JPH09113966A - Electronic flash device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform light emission with large light quantity by limited energy by setting light emitting time for performing light emission smaller than the full light emission by the charge of a main capacitor and having the large ratio of a visible light area, and repeating the small light emission in accordance with the set light emitting time. SOLUTION: In addition to a power source battery E1 and the main capacitor C5 in which charge is accumulated; a boosting power source circuit 23 for a stroboscope, a voltage detection circuit 24 for detecting the charging voltage of the capacitor C5, a trigger circuit 25, a discharge light emitting tube 26 and a diode D5 emitting the light by discharging the charge accumulated in the capacitor C5, and the series circuit of an IGBT 2T functioning as a gate control type switching element are connected to a CPU 21 in parallel. The CPU 21 sets the time for performing the light emission smaller than the full light emission where almost all of the charge in the capacitor C5 is discharged and having the large ratio of the visible light area, and controls the tube 26 to emit the light by repeating the small light emission in accordance with the light emitting time.

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 use in an image pickup device such as a camera and for flashing an object at the time of shooting.

[0002]

2. Description of the Related Art Conventionally, in an image pickup device such as a camera,
A strobe device that projects light onto a subject is used in order to perform good shooting even in a dark place. In such a strobe device, it is desired to improve the amount of emitted light.

Then, for example, JP-A-60-220323.
The publication discloses a technique in which a plurality of strobe main capacitors are connected in parallel to increase the emitted light amount, and further, the voltage of the strobe main capacitor is varied to improve the emitted light amount.

[0004]

However, in the technique disclosed in Japanese Patent Laid-Open No. 60-220323, a plurality of main capacitors are required, so that space and cost are increased and the amount of emitted light is increased. Requires a large amount of electrical energy. Further, a variable circuit for varying the voltage of the main capacitor is required, and a large amount of electric energy is required to increase the amount of emitted light.

The present invention has been made in view of the above problems, and its object is to be limited by controlling the light emission time of the discharge tube and performing light emission with the highest visible light region ratio. It is to emit a large amount of light with the energy.

[0006]

To achieve the above object, a strobe device according to the present invention comprises a main capacitor for accumulating electric charges, and a discharge arc tube for emitting the electric charges by discharging the electric charges accumulated in the main capacitor. , A light emission time setting means for setting a time for causing light emission with a small light emission and a large ratio in the visible light range to be emitted with less light emission than full light emission for discharging substantially all of the electric charge of the main capacitor, and the light emission time setting means. And a light emission control unit for controlling the discharge arc tube to emit light by repeating small light emission according to the light emission time.

Further, it is characterized by further comprising a light emission time changing means for changing the light emission time according to the voltage of the main capacitor. That is, in the strobe device of the present invention, the electric charge is accumulated in the main capacitor, and the discharge arc tube emits the electric charge accumulated in the main capacitor to emit light. At this time, the light emission time setting means sets a time for causing light emission with a small visible light emission and a large visible light region ratio to a full light emission in which substantially all of the electric charge of the main capacitor is emitted. The discharge arc tube is controlled to emit light by repeating small light emission according to the light emission time set by the light emission time setting means. Further, the light emission time changing means changes the light emission time according to the voltage of the main capacitor.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a conceptual diagram of a camera adopting the strobe device of the present invention, and will be described. As shown in the figure, the output of the control unit 8 is connected to the input of the light emitting unit 1 via the light emission control unit 3 and the strobe circuit 2, is connected to the film 12 via the film control unit 5, and the aperture control unit is connected. It is connected to the diaphragm 10 via 4, the shutter 11 via the shutter control unit 6, and is also connected to the distance measuring unit 7.

In such a configuration, the flash control circuit 3 controls the strobe circuit 2 under the control of the control section 8, and the strobe circuit 2 controls the light emission section 1 to operate.
Emission is controlled. Further, under the control of the control unit 8, the film control unit 5 controls the feeding of the film 12, the diaphragm control unit 4 controls the diaphragm 10, and the shutter control unit 6 controls the opening and closing of the shutter 11. Further, the distance measuring unit 7 measures the distance.

Next, FIG. 2 shows the configuration of the strobe device according to the embodiment, which will be described. In the figure, reference numeral 21 is C
The CPU 21 includes a power supply battery E1, a main capacitor C5, a power supply filter circuit 22, a strobe boosting power supply circuit 23, a voltage detection circuit 24 for detecting a charging voltage of the main capacitor C5, a trigger circuit 25, and a flashlight. A series circuit of a discharge tube (Xe tube) 26, a diode D5 and an IGBT 27 as a gate control type switching element is connected in parallel.

The power supply filter circuit 22 includes a power supply battery E.
It is composed of a capacitor C1 connected in parallel with 1, and a diode D1 connected between the positive side of the capacitor C1 and the positive side of the power supply battery E1.

The strobe boosting power supply circuit 23 has a resistor R
A series circuit of 1 and R2, transistors Q1 and Q2 and a resistor R4 connected in parallel with the power supply battery E1, a diode D2, a capacitor C2 and a transformer T1 connected in parallel, and a primary side of the transformer T1. The transistor Q3, the resistor R3 connected between the transistor Q3 and the resistor R4, the resistor R5 connected to the secondary side of the transformer T1 and the diode D3 constitute the structure as shown.

The voltage detection circuit 24 includes resistors R6 and R6.
7 series circuit, a capacitor C4 connected in parallel with the series circuit, and a diode D4 connected between the capacitor C4 and the main capacitor C5. Further, the trigger circuit 25 includes resistors R8, R9 and R1.
0, thyristor SCR1 and capacitors C6 and C7,
The resistor R11 and the trigger transformer T2 are connected as shown. This trigger transformer T2 applies a trigger to the flash discharge tube 26.

The IGBT 27 includes a flash discharge tube 26.
And a diode D5 in series. This IG
The BT 27 controls the emission amount by switching the emission current of the flash discharge tube 26, and operates according to the state of the signal SCONT from the CPU 21. Also, CPU
21, a power switch SW1 and a release switch S
W2 is connected.

From the CPU 21, in addition to the signal SCONT supplied to the IGBT 27, the signal CHG is supplied to the step-up power supply circuit 23, the signal VST is supplied to the voltage detection circuit 24, and the signal STRG is supplied to the trigger circuit 25. It has become so. Further, the CPU 21 controls the strobe circuit, and the power source VDD of the CPU 21 is supplied from the power source battery E1 through the power source filter circuit 22.

Before explaining the operation of the circuit, the above-mentioned I
The GBT 27 will be described. FIG. 3 is a general sectional structure view of the IGBT 27. As shown in the figure, a P layer 32 and an N layer 33 are sequentially formed above the collector electrode 31. The P layer 32 is formed on the surface of the N layer 33.
A P layer 34 having a lower impurity concentration and an N layer 35 having a higher impurity concentration than the N layer 33 are formed. The N layer 33 and N
The surface of the P layer 34 sandwiched between the layer 35 and the layer 35 serves as a channel region. A gate electrode 37 is formed on the region of this channel with a gate oxide film 36 interposed therebetween. In addition, an emitter electrode 39 is formed on the gate electrode 37 via an insulating film 38.
Is formed.

In the thus constructed IGBT 27, when a positive voltage is applied to the gate electrode 37 with respect to the emitter, the above-mentioned channel is formed and a current flows between the collector and the emitter. This gate voltage is usually 10V
A voltage of about 40V is required, but by adopting thinning and fine design rules of the gate oxide film 36, an IGBT 27 capable of flowing a sufficient collector-emitter current even if the gate voltage is 4V is manufactured. It is possible. This embodiment is based on this low voltage gate drive IGBT.
This is a description of a strobe device using T.

Next, the basic operation of this strobe device will be described with reference to the timing chart of FIG. When the signal CHG is set to the low level (see FIG. 4A), the strobe boosting power supply circuit 23 operates and the boosted voltage is charged in the main capacitor C5 (see FIG. 4B). This charging voltage is monitored by the voltage detection circuit 24, and when it reaches a predetermined charging voltage (see FIG. 4C), the signal CHG is output.
To high level to stop boosting operation.

Next, regarding the light emission, in order to turn on the IGBT 27 prior to the light emission start signal, the signal SC
The ONT is set to the high level (see FIG. 4 (d)). Then, in response to the light emission start signal, the signal STRG becomes high level (see FIG. 4 (e)), the thyristor SCR1 is turned on, and the trigger circuit 25 excites the flash discharge tube 26 to start light emission (see FIG. 4 (f)). After that, when the signal SCONT is set to low level during light emission, the IGBT2
7 is turned off and the light emission is stopped.

FIG. 5 shows the terminal CON inside the CPU 21.
The configuration of the circuit of the output part of T will be shown and described. The output section includes a NAND circuit 40, a NOR circuit 41, and an inverter 4.
2, P-channel (P-ch) transistor 43 and n
It is composed of a channel (N-ch) transistor 44, and the states of these structures are connected as shown. When the transistor 43 is turned on and the transistor 44 is turned off, the voltage VDD is output to the terminal CONT.

When the transistor 43 is off and the transistor 44 is on, a ground level voltage is output. Here, VDD is lowered by about VF of the diode D1 when the power source E1 is a 6V battery and is about 5.5.
V. At that time, the high-level voltage output to the terminal CONT is about 5.3V due to the voltage drop of the transistor 43. Since the IGBT 27 uses the low voltage drive IGBT described above,
The IGBT 27 can be sufficiently turned on even with a voltage of 3V.

The IGBT before the above-mentioned light emission start signal
The timing of turning on 27, that is, the high level of the signal SCONT may be any time before the signal STRG enters,
It may be when the camera is powered on, or when it is determined that a strobe is necessary, such as when the brightness is low. Furthermore, when the release is pressed, the mirror may be raised in the SLR.

FIG. 6 shows another configuration example of the strobe device and will be described. The same components as those in FIG. 2 are designated by the same reference numerals and the description thereof will be omitted. The difference from FIG. 2 is the IGBT
The voltage is applied to the gate of 27 via the buffer U1. In this configuration, the buffer U
1, the gate drive current to the IGBT 27 increases, and the IGBT 27 can be on / off controlled at high speed.

The operation will be described below with reference to the timing charts of FIGS. 7 (a) to 7 (g). Note that FIG.
7G is an enlarged view of the portion of the signal SCONT shown in FIG. 7D represented by the time t2.

When the signal CHG is set to the low level, the strobe boosting power supply circuit 23 operates and the boosted voltage is charged in the main capacitor C5. This charge voltage is monitored by the voltage detection circuit 24, and when it reaches a predetermined charge voltage, the signal CHG is set to high level to stop the boosting operation. Next, light emission, but in response to the light emission start signal, signals STRG and S
When CONT is set to the high level, at the same time as the IGBT 27 is turned on, the flash discharge tube 26 is excited by the trigger circuit 25 and starts emitting light.

The signal SCONT outputs a high / low level pulse train at a very fast cycle. IGBT
27 repeats on / off in synchronization with this. Once in the excited state, the flash discharge tube 26 can repeat a small light emission by turning the IGBT 27 on and off without triggering again from the trigger circuit 25, and can realize a substantially flat light emission. In a camera using a focal plane shutter using this flat light emission, a strobe can be used even during slit exposure, and high-speed strobe synchronization can be realized. The strobe circuits shown in FIGS. 2 and 6 can also perform pre-light emission for red-eye reduction.

This operation will be described below with reference to the timing chart of FIG. First, when the signal CHG is set to the low level, the booster circuit 23 operates and the boosted voltage is charged in the main capacitor C5. This charge voltage is monitored by the strobe voltage detection circuit 24, and when it reaches a predetermined charge voltage, the signal CHG is set to high level to stop the boosting operation.

Next, regarding light emission, when the signals STRG and SCONT are set to the high level in response to the light emission start signal, the flash discharge tube 26 is excited by the trigger circuit 5 to start light emission. Then, when the signal SCONT is set to the low level after tw, the light emission is stopped. After a small light emission corresponding to this tw is repeated at intervals of several tens of ms for about 1 second, main light emission for photographing is performed.

The normal flash light emission, the flat light emission, and the red-eye reducing pre-light emission have been described above. Next, the "high-efficiency light emission" which is a feature of the present invention will be described. Since the structure of the strobe device is the same as that shown in FIG. 6, the detailed description thereof will be omitted here, and only the characteristic points will be described below.

First, FIGS. 9A to 9C and FIG.
High-efficiency light emission will be described with reference to (a) to (c) before describing an actual operation. FIG. 9 (a) shows measured data obtained by measuring the emission spectrum intensity distribution of a stroboscopic arc tube actually used for photography, in which the horizontal axis represents wavelength and the vertical axis represents relative specific radiation intensity. There is.

The light emission time tw in FIG. 9 (a) is 3 ms, which is a state of almost full light emission. Here, the shaded area is 400 nm
The visible light region of ˜700 nm is shown. This figure 9
As is clear from (a), it is understood that much light other than visible light is emitted from the arc tube. That is, most of the electric energy input to the arc tube from the main capacitor is consumed as light other than visible light that does not contribute to illumination, and the luminous efficiency of the arc tube is significantly reduced.

In contrast to FIG. 9 (a), FIGS. 9 (b) to (c) and FIGS. 10 (a) to (c) show data obtained by sequentially measuring the light emission time. That is, FIG.
(B) shows tw = 200 μs, and FIG. 9 (c) shows tw = 60 μs.
s, tw = 20 μs in FIG. 10 (a) and t in FIG. 10 (b).
w = 10 μs, FIG. 10C shows the emission spectrum intensity distribution when tw = 6 μs.

From these figures, it can be seen that as the light emission time is shortened from 3 ms, the ratio of the visible light region to the whole increases, and the ratio is highest around tw = 10 μs. The present invention utilizes this phenomenon. That is, by causing the light emission time of the arc tube to emit light at the time when the visible light ratio is the highest, it becomes possible to convert the electric energy input from the main capacitor into visible light with high efficiency.

The actual operation of strobe light emission will be described below with reference to FIG. In response to the light emission start command,
Light emission starts when the signals SCONT and STRG are set to high level. After that, the above-mentioned highest luminous efficiency tw = 1
The signal SCONT is set to the low level in 0 μs to stop the light emission. Next, after the time t3, the signal SCONT is set to the high level again to restart the light emission. Where t3 is several tens of μ
Since it is about s and the inside of the arc tube is still in the ionized state, it is possible to restart the light emission without adding a trigger by the signal STRG again.

Thus, the light emission with the pulse width of tw is t
Repeat for 4 t4 is the normal full emission time, 3
ms. By repeating light emission with high luminous efficiency of the arc tube in this manner, it is possible to realize a highly efficient light emitting strobe that highly efficiently changes the electric energy input to the arc tube into visible light.

In the embodiment shown in FIG. 11, tw is t4.
It was constant for the whole period, but considering the drop in the main capacitor voltage during repeated light emission, the tw is changed sequentially so that the most efficient light emission time corresponding to the main capacitor voltage at that time is obtained. It may be allowed to.

To perform general GNo control, the total GNo can be controlled by shortening the time t4 during which light emission is repeated. According to the above embodiment of the present invention, the following configurations can be obtained. (1) A main capacitor that accumulates electric charges, a discharge arc tube that emits the electric charges accumulated in the main capacitor to emit light, and a small amount of visible light that is smaller than full emission that emits almost all the electric charges of the main capacitor. Control for causing the discharge arc tube to emit light by repeating light emission time setting means for setting a time for emitting light with a large area ratio and small light emission according to the light emission time set by the light emission time setting means Light emission control means, shutter means for controlling the exposure of the film, and light emission control means for controlling small light emission according to the light emission time to be repeatedly emitted while the shutter means is open. A camera that uses a strobe device. (2) A main capacitor that accumulates electric charges, a discharge arc tube that emits the electric charges accumulated in the main capacitor to emit light, and a smaller amount of visible light than full emission that emits almost all the electric charges of the main capacitor. The emission time setting means for setting the time for emitting light with a large area ratio, the shutter means for controlling the exposure to the film, the diaphragm means for controlling the exposure to the film, and the distance to the subject are set. Distance measuring means for measuring, guide number calculating means for calculating a required guide number from the subject distance and the diaphragm, and light emission number setting means for setting the number of times of emitting the small light emission corresponding to the guide number, Light emission control means for performing control so as to repeatedly emit a small amount of light for the number of times of light emission while the shutter is open. Camera using the in flash unit.

[0038]

As described in detail above, according to the present invention,
By controlling the light emission time of the discharge tube and performing light emission with the highest ratio in the visible light region, it is possible to provide a strobe device that emits a larger amount of light with limited energy.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of a camera adopting a strobe device of the present invention.

FIG. 2 is a diagram showing a configuration of a flash device according to an embodiment.

FIG. 3 is a cross-sectional structure diagram of a general IGBT.

FIG. 4 is a timing chart showing a basic operation of the strobe device.

FIG. 5 is a diagram showing a circuit configuration of an output unit of a CONT terminal inside the CPU 21.

FIG. 6 is a diagram showing another configuration example of a strobe device.

7 is a timing chart showing the operation of the strobe device having the configuration of FIG.

FIG. 8 is a timing chart showing the operation of pre-light emission for red-eye reduction by the strobe device according to the embodiment.

FIG. 9 is a diagram for explaining high efficiency light emission according to the present invention.

FIG. 10 is a diagram for explaining high efficiency light emission according to the present invention.

FIG. 11 is a timing chart showing an actual strobe highly efficient light emission operation.

[Explanation of symbols]

1 ... Light emitting unit, 2 ... Strobe circuit, 3 ... Light emitting control unit, 4 ...
Aperture control unit, 5 ... Film control unit, 6 ... Shutter control unit, 7 ... Distance measuring unit, 8 ... Control unit, 9 ... Lens, 1
0 ... Aperture, 11 ... Shutter, 12 ... Film.

Claims (2)

[Claims] 1. A main capacitor for storing electric charges, a discharge arc tube for emitting electric charges by discharging the electric charges accumulated in the main capacitor, and a light emission smaller than full light emission for discharging substantially all of the electric charges of the main capacitor. The discharge arc tube is made to emit light by repeating a light emission time setting means for setting a time for emitting light with a large visible light ratio and a small light emission according to the light emission time set by the light emission time setting means. And a light emission control means for controlling the flash device. 2. Depending on the voltage of the main capacitor,
The strobe device according to claim 1, further comprising a light emission time changing unit that changes the light emission time.