallel to the main capacitor Cm for supplying electric charge to the arc tube Xe, and therefore only a simple circuit addition is required. It is possible to perform light emission control at short distance shooting at low cost.
[0036]
Hereinafter, another preferred embodiment of the present invention will be described with reference to FIGS. 3 and 4, the same parts as those in FIG. 2 are denoted by the same reference numerals.
[0037]
FIG. 3 is a block diagram showing a main configuration of another embodiment.
[0038]
The strobe light emitting device 1 ′ of this embodiment is configured by adding a pre-light emission control circuit 7 to the strobe light emitting circuit 1 in the above-described embodiment.
[0039]
The pre-emission control circuit 7 is composed of bipolar transistors Q6 and Q7. When an ON signal (“H”) indicating close-up shooting is output as a control signal from the CPU 12, the emission control circuit 4 The bipolar transistors Q3 and Q4 are turned on, whereby a high potential level (“H”) voltage is applied to the IGBT to turn on the IGBT, and light emission by the arc tube Xe is performed for a predetermined time t.
[0040]
When the bipolar transistors Q3 and Q4 of the light emission amount control circuit 4 are turned off after a predetermined time t, a high potential level (“H”) voltage is applied to the base of the bipolar transistor Q6 to turn on the bipolar transistor Q6. When a low potential level (“L”) voltage is applied to the base of the bipolar transistor Q7 and the bipolar transistor Q7 is turned on, a high potential level (“H”) voltage is applied to the base of the bipolar transistor Q2. The bipolar transistor Q2 is turned on, a low potential level (“L”) voltage is applied to the IGBT, and the IGBT is turned off.
[0041]
Thereafter, a high potential level (“H”) voltage is applied to the base of the bipolar transistor Q3 again, whereby the bipolar transistor Q4 is turned on and the IGBT is turned on to emit light.
[0042]
FIG. 4 is a diagram for explaining the operation of another embodiment.
[0043]
That is, as a result of distance measurement by the distance measurement circuit 5, when it is determined that close-up shooting is in progress, first, as shown in FIG. 4A, pre-emission is performed before the shutter is opened, and the pre-emission control circuit After the light emission is stopped by 7, the light emission is performed at 270 V, for example, in synchronization with the shutter opening operation.
[0044]
On the other hand, if it is determined as a result of the distance measurement by the distance measurement circuit 5 that the long distance shooting is in progress, first, as shown in FIG. 4B, the pre-light emission control circuit 7 does not perform the pre-light emission control, and the shutter. In synchronization with the opening operation, for example, full light emission is performed at 330V.
[0045]
Therefore, in this embodiment, when the distance measurement by the distance measurement circuit 5 is not more than a predetermined distance (that is, a short distance), the pre-emission control circuit 7 discharges a part of the main capacitor Cm. After that, since the remaining electric charge is discharged, red-eye can be prevented by pre-emission before photographing.
[0046]
The invention made by the present inventor has been specifically described based on the preferred embodiments. However, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the scope of the invention. Needless to say.
[0047]
For example, the capacitance value of the main capacitor Cm constituting the charge storage capacitor is arbitrary, and the discharge voltage value limited by the Zener diode Z1 can also be set freely.
[0048]
Further, in the above description, the case where the invention made mainly by the inventor is applied to the strobe light emitting device alone, which is the field of use behind it, has been described. However, the present invention is not limited thereto. It can also be applied to cameras with built-in.
[0049]
【The invention's effect】
In invention of Claim 1,
As a result of distance measurement by the distance measuring means, if the distance is less than the predetermined distance, it is regarded as short-distance shooting, and the light emission amount control means suppresses the light emission amount of the main light emission synchronized with the shutter opening. For this purpose, after the shutter is opened, a part of the charge storage capacitor that supplies charges to the light emitting unit is discharged to cause the light emitting unit to pre-emit, and then the remaining charge storage capacitor is synchronized with the shutter opening. Since the light emitting means emits light by discharging the electric charge, it is possible to perform light emission control that suppresses the light emission amount of the main light emission at close distance shooting at low cost, and it is possible to prevent red-eye by pre-light emission before photographing. .
[Brief description of the drawings]
FIG. 1 is a principle view of a strobe light emitting device according to the present invention.
FIG. 2 is a block diagram showing a main configuration of the present embodiment.
FIG. 3 is a block diagram showing a main configuration of another embodiment.
FIG. 4 is a diagram for explaining the operation of another embodiment.
FIG. 5 is a diagram showing each light emission pattern at the time of short distance shooting and at the time of long distance shooting with respect to the maximum light emission.
FIG. 6 is a diagram showing light emission patterns depending on the presence or absence of a diffuser during close-up shooting.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Strobe light emission device 2 Light emission circuit (light emission means)
3 Photometric circuit (photometric means)
4 Light emission amount control circuit (light emission amount control means)
5 Distance measuring circuit (ranging means)
6 Light emission amount suppression circuit (light emission amount suppression means)
7 Pre-emission control circuit Cm Main capacitor (charge storage capacity)
R1 to R3 Resistor C1 Capacitor CP Comparator PT Phototransistor Q1 to Q7 Bipolar transistor Xe Arc tube

Claims (1)

A light emitting means for discharging the charge accumulated in advance at a predetermined timing and emitting light based on the generated discharge voltage;
Photometric means for measuring the illuminance of the reflected light from the subject when light is emitted by the light emitting means;
A light emission amount control means for controlling a light emission amount by the light emission means based on a photometric result of the light measurement means;
In the strobe light emitting device having
A distance measuring means for measuring a distance to the subject ;
The light emission amount control means suppresses the light emission amount of the main light emission of the light emission means synchronized with the opening of the shutter of the photographing apparatus when the distance measurement by the distance measurement means is less than a predetermined distance. Before the shutter is opened, a part of the charge storage capacitor that supplies charges to the light emitting unit is discharged to pre-emit the light emitting unit, and then the charge storage capacitor is synchronized with the opening of the shutter. A strobe light emitting device which discharges the remaining electric charge and causes the light emitting means to perform main light emission.

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