JP2003317992A - Stroboscopic device for camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a stroboscopic device for a camera capable of certainly emitting light even at a low voltage. <P>SOLUTION: As a capacitor for making a Xe tube 10 emit the light, this stroboscopic device is provide with two kinds of capacitors, i.e., a low charging voltage capacitor 9a and a high charging voltage capacitor 9b. The high voltage side capacitor 9b is used for power supply to a trigger circuit 13 exciting Xe gas inside the Xe tube 10. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flash device for a camera.

[0002]

2. Description of the Related Art When a strobe device is caused to emit light, a xenon (X
e) Light is emitted by supplying energy to the tube and causing the Xe tube to discharge. At this time, in order to make the Xe tube emit light, a high trigger voltage for exciting the Xe gas in the tube was required. Therefore, Japanese Patent Application No. 2001-278566
JP-A No. 2004-242242 and the like proposes a technique capable of generating a high-voltage trigger voltage by devising the structure of a trigger circuit for generating the trigger voltage.

[0003]

However, charging the capacitor to a high voltage and causing the strobe to emit light requires boosting 100 times or more the battery voltage, which is extremely inefficient. Therefore, even if the charging voltage is low, X
There is a demand for a strobe device capable of emitting light from the e-tube, but in the conventional strobe device, when the charging voltage of the capacitor is lowered, the trigger voltage also drops. For this reason, it becomes difficult to excite the Xe gas in the Xe tube, and as a result, there is a side effect that the strobe becomes difficult to emit light.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a strobe device for a camera capable of reliably emitting light even at a low voltage.

[0005]

To achieve the above object, a strobe device for a camera according to the present invention comprises a first capacitor for charging a first voltage and a voltage higher than the first voltage. A second capacitor for charging a second voltage, and a discharge arc tube that consumes the energy accumulated by charging the first or second capacitor to emit light,
A high-voltage generating circuit for exciting the inside of the discharge arc tube, wherein the high-voltage generating circuit is the + of the second capacitor.
It is characterized in that it is connected to the side.

That is, the strobe device of the camera of the present invention is
A high voltage is generated in the high voltage generating circuit by using a second capacitor capable of high voltage charging as a power source of the high voltage generating circuit.

In order to achieve the above object, a strobe device for a camera according to the present invention comprises a first capacitor for charging a first voltage and energy stored by charging the first capacitor. A discharge arc tube that consumes and emits light, and a high voltage generation circuit provided with a second capacitor that charges a second voltage higher than the first voltage in order to excite the inside of the discharge arc tube, And a charging circuit for charging the second capacitor prior to exciting the inside of the discharge arc tube.

That is, the strobe device of the camera of the present invention is
The second capacitor provided in the high voltage generating circuit is charged by the charging circuit.

Further, in order to achieve the above object, the strobe device for a camera according to the present invention comprises a first capacitor for charging a first voltage, and energy stored by charging the first capacitor. A discharge arc tube that consumes and emits light, and a high voltage generation circuit provided with a second capacitor that charges a second voltage higher than the first voltage in order to excite the inside of the discharge arc tube, It is characterized by comprising a step-up transformer having a common primary side, which is connected to the first capacitor and the second capacitor through a diode, respectively.

That is, the strobe device of the camera of the present invention is
With the primary side of the step-up transformer being common, the step-up transformer simultaneously charges the first capacitor and the second capacitor.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

[First Embodiment] FIG. 1 is a block circuit diagram of a camera equipped with a strobe device for a camera according to a first embodiment of the present invention.

The arithmetic and control circuit (CPU) 1 is composed of a one-chip microcomputer or the like, determines the operation state of the release switch 14 by the user, and controls the operation of the camera according to the sequence programmed in the built-in ROM.

The distance measuring device for calculating the object distance in order to focus the photographing lens is composed of a pair of light receiving lenses 2.
a, 2b, a pair of sensor arrays 3a, 3b, etc., the image of the subject 15 is received by the light receiving lenses 2a, 2b,
An image is formed on the sensor arrays 3a and 3b. Sensor array 3
In a and 3b, the subject image is converted into an electric signal and output.
The readout circuit 4 sequentially inputs the output results of the pixels of both sensor arrays 3a and 3b to an A / D conversion circuit (A / D) 1a built in the CPU 1. CPU1 is the internal R
The AM stores the image signal digitized by the A / D 1a. Next, the sensor array 3 stored in the RAM
The sensor array 3 is compared by comparing the image signals output from a and 3b.
The relative position difference x between the subject images incident on a and 3b is obtained.
It is known that there is a relation of x = Bf / L between this x, the parallax (base line length) B of the two light receiving lenses 2a and 2b, the focal length f, and the subject distance L. By detecting, the CPU 1 can calculate the subject distance L. After the focus position of the taking lens 6 is calculated based on the subject distance L, the focusing circuit 5 including an actuator and an encoder for detecting the focus position is controlled to drive the taking lens 6 to perform focusing. ,
The exposure control circuit 7 is controlled to perform exposure.

The brightness of the shooting scene and the subject distance L
Depending on, the flash is emitted at the time of exposure to obtain the proper exposure. At this time, when the subject distance L is a long distance, the light amount of the strobe light is reduced, and when the subject distance L is a short distance, the light amount of the strobe light is increased. Furthermore, when a clear image signal is not obtained during distance measurement, the strobe light is emitted with a small amount of light to serve as auxiliary light for distance measurement, or with the use of a small amount of strobe light to reduce the red-eye phenomenon described above. It may also emit light. That is, when implementing such techniques, it is preferable to control the light amount so as to switch between the large light amount strobe and the small light amount strobe according to the situation at the time of shooting control of the camera.

Therefore, in this embodiment, a plurality of capacitors for charging the energy for causing the Xe tube to emit light are provided inside the strobe device, and the light amount is controlled by properly using these capacitors according to the situation. That is, the flash device of the camera according to the present embodiment includes the charging circuit 8, the capacitors 9a and 9b, the Xe tube 10, and the IGBT.
The CPU 1 is configured to include 11a and 11b, a trigger circuit 13 and the like, and the CPU 1 selects one of the two types of capacitors 9a and 9b and causes the Xe tube 10 to emit light, thereby controlling the amount of strobe light. .

The capacitors 9a and 9b have different charging voltages, the capacitor 9a has a low charging voltage (for example, 230V), and the capacitor 9b has a high charging voltage (for example, 330V). Therefore, the capacitor 9a has a short charging time and a high charging efficiency. On the other hand, the capacitor 9b
The charging efficiency is lower than that of the capacitor 9a, but the energy stored in the capacitor during charging increases in proportion to the square of the applied voltage, and thus strobe light emission with a large amount of light becomes possible.

When the Xe tube 10 is caused to emit light by using the capacitor 9a, first, the emission of the Xe tube 10 is turned ON / OF.
In the IGBT to F, turn on the IGBT 11a,
The switch circuit 12 is controlled to turn off the BT 11b. Next, the charging circuit 8 charges the capacitor 9a. Then, a high voltage is applied from the trigger circuit 13 to the Xe tube 10 to excite the inside of the Xe tube 10 to cause the Xe tube 10 to emit light.

Similarly, using the condenser 9b, the Xe tube 1
In order to emit 0, the emission of the Xe tube 10 is turned off first.
In the IGBT that turns N / OFF, turn off the IGBT 11a.
The switch circuit 12 is controlled to turn off the FF and the IGBT 11b. Next, the charging circuit 8 causes the capacitor 9
Charge b. Then, from the trigger circuit 13 to the Xe tube 10
A high voltage is applied to the Xe tube 10 to excite the inside of the Xe tube 10, thereby causing the Xe tube 10 to emit light.

Light emission of the strobe device will be described with reference to FIG. First, at the time of so-called "pre-light emission", in which strobe light is emitted at a timing before exposure, a small amount of light emission is sufficient, and therefore light emission is performed using the capacitor 9a that places importance on charging efficiency.

On the other hand, at the time of "main light emission" during exposure,
As described above, strobe light is emitted using the condenser 9a or 9b according to the subject distance. That is, at short distance, the Xe tube 10 is caused to emit light by using the capacitor 9a. Further, when the medium distance is not the short distance or the long distance, the Xe tube 10 is caused to emit light by using the capacitor 9b. Furthermore,
For long distances, first use the condenser 9b to use the Xe tube 1
After 0 is made to emit a large amount of light, the exposure is supplemented by further making the Xe tube 10 emit a small amount of light by using the condenser 9a.

Such photographing control is performed by the program in the ROM incorporated in the CPU 1 according to the sequence shown in FIG. First, the CPU 1 determines whether or not the release switch has been turned on (step S1). When it is determined that the release switch is not turned on, it is determined whether or not the strobe has been charged (step S2). When it is determined that the charging is completed, the process returns to step S1. On the other hand, when it is determined that the charging is not completed, the capacitors 9a and 9b are charged (step S3), and the process returns to step S1.

When it is determined that the release switch is turned on in the determination in step S1, the subject distance is calculated, that is, the distance is measured (step S4). next,
It is determined whether or not the distance measurement in step S4 has been correctly performed (step S5). If it is determined that the distance can be correctly measured, the process proceeds to step S7. On the other hand, when it is determined that the distance measurement cannot be correctly performed because the output of the subject image signal is too small, the Xe tube 10 is pre-lighted by using the low-voltage side (230 V) capacitor 9a as auxiliary light. After performing the distance measurement again (step S6), the process proceeds to step S7.

When it is determined that the distance can be correctly measured, the photographing lens is focused on the basis of the calculated distance measurement result (step S7). Next, it is determined whether or not the result of the distance measurement performed in step S4 or step S6 is a short distance (step S8). If it is determined that the result of distance measurement is a short distance, it is possible to perform exposure even with a small amount of light,
After the Xe tube 10 is caused to emit light by using the condenser 9a for exposure (step S9), the photographing control in this flowchart is ended.

On the other hand, in the determination in step S8,
When it is determined that the result of distance measurement is not short distance,
It is determined whether or not the result of the distance measurement is a medium distance, which is neither a short distance nor a long distance (step S10). When it is determined that the distance is the middle distance, as in the case of the conventional stroboscopic light emission, the high voltage side (330V) capacitor 9b is used for X.
After exposing the e-tube 10 to emit light (step S1)
1), the shooting control in this flowchart is ended.

On the other hand, when it is determined in step S10 that the distance is not medium, that is, the distance is long, in order to obtain a large amount of light, as shown in FIG. After the Xe tube 10 is made to emit light by using (step S12), X is emitted by using the capacitor 9a.
After the e-tube 10 is caused to emit light (step S13) and exposure is performed, the shooting control in this flowchart ends.

That is, in a normal state, stroboscopic light emission is performed by using a capacitor on the low voltage side having a good charging efficiency to save energy, and a capacitor on the high voltage side is used only when a large amount of light emission is required. By strobe emission, correct exposure control is possible even for a long-distance subject.

Now, the charging circuit 8 and the trigger circuit 13 included in the strobe device will be described with reference to FIG. FIG. 4 is an electric circuit diagram of the strobe device according to the present embodiment.

First, the charging circuit 8 will be described. That is, the charging circuit 8 is configured to include the FETs 20 and 21 and the step-up transformers 22 and 26.

The gates of the FETs 20 and 21 in the charging circuit 8 are connected to the CPU 1, and the F
ON / OFF of the ETs 20 and 21 is controlled. CPU
When the FET 20 is turned on by 1, the power from the power supply 30 is supplied to the primary coil 23 of the step-up transformer 22, and the secondary coil 24 generates a voltage according to the winding ratio with the primary coil 23. . Further, a current corresponding thereto flows through the secondary coil 24, and the current generated in the secondary coil 24 of the step-up transformer 22 flows through the diode 25 into the capacitor 9a, and as a result, the capacitor 9a is charged.

Here, the switch 11a is the IGBT described above.
11a is a simplified view using the symbol of a switch. The switch 11a is turned on while the capacitor 9a is being charged.

On the other hand, when the FET 21 is turned on,
Power from the power supply 30 is supplied to the primary coil 27 of the step-up transformer 26, and the primary coil 2 is supplied to the secondary coil 28.
The voltage corresponding to the number of turns with respect to 7 is generated, and the corresponding current flows through the secondary coil 28, and the step-up transformer 26
Current generated in the secondary coil 28 of the capacitor 9b flows through the diode 29 to the capacitor 9b, and as a result, the capacitor 9b
Is charged.

Here, the switch 11b is the above-mentioned IGBT.
11b is a simplified view using the symbol of the switch. The switch 11b is turned on while the capacitor 9b is being charged.

A timing chart at the time of charging the FET and the capacitor is shown in FIG. That is, the capacitor 9a is charged by turning on / off the FET 20, and the capacitor 9b is charged by turning on / off the FET 21. At this time, since the charging voltage of the capacitor 9a is lower than that of the capacitor 9b, charging is completed in a shorter time than that of the capacitor 9b.

Next, the trigger circuit 13 will be described. That is, the trigger circuit 13 includes the thyristor 31 and the capacitor 3
3 and a trigger transformer 34.
In the trigger circuit 13, the anode side of the thyristor 31 is connected to the + side of the capacitor 9b via the resistor 32 and to one end of the capacitor 33.
The cathode side of the thyristor 31 is connected to the ground end. Further, the gate of the thyristor 31 is connected to the CPU 1, and the thyristor 31 is turned on by the control of the CPU 1.
/ OFF is performed.

The other end of the capacitor 33 is connected to the primary coil 35 of the trigger transformer 34. Then, a high voltage is applied to the Xe tube 10 from the secondary coil 36 of the trigger transformer 34 to excite the Xe gas in the Xe tube 10.

The IGBT 11b is turned on and the thyristor 31 is turned on.
While is OFF, energy is supplied from the capacitor 9b to the capacitor 33 and the capacitor 33 is charged. When the thyristor 31 is turned on with the electric charge accumulated in the capacitor 33, the capacitor 33 is discharged and a current flows through the primary coil 35 of the trigger transformer 34. As a result, a high voltage is generated in the secondary coil 36 of the trigger transformer 34, and the Xe gas in the Xe tube 10 is excited to cause the Xe tube 10 to emit light.

That is, as described above, the voltage for exciting the Xe tube 10 should be high, so that the capacitor for applying a high voltage to the Xe tube 10, that is, the capacitor for supplying energy to the capacitor 33 is The capacitor 9b on the high voltage side is used instead of the capacitor 9a on the low voltage side. This allows the Xe tube 10 to reliably emit light.

As described above, according to the first embodiment, the power source of the trigger circuit for applying the high voltage to the Xe tube is supplied from the high voltage side capacitor. It is possible to reliably cause the tube to emit light. Also, if you do not need a large amount of light, such as during pre-flash,
Since the Xe tube is caused to emit light by using the capacitor on the low voltage side, the efficiency is good.

[Second Embodiment] Next, the second embodiment of the present invention will be described.
The embodiment will be described with reference to FIGS. 6 and 7. In the first embodiment, two types of capacitors, a low-voltage side capacitor and a high-voltage side capacitor, were used as the Xe tube light emitting capacitors, but in the second embodiment, the Xe tube light emitting capacitors are used. In this configuration, one capacitor on the low voltage side is used as the capacitor, and the capacitor in the trigger circuit is charged by the transformer.

That is, in the present embodiment, as shown in FIG. 6, the secondary coil 28 of the step-up transformer 26 is directly connected to the capacitor 33 via the diode 29, which is different from the first embodiment. However, the other configurations are the same as those in the first embodiment.

The operation at the time of strobe light emission in such a circuit will be described with reference to FIG. That is, FET2
When 0 is turned ON / OFF, the charging of the capacitor 9a for emitting the Xe tube 10 is started as described above,
Energy is stored in the capacitor 9a. Also, FE
When T21 is turned on / off, step-up transformer 2
A current flows according to the voltage generated in the secondary coil 28 of No. 6, and the capacitor 33 is charged by this current.

In such a state, the thyristor 31
When is turned on, the charge accumulated in the capacitor 33 is discharged to the Xe tube 10 to excite the Xe tube 10, and the charge accumulated in the capacitor 9a is changed to Xe.
The Xe tube 10 emits light by being discharged to the tube 10. Note that, in FIG. 7, the flash device emits light once, but depending on the ON / OFF timing of the thyristor 31, light such as auxiliary light at the time of distance measurement and pre-light emission for red-eye prevention described above is also realized. it can. However, since the charging voltage of the capacitor is low, a large amount of light cannot be emitted.

As described above, according to the second embodiment, since the voltage applied to the Xe tube is only the low voltage from the low voltage side capacitor, the Xe tube, the capacitor for light emission, and the light emission. It is possible to reduce the breakdown voltage of the control IGBT and reduce the size thereof. Furthermore, since the capacitor in the trigger circuit is charged by a high voltage using a transformer, stroboscopic light emission can be reliably performed.

[Third Embodiment] Next, the third embodiment of the present invention will be described.
The embodiment will be described with reference to FIGS. 8 and 9. In the third embodiment, the number of FETs can be reduced. That is, in FIG.
The primary side coil 23 of the step-up transformer is commonly used and controlled by turning on / off one FET 20, and an intermediate tap is provided in the middle of the secondary side coil of the step-up transformer.
The secondary coil is divided into a secondary coil 24a and a secondary coil 24b having different numbers of turns.

That is, since a high voltage is required to charge the capacitor 33 in the trigger circuit 13 as described above, the capacitor 33 is charged by generating a high voltage using the coil 24b having many turns. And Xe tube 1
A coil 24a having a small number of turns is used to charge the zero emission capacitor 9a.

The operation at the time of strobe light emission in such a circuit will be described with reference to FIG. That is, FET2
When 0 is turned ON / OFF, the charging of the capacitor 9a for emitting the Xe tube 10 is started as described above,
Energy is stored in the capacitor 9a. Further, in the present embodiment, when the FET 20 is turned on / off, a current corresponding to the voltage generated in the secondary coil 24a of the step-up transformer flows in the secondary coil 24a. Then, this current charges the capacitor 33.

In such a state, the thyristor 31
When is turned on, the charge accumulated in the capacitor 33 is discharged to the Xe tube 10 to excite the Xe tube 10, and the charge accumulated in the capacitor 9a is changed to Xe.
The Xe tube 10 emits light by being discharged to the tube 10. Note that, in FIG. 7, the flash device emits light once, but depending on the ON / OFF timing of the thyristor 31, light such as auxiliary light at the time of distance measurement and pre-light emission for red-eye prevention described above is also realized. it can. However, since the charging voltage of the capacitor is low, a large amount of light cannot be emitted.

As described above, according to the third embodiment, the Xe tube can reliably emit light even at a low voltage, and the primary side coil of the step-up transformer is shared so that one FET can be used. By enabling the switching control, it is possible to reduce the number of parts for configuring the strobe device.

Although the present invention has been described based on the above embodiments, the present invention is not limited to the above embodiments, and various modifications and applications are possible within the scope of the gist of the present invention. Of course.

[0051]

As described in detail above, according to the present invention,
A strobe device for a camera that can reliably emit light even at a low voltage can be provided.

[Brief description of drawings]

FIG. 1 is a block circuit diagram of a camera equipped with a strobe device for a camera according to a first embodiment of the present invention.

FIG. 2 is a timing chart for explaining light emission of a strobe device.

FIG. 3 is a flowchart for explaining a shooting control procedure of a camera equipped with a strobe device for a camera according to a first embodiment of the present invention.

FIG. 4 is an electric circuit diagram of the flash device according to the first embodiment of the present invention.

FIG. 5 is an explanatory diagram for charging a capacitor.

FIG. 6 is an electric circuit diagram of a strobe device for a camera according to a second embodiment of the present invention.

FIG. 7 is a timing chart for explaining the operation of the flash device of the camera according to the second embodiment of the present invention.

FIG. 8 is an electric circuit diagram of a strobe device for a camera according to a third embodiment of the present invention.

FIG. 9 is a timing chart for explaining the operation of the flash device of the camera according to the third embodiment of the present invention.

[Explanation of symbols]

1 Arithmetic control circuit (CPU) 2a, 2b light receiving lens 3a, 3b sensor array 4 readout circuit 5 focusing circuit 6 Shooting lens 7 Exposure control circuit 8 charging circuit 9a, 9b, 33 capacitors 10 Xenon (Xe) tube 11a, 11b IGBT 12 switch circuits 13 Trigger circuit 14 Release switch 20,21 FET 22,26 Step-up transformer 25,29 diode 30 power 31 Thyristor 32 resistance 34 Trigger transformer

Claims (3)

[Claims] 1. A first capacitor for charging a first voltage, a second capacitor for charging a second voltage higher than the first voltage, and the first or second capacitor. A discharge arc tube that consumes the energy accumulated by charging the capacitor to emit light; and a high-voltage generation circuit that excites the inside of the discharge arc tube, wherein the high-voltage generation circuit is the + of the second capacitor. A strobe device for a camera, which is connected to the side. 2. A first capacitor for charging a first voltage, a discharge arc tube that consumes energy accumulated by charging the first capacitor to emit light, and excites the inside of the discharge arc tube. Therefore, in order to excite the inside of the discharge arc tube, a high voltage generating circuit provided with a second capacitor for charging a second voltage higher than the first voltage, the second capacitor A strobe device for a camera, comprising: a charging circuit for charging. 3. A first capacitor for charging a first voltage, a discharge arc tube that consumes energy accumulated by charging the first capacitor to emit light, and excites the inside of the discharge arc tube. Therefore, a high voltage generation circuit provided with a second capacitor for charging a second voltage higher than the first voltage, and the first capacitor and the second capacitor via a diode respectively A strobe device for a camera, comprising: a connected step-up transformer having a common primary side.