JP2013003438A - Image pickup apparatus, control method thereof, and control program thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform an optimal lighting control while suppressing the elongation of a release time lag.SOLUTION: An image pickup apparatus controls at least one of pre-light-emitting timing and read-out timing so as to read image data from an image pickup element 204 in a period when the pre-light-emission is performed by a light-emitting part 214; and determines information related to an amount of light emission when causing the light-emitting part 214 to emit light in a full scale on the basis of at least one of the plurality of pieces of image data whose exposure time is overlapped with the period when performing the pre-light-emission.

Description

  The present invention relates to an imaging apparatus that includes a light emitting unit such as a strobe and performs a pre-light emission (preliminary light emission) operation for light control before actual photographing, a control method thereof, and a control program.

  In general, in an imaging apparatus equipped with an illumination device such as a strobe, for example, when the brightness of a subject is not sufficient, it is necessary to adjust the light emission amount by the light emitting means in order to make the brightness of the subject appropriate. When adjusting the amount of light emitted by the light emitting means, first, a so-called pre-light emission operation is performed before actual photographing, and the reflected light from the subject is measured. Then, based on the measurement result, the optimum light emission amount at the time of actual photographing is determined.

  For example, there is one in which first pre-emission is performed and the brightness of the subject is measured, and then second pre-emission is performed (see Patent Document 1). Here, in the second pre-emission, the light-receiving sensitivity of the image pickup device such as a CCD is set to be different from that in the first pre-emission according to the distance between the subject and the imaging device. As a result, even if the distance from the imaging device to the subject is short and the dimming is over during the first pre-emission, the dimming is over if the light receiving sensitivity of the image sensor is lowered by the second pre-emission. Can be prevented.

  Similarly, even if the distance from the imaging device to the subject is far and the light is under dimming as a result of the first pre-emission, if the light receiving sensitivity of the image sensor is increased by the second pre-emission, the dimming under can be prevented. Can do. Note that “light control over” refers to receiving a light amount exceeding the upper limit of the dynamic range of the image sensor, and “light control under” refers to receiving a light amount below the lower limit of the dynamic range of the image sensor.

  As described above, the optimum light emission amount can be determined by performing pre-light emission twice.

JP 2009-290510 A

  However, in the technique described in Patent Document 1, it is necessary to perform pre-emission twice in order to perform dimming. For this reason, the release time lag from when the operator inputs the release until the actual shooting is started becomes long. Furthermore, the amount of light emission during the actual photographing is inevitably reduced because of the pre-light emission twice. In such a case, the electric energy consumed in the pre-light emission may need to be replenished before the actual photographing (that is, light emission).

  In view of the above, an object of the present invention is to suppress an increase in the release time lag and perform optimal light control.

  In order to achieve the above object, an imaging apparatus according to the present invention is an imaging apparatus that pre-emits an illuminating device before main light emission in order to determine a light emission amount when the illuminating device performs main light emission. An imaging unit that captures an image; a readout unit that reads out image data relating to a subject imaged from the imaging unit; and the illumination unit so that the readout unit performs readout during a period in which pre-light emission is performed by the illumination device. Based on control means for controlling at least one of the pre-light emission timing of the apparatus and the read timing of the reading means, and at least one of a plurality of image data whose exposure period overlaps with the period during which pre-light emission is performed by the illumination device And determining means for determining information relating to the amount of light emitted when the lighting device performs main light emission. That.

  In order to achieve the above object, a control method according to the present invention includes an imaging unit that captures an image of a subject, and a reading unit that reads out image data relating to the subject imaged from the imaging unit. An image pickup apparatus control method for pre-light-emitting the illuminating device before the main light emission in order to determine a light emission amount at the time of main light emission, wherein the reading unit performs the pre-light emission in a period during which pre-light emission is performed by the lighting device. A control step for controlling at least one of the pre-light emission timing of the lighting device and the read timing of the reading means so that the reading is performed, and a plurality of exposure periods overlapping with a period during which pre-light emission is performed by the lighting device A decision to determine information relating to the amount of light emitted when the illuminating device performs main light emission based on at least one of the image data of And having a step, the.

  In order to achieve the above object, a control program according to the present invention includes an imaging unit that images a subject, and a reading unit that reads out image data relating to the subject captured from the imaging unit. A control program used in an imaging apparatus that pre-emits the illumination device before main emission to determine the amount of light emitted when the main emission is performed, and the pre-emission is performed by the illumination device on a computer included in the imaging device. A control step for controlling at least one of a pre-light emission timing of the illumination device and a read timing of the read device so that reading by the reading device is performed during a period during which the reading device is performing; and an exposure period is pre-light emission by the illumination device Based on at least one of a plurality of image data overlapping with a period in which A determining step of determining information relating to light emission amount at the time of the main light emission of the illumination device, characterized in that to the execution.

  According to the present invention, it is possible to suppress the increase in the release time lag and perform optimal light control.

It is a block diagram showing an example of an imaging device by a 1st embodiment of the present invention. It is a figure which shows an example of a structure of the light emission part shown in FIG. It is a figure for demonstrating the relationship between the light emission time in the imaging device shown in FIG. FIG. 4 is a diagram for explaining an example of the relationship between the luminance and the number of pixels of an image obtained as a result of the pre-flash photographing described in FIG. 3, and (a) shows the relationship between the luminance and the number of pixels in the first field. FIG. 5B is a diagram showing the relationship between the luminance and the number of pixels in the second field, and FIG. 5C is a diagram showing the relationship between the total number of pixels in the first and second fields and the luminance. It is a figure for demonstrating the other example of the relationship between the brightness | luminance of an image obtained as a result of the pre flash photography demonstrated in FIG. 3, and the number of pixels, (a) is the brightness | luminance in the 1st field, and the number of pixels. FIG. 4B is a diagram showing the relationship between the luminance and the number of pixels in the second field, and FIG. 4C is a diagram showing the relationship between the total number of pixels in the first and second fields and the luminance. . It is a figure which shows an example of the light emission part used with the imaging device by the 2nd Embodiment of this invention. It is a figure for demonstrating an example of the relationship between the light emission time at the time of using the light emission part shown in FIG. 6, and emitted light quantity. It is a figure for demonstrating the other example of the relationship between the light emission time at the time of using the light emission part shown in FIG. 6, and emitted light quantity.

  Hereinafter, an imaging device according to an embodiment of the present invention will be described with reference to the drawings.

[First Embodiment]
FIG. 1 is a block diagram illustrating an example of an imaging apparatus according to the first embodiment of the present invention.

  In FIG. 1, the illustrated imaging apparatus is a so-called digital camera. The digital camera includes a lens 201, a diaphragm / shutter 202, and an image sensor (for example, a CCD) 204. The diaphragm / shutter 202 shields the image sensor 204. When the diaphragm / shutter 202 is opened, a subject image (optical image) is formed on the image sensor 204 via the lens 201. Under the control of the CPU 207, the driving unit 203 drives the lens 201 along the optical axis and adjusts the aperture for adjusting the focal length.

  The image sensor 204 outputs image data (analog signal) corresponding to the subject image. This analog signal is supplied to a CDS (correlated double sampling) and A / D converter 205, where sampling and A / D conversion are performed and output as a digital signal. A timing generator (TG) 206 outputs a timing signal for driving the image sensor 204.

  The output of the CDS and A / D converter 205 is given to the CPU 207. A CPU 207 controls the entire digital camera. A ROM 209, a RAM 210, a display unit 212, and a recording unit 213 are connected to the CPU 207 via a system bus 208. Further, the CPU 207 is connected with an operation unit 211 and a light emitting unit 214 as an illumination device such as a strobe.

  The ROM 209 stores a program (internal program) for controlling the digital camera, and the RAM 210 temporarily stores image data processed by the CPU 207. The operation unit 211 is operated by an operator, and the instruction is given to the CPU 207. Various information from the CPU 207 is displayed on the operation unit 211.

  The CPU 207 performs various processes on the image data. The CPU 207 displays an image corresponding to the image data on the display unit 212. The CPU 207 controls the recording unit 213 to store the image data in a recording medium (not shown) such as a memory card. Further, the CPU 207 performs light emission control of the light emitting unit 214 as described later.

  FIG. 2 is a diagram showing an example of the configuration of the light emitting unit 214 shown in FIG.

  In FIG. 2, in the illustrated light emitting unit 214, an Xe tube is used as a light emitter (light emitting element). The light emitting unit 214 includes a power supply terminal (power supply) 301 and a ground terminal (GND) 302, and the power supply 301 and the ground terminal are connected to a power supply unit (not shown). Further, the light emitting unit 214 includes a light emission control unit 303, a boosting transformer 305, and a backflow prevention diode 306. The light emitting unit 214 includes a smoothing capacitor 307, a main capacitor 308, a resistor 309, a capacitor 310, a trigger coil 311, an Xe tube 312, and an IGBT (Insulated Gate Bipolar Transistor) 313.

  The light emission control unit 303 performs charge / discharge control for light emission under the control of the CPU 207. The step-up transformer 305 boosts the power supply voltage to obtain a light emission voltage. A backflow prevention diode 306 and a smoothing capacitor 307 are disposed after the step-up transformer 305, and energy for Xe emission is stored in the main capacitor 308. The IGBT 313 is ON / OFF controlled by the light emission control unit 303, and light emission of the Xe tube 312 is started by a trigger pulse generated by the trigger coil 311.

  By the way, in the imaging apparatus shown in FIG. 1, the CPU 207 captures / records a still image and reproduces the recorded image data in response to an instruction input from the operation unit 211. At the time of still image shooting, the CPU 207 sets the sensitivity of the image sensor 204 by an instruction input from the operation unit 211. Further, the CPU 207 switches light emission in the light emitting unit 214 to automatic or manual.

  Here, an operation at the time of capturing a still image in the imaging apparatus shown in FIG. 1 will be described.

  Now, when a power switch (not shown) is turned on and the still image shooting mode is selected as the shooting mode in the operation unit 211, the CPU 207 enters the still image shooting mode. That is, when the power switch is turned on, power is supplied from a power supply IC (not shown) to the CPU 207, ROM 209, RAM 210, and the like. The CPU 207 sequentially reads out the control program stored in the ROM, and initializes the RAM 210 and initializes the imaging apparatus according to the control program. Thereafter, the CPU 207 looks at the mode selection state in the operation unit 211, and shifts to the still image shooting mode if the mode selection state is the still image shooting mode.

  In the still image shooting mode, the CPU 207 initializes the TG 206, the CDS, and the A / D converter 205, and then starts driving the image sensor 204. In addition, the CPU 207 performs power-on and initialization of the display unit 212 to prepare for displaying a live image before shooting. In parallel with these processes, the CPU 207 initializes the lens driving system including the lens 201, drives the lens 201 to a predetermined initial position, and performs the initial operation of the diaphragm shutter 202.

  When the above preparation is completed, the CPU 207 shifts to a live image display operation for still image shooting. First, the CPU 207 opens the iris / shutter 202 and performs settings for live image display on the TG 206, the CDS, and the A / D converter 205. Then, the CPU 207 sends a synchronization signal having an arbitrary period to the TG 206.

  The TG 206 applies a drive signal for driving the image sensor 204 to the image sensor 204 in accordance with the synchronization signal. Image data corresponding to the optical image formed on the image sensor 204 via the lens 201 is read from the image sensor 204.

  Although not shown, the image data read from the image sensor 204 is amplified by a buffer circuit, and then the direct current component is cut by a capacitor and supplied to the CDS and A / D converter 205.

  Then, after being processed by the CPU 207, it is temporarily recorded in the RAM 210. Further, the CPU 207 performs various processes on the image data recorded in the RAM 210 to generate display image data. Then, the CPU 207 sends display image data to the display unit 212 at a predetermined timing, and displays a live image on the display unit 212 (for example, LCD).

  In the still image shooting mode, when the light emission unit 214 is allowed to emit light as a shooting condition, charging operation for the main capacitor 308 shown in FIG. 2 from the power supply unit is performed in parallel. At this time, the CPU 207 sends a charge control signal for charging the main capacitor 308 to the light emission control unit 303. The light emission control unit 303 starts driving the step-up transformer 305 in response to the charge control signal. Thus, the boosting transformer 305 boosts the power supply voltage to the light emitting voltage. Then, the main capacitor 308 is charged with the fermentation voltage.

  When the charging voltage of the main capacitor 308 increases to a sufficient voltage (that is, a predetermined voltage) (here, charging is performed for a predetermined time), the light emission control unit 303 ends the charging operation and the light emission preparation is completed. The CPU 207 is notified of the fact. Accordingly, when the CPU 207 confirms that the light emission preparation is completed, the CPU 207 shifts to a shooting standby state.

  Next, when the operator operates a release switch provided in the operation unit, a release signal indicating a still image shooting instruction is given to the CPU 207. Thereby, the CPU 207 executes a still image shooting operation by the main exposure operation and an image data generation operation accompanying the still image shooting operation.

  First, when a release signal is input, the CPU 207 interrupts the display of the live image and starts a main exposure operation for still image shooting. The CPU 207 performs AE (automatic exposure) and AF (autofocus) before exposure. That is, the CPU 207 drives the diaphragm and the lens so that the subject is appropriately exposed and focused. Also in this case, if the light emission of the light emitting unit 214 is permitted and the light quantity is insufficient as the exposure determination, the CPU 207 shifts to the flash photography. First, the CPU 207 performs a pre-flash operation for flash photography. In the pre-flash operation, first, the CPU 207 performs pre-flash settings for pre-flash shooting for the TG 206, the CDS, and the A / D converter 205. Then, after performing the pre-flash setting, the CPU 207 performs pre-flash shooting.

  This pre-flash photographing is photographing performed to determine the amount of light emitted when the light emitting unit 214 performs main light emission before main photographing. In the pre-flash shooting, the subject is shot with the light emitting unit 214 emitting light for a very short flash time. Then, information relating to the light emission amount when the main light is emitted, for example, the light emission time, is determined according to the exposure in the photographing.

  Prior to the pre-flash operation, the amount of light of the subject is not sufficient, and thus the CPU 207 cannot accurately grasp the position of the subject. Accordingly, the pre-light emission time is shorter than the main light emission time, but if the distance from the imaging device to the subject is short, the dimming is over in the pre-light emission operation. If the light control is over, the CPU 207 may not accurately know the distance to the subject. For this reason, the CPU 207 controls the light emission time so that the exposure time at the time of pre-light emission extends over the exposure timings of a plurality of field exposure periods instead of within the single field exposure period.

  FIG. 3 is a diagram for explaining the relationship between the light emission time and the light emission amount in the imaging apparatus shown in FIG.

  In FIG. 3, at least one of the pre-light emission timing and the read timing is controlled so that reading is performed from the image sensor 204 during the pre-light emission period. That is, a plurality of image data whose exposure period overlaps with the period during which pre-emission is performed is read out. Here, the image data (analog signal) read out first from the image sensor 204 is referred to as first image data, and the image read out subsequently is referred to as second image data. In the example shown in the figure, a reading pulse 103 for driving the image sensor 204 and reading the first image data is applied to the image sensor 204 at substantially the center in the light emission period of the light emitting unit 214.

  As shown in the figure, since the readout pulse 103 is applied for a predetermined application period (1H period), the pre-emission time (that is, the time for turning on the emission enable signal) is longer than the application period of the readout pulse 103. Time is selected. Here, the 1H period (application period) is 50 μs, and the light emission period is 100 μs including the application period.

  Note that the relationship between the light emission period and the application period (that is, the readout time) can be arbitrarily determined. For example, in the first field exposure period (simply referred to as the first field), light emission is started 30 μs before the read pulse 103 is applied. In the second field exposure period (simply referred to as the second field), light emission is stopped 20 μs after the application of the readout pulse 103 is completed. Thus, if the light emission time is changed in the first field and the second field, a plurality of image data having different pre-light emission amounts in the exposure period can be obtained.

  At the time of pre-emission, the CPU 207 first starts exposure in the first field. After a predetermined time has elapsed from the start of exposure, the CPU 207 turns on a light emission enable signal (light emission control signal) to be given to the light emitting unit 214 and starts a light emission operation. When the light emission enable signal is turned on, the light emission control unit 303 amplifies the light emission enable signal by an internal buffer (not shown) and applies it to the gate of the IGBT 313.

  The IGBT 313 is turned on by applying a light emission enable signal. As a result, a trigger pulse is applied to the trigger coil 311, and this trigger pulse is converted into a pulse of several kV by the trigger coil 311 and applied to the Xe tube 312.

  When a trigger pulse is applied to the Xe tube 312, electrons are generated by the discharge generated in the Xe tube 312. Then, due to the generation of electrons, the charge of the main capacitor 308 causes arc discharge in the Xe tube 312 and light emission is started. After a predetermined time has elapsed from the start of light emission, the TG 216 applies a readout pulse to the image sensor 204 under the control of the CPU 207. Up to this point, the electric charge accumulated in the image sensor 204 is moved to the vertical CCD by the photoelectric effect.

  After application of the readout pulse, exposure of the captured image in the second field is started by the image sensor 204. The TG 216 sequentially reads out the charge of the vertical CCD under the control of the CPU 207 and sends it as an analog signal from the image sensor 204 to the CDS and A / D converter 205. The CDS and A / D converter 205 converts the analog signal into a digital signal and sends it to the CPU 207 as the first pre-emission image data.

  At this time, that is, until the first pre-flash image data is sent, the CPU 207 turns off the flash enable signal. In the example shown in the figure, this ends the light emission operation of 100 μs.

  Subsequently, in preparation for the main exposure operation, the CPU 207 controls the light emitting unit 214 to charge the main capacitor 308 to replenish the charge lost by the pre-light emission operation. After a predetermined time has elapsed from the start of exposure in the second field, the CPU 207 controls the drive unit 203 to close the aperture / shutter 202 (stop of exposure), thereby ending exposure in the second field. Then, after the image reading in the first field is completed, the TG 206 reads out the charges accumulated in the second field from the image sensor 204 under the control of the CPU 207. As a result, the second pre-flash image data is sent to the CPU 207.

  The CPU 207 confirms the exposure state of the subject according to the image data obtained by the pre-flash photography. Then, the CPU 207 determines the light emission time for the main light emission according to the confirmation result.

  FIG. 4 is a diagram for explaining an example of the relationship between the luminance of the image data obtained as a result of the pre-flash photography described in FIG. 3 and the number of pixels. FIG. 4A is a diagram showing the relationship between the luminance and the number of pixels in the first field, and FIG. 4B is a diagram showing the relationship between the luminance and the number of pixels in the second field. FIG. 4C shows the relationship between the total number of pixels in the first and second fields and the luminance. In FIG. 4, the pre-light emission period in the first field is 40 μs, and the pre-light emission period in the second field is 60 μs. In the example shown in FIG. 4, since the subject exists at a position away from the imaging device, the number of pixels in the portion that is the subject is small.

  For example, the CPU 207 detects the exposure state of the portion that is the subject based on the three luminance-pixel number distributions shown in FIG. For example, the CPU 207 obtains the difference between the number of pixels of the portion that is the subject and the number of pixels at the appropriate exposure. The ROM 209 shown in FIG. 1 stores a lookup table that defines the relationship between the difference and the light emission time. The CPU 207 searches the lookup table according to the difference and determines the light emission time based on the search result.

  FIG. 5 is a diagram for explaining another example of the relationship between the luminance of the image data obtained as a result of the pre-flash photography described in FIG. 3 and the number of pixels. FIG. 5A is a diagram showing the relationship between the luminance and the number of pixels in the first field, and FIG. 5B is a diagram showing the relationship between the luminance and the number of pixels in the second field. FIG. 5C shows the relationship between the total number of pixels in the first and second fields and the luminance. In FIG. 5, the pre-emission period in the first field is 40 μs, and the pre-emission period in the second field is 60 μs. In the example illustrated in FIG. 5, the subject is present at a position close to the imaging device.

  In FIG. 5C, which shows the result of adding the number of pixels in the first field shown in FIG. 5A and the number of pixels in the second field shown in FIG. 5B, many pixels are saturated in luminance. It is in a state. For this reason, it is difficult to estimate an appropriate exposure value in a saturated pixel from the distribution shown in FIG.

  Here, in the distribution shown in FIG. 5C, when the number of saturated pixels (the number of saturated pixels) is larger than a predetermined threshold, the CPU 207 stops using the distribution, that is, image data. Then, the CPU 207 shifts to analysis of image data having the shortest exposure period after FIG. That is, the CPU 207 analyzes the image data (FIG. 5B) in the second field whose exposure time is 60 μs.

  However, even in the distribution of FIG. 5B, when many pixels are close to saturation and the number of pixels in saturation is greater than a predetermined threshold, the CPU 207 estimates proper exposure from image data in the second field. Judge that it is not possible. The CPU 207 does not use the image data in the second field.

  As a result, the CPU 207 proceeds to analysis of the image data (FIG. 5A) in the first field with the shortest exposure time. Even in the image data in the first field, although there are saturated pixels (saturated pixels), there are fewer than saturated pixels in the second field. When the CPU 207 determines that the number of pixels in the saturated state (the number of saturated pixels) in the image data in the first field is equal to or less than the threshold value, the CPU 207 detects the exposure state of the portion that is the subject from the image data in the first field. Then, as described above, the CPU 207 refers to the look-up table according to the difference and determines the light emission time for the main exposure.

  Even in the image data in the first field with the shortest exposure time, if the number of saturated pixels is larger than the threshold value, the CPU 207 determines that the subject is very close to the imaging apparatus. Then, the CPU 207 estimates the distance to the subject according to the number of saturated pixels in the first field, and determines the light emission time (main exposure light emission time) at the time of main exposure.

  As described above, when shooting by the pre-flash operation is completed and the light emission time for the main exposure is determined, the CPU 207 shifts to the main shooting state. The CPU 207 controls the light emitting unit 214 to charge the main capacitor 308 with the charge consumed by the pre-light emission. Thereafter, the CPU 207 performs a main exposure read setting for performing the main exposure read to the TG 206, the CDS, and the A / D converter 205, and gives a synchronization signal to the TG 206 to start the main exposure operation.

  As a result, the TG 206 starts driving for the main exposure for the image sensor 204. On the other hand, the CPU 207 opens the diaphragm shutter 202 and starts exposure of the image sensor 204. Further, the CPU 207 starts the light emitting operation by the light emitting unit 214.

  When the light emission operation is started, the CPU 207 turns on the light emission enable signal. As a result, the light emission control unit 303 turns on the IGBT 313. When the IGBT 313 is turned on, the Xe tube 312 starts to emit light as described above.

  When the main exposure light emission time has elapsed, the CPU 207 turns off the light emission enable signal and ends the light emission operation by the light emitting unit 214. Further, after a predetermined exposure time has elapsed, the CPU 207 closes the aperture / shutter 202 to end the exposure, and proceeds to a reading operation.

  Based on the synchronization signal supplied from the CPU 207, the TG 206 drives the image sensor 204 and reads out image data relating to the imaged subject as an analog signal divided into a plurality of fields. Image data read from the image sensor 204 is sent to the CDS and A / D converter 205. The CDS and A / D converter 205 performs sampling with reference to a predetermined potential and performs gain processing to convert an analog signal into a digital signal. As described above, the CPU 207 temporarily records this digital signal in the RAM 210.

  After reading out all charges (that is, pixel signals) of the image sensor 204 and recording them as image data in the RAM 210, the CPU 207 sequentially reads out the image data recorded in the RAM 210 for each field so as to be in the original frame state. Then, the CPU 207 performs filter processing and conversion processing in the read order to generate recording main exposure image data (hereinafter simply referred to as recording image data). Further, the CPU 207 performs compression processing or the like on the recording image data, and then records it again in the RAM 210.

  Subsequently, the CPU 207 converts the number of pixels for display of the recording image data and generates display image data. At this time, the CPU 207 sequentially reads the image data for recording from the RAM 210 and performs filter processing and resampling processing. Then, the CPU 207 generates display image data in accordance with the display pixel array and the number of pixels of the display unit 212. The CPU 207 records the display image data in a region area of the RAM 210 different from the region where the recording image data is stored. Thereafter, the CPU 207 sequentially sends display image data to the display unit 212 and displays an image corresponding to the display image data on the display unit 212 for a predetermined time.

  Next, the CPU 207 converts the recording image data into image data in a predetermined format (format), and adds additional data such as date and time to generate an image file. The CPU 207 controls the recording unit 213 to record the image file on the recording medium.

  When the recording of the image file ends, the CPU 207 ends the main shooting operation, shifts to the live image display operation again, and starts a charging process for the main capacitor 308 as the next shooting preparation.

  As described above, in the first embodiment, when shooting is performed by causing the light emitting unit 214 to emit light, the readout timing of the image sensor 204 and the light emitting unit are set so that the light emission period spans a plurality of fields during pre-flash shooting. At least one of the pre-light emission timings 214 is controlled. Therefore, even when the subject exists near the imaging device, it is possible to select the image data with few saturated pixels and determine the light emission time during the main exposure. As a result, it is possible to increase the light control accuracy of the light emitting unit 214 during the actual photographing.

[Second Embodiment]
FIG. 6 is a diagram illustrating an example of a light emitting unit used in the imaging apparatus according to the second embodiment of the present invention. The configuration of the imaging apparatus according to the second embodiment is the same as that of the imaging apparatus shown in FIG. 6 is different from the light emitting unit 214 shown in FIG. 2 in the configuration thereof, and therefore, here, the light emitting unit 601 is shown.

  A light emitting unit 601 illustrated in FIG. 6 uses an LED 610 as a light emitter (light emitting element). The light emitting unit 601 has a power supply terminal (power supply) 602 and a ground terminal (GND) 603, and these power supplies 602 are connected to a power supply unit (not shown). The light emitting unit 601 further includes a light emission control unit 608, a capacitor 604, an inductor 605, FETs 606 and 607, a resistor 611, and a main capacitor 609.

  In the illustrated light emitting unit 601, the power supply voltage is boosted to the charging voltage by the inductor 605 and the capacitor 604, the charging voltage is applied to the main capacitor 609, and charges are accumulated in the main capacitor 609. The light emission control unit 608 controls the FETs 606 and 607 on / off under the control of the CPU 207 to charge the main capacitor 609. Then, the LED 610 emits light by the charge accumulated in the main capacitor 609.

  As described in the first embodiment, at the time of shooting, live image display is first performed, and if light emission by the light emitting unit 601 is permitted, the CPU 207 starts charging the main capacitor 609. At this time, the CPU 207 outputs a charge control signal to the light emission control unit 608. As a result, the light emission control unit 608 turns on the FET 607 and charges the main capacitor 609.

  Since the LED 610 is used as the light emitter in the light emitting unit 601 shown in FIG. 6, a step-up transformer that is necessary when an Xe tube is used is unnecessary. The inductor 605 only needs to boost the power supply voltage (input voltage) to Vf (forward voltage drop) of the LED 610 or more.

  When the charging of the main capacitor 609 is completed, the CPU 207 shifts to a shooting standby state and waits for an instruction input from the operation unit 211 while displaying a live image.

  When the operator operates the operation unit for still image shooting and a release signal is input to the CPU 207, as described above, the CPU 207 performs the still image shooting operation by the main exposure operation and the still image shooting operation. An accompanying image data generation operation is executed.

  Here, as described above, the CPU 207 interrupts the display of the live image and performs AE and AF before exposure. When the CPU 207 determines that the light amount is insufficient, the CPU 207 shifts to flash photography. The CPU 207 performs pre-flash shooting for the pre-flash shooting for the TG 206, the CDS, and the A / D converter 205 for pre-flash shooting.

  Since the LED 610 is used as the light emitter in the light emitting unit 601 shown in FIG. 6, flat light emission is possible at the time of pre-light emission unlike the case of the Xe tube.

  FIG. 7 is a diagram for explaining an example of the relationship between the light emission time and the light emission amount when the light emitting unit shown in FIG. 6 is used.

  In FIG. 7, the light emission period (light emission time) of the LED 610 extends over the first and second fields. Further, as shown in the figure, the light emission times in the first and second fields are different. That is, the ratio of the light emission time is different between the first and second fields. As a result, the first and second fields have different exposure states.

  FIG. 8 is a diagram for explaining another example of the relationship between the light emission time and the amount of light emitted when the light emitting unit shown in FIG. 6 is used.

  By the way, the LED 610 can set the light emission amount more accurately than the Xe tube. For this reason, as shown in FIG. 8, the light emission amount of the LED 610 may be set to about half of the light emission amount shown in FIG. When the light emission amount is halved, the light emission time is doubled to keep the energy consumption in the pre-light emission operation constant. As a result, the energy that can be used during the main exposure is kept constant, and the residual charge of the main capacitor 609 after the pre-light emission operation is made constant so as not to affect the main exposure.

  In addition, the pre-emission amount in the exposure period before reading and the pre-emission amount in the exposure period after reading can be set to a predetermined ratio.

  The pre-light emission control and the reading operation of the image sensor 204 when using the light emitting unit 601 shown in FIG. 6 are the same as those in the first embodiment. However, when the light emitting unit 601 shown in FIG. After setting the light emission amount for pre-light emission, the light emission enable signal is turned on. Accordingly, the light emission control unit 608 applies a light emission enable signal to an internal FET (not shown) so that a current flows to the cathode side of the LED 610. Further, the light emission control unit 608 performs light emission current control by monitoring the voltage of the current limiting resistor 611.

  When the Xe tube is used as the light emitter, the CPU 207 controls only the light emission time. However, when the LED is used as the light emitter, the CPU 207 controls the light emission time and the light emission current (light emission amount). That is, when the subject is located near the imaging apparatus or when the amount of light emission is small, the CPU 207 decreases the light emission amount by reducing the light emission current. After determining the light emission amount and the light emission time, the CPU 207 proceeds to the main exposure operation. Since the processing in this exposure operation is the same as that in the first embodiment, description thereof is omitted.

  Thus, in the second embodiment, an LED is used as a light emitter, and the light emission amount and the light emission time are controlled, so that the light emission timing is such that the light emission period spans a plurality of field exposure periods during pre-light emission. To control. In addition, reading is performed from the image sensor for each field. Therefore, even when the subject is present near the imaging device, it is possible to select an image with few saturated pixels and determine the light emission time during the main exposure. As a result, it is possible to improve the light control accuracy of the light emitting unit 601 at the time of actual photographing.

  As described above, in the embodiment of the present invention, the amount of light emitted during the main exposure can be determined by one pre-light emission, so that the longest release time lag is suppressed and optimal light control is performed. Can do. Furthermore, since the light emission amount at the time of pre-light emission is controlled, the light emission amount does not decrease during the main photographing. That is, in the embodiment of the present invention, an appropriate light control amount can be determined by one pre-emission operation even in a situation where the distance from the imaging device to the subject is short.

  As is clear from the above description, in FIG. 1, the CPU 207, the CDS and A / D converter 205, and the TG 206 function as reading means. The CPU 207 functions as a control unit and a determination unit.

  As mentioned above, although this invention was demonstrated based on embodiment, this invention is not limited to these embodiment, Various forms of the range which does not deviate from the summary of this invention are also contained in this invention. .

  For example, the function of the above embodiment may be used as a control method, and this control method may be executed by the imaging apparatus. Further, a program having the functions of the above-described embodiments may be used as a control program, and the control program may be executed by a computer included in the imaging apparatus. The control program is recorded on a computer-readable recording medium, for example.

  At this time, the control method and the control program have at least a reading step, a control step, and a determination step.

  The present invention can also be realized by executing the following processing. That is, software (program) for realizing the functions of the above-described embodiments is supplied to a system or apparatus via a network or various recording media, and a computer (or CPU, MPU, etc.) of the system or apparatus reads the program. It is a process to be executed.

204 Image sensor 207 CPU
214 Light Emitting Unit 303 Light Emission Control Unit 305 Booster Transformer 306 Backflow Prevention Diode 308 Main Capacitor 311 Trigger Coil 312 Xe Tube 313 IGBT

Claims (6)

An imaging device that pre-emits the illuminating device before the main light emission in order to determine a light emission amount when the illuminating device performs main light emission,
Imaging means for imaging a subject;
Reading means for reading image data relating to the subject imaged from the imaging means;
Control means for controlling at least one of the pre-light emission timing of the illumination apparatus and the read timing of the readout means so that readout by the readout means is performed during a period in which pre-light emission is performed by the illumination apparatus;
Determining means for determining information on a light emission amount when the illumination device is caused to perform main light emission based on at least one of a plurality of image data that overlaps a period in which pre-emission is performed by the illumination device;
An imaging device comprising:   In the case where the reading unit performs reading during a period in which pre-emission is performed by the illumination device, the control unit includes the pre-emission amount of the illumination device in the exposure period before performing the reading by the reading unit and the reading unit. The at least one of a pre-light emission timing of the illumination device and a read timing of the readout unit is controlled so that a pre-light emission amount of the illumination device in an exposure period after performing readout by the method is different. The imaging apparatus according to 1.   In the case where the reading unit performs reading during a period in which pre-emission is performed by the illumination device, the control unit includes the pre-emission amount of the illumination device in the exposure period before performing the reading by the reading unit and the reading unit. Controlling at least one of the pre-light emission timing of the illumination device and the read timing of the readout means so that the pre-emission amount of the illumination device in the exposure period after reading by the above becomes a predetermined ratio. The imaging apparatus according to claim 2.   The determining unit is configured to store the illumination device based on image data in which the number of pixels in a saturated state is equal to or less than a threshold value among a plurality of image data having an exposure period overlapping with a period in which pre-emission is performed by the illumination device. The imaging apparatus according to claim 1, wherein information relating to a light emission amount at the time of light emission is determined. An imaging unit that images the subject, and a reading unit that reads out image data relating to the subject imaged from the imaging unit, and the lighting device is used to determine the amount of light emitted when the lighting device performs main light emission. A method of controlling an imaging device that performs pre-flash before light emission,
A control step of controlling at least one of the pre-light emission timing of the illumination device and the read timing of the readout means so that readout by the readout means is performed during a period in which pre-light emission is performed by the illumination device;
A determination step of determining information relating to a light emission amount when the illumination device is caused to perform main light emission based on at least one of a plurality of image data in which an exposure period overlaps with a period in which pre-emission is performed by the illumination device;
A method for controlling an imaging apparatus, comprising: An imaging unit that images the subject, and a reading unit that reads out image data relating to the subject imaged from the imaging unit, and the lighting device is used to determine the amount of light emitted when the lighting device performs main light emission. A control program used in an imaging device that pre-flashes before light emission,
In the computer provided in the imaging device,
A control step of controlling at least one of the pre-light emission timing of the illumination device and the read timing of the readout means so that readout by the readout means is performed during a period in which pre-light emission is performed by the illumination device;
A determination step of determining information relating to a light emission amount when the illumination device is caused to perform main light emission based on at least one of a plurality of image data in which an exposure period overlaps with a period in which pre-emission is performed by the illumination device;
A control program characterized by causing

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