JP2012037803A - Strobe light emission device and camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a strobe light emission device and a camera capable of obtaining high quality images, through accurately measuring the color temperature of a subject to obtain strobe light whose color temperature is appropriate while taking a series of pictures by synchronous emission of the strobe light.SOLUTION: A color temperature measurement means 2 for measuring the color temperature of a subject, a main capacitor, a discharge emission tube for radiating the strobe light through discharging electric charge accumulated at the main capacitor, and a color temperature adjustment means for adjusting the color temperature of the strobe light through changing the charge voltage of the main capacitor based on the color temperature measured by the color temperature adjustment means 2 are provided. The color temperature measurement means measures the color temperature of the subject by a pre-emission prior to synchronous photography with a regular emission of the strobe light, and the color temperature adjustment means adjusts the color temperature by adjusting the charge voltage of the main capacitor and the emission time based on the result of the color temperature measurement of the subject.

Description

  The present invention relates to a strobe light emitting device and a camera equipped with the strobe light emitting device, and in particular, the color temperature of illumination light by strobe light emission can be adjusted to an optimum value according to shooting conditions. .

  When taking a picture using the illumination light from the strobe light as an auxiliary light, if the background is sunset, or if the shooting conditions are such that the light is illuminated by reddish illumination light such as incandescent light, the strobe light emitting device There is a problem that the main subject light such as a person in the vicinity and in front of the subject appears pale and becomes unnatural with respect to the background color. In order to solve such problems, various color temperature changing devices or color temperature control devices for strobe light emitting devices have been proposed.

  One of the inventions described in Patent Document 1 is a means for measuring the color temperature of a subject, and a color temperature for changing the color temperature of a flash light source, that is, a strobe light emitter, based on the color temperature measured by the color temperature measurement means. The color temperature changing means is configured to change the color temperature of the strobe light emitting light source by changing the inductance of the flash light emitting circuit. In another example, Patent Document 1 includes a plurality of filters for changing the color temperature arranged in front of a xenon tube included in the strobe light emitting device, and is optimized based on the color temperature measured by the color temperature measuring means. What is configured to select a filter is described.

  According to the invention described in Patent Document 1, a plurality of physical members are provided, such as changing the inductance of the flash light emitting circuit or selecting an optimum one from a plurality of filters. Therefore, there is a problem that the number of necessary parts increases and the cost becomes high.

  Patent Document 2 discloses a color temperature measuring means, a light receiving element having a specific spectral sensitivity, an integrating means for integrating an output signal of the light receiving element, and a color of ambient light based on color temperature information obtained by the color temperature measuring means. An appropriate integration amount setting means for setting an appropriate integration amount in the integration means for correcting a light emission amount error of strobe light caused by a deviation in temperature and spectral sensitivity of the light receiving element; and an output signal integrated by the integration means There is described a strobe device provided with strobe light emission control means for controlling the light emission stop timing of strobe light based on the integration amount and the proper integral value.

  An object of the invention described in Patent Document 2 is to provide a strobe device that can always obtain an optimum image even when there is ambient light having various spectral characteristics. However, since the color temperature of the illumination light of the strobe light emitter changes with the light emission time, controlling the strobe light emission stop timing based on the appropriate integral value as described above achieves both the correct exposure and the appropriate color temperature. In order to achieve the purpose of always obtaining an optimal image that cannot be achieved, further improvement is desired.

  In Patent Document 3, a plurality of flashlight emitting means capable of emitting flashlights having different spectral distributions, a single charge storage means for storing flashlight charges of these flashlight emitting means, and the color temperature of an object are measured. The colorimetric means, and based on the color temperature measured by the colorimetric means, each flash generation is performed in order to adapt the combined color temperature of the plurality of flashlight emitting means to the color temperature measured by the colorimetric means. There is described a strobe device provided with a light emission control means for determining the light emission ratio of the means and controlling the flash light generation means so that the light emission ratio is maintained in order by emitting light in order from a flash having a smaller spectral emission amount. .

  An object of the invention described in Patent Document 3 is to provide a strobe device that can make the color reproducibility of an image obtained by photographing accompanied by strobe light emission more natural. However, according to the invention described in Patent Document 3, it is necessary to have a plurality of flash light emitting means capable of emitting flash lights having mutually different spectral distributions. is there.

  Patent Document 4 includes a single flash light emitting unit and a charge accumulating unit, first and second color temperature conversion filters having different color temperature conversion capabilities, and a colorimetric unit for measuring the color temperature of a subject. Furthermore, the first and second color temperature conversion filters are flash light emitting means so that the color temperature of the light applied to the subject is the same as the measured color temperature based on the color temperature information from the color measuring means. And the second color temperature conversion filter is disposed in front of the flash light emitting means, and the second color temperature conversion filter is disposed in front of the flash light emitting means. Control for switching the color temperature conversion filter so as to emit light from the flash light emitting means by arranging the color temperature filter with the smaller light emission amount in front of the flash light emitting means in order from the color temperature filter with the smaller light emission quantity. Stroke with means Device is described.

  The invention described in Patent Document 4 is also intended to provide a strobe device that can make the color reproducibility of an image obtained by photographing accompanied by strobe light emission more natural. Since a temperature conversion filter is provided and a switching mechanism for these color temperature conversion filters is required, the strobe device is increased in size and cost.

  Patent Document 5 discloses a light emitting unit including an arc tube that emits strobe light with a specific color temperature, first color temperature conversion means for converting the strobe light into a color temperature higher than the specific color temperature, and the strobe light. Second color temperature conversion means for converting to a color temperature lower than the intrinsic color temperature, color temperature detection means for detecting the color temperature of ambient light, and strobe light of the first color temperature obtained via the first color temperature conversion means First control means for obtaining strobe light from the intrinsic color temperature to the first color temperature by combining the light and the strobe light of the intrinsic color temperature, and the second color temperature strobe light obtained via the second color temperature conversion means And a second control unit that obtains strobe light from the intrinsic color temperature to the second color temperature by combining the strobe light of the intrinsic color temperature and the first or second control unit based on the color temperature of the ambient light. Ambient light color temperature etc. Flash device having a flash light irradiating means for irradiating a flash light had is described.

  The invention described in Patent Document 5 is a strobe device in which strobe light with different color temperatures is irradiated to obtain a predetermined composite color temperature. Even if an error occurs in the amount of light emitted from these strobe lights, the composite color temperature is An object of the present invention is to provide a strobe device that can be controlled to a desired value as much as possible. However, the invention described in Patent Document 5 also requires first and second color temperature conversion means that can be switched by a physical mechanism, and there is a problem that the strobe device is increased in size and cost.

  Japanese Patent Application Laid-Open No. 2004-228561 is an image pickup apparatus having a strobe shooting mode in which a strobe device emits a flash to measure a voltage between both ends of a strobe tube at the start and end of light emission. Color temperature calculation means for calculating the color temperature shift amount of the flash based on the voltage, and in the flash photographing mode, the calculated color temperature shift amount of the flash light and an auto white balance (hereinafter referred to as “AWB”) evaluation value An imaging apparatus is described in which an AWB control value is calculated based on this, and white balance adjustment is performed by controlling white balance adjusting means based on the AWB control value.

  All of the flash technologies described in each patent document measure the color temperature during shooting with strobe light and adjust the color temperature, or calculate the color temperature after shooting with strobe light, and based on this calculated value To adjust the white balance. However, in the case of adjusting the color temperature by measuring the color temperature during the photographing operation, it is necessary to instantaneously measure and adjust the color temperature, and it is difficult to adjust the color temperature with high accuracy.

  In addition, in the case of performing white balance adjustment based on the calculated color temperature after shooting, a good image can be obtained only by white balance correction if the subject has a uniform color temperature. However, for example, if the color temperature of the long-distance side background and the near-distance side main subject are significantly different, even if the color temperature of the strobe light is predicted and multi-white balance correction is performed, it cannot be corrected, and the white balance Even if the correction is made, it is difficult to obtain a high-quality image.

  The present invention solves the above-described problems of the prior art, that is, an appropriate color temperature corresponding to this color temperature by accurately measuring the color temperature of the subject during a series of photography operations by synchronous light emission of strobe light. An object of the present invention is to provide a strobe light emitting device capable of obtaining a high quality image by obtaining the strobe light and a camera equipped with the strobe light emitting device.

  A strobe light emitting device according to the present invention includes a color temperature measuring means for measuring a color temperature of a subject, a main capacitor, and a discharge arc tube in which strobe light is emitted by discharging a charge stored in the main capacitor. Color temperature adjusting means for adjusting the color temperature of the strobe light by changing the charging voltage of the main capacitor based on the color temperature measured by the color temperature measuring means, and the color temperature measuring means is a strobe light. The color temperature of the subject is measured by pre-emission before the synchronous shooting with the main emission of light, and the color temperature adjusting means adjusts the charging voltage and the emission time of the main capacitor based on the measurement result of the color temperature of the subject. The most important feature is to adjust the color temperature.

The strobe light emitting device according to the present invention can take the following embodiments.
The color temperature adjusting means may lower the color temperature of the strobe light by lowering the voltage of the main capacitor.
The color temperature adjusting means may lower the color temperature of the strobe light by lowering the voltage of the main capacitor between the pre-light emission and the main light emission.
The color temperature adjusting means may lower the color temperature of the strobe light by lowering the voltage value of the main capacitor by dummy light emission different from the pre-light emission and the main light emission between the pre-light emission and the main light emission.
The dummy light emission can also serve as red-eye reduction light emission.

The color temperature adjusting means may be configured to lower the color temperature of the strobe light by discharging the charge charged in the main capacitor by a discharge circuit connected to the main capacitor.
The discharge circuit may include a detection circuit that detects a voltage value of the main capacitor during discharge.
The main capacitor may be composed of an aluminum electrolytic capacitor.

  The strobe light emitting device according to the present invention also includes a color temperature measuring means for measuring the color temperature of a subject, a main capacitor, and a discharge arc tube in which strobe light is radiated by discharging the charge stored in the main capacitor. And color temperature adjusting means for adjusting the color temperature of the strobe light by changing the charging voltage of the main capacitor based on the color temperature measured by the color temperature measuring means, and the color temperature measuring means The color temperature of the subject is measured by pre-flash before the synchronous shooting with the main flash of the flash light, and the color temperature adjusting means adjusts the charging voltage and the light emission time of the main capacitor based on the color temperature measurement result of the subject. When adjusting the color temperature, the main capacitor is charged with a low voltage, and this low charge voltage It may be configured to recharge the main capacitor when the insufficient charging voltage necessary.

The camera according to the present invention has a built-in strobe light emitting device, and the strobe light emitting device is the strobe light emitting device according to the present invention.
In the above camera, the color temperature adjusting means provided in the strobe light emitting device may be used as an arithmetic processing unit provided in the camera.

  According to the strobe light emitting device of the present invention, pre-light emission determines the main light emission conditions such as the main capacitor charging voltage and the light emission time during the main light emission corresponding to the color temperature of the subject. In addition, since the subject is photographed, the color temperature of the subject can be accurately measured in advance, and a strobe light appropriately corresponding to the measured color temperature is emitted to obtain a high-quality photographed image with accurate color. Can do.

  When adjusting the color temperature, the main capacitor is charged with a low voltage, and when the low charge voltage is not sufficient for the main capacitor to emit light, the main capacitor is recharged. According to this, it is possible to reduce the consumption of the power source battery without wasting the charging charge of the main capacitor. Also, when shooting a subject at close range as in the macro shooting mode, the flash light emission time can be extended to some extent while suppressing the flash light emission amount, so shooting with strobe light with a stable color temperature be able to.

It is a front view which shows the Example of the camera provided with the strobe light-emitting device based on this invention. It is a circuit diagram which shows the Example of the strobe light-emitting device based on this invention. It is a graph which shows the relationship between the charging voltage of the main capacitor | condenser in a strobe light-emitting device, light emission time, and light emission amount. It is a graph which shows the relationship between the charging voltage of the main capacitor | condenser in a strobe light-emitting device, light emission time, and the color temperature of strobe light. It is a graph which shows the relationship between the charging voltage of the main capacitor | condenser in the strobe light-emitting device, the light emission amount, and the color temperature of strobe light. It is a block diagram which shows the example of the control system used for the flash light-emitting device which concerns on this invention. It is a flowchart which shows operation | movement of the Example of the said flash light-emitting device. It is a circuit diagram which shows another Example of the strobe light-emitting device based on this invention. It is a flowchart which shows operation | movement of another Example of the said flash light-emitting device. It is a flowchart which shows another Example of the strobe light-emitting device based on this invention.

  FIG. 1 shows a simplified appearance of an embodiment of a camera provided with a strobe light emitting device according to the present invention. A photographing lens barrel is attached to the front of the camera body at the center, and the strobe light emitting device 10 and the color temperature measuring element 2 are attached side by side above the lens barrel. A release switch 3 is disposed on the upper surface of the body. The photographing operation is performed by depressing the release switch 3. The strobe light emitting device 10 emits light in synchronization with the photographing operation, and irradiates the strobe light toward the subject. The color temperature measuring element 2 divides the reflected light from the subject into R (red) / G (green) / B (blue) components and detects the intensity of these color components, and from the intensity of each color component, The color temperature of the reflected light from the subject is detected.

The illustrated embodiment includes a color temperature measuring element 2, but in the case of a strobe light emitting device incorporated in a digital camera, an R / G / B component is simply obtained from an output signal of an image sensor composed of a CCD, a CMOS, or the like. The color temperature may be obtained by measurement, and the color temperature measuring element 2 may be omitted.
Although FIG. 1 shows a compact type camera, the camera according to the present invention is not limited to a specific format, and may be applied to a single-lens reflex type camera, for example.

  FIG. 2 is a circuit diagram showing a first embodiment of the strobe light emitting device according to the present invention. In FIG. 2, the strobe light emitting device 10 includes a booster circuit 11 including a DC-DC converter for boosting the DC voltage of the battery power source to, for example, 300 V or more, as is well known. A main capacitor 12 is connected between the DC high voltage output terminals of the booster circuit 11. A xenon discharge tube 13, a diode 20, and an insulated gate bipolar transistor (hereinafter referred to as “IGBT”) 18 are connected to both ends of the main capacitor 12. Are connected in series. The IGBT 18 is a power transistor having a MOS structure in the input portion and a bipolar structure in the output portion, and is a semiconductor suitable for high withstand voltage and large current. In this embodiment, the IGBT 18 is used as a switching element. A capacitor 19 is connected in parallel to the diode 20. For example, an aluminum electrolytic capacitor is preferably used as the main capacitor 12.

  A primary winding of a resistor 21, a trigger capacitor 16, and a trigger transformer 17 is also connected in series with both ends of the main capacitor 12. The trigger transformer 17 is a step-up transformer, and is connected so that a high voltage generated in the secondary winding is applied to the trigger electrode 133 of the xenon tube 13 which is a discharge arc tube. The trigger electrode 133 is formed in contact with the cylindrical glass of the xenon tube 13 and is electrically connected to a reflector not shown. The resistor 21, the capacitor 19, and the resistor 32 are connected in series at both ends of the main capacitor 12, and a charging circuit for the capacitor 19 is configured. The polarity of charging of the capacitor 19 is opposite to that of the diode 20.

  In FIG. 2, the components including the IGBT 18, the capacitor 16, and the trigger transformer 17 surrounded by the dotted line block 14 constitute the trigger circuit 14. Further, the components including the capacitor 19, the diode 20, and the IGBT 18 surrounded by the dotted line block 15 constitute a voltage doubler circuit 15. The IGBT 18 is connected to operate as a switch for both the trigger circuit 14 and the voltage doubler circuit 15. The gate of the IGBT 18 is connected to the light emission control unit 5, and a signal synchronized with the imaging operation of the imaging apparatus, that is, the camera, and other signals for controlling the on / off operation of the IGBT 18 are input from the light emission control unit 5. Yes.

  When a power switch (not shown) of the strobe light emitting device is turned on, the booster circuit 11 operates to generate a high DC voltage, and the main capacitor 12 is charged with this high voltage. In parallel with this, the capacitor 16 in the charging circuit composed of the primary winding of the resistor 21, the capacitor 16 and the trigger transformer 17 and the capacitor 19 in the charging circuit composed of the resistor 21, the capacitor 19 and the resistor 32 are respectively main. The capacitor 12 is charged with the same high voltage as the voltage across the capacitor 12.

  When a signal synchronized with the photographing operation by the depression operation of the release switch 3 of the camera is input from the light emission control unit 5 to the gate of the IGBT 18, the IGBT 18 is turned on, and the charge of the trigger capacitor 16 is changed between the IGBT 18 and the trigger transformer 17. Discharged through the primary winding. The voltage applied to the primary winding of the trigger transformer 17 during discharge is substantially the same as the terminal voltage of the capacitor 16, and this voltage is boosted to several thousand volts by the secondary winding of the trigger transformer 17. When this high voltage is applied to the trigger electrode 133 of the xenon tube 13, the xenon in the xenon tube 13 is ionized, the inside of the xenon tube 13 becomes conductive, and the charge stored in the main capacitor 12 is transferred to the xenon tube 13. The xenon tube 13 emits strobe light.

  When the signal from the light emission control unit 5 is input to the gate of the IGBT 18 and the IGBT 18 is turned on, the voltage of the capacitor 19 of the voltage doubler circuit 15 is applied to the ground side (negative side) electrode of the xenon tube 13 and the potential of this electrode. Is applied in the direction of pulling down. In this way, a voltage approximately twice the terminal voltage of the main capacitor 12 is applied across the xenon tube 13, so that the xenon tube 13 emits light even if the terminal voltage of the main capacitor 12 drops to about 200V. Can be made.

  Here, the color temperature characteristics of the xenon tube used in the strobe light emitting device will be examined. FIG. 3 shows the voltage applied to the xenon tube 13, that is, the charging voltage of the main capacitor 12, such as 315V, 305V, 285V, 265V, 245V, 225V, and 205V. (GNo), that is, the result of actual measurement of the relationship between the light emission amounts. As can be seen from FIG. 3, the amount of light emitted from the xenon tube 13 increases as the charging voltage of the main capacitor 12 increases, and becomes saturated when there is a light emission time. However, as a matter of course, the light emission amount increases as the light emission time becomes longer.

ただし、発光時間と発光量（Ｇｎｏ値）の関係は、使用するキセノン管１３の特性とストロボ発光装置の回路構成によって異なり一意的に求めることはできない。そこで、本実施例は、図３に示す特性が得られるものとして説明する。また、本実施例は、メインコンデンサ１２の充電電圧が３１５Ｖ、発光時間を７００μｓｅｃとした場合をフル発光量としていて、これを基準発光量とする。このとき、ＧＮｏ＝６、色温度＝６０００Ｋである。以下、これらの仕様からなる実施例について、色温度制御方法を説明する。 Further, the light emission amount (Gno value) and the voltage value of the main capacitor 12 when the light emission time is constant, that is, when light is emitted in the same light emission time, can be obtained by calculation using the following Equation 1.
Formula 1

However, the relationship between the light emission time and the light emission amount (Gno value) differs depending on the characteristics of the xenon tube 13 used and the circuit configuration of the strobe light emitting device, and cannot be determined uniquely. Therefore, this embodiment will be described assuming that the characteristics shown in FIG. 3 can be obtained. Further, in this embodiment, when the charging voltage of the main capacitor 12 is 315 V and the light emission time is 700 μsec, the full light emission amount is set as the reference light emission amount. At this time, GNo = 6 and color temperature = 6000K. Hereinafter, a color temperature control method will be described with respect to an embodiment having these specifications.

  FIG. 4 shows the results of actual measurement of the relationship between the light emission time and the color temperature [K] for each charging voltage, with the charging voltage of the main capacitor 12 set as described above. As can be seen from FIG. 4, the color temperature of the strobe light has a property that the lower the charging voltage of the main capacitor 12, the lower the color temperature, and the shorter the light emission time, the higher the color temperature. Therefore, the color temperature of the strobe light can be changed by changing the voltage value of the main capacitor 12 and the light emission time.

  FIG. 5 shows the results of actually measuring the change in color temperature when the charging voltage of the main capacitor 12 is set as described above and GNo, that is, the amount of light emission is changed at each charging voltage. As can be seen from FIG. 5, the color temperature of the strobe light has a property of decreasing as the exposure amount increases.

Table 1 below summarizes the changes in color temperature when the charging voltage of the main capacitor 12 is set as described above, and the light emission amount (GNo) is changed to an EV value by 0.5 at each charging voltage. Is.
Table 1

表１、表２はストロボ発光装置の動作を制御する制御部あるいは演算処理ユニットが参照するテーブルとして適宜の記録媒体に記録されている。 Table 2 summarizes changes in the light emission amount (GNo) when the charging voltage of the main capacitor 12 is set as described above and the light emission time is changed at each charging voltage.
Table 2

Tables 1 and 2 are recorded on appropriate recording media as tables to be referenced by a control unit or an arithmetic processing unit that controls the operation of the strobe light emitting device.

  From the results shown in FIGS. 3 to 5 and Tables 1 and 2, the color temperature of the strobe light can be changed by controlling the light emission time or light emission amount (GNo) of the strobe light emitting device. Therefore, in the embodiment of the strobe light emitting device according to the present invention, pre-light emission is performed toward the subject before the main light emission, and the reflected light is measured, and the main capacitor charging voltage and light emission during the main light emission are measured based on the photometry result. The lighting conditions such as time were determined, and the main flash was emitted under the determined conditions.

  FIG. 6 shows an example of a control system that can be used in the present invention. In FIG. 6, the strobe light emitting device 10 includes a light emitting unit 8 and a light emission control unit 5. The light emission control unit 5 is as described above, and the light emission unit 8 is a component including the xenon tube 13, a reflector, and the like. The light emission control unit 5 controls the operation of the light emitting unit 8 in accordance with a command signal from an arithmetic processing unit 6 such as a CPU. The color temperature detection signal from the color temperature measuring element 2 and the image signal from the image sensor 7 are input to the arithmetic processing unit 6. The color temperature detection signal has already been described. The image pickup device 7 is composed of a solid-state image pickup device such as a CCD or CMOS, and other appropriate image pickup devices. In this embodiment, the image pickup device 7 also functions as a photometric sensor for measuring subject luminance from the image pickup signal. It is designed to be entered. The arithmetic processing unit 6 can use a CPU, MPU, or the like provided in the camera for autofocus, automatic exposure control, image processing, sequence control of each unit, and the like.

  FIG. 7 shows a control operation of the strobe light emitting device according to the present embodiment in which the color temperature of the strobe light can be adjusted. This control operation is executed mainly by software recorded in the arithmetic processing unit 6 by the control system shown in FIG. Symbols such as “S001”, “S002”... Are attached to the operation steps. The operation shown in FIG. 7 is depicted on the assumption that the power source of the strobe light emitting device is turned on and the main capacitor is sufficiently charged. In FIG. 7, when the shutter button is pressed down to start photographing, the color temperature measuring element 2 receives reflected light from the subject, and the color temperature T1 is determined from the intensity of each of the R / G / B components of the reflected light. Is measured (S001). Next, pre-flash for photometry is performed by the strobe light emitting device 10 (S002), and the reflected light from the subject of the strobe light by the pre-flash is received by the light receiving element, and a book for performing proper exposure at the time of the main flash. The light emission amount (GNo value = G1) at the time of light emission is determined (S003).

  Next, the charging voltage V1 and the light emission time t1 of the main capacitor 12 during the main light emission are obtained from the color temperature T1 of the subject measured in step S001 and the light emission amount (G1) during the main light emission determined in step S003 ( S004). As a specific example, when the result of the measurement in step S001, the subject color temperature T1 = 5400K, and the result of the pre-emission in S002, GNo = 4 in the main emission is obtained. A method for obtaining the charging voltage V1 and the light emission time t1 will be described. First, referring to Table 1, a value closest to the target GNo = 4 at the main light emission is searched, and GNo = 4.2 is selected. Next, the voltage value of the main capacitor 12 closest to the target color temperature T1 is searched from GNo = 4.2, and 5400K of 225V is selected. Next, the light emission time required to obtain GNo = 4.2 when the voltage of the main capacitor 12 is 225 V is searched with reference to Table 2, and the light emission time is determined to be 700 μsec. As described above, in step S004, the light emission condition during the main light emission is determined to be V1 = 225V and t1 = 700 μsec.

In this embodiment, dummy light emission is performed in order to set the charging voltage V1 of the main capacitor 12 during main light emission to the value obtained as described above. Before performing the dummy light emission, the dummy light emission is performed to determine a dummy light emission amount for setting the charging voltage V1 of the main capacitor 12 during the main light emission to a target voltage (S005). This dummy light emission amount is determined by the light emission amount at the time of dummy light emission (GNo = G2) and the light emission time t2. The dummy light emission amount is determined as follows. Here, it is considered simply that there is no decrease in the charging voltage of the main capacitor 12 due to the pre-emission (S002). As described above, since the main capacitor 12 is 315 V when fully charged, it is necessary to drop the voltage from 315 V to the target voltage 225 V described above. When the voltage difference between 315 V and 225 V is converted into an EV value, the EV value difference ΔEV is −0.97 EV according to the following equation 2.
Formula 2

電圧３１５ＶでＧ２＝４．３を得るのに必要な発光時間ｔ２は、表２より１５８μｓｅｃが最も近い値であり、よって、発光時間ｔ２＝１５８μｓｅｃと決定する。 When the EV value difference ΔEV = −0.97 EV is converted into GNo (G2) when light is emitted at a full charge voltage of 315 V, G2 = 4.3 is obtained from the following equation 3.
Formula 3

The light emission time t2 required to obtain G2 = 4.3 at a voltage of 315 V is the closest value to 158 μsec from Table 2, and therefore, the light emission time t2 = 158 μsec is determined.

  Thus, in step S005, the amount of dummy light emission is determined by obtaining G2 and t1, and dummy light emission is performed according to the dummy light emission conditions (S006), and the charging voltage of the main capacitor 12 reaches the target 225V. Descent. The main light emission is performed under the conditions of the charging voltage V1 = 225V and the light emission time t1 (= 700 μsec) already obtained in step S004 (S007), and the target GNo≈4 and the color temperature 5400K are optimum. Shooting is performed under the proper flash shooting conditions.

  According to the embodiment described above, in order to irradiate the strobe light of the color temperature corresponding to the subject, dummy light emission is performed so that an appropriate charging voltage of the main capacitor is obtained, and the charging voltage is lowered. The light emission time is appropriately controlled. Therefore, unlike conventional strobe light emitting devices capable of adjusting the color temperature, the color temperature is not adjusted by instantaneously measuring the color temperature during the photographing operation, so the color temperature can be adjusted with high accuracy. . Further, according to the conventional example in which the white balance adjustment is performed based on the color temperature calculation value after the photographing is finished, there is a limit in the color temperature correction, but according to the embodiment of the present invention, the color temperature correction by the white balance adjustment. Instead, the color temperature corresponding to the subject is determined in advance using a dummy flash of strobe light, and the strobe light is emitted at this color temperature to take a picture. A quality image can be obtained. By performing the dummy light emission before the main light emission, the so-called red-eye phenomenon in which the subject's eyes appear red can be reduced. Therefore, the dummy light emission also serves as red-eye reduction light emission.

  In the first embodiment shown in FIG. 2, the strobe light emitting device is configured to emit a strobe light with an appropriate color temperature corresponding to the subject by causing the strobe light emitting device to emit a dummy light and lowering the charging voltage of the main capacitor. However, in the second embodiment to be described next, the charging voltage of the main capacitor is lowered to an appropriate value by controlling the discharge circuit on and off. FIG. 8 shows a second embodiment, which is configured by adding a discharge circuit composed of a resistor, a switching transistor, etc. to the first embodiment shown in FIG. Therefore, the added discharge circuit will be described mainly. FIG. 9 shows the operation of the second embodiment.

  In FIG. 8, a transistor 32, a resistor 27, and a resistor 28 are connected in series to both ends (one end is grounded) of the main capacitor 12. This series circuit constitutes a discharge circuit of the main capacitor 12 when the transistor 32 is turned on. The base of the transistor 32 is grounded through the resistor 23 and the transistor 22, and is configured to turn on the transistor 32 when the transistor 22 is turned on. The base of the transistor 22 is grounded via a bias resistor 24 and a discharge control signal 29 is input via a resistor 25. The discharge control signal 29 is output from the arithmetic processing unit 6 or the light emission control unit 5 in the control system shown in FIG. A voltage detection signal 30 proportional to the terminal voltage of the main capacitor 12 is output from the connection point between the resistor 27 and the resistor 28 when the transistor 32 is on. The voltage detection signal 30 is input to the arithmetic processing unit 6 or the light emission control unit 5 and used for adjustment or control of the terminal voltage of the main capacitor 12. The transistors 22 and 32 are high breakdown voltage transistors.

  During a normal time when no light emission operation is performed, the discharge control signal 29 is at a low level, the transistor 22 is off, the transistor 32 is also off, and the charge of the main capacitor 12 is not discharged. When it is necessary to adjust the color temperature of the strobe light when performing synchronous flash photography with the strobe light emitting device, the discharge control signal 29 is set to the high level, the transistors 22 and 32 are turned on, the transistor 32, the resistor 27, the resistor The discharge circuit by 28 is closed, and the charge of the main capacitor 12 is discharged. A change in the terminal voltage of the main capacitor 12 due to the discharge is monitored by the arithmetic processing unit 6 or the like with a voltage detection signal 30 which is a divided value by the resistors 27 and 28. When the monitored voltage detection signal 30 drops to a voltage value corresponding to the terminal voltage of the main capacitor 12 capable of obtaining strobe light with a desired color temperature, the discharge control signal 29 is set to a low level to cause the transistors 22, 32 is turned off and the discharge of the main capacitor 12 is stopped. The main light emission is performed under the charging voltage of the main capacitor 12, and a photograph is taken in synchronization with the strobe light.

  FIG. 9 shows a series of operations of the second embodiment. In FIG. 9, until the measurement of the color temperature of the subject (S101), pre-emission (S102), photometry (main emission GNo value = G1 determination: S103), main emission condition determination (charge voltage V1, emission time t1: S104), This is the same as the operation up to step S004 in the first embodiment shown in FIG. As in the case of the first embodiment, the charging voltage V1 and the light emission time t1 that are the main light emission conditions are the charge voltage and the light emission time of the main capacitor 12 for obtaining the color temperature of the strobe light corresponding to the color temperature of the subject. It is. In the second embodiment, after the light emission condition determination step (S104), discharge (S105) is performed by closing the discharge circuit including the resistors 27 and 28 and the switching transistors 22 and 32 described with reference to FIG. The charging voltage of the main capacitor 12 is adjusted to a predetermined voltage value. The main light emission (S107) is performed by the charging voltage of the main capacitor 12, and the subject illuminated by the main light emission is photographed.

  According to the second embodiment, since the charging voltage of the main capacitor 12 is adjusted to a desired voltage by the discharge circuit including the resistors 27 and 28 and the switching transistors 22 and 32, the pre-light emission is compared with the first embodiment. Strobe light having a desired color temperature can be obtained without performing dummy light emission between the main light emission and the main light emission.

In both the first and second embodiments, the main capacitor 12 is fully charged, and the charge of the main capacitor 12 is discharged until the charging voltage of the main capacitor 12 at which strobe light with a desired color temperature is obtained. Is. Therefore, a part of the charge is wasted. Therefore, it is desirable to devise so as not to waste the charged charge.
Further, in the case of shooting in the macro mode, since the subject is generally at a close distance of several tens of centimeters or less, the light emission amount (GNo) required for the synchronous flash shooting with the strobe light is small.

  Therefore, in the third embodiment described below, when monitoring to determine the main light emission conditions, the charging voltage of the main capacitor 12 is suppressed to a low voltage, and the above charging voltage is sufficient as a result of photometry by pre-emission. Synchronous flash photography is performed as it is, and the main capacitor 12 is recharged when the charging voltage is insufficient. Further, when it is necessary to charge the main capacitor 12 from the pre-light emission to the main light emission for photometry, a new technical problem arises that this charging takes time. The idea is to make it as short as possible. FIG. 10 shows the operation of the third embodiment.

  In FIG. 10, until the subject's color temperature measurement (S201), pre-emission (S202), photometry (main emission GNo value = G1 determination: S203), main emission condition determination (charging voltage V1, emission time t1: S204), The operation is the same as that of the above embodiment. However, in pre-emission (S202), the charging voltage of the main capacitor 12 is suppressed to a low voltage Vlow, photometry is performed with a small amount of light emission, and the main emission conditions are determined based on the photometry result. The low voltage Vlow may be arbitrarily set based on the design concept, but may be set to a lower limit value of the charging voltage of the main capacitor 12 that is changed for color temperature adjustment. For example, when the charging voltage of the main capacitor 12 is switched to 315V, 305V, 285V, 265V, 245V, 225V, 205V as described above, the lower limit value 205V may be set to the low voltage Vlow.

  After the main light emission conditions are determined, the light emission amount (GNo) when full light emission is performed at the low charging voltage of the main capacitor 12 as described above (the light emission is performed by discharging all the charged charges) is the light emission amount necessary for the main light emission ( GNo) is determined (S205). If the amount of light emitted when full light emission is performed at a low charging voltage in step S205 is larger than the amount of light emission required for main light emission, synchronous light emission photographing is performed by main light emission (S206). If the amount of light emitted at the time of full light emission at a low charging voltage in step S205 is less than the amount of light necessary for main light emission, the main capacitor 12 is charged until the amount of light emission necessary for main light emission is obtained (S216). Next, synchronous flash photography is performed by the main flash (S206).

  According to the third embodiment, the main capacitor 12 is charged at the lower limit value of the charging voltage, and if the light emission amount under the charging voltage is sufficient for the light emission amount necessary for the main light emission, the charging voltage is obtained. When the main flash emits light and the amount of light required for the main flash is insufficient, it is configured to charge the insufficient amount to emit light, so the charge of the main capacitor can be used effectively. The waste of the power battery can be eliminated. Even when the main capacitor is charged to make up for the amount of light emission necessary for the main light emission, the time required for charging can be shortened.

  As is apparent from FIG. 4, the change amount of the color temperature is large in the light emission region for a short time, and the change amount of the color temperature is reduced as the light emission time is increased. According to the third embodiment, when shooting in the macro mode, the charging voltage of the main capacitor can be suppressed to reduce the amount of light emission and the light emission time can be lengthened. An image with a stable color temperature can be obtained by strobe light with a small amount of temperature change.

  As described above, an aluminum electrolytic capacitor can be used as the main capacitor of the strobe light emitting device according to the present invention. When a strobe light emitting device having an aluminum electrolytic capacitor as a main capacitor is built in a camera, generally, the specification of the aluminum electrolytic capacitor is set to a withstand voltage of 300 to 350 V and a capacity of about several tens to several hundreds μF. . Aluminum electrolytic capacitors can be obtained with a high withstand voltage and high capacity, but the self-discharge is relatively large, so the charging voltage becomes relatively fast over time even without strobe lighting or forced discharge. descend. Therefore, rather than controlling the charging voltage of the main capacitor at the timing of the first release at which photometry or distance measurement is started, the timing of the second release at which shooting is performed, that is, the timing of the main light emission, as in the embodiments of the present invention. Therefore, it is desirable to control the voltage of the main capacitor.

  The strobe light emitting device according to the present invention may be a strobe light emitting device built in the camera or a strobe light emitting device externally attached to the camera. In the case of a strobe light emitting device that is externally attached to the camera, it may be a general-purpose strobe light emitting device in which the color temperature adjustment is completed within the strobe light emitting device, or the color temperature adjustment can be performed in cooperation with the camera control circuit. A strobe light emitting device dedicated to a specific type of camera to be performed may be used.

2 Color temperature measuring element 5 Light emission control unit 10 Strobe light emitting device 11 Booster circuit 12 Main capacitor 13 Discharge arc tube (xenon tube)
14 Trigger Circuit 15 Voltage Booster 16 Trigger Capacitor 17 Trigger Transformer

JP 05-134301 A Japanese Patent No. 3340486 Japanese Patent No. 3417613 Japanese Patent No. 3367498 Japanese Patent No. 3320863 Japanese Patent No. 3753520

Claims (11)

Color temperature measuring means for measuring the color temperature of the subject;
A main capacitor;
A discharge arc tube in which strobe light is emitted by discharging the charge stored in the main capacitor;
Color temperature adjusting means for adjusting the color temperature of the strobe light by changing the charging voltage of the main capacitor based on the color temperature measured by the color temperature measuring means,
The color temperature measuring means measures the color temperature of the subject by pre-flash before synchronous shooting with the main flash of flash light,
The strobe light emitting device, wherein the color temperature adjusting means adjusts a color temperature by adjusting a charging voltage and a light emission time of the main capacitor based on a color temperature measurement result of the subject.   2. The strobe light emitting device according to claim 1, wherein the color temperature adjusting means lowers the color temperature of the strobe light by lowering the voltage of the main capacitor.   3. The strobe device according to claim 1, wherein the color temperature adjusting means lowers the color temperature of the strobe light by lowering the voltage of the main capacitor between the pre-light emission and the main light emission.   The color temperature adjusting means lowers the color temperature of the strobe light by lowering the voltage value of the main capacitor by dummy light emission different from the pre-light emission and the main light emission between the pre-light emission and the main light emission. The strobe light emitting device according to 1, 2 or 3.   5. The strobe light emitting device according to claim 4, wherein the dummy light emission also serves as light emission for reducing red eyes.   3. The strobe light emitting device according to claim 1, wherein the color temperature adjusting means lowers the color temperature of the strobe light by discharging the charge of the main capacitor by a discharge circuit connected to the main capacitor.   7. The strobe light emitting device according to claim 6, wherein the discharge circuit has a detection circuit for detecting a voltage value of the main capacitor during discharge. Color temperature measuring means for measuring the color temperature of the subject;
A main capacitor;
A discharge arc tube in which strobe light is emitted by discharging the charge stored in the main capacitor;
Color temperature adjusting means for adjusting the color temperature of the strobe light by changing the charging voltage of the main capacitor based on the color temperature measured by the color temperature measuring means,
The color temperature measuring means measures the color temperature of the subject by pre-flash before synchronous shooting with the main flash of flash light,
The color temperature adjusting means charges the main capacitor at a low voltage to adjust the color temperature by adjusting the charging voltage and light emission time of the main capacitor based on the color temperature measurement result of the subject. A strobe light emitting device, wherein the main capacitor is recharged when the voltage is not sufficient for a charging voltage necessary for the main light emission of the main capacitor.   The strobe light-emitting device according to any one of claims 1 to 8, wherein the main capacitor is an aluminum electrolytic capacitor.   A camera having a built-in strobe light emitting device, wherein the strobe light emitting device is the strobe light emitting device according to any one of claims 1 to 9.   11. The camera according to claim 10, wherein the color temperature adjusting means provided in the strobe light emitting device also serves as an arithmetic processing unit provided in the camera.

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