JP4194499B2 - Strobe device - Google Patents

Description

  The present invention relates to a stroboscopic device, and more particularly to a stroboscopic device that emits a stroboscope by electric charges stored in a capacitor, for example.

An example of a conventional strobe device of this type is disclosed in Patent Document 1. This prior art determines whether or not continuous charging has been performed at short intervals, and when the determination result is affirmative, a restriction process such as charging prohibition is performed. As a result, it is possible to prevent the circuit from being destroyed due to heat generation.
JP-A-9-61907 [G03B15 / 05, H05B 41/32]

  However, the conventional technique performs the above-described determination operation based on the number of times the main capacitor is charged and the interval of the charging operation, and the amount of light emitted from the strobe is not taken into consideration in the determination. For this reason, when the micro flash of the strobe is repeated, the charging operation is limited even though the temperature rise of the circuit is small.

  Therefore, a main object of the present invention is to provide a strobe device that can prevent a circuit from being destroyed and can accurately limit a charging operation.

  The strobe device according to the first aspect of the present invention discriminates a capacitor for accumulating electric charges for causing the strobe to emit light, a charging means for charging the capacitor every time the strobe is emitted, and a ratio between the charging period and the non-charging period of the capacitor. And a delay unit that delays the charging start timing of the capacitor as the ratio of the charging period increases based on the determination result of the determination unit.

  The strobe emits light by the charge accumulated in the capacitor. The capacitor is charged by the charging means each time the strobe emits light. The discriminating unit discriminates the ratio between the charging period and the non-charging period of the capacitor, and the delaying unit delays the charging start timing of the capacitor as the ratio of the charging period increases based on the discrimination result.

  By delaying the charging start timing of the capacitor, it is possible to prevent the circuit from being destroyed due to heat generation. Further, by delaying the charging start timing as the ratio of the charging period increases, the amount of charge remaining in the capacitor is reflected in the charging start timing, whereby the charging operation can be accurately limited.

  The strobe device according to the invention of claim 2 is dependent on claim 1, and the charging means stops the charging operation when the terminal voltage of the capacitor reaches a predetermined value. Thereby, destruction of the capacitor is prevented.

  The strobe device according to the invention of claim 3 is dependent on claim 1 or 2, wherein the discriminating means is updated in one of the increasing direction and the decreasing direction during the charging period, and is increased and decreased during the non-charging period. Includes a counter that is updated towards the other. As a result, the ratio between the charging period and the non-charging period is accurately obtained.

  A strobe device according to a fourth aspect of the invention is dependent on the third aspect, wherein the counter is updated at the first period during the charging period and at a second period longer than the first period during the non-charging period, and the delay means The charging start timing is delayed as the absolute value indicated by the counter increases.

  A strobe device according to a fifth aspect of the present invention is dependent on any one of the first to fourth aspects, further comprising accepting means for accepting an operation for causing the strobe to emit light after the terminal voltage of the capacitor reaches a predetermined value. This avoids a situation where the strobe emits light with an unexpected light emission amount.

  A camera according to a sixth aspect of the invention includes the strobe device according to any one of the first to fifth aspects.

  The charge control program according to the invention of claim 7 is a charge control program to be executed by a processor of a strobe device having a capacitor for accumulating charges for causing the strobe to emit light. (A) Each time the strobe is emitted, the capacitor is turned on. A charging step for charging; (b) a determining step for determining a ratio between the charging period and the non-charging period of the capacitor; and A delay step for delaying.

  Similarly to the first aspect, by delaying the charging start timing of the capacitor, it is possible to prevent the circuit from being destroyed due to heat generation. Further, the charging operation can be accurately limited by delaying the charging start timing as the charging period ratio increases.

  According to the present invention, it is possible to prevent a circuit from being destroyed due to heat generation and to accurately limit the charging operation.

  The above object, other objects, features and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the drawings.

  Referring to FIG. 1, a digital camera 10 of this embodiment includes a boost / charge circuit 12. Boost / charge circuit 12 boosts power supply voltage Vcc and charges electrolytic capacitor 16 with the boosted voltage. The terminal voltage of the electrolytic capacitor 16, that is, the charging voltage is detected by the charging voltage detection circuit 14. The booster / charge circuit 12 is turned off when the charge voltage reaches a specified value.

  The strobe (xenon tube) 20 emits light by the charge accumulated in the electrolytic capacitor 16 when a trigger is generated from the trigger circuit 18. The light emission period of the strobe 20, that is, the light emission amount is controlled by the light emission control circuit 22.

  Each of the frequency dividers 30 and 32 divides the oscillation clock output from the oscillator 34 to generate a divided clock having a frequency lower than the oscillation frequency. However, the frequency divider 30 outputs the frequency-divided clock once every 0.2 seconds, and the frequency divider 32 outputs the frequency-divided clock once every 0.5 seconds.

  In the period for charging the electrolytic capacitor 16, that is, the charging period, the switch SW1 is connected to the terminal T1, and the counter 28 is set to the increment mode. On the other hand, in a period when charging of the electrolytic capacitor 16 is stopped, that is, in a non-charging period, the switch SW1 is connected to the terminal T2, and the counter 28 is set to the decrement mode. As a result, the counter 28 is incremented every 0.2 seconds in response to the frequency-divided clock from the frequency divider 30 during the charging period, and responds to the frequency-divided clock from the frequency divider 32 during the non-charging period. Is decremented every 0.5 seconds. Note that the count value of the counter 28 is expressed by 8 bits and indicates any value from “0” to “255”.

  When the exposure command is given, the imaging device 36 performs photoelectric conversion on the optical image of the object scene to generate an image signal. The signal processing circuit 38 evaluates the luminance of the image signal output from the imaging device 36 when the luminance evaluation command is given, and records the image signal output from the imaging device 36 in a compressed state when the recording command is given. Recording on the medium 40.

  The system controller 24 executes processing according to the flowcharts shown in FIGS. The control program corresponding to these flowcharts is stored in the flash memory 42.

  First, in step S1, an initial value (= 48) is set in the counter 28, and in step S3, the boost / charge circuit 12 is turned on. The electrolytic capacitor 16 is charged by the boost / charge circuit 12. In step S5, the switch SW1 is connected to the terminal T1, and the counter 28 is set to the increment mode. Due to the processing in step S3, the charging period is started. Further, due to the processing in step S5, the counter 28 is incremented in response to the divided clock from the frequency divider 30.

  In step S7, the charging voltage detected by the charging voltage detection circuit 14 is compared with a specified value. When the charging voltage reaches the specified value, the boost / charge circuit 12 is turned off in step S9. In the subsequent step S11, the switch SW1 is connected to the terminal T2, and the counter 28 is connected to the decrement mode. Due to the processing in step S9, the charging period ends and the non-charging period starts. Further, due to the processing in step S11, the counter 28 is decremented in response to the frequency-divided clock from the frequency divider 32.

  When the charging of the electrolytic capacitor 16 is completed, the shutter button 26 can be operated. When the shutter button 26 is operated, the process proceeds from step S13 to step S15, and the brightness of the object scene is measured by the TTL method. Specifically, an exposure command and a luminance evaluation command are given to the imaging device 36 and the signal processing circuit 38, respectively, and the brightness of the object scene is measured based on the luminance evaluation value obtained by the signal processing circuit 38.

  In step S17, the optimum light emission amount of the strobe 20 is calculated based on the measurement result in step S15, and the light emission stop timing corresponding to the calculated optimum light emission amount is set in the light emission control circuit 22.

  In step S19, a photographing process is executed. Specifically, a light emission command is given to the trigger circuit 18, an exposure command is given to the imaging device 36, and a recording command is given to the signal processing circuit 38. As a result, the image signal of the object scene exposed to the light emitted from the strobe 20 is output from the imaging device 36. The signal processing circuit 38 records the output image signal on the recording medium 40 in a compressed state.

  In steps S21, S23 and S25, the count value of the counter 28 is compared with threshold values TH1 (= 96), TH2 (= 128) and TH3 (= 192), respectively. When the count value is less than the threshold value TH1, the process directly returns to step S3. When the count value is greater than or equal to the threshold value TH1 and less than the threshold value TH2, the process returns to step S3 after waiting for 1 second in step S27. When the count value is greater than or equal to the threshold value TH2 and less than the threshold value TH3, the process waits for 2 seconds in step S29 and then returns to step S3. When the count value is equal to or greater than the threshold value TH3, the process waits for 4 seconds in step S31 and then returns to step S3.

  Referring to FIG. 4, charging of electrolytic capacitor 16 is started when boost / charge circuit 12 is turned on. The time required to increase the terminal voltage of the electrolytic capacitor 16 from 0 V to the specified value is 2.0 seconds, and the booster / charge circuit 12 is turned off when 2.0 seconds have elapsed from the start of charging. When the shutter button 26 is operated after the charging is completed, the photometry and recording process is executed over a period of 2.5 seconds. When the recording process is completed, the charging of the electrolytic capacitor 16 is resumed after the waiting time corresponding to the count value of the counter 28 has elapsed.

  However, the period required for the second and subsequent charging depends on the amount of charge remaining in the electrolytic capacitor 16. That is, the smaller the amount of light emitted from the strobe 20, the more charge remains in the electrolytic capacitor 16 and the charging period becomes shorter.

  The count value of the counter 28 increases as the ratio of the charging period to the entire period increases, and decreases as the ratio of the non-charging period to the entire period increases. The standby time from the completion of the recording process to the resumption of the charging period is extended in the order of 0 seconds → 1 second → 2 seconds → 4 seconds as the count value increases. The charging start timing of the electrolytic capacitor 16 is delayed due to the extension of the standby time.

  When the shutter button 26 is frequently operated, the ratio of the charging period is gradually increased, and accordingly, the standby time is extended stepwise. By extending the standby time, the charging start timing is delayed, and the ratio of the non-charging period is increased. As a result, the ratio of the charging period reaches a certain value. That is, when photographing with full light emission of the strobe 20 is repeatedly executed, the count value changes as shown in FIG.

  According to FIG. 5, the count value reaches “96” at the time when photographing is performed about 20 times, and the standby time is updated from “0 second” to “1 second”. When photographing is performed about 30 times, the count value reaches “128”, and the standby time is updated from “1 second” to “2 seconds”. The count value indicates a value in the vicinity of “192” from when the number of photographing exceeds 90 times, and the standby time varies between “2 seconds” and “4 seconds”.

  As can be seen from the above description, the strobe 20 emits light by the electric charge accumulated in the electrolytic capacitor 16. The electrolytic capacitor 16 is charged by the boost / charge circuit 12 every time the strobe 20 emits light. The system controller 24 determines the ratio between the charging period and the non-charging period of the electrolytic capacitor 16 and delays the charging start timing of the electrolytic capacitor 16 as the ratio occupied by the charging period increases. By delaying the charging start timing of the electrolytic capacitor 16, it is possible to prevent the circuit from being destroyed due to heat generation. Further, by delaying the charging start timing as the ratio of the charging period increases, the amount of charge remaining in the electrolytic capacitor 16 is reflected in the charging start timing, whereby the charging operation can be accurately limited.

  In this embodiment, the frequency-divided clock is counted by a hardware counter, but the frequency-divided clock may be counted by a software counter prepared in the system controller. In this case, the count value is incremented / decremented by the interrupt process.

  In this embodiment, the digital camera has been described. However, the present invention can also be applied to a silver salt film camera.

It is a block diagram which shows one Example of this invention. It is a flowchart which shows a part of operation | movement of the system controller applied to the FIG. 1 Example. It is a flowchart which shows a part of other operation | movement of the system controller applied to the FIG. 1 Example. It is a wave form diagram which shows an example of operation | movement of the pressure | voltage rise / charge circuit applied to FIG. 1 Example. It is a graph which shows another part of operation | movement of FIG. 1 Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Digital camera 12 ... Boosting / charging circuit 14 ... Charging voltage detection circuit 16 ... Electrolytic capacitor 18 ... Trigger circuit 20 ... Strobe 22 ... Light emission control circuit 24 ... System controller 28 ... Counter

Claims (7)

A capacitor for accumulating electric charge for causing the strobe to emit light,
A charging means for charging the capacitor every time the strobe light is emitted;
Determining means for determining the ratio between the charging period and the non-charging period of the capacitor; and delay means for delaying the charging start timing of the capacitor as the ratio occupied by the charging period increases based on the determination result of the determining means. Strobe device.   The strobe device according to claim 1, wherein the charging means stops the charging operation when a terminal voltage of the capacitor reaches a predetermined value.   The determination unit includes a counter that is updated toward one of an increasing direction and a decreasing direction during the charging period and is updated toward the other of the increasing direction and the decreasing direction during the non-charging period. Or the strobe device according to 2. The counter is updated with a first period during the charging period and with a second period longer than the first period during the non-charging period,
The strobe device according to claim 3, wherein the delay means delays the charging start timing as the absolute value indicated by the counter increases.   5. The strobe device according to claim 1, further comprising a reception unit configured to receive an operation for causing the strobe to emit light after a terminal voltage of the capacitor reaches a predetermined value.   A camera comprising the strobe device according to claim 1. A charge control program to be executed by a processor of a strobe device including a capacitor for accumulating charges for causing the strobe to emit light,
(a) a charging step of charging the capacitor each time the strobe is emitted;
(b) a determination step of determining a ratio between a charging period and a non-charging period of the capacitor; and
(c) A charge control program comprising a delay step of delaying the charge start timing of the capacitor as the ratio of the charge period increases based on the determination result of the determination step.

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