JP2011039546A - Method and device for controlling light quantity of external flash for digital camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and device that shorten the waiting time until next photographing by a digital camera by decreasing the light quantity of the light emission of a built-in flash, and allow high-quality photographing by appropriately controlling the light quantity of previous light emission and main light emission of an external flash. <P>SOLUTION: Each of the built-in flash and external flash emits light in response to light emission start of the previous light emission of each of the built-in flash and external flash, and the external flash emits light in response to light emission start of the main light emission of the built-in flash. It is controlled that the light emission stopping timing of the previous light emission of the external flash is the same as or near that of the built-in flash. Adjustment is performed according to the situation so that the light emission stopping timing of the previous light emission of the external flash is delayed from that of the built-in flash. Light quantity is controlled so that the light of the previous light emission of the built-in flash and the light of the previous light emission of the external flash is appropriately radiated to a subject even when the light of the previous light emission of the built-in flash is shielded and is not radiated to the subject. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an improvement in light emission control technology for an external strobe used in a digital camera with a built-in strobe.

When using a digital camera (hereinafter sometimes simply referred to as a camera) for underwater photography, the digital camera 1 is used in a waterproof camera housing 4 as shown in FIG.
Since there are many dark places underwater compared to land, strobe light is required rather than land photography. In that case, when the built-in strobe 2 of the camera 1 is used, the light emitting part of the built-in strobe 2 is located near the lens 3 of the camera 1, so that dust floating in the water is reflected and appears strongly white. (Marine snow phenomenon) or when an external wide conversion lens with a large outer diameter is attached to the front outer frame 7 of the waterproof camera housing 4, the light from the built-in flash 2 is blocked by the conversion lens, You can't take good quality photos because of dark areas.

In order to solve such a problem, an external strobe 9 is used, and the external strobe 9 is attached to the waterproof camera housing 4. In order to avoid a marine snow phenomenon when the light of the built-in strobe 2 hits the subject, a black shading plate 6 or a tape or other equivalent product is pasted on the front surface of the diffusion plate 5 of the waterproof camera housing 4 to shield the light.
In the water, the external strobe 9 is used even when the distance to the subject is far and the built-in strobe 2 has insufficient light quantity.
On land, as with underwater, the built-in strobe uses a general external strobe when the amount of light is insufficient, and an external ring strobe is used to eliminate shadows. Note that when used on land, the waterproof camera housing 4 is not required except in places where there are many water drops.

  The external strobe 9 needs to emit light in synchronization with the built-in strobe 2. However, as a simple way to do this without using an electric cord called a sync cord, the light from the built-in strobe 2 is detected by the external strobe 9. There is a method of detecting light by the sensor 10 for synchronized light emission. Normally, the light from the built-in strobe 2 reaches the light detection sensor 10 sufficiently, so that it is not necessary to take special light transmission means. However, when the distance from the light emitting part of the built-in strobe 2 to the external strobe 9 is long If there is a disturbing factor, the light from the built-in strobe 2 can be reliably transmitted to the light detection sensor 10 by connecting the light emitting part of the built-in strobe 2 and the light detection sensor 10 with an optical fiber 8 as shown in FIG. Is transmitted to.

There are two methods (1) and (2) below depending on the camera specifications for the flash control method of the built-in flash of a digital camera, but the external flash is synchronized when the shutter is released in accordance with either of the two methods. There are two types: a dual-use type that emits light and a dedicated type that supports only one of the methods.
(1) A weak pre-emission (preliminary emission) occurs just before the shutter is released, the camera sensor measures the reflected light through the lens to determine the amount of main emission, and the next time the shutter is released (emits at the X contact) ) The main light emission with the determined light quantity.
(2) When the shutter is released, it emits light only once in synchronization with the normal X contact, detects the reflected light from the subject with the camera sensor, and integrates the signal to stop the light emission Method to do.
This is the same method as a conventional external auto strobe. (1) All of the methods (2) are known and conventionally used. Today's digital cameras are overwhelmingly more popular because of the ease of control.
The light quantity control method and apparatus according to the present invention is for synchronizing an external strobe with a built-in strobe of a digital camera according to the method (1).

The operation when an automatic strobe or manual strobe without a countermeasure is externally attached to the digital camera of the method (1) will be described with reference to FIGS. 1 and 2. The shutter operation of the digital camera 1 is shown in FIG. Thus, the light emission operation of the built-in flash 2 is as shown in FIG.
When the external strobe 9 is lit in sync with the shutter operation (X contact) of the camera, the weak pre-emission of the built-in strobe 2 that shines immediately before the camera shutter is released, that is, the light emission 11 of FIG. In this case, the external strobe 9 is triggered, and at this time, the external strobe emits light with a normal large amount of light.

  In this way, if the external strobe emits light with a large amount of light during the pre-flash of the built-in strobe, the remaining amount of energy is lost, and the external strobe emits synchronized light during the next camera shutter operation (X contact). (Hereinafter referred to as “main light emission”), light is emitted with an insufficient amount of light, or no light is emitted at all. Such a phenomenon often occurs especially when the distance from the camera to the subject is long.

Therefore, in the prior art, the external strobe does not emit light when the built-in strobe is pre-flashed, and the external strobe emits synchronized light only when the built-in strobe is fully fired. A circuit for this purpose is called a pre-light emission cancel circuit. FIG. 2C shows a light emission curve of an external strobe. The synchronized light emission 13 starts to be emitted at timing T1, and stops at an appropriate light amount at timing T2. A dotted line shows the time of full light emission.
In this prior art, as described with reference to FIG. 1, a black light shielding tape 6 or the like is pasted in front of the diffusion plate 5 of the waterproof camera housing 4 to shield the light. Therefore, the light from the built-in strobe 2 does not hit the subject and no reflected light comes. Also, when a ring strobe, a conversion lens or other parts having a large outer diameter are attached to the outer frame 7 of the waterproof camera housing 4, the light of the built-in strobe is shielded, resulting in the same result as described above.
In the conventional technology, when the pre-flash light from the built-in flash strikes the subject and the reflected light does not come from the subject (does not enter the camera lens) or the amount of reflected light is less than normal, the camera The main flash of the built-in flash is almost full. The pre-flash and the main flash of the built-in flash are shown in FIG.

In FIG. 2B, the main light emission is performed about 100 mS (milliseconds) after the pre-light emission 11. In the drawing, the scale of the horizontal axis is reduced in the 100 mS portion for easy understanding. As is well known, the flash time of the built-in strobe is about 3 mS with full light emission.
In the next second main light emission, full light emission is performed as described above, and this state is shown in a waveform 12a. When full light emission occurs in this way, the capacitor of the built-in flash 2 must be charged for the next shooting. Since this charging time takes 7 to 8 seconds with a general camera, the shutter of the digital camera is locked during that time, and the next shooting cannot be performed.
At the same time, the battery of the camera is consumed to charge the built-in flash, so that as the number of full flashes increases, the number of images taken with the same battery decreases and the battery life is shortened.

In addition, although there is a need for calculation time for shooting data and time to write to memory, some cameras cannot be calculated or written while the built-in strobe capacitor is charged while the battery voltage is low. It takes time until the next shooting. This state is also added, and during that time, shooting is not possible, causing a loss of photo opportunity.
In the case of shooting with a normal camera alone, if the distance is about 0.5 m to 3 m, the main flash of the built-in flash does not become full flash as shown by the dotted waveform 12b in FIG. Since light emission is stopped halfway, the amount of light is reduced. For this reason, it is possible to immediately move to the next shooting without requiring a charging time, so that a photo opportunity is not missed, and the battery consumption speed of the camera is also slowed down.

  The present invention has been made in view of such a conventional technique, and an object of the present invention is to reduce the waiting time until the next shooting by reducing the amount of main flash light of the built-in strobe, and the battery life of the camera. It is possible to provide a method and an apparatus for controlling the light quantity of an external strobe for a digital camera, which can control the pre-light emission and the main light quantity of the external strobe appropriately and perform high quality shooting.

  In order to solve the above-mentioned problem, the invention of claim 1 is based on the trigger of pre-flash emission of the built-in strobe with an external strobe used in a digital camera of a pre-flash and main flash with the built-in strobe. In the external flash unit's light intensity control method in which the external flash fires when the external flash fires and triggers the main flash of the built-in flash as a trigger, and the internal flash's pre-flash firing stop timing and built-in Control the flash pre-flash emission stop timing at or near the same time, adjust the pre-flash emission stop timing of the external flash to be longer than the pre-flash timing of the built-in flash, and adjust according to the situation. Pre-flash of the external flash even if the pre-flash of the built-in flash is blocked and the subject is not illuminated And performing light amount control such that the light is properly irradiated onto the subject.

  The invention of claim 2 is characterized in that, in addition to the configuration of the invention of claim 1, control is performed so that the amount of pre-emission of the external strobe is equal to or close to the amount of pre-emission of the built-in strobe. To do.

  The invention of claim 3 is characterized in that, in addition to the above-described configuration of the invention of claim 1 or 2, the light emission of the external strobe is stopped using the pre-light emission stop of the built-in strobe.

  In the invention of claim 4, the external strobe is triggered by the start of the pre-flash of the built-in strobe with an external strobe used in a digital camera that performs pre-flash and main flash with the built-in strobe. In the external strobe device that the external strobe emits with the start of the main flash firing as a trigger, the pre-flash firing timing of the external flash and the pre-flash firing timing of the built-in flash are at or near the same time And a means to adjust according to the situation so that the pre-flash emission stop timing of the external flash is longer than the pre-flash timing of the built-in flash, and the pre-flash light of the built-in flash is shielded Even if the subject is not illuminated, the preflash light from the external flash is properly illuminated. And performing light quantity control so.

  According to a fifth aspect of the invention, in addition to the configuration of the fourth aspect of the invention, there is provided means for controlling the amount of pre-emission of the external strobe to be equal to or close to the amount of pre-emission of the built-in strobe. It is characterized by that.

  The invention of claim 6 is characterized in that, in addition to the configuration of the invention of claim 4 or 5, the light emission of the external strobe is stopped using the pre-light emission stop of the built-in strobe.

  A seventh aspect of the invention is characterized in that, in addition to the configuration of the invention of any one of the fourth to sixth aspects, a switching circuit for adjusting the amount of light at the time of pre-emission is provided.

A specific example of the setup of the digital camera and the external strobe to which the method and apparatus of the present invention are applied is basically the same as that of FIG. 1 shown in connection with the description of the prior art.
As shown in FIG. 1, the digital camera 1 has a built-in flash 2 for pre-flash and main flash. The digital camera 1 is stored in a waterproof camera housing 4, and an external flash 9 is attached to the waterproof camera housing 4. It has been. A black shading plate 6 is affixed to the front surface of the diffusion plate 5 of the waterproof camera housing 4 facing the light emitting portion of the built-in flash 2 so that the light from the built-in flash 2 does not face the subject. Note that when used on land, the waterproof camera housing 4 is not required except in places where there are many water drops.
In order to transmit the light of the built-in strobe 2 to the light detection sensor 10 of the external strobe 9, the light emitting part of the built-in strobe 2 and the light detection sensor 10 are connected by an optical fiber 8 as necessary.

2, (D) shows a light emission curve of the built-in flash 2 of the digital camera 1, and (E) shows a light emission curve of the external flash 9.
The built-in flash 2 of the camera 1 performs a pre-flash operation 14 immediately before the shutter is released. The external strobe 9 receives the pre-emission light of the built-in strobe 2 by the light detection sensor 10 and performs a pre-emission operation 16 using the detection signal as a trigger. The pre-flash operation of the external strobe 9 is controlled by a required control circuit built in the external strobe 9 so as not to emit full light.
Assuming that the pre-flash start timing of the built-in flash 2 is T3 and the stop timing is T4, the pre-flash start timing of the external flash 9 is T7, which is the same as or almost the same as T3. The pre-flash stop timing T8 of the external strobe 9 need not be the same as the pre-flash stop timing T4 of the built-in flash 2. The main capacitor is left with a sufficient amount of electric power (electricity) necessary to execute the main flash of the external strobe 9 with an appropriate amount of light, which does not interfere with the main flash of the external strobe 9. The pre-light emission stop timing T8 is adjusted.

Increasing the amount of pre-emission of the external flash 9 more than the amount of pre-emission of the built-in flash 2 is more effective because the reflected light from the subject increases. Even if they are equivalent, there is an effect.
Next, the case where the built-in strobe 2 of the digital camera 1 emits the main light will be described. Since the above-described light shielding measures are taken, almost no reflected light from the subject is applied to the lens 3 of the camera 1 when the built-in strobe 2 is pre-flashed. Although the light does not return, the light at the time of pre-flash of the external strobe 9 hits the subject and returns (although there is a difference depending on the shooting distance, the explanation of the waveforms in FIG. 2 is premised on the order of 0.5 m to 2 m). Therefore, the digital camera 1 determines that the subject is at a short distance based on the incident light, and the main light emission of the built-in strobe 2 becomes a weak light amount like the light emission waveform 15. That is, light emission is started at timing T5 and light emission is stopped at timing T6.

In this way, with regard to the digital camera 1 side, the main flash of the built-in strobe 2 becomes weak light and power remains in the capacitor, so the charging time for the next shooting is shortened and the waiting time until the next shooting Is shortened. The waveform indicated by the dotted line from the peak of the light emission waveform 15 shows that the subject 1 is far away from the subject because there is no reflected light from the subject when the external strobe 9 does not pre-emit. This means that the built-in flash 2 emits light with full light emission.
The external strobe 9 performs the main light emission as shown by the waveform 17 at the same time or almost the same time as the main light emission of the built-in strobe light 2. The light emission start is timing T1, and the light emission stop is timing T2. The light amount control circuit of the external strobe 9 is normally an auto circuit, and stops light emission when the appropriate light amount is reached. The light level is set according to the aperture of the digital camera 1 in advance.
The external strobe 9 can be used practically if it is adjusted to an appropriate amount of light according to the shooting distance even in the case of manual light emission. In addition, since the power source of the external flash 9 is a power source different from that of the digital camera 1, the charging time can be independently increased by selecting the capacity of the power source battery and the power source circuit. However, the waiting time for the next shooting will be 2 to 3 seconds, so you won't miss a photo opportunity.

  As described above, according to the method and apparatus of the present invention, when shooting with an external strobe synchronized with the built-in strobe of a digital camera, the external strobe is pre-flashed with the pre-flash of the built-in strobe as a trigger, and from the subject. Based on the reflected light of the pre-flash of the returned external strobe, the amount of light emitted from the built-in flash is controlled so that the amount of light emitted from the built-in flash can be reduced. Since the built-in flash capacitor charging time for shooting is shorter than the conventional product, the waiting time until the next shooting is shortened, and the photo opportunity is not lost. In addition, the battery life of the digital camera is prolonged, and there are practical effects such as no need for frequent battery replacement.

  Further, in the method and apparatus of the present invention, the operation of the external strobe at the time of pre-flash is performed while leaving the power for the main flash at the main capacitor so that no trouble occurs during the main flash of the external strobe. Thus, the main flash of the external flash is performed with a necessary and sufficient appropriate light amount, and high quality shooting can be performed without being affected by the distance to the subject.

It is a schematic diagram explaining the connection state of the digital camera and external strobe in the prior art and the present invention. FIG. 6 is a timing chart and a waveform diagram for explaining a shutter operation of a digital camera and a light emission operation of a built-in strobe and an external strobe in the related art and the present invention. It is a block diagram (partially detailed circuit diagram) showing a circuit configuration of the present invention. FIG. 4 is a timing chart and a waveform diagram in the circuit configuration of FIG. 3. FIG. 4 is a detailed circuit diagram showing an example of a specific portion of the circuit configuration shown in FIG. 3. A new function is added to the circuit configuration shown in FIG. Another embodiment of the circuit configuration of the present invention is shown, and the operation is partially different from that of FIG. FIG. 8 is a timing chart and a waveform diagram in the circuit configuration of FIG. 7.

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 3 is a block diagram showing a circuit configuration of the external strobe 9 attached to the digital camera 1 (partly including an actual circuit diagram).
The circuit configuration and operation of this external strobe, commonly referred to as an auto strobe, are the same as known ones, and will be briefly described below.
The power of the battery 18 is converted into a high voltage of about 330 V at maximum by the DC-DC converter 20 including the rectifier diode 21 and charged to the main capacitor 22. When the voltage of the main capacitor 22 gradually increases and reaches a predetermined voltage, for example, about 260 V, the neon tube built in the voltage detection / ready circuit 23 is turned on to indicate that the external strobe is ready to be used. . Usually, this neon tube for display is called a ready light or a ready lamp.
The method for detecting and displaying that the voltage of the main capacitor has reached the predetermined voltage and the external strobe is in the ready state is not limited to the voltage detection / ready circuit 23, and is not limited to the DC-DC converter circuit. There is a method for detecting the voltage, and a light emitting diode may be used instead of the neon tube.
Thereafter, when the transistor 37 connected to the trigger circuit 24 is turned on, the trigger circuit 24 is turned on, and a high voltage pulse of about 3000 V is generated from the trigger coil and applied to the discharge tube 26.

When controlling from the outside, the X contact terminal 25 is used. Even in the case of the present invention, in order to synchronize with the pre-flash of the built-in strobe, it is necessary to detect the light of the built-in strobe, but the signal of the main flash is connected from the X contact by a known lead wire. Alternatively, this signal can be converted into light by a known method and connected to an external strobe with an optical fiber as described above. This is because even a general digital camera often has only an X contact.
Thereafter, the discharge tube 26 starts to emit light. At that time, the IGBT element 27 for light emission control is ON. A control signal is output from the trigger circuit 24 in synchronization with the operation of the trigger circuit 24 and applied to the gate voltage generation circuit 19, and a gate voltage is generated from the gate voltage generation circuit 19 in synchronization with this signal. The method of taking the control signal or the gate voltage is not limited to the method using the known gate signal generating circuit 19, and there is a method of taking it from the discharge tube circuit.
The auto side light emission control circuit 28 or the manual side light emission control circuit 30 operates by the generation of the gate voltage.

The gate voltage generation circuit 19 is a circuit that generates a signal for adjusting the operation timing of the external strobe. When the changeover switch 29 is set to auto, the auto light emission stop signal generating circuit 43 operates when the discharge tube 26 emits light as described above.
In this operation, a sensor 44 made of a phototransistor receives reflected light from a subject and converts it into an electrical signal, and charges the integrating capacitor 45 with the amount of electricity. The integration capacitor 45 is connected to the comparator 47. When the voltage of the integration capacitor 45 reaches a predetermined voltage (comparison voltage divided by the resistor 46), the exposure is appropriate, and a signal is output from the comparator 47. And the signal is applied to the auto-side light emission control circuit 28, a light emission stop signal is output from the auto-side light emission control circuit 28, and is applied to the IGBT element 27 which is a part of the light emission control circuit, and the IGBT element 27 is turned off. The discharge tube 26 stops emitting light.

The external control terminal 48 is used when an auto / manual light emission stop signal generating circuit or an equivalent circuit is external. Also used when inputting a light emission stop control signal from the camera.
When the changeover switch 29 is switched to the manual side, when the gate voltage from the gate voltage generation circuit 19 is applied to the integration capacitor 31a via a resistor and the voltage reaches a predetermined appropriate value, the manual side The light emission control circuit 30 is turned on, a light emission stop signal is applied to the IGBT element 27, and the discharge tube 26 stops light emission as described above.

Next, the configuration and operation of each means of the present invention will be described with reference to FIGS. Since the external strobe 9 of the present invention emits light with the pre-flash of the built-in strobe 2 of the digital camera 1 as a trigger, the light detecting circuit including the light detecting sensor 10 for detecting the light of the built-in strobe 2 and the signal thereof are used. A pre-emission signal generating means comprising a first pre-emission signal circuit 39 and a second pre-emission signal circuit 33 including a circuit for sorting is required.
The pre-light emission signal generating means generates a light emission stop signal by performing a light amount control operation during pre-light emission.
First, when the shutter button of the digital camera 1 is pressed, the built-in strobe 2 first emits light and emits light with a small amount of light as shown by a waveform 49 in FIG. Next, the circuit of the light emitting means shown below of the external strobe 9 operates.

With the connection shown in FIG. 1, the light of the built-in strobe 2 is first detected by the phototransistor 34 or a photodetection sensor 10 made of an equivalent product, and the signal is connected to the timer circuit 36 and the transistor via the DC component cut capacitor 35. 37 is applied.
The photodetection sensor 10 formed of the phototransistor 34 or a circuit in the vicinity of the photodetection sensor 10 can operate even if it is a separate part that is not built in the external strobe 9. It belongs to the scope of the invention.
For example, the light detection sensor and the peripheral circuit may be placed near the built-in strobe 2 of the camera 1 and connected to an external strobe with a lead wire therefrom. Alternatively, the signal can be converted into an optical signal and connected by an optical fiber.
The output signal of the transistor 37 to which the detection signal of the phototransistor 34 is applied is as shown by the waveform 51 in FIG. 4B. As described above, the trigger circuit 24 operates and the discharge tube 26 starts to emit light. To do.

Next, the first pre-emission signal circuit 39 shown in FIG. 3 will be described. The timer circuit 36 included in the first pre-emission signal circuit 39 is provided to detect only the first pre-emission among signals when the built-in strobe emits light twice. Configuration is simplified.
The circuit for setting the time according to the present invention is an example. That is, for the integration circuit, differentiation circuit, and timer circuit, a known one-shot multi-circuit or latch circuit or other equivalent circuit without using them, digitization If the equivalent circuit is used, and an operation equivalent to that of the integration circuit, differentiation circuit or timer circuit is performed, it can be substituted. That is, the circuit for setting the time according to the present invention includes a circuit that performs the same operation and operation.
In the case of the digitized method, for example, a counter 42 (for example, decimal) may be used to extract the first pre-emission signal. The waveform correction circuit 41 is inserted as necessary.
Furthermore, although the cost is high, if it is programmed at the timing shown in FIG. 4, it can be controlled by a microcomputer, and an equivalent function such as a digital timer function can be used. In this case, other control circuits can be controlled together.

Next, when a signal from the DC component cut capacitor 35 is applied to the timer 36, the timer is turned on as shown in FIG.
Since the timer 36 is ON for about 200 mS (milliseconds) or more, it is not affected by the second light emission of the built-in strobe, and generates a signal for operating only during pre-light emission as shown in FIG. With this signal, the first pre-emission signal circuit 39 and the second pre-emission signal circuit 33 operate only during pre-emission.
When the output signal of the timer 36 is differentiated by the differentiating circuit 38 from the position of the timing T9 in FIG. 4C, the waveform shown in FIG. 4D is obtained. When the signal is applied to the transistor 40, the transistor 40 The collector terminal is as shown in FIG.
The width of the signal can be changed by changing the constant of the differentiating circuit 38, and it is also possible to finally control the first light emission amount of the external strobe.

3 and 4, a waveform 53 in FIG. 4D is a waveform in the case of the reference capacitance, and a waveform 54 shows a case where the capacitance is increased as compared with the waveform 53. Corresponding waveforms of the transistor 40 are the waveform 55 and the waveform 56 in FIG. 4E, and the corresponding light amounts are shown in the light amount waveform 57a and the light amount waveform 57b in FIG. Become.
By varying the capacity in this way, the amount of pre-emission light can be increased or decreased, and can be adjusted to an optimum value according to the shooting situation.
The circuit corresponding to this includes the differential capacitors 38a and 38b of FIG. 3, and the capacitance is increased by adding the differential capacitor 38b to the differential capacitor 38a. In this case, if a plurality of capacitors are provided and a changeover switch SW1 is attached, the capacitors can be used at any time according to the shooting situation. In the above case, an example of changing the capacitance of the differential capacitor has been described. However, the same result can be obtained by changing the resistance attached to the differential circuit or changing the base resistance of the transistor 40.

The transistor 40 is connected to the second pre-emission signal circuit 33, and the signal is applied thereto.
The second pre-emission signal circuit 33 may operate differently as necessary as in the following (1), (2), and (3), but all operate as part of the emission stop means.
In this operation, when a predetermined value is reached, a light emission stop signal is generated and applied to the IGBT element 27 which is a part of the light emission control circuit. The IGBT element 27 is turned off, and the discharge tube 26 stops emitting light.

(1) When you want to make the flash time of the external flash pre-flash considerably longer than that of the built-in flash.
A timer circuit or an equivalent circuit is added to the second pre-light emission signal circuit 33 to extend the ON time (operation time), and then connected to the integration circuit 31. This is because the second pre-emission signal circuit 33 is turned off before the integration value reaches a predetermined value unless the time for which the second pre-emission signal circuit 33 supplies power to the integration circuit is lengthened. It is. In FIG. 3, the integration circuit 31 is partially shared by the manual side light emission control circuit 30, but another equivalent circuit may be provided.
When the value of the integrating capacitor 31a reaches a predetermined value by turning on the second pre-light emission signal circuit 33, the manual light emission control circuit 30 operates to issue a light emission stop signal, and the discharge tube 26 stops light emission.
If it is desired to adjust the flash time during the pre-flash of the external strobe 9, a plurality of different C / R time constants of the integration circuit 31 are provided, and the switch SW2 is used to switch according to the shooting situation in the same manner as described above. Can be used. As an example, when switching with a resistor, the resistor 31b and the resistor 31c are switched. When switching by capacitance, it is added to the capacitor 31a.
The integrating circuit 31 is equivalent to a timer circuit as a circuit combined with the manual light emission control circuit 30. In particular, when digitized, this portion becomes a digital timer circuit or the equivalent circuit described above.

(2) When you want to make the flash time of the external flash pre-flash equal to or slightly longer than the built-in flash.
The second pre-emission signal circuit 33 is connected to the integrating circuit 31 merely as a buffer circuit. In this case, the ON time of the second pre-light emission signal circuit 33 changes from the waveform 55 to the waveform 56 in FIG. Operation is possible if the time until the value of the integrating capacitor 31a reaches a predetermined value is set within the ON time of the second pre-light emission signal circuit 33. After that, it operates in the same manner as (1) above.

(3) When adjusting the flash time during pre-flash of the external strobe only by the operation of the differentiation circuit 38 and the transistor 40.
The second pre-emission signal circuit 33 is directly connected to a part of the manual side emission control circuit 30 without passing through the integration circuit 31 as indicated by a dotted line 32 as a buffer circuit only.
In this case, the light emission stop timing of the discharge tube 26 is as indicated by 55 to 56 in FIG. 4E. A light emission stop signal is applied from the second pre-light emission signal circuit 33 to the IGBT element 27, and the discharge tube 26. Stops emitting light.
For example, the discharge tube 26 starts emitting light at T10 in FIG. 4F, and corresponds to 57a (T11a) corresponding to 55 in FIG. 4E or 56 in FIG. The light emission is stopped at 57b (T11b).

The operations of (1), (2), and (3) during the pre-light emission are performed as described above and as shown in FIG. ) And the light amount is controlled so as to emit light. In particular, in the case of long-distance shooting or when the aperture of the lens is reduced, the main light emission requires a larger amount of light than the pre-light emission.
More specifically, the power (electrical quantity) of the main capacitor 22 is exclusively used for the light emission of the discharge tube 26 of the external strobe 9, but in the case of an operation close to full light emission at the time of pre-light emission, At the time of the second main light emission, the power (electric amount) of the main capacitor 22 becomes insufficient, resulting in an underexposed light amount or no light emission.

When the operations (1), (2), and (3) are finished, the built-in flash 2 of the digital camera 1 performs main light emission (second light emission) after about 100 ms.
In this case, as described above, the pre-flash light of the built-in flash 2 is shielded and does not enter the lens 3 of the camera 1, but the pre-flash light of the external flash 9 (from 57a in FIG. 4F). 57b) reflects from the subject and enters the lens 3 of the camera 1 (for example, the distance to the subject is 0.5 m to 2 m).
For this reason, the digital camera 1 determines that the distance to the subject is a short distance, and the main flash of the built-in flash 2 is stopped halfway as shown in the waveform 50 of FIG. Therefore, the purpose of controlling the amount of light is achieved because there is no full light emission.
In the external strobe 9, the main light emitted from the built-in strobe 2 is detected by the light detection sensor 10 including the phototransistor 34 in the same manner as described above, and the transistor 37 is turned on as indicated by the waveform 52 in FIG. Then, the discharge tube 26 emits light as shown by a waveform 58 in FIG. At this time, as described above, the first pre-emission signal circuit 39 and the second pre-emission signal circuit 33 do not operate and no signal is output.

Therefore, when the changeover switch 29 is set to the auto side, the auto light emission stop signal generating circuit 43 operates, and when the appropriate exposure is set in advance, a light emission stop signal is output, the discharge tube 26 stops light emission, and a series of operations are performed. finish. Explaining in the drawings, light emission starts at timing T12 in FIG. 4F, and light emission stops at timing T13.
Even when the changeover switch 29 is set to the manual side, the discharge tube 26 stops emitting light when the set value is reached, as described above, and the series of operations ends.
In the present invention, even if there is a deviation in the timing of each operation, it is sufficient that there is no influence on the image of the photograph, and it has been confirmed that there is no problem with some deviation from the past.
Therefore, the meanings of tuning, synchronization, and simultaneous are also within a certain range, and the deviation before and after is allowed as described above, and the timing diagram also includes the deviation before and after the perfectly matched part. To do.
As an example, since the pre-emission is a small amount of light, the flashing time is very short, being about 20 μS (microseconds) to 50 μS. For this reason, even if the pre-flash of the external strobe is started after the pre-flash of the built-in flash is stopped, this is not a problem.
The flash operation of the external flash will be in time even if the pre-flash emission stop signal of the built-in flash is triggered. If this operation is judged by human eyes, it is natural that it is simultaneous.
Incidentally, regarding the operation of the external strobe, when the operation is performed using the light of the built-in strobe as a trigger, the light emission is naturally delayed.

The present invention will be described more specifically based on the drawings. FIG. 5 shows the block diagram of FIG. 3 in further detail, with the known portions omitted and only the present invention portion.
A5 is connected to the gate voltage generation circuit 19 of FIG. B5 is connected to the main capacitor 22 of FIG. G1 and G2 are grounds, and are connected to the negative part of the battery 18. The plus circuit C5 is connected to the plus portion of the battery 18.
Since the circuit of FIG. 5 corresponds to the block diagram of FIG. 3, the same parts have already been described with reference to FIG. 3, and repeated description is omitted. The timer circuit 67 is one of the embodiments corresponding to the timer circuit 36 of FIG. 3, and when the transistor 66 is turned on by the light emission start signal, the capacitor of the timer circuit 67 is charged, whereby the timer operates.
The parts corresponding to the second pre-emission signal circuit 33 are a transistor 64 part and a capacitor 65 part. If a timer is required, this can be achieved by adding a capacitor 65.
As described above, this part of the timer can operate in other ways. Further, there are various connection methods of the circuit of the transistor 64 as described above, but in FIG. 5, it is connected to the integration circuit.

When the value of the integration circuit becomes a preset value, the transistors 63, 62, 61 are turned on, so that the IGBT element 27 is turned off, and the discharge tube 26 stops emitting light.
When the integration circuit is unnecessary as described above, it is possible to connect the collector side output of the transistor 64 to the base circuit of the transistor 61.
When the changeover switch 29 is set to the auto side, when a signal is received from the auto light emission stop signal generating circuit 43, the transistor 60 is turned on and the transistor 59 is also turned on, so that the IGBT element 27 is turned off and the discharge tube 26 is turned off. Stops emitting light.

Here, the following phenomenon occurs. The auto light emission stop signal generation circuit 43 operates both during pre-flash and main flash of the built-in flash. Therefore, if the distance to the subject is very close (for example, 0.5 m) and the aperture setting value is brightened to the F2 position during pre-flash, the auto flash stop signal will be displayed before the light amount set by the pre-flash signal circuit is reached. The generation circuit 43 reaches a predetermined value with a smaller amount of light, generates a light emission stop signal, and the discharge tube 26 stops light emission. Therefore, the amount of pre-emission of the external strobe 9 is less than the set value.
However, even if this phenomenon occurs, the distance is actually quite close as described above, and the aperture setting value is as bright as F2, so the reflected light returns from the subject even if the reflected light from the subject during pre-emission is somewhat reduced. If this is the case, the amount of main light emission on the digital camera 1 side will be small, and there will be almost no full light emission.
For this reason, there is no problem even if this measure is not implemented, but if the above problem occurs when bad shooting conditions overlap, this can be solved by adding a simple circuit.

As the operation principle, the operation of the auto flash stop signal generation circuit 43 or the auto-side flash control circuit 28 of the external strobe that emits light in synchronization with the pre-flash of the built-in flash may be stopped only during the pre-flash. FIG. 6 shows an embodiment thereof. Except for the added inhibit circuit, it is the same as FIG.
In order to stop the operation of the automatic light emission stop signal generating circuit 43 during the pre-light emission, a first inhibit circuit 89 is added. With this circuit configuration, in response to a signal generated from the first pre-emission signal circuit 39, the first inhibit circuit 89 is turned on, and the operation of the automatic emission stop signal generation circuit 43 is stopped.
The other is to stop the operation of the auto-side light emission control circuit 28 at the time of pre-emission by attaching the second inhibit circuit 86 to the auto-side light emission control circuit 28 side by the wiring 87. The problem is solved.

Next, FIGS. 7 and 8 show an embodiment which operates on a principle different from that of the first pre-light emission signal circuit 39 shown in FIG.
This is such that the light emission stop timing at the time of pre-flash of the built-in strobe and the light emission stop timing of the external strobe are the same, and the second main light emission is the same as described above.
FIG. 7 shows only the new operation part as described above, and the other parts are the same as those in FIG.
A6 in FIG. 7 is connected to the positive or equivalent potential of the battery. B6 is connected to the auto-side light emission control circuit 28 of FIG. C6 is connected to the trigger circuit 24 of FIG. G6 is ground and is connected to the negative or equivalent potential of the battery.
The operation will be described with reference to FIGS. 7 and 8. FIG. 8A shows a light emission curve of the built-in strobe, and the first pre-light emission has a waveform 76. The signal is differentiated by the capacitor 68 and becomes as shown in FIG. When the differential signal 78 is amplified by the AC amplifier circuit 69 and applied to the transistor 70, the transistor 70 is turned on only when the base is positive, so that the waveform 80 shown in FIG. A stop signal is applied to the IGBT element 27 via the auto-side light emission control circuit 28, and the discharge tube 26 stops light emission at the timing of T14 in FIG. 8C and T15 in FIG.

If a timer or an equivalent circuit that delays the operation before or after the transistor 70 is added, the light emission stop timing of the T15 can be extended, so that the amount of pre-light emission can be adjusted according to the situation.
FIG. 8E shows the operation of the transistor 75. The trigger circuit 23 is operated in synchronization with the light emission operations 76 and 77 of the built-in strobe, and the external strobe is shown in FIG. Light is emitted as shown by the waveforms 84 and 85 shown.
A circuit including the timer circuit 71, the integrating capacitor 72, the transistor 73, and the transistor 74 is an inhibit circuit that prevents the transistor 70 from operating during the second main light emission. Without this circuit, a pulse signal (79 in FIG. 8B) synchronized with the second flash stop (77 in FIG. 8A) of the built-in strobe is applied to the transistor 70, and the external strobe Stops light emission.
In this inhibit circuit, the transistor 74 is not turned on at the timing T14 shown in FIG. 8C by the operation of the timer circuit 71 and the integrating capacitor 72 during the first pre-emission.
Thereafter, in the second main light emission, the transistors 73 and 74 are turned on, the signal 81 shown in FIG. 8D is applied to the base of the transistor 70, and the transistor 70 is deactivated.

For this reason, the external strobe is not affected by the second main light emission stop of the built-in strobe.
Even if the built-in strobe is pre-flashed not twice, but twice or three times, it can be tuned by adjusting the timing of the inhibit circuit. In this circuit, the stop of the pre-flash of the external strobe can be stopped almost simultaneously with the stop of the built-in strobe, which makes it easier to control.
As described above, the method of generating the light emission stop signal for the pre-light emission of the external strobe is another method, but it has the same effect as the circuit described above.

DESCRIPTION OF SYMBOLS 1 Digital camera 2 Built-in flash 3 Camera lens 4 Waterproof camera housing 5 Diffusion plate 6 Black light-shielding plate 7 Outer frame 8 Optical fiber 9 External strobe 10 Photodetection sensor 18 Battery 19 Gate voltage generation circuit 20 DC-DC converter 22 Main capacitor 24 trigger circuit 26 discharge tube 27 IGBT element 28 auto-side light emission control circuit 29 changeover switch 30 manual-side light emission control circuit 31 integration circuit 33 second pre-light emission signal circuit 34 light detection sensor 36 timer circuit 38 differentiation circuit 39 first pre- Signal circuit for light emission 43 Automatic light emission stop signal generation circuit

Claims (7)

With an external flash used in a digital camera that uses pre-flash and main flash with the built-in flash, the external flash fires using the built-in flash's pre-flash as a trigger, and the built-in flash starts flashing. As a trigger, in the light control method of the external strobe device that the external strobe emits light,
The external flash's pre-flash emission stop timing and the built-in flash's pre-flash emission stop timing are controlled at the same time or close to each other, and the external flash's pre-flash emission stop timing is controlled by the built-in flash's pre-flash timing. The amount of light is controlled so that the pre-flash of the built-in strobe light is blocked and the subject is properly irradiated with the pre-flash light of the external strobe even if it is not irradiated to the subject. A method for controlling the amount of light of an external strobe for a digital camera.   2. The method for controlling the amount of light of an external strobe for a digital camera according to claim 1, wherein the amount of pre-flash of the external strobe is controlled to be equal to or close to the amount of pre-flash of the built-in strobe.   3. The method for controlling the amount of light of an external strobe for a digital camera according to claim 1, wherein the light emission of the external strobe is stopped using the pre-flash emission stop of the built-in strobe. With an external flash used in a digital camera that uses pre-flash and main flash with the built-in flash, the external flash fires using the built-in flash's pre-flash as a trigger, and the built-in flash starts flashing. In the external strobe device that the external strobe flashes as a trigger,
Means for controlling so that the pre-flash emission stop timing of the external flash and the pre-flash emission stop timing of the built-in flash are at or near the same time;
It has means to adjust according to the situation so that the flash stop timing of the pre-flash of the external flash is extended from the pre-flash timing of the built-in flash,
An external digital camera that controls the amount of light so that the subject's pre-flash light is properly irradiated to the subject even if the subject's pre-flash light is blocked and not illuminated on the subject. Strobe light intensity control device.   5. An external strobe for a digital camera according to claim 4, further comprising means for controlling the amount of pre-emission of the external strobe to be equal to or close to the amount of pre-emission of the built-in strobe. Light quantity control device.   6. The method for controlling the amount of light of an external strobe for a digital camera according to claim 4 or 5, wherein the light emission of the external strobe is stopped using the stop of the pre-flash of the built-in strobe.   7. A light amount control device for an external strobe for a digital camera according to claim 4, further comprising a switching circuit for adjusting the light amount during pre-emission.

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