JP2015032894A - LIGHT EMITTING CONTROL METHOD FOR LIGHTING DEVICE AND IMAGING DEVICE - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce light emission variance for each individual in an imaging apparatus comprising an illumination device.SOLUTION: A digital camera 100 comprises a stroboscope 90 that is an illumination device which emits flash light; and a nonvolatile memory 56 for storing light emission property information representing a relation between a flash light time and a light emission amount of the stroboscope. A system control part 50 of the digital camera 100 determines a light emission amount for obtaining a proper luminance with flash light emission of the stroboscope, calculates the flash light time of the stroboscope on the basis of the determined light emission amount and the light emission property information, detects an actual light emission amount in the case where main imaging is performed with flash light emission of the stroboscope for the calculated flash light time, on the basis of a luminance value that is calculated by using image data of the main imaging and corrects the light emission property information on the basis of a differential between the light emission amount determined for the main imaging and the actual light emission amount in the main imaging.

Description

  The present invention relates to an imaging device including a lighting device, and more particularly to a light emission control method for the lighting device.

  A dimming sensor is generally used to control the amount of flash emission (hereinafter abbreviated as “light emission amount”) in an imaging device such as a digital camera equipped with a lighting device that emits flash light (hereinafter referred to as “strobe device”). The method of controlling is known. The method of controlling using a light control sensor has the advantage of being able to control the amount of emitted light with relatively high accuracy, but the disadvantage is that it is expensive because the light control sensor must be mounted on the imaging device. There is.

  Further, as a method for controlling the light emission amount, a method for controlling a flash time (light emission time) is also known. Although the method for controlling the flash time can be realized at low cost, it is open loop control in which the light emission amount is not directly controlled. Therefore, in the method for controlling the flash time, the flash time-emission amount characteristic data (hereinafter referred to as the flash time-emission amount characteristic data) indicating how many microseconds (μs) the flash time should be stopped in order to cause the flash device to emit the predetermined light emission amount. (Referred to as “characteristic data”) must be held inside the imaging apparatus. Strictly speaking, this characteristic data needs to be obtained by finely changing the light emission amount for each imaging device. However, since the light emission amount by the strobe device varies for each light emission, accurate characteristic data must be obtained. In order to acquire, it is necessary to perform very many light emission. However, considering the man-hours at the production site, such data acquisition work is not realistic.

  Therefore, typical characteristic data is converted into a model curve, and for each imaging device, characteristic data is acquired by light emission of several points, and the model curve is corrected from the acquired characteristic data and held in the imaging device. Was common. However, with such a method, the accuracy of light emission control is not necessarily optimal. In view of this, there has been proposed a technique for updating the characteristic data by estimating the actual light emission amount during a flashing time from the accumulated charge amount of the main capacitor after light emission (see Patent Document 1).

JP 2003-330075 A

  However, in the technique described in Patent Document 1, the information used for the feedback of the characteristic data is the accumulated charge amount of the main capacitor, not the actually emitted light amount. The characteristic data cannot be updated. Therefore, it is difficult to make the accuracy of the updated characteristic data sufficiently high.

  An object of this invention is to provide the technique which reduces the light emission dispersion | variation for every individual | organism | solid of the imaging device provided with an illuminating device.

  An imaging apparatus according to the present invention includes a light emitting unit that emits flash light, an imaging unit, a luminance value calculating unit that calculates a luminance value of a predetermined region of image data obtained by imaging with the imaging unit, and the light emitting unit. Determining means for determining the main light emission amount, storage means for storing light emission characteristic information representing the relationship between the light emission time and the light emission amount of the light emitting means, the light emission characteristic information and the main light emission amount determined by the determining means And a calculation means for calculating a light emission time by the light emission means, and an actual light emission amount when the light emission means is flashed for the light emission time calculated by the calculation means when the flash light is emitted. Detection means for detecting based on image data obtained by imaging by the imaging means, and the light emission based on a difference between the main light emission amount determined by the determination means and the actual light emission amount detected by the detection means Characterized in that it comprises a correcting means for correcting the gender information.

  The light emission control method of the illumination device according to the present invention includes an illumination device that emits flash light, and a storage unit that stores light emission characteristic information representing a relationship between a flash time and a light emission amount of the illumination device. A light emission control method, comprising: a determination step for determining a main light emission amount of the illumination device; the light emission characteristic information stored in the storage means; and the main light emission amount determined in the determination step. A calculation step for calculating a light emission time according to the above, and an actual light emission amount when the illumination device is flashed with the light emission time calculated in the calculation step, based on the image data obtained when the flash light is emitted Based on the detection step to detect, and the difference between the actual light emission amount determined by the determination step and the actual light emission amount detected by the detection step, the storage means And having a correction step of correcting the pay said light emission characteristics information was.

  According to the present invention, it is possible to reduce the variation in light emission for each individual imaging device including the illumination device.

It is the external appearance perspective view which looked at the digital camera which concerns on embodiment of this invention from the back side. It is a block diagram which shows the structure of the digital camera of FIG. 2 is a flowchart showing a strobe shooting sequence according to the first embodiment in the digital camera of FIG. 1. It is a flowchart which shows the detail of the reflectance calculation process performed by step S311 of FIG. 6 is a flowchart showing a part of a strobe shooting sequence (determination as to whether or not to correct light emission characteristic information) according to a second embodiment of the digital camera of FIG. 1. It is a flowchart which shows the detail of a process of step S503 of FIG. It is a schematic diagram for demonstrating the content of the process of step S503 of FIG. It is a figure explaining the correction amount calculation process in step S316 of FIG.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Here, a so-called compact type digital camera (hereinafter referred to as “digital camera”) is taken up as an imaging apparatus including an illumination device.

  FIG. 1 is an external perspective view of a digital camera 100 according to an embodiment of the present invention as viewed from the back side. On the back surface of the digital camera 100, a display unit 28, a mode switch 60, an operation unit 70, and a controller wheel 73 are provided. The display unit 28 is, for example, a color liquid crystal panel, and can display various information such as an image being shot, a shot image, and shooting condition setting information. The mode change switch 60 is an operation member for switching the photographing mode. The controller wheel 73 is an operation member that can be rotated, and is used when a desired item is selected from a menu or icon displayed on the display unit 28. The operation unit 70 includes various switches, buttons, and operation members such as a touch panel provided on the display unit 28 that receive various operations from the user. In the present embodiment, the operation unit 70 is assumed to be an operation member other than the mode switch 60, the controller wheel 73, a shutter button 61 and a power switch 72 described later.

  A shutter button 61 and a power switch 72 are provided on the upper surface of the digital camera 100. Further, a terminal portion (not shown) for connecting a connection cable 111 for connecting the digital camera 100 to an external device via a connector 112 is provided on the side surface of the digital camera 100. A storage medium slot (not shown) for storing the storage medium 200 is provided on the bottom surface of the digital camera 100, and the storage medium slot can be freely opened and closed by a slot lid 202.

  The shutter button 61 is an operation member for instructing photographing, and the power switch 72 is an operation member for switching on / off the power of the digital camera 100. The connection cable 111 is used to connect the digital camera 100 to an external device (for example, an electronic device such as a personal computer or a printer), and is, for example, a USB cable. The storage medium 200 is a memory card such as an SD card.

  FIG. 2 is a block diagram showing the configuration of the digital camera 100. Among the constituent elements shown in FIG. 2, the same constituent elements as those described with reference to FIG.

  The digital camera 100 includes a shutter 101, a barrier 102, a photographing lens 103, an imaging unit 22, an A / D converter 23, an image processing unit 24, a memory control unit 15, a D / A converter 13, a display unit 28, and a memory 32. Prepare.

  The shutter 101 has a diaphragm function, and performs exposure with a predetermined exposure amount on an imaging element (image sensor) included in the imaging unit 22. The barrier 102 covers the imaging system including the photographing lens 103, the shutter 101, and the imaging unit 22, thereby preventing the imaging system from being dirty or damaged. The photographing lens 103 is a lens group including a zoom lens and a focus lens. The imaging unit 22 includes an imaging element such as a CCD sensor or a CMOS sensor that converts an optical image (photographed light beam) into an electrical signal. The A / D converter 23 converts the analog signal output from the imaging unit 22 into image data (digital data) that is a digital signal. Image data output from the A / D converter 23 is written to the memory 32 via the image processing unit 24 and the memory control unit 15 or via the memory control unit 15.

  The image processing unit 24 performs predetermined resizing processing such as pixel interpolation and reduction, color conversion processing, and the like on the image data acquired from the A / D converter 23 or the memory control unit 15. The image processing unit 24 performs predetermined calculation processing using image data of a subject to be photographed, and a system control unit 50 (to be described later) performs exposure control and focus control based on the obtained calculation result. As a result, TTL (through the lens) AF (autofocus) processing, AE (automatic exposure) processing, and EF (strobe light control) processing are performed. Further, the image processing unit 24 performs predetermined arithmetic processing using the captured image data, and performs TTL AWB (auto white balance) processing based on the obtained arithmetic result.

  The memory 32 stores image data output from the A / D converter 23 and image data to be displayed on the display unit 28. The memory 32 has a storage capacity sufficient to store a predetermined number of still images, a moving image and sound for a predetermined time. The memory 32 also serves as an image display memory (video memory). The D / A converter 13 converts the display image data stored in the memory 32 into an analog signal and supplies the analog signal to the display unit 28, whereby an image is displayed on the display unit 28 including a color liquid crystal panel. Is done. The digital signal converted into a digital signal by the A / D converter 23 and stored in the memory 32 is converted into an analog signal by the D / A converter 13 and sequentially transferred to the display unit 28, so-called electronic Through image display using the viewfinder function can be performed.

  The digital camera 100 further includes a system control unit 50, a nonvolatile memory 56, a system memory, a system timer 53, an operation unit 70, a shutter button 61, and a mode change switch 60.

  The system control unit 50 performs overall operation control and information processing of the digital camera 100 by executing a program stored in the nonvolatile memory 56. In addition, the system control unit 50 performs display control by controlling the memory 32, the D / A converter 13, the display unit 28, and the like. The nonvolatile memory 56 is an electrically erasable / storable memory such as a flash memory. The nonvolatile memory 56 stores constants for operation of the system control unit 50, programs for executing various flowcharts to be described later, and the like. A RAM is used as the system memory 52, and constants and variables for operation of the system control unit 50, programs read from the nonvolatile memory 56, and the like are expanded. The system timer 53 measures the time used for various controls and the time of a built-in clock.

  The mode switch 60, the shutter button 61, and the operation unit 70 are operation means for inputting various operation instructions to the system control unit 50. The mode switch 60 switches the operation mode of the system control unit 50 to any one of a still image recording mode, a moving image recording mode, a reproduction mode, and the like. Modes included in the still image recording mode include an auto shooting mode, an auto scene discrimination mode, a manual mode, various scene modes for shooting settings for each shooting scene, a program AE mode, a custom mode, and the like. Similarly, the moving image shooting mode may include a plurality of modes.

  The shutter button 61 includes a first shutter switch 62 and a second shutter switch 64. The first shutter switch 62 is turned on by a so-called half-press (shooting preparation instruction) during the operation of the shutter button 61, whereby the first shutter switch signal SW1 is generated. The system control unit 50 starts operations such as AF (autofocus) processing, AE (automatic exposure) processing, AWB (auto white balance) processing, and strobe emission determination processing in response to the first shutter switch signal SW1. The second shutter switch 64 is turned on by a so-called full press (shooting instruction) when the operation of the shutter button 61 is completed, whereby a second shutter switch signal SW2 is generated. Based on the second shutter switch signal SW2, the system control unit 50 performs a series of shooting processes from EF (strobe dimming) processing according to the scene, reading of signals from the imaging unit 22 to writing of image data into the storage medium 200 described later. Start the operation.

  The operation unit 70 includes operation members for selecting various function icons displayed on the display unit 28, and these operation members are used as various function buttons by appropriately assigning functions for each scene. Examples of the function buttons include an end button, a return button, an image advance button, a jump button, a narrowing button, and an attribute change button. For example, when a menu button is pressed, a menu screen for various functions that can be set is displayed on the display unit 28. The photographer can make various settings intuitively using the menu screen displayed on the display unit 28 and operation members (such as a four-way button and a SET button).

  Further, the digital camera 100 includes a power switch 72, a power control unit 80, a power supply unit 30, a strobe 90, a storage medium I / F 18, and a storage medium 200.

  The power control unit 80 includes a battery detection circuit, a DC-DC converter, a switch circuit that switches a block to be energized, and the like, and detects whether or not a battery is mounted, the type of battery, and the remaining battery level. Further, the power control unit 80 controls the DC-DC converter based on the detection result and an instruction from the system control unit 50, and supplies a necessary voltage to each unit including the storage medium 200 for a necessary period. The power supply unit 30 is a primary battery such as an alkaline battery or a lithium battery, a secondary battery such as a nickel metal hydride battery or a lithium ion battery, an AC adapter, or the like. The strobe 90 is a lighting device that compensates for illuminance when shooting in a low-light scene or shooting in a backlight scene by flashing light during shooting. Although not shown in FIG. 1, the strobe 90 is provided on the front surface of the digital camera 100, for example, as is well known, or appears on the appearance by popping up from the upper surface of the digital camera 100.

  The storage medium I / F 18 is an interface that enables communication between the storage medium 200 such as a memory card or a hard disk and the system control unit 50. The storage medium 200 is a semiconductor memory, a magnetic disk, an optical disk, or the like that stores captured images.

  In the digital camera 100, it is possible to shoot using a central one-point AF or a face AF. In the central one-point AF, AF is performed on one point at the central position in the shooting screen. In the face AF, AF is performed on the face in the shooting screen detected by the face detection function.

  Here, the face detection function will be described. The system control unit 50 sends the image data to be detected to the face to the image processing unit 24. Under the control of the system control unit 50, the image processing unit 24 applies a horizontal band pass filter to the received image data, and further applies a vertical band pass filter to the processed image data. Edge components are detected from the image data by these horizontal and vertical band-pass filters.

  Subsequently, the system control unit 50 performs pattern matching on the detected edge component, and extracts a candidate group of eyes, nose, mouth, and ears. Then, the system control unit 50 determines an eye pair that satisfies a preset condition (for example, distance between two eyes, inclination, etc.) from the extracted eye candidate group. Narrow down only those with eye candidates. Then, the system control unit 50 associates the narrowed-down eye candidate group with other parts (nose, mouth, ears) that form the corresponding face, and passes a preset non-face condition filter. , Detect the face. The system control unit 50 outputs face information according to the face detection result, and ends the process. At this time, feature quantities such as the number of faces are stored in the system memory 52.

  As described above, it is possible to detect the subject information by analyzing the image data displayed or reproduced and displaying the live view and extracting the feature amount of the image data. The subject information includes various other information such as red-eye determination, eye detection, eye-brow detection, and smile detection. In addition, the face AE, the face FE, and the face WB can be performed simultaneously with the face AF. In the face AE, the exposure of the entire screen is optimized according to the brightness of the detected face. In the face FE, strobe light is dimmed around the detected face. In the face WB, the WB of the entire screen is optimized in accordance with the detected face color.

  FIG. 3 is a flowchart showing a strobe shooting sequence in the digital camera 100. The strobe shooting sequence shows a processing flow of the system control unit 50 after the strobe shooting determination is performed by the processing executed when the first shutter switch 62 is turned on and then the second shutter switch 64 is turned on. Yes. Each step shown in FIG. 3 is realized by the system control unit 50 executing a predetermined program stored in the nonvolatile memory 56 and controlling each unit of the digital camera 100 under the control.

  In step S <b> 301, the system control unit 50 performs strobe dimming exposure control using the strobe 90. Here, strobe light control is performed using the imaging unit 22. For this reason, the exposure under the proper exposure is set so that the probability that the strobe preliminary light emission can be received within the range of the received light amount in which the output characteristic (photoelectric conversion characteristic) of the imaging unit 22 is substantially linear is increased. In subsequent step S <b> 302, the system control unit 50 exposes external light (imaging light flux) by the imaging unit 22 without causing the strobe 90 to emit light. In step S303, the system control unit 50 controls the strobe 90 to perform preliminary light emission with a predetermined light emission amount, and performs exposure with the imaging unit 22 to acquire imaging data including subject reflected light due to preliminary light emission. .

  Subsequently, in step S304, the system control unit 50 performs main subject extraction by a known main subject extraction method. Known main subject extraction methods include those using the reflectance of preliminary light emission and those using the face detection function described above, but the method is not limited. The main subject region extracted in step S304 is a target region that is controlled so that the proper luminance is obtained by the strobe main light emission at the time of actual photographing.

  Thereafter, in step S305, the system control unit 50 obtains the flash strobe light emission amount at the main subject brightness from the difference between the imaging data acquired in steps S302 and S303. In addition, the system control unit 50 calculates the main light emission amount so that the main subject region has the appropriate luminance at the time of the main photographing with reference to the preliminary light emission amount in consideration of the appropriate luminance and the exposure at the time of the main photographing. In subsequent step S306, the system control unit 50 represents the relationship between the light emission amount based on the preliminary light emission amount obtained in step S305, the flash time (light emission time) stored in the nonvolatile memory 56, and the light emission amount. From the light emission characteristic information, the flash time during the main flash emission is calculated. The light emission characteristic information includes a plurality of regions (hereinafter referred to as “region data”) representing the relationship between the flash time of the strobe 90 and the light emission amount according to the light emission amount (for example, the light emission amount is large, medium, or small). ”).

  Next, in step S307, the system control unit 50 performs exposure control for main photographing. In step S <b> 308, the system control unit 50 performs the main photographing by causing the strobe 90 to perform the main light emission and performing the main exposure by the imaging unit 22. At the end of the main exposure, the shutter 101 is closed and a series of image processing such as noise reduction and development processing is performed. Here, the series of processing is assumed to be main photographing.

  The processing after step S309 is a flow of processing for updating the light emission characteristic information stored in the nonvolatile memory 56. In step S309, the system control unit 50 makes the luminance of the main subject area (brightness at the time of preliminary light emission) of the imaging data acquired by the preliminary light emission of step S303 and the output characteristic (photoelectric conversion characteristic) of the imaging unit 22 substantially linear. It is determined whether the data is a region (hereinafter referred to as “substantially linear characteristic region”). Here, it cannot be said that the dynamic range of the imaging unit 22 is sufficiently wide. Therefore, when the preliminary light emission luminance is higher or lower than the substantially linear characteristic region (NO in S309), the system control unit 50 determines that the data is not trusted and the light emission characteristic information is not updated. Then, the process proceeds to step S318. On the other hand, if the preliminary light emission luminance is in the substantially linear characteristic region (YES in S309), the system control unit 50 advances the process to step S310.

  In step S <b> 310, the system control unit 50 determines that the flash time of the strobe main light emission determined in step S <b> 306 (actual flash time in the main flash light emission) is the flash time in the light emission characteristic information stored in the nonvolatile memory 56 ( Hereinafter, it is determined whether it is an upper limit value of “stored flash time”. If the actual flash time of the flash main flash is the upper limit value of the stored flash time (NO in S310), there is a possibility that the main subject area may not be flashed with the original flash time that makes the main subject area have an appropriate luminance during the main shooting. Therefore, in this case, the system control unit 50 determines that the light emission characteristic information is not updated, and the process proceeds to step S318. On the other hand, when the actual flash time of the main flash emission is not the upper limit value of the stored flash time (YES in S310), the system control unit 50 advances the process to step S311.

  In step S311, the system control unit 50 obtains the reflectance of the main subject by calculation. The calculation method of the reflectance will be described later with reference to FIG. In subsequent step S312, the system control unit 50 determines whether or not the reflectance obtained in step S311 is within a predetermined range. In the case of a subject such as a mirror having a very low reflectance or regular reflection, the reliability of the reflected light amount data decreases. Therefore, when the reflectance is not within the predetermined range (NO in S312), the system control unit 50 determines not to update the light emission characteristic information, and advances the process to step S318. On the other hand, if the reflectance is within the predetermined range (YES in S312), the system control unit 50 advances the process to step S313.

  In step S313, the system control unit 50 determines which area data (light emission amount: small, medium, large) in the light emission characteristic information has been referred to in the current strobe main light emission (S308). In step S 313, the system control unit 50 creates a coefficient depending on how many times the area data has been referred to in the previous flash photography from the numerical value stored in the nonvolatile memory 56. This coefficient becomes smaller as the reference count is smaller. In subsequent step S314, the system control unit 50 calculates the luminance value of the main subject area from the image data acquired in the actual photographing in step S308 as a luminance value calculating unit. Then, the system control unit 50 detects the light emission amount of the main light emission in the luminance of the main subject region in consideration of the difference between the external light only data acquired in step S302 and the exposure for light control and the exposure for main photographing.

  In subsequent step S315, the system control unit 50 calculates, as the light emission amount ratio calculating means, from the light emission amount of the preliminary light emission obtained in step S305 and the light emission amount of the strobe main light emission obtained in step S314 in the luminance of the main subject area. The light emission amount ratio between the preliminary light emission and the main light emission is calculated. The light emission amount ratio obtained here can be regarded as an actual measurement value for the light emission amount (target value) of the main light emission calculated based on the preliminary light emission amount in step S305. The difference between the target value and the actual measurement value includes not only the light emission variation of the strobe 90 but also the information stored in the nonvolatile memory 56 as the light emission characteristic information indicating the relationship between the flash time and the light emission amount, and the actual strobe 90. Deviations from the emission characteristics are included. Therefore, by correcting the light emission characteristic information stored in the nonvolatile memory 56 based on the actual measurement value, it is possible to improve the light control accuracy at the next flash photography.

Subsequently, in step S316, the system control unit 50 calculates a correction amount of the light emission characteristic information from the actually measured value obtained in step S315 and the coefficient obtained in step S313. FIG. 8 is a diagram for explaining the correction amount calculation processing in step S316. FIG. 8A shows area data (light emission amount: small, medium or large) referred to this time among the light emission characteristic information before correction. As shown in FIG. 8B, when the flash time of the main flash emission at the time of the current main photographing is t ₀ , the light emission amount corresponding to the flash time t ₀ in the light emission characteristic information stored in the nonvolatile memory 56. Is a target amount α. As shown in FIG. 8C, when the actual light emission amount obtained from the captured image data is the actual measurement value β, as shown in FIG. 8D, the flash time t ₀ in the corrected characteristic information. Correction is performed without changing the flashing time so that the amount of light emission with respect to is a predetermined value γ where α <γ <β.

  The predetermined value γ is, for example, a point that internally divides the target amount α and the actual measurement value β into x: y, and the ratio of x: y is determined depending on the coefficient obtained in step S313. The smaller the coefficient obtained in step S313, the closer the predetermined value γ is to the actual measurement value β. That is, the smaller the number of times of reference of the light emission characteristic information, the larger the correction amount in one shooting. The amount of change of each element of the light emission characteristic information is changed so that the correction amount becomes smaller as the distance from the point of the light emission amount α of the light emission characteristic information before correction becomes smaller, and FIG. The image of the amount of change according to the distance is also shown.

  Returning to the description of FIG. The fact that the target value and the actual measurement value of the light emission amount are different in step S315 means that the luminance of the main subject in the captured image is deviated from the target luminance. Therefore, in step S317, the system control unit 50 performs a luminance correction amount calculation process for the captured image captured in step S308. Here, in order to perform luminance correction by image processing in the subsequent step S318, in step S317, an object is to reduce the influence of deviation from the actual light emission characteristic information. Therefore, in step S317, the luminance correction amount adjustment process is performed according to the coefficient obtained in step S313 and the difference amount between the target value of the light emission amount and the actual measurement value. At this time, the processing is performed so that the luminance correction is performed more strongly as the reliability of the light emission characteristic information is lower, and the luminance correction amount is increased as the coefficient is smaller.

  In step S318, the system control unit 50 performs brightness correction processing of the captured image in consideration of the brightness correction amount obtained in step S317. Also, when the determinations in steps S309, 310, and 312 are “NO”, the brightness correction processing of the captured image is performed in step S318. In other words, the brightness correction processing of the captured image is performed by an amount that considers the light emission variation of the strobe 90 without updating the light emission characteristic information. The system control unit 50 ends this process after step S318 ends.

  FIG. 4 is a flowchart showing details of the reflectance calculation process performed in step S311. In step S401, the system control unit 50 measures (measures) the distance to the subject by focus control. As a distance measuring method using image data, any known method may be used, and detailed description thereof is omitted. Here, the subject refers to the main subject in the flowchart of FIG. 3, but it is also possible to set a subject frame other than the main subject in the image data and obtain distance information to the subject. Next, in step S402, the system control unit 50 obtains a luminance value in a predetermined frame area including the subject acquired in step S401 of the respective imaging data when the strobe is not lighted and when the preliminary light is emitted. As a result, the amount of reflected light from the subject when preliminary light emission with a predetermined light emission amount is performed toward the subject at a distance obtained by distance measurement.

  Therefore, in the subsequent step S403, the system control unit 50 uses the subject (subject) shown in step S401 from the data indicating the subject reflected light amount and the subject reflectance by preliminary light emission at a predetermined distance held in the nonvolatile memory 56. Frame)). In the flowchart of FIG. 3, the light emission characteristic information is updated only when the subject reflectance estimated in this way is within a predetermined range.

Second Embodiment
Since the second embodiment differs from the first embodiment only in the method for determining whether or not to correct the light emission characteristic information, this difference will be described below. FIG. 5 is a flowchart relating to determination as to whether or not to correct light emission characteristic information in the second embodiment, and steps S309 to S317 in the first embodiment are replaced with steps S501 to S511. .

  Since the process of step S501 is the same as the process of step S310, description here is abbreviate | omitted. If the actual flash time of the flash main flash is the upper limit value of the stored flash time (NO in S501), there is a possibility that the main subject area may not be flashed at the proper brightness at the time of main shooting, so system control is not possible. The unit 50 determines that the light emission characteristic information is not updated, and exits this process. On the other hand, if the actual flash time of the main flash is not the upper limit value of the stored flash time (YES in S501), the system control unit 50 advances the process to step S502.

  Since the process of step S502 is the same as the process of step S313, description here is omitted. In subsequent step S503, the system control unit 50 extracts a plurality of regions in order to determine whether or not to correct the light emission characteristic information. Here, the multiple region extraction processing in step S503 will be described with reference to the flowchart of FIG. 6 and FIG. FIG. 6 is a flowchart showing details of the process in step S503, and FIG. 7 is a schematic diagram for explaining the contents of the process in step S503.

  FIG. 7A shows a shooting angle of view and a subject. FIG. 7B shows an example of a block integration frame for obtaining a luminance value for each small block. In step S601, the system control unit 50 performs block integration with the integration frame shown in FIG. 7B on the respective imaging data at the time of non-flash emission (external light imaging) and preliminary emission. Find the block integration value.

  Next, in step S602, the system control unit 50 obtains a difference between the integration result of the imaging data at the time of preliminary light emission and the integration result of the imaging data at the time of non-flash emission, and obtains the amount of reflected light at the time of preliminary light emission. In step S603, the system control unit 50 extracts a region where the preliminary light emission has a great influence on the luminance, specifically, a block whose reflected light amount in the screen is equal to or greater than the average value. FIG. 7C shows the region (block) extracted in step S603.

  Subsequently, in step S604, the system control unit 50 applies a rectangular frame that is not adjacent to the boundary with the center of the integration frame in FIG. 7B as a vertex to the region extracted in step S603 according to a predetermined rule. To set. FIG. 7D shows the rectangular frame set in step S604. Thereafter, in step S605, the system control unit 50 selects a frame that is not adjacent from the rectangular frames set in step S604 according to a predetermined rule. FIG. 7E shows the rectangular frame selected in step S605. Note that the method of extracting a plurality of regions is not limited to the method described with reference to FIGS.

  Returning to the description of FIG. In step S504, the system control unit 50 obtains a luminance value for each of the plurality of areas extracted in step S503 for the imaging data acquired at the time of preliminary light emission, and determines whether each of the obtained luminance values is in a substantially linear characteristic area. judge. When all the areas are out of the substantially linear characteristic area (NO in S504), the system control unit 50 exits this process on the assumption that the light emission characteristic information is not corrected. On the other hand, if there is a region that falls within the substantially linear characteristic region (YES in S504), the system control unit 50 advances the process to step S505. At this time, the region out of the substantially linear property region among the plurality of regions. Is excluded from the target of subsequent processing. Hereinafter, one or a plurality of areas to be processed after step 505 are referred to as “processing target areas”, and in the following description, it is assumed that there are a plurality of processing target areas.

  In step S <b> 505, the system control unit 50 obtains a luminance value for each processing target area using the image data of the main shooting in which the strobe main flash is performed. In step S505, the system control unit 50 further performs main shooting for each processing target region in consideration of the imaging data obtained in step S302 when no flash is emitted and the difference between exposure for light control and exposure for main shooting. The amount of light emitted at the time (during main light emission) is obtained. Subsequently, in step S506, the system control unit 50, as a light emission amount ratio calculating unit, uses the preliminary light emission and the strobe light for the processing target region based on the light emission amount of the preliminary light emission and the light emission amount of the strobe light obtained in step S505. The light emission amount ratio of light emission is calculated.

  In step S507, the system control unit 50 obtains a variation in the light emission amount ratio of each processing target region obtained in step S506, and determines whether or not the obtained light emission amount ratio is within a predetermined range. If the light emission amount ratio is not within the predetermined range (NO in S507), the system control unit 50 exits this process, assuming that the light emission amount ratio is not reliable and the light emission characteristic information is not corrected. If the light emission amount ratio is within the predetermined range (YES in S507), the system control unit 50 determines that the light emission amount ratio is reliable and advances the process to step S508.

  In step S508, the system control unit 50 performs the reflectance calculation described above with reference to FIG. Note that the description of FIG. 4 has already been made in the first embodiment, and the description thereof is omitted here. In subsequent step S509, the system control unit 50 determines whether or not the reflectance of the processing target area obtained in step S508 is within a predetermined range. If all the reflectances are out of the predetermined range (NO in S509), the system control unit 50 exits this process on the assumption that the light emission characteristic information is not corrected. If there is a reflectance region within the predetermined range (YES in S509), the system control unit 50 advances the processing to step 510 after excluding the reflectance region outside the predetermined range.

  In step S510, the system control unit 50 calculates the correction amount of the light emission characteristic information from the average value (actually measured value) of the light emission amount ratio obtained in step S506 and the coefficient obtained in step S502. The specific processing content of step S510 is the same as the processing content of step S316 and has already been described with reference to FIG. In subsequent step S511, the system control unit 50 calculates an image luminance correction amount for the captured image obtained by the main photographing with the flash main light emission. Since the processing content of step S511 is the same as the processing content of step S317, description here is abbreviate | omitted.

  As described above, according to the embodiment of the present invention, the light emission characteristic information is considered in consideration of the difference between the light emission amount calculated for the main photographing using the light emission characteristic information and the actual light emission amount. And the light emission control of the strobe 90 is performed using the corrected light emission characteristic information. Therefore, the light emission characteristic information can be accurately corrected in each digital camera 100, and a good image can be obtained by flash photography. Further, when the preliminary light emission luminance is higher or lower than the substantially linear characteristic region of the photoelectric conversion characteristic of the imaging unit 22, when the subject reflectance is extremely low or high, the light emission amount of the preliminary light emission and the main flash light emission If the ratio is not within a predetermined range in a plurality of areas, the reliability of each data is low and the light emission characteristic information is not updated. Thereby, the accuracy of the light emission characteristic information can be maintained high.

<Other embodiments>
Although the present invention has been described in detail based on preferred embodiments thereof, the present invention is not limited to these specific embodiments, and various forms within the scope of the present invention are also included in the present invention. included. For example, in the above-described embodiment, the compact digital camera 100 is taken up. However, it is needless to say that the present invention can be applied to a digital single-lens reflex camera including a lighting device. Further, the present invention can also be applied to a camera system in which a lighting device that can be attached to and detached from a digital single-lens reflex camera is attached.

  The present invention can also be realized by executing the following processing. That is, software (program) that realizes the functions of the above-described embodiments is supplied to a system or apparatus via a network or various storage media, and a computer (or CPU, MPU, etc.) of the system or apparatus reads the program code. It is a process to be executed. In this case, the program and the storage medium storing the program constitute the present invention.

22 Imaging unit 50 System control unit 56 Non-volatile memory 90 Strobe 100 Digital camera

Claims (12)

A light emitting means for flashing;
Imaging means;
A luminance value calculating means for calculating a luminance value of a predetermined area of image data obtained by imaging with the imaging means;
Determining means for determining a main light emission amount of the light emitting means;
Storage means for storing light emission characteristic information representing a relationship between a light emission time and a light emission amount of the light emission means;
A calculation means for calculating a light emission time by the light emission means based on the light emission characteristic information and the main light emission amount determined by the determination means;
Detection that detects an actual light emission amount when the light emitting means is flashed for the light emission time calculated by the calculating means based on image data obtained by imaging with the imaging means when the flash light is emitted. Means,
An imaging apparatus comprising: a correction unit that corrects the light emission characteristic information based on a difference between the main light emission amount determined by the determination unit and the actual light emission amount detected by the detection unit.   The imaging apparatus according to claim 1, wherein the predetermined area is a main subject area. The determining means obtains the main light emission amount based on the subject reflected light amount obtained by the preliminary light emission performed with the predetermined light emission amount,
The luminance value calculating means includes image data obtained by imaging with the imaging means without causing the light emitting means to emit light, image data obtained by imaging with the imaging means when the preliminary light emission is performed, and a book Calculating a luminance value of each of the predetermined areas of the image data obtained by imaging with the imaging means when flashing with a light emission amount;
Based on the luminance value calculated by the luminance value calculating means, further comprising a light emission amount ratio calculating means for calculating a light emission amount ratio between the preliminary light emission amount and the main light emission amount in the predetermined region,
The imaging apparatus according to claim 1, wherein the correction unit corrects the light emission characteristic information based on the light emission amount ratio in the predetermined region calculated by the light emission amount ratio calculation unit. . The light emission amount ratio calculating means extracts a plurality of regions as the predetermined region and calculates the light emission amount ratio,
The said correction | amendment means correct | amends the said light emission characteristic information, when the light emission amount ratio calculated by the said light emission amount ratio calculation means is in the predetermined range about the said several area | region. Imaging device.   The correction unit corrects the light emission characteristic information when the luminance value calculated by the luminance value calculation unit is within a region where the photoelectric conversion characteristic of the imaging unit is approximately linear due to the preliminary light emission. The imaging apparatus according to claim 3 or 4, wherein Measuring means for measuring the distance to the subject;
An estimation unit that estimates the reflectance of the subject from the distance to the subject measured by the measurement unit and the luminance value in the preliminary light emission calculated by the luminance value calculation unit;
6. The imaging according to claim 3, wherein the correction unit does not correct the light emission characteristic information when the reflectance estimated by the estimation unit is not within a predetermined range. apparatus.   The correction means corrects the light emission characteristic information when the light emission time calculated by the calculation means does not exceed an upper limit value of the light emission time included in the light emission characteristic information. The imaging device according to any one of the above. The light emission characteristic information includes a plurality of region data representing a relationship between a light emission time and a light emission amount of the light emitting unit according to a light emission amount magnitude,
8. The correction unit according to claim 1, wherein the correction unit changes a correction amount for correcting the light emission characteristic information according to the number of times the calculation unit refers to the plurality of region data of the light emission characteristic information. The imaging apparatus of Claim 1.   The correction means is α for the light emission amount corresponding to the light emission time included in the light emission characteristic information before correction with the light emission time calculated by the calculation means, β for the actual light emission amount detected by the detection means, The light emission characteristic information is corrected so that the relationship of α <γ <β is satisfied, where γ is the light emission amount at the light emission time of the light emission characteristic information corrected by the light emission time calculated by the calculation means. The imaging apparatus according to claim 8, wherein:   The correction means is configured to change a correction amount of a light emission amount included in the light emission characteristic information so as to decrease as the distance from the α decreases without changing a light emission time included in the light emission characteristic information. 9. The imaging device according to 9.   According to the number of times the calculation means refers to the plurality of region data of the light emission characteristic information, and the difference between the actual light emission amount determined by the determination means and the actual light emission amount detected by the detection means, The apparatus further comprises a luminance correction amount calculating means for calculating a luminance correction amount for correcting the luminance of the image data obtained by imaging with the imaging means when flashing with the main light emission amount. The imaging device according to any one of 8 to 10. A lighting control method for the lighting device in an imaging device comprising: an illumination device that emits flash light; and a storage unit that stores light emission characteristic information representing a relationship between a flash time and a light emission amount of the illumination device,
A determination step of determining a main light emission amount of the illumination device;
A calculation step of calculating a light emission time by the lighting device based on the light emission characteristic information stored in the storage means and the main light emission amount determined in the determination step;
A detection step of detecting an actual light emission amount when the illumination device is caused to flash by the light emission time calculated in the calculation step based on image data obtained when the flash is emitted;
A correction step of correcting the light emission characteristic information stored in the storage unit based on a difference between the main light emission amount determined in the determination step and the actual light emission amount detected in the detection step. The light emission control method of the illuminating device.