Illumination device and method for controlling the same and program

Abstract

To provide an illumination device that does not restrict light emitting operations more than necessary, while preventing an increase in the temperature of a battery.SOLUTION: A stroboscopic device 100 comprises: a discharge tube 104; a main capacitor 102d that accumulates energy for causing the discharge tube 104 to emit light; a boosting unit 102a that charges the main capacitor 102d with a battery 200; and an FPU 101 that detects the voltage of the main capacitor 102d. The FPU 101 controls the light emission of the discharge tube 104 on the basis of the amount of change in the voltage of the main capacitor 102d.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a lighting device, a control method thereof, and a program. [Background technology]

[0002] In lighting devices (so-called strobe devices), which are one type of accessory for digital cameras and the like, the discharge tube serving as the light source generates heat when emitting light, and the elements of the electrical circuit and the battery also generate heat due to discharge during light emission and charging in preparation for light emission. To counteract the heat generated by the discharge tube, a control means is provided that appropriately controls the temperature rise of the optical panel placed in front of the discharge tube so that the optical panel remains within a safe operating temperature range (see, for example, Patent Document 1). Also, a control means is provided that controls the operation of the electrical circuit so that the various electronic and electrical components that make up the electrical circuit remain within a safe operating temperature range (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-60558 [Patent Document 2] Japanese Patent Application Laid-Open No. 2017-62275 Summary of the Invention [Problem to be solved by the invention]

[0004] Generally, in lighting devices that emit flashes, such as strobe devices, a certain amount of energy (charge) is stored in a capacitor, and the stored energy is supplied all at once to a discharge tube to generate a flash, so the capacitor is charged by a battery. Strobe devices generally use nickel-metal hydride batteries or alkaline batteries, but because batteries have internal resistance, they generate heat when charging the capacitor, causing the battery temperature to rise. While suppressing the rise in battery temperature is desirable as one means of suppressing the rise in the internal temperature of a strobe device, the above-mentioned Patent Documents 1 and 2 do not consider the rise in battery temperature. On the other hand, excessive suppression of the charging operation in order to suppress the rise in battery temperature can result in the problem of not being able to emit light at the desired shooting timing.

[0005] An object of the present invention is to provide a lighting device that suppresses a rise in battery temperature while not restricting light-emitting operation more than necessary. [Means for solving the problem]

[0006] The lighting device according to the present invention is characterized by comprising a light source, a capacitor for storing energy for making the light source emit light, charging means for charging the capacitor using a battery, detection means for detecting the voltage of the capacitor, and control means for controlling the light-emitting operation of the light source based on the amount of change in the voltage of the capacitor. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a lighting device that suppresses a rise in the temperature of the battery while not restricting the light-emitting operation more than necessary. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a block diagram showing a schematic configuration of a strobe device according to an embodiment. [Figure 2] FIG. 2 is a cross-sectional view showing a schematic configuration of the strobe device of FIG. [Figure 3] 2 is a flowchart of a light emission process in the strobe device of FIG. 1. [Figure 4] 10 is a flowchart of a state confirmation process in step S302. [Figure 5] 10 is a flowchart of a charging time control process in S305. [Figure 6] 10 is a flowchart of the gradient determination process of S505 and S507. [Figure 7] 1 is a graph showing the charging characteristics of the main capacitor for each type of battery. [Figure 8] FIG. 8 is a partial enlarged view of FIG. [Figure 9] FIG. 4 is a diagram illustrating the relationship between the type of battery, the voltage of the main capacitor, and the first to fourth threshold values. DETAILED DESCRIPTION OF THE INVENTION

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. Here, a strobe device that can be attached to an imaging device such as a digital camera as an accessory will be taken as an illumination device according to the present invention.

[0010] Fig. 1 is a block diagram showing a schematic configuration of a strobe device 100 according to an embodiment of the present invention. Fig. 2 is a cross-sectional view showing a schematic configuration of the strobe device 100. Note that the same reference numerals in Fig. 1 and Fig. 2 indicate the same components.

[0011] The strobe device 100 is composed of a main body 100a configured as a detachable part for an image capture device (not shown), and a light emitting part 100b that can rotate up and down and left and right relative to the main body 100a. Note that the up and down and left and right directions refer to the up and down and left and right directions when viewed from the front side of the image capture device to which the strobe device 100 is attached in a normal position.

[0012] The strobe device 100 includes an FPU 101, a battery 200, a boost circuit block 102, a trigger circuit 103, a light emission control circuit 105, a discharge tube 104, a photodiode 106, an integration circuit 107, a comparator 108, and an AND gate 109. The strobe device 100 also includes a reflector 110, an optical panel 111, an input unit 113, a cooling unit 117, a display unit 114, a zoom drive circuit 115, a camera connection terminal 116, and the cooling unit 117. The discharge tube 104 and the reflector 110 form a reflector unit 112.

[0013] The FPU 101 is a microcomputer that controls all components of the strobe device 100. The FPU 101 is configured as a one-chip IC with a built-in microcomputer, including a CPU, ROM, RAM, input / output control circuit (I / O control circuit), multiplexer, timer circuit, EEPROM, A / D, and D / A converters. The battery 200 is used as the power supply (VBAT) for the strobe device 100. The boost circuit block 102 includes a boost unit 102a, resistors 102b and 102c used for voltage detection, and a main capacitor 102d. The boost circuit block 102 boosts the voltage of the battery 200 to several hundred volts using the boost unit 102a, and stores the energy (charge) for light emission in the main capacitor 102d. The voltage (charging voltage) of the main capacitor 102d is divided by resistors 102b and 102c, and the divided voltage is input to an A / D conversion terminal MCV_AD of the FPU 101.

[0014] The trigger circuit 103 applies a pulse voltage to the discharge tube 104 to excite the discharge tube 104. The light emission control circuit 105 controls the start and stop of light emission of the discharge tube 104. The discharge tube 104 (light source) is excited by receiving a pulse voltage of several kilovolts applied from the trigger circuit 103, and emits a flash of light using the energy stored in the main capacitor 102d.

[0015] Photodiode 106 is a sensor that receives light emitted from discharge tube 104, and receives the light emitted by discharge tube 104 directly or via a glass fiber or the like. Integration circuit 107 integrates the light-receiving current of photodiode 106 and inputs its output to the inverting input terminal of comparator 108 and to A / D converter terminal INT_AD of FPU 101. The non-inverting input terminal of comparator 108 is connected to D / A converter terminal INT_DAC in FPU 101, and the output of comparator 108 is connected to one input terminal of AND gate 109. The other input terminal of AND gate 109 is connected to light emission control terminal FL_START of FPU 101, and the output of AND gate 109 is input to light emission control circuit 105.

[0016] The light-emitting unit 100b is mainly composed of a discharge tube 104, a reflector 110, and an optical panel 111, and the direction of light emitted by the discharge tube 104 can be changed by rotating the reflector 110 relative to the main body 100a. The reflector 110 reflects the light emitted by the discharge tube 104 and guides it in a predetermined direction. The optical panel 111 is included in a zoom optical system (not shown) and is incorporated so that its relative position (zoom position) with respect to the reflector unit 112 can be changed. By changing the relative position between the reflector unit 112 and the optical panel 111, the illumination angle of the strobe device 100 can be changed, and the guide number can be changed.

[0017] The input unit 113 includes a power switch, a mode setting switch for setting the operation mode of the strobe device 100, including the drive setting of the cooling unit 117, in response to a user operation, and setting buttons for setting various other parameters in response to a user operation. The FPU 101 receives signals from the input unit 113 and executes various processes. The display unit 114 has a liquid crystal panel and light-emitting elements, and displays various states of the strobe device 100.

[0018] The zoom drive circuit 115 includes a zoom detection unit 115a that detects information about the relative positions of the reflector unit 112 and the optical panel 111 using an encoder or the like, and a zoom drive unit 115b that has a motor that moves the reflector unit 112. The FPU 101 calculates the amount of movement of the reflector unit 112 by the zoom drive unit 115b using focal length information of the photographing lens that can be obtained via the imaging device.

[0019] The camera connection terminal 116 is composed of multiple terminals connected to the imaging device. Specifically, the camera connection terminal 116 includes an SCLK_S terminal for synchronizing communication between the imaging device and the strobe device 100, and a GND terminal for electrically connecting the imaging device and the strobe device 100. The camera connection terminal 116 also includes a MOSI_S terminal for receiving data transmitted from (the control unit of) the imaging device, and a MISO_S terminal for transmitting data from the strobe device 100 to (the control unit of) the imaging device.

[0020] The cooling unit 117 is a module having a fan for cooling the optical panel 111, and is connected to the FAN_PWM terminal and the FAN_FG terminal of the FPU 101. The cooling unit 117 can change the output air volume by changing the rotation speed of the fan through PWM control from the FPU 101. The cooling unit 117 can also maintain the instructed rotation speed by feeding back rotation speed information to the FPU 101.

[0021] Next, the light emission process in the strobe device 100 will be described. Figure 3 is a flowchart illustrating the light emission process in the strobe device 100. Each process (step) indicated by an S number in Figure 3 is realized by the CPU of FPU 101 loading a predetermined program stored in its own ROM into its own RAM and comprehensively controlling the operation of each part of the strobe device 100. When the power switch included in the input unit 113 is turned on and the FPU 101 of the strobe device 100 becomes operable, the FPU 101 starts the process of S301. Note that, although not shown in Figure 3, the light emission process ends when the power switch is turned off.

[0022] In S301, the FPU 101 initializes its own memory and ports, reads the state of the switches included in the input unit 113 and pre-set input information, and sets the method for determining the amount of light emitted in the set light emission mode, the light emission timing, etc.

[0023] In S302, the FPU 101 performs a status check process, which is a process of storing the status results checked in S301 in its own RAM, and the details of which will be described later.

[0024] In S303, the FPU 101 reads the voltage value of the main capacitor 102d from the MCV_AD terminal, which is an A / D conversion terminal, and stores it in its own RAM.

[0025] In S304, the FPU 101 starts the operation of the boost circuit block 102 to start charging the main capacitor 102d. After the charging starts, the process returns to S302 again, and the process of S304 is skipped.

[0026] In S305, the FPU 101 performs charging time control processing. The charging time control processing is roughly a processing for controlling the time for determining whether charging is complete in S310 with respect to the charging operation started in S304 after light emission (S312). The charging time control processing will be described in detail later.

[0027] In S306, FPU 101 acquires focal length information of the photographing lens from (the control unit of) the imaging device via the camera connection terminal 116, and stores the acquired focal length information in its own RAM. Note that if focal length information has already been stored in RAM, the stored focal length information is updated with the newly acquired focal length information in S306.

[0028] In S307, the FPU 101 drives the zoom drive circuit 115 to move the reflector unit 112 so that the light distribution angle of the light emitted by the discharge tube 104 falls within the range corresponding to the focal length information acquired in S306. Note that if there is no need to move the reflector unit 112, the processing of S307 is skipped.

[0029] In S308, the FPU 101 displays information about the light emission mode confirmed in S301 and information about the focal length information acquired in S306 on the display unit 114. Furthermore, if the FPU 101 detects in S302 that an error has occurred in any of the hardware related to the light emission processing, it issues a warning according to the detected error content (for example, by displaying a warning on the display unit 114).

[0030] In S309, the FPU 101 determines whether a predetermined charging completion waiting time has elapsed. The charging completion waiting time is set under predetermined conditions in the charging time control process of S305, and details thereof will be described later. If the FPU 101 determines that the charging completion waiting time has elapsed (YES in S309), it executes the process of S310, and if it determines that the charging completion waiting time has not elapsed (NO in S309), it executes the process of S302.

[0031] In S310, the FPU 101 determines whether charging of the main capacitor 102d is complete based on the voltage at the MCV_AD terminal. In this embodiment, the minimum voltage value at which the FPU 101 determines that charging of the main capacitor 102d is complete is set to 270 V. In other words, the flash device 100 enables the discharge tube 104 to emit light when the voltage of the main capacitor 102d is 270 V or higher.

[0032] If the FPU 101 determines that charging is complete (YES in S310), it transmits a charging completion signal to the image capture device (controller) via the camera connection terminal 116, and then executes the process of S311. On the other hand, if the FPU 101 determines that charging is not complete (NO in S310), it executes the process of S302.

[0033] In S311, the FPU 101 determines whether a light emission instruction has been received based on whether a light emission start signal has been received from (the control unit of) the imaging device. If the FPU 101 determines that a light emission instruction has been received (YES in S311), it executes the process of S312, and if it determines that a light emission instruction has not been received (NO in S311), it executes the process of S302.

[0034] In S312, the FPU 101 performs light emission processing. The light emission processing is performed by the FPU 101 issuing a light emission instruction to the light emission control circuit 105 in accordance with a light emission start signal received from the imaging device, and the light emission control circuit 105 causing the discharge tube 104 to emit light in accordance with the light emission instruction. After the light emission ends, the FPU 101 stores information related to the light emission, such as voltage information on the main capacitor 102d, in its own RAM. Note that if main light emission is performed after pre-emission for dimming, the processing of S313 is performed after main light emission ends.

[0035] In S313, the FPU 101 determines whether the light emission in S312 is the first light emission (whether it is the first light emission since the start of S301). If the FPU 101 determines that it is the first light emission (YES in S313), it executes the processing of S314, and if it determines that it is not the first light emission (it is the second or subsequent light emission) (NO in S313), it executes the processing of S302. This determination will be described later, but the FPU 101 calculates the expected temperature of the parts that should be protected from the heat generated by the strobe device 100, or a value that serves as a substitute for it, and if the calculated value is equal to or less than a predetermined value, it is determined that it is the first light emission.

[0036] In S314, the FPU 101 executes light emission control processing, and then executes the processing of S302. The light emission control processing is processing for controlling light emission and charging so that excessive heat is not generated abnormally even if heat from light emission is continuously applied to the panel, such as during continuous light emission. In the light emission control processing, the FPU 101 parameterizes the thermal effect on the strobe device 100 caused by light emission from the discharge tube 104 using the amount of heat generated, the amount of heat dissipation, the distance to the heat source, etc. Then, the FPU 101 controls the timing of the next light emission based on the estimated temperature of the area to be protected from heat or a calculated value that serves as a substitute for that temperature.

[0037] Once the light emission control process is started in S314, the FPU 101 continues to calculate the estimated temperature or its substitute value until the calculated value of the estimated temperature or its substitute value of the part to be protected falls below a predetermined value. In other words, after S314, the FPU 101 continues to calculate the estimated temperature or its substitute value in parallel with the processes from S302 onwards.

[0038] Also, after the light emission control process is performed in S314, if the calculation value of the parallel calculation is equal to or greater than a predetermined value, FPU101 determines in S310 that this is the second or subsequent light emission, and since there is no need to perform the light emission control process again, it performs the process of S302 without proceeding to S314.

[0039] FIG. 4 is a flowchart illustrating the status confirmation process in S302.

[0040] In S401, the FPU 101 performs a process of detecting target hardware. Target hardware is registered in advance in the ROM of the FPU 101, and the FPU 101 checks whether the registered target hardware is installed. The target hardware refers to components that have an effect as an optical system or a heat source, such as the cooling unit 117 that cools the optical panel 111, and optical accessories (not shown in FIG. 2 ) such as a color filter or bounce adapter that are attached in front of the optical panel 111. The target hardware may also include an external power supply (not shown) that speeds up charging of the main capacitor 102d, a modeling LED (not shown) that makes it easier to grasp the optical axis of the light emitted from the optical panel 111, and the like.

[0041] In S402, the FPU 101 acquires status information of the target hardware detected in S401, and performs error detection processing for the target hardware based on the acquired status information. Examples of status information include the specifications of the target hardware and information on whether the hardware is operational. For example, even if the cooling unit 117 is operational in the light emission mode setting performed in S301, the cooling unit 117, which is the target hardware, may be inoperable due to a malfunction or the like. In this case, the inoperability of the cooling unit 117 is detected as error information. The status information and error information are updated every time a change occurs in the status of the target hardware.

[0042] In S403, the FPU 101 stores the status information and error information of the target hardware acquired in S402 in its own RAM, and then ends this process and executes the process of S303.

[0043] 5 is a flowchart illustrating the charging time control process of 305. For convenience of explanation, it is assumed here that the maximum voltage value of the main capacitor 102d is 330V.

[0044] In step S501, the FPU 101 acquires the current voltage of the main capacitor 102d as a current voltage value and stores it in its own RAM.

[0045] In S502, the FPU 101 reads out the voltage value of the main capacitor 102d acquired in S303 and stored in the RAM as the previous voltage value.

[0046] In S503, the FPU 101 determines whether the previous voltage value read in S502 is equal to or less than 280 V. If the FPU 101 determines that the previous voltage value is equal to or less than 280 V (YES in S503), it ends this subflow and executes the process of S306, and if the FPU 101 determines that the previous voltage value is greater than 280 V (NO in S503), it executes the process of S504.

[0047] In S504, the FPU 101 determines whether the previous voltage value read in S502 is equal to or less than 300 V. If the FPU 101 determines that the previous voltage value is equal to or less than 300 V (YES in S504), it executes the process of S505, and if the FPU 101 determines that the previous voltage value is greater than 300 V (NO in S504), it executes the process of S506.

[0048] In S505, the FPU 101 executes the first gradient determination process, and then ends this subflow and executes the process of S306. Details of the first gradient determination process will be described later with reference to FIG.

[0049] In S506, the FPU 101 determines whether the previous voltage value read in S502 is equal to or less than 320 V. If the FPU 101 determines that the previous voltage value is equal to or less than 320 V (YES in S506), it executes the process of S507, and if it determines that the previous voltage value is greater than 320 V (NO in S506), it ends this subflow and executes the process of S306.

[0050] In S507, the FPU 101 executes the second gradient determination process, and then ends this subflow and executes the process of S306. Details of the second gradient determination process will be described later with reference to FIG.

[0051] FIG. 6(a) is a flowchart of the first gradient determination process (S505).

[0052] In S601, the FPU 101 reads the current voltage value stored in RAM in S501, and calculates the amount of change in the charging voltage of the main capacitor 102d (hereinafter referred to as the "voltage gradient ΔAD") based on the current voltage value read and the previous voltage value read in S502.

[0053] Here, we will explain how to calculate the voltage gradient ΔAD. The voltage gradient ΔAD is expressed by the following equation 1. Here, 'ADpre' represents the previous voltage value read out in S502, 'ADcur' represents the current voltage value acquired in S501, and 'N' represents the elapsed time from the acquisition of the previous voltage value to the acquisition of the current voltage value.

[0054]

number

[0055] In S602, the FPU 101 determines whether the voltage gradient ΔAD is equal to or less than a predetermined first threshold. The first threshold will be described in detail later, but generally, the first threshold is used to determine whether the temperature rise of the battery 200 due to charging of the main capacitor 102d by the battery 200 is small. If the FPU 101 determines that the voltage gradient ΔAD is greater than the first threshold (NO in S602), it ends this determination process and executes the process of S306, and if it determines that the voltage gradient ΔAD is equal to or less than the first threshold (YES in S602), it executes the process of S603.

[0056] In S603, the FPU 101 determines whether the voltage gradient ΔAD is equal to or less than a predetermined second threshold. The second threshold is a value smaller than the first threshold. Details of the second threshold will be described later, but generally, the second threshold is used to determine whether the temperature rise of the battery 200 due to charging of the main capacitor 102d by the battery 200 is large. If it is determined that the voltage gradient ΔAD is greater than the second threshold (NO in S603), the FPU 101 executes the process of S604, and if it is determined that the voltage gradient ΔAD is equal to or less than the second threshold (YES in S603), the FPU 101 executes the process of S605.

[0057] In S604, the FPU 101 stores in its RAM a setting to generate a charging completion wait time after the next light-emitting operation, terminates this determination flow, and executes the process of S306. The charging completion wait time is the time required to elapse after the next light-emitting operation (S312) is performed and before determining again whether charging is complete (S310) (in other words, the time required to delay the determination of S310 for a certain period of time). If a charging completion wait time is set, measurement of the charging completion wait time begins simultaneously with the end of the next light-emitting operation (S312), and the elapse of the charging completion wait time is determined in S309 after the process returns to S302. Regardless of the voltage value of the main capacitor 102d acquired in S303, the determination of charging completion in S310 is not made unless the charging completion wait time has elapsed.

[0058] In S605, the FPU 101 stores in its RAM that a charging completion waiting time will be generated after the next light emission operation, displays a warning on the display unit 114, ends this determination flow, and executes the process of S306. The charging completion waiting time generated in S605 may be the same as the charging completion waiting time generated in S604, or may be longer.

[0059] As will be described in detail later, the charge completion waiting time in S604 and S605 is set to suppress a temperature rise in the battery 200 due to discharge from the battery 200 when the main capacitor 102d is charged by the battery 200. In the first gradient determination process, the voltage gradient ΔAD in the voltage range of 280 V to 300 V of the main capacitor 102d is compared with a first threshold or a second threshold, and the temperature rise of the battery 200 is determined to be one of three levels: "large," "medium," or "small." If the voltage gradient ΔAD is determined to be greater than the first threshold, the temperature rise of the battery 200 is determined to be small. If the voltage gradient ΔAD is equal to or less than the first threshold and greater than the second threshold, the temperature rise of the battery 200 is determined to be medium. If the voltage gradient ΔAD is determined to be equal to or less than the second threshold, the temperature rise of the battery 200 is determined to be large.

[0060] Therefore, examples of the warning issued in S605 include a warning display on the liquid crystal panel of the display unit 114, and blinking or lighting of a light-emitting element. The contents of the warning display include notifying the user of a low battery level or a rise in temperature of the battery 200. In the case of still image shooting, the warning may be issued by emitting a sound (warning sound).

[0061] FIG. 6(b) is a flowchart of the second gradient determination process (S507). In the flowchart of FIG. 6(b), the "first threshold" in S602 of the flowchart of FIG. 6(a) is replaced with the "third threshold" in S612, and the "second threshold" in S603 of the flowchart of FIG. 6(a) is replaced with the "fourth threshold" in S613. The third threshold and the fourth threshold correspond to the first threshold and the second threshold, respectively. The processing content of S611 to S615 is the same as the processing content of S601 to S605 of the flowchart of FIG. 6(a), and therefore a description thereof will be omitted. Note that the charging completion waiting times issued in S614 and S615 may be the same as the charging completion waiting times issued in S604 and S605, respectively. The warning content issued in S615 is the same as the warning content issued in S605.

[0062] As explained for S604 and S605, the first gradient determination process and the second gradient determination process are controls that delay the next light-emitting operation by generating a charge completion waiting time to delay the execution of the charge completion determination, and do not perform control to stop the operation to start charging in S304. In this way, by performing the first or second gradient determination process during the charging operation after the voltage of the main capacitor 102d has dropped due to the light-emitting operation, the first and second gradient determination processes can be performed without depending on the light emission amount or light emission interval of the light-emitting operation.

[0063] In this embodiment, as explained above, the threshold value used in the gradient determination process is changed depending on the value of the previous voltage value. Before explaining the reason for this, the charging characteristics of the main capacitor 102d depending on the type of battery will be explained.

[0064] FIG. 7 is a graph showing the relationship between charging time and voltage when main capacitor 102d is charged using a nickel-metal hydride battery and an alkaline battery as battery 200, based on actual measurements.

[0065] The solid line graph 701 shows the charging characteristics when a nickel-metal hydride battery with sufficient remaining battery power is used, and it can be seen that the time required to reach the maximum voltage value of 330 V of the main capacitor 102d is shorter than that of any of the other batteries. The dashed line graph 702 shows the charging characteristics when a nickel-metal hydride battery with low remaining battery power is used, and it can be seen that the charging time is slightly longer than that of the solid line graph 701.

[0066] The dashed-dotted line graph 703 shows the charging characteristics when an alkaline battery with sufficient remaining battery power is used, and it can be seen that the charging time is slightly longer than that of the solid-line graph 701. The dashed-two-dot line graph 704 shows the charging characteristics when an alkaline battery with a low remaining battery power is used, and it can be seen that the charging time up to the maximum voltage value of 330 V is significantly longer than that of the other graphs 701 to 703.

[0067] Generally, alkaline batteries have a higher internal resistance than nickel-metal hydride batteries. Therefore, when charging the main capacitor 102d, alkaline batteries are more likely to heat up than nickel-metal hydride batteries. Furthermore, the charging time for alkaline batteries with low remaining charge is longer, and the main capacitor 102d continues to generate heat while charging. For example, with an alkaline battery with low remaining charge, the voltage of the main capacitor 102d reaches 320V approximately seven seconds after charging begins, and heat generation continues during this period. On the other hand, with nickel-metal hydride batteries (regardless of remaining charge), the voltage of the main capacitor 102d reaches 320V approximately four seconds after charging begins. This means that the next three seconds can be used to cool the battery, compared to alkaline batteries with low remaining charge. In other words, when alkaline batteries with low remaining charge are used, the state in which the battery temperature is likely to rise during charging continues for a longer period. The same can be said about the time it takes for the voltage of the main capacitor 102d to reach 270V, at which point light can be emitted; if alkaline batteries with low remaining capacity are continuously charged up to 270V, there is a risk that the battery temperature will rise.

[0068] Therefore, when a new alkaline battery is used for the battery 200, heat generation is not large at the beginning of use, but as the number of times light is emitted increases and the remaining charge decreases, the temperature tends to rise due to charging of the main capacitor 102d, and it is therefore necessary to suppress the temperature rise. The first and second gradient determination processes in S305 are executed to suppress the temperature rise of the battery 200 due to charging of the main capacitor 102d, in other words, to cool the battery by providing a period during which charging is not performed.

[0069] Next, a description will be given of the differences in charging characteristics in the graphs showing the charging characteristics for each battery in Fig. 7. Fig. 8 is a partially enlarged view of graphs 701 to 704 shown in Fig. 7.

[0070] Comparing the gradients of graphs 701 to 704 when the voltage of main capacitor 102d rises from 280 V to 300 V, the three types of batteries except for the alkaline battery with low remaining capacity have similar gradients, but the gradient of the alkaline battery with low remaining capacity is smaller than the other three types. The same can be said for the gradient when the voltage charged to main capacitor 102d rises from 300 V to 320 V.

[0071] It can also be seen that the voltage gradient when the voltage of the main capacitor 102d increases varies depending on the voltage range (for example, the range of 280V to 300V and the range of 300V to 320V) in one graph (for the same battery). It can also be seen that the voltage gradient of an alkaline battery with a low remaining charge is smaller than that of other batteries in both the range of 280V to 300V and the range of 300V to 320V.

[0072] As described above, the voltage rise curve as charging of the main capacitor 102d follows a different locus depending on the type of battery used and the remaining charge. Therefore, in this embodiment, two ranges are set: 280V to 300V and 300V to 320V, and a threshold value is set for comparison with the voltage gradient ΔAD for each range. Next, the relationship between the first to fourth threshold values used for comparison with the voltage gradient ΔAD in the first and second gradient determination processes and the state of the battery 200 will be described.

[0073] Fig. 9 is a diagram illustrating the relationship between the type of battery used in the battery 200, the voltage of the main capacitor 102d, and the first to fourth threshold values. Graphs 701 to 704 in Fig. 9 are the same as graphs 701 to 704 in Fig. 8, and threshold lines 905 to 908 representing the first to fourth threshold values have been added to Fig. 9.

[0074] The gradient of threshold line 905 represents a first threshold and is defined by the value obtained by dividing the line by a predetermined time 905a required to increase voltage difference 905b (=20V). Similarly, the gradient of threshold line 907 represents a second threshold and is defined by the value obtained by dividing the line by a predetermined time 907a required to increase voltage difference 907b (=20V). The gradient of threshold line 906 represents a third threshold and is defined by the value obtained by dividing the line by a predetermined time 906a required to increase voltage difference 906b (=20V). Similarly, the gradient of threshold line 908 represents a fourth threshold and is defined by the value obtained by dividing the line by a predetermined time 908a required to increase voltage difference 908b (=20V).

[0075] The gradients of the threshold lines 905 and 907 are set as follows. That is, an approximate line is determined for each of the graphs 701 to 704 within the voltage range of 280V to 300V of the main capacitor 102d. The threshold line 905 is set by determining a predetermined time 905a for a voltage difference 905b so that the line has a gradient slightly smaller than the gradients of the approximate lines of the graphs 701 to 703. The threshold line 907 is set by determining a time 907a for a voltage difference 907b so that the line has a gradient slightly larger than the gradient of the approximate line of the graph 704. The method for setting the gradients of the threshold lines 906 and 908 is similar to the method for setting the gradients of the threshold lines 905 and 907, and therefore a description thereof will be omitted.

[0076] Next, the first and second gradient determination processes in FIG. 6 will be described using a specific example, where the first threshold is 'A1', the second threshold is 'A2', the third threshold is 'A3', and the fourth threshold is 'A4'.

[0077] When the power supply of the strobe device 100 is turned on (when the power switch is turned on), the light emission process of the flowchart in Fig. 3 is started. The flow in Fig. 3 is configured so that, depending on a predetermined determination result, after the process in S314, the process returns to S302, and when the process returns to S302, the voltage value of the main capacitor 102d is acquired as the latest previous voltage value in S303.

[0078] Next, the first and second gradient determination processes in Figures 6(a) and (b) will be explained using the graph 701 as an example when the battery 200 of the strobe device 100 is a nickel-metal hydride battery with a high remaining capacity (when the remaining capacity of the nickel-metal hydride battery is large).

[0079] Assume that the voltage gradient ΔAD when a nickel-metal hydride battery with a high remaining capacity is used and the previous voltage value was greater than 280 V and equal to or less than 300 V can be represented by a straight line 901 in Figure 9. In this case, the slope of line 901 is greater than that of threshold line 905. In other words, the value of voltage gradient ΔAD is greater than the first threshold value A1 corresponding to threshold line 905. Therefore, when a nickel-metal hydride battery with a high remaining capacity is used, the determination in S602 is 'NO' and the first gradient determination process ends.

[0080] Also, assume that the voltage gradient ΔAD when a nickel-metal hydride battery with a high remaining capacity is used and the previous voltage value is greater than 300 V and equal to or less than 320 V can be represented by a straight line 902 in Figure 9. In this case, the slope of line 902 is greater than that of threshold line 906. In other words, the value of voltage gradient ΔAD is greater than the third threshold B1 corresponding to threshold line 906. Therefore, when a nickel-metal hydride battery with a high remaining capacity is used, the determination in S612 is 'NO' and the second gradient determination process ends.

[0081] In this embodiment, the same determination result is obtained when a nickel-metal hydride battery with a low remaining capacity and an alkaline battery with a high remaining capacity are used (when the nickel-metal hydride battery has a low remaining capacity and when the alkaline battery has a high remaining capacity).

[0082] Next, the first and second gradient determination processes of Figures 6(a) and (b) will be explained using graph 704 as an example when the battery 200 of the strobe device 100 is an alkaline battery with a low remaining charge (in other words, when the remaining charge of the alkaline battery is low).

[0083] Assume that the voltage gradient ΔAD when an alkaline battery with a low remaining charge is used and the previous voltage value is greater than 280 V and equal to or less than 300 V can be represented by line 903 in Figure 9. In this case, line 903 has a smaller slope than threshold line 905 and threshold line 907. In other words, the value of voltage gradient ΔAD is smaller than second threshold A2 corresponding to threshold line 907. Therefore, when an alkaline battery with a low remaining charge is used, the determination in S602 is 'YES' and the determination in S603 is also 'YES', and after the process of S605 is executed, the first gradient determination process ends.

[0084] Assume that the voltage gradient ΔAD when an alkaline battery with a low remaining charge is used and the previous voltage value is greater than 300 V and equal to or less than 320 V can be represented by a straight line 904 in Figure 9. In this case, the slope of line 904 is smaller than that of threshold line 906 and threshold line 908. In other words, the value of voltage gradient ΔAD is smaller than the fourth threshold B2 corresponding to threshold line 908. Therefore, when an alkaline battery with a low remaining charge is used, the determination in S612 is 'YES' and the determination in S613 is also 'YES', and after the process of S615 is executed, the second gradient determination process ends.

[0085] When the voltage of the main capacitor 102d is in the range of 280V to 320V, the charging characteristics of an alkaline battery with a high remaining capacity (graph 703) are very similar to the charging characteristics of a nickel-metal hydride battery with a high remaining capacity (graph 701). However, while nickel-metal hydride batteries exhibit only a small decrease in charging performance as the remaining capacity decreases, alkaline batteries exhibit a significant decrease in charging performance as the remaining capacity decreases. Therefore, when a new alkaline battery (with a high remaining capacity) is used, the determinations in S602 and S612 are both 'NO' at the beginning of use, but as the number of flashes increases and the remaining capacity decreases, the determinations in S602 and S612 become 'YES'. This indicates that the time required for charging is increasing, and therefore the heat generation time due to charging is also increasing, as explained with reference to FIG. 7. Therefore, a waiting time for charging completion is initiated after the next flash operation, and measures are taken to suppress the temperature rise of the alkaline battery. Thus, if the voltage gradient ΔAD is equal to or less than the first threshold A1 or the third threshold A3, but is greater than the second threshold A2 or the fourth threshold B2 (NO in S603 and S613), a charging completion waiting time is generated after the next light-emitting operation.

[0086] If the remaining capacity of the alkaline battery drops further, the determination results in S603 and S613 will be 'YES', a charging completion wait time will be initiated, and a warning will be issued. In light of this situation, the warnings issued in S605 and S615 inform the user that the battery temperature is likely to rise and that the remaining capacity of the battery is low.

[0087] The charging completion waiting time of each of S604 and S605 may be gradually extended depending on whether the voltage gradient ΔAD is between the first threshold A1 and the second threshold A2 or below the second threshold A2. The same can be done for the charging completion waiting time of each of S614 and S615. This makes it easier to grasp the state of battery 200 when lighting device 100 is continuously emitting light.

[0088] From the perspective of suppressing the temperature rise of the battery, the first and second gradient determination processes are not necessary for nickel-metal hydride batteries. However, since it is not easy to determine whether the battery being used is an alkaline battery or a nickel-metal hydride battery, in this embodiment, the first and second gradient determination processes are performed regardless of the type of battery 200.

[0089] As explained above, graphs 701-704 showing the charging characteristics of the main capacitor 102d, as shown in FIG. 7, draw different curves (loci) similar to quadratic curves depending on the type and remaining charge of the battery. Therefore, in this embodiment, multiple ranges are defined for the voltage of the main capacitor 102d, separated by a predetermined potential width, and a first gradient determination process or a second gradient determination process is performed depending on which range the previous voltage value belongs to. In this process, different thresholds are used for determining the voltage gradient ΔAD based on the previous voltage value and the current voltage value in the first gradient determination process and the second gradient determination process. This improves the accuracy of the gradient determination. In this embodiment, two ranges are defined for the voltage of the main capacitor 102d, but three or more ranges may be used.

[0090] To further improve the accuracy of the gradient determination process, the voltage of the main capacitor 102d may be divided into more ranges, a threshold may be set for each range, and the magnitude relationship with the voltage gradient ΔAD may be determined. Alternatively, a polynomial representing the threshold may be created based on the voltage curve of the main capacitor 102d, which changes depending on the capacity of the battery 200 expected to be used, and a threshold corresponding to the detected current voltage value may be determined from the polynomial. In this case, there is no need to set a range for the voltage of the main capacitor 102d.

[0091] In this embodiment, the first and second gradient determination processes are performed when the previous voltage value of the main capacitor 102d is in the range of 280 V to 320 V, but the determination processes may be performed when the previous voltage value is any voltage greater than 0 V. This is because, for example, if the minimum voltage value at which charging is determined to be complete is 300 V, and light emission is performed continuously the moment the voltage reaches 300 V, the gradient determination processes may not be performed correctly.

[0092] As described above, according to this embodiment, in the light emission control of the strobe device 100, when the battery 200 is not in a state where it is likely to generate heat, light can be emitted without providing an unnecessary waiting time for charging to complete. On the other hand, when the battery 200 is in a state where it is likely to generate heat, a temperature rise in the battery 200 can be suppressed by providing a waiting time for charging to complete. This makes it possible to protect the strobe device 100 from heat generation by the battery 200, and also makes it possible to avoid limiting (reducing) the number of flashes more than necessary even when continuous flashes are being performed.

[0093] Furthermore, according to this embodiment, since it is possible to limit light emission without stopping the charging circuit, it is possible to avoid complicating the control flow. Furthermore, one method of suppressing the temperature rise of the battery 200 is to provide a thermistor in the charging circuit to suppress current, but thermistors have large variations in resistance to temperature between components, which makes them prone to individual differences between strobe devices. In contrast, the above embodiment uses gradient judgment (control), so individual differences between strobe devices do not occur.

[0094] When continuous light emission is performed at a low light intensity, the voltage of the main capacitor 102d increases or decreases within a certain range, but even in this case, it is possible to determine whether the battery 200 is in a state where it is likely to generate heat for each light emission at a low light intensity. If a warning is issued in S605 or S615, this indicates that the remaining charge of the alkaline battery being used is low, making it easier for the user to determine when to replace the battery 200, etc.

[0095] Finally, a modification of the above embodiment will be described. For example, the processing order in the flowchart shown in the above embodiment is merely an example, and the processing order may be changed if no inconvenience occurs.

[0096] For example, in the above embodiment, the voltage gradient ΔAD is calculated from the previous voltage value and the current voltage value. Alternatively, the timer circuit included in the FPU 101 may measure the elapsed time from when the voltage of the main capacitor 102d reaches 280 V to when it reaches 300 V, and the voltage difference of 20 V may be divided by the elapsed time, and the resulting value may be used as the voltage gradient AD in the first gradient determination process. Similarly, the timer circuit included in the FPU 101 may measure the elapsed time from when the voltage of the main capacitor 102d reaches 300 V to when it reaches 320 V, and the voltage difference of 20 V may be divided by the elapsed time, and the resulting value may be used as the voltage gradient AD in the second gradient determination process. The processing content of S303 and S305 is changed to match this processing content.

[0097] In the above embodiment, the charging completion wait time is immediately initiated when the voltage gradient ΔAD becomes equal to or less than the first threshold or the third threshold. Alternatively, the charging completion wait time may be initiated only after a predetermined number of consecutive determinations that the voltage gradient ΔAD is equal to or less than the first threshold or the third threshold, and subsequently initiated depending on the determination results that the voltage gradient ΔAD is equal to or less than the first threshold or the third threshold. Furthermore, if a thermometer is provided at a predetermined position inside the strobe device 100 (e.g., the light-emitting unit 100b), the first and second gradient determination processes may be initiated when the temperature indicated by the thermometer exceeds a predetermined temperature. The first and second gradient determination processes may be executed based on the number of flashes or the elapsed time since the strobe device 100 was turned on.

[0098] In the above embodiment, the maximum voltage value of the main capacitor 102d is set to 330V. In this case, however, there is a voltage range in which the voltage of the main capacitor 102d changes (increases or decreases) due to discharging and intermittent charging after reaching the maximum voltage value of 330V. Therefore, since the battery 200 is not constantly charging within this voltage range, it may be determined that the battery 200 is not in a state where it generates heat, and the first and second gradient determination processes may not be performed. This reduces the load on the FPU 101 during the light emission control process of FIG. 3.

[0099] The disclosure of this embodiment includes the following configurations and methods. (Configuration 1) A lighting device comprising: a light source; a capacitor for storing energy for emitting light from the light source; charging means for charging the capacitor using a battery; detection means for detecting the voltage of the capacitor; and control means for controlling the light-emitting operation of the light source based on the amount of change in the voltage of the capacitor. (Configuration 2) The lighting device described in Configuration 1, wherein the control means compares the amount of change with a predetermined first threshold, and if the amount of change is equal to or less than the first threshold, waits for a predetermined waiting time after the next time the light source is turned on to determine whether charging of the capacitor has been completed. (Configuration 3) The lighting device according to Configuration 2, wherein the control means compares the amount of change with a second threshold value that is predetermined as a value smaller than the first threshold value, and when the amount of change is equal to or less than the second threshold value, sets the waiting time and issues a warning. (Configuration 4) The lighting device according to Configuration 3 is characterized in that it includes a setting means for setting a plurality of ranges in which the voltage of the capacitor is divided by a predetermined potential width, and for setting the first threshold value and the second threshold value for each of the plurality of ranges, and the control means compares the amount of change with the first threshold value and the second threshold value set for a range among the plurality of ranges to which the voltage of the capacitor belongs. (Configuration 5) The lighting device according to configuration 4, wherein the plurality of ranges are set between a minimum voltage value at which the light source can emit light and a maximum voltage value of the capacitor. (Configuration 6) The lighting device according to any one of configurations 2 to 5, wherein the control means, when the amount of change is greater than the first threshold, determines whether charging of the capacitor is completed after next causing the light source to emit light without waiting for the waiting time to elapse. (Configuration 7) The lighting device according to any one of configurations 2 to 6, wherein the control means generates the waiting time only when the amount of change is determined to be equal to or less than the first threshold value a predetermined number of times in succession. (Configuration 8) The lighting device according to any one of configurations 1 to 7, wherein a thermometer is provided at a predetermined position inside the lighting device, and the control means controls charging of the capacitor based on the amount of change in the voltage of the capacitor when the temperature indicated by the thermometer exceeds a predetermined temperature. (Configuration 9) A program that causes a computer to function as a control means for the lighting device according to any one of configurations 1 to 8. (Method 1) A method for controlling a lighting device, comprising the steps of: determining a change in voltage of a capacitor that stores energy for illuminating a light source when the capacitor is charged by a battery; comparing the change with a predetermined first threshold; and, if the change is equal to or less than the first threshold, waiting for a predetermined waiting time after illuminating the light source next time to determine whether charging of the capacitor is complete.

[0100] While the present invention has been described in detail above based on preferred embodiments thereof, the present invention is not limited to these specific embodiments, and various modifications within the scope of the gist of the present invention are also included in the present invention. For example, the processing order in the flowchart shown in the above embodiment is merely an example, and the processing order may be changed if no inconvenience occurs.

[0101] The present invention can also be realized by supplying a program that realizes one or more functions of the above-described embodiments to a system or device via a network or a storage medium, and having one or more processors in the computer of the system or device read and execute the program. It can also be realized by a circuit (e.g., ASIC) that realizes one or more functions. [Explanation of symbols]

[0102] 100 Strobe Device 100b Light-emitting part 101 FPU (microcomputer) 102a Booster section 102d Main capacitor 104 Discharge tube 114 Display Department 200 batteries

Claims

1. A light source and a capacitor for storing energy to cause the light source to emit light; charging means for charging the capacitor with a battery; a detection means for detecting the voltage of the capacitor; and a control means for controlling the light emitting operation of the light source based on the amount of change in the voltage of the capacitor.

2. 2. The lighting device according to claim 1, wherein the control means compares the amount of change with a predetermined first threshold value, and when the amount of change is equal to or less than the first threshold value, waits for a predetermined waiting time to elapse after the next time the light source is turned on, and then determines whether charging of the capacitor is completed.

3. 3. The lighting device according to claim 2, wherein the control means compares the amount of change with a second threshold value that is predetermined as a value smaller than the first threshold value, and when the amount of change is equal to or less than the second threshold value, sets the waiting time and issues a warning.

4. a setting unit for setting a plurality of ranges by dividing the voltage of the capacitor by a predetermined potential width, and for setting the first threshold value and the second threshold value for each of the plurality of ranges; 4. The lighting device according to claim 3, wherein the control means compares the amount of change with the first threshold value and the second threshold value set for a range to which the voltage of the capacitor belongs among the plurality of ranges.

5. 5. The lighting device according to claim 4, wherein the plurality of ranges are provided between a minimum voltage value at which the light source can emit light and a maximum voltage value of the capacitor.

6. 4. The lighting device according to claim 2, wherein the control means determines whether charging of the capacitor is completed after the next time the light source is turned on without waiting for the waiting time to elapse if the amount of change is greater than the first threshold value.

7. 4. The lighting device according to claim 2, wherein the control means starts the standby time only when it is determined that the amount of change is equal to or less than the first threshold value a predetermined number of times in succession.

8. a thermometer is provided at a predetermined position inside the lighting device; 3. The lighting device according to claim 1, wherein the control means controls the charging of the capacitor based on the amount of change in the voltage of the capacitor when the temperature indicated by the thermometer exceeds a predetermined temperature.

9. A method for controlling a lighting device, comprising: a step of determining a change in voltage of a capacitor that stores energy for emitting light from a light source when the capacitor is charged by a battery; comparing the amount of change with a predetermined first threshold; and if the amount of change is equal to or less than the first threshold, next emitting light from the light source and then waiting for a predetermined waiting time to elapse, determining whether charging of the capacitor is complete.

10. A program that causes a computer to function as a control means for the lighting device according to claim 1.

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