JP2014010304A - Strobe device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it difficult for omission of light emission to occur even when emission of a very small quantity of light is repeated in a strobe light.SOLUTION: A strobe device comprises: a main light emission control section configured to control main light emission that is carried out while the shutter of a camera is open; a light emission quantity determination section configured to determine whether a quantity of light emitted in the main light emission is equal to or smaller than a predetermined value; and a post light emission control section configured such that when the light emission quantity determination section determines that the quantity of light emitted in the main light emission is equal to or smaller than the predetermined value, post light emission is carried out with a quantity of light emitted, which is a predetermined value or larger, in a predetermined frequency including every time after the shutter of the camera is closed.

Description

  The present invention relates to a strobe device, and more particularly to a strobe device that emits light in synchronization with a shutter of a camera.

  As a strobe device for a camera, a strobe device that emits light in synchronization with a shutter of the camera is widely known (for example, Patent Documents 1, 2, and 3).

JP 2002-311479 A JP-A-2005-115161 JP 2007-178925 A

  In the above strobe device, it is considered to use a quartz tube as a glass tube of a xenon discharge tube in order to thermally withstand long-time repeated light emission. In the case of a quartz glass tube, an electron-emitting material for the cathode of the flash discharge tube preferably contains barium instead of cesium.

  However, when a material containing barium is used as an electron emissive material for the cathode of a flash discharge tube, if a slight light emission with a guide number of 1 to 2 is repeatedly performed, the phenomenon does not occur in synchronization with the camera shutter. It has been clarified by an experimental study by the present inventor that light emission is lost. This loss of light emission was increased as repeated minute light emission continued, and normal light emission was greatly reduced.

  With regard to this, the present inventor conducted further experimental research, and found that light emission with a large amount of light even after a small amount of light emission does not cause omission of light emission even if repeated minute light emission is performed. .

  The problem to be solved by the present invention is to prevent light emission from being lost even if repeated minute light emission is performed based on the knowledge obtained from the above-described experimental research.

  The strobe device according to the present invention includes a light emitting unit (12) including a flash discharge tube (13) and a control for controlling light emission of the light emitting unit (12) by inputting information related to opening / closing of a shutter from a camera (50). A flash unit (10) including a unit (20), wherein the control unit (20) controls a main light emission control unit that controls main light emission performed when a shutter of the camera (50) is open. 40), a light emission amount determination unit (42) for determining whether or not the light emission amount of the main light emission is less than or equal to a predetermined value, and the light emission amount of the main light emission is less than or equal to a predetermined value by the light emission amount determination unit (42). When it is determined that there is a post-emission control unit (44) that performs post-emission with a light emission amount equal to or greater than the predetermined value after the shutter of the camera (50) is closed at a predetermined frequency including every time.

  According to this configuration, if the light emission amount of the main light emission is equal to or less than the predetermined value, after the shutter of the camera (50) is closed, the post light emission is performed with the light emission amount equal to or greater than the predetermined value, and the flash discharge tube (13). Is refreshed. As a result, light emission omission due to minute light emission is avoided.

  In the strobe device according to the present invention, preferably, the post-emission control unit (44) is continuously determined a predetermined number of times (n by the light emission amount determination unit (42)) that the light emission amount of the main light emission is equal to or less than a predetermined value. ) The post-light emission is performed only when the above is performed.

  According to this configuration, after-emission is suppressed to the minimum necessary limit.

  According to the strobe device of the present invention, if the light emission amount of the main light emission is equal to or less than the predetermined value, after the camera shutter is closed, the post light emission is performed with the light emission amount equal to or greater than the predetermined value, and the flash discharge tube is refreshed. Therefore, light emission omission due to minute light emission is avoided.

1 is a block diagram showing one embodiment of a strobe device according to the present invention. 4 is a time chart showing a light emission pattern of the strobe device according to the present embodiment.

  Hereinafter, one embodiment of a strobe device according to the present invention will be described with reference to FIG.

  The strobe device 10 according to the present embodiment is of an electronic control type including a light emitting unit 12, a battery power supply unit 14, a drive circuit 16, and a strobe control microcomputer 20 that controls light emission of the light emitting unit 12. is there.

  The light emitting unit 12 includes a xenon discharge tube 13 as a flash discharge tube. The xenon discharge tube 13 is made of quartz as a glass tube and thermally contains barium as an electron-emitting material for a cathode in order to thermally withstand repeated light emission for a long time.

  The drive circuit 16 includes a DC-DC converter, a main capacitor, a trigger circuit, a switching transistor such as an IGBT, and the like. The power from the power supply unit 14 is boosted by the DC-DC converter and electric energy for flash discharge is supplied to the main capacitor. The light emission timing and the light emission amount of the light emitting unit 12 are quantitatively set in accordance with a control command signal from the flash control microcomputer 20.

  The strobe control microcomputer 20 is supplied with power from the power supply unit 14 whose voltage is adjusted by the constant voltage circuit 22 and operates. A communication unit 24, an operation switch group 26, a display unit 28, a light receiving sensor 30, a wireless sensor 32, and a sync cord connection unit 34 are connected to the strobe control microcomputer 20.

  The communication unit 24 communicates various information with the camera 50 when the strobe device 10 is attached to the hot shoe of the electronically controlled camera 50. The camera information (signal) received by the communication unit 24 from the camera 50 includes TTL photometric information, shutter speed information, shutter button press signal, shutter full open signal, shutter full close signal, and the like.

  The operation switch group 26 is operated by a user and includes a power switch and a multi-setting switch for setting a function mode and various manual setting values. The function modes selected and set by the multi-setting switch include a TTL automatic light control mode, an external light control mode, a manual mode, a multi-flash mode, an external sync mode, and a wireless TTL mode.

  In the TTL automatic light control mode, pre-emission (pre-emission) with a small amount of light is performed immediately before the shutter button is pressed and exposure is started (immediately before the shutter is opened), and based on TTL photometry information from the camera 50 at the time of pre-emission. In this mode, the main light emission is performed by automatically setting the light emission amount of light emission for exposure in the subsequent shutter open state.

  When the camera 50 is a focal plane shutter camera, if the shutter speed is a predetermined low speed or less, the entire exposure is performed in a state where the shutter is fully opened while the first curtain traveling is completed and the second curtain traveling is started next. On the other hand, if the shutter speed is higher than a predetermined speed, the front curtain and the rear curtain travel simultaneously, and the scanning movement type exposure is performed by the slit formed between the front curtain and the rear curtain. There is something to be said. When the shutter is fully opened and the entire surface is exposed, main flash emission is performed once by TTL automatic light control when the shutter is fully opened. On the other hand, in the case of scanning movement type exposure, light emission with a relatively low light quantity is continuously performed under the TTL automatic light control over the entire area of the scanning movement. The latter is called high-speed sync, and the main light emission state at this time is called flat light emission.

  In the external light control mode, main light emission is started from the time when the shutter button is pressed and exposure is started, and at the same time, the reflected light from the subject is measured in real time by the light receiving sensor 30, and the integrated value of the measured value is predetermined. In this mode, main light emission is stopped when the value is reached.

  In the manual mode, main flash is performed once with a manually set light emission amount. The multi-flash mode is a mode that is used when taking a disassembled photo of a moving subject (a top-down photo), and has a manually set flash count, flash cycle (interval), and flash output per flash. In this mode, main light emission is performed.

  The external sync mode is a mode in which main flash is performed by synchronizing with the camera 50 and a specific shutter speed (X) setting by a sync cord connected to the sync cord connecting portion 34 without using a hot shoe.

  In the wireless TTL mode, when the strobe device 10 is separately installed as a slave device other than another strobe device (master device) 10 connected to the hot shoe of the camera 50 in multi-strobe shooting, the wireless sensor from the master device. In this mode, the shutter button information, the shutter information, and the TTL metering information are received by 32 and the same TTL automatic light control mode as that of the master unit is executed.

  The display unit 28 is configured by a liquid crystal display panel or the like, and displays a function mode setting screen, a manual setting screen, and the like.

  The flash control microcomputer 20 embodies a main light emission control unit 40, a light emission amount determination unit 42, and a post light emission control unit 44 by executing a computer program.

  The main light emission control unit 40 sets the main light emission timing and the light emission amount in each of the above-described function modes, and outputs a control command signal for main light emission to the drive circuit 16. That is, the main light emission control unit 40 controls main light emission performed when the shutter of the camera 50 is open.

  The light emission amount determination unit 42 takes in information related to the main light emission amount from the main light emission control unit 40, and determines whether or not the current main light emission amount is equal to or less than a predetermined value (threshold value GnoS). The threshold value GnoS set in the light emission amount determination unit 42 is that the main light emission is a very small amount of light in the xenon discharge tube 13 in which a quartz glass tube and an electron emissive material for cathode are used containing barium. This is set based on the light emission amount of the main light emission that may cause the light emission omission that the next main light emission is not normally performed. Since the amount of main light emission that causes the loss of light emission varies depending on the characteristics of the xenon discharge tube 13, it may be set to an optimum value according to the xenon discharge tube 13.

  Actually, in many cases, when a minute light emission with a guide number of about 1 to 2 is repeatedly performed, light emission is lost. Therefore, the threshold GnoS set in the light emission amount determination unit 42 has a guide number of about 2 to 3. If it is.

  After the light emission amount determining unit 42 determines that the main light emission amount is equal to or less than a predetermined value (threshold GnoS), the post light emission control unit 44 closes the shutter of the camera 50 at a predetermined frequency including every time. Control light emission. Light emission performed after the shutter is closed is called post-light emission. The amount of post-emission is the amount of light that wipes out (refreshes) the state in which the xenon discharge tube loses light emission due to the emission of very small amount of light. The amount of light emitted thereafter may be set to the minimum necessary for refreshing the xenon discharge tube 13 so that the guide number is about 8 to 14 and flash photography with a short interval can be performed.

  The post-light emission may be performed every time the main light emission is performed with the threshold value GnoS or less, or may be performed after the main light emission with the threshold value GnoS or less is repeatedly performed a predetermined number of times. FIG. 2A shows a light emission pattern in the TTL automatic light control mode. As shown in FIG. 2A, in the case of the main light emission a with the light amount equal to or less than the threshold value GnoS, the post light emission is performed when the shutter of the camera 50 is fully closed, and the light amount exceeds the threshold value GnoS. In the case of the main light emission b with a large light quantity exceeding, unnecessary post-light emission is not performed.

  Actually, the light emission loss occurs when minute light emission is repeated tens of thousands of times. Therefore, as shown in FIG. 2B, the main light emission with the threshold value GnoS or less is repeated n times as shown in FIG. It may be performed only after it is repeated.

  As described above, the post-light emission is performed, whereby the xenon discharge tube 13 is refreshed, and the light emission omission due to the slight light emission is avoided.

  The post-light emission is performed in the above-described various function modes in the single flash in the TTL automatic light control mode, the external light control mode, the manual mode, the external sync mode, and the wireless TTL mode. In the flat light emission in the TTL automatic light control mode and the multi-light emission mode, the total light emission amount is large, and it is not necessary to perform the post light emission for refreshing the xenon discharge tube 13, and therefore the post light emission is not performed.

  In the external sync mode, the signal received by the strobe device 10 from the camera 50 is only the sync signal for pressing the shutter button, and does not receive the shutter fully closed signal or shutter speed information. If the number of repetitions of main light emission by GnoS or less is counted, and the number of repetitions reaches a predetermined value, after the completion of the main light emission, if the subsequent light emission is performed with a predetermined time lag that ensures that the shutter is fully closed Good.

  Although the present invention has been described with respect to one embodiment thereof, the present invention is not limited to such an embodiment, as will be readily understood by those skilled in the art, and departs from the spirit of the present invention. It is possible to change appropriately within the range not to be. The post-flash can be applied to, for example, a strobe device connected to a camera that performs strobe synchronization only at a specific shutter speed or a camera that does not perform TTL automatic light control. The strobe device according to the present invention can also be applied to a digital camera using an electronic shutter. In addition, all the components shown in the above embodiment are not necessarily essential, and can be appropriately selected without departing from the gist of the present invention.

DESCRIPTION OF SYMBOLS 10 Strobe device 12 Light emission part 13 Xenon discharge tube 14 Power supply part 16 Drive circuit 20 Strobe control microcomputer 22 Constant voltage circuit 24 Communication part 26 Operation switch group 28 Display part 30 Light reception sensor 32 Wireless sensor 34 Sync cord connection part 40 Main light emission Control unit 42 Light emission amount determination unit 44 Rear light emission control unit 50 Camera

Claims (2)

A strobe device comprising: a light emitting unit including a flash discharge tube; and a control unit that inputs information related to opening / closing of a shutter from a camera and controls light emission of the light emitting unit,
The controller is
A main light emission control unit for controlling main light emission performed under a state where the shutter of the camera is open;
A light emission amount determining unit for determining whether or not the light emission amount of the main light emission is equal to or less than a predetermined value;
When the light emission amount determining unit determines that the light emission amount of the main light emission is less than or equal to a predetermined value, after the shutter of the camera is closed at a predetermined frequency including every time, the light emission after the light emission amount is greater than or equal to the predetermined value. A light emission control unit,
Strobe device with.   2. The strobe according to claim 1, wherein the post-emission control unit performs the post-emission only when the determination that the light emission amount of the main light emission is equal to or less than a predetermined value is continuously performed a predetermined number of times or more by the light emission amount determination unit. apparatus.

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